Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1997-11-26
2001-06-12
Dye, Rena L. (Department: 1772)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S173000, C156S085000, C156S086000, C264S230000, C428S034900, C174SDIG008
Reexamination Certificate
active
06245174
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a tubular, dimensionally heat recoverable, polymeric article comprising a spirally wrapped polymeric sheet, to methods of making the article, and to methods of using the article to bridge two elongate substrates.
2. Introduction to the Invention
A dimensionally heat recoverable article is an article the dimensional configuration of which may be made substantially to change when subjected to heat treatment. Usually these articles recover towards an original shape from which they have previously been deformed but the term “recoverable”, as used herein, also includes an article which adopts a new configuration, even if it has not been previously deformed. In their most common form, heat recoverable articles comprise a shrinkable sleeve made from polymeric material.
Commonly, processes for producing heat recoverable articles involve cross-linking the polymer at some stage in the production process to enhance the desired dimensional recoverability. A particular method of producing a heat recoverable article comprises shaping the article into the desired heat stable form, subsequently cross-linking the polymeric material, heating the article to a temperature above the crystalline melting point or, for amorphous materials the softening point, as the case may be, of the polymer, deforming the article and cooling the article whilst in the deformed state so that the deformed state of the article is retained. In use since the deformed state of the article is heat unstable, application of heat will cause the article to assume its original heat stable shape. Cross-linking may conveniently be carried out by irradiation, or by chemical means.
European Publication No. 0158519 describes a heat recoverable article for covering elongate substrate(s), the article comprising a heat recoverable, cross-linked, polymeric sheet having a resistance heating element arranged in thermal contact with the sheet, the resistance element being connected to a source of electrical power to heat and hence recover the article. In order to install the article, the sheet containing the heating element is spirally wrapped one or more times around the substrate(s) prior to the heating. The sheet is usually lined with adhesive, and after heating and recovery, adjacent layers of the sheet are bonded to each other.
Relatively thin wall tubular products (wall thickness 0.4 to 2 mm), apparently comprising spirally wrapped, cross-linked, polyethylene layers, overlapping layers of which are pre-bonded to each other by copolymer bonding layers, probably an ethylene vinylacetate bonding layer, have been available on the market for a number of years. These thin wall sleeves typically range in diameter from about 50 to 1000 mm, and typically find application for pipe covering and the like.
Japanese Patent Publication No. 54-163974 (Hitachi) describes a method of making a heat shrinkable composite pipe by winding a tape of two or more water cross-linkable polymers around a mandrel, integrating the layers by heat, and subsequently cross-linking the polymers in water or humidity. The pipe is made heat shrinkable by introducing a pressurized fluid to expand it, and cooling in the expanded shape.
Japanese Patent Publication No. 61-249738 (Futukawa) describes a method of making a heat shrinkable polyolefin coating material by winding silane graft polyolefin sheet onto a mandrel, in the presence of a silanol condensation catalyst, to give a laminate of a desired thickness. The wound sheet is then heated to weld the overlapping layers and to cross-link. The cross-linked tube is then expanded and cooled in the expanded shape.
SUMMARY OF THE INVENTION
A first aspect of the present invention provides a heat recoverable, tubular article comprising a spirally wrapped, cross-linked, polymeric sheet, overlapping layers of the cross-linked sheet having been directly fused to each other to form a consolidated tubular article, the consolidated tube having a thickness of at least 2.2 mm.
In contrast to European Publication No. 0158519 described above, in the present invention the overlapping layers of the spirally wrapped layers of sheet are directly fused to each other prior to recovery of the sheet. This direct fusion step is typically carried out in the factory prior to supply of the product to the end-user. Hence a consolidated multi layer recoverable tubular article in which the layers are pre-bonded to each other, is available for installation by the end user.
In contrast to the thin-walled commercially available sleeves referred to above, articles according to the invention are much thicker walled, and do not incorporate a separate bonding layer between overlapped layers of the sheet. Furthermore, the thicker walled articles of the present invention, being much stronger, may be used for forming joints between substrates such as pipes. In contrast to the pipes and tubes made according to Japanese Patent Publication Nos. 54-163974 and 61-249738, the article according to the invention is made from a polymeric sheet that is cross-linked prior to its spiral wrapping, and consolidation. In the Japanese references, the cross-linking is carried out after wrapping.
DETAILED DESCRIPTION OF THE INVENTION
Heat recoverable articles according to the invention have a minimum wall thickness of 2.2 mm. Preferably the wall thickness is substantially uniform over the full length and/or over the entire periphery of the article. The minimum wall thickness of 2.2 mm is for the fused, wrapped layers alone, independent of any separate sealing material, or other material which may be used as a lining.
The spiral-wrap, or cigarette wrap, configuration of the article of the invention advantageously allows relatively thick wall products (e.g. 2.2 mm or higher, often 3 mm or higher, 5 mm or higher or even 8 mm, 10 mm, 15 mm or higher), to be made from sheet material of one or a few different thinner thicknesses. Different thicknesses of article can be achieved by using an increased number of layers in the spiral wrap, or by increasing the thickness of the component sheet, or by a combination of both. Furthermore, the spiral wrap configuration allows a number of different diameter tubular articles to be made from sheet material of a single thickness. For example, articles according to the invention, varying in diameter from about 90 to 1400 mm, or even up to about 2500 mm, can easily and conveniently be made. The invention therefore allows a large range of thickness and diameter tubular products to be produced, without the need to invest in tubular extrusion, expansion and/or molding equipment for each diameter and wall thickness product.
Overlapping layers of the spirally wrapped polymeric sheet are directly fused to each other. The term “directly fused to each other” is used herein to mean that sufficient molecular interaction between adjacent overlapping layers of the sheet occurs that a bond forms which will provide mechanical performance equal to or greater than that of the sheet itself. This direct fusion may be through viscoelastic contact as defined by J. N. Anand in Adhesion 1, 1969, pages 16 to 23 and Adhesion 2, 1970 pages 16 to 22, or through a molecular diffusion across the polymer/polymer interface. To test whether overlapping layers of a spirally wrapped article are directly fused to each other, peel strength measurements between the layers may be made.
The fact that overlapping layers are directly fused to each other does not preclude the presence of other materials between adjacent layers, provided a fusion bond can be formed around those materials. It may, for example, be useful to include reinforcing materials e.g. glass fibers, carbon fibers, ultra high modulus polyethylene fibers, aramid fibers, ceramic fibers or the like, either in non-woven, or in woven or other fabric form, between adjacent layers. Such reinforcing fibers may increase the strength in both the axial and hoop directions, and may also increase the impact strength. It may also be useful to include heatin
Cordia Johannes Maria
Ritter Robert
Seidel Robert
LandOfFree
Heat recoverable article does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Heat recoverable article, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Heat recoverable article will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2505064