|Title of Invention||
POLYOLEFIN LAMINATES HAVING IMPROVED PEEL STRENGTH
|Abstract||A polyolefin fabric laminate having improved peel strength, the laminate comprising a plurality of polyolefin fabric layers stacked one above another and heat sealed under pressure with a sealant materials coating having melting point lower that that of the fabric layers applied over the entire surface area of contact between adjacent fabric layers. A method for producing the laminate is also disclosed therein.|
|Full Text||FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
As amended by the Patents (Amendment) Act, 2005
THE PATENTS RULES, 2003
As amended by the Patents (Amendment) Rules, 2006
(See section 10 and rule 13)
TITLE OF THE INVENTION
Polyolefin fabric based sheets having improved peel strength
Reliance Industries Limited, 5th Floor, Maker Chamber IV, Nariman Point, Mumbai 400 021, Maharashtra, India, an Indian Company
PREAMBLE TO THE DESCRIPTION
The following specification describes the invention. :
Field of Invention :
The present invention relates to polyolefin fabric based sheets having improved peel strength and to a process for producing them.
Polyolefin sheets have wide range of applications. They are used in the manufacture of a variety of articles and products including disposable containers, luggage shells, automotive parts and chemical tanks. They also find medical, furniture and infrastructure related applications. Polyolefin sheets are generally prepared by extrusion of polyolefin melt. However, polyolefin sheets prepared by extrusion are prone to damages due to crack propagation due to, for instance, screwing, nailing or riveting while being formed into various articles and products or while being handled. To avoid propagation of cracks, polyolefin laminates have been prepared from layers of polyolefin fabrics. Polyolefin fabrics are usually woven from sealant coated polyolefin tapes, the sealant having melting point lower than the polyolefin of the tape. Such coated polyolefin tapes are usually prepared by cutting and stretching polyolefin films coated with sealant layers. The layers of polyolefin fabrics are then heat sealed under pressure to form polyolefin laminates. The polyolefin laminates have low peel strength as adhesion between adjacent layers takes place mostly at the tapes surfaces and not at the interstices between
the adjacent fabrics. It is desirable to have polyolefin sheets of improved peel strength to increase the life of the sheets and to widen the areas of use thereof.
Detailed Description of the invention:
Accordingly, the present invention provides a process for preparing polyolefin fabric based sheets of improved peel strength, the process comprising the steps of
1. Coating polyolefin fabric layers with a sealant material, the sealant material being a polyolefin based material having a melting point lower than the polyolefin of the fabric
2. Stacking plurality of coated fabric layers one above another
3. Optionally stitching the coated fabric layers with a polyolefin yarn
4. Heat sealing the coated fabric layers under pressure to form a sheet of fused polyolefin and
5. Cooling the fused polyolefin sheet in the pressed condition
Coating of polyolefin in the woven state allows the sealant material to cover the entire surface area of the fabrics including the interstices. On heating such coated polyolefin fabric layers, the sealant material melts and flows through the interstices in the layers. On cooling the heat sealed sheet, the sealant material binds the layers and the yarn, if any into an integral sheet. The polyolefin fabric layers can also be interposed with materials other than polyolefin. In one embodiment, the invention provides oriented polyolefin sheets prepared from oriented polyolefin fabrics and paper. The polyolefin tapes used for preparing the fabrics optionally comprises carbon black, UV resistant materials and calcium carbonate. In another embodiment, the invention provides polyolefin fabric based sheets of around 20 mm thickness. Sheets having thickness above 20 mm can also be prepared by the process of the present invention.
In a typical process, polyolefin fabrics are coated with sealant layers through a coat hanger die single screw extruder in a continuous process. 10-50 layers of such coated fabrics are fused among themselves at a temperature of 110 to 155°C and a pressure of 10 to 75 bars in a multi daylight hydraulic press and the sheets are then cooled under pressed condition. The fabric layers are optionally fused along with sealant coated paper. Oriented polyolefin fabric based sheets are obtained at an output rate of 200 kg/hr to 400 kg/hr.
The polyolefin fabric based sheets of the invention have improved mechanical properties like high tensile strength, flexural modulus and izod impact strength. They could be formed to various shapes suitable for preparing various articles and products. They find various applications including automobile, protective gear, luggage shell and roofing sheet applications.
Dated this the 29th day of May 2007
|Indian Patent Application Number||999/MUM/2007|
|PG Journal Number||39/2013|
|Date of Filing||29-May-2007|
|Name of Patentee||RELIANCE INDUSTRIES LIMITED|
|Applicant Address||5th FLOOR,MAKER CHAMBER IV, NARIMAN POINT, MUMBAI - 400 021,|
|PCT International Classification Number||B29C65/02|
|PCT International Application Number||N/A|
|PCT International Filing date|