Title of Invention	"A PROCESS FOR PREPARATION OF A COMPOSITE POLYMER SHEET AND A SHEET THEREOF"
Abstract	The present invention relates to a process for preparation of a composite polymer sheet or film composition comprising at least two members, the said members having similar or two different physical forms, the said members being made from similar polymers or two different polymers, said polymers being of similar or two different grades, the polymers being selected such that melting point of the polymer or the grade of polymer used for half of the members is at least 5°C lower than that of the remaining member, the process comprising the steps of assembling one member over the other such that the members having lower melting point are placed in intimate contact with the members having higher melting point, raising the temperature of the assembly of members to more than or equal to melting point of the member having lower melting point but less than or equal to the melting point of the remaining member, simultaneously applying a pressure on the assembly of members, holding the temperature and pressure to cause welding of each molten member with the adjacent member followed by rapidly quenching to obtain the composite polymer material.

Title of Invention

"A PROCESS FOR PREPARATION OF A COMPOSITE POLYMER SHEET AND A SHEET THEREOF"

Abstract

The present invention relates to a process for preparation of a composite polymer sheet or film composition comprising at least two members, the said members having similar or two different physical forms, the said members being made from similar polymers or two different polymers, said polymers being of similar or two different grades, the polymers being selected such that melting point of the polymer or the grade of polymer used for half of the members is at least 5°C lower than that of the remaining member, the process comprising the steps of assembling one member over the other such that the members having lower melting point are placed in intimate contact with the members having higher melting point, raising the temperature of the assembly of members to more than or equal to melting point of the member having lower melting point but less than or equal to the melting point of the remaining member, simultaneously applying a pressure on the assembly of members, holding the temperature and pressure to cause welding of each molten member with the adjacent member followed by rapidly quenching to obtain the composite polymer material.

Full Text	FIELD OF INVENTION The present invention relates to a process for preparation of composite polymer sheet and a sheet or film composition thereof made from two similar or dissimilar polymer materials in the form of films, fibers or fabric and product thereof. The materials used for a composite material may be of same form or different form. The polymers may be polyethylene (PE), polypropylene (PP) or polyethyleneterephthalate (PET) or any fiber forming polymer. The polymer materials may be two grades of same polymer e.g. high density polyethylene (HDPE) having different molecular weights or a polymer and a co-polymer eg HDPE and co-polymer containing say 85% HDPE and 15% polypropylene (PP) . The materials may be different forms of same polymers e.g. linear polyethylene (HDPE) and branched polyethylene (LDPE) BACKGROUND OF INVENTION Polymer sheets or films made from fibers of polymers are known in the art. US Patent 5,135,804 describes a 1-step compaction process for making a film from polyethene fibers at pressures from 4.6 MPa to 46 MPa. GB 2253420 B describes a 2-step compaction process whereby assembly of fibers of an oriented polymer may be hot compacted to form a sheet having good mechanical properties. In this process preferably a 5-10% portion of the fiber surface melts and subsequently recrystallises on cooling. The contact pressure is preferably in the range of 0.5 to 2.0 MPa and compaction pressure is 40-50 MPa. US 6,312,638 teaches a process for production of a monolithic article comprising subjecting an assembly of melt formed fibers of an oriented polyolefin polymer to a compaction process. The fibers maintained in intimate contact at elevated temperature such as to melt 10%-50% of the polymer, are subjected to a compaction pressure from 0.1 to 10 MPa such that monolithic article is produced. These prior art processes teach compaction of fibers or woven fabric formed from fibers and tapes to obtain monolithic articles but do not teach or suggest process for production of composite polymer material made from two similar or dissimilar polymer materials. Polymeric materials are known to be used in a variety of ways, such as plastics, fibers, rubbers etc. The combination of these various forms of polymers are known to be used with certain advantages, but such usage is limited to a possibility of combination of same or different forms of different polymers. A typical example of a material made from the different form but same polymer known in the art is that of fabric of high density polyethylene laminated with low density polyethylene film used in the making of woven sacks. Yet another known material is chopped high performance polyethylene fiber or HPPE fiber, processed with low density polyethylene or LDPE chips. This known polymeric material is made from different polymers having different characteristics namely HPPE fiber and LDPE chips and is prepared by melt mixing of components and suitable moulding. A distinct disadvantage of such known materials is that such materials are prepared from expensive high performance polyethylene (HPPE) fibers. Yet another disadvantage of such known materials is that the method of preparation has significant limitations due to high melt viscosity during melt processing. A further disadvantage of such known materials is that the high melt viscosity during melt processing results in insufficient mixing of the two components. A still further disadvantage is of a possibility of significant changes in properties of HPPE fibers during melt processing. Finally, the known process is limited to preparation of a combination of HPPE fibers and LDPE chips. A co-pending application No. 145/Del/2000 teaches a process for preparation of polymeric materials or composites comprising two members of same polymer but of different properties sealed to each other at melting temperature range of the polymer under suitable pressure. OBJECTS OF THE INVENTION A primary object of the present invention is to propose a process for preparation of polymeric composite material made from similar or dissimilar polymeric materials. Another object of the present invention is to propose a process for preparation polymeric composite materials made from different or same forms of similar or dissimilar polymeric materials. A further object of the present invention is to propose process for manufacture of the polymeric composite material with enhanced puncture resistance. Yet another object of the present invention is to propose a process for preparation of polymeric composite material with enhanced impact properties. Yet further object of the present invention is to propose a process for preparation of polymeric composite material which has excellent tensile strength and elongation. Yet another object of process invention is to propose a process for preparation of polymeric composite materials which is low cost and yet can be recycled thus eliminating disposal problem. Further objects and advantages of the present invention will be more apparent from the ensuing description. STATEMENT OF THE INVENTION According to this invention there is provided a process for preparation of a composite polymer sheet or film composition comprising at least two members, the said members having similar or two different physical forms, the said members being made from similar polymers or two different polymers, said polymers being of similar or two different grades, the polymers being selected such that melting point of the polymer or the grade of polymer used for half of the members is at least 5°C lower than that of the remaining member, the process comprising the steps of assembling at least one member over the other such that the members having lower melting point are placed in contact with the members having higher melting point, raising the temperature of the members to more than or equal to melting point of the member having lower melting point but less than or equal to the melting point of the remaining member, simultaneously applying a pressure on the assembly of members, holding the temperature and pressure to cause welding of each molten member with the adjacent member followed by rapidly quenching to obtain the composite polymer material. According to another aspect of the present invention there is provided a composite polymer sheet or film composition as claimed in claim 1 comprising at least two members, the said members having similar or two different physical forms, the said members being made from similar or two different polymers, said polymers being of similar or two different grades, the polymers being selected such that the melting point of the polymer used for half of the members is at least 5°C lower than that of the remaining members, the said members being placed over one another such that the members having lower melting point are in contact with the members having higher melting point and said members being interposed to one another in form of a composite sheet or film. DESCRIPTION OF THE INVENTION At the outset of the description which follows it is to be understood that the ensuing description only illustrates a particular form of this invention. However such a particular form is only an exemplary embodiment without intending to be understood as exemplary teaching of invention and not intended to be taken restrictively. In accordance with the invention, the process comprises at least a first material member and at least a second material member the said members are selected from fibers, films & fabrics of polymeric materials selected from polymers like polyethylene (PE) , polypropylene (PP) and Polyethyleneterephthalate (PET) . Thus the at least two members may be of similar material or dissimilar material for example (a) Two similar polymers: According to one embodiment of the invention the members may be made from two grades of same polymer having different molecular weights, for example: (i) High density polyethylene (HDPE) with number average molecular weight of 30,000 (ii) High density polyethylene (HDPE) with number average molecular weight of 20,000 or (b) Two different grades as polymer and copolymer: According to another embodiment, the members are made from two different grades of same materials, for example (i) HDPE (ii) copolymers of HDPE with a maximum upto 15% of second components e.g. 85% HDPE and 15% PP, or According to yet another embodiment the members may be made from (i) linear polyethylene (HDPE) and (ii) Branched polyethylene (LDPE) In accordance with the invention the members may be made from two similar polymers having a difference in melting point of at least 5°C. These members could be in different forms or same form. According to one embodiment one member is in fiber form and the other member is in film form. According to another embodiment one member is in fabric form and the other member is in film form. According to yet another embodiment both members are in film form. According to a further embodiment one member is of fabric and the other member is in fiber form. According to yet another embodiment both members are of fabric form. The thickness of the members could be varied. According to one embodiment, the first member is a LDPE film of 25 urn thickness and the other member is HDPE fabric of 200 GSM (g/square meter) with a thickness of approximately 0.25 mm. The fabrics for this purpose could be made from filament yarns or tapes with variations in fabric design/yarn design. Typical yarn/tape denier are in the range of 100 to 1000. The fabric used is typically plain weave. Other fabric designs used could be say twill weave. The process for preparation of polymeric sheet or film comprises assembling at least two layers of polymeric materials of same or different types on one another such that melting temperature of every alternate layer is at least 5° less than the other layers and subjecting them to a typical temperature, pressure and time cycle. The temperature selected is such that the polymeric material used in one layer melts and the other remains intact or melts partially. This allows intermingling of molten member in non-melting member and the composite polymeric material formed by the welding of two members is obtained in form of a sheet/film or takes up the shape of a mold. According to an embodiment the sheet/film is be prepared from two members, the first member being a film of LDPE and second member being a fabric of HDPE. The films are placed in contact with each other. The temperature of said members is raised 115-125°C for 5-7 minutes during which period a pressure of 1-1.5 MPa is applied. The pressure is removed and the resulting product is quenched to obtain the required sheet/film. According to yet another embodiment the sheet/film is prepared from two members, the first member being a film of LDPE, The second member being a fiber of PP. The temperature of the assembled members is initially raised to 100-105°C and then gradually raised to 115-125°C in 5-7 minutes simultaneously increasing the pressure on the sheets from atmospheric to 1-1.5 MPa. The temperature and pressure are held at this level for 2-4 minutes. The resulting product is quickly quenched in air or water to obtain the desired sheet/film. The process could be illustrated by the following non-limiting examples: Example - 1 The first member comprising of film of LDPE and the second member comprising a fabric of HDPE were placed one over the other. Temperature of the members was raised to 12 0°C for about 5 minutes during which period a pressure of lMpa was applied on them. The pressure was removed. Sheet obtained from this process was cooled rapidly by quenching in water. A polymeric composite sheet was obtained. Example - 2 A first member comprising of film of LDPE and the second member comprising fiber of PP were placed over one another. Temperature was increased from 105°C to 120°C in 5-7 minutes; simultaneously pressure acting on these members was increased to 1 MPa in the same time period. After the temperature of 12 0°C was reached the members were heated at 12 0°C for 2 minutes when the pressure of 1 MPa was acting on the members. The pressure was removed. The sheet formed was removed and rapidly quenched in air to obtain the polymeric composite sheet. The composite polymeric sheet or polymeric product produced by the above process has increased puncture resistance and impact properties with excellent tensile strength and elongation achieved at linear thickness. These sheets/products could specifically be used as geomembranes for reduction of water seepage. Further, the sheets/product are suitable as containers of water or liquids due to higher strength to weight ratio. These sheets/products can be recycled and do not pose disposal problems. WE CLAIMS :- 1. A process for preparation of a composite polymer sheet or film composition comprising at least two members, the said members having similar or two different physical forms, the said members being made from similar polymers or two different polymers, said polymers being of similar or two different grades, the polymers being selected such that melting point of the polymer or the grade of polymer used for half of the members is at least 5°C lower than that of the remaining member, the process comprising the steps of assembling one member over the other such that the members having lower melting point are placed in intimate contact with the members having higher melting point, raising the temperature of the assembly of members to more than or equal to melting point of the member having lower melting point but less than or equal to the melting point of the remaining member, simultaneously applying a pressure on the assembly of members, holding the temperature and pressure to cause welding of each molten member with the adjacent member followed by rapidly quenching to obtain the composite polymer material. 2. A process as claimed in claim 1, wherein the physical forms of the members are selected from fabric, or film, or fiber or yarn. 3. A process as claimed in any of the preceding claims, wherein the fabric is selected from plain weave and twill weave. 4. A process as claimed in claim 3, wherein the fabric is made from filament yarn or tape. 5. A process as claimed in claim 1, wherein the polymers are selected from polyethylene (PE), polypropylene (PP) and polyethyleneterephthalate (PET). 6. A process as claimed in any of the preceding claims 2 or 3 wherein the two grades of the polymers are selected from low density, medium density, high density, linear, branched and copolymer. 7. A process as claimed in any of the preceding claims wherein the two grades of polymers used for making the members are high density polyethylene with number average molecular weight of 30,000 and high density polyethylene with number average molecular weight of 20,000. 8. A process as claimed in any of the preceding claims, wherein the two polymers used for the members are high density polyethylene and co-polymer of high density polyethylene with a maximum upto 15% wt. of polypropylene. 9. A process as claimed in any of the preceding claims, wherein the two physical forms of polymers used in making the two members are LDPE film of 25 urn thickness and HDPE fabric of 200 g/m2 with a thickness of about 0.25 mm. 10. A process as claimed in any of the preceding claims, wherein the two physical forms of polymers used in the members are a fabric of HDPE and a film of LDPE. 11. A process as claimed in claim 10, wherein said assembly of two members is heated to 120°C for 5-7 minutes during which time a pressure of 1-1.5 MPa is applied to cause interposition between the two members. 12. A process as claimed in claim 11, wherein the film obtained is rapidly cooled by quenching in water. 13. A process as claimed in claim 10 wherein the assembly of two members is heated so as to increase temperature from 100-105°C to 115-125°C in 5-7 minutes, simultaneously increasing the pressure from atmospheric pressure to 1-1.5 MPa, thereafter the temperature and pressure being held at 115-125°C and 1-1.5 MPa respectively for 2-4 minutes. 14. A composite polymer sheet or film composition as claimed in claim 1 comprising at least two members, the said members having similar or two different physical forms, the said members being made from similar or two different polymers, said polymers being of similar or two different grades, the polymers being selected such that the melting point of the polymer used for half of the members is at least 5°C lower than that of the remaining members, the said members being placed over one another such that the members having lower melting point are in intimate contact with the members having higher melting point and said members being interposed to one another in form of a composite sheet or film. 15. A process for preparation of a composite polymer material, substantially as hereinbefore described with reference to the foregoing Examples. 16. A composite polymer sheet or film substantially as hereinbefore described with reference to the foregoing Examples.

Full Text

FIELD OF INVENTION
The present invention relates to a process for preparation of composite polymer sheet and a sheet or film composition thereof made from two similar or dissimilar polymer materials in the form of films, fibers or fabric and product thereof. The materials used for a composite material may be of same form or different form. The polymers may be polyethylene (PE), polypropylene (PP) or polyethyleneterephthalate (PET) or any fiber forming polymer. The polymer materials may be two grades of same polymer e.g. high density polyethylene (HDPE) having different molecular weights or a polymer and a co-polymer eg HDPE and co-polymer containing say 85% HDPE and 15% polypropylene (PP) . The materials may be different forms of same polymers e.g. linear polyethylene (HDPE) and branched polyethylene (LDPE)
BACKGROUND OF INVENTION
Polymer sheets or films made from fibers of polymers are known in the art. US Patent 5,135,804 describes a 1-step compaction process for making a film from polyethene fibers at pressures from 4.6 MPa to 46 MPa.
GB 2253420 B describes a 2-step compaction process whereby assembly of fibers of an oriented polymer may be hot compacted to form a sheet having good mechanical properties. In this process preferably a 5-10% portion of the fiber surface melts and subsequently recrystallises on cooling. The contact pressure is preferably in the range of 0.5 to 2.0 MPa and compaction pressure is 40-50 MPa.
US 6,312,638 teaches a process for production of a monolithic article comprising subjecting an assembly of melt formed fibers
of an oriented polyolefin polymer to a compaction process. The fibers maintained in intimate contact at elevated temperature such as to melt 10%-50% of the polymer, are subjected to a compaction pressure from 0.1 to 10 MPa such that monolithic article is produced.
These prior art processes teach compaction of fibers or woven fabric formed from fibers and tapes to obtain monolithic articles but do not teach or suggest process for production of composite polymer material made from two similar or dissimilar polymer materials.
Polymeric materials are known to be used in a variety of ways, such as plastics, fibers, rubbers etc. The combination of these various forms of polymers are known to be used with certain advantages, but such usage is limited to a possibility of combination of same or different forms of different polymers.
A typical example of a material made from the different form but same polymer known in the art is that of fabric of high density polyethylene laminated with low density polyethylene film used in the making of woven sacks.
Yet another known material is chopped high performance polyethylene fiber or HPPE fiber, processed with low density polyethylene or LDPE chips. This known polymeric material is made from different polymers having different characteristics namely HPPE fiber and LDPE chips and is prepared by melt mixing of components and suitable moulding.
A distinct disadvantage of such known materials is that such materials are prepared from expensive high performance
polyethylene (HPPE) fibers.
Yet another disadvantage of such known materials is that the method of preparation has significant limitations due to high melt viscosity during melt processing.
A further disadvantage of such known materials is that the high melt viscosity during melt processing results in insufficient mixing of the two components.
A still further disadvantage is of a possibility of significant changes in properties of HPPE fibers during melt processing.
Finally, the known process is limited to preparation of a combination of HPPE fibers and LDPE chips.
A co-pending application No. 145/Del/2000 teaches a process for preparation of polymeric materials or composites comprising two members of same polymer but of different properties sealed to each other at melting temperature range of the polymer under suitable pressure.
OBJECTS OF THE INVENTION
A primary object of the present invention is to propose a process for preparation of polymeric composite material made from similar or dissimilar polymeric materials.
Another object of the present invention is to propose a process for preparation polymeric composite materials made from different or same forms of similar or dissimilar polymeric materials.
A further object of the present invention is to propose process for manufacture of the polymeric composite material with enhanced
puncture resistance.
Yet another object of the present invention is to propose a process for preparation of polymeric composite material with enhanced impact properties.
Yet further object of the present invention is to propose a process for preparation of polymeric composite material which has excellent tensile strength and elongation.
Yet another object of process invention is to propose a process for preparation of polymeric composite materials which is low cost and yet can be recycled thus eliminating disposal problem.
Further objects and advantages of the present invention will be more apparent from the ensuing description.
STATEMENT OF THE INVENTION
According to this invention there is provided a process for preparation of a composite polymer sheet or film composition comprising at least two members, the said members having similar or two different physical forms, the said members being made from similar polymers or two different polymers, said polymers being of similar or two different grades, the polymers being selected such that melting point of the polymer or the grade of polymer used for half of the members is at least 5°C lower than that of the remaining member, the process comprising the steps of assembling at least one member over the other such that the members having lower melting point are placed in contact with the members having higher melting point, raising the temperature of the members to more than or equal to melting point of the member having lower melting point but less than or equal to the
melting point of the remaining member, simultaneously applying a pressure on the assembly of members, holding the temperature and pressure to cause welding of each molten member with the adjacent member followed by rapidly quenching to obtain the composite polymer material.
According to another aspect of the present invention there is provided a composite polymer sheet or film composition as claimed in claim 1 comprising at least two members, the said members having similar or two different physical forms, the said members being made from similar or two different polymers, said polymers being of similar or two different grades, the polymers being selected such that the melting point of the polymer used for half of the members is at least 5°C lower than that of the remaining members, the said members being placed over one another such that the members having lower melting point are in contact with the members having higher melting point and said members being interposed to one another in form of a composite sheet or film.
DESCRIPTION OF THE INVENTION
At the outset of the description which follows it is to be understood that the ensuing description only illustrates a particular form of this invention. However such a particular form is only an exemplary embodiment without intending to be understood as exemplary teaching of invention and not intended to be taken restrictively.
In accordance with the invention, the process comprises at least a first material member and at least a second material member the said members are selected from fibers, films & fabrics of polymeric materials selected from polymers like polyethylene
(PE) , polypropylene (PP) and Polyethyleneterephthalate (PET) . Thus the at least two members may be of similar material or dissimilar material for example
(a) Two similar polymers:
According to one embodiment of the invention the members may be made from two grades of same polymer having different molecular weights, for example:
(i) High density polyethylene (HDPE) with number average molecular weight of 30,000
(ii) High density polyethylene (HDPE) with number average molecular weight of 20,000 or
(b) Two different grades as polymer and copolymer:
According to another embodiment, the members are made from two different grades of same materials, for example (i) HDPE
(ii) copolymers of HDPE with a maximum upto 15% of second components e.g. 85% HDPE and 15% PP, or
According to yet another embodiment the members may be made from (i) linear polyethylene (HDPE) and (ii) Branched polyethylene (LDPE)
In accordance with the invention the members may be made from two similar polymers having a difference in melting point of at least 5°C. These members could be in different forms or same form.
According to one embodiment one member is in fiber form and the other member is in film form.
According to another embodiment one member is in fabric form and the other member is in film form.
According to yet another embodiment both members are in film form.
According to a further embodiment one member is of fabric and the other member is in fiber form.
According to yet another embodiment both members are of fabric form.
The thickness of the members could be varied.
According to one embodiment, the first member is a LDPE film of 25 urn thickness and the other member is HDPE fabric of 200 GSM (g/square meter) with a thickness of approximately 0.25 mm.
The fabrics for this purpose could be made from filament yarns or tapes with variations in fabric design/yarn design. Typical yarn/tape denier are in the range of 100 to 1000. The fabric used is typically plain weave. Other fabric designs used could be say twill weave.
The process for preparation of polymeric sheet or film comprises assembling at least two layers of polymeric materials of same or different types on one another such that melting temperature of every alternate layer is at least 5° less than the other layers and subjecting them to a typical temperature, pressure and time cycle. The temperature selected is such that the polymeric material used in one layer melts and the other remains intact or melts partially. This allows intermingling of molten member in non-melting member and the composite polymeric material formed by the welding of two members is obtained in form of a sheet/film or takes up the shape of a mold.
According to an embodiment the sheet/film is be prepared from two members, the first member being a film of LDPE and second member being a fabric of HDPE. The films are placed in contact with each other. The temperature of said members is raised 115-125°C for 5-7 minutes during which period a pressure of 1-1.5 MPa is applied. The pressure is removed and the resulting product is quenched to obtain the required sheet/film.
According to yet another embodiment the sheet/film is prepared from two members, the first member being a film of LDPE, The second member being a fiber of PP. The temperature of the assembled members is initially raised to 100-105°C and then gradually raised to 115-125°C in 5-7 minutes simultaneously increasing the pressure on the sheets from atmospheric to 1-1.5 MPa. The temperature and pressure are held at this level for 2-4 minutes. The resulting product is quickly quenched in air or water to obtain the desired sheet/film.
The process could be illustrated by the following non-limiting examples:
Example - 1
The first member comprising of film of LDPE and the second member comprising a fabric of HDPE were placed one over the other. Temperature of the members was raised to 12 0°C for about 5 minutes during which period a pressure of lMpa was applied on them. The pressure was removed. Sheet obtained from this process was cooled rapidly by quenching in water. A polymeric composite sheet was obtained.
Example - 2
A first member comprising of film of LDPE and the second member comprising fiber of PP were placed over one another. Temperature was increased from 105°C to 120°C in 5-7 minutes; simultaneously pressure acting on these members was increased to 1 MPa in the same time period. After the temperature of 12 0°C was reached the members were heated at 12 0°C for 2 minutes when the pressure of 1 MPa was acting on the members. The pressure was removed. The sheet formed was removed and rapidly quenched in air to obtain the polymeric composite sheet.
The composite polymeric sheet or polymeric product produced by the above process has increased puncture resistance and impact properties with excellent tensile strength and elongation achieved at linear thickness. These sheets/products could specifically be used as geomembranes for reduction of water seepage. Further, the sheets/product are suitable as containers of water or liquids due to higher strength to weight ratio. These sheets/products can be recycled and do not pose disposal problems.

WE CLAIMS :-
1. A process for preparation of a composite polymer sheet or film composition comprising at least two members, the said members having similar or two different physical forms, the said members being made from similar polymers or two different polymers, said polymers being of similar or two different grades, the polymers being selected such that melting point of the polymer or the grade of polymer used for half of the members is at least 5°C lower than that of the remaining member, the process comprising the steps of assembling one member over the other such that the members having lower melting point are placed in intimate contact with the members having higher melting point, raising the temperature of the assembly of members to more than or equal to melting point of the member having lower melting point but less than or equal to the melting point of the remaining member, simultaneously applying a pressure on the assembly of members, holding the temperature and pressure to cause welding of each molten member with the adjacent member followed by rapidly quenching to obtain the composite polymer material.
2. A process as claimed in claim 1, wherein the physical forms of the members are selected from fabric, or film, or fiber or yarn.
3. A process as claimed in any of the preceding claims, wherein the fabric is selected from plain weave and twill weave.
4. A process as claimed in claim 3, wherein the fabric is made from filament yarn or tape.
5. A process as claimed in claim 1, wherein the polymers are selected from polyethylene (PE), polypropylene (PP) and polyethyleneterephthalate (PET).
6. A process as claimed in any of the preceding claims 2 or 3 wherein the two grades of the polymers are selected from low density, medium density, high density, linear, branched and copolymer.
7. A process as claimed in any of the preceding claims wherein the two grades of polymers used for making the members are high density polyethylene with number average molecular weight of 30,000 and high density polyethylene with number average molecular weight of 20,000.
8. A process as claimed in any of the preceding claims, wherein the two polymers used for the members are high density polyethylene and co-polymer of high density polyethylene with a maximum upto 15% wt. of polypropylene.
9. A process as claimed in any of the preceding claims, wherein the two physical forms of polymers used in making the two members are LDPE film of 25 urn thickness and HDPE fabric of 200 g/m2 with a thickness of about 0.25 mm.
10. A process as claimed in any of the preceding claims, wherein the two physical forms of polymers used in the members are a fabric of HDPE and a film of LDPE.
11. A process as claimed in claim 10, wherein said assembly of two members is heated to 120°C for 5-7 minutes during which time
a pressure of 1-1.5 MPa is applied to cause interposition between the two members.
12. A process as claimed in claim 11, wherein the film obtained is rapidly cooled by quenching in water.
13. A process as claimed in claim 10 wherein the assembly of two members is heated so as to increase temperature from 100-105°C to 115-125°C in 5-7 minutes, simultaneously increasing the pressure from atmospheric pressure to 1-1.5 MPa, thereafter the temperature and pressure being held at 115-125°C and 1-1.5 MPa respectively for 2-4 minutes.
14. A composite polymer sheet or film composition as claimed in claim 1 comprising at least two members, the said members having similar or two different physical forms, the said members being made from similar or two different polymers, said polymers being of similar or two different grades, the polymers being selected such that the melting point of the polymer used for half of the members is at least 5°C lower than that of the remaining members, the said members being placed over one another such that the members having lower melting point are in intimate contact with the members having higher melting point and said members being interposed to one another in form of a composite sheet or film.
15. A process for preparation of a composite polymer material,
substantially as hereinbefore described with reference to the
foregoing Examples.
16. A composite polymer sheet or film substantially as
hereinbefore described with reference to the foregoing Examples.

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Patent Number

268241

Indian Patent Application Number

1627/DEL/2004

PG Journal Number

35/2015

Publication Date

28-Aug-2015

Grant Date

24-Aug-2015

Date of Filing

27-Aug-2004

Name of Patentee

INDIAN INSTITUTE OF TECHNOLOGY, DELHI

Applicant Address

HAUZ KHAS, NEW DELHI-110016, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	DR. DEOPURA BASANT LAL	TEXTILE TECHNOLOGY, OF INDIAN INSTITUTE OF TECHNOLOGY DELHI, HAUZ KHAS, NEW DELHI-110016, INDIA.

PCT International Classification Number

B29C 87/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA