WO2006123260A2

WO2006123260A2 - Solvent weldable / adhesive bondable polyolefin pipe and pipe-fitting

Info

Publication number: WO2006123260A2
Application number: PCT/IB2006/050904
Authority: WO
Inventors: Sanjay Agarwal; Amit Kumar
Original assignee: Sanjay Agarwal; Amit Kumar
Priority date: 2005-03-24
Filing date: 2006-03-23
Publication date: 2006-11-23
Also published as: WO2006123260A3

Abstract

Polyolefin pipes are in use since few decades in numerous applications. Polyolefins have numerous advantages vis-à-vis its competing polymer material the PVC. However PVC still continue to be the most preferred pipe making polymer all over the world. One of the main reasons which hinder growth of polyolefins in pipe applications is difficulty in joining/bonding of polyolefin pipes. To overcome this shortcoming of polyolefin pipes and pipe-fittings, we have devised a polyolefin pipe and pipe-fitting system which can be easily, economically and satisfactorily joined / bonded like PVC pipes and pipe-fittings. The scheme is to coextrude polyolefin pipe and coinjection mould polyolefin pipe- fitting in multilayers, where the outermost layer of pipe and innermost layer of pipe-fitting shall be made of material which is amenable (suitable) to solvent welding/bonding and/or adhesive bonding. And when solvent is applied to the outer surface of pipe and inner surface of pipe-fitting, the two surfaces shall become pliable and on mating, the surface shall weld / fuse/bond, thus bonding pipe to the pipe-fitting. Similarly pipe and pipe-fitting can be adhesive bonded.

Description

Solvent Weldable / Adhesive Bondable Polyolefin Pipe and Pipe- Fitting

Technical Field

[1] This invention is for the purpose of solving the problem of joining / bonding / welding of polyolefin pipe to another polyolefin pipe / non- polyolefin pipe and / or to polyolefin pipe-fitting / non-polyolefin pipe-fitting and / or to other devices.

[2] Through this invention, polyolefin pipes and polyolefin pipe-fittings shall become amenable [suitable] to solvent welding/fusion/bonding and/or adhesive bonding, ([term 'pipe' shall also mean tube, conduit, duct and hose throughout this document).

[3] Polyolefin and non- polyolefin pipe-fittings as mentioned above mean, injection moulded (or coinjection moulded or injection comoulded) or fabricated pipe-fittings like coupler, elbow, tee , reducer, junction box , bend, end cap et cetra, used in connecting /joining / assembling a pipeline or any piping system.

Background Art

[4] Polyolefin pipes are in use since few decades and have wide ranging applications.

[5] Polyolefin pipes are being used in applications like water supply, drainage and sewer, fluid and slurry conveying, gas distribution and transportation, irrigation, floor heating, cable conduits and ducts, industrial processes et cetra.

[6] Current methods in use, for joining / bonding / welding of polyolefin pipe to another polyolefin pipe / non-polyolefin pipe and / or to polyolefin / non- polyolefin pipe-fitting and / or to other devices, include thermal (heat) or wave (ultrasonic, infrared , radio frequency et cetra) welding / fusion / bonding by melting / making pliable the two surfaces to be joined / fused / bonded. This process of thermal / wave welding / bonding requires special equipments, and it often becomes a problem, if joining / welding / bonding of pipe is to be done in remote / rural areas or in homes, to arrange / carry these welding equipments. The problem is more pronounced in several developing countries, where such welding equipments are not widely available. Post installation repairs/changes become all the more problematic once the equipments are removed from site, more so in remote areas. This is one of the factors which affects growth of polyolefin pipes' application and use. And for bonding of polyolefin pipes and pipe- fittings by using adhesives like cyanoacrylate, epoxy, acrylic etc, surface treatments like plasma, corona, chemical etching, flame, liquid primer applying et cetra are required.

[7] Several non-polyolefin polymers like PVC, ABS, PS, Acrylic, some of the Thermoplastic Elastomers, Polycarbonate et cetra can be joined / welded / bonded by using common adhesives without the necessity of surface treatments like those mentioned above or by solvent welding/fusion/bonding process, using solvent cement and/or solvent(s).

[8] Solvent welding process requires one or more solvents like Tetrahydrofuran,

Methyl ethyl Ketone, Trichlorobenzene, Cyclohexanone et cetra, with or without polymer(s) and / or additive(s) and / or filler(s).

[9] These solvent cement and/or solvent(s) may be flammable or non flammable and / or biodegradable or non biodegradable and / or ecofreindly or non ecofreindly or of any other kind. Solvent cement and/or solvent(s) is applied on the surfaces of pipe and of pipe-fitting which are to be mated. The solvent cement and / or solvent(s) dissolves / softens / swollens the polymer surfaces of pipe and of pipe-fitting. These surfaces of pipe and pipe-fitting are mated, and welding / fusion / bonding takes place. This process of solvent welding / fusion / bonding using solvent cement and / or solvent(s), is long established for welding /joining / bonding of many non-polyolefin polymers.

[10] But polyolefin pipe and polyolefin pipe-fittings are not amenable (suitable) to solvent welding / fusion / bonding by solvent cement and / or solvent(s), as solvent cement and / or solvent(s) has little or no effect on pipe and pipe-fittings' surfaces and adhesives like cyanoacrylate, epoxy, acrylic et cetra respond poorly giving weak bond strength because of low surface energy of surfaces of these pipes and pipe- fittings.

[11] US Patent No.6583250 has dealt with the problem of bonding of polyolefins. It describes a method by which adhesive bonding of extruded and moulded polyolefin articles can be improved. However this patent (US Patent 6583250) is restricted in use because it gives a method which works with a particular type of adhesives the cyanoacrylate adhesive and not with other common adhesives like epoxy, acrylic et cetra and it does not makes the extruded and moulded polyolefin articles, solvent weldable / bondable. Disclosure of Invention

Technical Problem

[12] Polyolefins have excellent chemical resistance and have low surface energy. It's due to excellent chemical resistance of polyolefins, solvents don't effect them at room temperatures. But to get solvent welding / bonding in field conditions, solvents must dissolve / swollen the substrate at room temperatures. Similarly due to low surface enegy / non polar character of polyolefins adhesives don't respond or give weak bonds only. The most prevalant method to bond polyolefins is heat welding / fusion. Polyolefins are crystalline / semi crystalline polymers and don't have wide range of melting temperatures, but have rather sharp melting points, thus good expertise and sophisticated equipments are needed to heat weld polyolefins otherwise bond failures may occur. There is a trend to use crosslinked polyolefϊn pipes in water supply and gas distribution. But crosslinked polyolefin pipes are even more difficult to weld than normal polyolefin pipes because crosslinking of polymer does not easily permits poymer melting.

Technical Solution

[13] To overcome the above mentioned weakness of polyolefin pipes and pipe-fittings, we have devised a solution so as to retain all the desirable properties of polyolefins but to make up for it's weakness in bonding characterstics. Through our method, the bonding / welding operation shall be done on thin layer of non-polyolefin polymer materials and this thin layer of non-polyolefin polymers materials shall remain fused to the main pipe-substrate which shall be polyolefins or some other material which in turn shall be fused / bonded to polyolefins.

Advantageous Effects

[14] The advantage of this invention is that the user of pipes and pipe-fittings made through this invention can have all / most of the benefits of polyolefins pipes and bonding / welding ease of non-polyolefin pipes like PVC.

Description of Drawings

[15] Figurel on pagel of 4 gives a polyolefin pipe scheme where outer layer represented by A shows non-polyolefin polymer layer which is solvent weldable / bondable and / or adhesive bondable, and beneath this outer layer is polyolefin layer represented by B. Figure 2 on the same page gives a polyolefin pipe-fitting scheme where inner layer represented by A shows non-polyolefin polymer layer which is solvent weldable / bondable and / or adhesive bondable, and above this layer is polyolefin layer represented by B.

[16] Figure 4 on page 2 of 4 gives a polyolefin pipe scheme where the outermost layer represented by A shows non-polyolefin polymer layer which is solvent weldable / bondable and / or adhesive bondable, this outer most layer is followed by polyolefin layer, this polyolefin layer is followed by a layer of different material which may be a polymer or metal represented by C, and this layer is followed by polyolefin layer which is the innermost layer represented by B. Figure 3 on the same page gives a scheme of polyolefin pipe-fitting where innermost layer represented by A is made up of non-polyolefin polymer which is solvent weldable / bondable and / or adhesive bondable, above this layer ia a polyolefin layer represented by B, above this layer is a layer of different material which may be a polymer or metal represented by C, and above this layer is the outermost layer of polyolefin.

[17] Figure 6 on page 3 of 4 gives a scheme of polyolefin pipe where outer layer represented by B is made of polyolefin and beneath this, is a layer of non-polyolefin polymer which is solvent weldable / bondable and / or adhesive bondable represented by A. Figure 5 on the same page gives a scheme of polyolefin pipe-fitting where outer layer represented by A is made of non-polyolefin polymer which is solvent weldable / bondable and / or adhesive bondable, and beneath this is a layer of polyolefin represented by A.

[18] Figure 7 on page 4 of 4 gives a scheme of belled polyolefin pipe where the outermost layer represented by A is made of non-polyolefin polymer which is solvent weldable / bondable and or adhesive bondable, beneath this outermost layer is polyolefin layer represented by B and this layer is followed by an innermost layer represented by A which is made of non-polyolefin polymer and it is solvent weldable / bondable and / or adhesive bondable.

Best Mode

[19] Multilayer polyolefin pipes and multilayer polyolefin pipe-fittings which are solvent weldable / bondable and / or adhesive bondable shall have atleast two or more layers. If the pipe has to be used as male in joining/bonding operation , then solvent weldable / bondable and / or adhesive bondable layer should be the outermost layer of pipe and if the pipe has to be used as female in joining / bonding operation then the innermost layer should be of solvent weldable / bondable and / or adhesive bondable polymer. If the same pipe has to be used as both male and female in joining / bonding operation then both the outermost and innermost layers should be made of solvent weldable / bondable and / or adhesive bondable polymer. If the polyolefin pipe-fitting has to be used as female in bonding /joining operation then it's innermost layer should be made of solvent weldable / bondable and / or adhesive bondable polymer. If the polyolefin pipe-fitting has to be used as male in pipe joining / bonding operation then it's outermost layer should be made of solvent weldable / bondable and / or adhesive bondable polymer.

Mode for Invention

[20] In the present invention, in order to achieve solvent welding / fusion / bonding and

/ or adhesive bonding of polyolefin pipe and pipe-fittings, following method shall be adopted which shall make polyolefin pipe and pipe-fittings amenable (suitable) to solvent welding / fusion / bonding and / or adhesive bonding:

[21] Polyolefin pipe shall be coextruded in multilayers, where the outer layer shall be made of the material(s) which is amenable (suitable) to solvent welding / fusion / bonding and / or adhesive bonding (see A in Fig.l). If a pipe is coextruded with only two layers (excluding tie layer if any) then beneath the outer layer shall be a polyolefin layer and there may or may not be a tie layer in between these two layers (see B in Fig.l). There can be more than one layer of one or more materials including polyolefϊn, below the outermost layer (see C in Fig.4), but the outermost layer shall be made of the material(s) which is amenable (suitable) to solvent welding / fusion / bonding and / or adhesive bonding. Where interfacial adhesion between the layers is not sufficient, tie layer should be provided. Tie layer material shall depend upon the composition of different layer materials, however a general example of tie layer material may be MAH grafted Poly olefins.

[22] Poly olefin pipe-fittings shall be coinjection moulded or injection comoulded in multilayers. The inner layer of pipe- fittings shall be made of the material(s) which is amenable (suitable) to solvent welding / fusion / bonding and / or adhesive bonding (see A in Fig.2). If the pipe- fittings are coinjection moulded or injection comoulded with only two layers (excluding tie layer if any) then above the inner layer shall be a polyolefin layer with or without a tie layer in between these two layers (see B in Fig.2). There can be more than one layer of one or more materials including polyolefin (see C in Fig.3), above the innermost layer but the innermost layer shall be made of the material(s) which is amenable (suitable) to solvent welding / fusion / bonding and / or adhesive bonding. Where interfacial adhesion between the layers is not sufficient, tie layer should be provided. Tie layer material shall depend upon the composition of different layer materials. A general example of tie layer can be MAH grafted Polyolefins.

[23] Polyolefin pipe-fittings can also be made by fabrication in addition to or in place of coinjection moulding or injection comoulding, from pipe pieces.

[24] For fabrication of pipe-fittings from pipe pieces, such polyolefin pipe shall be coextruded in multilayers. The inner layer of this pipe shall be made of the material(s) which shall be amenable (suitable) to solvent welding / fusion / bonding and / or adhesive bonding (see A in Fig.6). If the pipe is coextruded with only two layers (excluding tie layer if any) then this inner layer shall have above it a polyolefin layer with or without a tie layer in between these two layers (see B in Fig.6). There can be more than one layer of one or more materials including polyolefin, above the innermost layer , but the innermost layer shall be made of the material(s) which is amenable (suitable) to solvent welding / fusion / bonding and / or adhesive bonding. Such coextruded multilayer polyolefin pipe having innermost layer which is amenable (suitable) to solvent welding / fusion / bonding and / or adhesive bonding can also be used as a regular pipe instead of for pipe-fitting fabrication, where in the process of joining / welding / bonding of pipe, the pipe has to be used as female (generally the pipes are used as male in welding /joining / bonding process), and pipe-fitting has to be used as male (generally pipe fitting is used as female). But for this purpose the polyolefin pipe-fitting shall be coinjection moulded or injection comoulded in multilayers with an outer layer which is amenable (suitable) to solvent welding / fusion / bonding and / or adhesive bonding (see A in Fig.5). If pipe fitting is coinjection moulded with only two layers (excluding tie layer if any) then beneath the outer layer shall be a polyolefin layer with or without a tie layer in between these two layers (see B in Fig.5). The outermost layer can have more than one layer beneath it, made up of one or more materials including polyolefin, but the outermost layer shall be made of the material(s) which is amenable (suitable) to solvent welding / fusion / bonding and / or adhesive bonding. Where interfacial adhesion between the layers is not sufficient, tie layer should be provided. Tie layer material shall depend upon the composition of different layer materials. A general example of tie layer material can be MAH grafted Polyolefins.

[25] The outermost layer of coextruded pipe, and the innermost layer of coextruded pipe

(pipe which is to be used for making fabricated pipe fitting or to be used as female in pipe joining / bonding / welding process), and the innermost layer of the coinjection moulded or injection comoulded pipe-fitting, and the outermost layer of coinjection moulded pipe fitting (pipe fitting which is to be used as male in pipe joining / bonding / welding process) shall be made up of a polymer, blends / alloys of two or more polymers, compound of polymer, grafted polymer, copolymer, filled / reinforced polymer, mixture of polymer, nucleated polymer, stretched / oriented polymer, modified polymer, vulcanized / crosslinked polymer, halogenated polymer, irradiated polymer, foamed / cellular polymer, all or some or any of these with or without non polymer, and it should be amenable (suitable) to solvent welding / fusion / bonding and / or adhesive bonding without the necessity of such surface treatment which is generally required for low surface energy polymers like polyolefins, and should have quite low or negligible solubility in water. Examples of such materials can be PVC- EVA blend (alloy), MAH grafted Polyolefins et cetra. Wall thickness of layer of this material in pipe and pipe fitting can be 0.01mm or more.

[26] Pipe-fitting may also be used , which is made up of non-polyolefin polymers like

PVC, ABS, PS, SAN or any other material which can be solvent welded / fused / bonded and / or adhesive bonded with polyolefin pipe made by using the method described above in this invention.

[27] The polyolefin pipe made by the above described method in this invention, having its outermost layer (or the innermost layer as the case may be) made of solvent weldable / fusible / bondable and / or adhesive bondable material(s), when solvent cement and / or solvent(s) is applied on the surface of OD of pipe (or the ID of pipe as the case may be), and polyolefin pipe-fitting made by the above described method in this invention, having its innermost layer (or the outermost layer as the case may be) made of solvent weldable / fusible / bondable and / or adhesive bondable material(s) or pipe fitting of non-polyolefin polymers like PVC, PS, ABS etc, when solvent cement and / or solvent(s) is applied on the surface of ID of pipe-fitting (or the OD of pipe- fitting as the case may be), then the surface of OD of pipe (or the ID of pipe as the case may be), and the surface of ID of pipe-fitting (or the OD of pipe-fitting as the case may be) shall dissolve / soften / swollen by the action of solvent cement and / or solvent(s). And when this pipe OD (or the ID of pipe as the case may be) is mated with ID of pipe-fitting (or the OD of pipe-fitting as the case may be), the mating surfaces shall weld / fuse / bond, thus welding /joining / bonding the poly olefin pipe with poly olefin or non-polyolefin pipe- fitting .

[28] Similarly adhesive like cyanoacrylate, epoxy, acrylic etc. may be applied on the surface of OD of polyolefin pipe (or the ID of pipe as the case may be) made as described above and on the surface of ID of polyolefin pipe-fitting (or the OD of pipe- fitting as the case may be) made as described above or non-polyolefin pipe-fitting made of PVC, ABS etc and these two surfaces of pipe and pipe-fitting are mated, the two surfaces shall be adhesive bonded, thus bonding /joining the polyolefin pipe with polyolefin or non-polyolefin pipe- fitting.

[29] Besides the above mentioned methods, in this invention, a polyolefin pipe can also be coextruded in multilayers, where both the outermost layer and the innermost layer of the pipe shall be made of material(s) which is amenable (suitable) to solvent welding / fusion / bonding and / or adhesive bonding (see A in Fig.7). If the pipe is coextruded in only three layers (excluding tie layer if any) then the intermediate layer shall be a polyolefin layer and there may or may not be a tie layer in between the outermost layer and the intermediate layer, and innermost layer and the intermediate layer (see B in Fig.7). The outermost layer and the innermost layer can have more than one layer in between outermost and innermost layers, made up of one or more materials including polyolefin, but the outermost layer and the innermost layer shall be made of material(s) which is amenable (suitable) to solvent welding / fusion / bonding and / or adhesive bonding. Where interfacial adhesion between the layers is not sufficient, tie layers should be provided. Selection of tie layer material shall depend upon the composition of materials in different layers, however a general example of tie layer material can be MAH grafted Poly olefins.

[30] The pipe so made, can have one of its end plain and the other end can be belled by pipe belling process.

[31] For welding /joining / bonding of two such pipes to one another, the plain end of one of the pipe can be male and the belled end of the other pipe can be female. These polyolefin pipes can be joined / welded / bonded by solvent welding / fusion / bonding process and/or by adhesive bonding.

[32] These polyolefin pipes having both, the innermost and the outermost layers made of the material(s) which is amenable to solvent welding / fusion / bonding and or adhesive bonding can be made having both ends plain instead of one end belled, and for joining / bonding / welding of such pipes, polyolefin pipe-fitting having its innermost layer (female pipe fitting) and polyolefin pipe-fitting having its outermost layer (male pipe-fitting), made of material(s) which is amenable to solvent welding / fusion / bonding and / or adhesive bonding, both these types of pipe-fittings can be used, along with non-polyolefin pipe-fittings.

[33] The outermost layer and the innermost layers of these pipes can be made of a polymer, blends / alloys of two or more polymers, mixture of polymer, reinforced / filled polymer, stretched / oriented polymer, copolymer, modified polymer, halogenated polymer, irradiated polymer, nucleated polymer, grafted polymer, compound of polymer, foamed / cellular polymer, vulcanized / crosslinked polymer, all or some or any of these, with or without non polymer and it should be amenable (suitable) to solvent welding / fusion / bonding and / or adhesive bonding without the necessity of such surface treatment which is generally required for low surface energy polymers like polyolefins, and should have quite low or negligible solubility in water. Examples of such materials can be PVC-EVA blend (alloy), MAH grafted Polyolefins et cetra. Wall thickness of layer of this material in pipe can be 0.01mm or more.

Industrial Applicability

[34] For extrusion of multilayer polyolefin pipes, multilayer pipe extruders are used. For making of moulded polyolefin pipe-fittings , injection comoulding or coinjection moulding machines can be used.

[35] Multilayer pipes and pipe-fittings can be used in the same or similar manner as monolayer pipes and pipe-fittings are used.

[36] However these multilayer polyolefin pipes and polyolefin pipe-fittings can be joined / bonded easily and conveniently using solvent cement / solvents / adhesives, unlike conventional polyolefin pipes and polyolefin pipe-fittings.

Sequence List Text

[37]

Claims

Claims[1] We claim that:

1. A polyolefϊn pipe and polyolefin pipe-fitting, which can be solvent welded / bonded and /or adhesive bonded and which is made in multilayers of which

(a) atleast one or more layer[s] contain[s] either all or some or one of the following material(s):

Polypropylene, polyethylene , homopolymers of polyolefin, copolymers of polyolefins , terpolymers of polyolefin, modified polyolefin , crosslinked polyolefin , reinforced polyolefin , filled polyolefin, blends / alloys / compounds / composites / mixtures of polyolefin , nucleated polyolefin, oriented / stretched polyolefin , irradiated polyolefin , foamed / cellular polyolefin , rigid polyolefin, semi-rigid polyolefin, flexible polyolefin, other polymers / copolymers/terpolymers of polyolefin family, and

(b) atleast one or more layer[s] of which, other than that mentioned in (a), contain[s] a polymer, blends/alloys of two or more polymers , compound of polymer [s], grafted polymer, copolymer, terapolymer, filled / reinforced polymer, mixture of polymer[s], nucleated polymer, stretched/oriented polymer, modified polymer, vulcanized / crosslinked polymer, halogenated polymer, grafted polymer, irradiated polymer , foamed/cellular polymer, all or some or any of these with or without non polymer, and it should be amenable[suitable] to solvent welding/ fusion/bonding and/or adhesive bonding without the necessity of such surface treatment which is generally required for low surface energy polymers like polyolefins, and

(c) a polyolefin pipe and polyolefin pipe-fitting, can be composed of only those layers of materials as mentioned in (a) & (b), or more other layers, wherein the layer or layers of other materials] than those mentioned in (a) & (b), can be made of either polymer or non-polymer or the both polymer and non-polymer material(s).

2. The wall thickness of layer of material(s) described in (a) of claiml can be 0.1mm or more and wall thickness of layer of material(s) described in (b) of claiml can be 0.01mm or more.

3. The different layers of polyolefin pipe and polyolefin pipe-fitting of claiml, may or may not have tie layer in between them.

4. Multilayer polyolefin pipe which is solvent weldable / bondable and / or adhesive bondable shall have atleast two or more layers, where it's Outermost layer' or 'the innermost layer' or 'the outermost and the innermost layer' shall be made of material as mentioned in [b] of claim 1, and shall have atleast one or more layer[s] of material as mentioned in [a] of claiml.

5. Multilayer poly olefin pipe-fitting which is solvent weldable / bondable and / or adhesive bondable shall have atleast two or more layers, where it's 'outermost layer' or 'the innermost layer' or 'the outermost layer and the innermost layer' shall be made of material as mentioned in [b] of claiml, and shall have atleast one or more layer[s] of material as mentioned in [a] of claiml.