WO2007043082A2

WO2007043082A2 - Plasticised pvc and chlorinated polyethylene cpe-based compound, method for obtaining said compound, and multi-layer material comprising said compound coupled with a different type of polymer

Info

Publication number: WO2007043082A2
Application number: PCT/IT2006/000708
Authority: WO
Inventors: Roberto Poppi
Original assignee: Sovere Spa
Priority date: 2005-10-12
Filing date: 2006-10-06
Publication date: 2007-04-19
Also published as: ITVR20050127A1; WO2007043082A3

Abstract

A plasticised polyvinyl chloride PVC-based compound, suitable for use in the production of multi-layer products obtained for example by coextrusion or overextrusion or overmoulding, consisting of at least one layer made of said compound and one layer made of a different type of polymer, includes a predetermined quantity of chlorinated polyethylene CPE.

Description

Plasticised PVC and chlorinated polyethylene CPE-based compound, method for obtaining said compound, and multilayer material comprising said compound coupled with a different type of polymer

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TECHNICAL FIELD

The present invention relates to a plasticised polyvinyl chloride PVC and chlorinated polyethylene CPE- based compound.

More specifically, the present invention relates to a compound suitable for the production of products obtained for example by coextrusion or overextrusion or overmoulding, consisting of a layer of material made of said compound and a layer of a different type of polymer, in particular a polyolefin or a thermoplastic rubber.

The material disclosed is applied in particular for the production of synthetic resin products, for example pipes, footwear components, etc.

BACKGROUND ART

Plasticised polyvinyl chloride PVC is an amorphous and polar polymer with the plasticiser molecules inserted between the polymer chains. The plasticiser makes it "rubbery - elastic" and as a result of these features it is a material widely used in diverse fields of application such as flexible pipes for transporting liquids which may even be aggressive, food substances and gases, seals, footwear or footwear components, films for food and non-food packaging, etc.

Amongst the most appreciated features of plasticised PVC are the fact that it can be painted and glued.

Polyolefins (polypropylene homopolymer, copolymer or random copolymer; high density, low density, linear, ultrahigh density polyethylene, etc.) are apolar polymers used, among other things, for applications similar to those of plasticised PVC.

Thermoplastic rubbers,. (SBS styrene butadiene styrene, SEBS styrene ethylene butadiene styrene, PP/EPDM polypropylene with ethylene propylene diene monomers , etc . ) , which exploit irreversible and reversible cross-links, cover applications in which elasticity is the fundamental requirement.

In some applications the use of polymers specifically targeted to obtain particular technical effects is preferable.

For example, for direct contact with drinking water or where a chemical or thermal resistance that cannot be guaranteed by plasticised PVC is required, or for aesthetic reasons or to house inserts in technical components, etc. For these applications use can be made of polyolefins or thermoplastic rubbers which cannot normally be painted or moulded or glued or sealed with plasticised PVC, preventing the production of products consisting of polymers of very different types, usually due to their polarity or apolarity. In the case of flexible pipes, whether they are produced using the pipe coaxial extrusion technique, with polyester yarn braiding, or obtained with the spiral coextrusion technique with rigid PVC or with a metal spiral, it is not currently possible to stably couple a layer of polyethylene or polypropylene or thermoplastic rubber with a layer of plasticised PVC. The need for a pipe consisting of two or more layers of different types depends on the type of liquid or fluid which must pass inside it, the desired barrier effect features, the possibility of moulding or gluing required or the flexibility the pipe must have.

For example, it is not currently possible to produce a pipe with the inner layer made of polyethylene or polypropylene for the passage of drinking water or petrol and to cover it with an outer layer of plasticised PVC. Similarly, it is not currently possible to produce polyolefin or thermoplastic rubber inserts for footwear made of plasticised PVC which are closely stuck to the structure of the footwear.

Therefore, in general when attempts are made to use coextrusion, overextrusion or overmoulding to couple a plasticised PVC with a polyolefin (polypropylene, polyethylene) or with a thermoplastic rubber (SBS, SEBS, PP/EPDM), no adhesion is obtained due to the incompatibility of the different polymers. In addition, chlorinated polyethylene CPE is a material used in the formulations of rigid PVC as a shockproof additive and to improve the behaviour of the compound relative to cold.

Moreover, chlorinated polyethylene CPE is also used as a universal coupling agent in polyolefins or as a homogenising agent for scrap and waste from various types of plastic material.

Document US-A-4910245 describes a vulcanisation method used to mix a CPE and a PE by vulcanising them. Document US-A-5087669 describes how to give shockproof properties to a mixture of rigid PVC with CPE without raising the melting point, mixing it with oxidised PE.

Patent US-A-5274013 describes insulating jackets for electric cables made of moisture-resistant CPE.

Finally, patent US-A-5286795 describes a method for obtaining a partly vulcanised chlorosulfonated CPE or PE.

DISCLOSURE, OF THE INVENTION

The present invention aims to supply a material able to overcome the disadvantages typical of the prior art, and in particular a compound consisting of plasticised polyvinyl chloride PVC suitably modified with CPE of a suitable grade, on its own or with the addition of thermoplastic rubbers, thermoplastic polyurethane, polyethylene, ethylene vinyl acetate, for the production of multi-layer products in which the various layers consist of different types of polymers, for example : multi-layer pipes suitable for transporting food substances, gases, aggressive liquids, with barrier effect, etc. made using axial coextrusion or with continuous spiral technology; footwear components such as soles with polyolefin inserts encased in PVC; accessories for valves; coextruded seals; various types of electric cables such as coaxial and multi-wire .

This aim is achieved by a compound which has the features described in the main claim.

The dependent claims outline particularly advantageous embodiments of the material disclosed. Moreover, claim 8 describes a method for obtaining such a compound. Finally, claims 9 to 11 describe a multi-layer product in which at least one layer is made of a compound in accordance with the present invention.

The compound disclosed substantially consists of a mixture of polyvinyl chloride PVC resin comprising suitable additives to make it plasticised and workable, and chlorinated polyethylene CEE.

Surprisingly, experiments carried out by the Applicant demonstrated that such material can easily be coextruded, or overextruded, or overmoulded with polyolefins or with thermoplastic rubbers which could not previously be stably coupled with simple plasticised PVC.

In a particularly advantageous embodiment of the invention, also added to the plasticised PVC and chlorinated polyethylene CPE-based material is a certain quantity of the material (polyolefin or thermoplastic rubber) on which the plasticised and CPE compound will subsequently be made to adhere. In this case the coupling is optimum in terms of its closeness and stability. By way of example, in the case of production of a multi-layer pipe reinforced with polyester yarn, where the inner layer is polyethylene and the outer layer is PVC, the close and .stable coupling between the two layers, made of PVC and PE, can only be guaranteed by using a layer made in accordance with the present invention, using the plasticised PVC and CPE-based compound, if necessary adding a certain quantity of polyethylene. The resulting product is a flexible, elastic pipe which is waterproof and can be moulded, thus grouping together the set of positive properties of the polymers of which the pipe consists.

Similarly, the plasticised PVC and chlorinated polyethylene CPE-based material can be stably coupled with polypropylene or with a thermoplastic rubber, obtaining a multi-layer product with the same positive properties as the respective starting materials, the multi-layer product being characterised by a stably and practically inseparable coupling between the various layers, unlike the prior art solutions .

DESCRIPTION OF SOME EMBODIMENTS OF THE INVENTION Several different embodiments of the plasticised PVC and chlorinated polyethylene CPE-based material in accordance with the present invention are described below.

The table below shows a basic formulation for obtaining a plasticised PVC and CPE-based material, designed to be stably coupled with a polyolefin or a thermoplastic rubber in a multi-layer product.

The PVC resin to be used may have different coefficient K values (for example from 50 to 100) depending on the applications. In this context it should be remembered that said coefficient K, well known to experts in the field, consists of a number indicating the length of the polymer chain, that is to say, the molecular weight. The greater the length of the molecule, the greater the molecular weight and the viscosity and the higher the K value will be. Selection of a PVC resin in suspension to be inserted in a formulation must be made firstly considering its "K value" which must be suited to the properties to be given to the final compound. Therefore, for example to obtain a compound with excellent mechanical properties it is a good idea to use a resin with a high K (80 - 100), bearing in mind that the mixture obtained will be difficult to work due to the high level of viscosity.

In contrast, a lower coefficient K (60 - 65) allows a compound which is easily transformable but has inferior mechanical properties to be obtained.

With reference to other aspects of the previous table: the plasticiser may be a phthalic ester such as the common DOP, DINP, DIDP or a polymeric plasticiser, a citrate, an adipate, a benzoate, a cycloparaffin ester, etc. or a mixture of them, based on the final properties to be obtained, in particular the resistance to extraction of the plasticiser, suitability for contact with foodstuffs, behaviour at low temperatures, etc. ; ^• the epoxidised soya-bean oil has a coupling agent function, since it has a positive synergic effect with the calcium zinc stabiliser packet; the stabiliser may be of various types, a calcium zinc stabiliser currently being preferred due to its low environmental impact; the lubricant is stearic acid, or stearine, and has the function of lubricating the compound during the various passages for transformation from powder to pellet and, subsequently, from pellet to product. Lubrication is required to prevent the melted polymer from adhering to the metal walls of the machine which works it. In this way there is no unwanted separation which would cause the compound to melt ._.before time and so it prevents a shorting of thermal stability times; finally, the CPE may be of various types depending on the final application (extrusion or moulding) and the performance to be obtained.

The tables below show several specific formulations which demonstrated the possibility of obtaining a multilayer material with stable and close coupling between a plasticised PVC and, respectively, polyethylene, polypropylene, thermoplastic rubber.

Example 1

Example 2

Example 3

Example 4

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Description of methods for obtaining a plasticised PVC and CPE-based compound in accordance with the invention

According to a particularly advantageous embodiment, a turbo-mixer and an extruder are used to produce the compound in accordance with the present invention.

The components of the mixture are loaded in the correct proportions in the turbo-mixer which mixes them together, heating them until they reach the compound temperature of around 110 - 12O⁰C.

The dry-blend obtained in this way is unloaded into a slow mixer -designed to cool the mixture to around 70⁰C.

At this point any additives required which cannot be inserted and heated to 12O⁰C in the turbo-mixer are added, for example thermoplastic rubber or expanding agents.

This is followed by the pelletising step, preferably using an extruder with twin screws, counter-rotating or co- rotating with suitable cutting force for a compound containing PVC.

The approximate thermal profile, pressures and speeds are shown in the following tables:

Table A

88 mm extruder. L/D 20

Table B

125mm extruder. L/D 26

Use of such methods allows the obtainment of an end product consisting of a compound basically consisting of plasticised PVC and CPE, suitable for close and stable coupling with a different type of polymer such as a polyolefin or a thermoplastic rubber.

Thanks to the use, in accordance with the invention, of chlorinated polyethylene together with the basic formulation of the PVC, a compound is obtained which is designed to be overmoulded, extruded or overextruded with a polyolefin or with a thermoplastic rubber, to form a multi-layer material in which the basic components (PVC and polyolefin, or PVC and thermoplastic rubber), in spite of their different polarity, adhere to one another closely and stably, unlike the prior art solutions in which the layers of PVC separate extremely easily from the,, coupled layers of polyolefin or thermoplastic rubber.

This makes possible a whole series of new applications, advantageously using the positive properties of both PVC and polyolefins or thermoplastic rubbers. For example, it is possible to obtain multi-layer pipes suitable for transporting food substances, gases, aggressive liquids, with barrier effect, etc., footwear components such as soles with polyolefin inserts encased in PVC, accessories for valves, coextruded seals, various types of electric cables such as coaxial and multi-wire.

Claims

1 . A plasticised polyvinyl chloride PVC-based compound, suitable for use in the production of multi-layer products obtained for example by coextrusion or overextrusion or overmoulding, consisting of at least one layer made of said compound and one layer made of a different type of polymer , characterised in that the compound includes a predetermined quantity of chlorinated polyethylene CPE .

2 . The compound according to claim 1 , characterised in that the plasticiser consists of a phthalic ester such as DOP , DINP , DIDP or a polymeric plasticiser, a citrate , an adipate , a benzoate , a cycloparaf fin ester, etc . or a mixture of them.

3 . The compound according to either of the foregoing claims , characterised in that it comprises a stabiliser, for example calcium zinc-based.

4. The compound according to any of the foregoing claims , characterised in that it also comprises a predetermined quantity of epoxidised soya-bean oil .

5. The compound according to any of the foregoing claims, characterised in that it also comprises a predetermined quantity of lubricating agent.

6. The compound according to any of the foregoing claims, characterised in that in one formulation it consists of the components shown in the following table:

7. The compound according to any of the foregoing claims, characterised in that a predetermined quantity of the polymer with which the compound must subsequently be coupled to form a multi-layer product is added to it.

8. A method for obtaining a compound according to any of the foregoing claims, wherein a turbo-mixer and an extruder are used, characterised in that the components of the mixture are loaded in the appropriate proportions in the turbo-mixer which mixes them together, heating them to a compound temperature of around 110 - 12O⁰C, and also characterised in that the dry-blend obtained in this way is unloaded into a slow mixer to cool the mixture to around 7O⁰C, and also characterised in that any additives required which cannot be inserted and heated to 120⁰C in the turbo- mixer are then added, for example thermoplastic rubber or expanding agents, and in that the resulting material is then subjected to pelletising, preferably using an extruder with twin screws counter-rotating or co- rotating with suitable cutting force for a compound containing PVC.

9. A multi-layer product obtained by coextrusion or overextrusion or overmoulding polymers of different types and with different polarities, wherein at least one layer consists of polyvinyl chloride PVC, characterised in that the polyvinyl chloride PVC is plasticised, in that it comprises a predetermined quantity of chlorinated polyethylene CPE, and in that it is made of a compound according to any of the foregoing claims.

10. The product according to claim 9, characterised in that the layer coupled with the layer made of the plasticised PVC and chlorinated polyethylene CPE compound is coupled with a layer consisting of a polyolefin or a thermoplastic rubber or an expanding agent.

11. The product according to claim 9 or 10, characterised in that it consists of: - a multi-layer pipe suitable for transporting food substances, gases, aggressive liquids, with barrier effect, etc. made using axial coextrusion or with continuous spiral technology; or a footwear component such as a sole with polyolefin insert encased in PVC; or an accessory for valves; or a coextruded seal; or an electric cable, such as a coaxial or multi-wire cable.