WO2013057670A1

WO2013057670A1 - Pipe of thermoplastic material

Info

Publication number: WO2013057670A1
Application number: PCT/IB2012/055657
Authority: WO
Inventors: Marco BATTAN
Original assignee: Agenzia Battan S.A.S. Di Battan Marco & C.
Priority date: 2011-10-18
Filing date: 2012-10-17
Publication date: 2013-04-25
Also published as: ITVI20110276A1

Abstract

A pipe of thermoplastic material, of the monostratum type, having a ratio between the thickness and diameter between 0.1 and 0.2, is formed by a polymer admixture comprising : - a fraction of from 20% to 50% of polyvinyl chloride; - a quantity of chlorinated polyethylene such that the weight ratio thereof with respect to the polyvinyl chloride is between 3/7 and 1.5; and - a quantity of filler such that the weight ratio between the chlorinated polyethylene and the filler is between 1 and 2.

Description

PIPE OF THERMOPLASTIC MATERIAL

DESCRIPTION

Field of application

The present invention relates to a pipe of thermoplastic material having the features set out in the preamble of the main claim.

Background art

A preferred application of the invention is in the technical sector of the construction of monostratum pipes constructed from polymer admixtures (known as "compound") based on polyvinyl chloride (PVC).

In this sector, there are known many formulations of thermoplastic polymer admixtures which can be used for constructing pipes having applications in specific technical sectors, which are also very different from each other and in which the PVC is added with different types of compounds capable of advantageously modifying the structural characteristics of the polymer admixture, particularly in terms of modulus of elasticity.

In some technical sectors, it is known to be necessary to provide a pipe of thermoplastic material having such mechanical characteristics as to allow an operator to bend the pipe manually, with reduced force, and further such characteristics as to maintain the bent shape conferred by the operator without involving undesirable kinking phenomena which involve the formation of a constriction at the region of curvature with a reduction of the useful cross- section of passage, including with particularly high bending angles of, for example, 180°. At the same time, however, the pipe must maintain a level of mechanical strength which is sufficient for the requirements connected with the specific application thereof. A first example of an application in which pipes having the characteristics described above are required, is constituted by the cannulae used in the dental sector for the suction of saliva.

Those cannulae are generally formed by a pipe of thermoplastic material having a relatively small diameter, generally of a few millimetres, which must have sufficient mechanical strength together with a high level of flexibility and resistance to kinking, even with great angles of bending.

In order to obtain cannulae having the characteristics required, there are typically used pipes having a plurality of layers of material (based on polymer or not) having different characteristics, which naturally increases the production costs.

WO2009150073 describes a cannula whose suction pipe is constructed by extrusion from a polymer admixture comprising plasticized PVC and an expansible material which is constituted by thermally expansible microspheres. That known solution, in addition to being relatively costly, is not very reliable and is economically disadvantageous.

A second application example in which pipes of thermoplastic material having the above-described characteristics are required is constituted by the feedthrough pipes for installations of electrical systems, whose structural characteristics, in terms of mechanical strength, fire- retard ant properties and thermal resistance, are advantageously sized in accordance with precise standards as a function of the application sectors.

In this type of system, the electrical wires extend inside pipes which, in turn, can be positioned inside the wall (embedded installation) or outside the wall. In the first case, there are generally used corrugated or coiled pipes which, owing to their special geometric configuration, have great deformability characteristics but do not allow the curved shape imposed by the operator to be maintained .

Furthermore, the presence of lateral walls having great friction, as in the case of corrugated pipes, may involve difficulties when introducing the wires, in particular for pipes of small diameter.

In the second case, there are generally used smooth pipes in order to facilitate the sliding of the wires inside and to reduce the accumulation of dust on the outer surface which, in order to comply with the reference standards, generally have greater rigidity characteristics. However, this requires the use of suitable curved connections between adjacent linear portions which complicate the installation work, further limiting the number of configurations which can be constructed .

In general, there are further known polymer admixtures based on polyvinyl chloride in which the deformability characteristics of the pipes derived therefrom are modified by using specific quantities of elastomer polymers such as chlorinated polyethylene (CPE) and a filler.

Examples of PVC-based polymer admixtures are described in GB 2214697, US 3936417 and EP 2375118.

However, those admixtures do not allow the construction of monostratum pipes having specific dimensional relationships which are capable of maintaining a curved shape with great angles imparted, including manually, by an operator, without involving undesirable bends.

It should be set out more specifically that, in the context of the present description and the subsequent claims, the term "monostratum pipe" is intended to refer to a pipe having a layer of substantially homogeneous composition forming a prevalent portion of the pipe, in particular having a thickness which represents at least 90% of the thickness of the pipe, and in which the mechanical characteristics of the pipe are determined substantially by the characteristics of that layer.

In other words, a monostratum pipe is formed by a single layer of the same material except for any coatings or superficial finishing coverings, internal or external, whose application is negligible in terms of mechanical characteristics and in particular deformability characteristics and characteristics of capacity for maintaining the curvature without involving kinking phenomena.

It is further set out that, in the context of the present description and the subsequent claims, the term "modulus of elasticity" of a material is intended to refer to the modulus of tensile elasticity measured in accordance with the standard ISO 527.

In the context of the present description and the subsequent claims, it is again considered that a pipe also maintains its curved configuration at the end of the bending action imposed by the operator when the pipe, once it has been bent to an angle of approximately 90° and then released, maintains a curve of at least 75°.

Furthermore, in the context of the present description and the subsequent claims, the term "index K" of the polyvinyl chloride is intended to refer to the index of viscosity measured according to the standard ISO 1628-2.

Finally, in the context of the present description and the subsequent claims, the percentages or fractions of a compound within an admixture refer, unless otherwise specified, to the total weight of the admixture itself. Disclosure of the invention

The problem addressed by the present invention is to provide a pipe of thermoplastic material which is structurally and functionally configured to comply with the demands set out above and to overcome the disadvantages described above with reference to the cited prior art.

In the scope of that problem, an object of the invention is to construct a pipe of thermoplastic material which is of the monostratum type by developing a polymer admixture which allows pipes to be obtained having a relatively high level of flexibility so as to be able to be readily bent without phenomena of constriction of the pipe and, at the same time, having a small resilient return so as to substantially maintain the shape imparted.

Another object of the present invention is to provide monostratum pipes which are particularly suitable for use as feedthrough pipes in electrical systems or as cannulae for dental use.

That problem is solved and those objects are achieved by a pipe of thermoplastic material produced in accordance with the appended claims.

In a first aspect thereof, the present invention relates to a pipe of thermoplastic material, preferably of the monostratum type, and preferably having a thickness/diameter ratio between 0.1 and 0.2, which comprises a layer formed by a polymer admixture comprising :

- a fraction of from 20% to 50% of polyvinyl chloride;

- a quantity of chlorinated polyethylene such that the weight ratio thereof with respect to the polyvinyl chloride is between 3/7 and 1.5; and

- a quantity of filler such that the weight ratio between the chlorinated polyethylene and the filler is between 1 and 2.

Owing to the quantities and the precise weight ratios set out above, the polymer admixture obtained allows construction of monostratum pipes having characteristics adapted to the applications described above and, in particular, pipes which are capable of being bent as desired, even at great angles, without causing constrictions in the region of the curve and allowing the degree of curvature also to be maintained when the pipe is released. Furthermore, those pipes have characteristics of mechanical strength which are adapted to the most common applications, in particular the application as cannulae and as feedthrough pipes.

PVC represents, in the polymer admixture mentioned above, the base thermoplastic polymer which, owing to the amorphous structure thereof, has fracture behaviour of the ductile type.

The PVC used is a PVC of the rigid type (PVC-U) with a modulus of tensile elasticity (E) preferably between 2.8 GPa and 3.5 GPa. Furthermore, the PVC used may have any K value, though a PVC having a K value between 57 and 65 is preferred .

In a greatly preferred manner, the percentage by weight of PVC with respect to the entire admixture is between 25% and 35%.

The second compound of the polymer admixture forming the pipe of the invention is a chlorinated polyethylene (CPE), an elastomer compound which is semi-compatible with PVC. The presence of that compound in the correct proportions confers on the pipe the necessary capacity for deformation for being bent at great angles without bringing about constrictions in the pipe (kinking). Preferably, the CPE used in the admixture set out comprises a percentage by weight of chloride with respect to the entire polymer between 25% and 42% and, in a greatly preferred manner, a percentage between 32% and 38%.

Furthermore, CPE has a modulus of tensile elasticity of less than 1.5 GPa, preferably less than 1 GPa.

In a particularly preferred formulation, the ratio between CPE and PVC is in a range between 2/3 and 11/9.

It is further preferable for the quantities by weight of PVC and CPE in total between them to represent a fraction between 50% and 75% of the entire polymer admixture and, in a greatly preferred manner, a fraction between 60% and 70% of the entire admixture.

The third component necessary for obtaining a polymer admixture capable of giving rise to pipes capable of solving the technical problem set out above is constituted by an organic or inorganic filler which is substantially incompatible with the base thermoplastic material . The presence in the correct proportions of that compound allows minimization of the resilient return movement of the pipe once it has been bent.

Preferably, the filler is formed of calcium carbonate but it may be constituted by any other compound which is suitable and/or known in the field for this use. In a preferred composition of the admixture, the quantity of filler is such that the weight ratio between the CPE and the filler is between 1.5 and 1.8.

Preferably, the polymer admixture from which the monostratum pipe according to the invention is formed comprises a fraction of plasticizer between 5% and 18%. Furthermore, there may be used in the admixture additives which are normally used in PVC-based polymer admixtures, such as, for example, stabilizers, co- stabilizers, colourants, process lubricants, etc., in the proportions typically used in the prior art.

The polymer admixture obtained in this manner may be processed by using any of the known processes which are adapted to obtaining a pipe having the desired dimensions.

Typically, the pipe is obtained by means of an extrusion process. The mechanical characteristics of the pipe obtained are also a function of the geometry thereof because, using the polymer admixture described above, the pipe has, in accordance with the variation of the ratio between the thickness and outer diameter, the values for modulus of tensile elasticity set out in Table 1 below.

Table 1

Preferably, the pipe according to the invention has a diameter smaller than 63 mm. Brief description of the drawings

Other features and advantages of the invention will be better appreciated in light of the detailed description of preferred though non-limiting embodiments of monostratum pipes which are constructed according to the invention and which are illustrated by way of non-limiting example with reference to the appended set of drawings, in which :

- Figure 1 is a cross-section of a monostratum pipe constructed according to the present invention;

- Figure 2 is a perspective view of the pipe of Figure 1;

- Figure 3 is a side view of a second embodiment of a monostratum pipe obtained according to the present invention.

Detailed description of a preferred embodiment

With initial reference to Figures 1 and 2, a pipe of thermoplastic material constructed according to the present invention is generally designated 1.

The pipe 1 is obtained by means of an extrusion method and is adapted for use as a feedthrough pipe in the installation of electrical systems.

The pipe 1 is of the monostratum type and has an outer diameter d corresponding to those of the standard values set out in the market for this type of application and, in particular, the pipe 1 has an outer diameter d of approximately 20 mm and a thickness s of approximately 2 mm.

The pipe 1 comprises a single layer 2 constructed from a polymer admixture having, apart from minor additives, the following composition (expressed in percent by weight with respect to the total weight of the admixture) :

PVC-U (K57) : 40

CPE (CI = 36%) : 26 Filler (CaC0₃) : 20

Plasticizer* : 10

Stabilizer: 3.3

* The plasticizer used is di-isononyl-phthalate (DINP)

The pipe 1 has relatively great flexibility which allows the manual shaping thereof without using specific equipment, obtaining curves not having any constrictions and having great angles of bending a, a' being between 0° and 120° (see Figure 2).

The pipe 1 further has a high level of surface finishing and complies with the provisions required by the norm CEI EN 61386-1 which is intended to regulate the positioning (inside a wall) of conductors for electrical systems or telecommunications systems up to 1000 V with alternating current and/or up to 1500 V with direct current.

In this manner, it will be possible to shape the pipe 1 in a manner substantially equal to that of the corresponding wall channel using connection members only in the region of the end portions 4, 5 thereof and not also in the intermediate curved portion 6.

Furthermore, the monostratum pipe 1 may be used as a feedthrough channel, which is external with respect to the wall, allowing the combination of two or more connector block(s) without the use of connection members in the curved portions thereof.

Figure 3 illustrates a pipe which is generally designated 10 and which defines a second embodiment of the invention.

The pipe 10, which is also of the monostratum type, has a specific use as a suction cannula 7 for dental use. The cannula 7 has an attachment 8 which is connected to a first end 10' of the pipe 10 and which can be connected in a detachable manner to suction means (not illustrated) for drawing in saliva.

The cannula 7 further comprises a cap 9 of known type which is connected in a fixed or removable manner to a second end 10" of the pipe 10 and which can be inserted inside the oral cavity of a patient. In an alternative version, the attachment 8 and/or the cap 9 can be formed in one piece with the pipe 10, for example, by means of injection moulding .

The pipe 10 of the cannula 7 advantageously has an outer diameter d which is substantially between 5 mm and 10 mm, preferably in the order of 6 mm. Furthermore, the thickness s of the pipe 10 may be between 0.5 mm and 2 mm and is preferably of 1 mm.

In particular, in the embodiment described herein, the pipe 10 has a diameter d of 6.55 mm and a thickness between 0.95 mm and 1 mm.

The pipe 10 has been constructed from two different polymer admixtures having the compositions set out below as Admixture A and Admixture B. The compositions of the admixtures A and B are set out in parts by weight so that the weight fraction of each compound can be obtained by dividing the parts by weight of the compound involved by the number of total parts.

Admixture A

PVC-U (K57) : 70

CPE (CI = 36%) : 30

Filler (CaC0₃) : 15

Plasticizer* : 24 Stabilizer: 5

for a total of 144 parts by weight.

Admixture B

PVC-U (K57) : 50

CPE (CI = 36%) : 50

Filler (CaCOs) : 30

Plasticizer* : 14

Stabilizer: 5

for a total of 149 parts by weight.

The pipes 10 formed from the above-mentioned admixtures A and B have demonstrated values of the modulus of tensile elasticity of 240 MPa and 150 MPa, respectively.

The bending tests carried out on the pipes 10 obtained from the admixtures A and B, though both being positive, demonstrate better behaviour for the pipe formed from the admixture B which is therefore preferred over admixture A. The pipe according to the present invention is capable of a number of modifications and variants which are all included within the inventive concept set out in the appended claims. All the details may be replaced by other technically equivalent elements and the materials may be different in accordance with requirements without thereby departing from the scope of the invention.

Claims

1. A pipe (1, 10) of thermoplastic material, of the monostratum type, having a ratio between the thickness (s) and diameter (d) between 0.1 and 0.2, characterized in that it is formed by a polymer admixture comprising :

- a fraction of from 20% to 50% of polyvinyl chloride;

- a quantity of chlorinated polyethylene such that the weight ratio between the chlorinated polyethylene and the polyvinyl chloride is between 3/7 and 1.5; and

2. A pipe according to claim 1, wherein the polymer admixture comprises a fraction of from 25% to 35% of polyvinyl chloride.

3. A pipe according to claim 1 or 2, wherein the polyvinyl chloride has a value K measured in accordance with the standard ISO 1628-2 of between 57 and 65.

4. A pipe according to any one of the preceding claims, wherein the ratio between chlorinated polyethylene and polyvinyl chloride is between 2/3 and 11/9.

5. A pipe according to any one of the preceding claims, wherein the chlorinated polyethylene comprises a percentage of chloride of between 25% and 42%.

6. A pipe according to any one of the preceding claims, wherein the chlorinated polyethylene comprises a percentage of chloride of between 32% and 38%.

7. A pipe according to any one of the preceding claims, wherein the sum of the polyvinyl chloride and the chlorinated polyethylene represents a fraction of between 50% and 75% of the admixture.

8. A pipe according to any one of the preceding claims, wherein the sum of the polyvinyl chloride and the chlorinated polyethylene represents a fraction of between 60% and 70% of the admixture.

9. A pipe according to any one of the preceding claims, wherein the quantity of filler is such that the weight ratio between the chlorinated polyethylene and the filler is between 1.5 and 1.8.

10. A pipe according to any one of the preceding claims, wherein the admixture comprises a fraction of plasticizer between 5% and 18%.

11. A pipe according to any one of the preceding claims, wherein, for a ratio between the thickness and the diameter of between 0.10 and 0.14, the pipe has a modulus of tensile elasticity of between 50 MPa and 150 MPa; for a ratio between the thickness and the diameter of between 0.14 MPa and 0.18, the pipe has a modulus of tensile elasticity of between 150 MPa and 500 MPa; and, for a ratio between the thickness and the diameter of between 0.18 and 0.20, the pipe has a modulus of tensile elasticity of between 500 MPa and 2000 MPa.

12. A pipe according to any one of the preceding claims, wherein the pipe has a diameter smaller than 63 mm.