ES2570654B1 - Flexible thermoplastic pipe for chlorine fluid conduction and manufacturing procedure - Google Patents

Abstract

Flexible thermoplastic pipe for conducting a fluid, comprising an inner layer of octene-1 in contact with said fluid and an outer layer of PVC, the inner layer being attached to the outer layer by a layer of adhesive. Method for simultaneously manufacturing four pipes for conduction of a fluid, comprising: (a) connecting four extruders, for extruding octene-1, for extruding an adhesive, for extruding rigid PVC and for extruding flexible PVC to an extrusion head and (b ) simultaneously extrude an octene-1 profile to form an inner layer, an adhesive profile to form an intermediate layer of adhesive, a rigid PVC profile and a flexible PVC profile to form on a fixed pitch calibrator (6) PVC outer layer, wherein said PVC outer layer comprises a rigid PVC spiral coextruded with flexible PVC.

Description

FIELD OF THE INVENTION

The field of the invention is related to the pipes for fluid conduction and its manufacturing processes. The present invention relates to a pipe for conducting a fluid comprising an inner layer of octene-1, an adhesive layer and an outer layer of PVC. This invention is applicable in the sector dedicated to the manufacture of tubes for swimming pools as well as for other applications where chlorine must be transported.

BACKGROUND OF THE INVENTION

Pool pipes are usually made of polyvinyl chloride (PVC). These pipes are constituted by a spiral of rigid PVC and covered by flexible PVC. With this structure, the pipes are flexible, have a low radius of curvature, thus facilitating their application. Due to their rigid PVC spiral, they resist minimum breaking pressures of 15 bar at 23 ° C and minimum pressures of 4.5 bar at 55 ° C. The pipes withstand vacuum pressures of the order of 300 mbar. The above properties are properties required in the UNE-EN ISO 3994: 2012 regulations.

PVC has a fairly limited resistance to chlorine, because PVC is made of chlorine and therefore has a high affinity for chlorine. As such, the deterioration of this type of pipes is quite fast, which leads to serious problems and expenses.

When PVC pipes are in contact with chlorine, damage to PVC pipes occurs, which is a problem in the state of the art.

DESCRIPTION OF THE INVENTION

In Example 1, PVC pipe samples have been immersed in a 50 ppm solution of trichloroisocyanuric acid for 30 days and the samples have been weighed before and after immersion. After that time, variations in weight between 4 and 11% have been determined for pipes made of PVC.

The results of Example 1 demonstrate that PVC pipes are damaged after contact with chlorine, which significantly alters their properties. Damage to lead pipes after contact with chlorine is a problem in the state of the art.

The problem in view of the closest state of the art can be defined as the contribution of a chlorine resistant pipe for conducting a fluid and the contribution of an alternative manufacturing process for a chlorine resistant pipe for conducting a fluid.

The solution to this problem is to provide a chlorine resistant pipe defined in the claims of the present application and to provide a method of manufacturing a chlorine resistant pipe defined in the claims of the present application.

In one aspect, the present invention provides a flexible thermoplastic pipe for conducting a fluid, comprising an inner layer (1) of octene-1 in contact with said fluid and an outer layer (3) of PVC, the inner layer ( 1) bonded to the outer layer (3) by a layer (2) of adhesive.

Octeno-1 is a polyolefin-based plastomer with a high chemical resistance to chlorine keeping its physical properties virtually intact.

Octeno-1 is able to resist chlorine since it has no affinity for it. From the point of view of solubility, chlorine is polar and the octene-1 plastomer is apolar, the solubility between them is very low.

In another aspect of the invention, said outer layer (3) comprises a spiral (4) of rigid PVC coextruded with the flexible PVC.

In another aspect of the invention, said adhesive is an anhydrous polymer.

There is a problem of incompatibility between the PVC and the octene-1 plastomer. To solve this problem a modified anhydride polymer has been selected.

In another aspect of the invention, said fluid is water comprising chlorine.

In another aspect, the present invention provides a method for simultaneously manufacturing four pipes for conducting a fluid, comprising:

(to)

connect four extruders, an extruder to extrude octeno-1, an extruder to extrude an adhesive, an extruder to extrude rigid PVC and an extruder to extrude flexible PVC to an exlrusion head (5) that has output for four profiles and

(b)

simultaneously extrude an octene profile (7) 1 to form an inner layer (1), an adhesive profile (8) to form an intermediate layer of adhesive on four fixed pitch calibrators (6). a profile (9) of rigid PVC and a profile (10) of flexible PVC to form an outer layer (3) of PVC, wherein said outer layer (3) of PVC comprises a spiral (4) of rigid PVC coextruded with the PVC flexible.

The extrusion head (5) has output for four profiles, which form four pipes in the calibration zone.

The fixed pitch calibrators (6) constitute a new type of calibrator with respect to the state of the art, more efficient, more robust and with greater cooling capacity.

The extrusion head (5) is prepared for the simultaneous entry of four different materials: rigid PVC, flexible PVC, adhesive and octeno-1 plastomer.

Four extruders are connected to the extrusion head (5), one for each type of material and four profiles will come out of the head that will generate four pipes in the calibration zone.

In Figure 4 a section of the extrusion head (5) can be seen with the output detail of the four polymer channels. The initial polymer feeding is carried out by a single channel, which is then divided into two and, finally, in the four polymer channels referred to.

Figure 5 shows a calibration table with capacity for four pipes.

One of the main features of this calibration table is the ability of vertical and horizontal displacement, and the ability of manual and automatic displacement

The fixed pitch calibrators (6) are fixed to the calibration table. These calibrators

(6) Fixed pitch have been developed in the present invention with the aim of increasing the productivity and efficiency of this manufacturing process.

The type of standard gauge in the state of the art is the variable pitch calibrator (variable pitch calibrators are shown in Figure 5), consisting of adjustable rings that hold the flexible shafts. These rings can be rotated and allow you to define the step that is needed, for which you need experience and a lot of practice on the part of the operators.

The main disadvantages identified for this type of calibrators are:

-

Little cooling capacity since there is no direct contact with the metal surface between the flexible shaft and the inner surface of the gauge. There is an air zone that makes direct cooling difficult by heat transfer by conduction

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Need for continuous adjustments both at the beginning of production and throughout the production periods. The rings that hold the flexible shafts can be rotated and are fixed by screws. With the pressures and temperatures of work this fixation yields and needs of continuous adjustments.

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Need to have highly qualified workers for continuous adjustment and readjustment of optimal production conditions.

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For the indicated reasons, an average of 5% of waste is generated in all the production carried out. In addition, these wastes are very difficult to recycle so it is necessary to resort to (and pay) to specialized companies for this.

The fixed pitch gauge (6) does not need the adjustment rings since longitudinal notches are made on the surface of the gauge with the defined pitch and where the flexible shafts will fit.

The main advantages of fixed pitch calibrators are:

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The beginnings of production are faster since the step is already defined and it is not necessary to carry out any manual adjustment or readjustments throughout the production, considerably reducing human intervention. In this way, the generation of waste throughout production is reduced up to 1% and the quality of the final product is improved considerably, which means a saving of 4% compared to traditional variable pitch calibrators.

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It considerably increases the internal cooling capacity of the pipes since the internal cooling system with water is closer to the outer surface. In this way, higher production speeds can be achieved. For example, a pipe of 43 by 50 mm and with a weight of 611 g / m, with variable pitch gauge can achieve a maximum speed of 120 m / h. However, using a fixed pitch gauge, speeds of 160 m / h can be achieved.

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The durability of these calibrators is considerably superior to those of variable pitch. The continuous adjustments and readjustments that are made in the calibrators of variable step cause a considerable deterioration diminishing their time of life in good conditions. However, fixed pitch calibrators do not need these adjustments and readjustments, so they have a longer lifetime.

In another aspect, said adhesive is an anhydrous polymer.

In another aspect, said fluid is water comprising chlorine.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1. Diagram of a section of a section of PVC pipe with its respective spirals in rigid PVC (PVC-R). The section of the pipe is circular, in this scheme the circular section is represented linearly. Comparative figure, it is not according to the invention.

Figure 2. Schematic of a section of a pipe section according to the invention. The section of the pipe is circular, in this scheme the circular section is represented linearly.

Figure 3. Input scheme of four different materials: rigid PVC, flexible PVC, adhesive and octeno-1 plastomer in the extrusion head.

Figure 4. Head for the production of four profiles.

Figure 5. This figure shows a calibration table for four pipes, variable pitch calibrators, the head for the production of four profiles and the four profiles on four variable pitch calibrators to form four pipes. Comparative figure, it is not according to the invention.

Figure 6. Fixed pitch calibrator.

PREFERRED MODES OF REALIZATION

Example 1

Several laboratory tests were carried out in order to determine the properties of a pipe according to the invention before and after being in contact with trichloroisocyanuric acid for 30 days.

The pipe according to the invention has an inner layer of octene-1, an outer layer of PVC, comprising a rigid PVC spiral coextruded with the flexible PVC, the inner layer being attached to the outer layer by a layer of anhydrous polymer adhesive modified.

The adhesive used is a modified anhydride with a polymeric base of vinyl acetate ethylene (Bynel® 386 t of DuPont).

Octene-1 was produced in a polymerization process with a metallocene catalyst.

In parallel, the same tests were carried out with two PVC samples of existing products in the market. It has been verified that the pipe of the invention hardly suffers a maximum weight variation of 0.34% while for the other two samples weight variations of 4.1% and 10.71% have been determined. Table 1 summarizes some physical properties before and after applying the solution with chlorine.

Table 1. Study of physical properties before and after applying the solution with chlorine.

Before applying the 50 ppm solution of trichloroisocyanuric acid.

After applying the 50 ppm solution of trichloroisocyanuric acid. 30 days.

Hardness (Shore Al

Voltage (MPa) Elongation (%)  Hardness (Shore Al Ion Tension (MPa) Lengthening (%)

Invention Pipe

85 18.1 783 87 17.69 733.4

Sample 1 of pve

75 17.57 431 85 13.4 301, 1

Sample 2 pve

74 16.3 492 81 14.2 323.3

The results in Table 1 confirm that traditional PVC-only products are damaged after contact with chlorine, which significantly alters their properties. On the contrary, the pipe of the invention is considerably more resistant, and, in addition to

5 present a negligible weight variation, it also maintains its flexibility (radius of curvature) and its hardness.

Therefore, the pipe of the invention is much superior to the existing PVC pipes in the market since both the hardness, tension and elongation change very little demonstrating that the pipe is not attacked by chlorine, contrary to what happens with the pipes of

PVC

Claims (7)

1. Flexible thermoplastic pipe for conducting a fluid, characterized in that it comprises an inner layer (1) of octene-1 in contact with said fluid and an outer layer (3) of PVC, the inner layer (1) being attached to the outer layer (3) by one layer (2) of adhesive.

2.

Pipe according to claim 1, characterized in that said outer layer (3) comprises a spiral (4) of rigid PVC coextruded with the flexible PVC.

3.

Pipe according to claim 1, characterized in that said adhesive is an anhydrous polymer.

Four.

Pipe according to claim 1, characterized in that said fluid is water comprising chlorine.

5.

Procedure for simultaneously manufacturing four pipes for conducting a fluid, characterized in that it comprises:

(to)

connect four extruders, an extruder to extrude octeno-1, an extruder to extrude an adhesive, an extruder to extrude rigid PVC and an extruder to extrude flexible PVC to an extrusion head (5) that has output for four profiles and

(b)

extrude simultaneously on four fixed-gauge gauges (6) an octene-1 profile (7) to form an inner layer (1), an adhesive profile (8) to form an intermediate layer of adhesive, a profile (9) of Rigid PVC and a flexible PVC profile (10) to form an outer layer (3) of PVC, wherein said outer layer (3) of PVC comprises a spiral (4) of rigid PVC coextruded with the flexible PVC.

6.

Process according to claim 1, characterized in that said adhesive is an anhydrous polymer.

7.

Process according to claim 1, characterized in that said fluid is water comprising chlorine.