FI106441B - Drinking water pipe - Google Patents

Description

> 106441 IL C L> · 4 1

Drinking water pipe

The present invention relates to a polyolefin pipe according to the preamble of claim 1, which is particularly suitable for domestic water supply.

It is known that pipes for domestic water supply can be made of polymeric materials. There are quite stringent requirements for the types of polymer used, as low molecular weight compounds may be released from the plastic, affecting the quality of the water, particularly its taste and odor. Therefore, only a polymeric material which is chemically inert and does not release substances into drinking water, even under the influence of the chlorine contained therein, is suitable as a pipe material. In addition, the material must have sufficient mechanical strength, be dense and easy to clean and, where necessary, disinfect. Because of these requirements, only 15 very expensive raw materials can be used in the production of drinking water pipes, which significantly increases the cost of the manufacturing process.

The object of the present invention is to eliminate the drawbacks of the prior art and to provide a completely new solution for making drinking water pipes from polyolefins.

20

The solution according to the invention is based on the idea of forming a polyolefin pipe suitable for domestic water supply. It thus comprises at least one first polyolefin layer forming the tube shell, i.e. its outer surface, and at least one second polyolefin layer disposed inside the tube 25 shell and forming an inner tube surface which comes into contact with the conduit water.

Multilayer polyolefin tubes are known per se. As an example of tubes made by coextrusion technology, 30 hot water tubes described in JP application 60002351, comprising an inner layer of silane-crosslinked polyethylene, on which is extruded a second polyethylene layer containing: and metal oxide. A similar multilayer structure is also described in JP application 63272549, where interlayer bonding is improved by incorporating functionalized styrene blocks into 106441 2 inner layer polyethylene material. DE application 3 903 436 discloses a multi-layer polyethylene tube in which the layers of the tube are joined together by means of a bonding layer.

5 The publications do not pay special attention to the additives contained in the sandwich materials.

According to the present invention there is provided a multilayer polyolefin pipe suitable for domestic water supply, the inner layer of which consists of a material which does not release any harmful substances upon contact with drinking water.

A lower cost polyolefin can be used as the material for the outer layer of the polyolefin tube. However, the inner and outer layers of the tube have at least substantially the same physical, mechanical and thermal properties, so that they can be processed in the same processes, for example by coextrusion technology, and so that the long-term operating properties of the tube are not substantially altered. The tubular structure according to the invention is further characterized in that the color of the inner surface of the tubular structure differs substantially from that of the outer layer of the tubular structure.

More specifically, the solution according to the invention is essentially characterized by what is stated in the characterizing part of claim 1.

The substantially cylindrical, layered tube obtained by the present invention may include multiple layers. However, it is essential that the inner layer consists of a material suitable for conducting domestic water, which is different in color from at least 25 adjacent layers, so that the continuity of the inner layer can be visually inspected.

To identify the intended use of the tubular structure, the outer surface of the tubular shell, i.e. the outer layer of the tubing, may be extruded, either partially or completely, in the same color as the inner surface of the tubular structure.

30: The thicknesses of the layers may vary within wide limits, however, so that the overall thickness of the layered pipe conforms to commonly used design criteria.

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Typically, the thickness of the inner layer is about 0.01 to 10 mm, preferably about 0.05 to 5 mm, most preferably about 0.1 to 2 mm. It is essential that the inner layer forms a uniform, uninterrupted surface that prevents fluid in the tube from coming into contact with the outer layer material. The other layers have a total thickness of about 2 to about 100 mm. Usually, the inner layer is made significantly thinner than the outer layer (s), thereby providing the important advantage of keeping the material costs of the tube low because the inner layer accounts for a relatively small proportion.

Preferably, the polyolefin comprises low density polyethylene (LD) having a density (g / cm 3) of about 0.910 to 0.925, medium density polyethylene (MDPE) having a density of about 0.925 to 0.940, or high density polyethylene (HDPE) having a density greater than 0.941. The polyethylene melt index (MFR 190/5) is preferably 0.01 to 10, preferably 0.1 to 2, and particularly preferably less than 1. Polyolefin material may also be used polypropylene.

15

The comonomers of polyolefins can influence the properties of the polymers, such as crystallinity and strength properties. Higher alpha-olefins such as propylene, butene, 4-methylpentene, hexene and octene may be used as the comonomer for the ethylene, preferably less than 10% of the total polymer content. Of the propylene comonomers, ethylene, 4-. . methyl pentene, 3-methylbutene and butene, with less than 10% comonomers. If butene is used as the sole comonomer, the upper limit of the comonomer is 12%.

Food grade polyolefin matrix for use on the inner surface of a tube according to the invention. The rial contains only minor amounts, typically up to about 0.1%, of catalyst, initiator, and emulsifier residues. For these substances, reference is made to Kunststoffe im Lebensmittelverkehr, Helmut Wieczorek (ed.), 44. Lieferung, Carl Heymanns Verlag KG, Cologne 1995.

30 * · In the case of plastics additives and additives, stabilizers, fillers (eg

carbon black), dyes, flame retardants, release agents. The plastic blend 106441 4 according to the invention preferably contains from about 0.005 to 5.0% by weight of additives and excipients. For these substances and their uses, reference should be made to the literature reference above.

Particularly suitable polyethylene materials are PE 63, PE 80 and PE 100. The melt indexes are preferably 0.1 to 1.0.

The invention provides considerable advantages. Thus, compounds or components causing odor and odor are not released from the surface in contact with household water. At the same time, however, the material costs 10 for the manufacture of the pipe can be kept low because the proportion of the inner layer of the entire pipe is quite small. Since the layer constituting the inner surface of the pipe is of a different color than the rest of the pipe, it can still be easily verified that the inner surface is made up of material suitable for conducting domestic water throughout.

If desired, the tube may be extruded to the same color as the inner surface of the tube, thereby improving the tube's recognizability according to its intended use.

BRIEF DESCRIPTION OF THE DRAWINGS In the following, the invention will be explored in greater detail with reference to the accompanying drawings and a detailed description, in which Figure 1 shows the principal structure of the tube in axonometric cross-section. . ' and Fig. 2 is a schematic diagram of the coextrusion process used in making the tube of the invention.

The polymer tube of the invention comprises two nested cylindrical v layers 1 and 2, the first, i.e., the outer layer 1, forming the tube shell and the second, inner layer 2 forming the inner surface of the tube. As stated above, the first layer 1 may in itself consist of a plurality of overlapping layers. Alternatively, other cylindrical profiles may be considered, such as U-, H- or X-shaped profiles, but the tube in its final application form is elongated and substantially cylindrical.

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Figure 2 illustrates the entire tube design method in its general form. As shown in the figure, extrusion devices E1 and E2 are used, followed by die S, which feeds the tube to the calibrator K performing the shaping process. The product is then fed through the refrigeration device J to bring it to ambient temperature via strainer V or a puller V.

Extruder devices E1 and E2 are known in the art and receive the thermoplastic raw material forcing it to pass through the die S, for example, at a temperature of 180 to 230 ° C, whereby the heater is used to achieve this temperature.

The extruder E1 produces the outer layer of the tube and the extruder E2 the inner layer of the tube. At nozzle S, the inner and outer layers of the tube combine to form a completely homogeneous joint.

Calibration K is known in the art and reduces the design temperature of the tube to e.g. 127 ° C. The cooling device J is preferably a vacuum cooling device and reduces the tube design temperature to ambient temperature, e.g., by supporting the cooling tube or the like.

20 During the cooling period, the shape of the shaped tube must be maintained until the tube>. reaches ambient temperature. It will be appreciated that the above temperatures may vary according to the conditions. The traction device V pulls the final shaped tube from the device above, with its pull force adjusted so that the thickness of the tube wall is adjusted.

In the example case, the polyethylene tube of Figure 1 was made according to Figure 2.

with such a device using materials of the type PE-80 which have substantially similar properties to both the outer and inner layers. Among the materials used for the outer layer are Hostalen GM 5010 T2, Borealis ME 2418, 30 Rigidex PC 002-50 R102. The materials used are black in color. The materials used for the inner layer i ... include the Hostalen GM 5010 T2 Blue, Borealis ME 2424,

Rigidex PC 002-50 R968. The materials used are blue in color.

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The mechanical properties of the manufactured pipe complied with the product standards SFS 4231 and SFS 2335 for PE 80 (PEH 63) materials.

On the basis of organoleptic taste and odor testing, the tube meets the quality requirements for drinking water provided by Food Regulation 5 539/91.

Claims (9)

106441 A polyolefin pipe for domestic water supply, comprising: - at least one first polyolefin layer (1) forming a tube 5 shell and a second polyolefin layer (2) disposed inside the tube shell and forming an inner tube surface, the first and second polyolefin layers (1) , 2) made of polyolefin materials having at least substantially the same properties, characterized in that the second layer (2) forms a continuous, uninterrupted inner surface of the pipe and - consists of a polyolefin material suitable for conducting domestic water, different from the polyolefin material forming the adjacent first layer. A pipe according to claim 1, characterized in that it comprises a shell (1) of black polyethylene layer, the inner surface of which is formed by a layer (2) of blue polyethylene suitable for domestic water supply. A pipe according to claim 1 or 2, characterized in that the thickness of the second layer 20 (2) is less than the thickness of the pipe shell (1). • ♦ A tube according to claim 3, characterized in that the second polyolefin layer (2) has a thickness of at least about 0.05 mm. Pipe according to one of the preceding claims, characterized in that it has at least two first layers (1). Pipe according to one of the preceding claims, characterized in that it consists of polypropylene materials. A pipe according to any one of the preceding claims, characterized in that the pipe is manufactured by coextrusion. 106441 Pipe according to Claim 5, characterized in that the outer surface (1) of the housing is partially or completely of the same color as the inner surface of the pipe structure. Tube according to claim 8, characterized in that the outer layer 5 (1) of the tube forming the outer surface of the shell is extruded at least in part with the same color as the inner surface of the tube structure. • · 9 106441