SK114798A3 - Multiple-layer pipe - Google Patents

Abstract

A pipe, with a bell preferably formed in place, whose radial rigidity is greater than 4 kN/m<2> for the wall thicknesses given in Table 1, consists of three layers (1, 2, 3). The middle layer (3) consists of a polyolefin, in particular polypropylene, that is reinforced with 25 % to 70 % by weight of a mineral, and is foamed to a density preferably at least 10 % less than the density of a comparable middle layer that is only reinforced in the same proportion. The outer layer (1) and the inner layer (2) consist preferably of the same synthetic material as the middle layer (3). The middle layer is preferably reinforced with talcum or chalk, or a mixture of the two.

Description

MULTILAYER TUBE

Technical field

BACKGROUND OF THE INVENTION The present invention relates to a multilayer pipe produced by coextrusion, optionally with a shaped neck, the central layer of which is composed of a mineral-enriched polyolefin.

BACKGROUND OF THE INVENTION

Until now, pipes in the drainage system of polyolefins such as polypropylene (PP) or polyethylene (PE) have the disadvantage of having a high material consumption (wall thickness) due to the required stiffness and deformation over time due to load. As a result, polyolefin channel pipes of nominal stiffness (SN) required for use, SN 4 (4 kN / m ² ), and SN 8 (8 kN / m ² ), as opposed to PVC or cavity tubes, are not required. they are economical and contain too high a polymer fraction.

Another disadvantage is the production of the formed neck of polyolefin pipes (PP and PE). Until now, precise shaping has been possible only with high technical costs associated with the process (both extrusion and blowing). Large tolerances were required to maintain shrinkage values over a long period of time. As a result, too much neck dimensions tolerances and different shrinkage values led to inaccurate miscibility at the joint ends of the pipes or fittings. For this reason, the heating and cooling times of the polyolefin pipes (PP and PE) are relatively high, so that the production rate and thus the economy are influenced depending on the wall thickness.

From AT 0 000 643 U1 a three-layer pipe is known, the middle layer of which consists of polypropylene which is filled with 25 to 50% by weight of talc. Due to the high density of the middle layer of the known tube (approximately 1.2 g / cm ³ ), there is a disadvantage of high weight at large wall thicknesses, especially a large thickness of the middle layer.

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SUMMARY OF THE INVENTION

It is an object of the invention to compensate for the disadvantages of the polyolefin (PP or PE) pipes described above.

In particular, it is an object of the invention to reduce the ecologically and economically disadvantageously high proportion of tube polymers to less than half the proportion of polymers in the tube material of the prior art without compromising the user-technical properties of the tube.

This object is solved by a tube having the features set forth in the first claim.

Preferred tube configurations according to the present invention are the subject of the subclaims.

In one embodiment, the pipe of the invention is a multilayer pipe, which is preferably produced by a coextrusion method. The multilayer pipe consists, for example, of at least one carrier layer, preferably a middle layer, of polyolefin, in particular of polypropylene, filled with mineral material and foamed. For example, the tube has one, especially a thin-walled, outer and inner layer.

The invention provides a pipe in the size range DN 100 to DN 1000, e.g. polyolefin, especially PP, to which the in-line process can be directly molded. For a pipe according to the invention, the radial pipe stiffness at the minimum wall thicknesses given in the table is not less than 4 kN / m ^ (tested according to ISO / DIS 9969). In the middle layer, the return material, regenerate or recycled material can be processed. In this case, the terms regenerate and recycle are to be understood as follows: Regenerate is a returnable material that is generated by production waste and - without further need - is reintroduced into the production process. Recyclate is a recovered material from a product already in use, which is processed into another or the same product.

In the present case, the concept of radial tubular stiffness needs to be brought to a level with peak stiffness (SN). Peak stiffness (SN) is any stiffness,

043 / B which counteracts the load at the top of the tube, defined by the peak deformation according to ISO / DIS 9969. The peak stiffness is in contrast to the axial stiffness of the tube. The differences in labeling originate in the assessment of the load and storage effects and the manner of reaction (bending, bulging, fracture, etc.) of the tubes to this load. Radial = pipe section deformation, e.g. bulge, axial = deformation in the longitudinal axis of the tube, e.g. bend.

Increase of tube rigidity, resp. In the present invention, the elastic modulus is ensured in particular by means of a layer filled with mineral material and foamed.

The foamed layer, which may be the middle layer of a three-layer pipe, may be filled with a mineral substance, e.g. talc, chalk or the like, or a mixture of several minerals.

In the invention, it is preferred that the foamed (middle) layer consists of polypropylene or polyethylene. In this case, it can be provided that the pipe layers according to the invention consist of the same plastic.

The outer layer provided outside the foamed middle layer may have a thickness of 0.2 to 2.0 mm in the pipe according to the invention. The inner layer provided within the foamed middle layer may have a thickness of 0.2 to 3.0 mm. For example, the inner layer may consist of a polypropylene copolymer.

The pipe according to the invention can have a radial pipe stiffness of more than 4 kN / m ² .

BRIEF DESCRIPTION OF THE DRAWINGS

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be explained in more detail with reference to the drawings, in which: FIG. 1 shows a section according to the invention, and FIG. 2 shows a foamed layer arrangement area.

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DETAILED DESCRIPTION OF THE INVENTION

An exemplary embodiment of a pipe according to the invention is shown in section in FIG. 1. Although a three-layer pipe is shown in the exemplary embodiment shown in the drawing, the invention is not limited to such a pipe. It is possible to design more or less than three layers, e.g. more than two foamed layers and / or more foamed layers.

In order to ensure an optimal ratio between sufficient impact strength and high strength, a blend consisting of a polyolefin filled with 25 to 70 masses, parts of talc or a polyolefin filled with 25 to 70 masses, parts of chalk or a mixture of chalk and talc may be used in approximately : 1, eg. PP (PP = polypropylene) or PP homopolymer, respectively. copolymer or mixtures thereof.

Through the reinforcement with mineral substances and the uniform distribution of the mineral substances, a strength in the E-modulus range of approximately 2,000 3,500 N / mm 2 in the middle layer material is achieved. The mineral content has the disadvantage of significantly increasing the weight of the pipe. The specific gravity of the PP (middle) layer filled with, for example, 35 parts of talc is 1.18 to 1.2 g / cm ³ . By means of a blowing agent, the (middle) layer filled with minerals is foamed in the extrusion process and the density is preferably reduced by at least 10%, for example from the original 1.2 g / cm ³ to a maximum of 1.08 g / cm ³ , preferably 0 , 8 to 0.9 g / cm ³ . However, the density may, for example, be as much as 0.2 g / cm ³ or less.

This material is the carrier material in the (middle) layer of the tube of the invention. Due to the high filling of the polyolefin material with the substances of the (middle) layer, for example polypropylene (PP), there is also less enthalpy, respectively. higher thermal conductivity, which is advantageous for faster and more uniform heating and cooling during the subsequent neck formation. Even distribution of wall thicknesses of all tubular layers and minerals in the material, e.g. they also provide a controllable rate of shrinkage to the tube and throat to the middle layer.

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The outer and inner layers of the tube support the desired internal compressive strength and impact resistance at low temperatures. The inner and outer layers of the invention may consist of a polyolefin, e.g. PP copolymer.

Until now, polyolefin tubes have mostly been made monolayer, which has led to problems with different crystallinity for the marginal fibers, since different regions of crystallinity could not be precisely defined, respectively. produced and, moreover, fluctuated into irregular areas during production.

However, since crystallinity is a very important factor for both short and long-term internal compression strength and tube impact strength, it is desirable, in order to optimize these mechanical values, to equalize and set the crystallization fraction as high as possible especially in the inner layer. The more thin the tube layer is, the better the crystallinity can be controlled in the cooling process, and the easier it is to keep the crystallization fraction constant (at a predetermined value) over the entire length and circumference of the tube.

This is made possible by the pipe according to the invention since at least one layer, which is reinforced with minerals and foamed, takes over a substantial part of the pipe carrying capacity. This makes it possible to keep the inner and outer layers thin and to bring them into line with current requirements as described below. In addition, partially crosslinked polypropylene may be used to increase the tube strength values, optionally in admixture with uncrosslinked polypropylene.

The wall thicknesses are adapted to the mechanical - chemical requirements and shown in relation to the dimensions with the overall thickness in Table 1.

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Table 1

Tube dimensions and wall thicknesses for three-layer pipes with peak stiffness 4 kN / m2 (SN 4)

DN d1 (Mm) min (mm) min (mm) min (mm) with ges min (mm) s real (mm) 110 110.00 0.60 2.30 0.50 3.40 3.70 125 125.00 0.60 2.70 0.50 3.80 4.20 160 160.00 0.60 3.60 0.50 4.70 5.30 200 200.00 0.60 4.70 0.50 5.80 6.60 250 250.00 0.70 5.90 0.60 7.20 8.30 315 315.00 0.80 7.50 0.70 9.00 10.40 400 400.00 1.00 9.50 0.80 11,30 13.20 500 500.00 1.10 12,00 0.90 14,00 16.50 600 600.00 1.20 15,30 1.00 17.50 20.80

Table 2

Pipe and wall thickness dimensions for three-layer pipe with peak rigidity 8 kN / m2 (SN 8)

DN d1 (Mm) min (mm) min (mm) min (mm) with ges min (mm) s real (mm) 110 110.00 0.60 3.00 0.50 4.10 4.60 125 125.00 0.60 3.50 0.50 4.60 5.20 160 160.00 0.60 4.70 0.50 5.80 6.70 200 200.00 0.60 6.00 0.50 7.10 8.30 250 250.00 0.70 7.50 0.60 8.80 10,30 315 315.00 0.80 9.50 0.70 11,00 13,00 400 400.00 1.00 12.10 0.80 13.90 16.50 500 500.00 1.10 15,30 0.90 17,30 20.70 600 600.00 1.20 19.40 1.00 21.60 26.00

043 / B where d1 = outside diameter

Sa = wall thickness of the outer layer

Sm = wall thickness of the middle layer

Si = wall thickness of the inner layer

Sges = wall thickness overall

Sreal = recommended wall thickness, example min = currently lowest values.

The inner layer 2 and / or the outer layer 1 may also consist of a material other than the material of the middle layer 3, which is PP, for example, when these are bonded to the middle layer 3 by means of an adhesive agent. These plastics for the outer and / or inner layers 1 and 2 may be, for example:

polyethylene (PE) acrylonitrile-styrene-butadiene-copolymer (ABS) styrene-acrylonitrile (SAN) copolymers polyamide

The invention allows for low deposition of polymers (improving the ecological balance) while meeting the requirements for non-pressurized drainage pipes, with improved efficiency over full-thickness pipes and pipes with only a filled middle layer. Furthermore, improved properties are achieved over tubes with only a foamed middle layer (not reinforced or unfilled):

thinner wall at the same rigidity, high rigidity for a long period, higher E-modulus, improved creep factor, higher production and better production cooling.

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The following advantages are offered over medium layer (unfoamed) pipes which are only reinforced with mineral material:

improved thermal insulation, improved internal heating efficiency, cost savings and low weight.

In the diagram appended as FIG. 2 is a preferred region of the foamed layer arrangement, which is preferably the middle layer of a three-layer tube, which is highlighted by cross-hatching, the PP portion preferably being between 25 and 70% by weight. Compared to a layer which is only reinforced with a mineral but not foamed, the density is at least 10% by weight. lower. For example, a middle layer composition is provided which comprises 30% talc, 55% polypropylene and 15% wt. share of PP.

For example, a preferred embodiment of the invention may be described as follows:

A pipe with a preferably formed neck, which can be used as a drainage pipe and whose radial stiffness at the wall thicknesses given in Table 1 is greater than 4 kN / m 2, consists of three layers 1, 2 and 3. The middle layer 3 consists of polyolefin, mainly polypropylene which is stiffened by 25 to 70% by weight of the mineral and is foamed to a specific weight 10% less than that of a comparable middle layer stiffened in the same ratio. The outer layer 1 and the inner layer 2 preferably consist of the same plastic as the middle layer 3. The middle layer is preferably reinforced with talc or chalk or a mixture thereof.

The amount of polymer is less than half that of comparable tubes that have not been mineralized and foamed.

Claims (17)

Multilayer plastic pipe, characterized in that at least one layer (3), preferably the middle layer (3), consists of a polyolefin reinforced with a mineral substance or a mixture of minerals, the proportion of polyolefin in this layer (3) being 25 to 70 and that the layer is foamed to a specific gravity which is at least 10% less than the specific weight of an unfoamed layer reinforced with minerals of identical composition. Tube according to claim 1, characterized in that the tube is molded in one piece to the tube. Tube according to claim 1 or 2, characterized in that the foamed layer (3) comprises a return material of tubes of the same plastic. Tube according to one of claims 1 to 3, characterized in that the plastic forming the foamed layer (3) contains up to 50% by weight of polyolefin recyclate. Tube according to one of claims 1 to 4, characterized in that the wall thickness of the layer (3) is at least 50% of the total wall thickness of the tube. Tube according to any one of claims 1 to 5, characterized in that the foamed layer (3) and / or the layer (2) provided therein consists of partially cross-linked polypropylene. A pipe according to any one of claims 1 to 5, characterized in that the foamed layer (3) and / or the layer (2) provided therein consists of a mixture of polypropylene and partially cross-linked polypropylene. 31,043 / B kJ Tube according to claim 7, characterized in that the mixture consists of 10 to 50% by weight, preferably 15 to 25% by weight, of partially crosslinked PP, based on 100 parts of PP base, in particular polypropylene copolymer. Tube according to one of Claims 1 to 8, characterized in that the foamed layer (3) is filled with talc and / or chalk as a mineral material. Tube according to one of Claims 1 to 9, characterized in that the middle layer is foamed to a density of up to 0.9 g / cm 2, preferably 0.8 g / cm 3 Tube according to one of Claims 1 to 5 and to 10, characterized in that the foamed layer (3) consists of a mineral-reinforced polypropylene. Tube according to any one of claims 1 to 11, characterized in that the outer layer (1) and the inner layer (2) consist of polypropylene. Tube according to one of Claims 1 to 12, characterized in that the inner layer (2) and the outer layer (1) consist of the same polyolefin as the foamed middle layer (3) reinforced with a mineral substance. A tube according to any one of claims 1 to 13, characterized in that the inner layer (2) has a higher, finely divided, medium proportion of crystallinity than the outer layer (1). A tube according to claim 14, characterized in that the polymer of the middle layer (3) has a higher, finely divided, medium proportion of crystallinity than the outer layer (1). Method for manufacturing a tube according to any one of claims 1 to 16, characterized in that the tube is produced in a coextrusion process with external cooling and internal tempering. Method according to claim 16, characterized in that the control is effected by the formation of a spherulite or a higher crystallinity of the inner layer (2).