RU2630057C1 - Thermal insulated multi-layer polymer pipe and method of its manufacture - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: pipe according to the invention comprises a pipe body made of a polymeric material, for example cross-linked polyethylene (PEX), at least one barrier layer, a polyurethane foam insulation layer and an outer protective layer of polyethylene. The pipe is characterized in that at least one barrier layer is disposed directly between the outer protective layer and the thermal insulation layer adhering to them and is made in the form of a five-layer film containing an oxygen-protective layer surrounded on both sides by layers of adhesive and high-pressure polyethylene. The method of manufacturing a pipe according to the invention is based on joining the layers of polymer materials after their activation due to diffusion interaction.

EFFECT: improving the protection of the thermal insulation layer of the pipe, improving the manufacturability of the pipes and expanding the range of technical equipment available in this field.

4 cl, 2 dwg

Description

FIELD OF THE INVENTION

The invention relates to polymer pipes, namely, to a thermally insulated multilayer polymer pipe for heat supply systems and hot water supply, and a method for its manufacture.

State of the art

Thermally insulated pipes are widely used in heating and hot water pipelines and consist of a central pipe (or pipe body), on top of which a layer of thermal insulation is placed, for example, polyurethane foam, which in turn is covered with a waterproofing layer, usually made of polyethylene, to protect the thermal insulation material from the external environment. As a pipe body, modern thermally insulated pipelines use pipes made of polymer materials that are not susceptible to corrosion and have chemical resistance, which can significantly reduce costs compared to traditional metal pipes. In addition, polymer pipes are flexible, making them easier to handle and install. Polymer pipes for hot water are usually made of polyolefins, for example, cross-linked polyethylene (PEX), high temperature resistant polyethylene (PERT), polypropylene or polybutylene. However, thermally insulated polymer pipes have their drawbacks.

One of the known problems solved by manufacturers of polymer pipes is the permeability of the polymer body of the pipe for oxygen, which, getting into the coolant from the environment, can cause corrosion of metal components in the composition of the pipeline, as well as accelerate the aging process of the pipe body, reducing the strength characteristics of the polymer material, especially at elevated temperatures. To prevent diffusion of oxygen from the environment into the coolant, an oxygen-protective layer is applied to the outer surface of the polymer body of the pipe from a material having barrier properties with respect to oxygen, for example, a copolymer of ethylene with vinyl alcohol (EVOH), polyamide, or aluminum, as described, for example, in RF patent for utility model No. 132857 (published September 27, 2013). In addition, at high temperatures (above 60 ° C), the permeability of the polymer body of the pipe for water and water vapor may occur, leading to the destruction of the insulation layer. A known solution to this problem is to apply a barrier layer of a liquid crystal polymer (LCP) to the polymer body of the pipe (and / or to place inside the pipe body) having barrier properties against diffusion of water and oxygen, as described in RF patent for invention No. 2224160 (published on 20.02 .2004). Thus, various techniques are known for creating barrier layers around the polymer body of a pipe.

On the other hand, an equally important problem facing manufacturers of thermally insulated multilayer polymer pipes is the protection of the insulation layer from the external environment. As mentioned above, traditionally, the insulation material is rigid or semi-rigid foamed polyurethane, to protect which the insulation layer is covered with an outer layer of waterproofing made of medium or high density polyethylene. Also, traditionally, technological polyethylene film is usually placed between the layers of thermal and waterproofing, usually from low density polyethylene, for example, as described in patent EP 0897788 A1 (published on 02.24.1999). However, polyethylene, being non-polar, is a good barrier against water (which is polar), but does not have sufficient barrier properties against non-polar gases such as oxygen and nitrogen. Therefore, in heat-insulated pipes, air (oxygen and nitrogen) from the environment over time penetrates through the protective layers of polyethylene into the cells of the polyurethane foam, and the initial gas mixture from the cells of the polyurethane foam (foaming agents and carbon dioxide) gradually comes out. Having taken place for a long time, these processes lead to the oxidation and destruction of the polyurethane foam layer of thermal insulation, peeling it from the body of the pipe, and further, to the loss of strength and destruction of the structure of the pipeline. In addition, air entering from the outside into the polyurethane foam cells has a higher thermal conductivity than the initial gas mixture inside the polyurethane foam, which affects the thermal insulation properties of the pipeline. These processes, having a long-term negative impact on the insulation material, reduce the service life of the insulated pipeline, which at present should exceed 30 years, and preferably more than 50 years.

To solve this problem, a barrier layer against gas diffusion is placed between the thermal insulation layer and the waterproofing layer. Thus, a water pipe with thermal insulation is known that contains an inner pipe, a polyurethane foam insulation layer surrounding the inner pipe, a film surrounding the thermal insulation layer, and an outer shell of thermoplastic polymer, which is described in the RF patent for invention No. 2338969 (published on November 27, 2008). To increase flexibility, the known pipe contains an intermediate layer of soft polymer foam, placed between the thermal insulation layer and the film, which is glued to the intermediate layer with an adhesive and has barrier properties with respect to water, water vapor and foaming agents. Heat-insulated pipes with a barrier layer between the layers of heat and waterproofing are available on the market, for example, you can specify the pipe "IZOPLOFLEKS", manufactured by Troupe POLIMERTEPLO LLC (see http://www.polymerteplo.ru/products/ISOPROFLEX/), containing both the barrier layer on top of the thermal insulation layer and the oxygen protective layer on top of the pipe body. The difference in the purpose of these layers allows us to conclude that the barrier layer of this pipe has barrier properties not with respect to oxygen, like an oxygen protective layer, but with respect to, for example water vapor.

Closest to the present invention is a known construction of a pre-insulated (i.e. thermally insulated) multilayer polymer pipe containing a pipe body, a layer of thermal insulation surrounding it, a barrier layer of an EVAL brand ethylene vinyl alcohol copolymer film (EVOH), an adhesive layer, bonding the EVOH film to the outer layer of waterproofing, and the outer layer of waterproofing from high density polyethylene, respectively, which is described, for example, in the document “Barrier sheaths for pre-insulated rub "(available on the Internet at http://www.evalevoh.com/media/129913/pip_ru_1510.pdf link). The EVOH film is an excellent barrier to oxygen, nitrogen, carbon dioxide and foaming agents (for example, cyclopentane), therefore, the known pipe design allows you to keep the structure of the thermal insulation layer unchanged for a long time.

With improved thermal insulation protection, the well-known design of a pre-insulated pipe with a barrier layer of EVOH film has its drawbacks. High density polyethylene of the outer layer of waterproofing is a solid and durable material, but it has a relatively high brittleness and low resistance to deformation. Therefore, when installing pipelines based on such pipes, there is often a violation of the homogeneity of the outer waterproofing layer in the form of various cracks and chips, which expose the EVOH film to the risks of direct external influences. Usually the EVOH film thickness is very small, on the order of 1 mm, so it is very easy to damage it in case of destruction of the outer waterproofing layer, which will nullify all the advantages of the construction of this pipe. In addition, the need for the population of the adhesive layer between the barrier film and the outer layer of waterproofing for gluing complicates the manufacturing process of the pipe and increases its cost.

Thus, there is a need to create a thermally insulated multilayer polymer pipe with a barrier layer against diffusion of gases into and out of the thermal insulation layer of an improved design, which allows to extend the service life of the pipeline based on such pipes, as well as a simple and technologically advanced method for manufacturing this pipe.

Disclosure of invention

The objective of the present invention was the creation of a thermally insulated multilayer polymer pipe with a barrier layer against diffusion of gases into and out of the thermal insulation layer of an improved design, as well as a simple and technologically advanced method of manufacturing such a pipe, which would eliminate the disadvantages of the prior art.

The object of the invention is solved by creating a thermally insulated multilayer polymer pipe containing a pipe body of polymer material, at least one barrier layer, a polyurethane foam insulation layer and an outer protective layer of polyethylene, in which at least one barrier layer is located directly between the outer protective a layer and a layer of thermal insulation adjacent to them and made in the form of a five-layer film containing, in the order of arrangement: the first layer of high-pressure polyethylene, he first adhesive layer, oxygen barrier layer, a second adhesive layer and a second layer of high density polyethylene.

The barrier film is located in the pipe directly between the outer protective layer and the thermal insulation layer, adjacent to them, without intermediate layers of adhesive. The oxygen barrier layer in the film is made of a polar polymer, preferably a copolymer of ethylene with vinyl alcohol (EVOH) or polyamide. Thus, this film prevents the diffusion of gases into and out of the thermal insulation layer. The external layers of adhesive and polyethylene increase the strength of the barrier film and protect the internal oxygen protective layer (EVOH) from possible external influences during installation of the pipeline.

The pipe body according to the invention is a reinforced pressure pipe, preferably made of cross-linked polyethylene (PEX), polypropylene or polybutylene, which allows the pipe to be used in heating and hot water systems.

In addition, the problem is solved by a method of manufacturing a thermally insulated multilayer polymer pipe, comprising the steps of applying a layer of polyurethane foam insulation to the pipe body from a polymeric material and covering the insulation layer with an outer protective layer of polyethylene, in which: applying a layer of insulation to the pipe body is performed after activation of the outer surface of the pipe body to ensure diffusion interaction of the polyurethane foam thermal insulation with the polymer material of the pipe body; and before coating the insulation layer with an external protective layer, a five-layer film barrier layer is applied to the insulation layer, containing, in order: the first layer of high pressure polyethylene, the first adhesive layer, an oxygen protective layer, the second adhesive layer and the second high pressure polyethylene layer, which was previously activated on both sides to ensure diffusion interaction of the polyurethane foam thermal insulation with polyethylene of the first layer of the mentioned film and polyethylene of the outer protective layer with polyethylene of the last layer of said film, respectively.

The proposed method allows to produce heat-insulated pipes in which the barrier film against gas diffusion is located directly between the outer protective layer and the thermal insulation layer and is connected with the thermal insulation polyurethane foam and the protective layer polyethylene by diffusion interaction, and not by gluing with intermediate layers of adhesive. Moreover, thermal insulation polyurethane foam is also applied to the activated body of the pipe, contacting it through diffusion interaction. The proposed method provides a monolithic structure of the pipe and simplifies its manufacture.

The technical result achieved in the invention consists in improving the protection of the thermal insulation layer and increasing the manufacturability of manufacturing thermally insulated multilayer polymer pipes, as well as expanding the range of available technical means in the field of using and manufacturing thermally insulated multilayer polymer pipes. In addition, the invention provides the possibility of increasing the life of the pipeline from insulated pipes.

Brief Description of the Drawings

The invention is described in more detail below on the example of preferred options for its implementation with reference to the attached drawings, in which:

FIG. 1 shows a schematic cross-sectional view of a thermally insulated multilayer polymer pipe according to the invention;

FIG. 2 shows a schematic representation of a five-layer film of a barrier layer of a pipe according to the invention.

The implementation of the invention

The structure of the thermally insulated multilayer polymer pipe according to the invention is illustrated in the drawing of the pipe (1) in cross section in FIG. one.

As seen in FIG. 1, the pipe (1) contains, from the core to the sheath: the pipe body (2), a thermal insulation layer (3), a barrier layer (4) and an outer protective layer (5). In a preferred embodiment, the body of the pipe (2) is a pressure reinforced pipe made of cross-linked polyethylene (PEX). However, the invention is not limited in this regard, and the pipe body (2) can equally well be made of polypropylene, polybutylene or other suitable polymeric material that allows the pipe to be used in heating and hot water systems. In addition, the pipe body may contain, in or around the pipe body, an oxygen barrier layer, for example a layer of liquid crystal polymer (LCP) and / or ethylene vinyl alcohol copolymer (EVOH) having barrier properties against diffusion of water and oxygen, as is known in the art .

The thermal insulation layer (3) is made of rigid or semi-rigid polyurethane foam, and the outer protective layer (5), which provides waterproofing of the layer (3), is made of medium or high density polyethylene (medium or low pressure). As shown in FIG. 1, the barrier layer (4) in the pipe (1) is located directly between the outer protective layer (5) and the thermal insulation layer (3) with abutment thereto.

As further shown in FIG. 2, the barrier layer (4) is made in the form of a five-layer film containing, in the order of arrangement: the first layer of high pressure polyethylene (6), the first adhesive layer (7), the oxygen barrier layer (8), the second adhesive layer (9) and the second layer high pressure polyethylene (10). Moreover, the oxygen-protective layer (8) in the film composition of the said barrier layer (4) is made of a polar polymer, preferably a copolymer of ethylene with vinyl alcohol (EVOH) or polyamide, which provides a barrier to oxygen, nitrogen, carbon dioxide and foaming agents, preventing the diffusion of gases into and out of the thermal insulation layer. The implementation of the barrier layer (4) in the form of the described five-layer film, where the oxygen-protective layer (8) is surrounded on both sides by adhesive and high-pressure polyethylene layers, significantly increases the strength of the barrier film and the protection of the polar polymer layer (EVOH) from possible external influences during pipeline installation.

A method of manufacturing a pipe (1) according to the invention comprises the steps of applying a thermal insulation layer (3) of polyurethane foam to the pipe body (2) from a polymeric material and coating the thermal insulation layer with an outer protective layer (5) of polyethylene. Moreover, the claimed method is characterized in that the deposition of the thermal insulation layer (3) on the pipe body (1) is performed after activation of the external surface of the pipe body to ensure diffusion interaction of the thermal insulation polyurethane foam with the polymer material of the pipe body. The activation of the surface of the pipe body (2) can be performed by any known method, in particular by chemical or mechanical treatment, or by corona treatment, however, it is preferable to activate the pipe body (2) by flame.

In addition, according to the claimed method, before coating the thermal insulation layer (3) with the outer protective layer (5), a barrier layer (4) of a five-layer film containing, as described above and shown in FIG. 2: a first layer of high pressure polyethylene (6), a first layer of adhesive (7), an oxygen barrier (8), a second layer of adhesive (9) and a second layer of high pressure polyethylene (10), which was previously activated on both sides to provide diffusion the interaction of the polyurethane foam thermal insulation (3) with polyethylene of the first layer (6) of said film and polyethylene of the outer protective layer (5) with polyethylene of the last layer (10) of said film, respectively. The mentioned activation of the film from two sides is the activation of the outer surfaces of the first (6) and second (10) layers of high-pressure polyethylene in the film. This activation can be performed by any known method, in particular by chemical or mechanical action, however, it is preferable to activate the surfaces of the film by corona discharge.

Due to the fact that all the connected surfaces of the functional layers of the pipe according to the invention are made of related polymer materials, the proposed method provides the possibility of their direct diffusion bonding to each other, after activation, without the use of intermediate adhesive layers. Thus, the proposed method, characterized by simplicity and high manufacturability, allows us to produce a thermally insulated multilayer polymer pipe with a monolithic structure and a barrier layer from the diffusion of gases into and out of a layer of thermal insulation of increased strength. The described advantages of thermally insulated polymer pipes according to the invention provide an opportunity to significantly increase the service life of pipelines constructed on their basis for heat supply and hot water supply systems.

The embodiments described above are presented to clarify the essence of the claimed invention by specific examples and do not limit the scope of legal protection of the invention, which is determined by the following claims.

Claims (6)

1. A thermally insulated multilayer polymer pipe containing a pipe body made of a polymer material, at least one barrier layer, a polyurethane foam insulation layer and an outer protective layer of polyethylene, characterized in that at least one barrier layer is located directly between the outer protective layer and the layer thermal insulation adjacent to them and is made in the form of a five-layer film containing, in the order of arrangement: the first layer of high-pressure polyethylene, the first adhesive layer, an oxygen-protective layer, a second a second adhesive layer and a second layer of high pressure polyethylene. 2. A pipe according to claim 1, characterized in that the oxygen-protective layer in the film composition of said barrier layer is made of a polar polymer, preferably a copolymer of ethylene with vinyl alcohol (EVOH) or polyamide. 3. The pipe according to claim 1, characterized in that the pipe body is a pressure-reinforced pipe, preferably made of cross-linked polyethylene (PEX), polypropylene or polybutylene. 4. A method of manufacturing a thermally insulated multilayer polymer pipe, comprising the steps of applying a layer of thermal insulation from polyurethane foam to the pipe body of a polymeric material and covering the thermal insulation layer with an outer protective layer of polyethylene, characterized in that applying a layer of thermal insulation to the pipe body is performed after activation of the outer surface of the pipe body to ensure diffusion interaction of the polyurethane foam thermal insulation with the polymer material of the pipe body, and before coating the thermal insulation layer with an external protective layer, a five-layer film barrier layer is applied to the thermal insulation layer, containing, in order: the first layer of high pressure polyethylene, the first adhesive layer, the oxygen protective layer, the second adhesive layer and the second high pressure polyethylene layer that has been previously activated on both sides to ensure diffusion interaction of the polyurethane foam thermal insulation with polyethylene of the first layer of the mentioned film and polyethylene of the outer protective layer with polyethylene of the last layer of said film, respectively.

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