PL247485B1 - Layered polyolefin pipe and method of making a polyolefin pipe - Google Patents

Abstract

The subject of the application is a layered polyolefin pipe (1), made by coextrusion from polyolefin materials, which consists of at least two layers of different polyolefin materials, joined together using a compatibilizer to give it a monolithic structure, wherein the outer polypropylene layer (3) constitutes 2-30% of the thickness of the pipe (1). The inner layer (2) of the pipe (1) is made of polyethylene. The compatibilizer is added to the outer polypropylene layer (3) or to the inner polyethylene layer (2) in an amount of 1-30%. The pipe (1) may also include a layer (4) acting as a compatibilizer. The application also concerns a method for making the polyolefin pipe in question.

Description

Description of the invention

The subject of the invention is a layered polyolefin pipe and a method for manufacturing a polyolefin pipe characterized by a monolithic structure, used for the construction of pressure water transmission networks, as well as for the construction of protective, overhead, indoor and underground installations.

Polyethylenes have been used as construction and installation materials for nearly 70 years, and their processing into pipes and fittings for drinking water began on a larger scale in the 1960s.

Water and gas transmission networks were often constructed from materials whose quality, according to current criteria and standards, would, for various reasons, be considered inadequate. This resulted not only in breakdowns and increased operating costs, but also in insufficient drinking water quality.

The material used so far for the production of pressure pipes was a virgin raw material, possibly containing additives of its own technological recyclates, which, according to applicable regulations and standardized recommendations, are not treated as recycled material and can be used in most applications.

The evaluation of pipes manufactured according to the above description, which were damaged or failed, often showed that one of the reasons for the observed pipe unreliability was the use of recycled or waste raw materials or various types of polyethylene in their production.

This damage was mainly due to the breakage of bonds in the polymer material in the area of weakness, thus increasing the size of the gap.

The gap growth at this stage was, however, slow, with a monotonically increasing velocity, and may occur in polymer materials at constant load.

Despite many undoubted advantages of polyethylene as a material for pressure pipes, it also has certain disadvantages that disqualify it from many applications.

The main ones include relatively low resistance to pressure, especially at elevated temperatures, compared to other materials such as polyvinyl chloride or polypropylene, which is why, in principle, polyethylene pipes cannot be used to construct pipelines operating at elevated temperatures.

Due to its very low surface energy, polyethylene does not adhere to most other materials. This characteristic is advantageous in many other applications, but it prevented the material from being reinforced and prevented the reinforcement from transferring stress. Therefore, it was impossible to improve the strength properties by incorporating active fillers, such as glass fibers, commonly used to reinforce other polymers.

Research has shown that the mechanical properties of composites increase with increasing filler aspect ratio and decreasing transverse dimension. This increases the filler's specific surface area and the sum of the forces interacting between the polymer matrix and its filler particles. This led to the search for fillers with structures corresponding to the nanometer scale and the initiation of work on the production of nanocomposites.

The aim of the invention was to develop a multilayer polyolefin pipe in which layers with low mutual adhesion would be joined together, combining the advantages of polyethylene and polypropylene, and to develop a method for manufacturing such a pipe.

The aim of the invention was achieved by inseparably combining an inner polyethylene layer made of polyethylene and an outer polypropylene layer.

The wall of the sandwich polyolefin pipe has an inner layer of polyethylene containing a compatibilizer in the form of ionomer compounds or maleic compounds or silane compounds in an amount of 1-30% and an outer layer of polypropylene.

The wall of the sandwich polyolefin pipe has an inner layer of polyethylene and an outer layer of polypropylene containing a compatibilizer in the form of ionomer compounds or maleic compounds or silane compounds in an amount of 1-30% polyethylene with an admixture of ionomer compounds or maleic compounds or silane compounds in an amount of 1-30%.

The wall of the sandwich polyolefin pipe between the inner layer of polyethylene and the outer layer of polypropylene comprises a third layer being a compatibilizer in the form of ionomer compounds or maleic compounds or silane compounds in an amount of 1-30% polyethylene with an admixture of ionomer compounds or maleic compounds or silane compounds in an amount of 1-30%.

The outer layer constitutes 2-30% of the pipe wall thickness and may be reinforced with 10% chopped glass fiber.

The ionomer compound contained in the compatibilizer is a copolymer of ethylene and acrylic acid.

The maleic compound contained in the compatibilizer is maleic acid anhydride.

Silane compounds are organic silicates.

A layered polyolefin pipe is made by co-extrusion of an inner polyethylene layer containing a compatibilizer and an outer polypropylene layer.

A layered polyolefin pipe is made by co-extrusion of an inner polyethylene layer and an outer polypropylene layer containing a compatibilizer.

The outer layer of the polyolefin sandwich pipe constitutes 2-30% of the pipe wall thickness and may be additionally reinforced with glass fiber.

A layered polyolefin pipe is also made by introducing a third layer, a compatibilizer, using the coextrusion method. The compatibilizer used contains polypropylene or polyethylene with an admixture of ionomer compounds in the form of a copolymer of ethylene and acrylic acid or maleic compounds in the form of maleic acid anhydride or silane compounds in the form of organic silicates in an amount of 1-30%. The compatibilizer constituting the intermediate layer is added in an amount of 1-30%.

The invention is presented in embodiment examples in the drawing, where Fig. 1 shows a pipe in an axial half-section, where one of the layers contains the compatibilizer, and Fig. 2 shows a pipe in an axial half-section with the compatibilizer introduced by co-extrusion as an intermediate layer.

Example I

The 1-layer polyolefin pipe is made by co-extrusion by combining polyethylene plasticized at a temperature of approximately 240°C and polypropylene plasticized at a temperature of approximately 270°C filled with 15% chopped glass fiber in the co-extrusion head.

The polyethylene constituting the inner layer 2 of pipe 1 is modified with a 20% addition of an ionomer in the form of a copolymer of ethylene and acrylic acid.

The process of plasticizing the material for each layer is carried out using a single-screw extruder with a standard plasticizing system, designed for the processing of polyolefin materials.

After extrusion, pipe 1 is calibrated using a vacuum calibrator and cooled with water in a cooling bath located behind the calibrator.

Example II

The 1-layer polyolefin pipe is made by co-extrusion by combining polyethylene plasticized at a temperature of approximately 240°C and polypropylene plasticized at a temperature of approximately 265°C in the co-extrusion head.

The polypropylene constituting the outer layer 3 of pipe 1 is modified with 25% addition of silane compounds in the form of organic silicates in a mixer.

The process of plasticizing the material for each layer is carried out using a single-screw extruder with a standard plasticizing system, designed for the processing of polyolefin materials.

After extrusion, pipe 1 is calibrated using a vacuum calibrator and cooled with water in a cooling bath located behind the calibrator.

Example III

The layered polyolefin pipe 1 is made by co-extrusion by combining in the co-extrusion head polyethylene plasticized at a temperature of about 240°C as the inner layer 2, polypropylene grafted with maleic anhydride plasticized at a temperature of about 250°C as the third layer 4 and polypropylene plasticized at a temperature of about 265°C filled with 10% chopped glass fiber.

The plasticization process for each layer is carried out using a separate single-screw extruder with a standard plasticization system designed for the processing of polyolefins.

After extrusion, the product is calibrated using a vacuum calibrator and cooled with water in a cooling bath located behind the calibrator.

The layered polyolefin pipe made according to the invention is characterized by positive features such as:

1. Higher circumferential stiffness;

2. Higher resistance to internal pressure;

3. Higher resistance to deformation under the influence of axial forces;

4. Lower value of the coefficient of thermal expansion;

5. Greater strength at elevated temperatures;

6. Resistance to crack propagation caused by damage and defects on the outer wall;

7. Greater resistance to chemical agents than polypropylene pipes;

8. Less susceptible to creep;

9. Possibility of giving the product antistatic properties;

10. Possibility of using the outer layer of recyclate for extrusion.

Claims (10)

1. Layered polyolefin pipe made of polyolefin materials, characterized in that the pipe wall (1) has an inner layer (2) of polyethylene containing a compatibilizer in the form of ionomer compounds or maleic compounds or silane compounds in the amount of 1-30% and an outer layer (3) of polypropylene, or an inner layer (2) of polyethylene and an outer layer (3) of polypropylene containing a compatibilizer in the form of ionomer compounds or maleic compounds or silane compounds in the amount of 1-30%, polyethylene with an admixture of ionomer compounds or maleic compounds or silane compounds in the amount of 1-30%, or between the inner layer (2) of polyethylene and the outer layer (3) of polypropylene, a third layer (4) constituting a compatibilizer in the form of ionomer compounds or maleic compounds or silane compounds in the amount of 1-30%, polyethylene with an admixture of ionomer compounds or maleic compounds or silane compounds in the amount of amounts of 1-30%, where the outer layer (3) constitutes 2-30% of the pipe wall thickness (1) and may be reinforced with 10% chopped glass fiber. 2. A layered pipe according to claim 1, characterized in that the ionomer compound contained in the compatibilizer is a copolymer of ethylene and acrylic acid. 3. The layered pipe according to claim 1, characterized in that the maleic compound contained in the compatibilizer is maleic acid anhydride. 4. A layered pipe according to claim 1, characterized in that the silane compound is an organic silicate. 5. A method of manufacturing a layered polyolefin pipe, characterized in that by co-extrusion, an inner layer (2) of polyethylene containing a compatibilizer and an outer layer (3) of polypropylene or an inner layer (2) of polyethylene and an outer layer (3) of polypropylene containing a compatibilizer are joined, wherein the outer layer (3) constitutes 2-30% of the pipe wall thickness and may be additionally reinforced with glass fiber or between the inner layer (2) of polyethylene or and the outer layer (3) of polypropylene of the pipe (1), a third layer (4) is introduced by co-extrusion, constituting a compatibilizer, wherein the compatibilizer used contains polypropylene or polyethylene with an admixture of ionomer compounds in the form of a copolymer of ethylene and acrylic acid or maleic compounds in the form of maleic acid anhydride or silane compounds in the form of organic silicates in the amount of 1-30%. 6. The method according to claim 5, characterized in that the compatibilizer constituting the third layer (4) is added in an amount of 1-30%. 7. A method according to claim 5 or 6, characterized in that the mixture containing polypropylene or polyethylene with an admixture of ionomer compounds or maleic compounds constituting a compatibilizer forming the third layer (4) is made directly during the co-extrusion process. 8. A method according to claim 5 or 6, characterized in that the mixture containing polypropylene or polyethylene with an admixture of ionomer compounds or maleic compounds constituting a compatibilizer forming the third layer (4) is prepared in a mixer. PL 247485 Β1 9. A method according to claim 4 or 6 or 7 or 8, characterized in that glass fiber is added to the polypropylene mixture forming the outer layer (3). 10. A method according to claim 5 or 6 or 7 or 8 or 9, characterized in that the compatibilizer forming the third layer (4) by co-extrusion is introduced between the polyethylene inner layer (2) and the outer layer (3).