CN110541975A - A kind of self-cleaning anti-fouling and waxing polyolefin pipe material and its preparation method and application - Google Patents

Abstract

The invention relates to a self-cleaning, anti-fouling and waxing polyolefin pipe material and a preparation method and application thereof. The polyolefin pipe material comprises a pipe material inner layer and a pipe material outer layer, and the material of the pipe material inner layer is a polyolefin modified with fluorine groups. The blending material of the material and the base polyolefin material, the material of the outer layer of the pipe is polyolefin material; the preparation method of the polyolefin pipe is: 1) Blend the polyolefin modified material containing fluorine groups with the base polyolefin material, The blended material is obtained; 2) the blended material and the polyolefin material are double-layered co-extruded to obtain the polyolefin pipe material with anti-scaling and waxing; the polyolefin pipe material can be used for making the inner pipe of the steel wire winding pipe. Compared with the prior art, the present invention reduces the surface energy of the inner wall of the pipeline by introducing fluorine-containing group segments, so that the pipeline has the functions of preventing scaling and waxing. In addition, the introduction of fluorine-containing groups is also conducive to improving the resistance of the pipeline. The high temperature resistance and corrosion resistance make the polyolefin pipe have a relatively broad application prospect.

Description

A kind of self-cleaning anti-fouling and waxing polyolefin pipe material and its preparation method and application

technical field

The invention belongs to the technical field of pipes, and relates to a self-cleaning anti-scaling and waxing polyolefin pipe material and a preparation method and application thereof.

Background technique

In the process of oilfield water injection and crude oil transportation, due to changes in environmental conditions such as pressure and temperature, as well as the adsorption between the fluid medium and the surface of the pipe, the wax and inorganic salts in the transportation medium will be deposited on the pipe wall to form a waxy scale layer. The flow area is reduced and the conveying resistance is increased. Waxing and scaling reduces the flow area of the pipeline, increases the frictional resistance, reduces the pipeline transportation capacity, and even causes the pipeline to be blocked in severe cases, resulting in significant economic losses. In addition, the northern heating is mainly centralized heating, and the water quality in the north is poor. After running for a period of time, scale will form on the inner wall of the pipeline, which will increase the water resistance and affect the heating effect. Generally, it needs to be cleaned once every 3-5 years, which is time-consuming. Efforts and money, seriously affect the user experience.

The theory of solid-liquid interface believes that the level of surface energy of materials is an important factor in causing wax formation and scaling. Reducing the surface energy of the pipe material can reduce the degree of fouling of the inner wall of the pipe. Therefore, in the process of investigation, it is proposed to modify the inner wall of the pipe, so that the inner wall of the pipe can form a lower surface energy, achieve hydrophobic-oleophobic performance, and fundamentally solve the problem of pipe scaling and waxing.

Polymer materials with low surface energy become the primary consideration, and the surface energy of fluorine-containing materials is the lowest among polymer materials. However, traditional fluorine-containing modifiers have low molecular weights and poor compatibility with polyolefin matrices. Although it can migrate to the surface, it can reduce the surface energy to a certain extent. However, due to the weak binding force between it and polyolefin, it will be gradually taken away with the liquid transportation in the pipeline and the scraping of impurities in the liquid, which will affect its continuous effect.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a self-cleaning anti-fouling and waxy polyolefin pipe material and its preparation method and application in order to overcome the above-mentioned defects of the prior art.

The object of the present invention can be realized through the following technical solutions:

A self-cleaning anti-scaling and waxing polyolefin pipe, comprising an inner layer of the pipe and an outer layer of the pipe, wherein the material of the inner layer of the pipe is a blend of a polyolefin modified material containing fluorine groups and a base polyolefin material Material, the material of the outer layer of the pipe is polyolefin material.

Further, the fluorine group-containing polyolefin modified material includes a polyolefin main chain segment and a fluorine group-containing chain segment grafted on the polyolefin main chain segment.

The main chain segment is a polyolefin chain segment, which has good compatibility with the base polyolefin material in the blend material, and because the chain length of the main chain segment is longer, it is beneficial to the main chain segment and the chain segment in the base polyolefin material. entanglement to improve the bonding force of the two materials in the blend material; the fluorine-containing group segment is grafted on the main segment of the polyolefin as a functional segment, and the fluorine-containing group segment with a smaller surface energy can be attached to the co-polymer. The surface of the blended material aggregates, that is, to the surface of the inner layer of the pipe, thereby reducing the surface energy of the inner wall of the pipe; in addition, the fluorine-containing group segments in the blended material that fail to migrate to the surface can also be anchored in the base polyolefin material. Between the main segment and the segment of the base polyolefin material, the entanglement between the two segments is strengthened, and the bonding force between the fluorine-containing polyolefin modified material and the base polyolefin material is further improved.

Further, the polyolefin main segment includes low density polyethylene (LDPE), linear low density polyethylene (LLDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), heat-resistant polyethylene ( PERT) or one of ultra-high molecular weight polyethylene (UHMWPE);

The fluorine-containing group segments include poly(trifluoroethyl acrylate), poly(hexafluorobutyl acrylate), poly(dodecafluoroheptyl acrylate, poly(dodecafluoroheptyl methacrylate), polyperfluorodecyl ethylene, etc. One of the functional groups produced by the graft polymerization of fluorine and double bond reactive monomers.

Further, the base polyolefin material in the blended material and the polyolefin material in the outer layer of the pipe are the same polyolefin material, and the polyolefin material includes high-density polyethylene, heat-resistant polyethylene, ultra-high molecular weight polyethylene. A type of ethylene.

Further, the mass percentage content of the fluorine group-containing polyolefin modified material in the blend material is 5-100 wt %.

Further, the thickness ratio of the inner layer of the pipe to the outer layer of the pipe is 1:(0-10), wherein the preferred thickness ratio is 1:(3-6), which can be adjusted appropriately according to the application requirements, and the inner layer is extruded. The mandrel used is mirror polished and coated with Teflon to ensure a sufficiently low roughness.

The above-mentioned preparation method of a self-cleaning anti-fouling and waxy polyolefin pipe, comprising:

1) blending the polyolefin modified material containing fluorine groups with the base polyolefin material to obtain a blended material;

2) Double-layer co-extrusion of the blended material and the polyolefin material to obtain a polyolefin pipe material with anti-scaling and waxing.

Wherein, the base polyolefin material is a conventional commercially available material, and the polyolefin modified material containing a fluorine group is a commercially available material, or prepared by the method reported in the currently disclosed literature, or prepared by the following steps:

1) Put the powder of the main segment of polyolefin (such as LDPE powder, MDPE powder, etc.) in a plasma device, carry out vacuum treatment with a vacuum degree of less than 200mTorr, and then introduce 250-1250mTorr of helium or argon Gas is used as protective gas, and then a glow discharge with a processing power of 10-250W (preferably 50-250W) is performed, that is, plasma treatment, and the plasma treatment conditions are adjusted to generate a large number of free radicals on the surface of the polyolefin powder, and the treatment is performed for 10-600s Then, the polyolefin main segment powder containing free radicals on the surface is obtained;

2) The polyolefin main chain segment powder containing free radicals on the surface is placed in the air for 5-1440 minutes, and the oxygen in the air converts the surface free radicals into surface peroxides, thereby obtaining the polyolefin main chain containing peroxides on the surface. segment powder;

3) The polyolefin main segment powder containing peroxide on the surface is added as a free radical initiator to the polymerized monomer of the fluorine-containing group segment (such as polytrifluoroethyl acrylate, polyhexafluorobutyl acrylate, etc.) The free-radical polymerization reaction of the polymerized monomer is carried out at 50-100 ° C under the protection of nitrogen or argon, and after 2-24 hours of reaction, polymer powder is obtained, wherein the surface of the polyolefin containing peroxide is The addition amount of the main segment powder is 5-95% of the mass of the polymerized monomer, the concentration of the polymerized monomer solution is 0.1-1g/mL, and the solvent is 1,4-dioxane, toluene, xylene, N- One of methylpyrrolidone, N-methylacetamide, N,N-dimethylformamide or N,N-dimethylacetamide;

4) After the polymer powder is washed and dried in sequence, a polyolefin modified material with surface grafted fluorine-containing group segments is obtained.

In addition, in step 3), the free radical polymerization reaction includes ordinary free radical polymerization reaction or living free radical polymerization reaction;

When the free-radical polymerization reaction is a common free-radical polymerization reaction, the polyolefin powder containing peroxide on the surface is directly added to the solvent containing the polymerized monomer as a free-radical initiator;

When the free-radical polymerization reaction is a living free-radical polymerization reaction, the polyolefin powder containing peroxide on the surface is first reacted with diisopropyl xanthate or dithiobenzoic anhydride, so that the surface of the polyolefin powder is formed The xanthate or dithioester is then added to the solvent containing the polymerized monomer. The polyolefin powder containing xanthate or dithioester on the surface can be used as a chain transfer agent for living radical polymerization, that is, RAFT reagent, so it can be grafted to acrylic polymer by RAFT polymerization.

The inner layer blended material can be directly extruded by an extruder with a high dispersion screw. In order to improve the dispersion effect, it can be granulated by a twin screw first, and then extruded by a pipe extruder.

As a preferred technical solution, in the blending process of step 1) and the double-layer co-extrusion molding process of step 2), conventional modified materials such as color masterbatch, antioxidant, extrusion modifier, etc. can be added as required.

The above-mentioned self-cleaning anti-fouling and waxing polyolefin pipe material can be used to make the inner pipe of the steel wire wound pipe.

The invention introduces a long-chain polyethylene modified material with fluorine-containing grafting, which ensures full combination with the matrix resin, gives the matrix material lower surface energy, realizes the effect of hydrophobicity and oleophobicity, and is finally applied to crude oil transportation and heating. , salt brine transportation, inorganic organic raw material transportation and other fields that need anti-scaling and waxing. In addition, the melting point of the fluorine-containing graft modified polyethylene material is slightly higher than that of the polyethylene material, which can improve the high temperature resistance to a certain extent; the fluorine-containing material can also block H ₂ S, O ₂ and other gases to a certain extent, further enhancing the Corrosion resistance of equipment.

Compared with the prior art, the present invention has the following characteristics:

1) The present invention introduces a low surface energy modified layer as the inner wall of the pipeline to improve the surface performance of the inner wall of the pipeline (in the hydrophobic performance test, the contact angle is increased from 87.7° to 98.4°, so that the pipeline has the functions of self-cleaning, anti-scaling and waxing. ;

2) The modified material is a polyolefin material modified by grafting of fluorine-containing group segments. The fluorine-containing group segments can migrate and concentrate on the surface of the inner wall of the pipeline, reducing the surface energy of the inner wall of the pipeline; fluorine-containing groups that do not migrate to the surface are The segment can also be anchored between the main segment of the polyolefin and the segment of the base polyolefin material to improve the bonding force of the two materials in the blended material;

3) The introduction of fluorine-containing groups is beneficial to improve the melting point of the material. In the performance test, the melting point of HDPE after graft modification can be increased from 136.4 °C to 141.0 °C. Therefore, the temperature resistance of the inner layer material of the pipe can be improved to a certain extent. Due to the introduction of fluorine-containing groups, it also has the effect of blocking gas to a certain extent and improving the corrosion resistance of equipment.

Description of drawings

Fig. 1 is the structural representation of a kind of self-cleaning anti-fouling and waxing polyolefin pipe material in Example 1;

Fig. 2 is the partial enlarged schematic diagram of A place in Fig. 1;

Fig. 3 is the contact angle test result diagram of water droplets on the HDPE tablet surface of the polyethylene modified material without fluorine-containing groups added in Example 1;

Fig. 4 is the contact angle test result diagram of water droplets on the surface of the fluorine group-containing polyethylene modified material and HDPE blended material tableting surface in Example 1;

5 is a graph showing the results of the first water drop rolling test performed on the surface of the HDPE tablet of the polyethylene modified material without fluorine-containing groups in Example 1;

6 is a graph showing the results of the second water drop rolling test performed on the surface of the HDPE tablet of the polyethylene modified material without fluorine-containing groups in Example 1;

7 is a graph showing the results of the first water drop rolling test performed on the surface of the fluorine group-containing polyethylene modified material and the HDPE blend material tableting surface in Example 1;

8 is a graph showing the results of the second water drop rolling test performed on the surface of the fluorine group-containing polyethylene modified material and the HDPE blend material tabletting surface in Example 1;

FIG. 9 is a graph showing the test results of the melting point and melting enthalpy of HDPE in Example 1. FIG.

FIG. 10 is a graph showing the test results of the melting point and melting enthalpy of the fluorine-containing grafted HDPE in Example 1. FIG.

Description of marks in the figure:

1—the inner layer of the pipe, 2—the outer layer of the pipe, 3—the fluorine-containing group segment, and 4—the main segment of polyolefin.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and provides a detailed implementation manner and a specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

In the following embodiments, the outer layer material of the polyolefin pipe material is a commercially available polyethylene material. The inner layer material is prepared by the following steps:

1) Put the powder of the main segment of polyolefin (such as LDPE powder, MDPE powder, etc.) in a plasma device, carry out vacuum treatment with a vacuum degree of less than 200mTorr, and then introduce 250-1250mTorr of helium or argon Gas is used as protective gas, and then a glow discharge with a processing power of 10-250W (preferably 50-250W) is performed, that is, plasma treatment, and the plasma treatment conditions are adjusted to generate a large number of free radicals on the surface of the polyolefin powder, and the treatment is performed for 10-600s Then, the polyolefin main segment powder containing free radicals on the surface is obtained;

2) The polyolefin main chain segment powder containing free radicals on the surface is placed in the air for 5-1440 minutes, and the oxygen in the air converts the surface free radicals into surface peroxides, thereby obtaining the polyolefin main chain containing peroxides on the surface. segment powder;

3) The polyolefin main segment powder containing peroxide on the surface is added as a free radical initiator to the polymerized monomer of the fluorine-containing group segment (such as polytrifluoroethyl acrylate, polyhexafluorobutyl acrylate, etc.) The free-radical polymerization reaction of the polymerized monomer is carried out at 50-100 ° C under the protection of nitrogen or argon, and after 2-24 hours of reaction, polymer powder is obtained, wherein the surface of the polyolefin containing peroxide is The addition amount of the main segment powder is 5-95% of the mass of the polymerized monomer, the concentration of the polymerized monomer solution is 0.1-1g/mL, and the solvent is 1,4-dioxane, toluene, xylene, N- One of methylpyrrolidone, N-methylacetamide, N,N-dimethylformamide or N,N-dimethylacetamide;

4) After the polymer powder is washed and dried in sequence, a polyolefin modified material with surface grafted fluorine-containing group segments is obtained.

Example 1:

As shown in Figure 1, a self-cleaning anti-fouling and waxing polyolefin pipe material, the material of the inner layer 1 of the pipe material is a blended material of a polyethylene modified material containing fluorine groups and a base polyethylene material; The material of the outer layer 2 of the pipe is polyethylene material.

As shown in Figure 2, the polyethylene modified material containing fluorine group in the inner layer 1 of the pipe is a modified material with polyethylene segment as polyolefin main segment 4 and fluorine group segment 3 as graft segment A flexible polyethylene material, wherein the polyethylene segment is HDPE, and the fluorine-containing group segment 3 is polyhexafluorobutyl acrylate.

The polyethylene modified materials containing fluorine groups will migrate to a certain extent, and most of the fluorine group segments 3 will gather on the inner wall of the pipeline to achieve the purpose of reducing the surface energy; the main chain end of the modified material is a long polyethylene segment. , which can be well blended with the base polyethylene material; part of the fluorine-containing groups that have not migrated to the surface can further anchor the force between the fluorine-containing group-containing polyethylene modified material and the base polyethylene material.

The inner layer 1 of the pipe material is a blended material of the fluorine group-containing polyolefin modified material and the base polyolefin material, wherein the added amount of the fluorine group-containing polyolefin modified material is 7.5 wt %.

The base polyolefin material and the outer layer material of the pipe are both HDPE.

The ratio of the thickness of the inner and outer layers of the pipe: 1:5.

The outer diameter of the pipe is 25mm, and the wall thickness is 2.8mm.

The pipe is double-layer co-extrusion, one-time molding. Among them, the mandrel used for inner layer extrusion is mirror polished and coated with PTFE coating to ensure sufficiently low roughness.

As shown in Figures 3 and 4, the contact angle of the inner layer HDPE after adding the modified material increased from 87.7° to 98.4°, and the surface hydrophobicity was significantly improved. The rolling behavior of the water droplets before and after the modification of the inner layer material was tested respectively. As shown in Figure 5 and Figure 6, the rolling water droplets on the surface of the HDPE material had obvious trailing phenomenon, as shown in Figure 7 and Figure 8, the modified water droplets It is easier to roll on the surface of the material without smearing. The above results all show that the addition of the modified material is beneficial to improve the surface hydrophobicity of the inner layer material of the pipe. In addition, as shown in Figure 9 and Figure 10, the melting point of HDPE is 136.4 °C, and the melting point of the fluorine-containing graft modified material is 141.0 °C. The melting temperature of the added fluorine-containing graft modified material is significantly higher than that of HDPE. Improve the temperature resistance of the pipe.

Example 2:

A self-cleaning anti-scaling and waxing polyolefin pipe material, the inner layer of the pipe material and the material of the outer layer of the pipe material are both fluorine group-containing polyethylene modified materials and UHMWPE blended materials.

The polyethylene modified material containing fluorine group is a modified polyethylene material with polyethylene segment as polyolefin main segment 4 and fluorine-containing group segment 3 as graft segment, wherein the polyethylene segment is LDPE, the fluorine-containing group segment 3 is dodecafluoroheptyl polyacrylate.

The added amount of the fluorine group-containing polyethylene modified material was 10 wt %.

The mandrel used is mirror polished and coated with Teflon to ensure a sufficiently low roughness.

The outer diameter of the pipe is 65mm and the inner diameter is 55mm. The produced pipe can subsequently be used as the inner pipe of the steel wire wound pipe.

Example 3:

An anti-scaling and waxing polyolefin pipe, as shown in Figure 1, the pipe has a two-layer structure, the inner layer 1 of the pipe is a blend of polyethylene modified material containing fluorine groups and PERT, and the outer layer 2 of the pipe The material is PERT.

The polyethylene modified material containing fluorine group is a modified polyethylene material with polyethylene segment as polyolefin main segment 4 and fluorine-containing group segment 3 as graft segment, wherein the polyethylene segment is PERT, the fluorine-containing group segment 3 is polytrifluoroethyl acrylate.

The addition amount of the fluorine group-containing polyethylene modified material in the blend material is 7.5 wt %.

The ratio of the inner layer 1 of the pipe to the outer layer 2 of the pipe is: 1:5.

The outer diameter of the pipe is 25mm, and the wall thickness is 2.8mm

The pipe is double-layer co-extrusion, one-time molding. Among them, the mandrel used for inner layer extrusion is mirror polished and coated with PTFE coating to ensure sufficiently low roughness.

Example 4:

A self-cleaning anti-scaling and waxing polyolefin pipe, comprising an inner layer 1 of a pipe and an outer layer 2 of the pipe, and the material of the inner layer 1 of the pipe is a blend of a polyolefin modified material containing fluorine groups and a base polyolefin material Material, the material of the outer layer 2 of the pipe is polyolefin material.

Wherein, the polyolefin modified material containing fluorine group includes a polyolefin main segment 4 and a fluorine group segment 3 grafted on the polyolefin main segment 4, and the polyolefin main segment 4 is LDPE, containing fluorine Radical segment 1 is polydodecafluoroheptyl methacrylate.

The base polyolefin material in the blended material and the polyolefin material in the outer layer 2 of the pipe are both high-density polyethylene. The mass percentage content of the fluorine group-containing polyolefin modified material in the blended material is 5 wt %.

The thickness ratio of the inner layer 1 of the pipe to the outer layer 2 of the pipe is 1:10. Among them, the mandrel used for inner layer extrusion is mirror polished and coated with PTFE coating to ensure sufficiently low roughness.

The anti-scaling and waxing polyolefin pipes in this embodiment are prepared by the following method:

1) blending the polyolefin modified material containing fluorine groups with the base polyolefin material to obtain a blended material;

2) Double-layer co-extrusion of the blended material and the polyolefin material to obtain a polyolefin pipe material with anti-scaling and waxing.

In the blending process of step 1) and the double-layer co-extrusion molding process of step 2), conventional modified materials such as color masterbatch, antioxidant, extrusion modifier, etc. are added.

Example 5:

A self-cleaning anti-scaling and waxing polyolefin pipe, comprising an inner layer 1 of a pipe and an outer layer 2 of the pipe, and the material of the inner layer 1 of the pipe is a blend of a polyolefin modified material containing fluorine groups and a base polyolefin material Material, the material of the outer layer 2 of the pipe is polyolefin material.

Among them, the polyolefin modified material containing fluorine group includes a polyolefin main segment 4 and a fluorine group segment 3 grafted on the polyolefin main segment 4, and the polyolefin main segment 4 is MDPE, fluorine-containing The group segment 1 is one of polyperfluorodecylethylene.

The base polyolefin material in the blend material and the polyolefin material in the outer layer of the pipe are both high-density polyethylene, and the mass percentage of the fluorine group-containing polyolefin modified material in the blend material is 20 wt %.

The thickness ratio of the inner layer 1 of the pipe to the outer layer 2 of the pipe is 1:10. Among them, the mandrel used for inner layer extrusion is mirror polished and coated with PTFE coating to ensure sufficiently low roughness.

The anti-scaling and waxing polyolefin pipes in this embodiment are prepared by the following method:

1) blending the polyolefin modified material containing fluorine groups with the base polyolefin material to obtain a blended material;

2) Double-layer co-extrusion of the blended material and the polyolefin material to obtain a polyolefin pipe material with anti-scaling and waxing.

The foregoing description of the embodiments is provided to facilitate understanding and use of the invention by those of ordinary skill in the art. It will be apparent to those skilled in the art that various modifications to these embodiments can be readily made, and the generic principles described herein can be applied to other embodiments without inventive step. Therefore, the present invention is not limited to the above-mentioned embodiments, and improvements and modifications made by those skilled in the art according to the disclosure of the present invention without departing from the scope of the present invention should all fall within the protection scope of the present invention.

Claims (8)

1. a self-cleaning anti-scaling and waxing polyolefin pipe material, characterized in that, this pipe material comprises pipe material inner layer and pipe material outer layer, and the material of described pipe material inner layer is a polyolefin modified material containing fluorine groups A blended material with a base polyolefin material, the material of the outer layer of the pipe is a polyolefin material. 2 . The self-cleaning anti-fouling and waxing polyolefin pipe material according to claim 1 , wherein the fluorine-containing group-containing polyolefin modified material comprises a polyolefin main segment and a polyolefin grafted on the Fluorine-containing group segment on the main segment of polyolefin. 3. The self-cleaning anti-fouling and waxing polyolefin pipe material according to claim 2, wherein the main segment of the polyolefin comprises low density polyethylene, linear low density polyethylene, medium density polyethylene One of ethylene, high-density polyethylene, heat-resistant polyethylene or ultra-high molecular weight polyethylene; The fluorine-containing group segment is one of the functional groups produced by the graft polymerization of fluorine-containing and double-bond reactive monomers, including poly(trifluoroethyl acrylate), poly(hexafluorobutyl acrylate), and poly(acrylic acid) dodecafluoride. Heptyl ester, polydodecafluoroheptyl methacrylate, polyperfluorodecyl ethylene. 4 . The self-cleaning anti-fouling and waxing polyolefin pipe according to claim 1 , wherein the base polyolefin material in the blended material is the same as the polyolefin material in the outer layer of the pipe. 5 . A polyolefin material comprising one of high density polyethylene, heat-resistant polyethylene and ultra-high molecular weight polyethylene. 5 . The self-cleaning anti-fouling and waxing polyolefin pipe material according to claim 1 , wherein the mass percentage content of the polyolefin modified material containing fluorine groups in the blended material is 5 . 5-100wt%. 6. The self-cleaning anti-fouling and waxing polyolefin pipe material according to claim 1, wherein the thickness ratio of the inner layer of the pipe material to the outer layer of the pipe material is 1:(0-10). 7. The preparation method of a self-cleaning anti-fouling and waxy polyolefin pipe material according to any one of claims 1 to 6, wherein the method comprises: 1) blending the polyolefin modified material containing fluorine groups with the base polyolefin material to obtain a blended material; 2) Double-layer co-extrusion of the blended material and the polyolefin material to obtain a polyolefin pipe with anti-scaling and waxing. 8 . The application of the self-cleaning anti-scaling and wax-forming polyolefin pipe material according to any one of claims 1 to 6 in making the inner pipe of a steel wire wound pipe.