Special anti-corrosion polypropylene material, preparation method and anti-corrosion steel pipe

Abstract

The invention discloses an anti-corrosion polypropylene special material, a preparation method and an anti-corrosion steel pipe, and relates to the 3PP anti-corrosion field, and the anti-corrosion polypropylene special material comprises the following components by mass: 10-30 parts of maleic anhydride grafted polypropylene, 40-70 parts of pipeline-grade polypropylene, 5-40 parts of co-polypropylene, 3-10 parts of an elastomer, 1-2 parts of rutile titanium dioxide, and 1-2 parts of an anti-aging auxiliary agent. According to the invention, maleic anhydride grafted polypropylene is compounded with different polypropylene, elastomers and assistants, and a traditional polypropylene adhesive and a special material for corrosion prevention of polypropylene are combined, so that the special material for polypropylene has bonding and corrosion prevention functions; the problems that a traditional adhesive is thin in thickness and prone to breakage in the extruding and winding process, so that adhesive lacking is caused, and delamination is caused between epoxy and polypropylene special materials are effectively solved.

Description

Technical Field

[0001] The invention relates to the field of 3PP anti-corrosion, and in particular to a special anti-corrosion polypropylene material, a preparation method and an anti-corrosion steel pipe. Background Art

[0002] 3PP anti-corrosion is a three-layer anti-corrosion technology composed of fused epoxy / polypropylene adhesive / extruded polypropylene layer, which is used for the surface protection of buried steel pipes. Its structure consists of the following three layers: the bottom layer is fused epoxy (60-80μm); the middle layer is maleic anhydride grafted modified polypropylene adhesive (170-250μm); the surface layer is extruded polypropylene special material (about 2.0-4.2mm). In the three-layer structure, the main function of epoxy is to directly bond with the surface of the steel pipe, which has good chemical corrosion resistance and anti-cathodic stripping performance; it reacts with the active group of the adhesive to form a chemical bond, ensuring that the overall anti-corrosion layer has good adhesion at higher temperatures. The middle layer is usually maleic anhydride grafted polypropylene adhesive. The polar anhydride functional group and the epoxy group of epoxy can react to form a chemical bond, so that the middle layer and the bottom layer form a good bond; and the non-polar polypropylene part has a good affinity with the surface layer polypropylene special material, so the middle layer and the surface layer have similar compatibility. The main function of the polypropylene surface layer is mechanical protection and anti-corrosion. The three-layer polypropylene anti-corrosion layer combines the excellent properties of epoxy coating and extruded polypropylene anti-corrosion layer, combining the interface characteristics and chemical resistance of epoxy coating with the mechanical protection characteristics of polypropylene anti-corrosion layer. According to relevant information, the melting point of polypropylene is as high as 167°C, and the maximum temperature of 3PP anti-corrosion can withstand 110°C. Compared with the maximum design temperature of 3PE anti-corrosion of 80°C, 3PP anti-corrosion steel pipe is mainly used for higher temperature media such as oil, gas and water transportation. It is currently recognized as one of the pipelines with the best anti-corrosion effect.

[0003] In the existing 3PP anti-corrosion technology, epoxy anti-corrosion adopts spraying process, and adhesive and special polypropylene materials are wrapped on the surface of epoxy powder by extrusion coating or lateral extrusion. Two single-screw extruders are required to extrude adhesive and special polypropylene materials respectively. The coating process is only suitable for the anti-corrosion of steel pipes with smaller diameters. When the adhesive is wrapped on the epoxy surface, due to the thin thickness of the adhesive (170-250μm) and the low melt strength of polypropylene itself, the polypropylene adhesive is prone to breakage during the extrusion and wrapping process, resulting in a lack of adhesive in the anti-corrosion layer. If the breakage is not discovered, the epoxy layer and the outer protective polypropylene layer in the three-layer anti-corrosion structure cannot be combined together through the chemical reaction between epoxy and the intermediate maleic anhydride grafted modified polypropylene, which will affect the overall anti-corrosion effect. Summary of the invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a special anti-corrosion polypropylene material, a preparation method and an anti-corrosion steel pipe. By compounding maleic anhydride grafted polypropylene with different polypropylenes, elastomers and additives, traditional polypropylene adhesives and polypropylene anti-corrosion special materials are combined, so that the polypropylene special material has both bonding and anti-corrosion functions; and effectively solves the problems of thin thickness of traditional adhesives, easy breakage during the extrusion and winding process leading to adhesive deficiency, and delamination between epoxy and polypropylene special materials.

[0005] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0006] In a first aspect, an embodiment of the present invention provides a special anti-corrosion polypropylene material, which comprises the following components in parts by mass:

[0007] 10-30 parts of maleic anhydride grafted polypropylene, 40-70 parts of pipeline grade polypropylene, 5-40 parts of copolymerized polypropylene, 3-10 parts of elastomer, 1-2 parts of rutile titanium dioxide, and 1-2 parts of anti-aging additive.

[0008] As a further implementation, the maleic anhydride grafted polypropylene consists of the following components:

[0009] Polypropylene 70-90 parts, vinyl copolymer 10-30 parts, maleic anhydride 1-2 parts, peroxide initiator 0.05-0.5 parts.

[0010] As a further implementation, the pipeline-grade polypropylene is one of homopolymer polypropylene, impact copolymer polypropylene, and random copolymer polypropylene;

[0011] 230℃, 2.16kg weight melt mass flow rate is 0.2-0.5g / 10min.

[0012] As a further implementation, the copolymerized polypropylene has a melt mass flow rate of 0.5-3 g / min at 230° C. and a weight of 2.16 kg.

[0013] As a further implementation, the elastomer is at least one of ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-octene copolymer, styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, and hydrogenated styrene-butadiene-styrene block copolymer.

[0014] As a further implementation, the anti-aging aid is composed of one or more of hindered phenol antioxidants, sulfur-containing hindered phenol antioxidants, phosphite antioxidants, hindered amine light stabilizers, ultraviolet light stabilizers, and acid absorbers.

[0015] As a further implementation method, the melt mass flow rate of the special anti-corrosion polypropylene material at 230°C and 2.16kg weight is 0.5-1.5g / 10min, the yield strength is greater than 20MPa, the nominal strain at break is greater than 400%, the Vicat softening point is greater than 130°C, the melt mass flow rate change rate of the product after thermal aging at 150°C for 960h is not more than 35%, and the peel strength of epoxy bonding after steel pipe anti-corrosion is: 23±5°C temperature, ≥300N / cm; 50±5°C temperature, ≥150N / cm; 110±5°C temperature, ≥80N / cm.

[0016] In the second aspect, an embodiment of the present invention also provides a method for preparing a special anti-corrosion polypropylene material, wherein maleic anhydride grafted polypropylene, pipeline-grade polypropylene, copolymer polypropylene, elastomer, rutile titanium dioxide, and anti-aging additive are mixed in a set proportion, and a screw extruder is used to melt-blend and granulate the mixture at 180-220°C and a screw speed of 350-500rpm to obtain the special anti-corrosion polypropylene material.

[0017] As a further implementation, the preparation method of the maleic anhydride grafted polypropylene is:

[0018] At 230° C. and 2.16 kg weight, 70-90 parts of polypropylene with a melt mass flow plastic of 8-40 g / min, 10-30 parts of vinyl copolymer, 1-2 parts of maleic anhydride, and 0.05-0.5 parts of peroxide initiator are mixed, and a grafting reaction is carried out at 180-220° C. through a twin-screw extruder, wherein the screw speed is 200-400 rpm.

[0019] In a third aspect, an embodiment of the present invention further provides an anti-corrosion steel pipe, comprising a steel pipe, wherein an epoxy anti-corrosion layer and a polypropylene anti-corrosion special material layer are sequentially provided on the outer side of the steel pipe, wherein the polypropylene anti-corrosion special material layer is made by the preparation method described.

[0020] The beneficial effects of the present invention are as follows:

[0021] (1) The present invention combines maleic anhydride grafted polypropylene, pipeline-grade polypropylene, copolymerized polypropylene, elastomer, rutile titanium dioxide, and anti-aging additives to make the special polypropylene material have both bonding and anti-corrosion functions; therefore, it can replace the traditional 3PP anti-corrosion adhesive (the standard requires a thickness of 170-250 μm) and the special polypropylene material. Therefore, after spraying epoxy on the surface of the steel pipe, there is no need to extrude and wrap a thinner adhesive layer. Only the anti-corrosion special polypropylene material (the standard requires a thickness of 1.8-4.2 mm) needs to be extruded. The thickness is large and the belt will not break during the extrusion and winding process.

[0022] (2) Since the special anti-corrosion polypropylene material of the present invention has the dual functions of bonding and anti-corrosion, there is no need to use adhesives. Therefore, the anti-corrosion equipment can save a single-screw extruder for adhesive extrusion, thereby reducing equipment investment. By combining the adhesive and the special anti-corrosion polypropylene material into one, the preparation process is simplified and the production efficiency is improved.

[0023] (3) The anti-corrosion steel pipe containing anti-corrosion polypropylene special material, combined with 3PP special material, has bonding and anti-corrosion functions, and has comprehensive properties such as excellent mechanical properties, good processing performance, and excellent long-term heat aging resistance. It solves the problem of poor anti-corrosion effect caused by the thin thickness of traditional 3PP anti-corrosion adhesive and easy breakage of glue during the anti-corrosion process. The combination of 3PP anti-corrosion epoxy layer and polypropylene special material layer is more reliable, avoiding the risk of the corrosion layer not being able to be organically combined due to undetected breakage during the traditional 3PP anti-corrosion process. Therefore, the anti-corrosion polypropylene special material can provide better protection for the steel pipe and extend the service life of the anti-corrosion steel pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0025] Figure 1 It is a schematic diagram of the structure of an anti-corrosion steel pipe according to one or more embodiments of the present invention.

[0026] Among them, 1. Steel pipe, 2. Epoxy anti-corrosion layer, 3. Polypropylene special anti-corrosion material layer. DETAILED DESCRIPTION

[0027] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0028] An embodiment of the present invention provides a special anti-corrosion polypropylene material, which comprises the following components in parts by mass:

[0029] 10-30 parts of maleic anhydride grafted polypropylene, 40-70 parts of pipeline grade polypropylene, 5-40 parts of copolymerized polypropylene, 3-10 parts of elastomer, 1-2 parts of rutile titanium dioxide, and 1-2 parts of anti-aging additive.

[0030] In some embodiments, the melt mass flow rate of maleic anhydride grafted polypropylene at 190° C. and 2.16 kg weight is 50-120 g / 10 min, and the maleic anhydride grafting ratio is 0.5%-1.5%.

[0031] In some embodiments, maleic anhydride grafted polypropylene is prepared by the following ratio and process: 70-90 parts of polypropylene with a melt mass flow plastic of 8-40g / min, 10-30 parts of vinyl copolymer, 1-2 parts of maleic anhydride, and 0.05-0.5 parts of peroxide initiator at 230°C and 2.16kg weight; the grafting reaction is carried out by a twin-screw extruder at 180-220°C and a screw speed of 200-400rpm.

[0032] The ethylene copolymer is one of ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-hexene copolymer, ethylene-octene copolymer and ethylene-propylene diene terpolymer.

[0033] The melt mass flow rate of copolymer polypropylene at 230°C and 2.16kg weight is 0.5-3g / min. Pipe-grade polypropylene is a type of homopolymer polypropylene, impact copolymer polypropylene, and random copolymer polypropylene, with a melt mass flow rate of 0.2-0.5g / 10min at 230°C and 2.16kg weight.

[0034] The elastomer is at least one of ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-octene copolymer, styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), and hydrogenated styrene-butadiene-styrene block copolymer (SEBS).

[0035] The anti-aging auxiliary agent is composed of one or more of hindered phenol antioxidants, sulfur-containing hindered phenol antioxidants, phosphite antioxidants, hindered amine light stabilizers and acid absorbers.

[0036] The preparation method of the above-mentioned anticorrosive polypropylene special material is:

[0037] Maleic anhydride grafted polypropylene, pipeline-grade polypropylene, copolymerized polypropylene, elastomer, rutile titanium dioxide and anti-aging additive are mixed in proportion, melt-blended and granulated by a screw extruder at 180-220° C. and a screw speed of 350-500 rpm to obtain 3PP anti-corrosion polypropylene special material.

[0038] The special anti-corrosion polypropylene material prepared by the above method has a melt mass flow rate of 0.5-1.5g / 10min at 230℃ and 2.16kg weight, a yield strength greater than 20MPa, a nominal strain at break greater than 400%, a Vicat softening point greater than 130℃, and a melt mass flow rate change rate of the product after thermal aging at 150℃ for 960h is no more than 35%. The peel strength of epoxy bonding after steel pipe anti-corrosion is: 23±5℃ temperature, ≥300N / cm; 50±5℃ temperature, ≥150N / cm; 110±5℃ temperature, ≥80N / cm.

[0039] The anticorrosive steel pipe prepared based on the above method is as follows Figure 1 As shown, it includes a steel pipe 1, on the outside of which an epoxy anti-corrosion layer 2 and a polypropylene anti-corrosion special material layer 3 are arranged in sequence; that is, according to the 3PP anti-corrosion process, epoxy powder is sprayed and then the anti-corrosion special polypropylene material is wrapped to obtain a steel pipe with double layers of epoxy and anti-corrosion special polypropylene materials.

[0040] Example 1

[0041] Maleic anhydride grafted polypropylene (M1): 70 parts of polypropylene S700 (melt mass flow plastic 14g / 10min, 230°C, 2.16kg weight), 30 parts of ethylene-propylene copolymer Vistamaxx 6202FL, 1.5 parts of maleic anhydride, and 0.5 parts of peroxide initiator di-tert-butyl peroxide diisopropylbenzene were mixed uniformly, and then grafted by a twin-screw extruder at 180°C and a rotation speed of 250rpm to obtain a maleic anhydride grafted polypropylene with a maleic anhydride grafting rate of 1.08% and a melt mass flow plastic 112g / 10min (190°C, 2.16kg weight).

[0042] The anti-corrosion polypropylene special material of this embodiment is composed according to Table 1:

[0043] Table 1 Formula of special anticorrosive polypropylene material in Example 1

[0044]

[0045] The information of the raw materials used in this embodiment is as follows:

[0046] Pipe grade polypropylene: C180, melt mass flow plastic 0.3g / 10min (230℃, 2.16kg weight);

[0047] Copolymer polypropylene: H2462, melt mass flow plastic 0.3g / 10min (230℃, 2.16kg weight);

[0048] Elastomer: Styrene-butadiene-styrene block copolymer, 1301;

[0049] Rutile titanium dioxide: R2219;

[0050] Anti-aging agent: It is mixed with 70% of hindered phenol antioxidant antioxidant 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, 10% of phosphite antioxidant bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphate, 10% of hindered amine light stabilizer 944, and 10% of acid absorbent calcium stearate.

[0051] The specific preparation steps of the anti-corrosion polypropylene special material of this embodiment are:

[0052] The components are uniformly mixed in a mixer according to the proportion, added into a twin-screw extruder, melt-blended at 200° C. and 450 rpm, and granulated to obtain 3PP anti-corrosion polypropylene special material.

[0053] According to SY / T7041-2016, the melt flow rate, yield strength, nominal strain at crack, Vicat softening point, oxidation induction time, and heat aging at 150°C for 960h were tested. The relevant data are shown in Table 5.

[0054] A Φ711mm steel pipe was selected. After shot blasting and rust removal, the steel pipe was preheated by medium frequency, sprayed with epoxy, and extruded with special anti-corrosion polypropylene material before the epoxy gelled. The special anti-corrosion polypropylene material was extruded at 225°C, and the thickness of the anti-corrosion layer was controlled to be 3.2-3.5mm. The peel strength at 20, 50, and 110°C was tested in accordance with SY / T7041-2016. The results are shown in Table 5.

[0055] Example 2

[0056] Maleic anhydride grafted polypropylene (M2): 90 parts of polypropylene K7735H (melt mass flow plastic 40g / 10min, 230°C, 2.16kg weight), 10 parts of ethylene-propylene-diene copolymer NORDEL IP 3760P (Dow Chemical), 2 parts of maleic anhydride, and 0.2 parts of peroxide initiator dicumyl peroxide were mixed uniformly, and then grafted using a twin-screw extruder at 200°C and a rotation speed of 400rpm to obtain a maleic anhydride grafted polypropylene with a maleic anhydride grafting rate of 1.47% and a melt mass flow plastic 65g / 10min (190°C, 2.16kg weight).

[0057] The anti-corrosion polypropylene special material of this embodiment is composed according to Table 2:

[0058] Table 2 Formula of special anticorrosive polypropylene material in Example 2

[0059]

[0060] The information of the raw materials used in this embodiment is as follows:

[0061] Pipe grade polypropylene: H2450, melt mass flow plastic 0.3g / 10min (230℃, 2.16kg weight);

[0062] Copolymer polypropylene: EPS30R, melt mass flow plastic 1.5g / 10min (230℃, 2.16kg weight);

[0063] Elastomer: Ethylene-octene copolymer, 5007;

[0064] Rutile titanium dioxide: BLR-886;

[0065] Anti-aging agent: It is prepared by mixing 50% of hindered phenol antioxidant 1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)1,3,5-triazine-2,4,6-(1H,3H,5H)-trione, 20% of phosphite antioxidant bis(2,4-dicumylphenyl)pentaerythritol-diphosphite, 10% of hindered amine light stabilizer 622, 10% of ultraviolet light absorber 3,5-di-tert-butyl-4-hydroxybenzoic acid hexadecyl ester, and 10% of acid absorber magnesium oxide.

[0066] The specific preparation steps of the anti-corrosion polypropylene special material of this embodiment are:

[0067] The components were mixed evenly in a mixer according to the proportion, added into a twin-screw extruder, melt-blended at 210° C. and 480 rpm, and granulated to obtain 3PP anti-corrosion polypropylene special material.

[0068] According to SY / T7041-2016, the melt flow rate, yield strength, nominal strain at crack, Vicat softening point, oxidation induction time, and heat aging at 150°C for 960h were tested. The relevant data are shown in Table 5.

[0069] A Φ711mm steel pipe was selected. After shot blasting and rust removal, the steel pipe was preheated by medium frequency, sprayed with epoxy, and extruded with special anti-corrosion polypropylene material before the epoxy gelled. The special anti-corrosion polypropylene material was extruded at 210°C, and the thickness of the anti-corrosion layer was controlled to be 3.2-3.5mm. The peel strength at 20, 50, and 110°C was tested in accordance with SY / T7041-2016. The results are shown in Table 5.

[0070] Comparative Example 1

[0071] Maleic anhydride grafted polypropylene (M1) is the same as in Example 1, and the raw materials used are the same as in Example 1.

[0072] The anti-corrosion polypropylene special material in Comparative Example 1 is composed according to Table 3:

[0073] Table 3 Formula of special anticorrosive polypropylene material in comparative example 1

[0074]

[0075] The specific preparation steps of anti-corrosion polypropylene special material are:

[0076] The components are uniformly mixed in a mixer according to the proportion, added into a twin-screw extruder, melt-blended at 200° C. and 450 rpm, and granulated to obtain a special anti-corrosion polypropylene material.

[0077] According to SY / T7041-2016, the melt flow rate, yield strength, nominal strain at crack, Vicat softening point, oxidation induction time, and heat aging at 150°C for 960h were tested. The relevant data are shown in Table 5.

[0078] A Φ711mm steel pipe was selected. After shot blasting and rust removal, the steel pipe was preheated by medium frequency, sprayed with epoxy, and extruded with special anti-corrosion polypropylene material before the epoxy gelled. The special anti-corrosion polypropylene material was extruded at 225°C, and the thickness of the anti-corrosion layer was controlled to be 3.2-3.5mm. The peel strength at 20, 50, and 110°C was tested in accordance with SY / T7041-2016. The results are shown in Table 5.

[0079] Comparative Example 2

[0080] Maleic anhydride grafted polypropylene (M2) is the same as in Example 2, and the raw materials used are the same as in Example 2.

[0081] The anticorrosive polypropylene special material of Comparative Example 2 is composed according to Table 4:

[0082] Table 4 Formula of special anticorrosive polypropylene material in comparative example 2

[0083]

[0084] The specific steps for preparing special anti-corrosion polypropylene materials are as follows:

[0085] The components are uniformly mixed in a mixer according to the proportion, added into a twin-screw extruder, melt-blended at 210° C. and 480 rpm, and granulated to obtain a special anti-corrosion polypropylene material.

[0086] According to SY / T7041-2016, the melt flow rate, yield strength, nominal strain at crack, Vicat softening point, oxidation induction time, and heat aging at 150°C for 960h were tested. The relevant data are shown in Table 5.

[0087] A Φ711mm steel pipe was selected. After shot blasting and rust removal, the steel pipe was preheated by medium frequency, sprayed with epoxy, and extruded with special anti-corrosion polypropylene material before the epoxy gelled. The special anti-corrosion polypropylene material was extruded at 210°C, and the thickness of the anti-corrosion layer was controlled to be 3.2-3.5mm. The peel strength at 20, 50, and 110°C was tested in accordance with SY / T7041-2016. The results are shown in Table 5.

[0088] Table 5 Test and application effect data of embodiments and comparative examples

[0089]

[0090]

[0091] It can be seen from Examples 1 to 2 that the anti-corrosion polypropylene special material prepared according to the ratio of the present invention meets the requirements of SY / T7041-2016 in all indicators, especially after being used for steel pipe anti-corrosion to replace the traditional three-layer anti-corrosion system of epoxy / adhesive / polypropylene special material, and the anti-corrosion layer has higher peeling strength: 23±5℃ temperature, ≥300N / cm; 50±5℃ temperature, ≥150N / cm; 110±5℃ temperature, ≥80N / cm.

[0092] By comparing 1A, 1B, 1C of Example 1 and Comparative Example 3A, it can be seen that adding 10-30 parts of maleic anhydride grafted polypropylene to the anti-corrosion polypropylene special material can make the anti-corrosion special material have the function of an adhesive, achieve effective bonding to the epoxy powder, and the peel strength of the anti-corrosion layer reaches: 23±5℃ temperature, ≥300N / cm; 50±5℃ temperature, ≥150N / cm; 110±5℃ temperature, ≥80N / cm.

[0093] From the comparison between 1A and 3A, it can be seen that when maleic anhydride grafted polypropylene is not added to the special anti-corrosion polypropylene material, the special material has no adhesion to the epoxy coating. At this time, there is no bonding force between the epoxy coating on the surface of the steel pipe and the special polypropylene anti-corrosion material. The two coatings of different polarities do not form an organic whole, and the durability of the anti-corrosion coating is poor. From the comparison between 1A and 3B, it can be seen that when the addition of maleic anhydride grafted polypropylene in the special anti-corrosion polypropylene material is less than 10 parts, even if the peeling at 20°C is qualified, the peeling strength at 110°C is lower than the standard requirement. From the comparison of 1C, 3C and 3D, it can be seen that when the addition of maleic anhydride grafted polypropylene in the special material for anti-corrosion polypropylene is higher than 30 parts, the peel strength of the anti-corrosion is not improved, especially the high-temperature peel strength becomes lower. This is mainly because the bonding strength is related to the cohesive strength of the maleic anhydride grafted polypropylene masterbatch and the special material for anti-corrosion. When the maleic anhydride reaches a certain proportion, the cohesive strength of the special material needs to be further improved to further improve the peel strength. Excessive addition of maleic anhydride grafted polypropylene will cause the degradation of the polypropylene grafted masterbatch to be serious, the melt index to increase, and the cohesive strength to decrease sharply due to the degradation side reaction of polypropylene during the grafting reaction. The content of maleic anhydride grafted polypropylene increases, which reduces the proportion of high cohesive polypropylene in the formula system, thereby causing the cohesive force of the special material for polypropylene to decrease and the high-temperature peel strength to decrease. It can be seen that the addition ratio of maleic anhydride grafted polypropylene is preferably 10-30 parts.

[0094] By comparing 2A, 2B, 2C and 4A in Example 2, it can be seen that adding 3-10 parts of elastomer to the special material for anti-corrosion polypropylene can improve the excellent mechanical properties and processing properties of the special material for anti-corrosion polypropylene, and good bonding strength. 4A without adding elastomer has the problem of unqualified nominal strain at break, and 4A is stretched thin during the anti-corrosion process, and melt fracture is prone to occur during the winding process. By comparing 2C with 4B and 4C, it can be seen that when the elastomer in the special material for anti-corrosion polypropylene exceeds 10 parts, although the nominal strain at break of the special material will be improved, the yield strength of the special material will be lower than 20MPa and the Vicat softening point will be lower than 130°C, and the high temperature peel strength, especially the 110°C peel strength is reduced and lower than the 40N / cm required by SY / T7041-2016, is mainly due to the low softening point and low cohesive strength of the elastomer itself. Although the toughness and processability of the special material can be improved, the strength and bonding force of the special material are also reduced.

[0095] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A special anti-corrosion polypropylene material, characterized in that: The following components are included by mass: 10-30 parts of maleic anhydride grafted polypropylene, 40-70 parts of pipeline grade polypropylene, 5-40 parts of copolymerized polypropylene, 3-10 parts of elastomer, 1-2 parts of rutile titanium dioxide, and 1-2 parts of anti-aging additive.

2. The anti-corrosion polypropylene special material according to claim 1, characterized in that: The maleic anhydride grafted polypropylene consists of the following components: Polypropylene 70-90 parts, vinyl copolymer 10-30 parts, maleic anhydride 1-2 parts, peroxide initiator 0.05-0.5 parts.

3. The anti-corrosion polypropylene special material according to claim 1, characterized in that: The pipeline-grade polypropylene is one of homopolymer polypropylene, impact copolymer polypropylene and random copolymer polypropylene; 230℃, 2.16kg weight melt mass flow rate is 0.2-0.5g / 10min.

4. The anti-corrosion polypropylene special material according to claim 1, characterized in that: The copolymerized polypropylene has a melt mass flow rate of 0.5-3 g / min at 230° C. and a weight of 2.16 kg.

5. The anti-corrosion polypropylene special material according to claim 1, characterized in that: The elastomer is at least one of ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-octene copolymer, styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer and hydrogenated styrene-butadiene-styrene block copolymer.

6. The anti-corrosion polypropylene special material according to claim 1, characterized in that: The anti-aging aid is one or more of hindered phenol antioxidants, sulfur-containing hindered phenol antioxidants, phosphite antioxidants, hindered amine light stabilizers, ultraviolet light stabilizers, and acid absorbers.

7. A special anti-corrosion polypropylene material according to any one of claims 1 to 6, characterized in that: The melt mass flow rate of the special anti-corrosion polypropylene material is 0.5-1.5g / 10min at 230°C and 2.16kg weight, the yield strength is greater than 20MPa, the nominal strain at break is greater than 400%, the Vicat softening point is greater than 130°C, the melt mass flow rate change rate of the product after heat aging at 150°C for 960h is not greater than 35%, and the peel strength of epoxy bonding after steel pipe anti-corrosion is: at 23±5°C, ≥300N / cm; at 50±5°C, ≥150N / cm; at 110±5°C, ≥80N / cm.

8. The method for preparing a special anti-corrosion polypropylene material according to any one of claims 1 to 7, characterized in that: Maleic anhydride grafted polypropylene, pipeline-grade polypropylene, copolymerized polypropylene, elastomer, rutile titanium dioxide and anti-aging additive are mixed in a set ratio, and melt-blended and granulated by a screw extruder at 180-220° C. and a screw speed of 350-500 rpm to obtain the special anti-corrosion polypropylene material.

9. The method for preparing a special anti-corrosion polypropylene material according to claim 8, characterized in that: The preparation method of the maleic anhydride grafted polypropylene is: At 230° C. and 2.16 kg weight, 70-90 parts of polypropylene with a melt mass flow plastic of 8-40 g / min, 10-30 parts of vinyl copolymer, 1-2 parts of maleic anhydride, and 0.05-0.5 parts of peroxide initiator are mixed, and a grafting reaction is carried out at 180-220° C. through a twin-screw extruder, wherein the screw speed is 200-400 rpm.

10. An anti-corrosion steel pipe, characterized in that: It comprises a steel pipe, the outer side of which is provided with an epoxy anti-corrosion layer and a polypropylene anti-corrosion special material layer in sequence, wherein the polypropylene anti-corrosion special material layer is made by the preparation method as described in claim 8 or 9.

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