Polyethylene composition powder as well as preparation method and application thereof

Abstract

The invention discloses polyethylene composition powder as well as a preparation method and application thereof. The polyethylene powder is prepared from 100 parts by weight of polyethylene resin, 0.2-2 parts by weight of a vinyl silane coupling agent and 0.002-1 part by weight of an initiator. The polyethylene composite material powder with high sphericity and uniformity is successfully prepared by innovatively modifying a polyethylene material and combining a conventional grinding process and an underwater pelletizing technology. The whole technological process is more concise and efficient, and the prepared product is particularly suitable for being applied to linings of hot water steel pipes and hot water storage tanks.

Description

Technical Field

[0001] The invention relates to thermoplastic powder coating for coaches, in particular to polyethylene composition powder and a preparation method and application thereof. Background Art

[0002] Improving the corrosion resistance of carbon steel by lining is a common method. Polyolefins, such as PPR and polybutylene pipes, are mostly used directly in hot water pipes because of their low price and good water and corrosion resistance. However, polyethylene cannot be directly used in hot water pipes or as a lining material because its long-term use temperature is 70°C. However, polyethylene has a good anti-corrosion effect on corrosive media such as acids, alkalis, seawater, and oils at room temperature, and its price is low, so it is mostly used for the lining anti-corrosion of hot rotomolded steel pipes.

[0003] Polyethylene is cross-linked to increase its heat resistance temperature to about 90°C before it can be used as the inner lining of hot roto-molded steel pipes. Common polyethylene cross-linking methods include radiation cross-linking, peroxide cross-linking and new silane cross-linking. Silane cross-linking slowly cross-links under the action of moisture or hot water after roto-molding, which can be well matched with the roto-molding process. However, the type and properties of polyethylene have a great influence on the silane cross-linking reaction. Different types of polyethylene (such as high-density polyethylene, low-density polyethylene, etc.) have different molecular chain structures and properties. Therefore, the selection of suitable polyethylene, coupling agents, catalysts for cross-linking, as well as the pretreatment of raw materials and the control of the mixing process are key factors in determining the quality of the roto-molding process. Summary of the invention

[0004] In view of this, the present invention provides a polyethylene composition powder and a preparation method and application thereof to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] On one hand, the present invention discloses a polyethylene composition powder, which is prepared by weight from 100 parts of polyethylene resin, 0.2-2 parts of vinyl silane coupling agent and 0.002-1 parts of initiator.

[0007] As a further solution of the present invention: the polyethylene resin is at least one of high-density polyethylene, low-density polyethylene, and linear low-density polyethylene.

[0008] As a further solution of the present invention: the polyethylene resin may contain no more than 10w% of other ethylene monomers, and the other monomers are at least one of 1-butene, 1-hexene, 1-octene, and vinyl acetate.

[0009] As a further solution of the present invention: the vinyl silane coupling agent is at least one of vinyl trimethoxy silane, vinyl tri (β-methoxyethoxy) silane, and vinyl triethoxy silane.

[0010] As a further solution of the present invention: when the half-life is 1 minute, the decomposition temperature of the initiator is greater than 140°C.

[0011] As a further embodiment of the present invention: the initiator is at least one of dicumyl peroxide, di-tert-butyl peroxide and 2,4-di-tert-butyl cumyl peroxide of the alkyl peroxide type.

[0012] As a further solution of the present invention: its melt index under the conditions of 190° C. and 2.16 kg is not less than 5 g / 10 min.

[0013] Another aspect of the present invention discloses a method for preparing the above-mentioned polyethylene composition powder, comprising the following steps:

[0014] The polyethylene resin, the vinyl silane coupling agent and the initiator are fully mixed according to weight parts, and then put into a twin-screw extruder, and extruded at a working temperature of 180-220° C. to obtain polyethylene composition pellets;

[0015] The polyethylene composition pellets are pelletized underwater to obtain polyethylene composition powder with an average particle size of less than 0.5 mm.

[0016] In a third aspect, the present invention discloses the use of the above-mentioned polyethylene composition as a hot water steel pipe lining or a hot water storage tank lining.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention successfully prepares a polyethylene composite powder with high sphericity and uniformity by innovatively modifying polyethylene materials and combining conventional grinding technology with underwater pelletizing technology. This overall process is more concise and efficient, and the resulting product is particularly suitable for lining applications in hot water steel pipes and hot water storage tanks. Its outstanding heat resistance allows it to maintain excellent performance even in high temperature environments, and the effect is more ideal after rotational molding. The resulting coating is not only smooth and delicate, but also completely free of bubbles, which significantly improves the practical value of the product. DETAILED DESCRIPTION

[0019] For ease of understanding of the present invention, the present invention will be described more fully below in conjunction with specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thoroughly understood.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0021] The specific information of the raw materials used in the following examples and comparative examples is as follows:

[0022] Polyethylene 1: DNDA7144, LLDPE, MI = 20g / 10min, manufactured by Sinopec;

[0023] Polyethylene 2: SH2902, HDPE, MI = 29g / 10min, manufactured by Sinopec;

[0024] Polyethylene copolymer: EVA, V3510K, MI = 5g / 10min, manufactured by BASF-Yangzi;

[0025] Silane coupling agent 1: Silquest A-172, vinyl tris (2-methoxyethoxy) silane, CAS No. 1067-53-4, manufactured by Momentive;

[0026] Silane coupling agent 2: Silquest A-151, vinyl triethoxysilane, CAS No. 78-08-0, manufactured by Momentive;

[0027] Initiator: 2,4-di-tert-butyl peroxide isopropylbenzene (BIBP), CAS No. 25155-25-3;

[0028] All materials are commercially available common products.

[0029] It is to be understood that the above raw materials and reagents are only examples of some specific embodiments of the present invention, so that the technical solution of the present invention is clearer, and it does not mean that the present invention can only use the above reagents, and the specific scope in the claims shall prevail. In addition, the "parts" described in the examples and comparative examples, unless otherwise specified, refer to parts by weight.

[0030] Any range described in the present invention includes the end value and any numerical value between the end values ​​and any sub-range formed by the end value or any numerical value between the end values.

[0031] The equipment information used in the embodiments and comparative examples is as follows:

[0032] Screw extruder: 40 mm diameter screw, Leistritz Machinery, Germany;

[0033] Underwater pelletizer: HCH underwater pelletizer unit, Wuxi Huachen Electromechanical;

[0034] Mill: Reduction Engineering Scheer REX Technology, MAAG USA.

[0035] Table 1: Allocation ratio of each embodiment and comparative example

[0036]

[0037]

[0038] The process steps of Examples 1-4 and Comparative Example 1 are as follows:

[0039] Step 1, weigh each component according to Table 1 above and mix them evenly, put them into an extruder, extrude them at 210°C at a feeding rate of 10 kg / h, and obtain polyethylene composition pellets; the temperature of zone 1 of the extruder is 90°C, the temperature of zone 2 is 130°C, the temperature of zone 3 is 190°C, the temperatures of zones 4 to 10 are all 210°C, the temperature of zone 11 is 200°C, and the temperature of the die head is 200°C;

[0040] Step 2: The obtained polyethylene composition pellets are transported to an underwater pelletizing device through a melt pump for pelletization to obtain polyethylene composition powder with a particle size D50 less than 0.5 mm.

[0041] The process steps of Comparative Examples 2 and 3 are as follows:

[0042] Step 1, weigh each component according to Table 1 above and mix them evenly, put them into an extruder, extrude them at 210°C at a feeding rate of 10 kg / h, and obtain polyethylene composition pellets; the temperature of zone 1 of the extruder is 90°C, the temperature of zone 2 is 130°C, the temperature of zone 3 is 190°C, the temperatures of zones 4 to 10 are all 210°C, the temperature of zone 11 is 200°C, and the temperature of the die head is 200°C;

[0043] Step 2: Use a grinding machine to grind the obtained polyethylene composition pellets to less than 30 meshes to obtain polyethylene composition powder.

[0044] The polyethylene composition powder obtained in each embodiment and comparative example was roto-molded on a 3mm thick steel pipe to obtain a 2mm composition coating. The roto-molding process is as follows: the powder is put into an iron pipe, and the external part is heated by flame or hot air to a temperature of 220-260°C. At the same time, the steel pipe is driven to roll with a roller to make the coating thickness uniform, and this condition is maintained for >20 minutes. Then, the coated thick steel pipe is put into 80°C hot water and boiled for 72 hours. The gel content, repose angle and powder particle size span of the coating before and after boiling are tested. The test standards / methods are as follows:

[0045] Melt index: refer to GB / T 3682.1-2018, 230℃, 2.16kg;

[0046] Gel content: The gel content of polyethylene is determined by the xylene reflux method, with specific reference to GB / T 18474-2001;

[0047] Powder fluidity: refer to GB / T 11986-1989, put the powder into a conical funnel, open the switch at the bottom of the conical funnel, let the powder fall onto the flat plate below, and measure the bottom angle of the cone formed by the powder, which is the angle of repose;

[0048] Particle size and distribution: Refer to GB_T 41949-2022, use the laser particle size analyzer method to test the powder particle size, and then calculate the span based on the measured particle size value, powder particle size span = (D90-D10) / D50.

[0049] The test results are shown in Table 2.

[0050] Table 2

[0051]

[0052] According to the comparison between Example 1 and Comparative Example 1, since no silane coupling agent and initiator are added in Comparative Example 1, there is almost no gel and no crosslinking occurs. Therefore, it can be judged that the heat resistance temperature is low according to the gel content.

[0053] Comparing Example 2 with Comparative Example 2, the crosslinking degrees of the two are similar. However, since the powder fluidity of Comparative Example 2 is poor and air is trapped during the rotational molding process, the appearance is not as good as that of Example 2 with a higher sphericity.

[0054] Comparison of Examples 3 and 4 with Comparative Example 3 shows that due to the poor sphericity of Comparative Example 3, air is trapped during rotational molding to form bubbles, and the surface is not smooth due to the bubbles, while Examples 3 and 4 have no appearance problems.

[0055] Although this specification is described according to implementation modes, not every implementation mode includes only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

[0056] Therefore, the above description is only a preferred embodiment of the present application and is not intended to limit the scope of implementation of the present application; that is, all equivalent changes made according to the scope of the claims of the present application are within the protection scope of the claims of the present application.

Claims

1. A polyethylene composition powder, characterized in that: The invention is prepared from 100 parts of polyethylene resin, 0.2-2 parts of vinyl silane coupling agent and 0.002-1 parts of initiator according to weight parts.

2. The polyethylene composition powder according to claim 1, characterized in that: The polyethylene resin is at least one of high-density polyethylene, low-density polyethylene and linear low-density polyethylene.

3. The polyethylene composition powder according to claim 1, characterized in that: The polyethylene resin may contain no more than 10w% of other ethylene monomers, and the other monomers are at least one of 1-butene, 1-hexene, 1-octene, and vinyl acetate.

4. The polyethylene composition powder according to claim 1, characterized in that: The melt index of the polyethylene resin is 10-40 g / 10 min at 190° C. and 2.16 kg.

5. The polyethylene composition powder according to claim 1, characterized in that: The vinyl silane coupling agent is at least one of vinyl trimethoxy silane, vinyl tri (β-methoxyethoxy) silane and vinyl triethoxy silane.

6. The polyethylene composition powder according to claim 1, characterized in that: When the half-life is 1 min, the decomposition temperature of the initiator is greater than 140°C.

7. The polyethylene composition powder according to claim 1, characterized in that: The initiator is at least one of alkyl peroxides such as dicumyl peroxide, di-tert-butyl peroxide and 2,4-di-tert-butyl cumyl peroxide.

8. The polyethylene composition powder according to claim 1, characterized in that: Its melt index at 190°C and 2.16 kg is not less than 5g / 10min.

9. A method for preparing the polyethylene composition powder according to any one of claims 1 to 8, characterized in that: The following steps are involved: The polyethylene resin, the vinyl silane coupling agent and the initiator are fully mixed according to weight parts, and then put into a twin-screw extruder, and extruded at a working temperature of 180-220° C. to obtain polyethylene composition pellets; The polyethylene composition pellets are pelletized underwater to obtain polyethylene composition powder with an average particle size of less than 0.5 mm.

10. Use of the polyethylene composition according to any one of claims 1 to 8 as a hot water steel pipe lining or a hot water storage tank lining.

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