A tubular process low density polyethylene composition and a process for its preparation and use

Abstract

The application relates to the technical field of polyethylene preparation, in particular to a tubular method low-density polyethylene composition and a preparation method and application thereof. The composition product of the application retains the advantages of high productivity and low cost of the tubular method process, the cost is 10-15% lower than that of a kettle method product, the production cost of a coating material can be greatly reduced, the market competitiveness of the product is improved, the composition product can be widely applied to the fields of high-end paper-plastic composite materials, food packaging, heavy packaging and the like, can completely replace the kettle method product, and has extremely high market application value. The preparation method provided by the application does not need to adjust the polymerization process of the tubular method, only needs to add a functional master batch with a specific composition in an extrusion granulation process, so that the performance can be improved, the compatibility is high, the existing tubular method device can be directly modified, large-scale equipment modification is not needed, the cost is low, and the method is easy to implement.

Description

Technical Field

[0001] This application relates to the field of polyethylene material technology, specifically to a tubular low-density polyethylene composition, its preparation method, and its application. Background Technology

[0002] Low-density polyethylene (LDPE) coating material is the core raw material for extrusion coating processes and is widely used in paper-plastic composites, aluminum-plastic composites, plastic-plastic composites, food packaging, heavy packaging and other fields. Its core performance requirements are excellent coating performance, including hot tack strength, peel strength, processing flowability and film-forming properties, to ensure the bonding performance and processing stability of composite products.

[0003] Currently, LDPE production processes are mainly divided into two types: batch reactor and tubular reactor. The batch reactor process has a long reaction residence time, resulting in the formation of more long branches during polymerization (approximately 6-9 branches with ≥6 carbon atoms per 1000C). This leads to a wide molecular weight distribution (approximately 8.0-20.0), resulting in excellent coating performance and making it the mainstream production process for high-end coatings. However, the batch reactor process has low capacity, high cost, and relatively low product purity. The tubular reactor process, on the other hand, has high reaction pressure and short residence time, producing products with low long-branch content and a narrow molecular weight distribution. This results in poor coating performance, low hot-tack strength, and insufficient peel strength, failing to meet the demands of high-end coating applications. However, the tubular reactor process has high capacity, low cost, and high product purity. If its coating performance shortcomings can be addressed, the production cost of coatings can be significantly reduced, enhancing product competitiveness.

[0004] Extensive research has been conducted on existing technologies to address the performance deficiencies of tubular coatings. For example, existing patent literature discloses a method for preparing tubular LDPE coatings by adjusting the initiator system in the polymerization process to increase the generation of long branches. However, this method is limited by the residence time inherent in the tubular process, resulting in a limited amount of long branches and minimal improvement in coating performance. Other patent literature discloses a method to improve coating performance by adding long-chain α-olefins during polymerization. However, this method leads to decreased stability of the polymerization reaction, a high risk of explosive polymerization, and high costs. Some existing technologies attempt to add peroxides during granulation to adjust the molecular weight distribution through degradation. However, the addition of peroxides easily triggers cross-linking reactions, leading to gelation in the product and severely affecting the appearance and performance of the coated product. Furthermore, improvements in other aspects of coating performance are limited.

[0005] In view of this, the industry urgently needs a technology that can effectively improve the performance of tubular LDPE coatings, thereby broadening the molecular weight distribution and increasing the content of long branches without generating gels, so that the coating performance of tubular products can reach or even exceed that of batch process products, while retaining the advantages of tubular process such as large capacity and low cost. Summary of the Invention

[0006] This application provides a tubular low-density polyethylene composition, its preparation method, and its application, to solve the problems of poor coating performance, low hot adhesion strength, and insufficient peel strength of tubular LDPE coatings in the prior art.

[0007] In a first aspect, this application provides a tubular low-density polyethylene composition, comprising, by weight, the following components in parts: Tubular LDPE matrix: 90-95 parts; Polyethylene functional masterbatch: 5-10 parts; The total mass of the polyethylene functional masterbatch includes the following components in parts by mass: Low melt index LDPE matrix: 95.0-98.0 parts; Polybutadiene: 0.5-1.0 parts; Free radical initiator: 0.01-0.02 parts; Antioxidant: 0.5-0.8 parts.

[0008] As an example, the amount of tubular LDPE matrix, based on the total mass of the composition, can be 90 parts, 91 parts, 92 parts, 93 parts, 94 parts, 95 parts, or within any of the above values; the amount of polyethylene functional masterbatch can be 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, or within any of the above values.

[0009] As an example, based on the total mass of the polyethylene functional masterbatch, the amount of low melt index LDPE matrix can be 95.0 parts, 95.5 parts, 96.0 parts, 96.5 parts, 97.0 parts, 97.5 parts, 98.0 parts, or within any range of the above values; the amount of polybutadiene can be 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1.0 parts, or within any range of the above values; the amount of free radical initiator can be 0.01 parts, 0.012 parts, 0.015 parts, 0.018 parts, 0.02 parts, or within any range of the above values; and the amount of antioxidant can be 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, or within any range of the above values.

[0010] In one optional embodiment, the melt index of the low melt index LDPE matrix is ​​0.2-4.0 g / 10 min; as an example, the melt index of the low melt index LDPE matrix can be 0.2 g / 10 min, 0.25 g / 10 min, 0.3 g / 10 min, 0.35 g / 10 min, 0.4 g / 10 min, 0.45 g / 10 min, 0.5 g / 10 min, 1.0 g / 10 min, 1.5 g / 10 min, 2.0 g / 10 min, 2.5 g / 10 min, 3.0 g / 10 min, 3.5 g / 10 min, 4.0 g / 10 min, or within any range of the above values.

[0011] In one alternative embodiment, the density of the low melt flow index LDPE matrix is ​​0.918-0.925 g / cm³. 3 As an example, the density of the low melt flow index LDPE matrix is ​​0.918 g / cm³. 3 0.919 g / cm 3 0.920 g / cm 3 0.921 g / cm 3 0.922 g / cm 3 0.923 g / cm 3 0.924 g / cm 3 0.925g / cm 3 , or within the range of any of the above values.

[0012] In one optional embodiment, the number-average molecular weight of the polybutadiene is 1000-10000; optionally, it is 1500-6000. As an example, the number-average molecular weight of the polybutadiene is 1000, 1500, 2000, 3000, 4000, 5000, 6000, 8000, 10000, or within any range of the above values.

[0013] In one optional embodiment, the antioxidant includes at least one of phosphate ester antioxidants and hindered phenolic antioxidants; In one optional embodiment, the antioxidant comprises a phosphate ester antioxidant and a hindered phenolic antioxidant in a mass ratio of 3-5:2-3.

[0014] As an example, the mass ratio of phosphate ester antioxidants to hindered phenolic antioxidants in the antioxidant is 3:2, 3:2.5, 3:3, 4:2, 5:2, 4:3, 5:3, or within any range of these values. Using both antioxidants in combination avoids the problems of yellowing and increased gel crystal points during coating, which occur when using only hindered phenolic antioxidants; and the oxidative embrittlement of the finished product during prolonged storage (e.g., 3-6 months), which occurs when using only phosphite ester antioxidants.

[0015] In one optional embodiment, the free radical initiator includes a peroxide-based free radical initiator, optionally including at least one of 1,3-bis(tert-butylperoxyisopropyl)benzene, dicumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-di-tert-butylperoxycyclohexane, and benzoyl peroxide.

[0016] In one optional embodiment, the tubular LDPE matrix has a melt index of 6.0-8.0 g / 10 min and a density of 0.915-0.920 g / cm³. 3 .

[0017] As an example, the melt index of the tubular LDPE matrix can be 6.0 g / 10 min, 6.5 g / 10 min, 7 g / 10 min, 7.5 g / 10 min, 8 g / 10 min, or within any range of the above values; the density can be 0.915 g / cm³. 3 0.916 g / cm 3 0.917 g / cm 3 0.918 g / cm³ 3 0.919 g / cm 3 0.920 g / cm 3 , or within the range of any of the above values.

[0018] In one optional embodiment, the molecular weight distribution (PDI) of the tubular LDPE matrix is ​​4.0-7.0, and the number of long branches with ≥6 carbon atoms is 1.5-4.0 per 1000C. As an example, the PDI of the tubular LDPE matrix can be 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, or any value within the range above; the number of long branches with ≥6 carbon atoms can be 1.5 per 1000C, 2.0 per 1000C, 2.5 per 1000C, 3.0 per 1000C, 3.5 per 1000C, 4.0 per 1000C, or any value within the range above.

[0019] Secondly, this application provides a method for preparing the above-mentioned tubular low-density polyethylene composition, comprising the following steps: S1, low melt index LDPE matrix, polybutadiene, free radical initiator and antioxidant are mixed and melt extruded into granules to obtain polyethylene functional masterbatch; S2, the polyethylene functional masterbatch is blended with the tubular LDPE matrix, and then melt-extruded and granulated to obtain the tubular low-density polyethylene composition.

[0020] In one optional embodiment, in S1, the mixing speed is 1000-1200 rpm and the mixing temperature is 50-60°C. As an example, in S1, the mixing speed can be 1000 rpm, 1050 rpm, 1100 rpm, 1150 rpm, 1200 rpm, or within any range of the above values; the mixing temperature can be 50°C, 53°C, 55°C, 58°C, 60°C, or within any range of the above values.

[0021] In one optional embodiment, in S1, the extrusion temperature is 120-140°C and the rotation speed is 150-180 rpm. As an example, in S1, the extrusion temperature can be 120°C, 125°C, 130°C, 135°C, 140°C, or any range thereof; the rotation speed can be 150 rpm, 155 rpm, 160 rpm, 165 rpm, 170 rpm, 175 rpm, 180 rpm, or any range thereof.

[0022] In one optional embodiment, in S2, the extrusion temperature is 180-200°C and the rotation speed is 200-220 rpm. As an example, in S2, the extrusion temperature can be 180°C, 185°C, 190°C, 195°C, 200°C, or any range thereof; the rotation speed can be 200 rpm, 205 rpm, 210 rpm, 215 rpm, 220 rpm, or any range thereof.

[0023] In one alternative embodiment, the tubular LDPE matrix can be obtained commercially or prepared in a laboratory. The specific preparation method is conventional and typically non-limiting within the art; laboratory preparation may include the following steps: (1) Ethylene monomer is pressurized to a reaction pressure of 220~300MPa by a secondary compressor, preheated to a reaction start temperature of 140~170℃ by a preheater, and fed into a tubular reactor; (2) Organic peroxide initiators are injected into multiple reaction zones of the tubular reactor. The initiators include one or more combinations of tert-butyl peroxypentanoate, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxy-3,5,5-trimethylhexanoate, and di-tert-butyl peroxide. The total amount of initiator is 0.005%~0.02% of the mass of ethylene; (3) The tubular reactor adopts a multi-point feeding and multi-zone temperature control process. The peak reaction temperature is controlled at 280~320℃, and the reaction residence time is 60~120 seconds; (4) The reaction products are separated by a high-pressure separator and a low-pressure separator. Unreacted ethylene is recycled by a circulating compressor; (5) The separated polymer is extruded, granulated, and dried to obtain tubular LDPE matrix resin.

[0024] Thirdly, this application provides an application of the above-mentioned tubular low-density polyethylene composition or the tubular low-density polyethylene composition prepared by the above-mentioned preparation method in paper-plastic composites, plastic-plastic composites, aluminum-plastic composites, fabric-coated materials, and building geosynthetics.

[0025] Specifically, in the building materials and geotechnical industry, tubular low-density polyethylene compositions are often processed into waterproof membranes, waterproof coatings, and building moisture-proof films, which can effectively prevent foundations and ground surfaces from getting damp and extend the service life of buildings.

[0026] In this application, a tubular process is used to polymerize ethylene to obtain a molten material of tubular LDPE matrix, which is then blended with polyethylene functional masterbatch and melt-extruded into granules. The operating parameters of the tubular process polymerization are conventional in the field, and those skilled in the art can adjust them according to the actual situation.

[0027] In this application, the low melt flow index LDPE matrix can be obtained through commercial channels, such as at least one of Wanhua Chemical 2420D and 2420H, and Daqing Petrochemical 1810E; the low melt flow index LDPE itself has a high molecular weight and a certain content of long branches, which can provide high molecular weight components for the product of this application, and can be used to broaden the molecular weight distribution.

[0028] In this application, polybutadiene acts as a chain transfer agent, which can regulate the reaction pathway of free radicals during the reaction initiated by the free radical initiator, avoid coupling and cross-linking between free radicals, thereby preventing gel formation, and at the same time promote the formation of long branches.

[0029] In this application, the amount of the free radical initiator added is ≤0.02 parts, which can initiate the grafting reaction between the molecular chains of low melt index LDPE and the molecular chains of matrix LDPE to generate long branched structures. At the same time, the amount added is controlled to be ≤0.02 parts to avoid excessive initiation leading to crosslinking reaction and increased gel content.

[0030] In this application, the role of the antioxidant is to promptly terminate the remaining free radicals after the extrusion reaction is completed, avoid over-reaction, and at the same time improve the long-term thermo-oxidative stability of the product, preventing aging and discoloration during processing and use.

[0031] The tubular low-density polyethylene composition provided in this application contains polybutadiene with a high double bond content. Combined with a low addition amount of free radical initiator, it can generate a controllable slight cross-linking reaction during granulation, increasing the content of long branches while avoiding excessive cross-linking. At the same time, the antioxidant terminates the remaining free radicals in time, ensuring that the gel content of the product is ≤0.08% and there are no gel defects. By adding low melt index LDPE products, the molecular weight distribution is broadened and the content of long branches is increased. In synergy with polybutadiene, the coating performance of the product reaches or even exceeds the level of batch process products, while retaining the advantages of high production capacity and low cost of tubular process products.

[0032] Specifically, the method for preparing the above-mentioned high-performance tubular LDPE composition provided in this application includes the following steps: S1: Preparation of polyethylene functional masterbatch: Weigh low melt index LDPE, polybutadiene, free radical initiator, and antioxidant according to the proportion, add them to a high-speed mixer, mix at 1000-1200 rpm for 8-10 min, and control the mixing temperature at 50-60℃ to obtain a premix; then add the premix to a twin-screw extruder for melt extrusion granulation at an extrusion temperature of 120-140℃ and a screw speed of 150-180 rpm to obtain polyethylene functional masterbatch; S2: Tubular polymerization: Using a tubular process, ethylene polymerization is carried out under pressure of 250-300MPa and temperature of 180-280℃ to obtain molten material of tubular LDPE matrix; S3: Extrusion Blending and Granulation: The polyethylene functional masterbatch obtained in step S1 is added to a twin-screw extruder in a certain proportion and blended with the tubular LDPE matrix melt material obtained in step S2. The mixture is then extruded and granulated at an extrusion temperature of 180-200℃ and a screw speed of 200-220rpm. During the extrusion process, a free radical initiator initiates a grafting reaction to generate long branches. After the reaction is completed, the mixture is extruded and granulated to obtain a high-performance tubular LDPE composition.

[0033] The preparation method provided in this application does not require adjustment to the tubular polymerization process. Performance improvement can be achieved simply by adding a functional masterbatch of a specific composition during the extrusion granulation step. It exhibits strong compatibility, can be directly modified from existing tubular polymerization equipment without large-scale equipment alterations, and is low-cost and easy to implement. The product of this application retains the advantages of the tubular process, such as low cost and high capacity, and its cost is 10-15% lower than that of the batch polymerization process. This significantly reduces the production cost of coatings and enhances the product's market competitiveness.

[0034] The composition provided in this application can be widely used in high-end paper-plastic composite materials, food packaging, heavy packaging and other fields. It can completely replace products produced by the autoclave process and has extremely high market application value.

[0035] In this application, the tubular LDPE matrix can also be obtained through commercial channels, such as Yanshan Petrochemical's LD607 tubular LDPE product.

[0036] The technical solution of this application has the following advantages: This application provides a tubular low-density polyethylene composition that addresses the shortcomings of tubular LDPE coatings, such as short residence time, low long-branch content, and narrow molecular weight distribution, leading to insufficient coating performance. In the extrusion granulation process after tubular polymerization, this application incorporates a specific composition of polyethylene functional masterbatch. This masterbatch is a compound of low melt index LDPE matrix, polybutadiene, free radical initiator, and antioxidant. It effectively broadens the molecular weight distribution and increases the long-branch content of the product, thereby improving coating performance without gelation. Compared to existing tubular products, the composition of this application broadens the molecular weight distribution from 6.4 to 14.5-16.8, increases the long-branch content from 2.8 / 1000C to 6.6-11.3 / 1000C, and reduces the gel content to ≤0.09%. Its hot tack strength and peel strength reach or even exceed those of batch-process compositions, while retaining the high purity and high production capacity advantages of tubular products. It can completely replace batch-process products in high-end coating applications, solving the industry pain point of insufficient coating performance in tubular products.

[0037] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Detailed Implementation

[0038] The following embodiments are provided to better understand this application. However, the following embodiments do not constitute a limitation on the content and scope of protection of this application. Any product that is the same as or similar to this application, derived by anyone under the guidance of this application or by combining the features of this application with other prior art, falls within the scope of protection of this application.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having” and any variations thereof in the text of this application are intended to cover non-exclusive inclusion.

[0040] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers from a to b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed herein, and "0-5" is merely a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥ 2, it is equivalent to disclosing that the parameter can be, for example, integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0041] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0042] In the description of the embodiments of this application, the term "at least one" refers to one or more (including two).

[0043] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, but sequentially is preferred.

[0044] Unless otherwise specified, all experimental steps or conditions in the examples were performed according to conventional experimental procedures and conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0045] The present application will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present application in any way.

[0046] The main raw materials used in the embodiments and comparative examples of this application are sourced from the following: Tubular LDPE matrix: Yanshan Petrochemical's LD607 tubular LDPE product, melt index 7.0 g / 10 min, density 0.918 g / cm³. 3 Molecular weight distribution 6.4, long branched chain content of ≥6 carbon atoms 2.8 / 1000C, commercially available; Low melt index LDPE 2420D: Wanhua Chemical 2420D, melt index 0.3 g / 10 min, density 0.922 g / cm³ 3 Commercially available; Low melt index LDPE 1810E: Daqing Petrochemical 1810E, melt index 0.5 g / 10 min, density 0.920 g / cm³ 3 Commercially available; Low melt index LDPE 2420H: Wanhua Chemical 2420H, melt index 2.0 g / 10 min, density 0.924 g / cm³ 3 Commercially available; Polybutadiene: Low molecular weight polybutadiene, number average molecular weight 1500, commercially available; BIPB: 1,3-Bis(tert-butylperoxyisopropyl)benzene, 99% purity, commercially available; Antioxidant 168: Tris[2,4-di-tert-butylphenyl]phosphite, commercially available; Antioxidant 1010: Pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], commercially available.

[0047] The test methods involved in the embodiments and comparative examples of this application are as follows: Melt flow index: Tested according to standard GB / T 3682.1-2018, temperature 190℃, load 2.16kg; Density: Tested according to the impregnation method in standard GB / T 1033.1-2008; Molecular weight and molecular weight distribution: determined by gel permeation chromatography (GPC) at 150°C using trichlorobenzene as solvent. Long branch content: determined by carbon NMR spectroscopy (NMR spectroscopy). 13 C-NMR analysis was performed at a temperature of 120°C to calculate the number of long branches (≥6 carbon atoms) in every 1000 carbon atoms. Gel content: The gel content was determined by xylene reflux extraction. The sample was refluxed with xylene for 24 hours, and the mass percentage of insoluble matter was calculated. Hot bonding strength: Tested according to standard GB / T 34445-2017, test temperature 120℃, hot bonding time 0.5s; Peel strength: The peel strength of the paper-plastic composite film was tested according to Method A in standard GB / T 8808-1988. Processing performance: The maximum processing line speed of the extrusion coating process is tested. The higher the line speed, the better the processing performance.

[0048] Example 1 This embodiment provides a tubular low-density polyethylene composition, the specific preparation method and operating parameters of which are as follows: According to the formula shown in Table 1, weigh 97.0 parts of low melt index LDPE 2420D, 0.8 parts of polybutadiene (number average molecular weight 1500), 0.015 parts of BIPB, 0.45 parts of antioxidant 168, and 0.235 parts of antioxidant 1010. Add them to a high-speed mixer and mix at 1100 rpm for 9 minutes. The mixing temperature is controlled at 55℃ to obtain a premix. Add the premix to a twin-screw extruder and control the extrusion temperature at 130℃ and the screw speed at 160 rpm. Melt extrusion granulation is performed to obtain polyethylene functional masterbatch.

[0049] Five parts of the functional masterbatch prepared above were added to a twin-screw extruder and blended with 95 parts of tubular LDPE matrix (LD607) melt material. The mixture was then extruded and granulated. The extrusion temperature was controlled at 190℃ and the screw speed at 210rpm. The product was then subjected to performance testing, and the results are shown in Table 2.

[0050] Example 2 This embodiment provides a tubular low-density polyethylene composition, the specific preparation method and operating parameters of which are as follows: According to the formula shown in Table 1, weigh 96.5 parts of low melt index LDPE 2420H, 0.7 parts of polybutadiene (number average molecular weight 1500), 0.018 parts of BIPB, 0.42 parts of antioxidant 168, and 0.262 parts of antioxidant 1010. Add them to a high-speed mixer and mix at 1100 rpm for 9 minutes. The mixing temperature is controlled at 55℃ to obtain a premix. Add the premix to a twin-screw extruder and control the extrusion temperature at 130℃ and the screw speed at 160 rpm. Melt extrusion granulation is performed to obtain polyethylene functional masterbatch.

[0051] The 8 parts of functional masterbatch prepared above were added to a twin-screw extruder and blended with 92 parts of tubular LDPE matrix (LD607) melt material. The extrusion temperature was controlled at 190℃ and the screw speed at 210rpm. The product was extruded and granulated, and the performance of the product was tested. The results are shown in Table 2.

[0052] Example 3 This embodiment provides a tubular low-density polyethylene composition, the specific preparation method and operating parameters of which are as follows: According to the formula shown in Table 1, weigh 96.0 parts of low melt index LDPE 2420D, 0.6 parts of polydibutylene (number average molecular weight 1500), 0.02 parts of BIPB, 0.4 parts of antioxidant 168, and 0.28 parts of antioxidant 1010. Add them to a high-speed mixer and mix at 1100 rpm for 9 minutes. The mixing temperature is controlled at 55℃ to obtain a premix. Add the premix to a twin-screw extruder and control the extrusion temperature at 130℃ and the screw speed at 160 rpm. Melt extrusion granulation is performed to obtain polyethylene functional masterbatch.

[0053] Ten parts of the functional masterbatch prepared above were added to a twin-screw extruder and blended with 90 parts of tubular LDPE matrix (LD607) melt material. The extrusion temperature was controlled at 190℃ and the screw speed at 210rpm. The product was extruded and granulated, and the performance of the product was tested. The results are shown in Table 2.

[0054] Example 4-Example 5 This embodiment provides a tubular low-density polyethylene composition, which differs from Example 2 in that the composition of the polyethylene functional masterbatch is different, as detailed in Table 1.

[0055] Example 6 This embodiment provides a tubular low-density polyethylene composition, which differs from Example 2 in that it uses a single antioxidant, and uses an equal mass of antioxidant 1010 instead of antioxidant 168.

[0056] Example 7 This embodiment provides a tubular low-density polyethylene composition, which differs from Example 2 in that the specific selection of raw materials is different. In this embodiment, the free radical initiator is dicumyl peroxide; and the number average molecular weight of polybutadiene is 1000.

[0057] Example 8 This embodiment provides a tubular low-density polyethylene composition, which differs from Example 2 in the specific selection of raw materials. In this embodiment, the number average molecular weight of the polybutadiene is 10,000; the melt index of the low melt index LDPE matrix is ​​0.5 g / 10 min, and the density is 0.920 g / cm³. 3 Daqing Petrochemical 1810E.

[0058] Example 9 This embodiment provides a tubular low-density polyethylene composition, which differs from Example 2 in that the parameters of the tubular LDPE matrix are different: melt index 8.0 g / 10 min and density 0.920 g / cm³. 3 .

[0059] Comparative Example 1 This comparative example does not add any functional masterbatch. The tubular LDPE matrix melt material from Example 1 is directly added to a twin-screw extruder, and the extrusion temperature is controlled at 190°C and the screw speed at 210 rpm. The material is directly extruded and granulated to obtain a pure tubular LDPE product. The product performance is tested, and the results are shown in Table 2.

[0060] Comparative Example 2 This comparative example provides a tubular low-density polyethylene composition, the specific preparation method and operating parameters of which are as follows: According to the formula shown in Table 1, weigh 97.2 parts of low melt index LDPE 2420H, 0.018 parts of BIPB, 0.42 parts of antioxidant 168, and 0.262 parts of antioxidant 1010, without adding polybutadiene. Add them to a high-speed mixer and mix at 1100 rpm for 9 minutes. The mixing temperature is controlled at 55℃ to obtain a premix. Add the premix to a twin-screw extruder and control the extrusion temperature at 130℃ and the screw speed at 160 rpm. Melt extrusion granulation is performed to obtain the comparative functional masterbatch.

[0061] The 8 parts of functional masterbatch prepared above were added to a twin-screw extruder and blended with 92 parts of tubular LDPE matrix (LD607) melt material. The extrusion temperature was controlled at 190℃ and the screw speed at 210rpm. The product was extruded and granulated, and the performance of the product was tested. The results are shown in Table 2.

[0062] Comparative Example 3 This comparative example provides a tubular low-density polyethylene composition, the specific preparation method and operating parameters of which are as follows: According to the formula shown in Table 1, weigh 96.488 parts of low melt index LDPE 2420H, 0.7 parts of polydibutylene, 0.03 parts of BIPB, 0.42 parts of antioxidant 168, and 0.262 parts of antioxidant 1010, add them to a high-speed mixer, mix at 1100 rpm for 9 minutes, and control the mixing temperature at 55℃ to obtain a premix; add the premix to a twin-screw extruder, control the extrusion temperature at 130℃ and the screw speed at 160 rpm, melt extrude and granulate to obtain the comparative functional masterbatch.

[0063] The 8 parts of functional masterbatch prepared above were added to a twin-screw extruder and blended with 92 parts of tubular LDPE matrix (LD607) melt material. The extrusion temperature was controlled at 190℃ and the screw speed at 210rpm. The product was extruded and granulated, and the performance of the product was tested. The results are shown in Table 2.

[0064] Comparative Example 4 We directly used commercially available Qilu Petrochemical's batch-process LDPE coating material 2102TN00, without any additional processing, for performance testing, as a comparison with high-end batch-process products.

[0065] Comparative Example 5 Compared with Example 2, the difference is that no free radical initiator is added to the polyethylene functional masterbatch, and an equal mass of low melt index LDPE 2420H matrix is ​​used instead of the free radical initiator.

[0066] Comparative Example 6 Compared with Example 2, the difference is that no antioxidant is added to the polyethylene functional masterbatch, and an equal mass of low melt index LDPE 2420H matrix is ​​used instead of antioxidant.

[0067] Table 1. Formulations (parts by mass) for some of the embodiments and comparative examples.

[0068] Table 2 Performance test results of each embodiment and comparative example

[0069] Note: In the unit "N / 15mm" for hot tack strength and peel strength, 15mm refers to the sample width.

[0070] The test results above show that: In the embodiments of this application, by adding functional masterbatch, the molecular weight distribution was broadened from the original 6.4 (Comparative Example 1, pure tubular process product) to 14.5-16.8, and the long branch content was increased from 2.8 to 6.6-11.3, achieving a broadening of the molecular weight distribution and an increase in the long branch content, reaching the level of batch process products (comparative Example 4, molecular weight distribution 14.5, long branch content 8.0), or even higher. In the embodiments of this application, the gel content was ≤0.09%, far below the industry standard for gel-free products (≤0.1%), indicating that the polybutadiene + low-addition free radical initiator system in this application effectively avoided the occurrence of cross-linking reaction and did not produce gel. In contrast, in Comparative Example 2, without the addition of polybutadiene, the gel content reached 0.78%, and obvious gelation occurred. In Comparative Example 3, the addition of free radical initiator exceeded the limit range of this application, and the gel content reached 1.25%, with more severe gelation, which would affect the appearance of the coated product, verifying the effectiveness of the gel-free control system of this application. Comparative Example 5, without the addition of a free radical initiator, had a long-chain branch content of only 2.2 molecule / 1000°C, and its hot tack strength and peel strength were significantly lower than those of other comparative examples and the Example. Comparative Example 6, without the addition of an antioxidant, had a gel content higher than the industry standard for gel-free gel, and its hot tack strength and peel strength were significantly lower than those of the Example.

[0071] The coating performance of the tubular low-density polyethylene composition products provided in this application embodiment is significantly improved, with hot tack strength reaching 18.6-24.8 N / 15 mm and peel strength reaching 14.1-17.8 N / 15 mm, which are far higher than the 10.0 N / 15 mm and 5.0 N / 15 mm of pure tubular products. Some embodiments are even higher than the 19.5 N / 15 mm and 14.8 N / 15 mm of batch-processed products, achieving a significant improvement in coating performance, reaching or even exceeding the level of high-end batch-processed products. At the same time, the processing line speed is also increased from 280 m / min to 320-450 m / min, and the processing performance is also greatly improved.

[0072] Component synergistic effect verification: With the increase of functional masterbatch addition, molecular weight distribution and long branch content gradually improved, coating performance gradually improved, gel content increased slightly, but was still lower than the industry standard for gel-free (≤0.1%); the addition of polybutadiene effectively reduced gel content without affecting the formation of long branches, verifying its role as a chain transfer agent; controlling the addition of free radical initiator within a certain range is the key to ensuring gel-free, exceeding this amount will result in severe gelation, verifying the rationality of the addition limit in this application.

[0073] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A tubular low-density polyethylene composition, characterized in that, The composition comprises, by weight, the following components in parts: Tubular LDPE matrix: 90-95 parts; Polyethylene functional masterbatch: 5-10 parts; The total mass of the polyethylene functional masterbatch includes the following components in parts by mass: Low melt index LDPE matrix: 95.0-98.0 parts; Polybutadiene: 0.5-1.0 parts; Free radical initiator: 0.01-0.02 parts; Antioxidant: 0.5-0.8 parts.

2. The tubular low-density polyethylene composition according to claim 1, characterized in that, The melt index of the low melt index LDPE matrix is ​​0.2-4.0 g / 10 min; And / or, the density of the low melt flow index LDPE matrix is ​​0.918-0.925 g / cm³. 3 .

3. The tubular low-density polyethylene composition according to claim 1, characterized in that, The number average molecular weight of the polybutadiene is 1000-10000; optionally, it is 1500-6000.

4. The tubular low-density polyethylene composition according to claim 1, characterized in that, The antioxidants include at least one of phosphate ester antioxidants and hindered phenolic antioxidants; Optionally, the antioxidant includes phosphate ester antioxidants and hindered phenolic antioxidants in a mass ratio of 3-5:2-3.

5. The tubular low-density polyethylene composition according to claim 1, characterized in that, The free radical initiator includes peroxide-based free radical initiators, optionally including at least one of 1,3-bis(tert-butylperoxyisopropyl)benzene, dicumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-di-tert-butylperoxycyclohexane, and benzoyl peroxide.

6. The tubular low-density polyethylene composition according to any one of claims 1-5, characterized in that, The tubular LDPE matrix has a melt index of 6.0-8.0 g / 10 min and a density of 0.915-0.920 g / cm³. 3 ; And / or, the molecular weight distribution (PDI) of the tubular LDPE matrix is ​​4.0-7.0, and the number of long branches with ≥6 carbon atoms is 1.5-4.0 per 1000C.

7. A method for preparing a tubular low-density polyethylene composition according to any one of claims 1-6, characterized in that, Includes the following steps: S1, low melt index LDPE matrix, polybutadiene, free radical initiator and antioxidant are mixed and melt extruded into granules to obtain polyethylene functional masterbatch; S2, the polyethylene functional masterbatch is blended with the tubular LDPE matrix, and then melt-extruded and granulated to obtain the tubular low-density polyethylene composition.

8. The method for preparing the tubular low-density polyethylene composition according to claim 7, characterized in that, In S1, the mixing speed is 1000-1200 rpm and the mixing temperature is 50-60℃; And / or, in S1, the extrusion temperature is 120-140℃ and the rotation speed is 150-180rpm.

9. The method for preparing the tubular low-density polyethylene composition according to claim 7 or 8, characterized in that, In S2, the extrusion temperature is 180-200℃ and the rotation speed is 200-220rpm.

10. The application of a tubular low-density polyethylene composition according to any one of claims 1-6 or a tubular low-density polyethylene composition prepared by the preparation method according to any one of claims 7-9 in paper-plastic composites, plastic-plastic composites, aluminum-plastic composites, fabric-coated materials, and building geosynthetics.

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