A processing aid masterbatch and its preparation method

Abstract

A processing aid masterbatch and its preparation method belong to the technical field of polyethylene processing aids. In the prior art, although the processing aids added during the production of metallocene polyethylene can improve the performance to a certain extent, there are often problems such as poor thermal stability and long time for the effect to take effect, resulting in low processing efficiency and poor product quality. The present invention uses 80-90 parts of low-density polyethylene resin, 10-20 parts of metallocene linear low-density polyethylene resin, 0.1-0.5 parts of antioxidant, and 0.5-1 part of processing aid; among them, the processing aid components include 45-60 parts of fluororubber, 35-55 parts of polyethylene glycol, and 5-6 parts of pumice powder; through the combination of specific polyethylene resins and processing aids, while fully exerting the respective characteristics of various components, it can ensure that when the processing aid masterbatch is applied to the processing of films, coffins, etc., the transparency, impact resistance and pressure resistance of the polyethylene substrate are less affected, making the best use of advantages and avoiding disadvantages, reducing the processing difficulty and improving the processing performance.

Description

Technical Field

[0001] A processing aid masterbatch and its preparation method belong to the technical field of polyethylene processing aids. Background Art

[0002] Metallocene polyethylene has excellent impact resistance, film optical properties, etc., and can be widely used in various application fields such as films, pipes, and bottle caps. However, due to its narrow molecular weight distribution, it is prone to melt fracture problems during high-speed processing. To improve the processing performance of metallocene polyethylene, generally, the method of blending with broad molecular weight distribution polyethylene or adding a processing aid masterbatch is adopted. Among them, although blending with broad molecular weight distribution polyethylene is beneficial to improving the processing performance, it will reduce the performance advantages of metallocene polyethylene, thereby reducing the comprehensive performance of the product. Since the addition amount of the processing aid masterbatch is small and has little impact on the comprehensive performance, currently, the processing performance of metallocene polyethylene is mostly improved by adopting the method of adding a processing aid masterbatch.

[0003] There is a method in the prior art that uses fluororubber as a processing aid. Its mechanism of action is that during the processing of polymers, fluororubber can migrate to the extrusion die and other metal surfaces to play a lubricating role, prevent die blockage, and improve the processing performance. Currently, commercially available fluororubbers are compounds mainly based on fluoropolymers, but there are significant differences in the improvement effect on the processing performance of metallocene polyethylene, and there are often problems such as poor thermal stability and long effect - exerting time, resulting in low processing efficiency and poor product quality. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a processing aid masterbatch and its preparation method with excellent thermal stability, which can effectively improve the processing performance of metallocene polyethylene and improve the production efficiency of metallocene polyethylene.

[0005] The technical solution adopted by the present invention to solve its technical problem is that the processing aid masterbatch is characterized by including the following components in parts by weight:

[0006] 80 - 90 parts of low - density polyethylene resin, 10 - 20 parts of metallocene linear low - density polyethylene resin, 0.1 - 0.5 part of antioxidant, 0.5 - 1 part of processing aid;

[0007] Among them, the processing aid includes the following components in parts by weight: 45 - 60 parts of fluororubber, 35 - 55 parts of polyethylene glycol, 5 - 6 parts of pumice powder;

[0008] The melt mass - flow rate of the low - density polyethylene resin is 1 - 2 g / 10 min;

[0009] The melt mass - flow rate of the metallocene linear low - density polyethylene resin is 20 - 30 g / 10 min.

[0010] Low-density polyethylene resin has good transparency and processing performance. On the one hand, metallocene linear low-density polyethylene resin can increase the production of masterbatch, reduce costs, and also reduce the overall viscosity of the masterbatch, avoiding the degradation of the masterbatch adhering to the surface of processing equipment during mixed application and preventing impurities from appearing on the surface of the product. On the other hand, the metallocene linear low-density polyethylene resin added to the masterbatch is beneficial to the dispersion of processing aids in the masterbatch and also beneficial to the dispersion of the masterbatch in the resin when the masterbatch is applied to metallocene polyethylene resin. At the same time, metallocene linear low-density polyethylene can also be well compatible with low-density polyethylene resin, providing a dispersion and compatibility effect between various components, reducing processing difficulty, being easy to mix evenly, and improving production efficiency. The melt flow rates of the defined low-density polyethylene resin and metallocene linear low-density polyethylene resin can ensure sufficient compatibility and good dispersion between the two components, improving processing performance and material uniformity.

[0011] By combining low-density polyethylene resin and metallocene linear low-density polyethylene resin, while fully exerting the respective characteristics of the two components, it is ensured that when the processing aid masterbatch is applied to the processing of films, pipes, etc., it has less impact on the transparency, impact resistance and pressure resistance of the polyethylene substrate, making the best use of advantages and avoiding disadvantages, reducing processing difficulty, and improving processing performance.

[0012] Preferably, the density of the metallocene linear low-density polyethylene resin is 0.90 - 0.95 g / cm³ 3 . The preferred density range can ensure that the metallocene linear low-density polyethylene resin has the above-mentioned melt flow rate and good compatibility with low-density polyethylene resin.

[0013] Preferably, the initial temperature of thermal weight loss of the processing aid is ≥400 °C and the content of the final residue is ≤5%; the thermal stability time is 260 °C, ≥5 min; the fluorine content is 10 - 15%.

[0014] Limiting the thermal weight loss temperature and residue content can, on the one hand, ensure that the elastomer contains a sufficient amount of effective components beneficial to processing, and on the other hand, control the adverse effects of inorganic substances on later processing applications, such as reducing the impurity content in the final product; the fluorine content is an important condition for improving processing performance, and by controlling its content, the needs of comprehensive cost and processing improvement effect can be met.

[0015] Preferably, the antioxidant is a hindered phenol antioxidant or a phosphite antioxidant system. During the preparation of the masterbatch, a high-temperature melting process is required. The carrier resin polyethylene will degrade or crosslink under the action of heat, oxygen, etc. during high-temperature melting, resulting in changes in structure and affecting the application performance. To avoid the influence of adverse factors such as heat and oxygen during the preparation of the masterbatch, an antioxidant needs to be added to the composition system to maintain the stability of the resin against heat and oxygen; at the same time, it can also prevent the generation of black impurities later.

[0016] Preferably, the dosage of the antioxidant is 0.2 - 0.4 parts.

[0017] Preferably, it includes the following components in parts by weight: 85 parts of low-density polyethylene resin, 15 parts of metallocene linear low-density polyethylene resin, 0.3 part of antioxidant, and 0.7 part of processing aid.

[0018] The preferred weight fraction composition can enable the low-density polyethylene resin, metallocene linear low-density polyethylene resin, and processing aid to exactly cooperate with each other, possess the best processing performance, and each component can fully play its own role.

[0019] Preferably, the processing aid includes the following components in parts by weight: 55 parts of fluororubber, 40 parts of polyethylene glycol, and 5 parts of pumice powder.

[0020] The preferred dosage of pumice powder can provide good thermal stability and dispersibility to the processing aid while avoiding turbidity of the final material caused by surplus calcium.

[0021] More preferably, the fluororubber is a copolymer of vinylidene fluoride and hexafluoropropylene.

[0022] The preferred processing aid is more conducive to ensuring the thermal stability of the processing aid and the compatibility of different components.

[0023] The preparation method of any of the above processing aid masterbatches is characterized by including the following steps:

[0024] 1) Grinding the low-density polyethylene resin and metallocene linear low-density polyethylene resin into particles, and controlling the particle size to be 40 - 80 mesh;

[0025] 2) Mixing the low-density polyethylene resin, metallocene linear low-density polyethylene resin, antioxidant, and processing aid in proportion by weight at 35 - 50 °C;

[0026] 3) Extruding and pelletizing the masterbatch.

[0027] Grinding low-density polyethylene resin and metallocene linear low-density polyethylene resin is more conducive to the mutual dispersion between low-density polyethylene resin and metallocene linear low-density polyethylene resin. The particle size can achieve the highest dispersion effect without destroying the structure of each resin and losing performance.

[0028] Further preferably, in step 1), the particle size is controlled to be 60 mesh.

[0029] Further preferably, in step 2), first mix at a low speed for 2 min, and then mix at a high speed for 3 min.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows: By combining low-density polyethylene resin and metallocene linear low-density polyethylene resin and cooperating with specific processing aids, the prepared processing aid masterbatch can have good dispersion performance when added to the production process of metallocene polyethylene, reduce the metal adhesion during the processing of metallocene polyethylene, improve the processing performance, improve the production efficiency, and further reduce the production cost; the impurities introduced into the product are few and have almost no influence on the advantageous properties of the product itself. Specific Embodiments

[0031] The following further illustrates the present invention with reference to embodiments, and Embodiment 2 is the best embodiment of the present invention.

[0032] In the following embodiments, the weight parts of the components of the processing aid masterbatch are shown in Table 1 below, and the components and weight parts of the processing aids in the processing aid masterbatch are shown in Table 2 below.

[0033] Among them, mLLDPE is metallocene linear low-density polyethylene resin, LDPE is low-density polyethylene resin, and the fluoroelastomer is selected from vinylidene fluoride-hexafluoropropylene copolymer.

[0034] Among them, the thermogravimetric curve of PPA is obtained by TGA, and its initial thermogravimetric temperature and final residue content can be obtained by combining software.

[0035] The test method for the thermal stability time is to put PPA into a glassware and heat it under different temperature and time conditions, and observe the change of the appearance color. When it changes from the original color to yellow or black, the thermal stability changes.

[0036] The fluorine content is tested by a fluorescence element analyzer.

[0037] The MFR test is carried out according to GB / T3682.1-2018, and the load used is 2.16 kg;

[0038] The density test is carried out according to GB / T1033.1-2008.

[0039] Embodiment 1

[0040] A processing aid masterbatch, the weight parts of the components are shown in Table 1 below, and the components and weight parts of the processing aid are shown in Table 2 below.

[0041] Among them, mLLDPE is a copolymer of ethylene and 1-hexene, MFR = 20.0 g / 10 min, density 0.920 g / cm 3 ;

[0042] LDPE has MFR = 1.0 g / 10 min and density 0.920 g / cm 3 ;

[0043] The initial temperature of thermal weight loss of the processing aid is 415 °C, the residue content is 4.3%, the thermal stability time is 260 °C, 6 min, and the fluorine content is 10.8%.

[0044] A preparation method of a processing aid masterbatch, comprising the following steps

[0045] 1) Grind the low-density polyethylene resin and the metallocene linear low-density polyethylene resin into particles, control the particle size distribution to be 60 mesh, control the grinding temperature at 80 °C, and the bulk density of the ground powder is 0.5 g / cm 3 ;

[0046] 2) Add the low-density polyethylene resin, the metallocene linear low-density polyethylene resin, the antioxidant and the processing aid to a high-speed mixer according to the weight parts ratio, and mix at a low speed (500 rpm) for 2 min and at a high speed (1000 rpm) for 3 min at 40 °C;

[0047] 3) Add the uniformly mixed material to a twin-screw extruder for melting, plasticizing, extruding and pelletizing. The pelletizing temperature is 170 - 190 °C, and the highest pelletizing temperature is 190 °C; the screw length-diameter ratio is 25:1, and there is no shear block in the screw structure.

[0048] Example 2

[0049] A processing aid masterbatch, the weight parts of the components are shown in Table 1 below, and the components and weight parts of the processing aid are shown in Table 2 below.

[0050] Among them, mLLDPE is a copolymer of ethylene and 1-hexene, MFR = 20.0 g / 10 min, density 0.920 g / cm 3 ;

[0051] LDPE has MFR = 1.0 g / 10 min and density 0.920 g / cm 3 ;

[0052] The initial temperature of thermal weight loss of the processing aid is 435 °C, the residue content is 3.0%, the thermal stability time is 260 °C, 10 min, and the fluorine content is 12.9%.

[0053] The preparation method of a processing aid masterbatch is the same as that in Example 1.

[0054] Example 3

[0055] A processing aid masterbatch, the weight parts of the components are shown in Table 1 below, and the components and weight parts of the processing aid are shown in Table 2 below.

[0056] Among them, mLLDPE is a copolymer of ethylene and 1-hexene, MFR = 30.0 g / 10 min, density 0.915 g / cm 3 ;

[0057] LDPE has MFR = 1.5 g / 10 min and density 0.920 g / cm 3 ;

[0058] The initial temperature of thermal weight loss of the processing aid is 443 °C, the residue content is 1.8%, the thermal stability time is 260 °C for 13 min, and the fluorine content is 12.1%.

[0059] A preparation method of a processing aid masterbatch, on the basis of Example 1, the grinding temperature in step 1) is set at 83 °C, and the particle size distribution is controlled at 50 mesh; in step 2), low-speed mixing is carried out for 1 min and high-speed mixing is carried out for 4 min; in step 3), the granulation temperature is set at 160 - 180 °C.

[0060] Example 4

[0061] A processing aid masterbatch, the weight parts of the components are shown in Table 1 below, and the components and weight parts of the processing aid are shown in Table 2 below.

[0062] Among them, mLLDPE is a copolymer of ethylene and 1-hexene, MFR = 25.0 g / 10 min, density 0.918 g / cm 3 ;

[0063] LDPE has MFR = 2.0 g / 10 min and density 0.920 g / cm 3 ;

[0064] The initial temperature of thermal weight loss of the processing aid is 423 °C, the residue content is 3.8%, the thermal stability time is 260 °C for 7 min, and the fluorine content is 14.2%.

[0065] The preparation method of a processing aid masterbatch is the same as that in Example 3.

[0066] Comparative Example 1

[0067] A processing aid masterbatch, the weight parts of the components are shown in Table 1 below, and the components and weight parts of the processing aid are shown in Table 2 below.

[0068] Among them, mLLDPE is a copolymer of ethylene and hexene-1, MFR = 5.0 g / 10 min, density 0.933 g / cm 3 ;

[0069] LDPE has MFR = 0.3 g / 10 min and density 0.920 g / cm 3 ;

[0070] The initial temperature of thermal weight loss of the processing aid is 369 °C, the residue content is 3.8%, the thermal stability time is 260 °C, 7 min, and the fluorine content is 14.2%.

[0071] A preparation method of the processing aid masterbatch is the same as that in Example 2.

[0072] Comparative Example 2

[0073] A processing aid masterbatch, the weight parts of the components are shown in Table 1 below, and the components and weight parts of the processing aid are shown in Table 2 below.

[0074] Among them, mLLDPE is a copolymer of ethylene and hexene-1, MFR = 25.0 g / 10 min, density 0.918 g / cm 3 ;

[0075] LDPE has MFR = 2.0 g / 10 min and density 0.920 g / cm 3 ;

[0076] The initial temperature of thermal weight loss of the processing aid is 423 °C, the residue content is 3.8%, the thermal stability time is 260 °C, 7 min, and the fluorine content is 14.2%.

[0077] A preparation method of the processing aid masterbatch, on the basis of Example 1, the grinding temperature is set at 90 °C, and the particle size distribution is controlled at 40 mesh.

[0078] Comparative Example 3

[0079] A processing aid masterbatch, the weight parts of the components are shown in Table 1 below, and the components and weight parts of the processing aid are shown in Table 2 below, where polyvinyl alcohol is replaced by polyethylene wax.

[0080] Among them, mLLDPE is a copolymer of ethylene and hexene-1, MFR = 2.0 g / 10 min, density 0.920 g / cm 3 ;

[0081] LDPE has MFR = 2.0 g / 10 min and density 0.920 g / cm 3 ;

[0082] The initial temperature of thermal weight loss of the processing aid is 351 °C, the residue content is 7.8%, the thermal stability time is 260 °C, 2 min, and the fluorine content is 10.2%.

[0083] The preparation method of a processing aid masterbatch is the same as that of Example 2.

[0084] Comparative Example 4

[0085] A processing aid masterbatch, the components in parts by weight are shown in Table 1 below, and the components and parts by weight of the processing aid are shown in Table 2 below, wherein the pumice powder is replaced with talc powder.

[0086] Wherein, mLLDPE is a copolymer of ethylene and 1-hexene, MFR = 5.0 g / 10 min, density 0.933 g / cm 3 ;

[0087] LDPE has MFR = 0.1 g / 10 min, density 0.920 g / cm 3 ;

[0088] The initial temperature of thermal weight loss of the processing aid is 369 °C, the residue content is 3.8%, the thermal stability time is 260 °C, 7 min, and the fluorine content is 14.2%.

[0089] Comparative Example 5

[0090] A processing aid masterbatch, the components and parts by weight of the processing aid are as in Example 1.

[0091] In the processing aid masterbatch, there are 10 parts of LLDPE, 90 parts of HDPE, 0.5 part of the processing aid, and 0.15 part each of antioxidant 1010 and 168. Among them, LLDPE is a copolymer of ethylene and 1-butene, MFR = 2.0 g / 10 min, density 0.921 g / cm 3 ;

[0092] HDPE has MFR = 1.0 g / 10 min, density 0.945 g / cm 3 ;

[0093] The initial temperature of thermal weight loss of the processing aid is 369 °C, the residue content is 3.8%, the thermal stability time is 260 °C, 7 min, and the fluorine content is 14.2%.

[0094] Table 1 Composition of the processing aid masterbatch

[0095] .

[0096] Table 2 Composition of the processing aid

[0097] .

[0098] Performance test

[0099] In 100 parts of mLLDPE resin (MFR = 0.6 g / 10 min, density 0.937 g / cm 3 ), 10 parts of the processing aid masterbatch obtained in Examples 1-4 and Comparative Examples 1-4 were respectively added, and after mixing and granulation, a metallocene linear low-density polyethylene composite material was obtained. The material was extruded into pipes at 200 °C using an extruder, and the pipe specification was ф20*2.0 mm.

[0100] The number of impurities was determined by observing the number of black or yellow impurities in 1 coil of pipes (300 m).

[0101] The pipe processing speed refers to the highest processing speed that can be achieved when the pipe is extruded. The pipe surface is smooth and the molding is stable.

[0102] The time for the pipe surface to become smooth: At the beginning of pipe production, the surface is rough. As the processing aid improves the processing performance of the pipe material, the pipe surface becomes smooth. This time refers to the time when the pipe surface changes from rough to smooth.

[0103] The performance test results are shown in Table 3.

[0104] Table 3 Performance test results

[0105] 。

[0106] It can be seen from the above examples and comparative examples that by adding the processing aid masterbatch of the present invention, the processing performance (production efficiency) of metallocene polyethylene is significantly improved, the number of impurities is small, and it can avoid leakage of pipe products during application due to the generation of impurities.

[0107] The aid masterbatch of the present invention is not limited to pipes only. Other application fields such as films, cables, and pipes can be improved on this basis when in use.

[0108] The above are only the preferred embodiments of the present invention, and are not limitations on the present invention in other forms. Any person skilled in the art may use the technical content disclosed above to make changes or modifications into equivalent embodiments with equivalent changes. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the technical solution content of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A processing aid masterbatch, characterized in that: Comprising the following components in parts by weight: 80 - 90 parts of low - density polyethylene resin, 10 - 20 parts of metallocene linear low - density polyethylene resin, 0.1 - 0.5 part of antioxidant, 0.5 - 1 part of processing aid; Among them, the processing aid comprises the following components in parts by weight: 45 - 60 parts of fluororubber, 35 - 55 parts of polyethylene glycol, 5 - 6 parts of pumice powder; The melt mass - flow rate of the low - density polyethylene resin is 1 - 2 g / 10min; The melt mass - flow rate of the metallocene linear low - density polyethylene resin is 20 - 30 g / 10min; The density of the metallocene linear low density polyethylene resin described is 0.90 to 0.95 g / cm 3 ; The initial temperature of thermal weight loss of the processing aid ≥ 400 °C and the content of the final residue ≤ 5%; the thermal stability time is 260 °C, ≥ 5 min; the fluorine content is 10 - 15%; The fluororubber is a copolymer of vinylidene fluoride and hexafluoropropylene.

2. The processing aid masterbatch according to claim 1, characterized in that: The antioxidant is a mixture of one or two in any proportion in the system of hindered phenol antioxidants and phosphite antioxidants.

3. The processing aid masterbatch according to claim 1, characterized in that: The dosage of the antioxidant is 0.2 - 0.4 part.

4. The processing aid masterbatch according to claim 1, characterized in that: Comprising the following components in parts by weight: 85 parts of low - density polyethylene resin, 15 parts of metallocene linear low - density polyethylene resin, 0.3 part of antioxidant, 0.7 part of processing aid.

5. The processing aid masterbatch according to claim 1, characterized in that: The processing aid comprises the following components in parts by weight: 55 parts of fluororubber, 40 parts of polyethylene glycol, 5 parts of pumice powder.

6. A preparation method of the processing aid masterbatch according to any one of claims 1 to 5, characterized in that: Comprising the following steps: 1) Grinding the low - density polyethylene resin and the metallocene linear low - density polyethylene resin into particles, controlling the particle size to be 40 - 80 mesh; 2) Mixing the low - density polyethylene resin, the metallocene linear low - density polyethylene resin, the antioxidant and the processing aid in proportion by weight at 35 - 50 °C; 3) Extruding and pelletizing the masterbatch.

7. The preparation method of the processing aid masterbatch according to claim 6, characterized in that: In step 1), the particle size is controlled to be 60 mesh.

8. The preparation method of the processing aid masterbatch according to claim 6, characterized in that: In step 2), mixing at low speed for 2 min first, and then mixing at high speed for 3 min.