Polyolefin composition for drypack and process for the preparation thereof

Abstract

The application discloses a polyolefin composition for desiccant packaging and a preparation method thereof, and relates to the technical field of modified plastics. The application provides a polyolefin composition for desiccant packaging, which comprises the following components in parts by weight: 30-50 parts of polyolefin resin, 35-70 parts of heavy calcium carbonate, 0.5-2 parts of antioxidant, and 0.5-2 parts of processing aid; the polyolefin resin is a mixture of low-density polyethylene and linear low-density polyethylene, and the weight ratio is (1-2):(3-6); the low-density polyethylene has a melt flow rate of 1-15 g / 10 min under the condition of 190 DEG C and 2.16 kg according to ISO 1133-1-2011; the linear low-density polyethylene has a density of 0.93-0.95 g / cm 3 ; and the heavy calcium carbonate has an average particle size D50 of 4-7 microns.

Description

Technical Field

[0001] This invention relates to the field of modified plastics technology, and in particular to a polyolefin composition for desiccant packaging and its preparation method. Background Technology

[0002] Polyolefin breathable membranes are made by stretching and pore-forming a polyolefin-filled system. The resin and inorganic filler interface form a continuous microporous network structure, allowing small water vapor molecules to pass through while preventing larger droplets from passing through, thus providing breathability and waterproofing. The polyolefin-filled system is typically a combination of polyolefin and heavy calcium carbonate. Polyolefin breathable membranes, as a key structural component, are widely used in functional packaging such as desiccant packaging, hygiene material bottom films such as diapers and sanitary napkins, and medical / industrial protective clothing.

[0003] Desiccant packaging breathable membranes are used in food, pharmaceuticals, clothing, and bags, with built-in silica gel particles or calcium oxide to absorb moisture from the air and maintain the dryness of the application environment. Unlike traditional breathable membrane products used in medical supplies and protective equipment, desiccant packaging breathable membranes have the following requirements: (1) Desiccant packaging breathable membranes have a high basis weight to maintain high mechanical strength, usually above 30 gsm; (2) Due to their high thickness, desiccant packaging breathable membranes are prone to appearance defects (surface bark texture) during the stretching and film-making process; (3) Desiccant packaging breathable membranes have ultra-high air permeability, with an air permeability of >3400 g / m³. 2 • For at least 24 hours, it needs to efficiently absorb moisture from the air. Traditional breathable films for desiccant packaging achieve this through two methods: first, improving permeability in the material stage by increasing the inorganic powder content; second, improving permeability in the film manufacturing process by increasing the stretch ratio and the number of micropores. However, the preparation of traditional breathable films for desiccant packaging can significantly impact product appearance, mechanical properties, and permeability, making it difficult to achieve a good balance among these three requirements.

[0004] Therefore, a polyolefin composition for desiccant packaging with high air permeability, good mechanical properties, and a good product appearance has broad application prospects. Summary of the Invention

[0005] Therefore, one objective of this invention is to overcome the shortcomings of the prior art and provide a polyolefin composition for desiccant packaging with high air permeability and good mechanical properties, as well as a method for preparing the same. Another objective of this invention is to provide a polyolefin composition for desiccant packaging with a good product appearance, as well as a method for preparing the same.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a polyolefin composition for desiccant packaging, comprising the following components in parts by weight: 30-50 parts of polyolefin resin, 35-70 parts of heavy calcium carbonate, 0.5-2 parts of antioxidant, and 0.5-2 parts of processing aid; wherein the polyolefin resin is a mixture of low-density polyethylene and linear low-density polyethylene in a weight ratio of (1-2):(3-6), wherein the low-density polyethylene has a melt flow rate of 1-15 g / 10 min at 190°C and 2.16 kg according to ISO 1133-1-2011, and the linear low-density polyethylene has a density of 0.93-0.95 g / cm³. 3 The average particle size D50 of the heavy calcium carbonate is 4-7 micrometers.

[0007] This invention utilizes a mixture of low-density polyethylene and linear low-density polyethylene in a specific ratio as the polyolefin resin, which facilitates pore formation at the calcium carbonate interface during stretching, thereby improving air permeability. Furthermore, by selecting heavy calcium carbonate with a specific average particle size, this invention enhances the material's pore-forming ability at the calcium carbonate / resin interface during stretching, further improving air permeability. Simultaneously, the selection of heavy calcium carbonate with a specific average particle size ensures the mechanical properties of the polyolefin composition used in desiccant packaging.

[0008] Preferably, the low-density polyethylene has a molecular weight distribution (Mw / Mn) of 10-15 and a density of 0.915-0.925 g / cm³. 3 .

[0009] Preferably, the linear low-density polyethylene has a molecular weight distribution Mw / Mn of 5-10, and the comonomer of the linear low-density polyethylene is at least one of hexene and octene.

[0010] Preferably, the linear low-density polyethylene has a melt flow rate of 0.5-2.0 g / 10 min at 190°C and 2.16 kg according to ISO 1133-1-2011.

[0011] During actual experiments, the inventors discovered that the polyolefin resin of this invention, which is a mixture of low-density polyethylene and linear low-density polyethylene in a specific ratio, can impart good appearance uniformity to the material during stretching.

[0012] The density of the low-density polyethylene and linear low-density polyethylene described in this invention is tested using the impregnation method in GB / T1033.1-2008 Plastics—Determination of Density of Non-Foamed Plastics. The weight-average molecular weight and number-average molecular weight of the low-density polyethylene and linear low-density polyethylene are obtained by gel permeation chromatography (GPC). The ratio of weight-average molecular weight to number-average molecular weight is the molecular weight distribution Mw / Mn. The average particle size D50 of the heavy calcium carbonate described in this invention is tested using the Malvern laser particle size distribution method.

[0013] Optionally, the average particle size D50 test method for heavy calcium carbonate is as follows: Add 3g of filler to 500mL of water, shake in an ultrasonic instrument for 1min, add the well dispersed sample, place it in a Malvern laser particle size analyzer, and test the sample. The laser wavelength is 630nm, the scattering angle of the particles is 90°, the test time is 300s, the correlator is low speed, the medium temperature is 21℃, the light intensity distribution type is selected, and the CONTIN2 analysis mode is used.

[0014] Optionally, the polyolefin resin is in the range of 30 parts, 32 parts, 35 parts, 38 parts, 40 parts, 42 parts, 45 parts, 48 ​​parts, and 50 parts by weight, or any two of these values; the heavy calcium carbonate is in the range of 35 parts, 38 parts, 40 parts, 42 parts, 45 parts, 48 ​​parts, 50 parts, 51 parts, 53 parts, 55 parts, 58 parts, 60 parts, 61 parts, 63 parts, 65 parts, 68 parts, and 70 parts by weight, or any two of these values; the antioxidant is in the range of 0.5 parts, 0.8 parts, 1 part, 1.5 parts, 1.8 parts, and 2 parts by weight, or any two of these values; and the processing aid is in the range of 0.5 parts, 0.8 parts, 1 part, 1.5 parts, 1.8 parts, and 2 parts by weight, or any two of these values.

[0015] Optionally, the polyolefin resin is a mixture of low-density polyethylene and linear low-density polyethylene, with a weight ratio of one or any two of the following: 1:3, 1:4, 1:5, 1:6, 2:3, 2:4, 2:5, 2:6.

[0016] Optionally, the low-density polyethylene, according to ISO 1133-1-2011 at 190°C and 2.16 kg, has a melt flow rate of 1 g / 10 min, 2 g / 10 min, 2.5 g / 10 min, 3 g / 10 min, 4 g / 10 min, 5 g / 10 min, 6 g / 10 min, 7 g / 10 min, 8 g / 10 min, 9 g / 10 min, 9.5 g / 10 min, 10 g / 10 min, 12 g / 10 min, 13 g / 10 min, and 15 g / 10 min, or any two of these values. The molecular weight distribution (Mw / Mn) of the low-density polyethylene is within the range of 10, 11, 12, 13, and 15, or any two of these values. The density of the low-density polyethylene is 0.915, 0.920, or 0.925 g / cm³. 3 The range of one or any two of them.

[0017] Optionally, the linear low-density polyethylene, according to ISO 1133-1-2011, has a melt flow rate at 190°C and 2.16 kg that is one or any two of the following: 0.5 g / 10 min, 0.8 g / 10 min, 1 g / 10 min, 1.5 g / 10 min, and 2.0 g / 10 min. The molecular weight distribution (Mw / Mn) of the linear low-density polyethylene is one or any two of the following: 5, 6, 7, 8, 9, and 10. The density of the linear low-density polyethylene is 0.93 g / cm³. 3 0.935g / cm 3 0.94g / cm 3 0.945g / cm 3 0.95g / cm 3 The range of one or any two of them.

[0018] Optionally, the average particle size D50 of the heavy calcium carbonate is a range of one or both of 4 micrometers, 5 micrometers, 6 micrometers, and 7 micrometers.

[0019] Preferably, the polyolefin resin accounts for not less than 25% by weight in the polyolefin composition for desiccant packaging.

[0020] Preferably, the heavy calcium carbonate is heavy calcium carbonate obtained by coating with a surface treatment agent, and the surface treatment agent is at least one of stearic acid, phosphate ester, titanate, and aluminate; more preferably, the surface treatment agent is phosphate ester.

[0021] Furthermore, the surface treatment agent is 0.5wt%-2wt% of the weight of the heavy calcium carbonate. Since the amount of surface treatment agent added is less than 2wt%, the effect on the particle size of the heavy calcium carbonate before and after coating can be ignored.

[0022] Optionally, the weight of the surface treatment agent is one or any two of the following values: 0.5 wt%, 0.7 wt%, 0.8 wt%, 1 wt%, 1.5 wt%, 1.6 wt%, 1.8 wt%, 1.9 wt%, and 2.0 wt% of the weight of the heavy calcium carbonate.

[0023] Preferably, the method for preparing heavy calcium carbonate obtained by surface treatment agent coating includes the following steps: preparing activated heavy calcium carbonate by high-speed mixer, matching different high-speed mixer speeds, adding a specific dose of surface treatment agent when the set temperature is reached, and achieving uniform coating of surface treatment agent under high-speed and high-temperature stirring and mixing.

[0024] Optionally, the high-speed mixer has a speed range of 400-600 rpm and a temperature range of 115-125℃.

[0025] Optionally, the heavy calcium carbonate obtained by surface treatment agent coating according to the present invention can be prepared by the above method or commercially available products can be purchased directly.

[0026] During actual experiments, the inventors discovered that when the heavy calcium carbonate is obtained by coating with a surface treatment agent, the resulting polyolefin composition for desiccant packaging has better appearance and mechanical properties. When the surface treatment agent is a phosphate ester, it can better improve air permeability through interfacial adsorption, and at the same time, it has a certain effect on improving the tensile strength of the film.

[0027] Optionally, the weight of the surface treatment agent is tested by the loss on ignition method: the heavy calcium carbonate obtained after coating with the surface treatment agent is first dried at 105-110℃ to remove the influence of moisture, and then ignited at 420-470℃ for 30-50 minutes. The weight percentage lost during the ignition stage is the weight percentage of the surface treatment agent.

[0028] Preferably, the weight ratio of the low-density polyethylene to the linear low-density polyethylene is 1:3-5.

[0029] During actual experiments, the inventors discovered that the weight ratio of low-density polyethylene to linear low-density polyethylene further affects the air permeability, mechanical properties, and product appearance of the polyolefin composition for desiccant packaging. When the weight ratio of low-density polyethylene to linear low-density polyethylene is 1:3-5, the performance of the polyolefin composition for desiccant packaging is better.

[0030] Preferably, the antioxidant is at least one of hindered phenols and phosphites, and the processing aid is a lubricant, which is at least one of fluorinated compounds, polyolefin waxes, low molecular weight esters, stearates, and amides, such as pentaerythritol stearate and zinc stearate.

[0031] Optionally, the hindered phenolic antioxidant includes at least one of 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanuric acid, β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, bis[β-(3,5-di-tert-butyl-4-hydroxyphenylpropionyl)]hydrazine, and tetrakis[β-(3,5-di-tert-butyl,4-hydroxyphenyl)propionate]pentaerythritol; the phosphite antioxidant includes at least one of bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphate, tetrakis(2,4-di-tert-butylphenol)-4,4-biphenyl diphosphite, and tris[2,4-di-tert-butylphenyl]phosphite.

[0032] In addition, the present invention provides a method for preparing the polyolefin composition for desiccant packaging, comprising the following steps: mixing the components in proportion, followed by melt extrusion and granulation to obtain the polyolefin composition for desiccant packaging.

[0033] Preferably, the length-to-diameter ratio of the extruder screw is 40:1-52:1, and the processing temperature is 180-220℃.

[0034] Furthermore, the present invention provides the application of the aforementioned polyolefin composition for desiccant packaging in the field of desiccant packaging. Optionally, the field of desiccant packaging includes food desiccant packaging, household desiccant packaging, clothing desiccant packaging, and the like.

[0035] Compared to existing technologies, the beneficial effects of this invention are as follows: The polyolefin resin of this invention uses a mixture of low-density polyethylene and linear low-density polyethylene in a specific ratio, which facilitates pore formation at the calcium carbonate interface during stretching, thus improving air permeability. This invention further enhances air permeability by selecting heavy calcium carbonate with a specific average particle size, thereby improving the pore-forming ability of the calcium carbonate / resin interface during stretching. Simultaneously, the selection of heavy calcium carbonate with a specific average particle size ensures the mechanical properties of the polyolefin composition for desiccant packaging. In actual experiments, the inventors discovered that the polyolefin resin of this invention, using a mixture of low-density polyethylene and linear low-density polyethylene in a specific ratio, can impart good appearance uniformity to the material during stretching. Detailed Implementation

[0036] To better illustrate the purpose, technical solution, and advantages of this invention, the invention will be further described below with reference to specific embodiments. The purpose is to provide a detailed understanding of the invention, not to limit it. All other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention. Unless otherwise specified, the experimental reagents and instruments designed in the embodiments and comparative examples of this invention are commonly used reagents and instruments, all of which are commercially available. Unless otherwise specified, the experimental methods used in the embodiments and comparative examples are conventional methods; and unless otherwise specified, the raw materials used in parallel experiments are from the same batch.

[0037] The raw materials used in the embodiments and comparative examples are described below, but are not limited to these materials:

[0038] Low-density polyethylene-1 (LDPE-1): melt flow rate 8 g / 10 min (190℃, 2.16 kg), density 0.916 g / cm³. 3 Grade LDPE 722, Manufacturer: DOW;

[0039] Low-density polyethylene-2 ​​(LDPE-2): melt flow rate 15 g / 10 min (190℃, 2.16 kg), density 0.918 g / cm³. 3 Grade EXCEED 0015XC, Manufacturer ExxonMobil;

[0040] Low-density polyethylene-3 (LDPE-3): melt flow rate 0.75 g / 10 min (190℃, 2.16 kg), density 0.92 g / cm³. 3 Grade LDPE 310E, Manufacturer: DOW;

[0041] Low-density polyethylene-4 (LDPE-4): melt flow rate 40 g / 10 min (190℃, 2.16 kg), density 0.92 g / cm³. 3 Grade LDPE M1840, Manufacturer: Yanshan Petrochemical;

[0042] Linear low-density polyethylene-1 (LLDPE-1): melt flow rate 0.9 g / 10 min (190℃, 2.16 kg), density 0.94 g / cm³. 3 Grade LLDPE 4009MC, Manufacturer: ExxonMobil;

[0043] Linear low-density polyethylene-2 ​​(LLDPE-2): melt flow rate 0.5 g / 10 min (190℃, 2.16 kg), density 0.935 g / cm³. 3 The grade is LLDPE ENABLE 3505, and the manufacturer is ExxonMobil.

[0044] Linear low-density polyethylene-3 (LLDPE-3): melt flow rate 1 g / 10 min (190℃, 2.16 kg), density 0.92 g / cm³. 3 Grade LLDPE ENABLE2010PA, Manufacturer: ExxonMobil;

[0045] High-density polyethylene-1 (HDPE-1): melt flow rate 0.85 g / 10 min (190℃, 2.16 kg), density 0.962 g / cm³. 3 Grade HDPE 5960G, Manufacturer: DOW;

[0046] HDPE-2: Melt flow rate 8 g / 10 min (190℃, 2.16 kg), density 0.958 g / cm³ 3 Grade HDPE8008, Manufacturer: Lanzhou Petrochemical.

[0047] Heavy calcium carbonate-1: average particle size D50 is 4.2 micrometers, grade AC-72, manufacturer (Lianzhou) Powder Technology;

[0048] Heavy calcium carbonate-2: average particle size D50 is 5.0 micrometers, grade AC-77, manufacturer Xinrong (Lianzhou) Powder Technology;

[0049] Heavy calcium carbonate-3: average particle size D50 is 6.5 micrometers, grade AC-64, manufacturer Xinrong (Lianzhou) Powder Technology;

[0050] Heavy calcium carbonate-4: average particle size D50 is 2.5 micrometers, grade AC-26, manufacturer Xinrong (Lianzhou) Powder Technology;

[0051] Heavy calcium carbonate-5: average particle size D50 is 8.0 micrometers, grade AC-88, manufacturer Xinrong (Lianzhou) Powder Technology;

[0052] Heavy calcium carbonate-6: average particle size D50 is 4.9 micrometers, grade OMYACARB 5T, surface treatment agent used is stearic acid, manufacturer OMYA.

[0053] Surface treatment agent-1: Phosphate ester, brand name RP-98, manufacturer Maoheng Chemical;

[0054] Surface treatment agent-2: Titanate, grade PN-130, manufacturer Pinning Chemical;

[0055] Surface treatment agent-3: stearic acid, brand name stearic acid 181, manufacturer: Hunan Chengcheng Oil & Chemical Co., Ltd.

[0056] Antioxidant: The antioxidant is a compound of commercially available hindered phenolic antioxidant 1010 and commercially available phosphite antioxidant 168 in a mass ratio of 1:1. The parallel examples and comparative examples use the same commercially available product.

[0057] Processing aid: Zinc stearate, commercially available; the parallel examples and comparative examples used the same commercially available product.

[0058] Examples 1-12 and Comparative Examples 1-9

[0059] The method for preparing heavy calcium carbonate coated with a surface treatment agent used in the examples and comparative examples includes the following steps: preparing activated heavy calcium carbonate using a high-speed mixer at a speed of 500 rpm, adjusting the mixer speed accordingly, adding a specific dosage of surface treatment agent when the temperature reaches 120°C, and achieving uniform coating of the surface treatment agent under high-speed, high-temperature stirring and mixing. In the coated heavy calcium carbonate, the weight of the surface treatment agent is 1 wt% of the weight of the heavy calcium carbonate.

[0060] The preparation methods of coated heavy calcium carbonate-1, coated heavy calcium carbonate-2, coated heavy calcium carbonate-3, coated heavy calcium carbonate-4, and coated heavy calcium carbonate-5 in Tables 1 and 2 are as described above. Among them, coated heavy calcium carbonate-1 is selected as the coating material, and so on. They will not be described in detail one by one.

[0061] Among them, the surface treatment agent used for coated heavy calcium carbonate-1, coated heavy calcium carbonate-2, coated heavy calcium carbonate-3, coated heavy calcium carbonate-4, and coated heavy calcium carbonate-5 is surface treatment agent-1: phosphate ester.

[0062] The surface treatment agent used for coated heavy calcium carbonate-11 is surface treatment agent-2: titanate, and the surface treatment agent used for coated heavy calcium carbonate-12 is surface treatment agent-3: stearic acid.

[0063] The preparation method of the polyolefin composition for desiccant packaging according to the present invention includes the following steps: mixing the components in proportion, followed by melt extrusion and granulation to obtain the polyolefin composition for packaging. The extruder screw has a length-to-diameter ratio of 48:1, and the processing temperature is in the range of 200-220℃.

[0064] Examples and comparative examples of the polyolefin composition for desiccant packaging according to the present invention are shown in Tables 1 and 2.

[0065] Table 1

[0066]

[0067]

[0068]

[0069] Table 2

[0070]

[0071] Performance testing

[0072] The polyolefin composition for desiccant packaging prepared in the above examples and comparative examples was cast and molded under processing conditions of 220-240℃. A microporous network channel was formed inside the film by MDO stretching process to prepare a 30gsm breathable film. The polyolefin breathable film composition was used to prepare film samples in the temperature range of 220-240℃, with a stretching ratio of 3.0 times, a preheating temperature of 80℃, a stretching temperature of 90℃, and a setting temperature of 105℃.

[0073] Air permeability: According to GB / T 12704.2-2009 "Textiles - Test Method for Moisture Permeability of Fabrics", the air permeability test temperature is 48℃ and the humidity is 50%RH.

[0074] Tensile properties: tested according to ASTM D882-2018 standard.

[0075] Appearance: 20*100cm film samples with a basis weight of 30gsm were prepared using the above casting process. The appearance of the film was observed under a light box, and the quality was graded into four levels, with level 1 being the best. Level 4 indicates severe bark texture, with densely distributed bark texture under the light box; Level 3 indicates obvious bark texture, with a relatively large amount of bark texture under the light box; Level 2 indicates slight bark texture, with indistinct texture under the light box; and Level 1 indicates no bark texture and a good product appearance.

[0076] In the application of desiccant pack breathable membrane products, the air permeability is required to be >3400g / m³. 2 • After 24 hours, the tensile strength is >4.0N, and the appearance has slight bark texture or no bark texture, that is, grades 1-2 meet the requirements.

[0077] Test results are shown in Table 3.

[0078] Table 3

[0079]

[0080]

[0081] As shown in the table above, the air permeability of the polyolefin composition breathable membrane for desiccant packaging prepared in the embodiments of the present invention is >3400 g / m³. 2 • After 24 hours, a tensile strength > 4.0 N and an appearance with slight bark texture or no bark texture are all acceptable.

[0082] As can be seen from the comparison of Examples 1, 8, and Comparative Examples 1-2, when the melt flow rate of low-density polyethylene (LDPE) is 1-15 g / 10 min, the resulting polyolefin composition breathable film for desiccant packaging has good mechanical properties, as well as high air permeability and good appearance.

[0083] As can be seen from the comparison of Examples 1, 9, and Comparative Example 3, the density of LLDPE is 0.93-0.95 g / cm³. 3 The prepared desiccant packaging polyolefin composition breathable film has good mechanical properties, as well as high air permeability and good appearance.

[0084] As can be seen from the comparison of Examples 1, 10-12, and Comparative Examples 5-6, the weight ratio of low-density polyethylene to linear low-density polyethylene affects the air permeability, mechanical properties, and appearance of the prepared polyolefin composition breathable film for desiccant packaging. When the weight ratio of low-density polyethylene to linear low-density polyethylene is 1:3-5, the prepared polyolefin composition breathable film for desiccant packaging has better mechanical properties or appearance.

[0085] As can be seen from the comparison of Examples 1-7 and Comparative Examples 7-8, when the average particle size D50 of heavy calcium carbonate is 4-7 micrometers, the resulting polyolefin composition breathable film for desiccant packaging exhibits good mechanical properties, as well as high air permeability and a good appearance. When the heavy calcium carbonate is obtained by coating with a surface treatment agent, the resulting polyolefin composition for desiccant packaging has even better appearance and mechanical properties. When the surface treatment agent is a phosphate ester, it can better improve air permeability through interfacial adsorption, while also having a certain effect on improving the tensile strength of the film.

[0086] As can be seen from the comparison of Example 1, Comparative Example 4, and Comparative Example 9, when HDPE is present in the polyolefin composition and LDPE and LLDPE of the present invention are not used in the specific components and weight parts of the present invention, the air permeability of the breathable membrane is improved, but the mechanical properties are significantly degraded and appearance defects occur, which does not meet the requirements.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A polyolefin composition for desiccant packaging, characterized in that, It includes the following components in parts by weight: 30-50 parts polyolefin resin, 35-70 parts heavy calcium carbonate, 0.5-2 parts antioxidant, and 0.5-2 parts processing aid; The polyolefin resin is a mixture of low-density polyethylene and linear low-density polyethylene in a weight ratio of (1-2):(3-6). The low-density polyethylene, according to ISO 1133-1-2011, has a melt flow rate of 1-15 g / 10 min at 190°C and 2.16 kg, and the linear low-density polyethylene has a density of 0.93-0.94 g / cm³. 3 The average particle size D50 of the heavy calcium carbonate is 4-7 micrometers. The heavy calcium carbonate is obtained by coating with a surface treatment agent. The surface treatment agent is at least one of stearic acid, phosphate ester, titanate, and aluminate. The weight of the surface treatment agent is 0.5wt%-2wt% of the weight of the heavy calcium carbonate.

2. The polyolefin composition for desiccant packaging as described in claim 1, characterized in that, The linear low-density polyethylene, according to ISO 1133-1-2011, has a melt flow rate of 0.5-2.0 g / 10min at 190°C and 2.16 kg, and the density of the low-density polyethylene is 0.915-0.925 g / cm³. 3 .

3. The polyolefin composition for desiccant packaging as described in claim 1, characterized in that, The surface treatment agent is a phosphate ester.

4. The polyolefin composition for desiccant packaging as described in claim 1, characterized in that, The weight ratio of the low-density polyethylene to the linear low-density polyethylene is 1:3-5.

5. The polyolefin composition for desiccant packaging as described in claim 1, characterized in that, The antioxidant is at least one of hindered phenols and phosphites, and the processing aid is a lubricant, which is at least one of fluorinated compounds, polyolefin waxes, low molecular weight esters, stearates, and amides.

6. A method for preparing a polyolefin composition for desiccant packaging as described in any one of claims 1-5, characterized in that, Includes the following steps: After mixing the components in proportion, the mixture is melt-extruded and granulated to obtain the polyolefin composition for desiccant packaging.

7. The application of a polyolefin composition for desiccant packaging as described in any one of claims 1-5 in the field of desiccant packaging.

8. The application as described in claim 7, characterized in that, The field of desiccant packaging includes food desiccant packaging, household product desiccant packaging, and clothing desiccant packaging.

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