Ultra-high breathable polyolefin breathable membrane material and preparation method thereof

Abstract

The present invention relates to an ultra-high-permeability polyolefin breathable membrane material and a preparation method thereof, comprising a polyethylene resin, micron-sized surface-modified heavy calcium carbonate, a dispersant, and an antioxidant. By optimizing the particle size distribution of the micron-sized surface-modified heavy calcium carbonate and adding high-density polyethylene, the present invention produces an ultra-high-permeability polyolefin breathable membrane material with a good appearance, a Wang Yanshi air permeability of less than 100s, and no surface defects such as crystal points and pinholes. Furthermore, the micron-sized surface-modified heavy calcium carbonate increases the number and average pore size of interfacial delamination pores formed during the stretching process of the polyolefin breathable membrane material, thereby improving its air permeability.

Description

Technical Field

[0001] The present invention belongs to the field of packaging, and in particular relates to an ultra-high breathable polyolefin breathable film material and a preparation method thereof. Background Art

[0002] Due to its breathable and waterproof properties, polyolefin breathable membrane is widely used in packaging fields such as desiccant packs, hot packs, steam eye masks, and fruit bags. Its preparation process is to first fill polyolefin with inorganic fillers mainly composed of calcium carbonate for blending and modification to prepare special materials for breathable membranes, and then obtain the breathable membrane through cast or blown film and stretching. During the stretching process, the polyolefin resin and the inorganic filler desorb at the interface and form tiny pores to achieve the breathable and waterproof functions. Since the air permeability of polyolefin breathable membranes significantly affects the use effects of products such as desiccant bags, hot packs, steam eye masks and fruit bags, the higher the air permeability of polyolefin breathable membranes, the better. Wang Yan's air permeability is less than 100s. Even if the calcium carbonate powder filling amount of conventional polyolefin breathable membranes is as high as 60% and the maximum stretching ratio is adopted in the film making process, its air permeability is only about 150s, which cannot meet the increasingly high product requirements of products such as desiccant bags and fruit bags. Therefore, how to prepare ultra-high air permeable breathable base membranes is also a technical problem that needs to be solved urgently in this field. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide an ultra-high breathable polyolefin breathable membrane material and a preparation method thereof, wherein the polyolefin breathable membrane has good breathability and moisture permeability.

[0004] The present invention provides an ultra-high breathable polyolefin breathable membrane material, comprising the following components in parts by weight:

[0005]

[0006] Wherein, the polyethylene resin is at least three of low-density polyethylene, linear low-density polyethylene, metallocene polyethylene and high-density polyethylene, and must include high-density polyethylene;

[0007] Preferably, the breathable membrane material comprises the following components calculated by percentage:

[0008]

[0009] Preferably, the proportion of the low-density polyethylene in the breathable membrane material is 3-15%;

[0010] Preferably, the weight ratio of the linear low-density polyethylene to the metallocene polyethylene is 1:0-1;

[0011] Preferably, the proportion of the high-density polyethylene in the breathable membrane material is 5-15%.

[0012] The particle size distribution of the micron-sized surface-modified heavy calcium carbonate is:

[0013] Less than 1.0μm content ≤5% (such as ≤1%, 2%, 3%, 4%, etc.),

[0014] The content of particles greater than or equal to 1.0μm and less than 3.0μm is ≤20% (such as ≤10%, 12%, 14%, 16%, 18%, etc.), the content of particles greater than or equal to 3.0μm and less than 5.5μm is ≥40% (such as ≥42%, 44%, 46%, 48%, 50%, etc.), the content of particles greater than or equal to 5.5 and less than or equal to 10μm is ≥25% (such as ≥28%, 30%, 32%, 34%, etc.), the content of particles greater than 10μm is ≤10% (such as ≤2%, 4%, 6%, 8%, etc.),

[0015] D50 4.0-5.5μm.

[0016] Furthermore, it includes at least one of the following (1) to (4);

[0017] (1) The low-density polyethylene melt index (at 190° C. and 2.16 kg (test standard: ISO 1133-1:2011)) is 5.0-10 g / 10 min;

[0018] (2) the linear low-density polyethylene has a melt index (at 190° C. and 2.16 kg (test standard: ISO 1133-1:2011)) of 0.5-5.0 g / 10 min;

[0019] (3) The metallocene polyethylene has a melt index (at 190° C. and 2.16 kg (test standard: ISO 1133-1:2011)) of 0.5-5.0 g / 10 min;

[0020] (4) The high-density polyethylene melt index (at 190° C. and 2.16 kg (test standard: ISO 1133-1:2011)) is 0.5-10 g / 10 min.

[0021] Furthermore, it includes at least one of the following (1) to (3);

[0022] (1) The linear low-density polyethylene has a density of 0.927-0.960 g / cm 3 ;

[0023] (2) The density of the metallocene polyethylene is 0.927-0.960 g / cm 3 ;

[0024] (3) The density of the high-density polyethylene is 0.940-0.970 g / cm 3 .

[0025] Furthermore, it includes at least one of the following (1) to (2);

[0026] (1) The linear low-density polyethylene has a crystallinity of 35-65%;

[0027] (2) The crystallinity of the metallocene polyethylene is 35-65%.

[0028] Furthermore, the melting temperature of the metallocene polyethylene is greater than 120°C.

[0029] The surface modifier used in the micron-sized surface-modified heavy calcium carbonate is at least one of stearic acid, titanate, aluminate, silane coupling agent, and maleic anhydride grafted polyethylene wax.

[0030] The dispersant is at least one of polyethylene wax, stearate, amides, and polymer dispersants.

[0031] The antioxidant is at least one of hindered phenols, phosphites and thioether antioxidants.

[0032] More preferably, the following components are included in parts by weight:

[0033]

[0034] More preferably, the breathable membrane material comprises the following components calculated by percentage:

[0035]

[0036] The present invention also provides a method for preparing an ultra-high breathable polyolefin breathable membrane material, comprising the following steps:

[0037] (1) uniformly mixing a polyethylene resin, a dispersant, and an antioxidant to obtain a mixture; feeding the mixture and micron-sized surface-modified heavy calcium carbonate into a twin-screw extruder for melt plasticization and extrusion; and obtaining a special material for ultra-high breathability polyolefin breathable membrane after strand pelletizing or underwater pelletizing;

[0038] (2) The ultra-high permeability polyolefin breathable membrane material is melted and plasticized and extruded through a casting extruder. The melt is continuously extruded through the slit die of the T-die head of the casting machine, and then cooled by a casting roller, and then uniaxially stretched and heat-set to obtain an ultra-high permeability polyolefin breathable membrane material.

[0039] In the step (1), the twin-screw extruder has a screw diameter of 58-96 mm and an aspect ratio of 52-56, and is respectively provided with a main feeding port and a side feeding system.

[0040] In the step (1), the processing temperature of the extruder is set at 160-240°C.

[0041] Furthermore, the mixture and part of the micron-sized surface-modified heavy calcium carbonate are added to the twin-screw extruder through the main feeding port, and the remaining micron-sized surface-modified heavy calcium carbonate is added to the twin-screw extruder through the extruder side feeding system. More preferably, the mass ratio of the micron-sized surface-modified heavy calcium carbonate added to the twin-screw extruder through the main feeding port and the side feeding system is 1:2.5-1:1.

[0042] The ultra-high breathability polyolefin breathable membrane special material obtained in step (1) is dehumidified and dried before being packaged as a finished product, and the dehumidification and drying temperature is 80-90°C.

[0043] The uniaxial stretching process parameters of step (2) are: the stretching ratio is controlled at 3.0-4.0, the film preheating temperature is set at 70-80°C, and the stretching temperature is set at 80-90°C.

[0044] The heat setting process parameters of step (2) are: temperature setting 95-110°C.

[0045] The present invention also provides an application of an ultra-high breathable polyolefin breathable film material in desiccant bags and fruit bagging.

[0046] The principle of the present invention is:

[0047] According to interfacial exfoliation theory, the effect of micron-sized calcium carbonate particle size distribution on air and moisture permeability is as follows: larger particles are more likely to form pores, resulting in larger average pore sizes and, consequently, higher air and moisture permeability. However, the effects of particle size on air and moisture permeability differ. Moisture permeability testing measures the diffusion of water vapor molecules from high-concentration areas to low-concentration areas via Brownian motion under no pressure, while air permeability testing measures the passage rate of other materials, such as air, under a certain pressure. Therefore, particle size distribution must be restricted.

[0048] Beneficial effects

[0049] (1) The present invention prepares an ultra-high permeability polyolefin breathable membrane with good appearance by optimizing the particle size distribution of micron-level surface-modified heavy calcium carbonate and adding high-density polyethylene. The Wang Yanshi air permeability is less than 100s, and the membrane surface has no defects such as crystal points and pinholes. At the same time, the micron-level surface-modified heavy calcium carbonate can increase the number of interfacial peeling holes and the average pore size during the stretching process of the polyolefin breathable membrane, thereby improving its air permeability.

[0050] (2) The present invention increases the number of interfacial peeling holes during the stretching process of polyolefin by preferably using high crystallinity and high density metallocene polyethylene and linear low density polyethylene, thereby improving its air permeability; in addition, the addition of high density polyethylene can further increase the number of interfacial peeling holes and the average pore size during the stretching process of the polyolefin breathable membrane, thereby improving its air permeability, but too high a content can easily lead to uneven stretching and the appearance of tiger stripes. DETAILED DESCRIPTION

[0051] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0052] Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0053] The raw materials used in the following examples and comparative examples are as follows:

[0054] Low-density polyethylene: LDPE 1C7A, manufactured by Yanshan Petrochemical, with a melt index of 7.5 g / 10 min at 190°C and 2.16 kg;

[0055] Linear low-density polyethylene 1#: brand LLDPE 2064G, manufacturer Dow Chemical, density 0.935g / cm 3 , the melt index at 190℃ and 2.16kg is 2.5g / 10min, and the crystallinity is 43%;

[0056] Linear low-density polyethylene 2#: brand LLDPE 1002YB, manufacturer ExxonMobil, density 0.918g / cm 3 , the melt index is 2.0g / 10min at 190℃ and 2.16kg, and the crystallinity is 30%;

[0057] Metallocene polyethylene 1#: brand LLDEP 3527PA, manufacturer ExxonMobil, density 0.927g / cm 3 , melt index is 3.5g / 10min, crystallinity is 40%;

[0058] Metallocene polyethylene 2#: brand LLDPE 2010PA, manufacturer ExxonMobil, density 0.920g / cm 3 , melt index is 1.0g / 10min, crystallinity is 30%;

[0059] High-density polyethylene 1#: brand HDPE 5000s, manufacturer Daqing Petrochemical, density 0.954g / cm 3 , the melt index is 0.9g / 10min.

[0060] High-density polyethylene 2#: Brand: HDPE DMDA-8008, manufacturer: Dushanzi Petrochemical, density: 0.955g / cm 3 , the melt index is 7.3g / 10min.

[0061] Micron-grade surface modified heavy calcium carbonate 1#: brand 5T-JI, manufacturer Omya, particle size distribution less than 3.0μm content 30%, greater than or equal to 3.0μm and less than 5.5μm content 30%, greater than or equal to 5.5μm and less than or equal to 10μm content 35%, greater than 10μm content 5%, D50 4.8-4.9μm.

[0062] Micron-grade surface-modified heavy calcium carbonate 2#: brand FilmLink 520, manufacturer Yingge Ceramics, particle size distribution less than 3.0μm content 68%, greater than or equal to 3.0μm and less than 5.5μm content 22%, greater than or equal to 5.5μm and less than or equal to 10μm content 9%, greater than 10μm content 1%, uniform particle size D50 2.0μm.

[0063] The micron-sized surface-modified heavy calcium carbonate is surface-treated with stearic acid, and the modification equipment and method are activation modification using a nail disc mill or a honeycomb mill.

[0064] Dispersant: polyethylene wax, commercially available;

[0065] Antioxidants: hindered phenols and phosphites in a mass ratio of 1:1, commercially available;

[0066] The same commercially available dispersant and antioxidant were used in each embodiment and comparative example.

[0067] The breathable membranes of the embodiments and comparative examples were prepared by the following process:

[0068] The raw material composition was extruded and granulated through a twin-screw extruder with a screw diameter of 75 mm and an aspect ratio of 52. The processing temperature was 200°C, and the mass ratio of calcium carbonate added to the twin-screw extruder through the main feed port and the side feed system was 1:2. The above-mentioned breathable film material was used to prepare a breathable film having a grammage of 40 gsm by cast extrusion. The film preheating temperature was 80°C, the stretching temperature was 90°C, the setting temperature was 105°C, and the stretch ratio was 3.0 times or 4.0 times.

[0069] The examples and comparative examples were subjected to the following test methods or test standards:

[0070] Wang Yan's air permeability test method refers to the standard JIS P8117-2009. The Gurley value is the time required for 100ml of air to pass through a specific area under a specific pressure (8.5KPa). The water vapor permeability test method refers to the standard GB / T 12704-2009.

[0071] Table 1 Components and test results of Examples and Comparative Examples

[0072]

[0073]

[0074] From the above experimental results, it can be seen that Examples 1-8 all have good air permeability and average moisture permeability. The air permeability is 61-90s / 100ml, but the average moisture permeability can reach 3325-3980g / m 2 24 hours. Comparative Example 1 and Example 1 show that the addition of high-density polyethylene further improves moisture permeability. Comparative Examples 2, 4, and 5 show that the specific selection of linear low-density polyethylene, metallocene polyethylene, and micron-sized surface-modified heavy calcium carbonate affects material properties. Comparative Example 3 shows that excessive addition of micron-sized surface-modified heavy calcium carbonate can affect film formation.

Claims

1. An ultra-high breathable polyolefin breathable membrane material, characterized by: In parts by weight, it comprises the following components: The polyethylene resin is at least three of low-density polyethylene, linear low-density polyethylene, metallocene polyethylene and high-density polyethylene, and must include high-density polyethylene; the proportion of high-density polyethylene in the breathable membrane material is 5-15%; the micron-grade surface-modified heavy calcium carbonate is Omya 5T-JI.

2. The ultra-high breathable polyolefin breathable membrane material according to claim 1, characterized in that: Contain at least one of the following (1) to (4); (1) The low-density polyethylene has a melt index of 5.5-9.5 g / 10 min at 190° C. and 2.16 kg; (2) the linear low-density polyethylene has a melt index of 0.3-4.5 g / 10 min at 190° C. and 2.16 kg; (3) the metallocene polyethylene has a melt index of 0.3-4.5 g / 10 min at 190° C. and 2.16 kg; (4) The high-density polyethylene has a melt index of 0.5-10 g / 10 min at 190° C. and 2.16 kg.

3. The ultra-high breathable polyolefin breathable membrane material according to claim 1, characterized in that: Contain at least one of the following (1) to (3); (1) The linear low-density polyethylene has a density of 0.927-0.960 g / cm 3 ; (2) The density of the metallocene polyethylene is 0.927-0.960 g / cm 3 ; (3) The density of the high-density polyethylene is 0.940-0.970 g / cm 3 .

4. The ultra-high breathable polyolefin breathable membrane material according to claim 1, characterized in that: Contain at least one of the following (1) to (2); (1) The linear low-density polyethylene has a crystallinity of 35-65%; (2) The crystallinity of the metallocene polyethylene is 35-65%.

5. The ultra-high breathable polyolefin breathable membrane material according to claim 1, characterized in that: The dispersant is at least one of polyethylene wax, stearate, amide, and polymer dispersants; the antioxidant is at least one of hindered phenol, phosphite, and thioether antioxidants.

6. The ultra-high breathable polyolefin breathable membrane material according to claim 1, characterized in that: In parts by weight, it comprises the following components:

7. A method for preparing the ultra-high breathable polyolefin breathable membrane material according to claim 1, comprising the following steps: (1) uniformly mixing a polyethylene resin, a dispersant, and an antioxidant to obtain a mixture; feeding the mixture and micron-sized surface-modified heavy calcium carbonate into a twin-screw extruder for melt plasticization and extrusion; and obtaining a special material for ultra-high breathability polyolefin breathable membrane after strand pelletizing or underwater pelletizing; (2) The ultra-high permeability polyolefin breathable membrane material is melted and plasticized and extruded through a casting extruder. The melt is continuously extruded through the slit die of the T-die head of the casting machine, and then cooled by a casting roller, and then uniaxially stretched and heat-set to obtain an ultra-high permeability polyolefin breathable membrane material.

8. Use of the ultra-high breathable polyolefin breathable film material according to claim 1 in desiccant bags and fruit bags.

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