Inorganic masterbatch, method for manufacturing the same, and polyethylene film using the masterbatch

Abstract

The present application discloses an inorganic masterbatch and a method for manufacturing the same, and a polyethylene film using the masterbatch, and relates to the field of pearlescent film technology. The present application prepares an inorganic masterbatch by mixing ultrafine calcium carbonate and polyethylene resin, and the ultrafine calcium carbonate is evenly distributed inside the inorganic masterbatch, and the material strips are uniform and stable during production, without abnormal broken strips and other problems. The inorganic masterbatch is used to prepare a uniaxially stretched polyethylene film, which has a bright pearlescent effect and good stiffness. The film thickness (15μm-100μm) can be effectively controlled during the production process. In flexible packaging applications, it can replace pre-coated pearlescent BOPP film or BOPP pearlescent composite film, and improve the defects of poor stiffness and poor printing of traditional inflatable or chemically foamed polyethylene.

Description

Technical Field

[0001] The present application relates to the technical field of pearlescent films, and in particular to an inorganic masterbatch and a manufacturing method thereof, and a polyethylene film using the masterbatch. Background Art

[0002] Among the current food packaging materials, the film products with high stiffness and pearlescent effect are mainly biaxially oriented polypropylene films (BOPP), which are made by adding calcium carbonate masterbatch, white masterbatch and other modifying additives to polypropylene, mixing and extruding into sheets, and then biaxially stretching to form holes. For example, the Chinese invention patent application with publication number CN110684279A discloses "a pearlescent masterbatch for biaxially oriented film and its preparation method and application", which includes the following components in weight percentage: polypropylene resin 24.4-39.4%; calcium carbonate powder 60-75%; additive A 0.2-5%; lubricant 0.2-5%; antioxidant masterbatch 0.2-1%; wherein the additive A is a compatibilizer, coupling agent or dispersant. The preparation method includes the following steps: S1: mixing and conveying raw materials; S2: melt extrusion; S3: granulation and post-processing. The use of the pearlescent masterbatch for biaxially oriented film has a lower pressure on the filter screen during BOPP film production, which can effectively avoid filter screen blockage, and the film has better pearlescent effect and light-shielding performance, and the production cost is lower. However, the pearlescent BOPP film itself has poor printing adaptability, and generally needs to be compounded with a PE film with good printability or coated with a layer of printing coating on the surface. The former is not friendly to the requirement of material uniformity (multi-layer composite structure is the same material, such as all polypropylene or all polyethylene, which is easy to recycle and use later), and the latter greatly increases the material cost.

[0003] In addition, the foaming effect can be achieved by injecting gas (physical foaming method) during the polyethylene (PE) processing, or by chemical foaming method (such as sodium bicarbonate producing carbon dioxide under the action of an acidifier), thereby obtaining a polyethylene film with a pearlescent effect to replace the polypropylene film. However, whether it is a physical foaming method or a chemical foaming method, since the foaming is difficult to control and the foaming gap is large, the film is generally thicker, about 40-200 microns. At the same time, the film is prone to creases after bending, and the foaming gap is easily squeezed during the printing process, resulting in printing defects. In addition, the physical foaming method requires the addition of special equipment, which requires large equipment investment and is difficult to control the foaming process.

[0004] Therefore, there is an urgent need to develop a pearlescent polyethylene film to replace the existing pearlescent BOPP film and foamed PE film, which can meet the requirements of packaging film while meeting the requirements of material uniformity. Summary of the invention

[0005] The purpose of this application is to provide an inorganic masterbatch and a method for manufacturing the same, and a polyethylene film using the masterbatch, which can replace the existing pearlescent BOPP film and foamed PE film, and can meet the requirements of packaging film in terms of performance while meeting the requirements of material uniformity.

[0006] To achieve the above purpose, the embodiment of the present application adopts the following technical solution: an inorganic masterbatch, comprising the following components: 20-49wt% polyethylene resin; 50-70% ultrafine calcium carbonate; 1-10wt% additive, and the MFR of the polyethylene resin is ≤30.

[0007] In the above technical scheme, the embodiment of the present application prepares an inorganic masterbatch by mixing ultrafine calcium carbonate and polyethylene resin, and the ultrafine calcium carbonate is evenly distributed inside the inorganic masterbatch, and the material strips are uniform and stable during production, without abnormal strip breakage and other problems. The inorganic masterbatch is used to prepare a uniaxially stretched polyethylene film, which has a bright pearlescent effect and good stiffness. The film thickness (15μm-100μm) can be effectively controlled during the production process. In flexible packaging applications, it can replace pre-coated pearlescent BOPP film or BOPP pearlescent composite film, and improve the defects of poor stiffness and poor printing of traditional inflatable or chemically foamed polyethylene.

[0008] Further, according to an embodiment of the present application, the polyethylene resin is one or more of HDPE, LDPE, LLDPE, m-LLDPE, and EVA.

[0009] Further, according to an embodiment of the present application, the particle size D50 of the ultrafine calcium carbonate is ≤3 μm.

[0010] Further, according to an embodiment of the present application, the particle size D50 of the ultrafine calcium carbonate is ≤2 μm.

[0011] Further, according to an embodiment of the present application, the particle size D50 of the ultrafine calcium carbonate is ≤1.2 μm.

[0012] Further, according to an embodiment of the present application, the auxiliary agent includes a dispersing agent, a lubricant or an antioxidant.

[0013] Further, according to an embodiment of the present application, the added amount of the dispersant is 1-5wt%.

[0014] Further, according to an embodiment of the present application, the added amount of the lubricant is 1-5wt%.

[0015] Further, according to an embodiment of the present application, the added amount of the antioxidant is less than or equal to 1 wt %.

[0016] In order to achieve the above object, the present application also discloses a method for preparing an inorganic masterbatch, comprising the following steps:

[0017] Weigh the raw materials according to the formula and put them into the mixer to mix evenly;

[0018] The mixed raw materials are fed into a twin-screw extruder for melt extrusion, and then cooled, air-dried, pelletized, screened, and dried to obtain the inorganic masterbatch; the L / D of the extruder is ≥48.

[0019] In order to achieve the above-mentioned purpose, an embodiment of the present application also discloses a polyethylene film, comprising a first surface layer, the first surface layer is made of PE material; a second surface layer, the second surface layer comprises PE and white masterbatch, and the second surface layer is arranged on one side of the first surface layer; a core layer, the core layer comprises PE and inorganic masterbatch, the inorganic masterbatch is the inorganic masterbatch described above, and the core layer is arranged on one side of the second surface layer; an inner layer, the inner layer is made of PE material, and the inner layer is arranged on one side of the core layer; a third surface layer, the material of the third surface layer is consistent with that of the second surface layer, and the third surface layer is arranged on one side of the inner layer.

[0020] Further, according to an embodiment of the present application, the material of the surface layer is LDPE, m-LLDPE, HDPE or a mixture thereof.

[0021] Further, according to an embodiment of the present application, the PE material of the second surface layer is selected from LDPE, m-LLDPE, HDPE or a mixture thereof, and the content of the PE material is greater than or equal to 70wt%.

[0022] Further, according to an embodiment of the present application, the white masterbatch of the second surface layer is a white masterbatch composite material whose carrier is EVA, PE, and PP, and the white masterbatch in the white masterbatch composite material accounts for 40wt% or more.

[0023] Further, according to an embodiment of the present application, the inorganic masterbatch in the core layer accounts for 10-20wt%.

[0024] Further, according to an embodiment of the present application, the PE material in the core layer is selected from LDPE, LLDPE, m-LLDPE, HDPE or a mixture thereof.

[0025] Further, according to an embodiment of the present application, the material of the inner layer is LDPE, m-LLDPE, HDPE or a mixture thereof.

[0026] In order to achieve the above object, the present application also discloses a method for preparing a polyethylene film, comprising the following steps:

[0027] Prepare the raw materials of the first surface layer, the second surface layer, the core layer, the inner layer and the third surface layer, and put them into a blender for mixing and stirring respectively;

[0028] The raw materials are added to a five-layer casting machine or a film blowing machine for uniaxial stretching, the stretching ratio is 3-10 times, the stretching direction is the MD direction, and the stretching temperature is 90-130°C.

[0029] Compared with the prior art, the present application has the following beneficial effects: the present application prepares inorganic masterbatch by mixing ultrafine calcium carbonate and polyethylene resin, and the ultrafine calcium carbonate is evenly distributed inside the inorganic masterbatch, and the material strips are evenly stable during production, without abnormal strip breakage and other problems. The inorganic masterbatch is used to prepare uniaxially stretched polyethylene film, which has a bright pearlescent effect and good stiffness. The film thickness (15μm-100μm) can be effectively controlled during the production process. In the application of flexible packaging, it can replace the pre-coated pearlescent BOPP film or BOPP pearlescent composite film, and improve the defects of poor stiffness and poor printing of traditional inflated or chemically foamed polyethylene. DETAILED DESCRIPTION

[0030] In order to make the purpose and technical solution of the present invention clearly and completely described, and the advantages more clearly understood, the embodiments of the present invention are further described in detail below. It should be understood that the specific embodiments described herein are part of the embodiments of the present invention, rather than all of the embodiments, and are only used to explain the embodiments of the present invention, and are not used to limit the embodiments of the present invention. All other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] In the description of the present invention, it should be noted that the terms "center", "middle", "upper", "lower", "left", "right", "inner", "outer", "top", "bottom", "side", "vertical", "horizontal" and the like indicating directions or positional relationships are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "one", "first", "second", "third", "fourth", "fifth", "sixth" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0032] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] For the purpose of simplicity and illustration, the principles of the embodiments are mainly described by reference to examples. In the following description, many specific details are proposed to provide a thorough understanding of the embodiments. However, it is obvious that for those of ordinary skill in the art, these embodiments may not be limited to these specific details in practice. In some instances, known methods and structures are not described in detail to avoid making these embodiments unnecessarily difficult to understand. In addition, all embodiments can be used in combination with each other.

[0034]

Inorganic masterbatch

[0035] The present application discloses an inorganic masterbatch for preparing pearlescent film. The inorganic masterbatch comprises polyethylene material and ultrafine calcium carbonate, the ultrafine calcium carbonate is evenly distributed inside the inorganic masterbatch, the material strips are evenly stable during production, and there are no abnormal strip breakage and other problems. The inorganic masterbatch is used to prepare a uniaxially stretched polyethylene film, which has a bright pearlescent effect and good stiffness. The film thickness (15 μm-100 μm) can be effectively controlled during the production process. In the application of flexible packaging, the inorganic masterbatch can replace the pre-coated pearlescent BOPP film or BOPP pearlescent composite film, and improve the defects of poor stiffness and poor printing of traditional inflated or chemically foamed polyethylene.

[0036] Specifically, the amount of polyethylene resin added is 20-49wt%, and one or more of HDPE, LDPE, LLDPE, m-LLDPE, and EVA are specifically used. Preferably, the MFR of the polyethylene resin is ≤30, but the requirements for MFR vary greatly depending on the polyethylene film stretching process. If a blown film single-stretching process is used, the polyethylene resin needs to have an MFR of ≤10; if a cast film single-stretching process is used, a polyethylene resin with an MFR of ≤30 needs to be used.

[0037] In addition, the addition amount of the ultrafine calcium carbonate is 50-70wt%. The particle size D50 of the ultrafine calcium carbonate is within 3μm, preferably within 2μm, and more preferably within 1.2μm. The activation degree of the ultrafine calcium carbonate is required to reach more than 95%.

[0038] Furthermore, the inorganic masterbatch also includes an auxiliary agent, and the amount of the auxiliary agent added is 1-10wt%. The auxiliary agent includes a dispersing agent, a lubricant or an antioxidant. The amount of the dispersant added is 1-5wt%, including silicone coupling agents, polar derivatives of long-chain alkanes (C30 and below), alcohol dispersants, ester dispersants and their derivatives, and compositions of these dispersing agents. The amount of the lubricant added is 1-5wt%, including polyolefin waxes, long-chain alkane derivatives, polysiloxane auxiliary agents, fluorine-containing polymers and their derivatives and different combinations. The amount of the antioxidant added is less than or equal to 1wt%, including primary antioxidants, auxiliary antioxidants and their compositions.

[0039]

Polyethylene film

[0040] The present application also discloses a polyethylene film, specifically a five-layer structure, which includes a first surface layer, a second surface layer, a core layer, an inner layer and a third surface layer in sequence, wherein the core layer is formed by mixing the above-mentioned inorganic masterbatch and PE.

[0041] In addition, the first surface layer is made of LDPE, m-LLDPE, HDPE or a mixture thereof.

[0042] The second surface layer and the third surface layer are made of the same material, including PE and white masterbatch, and the content of PE is greater than or equal to 70wt%. Among them, the PE material of the second surface layer is selected from LDPE, m-LLDPE, HDPE or a mixture thereof; the white masterbatch is selected from a white masterbatch composite material with EVA, PE, and PP as the carrier, and the white masterbatch in the white masterbatch composite material accounts for 40wt% or more.

[0043] The inorganic masterbatch in the core layer accounts for 10-20wt%, and the rest is PE. The PE material is selected from LDPE, LLDPE, m-LLDPE, HDPE or a mixture thereof.

[0044] The material of the inner layer is LDPE, m-LLDPE, HDPE or a mixture thereof, and other alpha olefin copolymers can also be added according to actual needs.

[0045] The present application also discloses a method for preparing a pearlescent film, which adopts a cast single-stretching process or a blown film single-stretching process, and specifically comprises the following steps:

[0046] Prepare the raw materials of the first surface layer, the second surface layer, the core layer, the inner layer and the third surface layer, and put them into a blender for mixing and stirring respectively;

[0047] The raw materials are added to a five-layer casting machine or a film blowing machine for uniaxial stretching, the stretching ratio is 3-10 times, the stretching direction is the MD direction, and the stretching temperature is 90-130°C.

[0048] The technical effects of the present application are further described below by listing embodiments and comparative examples, but the present application is not limited to these embodiments.

[0049] The polyethylene modified materials in the examples and comparative examples of the present application are made of raw materials as shown in Table 1, calculated by weight.

[0050] Table 1

[0051]

[0052] The inorganic masterbatch prepared in the above Examples 1-4 was made into polyethylene film. The raw materials, process conditions and properties of each layer of the polyethylene film are shown in Table 2-3.

[0053] Table 2

[0054]

[0055]

[0056] Table 3

[0057]

[0058] From Table 2-3, it can be seen from the comparison between Example 5 and Comparative Examples 1-3 that different stretching ratios have an impact on the pearlescent effect of the polyethylene film. When the stretching ratio is 5, a good pearlescent effect can be achieved, but if the stretching ratio is too large (such as Comparative Example 3), it is easy to cause film breakage. By comparing Examples 5-11 and Comparative Example 4, it can be seen that when the same cast stretching process is used, the inorganic masterbatch with the polyethylene resin having an MFR greater than 10 is added, and the film breakage phenomenon is easy to occur, while the blown film single stretching process will not.

[0059] Although the above describes the illustrative specific implementation methods of the present application so that technicians in this technical field can understand the present application, the present application is not limited to the scope of the specific implementation methods. For ordinary technicians in this technical field, as long as various changes are within the spirit and scope of the present application defined and determined by the attached claims, all application creations using the concept of the present application are protected.

Claims

1. A polyethylene film, characterized in that Specifically, it has a five-layer structure, which includes the first surface layer, the second surface layer, the core layer, the inner layer and the third surface layer in sequence; The first surface layer is made of PE material; The second surface layer includes PE and white masterbatch; The core layer includes PE and inorganic masterbatch; The inner layer is made of PE material; The material of the third surface layer is consistent with that of the second surface layer, The inorganic masterbatch comprises the following components: Polyethylene resin 28wt%; Ultrafine calcium carbonate 70%; Additive 2wt%; Among them, the inorganic masterbatch in the core layer accounts for 20wt%; The polyethylene film is a uniaxially stretched film; The particle size D50 of the ultrafine calcium carbonate is ≤1.2µm; the activation degree of the ultrafine calcium carbonate reaches more than 95%; The auxiliary agent includes a dispersing agent, a lubricant or an antioxidant; The PE material in the core layer is HDPE; The method for preparing the polyethylene film comprises the following steps: Prepare the raw materials of the first surface layer, the second surface layer, the core layer, the inner layer and the third surface layer, and put them into a mixer for mixing and stirring respectively; add the raw materials to a five-layer cast film machine or a blown film machine for uniaxial stretching, with a stretching ratio of 3-10 times, a stretching direction in the MD direction, and a stretching temperature of 90-130°C; When the film blowing single drawing process is adopted, the polyethylene resin in the inorganic masterbatch adopts a polyethylene resin with MFR≤10; When the cast single-draw process is adopted, the polyethylene resin in the inorganic masterbatch adopts a polyethylene resin with MFR≤30.

2. A polyethylene film according to claim 1, characterized in that: The polyethylene resin in the inorganic masterbatch is one or more of HDPE, LDPE, LLDPE and m-LLDPE.

3. A polyethylene film according to claim 1, characterized in that: The PE material of the second surface layer is selected from LDPE, m-LLDPE, HDPE or a mixture thereof, and the content of the PE material is greater than or equal to 70wt%.

4. A polyethylene film according to claim 1, characterized in that: The material of the inner layer is LDPE, m-LLDPE, HDPE or a mixture thereof.

5. A method for preparing a polyethylene film as claimed in claim 1, characterized in that: The following steps are involved: Prepare the raw materials of the first surface layer, the second surface layer, the core layer, the inner layer and the third surface layer, and put them into a mixer for mixing and stirring respectively; add the raw materials to a five-layer cast film machine or a blown film machine for unidirectional stretching, the stretching ratio is 3-10 times, the stretching direction is the MD direction, and the stretching temperature is 90-130°C.

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