Three-layer co-extrusion two-way stretch film and preparation process thereof
By adopting a bidirectional stretch film with a three-layer coextrusion structure, combined with a combination of high-density polyethylene, anti-adhesion masterbatch and PPA additives, the existing films have poor heat resistance and low stiffness, and a higher stretch ratio, lower haze and better light transmittance are achieved.
Patent Information
- Application Number
- CN202411942228.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-26
- Publication Date
- 2025-06-13
AI Technical Summary
The existing bidirectional tensile polyethylene films have problems such as poor heat resistance, low stiffness and obvious heat shrinkage in downstream applications, which limits its application range.
A three-layer coextruded bidirectional stretch film structure is adopted, where the upper and lower surface layers are anti-blocking layers, containing high-density polyethylene, anti-blocking masterbatch and PPA additives; the core layer contains high-density polyethylene, anti-static masterbatch and PPA additives, and the performance of the film is improved through bidirectional stretching process and corona treatment.
The stretching ratio of the film is improved, the haze value is reduced, the light transmittance is enhanced, and the heat resistance and stiffness of the film is improved.
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Figure CN120134758A_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to the technical field of composite films, and specifically, to a three-layer co-extruded biaxially oriented film and a preparation process thereof. Background Art
[0002] The biaxially oriented polyethylene film is abbreviated as B0PE film, which is obtained by stretching polyethylene synchronously or asynchronously in the longitudinal and transverse directions. After stretching, the molecular chains and lamellae of polyethylene are highly oriented in two directions, and the optical and mechanical properties of the film are greatly improved. Moreover, the B0PE film can be recycled, which is beneficial to environmental protection and the development of circular economy. At present, most of the raw materials for BOPE production are LLDPE. LLDPE can be well processed into films with good transparency and low haze, but it has poor heat resistance, low stiffness, and obvious thermal shrinkage, which will cause problems such as inaccurate printing registration in downstream use, restricting the application of BOPE in downstream. Compared with LLDPE, the HDPE film has high stiffness and low thermal shrinkage rate, which can ensure the stability of the film during printing and bag making. However, the HDPE stretched film has problems such as poor toughness and light transmittance, high haze value, and difficulty in processing. Summary of the Invention
[0003] The purpose of the embodiments of the present disclosure is to provide a three-layer co-extruded biaxially oriented film and a preparation process thereof to solve the above problems existing in the prior art.
[0004] To solve the above technical problems, on the one hand, an embodiment of the present disclosure provides a three-layer co-extruded biaxially oriented film, which adopts a multi-layer co-extrusion structure and includes a film body. The film body includes an upper surface layer, a core layer, and a lower surface layer. The upper surface layer and the lower surface layer are anti-blocking layers, and the upper surface layer and the lower surface layer include the following components in parts by weight: 80-98.5 parts of high-density polyethylene, 1-10 parts of anti-blocking masterbatch, and 0.5-10 parts of PPA additive; wherein, the melt index of the high-density polyethylene is 0.5-3 g / 10 min; the core layer includes the following components in parts by weight: 80-98.5 parts of high-density polyethylene, 1-10 parts of antistatic masterbatch, and 0.5-10 parts of PPA additive, wherein the melt index of the high-density polyethylene is 0.5-3 g / 10 min.
[0005] In some embodiments, the anti-blocking masterbatch includes siloxane and isotactic polypropylene, wherein the mass of siloxane accounts for 20-30% of the total mass of the anti-blocking masterbatch.
[0006] In some embodiments, the siloxane can be in the form of organic particles, and the particle size of the siloxane particles is 1-2 μm.
[0007] In some embodiments, the antistatic masterbatch comprises 75 to 85 parts by weight of isotactic polypropylene homopolymer and 15 to 25 parts by weight of a migrating antistatic agent.
[0008] In some embodiments, the migrating antistatic agent comprises 50 to 60 parts by weight of polypropylene, 20 to 25 parts by weight of ethoxyamine, and 20 to 25 parts by weight of glycerol monostearate.
[0009] In some embodiments, the component ratios of the upper surface layer and the lower surface layer are different.
[0010] In some embodiments, the thickness of the film body is 25 - 35 μm, the thickness of the upper surface layer and the lower surface layer is 7 - 10 μm, and the thickness of the core layer is 10 - 15 μm.
[0011] One aspect of the embodiments of the present disclosure provides a preparation process for a three - layer co - extruded biaxially stretched film. The three - layer co - extruded biaxially stretched film is the three - layer co - extruded biaxially stretched film described in any one of the above, and the preparation process comprises the following steps:
[0012] The raw materials of each component in each layer are uniformly mixed and then melt - co - extruded and cooled to form a thick sheet;
[0013] The formed thick sheet is successively passed through a longitudinal stretching device and a transverse stretching device to perform a biaxial stretching process to generate the film body:
[0014] The stretched film is subjected to corona treatment to increase the surface tension;
[0015] The film body after corona treatment is wound into a master roll for aging treatment;
[0016] The film after aging treatment is slit into products according to requirements.
[0017] In some embodiments, the step of uniformly mixing the raw materials of each component in each layer and then melt - co - extruding and cooling to form a thick sheet includes:
[0018] The lower surface layer is extruded through a first auxiliary extruder, and its outlet temperature is 230 - 250 °C; the core layer is extruded through a main extruder, and its outlet temperature is 230 - 250 °C; the upper surface layer is extruded through a second auxiliary extruder, and its outlet temperature is 230 - 250 °C and the die head temperature is 230 - 250 °C; the temperature of the cooling casting sheet device for cooling is controlled at 70 - 75 °C.
[0019] In some embodiments, the step of successively passing the formed thick sheet through a longitudinal stretching device and a transverse stretching device to perform a biaxial stretching process to generate the film body includes:
[0020] The operating temperature of the rollers in the longitudinal stretching device is controlled as follows: the preheating zone is 85 - 90 °C, the stretching zone is 110 - 115 °C, and the shaping zone is 90 - 95 °C, where the stretching ratio is 4.5 - 5.5; the operating temperature of the rollers in the transverse stretching device is controlled as follows: the preheating zone is 150 - 155 °C, the stretching zone is 125 - 130 °C, and the shaping zone is 95 - 100 °C, where the stretching ratio is 6 - 8.
[0021] The embodiments of the present disclosure can increase the stretching ratio of the biaxially stretched polyethylene film, while reducing the haze value and having good light transmittance. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present disclosure. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.
[0023] Figure 1 It is a schematic structural diagram of a three - layer co - extrusion biaxially stretched film in the embodiments of the present disclosure. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0024] Reference is made herein to the various aspects and features of the present disclosure with reference to the accompanying drawings.
[0025] It should be understood that various modifications can be made to the embodiments applied herein. Therefore, the above description should not be regarded as a limitation, but only as an example of the embodiments. Those skilled in the art will think of other modifications within the scope and spirit of the present disclosure.
[0026] The drawings included in the specification and forming a part of the specification illustrate the embodiments of the present disclosure, and together with the general description of the present disclosure given above and the detailed description of the embodiments given below, are used to explain the principles of the present disclosure.
[0027] These and other features of the present disclosure will become apparent from the following description of the preferred forms of the embodiments, given by way of non - limiting example with reference to the accompanying drawings.
[0028] It should also be understood that although the present disclosure has been described with reference to some specific examples, those skilled in the art can surely implement many other equivalent forms of the present disclosure, which have the features as described in the claims and thus are all within the protection scope defined thereby.
[0029] When combined with the accompanying drawings, in view of the following detailed description, the above and other aspects, features, and advantages of the present disclosure will become more apparent.
[0030] Specific embodiments of the present disclosure will be described hereinafter with reference to the accompanying drawings; however, it should be understood that the embodiments claimed are merely examples of the present disclosure and can be implemented in various ways. Well-known and / or repetitive functions and structures are not described in detail to avoid obscuring the present disclosure with unnecessary or redundant details. Therefore, the specific structural and functional details claimed herein are not intended to be limiting, but are merely used as a basis and representative basis for the claims to teach those skilled in the art to combine substantially arbitrarily.
[0031] The first embodiment of the present disclosure provides a three-layer coextruded biaxially oriented film, which adopts a multi-layer coextrusion structure and includes a film body. The thickness of the film body is 25-35 μm. The film body includes an upper surface layer 1, a core layer 2, and a lower surface layer 3. Among them, the thicknesses of the upper surface layer 1 and the lower surface layer 3 are 7-10 μm. Here, the thickness of the lower surface layer 3 can be greater than that of the upper surface layer 1, and the thickness of the core layer 2 is 10-15 μm.
[0032] Specifically, the upper surface layer 1 and the lower surface layer 3 are anti-blocking layers. The upper surface layer 1 and the lower surface layer 3 include the following components in parts by weight: 80-98.5 parts of high-density polyethylene, 1-10 parts of anti-blocking masterbatch, and 0.5-10 parts of PPA additive; among them, the melt index of the high-density polyethylene is 0.5-3 g / 10 min (190 °C, 2.16 Kg). Here, the component ratios of the upper surface layer 1 and the lower surface layer 3 can be different.
[0033] Further, the anti-blocking masterbatch includes siloxane and isotactic polypropylene. Among them, the mass of siloxane accounts for 20-30% of the total mass of the anti-blocking masterbatch. The siloxane can be in the form of organic particles, and the particle size of the siloxane particles is 1-2 μm.
[0034] Further, the core layer 2 includes the following components in parts by weight: 80-98.5 parts of high-density polyethylene, 1-10 parts of antistatic masterbatch, and 0.5-10 parts of PPA additive, where the melt index of the high-density polyethylene is 0.5-3 g / 10 min (190 °C, 2.16 Kg).
[0035] Here, by adding different proportions of PPA additive to the upper surface layer 1, the core layer 2, and the lower surface layer 3, the surface defects of the film can be improved, the wear of the mold during the processing can be reduced, the phenomenon of die build-up can be eliminated, and the processing temperature can be lowered. Specifically, after adding the PPA additive, the fluidity of the melt is improved, so that the processing temperature is somewhat reduced. At the same time, the temperature of the chill roll is lowered to about 70 °C - 75 °C, so that the thick sheet is rapidly cooled, the cooling rate is increased, and finally fine and small-sized crystals are formed. After transverse and longitudinal stretching to increase the draw ratio, a three-layer coextruded biaxially oriented film with a lower haze value and better light transmittance can be obtained.
[0036] Further, the antistatic masterbatch comprises 75 to 85 parts by weight of isotactic polypropylene homopolymer and 15 to 25 parts by weight of a migrating antistatic agent. The migrating antistatic agent herein comprises 50 to 60 parts by weight of polypropylene, 20 to 25 parts by weight of ethoxyamine, and 20 to 25 parts by weight of glycerol monostearate.
[0037] In a specific embodiment (PPA-3 added in the table), the main components of the upper surface layer 1 include 85 parts of high-density polyethylene, 8 parts of antiblocking masterbatch, and 7 parts of PPA additive. Among them, the antiblocking masterbatch comprises siloxane and isotactic polypropylene, and the mass of the siloxane accounts for 30% of the total mass of the antiblocking masterbatch; the main components of the lower surface layer 3 include 85 parts of high-density polyethylene, 8 parts of antiblocking masterbatch, and 7 parts of PPA additive. The antiblocking masterbatch comprises siloxane and isotactic polypropylene, and the mass of the siloxane accounts for 20% of the total mass of the antiblocking masterbatch.
[0038] The core layer 2 specifically comprises 90 parts of high-density polyethylene, 2 parts of antistatic masterbatch, and 8 parts of PPA additive. Among them, the antistatic masterbatch comprises 80 parts by weight of isotactic polypropylene homopolymer and 20 parts by weight of a migrating antistatic agent. The components of the migrating antistatic agent include 56 parts by weight of polypropylene, 22 parts by weight of ethoxyamine, and 22 parts by weight of glycerol monostearate.
[0039] In another specific embodiment (PPA-2 added in the table), the main components of the upper surface layer 1 include 90 parts of high-density polyethylene, 5 parts of antiblocking masterbatch, and 5 parts of PPA additive. The main components of the lower surface layer 3 include 90 parts of high-density polyethylene, 5 parts of antiblocking masterbatch, and 5 parts of PPA additive; the core layer 2 specifically comprises 90 parts of high-density polyethylene, 5 parts of antistatic masterbatch, and 5 parts of PPA additive.
[0040] In another specific embodiment (PPA-1 added in the table), the main components of the upper surface layer 1 include 95 parts of high-density polyethylene, 2 parts of antiblocking masterbatch, and 3 parts of PPA additive. The main components of the lower surface layer 3 include 95 parts of high-density polyethylene, 3 parts of antiblocking masterbatch, and 2 parts of PPA additive; the core layer 2 specifically comprises 92 parts of high-density polyethylene, 5 parts of antistatic masterbatch, and 3 parts of PPA additive.
[0041] The effects of adding PPA-1, PPA-2, and PPA-3 are as shown in the following table:
[0042]
[0043] As can be seen from the above table, adding the PPA additive improves the fluidity of the melt, reduces the processing temperature, and increases the draw ratio through transverse and longitudinal stretching, enabling the production of a three-layer coextruded biaxially stretched film with a low haze value and good light transmittance.
[0044] The embodiments of the present disclosure can increase the draw ratio of the biaxially stretched polyethylene film, while reducing the haze value and having good light transmittance.
[0045] The second embodiment of the present disclosure provides a preparation process for a three-layer coextruded biaxially stretched film, which includes the three-layer coextruded biaxially stretched film according to any one of the above first embodiments. The preparation process of the three-layer coextruded biaxially stretched film here includes the following steps:
[0046] S101, uniformly mix the raw materials of each component in each layer above, then perform melt coextrusion and cooling to form a thick sheet; specifically, extrude the lower surface layer 3 through the first auxiliary extruder, with an outlet temperature of 230 - 250°C; extrude the core layer 2 through the main extruder, with an outlet temperature of 230 - 250°C; extrude the upper surface layer 1 through the second auxiliary extruder, with an outlet temperature of 230 - 250°C and a die head temperature of 245 - 250°C; in addition, the temperature of the cooling casting device for cooling is controlled at 70 - 75°C;
[0047] S102, sequentially pass the thick sheet formed in step S101 through a longitudinal stretching device (Machine Direction Orientation, MDO) and a transverse stretching device (Transverse Direction Orientation, TDO) to perform a biaxial stretching process to generate the film body:
[0048] Among them, the operating temperature of the rollers in the longitudinal stretching device is controlled as follows: the preheating zone is 85 - 90°C, the stretching zone is 110 - 115°C, and the shaping zone is 90 - 95°C, where the draw ratio is 4.5 - 5.5; the operating temperature of the rollers in the transverse stretching device is controlled as follows: the preheating zone is 150 - 155°C, the stretching zone is 125 - 130°C, and the shaping zone is 95 - 100°C, where the draw ratio is 6 - 8;
[0049] Step S103, subject the film stretched in step S102 above to corona treatment to increase the surface tension;
[0050] Step S104, wind the film body processed in step S103 above into a master roll for aging treatment;
[0051] Step S105, cut the film processed in step S104 above into products according to requirements.
[0052] The embodiments of the present disclosure can increase the draw ratio of the biaxially oriented polyethylene film, while reducing the haze value and having good light transmittance.
[0053] In addition, the features of the embodiments shown in the drawings of the present application or various embodiments mentioned in this specification do not have to be understood as independent embodiments of each other. Instead, each feature described in one example of an embodiment can be combined with one or more other desired features from other embodiments, thereby generating other embodiments not described in words or with reference to the drawings.
[0054] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.
Claims
1. A three-layer co-extruded biaxially oriented film, characterized in that: A multi-layer co-extrusion structure is adopted, which includes a film body, and the film body includes an upper surface layer, a core layer and a lower surface layer. The upper surface layer and the lower surface layer are anti-adhesion layers, and the upper surface layer and the lower surface layer include components in the following weight ratio: 80-98.5 parts of high-density polyethylene, 1-10 parts of anti-adhesion masterbatch and 0.5-10 parts of PPA additives; wherein the melt index of the high-density polyethylene is 0.5-3g / 10min; the core layer includes components in the following weight ratio: 80-98.5 parts of high-density polyethylene, 1-10 parts of antistatic masterbatch and 0.5-10 parts of PPA additives, wherein the melt index of the high-density polyethylene is 0.5-3g / 10min.
2. The three-layer co-extruded biaxially oriented film according to claim 1, characterized in that: The anti-adhesion masterbatch comprises siloxane and isotactic polypropylene, wherein the mass of siloxane accounts for 20-30% of the total mass of the anti-adhesion masterbatch.
3. The three-layer co-extruded biaxially oriented film according to claim 2, characterized in that: The siloxane may be in the form of organic particles, and the particle size of the siloxane particles is 1 to 2 μm.
4. The three-layer co-extruded biaxially oriented film according to claim 1, characterized in that: The antistatic masterbatch comprises 75 to 85 parts by weight of isotactic homopolypropylene and 15 to 25 parts by weight of a migratory antistatic agent.
5. The three-layer co-extruded biaxially oriented film according to claim 4, characterized in that: The migratory antistatic agent comprises 50 to 60 parts by weight of polypropylene, 20 to 25 parts by weight of ethoxylated amine and 20 to 25 parts by weight of glycerol monostearate.
6. The three-layer co-extruded biaxially oriented film according to claim 1, characterized in that: The upper surface layer and the lower surface layer have different component ratios.
7. The three-layer co-extruded biaxially oriented film according to claim 1, characterized in that: The thickness of the film body is 25-35 μm, the thickness of the upper surface layer and the lower surface layer is 7-10 μm, and the thickness of the core layer is 10-15 μm.
8. A process for preparing a three-layer co-extruded biaxially oriented film, characterized in that: The three-layer co-extruded biaxially oriented film is a three-layer co-extruded biaxially oriented film according to any one of claims 1 to 7, and the preparation process comprises the following steps: The raw materials of each component in each layer are uniformly mixed, melt co-extruded and cooled to form a thick sheet; The formed thick sheet is sequentially passed through a longitudinal stretching device and a transverse stretching device to perform a biaxial stretching process to generate the film body: The stretched film is subjected to corona treatment to increase the surface tension; The corona treated film is wound into a mother roll for aging treatment; The film after aging treatment is cut into products according to demand.
9. The process for preparing a three-layer co-extruded biaxially oriented film according to claim 8, characterized in that: The process of uniformly mixing the raw materials of the components in each layer, performing melt co-extrusion and cooling to form a thick sheet comprises: The lower surface layer is extruded by the first auxiliary extruder, and its outlet temperature is 230-250°C; the core layer is extruded by the main extruder, and its outlet temperature is 230-250°C; the upper surface layer is extruded by the second auxiliary extruder, and its outlet temperature is 230-250°C and the die head temperature is 230-250°C; the temperature of the cooling casting device used for cooling is controlled at 70-75°C.
10. The process for preparing a three-layer co-extruded biaxially oriented film according to claim 8, characterized in that: The process of sequentially passing the formed thick sheet through a longitudinal stretching device and a transverse stretching device to perform a biaxial stretching process to generate the film body comprises: The operating temperature of the rollers in the longitudinal stretching device is controlled as follows: the preheating zone is 85-90°C, the stretching zone is 110-115°C, and the shaping zone is 90-95°C, wherein the stretching ratio is 4.5-5.5; the operating temperature of the rollers in the transverse stretching device is controlled as follows: the preheating zone is 150-155°C, the stretching zone is 125-130°C, and the shaping zone is 95-100°C, wherein the stretching ratio is 6-8.