Special self-adhesive protective film for surface of FPC (Flexible Printed Circuit) adhesive film for battery packaging

Abstract

The invention discloses a special self-adhesive protective film for the surface of an FPC (Flexible Printed Circuit) adhesive film for battery packaging. The special self-adhesive protective film is characterized by comprising a base material layer and an adhesive layer, wherein the base material layer comprises a surface layer, a middle layer and an outer layer; the middle layer is divided into a first middle layer, a second middle layer and a third middle layer. The special three-screw five-layer film distributor is adopted, different components are divided into an ABABC structure according to requirements during melt co-extrusion, amorphous nylon contained in the B layer has good compatibility with the base material PE, low-molecular wax substances contained in the FPC packaging adhesive film can be effectively blocked by adding a small amount of the amorphous nylon, and the low-molecular wax substances contained in the FPC packaging adhesive film can be effectively blocked. And migration to the surface of the protective film is prevented so as not to affect the battery packaging adhesion. The ethylene-octylene copolymer and the styrene block copolymer are mixed to serve as the adhesive layer, the product has micro-viscosity and high retention force, the protective film can be peeled off from an FPC adhesive film with small force when a film tearing and heat packaging procedure is carried out after a finished product is subjected to die cutting, the adhesive film is particularly suitable for blow molding method production, and the production cost is effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of protective films, and particularly to a special self-adhesive protective film for the surface of an FPC adhesive film used for battery packaging. Background Art

[0002] For the hot melt coating of FPC, before winding up after coating, when the colloid is not completely solidified, a protective film is pasted on, and then winding up is carried out. The wound-up finished product is slit and then die-cut into the size and shape required for battery packaging. Before use, the film is torn off so that the adhesive layer can be in a good bonding state.

[0003] The protective film used in the traditional hot melt coating of FPC is mainly a PET coated adhesive protective film. The PET film has a large amount of wear on the die during die-cutting and often needs to be replaced, with high cost and low efficiency. Moreover, there is a great risk of residual glue in the high-temperature and high-humidity environment in summer. In view of the above problems, customers use traditional PE protective films to replace them, which can solve the problem of short die life caused by large die wear. However, because PE itself does not have barrier properties to low molecular wax substances and water vapor, there is often a layer of low molecular substances on the surface of the finished product (which can be easily scraped off with a fingernail). During the battery packaging process, it often contaminates the battery shell, resulting in insufficient heat seal bonding force and causing bubbles and bulges. Seriously, it will also affect the high-voltage electrostatic shielding and anti-foreign object puncture effects of FPC due to poor bonding, greatly reducing the battery safety.

[0004] Therefore, how to provide a special self-adhesive protective film for the surface of an FPC adhesive film used for battery packaging to solve the problems existing in the prior art is of great significance for its application. Summary of the Invention

[0005] In view of this, the purpose of this application is to provide a special self-adhesive protective film for the surface of an FPC adhesive film used for battery packaging to solve the obvious disadvantages of traditional protective films.

[0006] To achieve the above purpose, the present invention provides the following technical solution: A special self-adhesive protective film for the surface of an FPC adhesive film used for battery packaging, including a base material layer and an adhesive layer; wherein the base material layer includes a surface layer, a middle layer, and an outer layer;

[0007] The thickness of the self-adhesive protective film is 42um, wherein the thickness of the surface layer is 12um, the thickness of the middle layer is 28um, and the thickness of the adhesive layer (outer layer) is 2um.

[0008] Preferably, the middle layer is divided into a middle layer 1, a middle layer 2, and a middle layer 3, with the thickness of the middle layer 1 being 8um, the thickness of the middle layer 2 being 12um, and the thickness of the middle layer 3 being 8um.

[0009] Preferably, the component ratio of the surface layer includes: LLDPE: 97%; silicone masterbatch: 3%.

[0010] Preferably, the component ratio of the middle layer 1 includes: LLDPE: 76 - 85%; amorphous nylon: 1 - 10%; indigo masterbatch: 4%; blown film edge material: 10%.

[0011] Preferably, the component ratio of the middle layer 2 includes: LLDPE: 97%; silicone masterbatch: 3%.

[0012] Preferably, the component ratio of the middle layer 3 includes: LLDPE: 76 - 85%; amorphous nylon: 1 - 10%; indigo masterbatch: 4%; blown film edge material: 10%.

[0013] Preferably, the component ratio of the adhesive layer includes: ethylene - octene copolymer: 59 - 99%; styrene block copolymer: 0 - 40%; antioxidant 1010: 1%.

[0014] Preferably, the base material layer is formed by a three - layer co - extrusion up - blowing method. The temperatures of the three - layer co - extrusion are respectively: the base material is 225 °C, the middle layer is 245 °C, the outer layer is 220 °C, and the die is 240 °C.

[0015] Preferably, the forming air temperature is 20 - 35 °C, and the production line speed is 160 - 200 kg / h.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] 1. The present invention utilizes the existing three - layer co - extrusion equipment, upgrades the distributor at the die to make the finished product into a five - layer structure, reduces the single - layer ratio difference, can maintain a stable film bubble during high - temperature processing, and the film surface is delicate, uniform, and has good flatness.

[0018] 2. The present invention uses a blending form to internally add amorphous nylon to achieve the barrier of low - molecular substances, greatly extends the precipitation period, and reduces the precipitation risk.

[0019] 3. The present invention adopts ethylene - octene copolymer and styrene block copolymer, which have excellent spreading force, initial adhesion, and small viscosity increase after high temperature.

[0020] 4. The present invention adopts indigo masterbatch with stable color, which is convenient for the subsequent distinction of the film - tearing process.

[0021] The above description is only an overview of the technical solution of this application. In order to understand the technical means of this application more clearly, so as to be implemented in accordance with the content of the specification, and in order to make the above and other purposes, features, and advantages of this application more obvious and understandable, the following describes in detail with the preferred embodiments of this application and accompanying drawings as follows.

[0022] Those skilled in the art will better understand the above and other objects, advantages and features of this application from the following detailed description of specific embodiments of this application in conjunction with the accompanying drawings. Description of the Drawings

[0023] In order to more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the following will briefly introduce the accompanying drawings required for use in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings. In all the drawings, similar elements or parts are generally denoted by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to actual scale.

[0024] Figure 1 Table of embodiments of the base material layer in the present invention;

[0025] Figure 2 Table of embodiments of the adhesive layer in the present invention;

[0026] Figure 3 Schematic diagram of a three-screw five-layer extrusion in the present invention;

[0027] Figure 4 Table of test results of the adhesive layer in the present invention. Detailed Embodiments

[0028] To make the objectives, technical solutions and advantages of the embodiments of this application clearer, the following will clearly and completely describe the technical solutions in the embodiments of this application in conjunction with the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are some, but not all, of the embodiments of this application. In the following description, providing specific details such as specific configurations and components is only to help a comprehensive understanding of the embodiments of this application. Therefore, those skilled in the art should clearly understand that various changes and modifications can be made to the embodiments described here without departing from the scope and spirit of this application. Additionally, for clarity and conciseness, descriptions of known functions and structures are omitted in the embodiments.

[0029] In addition, this application may repeat reference numerals and / or letters in different instances. This repetition is for the purpose of simplicity and clarity, and does not in itself indicate the relationship between the various embodiments and / or arrangements discussed.

[0030] In this text, the term "and / or" is merely a description of the associated relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent three situations: A exists alone, B exists alone, and both A and B exist simultaneously. In this text, the term " / and" describes another associated object relationship, indicating that two relationships can exist. For example, A / and B can represent two situations: A exists alone, and both A and B exist. Additionally, in this text, the character " / " generally indicates that the associated objects before and after are in an "or" relationship.

[0031] It should also be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise", or any other variant thereof are intended to cover non-exclusive inclusion.

[0032] Please refer to Figures 1-3 , the present invention provides a technical solution for a special self-adhesive protective film on the surface of an FPC film for battery packaging:

[0033] Selection of the base material layer

[0034] An ABABC structure is adopted, which is divided into a surface layer, a first middle layer, a second middle layer, a third middle layer, and an outer layer. Among them, the surface layer and the second middle layer have the same composition, and the first middle layer and the third middle layer have the same composition;

[0035] Example 1: Composition ratio of the surface layer: 97% LLDPE, 3% silicone masterbatch; Composition ratio of the first middle layer: 85% LLDPE, 1% amorphous nylon, 10% indigo blue masterbatch, 10% blown film edge material; Composition ratio of the second middle layer: 97% LLDPE, 3% silicone masterbatch; Composition ratio of the third middle layer: 85% LLDPE, 1% amorphous nylon, 10% indigo blue masterbatch, 10% blown film edge material, and the outer layer is LLDPE;

[0036] Example 2: Composition ratio of the surface layer: 97% LLDPE, 3% silicone masterbatch; Composition ratio of the first middle layer: 83% LLDPE, 3% amorphous nylon, 10% indigo blue masterbatch, 10% blown film edge material; Composition ratio of the second middle layer: 97% LLDPE, 3% silicone masterbatch; Composition ratio of the third middle layer: 83% LLDPE, 3% amorphous nylon, 10% indigo blue masterbatch, 10% blown film edge material, and the outer layer is LLDPE;

[0037] Example 3: The composition ratio of the surface layer is 97% LLDPE and 3% silicone masterbatch; the composition ratio of the middle layer is 81% LLDPE, 5% amorphous nylon, 10% indigo blue masterbatch, and 10% blown film edge material; the composition ratio of the middle layer is 97% LLDPE and 3% silicone masterbatch; the composition ratio of the middle layer is 81% LLDPE, 5% amorphous nylon, 10% indigo blue masterbatch, and 10% blown film edge material, and the outer layer is LLDPE;

[0038] Example 4: The composition ratio of the surface layer is 97% LLDPE and 3% silicone masterbatch; the composition ratio of the middle layer is 78% LLDPE, 8% non-crystalline nylon, 10% indigo blue masterbatch, and 10% blown film edge material; the composition ratio of the middle layer is 97% LLDPE and 3% silicone masterbatch; the composition ratio of the middle layer is 78% LLDPE, 8% non-crystalline nylon, 10% indigo blue masterbatch, and 10% blown film edge material, and the outer layer is LLDPE;

[0039] Example 5: The composition ratio of the surface layer is 97% LLDPE and 3% silicone masterbatch; the composition ratio of the middle layer is 76% LLDPE, 10% amorphous nylon, 10% indigo blue masterbatch, and 10% blown film edge material; the composition ratio of the middle layer is 97% LLDPE and 3% silicone masterbatch; the composition ratio of the middle layer is 76% LLDPE, 10% amorphous nylon, 10% indigo blue masterbatch, and 10% blown film edge material, and the outer layer is LLDPE;

[0040] Selection of each component:

[0041] LLDPE uses Exxon 1002BY, silicone masterbatch uses Dow Corning MB50-001, non-crystalline nylon uses Mitsubishi selar PA 3426, and indigo blue masterbatch uses Japan Kinzumi.

[0042] The three-layer co-extrusion blow molding method is used for molding. The co-extrusion temperatures of the three layers are: 225 degrees for the substrate, 245 degrees for the middle layer, 220 degrees for the outer layer, and 240 degrees for the mold. This process adopts a special blown film mold distributor to divide the materials extruded by the inner and middle layer screws in a molten state into two layers each, forming a 3-screw 5-layer film structure. The overall film changes from an ABC structure to an ABABC structure. The molding air temperature is 28 degrees, and the optimal production speed of the production line is 150kg / h. From the perspective of appearance, flatness and cost, this method preferably uses Option 3 as the self-adhesive film substrate.

[0043] The outer layer in Examples 1-5 is replaced by LLDPE to test the film quality. After the substrate layer is selected, the outer layer is prepared using the adhesive layer formula, and the outer layer is the adhesive layer.

[0044] Then there is the choice of the self-adhesive layer;

[0045] Adhesive Example 1: 99% ethylene-octene copolymer, 1% antioxidant;

[0046] Adhesive Example 2: 89% ethylene-octene copolymer, 10% styrene block copolymer, 1% antioxidant;

[0047] Adhesive Example 3: 79% ethylene-octene copolymer, 20% styrene block copolymer, 1% antioxidant;

[0048] Adhesive Example 4: 69% ethylene-octene copolymer, 30% styrene block copolymer, 1% antioxidant;

[0049] Adhesive Example 5: 59% ethylene-octene copolymer, 40% styrene block copolymer, 1% antioxidant;

[0050] The processing temperature of the adhesive layer is 225 °C. Using Example 3 as the substrate, the overall self-adhesive film has a thickness of 42 μm, a surface layer thickness of 25 μm, a middle layer thickness of 15 μm, and an adhesive layer thickness of 2 μm.

[0051] The test items include: unfolding force, initial adhesion, adhesion after high temperature, pollution, and film curling degree test.

[0052] (1) Unfolding force

[0053] The surface protective film was respectively wound around a PP core with an inner diameter of 3 inches to make a film roll with a width of 50 mm. According to JIS Z0237, the surface protective film was unrolled from the film roll at an unrolling speed of 20 m / min, and the high-speed unrolling force was measured. The test value is the unfolding force;

[0054] Internal standard: An unfolding force of 0.5 N / 50 mm is evaluated as A, more than 0.5 N / mm but not more than 1 N / 50 mm is B, and more than 1 N / 50 mm is C.

[0055] (2) Initial adhesion

[0056] Lamination was carried out within 3 days after the surface protective film was made to cover the surface of the black FPC barrier adhesive film. The lamination conditions were in an environment of room temperature 23 °C and relative humidity 50%, using a 2 kg rubber roller, and laminating at a speed of 300 mm / min. After placing in this state for 30 min, the 180° peel strength of a 25 mm width was tested at a speed of 300 mm / min according to JIS Z0237. The peel strength at this time is used as the initial adhesion.

[0057] (3) Adhesion after high temperature

[0058] Lamination shall be carried out within 3 days after the surface protective film is manufactured, so that it covers the surface of the FPC adhesive film. The lamination conditions are as follows: in an environment of room temperature 23°C and relative humidity 50%, use a 2 kg rubber roller and laminate at a speed of 300 mm / min. After placing it in this state for 30 min, place the laminated product in an environment of 150°C for 30 min for baking. After the baking is completed, take it out and let it stand for 30 min, and then test the 180° peel strength of a 25 mm width at a speed of 300 mm / min in accordance with JIS Z0237. The peel strength at this time is used as the adhesion after high temperature.

[0059] (4) Contamination

[0060] The laminated samples are kept in an environment of 60°C for 14 days. Take out the samples and conduct a concentrated light irradiation on the surface of the adherend in a dark room. Scratch the surface of the protective film with the back of a knife to see if there is powdery precipitation, and observe the surface contamination state with the naked eye. The determined states are: no contamination A, slight contamination B, contamination C.

[0061] (5) Test of film curling degree

[0062] For the laminated product, cut it into the size of A4 paper with a blade. At room temperature and after high temperature, place the laminated adherend product on a glass tabletop. After standing for 30 min, measure the distance from the edge to the tabletop. The judgment results are as follows: if the warping is less than 1 cm, it is A; if it is greater than 1 cm but less than 3 cm, it is B; if it is greater than 3 cm, it is C.

[0063] Test results:

[0064] (1) Test results of peel force at room temperature: The peel forces of Examples 1-5 are 0.01 N / 25 mm, 0.03 N / 25 mm, 0.05 N / 25 mm, 0.3 N / 25 mm, and 0.4 N / 25 mm respectively;

[0065] (2) Test results of peel force after high temperature: The peel forces of Examples 1-5 are 0.25 N / 25 mm, 0.38 N / 25 mm, 0.2 N / 25 mm, 1.0 N / 25 mm, and 1.2 N / 25 mm respectively;

[0066] (3) Test results of contamination: Examples 2, 3, and 4 are grade A, and Examples 1 and 5 are grade B;

[0067] (4) Test results of curling degree: Examples 1-5 are all grade A;

[0068] (5) Test results of unfolding force: Examples 1-3 are all grade A, and Examples 4 and 5 are all grade B;

[0069] After comprehensive evaluation, Example 3 is preferably selected.

[0070] The self-adhesive protective film is processed by blow molding co-extrusion. Conventional PA and PE are incompatible. The amorphous PA formed by Mitsubishi's unique polymerization process can be directly blended and added in the middle layer. The addition ratio is very low, but the barrier effect can be achieved, and the cost increase is very small. This formula also adopts a unique "three-screw five-layer film structure" to make the film have a secondary barrier function, greatly extending the precipitation period. This formula process is different from the traditional process. The processing temperature of the traditional protective film blown film is generally not more than 200 degrees, concentrated around 180 degrees. However, there is nylon in this formula, so only the middle layer can use high temperature. LLDPE can support high-temperature production, so the film bubble can be stable and the thickness can be uniform. After a special filtering process, the crystal points of the film can be well presented. Considering the characteristics of PA itself to prevent shrinkage and deformation in the later stage, using a wind temperature of about 28 degrees can give PA enough shaping time. In this way, the whole film surface is very delicate and uniform, and the shrinkage and deformation in the later stage are small.

[0071] The above are only the preferred embodiments of the present invention, and they do not limit the protection scope of the present invention. For those skilled in the art, the present invention can have various changes and modifications. All changes, modifications, substitutions, integrations, and parameter changes made to these embodiments by conventional substitutions or capable of achieving the same functions without departing from the principle and spirit of the present invention fall within the protection scope of the present invention.

Claims

1. A special self-adhesive protective film for the surface of an FPC adhesive film used for battery packaging, characterized in that: It includes a base material layer and an adhesive layer; the base material layer includes a surface layer, a middle layer, and an outer layer; The self-adhesive protective film has a thickness of 42 μm, where the surface layer has a thickness of 12 μm, the middle layer has a thickness of 28 μm, and the outer layer (adhesive layer) has a thickness of 2 μm.

2. The special self - adhesive protective film for the surface of FPC adhesive film used for battery packaging according to claim 1, wherein: The middle layer is divided into a first middle layer, a second middle layer, and a third middle layer. The first middle layer has a thickness of 8 μm, the second middle layer has a thickness of 12 μm, and the third middle layer has a thickness of 8 μm.

3. The special self - adhesive protective film for the surface of FPC adhesive film used in battery packaging according to claim 2, characterized in that: The component ratio of the surface layer includes: LLDPE: 97%; silicone masterbatch: 3%.

4. The special self-adhesive protective film for the surface of the FPC adhesive film used for battery packaging according to claim 3, wherein: The component ratio of the first middle layer includes: LLDPE: 76 - 85%; amorphous nylon: 1 - 10%; indigo blue masterbatch: 4%; blown film edge material: 10%.

5. The special self - adhesive protective film for the surface of the FPC adhesive film used for battery packaging according to claim 4, characterized in that: The component ratio of the second middle layer includes: LLDPE: 97%; silicone masterbatch: 3%.

6. The special self-adhesive protective film for the surface of the FPC adhesive film used for battery packaging according to claim 5, wherein: The component ratio of the third middle layer includes: LLDPE: 76 - 85%; amorphous nylon: 1 - 10%; indigo blue masterbatch: 4%; blown film edge material: 10%.

7. The special self - adhesive protective film for the surface of the FPC adhesive film used for battery packaging according to claim 6, characterized in that: The component ratio of the adhesive layer includes: ethylene-octene copolymer: 59 - 99%; styrene block copolymer: 0 - 40%; antioxidant 1010: 1%.

8. The special self - adhesive protective film for the surface of FPC adhesive film used for battery packaging according to claim 7, wherein: The base material layer is formed by the three-layer co-extrusion up-blowing method. The three-layer co-extrusion temperatures are respectively: the base material is 225 °C, the middle layer is 245 °C, the outer layer is 220 °C, and the die is 240 °C.

9. The special self-adhesive protective film for the surface of the FPC adhesive film used for battery packaging according to claim 8, characterized in that: The forming air temperature is 20 - 35 °C, and the production line speed is 160 - 200 kg / h.

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