A self-adhesive film for protecting curved surfaces with small curvature radius

Abstract

The present invention relates to a self-adhesive film for protecting a curved surface with a small curvature radius, comprising a self-adhesive layer, a core layer and a back layer, wherein the self-adhesive layer, the core layer and the back layer are compounded from top to bottom; the core layer component comprises an amorphous α-olefin copolymer and a hydrogenated styrene elastomer. The product made by the present invention can meet the surface protection of curved components with a small curvature radius within a radius of 75 mm, and the attached edge will not float, bubble or leave residue after long-term use.

Description

Technical Field

[0001] The invention relates to the technical field of self-adhesive films for protecting curved surfaces with small curvature radius, and in particular to a self-adhesive film for protecting curved surfaces with small curvature radius. Background Art

[0002] The curved surface protective films currently available on the market are mainly used for screen terminal protection of curved display devices such as computers and smart phones. Such protective films generally use TPU or PET as the base material, and are coated with functional layers such as optical adhesive, pressure-sensitive adhesive or hardening layer on the surface, and are bonded with a release film.

[0003] For curved components of various materials, whether metal or non-metal, the protective film of TPU or PET composite type used for curved display devices, or the protective film formed by using PP or PE substrate and then coating, is relatively complicated in process, with high manufacturing cost, unfriendly to the environment, and the protective film will leave residue after being torn off. For example, CN112574685A proposes a composite PE protective film for curved glass processing or shipment, including a PE substrate layer and an optical grade acrylic adhesive layer arranged on its lower surface.

[0004] On the other hand, the existing self-adhesive protective film provided by co-extrusion adopts polyolefin and polyolefin copolymer as the main material, which can be attached to the flat surface or the surface with large curvature, but cannot be attached to the surface of the curved component with a radius of curvature less than 75mm, such as the surface of the automobile sealing strip. For example, CN110546002A proposes a protective film for attaching to the resin substrate when the substrate is subjected to heat bending processing under heating, which is composed of: a base material with polyolefin resin as the main material is co-extruded through an adhesive layer with polyethylene, ethylene-propylene copolymer, etc. as the main material.

[0005] In addition, when the protective film is attached to the curved surface, it is subject to the influence of its own stiffness and tends to restore its own flatness, which is prone to floating. In addition, when the protective film is attached to the curved surface, there is a certain degree of extension deformation, and there is a tendency to restore its own tensile deformation, resulting in floating. Thirdly, it is well known that conventional polyethylene, polypropylene and olefin copolymers are semi-crystalline materials. After the protective film is attached to the curved surface, due to the post-crystallization and recrystallization of the material itself, its own deformation will produce bonding bubbles. The smaller the radius of curvature of the curved surface, the greater the degree of bending and stretching of the protective film on the curved surface, the easier it is to float; at the same time, the greater the degree of deformation caused by crystallization, the easier it is to produce bubbles. The existing self-adhesive protective films on the market can play a corresponding protective role for curved surfaces with larger curvature radii, but for curved surfaces with small curvature radii, especially those with a curvature radius of less than 75mm, it is easy to float or bubbles, and ultimately fail to protect the attached curved surface. Summary of the invention

[0006] Technical issues solved

[0007] In view of the above-mentioned shortcomings of the prior art, the present invention provides a self-adhesive curved surface protective film for a curvature radius less than 75 mm. The material consists of a three-layer structure: a self-adhesive layer, a core layer and a back layer. Since the core layer and the back layer are made of special polymer materials, their hardness, tensile modulus and crystallinity are effectively overcome through specific selection and design to solve the problems of floating and bubbling of the protective film. Moreover, since it is a self-adhesive protective film, the residual property is greatly reduced compared with that of a coating protective film.

[0008] Technical Solution

[0009] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0010] The present invention provides a self-adhesive film for protecting a curved surface with a small curvature radius, characterized in that it comprises a self-adhesive layer, a core layer and a back layer, wherein the self-adhesive layer, the core layer and the back layer are compounded from top to bottom;

[0011] The core layer components include amorphous α-olefin copolymer and hydrogenated styrene elastomer.

[0012] Furthermore, based on the total weight of the core layer components, the weight of the hydrogenated styrene elastomer accounts for 30% to 70%, the weight of the amorphous α-olefin copolymer accounts for 20% to 80%, and the total of the above components is 100%.

[0013] Furthermore, the weight of the hydrogenated styrene elastomer is 40% to 60%, the weight of the amorphous α-olefin copolymer is 40% to 60%, and the total weight of the above components is 100%.

[0014] Furthermore, the back layer component includes EVA elastomer and amorphous α-olefin copolymer.

[0015] Furthermore, the back layer also includes a release agent.

[0016] Furthermore, the anti-sticking agent is at least one of silica masterbatch, fluororesin, siloxane and olefin copolymer.

[0017] Furthermore, based on the total weight of the back layer components, the EVA elastomer accounts for 30% to 70% by weight, the amorphous α-olefin copolymer accounts for 30% to 80% by weight, the anti-sticking agent accounts for 0-5% by weight, and the total of the above components is 100%.

[0018] Furthermore, based on the total weight of the back layer components, the EVA elastomer accounts for 35% to 50% by weight, the amorphous α-olefin copolymer accounts for 40% to 60% by weight, the anti-sticking agent accounts for 1-3% by weight, and the total of the above components is 100%.

[0019] Furthermore, the number average molecular weight Mn of the amorphous α-olefin copolymer is 10,000 to 20,000.

[0020] Furthermore, the EVA elastomer is an EVA elastomer with a VA content of 40% to 80%.

[0021] Furthermore, the EVA elastomer uses an EVA elastomer with a VA content of 50% to 60%.

[0022] Furthermore, the self-adhesive layer includes hydrogenated styrene elastomer, a tackifier and a viscosity inhibitor.

[0023] Furthermore, the total thickness of the self-adhesive film is 20 to 100 um.

[0024] Furthermore, the thickness ratio of the three-layer structure of the self-adhesive layer, the core layer and the back layer is 1:3:1 to 1:10:1.

[0025] A method for preparing a self-adhesive film for protecting a curved surface with a small curvature radius. The self-adhesive layer, the core layer and the back layer are melted by three extruders respectively to obtain a composition of the self-adhesive layer, the core layer and the back layer, which is then co-extruded into a film through a distributor and a T-die. The processing temperature of the three extruders is 160°C to 200°C.

[0026] Beneficial Effects

[0027] Compared with the known public technology, the technical solution provided by the present invention has the following beneficial effects:

[0028] (1) The present invention provides a protective film for curved surface components with a curvature radius of less than 75 mm, which can be attached to the surface at room temperature. After the protective film is attached to the surface of the object, no bubbles will occur, the edges will not float for a long time, and no residue will remain after being torn off. The curved surface component to be attached can be a non-metallic object, such as PC, PET, PMMA and glass, etc., or a metal object, such as stainless steel, aluminum, etc. The surface of the curved surface component can be subjected to surface treatment such as electroplating and sputtering.

[0029] (2) In the core layer, when the SEBS mass fraction is higher than 75%, the crystallinity of the blended material is too high, and the produced protective film is prone to bubbles; when the SEBS mass fraction is lower than 20%, the stiffness of the blended material is too high, and the protective film is prone to float. In this system, the main function of APAO is to adjust the crystallinity level of the blended material. In addition, if the proportion of EVA elastomer is too high, the crystallinity of the blended material is too high; if the proportion of EVA elastomer is too low, the stiffness of the blended material is too high.

[0030] (3) Compared with the prior art, the product made by the present invention can meet the surface protection requirements of curved components with a small curvature radius within 75 mm, and the attached edge will not float, bubble or leave residue after long-term use. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on 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.

[0032] The present invention will be further described below in conjunction with the embodiments.

[0033] Amorphous α-olefin copolymer, referred to as APAO; hydrogenated styrene elastomer, referred to as SEBS.

[0034] A self-adhesive film for protecting a curved surface with a small curvature radius comprises a self-adhesive layer, a core layer and a back layer, wherein the self-adhesive layer, the core layer and the back layer are compounded from top to bottom; the core layer components comprise amorphous alpha-olefin copolymer and hydrogenated styrene elastomer.

[0035] As a preferred embodiment of the above technical solution, based on the total weight of the core layer components, the weight of the hydrogenated styrene elastomer accounts for 30% to 70%, the weight of the amorphous α-olefin copolymer accounts for 20% to 80%, and the total of the above components is 100%.

[0036] In the above technical solution, if the SEBS ratio is too high, the crystallinity of the blended material will be too high, and the produced protective film will easily produce bubbles; if the SEBS ratio is too low, the stiffness of the blended material will be too high, and the protective film will easily float. In this system, APAO mainly plays a role in adjusting the crystallinity level of the blended material.

[0037] As a preferred embodiment of the above technical solution, the weight of the hydrogenated styrene elastomer is 40% to 60%, the weight of the amorphous α-olefin copolymer is 40% to 60%, and the total weight of the above components is 100%.

[0038] As a preferred embodiment of the above technical solution, the back layer component includes EVA elastomer and amorphous α-olefin copolymer.

[0039] As a preferred embodiment of the above technical solution, the back layer also includes an anti-sticking agent.

[0040] As a preferred embodiment of the above technical solution, the anti-sticking agent is at least one of silica masterbatch, fluororesin, siloxane and olefin copolymer.

[0041] As a preferred embodiment of the above technical solution, based on the total weight of the back layer components, the EVA elastomer accounts for 30% to 70% by weight, the amorphous α-olefin copolymer accounts for 30% to 80% by weight, the anti-sticking agent accounts for 0-5% by weight, and the total of the above components is 100%.

[0042] As a preferred embodiment of the above technical solution, based on the total weight of the back layer components, the EVA elastomer accounts for 35% to 50% by weight, the amorphous α-olefin copolymer accounts for 40% to 60% by weight, the anti-sticking agent accounts for 1-3% by weight, and the total of the above components is 100%.

[0043] In the above technical solution, if the proportion of EVA elastomer is too high, the crystallinity of the blended material will be too high; if the proportion of EVA elastomer is too low, the stiffness of the blended material will be too high.

[0044] As a preferred embodiment of the above technical solution, the number average molecular weight Mn of the amorphous α-olefin copolymer is 10000 to 20000. If Mn is too small, subsequent processing will be difficult, and if Mn is too large, the hardness of the material will increase, which does not meet the requirement of controlling the stiffness of the material.

[0045] In the above technical solution, the number average molecular weight Mn of APAO is selected between 10000 and 20000. If Mn is too small and the resin fluidity is too high, it will cause difficulties in subsequent processing. If Mn is too large and the resin fluidity is too low, the material hardness will increase, resulting in increased material stiffness, which is not conducive to curved surface bonding. The preferred VESTOPLAST 708 or VESTOPLAST751 of Evonik Degussa of Germany has Mn of 11500 and 18800 respectively, and Shore hardness of 67 and 43 respectively.

[0046] As a preferred embodiment of the above technical solution, the hydrogenated styrene elastomer preferably has a 300% modulus of elongation less than 4 MPa.

[0047] In the above technical solution, for the selection of SEBS, when its stress is less than 3Mpa and its Shore hardness is less than 50A when stretched by 300%, the protective film is not able to recover sufficiently on the curved surface to cause floating; and when its stress is greater than 5Mpa and its Shore hardness is greater than 60A when stretched by 300%, the stiffness of the material is too high, resulting in poor conformability of the protective film and floating.

[0048] As a preferred embodiment of the above technical solution, the EVA elastomer is an EVA elastomer with a VA content of 40% to 80%.

[0049] As a preferred embodiment of the above technical solution, the EVA elastomer is an EVA elastomer with a VA content of 50% to 60%. Too high a VA content is not conducive to film processing, while too low a VA content results in a high hardness of the resin.

[0050] As a preferred embodiment of the above technical solution, the self-adhesive layer includes hydrogenated styrene elastomer, a tackifier and a viscosity inhibitor.

[0051] In the above technical solution, the tackifier is terpene phenolic resin.

[0052] The viscosity inhibitor is ethylene bisstearamide (EBS resin).

[0053] As a preferred embodiment of the above technical solution, the total thickness of the self-adhesive film is 20 to 100 um.

[0054] As a preferred embodiment of the above technical solution, the thickness ratio of the three-layer structure of the self-adhesive layer, the core layer and the back layer is 1:3:1 to 1:10:1.

[0055] A method for preparing a self-adhesive film for protecting a curved surface with a small curvature radius. The self-adhesive layer, the core layer and the back layer are melted by three extruders respectively to obtain a composition of the self-adhesive layer, the core layer and the back layer, which is then co-extruded into a film through a distributor and a T-die. The processing temperature of the three extruders is 160°C to 200°C.

[0056] (I) Preparation of self-adhesive membrane

[0057] Embodiment and comparative example:

[0058] A self-adhesive film for protecting a curved surface with a small curvature radius, comprising a self-adhesive layer, a core layer and a back layer, wherein the self-adhesive layer, the core layer and the back layer are compounded from top to bottom;

[0059] Wherein, the core layer component includes an amorphous α-olefin copolymer and a hydrogenated styrene elastomer; based on the total weight of the core layer components, the weight proportion of the amorphous α-olefin copolymer and the hydrogenated styrene elastomer is shown in the following table;

[0060] The backing layer components include EVA elastomer, amorphous α-olefin copolymer, and anti-sticking agent. Based on the total weight of the backing layer components, the weight proportions of EVA elastomer, amorphous α-olefin copolymer, and anti-sticking agent are shown in the table below. Among them, the anti-sticking agent uses the internal addition masterbatch TG-PP20PS of Daikin Fluorochemical; the EVA elastomer uses LEVAMELT500 of ARLANXEO, with a VA content of 50% and a resin crystallinity of 5%.

[0061] The self-adhesive layer includes a hydrogenated styrene elastomer, a tackifier and a viscosity inhibitor. Based on the total weight of the self-adhesive layer components, the weight proportions of the hydrogenated styrene elastomer, the tackifier and the viscosity inhibitor are shown in the table below. Among them, the tackifier is a terpene phenolic resin, and YS POLYSTER TH130 of Yasuhara Chemical Co., Ltd. of Japan is selected in both the examples and the comparative examples. The viscosity inhibitor is ethylene bis stearamide (EBS resin), and KAO WAX EB-G of Kao Corporation of Japan is selected in both the examples and the comparative examples.

[0062] Among them, the amorphous α-olefin copolymer (APAO) in the core layer and the back layer is VESTOPLAST708 from Evonik Degussa of Germany, with Mn of 11500 and Shore hardness of 67 respectively; the hydrogenated styrene elastomer (SEBS) in the core layer and the self-adhesive layer is G1657 from Kraton of the United States, with a 300% elongation modulus of 2.7Mpa and a Shore hardness of 47.

[0063] The self-adhesive layer, core layer and back layer are melted by three extruders respectively to obtain a composition of the self-adhesive layer, core layer and back layer, which is then co-extruded into a film through a distributor and a T-die. The processing temperature of the three extruders is 180°C.

[0064] The composition of each layer of the embodiment and the comparative example is as follows:

[0065]

[0066]

[0067] (II) Product performance test

[0068] The performance test results of Examples 1-3 and Comparative Examples 1-3 are shown in the following table:

[0069]

[0070] From the test results in the table above, it can be seen that in the core layer, when the mass fraction of SEBS is higher than 75%, the crystallinity of the blended material is too high, and the produced protection is prone to bubbles; when the mass fraction of SEBS is lower than 20%, the stiffness of the blended material is too high, and the protective film is prone to float. In this system, the main function of APAO is to adjust the crystallization level of the blended material. In addition, if the proportion of EVA elastomer is too high, the crystallinity of the blended material is too high; if the proportion of EVA elastomer is too low, the stiffness of the blended material is too high.

[0071] In the present invention, SEBS cannot be used as the back layer of the self-adhesive film due to its strong self-adhesiveness. Otherwise, the self-adhesive layer and the back layer will stick to each other, making it difficult to unwind the self-adhesive film and affecting its use. Meanwhile, EVA elastomer has a larger hardness and tensile modulus than SEBS, and is not suitable for the core layer.

[0072] In addition, the self-adhesive film of the present invention was attached to a commercially available EPDM sealing strip for sealing automobile doors (with a curvature radius of less than 75 mm), and placed in an oven at room temperature of 30° C. and 60° C., respectively, and observed for 30 days to visually check whether the self-adhesive film floated and whether there were bubbles between the self-adhesive film and the adhered object.

[0073] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the protection scope of the technical solutions of the embodiments of the present invention.

Claims

1. A self-adhesive film for protecting a curved surface with a small curvature radius, characterized in that: It comprises a self-adhesive layer, a core layer and a back layer, wherein the self-adhesive layer, the core layer and the back layer are compounded from top to bottom; based on the total weight of the core layer components, the weight of the hydrogenated styrene elastomer accounts for 40% to 60%, the weight of the amorphous α-olefin copolymer accounts for 40% to 60%, and the sum of the above components is 100%; Based on the total weight of the back layer components, the weight of the EVA elastomer accounts for 35% to 50%, the weight of the amorphous α-olefin copolymer accounts for 40% to 60%, the weight of the anti-sticking agent accounts for 1-3%, and the total weight of the above components is 100%.

2. The self-adhesive film for protecting a curved surface with a small curvature radius according to claim 1, characterized in that: The anti-sticking agent is at least one of silica masterbatch, fluororesin, siloxane and olefin copolymer.

3. The self-adhesive film for protecting a curved surface with a small curvature radius according to claim 1, characterized in that: The EVA elastomer is an EVA elastomer with a VA content of 40% to 80%.

4. A self-adhesive film for protecting a curved surface with a small curvature radius according to any one of claims 1 to 3, characterized in that: The number average molecular weight Mn of the amorphous α-olefin copolymer is 10,000-20,000.

5. The self-adhesive film for protecting a curved surface with a small curvature radius according to claim 1, characterized in that: The self-adhesive layer comprises hydrogenated styrene elastomer, a tackifier and a tack inhibitor.

6. The self-adhesive film for protecting a curved surface with a small curvature radius according to claim 1, characterized in that: The total thickness of the self-adhesive film is 20-100 μm, and the thickness ratio of the three-layer structure of the self-adhesive layer, the core layer and the back layer is 1:3:1 to 1:10:

1.

7. The method for preparing a self-adhesive film for protecting a curved surface with a small curvature radius according to claim 1, characterized in that: The self-adhesive layer, core layer and back layer are melted by three extruders respectively to obtain a composition of the self-adhesive layer, core layer and back layer, which is then co-extruded into a film through a distributor and a T-die. The processing temperature of the three extruders is 160°C to 200°C.

Images