Laser cutting protective film, manufacturing method thereof and polymer composition

Abstract

The invention provides a laser cutting protective film, which is characterized in that the laser cutting protective film has multiple layers and comprises an adhesive layer in contact with a workpiece to be protected, the adhesive layer at least comprises a first hydrogenated styrene / butadiene block copolymer, a second hydrogenated styrene / butadiene block copolymer, a laser absorbent and tackifying resin, and the styrene content of the first hydrogenated styrene / butadiene block copolymer is higher than that of the second hydrogenated styrene / butadiene block copolymer. And the weight-average molecular weight of the first hydrogenated styrene / butadiene block copolymer is lower than that of the second hydrogenated styrene / butadiene block copolymer. The invention also provides a manufacturing method of the laser cutting protective film and a polymer composition related to the laser cutting protective film.

Description

Technical Field

[0001] This invention relates to a laser cutting protective film, particularly a laser cutting protective film containing an adhesive layer of hydrogenated styrene / butadiene block copolymer, a laser absorber, and a tackifying resin. Background Technology

[0002] Laser cutting utilizes a high-energy-density laser beam to irradiate materials, causing them to melt, vaporize, or ablate instantaneously, thus creating a cut that penetrates the material. This process offers advantages such as high cutting speed, a small heat-affected zone, clean edges, and a wide range of applicable materials, and is commonly used for precision machining of metal sheets, plastics, films, and electronic components. A protective film for laser cutting is a thin film material used to protect the surface of the workpiece. It reduces the impact of heat and chemical reactions on the workpiece surface during laser cutting, thereby reducing thermal stress and chemical changes, and improving cutting quality and processing efficiency. Therefore, using a suitable protective film in laser cutting is of great significance for ensuring workpiece surface quality and improving processing speed.

[0003] However, since most common thin film materials are polymers, they typically cannot withstand the high energy of laser irradiation, leading to problems such as peeling, adhesive failure, and bubbling after cutting. While there are currently black and white protective films (white on top, black on the bottom) specifically for laser cutting on the market, their low light transmittance obscures the appearance of the protected surface, preventing operators from clearly observing the workpiece's position before cutting and the post-cut effect, thus affecting processing accuracy. Furthermore, their application is mainly limited to scenarios with low precision requirements, and their function is relatively simple. Summary of the Invention

[0004] The problem that the invention aims to solve

[0005] The inventors of this application discovered through research that commercially available black and white protective films for laser cutting, besides having low light transmittance, are mostly adhesive-coated products, and their adhesive layers still contain certain solvent residues and small molecule precipitation, easily producing "ghosting" marks on the protected surface after use. Furthermore, to ensure clean and neat cutting edges of the black and white film, pre-evaporation film removal is generally performed first. Pre-evaporation film removal involves using a weaker laser to remove the film along the outline of the pattern to be cut, making the outline visible first; then, high-energy formal cutting is performed. In other words, it requires outlining and film removal before cutting, making the process more complex and less efficient. In addition, existing technologies have proposed replacing adhesive-coated protective films with high light transmittance materials, such as the protective films disclosed in Chinese patents CN115746736A or CN115087712A, which use butadiene rubber or styrene-ethylene / butene-styrene block copolymers as rubber-based pressure-sensitive adhesive layers. However, when the inventors actually prepared and verified the protective film according to the methods in these documents, they still observed that the protective film had ghosting during laser cutting or residual adhesive during peeling. Moreover, the above defects may occur alone or simultaneously, making it difficult to meet the requirements of high-precision processing.

[0006] Problem-solving methods

[0007] One objective of this invention is to provide a laser cutting protective film that significantly reduces residue and ghosting issues. Another objective is to provide a laser cutting protective film that allows for direct laser cutting and produces a clean cut surface. A further objective is to ensure that the laser cutting protective film has sufficient light transmittance so that the surface condition of the workpiece (e.g., a steel sheet) can be observed during use.

[0008] On one hand, the inventors of this application unexpectedly discovered that using two hydrogenated styrene / butadiene block copolymers with significantly different properties in the adhesive layer system of the laser-cut protective film can significantly improve the ghosting and residual adhesive problems that occur after laser cutting. Specifically, this adhesive layer uses two hydrogenated styrene / butadiene block copolymers, wherein the high molecular weight, low styrene content hydrogenated styrene / butadiene block copolymer provides structural support and enhances the adhesion to the support layer; the low molecular weight, high styrene content hydrogenated styrene / butadiene block copolymer improves viscosity and flowability, and the two work together to improve the adhesive layer performance.

[0009] On the other hand, the inventors also unexpectedly discovered that when biotite is further introduced into the adhesive layer as a functional filler, defects such as burrs, curling, and film drift caused by localized carbonization during laser cutting can be effectively reduced. Biotite, as a laser absorber, can effectively block laser energy and reduce damage to the edges of the cut film. In a preferred embodiment, trioctahedral biotite is selected as the functional filler. This type of mica is more likely to absorb energy and undergo thermal decomposition among various mica materials. Under laser irradiation, it can absorb a large amount of laser heat through its own thermal decomposition, thereby further reducing the degree of thermal damage to polymer materials caused by the laser.

[0010] In some embodiments, the present invention provides at least one of the following features.

[0011] A laser cutting protective film, characterized in that the laser cutting protective film is multilayered, the laser cutting protective film includes an adhesive layer in contact with the workpiece to be protected, the adhesive layer at least includes a first hydrogenated styrene / butadiene block copolymer, a second hydrogenated styrene / butadiene block copolymer, a laser absorber, and a tackifying resin, wherein the styrene content of the first hydrogenated styrene / butadiene block copolymer is higher than the styrene content of the second hydrogenated styrene / butadiene block copolymer, and the weight-average molecular weight of the first hydrogenated styrene / butadiene block copolymer is lower than the weight-average molecular weight of the second hydrogenated styrene / butadiene block copolymer.

[0012] The laser-cut protective film described above is further characterized in that the content of the first hydrogenated styrene / butadiene block copolymer in the adhesive layer is less than the content of the second hydrogenated styrene / butadiene block copolymer in the adhesive layer.

[0013] The laser-cut protective film described above is further characterized in that the styrene content of the first hydrogenated styrene / butadiene block copolymer is between 20 wt% and 25 wt%, and the styrene content of the second hydrogenated styrene / butadiene block copolymer is between 10 wt% and 15 wt%.

[0014] The laser-cutting protective film described above is further characterized in that, before hydrogenation, the first hydrogenated styrene / butadiene block copolymer has a vinyl content of 35 wt% to 40 wt% of the total butadiene content of the first hydrogenated styrene / butadiene block copolymer, and before hydrogenation, the second hydrogenated styrene / butadiene block copolymer has a vinyl content of 60 wt% to 80 wt% of the total butadiene content of the second hydrogenated styrene / butadiene block copolymer.

[0015] The laser-cut protective film described above is further characterized in that the weight-average molecular weight of the first hydrogenated styrene / butadiene block copolymer is between 60,000 and 80,000, and the weight-average molecular weight of the second hydrogenated styrene / butadiene block copolymer is between 130,000 and 160,000.

[0016] The laser-cut protective film as described above is further characterized in that the first hydrogenated styrene / butadiene block copolymer and the second hydrogenated styrene / butadiene block copolymer account for 63 wt% to 73 wt% of the total weight of the adhesive layer.

[0017] The laser-cut protective film described above is further characterized in that the weight ratio of the first hydrogenated styrene / butadiene block copolymer to the second hydrogenated styrene / butadiene block copolymer is 4:6.

[0018] The laser-cut protective film described above is further characterized in that the laser absorber is biotite.

[0019] The laser-cut protective film described above is further characterized in that the biotite is trioctahedral with a particle size ranging from 8,000 mesh to 10,000 mesh, and the biotite accounts for 0.3 wt% to 7 wt% of the total weight of the adhesive layer.

[0020] The laser-cut protective film as described above is further characterized in that the tackifying resin accounts for 25 wt% to 35 wt% of the total weight of the adhesive layer.

[0021] The laser-cutting protective film as described above is further characterized in that the tackifying resin is hydrogenated petroleum resin C9. The laser-cutting protective film as described above is further characterized in that it further comprises a surface layer above the adhesive layer, wherein the surface layer comprises PE, PP, or PET and the biotite, and the biotite in the surface layer accounts for 0.3 wt% to 7 wt% of the total weight of the surface layer.

[0022] The laser-cutting protective film described above is further characterized in that the laser-cutting protective film further comprises a substrate layer located between the adhesive layer and the surface layer, wherein the substrate layer comprises PE, PP, or PET and the biotite, and the biotite contained in the substrate layer accounts for 0.3 wt% to 7 wt% of the total weight of the surface layer.

[0023] The laser-cut protective film described above is further characterized in that the peel strength of the laser-cut protective film is not less than 300gf / 25mm (measured 30 minutes after the completion of the adhesion).

[0024] The laser-cut protective film described above is further characterized in that the light transmittance of the laser-cut protective film is above 75%.

[0025] The laser-cut protective film described above is further characterized in that the total thickness of the laser-cut protective film is 20-200 micrometers, wherein the thickness ratio of the surface layer, the substrate layer and the adhesive layer is 11:11:3.

[0026] The laser-cut protective film described above is further characterized in that the total thickness of the laser-cut protective film is 20-60 micrometers, wherein the thickness ratio of the surface layer to the adhesive layer is 22:3.

[0027] The laser-cut protective film as described above is further characterized in that each of the multilayers contains a laser absorber.

[0028] A method for preparing a laser-cut protective film as described above, characterized in that the protective film is multilayered, and the preparation method is to use a multilayer co-extrusion cast film or a multilayer co-extrusion blown film.

[0029] The method for preparing the laser-cut protective film as described above is further characterized in that the mixture used in the multilayer is granulated at a temperature of 190°C to 220°C on its respective twin-screw extruder.

[0030] A polymeric composition for an adhesive layer of a laser-cut protective film, the adhesive layer being used to contact a workpiece to be protected, characterized in that the polymeric composition comprises at least a first hydrogenated styrene / butadiene block copolymer, a second hydrogenated styrene / butadiene block copolymer, a laser absorber, and a tackifying resin, wherein the styrene content of the first hydrogenated styrene / butadiene block copolymer is higher than that of the second hydrogenated styrene / butadiene block copolymer, and the weight-average molecular weight of the first hydrogenated styrene / butadiene block copolymer is lower than that of the second hydrogenated styrene / butadiene block copolymer.

[0031] The polymer composition as described above is further characterized in that the first hydrogenated styrene / butadiene block copolymer accounts for a smaller proportion of the adhesive layer than the second hydrogenated styrene / butadiene block copolymer accounts for the same proportion.

[0032] The polymer composition as described above is further characterized in that the styrene content of the first hydrogenated styrene / butadiene block copolymer is between 20 wt% and 25 wt%, and the styrene content of the second hydrogenated styrene / butadiene block copolymer is between 10 wt% and 15 wt%.

[0033] The polymer composition described above is further characterized in that, before hydrogenation, the first hydrogenated styrene / butadiene block copolymer has a vinyl content of 35 wt% to 40 wt% of the total butadiene content of the first hydrogenated styrene / butadiene block copolymer, and the second hydrogenated styrene / butadiene block copolymer has a vinyl content of 60 wt% to 80 wt% of the total butadiene content of the second hydrogenated styrene / butadiene block copolymer.

[0034] The polymer composition described above is further characterized in that the weight-average molecular weight of the first hydrogenated styrene / butadiene block copolymer is between 60,000 and 80,000, and the weight-average molecular weight of the second hydrogenated styrene / butadiene block copolymer is between 130,000 and 160,000.

[0035] The polymer composition as described above is further characterized in that the first hydrogenated styrene / butadiene block copolymer and the second hydrogenated styrene / butadiene block copolymer account for 63 wt% to 73 wt% of the total weight of the adhesive layer.

[0036] The polymer composition described above is further characterized in that the weight ratio of the first hydrogenated styrene / butadiene block copolymer to the second hydrogenated styrene / butadiene block copolymer is 4:6.

[0037] The polymer composition described above is further characterized in that the laser absorber is biotite.

[0038] The polymer composition described above is further characterized in that the biotite is trioctahedral with a particle size ranging from 8,000 mesh to 10,000 mesh, and the biotite accounts for 0.3 wt% to 7 wt% of the total weight of the adhesive layer.

[0039] The polymer composition as described above is further characterized in that the tackifying resin accounts for 25 wt% to 35 wt% of the total weight of the adhesive layer.

[0040] The laser-cut protective film described above is further characterized in that the tackifying resin is hydrogenated petroleum resin C9.

[0041] This invention also includes other aspects and various embodiments to address other problems. The foregoing and other aspects are disclosed in detail in the embodiments. Attached Figure Description

[0042] The invention will now be explained in more detail with reference to the exemplary embodiments shown in the accompanying drawings, wherein:

[0043] Figure 1This is a schematic diagram of a laser-cut protective film with a three-layer structure according to one embodiment of the present invention;

[0044] Figure 2 This is a schematic diagram of a laser cutting protective film with a two-layer structure according to one embodiment of the present invention;

[0045] Figure 3 A photograph of the laser-cut protective film according to one embodiment of the present invention; and

[0046] Figure 4 A photograph of a laser-cut protective film in an experimental example; and

[0047] Figure 5 This is a photograph showing the residual adhesive observed after the laser protective film was peeled off from the adhered surface in an experimental example.

[0048] [Symbol Explanation]

[0049] 1-1 Surface layer 1-2 Substrate layer 1-3 Adhesive layer 2-1 Surface layer 2-2 Adhesive layer 4-1 Edge curling

[0050] 4-2 Burrs; 4-3 Drift film; 5-1 Residual adhesive Detailed Implementation

[0051] To ensure a full understanding of this invention and its claimed scope, preferred embodiments of the invention will be demonstrated below. To avoid obscuring the scope of the invention, known components, related materials, and related processing techniques are omitted from the following description.

[0052] Structure of laser-cut protective film

[0053] The laser-cut protective film of this invention has a multi-layer structure, commonly a two-layer or three-layer structure. Figure 1 The laser-cut protective film has a three-layer structure, comprising a surface layer 1-1, a substrate layer 1-2, and an adhesive layer 1-3. Figure 2 This laser-cutting protective film has a two-layer structure, comprising a surface layer 2-1 and an adhesive layer 2-2. The adhesive layer is in contact with the workpiece to be protected. The surface layer primarily provides support and protection, while the substrate layer mainly serves as a thickening and protective layer. A release layer may be additionally provided to cover either the adhesive layer or the surface layer of the laser-cutting protective film to prevent contamination or failure during storage or processing. When using the laser-cutting protective film, the release layer typically separates cleanly without damaging the product itself.

[0054] In a preferred embodiment, the peel strength of the laser cutting protective film of the present invention is not less than 300 gf / 25 mm (measured 30 minutes after application). In a more preferred embodiment, the peel strength of the laser cutting protective film is between 300 and 900 gf / 25 mm (measured 30 minutes after application). After the laser cutting protective film of the present invention is bonded to the surface of the workpiece to be protected, the laser cutting protective film preferably provides sufficient transparency so that the surface is still visible to the naked eye. In a more preferred embodiment, the light transmittance of the laser cutting protective film is 75% or more, more preferably 85%. In a preferred three-layer embodiment, the total thickness of the laser cutting protective film is 20-200 micrometers, wherein the thickness ratio of the surface layer, the substrate layer, and the adhesive layer is 11:11:3. In a preferred two-layer embodiment, the total thickness of the laser cutting protective film is 20-60 micrometers, wherein the thickness ratio of the surface layer to the adhesive layer is 22:3.

[0055] Polymer composition for adhesive layer of laser cutting protective film

[0056] The adhesive layer of this invention comprises at least a first hydrogenated styrene / butadiene block copolymer, a second hydrogenated styrene / butadiene block copolymer, a laser absorber, and a tackifying resin. The hydrogenated styrene / butadiene block copolymer of this invention is preferably a block copolymer having the formula ABA, wherein A is a styrene block; and B is a hydrogenated 1,3-butadiene block with a hydrogenation degree of 90% or more, preferably 99% or more. A preferred specific example of a hydrogenated block copolymer is, for example, SEBS (styrene-ethylene-butene-styrene block copolymer).

[0057] The first hydrogenated styrene / butadiene block copolymer of this invention differs from the second hydrogenated styrene / butadiene block copolymer. Specifically, the styrene content range of the first hydrogenated styrene / butadiene block copolymer is greater than that of the second hydrogenated styrene / butadiene block copolymer. In a preferred embodiment, the first hydrogenated styrene / butadiene block copolymer has a lower vinyl content before hydrogenation than the second hydrogenated styrene / butadiene block copolymer. In a preferred embodiment, the weight-average molecular weight of the first hydrogenated styrene / butadiene block copolymer is lower than that of the second hydrogenated styrene / butadiene block copolymer. In a preferred embodiment, the content of the first hydrogenated styrene / butadiene block copolymer in the adhesive layer is less than that of the second hydrogenated styrene / butadiene block copolymer in the adhesive layer.

[0058] In a preferred embodiment, the styrene content of the first hydrogenated styrene / butadiene block copolymer ranges from 20 wt% to 25 wt%, and the styrene content of the second hydrogenated styrene / butadiene block copolymer ranges from 10 wt% to 15 wt%. In another preferred embodiment, the first hydrogenated styrene / butadiene block copolymer, before hydrogenation, has a vinyl content of 35 wt% to 40 wt% of the total butadiene content of the first hydrogenated styrene / butadiene block copolymer, and the second hydrogenated styrene / butadiene block copolymer, before hydrogenation, has a vinyl content of 60 wt% to 80 wt% of the total content of the second hydrogenated styrene / butadiene block copolymer. In yet another preferred embodiment, the weight-average molecular weight of the first hydrogenated styrene / butadiene block copolymer is between 60,000 and 80,000, and the weight-average molecular weight of the second hydrogenated styrene / butadiene block copolymer is between 130,000 and 160,000.

[0059] In a preferred embodiment, the first hydrogenated styrene / butadiene block copolymer and the second hydrogenated styrene / butadiene block copolymer account for 63 wt% to 73 wt% of the total weight of the adhesive layer. In a preferred embodiment, the weight ratio of the first hydrogenated styrene / butadiene block copolymer to the second hydrogenated styrene / butadiene block copolymer is 4:6.

[0060] A specific example of the synthesis of the first hydrogenated styrene / butadiene block copolymer – SEBS 1

[0061] A 10L jacketed heater equipped with a stirrer was filled with 4300 g of cyclohexane, 15.6 mmol of n-butyl lithium, and 9.5 g of tetrahydrofuran, and 67.4 g of styrene was added. The polymerization reaction was carried out at 45°C.

[0062] 451.2 g of 1,3-butadiene was added to the reaction system for reaction, followed by the addition of 67.4 g of styrene to continue polymerization into an unhydrogenated triblock copolymer of SBS (styrene-butadiene-styrene) with a solid content of 12% and a weight average molecular weight of 68,000. 1000 g of the polymer solution of the unhydrogenated SBS triblock copolymer prepared above was transferred to a pressure-resistant hydrogenation tank and maintained under nitrogen atmosphere. 0.25 mmol of propylene glycol oligomer with a weight average molecular weight of 700 (catalyst component (c)) was prepared at room temperature in 10 ml of cyclohexane. Separately, 0.25 mmol of bis(cyclopentadienyl)titanium dichloride (catalyst component (a)) and 0.5 mmol of triisobutylaluminum (catalyst component (b)) were pre-mixed in 10 ml of cyclohexane. All catalyst components were added to the unhydrogenated SBS triblock copolymer solution prepared above, wherein the copolymer solution contained catalyst components (a):(b):(c) in a molar ratio of 1:2:1. Hydrogen gas was blown into the copolymer solution to bring a partial pressure to 25 kg / cm². 2 Hydrogenation was carried out at an initial temperature of 80°C, during which the temperature rose to approximately 110°C. After about 60 minutes, the hydrogenated SBS triblock copolymer SEBS 1 was obtained. The styrene content of SEBS 1 was measured to be 23%. The vinyl content of SEBS 1 before hydrogenation was measured to be 38% of the total butadiene content. The weight average molecular weight of SEBS 1 was measured to be 69,000.

[0063] A specific example of the synthesis of a second hydrogenated styrene / butadiene block copolymer – SEBS 2

[0064] The specific synthesis example of SEBS 2 is similar to that of SEBS 1, except that: 4300 g of cyclohexane, 10.1 mmol of n-butyl lithium, and 6.9 g of ethylene glycol dibutyl ether were loaded into a 10 L jacketed heater equipped with a stirrer, and 38.1 g of styrene was added. The polymerization reaction was carried out at 45 °C. 510.1 g of 1,3-butadiene was added to the reaction system for further reaction, followed by the addition of another 38.1 g of styrene to continue polymerization into an unhydrogenated triblock copolymer of SBS (styrene-butadiene-styrene) with a solid content of 12% and a weight average molecular weight of 170,000. 1000 g of the polymer solution of the unhydrogenated SBS triblock copolymer prepared above was transferred to a pressure-resistant hydrogenation tank and maintained under a nitrogen atmosphere. Separately, 0.25 mmol of bis(cyclopentadienyl)titanium dichloride (catalyst component (a)) and 0.5 mmol of triisobutylaluminum (catalyst component (b)) were premixed in 10 mL of cyclohexane. All catalyst components were added to the unhydrogenated SBS triblock copolymer solution prepared above, wherein the copolymer solution contained catalyst components (a):(b):(c) in a molar ratio of 1:2:1. Hydrogen gas was blown into the copolymer solution to achieve a partial pressure of 25 kg / cm². 2 Hydrogenation was carried out at an initial temperature of 80°C, during which the temperature rose to approximately 110°C. The styrene content of SEBS 2 was measured to be 13%. Before hydrogenation, the vinyl content of SEBS 2 accounted for 76% of the total butadiene content of SEBS 2. The weight-average molecular weight of SEBS 2 was measured to be 145,000.

[0065] Various suitable choices can be made for the laser absorber used in the adhesive layer of this invention. In a preferred embodiment, the laser absorber accounts for more than 0.3 wt% of the total weight of the adhesive layer. In a preferred embodiment, biotite is used. Biotite is black or dark brown, rich in iron and magnesium, has good heat resistance, and is commonly found in magnesium-iron-rich rocks such as granite, basalt, and gneiss. Biotite differs from muscovite. Muscovite mainly contains aluminum and potassium, and almost no iron or magnesium, therefore it is lighter in color and has a lower specific gravity, and is more commonly found in granite, schist, and some aluminum-rich metamorphic rocks. Biotite has slightly higher electrical conductivity, while muscovite has better insulation properties. In a preferred embodiment, the laser absorber used in the adhesive layer is more preferably trioctahedral biotite with a particle size of 8000-10000 mesh. In a preferred embodiment, biotite preferably accounts for 0.3 wt% to 7 wt% of the total weight of the adhesive layer.

[0066] Various suitable choices can be made for the tackifying resin used in the adhesive layer of this invention. For adhesives, petroleum resins are preferred. Petroleum-based resins mainly include C5 resin, C9 resin, C5 / C9 copolymer resin, and their hydrogenated versions. In a preferred embodiment, the adhesive layer of this invention uses hydrogenated petroleum resin C9. In a preferred embodiment, the hydrogenated petroleum resin C9 accounts for 25 wt% to 35 wt% of the total weight of the adhesive layer.

[0067] Composition for the surface or base layer of a protective film for laser cutting

[0068] In a preferred embodiment, the surface or substrate layer of the present invention may be made of a suitable polyolefin plastic or polyester plastic, such as PE (polyethylene), PP (polypropylene), or PET (polyethylene terephthalate). In a preferred embodiment, the surface or substrate layer also contains the laser absorber described above. In embodiments where the surface or substrate layer also contains biotite, the biotite preferably accounts for 0.3 wt% to 7 wt% of the total weight of the layer.

[0069] Manufacturing method of laser-cut protective film

[0070] This invention provides a method for preparing the laser-cut protective film, wherein the multilayer is preferably three layers, and the preparation method involves using a three-layer co-extrusion cast film or a three-layer co-extrusion blown film. Specifically, the three-layer co-extrusion cast film or the three-layer co-extrusion blown film is a process in which three extruders are used to separately mix three kinds of molten plastics, and then simultaneously feed them into the same co-extrusion die, so that the three melts are combined into a three-layer structure in the die. The cast film is formed using a flat die, while the blown film is formed using an annular die. In a preferred embodiment, the mixture used for the three layers is granulated at a temperature of 190°C to 220°C on its respective twin-screw extruder. For the two-layer laser-cut protective film, two extruders are used to separately mix two kinds of molten plastics, and then simultaneously feed them into the same co-extrusion die.

[0071] The specific steps for manufacturing the laser cutting protective film of the present invention according to the proportions in Example 7 of Table 2 are as follows:

[0072] Step (1) Prepare the materials for the surface layer, the base layer and the adhesive layer according to the proportions in Example 7 of Table 2. After each layer of material is fully mixed in an independent mixer, it is fed into three twin-screw extruders and granulated at about 210°C to obtain granules with three different formulations.

[0073] Step (2) heats the three extruders on the co-extrusion production line to approximately 200°C, and adds the surface particles, matrix particles, and adhesive particles obtained in step (1) to the three extruders respectively; and

[0074] Step (3) Adjust the extrusion speed of the three extruders according to the thickness ratio of 35.2:35.2:9.6 to make the three melts merge into a film in the co-extrusion die, thus obtaining a three-layer protective film for laser cutting. Apply the protective film to the surface of the object to be processed and compact it evenly with a 2KG roller before laser cutting.

[0075] The preparation methods for the other three-layer structures in the embodiments and experimental examples are the same as those described above, and their formulations are shown in Tables 1 and 2. As for Example 9 in Table 2, which is a two-layer structure laser-cut protective film, its preparation steps can also be carried out according to the above method, but since one layer is reduced, the corresponding twin-screw extruder and extruder are omitted.

[0076] To evaluate the effectiveness of laser cutting of the protective film, the following method was used: First, the protective film was applied to the stainless steel surface and made flat and free of air bubbles. Then, the stainless steel with the film applied was placed on the cutting platform, and the appropriate laser energy (3000 W, blowing air pressure 8 bar), cutting speed (19 m / min), and focus were set before cutting was started, removing a circular pattern with a radius of approximately 1 cm. Figure 3 shows a photograph of the protective film of Example 7 in Table 2 after the above cutting. It can be seen that the cut surface is complete, without defects such as film drift, burrs, or curling edges, and there is no adhesive residue on the adhered surface after the protective film is peeled off. In contrast, Figure 4 The cutting results of Experimental Example i in Table 2 show that the entire cut surface was blown up by the airflow (severe film floating), accompanied by obvious curling and burrs. Figure 5 The photograph shows the residual adhesive residue observed after the protective film of Experimental Example j in Table 2 was peeled off from the adhered surface.

[0077] Table 1

[0078]

[0079] Table 2

[0080]

[0081] The thickness of each example shown in Table 1 is 22µm for the surface layer, 22µm for the substrate layer, and 6µm for the adhesive layer. The PE used is PE 2420H, a product of CNOOC Shell Petrochemicals Co., Ltd.; the biotite used is CAS No. 1302-27-8, the muscovite used is CAS No. 12001-26-2, the ferric oxide used is CAS No. 1332-37-2, and the titanium dioxide used is CAS No. 13463-67-7, all sourced from Shanghai Dingyuan Chemical Co., Ltd., with a particle size of 8000-10000 mesh and a purity of 99%.

[0082] Table 3

[0083]

[0084] Table 3 shows the performance of examples from Tables 1 and 2. The symbols in Table 3 have the following meanings: OO represents Excellent; O represents Good; X represents Poor; XX represents Poor; XXX represents Very Poor. Generally speaking, curling is caused by the protective film shrinking outwards under high temperatures; burrs are caused by uneven cutting; and film drift is caused by the protective film not adhering properly to the workpiece surface in certain areas.

[0085] As shown in Table 3, experimental examples i, j, and k are three-layer laser protective films, with their adhesive layers containing only a single type of SEBS. Compared to commercially available black and white coatings, experimental examples i, j, and k have a light transmittance increased by over 85%. However, experimental examples i, j, and k show significantly insufficient peel strength and exhibit ghosting and residue problems. In contrast to experimental examples i, j, and k, experimental example b contains both SEBS-1 and SEBS-2 in its adhesive layer. Experimental example b demonstrates that using two types of SEBS in the adhesive layer significantly improves peel strength while maintaining good light transmittance and eliminating ghosting and residue. Similarly, the results of experimental example a also prove that the combined use of two types of SEBS improves peel performance and provides excellent light transmittance, while avoiding ghosting and residue. The residue after peeling is mainly due to problems with the adhesive layer formulation itself, especially the combination of the two types of SEBS in the adhesive layer and the proportion of a certain amount of tackifying resin. In addition, controlling the peel strength to be no less than 300 gf / 25 mm is to ensure that the protective film has sufficient adhesion strength to the protected surface, so that it will not be lifted, peeled or blown away by the airflow during the laser cutting process.

[0086] This invention selects two different SEBSs, primarily based on their differences in molecular weight and styrene content, allowing them to perform different and complementary functions in the adhesive layer. SEBS2, with its higher molecular weight and lower styrene content, provides stronger mechanical support, while the lower styrene content effectively bridges the tackifying resin, thus facilitating adhesion to the substrate layer (such as PE) and effectively preventing adhesive layer detachment. SEBS1, with its lower molecular weight (higher flowability and better wetting properties) and higher styrene content (stronger surface adhesion), improves the initial tack of the adhesive layer to the bonded surface and enhances wetting and flow behavior, thereby adjusting the melt index and strengthening interfacial adhesion. In the preferred adhesive layer formulation, the addition amount of SEBS2 is higher, while SEBS1, as a component for adjusting viscosity and flowability, is added in a relatively lower proportion. As shown in Experimental Examples b and i, j, k, this invention, by selecting two different SEBSs, can effectively improve the problems of residual adhesive and ghosting in laser-cut protective films. On the other hand, Experimental Example b requires further treatment of defects such as burrs, curling edges, and film drift. Compared to Experimental Example b, which only added laser absorber to the adhesive layer, Example 1 added laser absorber to all three layers, which can simultaneously improve defects such as burrs, curling, and film drift.

[0087] Examples d, e, and f show that muscovite, ferric oxide, and titanium dioxide were used as laser absorbers in the three layers, respectively. Compared to examples d, e, and f, Example 1 shows that using biotite has better results in eliminating burrs, edge curling, and film drift. Compared to Example 1, example c shows that the addition amount of laser absorber is insufficient at 0.1 phr, so burr curling still exists. Example g shows that too little tackifying resin in the adhesive layer (20 phr) significantly reduces peel strength and worsens film drift. Example h shows that too much tackifying resin in the adhesive layer (40 phr) produces undesirable adhesive residue. Examples 1-8 are preferred embodiments of the three-layer laser protective film of the present invention, including a laser protective film with a total thickness of 80 μm and a transmittance of 86.24%, and a laser protective film with a total thickness of 150 μm that still maintains a transmittance of 75.75%, demonstrating that the present invention indeed provides an excellent laser protective film manufacturing formula. In addition to the three-layer structure, this invention also provides a two-layer laser protective film, as shown in Example 9. Examples 7 and 8 show that even with a higher overall thickness of the laser protective film and a corresponding increase in the adhesive layer thickness, the peel strength is further improved, and no adhesive residue appears after peeling. Therefore, the adhesive residue problem is mainly related to the adhesive layer formulation and its proportioning.

[0088] Analytical methods

[0089] The styrene content in the hydrogenated styrene / butadiene block copolymer was determined according to the relevant measurement method described in Chinese patent CN103476815B. The NMR was performed using a Bruker AV-500 (500MHz) NMR spectrometer with a 5mm dual probe and an automatic frequency tuning device. The NMR software used was TOPSPIN, and the solvent used was deuterated chloroform / tetramethylsilane (CDCl3 / TMS).

[0090] The hydrogenated styrene / butadiene block copolymer has a vinyl content as a percentage of the total butadiene content of the hydrogenated styrene / butadiene block copolymer before hydrogenation. The determination was performed according to the relevant measurement method described in Chinese Patent CN103476815B, wherein the NMR was performed using a Bruker AV-500 (500MHz) NMR spectrometer with a 5mm dual probe and an automatic frequency tuning device. The NMR software used was TOPSPIN, and the solvent used was deuterated chloroform / tetramethylsilane (CDCl3 / TMS).

[0091] The weight-average molecular weight (Mw) of the hydrogenated styrene / butadiene block copolymer was analyzed using gel permeation chromatography (GPC) with a Waters 1525 binary HPLC pump and a Waters 2414 refractive index detector. The eluent was tetrahydrofuran, and the eluent flow rate was 1 ml / min.

[0092] Peel strength between the laser-cut protective film and the surface of the workpiece to be protected: 180° peel strength test, referring to GB / T 2792-2014 standard, the sample size is 25×200mm, the sample is prepared according to the holding power test, the peeling rate is 300mm / min, and the peeling environment is room temperature peeling.

[0093] Light transmittance of laser-cut protective film: The light transmittance of laser-cut protective film was tested using a haze meter (model: HAM-200, Yuanfang Spectrum Technology Co., Ltd.).

[0094] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the patent application of the present invention; any equivalent changes or modifications made without departing from the spirit disclosed in the present invention shall be included in the scope of the patent application below.

Claims

1. A laser-cut protective film, characterized in that, The laser cutting protective film is multilayered, and includes an adhesive layer that contacts the workpiece to be protected. The adhesive layer includes at least a first hydrogenated styrene / butadiene block copolymer, a second hydrogenated styrene / butadiene block copolymer, a laser absorber, and a tackifying resin. The styrene content of the first hydrogenated styrene / butadiene block copolymer is higher than that of the second hydrogenated styrene / butadiene block copolymer, and the weight-average molecular weight of the first hydrogenated styrene / butadiene block copolymer is lower than that of the second hydrogenated styrene / butadiene block copolymer.

2. The laser-cut protective film according to claim 1, characterized in that, The first hydrogenated styrene / butadiene block copolymer accounts for a smaller proportion of the adhesive layer than the second hydrogenated styrene / butadiene block copolymer accounts for.

3. The laser-cut protective film according to claim 1, characterized in that, The styrene content of the first hydrogenated styrene / butadiene block copolymer ranges from 20 wt% to 25 wt%, the styrene content of the second hydrogenated styrene / butadiene block copolymer ranges from 10 wt% to 15 wt%, the weight-average molecular weight of the first hydrogenated styrene / butadiene block copolymer ranges from 60,000 to 80,000, and the weight-average molecular weight of the second hydrogenated styrene / butadiene block copolymer ranges from 130,000 to 160,000.

4. The laser-cut protective film according to claim 1, characterized in that, The first hydrogenated styrene / butadiene block copolymer has a vinyl content of 35 wt% to 40 wt% of the total butadiene content of the first hydrogenated styrene / butadiene block copolymer before hydrogenation, and the second hydrogenated styrene / butadiene block copolymer has a vinyl content of 60 wt% to 80 wt% of the total butadiene content of the second hydrogenated styrene / butadiene block copolymer before hydrogenation.

5. The laser-cut protective film according to claim 1, characterized in that, The first hydrogenated styrene / butadiene block copolymer and the second hydrogenated styrene / butadiene block copolymer account for 63 wt% to 73 wt% of the total weight of the adhesive layer, the laser absorber accounts for 0.3 wt% to 7 wt% of the total weight of the adhesive layer, and the tackifying resin accounts for 25 wt% to 35 wt% of the total weight of the adhesive layer.

6. The laser-cut protective film according to claim 1, characterized in that, The weight ratio of the first hydrogenated styrene / butadiene block copolymer to the second hydrogenated styrene / butadiene block copolymer is 4:

6.

7. The laser-cut protective film according to claim 1, characterized in that, The laser absorber is biotite.

8. The laser-cut protective film according to claim 1, characterized in that, The laser-cut protective film further includes a surface layer located above the adhesive layer, wherein the surface layer comprises PE, PP, or PET and biotite, and the biotite contained in the surface layer accounts for 0.3 wt% to 7 wt% of the total weight of the surface layer.

9. The laser-cut protective film according to claim 8, characterized in that, The laser-cut protective film further comprises a substrate layer located between the adhesive layer and the surface layer, wherein the substrate layer comprises PE, PP, or PET and biotite, and the biotite contained in the substrate layer accounts for 0.3 wt% to 7 wt% of the total weight of the surface layer.

10. The laser-cut protective film according to claim 1, characterized in that, The peel strength of the laser-cut protective film is not less than 300gf / 25mm (measured 30 minutes after the application is completed).

11. The laser-cut protective film according to claim 1, characterized in that, The light transmittance of the laser-cut protective film is above 75%.

12. A method for preparing a laser-cut protective film as described in any one of claims 1-11, characterized in that, The protective film is multilayered, and the preparation method is to use multilayer co-extrusion cast film or multilayer co-extrusion blown film.

13. A polymer composition for an adhesive layer of a laser-cut protective film, said adhesive layer being for contacting the workpiece to be protected, characterized in that, The polymer composition comprises at least a first hydrogenated styrene / butadiene block copolymer, a second hydrogenated styrene / butadiene block copolymer, a laser absorber, and a tackifying resin, wherein the styrene content of the first hydrogenated styrene / butadiene block copolymer is higher than that of the second hydrogenated styrene / butadiene block copolymer, and the weight-average molecular weight of the first hydrogenated styrene / butadiene block copolymer is lower than that of the second hydrogenated styrene / butadiene block copolymer.

14. The polymer composition according to claim 13, characterized in that, The first hydrogenated styrene / butadiene block copolymer accounts for a smaller proportion of the adhesive layer than the second hydrogenated styrene / butadiene block copolymer accounts for.

15. The polymer composition according to claim 13, characterized in that, The styrene content of the first hydrogenated styrene / butadiene block copolymer ranges from 20 wt% to 25 wt%, the styrene content of the second hydrogenated styrene / butadiene block copolymer ranges from 10 wt% to 15 wt%, the weight-average molecular weight of the first hydrogenated styrene / butadiene block copolymer ranges from 60,000 to 80,000, and the weight-average molecular weight of the second hydrogenated styrene / butadiene block copolymer ranges from 130,000 to 160,000.

16. The polymer composition according to claim 13, characterized in that, The first hydrogenated styrene / butadiene block copolymer has a vinyl content of 35 wt% to 40 wt% of the total butadiene content of the first hydrogenated styrene / butadiene block copolymer before hydrogenation, and the second hydrogenated styrene / butadiene block copolymer has a vinyl content of 60 wt% to 80 wt% of the total butadiene content of the second hydrogenated styrene / butadiene block copolymer before hydrogenation.

17. The polymer composition according to claim 13, characterized in that, The first hydrogenated styrene / butadiene block copolymer and the second hydrogenated styrene / butadiene block copolymer account for 63 wt% to 73 wt% of the total weight of the adhesive layer, the laser absorber accounts for 0.3 wt% to 7 wt% of the total weight of the adhesive layer, and the tackifying resin accounts for 25 wt% to 35 wt% of the total weight of the adhesive layer.

18. The polymer composition according to claim 13, characterized in that, The weight ratio of the first hydrogenated styrene / butadiene block copolymer to the second hydrogenated styrene / butadiene block copolymer is 4:

6.

19. The polymer composition according to claim 13, characterized in that, The laser absorber is biotite.

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