Bond-resistant polyolefin foam, method for its production and use

Abstract

This application belongs to the field of polyolefin foam technology, and more specifically, relates to an adhesive-resistant polyolefin foam, its preparation method, and its application. The adhesive-resistant polyolefin foam provided by this application is foamed from polyolefin resin, cyclic olefin copolymer resin, foaming agent, and additives, wherein the weight ratio of polyolefin resin, cyclic olefin copolymer resin, foaming agent, and additives is (50-70):(20-30):(5-15):(1-5). The polyolefin foam provided by this application has excellent and stable adhesive properties, while also possessing excellent cushioning properties and providing support. It can form numerous bonding points with adhesives, improving adhesive strength and facilitating direct bonding with subsequent adhesive tapes. It is suitable for use as a cushioning material or adhesive tape substrate for structural components in various application scenarios.

Description

Technical Field

[0001] This application belongs to the field of polyolefin foam technology, and more specifically, relates to an adhesive-resistant polyolefin foam, its preparation method and application. Background Technology

[0002] Polyolefin foam possesses excellent physical and chemical properties such as lightweight, shock absorption, compression resistance, thermal insulation, and sound insulation, making it widely used in packaging, construction, automotive, electronics, and other industrial fields. However, the non-polar surface and low surface tension of polyolefin foam result in poor adhesion, making it difficult to achieve good bonding with other materials or even with similar materials. This severely limits its application and process design in high-end composite materials and other fields. While heat sealing, the use of special adhesives, or physical surface treatments can improve the adhesion of polyolefin foam to other materials, these methods often come with increased costs, more complex processes, or insufficient bond strength.

[0003] Many applications of polyolefin foam require adhesive backing. However, during subsequent use, the polyolefin foam is prone to separation from the adhesive layer. Therefore, it is particularly important to develop a low-cost, simple-process, and inherently adhesive foam that is resistant to adhesion. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this application is to provide a non-adhesive polyolefin foam, its preparation method and application, which aims to solve the technical problems of low surface tension, poor adhesion performance and poor adhesion stability of existing polyolefin foams.

[0005] To achieve the above objectives, this application provides a bond-resistant polyolefin foam, which is foamed from polyolefin resin, cyclic olefin copolymer resin, foaming agent, and additives.

[0006] The weight ratio of the above polyolefin resin, cyclic olefin copolymer resin, foaming agent and additives is (50-70):(20-30):(5-15):(1-5).

[0007] Preferably, the glass transition temperature of the above-mentioned polyolefin resin is < -75°C, and the melt index is 1 g / 10 min to 5 g / 10 min.

[0008] Preferably, the polyolefin resin is selected from one or more of linear low-density polyethylene, low-density polyethylene, and high-density polyethylene.

[0009] Preferably, the glass transition temperature of the above-mentioned cyclic olefin copolymer resin is 60℃~80℃, and the melt index is 0.5g / 10min~5g / 10min.

[0010] Preferably, the average particle size of the above-mentioned foaming agent is ≤10μm, and it is selected from one or more of azodicarbonamide, OBSH foaming agent, N,N'-dinitrospentamethylenetetramine, 4,4-oxobisbenzenesulfonylhydrazine, inorganic carbonate and bicarbonate.

[0011] Preferably, the above-mentioned additives are one or more of antioxidants, heat stabilizers, sensitizers, dispersants, flame retardants, pigments, antistatic agents, and thermally conductive particles.

[0012] Preferably, the surface tension of the polyolefin foam is 40 dyn / cm to 45 dyn / cm. More preferably, after being placed at room temperature for 30 days, the surface tension of the polyolefin foam is ≥38 dyn / cm.

[0013] Preferably, the density of the above-mentioned polyolefin foam is 0.05 g / cm3 to 0.35 g / cm3, the tensile strength is 2 MPa to 5 MPa, the elongation at break is 50% to 200%, and the surface roughness is 10 μm to 60 μm.

[0014] This application also provides a method for preparing the above-mentioned adhesive-resistant polyolefin foam, comprising the following steps:

[0015] S1. The above-mentioned polyolefin resin, cyclic olefin copolymer resin, foaming agent and additives are mixed and kneaded, and then extruded, stretched, granulated and dried to obtain resin masterbatch. The resin masterbatch is then extruded to form a pre-foamed sheet substrate.

[0016] S2. The above-mentioned pre-foamed substrate is subjected to irradiation crosslinking to obtain a pre-foamed master sheet, and then the master sheet is subjected to foaming treatment to obtain a foamed sheet.

[0017] S3. The above-mentioned foamed sheet is shaped by traction rollers to obtain adhesive-resistant polyolefin foam.

[0018] Preferably, the irradiation dose for the above-mentioned irradiation crosslinking is 10Mrad to 20Mrad.

[0019] Preferably, the foaming temperature is 180℃~250℃.

[0020] Preferably, the surface roughness of the traction roller is 10μm to 60μm.

[0021] Preferably, the temperature of the traction roller is lower than the temperature of the foaming process, and the temperature difference is 20°C to 50°C.

[0022] This application also provides an adhesive tape substrate comprising the above-mentioned polyolefin foam cushioning material or structural device.

[0023] In summary, compared with the prior art, the technical solutions conceived in this application have the following main technical advantages:

[0024] (1) The adhesive-resistant polyolefin foam provided in this application is foamed from polyolefin resin, cyclic olefin copolymer resin, foaming agent and additives, wherein the weight ratio of the polyolefin resin, cyclic olefin copolymer resin, foaming agent and additives is (50-70):(20-30):(5-15):(1-5). Compared with existing polyolefin foams, the adhesive-resistant polyolefin foam provided in this application has excellent adhesive properties and stable and durable adhesive properties. It also has excellent cushioning properties and can play a supporting role. It can form more bonding points with adhesives, improve the bonding strength, and facilitate the direct bonding of subsequent adhesive tapes. It is suitable for cushioning materials or adhesive tape substrates for structural devices in different application scenarios.

[0025] (2) In a preferred embodiment, this application combines a cyclic olefin copolymer resin with a suitable parameter performance with a polyolefin resin, a foaming agent and an additive, and limits the weight ratio between each component, so that the blended resin system has good compatibility, which is conducive to resin extrusion and foaming, and avoids phenomena such as cell rupture, surface cracks and warping in the foam during the foaming process. It also synergistically controls the surface tension, density, tensile strength, elongation at break and surface roughness of the foam, and improves the surface energy and surface energy stability of the foam while improving the basic physical properties of the foam.

[0026] (3) Compared with existing preparation methods, the preparation method provided in this application does not require additional surface treatment to prepare polyolefin foam with good adhesive properties, and the preparation process is simple and the preparation cost is low. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0028] The surface tension of polyolefin foam is typically less than 38 dyn / cm. While it can be increased to above 38 dyn / cm through methods such as corona discharge, a period of time usually passes between foam production and customer use. During this time, the surface tension of the foam drops significantly, severely affecting the adhesion between the foam and the adhesive layer after bonding. Therefore, this application provides a bond-resistant polyolefin foam, which is foamed from polyolefin resin, cyclic olefin copolymer resin, foaming agent, and additives.

[0029] The weight ratio of the above polyolefin resin, cyclic olefin copolymer resin, foaming agent and additives is (50-70):(20-30):(5-15):(1-5).

[0030] The polyolefin foam provided in this application has a surface tension of 40 dyn / cm to 45 dyn / cm. After being placed at room temperature for 30 days, its surface tension is ≥38 dyn / cm, indicating good adhesion to adhesives. The adhesive-resistant polyolefin foam provided in this application requires no additional surface treatment; the foam itself has good adhesive properties and can be used as a cushioning material or adhesive tape substrate for structural components in various application scenarios.

[0031] The cyclic olefin copolymer resin (COC) mentioned in this application is a non-crystalline polyolefin resin obtained by copolymerizing ethylene and dicyclohepten using a metallocene catalyst. The inventors discovered through experiments that when the aforementioned cyclic olefin copolymer resin is blended with a polyolefin resin, the highly active CH atoms in the cyclic structure of the cyclic olefin copolymer resin are more easily oxidized to form polar groups, increasing the polarity of the foam surface. Simultaneously, the cyclic structure of the cyclic olefin copolymer resin has relatively stable molecular chains with significant steric hindrance, making it less prone to movement. This can, to a certain extent, prevent the migration of residual small molecules from inside the foam to the foam surface, thus maintaining the stability of the foam surface energy and slowing down its degradation. Furthermore, the aforementioned cyclic olefin copolymer resin can make the molecular chains on the foam surface relatively loose, improving the wetting effect of the adhesive on the foam surface, thereby increasing the adhesion performance of the foam surface. At the same time, the cyclic olefin copolymer resin has high water vapor barrier properties, making it difficult for moisture to penetrate the adhesive interface layer in high-temperature and high-humidity environments after the foam is backed with adhesive, thereby slowing down the adhesion failure of the interface layer.

[0032] In some embodiments, the glass transition temperature (Tg) of the aforementioned cyclic olefin copolymer resin is 60℃~80℃, and the melt index is 0.5g / 10min~5g / 10min. The inventors discovered through experiments that when the TG is too high, the rigidity and strength of the cyclic olefin copolymer resin increase significantly, affecting its blending and processing performance with polyolefin resins. This can lead to phenomena such as cell rupture and surface cracks during the foaming process, affecting the surface roughness of the foam and consequently its basic physical properties.

[0033] In some embodiments, the glass transition temperature (Tg) of the above-mentioned polyolefin resin is < -75°C, and the melt index is 1 g / 10 min to 5 g / 10 min, which can be selected from one or more of linear low-density polyethylene, low-density polyethylene and high-density polyethylene.

[0034] This application blends the aforementioned cyclic olefin copolymer resin with a polyolefin resin having a Tg temperature less than -75°C. By adjusting the ratio of the two, the blended resin system exhibits good miscibility, facilitating resin extrusion and foaming, and preventing abnormal phenomena such as pore breakage and warping during foaming. Simultaneously, it enhances the surface energy and surface energy stability of the foam without increasing its hardness, reducing its flexibility and cushioning performance, or affecting its basic physical properties. In some embodiments, the aforementioned cyclic olefin copolymer resin accounts for 20wt% to 30wt% of the total raw materials used in the preparation of polyurethane foam.

[0035] In some embodiments, the average particle size of the above-mentioned foaming agent is ≤10μm, which makes it easier to blend with the resin and uniformly disperse in the resin component. After subsequent foaming treatment, a greater number and relatively uniform number of cells are obtained, while improving the physical properties of the foam. This application does not have a particular limitation on the type of foaming agent, but prefers foaming agents with low cost and good foaming effect, such as, but not limited to, azodicarbonamide, OBSH foaming agent, N,N'-dinitrospentamethylenetetramine, 4,4-oxobisbenzenesulfonylhydrazine, inorganic carbonates and bicarbonates, or one or more of these.

[0036] In some embodiments, the above-mentioned additives may be one or more of antioxidants, heat stabilizers, sensitizers, dispersants, flame retardants, pigments, antistatic agents, and thermally conductive particles, but not limited to these.

[0037] In some embodiments, the density of the polyolefin foam is 0.05 g / cm³. 3 ~0.35g / cm 3 When polyolefin foam is used as a cushioning material or as a substrate for adhesive tape in structural components, it needs to have good shock absorption performance and suitable strength to provide support for some parts. This is especially important when the foam density is below 0.05 g / cm³. 3 When the foam expansion ratio is too high, the strength is too low and insufficient to provide support; when the density is greater than 0.35 g / cm³, the foam is also insufficient. 3 At that time, the foam expansion ratio was low, the strength was too high, and the shock absorption and cushioning performance was reduced.

[0038] In some embodiments, the tensile strength of the polyolefin foam is 2 MPa to 5 MPa, and the elongation at break is 50% to 200%. When the tensile strength of the foam is greater than 5 MPa or the elongation at break is less than 50%, the foam is too rigid, the strength is too high, the shock absorption and cushioning performance is reduced, and it does not meet the requirements of actual application scenarios. When the tensile strength of the foam is less than 2 MPa or the elongation at break is greater than 200%, the foam is too soft and does not meet the requirement of providing a certain degree of support for the foam. At the same time, in the subsequent adhesive application process, it is not conducive to matching the tension and tensile deformation between the foam and the adhesive tape, which can easily cause the foam tape to bend and deform.

[0039] In some embodiments, the surface roughness of the polyolefin foam is 10 μm to 60 μm. The inventors' experiments revealed that when the surface roughness of the foam is less than 10 μm, the surface crystallinity is high, resulting in fewer bonding points between the adhesive and the foam surface, and lower bonding strength. When the surface roughness is greater than 60 μm, the adhesive cannot fill the rough portions of the foam surface, the actual bonding area becomes smaller, and moisture and oxygen can also enter the interface layer between the adhesive and the foam, accelerating foam surface aging and affecting bonding performance.

[0040] This application also provides a method for preparing the above-mentioned polyolefin foam, including the following steps:

[0041] S1. The above-mentioned polyolefin resin, cyclic olefin copolymer resin, foaming agent and additives are mixed and kneaded, and then extruded, stretched, granulated and dried to obtain resin masterbatch. The resin masterbatch is then extruded to form a pre-foamed sheet substrate.

[0042] S2. The above-mentioned pre-foamed substrate is irradiated and crosslinked to obtain a pre-foamed master sheet, and then the master sheet is foamed to obtain a foamed sheet.

[0043] S3. The above-mentioned foamed sheet is shaped by traction rollers to obtain adhesive-resistant polyolefin foam.

[0044] In some embodiments, the mixing and extrusion temperatures are lower than the decomposition temperature of the foaming agent to prevent premature decomposition of the foaming agent, which would affect the performance of the foam. In some embodiments, the mixing temperature can be 130°C to 150°C, which can produce resin masterbatches with uniform particle size, facilitating subsequent uniform foaming.

[0045] In some embodiments, in step S2, the pre-foamed substrate is irradiated with a high-speed electron beam at a dose of 10-20 Mrad for crosslinking. This allows the free radicals generated by the polyethylene resin and cyclic olefin copolymer resin segments to crosslink through segment recombination. Simultaneously, the cyclic structure in the cyclic olefin copolymer resin has highly reactive CH atoms (tertiary carbon H atoms and bridging carbon H atoms), which are easily oxidized to form polar groups, resulting in a pre-foamed master sheet with high initial surface energy. Furthermore, this ensures that the degree of resin crosslinking is within a suitable range, which is beneficial for subsequent foaming.

[0046] In some embodiments, the foaming temperature is higher than the decomposition temperature of the foaming agent, enabling the foaming agent to fully foam and form a foamed sheet with an independent closed-cell structure. The foaming temperature is 180°C to 250°C. It is understood that adjusting the foaming temperature adaptively according to the specific type and amount of the selected foaming agent is within the scope of protection of this application.

[0047] In some embodiments, the surface roughness of the traction roller is 10μm to 60μm; the temperature of the traction roller is lower than the foaming temperature, and the temperature difference is 20℃ to 50℃. The foamed sheet is shaped by the traction roller. At this time, the foam still has a certain temperature, and the foam surface is in close contact with the traction roller, which can adjust the surface roughness of the foam and shape it. When the temperature difference between the traction roller and the foaming temperature is less than 20℃, the foam remains at a high foaming temperature, which is not conducive to foam shaping and is prone to stretching deformation during subsequent winding. When the temperature difference between the traction roller and the foaming temperature is greater than 50℃, the foam surface temperature drops too quickly, resulting in high surface crystallinity, which is not conducive to forming high surface tension and makes it impossible to obtain a resistant polyolefin foam.

[0048] On the other hand, this application also provides an adhesive tape substrate comprising the above-mentioned polyolefin foam cushioning material or structural device.

[0049] It should be understood that materials of the same or similar type, model, quality, properties, or function as the reagents and instruments used in the following embodiments can be used to implement this application. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods. Unless otherwise specified, the materials and reagents used in the following embodiments are commercially available.

[0050] The following are examples and comparative examples:

[0051] Example 1

[0052] The raw materials for preparing polyolefin foam provided in this embodiment include polyolefin resin (low-density linear polyethylene LLDPE, melt index 5 g / 10 min, glass transition temperature Tg -85℃), cyclic olefin copolymer resin (glass transition temperature Tg 63℃, melt index 5 g / 10 min), foaming agent (azodicarbonamide, average particle size 10 μm) and antioxidant 1010 in a weight ratio of 52:30:15:3. The melt flow rate was tested using the GB / T3682.1 2018 standard method at a test temperature of 190℃ and a nominal load of 2.16 kg to measure the melt index of the polyolefin resin and the cyclic olefin copolymer COC resin. The Tg temperature of the polyolefin resin and the cyclic olefin copolymer COC resin was also measured using a DMA device. The particle size of the foaming agent was measured using a BETTERSIZE2600 wet laser particle size analyzer, and the median particle size D50 was selected as the average particle size of the foaming agent.

[0053] The method for preparing polyolefin foam provided in this embodiment is as follows:

[0054] S1. Polyolefin resin, cyclic olefin copolymer resin, foaming agent and antioxidant are mixed and kneaded according to the above weight ratio. The temperature of the kneading chamber is 140℃, the pressure is 2MPa, and the kneading time is 15min. The kneaded resin is added to the hopper of a twin-screw extruder. The processing temperature inside the screw barrel is 135℃. After extrusion, stretching, pelletizing and drying, resin masterbatch with uniform particles is obtained. Then, the above resin masterbatch is extruded into sheets using a twin-screw extruder. The sheets are extruded by calendering and cooling to obtain pre-foamed substrate sheets.

[0055] S2. The above-mentioned pre-foamed substrate is subjected to high-speed electron beam irradiation for electron irradiation crosslinking. The irradiation dose is 10Mrad to obtain a pre-foamed master sheet. Then, the pre-foamed substrate is subjected to free foaming in a vertical foaming furnace at a foaming temperature of 245℃ to obtain a foamed sheet.

[0056] S3. The above-mentioned foamed sheet is shaped by a traction roller with a surface roughness of 50μm and a temperature of 195℃ to obtain a non-adhesive polyolefin foam.

[0057] The performance of the prepared polyolefin foam was tested using the following methods, and the results are shown in Table 1:

[0058] 1) Foam density: Select a 10cm×10cm standard foam sample, measure the thickness based on ASTM D3574 standard, weigh the mass, and calculate the density.

[0059] 2) Tensile strength and elongation at break: measured in accordance with GB / T6344-2008 standard.

[0060] 3) Surface roughness: Measured in accordance with ISO 4287 standard.

[0061] 4) Surface tension: Measured according to GB / T14216 standard, the surface energy of the foam surface is measured using a dyne pen. The larger the dyne value, the greater the surface energy.

[0062] Example 2

[0063] The raw materials for preparing polyolefin foam provided in this embodiment include polyolefin resin (low-density linear polyethylene LLDPE, melt index of 3 g / 10 min, glass transition temperature Tg of -80℃), cyclic olefin copolymer resin (glass transition temperature Tg of 78℃, melt index of 2 g / 10 min), foaming agent (OBSH, average particle size of 5 μm) and antioxidant 1010 in a weight ratio of 70:20:8:2.

[0064] The method for preparing polyolefin foam provided in this embodiment is as follows:

[0065] S1. Polyolefin resin, cyclic olefin copolymer resin, foaming agent and antioxidant are mixed and kneaded according to the above weight ratio. The temperature of the kneading chamber is 140℃, the pressure is 2MPa, and the kneading time is 15min. The kneaded resin is added to the hopper of a twin-screw extruder. The processing temperature inside the screw barrel is 135℃. After extrusion, stretching, pelletizing and drying, resin masterbatch with uniform particles is obtained. Then, the above resin masterbatch is extruded into sheets using a twin-screw extruder. The sheets are extruded by calendering and cooling to obtain pre-foamed substrate sheets.

[0066] S2. The above-mentioned pre-foamed substrate is subjected to high-speed electron beam irradiation for electron irradiation crosslinking. The irradiation dose is 20Mrad to obtain a pre-foamed master sheet. Then, the pre-foamed substrate is subjected to free foaming in a vertical foaming furnace at a foaming temperature of 185℃ to obtain a foamed sheet.

[0067] S3. The above-mentioned foamed sheet is shaped by a traction roller with a surface roughness of 50μm and a temperature of 165℃ to obtain a non-adhesive polyolefin foam.

[0068] Example 3

[0069] The raw materials for preparing polyolefin foam provided in this embodiment include polyolefin resin (low-density linear polyethylene LLDPE, melt index of 1 g / 10 min, glass transition temperature Tg of -75℃), cyclic olefin copolymer resin (glass transition temperature Tg of 60℃, melt index of 0.5 g / 10 min), foaming agent (azodicarbonamide, average particle size of 8 μm) and antioxidant 1010 in a weight ratio of 60:25:10:5.

[0070] The method for preparing polyolefin foam provided in this embodiment is as follows:

[0071] S1. Polyolefin resin, cyclic olefin copolymer resin, foaming agent and antioxidant are mixed and kneaded according to the above weight ratio. The temperature of the kneading chamber is 140℃, the pressure is 2MPa, and the kneading time is 15min. The kneaded resin is added to the hopper of a twin-screw extruder. The processing temperature inside the screw barrel is 135℃. After extrusion, stretching, pelletizing and drying, resin masterbatch with uniform particles is obtained. Then, the above resin masterbatch is extruded into sheets using a twin-screw extruder. The sheets are extruded by calendering and cooling to obtain pre-foamed substrate sheets.

[0072] S2. The above-mentioned pre-foamed substrate is subjected to high-speed electron beam irradiation for electron irradiation crosslinking. The irradiation dose is 15Mrad to obtain a pre-foamed master sheet. Then, the pre-foamed substrate is subjected to free foaming in a vertical foaming furnace at a foaming temperature of 240℃ to obtain a foamed sheet.

[0073] S3. The above-mentioned foamed sheet is shaped by a traction roller with a surface roughness of 15μm and a temperature of 200℃ to obtain a non-adhesive polyolefin foam.

[0074] Example 4

[0075] The raw materials for preparing the polyolefin foam provided in this embodiment include polyolefin resin (low-density linear polyethylene LLDPE, melt index of 5 g / 10 min, glass transition temperature Tg of -85℃; high-density polyethylene HDPE, melt index of 5 g / 10 min, glass transition temperature Tg of -75℃, and mass ratio of LLDPE to HDPE of 2:1) in a weight ratio of 69:20:6:5, cyclic olefin copolymer resin (glass transition temperature Tg of 60℃, melt index of 5 g / 10 min), foaming agent (azodicarbonamide, average particle size of 5 μm) and antioxidant 1010.

[0076] The method for preparing polyolefin foam provided in this embodiment is as follows:

[0077] S1. Polyolefin resin, cyclic olefin copolymer resin, foaming agent and antioxidant are mixed and kneaded according to the above weight ratio. The temperature of the kneading chamber is 140℃, the pressure is 2MPa, and the kneading time is 15min. The kneaded resin is added to the hopper of a twin-screw extruder. The processing temperature inside the screw barrel is 135℃. After extrusion, stretching, pelletizing and drying, resin masterbatch with uniform particles is obtained. Then, the above resin masterbatch is extruded into sheets using a twin-screw extruder. The sheets are extruded by calendering and cooling to obtain pre-foamed substrate sheets.

[0078] S2. The above-mentioned pre-foamed substrate is subjected to high-speed electron beam irradiation for electron irradiation crosslinking. The irradiation dose is 15Mrad to obtain a pre-foamed master sheet. Then, the pre-foamed substrate is subjected to free foaming in a vertical foaming furnace at a foaming temperature of 230℃ to obtain a foamed sheet.

[0079] S3. The above-mentioned foamed sheet is shaped by a traction roller with a surface roughness of 15μm and a temperature of 190℃ to obtain a non-adhesive polyolefin foam.

[0080] Comparative Example 1

[0081] The raw materials for preparing the polyolefin foam provided in this comparative example include polyolefin resin, cyclic olefin copolymer resin, foaming agent, and antioxidant 1010 in a weight ratio of 47:35:15:3, and other parameters are the same as in Example 1. The preparation method of the polyolefin foam in this comparative example is the same as in Example 1.

[0082] Comparative Example 2

[0083] The raw materials for preparing the polyolefin foam provided in this comparative example do not contain cyclic olefin copolymer resins. The weight ratio of polyolefin resin, foaming agent, and antioxidant 1010 is 82:15:3, and other parameters are the same as in Example 1. In the preparation method of the polyolefin foam in this comparative example, the irradiation dose in step S2 is 20 Mrad, and other parameters are the same as in Example 1.

[0084] Comparative Example 3

[0085] In this comparative example, the polyolefin foam is prepared using low-density linear polyethylene (LLDPE) resin (melt index 7 g / 10 min, glass transition temperature Tg -68 °C), and other parameters are the same as in Example 1. The preparation method of the polyolefin foam in this comparative example is the same as in Example 1.

[0086] Comparative Example 4

[0087] In the preparation of the polyolefin foam provided in this comparative example, the foaming agent is azodicarbonamide with an average particle size of 15 μm, and other parameters are the same as in Example 1. The preparation method of the polyolefin foam is the same as in Example 1.

[0088] The properties of the polyolefin foams prepared in Examples 2-4 and Comparative Examples 1-4 were tested using the method provided in Example 1. The results are shown in Table 1.

[0089] Table 1. Properties of the polyolefin foams prepared in Examples 1-4 and Comparative Examples 1-4

[0090]

[0091] Experimental results show that by controlling the amount of cyclic olefin copolymers added, a polyolefin foam with a surface tension of 40 dyn / cm to 45 dyn / cm was prepared, and after being left at room temperature for 30 days, the surface tension remained ≥38 dyn / cm. This foam exhibits excellent and stable adhesive properties. Simultaneously, the foam density is 0.05 g / cm³. 3 ~0.35g / cm 3 With a tensile strength of 2MPa to 5MPa and an elongation at break greater than 50%, it meets the cushioning performance requirements of various applications and can also provide support. Furthermore, the surface roughness of the polyolefin foam is 10μm to 60μm, which allows it to form numerous bonding points with adhesives, improving bond strength and facilitating the direct application of subsequent adhesive tapes.

[0092] Compared to the examples, the polyolefin foam prepared in Comparative Example 1 has a tensile strength greater than 5 MPa and an elongation at break of only 33%. This may be because the cyclic olefin copolymer resin content is too high, resulting in a higher overall rigidity and strength of the blended resin. This leads to incomplete foaming during subsequent foaming, resulting in poor cushioning performance of the foam. The surface roughness of the foam prepared in Comparative Example 1 reaches 93 μm. In subsequent applications, the adhesive cannot easily fill the rough areas on the foam surface, resulting in a small actual bonding area. Moisture and oxygen can also easily form an interface layer between the adhesive and the foam surface, accelerating the aging of the foam surface and affecting the bonding performance of the polyolefin foam.

[0093] The polyolefin foam prepared in Comparative Example 2 contains acyclic olefin copolymer resin. The resulting polyolefin foam has a surface tension of less than 38 dyn / cm, low foaming density, and high surface roughness, which is not conducive to direct bonding with adhesive tape. Secondary processes such as corona treatment or primer coating are required to laminate the adhesive layer.

[0094] In Comparative Example 3, the Tg temperature and melt index of the polyolefin resin used in preparation were too high, which reduced the compatibility between the polyolefin resin and the cyclic olefin copolymer resin. This resulted in a higher strength of the blended resin, which reduced the cushioning performance of the polyolefin foam. Furthermore, the physical properties of the foam were uneven, and the surface tension of the foam was low and difficult to maintain.

[0095] In Comparative Example 4, the average particle size of the foaming agent azodicarbonamide was relatively large. During the processing, the dispersion uniformity of the foaming agent deteriorated, and foaming agent agglomeration occurred. This led to abnormal phenomena such as large pores and co-occurrence in the polyolefin foam after foaming, increasing the surface roughness of the foam.

[0096] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A type of adhesive-resistant polyolefin foam, characterized in that, The polyolefin foam is foamed from polyolefin resin, cyclic olefin copolymer resin, foaming agent, and additives. The polyolefin resin has a glass transition temperature < -75℃ and a melt index of 1g / 10min to 5g / 10min at 190℃ and a load of 2.16kg; the cyclic olefin copolymer resin has a glass transition temperature of 60℃ to 80℃ and a melt index of 0.5g / 10min to 5g / 10min at 190℃ and a load of 2.16kg; the foaming agent has an average particle size ≤ 10μm. The weight ratio of the polyolefin resin, cyclic olefin copolymer resin, foaming agent and additives is (50~70):(20~30):(5~15):(1~5); The surface tension of the polyolefin foam is 40 dyn / cm to 45 dyn / cm, and the surface roughness is 10 μm to 60 μm; after the polyolefin foam is placed at room temperature for 30 days, its surface tension is ≥38 dyn / cm.

2. The polyolefin foam according to claim 1, characterized in that, The polyolefin resin is selected from one or more of linear low-density polyethylene, low-density polyethylene, and high-density polyethylene.

3. The polyolefin foam according to claim 1, characterized in that, The foaming agent is selected from one or more of azodicarbonamide, OBSH foaming agent, N,N'-dinitrospentamethylenetetramine, 4,4-oxobisbenzenesulfonylhydrazine, inorganic carbonates, and bicarbonates.

4. The polyolefin foam according to claim 1, characterized in that, The additives are one or more of the following: antioxidants, heat stabilizers, sensitizers, dispersants, flame retardants, pigments, antistatic agents, and thermally conductive particles.

5. The method for preparing polyolefin foam according to claim 1, characterized in that, Includes the following steps: S1. The polyolefin resin, cyclic olefin copolymer resin, foaming agent and additives are mixed and kneaded, and then extruded, stretched, granulated and dried to obtain resin masterbatch. The resin masterbatch is then extruded to form a pre-foamed sheet substrate. S2. The pre-foamed substrate is irradiated and crosslinked to obtain a pre-foamed master sheet, and then the master sheet is foamed to obtain a foamed sheet. S3. The foamed sheet is shaped by a traction roller to obtain a non-adhesive polyolefin foam.

6. The preparation method according to claim 5, characterized in that, The irradiation dose for the irradiation crosslinking is 10 Mrad to 20 Mrad; and / or, The foaming temperature is 180℃~250℃; and / or, The surface roughness of the traction roller is 10μm~60μm.

7. The preparation method according to claim 6, characterized in that, The temperature of the traction roller is lower than the temperature of the foaming process, and the temperature difference is 20℃~50℃.

8. An adhesive tape substrate comprising a cushioning material or structural device of polyolefin foam as described in any one of claims 1 to 4.

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