Bonding-resistant polyolefin foam as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of polyolefin foam, and particularly relates to adhesion-resistant polyolefin foam as well as a preparation method and application thereof. The adhesion-resistant polyolefin foam provided by the invention is formed by foaming polyolefin resin, cycloolefin copolymer resin, a foaming agent and an auxiliary agent, wherein the weight ratio of the polyolefin resin to the cycloolefin copolymer resin to the foaming agent to the auxiliary agent is (50-70): (20-30): (5-15): (1-5). The polyolefin foam provided by the invention has excellent and stable and lasting bonding performance, also has excellent buffer performance, can play a supporting role, can form more bonding points with an adhesive, improves the bonding strength, is beneficial to subsequent direct bonding of an adhesive tape, and has a good application prospect. The adhesive tape base material is suitable for buffer materials or structural device adhesive tape base materials in different application scenes.

Description

Technical Field

[0001] The present application belongs to the technical field of polyolefin foams, and more specifically, relates to an adhesion-resistant polyolefin foam, a preparation method thereof, and an application thereof. Background Art

[0002] Polyolefin foam has good physical and chemical properties such as light weight, shock absorption, pressure resistance, heat preservation, and sound insulation, and is widely used in packaging, construction, automobiles, electronics, and other industrial fields. However, the non-polar surface and low surface tension of polyolefin foam make its bonding performance poor, making it difficult to achieve good bonding effects with other materials or the same materials, which seriously limits its application and process design in high-end composite materials and other fields. The use of heat sealing, special adhesives, or physical surface treatment can improve the bonding effect of polyolefin foam with other materials, but it is often accompanied by problems such as increased costs, complex processes, or insufficient bonding strength.

[0003] Many application scenarios of polyolefin foam require backing adhesive. During subsequent use, the polyolefin foam is prone to separation from the adhesive layer. Therefore, it is particularly important to develop an adhesive-resistant foam with low manufacturing cost, simple process and excellent bonding properties. Summary of the invention

[0004] In view of the defects of the prior art, the purpose of this application is to provide an adhesion-resistant polyolefin foam, a preparation method and application thereof, aiming to solve the technical problems of the existing polyolefin foam such as low surface tension, poor bonding performance and poor stability of bonding performance.

[0005] To achieve the above-mentioned purpose, the present application provides an adhesion-resistant polyolefin foam, which is foamed by polyolefin resin, cycloolefin copolymer resin, foaming agent and auxiliary agent.

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

[0007] Preferably, the glass transition temperature of the polyolefin resin is less than -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 cycloolefin copolymer resin has a glass transition temperature of 60° C. to 80° C. and a melt index of 0.5 g / 10 min. to 5 g / 10 min.

[0010] Preferably, the foaming agent has an average particle size of ≤10 μm and is selected from one or more of azodicarbonamide, OBSH foaming agent, N,N'-dinitrosopentamethylenetetramine, 4,4-oxobisbenzenesulfonylhydrazide, inorganic carbonates and bicarbonates.

[0011] Preferably, the auxiliary agent is one or more of an antioxidant, a heat stabilizer, a sensitizer, a dispersant, a flame retardant, a pigment, an antistatic agent and thermally conductive particles.

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

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

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

[0015] S1, mixing and kneading the above-mentioned polyolefin resin, cycloolefin copolymer resin, foaming agent and auxiliary agent, extruding, drawing, pelletizing, and drying to obtain a resin masterbatch, and then extruding the resin masterbatch to obtain a pre-foamed sheet substrate;

[0016] S2, irradiating and cross-linking the pre-foamed substrate to obtain a pre-foamed mother sheet, and then foaming the mother sheet to obtain a foamed sheet;

[0017] S3, the foamed sheet is subjected to shaping treatment by a traction roller to obtain a polyolefin foam that is resistant to adhesion.

[0018] Preferably, the radiation dose of the radiation cross-linking is 10 Mrad to 20 Mrad.

[0019] Preferably, the foaming temperature is 180°C to 250°C.

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

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

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

[0023] In general, the above technical solutions conceived by this application have the following technical advantages compared with the prior art:

[0024] (1) The adhesion-resistant polyolefin foam provided in the present application is foamed by polyolefin resin, cycloolefin copolymer resin, foaming agent and auxiliary agent, and the weight ratio of the above-mentioned polyolefin resin, cycloolefin copolymer resin, foaming agent and auxiliary agent is (50-70): (20-30): (5-15): (1-5). Compared with the existing polyolefin foam, the adhesion-resistant polyolefin foam provided in the present application has excellent bonding performance and stable and long-lasting bonding performance. At the same time, it has excellent cushioning performance and can play a supporting role. It can form more bonding points with the adhesive, improve the bonding strength, and facilitate the subsequent direct bonding of the adhesive tape. It is suitable for cushioning materials or adhesive tape substrates of structural devices in different application scenarios.

[0025] (2) In a preferred embodiment, the present application compounds a cycloolefin copolymer resin with suitable parameter performance with a polyolefin resin, a foaming agent and an auxiliary agent and limits the weight ratio between the components, so that the blended resin system has good miscibility, which is beneficial to resin extrusion and foaming, avoids the occurrence of bubble rupture, surface cracks, warping and other phenomena in the foaming process, and synergistically regulates the surface tension, density, tensile strength, elongation at break, surface roughness, etc. of the foam, thereby improving the surface energy and surface energy stability of the foam while improving the basic physical properties of the foam.

[0026] (3) Compared with the existing preparation methods, the preparation method provided in the present application can prepare polyolefin foam with good bonding properties without the need for additional surface treatment, and the preparation process is simple and the preparation cost is low. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the present application more clear, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described here are only used to explain the present application and are not used to limit the present application.

[0028] The surface tension of polyolefin foam is usually less than 38 dyn / cm. Its surface tension can be increased to above 38 dyn / cm by corona treatment or other methods. However, it usually takes some time from the production of foam to its formal use by the customer. By then, the surface tension of the foam will drop significantly, which will seriously affect the adhesion between the foam and the adhesive layer after gluing. Based on this, the present application provides a polyolefin foam that is resistant to adhesion, which is foamed by polyolefin resin, cycloolefin copolymer resin, foaming agent and auxiliary agent.

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

[0030] The surface tension of the polyolefin foam provided in the present application is 40 dyn / cm to 45 dyn / cm. After the polyolefin foam is placed at room temperature for 30 days, its surface tension is ≥38 dyn / cm, and it can have good bonding performance with adhesives. The adhesion-resistant polyolefin foam provided in the present application does not require additional surface treatment. The foam itself has good bonding performance and can be applied to cushioning materials or adhesive tape substrates of structural devices in different application scenarios.

[0031] In the present application, the above-mentioned cycloolefin copolymer resin (COC) is a non-crystalline polyolefin resin obtained by copolymerizing ethylene and bicycloheptene using a metallocene catalyst. The inventor found through experiments that after the above-mentioned cycloolefin copolymer resin is blended with a polyolefin resin, the highly active CH atoms in the cyclic structure of the cycloolefin copolymer resin are more easily oxidized to form polar groups, increasing the polarity of the foam surface. At the same time, the molecular chain of the cyclic structure of the cycloolefin copolymer resin is relatively stable, has a large steric hindrance, is not easy to produce movement, can prevent the residual small molecules inside the foam from migrating to the foam surface to a certain extent, so that the surface energy of the foam surface remains stable and slows down the attenuation. In addition, the above-mentioned cycloolefin copolymer resin can make the molecular chain on the foam surface relatively loose, improve the wetting effect of the adhesive on the foam surface, thereby increasing the bonding performance of the foam surface. At the same time, the cycloolefin copolymer resin has a high water vapor barrier, which can make it difficult for water vapor to penetrate the bonding interface layer under a high temperature and high humidity environment after the foam is back-adhesed, thereby slowing down the bonding failure of the interface layer.

[0032] In some embodiments, the glass transition temperature (Tg) of the cycloolefin copolymer resin is 60°C to 80°C, and the melt index is 0.5g / 10min to 5g / 10min. The inventors have found through experiments that when TG is too high, the rigidity and strength of the cycloolefin copolymer resin are greatly increased, affecting its blending processing performance with polyolefin resins, such as cell rupture and cracks on the surface during the foaming process, affecting the surface roughness of the foam, and further affecting the basic physical properties of the foam.

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

[0034] The present application blends the above-mentioned cycloolefin copolymer resin with a polyolefin resin having a Tg temperature of less than -75°C, and by adjusting the ratio of the two, the blended resin system has good miscibility, which is beneficial to resin extrusion and foaming, and avoids abnormal phenomena such as pores and warping in the foaming process. At the same time, it can improve the surface energy and surface energy stability of the foam, and will not increase the hardness of the foam, reduce the flexibility and cushioning performance of the foam, and affect the basic physical properties of the foam. In some embodiments, the above-mentioned cycloolefin copolymer resin accounts for 20wt% to 30wt% of the total raw materials for preparing the polyurethane foam.

[0035] In some embodiments, the average particle size of the foaming agent is ≤10 μm, which makes it easier to blend with the resin and evenly disperse in the resin component, and obtain a larger number of relatively uniform pores after subsequent foaming treatment, while improving the physical properties of the foam. The present application does not specifically limit the type of the foaming agent, and preferably uses a foaming agent with low cost and good foaming effect, such as but not limited to one or more of azodicarbonamide, OBSH foaming agent, N,N'-dinitrosopentamethylenetetramine, 4,4-oxobisbenzenesulfonylhydrazide, inorganic carbonates and bicarbonates.

[0036] In some embodiments, the auxiliary agent may be, but is not limited to, one or more of an antioxidant, a heat stabilizer, a sensitizer, a dispersant, a flame retardant, a pigment, an antistatic agent, and thermally conductive particles.

[0037] In some embodiments, the density of the polyolefin foam is 0.05 g / cm 3 ~0.35g / cm 3 When polyolefin foam is used as a cushioning material or adhesive tape substrate for structural components, it needs to have good shock absorption performance and appropriate strength to support some parts. When the foam density is lower than 0.05g / cm 3 When the density is greater than 0.35g / cm 3 When the foam is used, the foaming ratio is low, the strength is relatively large, and the shock absorbing and cushioning performance is reduced.

[0038] In some embodiments, the tensile strength of the polyolefin foam is 2MPa to 5MPa, and the elongation at break is 50% to 200%. When the tensile strength of the foam is greater than 5MPa or the elongation at break is less than 50%, the foam is rigid, the strength is too high, and the shock absorption and buffering performance is reduced, which does not meet the requirements of actual application scenarios; when the tensile strength of the foam is less than 2MPa or the elongation at break is greater than 200%, the foam is too soft and does not meet the requirements for the foam to have a certain degree of support. At the same time, in the subsequent gluing process, it is not conducive to matching the tension and tensile deformation of the foam and the adhesive tape, and it is easy to 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 have found through experiments that when the surface roughness of the foam is less than 10 μm, the surface crystallinity is high, the adhesive and the foam surface form fewer bonding points, and the bonding strength is low; when the surface roughness is greater than 60 μm, the adhesive cannot fill the rough part of the foam surface, the actual bonding area becomes smaller, and water vapor and oxygen will also enter the interface layer between the adhesive and the foam, accelerating the aging of the foam surface and affecting the bonding performance.

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

[0041] S1, mixing and kneading the above-mentioned polyolefin resin, cycloolefin copolymer resin, foaming agent and auxiliary agent, extruding, drawing, pelletizing, drying to obtain resin masterbatch, and then extruding the resin masterbatch to obtain a pre-foamed sheet substrate;

[0042] S2, irradiating and cross-linking the pre-foamed substrate to obtain a pre-foamed mother sheet, and then foaming the mother sheet to obtain a foamed sheet;

[0043] S3, the foamed sheet is subjected to shaping treatment by a traction roller to obtain a polyolefin foam that is resistant to adhesion.

[0044] In some embodiments, the temperature of the mixing and kneading and the extrusion molding are lower than the decomposition temperature of the foaming agent, in order to prevent the foaming agent from decomposing prematurely and affecting the performance of the foam. In some embodiments, the temperature of the mixing and kneading can be 130°C to 150°C, which can produce a resin masterbatch with uniform particle size, which is conducive to subsequent uniform foaming.

[0045] In some embodiments, in step S2, the pre-foamed substrate is subjected to high-speed electron beam irradiation, and the irradiation dose for irradiation crosslinking is 10Mrad to 20Mrad, which can make the free radicals generated by the polyethylene resin and cycloolefin copolymer resin segments produce crosslinking through segment recombination. At the same time, the cyclic structure in the cycloolefin copolymer resin has a highly reactive CH atom, i.e., a tertiary carbon H atom and a bridge carbon H atom, which is easily oxidized to form a polar group, thereby obtaining a pre-foamed mother sheet with a higher initial surface energy. In addition, the crosslinking degree of the resin can be within a suitable range, which is conducive to subsequent foaming.

[0046] In some embodiments, the foaming temperature is higher than the decomposition temperature of the foaming agent, so that the foaming agent can be fully foamed to form a foamed sheet with an independent closed pore structure. The foaming temperature is 180°C to 250°C. It is understood that the foaming temperature can be adaptively adjusted according to the specific type and amount of the selected foaming agent, which 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 above-mentioned foaming temperature, and the temperature difference is 20℃ to 50℃. The above-mentioned foamed sheet is shaped by the traction roller. At this time, the foam still has a certain temperature. The foam surface is in contact with the traction roller, which can adjust the surface roughness of the foam and shape the foam. When the temperature difference between the traction roller temperature and the foaming temperature is less than 20℃, the foam always maintains the high foaming temperature, which is not conducive to foam shaping, and is also prone to tensile deformation during the subsequent winding process; when the temperature difference between the traction roller temperature and the foaming temperature is greater than 50℃, the foam surface temperature drops too fast, the surface crystallinity is high, which is not conducive to the formation of a high surface tension, and it is impossible to obtain a polyolefin foam that is resistant to adhesion.

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

[0049] It should be understood that materials of the same or similar type, model, quality, properties or functions as the reagents and instruments used in the following examples can be used to implement the present application. The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, etc. used in the following examples, unless otherwise specified, can be obtained from commercial sources.

[0050] The following are examples and comparative examples:

[0051] Example 1

[0052] The raw materials for preparing the polyolefin foam provided in this embodiment include a polyolefin resin (low-density linear polyethylene LLDPE, melt index of 5g / 10min, glass transition temperature Tg of -85°C) with a weight ratio of 52:30:15:3, a cycloolefin copolymer resin (glass transition temperature Tg of 63°C, melt index of 5g / 10min), a foaming agent (azodicarbonamide, average particle size of 10μm) and an antioxidant 1010. Among them, the GB / T3682.1 2018 standard method is adopted, and the melt flow rate meter is used for testing. The test temperature is selected as 190°C, and the nominal load is selected as 2.16kg. The melt index of the polyolefin resin and the cycloolefin copolymer COC resin is tested, and the Tg temperature of the polyolefin resin and the cycloolefin copolymer COC resin is tested using a DMA device; the particle size of the foaming agent is tested using a BETTERSIZE2600 wet laser particle size distribution analyzer, and the median particle size D50 is selected as the average particle size of the foaming agent.

[0053] The preparation method of the polyolefin foam provided in this embodiment is as follows:

[0054] S1. According to the above weight ratio, the polyolefin resin, cycloolefin copolymer resin, foaming agent and antioxidant are mixed and kneaded, the kneading chamber temperature is 140°C, the pressure is 2MPa, the kneading time is 15min, the kneaded resin is added to the hopper of the twin-screw, the processing temperature in the screw barrel is 135°C, and the resin masterbatch with uniform particles is obtained through extrusion, drawing, pelletizing and drying processes; then the resin masterbatch is extruded into sheets by a twin-screw extruder, and the sheets are extruded by calendering and cooling to obtain a pre-foamed substrate;

[0055] S2, subjecting the above-mentioned pre-foamed substrate to high-speed electron beam irradiation, electron irradiation cross-linking, the irradiation dose is 10Mrad, to obtain a pre-foamed mother sheet; then the pre-foamed substrate is freely foamed in a vertical foaming furnace, the foaming temperature is 245° C., to obtain a foamed sheet;

[0056] S3, the foamed sheet is subjected to shaping treatment by a traction roller, the surface roughness of the traction roller is 50 μm, the temperature of the traction roller is 195° C., and a polyolefin foam resistant to adhesion is obtained.

[0057] The prepared polyolefin foam was subjected to a performance test, and the test method was as follows. The results are shown in Table 1:

[0058] 1) Foam density: Select a 10 cm × 10 cm foam standard sample, measure the thickness based on the 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: Refer to GB / T14216 standard and use a dyne pen to measure the surface energy of the foam surface. The larger the dyne value, the greater the surface energy.

[0062] Example 2

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

[0064] The preparation method of the polyolefin foam provided in this embodiment is as follows:

[0065] S1. According to the above weight ratio, the polyolefin resin, cycloolefin copolymer resin, foaming agent and antioxidant are mixed and kneaded, the kneading chamber temperature is 140°C, the pressure is 2MPa, the kneading time is 15min, the kneaded resin is added to the hopper of the twin-screw, the processing temperature in the screw barrel is 135°C, and the resin masterbatch with uniform particles is obtained through extrusion, drawing, pelletizing and drying processes; then the resin masterbatch is extruded into sheets by a twin-screw extruder, and the sheets are extruded by calendering and cooling to obtain a pre-foamed substrate;

[0066] S2, subjecting the above-mentioned pre-foamed substrate to high-speed electron beam irradiation, electron irradiation cross-linking, the irradiation dose is 20Mrad, to obtain a pre-foamed mother sheet; then the pre-foamed substrate is freely foamed in a vertical foaming furnace, the foaming temperature is 185° C., to obtain a foamed sheet;

[0067] S3, the foamed sheet is subjected to shaping treatment by a traction roller, the surface roughness of the traction roller is 50 μm, the temperature of the traction roller is 165° C., and a polyolefin foam resistant to adhesion is obtained.

[0068] Example 3

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

[0070] The preparation method of the polyolefin foam provided in this embodiment is as follows:

[0071] S1. According to the above weight ratio, the polyolefin resin, cycloolefin copolymer resin, foaming agent and antioxidant are mixed and kneaded, the kneading chamber temperature is 140°C, the pressure is 2MPa, the kneading time is 15min, the kneaded resin is added to the hopper of the twin-screw, the processing temperature in the screw barrel is 135°C, and the resin masterbatch with uniform particles is obtained through extrusion, drawing, pelletizing and drying processes; then the resin masterbatch is extruded into sheets by a twin-screw extruder, and the sheets are extruded by calendering and cooling to obtain a pre-foamed substrate;

[0072] S2, subjecting the above-mentioned pre-foamed substrate to high-speed electron beam irradiation, electron irradiation cross-linking, the irradiation dose is 15Mrad, to obtain a pre-foamed mother sheet; then the pre-foamed substrate is freely foamed in a vertical foaming furnace, the foaming temperature is 240°C, to obtain a foamed sheet;

[0073] S3. The foamed sheet is shaped by a traction roller, the surface roughness of the traction roller is 15 μm, and the temperature of the traction roller is 200° C., to obtain a polyolefin foam that is resistant to adhesion.

[0074] Example 4

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

[0076] The preparation method of the polyolefin foam provided in this embodiment is as follows:

[0077] S1. According to the above weight ratio, the polyolefin resin, cycloolefin copolymer resin, foaming agent and antioxidant are mixed and kneaded, the kneading chamber temperature is 140°C, the pressure is 2MPa, the kneading time is 15min, the kneaded resin is added to the hopper of the twin-screw, the processing temperature in the screw barrel is 135°C, and the resin masterbatch with uniform particles is obtained through extrusion, drawing, pelletizing and drying processes; then the resin masterbatch is extruded into sheets by a twin-screw extruder, and the sheets are extruded by calendering and cooling to obtain a pre-foamed substrate;

[0078] S2, subjecting the above-mentioned pre-foamed substrate to high-speed electron beam irradiation, electron irradiation cross-linking, the irradiation dose is 15Mrad, to obtain a pre-foamed mother sheet; then the pre-foamed substrate is freely foamed in a vertical foaming furnace, the foaming temperature is 230°C, to obtain a foamed sheet;

[0079] S3, the foamed sheet is subjected to shaping treatment by a traction roller, the surface roughness of the traction roller is 15 μm, the temperature of the traction roller is 190° C., and a polyolefin foam resistant to adhesion is obtained.

[0080] Comparative Example 1

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

[0082] Comparative Example 2

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

[0084] Comparative Example 3

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

[0086] Comparative Example 4

[0087] In the raw materials for preparing 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 those in Example 1. The preparation method of the polyolefin foam is the same as that in Example 1.

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

[0089] Table 1 Properties of polyolefin foams prepared in Examples 1 to 4 and Comparative Examples 1 to 4

[0090]

[0091] The experimental results show that by controlling the amount of cycloolefin copolymer added, the surface tension of the polyolefin foam is 40 dyn / cm to 45 dyn / cm, and after being placed at room temperature for 30 days, the surface tension is still ≥ 38 dyn / cm, which has excellent bonding performance and stable and long-lasting bonding performance. At the same time, the foam density is 0.05 g / cm 3 ~0.35g / cm 3 , tensile strength is 2MPa~5MPa, elongation at break is greater than 50%, which meets the requirements of application scenarios for cushioning performance and can play a supporting role. In addition, the surface roughness of polyolefin foam is 10μm~60μm, which can form more bonding points with adhesives, improve bonding strength, and facilitate direct bonding of subsequent adhesive tapes.

[0092] Compared with the examples, the tensile strength of the polyolefin foam prepared in Comparative Example 1 is greater than 5MPa, and the elongation at break is only 33%. The reason may be that the content of the cycloolefin copolymer resin is too high, which makes the overall rigidity of the blended resin too large and the strength too high, and the foaming is incomplete during the subsequent foaming, resulting in poor cushioning performance of the foam. The surface roughness of the foam prepared in Comparative Example 1 is 93μm. In subsequent applications, the adhesive is not easy to fill the rough position on the foam surface, resulting in a small actual bonding area. Water vapor and oxygen are also easy to enter the 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 of Comparative Example 2 is prepared from acyclic olefin copolymer resin as raw material. The surface tension of the prepared polyolefin foam is less than 38 dyn / cm, and the foaming density is low. The surface roughness is high, which is not conducive to the direct pasting of the subsequent adhesive tape. Secondary processes such as corona treatment or primer coating are required to composite the adhesive layer.

[0094] In Comparative Example 3, the Tg temperature and melt index of the raw material polyolefin resin prepared are relatively high, and the compatibility of the polyolefin resin and the cycloolefin copolymer resin is reduced, which makes the strength of the blended resin relatively large, reduces the cushioning performance of the polyolefin foam, and the physical properties of the foam are uneven, and the surface tension of the foam part is low and difficult to maintain.

[0095] The average particle size of the raw material foaming agent azodicarbonamide prepared in Comparative Example 4 is relatively large. During the processing, the dispersion uniformity of the foaming agent deteriorates, and the foaming agent agglomerates. This leads to the abnormal phenomenon of large cells and combined bubbles in the polyolefin foam after foaming, and increases the surface roughness of the foam.

[0096] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A polyolefin foam resistant to adhesion, characterized in that: The polyolefin foam is foamed by polyolefin resin, cycloolefin copolymer resin, foaming agent and auxiliary agent. The weight ratio of the polyolefin resin, the cycloolefin copolymer resin, the foaming agent and the auxiliary agent is (50-70):(20-30):(5-15):(1-5).

2. The polyolefin foam according to claim 1, characterized in that: The polyolefin resin has a glass transition temperature of less than -75°C and a melt index of 1 g / 10 min to 5 g / 10 min; and 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 cycloolefin copolymer resin has a glass transition temperature of 60° C. to 80° C. and a melt index of 0.5 g / 10 min. to 5 g / 10 min.

4. The polyolefin foam according to claim 1, characterized in that: The foaming agent has an average particle size of ≤10 μm and is selected from one or more of azodicarbonamide, OBSH foaming agent, N,N'-dinitrosopentamethylenetetramine, 4,4-oxobisbenzenesulfonylhydrazide, inorganic carbonate and bicarbonate.

5. The polyolefin foam according to claim 1, characterized in that: The auxiliary agent is one or more of an antioxidant, a heat stabilizer, a sensitizer, a dispersant, a flame retardant, a pigment, an antistatic agent and thermal conductive particles.

6. The polyolefin foam according to any one of claims 1 to 5, characterized in that: The surface tension of the polyolefin foam is 40 dyn / cm to 45 dyn / cm; After the polyolefin foam is placed at room temperature for 30 days, its surface tension is ≥38 dyn / cm.

7. The method for preparing polyolefin foam according to claim 1, characterized in that: The steps include: S1, mixing and kneading the polyolefin resin, cycloolefin copolymer resin, foaming agent and auxiliary agent, extruding, drawing, pelletizing and drying to obtain a resin masterbatch, and then extruding the resin masterbatch to obtain a pre-foamed sheet substrate; S2, irradiating and cross-linking the pre-foamed substrate to obtain a pre-foamed mother sheet, and then foaming the mother sheet to obtain a foamed sheet; S3, the foamed sheet is subjected to shaping treatment by a traction roller to obtain a polyolefin foam that is resistant to adhesion.

8. The preparation method according to claim 7, characterized in that: The radiation dose of the radiation cross-linking is 10 Mrad to 20 Mrad; and / or, The foaming temperature is 180°C to 250°C; and / or, The surface roughness of the traction roller is 10 μm to 60 μm.

9. The preparation method according to claim 8, characterized in that: The temperature of the pulling roller is lower than the foaming temperature, and the temperature difference is 20°C to 50°C.

10. An adhesive tape substrate for a cushioning material or a structural device comprising the polyolefin foam according to any one of claims 1 to 6.

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