An easy die-cutting BOPP pearlescent film and a preparation method and application thereof

Abstract

The present application relates to a kind of easy die-cutting BOPP pearlescent film and its preparation method and application, belong to the technical field of pearlescent film.The easy die-cutting BOPP pearlescent film described in the present application includes printable surface layer, core layer and lower surface layer arranged in sequence;The core layer includes homopolymer polypropylene, 28-38wt% calcium carbonate masterbatch and 5-10wt% ethylene-propylene-5-norbornene-2-methanol tri-block copolymer, and the lower surface layer includes homopolymer polypropylene and 12-16wt% saponified ethylene-vinyl acetate copolymer.The easy die-cutting BOPP pearlescent film of the present application has suitable brittleness, excellent die-cutting performance, and when being used to make adhesive label, die-cutting processing is smooth, effectively improves the "flying label" phenomenon in die-cutting process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pearl film, in particular to an easy-to-cut BOPP pearl film, a preparation method and application thereof. BACKGROUND

[0002] The structure of the adhesive label usually comprises a pattern layer, a BOPP pearl film, a glue layer and a release base paper layer arranged in sequence. In the production process of the adhesive label, the die cutting process is a key link in the whole production process. Die cutting, that is, using a die cutting technology to cut the adhesive material into a specific shape, plays a decisive role in the molding of the adhesive label. Most die cutting processes use a half-cutting method, that is, only the pattern layer, the BOPP pearl film and the glue layer of the adhesive label are penetrated, and the integrity of the release base paper layer is preserved. After die cutting, the excess pattern layer, BOPP pearl film and glue layer are usually treated as waste to obtain the required label part.

[0003] However, during the die cutting process, the label may sometimes be carried up with the waste edge, which is usually referred to as the "label flying" phenomenon, which not only affects the molding quality of the label, but also may adversely affect the subsequent process. One of the reasons for the "label flying" phenomenon is that the die cutting is not continuous, that is, during the die cutting process, the die cutting knife does not completely penetrate the BOPP pearl film of the adhesive material, so that the required label part may be carried up with the waste edge during the waste treatment, that is, the die cutting performance of the BOPP pearl film is insufficient. The second reason for the "label flying" phenomenon is the glue (or adhesive) back-sticking problem during die cutting. Although the adhesive label has been completely cut off, due to the flowability of the glue, the glue at the die cutting position re-sticks when the label passes through the pressure roller, thereby causing label dropping or poor waste removal. Especially when hot melt glue or thickly coated adhesive material is used, the glue backflow problem often occurs during the die cutting process, resulting in serious glue stringing. SUMMARY

[0004] Therefore, the purpose of the present application is to provide an easy-to-cut BOPP pearl film, a preparation method and application thereof. The easy-to-cut BOPP pearl film of the present application has appropriate brittleness and excellent die cutting performance, and the die cutting process is smooth when used to make adhesive labels, effectively improving the "label flying" phenomenon during die cutting.

[0005] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0006] The application provides a die-cuttable BOPP pearlescent film, which comprises a printable surface layer, a core layer and a lower surface layer arranged in sequence; the core layer comprises homopolymer polypropylene, 28-38 wt% calcium carbonate masterbatch and 5-10 wt% ethylene-propylene-5-norbornene-2-methanol triblock copolymer, the content of ethylene in the ethylene-propylene-5-norbornene-2-methanol triblock copolymer is 8-15 mol%, and the content of 5-norbornene-2-methanol is 10-20 mol%; the lower surface layer comprises homopolymer polypropylene and 12-16 wt% saponified ethylene-vinyl acetate copolymer; and the saponification degree of the saponified ethylene-vinyl acetate copolymer is 20-30%.

[0007] The application considers that the die-cutting failure of the BOPP pearlescent film is caused by the fact that the toughness of the film is too high and the brittleness is insufficient; 5-10 wt% ethylene-propylene-5-norbornene-2-methanol triblock copolymer (i.e. the triblock copolymer is a copolymer formed by connecting polyethylene segments, polypropylene segments and poly-5-norbornene-2-methanol segments) is added to the core layer; on the one hand, the ethylene-propylene-5-norbornene-2-methanol triblock copolymer has relatively soft segments (polyethylene segments + polypropylene segments, equivalent to elastomers), which is beneficial to the compatibility of the ethylene-propylene-5-norbornene-2-methanol triblock copolymer and other components in the core layer, and ensures the required sticking roller performance in the film production process; on the other hand, the block structure of the ethylene-propylene-5-norbornene-2-methanol triblock copolymer maintains a certain regularity of molecular structure, and the ethylene-propylene-5-norbornene-2-methanol triblock copolymer also has relatively rigid hard segments (poly-5-norbornene-2-methanol segments), the hydrogen bond interaction between the hydroxyl groups in 5-norbornene-2-methanol forms a network structure, which is beneficial to inhibiting the molecular chain movement of homopolymer polypropylene, and through the regulation of the soft segments and the hard segments, the brittleness of the core layer is improved to a certain extent, and the toughness is reduced, which is beneficial to the smooth die-cutting of the relatively thick core layer, thereby improving the die-cutting performance of the whole film. In addition, the hydroxyl groups in the 5-norbornene-2-methanol in the ethylene-propylene-5-norbornene-2-methanol triblock copolymer can form hydrogen bond interaction force with the low molecular dispersant (such as stearic acid dispersant) in the calcium carbonate masterbatch, which is beneficial to reducing the migration of the low molecular dispersant to the surface of the film, and reducing the adverse effects of the migration of the low molecular dispersant to the surface of the film on the printing performance of the printable surface layer or the gluing performance of the lower surface layer.

[0008] The content of the ethylene-propylene-5-norbornene-2-methanol triblock copolymer in the core layer is 5-10 wt%; if the content of the ethylene-propylene-5-norbornene-2-methanol triblock copolymer in the core layer is too low, the brittleness of the core layer cannot be effectively improved, the toughness of the core layer cannot be effectively reduced, and the low molecular dispersant in the calcium carbonate master batch cannot be locked, so that the migration of the low molecular dispersant cannot be effectively reduced, which easily causes adverse effects on the printing performance of the printable surface layer and the gluing performance of the lower surface layer; if the content of the ethylene-propylene-5-norbornene-2-methanol triblock copolymer in the core layer is too high, the brittleness of the core layer is too large, which is not conducive to the smoothness of the biaxial stretching, and even the stretching cannot be performed, which affects the film production.

[0009] The content of 5-norbornene-2-methanol (poly-5-norbornene-2-methanol segment) in the ethylene-propylene-5-norbornene-2-methanol triblock copolymer is 10-20 mol%, and the 5-norbornene-2-methanol segment in the ethylene-propylene-5-norbornene-2-methanol triblock copolymer acts as a hard segment and provides rigidity; if the content of 5-norbornene-2-methanol in the ethylene-propylene-5-norbornene-2-methanol triblock copolymer is too low, the brittleness of the core layer cannot be effectively improved, which leads to poor die cutting performance; if the content of 5-norbornene-2-methanol in the ethylene-propylene-5-norbornene-2-methanol triblock copolymer is too high, the intermolecular hydrogen bond network is easily formed, which leads to too large rigidity of the core layer of the film, is not conducive to the realization of the large-ratio biaxial stretching process, easily causes the film breaking phenomenon, and also leads to too large polarity difference between the core layer and the other two layers, which may cause the delamination phenomenon.

[0010] The content of the ethylene in the ethylene-propylene-5-norbornene-2-methanol triblock copolymer (content of polyethylene segment) is 8-15 mol%, which can make the polypropylene segment in the ethylene-propylene-5-norbornene-2-methanol triblock copolymer still maintain a relatively high and appropriate regularity, so that the ethylene-propylene-5-norbornene-2-methanol triblock copolymer obtains a relatively high and appropriate melting point; if the content of the ethylene in the ethylene-propylene-5-norbornene-2-methanol triblock copolymer is too low, the block structure regularity of the ethylene-propylene-5-norbornene-2-methanol triblock copolymer will be excessively increased, so that the crystallinity of the polypropylene segment is too high, which, together with the poly-5-norbornene-2-methanol segment that plays a rigid role, will cause the ethylene-propylene-5-norbornene-2-methanol triblock copolymer to be too rigid as a whole, which is not conducive to the film to obtain good roll sticking performance, thereby causing problems such as uneven thickness and wrinkles, and affecting the film production efficiency and yield; if the content of the ethylene in the ethylene-propylene-5-norbornene-2-methanol triblock copolymer is too high, it will hinder the crystallization of the polypropylene segment, so that the melting point of the ethylene-propylene-5-norbornene-2-methanol triblock copolymer is reduced, which is not conducive to the matching of the ethylene-propylene-5-norbornene-2-methanol triblock copolymer and the film production and processing temperature, and will cause the flowability and toughness to be too high, which is not conducive to improving the die cutting performance of the core layer.

[0011] The easy die-cutting BOPP pearlescent film needs to be coated with glue (commonly acrylate or hot melt glue) on the lower surface to form a glue layer in subsequent applications. The application considers that the phenomenon of glue back sticking of the BOPP pearlescent film applied to the adhesive label during die cutting is due to the low adhesion of the BOPP pearlescent film to the glue. In order to ensure the adhesion between the BOPP pearlescent film and the glue, more glue needs to be coated, which will cause the adhesive label to be prone to glue back sticking during die cutting due to the thick coating of glue and the flowability of the glue itself, thereby resulting in poor die cutting performance. The application adds 5-10 wt% of saponified ethylene-vinyl acetate copolymer to the lower surface, and the saponification degree of the saponified ethylene-vinyl acetate copolymer is designed to be 15-25%. The saponified ethylene-vinyl acetate copolymer is obtained by alcoholysis of ethylene-vinyl acetate copolymer, in which part of the ester groups are changed to hydroxyl groups by alcoholysis, which is beneficial to form a hydrogen bond network with the migrated low molecular dispersant, reduce the migration and precipitation of the low molecular dispersant to the outside of the lower surface, reduce the adverse effects on the gluing performance of the lower surface, and also beneficial to the firm combination between the lower surface and the glue layer. The existence of hydroxyl groups is also beneficial to reduce the flowability of the coated glue, synergistically improve the problems of label falling or poor waste discharge caused by glue back sticking during die cutting, synergistically improve the die cutting performance of the label, and reduce the occurrence of the flying label phenomenon. At the same time, part of the ester groups in the saponified ethylene-vinyl acetate copolymer are maintained, which is beneficial to enhance the adhesion between the lower surface and the glue layer formed by subsequent coating when the film is used to make the adhesive label, improve the die cutting performance of the adhesive label, and reduce the phenomenon that the adhesive label is easily carried with the waste edge during the die cutting process.

[0012] The application limits the content of the saponified ethylene-vinyl acetate copolymer in the lower surface to be 12-16 wt%, and limits the saponification degree of the saponified ethylene-vinyl acetate copolymer to be 20-30%. If the content of the saponified ethylene-vinyl acetate copolymer in the lower surface is too low, and / or if the saponification degree of the saponified ethylene-vinyl acetate copolymer is too low, the gluing performance of the lower surface is poor, and the adhesion to the glue is low, more glue needs to be coated to ensure the adhesion, which will cause the film to be prone to glue back sticking during die cutting when applied to the adhesive label, resulting in poor die cutting performance. If the content of the saponified ethylene-vinyl acetate copolymer in the lower surface is too high, and / or if the saponification degree of the saponified ethylene-vinyl acetate copolymer is too high, the film may be stuck to the roller during preparation.

[0013] Further, the printable surface layer comprises random copolymerized polypropylene and 1-2wt% maleic anhydride grafted polypropylene, the grafting rate of maleic anhydride in the maleic anhydride grafted polypropylene is 0.5-1%. By adding 1-2wt% maleic anhydride grafted polypropylene in the printable surface layer, the present application is beneficial to the interlayer bonding force between the printable surface layer and the core layer, and is beneficial to improve the surface tension of the printable surface layer, so as to facilitate the formation of a pattern layer on the surface of the printable surface layer by ink printing in subsequent application.

[0014] Further, the random copolymerized polypropylene has a melt index of 5-10g / 10min under a load of 2.16kg at 230℃, and a melting point of 120-150℃.

[0015] Further, the random copolymerized polypropylene is selected from one or two of ethylene-propylene copolymerized polypropylene and ethylene-propylene-butylene copolymerized polypropylene.

[0016] Further, the calcium carbonate masterbatch comprises homopolymerized polypropylene and 65-75wt% low-molecular dispersant coated calcium carbonate. The addition of calcium carbonate masterbatch in the core layer can provide good pearlescent effect for the easy die-cutting BOPP pearlescent film. Preferably, the particle size D50 of calcium carbonate in the calcium carbonate masterbatch is 1.0-1.5μm, by limiting the particle size of calcium carbonate in the calcium carbonate masterbatch, it is beneficial to the effective dispersion of calcium carbonate masterbatch in the core layer, and a relatively uniform "cavitation" effect can be obtained to ensure the pearlescent effect of the film.

[0017] Further, the glass transition temperature of the ethylene-propylene-5-norbornene-2-methanol triblock copolymer is 145-155℃. By limiting the glass transition temperature of the ethylene-propylene-5-norbornene-2-methanol triblock copolymer to 145-155℃, it is beneficial to improve the glass transition temperature of the core layer, thereby improving the brittleness of the core layer and the die-cutting performance of the film.

[0018] Further, the saponified ethylene-vinyl acetate copolymer of the present application is preferably obtained by alcoholysis of unsaponified ethylene-vinyl acetate copolymer, the content of vinyl acetate monomer in the unsaponified ethylene-vinyl acetate copolymer is 15-18wt%, and the melt index of the unsaponified ethylene-vinyl acetate copolymer under a load of 2.16kg at 190℃ is 10-20g / 10min. The saponified ethylene-vinyl acetate copolymer prepared by the above method is beneficial to its melt matching with the homopolymerized polypropylene in the lower layer, and a suitable biaxially stretched sheet is obtained, which ensures the smoothness of the biaxial stretching process.

[0019] Further, the lower surface layer further comprises 0.1-0.2wt% (i.e. 1000-2000ppm) anti-blocking agent. By adding the anti-blocking agent in the lower surface layer, it is beneficial to the smoothness of the film production and application process.

[0020] Further, the melt index of the homopolypropylene in the core layer and the lower surface layer is 2.8-3.8g / 10min under the load of 230℃ and 2.16kg, and the melting point of the homopolypropylene in the core layer and the lower surface layer is 160-180℃. By selecting the homopolypropylene with appropriate melt index and melting point, it is beneficial to the heat resistance and mechanical properties of the whole film, and too low melt index will reduce the ductility of the material, making it difficult to effectively perform the stretching process, and increasing the risk of smoothness problems such as film breakage and poor stretching.

[0021] Further, the total thickness of the easy-to-cut BOPP pearlescent film is 30-70μm, wherein the thickness of the printable surface layer is 1-2μm, and the thickness of the lower surface layer is 1-1.5μm.

[0022] The application also provides a preparation method of the easy-to-cut BOPP pearlescent film as described above, comprising the following steps:

[0023] The raw materials of each layer are respectively added to the corresponding extruders to form homogenized melt, and the melt passes through the filter and is extruded through the die;

[0024] Then, according to the flat film method, the thick sheet is formed by chill casting, and the thick sheet is stretched in the longitudinal direction first and then in the transverse direction or is stretched in the longitudinal direction and the transverse direction simultaneously by the two-way stretching method to form a biaxially stretched film; or according to the tube film method, the melt is formed into a primary tube film after leaving the die, and the primary tube film is transversely blown and longitudinally stretched after being rapidly cooled to form a biaxially stretched film;

[0025] The film is cooled and then subjected to corona treatment, and then is wound to form a mother roll, and the mother roll is subjected to aging treatment and then is cut to form a finished product.

[0026] In the above process: the melt extrusion temperature of the printable surface layer and the lower surface layer is 200-260℃; the melt extrusion temperature of the core layer is 230-260℃; the temperature of the chill water and the chill roller is 20-40℃; the temperature of the longitudinal stretching zone is 100-130℃; the temperature of the transverse stretching zone is 140-180℃; the longitudinal stretching ratio is 4.5-5.5 times; and the transverse stretching ratio is 8-10 times.

[0027] The application also provides an application of the easy-to-cut BOPP pearlescent film as described above in a self-adhesive label.

[0028] Preferably, the adhesive label comprises a pattern layer, the above-mentioned easy-to-cut BOPP pearlescent film, a glue layer and a release backing layer arranged in sequence. The pattern layer is formed by ink printing on the printable surface layer of the easy-to-cut BOPP pearlescent film; the glue layer is formed by coating glue (commonly acrylate or hot melt glue) on the lower surface layer of the easy-to-cut BOPP pearlescent film. DETAILED DESCRIPTION

[0029] The application is further described below in conjunction with examples. These examples are only used to illustrate the application and not to limit the scope of the application. The experimental methods in the following example embodiments are not specified, which are generally in accordance with the conventional conditions in the art or in accordance with the conditions suggested by the manufacturers; the raw materials, reagents and the like used, if not specifically stated, are all raw materials and reagents that can be obtained by commercial means. Any non-essential changes and substitutions made by those skilled in the art on the basis of the application shall fall within the scope of the application.

[0030] In the following examples or comparative examples:

[0031] (1) In the printable surface layer:

[0032] Random copolymerized polypropylene: specifically ethylene-propylene copolymerized polypropylene, the melt index under a load of 2.16 kg at 230°C is 6 g / 10 min, and the melting point is 140°C.

[0033] Maleic anhydride grafted polypropylene: the grafting rate of maleic anhydride is 0.5%.

[0034] (2) In the core layer:

[0035] Homopolymerized polypropylene: the melt index under a load of 2.16 kg at 230°C is 3.5 g / 10 min.

[0036] Calcium carbonate masterbatch: including homopolymerized polypropylene and 65 wt% of calcium carbonate coated by a low molecular dispersant (stearic acid); the particle size D50 of the calcium carbonate in the calcium carbonate masterbatch is 1.5 μm; the melt index of the homopolymerized polypropylene in the calcium carbonate masterbatch under a load of 2.16 kg at 230°C is 6 g / 10 min.

[0037] (3) In the lower surface layer:

[0038] Homopolymerized polypropylene: the melt index under a load of 2.16 kg at 230°C is 3.5 g / 10 min.

[0039] Saponified ethylene-vinyl acetate copolymer: obtained by alcoholysis of unsaponified ethylene-vinyl acetate copolymer.

[0040] Unsaturated ethylene-vinyl acetate copolymer: melt index of 10 g / 10 min at 190 °C under a load of 2.16 kg, content of vinyl acetate monomer 15 wt%.

[0041] Anti-blocking agent: silica.

[0042] Example 1

[0043] The present example provides a die-cuttable BOPP pearlescent film, comprising a printable surface layer, a core layer and a lower surface layer arranged in sequence. The components and contents of each layer are shown in Table 1 and the following:

[0044] Printable surface layer: 98.5 wt% random copolymerized polypropylene and 1.5 wt% maleic anhydride grafted polypropylene;

[0045] Core layer: 65 wt% homopolymerized polypropylene, 30 wt% calcium carbonate masterbatch and 5 wt% ethylene-propylene-5-norbornene-2-methanol triblock copolymer (ethylene content of 15 mol%, 5-norbornene-2-methanol content of 20 mol%, glass transition temperature of 155 °C);

[0046] Lower surface layer: 87.8 wt% homopolymerized polypropylene, 12 wt% saponified ethylene-vinyl acetate copolymer (saponification degree of 30%) and 0.2 wt% anti-blocking agent.

[0047] The method for preparing the die-cuttable BOPP pearlescent film of the present example comprises the following steps:

[0048] The raw materials of each layer are respectively added to the corresponding extruder to form a homogeneous melt, which is then filtered and multi-layer co-extruded through a die. Then, according to the flat film method, the cast sheet is chilled into a thick sheet, which is then stretched in both longitudinal and transverse directions to form a biaxially stretched film. The film is cooled and then subjected to a corona treatment (corona power factor of 25 W·min / m), and then wound into a master roll. After aging treatment, the master roll is cut into finished products.

[0049] In the above process flow, the melt extrusion temperature of the printable surface layer and the lower surface layer is 230 °C; the melt extrusion temperature of the core layer is 250 °C; the chilling water and chilling roller temperature is 40 °C; the longitudinal stretching zone temperature is 120 °C; the transverse stretching zone temperature is 150 °C; the longitudinal stretching ratio is 4.5 times; and the transverse stretching ratio is 10 times.

[0050] The total thickness of the die-cuttable BOPP pearlescent film of the present example is 40 μm; wherein the thickness of the printable surface layer is 2 μm, and the thickness of the lower surface layer is 1 μm.

[0051] Example 2

[0052] The present example provides a die-cuttable BOPP pearlescent film, which comprises a printable skin layer, a core layer and a lower skin layer arranged in sequence. The components and contents of each layer are shown in Table 1 and the following content:

[0053] Printable skin layer: 98.5wt% random copolymerized polypropylene and 1.5wt% maleic anhydride grafted polypropylene;

[0054] Core layer: 62wt% homopolymerized polypropylene, 30wt% calcium carbonate masterbatch and 8wt% ethylene-propylene-5-norbornene-2-methanol triblock copolymer (ethylene content of 12mol%, 5-norbornene-2-methanol content of 15mol%, glass transition temperature of 150℃);

[0055] Lower skin layer: 85.8wt% homopolymerized polypropylene, 14wt% saponified ethylene-vinyl acetate copolymer (saponification degree of 25%) and 0.2wt% anti-blocking agent.

[0056] The preparation method of the die-cuttable BOPP pearlescent film of the present example is the same as that of Example 1.

[0057] The total thickness and the thickness of each layer of the die-cuttable BOPP pearlescent film of the present example are the same as those of Example 1.

[0058] Example 3

[0059] The present example provides a die-cuttable BOPP pearlescent film, which comprises a printable skin layer, a core layer and a lower skin layer arranged in sequence. The components and contents of each layer are shown in Table 1 and the following content:

[0060] Printable skin layer: 98.5wt% random copolymerized polypropylene and 1.5wt% maleic anhydride grafted polypropylene;

[0061] Core layer: 60wt% homopolymerized polypropylene, 30wt% calcium carbonate masterbatch and 10wt% ethylene-propylene-5-norbornene-2-methanol triblock copolymer (ethylene content of 8mol%, 5-norbornene-2-methanol content of 10mol%, glass transition temperature of 145℃);

[0062] Lower skin layer: 83.8wt% homopolymerized polypropylene, 16wt% saponified ethylene-vinyl acetate copolymer (saponification degree of 20%) and 0.2wt% anti-blocking agent.

[0063] The preparation method of the die-cuttable BOPP pearlescent film of the present example is the same as that of Example 1.

[0064] The total thickness and the thickness of each layer of the die-cuttable BOPP pearlescent film of the present example are the same as those of Example 1.

[0065] Comparative Example 1

[0066] The comparative example 1 provides a BOPP pearlescent film comprising a printable top layer, a core layer and a bottom layer arranged in sequence. The components and contents of each layer are shown in Table 1 and described as follows: the components and contents of each layer are substantially the same as those of the example 2, except that the core layer does not contain the ethylene-propylene-5-norbornene-2-methanol triblock copolymer, i.e.:

[0067] The core layer contains 70 wt% of homopolymer polypropylene and 30 wt% of calcium carbonate masterbatch.

[0068] The BOPP pearlescent film of the comparative example 1 is prepared in the same way as the example 1.

[0069] The total thickness and the thickness of each layer of the BOPP pearlescent film of the comparative example 1 are the same as those of the example 1.

[0070] Comparative example 2

[0071] The comparative example 2 provides a BOPP pearlescent film comprising a printable top layer, a core layer and a bottom layer arranged in sequence. The components and contents of each layer are shown in Table 1 and described as follows: the components and contents of each layer are substantially the same as those of the example 2, except that the amount of the ethylene-propylene-5-norbornene-2-methanol triblock copolymer in the core layer is too low, i.e.:

[0072] The core layer contains 68 wt% of homopolymer polypropylene, 30 wt% of calcium carbonate masterbatch and 2 wt% of the ethylene-propylene-5-norbornene-2-methanol triblock copolymer (ethylene content of 12 mol%, 5-norbornene-2-methanol content of 15 mol%, glass transition temperature of 150°C).

[0073] The BOPP pearlescent film of the comparative example 2 is prepared in the same way as the example 1.

[0074] The total thickness and the thickness of each layer of the BOPP pearlescent film of the comparative example 2 are the same as those of the example 1.

[0075] Comparative example 3

[0076] The comparative example 3 provides a BOPP pearlescent film comprising a printable top layer, a core layer and a bottom layer arranged in sequence. The components and contents of each layer are shown in Table 1 and described as follows: the components and contents of each layer are substantially the same as those of the example 2, except that the amount of the ethylene-propylene-5-norbornene-2-methanol triblock copolymer in the core layer is too high, i.e.:

[0077] The core layer contains 55 wt% of homopolymer polypropylene, 30 wt% of calcium carbonate masterbatch and 15 wt% of the ethylene-propylene-5-norbornene-2-methanol triblock copolymer (ethylene content of 12 mol%, 5-norbornene-2-methanol content of 15 mol%, glass transition temperature of 150°C).

[0078] The BOPP pearlescent film of the present comparative example was prepared in the same way as Example 1.

[0079] The total thickness and the thickness of each layer of the BOPP pearlescent film of the present comparative example were the same as Example 1.

[0080] Comparative Example 4

[0081] The present comparative example provided a BOPP pearlescent film, which included a printable surface layer, a core layer and a lower surface layer arranged in sequence. The components and contents of each layer were as shown in Table 1 and the following: substantially the same as those of Example 2, except that the content of 5-norbornene-2-methanol in the ethylene-propylene-5-norbornene-2-methanol triblock copolymer added in the core layer was too low, i.e.

[0082] The core layer: 62wt% homopolymer polypropylene, 30wt% calcium carbonate masterbatch and 8wt% ethylene-propylene-5-norbornene-2-methanol triblock copolymer (ethylene content 12mol%, 5-norbornene-2-methanol content 5mol%, glass transition temperature 130°C).

[0083] The BOPP pearlescent film of the present comparative example was prepared in the same way as Example 1.

[0084] The total thickness and the thickness of each layer of the BOPP pearlescent film of the present comparative example were the same as Example 1.

[0085] Comparative Example 5

[0086] The present comparative example provided a BOPP pearlescent film, which included a printable surface layer, a core layer and a lower surface layer arranged in sequence. The components and contents of each layer were as shown in Table 1 and the following: substantially the same as those of Example 2, except that the content of 5-norbornene-2-methanol in the ethylene-propylene-5-norbornene-2-methanol triblock copolymer added in the core layer was too high, i.e.

[0087] The core layer: 62wt% homopolymer polypropylene, 30wt% calcium carbonate masterbatch and 8wt% ethylene-propylene-5-norbornene-2-methanol triblock copolymer (ethylene content 12mol%, 5-norbornene-2-methanol content 25mol%, glass transition temperature 161°C).

[0088] The BOPP pearlescent film of the present comparative example was prepared in the same way as Example 1.

[0089] The total thickness and the thickness of each layer of the BOPP pearlescent film of the present comparative example were the same as Example 1.

[0090] Comparative Example 6

[0091] The comparative example 1 provides a BOPP pearlescent film comprising a printable skin layer, a core layer and a lower skin layer arranged in sequence. The components and contents of each layer are shown in Table 2 and described as follows: the components and contents of each layer are substantially the same as those of the example 1, except that the content of the ethylene- propylene-5-norbornene-2-methanol triblock copolymer added in the core layer is too low, i.e.:

[0092] The core layer: 62wt% homopolymer polypropylene, 30wt% calcium carbonate masterbatch and 8wt% ethylene-propylene-5-norbornene-2-methanol triblock copolymer (the content of ethylene is 5mol%, the content of 5-norbornene-2-methanol is 15mol%, and the glass transition temperature is 153°C).

[0093] The BOPP pearlescent film of the comparative example 1 is prepared by the same method as the example 1.

[0094] The total thickness and the thickness of each layer of the BOPP pearlescent film of the comparative example 1 are the same as those of the example 1.

[0095] Comparative example 7

[0096] The comparative example 2 provides a BOPP pearlescent film comprising a printable skin layer, a core layer and a lower skin layer arranged in sequence. The components and contents of each layer are shown in Table 2 and described as follows: the components and contents of each layer are substantially the same as those of the example 2, except that the content of the ethylene- propylene-5-norbornene-2-methanol triblock copolymer added in the core layer is too high, i.e.:

[0097] The core layer: 62wt% homopolymer polypropylene, 30wt% calcium carbonate masterbatch and 8wt% ethylene-propylene-5-norbornene-2-methanol triblock copolymer (the content of ethylene is 20mol%, the content of 5-norbornene-2-methanol is 15mol%, and the glass transition temperature is 146°C).

[0098] The BOPP pearlescent film of the comparative example 2 is prepared by the same method as the example 2.

[0099] The total thickness and the thickness of each layer of the BOPP pearlescent film of the comparative example 2 are the same as those of the example 2.

[0100] Comparative example 8

[0101] The comparative example 3 provides a BOPP pearlescent film comprising a printable skin layer, a core layer and a lower skin layer arranged in sequence. The components and contents of each layer are shown in Table 2 and described as follows: the components and contents of each layer are substantially the same as those of the example 2, except that no saponified ethylene-vinyl acetate copolymer is added in the lower skin layer, i.e.:

[0102] The lower skin layer: 99.8wt% homopolymer polypropylene and 0.2wt% anti-blocking agent.

[0103] The BOPP pearlescent film of the present comparative example was prepared by the same method as that of Example 1.

[0104] The total thickness and the thickness of each layer of the BOPP pearlescent film of the present comparative example were the same as those of Example 1.

[0105] Comparative Example 9

[0106] The present comparative example provided a BOPP pearlescent film comprising a printable surface layer, a core layer and a lower surface layer arranged in sequence. The components and contents of each layer were as shown in Table 2 and the following: substantially the same as those of Example 2, except that the addition amount of saponified ethylene-vinyl acetate copolymer in the lower surface layer was too low, i.e.

[0107] Lower surface layer: 94.8 wt% homopolypropylene, 5 wt% saponified ethylene-vinyl acetate copolymer (saponification degree 25%) and 0.2 wt% anti-blocking agent.

[0108] The BOPP pearlescent film of the present comparative example was prepared by the same method as that of Example 1.

[0109] The total thickness and the thickness of each layer of the BOPP pearlescent film of the present comparative example were the same as those of Example 1.

[0110] Comparative Example 10

[0111] The present comparative example provided a BOPP pearlescent film comprising a printable surface layer, a core layer and a lower surface layer arranged in sequence. The components and contents of each layer were as shown in Table 2 and the following: substantially the same as those of Example 2, except that the addition amount of saponified ethylene-vinyl acetate copolymer in the lower surface layer was too high, i.e.

[0112] Lower surface layer: 79.8 wt% homopolypropylene, 20 wt% saponified ethylene-vinyl acetate copolymer (saponification degree 25%) and 0.2 wt% anti-blocking agent.

[0113] The BOPP pearlescent film of the present comparative example was prepared by the same method as that of Example 1.

[0114] The total thickness and the thickness of each layer of the BOPP pearlescent film of the present comparative example were the same as those of Example 1.

[0115] Comparative Example 11

[0116] The present comparative example provided a BOPP pearlescent film comprising a printable surface layer, a core layer and a lower surface layer arranged in sequence. The components and contents of each layer were as shown in Table 2 and the following: substantially the same as those of Example 2, except that the saponification degree of saponified ethylene-vinyl acetate copolymer added in the lower surface layer was too low, i.e.

[0117] Lower surface layer: 85.8wt% homopolymer polypropylene, 14wt% saponified ethylene-vinyl acetate copolymer (saponification degree is 15%) and 0.2wt% anti-blocking agent.

[0118] The BOPP pearlescent film of the present comparative example was prepared by the same method as that of Example 1.

[0119] The total thickness and the thickness of each layer of the BOPP pearlescent film of the present comparative example were the same as those of Example 1.

[0120] Comparative Example 12

[0121] The present comparative example provided a BOPP pearlescent film, which comprised a printable surface layer, a core layer and a lower surface layer arranged in sequence. The components and contents of each layer were substantially the same as those of Example 2, except that the saponification degree of the saponified ethylene-vinyl acetate copolymer added in the lower surface layer was too high, i.e.

[0122] Lower surface layer: 85.8wt% homopolymer polypropylene, 14wt% saponified ethylene-vinyl acetate copolymer (saponification degree is 35%) and 0.2wt% anti-blocking agent.

[0123] The BOPP pearlescent film of the present comparative example was prepared by the same method as that of Example 1.

[0124] The total thickness and the thickness of each layer of the BOPP pearlescent film of the present comparative example were the same as those of Example 1.

[0125] Table 1 Film layer composition of Examples 1-3 and Comparative Examples 1-5

[0126]

[0127] Table 2 Film layer composition of Comparative Examples 6-12

[0128]

[0129] Performance evaluation

[0130] The easy-to-die-cut BOPP pearlescent films of Examples 1-3 and the BOPP pearlescent films of Comparative Examples 1-12 were respectively subjected to the following performance tests:

[0131] 1. Die-cutting performance: evaluated by quantitative and qualitative methods

[0132] (1) Quantitative: elongation at break (%), tested in accordance with GB / T 1040.3-2006, testing instrument: microcomputer-controlled electronic universal testing machine (produced by Metzler Industrial Systems (China) Co., Ltd., model: CMT6502), the elongation at break should be in a suitable range in general, so as to ensure that the die-cutting can be smoothly broken without the phenomenon of die-cutting not being broken.

[0133] (2) Qualitative: The upper surface of the BOPP pearlescent film of Examples 1-3 and Comparative Examples 1-12 was printed with ink to form a pattern layer, and the surface of the lower surface was coated with hot melt adhesive (unsaponified ethylene-vinyl acetate copolymer, VA content of 18wt%, melt index of 15g / 10min, coating thickness of 8μm) to form a release paper, then kept at 25℃ for 5min to form an adhesive label; then a half-cut-through method was used, i.e. only the face layer (pattern layer, BOPP pearlescent film) and adhesive of the adhesive label were penetrated, while the integrity of the release paper was maintained, after die cutting (the excess pattern layer, BOPP pearlescent film and adhesive layer) waste disposal was carried out, and the situation during waste disposal was recorded, mainly including: whether the die cutting was broken, the label was brought up by the waste edge and the adhesive was back-stuck, and the number of broken die cutting or waste edge in 100 times was calculated.

[0134] 2, Surface tension of printed surface layer: tested according to GB / T 14216-2008, mN / m.

[0135] 3, Film thickness was determined according to GB / T 6672-2001, unit: μm.

[0136] 4, Adhesion performance evaluation of lower surface and adhesive layer: the BOPP pearlescent film of Examples 1-3 and Comparative Examples 1-12 of the application was taken, and hot melt adhesive (unsaponified ethylene-vinyl acetate copolymer, VA content of 18wt%, melt index of 15g / 10min) was coated on the surface of the lower surface, with a coating thickness of 8μm, and then kept at 25℃ for 5min to form an adhesive layer (hot melt adhesive layer) on the surface of the lower surface of the BOPP pearlescent film, thus obtaining a sample; the sample was cut into a sample strip with a width of 15mm and a length of 15cm, and interlayer peeling test was carried out using 3M adhesive tape, and the peeling force required for peeling the lower surface and the adhesive layer was recorded, the greater the peeling force, the more firmly the lower surface and the adhesive layer were combined.

[0137] The test results are shown in Table 3

[0138] Table 3 Performance test results of the film of Examples 1-3 and Comparative Examples 1-12

[0139]

[0140] As can be seen from Table 3, the easy-to-cut BOPP pearlescent film of Examples 1-3 of the application has suitable brittleness and excellent die cutting performance, and the die cutting process is smooth when used to make adhesive labels, effectively improving the "label flying" phenomenon in the die cutting process.

[0141] The BOPP pearlescent film of Comparative Example 1, without the addition of ethylene-propylene-5-norbornene-2-methanol triblock copolymer in the core layer, cannot effectively improve the brittleness of the core layer and cannot effectively reduce the toughness of the core layer, resulting in higher transverse and longitudinal elongation at break of the BOPP pearlescent film of Comparative Example 1; in addition, it also cannot lock the low molecular dispersant in the calcium carbonate masterbatch, thereby failing to effectively reduce the migration of the low molecular dispersant, resulting in a decrease in the surface tension of the printable surface layer and the peel strength of the lower surface layer and the glue layer, thereby adversely affecting the printing performance of the printable surface layer and the gluing performance of the lower surface layer; and the BOPP pearlescent film of Comparative Example 1 is prone to die cutting failure or waste edge lifting when applied to adhesive labels.

[0142] The BOPP pearlescent film of Comparative Example 2, with an excessively low amount of ethylene-propylene-5-norbornene-2-methanol triblock copolymer added in the core layer, cannot significantly improve the brittleness of the core layer and reduce the toughness of the core layer, resulting in relatively high transverse and longitudinal elongation at break of the BOPP pearlescent film of Comparative Example 2; and also cannot effectively reduce the migration of the low molecular dispersant, resulting in a relatively low surface tension of the printable surface layer and a relatively low peel strength of the lower surface layer and the glue layer, thereby also adversely affecting the printing performance of the printable surface layer and the gluing performance of the lower surface layer; and the BOPP pearlescent film of Comparative Example 2 is also prone to die cutting failure or waste edge lifting when applied to adhesive labels.

[0143] The BOPP pearlescent film of Comparative Example 3, with an excessively high amount of ethylene-propylene-5-norbornene-2-methanol triblock copolymer added in the core layer, results in excessive brittleness of the core layer, making it difficult to stretch in two directions and poor in roll adhesion during film production.

[0144] The BOPP pearlescent film of Comparative Example 4, with an excessively low content of 5-norbornene-2-methanol in the ethylene-propylene-5-norbornene-2-methanol triblock copolymer added in the core layer, cannot effectively improve the brittleness of the core layer, thereby resulting in poor die cutting performance of the BOPP pearlescent film of Comparative Example 4 when applied to adhesive labels.

[0145] The BOPP pearlescent film of Comparative Example 5, with an excessively high content of 5-norbornene-2-methanol in the ethylene-propylene-5-norbornene-2-methanol triblock copolymer added in the core layer, makes it difficult to stretch in two directions and poor in roll adhesion during film production.

[0146] The BOPP pearlescent film of Comparative Example 6, with an excessively low content of ethylene in the ethylene-propylene-5-norbornene-2-methanol triblock copolymer added in the core layer, is poor in roll adhesion during film production.

[0147] The BOPP pearlescent film of Comparative Example 7 has too high content of ethylene in the ethylene-propylene-5-norbornene-2-methanol tri-block copolymer added in the core layer, which results in too high toughness of the BOPP pearlescent film of Comparative Example 7, and poor die-cutting performance of the BOPP pearlescent film of Comparative Example 7 when applied to the adhesive label.

[0148] The BOPP pearlescent film of Comparative Example 8 has no saponified ethylene-vinyl acetate copolymer added in the lower surface layer, which results in low peeling force between the lower surface layer and the glue layer (hot melt adhesive layer) formed by coating, i.e. poor adhesion between the lower surface layer and the glue; and the BOPP pearlescent film of Comparative Example 8 has the problem of glue sticking back when die-cutting after being applied to the adhesive label, resulting in poor die-cutting performance.

[0149] The BOPP pearlescent film of Comparative Example 9 has too low amount of saponified ethylene-vinyl acetate copolymer added in the lower surface layer, which results in relatively low peeling force between the lower surface layer and the glue layer (hot melt adhesive layer) formed by coating, i.e. relatively poor adhesion between the lower surface layer and the glue; and the BOPP pearlescent film of Comparative Example 9 has the problem of glue sticking back when die-cutting after being applied to the adhesive label, resulting in poor die-cutting performance.

[0150] The BOPP pearlescent film of Comparative Example 10 has too high amount of saponified ethylene-vinyl acetate copolymer added in the lower surface layer, which results in the problem of sticking to the roller during the film preparation process, which is not conducive to smooth production of the film.

[0151] The BOPP pearlescent film of Comparative Example 11 has too low saponification degree of the saponified ethylene-vinyl acetate copolymer added in the lower surface layer, which results in relatively low peeling force between the lower surface layer and the glue layer (hot melt adhesive layer) formed by coating, i.e. relatively poor adhesion between the lower surface layer and the glue; and the BOPP pearlescent film of Comparative Example 11 has the problem of glue sticking back when die-cutting after being applied to the adhesive label, resulting in poor die-cutting performance.

[0152] The BOPP pearlescent film of Comparative Example 12 has too high saponification degree of the saponified ethylene-vinyl acetate copolymer added in the lower surface layer, which results in the problem of sticking to the roller during the film preparation process, which is not conducive to smooth production of the film.

[0153] The above-described embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it should not be understood as limiting the scope of the patent. It should be noted that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, and the present application also intends to include these modifications and improvements.

Claims

1. A die-cuttable BOPP pearlescent film, characterized in that: The BOPP film comprises a printable surface layer, a core layer and a lower surface layer arranged in sequence; the core layer comprises homopolymer polypropylene, 28-38 wt% calcium carbonate masterbatch and 5-10 wt% ethylene-propylene-5-norbornene-2-methanol triblock copolymer, the content of ethylene in the ethylene-propylene-5-norbornene-2-methanol triblock copolymer is 8-15 mol%, the content of 5-norbornene-2-methanol is 10-20 mol%; the lower surface layer comprises homopolymer polypropylene and 12-16 wt% saponified ethylene-vinyl acetate copolymer, the saponification degree of the saponified ethylene-vinyl acetate copolymer is 20-30%.

2. The easy die cut BOPP pearlescent film according to claim 1, characterized in that: The printable surface layer comprises random copolymer polypropylene and 1-2 wt% maleic anhydride grafted polypropylene, the grafting rate of maleic anhydride in the maleic anhydride grafted polypropylene is 0.5-1%.

3. The easy die cut BOPP pearlescent film according to claim 2, characterized in that: The melt index of the random copolymer polypropylene under a load of 2.16 kg at 230 ℃ is 5-10 g / 10 min, and the melting point of the copolymer polypropylene is 120-150 ℃; the random copolymer polypropylene is selected from one or both of ethylene-propylene copolymer polypropylene and ethylene-propylene-butylene copolymer polypropylene.

4. The easy die cut BOPP pearlescent film according to claim 1, characterized in that: The glass transition temperature of the ethylene-propylene-5-norbornene-2-methanol triblock copolymer is 145-155 ℃.

5. The easy die cut BOPP pearlescent film according to claim 1, characterized in that: The calcium carbonate masterbatch comprises homopolymer polypropylene and 65-75 wt% low-molecular dispersant coated calcium carbonate.

6. The easy die cut BOPP pearlescent film according to claim 1, characterized in that: The saponified ethylene-vinyl acetate copolymer is obtained by alcoholysis of unsaponified ethylene-vinyl acetate copolymer, the content of vinyl acetate monomer in the unsaponified ethylene-vinyl acetate copolymer is 15-18 wt%, and the melt index of the unsaponified ethylene-vinyl acetate copolymer under a load of 2.16 kg at 190 ℃ is 10-20 g / 10 min.

7. The easy die cut BOPP pearlescent film according to claim 1, characterized in that: The lower surface layer further comprises 0.1-0.2 wt% anti-blocking agent.

8. The easy die cut BOPP pearlescent film according to claim 1, characterized in that: The total thickness of the easy die-cutting BOPP pearlescent film is 30-70 μm, wherein the thickness of the printable surface layer is 1-2 μm, and the thickness of the lower surface layer is 1-1.5 μm.

9. A process for the preparation of easy die cut BOPP pearlescent film as claimed in any one of claims 1 to 8, characterized in that: The method comprises the following steps: The raw materials of each layer are respectively added to the corresponding extruders to form homogenized melt, and the melt passes through the filter and then is multi-layer co-extruded through the die head; Then, according to the flat film method, the cast sheet is quenched into a thick sheet, and the thick sheet is stretched in the longitudinal direction first and then in the transverse direction or is stretched in the longitudinal direction and the transverse direction simultaneously to form a biaxially stretched film; or according to the tubular film method, the melt is formed into a primary tubular film after leaving the die, and the primary tubular film is transversely blown and longitudinally stretched after being quenched to form a biaxially stretched film; The film is cooled and then subjected to corona treatment, and then is wound into a master roll, which is aged and then cut into finished products.

10. Use of the easy die-cutting BOPP pearlescent film according to any one of claims 1-8 in adhesive label.

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