CN115534464A

CN115534464A - High-gloss and high-transparency BOPP film and preparation method and application thereof

Info

Publication number: CN115534464A
Application number: CN202211301969.3A
Authority: CN
Inventors: 胡卓荣; 徐文树; 何文俊; 邹晓明; 梁杰兴
Original assignee: Guangdong Decro Package Films Co ltd; GUANGDONG DECRO FILM NEW MATERIALS CO Ltd
Current assignee: Guangdong Decro Package Films Co ltd; GUANGDONG DECRO FILM NEW MATERIALS CO Ltd
Priority date: 2022-10-24
Filing date: 2022-10-24
Publication date: 2022-12-30

Abstract

The invention relates to a high-gloss high-transparency BOPP film and a preparation method and application thereof, wherein the film comprises an anti-adhesion layer, a supporting layer and a functional layer which are sequentially arranged, the anti-adhesion layer comprises isotactic polypropylene, the supporting layer comprises isotactic polypropylene, the functional layer comprises 99-100wt% of syndiotactic polypropylene, and the isotacticity of the syndiotactic polypropylene is 70-82%. The invention also provides a preparation method and application of the high-gloss high-transparency BOPP film. The high-gloss high-transparency BOPP film disclosed by the invention adopts syndiotactic polypropylene to replace propylene-alpha-olefin copolymer, avoids the compatibility problem of a propylene chain segment and an alpha-olefin copolymerization unit chain segment in the traditional propylene-alpha-olefin copolymer, improves the gloss and transparency of the BOPP film, and can control the crystallinity of the polypropylene by controlling the isotacticity of the syndiotactic polypropylene on the basis, so as to obtain a low melting point required by mould pressing, so that the film has the advantages of high gloss, high transparency and good mould pressing effect.

Description

High-gloss and high-transparency BOPP film and preparation method and application thereof

Technical Field

The invention relates to a polypropylene film, in particular to a high-gloss high-transparency BOPP film and a preparation method and application thereof.

Background

The laser film is a film with holographic images of rainbow dynamic and three-dimensional effects on the surface after mould pressing, and the commodity package can obtain specific laser effect on the surface of the package through compounding, hot stamping, transferring and other modes of the laser film. The laser packaging material not only has novel and beautiful appearance effect, but also has high-technology anti-counterfeiting function, and is called the forefront technical product in the world packaging printing industry. The application field of the laser material is very wide, and the laser material is rapidly popularized in the industries of food, medicine, daily chemical products, cigarette and wine, clothes, gift packaging, decorative materials and the like.

The traditional BOPP laser base film is generally formed by laminating a layer of propylene-alpha-olefin copolymer material on a surface layer of BOPP, the propylene-alpha-olefin copolymer material generally takes propylene as a main unit, and other alpha-olefin monomers are used for destroying the regularity of isotactic polypropylene, so that the crystallinity of the isotactic polypropylene is reduced, and the melting point of the propylene-alpha-olefin copolymer material is lower than that of the isotactic polypropylene. Generally, the alpha-olefin comonomer of the propylene-alpha-olefin copolymer is composed of one or more of ethylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, and the like.

However, in a propylene- α -olefin copolymer material, a propylene chain segment and an α -olefin copolymerization unit chain segment have a compatibility problem, which may have an adverse effect on the appearance performance of a film, particularly, the reduction in the glossiness and transparency of the film to a certain extent is reflected, and among the numerous performances of a laser film, the appearance performance such as the glossiness and transparency of the film is particularly important, so that the conventional BOPP laser base film inevitably conflicts with the laser application thereof.

Disclosure of Invention

Based on the above, the present invention provides a high gloss and high transparency BOPP film, wherein the film uses syndiotactic polypropylene instead of propylene- α -olefin copolymer, thereby avoiding the problem of poor compatibility between propylene segment and α -olefin copolymer unit segment in the conventional propylene- α -olefin copolymer, resulting in reduced appearance performance, improving the gloss and transparency of the BOPP film, and on the basis, the degree of crystallinity of the polypropylene can be controlled by controlling the isotacticity of the syndiotactic polypropylene, so as to obtain a low melting point required for molding, and the film has the advantages of high gloss, high transparency and good molding effect.

The utility model provides a high transparent BOPP film of high gloss, is including the anti-adhesion layer, supporting layer and the functional layer that set gradually, anti-adhesion layer includes isotactic polypropylene, the supporting layer includes isotactic polypropylene, the functional layer includes 99-100wt% syndiotactic polypropylene, syndiotactic polypropylene's isotacticity is 70-82%.

According to the high-gloss high-transparency BOPP film, syndiotactic polypropylene is adopted to replace propylene-alpha-olefin copolymer to serve as a functional layer for mould pressing, on one hand, the syndiotactic polypropylene is a homopolymer, the problem of poor compatibility of a propylene chain segment and an alpha-olefin copolymerization unit chain segment in the propylene-alpha-olefin copolymer is solved, the film can obtain high-gloss and high-transparency appearance performance, on the other hand, the syndiotactic polypropylene and the isotactic polypropylene are identical in molecular composition, so that the functional layer and the supporting layer have good compatibility, the appearance performance cannot be reduced due to the fact that refractive index differences of different materials are different, and the interlayer bonding force is improved; furthermore, the crystallinity of the polypropylene is controlled by limiting the isotacticity of the syndiotactic polypropylene, so that the low melting point required by mould pressing is obtained, the mould pressing function is not influenced, and the advantages of high gloss, high transparency and good mould pressing effect are achieved. Although the isotactic degree of the syndiotactic polypropylene is lower than 70%, the melting point of the syndiotactic polypropylene is lower, the functional layer is softer due to the lower melting point, the functional layer is in a state similar to rubber and is difficult to process, and the functional layer after mould pressing has low hardness, so that the appearance of a product is difficult to maintain completely, and the good mould pressing performance is not easy to obtain; on the contrary, if the isotacticity is higher than 82%, not only the gloss and transparency of the film are deteriorated and the appearance of the film is deteriorated, but also the melting point of the syndiotactic polypropylene is too high to transfer the molded appearance to the surface of the functional layer.

Further, the melt index of the syndiotactic polypropylene is 3-8g/10min, and the melting point of the syndiotactic polypropylene is 118-139 ℃. The isotactic polypropylene within the range of the melt index and the melting point is selected, so that the film is favorable for obtaining the appearance performance of high gloss and high transparency, and the die pressing performance and the die pressing effect of the film are ensured. The melt index is less than 3g/10min, so that the mould pressing is not facilitated, and the appearance is difficult to copy to the surface of the functional layer; the melt index is more than 8g/10min, which is not beneficial to maintaining the appearance and causes appearance distortion.

Further, the isotactic degree of the syndiotactic polypropylene is 75-80%. The preferred isotacticity provides the film with superior appearance and moldability.

Further, the melt index of the syndiotactic polypropylene is 5.5-6g/10min, and the melting point of the syndiotactic polypropylene is 127-135 ℃. The syndiotactic polypropylene with the melting index and the melting point range is selected, so that the film has more excellent appearance properties of high gloss and high transparency, and good moldability is obtained.

Further, the functional layer also comprises 0.05-1wt% of auxiliary release agent, and the auxiliary release agent comprises one or more of silicone, erucamide and oleamide. The addition proportion of the auxiliary release additive is less than 0.05wt%, so that the additive cannot be uniformly distributed on the surface of the film and cannot completely play a role; the addition proportion of the auxiliary release additive is more than 1wt%, a large amount of smoke is easily generated at high temperature, and the smoke forms oil drops after accumulation, and is easily dropped on the surface of the film to pollute the appearance of the product.

Further, the support layer comprises 99-100wt% of isotactic polypropylene and 0.1-1wt% of auxiliary release agent; the isotacticity of the isotactic polypropylene is 95-99%, the melt index of the isotactic polypropylene is 2.5-3.5g/10min, and the melting point of the isotactic polypropylene is 160-168 ℃; the auxiliary release agent comprises one or more of silicone, erucamide and oleamide. The adding proportion of the auxiliary release agent in the supporting layer is required to be larger than that of the auxiliary release agent in the functional layer, so that the auxiliary release agent in the supporting layer can be diffused to the surface layer through concentration difference. If the isotactic degree of the isotactic polypropylene is less than 95%, the degree of crystallization of the isotactic polypropylene is low, resulting in a decrease in the heat resistance of the isotactic polypropylene; conversely, if the isotacticity is higher than 99%, it will cause difficulty in film formation and easy film rupture during production.

Further, the anti-blocking layer comprises 99.7 to 99.8wt% of isotactic polypropylene and 0.2 to 0.3wt% of anti-blocking agent; the isotacticity of the isotactic polypropylene is 95-99%, the melt index of the isotactic polypropylene is 2.5-3.5g/10min, and the melting point of the isotactic polypropylene is 160-168 ℃; the anti-blocking agent comprises one or more of silicon dioxide, polymethyl methacrylate and polysiloxane resin, and the particle size of the anti-blocking agent is 4-5 mu m. If the isotactic degree of the isotactic polypropylene is less than 95%, the degree of crystallization of the isotactic polypropylene is low, resulting in a decrease in the heat resistance of the isotactic polypropylene; conversely, if the isotacticity is higher than 99%, the film forming difficulty is caused, and the film is easy to break in the production process; if the particle size of the anti-blocking agent is less than 4 μm, the anti-blocking effect is not significant, and if the particle size of the anti-blocking agent is more than 5 μm, the anti-blocking agent is easy to rub off in the manufacturing process, so that equipment pollution is caused.

Further, the functional layer has a thickness of 1.2 to 10 μm. The thickness of the functional layer can be adjusted according to the requirement when the purpose of mould pressing is different, for example, when the mould pressing three-dimensional shape is required.

The invention also provides a preparation method of any one of the high-gloss high-transparency BOPP films, which comprises the following steps: the method comprises the steps of premixing screened raw materials according to a designed formula, uniformly stirring, weighing and calculating the input proportion, respectively sending the raw materials into each layer of extruder to be processed into uniformly plasticized melt, conveying the melt through a pipeline, filtering the melt through a filter, then carrying out multilayer coextrusion through a die head, then casting the melt into a thick sheet through a casting chilling process, preparing the thick sheet into a bidirectional stretching film by a bidirectional stretching method which is synchronous longitudinally and then transversely or longitudinally and transversely, shaping the film, cooling, trimming two sides, drawing and measuring the thickness, winding the mother roll to obtain a film mother roll, and finally forming a film finished product after the film mother roll is subjected to aging slitting.

The invention also provides an application of the high-gloss and high-transparency BOPP film, which comprises the application of the high-gloss and high-transparency BOPP film as a laser transfer film, a laser composite film and a laser label film.

For a better understanding and practice, the invention is described in detail below with reference to the accompanying drawings.

Drawings

Fig. 1 is a schematic structural diagram of a high gloss and high transparency BOPP film described in example 1;

FIG. 2 is a schematic flow chart of a process for producing a high gloss and high transparency BOPP film according to example 1;

FIG. 3 is a schematic structural diagram of a high-gloss and high-transparency BOPP film used as a laser transfer film in example 1 after being adhered to a target surface layer;

FIG. 4 is a schematic structural diagram of a high-gloss high-transparency BOPP film used as a laser transfer film and a functional layer peeled off in example 1;

fig. 5 is a schematic structural diagram of the high-gloss and high-transparency BOPP film used in example 2 after being compounded on a target surface layer as a laser composite film;

fig. 6 is a schematic structural diagram of the high-gloss and high-transparency BOPP film of example 3 after being used as a transparent laser label film;

the anti-adhesion layer comprises an anti-adhesion layer 1, a supporting layer 2, a functional layer 3, laser lines 4, a metal layer 5, a glue layer 6 and a target surface layer 7.

Detailed Description

The high-gloss high-transparency BOPP film comprises an anti-adhesion layer, a supporting layer and a functional layer which are sequentially arranged, wherein the supporting layer 2 is mainly arranged for ensuring the mechanical property of the film, the functional layer 3 is mainly arranged for meeting the laser mould pressing requirement, and the anti-adhesion layer 1 is mainly arranged for preventing unwinding and adhesion.

In some embodiments, the isotactic degree of the syndiotactic polypropylene adopted in the functional layer 3 can be adjusted between 70% and 82%, the melt index of the syndiotactic polypropylene can be adjusted between 3g/10min and 8g/10min, and the melting point of the syndiotactic polypropylene can be adjusted between 120 ℃ and 145 ℃, although the low isotactic degree is beneficial to reducing the crystallization of the polypropylene and improving the gloss and haze performance, if the isotactic degree of the syndiotactic polypropylene is lower than 70%, the melting point is lower, the melting point can make the functional layer 3 softer, and the shape of the product is difficult to keep complete after the mold pressing; conversely, if the isotacticity is higher than 82%, not only will the gloss and transparency of the film be deteriorated and the appearance of the film be degraded, but also the melting point of the syndiotactic polypropylene will be higher, so that the molding morphology is difficult to transfer to the surface of the functional layer 3; in a preferred embodiment, the isotactic index of syndiotactic polypropylene can be adjusted between 75-80%, the melt index of syndiotactic polypropylene can be adjusted between 5.5-6g/10min, and the melting point of syndiotactic polypropylene can be adjusted between 125-135 deg.C, so that the film has better moldability and appearance.

In some embodiments, an auxiliary release agent can be added into the functional layer 3 according to the difference of the use scenes, for example, 0.05-1wt% of the auxiliary release agent (such as silicone, erucamide and oleamide) can be added for laser transfer film application to reduce the peeling force of the aluminum layer on the surface of the laser transfer film during transfer. The auxiliary release additive is added in a proportion of less than 0.05wt%, so that the additive cannot be uniformly distributed on the surface of the film and cannot completely play a role; the addition proportion of the auxiliary release additive is more than 1wt%, a large amount of smoke is easily generated at high temperature, and the smoke forms oil drops after accumulation, and is easily dropped on the surface of the film to pollute the appearance of the product.

In some embodiments, the isotactic polypropylene used for the support layer 2 or the anti-blocking layer 1 may be adjusted to have an isotactic degree of 95-99%, the melt index of the isotactic polypropylene may be adjusted to be 2.5-3.5g/10min, the melting point of the isotactic polypropylene may be adjusted to be 160-168 ℃, and if the isotactic degree of the isotactic polypropylene is less than 95%, the degree of crystallinity of the isotactic polypropylene is low, resulting in a decrease in the heat resistance of the isotactic polypropylene; conversely, if the isotacticity is higher than 99%, the film forming difficulty is caused, and the film is easy to break in the production process; in a preferred embodiment, the isotacticity of the isotactic polypropylene can be adjusted between 96% and 99%, the melt index of the isotactic polypropylene can be adjusted between 2.8 and 3g/10min, and the melting point of the isotactic polypropylene can be adjusted between 161 ℃ and 168 ℃, so that the film has better film-forming property, heat resistance and mechanical property.

In some embodiments, an auxiliary release agent may be added to the support layer 2 according to the difference of the usage scenarios, for example, 0.1 to 1wt% of the auxiliary release agent (such as silicone, erucamide, and oleamide) may be added for laser transfer film application, and it is required to ensure that the addition ratio of the auxiliary release agent in the support layer 2 is greater than that of the auxiliary release agent in the functional layer 3, so as to ensure that the auxiliary release agent in the support layer 2 can diffuse to the surface layer through the concentration difference. Because the laser transfer film has a large amount of heat in the aluminum evaporation coating process, the glue coating process and the curing process, the heat can make the auxiliary release agent in the supporting layer 2 migrate to the surface of the functional layer 3 through diffusion, supplement the auxiliary release agent in the functional layer 3 of the laser transfer film, and is beneficial to the repeated transfer and use of the laser transfer film. In some embodiments, the anti-blocking agent used in the anti-blocking layer 1 may also be one or more of silicon dioxide, polymethyl methacrylate and polysiloxane resin, the average particle size of the anti-blocking agent may be adjusted between 4 μm and 5 μm, if the particle size of the anti-blocking agent is smaller than 4 μm, the anti-blocking effect is not significant, and if the particle size of the anti-blocking agent is larger than 5 μm, the anti-blocking agent is easy to rub off in the process, resulting in equipment contamination.

The thickness of the functional layer 3 can be adjusted between 1.2 and 10 mu m according to the die pressing requirement, for example, when the die pressing three-dimensional shape (such as the shape of a cat eye) is required, the thickness of the functional layer 3 can be adjusted according to the requirement; in some embodiments, the thickness of the supporting layer 2 can be adjusted between 13 μm and 50 μm, and it should be noted that, if the thickness of the supporting layer 2 is less than 13 μm, it is difficult to ensure the mechanical properties of the film, and if the thickness of the supporting layer 2 is greater than 50 μm, the manufacturing cost of the film is too high; in some embodiments, the thickness of the anti-blocking layer 1 may be adjusted between 0.5 to 1.5 μm.

The preparation method of the high-gloss and high-transparency BOPP film is a step-by-step biaxial stretching flat film method, and as shown in figure 2, the specific process comprises the following steps: the method comprises the following steps of premixing screened raw materials A (including main raw materials and additive master batches) according to a designed formula, uniformly stirring, weighing, calculating and feeding the raw materials A into each extruder according to a calculated input proportion, plasticizing the raw materials into a melt B in an extrusion process F, conveying the melt through a pipeline, filtering the melt through a filter, distributing the melt to a die head through a flow channel for coextrusion, then carrying out chilling process G on the melt B through a chill roll to form a thick sheet C, and carrying out biaxial tension process H on the thick sheet C to form a film, wherein the biaxial tension process is a step-by-step biaxial tension process of longitudinal tension and transverse tension. And (3) shaping, cooling, trimming two sides of the film, drawing and measuring thickness, and rolling the mother roll I to obtain a film mother roll D, and performing aging slitting J on the film mother roll D to finally form a film finished product E.

Wherein, the production equipment is a flat film method step biaxial stretching polypropylene production line provided by Brukner (BRUECKNER) company in Germany, a screw of a main extruder (a support layer 2) is a single screw extruder with the diameter of 150mm and the length-diameter ratio of 33, and an auxiliary extruder (a functional layer 3) is a single screw extruder with the screw diameter of 120mm and the length-diameter ratio of 30. The temperature of the extruder is 250 ℃ except for the feeding section, the temperature of each section of the filter, the runner and the die head is 250 ℃, and the temperature of the quenching (tape casting) is 30 ℃; the corresponding temperatures of a preheating zone, a stretching zone and a shaping zone through which the longitudinal stretching support layer 2 passes are 140 ℃, 135 ℃ and 140 ℃, and the corresponding temperatures of the preheating zone, the stretching zone and the shaping zone through which the longitudinal stretching functional layer 3 passes are 110 ℃, 110 ℃ and 110 ℃, wherein the surface of a heating roller through which the longitudinal stretching functional layer 3 passes is treated by Teflon, and the stretching ratio is 4.8; the preheating zone, the stretching zone and the shaping zone which are passed by the transverse stretching are respectively 176 ℃, 157 ℃, 168 ℃ and 8.5 in the stretching ratio; the production speed was 330m/min.

According to the high-gloss high-transparency BOPP film, syndiotactic polypropylene is adopted to replace propylene-alpha-olefin copolymer, the problem of poor compatibility of a propylene chain segment and an alpha-olefin copolymerization unit chain segment in the propylene-alpha-olefin copolymer is solved, the film can obtain high-gloss and high-transparency appearance performance, and on the other hand, the syndiotactic polypropylene and the isotactic polypropylene are identical in molecular composition, so that the functional layer and the supporting layer have good compatibility, the appearance performance is not reduced due to the difference of refractive indexes of different materials, and the interlayer bonding force is improved; further, the crystallinity of the polypropylene is controlled by limiting the isotacticity of the syndiotactic polypropylene, so that the low melting point required by the mould pressing is obtained, and the film has the advantages of high gloss, high transparency and good mould pressing effect.

Example 1

The embodiment provides a high transparent BOPP film of high gloss, including anti-adhesion layer 1, supporting layer 2 and functional layer 3 that set gradually, anti-adhesion layer 1 with functional layer 3 sets up respectively in the both sides of supporting layer 2, and the concrete structure is as shown in figure 1.

Anti-blocking layer 1:99.8wt% isotactic polypropylene and 0.2wt% polymethyl methacrylate; wherein the isotactic polypropylene has an isotacticity of 98% and a melt index of 3g/10min (under the conditions of the melt index test, the melting temperature is 230 ℃ and the load weight is 2.16 Kg); the polymethyl methacrylate had an average particle diameter of 4 μm.

Support layer 2:99wt% isotactic polypropylene, 0.5wt% glyceryl monostearate and 0.5wt% erucamide; wherein the isotactic polypropylene has an isotacticity of 99% and a melt index of 3g/10min (melt index test conditions: melt temperature of 230 ℃ C., load weight of 2.16 Kg).

Functional layer 3:99wt% syndiotactic polypropylene and 1wt% polydimethylsiloxane; wherein the syndiotactic polypropylene has isotacticity of 80%, melting point of 135 deg.C, and melt index of 3g/10min (melt index test conditions: melting temperature of 230 deg.C, and load weight of 2.16 Kg); the molecular weight of the polydimethylsiloxane is 10 ten thousand.

The total thickness of the prepared product is 22 mu m, the thickness of the functional layer 3 is 2 mu m, the thickness of the supporting layer 2 is 19 mu m, and the thickness of the anti-adhesion layer 1 is 1 mu m;

the high transparent BOPP film of high gloss of this embodiment mainly is used as radium-shine transfer film, and its application process is: firstly, mould pressing is carried out on the surface of a functional layer 3 through unreeling, mould pressing and reeling processes to obtain laser lines 4, a high-gloss laser morphology template is obtained, then a metal layer 5 is obtained through unreeling, evaporation and reeling processes on the laser lines 4, the metal layer 5 can be an aluminum layer, then coating is carried out on the surface of the metal layer 5 through unreeling, gluing and reeling processes to obtain a glue layer 6, then the glue layer 6 is bonded with a target surface layer 7, the structure of the metal layer is shown in figure 3, the metal layer 5 and the functional layer 3 are separated in a stripping mode through a stripping process, and the metal layer 5 with the laser lines 4 is compounded on the target surface layer 7, and the structure of the metal layer is shown in figure 4. When the high-gloss and high-transparency BOPP film is applied, the film can be repeatedly used until the laser appearance distortion occurs, and in other embodiments, the film can be generally recycled for 3-10 times after the auxiliary release agent is added.

Example 2

This embodiment provides a high-gloss high-transparency BOPP film, and the structure, the preparation method, and the process conditions of the high-gloss high-transparency BOPP film described in this embodiment are the same as those in embodiment 1, and therefore are not described herein, and compared with embodiment 1, the difference between the film in this embodiment and the film in embodiment 1 is:

anti-blocking layer 1:99.7wt% isotactic polypropylene and 0.3wt% polymethyl methacrylate; wherein the isotactic polypropylene has an isotacticity of 96% and a melt index of 3g/10min (melt index test conditions: melt temperature of 230 ℃ C., load weight of 2.16 Kg).

Support layer 2:100wt% isotactic polypropylene; wherein the isotactic polypropylene has an isotacticity of 96% and a melt index of 2.8g/10min (melt index test conditions: melt temperature of 230 ℃ C., load weight of 2.16 Kg).

Functional layer 3:100wt% syndiotactic polypropylene; wherein the syndiotactic polypropylene has an isotacticity of 70%, a melting point of 118 ℃ and a melt index of 8g/10min (melt index test conditions: a melting temperature of 230 ℃ and a load weight of 2.16 Kg).

The total thickness of the prepared product is 18 μm, and the thickness of the support layer 2 is 15 μm.

The high-gloss and high-transparency BOPP film is mainly used as a laser composite film, and the application process is as follows: firstly, mould pressing is carried out on the surface of a functional layer 3 through unreeling, mould pressing and reeling processes to obtain laser grains 4 and obtain high-gloss laser shapes, then evaporation is carried out on the laser grains 4 through unreeling, evaporation and reeling processes to obtain a metal layer 5, the metal layer 5 can be an aluminum layer, then coating is carried out on the surface of the metal layer 5 through unreeling, gluing and reeling processes to obtain a glue layer 6, then the glue layer 6 is bonded with a target surface layer 7, and the laser composite film is compounded on the target surface layer 7, wherein the structure of the laser composite film is shown in figure 5.

Example 3

The present embodiment provides a high-gloss and high-transparency BOPP film, and the structure, the preparation method, and the process conditions of the high-gloss and high-transparency BOPP film described in the present embodiment are the same as those of embodiment 2, and therefore are not described herein, and the differences between the film of the present embodiment and the film of embodiment 2 are:

anti-blocking layer 1: the isotactic degree of isotactic polypropylene is 97%.

Support layer 2: the isotactic polypropylene had an isotacticity of 97% and a melt index of 3g/10min (melt index test conditions: melt temperature of 230 ℃ C., load weight of 2.16 Kg).

Functional layer 3: the syndiotactic polypropylene had an isotacticity of 82%, a melting point of 139 ℃ and a melt index of 6g/10min (melt index test conditions: melt temperature of 230 ℃ and weight of load of 2.16 Kg).

The total thickness of the prepared product is 48 mu m, and the thickness of the supporting layer 2 is 45 mu m.

The high-gloss and high-transparency BOPP film is mainly used as a transparent laser label film, and the application process is as follows: firstly, mould pressing is carried out on the surface of the functional layer 3 through the processes of unreeling, mould pressing and reeling to obtain laser grains 4 and obtain high-gloss laser shapes, then evaporation is carried out on the laser grains 4 through the processes of unreeling, evaporation and reeling to obtain a metal layer 5, wherein the metal layer 5 can be an aluminum layer, and the laser label film for the self-adhesive label is obtained, and the structure of the laser label film is shown in fig. 6.

Example 4

The present embodiment provides a high-gloss and high-transparency BOPP film, and the structure, the preparation method, and the process conditions of the high-gloss and high-transparency BOPP film described in the present embodiment are the same as those of embodiment 3, and therefore are not described in detail, and the difference between the film of the present embodiment and embodiment 3 is:

functional layer 3: the syndiotactic polypropylene had an isotacticity of 75%, a melting point of 127 ℃ and a melt index of 5.5g/10min (conditions for the melt index test: melt temperature of 230 ℃ and weight of load of 2.16 Kg).

The total thickness of the prepared product is 38 μm, and the thickness of the support layer 2 is 35 μm.

The high-gloss and high-transparency BOPP film of this embodiment is mainly used as a laser label film for a surrounding label, and the application process thereof is similar to that of embodiment 3, and therefore, the details are not described herein.

Comparative example 1

The structure, the components of the anti-adhesion layer 1, the components of the support layer 2, the preparation method and the process conditions of the BOPP film in the comparative example are the same as those of the example 1, so that the description is omitted, and the difference between the film of the comparative example and the film of the example 1 is as follows:

functional layer 3: 99% by weight of an ethylene-propylene-butene copolymer and 1% by weight of polydimethylsiloxane; wherein the propylene-ethylene-butene copolymer has a propylene content of 90wt%, an ethylene content of 3wt%, a butene content of 7wt%, and an isotacticity of 80%, and has a melting point of 134 ℃ and a melt index of 5.5g/10min (under the conditions of the melt index test: the melt temperature is 230 ℃ and the load weight is 2.16 Kg).

The BOPP film of the present comparative example is mainly used as a laser transfer film, and the application process is similar to that of example 1, and therefore, the description is omitted.

Comparative example 2

This comparative example provides a high transparent BOPP film of high gloss, and the structure, preparation method and the technological condition of a high transparent BOPP film of high gloss that this comparative example said are the same with example 1, do not need to be repeated for this reason, and the film of this comparative example compares with example 1, and the difference lies in:

anti-blocking layer 1:99.7wt% isotactic polypropylene and 0.3wt% polymethyl methacrylate; wherein the isotactic degree of the isotactic polypropylene is 96 percent.

Functional layer 3:100wt% syndiotactic polypropylene; wherein the syndiotactic polypropylene has an isotacticity of 90%, a melting point of 152 ℃ and a melt index of 5.5g/10min (conditions for the melt index test: melt temperature of 230 ℃ and weight of load of 2.16 Kg).

After the high-gloss and high-transparency BOPP film is subjected to die pressing at 135-137 ℃ and under 3MPa, the problems that the appearance of a laser template is difficult to transfer to the surface of the functional layer 3 and the laser appearance is unclear are found.

Comparative example 3

anti-blocking layer 1:99.7wt% isotactic polypropylene and 0.3wt% silica; wherein the isotacticity of the isotactic polypropylene is 97 percent; the average particle size of the silica was 4 μm.

Support layer 2:100wt% isotactic polypropylene; wherein the isotactic degree of the isotactic polypropylene is 97%.

Functional layer 3:100wt% syndiotactic polypropylene; wherein the syndiotactic polypropylene has an isotacticity of 65%, a melting point of 110 ℃ and a melt index of 7g/10min (melt index test conditions: melting temperature of 230 ℃ and weight of load of 2.16 Kg).

After the high-gloss and high-transparency BOPP film is subjected to die pressing at 135-137 ℃ and under the condition of 3MPa, the problem that the functions of the film are easy to scratch in the unreeling and reeling processes, so that the die pressing appearance is distorted is found.

The criteria according to which the product performance tests in the above examples were carried out are given in the following table:

physical Properties	Unit of	Test standard
			Thickness of	μm	GB/T6672
Haze (haze)	％	GB/T2410
			Degree of gloss	％	GB/T8807

The physical property indexes of the above examples and comparative examples are as follows through tests:

according to the appearance performance test results of the table, it can be seen from the comparative example and the comparative example 1 that the glossiness and haze index of the functional layer 3 adopting syndiotactic polypropylene are obviously superior to those of the conventional functional layer 3 adopting propylene-ethylene-butylene copolymer, on the premise that the high-gloss and high-transparency BOPP film can improve the appearance performance of a laser transfer film, a laser composite film and a laser label film, and the appearance effect of the product is further improved; it can be seen from the comparison of example 1, the comparison of example 2 and the comparison of example 3 that the excessive isotacticity of syndiotactic polypropylene can cause the glossiness of the functional layer 3 to drop, and cause the melting point of the functional layer 3 to be too high, the appearance of the laser template is difficult to transfer to the surface of the functional layer 3, and the too small isotacticity of syndiotactic polypropylene can cause the functional layer 3 of the film to be easily scratched in the unreeling and reeling processes, so that the problem of appearance distortion of the mould pressing can easily occur.

The invention adopts syndiotactic polypropylene to replace propylene-alpha-olefin copolymer to obtain a high-gloss high-transparency BOPP film, and the problem of poor compatibility of a propylene chain segment and an alpha-olefin copolymerization unit chain segment in the propylene-alpha-olefin copolymer does not exist, so that the film can obtain the appearance performance of high gloss and high transparency; the syndiotactic polypropylene and the isotactic polypropylene have the same molecular composition, so that the functional layer and the supporting layer have good compatibility, the appearance performance is not reduced due to the difference of refractive indexes of different materials, and the interlayer bonding force is ensured; further, the crystallinity of the polypropylene is controlled by limiting the isotacticity of the syndiotactic polypropylene, so that the low melting point required by the die pressing is obtained, and the advantages of high gloss, high transparency and good die pressing effect are achieved.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, to those skilled in the art, changes and modifications may be made without departing from the spirit of the present invention, and it is intended that the present invention encompass such changes and modifications.

Claims

1. The high-gloss high-transparency BOPP film is characterized by comprising an anti-adhesion layer, a supporting layer and a functional layer which are sequentially arranged, wherein the anti-adhesion layer comprises isotactic polypropylene, the supporting layer comprises isotactic polypropylene, the functional layer comprises 99-100wt% of syndiotactic polypropylene, and the isotacticity of the syndiotactic polypropylene is 70-82%.

2. The high gloss high transparent BOPP film according to claim 1, wherein the syndiotactic polypropylene has a melt index of 3-8g/10min and a melting point of 118-139 ℃.

3. A high gloss high transparent BOPP film according to claim 1, wherein the isotactic degree of the syndiotactic polypropylene is 75-80%.

4. The high gloss high transparent BOPP film according to claim 3, wherein the melt index of the syndiotactic polypropylene is 5.5-6g/10min, and the melting point of the syndiotactic polypropylene is 127-135 ℃.

5. The high gloss high transparent BOPP film according to claim 1, wherein the functional layer further comprises 0.05 to 1wt% of an auxiliary release agent, and the auxiliary release agent comprises one or more of silicone, erucamide and oleamide.

6. The high gloss and high transparency BOPP film according to claim 1, wherein the support layer comprises 99-100wt% isotactic polypropylene and 0.1-1wt% auxiliary release agent; the isotactic degree of the isotactic polypropylene is 95-99%, the melt index of the isotactic polypropylene is 2.5-3.5g/10min, and the melting point of the isotactic polypropylene is 160-168 ℃; the auxiliary release agent comprises one or more of silicone, erucamide and oleamide.

7. A high gloss high transparent BOPP film according to claim 1, wherein the anti-blocking layer comprises 99.7-99.8wt% isotactic polypropylene and 0.2-0.3wt% anti-blocking agent; the isotactic polypropylene has an isotacticity of 95-99%, a melt index of 2.5-3.5g/10min, and a melting point of 160-168 ℃; the anti-blocking agent comprises one or more of silicon dioxide, polymethyl methacrylate and polysiloxane resin, and the particle size of the anti-blocking agent is 4-5 mu m.

8. The high gloss high transparent BOPP film according to claim 1, wherein the thickness of the functional layer is 1.2-10 μm.

9. A method for preparing a high gloss high transparent BOPP film according to claims 1-8, comprising the steps of: the method comprises the steps of premixing screened raw materials according to a designed formula, uniformly stirring, weighing and calculating the input proportion, respectively sending the raw materials into each layer of extruder to be processed into uniformly plasticized melt, conveying the melt through a pipeline, filtering the melt through a filter, then carrying out multilayer coextrusion through a die head, then casting the melt into a thick sheet through a casting chilling process, preparing the thick sheet into a bidirectional stretching film by a bidirectional stretching method which is synchronous longitudinally and then transversely or longitudinally and transversely, shaping the film, cooling, trimming two sides, drawing and measuring the thickness, winding the mother roll to obtain a film mother roll, and finally forming a film finished product after the film mother roll is subjected to aging slitting.

10. Use of a high gloss high transparent BOPP film according to any one of claims 1 to 8 as a laser transfer film, a laser composite film and a laser label film.