CN117621586A

CN117621586A - BOPP film and preparation method and application thereof

Info

Publication number: CN117621586A
Application number: CN202410107855.8A
Authority: CN
Inventors: 徐文树; 王艳艳; 何文俊; 梁啟骞; 乔胜琦
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: 2024-01-26
Filing date: 2024-01-26
Publication date: 2024-03-01
Anticipated expiration: 2044-01-26
Also published as: CN117621586B

Abstract

The invention relates to the technical field of films, in particular to a BOPP film and a preparation method and application thereof, wherein the BOPP film comprises a thermal composite functional layer, a core layer and a printable surface layer, and the thermal composite functional layer comprises 95-98wt% of metallocene ethylene-propylene copolymer and 2-5wt% of maleic anhydride grafted ethylene-butene copolymer; the core layer comprises polypropylene, 40-60 wt% of nano calcium carbonate and 2-4 wt% of polyethylene glycol, and the density of the core layer is 0.60-0.70 g/cm ³ The method comprises the steps of carrying out a first treatment on the surface of the The surface tension of the printable surface layer is 38-44 dyne/cm, and the surface tension of the thermal composite functional layer is 28-30 dyne/cm. The BOPP film can be directly compounded with the propylene copolymer material or/and the polyethylene material with higher calcium carbonate content in a hot pressing way without high-pressure conditions and glue coating procedures, ensures the compounding fastness, can meet the biaxial stretching process conditions with a larger ratio on the premise that the core layer has higher content of nano calcium carbonate, has the advantages of environmental protection, excellent performance and capability of being directly printed on the surface, and can be used for compounding with stone paper honeycomb plates.

Description

BOPP film and preparation method and application thereof

Technical Field

The invention relates to the technical field of films, in particular to a BOPP film and a preparation method and application thereof.

Background

Corrugated board is a common raw material for paper packaging boxes, is formed by sequentially bonding films// printing ink-facial tissues// corrugated paper up and down, has the characteristics of light weight, flexibility, convenience in processing and transportation cost saving, but has the following problems: poor pressure resistance, is not suitable for bearing heavy objects and is easy to damage; poor waterproof and moistureproof performance, and is easy to deform in a humid environment, thereby influencing the packaging effect; poor protection and unsatisfactory protection effect on some fragile commodities. In addition, along with the increasing environmental protection concept of people, the increasing shortage of forest resources and the increasing shortage of water and soil resources, the harvesting of wood required for producing paper for cartons is increasingly limited in many countries.

The stone paper is a novel material integrating the characteristics and performances of paper and plastics, is prepared from limestone mineral resources (calcium carbonate) with large reserves and wide distribution as main raw materials (the content is 60-80 wt%) and high-molecular polymers as main auxiliary materials (the content is 20-30 wt%) by using the chemical principle of a high-molecular interface and the characteristic of high-molecular modification, and is prepared by adopting a polymer extrusion and blow molding process after being processed by a special process. The stone paper belongs to a green environment-friendly product, does not adopt plant fibers, does not cut trees, can save a large amount of wood, protects natural ecology, does not discharge waste water, waste residue and toxic and harmful gas, and has the characteristics of high mechanical strength, excellent waterproof and moistureproof performances, durability and the like in performance. Those skilled in the art will therefore consider using stone paper honeycomb made from stone paper to replace conventional corrugated board.

When the existing stone paper honeycomb plate is compounded with the film, a layer of glue is required to be coated to ensure the compounding fastness of the functional layer and the surface of the stone paper honeycomb plate, and after the glue is coated, drying is required, so that energy is not saved, and more toxic solvents are discharged and volatilized to pollute the environment.

Therefore, the film (including non-adhesive film, precoat film and the like) with the hot melt adhesive layer is considered to be adopted, and the thermal composite functional layer is used for compositing with the stone paper honeycomb board, so that the glue coating process is omitted. However, on one hand, because the main component of the stone paper is polypropylene with weak polarity, the main component has larger polarity difference with the existing thermal composite functional layer, and because the stone paper has higher content of calcium carbonate, the composite fastness of the existing thermal composite functional layer and the stone paper cannot be effectively ensured; on the other hand, since the conventional thermal composite functional layer is usually required under high temperature and high pressure conditions (the pressure at the time of compounding is usually 100 kg/cm) ² Above) and paper, and if it is directly used for compounding with a stone paper honeycomb plate, the honeycomb structure in the stone paper honeycomb plate is deformed by the high pressure during compoundingThereby affecting subsequent packaging applications.

The existing film with the hot melt adhesive layer is usually a transparent film, if the film is used as a packaging material for compounding with a stone paper honeycomb plate, in a compounding process, characters and patterns need to be printed on the back surface of the film, white background is then printed, glue is then coated, and finally the film is bonded with the honeycomb plate, so that the process is complicated and complex, and the improvement of the compounding efficiency is not facilitated. It is therefore desirable to provide a white BOPP film that can be surface printed and compounded with a relatively high calcium carbonate co-polypropylene material such as a stone paper honeycomb without the need for white bottoms and glue. It is common practice to add a proportion of stearic acid coated calcium carbonate to the core layer of the film, but a large amount of calcium carbonate cannot be added due to the limitations of the existing composition formula of the core layer of the film with the hot melt adhesive layer and the biaxial stretching production process.

Disclosure of Invention

Based on the above, the invention aims to provide a BOPP film, a preparation method and application thereof, wherein a thermal composite functional layer of the BOPP film can be directly and thermally pressed and compounded with a propylene copolymer material or/and a polyethylene material with higher content of calcium carbonate without high pressure, can ensure the compounding fastness, can dispense with the process of coating glue, and has the advantages of energy conservation and environmental protection; when the BOPP film is applied to the composite stone paper honeycomb plate, the deformation of the honeycomb plate can not be caused, and the subsequent packaging application can not be influenced; the BOPP film can meet the biaxial stretching process condition of a larger ratio on the premise that the core layer has higher content of nano calcium carbonate, so that the white BOPP film which can be directly printed on the surface without white background and glue is obtained, the production cost is further reduced, the BOPP film is particularly suitable for compounding with stone paper honeycomb plates, and the traditional corrugated board is replaced in a larger range; has the advantages of green environmental protection, excellent performance and capability of directly printing on the surface.

The technical scheme of the invention is realized by the following steps:

a BOPP film comprises a thermal composite functional layer, a core layer and a printable surface layer which are sequentially arranged, wherein the thermal composite functional layer comprises 95-98wt% of metallocene ethylene-propylene copolymerThe preparation method comprises the steps of (1) polymerizing a polymer and 2-5wt% of maleic anhydride grafted ethylene-butene copolymer, wherein the melt index of the metallocene ethylene-propylene copolymer is 8-15 g/10min, and the temperature of the metallocene ethylene-propylene copolymer when the crystallization melt conversion rate is 50% is 80-90 ℃; the core layer comprises polypropylene, 40-60 wt% of nano calcium carbonate and 2-4 wt% of polyethylene glycol, and the density of the core layer is 0.60-0.70 g/cm ³ The method comprises the steps of carrying out a first treatment on the surface of the The surface tension of the printable surface layer is 38-44 dynes/cm, and the surface tension of the thermal composite functional layer is 28-30 dynes/cm.

According to the BOPP film, from the particularity that the stone paper honeycomb plate mainly consists of 60-80% of calcium carbonate and 20-30% of high polymer, on one hand, through the component formula design of the thermal composite functional layer, the metallocene ethylene-propylene copolymer with a specific melt index range is added into the thermal composite functional layer, and the temperature range corresponding to the temperature range when the crystallization melt conversion rate is 50% is controlled, so that the thermal composite functional layer can complete hot-press compounding without high-pressure conditions by only utilizing the surface temperature of the immediately processed copolymer propylene material or/and the polyethylene material, the compounding fastness can be ensured, the glue coating process required by the conventional film during compounding is omitted, the heating process required by the conventional thermal composite functional layer during compounding is omitted, and the BOPP film is energy-saving and environment-friendly; on the other hand, by designing the component formula of the core layer, the biaxial stretching process condition with larger stretching ratio can be satisfied on the premise that the higher content of nano calcium carbonate is added into the core layer, thereby being beneficial to further reducing the production cost; the BOPP film is a white BOPP film, can be thermally compounded with a copolymer propylene material or/and a polyethylene material with higher calcium carbonate content without white background and glue, can be directly printed on the surface of the film, is particularly suitable for compounding with stone paper honeycomb plates, and is beneficial to realizing greener and environment-friendly stone paper honeycomb plates with better performance to replace the traditional corrugated paper plates in a larger range.

The metallocene ethylene-propylene copolymer is a semi-crystalline copolymer prepared by the catalysis of a metallocene catalyst, a fine crystalline phase rich in propylene chain segment sequences is dispersed in an amorphous copolymer matrix, different macromolecular chains form crystals through certain chain segments, so that connection points are formed, the crystallinity is 5-15%, the intermolecular and intramolecular composition distribution is very uniform, the metallocene ethylene-propylene copolymer has excellent elasticity and adhesion at normal temperature, the connection points are destroyed after the temperature exceeds the crystallization melting point, and the material is easy to process.

Through a great deal of researches and experiments, the inventor selects to add 95-98wt% of metallocene ethylene-propylene copolymer with the melt index of 8-15 g/10min and the crystallization melt conversion rate of 50% and the temperature of 80-90 ℃ into the thermal composite functional layer, so that the film can be ensured to be smoothly not stuck to rollers in the manufacturing process, and meanwhile, the composite fastness between the thermal composite functional layer of the film and the polypropylene material or/and the polyethylene material is ensured. If the melt index of the metallocene ethylene-propylene copolymer is less than 8g/10min, the melt extrusion stability and uniformity of the thermal composite functional layer are not guaranteed, a thick sheet suitable for biaxial stretching with a large ratio is not beneficial to be obtained, and the thermal composite functional layer can be fully softened and flowed under the compounding condition of the invention, so that the adhesion between the thermal composite functional layer and the polypropylene material or/and the polyethylene material is not guaranteed; if the melt index of the metallocene ethylene-propylene copolymer is more than 15g/10min, the thermal composite functional layer is easy to stick to the roller and cannot be smoothly produced; according to the invention, the temperature is 80-90 ℃ when the crystallization and melting conversion rate of the metallocene ethylene-propylene copolymer is 50%, so that the film can be ensured to be smooth and free from sticking to rollers in the manufacturing process, the thermal composite functional layer does not need high pressure conditions during thermal composite, the temperature of the surface of the immediately processed copolymer propylene material or/and polyethylene material can be effectively softened and compounded with the copolymer propylene material or/and polyethylene material, and the compounding fastness is ensured. If the temperature at which the crystallization melt conversion rate is 50% is less than 80 ℃, the film is likely to be stuck to a roll during the production process and is not smoothly produced, and if the temperature at which the crystallization melt conversion rate is 50% is more than 90 ℃, the thermal composite functional layer is not favorable to ensure that the thermal composite functional layer can be sufficiently softened and flowed under the composite condition of the present invention, so that the adhesion between the thermal composite functional layer and the co-polypropylene material or/and the polyethylene material is not favorable to be ensured. In order to further enhance the binding force between the thermal composite functional layer and the polypropylene material or/and the polyethylene material, and enhance the binding force between the thermal composite functional layer and the core layer, 2-5wt% of maleic anhydride grafted ethylene-butene copolymer is added into the thermal composite functional layer, the anhydride group in the maleic anhydride grafted ethylene-butene copolymer is beneficial to the interaction between the polypropylene material or/and the polyethylene material and nano calcium carbonate in the core layer, and the ethylene-butene copolymer can further enhance the interaction between the polypropylene material or/and the polyethylene material, and the interaction between the polypropylene material or/and the polyethylene material is synergistically enhanced, so that the composite fastness between the thermal composite functional layer and the polypropylene material or/and the polyethylene material is synergistically enhanced, and meanwhile, the thermal composite functional layer and the adjacent layer are not layered in the production process. If the addition amount of the maleic anhydride grafted ethylene-butene copolymer is more than 5wt%, the maleic anhydride grafted ethylene-butene copolymer is a substance with a low melting point, so that the phenomenon of sticking rollers in the film production process is easily caused, and if the addition amount of the maleic anhydride grafted ethylene-butene copolymer is less than 2wt%, the compound fastness between the thermal compound functional layer and the polypropylene material or/and the polyethylene material cannot be effectively further enhanced.

The invention controls the density of the core layer to be 0.60-0.70 g/cm by limiting the core layer to comprise polypropylene, 40-60 wt% of nano calcium carbonate and 2-4 wt% of polyethylene glycol ³ The content of the nano calcium carbonate which can be added into the core layer is higher when the biaxial stretching process condition with larger ratio is satisfied, the production cost is reduced, and if the overall density of the core layer is smaller than 0.60g/cm ³ Is unfavorable for the stability of production and is easy to break membrane, if the overall density of the core layer is more than 0.70g/cm ³ The insufficient content of nano calcium carbonate does not meet the relatively high concentration requirement of the stone paper, and the cost reduction is not obvious. The nano calcium carbonate surface of the invention has certain compatibility with polypropylene, good dispersion performance, and is favorable for uniformly dispersing the nano calcium carbonate in a core layer by selecting and adding 40-60wt% of nano calcium carbonate, and is favorable for adding higher content of nano calcium carbonate, if the adding amount of the nano calcium carbonate is less than 40wt%, the production cost is not favorable to be reduced, and if the adding amount of the nano calcium carbonate is more than 60wt%, the two-way pulling with larger ratio is not favorable to be realizedStability and smoothness of stretching process. In order to further improve the dispersibility of the nano calcium carbonate in the core layer, 2-4wt% of polyethylene glycol is added into the core layer, hydroxyl and ether bond in the polyethylene glycol are beneficial to enhancing the affinity of the polyethylene glycol with the weak-polarity nano calcium carbonate, and ethylene on the polyethylene glycol chain is beneficial to the compatibility of the polyethylene glycol with polypropylene in the core layer. If the polyethylene glycol addition is more than 4wt%, the processing fluidity of the core layer is not facilitated, and if the polyethylene glycol addition is less than 2wt%, the effect of further improving the compatibility and dispersibility of the nano calcium carbonate in the core layer is not obvious. The compatibility and the dispersibility of the nano calcium carbonate in the core layer are enhanced by selecting the content of the nano calcium carbonate and adding polyethylene glycol with specific content, and the density of the core layer can be controlled to be 0.60-0.70 g/cm ³ The process conditions of biaxial stretching with larger ratio can be met, the content of nano calcium carbonate added into the core layer is higher, and the production cost is reduced.

The surface tension of the printable surface layer is 38-44 dyne/cm, so that the adhesive force of the printing ink on the printable surface layer can be enhanced, and the prepared film has excellent printing applicability; the surface tension of the thermal composite functional layer is 28-30 dyne/cm, which is favorable for the smooth winding and unwinding of production and post-processing application.

Further, the melting point of the maleic anhydride grafted ethylene-butene copolymer is 65-75 ℃, and the grafting rate of the maleic anhydride grafted ethylene-butene copolymer is 1-2%. The maleic anhydride grafted ethylene-butene copolymer with the melting point of 65-75 ℃ is selected, so that the matching of the melting point of the maleic anhydride grafted ethylene-butene copolymer and the metallocene ethylene-propylene copolymer is ensured, the thermal composite functional layer can be effectively and fully softened during compounding, the compounding fastness between the thermal composite functional layer and a polypropylene material or/and a polyethylene material is enhanced, if the melting point of the maleic anhydride grafted ethylene-butene copolymer is less than 65 ℃, the roll sticking phenomenon is easily caused in the film production process, and if the melting point of the maleic anhydride grafted ethylene-butene copolymer is greater than 75 ℃, the thermal composite functional layer can be effectively and fully softened during compounding. The grafting rate of the maleic anhydride grafted ethylene-butene copolymer is 1-2%, if the grafting rate is less than 1%, the bonding force between the thermal composite functional layer and calcium carbonate in the honeycomb panel is not facilitated, the bonding force between the thermal composite functional layer and a weak-polarity propylene copolymer material or/and a polyethylene material is not facilitated, and the composite fastness between the thermal composite functional layer and the polypropylene copolymer material or/and the polyethylene material cannot be effectively further enhanced.

Further, the particle size D50 of the nano calcium carbonate is 0.75-0.85 mu m, and the viscosity average molecular weight of the polyethylene glycol is 5500-8000. According to the invention, the dispersibility of the nano calcium carbonate in the core layer is improved through the cooperation of the nano calcium carbonate and the core layer, so that the adding amount of the nano calcium carbonate can be increased, and the method is applicable to a larger-ratio biaxial stretching process. Preferably, the polyethylene glycol has a viscosity average molecular weight of 6000. Based on the dispersibility advantage of the nano calcium carbonate, preferably, the particle size D50 of the nano calcium carbonate is 0.80 mu m, the effective concentration is 70wt%, and the model is PF803NC005 (manufacturer: guangzhou Jinfa science and technology Co., ltd.).

Further, the polypropylene is homo-polypropylene; the BOPP film further comprises a compatibilizer layer, wherein the compatibilizer layer is positioned between the thermal composite functional layer and the core layer, the compatibilizer layer comprises 50-100 wt% of copolymerized propylene, and the copolymerized propylene is ethylene propylene butylene copolymer and/or ethylene propylene copolymer. When the polypropylene in the core layer is homo-polypropylene, a compatibilizer layer can be arranged between the core layer and the thermal composite functional layer, and the compatibilizer layer contains more than or equal to 50wt% of propylene copolymer, so that the bonding force between the core layer and the thermal composite functional layer is ensured, and the thermal composite functional layer and the adjacent layer are not layered in the production and processing process.

As another embodiment, the core layer comprises 30-50wt% of homo-polypropylene and 6-10wt% of propylene copolymer, wherein the propylene copolymer is ethylene propylene butylene copolymer and/or ethylene propylene copolymer. The core layer contains 6-10wt% of copolymerized propylene, at the moment, the binding force between the core layer and the thermal composite functional layer can be ensured without arranging a compatibilizer layer, and the thermal composite functional layer and the adjacent layer are not layered in the production and processing process.

Further, the printable surface layer is a matting layer and comprises (by weight) propylene copolymer, high-density polyethylene, 1% of maleic anhydride grafted ethylene-butene copolymer and 2% of nano calcium carbonate, wherein the weight ratio of the propylene copolymer to the high-density polyethylene is (42-52) (55-45). The printable surface layer is provided with a extinction layer, which is beneficial to the smoothness of winding and unwinding of the film in manufacturing, slitting and post-processing applications. And 1 weight percent of maleic anhydride grafted ethylene-butene copolymer and 2 weight percent of nano calcium carbonate are added, so that the bonding force between the printable surface layer and the printing ink is ensured, the printing applicability is improved, and the printing effect is ensured.

Further, the grain diameter D50 of the nano calcium carbonate in the printable surface layer is 0.75-0.85 mu m, the propylene copolymer is ethylene propylene butylene copolymer and/or ethylene propylene copolymer, and the melt index of the propylene copolymer is 7-10 g/10min; the melt index of the high-density polyethylene is 0.03-0.05 g/10min. The adoption of the nano calcium carbonate with the particle size range is beneficial to the dispersibility of the nano calcium carbonate in the printable surface layer. The melt indexes of the propylene copolymer and the high-density polyethylene are in the range, so that the overall haze of the BOPP film extinction layer is more ideal.

The invention also provides a preparation method of the BOPP film, which comprises the following steps: the method comprises the steps of feeding the raw materials of all layers into a batching unit, metering, feeding the raw materials into an extruder, feeding the raw materials into a runner distributor after melting plasticization and homogenization metering, extruding the raw materials through a T-shaped die head, casting the raw materials into thick sheets through a chill roll, longitudinally stretching the thick sheets by 4.5-4.8 times, transversely stretching the thick sheets by 5-7.5 times to form films, air shower cooling the films, thickness measurement control of an edge trimmer, corona treatment of the films, rolling the films into film parent rolls, aging treatment, slitting and packaging the film parent rolls to obtain finished products. The BOPP film containing 40-60wt% of nano calcium carbonate in the core layer can be smoothly produced by controlling longitudinal stretching to 4.5-4.8 times and transverse stretching to 5-7.5 times, and the preparation method is simple. If the surface stretch ratio formed by "longitudinal stretching×transverse stretching" is too high, the smoothness of production is impaired, and if the surface stretch ratio is too low, the flatness and coverage of the film are impaired. BOPP film that the preparation obtained, total thickness is 20~50 mu m, and thermal composite functional layer is 1-5 mu m, and printable top layer is 1~2 mu m, and the compatibilization layer is 1~2 mu m.

The invention also provides an application of the BOPP film, which is used for preparing a thermal composite substrate, and the thermal composite functional layer of the BOPP film is compounded with a co-polypropylene material or/and a polyethylene material. The usual method of thermal compounding is: firstly, directly performing temperature-resistant ink printing on a printable surface layer of a BOPP film, wherein the last step is temperature-resistant protective gloss oil, and then, directly performing hot-pressing and compounding on the film and a copolymerized propylene material or/and a polyethylene material with the surface reaching a certain temperature by mild hot pressing, wherein the thermal compounding process conditions are as follows: the temperature is more than or equal to 130 ℃, the sealing time is more than or equal to 2s, and the hot pressing pressure is 5-10 kg/cm ² 。

Further, the propylene copolymer material or/and the polyethylene material comprises 60-80 wt% of calcium carbonate and 20-30 wt% of propylene copolymer or/and polyethylene. The BOPP film prepared by the invention is particularly suitable for thermal compounding of a propylene copolymer material or/and a polyethylene material with higher calcium carbonate content, such as a stone paper honeycomb board, whereas a common BOPP film cannot be suitable for thermal compounding of a propylene copolymer material or/and a polyethylene material with higher calcium carbonate content.

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

Drawings

FIG. 1 is a schematic view of a BOPP film according to an embodiment of the present invention;

FIG. 2 is a schematic view of a BOPP film according to another embodiment of the present invention;

FIG. 3 is a schematic diagram of a BOPP film and a stone paper honeycomb board according to an embodiment of the present invention after thermal lamination;

FIG. 4 is a schematic view of a BOPP film and a stone paper honeycomb board according to another embodiment of the present invention after thermal lamination;

wherein, the thermal composite functional layer 1 can print the surface layer 2, the core layer 3, the compatibilizing layer 4, the stone paper honeycomb board 5 and the ink layer 6.

Detailed Description

It should be understood that the described embodiments are merely some, but not all, of the embodiments of the present application. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the embodiments of the present application, are within the scope of the embodiments of the present application.

The terminology used in the embodiments of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the embodiments of the application. As used in this application and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and encompasses any or all possible combinations of one or more of the associated listed items.

Furthermore, in the description of the present application, unless otherwise indicated, "a plurality" means two or more. "and/or", describes an association relationship of an association object, and indicates that there may be three relationships, for example, a and/or B, and may indicate: a exists alone, A and B exist together, and B exists alone. The character "/" generally indicates that the context-dependent object is an "or" relationship.

It is to be understood that the embodiments of the present application are not limited to the precise arrangements and instrumentalities shown in the drawings, which have been described above, and that various modifications and changes may be made without departing from the scope thereof. The scope of embodiments of the present application is limited only by the appended claims.

Referring to fig. 1, as an embodiment of the present invention, the BOPP film of the present embodiment includes a thermal composite functional layer 1, a printable surface layer 2, and a core layer 3, wherein the thermal composite functional layer 1, the core layer 3, and the printable surface layer 2 are sequentially disposed. The thermal composite functional layer 1 comprises 95-98wt% of metallocene ethylene-propylene copolymer and 2-5wt% of maleic anhydride grafted ethylene-butene copolymer, wherein the melt index of the metallocene ethylene-propylene copolymer is 8-15 g/10min, and the temperature is 80-90 ℃ when the crystallization melt conversion rate of the metallocene ethylene-propylene copolymer is 50%; the core layer 3 comprises polypropylene, 40-60wt% of nano calcium carbonate and 2-4wt% of polyethylene glycol, and the density of the core layer 3 is 0.60-0.70 g/cm ³ The method comprises the steps of carrying out a first treatment on the surface of the The surface tension of the film printable surface layer 2 is 38-44 dyne/cm, and the surface tension of the thermal composite functional layer 1 is 28-30 dyne/cm.

Further, the melting point of the maleic anhydride grafted ethylene-butene copolymer is 65-75 ℃, and the grafting rate is 1-2%.

Further, the particle size D50 of the nano calcium carbonate is 0.75-0.85 mu m, and the viscosity average molecular weight of the polyethylene glycol is 5500-8000. Preferably, the polyethylene glycol has a viscosity average molecular weight of 6000. Based on the dispersibility advantage of the nano calcium carbonate, preferably, the particle size D50 of the nano calcium carbonate is 0.80 mu m, the effective concentration is 70wt%, and the model is PF803NC005 (manufacturer: guangzhou Jinfa science and technology Co., ltd.).

Further, the core layer 3 comprises 30-50wt% of homo-polypropylene and 6-10wt% of propylene copolymer, wherein the propylene copolymer is ethylene propylene butylene copolymer and/or ethylene propylene copolymer.

Referring to fig. 2, as an embodiment of the present invention, the BOPP film of this embodiment includes a thermal composite functional layer 1, a printable surface layer 2, a core layer 3, and a compatibilizer layer 4, where the thermal composite functional layer 1, the compatibilizer layer 4, the core layer 3, and the printable surface layer 2 are sequentially disposed. The compatibilizing layer 4 comprises 50-100 wt% of propylene copolymer, wherein the propylene copolymer is ethylene propylene butylene copolymer and/or ethylene propylene copolymer.

Further, the printable surface layer 2 is a matting layer and comprises (by weight) propylene copolymer, high-density polyethylene, 1% of maleic anhydride grafted ethylene-butene copolymer and 2% of nano calcium carbonate, wherein the weight ratio of the propylene copolymer to the high-density polyethylene is (42-52) (55-45).

Further, the particle size D50 of the nano calcium carbonate in the printable surface layer is 0.75-0.85 mu m; the propylene copolymer is an ethylene propylene butylene copolymer and/or an ethylene propylene copolymer, and the melt index of the propylene copolymer is 7-10 g/10min; the melt index of the high-density polyethylene is 0.03-0.05 g/10min.

The invention also provides a preparation method of the BOPP film, which comprises the following steps: the method comprises the steps of feeding all layer component raw materials into a batching unit, metering the raw materials, feeding the raw materials into an extruder, controlling the extrusion temperature corresponding to a core layer 3, a compatibilizing layer 4 and a printable surface layer 2 to be 240-260 ℃, controlling the extrusion temperature corresponding to a thermal composite functional layer 1 to be 210-240 ℃, converging the raw materials at a multi-layer die head after passing through a flow channel distributor to form a resin melt with a multi-layer structure, and cooling the resin melt by a chilled roll with the temperature of 25-35 ℃ to form a resin sheet with the multi-layer structure; introducing the resin sheet into a longitudinal stretching device in a biaxial stretching device, preheating the surface of the printable surface layer 2 at 130-135 ℃, controlling the stretching temperature of the core layer 3, the compatibilizer layer 4 and the printable surface layer 2 at 110-130 ℃, preheating the thermal composite functional layer 1 at 80-100 ℃, controlling the stretching temperature at 60-80 ℃ and the stretching ratio at 4.5-4.8 times; and then introducing a transverse stretching device, preheating at 165-175 ℃, stretching at 156-160 ℃ for 5-7.5 times, shaping at 165-170 ℃, air-spraying and cooling, carrying out corona or flame treatment on the surface of the printable surface layer 2, carrying out no corona treatment on the thermal composite functional layer 1, obtaining a film parent roll, and finally carrying out aging treatment, slitting and packaging to obtain the BOPP film.

The invention also provides an application of the BOPP film to preparing a thermal composite substrate, wherein the thermal composite functional layer is compounded with a polypropylene material or/and a polyethylene material, and the polypropylene material or/and the polyethylene material comprises a stone paper honeycomb plate 5. The usual method of thermal compounding is: firstly, directly performing temperature-resistant ink printing on a printable surface layer of a BOPP film, wherein the last step is temperature-resistant protective gloss oil to form an ink layer 6, and then, performing light hot pressing to directly perform hot pressing and compounding on the film and a copolymer propylene material or/and a polyethylene material with the surface reaching a certain temperature, wherein the thermal compounding process conditions are as follows: the temperature is more than or equal to 130 ℃, the sealing time is more than or equal to 2s, and the hot pressing pressure is 5-10 kg/cm ² . Preferably, the propylene copolymer comprises ethylene propylene butylene copolymer and/or ethylene propylene copolymer, the melt index of the propylene copolymer is 1-10 g/10min (230 ℃,2.16 kg), the melting point of the propylene copolymer is 130-142 ℃, the melt index of the polyethylene is 1-10 g/10min (190 ℃,2.16 kg), and the melting point of the polyethylene is 120-130 ℃. The BOPP film prepared by the invention can be suitable for the copolymerization propylene material prepared from the copolymerization propylene or/and the polyethylene with the melt index and the melting point range or/and the copolymerization propylene material prepared from the polyethylene material. Referring to fig. 3 and 4 for specific structure, fig. 3 is a block diagram of BOPP film and co-polypropylene material or/and polyethylene material according to the present invention corresponding to fig. 1 FIG. 4 is a schematic diagram of the structure of the BOPP film and the polypropylene material or/and the polyethylene material according to FIG. 2.

It should be noted that the certain temperature in the propylene copolymer material or/and the polyethylene material reaching a certain temperature in the present invention generally refers to a temperature reached by the propylene copolymer material or/and the polyethylene material during the molding process, and does not refer to a temperature reached by the propylene copolymer material or/and the polyethylene material after being additionally heated in order to enable the propylene copolymer material or/and the polyethylene material to be compounded with the thermal composite functional layer.

Further, the propylene copolymer material or/and the polyethylene material comprises 60-80wt% of calcium carbonate and 20-30wt% of propylene copolymer or/and polyethylene. The BOPP film prepared by the invention is particularly suitable for thermal compounding of a propylene copolymer material or/and a polyethylene material with higher calcium carbonate content, such as a stone paper honeycomb board, whereas a common BOPP film cannot be suitable for thermal compounding of a propylene copolymer material or/and a polyethylene material with higher calcium carbonate content.

The physical property indexes of the embodiment or the comparative example and the testing method thereof are specifically as follows:

Film thickness was determined according to GB/T6672-2001;

melt index (melt mass flow rate MFR) according to GB/T3682-2018, polypropylene according to 2.16kg at 230℃and high density polyethylene according to 2.16kg at 190℃in g/10min;

melting point is measured according to GB/T16582-2008 in degrees Celsius;

temperature at which the crystallization melt conversion was 50%: DSC measurement is adopted, and the unit is DEG C;

the light transmittance is measured according to GB/T2410-2008, and the unit is;

the surface tension is determined according to GB/T14216 in dynes/cm.

The method for testing the composite effect of the film and the polypropylene material or/and the polyethylene material comprises the following steps: compounding (thermal compounding) of a propylene copolymer material and/or a polyethylene material with a BOPP film (printed pattern) prepared in the examples or comparative examples of the present inventionThe technological conditions are as follows: the temperature is 130 ℃, the sealing time is 2s, and the hot pressing pressure is 8kg/cm ² ) A thermal composite template of 100mm by 100mm size was cut out to obtain test samples. Cooling for 3 minutes in a test standard environment, pulling at a speed of 5-10 mm/s under a force of 2.5N/15mm, and finally visually observing the stripping degree of the film and the copolymer material or/and the polyethylene material. The complete sealing of the thermal lamination contact interface based on the film thermal lamination functional layer-co-propylene material or/and polyethylene material often corresponds to the interfacial separation between the film bulk core layer-thermal lamination functional layer and the compatibilizer layer during the peel test.

The film body is separated by 100%, the composite effect is rated as qualified, the film body is separated by less than 100%, and the composite effect is rated as unqualified.

The percentages expressed in the following examples or comparative examples are by weight, and the composition and content of each layer in the examples and comparative examples of the present invention are shown in Table 1 below.

TABLE 1

Wherein the temperature at which the crystalline melt conversion of the metallocene ethylene-propylene copolymer of comparative example 3 was 50% was too low and the melt index was too high; the metallocene ethylene-propylene copolymer of comparative example 4 had a melt index too low at a temperature too high for a crystalline melt conversion of 50%.

Example 1

The embodiment provides a BOPP film, which includes a thermal composite functional layer 1, a core layer 3 and a printable surface layer 2, and the specific structure can be referred to fig. 1. The preparation method of the BOPP film resin of each layer of the embodiment comprises the following steps:

preparing a thermal composite functional layer resin: uniformly mixing 95wt% of metallocene ethylene-propylene copolymer (the melt index is 8g/10min, the temperature at which the crystallization melt conversion rate of the metallocene ethylene-propylene copolymer is 50% is 90 ℃) and 5wt% of maleic anhydride grafted ethylene-butene copolymer (the melting point is 65 ℃, and the grafting rate is 1%) to obtain the thermal composite functional layer resin.

Preparing core layer resin: uniformly mixing 30wt% of homopolypropylene (with a melt index of 3.8g/10 min), 6wt% of ethylene propylene butene copolymer (with a melt index of 8g/10 min), 60wt% of nano calcium carbonate (with a D50 of 0.80 mu m) and 4wt% of polyethylene glycol (with a viscosity average molecular weight of 6000) to obtain the core layer resin.

Preparation of printable surface layer resin: 42wt% of ethylene propylene butene copolymer (with a melt index of 8g/10 min), 55wt% of high-density polyethylene (with a melt index of 0.05g/10 min), 1wt% of maleic anhydride grafted ethylene-butene copolymer (with a melting point of 65 ℃ C. And a grafting rate of 1%) and 2wt% of nano calcium carbonate (with a D50 of 0.80 mu m) are taken and uniformly mixed to obtain the printable surface layer resin.

The preparation method of the BOPP film of the embodiment comprises the following steps:

the method comprises the steps of feeding raw materials of all layers into a batching unit, metering the raw materials into an extruder, controlling the extrusion temperature corresponding to a core layer 3 and a printable surface layer 2 to be 240-260 ℃, controlling the extrusion temperature corresponding to a thermal composite functional layer 1 to be 210-240 ℃, converging the raw materials at a multi-layer die head after passing through a flow channel distributor to form a resin melt with a multi-layer structure, and cooling the resin melt by a chilled roll with the temperature of 25-35 ℃ to form a resin sheet with the multi-layer structure; introducing the resin sheet into a longitudinal stretching device in a biaxial stretching device, preheating the surface of the printable surface layer 2 at 130-135 ℃, controlling the stretching temperature of the core layer 3 and the printable surface layer 2 at 110-130 ℃, preheating the thermal composite functional layer 1 at 80-100 ℃, controlling the stretching temperature at 60-80 ℃ and the stretching ratio at 4.5-4.8 times; then introducing a transverse stretching device, preheating at 165-175 ℃, stretching at 156-160 ℃ for 5-7.5 times, shaping at 165-170 ℃, cooling by air shower, and carrying out corona treatment on the surface of the printable surface layer 2 (the energy density of the corona treatment is 1.8 KJ/m) ² ) And (3) the thermal composite functional layer 1 is not subjected to corona treatment, a film parent roll is obtained, and finally the BOPP film is obtained through ageing treatment, slitting and packaging.

The surface tension of the thin-film printable surface layer 2 is 38 dynes/cm, the surface tension of the thermal composite functional layer 1 is 28 dynes/cm, the total thickness of the thin film is 20 mu m, the thickness of the thermal composite functional layer 1 is 1 mu m, the thickness of the core layer 3 is 18 mu m, and the thickness of the printable surface layer 2 is 1 mu m. The preparation method has smooth technical process and smooth winding and unwinding.

The BOPP film of the present embodiment is used for preparing a thermal composite substrate, and is compounded with a co-polypropylene material or/and a polyethylene material through a thermal composite functional layer, specifically, the BOPP film of the present embodiment is thermally compounded with a stone paper honeycomb board 5, the structure after the compounding is shown in fig. 3, and the compounding effect is tested after the compounding is completed. The compounding method comprises the following steps: firstly, directly performing temperature-resistant ink printing on a printable surface layer of a BOPP film, wherein the last step is temperature-resistant protective gloss oil to form an ink layer 6, and then, directly performing hot pressing and compounding on the film and a stone paper honeycomb plate with the surface reaching a certain temperature by mild hot pressing, wherein the thermal compounding process conditions are as follows: the temperature is 130 ℃, the sealing time is 2s, and the hot pressing pressure is 8kg/cm ² 。

Example 2

preparing a thermal composite functional layer resin: and uniformly mixing 98wt% of metallocene ethylene-propylene copolymer (the melt index is 15g/10min, the temperature at which the crystallization and melt conversion rate of the metallocene ethylene-propylene copolymer is 50% is 80 ℃) and 2wt% of maleic anhydride grafted ethylene-butene copolymer (the melting point is 75 ℃, and the grafting rate is 2%), so as to obtain the thermal composite functional layer resin. Preparing core layer resin: 50wt% of homopolymerized polypropylene (with a melt index of 3.8g/10 min), 8wt% of ethylene propylene butene copolymer (with a melt index of 8g/10 min), 40wt% of nano calcium carbonate (with a D50 of 0.80 mu m) and 2wt% of polyethylene glycol (with a viscosity average molecular weight of 6000) are uniformly mixed to obtain the core layer resin.

Preparation of printable surface layer resin: the printable surface layer resin was obtained by uniformly mixing 52wt% of an ethylene propylene butene copolymer (melt index: 8g/10 min), 45wt% of a high density polyethylene (melt index: 0.05g/10 min), 1wt% of a maleic anhydride grafted ethylene butene copolymer (melting point: 75 ℃ C., grafting ratio: 2%) and 2wt% of nano calcium carbonate (D50: 0.80. Mu.m).

The BOPP film of this example was prepared in the same manner as in example 1.

The surface tension of the thin-film printable surface layer 2 is 40 dyne/cm, the surface tension of the thermal composite functional layer 1 is 29 dyne/cm, the total thickness of the thin film is 30 mu m, the thickness of the thermal composite functional layer 1 is 2 mu m, the thickness of the core layer 3 is 26 mu m, and the thickness of the printable surface layer 2 is 2 mu m. The preparation method has smooth technical process and smooth winding and unwinding.

The BOPP film of the present embodiment is used for preparing a thermal composite substrate, and is compounded with a co-polypropylene material or/and a polyethylene material through a thermal composite functional layer, specifically, the BOPP film of the present embodiment is thermally compounded with a stone paper honeycomb board 5, the structure after the compounding is shown in fig. 3, and the compounding effect is tested after the compounding is completed. The compounding method of this example is the same as that of example 1.

Example 3

preparing a thermal composite functional layer resin: 96wt% of metallocene ethylene-propylene copolymer (the melt index is 10g/10min, the temperature at which the crystallization melt conversion rate of the metallocene ethylene-propylene copolymer is 50% is 85 ℃) and 4wt% of maleic anhydride grafted ethylene-butene copolymer (the melting point is 70 ℃ and the grafting rate is 2%) are uniformly mixed, so that the thermal composite functional layer resin is obtained.

Preparing core layer resin: uniformly mixing 37wt% of homopolypropylene (with a melt index of 3.8g/10 min), 10wt% of ethylene propylene butene copolymer (with a melt index of 8g/10 min), 50wt% of nano calcium carbonate (with a D50 of 0.80 mu m) and 3wt% of polyethylene glycol (with a viscosity average molecular weight of 6000) to obtain the core layer resin.

Preparation of printable surface layer resin: the printable surface layer resin was obtained by uniformly mixing 47wt% of ethylene propylene butene copolymer (melt index: 8g/10 min), 50wt% of high density polyethylene (melt index: 0.05g/10 min), 1wt% of maleic anhydride grafted ethylene-butene copolymer (melting point: 70 ℃ C., grafting ratio: 2%) and 2wt% of nano calcium carbonate (D50: 0.80. Mu.m).

The BOPP film of this example was prepared in the same manner as in example 1.

The surface tension of the thin-film printable surface layer 2 is 42 dyne/cm, the surface tension of the thermal composite functional layer 1 is 29 dyne/cm, the total thickness of the thin film is 40 mu m, the thickness of the thermal composite functional layer 1 is 4 mu m, the thickness of the core layer 3 is 34 mu m, and the thickness of the printable surface layer 2 is 2 mu m. The preparation method has smooth technical process and smooth winding and unwinding.

Example 4

The embodiment provides a BOPP film, which includes a thermal composite functional layer 1, a compatibilizer layer 4, a core layer 3 and a printable surface layer 2, and the specific structure can be referred to fig. 2. The preparation method of the BOPP film resin of each layer of the embodiment comprises the following steps:

Preparing a compatibilizer layer resin: 40wt% of homo-polypropylene (melt index: 3.8g/10 min) and 60wt% of ethylene propylene butene copolymer (melt index: 8g/10 min) were uniformly mixed to obtain a compatibilized layer resin.

Preparing core layer resin: uniformly mixing 47wt% of homopolypropylene (with a melt index of 3.8g/10 min), 50wt% of nano calcium carbonate (with a D50 of 0.80 mu m) and 3wt% of polyethylene glycol (with a viscosity average molecular weight of 6000) to obtain core layer resin.

the method comprises the steps of feeding all layer component raw materials into a batching unit, metering the raw materials, feeding the raw materials into an extruder, controlling the extrusion temperature corresponding to a core layer 3, a compatibilizing layer 4 and a printable surface layer 2 to be 240-260 ℃, controlling the extrusion temperature corresponding to a thermal composite functional layer 1 to be 210-240 ℃, converging the raw materials at a multi-layer die head after passing through a flow channel distributor to form a resin melt with a multi-layer structure, and cooling the resin melt by a chilled roll with the temperature of 25-35 ℃ to form a resin sheet with the multi-layer structure; introducing the resin sheet into a longitudinal stretching device in a biaxial stretching device, preheating the surface of the printable surface layer 2 at 130-135 ℃, controlling the stretching temperature of the core layer 3, the compatibilizer layer 4 and the printable surface layer 2 at 110-130 ℃, preheating the thermal composite functional layer 1 at 80-100 ℃, controlling the stretching temperature at 60-80 ℃ and the stretching ratio at 4.5-4.8 times; then introducing a transverse stretching device, preheating at 165-175 ℃, stretching at 156-160 ℃ for 5-7.5 times, shaping at 165-170 ℃, cooling by air shower, and carrying out corona treatment on the surface of the printable surface layer 2 (the energy density of the corona treatment is 1.8 KJ/m) ² ) And (3) the thermal composite functional layer 1 is not subjected to corona treatment, a film parent roll is obtained, and finally the BOPP film is obtained through ageing treatment, slitting and packaging.

The surface tension of the thin film printable surface layer 2 is 44 dyne/cm, the surface tension of the thermal composite functional layer 1 is 30 dyne/cm, the total thickness of the thin film is 50 mu m, the thickness of the thermal composite functional layer 1 is 5 mu m, the thickness of the compatibilizing layer 4 is 2 mu m, the thickness of the core layer 3 is 41 mu m, and the thickness of the printable surface layer 2 is 2 mu m. The preparation method has smooth process.

The BOPP film of the present embodiment is used for preparing a thermal composite substrate, and is compounded with a co-polypropylene material or/and a polyethylene material through a thermal composite functional layer, specifically, the BOPP film of the present embodiment is thermally compounded with a stone paper honeycomb board 5, the structure after the compounding is shown in fig. 4, and the compounding effect is tested after the compounding is completed. The compounding method of this example is the same as that of example 1.

Comparative example 1

This comparative example provides a BOPP film comprising a thermal composite functional layer 1, a core layer 3 and a printable surface layer 2, which are sequentially arranged, and the specific structure can be seen in fig. 1. The preparation method of the BOPP film resin of the comparative example comprises the following steps:

preparing a thermal composite functional layer resin: and uniformly mixing 85wt% of metallocene ethylene-propylene copolymer (the melt index is 10g/10min, the temperature at which the crystallization and melt conversion rate of the metallocene ethylene-propylene copolymer is 50% is 85 ℃) and 15wt% of maleic anhydride grafted ethylene-butene copolymer (the melting point is 70 ℃, and the grafting rate is 2%) to obtain the thermal composite functional layer resin.

The BOPP film of this comparative example was prepared in the same manner as in example 1.

The surface tension of the thin-film printable surface layer 2 is 40 dyne/cm, the surface tension of the thermal composite functional layer 1 is 29 dyne/cm, the total thickness of the thin film is 30 mu m, the thickness of the thermal composite functional layer 1 is 2 mu m, the thickness of the core layer 3 is 26 mu m, and the thickness of the printable surface layer 2 is 2 mu m. The preparation method has the defects of unsmooth technological process and roller sticking.

The BOPP film of this comparative example was used to prepare a thermal composite substrate, and was compounded with a co-polypropylene material or/and a polyethylene material through a thermal composite functional layer, specifically, this comparative example was thermally compounded with a stone paper honeycomb panel 5, the structure after compounding was shown in fig. 3, and after compounding was completed, the compounding effect was tested. The compounding method of this comparative example was the same as that of example 1.

Comparative example 2

preparing a thermal composite functional layer resin: 100wt% of metallocene ethylene-propylene copolymer (melt index 10g/10min, temperature at which the crystallization melt conversion of the metallocene ethylene-propylene copolymer is 50% is 85 ℃) is taken to obtain the thermal composite functional layer resin.

Comparative example 3

preparing a thermal composite functional layer resin: 96wt% of metallocene ethylene-propylene copolymer (the melt index is 20g/10min, the temperature at which the crystallization melt conversion rate of the metallocene ethylene-propylene copolymer is 50% is 70 ℃) and 4wt% of maleic anhydride grafted ethylene-butene copolymer (the melting point is 70 ℃ and the grafting rate is 2%) are uniformly mixed, so that the thermal composite functional layer resin is obtained.

Comparative example 4

preparing a thermal composite functional layer resin: 96wt% of metallocene ethylene-propylene copolymer (the melt index is 5g/10min, the temperature at which the crystallization melt conversion rate of the metallocene ethylene-propylene copolymer is 50% is 100 ℃) and 4wt% of maleic anhydride grafted ethylene-butene copolymer (the melting point is 70 ℃ and the grafting rate is 2%) are uniformly mixed, so that the thermal composite functional layer resin is obtained.

The surface tension of the thin-film printable surface layer 2 is 40 dyne/cm, the surface tension of the thermal composite functional layer 1 is 29 dyne/cm, the total thickness of the thin film is 30 mu m, the thickness of the thermal composite functional layer 1 is 2 mu m, the thickness of the core layer 3 is 26 mu m, and the thickness of the printable surface layer 2 is 2 mu m. The preparation method has smooth process.

Comparative example 5

Preparing core layer resin: 50wt% of homopolypropylene (with a melt index of 3.8g/10 min), 10wt% of ethylene propylene butene copolymer (with a melt index of 8g/10 min) and 40wt% of nano calcium carbonate (with a D50 of 0.80 mu m) are taken and uniformly mixed to obtain the core resin.

The surface tension of the thin-film printable surface layer 2 is 40 dyne/cm, the surface tension of the thermal composite functional layer 1 is 29 dyne/cm, the total thickness of the thin film is 30 mu m, the thickness of the thermal composite functional layer 1 is 2 mu m, the thickness of the core layer 3 is 26 mu m, and the thickness of the printable surface layer 2 is 2 mu m. The preparation method has unsmooth technological process and is easy to break membranes.

Comparative example 6

Preparing core layer resin: uniformly mixing 40wt% of homopolypropylene (with a melt index of 3.8g/10 min), 10wt% of ethylene propylene butene copolymer (with a melt index of 8g/10 min), 40wt% of nano calcium carbonate (with a D50 of 0.80 mu m) and 10wt% of polyethylene glycol (with a viscosity average molecular weight of 6000) to obtain the core layer resin.

The surface tension of the thin-film printable surface layer 2 is 40 dyne/cm, the surface tension of the thermal composite functional layer 1 is 29 dyne/cm, the total thickness of the thin film is 30 mu m, the thickness of the thermal composite functional layer 1 is 2 mu m, the thickness of the core layer 3 is 26 mu m, and the thickness of the printable surface layer 2 is 2 mu m. The preparation method has poor extrusion stability of the core layer melt and unsmooth technological process.

Comparative example 7

Preparing core layer resin: uniformly mixing 57wt% of homopolypropylene (with a melt index of 3.8g/10 min), 10wt% of ethylene propylene butene copolymer (with a melt index of 8g/10 min), 30wt% of nano calcium carbonate (with a D50 of 0.80 mu m) and 3wt% of polyethylene glycol (with a viscosity average molecular weight of 6000) to obtain the core layer resin.

The surface tension of the thin-film printable surface layer 2 is 40 dyne/cm, the surface tension of the thermal composite functional layer 1 is 29 dyne/cm, the total thickness of the thin film is 30 mu m, the thickness of the thermal composite functional layer 1 is 2 mu m, the thickness of the core layer 3 is 26 mu m, and the thickness of the printable surface layer 2 is 2 mu m. The preparation method has smooth process, but the nano calcium carbonate has small addition amount, which is not beneficial to reducing the cost.

Comparative example 8

Preparing core layer resin: uniformly mixing 20wt% of homopolypropylene (with a melt index of 3.8g/10 min), 6wt% of ethylene propylene butene copolymer (with a melt index of 8g/10 min), 70wt% of nano calcium carbonate (with a D50 of 0.80 mu m) and 4wt% of polyethylene glycol (with a viscosity average molecular weight of 6000) to obtain the core layer resin.

The surface tension of the thin-film printable surface layer 2 is 40 dyne/cm, the surface tension of the thermal composite functional layer 1 is 29 dyne/cm, the total thickness of the thin film is 30 mu m, the thickness of the thermal composite functional layer 1 is 2 mu m, the thickness of the core layer 3 is 26 mu m, and the thickness of the printable surface layer 2 is 2 mu m. According to the preparation method, the technological process is not smooth, membrane rupture occurs, the interlayer combination of the thermal composite functional layer and the core layer is poor, and layering phenomenon exists.

Comparative example 9

preparing a thermal composite functional layer resin: the components of the thermal composite first surface layer 1 in example 1 of the chinese patent No. cn202111556317.X were uniformly mixed to obtain a thermal composite functional layer resin.

The BOPP film preparation method of this comparative example is different from the BOPP film preparation method of example 1 in that the longitudinal stretching preheating temperature of the thermal composite functional layer 1 is 70 to 90 ℃ and the stretching temperature is 60 to 80 ℃.

The surface tension of the thin-film printable surface layer 2 is 40 dyne/cm, the surface tension of the thermal composite functional layer 1 is 29 dyne/cm, the total thickness of the thin film is 30 mu m, the thickness of the thermal composite functional layer 1 is 2 mu m, the thickness of the core layer 3 is 26 mu m, and the thickness of the printable surface layer 2 is 2 mu m. The preparation method needs lower longitudinal preheating temperature, so that the production difficulty is increased.

The BOPP film can be used for compounding with a polypropylene material or/and a polyethylene material, and particularly, the BOPP film can be suitable for compounding with a propylene copolymer material or/and a polyethylene material which consists of 60-80 wt% of calcium carbonate and 20-30 wt% of propylene copolymer or/and polyethylene, wherein the propylene copolymer material or/and the polyethylene material has higher content of calcium carbonate, and can also be compounded with a common propylene copolymer material or/and polyethylene material.

In a specific embodiment, the BOPP film of the present invention may be compounded with a calendered propylene copolymer sheet prepared by: and selecting an ethylene propylene copolymer with a melting point of 141 ℃ and a melt index of 6g/10min, and processing the ethylene propylene copolymer into the calendered propylene copolymer sheet through a calendering process. And compounding the calendered and copolymerized propylene sheet with the BOPP films prepared in examples 1-4 according to the compounding method of example 1 to obtain a thermal composite substrate, wherein the compounding effect is qualified.

In a specific embodiment, the BOPP film of the present invention may also be compounded with a calendered polyethylene sheet prepared by the following method: selecting polyethylene with a melting point of 125 ℃ and a melt index of 4g/10min, and processing the polyethylene into the rolled polyethylene sheet through a rolling process. And compounding the calendered polyethylene sheet with the BOPP films prepared in examples 1-4 according to the compounding method of example 1 to obtain a thermal composite substrate, wherein the compounding effect is qualified.

In a specific embodiment, the BOPP film of the present invention may also be compounded with a calendered sheet comprising propylene copolymer and polyethylene (weight ratio of 1:1), said calendered sheet being prepared by the following method: and (3) uniformly mixing 50wt% of ethylene-propylene copolymer with the melting point of 141 ℃ and the melt index of 6g/10min and 50wt% of polyethylene with the melting point of 125 ℃ and the melt index of 4g/10min, and processing the mixture into the rolled sheet through a rolling process. And compounding the rolled sheet with the BOPP films prepared in examples 1-4 according to the compounding method of example 1 to obtain a thermal composite substrate, wherein the compounding effect is qualified.

The results of the performance test and the composite effect test of the BOPP films of examples 1 to 4 and comparative examples 1 to 9 are shown in table 2 below.

TABLE 2

From the above performance test data, it is known that the BOPP film prepared in comparative example 1 is 100% separated from the stone paper honeycomb panel after being compounded, but the low melting point maleic anhydride grafted ethylene-butene copolymer content in the thermal composite functional layer is too high, so that the thermal composite functional layer has problems of sticking to rollers and poor production smoothness; in comparative example 2, although the production smoothness is good, the bulk separation ratio is only 60-70% because the low-melting-point maleic anhydride grafted ethylene-butene copolymer is not added, and the composite effect is not qualified; in comparative example 3, the temperature at which the crystallization and melt conversion rate of the metallocene ethylene-propylene copolymer in the thermal composite functional layer is 50% is too low, the melt index is too high, and the problems of sticking to the roll and poor production smoothness of the thermal composite functional layer exist; in comparative example 4, the temperature is too high when the crystallization and melting conversion rate of the metallocene ethylene-propylene copolymer is 50%, the melt index is too low, the bulk separation ratio is only 30-40%, and the composite effect is not qualified; in comparative example 5, polyethylene glycol is not added in the core layer, so that membrane rupture easily occurs on the premise of the specific nano calcium carbonate addition amount and the biaxial stretching ratio of the invention; in comparative example 6, the melt extrusion stability of the core layer is poor due to the excessive amount of polyethylene glycol added into the core layer, which is unfavorable for obtaining a thick sheet meeting the biaxial stretching process; in comparative example 7, although the composite effect is qualified and the production smoothness is good, the addition amount of the nano calcium carbonate in the core layer is too low, the requirement of the nano calcium carbonate with relatively high content in the invention is not met, and compared with example 2 with the same thickness, the light transmittance is increased, and the covering property of the film is affected; the content of the nano calcium carbonate in the core layer in the comparative example 8 is too high, and the membrane rupture phenomenon is serious; in comparative example 9, a conventional thermal composite functional layer containing ethylene-vinyl acetate copolymer was selected, and because of its poor matching with the core layer and too large polarity difference with the honeycomb panel component, the thermal compression composite effect was not acceptable and a lower longitudinal preheating temperature was required, thereby increasing the difficulty of film production.

According to the invention, from the special that the stone paper honeycomb board mainly consists of 60-80 wt% of calcium carbonate content and 20-30 wt% of high polymer, a BOPP film is provided, on one hand, through the component formula design of a thermal composite functional layer, a metallocene ethylene-propylene copolymer with a specific melt index range is added into the thermal composite functional layer, and the corresponding temperature range when the crystallization melt conversion rate is 50% is controlled, so that the thermal composite functional layer does not need high-pressure conditions, and can be directly hot-pressed and compounded with a copolymer propylene material or/and a polyethylene material with higher content of calcium carbonate by utilizing the surface temperature of the copolymer propylene material or/and the polyethylene material which are processed immediately, thereby saving the glue coating procedure, saving energy and protecting the environment, and ensuring the compounding fastness; on the other hand, through the component formula design of the core layer, under the condition of meeting the biaxial stretching process, the nano calcium carbonate with higher content can be added into the film core layer, so that the production cost is further reduced, the white BOPP film which can be directly printed on the surface of the film and can be compounded without white background and glue is obtained, the applicability is wider, the stone paper honeycomb board is particularly suitable for compounding stone paper honeycomb boards, and the stone paper honeycomb board is more environment-friendly and has better performance, and can replace the traditional corrugated board in a larger range.

The above examples illustrate only a few embodiments of the invention, which are described in detail and are not to be construed as limiting the scope of the invention. It should be noted that modifications and improvements can be made by those skilled in the art without departing from the spirit of the invention, and the invention is intended to encompass such modifications and improvements.

Claims

1. The BOPP film is characterized by comprising a thermal composite functional layer, a core layer and a printable surface layer which are sequentially arranged, wherein the thermal composite functional layer comprises 95-98wt% of metallocene ethylene-propylene copolymer and 2-5wt% of maleic anhydride grafted ethylene-butene copolymer, the melt index of the metallocene ethylene-propylene copolymer is 8-15 g/10min, and the temperature when the crystallization melt conversion rate of the metallocene ethylene-propylene copolymer is 50% is 80-90 ℃; the core layer comprises polypropylene, 40-60 wt% of nano calcium carbonate and 2-4 wt% of polyethylene glycol, and the density of the core layer is 0.60-0.70 g/cm ³ The method comprises the steps of carrying out a first treatment on the surface of the The surface tension of the printable surface layer is 38-44 dynes/cm, and the surface tension of the thermal composite functional layer is 28-30 dynes/cm.

2. The BOPP film of claim 1, wherein the melting point of the maleic anhydride grafted ethylene-butene copolymer is 65-75 ℃, and the grafting ratio of the maleic anhydride grafted ethylene-butene copolymer is 1-2%.

3. The BOPP film of claim 1, wherein the nano calcium carbonate has a particle size D50 of 0.75-0.85 μm and the polyethylene glycol has a viscosity average molecular weight of 5500-8000.

4. The BOPP film of claim 1, wherein the polypropylene is a homo-polypropylene; the BOPP film further comprises a compatibilizer layer, wherein the compatibilizer layer is positioned between the thermal composite functional layer and the core layer, the compatibilizer layer comprises 50-100 wt% of copolymerized propylene, and the copolymerized propylene is ethylene propylene butylene copolymer and/or ethylene propylene copolymer.

5. The BOPP film of claim 1, wherein the core layer comprises 30-50wt% of the homo-polypropylene and 6-10wt% of the co-propylene, wherein the co-propylene is an ethylene propylene butylene copolymer and/or an ethylene propylene copolymer.

6. The BOPP film of claim 1, wherein the printable surface layer is a matt layer, the printable surface layer comprises propylene copolymer, high density polyethylene, 1wt% maleic anhydride grafted ethylene-butene copolymer, and 2wt% nano calcium carbonate, and the weight ratio of propylene copolymer to high density polyethylene is (42-52): (55-45).

7. The BOPP film of claim 6, wherein the particle size D50 of the nano calcium carbonate in the printable surface layer is 0.75-0.85 μm, the propylene copolymer is ethylene propylene butylene copolymer and/or ethylene propylene copolymer, and the propylene copolymer melt index is 7-10 g/10min; the melt index of the high-density polyethylene is 0.03-0.05 g/10min.

8. A method for preparing the BOPP film according to any one of claims 1 to 7, characterized in that: the method comprises the following steps: the method comprises the steps of feeding the raw materials of all layers into a batching unit, metering, feeding the raw materials into an extruder, feeding the raw materials into a runner distributor after melting plasticization and homogenization metering, extruding the raw materials through a T-shaped die head, casting the raw materials into thick sheets through a chill roll, longitudinally stretching the thick sheets by 4.5-4.8 times, transversely stretching the thick sheets by 5-7.5 times to form films, air shower cooling the films, thickness measurement control of an edge trimmer, corona treatment of the films, rolling the films into film parent rolls, aging treatment, slitting and packaging the film parent rolls to obtain finished products.

9. Use of a BOPP film according to any one of claims 1-7 for the preparation of a thermal composite substrate by compounding the thermal composite functional layer of a BOPP film according to any one of claims 1-7 with a co-polypropylene material or/and a polyethylene material.

10. The use of BOPP film according to claim 9, wherein the co-propylene material or/and the polyethylene material comprises 60-80 wt% calcium carbonate and 20-30 wt% co-propylene or/and polyethylene.