An anti-fog masterbatch and its preparation method, and a BOPP anti-fog film and its preparation method.

Abstract

This invention relates to an anti-fog masterbatch and its preparation method, and a BOPP anti-fog film and its preparation method, belonging to the field of anti-fog film technology. The anti-fog masterbatch comprises 40-50 wt% homopolymer polypropylene resin, 40-50 wt% modified polypropylene resin, and 10-20 wt% nonionic surfactant; the modified polypropylene resin is obtained by grafting polypropylene with butyl acrylate, glycidyl methacrylate, and maleic anhydride; the nonionic surfactant is at least one selected from octadecanoic acid-2-[2-(hydroxyethyl)octadecylaminoethyl ester], diethanolamine stearate, and stearyl ethoxylated amine. By adding the modified polypropylene resin and the nonionic surfactant, the synergistic effect of the BOPP anti-fog film containing the masterbatch enables rapid onset and long-lasting anti-fog performance; when the BOPP anti-fog film is used to make packaging materials, the adhesive seal is not easily opened.

Description

Technical Field

[0001] This invention relates to the field of anti-fog film technology, and in particular to an anti-fog masterbatch and its preparation method, and a BOPP anti-fog film and its preparation method. Background Technology

[0002] Biaxially oriented polypropylene (BOPP) film, due to its colorless, odorless, and non-toxic properties, high tensile strength, and good transparency, is widely used in the packaging of fresh fruits and vegetables and other foods. This type of packaging film typically has a self-adhesive (pressure-sensitive adhesive) on one side of the opening. When packaging food, the release film on the self-adhesive is peeled off, and the film adheres to the other side of the opening to achieve a seal. When BOPP film is used as packaging material for fruits, vegetables, fresh produce, and frozen foods, fogging often occurs on the film surface due to air humidity or during cold chain transportation, affecting the product's display. Existing anti-fog films work by adding small-molecule or large-molecule anti-fog agents to the film, causing the fogging droplets to spread and form a water film on the film surface. However, this method cannot achieve both rapid onset and long-lasting anti-fog effects (maximum 3-6 months; for frozen foods with long shelf lives, it cannot maintain anti-fog effects throughout the shelf life). This is because small-molecule anti-fog agents migrate quickly but are prone to precipitation, resulting in short-lasting anti-fog effects; large-molecule anti-fog agents are beneficial for long-lasting anti-fog effects, but they migrate slowly and take effect slowly. In addition, when existing anti-fog films are used as packaging materials for vegetables, fruits, fresh produce, and frozen foods, the films often have poor adhesion and are prone to opening. Summary of the Invention

[0003] Based on this, the purpose of this invention is to provide an anti-fog masterbatch and its preparation method, and a BOPP anti-fog film and its preparation method. The anti-fog masterbatch of this invention, by adding 40-50wt% modified polypropylene resin and 10-20wt% nonionic surfactant, allows the BOPP anti-fog film prepared using this anti-fog masterbatch to quickly take effect on the surface of the film, providing a strong and long-lasting anti-fog effect against droplets on the film surface. When the BOPP anti-fog film is used to make packaging materials, the adhesive seal is not easy to open.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] An antifog masterbatch comprises 40-50 wt% homopolymer polypropylene resin, 40-50 wt% modified polypropylene resin, and 10-20 wt% nonionic surfactant; wherein the modified polypropylene resin is obtained by grafting polypropylene with butyl acrylate (BA), glycidyl methacrylate (GMA), and maleic anhydride (MAH); and the nonionic surfactant is at least one selected from 2-[2-(hydroxyethyl)octadecanoic acid], diethanolamine stearate, and stearyl ethoxylated amine.

[0006] When existing BOPP anti-fog films are used for packaging fresh fruits and vegetables and other foods, the interaction between the hydrophilic groups of the small-molecule anti-fog agent and water droplets causes the water droplets to form a water film on the surface of the BOPP anti-fog film, thus achieving an anti-fog effect. However, after years of research, the inventors discovered that the anti-fog effect of existing BOPP anti-fog films is not durable because the anti-fog agent gradually migrates from the inside of the film to the surface to achieve its anti-fog effect. However, the anti-fog agent that precipitates outwards to the surface denatures and loses its effectiveness over time, leading to a weakening or even elimination of the anti-fog effect. Furthermore, the inventors' research also revealed that the precipitation of small-molecule anti-fog agents further reduces the already weak adhesion between the BOPP anti-fog film and the pressure-sensitive adhesive, making the pressure-sensitive adhesive seal easier to open.

[0007] The antifogging masterbatch of the present invention contains 40-50 wt% homopolymer polypropylene resin, 40-50 wt% modified polypropylene resin, and 10-20 wt% nonionic surfactant. The modified polypropylene resin is obtained by grafting polypropylene with butyl acrylate, glycidyl methacrylate, and maleic anhydride, meaning that the propylene segments of the modified polypropylene resin contain butyl acrylate graft chains, glycidyl methacrylate graft chains, and maleic anhydride graft chains. The nonionic surfactant is a specific nonionic surfactant, namely at least one of 2-[2-(hydroxyethyl)octadecanoic acid], diethanolamine stearate, and stearyl ethoxylated amine. These nonionic surfactants contain amino or imino groups, which can act as hydrogen bond donors, while the carbonyl group in the maleic anhydride graft chain of the modified polypropylene resin acts as a hydrogen bond acceptor, enabling the modified polypropylene resin and the nonionic surfactant to form significant hydrogen bond interactions.

[0008] When the anti-fogging masterbatch of the present invention is added to the anti-fogging surface layer and core layer of a BOPP anti-fogging film to prepare a BOPP anti-fogging film, on the one hand, the modified polypropylene resin can significantly improve the compatibility of nonionic surfactants with homopolymer polypropylene resin, promote the dispersion of nonionic surfactants in the film layer, and make small-molecule nonionic surfactants tightly anchored in the film layer; on the other hand, because the modified polypropylene resin has good compatibility with the matrix resin, i.e., homopolymer polypropylene resin, the nonionic surfactants are evenly distributed in the film layer; furthermore, in the anti-fogging surface layer, homopolymer polypropylene resin is selected as the matrix resin of the anti-fogging masterbatch, which has good structural regularity and nonpolar segments tend to be located in the anti-fogging surface layer. Internally, the grafted side chains of the modified polypropylene resin tend to be located on the outer surface of the anti-fog layer. Specifically, the maleic anhydride, butyl acrylate, and glycidyl methacrylate grafted chains on the modified polypropylene resin are closer to the outer surface of the anti-fog layer. Since the epoxy groups in the glycidyl methacrylate grafted chains and the ester groups in the butyl acrylate grafted chains are hydrophilic, they help form a water film on the anti-fog layer surface, resulting in a rapid onset of anti-fog effect. Simultaneously, because the nonionic surfactant is uniformly dispersed in the anti-fog layer, the nonionic surfactant near the outer surface of the anti-fog layer also synergistically contributes to the formation of a water film with the aforementioned hydrophilic groups. Therefore, by utilizing the hydrophilicity of the glycidyl methacrylate and butyl acrylate grafted chains on the modified polypropylene resin, combined with the anti-fog properties of the nonionic surfactant, the anti-fog effect of the film prepared from this anti-fog masterbatch can be rapidly achieved, providing a strong anti-fog effect against droplets on the anti-fog surface. Furthermore, because the modified polypropylene resin and the nonionic surfactant can form significant hydrogen bonds, the carbonyl groups on the maleic anhydride grafted chains on the outer surface of the anti-fog layer have a certain adsorption effect on the nonionic surfactant. This attracts the nonionic surfactant in the anti-fog layer and core layer to migrate to the anti-fog surface while "preventing" the nonionic surfactant from precipitating out too quickly, thus playing a certain role in slow release. This allows the nonionic surfactant to slowly migrate to the anti-fog surface, achieving a long-lasting anti-fog effect (the anti-fog effect declining to grade C or below in the performance evaluation indicates that the anti-fog effect is not long-lasting). In addition, when the film prepared using the anti-fog masterbatch of this invention is used for packaging fresh fruits and vegetables and food, the good compatibility between the butyl acrylate grafted chains and the acrylate system of the pressure-sensitive adhesive can improve the initial viscosity of the film-pressure-sensitive adhesive bond. Furthermore, because glycidyl methacrylate contains epoxy groups, it can react with the carboxyl or hydroxyl groups in the pressure-sensitive adhesive under pressure in a humid environment to form chemical bonds, thereby enhancing the adhesion between the film surface and the pressure-sensitive adhesive. After the packaging bag is sealed, it is firmly bonded and not easy to open. Preferably, the raw material components of the anti-fog masterbatch are all food-grade, so that the film from Xincheng can be used for packaging food when it is used as a packaging material.

[0009] The anti-fogging masterbatch of this invention is added to the anti-fogging surface layer and core layer of a BOPP anti-fogging film, resulting in a BOPP anti-fogging film with excellent anti-cold fog and anti-hot fog effects. When water vapor condenses on the film surface in a low-temperature, high-humidity environment, traditional anti-fogging agents may migrate more slowly or easily crystallize and fail after migrating or precipitating onto the film surface. In this application, the carbonyl group in the maleic anhydride grafted chain on the modified polypropylene resin forms a significant hydrogen bond with the nonionic surfactant, ensuring a continuous supply of nonionic surfactant at low temperatures. The surfactant can still migrate slowly and in a controlled manner to the film surface, maintaining low surface tension, preventing the formation of tiny water droplets, and achieving a long-lasting anti-cold fog effect. When high-temperature steam comes into contact with the low-temperature film surface, the surfactant is anchored by hydrogen bonds, reducing the rapid loss of nonionic surfactant caused by high-temperature steam impact. Even if the nonionic surfactant is temporarily lost, the glycidyl methacrylate grafted chain and butyl acrylate grafted chain of the modified polypropylene resin can still provide basic hydrophilicity, resisting frequent hot steam impacts and maintaining the long-term effectiveness of the anti-fogging effect. This invention achieves both cold fog and hot fog protection in cold / hot fog scenarios through the synergistic design of modified polypropylene resin and nonionic surfactant.

[0010] If the content of the modified polypropylene resin in the anti-fogging masterbatch is too high, it can easily lead to oversaturation of the hydrophilic groups on the surface of the anti-fogging layer, resulting in excessive accumulation of the water film on the surface of the anti-fogging layer. This can prevent the formation of a uniform water film, potentially causing the surface of the anti-fogging layer to turn white, foggy, and blurry, thus losing transparency. If the content of the modified polypropylene resin in the anti-fogging masterbatch is too low, there will be insufficient hydrogen bond acceptors, weak anchoring effect of nonionic surfactants, uneven anti-fogging effect, and poor anti-fogging durability. In addition, when the film prepared from the anti-fogging masterbatch is used for packaging fresh fruits and vegetables and food, the adhesion to pressure-sensitive adhesive is insufficient, and the effect of improving the ease of opening of the pressure-sensitive adhesive seal is not obvious.

[0011] If the content of the nonionic surfactant in the antifogging masterbatch is too high, it can easily lead to excessive spreading of water on the surface of the antifogging layer, forming an excessively thick water layer or even water flow, causing light scattering and making the antifogging surface appear white and blurry, thus losing transparency and failing to achieve the ideal transparent water film effect. Furthermore, excessive nonionic surfactant is difficult to disperse evenly in the matrix, easily accumulating locally and rapidly precipitating, resulting in uneven antifogging effect on the film surface, appearing as "spots" or streaks. Additionally, when the film prepared from the antifogging masterbatch is used for packaging fresh fruits and vegetables and other food products, the precipitated nonionic surfactant can lead to insufficient adhesion to the pressure-sensitive adhesive. If the content of the nonionic surfactant in the antifogging masterbatch is too low, the antifogging effect will be relatively slow to take effect and the antifogging performance will be poor.

[0012] Furthermore, the preparation method of the modified polypropylene resin includes the following steps:

[0013] (1) Premix: 100 parts of homopolymer polypropylene, 2-4 parts of molten maleic anhydride (maleic anhydride is pre-melted at 60℃), 11-13 parts of butyl acrylate and 0.1-0.3 parts of antioxidant are put into a high-speed mixer and mixed at 400-600 rpm for 6-10 minutes to obtain a premix.

[0014] (2) Melt grafting: The premixed material is added through the main feed port of a twin-screw extruder (preferably screw L / D=48, speed 250rpm). The temperature zones of the twin-screw extruder are set as follows: Zone 1-2 170℃, Zone 3 180℃, Zone 4-5 195℃, Zone 6-7 185℃, Zone 8 175℃. Among them, 7-9 parts of glycidyl methacrylate and 0.1-0.3 parts of initiator DCP are injected into Zone 3. The initiator DCP is preferably dissolved in 4-6 parts of acetone in advance. The vacuum degree of Zone 6-7 is -(0.095-0.1)MPa.

[0015] (3) Purification: The extruded strips were water-cooled and pelletized, and extracted with boiling acetone in a Soxhlet extractor. The mixture was then vacuum-dried to constant weight to obtain the modified polypropylene resin.

[0016] The modified polypropylene resin of the present invention, in the (1) premixing step, forms a maleic anhydride-butyl acrylate hydrogen bonded association and uniformly coats the surface of the homopolymer polypropylene; inhibits maleic anhydride crystallization and reduces the high-temperature volatilization loss of butyl acrylate; in the (2) melt grafting step, the premix is ​​melted in zone 1-2, and the maleic anhydride-butyl acrylate hydrogen bonded association is dissociated at high temperature. By injecting glycidyl methacrylate and initiator DCP in zone 3, the premature high-temperature self-polymerization of glycidyl methacrylate and its failure can be avoided, and the premature decomposition of initiator DCP can also be prevented; in zone 4-5, butyl acrylate, glycidyl methacrylate and maleic anhydride are grafted and modified onto the homopolymer polypropylene; in zone 6-7, unreacted monomers and acetone are removed by vacuum; in zone 8, strips are stably extruded; after the (3) purification step, unreacted monomers are further removed by boiling acetone drawer, and finally, granular modified polypropylene resin is obtained.

[0017] The modified polypropylene resin prepared by the above method in this invention has butyl acrylate, glycidyl methacrylate, and maleic anhydride grafted onto the polypropylene surface. When the antifogging masterbatch is added to the antifogging surface layer and core layer of a BOPP antifogging film to prepare the BOPP antifogging film, it helps to transform the hydrophobic surface of the antifogging surface into a hydrophilic surface. After the antifogging surface adsorbs water vapor, it works synergistically with nonionic surfactants to cause the water vapor to spread on the surface of the antifogging surface to form a water film that is not easy to remove, thereby achieving the purpose of antifogging.

[0018] Furthermore, the nonionic surfactant comprises 40-45 wt% 2-[2-(hydroxyethyl)octadecanoic acid], 25-30 wt% diethanolamine stearate, and 25-35 wt% stearyl ethoxylated amine. The 2-[2-(hydroxyethyl)octadecanoic acid], diethanolamine stearate, and stearyl ethoxylated amine all possess amino or imino groups, which can form hydrogen bonds with the carbonyl groups in the maleic anhydride grafted chains on the modified polypropylene resin. This allows these nonionic surfactants to migrate to the antifogging surface under hydrogen bonding, providing a durable antifogging effect. The nonionic surfactant of this invention uses a relatively high proportion (40-50 wt%) of 2-[2-(hydroxyethyl)octadecanoic acid], which has a large molecular weight, long carbon chain, and relatively complex structure, increasing its migration resistance in the system. It can migrate but is not easily precipitated, thus exhibiting a certain sustained-release effect. The nonionic surfactant of this invention incorporates 25-35 wt% stearic acid-based ethoxylated amine. This component also contains hydrophilic polyethylene oxide chains, exhibiting strong hydrophilicity and relatively easy migration to the anti-fogging surface, providing sufficient hydrophilic groups to interact with water molecules, promoting rapid and uniform spreading of the water film, and achieving a fast-acting and long-lasting anti-fogging effect. The nonionic surfactant of this invention also contains 25-30 wt% stearic acid diethanolamine. This component has a certain thickening effect, helping to improve the melt rheological behavior or dispersion stability of the anti-fogging masterbatch during processing; furthermore, this component contains hydroxyl groups, providing a certain degree of hydrophilicity, synergistically ensuring the surface wettability of the anti-fogging layer with other components.

[0019] Furthermore, the melt index of the homopolymer polypropylene resin is 6.0-7.0 g / 10 min (230℃, 2.16 kg). Using the above melt index ensures melt strength, facilitates stretching into a film, and promotes the regular arrangement of non-polar segments, favoring the interior of the anti-fog surface layer.

[0020] Furthermore, the modified polypropylene resin has a melt index of 9-11 g / 10 min (230°C, 2.16 kg). Using the modified polypropylene resin with the above melt index can reduce melt viscosity and promote the uniform dispersion of nonionic surfactants.

[0021] The present invention also provides a method for preparing any of the above-mentioned anti-fog masterbatches, comprising the following steps: mixing the raw materials and adding them to a screw extruder for melt extrusion, and then drawing and granulating them underwater to obtain the anti-fog masterbatch.

[0022] The present invention also provides a BOPP anti-fog film, comprising an anti-fog surface layer, a core layer and a lower surface layer arranged in sequence; the anti-fog surface layer comprises homopolymer polypropylene resin and 1-2 wt% of any of the above-mentioned anti-fog masterbatches.

[0023] Furthermore, the core layer comprises homopolymer polypropylene resin and 2-4 wt% of any of the above-described antifog masterbatches.

[0024] Furthermore, the lower surface layer comprises 95 wt% homopolymer polypropylene resin and 5 wt% anti-blocking masterbatch.

[0025] This invention also provides a method for preparing any of the above-mentioned BOPP anti-fog films, comprising the following steps: weighing the raw materials of each layer according to the proportion and adding them to each extruder; after melting and plasticizing, metering by a metering pump, and extruding them into the dies of different extruders; casting them into thick sheets by a chilled roller; cutting the thick sheets into the required size (preferably 150mm*150mm*180~200μm); stretching them in a static stretching machine (preferably stretching 3*3=9 times, i.e., stretching 3 times in the transverse direction, 3 times in the longitudinal direction, and 9 times in the thickness); and preparing a film (preferably with a film size of 450mm*450mm*20μm); and after the film is corona treated (so that the surface value of the anti-fog layer is above 38dyn / cm), the finished product is obtained.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] The anti-fogging masterbatch of the present invention, under short-term action, utilizes the hydrophilicity of the butyl acrylate grafted chains and glycidyl methacrylate grafted chains on the modified polypropylene resin, which can synergistically work with nonionic surfactants to rapidly enhance the anti-fogging effect on the surface of the anti-fogging layer. Under long-term action, because the nonionic surfactants contain amino or imino groups, they can act as hydrogen bond donors, while the carbonyl groups in the maleic anhydride grafted chains on the modified polypropylene resin act as hydrogen bond acceptors, generating hydrogen bonding. This allows the nonionic surfactants to migrate to the surface of the anti-fogging layer under the influence of hydrogen bonding, resulting in a more uniform and consistent water film formed on the surface of the anti-fogging layer, thus maintaining a better anti-fogging effect. In addition, when the anti-fog masterbatch of the present invention is added to the anti-fog surface layer and core layer of the BOPP anti-fog film, the film prepared is used for packaging fresh fruits and vegetables and food. Because the butyl acrylate graft chain has good compatibility with the acrylate system of the pressure-sensitive adhesive, it can improve the initial viscosity of the film and the pressure-sensitive adhesive. Furthermore, because glycidyl methacrylate contains epoxy groups, it can react with the carboxyl or hydroxyl groups in the pressure-sensitive adhesive under pressure in a humid environment to form chemical bonds, thereby enhancing the adhesion between the film surface and the pressure-sensitive adhesive. After the packaging bag is sealed, it is firmly bonded and not easy to open. Detailed Implementation

[0028] The present invention will now be described more fully. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Experimental methods in the following examples or comparative examples, where specific conditions are not specified, are generally performed under conventional conditions in the art or as recommended by the manufacturer; the raw materials, reagents, etc., used, unless otherwise specified, are all commercially available from the conventional market.

[0029] Melt index was determined according to GB / T3682-2018.

[0030] All materials used in the following examples or comparative examples are food-grade materials:

[0031] The melt index of the homopolymer polypropylene resin in the anti-fog surface layer, anti-fog masterbatch, core layer, or lower surface layer is 7 g / 10 min (230℃, 2.16 kg).

[0032] The nonionic surfactant comprises 42 wt% 2-[2-(hydroxyethyl)octadecanoic acid], 28 wt% diethanolamine stearate, and 30 wt% stearyl ethoxylated amine; wherein the CAS number of 2-[2-(hydroxyethyl)octadecanoic acid] is 52497-24-2; the CAS number of diethanolamine stearate is 10213-78-2; and the CAS number of stearyl ethoxylated amine is 26635-92-7. The preparation method of the nonionic surfactant is as follows:

[0033] 1) Material Pretreatment: First, weigh the raw materials according to their mass fractions: octadecanoic acid-2-[2-(hydroxyethyl)octadecanoic acid ethyl ester] (42% mass fraction, CAS No. 52497-24-2), stearic acid diethanolamine (28% mass fraction, CAS No. 10213-78-2), and stearic acid ethoxylated amine (30% mass fraction, CAS No. 26635-92-7). Then, dry the stearic acid diethanolamine at 60℃ using a vacuum dryer for 3-4 hours. The vacuum dryer should be an eccentric horizontal vacuum drum with an angle >25° between the shaft and the centerline of the drum, and an external oil or steam heating jacket. Note that the loading amount should not exceed 65% of the drum's volume.

[0034] 2) Main material melting and processing: After the material pretreatment is completed, use an air knife feeder or vacuum extraction device to feed the material to avoid secondary contamination. In the reactor, first add diethanolamine stearate and stir at a low speed of 50 rpm and a temperature of 85°C; then, slowly add the main agent, namely 2-[2-(hydroxyethyl)octadecanoic acid], and at this stage, the temperature should be raised to 90°C and stabilized, with the temperature difference controlled not exceeding ±2°C.

[0035] 3) Degassing of excipient mixture: The temperature should be raised to 95℃ and stabilized at this stage. Erucamide should be added and stirred at high speed for 15 minutes. Then, vacuuming should be carried out for 30 minutes until no bubbles are precipitated.

[0036] 4) Granulation of Mixed Raw Materials: Since octadecanoic acid-2-[2-(hydroxyethyl)octadecylaminoethyl ester] is prone to hydrolysis at around 105℃, a granulator should be installed in the aforementioned reactor to further process the molten raw material into granules for subsequent processing. Special attention should be paid to controlling the die temperature during this process; specifically, the extrusion temperature of the granulator die should not exceed 90℃. Simultaneously, to maintain good raw material properties, underwater pelletizing and granulation methods should be avoided as much as possible. At the granulation end, a combination of a vacuum feeder and an industrial fan should be used for cooling and suction to prevent contamination of the granulated raw material.

[0037] Modified polypropylene resin: Polypropylene is obtained by grafting and modifying it with butyl acrylate, glycidyl methacrylate, and maleic anhydride. Specifically, the preparation method of the modified polypropylene resin includes the following steps:

[0038] (1) Premix: 100 parts of homopolymer polypropylene, 3 parts of maleic anhydride (melted at 60°C in advance), 12 parts of butyl acrylate (removed by vacuum distillation to remove polymerization inhibitors in advance) and 0.2 parts of antioxidant (Irganox 1010) are put into a high-speed mixer and mixed at 500 rpm for 8 minutes to obtain a premix.

[0039] (2) Melt grafting: The premixed material is added through the main feed port of the twin-screw extruder (screw L / D=48, speed 250rpm). The temperature zones are set as follows: Zone 1-2 170℃, Zone 3 180℃ (8 parts of glycidyl methacrylate and 0.2 parts of initiator DCP are injected, wherein the initiator DCP is dissolved in 5 parts of acetone in advance and injected in the form of solution), Zone 4-5 195℃ (main reaction zone, residence time 2 minutes, pressure 8-10MPa), Zone 6-7 185℃ (vacuum evaporation, -0.095MPa), Zone 8 175℃ extrusion;

[0040] (3) Purification: The extruded strips were water-cooled and pelletized, and extracted with boiling acetone in a Soxhlet extractor for 24 hours (6 cycles / hour). The mixture was then vacuum-dried at 80°C to constant weight to obtain the modified polypropylene resin. FTIR analysis confirmed that it had a 1730 cm⁻¹ diameter. -1 (BA ester group), 1780cm -1 (MAH anhydride group), 910cm -1 The characteristic peak of (GMA epoxy group) indicates that the corresponding structure has been grafted onto the modified polypropylene resin.

[0041] The melt index of the modified polypropylene resin is 10 g / 10 min (230℃, 2.16 kg).

[0042] Example 1

[0043] This embodiment provides an anti-fog masterbatch, comprising 50wt% homopolymer polypropylene resin, 40wt% modified polypropylene resin and 10wt% nonionic surfactant.

[0044] Among them, the nonionic surfactants include 42wt% octadecanoic acid-2-[2-(hydroxyethyl)octadecanoic acid ethyl ester], 28wt% stearic acid diethanolamine and 30wt% stearic acid ethoxylated amine.

[0045] The method for preparing the anti-fog masterbatch in this embodiment includes the following steps: mixing the raw materials and adding them to a screw extruder for melt extrusion, and then drawing and granulating them underwater to obtain the anti-fog masterbatch.

[0046] This embodiment also provides a BOPP anti-fog film, comprising an anti-fog surface layer, a core layer, and a lower surface layer arranged sequentially. The components and contents of each layer are as follows:

[0047] Anti-fog surface layer: 98wt% homopolymer polypropylene resin and 2wt% anti-fog masterbatch of this embodiment;

[0048] Core layer: 96wt% homopolymer polypropylene resin and 4wt% antifog masterbatch of this embodiment;

[0049] Bottom layer: 95wt% homopolymer polypropylene resin and 5wt% anti-blocking masterbatch.

[0050] The preparation method of BOPP anti-fog film in this embodiment includes the following steps: the raw materials of each layer are weighed according to the ratio and added to each extruder. After melting and plasticizing, they are metered by a metering pump and fed into the dies of different extruders for extrusion. The extruded material is then cast into a thick sheet by a chilled roller. The thick sheet is cut into the required size (150mm*150mm*180μm) and then stretched in a static stretching machine (stretched 3*3=9 times, that is, stretched 3 times in the transverse direction, stretched 3 times in the longitudinal direction, and stretched 9 times in thickness) to prepare a film (the specifications of the film are 450mm*450mm*20μm). After the film is corona treated (so that the surface value of the anti-fog layer is above 38dyn / cm), the finished product is obtained.

[0051] In this embodiment, the total thickness of the BOPP anti-fog film is 20 μm, the thickness of the anti-fog layer is 2.0 μm, and the thickness of the lower surface layer is 1.8 μm.

[0052] Example 2

[0053] This embodiment provides an anti-fogging masterbatch, comprising 40wt% homopolymer polypropylene resin, 40wt% modified polypropylene resin, and 20wt% nonionic surfactant.

[0054] The preparation method of the anti-fog masterbatch in this embodiment is the same as that of the anti-fog masterbatch in Example 1.

[0055] This embodiment also provides a BOPP anti-fog film, comprising an anti-fog surface layer, a core layer, and a lower surface layer arranged sequentially. The components and contents of each layer are as follows:

[0056] Anti-fog surface layer: 99wt% homopolymer polypropylene resin and 1wt% anti-fog masterbatch of this embodiment;

[0057] Core layer: 98wt% homopolymer polypropylene resin and 2wt% antifog masterbatch of this embodiment;

[0058] Bottom layer: 95wt% homopolymer polypropylene resin and 5wt% anti-blocking masterbatch.

[0059] The preparation method of the BOPP anti-fog film in this embodiment is the same as that of the BOPP anti-fog film in Example 1.

[0060] The total thickness and the thickness of each layer of the BOPP anti-fog film in this embodiment are the same as those of the BOPP anti-fog film in Embodiment 1.

[0061] Example 3

[0062] This embodiment provides an antifogging masterbatch, comprising 40wt% homopolymer polypropylene resin, 45wt% modified polypropylene resin and 15wt% nonionic surfactant.

[0063] The preparation method of the anti-fog masterbatch in this embodiment is the same as that of the anti-fog masterbatch in Example 1.

[0064] This embodiment also provides a BOPP anti-fog film, comprising an anti-fog surface layer, a core layer, and a lower surface layer arranged sequentially. The components and contents of each layer are as follows:

[0065] Anti-fog surface layer: 98wt% homopolymer polypropylene resin and 2wt% anti-fog masterbatch of this embodiment;

[0066] Core layer: 97wt% homopolymer polypropylene resin and 3wt% antifog masterbatch of this embodiment;

[0067] Bottom layer: 95wt% homopolymer polypropylene resin and 5wt% anti-blocking masterbatch.

[0068] The preparation method of the BOPP anti-fog film in this embodiment is the same as that of the BOPP anti-fog film in Example 1.

[0069] The total thickness and the thickness of each layer of the BOPP anti-fog film in this embodiment are the same as those of the BOPP anti-fog film in Embodiment 1.

[0070] Comparative Example 1

[0071] This comparative example provides an antifogging masterbatch comprising 55 wt% homopolymer polypropylene resin, 40 wt% modified polypropylene resin, and 5 wt% nonionic surfactant.

[0072] The preparation method of the anti-fog masterbatch in this comparative example is the same as that of the anti-fog masterbatch in Example 1.

[0073] This comparative example also provides a BOPP anti-fog film, comprising an anti-fog surface layer, a core layer, and a lower surface layer arranged sequentially. The components and contents of each layer are as follows:

[0074] Anti-fog surface layer: 98wt% homopolymer polypropylene resin and 2wt% anti-fog masterbatch of this comparative ratio;

[0075] Core layer: 96wt% homopolymer polypropylene resin and 4wt% antifog masterbatch of this comparative example;

[0076] Bottom layer: 95wt% homopolymer polypropylene resin and 5wt% anti-blocking masterbatch.

[0077] The preparation method of the BOPP antifog film in this comparative example is the same as that of the BOPP antifog film in Example 1.

[0078] The total thickness and the thickness of each layer of the BOPP antifog film in this comparative example are the same as those of the BOPP antifog film in Example 1.

[0079] Comparative Example 2

[0080] This comparative example provides an antifogging masterbatch comprising 35 wt% homopolymer polypropylene resin, 40 wt% modified polypropylene resin, and 25 wt% nonionic surfactant.

[0081] The preparation method of the anti-fog masterbatch in this comparative example is the same as that of the anti-fog masterbatch in Example 1.

[0082] This comparative example also provides a BOPP anti-fog film, comprising an anti-fog surface layer, a core layer, and a lower surface layer arranged sequentially. The components and contents of each layer are as follows:

[0083] Anti-fog surface layer: 98wt% homopolymer polypropylene resin and 2wt% anti-fog masterbatch of this comparative ratio;

[0084] Core layer: 96wt% homopolymer polypropylene resin and 4wt% antifog masterbatch of this comparative example;

[0085] Bottom layer: 95wt% homopolymer polypropylene resin and 5wt% anti-blocking masterbatch.

[0086] The preparation method of the BOPP antifog film in this comparative example is the same as that of the BOPP antifog film in Example 1.

[0087] The total thickness and the thickness of each layer of the BOPP antifog film in this comparative example are the same as those of the BOPP antifog film in Example 1.

[0088] Comparative Example 3

[0089] This comparative example provides an antifogging masterbatch comprising 55 wt% homopolymer polypropylene resin, 35 wt% modified polypropylene resin, and 10 wt% nonionic surfactant.

[0090] The preparation method of the anti-fog masterbatch in this comparative example is the same as that of the anti-fog masterbatch in Example 1.

[0091] This comparative example also provides a BOPP anti-fog film, comprising an anti-fog surface layer, a core layer, and a lower surface layer arranged sequentially. The components and contents of each layer are as follows:

[0092] Anti-fog surface layer: 98wt% homopolymer polypropylene resin and 2wt% anti-fog masterbatch of this comparative ratio;

[0093] Core layer: 96wt% homopolymer polypropylene resin and 4wt% antifog masterbatch of this comparative example;

[0094] Bottom layer: 95wt% homopolymer polypropylene resin and 5wt% anti-blocking masterbatch.

[0095] The preparation method of the BOPP antifog film in this comparative example is the same as that of the BOPP antifog film in Example 1.

[0096] The total thickness and the thickness of each layer of the BOPP antifog film in this comparative example are the same as those of the BOPP antifog film in Example 1.

[0097] Comparative Example 4

[0098] This comparative example provides an antifogging masterbatch comprising 35 wt% homopolymer polypropylene resin, 55 wt% modified polypropylene resin, and 10 wt% nonionic surfactant.

[0099] The preparation method of the anti-fog masterbatch in this comparative example is the same as that of the anti-fog masterbatch in Example 1.

[0100] This comparative example also provides a BOPP anti-fog film, comprising an anti-fog surface layer, a core layer, and a lower surface layer arranged sequentially. The components and contents of each layer are as follows:

[0101] Anti-fog surface layer: 98wt% homopolymer polypropylene resin and 2wt% anti-fog masterbatch of this comparative ratio;

[0102] Core layer: 96wt% homopolymer polypropylene resin and 4wt% antifog masterbatch of this comparative example;

[0103] Bottom layer: 95wt% homopolymer polypropylene resin and 5wt% anti-blocking masterbatch.

[0104] The preparation method of the BOPP antifog film in this comparative example is the same as that of the BOPP antifog film in Example 1.

[0105] The total thickness and the thickness of each layer of the BOPP antifog film in this comparative example are the same as those of the BOPP antifog film in Example 1.

[0106] Comparative Example 5

[0107] This comparative example provides an antifogging masterbatch, comprising 50 wt% homopolymer polypropylene resin and 50 wt% modified polypropylene resin.

[0108] The preparation method of the anti-fog masterbatch in this comparative example is the same as that of the anti-fog masterbatch in Example 1.

[0109] This comparative example also provides a BOPP anti-fog film, comprising an anti-fog surface layer, a core layer, and a lower surface layer arranged sequentially. The components and contents of each layer are as follows:

[0110] Anti-fog surface layer: 98wt% homopolymer polypropylene resin and 2wt% anti-fog masterbatch of this comparative ratio;

[0111] Core layer: 96wt% homopolymer polypropylene resin and 4wt% antifog masterbatch of this comparative example;

[0112] Bottom layer: 95wt% homopolymer polypropylene resin and 5wt% anti-blocking masterbatch.

[0113] The preparation method of the BOPP antifog film in this comparative example is the same as that of the BOPP antifog film in Example 1.

[0114] The total thickness and the thickness of each layer of the BOPP antifog film in this comparative example are the same as those of the BOPP antifog film in Example 1.

[0115] Comparative Example 6

[0116] This comparative example provides an antifogging masterbatch, comprising 80 wt% homopolymer polypropylene resin and 20 wt% nonionic surfactant; wherein the nonionic surfactant comprises 42 wt% octadecanoic acid-2-[2-(hydroxyethyl)octadecanoic acid ethyl ester], 28 wt% diethanolamine stearate and 30 wt% stearic acid ethoxylated amine.

[0117] The preparation method of the anti-fog masterbatch in this comparative example is the same as that of the anti-fog masterbatch in Example 1.

[0118] This comparative example also provides a BOPP anti-fog film, comprising an anti-fog surface layer, a core layer, and a lower surface layer arranged sequentially. The components and contents of each layer are as follows:

[0119] Anti-fog surface layer: 98wt% homopolymer polypropylene resin and 2wt% anti-fog masterbatch of this comparative ratio;

[0120] Core layer: 96wt% homopolymer polypropylene resin and 4wt% antifog masterbatch of this comparative example;

[0121] Bottom layer: 95wt% homopolymer polypropylene resin and 5wt% anti-blocking masterbatch.

[0122] The preparation method of the BOPP antifog film in this comparative example is the same as that of the BOPP antifog film in Example 1.

[0123] The total thickness and the thickness of each layer of the BOPP antifog film in this comparative example are the same as those of the BOPP antifog film in Example 1.

[0124] Performance testing:

[0125] (1) Production smoothness: Observe whether the production of BOPP anti-fog film is smooth;

[0126] (2) Contact angle test: Tested according to standard ISO 19403-1;

[0127] (3) Heat fog protection test:

[0128] Test conditions:

[0129] a) Wide-mouth beaker: capacity 250mL, outer diameter (70±2)mm, total height (95±2)mm;

[0130] b) Stopwatch: accuracy not less than 1 second;

[0131] c) Constant temperature water bath: The constant temperature range is room temperature to 90℃, and the temperature control accuracy is not less than 1℃;

[0132] d) Thermometer: Measuring up to 90℃, with a scale division of 0.1℃;

[0133] e) Sampling Requirements: Samples should be taken evenly along the entire width of the BOPP anti-fog film, and the surface must be free of wrinkles, impurities, or other appearance defects that could affect the test results. The sample size is (120±3)mm × (120±3)mm, and it must completely cover the mouth of the beaker. Samples of the same shape and size should be used in each group of tests, and each group should be tested in triplicate. If the results are inconsistent, two additional tests are required; if three different grades of results appear in a single group of tests, the test should be repeated.

[0134] f) Sample conditions: BOPP antifog films of Examples 1-3 and Comparative Examples 1-6.

[0135] Test Procedure: Place the wide-mouth beaker on the standard logarithmic near vision chart according to GB 11533-2011, aligning the center of the bottom of the beaker with the 0.1 center line of the chart. Pour in (200±10) mL of Grade III water conforming to GB / T 6682-2008, maintaining the water temperature at (85±2)℃. Quickly fix the sample with double-sided tape or a rubber band, ensuring the anti-fogging performance test surface is flush with the beaker opening, keeping the test area flat. Start timing at this point; the test duration is 60 seconds. The total time for fixing the sample should not exceed 20 seconds. At 60 seconds, observe the surface condition of the thin film sample from top to bottom, perpendicular to the bottom of the beaker, under natural light or a 40W fluorescent lamp. The observation should be completed within 5 seconds.

[0136] Additional evaluation criteria for testing: Since the observation criteria under GB 11533-2011 do not provide further subdivisions for the final effect, this section further categorizes the final anti-fog effect according to the rating of GB / T 31726-2015 to comprehensively evaluate the final effect. The specific categorization criteria are as follows:

[0137]

[0138] Among them, grades A, B, C, D, and E correspond to grades 5, 4, 3, 2, and 1 in GB / T 31726-2015, respectively.

[0139] (4) Anti-cold fog test:

[0140] The test conditions are basically the same as those for the heat fog protection test, with the following differences:

[0141] c) Constant temperature water bath: constant temperature range 0℃~10℃, temperature control accuracy not less than 1℃;

[0142] d) Thermometer: can measure 23℃, with a scale division of 0.1℃.

[0143] Test Procedure: Pour (200±10) mL of Grade III water conforming to GB / T 6682-2008 standard into a wide-mouth beaker, and control the water temperature at (23±2)℃. Fix the sample with double-sided tape or rubber band, ensuring the anti-fog test surface is tightly attached to the mouth of the beaker and the test area is flat. Place the beaker with the fixed sample in a 0℃ low-temperature incubator or refrigerator and start timing immediately. After 5 minutes, remove the beaker with the sample and place it on the GB 11533-2011 standard logarithmic near vision chart, aligning the center of the bottom of the beaker with the 0.1 center line of the chart. Under natural light or 40W fluorescent lamp illumination, observe the surface condition of the thin film sample from top to bottom, perpendicular to the bottom of the beaker. The observation process should be completed within 5 seconds.

[0144] Additional evaluation criteria for testing: Same as the evaluation criteria for heat fog prevention.

[0145] (5) Anti-fog activation time: After the film is produced, the film is placed in a normal temperature and pressure environment. If the anti-fog effect reaches level C or above in the above-mentioned anti-cold fog or anti-heat fog test, it indicates that the anti-fog effect is activated and the anti-fog activation time (days) is recorded. In addition, the effective anti-cold fog or anti-heat fog level can be recorded as the level of (3) and (4) above.

[0146] (6) Durability of cold / hot fog protection: The fog protection level shall be re-evaluated every 30 days according to the above-mentioned standards for hot fog protection test and cold fog protection test; when the fog protection level drops to below level C (excluding level C), the duration (months) shall be recorded.

[0147] (7) Sealing strength: The BOPP anti-fog films of Examples 1-3 and Comparative Examples 1-6 were made into packaging bags similar to those for packaging vegetables, fruits, fresh produce, and frozen foods. Self-adhesive (pressure-sensitive adhesive) was applied to one side of the opening of the packaging bag. After removing the release film on the self-adhesive, it was bonded to the film on the other side of the opening to achieve sealing. After storing the above packaging bags at an ambient humidity of 80% for 3 months, it was observed whether there was any problem with the sealing being weak.

[0148] The results are as follows:

[0149] Table 1. Performance evaluation results of BOPP antifog films in Examples 1-3 and Comparative Examples 1-6

[0150]

[0151] The anti-fogging masterbatch in Examples 1-3 of this invention, by adding 40-50wt% modified polypropylene resin and 10-20wt% nonionic surfactant, allows the anti-fogging masterbatch to be added to both the anti-fogging surface layer and the core layer of the BOPP anti-fogging film. The resulting BOPP anti-fogging film exhibits rapid anti-cold / hot fogging effects on the anti-fogging surface layer, providing a strong and long-lasting anti-fogging effect on droplets. Furthermore, when the BOPP anti-fogging film of this invention is used as packaging bags for fresh fruits and vegetables and other food products, the good compatibility between the butyl acrylate grafted chains and the acrylate system of the pressure-sensitive adhesive increases the initial viscosity of the bond between the film and the pressure-sensitive adhesive. Additionally, the epoxy groups in glycidyl methacrylate can react with the carboxyl or hydroxyl groups in the pressure-sensitive adhesive under pressure in a humid environment to form chemical bonds, thus enhancing the adhesion between the film surface and the pressure-sensitive adhesive. This results in a firmly bonded packaging bag that is difficult to open after sealing.

[0152] The amount of nonionic surfactant added in the antifog masterbatch of Comparative Example 1 was too low, resulting in a relatively poor antifog effect of the BOPP antifog film of Comparative Example 1, a slower onset time, and relatively weak antifog effect durability.

[0153] The excessive amount of nonionic surfactant in the antifogging masterbatch of Comparative Example 2 caused the BOPP antifogging film of Comparative Example 2 to easily precipitate and aggregate nonionic surfactant on the film surface during production. This resulted in uneven antifogging performance and easily led to excessive water spreading on the antifogging surface, forming an excessively thick water layer or even water flow. This caused light scattering, resulting in localized whitening and blurring of the antifogging surface, failing to achieve the ideal transparent water film effect, and exhibiting poor antifogging durability. Furthermore, the BOPP antifogging film of Comparative Example 2 was prone to opening problems when used to seal packaging bags with pressure-sensitive adhesive.

[0154] The amount of modified polypropylene resin added to the antifog masterbatch of Comparative Example 3 was too low, resulting in uneven antifog effect of the BOPP antifog film in Comparative Example 3 and relatively poor antifog durability.

[0155] The amount of modified polypropylene resin added to the antifog masterbatch in Comparative Example 4 is too high, which can easily lead to oversaturation of the hydrophilic groups on the surface of the antifog layer, excessive aggregation of the water film on the surface of the antifog layer, failure to form a uniform water film, relatively poor antifog effect, and the antifog effect is not long-lasting.

[0156] No nonionic surfactants were added to the antifog masterbatch of Comparative Example 5, and the antifog effect of the BOPP antifog film of Comparative Example 5 was relatively poor.

[0157] In Comparative Example 6, no modified polypropylene resin was added to the anti-fog masterbatch. During the production process of the BOPP anti-fog film of Comparative Example 6, the compatibility between the nonionic surfactant and the homopolymer polypropylene resin was relatively poor. The nonionic surfactant was prone to precipitation and aggregation on the film surface, and the anti-fog durability was poor. The BOPP anti-fog film of Comparative Example 6 was prone to opening problems when used to seal packaging bags with pressure-sensitive adhesive.

[0158] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and the present invention also intends to include these modifications and variations.

Claims

1. An anti-fog masterbatch characterized in that: The composition comprises 40-50 wt% homopolymer polypropylene resin, 40-50 wt% modified polypropylene resin and 10-20 wt% non-ionic surfactant; the modified polypropylene resin is obtained by grafting modification of polypropylene with butyl acrylate, glycidyl methacrylate and maleic anhydride; the non-ionic surfactant comprises 40-45 wt% octadecanoic acid-2-[2- (hydroxyethyl) octadecylaminoethyl ester], 25-30 wt% stearic acid diethanolamine and 25-35 wt% stearic acid-based ethoxylated amine.

2. The anti-fog masterbatch according to claim 1, characterized in that: The preparation method of the modified polypropylene resin comprises the following steps: Premixing: 100 parts of homopolymer polypropylene, 2-4 parts of molten maleic anhydride, 11-13 parts of butyl acrylate and 0.1-0.3 parts of antioxidant are put into a high-speed mixer, mixed at 400-600 rpm for 6-10 minutes to obtain a premix; Melt grafting: the premix is added into a double-screw extruder through a main feeding port, and the temperature zones of the double-screw extruder are set as follows: 170℃ for zone 1-2, 180℃ for zone 3, 195℃ for zone 4-5, 185℃ for zone 6-7 and 175℃ for zone 8 to form an extruded strip; wherein, 7-9 parts of glycidyl methacrylate and 0.1-0.3 parts of initiator DCP are injected into zone 3; the vacuum degree of zone 6-7 is - (0.095-0.1) MPa; Purification: the extruded strip is water-cooled, granulated, extracted with boiling acetone in a Soxhlet extractor and vacuum dried to constant weight to obtain the modified polypropylene resin.

3. The anti-fog masterbatch according to claim 1, characterized in that: The melt index of the homopolymer polypropylene resin is 6.0-7.0 g / 10 min.

4. The anti-fog masterbatch according to claim 1, characterized in that: The melt index of the modified polypropylene resin is 9-11 g / 10 min.

5. A process for the preparation of an anti-fog masterbatch according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: After the raw materials of each layer are mixed, they are added to a screw machine for melt extrusion, and then underwater wire drawing and granulation are performed to obtain the anti-fog master batch.

6. A BOPP anti-fog film characterized in that: The anti-fog master batch comprises the following steps:

7. The BOPP anti-fog film according to claim 6, characterized in that: The core layer comprises homopolymer polypropylene resin and 2-4 wt% of the anti-fog master batch according to any one of claims 1-4.

8. The BOPP anti-fog film according to claim 6, characterized in that: The lower surface layer comprises homopolymer polypropylene resin and an anti-blocking master batch.

9. A process for the preparation of a BOPP anti-fog film as claimed in any one of claims 7-8, characterized in that: The method comprises the following steps: After the raw materials of each layer are weighed according to the proportion, they are added to the extruders, melt-plasticized, metered by a metering pump, combined and extruded at the die head of different extruders, and then drawn into thick sheets by a chill roll, cut into the required size, stretched in a static stretching machine and prepared into a film; after the film is treated by corona discharge, a finished product is obtained.

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