Anti-fog high-transparency BOPP heat-sealing film and preparation method thereof

Abstract

The invention provides an anti-fog high-transmittance BOPP heat-sealing film and a preparation method thereof.The anti-fog high-transmittance BOPP heat-sealing film comprises a matrix film and anti-reflection anti-fog films compounded on the upper surface and the lower surface of the matrix film, the matrix film is prepared from raw materials including co-polypropylene, a composite nucleating agent and a first auxiliary agent, the composite nucleating agent is prepared from dicarboxylic acid metal salt and rare earth elements, and the first auxiliary agent is prepared from a second auxiliary agent; the anti-reflection antifogging film is prepared from raw materials including low-density polyethylene, a composite antifogging agent and a second auxiliary agent, and the composite antifogging agent is formed by compounding polyglycerol fatty acid ester and glyceryl monostearate. According to the anti-fog and high-transmittance BOPP heat-sealing film disclosed by the invention, the stability of the BOPP heat-sealing film is improved through interaction of glyceryl monostearate and polyglycerol fatty acid ester in the composite anti-fog agent which is added into the anti-reflection and anti-fog film and cooperates with the composite anti-fog agent, and the BOPP heat-sealing film disclosed by the invention can continuously play an anti-fog role for a long time.

Description

Technical Field

[0001] The invention belongs to the field of BOPP heat-sealing film preparation, and in particular relates to an anti-fog high-transmittance BOPP heat-sealing film and a preparation method thereof. Background Art

[0002] BOPP heat-sealing film refers to biaxially oriented polypropylene film, which is a plastic film material prepared by a specific process. BOPP heat-sealing film is made by co-extruding polypropylene particles into sheets and then stretching them in both the longitudinal and transverse directions. Due to the orientation of the stretched molecules, this film has good physical stability, mechanical strength, and air tightness, high transparency and gloss, and is tough and wear-resistant. It is a widely used printing film.

[0003] In terms of improving the anti-fogging performance of BOPP heat-sealing film, the existing technology generally uses anti-fogging agents. Anti-fogging agents are mainly divided into internal addition type and external coating type. Internal addition anti-fogging agents are mixed with PP resin during the film production process, and commonly used ones are polyol fatty acid esters, polyglycerol fatty acid esters, etc. These anti-fogging agents can reduce the surface tension of the film surface, so that water vapor forms a uniform water film on the film surface instead of water droplets, thereby achieving an anti-fogging effect. For example, sorbitan monostearate (Span60) is a commonly used polyol fatty acid ester anti-fogging agent, and the addition amount is generally around 1% - 3%.

[0004] In order to improve the light transmittance of BOPP heat-sealing film, the existing technology will add nucleating agents. Nucleating agents can promote the crystallization of PP resin, refine the grains, and reduce the scattering of light. Common nucleating agents include organic phosphates, sorbitol, etc. For example, the dibenzylidene sorbitol (DBS) nucleating agent, the addition amount is generally around 0.1% - 0.3%, which can reduce the haze of BOPP heat-sealing film by 10% - 20%.

[0005] However, the addition of antifogging agents and nucleating agents to achieve antifogging and light transmission properties will lead to unstable antifogging performance of BOPP heat-sealing film over time and reduced transparency of the film. Summary of the invention

[0006] In view of this, the present invention aims to overcome the technical problems in the prior art that the anti-fog performance of BOPP heat-sealing film is unstable after a long time and the transparency of the film is reduced, and proposes an anti-fog and high-transparency BOPP heat-sealing film and a preparation method thereof.

[0007] To achieve the above object, the technical solution of the present invention is achieved as follows: In the first aspect, the present invention provides an anti-fog and high-transmittance BOPP heat-sealing film, comprising a base film and an anti-reflection anti-fog film composited on the upper and lower surfaces of the base film, wherein the base film is prepared from raw materials comprising copolymerized polypropylene, a composite nucleating agent and a first auxiliary agent, the composite nucleating agent comprises a dicarboxylic acid metal salt and a rare earth element, the anti-reflection anti-fog film is prepared from raw materials comprising low-density polyethylene, a composite anti-fog agent and a second auxiliary agent, and the composite anti-fog agent is compounded from polyglycerol fatty acid ester and glyceryl monostearate.

[0008] In some embodiments of the present invention, the base film comprises the following constituent materials in parts by weight: 50-80 parts of copolymerized polypropylene, 1-10 parts of a composite nucleating agent, and 1-15 parts of a first auxiliary agent.

[0009] In some embodiments of the present invention, the mass ratio of the dicarboxylic acid metal salt to the rare earth element in the composite nucleating agent is 5:(1-3).

[0010] In some embodiments of the present invention, the mass ratio of the dicarboxylic acid metal salt to the rare earth element in the composite nucleating agent is 5:1.

[0011] The carboxyl groups of the dicarboxylic acid metal salts will attract each other with a small amount of polar groups in the copolymerized polypropylene molecular chain. This interaction makes the polymer molecular chains adsorbed and orderly arranged on the surface of the composite nucleating agent, reducing the nucleation free energy of polymer crystallization. At the same time, the growth direction of the spherulites is restricted to a certain extent, thereby reducing the size of the spherulites.

[0012] Rare earth elements have special electronic structures and chemical properties. Rare earth element ions can form coordination bonds with copolymerized polypropylene molecular chains. This coordination bond makes the copolymerized polypropylene molecular chains locally ordered around the rare earth elements, playing a role in inducing crystallization. Moreover, rare earth elements can also regulate the crystallization kinetics of polymers, changing the growth mode of crystals from spherulite growth to fibrous crystal growth, which helps to improve the mechanical properties of the base film.

[0013] Dicarboxylic acid metal salts and rare earth elements cooperate synergistically to complement the nucleation sites in copolymerized polypropylene. Dicarboxylic acid metal salts provide nucleation sites based on polar interactions, while rare earth elements provide nucleation sites based on coordination. Dicarboxylic acid metal salts mainly affect the initial stage of crystallization, increase the crystallization temperature and initial crystallization speed; rare earth elements have an important influence on the morphology and speed of the crystal growth stage. Their combined effect can make the crystallization process more uniform and rapid. Secondly, the synergistic effect of the two can optimize the crystal morphology. By limiting the excessive growth of spherulites, it promotes the formation of a smaller and more uniform crystal structure. This is because the co-existence of dicarboxylic acid metal salts and rare earth elements constrains the polymer molecular chain in multiple directions, thereby changing the growth mode of the crystal, obtaining a crystal morphology with better physical properties, and can ensure that the transparency and mechanical properties of the BOPP heat-sealing film do not decrease for a long time.

[0014] In some embodiments of the present invention, the rare earth element is a rare earth oxide or a rare earth stearate, and the rare earth oxide is one or a mixture of two or more of lanthanum oxide, cerium oxide, cerium stearate, and lanthanum stearate.

[0015] In some embodiments of the present invention, the dicarboxylic acid metal salt is one or a mixture of two or more of dicarboxylic acid sodium salt, dicarboxylic acid potassium salt, dicarboxylic acid zinc salt, dicarboxylic acid calcium salt or dicarboxylic acid barium salt, such as barium glutarate, potassium suberate, zinc suberate, calcium pimelate, sodium glutarate, calcium phthalate, zinc adipate, etc.

[0016] In some embodiments of the present invention, the anti-reflection and anti-fog film comprises the following constituent materials in parts by weight: 45-90 parts of low-density polyethylene, 1-3 parts of a composite anti-fog agent, and 1-3 parts of a second auxiliary agent.

[0017] In some embodiments of the present invention, the mass ratio of polyglycerol fatty acid ester to glyceryl monostearate in the composite anti-fog agent is (1-5):10.

[0018] In some embodiments of the present invention, the mass ratio of polyglycerol fatty acid ester to glyceryl monostearate in the composite anti-fog agent is 3:10.

[0019] The hydrophilicity and surface tension reduction effects of polyglycerol fatty acid esters combined with the dispersion and auxiliary film-forming effects of glycerol monostearate can more effectively prevent the generation of fog. Polyglycerol fatty acid esters attract and disperse water vapor, and glycerol monostearate ensures that this anti-fog effect can continue and evenly cover the surface of the material. In addition, the combination of the two can also improve the stability and durability of the anti-fog film. The film formed by the interaction between glycerol monostearate and polyglycerol fatty acid esters is more stable. This stable anti-fog film can resist interference from external environmental factors. Improve the compatibility and applicability of anti-fog agents: The combination of the two can make the anti-fog agent better compatible with low-density polyethylene and copolymer polypropylene materials. This synergistic anti-fog agent can better adhere to the surface of the material and play an anti-fog role.

[0020] In a first aspect, the present invention provides a method for preparing an anti-fog high-transmittance BOPP heat-sealing film, comprising the following steps: S1: drying the copolymerized polypropylene, the composite nucleating agent and the first auxiliary agent, mixing and stirring them evenly, and then putting them into a twin-screw extruder for melt extrusion and granulation to obtain a matrix masterbatch; S2: drying the low-density polyethylene, the composite antifogging agent and the second auxiliary agent, mixing and stirring them evenly, and then putting them into a twin-screw extruder for melt extrusion and granulation to obtain an anti-transmission masterbatch; S3: The base masterbatch and the anti-transmittance and anti-fog masterbatch are co-extruded through a three-layer co-extrusion die head. After the melt sheet is cooled and formed, longitudinal stretching and transverse stretching are performed in sequence to obtain an anti-fog and high-transmittance BOPP heat-sealing film.

[0021] Compared with the prior art, the present invention has the following advantages: (1) The anti-fog and high-transmittance BOPP heat-sealing film of the present invention reduces the size of crystals by adding a synergistic composite nucleating agent to the base film, which is beneficial to improving the physical properties of the BOPP heat-sealing film; (2) The anti-fog and high-transmittance BOPP heat-sealing film of the present invention improves the stability of the BOPP heat-sealing film by adding glyceryl monostearate and polyglycerol fatty acid ester in the synergistic composite anti-fogging agent to the anti-transmittance anti-fogging film, so that the BOPP heat-sealing film of the present invention can continuously exert the anti-fogging effect for a long time. DETAILED DESCRIPTION

[0022] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be understood as limiting the present invention.

[0023] Unless defined otherwise herein, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0024] Where values ​​are described herein as a range, it should be understood that such disclosure includes disclosure of all possible sub-ranges within that range, as well as specific values ​​falling within that range, regardless of whether a specific value or a specific sub-range is explicitly stated.

[0025] In this document, "multiple" and the like, unless otherwise specified, refer to a number greater than 2 or equal to 2. For example, "one or more" means one or greater than or equal to two.

[0026] In this document, the terms “preferred” and “more preferred” are only used to describe implementation methods or examples with better effects, and it should be understood that they do not constitute limitations on the scope of protection of the present invention.

[0027] In this document, the words "further" and the like are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of the present invention.

[0028] In this article, the term "and / or" is a description of the association relationship of objects, indicating that three relationships may exist. For example, A and / or B means: A or B, or A and B.

[0029] The terms “include,” “including,” “have,” “contain,” etc. used in this article are open-ended terms, meaning including but not limited to.

[0030] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the invention pertains. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention.

[0031] The present invention will be described in detail below with reference to the embodiments.

[0032] Example 1

[0033] An anti-fog high-transmittance BOPP heat-sealing film comprises the following components in parts by weight: Base film: 65 parts of copolymerized polypropylene, 5 parts of composite nucleating agent, and 5 parts of antioxidant 168, wherein the composite nucleating agent is compounded by barium glutarate and lanthanum oxide in a mass ratio of 5:2.

[0034] Anti-reflection and anti-fog film: 85 parts of low-density polyethylene, 2 parts of composite anti-fog agent, 3 parts of antioxidant 168, wherein the composite anti-fog agent is compounded by polyglycerol fatty acid ester and glyceryl monostearate in a mass ratio of 1:2.

[0035] The preparation method of the above-mentioned anti-fog high-transmittance BOPP heat-sealing film comprises the following steps: S1: drying the copolymerized polypropylene, the composite nucleating agent and the first auxiliary agent (antioxidant 168), mixing and stirring them evenly, and then putting them into a twin-screw extruder for melt extrusion and granulation at 250°C to obtain a matrix masterbatch; S2: low-density polyethylene, composite antifogging agent and second auxiliary agent (antioxidant 168) are dried, mixed and stirred evenly, and then put into a twin-screw extruder for melt extrusion and granulation at 250°C to obtain anti-transmission masterbatch; S3: The matrix masterbatch and the anti-transmittance and anti-fog masterbatch are co-extruded through a three-layer co-extrusion die head. After the melt sheet is cooled and formed at 30°C, it is longitudinally stretched and transversely stretched in sequence to obtain an anti-fog and high-transmittance BOPP heat-sealing film.

[0036] Example 2

[0037] An anti-fog high-transmittance BOPP heat-sealing film comprises the following components in parts by weight: Base film: 50 parts of copolymerized polypropylene, 1 part of composite nucleating agent, and 1 part of antioxidant 168, wherein the composite nucleating agent is compounded by zinc suberate and lanthanum stearate in a mass ratio of 5:3.

[0038] Anti-reflection and anti-fog film: 90 parts of low-density polyethylene, 3 parts of composite anti-fog agent, 2 parts of antioxidant 168, wherein the composite anti-fog agent is compounded by polyglycerol fatty acid ester and glyceryl monostearate in a mass ratio of 1:10.

[0039] The preparation method of the above-mentioned anti-fog high-transmittance BOPP heat-sealing film comprises the following steps: S1: drying the copolymerized polypropylene, the composite nucleating agent and the first auxiliary agent (antioxidant 168), mixing and stirring them evenly, and then putting them into a twin-screw extruder for melt extrusion and granulation at 250°C to obtain a matrix masterbatch; S2: low-density polyethylene, composite antifogging agent and second auxiliary agent (antioxidant 168) are dried, mixed and stirred evenly, and then put into a twin-screw extruder for melt extrusion and granulation at 250°C to obtain anti-transmission masterbatch; S3: The matrix masterbatch and the anti-transmittance and anti-fog masterbatch are co-extruded through a three-layer co-extrusion die head. After the melt sheet is cooled and formed at 30°C, it is longitudinally stretched and transversely stretched in sequence to obtain an anti-fog and high-transmittance BOPP heat-sealing film.

[0040] Example 3

[0041] An anti-fog high-transmittance BOPP heat-sealing film comprises the following components in parts by weight: Base film: 80 parts of copolymerized polypropylene, 10 parts of composite nucleating agent, and 15 parts of antioxidant 168, wherein the composite nucleating agent is compounded by calcium phthalate and cerium oxide in a mass ratio of 5:1.

[0042] Anti-reflection and anti-fog film: 45 parts of low-density polyethylene, 1 part of composite anti-fog agent, 1 part of antioxidant 168, wherein the composite anti-fog agent is compounded by polyglycerol fatty acid ester and glyceryl monostearate in a mass ratio of 3:10.

[0043] The preparation method of the above-mentioned anti-fog high-transmittance BOPP heat-sealing film comprises the following steps: S1: drying the copolymerized polypropylene, the composite nucleating agent and the first auxiliary agent (antioxidant 168), mixing and stirring them evenly, and then putting them into a twin-screw extruder for melt extrusion and granulation at 250°C to obtain a matrix masterbatch; S2: low-density polyethylene, composite antifogging agent and second auxiliary agent (antioxidant 168) are dried, mixed and stirred evenly, and then put into a twin-screw extruder for melt extrusion and granulation at 250°C to obtain anti-transmission masterbatch; S3: The matrix masterbatch and the anti-transmittance and anti-fog masterbatch are co-extruded through a three-layer co-extrusion die head. After the melt sheet is cooled and formed at 30°C, it is longitudinally stretched and transversely stretched in sequence to obtain an anti-fog and high-transmittance BOPP heat-sealing film.

[0044] Comparative Example 1 The raw material ratio and preparation method of Example 1 were used for preparation, except that lanthanum oxide was not added to the composite nucleating agent.

[0045] Comparative Example 2 The composite nucleating agent was prepared according to the raw material ratio and preparation method of Example 1, except that barium glutarate was not added to the composite nucleating agent.

[0046] Comparative Example 3 The composite antifogging agent was prepared according to the raw material ratio and preparation method of Example 1, except that no polyglycerol fatty acid ester was added to the composite antifogging agent.

[0047] Comparative Example 4 The composite antifogging agent was prepared according to the raw material ratio and preparation method of Example 1, except that glyceryl monostearate was not added to the composite antifogging agent.

[0048] Comparative Example 5 The composite nucleating agent was prepared according to the raw material ratio and preparation method of Example 1, except that the mass ratio of barium glutarate to lanthanum oxide in the composite nucleating agent was 5:4.

[0049] Comparative Example 6 The composite antifogging agent was prepared according to the raw material ratio and preparation method of Example 1, except that the mass ratio of the composite antifogging agent in the composite nucleating agent was 3:5.

[0050] Performance Testing: (1) Anti-fog performance test The anti-fog performance of the BOPP heat-sealed films obtained in Examples 1-3 and Comparative Examples 1-6 was tested by the cold fog method in the national standard GB / T31726-2015 Anti-fog Test Method for Plastic Films. The anti-fog grade judgment criteria are as follows: Grade 1, completely transparent, no water droplets. The clarity of the eye chart is exactly the same as before the test; Grade 2, good transparency, a small amount of uneven large water droplets, and the clarity of the eye chart of more than 50% area is exactly the same as before the test; Grade 3, basically transparent, with more water droplets, and the font of the eye chart is deformed; Grade 4, translucent, with many small water droplets, and a small amount of less than 0.1 of the eye chart is visible; 5, completely opaque, the eye chart is completely unclear; (2) Light transmission performance test The light transmittance of the BOPP heat-sealing films prepared in Examples 1-3 and Comparative Examples 1-6 was tested according to the national standard GB / T 2410-2008 “Determination of light transmittance and haze of transparent plastics”.

[0051] (3) Heat seal strength test According to the national standard GB / T10003-2008 "General Purpose Biaxially Oriented Polypropylene (BOPP) Film" heat sealing strength test, the heat sealing strength (N / 15mm) of the BOPP heat sealing films prepared in Examples 1-3 and Comparative Examples 1-6 was tested, and the sample was stretched at a rate of 300mm / min.

[0052] The test results are shown in Table 1.

[0053] Table 1 Performance test of BOPP heat-sealing films prepared in Examples 1-3 and Comparative Examples 1-11

[0054] It can be seen from the above table that the component selection and ratio of the dicarboxylic acid metal salt and the rare earth element in the composite antifogging agent and the polyglycerol fatty acid ester and glyceryl monostearate in the composite nucleating agent in the present invention can significantly improve the antifogging performance, transparency and heat sealing strength of the BOPP heat-sealing film, and the test results of the antifogging performance and transparency are relatively stable with the increase of the test time, and the change is small, which also shows that the antifogging performance and transparency of the BOPP heat-sealing film of the present invention are relatively stable.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An anti-fog high-transmittance BOPP heat-sealing film, characterized by: The invention comprises a base film and an anti-reflection and anti-fog film compounded on the upper and lower surfaces of the base film, wherein the base film is prepared from raw materials comprising copolymerized polypropylene, a composite nucleating agent and a first auxiliary agent, wherein the composite nucleating agent comprises a dicarboxylic acid metal salt and a rare earth element, and the anti-reflection and anti-fog film is prepared from raw materials comprising low-density polyethylene, a composite anti-fog agent and a second auxiliary agent, wherein the composite anti-fog agent is compounded from polyglycerol fatty acid ester and glyceryl monostearate.

2. The anti-fog high-transmittance BOPP heat-sealing film according to claim 1, characterized in that: The base film comprises the following constituent materials in parts by weight: 50-80 parts of copolymerized polypropylene, 1-10 parts of a composite nucleating agent and 1-15 parts of a first auxiliary agent.

3. The anti-fog high-transmittance BOPP heat-sealing film according to claim 1, characterized in that: The mass ratio of the dicarboxylic acid metal salt to the rare earth element in the composite nucleating agent is 5:(1-3).

4. The anti-fog high-transmittance BOPP heat-sealing film according to claim 1, characterized in that: The mass ratio of the dicarboxylic acid metal salt to the rare earth element in the composite nucleating agent is 5:

1.

5. The anti-fog high-transmittance BOPP heat-sealing film according to claim 1, characterized in that: The rare earth element is a rare earth oxide or a rare earth stearate, and the rare earth oxide is one or a mixture of two or more of lanthanum oxide, cerium oxide, cerium stearate, and lanthanum stearate.

6. The anti-fog high-transmittance BOPP heat-sealing film according to claim 1, characterized in that: The dicarboxylic acid metal salt is one of dicarboxylic acid sodium salt, dicarboxylic acid potassium salt, dicarboxylic acid zinc salt, dicarboxylic acid calcium salt or dicarboxylic acid barium salt, or a mixture of two or more thereof.

7. The anti-fog high-transmittance BOPP heat-sealing film according to claim 1, characterized in that: The anti-reflection and anti-fogging film comprises the following constituent materials in parts by weight: 45-90 parts of low-density polyethylene, 1-3 parts of a composite anti-fogging agent and 1-3 parts of a second auxiliary agent.

8. The anti-fog high-transmittance BOPP heat-sealing film according to claim 1, characterized in that: The mass ratio of polyglycerol fatty acid ester to glyceryl monostearate in the composite antifogging agent is (1-5):

10.

9. The anti-fog high-transmittance BOPP heat-sealing film according to claim 1, characterized in that: The mass ratio of polyglycerol fatty acid ester to glyceryl monostearate in the composite antifogging agent is 3:

10.

10. The method for preparing the anti-fog high-transmittance BOPP heat-sealing film according to any one of claims 1 to 9, characterized in that: The steps include: S1: drying the copolymerized polypropylene, the composite nucleating agent and the first auxiliary agent, mixing and stirring them evenly, and then putting them into a twin-screw extruder for melt extrusion and granulation to obtain a matrix masterbatch; S2: drying the low-density polyethylene, the composite antifogging agent and the second auxiliary agent, mixing and stirring them evenly, and then putting them into a twin-screw extruder for melt extrusion and granulation to obtain an anti-transmission masterbatch; S3: The base masterbatch and the anti-transmittance and anti-fog masterbatch are co-extruded through a three-layer co-extrusion die head. After the melt sheet is cooled and formed, longitudinal stretching and transverse stretching are performed in sequence to obtain an anti-fog and high-transmittance BOPP heat-sealing film.

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