CN117087261B - Packaging material with high brightness and luster and preparation method thereof - Google Patents

Abstract

The invention discloses a packaging material with high brightness, which sequentially comprises the following components from inside to outside: BOPP layer, aluminum foil layer, primer layer, ink layer and gloss oil layer; wherein the thickness of the BOPP layer is 18-38 μm, the thickness of the aluminum foil layer is 7-15 μm, and the thickness of the gloss oil layer is 2-10 μm. The ink layer is made of highlight ink, and the highlight ink comprises polymerized linseed oil, dibutyl hydroxyl toluene, terpineol, acetone, n-butyl acetate, maleated rosin glyceride resin, vinyl chloride-vinyl acetate, polyamide resin, activated benzidine yellow and hydroxylated aluminum powder. The invention has good glossiness, bright color and extremely high stability, and the obtained finished product packaging film is extremely suitable for packaging the block butter.

Description

A packaging material with high gloss and preparation method thereof

Technical Field

The invention relates to the technical field of packaging materials, and in particular to a packaging material with high gloss and a preparation method thereof.

Background technique

Packaging materials are the general name for containers, materials and auxiliary materials used in the circulation process to protect products, facilitate storage and transportation, promote sales, and according to certain technical methods. Among them, aluminum-plastic structure packaging is a packaging product that integrates various packaging advantages. It is not only low in cost and beautifully printed, but also has the characteristics of anti-static, UV protection, moisture-proof, oxygen-proof, light-shielding, cold-resistant, oil-resistant, high-temperature-resistant, fresh-keeping, oxygen-proof and easy-to-seal. It can be used in food packaging and has excellent prospects.

At present, the commonly used aluminum-plastic structure food packaging can be divided into two-layer, three-layer and four-layer composite. The block butter packaging is an aluminum-plastic structure with printing on the aluminum foil surface. Not only does the ordinary aluminum foil have low brightness and the printed color lacks metallic feel, but the existing aluminum-plastic packaging ink has low adhesion strength and poor heat resistance. Long-term exposure to sunlight or ultraviolet light will cause certain changes in its molecular chemical structure, causing fading and darkening of the color, thus affecting the use of printed packaging.

Summary of the invention

The purpose of the present invention is to solve the shortcomings of the prior art and to propose a packaging material with high gloss and a preparation method thereof.

A packaging material with high gloss, comprising from inside to outside: a BOPP layer, an aluminum foil layer, a primer layer, an ink layer and a varnish layer; wherein the thickness of the BOPP layer is 18-38 μm, the thickness of the aluminum foil layer is 7-15 μm, and the thickness of the varnish layer is 2-10 μm.

Preferably, the aluminum foil layer is made of soft food-grade aluminum foil material.

The method for preparing the packaging material having high gloss comprises the following steps:

S1. Mix waterborne polyurethane resin and water evenly, add film-forming aid and continue stirring for 1-2 hours to obtain a binder;

S2, mixing polyurethane acrylate, monofunctional acrylate monomer and photoinitiator to obtain a varnish composition;

S3. Apply adhesive on the surface of BOPP film, then stick aluminum foil on the adhesive, dry at 70-80℃, and age at 50-55℃ for 2-3 days;

S4. After the surface of the aluminum foil layer is primed, a high-gloss ink is printed, a varnish composition is applied, and ultraviolet light is cured to obtain a packaging material with a high-gloss gloss.

Preferably, in S1, the mass ratio of the waterborne polyurethane resin to the film-forming aid is 10-30:1-2.

Preferably, in S2, the photoinitiator is an α-hydroxyalkanone photoinitiator; the mass ratio of polyurethane acrylate, monofunctional acrylate monomer, and α-hydroxyalkanone photoinitiator is 5-10:1-5:0.1-1.

Preferably, in S3, the coating amount of the adhesive is 1.5-2 g/m ² .

Preferably, in S4, the highlight ink is prepared by the following steps: polymerized linseed oil, butylated hydroxytoluene, pinene alcohol, acetone, and n-butyl acetate are stirred for 10-20 minutes, the temperature is raised to 60-70°C, maleic rosin glycerol ester resin, vinyl chloride-vinyl acetate, and polyamide resin are added under stirring, stirring is continued for 1-2 hours, activated benzidine yellow and hydroxylated aluminum powder are added, and stirred evenly to obtain the highlight ink.

Preferably, the mass ratio of polymerized linseed oil, butylated hydroxytoluene, pinene alcohol, acetone, n-butyl acetate, maleic rosin glycerol ester resin, vinyl chloride-vinyl acetate, polyamide resin, activated benzidine yellow, and hydroxylated aluminum powder is 2-6:1-5:5-15:20-40:20-30:10-20:10-20:10-20:2-6:1-3.

Since benzidine yellow itself has relatively poor light resistance and adhesion, long-term exposure to sunlight or ultraviolet light will cause certain changes in its molecular chemical structure, causing fading and darkening of the color, thus affecting the use of printed materials.

In the activated benzidine yellow, benzidine yellow, calcium alginate and coconut oil are mixed, homogenized at 70-80°C for 1-2 minutes, and the homogenization pressure is 30-40MPa to obtain a prefabricated material; xanthan gum, hydroxypropyl-β-cyclodextrin, calcium lactate and water are mixed, stirred evenly at 70-80°C, the prefabricated material is added dropwise under stirring, and stirring is continued for 1-2 hours after the addition is complete, and the activated benzidine yellow is obtained by filtering, washing and drying.

More preferably, the mass ratio of benzidine yellow, calcium alginate, coconut oil, xanthan gum, hydroxypropyl-β-cyclodextrin and calcium lactate is 2-4:1-2:5-10:10-20:2-6:0.1-0.2.

Preferably, the hydroxylated aluminum powder is prepared by the following steps: washing the aluminum powder, adding it to ethanol and stirring for 10-30 minutes, adding triethanolamine under stirring, stirring at 70-80° C. for 1-3 hours, filtering, and washing to obtain the hydroxylated aluminum powder.

More preferably, the mass ratio of aluminum powder, ethanol and triethanolamine is 2-10:50-80:1-2.

The present invention adjusts the ink so that the aluminum powder and benzidine yellow have excellent dispersion and color development properties, the ink has bright color, excellent gloss, good fluidity, good printability, and is particularly suitable for printing on the surface of an aluminum foil layer, with significant effects.

Under the action of triethanolamine, the present invention performs hydroxylation on the surface of aluminum powder, which is not only conducive to the combination of aluminum powder and activated benzidine yellow, the synergistic effect of the two can greatly improve the brightness of the ink, and the high-brightness ink is printed on the surface of the aluminum foil layer with excellent adhesion. The ink can withstand more than 1,000 friction times and the heat-resistant temperature can reach more than 350°C, effectively improving product quality.

The high-gloss ink obtained by the present invention has excellent adhesion to the aluminum foil layer. After printing the high-gloss ink, a varnish layer is coated on the surface thereof, and after curing, the varnish layer can be firmly combined with the ink, so that the obtained packaging film has extremely high adhesion and durable usability. The preparation process of the present invention is simple, and the brightness of the obtained finished packaging film is significantly improved and improved compared with the general aluminum composite film. The obtained high-gloss ink has excellent heat resistance. When the obtained packaging film is in a high temperature state or contains high-temperature items, the ink is not easy to peel off, and the ink has good gloss, bright color and extremely high stability. The obtained finished packaging film of the present invention is very suitable for the packaging of block butter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a comparison chart of the 60° specular gloss of the high-gloss ink obtained in Example 5 and Comparative Examples 1-2 before and after exposure after curing.

FIG. 2 is a comparison chart of the barrier properties of the packaging materials obtained in Example 5 and Comparative Examples 1-2.

Detailed ways

The present invention will be further explained below in conjunction with specific embodiments.

Example 1

A packaging material with high gloss, comprising from inside to outside: a BOPP layer, an aluminum foil layer, a primer layer, an ink layer and a varnish layer.

The method for preparing the packaging material with high gloss comprises the following steps:

S1. Mix 10 g of waterborne polyurethane resin and 30 g of water, add 1 g of dodecyl alcohol ester and continue stirring for 1-2 hours to obtain a binder;

S2, 5 g of polyurethane acrylate, 1 g of ethyl acrylate (CAS No. 140-88-5), and 0.1 g of photoinitiator 160 were mixed uniformly to obtain a varnish composition;

S3. Apply adhesive on the surface of BOPP film with a coating amount of 1.5 g/m ² , then apply aluminum foil on the adhesive, dry at 70°C, and age at 50°C for 2 days;

S4. After the surface of the aluminum foil layer is primed, a high-gloss ink is printed, a varnish composition is applied, and ultraviolet light is cured to obtain a packaging material with a high-gloss gloss.

The highlight ink is prepared by the following steps: add 2g polymerized linseed oil, 1g dibutyl hydroxytoluene, 5g pine alcohol, 20g acetone, and 20g n-butyl acetate into a reactor, stir at room temperature at a speed of 500r/min for 10min, raise the temperature to 60°C, add 10g maleic rosin glycerol ester resin, 10g vinyl chloride-vinyl acetate, and 10g polyamide resin under stirring, continue stirring for 1h, add 2g activated benzidine yellow and 1g hydroxylated aluminum powder and stir evenly to obtain a highlight ink.

Activated benzidine yellow is prepared by the following steps: 2g of benzidine yellow, 1g of calcium alginate, and 5g of coconut oil are mixed, homogenized at a temperature of 70°C for 1min, and a homogenization pressure of 30MPa to obtain a prefabricated material; 10g of xanthan gum, 2g of hydroxypropyl-β-cyclodextrin, 0.1g of calcium lactate, and 50g of water are mixed, stirred evenly at a temperature of 70°C, and a stirring speed of 1000r/min, and the prefabricated material is added dropwise thereto under stirring, and stirring is continued for 1h after the addition is complete, and the activated benzidine yellow is obtained by filtering, washing, and drying.

Hydroxylated aluminum powder is prepared by the following steps: 2 g of aluminum powder is washed with acetone, added to 50 g of ethanol and stirred for 10 min, 1 g of triethanolamine is added under stirring, stirred at 70° C. for 1 h at a stirring speed of 100 r/min, filtered, and washed with acetone to obtain hydroxylated aluminum powder.

Example 2

A packaging material with high gloss, comprising from inside to outside: a BOPP layer, an aluminum foil layer, a primer layer, an ink layer and a varnish layer.

The method for preparing the packaging material having high gloss comprises the following steps:

S1, 30g of waterborne polyurethane resin and 50g of water were mixed evenly, 2g of dodecyl alcohol ester was added and stirred for 2h to obtain a binder;

S2, 10 g of polyurethane acrylate, 5 g of ethyl acrylate (CAS No. 140-88-5), and 1 g of photoinitiator 160 were mixed uniformly to obtain a varnish composition;

S3. Apply adhesive on the surface of BOPP film with a coating amount of 2g/ ^m2 , then apply aluminum foil on the adhesive, dry at 80℃, and age at 55℃ for 3 days;

S4. After the surface of the aluminum foil layer is primed, a high-gloss ink is printed, a varnish composition is applied, and ultraviolet light is cured to obtain a packaging material with a high-gloss gloss.

The highlight ink is prepared by the following steps: 6g polymerized linseed oil, 5g dibutylhydroxytoluene, 15g pine alcohol, 40g acetone, and 30g n-butyl acetate are added to a reactor, stirred at room temperature at a speed of 700r/min for 20min, heated to 70°C, 20g maleic rosin glycerol ester resin, 20g vinyl chloride-vinyl acetate, and 20g polyamide resin are added under stirring, stirring is continued for 2h, 6g activated benzidine yellow and 3g hydroxylated aluminum powder are added and stirred evenly to obtain a highlight ink.

Activated benzidine yellow is prepared by the following steps: 4g of benzidine yellow, 2g of calcium alginate, and 10g of coconut oil are mixed, homogenized at a temperature of 80°C for 2min, and a homogenization pressure of 40MPa to obtain a prefabricated material; 20g of xanthan gum, 6g of hydroxypropyl-β-cyclodextrin, 0.2g of calcium lactate, and 100g of water are mixed, stirred evenly at a temperature of 80°C, and a stirring speed of 2000r/min, and the prefabricated material is added dropwise thereto under stirring, and stirring is continued for 2h after the addition is complete, and the activated benzidine yellow is obtained by filtering, washing, and drying.

Hydroxylated aluminum powder is prepared by the following steps: 10 g of aluminum powder is washed with acetone, added to 80 g of ethanol and stirred for 30 min, 2 g of triethanolamine is added under stirring, stirred at 80° C. for 3 h at a stirring speed of 500 r/min, filtered, and washed with acetone to obtain hydroxylated aluminum powder.

Example 3

A packaging material with high gloss, comprising from inside to outside: a BOPP layer, an aluminum foil layer, a primer layer, an ink layer and a varnish layer.

The method for preparing the packaging material having high gloss comprises the following steps:

S1, 15g of waterborne polyurethane resin and 45g of water were mixed evenly, 1.3g of dodecyl alcohol ester was added and stirred for 110min to obtain a binder;

S2, 7 g of polyurethane acrylate, 4 g of ethyl acrylate (CAS No. 140-88-5), and 0.3 g of photoinitiator 160 were mixed to obtain a varnish composition;

S3. The adhesive is coated on the surface of the BOPP film at a coating amount of 1.9 g/m ² , and then the aluminum foil is pasted on the adhesive, dried at 73°C, and aged at 53°C for 2.5 days;

S4. After the surface of the aluminum foil layer is primed, a high-gloss ink is printed, a varnish composition is applied, and ultraviolet light is cured to obtain a packaging material with a high-gloss gloss.

The highlight ink is prepared by the following steps: 3g polymerized linseed oil, 4g dibutylhydroxytoluene, 8g pineol, 35g acetone, and 22g n-butyl acetate are added to a reactor, stirred at room temperature for 12min at a speed of 650r/min, heated to 66°C, 12g maleic rosin glycerol ester resin, 17g vinyl chloride-vinyl acetate, and 12g polyamide resin are added under stirring, stirring is continued for 100min, 3g activated benzidine yellow and 2.5g hydroxylated aluminum powder are added and stirred evenly to obtain a highlight ink.

The activated benzidine yellow is prepared by the following steps: 2.5g of benzidine yellow, 1.7g of calcium alginate and 6g of coconut oil are mixed, homogenized at a temperature of 77°C for 1.5min and a homogenization pressure of 33MPa to obtain a prefabricated material; 18g of xanthan gum, 3g of hydroxypropyl-β-cyclodextrin, 0.18g of calcium lactate and 70g of water are mixed, stirred evenly at a temperature of 77°C and a stirring speed of 1200r/min, the prefabricated material is added dropwise thereto under stirring, stirring is continued for 100min after the addition is complete, and the activated benzidine yellow is obtained by filtering, washing and drying.

Hydroxylated aluminum powder is prepared by the following steps: 4 g of aluminum powder is washed with acetone, added to 70 g of ethanol and stirred for 15 min, 1.7 g of triethanolamine is added under stirring, stirred at 73° C. for 2.5 h at a stirring speed of 200 r/min, filtered, and washed with acetone to obtain hydroxylated aluminum powder.

Example 4

A packaging material with high gloss, comprising from inside to outside: a BOPP layer, an aluminum foil layer, a primer layer, an ink layer and a varnish layer.

The method for preparing the packaging material with high gloss comprises the following steps:

S1, 25g of waterborne polyurethane resin and 35g of water were mixed evenly, 1.7g of dodecyl alcohol ester was added and stirred for 70min to obtain a binder;

S2, 9 g of polyurethane acrylate, 2 g of ethyl acrylate (CAS No. 140-88-5), and 0.7 g of photoinitiator 160 were mixed to obtain a varnish composition;

S3. The adhesive is coated on the surface of the BOPP film at a coating amount of 1.7 g/m ² , and then the aluminum foil is pasted on the adhesive, dried at 77°C, and aged at 51°C for 2.5 days;

S4. After the surface of the aluminum foil layer is primed, a high-gloss ink is printed, a varnish composition is applied, and ultraviolet light is cured to obtain a packaging material with a high-gloss gloss.

The highlight ink is prepared by the following steps: 5g polymerized linseed oil, 2g dibutyl hydroxytoluene, 12g pine alcohol, 25g acetone, and 28g n-butyl acetate are added to a reactor, stirred at room temperature for 18 minutes at a speed of 550r/min, heated to 64°C, 18g maleic rosin glycerol ester resin, 13g vinyl chloride-vinyl acetate, and 18g polyamide resin are added under stirring, and stirring is continued for 80 minutes. 5g activated benzidine yellow and 1.5g hydroxylated aluminum powder are added and stirred evenly to obtain a highlight ink.

The activated benzidine yellow is prepared by the following steps: 3.5g of benzidine yellow, 1.3g of calcium alginate and 8g of coconut oil are mixed, homogenized at a temperature of 73°C for 1.5min and a homogenization pressure of 37MPa to obtain a prefabricated material; 12g of xanthan gum, 5g of hydroxypropyl-β-cyclodextrin, 0.12g of calcium lactate and 90g of water are mixed, stirred evenly at a temperature of 73°C and a stirring speed of 1800r/min, the prefabricated material is added dropwise thereto under stirring, stirring is continued for 80min after the addition is complete, and the activated benzidine yellow is obtained by filtering, washing and drying.

Hydroxylated aluminum powder is prepared by the following steps: 8 g of aluminum powder is washed with acetone, added to 60 g of ethanol and stirred for 25 min, 1.3 g of triethanolamine is added under stirring, stirred at 77° C. for 1.5 h at a stirring speed of 400 r/min, filtered, and washed with acetone to obtain hydroxylated aluminum powder.

Example 5

A packaging material with high gloss, comprising from inside to outside: a BOPP layer, an aluminum foil layer, a primer layer, an ink layer and a varnish layer.

The method for preparing the packaging material having high gloss comprises the following steps:

S1, 20g of waterborne polyurethane resin and 40g of water were mixed evenly, 1.5g of dodecyl alcohol ester was added and stirred for 90min to obtain a binder;

S2, 8 g of polyurethane acrylate, 3 g of ethyl acrylate (CAS No. 140-88-5), and 0.5 g of photoinitiator 160 were mixed uniformly to obtain a varnish composition;

S3. Apply adhesive on the surface of BOPP film with a coating amount of 1.8 g/m ² , then apply aluminum foil on the adhesive, dry at 75°C, and age at 52°C for 2.5 days;

S4. After the surface of the aluminum foil layer is primed, a high-gloss ink is printed, a varnish composition is applied, and ultraviolet light is cured to obtain a packaging material with a high-gloss gloss.

The highlight ink is prepared by the following steps: 4g polymerized linseed oil, 3g dibutyl hydroxytoluene, 10g pineol, 30g acetone, and 25g n-butyl acetate are added to a reactor, stirred at room temperature for 15min at a speed of 600r/min, heated to 65°C, 15g maleic rosin glycerol ester resin, 15g vinyl chloride-vinyl acetate, and 15g polyamide resin are added under stirring, stirring is continued for 90min, 4g activated benzidine yellow and 2g hydroxylated aluminum powder are added and stirred evenly to obtain a highlight ink.

The activated benzidine yellow is prepared by the following steps: 3g of benzidine yellow, 1.5g of calcium alginate and 7g of coconut oil are mixed, homogenized at a temperature of 75°C for 1.5min and a homogenization pressure of 35MPa to obtain a prefabricated material; 15g of xanthan gum, 4g of hydroxypropyl-β-cyclodextrin, 0.15g of calcium lactate and 80g of water are mixed, stirred evenly at a temperature of 75°C and a stirring speed of 1500r/min, the prefabricated material is added dropwise thereto under stirring, stirring is continued for 90min after the addition is complete, and the activated benzidine yellow is obtained by filtering, washing and drying.

Hydroxylated aluminum powder is prepared by the following steps: 6 g of aluminum powder is washed with acetone, added to 65 g of ethanol and stirred for 20 min, 1.5 g of triethanolamine is added under stirring, stirred at 75° C. for 2 h at a stirring speed of 300 r/min, filtered, and washed with acetone to obtain hydroxylated aluminum powder.

Comparative Example 1

A packaging material with high gloss, comprising from inside to outside: a BOPP layer, an aluminum foil layer, a primer layer, an ink layer and a varnish layer.

The method for preparing the packaging material having high gloss comprises the following steps:

S1, 20g of waterborne polyurethane resin and 40g of water were mixed evenly, 1.5g of dodecyl alcohol ester was added and stirred for 90min to obtain a binder;

S2, 8 g of polyurethane acrylate, 3 g of ethyl acrylate (CAS No. 140-88-5), and 0.5 g of photoinitiator 160 were mixed uniformly to obtain a varnish composition;

S3. Apply adhesive on the surface of BOPP film with a coating amount of 1.8 g/m ² , then apply aluminum foil on the adhesive, dry at 75°C, and age at 52°C for 2.5 days;

S4. After the surface of the aluminum foil layer is primed, a high-gloss ink is printed, a varnish composition is applied, and ultraviolet light is cured to obtain a packaging material with a high-gloss gloss.

The highlight ink is prepared by the following steps: 4g polymerized linseed oil, 3g dibutylhydroxytoluene, 10g pineol, 30g acetone, and 25g n-butyl acetate are added to a reactor, stirred at room temperature for 15min at a speed of 600r/min, heated to 65°C, 15g maleic rosin glycerol ester resin, 15g vinyl chloride-vinyl acetate, and 15g polyamide resin are added under stirring, stirring is continued for 90min, 4g benzidine yellow and 2g hydroxylated aluminum powder are added and stirred evenly to obtain a highlight ink.

Hydroxylated aluminum powder is prepared by the following steps: 6 g of aluminum powder is washed with acetone, added to 65 g of ethanol and stirred for 20 min, 1.5 g of triethanolamine is added under stirring, stirred at 75° C. for 2 h at a stirring speed of 300 r/min, filtered, and washed with acetone to obtain hydroxylated aluminum powder.

Comparative Example 2

A packaging material with high gloss, comprising from inside to outside: a BOPP layer, an aluminum foil layer, a primer layer, an ink layer and a varnish layer.

The method for preparing the packaging material having high gloss comprises the following steps:

S1, 20g of waterborne polyurethane resin and 40g of water were mixed evenly, 1.5g of dodecyl alcohol ester was added and stirred for 90min to obtain a binder;

S2, 8 g of polyurethane acrylate, 3 g of ethyl acrylate (CAS No. 140-88-5), and 0.5 g of photoinitiator 160 were mixed uniformly to obtain a varnish composition;

S3. Apply adhesive on the surface of BOPP film with a coating amount of 1.8 g/m ² , then apply aluminum foil on the adhesive, dry at 75°C, and age at 52°C for 2.5 days;

S4. After the surface of the aluminum foil layer is primed, a high-gloss ink is printed, a varnish composition is applied, and ultraviolet light is cured to obtain a packaging material with a high gloss.

The highlight ink is prepared by the following steps: 4g polymerized linseed oil, 3g dibutylhydroxytoluene, 10g pineol, 30g acetone, and 25g n-butyl acetate are added to a reactor, stirred at room temperature for 15min at a speed of 600r/min, heated to 65°C, 15g maleic rosin glycerol ester resin, 15g vinyl chloride-vinyl acetate, and 15g polyamide resin are added under stirring, stirring is continued for 90min, 4g activated benzidine yellow and 2g aluminum powder are added and stirred evenly to obtain a highlight ink.

The activated benzidine yellow is prepared by the following steps: 3g of benzidine yellow, 1.5g of calcium alginate and 7g of coconut oil are mixed, homogenized at a temperature of 75°C for 1.5min and a homogenization pressure of 35MPa to obtain a prefabricated material; 15g of xanthan gum, 4g of hydroxypropyl-β-cyclodextrin, 0.15g of calcium lactate and 80g of water are mixed, stirred evenly at a temperature of 75°C and a stirring speed of 1500r/min, the prefabricated material is added dropwise thereto under stirring, stirring is continued for 90min after the addition is complete, and the activated benzidine yellow is obtained by filtering, washing and drying.

The high-gloss ink obtained in Example 5 and Comparative Examples 1-2 was applied to tinplate and cured and dried. The 60° specular gloss of the dried ink film was tested with reference to GB/T9754-2007 "Determination of 20°, 60° and 85° specular gloss of paints and varnishes without metallic pigments". Then, the ink film was exposed to the sun on a sunny day in July or August for a total of 20 days, and the 60° specular gloss was tested again to calculate the gloss value change rate.

As shown in Figure 1, the high-gloss ink obtained in Example 5 not only has a high initial gloss value, but also can maintain a relatively high gloss value after exposure to sunlight. The applicant believes that this is because the present invention uses hydroxylated aluminum powder and activated benzidine yellow in synergistic use, which is conducive to the combination of aluminum powder and activated benzidine yellow, and can greatly improve the brightness of the ink.

After the soft food-grade aluminum foil surface was primed, the high-gloss ink obtained in Example 5 and Comparative Examples 1-2 was printed and cured and dried. The adhesion of the ink film after drying was tested with reference to the method of GB/T 9286-2021 "Scratch test for paints, varnishes and paint films". The hardness of the ink film after drying was tested with reference to the method of GB/T 6739-2022 "Determination of paint film hardness by pencil method for paints and varnishes". The results are as follows:

Example 5 Comparative Example 1 Comparative Example 2 Adhesion Level 0 level 2 Level 3 hardness 4H H HB

As shown in the table above, the high-gloss ink obtained in Example 5 has good adhesion and high hardness. The applicant believes that this is because the present invention performs hydroxylation on the surface of aluminum powder, which is not only conducive to the combination of aluminum powder and activated benzidine yellow, but also the synergistic effect of the two makes the high-gloss ink printed on the surface of the aluminum foil layer have excellent adhesion.

Referring to HG/T 4303-2012 "Measurement Method for Abrasion Resistance of Surface Hardened Polyester Film", the ink film surface was rubbed 2000 times after drying. The ink film surface was observed and it was found that the ink film obtained in Example 5 had no scratches, while the ink films obtained in Comparative Examples 1-2 were all slightly scratched. This proves that the high-gloss ink obtained in the present invention has excellent abrasion resistance.

The mechanical properties of the packaging materials obtained in Example 5 and Comparative Examples 1-2 were measured as follows: tensile strength and elongation at break were tested with reference to GB/T1040.3-2006 "Determination of tensile properties of plastics Part 3: Test conditions for thin plastics and sheets"; dart impact strength test was performed with reference to Method A in GB/T 9639.1-2008 "Test method for impact resistance of plastic film and sheeting - Free-fall dart method Part 1: Step method"; and drop test was performed with reference to GB/T 4857.5-1992 "Drop test method for packaging and transport packages".

It can be seen from the table above that the mechanical properties of each group are good and the impact strength is high, which proves that the packaging material obtained by the present invention can effectively extend the shelf life of block butter packaging.

The barrier properties of the packaging materials obtained in Example 5 and Comparative Examples 1-2 were measured, and water vapor permeability and oxygen permeability were used to characterize the barrier properties of the materials. The water vapor permeability test was carried out by the weight gain method in reference to GB/T 1037-2021 "Determination of water vapor permeability of plastic films and sheets by cup weight gain and weight loss method", the test temperature was 38°C, the humidity was 90% RH, the preheating time was 2h, the rotation interval was 10min, and 3 parallels were set for each group. The oxygen permeability test was carried out by reference to GB/T 1038.1-2022 "Test method for gas permeability of plastic films and sheets Part 1: Differential pressure method", the test temperature was 23°C, the humidity was 50% RH, and the vacuum time was 4h. Ensure that the surface of the sample is free of contamination and scratches, and set 3 parallels for each group.

As shown in Figure 2, the water barrier and oxygen barrier properties of the packaging materials obtained in Example 5 and Comparative Examples 1-2 are similar (P>0.05), which proves that the packaging materials obtained in the present invention have good water barrier and oxygen barrier properties and are suitable for the packaging of butter blocks.

The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims (8)

1. A packaging material with high gloss, characterized in that it comprises, from inside to outside, a BOPP layer, an aluminum foil layer, a primer layer, an ink layer and a varnish layer; wherein the thickness of the BOPP layer is 18-38 μm, the thickness of the aluminum foil layer is 7-15 μm, and the thickness of the varnish layer is 2-10 μm; The ink layer is made of high-gloss ink, and the raw materials of the high-gloss ink include polymerized linseed oil, butylated hydroxytoluene, pinene alcohol, acetone, n-butyl acetate, maleic rosin glycerol ester resin, vinyl chloride-vinyl acetate, polyamide resin, activated benzidine yellow, and hydroxylated aluminum powder; In the activated benzidine yellow, benzidine yellow, calcium alginate and coconut oil are mixed, homogenized at 70-80°C for 1-2 minutes, and the homogenization pressure is 30-40MPa to obtain a prefabricated material; xanthan gum, hydroxypropyl-β-cyclodextrin, calcium lactate and water are mixed, stirred evenly at 70-80°C, and the prefabricated material is added dropwise thereto under stirring, and the stirring is continued for 1-2 hours after the addition is complete, and the activated benzidine yellow is filtered, washed and dried to obtain the activated benzidine yellow; The hydroxylated aluminum powder is prepared by the following steps: washing the aluminum powder, adding it to ethanol and stirring for 10-30 minutes, adding triethanolamine under stirring, stirring at 70-80° C. for 1-3 hours, filtering, and washing to obtain the hydroxylated aluminum powder. 2. The packaging material with high gloss according to claim 1 is characterized in that the high gloss ink is prepared by the following steps: polymerized linseed oil, butylated hydroxytoluene, terpineol, acetone, and n-butyl acetate are stirred for 10-20 minutes, heated to 60-70°C, maleic rosin glycerol ester resin, vinyl chloride-vinyl acetate, and polyamide resin are added under stirring, stirring is continued for 1-2 hours, activated benzidine yellow and hydroxylated aluminum powder are added, and stirred evenly to obtain the high gloss ink. 3. The packaging material with high gloss according to claim 1 is characterized in that the mass ratio of polymerized linseed oil, butylated hydroxytoluene, terpineol, acetone, n-butyl acetate, maleic rosin glycerol ester resin, vinyl chloride-vinyl acetate, polyamide resin, activated benzidine yellow, and hydroxylated aluminum powder is 2-6:1-5:5-15:20-40:20-30:10-20:10-20:10-20:2-6:1-3. 4. The packaging material with high gloss according to claim 1, characterized in that the aluminum foil layer is made of soft food-grade aluminum foil material. 5. A method for preparing a packaging material having high gloss as claimed in any one of claims 1 to 4, characterized in that it comprises the following steps: S1. Mix waterborne polyurethane resin and water evenly, add film-forming aid and continue stirring for 1-2 hours to obtain a binder; S2, uniformly mixing polyurethane acrylate, monofunctional acrylate monomer and photoinitiator to obtain a varnish composition; S3. Apply adhesive on the surface of BOPP film, then stick aluminum foil on the adhesive, dry at 70-80℃, and age at 50-55℃ for 2-3 days; S4. After the surface of the aluminum foil layer is primed, a high-gloss ink is printed, a varnish composition is applied, and ultraviolet light is cured to obtain a packaging material with a high gloss. 6. The method for preparing a packaging material with high gloss according to claim 5, characterized in that in S1, the mass ratio of the waterborne polyurethane resin to the film-forming aid is 10-30:1-2. 7. The method for preparing a packaging material with high gloss according to claim 5, characterized in that in S2, the photoinitiator is an α-hydroxyalkane photoinitiator; the mass ratio of polyurethane acrylate, monofunctional acrylate monomer, and α-hydroxyalkane photoinitiator is 5-10:1-5:0.1-1. 8. The method for preparing a packaging material with high gloss according to claim 5, characterized in that in S3, the amount of adhesive applied is 1.5-2 g/ ^m2 .