A back printing ink suitable for aluminized BOPP film and a preparation method thereof, and aluminized printing film

Abstract

The present invention relates to the field of packaging, and specifically to a back printing ink suitable for aluminum-coated BOPP film, a preparation method thereof, and an aluminum-coated printed film. The printed film body is a double-layer composite structure, wherein the surface layer is an aluminum-coated printed layer VMBOPP, and the inner layer is a structural layer PE, and the structural layer PE is divided from top to bottom into a corona layer, an intermediate layer, and a low-temperature heat-sealing layer. The surface of the aluminum-coated printed film also has an ink layer, and the ink layer is made by printing with an improved back printing ink. The present invention uses a barrier material aluminum-coated BOPP printing combined with PE as a packaging material, the barrier performance is not affected, and the packaging cost is reduced. The PE layer formula is adjusted to meet the low-temperature sealing requirements. In addition, the present invention improves the back printing ink formula, so that ordinary gravure back printing ink can be used for aluminum-coated surface printing, and solves the problems of shallow screen transition color and overlapping color inking in printing, which greatly reduces the packaging cost. The present invention can meet the market demand for lightweight flexible packaging films in terms of recyclability, barrier properties, and printability.

Description

Technical Field

[0001] The invention relates to the field of packaging, and in particular to an inner printing ink suitable for an aluminized BOPP film and a preparation method thereof, and an aluminized printing film. Background Art

[0002] At present, most flexible packaging on the market adopts a three-layer structure: the outer layer is mainly printed with PET, BOPP, and BOPA, which have stable performance and are easy to print; the middle layer is a barrier material, generally aluminized PET, aluminized BOPP, aluminum foil, etc.; the inner layer uses polyethylene PE and polypropylene CPP as heat-sealing materials.

[0003] The printing of this composite flexible packaging is different from that of general packaging. The former is called inner printing and the latter is called surface printing. The inks used in the two are called inner printing ink and surface printing ink respectively. There are differences between inner printing ink and surface printing ink in many aspects such as wear resistance, printing process, and formula.

[0004] As society's requirements for environmental protection continue to increase, lightweight, recyclable and degradable plastic flexible packaging has become a development trend. The original packaging cannot be lightweight. Although the three-layer structure material can meet the packaging of products with barrier requirements, the cost is high; and some of the materials used, such as PET and BOPA, are not recyclable. Aluminum-coated BOPP then appeared.

[0005] However, when using barrier material aluminum-plated BOPP for printing, because the ink is printed on the surface, the scratch resistance and adhesion of the ink must be met. To meet the above requirements, a primer must first be applied on the aluminum layer to enhance the adhesion of the ink. After the printed pattern is completed, a protective varnish is applied to enhance the scratch resistance of the ink. The middle ink is surface printing ink according to the normal printing process. Surface printing ink has good ink-on effect and ink-overlapping effect, but the ink price is very high. If ordinary inner printing ink (polyurethane ink) is used, there will be problems of overlapping and poor ink-on transition of shallow screens.

[0006] The applicant's early patent CN104693887A disclosed a flexographic printing ink and a preparation method thereof, but the ink has weak adhesion to the aluminum-plated layer, lacks gloss after printing, and its weather resistance needs to be improved.

[0007] Therefore, the improvement of aluminized BOPP and printing technology is an issue to be solved in the industry. It is urgent to develop a recyclable, lightweight flexible packaging film preparation process that meets barrier and printing requirements to meet market demand. Summary of the invention

[0008] In order to solve the problems in the prior art, one of the objects of the present invention is to provide a back printing ink suitable for aluminum-plated BOPP film.

[0009] The technical solution adopted by the present invention is:

[0010] A back printing ink suitable for aluminum-plated BOPP film, comprising the following raw materials in percentage by weight:

[0011] Ester soluble cellulose resin solution 43-47%;

[0012] Ester soluble synthetic resin liquid 5-7%;

[0013] Body pigment 4-6%;

[0014] Polyethylene wax 1-2%;

[0015] Matt powder 0.2-0.4%;

[0016] Additives 1-3%;

[0017] Ethyl acetate 18-22%;

[0018] n-propyl ester 18-22%;

[0019] The ester-soluble cellulose resin liquid is prepared by dissolving cellulose resin solids in a certain proportion of ethyl acetate and n-propyl ester, and the ester-soluble synthetic resin liquid is prepared by dissolving ester-soluble modified synthetic resin solids in a certain proportion of ethyl ester.

[0020] Preferably, the back printing ink comprises the following raw materials in weight percentage: 45% ester-soluble cellulose resin liquid, 6% ester-soluble synthetic resin liquid, 5% extender pigment, 1% polyethylene wax, 0.3% matte powder, 2% additive, 20.7% ethyl acetate, and 20% n-propyl acetate.

[0021] Preferably, in the ester-soluble cellulose resin liquid, the weight percentage of ethyl acetate is 35%, the weight percentage of n-propyl acetate is 35%, and the weight percentage of cellulose resin solids is 30%.

[0022] Preferably, in the ester-soluble synthetic resin liquid, the weight percentage of ethyl acetate is 50%, and the weight percentage of the ester-soluble modified synthetic resin solid is 50%.

[0023] Preferably, the extender pigment consists of kaolin and barium sulfate in a mass ratio of 1:1.

[0024] Preferably, the matte powder is silicon dioxide powder.

[0025] Preferably, the auxiliary agent comprises a dispersant and an adhesion promoter mixed in a mass ratio of 1:1, the dispersant is a polyester dispersant, and the adhesion promoter is a silane coupling agent. Preferably, the silane coupling agent is γ-aminopropyltriethoxysilane.

[0026] The second object of the present invention is to provide a method for preparing a back printing ink suitable for aluminum-plated BOPP film as described above, comprising the following steps:

[0027] S1. Weigh the required mass of raw materials in proportion, mix the ester-soluble cellulose resin liquid, ester-soluble synthetic resin liquid, extender pigment, polyethylene wax and matte powder, add ethyl acetate and n-propyl acetate, stir and grind, mix the ingredients evenly, and obtain a semi-finished ink;

[0028] S2. Add additives to the semi-finished ink, stir evenly, use ethyl acetate and / or n-propyl acetate to adjust the viscosity of the ink to 12 to 14S, filter, and obtain the desired backing ink.

[0029] In this application, the viscosity is measured using a flow cup commonly used in the printing industry, and the unit is seconds (S). The measurement method in this application is: use a No. 13 Zahn cup to detect the time it takes to flow out a cup of ink. The thinner the ink, the shorter the flow time, and the thicker the ink, the longer the flow time.

[0030] A third object of the present invention is to provide a recyclable aluminized printed film, wherein the aluminized printed film comprises an ink layer, and the ink layer is printed using the above-mentioned back printing ink.

[0031] Preferably, the printed film body is a double-layer composite structure, wherein the surface layer is an aluminum-plated printing layer VMBOPP, and the inner layer is a structural layer PE.

[0032] The structural layer PE is divided into three layers from top to bottom:

[0033] The first layer is a corona layer that contacts the aluminized printed layer VMBOPP, and is composed of two raw materials: 70wt% linear low-density polyethylene LLDPE and 30wt% low-density polyethylene LDPE;

[0034] The second layer is the middle layer: it is composed of three raw materials: 60wt% linear low-density polyethylene LLDPE, 20wt% metallocene linear polyethylene m-LLDPE, and 20wt% high-density polyethylene HDPE;

[0035] The third layer is a low-temperature heat-sealing layer: it is composed of three raw materials: 70wt% metallocene linear very low density polyethylene m-VLDPE, 20wt% low density polyethylene LDPE, and 10wt% polyolefin elastomer POE.

[0036] Preferably, in the corona layer, the linear low-density polyethylene LLDPE is selected from Zhejiang Petrochemical brand 7042, and the low-density polyethylene LDPE is selected from Yangba brand 2420H;

[0037] In the middle layer, the linear low-density polyethylene LLDPE is selected from Zhejiang Petrochemical brand 7042, the metallocene linear polyethylene m-LLDPE is selected from ExxonMobil brand 2010MA, and the high-density polyethylene HDPE is selected from Thailand PTT brand HD3355F;

[0038] In the low-temperature heat-sealing layer, the metallocene linear very low-density polyethylene m-VLDPE is selected from ExxonMobil brand 2012MA, the low-density polyethylene LDPE is selected from ExxonMobil brand 100AC, and the polyolefin elastomer POE is selected from Sabic brand 8102L.

[0039] Preferably, the thickness of the aluminum-plated printing layer VMBOPP is 18 μm, the thickness of the structural layer PE is 32 μm, and the thickness ratio of the corona layer, the intermediate layer and the low-temperature heat-sealing layer is 8:15:9.

[0040] The beneficial effects of the present invention are:

[0041] The traditional three-layer material flexible packaging is improved by using barrier material aluminum-plated BOPP printing, and two-layer material replaces three-layer material. The barrier performance of the packaging material is not affected, saving packaging costs.

[0042] The film finally uses VMBOPP / PE recyclable materials to meet environmental protection requirements. Since there is no heat-resistant material such as PET, the materials including the outer layer of aluminum-plated BOPP have poor heat resistance and are prone to heat-sealing wrinkles. Therefore, the PE layer formula was adjusted, and the PE layer adopted a low-temperature design scheme, in which the corona layer has good bonding with VMBOPP, the middle layer formula design enhances the film's tensile properties, and the low-temperature heat-sealing layer meets the low-temperature sealing requirements.

[0043] Ink adhesion is the difficulty that limits ordinary back printing ink to be directly printed on the aluminum-plated surface. Generally, there are special surface printing inks for aluminum-plated surface printing, but the cost is high. The present invention improves the back printing ink formula. The ink viscosity is lower than that of the back printing ink during printing, which is conducive to printing shallow screen transfer, so that ordinary gravure back printing ink can be used for aluminum-plated surface printing, and solves the problem of shallow screen transition color and overlapping color inking in printing, greatly reducing the packaging cost. After printing, the back printing ink can also make the metallic luster of the aluminum-plated film and the luster of the ink merge with each other, so that the product has a special luster effect that is difficult to achieve with traditional back printing ink.

[0044] The transition pattern effect of the surface printing ink is poor due to its high viscosity. The solid content of the binder resin in the back printing ink provided by the present invention is high, while the amount of dilution solvent remains unchanged, ensuring low viscosity and ensuring the inking effect of the transition pattern. The resin and other components in the ink improved by the present application have good weather resistance and can resist ultraviolet rays, oxidation and chemical corrosion. In outdoor or harsh environments, the color and performance of the aluminum film printed with the aluminum film back printing ink are more stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a schematic diagram of the structure of the aluminized printed film provided by the present invention.

[0046] The meanings of the symbols in the figure are as follows:

[0047] 10-Aluminum-plated printing layer VMBOPP

[0048] 20-Structural layer PE 21-Corona layer 22-Middle layer 23-Low temperature heat sealing layer

[0049] 30-Ink layer DETAILED DESCRIPTION

[0050] The technical solution of the present invention is described below in conjunction with the accompanying drawings and embodiments for easy understanding by those skilled in the art.

[0051] Example 1

[0052] Heat sealing temperature test

[0053] VMBOPP / PE double-layer packaging, because there is no heat-resistant material such as PET, the material itself is easy to wrinkle after heat sealing. To solve the wrinkling problem, the inner layer PE formula must be adjusted. Heat sealing tests were conducted on PE layers with different formulas to test the heat sealing strength. The results are shown in Table 2 below.

[0054] Table 2 Heat sealing strength at different heat sealing temperatures

[0055]

[0056] It can be seen that among the above three formulas, the sealing temperature of Scheme 1 is 105°C, the sealing temperature of Scheme 2 is 100°C, and the sealing temperature of Scheme 3 is 95°C. Scheme 3 has the lowest sealing temperature. Therefore, Scheme 3 is selected as the inner layer PE formula adjusted in this application to meet the ultra-low temperature sealing requirements.

[0057] Example 2

[0058] like Figure 1 As shown, a recyclable aluminized printed film, the printed film body is a 18μm VMBOPP / 32μm PE double-layer composite structure, wherein the surface layer is an aluminized printed layer VMBOPP, and the inner layer is a structural layer PE.

[0059] The structural layer PE is divided into three layers from top to bottom, and the thickness ratio of the corona layer, the middle layer and the low-temperature heat sealing layer is 8:15:9:

[0060] The first layer is a corona layer in contact with the aluminized printed layer VMBOPP, which is composed of two raw materials: 70wt% of Zhejiang Petrochemical 7042 linear low-density polyethylene LLDPE and 30wt% of Yangba 2420H low-density polyethylene LDPE, which can improve the composite strength with VMBOPP.

[0061] The second layer is the middle layer: it is composed of three raw materials: 60wt% Zhejiang Petrochemical brand 7042 linear low-density polyethylene LLDPE, 20wt% ExxonMobil brand 2010MA metallocene linear polyethylene m-LLDPE, and 20wt% Thailand PTT brand HD3355F high-density polyethylene HDPE, which are used to ensure the overall toughness of the film.

[0062] The third layer is a low-temperature heat-sealing layer: it is composed of three raw materials: 70wt% ExxonMobil 2012MA metallocene linear very low-density polyethylene m-VLDPE, 20wt% ExxonMobil 100AC low-density polyethylene LDPE, and 10wt% Sabic 8102L polyolefin elastomer POE. This layer is designed for low-temperature heat sealing and has good heat sealing performance.

[0063] The surface of the aluminized printed film also has an ink layer, which is made by printing with an inner printing ink. The inner printing ink has a formula of: 43-47wt% ester-soluble cellulose resin liquid, 5-7wt% ester-soluble synthetic resin liquid, 4-6wt% body pigment, 1-2wt% polyethylene wax, 0.2-0.4wt% matte powder, 1-3wt% additive, 18-22wt% ethyl acetate, and 18-22wt% n-propyl acetate.

[0064] In the formula, the body pigment is composed of kaolin and barium sulfate in a mass ratio of 1:1, and the matte powder is silicon dioxide powder; the ester-soluble cellulose resin liquid is prepared by dissolving cellulose resin solids in ethyl acetate and n-propyl ester in a certain proportion, for example, ethyl acetate accounts for 35wt%, n-propyl ester accounts for 35wt%, and cellulose resin solids account for 30wt%; the ester-soluble synthetic resin liquid is prepared by dissolving ester-soluble modified synthetic resin solids in ethyl ester in a certain proportion, for example, ethyl acetate accounts for 50wt%, and ester-soluble modified synthetic resin solids account for 50wt%.

[0065] In the formula, the additives include dispersants and adhesion promoters. The dispersant can be a polyester dispersant, which contains multiple ester bonds (—COO—) in its molecular structure. It forms physical adsorption or chemical adsorption with the pigment to wrap the pigment particles and achieve a good dispersion effect. The adhesion promoter is a silane coupling agent, such as γ-aminopropyltriethoxysilane, which has an organic functional group in its molecular structure that can react with organic components such as resins in the ink, and a siloxy group that can react with groups such as hydroxyl groups on the surface of the printed substrate, which can enhance the adhesion of the ink to the substrate.

[0066] The preparation method of the above-mentioned back printing ink comprises the following steps:

[0067] S1. Weigh the required mass of raw materials in proportion, mix the ester-soluble cellulose resin liquid, ester-soluble synthetic resin liquid, body pigment, polyethylene wax and matte powder, stir evenly to fully blend the ingredients; then add ethyl acetate and n-propyl acetate, stir and grind to evenly disperse the pigment and other solid particles in the system to obtain a semi-finished ink with fine texture and uniform color.

[0068] S2. Add additives to the semi-finished ink and stir evenly to improve the adhesion of the ink on the aluminized film; then use ethyl acetate and / or n-propyl acetate to adjust the viscosity of the ink to a viscosity range suitable for printing; finally filter the ink to remove impurities and incompletely ground particles to obtain a pure and delicate aluminized film inner printing ink.

[0069] The preparation steps of the above-mentioned aluminum-plated printed film include conventional steps such as printing, dry lamination, aging, slitting, testing and warehousing, among which the printing process is:

[0070] First color primer: DIC ALCOLOR-SP aluminum foil primer (solvent: 100% ethyl ester, viscosity: 15-20s, drying temperature: 70-80°C)

[0071] The 2nd to 8th colors: the printing ink of this application (solvent: 100% n-propyl ester, viscosity: 13-15s, drying temperature: 40-60°C).

[0072] Ninth color varnish: DIC GOP-500 varnish (HA) (solvent: ethyl ester 100%, viscosity: 15-20s, drying temperature: 70-80°C).

[0073] Example 2

[0074] Refer to Table 1 below. According to the printing process, different primers and varnishes are selected to conduct scratch resistance and adhesion tests of printing inks.

[0075] The formula of the back printing ink used in the test is: 45wt% of ester-soluble cellulose resin liquid (35wt% of ethyl acetate, 35wt% of n-propyl acetate, and 30wt% of cellulose resin solids), 6wt% of ester-soluble synthetic resin liquid (ethyl acetate and ester-soluble modified synthetic resin solids mixed in a mass ratio of 1:1), 5wt% of body pigment (kaolin and barium sulfate mixed in a mass ratio of 1:1), 1wt% of polyethylene wax, 0.3wt% of matte powder (silicon dioxide powder), 2wt% of additives (polyester dispersant and γ-aminopropyltriethoxysilane mixed in a mass ratio of 1:1), 20.7wt% of ethyl acetate, and 20wt% of n-propyl acetate.

[0076] Table 1 Printing formula

[0077]

[0078] After printing, use 25mm wide 3M 600 adhesive tape to stick on the printed surface of the label, press it with your fingers 3 times to avoid wrinkling of the adhesive tape and label, then tear off the adhesive tape at a speed of 150mm / s and 180° in the opposite direction to observe the shedding of the ink layer.

[0079] result:

[0080] In solution 1, the ink layer falls off directly and is unqualified;

[0081] In scheme 2, the ink layer does not fall off and the adhesion meets the requirements;

[0082] In scheme 3, the ink layer does not fall off and the adhesion meets the requirements;

[0083] Continue to test the wear resistance, load 40N, friction speed 43 times / min, rub the paper shaft with a cotton swab 20 times, measure 6 groups in parallel, and observe the ink shedding situation.

[0084] result:

[0085] In scheme 2, the ink layer falls off directly, which does not meet the requirements;

[0086] In scheme 3, the ink layer does not fall off obviously, and the effect meets the requirements;

[0087] It can be seen that in the case of an aluminum-plated primer, the use of the inner printing ink provided by the present invention can achieve surface printing on the aluminum-plated surface. The inner printing ink of the present invention replaces the aluminum-plated surface printing ink, which can effectively reduce costs.

[0088] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, a person of ordinary skill in the art should understand that any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A back printing ink suitable for aluminum-plated BOPP film, characterized in that: The following raw materials are included in weight percentage: Ester soluble cellulose resin solution 43-47%; Ester soluble synthetic resin liquid 5-7%; Body pigment 4-6%; Polyethylene wax 1-2%; Matt powder 0.2-0.4%; Additives 1-3%; Ethyl acetate 18-22%; n-propyl ester 18-22%; The ester-soluble cellulose resin liquid is prepared by dissolving cellulose resin solids in a certain proportion of ethyl acetate and n-propyl ester, and the ester-soluble synthetic resin liquid is prepared by dissolving ester-soluble modified synthetic resin solids in a certain proportion of ethyl ester.

2. The back printing ink suitable for aluminum-plated BOPP film according to claim 1, characterized in that: The invention comprises the following raw materials in percentage by weight: 45% of ester-soluble cellulose resin liquid, 6% of ester-soluble synthetic resin liquid, 5% of body pigment, 1% of polyethylene wax, 0.3% of matte powder, 2% of auxiliary agent, 20.7% of ethyl acetate and 20% of n-propyl acetate.

3. The back printing ink suitable for aluminum-plated BOPP film according to claim 1, characterized in that: In the ester-soluble cellulose resin liquid, the weight percentage of ethyl acetate is 35%, the weight percentage of n-propyl acetate is 35%, and the weight percentage of cellulose resin solid is 30%.

4. The back printing ink suitable for aluminum-plated BOPP film according to claim 1, characterized in that: In the ester-soluble synthetic resin liquid, the weight percentage of ethyl acetate is 50%, and the weight percentage of the ester-soluble modified synthetic resin solid is 50%.

5. The back printing ink suitable for aluminum-plated BOPP film according to claim 1, characterized in that: The body pigment is composed of kaolin and barium sulfate in a mass ratio of 1:1, and the matte powder is silicon dioxide powder; the auxiliary agent includes a dispersant and an adhesion promoter mixed in a mass ratio of 1:1, the dispersant is a polyester dispersant, and the adhesion promoter is a silane coupling agent.

6. A method for preparing a back printing ink suitable for aluminum-plated BOPP film as claimed in claim 1, characterized in that: The following steps are involved: S1. Weigh the required mass of raw materials in proportion, mix the ester-soluble cellulose resin liquid, ester-soluble synthetic resin liquid, extender pigment, polyethylene wax and matte powder, add ethyl acetate and n-propyl acetate, stir and grind, mix the ingredients evenly, and obtain a semi-finished ink; S2. Add additives to the semi-finished ink, stir evenly, use ethyl acetate and / or n-propyl acetate to adjust the viscosity of the ink to 12 to 14S, filter, and obtain the desired backing ink.

7. A recyclable aluminized printed film, characterized in that: The aluminized printed film comprises an ink layer (30), and the ink layer (30) is printed using the back printing ink as described in any one of claims 1 to 6.

8. A recyclable aluminized printed film as claimed in claim 7, characterized in that: The printed film body is a double-layer composite structure, wherein the surface layer is an aluminum-plated printed layer VMBOPP (10), and the inner layer is a structural layer PE (20); The structural layer PE (20) is divided into three layers from top to bottom: The first layer is a corona layer (21) in contact with the aluminum-plated printed layer VMBOPP (10), and is composed of two raw materials: 70 wt% linear low-density polyethylene LLDPE and 30 wt% low-density polyethylene LDPE; The second layer is an intermediate layer (22): composed of three raw materials: 60wt% linear low-density polyethylene LLDPE, 20wt% metallocene linear polyethylene m-LLDPE, and 20wt% high-density polyethylene HDPE; The third layer is a low-temperature heat-sealing layer (23): it is composed of three raw materials: 70 wt% of metallocene linear very low density polyethylene m-VLDPE, 20 wt% of low density polyethylene LDPE, and 10 wt% of polyolefin elastomer POE.

9. The recyclable aluminized printed film according to claim 7, characterized in that: In the corona layer (21), the linear low-density polyethylene (LLDPE) is selected from Zhejiang Petrochemical brand 7042, and the low-density polyethylene (LDPE) is selected from Yangba brand 2420H; In the intermediate layer (22), the linear low-density polyethylene (LLDPE) is selected from Zhejiang Petrochemical brand 7042, the metallocene linear polyethylene (m-LLDPE) is selected from ExxonMobil brand 2010MA, and the high-density polyethylene (HDPE) is selected from Thailand PTT brand HD3355F; In the low-temperature heat-sealing layer (23), the metallocene linear very low density polyethylene m-VLDPE is selected from ExxonMobil brand 2012MA, the low density polyethylene LDPE is selected from ExxonMobil brand 100AC, and the polyolefin elastomer POE is selected from Sabic brand 8102L.

10. The recyclable aluminized printed film according to claim 7, characterized in that: The thickness of the aluminum-plated printing layer VMBOPP (10) is 18 μm, the thickness of the structural layer PE (20) is 32 μm, and the thickness ratio of the corona layer (21), the intermediate layer (22) and the low-temperature heat-sealing layer (23) is 8:15:9.

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