Base material for producing pre-coating film, pre-coating film, and preparation method and application of pre-coating film

Abstract

The invention relates to the field of laminating materials, and discloses a base material for producing a pre-coating film, the pre-coating film and a preparation method and application of the pre-coating film. The base material for producing the pre-coating film comprises a base layer, a core layer and a bonding layer which are sequentially stacked, a raw material composition for forming the core layer contains polypropylene random copolymer, maleic anhydride and an initiator; a raw material composition for forming the bonding layer contains an ethylene-vinyl acetate copolymer and an ethylene-methacrylic acid copolymer. The pre-coating film provided by the invention has the advantages that the pre-coating film does not need to be coated with a primer, the interlayer bonding performance of the pre-coating film is good, the bonding performance with a film-coated substrate is good, the processability is good, the preparation process is simple, and the processing process is safe.

Description

Technical Field

[0001] The invention relates to the technical field of coating materials, and in particular to a substrate for producing a pre-coating film, a pre-coating film, and a preparation method and application thereof. Background Art

[0002] Pre-coated film is a type of laminating material and is widely used in books, card materials, medicine boxes, food packaging and other fields.

[0003] Ordinary pre-coated films are usually composed of a substrate layer, a primer layer and a hot-melt adhesive layer. However, in actual industrial applications, polyethyleneimine solution is usually used as the primer layer, and the polyethyleneimine solution contains a large amount of toxic, harmful and flammable substances such as methanol, ethanol, and benzene. During the processing, due to the volatilization of toxic and harmful substances, it not only has serious harm to the environment, but the volatilized flammable substances are very likely to cause fires and even explosions. In addition, during use, residual solvents will also cause harm to the human body and pose a potential threat to consumers' health.

[0004] If ordinary pre-coated films do not use a primer layer, the adhesion between the substrate layer and the hot melt adhesive layer is poor, making it difficult to use in practice.

[0005] In addition, in practical applications, the hot melt adhesive layer is the main bonding layer of ordinary pre-coated films. However, the hot melt adhesive layer currently usually uses ethylene-vinyl acetate (EVA) resin, which has the defect of low bonding strength with the coating substrate.

[0006] At present, although existing technologies have been studied separately for the above-mentioned defects, it is difficult to solve the above-mentioned defects at the same time. Moreover, even if some defects of ordinary pre-coated films can be overcome, their processing performance is easily damaged, resulting in new problems such as increased production costs and reduced quality of the produced pre-coated films.

[0007] CN105479884A discloses a biaxially oriented polypropylene pre-coated film substrate, comprising a polypropylene surface layer, a polypropylene core layer and an ethylene-vinyl acetate layer; the substrate is prepared by coextrusion and biaxial stretching of a surface layer polypropylene resin, a core layer polypropylene resin and an ethylene-vinyl acetate resin. The biaxially oriented polypropylene pre-coated film provided by the prior art can be directly coated with EVA hot melt adhesive without the need for a primer, but the technology is a pre-coated film prepared by biaxial stretching technology, the processing technology is complicated, and no improvement is made in terms of the bonding performance between film layers, the bonding performance with the film-coated substrate, and the processing performance. Summary of the invention

[0008] The purpose of the invention is to overcome the defects of poor bonding performance and poor processing performance of the existing pre-coating film without primer.

[0009] In order to achieve the above-mentioned object, the first aspect of the present invention provides a substrate for producing a pre-coated film, the substrate comprising a base layer, a core layer, and a bonding layer stacked in sequence; the raw material composition forming the core layer contains random copolymerized polypropylene, maleic anhydride, and an initiator; the raw material composition forming the bonding layer contains ethylene-vinyl acetate copolymer and ethylene-methacrylic acid copolymer;

[0010] In the raw material composition for forming the core layer, relative to 100 parts by weight of the random copolymer polypropylene, the content of the maleic anhydride is 1-5 parts by weight, and the content of the initiator is 0.1-1 parts by weight;

[0011] In the raw material composition for forming the bonding layer, based on the total weight of the bonding layer, the content of the ethylene-vinyl acetate copolymer is 80-95wt%, and the content of the ethylene-methacrylic acid copolymer is 5-20wt%;

[0012] The random copolymer polypropylene has a melt mass flow rate of 20-30 g / 10 min at 230° C. and a load of 2.16 kg, and a melting point of 143-150° C.;

[0013] The content of vinyl acetate structural units in the ethylene-vinyl acetate copolymer is 15-25wt%, the melt mass flow rate is 20-30g / 10min at 190°C and a load of 2.16kg, the weight average molecular weight is 100,000-200,000, the molecular weight distribution is 6-15, and the number of branches per 1,000 carbon atoms in the main chain is 0.005-0.015.

[0014] The second aspect of the present invention provides a method for preparing a pre-coating film, which is carried out using the substrate described in the first aspect, comprising:

[0015] (1) subjecting the components of the raw material composition for forming the core layer to a first mixing process to obtain a material I; and subjecting the components of the raw material composition for forming the bonding layer to a second mixing process to obtain a material II;

[0016] (2) introducing the material I into a twin-screw extruder I for a first melt extrusion process to obtain a melt I;

[0017] (3) subjecting the melt I to a first contact treatment with a base layer to obtain a film I comprising a base layer and a core layer stacked in sequence; and introducing the material II into a twin-screw extruder II for a second melt extrusion treatment to obtain a melt II;

[0018] (4) The melt II and the film I are subjected to a second contact treatment to obtain the pre-coated film including a base layer, a core layer, and an adhesive layer stacked in sequence.

[0019] The third aspect of the present invention provides a pre-coated film prepared by the method described in the second aspect.

[0020] The fourth aspect of the present invention provides application of the pre-coating film described in the third aspect in the field of coating materials.

[0021] The technical solution provided by the present invention has at least the following advantages compared with the prior art:

[0022] (1) The raw material composition of the core layer and the bonding layer provided by the present invention has simple and readily available components, low price, strong practicality, and simple process steps for preparing the core layer and the bonding layer;

[0023] (2) The pre-coated film provided by the present invention does not need to be coated with a primer, has strong adhesion between film layers, and has excellent bonding performance with the film-coated substrate. In addition, the preparation process is simpler and the processing process is safer. DETAILED DESCRIPTION

[0024] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0025] It should be noted that, in various aspects of the present invention, for the same components or terms in various aspects, the present invention is described only once in one aspect without repeated description, which should not be understood by those skilled in the art as a limitation of the present invention.

[0026] In the present invention, the method for determining the melt mass flow rate refers to GB / T 3682.1-2018; the molecular weight distribution refers to the ratio of the weight average molecular weight to the number average molecular weight (Mw / Mn); the method for determining the friction coefficient refers to GB / T10006-2021; the method for determining the content of the vinyl acetate structural unit in the ethylene-vinyl acetate copolymer refers to GB / T 30925-2014; the weight average molecular weight and the molecular weight distribution are tested by gel permeation chromatography.

[0027] As mentioned above, the first aspect of the present invention provides a substrate for producing a pre-coated film, the substrate comprising a base layer, a core layer, and a bonding layer stacked in sequence; the raw material composition forming the core layer contains random copolymerized polypropylene, maleic anhydride, and an initiator; the raw material composition forming the bonding layer contains ethylene-vinyl acetate copolymer (EVA) and ethylene-methacrylic acid copolymer (EMAA);

[0028] In the raw material composition for forming the core layer, relative to 100 parts by weight of the random copolymer polypropylene, the content of the maleic anhydride is 1-5 parts by weight, and the content of the initiator is 0.1-1 parts by weight;

[0029] In the raw material composition for forming the bonding layer, based on the total weight of the bonding layer, the content of the ethylene-vinyl acetate copolymer is 80-95wt%, and the content of the ethylene-methacrylic acid copolymer is 5-20wt%;

[0030] The random copolymer polypropylene has a melt mass flow rate of 20-30 g / 10 min at 230° C. and a load of 2.16 kg, and a melting point of 143-150° C.;

[0031] The content of vinyl acetate structural units in the ethylene-vinyl acetate copolymer is 15-25wt%, the melt mass flow rate is 20-30g / 10min at 190°C and a load of 2.16kg, the weight average molecular weight is 100,000-200,000, the molecular weight distribution is 6-15, and the number of branches per 1,000 carbon atoms in the main chain is 0.005-0.015.

[0032] Preferably, relative to 100 parts by weight of random copolymer polypropylene, the content of maleic anhydride is 1-3 parts by weight, and the content of the initiator is 0.1-0.5 parts by weight.

[0033] More preferably, relative to 100 parts by weight of random copolymer polypropylene, the content of maleic anhydride is 1.5-2 parts by weight, and the content of the initiator is 0.15-0.2 parts by weight. The inventors of the present invention have found that in this preferred case, the pre-coated film provided by the present invention has better inter-layer bonding performance, bonding performance with the coated substrate, and processing performance.

[0034] Preferably, in the raw material composition for forming the bonding layer, based on the total weight of the bonding layer, the content of the ethylene-vinyl acetate copolymer is 85-95wt%, and the content of the ethylene-methacrylic acid copolymer is 5-15wt%.

[0035] More preferably, in the raw material composition forming the bonding layer, based on the total weight of the bonding layer, the content of the ethylene-vinyl acetate copolymer is 90-95wt%, and the content of the ethylene-methacrylic acid copolymer is 5-10wt%. The inventors of the present invention have found that in this preferred case, the bonding performance between the film layers provided by the present invention, the bonding performance with the film-coated substrate, and the processing performance are better.

[0036] Preferably, the random copolymer polypropylene is selected from at least one of a copolymer of propylene and ethylene, a copolymer of propylene and butene, and a copolymer of propylene and a diene.

[0037] Preferably, the random copolymer polypropylene is a copolymer of propylene and butene. The inventors of the present invention have found that in this preferred embodiment, the pre-coated film provided by the present invention has better inter-film bonding performance, bonding performance with the film-coated substrate, and processing performance.

[0038] More preferably, the content of propylene structural units in the random copolymer polypropylene is 85-95wt%.

[0039] Preferably, the initiator is selected from at least one of dicumyl peroxide (DCP), dibenzoyl peroxide (BPO), di-tert-butyl peroxide (DTBP), and tert-amyl peroxy-2-ethylhexyl carbonate (TAEC).

[0040] Preferably, the content of methacrylic acid structural units in the ethylene-methacrylic acid copolymer is 5-10 wt %, and the melt mass flow rate at 190° C. and a load of 2.16 kg is 5-10 g / 10 min.

[0041] Preferably, the base layer is a polypropylene film.

[0042] More preferably, the base layer is a biaxially oriented polypropylene film (BOPP).

[0043] Preferably, the heat shrinkage rate of the biaxially oriented polypropylene film is 1.0-1.5%, and the friction coefficient is 0.3-1.0.

[0044] In the present invention, the heat shrinkage rate of the biaxially oriented polypropylene film = L0-L1 / L0×100%;

[0045] L0: initial width of the biaxially oriented polypropylene film;

[0046] L1: the width of the biaxially oriented polypropylene film after being treated in an oven at 100° C. for 20 minutes.

[0047] Preferably, the thickness ratio of the base layer, the core layer and the bonding layer is 1:0.25-0.75:0.5-1.

[0048] As mentioned above, the second aspect of the present invention provides a method for preparing a pre-coating film, which is performed using the substrate described in the first aspect, comprising:

[0049] (1) subjecting the components of the raw material composition for forming the core layer to a first mixing process to obtain a material I; and subjecting the components of the raw material composition for forming the bonding layer to a second mixing process to obtain a material II;

[0050] (2) introducing the material I into a twin-screw extruder I for a first melt extrusion process to obtain a melt I;

[0051] (3) subjecting the melt I to a first contact treatment with a base layer to obtain a film I comprising a base layer and a core layer stacked in sequence; and introducing the material II into a twin-screw extruder II for a second melt extrusion treatment to obtain a melt II;

[0052] (4) The melt II and the film I are subjected to a second contact treatment to obtain the pre-coated film including a base layer, a core layer, and an adhesive layer stacked in sequence.

[0053] It should be noted that the present invention has no special requirements on the equipment and method of the first mixing treatment and the second mixing treatment. Those skilled in the art can use technical means known in the art to operate. The present invention exemplarily provides a preferred specific implementation mode in the following text. Exemplarily, the first mixing treatment and the second mixing treatment are each independently adopted: introducing each component in the raw material composition into a mixing device for mixing, and mixing them evenly. The present invention has no special requirements on the operating parameters of the mixing device, and the present invention will not be repeated here. Those skilled in the art should not understand it as a limitation of the present invention.

[0054] Preferably, in step (2), the main engine speed of the twin-screw extruder I is 100-300 rpm, and the screw aspect ratio is 30-53:1.

[0055] Preferably, the temperature of the first melt extrusion process is 220-240°C.

[0056] Preferably, in step (3), the main engine speed of the twin-screw extruder II is 100-300 rpm, and the screw aspect ratio is 30-53:1.

[0057] Preferably, the temperature of the second melt extrusion treatment is 220-255°C.

[0058] It should be noted that the present invention does not particularly limit the method of introducing materials into the twin-screw extruder. Those skilled in the art can use technical means known in the art to operate. The present invention exemplarily provides a preferred specific implementation mode in the following text. For example, after the material is sucked into the hopper of the twin-screw extruder by a vacuum suction machine, it enters the space of the screw groove of the twin-screw extruder by its own weight or under the action of a forced feeder, thereby being melt-extruded. Those skilled in the art should not understand this as a limitation of the present invention.

[0059] It should be noted that the present invention has no special requirements for the methods adopted by the first contact treatment and the second contact treatment. Those skilled in the art can use technical means known in the art to perform the operations. The present invention exemplarily provides a preferred specific implementation mode in the following text. By way of example, the first contact treatment and the second contact treatment are carried out in the same manner, and the melt I and / or the melt II are respectively and evenly dropped onto the base layer and / or the film I. Under the action of gravity, the melt I and / or the melt II are evenly spread on the base layer and / or the film I. After natural cooling, the film I and / or the pre-coated film are respectively formed. The present invention will not be described in detail here, and those skilled in the art should not understand it as a limitation of the present invention.

[0060] As mentioned above, the third aspect of the present invention provides a pre-coated film prepared by the method described in the second aspect.

[0061] As mentioned above, the fourth aspect of the present invention provides the use of the pre-coating film described in the third aspect in the field of coating materials.

[0062] The present invention will be described in detail below by way of examples. In the following examples, unless otherwise specified, the raw materials used are all commercially available products.

[0063] The raw materials and sources used in the following examples are shown in Table 1:

[0064] Table 1

[0065]

[0066] In the following examples, unless otherwise specified, each "part" or each "part by weight" means 100 g.

[0067] The addition amount of each component in the adhesive layer is based on the total weight of each component in the adhesive layer, and the total weight of each component in the adhesive layer is 10 kg.

[0068] Example 1

[0069] This example is used to illustrate that the pre-coating film of the present invention is prepared using the formula and process parameters in Table 2 and according to the following method. It includes:

[0070] (1) random copolymer polypropylene, maleic anhydride and initiator are mixed to obtain material I; and ethylene-vinyl acetate copolymer and ethylene-methacrylic acid copolymer are mixed for a second time to obtain material II;

[0071] (2) introducing material I into a twin-screw extruder I for a first melt extrusion process to obtain a melt I;

[0072] (3) subjecting the melt I to a first contact treatment with a base layer to obtain a film I having a base layer and a core layer stacked in sequence; and introducing material II into a twin-screw extruder II for a second melt extrusion treatment to obtain a melt II;

[0073] (4) The melt II is subjected to a second contact treatment with the film I to obtain a pre-coated film including a base layer, a core layer, and a bonding layer stacked in sequence, which is named M1.

[0074] Unless otherwise specified, the remaining embodiments are carried out using a method similar to that of Embodiment 1, except that the formulations and process parameters are different. The differences are specifically shown in Table 2.

[0075] Table 2

[0076]

[0077]

[0078] Example 5

[0079] This embodiment is carried out in a similar manner to that of Embodiment 1, except that:

[0080] In this example, EMAA-I was replaced by EMAA-II of equal weight, the total weight of each component in the adhesive layer remained unchanged, and the prepared pre-coating film was named M5.

[0081] Example 6

[0082] This embodiment is carried out in a similar manner to that of Embodiment 1, except that:

[0083] In this embodiment, the type of base layer used is BOPP-II, and the prepared pre-coated film is named M6.

[0084] Comparative Example 1

[0085] This comparative example was carried out in a similar manner to Example 1, except that:

[0086] In this comparative example, random copolymer polypropylene I was replaced by random copolymer polypropylene III in equal parts by weight, and the prepared pre-coating film was named DM1.

[0087] Comparative Example 2

[0088] This comparative example was carried out in a similar manner to Example 1, except that:

[0089] In this comparative example, EVA-I was replaced with an equal weight portion of EVA-III, and the prepared pre-coating film was named DM2.

[0090] Comparative Example 3

[0091] This comparative example was carried out in a similar manner to Example 1, except that:

[0092] The amount of maleic anhydride used in this comparative example is 10 parts by weight, and the prepared pre-coating film is named DM3.

[0093] Comparative Example 4

[0094] This comparative example was carried out in a similar manner to Example 1, except that:

[0095] In this comparative example, the addition amount of EVA-I in the bonding layer is 75wt%, the addition amount of EMAA-I is 25wt%, the total weight of each component in the bonding layer remains unchanged, and the prepared pre-coated film is named DM4.

[0096] Comparative Example 5

[0097] This comparative example was carried out in a similar manner to Example 1, except that:

[0098] In this comparative example, the prepared pre-coating film does not contain a core layer and is prepared as follows:

[0099] include:

[0100] (1) subjecting ethylene-vinyl acetate copolymer and ethylene-methacrylic acid copolymer to a second mixing process to obtain material II;

[0101] (2) introducing the material II into a twin-screw extruder II for a second melt extrusion process to obtain a melt II;

[0102] (3) The melt II is subjected to a second contact treatment with the base layer to obtain a pre-coated film including a base layer and an adhesive layer laminated in sequence, which is named DM5.

[0103] Test Example 1

[0104] Referring to the standard GB / T 2790-1995, the interlayer adhesion (peel strength I) and the adhesion to the film-coated substrate (peel strength II) of the pre-coated film prepared above were tested. The specific results are shown in Table 3.

[0105] Test Example 2

[0106] The processing performance of the pre-coated film prepared above was tested using the following method:

[0107] Characterize the processing performance of pre-coated film by shrinkage and maximum processing speed;

[0108] Shrinkage: The difference between the initial width of the base layer (BOPP) and the width of the prepared pre-coated film when the processing speed is 200m / min. The calculation method is as follows:

[0109] Shrinkage (cm) = initial width of base layer (BOPP) - width of pre-coated film;

[0110] The processing speed is 200m / min: 200m of pre-coated film is prepared per minute;

[0111] Maximum processing speed (m / min): The maximum processing speed when the shrinkage is controlled at 3cm.

[0112] The specific results are shown in Table 3.

[0113] Table 3

[0114]

[0115]

[0116] It can be seen from the above results that the pre-coated film provided by the present invention does not need to be coated with a primer, has a simple preparation process, and a safe processing process, and the prepared pre-coated film has excellent anti-stripping ability and processing performance, and has a high market value.

[0117] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A substrate for producing a pre-coating film, characterized in that: The substrate comprises a base layer, a core layer and a bonding layer which are stacked in sequence; the raw material composition forming the core layer contains random copolymerized polypropylene, maleic anhydride and an initiator; the raw material composition forming the bonding layer contains ethylene-vinyl acetate copolymer and ethylene-methacrylic acid copolymer; In the raw material composition for forming the core layer, relative to 100 parts by weight of the random copolymer polypropylene, the content of the maleic anhydride is 1-5 parts by weight, and the content of the initiator is 0.1-1 parts by weight; In the raw material composition for forming the bonding layer, based on the total weight of the bonding layer, the content of the ethylene-vinyl acetate copolymer is 80-95wt%, and the content of the ethylene-methacrylic acid copolymer is 5-20wt%; The random copolymer polypropylene has a melt mass flow rate of 20-30 g / 10 min at 230° C. and a load of 2.16 kg, and a melting point of 143-150° C.; The content of vinyl acetate structural units in the ethylene-vinyl acetate copolymer is 15-25wt%, the melt mass flow rate is 20-30g / 10min at 190°C and a load of 2.16kg, the weight average molecular weight is 100,000-200,000, the molecular weight distribution is 6-15, and the number of branches per 1,000 carbon atoms in the main chain is 0.005-0.

015.

2. The substrate according to claim 1, wherein The random copolymer polypropylene is selected from at least one of a copolymer of propylene and ethylene, a copolymer of propylene and butene, and a copolymer of propylene and diene.

3. The substrate according to claim 1 or 2, wherein The initiator is selected from at least one of dicumyl peroxide, dibenzoyl peroxide, di-tert-butyl peroxide, and tert-amyl peroxy-2-ethylhexyl carbonate.

4. The substrate according to any one of claims 1 to 3, wherein The content of methacrylic acid structural units in the ethylene-methacrylic acid copolymer is 5-10 wt %, and the melt mass flow rate at 190° C. and a load of 2.16 kg is 5-10 g / 10 min.

5. The substrate according to any one of claims 1 to 4, wherein The base layer is a polypropylene film; And / or, the base layer is a biaxially oriented polypropylene film; And / or, the heat shrinkage rate of the biaxially oriented polypropylene film is 1.0-1.5%, and the friction coefficient is 0.3-1.

0.

6. The substrate according to any one of claims 1 to 5, wherein The thickness ratio of the base layer, the core layer and the bonding layer is 1:0.25-0.75:0.5-1.

7. A method for preparing a pre-coating film, characterized in that: The method is carried out using the substrate according to any one of claims 1 to 6, comprising: (1) subjecting the components of the raw material composition for forming the core layer to a first mixing process to obtain a material I; and subjecting the components of the raw material composition for forming the bonding layer to a second mixing process to obtain a material II; (2) introducing the material I into a twin-screw extruder I for a first melt extrusion process to obtain a melt I; (3) subjecting the melt I to a first contact treatment with a base layer to obtain a film I having a base layer and a core layer stacked in sequence; and introducing the material II into a twin-screw extruder II for a second melt extrusion treatment to obtain a melt II; (4) The melt II and the film I are subjected to a second contact treatment to obtain the pre-coated film including a base layer, a core layer, and an adhesive layer stacked in sequence.

8. The method according to claim 7, wherein: In step (2), the main engine speed of the twin-screw extruder I is 100-300 rpm, and the screw aspect ratio is 30-53:1; And / or, the temperature of the first melt extrusion process is 220-240°C.

9. The method according to claim 7 or 8, wherein: In step (3), the main engine speed of the twin-screw extruder II is 100-300 rpm, and the screw aspect ratio is 30-53:1; And / or, the temperature of the second melt extrusion process is 220-255°C.

10. A pre-coated film prepared by the method according to any one of claims 7 to 9.

11. Use of the pre-coating film according to claim 10 in the field of coating materials.

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