Plastic 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 plastic base material for producing a pre-coating film, the pre-coating film as well as a preparation method and application of the pre-coating film. The plastic base material 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, and relative to 100 parts by weight of polypropylene random copolymer, the content of maleic anhydride is 1-5 parts by weight, and the content of the initiator is 0.1-1 part by weight. The pre-coating film provided by the invention has the advantages of no need of being coated with a primer, good adhesive property and processability and the like, and the pre-coating film is simple in preparation process and safe in processing process.

Description

Technical Field

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

[0002] Pre-coated films are usually composed of a substrate layer, a primer layer and a hot-melt adhesive layer. They are widely used in the sealing and protection of card materials such as identity cards, historical materials, photos, credit cards, the outer packaging protection of items such as books, cartons, medicine boxes, and food packaging.

[0003] The substrate layer is usually a biaxially oriented polyester (BOPET) film or a biaxially oriented polypropylene (BOPP) film, the primer layer is usually a high molecular weight polyethyleneimine aqueous solution (AC agent), and the hot melt adhesive layer is usually ethylene-vinyl acetate resin (EVA), and the thickness of the hot melt adhesive layer is 5-15μm.

[0004] Since the bonding strength of EVA coated on the surface of unprimed BOPP film is poor, AC agent is often required to be coated on the BOPP film before coating EVA, and the processing performance is poor.

[0005] However, AC agent usually contains a large amount of organic solvents such as methanol and ethanol. After coating, the solvent of the AC agent needs to be dried to form a primer layer on the surface of the BOPP film.

[0006] Such a process is not only prone to flammable and explosive safety hazards, but also requires a longer drying tunnel and heat to dry the AC agent, resulting in energy consumption.

[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 biaxially oriented polypropylene resin of the surface layer, the core layer polypropylene resin and the ethylene-vinyl acetate resin. Although the biaxially oriented polypropylene pre-coated film provided by the prior art can be directly coated with EVA hot melt adhesive without coating a primer, the technology is a pre-coated film prepared by biaxially oriented technology, and the processing technology is complicated. Summary of the invention

[0008] The purpose of the invention is to overcome the defects of poor interlayer bonding strength 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 plastic substrate for producing a pre-coated film, the plastic 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;

[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] 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.

[0012] The second aspect of the present invention provides a method for preparing a pre-coated film, which is carried out using the plastic substrate described in the first aspect, comprising:

[0013] (1) mixing the components in the raw material composition for forming the core layer to obtain material I;

[0014] (2) introducing the material I into a twin-screw extruder I for a first melt extrusion process to obtain a melt I;

[0015] (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 ethylene-vinyl acetate copolymer into a twin-screw extruder II for a second melt extrusion treatment to obtain a melt II;

[0016] (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.

[0017] The third aspect of the present invention provides a pre-coated film prepared by the method described in the second aspect.

[0018] 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.

[0019] The technical solution provided by the present invention has at least the following advantages compared with the prior art:

[0020] (1) The core layer raw material composition provided by the present invention has simple components, is easy to obtain, is inexpensive, and has strong practicality, and the process steps for preparing the core layer are simple;

[0021] (2) The pre-coated film provided by the present invention does not need to be coated with a primer, has excellent bonding performance and processing performance, and has a simpler preparation process and a safer processing process. DETAILED DESCRIPTION

[0022] 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.

[0023] 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.

[0024] 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.

[0025] As mentioned above, the first aspect of the present invention provides a plastic substrate for producing a pre-coated film, the plastic 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;

[0026] 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;

[0027] 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.

[0028] Preferably, in the raw material composition for forming the core layer, 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 relative to 100 parts by weight of random copolymer polypropylene.

[0029] Preferably, in the raw material composition forming the core layer, 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 relative to 100 parts by weight of random copolymer polypropylene. The inventors of the present invention have found that in this preferred case, the pre-coated film provided by the present invention has better bonding performance and processing performance.

[0030] 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.

[0031] 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-coating film provided by the present invention has better bonding performance and processing performance.

[0032] More preferably, the content of propylene structural units in the random copolymer polypropylene is 85-95wt%.

[0033] 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).

[0034] Preferably, the initiator is DCP. The inventors of the present invention have found that in this preferred embodiment, the pre-coating film provided by the present invention has better bonding performance and processing performance.

[0035] Preferably, the base layer is a polypropylene film.

[0036] More preferably, the base layer is a biaxially oriented polypropylene film (BOPP).

[0037] 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.

[0038] In the present invention, the heat shrinkage rate of the biaxially oriented polypropylene film = L0-L1 / L0×100%;

[0039] L0: initial width of biaxially oriented polypropylene film;

[0040] L1: Width of biaxially oriented polypropylene film after being treated in an oven at 100°C for 20 min.

[0041] Preferably, the adhesive layer contains ethylene-vinyl acetate copolymer (EVA).

[0042] Preferably, the content of vinyl acetate structural units in the ethylene-vinyl acetate copolymer is 15-25wt%, the melt mass flow rate at 190°C and a load of 2.16kg is 20-30g / 10min, 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.

[0043] Preferably, the thickness ratio of the base layer, the core layer and the bonding layer is 1:0.25-0.75:0.5-1.

[0044] As mentioned above, the second aspect of the present invention provides a method for preparing a pre-coating film, which is carried out using the plastic substrate described in the first aspect, comprising:

[0045] (1) mixing the components in the raw material composition for forming the core layer to obtain material I;

[0046] (2) introducing the material I into a twin-screw extruder I for a first melt extrusion process to obtain a melt I;

[0047] (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 ethylene-vinyl acetate copolymer into a twin-screw extruder II for a second melt extrusion treatment to obtain a melt II;

[0048] (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.

[0049] It should be noted that the present invention has no special requirements for the equipment and method of the mixing process. 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, the components in the raw material composition are introduced into the mixing equipment for mixing until they are evenly mixed. The present invention has no special requirements for the operating parameters of the mixing equipment, which will not be described in detail herein. Those skilled in the art should not understand this as a limitation to the present invention.

[0050] 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.

[0051] Preferably, the temperature of the first melt extrusion process is 220-240°C.

[0052] 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.

[0053] Preferably, the temperature of the second melt extrusion treatment is 220-255°C.

[0054] 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.

[0055] 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 operate. 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, and after natural cooling, the film I and / or the pre-coated film are 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.

[0056] As mentioned above, the third aspect of the present invention provides a pre-coated film prepared by the method described in the second aspect.

[0057] 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.

[0058] 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.

[0059] Base layer:

[0060] Biaxially oriented polypropylene film I (BOPP-I): purchased from Shandong Shunkai Composite Materials Co., Ltd., with a heat shrinkage rate of 1.3% and a friction coefficient of 0.4;

[0061] Biaxially oriented polypropylene film II (BOPP-II): purchased from Shandong Shunkai Composite Materials Co., Ltd., with a heat shrinkage rate of 1.7% and a friction coefficient of 0.25.

[0062] Adhesive layer:

[0063] Ethylene-vinyl acetate copolymer I (EVA-I): purchased from Yanshan Petrochemical, brand EVAC19F28, the content of vinyl acetate structural units in the ethylene-vinyl acetate copolymer is 18wt%, the melt mass flow rate (190°C, 2.16kg) is 25g / 10min, the weight average molecular weight is 152,000, the molecular weight distribution is 10.9, and the number of branches per 1000 carbon atoms in the main chain is 0.01;

[0064] Ethylene-vinyl acetate copolymer II (EVA-II): purchased from Yanshan Petrochemical, brand EVAC19F20, the content of vinyl acetate structural units in the ethylene-vinyl acetate copolymer is 18wt%, the melt mass flow rate (190°C, 2.16kg) is 20g / 10min, the weight average molecular weight is 180,000, the molecular weight distribution is 12, and the number of branches per 1000 carbon atoms in the main chain is 0.012;

[0065] Ethylene-vinyl acetate copolymer III (EVA-III): purchased from Yanshan Petrochemical, brand EVA18F10, the content of vinyl acetate structural units in the ethylene-vinyl acetate copolymer is 18wt%, the melt mass flow rate (190°C, 2.16kg) is 10g / 10min, the weight average molecular weight is 98,000, the molecular weight distribution is 5.5, and the number of branches per 1000 carbon atoms in the main chain is 0.001.

[0066] Random copolymer polypropylene:

[0067] Random copolymer polypropylene I: propylene-butene copolymer, purchased from Yanshan Petrochemical, brand PP4028, melt mass flow rate (230°C, 2.16kg) 28g / 10min, melting point 145°C, propylene structural unit content 91wt%;

[0068] Random copolymer polypropylene II: propylene-ethylene copolymer, purchased from Yanshan Petrochemical, brand PP4912, melt mass flow rate (230° C., 2.16 kg) is 12 g / 10 min, melting point is 150° C., propylene structural unit content is 93 wt%.

[0069] Initiator: DCP, purchased from Shanghai Chemical Reagent Company.

[0070] Maleic anhydride: purchased from Tianjin Botong Chemical Co., Ltd.

[0071] In the following examples, unless otherwise specified, each "part" or each "part by weight" means 100 g.

[0072] Example 1

[0073] This example is used to illustrate that the pre-coating film of the present invention is prepared by using the formula and process parameters in Table 1 and the following method. It includes:

[0074] (1) mixing random copolymer polypropylene, maleic anhydride and initiator to obtain material I;

[0075] (2) introducing material I into a twin-screw extruder I for a first melt extrusion process to obtain a melt I;

[0076] (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 ethylene-vinyl acetate copolymer into a twin-screw extruder II for a second melt extrusion treatment to obtain a melt II;

[0077] (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.

[0078] The ethylene-vinyl acetate copolymer is introduced into the twin-screw extruder II in a continuous feeding manner until the production is completed.

[0079] 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 1.

[0080] Table 1

[0081]

[0082]

[0083] Example 5

[0084] This embodiment is carried out in a similar manner to that of Embodiment 1, except that:

[0085] In this example, EVA-I was replaced with an equal weight portion of EVA-III, and the prepared pre-coating film was named M5.

[0086] Example 6

[0087] This embodiment is carried out in a similar manner to that of Embodiment 1, except that:

[0088] In this embodiment, the type of base layer used is BOPP-II, and the prepared pre-coated film is named M6.

[0089] Comparative Example 1

[0090] This comparative example was carried out in a similar manner to Example 1, except that:

[0091] In this comparative example, random copolymer polypropylene I was replaced with random copolymer polypropylene II in equal parts by weight, and the prepared pre-coating film was named DM1.

[0092] Comparative Example 2

[0093] This comparative example was carried out in a similar manner to Example 1, except that:

[0094] The amount of maleic anhydride used in this comparative example is 10 parts by weight, and the prepared pre-coating film is named DM2.

[0095] Comparative Example 3

[0096] This comparative example was carried out in a similar manner to Example 1, except that:

[0097] In this comparative example, the raw material composition for forming the core layer contains only random copolymerized polypropylene I, the total weight of the raw material composition for forming the core layer remains unchanged, and is prepared according to the following method, including:

[0098] (1) introducing random copolymerized polypropylene into a twin-screw extruder I for a first melt extrusion process to obtain a melt I;

[0099] (2) 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 ethylene-vinyl acetate copolymer into a twin-screw extruder II for a second melt extrusion treatment to obtain a melt II;

[0100] (3) 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 DM3.

[0101] Comparative Example 4

[0102] This comparative example was carried out in a similar manner to Example 1, except that:

[0103] In this comparative example, the prepared pre-coating film does not contain a core layer and is prepared as follows:

[0104] include:

[0105] (1) introducing ethylene-vinyl acetate copolymer into a twin-screw extruder II for a second melt extrusion process to obtain a melt II;

[0106] (2) 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 stacked in sequence, which is named DM4.

[0107] Test Example 1

[0108] Referring to the standard GB / T 2790-1995, the interlayer bonding performance (peel strength) of the pre-coated film prepared as above was tested. The specific results are shown in Table 2.

[0109] Test Example 2

[0110] The processing performance of the pre-coated film prepared above was tested using the following method:

[0111] Characterize the processing performance of pre-coated film by shrinkage and maximum processing speed;

[0112] Shrinkage: When the processing speed is 200m / min, the initial width of the base layer (BOPP) minus the width of the prepared pre-coated film is calculated as follows:

[0113] Shrinkage (cm) = initial width of base layer (BOPP) - width of pre-coated film;

[0114] A processing speed of 200 m / min means that 200 m of pre-coated film can be produced per minute;

[0115] Maximum processing speed (m / min): The maximum processing speed when the shrinkage is controlled at 3cm.

[0116] The specific results are shown in Table 2.

[0117] Table 2

[0118] Pre-coated film type Peel strength (N / 15mm) Shrinkage(cm) Maximum processing speed (m / min) M1 4.6 2.0 300 M2 4.3 2.1 300 M3 4.2 2.1 290 M4 4.0 2.0 270 M5 4.2 2.8 240 M6 3.9 2.4 280 DM1 3.0 2.3 200 DM2 3.5 3.6 200 DM3 1.8 2.1 280 DM4 1.2 2.0 300

[0119] It can be seen from the above results that the pre-coated film provided by the present invention does not require coating of a primer, has a simple preparation process, and a safe processing process, and the prepared pre-coated film has both excellent anti-stripping ability and processing performance, and can obtain a pre-coated film with excellent performance at a higher processing speed, and has a higher market value.

[0120] 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 plastic substrate for producing a pre-coating film, characterized in that: The plastic 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; 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; 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.

2. The plastic 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 plastic 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 plastic substrate according to any one of claims 1 to 3, 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.

5. The plastic substrate according to any one of claims 1 to 4, wherein The adhesive layer contains ethylene-vinyl acetate copolymer; And / or, the content of vinyl acetate structural units in the ethylene-vinyl acetate copolymer is 15-25wt%, the melt mass flow rate at 190°C and a load of 2.16kg is 20-30g / 10min, 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.

6. The plastic 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 plastic substrate according to any one of claims 1 to 6, comprising: (1) mixing the components in the raw material composition for forming the core layer to obtain material I; (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 ethylene-vinyl acetate copolymer 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 treatment 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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