A polyolefin material for a film with a soft surface property, and a preparation method and application thereof

Abstract

This invention relates to the packaging field, specifically to a flexible polyolefin material for lamination, its preparation method, and its application. The polyolefin material is a film comprising three layers from the outside in: a surface modified heat-resistant layer composed of polypropylene homopolymer resin and polypropylene modifying additives; a middle support layer composed of homopolymer polypropylene resin and polypropylene homopolymer resin; and an inner heat-bonding sealing layer composed of polypropylene copolymer resin, n-butene-based olefin copolymer, and additives. This invention, through a specially designed functional formulation and a multi-layer co-extrusion casting process, achieves a polyolefin film with good extensibility, particularly suitable for laminating irregular items. It solves the problems of existing BOPP or BOPET pre-coated films, such as high rigidity, poor extensibility, and poor adhesion when laminating irregular items.

Description

Technical Field

[0001] This invention relates to the field of packaging, specifically to a flexible polyolefin material for coating, its preparation method, and its application. Background Technology

[0002] Pre-coated film is a laminated product made by combining a hot melt adhesive layer with a film substrate. Its production process involves coating the film material (BOPP, BOPET) with hot melt adhesive under specific production conditions, cooling and shaping it, and then processing it into a finished product that meets the size requirements of the packaged laminated product through a slitting machine. When in use, the product can be laminated by heating and pressurizing it through a laminating machine.

[0003] The main market applications of pre-coated film are industrial pre-coated film and commercial pre-coated film. The industrial market is mainly the film coating market for printed publications and packaging of consumer goods such as food, pharmaceuticals, and daily necessities; the commercial market is mainly the film coating market for emerging fields such as digital printing, cards, anti-counterfeiting, commercial advertising, and building materials.

[0004] With the promotion and development of pre-coated film, many new markets for special applications have emerged. Pre-coated films produced using traditional BOPP (biaxially oriented polypropylene film) and BOPET (biaxially oriented polyester film) as base materials have drawbacks and shortcomings in some special emerging markets. Due to the high rigidity and poor extensibility of traditional pre-coated films, it is difficult to achieve and be competent for post-processing lamination on some irregular products.

[0005] Therefore, it is necessary to improve existing pre-coated films to meet the coating needs of special purpose markets for irregular items. Summary of the Invention

[0006] To address the problems in the prior art, one of the objectives of this invention is to provide a flexible polyolefin material for lamination. By optimizing the formulation of the modified polyolefin film, the invention solves the problems of existing BOPP or BOPET pre-coated films, such as high rigidity, poor ductility, and poor adhesion to irregular items.

[0007] The present invention adopts the following technical solution:

[0008] A flexible polyolefin material for coating, wherein the polyolefin material is in the form of a film and comprises three layers from the outside to the inside:

[0009] The surface layer is a modified heat-resistant layer with a thickness of 20-24 μm, composed of 99.5 wt% polypropylene homopolymer resin and 0.5 wt% polypropylene modifying additives;

[0010] The intermediate layer is a support layer with a thickness of 38-42 μm, and is composed of 60 wt% homopolymer polypropylene resin and 40 wt% polypropylene homopolymer resin.

[0011] The inner layer is a heat-bonded sealing layer with a thickness of 16-20 μm, composed of (42-48) wt% polypropylene copolymer resin, (47-53) wt% n-butenyl olefin copolymer and 5 wt% additives.

[0012] Preferably, the polypropylene modifying agent is a stiffening nucleating agent, and the additive includes open-cell masterbatch and slip masterbatch in a mass ratio of 3:2.

[0013] Preferably, the polypropylene homopolymer resin is grade HD915CF, the homopolymer polypropylene resin is grade FC801, the polypropylene copolymer resin is grade FL7642, the n-butenyl olefin copolymer is grade BL2491M, the stiffening nucleating agent is grade NA-27, the open-cell masterbatch is grade ABPP 10S, and the slip masterbatch is grade SLPP-7.

[0014] Preferably, the total thickness of the polyolefin material is 70–90 μm.

[0015] Preferably, the polyolefin material has a thickness of 80 μm, the surface layer has a thickness of 22 μm, the intermediate layer has a thickness of 40 μm, and the inner layer has a thickness of 12 μm.

[0016] The second objective of this invention is to provide a method for preparing a coating polyolefin material with flexible properties as described above, comprising the following steps:

[0017] S1. The raw materials for the surface layer, middle layer and inner layer are prepared according to the proportion and then put into the mixer to mix evenly, and then fed into the extruder to melt.

[0018] S2. Following the order of the surface layer, intermediate layer, and inner layer, co-extrude and cast the material using an extruder, then cool and set it.

[0019] S3. The shaped film is subjected to corona treatment to obtain the desired thin-film polyolefin material.

[0020] The third objective of this invention is to provide an application of a flexible polyolefin material for coating as described above in product coating.

[0021] The beneficial effects of this invention are as follows:

[0022] This invention provides a flexible polyolefin material for coating. This material has a three-layer composite film structure and, through a special functional formulation design and a multi-layer co-extrusion casting process, achieves a polyolefin film with good extensibility, making it particularly suitable for coating irregular items. Furthermore, this polyolefin film has low production costs, requires minimal equipment investment, and has a simple process, effectively meeting market demands and demonstrating high application value.

[0023] In this polyolefin material, the surface layer is a modified heat-resistant layer, composed of high-crystallinity polypropylene homopolymer resin HD915CF produced by Borealis and stiffening nucleating agent NA-27 from Asahi Denka. Borealis HD915CF is a high-crystallinity polypropylene homopolymer resin produced based on Borealis polymerization technology and using a unique Borealis nucleation technology (BNT), which provides better rigidity and toughness to the film structure. Asahi Denka's stiffening nucleating agent NA-27 is an organophosphate salt mixture that increases the crystallization temperature (Tc) of polypropylene and improves its heat distortion temperature (HDT) and flexural modulus, thereby achieving an excellent balance of physical properties (especially stiffness / impact).

[0024] The intermediate layer serves as a support layer, composed of homopolymer polypropylene resin FC801 produced by Shanghai Petrochemical and high-crystallinity polypropylene homopolymer resin HD915CF produced by Borealis. FC801 homopolymer polypropylene (PP-H) is polymerized from a single propylene monomer, exhibiting high molecular chain regularity, high crystallinity, good strength, and corrosion resistance. HD915CF is a high-crystallinity polypropylene homopolymer resin produced based on Borealis polymerization technology and utilizing unique Borealis nucleation technology (BNT), which further enhances the rigidity and toughness of the film structure.

[0025] The inner layer is a heat-bonded sealing layer, made of polypropylene copolymer resin FL7642 produced by TPC in Singapore and a special n-butene-based olefin copolymer TAFMER produced by Mitsui in Japan. TM The composition consists of BL2491M, AB PP 10S open-face masterbatch provided by Baolide, and SLPP-7 PP slip masterbatch provided by Beijing Yalun. Among these, FL7642 exhibits good flowability at the melt temperature, good molding performance, excellent processing properties, and good thermal stability (decomposition temperature is 310℃). TAFMER TM BL2491M is a special n-butene-based olefin copolymer used to lower the sealing temperature of polypropylene films. It features a low melting point and good compatibility with polypropylene.

[0026] Experiments show that the polyolefin film prepared by this invention has good ductility, with a tensile strength of up to 80.1 MPa in the MD direction and an elongation at break of more than 726% in the TD direction. It also has a good balance between stiffness and impact resistance, with a puncture strength of more than 12.7 N. When used for film coating, it can provide good protection for the contents and the coated items. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the polyolefin material provided by the present invention.

[0028] The meanings of the symbols in the diagram are as follows:

[0029] 10-Modified heat-resistant layer; 20-Supporting layer; 30-Thermal-bonded sealing layer Detailed Implementation

[0030] The technical solution of the present invention will be described below with reference to the accompanying drawings and embodiments, so as to enable those skilled in the art to understand it.

[0031] like Figure 1 As shown, a flexible polyolefin material for coating is disclosed. This polyolefin material is a three-layer composite film, consisting of a surface layer (modified heat-resistant layer 10), a middle layer (support layer 20), and an inner layer (heat-bonding sealing layer 30) from the outside in. The total thickness of the three-layer composite film is 70–90 μm, preferably 80 μm.

[0032] The modified heat-resistant layer 10 has a thickness of 20-24 μm and is composed of 99.5 wt% polypropylene homopolymer resin HD915CF and 0.5 wt% polypropylene stiffening nucleating agent NA-27; the intermediate layer is the support layer 20, with a thickness of 38-42 μm, composed of 60 wt% homopolymer polypropylene resin FC801 and 40 wt% polypropylene homopolymer resin HD915CF; the inner layer is the heat-bonded sealing layer 30, with a thickness of 16-20 μm, composed of (42-48) wt% polypropylene copolymer resin FL7642, (47-53) wt% n-butenyl olefin copolymer BL2491M, 3 wt% open-pore masterbatch ABPP 10S and 2 wt% slip masterbatch SLPP-7.

[0033] The polyolefin material of this invention is produced by a non-stretching, non-directional flat extrusion process using a three-layer casting film equipment to extrude melt from multiple twin-screw extruders, followed by rapid cooling in a casting film equipment. The steps are as follows:

[0034] S1. The raw materials for the surface layer, middle layer and inner layer are prepared according to the proportion and then put into the mixer to mix evenly, and then fed into the extruder to melt.

[0035] S2. Following the order of the surface layer, intermediate layer, and inner layer, co-extrude and cast the material using an extruder, then cool and set it.

[0036] S3. The shaped film is subjected to corona treatment to obtain the desired thin-film polyolefin material.

[0037] Polyolefin three-layer films were prepared using the MIDEX2500 three-layer casting equipment from Reifenhaüth GmbH, Germany, according to the method described above.

[0038] Surface, support, and inner layer materials are added to the three barrels of the co-extrusion casting equipment, respectively. After co-extrusion, the materials in the three barrels enter the casting station. The temperatures of the three barrels of the extruder are set as follows: first section: 220°C, second section: 255°C, third section: 250°C, and die head temperature: 240°C. In the casting process, the surface temperature of the casting roller is set to 15°C. After casting and shaping, the surface layer is subjected to corona treatment. After corona treatment, a film material is obtained.

[0039] Referring to Table 1 below, the following Examples 1-3 were obtained by adjusting the thickness ratio:

[0040] Table 1. Raw material formulations for each layer prepared in Examples 1-3

[0041]

[0042]

[0043] Comparative Example 1 was prepared using a commonly used production formula for three-layer cast polypropylene film in the existing technology. The formula information for Comparative Example 1 is shown in Table 2 below, where FC801MX is Shanghai Petrochemical homopolymer polypropylene resin and SFC750R is Hunan Petrochemical copolymer polypropylene resin.

[0044] Table 2 Comparative Example 1 Raw Material Formulation

[0045]

[0046] Meanwhile, the laminated product produced by coating hot melt adhesive with commonly used BOPP (biaxially oriented polypropylene film) under specific production process conditions and then cooling and shaping it was used as Comparative Example 2. Its performance was tested with Examples 1-3 and Comparative Example 1 respectively, and the results are shown in Table 3.

[0047] Table 3 Performance comparison of Examples 1-3 and Comparative Examples 1-2

[0048]

[0049]

[0050] It can be seen that the polyolefin film prepared by this invention has good ductility, with a tensile strength in the MD direction reaching up to 80.1 MPa, which is superior to the comparative example. Its elongation at break in the TD direction is greater than 726%, making it suitable for coating irregularly shaped goods. Furthermore, it exhibits a good balance between stiffness and impact resistance, with a puncture strength greater than 12.7 N, significantly higher than the comparative example. The film prepared by this invention can provide good protection for both the contents and the coated item when used for coating.

[0051] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled 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 within the scope of protection of the present invention.

Claims

1. A polyolefin material for coating with flexible properties, characterized in that, The polyolefin material is in the form of a film, comprising three layers from the outside in: The surface layer is a modified heat-resistant layer (10) with a thickness of 20~24 μm, composed of 99.5 wt% polypropylene homopolymer resin and 0.5 wt% polypropylene modifier; The intermediate layer is a support layer (20) with a thickness of 38~42 μm, composed of 60 wt% homopolymer polypropylene resin and 40 wt% polypropylene homopolymer resin; The inner layer is a heat-bonded sealing layer (30) with a thickness of 16~20 μm, composed of (42~48)wt% polypropylene copolymer resin, (47~53)wt% n-butenyl olefin copolymer and 5wt% additives; The polypropylene modifying agent is a stiffening and nucleating agent, brand name NA-27; the polypropylene homopolymer resin is brand name HD915CF, the homopolymer polypropylene resin is brand name FC801, the polypropylene copolymer resin is brand name FL7642, and the n-butenyl olefin copolymer is brand name BL2491M.

2. The polyolefin material for coating with flexible surface properties as described in claim 1, characterized in that, The additives include open-cell masterbatch and slip masterbatch in a mass ratio of 3:

2.

3. The polyolefin material for coating with flexible surface properties as described in claim 2, characterized in that, The open-face masterbatch is designated ABPP 10S, and the slip masterbatch is designated SLPP-7.

4. The polyolefin material for coating with flexible surface properties as described in claim 1, characterized in that, The total thickness of the polyolefin material is 70~90 μm.

5. The polyolefin material for coating with soft surface properties as described in claim 4, characterized in that, The polyolefin material has a thickness of 80 μm, the surface layer has a thickness of 22 μm, the intermediate layer has a thickness of 40 μm, and the inner layer has a thickness of 12 μm.

6. A method for preparing a coating polyolefin material with a soft surface properties as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. The raw materials for the surface layer, middle layer and inner layer are prepared according to the proportion and then put into the mixer to mix evenly, and then fed into the extruder to melt. S2. Following the order of the surface layer, intermediate layer, and inner layer, co-extrude and cast the material using an extruder, then cool and set it. S3. The shaped film is subjected to corona treatment to obtain the desired thin-film polyolefin material.

7. The application of a polyolefin material with a smooth surface finish for coating as described in any one of claims 1-5 in product coating.

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