WO2021194003A1 - Multilayer polyethylene film and method for manufacturing same - Google Patents

Abstract

The present invention provides a multilayer polyethylene film comprising: a first polyethylene layer including a first polyethylene-based resin; a second polyethylene layer including a second polyethylene-based resin; and an intermediate layer located between the first polyethylene layer and the second polyethylene layer, and including an elastic polyethylene resin having an elongation at break of 500% or more, wherein the multilayer polyethylene film has excellent elasticity and mechanical properties by means of including the intermediate layer in an amount of 40% to 90% of the total film thickness.

Description

Multilayer polyethylene film and method for manufacturing the same

The present invention relates to a multilayer polyethylene film having improved mechanical properties such as elasticity and tensile strength, and a method for manufacturing the same.

PVC (Poly Vinyl Chloride) film has been generally used as a protective film attached to the surface for corrosion prevention or product protection during the production of cold-rolled steel sheets. Because PVC film has excellent tensile strength and elasticity, it has been usefully used to protect the surface of the adherend from damage such as press-fitting and scratches during processing (bending) of steel plates.

However, PVC film is decomposed into vinyl chloride and hydrochloric acid (HCl) by dehydrochlorination during incineration. . Due to these problems, it is impossible to reduce the cost because PVC film cannot be recycled.

In addition, a large amount of plasticizer is added to the PVC film to give it softness, which is known to be harmful to the human body.

Due to the various environmental problems as described above, not only countries around the world, but also governments or the private sector are developing alternative materials at the same time as PVC usage restrictions.

Polyethylene (PE, Polyethylen) is one of the inexpensive and easy-to-process plastic materials. Polyethylene is a polymer material with a simple structure and can be applied to various processing methods, so it is widely applied to mass-produced products or materials.

Polyethylene does not detect harmful substances such as dioxin, a problem with PVC, so it is used as a plastic material in various household and industrial fields such as wraps, films, food containers, agricultural films, buckets and washbasins.

In addition, the recovered polyethylene product can be decomposed and melted in the form of pellets, processed and reused, so that it can be recycled.

The problem to be solved by the present invention relates to a multilayer polyethylene film having improved elasticity.

The present invention also provides a method for producing the multilayer polyethylene film.

In order to solve the problem of the present invention,

A first polyethylene layer comprising a first polyethylene-based resin;

a second polyethylene layer comprising a second polyethylene-based resin; and

A multilayer polyethylene film positioned between the first polyethylene layer and the second polyethylene layer, comprising an intermediate layer comprising an elastic polyethylene resin having an elongation at break of 500% or more, and comprising the intermediate layer in an amount of 40 to 90% of the total film thickness provides

According to an embodiment, the tensile strength at break of the elastic polyethylene resin included in the intermediate layer may be 40 MPa or more, and the tear strength (Elmendorf Tear) may be 10 g/㎛ or more.

According to an embodiment, the first polyethylene-based resin and the second polyethylene-based resin each include at least one selected from low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE), respectively, a melting temperature of 100 to 130 ℃, It may have a melt index of 1.0 to 3.0 g/10min, and a density of 0.915 to 0.95 g/cm 3 .

According to one embodiment, the elastic polyethylene resin comprises at least one selected from a copolymer of polyolefin-based elastomer, polyolefin-based plastomer, m-LLDPE (Metallocene linear low density polyethylene) and EVA (Ethylene Vinyl Acetate), It may have a melting temperature of 80 °C to 120 °C, a melt index of 0.6 to 2.5 g/10min, and a density of 0.85 to 0.96 g/cm 3 .

In order to solve another problem of the present invention, in the multilayer polyethylene film,

storing the raw material chips of the first polyethylene layer in a hopper 100 for raw material chips;

storing the raw material chips of the intermediate layer in a hopper 200 for raw material chips;

storing the raw material chips of the second polyethylene layer in a hopper 300 for raw material chips;

sequentially supplying the raw materials stored in the hoppers 100, 200, and 300 for each raw material chip to the heating spraying device 400;

The multilayer having a first polyethylene layer 10, an intermediate layer 20, and a second polyethylene layer 30 by melting the raw material supplied from each of the raw material chip hoppers 100, 200, and 300 in the heating spraying device 400 and co-extruding it. It provides a method of manufacturing a multilayer polyethylene film comprising a; forming a polyethylene film (40).

The present invention provides a multilayer polyethylene film capable of exhibiting physical properties equivalent to or higher than that of a PVC film by including a polyethylene resin having excellent elasticity as a main component. In addition, by placing the elastic polyethylene resin in the middle of the first polyethylene resin and the second polyethylene resin, it is possible to manufacture a multilayer polyethylene film through co-extrusion.

1 is an exemplary cross-sectional view of a multilayer polyethylene film according to the present invention.

Figure 2 is a front view showing a state in which the main part of the present invention is installed and operated.

3 is an exemplary structural diagram of a protective film including a multilayer polyethylene film according to the present invention.

Since the present invention can apply various transformations and can have various embodiments, specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention. In describing the present invention, if it is determined that a detailed description of a related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted.

And in order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and similar reference numerals are attached to similar parts throughout the specification.

The present invention in order to solve the problems of the prior art,

A first polyethylene layer comprising a first polyethylene-based resin;

a second polyethylene layer comprising a second polyethylene-based resin; and

A multilayer polyethylene film positioned between the first polyethylene layer and the second polyethylene layer, comprising an intermediate layer comprising an elastic polyethylene resin having an elongation at break of 500% or more, wherein the intermediate layer is 40 to 90% of the total film thickness provides

The present invention can provide a polyethylene film having remarkably improved elasticity and tensile strength compared to the conventional polyethylene film by laminating elastic polyethylene having excellent elasticity with a conventional polyethylene film.

In this case, the conventional polyethylene film may refer to a polyethylene film typically used as an industrial film, such as for product packaging or for a protective film.

In the present invention, in the "multilayer polyethylene film" or "multilayer film", each layer constituting the multilayer film is not separately separated, but each layer is integrated to form one film may mean

According to one embodiment, the elastic polyethylene resin included in the intermediate layer may have an elongation at break of 500% or more, for example, the elongation at break measured using ASTM D882 may be 500% or more, preferably in the MD direction. The elongation at break of may be 500% or more, 520% or more, or 550% or more, and the elongation at break in the TD direction may be 500% or more, 520% or more, or 550% or more. According to an embodiment, the elongation at break may be higher in the TD direction.

According to one embodiment, the elastic polyethylene resin is one selected from polyolefin-based elastomer (POE), polyolefin-based plastomer (POP), m-LLDPE (metallocene-linear low-density polyethylene) or EVA (ethylene vinyl acetate) It may include more than one.

At this time, since the polyolefin-based resin has an elasticity similar to that of synthetic rubber as the density is lower, a polyolefin having an ultra-low density (density 0.885 g/cm ³ or less) is called a polyolefin elastomer (POE), and a higher density (density) 0.885 to 0.915 g/cm ³ ) Polyolefin is called polyolefin plastomer (POP) because it has plasticity rather than elasticity.

According to one embodiment, the tensile strength at break of the elastic polyethylene resin included in the intermediate layer may be 30 MPa or more, for example, the tensile strength at break measured using ASTM D882 may be 30 MPa or more, preferably, The tensile strength at break in the MD direction may be 30 MPa or more, 35 MPa or more, 40 MPa or more, or 45 MPa or more, and the tensile strength at break in the TD direction is 30 MPa or more, 35 MPa or more, 40 MPa or more, or 45 MPa or more. can

According to one embodiment, the tear strength (Elmendorf Tear) of the elastic polyethylene resin included in the intermediate layer may be 10 g/㎛ or more, for example, the tear strength measured by ASTM D1992 may be 10 g/㎛ or more and, preferably, the tear strength in the MD direction may be 10 g/㎛ or more, or 12 g/㎛ or more, and the tear strength in the TD direction is 10 g/㎛ or more, 12 g/㎛ or more, 14 g/㎛ or more. or more, or 15 g/㎛ or more, preferably, the tear strength in the TD direction may be higher than the tear strength in the MD direction.

According to one embodiment, the falling impact strength of the elastic polyethylene resin included in the intermediate layer may be 500 g or more, for example, the falling impact strength measured by ASTM D1709 may be 500 g or more, or 600 g or more. , 700 g or more, preferably 800 g or more.

In this case, the mechanical properties such as the modulus of elasticity at break, tensile strength at break, tear strength, and drop impact strength may be values measured at a film thickness of 20 μm to 80 μm.

According to one embodiment, the melting temperature of the elastic polyethylene resin included in the intermediate layer may be 80 ℃ to 120 ℃, preferably 90 to 120 ℃, the melt index is 0.6 to 2.5 g / 10min, preferably may be 0.6 to 2.0 g/10min, more preferably 0.6 to 1.5 g/10min.

In addition, the density of the elastic polyethylene resin included in the intermediate layer may be 0.85 g/cm 3 to 0.96 g/cm 3 , preferably 0.85 g/cm 3 or more, 0.87 g/cm 3 or more, or 0.90 g/cm 3 or more, and 0.94 or more. g/cm 3 or less, 0.93 g/cm 3 or less, or 0.92 g/cm 3 or less. For example, when the elastic polyethylene is at least one selected from a thermoplastic polyolefin-based elastomer and a polyolefin-based plastomer, it may be 0.85 to 0.91 g/cm 3 , and the elastic polyethylene included in the intermediate layer is m-LLDPE and EVA air. When one or more selected from coalescence is included, it may have a density of 0.91 to 0.96 g/cm 3 .

According to one embodiment, the melting temperature of the first polyethylene-based resin and the second polyethylene-based resin is 100 to 130 ℃, preferably 100 to 120 ℃, the melt index is 1.0 to 3.0 g / 10 min, preferably 1.0 to 2.5 g/10 min, and the density may be 0.915 to 0.95 g/cm 3 , preferably 0.915 to 0.93 g/cm 3 .

According to one embodiment, the first polyethylene-based resin and the second polyethylene-based resin may be a mixture of one or more polyethylene-based resins, preferably, the first polyethylene-based resin and the second polyethylene-based resin are each low-density. It may include one or more selected from polyethylene (LDPE) and linear low-density polyethylene (LLDPE).

According to an embodiment, the intermediate layer may further include another polyethylene-based resin in addition to the elastic polyethylene resin, for example, one or more polyethylene-based resins selected from LLDPE or LDPE in 100 parts by weight of the elastic polyethylene resin. It may be further included in an amount of 0.5 to 10 parts by weight, and the elastic modulus may be lowered in an amount of 10 parts by weight or more.

The polyethylene film according to the present invention may have a thickness of 60 to 100 μm, and according to one embodiment, the intermediate layer may be 40 to 90% of the total thickness of the film, for example, 40% or more of the total film thickness , 50% or more, or 60% or more, and may be provided in a ratio of 90% or less, 85% or less, or 80% or less. The first polyethylene layer and the second polyethylene layer may each be 5 to 30% of the total thickness of the film, preferably 5% or more, 10% or more, or 15% or more, 30% or less, 25% or less, or 20% or more may be below. If the intermediate layer is less than 40% of the total thickness, physical properties such as tensile force and elastic modulus may be reduced, and if the intermediate layer is thicker than 90%, fairness may be lowered, which may make it difficult to manufacture a thin film.

According to an embodiment, the first polyethylene layer, the intermediate layer, and the second polyethylene layer may each be further added with additives as needed, for example, pigments, UV stabilizers, flame retardants, lubricants, plasticizers, antioxidants, Additives such as anti-blocking agents, slip agents, impact modifiers, processing aids and softeners may be further added, but are not limited thereto.

According to one embodiment, the intermediate layer may include one or more additives selected from antioxidants, anti-blocking agents, impact modifiers, slip agents, and processing aids, and the additive is added to 100 parts by weight of the elastic polyethylene resin. 0.05 to 0.5 parts by weight, preferably 0.05 to 0.3 parts by weight, may be further added.

According to an embodiment, the first polyethylene layer and the second polyethylene layer may not include a slip agent and an anti-blocking agent as additives.

The present invention also, in the multilayer polyethylene film,

storing the raw material chips of the first polyethylene layer in a hopper 100 for raw material chips;

storing the raw material chips of the intermediate layer in a hopper 200 for raw material chips;

storing the raw material chips of the second polyethylene layer in a hopper 300 for raw material chips;

sequentially supplying the raw materials stored in the hoppers 100, 200, and 300 for each raw material chip to the heating spraying device 400; and

The multilayer having a first polyethylene layer 10, an intermediate layer 20, and a second polyethylene layer 30 by melting the raw material supplied from each of the raw material chip hoppers 100, 200, and 300 in the heating spraying device 400 and co-extruding it. It provides a method of manufacturing a multilayer polyethylene film comprising a; forming a polyethylene film (40).

According to one embodiment, in the present invention, the method of co-extruding the resins of each layer may be made using a co-extruder in which a plurality of extruders are connected to a lamination die. For example, the heating spraying device 400 may be a T-type die for co-extrusion or a circular die. The co-extruded raw material may be formed in the form of a straight laminated sheet through a T-die, or may be formed in a cylindrical laminated sheet through a circular die.

According to one embodiment, the present invention may use an air-cooled blow method of forming a cylindrical laminated sheet through a circular die. For example, the molten resin in the extruder barrel passes through a circular die and is extruded into a tube state. It creates a hollow cylinder called a "bubble". At this time, when the desired film width is determined, no more air is put into the tube. The bubble is taken off by a nip roll, passed through several guide rolls, and then wound into two layers of film on a winder. At this time, the width of the film is determined by the bubble size, and when the extrusion amount is constant, the thickness can be controlled by the nip roll speed.

According to an embodiment, the heating spraying device 400 may further include a thickness adjusting device (not shown) for adjusting the thickness of each layer, and the thickness of each layer may be individually adjusted from the device. have. For example, in the step of co-extruding each raw material from the heating spraying device 400, the thickness control device may adjust the thickness ratio of each layer.

In general, POE, POP, and EVA have a high melt viscosity, so film formation by extrusion is not easy, so there may be a problem in that it is difficult to manufacture a single film by extrusion. In order to solve this problem, the present invention prepares a film by disposing a polyethylene resin with easy extrusion processability on both sides of an elastic polyethylene resin selected from a polyolefin-based elastomer, a polyolefin-based plastomer, or EVA, which is a raw material having high elasticity. By doing so, it may be possible to manufacture a film containing the elastic polyethylene as a main component as described above using a co-extrusion process. The film prepared as described above may have mechanical properties, such as elasticity and tensile force, on the same level as that of the elastic polyethylene resin included in the intermediate layer.

In this case, as the polyethylene film having easy extrusion processability, a polyethylene film that has been used as an industrial film such as a conventional product packaging and protective film may be used.

In the present invention, the multilayer polyethylene film may be laminated with a release paper for preservation until use. In the practice of the present invention, the release paper may use a normal release paper that can be peeled off from the film during use, and there is no particular limitation on the material.

According to one embodiment, the multilayer polyethylene film according to the present invention may be used as a steel plate protective film.

In general, the soft PVC film, which is mainly used as a protective film, has excellent flexibility and exhibits high tensile strength and elongation. has been

However, PVC film can be decomposed into vinyl chloride and hydrochloric acid (HCl) by dehydrochlorination during incineration, which is not only harmful to the human body, but also generates chlorine compounds and dioxine that can corrode the adherend. There is a fatal problem with doing it.

The elastic polyethylene film according to the present invention does not generate harmful substances such as dioxins and chlorine compounds while retaining the physical properties (softness and tensile strength) of the existing soft PVC films, so it can be used as a protective film to replace the existing PVC. can

According to one embodiment, as shown in FIG. 3 , a steel sheet protective film having a release layer (A) and a pressure-sensitive adhesive coating layer (C) on both sides of the multilayer polyethylene film (B) according to the present invention may be provided. For example, the release layer (A) is a layer that can be separated during printing and winding, and a corona treatment function for printing and a back treatment function that is separated during film winding can be added, and the pressure-sensitive adhesive coating layer (C) is A function of facilitating subsequent detachment while adhering the steel plate and the protective film, such as a corona treatment function, may be added.

According to one embodiment, the multilayer polyethylene film according to the present invention may be used as a packaging film.

Hereinafter, embodiments of the present invention will be described in detail so that those of ordinary skill in the art can easily carry out the present invention. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein.

<Example 1> Polyolefin plastomer elastic film

LDPE (Low Density Polyethylene) having the physical properties of Table 1 below was used as a raw material for the first polyethylene layer and the second polyethylene layer, and the middle layer is a POP (Polyolefin plastomer) resin having the physical properties of Table 1 below using a first high elasticity A polyethylene film was prepared.

<Example 2> m-LLDPE elastic film

LDPE (Low Density Polyethylene) having the physical properties of Table 1 below was used as a raw material for the first polyethylene layer and the second polyethylene layer, and m-LLDPE (Linear Low Density Polyethylene) resin having the physical properties of Table 1 below was used for the intermediate layer. Thus, a second high elastic polyethylene film was prepared.

	Elongation at break (%) ASTM D882		Tensile strength at break (MPa) ASTM D882		Drop impact strength (g) ASTM D1709	Tear strength (g/㎛) ASTM D1922		DensityASTMD1505 (g/cm 3 )	Melting point (℃)	MFR(g/10min)ASTMD1238)
	MD	TD	MD	TD		MD	TD
LDPE	300	550	27	24	65	-	-	0.924	112	2.0
POP	570	600	50	50	830	13.5	17.5	0.902	98	1.2
m-LLDPE	600	650	50	45	>950	-	-	0.918	117	1.0

* MFR (melting index): measured at 190℃, 2.16kg.

As described above in detail a specific part of the content of the present invention, for those of ordinary skill in the art, it is clear that this specific description is only a preferred embodiment, and the scope of the present invention is not limited thereby. something to do. Accordingly, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

Claims (5)

1. A first polyethylene layer comprising a first polyethylene-based resin;

   a second polyethylene layer comprising a second polyethylene-based resin; and

   A multilayer polyethylene film positioned between the first polyethylene layer and the second polyethylene layer, comprising an intermediate layer comprising an elastic polyethylene resin having an elongation at break of 500% or more, and comprising the intermediate layer in an amount of 40 to 90% of the total film thickness .
2. According to claim 1,

   A multilayer polyethylene film having a tensile strength at break of 40 MPa or more and a tear strength (Elmendorf Tear) of 10 g/㎛ or more of the elastic polyethylene resin included in the intermediate layer.
3. According to claim 1,

   Each of the first polyethylene-based resin and the second polyethylene-based resin includes at least one selected from low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE), respectively, and a melting temperature of 100 to 130° C., 1.0 to 3.0 g/10 min. of a melt index, and a multilayer polyethylene film having a density of 0.915 to 0.95 g/cm 3 .
4. According to claim 1,

   The elastic polyethylene resin includes at least one selected from a polyolefin-based elastomer, a polyolefin-based plastomer, a copolymer of m-LLDPE and EVA, a melting temperature of 80 to 120° C., a melt index of 0.6 to 2.5 g/10 min, and a multilayer polyethylene film having a density of 0.85 to 0.96 g/cm 3 .
5. The multilayer polyethylene film according to any one of claims 1 to 4,

   storing the raw material chips of the first polyethylene layer in a hopper 100 for raw material chips;

   storing the raw material chips of the intermediate layer in a hopper 200 for raw material chips;

   storing the raw material chips of the second polyethylene layer in a hopper 300 for raw material chips;

   sequentially supplying the raw materials stored in the hoppers 100, 200, and 300 for each raw material chip to the heating spraying device 400;

   The multilayer having a first polyethylene layer 10, an intermediate layer 20, and a second polyethylene layer 30 by melting the raw material supplied from each of the raw material chip hoppers 100, 200, and 300 in the heating spraying device 400 and co-extruding it. A method of manufacturing a multilayer polyethylene film comprising; forming a polyethylene film (40).

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