KR20230035894A - Manufacturing method of polymethylmethacrylate blown film - Google Patents

Abstract

The present invention provides a manufacturing method of a polymethyl methacrylate (PMMA) blown film. The manufacturing method comprises the steps of: supplying a polyethylene (PE) resin to each of a plurality of extruders of a blown film manufacturing device; supplying a polymethyl methacrylate (PMMA) resin to a separate extruder of the blown film manufacturing device; co-extruding the polymethyl methacrylate (PMMA) resin with a polyethylene melt-extrusion resin which is melt-extruded from the extruder to obtain a mixed melt-extruded resin; extruding the mixed melt-extruded resin into a tube and forming bubbles; compressing the bubbles to form a multilayer film in which a polyethylene (PE) film is laminated on both surfaces of a polymethyl methacrylate (PMMA) film; and peeling off the polyethylene (PE) film from the multilayer film and winding only the polymethyl methacrylate (PMMA) film. In the polymethyl methacrylate (PMMA) blown film manufactured according to the present invention, the molecular orientation of the resin occurs in both a machine direction (MD) and a machine transverse direction (TD). Therefore, the polymethyl methacrylate (PMMA) blown film can be biaxially stretched to improve physical properties.

Description

Manufacturing method of polymethylmethacrylate (PMMA) blown film {Manufacturing method of polymethylmethacrylate blown film}

The present invention relates to a method for producing a polymethyl methacrylate (PMMA) blown film.

Polymethylmethacrylate (PMMA) is a synthetic polymer of methyl methacrylate commonly called acrylic. It has excellent transparency, optical properties, abrasion resistance, and printability, maintains long-term weather resistance and transparency, and can be vacuum-formed. In addition, it is a material that is widely applied to exterior plate materials for construction, high-brightness reflective film, automobile interior materials, and optical applications.

Recently, demand for a high-strength, long-width PMMA film having a width of 2,000 mm or more is particularly increasing, but it is difficult to produce such a long-width PMMA film according to a casting extrusion method, which is a conventional PMMA film production method. In addition, since the PMMA film produced by the casting extrusion method is stretched only in the machine direction (MD), there is a lot of room for improvement in terms of physical properties.

Korean Patent Registration No. 10-2106435 discloses a method for manufacturing an impact-modified PMMA film by co-extrusion, and Korean Patent Registration No. 10-0643549 discloses a method for manufacturing a surface-cured PMMA film by a film-insert molding method. However, the production of long-width PMMA films with improved physical properties is not described.

The molten resin is passed through a circular die of an extruder to form a tube-shaped bubble, and a certain level of air is blown into the bubble to determine the film width, and then the film is folded by nip-rolls and wound into a tube. The method is called inflation or tube method. do.

The present inventors have completed the present invention by confirming that a high-strength and long-width PMMA blown film can be manufactured by applying the inflation or tube method to the production of a PMMA blown film.

KR 10-2106435 B1 KR 10-0643549 B1

An object of the present invention is to provide a method for producing a long-width polymethyl methacrylate (PMMA) blown film having excellent physical properties.

In order to solve the above problems, the present invention

a) supplying polyethylene (PE) resin to the first extruder and the third extruder of the blown film manufacturing apparatus, respectively; b) supplying polymethyl methacrylate (PMMA) resin to the second extruder of the blown film manufacturing apparatus; c) obtaining a mixed melt extrusion resin by co-extruding a polymethyl methacrylate (PMMA) resin with each polyethylene melt extrusion resin melt-extruded from the first extruder and the third extruder; d) passing the mixed melt extrusion resin through a circular die to extrude it into a tube state and form bubbles; e) forming a multi-layer film in which polyethylene (PE) films are laminated on both sides of a polymethyl methacrylate (PMMA) film by compressing the bubble by passing it through nip rolls; and f) peeling the polyethylene (PE) film from the multilayer film and winding only the polymethyl methacrylate (PMMA) film.

In addition, the present invention provides a polymethyl methacrylate (PMMA) blown film prepared according to the above manufacturing method.

According to the present invention, a long-width PMMA blown film having a width of 2,000 to 4,000 mm can be manufactured.

The PMMA blown film prepared according to the present invention can be biaxially stretched to improve physical properties because the molecular orientation of the resin occurs in both the machine direction (MD) and the machine direction (TD).

Since the PMMA blown film manufactured according to the present invention can adjust the molecular orientation according to the adjustment of the expansion ratio, it has the advantage of balancing physical properties in both the machine direction (MD) and the machine direction (TD) direction.

1 schematically shows an example of a blown film manufacturing apparatus.
2 schematically shows a multilayer film in which polyethylene (PE) films (A-1 and A-2) are laminated on both sides of a polymethyl methacrylate (PMMA) film (B) prepared according to the present invention. .

1 is a block composed of an extruder (10) having a screw, a blown film die (20), an air ring (30), a nip roll (40), and the like. It schematically shows an example of a new film manufacturing apparatus.

Referring to FIG. 1, the polymethyl methacrylate (PMMA) blown film manufacturing method of the present invention is a mixture of polyethylene (PE) resin and polymethyl methacrylate (PMMA) resin melted in the extruder 10 barrel. The molten resin 80 is passed through a circular blown film die 20 to form a film, and at the same time cooled by air cooling, the cooled film is molded into a tube shape, air is injected into the tube to expand it, and at the same time an air ring 30 Cooling air is introduced to the outside of the tube to create an inflated tube, also referred to as "bubble", and then the bubble is taken off from the nip roll 40 and passed through several guide rolls. It may be a process of peeling only the PE with the further 70 and winding only the PMMA film alone.

Figure 2 schematically shows a multilayer film in which polyethylene (PE) films (A-1, A-2) are laminated on both sides of a polymethyl methacrylate (PMMA) film (B) obtained during the manufacturing process of the present invention. will be.

The manufacturing method of the present invention is a skin layer (skin layer) on both sides of the polymethyl methacrylate (PMMA) film (B) as a core layer (core layer) or a polyethylene (PE) film (A-1, A as a support film) -2) manufacturing a multilayer film in which these are laminated.

In the multilayer film, the polyethylene (PE) films (A-1 and A-2) serve as a support so that the polymethyl methacrylate (PMMA) resin can be bubble molded stably.

In step a), polyethylene (PE) resin is separately supplied to two extruders (a first extruder and a second extruder) to serve as a support for the polymethyl methacrylate (PMMA) film during extrusion and blowing.

The polyethylene (PE) resin may be low density polyethylene (LDPE), linear low density polyethylene (LLDPE), or a mixture thereof.

The polyethylene (PE) resin has a relatively wide molecular weight distribution, and low density polyethylene (LDPE) is most suitable, and products can be produced by mixing linear low density polyethylene (LLDPE) and low density polyethylene (LDPE). Low-density polyethylene (LDPE) exhibits high viscosity at low shear rates (less than 1 s-1), contributing to parison stability during blow molding, and low viscosity in the actual extrusion processing range (102 ~ 103 s-1) It has the advantage that the processing load is low. In addition, since low-density polyethylene (LDPE) resin has more long-chain branches than LLDPE or HDPE, it has relatively high melt tension, so it has the advantage of bubble stability during blown film extrusion and less neck-in problems in extrusion coating.

In the present invention, polyethylene (PE) resin is co-extruded with polymethyl methacrylate (PMMA) resin, and serves as a support so that polymethyl methacrylate (PMMA) resin can be bubble molded stably during extrusion and blowing. .

Polyethylene (PE) resin has a non-polar property, so even when polyethylene (PE) films are laminated on both sides of the polymethyl methacrylate (PMMA) film, it does not adhere to the polar polymethyl methacrylate (PMMA) film and wine It can be peeled off using a winder.

The polyethylene (PE) resin preferably has a melt index (MI) of 0.3 to 5 g/10 min when measured under a load condition of 190° C./2.16 kg according to ASTM (D-1238).

When using a low-density polyethylene (LDPE) resin, the melt index (MI) is preferably 0.3 to 3 g/10 min, and when using a linear low-density polyethylene (LLDPE) resin, the melt index (MI) is 1 to 3 g/10 Minutes are more preferred.

The polyethylene (PE) resin may have a molecular weight of 120,000 to 140,000 g/mol.

The polymethyl methacrylate (PMMA) resin preferably has a melt index (MI) of 3 to 5 g/10 min, when measured under a load condition of 230° C./2.16 kg according to ASTM (ASTM D1238), and More preferably g/10 min.

The polymethyl methacrylate (PMMA) resin may have a molecular weight of 260,000 to 400,000 g/mol.

Co-extrusion in step c) may be performed at 100 to 260 ° C, but is not limited thereto.

Step d) may be a step of forming a tubular film, also known as “bubble”, by passing a mixed melt extrusion resin composed of polyethylene molten resin and polymethyl methacrylate molten resin through a circular die. .

Step d) may be a step of inflating the bubble to a desired diameter by injecting air into the inside of the bubble.

The air pressure can be characterized by the blow-up ratio, defined as the diameter of the bubble divided by the diameter of the die.

In addition, the bubble size may be adjusted according to the width of the blown film to be obtained.

For example, a blown film having a width of 1,413 to 4,000 mm may be manufactured by adjusting the diameter of the bubble to be 450 to 1,273 mm.

In step e), the bubbles may be cooled and molded into a film form.

Cooling can be air-cooled or water-cooled. Air-cooling may be a process of flowing cooling air in a tangential direction to the film surface or in a direction perpendicular to the film surface within the entire tube forming section. Since the crystal structure of the resin changes depending on the cooling rate, a film with excellent transparency can be made in the case of water cooling.

The bubble formed in the form of a film in step e) is flattened into a film while passing between nip rolls, and polyethylene (PE) films are laminated on both sides of the polymethyl methacrylate (PMMA) film to form a multilayer film. can do. At this time, lamination does not mean attachment. Since the polyethylene (PE) film has a non-polar property, it is not attached to a polymethyl methacrylate (PMMA) film having a polar property.

In step e), the nip roll speed may be adjusted to 10 m/min to 20 m/min. If it is less than 10 m/min, tube molding may not be possible, and if it exceeds 20 m/min, quality defects may occur due to wrinkles during film winding.

When the amount of extrusion is constant, the thickness of the film can be controlled by adjusting the speed of the nip roll.

Preferably, the thickness of the film is adjusted to 20 μm to 100 μm by adjusting the nip roll speed. If it is less than 20 μm, the film may be cut in the middle and normal film winding may not be possible, and if it is more than 100 μm, bubble molding may not be possible.

In step f), the polyethylene (PE) film may be peeled from the multilayer film using a separate winder.

Since the polyethylene (PE) film has a non-polar property, it is not attached to the polar polymethyl methacrylate (PMMA) film, so it is not affected by the polymethyl methacrylate (PMMA) film by using a separate winder. The polyethylene (PE) film can be peeled off without giving.

When producing a PMMA film by the blown extrusion method according to the manufacturing method of the present invention, only one edge of the film produced in the form of a tube is cut and wound, and when used unfolded during processing, the width is 700 to 4,000 mm, preferably 2,000 mm. It is possible to produce long-width films of ~ 4,000 mm, more preferably 3,000 ~ 4,000 mm.

The polymethyl methacrylate (PMMA) blown film prepared according to the present invention was far superior to the cast film in tensile strength, elongation, impact strength, and tear strength as a result of the experiment.

The polymethyl methacrylate (PMMA) blown film prepared according to the present invention has a tensile strength of 310 kgf/cm 2 or more, an elongation of 60% or more, an impact strength of 140 J/m or more, and a tear strength of 4 It can be more than gf.

Therefore, the polymethyl methacrylate (PMMA) blown film of the present invention is very useful as an exterior panel material for construction, a high-brightness reflective film, an automobile interior material, and an optical material.

Hereinafter, an embodiment of the present invention will be described in more detail. These examples are only presented as an example to explain the present invention in more detail, and it will be apparent to those skilled in the art that the scope of the present invention is not limited by these examples. .

<Material>

Polyethylene (PE) resin: MI 1.6 g/10 min, molecular weight 120,000 ~ 140,000 g/mol, manufacturer Hanwha Chemical

Polymethyl methacrylate (PMMA) resin: MI 3 g/10 min, molecular weight 260,000-400,000 g/mol, manufacturer LX MMA.

<Example 1> Preparation of blown film

Blow extrusion was performed on a blown film line apparatus using a low density structure featuring a die diameter of 50 mm, a blowing speed of 2.5, no neck, and a die spacing of 1.4 mm. Cooling of the bubble was carried out via room temperature air, which was carried out only outside the bubble at a rate of 12 kg/h.

The polyethylene (PE) resin is supplied to the first extruder and the third extruder, respectively, and the polymethyl methacrylate (PMMA) resin is supplied to the second extruder, and is melt-extruded from the first extruder and the third extruder. Polymethyl methacrylate (PMMA) resin was co-extruded at 240 ° C. with each polyethylene melt extrusion resin to obtain a mixed melt extrusion resin, and then passed through a circular die to extrude into a tube state and form bubbles. . At this time, the diameter of the bubble was adjusted to 955 mm. The bubble was passed between nip rolls at a speed of 17 m/min to obtain a multilayer film in which polyethylene (PE) films (thickness: 20 μm) were laminated on both sides of the polymethyl methacrylate (PMMA) film. A polymethyl methacrylate (PMMA) film (thickness: 100 μm) having a width of 3000 mm was obtained by peeling the polyethylene film from the multilayer film using a separate winder.

<Comparative Example 1> Preparation of casting film

Multi-layer polyethylene (PE) film laminated on both sides of a polymethyl methacrylate (PMMA) film (thickness: 100㎛) using a 3-layer T-die cast extrusion method A film was obtained. At this time, the width of the polymethyl methacrylate (PMMA) film was 1,500 mm.

<Experimental Example 1>

In order to compare the physical properties of the blown film prepared in Example 1 and the cast film prepared in Comparative Example 1, the tensile strength, elongation, impact strength, and tear strength were measured by the experimental method described in Table 1 below. The results are shown in Table 1 below.

division tensile strength
[kgf/cm ² ] elongation rate
[%] Impact strength [J/m] tear strength
[gf] MD TD MD TD PMMA film
(100 μm) casting film
(Comparative Example 1) 350 270 85 50 below 120 2.5 blown film
(Example 1) 400 310 90 60 140 4 Test Methods ASTM D882 ASTM D882 ASTM D785 KS M ISO 6383-2:2010

As shown in Table 1, the blown film prepared in Example 1 was far superior to the cast film prepared in Comparative Example 1 in tensile strength, elongation, impact strength, and tear strength.

10: extruder
20: blown film die
30: air ring
40: nip roll
50: tube collapsing frame
60: edge trim
70: winder
80: mixed molten resin

Claims (12)

a) supplying polyethylene (PE) resin to the first extruder and the third extruder of the blown film manufacturing apparatus, respectively;
b) supplying polymethyl methacrylate (PMMA) resin to the second extruder of the blown film manufacturing apparatus;
c) obtaining a mixed melt extrusion resin by co-extruding a polymethyl methacrylate (PMMA) resin with each polyethylene melt extrusion resin melt-extruded from the first extruder and the third extruder;
d) passing the mixed melt extrusion resin through a circular die to extrude it into a tube state and form bubbles;
e) forming a multi-layer film in which polyethylene (PE) films are laminated on both sides of a polymethyl methacrylate (PMMA) film by compressing the bubble by passing it through nip rolls; and
f) peeling the polyethylene (PE) film from the multilayer film and winding only the polymethyl methacrylate (PMMA) film
Polymethyl methacrylate (PMMA) blown film manufacturing method comprising a.
According to claim 1,
The polyethylene (PE) resin is low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or a mixture thereof.
According to claim 1,
The polyethylene (PE) resin has a melt index (MI) of 0.3 to 5 g/10 min and a molecular weight of 120,000 to 140,000 g/mol when measured under a load condition of 190° C./2.16 kg according to ASTM (D-1238) Phosphorus manufacturing method.
According to claim 1,
The polymethylmethacrylate (PMMA) resin has a melt index (MI) of 3 to 5 g/10 min and a molecular weight of 260,000 to 400,000 g/10 min when measured under a load condition of 230° C./2.16 kg according to ASTM (ASTM D1238). A manufacturing method that will be mol.
According to claim 1,
The co-extrusion in step c) is a manufacturing method that is carried out at 100 to 260 ℃.
According to claim 1,
A manufacturing method in which the diameter of the bubble is adjusted to 450 to 1,273 mm in step d).
According to claim 1,
When the extrusion amount is constant in step e), the thickness of the polymethyl methacrylate (PMMA) blown film is adjusted to 20 μm to 100 μm by adjusting the nip roll speed to 10 m / min to 20 m / min manufacturing method.
According to claim 1,
In the step f), the manufacturing method of peeling the polyethylene (PE) film from the multilayer film using a separate winder.
According to claim 1,
The width of the polymethyl methacrylate (PMMA) blown film is a manufacturing method of 700 to 4,000 mm.
A polymethylmethacrylate (PMMA) blown film prepared according to any one of claims 1 to 9.
According to claim 10,
The width of the polymethyl methacrylate (PMMA) blown film is 700 to 4,000 mm of polymethyl methacrylate (PMMA) blown film.
According to claim 11,
The polymethyl methacrylate (PMMA) blown film has a tensile strength of 310 kgf / cm 2 or more, an elongation of 60% or more, an impact strength of 140 J / m or more, and a tear strength of 4 gf or more. Methyl methacrylate (PMMA) blown film.

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