CN105916657A - Stretched film manufacturing method - Google Patents

Abstract

The present invention provides a method for producing a stretched film. The method for producing a stretched film comprises: a composite film forming step in which a first thermoplastic film is melted and coextruded through a self-forming die (220). The resin and the second thermoplastic resin different from the first thermoplastic resin are then cooled to solidify the first thermoplastic resin and the second thermoplastic resin, thereby forming a central portion including the first thermoplastic resin. , a composite film (100) formed at both ends of the central portion in the width direction and composed of the second thermoplastic resin at both ends; and a stretching step, in which the composite film is (100) Stretching by heating at least in the longitudinal direction to form a stretched film, the method for producing the stretched film is characterized in that as the first thermoplastic resin and the second thermoplastic resin, a difference in glass transition temperature between Thermoplastic resins below 10°C.

Description

Stretch film manufacturing method

technical field

The invention relates to a method for manufacturing a stretched film.

Background technique

When manufacturing a stretched film, prepare a film as a material, and use the method of stretching the prepared film to stretch the film. As a method for stretching a film, the following synchronous biaxial stretching method, etc. are known: The film is conveyed into a heating furnace while holding both ends of the film with clips, and in the heating furnace, the film is simultaneously heated and stretched in the longitudinal direction and the width direction by the clips holding both ends of the film.

In this synchronous biaxial stretching method, the film is heated and stretched to the required stretching ratio by stretching the film in the length direction and width direction in a heating furnace. However, when stretching the film, due to A large stress is applied to both ends of the film held by the jigs, so cracks are generated at both ends, and this may cause the entire film to break. Therefore, a technique is known in which both ends held by clips are reinforced with a resin stronger than the resin constituting the originally intended film in order to prevent the film from breaking when heated and stretched.

For example, Patent Document 1 discloses a technique of manufacturing a stretched film by heating and stretching the reinforced film using a reinforcing film using the tensile stress value at the time of heating and stretching. The thermoplastic resin having a larger tensile stress value when heated and stretched than the thermoplastic resin constituting the central portion of the film forms both end portions at both ends in the width direction of the film.

prior art literature

patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2008-149511

Contents of the invention

The problem to be solved by the invention

However, in the technology of this patent document 1, in order to increase the tensile stress value at the time of heating and stretching at both ends of the film, as the thermoplastic resin constituting both ends of the film, a thermoplastic resin having a higher temperature than that constituting the central portion of the film is used. A thermoplastic resin having a high glass transition temperature (for example, having a high glass transition temperature of 35° C. or higher) has the following problems.

That is, in the technology of Patent Document 1, when heating and stretching, if the heating temperature in the heating furnace is set to be near the glass transition temperature of the central portion of the film, the heating temperature in the heating furnace will be higher than that of the film. The glass transition temperature of both ends is too low, so there is also a problem that both ends are not softened enough, and when the two ends are held by the clips and stretched, the clips will fall off, Breakage of the film. On the other hand, in the technology of Patent Document 1, if the heating temperature in the heating furnace is set near the glass transition temperature of both ends of the film, the heating temperature in the heating furnace will be lower than that of the glass in the center of the film. The transition temperature is too high, so there are problems that the center portion will be too softened to properly stretch the center portion, the molecular orientation of the center portion will become non-uniform when exposed to high temperature, and the resulting stretched The strength of the stretched film is reduced.

The present invention has been made in view of such actual conditions, and its object is to provide a method for producing a stretched film. In this production method, the following composite film is used, and such a composite film is stretched under heating to produce When stretching a film, heating and stretching can be appropriately performed, and a stretched film excellent in productivity and quality can be obtained. This composite film is formed by forming both end portions at both ends in the width direction of the film using a thermoplastic resin different from the thermoplastic resin constituting the central portion of the film.

solutions to problems

The inventors of the present invention found that when producing a stretched film, as the thermoplastic resin constituting the center portion of the film before heating stretching and the thermoplastic resin constituting both end portions, a glass transition temperature difference of 10° C. or less is used. Resin can achieve the above objects, thus completing the present invention.

That is, according to the method for producing a stretched film of the present invention, the method for producing a stretched film includes: a composite film forming step in which the first thermoplastic resin and the A second thermoplastic resin different from the first thermoplastic resin is then cooled to solidify the first thermoplastic resin and the second thermoplastic resin to form a central portion made of the first thermoplastic resin, along the a composite film formed at both ends of the central portion in the width direction and at both ends of the second thermoplastic resin; and a stretching step of heating the composite film at least in the longitudinal direction Stretching to form a stretched film. The method for producing the stretched film is characterized in that a thermoplastic resin having a difference in glass transition temperature of 10° C. or less is used as the first thermoplastic resin and the second thermoplastic resin.

In the production method of the present invention, it is preferable that the elongation at break at normal temperature of the both ends made of the second thermoplastic resin in the composite film before heating stretching is greater than that obtained by the composite film. Elongation at break at room temperature of the central portion made of the first thermoplastic resin.

In the production method of the present invention, it is preferable that the tensile stress value at the time of heated stretching of the both end portions made of the second thermoplastic resin be equal to that of the central portion made of the first thermoplastic resin. Within 4 times of the tensile stress value during heating and stretching.

In the production method of the present invention, it is preferable that the viscosity of the second thermoplastic resin when melted and coextruded from the molding die is equal to that of the first thermoplastic resin melted and coextruded from the molding die. 0.5 times to 2 times the viscosity at that time.

In the production method of the present invention, preferably, in the stretching step, a synchronous biaxial stretching process that stretches not only the longitudinal direction of the composite film but also the width direction of the composite film is used. Stretching method is used to heat and stretch the composite film.

In the production method of the present invention, it is preferable that the first thermoplastic resin is an acrylic resin.

In addition, in the production method of the present invention, it is preferable that the second thermoplastic resin is polycarbonate (PC) mixed with a thermoplastic resin having a glass transition temperature lower than that of the acrylic resin. made of mixed resin.

Furthermore, in the production method of the present invention, it is preferable that the composite film is heated and stretched in the stretching step so that the thickness of the central portion of the composite film after heating and stretching is 15 μm. ~50μm range.

The effect of the invention

According to the present invention, it is possible to provide a method for producing a stretched film capable of preventing breakage during stretching and having excellent productivity and yield.

Description of drawings

FIG. 1 is a diagram for explaining a method of producing a composite thin film in a composite thin film forming step.

Fig. 2 is a diagram for explaining a method of stretching a composite film by a simultaneous biaxial stretching method in a stretching step.

Fig. 3 is a graph showing the glass transition temperature of a mixed resin obtained by mixing polycarbonate (PC) with polyethylene terephthalate (PET).

Fig. 4 is a graph showing tensile stress values corresponding to stretch ratios when thermoplastic resins used in Examples and Comparative Examples are stretched under heating at a temperature of 140°C.

detailed description

Hereinafter, embodiments of the present invention will be described based on the drawings.

The manufacturing method of the stretched film according to this embodiment includes the following steps: a composite film forming step in which the first thermoplastic resin and the second thermoplastic resin different from the first thermoplastic resin are formed by using a T-die for forming. thermoplastic resins are melted and co-extruded to form a composite film; and a stretching process of heating and stretching the composite film in a length direction and a width direction.

Composite film forming process

The composite film forming step is a step of obtaining the composite film 100 by melt-coextruding the first thermoplastic resin and the second thermoplastic resin from a T-die. Here, FIG. 1 is a diagram for explaining a composite thin film forming process. In this embodiment, as the composite film 100, as shown in FIG. The portion 110 is formed of a first thermoplastic resin, and the both end portions 120 are formed of a second thermoplastic resin. In addition, the central part 110 of the composite film 100 is a part which becomes a stretched film by heating and stretching in the stretching process mentioned later. In addition, the both ends 120 of the composite film 100 are used to reinforce the central portion 110 when the composite film 100 is heated and stretched. After the composite film 100 is heated and stretched, the both ends 120 can be removed by cutting as necessary. When cutting the composite film 100 , it is desirable to completely remove both end portions 120 by cutting a part of both end portions of the central portion 110 . In this case, a part of both ends of the central part 110 is also removed, but it is preferable to remove all the parts held by the jig 310 described later.

In this embodiment, as the first thermoplastic resin constituting the central portion 110 of the composite film 100 and the second thermoplastic resin constituting both end portions 120, the glass transition temperature Tg1 of the _first thermoplastic resin and the second thermoplastic resin are respectively used. A thermoplastic resin whose glass transition temperature Tg ₂ difference (|Tg ₁ -Tg ₂ |) is 10°C or less. Thus, in the present embodiment, when the composite film 100 is heated and stretched in the stretching step as described later, it is possible to prevent the composite film 100 from being broken, and to improve the productivity of the stretched film.

In the composite film forming step, first, the first thermoplastic resin and the second thermoplastic resin are supplied to the T-die 220 through the supply block 210 in a heated and melted state.

In this embodiment, a first melt extruder (not shown) for melt extruding the first thermoplastic resin and a second melt extruder for melt extruding the second thermoplastic resin are connected to the supply head 210, respectively. machine (not shown). These melt extruders are not particularly limited, and any of a single-screw extruder and a twin-screw extruder can be used. Furthermore, in this embodiment, by using each melt extruder, the first thermoplastic resin is melt-extruded at a temperature equal to or higher than the melting point (melting) temperature of the first thermoplastic resin, and the melting point (melting) temperature of the second thermoplastic resin is The second thermoplastic resin is melt-extruded at the above temperature to supply the first thermoplastic resin and the second thermoplastic resin to the supply head 210 .

In addition, when the first thermoplastic resin and the second thermoplastic resin are supplied from the supply head 210 to the T-die 220, the supply of the first thermoplastic resin and the second thermoplastic resin is performed as follows, that is, as shown in FIG. The composite film 100 obtained by the mold 220 is configured such that both ends 120 made of the second thermoplastic resin are formed on both ends of the central part 110 made of the first thermoplastic resin.

Specifically, the feed head 210 is provided with an inlet for supplying the first thermoplastic resin and, relative to the inlet for supplying the first thermoplastic resin, an inlet for widening the T-die 220 (Japanese: The inlets for the second thermoplastic resin are supplied on both sides in the horizontal direction). In addition, in this embodiment, the first thermoplastic resin and the second thermoplastic resin respectively flowed in from the inlet of the supply block 210 are merged in the supply block 210, and the first thermoplastic resin and the second thermoplastic resin flow in the supply block 210. The outlet flows out in such a manner that the first thermoplastic resin flows toward the central portion and the second thermoplastic resin flows toward both end portions of the first thermoplastic resin with respect to the widening direction of the T-die 220. , and supplied to the T-die 220.

And, in the T-die 220, the first thermoplastic resin and the second thermoplastic resin supplied from the supply head 210 are arranged in the width direction (the first thermoplastic resin and the second thermoplastic resin) by the manifold 221 provided in the T-die 220. The direction in which the resins are arranged) is widened, whereby the first thermoplastic resin and the second thermoplastic resin are co-extruded from the die lip 222 in a sheet shape.

Next, as shown in FIG. 1 , the first thermoplastic resin and the second thermoplastic resin in the form of a co-extruded sheet are continuously drawn and pinched by the touch roll 230 and the cooling roll 240, so that the first thermoplastic resin and the second thermoplastic resin It is cooled and solidified to produce a composite film 100 including a central portion 110 formed of the first thermoplastic resin and both end portions 120 formed at both ends of the central portion 110 and formed of the second thermoplastic resin. Then, the prepared composite film 100 can be wound up with a composite film winding roll (not shown), whereby the composite film 100 can be continuously obtained.

stretching process

The stretching step is a step of heating and stretching the composite film 100 obtained in the composite film forming step in the longitudinal direction and the width direction. Here, FIG. 2 is a diagram for explaining the stretching step. In the stretching process of this embodiment, the composite film 100 is sent out from the composite film winding roll, and as shown in FIG. The composite film 100 is heated and stretched by a synchronous biaxial stretching method in which the composite film 100 is stretched simultaneously in the horizontal direction and the width direction.

Specifically, in the stretching process, the composite film 100 is continuously sent out from the composite film winding roll, and the both ends 120 of the composite film 100 are held at constant intervals using a plurality of clamps, and the composite film is stretched by each clamp 310. The composite film 100 is transported to the stretching furnace 320 , and in the stretching furnace 320 , the composite film 100 is stretched in the longitudinal direction and the width direction by the respective clips 310 to be stretched. At this time, the composite film 100 is conveyed while being held by the clamps 310 and passes through the stretching furnace 320 . After the glass transition temperature of the second thermoplastic resin in both ends 120 is higher by about 10°C to 30°C, in the stretching belt in the stretching furnace 320, the composite film 100 is kept at the temperature by using a clip. 310 stretches the composite film 100 lengthwise and widthwise so that it expands lengthwise and widthwise. Then, the stretched film can be obtained by cooling and solidifying the stretched film in a cooling thermosetting belt. Then, the stretched film can be obtained continuously by opening the clamp 310 and winding it up with a roll.

In addition, in the present embodiment, a pair of guide rails for moving the clips 310 is provided to allow the composite film 100 to pass through the stretching furnace 320 . A pair of guide rails are respectively arranged on the positions of the clamps 310 that hold the upper side of the two ends 120 of the composite film 100 shown in FIG. In the preheating zone in the furnace 320, a pair of guide rails are parallel to each other. In the stretching zone, the pair of guide rails are separated from each other along the width direction of the composite film 100. In the cooling heat curing zone, the pair of guide rails are parallel to each other. Alternatively, it is also possible to set the distance between a pair of guide rails in the cooling thermosetting belt in consideration of the shrinkage of the stretched film after being heated and stretched in the stretching belt when it is solidified in the cooling thermosetting belt. Based on the width when the stretched film is positioned on the output side of the stretching belt, they are close to each other by about several percent in the width direction. In the present embodiment, the composite film 100 can be conveyed and stretched by moving the grippers 310 holding both ends 120 of the composite film 100 along such guide rails.

In the present embodiment, the composite film 100 is stretched in a stretching belt in a stretching furnace 320 using a gripper 310 moving along such rails. That is, in the stretching belt in the stretching furnace 320, the grippers 310 that hold the both ends 120 of the composite film 100 are moved so as to be apart in the width direction along the guide rails, and at the same time, the grippers 310 are separated from each other. Controlling the expansion of the gap, the both ends 120 of the composite film 100 are stretched in the longitudinal direction and the width direction as shown by the arrows in FIG. 2 . Thus, the central portion 110 and both end portions 120 of the composite film 100 are heated and stretched in the longitudinal direction and the width direction respectively to a required stretching ratio. Then, the heated and stretched composite film 100 is cooled and solidified in the cooling thermosetting belt in the stretching furnace 320, and is wound up with a roll provided outside the stretching furnace 320, thereby continuously obtaining a stretched film 100. Stretch film.

As described above, in the present embodiment, the composite film 100 including the central portion 110 formed of the first thermoplastic resin and the both end portions 120 formed of the second thermoplastic resin is formed by using the composite film forming process, and the composite film 100 is formed by stretching. Step The central part 110 and both end parts 120 of the composite film 100 are heated and stretched to obtain a stretched film.

In addition, in the present embodiment, the stretched film may be obtained by making the stretching step and the composite film forming step a continuous continuous line.

In addition, in this embodiment, with respect to the stretched film obtained in this way, the part of both ends 120 can be cut as needed. Thereby, the stretched film can be made into the film which consists of the center part 110 only.

In addition, in this embodiment, the thickness of the central portion 110 of the composite film 100 after heating and stretching is preferably 15 μm to 50 μm, and more preferably 20 μm to 40 μm. By controlling the thickness of the central portion 110 of the composite film 100 after heating and stretching within the above range, it is possible to prevent the composite film 100 from being broken during the heating and stretching, and to perform heating and stretching of the composite film 100 appropriately.

Here, in this embodiment, as the first thermoplastic resin constituting the central portion 110 of the composite film 100 and the second thermoplastic resin constituting both end portions 120, the glass transition temperature Tg1 of the _first thermoplastic resin and the second thermoplastic resin are used. A thermoplastic resin in which the difference (|Tg ₁ −Tg ₂ |) between the glass transition temperatures Tg ₂ of the thermoplastic resin is 10° C. or less. Thus, according to the present embodiment, when the composite film 100 is heated and stretched, it is possible to prevent the jigs 310 holding the composite film 100 from detaching and the composite film 100 from breaking, and the productivity of the stretched film can be improved.

That is, in the composite film 100, if the glass transition temperature Tg ₂ of both end portions 120 is too high compared with the glass transition temperature Tg ₁ of the central portion 110, the heating temperature in the stretching furnace 320 will The glass transition temperature Tg ₂ of the both ends 120 is not reached, and the softening of the both ends 120 becomes insufficient (a state where the tensile stress value required to stretch the both ends 120 is high), therefore, in the 2, there is a problem that the clips 310 may come off when both ends 120 are gripped and stretched by the clips 310. Moreover, at this time, the tensile stress value required to stretch the both ends 120 is high, therefore, when the both ends 120 are stretched by the jig 310 as shown in FIG. , the both end portions 120 are not stretched but are broken, or a crack occurs at the boundary portion between the central portion 110 and the both end portions 120, thereby causing a problem that the composite film 100 is broken. In this regard, when heating the composite film 100 in the stretching furnace 320, while heating the composite film 100 as a whole, only the both ends 120 are further locally heated at a high temperature to soften them, thereby making both ends 120 soft. The stretching of the end portion 120 becomes easy, but, as shown in FIG. 2, in the stretching furnace 320, the positions of the both ends 120 gradually change along with the conveyance and stretching of the composite film 100. Therefore, there are also the following: The problem is that the control of the temperature in the drawing furnace 320 is cumbersome in order to heat only the both ends 120 at a high temperature.

On the other hand, when the glass transition temperature Tg ₂ of both end portions 120 of the composite film 100 is too low compared with the glass transition temperature Tg ₁ of the central portion 110, the stretching furnace 320 If the heating temperature inside exceeds the glass transition temperature Tg ₂ of the two ends 120, the two ends 120 will be excessively softened. Therefore, as shown in FIG. During stretching, both ends 120 are preferentially stretched, and the force of stretching by the jig 310 cannot be transmitted to the central portion 110 , resulting in insufficient stretching of the central portion 110 . Moreover, due to the excessive softening of both ends 120 during heating and stretching, the two ends 120 are thermally bonded to the jig 310, or the two ends 120 shrink after heating and stretching, thus, there are also problems in the productivity and finished product of the stretched film. rate reduction problem.

In this regard, according to the present embodiment, in the composite film 100, the glass transition temperature Tg ₁ of the first thermoplastic resin forming the central portion 110 and the glass transition temperature Tg ₂ of the second thermoplastic resin forming the end portions 120 If the difference (|Tg ₁ -Tg ₂ |) is in the above range, it is possible to prevent the detachment of the clip 310 and the breakage of the composite film 100 when the composite film 100 is heated and stretched, and the composite film 100 can be properly processed. Stretching by heating can improve the productivity and yield of the stretched film.

In addition, in this embodiment, as the first thermoplastic resin and the second thermoplastic resin, thermoplastic resins having a glass transition temperature difference (|Tg ₁ −Tg ₂ |) as described above can be used at 10° C. or less, but the glass transition temperature The difference (|Tg ₁ −Tg ₂ |) is preferably 5°C or lower, more preferably 3°C or lower.

In addition, in order to prevent the detachment of the clip 310 and the breakage of the composite film 100 when the composite film 100 is heated and stretched by the clip 310, a known method is to add rubber elastic particles to the both ends 120 of the composite film 100 to A method of softening both ends 120 (increasing the elongation at break at room temperature). However, in this method, since the rubber elastic particles in both end portions 120 are easily deteriorated by heat, there is a problem as follows. That is, when the composite film 100 is melted and co-extruded from the T-die 220, rubber elastic particles degraded by heat are precipitated on the lip 222 of the T-die 220 to form deposits, which may cause damage to the film due to the deposits. There is a possibility that the composite film 100 will be indented, or deposits may be mixed into the product roll of the stretched film, thereby deteriorating the quality of the stretched film. Moreover, if such deposits of rubber elastic particles are formed, the deposits may enter between the composite film 100 and the clips 310 when the composite film 100 is heated and stretched by the clips 310 as shown in FIG. As a result, the composite film 100 may be easily broken.

On the other hand, according to this embodiment, it is not necessary to add such rubber elastic particles to the both ends 120 of the composite film 100, or the amount of rubber elastic particles added to the both ends 120 can be reduced, therefore, it is possible to suppress When the composite film 100 is melt-coextruded, rubber elastic particles are precipitated, so that the quality of the obtained stretched film can be excellent.

In addition, in this embodiment, as the first thermoplastic resin for forming the central portion 110, it is only necessary to select according to the application of the desired stretched film, for example, acrylic resin (PMMA), cyclic olefin copolymerized resin, etc., can be used. substance (COC), etc.

In addition, as the second thermoplastic resin for forming both ends 120 , a thermoplastic resin whose glass transition temperature difference (|Tg ₁ −Tg ₂ |) from the above-mentioned first thermoplastic resin is in the above-mentioned range may be selected.

In addition, as the second thermoplastic resin for forming the both end portions 120, in addition to selecting a thermoplastic resin having a glass transition temperature difference (|Tg ₁ −Tg ₂ |) from the first thermoplastic resin within the above-mentioned range, it can also be selected from Choose from the following points of view.

For example, as the second thermoplastic resin, it is preferable to use a thermoplastic resin whose viscosity when melted and co-extruded from the T-die 220 is 0.5 to 2 times the viscosity of the first thermoplastic resin. Here, the viscosity can be measured, for example, with a rheometer (Japanese: Capirograph) based on JIS K7199. Thus, the difference in viscosity between the first thermoplastic resin and the second thermoplastic resin during melt coextrusion can be reduced, and in the composite film 100 melt coextruded from the T-die 220, it is possible to prevent the central portion 110 and both ends from being formed. The phenomenon that the resins of the part 120 are doped with each other.

That is, when performing melt co-extrusion, if the viscosity of the second thermoplastic resin is too high compared with the viscosity of the first thermoplastic resin, the composite film 100 formed by melt co-extrusion will be composed of the second thermoplastic resin with higher viscosity. The two end portions 120 will flow toward the surface of the central portion 110 and cover a part of the central portion 110 , resulting in mutual doping between the resins. On the other hand, if the viscosity of the second thermoplastic resin is too low compared with the viscosity of the first thermoplastic resin, in the melt-coextruded composite film 100, the central portion 110 made of the higher-viscosity first thermoplastic resin will Covering a part of both ends 120 results in doping between the resins.

Therefore, in the present embodiment, by reducing the difference in viscosity between the first thermoplastic resin and the second thermoplastic resin during melt coextrusion to the above-mentioned range, it is possible to prevent the central portion 110 from forming in the composite film 100 after thermal stretching. The resin and the resin constituting the both ends 120 are mixed with each other, thereby reducing the number of cut parts when cutting the ends 120 as described above when obtaining a stretched film, and improving the yield of the stretched film.

In addition, as the second thermoplastic resin, it is preferable to use a thermoplastic resin that can make the tensile stress value of the central portion 110 during thermal stretching and the two The difference in the tensile stress value of the end portion 120 is within a predetermined range. Specifically, as the second thermoplastic resin, it is preferable to use a thermoplastic resin whose tensile stress value during heated stretching of both end portions 120 formed of this thermoplastic resin is the tensile stress value of the central portion 110 during heated stretching. within 4 times of the value. In addition, the tensile stress value is a value indicating the tensile load required to stretch the central portion 110 and both end portions 120 when the composite film 100 is stretched to a desired stretching ratio. Thus, when the composite film 100 is heated and stretched, the deformation amounts of the central portion 110 and both end portions 120 relative to the tensile stress are similar to each other, and the fracture of the stretched film and the detachment of the clips during the heating and stretching can be more effectively prevented. The productivity of the stretched film can be further improved.

It is further preferable to use, as the second thermoplastic resin, a thermoplastic resin capable of making the elongation at break at the normal temperature of both end parts 120 higher than that of the central part 110 in the obtained composite film 100 before heating and stretching. elongation at break. In addition, the elongation at break at normal temperature is a value indicating the elongation of the dimension when the central portion 110 and both end portions 120 are stretched to break in a normal temperature environment of about 10° C. to 30° C. with respect to the dimension before stretching. . Thus, when the composite film 100 is heated and stretched, the both ends 120 are less likely to be broken than the central portion 110 , and cracks can be prevented from occurring at the both ends 120 , thereby preventing the entire composite film 100 from being broken.

Moreover, as a 2nd thermoplastic resin, the following thermoplastic resin can be specifically used from the said viewpoint. For example, when an acrylic resin is used as the first thermoplastic resin, as the second thermoplastic resin, one of polyethylene naphthalate (PEN), cycloolefin polymer (COP) and the like can be used alone, or can be A mixed resin obtained by mixing two or more of the aforementioned materials is used.

In addition, as the second thermoplastic resin, a resin obtained by adding a small amount of rubber elastic particles to the first thermoplastic resin within a range that does not hinder the productivity of the stretched film may be used.

Alternatively, as the second thermoplastic resin, a thermoplastic resin (heat-resistant thermoplastic resin) having a glass transition temperature higher than that of the first thermoplastic resin and having a difference of more than 10° C. from the glass transition temperature of the first thermoplastic resin can be used. A mixed resin obtained by mixing a thermoplastic resin (low-temperature meltable thermoplastic resin) that has a lower glass transition temperature than the first thermoplastic resin. At this time, by adjusting the mixing ratio between the above-mentioned heat-resistant thermoplastic resin and the low-temperature melting thermoplastic resin, the glass transition temperature of the obtained mixed resin is adjusted so that the glass transition temperature of the first thermoplastic resin The difference between the temperature and the glass transition temperature of the second thermoplastic resin (|Tg ₁ −Tg ₂ |) is within the above range.

Here, when an acrylic resin having a glass transition temperature Tg1 _of about 120°C is used as the first thermoplastic resin, as the second thermoplastic resin, for example, an acrylic resin having a higher glass transition temperature of about 150°C can be used. Polyethylene terephthalate (PET), which has a relatively low glass transition temperature of around 70°C, is mixed with polycarbonate (PC) to adjust the glass transition temperature to the same level as the above-mentioned glass transition temperature Tg ₁ A mixed resin obtained near 120°C.

In addition, when such a mixed resin is used as the second thermoplastic resin, polycarbonate (PC), cycloolefin polymer (COP), or the like can be used as the heat-resistant thermoplastic resin. In addition, polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), acrylonitrile-butadiene-styrene ( ABS), polyethylene (PE), polyester (PES), polybutylene terephthalate (PBT), etc. In the present embodiment, among these materials, polycarbonate (PC) is preferably used as the heat-resistant thermoplastic resin from the viewpoint of easy adjustment of the glass transition temperature of the mixed resin obtained, and polycarbonate (PC) is preferably used as the low-temperature melting resin. As the thermoplastic resin, polyethylene terephthalate (PET) is preferably used.

Here, FIG. 3 is a graph showing the measurement results of the glass transition temperature of a mixed resin obtained by mixing polyethylene terephthalate (PET) with polycarbonate (PC). In addition, as shown in FIG. 3, the content ratios of polyethylene terephthalate (PET) to polycarbonate (PC) by differential scanning calorimetry (DSC) were 0%, 25%, and 50%, respectively. %, 75%, 100% of the glass transition temperature of the resin to measure the results. Here, in the differential scanning calorimetry (DSC) measurement, regardless of the content ratio of polyethylene terephthalate (PET), the glass transition temperature of the mixed resin did not increase, while is roughly fixed at one point.

As shown in FIG. 3, for a mixed resin obtained by mixing polycarbonate (PC) with polyethylene terephthalate (PET), it is possible to The glass transition temperature changes accordingly. Therefore, in the present embodiment, when such a mixed resin is used as the second thermoplastic resin, the glass transition temperature Tg ₂ of the second thermoplastic resin can be easily adjusted, and the glass transition temperature of the first thermoplastic resin can be adjusted. The difference (|Tg ₁ −Tg ₂ |) between the transition temperature Tg ₁ and the glass transition temperature Tg ₂ of the second thermoplastic resin is controlled within the above range.

In addition, as a method of heating and stretching the composite film 100 obtained by such a first thermoplastic resin and a second thermoplastic resin, as shown in FIG. Although this is an example of a simultaneous biaxial stretching method that heats and stretches in two directions, the width direction and the width direction, in this embodiment, a method of uniaxially stretching the composite film 100 only in the longitudinal direction may also be used.

At this time, heating and stretching of the composite film 100 in the longitudinal direction can be performed in the same manner as the simultaneous biaxial stretching method shown in FIG. 2 . That is, a method of transporting the composite film 100 into the stretching furnace 320 while holding both ends 120 of the composite film 100 with the jigs 310, and then, in the stretching furnace 320, the person holding the composite film 100 can be used. Each clip 310 of both end parts 120 is moved in the width direction, but heat-stretching is performed only in the longitudinal direction by increasing the distance between the clips 310 .

In this embodiment, regardless of whether simultaneous biaxial stretching is performed in the longitudinal direction and the width direction or in the case of uniaxial stretching only in the longitudinal direction, by using the jig 310 as shown in FIG. Stretching while holding the both ends 120 of the composite film 100 can improve the productivity of the stretched film and improve the quality of the stretched film obtained compared with the conventional sequential biaxial stretching method.

In addition, the conventional sequential biaxial stretching method is a method of heating and stretching the composite film 100 produced by the method shown in FIG. 1 first in the longitudinal direction and then heating and stretching in the width direction. In the sequential biaxial stretching method, after the composite film 100 is heated and stretched in the longitudinal direction by conveying the composite film 100 with a plurality of rollers, as shown in FIG. 120 while heating and stretching the composite film 100 in the width direction.

Here, in the sequential biaxial stretching method, specifically, the composite film 100 is stretched in the longitudinal direction as follows. That is, the sequential biaxial stretching method is adopted, and the composite film 100 is preheated to about the glass transition temperature of both ends 120 while conveying the composite film 100 by a plurality of preheated preheating rolls, and then heated by infrared rays. The preheated composite film 100 is further heated to a temperature about 10° C. to 30° C. higher than the glass transition temperature of both ends 120 by using a device or the like, and the composite film 100 is continuously conveyed by cooling rolls. At this time, by making the conveying speed of the cooling roller faster than the conveying speed of the preheating roller, tension is generated between the preheating roller and the cooling roller, and the composite film 100 is stretched in the longitudinal direction to the required tension by using the tension. Magnification.

Here, in the sequential biaxial stretching method, when the composite film 100 is stretched in the longitudinal direction, since the surface of the composite film 100 is in contact with the preheating roll and the cooling roll, the surface of the composite film 100 may be rubbed. The appearance quality of the obtained stretched film deteriorates due to scratches. In addition, in the sequential biaxial stretching method, when the composite film 100 is heated and stretched in the longitudinal direction, since the positions of the two ends 120 of the composite film 100 in the width direction are not fixed, the composite film 100 may be damaged due to Heat shrinks in the width direction, thereby reducing the productivity of the stretched film.

In contrast, in this embodiment, by using the simultaneous biaxial stretching method or the method of uniaxial stretching only in the longitudinal direction (that is, as shown in FIG. The two ends 120 of 100 stretch the composite film 100 along the longitudinal direction) to carry out the stretching of the composite film 100 along the longitudinal direction, which can avoid the contact between the composite film 100 and the roller, so the heating and stretching can be reduced. After the surface of the composite film 100 is scratched. Thus, for the stretched film obtained by cutting the both ends 120 of the heated and stretched composite film 100, the appearance quality can be improved, and in particular, it can be preferably applied to optical films and the like that require strict appearance quality. . And, according to this embodiment, since the both ends 120 of the composite film 100 are held by the clips 310 when the composite film 100 is stretched in the longitudinal direction, it is possible to prevent the composite film 100 from shrinking in the width direction due to heat, thereby improving the tensile strength. stretch film productivity.

Example

Hereinafter, although an Example is given and this invention is demonstrated more concretely, this invention is not limited to these Examples.

Example 1

As the first thermoplastic resin for forming the central portion 110 of the composite film 100, an acrylic resin (glass transition temperature Tg ₁ : 123° C., elongation at break at room temperature: 5%) was prepared as the first thermoplastic resin for forming the composite film 100. As the second thermoplastic resin at both ends 120 of 100, an acrylic resin (glass transition temperature Tg ₂ : 125° C., elongation at break at room temperature: 18%) added with a small amount of rubber elastic particles was prepared.

Here, for the first thermoplastic resin and the second thermoplastic resin, the glass transition temperatures of both were measured by differential scanning calorimetry (DSC), and measured by a tensile tester (manufactured by ORIENTEC CORPORATION, model: RTC-1210A) The elongation at break at room temperature for both. The same applies to the following Examples 2 to 5 and Comparative Example 1.

In addition, for the first thermoplastic resin and the second thermoplastic resin, the tensile stress when the monomer film was gradually stretched in a state heated to 140° C. measured. The results are shown in (A) of FIG. 4 . Here, in (A) of FIG. 4 , it shows the percentage of stretching the size before stretching in any one direction with respect to the stretching ratio (representing the size of the monomer film before stretching). In terms of the value of the amount of a few), the stretching stress value required for stretching to the stretching ratio. In addition, in (A) of FIG. 4 , the measurement result of the first thermoplastic resin is taken as the central portion 110 , and the measurement result of the second thermoplastic resin is taken as both ends 120 .

Next, using the prepared first thermoplastic resin and second thermoplastic resin, the composite film 100 was produced under the following conditions by the method shown in FIG. 1 . Here, the overall width of the produced composite film 100 is about 315 mm, wherein the regions with a width of about 50 mm from both ends are the two ends 120 , and the remaining central regions are the center 110 . In addition, in this embodiment, the acrylic resin added with rubber elastic particles was used as the second thermoplastic resin, but since the amount of rubber elastic particles added is small, it is possible to suppress the occurrence of the rubber when the composite film 100 is melted and co-extruded. The precipitation of elastic particles.

T-die 220 outlet width: 380mm

Traction speed of chill roll 240: 6mpm

Supply amount of the first thermoplastic resin supplied to the supply head 210: 15kg/hr

Supply amount of the second thermoplastic resin supplied to the supply head 210: 5kg/hr

Here, in the obtained composite film 100 , the boundary between the central portion 110 and both end portions 120 was clearly confirmed by observation, and it was confirmed that the resins in the composite film 100 were not mixed.

Next, as shown in FIG. 2 , both ends 120 of the obtained composite film 100 were grasped by clamps 310 , and heated and stretched in the longitudinal direction and the width direction under the following conditions by simultaneous biaxial stretching. In addition, for the composite film 100 after heating and stretching, when the thickness and breaking strength were measured in the region of the width 400 mm of the central part 110 after heating and stretching, the thickness and breaking strength (stretched to break at room temperature When the tensile strength) distribution within ± 5%.

Input side speed before heating and stretching: 1mpm

Output side speed after heating and stretching: 2mpm

Stretch ratio: 100% in the length direction x 100% in the width direction (twice in the length direction x twice in the width direction)

Gripping position of the jig 310: 15 mm from the end of the composite film 100

Preheating temperature, distance: 140°C, 350mm

Stretch belt temperature, distance: 140°C, 500mm

Cooling heat curing temperature, distance: 90 ℃, 700mm

In addition, in the present example, during heating and stretching of the composite film 100 , no detachment of the clips 310 and no breakage of the composite film 100 occurred, and a stretched film of excellent quality could be continuously produced.

Example 2

As the second thermoplastic resin for forming both ends 120 of the composite film 100, 25% by weight of polyethylene terephthalate (PET) was mixed with 75% by weight of polycarbonate (PC). Except for the obtained mixed resin (glass transition temperature Tg ₂ : 125° C., elongation at break at normal temperature: 20%), a stretched film was obtained in the same manner as in Example 1, and both were measured in the same manner. Tensile stress of the monomer film at the end portion 120 (second thermoplastic resin). The results are shown in (A) of FIG. 4 .

In addition, in Example 2, as in Example 1, for the composite film 100 obtained by melt coextrusion, the boundary between the central part 110 and both end parts 120 can be clearly confirmed by observation, and it is confirmed that No intermingling of resins occurs in the composite film 100 . In addition, during stretching of the composite film 100 by heating, the separation of the clips 310 and the breakage of the composite film 100 do not occur, and a stretched film of excellent quality can be continuously produced.

Example 3

As the second thermoplastic resin for forming both ends 120 of the composite film 100, a mixed resin (glass transition temperature Tg ₂ : 122°C, Elongation at break at room temperature: 25%), except that, a stretched film was obtained in the same manner as in Example 1, and the elongation of the monomer film at both ends 120 (the second thermoplastic resin) was measured in the same manner. tensile stress. The results are shown in (A) of FIG. 4 .

In addition, in Example 3, as in Example 1, for the composite film 100 obtained by melt coextrusion, the boundary between the central part 110 and both end parts 120 can be clearly confirmed by observation, and it is confirmed that No mixing between the resins in the composite film 100 occurs. In addition, during heating and stretching of the composite film 100 , detachment of the clips 310 and breakage of the composite film 100 do not occur, and a stretched film of excellent quality can be continuously produced.

Example 4

As the second thermoplastic resin for forming both ends 120 of the composite film 100, a PC/ABS alloy ( Glass transition temperature Tg ₂ : 120°C, elongation at break at normal temperature: 180%), except that, a stretched film was obtained in the same manner as in Example 1, and 120° at both ends were measured in the same manner. Tensile stress of the monomer film of (the second thermoplastic resin). The results are shown in (B) of FIG. 4 . In addition, like FIG. 4(A), FIG. 4(B) is a graph showing the measurement results of the tensile stress of the monomer film made of the first thermoplastic resin and the second thermoplastic resin, and FIG. 4( The scale of the vertical axis of B) is different from that of (A) of FIG. 4 .

Here, in Example 4, as in Example 1, for the composite film 100 obtained by melt coextrusion, the boundary between the central part 110 and both end parts 120 can be clearly confirmed by observation, and it is confirmed that No intermingling of resins occurs in the composite film 100 .

On the other hand, in Example 4, since the tensile stress of both end portions 120 is higher than that of the central portion 110 when the stretching ratio is 100%, the tensile stress of the central portion 110 is about 100%. 7.7 times the stress. Therefore, when heating and stretching the composite film 100, it is difficult to stretch the both ends 120, and the clip 310 may occasionally come off. However, in Example 4, the occurrence frequency of detachment of the clips 310 was low, and thus a stretched film of excellent quality could be continuously produced.

Example 5

As the second thermoplastic resin for forming both ends 120 of the composite film 100, polyethylene naphthalate (PEN) (glass transition temperature Tg ₂ : 120°C, elongation at break at room temperature: 300%), except that a stretched film was obtained in the same manner as in Example 1, and the tensile stress of the monomer film at both ends 120 (second thermoplastic resin) was measured in the same manner. The results are shown in (A) of FIG. 4 .

Here, in Example 5, when the first thermoplastic resin and the second thermoplastic resin were melt-coextruded, the boundary between the central portion 110 and both end portions 120 in the obtained composite film 100 became slightly inconspicuous. The reason for this is considered to be that the central portion 110 and both end portions 120 are slightly mixed together because the viscosity difference between the first thermoplastic resin and the second thermoplastic resin is large during melt coextrusion. However, in Example 5, there was no quality problem in the obtained stretched film.

In addition, in Example 5, as in Example 1, during heating and stretching of the composite film 100 , no detachment of the clips 310 and no breakage of the composite film 100 occurred, and a stretched film of excellent quality could be continuously produced.

Comparative example 1

As the second thermoplastic resin for forming both ends 120 of the composite film 100, polycarbonate (PC) (glass transition temperature Tg ₂ : 143°C, elongation at break at room temperature: 170%) was used, except Otherwise, a stretched film was obtained in the same manner as in Example 1, and the tensile stress of the single film at both ends 120 (second thermoplastic resin) was measured in the same manner. The results are shown in (B) of FIG. 4 .

In addition, as in Example 1, for the composite film 100 obtained by melt coextrusion in Comparative Example 1, the boundary between the central part 110 and both end parts 120 can also be clearly confirmed by observation, and it is confirmed that the composite film 100 in the composite No mixing between the resins in the film 100 occurs.

However, in Comparative Example 1, when heating and stretching the composite film 100, the temperature (140° C.) of the preheating zone and the stretching zone did not reach the glass transition temperature Tg ₂ ( 143° C.), therefore, both ends 120 are not sufficiently softened, and thus, detachment of the clips 310 often occurs, and a stretched film cannot be obtained. On the other hand, in Comparative Example 1, the temperature of the preheating belt and the stretching belt when heating and stretching by the simultaneous biaxial stretching method was changed from 140°C to 160°C, thereby softening the both ends 120 Thus, heating and stretching is performed, but since the obtained stretched film is exposed to high temperature, the molecular orientation becomes non-uniform and the strength decreases, and the film thickness also becomes non-uniform, resulting in poor quality.

As described above, in Examples 1 to 5 in which the difference between the glass transition temperature Tg ₁ of the first thermoplastic resin and the glass transition temperature Tg ₂ of the second thermoplastic resin (|Tg ₁ −Tg ₂ |) was 10°C or less Therefore, when the composite film 100 is heated and stretched, since the fracture of the composite film 100 and the detachment of the clips 310 can be suppressed, a stretched film with excellent quality can be obtained, and the productivity of the stretched film can be improved.

On the other hand, in Comparative Example 1 in which the difference (|Tg ₁ −Tg ₂ |) between the glass transition temperature Tg ₁ of the first thermoplastic resin and the glass transition temperature Tg ₂ of the second thermoplastic resin exceeded 10°C, In other words, when the composite film 100 is heated and stretched, the clips 310 often detach, the stretched film cannot be obtained, and the productivity of the stretched film is poor.

Explanation of reference signs

100…Composite film

110…Central part

120...both ends

210…feed head

220…T type die

230…contact roller

240...cooling roll

310...Clamp

320…drawing furnace

Claims (8)

1. a manufacture method for oriented film, the manufacture method of this oriented film includes:

Laminated film formation process, in this laminated film formation process, by melting from shaping mould After coextrusion the 1st thermoplastic resin and the 2nd thermoplastic resin different from described 1st thermoplastic resin right Described 1st thermoplastic resin and described 2nd thermoplastic resin carry out cooling and make it solidify, thus are formed and possess The central part being made up of described 1st thermoplastic resin, the two ends being formed at described central part in the width direction And the laminated film at the both ends being made up of described 2nd thermoplastic resin；And

Stretching process, in this stretching process, adds hot-stretch the most along its length by described laminated film Thus form oriented film,

The manufacture method of this oriented film is characterised by,

As described 1st thermoplastic resin and described 2nd thermoplastic resin, use glass transition temperature it Difference is the thermoplastic resin of less than 10 DEG C.

The manufacture method of oriented film the most according to claim 1, it is characterised in that

Add in the described laminated film before hot-stretch, be made up of described 2nd thermoplastic resin described two Elongation at break under the room temperature of end is more than the described central part being made up of described 1st thermoplastic resin Elongation at break under room temperature.

The manufacture method of oriented film the most according to claim 1 and 2, it is characterised in that

Tensile stress values when adding hot-stretch at the described both ends being made up of described 2nd thermoplastic resin is 4 times of tensile stress values when adding hot-stretch of the described central part being made up of described 1st thermoplastic resin Within.

4. according to the manufacture method of the oriented film according to any one of claim 1-3, it is characterised in that The viscosity when described shaping mould melts coextrusion of described 2nd thermoplastic resin is the described 1st 0.5 times～2 times of the viscosity when described shaping mould melts coextrusion of thermoplastic resin.

5. according to the manufacture method of the oriented film according to any one of claim 1-4, it is characterised in that In described stretching process, not only length direction along described laminated film is utilized to carry out stretching, also The synchronization biaxial stretching process that width along described laminated film carries out stretching comes described laminated film Carry out adding hot-stretch.

6. according to the manufacture method of the oriented film according to any one of claim 1-5, it is characterised in that

Described 1st thermoplastic resin is acrylic resin.

The manufacture method of oriented film the most according to claim 6, it is characterised in that

Described 2nd thermoplastic resin has than described acrylic resin for mixing in Merlon (PC) The hybrid resin of thermoplastic resin of the low glass transition temperature of glass transition temperature.

8. according to the manufacture method of the oriented film according to any one of claim 1-7, it is characterised in that

In described stretching process, described laminated film is added hot-stretch so that described laminated film Add the thickness of the described central part after hot-stretch in the range of 15 μm～50 μm.