JP7253436B2 - Method for producing (meth)acrylic resin film - Google Patents

Description

The present invention relates to a method for producing a (meth)acrylic resin film.

(Meth)acrylic resin films are used for optical applications and decorative applications because they are excellent in optical properties such as high transparency and low birefringence and can be easily formed into films by melt molding. One of the common methods for forming (meth)acrylic resin films is to supply the raw material (meth)acrylic resin from a hopper to an extruder, heat and melt it, and then extrude it through a die to form a film. There is a way.
However, when a (meth)acrylic resin is formed into a film by extrusion molding, there is a problem that thickness unevenness occurs in the width direction of the film. If the thickness of the film is uneven, not only will mechanical property unevenness and optical property unevenness occur, but it may also cause poor appearance when a coating layer is applied to the film surface.

As a method of solving these problems and forming a (meth)acrylic resin film having a uniform thickness, Patent Document 1 proposes a method of suppressing thickness unevenness by controlling the temperature of the film edge. ing. Further, Patent Literature 2 proposes a method for equalizing the temperature after die ejection by measuring the temperature distribution before and after die ejection and feeding it back. Furthermore, Patent Document 3 proposes a method of reheating the resin after it has been discharged from a die.

Japanese Patent Application Laid-Open No. 2006-123460 JP 2017-30279 A JP 2009-78359 A

According to the methods described in Patent Documents 1 to 3, although it is possible to control the film thickness at the edges in the width direction of the film, there is still the problem that film thickness fluctuations occur at the central portion in the width direction of the film. . In addition, by heating the discharged resin for a long time, there is a problem that deposits due to resin burning occur on the T die lip and uneven thickness occurs, and volatile components generated by heating adhere to the heating device, which reduces productivity. I had a problem with the drop.

An object of the present invention is to provide a method for producing a (meth)acrylic resin film that can produce a film having a uniform film thickness.

As a result of repeated studies to solve the above problems, the present inventors have found that the temperature distribution of the (meth)acrylic resin composition discharged from the T-die is changed by heating a pipe in which a static mixer is arranged. The inventors have found that uniformity can be achieved, and based on this finding, further studies have been made, and the present invention has been completed.

That is, the gist of the present invention is the following [1] to [4].
[1] A (meth)acrylic resin composition having a melt viscosity of 200 to 2,000 Pa s at 270° C. and a shear rate of 61/sec is mixed with a static mixer and extruded through a T-die (meth). A method for producing an acrylic resin film,
A method for producing a (meth)acrylic resin film, wherein the static mixer is arranged inside a tube, has 5 to 30 elements, and heats the tube.
[2] Regarding the temperature of the melt curtain of the (meth)acrylic resin composition measured at a position 5 cm below the T-die outlet, the temperature (T ₁ ) at the center of the melt curtain The ratio [[(T ₂ )/(T ₁ )]×100] of the temperature (T ₂ ) having a larger absolute value of difference from T ₁ among the temperatures 100 mm from both ends on the center side is 95 to 105%. The method for producing a (meth)acrylic resin film according to [1].
[3] The (meth)acrylic resin film according to [1] or [2], wherein the distance from the outlet of the tube in which the static mixer is arranged to the inlet of the T-die is 2.0 m or less. Production method.
[4] The method for producing a (meth)acrylic resin film according to any one of [1] to [3], wherein the (meth)acrylic resin composition contains an acrylic polymer (B) having a multilayer structure. .

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the (meth)acrylic-type resin film which can manufacture the film which has a uniform film thickness can be provided.

It is a figure which shows an example of the shaping|molding apparatus in the manufacturing method of a film.

When a film is formed by a melt extrusion method, a static mixer is sometimes used for the purpose of generating a laminar flow in a molten resin and efficiently stirring the resin while suppressing pressure loss. A static mixer is usually used as a static mixer section composed of a pipe and a static mixer arranged inside the pipe. heat dissipation), and the degree of heat dissipation is affected by the external environment, the thermal conductivity of the internal fluid, and the like. Moreover, when the fluid inside is a high-viscosity fluid (paste), it may be affected by shear heat generation of the resin. If the degree of heat radiation or shear heat generation is large, it may lead to uneven temperature of the fluid inside, and the uneven temperature may lead to uneven thickness of the film. Therefore, the present invention is characterized in that the thickness unevenness is eliminated by placing a static mixer inside a pipe that can be heated and using a (meth)acrylic resin composition having a melt viscosity within a specific range. is.

[Method for producing (meth)acrylic resin film]
In the method for producing a (meth)acrylic resin film of the present invention, a (meth)acrylic resin composition having a melt viscosity of 200 to 2,000 Pa·s at 270° C. and a shear rate of 61/sec is mixed with a static mixer. A method for producing a (meth)acrylic resin film comprising a step of extruding from a T-die with a static mixer, wherein the static mixer is arranged inside a tube, has 5 to 30 elements, and heats the tube characterized by

According to the method for producing a (meth)acrylic resin film of the present invention, a static mixer having the number of elements within a specific range is arranged inside the pipe, and furthermore, in order to heat the pipe, The temperature of the (meth)acrylic resin composition (raw material resin composition) is sufficiently homogenized and sent to the T-die without being affected by heat radiation to the outside. As a result, the temperature unevenness of the raw material resin composition in the T-die can be suppressed, the film thickness can be easily controlled, and the raw material resin is particularly susceptible to temperature and is relatively difficult to eliminate temperature unevenness. Even when the composition is used, it becomes possible to produce a (meth)acrylic resin film having a uniform film thickness.

The method for producing a (meth)acrylic resin film of the present invention can be carried out, for example, by the apparatus shown in FIG.
In the apparatus shown in FIG. 1, first, a (meth)acrylic resin composition, which is a raw material resin, is melted in an extruder 1 . Next, the molten (meth)acrylic resin composition passes through the gear pump 2 and is filtered through the polymer filter 3 . After that, the thermoplastic resin composition passes through a static mixer section 4 composed of a tube and a static mixer arranged inside the tube, and is discharged in the form of a film from a T-die 5 . The discharged molten resin is pressed between rolls 6 and 7 to form a desired film thickness. The molded (meth)acrylic resin film is wound into a roll, for example.

<Extruder>
As an extruder for melting and extruding the (meth)acrylic resin composition, for example, a single-screw extruder, a twin-screw extruder, a multi-screw extruder, or the like can be used. The extruder preferably has a vent mechanism in order to remove volatile matter generated when mixing the (meth)acrylic resin composition.
As the screw of the extruder, a barrier flight, a screw with a mixing section, or the like can be used. From the viewpoint of obtaining sufficient plasticization and mixing state of the (meth)acrylic resin composition, the screw _LS / _DS ( _LS is the cylinder length of the extruder and _DS is the cylinder inner diameter), It is preferably 10 or more, more preferably 20 or more, still more preferably 25 or more, and preferably 100 or less, more preferably 50 or less, still more preferably 40 or less. Sufficient plasticization and a mixed state of the (meth)acrylic resin composition can be obtained when L _S /D _S is at least the lower limit. Further, when L _S /D _S is equal to or less than the upper limit, mixing can be performed while suppressing decomposition of the (meth)acrylic resin composition due to heat generation by shearing.

The cylinder temperature of the extruder depends on the composition of the (meth)acrylic resin composition used and its glass transition temperature, but is preferably 150° C. or higher, more preferably 180° C. or higher, and preferably It is 310° C. or lower, more preferably 280° C. or lower. When the cylinder temperature is at least the lower limit, the (meth)acrylic resin composition can be sufficiently melted. On the other hand, when the cylinder temperature is equal to or lower than the above upper limit, it is possible to suppress low-boiling decomposed products, burning, gelation, etc. generated by decomposition accompanying thermal deterioration of the (meth)acrylic resin composition.

<Gear pump>
In the present invention, a gear pump may be installed after the extruder in order to compensate for pressure loss in the polymer filter and static mixer, which will be described later. The gear pump is not particularly limited, but an inverter-controlled gear pump is preferable. By using the inverter-controlled gear pump, it is possible to suppress the pulsation of the flow rate of the molten resin discharged from the extruder.
The resin pressure at the inlet of the gear pump is preferably 10 MPa or less, more preferably 8 MPa or less. When the resin pressure at the inlet of the gear pump is equal to or lower than the upper limit, even when the number of elements in the static mixer is increased, poor extrusion is less likely to occur. The lower limit of the resin pressure is preferably 1 MPa, more preferably 3 MPa. When the resin pressure at the inlet of the gear pump is equal to or higher than the lower limit, fluctuations in the amount of resin discharged from the gear pump become small.

<Polymer filter>
In the present invention, it is preferred to use a polymer filter between the gear pump and the static mixer. The polymer filter may consist of a filter element portion for filtering the (meth)acrylic resin composition and a housing portion for introducing and discharging the (meth)acrylic resin composition in a molten state (molten resin composition). preferable.
The filter element may be disk-shaped or cylindrical, but it is preferable to use a cylindrical filter element, since a cylindrical filter element can have a large filtering area per element and is superior in terms of cost.
Cylindrical filter elements usually have a filtration portion that filters fluid from the outer peripheral surface, a hollow portion through which the filtered fluid flows, a discharge portion that is present at the end and discharges the fluid from the hollow portion, and a tip portion of the filter element. Prepare. The cylindrical filter element includes, for example, a tube type, a candle type, etc. Among them, a candle type filter element is preferable.
The shape of the candle-type filter element is not particularly limited, and a corrugated shape, pleated shape, or the like can be used. The pleats in the pleat type may extend in the radial direction of the filter element, or may be so-called spiral pleats extending obliquely to the radial direction and having a curved or arched cross-sectional shape. .

The filtration accuracy of the filter element is preferably 5 µm or more, more preferably 8 µm or more, and preferably 50 µm or less, more preferably 30 µm or less. When the filtration accuracy is within the above range, it is possible to improve the balance between productivity and suppression of contamination. In particular, when the filtration accuracy is equal to or higher than the lower limit, it is possible to suppress thermal deterioration due to shear heat generated when the molten (meth)acrylic resin composition is passed through the filter element. On the other hand, when the filtration accuracy is equal to or less than the upper limit, foreign matter can be effectively removed.

<Static Mixer>
In the present invention, a static mixer is used in order to efficiently stir and mix a high-viscosity fluid (paste) by laminar flow generated inside while reducing pressure loss. The number of unit mixing elements) is 5-30. If the number of elements is less than the above lower limit, the temperature uniformity of the (meth)acrylic resin composition and the uniformity of each compounding component are deteriorated. Further, when the number of elements exceeds the above upper limit, the surface area of the elements increases, and deteriorated resin adheres to the surfaces of the elements, leading to deterioration of film quality. From these viewpoints, the number of elements is preferably 6 or more, more preferably 8 or more, still more preferably 11 or more, and preferably 28 or less, more preferably 25 or less, More preferably, it is 20 or less.
The elements are arranged alternately in the pipe, with the right element formed by twisting a square plate to the right by 180° and the left element formed by twisting a square plate by 180° to the left inside the pipe. preferably. By arranging the elements as described above, effective mixing can be achieved while suppressing shearing.

Although the length Le per element of the static mixer of the present invention depends on the scale to be implemented, it is preferably 30 mm or more from the viewpoint of suppressing thermal deterioration due to retention of the (meth)acrylic resin composition, It is more preferably 40 mm or more, preferably 160 mm or less, and more preferably 100 mm or less. From the same point of view, the diameter De per element of the static mixer is preferably 25 mm or more, more preferably 30 mm or more, and preferably 110 mm or less, more preferably 80 mm or less. .
Furthermore, the ratio Le/De of the length Le to the diameter De per element of the static mixer of the present invention is preferably 1.0 from the viewpoint of suppressing thermal deterioration due to retention of the (meth)acrylic resin composition. It is 2 or more, more preferably 1.3 or more, and preferably 1.8 or less, more preferably 1.7 or less.

It is not necessary to connect all the elements of the static mixer continuously, and it is possible to connect them by dividing them into multiple pipes. It is desirable to install

The temperature ( _TSB ) of the (meth)acrylic resin composition immediately before passing through the pipe in which the static mixer is arranged and the temperature ( _TSA ) of the (meth)acrylic resin composition immediately after passing are Depending on the glass transition temperature of the (meth)acrylic resin composition, it is preferably 230°C or higher, more preferably 250°C or higher, and preferably 300°C or lower, more preferably 280°C. It is below. By setting the temperature of the (meth)acrylic resin composition to the above lower limit or higher, the viscosity of the (meth)acrylic resin composition is reduced, and the pressure loss in the static mixer section can be reduced. On the other hand, by setting the temperature of the (meth)acrylic resin composition to the above upper limit or less, it is possible to suppress decomposition of the resin due to shear heat generation. T _SA is preferably (T _SB -5) °C or higher and T _SB °C or lower, more preferably (T _SB -3) °C or higher and T _SB °C or lower, and (T _SB -1) °C or higher and T _SB °C or less, and _TSA and _TSB may be the same.

The static mixer is arranged between the polymer filter and the T die described later, and from the viewpoint of uniforming the temperature distribution of the (meth)acrylic resin composition, T The distance to the die entrance is preferably 2.0 m or less, more preferably 1.8 m or less, and even more preferably 1.5 m or less. The distance from the outlet of the tube in which the static mixer is arranged to the inlet of the T-die is usually 0.3 m or more. When the distance from the outlet of the tube in which the static mixer is arranged to the inlet of the T-die is equal to or less than the above upper limit, it becomes possible to form a film while maintaining the temperature distribution uniformed by the static mixer. .

The present invention is characterized in that the pipe in which the static mixer is placed is heated. As a result, the temperature distribution of the (meth)acrylic resin composition can be made uniform, making it easier to form a film having a uniform thickness.
The method for heating the tube is not particularly limited as long as it is a method that uniformly heats the tube. A method in which a heater is wound around a pipe is preferable from the viewpoint of easy uniformity of the temperature distribution of the (meth)acrylic resin composition and ease of construction of a manufacturing apparatus.

Tubes that can be used in the present invention include, for example, those made of copper, stainless steel, etc. and having an inner diameter of preferably 25 to 110 mm, more preferably 30 to 50 mm. The inner diameter of the pipe can be appropriately changed according to the diameter of the static mixer arranged inside.

The heating temperature of the pipe depends on the glass transition temperature of the (meth)acrylic resin composition that is the raw material resin composition, but is preferably 230° C. or higher, more preferably 250° C. or higher, and preferably is 300° C. or less, more preferably 280° C. or less. By setting the heating temperature to the above lower limit or more, the viscosity of the (meth)acrylic resin composition becomes small, and the pressure loss can be reduced. On the other hand, by setting the heating temperature to the above upper limit or less, it is possible to suppress decomposition of the resin.
Also, the difference between the temperature inside the tube (the temperature of the thermoplastic resin composition in the static mixer section) and the heating temperature of the tube is preferably 3°C or less, more preferably 2°C or less. It is preferably 1° C. or less, more preferably 1° C. or less.

<T die>
In the present invention, T dies such as manifold dies, fish tail dies, and coat hanger dies can be used. In order to stabilize the film thickness, it is preferable to use an automatic adjusting die equipped with a mechanism for measuring the thickness of the formed film and automatically adjusting the lip opening bolt.

In the present invention, although the discharge rate Q from the die depends on the die size, it is preferably 100 to 1,000 kg/hour, more preferably 100 to 800 kg/hour, still more preferably 100 to 700 kg/hour. is.

The die lip clearance L is preferably from 0.2 to 2.0 mm, more preferably from 0.3 to 1.0 mm, from the viewpoint of increasing film thickness accuracy and facilitating the production of a film with few die lines.
From the same viewpoint as the die lip clearance L, the die lip width W is preferably 300 to 4,000 mm, more preferably 1,000 to 3,500 mm, still more preferably 1,500 to 3,200 mm.

In the present invention, the speed (V ₁ ) at which the molten (meth)acrylic resin composition is extruded from the die is preferably 0.4 to 24 m/min, more preferably 0.8 to 21 m/min. and more preferably 1.1 to 18 m/min.
Note that _V1 is defined as follows.
_V1 (m/min) = Q / 60 / D / (L x W) x 1000 Formula (2)
In formula (2), Q (kg/hour) is the amount discharged from the die, D is the density of the resin composition (g/cm ³ ), L (mm) is the die lip clearance, and W (mm) is the die lip width. .

In the present invention, the take-up speed (V ₂ ) of the film is preferably 5 to 80 m/min, more preferably 10 to 50 m/min, still more preferably 15 to 30 m/min. When V ₁ and V ₂ are each within the above ranges, it is possible to obtain a (meth)acrylic resin film having excellent film thickness accuracy even when the film forming speed is increased.
The take-up speed (V ₂ ) of the film can be calculated from the diameter and number of rotations of the metal roll that initially takes up the melt expelled from the die.

In the present invention, from the viewpoint of obtaining a film with a uniform thickness, the temperature of the melt curtain of the (meth)acrylic resin composition measured at a position 5 cm below the T-die discharge port is measured at the center of the melt curtain. The ratio of the temperature (T ₂ ) of the temperature 100 mm from both ends of the melt curtain to the temperature (T ₁ ) of the melt curtain, which has a larger absolute value of difference from T ₁ [[(T ₂ )/( T ₁ )]×100] is preferably 95 to 105%. If the temperature in the width direction of the film immediately after ejection from the die is uniform, it becomes easier to obtain a uniform film. From this point of view, the ratio is more preferably 96% or more, preferably 103% or less, and more preferably 101% or less.

<Roll>
In the present invention, from the viewpoint of improving the surface smoothness and film thickness accuracy of the (meth)acrylic resin film, the extruded melt is preferably taken up using a metal mirror roll or mirror belt and pinched. is preferred. Examples of the mirror surface roll made of metal include elastic metal rolls and rigid metal rolls. From the viewpoint of improving the surface smoothness of the (meth)acrylic resin film, it is preferable to use a combination of an elastic metal roll and a rigid metal roll. is preferred.
When a mirror roll or mirror belt is used, the linear pressure is preferably 5 N/mm or more, more preferably 10 N/mm or more, from the viewpoint of improving the surface smoothness of the (meth)acrylic resin film. It is preferably 15 N/mm or more. Also, the linear pressure is usually 45 N/mm or less.
When a mirror roll or mirror belt is used, the surface temperature thereof is preferably 50 to 130° C., more preferably 50 to 130° C., from the viewpoint of improving the surface smoothness, haze, appearance, etc. of the (meth)acrylic resin film. 60 to 100°C.

<(Meth)acrylic resin composition>
The (meth)acrylic resin composition used in the present invention has a melt viscosity of 200 to 2,000 Pa·s at 270° C. and a shear rate of 61/sec.
If the melt viscosity at 270° C. and a shear rate of 61/sec is less than the above lower limit, the viscosity may be too low and the film formability may be reduced. On the other hand, if the above upper limit is exceeded, the temperature distribution will not be uniform due to insufficient mixing, and as a result, uneven film thickness will easily occur. From these viewpoints, the melt viscosity at 270° C. and a shear rate of 61/sec is preferably 300 Pa·s or more, more preferably 400 Pa·s or more, still more preferably 500 Pa·s or more, and preferably is 1,500 Pa·s or less, more preferably 1,300 Pa·s or less, and still more preferably 1,000 Pa·s or less.
The melt viscosity at 270°C and a shear rate of 61/sec can be measured by the method described in Examples.

The glass transition temperature of the (meth)acrylic resin composition used in the present invention is preferably 95°C or higher, more preferably 100°C or higher, and even more preferably 105°C or higher. When the glass transition temperature is within the above range, the film thickness accuracy of the (meth)acrylic resin film is further improved. The glass transition temperature of the (meth)acrylic resin composition used in the present invention is usually 130° C. or lower.
The glass transition temperature of the (meth)acrylic resin composition can be measured according to JIS K7121:2012 by the method described in Examples.
Moreover, when multiple glass transition temperatures exist, let the highest value of them be the glass transition temperature of a (meth)acrylic resin composition.

[(Meth) acrylic resin (A)]
The (meth)acrylic resin composition used in the present invention contains at least (meth)acrylic resin (A). Although the (meth)acrylic resin (A) is not particularly limited, it preferably contains a structural unit derived from methyl methacrylate and, if necessary, a structural unit derived from an acrylic acid ester. Examples of acrylic acid esters that can be used in the (meth)acrylic resin (A) include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, s-butyl acrylate, and t-butyl. acrylate, amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, pentadecyl acrylate, dodecyl acrylate, cyclohexyl acrylate, norbornenyl acrylate, isobornyl acrylate, benzyl acrylate, phenoxyethyl acrylate, 2 -hydroxyethyl acrylate, 2-ethoxyethyl acrylate, glycidyl acrylate, allyl acrylate, phenyl acrylate and the like. Among these, alkyl acrylates in which the alkyl group has 1 to 6 carbon atoms are preferred.

The amount of the structural unit derived from methyl methacrylate in the (meth)acrylic resin (A) is preferably 85 to 100% by mass, more preferably from the viewpoint of improving the mechanical strength of the (meth)acrylic resin film. is 90 to 100% by mass, more preferably 95 to 100% by mass, and even more preferably 99 to 100% by mass.
In addition, from the viewpoint of improving the film thickness accuracy of the (meth)acrylic resin film, the content of the structural unit derived from the acrylic acid ester in the (meth)acrylic resin (A) is determined by the (meth)acrylic resin ( In A), it is preferably 0 to 15% by mass, more preferably 0 to 10% by mass, even more preferably 0 to 5% by mass, and particularly preferably 0 to 1% by mass.

The (meth)acrylic resin (A) preferably has a weight average molecular weight of 60,000 to 150,000. When the weight average molecular weight is at least the lower limit, the mechanical properties are enhanced, and when it is at most the upper limit, the workability is improved. From the above viewpoint, the weight average molecular weight is more preferably 70,000 to 120,000, still more preferably 80,000 to 100,000.
The weight average molecular weight of the (meth)acrylic resin (A) can be measured by the method described in Examples.

The method for producing the (meth)acrylic resin (A) is not particularly limited, and for example, it can be produced by known polymerization methods such as radical polymerization and anionic polymerization. The production conditions are not particularly limited, and the desired (meth)acrylic resin (A) can be obtained by appropriately adjusting the polymerization temperature, polymerization time, type and amount of chain transfer agent, type and amount of polymerization initiator, etc. can be done.

The content of the (meth)acrylic resin (A) in the (meth)acrylic resin composition used in the present invention is preferably 60% by mass or more from the viewpoint of improving the transparency of the (meth)acrylic resin film. , more preferably 70% by mass or more, and still more preferably 75% by mass or more.

[Acrylic polymer (B) having a multilayer structure]
The (meth)acrylic resin composition used in the present invention may contain an acrylic polymer (B) having a multilayer structure.
The acrylic polymer (B) having a multilayer structure is not particularly limited as long as it has a multilayer structure, and examples thereof include acrylic polymers having a core-shell multilayer structure. Moreover, the number of layers constituting the multilayer structure is not particularly limited, and may be two layers or three layers or more.
Among these, from the viewpoint of improving the impact resistance of the (meth)acrylic resin film, an acrylic elastic polymer having a core-shell multilayer structure is preferable. More specifically, a core (inner layer) and an inner shell An acrylic elastic polymer having a core-shell multi-layer structure consisting of three layers (intermediate layer) and an outer shell (outer layer) is preferred. In the present invention, the acrylic polymer having a core-shell multilayer structure consisting of three layers means that the core and the inner shell, and the inner shell and the outer shell are respectively composed of different polymers.
In addition, when the acrylic polymer having a core-shell multilayer structure consisting of three layers is mixed with a (meth)acrylic resin composition containing it, all or part of the outer shell is (meth)acrylic It fuses and coalesces with the resin (A) to form a matrix, and the matrix contains core-shell particles consisting of two layers of a core and an inner shell.

The acrylic polymer having a core-shell multilayer structure composed of three layers, a core (inner layer), an inner shell (intermediate layer), and an outer shell (outer layer), will be described below in detail. The polymer constituting the core is referred to as "polymer (a)", the polymer constituting the inner shell as "polymer (b)", and the polymer constituting the outer shell as "polymer (c)". explain.

(Polymer (a): polymer constituting the core)
The polymer (a) is a polymer containing a structural unit derived from methyl methacrylate, a structural unit derived from an alkyl acrylate, a structural unit derived from a grafting agent, and optionally a structural unit derived from a cross-linking agent. is preferred. In the present invention, the term "grafting agent" means a monomer having two or more different polymerizable groups, and the term "crosslinking agent" means a monomer having two or more of the same type of polymerizable groups (wherein the graft agent).

Although the alkyl acrylate used in the polymer (a) is not particularly limited, the alkyl group preferably has 1 to 8 carbon atoms, more preferably 1 to 6 carbon atoms. When the carbon number of the alkyl group in the alkyl acrylate is within the above range, the thermal decomposition resistance of the acrylic polymer (B) having a multilayer structure is improved, and the (meth)acrylic resin film is resistant to hot water whitening. Boiling water whitening resistance is improved. Specific alkyl acrylates include methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, t-butyl acrylate, n-butylmethyl acrylate, n-heptyl acrylate, 2-ethylhexyl acrylate, Examples include n-octyl acrylate and the like. These can be used individually by 1 type or in combination of 2 or more types.
Among these, methyl acrylate is particularly preferable from the above viewpoint.

The polymer (a) is used for the purpose of chemically bonding the polymer (a) and the polymer (b), and for the purpose of assisting the formation of the crosslinked structure of the polymer (a). It preferably contains a structural unit derived from the grafting agent.
Grafting agents used in the polymer (a) include, for example, allyl methacrylate, allyl acrylate, mono- or di-allyl maleate, mono- or di-allyl fumarate, crotyl acrylate, and crotyl methacrylate. be able to. These grafting agents can be used singly or in combination of two or more.
Among these, allyl methacrylate is preferable from the viewpoint of improving the bonding ability between the polymer (a) and the polymer (b) and improving the stress whitening resistance and transparency of the (meth)acrylic resin film. .

The polymer (a) is used for the purpose of forming a crosslinked structure in the polymer (a) and for the purpose of forming a graft structure between the polymer (a) and the polymer (b). , may contain a structural unit derived from a cross-linking agent.
Examples of the cross-linking agent used for the polymer (a) include diacryl compounds, dimethacryl compounds, diallyl compounds, divinyl compounds, diene compounds, trivinyl compounds and the like. More specifically, ethylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, divinylbenzene, trivinylbenzene, ethylene glycol diallyl ether, Propylene glycol diallyl ether, butadiene and the like can be mentioned. These cross-linking agents can be used singly or in combination of two or more.

The amount of structural units derived from methyl methacrylate in the polymer (a) is preferably 40 to 98.99% by mass, more preferably 45 to 96.9% by mass, based on the total structural units of the polymer (a). %. When the amount of the structural unit derived from methyl methacrylate is at least the lower limit, the weather resistance of the (meth)acrylic resin film is improved, and when it is at most the upper limit, the impact resistance of the (meth)acrylic resin film is improved. improve sexuality.

The amount of structural units derived from alkyl acrylate in the polymer (a) is preferably 1 to 59% by mass, more preferably 3 to 55% by mass, based on the total structural units of the polymer (a). When the amount of structural units derived from alkyl acrylate is at least the lower limit, the acrylic polymer (B) having a multilayer structure has improved thermal decomposition resistance. The hot water whitening resistance and boiling water whitening resistance of the resin film are improved.

The amount of structural units derived from the grafting agent in the polymer (a) is preferably 0.01 to 1% by mass, more preferably 0.1 to 0, based on the total structural units of the polymer (a). 0.5 mass %. When the amount of structural units derived from the grafting agent is at least the lower limit, the bonding strength between the polymer (a) and the polymer (b) is improved, and when it is at most the upper limit (meta ) The impact resistance of the acrylic resin film is improved.

The amount of the structural unit derived from the cross-linking agent in the polymer (a) is preferably 0 to 0.5% by mass, more preferably 0 to 0.2% by mass, based on the total structural units of the polymer (a). %. When the amount of structural units derived from the cross-linking agent is within the above range, the impact resistance of the (meth)acrylic resin film is improved.

Polymer (a) and polymer (b), which will be described later, are preferably insoluble in solvents such as acetone, that is, grafted. When the polymer (a) and the polymer (b) are grafted, the polymer (a) and the polymer (b) form particles having a two-layer structure in the matrix of the polymer (c) described later. It is preferable because it becomes present and improves the impact resistance of the (meth)acrylic resin film.

(Polymer (b): polymer constituting the inner shell)
The polymer (b) is a polymer containing a structural unit derived from an alkyl acrylate, a structural unit derived from a grafting agent, and optionally a structural unit derived from an aromatic vinyl compound and a structural unit derived from a cross-linking agent. is preferably

Examples of the alkyl acrylate used for the polymer (b) include the alkyl acrylates exemplified for the polymer (a). ) n-butyl acrylate is particularly preferred from the viewpoint of improving the hot water whitening resistance and boiling water whitening resistance of the acrylic resin film.

Examples of the aromatic vinyl compound used for the polymer (b) include aromatic vinyl compounds such as styrene, α-methylstyrene, p-methylstyrene, and m-methylstyrene, and acrylic polymers having a multilayer structure. Styrene is preferred from the viewpoint of improving the thermal decomposition resistance of (B).

Examples of the grafting agent used for the polymer (b) include the grafting agents exemplified for the polymer (a). Allyl methacrylate is preferable from the viewpoint of improving the stress whitening resistance and transparency of the (meth)acrylic resin film.

Examples of the cross-linking agent used for the polymer (b) include the cross-linking agents exemplified for the polymer (a). From the viewpoint of forming a crosslinked structure with the polymer (b), diacryl compounds, dimethacryl compounds, diallyl compounds, divinyl compounds and the like are preferable.

The amount of structural units derived from alkyl acrylate in the polymer (b) is preferably 70 to 99.5% by mass, more preferably 80 to 99% by mass, based on the total structural units of the polymer (b). be. When the structural unit derived from alkyl acrylate is at least the lower limit, the impact resistance of the (meth)acrylic resin film is improved, and when it is at most the upper limit, the stress whitening resistance of the (meth)acrylic resin film is improved. enhanced transparency and transparency.

The amount of the structural unit derived from the aromatic vinyl compound in the polymer (b) is preferably 0 to 29% by mass, more preferably 0 to 20% by mass, based on the total structural units of the polymer (b). be. When the amount of structural units derived from methyl methacrylate is within the above range, the transparency of the (meth)acrylic resin film is improved.

The amount of structural units derived from the grafting agent in the polymer (b) is preferably 0.5 to 5% by mass, more preferably 1 to 4% by mass, based on the total structural units of the polymer (b). is. When the amount of structural units derived from the grafting agent is at least the above lower limit, the stress whitening resistance of the (meth)acrylic resin film is improved. On the other hand, the impact resistance of the (meth)acrylic resin film is improved by setting it to the above upper limit or less.

The amount of the structural units derived from the cross-linking agent in the polymer (b) is preferably 0 to 5% by mass, more preferably 0 to 2% by mass, based on the total structural units of the polymer (b). When the amount of structural units derived from the cross-linking agent is within the above range, the impact resistance of the (meth)acrylic resin film is improved.

In the present invention, polymer (b) is preferably softer than polymer (a) and polymer (c). The polymer (b) is softer than the polymer (a) and the polymer (c), thereby improving the impact resistance.

(Polymer (c): polymer constituting the outer shell)
Polymer (c) is preferably a polymer containing a structural unit derived from methyl methacrylate and a structural unit derived from alkyl acrylate.
Examples of the alkyl acrylate used for the polymer (c) include the alkyl acrylates exemplified for the polymer (a) above. ) Methyl acrylate is particularly preferred from the viewpoint of improving the hot water whitening resistance and boiling water whitening resistance of the acrylic resin film.

The amount of structural units derived from methyl methacrylate in the polymer (c) is preferably 80 to 99% by mass, more preferably 85 to 98% by mass, based on the total structural units of the polymer (c). When the amount of the structural unit derived from methyl methacrylate is at least the above lower limit, the stress whitening resistance of the (meth)acrylic resin film is improved. On the other hand, the heat decomposition resistance of the (meth)acrylic resin film is improved when the content is equal to or less than the upper limit.

The amount of structural units derived from alkyl acrylate in the polymer (c) is preferably 1 to 19% by mass, more preferably 2 to 15% by mass, based on the total structural units of the polymer (c). When the amount of structural units derived from alkyl acrylate is at least the lower limit, the acrylic polymer (B) having a multilayer structure has improved thermal decomposition resistance. The stress whitening resistance of the resin film is improved.

Polymer (c) is preferably soluble in solvents such as acetone, ie, not crosslinked. When the polymer (c) is not crosslinked, when using the acrylic polymer (B) having a multilayer structure consisting of the polymer (a), the polymer (b), and the polymer (c), the polymer (c) forms a matrix in which particles composed of the polymer (a) and the polymer (b) are present, improving the ease of production of the (meth)acrylic resin film.

(Mass ratio of polymer (a), polymer (b) and polymer (c))
The amount of the polymer (a) in the acrylic polymer (B) having a multilayer structure is preferably 1 to 50% by mass, more preferably 5 to 45% by mass, still more preferably 10 to 40% by mass. %. When the amount of the polymer (a) is at least the lower limit, the thermal stability and productivity of the (meth)acrylic resin film are improved. On the other hand, when the amount of the polymer (a) is equal to or less than the upper limit, the impact resistance and flexibility of the (meth)acrylic resin film are improved.

The amount of the polymer (b) in the acrylic polymer (B) having a multilayer structure is preferably 20 to 60% by mass, more preferably 25 to 55% by mass, still more preferably 30 to 50% by mass. %. When the amount of the polymer (b) is at least the lower limit, the thermal stability and productivity of the (meth)acrylic resin film are improved. On the other hand, when the amount of the polymer (b) is equal to or less than the upper limit, the impact resistance and flexibility of the (meth)acrylic resin film are improved.

The amount of the polymer (c) in the acrylic polymer (B) having a multilayer structure is preferably 5 to 40% by mass, more preferably 10 to 35% by mass, still more preferably 15 to 30% by mass. %. When the amount of the polymer (c) is at least the above lower limit, the fluidity of the acrylic polymer (B) having a multilayer structure and the moldability of the (meth)acrylic resin film are improved. When the amount of the polymer (c) is equal to or less than the upper limit, the impact resistance and stress whitening resistance of the (meth)acrylic resin film are improved.

(Method for producing acrylic polymer (B) having multilayer structure)
The method for producing the acrylic polymer (B) having a multilayer structure used in the present invention is not particularly limited, but for example, it may be produced by the methods described in WO 2014/167868 and WO 2017/204243. can be done.

The average particle size of the acrylic polymer (B) having a multilayer structure is preferably 0.01 μm or more, more preferably 0.04 μm or more, still more preferably 0.05 μm or more, and particularly preferably 0 07 μm or more, preferably 0.35 μm or less, more preferably 0.30 μm or less. If the average particle size is too large, the stress whitening resistance of the (meth)acrylic resin film tends to decrease. The average particle size is obtained by the method described in Examples based on the light scattering method.

From the viewpoint of improving the mechanical strength and workability of the (meth)acrylic resin film, the content of the acrylic polymer (B) having a multilayer structure is preferably based on 100 parts by mass of the (meth)acrylic resin It is 5 to 50 parts by mass, more preferably 10 to 40 parts by mass, still more preferably 15 to 30 parts by mass.

<Optional component>
The (meth)acrylic resin composition used in the present invention may optionally contain known additives such as ultraviolet absorbers, antioxidants, light stabilizers, plasticizers, polymer processing aids, lubricants, dyes and pigments. may contain
When the (meth)acrylic resin composition contains an additive, the content thereof is preferably 20% by mass or less in the (meth)acrylic resin composition.
The additive may be added, for example, to the (meth)acrylic resin composition that is molten in the film forming machine, or may be dry-blended into the pelletized (meth)acrylic resin composition. , may be added when the acrylic polymer (B) having a multilayer structure and/or the (meth)acrylic resin are pelletized (masterbatch method).

The (meth)acrylic resin composition used in the present invention preferably contains an ultraviolet absorber. Examples of UV absorbers include 2,2'-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol]. The content of the ultraviolet absorber is preferably 0.05 to 5 parts by mass with respect to 100 parts by mass of the total amount of the resin composition.

The method for producing the (meth)acrylic resin composition used in the present invention is not particularly limited. It can be produced by mixing according to the mixing method of

According to the present invention, for example, a (meth)acrylic resin film having a thickness of 20 to 200 μm can be obtained with high thickness accuracy. From the viewpoints of improving the handleability of the (meth)acrylic resin film and keeping the cost low, the film thickness is preferably 25 to 180 μm, more preferably 30 to 150 μm, still more preferably 40 to 80 μm. When the film thickness is at least the lower limit value, the rigidity is increased, and the handleability of the (meth)acrylic resin film is improved. Moreover, when the film thickness is equal to or less than the upper limit, the balance between the strength of the (meth)acrylic resin film and the manufacturing cost is improved.

The coefficient of variation of the film thickness of the (meth)acrylic resin film obtained by the present invention is preferably 10% or less, more preferably 5% or less, still more preferably 3% or less, and particularly preferably 1 % or less. When the coefficient of variation of the film thickness is equal to or less than the upper limit, a uniform film without unevenness in film thickness can be obtained.
In this specification, the variation coefficient of the film thickness of the (meth)acrylic resin film means that the produced film is measured at 200 points at equal intervals in the width direction, and a total of 10,000 points are measured over the entire width and length of the roll. It is a value calculated from the measured value obtained by measuring the film thickness, and specifically, it is a value measured according to the method described in Examples.

The difference between the maximum value and the minimum value of the film thickness of the (meth)acrylic resin film obtained by the present invention is preferably 10% or less, more preferably 8% or less, with respect to the average film thickness. It is preferably 7% or less, more preferably 7% or less. When this value is 10% or less, unevenness in mechanical properties and optical properties becomes small.

The (meth)acrylic resin film obtained by the present invention can be used for the following various applications. For example, automobile interiors and exteriors, personal computer interiors and exteriors, mobile phone interiors and exteriors, solar cell interiors and exteriors, solar cell backsheets, road signs, bathroom equipment, flooring materials, road translucent plates, double glass lenses, lighting windows, carports, It can be used in the field of construction and building materials such as lighting covers, sizing for building materials, microwave oven cooking containers (tableware), housings for home appliances, toys, sunglasses, stationery, and the like. It can also be used as a substitute for a molded product using a transfer foil sheet.
It is also suitable for optical films such as light guide plates for liquid crystals, diffusion plates, back sheets, reflection sheets, polarizing films, transparent resin sheets, retardation films, light diffusion films, prism sheets, optically isotropic films, and polarizer protection. It can be applied to known optical applications such as liquid crystal display films such as films and transparent conductive films for the periphery of liquid crystal display devices; the field of information equipment such as surface protective films; and organic EL devices as films for organic EL devices.

The present invention will be described in more detail based on examples below, but the present invention is not limited to these examples. Incidentally, the measuring method and the like in the present example are as follows.

<Temperature of melt curtain 5 cm below T die outlet>
While the resin composition extruded from the T-die is dripping before the start of narrowing pressure by the roll, the temperature is measured with an infrared thermography (R300SR, Nippon Avionics, emissivity setting 1.0) from a position 1 m away from the melt curtain. bottom. Due to the viewing angle of the infrared thermography, the entire width of the dripping resin was divided into 5 shots. Analysis software (InfReC Analyzer, Nippon Avionics) was used to analyze the temperature distribution at the photographed location. Linear analysis was performed on the temperature of the melt curtain at a position 5 cm below the resin discharge port of the T die, and the temperature (T ₁ ) at the center of the melt curtain and the temperature 100 mm from both ends of the melt curtain on the center side T ₁ The temperature (T ₂ ) with the larger absolute value of the difference between the two was measured, and the ratio between T ₁ and T ₂ [[(T ₂ )/(T ₁ )]×100] was obtained.

<Film thickness measurement>
A β-ray type film thickness meter (manufactured by Thermo Fisher Co.) was used to measure the thickness of the transported film while traversing the β-ray portion. While measuring 200 points at equal intervals in the width direction, the film thickness was measured at a total of 10,000 points over the entire width and length of the roll. From the film thickness at 10,000 points, the average film thickness and standard deviation were calculated from the following formulas.
Average film thickness: μ = (Z1 + Z2 + ... Zn) / n
Standard deviation: σ = (1/nΣ(Zn-μ) ² ) ^0.5
Coefficient of variation (%): CV = σ / μ × 100
Z1 to Zn: each film thickness data, n: number of data

<Weight average molecular weight (Mw)>
It was obtained by standard polystyrene conversion molecular weight by GPC (gel permeation chromatography). The measuring equipment and conditions are as follows.
・ Apparatus: GPC apparatus "HLC-8320" manufactured by Tosoh Corporation
・ Separation column: Direct connection of “TSKgel SuperMultipore HZM-M” and “SuperHZ4000” manufactured by Tosoh Corporation ・ Detector: “RI-8020” manufactured by Tosoh Corporation
・Eluent: tetrahydrofuran ・Eluent flow rate: 0.35 ml/min ・Sample concentration: 8 mg/10 ml
・Column temperature: 40°C

<Glass transition temperature (Tg)>
The glass transition temperature was measured according to JIS K7121:2012. That is, the sample is heated once to 200 ° C., then cooled to room temperature, and then heated from room temperature to 200 ° C. at a rate of 10 ° C./min, and the DSC curve is measured by differential scanning calorimetry, The midpoint glass transition temperature obtained from the DSC curve measured during the second heating was taken as the glass transition temperature in the present invention.

<Average particle size of the acrylic polymer (B) having a multilayer structure>
The average particle size of the acrylic polymer (B) having a multilayer structure was measured by diluting the latex containing the sample particles 200 times with water and using a laser diffraction scattering particle size distribution analyzer (manufactured by Horiba, Ltd., device name " LA-950V2”) was used to analyze such dilutions at 25° C. to determine the particle size. At this time, the absolute refractive indices of the acrylic polymer (B) having a multilayer structure and water were set to 1.4900 and 1.3333, respectively.

<Melt viscosity>
The melt viscosity was measured using a capillograph (model 1D manufactured by Toyo Seiki Seisakusho Co., Ltd., capillary diameter 1 mm, length 40 mm) under conditions of 270° C. and a shear rate of 61/sec.

<Production Example 1: Production of (meth)acrylic resin (A)>
99.3 parts by mass of methyl methacrylate and 0.7 parts by mass of methyl acrylate, polymerization initiator [2,2'-azobis(2-methylpropionitrile), hydrogen abstraction capacity: 1%, 1 hour half-life temperature: 83 ° C. ] and 0.26 parts by mass of a chain transfer agent (n-octyl mercaptan) were added and dissolved to obtain 3000 kg of raw material liquid.
100 parts by mass of ion-exchanged water, 0.03 parts by mass of sodium sulfate, and 0.45 parts by mass of potassium polymethacrylate were mixed to obtain 6000 kg of a mixed liquid. A pressure-resistant polymerization tank was charged with the mixed solution and the raw material solution (total of 9000 kg), and the temperature was raised to 70° C. to initiate a polymerization reaction while stirring in a nitrogen atmosphere. After 3 hours from the initiation of the polymerization reaction, the temperature was raised to 90° C. and stirring was continued for 1 hour to obtain a liquid in which the bead-like copolymer was dispersed. A small amount of polymer adhered to the wall surface of the polymerization vessel or to the stirring blades, but no bubbling occurred and the polymerization reaction proceeded smoothly.
The resulting copolymer dispersion was washed with an appropriate amount of ion-exchanged water, and the bead-like copolymer was taken out with a bucket-type centrifuge and dried with a hot air dryer at 80° C. for 12 hours. ) An acrylic resin (A) was obtained.
The resulting (meth)acrylic resin (A) had a methyl methacrylate unit content of 99.3% by mass, a methyl acrylate unit content of 0.7% by mass, and a weight average molecular weight (Mw) of was 92,000 and the glass transition temperature was 120°C.

<Production Example 2: Production of acrylic polymer (B) having a multilayer structure>
An acrylic polymer (B) having a core-shell multilayer structure consisting of three layers, a core (inner layer), an inner shell (intermediate layer), and an outer shell (outer layer), was produced according to the following procedure.
(1) Synthesis of inner layer In a reactor equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, a monomer inlet tube and a reflux condenser, 1050 parts by mass of ion-exchanged water and 0 part of sodium polyoxyethylene tridecyl ether acetate were added. 3 parts by mass and 0.7 parts by mass of sodium carbonate (2100 kg in total) were charged, and the inside of the reactor was sufficiently replaced with nitrogen gas. Then, the internal temperature was adjusted to 80° C., 0.25 parts by mass of potassium persulfate was added, and the mixture was stirred for 5 minutes. To this, 245 parts by mass of a monomer mixture consisting of 95.4% by mass of methyl methacrylate, 4.4% by mass of methyl acrylate and 0.2% by mass of allyl methacrylate was continuously added dropwise over 60 minutes. After the completion of dropping, the polymerization reaction was further carried out for 30 minutes so that the polymerization conversion rate was 98% or higher.

(2) Synthesis of Intermediate Layer Next, 0.32 parts by mass of potassium persulfate was charged into the same reactor and stirred for 5 minutes. Thereafter, 315 parts by mass of a monomer mixture consisting of 80.5% by mass of n-butyl acrylate, 17.5% by mass of styrene and 2% by mass of allyl methacrylate was continuously added dropwise over 60 minutes. After the completion of dropping, the polymerization reaction was further carried out for 30 minutes so that the polymerization conversion rate was 98% or higher.

(3) Synthesis of Outer Layer Next, 0.14 parts by mass of potassium persulfate was charged into the same reactor and stirred for 5 minutes. After that, 140 parts by mass of a monomer mixture consisting of 95.2% by mass of methyl methacrylate, 4.4% by mass of methyl acrylate and 0.4% by mass of n-octylmercaptan was continuously added dropwise over 30 minutes. After the completion of dropping, the polymerization reaction was further carried out for 60 minutes so that the polymerization conversion rate was 98% or higher.

After the latex containing the acrylic polymer (B) having a multilayer structure was obtained by the above operation, the latex containing the acrylic polymer (B) having a multilayer structure was frozen and solidified. Then, it was washed with water and dried to obtain an acrylic polymer (B) having a multilayer structure. The average particle diameter of the particles was 0.23 μm.

<Example 1>
A (meth)acrylic resin film was prepared using the apparatus shown in FIG. Specifically, (meth)acrylic resin (A) 80 parts by mass, acrylic polymer (B) 20 parts by mass having a multilayer structure, and Adeka Stab LA-31 (manufactured by Adeka Co., Ltd.) as a UV absorber 2 parts by mass were mixed with a Henschel mixer, and mixed using a twin-screw extruder with a screw diameter of 58 mm and a vent set at 260° C. to obtain a (meth)acrylic resin composition.
This (meth)acrylic resin composition was melted using a vented single-screw extruder with a screw diameter of 75 mm (L _S /D _S = 34) set at 265 ° C., and a static mixer section (the static mixer After passing through a distance of 1 m from the outlet of the tube arranged inside) to the inlet of the T die, it is extruded into a film from a T die with a lip width of 1850 mm and a lip clearance of 0.8 mm at a discharge rate of 170 kg / hour. C. and metal rigid rolls set at 90.degree. A meth)acrylic resin film was obtained.

As the gear pump, a spur-tooth circumscribed gear pump (manufactured by Toshiba Machine Co., Ltd.) was used, and the powder was delivered at an inlet pressure of 5 MPa.
As the polymer filter, four candle filters with a filtration accuracy of 10 µm were arranged in parallel.
The static mixer was equipped with seven twisted vane elements with Le/De=1.5 (Le=57 mm, De=38 mm).
In addition, a heater was attached to the tube (made of stainless steel, inner diameter 38 mm) in which the static mixer was placed, and the set temperature before and after the static mixer was set to 265°C, and the temperature up to the die was also set to 265°C (meta). An acrylic resin film was produced. The thickness of the produced film was measured by the method described above.

[Examples 2-3, Comparative Examples 1-3]
In Example 1, the (meth)acrylic resin film was prepared in the same manner as in Example 1 except that the number of elements of the static mixer and the presence or absence of heating of the pipe in which the static mixer was arranged were changed as shown in Table 1. was formed. Table 1 shows the evaluation results.

According to the method for producing a (meth)acrylic resin film of the present invention, a (meth)acrylic resin film having a uniform film thickness can be produced.

1 Extruder 2 Gear Pump 3 Polymer Filter 4 Static Mixer Part 5 T Die 6, 7 Roll

Claims (3)

A (meth)acrylic resin comprising a step of mixing a (meth)acrylic resin composition having a melt viscosity of 200 to 2,000 Pa s at 270° C. and a shear rate of 61/sec with a static mixer and extruding through a T-die. A method for producing a film,
Regarding the temperature of the melt curtain of the (meth)acrylic resin composition measured at a position 5 cm below the T-die discharge port, the temperature (T 1 ) at the center of the melt curtain, from both ends of the _melt curtain The ratio [[(T ₂ )/(T ₁ )]×100] of the temperature (T ₂ ) having a larger absolute value of the difference from T ₁ among the temperatures on the 100 mm center side is 95 to 105%,
A method for producing a (meth)acrylic resin film, wherein the static mixer is arranged inside a tube, has 5 to 30 elements, and heats the tube to 250 to 280°C . 2. The method for producing a (meth)acrylic resin film according to claim 1 , wherein the distance from the outlet of the tube in which the static mixer is arranged to the inlet of the T-die is 2.0 m or less. The method for producing a (meth)acrylic resin film according to claim 1 or 2 , wherein the (meth)acrylic resin composition contains an acrylic polymer (B) having a multilayer structure.

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