Method of manufacturing thermoplastic film

Abstract

To provide a method of manufacturing a thermoplastic film by a melt extrusion method that can suppress the occurrence of chronological appearance defects, in a situation where: although appearance defects of a film roll wound into a roll shape can basically be detected during a winding step, which is the final step in film production, there are cases where, despite no appearance defects being observed immediately after winding, the appearance of the film roll changes during storage and abnormalities become noticeable.SOLUTION: In a melt extrusion film production step, the problem is solved by providing one or more temperature-regulated rolls with a regulated surface temperature between a cast roll and a conveying roll, setting the surface temperature of the temperature-regulated rolls to 90 to 110°C and at least 5°C higher than the surface temperature of the cast roll, and setting the ratio v2 / v1 between a circumferential speed v1 (m / min) of the cast roll and a circumferential speed v2 (m / min) of the conveying roll to be 0.991 or more and 0.995 or less.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for producing a thermoplastic film formed by melt extrusion. [Background technology]

[0002] Thermoplastic films used for display members, automobile interior members, etc. are formed by, for example, a melt extrusion film forming method.

[0003] To provide an overview of the melt extrusion film-forming method with reference to Figure 1, a thermoplastic resin, which is the raw material for the thermoplastic film, is supplied to an extrusion process, melted in an extruder (not shown), and extruded into a sheet from a T-die 1. The thermoplastic resin 2 extruded into a sheet is sandwiched between sandwich rolls 3 and 4 in a film-forming process, where a film with a uniform thickness is formed. The formed film 5 comes into contact with cooling rolls (three rolls, 6a, 6b, and 6c in the example of Figure 1) provided in a cooling process, then passes through an intermediate roll 8 (typically a flat roll or expander roll) provided as needed, and is transported by transport rolls 9 in a transport process to a winding process equipped with a winder 11, where a film roll 12 is obtained.

[0004] The conveying process involves taking up the film that has passed through the cooling process and sending it to the next process, the winding process. To ensure more reliable film conveyance, it is common to use a drivable conveying roll 9 as the roll that comes into surface contact with the running film, and to provide a nip roll 10 opposite the drivable conveying roll 9 to apply a nip pressure to the film that is sufficient to prevent the film from slipping.

[0005] 1, the roll with which the thermoplastic resin 2 extruded into a sheet contacts on its surface is referred to as the cast roll 4, and the roll with which the thermoplastic resin 2 extruded into a sheet contacts in a roughly linear manner is referred to as the touch roll 3. The ratio of the peripheral speed v1 (m / min) of the cast roll to the peripheral speed v2 (m / min) of the transport roll: v2 / v1 is referred to as the draw ratio.

[0006] In the film rolls manufactured as described above, slack and wrinkles in the film during transport through the film-forming process are crushed on the transport rolls, resulting in creases and other defects in appearance, and defects in appearance due to thickness variations in the width direction, called gauge bands, that become apparent in the film roll when it is wound up into a roll. These defects in appearance lead to coating variations and printing variations when the film is subjected to hard coating treatment, printing, etc., and therefore efforts have been made to improve these problems.

[0007] The inventions of Patent Documents 1 and 2 both address the issue of providing a thermoplastic film that does not cause defects in the appearance of the film roll. They clarify the relationship between the likelihood of appearance defects occurring after long-term storage of film rolls produced by melt extrusion film-forming and the shrinkage rate after leaving the film at room temperature for one month in the MD direction (the direction of flow during film formation). They reveal that a film with a shrinkage rate of 0.01 to 0.10% after leaving the film at room temperature for one month is important for suppressing the occurrence of gauge bands when the film roll is left at room temperature for one month, and disclose that it is preferable to adjust the draw ratio to 0.970 to 1.001 in order to obtain a film with a shrinkage rate of 0.01 to 0.10%. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-171157 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-187874 Summary of the Invention [Problem to be solved by the invention]

[0009] Although defects in the appearance of a film roll wound into a roll can basically be detected during the winding process, which is the final step in film production, there are cases in which no defects in appearance are observed immediately after winding, but the appearance of the film roll changes during storage and abnormalities become noticeable. The problem that the present invention aims to solve is to prevent the occurrence of such defects in appearance over time.

[0010] As already mentioned, Patent Documents 1 and 2 disclose an invention in which a film with a small shrinkage rate is obtained by setting the draw ratio v2 / v1, which is determined by the peripheral speed v1 (m / min) of the casting roll and the peripheral speed v2 (m / min) of the transport roll, to 0.970 to 1.001. The examples show that the smaller the v2 / v1, the easier it is to obtain a film with a small shrinkage rate, and improvement in appearance defects is also observed.

[0011] The present inventors further investigated the relationship between the shrinkage rate of a film and defective appearance and found that in order to more preferably suppress the occurrence of defective appearance, it is highly necessary to obtain a film having a shrinkage rate of approximately 0.07% or less. However, as shown in the examples of Patent Documents 1 and 2, in order to obtain a film having such a low shrinkage rate, it is highly necessary to adopt a draw ratio of 0.990 or less, which has led to the facing of a new problem.

[0012] In other words, a draw ratio smaller than 1 means that the peripheral speed of the transport roll is slower than the peripheral speed of the cast roll. However, this makes it difficult to apply tension to the running film in the running direction, causing it to tend to become "slack" and making it more susceptible to wrinkles. Therefore, in Patent Document 1, in examples where a draw ratio of 0.990 or less is applied, a roll (in the example, an expander roll) with a mechanism for eliminating wrinkles or slack that occur in the flow direction of the film is provided on at least either the top or bottom of the running film.

[0013] Furthermore, in the invention of Patent Document 2, in order to prevent wrinkles from occurring even when the draw ratio is 1.001 or less, the ratio De / Dc of the maximum thickness De (μm) from the edge of the film in the width direction (TD) up to 50 mm inward to the average thickness Dc (μm) at the center is set to 3.5 or less, so that a certain degree of tension is applied in the machine direction of the film across the entire width of the film (especially in the center) to prevent noticeable "sagging," and it is essential that De / Dc be 0.4 or more to prevent the edges from tearing due to tension.

[0014] However, the expander roll used to prevent wrinkles in Patent Document 1 has the problem that the roll acts as a kind of wrinkle smoothing action when the film comes into contact with the roll, causing fine scratches on the film surface. Also, although the invention in Patent Document 2 specifies De / Dc to be 3.5 or less, there are cases in which the edges of the film are intentionally made thicker so that the center of the film is not tightly wound during the film winding process, i.e., a De / Dc of more than 3.5 is desired, and there is a problem that this invention cannot fully address such cases.

[0015] In view of such circumstances, the present inventors have conducted extensive research into a method for more preferably preventing the occurrence of poor appearance by applying a draw ratio at which the occurrence of wrinkles does not become a problem, and have arrived at the present invention. [Means for solving the problem]

[0016] That is, the gist of the present invention is as follows.

[0017] (1) A method for producing a thermoplastic film, comprising: an extrusion step of extruding a sheet-shaped thermoplastic resin from a T-die by a melt extrusion method; a film formation step of sandwiching the sheet-shaped thermoplastic resin extruded from the extrusion step between a pair of sandwich rolls to form a film; a temperature control step of bringing the film that has undergone the film formation step into contact with one or more temperature control rolls whose surface temperatures are adjusted; and a transport step of transporting the film that has undergone the temperature control step by transport rolls, The pair of sandwiching rolls in the film forming step is composed of a touch roll and a cast roll, and the surface temperature of at least the most downstream temperature-controlled roll of the single or multiple temperature-controlled rolls whose surface temperature is adjusted is 90°C to 110°C, and the surface temperature of at least the most downstream temperature-controlled roll of the single or multiple temperature-controlled rolls whose surface temperature is adjusted is 5°C or more higher than the surface temperature of the cast roll, A method for producing a thermoplastic film, wherein the ratio of the peripheral speed v1 (m / min) of the casting roll in the film forming step to the peripheral speed v2 (m / min) of the transport roll in the transport step: v2 / v1 satisfies the following formula (I): 0.991≦v2 / v1≦0.995 Formula (I) (2) The method for producing a thermoplastic film according to (1), wherein the surface temperatures of all of the single or multiple temperature-controlled rolls whose surface temperatures are adjusted are 90°C to 110°C, and the surface temperatures of all of the single or multiple temperature-controlled rolls whose surface temperatures are adjusted are 5°C or more higher than the surface temperature of the casting roll.

[0018] (3) The method for producing a thermoplastic film according to (1) or (2), wherein the thermoplastic resin is an acrylic resin composition.

[0019] (4) The method for producing a thermoplastic film according to (1) or (2), wherein the thermoplastic resin is an acrylic resin composition containing an acrylic graft copolymer. [Effects of the Invention]

[0020] The thermoplastic film manufacturing method of the present invention can provide a low-shrinkage film that provides a thermoplastic film roll in which the occurrence of poor appearance during storage is suppressed, even though a small draw ratio that would lead to the occurrence of wrinkles during film formation is not adopted.

[0021] In another aspect, the thermoplastic film manufacturing method of the present invention is less likely to cause wrinkles in the film during film formation, so there is no need to install a roll with a mechanism for eliminating wrinkles or slack that occur in the film's flow direction, and it is possible to set with a high degree of freedom the ratio De / Dc of the maximum thickness De (μm) from the end of the film in the width direction (TD) to the average thickness Dc (μm) at the center.

[0022] Furthermore, the production method of the present invention can utilize conventional melt extrusion film-forming equipment either as is or with minor modifications that utilize the same roll arrangement, and does not require a significant extension of the path length from the T-die to winding. Furthermore, even with the same path length, the effects of the present invention can be achieved at the same film-forming speed as conventional methods, so that offline processing equipment is not required except in special cases. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a diagram showing an example of an apparatus for carrying out a melt extrusion film forming method. [Figure 2] 1 is a diagram showing an example of an apparatus for carrying out the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0024] The method for producing a thermoplastic film according to the present embodiment includes an extrusion step, a film-forming step, a temperature control step, a transport step, and a winding step. Each step will be described below.

[0025] [Extrusion process] In the extrusion step, a sheet-like thermoplastic resin 2, which is a raw material for the film, is extruded by melt extrusion from the discharge opening of a T-die 1. There are no particular limitations on the T-die 1, and any known T-die can be used as appropriate. The T-die 1 preferably has a discharge opening shaped so that it can extrude the sheet-like thermoplastic resin 2 described below, but the shape is not particularly limited.

[0026] The thermoplastic resin extruded from the discharge port of the T-die 1 may be in the form of a sheet, and its thickness and width are not particularly limited. For example, the thickness of the sheet-like thermoplastic resin 2 is not particularly limited, as long as it is thick enough to allow the thermoplastic resin to be sandwiched between the two rolls, the cast roll 4 and the touch roll 3, in the subsequent film-forming process. For example, the thickness of the sheet-like thermoplastic resin 2 is preferably approximately 20 μm to 300 μm, but is not limited thereto. If the thickness of the thermoplastic resin is thinner than 20 μm, it will be significantly affected by the deflection of the rolls, and the thickness of the produced thermoplastic film will tend to be uneven. On the other hand, if the thickness of the thermoplastic resin is thicker than 300 μm, the thermoplastic resin cannot be thinly spread by the rolls. As a result, it will be difficult to produce a thermoplastic film in the subsequent process, and the produced thermoplastic film will tend to be thick.

[0027] Furthermore, the width of the sheet-like thermoplastic resin 2 extruded from the discharge opening of the T-die 1, i.e., the length of the thermoplastic resin in a direction substantially perpendicular to the extrusion direction, i.e., the length of the thermoplastic resin in a direction substantially perpendicular to the direction of the force applied to the thermoplastic resin in the subsequent film-forming step, is not particularly limited and may be determined appropriately depending on the desired product width.

[0028] The melt viscosity of the thermoplastic resin extruded from the outlet of the T-die 1 in the extrusion step is not particularly limited, but is preferably 1500 Pa·sec or less. The melt viscosity can be adjusted, for example, by changing the content of each structural unit in the acrylic resin. The melt viscosity can be measured using any known method. If the melt viscosity of the thermoplastic resin extruded from the outlet of the T-die 1 is within the above range, it is possible to more reliably reduce thickness variations in the produced film and prevent the occurrence of defects known as die lines.

[0029] The thermoplastic resin used in the present invention is not particularly limited, but is preferably, for example, an acrylic resin, a cellulose resin, a polycarbonate, a cyclic olefin copolymer, a polyglutarimide resin, or a PHBH (poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)) resin. The acrylic resin is also not particularly limited, but is preferably, for example, an acrylic resin composition (A) constituting the acrylic resin, which contains an acrylic graft copolymer (a-1).

[0030] The acrylic resin composition (A) is preferably an acrylic resin composition comprising 5 to 100% by weight of an acrylic crosslinked elastomer-containing graft copolymer (a-1) and 0 to 95% by weight of a methacrylic polymer (a-2) [the total amount of (a-1) and (a-2) is 100% by weight], due to its excellent impact resistance, solvent resistance, plasticizer migration resistance, and transparency. The resin composition (A) can be obtained by polymerizing the acrylic crosslinked elastomer-containing graft copolymer (a-1) and the methacrylic polymer (a-2) separately and mixing them. However, during production, the acrylic crosslinked elastomer-containing graft copolymer (a-1) can be produced in the same reactor, followed by the production of the methacrylic polymer (a-2). The materials can be mixed in the form of latex, powder, beads, pellets, etc.

[0031] The acrylic crosslinked elastomer-containing graft copolymer (a-1) is obtained by polymerizing a (meth)acrylic acid ester monomer (a-1b) in the presence of an acrylic acid ester crosslinked elastomer (a-1a) [a crosslinked elastomer mainly composed of an acrylic acid ester].

[0032] The acrylic ester-based crosslinked elastic material (a-1a) is obtained by polymerizing a monomer mixture consisting of 50 to 100% by weight of an acrylic ester and 0 to 50% by weight of another copolymerizable vinyl-based monomer, and a specific amount of a polyfunctional monomer having two or more non-conjugated double bonds per molecule relative to the monomer mixture. The monomers and polyfunctional monomers may be used in a single stage, or may be used in two or more stages with different compositions of the monomers and polyfunctional monomers.

[0033] As the acrylic ester in the acrylic ester-based crosslinked elastic material (a-1a), from the viewpoints of polymerizability and cost, an acrylic ester having an alkyl group with a carbon number of 1 to 12 can be used. Specific examples thereof include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and n-octyl acrylate, and these monomers may be used alone or in combination of two or more.

[0034] The amount of acrylic acid ester in the acrylic acid ester-based crosslinked elastic material (a-1a) is preferably 50 to 100% by weight, more preferably 70 to 100% by weight, and most preferably 80 to 100% by weight. If the amount of acrylic acid ester is less than 50% by weight, impact resistance and elongation at tensile break tend to decrease, and cracks tend to occur more easily when the film is cut.

[0035] Examples of other copolymerizable vinyl monomers in the acrylate ester-based crosslinked elastomer (a-1a) include alkyl methacrylate esters (preferably those in which the alkyl group has 1 to 12 carbon atoms, and which may be linear or branched) such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, and t-butyl methacrylate; vinyl halides such as vinyl chloride and vinyl bromide; vinyl cyanides such as acrylonitrile and methacrylonitrile; vinyl esters such as vinyl formate, vinyl acetate, and vinyl propionate, and aromatic vinyl derivatives such as styrene, vinyl toluene, and α-methylstyrene; vinylidene halides such as vinylidene chloride and vinylidene fluoride; acrylic acid and salts thereof such as acrylic acid, sodium acrylate, and calcium acrylate; alkyl acrylate derivatives such as β-hydroxyethyl acrylate, dimethylaminoethyl acrylate, glycidyl acrylate, acrylamide, and N-methylol acrylamide; Examples of suitable monomers include methacrylic acid and its salts such as methacrylic acid, sodium methacrylate, and calcium methacrylate; and methacrylic acid alkyl ester derivatives such as methacrylamide, β-hydroxyethyl methacrylate, dimethylaminoethyl methacrylate, and glycidyl methacrylate. These monomers may be used alone or in combination of two or more. Among these, methacrylic acid esters are particularly preferred from the viewpoints of weather resistance and transparency.

[0036] The amount of other copolymerizable vinyl monomers in the acrylate ester-based crosslinked elastic material (a-1a) is preferably 0 to 50% by weight, more preferably 0 to 30% by weight, and most preferably 0 to 20% by weight. If the amount of other vinyl monomers exceeds 50% by weight, impact resistance decreases, elongation at tensile break decreases, and cracks may easily occur when the film is cut.

[0037] The amount of copolymerizable polyfunctional monomer in the acrylate ester-based crosslinked elastomer (a-1a) greatly affects stress whitening, elongation at tensile break, and transparency, as well as the average particle size of the acrylate ester-based crosslinked elastomer.

[0038] The polyfunctional monomer used for the above purpose may be a commonly used one, such as allyl methacrylate, allyl acrylate, triallyl cyanurate, triallyl isocyanurate, diallyl phthalate, diallyl maleate, divinyl adipate, divinyl benzene, ethylene glycol dimethacrylate, diethylene glycol methacrylate, triethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, tetramethylolmethane tetramethacrylate, dipropylene glycol dimethacrylate, and acrylates thereof. These polyfunctional monomers may be used alone or in combination of two or more.

[0039] The copolymerization amount of the polyfunctional monomer in the acrylate ester-based crosslinked elastic particles (a-1a) of the present invention is preferably 0.1 to 10 parts by weight, more preferably 1.0 to 4 parts by weight, based on 100 parts by weight of the monomer mixture. A copolymerization amount of 0.1 to 10 parts by weight of the polyfunctional monomer is preferable from the viewpoints of bending resistance, bending whitening resistance, and resin fluidity.

[0040] Examples of initiators that can be used in the polymerization of the acrylate ester-based crosslinked elastomer (a-1a) include known organic peroxides, inorganic peroxides, and azo compounds. Specifically, examples include organic peroxides such as t-butyl hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, succinic acid peroxide, t-butyl peroxymaleate, cumene hydroperoxide, and benzoyl peroxide; inorganic peroxides such as potassium persulfate and sodium persulfate; and oil-soluble initiators such as azobisisobutyronitrile. These initiators can be used alone or in combination. These initiators can also be used as conventional redox initiators in combination with reducing agents such as sodium sulfite, sodium thiosulfate, sodium formaldehyde sulfoxylate, ascorbic acid, hydroxyacetoic acid, ferrous sulfate, and a complex of ferrous sulfate and disodium ethylenediaminetetraacetate.

[0041] The organic peroxide can be added by a known method, such as adding it directly to the polymerization system, mixing it with a monomer and adding it, or dispersing it in an aqueous emulsifier solution and adding it. From the viewpoint of transparency, however, the method of adding it by mixing it with a monomer or dispersing it in an aqueous emulsifier solution and adding it is preferred.

[0042] In addition, from the viewpoints of polymerization stability and particle size control, it is preferable to use the organic peroxide as a redox initiator in combination with an inorganic reducing agent such as a divalent iron salt and / or an organic reducing agent such as sodium formaldehyde sulfoxylate, reducing sugar, or ascorbic acid.

[0043] The surfactant used in the emulsion polymerization is not particularly limited, and any surfactant commonly used in emulsion polymerization can be used. Specific examples include anionic surfactants such as sodium alkyl sulfonate, sodium alkylbenzene sulfonate, dioctyl sodium sulfosuccinate, sodium lauryl sulfate, and fatty acid sodium salts, and nonionic surfactants such as reaction products of alkylphenols, aliphatic alcohols with propylene oxide, and ethylene oxide. These surfactants may be used alone or in combination of two or more. Furthermore, if necessary, cationic surfactants such as alkylamine salts may also be used.

[0044] The average particle size of the acrylic ester-based crosslinked elastomer (a-1a) is preferably 50 to 200 nm, more preferably 50 to 160 nm, even more preferably 50 to 120 nm, and particularly preferably 60 to 120 nm. If the average particle size of the acrylic ester-based crosslinked elastomer (a-1a) is less than 50 nm, impact resistance and the like tend to decrease, elongation at tensile break decreases, and cracks tend to occur more easily when the film is cut. If the average particle size exceeds 200 nm, stress whitening tends to occur more easily, transparency tends to decrease, and transparency after vacuum molding also tends to decrease. The average particle size in the present invention is a value measured in a latex state by a light scattering method using a Microtrac particle size distribution analyzer MT3000 manufactured by Nikkiso Co., Ltd.

[0045] The acrylic crosslinked elastomer-containing graft copolymer (a-1) is obtained by polymerizing a monomer mixture (a-1b) mainly composed of a methacrylic acid ester in the presence of the acrylic acid ester crosslinked elastomer (a-1a). Preferably, the copolymer is obtained by polymerizing, in one stage or two or more stages, 95 to 15 parts by weight of a monomer mixture (a-1b) mainly composed of a methacrylic acid ester [the total amount of (a-1a) and (a-1b) being 100 parts by weight] in the presence of 5 to 85 parts by weight of the acrylic acid ester crosslinked elastomer (a-1a).

[0046] The methacrylic acid ester content in the graft copolymerization composition (monomer mixture) (a-1b) is preferably 80% by weight or more, more preferably 85% by weight, and even more preferably 90% by weight. If the methacrylic acid ester content is less than 80% by weight, the resulting film tends to have reduced hardness and rigidity. The monomers used in the graft copolymerization are methacrylic acid esters and acrylic acid esters. Specific examples of suitable monomers include those used in the acrylic acid ester-based crosslinked elastomer (a-1a). In this case, the graft copolymerization composition (monomer mixture) (a-1b) generates a component (free polymer) that does not undergo a graft reaction with the acrylic acid ester-based crosslinked elastomer (a-1a) and becomes an ungrafted polymer. This component (free polymer) constitutes part or all of the methacrylic polymer (B). A portion of the acrylic crosslinked elastomer-containing graft copolymer (a-1) ((a-1a) and the grafted (a-1b)) is insoluble in methyl ethyl ketone.

[0047] The graft ratio of the acrylic ester-based crosslinked elastic material (a-1a) is preferably 30 to 250%, more preferably 50 to 230%, and even more preferably 70 to 220%. If the graft ratio is less than 30%, the resistance to whitening due to bending will decrease, and the transparency will decrease, and the elongation at tensile break will decrease, making the film more susceptible to cracking when cut. If the graft ratio is more than 250%, the melt viscosity during film formation will increase, and the film formability will tend to decrease.

[0048] The method for producing the acrylic crosslinked elastomer-containing graft copolymer (a-1) is not particularly limited, and known emulsion polymerization, emulsion-suspension polymerization, suspension polymerization, bulk polymerization, or solution polymerization methods can be applied, with emulsion polymerization being particularly preferred.

[0049] The average particle size of the resulting acrylic crosslinked elastomer-containing graft copolymer (a-1) is preferably more than 100 nm and not more than 400 nm, more preferably more than 100 nm and not more than 350 nm, and even more preferably more than 100 nm and not more than 300 nm. If the average particle size of the acrylic crosslinked elastomer-containing graft copolymer (a-1) is 100 nm or less, the impact resistance and flex crack resistance of the film that can be formed from the resulting acrylic resin composition (A) tend to decrease, while if it exceeds 400 nm, the transparency of the film tends to decrease.

[0050] The acrylic crosslinked elastomer-containing graft copolymer (a-1) latex obtained as described above is subjected to the usual coagulation, washing and drying procedures, or to treatments such as spray drying and freeze drying, to separate and recover the resin composition.

[0051] The methacrylic polymer (a-2) contains 80% by weight or more, more preferably 85% by weight or more, and even more preferably 90% by weight or more, of methyl methacrylate. If the methyl methacrylate content is less than 80% by weight, the hardness and rigidity of the resulting film tend to decrease.

[0052] The monomer other than methyl methacrylate in the methacrylic polymer (a-2) may be the same as that used in the acrylic crosslinked elastomer-containing graft copolymer (a-1). These monomers may be used alone or in combination of two or more.

[0053] The methacrylic polymer (a-2) can be polymerized separately from the acrylic crosslinked elastomer-containing graft copolymer (a-1). In this case, the polymerization method is not particularly limited, and known methods such as emulsion polymerization, emulsion-suspension polymerization, suspension polymerization, bulk polymerization, and solution polymerization can be used.

[0054] As the initiator for the polymerization of the methacrylic polymer (a-2), known organic peroxides, inorganic peroxides, azo compounds, and the like can be used. Specific examples include organic peroxides such as t-butyl hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, succinic acid peroxide, peroxymaleic acid t-butyl ester, cumene hydroperoxide, benzoyl peroxide, lauroyl peroxide, t-butyl peroxybenzoate, isopropyl-t-butyl peroxycarbonate, butyl perbenzoate, 1,1-bis(alkylperoxy)3,3,5-trimethylcyclohexane, and 1,1-bis(alkylperoxy)cyclohexane; inorganic peroxides such as potassium persulfate and sodium persulfate; and azo compounds such as azobisisobutyronitrile. These may be used alone or in combination of two or more.

[0055] The organic peroxide can be added by a known method, such as adding it directly to the polymerization system, mixing it with a monomer and adding it, or dispersing it in an aqueous emulsifier solution and adding it. From the viewpoint of the transparency of the resulting film, however, the method of adding it by mixing it with a monomer and adding it is preferred.

[0056] Dispersants used in the suspension polymerization include dispersants commonly used in suspension polymerization, such as polymeric dispersants such as polyvinyl alcohol, polyvinylpyrrolidone, and polyacrylamide, and poorly water-soluble inorganic salts such as calcium phosphate, hydroxyapatite, and magnesium pyrophosphate. When using poorly water-soluble inorganic salts, it is effective to use an anionic surfactant such as sodium α-olefin sulfonate or sodium dodecylbenzene sulfonate in combination, as this increases dispersion stability. These dispersants may be added once or twice or more during polymerization to adjust the particle size of the resulting resin particles.

[0057] The content of the acrylic ester crosslinked elastomer (a-1a) in the acrylic resin composition (A) is preferably 5 to 45% by weight, more preferably 10 to 30% by weight. If the content of the acrylic ester crosslinked elastomer (a-1a) is less than 5% by weight, the tensile elongation at break of the resulting film tends to decrease, cracks tend to occur when the film is cut, and stress whitening tends to occur. If the content exceeds 45% by weight, the hardness and rigidity of the resulting film tend to decrease.

[0058] The reduced viscosity of the methyl ethyl ketone soluble matter of the acrylic resin composition (A) is preferably 0.2 to 0.8 dL / g, more preferably 0.2 to 0.7 dL / g, and even more preferably 0.2 to 0.6 dL / g. If the reduced viscosity of the methyl ethyl ketone soluble matter of the resin composition (A) is less than 0.2 dL / g, the tensile elongation at break of the obtained film decreases, cracks tend to occur when the film is cut, and solvent resistance tends to decrease. If the reduced viscosity exceeds 0.8 dL / g, the formability of the film tends to decrease.

[0059] The acrylic resin composition (A) can be melt-kneaded using various common kneaders to produce resin pellets. Examples of the kneader include a single-screw extruder, a twin-screw extruder, a roll, a Banbury mixer, and a kneader. For example, using a single-screw extruder with a screw diameter of 40 mm, the composition is melt-kneaded at a barrel temperature of 180 to 280°C, a discharge rate of 100 to 150 kg / hr, and a screw rotation speed of 50 to 150 rpm. A strand is taken out of a die, cooled with water, and then cut using a strand cutter to obtain resin pellets.

[0060] The shear rate of the resin pellets is 122S. -1 The melt viscosity in the extrusion process is preferably 7000 to 20000 Pa·s, and more preferably 10000 to 19000 Pa·s. If the melt viscosity of the resin pellets is less than 7000 Pa·s, back pressure will not be generated at the tip of the extruder during film molding, etc., and it will tend to be difficult to obtain a molded product, while if the melt viscosity exceeds 20000 Pa·s, the resin pressure will be too high, making it difficult to extrude.

[0061] The fluidity (melt flow rate) of the resin pellets is preferably 0.5 to 3.0 g / 10 min, and more preferably 1.0 to 2.0 g / 10 min, under conditions of a temperature of 230° C. and a load of 37.5 N. A fluidity of 0.5 to 3.0 g / min is preferred in that molding is easy even at low molding temperatures and problems such as resin decomposition that occur during high-temperature molding can be solved.

[0062] The acrylic resin composition (A) described above can be processed into various molded articles by various plastic processing methods, such as injection molding, blow molding, and compression molding, in addition to T-die extrusion molding as in the present invention. In particular, the acrylic resin composition (A) is useful as a film, and can be successfully processed by, for example, inflation, which is a common melt extrusion method similar to T-die extrusion, or by calendaring, or even solvent casting. If necessary, when molding the film, it is also possible to obtain a film with improved surface properties by simultaneously contacting both sides of the film with rolls or metal belts, particularly rolls or metal belts heated to a temperature above the glass transition temperature. Furthermore, depending on the purpose, film lamination molding or film modification by biaxial stretching is also possible.

[0063] The acrylic resin composition (A) may also be blended with polyglutarimide, glutaric anhydride polymer, lactone-cyclized methacrylic resin, methacrylic resin, polyethylene terephthalate resin, polybutylene terephthalate resin, etc., as needed. The blending method is not particularly limited, and known methods can be used.

[0064] Furthermore, to the acrylic resin composition (A), inorganic pigments or organic dyes may be added for coloring, antioxidants, heat stabilizers, ultraviolet absorbers, ultraviolet stabilizers, etc. for further improving stability against heat and light, or antibacterial agents, deodorizers, lubricants, etc. may be added alone or in combination of two or more kinds, as needed.

[0065] [Film forming process] In the film-forming process, the sheet-like thermoplastic resin 2 extruded in the extrusion process is sandwiched between a pair of sandwiching rolls consisting of a casting roll 4 and a touch roll 3. A force is applied to the thermoplastic resin, forming a film from the thermoplastic resin. More specifically, the casting roll 4 and the touch roll 3 are disposed opposite each other, and the sheet-like thermoplastic resin is sandwiched between them. The force applied to the thermoplastic resin by these rolls results in a uniform thickness of the thermoplastic resin in the transverse direction (TD). As a result, a desired thermoplastic film can be produced. Here, the sandwiching force between the casting roll and the touch roll on the thermoplastic resin is preferably such that the relationship between P (unit: N) and H (cm) satisfies the relationship 30.0≦P / H≦300.0.

[0066] For example, as shown in FIG. 2 , in the manufacturing method of this embodiment, a touch roll 3 and a casting roll 4 are arranged facing each other, and the sheet-shaped thermoplastic resin 2 extruded from the discharge port of a T-die is sandwiched between the touch roll 3 and the casting roll 4. At this time, a force P (unit: N) is applied to the sheet-shaped thermoplastic resin 2 having a width H (cm) by being sandwiched between the touch roll 3 and the casting roll 4. Note that the width H (cm) of the sheet-shaped thermoplastic resin 2 refers to the length of the sheet-shaped thermoplastic resin 2 in a direction perpendicular to the direction in which the force P (N) is applied and also perpendicular to the extrusion direction of the sheet-shaped thermoplastic resin 2. The force P (N) refers to the force applied perpendicular to the sheet-shaped thermoplastic resin 2. Note that this force is applied to the sheet-shaped thermoplastic resin 2 by the touch roll 3 and the casting roll 4.

[0067] The types of the touch roll 3 and the cast roll 4 are not particularly limited, and known rolls can be used as appropriate. For example, the touch roll 3 and the cast roll 4 can be made of the same material, or can be made of different materials. For example, when the touch roll 3 and the cast roll 4 are made of different materials, it is preferable to use an elastic roll as the touch roll 3 and a rigid roll as the cast roll 4. The elastic roll and the rigid roll are not particularly limited.

[0068] There are no particular limitations on the method for applying the force P(N) to the sheet-like thermoplastic resin 2. For example, if the width of the sheet-like thermoplastic resin 2 changes, at least one of the rolls may be moved relative to the other roll so that the force P(N) can be changed accordingly. Furthermore, if the width of the sheet-like thermoplastic resin 2 is approximately constant, the distance between the touch roll 3 and the casting roll 4 may be fixed according to the width.

[0069] The temperature of each of the touch roll 3 and the cast roll 4 is not particularly limited and can be set appropriately within a range that satisfies the conditions of the manufacturing method of the present invention. For example, when the glass transition temperature of the thermoplastic resin is Tg (°C) and the roll temperature is T (°C), it is preferable to set the temperature of each roll so that Tg - 70 ≦ T ≦ Tg + 30. Note that the glass transition temperature (Tg) here refers to the glass transition temperature measured by a differential scanning calorimeter (DSC).

[0070] With the above configuration, the difference between the temperatures of the touch roll 3 and the cast roll 4 and the glass transition temperature of the thermoplastic resin is small, so that linear pressure can be applied to the sheet-shaped thermoplastic resin 2 under temperature conditions close to the glass transition temperature. As a result, thickness variations in the thermoplastic film that is finally produced can be reduced, and the occurrence of die line and dent defects can be suppressed.

[0071] [Temperature control process] The thermoplastic film thus formed, sandwiched between the touch roll 3 and the casting roll 4 shown in Fig. 2, is then transported to a temperature control step in which one or more temperature control rolls with regulated surface temperatures are disposed. In the example of Fig. 2, the film is brought into contact with three temperature control rolls 7a, 7b, and 7c, where it is temperature-controlled. The surface temperature of at least the most downstream temperature control roll (7c in Fig. 2) is preferably 90°C to 110°C and at least 5°C higher than the surface temperature of the casting roll 4, and more preferably 95°C to 105°C and at least 10°C higher than the surface temperature of the casting roll 4. When multiple temperature control rolls are disposed in the temperature control step, the surface temperature is preferably maintained at all of the temperature control rolls, not just the most downstream temperature control roll.

[0072] The temperature-control roll is not particularly limited, and any known roll can be used as appropriate. The surface temperature can be controlled by flowing a heat medium such as water or oil through the roll, blowing hot air onto the roll, or by a heat source such as an electric heater embedded in the roll; the method is not limited to these. When controlling the surface temperature of the roll using a heat medium, if the direct target of control is the heat medium temperature, the heat medium temperature can be regarded as the surface temperature. Furthermore, when controlling the surface temperature of the roll by controlling the output of a heat source using a temperature sensor such as a thermocouple embedded in the roll, the temperature detected by the thermocouple can be regarded as the surface temperature. However, for rolls with low thermal conductivity, such as rubber rolls, it is preferable to measure the surface temperature using a contact-type surface thermometer or the like as necessary to more reliably implement the present invention. The surface temperature of the cast roll 4 can also be determined in the same manner as above.

[0073] The number of temperature control rolls is not particularly limited, and may be determined depending on the desired difference in surface temperature between the most downstream temperature control roll and the casting roll 4, the number of rolls preferred for stable film production, and the like.

[0074] One of the practical advantages of the present invention is that it can be used without updating or modifying a conventional melt extrusion film-forming apparatus, as long as the surface temperature of the temperature-controlled roll does not exceed the upper limit temperature specified for the cooling roll of the conventional apparatus. Not only is there no need for additional equipment costs, but it can also be a great advantage in that it is possible to omit setting new conditions for the extrusion process, film-forming process, etc., which have been used for carrying out the conventional method.

[0075] [Transportation process] The film, whose temperature has been adjusted by contact with the temperature-adjusting roll in this way, is then transported by transport roll 9 and nip roll 10 located close thereto.

[0076] If the film becomes unstable or wrinkles occur when it travels between the temperature-controlling roll 7c on the most downstream side and the transport roll 9, the film may be stabilized by disposing an intermediate roll 8 between the temperature-controlling roll 7c and the transport roll 9. Examples of intermediate rolls include, but are not limited to, flat rolls, crown rolls, concave rolls (reverse crown rolls), and expander rolls.

[0077] The transport roll 9 and the adjacent nip roll 10 are not particularly limited, and known rolls can be used as appropriate. In implementing the present invention, the draw ratio (v2 / v1) when the peripheral speed of the casting roll 4 is v1 (m / min) and the peripheral speed of the transport roll is v2 (m / min) is preferably 0.991 or more and 0.995 or less, and more preferably 0.992 or more and 0.994 or less. If the draw ratio is smaller than this, the film may slacken between the casting roll 4 and the transport roll 9, hindering stable film production or causing wrinkles. Furthermore, if the draw ratio exceeds the above range, the film is more likely to shrink in the MD direction (the flow direction during film production) during film roll storage.

[0078] [Roll center distance] The center-to-center distance between the rolls provided in each process is not particularly limited, but if the center-to-center distance between the rolls in the temperature control process is too small, there is a risk that the workability will be reduced when the film is passed through the process, or that adjacent rolls will interfere with each other during film production, making temperature control difficult, so it is preferable not to make it too small more than necessary. Also, if the center-to-center distance between the rolls is too large, there is a risk that the product temperature of the film will become unstable during running, making the effect of the temperature control rolls unclear, so it is preferable not to make the center-to-center distance between the rolls too large more than necessary.

[0079] [Thickness of thermoplastic film] The thickness of the thermoplastic film of the present invention is preferably 20 to 300 μm, more preferably 30 to 200 μm. If the film thickness is less than 20 μm, the impact resistance tends to decrease, and if it exceeds 300 μm, the formability of the film tends to decrease. The film thickness can be appropriately set by the thickness of the thermoplastic resin extruded from the discharge opening of the T-die 1 and the clearance and speed of the sandwiching rolls.

[0080] [Uses of thermoplastic films] The uses of the thermoplastic film of the present invention are not particularly limited, and it can be used for various uses requiring an appearance design, such as automobile interiors, automobile exteriors, components for mobile phones, components for AV equipment, components for personal computer equipment, furniture products, various displays, lenses, window glass, small items, and miscellaneous goods.

[0081] The acrylic film, which is a preferred embodiment of the thermoplastic film of the present invention, is printed by an appropriate printing method as needed. When molding into a laminate, it is preferable to use the printed surface as the adhesive surface with the base resin in order to protect the printed surface and impart a luxurious feel. [Example]

[0082] The present invention will be described in more detail below with reference to examples and comparative examples, but these are not intended to limit the present invention in any way. In the following description, "parts" and "%" refer to "parts by weight" and "% by weight", respectively, unless otherwise specified. However, this does not apply to properties such as the shrinkage rate and draw ratio of the film, whose properties are clear from the formula.

[0083] (Film thickness measurement method) The thickness of the film was measured using a tabletop continuous film thickness meter (contact type, TOF-5R) manufactured by Yamabun Denki Co., Ltd. Specifically, a 50 mm wide piece was cut out from the film in the extrusion direction (MD) from a region excluding 50 mm from each end of the film in the transverse direction (TD), and the thickness of the cut film was continuously measured in the transverse direction (TD). Data was obtained by sampling the measured values ​​every 1 mm, and the average of each obtained data was taken as the film thickness.

[0084] (Method for measuring shrinkage in film extrusion direction (MD)) The center of the film in the width direction (TD) was cut into a square measuring 50 mm in the extrusion direction (MD) and 50 mm in the transverse direction (TD), and markings were made at 40 mm intervals in the film extrusion direction (MD). The exact distance was measured using an image dimension measuring device (IM-6700, manufactured by Keyence Corporation). The film was stored for one month in a thermo-hygrostat at a temperature of 25°C and a humidity of 55% RH, and after one month the distance between the markings was again accurately measured using a laser microscope, and the rate of change from one month before was calculated.

[0085] (Evaluation of wrinkles during film molding) The occurrence of wrinkles on the film during molding was evaluated by visual inspection, with a rating of x if wrinkles were observed on the film during molding and a rating of ◯ if no wrinkles were observed.

[0086] (Gauge band evaluation method) The formed film roll was stored in a warehouse where temperature and humidity were not controlled, and the gauge bands of the film roll after leaving it for one month were evaluated. The gauge band evaluation method for the film roll was as follows: if gauge bands were generated by visual inspection, it was marked with "X", and if they were not generated, it was marked with "O".

[0087] (glass transition temperature) 10 mg of the resin was measured using a differential scanning calorimeter (DSC, Shimadzu Corporation, Model DSC-50) under a nitrogen atmosphere at a heating rate of 20°C / min. The glass transition temperature was then determined based on the measurement results by the midpoint method.

[0088] Example 1 <Method for producing acrylic crosslinked elastomer-containing graft copolymer (a-1)> The following materials were added to an 8-liter polymerization reactor equipped with a stirrer, thermometer, nitrogen gas inlet pipe, monomer supply pipe, and reflux condenser: 200 parts water (ion-exchanged water) Sodium formaldehyde sulfoxylate 0.15 parts Ferrous sulfate dihydrate 0.0015 parts 0.006 parts of 2-sodium ethylenediaminetetraacetate Dioctyl sodium sulfosuccinate 0.0015 parts The inside of the vessel was thoroughly purged with nitrogen gas to make it substantially oxygen-free, and then the inside temperature was raised to 60°C, and a mixture of 27 parts of butyl acrylate, 3 parts of methyl methacrylate, 3 parts of allyl methacrylate, and 0.2 parts of cumene hydroperoxide was continuously added at a rate of 15 parts / hour to polymerize. After the addition was completed, the polymerization was continued for another hour, and the polymerization conversion rate was increased to 98% or more, yielding an elastic copolymer (a-1a). Next, in the presence of the elastic copolymer (a-1a), a mixture of 63 parts of methyl methacrylate, 7 parts of butyl acrylate, 0.2 parts of tertiary decyl mercaptan, and 0.3 parts of cumene hydroperoxide was continuously added at a rate of 10 parts / hour to polymerize, and the polymerization was continued for another hour, and the polymerization conversion rate reached 98% or more, and the polymerization of the multi-layered acrylic copolymer (a-1) was terminated, and a latex was obtained. The latex was salted out with calcium chloride, washed with water, and dried to obtain a resin powder of the acrylic crosslinked elastic graft copolymer (a-1).

[0089] <Methacrylic polymer (a-2)> As the methacrylic thermoplastic resin (a-2), a methyl methacrylate-methyl acrylate copolymer (manufactured by Sumitomo Chemical Co., Ltd., Sumipex (registered trademark) MM, bead-shaped, volume average particle diameter 224 μm, area average particle diameter 171 μm, proportion of particles with a particle diameter of 50 μm or less 0%) was used.

[0090] <Pelletization of acrylic resin composition (A)> A 40mmφ single-screw extruder (Osaka Seiki Kogyo Co., Ltd.) with a barrel temperature adjusted to 200°C was used to feed a resin composition containing 70% acrylic crosslinked elastomer-containing graft copolymer (a-1) and 30% methacrylic polymer (a-2) Sumipex (registered trademark) MM. The resin composition was melt-mixed at a screw rotation speed of 90 rpm and a discharge rate of 15 kg / hour. The resulting strand was taken up, cooled in a water bath, and cut using a pelletizer to produce resin pellets of the acrylic resin composition (A). The glass transition temperature of the pelletized acrylic resin composition (A) was 105°C.

[0091] <Film adaptation> The obtained resin pellets were extruded into a sheet-like thermoplastic resin sheet from a T-die (temperature adjusted to 240°C) attached to the tip of a 90mmφ single-screw extruder (manufactured by Hitachi Zosen Corporation) with the barrel temperature adjusted to 200°C. The extruded film was sandwiched between two rolls, a cast roll and a touch roll, to form a film. The film was then brought into contact with three temperature-adjusting rolls to adjust the temperature, and five 1000m film rolls of a film-like molded product with a thickness of 75.1 μm were produced.

[0092] In this example, the target width of the film to be formed was 1400 mm, and the positional relationship of the discharge outlet of the T-die 1, the cast roll 4, the touch roll 3, the three temperature-controlling rolls 7a, 7b, and 7c, the flat roll 8, the conveying roll 9, and the nip roll 10 in the film forming process was as shown in Figure 2. The outer diameter of the cast roll 4 was 150 mm, the outer diameters of the three temperature-controlling rolls 7a, 7b, and 7c and the outer diameter of the conveying roll 9 were all 100 mm, and the outer diameter of the flat roll 8 was 50 mm. The distance from the discharge outlet of the T-die 1 to the contact point of the cast roll 4 and the touch roll 3 with the sheet-shaped thermoplastic resin 2 was 8 cm. Furthermore, the center distance between the cast roll 4 and the temperature-control roll 7a closest to the cast roll 4 on the most upstream side, the center distance between the three temperature-control rolls, i.e., between 7a and 7b and between 7b and 7c, the center distance between the temperature-control roll 7c closest to the transport roll 9 on the most downstream side and the flat roll 8, and the center distance between the flat roll 8 and the transport roll 9 were all 300 mm.

[0093] In Example 1, the temperature of the casting roll 4 was 85°C, the temperature of the touch roll 3 was 50°C, the temperature of the temperature regulating roll 7a was 99°C, the temperature of the temperature regulating roll 7b was 99°C, and the temperature of the temperature regulating roll 7c was 99°C.

[0094] The draw ratio (v2 / v1) calculated from the peripheral speed (v1) of cast roll 4 and the peripheral speed (v2) of transport roll 9 at this time was 0.993, and because the film was produced under conditions where the draw ratio was close to 1 without being extremely small, there was no need to pay attention to the ratio (De / Dc) of the maximum thickness (De) (μm) from the edge of the film in the cross direction (TD) to the average thickness (Dc) (μm) at the center. In other words, no wrinkles occurred during film formation, and the average shrinkage in the MD direction after one month (720 hours) of storage at room temperature for evaluation samples taken from each of the five film rolls was 0.059%, and the average shrinkage in the MD direction after one month (720 hours) of storage in a warehouse was 0.037%.

[0095] Furthermore, after storing the five film rolls at room temperature for one month (720 hours), no gauge bands were observed, and there were no other changes in the appearance of the film rolls.

[0096] (Comparative Example 1) Five film rolls of approximately 1000 m each were produced in the same manner as in Example 1, except that the temperatures of temperature-controlled roll 7a, temperature-controlled roll 7b, and temperature-controlled roll 7c were set to 85°C, 85°C, and 80°C, respectively, and the value of the draw ratio v2 / v1 calculated from the peripheral speed v1 of cast roll 4 and the peripheral speed v2 of transport roll 9 was changed to 0.996.

[0097] Since the film was produced under conditions where the draw ratio was close to 1 without being extremely small, there was no need to pay attention to the ratio De / Dc, which is the ratio of the maximum thickness De (μm) from the edge of the film in the transverse direction (TD) to the innermost 50 mm, to the average thickness Dc (μm) at the center. In other words, no wrinkles occurred during film formation.

[0098] After storing the five film rolls at room temperature for one month (720 hours), no gauge bands were observed, and no other changes were observed in the appearance of the film rolls. However, the average shrinkage in the MD direction of the evaluation samples taken from each of the five film rolls after storing them at room temperature for one month (720 hours) was 0.108%, and the average shrinkage in the MD direction after storing them in a warehouse for one month (720 hours) was 0.065%. Both average shrinkages were larger than those in Example 1. [Industrial Applicability]

[0099] The thermoplastic film obtained by the production method of the present invention can be used for various applications requiring a decorative appearance, such as automobile interiors, automobile exteriors, components for mobile phones, components for AV equipment, components for personal computer equipment, furniture products, various displays, lenses, window glass, small items, and miscellaneous goods. [Explanation of symbols]

[0100] 1 T-die 2. Thermoplastic resin extruded into sheet form 3 Touch roll (sandwich roll) 4 Cast roll (sandwich roll) 5. Formed film 6a Cooling roll 6b Cooling roll 6c cooling roll 7a Temperature control roll 7b Temperature control roll 7c Temperature Control Roll 8 Flat roll or expander roll 9 Transport roll 10 Nip Roll 11 Winder 12 film rolls

Claims

1. an extrusion step of extruding a sheet-shaped thermoplastic resin from a T-die by a melt extrusion method; a film forming step in which the sheet-shaped thermoplastic resin extruded in the extrusion step is sandwiched between a pair of sandwich rolls to form a film; a temperature control step of contacting the film that has undergone the film forming step with a single or multiple temperature control rolls whose surface temperatures are controlled; a conveying step of conveying the film that has been subjected to the temperature adjusting step by a conveying roll, The pair of sandwiching rolls in the film forming step is composed of a touch roll and a cast roll, The surface temperature of at least the most downstream temperature-controlled roll of the single or multiple temperature-controlled rolls whose surface temperature has been adjusted is 90°C to 110°C, and the surface temperature of at least the most downstream temperature-controlled roll of the single or multiple temperature-controlled rolls whose surface temperature has been adjusted is 5°C or more higher than the surface temperature of the casting roll; The ratio of the peripheral speed v1 (m / min) of the casting roll in the film forming step to the peripheral speed v2 (m / min) of the transport roll in the transport step: v2 / v1 satisfies the following formula (I): 0.991≦v2 / v1≦0.995 Formula (I)

2. 2. The method for producing a thermoplastic film according to claim 1, wherein the surface temperatures of all of the single or multiple temperature-controlled rolls whose surface temperatures are adjusted are 90°C to 110°C, and the surface temperatures of all of the single or multiple temperature-controlled rolls whose surface temperatures are adjusted are 5°C or more higher than the surface temperature of the casting roll.

3. The method for producing a thermoplastic film according to claim 1 or 2, wherein the thermoplastic resin is an acrylic resin composition.

4. The method for producing a thermoplastic film according to claim 1 or 2, wherein the thermoplastic resin is an acrylic resin composition containing an acrylic graft copolymer.

Images