JP2008030475A - Laminated polyester film for molding and its manufacturing process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated polyester film for molding excellent in moldability at low temperatures and under low pressures, transparency, solvent resistance, shape stability (heat shrinkage properties and thickness variations), and impact resistance, and also to provide its manufacturing process. <P>SOLUTION: The laminated polyester film for molding is a biaxially oriented laminated polyester film obtained by laminating layer B on one or both sides of layer A. The layer A and the layer B are both composed of a copolymeric polyester or a copolymeric polyester and a homo-polyester. The melting point of the layer A (TmA:°C) and that of the layer B (TmB:°C) satisfy formulas (1): 260>TmB>TmA>200, and (2): 50>TmB-TmA>5, at the same time. Both the layer A and the layer B have an oriented structure and have a heat shrinkage at 150°C of ≤6.0%, and a thickness variation of ≤10%. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is excellent in moldability, particularly moldability at low temperature and low pressure, particularly moldability at low temperature and low pressure, transparency, solvent resistance, and shape stability (heat shrinkage characteristics, thickness unevenness), Furthermore, the present invention relates to a laminated polyester film for molding which is excellent in impact resistance and suitable as an interior material or exterior material for home appliances, mobile phones, automobiles, or a member for building materials, and a method for producing the same.

  Conventionally, as a sheet | seat for shaping | molding, a polyvinyl chloride film is typical and has been preferably used at points, such as workability. However, there are problems in terms of environmental suitability, such as generation of toxic gas when the film is burned and bleeding out of the plasticizer.

  On the other hand, unstretched sheets made of polyester, polycarbonate, or acrylic resin have been used in a wide range of fields as materials excellent in environmental suitability. In particular, an unstretched sheet made of a polyester resin is excellent in moldability and laminate suitability. However, since it is an unstretched sheet, it is inferior in terms of heat resistance and solvent resistance.

  Moreover, the unstretched sheet has insufficient impact resistance and form stability (heat shrinkage characteristics). For this reason, (a) if the speed during printing or molding is increased in order to improve productivity, there will be breaks or holes during processing, (b) printing misalignment will occur due to heating during molding, or (c) molding When the product is exposed to a temperature higher than room temperature, there is a problem that the molded product is distorted.

  Furthermore, when vapor-depositing a metal such as aluminum on an unstretched sheet, if the heat shrinkage property is inferior, there are problems such as small wrinkles during vapor deposition, making winding difficult, or insufficient glossiness. . When vacuum deposition is performed, the processing speed is further increased. Therefore, if the impact resistance is not sufficient, the sheet may be broken during the deposition.

As a method for solving the above problem, a method using a biaxially stretched polyethylene terephthalate film in which the stress at 100% elongation of the film is controlled within a specific range is disclosed (for example, see Patent Documents 1 and 2).
JP-A-2-204020 JP 2001-347565 A

  However, in the invention described in Patent Document 1, by using a copolyester containing an aliphatic glycol, by adjusting the blending amount of the aliphatic glycol, the stress at 100% elongation under an atmosphere of 150 ° C. is reduced. It is described that excellent moldability, flatness and heat resistance can be obtained. However, it was insufficient in terms of both moldability and heat resistance. On the other hand, in the invention described in Patent Document 2, problems remain in lowering the molding temperature and finishing of the molded body.

The present inventor has a copolymer polyester resin as a constituent component, a film 100% elongation stress (25 ° C., 100 ° C.), storage elastic modulus (100 ° C., 180 ° C.), thermal deformation under micro tension in the longitudinal direction. A method for improving the above-mentioned problems was proposed by using a biaxially oriented polyester film having a rate (175 ° C.) in a specific range (see, for example, Patent Document 3).
JP-A-2005-290354

  By this method, the above-mentioned problems are greatly improved, and in a mold molding method having a high molding pressure at the time of molding, a film satisfying market demand can be industrially provided. Furthermore, the finishing performance is improved even in molding methods with a low molding pressure during molding, such as a pressure-air molding method and a vacuum molding method, which have strong market demand.

  However, the above-mentioned biaxially oriented polyester film for molding can be produced continuously for a long time, during post-processing on the film (printing, lamination of metal film or metal oxide film, etc.), during molding process, or molded product It was found that film breakage and blocking are likely to occur during use. Therefore, it is desired to improve the impact resistance of the film and further enhance the productivity and the stability of quality.

In addition, we propose an invention that aims to achieve both chemical resistance and moldability by making the film a laminated structure, sharing the functions of each layer so that the skin layer has chemical resistance and the core layer has sufficient moldability. (For example, see Patent Document 4).
JP 2005-335276 A

  However, in the present invention, in order to increase the heat treatment temperature until the core layer has a substantially non-oriented structure, (1) the elongation at room temperature is extremely low, and (2) the processing temperature for whitening during heating. There is a problem that the range of use is narrow, and (3) the thickness unevenness is poor, the appearance quality, stability during processing, and reproducibility deteriorate.

  An object of the present invention is to solve the above-mentioned conventional problems, and is capable of moldability, particularly moldability at a low temperature and low pressure, transparency, solvent resistance, and shape stability (heat shrinkage characteristics, thickness unevenness). It is to provide a laminated polyester film for molding and a method for producing the same.

The laminated polyester film for molding and the method for producing the same according to the present invention, which can solve the above problems, have the following configurations.
That is, the first invention in the present invention is a biaxially oriented laminated polyester film formed by laminating a polyester B layer on one or both sides of a polyester A layer,
Each of the A layer and the B layer comprises a copolymer polyester, or a copolymer polyester and a homopolyester, and the melting point of the A layer (TmA: ° C) and the melting point of the B layer (TmB: ° C) are represented by the following formula (1). And (2) at the same time,
The laminated polyester film has an orientation structure in both the A layer and the B layer, the thermal shrinkage rate at 150 ° C. is 6.0% or less in both the longitudinal direction and the width direction, and the thickness variation rate in the width direction is 10% or less. This is a laminated polyester film for molding.
260>TmB>TmA> 200 (1)
50>TmB-TmA> 5 (2)

  According to a second invention, the copolymer polyester comprises (a) a copolymer polyester comprising an aromatic dicarboxylic acid component, ethylene glycol, and a glycol component containing a branched aliphatic glycol or alicyclic glycol, or (b 1) The laminated polyester film for molding according to the first invention, comprising an aromatic dicarboxylic acid component containing terephthalic acid and isophthalic acid and a glycol component containing ethylene glycol.

  According to a third invention, the homopolyester is at least one selected from the group consisting of polyethylene terephthalate, polytetramethylene terephthalate, and polybutylene terephthalate, and the laminated polyester film for molding according to the first invention It is.

  4th invention is the laminated polyester film for shaping | molding as described in 1st invention whose total thickness of a laminated polyester film is 10-500 micrometers, and the thickness of B layer is 1 to 30% of the whole It is.

  The fifth invention is characterized in that the stress at 100% elongation in the longitudinal direction and width direction of the laminated polyester film is 40 to 300 MPa at 25 ° C. and 1 to 100 MPa at 100 ° C. It is the laminated polyester film for molding described.

  A sixth invention is the laminated polyester film for molding described in the first invention, wherein the haze of the laminated polyester film is 2.0% or less.

  7th invention uses the laminated polyester film as described in 1st invention as a base material, and further laminate | stacks the coating layer (C layer) whose thickness is 0.01-5 micrometers on the single side | surface or both surfaces of this base material. A laminated polyester film for molding, wherein the coating layer is composed of a composition containing at least one resin and particles selected from polyester, polyurethane, acrylic polymer, or a copolymer thereof, and is applied to a substrate. Is a laminated polyester film for molding characterized by being substantially free of particles.

The eighth invention is a process for producing an unstretched sheet obtained by laminating a polyester B layer on one or both sides of a polyester A layer using a coextrusion method, and the unstretched sheet is biaxial in the longitudinal direction and the width direction. A process for producing a laminated polyester film for molding comprising a step of stretching, a step of heat-treating while holding a biaxially stretched film with a clip,
The polyester constituting the A layer and the B layer is a copolymer polyester, or a mixture of a copolymer polyester and a homopolyester,
The heat treatment process has two or more stages of heat treatment, the maximum temperature increase rate in the heat treatment section is 10 to 30 ° C./second, and the maximum heat treatment temperature is (the melting point of layer A−10 ° C.) to (the melting point of layer A) + 20 ° C.) The method for producing a laminated polyester film for molding according to the first aspect of the invention.

In the ninth aspect, when the transverse stretching and heat treatment are performed while holding the film with the clip in the tenter, the vicinity of the clip is cooled using at least one of the following methods (i) to (v): Next, the method for producing a laminated polyester film for molding according to the eighth invention is characterized in that the film is released from the clip at the tenter outlet.
(I) A method of providing a heat shielding wall at the clip portion (ii) A method of adding a clip cooling mechanism to the tenter (iii) A method of sufficiently cooling the entire film by setting a long cooling section after heat setting (iv) Cooling Method of increasing the cooling efficiency by increasing the length of the section and the number of sections (v) Method of enhancing the cooling of the clip using a type in which the return part of the clip travels outside the furnace

  The laminated polyester film for molding of the present invention has a skin layer (B layer) on one or both sides of the core layer (A layer), the melting point of the skin layer is higher than the melting point of the core layer, and the core layer also has an oriented structure. Since the laminated structure which has is employ | adopted, functions, such as the further improvement of chemical resistance and heat resistance, protection of a core layer, can be provided to a skin layer. Moreover, sufficient flexibility can be given to the core layer (A layer) to further improve the moldability. Moreover, the thickness unevenness is improved by biaxial stretching, and the function of improving heat resistance and chemical resistance by orientation crystallization is expressed. Furthermore, by making the melting point of the skin layer (B layer) relatively high and adopting specific heat treatment conditions, it is possible to suppress deterioration of slipperiness and improve impact resistance. For this reason, when manufacturing a film continuously for a long time, productivity or quality during post-processing of the film (printing, lamination of metal film or metal oxide film, etc.), molding process, or use of molded products Stability can be further increased.

  By using the laminated polyester film for molding according to the present invention, it is difficult to mold with a conventional biaxially oriented polyester film, vacuum molding or pressure molding under a low molding pressure of 10 atm or less. Also in a molding method such as the above, a molded product with good finish can be obtained. In addition, these molding methods are advantageous in terms of economy in the production of molded products because the molding costs are low. Therefore, the characteristics of the laminated polyester film for molding of the present invention can be exhibited most effectively by applying to these molding methods.

  On the other hand, the mold molding is expensive in terms of mold and molding equipment and disadvantageous in terms of economy, but has a feature that a molded product having a more complicated shape than the above molding method is molded with high accuracy. . Therefore, when the mold is molded using the laminated polyester film for molding used in the present invention, it can be molded at a lower molding temperature than the conventional biaxially oriented polyester film, and the finished product is finished. The remarkable effect that this is improved is expressed.

  Therefore, since the laminated polyester film for molding of the present invention is excellent in moldability at the time of heat molding, particularly at low temperature and low pressure, a wide range of molding methods such as mold molding, pressure molding and vacuum molding are applied. can do. Furthermore, when a molded product molded by such a method is used in a normal temperature atmosphere, it is excellent in elasticity and shape stability (heat shrinkage characteristics, thickness unevenness), and also in transparency, solvent resistance and heat resistance. Furthermore, since it is excellent in impact resistance, it is suitable as an interior material or exterior material for home appliances, mobile phones, automobiles, or building material members.

  Moreover, the laminated polyester film for molding of the present invention is also suitable as a molding material for molding using a molding method such as press molding, laminate molding, in-mold molding, drawing molding, bending molding, etc. in addition to the above-described molding method. It is.

  First, the technical value of the characteristic value used in each invention of this application and the characteristic value used for evaluation is demonstrated. Subsequently, the raw material used when manufacturing the lamination | stacking polyester film for shaping | molding of this invention, and the manufacturing method of a film are demonstrated.

(1) Thermal shrinkage at 150 ° C. (HS150)
In the laminated polyester film for molding of the present invention, the heat shrinkage (HS150) at 150 ° C. is preferably 6.0% or less in both the longitudinal direction and the width direction. The upper limit value of HS150 is more preferably 5.0%, still more preferably 4.0%, and particularly preferably 3.0%. On the other hand, the lower limit of HS150 is preferably 0.01%, more preferably 0.1%, and particularly preferably 0.5% from the practical point of view. HS150 is preferably small, but depending on the heat treatment temperature during the post-processing of the molding film and the temperature atmosphere in which the molded product is used, from the viewpoint of practical effect and productivity, an appropriate management standard can be determined. Good. However, even if a film having an HS 150 of less than 0.01% is produced, there is no significant difference in practical effects. Rather, productivity is greatly reduced, so there is no necessity to make HS150 less than 0.01%.

  On the other hand, by setting HS150 in the longitudinal direction and the width direction of the film to 6.0% or less, deformation such as wrinkles of the film can be suppressed in a post-processing step that requires heat, such as vapor deposition, sputtering, or printing. As a result, the appearance and design properties of the post-processed film can be maintained in a good state. Furthermore, it is possible to suppress printing deviation due to heating during molding, and to suppress distortion in the molded product when the molded product is exposed to a high temperature atmosphere. Therefore, it becomes possible to use a molded product in a wide temperature range.

(3) Thickness variation rate in the width direction In the present invention, the thickness variation rate of the film is used as a characteristic value related to macroscopic impact resistance.
The film thickness variation rate (thickness unevenness) is generally used as one of the characteristic values indicating the quality of the appearance of the film. A large thickness variation rate of the film means that the physical properties that affect the thickness of the film vary. When the thickness variation rate of the film is increased, the impact resistance is reduced at the thin portion. Therefore, when the film is manufactured continuously for a long time, when it is post-processed on the film (printing, lamination of metal film or metal oxide film, etc.), during molding process, or when using a molded product, Film tearing is likely to occur. In addition, when the film is molded, the deformation of the film becomes non-uniform, and the stability is lowered, for example, the moldability becomes non-uniform.

  Impact resistance can be improved by setting the thickness variation rate of the film to 10% or less in the width direction. Therefore, the frequency at which the film is broken can be reduced during continuous production, post-processing, molding, or use of a molded product. The thickness variation rate in the longitudinal direction is equally important, but since it is linked with the width direction, the thickness variation rate in the width direction is used as a representative in the present invention.

(3) Stress at 100% elongation (F100)
In the present invention, the stress at 100% elongation (F100) is a measure closely related to the moldability of the film. The reason why F100 is closely related to the moldability of the film is, for example, when a biaxially oriented polyester film is molded using a vacuum forming method, the film locally expands to 100% or more near the corner of the mold. There is a case. In a film having a high F100, it is considered that the stress necessary for deformation is too high, resulting in insufficient deformation, resulting in a decrease in formability. On the other hand, a film with F100 being too small can be deformed with low stress. However, only very weak tension is generated. For this reason, it is presumed that the film cannot be uniformly stretched at the portion, and the molding is distorted.

Therefore, in the present invention, 100% elongation stress (F100 ₁₀₀ ) at 100 ° C. is used as a physical property related to the moldability corresponding to the molding temperature. Further, the mold for molding may be used at a temperature near room temperature, and the F100 value is required not to be too large even near the room temperature. Therefore, 100% elongation stress (F100 ₂₅ ) at 25 ° C. is used as a physical property related to formability near room temperature.

The polyester film for molding in the present invention preferably has a stress at 100% elongation (F100 ₂₅ ) at 25 ° C. in the longitudinal and width directions of the film of 40 to 300 MPa.

The lower limit of F100 ₂₅ in the longitudinal direction and the width direction of the film is more preferably 50 MPa, and particularly preferably 60 MPa. On the other hand, the upper limit value is more preferably 250 MPa, more preferably 200 MPa, and particularly preferably 180 MPa. By setting F100 ₂₅ to 40 MPa or more, when a roll-shaped film is unwound, elongation and tearing of the film can be prevented, and workability is improved. On the other hand, moldability becomes favorable by making F100 ₂₅ into 300 MPa or less.

In addition, the polyester film for molding in the present invention preferably has a 100% elongation stress (F100 ₁₀₀ ) at 100 ° C. in the longitudinal direction and the width direction of the film of 1 to 100 MPa.

From the viewpoint of moldability, the upper limit of F100 ₁₀₀ in the longitudinal direction and the width direction of the film is more preferably 90 MPa, further preferably 80 MPa, and particularly preferably 70 MPa. On the other hand, the lower limit of F100 ₁₀₀ is more preferably 5 MPa, more preferably 10 MPa, and particularly preferably 20 MPa from the viewpoint of elasticity and shape stability when using a molded product.

(4) Haze It is preferable that the laminated polyester film for molding of the present invention has a haze of 2% or less. When the haze is 2% or less, the clarity and luxury of various decorations such as printing, metal vapor deposition, sputtered layer, and transfer layer are enhanced, and the commercial value can be remarkably increased. The haze is more preferably 1.8% or less, and particularly preferably 1.6% or less.

(5) Elongation at break at 25 ° C. (TE ₂₅ )
In the evaluation of the film of the present invention, the elongation at break at 25 ° C. is a characteristic value related to the handleability of the film near room temperature. For example, by managing the elongation at break at 25 ° C., the passability of post-processing such as printing and slitting can be maintained in a good state.

(Laminated structure)
The laminated polyester film for molding of the present invention is a biaxially oriented laminated polyester film formed by laminating a polyester B layer (skin layer) on one or both sides of a polyester A layer (core layer).

  That is, the laminated structure of the laminated polyester film of the present invention is basically composed of B / A / B type 2 layers 3 or B / A type 2 layers. In addition, using the laminated film as a base material, a coating layer (C layer) may be provided on at least one side of the base material in order to improve quality or to provide other functions on one side or both sides of the film of the present invention. it can.

In the laminated polyester film for molding of the present invention, both the A layer and the B layer are composed of a copolymer polyester, or a copolymer polyester and a homopolyester, and the melting point of the A layer (TmA: ° C.) and the melting point of the B layer ( TmB: ° C.) simultaneously satisfies the following formulas (1) and (2).
260>TmB>TmA> 200 (1)
50>TmB-TmA> 5 (2)

  That is, in this invention, the skin layer (B layer) which consists of polyester B whose melting | fusing point is higher than polyester A of a core layer (A layer) is laminated | stacked on the single side | surface or both surfaces of a core layer, and a core layer also has an orientation structure Is a feature. The reason for leaving the alignment structure in the core layer (A layer) will be described in detail later.

Furthermore, it is important that the laminated polyester film for molding of the present invention satisfies the following relational expression (1) when the melting point (° C.) of the A layer is TmA and the melting point (° C.) of the B layer is TmB. . The melting point means an endothermic peak temperature at the time of melting, which is detected at the time of primary temperature increase in differential scanning calorimetry (DSC).
260>TmB>TmA> 200 (1)

  TmA and TmB are preferably less than 260 ° C. from the viewpoint of moldability of the entire film. Further, it is important that TmB and TmA be higher than 200 ° C. in order to maintain the heat resistance of the entire film and to reduce thermal deformation at high temperatures. TmB and TmA are preferably higher than 205 ° C., particularly preferably higher than 210 ° C.

  In the present invention, the melting point (TmB) of the skin layer (B layer) is larger than the melting point (TmA) of the core layer (A layer), so that flexibility, slipperiness, chemical resistance, and heat resistance are increased. It is important from the point of balancing to a high degree.

Furthermore, it is important that the laminated polyester film for molding of the present invention satisfies the following relational expression (2) when the melting point (° C.) of the A layer is TmA and the melting point (° C.) of the B layer is TmB. .
50>TmB-TmA> 5 (2)

  When “TmB-TmA” is 50 ° C. or higher, the difference in melting point between the A layer and the B layer is too large, so that the thermal shrinkage rate, flexibility, impact strength, stability over time, and processing stability are highly satisfied. become unable. “TmB-TmA” is preferably less than 40 ° C., more preferably less than 35 ° C. Further, when “TmB−TmA” is 5 ° C. or less, the difference in melting point is too small, and it is difficult to highly balance flexibility, slipperiness, chemical resistance, and heat resistance. “TmB-TmA” is preferably higher than 10 ° C., particularly preferably higher than 15 ° C.

  A polyester film obtained by using a copolymer polyester containing 5 to 50 mol% of a copolymer component as a raw material as in the present invention has a slower crystallization rate and lower crystallinity than a polyethylene terephthalate film or the like. In addition, in order to reduce the degree of plane orientation and the thermal shrinkage at 150 ° C., when the method of heat treatment at a higher temperature than usual described in Patent Document 3 is used, the heat treatment is suddenly performed at a high temperature after the end of stretching. In the heat treatment section, the mobility of molecules constituting the material having low crystallinity is increased. Therefore, the surface protrusions formed by the bulging of the particles (particles in the biaxially oriented film or particles in the coating layer) in the stretching process are buried again in the heat treatment section, and unevenness on the surface of the film is hardly formed. . Therefore, the slipperiness of the film is deteriorated, and when the film is wound up in a roll shape, and when the film wound up in a roll shape is unwound, blocking and tearing are likely to occur. In order to avoid these problems, if the content of the particles is increased more than necessary, the transparency of the film is deteriorated.

  In the present invention, a manufacturing method is used in which the heat treatment step is divided into multi-stage heat treatment sections and the heating rate in the heat treatment section is set to a specific range so as to promote crystallization of the film and relax the orientation. By using this method, the crystallization of the film can be promoted to some extent before the particles are buried inside the film, and the sinking of the particles can be suppressed. Furthermore, a film having a low thermal shrinkage rate can be obtained by increasing the heat treatment temperature to promote crystallinity. Moreover, it is not necessary to contain particles more than necessary from the viewpoint of transparency.

  There are a number of factors that determine the melting point (Tm) of polyester, but it is considered that Tm is determined depending on how the crystallinity of the main polyester is disturbed. That is, by blending a copolymer polyester with a main homopolyester or copolymerizing a homopolyester, the crystallinity of the main polyester can be lowered, and the necessary Tm can be obtained.

  Specifically, in the copolymerization, the melting point is obtained when the transesterification is completely random. In the blending, the operating conditions of the extruder, the residence time in the melt line, the raw material composition, the molecular weight, the raw material moisture content, additives such as a catalyst, acid, etc. The transesterification rate is determined by the value. If all these factors are fixed, a constant melting point can be obtained with good reproducibility, and if only one factor is changed, a transesterification rate corresponding to that can be obtained, and a melting point with good reproducibility under these conditions can be obtained. It is done.

(Preferable production method of film)
In the laminated polyester film for molding of the present invention, the polyester used for the core layer (A layer) and the skin layer (B) is a copolyester or a blend of copolyester and homopolyester.

  Examples of the copolyester include (a) a copolyester composed of an aromatic dicarboxylic acid component, ethylene glycol, and a glycol component containing a branched aliphatic glycol or alicyclic glycol, or (b) terephthalic acid and isophthalic acid. A copolyester composed of an aromatic dicarboxylic acid component containing an acid and a glycol component containing ethylene glycol is preferred.

  When the copolymerization component of the copolymerized polyester is a branched aliphatic glycol or alicyclic glycol, molecular mobility at high temperatures can be suppressed due to the bulkiness of the molecular structure of the glycol. Therefore, a film using a copolymerized polyester containing a branched aliphatic glycol or alicyclic glycol as a copolymerization component has improved heat resistance. On the other hand, the heat resistance is also improved when the carboxylic acid component of the copolymer component consists only of an aromatic dicarboxylic acid component.

  Moreover, it is preferable from the point which further improves the moldability that the polyester which comprises a biaxially-oriented polyester film further contains a 1, 3- propanediol unit or a 1, 4- butanediol unit as a glycol component. Moreover, by introducing these units into the copolyester, microcrystals are formed in the molecule, and for example, a decrease in elastic modulus at 180 ° C. can be suppressed. These units may be introduced as a copolymerization component of the copolyester, or a method of blending a homopolyester such as polytrimethylene terephthalate (PTT) or polybutylene terephthalate (PBT) may be used.

  In the present invention, as the film raw material, any method of copolymer polyester alone, a blend of two or more copolymer polyesters, or a blend of at least one homopolyester and at least one copolymer polyester is possible. is there. Among these, a blend of a homopolyester and a copolyester is preferable from the viewpoint of suppressing a decrease in melting point.

  When using a copolymer polyester composed of an aromatic dicarboxylic acid component, ethylene glycol, and a glycol component containing a branched aliphatic glycol or alicyclic glycol as the copolymer polyester, the aromatic dicarboxylic acid component is Terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid or ester-forming derivatives thereof are preferred. The amount of terephthalic acid units and / or 2,6-naphthalenedicarboxylic acid units relative to the total dicarboxylic acid component is 70 mol% or more, preferably 85 mol% or more, more preferably 95 mol% or more, and particularly preferably 100 mol%. . The molar ratio of the terephthalic acid unit to the 2,6-naphthalenedicarboxylic acid unit is preferably 100/0 to 50/50.

  Examples of branched aliphatic glycols include neopentyl glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, and the like. Examples of the alicyclic glycol include 1,4-cyclohexanedimethanol and tricyclodecane dimethylol.

  Among these, neopentyl glycol and 1,4-cyclohexanedimethanol are particularly preferable. Use of these glycols as a copolymerization component is suitable for imparting the above-mentioned properties, and is excellent in transparency and heat resistance, and has good adhesion with the coating layer when the coating layer is provided. It is preferable also from the point of improving.

  When the copolymer polyester is composed of an aromatic dicarboxylic acid component containing terephthalic acid and isophthalic acid and a glycol component containing ethylene glycol, the amount of ethylene glycol is based on the total glycol component. It is 70 mol% or more, preferably 85 mol% or more, particularly preferably 95 mol% or more, and particularly preferably 100 mol%. As the glycol component other than ethylene glycol, the above-mentioned branched aliphatic glycol, alicyclic glycol, or diethylene glycol is preferable. The molar ratio of the terephthalic acid unit to the isophthalic acid unit is preferably in the range of 100/0 to 50/50.

  Examples of the catalyst used for producing the copolymer polyester include alkaline earth metal compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, titanium compounds, titanium / silicon composite oxides, and germanium compounds. it can. Of these, titanium compounds, antimony compounds, germanium compounds, and aluminum compounds are preferred from the viewpoint of catalytic activity.

  When manufacturing the said copolyester, it is preferable to add a phosphorus compound as a heat stabilizer. As said phosphorus compound, phosphoric acid, phosphorous acid, etc. are preferable, for example.

  The copolymer polyester preferably has an intrinsic viscosity of 0.50 dl / g or more, more preferably 0.55 dl / g or more, and particularly preferably 0.60 dl / g from the viewpoint of moldability and film forming stability. g or more. If the intrinsic viscosity is less than 0.50 dl / g, the moldability tends to decrease. On the other hand, from the point of impact resistance, by setting the intrinsic viscosity of the film to 0.60 dl / g or more, the impact strength of the film is improved, and the frequency of breakage during film formation or processing may be reduced. it can. In addition, when a filter for removing foreign substances is provided in the melt line, the upper limit of the intrinsic viscosity is preferably 1.0 dl / g from the viewpoint of ejection stability during extrusion of the molten resin.

  In the present invention, at least one type of homopolyester and at least one type of copolymerized polyester are used as film raw materials, and these are blended to form a film, so that the same flexibility as when only the copolymerized polyester is used is used. Transparency and high melting point (heat resistance) can be achieved while maintaining the properties. In addition, when only a high melting point homopolyester (for example, polyethylene terephthalate) is used, it is possible to realize a melting point (heat resistance) having no flexibility and practical problem while maintaining high transparency.

  Also, blending at least one or more of the above copolyester with a homopolyester other than polyethylene terephthalate (for example, polytetramethylene terephthalate or polybutylene terephthalate) and using it as a raw material for the laminated polyester film for molding of the present invention Further, it is further preferable from the viewpoint of moldability.

  Furthermore, you may use together the following dicarboxylic acid component and / or glycol component as a copolymerization component in the said copolyester as needed, if necessary.

  Other dicarboxylic acid components that can be used in combination with terephthalic acid or its ester-forming derivatives include (1) isophthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyl-4,4′-dicarboxylic acid, diphenoxyethanedicarboxylic acid Aromatic dicarboxylic acids such as acid, diphenylsulfone dicarboxylic acid, 5-sodium sulfoisophthalic acid, phthalic acid or their ester-forming derivatives, (2) oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid Aliphatic dicarboxylic acids such as fumaric acid and glutaric acid or ester-forming derivatives thereof; (3) alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid or ester-forming derivatives thereof; (4) p-oxybenzoic acid; Oxycarboxylic acids such as oxycaproic acid or their esthetics Forming derivatives, and the like.

  On the other hand, other glycol components that can be used in combination with ethylene glycol and branched aliphatic glycol and / or alicyclic glycol include aliphatic glycols such as pentanediol and hexanediol, bisphenol A, bisphenol S, and the like. Aromatic glycols and their ethylene oxide adducts, diethylene glycol, triethylene glycol and the like can be mentioned.

  Furthermore, a polyfunctional compound such as trimellitic acid, trimesic acid, and trimethylolpropane can be further copolymerized with the copolymerized polyester as necessary.

  Further, it is preferable to form irregularities on the film surface in order to improve handling properties such as slipperiness and winding property of the film. As a method for forming irregularities on the film surface, a method of incorporating particles in the film is generally used.

  However, since the particles contained in the film generally have a refractive index different from that of polyester, it causes a decrease in the transparency of the film. In many cases, the molded product is printed on the surface of the film before the film is molded in order to improve the design. Since such a printing layer is often applied to the back side of a molding film, it is desired that the transparency of the film is high from the viewpoint of printing clarity.

  Therefore, in the present invention, it is preferable to employ the following two configurations in order to improve transparency. In the first configuration, the thickness of the skin layer (B layer) of the laminated polyester film is 1 to 5 μm, and only the skin layer (B layer) contains particles, and the core layer (A layer) substantially contains particles. It is the structure which is not contained in. In the second configuration, a laminated polyester film is used as a base material, and a coating layer (C layer) having a thickness of 0.01 to 5 μm is further laminated on one side or both sides of the base material. It is composed of a composition containing at least one resin selected from an acrylic polymer or a copolymer thereof and particles, and the substrate does not substantially contain particles. The upper limit of the thickness of the surface layer containing the particles is preferably 3 μm, particularly preferably 1 μm. In addition, the method using the coating layer (C layer) has an advantage of being excellent in adhesion to the printing layer in addition to providing transparency and slipperiness.

  Note that “substantially no particles are contained in the base film” as used above means, for example, in the case of inorganic particles, the content that is below the detection limit when inorganic elements are quantified by fluorescent X-ray analysis. means. This is because contaminants derived from foreign substances may be mixed without intentionally adding particles to the base film.

  Examples of the particles include known internal particles having an average particle size (number-based average particle size by SEM) of 0.01 to 10 μm, external particles such as inorganic particles and / or organic particles. When particles having an average particle diameter exceeding 10 μm are used, defects in the film are liable to occur and the design properties tend to deteriorate. On the other hand, in the case of particles having an average particle diameter of less than 0.01 μm, handling properties such as film slipperiness and winding property tend to be lowered.

  The average particle size of the particles is taken by taking a plurality of photographs of at least 200 particles by electron microscopy, tracing the outline of the particles on an OHP film, and converting the trace image to an equivalent circle diameter with an image analyzer. To calculate.

  Examples of the external particles include inorganic particles such as wet and dry silica, colloidal silica, aluminum silicate, titanium oxide, calcium carbonate, calcium phosphate, barium sulfate, alumina, mica, kaolin, clay, hydroxyapatite, and styrene, silicone, acrylic acids. The organic particle etc. which use these as a structural component can be used. Among these, inorganic particles such as dry, wet and dry colloidal silica and alumina and organic particles containing styrene, silicone, acrylic acid, methacrylic acid, polyester, divinylbenzene and the like as constituent components are preferably used. Furthermore, silica particles, glass fillers, and silica-alumina composite oxide particles are particularly suitable from the viewpoint of transparency because the refractive index is relatively close to that of polyester. Two or more of these internal particles, inorganic particles and / or organic particles may be used in combination as long as the properties are not impaired.

  Furthermore, the content of the particles in the layer containing the particles is 0.001 to 10 in a range in which the haze of the laminated film is 2.0% or less and the slipperiness and winding properties of the film are not problematic. It is preferable to adjust in the mass% range.

  It is important that the laminated polyester film for molding of the present invention is a biaxially stretched film. In the present invention, solvent resistance and dimensional stability, which are disadvantages of an unstretched sheet, are improved by molecular orientation by biaxial stretching. That is, it is one of the features of the present invention that the solvent resistance and heat resistance, which are defects of the unstretched sheet, are improved while maintaining the good formability of the unstretched sheet.

  As a manufacturing method of the laminated biaxially oriented polyester film, for example, the following method is used. After drying the polyester used for the polyester A layer and the polyester B layer, they are separately supplied to two or more melt extruders and laminated in a molten state to B / A or B / A / B by a coextrusion method. They are extruded into a sheet form from a slit-shaped die, brought into close contact with a casting drum by a method such as electrostatic application, and cooled and solidified to obtain an unstretched sheet. Next, a method of biaxially stretching this unstretched sheet is exemplified. In addition, when using a vent type extruder, drying of a film raw material chip | tip is not necessarily required.

  In the co-extrusion step, for each of the A layer and B layer, the melt extrusion conditions are appropriately adjusted according to the raw materials used, and the melting point of the film is adjusted to an appropriate range while suppressing the progress of hydrolysis and thermal deterioration. Select a condition. In the case of a raw material having a melting point, the extrusion temperature is set to (melting point + 100 ° C.) or lower, preferably (melting point + 90 ° C.) or lower, more preferably (melting point + 80 ° C.) or lower, to suppress decomposition and melting point drop. The residence time to the die outlet is also set to 20 minutes or less, preferably 18 minutes, and more preferably 16 minutes or less to suppress decomposition and melting point drop.

  As the melt extruder used for the A layer and the B layer, for example, an extruder having a feed portion, a compression portion, a metering portion, and a melt line portion is used.

  Further, in the melt extruder, from the feed part to the compression part, the temperature of the resin is gradually raised, and the upper limit of the resin temperature is controlled within the above range to completely melt the resin. Further, in the metalling part and the melt line part, in order to suppress a decrease in the intrinsic viscosity of the film, for example, in the resin for the core layer (A layer), it is preferable that the resin temperature is lower than 280 ° C. In particular, in the melt line portion, in order to suppress the progress of the deterioration of the resin as much as possible, the temperature is preferably 275 ° C. or less, more preferably 270 ° C.

  As the biaxial stretching method, a method of stretching a non-stretched sheet in the longitudinal direction (MD) and the width direction (TD) of the film and heat-treating to obtain a biaxially stretched film having desired physical properties is employed. Among these methods, in terms of film quality, the MD / TD method in which the film is stretched in the longitudinal direction and then stretched in the width direction, or the TD / MD method in which the film is stretched in the width direction and then stretched in the longitudinal direction. An axial stretching method and a simultaneous biaxial stretching method in which the longitudinal direction and the width direction are stretched almost simultaneously are desirable. In the case of the simultaneous biaxial stretching method, a tenter driven by a linear motor may be used. Furthermore, if necessary, a multistage stretching method in which stretching in the same direction is performed in multiple stages may be used.

  The film stretch ratio in biaxial stretching is preferably 1.6 to 4.2 times in the longitudinal direction and the width direction, and particularly preferably 1.7 to 4.0 times. In this case, the stretching ratio in the longitudinal direction and the width direction may be either larger or the same ratio. More preferably, the stretching ratio in the longitudinal direction is 2.8 to 4.0 times, and the stretching ratio in the width direction is 3.0 to 4.5 times.

  In the stretching in the longitudinal direction, it is preferable that the stretching temperature is 50 to 110 ° C. and the stretching ratio is 1.5 to 4.0 so that the subsequent stretching in the width direction can be performed smoothly.

  Usually, when stretching the polyethylene terephthalate, if the stretching temperature is lower than the appropriate conditions, the yield stress increases rapidly at the beginning of the lateral stretching, and therefore stretching cannot be performed. Moreover, even if it can extend | stretch, since thickness and a draw ratio become easy to become nonuniform, it is unpreferable. Therefore, in the present invention, it is preferable to employ the following stretching conditions.

  First, the preheating temperature is preferably 90 to 140 ° C. Next, in the first half of the stretching in the width direction, the stretching temperature is preferably −10 to 25 ° C., particularly preferably −10 to 20 ° C. with respect to the preheating temperature. In the second half of the stretching in the width direction, the stretching temperature is preferably 0 to + 20 ° C., more preferably +5 to + 20 ° C. with respect to the stretching temperature of the first half. By adopting such conditions, a relatively large stretching stress is applied in the first half of the stretching in the width direction, and uniform stretching is possible. In the latter half, the stretchability is improved by the temperature rise. The draw ratio in the width direction is preferably 2.5 to 5.0 times.

  Further, the film is heat-treated after biaxial stretching. This heat treatment can be performed by a conventionally known method such as in a tenter or on a heated roll. Further, the heat treatment temperature and the heat treatment time can be arbitrarily set according to the required level of heat shrinkage.

  In the present invention, the heat treatment step is performed in two or more heat treatment sections, the maximum temperature increase rate in the heat treatment section is 10 to 30 ° C./second, and the maximum heat treatment temperature is (melting point −10 ° C. of layer A) to (A It is preferable to control the melting point of the layer + 20 ° C. Further, the heat treatment section is more preferably 3 sections or more, and particularly preferably 4 sections or more. An appropriate range of the heat treatment time is determined by the film feed rate and the length of the heat treatment step, but it is preferably performed for 1 to 60 seconds, for example. In addition, you may perform this heat processing, relaxing a film to the longitudinal direction and / or the width direction.

  In order to reduce the heat shrinkage rate at 150 ° C. in the longitudinal and lateral directions of the film, it is preferable to increase the heat treatment temperature, lengthen the heat treatment time, and perform relaxation treatment. Specifically, in order to set the heat shrinkage rate at 150 ° C. in the longitudinal direction and the width direction of the film to 6.0% or less, the maximum heat treatment temperature in the heat treatment step (the melting point of the layer A−10 ° C.) It is preferable to carry out while relaxing at a relaxation rate of 1 to 8%. Furthermore, re-stretching may be performed once or more for each direction, and then heat treatment may be performed.

  Further, the upper limit of the maximum heat treatment temperature in the heat treatment step is preferably (the melting point of the A layer + 15 ° C.), more preferably (the melting point of the A layer + 10 ° C.), particularly preferably in order to leave the orientation structure in the A layer. (Melting point of layer A + 5 ° C.). The heat treatment temperature is a set temperature, not the actual temperature of the film.

  However, it is difficult to lengthen the production line and lengthen the heat treatment time due to restrictions on equipment. Further, when the film feeding speed is slowed, productivity is lowered. Thus, although the film is heated at a relatively low temperature near 100 ° C. until the stretching section in the tenter, the film that has passed through the stretching section enters the heat treatment section and quickly rises to a high temperature near 200 ° C. It needs to be warmed. Therefore, it is recommended as a preferred embodiment to install a far infrared heater in the heat treatment section to reinforce the heating of the film.

  For example, it is preferable to use a method in which a heat insulation section of 1 m or more is provided between the stretching section and the heat treatment section and the subsequent heating efficiency is increased. That is, the heating efficiency is increased by strengthening the partition for each section to reduce the leakage of the heat flow. By adjusting the balance and strength of the air volume, it is possible to adjust the pressure in the tenter while suppressing the air volume and suppress the leakage of heat flow. Moreover, it is preferable to add an infrared heater to a strong heating section regarding the heating which is insufficient in hot air heating. In addition, a method of increasing the heating amount by increasing the length of the heat fixing section and the number of sections is also effective.

Furthermore, when the thickness of the film is 50 μm or less, the maximum heat treatment temperature in the heat treatment section from the low temperature around 100 ° C. after the end of stretching is (melting point of layer A−10 ° C.) or more and (melting point of layer A + 20 ° C.) or less. When the temperature is rapidly increased to the range, the following problem occurs.
That is, since the laminated film of the present invention uses a copolymerized polyester, the degree of crystallinity is low. Therefore, in the heat treatment section, not only the thickness unevenness of the film is deteriorated and the impact strength is lowered, but the film is perforated in the heat treatment section during film formation, and continuous film formation may not be possible.

  In order to solve this problem, it is important to gradually increase the temperature in the heat treatment section, and to promote the crystallization of the film while relaxing the orientation of the film by the heat treatment. Specifically, when producing the laminated film of the present invention, it is important to raise the temperature stepwise so that the rate of temperature rise in the heat treatment section is 10 to 30 ° C./sec. The temperature rising rate in the heat treatment section is preferably 15 to 25 ° C./sec.

  On the other hand, if the heating rate in the heat treatment section is too high, the film crystallizes before the orientation of the film is relaxed by the heat treatment. For this reason, the polyester constituting the film becomes brittle and the impact strength of the film is reduced, and the film is perforated in the heat treatment section during film formation, making continuous film formation difficult. On the other hand, if the rate of temperature increase in the heat treatment section is too slow, the film passes through the heat treatment section before reaching the required maximum heat treatment temperature due to equipment limitations. Therefore, the heat shrinkage rate in the longitudinal direction and the width direction at 150 ° C. of the film is increased due to insufficient heat treatment temperature.

  In order to satisfy the characteristics of the film defined in the present invention at the same time, it is also preferable to suppress a decrease in the intrinsic viscosity of the film. In order to maintain the intrinsic viscosity of the film at 0.50 dl / g or more, it is preferable to employ, for example, the above-described temperature conditions during melt extrusion. Moreover, it is also preferable to suppress a decrease in intrinsic viscosity due to hydrolysis of the polyester during melt extrusion by reducing the moisture content of the raw material polyester.

  Moreover, what is necessary is just to set the total thickness of the laminated polyester film of this invention suitably in the range of 10-500 micrometers according to a use. In general, the film is often used in a thickness range of 20 to 188 μm. Moreover, it is preferable that the thickness of B layer exists in the range of 1-30% of total thickness, More preferably, it is 2-27% More preferably, it is the range of 3-25%. When the thickness of the B layer is 1% or more of the total thickness, a decrease in chemical resistance and heat resistance due to the B layer can be prevented. Moreover, it is excellent also in film forming stability. On the other hand, when the thickness of the B layer is 30% or less of the total thickness, deterioration of moldability and heat shrinkage rate can be suppressed.

  In order to improve the moldability of the film, a method of reducing the plane orientation is generally used. For example, as a means for reducing the degree of plane orientation, a method for reducing the draw ratio is known. However, this method deteriorates the uneven thickness of the film. On the other hand, in the present invention, a method is used in which the orientation relaxation is performed while growing the crystal of the film by increasing the heat treatment temperature higher than usual and controlling the heating rate in the heat treatment section to a certain range.

In the present invention, necessary physical properties are created by devising the heat treatment temperature using the above-described technique. However, if the heat treatment temperature is too high, the core layer becomes non-oriented and many defects are generated.
(1) Due to the decrease in elongation at break at room temperature, the film becomes very brittle, and winding and slitting in the manufacturing process become difficult.
(2) Since it is easily cut during use, a problem occurs in handling.
(3) Unevenness in thickness becomes very bad, and handling property, appearance quality deterioration, processing quality, and processing reproducibility deteriorate.
(4) At the time of molding, post-processing with heating such as printing, or when using a molded product in a high-temperature atmosphere, the non-oriented portion may be whitened by heating, resulting in a poor appearance. For this reason, the temperature range at the time of use or processing is limited.

  In order to avoid these problems, an appropriate heat treatment temperature should be selected so that the core layer is not oriented.

  In the present invention, the copolymer polyester used as the raw material of the film has a lower melting point than that of the homopolymer. Therefore, when the heat treatment temperature is increased, the film adheres to the clip holding the film in the tenter and is difficult to peel off. There is a problem of becoming. Therefore, when the clip releases the film at the tenter outlet, it is important that the vicinity of the clip is sufficiently cooled in continuous film formation.

  Specifically, in order to prevent adhesion between the film and the clip, (1) a method of providing a heat shielding wall on the clip portion so that the clip is difficult to be heated, and (2) a method of adding a clip cooling mechanism to the tenter. (3) A method in which the cooling section after heat setting is set long in order to enhance the cooling capacity, and the entire film is sufficiently cooled. (4) The cooling efficiency is increased by increasing the length of the cooling section and the number of sections. It is preferable to adopt a method of increasing the clip, and (5) a method of enhancing the cooling of the clip by using a type that travels outside the furnace at the clip return portion.

  Hereinafter, the present invention will be described in detail by way of examples. The film properties obtained in each example were measured and evaluated by the following methods.

(1) Intrinsic viscosity 0.1 g of the chip sample was precisely weighed and dissolved in 25 ml of a mixed solvent of phenol / tetrachloroethane = 6/4 (mass ratio), and measured at 30 ° C. using an Ostwald viscometer. In addition, the measurement was performed 3 times and the average value was calculated | required.

(2) Melting point of film Using a differential scanning calorimeter (Du Pont Corp., V4 OB2000 type), measuring about 0.010 g of sample, measuring temperature range from room temperature to 300 ° C., temperature rising rate 20 ° C./min. did. To determine the melting point of the A layer and the B layer, the film is cut into A4 size, adhered and fixed to a flat plate, then the surface is scraped with a single-blade razor, and DSC measurement is performed to measure the melting point of the B layer. Next, the melting point of the A layer was determined by determining the melting point of the entire film by DSC measurement and removing the melting peak information relating to the melting point of the B layer.

(3) Presence / absence of orientation of layer A (core layer) The sample for determination was prepared using a microtome, and a thin section (thickness: 10 μm) for observing the cross section in the thickness direction in parallel with the MD direction of the film. create. Subsequently, the brightness of the image in the A layer when the polarizing plate is rotated is visually determined using a transmission polarizing microscope according to the following criteria. The enlargement magnification was 200 times.
No orientation: The brightness of the image in the A layer does not substantially change.
With orientation: The brightness of the image in layer A changes.

(4) Film thickness Measured in accordance with JIS K 7105 “Plastic-Film and Sheet-Thickness Measuring Method” by mechanical scanning (Method A). As a measuring instrument, an electronic micrometer (manufactured by Marl, Millitron 1240) was used. The film thickness was 5 points per film, a total of 15 points were measured, and the average value was determined.

(5) 100% elongation stress (F100) and elongation at break (TE)
With respect to the longitudinal direction and the width direction of the biaxially stretched film, the sample was cut into a strip shape having a length of 180 mm and a width of 10 mm, respectively, with a single-blade razor. Next, the strip-shaped sample was pulled using a tensile tester (manufactured by Toyo Seiki Co., Ltd.), and the 100% elongation stress (MPa) and elongation at break (%) in each direction were determined from the obtained load-strain curve. .

  The measurement was performed in an atmosphere of 25 ° C. under the conditions of an initial length of 40 mm, a distance between chucks of 100 mm, a crosshead speed of 100 mm / min, a recorder chart speed of 200 mm / min, and a load cell of 25 kgf. In addition, this measurement was performed 10 times and the average value was used.

In addition, a tensile test was performed under the same conditions as described above even in an atmosphere at 100 ° C. At this time, the sample was held for 30 seconds in an atmosphere at 100 ° C. and then measured. In addition, the measurement was performed 10 times and the average value was used.
(6) Thermal shrinkage rate at 150 ° C. Based on JIS C 238-1997 5.3.4 (dimensional change), the thermal shrinkage rate at 150 ° C. in the longitudinal direction and the width direction of the film is measured by the following procedure. did.
A strip sample having a length of 250 mm and a width of 20 mm is cut out in the longitudinal direction and the width direction of the film, respectively. Two marks are marked at intervals of 200 mm in the length direction of each sample, and the distance A between the two marks is measured under a constant tension (tension in the length direction) of 5 g. Subsequently, one side of each strip-shaped sample is hung with a clip on a basket under no load, and placed in a gear oven under an atmosphere of 150 ° C., and time is taken. After 30 minutes, the basket is removed from the gear oven and left at room temperature for 30 minutes. Next, for each sample after heat treatment, under a constant tension of 5 gf (tension in the length direction), an interval B between two marks (interval between two marks after the heat treatment) is read in units of 0.25 mm with a gold finger. From the read intervals A and B, the thermal shrinkage rate at 150 ° C. of each sample was calculated by the following formula and judged according to the following criteria. The measurement was performed 3 times, and the average value was obtained. The numerical values are rounded to the first decimal place by rounding off the second decimal place.
Thermal contraction rate (%) = ((A−B) / A) × 100

(7) Thickness variation rate in the width direction A continuous tape-like sample having a length of 3 m in the width direction and 5 cm in the longitudinal direction is wound up, and the film thickness is measured with a film thickness continuous measuring machine (manufactured by Anritsu Corporation). Measure and record on the recorder. From the chart, the maximum value (dmax), minimum value (dmin), and average value (d) of the thickness were obtained, and the thickness variation rate (%) was calculated by the following formula. In addition, the measurement was performed 3 times and the average value was calculated | required. If the length in the width direction is less than 3 m, the stitching is performed. The connecting part is deleted from the data.
Thickness variation rate (%) = ((dmax−dmin) / d) × 100

(8) Haze Based on JIS K 7136, the haze was measured using a haze meter (Nippon Denshoku Industries Co., Ltd., 300A). In addition, the measurement was performed twice and the average value was calculated | required.

(9) Impact strength Using a film impact tester (manufactured by Toyo Seiki Seisakusho, production number T-84-3), press the measurement film with a clamp, pierce it with a 1/2 inch hemispherical impact head, Impact strength was measured. The sample was cut to 100 mm × 100 mm or more, and the ring for fixing the sample had an inner diameter of 30 mm. In addition, the measurement was performed 10 times and the average value was calculated | required. The average value was converted per 1 mm thickness and determined as the impact strength (J / mm) of the film, and judged according to the following criteria.
○: 10 J / mm or more ×: less than 10 J / mm

(10) Formability (a) Vacuum formability After 5 mm square printing is performed on the film, the film is heated with an infrared heater heated to 500 ° C for 10 to 15 seconds, and then at a mold temperature of 30 to 100 ° C. Vacuum forming was performed. In addition, the heating conditions selected the optimal conditions within the said range with respect to each film. The shape of the mold was a cup shape, the opening had a diameter of 50 mm, the bottom part had a diameter of 40 mm, the depth was 50 mm, and all corners were curved with a diameter of 0.5 mm. .

Five molded products that were vacuum-molded under the optimum conditions were evaluated for moldability and finish, and ranked according to the following criteria. In addition, (double-circle) and (circle) were set as the pass, and x was set as the disqualification.
A: (i) The molded product is not torn,
(Ii) The corner radius of curvature is 1 mm or less, and the printing deviation is 0.1 mm or less,
(Iii) Further, there is no appearance defect corresponding to ×: (i) The molded product is not torn,
(Ii) The corner radius of curvature is more than 1 mm and not more than 1.5 mm, or printing deviation is 0.1
greater than 0.2 mm and less than 0.2 mm,
(Iii) Further, there is no appearance defect corresponding to ×, and there is no problem in practical use. ×: The molded product is torn, or even if it is not torn, it falls under any of the following items (i) to (iv) (I) A corner with a radius of curvature exceeding 1.5 mm (ii) A large wrinkle and a poor appearance
(Iii) The film is whitened and the transparency is lowered
(Iv) Print misalignment exceeding 0.2 mm

(B) Compressive air moldability After 5 mm square printing is performed on the film, the film is heated for 10 to 15 seconds with an infrared heater heated to 500 ° C., and then subjected to 4 atm at a mold temperature of 30 to 100 ° C. Crushing was performed under pressure. In addition, the heating conditions selected the optimal conditions within the said range with respect to each film. The shape of the mold is a cup shape, the opening has a diameter of 60 mm, the bottom has a diameter of 55 mm, a depth of 50 mm, and all corners are curved with a diameter of 0.5 mm. .

The moldability and finish of five molded products that were pressure-molded under optimal conditions were evaluated and ranked according to the following criteria. In addition, (double-circle) and (circle) were set as the pass, and x was set as the disqualification.
A: (i) There is no tear in the molded product,
(Ii) The corner radius of curvature is 1 mm or less, and the printing deviation is 0.1 mm or less,
(Iii) Further, there is no appearance defect corresponding to ×: (i) The molded product is not torn,
(Ii) The corner radius of curvature is more than 1 mm and not more than 1.5 mm, or printing deviation is 0.1
greater than 0.2 mm and less than 0.2 mm,
(Iii) Further, there is no appearance defect corresponding to ×, and there is no problem in practical use. ×: The molded product is torn, or even if it is not torn, it falls under any of the following items (i) to (iv) (I) A corner with a radius of curvature exceeding 1.5 mm (ii) A poor appearance with large wrinkles (iii) A whitened film with reduced transparency (iv) A print misalignment of 0.2 mm More than

(C) Mold formability After printing on the film, contact heating with a hot plate heated to 100 to 140 ° C for 4 seconds, followed by press molding at a mold temperature of 30 to 70 ° C and a holding time of 5 seconds. It was. In addition, the heating conditions selected the optimal conditions within the said range with respect to each film. The shape of the mold is a cup shape, the opening has a diameter of 50 mm, the bottom has a diameter of 40 mm, a depth of 30 mm, and all corners are curved with a diameter of 0.5 mm. .

The moldability and finish of the five molded products molded under optimal conditions were evaluated and ranked according to the following criteria. In addition, (double-circle) and (circle) were set as the pass, and x was set as the failure.
A: (i) There is no tear in the molded product,
(Ii) The corner radius of curvature is 1 mm or less, and the printing deviation is 0.1 mm or less,
(Iii) Further, there is no appearance defect corresponding to ×: (i) The molded product is not torn,
(Ii) The corner radius of curvature is more than 1 mm and not more than 1.5 mm, or printing deviation is 0.1
greater than 0.2 mm and less than 0.2 mm,
(Iii) Furthermore, there is no appearance defect corresponding to ×, and there is no problem in practical use. ×: The molded product is broken, or even if there is no breakage, it falls under any of the following items (i) to (iv) (I) A corner with a radius of curvature exceeding 1.5 mm (ii) A bad appearance with large wrinkles (iii) A film with whitened and reduced transparency (iv) A deviation of printing of 0.2 mm More than

(11) Solvent resistance The sample was immersed in toluene adjusted to 25 ° C. for 30 minutes, and the appearance change before and after immersion was judged according to the following criteria, and “◯” was determined to be acceptable. The haze value was measured by the method described above.
○: Little change in appearance, change in haze value is less than 1% ×: Change in appearance is observed, or change in haze value is 1% or more

(12) Static friction coefficient μs and dynamic friction coefficient μd
Based on JIS-C2151, the following conditions evaluated.
Test piece for flat plate: 130 mm in width and 250 mm in length, using non-printing surface side Test piece for warping: 120 mm in width, using 120 mm in length and printing surface side Measurement atmosphere: 23 ° C., 50% RH
Sled mass: 200g
Test speed: 150mm / min

The measured value was judged according to the following criteria.
○: Both μs and μd are less than 0.8 ×: Either μs or μd is 0.8 or more

(13) Heating Whitening After heat treatment at 150 ° C. for 30 minutes, visual appearance observation was performed according to the following criteria. In addition, (circle) is a pass.
○: No change ×: The film is whitish and changes are observed.

Example 1
(Preparation of water-dispersed polyester-based graft copolymer)
In a reactor equipped with a stirrer, thermometer, refluxing device and quantitative dropping device, 75 parts by mass of hydrophobic copolymer polyester, 56 parts by mass of methyl ethyl ketone and 19 parts by mass of isopropyl alcohol are heated and stirred at 65 ° C. Dissolved. After the resin was completely dissolved, 15 parts by mass of maleic anhydride was added to the polyester solution. Subsequently, a solution prepared by dissolving 10 parts by mass of styrene and 1.5 parts by mass of azobisdimethylvaleronitrile in 12 parts by mass of methyl ethyl ketone was dropped into the polyester solution at 0.1 ml / min, and stirring was further continued for 2 hours. After sampling for analysis from the reaction solution, 5 parts by mass of methanol was added. Next, 300 parts by mass of ion-exchanged water and 15 parts by mass of triethylamine were added to the reaction solution and stirred for 1.5 hours. Thereafter, the reactor internal temperature was raised to 100 ° C., and methyl ethyl ketone, isopropyl alcohol, and excess triethylamine were distilled off to obtain a water-dispersed polyester graft copolymer. The obtained polyester-based graft copolymer was light yellow and transparent, and the glass transition temperature was 40 ° C.

(Preparation of coating solution a for printability improving layer)
A polyester graft copolymer dispersed in water so that the total solid concentration is 5% by mass in a mixed solvent of ion-exchanged water and isopropyl alcohol (mass ratio: 60/40), and the average particle size as particles 2.2 μm styrene-benzoguanamine-based spherical organic particles (manufactured by Nippon Shokubai Kogyo Co., Ltd.) and colloidal silica having an average particle size of 0.02 μm (manufactured by Catalyst Kasei Co., Ltd.) are mixed so that the solids mass ratio is 50/1/3. Then, a coating solution A was prepared.

(Preparation of coating solution b for the slipperiness improving layer)
In a mixed solvent of ion-exchanged water and isopropyl alcohol (mass ratio: 60/40), a water-dispersible polyester copolymer (manufactured by Toyobo Co., Ltd., Bayroner) so that the total solid content concentration is 5% by mass. MD-16), sodium dodecyl diphenyl oxide disulfonate (manufactured by Matsumoto Yushi Co., Ltd., an anionic antistatic agent) as a sulfonic acid metal salt, polyethylene emulsion wax (manufactured by Toho Chemical Co., Ltd.) as a polymer wax agent, and particles Styrene-benzoguanamine-based spherical organic particles (manufactured by Nippon Shokubai Kogyo Co., Ltd.) having an average particle size of 2.2 μm and colloidal silica (manufactured by Nissan Chemical Co., Ltd.) having an average particle size of 0.04 μm in a solid content mass ratio of 50 / 2.5 / The mixture was mixed to 2.5 / 0.5 / 5 to prepare coating solution B.

(Manufacture of film raw materials)
The resin having the composition described in Table 1 was dried and used as a raw material for the core layer (A layer) and the skin layer (B layer).

(Manufacture of laminated film)
Using a co-extrudable extruder having a feed block and a T die, the raw material for the B layer was coextruded under the B layer extrusion conditions in Table 2, and the raw material for the A layer was similarly coextruded under the A layer extrusion conditions in Table 2. The constitution of the layer is 2 types / 3 layers of B / A / B. Moreover, the discharge amount of the resin at the time of melt extrusion was adjusted so that the final film thickness was 100 μm and the thickness of each layer was a ratio of B / A / B = 8/84/8. The residence time of the skin layer (B layer) was 18 minutes, the residence time of the core layer (A layer) was 8 minutes, and solidified rapidly on a cast drum having a surface temperature of 40 ° C. to obtain an amorphous sheet.

The obtained sheet was stretched 3.3 times in the longitudinal direction at 83 ° C. by a difference in rotational speed between the preheating roll and the cooling roll. The coating liquid a was applied to one side of the obtained uniaxially stretched film, and the coating liquid b was applied to the other side by a reverse coating method. In addition, each coating liquid applied a shear rate of 1000 (1 / second) or more between the roll gaps, applied to the substrate film within 2 seconds, and in an environment of 65 ° C., 60% RH, and wind speed of 15 m / second, Dry for 2 seconds. Further, it is dried for 3 seconds in an environment of 130 ° C. and a wind speed of 20 m / second to remove moisture and lead to a tenter, preheated at 100 ° C. for 3 seconds, and the first half of transverse stretching is 100 ° C. and the latter half is 95 ° C. By stretching 8 times and heating at 140 ° C for 3 seconds, 170 ° C for 3 seconds, 205 ° C for 3 seconds, heat treatment at 205 ° C, and 5% lateral relaxation, A laminated biaxially stretched polyester film having a thickness of 100 μm having a coating layer a and a coating layer b on the other surface was obtained. The intrinsic viscosity of the obtained film was 0.65 dl / g. Further, the final dry coating amounts of the coating layer a and the coating layer b were both 0.1 g / m ² .

  In the tenter, the clip return was installed with an external return method, a clip cooling device, forcibly cooled with cold air of 20 ° C, and the clip temperature at the TD outlet was set to 40 ° C or less, and measures were taken to prevent adhesion with the clip. . Table 3 shows the properties and evaluation results of the obtained film.

Example 2
In Example 1, a thickness of 100 μm having a coating layer a on one side and a coating layer b on the other side is the same as in Example 1 except that the raw material shown in Table 1 and the film forming conditions shown in Table 4 are changed. A laminated biaxially stretched polyester film was obtained. The intrinsic viscosity of the obtained film was 0.66 dl / g. Further, the final dry coating amounts of the coating layer a and the coating layer b were both 0.1 g / m ² . Table 6 shows the properties and evaluation results of the obtained film.

Example 3
In Example 1, a thickness of 100 μm having a coating layer a on one side and a coating layer b on the other side is the same as in Example 1 except that the raw material shown in Table 1 and the film forming conditions shown in Table 4 are changed. A laminated biaxially stretched polyester film was obtained. The intrinsic viscosity of the obtained film was 0.66 dl / g. Further, the final dry coating amounts of the coating layer a and the coating layer b were both 0.1 g / m ² . Table 6 shows the properties and evaluation results of the obtained film.

Example 4
In Example 1, a thickness of 100 μm having a coating layer a on one side and a coating layer b on the other side is the same as in Example 1 except that the raw material shown in Table 1 and the film forming conditions shown in Table 4 are changed. A laminated biaxially stretched polyester film was obtained. The obtained film had an intrinsic viscosity of 0.70 dl / g. Further, the final dry coating amounts of the coating layer a and the coating layer b were both 0.1 g / m ² . Table 6 shows the properties and evaluation results of the obtained film.

Example 5
In Example 1, the raw material shown in Table 1 was changed, the discharge amount during melt extrusion was adjusted to change the thickness of the unstretched sheet, the film forming conditions shown in Table 4 were changed, and a coating layer was further provided. A laminated biaxially stretched polyester film having a thickness of 25 μm was obtained in the same manner as Example 1 except that there was not. The intrinsic viscosity of the obtained film was 0.65 dl / g. Table 6 shows the properties and evaluation results of the obtained film.

Example 6
In Example 1, Example 1 was used except that the same raw material as in Example 2 was used, the thickness of the unstretched sheet was changed by adjusting the discharge amount during melt extrusion, and the film forming conditions shown in Table 4 were changed. In the same manner as above, a laminated biaxially stretched polyester film having a thickness of 50 μm and having a coating layer a on one side and a coating layer b on the other side was obtained. The obtained film had an intrinsic viscosity of 0.64 dl / g. Further, the final dry coating amounts of the coating layer a and the coating layer b were both 0.1 g / m ² . Table 6 shows the properties and evaluation results of the obtained film.

Example 7
In Example 1, a layer having a thickness of 50 μm having a coating layer a on one side and a coating layer b on the other side is the same as Example 1 except that the raw material for the B layer is changed to the raw material shown in Table 2. A biaxially stretched polyester film was obtained. The obtained film had an intrinsic viscosity of 0.70 dl / g. Further, the final dry coating amounts of the coating layer a and the coating layer b were both 0.1 g / m ² . Table 6 shows the properties and evaluation results of the obtained film.

Comparative Example 1
In Example 1, the raw material shown in Table 2 and the film forming conditions shown in Table 5 were changed, and a single layer structure having a thickness of 100 μm was formed in the same manner as in Example 1 except that the skin layer (B) was not provided. A biaxially stretched polyester film was obtained. Table 7 shows the properties and evaluation results of the obtained film.

Comparative Example 2
In Example 1, the raw material shown in Table 2 and the film forming conditions shown in Table 5 were changed, and a single layer structure having a thickness of 100 μm was formed in the same manner as in Example 1 except that the skin layer (B) was not provided. A biaxially stretched polyester film was obtained. Table 7 shows the properties and evaluation results of the obtained film.

Comparative Example 3
In Example 1, a laminated biaxially stretched polyester film having a thickness of 100 μm having a coating layer a on one side and a coating layer b on the other side, except that the film forming conditions shown in Table 5 were changed. Got. The intrinsic viscosity of the obtained film was 0.71 dl / g. Further, the final dry coating amounts of the coating layer a and the coating layer b were both 0.1 g / m ² . Table 7 shows the properties and evaluation results of the obtained film.

Comparative Example 4
In Example 1, the coating layer a on one side and the other side in the same manner as in Example 1 except that the raw material for the B layer is changed to the raw material shown in Table 3 and the film forming conditions shown in Table 5 are changed. A laminated biaxially stretched polyester film having a coating layer b and having a thickness of 100 μm was obtained. The intrinsic viscosity of the obtained film was 0.71 dl / g. Further, the final dry coating amounts of the coating layer a and the coating layer b were both 0.1 g / m ² . Table 7 shows the properties and evaluation results of the obtained film.

Comparative Example 5
In Example 4, a laminated biaxially stretched polyester having a thickness of 100 μm and having a coating layer a on one side and a coating layer b on the other side, except that the film forming conditions shown in Table 5 were changed. A film was obtained. The intrinsic viscosity of the obtained film was 0.71 dl / g. Further, the final dry coating amounts of the coating layer a and the coating layer b were both 0.1 g / m ² . Table 7 shows the properties and evaluation results of the obtained film.

Comparative Example 6
In Example 1, a thickness of 100 μm having a coating layer a on one side and a coating layer b on the other side is the same as in Example 1 except that the raw material shown in Table 3 and the film forming conditions shown in Table 5 are changed. A laminated biaxially stretched polyester film was obtained. The obtained film had an intrinsic viscosity of 0.70 dl / g. Further, the final dry coating amounts of the coating layer a and the coating layer b were both 0.1 g / m ² . Table 7 shows the properties and evaluation results of the obtained film.

Comparative Example 7
Resins listed in Table 3 were prepared, dried, and used as raw materials for the A layer and B layer. Next, using a co-extrudable melt extruder having a feed block and a T die, the raw material for the B layer was melted at 285 ° C., and the raw material for the A layer was melted at 285 ° C. in separate melt extruders. Next, the layer configuration was B / A / B, the B layer / A layer thickness ratio was 0.11, co-extruded, and rapidly cooled and solidified on a cast drum to obtain an unstretched laminated sheet.

  The obtained unstretched laminated sheet was successively biaxially stretched 3.0 times at 110 ° C. in the vertical direction and 3.2 times at 120 ° C. in the horizontal direction, and then heat treated at 235 ° C. A laminated biaxially stretched polyester film was obtained. Table 7 shows the properties and evaluation results of the obtained film.

Comparative Example 8
In Example 1, a thickness of 100 μm having a coating layer a on one side and a coating layer b on the other side is the same as in Example 1 except that the raw material shown in Table 3 and the film forming conditions shown in Table 5 are changed. A laminated biaxially stretched polyester film was obtained. The obtained film had an intrinsic viscosity of 0.70 dl / g. Further, the final dry coating amounts of the coating layer a and the coating layer b were both 0.1 g / m ² . Table 7 shows the properties and evaluation results of the obtained film.

Comparative Example 9
In Example 1, a thickness of 100 μm having a coating layer a on one side and a coating layer b on the other side is the same as in Example 1 except that the raw material shown in Table 3 and the film forming conditions shown in Table 5 are changed. An attempt was made to obtain a laminated biaxially stretched polyester film, but breakage occurred in the tenter, and the film could not be obtained.

  The laminated polyester film for molding according to the present invention is excellent in moldability at the time of heat molding, particularly at low temperature and low pressure, so that it can be applied to a wide variety of molding methods and used as a molded body in a room temperature atmosphere. In addition, it has excellent elasticity and shape stability (heat shrinkage characteristics, thickness unevenness), transparency, printability, solvent resistance, heat resistance, and impact resistance. There is an advantage that it can be suitably used as an interior material, exterior material, or building material member, which greatly contributes to the industry.

Claims (8)

A biaxially oriented laminated polyester film obtained by laminating a polyester B layer on one or both sides of a polyester A layer,
Each of the A layer and the B layer comprises a copolymer polyester, or a copolymer polyester and a homopolyester, and the melting point of the A layer (TmA: ° C) and the melting point of the B layer (TmB: ° C) are represented by the following formula (1). And (2) at the same time,
The laminated polyester film has an orientation structure in both the A layer and the B layer, the thermal shrinkage rate at 150 ° C. is 6.0% or less in both the longitudinal direction and the width direction, and the thickness variation rate in the width direction is 10% or less. A laminated polyester film for molding characterized by the above.
260>TmB>TmA> 200 (1)
50>TmB-TmA> 5 (2)   A copolymer polyester comprising (a) an aromatic dicarboxylic acid component, ethylene glycol, and a glycol component containing a branched aliphatic glycol or alicyclic glycol; or (b) terephthalic acid and isophthalic acid The laminated polyester film for molding according to claim 1, comprising an aromatic dicarboxylic acid component containing glycerine and a glycol component containing ethylene glycol.   The laminated polyester film for molding according to claim 1, wherein the homopolyester is at least one selected from the group consisting of polyethylene terephthalate, polytetramethylene terephthalate, and polybutylene terephthalate.   The laminated polyester film for molding according to claim 1, wherein the laminated polyester film has a total thickness of 10 to 500 µm, and the B layer has a thickness of 1 to 30% of the whole.   The laminated polyester film has a 100% elongation stress in the longitudinal direction and the width direction of the film of 40 to 300 MPa at 25 ° C and 1 to 100 MPa at 100 ° C, respectively. Laminated polyester film.   The laminated polyester film for molding according to claim 1, wherein the laminated polyester film has a haze of 2.0% or less. A step of producing an unstretched sheet in which a polyester B layer is laminated on one or both sides of a polyester A layer using a coextrusion method, a step of biaxially stretching the unstretched sheet in the longitudinal direction and the width direction, biaxial A method for producing a laminated polyester film for molding comprising a step of heat-treating while holding a stretched film with a clip,
The polyester constituting the A layer and the B layer is a copolymer polyester, or a mixture of a copolymer polyester and a homopolyester,
The heat treatment process has two or more stages of heat treatment, the maximum temperature increase rate in the heat treatment section is 10 to 30 ° C./second, and the maximum heat treatment temperature is (the melting point of layer A−10 ° C.) to (the melting point of layer A) The method for producing a laminated polyester film for molding according to claim 1, wherein the temperature is controlled to + 20 ° C. When transverse stretching and heat treatment are performed while holding the film with a clip in the tenter, the vicinity of the clip is cooled using at least one of the following methods (i) to (v), and then from the clip at the tenter outlet. The method for producing a laminated polyester film for molding according to claim 7, wherein the film is opened.
(I) A method of providing a heat shielding wall at the clip portion (ii) A method of adding a clip cooling mechanism to the tenter (iii) A method of sufficiently cooling the entire film by setting a long cooling section after heat setting (iv) Cooling Method of increasing the cooling efficiency by increasing the length of the section and the number of sections (v) Method of enhancing the cooling of the clip using a type in which the return part of the clip travels outside the furnace