JP2012045942A - Polyester film for in-mold transfer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biaxially stretched polyester film having sufficient moldability, heat resistance and transfer properties.SOLUTION: The polyester film for in-mold transfer includes a structure that an A-layer comprising a polyester in which the main constituent component is contained in an amount of 80 mol% or above is laminated at least on one side of a B-layer comprising a polyester which contains at least one kind of a copolymer component other than its main constituent component and in which the main constituent component is contained in an amount of 90 mol% or below. The maximum value of a storage elastic modulus E' in the temperature range of 80-180°C is in the range of 810-1,100 MPa. The tensile break elongation at 100°C is 180% or higher. The tensile break strength at 100°C is 50 MPa or less.

Description

  The present invention relates to a polyester film for simultaneous molding and transfer having excellent moldability. Specifically, the present invention relates to a polyester film for molding transfer suitable for deep drawing with a high squeezing ratio because it has excellent moldability, heat resistance and transfer suitability.

  In recent years, a so-called simultaneous molding transfer method in which transfer printing is performed simultaneously with molding has become widespread as a printing method for molded products. As a film used in this method, a biaxially stretched polyester film is used from the viewpoint of properties such as strength and heat resistance.

  In recent years, the molding rate has been increasing, and high-quality molding transfer has been required. As the demand has increased, advanced characteristics relating to deep drawability and dimensional stability have been demanded of conventional films, and improvement of the film has been strongly desired.

  Furthermore, since the squeezing rate is increased, it is necessary to improve the deformability of the film by heating at the time of deformation, so that the durability of the film at high temperatures is also required. Durability means that the film does not melt at the processing temperature, and that even if softened at a high temperature, problems such as deformation and tearing of the film due to expansion of air between the mold and the film do not occur.

  In addition, when the resin is injected after the film is placed along the mold (hereinafter referred to as pre-molding), the temperature of the resin is usually 200 ° C. or higher. Therefore, if the crystallinity of the film is too low, Due to the shear stress between the heat and the resin due to the injection, there is a problem that wrinkles enter the film and precise transfer cannot be performed. From this point of view, a film having excellent transferability is desired.

JP-A 64-40400 Japanese Patent Laid-Open No. 7-196821 JP-A-8-3227 JP 2006-281732 A

  This invention is made | formed in view of the said actual condition, The solution subject is to provide the biaxially stretched polyester film which has sufficient moldability, heat resistance, and transferability.

  As a result of intensive studies in view of the above problems, the present inventor has found that the above problems can be easily solved by a film having a specific configuration, and has completed the present invention.

  That is, the gist of the present invention is that at least one side of a B layer comprising a polyester containing at least one copolymer component other than the main component and having a main component content of 90 mol% or less is a main component. A film having a structure in which an A layer made of polyester having a content of 80 mol% or more is laminated, and the maximum value of the storage elastic modulus E ′ in the temperature range of 80 ° C. to 180 ° C. is in the range of 810 to 1100 MPa. Yes, the polyester film for simultaneous molding and transfer has a tensile elongation at break at 100 ° C. of 180% or more and a tensile strength at 100 ° C. of 50 MPa or less.

  According to the present invention, by keeping the melting point and storage elastic modulus within specific ranges, a film suitable for deep drawing simultaneous transfer having excellent moldability, heat resistance and transferability can be obtained. The present invention can be applied to other uses, and the industrial value of the present invention is high.

It is a conceptual diagram of the simultaneous molding transfer apparatus which evaluates the film of this invention.

  First, the main component in the present invention refers to a hydroxycarboxylic acid called a repeating unit obtained by dehydration condensation of a dicarboxylic acid and a diol.

  The polyester constituting the film of the present invention is preferably terephthalic acid as the dicarboxylic acid component. Besides these, oxalic acid, malonic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, One or more known dicarboxylic acids such as naphthalenedicarboxylic acid, diphenyl ether dicarboxylic acid, and cyclohexanedicarboxylic acid may be included as a copolymerization component. The diol component is preferably ethylene glycol. Besides these, propylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, One or more known diols such as neopentyl glycol may be included as a copolymerization component.

  In the present invention, the constituent components of the polyester can include various acid components and alcohol components in addition to the above-mentioned dicarboxylic acid component and diol component. For example, monofunctional compounds such as oxycarboxylic acid such as p-oxybenzoic acid, benzoic acid, benzoylbenzoic acid, and methoxypolyalkylene glycol are used as modifying components, and polyfunctional such as trimesic acid, trimellitic acid, glycerin, and pentaerythritol. The functional compound can be used as a copolymerization component as long as the product polyester can retain a substantially linear polymer.

  Next, as the polyester resin constituting the A layer in the present invention, the main constituents described above are preferably used, but from the viewpoint of heat resistance and dimensional stability, the content of the main constituents is 80 mol% or more. Is required, preferably 85 mol% or more.

  On the other hand, the polyester resin constituting the B layer needs to contain at least one copolymer component other than the main constituent components described above. When the layer B does not contain a copolymer component other than the main constituent component, it is not preferable because sufficient heat resistance can be obtained but moldability is lost. Further, from the viewpoint of achieving both heat resistance and moldability, the content of the main constituent component is required to be 90 mol% or less, and preferably 80 mol% or less.

  In the present invention, from the viewpoint of heat resistance, molding processability, transferability, the maximum value of the storage elastic modulus E ′ measured at 80 to 180 ° C. at a frequency of 10 Hz by a dynamic viscoelasticity measuring device is in the range of 810 to 1100 MPa. It is preferably in the range of 10 MPa to 400 MPa in the temperature range of 100 ° C. to 180 ° C., more preferably in the range of 10 MPa to 200 MPa in the temperature range of 120 ° C. to 180 ° C.

  In the present invention, the tensile breaking elongation at 100 ° C. is 180% or more, preferably 190% or more, more preferably 200% or more, and the tensile breaking strength is 50 MPa or less, preferably 45 MPa or less, more preferably 40 MPa. Must be: If the tensile elongation at break is less than 200% or the tensile strength at break exceeds 50 MPa, the moldability and productivity are inferior.

  In the present invention, the plane orientation coefficient ΔP of the film is usually in the range of 0.020 to 0.150, and preferably in the range of 0.030 to 0.140. When the plane orientation coefficient ΔP exceeds 0.150, the moldability tends to be inferior, and when it is less than 0.020, the heat resistance tends to be inferior.

  In the present invention, the birefringence Δn of the film is usually 0.020 or less and preferably 0.015 or less. When Δn exceeds 0.020, the elongation at the time of molding varies, which may cause printing distortion.

  In the present invention, the melting point of the A layer is preferably in the range of 190 ° C to 260 ° C, and more preferably in the range of 200 ° C to 255 ° C. The melting point of the B layer is preferably in the range of 180 ° C to 225 ° C, and more preferably in the range of 185 ° C to 220 ° C. When the melting point of the A layer is less than 190 ° C., the heat resistance and the transferability tend to be inferior, and when the melting point of the B layer exceeds 225 ° C., the moldability tends to be inferior.

  Regarding the shrinkage characteristics of the film of the present invention, the measurement method will be described in detail later, but it is preferable that the heat shrinkage ratio after treatment at 150 ° C. for 3 minutes is 4.0% or less in both the vertical and horizontal directions. A film having a vertical or horizontal heat shrinkage ratio of more than 4.0% may be unfavorable in terms of operation because the film shrinks greatly in the heating zone during the processing step.

  In the present invention, it is also preferable to add particles in order to improve the slipperiness of the film. For example, in order to improve the slipperiness of the film, the polyester composition preferably contains organic and inorganic fine particles, and if necessary, a stabilizer, a colorant, an antioxidant, an antifoaming agent, a charging agent. An additive such as an inhibitor may be further blended. The fine particles imparting slipperiness are roughly classified into external particles and internal particles according to the blending method. Examples of the former include kaolin, clay, various calcium carbonates, silicon oxide, calcium terephthalate, aluminum oxide such as α-, γ-, δ-, θ-, titanium oxide, calcium phosphate, lithium fluoride, carbon black, etc. Known inert external particles may be mentioned. Examples of the latter include high-melting-point organic compounds that are insoluble during melt film formation of polyester, monodispersed spherical organic particles, pulverized organic particles, cross-linked polymers, and metal compound catalysts used during polyester synthesis, such as alkali metal compounds, Examples thereof include internal particles formed inside the polymer by the alkaline earth metal compound during the production of the polyester. These fine particles usually have a content of 0.002 to 2.0% by weight with respect to the layer constituting the surface in the film, and an average particle size in the range of 0.001 to 3.5 μm. Is preferred.

  The two-dimensional surface roughness Ra of the film of the present invention is preferably 40 nm or less, and more preferably 35 nm or less. When Ra exceeds 40 nm, the surface roughness may be transferred to the printing layer and the surface gloss of the molded product may be lost.

  Next, although the manufacturing method of the film of this invention is demonstrated concretely, as long as the structural requirements of this invention are satisfied, it is not limited only to the following illustrations.

  A polyester composition obtained by blending appropriate amounts of organic and inorganic fine particles as a slipping agent into a chip is dried using a commonly used dryer or vacuum dryer such as a hopper dryer, paddle dryer or oven. In the former stage, the chips are crystallized so that mutual fusion does not occur (also referred to as preliminary crystallization), and in the latter stage, the moisture content is sufficiently reduced (also referred to as main drying). After drying in this way, it is extruded into sheets at 200-320 ° C. At the time of extrusion, two or three or more polyester melt extruders can be used to form a laminated film of two layers or three or more layers by a so-called coextrusion method. As the layer structure, an A / B structure using an A raw material and a B raw material, or an A / B / A structure, and further using a C raw material to form an A / B / C structure or other film. Can do. For example, the surface shape of the A layer can be designed using specific particles as the A raw material, and a film having an A / B or A / B / A structure can be formed using a raw material not containing particles as the B raw material. In this case, since the raw material of B layer can be selected freely, a cost advantage etc. are large. Further, even if the recycled material of the film is blended with the B layer, the surface roughness can be designed by the surface A layer, so that the cost advantage is further increased. Next, the molten polymer is extruded from a die and rapidly cooled and solidified on a rotary cooling drum so that the temperature is equal to or lower than the glass transition temperature to obtain a substantially amorphous unoriented sheet. In this case, in order to improve the flatness of the sheet, it is preferable to improve the adhesion between the sheet and the rotary cooling drum. In the present invention, an electrostatic application adhesion method and / or a liquid application adhesion method is preferably employed.

  The obtained unoriented sheet is stretched in the longitudinal and transverse directions so as to be at least 6 times, preferably 8 times or more, more preferably 8 times or more and 16 times or less in the area magnification to obtain a biaxially oriented film. If necessary, the film is restretched in the machine direction and / or transverse direction, and then heat-treated at a temperature preferably in the range of 120 ° C. to 210 ° C. to obtain a desired film.

  A preferred embodiment of the heat treatment step is to perform 0.1-15% relaxation in the transverse direction and / or the longitudinal direction in the zone of the highest temperature of the heat treatment and / or the cooling zone at the heat treatment outlet. In particular, it is preferable to perform 1 to 15% relaxation in the lateral direction. Further, the heat treatment step can be performed in two stages.

  In the stretching step or after, in order to impart adhesion, antistatic property, slipperiness, releasability, etc. to the film, a coating layer is formed on one or both sides of the film, or a discharge treatment such as corona treatment is performed. It can also be given.

  The thickness of the film of this invention is 10-200 micrometers normally, Preferably it is 20-150 micrometers, More preferably, it is 30-100 micrometers.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples unless it exceeds the gist. The measurement and evaluation methods of various physical properties of the film are as follows.

(1) Storage elastic modulus E ′
A dynamic viscoelasticity measuring device (DVA-200 type) manufactured by IT Measurement Control Co., Ltd. was used. A film with a width of 5 mm was set in a measuring apparatus so that the distance between chucks was 20 mm, and the temperature was changed from 0 ° C. to 30 ° C. at 10 ° C./min. The transition of viscoelasticity was measured at a frequency of 10 Hz while raising the temperature at a rate of.

(2) Tensile test Using an Intesco Corporation tensile testing machine Intesco 2001 type with a thermostat, set the thermostat to 100 ° C, and set a film with a width of 15 mm on the tester so that the gap between chucks is 50 mm. After standing for 2 minutes, pulling at a pulling speed of 200 mm / min, and obtaining the following values from the tensile stress-strain curve.
The tensile strength at break is calculated by the following formula.
Tensile strength at break (MPa) = F / A
However, in said formula, F is the load (N) in the time of a fracture | rupture, A is the original cross-sectional area (mm < ² >) of a test piece.
The tensile elongation at break is calculated by the following formula.
Tensile elongation at break (%) = 100 × (L−L ₀ ) / L ₀
However, in the above formula, L is the distance between the gauge marks at break (mm), L ₀ is between the original gage length (mm).

(3) Degree of plane orientation (ΔP), birefringence (Δn)
An Atago Abbe refractometer was used. Methylene iodide is mounted, the sample film is closely attached to the prism so that the measurement surface is down, and the refractive index nγ in the main orientation direction, with the monochromatic light sodium D line (589 nm) as the light source. The refractive index nβ and the refractive index nα in the thickness direction were measured. From the obtained values, the plane orientation coefficient ΔP and birefringence Δn of each layer were determined by the following formula. The measurement sample was collected from the center of the product master roll.
ΔP = (nγ + nβ) / 2−nα
Δn = nγ−nβ

(4) Centerline average roughness (Ra)
The center line average roughness Ra (μm) is defined as the surface roughness. It calculated | required as follows using the Kosaka Laboratory Co., Ltd. surface roughness measuring machine (SE-3F). That is, a portion having a reference length L (2.5 mm) is extracted from the film cross-sectional curve in the direction of the center line, the roughness line y = f with the center line of the extracted portion as the x axis and the direction of the vertical magnification as the y axis. When represented by (x), the value given by the following equation is represented by [μm]. The center line average roughness was represented by the average value of the center line average roughness of the extracted portion obtained from 10 cross section curves obtained from the sample film surface. The tip radius of the stylus was 2 μm, the load was 30 mg, and the cutoff value was 0.08 mm.
Ra = 1 / L∫ ₀ ^L | f (x) | dx

(5) Melting peak temperature (Tm)
Using a differential scanning calorimeter “DSC-2920 type” manufactured by TA Instruments, a sample of 5 mg from 0 ° C. to 300 ° C. at 20 ° C./min. The temperature of the endothermic peak that accompanies the melting obtained when the temperature was raised at a rate of T was defined as Tm. Among melting peak temperatures obtained by the above-mentioned method, the B layer melting point is the melting peak temperature obtained from the film obtained by removing the surface layer (A layer) of the formed film, and the A layer melting point is different from the B layer melting point. The melting peak temperature was taken.

(6) Intrinsic viscosity A measurement sample was dissolved in a solvent of phenol / tetrachloroethane = 50/50 (parts by weight) to prepare a solution having a concentration c = 0.01 g / cm ³ , and a relative viscosity with the solvent at 30 ° C. nγ was measured to determine the intrinsic viscosity [η].

(7) Heat shrinkage rate In an oven at a temperature of 150 ± 2 ° C., a film 10 cm long and 10 cm wide was shrunk for 3 minutes in an unloaded state, and the heat shrinkage rate in the vertical and horizontal directions was calculated by the following equation. .
Heat shrinkage rate (%) = 100 × (L ₀ −L) / L ₀
In the above formula, L ₀ is the original length (cm), and L is the length after contraction (cm).

(8) Heat resistance as a film for molding simultaneous transfer A release layer, a printing layer and an adhesive layer (4) are formed on the polyester film (3) shown in FIG. 1, and the length is 35 cm, the width is 25 cm, and the maximum depth is 3.0 cm. The mold (1) was preheated with an IR heater and then premolded inside the mold by vacuum or compressed air molding. The heat resistance was evaluated according to the following criteria based on the state of melting of the film by preheating.
○: Can withstand processing temperatures and can be used for preforming △: Can be used for preforming, but rarely expands due to film softening ×: Frequent expansion due to film melting or softening of film occurs

(9) Formability as a film for simultaneous molding transfer When preforming was carried out by the method of (8) above, the formability was evaluated according to the following criteria by the frequency of breakage of the film by molding.
A: Molded at a uniform thickness with no film rupture and conforms to the mold. O: Molded at a uniform thickness without a film rupture, but a gap is formed between the molds. No, but there is a part where the film is extremely thin locally ×: The film breaks frequently

(10) Suitability as a film for simultaneous molding and transfer Preliminary molding was performed by the method of (8) above, and then a resin was injected to perform molding and transfer. The suitability was evaluated according to the following criteria, depending on the state of missing or distorted patterns of printing on the obtained molded product.
○: No printing omission or distortion △: No printing omission or distortion ×: Printing omission or distortion

Next, the polyester raw materials used in Examples and Comparative Examples will be described.
<Method for producing polyester (1)>
Using 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol as starting materials, 0.09 parts by weight of magnesium acetate tetrahydrate as a catalyst is placed in the reactor, the reaction start temperature is set to 150 ° C., and the methanol is distilled off gradually. The reaction temperature was raised to 230 ° C. after 3 hours. After 4 hours, the transesterification reaction was substantially terminated. After 0.04 part of ethyl acid phosphate was added to this reaction mixture, 0.03 part of antimony trioxide was added and a polycondensation reaction was carried out for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.680 due to a change in stirring power of the reaction vessel, and the polymer was discharged under nitrogen pressure. The intrinsic viscosity of the obtained polyester (1) was 0.680.

<Method for producing polyester (2)>
The starting material is 100 parts by weight of dimethyl terephthalate, 54 parts by weight of ethylene glycol and 25 parts by weight of 1,4-cyclohexanedimethanol, 0.011 part by weight of tetrabutyl titanate is used as a catalyst, and the reaction start temperature is 150 ° C. The reaction temperature was gradually raised with the distillation of methanol, and the temperature was raised to 230 ° C. after 3 hours, and the reaction was continued for another hour. Thereafter, the temperature was gradually raised from 230 ° C. and the pressure was gradually reduced from the normal pressure, and finally the temperature was 280 ° C. and the pressure was 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.70 due to a change in stirring power of the reaction vessel, and the polymer was discharged under nitrogen pressure. The intrinsic viscosity of the obtained polyester (2) was 0.700, and the content of 1,4-cyclohexanedimethanol was 33 mol%.

<Method for producing polyester (3)>
In the production method of polyester (1), after adding 0.04 part of ethyl acid phosphate, 0.3 part of silica particles having an average particle diameter of 2.2 μm dispersed in ethylene glycol and 0.03 part of antimony trioxide are added. In addition, polyester (3) was obtained using the same method as the production method of polyester (1) except that the polycondensation reaction was stopped at the time corresponding to the intrinsic viscosity of 0.610. The obtained polyester (3) had an intrinsic viscosity of 0.610.

<Method for producing polyester (4)>
Isophthalic acid and terephthalic acid were used as the dicarboxylic acid component, and ethylene glycol was used as the polyhydric alcohol component, respectively, and those produced by the usual melt polycondensation method were used. The content of isophthalic acid in the dicarboxylic acid component of this raw material was 22 mol%.

Example 1:
Polyester (3) and polyester (4) are mixed and mixed at a room temperature of 35:65 at room temperature. Layer A, polyester (1), polyester (2) and polyester (4) are mixed with 10: An amorphous sheet that was similarly stirred and mixed at a blending ratio of 50:40 was extruded from an extruder having a T die at 280 ° C. so as to correspond to layer B, and rapidly cooled and solidified by applying an electrostatic application method. Got. The obtained sheet was stretched 3.4 times in the longitudinal direction at 80 ° C., then stretched 3.4 times in the transverse direction at 100 ° C., and heat-treated at 182 ° C. while relaxing in the width direction of 5%. It was. The average thickness of the obtained film was 75 μm. The properties of the obtained film are as shown in Table 1 below and showed excellent properties.

Example 2:
The mixing ratio of the resin used in the A layer was changed to polyester (3): polyester (4) = 70: 30, and the B layer had a 1,4-cyclohexanedimethanol content of 16 mol% and an isophthalic acid content. A film having a thickness of 75 μm was obtained in the same manner as in Example 1 except that polyethylene terephthalate polymerized so as to be 7 mol% was used. The properties of the obtained film are as shown in Table 1 and showed excellent properties.

Comparative Example 1:
The mixing ratio of the resin used for the A layer was changed to polyester (3): polyester (4) = 25: 75, and the mixing ratio of the resin used for the B layer was changed to polyester (2): polyester (4) = 50: 50. Except for the above, a film having a thickness of 75 μm was obtained in the same manner as in Example 1. The characteristics of the obtained film are as shown in Table 1. Since the storage elastic modulus is lower than the lower limit of 10 MPa in the temperature range from 80 ° C. to 180 ° C., the heat resistance is inferior. It was inferior.

Comparative Example 2:
The mixing ratio of the resin used for the A layer was changed to polyester (1): polyester (3) = 70: 30, and the mixing ratio of the resin used for the B layer was changed to polyester (1): polyester (4) = 60: 40. Except for the above, a film having a thickness of 75 μm was obtained in the same manner as in Example 1. The characteristics of the obtained film are as shown in Table 1, and the storage elastic modulus exceeded the upper limit of 2000 MPa in the temperature range from 80 ° C. to 180 ° C., which was excellent in heat resistance. It was inferior.

Comparative Example 3:
The mixing ratio of the resin used for the A layer is polyester (3): polyester (4) = 70: 30, and the mixing ratio of the resin used for the B layer is polyester (1): polyester (2): polyester (4) = 10. : A film having a thickness of 75 μm was obtained in the same manner as in Example 1 except that the ratio was changed to 50:40. The characteristics of the obtained film are as shown in Table 1. The storage elastic modulus was within the range of 10 MPa to 2000 MPa in the temperature range of 80 ° C. to 180 ° C., but the heat resistance was good, but the tensile elongation at break was small. Therefore, it was inferior in moldability and did not show sufficient suitability as a film for simultaneous transfer of molding.

Comparative Example 4:
Polyester (2), polyester (3), and polyester (4) blended at a blending ratio of 55: 5: 40 were extruded in a single layer at 280 ° C. from an extruder having a T die, and the same method as in Example 1 A film having a thickness of 50 μm was obtained. The characteristics of the obtained film are as shown in Table 1. Since the storage elastic modulus is lower than the lower limit of 10 MPa in a single layer and in the temperature range from 80 ° C. to 180 ° C., the film is inferior in heat resistance and cannot be pre-molded. The sex could not be evaluated.

  In the above table, IPA means isophthalic acid, CHDM means 1,4-cyclohexanedimethanol, and ET means ethylene terephthalate.

  The film of the present invention can be suitably used as a base film for simultaneous molding and transfer, for example.

DESCRIPTION OF SYMBOLS 1 Mold 2 Injection molding machine 3 Film 4 Layer which consists of mold release layer, printing layer, and adhesive layer

Claims (1)

The content of the main component is 80 mol% or more on at least one side of the B layer made of polyester containing at least one copolymer component other than the main component and the content of the main component being 90 mol% or less. A film having a structure in which an A layer made of polyester is laminated, wherein the maximum value of the storage elastic modulus E ′ in the temperature range of 80 ° C. to 180 ° C. is in the range of 810 to 1100 MPa, and the tensile elongation at break at 100 ° C. A polyester film for simultaneous molding transfer, having a degree of 180% or more and a tensile strength at 100 ° C of 50 MPa or less.

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