JP5404521B2 - Biaxially stretched polyester film for deep drawing simultaneous transfer - Google Patents

Description

  The present invention relates to a deep drawing simultaneous use useful as a base film of a simultaneous molding decorative sheet used for decorating the surface of a resin molded product having a curved surface and a slightly complicated shape such as an electric product or an automobile part in a matte tone. The present invention relates to a biaxially stretched polyester film for transfer.

  As a method for decorating a plastic molded product having a curved surface such as an electric appliance, a so-called in-mold molding method in which transfer printing is performed simultaneously with molding is widely used. The in-mold molding method uses a heat and pressure during plastic injection molding to create a transfer sheet in which a printing layer consisting of a release layer, ink layer, adhesive layer, etc. is laminated on a substrate film in advance. Transfer printing. TECHNICAL FIELD The present invention relates to a biaxially stretched polyester film for simultaneous transfer molding used for producing a matte appearance having excellent matting properties on the surface of a molded product.

The surface in contact with the release layer of the base film has fine irregularities on the surface in order to transfer the matte appearance to the molded product. There are methods for providing fine irregularities on the surface of the base film, such as embossing and a method of coating a coating solution containing fine particles, but there is a problem that the manufacturing process of the base film increases. Moreover, although the film which added a comparatively large quantity of particle | grains at the time of polyester film manufacture and the surface was roughened is disclosed by patent document 1, it cannot be said that the glossiness of a molded article is low enough. On the other hand, if the particle concentration in the film is increased in order to increase the film surface roughness, there arises a problem that the film is torn during the simultaneous transfer processing. Patent Document 2 proposes a polyester film suitable for deep drawing in which particles are added to the surface layer of a co-extrusion laminated structure. However, there is a problem that glossiness changes between a flat portion and a curved portion of a molded product.

JP 2007-268708 A JP 2008-163275 A

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned actual situation, and its solution is to decorate the surface of a resin molded product having a slightly complicated shape such as an electric product or an automobile part in a matte tone with less gloss unevenness. and to provide a deep drawing having excellent molding simultaneous transfer biaxially stretched polyether scan ether film was used.

  As a result of intensive studies, the present inventors have found that the above problem can be easily solved by using a polyester film having a specific configuration, and have completed the present invention.

That is, the gist of the present invention consists of a copolymerized polyester containing 5 to 25 mol% of isophthalic acid units, and contains 0.1 to 10.0 wt% of particles having an average particle diameter of 2.0 to 20 μm on at least one surface. It consists in deep-drawing simultaneously transfer biaxially stretched polyether scan ether film characterized by having a co-extruded layer of particle-containing thick 4.0~20μm to.

According to the present invention, it is possible to provide a molding simultaneous transfer biaxially stretched polyether scan Tel film capable of obtaining a small molded article gloss unevenness superior matte appearance to the deep drawability, industrial invention Target value is high.

  The polyester used in the present invention comprises a copolyester containing an isophthalic acid unit in a concentration of 5 to 25 mol%, preferably 7 to 22 mol%, more preferably 10 to 20 mol%. A copolymer polyester containing 5 to 25 mol% of isophthalic acid unit is a mixture of an aromatic dicarboxylic acid such as terephthalic acid or naphthalene-2,6-dicarboxylic acid and 5 to 25 mol% of isophthalic acid, ethylene glycol, It is a polyester made by condensation polymerization of diethylene glycol or tetramethylene glycol.

  If the isophthalic acid unit concentration is 5 mol% or less, the elongation rate of the film becomes small and a film suitable for deep drawing cannot be produced. On the other hand, if the concentration exceeds 30 mol%, the film shrinkage during the simultaneous transfer processing of the film becomes large and the forming process becomes difficult. Alternatively, if the heat treatment temperature is increased in order to reduce the shrinkage rate, the film is broken during film formation.

  The film of the present invention has a co-extruded multilayer structure, and has at least one surface containing particles having a thickness of 4.0 to 20 μm, preferably 5.0 to 20 μm, and more preferably 6.0 to 20 μm. It has an extruded layer. When the thickness of the particle-containing layer is less than 4.0 μm, the degree to which the film is stretched during deep drawing differs between the flat part and the curved part of the molded product, so the gloss of the molded product appearance changes partially and molding Product appearance quality deteriorates. In the single layer configuration, since particles exist in the entire film, the moldability is lowered due to a decrease in the film elongation. Further, even if the thickness of the particle-containing layer exceeds 20.0 μm, the improvement effect of reducing unevenness in molded product gloss hardly changes.

  The particles contained in the particle-containing layer of the film of the present invention are inorganic or organic particles, and the average particle size thereof is 2.0 to 20 μm, preferably 2.2 to 15 μm, more preferably 2.5 to 10 μm. It is. When the average particle size is less than 2.0 μm, the surface roughness becomes small, and a molded product having a matte appearance cannot be produced. On the other hand, when the average particle diameter exceeds 20 μm, a problem arises in that the increase in the pressure of the filter in the polyester extrusion process at the time of film production increases and the productivity decreases.

  The content of such particles is 0.1 to 10.0% by weight with respect to the film, preferably 0.2 to 8.0% by weight, and more preferably 0.3 to 5.0% by weight. If it is less than 0.1% by weight, it is difficult to increase the film surface roughness, and a molded product having a matte appearance cannot be produced. On the other hand, addition exceeding 10% by weight decreases the elongation of the film, and a film suitable for deep drawing cannot be produced.

The inorganic or organic particles used in the present invention may be a single component, or two or more components may be used simultaneously. Specific examples of the particles include inorganic fine particles such as calcium carbonate, silica, aluminum oxide, barium carbonate, barium sulfate, and glass, and organic particles such as melamine resin, polystyrene, organic silicone resin, and acrylic-styrene copolymer. It is done.
The polyester composition of the particle-containing layer of the present invention comprises a copolyester containing 5 to 25 mol% isophthalic acid unit, preferably 7 to 22 mol%, more preferably 10 to 20 mol%. Furthermore, when the isophthalic acid unit of the polyester of the particle-containing layer is A mol% concentration, the isophthalic acid unit of the coextruded layer in contact with the particle-containing layer is preferably 0.5A to 2.0A, more preferably 0.6A to 1.A. The concentration is 7A, particularly preferably 0.7 to 1.5A mol%.

  Outside this range, the difference in physical properties between the coextruded layer and the coextruded layer in contact with the particle-containing layer becomes large, and peeling occurs at the layer interface during molding.

  The 25 ° C. breaking elongation of the film of the present invention is preferably 130% or more, more preferably 150% or more, and particularly preferably 160% or more. If the 25 degreeC elongation rate of a film is less than 130%, a film will be easy to tear at the time of shaping | molding simultaneous transfer processing.

  The surface roughness Sa of the film of the present invention is preferably 200 nm or more, more preferably 220 nm or more, and particularly preferably 250 nm or more. If the surface roughness Sa is less than 200 nm, it may not be possible to produce a molded product for matte simultaneous molding transfer. The matte tone referred to in the present invention means that the gloss of the molded product is 90 or less, and therefore the gloss of the film is preferably 100 or less, more preferably 90 or less, and particularly preferably 80 or less.

  In the present invention, a coating layer such as a release layer, an antistatic layer, and an easy adhesion layer may be provided on the film surface as necessary, or chemical treatment or discharge treatment may be performed.

  Moreover, the thickness of the film in this invention is 25-150 micrometers normally, Preferably it is 30-100 micrometers.

  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 specifically limited to the following illustrations.

  In the production of the film of the present invention, each film is melted by heating to a temperature equal to or higher than the melting point of the polyester. Next, the molten polymer from each extruder is merged with a feed block through a gear pump and a filter and extruded from a die as a molten sheet. Subsequently, the molten sheet is rapidly cooled to below the glass transition temperature on a rotary cooling drum to obtain an amorphous unstretched film. At this time, in order to improve the flatness of the unstretched film, the adhesion between the unstretched film and the rotating cooling drum may be improved by an electrostatic application adhesion method, a liquid application adhesion method, or the like.

  Next, a uniaxially stretched film is obtained by stretching the unstretched film in the longitudinal direction (longitudinal stretching) using a roll stretching machine. The stretching temperature at this time is stretched in a temperature range of minus 10 ° C. to plus 40 ° C. of the glass transition temperature (Tg) of the raw material resin. The draw ratio is preferably 1.5 to 6.0 times, more preferably 2.0 to 5.0 times. Furthermore, longitudinal stretching may be performed in only one stage, or may be performed in two or more stages. Next, the biaxially stretched film is obtained by stretching the uniaxially stretched film in the width direction (lateral stretching) using a tenter stretching machine. The stretching temperature at this time is stretched in a temperature range of + 50 ° C. from the glass transition temperature (Tg) of the raw material resin. The draw ratio is preferably 2.5 to 6.0 times, more preferably 3.0 to 5.0 times. Further, the transverse stretching may be performed only in one stage, or may be performed in two or more stages. Moreover, you may perform simultaneous biaxial stretching which performs vertical and horizontal simultaneously.

  A laminated film is manufactured by heat-treating the obtained biaxially stretched film. The heat treatment temperature at this time is usually Tm-6 to Tm-18 ° C, and the heat setting time is usually 1.5 to 10 seconds. Moreover, when heat-treating a biaxially stretched film, the biaxially stretched film may be relaxed within 20%.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded. The measurement methods and terms used in the examples and the present invention are defined as follows.

(1) Average particle diameter of particles After ashing the surface in the film stretching direction to 1 μm with a low-temperature ashing plasma apparatus, the major axis and the minor axis of particles having a particle diameter of 1 μm or more are at least 100 with a scanning electron microscope. It calculates | requires about a piece and makes an arithmetic mean the average particle diameter.

(2) Elongation at break 50 mm between chucks taken in the vertical and horizontal directions in a room adjusted to a temperature of 25 ° C. and a humidity of 50% RH using an Intesco tensile tester, Intesco Model 2001 type A sample film with a width of 15 mm is pulled at a speed of 200 mm / min, and each N = 3 times is measured, and the average value is taken as the breaking elongation of the sample.

(3) Film surface roughness Sa
Measurement is performed using a three-dimensional non-contact surface shape measurement system MN537N-M100 (Ryoka System Co., Ltd.).

(4) Thickness of the particle-containing layer The sample film is embedded with an epoxy resin, sectioned with an ultramicrotome, and the obtained flakes are observed with a scanning electron microscope. The observed range was measured at 50 points, and the average value was defined as the thickness of the particle-containing layer.

(5) Glossiness Measured by making light incident on the film surface according to method 3 (60 ° glossiness) of JIS Z-8741-1983.

(6) Formability An organic solvent solution in which a melamine resin is dissolved is applied to the release layer forming surface (A layer) of the film to form a release layer having a dry thickness of 1 μm, and the length is 35 cm, the width is 25 cm, and the maximum depth is 3. Using a 0 cm mold, the film was preheated with an IR heater, preliminarily molded inside the mold with vacuum and compressed air, and then the heated resin was injected for molding. The moldability was evaluated as follows.
○: Can be used without film breakage.
Δ: Film breakage does not occur, but it can be used even though there is a locally thin film portion.
X: Film tear frequently occurs and cannot be used.

(7) Evaluation of molded product gloss unevenness The appearance of the molded product prepared in (6) above was visually observed to evaluate the molded product gloss unevenness as follows.
○: The gloss of the corner is almost the same as that of the flat part, and there is no problem in the molding appearance quality. △: The gloss of the corner is slightly higher than that of the flat part. Acceptable ×: The gloss of the corner portion is higher than that of the flat portion, and the molding appearance quality is not acceptable.

(Raw material adjustment)
・ Polyester a
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 adding 0.04 part of ethyl acid phosphate to this reaction mixture, 0.04 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 0.63 due to a change in stirring power of the reaction tank, and the polymer was discharged under nitrogen pressure. The intrinsic viscosity of the obtained polyester a is 0.63.

・ Polyester b
It is a copolyester resin having an intrinsic viscosity of 0.72 obtained by synthesizing a copolyester containing 30 mol% of isophthalic acid by a conventional method using dimethyl terephthalate, dimethyl isophthalate and ethylene glycol.

・ Polyester c
Polyester a is kneaded with 10% by weight of crosslinked styrene-acrylic organic particles having an average particle diameter of 4.5 μm.

・ Polyester d
Polyester a is kneaded with 10% by weight of crosslinked styrene-acrylic organic particles having an average particle size of 6.0 μm.

・ Polyester e
This is a polyethylene terephthalate resin having an intrinsic viscosity of 0.68 and containing 2.0% by weight of the particles, which is synthesized by adding amorphous silica particles having an average particle size of 3.5 μm at the time of polycondensation of polyethylene terephthalate.

・ Polyester f
This is a polyethylene terephthalate resin having an intrinsic viscosity of 0.68 and containing 1.8% by weight of synthetic calcium carbonate particles having an average particle size of 0.7 μm, which are synthesized by polycondensation of polyethylene terephthalate.

・ Polyester g
Polyester a is kneaded with silica particles having an average particle size of 80 μm and contains 10% by weight.

Example 1:
A mixture of the ratio of polyester a / polyester b / polyester c forming the surface layer (A layer) is 30/40/30 (weight ratio) is fed to a vented twin screw extruder (sub), and the intermediate layer (B layer) A mixture of polyester a / polyester b in the ratio of 60/40 (weight ratio) is supplied to another twin-screw extruder with a vent (main) and melted at a melting temperature of 280 ° C. The molten polymer was merged with a feed block via a gear pump and a filter, and was drawn on a casting drum through a die to obtain an unstretched film of two types and three layers. The unstretched film thus obtained was fed into a longitudinal stretching roll, first stretched 3.4 times at a film temperature of 80 ° C., then led to a tenter and stretched 3.6 times in the transverse direction at 95 ° C. to obtain a biaxially oriented film. It was. Next, the obtained biaxially oriented film was introduced into a heat setting zone and heat-treated at 185 ° C. to obtain a polyester film having a thickness of 5/40/5 μm described in Table 1.

Example 2:
The same as in Example 1, except that the amount of resin supplied to the surface layer (A layer) and the amount of resin supplied to the intermediate layer (B layer) were adjusted to obtain a polyester film having a thickness of 7/36/7 μm.

Example 3:
A mixture having a ratio of polyester a / polyester b / polyester c forming the surface layer (A layer) of 10/60/30 (weight ratio) is supplied to a twin screw extruder (sub) with a vent, and an intermediate layer (B layer) A mixture of polyester a / polyester b in the ratio of 40/60 (weight ratio) was supplied to another twin-screw extruder with a vent (main), and the same as in Example 2.

Comparative Example 1:
The amount of resin supplied to the surface layer (A layer) and the amount of resin supplied to the intermediate layer (B layer) were adjusted to obtain a polyester film having a thickness of 3/44/3 μm, and the same as in Example 1.

Comparative Example 2:
Same as Comparative Example 1 except that a mixture of polyester a / polyester e with a ratio of 60/40 (weight ratio) was supplied to a vented twin screw extruder and heat treated at 225 ° C.

Comparative Example 3:
Using a mixture of the ratio of polyester b / polyester f forming the surface layer (A layer) of 60/40 (weight ratio), the amount of resin supplied to the surface layer (A layer) and the amount of resin supplied to the intermediate layer (B layer) Was adjusted to obtain a polyester film having a thickness of 5/40/5 μm, and the same as in Example 3.

Comparative Example 4:
The ratio of the polyester raw material was set to polyester a / polyester b / polyester e = 34.5 / 63 / 2.5 (weight ratio), and the same as Comparative Example 2 except that the heat treatment was performed at 185 ° C.

Comparative Example 5:
The ratio of the polyester raw material was set to polyester b / polyester d = 30/70 (weight ratio), and heat treatment at 200 ° C. was the same as Comparative Example 2.

Comparative Example 6:
Film formation was attempted in the same manner as in Example 1 using polyester g instead of polyester c, but the production of the film was abandoned because of an increase in the pressure of the filter in the polyester extrusion process during film production.

Comparative Example 7:
A polyester master a was kneaded with crosslinked styrene-acrylic organic particles having an average particle size of 4.5 μm to make a particle masterbatch containing 30% by weight. However, the resin could not be made into chips and 20 particles were added to the surface layer (A layer). A film to which wt% was added could not be prepared.

Comparative Example 8:
The ratio of the polyester raw material forming the surface layer (A layer) is polyester b / polyester c = 92/8 (weight ratio), and the ratio of polyester a / polyester b constituting the intermediate layer (B layer) is 8/92 (weight). Ratio) was used and film formation was attempted under the same conditions as in Example 1, but the film was broken during film formation and could not be collected.

  The evaluation results of the collected films are summarized in Table 1 and Table 2 below.

  The films of Examples 1 to 3 are films capable of obtaining a molded article having a matte appearance with excellent deep drawability and less gloss unevenness. Particularly in Examples 2 and 3, the surface layer thickness is as thick as 7 μm, and gloss unevenness is small. On the other hand, Comparative Example 1 has large gloss unevenness because the surface layer thickness is less than 4.0 μm. In Comparative Example 2, the moldability is poor because the isophthalic acid unit is less than 5 mol% concentration. Since Comparative Example 3 has a small particle size of the surface layer, and Comparative Example 4 has a small particle addition concentration, a product having a matte appearance cannot be produced. Moreover, since the comparative example 5 is a single layer structure, the moldability is inferior.

  The film of the present invention can be suitably used as a film for deep drawing simultaneous transfer.

Claims (1)

A film comprising a copolymerized polyester containing an isophthalic acid unit in a concentration of 5 to 25 mol%, and containing 0.1 to 10.0% by weight of particles having an average particle size of 2.0 to 20 μm on at least one surface polyether scan ether film, wherein the deep drawing molding simultaneous transfer biaxial stretching to have a coextruded layer of 4.0～20Myuemu.