JP5876750B2 - Translucent biaxially stretched polyester film for glass lamination - Google Patents

Description

  The present invention relates to a translucent biaxially stretched polyester film base material that can be suitably used for laminating laminated glass, which is useful for preventing glass scattering, crime prevention, privacy protection, etc. for windows of buildings, indoor doors, bathtub doors, etc. is there.

  In some cases, frosted glass is used to protect the privacy of building windows, interior doors, and bathtub doors. Ground glass alone is inferior in preventing glass scattering and crime prevention. For example, there is a case where the glass of an indoor door is broken and the limbs are cut. Therefore, laminated glass bonded between two glass plates through a resin is effective for preventing glass scattering and preventing crime.

  For example, according to Patent Document 1, an interlayer film of laminated glass is provided, but a film excellent in strength and stability is not used for the interlayer film, and improvement is required.

  According to Patent Document 2, it is disclosed that a polyester sheet having a thickness of 0.4 to 3 mm is used as a protective sheet for window glass, but it is a protective sheet and cannot improve the above problem. .

According to Patent Document 3, a light-shielding film for magnetic recording media containing carbon black is disclosed, but light scattering like ground glass cannot be expected.

JP-A-8-259279 JP 2004-338365 A JP 61-237622 A

  The present invention has been made in view of the above circumstances, and its solution is to protect the privacy in the same way as frosted glass used by being attached to glass, and to contribute to energy saving in the room. The object is to provide a translucent biaxially stretched polyester film having properties.

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

That is, the gist of the present invention is a biaxially stretched polyester film containing 0.005 to 0.39 % by weight of carbon black and 0.01 to 5% by weight of particles having an average particle diameter of 2.1 to 30 μm. The translucent biaxially stretched polyester film for glass bonding is characterized in that the total light transmittance of the biaxially stretched polyester film is 20 to 80%.

  According to the present invention, it is possible to provide a translucent biaxially stretched polyester film that is used for bonding to glass that contributes to energy conservation in the room and helps protect privacy in the same way as rubbed glass, and the industrial value of the present invention is high.

  The polyester used in the biaxially oriented polyester film of the present invention is obtained by polycondensation of aromatic dicarboxylic acid and aliphatic glucose. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glucose include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Representative polyesters include polyethylene terephthalate (PET), polyethylene-2,6-naphthalene carboxylate (PEN), and the like. Among these, PET has a good balance between physical properties and cost, and is the most frequently used polyester.

  The polyester used in the present invention may be a copolymer containing a third component as long as it is within 10 mol%, preferably within 5 mol% in total. Examples of the dicarboxylic acid component of the copolyester include one or two of isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenecarboxylic acid, adipic acid, sebacic acid, and oxycarboxylic acid (for example, P-oxybenzoic acid). The glycol component includes one or more of ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, and the like.

  The carbon black used for the polyester film of the present invention is not particularly limited, but carbon black produced by a furnace method having an average primary particle size in the range of 5 to 100 nm is preferable because the physical properties and quality are stable. The amount of carbon black added is 0.005 to 1.5% by weight, preferably 0.01 to 1.0% by weight. The addition amount of carbon black is effective in controlling the total light transmittance of the film, and an appropriate addition amount is determined according to the film thickness.

  The average particle diameter of particles other than carbon black used in the film of the present invention is 2.1 to 30 μm, preferably 3.0 to 20 μm, more preferably 3.5 to 15 μm. Although the kind of particle | grain is not specifically limited, For example, a silica, spherical silica, a calcium carbonate, an organic crosslinked particle, etc. are mentioned. If the particle size is less than 1.5 μm, the effect of improving the winding property of the film is small, the effect of scattering light is small, and the effect of blurring the image through the glass (privacy protection) decreases. On the other hand, when it exceeds 30 μm, the surface appearance and productivity of the film are adversely affected.

  Moreover, the addition amount of particle | grains is 0.01 to 5 weight%, Preferably it is 0.05 to 3 weight%, More preferably, it is 0.1 to 1 weight%. If the amount of added particles is less than 0.01% by weight, the running property and winding property of the film are adversely affected. On the other hand, if it exceeds 5% by weight, it tends to break during production and adversely affects productivity.

  The total light transmittance of the film of the present invention is usually 20 to 80%, preferably 25 to 75%, more preferably 30 to 70%. When the total light transmittance is less than 20%, the indoor brightness tends to be poor, and when it exceeds 80%, the light shielding property tends to be inferior, and the indoor temperature rises in summer.

  The haze value of the film of the present invention is preferably 90% or more, more preferably 95% or more, and particularly preferably 97% or more. If the haze value is less than 90%, the linear light transmittance tends to be high and the privacy protection tends to be lowered.

  Although the film thickness of this invention is not specifically limited, it is 10-300 micrometers, Preferably it is 20-200 micrometers. When the film thickness is smaller than 10 μm, the glass laminating workability is deteriorated. On the other hand, when the film thickness is larger than 300 μm, the mechanical load during film formation increases and the productivity may be lowered. .

  Further, the heat shrinkage rate of the film of the present invention at 180 ° C. for 5 minutes is preferably 0.8 to 4.0% in the film flow direction and −1.0 to 0.5% in the film width direction. Preferably, the film flow direction is 1.2 to 3.0%, and the film width direction is -0.5 to 0.3%. If the shrinkage rate is out of these ranges, the workability of the film on the curved glass tends to deteriorate.

  The film of the present invention may contain additives such as an ultraviolet absorber, an antistatic agent, an antioxidant, and a fluorescent brightening agent as necessary.

  Further, the film may have a coextruded laminated structure of two or more layers other than the single layer structure.

  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.

  When the film of the present invention is produced, the polyester is supplied to an extruder and heated to a temperature equal to or higher than the melting point of each polyester to be melted. Next, the molten polymer 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. And a uniaxially stretched film is obtained by extending | stretching an 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. Thereafter, the film is guided to a tenter and a biaxially stretched film is obtained by stretching (laterally stretching) the uniaxially stretched film in the width direction 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. And a laminated film is manufactured by heat-processing a biaxially stretched film. The heat treatment temperature at this time is Tm-6 to Tm-100 ° C., where Tm is the melting point of the polyester used for the surface layer (A layer) of the coextrusion lamination. The heat setting time is 1.5 to 10 seconds. Moreover, when heat-treating a biaxially stretched film, it is preferable to perform relaxation in the film width direction within 6% of the biaxially stretched film.

  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) Total light transmittance of film Using a turbidimeter NDH300A (manufactured by Nippon Denshoku Co., Ltd.), the total light transmittance of the film is measured.

(3) Privacy protection A film that makes it impossible to distinguish numbers from a distance of 30 cm from a surface light source through a test film by placing A4 copy paper with numbers 1 to 9 of font 24 printed on it in an MS Gothic typeface. Measure the distance from the A4 copy paper on which the numbers are printed. Privacy protection is evaluated as follows.
○: The distance at which numbers cannot be discriminated is 3 cm or less, and privacy protection is excellent. Δ: The distance at which numbers cannot be discriminated is 3 to 10 cm, and privacy protection is somewhat. ×: The distance at which numbers cannot be discriminated exceeds 10 cm , Poor privacy protection

(4) Daylighting property It evaluated as follows from the value of the total light transmittance of a film.
○: Appropriate amount of light enters when the total light transmittance is between 20% and 80%, and the light-collecting property is good. X1: The total light transmittance exceeds 80%, resulting in poor light shielding. × 2: Total light transmittance is low. Because it is less than 20%, the room is dark and the lighting is poor.

(5) Film winding workability The winding workability in the film forming process was evaluated and divided into the following three ranks.
○: Can be rolled up smoothly, end faces are aligned, and no traces of wrinkles or wrinkles are generated. Wrinkles are likely to enter, and the end faces are likely to be uneven.

(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 obtained polyester a has an intrinsic viscosity of 0.70 and a melting point of 253 ° C.

・ Polyester b
Polyester a was subjected to a twin screw extruder with a vent, and carbon black (oil furnace black average primary particle size 70 nm) was supplied to a concentration of 2.0% by weight and melt kneaded to form chips. The intrinsic viscosity of the obtained polyester d is 0.60.

・ Polyester c
In the production of polyester a, 0.04 part of antimony trioxide was added, and then amorphous silica particles having an average particle diameter of 2.5 μm were added. The concentration of the amorphous silica particles of the obtained polyester c is 1.0% by weight and the intrinsic viscosity is 0.65.

・ Polyester d
Using a biaxial extruder with a vent, crosslinked styrene-acrylic organic particles having an average particle size of 4 μm were added to polyester a so as to have a concentration of 10% by weight, and melt-kneaded to form chips. The intrinsic viscosity of the obtained polyester d is 0.65.

・ Polyester e
Using a twin screw extruder with a vent, cross-linked styrene-acrylic organic particles having an average particle diameter of 6 μm were added to polyester a so as to have a concentration of 10% by weight, and melt kneading was performed to obtain chips. The intrinsic viscosity of the obtained polyester e is 0.65.

・ Polyester f
In the production of polyester a, 0.04 part of antimony trioxide was added, and then synthetic calcium carbonate particles having an average particle diameter of 0.7 μm were added. The resulting polyester f has a synthetic calcium carbonate particle concentration of 1.0% by weight and an intrinsic viscosity of 0.66.

・ Polyester g
Using a vented twin screw extruder, spherical silica particles having an average particle diameter of 70 μm were added to polyester a so as to have a concentration of 1.0% by weight, and melt-kneaded to form chips. The intrinsic viscosity of the obtained polyester g is 0.65.

Example 1:
A mixture of polyester a, polyester b and polyester c in a ratio of 77.5 / 2.5 / 20.0 (weight ratio) is supplied to a twin screw extruder with a vent and melted at a melting temperature of 280 ° C. The film was drawn on a casting drum through a die through a gear pump and a filter to obtain an unstretched film. The unstretched film thus obtained was fed into a longitudinal stretching roll, first stretched 3.6 times at a film temperature of 90 ° C., then led to a tenter and stretched 4.5 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, heat-treated at 220 ° C., and subjected to 5.0% thermal relaxation in the width direction to obtain a polyester film described in Table 1 below.

Example 2:
A mixture of polyester a, polyester b and polyester c in a ratio of 75.0 / 5.0 / 20.0 (weight ratio) is supplied to a twin screw extruder with a vent and melted at a melting temperature of 280 ° C. The film was drawn on a casting drum through a die through a gear pump and a filter to obtain an unstretched film. The unstretched film thus obtained was fed into a longitudinal stretching roll, first stretched 3.1 times at a film temperature of 90 ° C., then led to a tenter and stretched 3.3 times in the transverse direction at 95 ° C. to obtain a biaxially oriented film. It was. Subsequently, the obtained biaxially oriented film was introduced into a heat setting zone, heat-treated at 230 ° C., and subjected to 4.0% thermal relaxation in the width direction to obtain a polyester film described in Table 1 below.

Example 3:
Same as Example 2 except that a mixture of polyester a, polyester b and polyester d in a ratio of 82.0 / 16.0 / 2.0 (weight ratio) was fed to a vented twin screw extruder.

Example 4:
Same as Example 1 except that a mixture of polyester a, polyester b and polyester e in a ratio of 78.5 / 19.5 / 2.0 (weight ratio) was fed to a vented twin screw extruder.

Example 5:
Same as Example 2 except that a mixture of polyester a, polyester b and polyester e in a ratio of 96.0 / 2.0 / 2.0 (weight ratio) was fed to a vented twin screw extruder.

Comparative Example 1:
Same as Example 2, except that a mixture of polyester a, polyester b and polyester c in a ratio of 37.0 / 43.0 / 20.0 (weight ratio) was fed to a twin screw extruder with a vent.

Comparative Example 2:
Same as Example 1 except that a mixture of polyester a and polyester c in a ratio of 80.0 / 20.0 (weight ratio) was fed to a vented twin screw extruder.

Comparative Example 3:
Same as Example 1, except that a mixture of polyester a and polyester b in a ratio of 84.0 / 16.0 (weight ratio) was fed to a vented twin screw extruder.

Comparative Example 4:
Same as Example 2 except that a mixture of polyester a, polyester b and polyester f in a ratio of 64.0 / 16.0 / 20.0 (weight ratio) was fed to a vented twin screw extruder.

Comparative Example 5:
A mixture of polyester a, polyester b and polyester e in a ratio of 14.0 / 16.0 / 70.0 (weight ratio) was supplied to a twin screw extruder with a vent to form a film under the same conditions as in Example 1. However, the film could not be collected because the film broke frequently.

Comparative Example 6:
A mixture of polyester a, polyester b and polyester g in a ratio of 44.0 / 16.0 / 40.0 (weight ratio) was fed to a twin screw extruder with a vent to form a film under the same conditions as in Example 1. However, the film could not be collected because the film broke frequently.

  In Examples 1 to 5, since carbon black and particles are appropriate and added in a predetermined amount, they are excellent in daylighting and privacy protection. On the other hand, Comparative Example 1 is inferior in daylighting because the amount of carbon black added is large, Comparative Example 2 is inferior in light shielding property because no carbon black is added, and Comparative Example 3 is inferior in film winding because no particles are added Comparative Example 4 is inferior in privacy protection because the particle size of the added particles is small.

  The film of the present invention can be suitably used, for example, as a base film for glass bonding that requires daylighting and privacy protection.

Claims (1)

A biaxially stretched polyester film containing 0.005 to 0.39 % by weight of carbon black and 0.01 to 5% by weight of particles having an average particle diameter of 2.1 to 30 μm, A translucent biaxially stretched polyester film for laminating glass, wherein the total light transmittance is 20 to 80%.