JPH07118433A - Polyester film for delivery slips - Google Patents

Abstract

PURPOSE:To obtain polyester film for delivery slips having excellent opacity, drawability, film-forming properties and the like by melt-extruding a mixture of polyester, inorganic particles and/or non-compatible thermoplastic resin and orienting the film in one or more directions. CONSTITUTION:(A) Polyester is mixed with (B) inorganic particles such as titanium dioxide, calcium carbonate and/or (C) a thermoplastic resin non- compatible to polyester, preferably a polyolefin resin such as polystyrene or poly(methylpentene), melt-extruded and oriented at least in one direction to give the objective film of 10 to 40mum thickness, less than 30% light transmission, more than 75 whiteness degree. Or component A and component C are mixed, molten, extruded and oriented at least in one direction to give the objective film having a number of fine pares inside, 1.0-1.3 apparent specific gravity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film for use which is thin but has good concealing properties and drawing properties and which is excellent in productivity and film-forming property.

[0002]

2. Description of the Related Art A delivery slip in which an address, an address, etc. are written is pasted on parcels such as a courier service and a parcel post. This delivery slip is used by stacking 5 to 10 sheets. Therefore, when paper or polyolefin synthetic paper is used as the base material, there is a problem in that it becomes thick. Therefore, those using a polyester film have been developed in recent years. However, when it becomes thin, the concealing property is lost, and the problem is that the letters below can be seen through. Also,
When trying to form a film that is thin but has concealing properties, it is necessary to contain a large number of inorganic particles and cavities inside the film, which may result in unstable film forming properties and poor film strength. It was a problem.

[0003]

DISCLOSURE OF THE INVENTION The present invention is intended to provide a base material for a delivery slip, which is excellent in concealing property, film strength, film-forming property, productivity, etc., even though the above-mentioned drawbacks are solved. is there.

[0004]

That is, according to the present invention, polyester is mixed with inorganic particles and / or thermoplastic resin incompatible with the polyester, and the mixture is extruded and oriented at least uniaxially and has a thickness of 10 μm or more and 40 μm or more. Below, the light transmittance is 3
The present invention relates to a polyester film for a delivery slip, which has a whiteness of 75% or more and 0% or less. The polyester in the present invention, terephthalic acid, isophthalic acid,
A polyester produced by polycondensing an aromatic dicarboxylic acid such as naphthalenedicarboxylic acid or an ester thereof and a glycol such as ethylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol. These polyesters may be obtained by directly reacting an aromatic dicarboxylic acid with a glycol, and then transesterifying an alkyl ester of an aromatic dicarboxylic acid with a glycol, followed by polycondensation, or a diglycol ester of an aromatic dicarboxylic acid. Is produced by a method such as polycondensation. Typical examples of such polyesters include polyethylene terephthalate, polyethylene butylene terephthalate and polyethylene-
2,6-naphthalate and the like can be mentioned. This polyester may be a homopolymer or a copolymer of a third component. In any case, in the present invention, a polyester having an ethylene terephthalate unit, a butylene terephthalate unit or an ethylene-2,6-naphthalate unit in an amount of 70 mol% or more, preferably 80 mol% or more, more preferably 90 mol% or more is preferable. .

In the present invention, a particularly important point is that the thickness can be reduced to 40 μm or less even though the inorganic particles are present in the polyester. Usually, as a means for imparting concealing property to a plastic film, that is, a means for lowering the light transmittance, a method of expressing a large number of internal cavities, applying a pigment or a dye to the surface layer of the film, or containing a large number of inorganic particles inside is used. There is. However, if the content of cavities or inorganic particles is further increased in order to further improve the hiding property, there arises a problem that the strength of the film decreases and the film-forming property becomes unstable. Further, when the coating amount of the pigment is increased, there is a problem that the pigment comes off. Therefore, as a method for improving the hiding property so as not to cause these problems, it is possible to secure the stretchability even if a large number of inorganic particles are contained inside the film.

In the case of a usual void-containing polyester film, the added inorganic particles such as titanium dioxide, calcium carbonate, silicon dioxide and barium sulfate are all present in the matrix polyester. Therefore, when the addition amount of the inorganic particles is increased, the interface generated between the polyester and the inorganic particles is increased, and the tensile strength and film formability of the film are likely to decrease. This is 40μ thick
This is a particularly serious problem with a film having a thickness of m or less. Therefore, as one of the means for solving these problems, there has been a method of treating the surface of inorganic particles with an inorganic substance containing aluminum, silicon, zinc, etc. to improve the affinity with polyester or a method of adding a large amount to the surface layer of a laminated film. It is disclosed. However, in these methods, it is not possible to maintain the film strength, the surface strength and the film-forming property by containing a large amount of inorganic particles so as to achieve a light transmittance of 30% or less at a thickness of 40 μm or less, preferably 30 μm or less. It is possible.
This is because the inorganic particles have a high surface energy and thus have a higher affinity for the polyester having a higher surface energy than the cavity developing agent.

[0007] Therefore, as a means for reaching the present invention, it is possible to increase the amount of the inorganic particles to be added in order to improve the hiding property, and to mix the stretching aid. As a result, even if the content of the inorganic particles is increased, problems such as film strength and film forming property are eliminated. Polyethylene glycol such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and / or the like as a drawing aid.
Alternatively, derivatives and / or copolymers thereof may be used. Examples of the derivative include those obtained by blocking the terminal group with another bond, those obtained by polyesterification by reaction with a dicarboxylic acid, and the like. Among these, polyethylene glycol, polyethylene glycol copolymers and polyesters or copolymerized polyesters obtained by dioling these are particularly preferable. The polyethylene glycol and / or its derivative has a molecular weight of 200 to 200,000, preferably 1,000 to 50,000. The addition amount is 0.05 to 5% by weight, preferably 0.1 to 1% by weight, based on the entire film. If it is less than 0.05% by weight, stretching becomes difficult, and if it exceeds 5% by weight, the film becomes stiff and the processability such as printing is deteriorated.

Therefore, as another means, the polyester is added to the polyester in order to increase the amount of the inorganic particles added to improve the hiding property and to contain a large number of cavities inside by the method described later. An incompatible thermoplastic resin (cavity-developing agent) is mixed. At that time, not all the inorganic particles are uniformly dispersed in the polyester, but the increased inorganic particles are made to exist around the cavities and the cavity developing agent, preferably in the cavity developing agent. As a result, even if the content of the inorganic particles is increased, the interface with the polyester is not increased, so that problems such as film strength and film formability are eliminated. In order to achieve this, the surface of inorganic particles such as titanium dioxide, calcium carbonate, and barium sulfate, which are commonly used, is subjected to water rehydration treatment to lower the surface energy, thereby increasing the affinity between the inorganic particles and the cavity developing agent. Improves that of polyester. Examples of the treating agent include silicon-based resins, siloxane-based resins, fluorine-based resins, silane coupling agents and titanate coupling agents, and more preferably those surface-treated with aromatic or aliphatic polymer compounds. Specifically, those that organically bond the inorganic particles and the cavity developing agent, such as polyvinyl pyridine, are preferable. However, it is not limited to this. Further, it becomes effective by using the inorganic particles treated in this way as a masterbatch pellet pre-kneaded with a void-forming agent. In the case where the pre-kneading is not carried out, the inorganic particles are all present in the polyester even if the surface treatment is carried out, so that the object of the present invention cannot be achieved. As another method, a laminated film may be used, and the amount of inorganic particles in the surface layer of the film may be larger than that in the central layer. In this case, the whiteness of the film is improved and the matte feeling is imparted, and a high-grade image is provided, especially because the content of the inorganic particles is increased in the surface layer.

The inorganic particles used in the present invention are not particularly limited. Examples include titanium dioxide, calcium carbonate, barium sulfate, silicon dioxide, aluminum oxide, talc, kaolin and the like. Further, these inorganic particles may be surface-treated as necessary. Examples of the treating agent include, but are not limited to, aluminum oxide, silicon dioxide, zinc oxide, silicon-based resin, siloxane-based resin, fluorine-based resin, silane coupling agent or titanate coupling agent, polyol or polyvinyl pyridine. Not something. In the present invention, it preferably contains a large number of cavities inside.
The method of containing the cavities is not particularly limited, but preferably an unstretched sheet obtained by mixing, melting, and extruding an incompatible thermoplastic resin (cavity-developing agent) in the polyester is at least obtained. By orienting it uniaxially,
This is a method in which the interface between the polyester and the void-developing agent is peeled off to obtain a large number of voids inside. The cavity-developing agent must be incompatible with the polyester described above.
Specific examples include polystyrene resins, polyolefin resins, polyacrylic resins, polycarbonate resins, polysulfone resins, cellulose resins, polyamide resins, and the like. In particular, polystyrene resins, polyolefin resins such as polymethylpentene and polypropylene are preferable.

The polymer mixture obtained by mixing the polyester of the present invention and an incompatible thermoplastic resin with the polyester is prepared by, for example, mixing chips of each resin, melt-kneading in an extruder, and then extruding and solidifying. Method, or a method in which both resins are kneaded in advance by a kneader and further melt-extruded by an extruder to solidify, or an incompatible thermoplastic resin is added to the polyester in the polyester polymerization step and dispersed by stirring. It can also be obtained by a method of melt-extruding and solidifying the obtained chips. The polymer obtained by solidifying (unstretched sheet) is usually in a non-oriented state or a weakly oriented state. Further, the thermoplastic resin incompatible with the polyester is present in the polyester in a form dispersed in various shapes such as a spherical shape, an elliptic spherical shape, or a thread shape.

The polymer mixture obtained by mixing the polyester of the present invention and an incompatible thermoplastic resin to the polyester is prepared by, for example, mixing chips of each resin, melt-kneading in an extruder, and then extruding and solidifying. Method, or a method in which both resins are kneaded in advance by a kneader to be melt-extruded and solidified by an extruder, or an incompatible thermoplastic resin is added to the polyester in the polyester polymerization step and dispersed by stirring. It can also be obtained by a method of melt-extruding and solidifying the obtained chips. It is possible to add a colorant, a light-proofing agent, a fluorescent agent, an antistatic agent, etc. to the polymer mixture depending on the application.

The resulting polymer mixture is further stretched between rolls having different speeds (roll stretch), stretched by gripping and expanding with a clip (tenter stretch) and stretched by expanding by air pressure (stretching). At least uniaxially oriented by, for example, inflation stretching). By the orientation treatment, peeling occurs at the interface between the polyester and the void-developing agent, and voids are developed. Therefore, the amount of the thermoplastic resin which is incompatible with the polyester and mixed with the polyester varies depending on the amount of the target cavities, but is 3% by weight to 40% by weight based on the whole polymer mixture,
It is preferably 8% by weight to 20% by weight. . If it is less than 3% by weight, there is a limit to increase the amount of cavities generated, and the desired flexibility, lightness, and drawability cannot be obtained. Conversely, 40
If it is more than 10% by weight, the heat resistance and strength of the polyester film are significantly impaired.

The conditions for orienting the polymer mixture are closely related to the formation of cavities. Therefore, the conditions for achieving the object of the present invention include, for example, the most commonly used sequential biaxial stretching step, in which a continuous sheet of the polymer mixture is roll-stretched in the longitudinal direction and then in the width direction. In the case of the sequential biaxial stretching method in which the tenter stretching is performed, it is as follows. In roll stretching, it is preferable to set the temperature to a biaxial stretching temperature of polyester + 30 ° C. or less and a draw ratio of 1.2 to 5 times in order to generate a large number of cavities. In the tenter stretching, the temperature is 100 to 14 in order to form a stable film without breaking.
It is preferable that the temperature is 0 ° C. and the magnification is 1.2 to 5 times. It is desirable to carry out the heat treatment condition after stretching by the method described below. After the stretching, the heat treatment must be performed at 200 ° C. or higher, preferably 220 ° C. or higher, more preferably 230 ° C. or higher. Further, at this time, heat fixation must be performed while relaxing by 3 to 8%. If it is less than 200 ° C or less than 3%, a void-containing film having a heat shrinkage rate at 150 ° C of less than 2%, preferably less than 1.7%, and more preferably less than 1.5% cannot be obtained.

The average porosity of the whole is preferably 40% by volume or less, preferably 30% by volume or less, and the average porosity is 4 or less.
A void-containing film of 0% by volume or more is difficult to manufacture because it frequently breaks during the stretching process, and the resulting film is not preferable because the surface strength and tensile strength are insufficient. The film of the present invention preferably has an apparent specific gravity of 1.
It is 0 to 1.3, more preferably 1.06 to 1.25. If it is less than 1.0, winding misalignment tends to occur when the paper is rolled and set in the printer. Also, 1.3
With the above, the hand-cutability from the cut becomes poor. The light transmittance of the film of the present invention is preferably 30% or less, more preferably 25% or less, more preferably 20% or less, and particularly preferably 17% or less. This is because the back side can be seen through when it exceeds 30%. Especially this is 40μm
The following can be said for a thin film having a thickness of preferably 30 μm or less, but a film having a thickness larger than that may be used.

The film of the present invention must have a whiteness of 75 or more, preferably 80 or more. When it is less than 75, the printed characters are unclear. . In the present invention, a so-called composite film in which a surface layer and a center layer are laminated may be used. The method is not particularly limited. However, from the viewpoint of productivity, it is most preferable to use a so-called co-extrusion method in which the raw materials for the surface layer and the central layer are extruded from different extruders, introduced into one die to obtain an unstretched sheet, and then oriented at least uniaxially. . In this case, the thermoplastic resin provided in the B layer is not particularly limited, and specifically,
Examples thereof include polystyrene resin, polyolefin resin, polyacrylic resin, polycarbonate resin, polysulfone resin, cellulose resin, polyamide resin and the like. However, polyester resins are preferred in the present invention. Moreover, you may contain an inorganic particle as needed. Further, the polyalkylene glycol and / or its derivative can be added to only the A layer or the B layer or both the A layer and the B layer. In this case, addition to the layer A makes it possible to improve the surface adhesiveness, water wettability, and the like.

Further, by providing a coating layer on the film surface, the wettability and adhesiveness of ink, coating agent and the like are improved. The compound constituting the coating layer,
Polyester resins are preferred, but in addition to these, compounds disclosed as means for improving the adhesiveness of ordinary polyester films such as polyurethane resins, polyester urethane resins and acrylic resins can be applied. As a method for providing the coating layer, a commonly used method such as a gravure coating method, a kiss coating method, a dip method, a spray coating method, a curtain coating method, an air knife coating method, a blade coating method, and a reverse roll coating method can be applied. As the step of applying, a method of previously applying to the surface of the mixed polymer before the orientation treatment, a method of applying to the surface of the uniaxially oriented cavity-containing film and further orienting it in the orthogonal direction, Any method such as coating on the finished film surface is possible.

The thus-obtained film has excellent concealing properties even though it is thin, so that characters can be seen clearly and the film strength,
It is a good base material for delivery slip paper with excellent film forming properties. Example 2 Next, an example of the present invention will be described. 1) Intrinsic viscosity of polyester Polyester was dissolved in a mixed solvent of phenol (6 parts by weight) and tetrachloroethane (4 parts by weight) and measured at 30 ° C.

2) Melt flow index of polystyrene resin Measured at 200 ° C. under a load of 5 kg according to JIS-K7210.

3) Apparent specific gravity The film was cut into a square of 5.00 cm × 5.00 cm and the thickness was measured at 50 points to obtain an average thickness of t μm.
The weight was calculated up to 0.1 mg to be wg, and the weight was calculated by the following formula.

[0020]

[Equation 1] 4) Average porosity of film Calculated by the following formula.

[0021]

[Equation 2] However,

[0022]

[Equation 3]

[0023]

[Equation 4] In the above equation, xi represents the weight fraction of the i component, and di represents the true specific gravity of the i component. The values of true specific gravity used in the calculations in the examples are polyethylene terephthalate 1.40, general-purpose polystyrene 1.05, and anatase-type titanium dioxide 4.2.
Was used.

5) Light transmittance According to JIS-K6714, Poic integrating sphere type H.264. T.
The light transmittance of the film was measured using an R meter (manufactured by Nippon Seimitsu Optical Co., Ltd.). The smaller this value, the higher the concealing property.

6) Tensile Strength of Film It was performed based on JIS-C2318.

7) Whiteness The whiteness was measured according to JIS-L1015-1981-B method using Nippon Denshoku Industries Co., Ltd. Z-1001DP.

8) Heat shrinkage rate A film having a width of 10 mm and a length of 250 mm is 200 m
Mark at m intervals and fix under a constant tension of 5 g, and mark intervals A
Measure Subsequently, the space B between the marks after being placed in an oven in an atmosphere of 150 ° C. for 30 minutes under no tension was determined, and the heat shrinkage rate was calculated by the following formula.

[0028]

[Equation 5]

Example 1 Polyester resin obtained by copolymerizing 75% by weight of polyethylene terephthalate resin having an intrinsic viscosity of 0.62 as a raw material with dimethyl terephthalate as a dicarboxylic acid component and butanediol and polytetramethylene glycol as a glycol component in a molar ratio of 85:15. 5% by weight of elastomer, 15% by weight of general-purpose polystyrene with a melt flow index of 2.0 g / 10 minutes, 5% by weight of anatase type titanium dioxide having an average particle size of 0.3 μm as the raw material of the A layer, and polyethylene as the raw material of the B layer. 60% by weight of terephthalate resin,
40 wt% of anatase type titanium dioxide was melt extruded from a T-die at 290 ° C. by separate twin screw extruders, electrostatically adhered and solidified on a cooling rotary roll, and each layer had B / A / B = 15. An unstretched sheet of a / 220/15 μm polymer mixture was obtained. Subsequently, the unstretched sheet was longitudinally stretched 3.5 times at 83 ° C. by a roll stretching machine, and then horizontally stretched 3.5 times at 130 ° C. by a tenter and then 23 times.
Heat treatment was carried out at 5 ° C. with 4% relaxation to obtain a polyester film containing a large number of cavities inside. Thickness is B / A
/B=1.5/22/1.5 μm. The void content of the entire obtained film was 20% by volume. Apparent specific gravity is 1.18, light transmittance is 15%, thickness is 25 μm,
The gloss was 28% whiteness 83, the tensile strength of the film in the longitudinal and transverse directions was 13/13 kg / mm ^{2, and the} heat shrinkage ratio was 1.1 / 0.7% in the longitudinal and transverse directions, respectively. Example 1
Solvent-based polyester adhesive Byron (manufactured by Toyobo Co., Ltd.) and polyurethane-based curing agent Takenate D110N (manufactured by Takeda Pharmaceutical Co., Ltd.) were mixed with the void-containing polyester film obtained in Step 2 such that the solid weight ratio was 250: 1. The coating agent was applied with a gravure coater. The thickness of the coating film after drying was 0.15 μm. When a water-based ink was printed on the surface of this coating film and a delivery slip was prepared by stacking 10 sheets, a good paper was obtained in which the underlying paper could not be seen through.

Comparative Example 1 A delivery slip sheet was obtained in the same manner as in Example 1 except that the amount of titanium dioxide in the layer B was changed to 5% by weight. Apparent specific gravity is 1.11, light transmittance is 32%, thickness is 25μ
m, the gloss was 75% whiteness 73, and the tensile strengths in the longitudinal and transverse directions of the film were 16 kg / mm ² .
The letters were unclear and not at a practical level.

Example 2 First, general-purpose polystyrene having a melt flow index of 2.0 g / 10 min and rutile titanium dioxide (TR made by Fuji Titanium) which had been subjected to silane coupling treatment with an average particle size of 0.3 μm.
-700S) was preliminarily kneaded at a weight ratio of 1: 1 with a twin-screw extruder at 240 ° C to prepare masterbatch pellets I. Next, a master batch pellet II was prepared in the same manner with a polyethylene terephthalate resin having an intrinsic viscosity of 0.62 and an anatase type titanium dioxide treated with alumina at a weight ratio of 95: 5. A mixture of this masterbatch pellet I and polyethylene terephthalate in a weight ratio of 20:80 was used as a raw material for layer A, and a masterbatch pellet was prepared.
II was used as the raw material for the B layer. At this time, the temperature of the extruder for the layer A was set to 250 ° C. at the position closest to the raw material feeding part, and gradually raised to 295 ° C. at the melting part. The kneading was carried out for about 10 minutes in the melting part, and the tip of the screw was kept at 290 ° C. After that, the melt line temperature was gradually lowered to finally reach 280 ° C. in the T-die. The temperature of the layer B was set so that the temperature of the extruder closest to the raw material charging part was 250 ° C., and the temperature was gradually raised to a maximum of 285 ° C. in the melting part. Knead for about 1 minute in the melting section,
The tip of the screw was set to 280 ° C. After that, the raw material is supplied to the melt line at the same temperature and T-
Immediately before the die, both sides of the layer A were joined and supplied to the T-die as they were. Then, electrostatically adhered and solidified on a cooling rotating roll, and each layer was B / A / B = 40/280/4.
An unstretched sheet of 0 μm polymer mixture was obtained. This time,
The T-die slit interval was 0.9 mm, and the average flow rate of the melt of the polymer mixture in that portion was 8.8 m / sec.
Subsequently, the unstretched sheet was rolled by a roll stretching machine at 83 ° C. for 3.
Longitudinal stretching of 5 times is performed, and subsequently, at 145 ° C. with a tenter, 3.
The film was transversely stretched 5 times and then heat-treated at 235 ° C. while being relaxed by 4% to obtain a polyester film containing a large number of cavities inside. The thickness was B / A / B = 4/30/4 μm. The porosity of the surface layer portion of the layer A of the obtained film was 2% by volume, and the whole was 19% by volume. The portion with few cavities was present from the surface layer to a depth of about 3 μm. The surface strength of the void-containing film obtained in this example was class 1. The cross section of the unstretched sheet of the polymer mixture of this example was observed by a scanning electron microscope. As a result, the average dispersed particle diameter of polystyrene in the central portion was 5.0 μm, while the dispersed particle diameter near the surface layer was The average was 0.7 μm. Further, the polystyrene existing at the interface between the A layer and the B layer was in the form of threads.

The apparent specific gravity is 1.16, the porosity of the surface layer of the A layer is 2% by volume, the average porosity of the whole is 19% by volume, the light transmittance is 10%, the thickness is 38 μm, the whiteness is 80, and the gloss is 5.
0%, tensile strength in the longitudinal and transverse directions of the film is 14/15 kg / mm ² respectively, and heat shrinkage is 1.2 / 0.6%
Met. The obtained film contained a large amount of titanium dioxide not only in polyethylene terephthalate, which is a cavity developing agent, but also around polystyrene and in polystyrene. Post-treatment was carried out in the same manner as in Example 1, and the same result was obtained when used. In addition, cellophane tape (Nichiban ┷
The surface layer was not peeled off even if it was quickly peeled off.

[0033]

INDUSTRIAL APPLICABILITY The void-containing polyester film of the present invention has the same lightness, flexibility, matteness and drawability as the void-containing polyester film obtained by using conventional polystyrene or polyolefin as a void-developing agent. In addition to having the above properties, it has an effect that it has high concealing property and good hand-cutting property even if it is thin as compared with the conventional film. Therefore, the void-containing polyester film of the present invention can be used as delivery slip paper.

Claims (3)

[Claims] 1. An inorganic particle and / or an incompatible thermoplastic resin is mixed with polyester and extruded,
Oriented at least uniaxially and has a thickness of 10 μm or more and 40 μm
Hereinafter, a polyester film for a delivery slip, which has a light transmittance of 30% or less and a whiteness of 75 or more. 2. An incompatible thermoplastic resin is mixed with polyester, melted, extruded, or even uniaxially oriented to have a large number of fine voids inside, and an apparent specific gravity of 1.0.
It is 1.3 or more and 1.3 or less, The polyester film for delivery slips of Claim 1 characterized by the above-mentioned. 3. The polyester film according to claim 1, which has a light transmittance of 20% or less.