JPH10119978A - Thermoplastic resin film for envelope window - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent clogging of a film and defective sticking due to meandering even in high-speed sticking by a method wherein for a thermoplastic resin film which is used for an envelope window, a film wherein the half-line of charge damping factor, an uneven thickness, and a heat-shrinking stress, of at least one surface of the film are specified values respectively, is used. SOLUTION: For a film for envelope window, the half-line of the charge damping factor of at least one surface of the film, is made 200sec or less by a measurement at 20 deg.C and which a moisture of 20% RH, conforming to JIS-L-1094 method. Also, a film with physical properties such as the deflected thickness in the longitudinal and lateral directions is 10% or less, and the average heat-shrink stress in the longitudinal and lateral directions, which is measured conforming to ASTM-D1504 method, is 2-20kg/cm<2> , is used. For such a film, a film of a thermoplastic resin such as a styrene based polymer, and a polyolefin based resin, is used, and preferably, a drawn styrene based resin film is used, and to this film, a release agent, a heat stabilizer, an ultraviolet ray absorbent, and an antioxidant can be mixed within a range wherein the characteristics are not spoiled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoplastic resin film used for an envelope window, particularly to a stretched polystyrene film.

[0002]

2. Description of the Related Art Conventionally, styrene-based films for envelope windows,
PVC-based films and polypropylene-based films have been used. Above all, a styrene-based stretched film has been used more than the high elastic modulus of the film. Windowed envelopes are made by applying a film cut to the desired length and width to an envelope having one or more openings with an adhesive. Film sticking is performed by a film sticking apparatus, which has conventionally been performed at a speed of 400 to 600 sheets / min. Recently, it is performed at a high speed of 800 to 1000 sheets / minute, and even 1500 sheets / minute. It is becoming.

[0003] For this reason, Japanese Patent Application Laid-Open No. 2-72050 discloses a styrene-based film formed by mixing a waxy anti-flecking agent in order to cope with an increase in the film sticking speed. The gazette discloses a styrene-based film in which a film is formed by mixing a granular anti-flecking agent to improve the slip property. However, the styrene-based films described in JP-A-2-72050 and JP-A-2-72051 can improve the scratching and friction of a film passing at high speed in an envelope film sticking apparatus, and can reduce film dust. Although generation is suppressed, sticking of the film in the machine due to static electricity generated by friction between the film and the machine cannot be prevented. For this reason, film clogging occurs, and the machine must be stopped and the film must be removed each time, resulting in a significant decrease in productivity.

On the other hand, in the case of a film having a large thickness deviation, there is a problem that the film is meandered due to the high-speed film passage and a waving phenomenon occurs, thereby making it impossible to apply the film accurately.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to
An object of the present invention is to provide a thermoplastic resin film for an envelope window which does not cause clogging due to sticking of a film in a machine and poor sticking due to meandering of a film even in window sticking at a high speed of 00 to 1500 sheets / minute. .

[0006]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and as a result, have reached the present invention. That is, the film of the present invention has a half-time of at least one-side charge decay rate of 200 seconds or less measured at 20 ° C. and 20% RH in accordance with the JIS-L-1094 method, and the uneven thickness is vertical. , 10% or less in both the horizontal and
The heat shrinkage stress measured according to the STM-D1504 method has a vertical and horizontal average of ² to 20 kg / cm ² . Hereinafter, the contents of the present invention will be described.

The half-life of the charge decay rate of at least one side of the film of the present invention must be 200 seconds or less as measured at 20 ° C. and 20% RH according to the JIS-L-1094 method, and is preferably. It is 150 seconds or less. If the half-time of the charge decay rate of the film is more than 200 seconds on both sides of the film, the film sticks to the machine due to the generated static electricity when the window is applied at a high speed of 1000 to 1500 sheets / minute, and the film is clogged. Each time, the machine must be stopped and the film removed, which significantly reduces productivity. Under such characteristics, the film of the present invention is disclosed in JP-A-2-72050 and JP-A-2-720.
This is significantly different from the styrene-based film described in JP-A-51. That is, these prior arts focus on improving the slipperiness, and do not have the concept of antistatic. In addition, the films described in these prior arts have actually low antistatic properties due to the type of anti-flecking agent, the manner of application, and the like, and the half-time of the charge decay rate measured under the above conditions far exceeds 200 seconds. It seems to be.

The antistatic property is evaluated by methods such as surface resistance measurement, charge potential measurement, and charge decay measurement, but the measurement of surface resistance depends on the electrode structure, applied voltage, contact force with the sample surface, and the like. Is big. For this reason, in the present invention, the antistatic property is defined by the electrification decay measurement with little fluctuation. Although the antistatic property depends on measurement conditions such as temperature and humidity, the evaluation criteria were a temperature of 20 ° C. and a humidity of 20% RH in consideration of a winter use environment in which antistatic property is easy.

The film of the present invention is required to have a thickness deviation in the vertical and horizontal directions of 10% or less, as determined by the method described below. In this case, the thickness deviation is preferably a lower value, more preferably 8% or less. If it is larger than 10%, 1000-1
When a window is applied at a high speed of 500 sheets / minute, the film meanders, and the film is not fed straight out, so that there is a problem that the window cannot be applied accurately.

[0010] The film of the present invention is ASTM-D150
Heat shrinkage stress measured according to Method 4 is 2 to 20 kg / c
m^TwoAnd desirably 2.5 to 18 kg /
cm ^TwoIt is. 2kg / cm^TwoLess than one has sufficient orientation
Low rigidity and easy to meander when pasting
No. Also, 20kg / cm^TwoThe larger ones are over-distributed.
Due to heat shrinkage during drying after application with adhesive and wrinkles
Easy to grow.

As the film of the present invention, a film of a thermoplastic resin such as a polyolefin resin such as a styrene polymer or a polypropylene resin or a vinylidene chloride resin is used. Above all, a stretched styrene resin film is preferred. As the styrene polymer, general-purpose polystyrene (GPPS), so-called high-impact polystyrene (HIPS), styrene-butadiene block copolymer (SBBC), or a combination of two or more of these resins is used.

[0012] In addition to the above resins, the film of the present invention
Release agents, heat stabilizers, ultraviolet absorbers, antioxidants, coloring agents, plasticizers, oligomers, other conventional additives, etc.
It is also possible to mix them within a range that does not impair the properties of the present invention. The thickness of the film of the present invention is preferably 0.0
05 to 0.1 mm, more preferably 0.01 to 0.08
mm.

Next, a method for producing the film of the present invention will be described. The film of the present invention can be obtained by stretching the above resin by an inflation method or a tenter method.
For example, while the resin is melt-kneaded in an extruder, a film is formed by a T-die, and in the case of a sequential biaxial stretching method in which longitudinal stretching is performed between rolls and transverse stretching is performed by a tenter method, the stretching temperature is set to Select from the range of Vicat softening point of the target resin + 20 ° C to Vicat softening point + 40 ° C.
It is desirable that the ratio be 4 times, and that the ratio of (longitudinal stretching ratio / lateral stretching ratio) be kept in the range of 1 to 1.3. When the film is stretched at a temperature lower than the Vicat softening point + 20 ° C., the heat shrinkage stress becomes too large. On the other hand, when the film is stretched at a temperature higher than the Vicat softening point + 40 ° C., the heat shrinkage stress becomes low, and the desired film cannot be obtained. It is important that the stretching is performed at a relatively slow stretching in the range of 500% / min to 1000% / min. Particularly, in the sequential biaxial stretching method of the tenter method, local stretching occurs at a high stretching speed, and the thickness of the film becomes uneven. Only by stretching slowly over time, uniform stretching becomes possible and uneven wall thickness is reduced.

The film of the present invention has been subjected to an antistatic treatment in order to achieve the above antistatic properties. As the antistatic treatment of plastic, a method of applying an antistatic agent is generally used. Examples of the antistatic agent include anionic surfactants such as sulfonate and phosphate ester salts, cationic surfactants such as quaternary ammonium salts, imidazoline-type, betaine-type and alanine-type amphoteric surfactants, and polyoxygen-containing surfactants. Ethylene alkyl ether type, polyoxyethylene alkyl phenol ether type and polyoxyethylene alkylamine type nonionic surfactants have been raised. Among them, amphoteric surfactants have been shown to exhibit stable antistatic properties even under dry conditions in winter. Agents and nonionic surfactants are preferred. These can be used alone or in combination of two or more kinds, but at 20 ° C. and a humidity of 20% RH.
In order to have a specific charge decay rate of 200 seconds or less under the above conditions, it is preferable to use a combination of two or more of these.

The method of applying the antistatic agent is generally classified into a surface coating type and a kneading type. In the case of the envelope window film of the present invention, it is necessary to prevent static electricity generated by friction with the film sticking machine from leaking. Since surface conduction is an important factor, a surface coating type is preferable. In the case of the surface coating type, a solution of the antistatic agent diluted with a suitable solvent such as water or alcohol is applied to the surface by a method such as spraying, and the solvent is dried and removed to form a thin film of the antistatic agent on the surface. Let it form. The amount of the antistatic agent to be applied can be appropriately selected depending on the type of the film and the type of the antistatic agent as long as the above antistatic property can be achieved. / M ² .

The film according to the present invention has the characteristics of a conventional envelope window film, and further has a specific antistatic property, uneven thickness, and heat shrinkage stress so that the envelope can be produced at a high speed of 1,000 to 1500 sheets / minute. It is also suitably used in the window sticking step.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION

[Method for Measuring and Evaluating Physical Properties of Film] The method for measuring and evaluating the film in the present invention is as follows. (1) Charge decay rate According to the JIS-L-1094 method, the half-life was determined by measuring with a static neo nest meter manufactured by Shisido Electrostatic Co., Ltd. under the following conditions.

Measurement temperature: 20 ° C. Measurement humidity: 20% RH Applied voltage: 10 KV Rotation speed: 1550 rpm Measurement sample 32 mm × 32 mm Electrode-sample distance: 20 mm (2) Uneven thickness Using a dial gauge, the width (width) of the film ) Direction and the flow (longitudinal) direction, the thickness was measured at 1 cm intervals, and the average value was calculated. The value of 1/2 of the difference between the maximum value and the minimum value is
The average in the width direction and the flow direction was calculated by expressing the value in percentage with respect to the previously calculated average value. (3) Heat shrinkage stress According to ASTM-D1504, the average value of the vertical and horizontal peak stress values in a silicon hot water at a temperature of Vicat softening point of the film + 30 ° C was determined. (4) Suitability for high-speed window sticking One window frame of 50 mm x 90 mm, 105 mm x 2
A 60 × 90 mm film was stuck inside the window frame of a 35 mm (Western type 4) kraft paper postal envelope. The window pasting machine used was HELIOS 380RD manufactured by Winkler Co., Ltd., and performed at a speed of 1500 sheets / min in an environment of 20 ° C. and 20% RH. The adhesive used was a vinyl acetate adhesive (H tack X10, Hirano Chemical Laboratory Co., Ltd.), and the temperature of the dry hot air was 120 ° C. 5000 films of envelopes were attached, and the number of film clogging in the machine due to static electricity was determined. In addition, the number of sheets having wrinkles on the film surface after application to the window was determined. The number of defective sticking positions was determined as the number of defective sheets that deviated from the original sticking position by 1 mm or more as defective. [Resin Used and Antistatic Agent] The resins used in Examples and Comparative Examples are shown in Table 1. Table 2 shows antistatic agents used in Examples and Comparative Examples, and Table 3 shows other surface treatment agents. [Film Production Method] A basic film production method used in the following Examples and Comparative Examples will be described.

The target mixture is supplied to a single-screw extruder having a diameter of 40 mmφ and extruded into a sheet from a T-die attached to the tip of the extruder while being melt-kneaded at the Vicat softening point of the target resin + 80 ° C. The extruded sheet is brought into contact with a cooling roll, then fed into a heating roll, and stretched under tension in the extrusion direction (longitudinal direction). Subsequently, the sheet is fed into a tenter while keeping the temperature, and both ends of the sheet are gripped by grips, and the sheet is oriented at a predetermined speed in a direction perpendicular to the extrusion direction (transverse direction). The stretching conditions for the stretching rolls are as follows: the stretching temperature is the Vicat temperature of the target resin + 15 ° C. to 45 ° C.
Stretching magnification 2 to 4 times, stretching speed 300 to 2000% / mi
n. The stretching conditions in the tenter are as follows: the stretching temperature is the Vicat temperature of the target resin + 15 ° C. to 45 ° C .;
~ 4 times, stretching speed 300 ~ 2000% / min,
(Longitudinal stretching ratio / transverse stretching ratio) = 1 to 1.3. A film with a target thickness of 30 microns.

[0020]

Example 1 and Comparative Example 1 The present Example and Comparative Example are experiments conducted by paying attention to the charge decay rate of the film. Therefore,
The same film was used. Film A was used among the films formed according to the target resin and production conditions shown in Table 4 and a surface treating agent was applied to one or both sides of the film so as to have a specified amount as shown in Table 5, and dried at 100 ° C. with hot air. Dried on board. Various physical properties of the obtained film were measured by the above measuring methods and evaluated by the above evaluation methods. Table 5 also shows the results.

Experiment Nos. 1 to 5 are examples, and are films in which the half time of the charge decay rate of at least one side is 200 seconds or less. Experiment Nos. 6 to 10 are comparative examples, in which 6 has no surface treatment agent, and 7 has silicon dioxide particles applied as a slipping agent. 7 to 9 were coated with a surface treatment agent,
It is a film in which the half time of the charge decay rate is 200 seconds or more on both sides.

According to the results shown in Table 5, the film of the present invention in which the half-time of the charge decay rate of at least one side is 200 seconds or less is excellent at 1500 sheets / min, and is excellent in sticking to an envelope window, and the film is stuck in a machine. There is no clog. In contrast,
Regarding the untreated film, the lubricant alone, or the film coated with an antistatic agent, the film whose half-time of the charge decay rate was 200 seconds or more on both sides was frequently clogged due to sticking of the film in the machine.

[0023]

Example 2 and Comparative Example 2 The present example and comparative example are experiments conducted with attention paid to uneven thickness and heat shrinkage stress of the film. For this reason, the surface treatment prescription was unified. Using the target resin shown in Table 4 and a film formed in accordance with the manufacturing conditions, the same surface coating agent as in Experiment No. 2 of Example 1 was applied to the film surface, and the physical properties of the obtained film were measured by the above-mentioned measuring methods. And evaluated by the above evaluation method.

Experiment Nos. 11 to 14 are examples, and are films having an uneven thickness of 2 to 10% and a heat shrinkage stress of ^{2 to 20} kg / cm ² . Experiment Nos. 15 and 16 are comparative examples with uneven thickness of 10
% Film. Experiment Nos. 17 and 18 are comparative examples in which the film has a heat shrinkage stress of 20 kg / cm ² or more. Experiment No. 19 is also a comparative example in which the heat shrinkage stress is 2 kg /
It is a film of less than cm ² .

According to the results in Table 6, the uneven thickness exceeds 10%.
Of sticking position due to meandering of film
No. The heat shrinkage stress is 20 kg / cm.^TwoMore than
This was due to the occurrence of wrinkles on the film surface due to heat shrinkage after drying.
Heat shrinkage stress 2kg / cm^TwoThe lower one is filled
Poor rigidity and poor sticking due to meandering of the film
High rate. The uneven thickness is less than 10% and the heat shrinkage
Power is 2-20kg / cm ^TwoFilm at high speed window pasting
The film at the time of feeding is sent straight without meandering
Window can be applied accurately, and wrinkles after pasting and drying
Nor.

From the above results, the half-life of the charge decay rate of at least one surface of the film is 200 seconds or less measured at 20 ° C. and 20% RH according to the JIS-L-1094 method, and 10% uneven thickness in both vertical and horizontal directions
The average of heat shrinkage stress and width measured according to ASTM-D1504 method is 2 to 20 kg / cm.
² , a styrene-based stretched film characterized by the fact that
It is clear that it can be suitably used also in a high-speed window sticking process of 1000 to 1500 sheets / min for envelope windows.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

[Table 3]

[0030]

[Table 4]

[0031]

[Table 5]

[0032]

[Table 6]

[0033]

Since the present invention has a specific antistatic property, uneven wall thickness, and heat shrinkage stress, clogging due to film sticking in a machine even in a high-speed window sticking process of 1000 to 1500 sheets / minute, window sticking. Provided is a film for an envelope window which is free from displacement and wrinkles on a window-attached film surface.

Claims (2)

[Claims] 1. A half-life of at least one side of a charge decay rate at 20 ° C. and a humidity of 20 according to the JIS-L-1094 method.
% Less than 200 seconds measured at RH, and uneven thickness is vertical,
It is 10% or less in both lateral directions, and the average of the heat shrinkage stress measured in accordance with the ASTM-D1504 method is 2
A thermoplastic resin film for an envelope window, which has a weight of from about 20 kg / cm ² to about ²⁰ kg / cm ² . 2. The thermoplastic resin film for an envelope window according to claim 1, wherein the film is a stretched polystyrene film.