KR100964295B1 - Heat shrinkable polyester film and preparation method thereof - Google Patents

Abstract

PURPOSE: A heat-shrinkable polyester film is provided to enable labeling without complex process and to use as a material for labeling and packing. CONSTITUTION: A method for manufacturing heat-shrinkable polyester film comprises: a step of fusing a composition for forming a polyester film at 220-285°C and performing extrusion molding to prepare a molten sheet; a step of cooling and solidifying the molten sheet to obtain a freeze-solidified polyester undrawn sheet; and a step of extending the undrawn sheet.

Description

Heat-shrinkable polyester film and manufacturing method thereof {HEAT SHRINKABLE POLYESTER FILM AND PREPARATION METHOD THEREOF}

The present invention relates to a heat-shrinkable polyester film and a method for producing the same, and more particularly, to a heat-shrinkable polyester film and a method for producing the same having excellent mechanical strength and labeling property in the longitudinal direction as the main shrinkage direction.

Heat-shrinkable films are generally used for various purposes such as labeling of plastics, glass bottles, batteries or electrolytic capacitors, and whole coatings of packaging containers, as well as for packaging or tight packaging for stationery or several containers. As such a heat-shrinkable film, a polyvinyl chloride film, a polystyrene film, a polypropylene film, and the like are used, and in recent years, many polyester films are also used.

In order to be used for various packaging materials or labels, polyester-based heat-shrinkable films are not only basic properties such as heat resistance, chemical resistance, weather resistance, and printing characteristics, but also container sealing properties, heat shrink uniformity, running characteristics and crack resistance in the longitudinal direction, etc. Is required.

However, the conventional polyester heat-shrink film used for labeling or coating has a main direction in which the main stretching direction is a width direction rather than a length direction of the roll, and thus is mainly contracted in the stretched width direction. Mechanical properties were structurally weak. That is, in the conventional heat shrink film, since the main shrinkage direction is in the width direction (lateral direction), the strength in the longitudinal direction in the winding or post-processing process is low, and the running characteristics in the longitudinal direction are easily broken even in the slight tension change. Fell significantly.

In addition, depending on the application, the heat shrink film used for the battery and medical ampoule has a small label size due to the characteristics of the product, and is applied to the container by applying an adhesive to the film and then subjected to shrinkage by applying hot air. For the same reason, the widthwise heat-shrink film undergoing seaming and shooting processes cannot be used for batteries and medical ampoules. In addition, since the batteries and medical ampoules undergo high temperature storage conditions of 60 to 70 ° C., the shrink labels must have good thermal stability at 70 ° C.

Patent No. 517064 describes a method for producing a heat-shrinkable polyester film having excellent high-speed mounting ability and shrinkage finish as a film shrinking in the longitudinal direction using a polyester comprising a dicarboxylic acid component and a diol component. It is starting. However, this method also has a high shrinkage at 70 ° C., therefore, there is still a need for improvement in thermal stability for application to batteries and medical ampoules.

Accordingly, an object of the present invention is to be able to label without complicated processes such as seaming in a later process, and to produce a heat-shrinkable polyester film having excellent mechanical strength, labeling property, and thermal stability with respect to the longitudinal direction of the film, which is the main shrinkage direction, and a preparation thereof. To provide a way.

The present invention also aims to provide a container packaging or labeling method using the heat-shrinkable polyester film.

The present invention also aims to provide a packaging material or label comprising the heat-shrinkable polyester film.

In order to achieve the above object, ethylene terephthalate is included as a main repeating unit, the in-plane retardation is 4500 nm or more, the shrinkage in the longitudinal direction, which is the main shrinkage direction of the film after 20 seconds at 90 ℃ hot water is at least 20% After 60 seconds in hot water at 70 ℃ provides a heat-shrinkable polyester film, characterized in that the shrinkage in the longitudinal direction of the main shrinkage direction of the film is 10% or less.

The present invention also comprises the steps of melting and extrusion molding the polyester-based film-forming composition containing dicarboxylic acid and glycol as a main component at a temperature of 220 to 285 ℃ to prepare a melt sheet; Cooling and solidifying the molten sheet to prepare a cooled solidified polyester unstretched sheet; And stretching the non-stretched sheet by a roll-to-roll speed difference at a total draw ratio of 4.8 to 6 times the length direction of the sheet.

The present invention also comprises the steps of coating the heat-shrinkable polyester film with an adhesive to produce a film roll; Printing and die-cutting the roll of film applied with the adhesive; It provides a container packaging or labeling method comprising the step of continuously unwinding the printed film roll to wrap the container and heat shrink.

The present invention also provides a packaging or label comprising the heat-shrinkable polyester film.

Heat-shrinkable polyester film according to the present invention is a film shrinking in the longitudinal direction, excellent transparency, printing properties, solvent adhesion, stretching processability, shrinkage characteristics, mechanical strength and labeling properties in the longitudinal direction, containers, batteries It is useful for labels or packaging materials, and particularly, because of its excellent thermal stability, it can be usefully applied to labels for batteries, labels for medical ampoules, and the like.

In addition, after a predetermined operation such as printing in the post-processing process, labeling is possible without a complicated process such as sleeve production through a separate seaming process.

1 is a schematic diagram schematically showing a processing process for a conventional shrinkage film in the width direction.
2 is a process diagram schematically showing a processing process for a heat-shrinkable polyester film according to the present invention.

Conventionally, when labeling a battery or a medical ampoule, a method of mainly applying a film whose main shrinkage direction is a longitudinal direction (longitudinal direction) is applied to the container by applying an adhesive to the film, and then attaching and contracting the container by applying hot air. Mainly used. However, battery labels are frequently exposed to high temperatures during distribution and consumer use, and in particular, medical ampoules are exposed to high temperatures of 60 to 70 ° C. during the sterilization process. High labeling frequently occurred.

Thus, in order to prevent label opening at a high temperature, the heat-shrinkable polyester film according to the present invention uses an unstretched sheet containing ethylene terephthalate as a main component at a total draw ratio of 4.8 to 6 times in the longitudinal direction by the peripheral speed difference between rolls. Stretching induces stretching crystallization to control shrinkage at 70 to 90 ° C.

As a result, the heat-shrinkable polyester film according to the present invention exhibits excellent labeling property even at high temperature with a shrinkage rate of 20% or more in the longitudinal direction, which is the main shrinkage direction of the film, after being maintained at 90 ° C. for 10 seconds in hot water. After holding for 60 seconds at 60% of the shrinkage in the longitudinal direction of the film after labeling shows excellent thermal stability at 60 to 70 ℃.

In addition, the heat-shrinkable polyester film according to the present invention has an in-plane retardation of 4500 nm or more, preferably 4500 to 4800 nm. By having such high in-plane retardation, excellent mechanical strength can be exhibited, and stretched crystallization can be induced to induce thermal stability at 70 ° C. Specifically, the polyester film has a breaking strength in the longitudinal direction of 22 kgf / mm ² The elongation at break in the longitudinal direction is 80% or less.

The heat-shrinkable polyester film according to the present invention having the above characteristics includes ethylene terephthalate as a main repeating unit, specifically 60 to 97 mol% of ethylene terephthalate repeating units; And a polyester resin comprising 3 to 40 mol% of repeating units derived from an acid component such as terephthalic acid, naphthalenedicarboxylic acid or a mixture thereof and a branched alkylene glycol component having 3 or more carbon atoms.

The polyester resin used in the heat-shrinkable polyester film as described above includes within the range repeating units derived from an acid component such as terephthalic acid, naphthalenedicarboxylic acid or a mixture thereof and a branched alkylene glycol component having 3 or more carbon atoms. If there is no fear that the cracking phenomenon occurs after labeling due to a sharp increase in stretch crystallization, the crystallinity of the film is excessively impaired, the heat resistance is lowered, or the thermal stability at 70 ° C. is lowered.

It is preferable that the heat-shrinkable polyester film which concerns on this invention is 12-75 micrometers in thickness. Excellent stretching uniformity when the film has a thickness in the above range, excellent heat shrink uniformity, ink adhesion, moisture and gas barrier properties, crack resistance, fracture resistance, etc., especially when used for labels or packaging, especially for batteries Excellent thermal stability when used as labels for labels and medical ampoules.

The heat-shrinkable polyester film according to the present invention comprises the steps of melting and extruding a polyester film-forming composition comprising dicarboxylic acid and glycol at a temperature of 220 to 285 ° C. to produce a molten sheet; Cooling and solidifying the molten sheet to prepare a cooled solidified polyester unstretched sheet; And stretching the undrawn sheet to a total draw ratio of 4.8 to 6 times using a stretching method in the longitudinal direction giving a circumferential speed difference between rolls.

Examples of the dicarboxylic acid include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid and orthophthalic acid; Aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and decanedicarboxylic acid; Alicyclic dicarboxylic acid; And esterified products thereof.

Ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, etc. may be used as the glycol.

In addition, the polyester film-forming composition may include a branched alkylene glycol having 3 or more carbon atoms, specifically 1,2-octanediol, 1,3-octanediol, 2,3-butanediol, 1,3 -Butanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2-butyl-2-ethyl-1,3-propanediol, 2,2-diethyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,1-dimethyl-1,5-pentanediol and the like can be used.

In addition, the composition for forming a polyester film may include various additives such as a polymerization catalyst, a dispersant, an electrostatic agent, an antiblocking agent, and other lubricants within a range that does not impair the effects of the present invention.

The production method according to the invention may optionally further perform the step of trimming both ends prior to the stretching step.

In the stretching step, it is preferable that the total stretch rate in the longitudinal direction of the sheet is 4.8 to 6 times, preferably 4.8 to 5.4 times, with respect to the unstretched polyester sheet.

Conventional widthwise heat shrink film realizes shrinkage characteristics at 70 ° C. through heat treatment in the tenter using the tenter method. However, the polyester film according to the present invention is a shrinkage film in the longitudinal direction, and is manufactured by a method of stretching by a roll speed difference between rolls, and therefore, a conventional heat treatment method cannot be used, and heat shrinkage characteristics are particularly suitable for the purpose of the present invention. In order to realize the drawing, it must be drawn at a high longitudinal drawing ratio of 4.8 to 6 to induce drawing crystallization.

The stretching step of giving a circumferential speed difference between the rolls is one or two or more separate sections, and the stretching step is performed two or more times in a separate section. It is preferable to make necking higher than the circumferential speed of the stretching roll of to prevent necking.

In addition, the stretching process is preferably carried out at the temperature of the roll Tg + 10 ℃ to Tg + 30 ℃ (Tg is the glass transition temperature), and the temperature of the radiator heater 400 to 750 ℃.

The film made by this stretching method has improved leveling properties, high breaking strength in the longitudinal direction, and thus improves breaking characteristics, and has excellent thermal stability at 70 ° C.

Accordingly, the present invention also provides a label or packaging material comprising the heat-shrinkable polyester film.

For example, when applied for a label, the heat-shrinkable polyester film according to the present invention, since the main shrinkage direction is in the longitudinal direction, the process of wrapping the film while winding the film in a continuous process after the printing process, the process of heat shrink can be made continuously It is possible to label simply. That is, the heat-shrinkable polyester film according to the present invention does not need a seaming process for manufacturing a sleeve roll, and can be labeled in a simple and continuous process, thereby greatly improving productivity.

The present invention also provides a container packaging or labeling method using the heat-shrinkable polyester film.

Specifically, the container packaging or labeling method, the step of preparing a film roll by applying a heat-shrinkable polyester film with an adhesive; Printing and die cutting the film roll coated with the adhesive; And continuously unwinding the printed film roll to heat shrink while wrapping the container.

1 is a schematic diagram schematically showing a packaging process using a conventional shrinkage film, Figure 2 is a process diagram schematically showing a packaging process using a heat-shrinkable polyester film according to the present invention.

As shown in Figure 1 and 2, in the case of the conventional shrinkage film after the printing process has to go through a labeling process for slitting, sleeve seaming, cutting, shooting and heat shrink, whereas the longitudinal shrinkage film according to the present invention is a sleeve roll There is no need for a seaming process, so labeling in a simple and continuous process can greatly improve productivity.

Hereinafter, although an Example and a comparative example are given and demonstrated this invention, this invention is not limited to this.

Production Example  1: 2,2-dimethyl-1,3- Propanediol  Preparation of Copolyester (Resin A)

To 100 mol parts of dimethyl terephthalate, 130 mol parts of ethylene glycol and 30 mol parts of neopentyl glycol were charged to an autoclave equipped with a stirrer and a distillation column, and 0.07% by weight of manganese acetate was added to dimethyl terephthalate as a transesterification catalyst The reaction was carried out while removing the byproduct methanol while raising the temperature to 220 ℃.

When the transesterification reaction was completed, 0.07 wt% of silica having an average particle diameter of 0.28 μm was added to dimethyl terephthalate, and 0.4 wt% of trimethyl phosphate was added as a stabilizer. After 5 minutes, 0.035% by weight of antimony trioxide and 0.005% by weight of tetrabutylene titanate were added as a polymerization catalyst, followed by stirring for 10 minutes. Subsequently, the reaction product was transferred to a second reactor equipped with a vacuum equipment, and then gradually reduced in pressure while heating up to 285 ° C., and then polymerized for about 210 minutes to give 2,2-dimethyl-1,3 having an ultimate viscosity of 0.68 dL / g. Propane-diol copolyester was obtained. The copolymer obtained was analyzed by gas chromatography, and the content of the repeating unit derived from 2,2-dimethyl-1,3-propane-diol accounted for about 20 mol% of the total glycol component.

Production Example  2: Of polyethylene terephthalate (resin B)  Produce

A polyethylene terephthalate having an intrinsic viscosity of 0.72 dL / g was obtained by following the same procedure as in Preparation Example 1, except that 180 mol parts of ethylene glycol was used as the glycol component with respect to 100 mol parts of dimethyl terephthalate.

Example  1 to 3 and Comparative example  One: Heat shrinkability Polyester  Manufacture of film

The resins A to B obtained in Production Examples 1 to 2 were mixed at the ratios shown in Table 1 below, melted at 280 ° C., extruded from a T die, and then quenched on a cooling roller to obtain an unstretched sheet. After the obtained non-stretched sheet was heated through a heating roll, the longitudinal stretching process by the circumferential speed difference between the rolls consisting of three sections was carried out at the draw ratio shown in Table 1 below, and the heat shrinkage having a thickness of 50 μm mainly contracted in the longitudinal direction was performed. Each obtained polyester film was obtained.

In Table 1 below, the blending ratio (wt%) of each resin constituting the heat-shrinkable polyester film obtained from Examples 1 to 3 and Comparative Example 1, the ratio of the repeating units, and the stretching ratio are shown.

Resin compounding ratio (% by weight) Repeat unit composition ratio (mol%) Longitudinal draw ratio A B NPG EG Example 1 100 0 20 80 5.0 Example 2 100 0 20 80 6.0 Example 3 70 30 14 86 5.5 Comparative Example 1 100 0 20 80 3.0 Resin A: Copolyester of neopentyl glycol and ethylene glycol
Resin B: Polyethylene Terephthalate
EG: ethylene glycol
NPG: neopentyl glycol

The heat-shrinkable polyester films in Examples 1 to 3 and Comparative Example 1 were subjected to performance evaluation as a heat shrinkable film as follows, and the results are shown in Table 2 below.

(1) film strength and elongation

Measured according to ASTM D 288, the film produced using an universal testing machine (UTM, model name 6021) manufactured by INSTRON (UTM, model name 6021) after cutting to about 100 mm in length, 15 mm in width, the interval between the chuck (50) It was attached so as to make a mm, and it pulled at the speed | rate of 200 mm / min of tensile velocity, and measured the breaking strength at break (kg / mm <2>) and elongation at break (%), respectively.

(2) in-plane phase difference

The in-plane phase difference (unit: nm) in wavelength 590 nm was measured using the phase difference measuring device (MC-29033, the Otsuka Instrument Co., Ltd., Japan).

(3) 70 ℃ heat shrink rate

The film is cut into a width of 15 mm and a length of 300 mm with respect to the direction to be measured, and heat treated for 60 seconds in a constant temperature bath maintained at 70 ° C., and then the length (L) of the film is measured. Was calculated.

(4) 90 ℃ heat shrink rate

The film is cut into a width of 15 mm and a length of 300 mm with respect to the direction to be measured, heat treated for 10 seconds in a constant temperature bath maintained at 90 ° C., and then the length (l) of the film is measured. Was calculated.

(5) Labeling evaluation

In order to determine the uniform shrinkage of the prepared heat-shrinkable polyester film, after printing a grid such as grid paper, the battery was labeled using the process of FIG.

For evaluation of labeling, the label has a hot air nozzle in multiple stages up and down on the tunnel wall, the nozzle can be opened and closed as needed, and the label shrinks when it passes through the hot air tunnel which is designed to rotate the battery while passing through the tunnel. The condition was evaluated.

- Evaluation standard

OK: If the appearance is beautiful due to uniform shrinkage after shrinkage

NG: When non-uniform shrinkage occurs, such as shrinkage curl, print pull, or label fold

(6) gaping label

After the labeling test in the above (5), the label flaring phenomenon was observed by visual observation after storage for 7 days at 70 ℃ oven. In (5), the label phenomena were also identified for the labels in which the defect occurred when the labeling property was evaluated.

- Evaluation standard

Good: no label splay is visually observed

Poor: Label flare is visually observed

Analysis item Example 1 Example 2 Example 3 Comparative Example 1 Breaking Strength (MD) kg / mm ² 30.2 33.5 31.2 15.6 Breaking Strength (TD) kg / mm ² 5 5 5 5 Elongation at Break (MD)% 45 27 35 95 Elongation at Break (TD)% 550 580 550 450 In-plane phase difference 4600 5400 5200 3200 Heat shrinkage
% MD at 70 ℃, 60 seconds 5 3 4.5 55 TD at 70 ℃, 60 seconds One One One One MD at 90 ℃, 10 seconds 43 35 40 65 TD at 90 ℃, 10 seconds 2 2 2 2.5 Labeling property OK OK OK OK Label flapping Good Good Good Bad

In Table 2 above, MD and TD are in the longitudinal and width directions, respectively.

As shown in Table 2, the heat-shrinkable polyester film of Examples 1 to 3 prepared in accordance with the present invention, the breaking strength and elongation at break in the longitudinal direction of the main shrinkage direction, respectively 30 kg _f / mm ² or more As compared to the polyester film of Comparative Example 1 exhibited improved mechanical properties. In particular, in the heat-shrinkable polyester film according to the present invention, no label spreading was observed even after labeling.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, It is to be understood that the invention may be practiced within the scope of the appended claims.

Claims (6)

Ethylene terephthalate is included as a main repeating unit, stretched at a total draw ratio of 4.8 to 6 times in the longitudinal direction, the in-plane retardation is 4500 nm or more, the longitudinal direction is the main shrinkage direction of the film after holding for 10 seconds in 90 ℃ hot water The shrinkage ratio of is 20% or more, the heat shrinkable polyester film characterized in that the shrinkage in the longitudinal direction of the main shrinkage direction of the film is 10% or less after holding for 60 seconds in 70 ℃ hot water. delete The method of claim 1,
The polyester film has a breaking strength in the longitudinal direction of 22 kgf / mm ² The elongation at break of the longitudinal direction is 80% or less, The heat shrinkable polyester type film characterized by the above-mentioned. Preparing a melted sheet by melting and extrusion molding a polyester-based film forming composition containing dicarboxylic acid and glycol as a main component at a temperature of 220 to 285 ° C;
Cooling and solidifying the molten sheet to prepare a cooled solidified polyester unstretched sheet; And
Drawing the unstretched sheet by the circumferential speed difference between rolls at a total draw ratio of 4.8 to 6 times the length direction of the sheet.
The manufacturing method of the heat-shrinkable polyester film of Claim 1 or 3 containing. Preparing a film roll by applying the heat-shrinkable polyester film according to claim 1 with an adhesive;
Printing and die cutting the roll of film to which the adhesive is applied; And
Continuously unwinding the printed film roll to heat shrink while wrapping the container
Container packaging or labeling method comprising a. Packaging material or label comprising the heat-shrinkable polyester film according to claim 1 or 3.

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