JP2008284794A - Heat shrinkable label and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a label using a good heat shrinkable polyester film which can be stuck quickly with a good finish when being stuck to a container, and further to provide a label using a heat shrinkable polyester film with a primary shrinking direction oriented in the longitudinal direction suitable for sticking to a container. <P>SOLUTION: The heat shrinkable label formed in a tube shape comprises a heat shrinkable polyester film extended by at least one axis, and is characterized in that a film end is put on a predetermined position of a film, and a film lapping portion is irradiated with a laser beam and welded to form a tube shape. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a heat-shrinkable label, and more particularly to a heat-shrinkable label for coating bottles such as PET bottles (polyethylene terephthalate (PET) bottles) and glass bottles and a method for producing the same.

  In recent years, heat from various resins has been used for exterior packaging to improve the appearance of packages, packaging to avoid direct collision of contents, label packaging that protects glass bottles or plastic bottles and displays products. Shrinkable plastic films are widely used. Among these heat-shrinkable plastic films, stretched films made of polyvinyl chloride resin, polystyrene resin, polyester resin, etc. are used in various containers such as PET containers, polyethylene containers, glass containers, labels, cap seals or Used for integrated packaging purposes.

However, although the polyvinyl chloride film has excellent shrinkage properties, it has low heat resistance and also has problems such as generation of hydrogen chloride gas during incineration and causing dioxins. In addition, when a polyvinyl chloride film is used as a shrink label for a PET container or the like, there is also a problem that when the container is recycled, the label and the container must be separated. On the other hand, polystyrene-based films have a good finished appearance after shrinkage, but have poor solvent resistance, so that there is a problem that an ink having a special composition must be used for printing. In addition, the polystyrene film needs to be incinerated at a high temperature and has a problem that a large amount of black smoke is generated with a strange odor during incineration.
For this reason, polyester films having high heat resistance, easy incineration, and excellent solvent resistance have come to be widely used as heat-shrinkable labels, which increases the circulation of PET containers. Along with this, usage tends to increase.

  Up to now, as the heat-shrinkable polyester film, those which are largely shrunk in the width direction have been widely used. The heat-shrinkable polyester film whose width direction is the main shrinkage direction is stretched at a high magnification in the width direction in order to develop shrinkage characteristics in the width direction. In many cases, low-stretching is only performed, and some are not stretched. Such a film that has only been stretched at a low magnification in the longitudinal direction or a film that has been stretched only in the width direction has a disadvantage that the mechanical strength in the longitudinal direction is inferior.

  In addition, since the label of the bottle must be circular and heat-shrinked in the circumferential direction after being attached to the bottle, when the heat-shrinkable film that heat-shrinks in the width direction is attached as a label, the width direction of the film is After an annular body (tube) is formed so as to be in the circumferential direction, the annular body must be cut into predetermined lengths and attached to the bottle. Therefore, it becomes more difficult to attach a label made of a heat-shrinkable film that heat-shrinks in the width direction to the bottle as the production speed increases.

  For this reason, recently, there has been a demand for a film that is heat-shrinkable in the longitudinal direction and can be mounted directly around the bottle from a film roll. Furthermore, in recent years, a wrapping method has been developed in which a container is closed by covering the periphery of a synthetic resin single-open container such as a lunch box with a strip-shaped film. It is also suitable for such packaging applications. Therefore, the demand for the film shrinking in the longitudinal direction is expected to increase dramatically in the future.

  In order to form a film continuum (label) by attaching a film shrinking in the longitudinal direction to a container such as a bottle, one end of a film of an appropriate length is stuck on the container, and the film is wound around the outer periphery of the container. In addition, a method is used in which the film ends are overlapped and bonded so that the other film end is on top (for example, Patent Document 1). Examples of the adhesion between these containers and films, or film edges include adhesion with an adhesive, adhesion with an adhesive, adhesion with a solvent, and adhesion with a heat seal.

  However, as a sticking method used in the process of attaching these films to a container, sufficient adhesive strength cannot be obtained when a pressure sensitive adhesive is used, and label displacement or peeling occurs during heat treatment for shrinkage. Resulting in. Further, since the label is wound in a state where the container is standing, there is a problem that the viscosity of the solvent is too low in the solvent adhesion, and the coating becomes uneven due to dripping or scattering, or the surroundings are contaminated. Also, considering high-speed mounting from the viewpoint of improving productivity, it is important to perform the bonding process in a short time, but it is difficult to perform high-speed and uniform processing with heat sealing. Furthermore, for example, when a hot melt adhesive is used as the adhesive, there is a problem that label distortion due to the heat of the adhesive, shrinkage insufficiency in the subsequent process, etc. are likely to occur.

In addition, from the viewpoint of design and strength, the use of complicated containers with large irregularities is increasing as the shape of containers such as bottles, but if you try to stick the film directly to these complicated shaped containers, In some cases, it is difficult to press the overlapping portion of the film in the concave portion, and the method of sticking with an adhesive or the like may not adhere well.
JP 2005-292195 A

  An object of the present invention is to solve the above-mentioned problems and to provide a label using a heat-shrinkable polyester film that can be bonded at high speed when mounted on a container and has good finish. It is another object of the present invention to provide a lapel using a heat-shrinkable polyester film whose main shrinkage direction is a longitudinal direction suitable for mounting on a container.

  The present invention that has achieved the above-mentioned object is a heat-shrinkable label formed in a tube shape made of a heat-shrinkable polyester film stretched at least uniaxially, and the film end is positioned at a predetermined position of the film. The heat-shrinkable label is characterized by being formed into a tube shape by laminating and irradiating the overlapped portions of the films with laser to weld the overlapped portions of the films.

  The laser used to weld the overlapped portions of the films is preferably a carbon dioxide gas laser.

  The heat-shrinkable polyester film is more preferably drawn out from a heat-shrinkable polyester film roll whose longitudinal direction is the main shrinkage direction.

  At least one end of the heat-shrinkable polyester film stretched uniaxially is overlapped at a predetermined position of the film, and the overlapped portion of the film is irradiated with laser, and the overlapped portions of the films are welded into a tube shape. A method for producing a heat-shrinkable label characterized by molding is also included.

  The above manufacturing method includes a step of irradiating the overlapped part of the film with a laser in advance before attaching to the container, welding the overlapped part of the films to form a tube, and then attaching to the container. It is desirable.

  Further, the present invention is characterized in that after film is directly wound around a container, a laser is irradiated on the overlapped portion of the film, and the overlapped portions of the films are welded and formed into a tube shape. A method for producing sex labels is also included.

  According to the present invention, it was possible to provide a label using a heat-shrinkable polyester film that can be bonded at high speed when mounted on a container and has good finish. Furthermore, it was also possible to provide a label using a heat-shrinkable polyester film whose main shrinkage direction is the longitudinal direction suitable for mounting on a container. Therefore, it is useful as a heat-shrinkable label for bottles such as PET bottles and glass bottles.

  The present invention is a heat-shrinkable label formed in a tube shape made of a heat-shrinkable polyester film stretched at least uniaxially, and the film end portion is overlapped at a predetermined position of the film, and the overlapping portion of the film The present invention relates to a heat-shrinkable label, which is formed in a tube shape by welding a portion where films are overlapped by irradiating a laser. Note that “the film end is overlapped with a predetermined position of the film” means that the film end and the film are overlapped so as to form a tubular body having a size corresponding to the outer periphery of the container to be mounted. .

  The dicarboxylic acid component constituting the polyester used as a raw material for the heat-shrinkable polyester film used in the present invention includes terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, orthophthalic acid and other aromatic dicarboxylic acids, adipic acid, and azelaic acid. And aliphatic dicarboxylic acids such as sebacic acid and decanedicarboxylic acid, and alicyclic dicarboxylic acids.

  It is preferable not to use a trivalent or higher polyvalent carboxylic acid (for example, trimellitic acid, pyromellitic acid, and their anhydrides). The heat-shrinkable polyester film obtained using the polyester containing these polyvalent carboxylic acids is difficult to achieve the necessary high shrinkage rate.

  Examples of the diol component constituting the polyester used in the present invention include aliphatic diols such as ethylene glycol, 1-3 propanediol, 1-4 butanediol, neopentyl glycol, and hexanediol, and 1,4-cyclohexanedimethanol. Examples thereof include aromatic diols such as alicyclic diols and bisphenol A.

  The polyester used in the heat-shrinkable polyester film of the present invention is a cyclic diol such as 1,4-cyclohexanedimethanol, or a diol having 3 to 6 carbon atoms (for example, 1-3 propanediol, 1-4 butanediol). , Neopentyl glycol, hexanediol, and the like), and a polyester having a glass transition point (Tg) adjusted to 60 to 80 ° C. is preferable.

  Further, in the polyester used for the heat-shrinkable polyester film, the total of at least one diol component that can be an amorphous component in 100 mol% of the diol component is preferably 15 mol% or more, and 17 mol% or more. More preferably, it is more preferably 20 mol% or more. Here, examples of the diol that can be an amorphous component include neopentyl glycol and 1,4 monocyclohexanediol. Further, since isophthalic acid can also be an amorphous component, isophthalic acid may be used in an amount of 15 mol% or more in 100 mol% of the dicarboxylic acid component.

  When synthesizing a polyester used for a heat-shrinkable polyester film, a diol having 8 or more carbon atoms (for example, octanediol) or a trihydric or higher polyhydric alcohol (for example, trimethylolpropane, trimethylolethane, glycerin). , Diglycerin and the like) are preferably not used. The heat-shrinkable polyester film obtained by using polyesters containing these diols or polyhydric alcohols is difficult to achieve the necessary high shrinkage rate.

Moreover, it is preferable not to contain diethylene glycol, triethylene glycol, and polyethylene glycol as much as possible in the polyester used for the heat-shrinkable polyester film. In particular, although diethylene glycol is likely to be present because it is a by-product component during polyester polymerization, it is preferable that the content of diethylene glycol is less than 4 mol% in the polyester used in the present invention.
When the heat-shrinkable polyester film is treated in warm water at 90 ° C. for 10 seconds in a no-load state, the heat shrinkage rate in the longitudinal direction of the film calculated by the following formula 1 from the length before and after shrinkage ( That is, it is preferable that the hot water heat shrinkage rate at 90 ° C. is 15% or more and 80% or less.
Thermal shrinkage rate = {(length before shrinkage−length after shrinkage) / length before shrinkage} × 100 (%) Equation 1

  If the hot water thermal contraction rate in the longitudinal direction at 90 ° C. is 15% or less, the shrinkage amount is small, so that wrinkles and walnuts are generated on the label after thermal contraction. If the hot-water heat shrinkage rate in the direction is 80% or more, when used as a label, the shrinkage tends to occur during heat shrinkage, or so-called “flying up” occurs, which is not preferable. The hot water heat shrinkage in the longitudinal direction at 90 ° C. is preferably 20% or more, more preferably 30% or more, and particularly preferably 40% or more. Further, the hot water heat shrinkage in the longitudinal direction at 90 ° C. is preferably 75% or less, more preferably 70% or less, and particularly preferably 65% or less.

  The heat-shrinkable polyester film has a hot-water heat shrinkage ratio in the width direction of the film calculated by the above equation 1 from the length before and after shrinkage when treated in warm water at 90 ° C. for 10 seconds without load. , Preferably from -5% to 20%.

  If the hot shrinkage in the width direction at 90 ° C. is less than −5%, a good shrink appearance cannot be obtained when used as a bottle label, and conversely, the hot water in the width direction at 90 ° C. When the thermal shrinkage rate exceeds 20%, it is not preferable because when used as a label, the shrinkage tends to occur during the thermal shrinkage. The hot water heat shrinkage in the width direction at 90 ° C. is preferably −2% or more, more preferably 0% or more, and particularly preferably 2% or more. Moreover, the hot water heat shrinkage in the width direction at 90 ° C. is preferably 17% or less, more preferably 14% or less, and particularly preferably 11% or less.

  A heat-shrinkable polyester film was subjected to 10% shrinkage in the longitudinal direction in warm water at 80 ° C., and then the right-angled tear strength in the width direction was obtained when the transverse tear strength per unit thickness was determined by the following method. The strength is preferably 100 N / mm or more and 300 N / mm or less.

[Measurement method of right-angle tear strength]
The film before heat shrinkage is cut so that the main shrinkage direction is the longitudinal direction, and both ends in the longitudinal direction are fixed to a rectangular frame. At this time, the sample is loosened and fixed to the frame so as to be 10% longer than the length of the frame. The sample is immersed frame by frame in warm water of 80 ± 0,5 ° C., and the film is contracted by 10% in the main contraction direction for about 5 seconds until the loose film becomes a tension state in the frame. Then, after immersing in 25 degreeC water, it may take out and may wipe off moisture.
Then, it samples as a test piece of a predetermined | prescribed magnitude | size according to JISK-7128-3 from the film after the said shrinkage | contraction. Thereafter, both ends of the test piece are extreme with a universal tensile tester, and the strength (N) at the time of tensile fracture in the width direction of the film is measured under the condition of a tensile speed of 200 mm / min. Then, the right angle tear strength (N / mm) per unit thickness (mm) is calculated using the following formula 2.
Right angle tear strength = strength at tensile fracture ÷ thickness Equation 2

  If the right-angled tear strength after shrinking 10% in the longitudinal direction in warm water at 80 ° C is less than 100 N / mm, when used as a label, it may be easily broken by an impact such as dropping during transportation. On the other hand, if the right-angled tear strength is greater than 300 N / mm, the cutability (ease of tearing) when tearing the label becomes unfavorable. The right-angled tear strength is preferably 125 N / mm or more, more preferably 150 N / mm or more, and particularly preferably 175 N / mm or more. The right-angled tear strength is preferably 275 N / mm or less, more preferably 250 N / mm or less, and particularly preferably 225 N / mm or less.

  A heat-shrinkable polyester film was subjected to 10% shrinkage in the longitudinal direction in warm water at 80 ° C., and then the Elmendorf tear load in the longitudinal direction and the width direction was determined by the following method. The Elmendorf ratio is preferably 0.15 or more and 1.5 or less.

[Measurement method of Elmendorf ratio]
The film is shrunk by 10% in the longitudinal direction in the same way as in the case of right-angle tear strength. Thereafter, the Elmendorf tearing force is measured according to JISK7128-2. The Elmendorf ratio is calculated by using the following equation 3 to measure the Elmendorf tear load (N) in the longitudinal direction and the width direction of the film.
Elmendorf ratio = Elmendorf tear load in the longitudinal direction ÷ Elmendorf tear load in the width direction Equation 3

  When the Elmendorf ratio is less than 0.15, it is not preferable because the Elmendorf ratio is difficult to tear straight along a notch (notch) when used as a label. On the other hand, if the Elmendorf ratio exceeds 1.5, it is not preferable because it easily tears at an obliquely shifted position. The Elmendorf ratio is preferably 0.20 or more, more preferably 0.25 or more, and particularly preferably 0.3 or more. The Elmendorf ratio is preferably 1.4 or less, more preferably 1.3 or less, and particularly preferably 1.2 or less.

The heat shrinkable polyester film preferably has a natural shrinkage ratio of 0.05% or more and 1.5% or less after aging (storage) in an atmosphere of 40 ° C. and 65% RH for 700 hours or more. The natural shrinkage rate can be calculated using the following equation 4.
Natural shrinkage = {(length before aging−length after aging) / length before aging) × 100 (%) Formula 4

  When the natural shrinkage rate is 1.5% or less, when a product wound in a roll shape is stored, winding tightening occurs and wrinkles are easily formed in the film, which is not preferable. The smaller the natural shrinkage rate, the better. However, from the viewpoint of measurement accuracy, about 0.05% is considered to be the lower limit. The natural shrinkage rate is preferably 1.3% or less, more preferably 1.1% or less, and particularly preferably 1.0% or less.

  The heat-shrinkable polyester film can be obtained by melt-extruding the above-described polyester raw material with an extruder to form an unstretched film, and biaxially stretching the unstretched film by the method shown below and heat-treating it. it can. Polyester can be obtained by polycondensing the above-mentioned preferred dicarboxylic acid components and a diol component by a known method. Usually, two or more kinds of chip-like polyester are mixed and used as a raw material for the film.

  When the raw material resin is melt-extruded, the polyester raw material is preferably dried using a dryer such as a hopper dryer or a paddle dryer, or a vacuum dryer. After the polyester raw material is dried in such a manner, it is melted at a temperature of 200 to 300 ° C. and extruded into a film using an extruder. In extruding, any existing method such as a T-die method or a tubular method can be employed.

  And an unstretched film can be obtained by rapidly cooling the sheet-like molten resin after extrusion. In addition, as a method of rapidly cooling the molten resin, a method of obtaining a substantially unoriented resin sheet by casting the molten resin from a die onto a rotating drum and rapidly solidifying it can be suitably employed.

  Further, as will be described later, the obtained unstretched film is stretched in the width direction under predetermined conditions, and then once heat-treated, and then stretched in the longitudinal direction (longitudinal stretching) under the predetermined conditions. By rapidly cooling the subsequent film, a heat-shrinkable polyester film used for the label of the present invention is obtained. Hereinafter, a preferable biaxial stretching / heat treatment method for obtaining a heat-shrinkable polyester film will be described in detail in consideration of differences from the conventional biaxial stretching / heat treatment method of a heat-shrinkable polyester film.

[Preferable stretching and heat treatment method for heat-shrinkable polyester film]
A normal heat-shrinkable polyester film is produced by stretching an unstretched film in the direction in which it is desired to shrink. Although there was a high demand for heat-shrinkable polyester films that shrunk in the longitudinal direction from the past, simply stretching an unstretched film in the longitudinal direction makes it impossible to produce a wide film, resulting in poor productivity. A film with good thickness unevenness cannot be produced. Moreover, if the method of extending | stretching to a longitudinal direction after extending | stretching previously to the width direction is employ | adopted, the shrinkage | contraction amount to a longitudinal direction will become inadequate, or it will shrink | contract unnecessarily in the width direction.

  For example, JP-A-8-244114 discloses a method of stretching an unstretched film in the order of length-width-length under predetermined conditions in order to improve the mechanical properties in the longitudinal direction. According to their pilot test, it was not possible to obtain a film with sufficient shrinkage in the longitudinal direction, which is the main shrinkage direction, and wrinkles in the width direction were produced on the produced film roll. It became clear that it became easy to do. In addition, if the longitudinal stretching ratio (the first stage longitudinal stretching ratio or the second stage longitudinal stretching ratio) is increased to increase the contractibility in the longitudinal direction, the film is finally stretched in the longitudinal direction. It has also been found that it is difficult to carry out a continuous and stable production due to frequent breaks. Moreover, the film obtained by the additional test had a large natural shrinkage rate, wrinkles in the longitudinal direction were generated in the produced film roll, and the notch opening property was also poor.

In order to finally increase the amount of contraction in the longitudinal direction, the present inventors have disadvantaged the method of stretching in the longitudinal direction after biaxial stretching in the longitudinal direction and the width direction as disclosed in JP-A-8-244114. It was considered that it would be more advantageous to simply stretch in the width direction and then stretch in the longitudinal direction. And in such a method of stretching in the longitudinal direction after stretching in the width direction (hereinafter, simply referred to as a transverse-longitudinal stretching method), the hot water temperature shrinkage rate in the longitudinal direction of the film, the natural shrinkage rate, depending on the conditions in each stretching step, We intensively studied how the notch openability changes. As a result, the present inventors have found out that when the film is manufactured by the transverse-longitudinal stretching method, the following measures are taken to increase the amount of shrinkage in the longitudinal direction, thereby enabling continuous and stable production. In addition, when the following measures are taken, the natural shrinkage rate of the film is reduced, the film roll after manufacture is less likely to wrinkle, and the notch opening property of the film is dramatically improved. It turns out that there is a surprising side effect of becoming. And the present inventors came to devise this invention based on those knowledge.
(1) Control of shrinkage stress after stretching in the width direction (2) Blocking of heat between the stretching in the width direction and intermediate heat treatment (3) Trimming of the film edge before stretching in the longitudinal direction (4) ) Control of cooling rate of film after longitudinal stretching Hereinafter, each of the above-mentioned means will be sequentially described.

(1) Control of shrinkage stress after stretching in the width direction In the production of a film by the transverse-longitudinal stretching method of the present invention, after stretching an unstretched film in the width direction, the temperature is 100 ° C. or more and less than 170 ° C. It is necessary to perform heat treatment (hereinafter referred to as intermediate heat treatment) for a period of time between 0.0 seconds and 10.0 seconds. By performing this intermediate heat treatment, it becomes possible to obtain a label having good notch unsealing properties and no shrinkage spots. Thus, by performing a specific intermediate heat treatment after transverse stretching, the notch unsealing property is good and shrinkage unevenness is produced. The reason why it is possible to obtain a film that does not occur is not clear, but by applying a specific intermediate heat treatment, it is possible to reduce the shrinkage stress in the width direction while leaving some molecular orientation in the width direction. I think that is to become. The heat treatment temperature is preferably 110 ° C. or higher, and more preferably 115 ° C. or higher. Further, the heat treatment temperature is preferably 165 ° C. or lower, and more preferably 160 ° C. or lower. On the other hand, the heat treatment time may be appropriately adjusted in accordance with the raw material composition within a range of 1.0 second to 10.0 seconds.

  Stretching of the unstretched film in the width direction is a ratio of 2.5 times or more and 6.0 times or less at a temperature of Tg + 5 ° C. or more and Tg + 40 ° C. or less in a state where both ends of the width direction are held by clips in the tenter. Need to do so. If the stretching temperature is lower than Tg + 5 ° C., it is not preferable because breakage is likely to occur during stretching. On the other hand, if it exceeds Tg + 40 ° C., thickness unevenness in the width direction is deteriorated, which is not preferable. The transverse stretching temperature is preferably Tg + 10 ° C. or higher, and more preferably Tg + 15 ° C. or higher. Further, the transverse stretching temperature is preferably Tg + 35 ° C. or lower, and more preferably Tg + 30 ° C. or lower. On the other hand, if the draw ratio in the width direction is less than 2.5 times, not only the productivity is deteriorated but also the thickness unevenness in the width direction is deteriorated, and on the contrary, if it exceeds 6.0 times, breakage occurs at the time of drawing. In addition, it is not preferable because a large amount of energy and a large apparatus are required for relaxation, and productivity deteriorates. The transverse draw ratio is preferably 3.0 times or more, and more preferably 3.5 times or more. The transverse draw ratio is preferably 5.5 times or less and more preferably 5.0 times or less.

(2) Interruption of heating at the time of stretching in the width direction and intermediate heat treatment In the production of a film by the transverse-longitudinal stretching method of the present invention, as described above, it is necessary to perform an intermediate heat treatment after transverse stretching. Between the transverse stretching and the intermediate heat treatment, it is necessary to pass through an intermediate zone where no aggressive heating operation is performed for a period of 0.5 seconds to 3.0 seconds. That is, when considering the production cost, it is preferable to carry out transverse stretching and intermediate heat treatment in the same tenter, but in the production of the film of the present invention, between the transverse stretching zone and the heat treatment zone in the tenter. It is preferable to provide an intermediate zone. In addition, in the intermediate zone, when the strip-shaped paper piece is hung in a state where the film is not passed through, the hot air from the stretching zone and the heat treatment zone is blocked so that the paper piece hangs almost completely in the vertical direction. Is preferred. And in manufacture of a film, it is preferable to guide the film after lateral stretching to an intermediate zone, and to let the intermediate zone pass over predetermined time. If the time for passing through the intermediate zone is less than 0.5 seconds, the hot air in the transverse stretching zone flows into the heat fixing zone due to the accompanying flow of the passing film, which makes it difficult to control the temperature of the intermediate heat treatment in the heat fixing zone. . On the contrary, it is sufficient that the time for passing through the intermediate zone is 3.0 seconds, and setting it longer than that is not preferable because it wastes equipment. The time for passing through the intermediate zone is preferably 0.7 seconds or more, and more preferably 0.9 seconds or more. The time for passing through the intermediate zone is preferably 2.5 seconds or less, and more preferably 2.0 seconds or less.

(3) Trimming of film edge before stretching in the longitudinal direction In the production of the film by the horizontal and longitudinal stretching method of the present invention, before stretching the film subjected to the intermediate heat treatment in the longitudinal direction, It is preferable to trim a thick portion that is not sufficiently stretched laterally (mainly a clip gripping portion during transverse stretching). That is, since there is a portion (thick portion) about 1.1 to 1.3 times as thick as the central portion in the vicinity of the left and right edges of the film, this film can be used with a tool such as a cutter. It is preferable that only the remaining portion is stretched in the longitudinal direction while cutting and removing the thick portion at the end. When trimming the film edge, it is preferable to cool the film so that the surface temperature of the film before trimming is 50 ° C. or lower. By cooling the film in this way, trimming can be performed without disturbing the cut surface. In addition, trimming of the film edge can be performed using a normal cutter or the like, but if a round blade having a circumferential cutting edge is used, a situation in which the cutting edge is locally dulled does not occur, and the film edge is This is preferable because it can continue to be cut sharply over a long period of time and does not cause a breakage during stretching in the longitudinal direction.

  By trimming the end of the film before stretching in the longitudinal direction in this way, it becomes possible to stretch the heat-fixed film uniformly in the longitudinal direction, and for the first time, it is possible to continuously produce a stable film without breaking for the first time. It becomes. In addition, it is possible to obtain a film having a large shrinkage in the longitudinal direction (main shrinkage direction). Furthermore, since the film can be uniformly stretched in the longitudinal direction, a film having a small thickness unevenness in the longitudinal direction can be obtained. In addition, by trimming the end of the film, bowing during stretching in the longitudinal direction is avoided, and a film having a small difference in physical properties between the left and right can be obtained.

(4) Control of cooling rate of film after longitudinal stretching In the production of the film by the transverse-longitudinal stretching method of the present invention, as described above, the film is stretched in the longitudinal direction after being subjected to an intermediate heat treatment after the transverse stretching. After the longitudinal stretching, the film is preferably cooled at a cooling rate of 30 ° C./second or more and 70 ° C./second or less until the surface temperature becomes 45 ° C. or more and 75 ° C. or less. In this way, the natural shrinkage rate is effectively reduced by cooling the mud at an appropriate speed. If the cooling rate is lower than 30 ° C./second or the surface temperature after cooling is higher than 75 ° C., it is not preferable because a low natural shrinkage rate cannot be obtained. On the other hand, if the cooling rate is so rapid that the cooling rate exceeds 70 ° C./second, the degree of shrinkage in the width direction of the film (so-called neck-in) increases, and the film surface is easily damaged, which is not preferable. .
In addition, any one of the above-mentioned means (1) to (4) only contributes effectively to the heat shrinkability in the longitudinal direction of the film, the notch opening property, the low natural shrinkage rate, and the stable film forming property. Rather than using the means (1) to (4) in combination, the heat shrinkage in the longitudinal direction, notch opening, low natural shrinkage, and stable film-forming properties are expressed very efficiently. It is thought that it will be possible.
Although the thickness of the heat-shrinkable polyester film is not particularly limited, the heat-shrinkable film for labels is preferably 10 to 200 μm, and more preferably 20 to 100 μm.

  Next, film adhesion using a carbon dioxide laser will be described. The heat-shrinkable label of the present invention is irradiated with a laser from the outer surface of the overlapped portion of the heat-shrinkable polyester film, and the contact surface between the film and the film is partially melted to bring the contact surface into close contact with each other. It is obtained by joining and integrating both.

   As a laser light source used for laser welding, various lasers such as a solid laser (Nd: YAG excitation, semiconductor laser excitation, etc.), a semiconductor laser (650, etc.) may be used as long as an absorber corresponding to each wavelength laser is included. ˜980 nm), tunable diode laser (630 to 1550 nm), titanium sapphire laser (Nd: YAG excitation, 690 to 1000 nm), carbon dioxide laser (10600 nm), and the like can be used. Among these laser light sources, carbon dioxide laser can be bonded between colorless and transparent heat-shrinkable polyester film without adding a specific absorbent, and can be used for various printing and designs. In the present invention, a label is produced by irradiation with a carbon dioxide laser.

   In the present invention, since the film is bonded by laser welding without using a solvent or a pressure-sensitive adhesive, a label can be produced in a clean state without a solvent odor, and a label having sufficient adhesive strength can be obtained at high speed. . Further, the adhesive strength can be adjusted by adjusting the intensity of the laser light, the irradiation time (exposure amount, etc.), and the bonding strength can be reduced with a relatively small exposure amount, for example. Therefore, if necessary, the label can be easily peeled from the container to facilitate recycling.

  Next, the manufacturing method of the heat-shrinkable label of this invention is demonstrated. First, a label design is printed on a heat-shrinkable polyester film, if necessary, and wound into a roll. The film is fed out from the roll, and the entire circumference of the cylindrical body is covered so that the film is superimposed on the end of the film while the film is wound around a cylindrical body of an appropriate size that matches the outer periphery of the container. The part where the film is overlaid is irradiated with a laser to partially melt the contact surface between the film and adhere to the contact surface. The heat shrinkable label of the present invention is obtained by cutting excess film along the line. After unwinding the film from the roll, the film is cut into a predetermined length in advance, and the other end is overlapped on the end of the film while the cut film is wound around the tubular body to cover the entire circumference of the tubular body The label of the present invention can also be obtained by irradiating the overlapped portion with a laser to join the contact surfaces of the films. A package in which the label is in close contact with the container can be manufactured by attaching the obtained label to a desired position of the container and applying a shrinkage treatment. Alternatively, the label of the present invention can be obtained by wrapping the film directly around the container so as to cover the entire circumference of the container and irradiating the laser beam onto the overlapped portion of the film. Also in this case, the film fed out from the roll may be wound around the container as it is, or the film fed out may be wound around the container after being cut into a predetermined length.

  As laser irradiation conditions, it is necessary to adjust appropriately according to the composition and thickness of the heat-shrinkable polyester film to be used. For example, in the case of a carbon dioxide laser, the scanning speed is 20 m / min to 200 m / min, the beam diameter is 1 to The conditions of 4 mm, focal length 20 to 100 mm, and output 10 to 100 W are preferable. Under conditions outside this range, sufficient partial dissolution of the film cannot be obtained by the laser, resulting in poor adhesion, and the label may be peeled off during shrinkage mounting or product distribution, or the film will be excessively dissolved by the laser and the film will adhere. It may be cut without it.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not restrict | limited to these Examples at all. First, the evaluation method of the film and label produced in the Example and the comparative example is demonstrated. The evaluation results of the film are summarized in Table 2, and the evaluation results of the label are summarized in Table 3. In the following description, “part” means “part by mass”.

[Heat shrinkage (hot water heat shrinkage)]
The film was cut into a 10 cm × 10 cm square and heat-shrinked by treatment for 10 seconds in warm water at a predetermined temperature of ± 0.5 ° C. under no load. The film was immediately immersed in water at 25 ° C. ± 0.5 ° C. for 10 seconds, and then the vertical and horizontal dimensions of the film were measured. The direction in which the heat shrinkage rate is large was taken as the maximum shrinkage direction.
Thermal shrinkage rate = {(length before shrinkage−length after shrinkage) / length before shrinkage} × 100 (%) Formula 1

[Measurement method of right-angle tear strength]
The film before heat shrinkage is cut so that the main shrinkage direction is the longitudinal direction, and both ends in the longitudinal direction are fixed to a rectangular frame. At this time, the sample is loosened and fixed to the frame so as to be 10% longer than the length of the frame. The sample is immersed in warm water at 80 ± 0.5 ° C. together with the frame, and the film is contracted by 10% in the main contraction direction for about 5 seconds until the loose film becomes a tension state in the frame. Then, after immersing in 25 degreeC water, it may take out and may wipe off moisture.
Then, the test piece of the shape shown in FIG. 1 was cut out from the film after shrinkage according to JIS K-7128-3. When cutting out, the longitudinal direction of the test piece was set as the main shrinkage direction of the film. Thereafter, both ends of the test piece are grasped with a universal tensile tester (trade name “Tensilon”; manufactured by Toyo Seiki Co., Ltd.), and the strength (N) at the time of tensile fracture in the width direction of the film is measured at a tensile speed of 200 mm / min. Went. The right angle tear strength (N / mm) per unit thickness (mm) was calculated using the following formula 2.
Right angle tensile strength = Strength at tensile failure ÷ Thickness Formula 2

[Measurement method of Elmendorf ratio]
The film is shrunk by 10% in the longitudinal direction in the same manner as in the case of the right angle tear strength. After that, in accordance with JIS K7128-2, a sample having a length of 63 mm in the main contraction direction and a length (width) of 75 mm in the direction orthogonal to the main contraction direction is cut out, and orthogonal to the edge from the center in the longitudinal direction edge. In this way, a 20 mm slit (cut) was inserted to make a test piece, and a sample with a length (width) of 75 mm in the main contraction direction and a length of 63 mm in the orthogonal direction was cut to reverse the length and width of the test piece. A test piece was also prepared. About these test pieces, the Elmendorf tear load (N) in the longitudinal direction and the width direction of the film was measured using a light load tearer (manufactured by Toyo Seiki Co., Ltd.), and the Elmendorf ratio was calculated using the following equation 3. .
Elmendorf ratio = Elmendorf tear load in the longitudinal direction ÷ Elmendorf tear load in the width direction Equation 3

[Natural shrinkage]
The obtained film was cut into a main shrinkage direction × orthogonal direction = 200 mm × 30 mm size and allowed to stand for 700 hours in an atmosphere of 40 ° C. × 65% RH, and then the amount of shrinkage in the main shrinkage direction of the film was determined. Measured and the natural shrinkage rate was calculated by Equation 4.
Natural shrinkage rate = {(length before aging−length after aging) / length before aging} × 100 (%) Formula 4

[Tg (glass transition temperature)]
Using a differential scanning calorimeter (model: DSC220) manufactured by Seiko Denshi Kogyo Co., Ltd., 5 mg of an unstretched film was sampled and heated from −40 ° C. to 120 ° C. at a heating rate of 10 ° C./min. The curve (DSC curve) was measured. A tangent line was drawn before and after the inflection point of the DSC curve, and the intersection was defined as Tg (glass transition temperature).

[Tm (melting point)]
Using the above differential scanning calorimeter (model: DSC220), 5 mg of unstretched film was sampled, and the peak of the heat flow rate curve (DSC curve) when the temperature was raised from room temperature (23 ° C) at a rate of temperature rise of 10 ° C / min. Was set to Tm (melting point).

[Label adhesion]
Sensory evaluation was performed on the degree of label displacement when the bottle after heat shrinkage and the label attached to the bottle were lightly twisted. When the label did not move, it was marked as “C”, when it slipped through, or when the label and the bottle shifted.

[Adhesiveness of label bonding part]
About the label after heat shrink with which the bottle was mounted | worn, sensory evaluation was carried out about how the film peeled when the film edge which has come out on the surface of the part where films were bonded together was scratched by hand. Those that did not peel off and adhered well were marked with ◯, those that adhered but peeled off with a light force were marked with Δ, and those that did not adhere were marked with ×.

[Shrink finish]
The finish of the bottle after heat shrinkage was evaluated visually, and the criteria were as follows.
◎: No wrinkles, jumping up, insufficient shrinkage, and no color spots are observed ○: Wrinkles, jumping up, or insufficient shrinkage cannot be confirmed, but some color spots are seen △: Jumping Neither ascending nor insufficient shrinkage has occurred, but spots on the neck are observed. ×: Wrinkles, jumping up, insufficient shrinkage occurred

[Label openability]
A label having a notch with a length of 2 mm in a direction perpendicular to the main shrinkage direction was attached to a PET bottle and thermally shrunk. However, the notch was provided on the upper side of the label when the bottle was erected. Thereafter, the bottle with the label attached was refrigerated at 5 ° C. for 24 hours, and the label of the bottle immediately after being taken out of the refrigerator was torn with a fingertip from the notch portion. The number of bottles that could be easily and vertically separated and the label could be easily removed from the bottles was counted, and the ratio (%) to 50 samples was calculated.

[Production Method of Polyester Film 1]
90 parts of polyester 1 (IV 0.72 dl / g) composed of 70 mol% of ethylene glycol, 30 mol% of neopentyl glycol and 100 mol% of terephthalic acid, and 10 parts of polyethylene terephthalate (IV 0.75 dl / g: hereinafter, polyester 2) Were mixed and put into an extruder. Thereafter, the mixed resin was melted at 280 ° C., extruded from a T-die, wound around a rotating metal roll cooled to a surface temperature of 30 ° C., and rapidly cooled to obtain an unstretched film having a thickness of 360 μm. At this time, the take-up speed of the unstretched film (the rotation speed of the metal roll) was about 20 m / min. Moreover, Tg of the unstretched film was 67 degreeC. Thereafter, the unstretched film was led to a tenter (first tenter) in which a transverse stretching zone, an intermediate zone, and an intermediate heat treatment zone were continuously provided. In the tenter, the length of the intermediate zone located between the transverse stretching zone and the intermediate heat treatment zone was set to about 40 cm. In addition, in the intermediate zone, when the strip-shaped paper piece is hung in a state where the film is not passed through, the hot air from the stretching zone and the hot air from the heat treatment zone are blown so that the paper piece hangs almost completely in the vertical direction. It was cut off.

  The pre-stretched film led to the tenter was preheated until the film temperature reached 90 ° C., and then stretched 4 times at 75 ° C. in the transverse direction in the transverse stretching zone and passed through the intermediate zone (passing time = About 1.2 seconds), the film was led to an intermediate heat treatment zone and heat treated at a temperature of 130 ° C. for 2.0 seconds to obtain a transversely uniaxially stretched film having a thickness of 90 μm. Thereafter, using a pair of left and right trimming devices (configured by a round blade having a circumferential cutting edge) provided at the rear of the tenter, both end portions (about 1.. 2 times thick part) was cut, and the end of the film located outside the cut site was continuously removed.

  The film trimmed at the end is guided to a longitudinal stretching machine in which a plurality of roll groups are continuously arranged, preheated on a preheating roll until the film temperature reaches 70 ° C., and then stretched at a surface temperature of 95 ° C. The film was stretched 3 times between rolls. Thereafter, the longitudinally stretched film was forcibly cooled by a cooling roll set at a surface temperature of 25 ° C. The surface temperature of the film before cooling was about 75 ° C., and the surface temperature of the film after cooling was about 25 ° C. The time required for cooling from 70 ° C. to 25 ° C. was about 1.0 second, and the film cooling rate was 45 ° C./second.

  The cooled film was guided to a tenter (second tenter), heat-treated in an atmosphere of 95 ° C. for 2.0 seconds in the second tenter, cooled, and both ends were cut and removed. In this manner, a biaxially stretched film of about 30 μm was continuously formed over a predetermined length to obtain a film roll made of a heat-shrinkable polyester film. The production conditions are summarized in Table 1.

[Production Method of Polyester Film 2]
A heat-shrinkable film was continuously produced by the same method as for polyester film 1 except that polyester 1 and polyester 2 were mixed at a mass ratio of 70:30 and charged into an extruder. The production conditions are summarized in Table 1.

[Production Method of Polyester Film 3]
A heat-shrinkable film was continuously produced by the same method as the polyester film 1 except that the temperature of the stretching roll in the longitudinal stretching machine was changed to 92 ° C. and the stretching ratio in the longitudinal direction was changed to 5.0 times. The thickness of this biaxially stretched heat-shrinkable polyester film was about 18 μm. The production conditions are summarized in Table 1.

Example 1
Using the polyester film 1 roll, three-color printing was performed with grass, gold, and white ink from Toyo Ink Manufacturing Co., Ltd., slit into a width of 100 mm, and a printed film roll was prepared. The above-mentioned printed film roll is unwound on an upright paper cylinder having a diameter of 70 mm and a height of 150 mm so that the printing surface is inward and the longitudinal direction of the film is parallel to the cylinder circumferential direction of the cylinder The film is wound, and the laser beam wavelength is 10.6 μm, the output is 20 W, the focal length is 20 mm, and the laser scanning is performed at the place where the film just goes around the outer periphery of the cylindrical body and the film is overlapped. A heat-shrinkable label was produced as a continuous body by irradiating a carbon dioxide laser under conditions of a speed of 50 m / min and adhering the wound film. With the 290 ml aluminum bottle can upright (maximum diameter of the barrel is 68 mm, diameter of the neck is 30 mm), the printing surface faces the outer surface of the bottle so that one end of the film is along the bottom of the can Put the label on it, put it into a steam furnace shrink tunnel that is 3m long and kept at 92 ° C, and let it pass for 10 seconds, so that the label shrinks and adheres to the outer periphery of the bottle can. (Container with label after shrinkage) was obtained. The package had good shrinkage finish and good adhesion at the label bonding part. The evaluation results are shown in Table 3.

Example 2
A package was obtained in the same manner as in Example 1 except that the polyester film 2 was used as the heat-shrinkable polyester film. The evaluation results are shown in Table 3.

Example 3
A package was obtained in the same manner as in Example 1 except that the polyester film 3 was used as the heat-shrinkable polyester film. The evaluation results are shown in Table 3.

Example 4
A package was obtained in the same manner as in Example 1 except that the output was set to 30 W as the irradiation condition of the carbon dioxide laser at the time of bonding the film ends. The evaluation results are shown in Table 3.

Example 5
A package was obtained in the same manner as in Example 1 except that the scanning speed was set to 30 m / min as the irradiation condition of the carbon dioxide laser at the time of bonding the film ends. The evaluation results are shown in Table 3.

Comparative Example 1
A package was obtained by the same method as in Example 1 except that the film edges were bonded to each other using a commercially available ethylene-vinyl acetate hot melt adhesive (softening point: 85 ° C.). Due to the heat at the time of applying the hot melt adhesive, the shrinkage finish was deteriorated, and the label bonded portion was also lightly peeled off by hand, so that sufficient adhesiveness was not obtained.

Comparative Example 2
The attachment of the label was tried by the same method as in Example 1 except that the film edges were bonded together by solvent adhesion using 1,3-dioxolane. The film could not be laminated successfully.

  The heat-shrinkable label of the present invention is suitable for bottle labels such as PET bottles and glass bottles.

It is explanatory drawing which shows the shape of the test piece at the time of measuring a right-angled tear strength.

Claims (7)

  A heat-shrinkable label formed in a tube shape made of a heat-shrinkable polyester film stretched at least uniaxially, with the film end overlapped at a predetermined position on the film and the overlapped part of the film irradiated with laser Then, the heat-shrinkable label is formed by welding the overlapped portions of the films to form a tube shape.   The heat-shrinkable label according to claim 1, wherein the laser used for welding the overlapped portions of the films is a carbon dioxide laser.   The heat-shrinkable label according to claim 1 or 2, wherein the heat-shrinkable polyester film is drawn from a heat-shrinkable polyester film roll whose longitudinal direction is the main shrinkage direction.   At least one end of the heat-shrinkable polyester film stretched uniaxially is overlapped at a predetermined position of the film, and the overlapped portion of the film is irradiated with laser, and the overlapped portions of the films are welded into a tube shape. A method for producing a heat-shrinkable label, comprising molding.   The method for producing a heat-shrinkable label according to claim 4, wherein the laser used for welding the overlapped portions of the films is a carbon dioxide gas laser.   The method according to claim 3 or 4, further comprising the step of irradiating the overlapped portion of the film with a laser in advance before being attached to the container, welding the overlapped portions of the films to form a tube, and then attaching to the container. The manufacturing method of the heat-shrinkable label of description.   5. The film according to claim 3, wherein the film is directly wound around the container, and then the laser is irradiated on the overlapped portion of the film to weld the overlapped portions of the films to form a tube shape. Manufacturing method of heat-shrinkable label.

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