JP2005335111A - Heat-shrinkable polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-shrinkable polyester film having excellent shrink characteristics and shrink finish properties in a wide temperature range from a low temperature to a high temperature, excellent in solvent adhesiveness, extremely reduced in the occurrence of shrink whitening even if the film is preserved over a long period of time and suitably used as a label having excellent tear resistance. <P>SOLUTION: The heat-shrinkable polyester film is characterized in that the heat shrinkage factor in the maximum shrink direction of a sample having a square shape of 10×10 cm after the sample is immersed in a hot water of 70°C for 10 sec is 30-50%, the heat shrinkage factor in the direction crossing the maximum shrink direction at a right angle of the sample after the sample is immersed in hot water of 98°C for 10 sec is 0-15%, the difference between the haze of the heat-shrinkable polyester film after the film is preserved for four weeks under an environment with a temperature of 30°C and a relative humidity of 85% and thermally shrunk under a predetermined condition after preservation and the haze of the film before shrink treatment is 5% or below, and the number of test pieces broken under a condition of an elongation at break of 5% or below is 10% or below of the total number (20) of the test pieces. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heat-shrinkable polyester film, and more specifically, the occurrence of defects such as wrinkles, shrinkage spots, distortion, and jumping due to shrinkage is extremely small, and shrinkage whitening after shrinkage of the aged film is small. The present invention relates to a heat-shrinkable polyester film suitably used for a cap-seal tubular label (hereinafter simply referred to as a cap-seal label) such as a bottle container (for example, a milk bottle) with few troubles in the process.

  2. Description of the Related Art In recent years, a seal called a cap seal is applied to a stopper or lid of containers such as bottles for beverages and foods. The cap seal is applied not only for the purpose of imparting a decorative property but also for the purpose of preventing the entry of a poisonous substance or the like because it is a proof that the stopper or the lid is not opened.

  Cap seal labels have been mainly made of heat-shrinkable film made of polyvinyl chloride, polystyrene, etc., as with normal labels. Polyvinyl chloride films have low heat resistance, and hydrogen chloride during incineration. It has problems such as generating gas and causing dioxins. Further, when a heat-shrinkable vinyl chloride resin film is used as a shrink label for a PET container or the like, there is a problem in that the label and the container must be separated when the container is recycled.

  On the other hand, a polystyrene film can be evaluated for its good finished appearance after shrinkage, but it is poor in solvent resistance, so an ink with a special composition must be used for printing. In addition, heat-shrinkable films have recently been used in hot beverage PET bottle labels, but when stored in warming equipment such as hot-warmers, the heat-shrinkable polystyrene film comes into contact with hot wires that have become hot. There is a problem that the shrinkage label melts instantly. Furthermore, the polystyrene resin needs to be incinerated at a high temperature, and has a problem that a large amount of black smoke and off-flavor are generated at the time of incineration.

  Polyester films without these problems (excellent in solvent resistance, heat resistance, and environmental suitability) are highly expected as shrink labels to replace polyvinyl chloride films and polystyrene films. Along with the increase, the usage amount is also increasing.

However, the conventional heat-shrinkable polyester film has also been required to have further improvement in shrinkage characteristics. In particular, when compared with heat-shrinkable polystyrene film, shrinkage spots and wrinkles occur during shrinkage, and characters and designs printed before shrinkage are coated and attached to containers such as PET bottles, polyethylene bottles, glass bottles, There has been a demand from the user side that it may be distorted after contraction and it is desired to reduce this distortion as much as possible.
In addition, the polyester film may be inferior in shrinkability at a low temperature, and in order to obtain a necessary shrinkage amount, it has to be shrunk at a high temperature, and the bottle body may be deformed or whitened.

  By the way, when using a heat-shrinkable film for coating a real container, after performing a printing process as necessary, it is processed into a form such as a label (tubular label) or a tube, and these processed films The inside of a shrinking tunnel (steam tunnel) that heats and shrinks by blowing steam on the container, or a shrinking tunnel (hot air tunnel) that heats and shrinks by blowing hot air is placed on a belt conveyor, etc. It is allowed to pass through and is heat-shrinked so as to be closely attached to the container.

  When using a hot-air tunnel in which heat-shrinkable polyester films tend to cause temperature spots during heat shrinkage, the polyester-based films are likely to cause shrinkage whitening, shrinkage spots, wrinkles, distortion, and the like.

  In addition, steam tunnels have better heat transfer efficiency than hot air tunnels and can be heated and shrunk more uniformly, and can provide a better shrink finish appearance than hot air tunnels. The film has a problem that the shrinkage finish after passing through the steam tunnel is not so good as compared with the polyvinyl chloride film and the polystyrene film.

  Furthermore, when stored in a high temperature environment of 30 ° C. or higher, shrinkage whitening is likely to occur, which is a problem in terms of product appearance.

  Furthermore, if the degree of stretching is increased to ensure the shrinkage rate, the film is likely to break in the direction orthogonal to the shrinkage direction, which may cause troubles in the printing process, the label processing process, or the film after shrinkage. is there. This breaking trouble is likely to occur when stored for a long time in a relatively high temperature atmosphere of 30 ° C. or higher, and improvement of this breaking trouble has been desired.

So far, there has been disclosed a heat-shrinkable polyester film that suppresses the occurrence of shrinkage whitening, shrinkage spots, wrinkles, distortion and the like and improves the finish at low temperatures (see, for example, Patent Document 1).
JP 2002-275288 A

  However, even in this heat-shrinkable polyester film, no effect of improving tear resistance and shrinkage whitening was observed.

  The present invention solves the problems of the conventional heat-shrinkable polyester film as described above, has excellent shrinkage properties and shrinkage finish properties in a wide temperature range from low temperature to high temperature, and excellent solvent adhesion, Furthermore, even when the film is stored for a long period of time, it is an object to provide a heat-shrinkable polyester-based film suitable for label use having extremely little shrinkage whitening and having excellent tear resistance.

  The heat-shrinkable polyester film of the present invention is obtained when a sample cut into a 10 cm × 10 cm square shape is dipped in 70 ° C. warm water for 10 seconds and then dipped in 25 ° C. water for 10 seconds. The heat shrinkage rate in the maximum shrinkage direction is 30-50%, the heat-shrinkable polyester film is stored for 4 weeks in an environment with a temperature of 30 ° C. and a relative humidity of 85%. The difference between the haze of the film after the shrinkage and the haze of the film before the shrinking treatment is 5% or less, and a tensile test in a direction perpendicular to the maximum shrinkage direction of the film was performed by a distance between chucks of 20 mm and a specimen width of 15 mm When the test was carried out under the conditions of a temperature of 23 ° C. and a tensile speed of 200 mm / min, the summary was that the number of test pieces fractured at a breaking elongation of 5% or less was 10% or less of the total number of test pieces (20). To.

  Since the film of the present invention hardly causes shrinkage whitening, the difference between the haze after shrinkage and the haze before shrinkage is set to 5% or less.

  Here, the haze measurement is performed as follows. First, the heat-shrinkable polyester film is stored for 4 weeks in an environment of a temperature of 30 ° C. and a relative humidity of 85%. Next, using this film, a tube-shaped label is prepared so that the maximum shrinkage direction of the film is the circumferential direction by a solvent adhesion method or a heat seal method, and this label is covered with a glass bottle adjusted to a temperature of 40 ° C. Then, heat shrinkage is performed by applying hot air at 150 ° C. (wind speed 10 m / sec) for 13 seconds. A film sample is cut out from each label (number of label samples: 10) after the heat shrinkage. About these film samples, it measures based on JISK7136 and calculates | requires an average value. The haze difference is a numerical value obtained by subtracting the average value of 10 samples measured in accordance with JIS K 7136 for the sample cut from the heat-shrinkable polyester film immediately after production from the average value in this method.

The “maximum shrinkage direction” means the direction in which the sample is most contracted, and the thermal shrinkage rate in the maximum shrinkage direction is determined by the shrinkage rate in the vertical direction or the horizontal direction of the square sample. That is, the heat shrinkage rate (%) in the maximum shrinkage direction was measured by measuring the length of the film in the vertical and horizontal directions after immersing a 10 cm × 10 cm sample in 95 ° C. ± 0.5 ° C. water for 10 seconds under no load. By doing so, it can be obtained by the following equation.
Heat shrinkage rate = 100 × (length before shrinkage−length after shrinkage) ÷ (length before shrinkage)

In this case, it is preferable that adhesion is possible with a non-chlorine solvent.
Here, “adhesion with a non-chlorine solvent” means a case where the evaluation is “good”.
The film was joined into a tube shape using 1,3-dioxolane and tetrahydrofuran (THF) and left in an environment at a temperature of 23 ° C. and a relative humidity of 65% for 24 hours. A sample is taken by cutting to a width of 15 mm in the orthogonal direction, and a T-type peel test is performed on the bonded portion in the above direction according to JIS K 6854.
The number of test pieces was 20, and the test piece length was 60 mm, the chuck was 20 mm, the test piece width was 15 mm, the temperature was 23 ° C., and the tensile speed was 200 mm / min.
The solvent adhesion was evaluated based on the following criteria.
Peel adhesion strength 3N / 15mm or more: ○
Peel adhesion strength 1N / 15mm or more: △
Peeling adhesive strength less than 1N / 15mm: ×

In the heat-shrinkable polyester film of the second invention, the polyester contains a polyester elastomer containing 1 to 30 mol% of ε-caprolactone component, and among the polyhydric alcohol components, 1,4-cyclohexanedimethanol component is contained. It is characterized by containing 1 mol% or more.
The use of these polyhydric alcohol components further reduces the occurrence of shrinkage whitening, shrinkage spots, wrinkles, distortion, vertical shrinkage, etc., and is particularly effective in suppressing shrinkage whitening in hot air tunnels. Furthermore, the appearance of the shrink-finished finish is particularly beautiful at low temperatures.

In this case, it is preferable that the polyester contains butanediol in the polyhydric alcohol component.
At this time, the adhesive strength with a non-chlorinated solvent is improved, which is preferable.

  The heat-shrinkable polyester film of the present invention has very few occurrences of defects such as shrinkage whitening and shrinkage spots, wrinkles and vertical shrinkage after shrinkage, and also has excellent solvent adhesion, so that it can be used for shrink labels, cap seals, shrinkage It can be suitably used for applications such as packaging.

  The heat-shrinkable polyester film of the present invention is obtained when a sample cut into a 10 cm × 10 cm square shape is dipped in 70 ° C. warm water for 10 seconds and then dipped in 25 ° C. water for 10 seconds. The heat shrinkage in the maximum shrinkage direction must be 30-50%. If the film has a heat shrinkage ratio of less than 30%, the film does not have sufficient heat shrinkage, and when the container is coated and shrunk to a container or the like, it does not adhere to the container and an appearance defect occurs. However, when the thermal shrinkage rate exceeds 50%, the label jumps up, which is not preferable. A more preferable lower limit of the heat shrinkage rate is 35%, and a more preferable upper limit is 45%.

  The heat-shrinkable polyester film of the present invention is obtained when a sample cut into a 10 cm × 10 cm square shape is dipped in 98 ° C. warm water for 10 seconds and then dipped in 25 ° C. water for 10 seconds. The heat shrinkage rate in the direction orthogonal to the maximum shrinkage direction should be 0-15%. If the thermal shrinkage of the film is less than 0%, the balance between the strength in the direction orthogonal to the maximum shrinkage and the finish cannot be achieved. However, if the heat shrinkage rate exceeds 15%, it is not preferable because the finish is inferior due to the occurrence of label jumping. A more preferable lower limit of the heat shrinkage rate is 3%, and a more preferable upper limit is 13%.

  The present invention also provides a heat-shrinkable polyester film that hardly causes shrinkage whitening. As a guide, the heat-shrinkable polyester film is stored for 4 weeks in an environment of a temperature of 30 ° C. and a relative humidity of 85%. The difference between the haze of the film after heat-shrinking the film after storage under a predetermined condition and the haze of the film before shrinkage treatment is 5% or less. When the haze difference exceeds 5%, the transparency of the film coated and mounted on the transparent glass bottle is impaired, and the level is recognized as whitening by visual judgment. The haze difference is preferably as small as possible, more preferably 3% or less, and even more preferably 1% or less.

  Note that the heat-shrinkable polyester film is stored for 4 weeks in an environment of temperature 30 ° C. and relative humidity 85% before heat-shrinking. This is because it has been found to be easy.

  The mechanism of the whitening phenomenon is not clear, but shrinking whitening occurs when heat shrinks in a hot air tunnel or when heat shrinks after being stored for a long time in an atmosphere of 30 ° C or higher as described above. The phenomenon is known to occur easily. In addition, during heat shrinkage, a temperature difference occurs between the inner surface of the film (the surface that contacts the container) and the outer surface (the surface that does not contact the container), resulting in shrinkage spots, and the film surface of the spots is roughened and visually observed as whitening. Recognized. That is, while the movement of the film on the surface in contact with the container is restricted, heat is transferred on the outer surface side, and since the movement is not restricted by the amount of contact with the container, shrinkage occurs between the inner surface side and the outer surface side of the film. If it becomes non-uniform and this non-uniformity becomes extreme, it will whiten. This shrinkage whitening phenomenon is thought to occur because the molecular chain of the polyester is partially crystallized and the refractive index of light in the crystal part is different from that of the amorphous part. Shrinkage whitening is undesirable because it reduces the transparency of some of the shrinkage labels.

  In the present invention, when the difference between the haze after heat shrinkage measured by the above method and the haze immediately after production exceeds 5%, shrinkage whitening occurs when stored for a longer period of time. As a non-defective product. Therefore, in the present invention, the upper limit of the haze difference is set to 5%.

  Moreover, in this invention, it is suitable that it can adhere | attach with a non-chlorine-type solvent. The label is rolled into a cylindrical shape so that the maximum shrinkage direction of the heat-shrinkable polyester film of the present invention is the circumferential direction, and the ends are bonded to each other to create a tubular body. It is created by cutting. Adhesive solvents include aromatic hydrocarbons such as benzene, toluene, xylene and trimethylbenzene; halogenated hydrocarbons such as methylene chloride and chloroform; phenols such as phenol; furans such as tetrahydrofuran; 1,3-dioxolane. Organic solvents such as oxolanes are used, but in consideration of the generation of toxic substances caused by halogens such as chlorine atoms, it is preferable that they can be bonded with non-chlorine organic solvents, and in particular, from the viewpoint of safety Therefore, it is desirable to use tetrahydrofuran and 1,3-dioxolane.

  In addition, the present invention provides a heat-shrinkable polyester film having excellent shrinkage characteristics and shrinkage finish properties in a wide temperature range from low temperature to high temperature. The shrinkage and finish were evaluated visually, and the shrinkage finish score was 4 or more.

Here, the finish property is evaluated as follows. First, using a printing machine on the film, printing is performed in the order of grass, blue gold, and white. Next, using this film, a tube-like label was prepared so as to be in the maximum shrinkage direction of the film by a solvent adhesion method or a heat seal method, and this label was put on a glass bottle adjusted to a temperature of 60 ° C., and 130 ° C. , 160 ° C., 190 ° C. (wind speed 12 m / sec) is applied for 10 seconds to cause heat shrinkage. The shrinkage and finish of the entire label were visually evaluated in five stages (measurement number 200).
The criteria are as follows.
5: Best finish 4: Excellent finish 3: Some defects (within 2 locations)
2: There are defects (3-5 locations)
1: Many defects (over 6 locations)
As a result, 4 or higher was regarded as acceptable, and 4 or lower was regarded as defective.
In addition, a fault refers to what generically refers to jumping, wrinkles, insufficient shrinkage, label edge folding, and shrinkage whitening.

  The present invention also provides a heat-shrinkable polyester film having excellent tear resistance. As a guide, the heat-shrinkable polyester film is stored for 2 weeks in an environment of a temperature of 30 ° C. and a relative humidity of 85%. After that, a tensile test in the direction perpendicular to the maximum shrinkage direction of the film after storage was performed under the conditions of a distance between chucks of 20 mm, a test piece width of 15 mm, a temperature of 23 ° C., and a tensile speed of 200 mm / min. When done, the number of specimens with a breaking elongation of 5% or less must be 10% or less of the total number of specimens. In addition, the reason why the heat-shrinkable polyester film is stored for 4 weeks in an environment of a temperature of 30 ° C. and a relative humidity of 85% before the tensile test is that the heat-shrinkable film is usually stored at 20 to 25 ° C. This is because the deterioration of the tear resistance is promoted by storing for 4 weeks at a temperature higher than the normal storage condition of 30 ° C. and a high humidity of 85% relative humidity. Further, the tensile test in the direction orthogonal to the maximum shrinkage direction is because the polyester molecular chains are aligned along the shrinkage direction by stretching and the strength in the maximum shrinkage direction is increased, whereas the direction orthogonal to this direction is This is because the entanglement between adjacent molecular chains is reduced, the strength is lowered, and it is easily broken, that is, it is easily broken along the alignment direction of the molecular chains.

  The number of test pieces having a breaking elongation of 5% or less is 10% or less of the total number of test pieces. In other words, the film that breaks before 5% of elongation is 10% of the total number of test pieces. (10%) or less. The smaller the number of specimens having a breaking elongation of 5% or less, the better. Films that satisfy the above conditions have excellent tear resistance even when stored at high temperatures and high humidity, so that loss due to film cutting during printing and tubing can be reduced. Processing becomes possible.

  Here, by stretching the film in a direction perpendicular to the maximum shrinkage direction, polyester molecular chains in a direction perpendicular to the maximum shrinkage direction can be arranged and the strength can be increased. However, if the stretch ratio is increased too much, shrinkage finish and inconvenience of the shrinkage label mounted on the container will be inferior, which is not preferable. A stretching of 1.01 to 1.2 times that can ensure a fracture number of 10% or less and a finish of 4 or more is preferable.

  Next, the preferable composition of the heat-shrinkable polyester film of the present invention will be described. In order to maintain physical strength properties such as tear resistance, strength and heat resistance of the film, it is preferable that a crystalline unit (such as an ethylene terephthalate unit) is present in the polyester film. Only the sex unit has a low heat shrinkage rate, and it is difficult to develop a high shrinkage rate of 40% by 70 ° C., 10 second hot water treatment. Moreover, since solvent resistance becomes high too much, it is difficult to obtain the solvent adhesiveness used when processing a shrink film into a tube shape.

  As the dicarboxylic acid component constituting the polyester, aromatic dicarboxylic acids or ester-forming derivatives thereof, or aliphatic dicarboxylic acids can be used. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, naphthalene-1,4- or -2,6-dicarboxylic acid, and 5-sodium sulfoisophthalic acid. Examples of these ester derivatives include derivatives such as dialkyl esters and diaryl esters. Examples of the aliphatic dicarboxylic acid include dimer acid, glutaric acid, adipic acid, sebacic acid, azelaic acid, oxalic acid, and succinic acid. Further, an oxycarboxylic acid such as p-oxybenzoic acid, and a polyvalent carboxylic acid such as trimellitic anhydride or pyromellitic anhydride may be used in combination as necessary.

  1,4-cyclohexanedimethanol has the effect of increasing the degree of amorphousization and developing heat shrinkability. Further, the use of 1,4-cyclohexanedimethanol improves the shrink finish and improves the solvent adhesion. In order to sufficiently obtain these effects, it is preferable that 1,4-cyclohexanedimethanol is 1 mol% or more in 100% of the polyhydric alcohol component. Further, the shrinkage whitening phenomenon can be suppressed by using 1,4-cyclohexanedimethanol, and the resulting film satisfies the above-mentioned haze requirements.

  As described above, in the heat-shrinkable polyester film of the present invention, it is desirable to use a crystalline ethylene terephthalate unit as a constituent component of the polyester base in order to exhibit tear resistance, strength, and heat resistance. For example, by using 1,4-cyclohexanedimethanol, it is preferable to lower the crystallinity of the polyester to increase the degree of amorphization and develop a high heat shrinkage rate. Therefore, if 1,4-cyclohexanedimethanol is less than 1 mol%, the ethylene terephthalate unit increases and the crystallinity of the polyester increases, so that there is a risk of whitening due to insufficient shrinkage or partial crystallization. In addition, since the solvent resistance becomes too high, adhesion failure may occur when a film is bonded to a tubular body using a solvent such as tetrahydrofuran or 1,3-dioxolane, which is not preferable.

However, 1,4-cyclohexanedimethanol is preferably suppressed to 40 mol% or less in 100 mol% of the polyhydric alcohol component. If it exceeds 40 mol%, the shrinkage rate of the film becomes excessively high, and there is a risk of label displacement and pattern distortion in the heat shrinking process. Further, since the solvent resistance of the film is lowered, the film is whitened by an ink solvent (such as ethyl acetate) in the printing process, or the tear resistance of the film is lowered. Therefore, 37 mol% or less is more preferable, and 35 mol% or less is more preferable.
In addition, when 1,4-cyclohexanedimethanol is less than 10% in 100 mol% of the polyhydric alcohol component, solvent adhesion and shrink finish cannot be obtained. It is preferable that 1, 4-cyclohexane dimethanol is 10 mol% or more out of 100% of the components. Further, the whitening phenomenon can be suppressed by using 1,4-cyclohexanedimethanol, and the obtained film satisfies the above-mentioned haze requirement. The amount of 1,4-cyclohexanedimethanol is more preferably 12 mol% or more, and further preferably 14 mol% or more.

Other diol components constituting the polyester used in the present invention include ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, and 3-methyl 1 , 5-pentanediol, 2-methyl-1,5-pentanediol, 2,2-diethyl-1,3-propanediol, 1,9-nonanediol, alkylene glycol such as 1,10-decanediol, polyoxy Examples include ether glycols such as tetramethylene glycol, polyethylene glycol, bisphenol compounds or alkylene oxide adducts thereof, dimer diols, and the like. Trihydric or higher alcohols include trimethylolpropane, glycerin, pentaerythritol and the like. Among the polyhydric alcohol components, a neopentyl glycol component and the like are useful components for amorphizing the film, and can increase the heat shrinkability of the film. Moreover, a 1, 4- butanediol component, a propylene glycol component, etc. are useful components for lowering the glass transition temperature of the film and enabling heat shrinkage even at low temperatures.
The ratio of the second alcohol component other than 1,4-cyclohexanedimethanol is, for example, about 15 to 80 mol%, preferably about 18 to 75 mol% in 100 mol% of the polyhydric alcohol component.

In addition, the use of a polyester-based elastomer is preferable because the degree of amorphousness is increased, and heat shrinkage characteristics, particularly heat shrinkage characteristics in a low temperature region, are increased.
The polyester elastomer (polyester block copolymer) used in the present invention is a polyester block copolymer comprising a high melting crystalline polyester segment (hard segment) and a low melting point soft polymer segment (soft segment) having a molecular weight of 400 or more. These segments are polymers, and the high melting point crystalline polyester segment has a melting point of 200 ° C. or higher when a high polymer is formed only from its constituent components, and the low melting point soft polymer segment has a constitution It refers to a copolymer having a melting point or softening point of 80 ° C. or lower when measured by components alone. The high-melting crystalline polyester segment (hard segment) has a melting point of 200 ° C. or higher when it is made into a fiber-forming high polymer only with its constituent components. The high-melting crystalline polyester segment includes, for example, residues of aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, ethylene glycol, propylene glycol, 1, Aliphatic, aromatic, or alicyclic such as 4-butanediol, tetramethylene glycol, pentamethylene glycol, 2,2-dimethyltrimethylene glycol, hexamethylene glycol, decamethylene glycol, p-xylene glycol, cyclohexanedimethanol Polyesters composed of diol residues; or polyesters composed of oxyacid residues such as p- (β-hydroxyethoxy) benzoic acid and p-oxybenzoic acid pivalolactone; or 1,2-bis (4,4′- Dicarboxymethyl A polyether ester comprising a residue of an aromatic ether dicarboxylic acid such as (noxy) ethane or di (4-carboxyphenoxy) ethane and a residue of the above aliphatic, aromatic or alicyclic diol; or bis (N Polyamide ester composed of a residue of an aromatic amide dicarboxylic acid such as -paracarboethoxyphenyl) terephthalimide and a residue of the above aliphatic, aromatic, or alicyclic diol.

  Furthermore, a copolyester using two or more of the above dicarboxylic acid residues and / or diol residues can also be used. The low melting point soft polymer segment (soft segment) having a molecular weight of 400 or more shows a substantially amorphous state in the polyester block copolymer, and has a melting point or a melting point when measured only with the constituent components of the segment. The softening point is 80 ° C. or lower. The molecular weight of the low melting point soft polymer segment is 400 to 8000, preferably 700 to 5000. Moreover, it is preferable that the ratio of the low melting-point soft polymer segment in a polyester-type elastomer is 1 to 90 weight%. A particularly desirable ratio is 5 to 80% by weight. Typical low melting point soft polymer segments include polyethylene oxide glycol, polypropylene oxide glycol, polytetramethylene oxide glycol, glycol of ethylene oxide / propylene oxide copolymer, glycol of ethylene oxide / tetrahydrofuran copolymer. Polyethers such as polyneopentyl azelate, polyneopentyl adipate, polyneopentyl sebacate, etc., but from the point of compatibility with the polyester constituting the polyester film, poly-ε -Polyester elastomers using polylactones such as caprolactone in the soft segment are particularly preferred.

  In the present invention, a polyester elastomer composed of a copolyester of polybutylene terephthalate and ε-caprolactone is preferable because it has a high effect of increasing the degree of amorphousness and heat shrinkage characteristics, particularly in the low temperature range. In addition, the use of a polyester elastomer made of a copolyester of polybutylene terephthalate and ε-caprolactone improves the shrinkage finish. In order to sufficiently obtain these effects, it is preferable that ε-caprolactone is 1 to 30 mol% in 100 mol% of the polyester component constituting the polyester film. The content is preferably 3 to 25 mol%, particularly preferably 5 to 20 mol%. If the amount of ε-caprolactone is 1 mol% or less, heat shrinkability in a low temperature range cannot be obtained, and there is a risk of causing insufficient shrinkage or shrinkage finish. On the other hand, if it is 30 mol% or more, physical strength such as tear resistance, strength and heat resistance of the film cannot be obtained sufficiently.

  The polyester composition used in the present invention further includes, for example, inorganic lubricants such as titanium dioxide, fine-particle silica, kaolin, and calcium carbonate, and, for example, long chains to improve the slipperiness of the heat-shrinkable film. It is also preferable to contain an organic lubricant such as a fatty acid ester. Moreover, you may contain additives, such as a stabilizer, a coloring agent, antioxidant, an antifoamer, an antistatic agent, and an ultraviolet absorber, as needed.

  In the heat-shrinkable polyester film of the present invention, inorganic particles, organic salt particles and crosslinked polymer particles can be added as a lubricant.

  Inorganic particles include calcium carbonate, kaolin, talc, magnesium carbonate, barium carbonate, calcium sulfate, barium sulfate, lithium phosphate, calcium phosphate, magnesium phosphate, aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, riotium fluoride, etc. Is mentioned.

  In particular, in order to obtain a film with a lower haze while obtaining good handling properties, the inorganic particles are preferably agglomerated silica particles formed by agglomerating primary particles.

  Examples of the organic salt particles include terephthalate such as calcium oxalate, calcium, barium, zinc, manganese, and magnesium.

  Examples of the crosslinked polymer particles include homopolymers or copolymers of vinyl monomers such as divinylbenzene, styrene, acrylic acid or methacrylic acid. In addition, organic particles such as polytetrafluoroethylene, benzoguanamine resin, thermosetting urea resin, and thermosetting phenol resin may be used.

  Examples of the method for adding the lubricant include a method in which the lubricant is dispersed in the polymerization step of the polyester used as the film raw material, a method in which the polyester after polymerization is melted again, and the like. In order to disperse the lubricant uniformly in the film roll, after the lubricant is dispersed in the polyester by any of the methods described above, the shape of the polymer chip in which the lubricant is dispersed is matched and the raw material segregation in the hopper It is preferable to suppress this phenomenon. Taking polyester as an example, a polyester chip that is taken out in a molten state from a polymerization apparatus in a molten state after polymerization and immediately cooled with water and then cut with a strand cutter has a cylindrical shape with an elliptical bottom surface. It is preferable to use different raw material chips in which the average size of the major axis, minor axis, and cylindrical height of the elliptical bottom surface is within the range of the chip size ± 20% of the raw material species with the highest usage ratio, More preferably, the size is within a range of ± 15%.

  Moreover, although the thickness of the film which comprises the heat-shrinkable film roll of this invention is not specifically limited, For example, 10-200 micrometers is preferable as a shrink film for labels, and 20-100 micrometers is more preferable.

  Hereinafter, although the case where it comprises with a polyester-type heat-shrinkable film is mentioned as an example and demonstrated, this invention is not limited to this. The polyester raw material which comprises a polyester-type heat-shrinkable film may be individual, and may mix and use 2 or more types. When using 2 or more types together, a mixed system of polyethylene terephthalate and copolymerized polyester may be used, or a combination of copolymerized polyesters may be used. A combination with a homopolyester such as polybutylene terephthalate, polycyclohexylene dimethyl terephthalate, or polyethylene naphthalate may also be used. A method of mixing two or more kinds of polyesters having different Tg can also be an effective achievement means from the viewpoint of shrink finish. As a specific configuration, for example, a polyester having a dicarboxylic acid component consisting of terephthalic acid and 2,6-naphthalenedicarboxylic acid, and a diol component consisting of ethylene glycol, dimer diol and polytetramethylene glycol (molecular weight 650), and the like can be mentioned. There is a method of making these into a single copolymer system or a mixed system of two or more. The polyester can be produced by melt polymerization according to a conventional method, but is not limited thereto, and may be a polyester obtained by other polymerization methods. The degree of polymerization of the polyester is preferably from 0.3 to 1.3 in terms of intrinsic viscosity.

  In addition to polymerization catalysts such as antimony oxide, germanium oxide, and titanium compounds, the polyester includes Mg salts such as magnesium acetate and magnesium chloride, calcium acetate, and calcium chloride for the purpose of improving heat resistance such as coloring and gel generation. Mn salt such as manganese acetate and manganese chloride, Zn salt such as zinc chloride and zinc acetate, Co salt such as cobalt chloride and cobalt acetate, respectively, as a metal ion with respect to the resulting polyester, 300 ppm or less, phosphoric acid or Phosphoric acid ester derivatives such as phosphoric acid trimethyl ester and phosphoric acid triethyl ester can be added in an amount of 200 ppm or less in terms of phosphorus (P).

When the total amount of metal ions other than the polymerization catalyst exceeds 300 ppm and the amount of P exceeds 200 ppm with respect to the produced polyester, not only the coloring of the polymer becomes remarkable, but also the heat resistance and hydrolysis resistance of the polymer are remarkably lowered.
At this time, in terms of heat resistance, hydrolysis resistance, etc., the molar atomic ratio (P / M) of the total P amount (P) and the total metal ion amount (M) is 0.4 to 1.0. It is preferable. When the molar atomic ratio (P / M) is less than 0.4 or exceeds 1.0, coloring of the composition of the present invention and generation of coarse particles become remarkable, which is not preferable.

  The production method of the polyester is not particularly limited, but a so-called direct polymerization method in which an oligomer obtained by directly reacting a dicarboxylic acid and a glycol is polycondensed, and a dimethyl ester of dicarboxylic acid and a glycol are transesterified. Examples include a so-called transesterification method in which polycondensation is performed later, and any production method can be applied.

  The timing of adding the above metal ions, phosphoric acid and derivatives thereof is not particularly limited. Generally, metal ions are added at the time of raw material charging, that is, before transesterification or esterification, and phosphoric acids are added before polycondensation reaction. Is preferred.

  Moreover, antioxidants, ultraviolet absorbers, antistatic agents, colorants, antibacterial agents, and the like can be added as necessary. The preferred intrinsic viscosity for forming the film is not limited, but is usually 0.50 to 1.30 dl / g.

  The polyester raw material used for this invention is dried using dryers, such as a hopper dryer and a paddle dryer, or a vacuum dryer, and it extrudes in the form of a film at the temperature of 200-300 degreeC. Alternatively, an undried polyester raw material is similarly extruded into a film while removing moisture in a vented extruder. At this time, it is preferable to take measures to reduce the composition fluctuation of the polymer component described above. When extruding, any existing method such as a T-die method or a tubular method may be adopted. After extrusion, it is cooled rapidly to obtain an unstretched film. Stretching is performed on the unstretched film, but in order to achieve the object of the present invention, the lateral direction is practical as the main shrinking direction. For example, when the main shrinkage direction is the longitudinal direction, the film can be formed in accordance with a normal operation in addition to changing the stretching direction in the following method by 90 degrees.

In addition, when paying attention to uniforming the thickness distribution of the desired heat-shrinkable polyester film, the thermal conductivity coefficient is preliminarily applied in the preheating step prior to the stretching step when stretching in the transverse direction using a tenter. Is preferably heated at a low wind speed of 0.0013 calories / cm ² · sec · ° C. or less until the film temperature reaches Tg−20 ° C. to Tg + 60 ° C. Stretching in the transverse direction is performed at a temperature of −25 ° C. to Tg + 35 ° C., more preferably at a temperature of −5 ° C. to Tg + 5 ° C., and 2.3 to 7.3 times, preferably 3.5 to 6.0 times. Thereafter, heat treatment is performed at a temperature of 60 ° C. to 80 ° C. while stretching 0 to 15% or relaxation of 0 to 15%, and further heat treatment is performed at a temperature of 40 ° C. to 100 ° C. as necessary. A conductive polyester film is obtained. In this transverse stretching process, it is preferable to take measures to suppress temperature fluctuations in the aforementioned process.

As a stretching method, not only horizontal uniaxial stretching with a tenter, but also stretching in the longitudinal direction is 1.03 times or more, preferably 1.05 times to 1.2 times. The biaxial stretching may be either sequential biaxial stretching or simultaneous biaxial stretching, and may be re-stretched as necessary. Further, in sequential biaxial stretching, any of stretching methods such as vertical and horizontal, horizontal and vertical, vertical and horizontal and horizontal and vertical and horizontal directions may be used. Even when these longitudinal stretching steps or biaxial stretching steps are adopted, the film roll of the present invention is subject to fluctuations in the film surface temperature measured at a fixed position in the preheating step, stretching step, etc., similarly to the transverse stretching. Within the range of the distance in the flow direction corresponding to the film winding length, the average temperature is preferably within ± 1 ° C, and more preferably within the average temperature ± 0.5 ° C. From the viewpoint of suppressing the internal heat generation of the film accompanying stretching and reducing the film temperature unevenness in the width direction, the heat transfer coefficient in the stretching process is preferably 0.0037 J / cm ² · sec · ° C. or more. More preferably, the condition of 0.00544 to 0.00837 J / cm ² · sec · ° C. is good.

  Next, the present invention will be described in more detail using examples and comparative examples, but is not limited to the following examples. Moreover, the measuring method of the physical property of the film obtained by the Example and the comparative example is shown below.

(1) Composition A sample (chip or film) is dissolved in a solvent in which chloroform D (manufactured by Usolip) and trifluoroacetic acid D1 (manufactured by Usolip) are mixed at a ratio of 10: 1 (volume ratio) to prepare a sample solution. , NMR (“GEMINI-200”; manufactured by Varian) was used to measure the proton NMR of the sample solution under the measurement conditions of a temperature of 23 ° C. and an integration count of 64 times. Based on the peak intensity of protons measured by NMR measurement, the composition ratio of monomers constituting the sample was calculated.

(2) The heat shrinkage film is cut into a 10 cm × 10 cm square, and is heat-shrinked in hot water at 70 ° C. ± 0.5 ° C. under no load for 10 seconds, and then 25 ° C. ± 0.5 ° C. After being immersed in water for 10 seconds, the length of the sample in the vertical and horizontal directions was measured, and the thermal shrinkage rate was determined according to the following formula.
Heat shrinkage rate (%) = (length before shrinkage−length after shrinkage) ÷ length before shrinkage × 100

(3) A heat-shrinkable polyester film is stored for 4 weeks in an environment having a haze temperature of 30 ° C. and a relative humidity of 85%. Next, using this film, a tube-shaped label is prepared so that the maximum shrinkage direction of the film is the circumferential direction by a solvent adhesion method or a heat seal method, and this label is covered with a glass bottle adjusted to a temperature of 40 ° C. Then, heat shrinkage is performed by applying hot air at 150 ° C. (wind speed 10 m / sec) for 13 seconds. A film sample is cut out from each label (number of label samples: 10) after the heat shrinkage. About these film samples, it measures based on JISK7136 and calculates | requires an average value. The haze difference is a numerical value obtained by subtracting the average value of 10 samples measured in accordance with JIS K 7136 for the sample cut from the heat-shrinkable polyester film immediately after production from the average value in this method.

(4) A printing machine is used for the shrinkable finish film, and the ink is printed in the order of grass, blue gold, and white. Next, using this film, a tube-like label was prepared so as to be in the maximum shrinkage direction of the film by a solvent adhesion method or a heat seal method, and this label was put on a glass bottle adjusted to a temperature of 60 ° C., and 130 ° C. , 160 ° C., 190 ° C. (wind speed 12 m / sec) is applied for 10 seconds to cause heat shrinkage. The overall shrinkage and finish of this label were visually evaluated on a five-point scale. The criteria are as follows.
5: Best finish 4: Excellent finish 3: Some defects (within 2 locations)
2: There are defects (3-5 locations)
1: Many defects (over 6 locations)
As a result, 4 or higher was regarded as acceptable, and 3 or lower was regarded as defective.
In addition, a fault refers to what generically refers to jumping, wrinkles, insufficient shrinkage, label edge folding, and shrinkage whitening.

(5) Solvent adhesion The film was joined into a tube shape using 1,3-dioxolane and tetrahydrofuran (THF), and left in an environment at a temperature of 23 ° C. and a relative humidity of 65% for 24 hours. A sample is taken by cutting it to a width of 15 mm in the flow direction and the orthogonal direction at the time of processing, and a T-type peel test is performed on the joint portion in the above direction according to JIS K 6854.
The number of test pieces was 20, and the test piece length was 60 mm, the chuck was 20 mm, the test piece width was 15 mm, the temperature was 23 ° C., and the tensile speed was 200 mm / min.
The solvent adhesion was evaluated based on the following criteria.
Peel adhesion strength 3N / 15mm or more: ○
Peel adhesion strength 1N / 15mm or more: △
Peeling adhesive strength less than 1N / 15mm: ×

(6) The film is stored for 4 weeks in an environment with a tear resistance temperature of 30 ° C. and a relative humidity of 85%. A tensile test is performed in a direction orthogonal to the maximum shrinkage direction of the film after storage. The number of test pieces was 20. The test piece length was 70 mm, the distance between chucks was 20 mm, the test piece width was 15 mm, the temperature was 23 ° C., and the tensile speed was 200 mm / min. The number of test pieces that broke at an elongation of 5% or less was counted, and the percentage with respect to the total number of test pieces (20 pieces) was determined to determine the tear resistance (%).

(Synthesis of polyester)
(Synthesis Example 1)
A stainless steel autoclave equipped with a stirrer, a thermometer and a partial recirculating cooler contains 100 mol% of dimethyl terephthalate (DMT) as a dicarboxylic acid component and 100 mol% of ethylene glycol (EG) as a polyhydric alcohol component. The polyhydric alcohol was charged so that the molar ratio was 2.2 times that of the methyl ester, 0.05 mol of zinc acetate as the transesterification catalyst (based on the acid component), and 0.025 mol% of antimony trioxide as the polycondensation catalyst. The transesterification reaction was carried out while adding methanol (to the acid component) and distilling off the produced methanol out of the system. Thereafter, a polycondensation reaction was performed at 280 ° C. under a reduced pressure condition of 26.7 Pa to obtain a polyester (A) having an intrinsic viscosity of 0.75 dl / g. The composition is shown in Table 1.

(Synthesis Examples 2 to 4)
By the same method as in Synthesis Example 1, polyesters (B) to (E) shown in Table 1 were obtained. In the table, CHDM is 1,4-cyclohexanedimethanol, NPG is neopentyl glycol, BD is 1,4-butanediol, DEG is diethylene glycol, and ε-CL is ε-caprolactone. The intrinsic viscosity of each polyester was (B): 0.72 dl / g, (C): 0.80 dl / g, (D): 1.20 dl / g (E): 0.77 dl / g. Each polyester was chipped. Table 1 shows the composition of each synthesis example.

  In addition, as for the inorganic lubricant, a master batch was prepared by adding 0.7% by mass of the inorganic lubricant used in the polyester (A) to the polyester (A), and the required amount was used. The lubricant was added in advance by dispersing the lubricant in ethylene glycol and polymerizing by the above method.

(Example 1)
Each of the preliminarily dried polyester A shown in Table 1 is 6 wt%, B is 18 wt%, C is 61 wt% E is 15 wt% in a resin state, and continuously in a hopper directly above the extruder with a quantitative screw feeder. The mixture was mixed in the hopper while being separately supplied, melt-extruded by a single screw extruder at 275 ° C., and then rapidly cooled to obtain an unstretched film having a thickness of 180 μm. This pre-stretched film was preheated until the film temperature reached 80 ° C., then stretched 1.05 times in the longitudinal direction at 85 ° C. with an MD roll, and then preheated until the film temperature reached 62 ° C. The film was stretched 4.0 times at 60 ° C. in the transverse direction with a tenter. Next, heat treatment was performed at 74 ° C. for 14 seconds to obtain a heat-shrinkable polyester film having a thickness of 45 μm.
Table 2 shows the physical property values of the film of the obtained film roll.

(Example 2)
Each separately preliminarily dried polyester A shown in Table 1 is 6 wt%, B is 13 wt%, C is 61 wt% E is 20 wt% each in a resin state. The mixture was mixed in the hopper while being separately supplied, melt-extruded by a single screw extruder at 275 ° C., and then rapidly cooled to obtain an unstretched film having a thickness of 180 μm.
This pre-stretched film was preheated until the film temperature reached 80 ° C., then stretched 1.10 times in the longitudinal direction at 85 ° C. with an MD roll, and then preheated until the film temperature reached 62 ° C. A heat-shrinkable polyester film having a thickness of 45 μm was obtained by stretching 4.0 times at 60 ° C. in the transverse direction with a tenter. The physical properties of the film roll obtained are shown in Table 2.

(Comparative Example 1)
Each of the preliminarily dried polyester A shown in Table 1 is 6 wt%, B is 18 wt%, C is 61 wt% E is 15 wt% in a resin state, and continuously in a hopper directly above the extruder with a quantitative screw feeder. The mixture was mixed in the hopper while being separately supplied, melt-extruded by a single screw extruder at 275 ° C., and then rapidly cooled to obtain an unstretched film having a thickness of 180 μm. This unstretched film was preheated until the film temperature reached 62 ° C., and then stretched 4.0 times in the transverse direction at 60 ° C. with a tenter to obtain a heat-shrinkable polyester film having a thickness of 45 μm.
Table 2 shows the physical property values of the film of the obtained film roll.

(Comparative Example 2)
Each of the preliminarily dried polyester A shown in Table 1 is 6 wt%, B is 18 wt%, C is 61 wt% E is 15 wt% in a resin state, and continuously in a hopper directly above the extruder with a quantitative screw feeder. The mixture was mixed in the hopper while being separately supplied, melt-extruded by a single screw extruder at 275 ° C., and then rapidly cooled to obtain an unstretched film having a thickness of 180 μm. This pre-stretched film was preheated until the film temperature reached 80 ° C., then stretched 1.3 times in the longitudinal direction at 85 ° C. with an MD roll, and then preheated until the film temperature reached 62 ° C. The film was stretched 4.0 times in the transverse direction at 55 ° C. with a tenter to obtain a heat-shrinkable polyester film having a thickness of 44 μm.
The physical properties of the film roll obtained are shown in Table 2.

(Comparative Example 3)
Each separately preliminarily dried polyester A shown in Table 1, 36 wt%, B 49 wt%, E 15 wt%, respectively, in a resin state is continuously supplied separately to the hopper directly above the extruder by a quantitative screw feeder. The mixture was then mixed in the hopper, melt extruded at 280 ° C. using a single screw extruder, and then rapidly cooled to obtain an unstretched film having a thickness of 180 μm. This unstretched film was preheated until the film temperature reached 80 ° C., and then stretched 4.0 times at 65 ° C. in the transverse direction with a tenter to obtain a heat-shrinkable polyester film having a thickness of 44 μm.
Table 2 shows the physical property values of the film of the obtained film roll.

(Comparative Example 4)
Each of the preliminarily dried polyester A shown in Table 1, 6 wt%, B 14 wt%, C 56 wt%, and D 24 wt%, respectively, is continuously in a resinous state with a fixed screw feeder to the hopper directly above the extruder. While being separately supplied, they were mixed in the hopper, melt-extruded by a single screw extruder at 280 ° C., and then rapidly cooled to obtain an unstretched film having a thickness of 175 μm. This pre-stretched film was preheated until the film temperature reached 80 ° C., then stretched 1.1 times at 85 ° C. in the longitudinal direction with an MD roll, and then preheated until the film temperature reached 72 ° C. The film was stretched 4.0 times in the transverse direction at 69 ° C. with a tenter to obtain a heat-shrinkable polyester film having a thickness of 45 μm.
Table 2 shows the physical property values of the film of the obtained film roll.

(Comparative Example 5)
Each separately pre-dried polyester A shown in Table 1, 10 wt%, B 66 wt%, D 24 wt%, respectively, in a resin state is continuously fed separately to the hopper directly above the extruder by a quantitative screw feeder. The mixture was then mixed in the hopper, melt extruded at 280 ° C. using a single screw extruder, and then rapidly cooled to obtain an unstretched film having a thickness of 175 μm. This unstretched film was preheated until the film temperature reached 87 ° C., and then stretched 4.0 times at 70 ° C. in the transverse direction with a tenter to obtain a heat-shrinkable polyester film having a thickness of 45 μm.
Table 2 shows the physical property values of the film of the obtained film roll.

Claims (4)

  In a heat-shrinkable polyester film, a sample cut into a 10 cm × 10 cm square shape is dipped in 70 ° C. warm water for 10 seconds, then dipped in water at 25 ° C. for 10 seconds and then pulled up. The heat shrinkage ratio of the film was 30-50%, and was immersed in 98 ° C. warm water for 10 seconds and then pulled up and then immersed in 25 ° C. water for 10 seconds. A heat shrinkable polyester film was stored for 4 weeks in an environment with a heat shrinkage rate of 0 to 15%, a temperature of 30 ° C. and a relative humidity of 85%. The difference between the haze of the film and the haze of the film before the shrinkage treatment is 5% or less, and a tensile test in a direction perpendicular to the maximum shrinkage direction of the film was performed using a chuck distance of 20 mm and a test piece width. Heat shrinkability, characterized in that the number of test pieces fractured at a breaking elongation of 5% or less is 10% or less of the total number of test pieces when performed at 5 mm, a temperature of 23 ° C., and a tensile speed of 200 mm / min. Polyester film.   The heat-shrinkable polyester film according to claim 1, wherein the heat-shrinkable polyester film can be bonded with a non-chlorine organic solvent.   A heat-shrinkable polyester film, wherein the polyester contains a polyester elastomer containing 1 to 30 mol% of ε-caprolactone component, and among the polyhydric alcohol components, 1 mol% of 1,4-cyclohexanedimethanol component A heat-shrinkable polyester film characterized by being contained above.   The heat-shrinkable polyester film according to claim 3, wherein the polyhydric alcohol component contains butanediol.