JP2008239999A - Heat-shrinkable polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-shrinkable polyester film excellent in impact resistance during transportation, especially under low temperature, with favorable finishing under contracted state and having sufficient solvent adhesiveness, particularly for canned product accumulation. <P>SOLUTION: The heat-shrinkable polyester film shows shrinkage rate of 55% or over in warm water in main shrinking direction at 95°C for 10 seconds and 20% or less of rejection rate of transversal rupture under following vibration test. The rejection rate in transversal rupture is defined as follows: accumulation of adhesively processed film in a tube form covering a specific size squeezed and accumulated three cans of canned food in the height direction, shrinking and fixing in a shrink tunnel, packaging in a specific size corrugated card board box in six lines in the vertical direction and three lines in the horizontal direction, 18 packs in total and sealing. Then, the packed corrugated board is shaken in the vertical direction and horizontally at 180 reciprocates/min. for 30 min., and those resulted in a rupture of 30 mm or over on the circumference of the can were judged for rejection. The rate of transversally ruptured defective packs in 18 packs is defined as the rejection incidence rate (%). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a heat-shrinkable polyester film, and more particularly to a heat-shrinkable polyester film suitable for label applications. More specifically, it is used for labels for integrated packaging, especially for canned labels, and has excellent impact resistance during transportation, especially at low temperatures, and has a good finish when contracted, and has sufficient solvent adhesion. The present invention relates to a shrinkable polyester film.

  In the field of shrinkable films for integrated packaging such as cans, heat-shrinkable films have been used mainly with films made of polyvinyl chloride, polystyrene, etc., but in recent years, when polyvinyl chloride burns when discarded. There is a problem of generation of chlorine gas, a problem that printing is difficult for polystyrene, and heat shrinkable polyester films are attracting attention.

  However, in the case of shrink-wrapping using a conventional heat-shrinkable polyester film for labels, scratches are likely to occur due to impacts between the aggregates during transportation, friction with the box packing the aggregates, etc., and film formation In this case, there is a problem that the film is largely broken in the main shrinkage direction due to the property that the film is stretched in one direction, the packaged body cannot be held, and the commercial value is impaired. In particular, at low temperatures, there is a problem that the film is similarly torn even when polyvinyl chloride that is flexible and resistant to tearing is used.

  To deal with these problems, it is possible to orient in the direction perpendicular to the main shrinkage direction during film formation, and to prevent tearing in one direction, but when the balance of orientation with the direction perpendicular to the main shrinkage direction is poor The problem is that the balance of shrinkage is not balanced, the finish is poor at the time of shrinkage attachment, and sufficient solvent adhesion cannot be obtained when producing a tube from a film using a non-chlorine solvent that is preferred for environmental problems. Will occur.

  The present invention solves the above-mentioned problems of the conventional heat-shrinkable polyester film, has excellent impact resistance at the time of transportation, particularly at low temperatures, has a good finish at the time of shrinkage, and has sufficient solvent adhesion. An object is to provide a heat-shrinkable polyester film.

  Another object of the present invention is to provide a heat-shrinkable polyester film for packaging labels having the above-mentioned characteristics, particularly for canned packaging.

In order to achieve the above object, the heat shrinkable polyester film of the present invention has a hot water shrinkage of 55% or more in the main shrinkage direction at 95 ° C. for 10 seconds. The rate is 20% or less.

  Vibration test: Films joined in a tube shape are covered with three edible cans with a diameter of 72 mm and a height of 55 mm (total weight: 660 g), and after shrinking and mounting in a shrink tunnel, The stack is put into a cardboard box having a length of 455 mm, a width of 230 mm, and a height of 165 mm. Next, this corrugated cardboard package is vibrated for 30 minutes at a vibration width of 50 mm and a vibration speed of 180 reciprocations / minute horizontally in the vertical direction, and then the tearing condition of the film is visually evaluated.

  A crack having a crack of 30 mm or more on the circumference of the can is regarded as defective, and the ratio of the number of defective packs in 18 packs is defined as a lateral crack defect occurrence rate (%).

  In a preferred embodiment of the present invention, the refractive index Nx in the longitudinal direction of the film and the refractive index Ny in the lateral direction of the film satisfy the following expressions (1) and (2).

1.561 <Nx <1.566 (1)
0.040 <Ny−Nx <0.070 (2)

  In a preferred embodiment of the present invention, the hot water shrinkage rate in the direction orthogonal to the main shrinkage direction at 95 ° C. for 10 seconds is 10 to 25%.

  In a preferred embodiment of the present invention, it has a solvent adhesiveness due to 1,3-dioxolane.

  In a preferred embodiment of the present invention, the film is an integrated packaging film.

  According to the heat-shrinkable polyester film of the present invention, it has excellent impact resistance during transportation, particularly at low temperatures, has a good finish when shrinking, and has sufficient solvent adhesion.

  Therefore, it is suitable as a heat-shrinkable polyester film for packaging labels for accumulation, particularly for canning accumulation.

  Hereinafter, embodiments of the heat-shrinkable polyester film of the present invention will be described.

  The polyester used in the heat-shrinkable polyester film of the present invention can typically represent polyethylene terephthalate, polyethylene naphthalate, or polyester obtained by copolymerizing an aliphatic acid component or a long-chain glycol component with these polyesters. .

  In the present invention, besides the acid component consisting of terephthalic acid and naphthalenedicarboxylic acid constituting the polyester, oxalic acid, malonic acid, succinic acid, adipic acid, azelaic acid, isophthalic acid, decanedicarboxylic acid, dimer acid and the like are known. One or two or more of the dicarboxylic acids may be used, and ethylene glycol, neopentyl glycol, hexamethylene glycol, 1,4-cyclohexanedimethanol, dimer acid diol are also included in the diol component consisting of butanediol. One or more known diols such as tetramethylene glycol ethylene oxide adduct may be used.

  In order to obtain a heat-shrinkable polyester film particularly excellent in vibration tests, it is preferable to use neopentyl glycol as one kind of diol component.

  Furthermore, in order to improve the slipperiness of the heat-shrinkable polyester film, those containing an inorganic lubricant and an organic lubricant are preferable. Moreover, you may contain additives, such as a stabilizer, a coloring agent, antioxidant, a solvent elimination, an antistatic agent, as needed.

  The heat-shrinkable polyester film of the present invention is required to have a lateral tear failure occurrence rate of 20% or less in a vibration test. Preferably it is 10% or less. When the occurrence rate of lateral tear failure exceeds 20%, many tears occur in the film during actual transportation, which is not preferable.

  Furthermore, in the present invention, it is preferable that the refractive indexes Nx and Ny satisfy the following expressions (1) and (2).

1.561 <Nx <1.566 (1)
0.040 <Ny−Nx <0.070 (2)
A more preferable range of the refractive index Nx is 1.562 to 1.565. Further, a more preferable range of the value (Ny−Nx) is 0.050 to 0.060. When the value of the refractive index Nx is less than 1.561, the strength against transverse tearing is insufficient, and when it exceeds 1.566, the shrinkage rate in the direction orthogonal to the main shrinkage direction is increased, and the shrinkage finish is improved. Deteriorate.

  Further, when the value (Ny−Nx) is less than 0.040, the shrinkage balance in the film longitudinal direction and the transverse direction is deteriorated, and unevenness of shrinkage occurs. Gets worse.

  The film of the present invention preferably has a hot water shrinkage in the main shrinkage direction at 95 ° C. for 10 seconds of 50% or more. More preferably, it is 55% or more. When the hot water shrinkage rate in the main shrinkage direction at 95 ° C. for 10 seconds is less than 50%, shrinkage insufficiency and shrinkage unevenness easily occur and the finish is poor.

  The film of the present invention preferably has a hot water shrinkage of 10 to 25% in a direction orthogonal to the main shrinkage direction at 95 ° C. for 10 seconds. More preferably, it is 10 to 20% or more. If the hot water shrinkage is less than 10%, the strength against transverse tearing cannot be balanced, and if it exceeds 25%, shrinkage unevenness and jumping occur, resulting in poor finish.

  Furthermore, the film of the present invention preferably has solvent adhesiveness due to 1,3-dioxolane.

  In order to achieve the object of the present invention, a polyester film whose main shrinkage direction is the transverse direction (width direction) of the film is practical, so an example of a film forming method in the case where the main shrinkage direction is the transverse direction is shown below. However, the present invention naturally includes the case where the main shrinkage direction is the longitudinal direction. In the present invention, the polyester raw material dried using a dryer such as a hopper dryer or a battle dryer or a vacuum dryer is heated to a temperature of 200 to 300 ° C. Extrude and quench to obtain an unstretched film. In order to produce a heat-shrinkable polyester film whose main shrinkage direction is the transverse direction, the obtained unstretched film was longitudinally stretched 1.1 to 1.3 times at 80 to 95 ° C, and then at 70 to 85 ° C. A method of 3 to 5 times transverse stretching is typical, but it goes without saying that stretching conditions can be appropriately set.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples as long as the gist of the present invention is not exceeded.

(1) The heat shrinkage rate film is cut into a 10 cm × 10 cm square, immersed in warm water of 95 ± 0.5 ° C. for 10 seconds under heat-free conditions, and then thermally shrunk. The dimensions were measured, and the thermal shrinkage rate was determined according to the following formula. The direction in which the thermal contraction rate was large was taken as the main shrinkage direction.

Thermal shrinkage rate = {(length before shrinkage−length after shrinkage) / length before shrinkage} × 100 (%)

(2) Using a refractive index Abbe refractometer, the refractive index in the vertical, horizontal and thickness directions of the film was measured.

However, the refractive index in the vertical direction (main contraction direction) is Nx, and the refractive index in the horizontal direction (direction orthogonal to the main contraction direction) is Ny.

(3) Solvent adhesiveness 1,3-dioxolane is used to join the film into a tube shape, the tube-like body is cut to a width of 15 mm in the direction perpendicular to the flow direction at the time of processing, a sample is taken, A film that was pulled and peeled in the above direction to obtain a sufficient peel resistance was defined as solvent adhesion “◯”.

(4) Shrinkage finish property Using a universal shrinker (model: K2000) manufactured by Kyowa Denki Co., Ltd., mounted on a commercially available drawing can (Friskey manufactured by Frisky), a shrinker passage time of 15 seconds, (one zone temperature / 2 zones The finish was evaluated as follows with (temperature) = (170 ° C./170° C.). (N = 10)
O: No appearance defect ×: Wrinkle, insufficient shrinkage

(5) Vibration test As shown in FIG. 1, an integrated body 2 (total of 3 cans) in which edible cans having a diameter of 72 mm and a height of 55 mm are accumulated in the height direction on a tube 1 formed by joining films into a tube shape. As shown in FIG. 2, the aggregate 3 is placed in a corrugated cardboard box 4 having a length of 455 mm, a width of 230 mm, and a height of 165 mm, for a total of 18 packs. And sealed.

  The cardboard package 4 was vibrated for 30 minutes at a vibration width of 50 mm and a vibration speed of 180 reciprocations / minute horizontally in the vertical direction (arrow A direction), and the tearing condition of the film was visually evaluated.

  As shown in FIG. 3, on the circumference of the can 5, a film 7 having a tear 7 of 30 mm or more (dimension L in the figure) is regarded as defective, and the ratio of the number of defective packs in 18 packs is defined as a defective rate. (%) Was defined as “◯” when the defect rate was 20% or less, and “X” when the defect rate exceeded 20%.

(6) Actual transportation test Three cases of the corrugated cardboard package 4 described in the above "vibration test" are transported to land, and the ratio of the number of defective packs in 54 packs is defined as a defective rate (%), with a defective rate of 20% or less. Was marked with “◯”, and when over 20% was marked with “x”.

In addition, the polyester used for the Example and the comparative example is as follows.
Polyester A: Polyethylene terephthalate (IV 0.75)
Polyester B: Polyester composed of 70 mol% ethylene glycol, 30 mol% neopentyl glycol and terephthalic acid (IV 0.72)
Polyester C: Polybutylene terephthalate (IV 1.20)

Example 1
As shown in Table 1, a polyester blended with 37% by weight of polyester A, 53% by weight of polyester B and 10% by weight of polyester C was melt extruded from a T die at 280 ° C., and quenched with a chill roll to form an unstretched film. Obtained. The unstretched film was longitudinally stretched 1.1 times with a multiple roll type vertical stretching machine (roll temperature 80 ° C.), then stretched 3.9 times in the transverse direction at a film temperature 73 ° C. with a tenter, and 10 at 82 ° C. A heat-shrinkable polyester film having a thickness of 45 μm was obtained by heat treatment for 2 seconds.

(Examples 2 to 4 and Comparative Examples 1 to 4)
As shown in Table 1, a heat-shrinkable polyester film having a thickness of 45 μm was obtained in the same manner as in Example 1 except that the blending ratio of the polyester and the stretching conditions were changed.

  The evaluation results of the films obtained in Examples 1 to 4 and Comparative Examples 1 to 4 are shown in Table 1.

  As is apparent from Table 1, the heat-shrinkable polyester films obtained in Examples 1 to 4 all show a good shrinkage finish (no defects such as insufficient shrinkage, wrinkles, distortion, etc.) and have solvent adhesion. The impact resistance in the vibration test and the impact resistance in actual transportation were good.

  Thus, the heat-shrinkable polyester film of the present invention has high quality and high practicality, and is particularly suitable for use in canned and integrated labels used at low temperatures.

  On the other hand, the heat-shrinkable polyester film obtained in Comparative Examples 1 to 4 was inferior in impact resistance. Thus, the heat-shrinkable polyester film of the comparative example was inferior in quality and low in practicality.

  According to the heat-shrinkable polyester film of the present invention, it has excellent impact resistance during transportation, particularly at low temperatures, has a good finish when shrinking, and has sufficient solvent adhesion.

  Therefore, it is suitable as a heat-shrinkable polyester film for packaging labels for accumulation, particularly for canning accumulation.

It is explanatory drawing of the vibration test of a heat-shrinkable polyester-type film. It is explanatory drawing of the vibration test of a heat-shrinkable polyester-type film. It is explanatory drawing at the time of a tear having arisen in the film on the circumference of a can.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tube 2 Accumulation of cans 3 Accumulation 4 Corrugated cardboard packaging 5 Cans 6 Rips

Claims (5)

Heat shrinkable polyester film characterized in that the hot water shrinkage in the main shrinkage direction at 95 ° C. for 10 seconds is 55% or more, and the occurrence rate of lateral tear failure is 20% or less in the vibration test shown below. .
Vibration test: Films joined in a tube shape are covered with three edible cans with a diameter of 72 mm and a height of 55 mm (total weight: 660 g), and after shrinking and mounting in a shrink tunnel, The stack is put into a cardboard box of 455 mm in length, 230 mm in width, and 165 mm in height. Next, this corrugated cardboard package is vibrated for 30 minutes at a vibration width of 50 mm and a vibration speed of 180 reciprocations / minute horizontally in the vertical direction, and then the degree of film tearing is visually evaluated. A crack having a crack of 30 mm or more on the circumference of the can is regarded as defective, and the ratio of the number of defective packs in 18 packs is defined as a lateral crack defect occurrence rate (%). The heat-shrinkable polyester film according to claim 1, wherein the refractive index Nx in the longitudinal direction of the film and the refractive index Ny in the lateral direction of the film satisfy the following expressions (1) and (2).
1.561 <Nx <1.566 (1)
0.040 <Ny−Nx <0.070 (2) The heat-shrinkable polyester film according to claim 1, wherein the hot-water shrinkage in a direction orthogonal to the main shrinkage direction at 95 ° C for 10 seconds is 10 to 25%. The heat-shrinkable polyester film according to claim 1, which has solvent adhesion with 1,3-dioxolane. The heat-shrinkable polyester film according to claim 1, wherein the heat-shrinkable polyester film is an integrated packaging film.

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