JP4695267B2 - Heat-shrinkable polyester film for hot beverages - Google Patents

Description

【００３７】
【表２】

【００３８】
【表３】

【００３９】
【発明の効果】
以上詳細に説明したように、本発明の熱収縮性ポリエステルフィルムは、収縮工程でシワ、ムラのない外観の良好な収縮フィルムであり、温飲料として使用される場合の加温後にも良好な強度を有するボトル等のキャップシール、ラベル、被覆等の用途で良好な性能を有する熱収縮性ポリエステルフィルムである。[0001]
[Industrial application fields]
The present invention relates to a heat-shrinkable polyester film for hot beverages used for bottle / bottle labels, cap seals, coatings, and the like. More specifically, the present invention relates to a label used for hot beverages and is cracked by impact after heating. In addition, the present invention relates to a heat-shrinkable polyester film for hot beverages that does not cause appearance defects such as wrinkles in the shrinking process.
[0002]
[Prior art]
Plastic shrink films are used for labeling bottles and bottles, cap seals, electronic parts, batteries, binding of long objects, coverings, and the like. Conventionally, resins for shrink film include polyvinyl chloride, polystyrene, polypropylene, etc. These are, for example, films made of polyvinyl chloride, which easily form a polymer or additive gel, and are not printed during printing. May occur. A film made of polystyrene has a problem that it is inferior in weather resistance and solvent resistance and is liable to crack, and the dimensions of the film are not stable. A film made of polypropylene has a problem that the shrinkability in a low temperature range is poor, and wrinkles and spots are easily generated in the contracted portion.
[0003]
On the other hand, polyester is a very excellent material in terms of heat resistance, weather resistance, and solvent resistance. The shrinkage film has problems such as insufficient shrinkage, high shrinkage starting temperature, and poor appearance due to rapid shrinkage. However, the shrinkage is imparted by copolymerization of neopentyl glycol or isophthalic acid (Japanese Patent Laid-Open No. 1-4326). JP-A 63-222845), reduction of shrinkage start temperature by copolymerization of aliphatic dicarboxylic acid (JP-A-2-153941), or relaxation of shrinkage rate by blending PBT (JP-A-4-170436). Improved polyester film has been proposed.
[0004]
PET has a lower thermal conductivity than metal, so that PET bottles have good heat retention and are not hot when held. For this reason, PET bottles have a demand not only for conventional cold drinks but also for hot drinks. However, since warm beverages are heated at a relatively high temperature of about 60 ° C., the heat-shrinkable polyester film used for the label becomes brittle in the conventional film and has a problem that breakage such as cracking occurs due to impact such as dropping. is there.
[0005]
[Problems to be solved by the invention]
In view of the technical background as described above, the present invention aims at a heat-shrinkable polyester film that has good shrinkage and does not cause cracking or the like even after heating when used as a hot beverage. Is to provide.
[0006]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have found that a polyester containing a specific amount of polyoxytetramethylene glycol blended with a modified polybutylene terephthalate copolymerized with a specific amount of an aromatic dicarboxylic acid other than terephthalic acid, A heat-shrinkable polyester resin composition excellent in shrinkage and heat resistance is obtained by a heat-shrinkable polyester resin composition in which a polyester mainly composed of ethylene terephthalate with limited physical properties, modified species, and modification rate is mixed. Succeeded.
[0007]
That is, in the present invention, a polyester resin (A) containing a butylene terephthalate unit as a main repeating unit, containing 1 to 30 wt% of polyoxytetramethylene glycol and 3 to 30 mol% of isophthalic acid , 30 to 50 wt%, ethylene The main repeating unit is a terephthalate unit, and it contains at least one of isophthalic acid, cyclohexanedimethanol and neopentyl glycol, and the total of these (isophthalic acid is mol% of all acid components, cyclohexanedimethanol, neopentyl) The glycol has a glass transition temperature of 50-100 ° C. when the temperature is raised at 10 ° C./min with a differential scanning calorimeter that is 10-50 mol% and is rapidly cooled after heat treatment at 280 ° C. for 5 minutes in nitrogen. 50-70 polyester resin (B) is there is provided a polyester resin composition temperature beverage heat-shrinkable polyester film comprising a containing t%, further comprising the polyester resin composition, shrinkage of 10 seconds in hot water 3 to 25% in the 60 ° C., It is 35 to 75% at 80 ° C. and has a breaking elongation of 100% or more when subjected to a tensile test in a direction perpendicular to the main shrinkage direction when treated at 80 ° C. and 50% RH for 10 days. The present invention provides a heat-shrinkable film for hot beverages . The present invention will be described in detail below.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The heat-shrinkable polyester film of the present invention comprises a polybutylene terephthalate-modified product (PBT-modified product) and a polyethylene terephthalate-modified product (PET-modified product). It has impact resistance after heating.
[0009]
The polyester resin (A) of the present invention has a butylene terephthalate unit as a main repeating unit, contains 1 to 30 wt% of polyoxytetramethylene glycol, and further contains 3 to 30 mol% of isophthalic acid , 30 to 50 wt%. If the polyoxytetramethylene glycol in the polyester resin is less than 1 wt%, cracking is likely to occur due to impact after heating, and if it is 30 wt% or more, the shrinkage start temperature becomes low and spontaneous shrinkage occurs at room temperature, resulting in poor dimensional stability. Preferably it is 5-20 wt%. The molecular weight of polyoxytetramethylene glycol is preferably 500 to 3000 in terms of number average molecular weight. When isophthalic acid is less than 3 mol% with respect to the total acid component, sufficient low temperature region shrinkage cannot be obtained, and when it exceeds 30 mol%, shrinkage occurs at room temperature (natural shrinkage), which is disadvantageous in terms of dimensional stability. Preferably it is 5-20 mol%.
[0011]
It is also possible to copolymerize aliphatic dicarboxylic acids. Examples include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, pimelic acid, suberic acid, undecanoic acid, dodecanedicarboxylic acid, brassic acid, tetradecanedicarboxylic acid, tapsinic acid, nonadecanedicarboxylic acid An acid, docosane dicarboxylic acid, etc. are mentioned. Furthermore, examples of the alicyclic dicarboxylic acid include 1,4-dicarboxycyclohexane and 1,3-dicarboxycyclohexane.
[0012]
It is also possible to copolymerize glycol components other than butanediol, such as aliphatic diols, alicyclic diols, and aromatic diols. Examples of the aliphatic diol include ethylene glycol, diethylene glycol, propylene glycol, 1,6-hexanediol, 1,10-decanediol, neopentyl glycol, 2-methyl-2-ethyl-1,3-propanediol, 2,2 -Diethyl-1,3-propanediol, 2-ethyl-2-n-butyl-1,3-propanediol, or polyalkylene glycol such as polyethylene glycol or polypropylene glycol. Examples of the alicyclic diol include 1,3-cyclohexanedimethanol and 1,4-cyclohexanedimethanol. Further, as aromatic diols, ethylene oxide adducts of bisphenol compounds such as 2,2-bis (4′-β-hydroxyethoxydiphenyl) propane and 2,2-bis (4′-β-hydroxyethoxydiphenyl) sulfone, or Examples include xylylene glycol.
[0013]
The degree of polymerization of the polyester resin (A) is not particularly limited, but the intrinsic viscosity (measured at 25 ° C. using a mixed solution of phenol / tetrachloroethane or the like as a solvent) is 0.50 to 1 due to the moldability of the raw film. It is preferably 5 dl / g. Moreover, the compounding quantity of a polyester resin (A) is 30-50 wt %.
[0014]
On the other hand, the polyester resin (B) of the present invention contains at least one of isophthalic acid, cyclohexanedimethanol, and neopentyl glycol having ethylene terephthalate units as the main repeating unit, and the total of these (isophthalic acid is the total acid). Mol% in the components, cyclohexanedimethanol, neopentylglycol is 10-50 mol% in all glycol components), treated in nitrogen atmosphere at 280 ° C. for 5 minutes, and heated by DSC at 10 ° C./min. In this case, the glass transition temperature is 50 to 100 ° C., and it is blended in the heat-shrinkable polyester film at a ratio of 50 to 70 wt%.
[0015]
The polyester resin (B) contains at least one of isophthalic acid, cyclohexanedimethanol, and neopentyl glycol, and the total of these (isophthalic acid is mol% in the total acid component, cyclohexanedimethanol, neopentyl glycol) Is less than 10 mol%, sufficient shrinkage cannot be obtained, and when it exceeds 50 mol%, oligomers are deposited on the film surface during heating, causing poor appearance. become. Preferably it is 15-45 mol%.
When the glass transition temperature is lower than 50 ° C., shrinkage occurs at a low temperature and the effect of suppressing the appearance defect is small, and when it exceeds 100 ° C., the shrinkage does not occur sufficiently, resulting in poor adhesion.
Preferably it is 60-85 degreeC.
On the other hand, when the blending amount of the polyester resin (B) is less than 30 wt%, the shrinkage rate is not increased at the high temperature part and sufficient adhesion cannot be obtained. On the other hand, if it exceeds 90 wt%, the shrinkage rate rises rapidly, resulting in poor appearance such as uneven shrinkage. Preferably it is 50 to 80%.
[0016]
The above polyester resin having thermophysical properties is preferably an acid component or a glycol component, or the acid component and the glycol component are copolymers of components other than terephthalic acid and ethylene glycol. Is mentioned.
As the acid component other than terephthalic acid and isophthalic acid, any of aromatic dicarboxylic acid, aliphatic dicarboxylic acid, and alicyclic dicarboxylic acid can be used.
[0017]
Examples of the aromatic dicarboxylic acid include orthophthalic acid, benzenedicarboxylic acid such as 5-tert-butylisophthalic acid, naphthalenedicarboxylic acids such as 2,6-naphthalenedicarboxylic acid, 4,4′-dicarboxydiphenyl, 2,2, Dicarboxybiphenyls such as 6,6-tetramethylbiphenyl-4,4′-dicarboxylic acid, 1,1,3-trimethyl-3-phenylindene-4,5-dicarboxylic acid and substituted products thereof, 1,2- Examples include diphenoxyethane-4,4′-dicarboxylic acid and substituted products thereof.
[0018]
Examples of the aliphatic dicarboxylic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, pimelic acid, suberic acid, undecanoic acid, dodecanedicarboxylic acid, brassic acid, tetradecanedicarboxylic acid, Tapsic acid, nonadecane dicarboxylic acid, docosane dicarboxylic acid and the like can be mentioned. Furthermore, examples of the alicyclic dicarboxylic acid include 1,4-dicarboxycyclohexane and 1,3-dicarboxycyclohexane.
[0019]
Furthermore, as glycol components other than ethylene glycol, neopentyl glycol, and cyclohexanedimethanol, both aliphatic diols and aromatic diols are used.
Examples of the aliphatic diol include diethylene glycol, propylene glycol, butanediol, 1,6-hexanediol, 1,10-decanediol, 2-methyl-2-ethyl-1,3-propanediol, and 2,2-diethyl-1. , 3-propanediol, 2-ethyl-2-n-butyl-1,3-propanediol, or polyalkylene glycol such as polyethylene glycol or polypropylene glycol. The aromatic diol includes ethylene oxide adducts of bisphenol compounds such as 2,2-bis (4′-β-hydroxyethoxydiphenyl) propane and 2,2-bis (4′-β-hydroxyethoxydiphenyl) sulfone. Or a xylylene glycol etc. are mentioned.
[0020]
The degree of polymerization of the polyester resin (B) is not particularly limited, but the intrinsic viscosity (measured at 25 ° C. using a mixed solution of phenol / tetrachloroethane or the like as a solvent) is 0.50 to 1 due to the moldability of the original film. It is preferably 5 dl / g.
[0021]
Both the polyester resin (A) and the polyester resin (B) of the present invention can be produced by a known direct polymerization method, transesterification method or the like, and may be prepared by any of continuous or batch methods.
The polyester resins (A) and (B) obtained as described above are formed into a heat-shrinkable polyester film, for example, by the following method. First, polyester resins (A) and (B) may be melt blended in advance using an extruder and formed into a film, or a method of directly forming a film obtained by chip blending at the time of film formation may be used. In order to obtain an unstretched original fabric, it is extruded onto a cooling drum from an extruder to produce a film original fabric.
[0022]
Next, the film original fabric is 1.5 ° C. in the film winding direction or at a direction perpendicular to this at a temperature 3 ° C. or more higher than the glass transition temperature of the mixture calculated from the glass transition temperatures of the polyester resins (A) and (B). The film is stretched up to 5.0 times, preferably 1.0 to 4.8 times to give a high shrinkage rate to the film. Further, if necessary, the film is stretched 1.0 to 1.8 times, preferably 1.0 to 1.5 times in the direction perpendicular to the previous stretching direction. This is effective for improving the strength in the direction perpendicular to the main shrinkage direction of the film and preventing the shrinkage in the main shrinkage direction from being unnecessarily large. Although the stretched heat-shrinkable film can be used as a product as it is, a heat treatment may be performed at a temperature of 50 to 150 ° C. for several seconds to several tens of seconds from the viewpoint of dimensional stability. By performing such heat treatment, favorable properties such as adjustment of the shrinkage rate in the main shrinkage direction of the polyester film of the present invention, reduction of shrinkage with time during storage of the unshrinked film, reduction of shrinkage unevenness, etc. can be exhibited. .
[0023]
In the present invention, various conventionally known processings may be performed in order to impart further specific performance, and appropriate additives may be blended. Examples of processing treatments include irradiation with ultraviolet rays, α rays, β rays, γ rays, or electron beams, treatments such as corona treatment, flame treatment, application of resins such as vinylidene chloride, polyvinyl alcohol, polyamide, polyolefin, lamination, Or metal vapor deposition etc. are mentioned. Additives include polyamide, polyolefin, polymethyl methacrylate, polycarbonate and other resins, titanium dioxide, fine particle silica, kaolin, calcium carbonate and other lubricants, titanium oxide, carbon black and other pigments, UV absorbers, mold release Agents, flame retardants, antistatic agents and anti-aging agents.
[0024]
The shrinkage behavior of the film comprising the polyester resin composition obtained as described above has the following shrinkage characteristics, so that it can be made into a shrinkable film having a good appearance without wrinkles or unevenness even in a high-temperature shrinkage process. . The shrinkage characteristics are as follows: shrinkage when immersed in warm water for 10 seconds is 3-25% at 60 ° C, 35-75% at 80 ° C, preferably 5-20% at 60 ° C, 40-70 at 80 ° C. %. When the shrinkage rate at 60 ° C. is lower than 3%, the shrinkage rapidly occurs and the appearance defect occurs after shrinkage. On the other hand, if it exceeds 25%, it is inconvenient because it causes spontaneous shrinkage. When the shrinkage rate at 80 ° C. is lower than 35%, a sufficient shrinkage rate cannot be obtained, and the adhesion of the label to the coating becomes insufficient. When the shrinkage rate exceeds 75%, the appearance shrinks due to rapid shrinkage.
[0025]
The elongation at break in the direction perpendicular to the main shrinkage direction when treated at 80 ° C. and 50% RH for 10 days is 100% or more. If the elongation at break is less than 100%, there is a possibility of cracking due to impact after heating when used in a hot beverage.
Next, the present invention will be described in more detail with reference to examples and comparative examples.
[0026]
【Example】
1. Preparation of resin 1) Resins 1-8
Put the raw materials listed in Table 1 into a reaction vessel equipped with a reflux tower and a stirrer, add 500 ppm of tetrabutylentitanate to the raw materials, and distill off methanol produced as a by-product at a reaction temperature of 140 to 240 ° C. Was reacted until 90% of the theoretical amount was obtained. 700 ppm of amorphous silicon dioxide is added to the esterified product with respect to the raw material, and the glycol component by-produced at 250 ° C. is distilled off at a high vacuum of 0.6 KPa or less, and melt polymerization is performed until the solution viscosity shown in Table 2 is reached. A polyester resin was obtained.
[0027]
2) Resin 9-15
The raw materials listed in Table 1 were put into a reaction vessel equipped with a reflux tower and a stirrer, and the esterified product was reacted while distilling off the water produced as a by-product at 200 to 240 ° C. until the distillate of water reached 90% of the theoretical amount. Got. Next, 100 ppm of tetraethyl phosphate, 500 ppm of antimony trioxide, and 700 ppm of amorphous silicon dioxide are added to this esterified product with respect to the weight of the raw material, and the glycol component by-produced at 285 ° C. is distilled at a high vacuum of 0.6 KPa or less. The polyester resin was obtained by melt polymerization until the solution viscosity shown in Table 2 was reached.
[0028]
3) Resin 16
Put the raw materials listed in Table 1 into a reaction vessel equipped with a reflux tower and a stirrer, add 400 ppm of manganese acetate tetrahydrate to the raw materials, and distill off methanol produced as a by-product at a reaction temperature of 140 to 240 ° C. The esterification product was obtained by reacting until the distillation amount reached 90% of the theoretical amount. Next, 200 ppm of tetraethyl phosphate, 500 ppm of antimony trioxide, and 700 ppm of amorphous silicon dioxide were added to the esterified product based on the weight of the raw material, and the glycol component by-produced at 285 ° C. was distilled at a high vacuum of 0.6 KPa or less. The polyester resin was obtained by melt polymerization until the solution viscosity shown in Table 2 was reached. Table 2 shows the composition, glass transition temperature, and intrinsic viscosity of the obtained polyester resin.
[0029]
The resin composition was determined by gas chromatography and liquid chromatography after hydrolyzing the resin with hydrazine. The glass transition temperature was 10 mg of polyester resin in an aluminum pan for measurement, heated in nitrogen at 280 ° C. for 5 minutes, and rapidly cooled with dry ice. The sample was gradually heated from room temperature at 10 ° C./min, and the glass transition temperature was determined from the shoulder. Intrinsic viscosity was measured at 25 ° C. using a mixed solution of phenol / tetrachloroethane and the like as a solvent.
[0030]
2. Film production These resins were dried by vacuum drying until the water content was 100 ppm or less, and the resin composition was such that the blending ratio shown in Table 3 was obtained, and this was extruded onto a cooling drum (20 ° C.) at 260 ° C. A film stock was obtained.
This raw film is stretched 4.0 times in the direction perpendicular to the film forming direction at a temperature 5 ° C. higher than the glass transition temperature of the mixture by a batch type stretching machine (1.0 times in the film forming direction). A 50 μm polyester film was obtained.
The obtained film was evaluated for shrinkage at each temperature, appearance after shrinkage, elongation at break after heating, drop strength, and natural shrinkage during storage.
[0031]
3. Measurement method and evaluation of physical properties 1) Shrinkage rate 150 mm in the stretching direction A polyester film cut to a size of 20 mm in the direction perpendicular to it is provided with a marked line at an interval of 100 mm and immersed in a hot water bath at 60 ° C. and 80 ° C. for 10 seconds. Obtained by the formula.
Shrinkage rate (%) = {(L−L ′) / L} × 100
L: Length between marked lines before contraction L ′: Length between marked lines after contraction [0032]
2) Appearance Evaluation after Shrinkage Treatment (1) The shrinkage-treated film was formed into a tube so that the stretching direction was the circumferential direction, covered with a heat-resistant PET bottle (for 300 cc), and passed through a shrink tunnel. The outer diameter of the tube was increased by 5% of the PET bottle body. The conditions for passing through the shrink tunnel were 150 ° C. and a residence time of 2.5 seconds.
(2) Appearance after shrinkage The shrinkage finish of the tube-like material subjected to the shrinking treatment in (1) was visually evaluated.
○: No appearance defect △: No shrinkage unevenness, but shrinkage rate is insufficient and poor adhesion ×: Shrinkage unevenness is remarkable [0033]
3) Heating treatment The PET bottle equipped with the shrink film by the above method was treated at 80 ° C. and 50% RH for 10 days to evaluate the drop strength and elongation at break.
(1) Drop strength The PET bottle was filled with water, dropped onto a concrete floor from a height of 2 m, and the drop strength was evaluated from the number of broken labels in 10 samples.
◎: Label cracks 0 out of 10 ○: １〜 1-2 of 10 ×: ３ 3 or more out of 10 ▲ 2 ▼ Breaking elongation shrinkage treatment, heating treatment label with respect to the circumferential direction Then, it was cut into a width of 10 mm in the perpendicular direction, and the elongation at break was measured when a tensile test was performed at a distance between chucks of 50 mm and a speed of 100 mm / min.
[0034]
4) The film after natural shrinkage stretching of the film was marked at intervals of 200 mm in the stretching direction, and the natural shrinkage was measured from the rating interval after holding at 30 ° C. for 72 hours.
[0035]
Table 3 shows the composition and physical property values of the shrink films described in Examples and Comparative Examples of the present invention, which were performed by the above method.
In addition, each symbol in Table 1 and Table 2 represents the following compound.
DMT: dimethyl terephthalate DMI: dimethyl isophthalate TPA: terephthalic acid IPA: isophthalic acid ADA: adipic acid NDCM: 2,6 naphthalene dicarboxylic acid dimethyl ester BDO: 1,4-butanediol PTMG: polyoxytetramethylene glycol ( Number average molecular weight 1000)
EG: ethylene glycol NPG: neopentyl glycol CHDM: cyclohexanedimethanol NDA: 2,6 naphthalene dicarboxylic acid
[Table 1]

[0037]
[Table 2]

[0038]
[Table 3]

[0039]
【The invention's effect】
As described in detail above, the heat-shrinkable polyester film of the present invention is a shrinkable film having a good appearance without wrinkles and unevenness in the shrinking process, and has good strength even after heating when used as a hot beverage. It is a heat-shrinkable polyester film having good performance in applications such as cap seals such as bottles, labels, and coatings.

Claims (2)

30 to 50 wt% of a polyester resin (A) containing 1 to 30 wt% of polyoxytetramethylene glycol and 3 to 30 mol% of isophthalic acid , with the main repeating unit having a butylene terephthalate unit as a main repeating unit And at least one of isophthalic acid, cyclohexanedimethanol, and neopentyl glycol, and the total of these (isophthalic acid is mol% in all acid components, and cyclohexanedimethanol and neopentyl glycol are in all glycol components) Polyester resin (B) having a glass transition temperature of 50 to 100 ° C. when the temperature is raised at 10 ° C./min with a differential scanning calorimeter that is 10-50 mol% in nitrogen and rapidly cooled after heat treatment at 280 ° C. for 5 minutes in nitrogen. polyether that) the containing 50~70 wt% Warm beverage heat-shrinkable polyester film comprising ether resin composition. Tensile test in the direction perpendicular to the main shrinkage direction when the shrinkage rate for 10 seconds in warm water is 3-25% at 60 ° C, 35-75% at 80 ° C, and treated at 80 ° C and humidity 50% RH for 10 days The heat-shrinkable polyester film for hot drinks according to claim 1, wherein the elongation at break is 100% or more.