JP2001064412A - Thermally shrinkable polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-shrinkable polyester film that has a large heat- shrinkability and causes no bad-looking appearance by high-temperature heat treatment without the preheating step. SOLUTION: This heat-shrinkable polyester film comprises (A) 10-40 wt.% of polybutylene terephthalate copolymer and (B) 60-90 wt.% of polyethylene terephthalate in which the content of the acid components of the aromatic dicarboxylic acid other than terephthalic acid is 5-20 mol.% in the acid components in (A), while the content of the acid components of the aromatic dicarboxylic acid other than terephthalic acid is 5-50 mol.% and/or the amount of the glycols other than ethylene glycol in the glycol components is 5-50 mol.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a heat-shrinkable polyester film.

[0002]

2. Description of the Related Art Plastic shrink films are used for labeling and sealing caps on bottles and bottles, binding and coating electronic components, batteries and long objects. Conventionally, resins for shrink film include polyvinyl chloride, polystyrene, polypropylene, etc., but these generally have poor heat resistance, many of which cannot withstand boil or retort treatment, and also have other defects as shrink films. . For example, in a film made of polyvinyl chloride, a gel-like substance of a polymer or an additive is easily generated, and when printing is performed, a pinhole may be generated on a printing surface. A film made of polystyrene is inferior in weather resistance and solvent resistance and has a problem that cracks are easily generated and the dimensions of the film are not stable. A film made of polypropylene has poor shrinkage in a low temperature range, and has a problem that wrinkles and spots are easily generated in a shrinkage portion.

[0003] On the other hand, polyester, especially polyethylene terephthalate is a material excellent in heat resistance, weather resistance and solvent resistance. Initially, the shrinkage rate was insufficient as a shrink film, or the shrink temperature was relatively high, so there was a problem for labeling plastic bottles.However, the improvement in shrink rate due to copolymerization of neopentyl glycol and isophthalic acid, Alternatively, the shrinkage onset temperature is lowered by copolymerization of an aliphatic dicarboxylic acid to improve a practical shrinkable film.

[0004] Usually, the shrink film is from 140 ° C to 180 ° C.
Although the shrinkage treatment is performed at a relatively high temperature of ℃, the shrinkage rate of the polyester-based shrink film rapidly increases from the start of shrinkage, and therefore, it is easy to cause poor appearance such as wrinkles, distortion, and shrinkage spots. To prevent this, set the temperature of the shrink tunnel to 100 ° C.
Divided into a low temperature zone of about 150 ° C and a high temperature zone of about 150 ° C,
It responds to poor appearance by gradually shrinking,
There is a demand for shrinkability under normal conditions for the purpose of speeding up the shrinking step (there is no appearance defect even without the preheating step).

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-shrinkable polyester film which has a sufficiently high heat shrinkage and which does not cause a poor appearance when treated at a high temperature without a preheating step.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above problems, and as a result, by forming a film from a composition of copolymerized polybutylene terephthalate and copolymerized polyethylene terephthalate, the shrinkage behavior has been improved. As a result, a shrinkable film having a good appearance after shrinkage was provided.

That is, the gist of the present invention is that the polybutylene terephthalate copolymer (A) is 10 to 40% by weight and the polyethylene terephthalate copolymer (B) is 60 to 90% by weight.
In the acid component of (A), an aromatic dicarboxylic acid component other than terephthalic acid is 5 to 20 mol%, and in the acid component of (B), a component other than terephthalic acid is 5 to 5 mol%.
The heat-shrinkable polyester film is characterized in that components other than ethylene glycol in 0 mol% and / or the glycol component are 5 to 50 mol%.

Further, the shrinkage rate is 10 to 35% at 65 ° C., 8
It is a heat-shrinkable polyester film characterized by being 45 to 65% at 0 ° C and 55 to 80% at 100 ° C.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The heat-shrinkable polyester film of the present invention is formed by molding a polybutylene terephthalate copolymer (hereinafter referred to as PBT copolymer) and a polyethylene terephthalate copolymer (hereinafter referred to as PET copolymer). The shrinkage behavior is improved.

This is because the glass transition point of the PBT copolymer is
Since the ET copolymer is significantly different from the ET copolymer, the temperature range in which the shrinkage rate increases is expanded, and rapid shrinkage from the start of shrinkage is suppressed. There have been patents in which the shrinkage behavior has been improved by blending a homo-PBT and a PET copolymer, but these have the problem that although the shrinkage behavior is improved, a sufficient shrinkage cannot be obtained due to the crystallinity of the homo-PBT. . Further, a blend of PET copolymers having different Tg has a problem that heat resistance in a sterilization treatment step is poor because the PET copolymer has low crystallinity.

For this reason, in the present invention, a PBT copolymer is used, and by suppressing the crystallinity of PBT, a sufficient shrinkage ratio does not cause a poor appearance even at a high temperature treatment without a preheating step. A shrink film having good heat resistance was obtained.

In the present invention, the PBT copolymer (A) and PET
The mixing ratio of the copolymer (B) is preferably such that (A) is 10%.
-40% by weight, (B) 60-90% by weight, more preferably (A) 15-35% by weight, (B) 65% by weight.
~ 85% by weight.

When the content of (A) is less than 10% by weight, the effect on improving the shrinkage behavior is low. On the other hand, when it exceeds 40% by weight, the composition shrinks at room temperature and may have poor storage stability.

If (B) is less than 60% by weight, PET
When the blending ratio of the copolymer (B) is low, a sufficient shrinkage ratio cannot be obtained. When the amount exceeds 90% by weight, the effect of improving the shrinkage behavior by blending may be low.

[0015] In the PBT copolymer (A), among the acid components, an aromatic dicarboxylic acid component other than terephthalic acid is 5%.
-20 mol%, preferably 10-20 mol%. If the content of the aromatic dicarboxylic acid component other than terephthalic acid is less than 5 mol%, sufficient shrinkage cannot be obtained because of high crystallinity,
Conversely, if it exceeds 30 mol%, the shrinkage in the low temperature range increases and shrinks at room temperature, resulting in poor storage stability or inconvenience such as fusion of labels during heat sterilization. .

Examples of aromatic dicarboxylic acids other than terephthalic acid include isophthalic acid, orthophthalic acid, 5-tert.
benzenedicarboxylic acid such as t-butyl isophthalic acid,
Naphthalenedicarboxylic acids such as 2,6-naphthalenedicarboxylic acid, 4,4′-dicarboxydiphenyl,
Dicarboxybiphenyls such as 2,6,6-tetramethylbiphenyl-4,4′-dicarboxylic acid, 1,1,3
-Trimethyl-3-phenylindene 4,5-dicarboxylic acid and its substituted product, 1,2-diphenoxyethane-
4,4′-dicarboxylic acid and its substituted products are exemplified.

In the present invention, aliphatic dicarboxylic acids, alicyclic dicarboxylic acids and the like can be used as acid components other than aromatic dicarboxylic acids.

As the aliphatic dicarboxylic acid, 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, nonadecanedicarboxylic acid, docosandicarboxylic acid and the like.

Examples of the alicyclic dicarboxylic acid include 1,4-dicarboxycyclohexane and 1,3-dicarboxycyclohexane.

The modification with an acid component is more effective as a low-temperature shrinkage component than the modification with a glycol, because the effect of suppressing crystallization and maintaining the glass transition point at a low temperature is better than that of modification with a glycol. And modification with a glycol component may be used in combination. As glycol components other than butanediol, aliphatic diols, alicyclic diols,
And aromatic diols.

The aliphatic diols include ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1,6-hexanediol,
10-decanediol, neopentyl glycol, 2-
Methyl-2-ethyl-1,3-propanediol, 2-
Diethyl-1,3-propanediol, 2-ethyl-2
-N-butyl-1,3 propanediol and the like. Examples of the alicyclic diol include 1,3-cyclohexane dimethanol and 1,4-cyclohexane dimethanol. Examples of the aromatic diol include ethylene oxide adducts of bisphenol compounds such as 2,2-bis (4′-β-hydroxyethoxydiphenyl) propane and 2,2-bis (4′-β-hydroxyethoxydiphenyl) sulfone. , Xylylene glycol. And polyalkylene glycols such as polyethylene glycol and polypropylene glycol.

In the PET copolymer (B), the acid component other than terephthalic acid is 5 to 50 mol%, preferably 10 to 50 mol%.
-40 mol%, more preferably 15-35 mol%.

The glycol component other than ethylene glycol is 5 to 50 mol%, preferably 10 to 40 mol%,
More preferably, it is 15 to 35 mol%.

In the PET copolymer (B), at least one of a carboxylic acid component and a glycol component may be copolymerized.

As the acid component other than terephthalic acid, any of aromatic dicarboxylic acid, aliphatic dicarboxylic acid and alicyclic dicarboxylic acid can be used.

Examples of the aromatic dicarboxylic acid include benzenedicarboxylic acid such as isophthalic acid, orthophthalic acid, and 5-tert-butylisophthalic acid; naphthalenedicarboxylic acids such as 2,6-naphthalenedicarboxylic acid;
Dicarboxydiphenyls such as dicarboxydiphenyl, 2,2,6,6-tetramethylbiphenyl-4,4′-dicarboxylic acid, 1,1,3-trimethyl-3-phenylindene 4,5-dicarboxylic acid and Its replacement,
Examples thereof include 1,2-diphenoxyethane-4,4′-dicarboxylic acid and a substituted product thereof.

As the aliphatic dicarboxylic acid, 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, nonadecanedicarboxylic acid, docosandicarboxylic acid and the like.

Examples of the alicyclic dicarboxylic acid include 1,4-dicarboxycyclohexane and 1,3-dicarboxycyclohexane.

As glycol components other than ethylene glycol, any of aliphatic diols, alicyclic diols and aromatic diols can be used. Examples of the aliphatic diol include butanediol, diethylene glycol, propylene glycol, butanediol, triethylene glycol, neopentyl glycol, 1,6-hexanediol, 1,10-decanediol, neopentyl glycol, and 2-methyl-2-ethyl. -1,3-propanediol, 2-diethyl-1,3-propanediol, 2
-Ethyl-2-n-butyl-1,3 propanediol and the like.

Examples of the alicyclic diol include 1,3-cyclohexanedimethanol and 1,4-cyclohexanedimethanol.

As the aromatic diol, ethylene oxide addition of a bisphenol compound such as 2,2-bis (4'-β-hydroxyethoxydiphenyl) propane or 2,2-bis (4'-β-hydroxyethoxydiphenyl) sulfone is used. Thing, xylylene glycol. And polyalkylene glycols such as polyethylene glycol and polypropylene glycol.

Further, the PBT copolymer (A) and the PET copolymer (B) used in the present invention include trimethylolpropane, pentaerythritol, and trimethylolpropane in order to shorten the polymerization time and to give specific properties to shrinkage characteristics. Trihydric or higher polyhydric alcohols such as trimellitic acid and pyromellitic acid,
Polybasic acids may be used.

The PBT copolymer (A) and PET copolymer (B) used in the present invention can be produced by a known direct polymerization method, transesterification method, or the like, and can be either continuous or batch method. May be prepared.

The degree of polymerization of the above copolymer is not particularly limited, but the intrinsic viscosity (measured at 25 ° C. using a mixed solution of phenol / tetrachloroethane and the like as a solvent) is 0.50 from the moldability of the film raw material. It is preferably 1.5 to 1.5 dl / g.

The obtained polyester resin is formed into a heat-shrinkable polyester film by, for example, the following method. First, the polyester resin is dried, or a decrease in the degree of polymerization due to hydrolysis is suppressed by a vent-type extruder, and extruded from a T-die onto a cooling drum to form a raw film.

Next, this film raw material is used as the polymer Tg.
1.5 ° vertically or horizontally at a temperature higher than 3 ° C.
The film is stretched up to 5.0 times, preferably 1.0 to 4.8 times to impart a high shrinkage to the film. Further, if necessary, 1.0 to 1.8 times, preferably 1.0 to 1.8 times in the direction perpendicular to the stretching direction.
Stretch up to 1.5 times. This is effective for increasing the strength in the direction perpendicular to the main shrinkage direction of the film and preventing the shrinkage in the stretching direction from unnecessarily shrinking. The stretching of the film is performed by a method of simultaneous biaxial stretching, sequential biaxial stretching, or uniaxial stretching, and the stretching in the transverse direction or the stretching in the longitudinal direction may be performed first. Although the stretched heat-shrinkable film can be used as a product as it is, heat treatment may be performed at a temperature of 50 ° C. to 150 ° C. for several seconds to several tens of seconds from the viewpoint of dimensional stability. By performing such a heat treatment, adjustment of the shrinkage ratio in the shrinkage direction of the polyester film of the present invention, reduction of shrinkage over time during storage of the unshrinkable film,
Preferred properties such as a reduction in shrinkage unevenness can be exhibited.

The thickness of the heat-shrinkable polyester film of the present invention is not particularly limited, but a thickness of 1 to 600 μm is practically used.

In the present invention, conventionally known various processings and appropriate additives can be blended in order to further impart specific performance. Examples of processing are ultraviolet light,
Irradiation with α-rays, β-rays, γ-rays, or electron beams, treatments such as corona treatment and flame treatment, application of resins such as vinylidene chloride, polyvinyl alcohol, polyamide, and polyolefin, lamination, and metal vapor deposition. .

The heat-shrinkable polyester film of the present invention contains various known additives, if necessary, in addition to the polyester having the above composition. Examples thereof include polyamide, polyolefin, polymethyl methacrylate, resins such as polycarbonate, titanium dioxide, particulate silica, kaolin, lubricants such as calcium carbonate, titanium oxide,
Examples include pigments such as carbon black, ultraviolet absorbers, release agents, flame retardants, etc., and antistatic agents and antioxidants.

The shrinkage behavior of the polyester film obtained as described above is to provide a shrinkable film having good appearance without wrinkles or unevenness by high-temperature shrinkage treatment without a preheating step by having the following shrinkage characteristics. Can be.

The shrinkage characteristics are as follows: shrinkage when immersed in warm water for 1 minute is 10 to 35% at 65 ° C. and 4% at 80 ° C.
5 to 65%, 55 to 80% at 100 ° C. Also preferably, 20 to 30% at 65 ° C, 50 to 60, 10 at 80 ° C.
It is 60 to 80% at 0 ° C, and the difference between the shrinkage at 80 ° C and 100 ° C is preferably 5% or more.

When the shrinkage at 65 ° C. is less than 10%,
If the shrinkage rate of the low-temperature portion is insufficient, and if it exceeds 35%, shrinkage will occur rapidly immediately after the shrinkage treatment, causing poor appearance. If the shrinkage at 80 ° C. is less than 40%, a sufficient shrinkage cannot be obtained, and if it exceeds 70%, rapid shrinkage causes poor appearance. If the shrinkage at 100 ° C. is less than 60%, it will be inconvenient because it will not adhere sufficiently.

The heat-shrinkable polyester film obtained as described above has good shrinkage characteristics which do not cause appearance defects by high-temperature shrinkage treatment.

[0044]

EXAMPLES Preparation of Polyester Resin (Resins 1-4) The raw materials listed in Table 1 were put into a reaction vessel equipped with a reflux tower and a stirrer, and 500 ppm of tetrabutylentitanate was added to the raw materials. 24
The reaction was carried out at 0 ° C. while distilling off the methanol by-produced until the methanol distillation amount reached 90% of the theoretical amount to obtain an esterified product. This esterified product is distilled at 250 ° C. under a high vacuum of 600 Pa or less while distilling off by-product glycol components.
The polyester resin was obtained by melt polymerization until the torque value corresponded to the torque value of PET having an intrinsic viscosity of 0.7 at 285 ° C.

(Resins 5 to 10) The raw materials shown in Table 1 were placed in a reaction vessel equipped with a reflux tower and a stirrer, and the temperature was lowered from 200 ° C to 24 ° C.
The reaction was carried out at 0 ° C. while distilling off by-produced water until the amount of distilled water became 90% of the theoretical amount to obtain an esterified product.

Then, 500 ppm of antimony trioxide based on the weight of the raw material was added to the esterified product, and 285
PET with a limiting torque of 0.7 with stirring torque while distilling off by-product glycol components at a high vacuum of 600 ° C. or less at 600 ° C.
Was melt-polymerized until the torque value became equal to 285 ° C. to obtain a polyester resin.

(Resin 11) The raw materials shown in Table 1 were placed in a reaction vessel equipped with a reflux tower and a stirrer, and 600 p
manganese acetate dihydrate at 140 ° C
The reaction was carried out at 40 ° C. while distilling off the methanol by-produced until the amount of methanol distilled out reached 90% of the theoretical amount, to obtain an esterified product.

Then, 500 ppm of antimony trioxide based on the weight of the raw material was added to the esterified product, and 285
PET with a limiting torque of 0.7 with stirring torque while distilling off by-product glycol components at a high vacuum of 600 ° C. or less at 600 ° C.
Was melt-polymerized until the torque value became equal to 285 ° C. to obtain a polyester resin.

[0049]

[Table 1] Table 2 shows the composition of the obtained polyester resin.

The resin composition was determined by chromatography after hydrolyzing the resin with hydrazine.

[0051]

[Table 2] -Preparation of film These resins were dried by vacuum drying until the water content became 100 ppm or less, blended in the ratio shown in Table 3, and
An extruded film was obtained at 60 ° C. on a cooling drum (20 ° C.).

This film was stretched 4.0 times in the TD direction and 1.0 times in the MD direction at 90 ° C. using a batch stretching machine to obtain a polyester film having a thickness of 50 μm.

The resulting film was evaluated for shrinkage at each temperature, appearance after shrinkage, anti-blocking property and preservability assuming a sterilization treatment. Table 3 shows the results.

[0054]

[Table 3] The measurement conditions are described below.

Shrinkage: A polyester film cut into a size of 150 mm in the stretching direction and 20 mm in the direction perpendicular to the stretching direction is marked with a mark at a distance of 100 mm.
mm, immersed in warm water at 65, 80, and 100 ° C. for 1 minute, and determined by the following equation.

Shrinkage (%) = {(L−L ′) / L} × 100 L: Length between marked lines before shrinkage L ′: Length between marked lines after shrinkage ・ Shrinkage and appearance by general-purpose shrinking device Evaluation After the film was formed into a cylindrical tube, the film was covered with a 300 ml round glass bottle as a shrink label and passed through a shrink tunnel. The conditions for passing through the shrink tunnel were 150 ° C. and a residence time of 10 seconds. The shrinkage finish was visually evaluated from the viewpoint of wrinkles, distortion, and uneven shrinkage.

○: Appearance without shrinkage unevenness Δ: No shrinkage unevenness, but insufficient shrinkage rate and poor adhesion ×: Appearance with remarkable shrinkage unevenness Blocking resistance (heat resistance) They were bound so as to be in contact with each other, immersed in warm water at 90 ° C. for 10 minutes, and the blocking state between the labels was determined as follows.

：: No blocking Δ: There is a trace of blocking, but it is easily removed.

×: Blocking and easy peeling.

Film Preservation The film was kept in an oven at 40 ° C. for 74 hours, and the appearance was observed and evaluated according to the following criteria.

：: No change such as shrinkage was observed.

Δ: A slight change such as shrinkage is observed.

×: A remarkable change such as shrinkage is observed.

[0064]

According to the heat-shrinkable polyester film of the present invention, abrupt shrinkage behavior is suppressed, and even when heat treatment is performed at a high temperature without a preheating step, a good appearance without wrinkles and unevenness is obtained. Is a heat-shrinkable polyester film having good performance in applications such as cap seals, labels, and coatings.

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 4F071 AA43 AA46 AF52 AF61 AH05 BB02 BC01 BC12 4J002 CF061 CF072 GG02 4J029 AA03 AB07 AC02 AE03 BA01 BA02 BA03 BA05 BA08 BA09 BB12A BD07A BF09 CA01 CA02 CA03 CB04A05 CB12 CB11A CC06A CD03 CD05 CE01 HA01 HB01 JE182 KC02 KE05

Claims (2)

[Claims] 1. A polybutylene terephthalate copolymer (A) comprising 10 to 40% by weight and a polyethylene terephthalate copolymer (B) 60 to 90% by weight, and among the acid components of (A), other than terephthalic acid. 5 to 20 mol% of an aromatic dicarboxylic acid component, and 5 to 50 mol% of a component other than terephthalic acid in the acid component of (B) and / or 5 to 5 mol% of a glycol component other than ethylene glycol.
A heat-shrinkable polyester film characterized by being in an amount of from 50 to 50 mol%. 2. The shrinkage rate is 10 to 35% at 65 ° C. and 80 ° C.
The heat-shrinkable polyester film according to claim 1, wherein the heat-shrinkable polyester film has a particle size of 45 to 65% and a temperature of 100 to 55% to 80%.