JP2986197B2 - Heat-shrinkable polyester film - Google Patents

Description

The present invention relates to a heat-shrinkable polyester film,
More specifically, it has excellent low-temperature shrinkage and uniform shrinkage,
In particular, it relates to a heat-shrinkable polyester film useful as a shrink label for various containers.

[Conventional technology]

The heat shrinkable film is widely used for applications such as shrink wrapping, shrink labels, and cap seals, utilizing the property of shrinking by reheating.

By the way, a uniaxially stretched film such as a vinyl chloride resin or expanded polystyrene is mainly used for shrink labels used for labels on various containers such as polyethylene terephthalate (PET) containers and glass containers. Among them, a heat-shrinkable vinyl chloride film is generally used because of its low-temperature shrinkage and good printing characteristics.

By the way, vinyl chloride resin has low heat resistance,
It has problems such as generation of hydrogen chloride during incineration. Further, when a heat-shrinkable vinyl chloride film is used as a shrink label, the PET container cannot be collected and used together with the shrink label.

On the other hand, heat-shrinkable films of polyester resins such as polyethylene terephthalate have excellent heat resistance and do not generate hydrogen chloride during incineration. It is expected to be used as a shrinkable label for containers instead of a shrinkable film.

However, since the polyester-based resin has high crystallinity, in the heat-shrinkable film, the heat-shrinkage start temperature is relatively high, and the shrinkage rate tends to sharply increase with the temperature rise, Applications of shrink labels for various containers have problems in productivity and uniform shrinkage.

Therefore, recently, various improvement proposals have been made for heat-shrinkable films of polyester resin.

For example, JP-A-57-42726 discloses a transparent and heat-sealing property using a copolymerized polyester comprising terephthalic acid as a dicarboxylic acid component, ethylene glycol and 1,4-dichlorohexanedimethanol as a diol component. Heat shrink wrapping films have been proposed.

Japanese Examined Patent Publication No. 63-7373 proposes that isophthalic acid is contained as a copolymer component to reduce high crystallinity and to improve uneven shrinkage and heat sealability.

JP-B-64-10332 discloses tetraphthalic acid or a derivative thereof and ethylene glycol with 1,4-
Disclosed is a highly shrinkable polyester film obtained by subjecting a composition comprising an amorphous copolymerized polyester derived from dichlorohexanedimethanol and a polyester-based polymer comprising terephthalic acid or a derivative thereof to ethylene glycol to a film-forming stretching treatment. Have been.

In the above prior art documents, as a raw material of the heat-shrinkable polyester film, an amorphous copolymerized polyester, or
An amorphous copolyester and a crystalline polyester are mixed to suppress crystallization of the polyester. These have a higher shrinkage ratio, a higher heat seal strength, a lower shrinkage stress, an improved shrinkage unevenness, and easier tearing of the heat seal portion as compared to a heat shrinkable film made of crystalline polyester terephthalate. It is said that.

However, these conventional techniques have not yet obtained a heat-shrinkable polyester film having sufficient shrinkage characteristics.

That is, the known heat-shrinkable polyester film has a disadvantage that the shrinkage temperature is still higher than that of the heat-shrinkable vinyl chloride film, and the shrinkage rate rapidly increases at the temperature at which shrinkage starts. I have.

Therefore, problems such as a decrease in productivity and occurrence of uneven shrinkage in the shrinking step are inevitable. In particular, when used as a shrink label for containers of different sizes at the neck and body, such as bottles, the sudden increase in shrinkage with temperature rise is
This causes non-uniform adhesion and distortion of printing, which is a serious problem in practical use.

[Problems to be solved by the invention]

An object of the present invention is to provide a heat-shrinkable polyester film that has a good low-temperature shrinkage and can achieve uniform shrinkage without uneven shrinkage.

The present inventors have conducted intensive studies to overcome the problems of the conventional technology, and as a result, a polyester resin derived from a dicarboxylic acid and a diol component, a phthalate ester plasticizer, a polyester plasticizer, Aliphatic dibasic acid ester plasticizer, aliphatic monobasic acid ester plasticizer, phosphate ester plasticizer, citrate ester plasticizer, epoxy plasticizer, trimellitate ester plasticizer, tetrahydrophthalic acid A heat-shrinkable polyester film obtained by forming a film using a composition containing a plasticizer such as an ester-based plasticizer, a glycol-based plasticizer, and a bisphenol A alkylene oxide derivative has a heat-shrinkable vinyl chloride-based film. It can be reduced to the same level as the film, and the shrinkage gradually increases as the temperature of the film rises. It found that the Do not contraction can be achieved.

The present invention has been completed based on these findings.

[Means for solving the problem]

According to the present invention, 100 parts by weight of a polyester resin derived from a dicarboxylic acid component and a diol component, a phthalate ester plasticizer, a polyester plasticizer, an aliphatic dibasic ester plasticizer, an aliphatic Basic acid ester plasticizer, phosphate ester plasticizer, citrate ester plasticizer, epoxy plasticizer, trimellitate ester plasticizer, tetrahydrophthalate ester plasticizer, glycol plasticizer, and bisphenol A At least one plasticizer selected from alkylene oxide derivatives 1
There is provided a heat-shrinkable polyester film obtained by forming a composition containing from 40 to 40 parts by weight.

 Hereinafter, the present invention will be described in detail.

(Polyester Resin) The polyester resin used in the present invention is a polyester resin derived from a dicarboxylic acid component and a diol component, a polyester resin derived from an oxycarboxylic acid component, or a mixture thereof. Ingredients include terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, diphenylenedicarboxylic acid, diphenylether dichambonic acid, phenylenediacetic acid, adipic acid, azelaic acid, sebacic acid, oxalic acid, succinic acid, malonic acid, glutaric acid Examples of diol components such as acid, pimelic acid, suberic acid, dodecadionic acid, cyclohexanedicarboxylic acid, and carbonic acid include ethylene glycol, propylene glycol, neopentyl glycol, butanediol, hexanediol, and 1,4-cyclohexane. Xanthimethanol, diethylene glycol, polyalkylene glycol, xylene glycol, hydroquinone, resorcinol, dihydroxydiphenyl, alkylene oxide adducts of bisphenol A, such as oxycarboxylic acid components, oxybenzoic acid, oxyalkylbenzoic acid, oxyalkoxyphenylacetic acid, Oxynaphthoic acid, glycolic acid and the like can be mentioned.

Among them, terephthalic acid accounts for 50 mol% or more of the dicarboxylic acid component, and a polyester resin in which 50 mol% or more of the diol component is ethylene glycol easily suppresses crystallization and is excellent in heat sealability. Therefore, it is particularly preferably used.

The plasticizer used in the present invention is at least one plasticizer selected from the plasticizers described above, and will be described in more detail.

Examples of the phthalate plasticizer include dialkyl phthalates such as dibutyl phthalate, dioctyl phthalate, and diheptyl phthalate, and dibenzyl phthalate.

Polyester plasticizers include ethylene glycol, propylene glycol, 1,3-butanediol, 1,6
-A polymer of hexanediol or the like with adipic acid, sebacic acid or phthalic acid.

Examples of the aliphatic dibasic ester plasticizer include dioctyl adipate, diisodecyl adipate, cyoctyl azelate, dihexyl azelate, dioctyl sebacate, and diisooctyl sebacate.

Examples of the aliphatic monobasic acid ester-based plasticizer include butyl stearate, amyl stearate, and butyl oleate.

Examples of the phosphate plasticizer include trioctyl phosphate, triphenyl phosphate, diphenyl 2-ethylhexyl phosphate, and the like.

Examples of the citrate-based plasticizer include tributyl citrate, tributyl acetyl citrate, and tri-2-ethylhexyl acetyl citrate.

Epoxy plasticizers include epoxidized soybean oil, epoxidized linseed oil, and octyl epoxy stearate.

Examples of the trimellitate plasticizer include tributyl trimetate, trihexyl trimellitate, and trioctyl trimellitate.

Examples of the tetrahydrophthalate-based plasticizer include dioctyl tetrahydrophthalate, diisodecyl tetrahydrophthalate, and the like.

Examples of the glycol plasticizer include polyethylene glycol and polyethylene glycol benzoate.

Examples of the bisphenol A alkylene oxide derivative include compounds obtained by adding ethylene oxide or propylene oxide to bisphenol A.

These plasticizers can be used alone or in combination of two or more.

(Blending ratio) The mixing ratio of the polyester resin and the plasticizer in the present invention is 1 to 40 parts by weight of a plasticizer, preferably 2 to 30 parts by weight, and more preferably 100 parts by weight of the polyester resin. Preferably it is 3 to 15 parts by weight.

By compounding the above plasticizer, crystallization of the polyester-based resin is suppressed, and it is possible to make it easy to slide between molecular chains. When a heat-shrinkable film is formed, the shrinkage is gradually started from a low temperature. It becomes possible. If the amount of these plasticizers is less than 1 part by weight, slippage between molecular chains does not sufficiently occur, and low-temperature shrinkage becomes insufficient. At the stretching temperature at the time of producing the film, the elastic modulus of the film is remarkably reduced and stretching becomes difficult, and a heat-shrinkable film cannot be obtained.

In the composition of the present invention, additives such as a filler and a colorant may be blended as required.

(Production of heat-shrinkable non-film) A resin composition containing a polyester-based resin and a plasticizer,
By a conventional method, the sheet is melt-extruded into a sheet by a T-die method, a tubular method, or the like to obtain an unstretched film. Then
The heat-shrinkable polyester film can be obtained by stretching the unstretched film at least about 1.5 to 6 times in a uniaxial direction by a roll, tenter, tubular method or the like.

[Action]

The heat-shrinkable polyester film obtained by containing the specific plasticizer as described above has a low-temperature shrinkage of about 70 ° C., which is almost the same as the heat-shrinkable vinyl chloride film due to the action of the plasticizer. ing.

Moreover, as the temperature rises from the temperature at which thermal contraction starts,
The heat shrinkage tends to increase gradually.

Therefore, when the heat-shrinkable polyester film is used as a shrink label for a container having a thin portion such as a neck portion of a bottle and a thick portion such as a torso portion, the shrinkage rate gradually increases. Even when a cylindrical shrinkable label is applied to a narrow portion and a thick portion, shrinkage does not become nonuniform, adhesion is good, and printing distortion does not occur.

Since this heat-shrinkable polyester film has better heat resistance than that of a vinyl chloride resin, for example,
Used as a shrinkable label for PET containers, the label does not deform even after retort treatment.

Further, unlike a vinyl chloride resin, hydrogen chloride is not generated during incineration. Further, since the heat-shrinkable polyester film is made of the same raw material as the PET container, the PET resin can be recovered and reused with the label attached.

As described above, the heat-shrinkable polyester film of the present invention shrinks at a lower temperature compared to the conventional heat-shrinkable polyester film, so that the productivity is improved, and the shrinkage rate gradually increases with the temperature rise of the film. , And exhibits excellent shrinkage characteristics such as non-uniform shrinkage.

〔Example〕

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

 Hereinafter, parts by weight are simply referred to as parts.

(Example 1) Copolyester 10 composed of terephthalic acid as the carboxylic acid component, 70 mol% of ethylene glycol and 30 mol% of 1,4-cyclohexadimethanol as the diol component
A composition comprising 0 parts and 5 parts of dibutyl phthalate (DBP) as a plasticizer was melt-extruded to obtain an unstretched film having a thickness of 120 μm.

The unstretched film was stretched 3.0 times in the transverse direction at 80 ° C. to obtain a heat-shrinkable film having a thickness of 40 μm.

With respect to this heat-shrinkable film, the respective shrinkage rates in the horizontal direction were measured at every 10 ° C in a temperature range of 60 ° C to 110 ° C.

To measure the shrinkage, place the sample in the horizontal direction with a length of 100 mm and a width of 1
It was cut to 0 mm and shrunk in hot air set to the measurement temperature for 5 minutes, and the shrinkage was measured.

(Examples 2 to 19) A heat-shrinkable film was obtained in the same manner as in Example 1, except that a composition composed of 100 parts of a polyester resin and 5 parts of a plasticizer as shown in Table 1 was used. Was evaluated.

(Comparative Examples 1 and 2) A heat-shrinkable film was obtained and evaluated in the same manner as in Example 1, except that the polyester resins shown in Table 1 were used and no plasticizer was used.

Table 2 shows the results of Examples 1 to 19 and Comparative Examples 1 and 2 collectively.

As is clear from Table 2, the heat-shrinkable polyester film of the present invention can perform low-temperature shrinkage at around 70 ° C., which is the heat shrinkage initiation temperature of the heat-shrinkable vinyl chloride film. More importantly, the shrinkage tends to increase gradually as the shrinkage temperature increases. Therefore, it is possible to overcome the non-uniform shrinkage phenomenon caused by the sudden increase in the shrinkage rate.

On the other hand, Comparative Examples 1-2 without using a plasticizer
The heat-shrinkable polyester-based film shows a sharp increase in shrinkage at a heat-shrink start temperature of 80 ° C.

〔The invention's effect〕

According to the present invention, it is possible to provide a heat-shrinkable polyester film which can be shrunk at a low temperature and has excellent uniform shrinkage without uneven shrinkage.

The heat-shrinkable polyester film of the present invention has good heat resistance and does not generate hydrogen chloride during incineration unlike a vinyl chloride resin. In addition, the shrinkage rate increases gradually without increasing the shrinkage temperature as the shrinkage temperature rises, and uniform shrinkage without uneven shrinkage can be achieved, which is particularly useful in the field of shrink labels for various containers such as PET containers. is there.

Continued on the front page (51) Int.Cl. ⁶ Identification code FI B29L 7:00

Claims (1)

(57) [Claims] 1. 100 parts by weight of a polyester resin derived from a dicarboxylic acid component and a diol component, a phthalate ester plasticizer, a polyester plasticizer, an aliphatic dibasic ester plasticizer, and an aliphatic monobasic. Acid ester plasticizer, phosphate ester plasticizer, citrate ester plasticizer, epoxy plasticizer, trimellitate ester plasticizer, tetrahydrophthalate ester plasticizer, glycol plasticizer, and bisphenol A alkylene At least one plasticizer selected from oxide derivatives 1 to 40
A heat-shrinkable polyester film formed by forming a composition containing parts by weight.