JPH04117432A - Heat-shrinkable polyester film - Google Patents

Abstract

PURPOSE:To obtain a heat-shrinkable film capable of being shrunk at low temperatures, free of uneven shrinkage and excellent in uniform shrinkage by adding a specified plasticizer to a polyester resin derived from a dicarboxylic acid component and a diol component. CONSTITUTION:A thermoplastic polyester film obtained from a composition comprising 100 pts.wt. polyester resin derived from a dicarboxylic acid component and a diol component and 1-40 pts.wt. at least one plasticizer selected from among those based on phthalic ester, polyester, aliphatic dibasic acid ester, aliphatic monobasic acid ester, phosphoric ester, citric ester, epoxy compound, trimellitic ester, tetrahydrophthalic ester, glycol and bisphenol A alkylene oxide derivative.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a heat-shrinkable polyester film, and more specifically, it has excellent low-temperature shrinkability and uniform shrinkability, and is particularly useful as shrink labels for various containers. The present invention relates to a heat-shrinkable polyester film.

[Conventional technology]

Heat-shrinkable films are widely used in applications such as shrink packaging, shrink labels, and cap seals due to their ability to shrink when reheated.

By the way, uniaxially stretched films such as vinyl chloride resin and expanded polystyrene are mainly used for shrink labels used for various containers such as polyethylene terephthalate (PET) containers and glass containers. Among them, heat-shrinkable vinyl chloride films are commonly used because they have good low-temperature shrinkability and printing properties.

However, vinyl chloride resins have problems such as low heat resistance and generation of hydrogen chloride when incinerated. In addition, there is a problem that a PET container using a heat-shrinkable vinyl chloride film as a shrinkable label cannot be recycled together with the shrinkable label.

On the other hand, heat-shrinkable films made of polyester resins such as polyethylene terephthalate have properties that vinyl chloride resins do not have, such as excellent heat resistance and no generation of hydrogen chloride when incinerated. It is expected to be used as a shrink label for containers in place of shrink film.

However, since polyester resins have high crystallinity, their heat-shrinkable films have a relatively high heat-shrinkage start temperature, and the shrinkage rate tends to increase rapidly as the temperature rises. Shrink labels for various containers have problems in terms of productivity and uniform shrinkability.

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

For example, JP-A No. 57-42726 discloses a transparent, heat-sealable, heat-shrinkable polyester using a copolymerized polyester consisting of terephthalic acid as a dicarboxylic acid component, ethylene glycol and 14-cyclohexane dimetatool as a diol component. Packaging films have been proposed.

Japanese Patent Publication No. Sho 63-7573 proposes to contain isophthalic acid as a copolymerization component to alleviate high crystallinity and improve shrinkage unevenness and heat sealability.

In addition, Japanese Patent Publication No. 10332/1983 discloses that terephthalic acid or its derivatives and ethylene glycol and 1.
A highly shrinkable polyester film obtained by forming and stretching a composition consisting of an amorphous copolymerized polyester derived from 4-cyclohexane dimetatool, a polyester polymer consisting of terephthalic acid or its derivative, and ethylene glycol. is disclosed.

In the above-mentioned prior literature, as a raw material for a heat-shrinkable polyester film, an amorphous copolymerized polyester, or a mixture of an amorphous copolymerized polyester and a crystalline polyester to suppress the crystallization of the polyester is used. I am using it. Compared to heat-shrinkable films made from crystalline polyethylene terephthalate, these films have a higher shrinkage rate, higher heat-sealing strength, lower shrinkage force stress, and are less prone to uneven shrinkage and tearing at the heat-sealed part. It is said that it will be improved.

However, with these conventional techniques, a heat-shrinkable polyester film with sufficient shrinkage characteristics has not yet been obtained.

That is, the above-mentioned known heat-shrinkable polyester film is
Compared to aged vinyl chloride films, it still has a high shrinkage temperature (and also has the disadvantage that the shrinkage rate increases rapidly at the temperature at which shrinkage begins).

For this reason, problems such as decreased productivity and uneven shrinkage during the shrinking process are unavoidable.Especially when used as a shrink label for a container such as a bottle whose neck and body are different sizes, the temperature rises. The rapid increase in shrinkage rate associated with this causes non-uniform adhesion and distortion of printing, which poses a serious problem in practice.

(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 rate and can achieve uniform shrinkage without uneven shrinkage.

As a result of intensive research in order to overcome the problems of the conventional techniques, the present inventors discovered that 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, citric ester plasticizer,
Epoxy plasticizer, trimellitic acid ester plasticizer,
A heat-shrinkable polyester film obtained by forming a film using a composition containing a plasticizer such as tetrahydrophthalic acid ester plastic IPj, a glycol plasticizer, and a bisphenol A alkylene oxide derivative has a shrinkage temperature of It has been found that the shrinkage can be reduced to the same level as that of a vinyl chloride film, and that the shrinkage gradually increases as the temperature of the film increases, achieving uniform shrinkage without uneven shrinkage.

The present invention has been completed based on these findings.

[Means to solve 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 plasticizer, a polyester plasticizer, an aliphatic dibasic acid ester plasticizer, an aliphatic Basic acid ester plasticizers, phosphate ester plasticizers, citric acid ester plasticizers, epoxy plasticizers, trimellitic acid ester plasticizers, tetrahydrophthalate plasticizers, glycol plasticizers, and bisphenol A At least one plasticizer selected from alkylene oxide derivatives 1
Provided is a heat-shrinkable polyester film formed from a composition containing up to 40 parts by weight.

The present invention will be explained in detail below.

(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, naphthalene dicarboxylic acid, diphenylene dicarboxylic acid, diphenyl etherdicanboxylic acid, phenylene diacetic acid, adipic acid, azelaic acid, sebacic acid, oxalic acid,
Succinic acid, malonic acid, glutaric acid, pimelic acid, speric acid, dodecadionic acid, cyclohexanedicarboxylic acid,
Diol components such as carbonic acid include ethylene glycol, propylene glycol, neopentyl glycol, butanediol, hexanediol, 14-cyclohexane dimetatool, diethylene glycol, polyalkylene glycol, xylene glycol, hydroquinone,
Examples of oxycarboxylic acid components such as resorcinol, dihydroxydiphenyl, and alkylene oxide adducts of bisphenol A include oxybenzoic acid, oxyalkylbenzoic acid, oxydialkoxyphenylacetic acid, oxynaphthoic acid, and glycolic acid.

Among these, those using a polyester resin in which 50 mol% or more of the dicarboxylic acid content is terephthalic acid and 50 mol% or more of the diol component is ethylene glycol are easy to suppress crystallization and have excellent heat sealability. Therefore, it is particularly suitable for use.

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

Examples of phthalate ester plasticizers include dialkyl phthalate esters such as dibutyl phthalate, dioctyl phthalate, and diheptyl phthalate, and dibenzyl phthalate.

Examples of polyester plasticizers include ethylene glycol,
Propylene glycol, 1,3-butanediol, 1,
6-hexanediol etc. and adipic acid, cepatic acid,
Examples include polymers with phthalic acid.

Examples of the aliphatic dibasic acid ester plasticizer include dioctyl adipate, diisodecyl adipate, dioctyl azelate, dihexyl azelate, dioctyl sepatate, diisooctyl sepatate, and the like.

Examples of aliphatic monobasic acid ester plasticizers include butyl stearate, amyl stearate, butyl oleate, and the like.

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

Examples of citric acid ester plasticizers include tributyl citrate, tributyl acetyl citrate, and tri-2-ethylhexyl acetyl citrate.

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

Examples of trimellitic acid ester plasticizers include tributyl trimellitate, trihexyl trimellitate, and trioctyl trimellitate.

Examples of the tetrahydrophthalate plasticizer include dioctyl tetrahydrophthalate and diisodecyl tetrahydrophthalate.

Examples of glycol plasticizers include polyethylene glycol and polyethylene glycol henzoate.

Examples of bisphenol A alkylene oxide derivatives 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 HIM and the plasticizer in the present invention is 1 to 40 parts by weight, preferably 2 to 3 parts by weight, of the plasticizer per 100 parts by weight of the polyester resin.
0 parts by weight, more preferably 3 to 15 parts by weight.

By blending the above plasticizer, it is possible to suppress the crystallization of the polyester resin and make it easier to slip between the molecular chains, and when it is made into a heat-shrinkable film, it starts shrinking gradually from a low temperature. becomes possible. If the amount of these plasticizers is less than 1 part by weight, slippage between molecular chains will not occur sufficiently, resulting in insufficient low-temperature shrinkability.
On the other hand, if it exceeds 40 parts by weight, the elastic modulus of the film decreases significantly at the stretching temperature used to produce a heat-shrinkable film, making it difficult to stretch, making it impossible to obtain a heat-shrinkable film.

Additionally, additives such as fillers and colorants may be added to the composition of the present invention as desired.

(Production of heat-shrinkable non-film) A resin composition containing a polyester resin and a plasticizer is melt-extruded into a sheet shape by a T-die method, a tubular method, etc. to obtain an unstretched film. A heat-shrinkable polyester film can be obtained by stretching an unstretched film by a small amount (approximately 1.5 to 6 times in both axial directions) using a roll, tenter, or tubular method.

[Effect]

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

Moreover, as the temperature rises from the temperature at which heat shrinkage begins, the heat shrinkability tends to gradually increase.

Therefore, this heat-shrinkable polyester film
When used as a shrink label for containers such as bottles, which have a thin part like the neck part and a thick part like the body part,
Since the shrinkage rate increases gradually, even if a cylindrical shrink label is applied between thin and thick areas, the shrinkage will not be uneven, the adhesion will be good, and the printing will not be distorted.

This heat-shrinkable polyester film has better heat resistance than vinyl chloride resin, so for example,
Used as a shrink label for ET containers, and the label does not deform even after retort processing.

In addition, unlike vinyl chloride resin, it does not generate hydrogen chloride when incinerated.Furthermore, since this heat-shrinkable polyester film is made from the same raw material as PET containers, the PET resin can be recovered and reused with the label still attached. is possible.

2, the heat-shrinkable polyester fiber of the present invention
Compared to conventional heat-shrinkable polyester films, ZM shrinks at low temperatures, improving productivity, and the shrinkage rate gradually increases as the film temperature rises, so uneven shrinkage does not occur. Demonstrates excellent shrinkage properties.

〔Example〕

Hereinafter, this invention will be specifically explained by giving Examples and Comparative Examples.

Note that hereinafter, parts by weight are simply referred to as parts.

(Example 1) 100 parts of a copolymerized voluster whose dicarboxylic acid component is terephthalic acid, whose diol components are 70 mol% ethylene glycol and 30 mol% 14-cyclohexane dimetatool, and dibutyl phthalate (DBP) as a plasticizer.
) was melt-extruded to obtain an unstretched film with a thickness of 120 μm.

This unstretched film was rolled at 80°C in the transverse direction for 3. A heat-shrinkable film with a thickness of 40 μm was obtained by stretching 0 times.

Regarding this pH-sensitive film, each shrinkage rate in the transverse direction was measured at every 10°C in a temperature range of 60°C to 110°C.

The shrinkage rate was measured by cutting the sample in the transverse direction into 100 lengths and 10 squares, shrinking the sample in hot air set at the measurement temperature for 5 minutes, and measuring the shrinkage rate.

(Examples 2 to 19) Heat-shrinkable films were obtained in the same manner as in Example 1, except that compositions consisting of 100 parts of polyester resin and 5 parts of plasticizer as shown in Table 1 were used. It was evaluated as follows.

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

The results of the above Examples 1 to 19 and Comparative Examples 1 to 2 are collectively shown in Table 2.

(Margin below) Note) *1゜*2゜*3: Dainippon Ink Chemical Co., Ltd. Table 1 (Part 2) Table 1 (Part 3) Table 2 (Part 2) As is clear from Table 2 The heat-shrinkable polyester film of the present invention can undergo low-temperature shrinkage at around 70°C, which is the heat-shrinkage start temperature of a heat-shrinkable vinyl chloride film. Furthermore, what is important is that the shrinkage rate tends to gradually increase as the shrinkage temperature increases. Therefore, it is possible to overcome the uneven shrinkage phenomenon caused by a sudden increase in shrinkage rate.

On the other hand, the heat-shrinkable polyester films of Comparative Examples 1 and 2 in which no plasticizer was used showed a rapid increase in shrinkage rate at a heat-shrinkage start temperature of 80°C.

〔Effect of the invention〕

According to the present invention, it is possible to provide a heat-shrinkable polyester film that is capable of shrinking at low temperatures and has excellent uniform shrinkability without uneven shrinkage.

The heat-shrinkable polyester film of the present invention has good heat resistance and does not generate hydrogen chloride when incinerated unlike vinyl chloride resins. In addition, the shrinkage rate does not increase rapidly as the shrinkage temperature rises, but increases gradually, and uniform shrinkage without unevenness can be achieved, making it particularly useful in the field of shrinkage lathes for various containers such as PET containers. be.

Claims (1)

[Claims] (1) 100 parts by weight of a polyester resin derived from a dicarboxylic acid component and a diol component, a phthalate plasticizer, a polyester plasticizer, an aliphatic dibasic acid ester plasticizer, and an aliphatic monobasic acid ester plasticizers, phosphate ester plasticizers, citric ester plasticizers, epoxy plasticizers, trimellitic ester plasticizers, tetrahydrophthalate ester plasticizers, glycol plasticizers, and bisphenol A alkylene oxide derivatives. A thermoplastic polyester film formed from a composition containing 1 to 40 parts by weight of at least one type of plasticizer selected from the following.