WO2006091003A1

WO2006091003A1 - Thermo-shrinkable polyester film

Info

Publication number: WO2006091003A1
Application number: PCT/KR2006/000593
Authority: WO
Inventors: Gi Sang Song; Ji Yong Park; Seung Hwan Lee
Original assignee: Kolon Industries Inc
Current assignee: Kolon Industries Inc
Priority date: 2005-02-22
Filing date: 2006-02-22
Publication date: 2006-08-31
Anticipated expiration: 2007-08-22

Abstract

Disclosed is a polyester film having an excellent thermo-shrinking property since it is manufactured from the copolymerized polyester resin. The thermo-shrinkable polyester film of the present invention, manufactured from the copolymerized polyester resin prepared from the diol components and the acid components including a compound represented by the following Formula 1, has the excellent thermo-shrinkability in a main shrinkage direction, and also an excellent solvent adhesion if PBT polymers or copolymers are further used herein. Formula(1)wherein m, n and o are independently an integer from 1 to 4; and R1 to R4 are independently identical or different to each other, and represent C1 ~ C4 alkyl group.

Description

[DESCRIPTION]

[invention Title]

THERMO-SHRINKABLE POLYESTER FILM

[Technical Field]

The present invention relates to a polyester film having an excellent thermo-shrinking property, and more specifically to a thermo-shrinkable polyester film having an excellent thermo-shrinkability in a main shrinkage direction and an excellent solvent adhesion, wherein the polyester film is prepared from a copolymerized polyester resin including acid components, and diol components including a predetermined content of a compound having an aliphatic group (s), alone or in combination with a polybutyleneterephthalate polymer or its copolymer.

[Background Art]

The thermo-shrinkable films have been used for various applications such as a wrapper for tying various products into a bundle in the large discount stores due to a recent change of a distribution system, or labelings and coatings of various plastic vessels including a glass, etc. Polyvinyl chloride, polystyrene, etc. have been widely for such a thermo-shrinkable film, and they have a problem that they have insufficient properties such as heat resistance, chemical resistance, weather resistance, etc. Especially, the polyvinyl chloride is harmful to the environment since it generates a large amount of smoke, as well as toxic gases upon its combustion. The thermo- shrinkable film also has a problem that a label should be detached from the vessel so as to reuse the label if it is used as a label of drinking PET bottle. In order to solve the problems, there have been continuous attempts to use polyester-based materials instead of the conventional materials .

The polyester-based materials represented by polyethyleneterephthalate have an advantage that they have excellent properties such as heat resistance, chemical resistance, weather resistance, etc. unlike the polyvinyl chloride or polystyrene as described above, but they also have a problem that they do not give a desired thermo- shrinkability due to their excellent crystallization behaviour by regularity of their molecular chains, and their excellent dimensional stability after heat setting. Also, the polyester-based materials may exhibit various problem when they are directly labelled on the bottle or cover all the bottle since they have a very high shrinkage stress and a very rapid shrinkage rate upon heat shrinkage. In addition, they may exhibit a problem of ununiformity by shrinkage.

Accordingly, it is difficult to manufacture a thermo- shrinkable film using polyethyleneterephthalate.

In the industrial method for manufacturing a conventional polyethyleneterephthalate film, a polyethyleneterephthalate polymer was melt-extruded and cooled in a cooling drum to manufacture an amorphous sheet, and then the resultant sheet was drawn and heat-set to obtain a biaxially drawn film. At this time, the industrial method for manufacturing a polyethyleneterephthalate polymer used for manufacturing the polyethyleneterephthalate film generally includes a direct esterification method where dicarboxylic acid such as terephthalic acid, and ethyleneglycol, used as a main component, are heated to a reaction temperature of 200 to 280 ^°C under an ambient pressure or a predetermined pressure; and an ester-exchanging method where dimethylcarboxylate such as dimethylterephthalate and glycol such as ethyleneglycol, used as a main component, are heated to a reaction temperature of 140 to 240 ^°C in the presence of a catalyst, wherein esters including bis (beta-hydroxyethyl) terephthalate and its oligomeric condensates as a main component are obtained by means of the said methods, and the resultant esters are sequentially polycondensated with a polycondensation catalyst at a reaction temperature of 260 to 300 ^°C under a high- vacuum condition. Also, the shrinkable film gives a shrinkage property at the temperature of at least 70 to 80 ^°C, which may be accomplished by heat treatment below the temperature range.

Control of a shrinkage behavior by such heat treatment temperature is limited by its shrinkability itself when the conventional polyethyleneterephthalate is used alone, and the shrinkage behavior is carried out smoothly when the shrinkage temperature is increased to at least 100 ^°C . However, the shrinkage temperature is preferably maintained at 100 ^°C or less as low as possible since wrapped materials may be deteriorated due to a high shrinkage temperature.

In order to reduce the shrinkage temperature to 100 ^°C or less, there has, however, been required a polymer structure having a shrinkage property even at a low temperature by using a copolymerization component in addition to polyethyleneterephthalate.

The conventional high-shrinkable films gave a dynamic structure capable of being shrunk smoothly after drawing by hampering crystallinity of polyethylene terephthalate using 2,2-dimethyl-l,3-propandiol (NPG), 1, 4-cyclohexanedimethanol (CHDM), etc. as the copolymerization component.

Also, 1, 4-cyclohexanedimethanol (CHDM), 2, 2-dimethyl-

1,3-propandiol (NPG), bisphenol A ethoxylate (BPE), etc. are the most widely used as the diol-based copolymerization component, and isophthalic acid or adipic acid is also generally used as the acid component.

If such a copolymerization component is used, it is possible to manufacture a film capable of suppressing its crystallinity and preventing a glass transition temperature from rising by reducing its suitable uniformity for forming a crystalline structure of polyethyleneterephthalate.

Therefore, there has been required a film capable of removing the dimensional stability which makes crystalline destruction and shrinkage difficult, as well as giving a low shrinkage stress and a high shrinkability by manufacturing a polyester copolymer in order to maintain excellent physical properties, such as heat resistance, chemical resistance, weather resistance, etc., of polyethyleneterephthalate, and simultaneously to give a satisfactory thermo-shrinking property.

Accordingly, the present inventors have ardently studied to solve the problems caused when a shrinkable film is manufactured with a copolymerized polyester resin represented by the conventional polyethyleneterephthalate as described above. As a result, they found that a copolymerized polyester resin can be manufactured using a predetermined amount of a branched diol component as the diol component, and then a thermo-shrinkable polyester film can be also manufactured with the copolymerized polyester_. resin manufactured thus, alone or in combination with the polybutyleneterephthalate polymer and its copolymer, and therefore the thermo-shrinkable polyester film having the excellent thermo-shrinkability can be also manufactured since the diol component destructs a crystal structure of its main chains. Therefore, the present invention was completed.

[Disclosure] [Technical Problem]

Therefore it is an object of the present invention to provide a thermo-shrinkable polyester film manufactured from a copolymerized polyester resin capable of maintaining an equivalent level of excellent physical properties such as heat resistance, chemical resistance, weather resistance, etc. of polyethyleneterephthalate, as well as giving a satisfactory thermo-shrinking property.

[Technical Solution] In order to accomplish the above object, the present invention provides a thermo-shrinkable polyester film manufactured from the copolymerized polyester resin including acid components and diol components, wherein the diol components include a compound represented by the following Formula 1 :

Formula 1

wherein, m, n and o are independently an integer from 1 to 4; and

Ri to R₄ are independently identical or different to each other, and represent Ci ~ C₄ alkyl group.

In the thermo-shrinkable polyester film of the present invention, the diol components include 3 to 30 mol% of a compound represented by the Formula 1 based on a total weight of the diol component.

The thermo-shrinkable polyester film of the present invention further includes a polybutyleneterephthalate polymer or copolymer in addition to the thermo-shrinkable polyester resin including the copolymerized polyester resin.

In the thermo-shrinkable polyester film of the present invention, the polybutyleneterephthalate polymer or its copolymer is included in an amount of 3 to 30 % based on a total weight of the resin.

In the thermo-shrinkable polyester film of the present invention, the thermo-shrinkable polyester film has at least 30 % of thermo-shrinkability in a main shrinkage direction when it is kept at a hot wind of 100 ^°C for 1 minute. Hereinafter, preferred embodiments of the present invention will be described in detail.

The copolymerized polyester resin used for manufacturing a thermo-shrinkable film of the present invention is prepared from a resin composition including the acid component, for example terephthalic acid as a main component and the diol component, for example ethyleneglycol as a main component, and further including 3 to 30 mol% of the compound represented by the Formula 1 based on a total weight of the diol component.

The copolymerized polyester composition including a predetermined content of aliphatic diol having a structure represented by the Formula 1 may be suitable to manufacture a polyester-based film having a desired thermo-shrinkability since its crystallinity is deteriorated and its dimensional stability which makes its shrinkage difficult is reduced by destroying a crystal structure of polyethyleneterephthalate. Content of the diol monomer represented by the Formula 1 is preferably 3 to 30 mol% based on a total weight of the diol component. It is difficult to give a thermo-shrinking property since it is difficult to effectively destroy uniformity of film molecules at the content of less than 3 mol%, while a polyester polymerization reaction is not normally carried out at the content of more than 30 mol%, and it could not be expected that the polyester film have excellent physical properties such as an abnormal excessive processing and heat resistance of polyethyleneterephthalate although a polyester film is manufactured herein.

Meanwhile, it is preferred that m, n and o independently range from 1 to 4 in the Formula 1. If they exceed 4, the polyester film has problems that a glass transition temperature and a melting temperature of the polymer are significantly reduced due to its increased aliphatic chains and its crystallinity is not effectively deteriorated.

Also, Ri, R₂, R₃ and R₄ of the Formula 1 are independently identical or different to each other, and preferably saturated aliphatic groups having 1 to 4 carbon atoms. If they have greater than 4 carbon atoms, then it is difficult for a polymerization reaction and it is also difficult to maintain physical properties of the main component polyethyleneterephthalate. Also, if they are unsaturated aliphatic groups, then properties of the composition may be deteriorated because the side reactions may be generated in the polyester polymerization reaction. Accordingly, R₁ to R₄ are preferably independently alkyl groups having 1 to 4 carbon atoms among the saturated aliphatic groups in the Formula 1.

The thermo-shrinkable polyester resin composition of the present invention includes the main component, for example terephthalic acid as an acid component, but other acid components may be copolymerized without departing from the objects of the present invention. For example, the acid component includes, but is not limited to, aliphatic dibasic acid such as adipic acid, sebacic acid, azelaic acid; and aromatic dibasic acid such as isophthalic acid, diphenyldicarboxylic acid, 5-tert-butylisophthalic acid, 2, 2, 6, 6-tetramethylbiphenyl-4, 4-dicarboxylic acid, 2,6- naphthalenedicarboxylic acid, 1, 1, 3-trimethyl-3-phenylindene- 4, 5-dicarboxylic acid. Also, the thermo-shrinkable polyester resin composition of the present invention includes the main component ethyleneglycol as the diol component, and the aliphatic diol represented by the Formula 1 as the copolymerization component, but other diol components may be copolymerized without departing from the objects of the present invention. For example, the diol component includes aliphatic diol such as diethyleneglycol, propyleneglycol, butanediol, hexanediol; or cycloaliphatic or aromatic diol such as 1, 4-cyclohexanemethanol, xyleneglycol, etc.

If necessary, lubricants such as titanium dioxide, silica particle, Kaolin, calcium carbonate, etc. may be also suitably added, and heat stabilizers, UV stabilizers, antioxidants, dyes, antistatic agents, fluorescent brighteners, antibacterial agents, etc. may be further added at a suitable amount.

The thermo-shrinkable polyester film may be also manufactured by using such a copolymerized polyester resin alone, or by mixing 3 to 30 % by weights of a polybutyleneterephthalate polymer or its copolymer with the copolymerized polyester resin. The thermo-shrinkable polyester film manufactured thus is swollen in a solvent such as tetrahydrofuran or 1, 3-dioxolane, etc. to give an adhesive property, which is especially useful when it is used for application of shrinkable labels.

If the polybutyleneterephthalate polymer or its copolymer included in combination with the copolymerized polyester resin has a content of less than 3 % by weights, then its solvent adhesion is poor, while the content of the polybutyleneterephthalate polymer or its copolymer exceeds 30 % by weights, then possibility of poor films may be increased upon drawing.

Meanwhile, the conventional thermo-shrinkable films may be generally manufactured by varying drawing . in a mechanical direction and a transverse direction of the film according to the desired purposes, and a main shrinkage direction is referred to as a direction where the film has a higher drawing. The thermo-shrinkable polyester film manufactured from the thermo-shrinkable polyester resin composition of the present invention satisfies at least 30 % of thermo-shrinkability in the main shrinkage direction when it is kept at a hot wind of 100 ^°C for 1 minute.

As such, there is not limitation to the method for manufacturing a thermo-shrinkable film, but a method is the most effective, wherein the composition is melted and closely attached to a casting drum via a T-die using an electrostatic cooling system, and an unelongated sheet is then obtained, and then the resultant unelongated sheet is drawn at least threefold in either a mechanical direction (MD) or a transverse direction (TD) and heat-set at the temperature of 100 ^°C or less.

[Best Mode] Hereinafter, the description proposed herein is just a preferable example for the purpose of illustrations only, not intended to limit the scope of the invention. <Example 1> A copolymerized polyester resin was polycondensated in the presence of 0.05 mole of the catalyst antimony trioxide

(based on the acid component) by the direct esterification method, using 100 mol% terephthalic acid (TPA) as a dibasic acid component, 90 mol% ethyleneglycol (EG) as a diol component, and 10 mol% aliphatic diol (aliphatic diol K) of the Formula 1 wherein m, n and o are all independently 1, and Ri to R₄ is independently methyl (CH₃) .

The resultant copolymerized polyester resin was melted at 300 ^°C, and then subject to an electrostatic cooling system to obtain an unelongated sheet. The sheet was drawn 1.4 times in a mechanical direction and 4.5 times in a transverse direction, and then heat-set at 75 ^°C to obtain a thermo-shrinkable polyester film having a thickness of 15 IM. <Example 2> A thermo-shrinkable polyester film having a thickness of 15.1 //ill was prepared in the same manner as in Example 1, using 100 mol% terephthalic acid (TPA) as a dibasic acid component, 85 mol% ethyleneglycol (EG) as a diol component, and 15 mol% aliphatic diol (aliphatic diol K) of the Formula 1 wherein m, n and o are all independently 1, and Ri to R₄ is independently methyl (CH₃) . <Example 3>

A thermo-shrinkable polyester film having a thickness of 15 [M was prepared in the same manner as in Example 1, using 100 mol% terephthalic acid (TPA) as a dibasic acid component, 80 mol% ethyleneglycol (EG) as a diol component, and 20 mol% aliphatic diol (aliphatic diol K) of the Formula 1 wherein m, n and o are all independently 1, and Ri to R₄ is independently methyl (CH₃) . <Example 4>

A copolymerized polyester resin was polycondensated in the presence of 0.05 mole of the catalyst antimony trioxide (based on the acid component) by the direct esterification method, using 100 mol% terephthalic acid (TPA) as a dibasic acid component, 90 mol% ethyleneglycol (EG) as a diol component, and 10 mol% aliphatic diol (aliphatic diol K) of the Formula 1 wherein m, n and o are all independently 1, and Ri to R₄ is independently methyl (CH₃) . 90 % by weight of the resultant copolymerized polyester resin was mixed with 10 % by weight of the polybutyleneterephthalate polymer (PBT) , and melted at 280 ^°C, and then subject to an electrostatic cooling system to obtain an unelongated sheet. The sheet was drawn 1.2 times in a mechanical direction at 90 ^°C and 4.5 times in a transverse direction, and then heat-set at 75 ^°C to obtain a thermo-shrinkable polyester film having a thickness of 15 [M. <Example 5> A copolymerized polyester resin was prepared in the same manner as in Example 4, using 100 mol% terephthalic acid (TPA) as a dibasic acid component, 85 mol% ethyleneglycol (EG) as a diol component, and 15 mol% aliphatic diol (aliphatic diol K) of the Formula 1 wherein m, n and o are all independently 1, and Ri to R₄ is independently methyl (CH₃) .

A thermo-shrinkable polyester film having a thickness of 15.1 [M was obtained in the same manner as in Example 4 by mixing 90 % by weight of the resultant copolymerized polyester resin with 10 % by weight of the polybutyleneterephthalate polymer (PBT) . <Example 6>

A copolymerized polyester resin was prepared in the same manner as in Example 4, using 100 mol% terephthalic acid (TPA) as a dibasic acid component, 80 mol% ethyleneglycol (EG) as a diol component, and 20 mol% aliphatic diol (aliphatic diol K) of the Formula 1 wherein m, n and o are all independently 1, and Ri to R₄ is independently methyl (CH₃) . A thermo-shrinkable polyester film having a thickness of 15 μm was obtained in the same manner as in Example 4 by mixing 90 % by weight of the resultant copolymerized polyester resin with 10 % by weight of the polybutyleneterephthalate polymer (PBT) . <Examples 7 to 9>

Unelongated sheets were obtained in the same manners as in said Examples 4 to 6, except that 70 % by weight of the copolymerized polyester resin was mixed with 30 % by weight of the polybutyleneterephthalate polymer (PBT) , and melted at 280 ^°C, and then subject to an electrostatic cooling system. The sheets were drawn 1.2 times in a mechanical direction at 90 ^°C and 4.5 times in a transverse direction, and then heat- set at 75 ^°C to obtain films having a thickness of 15 μm. <Exaiτιples 10 to 12>

Thermo-shrinkable polyester films having a thickness of 15 IM were obtained in the same manners as in said Examples 4 to 6, except that a polybutyleneterephthalate copolymer (copolymerized PBT) prepared from 70 mol% terephthalic acid, 30 mol% isophthalic acid and 100 mol% butanediol was used instead of the polybutyleneterephthalate polymer. <Examples 13 to 15> Thermo-shrinkable polyester films having a thickness of 15 jM were obtained in the same manners as in said Examples 7 to 9, except that a polybutyleneterephthalate copolymer (copolymerized PBT) prepared from 70 mol% terephthalic acid, 30 mol% isophthalic acid and 100 mol% butanediol was used instead of the polybutyleneterephthalate polymer, <Comparative example 1>

A thermo-shrinkable polyester film having a thickness of 15.2 IM was prepared in the same manner as in Example 1, using 100 mol% terephthalic acid (TPA) as a dibasic acid component and 100 mol% ethyleneglycol (EG) as a diol component .

Thermo-shrinkability and solvent adhesion were measured for the thermo-shrinkable polyester films prepared in the examples and the comparative example, as follows. The results are listed in Table 1.

(1) Measurement of Thermo-shrinkability in Transverse Direction (TD) TD Thermo-shrinkability (%) = (Primary length - Length after Modification ) /Primary length * 100

In the equation, the primary length was set to 20 cm, and the shrunk length was measured after it was put in at the hot wind of 100 ^°C for 1 minute and taken out. (2) Solvent adhesion

A 1,3-dioxolan solvent was spread on an 1 cm X 5 cm area of one film surface with a cotton swab, and attached to another film by pushing the other surface of the film with a hand. The film was kept at a room temperature for about 1 hour, and the solvent adhesion was relatively measured by pulling and detaching the attached film with hand, as follows .

[Table l]

As seen from the Table 1, it was revealed that the thermo-shrinkable polyester films of Examples manufactured from the copolymerized polyester resin further including an aliphatic diol component represented by the Formula 1 as a diol component had the excellent thermo-shrinkability due to the destruction of regularity in their molecular chains and the deteriorated dimensional stability, and also exhibited the excellent solvent adhesion in addition to the excellent thermo-shrinkability if they were manufactured by mixing the polybutyleneterephthalate polymer or its copolymer with such a copolymerized polyester resin.

[industrial Applicability]

As described above, the present invention may be useful to manufacture the polyester film having the excellent thermo-shrinkability in a main shrinkage direction and the excellent solvent adhesion by manufacturing a film using the copolymerized polyester resin manufactured from acid components, and diol components including a predetermined content of a compound having an aliphatic group (s), alone or in combination with the polybutyleneterephthalate polymer or its copolymer.

Claims

[CLAIMS]

[Claim l]

A thermo-shrinkable polyester film manufactured from a copolymerized polyester resin including acid components and diol components, wherein the diol components include a compound represented by the following Formula 1 :

Formula 1

wherein, m, n and o are independently an integer from 1 to 4; and

[Claim 2]

The thermo-shrinkable polyester film according to claim 1, wherein the diol component includes 3 to 30 mol% of the compound represented by the Formula 1 based on a total weight of the diol components.

[Claim 3] The thermo-shrinkable polyester film according to claim 1, further comprising a polybutyleneterephthalate polymer or copolymer.

[Claim 4]

The thermo-shrinkable polyester film according to claim 3, wherein the polybutyleneterephthalate polymer or copolymer is included in an amount of 3 to 30 % based on a total weight of the resin.

[Claim 5]

The thermo-shrinkable polyester film according to claim 1, wherein the thermo-shrinkable polyester film has at least 30 % of thermo-shrinkability in a main shrinkage direction when it is kept at a hot wind of 100 ^°C for 1 minute .