WO2006087795A1

WO2006087795A1 - Easy-to-tear polyester resin film

Info

Publication number: WO2006087795A1
Application number: PCT/JP2005/002544
Authority: WO
Inventors: Kazumoto Imai; Naonobu Oda
Original assignee: Toyo Boseki Kabushiki Kaisha
Priority date: 2005-02-18
Filing date: 2005-02-18
Publication date: 2006-08-24

Abstract

[PROBLEMS] To inexpensively provide a stretched polyester film which has satisfactory tearableness without losing strength, transparency, heat resistance, barrier properties, etc. and is useful as a packaging film or a film for tape use or as an opening material in a PTP package or beverage pack. [MEANS FOR SOLVING PROBLEMS] The easy-to-tear polyester resin film comprises two or more superposed polyester resin layers differing in melting point, and is characterized by having a piercing strength of 8.0 N or lower.

Description

Specification

Bow I Polyester resin film with good tearability

Technical field

[0001] The present invention relates to a stretched polyester film. More specifically, as a packaging film or tape film that maintains practical properties without losing transparency, heat resistance, barrier properties, etc. and has good tearability, or for PTP packaging and beverages The present invention relates to a stretched polyester film useful as an opening for a pack.

Background art

Conventionally, cellophane has been known as a film having excellent cutting properties! Cellophane is widely used for various packaging materials and adhesive tapes due to its excellent transparency, easy cutting property, twist fixing property and the like. On the other hand, however, cellophane has a hygroscopic property, and its characteristics fluctuate depending on the season, storage condition, or atmosphere during processing, and it was difficult to always supply a product of a certain quality.

[0003] In addition, packaging bags and adhesive tapes using polyethylene terephthalate as a base film are used because of the excellent properties of stretched polyethylene terephthalate film such as toughness, heat resistance, water resistance, and transparency. Although it has these excellent characteristics, it has the disadvantage that it is difficult to tear the opening of a packaging bag that is difficult to cut and the adhesive tape is difficult to cut.

[0004] As a method for solving the above-mentioned problem, a polyester film oriented in a uniaxial direction is copolymerized with a diethylene glycol component, a low molecular weight polyester resin, or a polyester resin layer (A ) On at least one surface of the polyester resin layer (B) having a melting point higher by 10 ° C or more than the melting point of the polyester resin layer (A) and a thickness of 5% or more and 60% or less of the total thickness. The laminated unstretched laminated film is heat-treated at least at a temperature lower than the melting point of the polyester resin layer (A) by at least 10 ° C. after the axial extension and at a temperature lower than the melting point of the polyester resin layer (B). A method for producing a polyester film having good tearability and twistability has been proposed. (See Patent Document 1-14) Patent Document 1: Japanese Patent Publication No. 55-8551

Patent Document 2: Japanese Patent Publication No. 56-50692

Patent Document 3: Japanese Patent Publication No. 55-20514

Patent Document 4: JP-A-5-104618

[0005] However, the method of stretching in the uniaxial direction in the above-described prior art is a method of easily cutting linearly in the alignment direction but difficult to cut in directions other than the alignment direction, and copolymerizing a large amount of diethylene glycol components and the like. Has the disadvantage that the inherent properties of polyethylene terephthalate are lost by copolymerization. In addition, the method using low molecular weight polyester resin has been practically powerful because it easily causes troubles of film breakage in the stretching process.

[0006] Further, at least one surface of the polyester resin layer (A) has a melting point higher by 10 ° C or more than the melting point of the polyester resin layer (A), and 5% or more and 60% or less of the total thickness. The polyester resin layer (B) is 10 ° C. lower than the melting point of the polyester resin layer (A) at least after the unstretched laminated film having the polyester resin layer (B) having a thickness of at least uniaxially stretched. When the heat treatment is performed at a temperature lower than the melting point of the polyester, the polyester resin layer (A) is brittle due to the progress of crystallization over time, and the film characteristics may change immediately after film formation and during processing. In this case, there was a failure in that the tension fluctuation during processing was broken when changing.

Brief Description of Drawings

[0007] [Fig. 1] Jig strength measuring jig and measuring method of the present invention

Disclosure of the invention

Problems to be solved by the invention

[0008] The present invention has been made against the background of the problems of the prior art, and has excellent properties of a polyester film, such as heat resistance, cold resistance, moisture resistance, transparency, fragrance retention, and easy-to-cut properties. However, there is a problem that tension fluctuation during processing is difficult to break when changing.

Means for solving the problem

[0009] As a result of intensive studies to solve the above problems, the present inventors have finally completed the present invention. That is, the present invention is a polyester film in which two or more types of polyester resin layers having different melting points are laminated, and the piercing strength is 8. ON or less and the previous A polyester-based resin film with good bow I tearability, characterized in that the tensile elongation at break in the longitudinal direction of the film is 50% or more.

In this case, a polyester resin layer having a melting point higher by 10 ° C. or more than the melting point of the polyester resin layer is laminated on at least one surface of the polyester resin layer, and at least uniaxial It is preferable to be stretched.

[0011] By this, there is an effect that the change in tension at the time of processing becomes an obstacle to breaking at the time of replacement.

The invention's effect

[0012] The polyester-based resin film according to the present invention can produce a film having excellent heat resistance, cold resistance, moisture resistance, transparency, fragrance retention, etc. and having stable and easy-cutting properties at low cost. Has the advantage.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail.

[0014] The polyester resin film in the present invention is a polyester film composed of two or more polyester resin layers having different melting points, and the polyester resin layer used in each layer is crystalline. It is selected from polyester resin or amorphous polyester resin.

[0015] For example, as the polyester resin having a higher melting point, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, or a copolymer containing these constituents as main components can be used. Is a polyester comprising terephthalic acid as the main acid component and ethylene glycol as the main alcohol component, and more preferably a polyester comprising 95 mol% or more of terephthalic acid and 95 mol% or more of ethylene glycol.

The intrinsic viscosity of the above-mentioned polyethylene terephthalate! /, A copolymer mainly composed of these components, is preferably 0.55-1.3 dlZg, more preferably 0.6 0-0. 74 dlZg, particularly preferably 0.60-0.65 dlZg.

[0016] In addition, the polyester resin having a lower melting point includes terephthalic acid isophthalic acid-ethylene glycol copolymer, terephthalic acid ethylene glycol-neopentylglycol. Polyesters containing terephthalic acid and ethylene glycol as the main components, such as a copper copolymer, and other acid components and Z or other darlicol components as copolymerization components are preferred. Other acid components include aliphatic dibasic acids (eg, adipic acid, sebacic acid, azelaic acid) and aromatic dibasic acids (eg, isophthalic acid, diphenyldicarboxylic acid, 5-tert-butyl). Isophthalic acid, 2, 2, 6, 6-tetramethylbiphenyl 4,4-dicarboxylic acid, 2,6 naphthalenedicarboxylic acid, 1, 1,3-trimethyl-3-phenolindene 4,5-dicarboxylic acid) Used. Examples of the glycol component include aliphatic diols (for example, neopentinoglycolanol, diethylene glycol, propylene glycol, butanediol, hexanediol), alicyclic diols (for example, 1,4-cyclohexanedimethanol) or aromatics. Diols (for example, xylylene glycol, bis (4-j8-hydroxyphenyl) sulfone, 2,2- (4-hydroxyphenol) propane derivatives) are used.

The intrinsic viscosity of the copolyester is preferably 0.70-080 dlZg.

[0017] It is preferable that two or more types of polyester resin layers having different melting points selected from these are laminated.

[0018] Furthermore, the layer structure of the film of the present invention is the best in the laminated structure of a layer having a high melting point and a layer having a low melting point due to film forming properties such as fusion and adhesion in the film stretching step. It is preferable that both outer layers have a high melting point.

[0019] The polyester resin layer of the present invention preferably has a difference in melting point of 10 ° C or more between the layer having the highest melting point and the layer having the lowest melting point, more preferably 20 °. C or higher.

[0020] When the difference between the melting points is less than 10 ° C, in order to disrupt the orientation of the low-melting polyester resin layer in the film-forming process, when exposed to a temperature higher than the melting point of the resin layer. The high melting point polyester resin layer becomes soft or melts and the film formation becomes unstable.

[0021] Further, since the heat setting temperature is limited to the melting point or less of the polyester resin layer having a high melting point, if the polyester resin layer has a low melting point, sufficient heat setting cannot be performed, and the heat shrinkage rate is reduced. Is unfavorable because it increases. Therefore, polyethylene terephthalate or polyethylene naphthalate is preferred for the high melting point polyester resin layer!

[0022] In the present invention, the puncture strength is preferably 8. ON or less, more preferably 6.0. N or less, more preferably 5. ON or less. If the piercing strength exceeds 8. ON, the strength of the film will increase and it will not be possible to tear it by hand.

[0023] In the present invention, the breaking elongation in the longitudinal direction is preferably 20% or more, more preferably 50% or more. If the elongation at break is less than 20%, there is a risk of breaking due to a change in tension during processing, making stable processing difficult.

In the present invention, it is preferable to add an elastomer component to the layer on the low melting point side so that the elongation at break in the longitudinal direction is 50% or more. In this case, as the elastomer component, Polyolefins such as polypropylene and polyethylene that have a glass transition temperature of 20 ° C or less, polyesters that are copolymerized with polytetramethylene glycol, and the like, are copolymers of polybutylene terephthalate and polytetramethylene glycol. Is preferred. It is preferable that the elastomer component is contained in the lower melting point layer at 1 to 5% by weight, and preferably 1 to 3% by weight!

In the present invention, the stretched film has a thickness of 9 μm force or 40 μm, but is not particularly limited.

[0026] The polyester film of the present invention may be added with various known additives such as a lubricant, a pigment, an antioxidant, an antistatic agent and the like within a range not inhibiting the effects of the present invention. .

[0027] Next, an example of a method for producing the film of the present invention will be described.

[0028] The resin used for the polyester resin layer (A) on the side having the high and melting point and the polyester resin layer (B) having the low and melting point were prepared, respectively, and each was supplied to another two extruders. Supply, melt and extrude at temperatures above their melting points, pass through the composite adapter, and extrude from the die as a 2 type 3 layer (AZBZA), solidify by cooling, and form an unstretched laminated film.

[0029] As used herein, the unstretched laminated film includes a method of forming an unstretched film by extrusion from a die outlet in a state of being laminated by a coextrusion method. As another method, there is a method of laminating unstretched films which are melted separately at a temperature equal to or higher than the melting point in a plurality of extruders and formed by extruding a die outlet force in a heated state.

[0030] The unstretched laminated film thus obtained is subjected to -axial stretching at a temperature not lower than the glass transition temperature of the polyester resin layer (A) and not higher than the melting point of the polyester resin layer (B). At this time The draw ratio is 2 to 30 times, preferably 9 to 16 times in terms of stretch area. The stretching method may be sequential biaxial stretching or simultaneous biaxial stretching.

[0031] The laminated film thus obtained is heat-set at a temperature not lower than 5 ° C of the polyester resin layer (B) and lower than the melting point of the polyester resin layer (A).

[0032] In the present invention, the presence of the layer in which the molecular orientation has disappeared and the layer in which the molecular orientation has been maintained make it possible to achieve both the strength of the film and the easy-cut property, and the state of the layer configuration and heat setting. It is possible to control hand cutting by controlling.

[0033] In the present invention, when the puncture strength is 8. ON or less, a film having excellent production processability and excellent tearability can be obtained.

Example

Next, the present invention will be specifically described with reference to examples and comparative examples. The evaluation methods in Examples and Comparative Examples were carried out by the methods (a) and (b).

[0035] (A) Puncture strength

Cut out a specimen with a length of 200 mm and a width of 20 mm. Using a tensile tester (manufactured by Shimadzu Corporation, Autograph AGC-1KNG type), fold the sample in half so that the length from the chuck is 50 mm. Pull at a speed of 50mmZmin so that a steel ball with a diameter of 0.7mm will pierce the folded part, and determine the load when the hole is pierced. Measurements were made with an average of 3 points, n = 5 lines, excluding the highest and lowest values!

[0036] (b) Hand cutting

Performed by sensory test, the polyester film ZZ9 μm aluminum foil Z15 m extruded Laminate by laminating with LDPE, then bag-making with heat seal, and unsealing when the seal part is cut by hand It was evaluated with. In addition, when holding the bag with both hands, there was an interval of about 3 mm, and it was performed both in the longitudinal direction and in the width direction.

○: Can be opened easily without raising nails

Δ: Can be easily opened by raising nails

X: Cannot be opened easily even if the nails are raised

[0037] (c) Longitudinal tensile elongation at break

JIS K 7127 “Plastic film and sheet after standing in a 50 ° C atmosphere for 3 days Measured according to “Tensile test method”.

[0038] (Example 1)

Terephthalic acid isophthalic acid-ethylene glycol mosquitoゝRanaru, melting point 221 ° C, the polyester榭脂98 weight ^_0/0 of intrinsic viscosity 0. 64DlZg, also terephthalic acid ethylene glycol polytetramethylene glycol force, melting point 170 ° C A layer (B) consisting of an elastomer with an intrinsic viscosity of 0.76 dlZg, 1% by weight, and an ethylene glycol terephthalate, melting point 265. C. Polyester resin (A) with an intrinsic viscosity of 0.62 dlZg was melted by a separate extruder at a temperature of 285 ° C. The melt was joined by a composite adapter, then extruded from a T die, and cooled by a cooling drum. Quenched to obtain a three-layer unstretched laminated film (AZBZA)

[0039] The unstretched laminated film was first stretched 3.8 times in the longitudinal direction at 95 ° C, then 4.0 times in the transverse direction at 110 ° C, and then relaxed by 3% and then at 220 ° C. The film was heat-treated at a temperature to obtain a 16 μm film having a total thickness of layer A of 3.0 μm. The obtained film had a puncture strength of 4.5 N, and was excellent in hand cutting. Table 1 shows the characteristics.

[0040] (Example 2)

A film having a thickness of 16 μm was obtained by changing the total thickness of the layer A to 8 μm using the same raw materials and method as in Example 1. The film obtained had a pin puncture strength of 7.2 N and excellent hand cutting properties. Table 1 shows the characteristics.

[0041] (Comparative Example 1)

Using the same raw materials and method as in Example 1, a 16 μm film was obtained in which only the thickness of layer A was changed to 12 μm. The puncture strength of the film obtained by force was 8.5 N, which was inferior to hand cutting.

[0042] (Comparative Example 2)

The total thickness of the layer A was 8 μm in the same manner as in Example 1 except that the polyester resins (A) and (B) of Example 1 had the intrinsic viscosities of 0.74 and 0.76 dl / g, respectively. A 16 μm film was obtained. The puncture strength of the film obtained by caulking was 9.5 N, which was inferior to hand cutting.

[0043] (Comparative Example 3) The same as in Example 1, except that the polyester resin layer (A) and (B) was a polyester resin having an ethylene glycol terephthalate melting point of 265 ° C and an intrinsic viscosity of 0.62 dlZg. A 16 m film was obtained. The film obtained by strengthening had a puncture strength of 10.5 N and was inferior to hand cutting.

[0044] (Comparative Example 4)

16 μm in the same manner as in Example 1 except that the polyester resin layer (B) was made of terephthalic acid, isophthalic acid-ethylene glycol, having a melting point of 221 ° C and an intrinsic viscosity of 0.664 dlZg. m films were obtained. The obtained film had a significantly reduced breaking strength after being left in an atmosphere of 50 ° C.

[0045] Table 1 shows the evaluation results of the films obtained in Example 12 and Comparative Example 14.

[0046] [Table 1]

[0047] As is clear from Example 1 2 and Comparative Example 1 3, the piercing strength is 8. ON or less, comprising a polyester film in which two or more polyester resin layers having different melting points are laminated. It can be seen that a certain polyester-based resin film has excellent hand cutting properties.

Industrial applicability

[0048] The polyester-based resin film of the present invention has excellent hand cutting properties, and can be used in a wide range of fields as a packaging film or tape film, or as an opening for PTP packaging or beverage packs. Can contribute to the industry.

Claims

The scope of the claims

[1] A polyester film in which at least two types of polyester resin layers having different melting points are laminated, the piercing strength is 8. ON or less, and the tensile breaking elongation in the longitudinal direction of the film is Polyester-based resin film having good tearability, characterized by being 50% or more.

[2] A polyester-based resin film having good tearability according to claim 1, wherein at least one surface of the polyester resin layer has a melting point higher by 10 ° C or more than the melting point of the polyester resin layer. A polyester-based resin film having good bow I cracking characteristics, wherein the polyester resin-coated layer is laminated and is stretched at least uniaxially.