Search

JP-7855132-B1 - Polyester heat-shrinkable film and method for manufacturing polyester heat-shrinkable film

JP7855132B1JP 7855132 B1JP7855132 B1JP 7855132B1JP-7855132-B1

Abstract

[Problem] To provide a polyester heat-shrinkable film with excellent wrinkle resistance, even when applied to drug containers, dry cell batteries, tapes, etc. [Solution] In a polyester heat-shrinkable film, when the main shrinkage direction is the MD direction and the direction perpendicular to the main shrinkage direction is the TD direction, (a) the 2θ value of the XRD includes a crystal peak that shows the maximum value at a predetermined diffraction angle of the (-105) plane, and the full width at half maximum of the crystal peak is set to a value of 6° or less, the crystallite size measured by XRD is set to a value of 3.2 nm or less, the heat shrinkage rate A1 in the MD direction at 80°C for 30 seconds is set to a value in the range of 15 to 60%, and the refractive index in the TD direction is set to a value in the range of 1.55 to 1.60. [Selection Diagram] Figure 2

Inventors

  • 田中 昭裕
  • 金子 琢磨
  • 弓削 秀太
  • 宮本 大輔
  • ステファニー ベックラー
  • ジェフリー ホーキンス
  • クリス ウィザースプーン
  • ダグ アンダーソン

Assignees

  • タキロンシーアイ株式会社
  • ボンセット アメリカ コーポレーション

Dates

Publication Date
20260507
Application Date
20251205
Priority Date
20250918

Claims (8)

  1. A polyester heat-shrinkable film derived from a polyester resin, characterized in that when the main shrinkage direction is the MD direction and the direction perpendicular to the main shrinkage direction is the TD direction, the following configurations (a) to (c) are satisfied. (a) The 2θ value obtained by the X-ray diffraction measuring device includes a crystal peak (including crystalline domains; the same applies hereinafter) that shows the maximum value at the diffraction angle of the (-105) plane (in the range of 42° or more to less than 44°), and the full width at half maximum of the crystal peak is 6° or less. (b) The crystallite size of the (-10⁵) plane obtained by the X-ray diffraction analyzer shall be 3.2 nm or less. (c) When the thermal shrinkage rate is A1 when the material is heat-shrunk in the MD direction under shrinkage conditions of 80°C for 30 seconds, A1 shall be a value within the range of 15 to 60%.
  2. The polyester heat-shrinkable film according to claim 1, characterized in that it satisfies the following configuration (d). (d) The refractive index in the TD direction shall be within the range of 1.55 to 1.60.
  3. A polyester heat-shrinkable film according to claim 1 or 2, characterized in that it satisfies the following configuration (e). (e) When the thermal shrinkage rate is A2 when the material is heat-shrunk in the MD direction under shrinkage conditions of 70°C for 30 seconds, A2 shall be a value within the range of 1 to 35%.
  4. A polyester heat-shrinkable film according to claim 1 or 2, characterized in that it satisfies the following configuration (f). (f) When the thermal shrinkage rate is A3 when heat shrinkage is performed in the MD direction under shrinkage conditions of 100°C for 30 seconds, the value of A3 shall be within the range of 25 to 80%.
  5. A polyester heat-shrinkable film according to claim 1 or 2, characterized in that it satisfies the following configuration (g). (g) The haze value measured in accordance with JIS K 7136:2000 shall be 10% or less.
  6. A polyester heat-shrinkable film according to claim 1 or 2, characterized in that it satisfies the following configuration (h). (h) The polyester heat shrinkable film according to claim 1 or 2, characterized in that the neck-in ratio measured under the condition of being in 70°C hot water for 10 seconds is 4% or less.
  7. A polyester-based heat-shrinkable film according to claim 1 or 2, characterized in that its thickness is within the range of 10 to 100 μm.
  8. A method for producing a polyester heat-shrinkable film derived from a polyester resin, characterized in that, when the main shrinkage direction is the MD direction and the direction perpendicular to the main shrinkage direction is the TD direction, the method comprises at least the following steps (1) to (2). Step (1): A step to prepare a dicarboxylic acid compound and a diol compound as reaction components and react them to produce a polyester resin. Step (2): A step of stretching a polyester resin mainly along the MD direction to obtain a polyester heat-shrinkable film having the following configurations (a) to (c). (a) The 2θ value obtained by the X-ray diffraction measuring device includes a crystal peak that shows the maximum value at the diffraction angle of the (-105) plane (in the range of 42° or more to less than 44°), and the full width at half maximum of the crystal peak is 6° or less. (b) The crystallite size of the (-10⁵) plane obtained by the X-ray diffraction analyzer shall be 3.2 nm or less. (c) When shrinkage is performed under shrinkage conditions of 80°C for 30 seconds, the thermal shrinkage rate is A1, and A1 is set to a value within the range of 15 to 60%.

Description

The present invention relates to a polyester-based heat-shrinkable film and a method for producing a polyester-based heat-shrinkable film, with the MD direction being the primary shrinkage direction. More specifically, this invention relates to a polyester heat-shrinkable film (hereinafter sometimes simply referred to as a heat-shrinkable film) whose main shrinkage direction is the median-dimension (MD) direction, which is subjected to so-called longitudinal stretching to accommodate various containers, and whose crystal peak full width at half maximum (FWHM) is controlled using an X-ray diffraction measuring device (hereinafter sometimes referred to as XRD), allowing for accurate and quantitative thermal shrinkage, and to an efficient method for manufacturing the same. Traditionally, heat-shrinkable films have been widely used not only for PET bottles but also as base films for labels on dry cell batteries and tapes, and are composed of various materials, including polyester resins. These heat-shrinkable films are heat-shrinked by passing them through a tunnel that generates hot air or steam, and then attached to containers. However, uneven shrinkage can occur during the heat-shrinking process, which may result in wrinkles or color inconsistencies. Therefore, various heat-shrinkable films have been proposed to prevent wrinkles and color inconsistencies caused by uneven shrinkage during heat shrinkage. For example, a polyester heat-shrinkable film has been proposed that has a high heat shrinkage rate in the TD direction (width direction), a low heat shrinkage rate in the MD direction (longitudinal direction), high mechanical strength in the longitudinal direction, good perforation opening properties, and excellent shrinkage finish (see Patent Document 1). More specifically, the material is composed of a polyester resin, wherein the proportion of acid components other than terephthalic acid in the total acid components (A mol%) and the proportion of alcohol components other than ethylene glycol in the total alcohol components (B mol%) are in the range of 5 mol% ≤ A + B ≤ 40 mol%. Furthermore, the polyester-based heat-shrinkable film is characterized by containing 1 to 30 mol% of naphthalenedicarboxylic acid and 0.3 to 3 mol% of an alkali metal salt of sulfobenzenedicarboxylic acid in the total acid components. Furthermore, a polyester heat-shrinkable film has been proposed that strictly controls the amount of amorphous components in the total polyester resin components, and limits the hot water shrinkage rate at 80°C and 90°C in the longitudinal direction of the film, as well as the hot water shrinkage rate at 90°C in the width direction of the film (see Patent Document 2). More specifically, it has ethylene terephthalate as its main component and contains one or more monomer components that can be amorphous components in the total polyester resin components, with the total amount of these monomer components being 15 mol% or more. Furthermore, the polyester heat shrinkable film is characterized by a hot water shrinkage rate of 30% or more in the longitudinal direction (MD direction) at a processing temperature of 80°C and a processing time of 10 seconds, and 40% or more at a processing temperature of 90°C and a processing time of 10 seconds, while the hot water shrinkage rate in the width direction (TD direction) is 10% or less at 90°C and a processing time of 10 seconds. Furthermore, a heat-shrinkable polyester film has been proposed that is less prone to insufficient shrinkage and primarily shrinks in the longitudinal direction (MD direction) of the film (see Patent Document 3). More specifically, the heat-shrinkable polyester film is derived from amorphous polyester resin and does not exhibit a peak in the endothermic curve during film melting point measurement using differential scanning calorimetry (DSC), and is formed by first stretching the film by more than twice its width in the film width direction, and then stretching it by more than twice its length in the film longitudinal direction during the film manufacturing stretching process. Japanese Patent Publication No. 08-027259 (Claims, etc.)Japanese Patent Publication No. 2007-016120 (Claims, etc.)Japanese Patent Publication No. 2015-34061 (Claims, etc.) Figures 1(a) to 1(c) are diagrams illustrating the morphology of polyester heat-shrinkable films.Figure 2 illustrates the relationship between the full width at half maximum (°) and the crystallite size (nm) obtained from XRD measurements of a polyester heat-shrinkable film.Figure 3 is provided to illustrate the relationship between the full width at half maximum (°) and the refractive index (-) obtained from XRD measurements of a polyester heat-shrinkable film.Figures 4(a) to 4(c) are provided to illustrate the relationship between the full width at half maximum (°) obtained from XRD measurements of polyester heat-shrinkable films and the heat shrinkage rates A1 (%) at 80°C and 30 seconds, A2 (%) a