BR102013029726A2 - METHOD FOR PRODUCING THERMOSOLABLE POLYESTER FILM - Google Patents

Abstract

SUMMARY "METHOD FOR PRODUCING THERMOSABLE POLYESTER FILM" A method for producing a heat shrinkable polyester film includes the following steps: (a) providing a polyester film having a glass transition temperature (Tg) ° C; (b) preheating the polyester film to a preheating temperature ranging from (Tg + 20) ° C to (Tg + 30) ° C; (c) profiling the preheated polyester film along a transverse direction that is perpendicular to a machine direction a profiling ratio ranging from 2.7 to 7.7; and (d) annealing the profiled polyester film at an annealing temperature ranging from (Tg-10) ° C to Tg ° C, followed by cooling at room temperature to obtain the heat shrinkable polyester film.

Description

“METHOD FOR PRODUCING THERMOSOLABLE POLYESTER FILM”

Cross Reference for Related Orders

This claim claims priority for Taiwanese Order No. 102103747, filed January 31, 2013.

Background of the invention

1. Field of the Invention

The invention relates to a method for producing a heat shrinkable film, more particularly to a method for producing a heat shrinkable polyester film.

2. Description of Related Art

Heat shrink films are widely used as packaging and labeling materials. Among these, heat-shrinkable polyester films, which have good mechanical properties and are odorless and non-toxic, are currently adopted to replace polyvinyl chloride films due to environmental protection issues. For example, heat shrinkable polyethylene terephthalate (PET) films may be adopted for packaging or labeling bottles that are made of PET as well, so that heat shrinkable PET films can be recycled together with PET bottles.

However, the shrinkage ratio of polyester films convinced

is less than 30%. For the highest shrinkage ratio modifiers such as isophthalic acid (I PA), Neopentyl glycol (NPG) and 1,4-cyclohexanedimethanol (CHDM) are generally used. Conventionally, the polyester films will be heated to a temperature above 100 ° C to perform the heat shrinkage process during packaging or labeling, but such a high temperature results in high energy consumption and increased production cost. US Patent No. 7000098 describes a modified polyester film which has a heat shrink ratio of 50% at 80 ° C for 10 seconds, but requires at least two design steps to achieve such a heat shrink ratio at a temperature lower than 100 ° C. Ç. European Patent No.1055506B1 describes a method for lowering the heat shrinkable temperature. The method includes a step of profiling the polyester film at a temperature ranging from (Tg-5) ° C to (Tg + 15) ° C with a profiling ratio ranging from

1.05 to 1.2 along a machine direction, and a step of profiling the polyester films twice along a transverse direction that is perpendicular to the machine direction. The heat shrinkable polyester film produced by this method has a heat shrink ratio ranging from 50% to 60% at 80 ° C, but has a heat shrink ratio greater than 20% at 70 ° C for 5 seconds and a heat shrink ratio greater than 35 % at 75 ° C for 5 seconds. Such high shrinkage ratio (s) at 70 ° C (and 75 ° C) may result in unwanted deformation of the heat shrinkable polyester film during cargo transport since the temperature while being transported in containers can reach 70 ° C.

Therefore, there is a need in the art for providing a heat shrinkable polyester film that not only has a relatively high heat shrink ratio that is greater than 60% at 800 ° C for 5 seconds, but also has a heat shrink ratio lower than 0.5 % at 70 ° C for 5 seconds to achieve good dimensional stability.

Summary of the invention

Therefore, the object of the present invention is to provide a method for producing a shrinkable polyester film which can alleviate the disadvantages mentioned above.

Accordingly, a method for producing a shrinkable polyester film of the present invention includes the following steps:

(a) providing a polyester film having a glass transition temperature (Tg) 0C;

(b) preheating the polyester film to a preheating temperature of (Tg + 20) ° C to (Tg + 30) ° C;

(c) profiling the preheated polyester film along a transverse direction that is perpendicular to a machine direction a profile of

ranging from 2.7 to 7.7; and

(d) annealing the profiled polyester film at an annealing temperature ranging from (Tg-10) 0C to Tg0C, followed by cooling at room temperature to obtain the heat shrinkable polyester film.

Detailed description of preferred embodiments

The preferred embodiment of a method of producing a shrinkable polyester film according to the present invention includes the following steps:

(a) providing a polyester film having a glass transition temperature (Tg) 0C;

(b) preheating the polyester film to a preheating temperature ranging from (Tg + 20) ° C to (Tg + 30) ° C;

(c) profiling the preheated polyester film along one direction

transverse that is perpendicular to a machine direction with a profiling ratio ranging from 2.7 to 7.7; and

(d) annealing the profiled polyester film at an annealing temperature ranging from (Tg-10) 0C to Tg0C, followed by cooling at room temperature to obtain the heat shrinkable polyester film.

In step (a), the polyester film may be prepared by generally known techniques, such as by fusing polyester or modified polyester through a single or double helix extruder at an operating temperature ranging from 2000 ° C to 300 ° C, followed by extrusion of the melt through a T-matrix. Preferably, the polyester film is made of a modified polyester, and the modified polyester is made by polymerizing a diol, a diacid and a crystallinity modifier. The modified polyester may be one described in US Patent Nos. 6939616 and 7829655 and Taiwanese Patent No. 1335922, preferably a modified polyethylene terephthalate (PET). Preferably, the diacid may be, but not limited to, terephthalic acid (TPA). The diol may preferably be, but not limited to, one of ethylene glycol (EG), propylene glycol (PG), and butylene glycol (BG), and more preferably ethylene glycol (EG). The crystallinity modifier is adopted to decrease the polyitality of the modified polyester, and is preferably selected from the group consisting of 2-methyl-1,3-propanediol (MPDO), ne30 opentyl glycol (NPG), isophthalic acid (IPA), 1 , 4-cyclohexanedimethanol (CHDM), and combinations thereof, more preferably neopentyl glycol (NPG). In this embodiment, the glass transition temperature of the modified polyester film preferably ranges from 70 ° C to 80 ° C, more preferably from 73 ° C to 79 ° C.

In this embodiment, preferably, the preheating temperature in step (b) ranges from 90 ° C to 110 ° C as determined from the glass transition temperature of the modified polyester film, more preferably from 930 ° C to 109 ° C, preferably from 990C to 1080C. It should be noted that the purpose of step (b) is to preheat the polyester film to soften the polyester film evenly. Profiling should not be performed in step (b), so the profiling ratio of the preheated polyester film is not greater than 1.05, and is more preferably 1. Preferably, the polyester film is preheated for 5 to 9 seconds, more preferably for 7 to 9 seconds.

In this embodiment, in step (c) the preheated polyester film is profiled at a temperature preferably ranging from 70 ° C to 90 ° C, more preferably from 80 ° C to 85 ° C. In step (c), the profile ratio of the preheated polyester film preferably ranges from 3.5 to 6.5, more preferably from

4.5 to 5.2. In this embodiment, the preheated polyester film may be periled for no more than 15 seconds, preferably from 1 to 12 seconds, more preferably from 5 to 11 seconds.

In this embodiment, the annealing temperature of the polyester film

Profiled in step (d) ranges from 60 ° C to 80 ° C as determined based on the preferred Tg range of the polyester film, preferably from 63 ° C to 79 ° C, more preferably from 70 ° C to 78 ° C. In this embodiment, the profile ratio of the annealed polyester film in step (d) is not greater than 1.05, and is more preferably 251 (i.e. completely undrawn in step (d)). Preferably, the profiled polyester film in step (d) is looped for no more than 10 seconds, more preferably from 1 to 8 seconds. In this embodiment, the ambient temperature in step (d) ranges from 200 ° C to 30 ° C.

Examples

[Synthesis Example 1 (SE 1): Modified Polyester

80 mol% TPA, 100 mol% EG and 20 mol% IPA were placed on a shaker and shaken to form a paste-like mixture, followed by adding 75 ppm heat stabilizer (phosphoric acid) to the similar mixture. folder. The slurry-like mixture was then placed in an esterification reactor and was stirred under heating to perform esterification reaction with a controlled reactor pressure of no more than 3 kg / cm 2. Water, as a reaction byproduct, was ground outside the esterification reactor by a grounding tube during the esterification reaction. An esterified product was obtained at a temperature of 250 ° C after 6 to 7 hours of esterification reaction. The esterification product was then placed in a condensation reactor together with 300 ppm antimony trioxide serving as a catalyst, followed by gradually raising the temperature to 285 ° C and simultaneously aspirating the condensation reactor by approximately 1 torr in two hours to perform the condensation reaction. The condensation reaction was carried out for 4 to 5 hours until the intrinsic viscosity of the product ranged from 15 0.6 to 0.9, followed by shaping, cooling, cutting the product to obtain the modified SE polyester. 1 in a granular form.

[Synthesis Examples 2 and 3 (SE2 and SE3): Modified Polyester

The method for preparing the modified polyester of each SE2 and SE3 according to the present invention is similar to that of SE1 except for

reagent compositions thereof. The reagent compositions of SE2 and SE3 are listed in Table 1.

[Physical Property Analysis]

1. Glass Transition Temperature (Tg):

The glass transition temperature of each Synthesis Example was measured by differential scanning calorimetry (MODEL: DSC 2910 modulated DSC, commercially available from TA Instruments Inc.). The results of SE1, SE2 and SE3 are recorded in Table 1.

2. Intrinsic Viscosity (IV):

1 gram of modified polyester from each of Synthesis Examples 1, 2 and 3 was dissolved in 100 grams of a phenol / tetrachloroethane solvent (50/50) to

A dilute solution is formed, followed by measuring the intrinsic viscosity of the solution using Ubbelohde Viscometer at 30 ° C. The results of SE 1, SE2, and SE3 are recorded in Table 1.

Table 1

Synthesis Example (SE) 1 2 3 TPA Diacid Reagent 80 100 100 Diol EG 100 82 70 IPA Modifier 20 - NPG - 18 15 MPDO - - 15 Physical Property IV (ml / g) 0.723 0.691 0.647 Tg (0C) 74.5 79 .0 73.0 [Example (EX) 1)]

The heat shrinkable polyester film of the EX1 according to the present

The invention was produced by a method including the following steps:

(a) melt and extrude the modified SE2 polyester through a single propeller extruder at an operating temperature above 2000 ° C and through a T die to form a polyester film;

(b) preheat the polyester film to 99 ° C for 7.2 seconds with

a profiling ratio of 1 (i.e. without profiling the polyester film) to obtain a preheated polyester film;

(c) profiling the preheated polyester film along the transverse direction (TD) which is perpendicular to the machine direction (MD) at 80 ° C with a

profiling of 4.7 for 10.8 seconds to obtain a profiled polyester film; and

(d) anneal the profiled polyester film at 76 ° C for 7.2 seconds at a profiling ratio of 1 (i.e. without profiling the profiled polyester film), followed by cooling to room temperature (about 25 ° C) to

obtain EX1 heat shrinkable polyester film.

[Examples (EXs) 2 to 51

The method for producing the heat shrinkable polyester film of each EX2 to EX5 is similar to that of EX1, except for the modified polyester adopted in step (a), the preheat temperature in step (b), and the temperature of

girdling in step (d). The process parameters of the method for producing each of EX2 to EX5 are recorded in Table 2. [Comparative Examples (CEs) 1 to 6]

The method for producing the heat shrinkable polyester film each of CE1 to CE6 is similar to that of Example 1, except for the preheat temperature in step (b) and the annealing temperature in step (d). The process parameters of the method for each of CE1 through CE6 are recorded in Table 2.

Method of Measuring Heat Shrink Relationship

The heat shrinkable polyester film of each of the Examples (EXs) and the Comparative Examples (CEs) was subjected to heat shrinkage ratio 10 according to Japanese Industry Standard JIS-Z1709. Multiple 10OmmxIOOmm square samples (along MD and TD) were taken from the heat shrinkable polyester film of each of the Examples and Comparative Examples and were subjected to a hot water bath separately at 60 ° C, 70 ° C, and 80 ° C for 5 seconds to measure its shrinkage ratio by applying the following formula (1):

Shrinkage Ratio (%) = [(Lo-L ^ / Ulx100% (I)

where L0 represents an original sample length and L1 represents a sample length after shrinkage. The heat shrinkable ratio of the heat shrinkable polyester film of each of the Examples and Comparative Examples is recorded in Table 2.

Table 2

Polyester Step (b) Step (c) Shrink Rate (%) Modified Preheating Ringing (5 seconds) SE Tg (0C) Temperature Temperature 60 0C 70 0C 80 0C (T1 ° C) [T1-Tgl (T2 ° C ) [T2-Tgl EX 1 2 79 99Γ + 201 76Γ-31 0 0.2 63.4 EX 2 2 79 108Γ + 291 78Γ-11 0 0 61.8 EX 3 2 79 100 [+21] 70 [-9 ] 0 0.4 69.5 EX 4 1 74.5 102Γ + 27.51 74 [-0.51 0 0.3 64.9 EX 5 3 73 99 [+26] 70 [-3] 0 0.1 67.5 EC 1 2 79 93Γ + 141 76 [-3l 0 0.8 64.8 EC 2 2 79 93Γ + 141 82Γ + 31 0 1.2 58.3 EC 3 2 79 99 [+201 82Γ + 31 0 2.4 57, 1 EC 4 2 79 94Γ + 151 85 [+ 61 0 1.0 55.6 EC 5 2 79 85Γ + 61 78 [-1l 0 1.8 63.2 EC 6 2 79 100 [+21] 65 [-14 ] 0 3.6 71.3 According to industrial demands, the shrinkage ratio is preferably 0% at 60 ° C, <0.5% at 700C and> 60% at 80 ° C. As shown in Table 2, the preheating temperature of each of CE1 and CE5 in step (b) is lower than (Tg + 20) ° C, and the shrinkage ratio of the heat shrinkable polyester film thereof at 70 ° C ° C is higher than

0.5% and does not meet dimensional stability requirements for cargo transportation.

As for CE2 and CE4, preheat temperatures are lower than (Tg + 20) ° C and annealing temperatures are higher than Tg ° C. Thus, not only is the shrinkage ratio of the heat shrinkable polyester film lower than 60% at 80 ° C for 5 seconds, but the shrinkage ratio of the heat shrinkable polyester film is also higher than 0, 5% at 700C for 5 seconds that do not meet dimensional stability requirements for cargo transport.

As for CE3, the preheat temperature is in the range between (Tg + 20) ° C and (Tg + 30) ° C, but the annealing temperature is higher than Tg0C which is not in the preferable temperature range. girdling according to the present invention. Thus, the shrinkage ratio of the heat shrinkable polyester film is lower than 60% at 80 ° C for 5 seconds.

As for CE6, the annealing temperature is lower than (Tg-10) ° C which is not in the preferable range according to the present invention thus the shrinkage ratio of the heat shrinkable polyester film is higher than 0 ° C, 5% at 70 ° C for 5 seconds and does not meet dimensional stability requirements for cargo transport.

In contrast, the shrinkage ratio of the heat shrinkable polyester film of each of the Examples (EXs) is less than 0.5% at 70 ° C for 5 seconds and is greater than 60% at 80 ° C for 5 seconds.

To summarize, by controlling the preheat temperature in the range from (Tg + 20) ° C to (Tg + 30) ° C and the annealing temperature in the range from (Tg-10) ° C to (Tg) 0C Accompanied with a single profiling step, the shrinkable polyester film produced by the method according to the present invention met the industrial demand to ensure the dimensional stability of the film while transporting in cargo containers, as well as effectively reducing the shrinkage temperature to 80 ° C.

While the present invention has been described with regard to what are considered the most practical and preferred embodiments, it is understood that this invention is not limited to the described embodiments but is intended to encompass various provisions within the spirit and scope of the broader interpretation to encompass all of the embodiments. such modifications and equivalent provisions.

Claims (15)

Method for producing a heat shrinkable polyester film, characterized by the following steps: (a) providing a polyester film having a glass transition temperature (Tg) ° C; (b) preheating the polyester film to a preheating temperature ranging from (Tg + 20) ° C to (Tg + 30) ° C; (c) profiling the preheated polyester film along a transverse direction that is perpendicular to a machine direction a profiling ratio ranging from 2.7 to 7.7; and (d) annealing the profiled polyester film at an annealing temperature ranging from (Tg-10) 0C to Tg ° C, followed by cooling at room temperature to obtain the heat shrinkable polyester film. A method as claimed in Claim 1, characterized in that, in step (a), the polyester film is made of a modified polyester, the modified polyester being made by polymerizing a diol, a diacid, and a crystallinity modifier. A method as claimed according to Claim 2, further characterized by the fact that the crystallinity modifier is selected from the group consisting of 2-methyl-1,3-propanediol, neopentyl glycol, isophthalic acid, 1,4-cyclohexanedimethanol. and combinations thereof. A method as claimed in claim 2, further characterized in that the diol is an ethylene glycol, propylene glycol and butylene glycol. A method as claimed in Claim 4, further characterized in that the diol is ethylene glycol. A method as claimed according to Claim 2, further characterized in that the diacid is terephthalic acid. Method as claimed according to Claim 1, characterized in that the glass transition temperature of polyester films ranges from 70 ° C to 80 ° C. A method as claimed in claim 1, characterized in that a profiling ratio of the preheated polyester film in step (b) is not greater than 1.05. A method as claimed in Claim 1, characterized in that in step (b) the polyester film is preheated for 5 to 9 seconds. A method as claimed in Claim 1, characterized in that in step (c) the preheated polyester film is profiled at a temperature ranging from 80 ° C to 85 ° C. A method as claimed in Claim 1, characterized in that, in step (c), the preheated polyester film is profiled for no more than 15 seconds. A method as claimed in claim 1, characterized in that in step (c) the profiling ratio of the preheated polyester films ranges from 4.5 to 5.2. A method as claimed in claim 1, characterized in that in step (d), a ring polyester film profiling ratio is not greater than 1.05. A method as claimed according to Claim 1, characterized in that in step (d) the profiled polyester film is looped for no more than 10 seconds. A method as claimed in Claim 14, further characterized in that in step (d) the profiled polyester film is looped for 1 to 8 seconds.