KR101176689B1 - Thermo-shrinkable polyester film - Google Patents

Abstract

The present invention relates to a heat-shrinkable polyester film, which is distributed in a roll state by providing a heat-shrinkable polyester film having a length change rate of 3.0% or less in the main shrinkage direction after being left at 50 ° C. ± 1 ° C. for 672 hours. By preventing deformation during storage, there is no substantial change in shrinkage rate, thereby improving product quality and stabilizing the appearance and shrinkage of the product.

Description

Heat-shrinkable polyester film {Thermo-shrinkable polyester film}

The present invention relates to a polyester film having heat shrink properties.

Heat-shrinkable film is used for coating, binding, or exterior of various containers such as bottles and cans and long lengths such as pipes and rods, and is used for various packaging materials or labels, and is mainly heat-shrinkable polyester It is a film.

Heat-shrinkable films are used for the purpose of shrinkage (integral) packaging, shrinkage labels, cap seals, etc. for various containers such as PET containers, polyethylene containers, glass containers, etc., by using properties that shrink by heating.

In order to manufacture a label or the like, the raw polymer is usually melt-extruded continuously to produce an unstretched film. Then, it stretches and obtains a heat shrinkable film roll. The film is unwound from this roll while slit to the desired width and rewound onto the roll. Subsequently, text information or drawings such as various product names are printed. After the end of printing, the tubes are manufactured by overlapping the left and right ends of the film with each other by means of solvent bonding or the like (tubing process). At this time, the slit process and the printing process may be reversed in order. The obtained tube is again wound onto a roll, and then unwound in a later step to cut the tube to an appropriate length, thereby forming a label. If one opening of the label is joined, a bag can be produced.

Put the label or bag obtained in this way on the container, and the inside of the shrink tunnel (steam tunnel) of the type which spouts steam and heat shrinks, or the shrink tunnel (hot wind tunnel) of the type which spouts hot air and heat shrinks, By passing through and heat shrinking a label, a bag, or the like, the final product, that is, a labeling container can be obtained by being in close contact with the container.

Since the heat-shrink film is manufactured into a film and then finalized through such a post-process, the shrinkage rate is reduced from the scheduled shrinkage rate at the time of filming when the film is stored for a long time to undergo the post-process or in consideration of export.

Such a change in shrinkage occurred during the process of producing a film and then going through a printing process or the like, as well as winding it up after tubing and using it in a container.

This change in shrinkage reduces the reliability of the product, and furthermore, the change in shrinkage that occurs after printing causes a serious problem of the total disposal of the product.

In this regard, great care must be taken in storing and distributing the film or tube on the roll. In case of long-term storage or export through a warm area, the transfer using a frozen container should be considered.

The present invention provides a heat-shrinkable polyester film that ensures the storage stability of the film.

In another aspect, the present invention provides a heat-shrinkable polyester-based film that can prevent the deterioration of the quality of the product from the production of the film to the printing process or the manufacturing process to the label or encapsulation.

In another aspect, the present invention provides a heat-shrinkable polyester film that can ensure a stable post-process does not cause a change in the appearance of the product.

The present invention also provides a heat-shrinkable polyester film that can reduce the cost in distribution and storage.

In another aspect, the present invention provides a heat-shrinkable polyester film that can ensure a stable shrinkage process.

According to one embodiment of the present invention, after leaving for 672 hours at 50 ℃ ± 1 ℃ conditions to provide a heat-shrinkable polyester film having a length change rate of 3.0% or less in the main shrinkage direction.

According to an exemplary embodiment of the present invention, the heat-shrinkable polyester film is terephthalic acid, oxalic acid, malonic acid, succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, naphthalenedicarboxylic acid And dicarboxylic acid components containing at least one dicarboxylic acid such as diphenyl ether dicarboxylic acid, ethylene glycol, neopentyl glycol, propylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, diethylene At least one copolyester selected from the copolyesters obtained from a diol component comprising at least one diol such as glycol, polyalkylene glycol, 1,4-cyclohexane dimethanol; Or a mixture of homopolyester and copolyester.

According to one embodiment of the invention, the copolyester may have a molecular weight distribution of 3.5 to 7.5.

According to one embodiment of the present invention, the homo polyester may have a molecular weight distribution of 1.8 to 4.0.

At this time, the homo polyester may be polybutylene terephthalate or polytriethylene terephthalate. In addition, polybutylene terephthalate may be included in 7 to 15% by weight of the total polyester resin.

According to an embodiment of the present invention, the film may have a molecular weight distribution of 2.0 to 4.0.

In another embodiment of the present invention, a method for producing a heat-shrinkable polyester film by extruding and stretching a polyester is as follows: Copolyester having a molecular weight distribution of 3.5 to 7.5 alone or with 7 to 15% by weight of homopolyester. Extruding the mixture at 200 to 350 ° C; And a drawing step, wherein the obtained heat-shrinkable polyester film has a length change rate in the main shrinkage direction of 3.0% or less after being left for 672 hours under a condition of 50 ° C ± 1 ° C. To provide.

According to the present invention can ensure the storage stability of the film, can prevent the degradation of the product quality from the manufactured heat-shrink film to the printing process or the manufacturing process to the label or encapsulation, and do not cause a change in the appearance of the product after stable The process can be guaranteed, thereby reducing costs in distribution and storage. In addition, the present invention can ensure a stable shrinking process.

Hereinafter, the present invention will be described in detail.

Shrink film achieves maximal uniaxial orientation through low temperature uniaxial stretching, and eliminates the residual stress relief through heat treatment, so that uniaxially oriented molecular chains retain their residual stress. The film is manufactured on the principle that shrinkage is made by force, and unlike a conventional polymer film, crystallization by orientation is not performed, and only molecular chain orientation occurs.

Due to this non-crystallization property, the shrink film has a strong tendency to be restored in the stretched state, and has sufficient probability of changing the original shrinkage rate by various factors.

This may result in a change in shrinkage rate, in particular, due to external temperature conditions, such that the heat-shrinkable polyester film according to one embodiment of the present invention is allowed to stand for 672 hours under 50 ° C. ± 1 ° C. in the main shrinkage direction. It is a heat shrinkable polyester film whose length change rate is 3.0% or less.

If the measured length change rate exceeds 3.0%, the stability against time change cannot be secured, and the shrinkage rate can be reduced from the shrinkage rate of the original film due to temperature change during storage and distribution.

This reduction in shrinkage can occur even with slitting to a predetermined specification for the manufacture of labels and also in the atmosphere after tubing. If the shrinkage rate is lower than the predetermined value, the label adheres to the container for the production of the labeling container and then passes through the steam tunnel or the hot-air tunnel under the same process, resulting in poor label adhesion to the container and consequently product failure.

However, in the case of the heat shrinkable polyester film having a length change rate of 3.0% or less in the main shrinkage direction after being left for 672 hours at 50 ° C. ± 1 ° C. as described above, there is almost no change in shrinkage even after long-term storage. It does not cause any inhibition at all.

The heat-shrinkable polyester film of the present invention that satisfies the above film properties is terephthalic acid, oxalic acid, malonic acid, succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, naphthalenedicarboxylic acid Dicarboxylic acid component containing at least one known dicarboxylic acid such as diphenyl ether dicarboxylic acid, ethylene glycol, neopentyl glycol, propylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene At least one copolyester selected from copolyesters obtained from a diol component comprising at least one known diol such as glycol, diethylene glycol, polyalkylene glycol, 1,4-cyclohexane dimethanol and the like; Or from mixtures with homopolyesters.

In this case, the copolyester may be a copolyester in which terephthalic acid units constitute 80 mol% or more of dicarboxylic acid units, and ethylene glycol units constitute 60 mol% or more of diol units, and have a molecular weight distribution of 3.5 to 7.5. It may be.

In this invention, the said copolyester itself can be manufactured by the manufacturing method of polyester generally performed. For example, the direct esterification method which reacts diol directly with dicarboxylic acid, the transesterification method which makes diol act on the dimethyl ester of dicarboxylic acid, etc. are mentioned.

According to an embodiment of the present invention, the glass transition temperature of the copolyester is 67 ~ 78 ℃, the intrinsic viscosity is 0.60 ~ 0.72 dl / g. At this time, the glass transition temperature may be adjusted according to the composition of the monomer used to prepare the polymer, the intrinsic viscosity may vary depending on the degree of polymerization, in the present invention, the glass transition temperature and intrinsic viscosity within the above range through such adjustment Copolyesters can be used.

On the other hand, in the case of a mixture of two or more kinds of polyesters, that is, polyester resins, at least 80 mol% of the total dicarboxylic acid units of the polyester resin mixture is terephthalic acid, and at least 60 mol% of the total diol units of the polyester mixture is Ethylene glycol units may be used, and in this case, it is advantageous to mix them so that the molecular weight distribution is 2.0 to 4.0 based on the film.

As an example, in the present invention, a polybutylene terephthalate resin is included as a homopolyester, and a film can be produced using a mixture of such polybutylene terephthalate resin and copolyester. At this time, the content of the polybutylene terephthalate resin may be 7 to 15% by weight of the total polyester resin. As the homopolyester, polytriethylene terephthalate may be used to replace or use polybutylene terephthalate. The molecular weight distribution of the homopolyester is preferably 1.8 to 4.0.

In general, when the shrinkage film is used in commercial use, the adhesive film is adopted by dissolving the shrink film in a solvent. If the content of polybutylene terephthalate is too low, the adhesive strength of the solvent may be low, and thus commercial use may be difficult. On the other hand, if the content is too high, the shrinkage in the width direction (main contraction direction) may be lowered, and the mechanical properties (strength) in the direction perpendicular to the main contraction direction (machine direction) may occur.

The molecular weight distribution of the polyester raw material to be used for extrusion may affect the rate of change of the length, so that the uniformity of the polymer chains prevents slippage between the polymer chains. The tendency to restore again under natural circumstances can be reduced. As a result, a heat-shrinkable polyester film that can cope with changes over time can be obtained. In general, when there are many short polymer chains, the ends are large, which causes slip between polymer chains. Such slip may promote the tendency of the film to shrink as a result, thereby lowering the shrinkage as compared to the shrinkage given at the time of initial film production.

Therefore, in the present invention, it may be advantageous to control the molecular weight distribution of the raw polyester to be as narrow as possible.

On the other hand, the molecular weight distribution of the final film, in particular, the molecular weight distribution of the film obtained from the copolyester and the homopolyester may be implemented to have a somewhat narrow molecular weight distribution compared to the results inferred from the molecular weight distribution of the raw chip state. Raw chips, especially copolyester chips with a broad molecular weight distribution, undergo a series of processes such as melting, extruding, stretching, and heat treatment, resulting in post-reaction of short chains that make up the copolyester, resulting in overall distribution of long chains. As a result, it appears that a narrow molecular weight distribution film can be obtained.

Therefore, in addition to the mixing ratio of copolyester and homopolyester, it is possible to control the molecular weight distribution of the final film to be 2.0 to 4.0 by controlling various factors during the manufacturing process, thereby ultimately reducing the heat shrinkable polyester film having a small length strain. Provision can be made possible.

In addition, in order to improve the slipperiness in the film production, lubricants such as silicon dioxide, titanium dioxide, silica powder, calcium carbonate may be added, and various additives such as antistatic agent, anti-aging agent, UV-protective agent, and dye may be added if necessary. It can also be added.

Polyester heat-shrink film of the present invention having the above characteristics can be produced by, for example, the manufacturing process as follows.

The material for producing a polyester film adjusted to have a molecular weight distribution of 2.0 to 4.0 is dried using a conventional dryer, and then extruded at 200 to 350 ° C. Any known method such as T-die extrusion or tubular extrusion may be used for the extrusion.

The extruded product is rapidly cooled, for example by a method such as electrostatic contact, to obtain an unstretched film.

Then, the unstretched film may be preheated, and during preheating, the unstretched film may be heat-treated at about 20 seconds or less at a glass transition temperature (Tg) + 30 ° C. or less.

Stretching is performed after preheating. In general, the drawing temperature is a glass transition temperature (Tg) to a glass transition temperature (Tg) + about 30 ° C. of the copolyester, and low temperature stretching may be performed near the glass transition temperature.

If the stretching temperature is too low, it may not be stretched to cause breakage or uneven stretching, and if the stretching temperature is too high, shrinkage may decrease, so the stretching temperature is "Tg-10 ° C" to "Tg + 30 of the copolyester used. Can be determined within the range "C".

In addition, if the draw ratio of the shrink film is small, the shrinkage may be reduced. On the other hand, if the draw ratio is too high, it is difficult to cause breakage or improvement of physical properties, and thus the draw ratio is about 3.0 relative to the original length. It can be selected within the range of fold to about 5.0 times.

As the stretching method, a conventional apparatus is used, and known methods such as roll stretching, tenter stretching, tubular stretching, and the like can be applied.

Hereinafter, examples of the present invention will be described in more detail, but the scope of the present invention is not limited to these examples.

The evaluation method used in the present invention is as follows.

(1) Molecular weight distribution of raw polyester

The number average molecular weight (Mn) and the weight average molecular weight (Mw) were measured by GPC (Gel Permeation Chromatography) analysis, and the molecular weight distribution (MWD; Molecular Weight Distribution) was obtained by the following formula (1).

For analysis of GPC (Waters GPC System, Pump Waters 515, Detector Waters 410 RI Detector), PMMA (Polymethylmethacrylate) was dissolved in 5 mg / mL in a solvent (HFIP + 0.01 N TFAcNa) as a standard sample. 100 μL into 803L + Shodex K-805L), the flow rate was 1.0mL / min under 35 ° C, and the molecular weight value according to the residence time was calculated using an EMPOWER, and a calibration curve was made. Obtain the molecular weight value of the polyester resin and the film according to the residence time under the same conditions to obtain the number average molecular weight (Mn) and weight average molecular weight (Mw) by using a data processor (EMPOWER), the molecular weight distribution according to the following formula 1 Was obtained.

 <Formula 1>

Molecular weight distribution (MWD) = weight average molecular weight (Mw) / number average molecular weight (Mn)

(2) heat shrinkage

 -Measurement of shrinkage rate in main shrinkage direction (TD; width direction) Sample preparation: Cut a sample 400 mm in length and 15 mm in width perpendicular to the main shrinkage direction as follows.

(MD × TD = 15mm × 400mm)

(MD × TD = 15mm × 400mm)

-Measurement of shrinkage in the direction perpendicular to the main shrinkage direction (MD; machine direction) Sample preparation: Cut a sample 15 mm wide and 400 mm long perpendicular to the main shrinkage as shown below.

(MD × TD = 400mm × 15mm)

(MD × TD = 400mm × 15mm)

-Sample length before shrink

As shown below, draw a line using a planetary pen perpendicular to the longitudinal direction at both ends of 50 mm in the longitudinal direction (the direction corresponding to 400 mm), and set the total length of the measured sample to be 300 mm.

-Shrinkage treatment

After heat shrinking for 10 seconds in a no-load state in an oil bath filled with ethylene glycol at 100 ° C. ± 0.5 ° C., the numerical value in the longitudinal direction of each sample was measured, and the main shrinkage direction (TD; The thermal contraction rate in the width direction) and the direction perpendicular to the main contraction direction (MD; machine direction).

<Formula 2>

On the other hand, the heat shrinkage rate after aging is shrinkage treatment in the same manner as described above for the film after the aging in the same manner as the aging process for measuring the length change rate below, after heat aging according to the following equation 3 Shrinkage was evaluated.

<Formula 3>

(3) length change rate

After the sample was prepared in the same manner as the heat shrinkage measurement sample, the sample was left unloaded in a hot air oven at 50 ° C. ± 1 ° C. and left for 672 hours (aging, aging), and then changed to a reference length (300 mm). Was measured and the length change rate was evaluated according to the following equation (4).

 <Equation 4>

&Lt; Example 1 >

Polycondensation was carried out by direct esterification using 100 mol% of terephthalic acid as a dibasic acid component, 93 mol% of ethylene glycol and 31 mol% of neopentyl glycol as glycol components, and 0.05 mol of antimony trioxide (relative to acid components) as a catalyst. Combined. The polymer thus obtained contained 500 ppm of silicon dioxide powder having an average particle diameter of 2.7 μm, and dried by a conventional method to prepare a copolyester having an intrinsic viscosity of 0.64 dl / g, a glass transition temperature of 68 ° C., and a molecular weight distribution of 7.15. .

On the other hand, 100 mol% of terephthalic acid and 100 mol% of 1,4-butanediol were used as the catalyst, and 0.015 parts by weight of tetrabutyl titanate was added, and the inherent viscosity was 0.97 dl / g, the glass transition temperature was 30 ° C, and the molecular weight distribution was 2.85. Butylene terephthalate resin was obtained.

90 wt% of the copolyester and 10 wt% of polybutylene terephthalate were blended and extruded from an extruder at 270 ° C., followed by rapid cooling and solidification to obtain an unstretched film.

The unstretched film was placed in a tenter, stretched at 4.0 times the width at 75 ° C., and then subjected to a heat treatment section at room temperature to prepare a film. The obtained film is a heat shrink film having a thickness of 50 µm, and the physical property values of the film are shown in Table 2.

<Example 2>

Polycondensation was carried out by direct esterification using 100 mol% of terephthalic acid as a dibasic acid component, 100 mol% of ethylene glycol and 24 mol% of neopentyl glycol as glycol components, and 0.05 mol of antimony trioxide (relative to acid components) as a catalyst. Combined. The polymer thus obtained contained 500 ppm of silicon dioxide powder having an average particle diameter of 2.7 μm, and dried by a conventional method to prepare a copolyester having an intrinsic viscosity of 0.64 dl / g, a glass transition temperature of 74 ° C., and a molecular weight distribution of 6.14. .

On the other hand, 100 mol% of terephthalic acid and 100 mol% of 1,4-butanediol were used as the catalyst, and 0.015 parts by weight of tetrabutyl titanate was added, and the inherent viscosity was 0.97 dl / g, the glass transition temperature was 30 ° C, and the molecular weight distribution was 2.85. Butylene terephthalate resin was obtained.

90 wt% of the copolyester and 10 wt% of polybutylene terephthalate were blended and extruded from an extruder at 275 ° C, followed by rapid cooling and solidification to obtain an unstretched film.

The unstretched film was placed in a tenter, stretched at 4.0 times the width at 75 ° C., and then subjected to a heat treatment section at room temperature to prepare a film. The obtained film is a heat shrink film having a thickness of 50 µm, and the physical property values of the film are shown in Table 2.

<Examples 3 to 5>

Blending the copolyester and polybutylene terephthalate in the same manner as in Example 1, but adjusted the molecular weight distribution by adjusting the intrinsic viscosity of the copolyester as shown in Table 1, and adjusted the molecular weight distribution of the film To adjust the extruder temperature.

Thereafter, a heat shrinkable film having a thickness of 50 μm was obtained by the same method as in Example 1, and the physical property values of the film are shown in Table 2.

division Copolyester Extruder temperature
(℃) Molecular weight distribution
(MWD) Intrinsic viscosity
(dl / g) Example 3 6.14 0.64 260 Example 4 5.52 0.70 275 Example 5 5.52 0.70 265

<Example 6>

Polycondensation was carried out by direct esterification using 100 mole% of terephthalic acid as the dibasic acid component, 104 mole% of ethylene glycol and 20 mole% of neopentyl glycol as the glycol component, and 0.05 mole of antimony trioxide (relative to the acid component) as a catalyst. Combined. The polymer thus obtained contained 500 ppm of silicon dioxide powder having an average particle diameter of 2.7 μm, and dried by a conventional method to prepare a copolyester having an intrinsic viscosity of 0.67 dl / g, a glass transition temperature of 77 ° C., and a molecular weight distribution of 4.15. .

On the other hand, 100 mol% of terephthalic acid and 100 mol% of 1,4-butanediol were used as the catalyst, and 0.015 parts by weight of tetrabutyl titanate was added, and the inherent viscosity was 0.97 dl / g, the glass transition temperature was 30 ° C, and the molecular weight distribution was 2.85. Butylene terephthalate resin was obtained.

90 wt% of the copolyester and 10 wt% of polybutylene terephthalate were blended and extruded from an extruder at 270 ° C., followed by rapid cooling and solidification to obtain an unstretched film.

The non-stretched film thus obtained was subjected to a post-process in the same manner as in Example 1 to prepare a heat-shrinkable polyester film.

The obtained film is a heat shrink film having a thickness of 50 μm, and the physical property values of the film are shown in Table 2 below.

&Lt; Comparative Example 1 &

A heat shrinkable film was prepared in the same manner as in Example 1, except that the molecular weight distribution of the raw material copolyester was adjusted to be 7.6.

Film
Molecular weight distribution
(MWD) Length change rate
(%, 50 ℃ × 672 hours left) Heat shrinkage
[%] Heat shrinkage after aging
(%, 50 ℃ × 672 hours left) MD TD MD TD MD TD Example 1 3.67 1.0 2.9 4.3 77.5 3.5 73.3 Example 2 2.97 0.7 2.6 4.1 74.0 3.5 72.0 Example 3 2.79 0.6 2.4 4.2 76.2 3.5 74.7 Example 4 2.65 0.6 2.5 4.2 74.3 3.6 73.0 Example 5 2.45 0.5 2.2 4.3 76.5 3.7 75.2 Example 6 2.35 0.4 1.9 3.8 72.5 3.4 71.8 Comparative Example 1 4.15 1.7 4.0 4.2 76.5 2.8 65.5

As shown in Table 2, after leaving at 50 ° C. for 672 hours, the film having a length change rate of 3.0% or less compared to before aging in the main shrinkage direction showed little change in shrinkage rate before or after aging. Can be.

Claims (8)

At least one dicarboxylic acid such as terephthalic acid, oxalic acid, malonic acid, succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyl ether dicarboxylic acid Dicarboxylic acid component to contain, such as ethylene glycol, neopentyl glycol, propylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, diethylene glycol, polyalkylene glycol, 1,4-cyclohexane dimethanol At least one copolyester selected from copolyesters obtained from a diol component comprising at least one diol; Or a mixture of homopolyester and copolyester, The copolyester has a molecular weight distribution of 3.5 to 7.5, The homo polyester has a molecular weight distribution of 1.8 to 4.0, The heat-shrinkable polyester film whose length change rate of a principal contraction direction is 3.0% or less after leaving for 672 hours in 50 degreeC +/- 1 degreeC conditions. delete delete delete The heat-shrinkable polyester film of claim 1, wherein the homo polyester is polybutylene terephthalate or polytriethylene terephthalate. The heat-shrinkable polyester film according to claim 5, wherein the polybutylene terephthalate comprises 7 to 15% by weight of the total polyester resin. The heat-shrinkable polyester film of claim 1, wherein the heat-shrinkable polyester film has a molecular weight distribution of 2.0 to 4.0. delete