KR20090053702A - Thermo-shrinkable polyester film - Google Patents

Abstract

The present invention relates to a heat-shrinkable polyester film, a heat shrinkable polyester film having a shrinkage speed of 0.5 to 3.5% / ℃ defined by the ratio of the strain according to the temperature change in the transverse direction (TD) By providing a, to ensure the uniformity of the shrinkage in the shrinkage process is excellent in appearance quality, there is no occurrence of print distortion, and at the same time there is an effect that can reduce the production cost in the shrinkage process and improve the productivity.

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.

In a shrinking process such as a steam tunnel or a hot wind tunnel, steam or hot air is injected from the entrance of the tunnel to the end of the tunnel, but both ends and the center of the tunnel are hardly considered uniform in temperature. Due to this temperature change, the degree of shrinkage of the label, etc. slightly varies.

This difference in shrinkage, that is, non-uniformity of shrinkage, may cause a deterioration of the appearance of the label, and if the degree is severe, print distortion may occur.

In addition, as shrinkage nonuniformity occurs, the shrinkage process is delayed, which inevitably leads to a decrease in productivity.

The present invention provides a heat-shrinkable polyester film having an improved strain rate according to temperature change in the transverse direction (TD).

In addition, the present invention is a heat-shrinkable polyester system that can be evenly contracted in a certain temperature range is improved in the main shrinkage (transverse direction (TD)) is the shrinkage rate according to the temperature change and the maximum shrinkage temperature is low Provide a film.

In one embodiment of the present invention provides a heat-shrinkable polyester film having a shrinkage speed of 0.5 to 3.5% / ℃ in the transverse direction (TD) determined by the following equation (1).

Equation 1

Shrinkage Speed = ΔL / ΔT

The above equation is derived by a method of detecting a dimension change due to expansion and contraction of a sample according to temperature change by a linear variable differential transformer (LVDT), and ΔT is a temperature change value, ΔL is a strain rate in the transverse direction (TD) and is a value measured in a temperature change section of 70 to 85 ° C.

According to the embodiment of the present invention, the heat-shrinkable polyester film may have a shrinkage strain rate of 3.5 to 8.5 in a transverse direction (TD) determined by Equation 2 below.

Equation 2

Shrinkage Rate = dL / dT

The above equation is a derivative of the value according to Equation 1 derived by a method of detecting a change in size due to expansion and contraction of a sample according to temperature change by a linear variable differential transformer (LVDT). It is derived from, and it is a value obtained by differentiating the strain in the transverse direction (TD) according to the temperature measured in the temperature change section 30 to 90 ℃, the maximum shrinkage strain value of the measured temperature section is obtained.

At this time, the temperature section at the time when the shrinkage strain rate indicates the maximum value may be 80 to 88 ℃.

According to the embodiment of the present invention, the heat shrinkable polyester film may have a heat shrinkage of 60% or more.

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

In this case, the copolyester may include 80 mol% or more of terephthalic acid units in the dicarboxylic acid units, and 14 to 24 mol% of units other than ethylene glycol in the diol units.

In this case, the homo polyester may be polybutylene terephthalate or polytriethylene terephthalate.

In addition, polybutylene terephthalate may be to include 7 to 15% by weight of the total resin.

According to an embodiment of the present invention, the heat-shrinkable polyester film of the present invention includes a process of extruding a polyester, preheating, stretching in the width direction, and then performing heat treatment, but setting the heat treatment section temperature to be lower than the preheat section temperature. It may be prepared by the manufacturing method.

At this time, the preheating section temperature is 80 to 100 ℃, the heat treatment section temperature may be a room temperature to 95 ℃.

According to a preferred embodiment of the present invention, the heat-shrinkable polyester-based film further includes, after extruding the polyester, additionally stretching in the mechanical direction by a ratio of 0.1 to 5% of the natural draw ratio naturally occurring in the process in the mechanical direction. It may be prepared by.

In another embodiment of the present invention is a method for producing a heat-shrinkable polyester film by extruding and stretching the polyester as the following steps: extruding the polyester at 200 ~ 350 ℃; Preheating the extruded sheet; Stretching; And including the step of heat treatment, the temperature of the heat treatment section is set to be lower than the temperature of the preheating section, the shrinkage speed is 0.5 to 3.5% / in the transverse direction (TD) determined by the following equation 1 It provides a method for producing a heat-shrinkable polyester film, characterized in that the ℃.

Equation 1

Shrinkage Speed = ΔL / ΔT

The above equation is derived by a method of detecting a dimension change due to expansion and contraction of a sample according to temperature change by a linear variable differential transformer (LVDT), and ΔT is a temperature change value, ΔL is a strain rate in the transverse direction (TD) and is a value measured in a temperature change section of 70 to 85 ° C.

Preferably, the preheating section temperature is 80 to 100 ℃, the heat treatment section temperature may be a room temperature to 95 ℃.

In the preferred manufacturing method according to the invention, after the step of extruding the polyester, it may further comprise the step of additionally stretching in the mechanical direction by 0.1 to 5% ratio than the natural draw ratio naturally occurring in the process in the mechanical direction.

The present invention exhibits a uniform shrinkage rate within a certain temperature range and the shrinkage speed is improved to reduce the occurrence of shrinkage unevenness during the shrinking process, lowering the label appearance defect rate and no occurrence of print distortion, resulting in improved productivity. It can be effective.

Hereinafter, the present invention will be described in more 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. It is manufactured on the principle of contraction by force.

In the contraction process, the heat applied for contraction has a partial temperature gradient. As a result of this temperature gradient, as the container passes through the contraction tunnel, there is a large and small contraction. Such shrinkage nonuniformity is not preferable in terms of stability of quality, and also shrinkage nonuniformity may occur in one label, so that the appearance of the label may be poor and distortion of printing may occur.

According to one embodiment of the present invention, the heat-shrinkable polyester film of the present invention is a heat shrinkability of the shrinkage speed of 0.5 to 3.5% / ℃ in the transverse direction (TD) determined by the following equation 1 It is a polyester film.

Equation 1

Shrinkage Speed = ΔL / ΔT

The above equation is derived by a method of detecting a dimension change due to expansion and contraction of a sample according to temperature change by a linear variable differential transformer (LVDT), and ΔT is a temperature change value, ΔL is a strain rate in the transverse direction (TD) and is a value measured in a temperature change section of 70 to 85 ° C.

An example of a measuring instrument that can implement this principle is a thermomechanical analyzer.

As an example of a measurement method using a thermomechanical analyzer, a temperature program is applied to a sample to measure the deformation of the sample under a constant load. The heat shrinkable film according to the present invention has a temperature change derived from a temperature range of 70 to 85 ° C. The strain value in the transverse direction (TD) is 0.5 to 3.5% / ° C.

If the shrinkage rate is less than 0.5% / ℃ incomplete shrinkage to reduce the binding force of the label, it may cause the label distortion at the upper and lower portions of the label, if greater than 3.5% / ℃ container due to excessive shrinkage stress Distortion may occur.

In addition, in the heat-shrinkable polyester film according to the present invention, the shrinkage strain rate in the transverse direction (TD) derived from Equation 2 obtained by differentiating a value derived from Equation 1 may be 3.5 to 8.5. And the temperature range where the maximum shrinkage strain rate is obtained is 80 to 88 ° C.

Equation 2

Shrinkage Rate = dL / dT

The above equation is a derivative of the value according to Equation 1 derived by a method of detecting a change in size due to expansion and contraction of a sample according to temperature change by a linear variable differential transformer (LVDT). Derived by the derivative, the derivative value of the strain in the transverse direction (TD) according to the temperature measured in the temperature change section 30 to 90 ℃, it means the maximum shrinkage strain value of the measured temperature section.

This is also a value derived using a thermomechanical analyzer, which is a case where the temperature change interval is set to 30 to 90 ℃.

In spite of such a wide temperature change section, if the shrinkage strain rate in the transverse direction (TD) is 3.5 to 8.5, it may be advantageous in terms of shrinkage uniformity by reducing shrinkage unevenness due to temperature deviation.

In addition, since the maximum shrinkage rate can be achieved in the low temperature range of 80 to 88 ° C, the maximum shrinkage rate can be achieved by passing the shrinkage tunnel using hot air or steam. It may be desirable in solving.

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

In addition, the heat-shrinkable polyester film of the present invention can be usefully used for the production of a container requiring high heat shrinkage, such as a container having a high bending rate, from its simple in shape to a heat shrinkage ratio of 60% or more.

In this case, the copolyester may be a copolyester in which terephthalic acid units constitute 80 mol% or more of dicarboxylic acid units, and 14 to 24 mol% of units other than ethylene glycol units in diol units. Units other than the ethylene glycol unit in the copolyester have a function of increasing the shrinkage rate by lowering the crystallinity of the polyester polymer, and the ratio of the unit within the above range controls drying process and melting characteristics in the film manufacturing process. It may be advantageous in terms of controlling.

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 to 77 ° C, and the intrinsic viscosity is 0.60 to 0.70 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 through such control the glass transition temperature and intrinsic viscosity is within the above range 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 are terephthalic acid, and 14 to 24 mol% of the total diol units of the polyester mixture. The thing which is a unit other than an ethylene glycol unit can be used.

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 polybutylene terephthalate content may be 7 to 15% by weight of the total polyester resin.

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 main contraction direction (for example, the width direction (TD)) may be lowered, and the mechanical properties of the direction perpendicular to the main contraction direction (for example, the mechanical direction (MD)) A decrease in (strength) may occur. In general, the film undergoes many roll processes in commercial use, and mechanical properties of the mechanical direction are required. If the mechanical properties are bad, breakage or breakage of the film may occur.

On the other hand, polytriethylene terephthalate may be used instead of or in combination with polybutylene terephthalate as a homopolyester.

In addition, in order to improve the slidability 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, anti-UV agent, dye, etc. may be added if necessary. It can also be added.

The polyester heat-shrink film of the present invention having the above characteristics can be produced by, for example, the following manufacturing process.

The material for producing a polyester film 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.

The unstretched film is subjected to a roller or the like that is naturally advanced in the mechanical direction, and then preheated, stretched in the width direction, and then heat treated.

In this case, when the temperature of the heat treatment section is lower than the temperature of the preheating section, it may be advantageous in increasing the residual stress on the shrink film to increase the shrinkage rate and shrinkage rate.

As a preferred example, the temperature of the preheating section is 80 to 100 ℃, the temperature of the heat treatment section may be adjusted in the room temperature to 95 ℃ range.

On the other hand, before the pre-heating, in addition to the draw ratio generated by the natural progression in the mechanical direction, in addition to the stretching ratio in the mechanical direction at 0.1 to 5% draw ratio can be further improved in the mechanical direction of the film properties, which is a shrinkage uniformity It is also advantageous from the side.

The stretching in the width direction may be performed to be 3.0 to 5.0 times the original length.

In addition, when the draw ratio of the shrink film is small, the shrinkage rate may be reduced. On the other hand, when 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 times the original length. It can be selected within the range of 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.

Principle of measurement of shrinkage speed, shrinkage rate, maximum shrinkage temperature in the transverse direction (TD) of the heat-shrinkable polyester film of the present invention, and the resulting shrinkage speed, shrinkage rate, maximum The shrinkage deflection temperature is defined as follows.

(1) principle

It is derived by the method of detecting the change in size due to the expansion and contraction of the sample according to the temperature change by the Linear Variable Differential Transformer (LVDT). Direction (TD)) is expressed by the following equation 1, which is defined as the shrinkage speed.

Equation 1

Shrinkage Speed = ΔL / ΔT

In the above formula, ΔT is the temperature change value, ΔL is the strain rate in the transverse direction (TD), and is a value measured in the temperature change section of 70 to 85 ° C.

On the other hand, when the value by the said Formula 1 is differentiated, it is represented by following Formula 2, and the maximum value obtained is defined as shrinkage strain rate.

Equation 2

Shrinkage Rate = dL / dT

The above equation is a value obtained by differentiating the strain rate in the transverse direction (TD) according to the temperature measured in the temperature change section 30 to 90 ° C, and obtains the maximum value in the measured temperature section.

In this way, the maximum contraction strain temperature is defined as the maximum contraction strain temperature among the contraction strain rates derived by Equation 2.

As an example of a device that implements the above principle, a thermomechanical analyzer was used in the following Examples and Comparative Examples.

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) intrinsic viscosity

200 mg of the specimen was added to 20 ml of a mixed solvent of phenol and tetrachloroethane 50/50, and the mixture was heated at about 110 ° C. for 1 hour and then measured at 30 ° C.

(2) Glass transition temperature by DMTA-method

Hold the sample at an initial load of 2.5N for a sample with a width of 10mm and a length of 30mm (main contraction direction), and raise the temperature by setting the static force, which is the force holding the sample, to 2.5N to prevent deformation of the sample due to flow. Storage modulus using a dynamic mechanical thermal analyzer (EPLEXOR 500, Gabo) with a measurement frequency of 10 Hz and a dynamic force of 2.5% in the temperature range of 0 to 150 ° C. , E ') and loss modulus (E "), and the loss tangent (Loss tangent, tanδ) according to the following Equation 3. At this time, the temperature corresponding to the maximum tanδ value as the dynamic glass transition temperature (Tg) This was obtained.

<Equation 3>

 Loss tangent (tanδ) = Loss Modulus (E ") / Storage Modulus (E ')

(3) heat shrinkage

 The film was cut in the forward direction of 20 cm × 20 cm, and thermally contracted for 10 seconds in a hot water at 95 ° C. ± 0.5 ° C. under no load, and then the numerical values in the mechanical direction (MD) and the width direction (TD) of the film were measured, and the following Equation 4 The thermal contraction rate was calculated according to.

<Equation 4>

(4) Shrink start temperature, maximum shrinkage expression temperature, maximum shrinkage stress

Using a thermal stress tester (KE-2, Kanebo Eng.), The film specimen having a width of 4 mm (MD direction) and a length of 50 mm (TD direction) was fixed at an initial load of 0.125 kg / mm2, followed by a temperature increase rate of 2.5 The graph was obtained by measuring the shrinkage stress according to the temperature while raising the temperature to ℃ / sec.

In this graph, the temperature at which the shrinkage stress value equal to the initial load of 0.125kg / mm2 is first shown is the shrinkage start temperature (Ts), and the temperature at the point where the maximum shrinkage stress value is first appeared is the maximum shrinkage expression temperature (T). _(Smax) ), and the stress value at this time was defined as the maximum shrinkage stress (S _max ).

(5) Shrinkage speed, shrinkage strain rate, maximum shrinkage strain temperature

Using a thermomechanical analyzer (model Diamond TMA, manufacturer Perkin Elmer), prepare a film specimen in the dimensions of 4mm in width (MD direction) and 15mm in length (TD direction) to give a load of 2mN / μm to the specimen. , The strain rate in the transverse direction (TD) according to the temperature change in the temperature range 30 to 90 ℃ at a temperature increase rate of 10 ℃ / min, and the main shrinkage according to the temperature in the temperature range 70 to 85 ℃ The rate of change of the length of the transverse direction (TD) was calculated to determine the shrinkage speed.

For example, the length variation in the main contraction direction according to temperature by the thermomechanical analyzer is represented by a graph as shown in FIG. 1, that is, a graph of a probe position according to temperature.

This can be calculated using Equation 5 below to calculate the shrinkage at each temperature.

<Equation 5>

Shrinkage Ratio = {1-((First Length + Probe Position) / First Length)} × 100

For example, when the probe position is -5.0 mm from the graph of FIG. 1, the shrinkage ratio is calculated as {1-((15mm + (-5mm)) / 15mm)} × 100 = 33.3%. Here, 15 mm is the length in the main contraction direction of the specimen.

On the other hand, the temperature range was 30 to 90 ° C, and the strain in the transverse direction (TD) was measured according to the temperature change, and then the derivative was deduced to derive the shrinkage strain rate, and the maximum value was defined as the shrinkage strain rate. It was.

In addition, in the shrinkage strain rate graph, the temperature of the section in which the maximum shrinkage strain rate appeared was measured as the maximum shrinkage strain temperature.

(6) Rate of shrinkage change with a certain time under a certain temperature

Testrite MKV Shrinkage-Force Tester (manufactured by Testrite Ltd., maximum shrinkage measuring range 35.8%, reference sample length 250mm) is used to evaluate shrinkage, but the instrument is intended for the evaluation of shrinkage of yarn or cord. In order to evaluate the heat shrinkage rate of the shrink film, it is necessary to prepare the specimen as described below, and to correct or convert the result.

Specifically, it is as follows.

-Fabrication of specimen: length (main contraction direction) 120mm, width 15mm

-Fixation of specimens: Samples in which the shrinkage caused by heat is produced by binding 10 mm of each end in the longitudinal direction of the specimens to a film which does not generate heat deformation at the corresponding measurement temperature, that is, the lengths of the samples according to Examples and Comparative Examples to be 100mm, and at the end of the coupling to the film deformation is not caused by heat to one flat of the sample gives an initial load 20g / mm ^2, is mounted in the measuring device is positioned in the forward central portion of the measuring device.

At this time, the length of the sample that caused the shrinkage due to heat was selected as 100 mm, and the result of confirming the measurement range of the maximum shrinkage rate of the test equipment was 35.8%, and the measurable length strain value of the corresponding device was 89.5mm. It was because the shrinkage rate could be measured most stably as a result of calculating the maximum length of the sample.

The maximum length of the sample may vary depending on the shrinkage rate. The maximum sample length according to the shrinkage rate is calculated as follows.

For example, in the case of a film having a shrinkage rate of 70% under the above measurement conditions, the maximum sample length is 127.9 mm (89.5 mm / 0.7), and when the shrinkage rate is 80%, 111.9 mm (89.5 mm / 0.8).

Therefore, from the calculation based on the measurable length strain value derived from the above maximum shrinkage at the reference sample length of 250 mm, it is most stably that the length of the sample capable of measuring the shrinkage for high shrinkage of 70% or more is 100 mm. Since the measurement can be performed, the length of the measurement sample was set to 100 mm.

-Method of measurement: Measure shrinkage with time under the condition of 95 ℃ under the condition of measuring device.

-Correction of the result value: Obtain the length deformation value of the measured sample measured on the basis of the sample length (250mm) set in the measuring device, and convert it to the value based on the length of the measured sample.

E.g.) If the length strain of the sample to be measured is 10%,

Actual length deformation of the sample = 250 mm × 0.1 = 25 mm

Length strain of measured sample = 25mm / 100mm × 100 = 25%

The length strain of the measurement sample thus obtained was defined as the shrinkage rate.

-Interpretation of results: The shrinkage of the measurement sample begins in calculating the shrinkage rate with time to prevent confusion in the analysis of shrinkage behavior that may be caused by binding to a film that does not generate heat deformation for the production of the measurement sample. The time immediately before the starting point was set to "0" seconds, and the shrinkage rate from this point of time to 5 seconds was converted from the value of the measuring device.

<Equation 6>

Rate of shrinkage change (% / sec) = value of shrinkage change / elapsed time

(7) shrinkage stress

Using the Testrite MKV Shrinkage-Force Tester (Testrite Ltd), the shrinkage stress in the main shrinkage direction was measured over time at a temperature of 95 ° C., and the shrinkage stress value was obtained by dividing the cross section by the following equation (7).

At this time, the width of the sample was 15mm, and the initial load was 20g / mm ² to fix the sample flat.

<Equation 7>

Shrinkage stress = measured shrinkage stress (Kg) / cross-sectional area of sample (width × thickness; mm ² )

Ex) Shrinkage stress measurement value: 10N (1.02Kg = 10 / 9.8 Kg)

Sample cross section: 0.75 mm ² (for sample width 15 mm and thickness 50 μm)

    Shrinkage Stress (Kg / mm2) = 1.02 / 0.75 = 1.36

(8) Shrinkage Uniformity Evaluation

The label printed on the shrink film and the label made by gluing the end with the solvent was put on the container and passed through the steam-type shrink tunnel, and the label appearance defect of the final product (labeled container) and the number of defects due to print distortion By evaluating the shrinkage uniformity.

At this time, the length of the steam tunnel was 1.5m, and the steam was installed at the top and bottom of two 1.2m long injection pipes so that the label of the container passed inside could be shrunk. . The steam temperature is equipped with a temperature controller and a heater to control the temperature of the tunnel inlet and the outlet, respectively, and set the inlet temperature to 77 ° C and the outlet temperature to 86 ° C. By shrinking the label with a time of 5 seconds, shrinkage uniformity was measured by measuring the number of appearance defects and print distortion defects in the final product (labeled container).

Based on 1000 evaluation samples, the ratio of the normal product was defined as shrink uniformity, and this was calculated by the following Equation 8.

<Equation 8>

(9) Confirmation of shrinkage process characteristics through container manufacturing

The label printed on the shrink film and the label made by gluing the end with the solvent was put on the container and passed through the steam-type shrink tunnel, and the label appearance defect of the final product (labeled container) and the number of defects due to print distortion Was evaluated.

At this time, the length of the steam tunnel was 1.5m, and the steam was installed at the top and bottom of the 1.2m length of the injection pipe so that the label of the container passed inside could be contracted, and the pressure was 0.2bar to inject steam. . The steam temperature is equipped with a temperature controller and a heater to control the temperature of the tunnel inlet and the outlet respectively.

The tunnel inlet temperature is set to 80 ℃ and the outlet temperature is set to 90 ℃, and the label is shrunk with the residence time of the labeled container in the tunnel as 5 seconds, resulting in defects in appearance and print distortion in the final product (labeled container). By measuring the high temperature shrinkage uniformity (yield A).

In addition, the tunnel inlet temperature is set at 75 ° C and the outlet temperature is 84 ° C, and the label is shrunk with the residence time of the container with the label inside the tunnel as 4 seconds, resulting in poor appearance and print distortion in the final product (labeled container). The number of occurrence was measured to measure the low temperature shrinkage uniformity (yield B).

The shrinkage uniformity was defined as the shrinkage uniformity of the ratio of the normal product based on 1000 evaluation samples, and obtained by the following equation 9.

<Equation 9>

Relative process efficiency (R) = (Yield B / Yield A) × 100 (%)

<Example 1>

Polycondensation was carried out by direct esterification using 100 mol% of terephthalic acid as a dibasic acid component, 100 mol% of ethylene glycol and 23 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 0.67 dl / g and a glass transition temperature of 76 ° C.

On the other hand, by using 100 mol% of terephthalic acid and 100 mol% of 1,4-butanediol, 0.015 parts by weight of tetrabutyl titanate was added as a catalyst to obtain a polybutylene terephthalate resin (high viscosity 0.97 dl / g, glass transition temperature 30 ° C). .

90 wt% of the copolyester and 10 wt% of polybutylene terephthalate were blended and extruded from an extruder at 280 ° C., followed by rapid cooling and solidification to obtain an unstretched film.

The unstretched film was continuously transferred through a roller conveyed in a mechanical direction, passed through a preheating section with a temperature of 87 ° C, stretched at 4.0 times the width at 82 ° C, and then subjected to a heat treatment section at room temperature. . 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 1.

<Example 2>

An unstretched film obtained in the same manner as in Example 1 was used.

In the case of continuously conveying the unstretched film through a roller conveyed in the mechanical direction, in addition to the naturally occurring draw ratio, the film was further stretched in the mechanical direction by 0.4% magnification, and then the heat-shrinkable polyester film was prepared in the same manner as in Example 1. Got it. 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 1.

<Example 3>

An unstretched film obtained in the same manner as in Example 1 was used.

Thereafter, the heat-shrinkable polyester film was obtained in the same manner as in Example 1 except that the temperature was set to 95 ° C. and the heat treatment period was set to 87 ° C. in the preheating period. 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 1.

<Example 4>

In the same manner as in Example 3, a heat-shrinkable polyester film was prepared, except that the extruded unstretched film was subjected to a stretching roll having a draw ratio of 3% naturally occurring in the mechanical direction (natural draw ratio + 3.4%). ) In the mechanical direction at the draw ratio.

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 1.

Reference Examples 1 and 2

Heat-shrinkable polyester films were obtained in the same manner as in Example 2 and Example 4, except that the stretching ratio in the mechanical direction was adjusted to (natural stretching ratio + 7%).

<Comparative Examples 1 and 2>

A heat shrinkable film was prepared in the same manner as in Examples 1 to 2, except that the preheating temperature was 85 ° C. and the heat treatment section temperature was 95 ° C.

Intrinsic viscosity (도 / g) Dynamic Tg (℃) Heat Shrinkage [%] Analysis by heat shrink stress tester Shrinkage Process Characteristics Shrinkage Speed (ΔL / ΔT) Shrinkage Rate (dL / dT) Max Shrinkage Deformation Temperature (℃) Shrinkage Uniformity (%) Shrinkage rate change rate (% / sec) Shrinkage Stress (kg / ㎡) MD TD Ts (℃) T (S _max ) (℃) S _max ) (kg / ㎡) Yield A (%) Yield B (%) Relative Process Efficiency (R%) Example 1 0.692 94.5 2.2 72.4 82.0 93.9 1.15 99.9 99.8 99.9 2.8 6.9 81.9 99.7 8.9 1.25 Example 2 0.691 95.2 3.2 74.5 80.7 92.7 1.27 99.9 99.8 99.9 3.3 7.7 80.5 99.8 9.2 1.20 Example 3 0.670 93.4 1.8 62.3 85.3 96.0 0.87 99.7 99.5 99.8 1.2 4.9 85.0 99.5 5.8 0.85 Example 4 0.668 93.8 4.7 61.1 86.7 96.2 0.85 98.7 96.7 98.0 0.9 4.0 86.5 99.4 4.9 0.83 Reference Example 1 0.683 98.2 7.9 74.0 83.2 97.3 1.05 90.3 75.2 83.3 3.1 5.9 82.7 75.4 7.7 1.14 Reference Example 2 0.671 97.4 7.5 60.3 87.5 98.7 0.90 88.7 74.5 84.0 0.6 4.2 87.3 76.7 4.3 0.64 Comparative Example 1 0.665 90.4 1.5 58.7 91.4 100.3 0.72 99.8 59.4 59.5 0.3 3.2 90.0 54.3 3.9 0.60 Comparative Example 2 0.663 90.2 2.4 57.0 92.7 101.1 0.68 98.8 57.5 58.2 0.1 2.8 90.0 57.3 3.8 0.59

As a result of measuring the physical properties, it can be seen that when the shrinkage speed is 0.5 to 3.5% / ° C., the shrinkage uniformity of the final product can be improved to improve the productivity of the product.

In addition, when the shrinkage strain rate is 3.5 to 8.5, and the maximum shrinkage strain temperature range is 80 to 88 ℃ it can be seen that the excellent shrinkage uniformity.

On the other hand, Figure 1 shows a graph measuring the strain according to the temperature change of the heat-shrinkable polyester film obtained in Example 1 using a thermomechanical analyzer.

FIG. 1 is a graph illustrating a result of analyzing a thermally shrinkable polyester film obtained according to Example 1 by a thermomechanical analyzer.

Claims (14)

A heat shrinkable polyester film having a shrinkage speed of 0.5 to 3.5% / 占 폚 in a transverse direction (TD) determined by the following Equation 1. Equation 1 Shrinkage Speed = ΔL / ΔT The above equation is derived by a method of detecting a dimension change due to expansion and contraction of a sample according to temperature change by a linear variable differential transformer (LVDT), and ΔT is a temperature change value, ΔL is a strain rate in the transverse direction (TD) and is a value measured in a temperature change section of 70 to 85 ° C. The heat-shrinkable polyester film according to claim 1, wherein the shrinkage strain rate in the transverse direction (TD) determined by the following equation (2) is 3.5 to 8.5. Equation 2 Shrinkage Rate = dL / dT The above equation is a derivative of the value according to Equation 1 derived by a method of detecting a change in size due to expansion and contraction of a sample according to temperature change by a linear variable differential transformer (LVDT). Derived from the equation, the equation is the derivative of the strain in the transverse direction (TD) according to the temperature measured in the temperature change section 30 to 90 ℃, means the maximum strain rate value in the measured temperature section . The heat-shrinkable polyester film of claim 2, wherein the temperature section at the time when the shrinkage strain rate in the transverse direction (TD) exhibits a maximum value is 80 to 88 ° C. The heat-shrinkable polyester film according to any one of claims 1 to 3, wherein the heat shrinkage rate is at least 60% (@ 95 ° C, 10 seconds, free state). The heat-shrinkable polyester film of claim 1, 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 heat shrinkable polyester film, characterized in that it comprises a mixture of homopolyester and copolyester. The heat-shrinkable polypolyester according to claim 5, wherein the copolyester comprises at least 80 mol% of terephthalic acid units in the dicarboxylic acid units and about 14 to 24 mol% of units other than ethylene glycol in the diol units. Ester film. The heat-shrinkable polyester film of claim 5, wherein the homo polyester is polybutylene terephthalate or polytriethylene terephthalate. 8. The heat-shrinkable polyester film according to claim 7, wherein the polybutylene terephthalate comprises 7 to 15% by weight of the total resin. The method of claim 1, wherein the heat-shrinkable polyester-based film comprises a step of extruding the polyester, preheating, stretching in the width direction, and then heat treating the heat-shrinkable polyester film. Heat-shrinkable polyester film, characterized in that produced by. 10. The heat-shrinkable polyester film of claim 9, wherein the preheating section temperature is 80 to 100 ° C., and the heat treatment section temperature is room temperature to 95 ° C. 11. The method of claim 10, wherein after the step of extruding the polyester, the heat-shrinkable, characterized in that further comprising the step of stretching in the mechanical direction additionally by 0.1 to 5% ratio than the natural draw ratio naturally occurring in the process in the mechanical direction Polyester film. The following steps as a method for producing a heat-shrinkable polyester film by extruding and stretching the polyester: Extruding the polyester at 200 to 350 ° C .; Preheating the extruded sheet; Stretching; And Including the step of heat treatment, the temperature of the heat treatment section is set to be lower than the temperature of the preheating section, the shrinkage speed of the transverse direction (TD) determined by the following equation 1 is 0.5 to 3.5% / ℃ Method for producing a heat-shrinkable polyester film, characterized in that. Equation 1 Shrinkage Speed = ΔL / ΔT The above equation is derived by a method of detecting a dimension change due to expansion and contraction of a sample according to temperature change by a linear variable differential transformer (LVDT), and ΔT is a temperature change value, ΔL is a strain rate in the transverse direction (TD) and is a value measured in a temperature change section of 70 to 85 ° C. 13. The heat-shrinkable polyester film of claim 12, wherein the preheating section temperature is 80 to 100 ° C, and the heat treatment section temperature is room temperature to 95 ° C. 13. The heat-shrinkable polyester of claim 12, further comprising, after extruding the polyester, additionally stretching in the mechanical direction by a ratio of 0.1 to 5% more than the naturally occurring ratio naturally occurring in the process in the mechanical direction. Method for producing a film.

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