KR101414241B1 - Disclosed is a biodegradable aliphatic polyester film which is easy to open and a method for producing the same. - Google Patents

Abstract

The present invention relates to a biodegradable aliphatic polyester film which is easy to open and a method for producing the same, which is made of a polylactic acid polymer resin having a melting temperature of 140 ° C or higher and a content of D-lactide of 12% Characterized by having a crystallinity of 60 to 60%, a longitudinal elongation of 70% or less, a longitudinal strength of 5 kgf / mm ² or more and a biodegradation rate of 90% or more will be.

The aliphatic polyester film according to the present invention has excellent mechanical properties and is excellent in biodegradability and can be used for eco-friendly packaging. The aliphatic polyester film can also be used as a film for easy packaging and adhesive tape .

Description

FIELD OF THE INVENTION [0001] The present invention relates to a biodegradable aliphatic polyester film and a biodegradable aliphatic polyester film,

The present invention relates to a biodegradable aliphatic polyester film, and more particularly, to a biodegradable aliphatic polyester film for packaging and a pressure-sensitive adhesive tape having easy-openability with a thermosetting property.

Examples of plastic films commonly used for packaging include polyethylene terephthalate (PET), nylon, polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC). However, all of them are not decomposed at all in the soil, so they do not help the environment. In addition, various byproducts are generated according to the waste disposal method. Especially, in the case of polyvinyl chloride, harmful substances such as dioxin are generated at the incineration, which hurts not only the global environment but also the health of the people.

Despite these side effects, however, most of the raw materials are mostly used for packaging and industrial purposes, but are exposed to environmental problems unprotected.

Therefore, 100% decomposed raw materials are attracting much attention when land is buried. These raw materials can be largely classified into plant and petroleum based on the raw material extraction method. Representative plant raw materials include polylactic acid and polyhydroxybutylate, and petroleum-based ones include polycarprolactone, , Polybutylenesuccinate, and the like. Of these, polylactic acid is the most excellent in terms of physical properties, and researches thereof are currently underway.

Polylactic acid, which is an aliphatic polyester, is a polymer produced by intensifying lactic acid. Acid is an optical isomer of the L- lactic acid and D- lactic acid, and thus the polylactic acid is usually present in a random copolymer between the two optical isomers, and the melting temperature (T _m) is near 180 ℃ and has a glass transition temperature (T _g) Lt; / RTI > Such a random copolymer does not have crystallinity and can be used for a general bag which is made of a blown film or the like in an amorphous state and does not require heat resistance and mechanical properties.

Further, in order to impart crystallinity to the random copolymer, it is possible to prepare a stretched film by adding a large amount of an inorganic substance or a large amount of a nanocomposite or the like, but it is difficult to control the degree of crystallization properly, There is a problem that becomes extremely bad. Further, the flexibility of the stretched film is lowered by a large amount of inorganic substances and nanocomposites, and the film becomes a stiff film having low mechanical properties, which is problematic for use as a good packaging film, and biodegradability is also deteriorated.

On the other hand, a polymer composed of L-lactide alone or D-lactide alone can be a useful raw material that can be used as a stretched film as a semi-crystalline resin having a high melting temperature (around 180 ° C) However, the flexibility of the film is insufficient and the stiff technical disadvantages can not be completely solved, and the manufacturing cost of the pure homopolymer is too high, so there are many problems to be put to practical use.

On the other hand, in the case of polybutylenesulfonate, although the polybutylenesulfonate has a melting point of 115 캜 and a glass transition temperature of -32 캜, it has a flexible property, but exhibits a fatal weakness in heat resistance. Since polycaprolactone has a melting point of 60 캜, And the polyhydroxybutyrate has a melting point of 175 DEG C but is too stiff to have difficulty in stretching when the film is formed.

Generally, a cellophane film is mainly used to impart tearing property to a film. Such cellophane films cause environmental pollution in the manufacturing process, and the use amount thereof has recently been decreasing due to high use cost.

In addition, in the case of polyethylene terephthalate or polypropylene film, the film has high mechanical strength due to its molecular structure, thereby imparting forcible heat resistance through notch processing in order to secure heat resistance. However, not only the manufacturing cost increases due to the notch processing but also the external appearance of the finished product can not be attained due to the outer folded portion for notch processing, which leads to a bulky and tearable package.

Accordingly, an object of the present invention is to provide a biodegradable aliphatic polyester film having excellent biodegradation rate, excellent mechanical properties and excellent heat resistance, which makes it easy to cut an article without using a random polylactic acid copolymer, and its manufacture Method.

In order to achieve the above object, the present invention provides a polylactic acid resin composition which is made of a polylactic acid polymer resin having a melting temperature of 140 캜 or more and a content of D-lactide of 12% or less and has a crystallinity of 35% to 60% A biodegradable aliphatic polyester film characterized by having an elongation, a longitudinal strength of 5 kgf / mm < ² > or more and a biodegradation rate of 90% or more.

In the present invention, a polylactic acid copolymer resin having a melting temperature (T _m ) of 140 ° C or more is melt-extruded, the melt-extruded sheet is longitudinally stretched at 1.2 to 2.5 times, transversely stretched at 3 to 5 times, Wherein the ratio of the longitudinal stretching to the transverse stretching is 1: 2 or more. The present invention also provides a method for producing a biodegradable aliphatic polyester film.

Hereinafter, the present invention will be described more specifically.

The polylactic acid polymer according to the present invention can be used as a homopolymer or as a copolymer having a small amount of other hydroxycarboxylic acid units.

The melting temperature of the polylactic acid polymer is preferably 140 ° C or more and less than 200 ° C, and more preferably 150 ° C or more and less than 180 ° C. If the melting temperature is lower than 140 占 폚, heat resistance and mechanical properties are not properly exhibited.

The polylactic acid polymer is a random copolymer of L-lactide and D-lactide having a content of D-lactide of 12% or less, which is a polymer obtained by polycondensation of lactic acid produced from a vegetable raw material such as corn, mol to 500,000 g / mol. If the weight average molecular weight is less than 80,000, heat resistance and mechanical properties are not properly exhibited. If the weight average molecular weight is more than 500,000, the viscosity is too high, so that a proper biaxially stretched film can not be processed.

The small amount of the hydroxycarboxylic acid unit that can be used in the present invention includes glycolic acid or 2-hydroxy-3,3-dimethylbutyric acid, and the amount of the hydroxycarboxylic acid unit is preferably 10% by weight or less Can be used.

In addition, the resin composition for a film of the present invention may be added with a conventional electrostatic agent, an antistatic agent, an ultraviolet screening agent, an antiblocking agent and other inorganic lubricants within the range not impairing the effect of the present invention.

The film according to the present invention is prepared by melt-extruding, biaxially stretching and thermo fixing the resin composition for a film in a conventional manner. In the present invention, in order to control the crystallinity, longitudinal elongation, longitudinal strength and biodegradation rate of the film, It is preferable that the film has a longitudinal stretching ratio of 1.2 to 2.5 times and a transverse stretching ratio of 3 to 5 times. The ratio of longitudinal stretching ratio to transverse stretching ratio is preferably 1: 2 or more.

If the longitudinal mysterious ratio is less than 1.2 times, the molecules are not oriented in the longitudinal direction so that the longitudinal strength is less than 5 kgf / mm < ² > so that the film is easily broken. On the other hand, So that the heat resistance in the transverse direction is lowered.

If the transverse stretching ratio is less than 3 times, the thickness of the film becomes poor due to insufficient stretching, and the lateral orientation of the molecules becomes relatively small, resulting in poor thermal stability in the transverse direction. On the other hand, .

In addition, the degree of molecular orientation is the most important measure in order to have heat resistance in the transverse direction. If the ratio between the longitudinal mystery ratio and the transverse stretching ratio is less than 1: 2, the molecules in the longitudinal direction and the transverse direction are excessively oriented, 70% or more, and the tearing property in the transverse direction is deteriorated. On the other hand, when the ratio is 1: 2 or more, the transverse direction of molecular orientation dominates the longitudinal direction of the molecule, so that the elongation in the longitudinal direction becomes 70% or less.

The aliphatic polyester film of the present invention produced according to the above is characterized by having a crystallinity of 35% to 60%, a longitudinal elongation of 70% or less, a longitudinal strength of 5 kgf / mm ² or more, and a biodegradation rate of 90% do.

If the crystallinity of the film is less than 35%, the heat treatment must be carried out at a low temperature. If the crystallinity in the film is lowered, the stress applied during stretching is not relaxed, and the film shrinks sharply so that shrinkage occurs in the printing or post- If the crystallinity exceeds 60%, the film becomes too stiff to be stretched.

If the longitudinal elongation of the film is within 70% and the strength in the longitudinal direction is 5 kgf / mm ² or more, the transverse direction thermal property and the process stability upon film formation can be achieved. If the longitudinal elongation exceeds 70% Since the molecular orientation is uniformly distributed in various directions without being deviated to one side, it can be effective for process stability such as fracture, but the thermostability of the molecule, which has a definite molecular orientation, is deteriorated. On the contrary, if the longitudinal strength is less than 5 kgf / mm < ^{2 >,} the strength of the film is too weak to react sensitively to the minute tension of the winder,

In order to control the degree of crystallization as described above, in the present invention, the temperature of the first and fourth sections is set in the range of T _m -50 ° C to T _m -10 ° C with at least four sections after the transverse stretching, It is preferable that the temperature of the section 3 is in the range of T _m -20 ° C to T _m -10 ° C, and the length of the heat fixing section is preferably 40% or more of the total length of the tenter (transverse stretching and heat fixing device).

The aliphatic polyester film of the present invention produced according to the above is characterized in that the heat shrinkage rate at 100 ° C for 5 minutes is 5% or less.

If the heat shrinkage exceeds 5%, the crystallinity drops to 35% or less, which causes shrinkage in the printing or post-processing process when used as a packaging film, and thus can not have a good appearance.

In the present invention, in order to control the linear expansion coefficient and the heat distortion temperature, the longitudinal stretching and transverse stretching sections are divided into preheating and stretching sections, respectively, and controlled under specific conditions for each section.

Longitudinal drawing synthesizer pre-heating temperature is preferably higher 10 ℃ than this is the range from T _g + 20 ℃ to T _g + 50 ℃, stretching temperature, into a lateral, the warm-up period during stretching by at least three step initial temperature T _g + in the range of 30 ℃ to T _g + 50 ℃, medium temperature is lower 5 ℃ than the initial temperature, the end temperature is preferably low 5 ℃ and stretching period is divided into at least two steps initial temperature than the medium temperature T _g + to 20 ℃ to the range of T _g + 50 ℃, the end temperature is preferably in the range from T _g + 30 ℃ to T _g + 80 ℃.

The aliphatic polyester film of the present invention produced according to the above is characterized in that the coefficient of linear expansion at a temperature of 25 캜 to 75 캜 is 0.2 탆 / cm 캜 or less and the heat distortion temperature is 70 캜 or higher.

When the coefficient of linear expansion is less than 0 占 퐉 / cm 占 폚 (-), the film shrinks at the above temperature. When the linear expansion coefficient exceeds 0.2 占 퐉 / cm 占 폚, the film is excessively stretched at the above temperature, Making it difficult to use as an application.

If the thermal deformation temperature is less than 70 캜, shrinkage easily occurs, and shrinkage occurs severely after printing, which lowers the value as a packaging material having a good appearance.

The film produced according to the present invention has excellent mechanical properties and excellent biodegradability and can be used for eco-friendly packaging. Since it is excellent in heat resistance, it is easy to cut an article without a notch, It can also be used as a film for an adhesive tape.

Hereinafter, the present invention will be described in more detail based on the following examples. However, the following examples are intended to illustrate the present invention and are not to be construed as limiting the scope of the present invention. The properties and various properties of the films prepared in Examples and Comparative Examples of the present invention were evaluated in the following manner.

(1) Melting temperature (T _m, ° C)

Using a differential scanning calorimeter (Perkin Elmer Corp., DSC-7), the crystal melting temperature was measured at a heating rate of 20 ° C per minute.

(2) Biodegradation rate (%)

The ratio of the biodegradation value measured for 180 days according to the standard measurement method of ASTM D5338 to the reference material was calculated according to the following formula.

(3) Crystallinity (%)

The crystal melting energy (Hc, J / g) measured at a heating rate of 20 ° C per minute using a differential scanning calorimeter (Perkin Elmer Corp., DSC-7) g) according to the following formula.

(4) Coefficient of linear expansion (占 퐉 / cm 占 폚)

And measured at a heating rate of 0.05 N and 10 DEG C / min under a constant load using a thermal deformation analyzer (TA, TMA 2940) and calculated according to the following equation.

(5) Heat shrinkage (%)

The prepared film was cut into 15 mm width and 200 mm length in the transverse direction (width), followed by heat treatment in a hot air oven maintained at a temperature of 100 캜 for 5 minutes, and then the lengths before and after the heat treatment were measured, Respectively.

(6) Strength and elongation of film

The prepared film was cut into a length of 15 mm and a length of 50 mm and then stretched at room temperature (23 2 캜) using a UTM (Instron, 4206-001) according to ASTM D882 at a tensile rate of 20 mm / The elongation at break and the breaking strength were measured.

(7) Persistence

The prepared film was cut into 15 mm in width (width) and 300 mm in length (length), and then the gap of 10 mm between the centers was gripped by hand and pulled slowly to observe the tearing state of the film. At this time, when the film is cleanly cut, the film is stretched, and the film is classified as defective if the cut surface is not clean or can not be cut by hand.

Example 1

The content of D- lactide 5% by weight, the melting temperature (T _m) is 150 to 180 ℃, the glass transition temperature of the process (T _g) is a polylactic acid polymer (4042D, Natureworks LLC, USA) 55 ℃ a pellet form And then extruded at an extrusion temperature of 240 DEG C, and then adhered to a cooling roll at 20 DEG C to obtain a sheet. Thereafter, the film was preheated to 75 deg. C for longitudinal drawing, passed through a drawing roll at 85 deg. C, and longitudinally drawn at 1.2 times.

The stretched film was preheated in a preheating section having initial, middle, and late temperatures of 100 deg. C, 95 deg. C, and 90 deg. C, respectively, and then stretched four times in the elongation period in which initial and final temperatures were 83 deg. Lt; / RTI >

The above sheet was heat set in a heat fixation section of a tenter having a temperature of 140 ° C for one section and four sections and a temperature of 150 ° C for two sections and three sections to prepare a polylactic acid biaxially stretched film which is an aliphatic polyester, The length of the fixed section was 40% of the total tenter length.

The longitudinal elongation, longitudinal strength, crystallinity, shrinkage, linear expansion coefficient, heat distortion temperature, biodegradation rate and tearing property of the film were measured and are shown in Table 1 below.

Example 2

The 2% by weight content of D- lactide, melting temperature (T _m) is 150 to 180 ℃, the glass transition temperature of the process (T _g) is a polylactic acid polymer (4032D, Natureworks LLC, USA) 55 ℃ a pellet form The sheet was then melted at an extrusion temperature of 220 캜 and then adhered to a cooling roll at 25 캜 to obtain a sheet. Thereafter, the film was preheated at 78 캜 for longitudinal stretching, passed through a stretching roll at 88 캜, and longitudinally stretched at a stretch ratio of 1.5 times.

The stretched film was preheated in a preheating section having initial, middle, and late temperatures of 105 DEG C, 100 DEG C, and 95 DEG C, respectively, and then 3.2 times in the stretching section in which initial and final temperatures were 80 DEG C and 85 DEG C, respectively And then transversely stretched.

The above sheet was heat set in a heat-setting zone of a tenter having a temperature of 150 DEG C and a temperature of 160 DEG C for two sections and four sections, thereby preparing a polylactic acid biaxially stretched film which is an aliphatic polyester, The length of the fixed section was 40% of the total tenter length.

The properties of the film were measured and shown in Table 1 below. The heat shrinkage rate was lowered by heating at a higher temperature than in Example 1, and the other properties were all good.

Comparative Example 1

(T _m ) of 150 ° C and a glass transition temperature (T _g ) of 8% by weight, a content of D-lactide prepared by mixing PLA chips 4032D and 4060D (Natureworks LLC, USA) ) At 55 DEG C was processed into a pellet form and dissolved at an extrusion temperature of 240 DEG C and then adhered to a cooling roll at 20 DEG C to obtain a sheet. Thereafter, the film was preheated at 60 캜 for longitudinal stretching, passed through a stretching roll at 75 캜, and longitudinally stretched three times.

The stretched film was preheated in a preheating section at the initial, middle, and late temperatures of 85 ° C, 80 ° C and 75 ° C, respectively, and then stretched four times in the stretching section at the initial and final temperatures of 75 ° C and 80 ° C, Lt; / RTI >

The sheet was heat set in a heat-setting zone of a tenter having a temperature range of 1 to 4, both of which were 120 ° C, to produce a polylactic acid biaxially stretched film which was an aliphatic polyester. The length of the heat fixing zone was 37 %.

The properties of the film were measured and shown in Table 1 below. The heat shrinkage rate was increased by heating at a lower temperature than that of Example 1, and the ratio of longitudinal extension ratio and transverse extension ratio was 1: 1.33 And a poor state was observed in the heat resistance in which the degree of longitudinal orientation was deep.

Comparative Example 2

Chip PLA 4032D and 4060D (Natureworks LLC, USA) 2: manufactured by mixing in a ratio of 8, 10% by weight content of D- lactide, a 150 ℃ melting temperature (T _m), a glass transition temperature (T _g ) At 55 캜 was processed into a pellet form and melted at an extrusion temperature of 260 캜 and then adhered to a cooling roll at 25 캜 to obtain a sheet. Thereafter, the film was preheated at 65 ° C for longitudinal drawing, passed through a drawing roll at 75 ° C, and longitudinally drawn 3.5 times.

The stretched film was preheated in a preheating section having initial, middle, and late temperatures of 90 DEG C, 85 DEG C, and 80 DEG C, respectively, and then stretched 4.5 times in the stretching section in which the initial and late temperatures were 100 DEG C and 105 DEG C, Lt; / RTI >

The sheet was heat set in a heat-setting zone of a tenter having a temperature of 110 ° C for one section and four sections and a temperature of 115 ° C for two sections and three sections to prepare a polylactic acid biaxially stretched film which is an aliphatic polyester, The length of the fixed section was 35% of the total tenter length.

The properties of the film were measured and the results are shown in Table 1. The heat shrinkage rate was increased by heating at a lower temperature than in Example 1. As the longitudinal mystery ratio and the transverse stretching ratio were increased to 3.5 times and 4.5 times, The ratio of the stretching ratio was as small as 1: 1.28, indicating a poor state in heat resistance in which the degree of longitudinal orientation was deep.

Comparative Example 3

Of D- lactide and the amorphous prepared by self-polymerization of the L- lactide, 15% by weight content of D- lactide, a glass transition temperature (T _g) is 55 ℃ polylactic acid polymer (4060D, Natureworks LLC, USA ) At 240 캜 for extrusion, and then the sheet was brought into close contact with a cooling roll at 20 캜, but the film could not be stretched because stretching was impossible.

Comparative Example 4

The film was prepared in the same manner as in Example 1, except that the stretching ratio was 3.2 times and the lateral stretching ratio was 4.3 times. The properties of the film are shown in Table 1 below.

As shown in Table 1, the polyester films of Examples 1 and 2 according to the present invention are superior in terms of biodegradation rate to pyrolysis and mechanical properties, as compared with the films of Comparative Examples 1 to 4 .

The aliphatic polyester film according to the present invention has excellent biodegradation rate as well as mechanical properties such as longitudinal elongation, longitudinal strength, crystallinity, shrinkage, linear expansion coefficient, thermal equilibrium temperature and tearing property and can be used as an environmentally friendly packaging material . In particular, the film according to the present invention is excellent in heat resistance and can be used as a film for packaging for barrier ribbons and a film for pressure-sensitive adhesive tapes, because it is easy to cut the finished product without a notch.

Claims (10)

delete delete delete delete Extruding a polylactic acid copolymer resin having a melting temperature ( _Tm ) of 140 DEG C or higher, longitudinally stretching the melt-extruded sheet at a stretching ratio of 1.2 to 2.5 times, transversely stretching at a stretching ratio of 3 to 5 times, Including, The ratio of the longitudinal extension ratio to the transverse stretching ratio is 1: 2 or more, Wherein the transverse stretching, the longitudinal stretching of the sheet, and a third step in the early polylactic acid resin with a glass transition temperature (T _g) + 30 ℃ to T the temperature of the _g + 50 ℃, the medium is 5 ℃ lower than the initial temperature After preheating at a temperature of 5 [deg.] C below the mid-term temperature at the end; Characterized in that it is carried out in two stages by transversely stretching at a temperature of T _g + 20 ° C to T _g + 50 ° C at the beginning and at a temperature of T _g + 30 ° C to T _g + 80 ° C at the end. Wherein the aliphatic polyester film is a polyester film. 6. The method of claim 5, Extruded sheet is longitudinally stretched at a temperature higher than the glass transition temperature (T _g ) of the polylactic acid resin at a temperature of + 20 ° C. to T _g + 50 ° C. before the longitudinal stretching, , A method for producing a biodegradable biodegradable polyester film. delete Extruding a polylactic acid copolymer resin having a melting temperature ( _Tm ) of 140 DEG C or higher, longitudinally stretching the melt-extruded sheet at a stretching ratio of 1.2 to 2.5 times, transversely stretching at a stretching ratio of 3 to 5 times, Including, The ratio of the longitudinal extension ratio to the transverse stretching ratio is 1: 2 or more, The heat-set transversely stretched sheet is divided into four sections at a temperature of T _m -50 ° C to T _m -10 ° C for one section and four sections, at a temperature of T _m -20 ° C to T _m- Wherein the heat treatment is carried out by heat setting at a temperature of < RTI ID = 0.0 > 10 C < / RTI > delete delete