KR20120013707A - Biodegradable polyester film and preparation method thereof - Google Patents

Abstract

PURPOSE: A biodegradable polyester film and a manufacturing method thereof are provided to maximize the flexibility and transparency of biodegradable polyester film and prevent steam vapor generation during manufacturing process and bleed-out phenomenon after extrusion. CONSTITUTION: A biodegradable polyester film is produced by compounding of a polycaprolactone which has less than 10,000 average molecular weight(Mn) and a polylactic acid. A method for manufacturing the biodegradable polyester film comprises the following steps: obtaining a resin by compounding a polycaprolactone which has less than 10,000 average molecular weight(Mn) and a polylactic acid; obtaining an undrawn sheet by melting and extruding the resin; stretching the undrawn sheet vertically or horizontally and heat setting the drawn sheet.

Description

Biodegradable polyester film and manufacturing method thereof {BIODEGRADABLE POLYESTER FILM AND PREPARATION METHOD THEREOF}

The present invention relates to a biodegradable polyester film used in a packaging film and the like and a method for producing the same.

Polyvinyl chloride (PVC), polyethylene (PE), and polypropylene (PP), which are general purpose plastics derived from petroleum, are currently used in various applications, but when incinerated, they generate harmful substances such as dioxins and generate a lot of carbon dioxide. There is a problem of accelerating the effect of greenhouse gases in the atmosphere. In addition, since these plastic films are chemically and biologically stable, they hardly decompose, and thus shorten the life of landfills, causing problems with global soil pollution.

In recent years, carbon tax and carbon credit trading systems have been actively reviewed to secure green growth resources and reduce global greenhouse gas emissions. Accordingly, research and development on biopolymers derived from biomass are being conducted.

In particular, many studies and applications of polylactic acid (PLA), a biodegradable aliphatic polyester, have been conducted. The polylactic acid film maintains mechanical properties and transparency, but has high flexibility due to high crystallinity due to molecular structure. Its use is limited due to lack of packaging, and especially in the case of refrigerated and frozen foods to be stored at a low temperature, the pinhole resistance is not sufficient, so that the packaging material may rupture during storage and transportation. Many studies have been conducted to solve this problem.

Japanese Laid-Open Patent Publication No. 2003-147098 discloses a biodegradable polylactic acid film having excellent transparency and flexibility, and is characterized by improving roll adhesion of polylactic acid to facilitate T-die molding. According to the above document, since the sticking occurs when the D-lactic acid content of the polylactic acid is 4% by weight or more, in order to solve this problem, polylactic acid, poly (butylene adipate / terephthalate) (PBAT) and polycaprolactone 3 Films are prepared by blending and extruding components. Although the document states that the film thus prepared is transparent, an opaque film is obtained because of high haze due to poor compatibility between resins even if the light transmittance is high.

Japanese Laid-Open Patent Publication No. 2004-244553 discloses a film in which a ternary copolymer of butanediol / amber acid / caprolactone and an amorphous polylactic acid are laminated as a low temperature heat seal laminated film for packaging with added flexibility. In addition, PBAT is added to improve the burst strength and the melt seal strength of the film disclosed in the patent document, Japanese Patent Laid-Open No. 2004-237473 discloses aliphatic poly of succinic acid / 1,4-butanediol / caprolactone Aromatic polyester copolymers of ester copolymers and PBAT / 1,4-butanediol are disclosed. However, the film is difficult to secure sufficient flexibility.

Thus, there is a need for a new biodegradable film that satisfies transparency and flexibility at the same time.

Japanese Laid-Open Patent Publication No. 2003-147098 (2003.5.21, CI KASEI Co. Ltd.) Japanese Laid-Open Patent Publication No. 2004-244553 (2004.9.2, TOHCELLO) Japanese Laid-Open Patent Publication No. 2004-237473 (2004.8.26, TOHCELLO)

Accordingly, it is an object of the present invention to provide a biodegradable film having sufficient flexibility and a method for producing the same while maintaining the transparency of the biodegradable resin (PLA) film.

In accordance with the above object, the present invention provides a biodegradable polyester film comprising a compound of polycaprolactone and polylactic acid having a number average molecular weight (Mn) of 10,000 or less.

According to the above another object, the present invention comprises the steps of: a) compounding polycaprolactone and polylactic acid having a number average molecular weight of 10,000 or less to obtain a resin; b) melting and extruding the mixed resin to obtain an unstretched sheet; And c) stretching and heat setting the unstretched sheet in the longitudinal and / or transverse directions.

The film according to the present invention is made of biodegradable resin, which is environmentally friendly, has excellent transparency, maximizes flexibility, does not generate steam during extrusion during the manufacturing process, and does not bleed out after extrusion.

Hereinafter, the present invention will be described in more detail.

The biodegradable polyester film of the present invention is characterized in that the polycaprolactone and polylactic acid having a number average molecular weight of 10,000 or less are compounded.

The film of the present invention was prepared by compounding polycaprolactone and polylactic acid having a number average molecular weight of 10,000 or less, thereby maximizing flexibility. Polycaprolactone is obtained by ring-opening a cyclic caprolactone monomer, which can impart sufficient flexibility to the polylactic acid film. When the molecular weight of the polycaprolactone is too large, the kneading and compatibility with the polylactic acid is lowered and the haze increases, so that transparency of the film cannot be maintained. The number average molecular weight of the polycaprolactone is 10,000 or less, preferably 200 to 8,000, more preferably 500 to 5,000.

The polylactic acid is a random copolymer of L-lactic acid and D-lactic acid, and having a weight average molecular weight of 80,000 to 500,000 g / mol is preferable in consideration of heat resistance and mechanical properties of the film and film processability. In addition, the melting temperature of the polylactic acid is preferably 135 ° C or more and 180 ° C or less, more preferably 140 ° C or more. If the melting temperature is lower than 135 ℃ heat resistance and mechanical properties are not properly expressed because it is not preferable.

In addition, the higher the content of polylactic acid, the more fragile the film, the poor compatibility and kneading with polycaprolactone. Based on the weight of the film, the content of polycaprolactone is 5 to 40% by weight, and the content of polylactic acid is 60 to 95% by weight is preferable in that the transparency of the film is maintained while improving the fragile property of the polylactic acid. Do. Most preferably, the content of polycaprolactone is 10-20 wt% and the content of polylactic acid is 80-90 wt%.

Moreover, it is preferable that the said film is a stretched film manufactured through the extending process of a longitudinal direction and / or a lateral direction at a constant extending | stretching temperature.

Moreover, it is preferable that the heat shrinkage of the longitudinal direction and / or the lateral direction in 100 degreeC and 5 minutes of hot air conditions is 1 to 70% or less, respectively.

In addition, the film, the initial elastic modulus is preferably 50 to 480 kgf / mm 2. When the elastic modulus is 50 kgf / mm 2 or less, the resistance to mechanical tension is not sufficient, so that breakage occurs during driving, which is not preferable. On the contrary, when it is 480 kgf / mm <2> or more, since the rigidity of a film rises and it is easily broken by an external shock, it is not preferable. More preferably, it is in the range of 200 to 400 kgf / mm 2.

Moreover, it is preferable that the number of the pinholes after the pinhole resistance test of the said film is 100 or less. If the number of pinholes is more than 100 or cracks, it is not good because the impact resistance is weak and can be easily broken when subjected to continuous shock during transportation and handling. In particular, since the film becomes more fragile in winter, pinholes may occur due to repeated wrinkles, which may cause defects. More preferably, the number of pinholes is 15 or less.

Moreover, it is preferable that haze is 30% or less of the said film. If the haze is more than 30%, the transparency of the film becomes remarkably turbid so that it cannot be used for packaging purposes in which the contents of the inside are visible. More preferably, the haze is 20% or less, most preferably the haze of the final film is 10% or less.

It is preferable that the said film is 10 micrometers-300 micrometers in thickness. More preferably, they are 10 micrometers-100 micrometers.

Such a biodegradable polyester film of the present invention comprises the steps of: a) compounding polycaprolactone and polylactic acid having a number average molecular weight of 10,000 or less to obtain a resin; b) melting and extruding the resin to obtain an unstretched sheet; And c) stretching and heat setting the unstretched sheet in the longitudinal and / or transverse directions.

The melt extrusion temperature in step b) is preferably 180 to 220 ° C.

In addition, in step c), the stretching ratio in the longitudinal direction and the transverse direction is 2.5 to 3.5 times and 3.5 to 4.5 times, respectively, and the heat setting temperature is 80 to 100 ° C. for the heat shrinkable packaging film and 150 to 200 for the general packaging film. It is preferable that it is ° C.

The invention also provides a packaging comprising a biodegradable polyester film according to the invention.

The film according to the present invention is made of a biodegradable resin, while being environmentally friendly and excellent in transparency (light transmittance of 50% or more and haze of 30% or less), and also using polycaprolactone having a number average molecular weight of 10,000 or less while maximizing softening characteristics. , There is an advantage that can prevent the bleed out which is a problem when using the caprolactone monomer.

Biodegradable polyester film according to the present invention prepared as described above, general packaging film, high-quality packaging film, general label, heat shrink label, agricultural mulching film, overlapping (overwrapping) film, paper lamination, non-woven lamination, disposable gown, wallpaper It can be used for lamination and flooring lamination.

Example

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are only examples of the present invention and the present invention is not necessarily limited thereto.

Example 1

10 parts by weight of polycaprolactone (PL500 from Perstorp) having a number average molecular weight of 500 and 90 parts by weight of polylactic acid (4032D from NatureWorks) having a melting temperature (T _m ) of 170 ° C. and a glass transition temperature (T _g ) of 65 ° C. Compounded with twinscrew type at.

The obtained resin was melt-extruded at 180 ° C. and brought into close contact with a casting roll at 15 ° C., stretched at 80 ° C. at 3.0 times in the longitudinal direction, and stretched at 110 ° C. at 4.0 times in the transverse direction to obtain a sheet. This was heat-set at 90 degreeC, and the polyester film of thickness 20micrometer was obtained.

Example 2

A polyester film having a thickness of 20 μm was obtained in the same manner as in Example 1, except that polycaprolactone having a number average molecular weight of 1,000 (PL1000 manufactured by Perstorp) was heat-set at 100 ° C.

Example 3

20 parts by weight of polycaprolactone having a number average molecular weight of 1,000 and 80 parts by weight of polylactic acid (4032D from NatureWorks) having a melting temperature (T _m ) of 170 ° C. and a glass transition temperature (T _g ) of 65 ° C. at 185 ° C. as a twin screw type. Compounding.

The obtained resin was melt-extruded at 200 ° C. and brought into close contact with a casting roll at 10 ° C., stretched at 80 ° C. at 3.0 times in the longitudinal direction, and stretched at 105 ° C. at 4.0 times in the transverse direction to obtain a sheet. This was heat-set at 90 degreeC, and the polyester film of thickness 20micrometer was obtained.

Example 4

10 parts by weight of polycaprolactone (PL2000 from Perstorp) having a number average molecular weight of 2,000 and 90 parts by weight of polylactic acid (4032D from NatureWorks) having a melting temperature (T _m ) of 170 ° C. and a glass transition temperature (T _g ) of 65 ° C. Compounded with twinscrew type at.

The obtained resin was melt-extruded at 210 ° C. and adhered to a casting roll at 13 ° C., stretched at 90 ° C. at 3.0 times in the longitudinal direction, and stretched at 110 ° C. at 4.0 times in the transverse direction to obtain a sheet. This was heat-set at 150 degreeC, and the polyester film of 20 micrometers in thickness was obtained.

Example 5

10 parts by weight of polycaprolactone (PL5000 from Perstorp) having a number average molecular weight of 5,000 and 90 parts by weight of polylactic acid (4032D from NatureWorks) having a melting temperature (T _m ) of 170 ° C. and a glass transition temperature (T _g ) of 65 ° C. Compounded with twinscrew type at.

The obtained resin was melt-extruded at 200 ° C. and brought into close contact with a casting roll at 9 ° C., stretched at 95 ° C. at 3.0 times in the longitudinal direction, and stretched at 110 ° C. at 4.0 times in the transverse direction to obtain a sheet. This was heat-set at 150 degreeC, and the polyester film of 20 micrometers in thickness was obtained.

Comparative Example 1

Compounding 10 parts by weight of a caprolactone monomer having a molecular weight of 114.14 and 90 parts by weight of polylactic acid (4032D from NatureWorks) having a melting temperature (T _m ) of 170 ° C. and a glass transition temperature (T _g ) of 65 ° C. at 180 ° C. as a twin screw type It was.

The obtained resin was melt-extruded at 190 ° C. and brought into close contact with a casting roll at 20 ° C., stretched at 75 ° C. at 3.0 times in the longitudinal direction, and stretched at 95 ° C. at 4.0 times in the transverse direction to obtain a sheet. This was heat-set at 140 degreeC, and the polyester film of 20 micrometers in thickness was obtained.

Comparative Example 2

20 parts by weight of poly (butylene adipate-co-succinate) (PBAS) (EnPol G4460 from Irechem) with a number average molecular weight of 70,000, a melting temperature (T _m ) of 170 ° C. and a glass transition temperature (T _g ) of 65 80 parts by weight of polylactic acid (4032D manufactured by NatureWorks), which was 0 ° C., was compounded at 200 ° C. in a twin screw type.

The obtained resin was melt-extruded at 220 ° C. and brought into close contact with a casting roll at 18 ° C., stretched at 70 ° C. in 3.0 times in the longitudinal direction and at 85 ° C. in 3.9 times in the transverse direction to obtain a sheet. This was heat-fixed at 130 degreeC and the polyester film of thickness 20micrometer was obtained.

Comparative Example 3

20 parts by weight of polycaprolactone (Capa6500 from Perstop) having a number average molecular weight of 50,000 and 80 parts by weight of polylactic acid (4032D from NatureWorks) having a melting temperature (T _m ) of 170 ° C. and a glass transition temperature (T _g ) of 65 ° C. Compounded with twinscrew type at.

The obtained resin was melt-extruded at 200 ° C. and brought into close contact with a casting roll at 18 ° C., stretched at 90 ° C. at 3.0 times in the longitudinal direction, and stretched at 105 ° C. at 3.8 times in the transverse direction to obtain a sheet. This was heat-set at 95 degreeC, and the polyester film of 20 micrometers in thickness was obtained.

Comparative Example 4

A polylactic acid resin (4032D manufactured by NatureWorks) having a melting temperature (T _m ) of 170 ° C. and a glass transition temperature (T _g ) of 65 ° C. was melt-extruded at 220 ° C. and adhered to a casting roll of 15 ° C. to 3.0 in the longitudinal direction. It extended | stretched at 80 degreeC by boat, and extended | stretched at 100 degreeC by 3.9 times with respect to a lateral direction, and obtained the sheet | seat. This was heat-set at 140 degreeC, and the polyester film of 20 micrometers in thickness was obtained.

The composition and manufacturing process of the film according to each Example and Comparative Example are summarized in Table 1.

Test Example

The physical properties of the films prepared in Examples and Comparative Examples were evaluated in the following manner, and summarized in Table 1.

(1) vapor generation

The more steam is generated, the less fairness is, and the flexibility is reduced over time as the monomer escapes from the sheet.

◎: Steam is prominently generated at the T-Die extrusion port

X: Molten resin discharged stably without steam from the T-die extrusion port

(2) bleed out

The film was cut into 20 × ²⁰ cm ² and placed in a 150 ° C. hot air oven for 2 hours, and evaluated according to the following criteria.

(Double-circle): There is little lubricity of the film surface, and there is little slipperiness between films.

X: The lubricity of the film surface is large, and the slipperiness | lubricacy between films is large.

(3) initial elastic modulus

According to ASTM D 882, it was measured using a universal testing machine (UTM 4206-001, INSTRON Co., Ltd.). The initial elastic modulus (kgf / mm 2) value calculated by the program embedded in the installation was obtained. Lower initial elastic modulus provides greater flexibility.

(4) Haze

It was measured with a haze meter (SEP-H, Nihon Semitsu Kogaku, Japan) and used a C-light source.

(5) Pin Hole Resistance (Number)

Using Gelbo Flex (Gelbo Flex, Gelbo Co., USA) (Configuration-sample mounting table: 165mm, sample mounting diameter: 88mm, reciprocating movement distance: 125mm), rotation and reciprocation at a rotation angle of 450 degrees at room temperature for about 10 minutes After 450 times, the film was laid flat on white paper. After applying a conventional solvent-based nitroglycerin (NC) ink using a doctor blade on it, the ink spots appearing on the white paper were counted as the number of pinholes of the sample, and the average value obtained by repeating these measurements three times per sample was measured as the pinhole. The number was compared.

(6) thermal shrinkage of film

After the sample was cut into a length of 200 mm and a width of 15 mm in the direction to be measured and held for 5 minutes in an air circulation oven maintained at 100 ° C., the length of the film was measured to calculate shrinkage in the longitudinal and transverse directions according to the following equation. .

Shrinkage (%) = (length before shrink-length after shrink) / length before shrink x 100

(7) elongation and strength

Using a tensile strength tester (MODEL6021, INSTRON Co., Ltd.), the sample was cut to 5 cm or more in the direction orthogonal to the sample's main shrinkage direction and 15 mm in the main shrinkage direction, and then attached to clips at 5 cm intervals, followed by elongation at room temperature. The stress-strain curve until it was obtained was obtained. The force applied when the fracture occurred was set as the strength (kgf / mm ² ), and the elongation ratio until the fracture occurred as the elongation (%).

As can be seen in Table 1, it can be seen that the film of Examples 1 to 5 according to the present invention is superior in the properties of steam generation, bleed out, elastic modulus, pinhole resistance and haze, etc., compared to the films of Comparative Examples 1 to 4 Can be.

Particularly, in Comparative Example 1 in which the caprolactone monomer was compounded with polylactic acid, a small molecular weight of the caprolactone monomer was pyrolyzed during extrusion to generate a large amount of vapor, and bleed out occurred after extrusion, thereby decreasing flexibility and transparency. have.

In addition, in Comparative Example 2, poly (butylene adipate-co-succinate) having a number average molecular weight of 70,000 was used. This shows good thermal stability, but the haze is rapidly increased (30.50%), causing the film to lose transparency. In the case of Comparative Example 3, polycaprolactone having a number average molecular weight of 50,000 was used, and these had poor compatibility and kneading with polylactic acid, leading to a sharp increase in haze (45.80%) and very low transparency. This is not suitable for the packaging film that the internal product should be visible.

In addition, Examples 1 to 5 show that as the number average molecular weight of the polycaprolactone plasticizing the polylactic acid increases, that is, as the polycaprolactone chain lengthens, the elastic modulus and the number of pin holes decrease, thereby increasing flexibility.

In addition, in Comparative Examples 1, 2, and 4 without using polycaprolactone, it can be seen that the elastic modulus and the pinhole number are very large, and thus the film is easily broken.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, It is to be understood that the invention may be practiced within the scope of the appended claims.

Claims (9)

A biodegradable polyester film formed by compounding polycaprolactone and polylactic acid having a number average molecular weight (Mn) of 10,000 or less.
The method of claim 1,
Biodegradable polyester film having a number average molecular weight of the polycaprolactone 200 to 8,000.
The method of claim 1,
Biodegradable polyester film having a number average molecular weight of the polycaprolactone 500 to 5,000.
The method of claim 1,
A biodegradable polyester film, characterized in that the content of polycaprolactone and polylactic acid is 40:60 to 5:95 by weight.
The method of claim 1,
The polylactic acid has a melting temperature of 135 ℃ to 180 ℃, biodegradable polyester film.
The method of claim 1,
Biodegradable polyester film, characterized in that the film is drawn in at least one direction.
The method of claim 1,
The film has a thickness of 10 ㎛ to 300 ㎛, biodegradable polyester film.
a) compounding polycaprolactone having a number average molecular weight of 10,000 or less and polylactic acid to obtain a resin;
b) melting and extruding the resin to obtain an unstretched sheet; And
c) stretching and heat setting the unstretched sheet in at least one of longitudinal and transverse directions.
A packaging material comprising the biodegradable polyester film according to claim 1.