KR100428687B1 - Biodegradable polyester resin composition which has superior tear strength - Google Patents

Abstract

The present invention relates to a biodegradable polyester resin composition reinforced with tear strength, and fully biodegradable aliphatic polyesters and aromatic-aliphatic polyester resins, and biodegradation containing polylactic acid as a component for improving mechanical properties, particularly tear strength. The present invention relates to a polyester resin composition. In addition, heat stabilizers, light stabilizers, light absorbers, lubricants, plasticizers, inorganic fillers, colorants, pigments, and the like may be added to these mixtures for the purpose of adjusting overall physical properties when forming into films.

Description

Biodegradable polyester resin composition reinforced with tear strength {BIODEGRADABLE POLYESTER RESIN COMPOSITION WHICH HAS SUPERIOR TEAR STRENGTH}

Plastic is widely used as an indispensable packaging material in modern life because of its cheap properties and low cost. However, the problem of environmental pollution caused by plastic products pouring out all over the world is getting serious day by day.

Polyethylene, polypropylene, polyethylene terephthalate (hereinafter referred to as 'PET') and the like are widely used as general packaging plastics. However, these materials may damage the incinerator because of high heat generation during combustion. In addition, plastic products remain almost decomposed due to their chemical and biological stability even when they are landfilled, causing problems such as shortening the life of landfills.

In order to solve this problem, low heat of combustion, decomposed in the soil, biodegradable plastics that can achieve the early stabilization of landfill by decomposing at landfill has been developed and applied to various applications.

The fact that aliphatic polyesters are biodegradable has long been known (see J. MACROMOL. SCI.-CHEM, A23 (3), pp. 393-409, 1986). Tear strength, tensile strength and elongation are known to be significantly lower than general-purpose polyolefin resins due to performance and molecular weight.

As an example, aliphatic polyester films containing succinic acid or adipic acid, or both and diol components as main structural units are flexible, have high elongation and impact resistance, and have excellent heat seal properties. I can make it and use it.

However, the aliphatic polyester has both a glass transition point and a crystallization point of less than or equal to room temperature, and it is difficult and opaque to inhibit the growth of crystals even if the aliphatic polyester is rapidly cooled after melt extrusion. In addition, when the film is too flexible and the printing, or other film, paper, metal thin film and the like laminated on the film, the film is pulled and stretched in the process, causing problems such as inconsistent printing or laminating uniformly.

In addition, when the aliphatic polyester is produced by condensation polymerization of aliphatic glycol and aliphatic dicarboxylic acid, a copolyester resin containing a part of aliphatic dicarboxylic acid as an aromatic component (hereinafter referred to as 'aromatic-aliphatic polyester resin') Although it is known that the biodegradability is greatly reduced by the aromatic component added to compensate for the problem of lack of physical properties of aliphatic polyester, it is biodegradable by the manufacturing method of Korean Patent Application Nos. 10-1999-0058816 and WO 96/25448. A method for producing improved physical properties while maintaining the properties has been published.

These aromatic-aliphatic polyester resins exhibit rubbery properties as copolymers, and when forming blown films alone, the inner surfaces of the films stick to each other, and various problems such as softening from the rolls during secondary processing such as printing are problematic. have.

MEANS TO SOLVE THE PROBLEM This inventor came to complete this invention as a result of earnestly examining in order to solve the above problems. That is, the gist of the present invention relates to a biodegradable polyester resin composition in which polylactic acid is added as a component for improving mechanical properties, particularly tear strength, to fully biodegradable aliphatic polyester and aromatic-aliphatic polyester resin. To these mixtures, thermal stabilizers, light stabilizers, light absorbers, lubricants, plasticizers, inorganic fillers, colorants, pigments and the like may be added for the purpose of adjusting various properties.

As a preferred embodiment of the present invention, polylactic acid is used as a component for improving mechanical properties, in particular, tear strength, based on 100 parts by weight of the resin containing the aliphatic polyester and the aromatic-aliphatic polyester in a weight ratio of 10:90 to 90:10. It consists of 3 to 65 parts by weight. To these mixtures, thermal stabilizers, light stabilizers, light absorbers, lubricants, plasticizers, inorganic fillers, colorants, pigments and the like may be added for the purpose of adjusting various properties.

Aliphatic polyesters include aliphatic (including cyclic aliphatic) containing succinic acid, dicarboxylic acid (or acid anhydride thereof), and aliphatic (including cyclic aliphatic) including any one or more selected from 1,4-butanediol and ethylene glycol. Polycaprolactone and resins prepared by condensation polymerization of glycols. In addition, a copolymer containing an aromatic dicarboxylic acid (or an acid anhydride thereof) containing aromatics in a molecular structure such as dimethyl terephthalate or terephthalic acid as a small amount of copolymers in an amount of 5 parts by weight or less in the total aliphatic polyester may be used. As described above, the copolymer containing 5 parts by weight or less of the aromatic component belongs to an aromatic-aliphatic polyester, but since the physical properties thereof are similar to those of the aliphatic polyester, it will be included here in the aliphatic polyester.

In addition, the aromatic-aliphatic polyester may include some of the aliphatic (including cyclic aliphatic) dicarboxylic acid (or its acid anhydride) components including succinic acid in the condensation polymerization of the aliphatic polyester in a molecular structure such as dimethyl terephthalate or terephthalic acid. It is resin manufactured by adding with aromatic dicarboxylic acid (or its acid anhydride) containing aromatic.

The polylactic acid polymer is a polymer containing L-, D- or DL-lactic acid units as a main component. The polylactic acid polymer may be a homopolymer of L- or D-lactic acid, a copolymer of L- and D-lactic acid, or may be a copolymer including other hydroxycarboxylic acid units as a small amount of copolymerization components. These homopolymers or copolymers may also contain small amounts of CHAIN EXTENDER residues.

The content ratio of the aliphatic polyester and the aromatic-aliphatic polyester is 10:90 to 90:10, preferably 20:80 to 80:20. In other words, the ratio of the aliphatic polyester component to the total of the aliphatic polyester component and the aromatic-aliphatic polyester component needs to be in the range of 10 to 90% by weight. If the ratio of the aliphatic polyester is less than 10% by weight, the rubber-like property of the aromatic-aliphatic polyester is strong, so that the films stick together. On the contrary, if the ratio of the aliphatic polyester exceeds 90%, the tear strength is high due to the high crystallinity of the aliphatic polyester. Lowers.

The content of the polylactic acid is 3 to 65 parts by weight, preferably 7 to 50 parts by weight based on 100 parts by weight of the total amount of the aliphatic polyester and the aromatic-aliphatic polyester. When the content of polylactic acid is less than 3 parts by weight, the improvement of mechanical properties is less. When the content of polylactic acid is more than 65 parts by weight, the elongation of the film is greatly reduced. As a result of the high melting point difference between the polylactic acid, aliphatic polyester and aromatic-aliphatic polyester, Due to poor workability, it is not suitable for use.

To these mixtures, thermal stabilizers, light stabilizers, light absorbers, lubricants, plasticizers, inorganic fillers, colorants, pigments and the like may be added for the purpose of adjusting various properties.

In order to mold the composition of the present invention into a film, the additive is compounded using a BANBURY MIXER, KNEADER or a twin screw extruder, and then molded into a blown film or a T-DIE film. In addition, the additive may be formed by a known method such as adding the additive to a high concentration of master batch. The film molding machine can be molded using the existing polyethylene film molding machine as it is.

The present invention can be understood in more detail by the following examples and comparative examples, the following examples are only for illustrating the present invention and are not intended to limit the protection scope of the present invention. In addition, the measurement and evaluation shown by the Example were performed on the conditions shown next.

(1) Tensile strength (ASTM D 638 method)

Using an INSTRON UTM 4520 tensile tester, the measurement was performed at a standard line spacing of 25 mm and a tensile speed of 500 mm / min at a temperature of 23 ° C. and a relative humidity of 50%. In addition, MD and the width direction were shown for the longitudinal direction of the film by TD.

(2) Elongation (ASTM D 638 Act)

Elongation until fracture of the film was determined under the same conditions as the tensile strength.

(3) Tear strength (ASTM D 1004 method)

Using an Instron UTM 4520 tensile tester, the measurement was performed at a tensile rate of 500 mm / min at a temperature of 23 ° C. and a relative humidity of 50%. In addition, MD and the width direction were shown for the longitudinal direction of the film by TD.

Example 1

80 parts by weight of 1,4-EnPol G8000 (Chemical Co., Ltd. Melt Index = 4 g / 10 min), an aromatic-aliphatic polyester made of a condensate of 1,4-butanediol and succinic acid, adipic acid and dimethyl terephthalate 20 parts by weight of EnPol G4600, an aliphatic polyester made from a condensate of butanediol, succinic acid and adipic acid (since Chemical Co., Ltd., Melt Index = 4.5g / 10min), LACTY 9030 made from polylactic acid (Japan, Shimadzu) Shimadzu Corporation product, weight average molecular weight 140,000, Tg = 60.5 ° C., 7 parts by weight, 1.5 parts by weight of calcium stearate (Songwon Industry) and 1.0 parts by weight of antioxidant, and pellets using twin screw extruder It was prepared in a state. Next, the obtained pellets were sufficiently dehumidified and molded into a film having a thickness of 30 μm using a single screw blown film extruder having a diameter of 40 mm. Using this film, specimens were fabricated, tensile strength, elongation and tear strength were measured, and the results are shown in Table 1.

Example 2

The film was prepared in the same manner as in Example 1 except that 20 parts by weight of the aromatic-aliphatic polyester EnPol G8000, 80 parts by weight of the aliphatic polyester EnPol G4600 and 7 parts by weight of the polylactic acid LACTY 9030 were added. Molded. At this time, the same amount of lubricant and antioxidant were added. Using the prepared film, the specimen was prepared, tensile strength, elongation and tear strength were measured, and the results are shown in Table 1.

Example 3-6

50 parts by weight of the aromatic-aliphatic polyester EnPol G8000 and 50 parts by weight of the aliphatic polyester EnPol G4600 were changed to 10, 20, 30 and 50 parts by weight of polylactic acid, respectively. After the film was molded. At this time, the same amount of lubricant and antioxidant were added. Using the prepared film, the specimen was prepared, tensile strength, elongation and tear strength were measured, and the results are shown in Table 1.

Comparative Example 1

80 parts by weight of the aromatic-aliphatic polyester EnPol G8000 and 20 parts by weight of the aliphatic polyester EnPol G4600, 1.5 parts by weight of calcium stearate and 1.0 parts by weight of antioxidant as pellets, and then pelleted in the same manner as in Example 1. After the production was carried out to form a film, the results are shown in Table 1.

Comparative Example 2

Except that 50 parts by weight of the aromatic-aliphatic polyester EnPol G8000 and 50 parts by weight of the aliphatic polyester EnPol G4600 was carried out in the same manner as in Example 1, the results are shown in Table 1.

Comparative Example 3

Except that 20 parts by weight of the aromatic-aliphatic polyester EnPol G8000 and 80 parts by weight of the aliphatic polyester EnPol G4600 was carried out in the same manner as in Example 1, the results are shown in Table 1.

Comparative Example 4

Except that 50 parts by weight of EnPol G8000, an aromatic-aliphatic polyester, 50 parts by weight of EnPol G4600, an aliphatic polyester, and 70 parts by weight of LACTY 9030, which is a polylactic acid, the remaining additive content and molding method were the same as in Example 1. The results are shown in Table 1.

In Examples 1 to 6 within the scope of the present invention it can be seen that the high tear strength by the addition of polylactic acid. However, as can be seen in Comparative Examples 1 to 3, the composition without polylactic acid is not applicable to a shopping bag or a trash bag requiring low tear strength because of low tear strength. In addition, when the amount of polylactic acid added is too large as in Comparative Example 4, workability is poor due to a large melting point difference (about 50 ° C) from aliphatic polyester, and elongation is greatly reduced.

TABLE 1

As can be seen in Table 1, the biodegradable polyester resin composition according to the present invention has been greatly improved in tear strength, and can be molded in a polyethylene film molding machine which is generally used, due to lack of conventional tensile strength and tear strength. It can be put to practical use by solving problems that cannot be applied to shopping bags or garbage bags, and can greatly contribute to environmental improvement by being fully biodegradable in the natural state.

Claims (5)

Biodegradable polyester resin composition, comprising 3 to 65 parts by weight of polylactic acid (PLA) based on 100 parts by weight of the aliphatic polyester and the total amount of the aromatic-aliphatic polyester. The biodegradable polyester resin composition according to claim 1, wherein the weight ratio of the aliphatic polyester and the aromatic-aliphatic polyester is 10:90 to 90:10. The aliphatic (cyclic) according to claim 1, wherein the aliphatic polyester comprises aliphatic (including cyclic aliphatic) dicarboxylic acid (or its acid anhydride) containing succinic acid, and any one or more selected from 1,4-butanediol and ethylene glycol. Aromatic dicarboxylic acid (or anhydride thereof) containing polycaprolactone and polycaprolactone prepared by condensation polymerization of glycol, and containing aromatics in molecular structures such as dimethyl terephthalate and terephthalic acid as small copolymers. Biodegradable polyester resin composition, characterized in that the copolymer containing less than 5 parts by weight of the total aliphatic polyester The method of claim 1, wherein the aromatic-aliphatic polyester comprises a portion of the aliphatic (including cyclic aliphatic) dicarboxylic acid (or acid anhydride thereof) containing succinic acid in the polycondensation of aliphatic polyester, such as dimethyl terephthalate, terephthalic acid, Biodegradable polyester resin composition characterized in that the resin produced by adding an aromatic dicarboxylic acid (or an acid anhydride thereof) containing an aromatic in the molecular structure The polylactic acid polymer according to claim 1, wherein the polylactic acid polymer is a homopolymer of L- or D-lactic acid, a copolymer of L- and D-lactic acid, or a copolymer including other hydroxycarboxylic acid units as a small amount of copolymerization components. Biodegradable polyester resin composition.