KR100354496B1 - Preparation method of biodegradable resin composition and the composition thereof - Google Patents

Abstract

PURPOSE: A method for preparing a biodegradable resin composition and the composition prepared by the method are provided, to improve the interface adhesive strength between a matrix resin and starch, thereby enhancing the mechanical properties of the biodegradable resin composition. CONSTITUTION: The method comprises the steps of mixing 20-90 parts by weight of a biodegradable aliphatic polyester resin, 10-80 parts by weight of starch and 0.05-5 parts by weight of a metal-based catalyst homogeneously; and inserting the mixture into a twin screw extruder to induce the transesterification between the biodegradable aliphatic polyester resin and the starch, and extruding the biodegradable resin composition. Preferably the transesterification is carried out at a temperature of 150-220 deg.C. Optionally the composition comprises further 0.5-10 parts by weight of a lubricant, and 0.1-20 parts by weight of a plasticizer.

Description

Method for producing biodegradable resin composition and composition obtained by the method

The present invention relates to a method for producing a biodegradable resin composition and a composition obtained by the method. More specifically, by using a metal catalyst in a resin composition consisting of aliphatic polyester and starch, inducing a chemical bond by transesterification reaction between aliphatic polyester resin and starch during the extrusion process in a twin screw extruder, The present invention relates to a method capable of producing a biodegradable resin composition having excellent mechanical properties by improving interfacial adhesion at a low cost, and a biodegradable resin composition obtained by the method.

Plastics continue to increase in consumption from industrial materials to disposables and packaging because of their lightness, strength, ease of processing, and ease of disassembly. However, in recent years, as the concern about environmental problems is heightened and the problem of treating various solid wastes becomes serious, the problem of waste plastics is emerging as a problem. Various solid wastes, including plastics, have been treated mainly by landfilling, incineration and recycling, but these methods cannot solve the environmental pollution problem completely. Thus, as one solution to this problem, much attention has been paid to the development of biodegradable plastics that retain their function and structure during use but are once decomposed into water and carbon dioxide by microorganisms.

As known in the art, US Pat. No. 4,021,388 and EP 409,789 describe a technique for producing biodegradable plastics by mixing biodegradable starch, which is inexpensive and biodegradable, with non-degradable plastics such as polyethylene, polypropylene, and polystyrene. However, there is a disadvantage in that the physical properties are significantly lowered by the addition of starch and the starch is biodegraded upon disposal but other matrix resins remain undecomposed.

The inventions described in U.S. Patent Nos. 4,133,784 and 4,337,181 relate to a film production technique in which starch in a gelatinized state is added to an ethylene-acrylic acid copolymer. It is extremely fragile and has the disadvantage of poor biodegradability.

U.S. Pat.Nos. 5,254,607, 5,256,711, and 5,258,430 describe techniques using luxury starch, but not only require an apparatus for adding excessive amounts of water and plasticizer to gelatinize starch, but also suffer from poor processability. There is this.

Korean Patent Publication Nos. 94-11542, 94-11556, and 94-11558 induce reaction extrusion using an organic acid catalyst and a binder to induce chemical bonding of starch and polyethylene, but unreacted co-monomer remains. If the starch content is more than 30 parts by weight, it is difficult to overcome remarkable mechanical properties, and polyethylene used as a matrix resin has a disadvantage that it does not decompose.

An object of the present invention is to provide a method for producing a biodegradable resin composition having excellent processability and mechanical properties and low cost.

It is further an object of the present invention to provide a biodegradable resin composition obtained by the above production method.

As a result of efforts to achieve the above object, the present inventors induce a chemical bond by a transesterification reaction in a twin screw extruder using a metal catalyst in a resin composition composed of an aliphatic polyester resin having excellent biodegradability and starch in a particulate state, It was found that the biodegradable resin composition having excellent processability, biodegradability and mechanical properties can be prepared by improving the interfacial adhesion between the resin and the starch, and completed the present invention.

Hereinafter, the present invention will be described in detail.

The method for producing a biodegradable resin composition of the present invention is characterized by comprising the following steps:

A) a) 20 to 90 parts by weight of the biodegradable aliphatic polyester resin,

b) 10 to 80 parts by weight of starch and

c) 0.05 to 5 parts by weight of the metal catalyst

Mix uniformly,

B) The mixture is introduced into a twin screw extruder, and the biodegradable resin composition is extruded after inducing a transesterification reaction between the biodegradable aliphatic ester and the starch induced by the metal catalyst in the twin screw extruder.

In addition, the mixture may include 0.5 to 10 parts by weight of lubricant, 0.1 to 20 parts by weight of plasticizer.

The biodegradable resin composition obtained by the method of the present invention has excellent mechanical properties by improving the interfacial adhesion between the biodegradable aliphatic polyester resin and starch due to the transesterification reaction induced in the manufacturing process.

A) Biodegradable aliphatic polyester resins used as the matrix resin include polytetramethylene succinate, polytetramethylene adipate, polypropiolactone, polycaprolactone, polylactic acid, polyhydroxybutylate, polyhydroxy Butylate-barylate copolymers can be used, and the use of polycaprolactone is preferred.

The amount of polycaprolactone used in the present invention can be used up to 20 to 90 parts by weight, when 20 parts by weight or less is not easy to process, when more than 90 parts by weight economical aspect or biodegradation rate is lowered. Preferably 30 to 80 parts by weight may be used.

In general, starch is composed of linear amylose and branched amylopectin, and three hydroxyl groups per amylose glucose unit are hydrophilic and have strong hydrogen bonds. B) starch that can be used in the present invention includes corn starch, rice starch, potato starch, tapioca starch, wheat starch, sweet potato starch and the like, α-starch (pregelatinized starch), acid-treated starch, oxidized starch, cationic starch, Modified starch obtained by physically and chemically treating starch such as ester starch and ether starch may be used, and corn starch is preferable in view of the particle size and economical aspect of starch.

The amount of starch used can be used 10 to 80 parts by weight, less than 10 parts by weight economical advantage, less than 80 parts by weight is not easy to process. Preferably 20 to 70 parts by weight may be used.

C) Metal catalysts used to induce transesterification of starch with biodegradable aliphatic polyester resins include tetraethyl tin hydroxide, triethyl tin hydroxide, tetraphenyl tin hydroxide and triisobutyl tin. Organic tin compounds such as acetates, dibutyl tin diacetate, monobutyl tin chloride, tributyl tin chloride, monobutyl tin oxide, dididodecyl tin oxide, butylhydroxy tin oxide, zinc acetate, lead acetate, manganese acetate, calcium acetate, Metal salts such as lithium acetate and magnesium acetate, antimony compounds such as antimony trioxide and antimony acetate may be used, and these may be used alone or in combination of two or more thereof.

Titanium-based catalysts are inappropriate for use because they oxidize to titanium dioxide in the presence of water.

The amount of the metal catalyst used in the present invention can be used 0.05 to 5 parts by weight based on 100 parts by weight of the resin composition. Generally, the transesterification reaction in the reactor can be used as a small amount of catalyst, but the transesterification reaction using the twin screw extruder has a short residence time, so that the reaction hardly occurs when the amount of the catalyst is used at 0.05 parts by weight or less. When used, the amount of the catalyst is high, thereby reducing the molecular weight of the aliphatic polyester resin rather than the transesterification reaction, thereby lowering the physical properties of the final resin composition. Preferably 0.1 to 3 parts by weight is used.

Lubricants are added to improve the flowability of the resin composition and the releasability in the mold during resin composition preparation and molding processing. As the lubricant of the present invention, fatty acids such as lauric acid, myristic acid, palmitic acid and stearic acid, fatty acid esters such as glycerol monostearate and glycerol monooleate, ethylene bis stearamide, ester complexes and fatty alcohols are used. The said lubricant is used 1 type or in mixture of 2 or more types. In the present invention, the lubricant is added 0.5 to 10 parts by weight based on 100 parts by weight of the resin composition.

As a plasticizer used to improve physical properties and processability of the biodegradable resin composition, glycerin, ethylene glycol, polyethylene glycol, propylene glycol, sorbitol, or the like may be used. In the present invention, a plasticizer is used in an amount of 0.1 to 20 parts by weight based on the resin composition.

In order to induce transesterification in the extruder, high shear forces, long residence times and appropriate reaction temperatures must be maintained. Therefore, the present invention used a screw that can maintain a high shear force and a long residence time, the reaction temperature was maintained at 150 to 220 ℃. When the reaction temperature is 150 ℃ or less, the transesterification reaction hardly occurred, and the starch carbonization phenomenon appeared at 220 ℃ or more.

The biodegradable resin composition according to the present invention is prepared by mixing the biodegradable aliphatic polyester with starch, a metal catalyst, a lubricant, and a plasticizer as appropriate, and is equipped with a screw capable of maintaining high shear force and long residence time. After the transesterification reaction at a temperature of 150 to 220 ℃ using a twin screw extruder, it is extruded, cut into a pelletizer and prepared in pellet form. The average moisture content of the pellets thus prepared is 1 to 2 parts by weight based on the resin composition.

The biodegradable resin composition of the present invention is a compression molding film, a flat film, and a blow molding machine using an extruder for manufacturing disposable injections, bottles, sheets, packaging materials, and films such as golf tee through injection molding, blow molding, extrusion molding, and thermoforming. It can be produced in a new film.

In addition, using the biodegradable resin composition as a master batch, polyethylene, polypropylene, polystyrene, polyvinylacetate, polyethylene terephthalate, polybutylene terephthalate, polyvinyl chloride, styrene-acrylonitrile copolymer, acrylonitrile-butadiene It can be used as a biodegradable resin by mixing with a thermoplastic resin such as styrene copolymer and polycarbonate.

The biodegradable resin composition prepared according to the present invention measured tensile strength and tensile elongation according to ASTM D 638, and physical properties such as impact strength (1/4 inch specimen) according to ASTM D 256.

In addition, in order to examine the degree of biodegradability of the resin composition prepared by the mold resistance test method (ASTM G 21-70) 21 days incubation in accordance with the mold was covered on the surface of the 5 × 5 × 0.3cm specimens as follows. The biodegradability was measured by dividing.

At 0%: 0

10% or less: 1

10-30%: 2

30-60%: 3

60-100%: 4

The present invention will be described in detail with reference to the following Examples and Comparative Examples, and the physical properties of the resin compositions prepared in Examples and Comparative Examples are measured, and the results are shown in Table 1.

However, the present invention is not limited to the examples.

Example 1

40 parts by weight of corn starch (water content 13%), 60 parts by weight of polycaprolactone, which is a biodegradable aliphatic polyester resin, 2 parts by weight of lithium acetate and 2 parts by weight of stearic acid, uniformly mixed with 100 parts by weight of the composition, Using a twin screw extruder with a L / D of 35 with a screw that can induce high shear and long residence time, it is extruded at 190 ° C and extruded to produce pellets. Was measured and biodegradability experiment was performed. Table 1 shows the physical property values and biodegradation results measured through the above experiments.

Example 2

Except that 20 parts by weight of corn starch (13% water content) and 80 parts by weight of polycaprolactone under the experimental conditions of Example 1 was carried out in the same manner as in Example 1, the results are shown in Table 1.

Example 3

Except for using 60 parts by weight of corn starch (water content 13%) and 40 parts by weight of polycaprolactone under the experimental conditions of Example 1, it was carried out in the same manner as in Example 1, the results are shown in Table 1.

Example 4

The experiment was carried out in the same manner as in Example 1, except that 70 parts by weight of corn starch (13% of water), 30 parts by weight of polycaprolactone, and 5 parts by weight of glycerin as a plasticizer were used in the experimental conditions of Example 1, and the results are shown in Table 1 below. Shown in

Example 5

The catalyst was carried out in the same manner as in Example 1 except that 0.1 parts by weight of monobutyl tin oxide was used for the biodegradable resin composition under the experimental conditions of Example 1, and the results are shown in Table 1.

Example 6

The catalyst was carried out in the same manner as in Example 1 except that 0.5 parts by weight of dibutyltin acetate was used for the biodegradable resin composition under the experimental conditions of Example 1, and the results are shown in Table 1.

Example 7

Except that 1.5 parts by weight of manganese acetate was used for the biodegradable resin composition under the experimental conditions of Example 1, it was carried out as in Example 1, the results are shown in Table 1.

Example 8

Except that 3 parts by weight of antimony trioxide was used for the biodegradable resin composition under the experimental conditions of Example 1, it was carried out as in Example 1, the results are shown in Table 1.

Example 9

Except that 1 part by weight of calcium acetate was used for the biodegradable resin composition under the experimental conditions of Example 1, it was carried out in the same manner as in Example 1, the results are shown in Table 1.

Example 10

Except that 1.5 parts by weight of magnesium acetate was used for the biodegradable resin composition under the experimental conditions of Example 1, it was carried out in the same manner as in Example 1, the results are shown in Table 1.

Comparative Example 1

The experiment was carried out in the same manner as in Example 1 without using a catalyst in the experimental conditions of Example 1, the results are shown in Table 1.

Comparative Example 2

Except for using 2 parts by weight of lithium acetate as a catalyst in the experimental conditions of Example 1 and reacted and extruded at 130 ℃ was carried out in the same manner as in Example 1, the results are shown in Table 1.

Comparative Example 3

Except for using 2 parts by weight of lithium acetate as a catalyst in the experimental conditions of Example 1 and reacted and extruded at 230 ℃ was carried out in the same manner as in Example 1, the results are shown in Table 1.

TABLE 1

Example Starch content (parts by weight) Catalyst content (parts by weight) Tensile Strength (kg / cm ² ) Impact Strength (kg.cm/cm) Elongation * (%) Machinability ** Exploded view One 40 2 110 32 N.B ○ 4 2 20 2 130 38 N.B ○ 4 3 60 2 160 15 350 ○ 4 4 70 2 135 10 160 △ 4 5 40 0.1 120 9 310 ○ 4 6 40 0.5 115 25 N.B ○ 4 7 40 1.5 125 34 N.B ○ 4 8 40 3 120 22 N.B ○ 4 9 40 One 125 29 N.B ○ 4 10 40 1.5 123 35 N.B ○ 4 Comparative example One 40 0 115 5 180 ○ 4 2 40 2 116 5.2 192 △ 4 3 40 2 96 6.1 210 △ 4 *: When tensile specimens are not broken at elongation of 500% or more, N.B is indicated **: Workability during extrusion and injection (○: Excellent, △: Good, X: Poor)

As can be seen from the above examples and the biodegradable resin composition obtained by the production method of the present invention it was found that the mechanical properties and biodegradability is also superior to the biodegradable resin composition of the comparative example.

Claims (8)

A method for producing a biodegradable resin composition, comprising the following steps: A) a) 20 to 90 parts by weight of the biodegradable aliphatic polyester resin, b) 10 to 80 parts by weight of starch and c) 0.05 to 5 parts by weight of the metal catalyst Uniformly mixing, B) injecting the mixture into a twin screw extruder and inducing a transesterification reaction between the biodegradable aliphatic ester and the starch induced by the metal catalyst in the twin screw extruder and then extruding the biodegradable resin composition. The method of claim 1, wherein a) the biodegradable aliphatic polyester is polytetramethylene succinate, polytetramethylene adipate, polypropiolactone, polycaprolactone, polylactic acid, polyhydroxybutylate, polyhydroxybutylate A method for producing a biodegradable resin composition, characterized in that it is selected from the group consisting of barylate copolymers. The starch according to claim 1 or 2, wherein the starch is pure starch of corn starch, rice starch, potato starch, tapioca starch, wheat starch, sweet potato starch, α-starch, acid treated starch, oxidized starch, amphoteric starch, ester. A method for producing a biodegradable resin composition, characterized in that selected from the group consisting of modified starches subjected to physical and chemical treatments of starch and starch of ether starch. 3. The metal catalyst of claim 1, wherein the metal catalyst is tetraethyl tin hydroxide, triethyl tin hydroxide, tetraphenyl tin hydroxide, triisobutyl tin acetate, dibutyl tin diacetate, monobutyl tin Chloride, tributyl tin chloride, monobutyl tin oxide, dododecyl tin oxide, organic tin compounds of butylhydroxy tin oxide, zinc acetate, lead acetate, manganese acetate, metal acetates of calcium acetate, lithium acetate and magnesium acetate, antimony trioxide, A method for producing a biodegradable resin composition, characterized in that at least one kind selected from the group consisting of antimony compounds of antimony acetate. The method for producing a biodegradable resin composition according to claim 1, wherein the extrusion temperature for inducing a transesterification reaction is 150 to 220 캜. The method for producing a biodegradable resin composition according to claim 1 or 5, wherein the twin screw extruder is equipped with a screw capable of maintaining a high shear force and a long residence time. The method for producing a biodegradable resin composition according to claim 1 or 2, wherein the mixture further contains 0.5 to 10 parts by weight of a lubricant and 0.1 to 20 parts by weight of a plasticizer. A biodegradable resin composition obtained according to the method of claim 1.