KR100493647B1 - Biodegradable Film - Google Patents

Abstract

The present invention kneads 30-90% by weight of linear low density polyethylene, 10-40% by weight of aliphatic polyester and 0-30% by weight of ethylene vinyl acetate copolymer, and 0.01-0.3 parts by weight of fatty acids and fatty acid esters based on 100 parts by weight of these resins. In addition, the present invention relates to a linear low density polyethylene base biodegradable film produced by kneading, extruding, pelletizing, and extruding in a blown film machine.

The biodegradable film according to the present invention is excellent in physical properties and processability, so that mass production is possible, and biodegradable by microorganisms in the soil, it can be used as various packaging materials, agricultural films, in particular, bags for garbage separation and the like.

Description

Biodegradable film

The present invention relates to a biodegradable film that is easy to process and has excellent physical properties. More specifically, a biodegradable aliphatic polyester and an automatic oxide are added to a linear low density polyethylene resin, which is a thermoplastic resin, and mixed in a kneader. The present invention relates to a biodegradable film produced by a one-step process of producing a biodegradable mixture by extrusion, pelletizing and a two-step process of film forming the prepared biodegradable mixture in a blown extruder.

In general, synthetic plastics, which are petrochemical products, have excellent physical properties (transparency, flexibility, rigidity), processability, and economic efficiency, compared to natural materials, and thus are used for various purposes such as industrial, agricultural, and commercial purposes. However, plastics have high microbial resistance and do not decompose in the natural ecosystem after disposal, which causes serious environmental pollution problems. Incineration and recycling methods have been implemented to solve the environmental pollution problem of plastics, but there are problems such as generation of toxic gas, difficulty of separate collection and cost, and environmental pollution by plastic only by incineration and recycling. Can not be solved fundamentally. Accordingly, research on degradable plastics that can decompose in natural ecosystems has attracted much attention from all over the world, including Korea.

Degradable plastics are largely divided into photo-degradable plastics and bio-degradable plastics. Degradable plastics that can be decomposed by sunlight (ultraviolet rays) have a cost problem and a hazard of added transition metals. In case of embedding plastic, there is a disadvantage that it cannot be disassembled. In particular, since most of the landfills are disposed of in Korea, there are questions about the effects of photodegradable plastics. Therefore, degradable resins that are most developed in Korea are biodegradable resins that are degraded in nature by microorganisms such as bacteria and bacteria.

Biodegradable resins were first disclosed in U.S. Patent Nos. 4,021,388 and 4,133,784, and Korean Patent Publication Nos. 90-6336, 91-8553, 95-13176, etc. The technique is described. However, the starch used as a biodegradable material in this technology exhibits high hygroscopicity, which causes difficulties in dispersing and film forming, and in which the starch is carbonized during processing, making it difficult to apply to commercial processes requiring long-term continuous production processing. there is a problem.

Recently, there has been a description of a process for producing aliphatic polyester (Korean Patent Publication Nos. 95-025072, 95-018272, 95-008690), and a technique for biodegradable resins filling aliphatic polyesters with polyolefin resins with starch. Although it was developed (Korean Patent Publication Nos. 94-000514 and 95-013175), the biodegradable films prepared according to the present invention have not been used in large quantities due to their poor physical properties and processability.

Therefore, the present invention is to provide a biodegradable film and a method of manufacturing the same that can be mass-produced excellent in physical properties and processability.

To this end, according to the present invention, 30-90% by weight of linear low density polyethylene, 10-40% by weight of aliphatic polyester and 0-30% by weight of ethylene vinyl acetate copolymer, and 100 parts by weight of fatty acids and fatty acid esters 0.01- There is provided a linear low density polyethylene base biodegradable film prepared by adding 0.3 parts by weight to a kneader, mixing the dough, extruding and pelletizing, and extruding in a blown film machine.

The inventors of the present invention have analyzed the physical properties of the aliphatic polyester-filled biodegradable films of the prior patents and the reason why they are not excellent. It is difficult to select the temperature, and secondly, the polyolefin resin used as the matrix resin is nonpolar because the aliphatic polyester used as the biodegradable filler is non-polar, so it is less compatible with each other and is not sufficiently kneaded in the film extruder during simple mixing. Figured out. Accordingly, the present inventors have found that the solution of the problem is firstly selecting the optimal raw material and secondly the best mixing method between the selected raw materials.

The inventors of the present invention selected aliphatic polyester and polyolefin resins as much as possible to solve the first problem and have as little melting point as possible, and to solve the second problem, step 2 to prepare a biodegradable film. The biodegradable mixture in which the aliphatic polyester, polyolefin and autooxide are uniformly melt mixed before final film molding is prepared, and the film is formed from the prepared biodegradable mixture to prepare a biodegradable film having excellent physical properties and processability. Was intended.

In consideration of physical properties and melting points of each other, in the preparation of the biodegradable film according to the present invention, linear low density polyethylene and ethylene vinyl acetate are used as polyolefin, and polyethylene succinate and polybutylene succinate are used as aliphatic polyester. It is most preferable to each.

In the present invention, a homogeneously mixed biodegradable mixture can be prepared using the kneader of FIG. 1, the twin feeder of FIG. 2, and the single screw extruder. In the mixing chamber of FIG. 1, the aliphatic polyester, the olefin resin, and the automatic oxide are mixed so that they can be mixed well. The sample mixed in FIG. 1 is melted and extruded by the apparatus of FIG. . This device is essential for processing the kneaded mass sample into pellets. The biodegradable mixture may be molded in a blown extruder to obtain a biodegradable film, which is excellent in processability, tensile strength and tear strength, and may be used for various applications such as various packaging materials, agricultural films, and garbage bag. .

Hereinafter, the content of the present invention will be described in detail.

As the matrix resin used for producing the biodegradable film of the present invention, linear low density polyethylene is preferable.

High density polyethylene has a large processing temperature difference from aliphatic polyester used as a biodegradable filler. When the processing temperature is set to aliphatic polyester, the high density polyethylene melt behavior is incomplete and film formation of these blends is impossible. When matched, the aliphatic polyethylene is too low in viscosity and the film formability of these blends is also markedly inferior.

Although low density polyethylene has a similar processing temperature range with aliphatic polyester, it is not suitable for various packaging materials or bags for waste separation because of poor physical film properties.

Therefore, in the present invention, linear low density polyethylene showing excellent basic physical properties after processing is used as the matrix resin. In particular, linear low density polyethylene produced by copolymerization from monomers such as butene-1, hexene-1 or octene-1 is preferable. Although the linear low density polyethylene obtained using butene-1 as a copolymerization monomer is inferior in the film properties of itself compared with the linear low density polyethylene obtained using octene-1, it is excellent in kneading property with aliphatic polyester. Its amount is preferably 30-90% by weight based on the total composition.

Furthermore, the said linear low density polyethylene and ethylene vinyl acetate resin which is a polyethylene and a vinyl acetate copolymer can also be mixed and used as a matrix resin. Ethylene vinyl acetate copolymer may be used in various kinds depending on the content of the vinyl acetate to be copolymerized (3-21%), the content is to be 30% by weight or less based on the total composition. If the content of the ethylene vinyl acetate copolymer exceeds 30% by weight, there is a problem in that the physical properties and opening properties of the film are rather reduced.

In the present invention, instead of using starch, which has high hygroscopicity and carbonization problems during processing, as a biodegradable filler, synthetic aliphatic polyester which is fully degradable and easy to manufacture in an ecosystem is used as a biodegradable filler.

As the aliphatic polyester, polyhydroxybutylate (PHB), polycaprolactone (PCL), polylactide (PL), polyethylene succinate (PES), polybutylene succinate (PBSU) and the like can be used. However, polyhydroxybutylate and polylactide have a high decomposition rate but are too expensive, and polycaprolactone has a low melting point (Tm = 67 ° C.), which makes it difficult to prepare a linear low density polyethylene resin and a blend. Therefore, when preparing a biodegradable film according to the present invention, it is preferable to use linear low density polyethylene and polyethylene succinate, polybutylene succinate or a mixture thereof, which are easy to prepare a blend, and use 10-40% by weight based on the total composition. do. If the aliphatic polyester is less than 10% by weight, the biodegradability does not meet the expectation. If the aliphatic polyester is more than 40% by weight, the biodegradable film is not only economically inferior, but the physical properties are deteriorated, making it unsuitable for general use such as garbage bags or shopping bags. do.

In the manufacture of the film according to the present invention, in addition to the auto-oxide which promotes film decomposition and a plasticizer for improving film properties may be added.

Automated oxides are combinations of unsaturated fatty acids and fatty acid esters with at least one double bond per molecule, where fatty acids attract the transition metals in the soil and fatty acid esters react with the induced transition metals to break the C = C bond. Acts to produce peroxides or hydroperoxides. It is preferable to use oleic acid as the fatty acid and ethyl oleate as the fatty acid ester, and add 0.01-0.3 parts by weight based on 100 parts by weight of the total resin composition using a mixture ratio of oleic acid and ethyl oleate at 50 to 50. Preferably, 0.05-0.2 parts by weight is added. If the amount of the autooxide is greater than 0.3 parts by weight, the surface of the autooxide is excessively spilled during film forming, which adversely affects the formability and appearance of the film. If the amount is less than 0.01 parts by weight, the effect of the autooxide is insignificant.

In order to improve the processability and film forming property of the film according to the present invention, an amide-based plasticizer may be added, and the amount thereof is preferably about 0.01 to 0.05 parts by weight based on 100 parts by weight of the total resin composition. As the plasticizer, oleamide and stearamide can be used as in the usual film.

Accordingly, the linear low density polyethylene base biodegradable aliphatic polyester film is based on 30-90% by weight of linear low density polyethylene, 10-40% by weight of aliphatic polyester and 0-30% by weight of ethylene vinyl acetate copolymer, and 100 parts by weight of these resins. It is preferable to contain 0.01-0.3 weight part of fatty acids and fatty acid ester.

In order to manufacture the biodegradable film according to the present invention, linear low density polyethylene or linear low density polyethylene and ethylene vinyl acetate resin are used as matrix resin, and aliphatic polyester which is a biodegradable filler, autooxide, plasticizer, etc. After kneading for 30 minutes in a kneader under a nitrogen atmosphere at 120 ° C., pelletized through an extruder to prepare a biodegradable mixture, and then processing the prepared biodegradable mixture in a 150-160 ° C. blown film machine to form a film. do.

The reason for using the nitrogen atmosphere kneader in the first step is to minimize the decomposition of aliphatic polyester when kneading to maintain excellent physical properties during film production.The kneading temperature of 120 ℃ is linear low density polyethylene and aliphatic The temperature is selected in consideration of the viscosity of the polyester. If the kneading temperature is significantly lower than 120 ℃ linear low-density polyethylene is not melted uniform mixing is difficult, and if it is significantly higher than 120 ℃ the viscosity of the aliphatic polyester is lowered and there is difficulty in uniform mixing. For the same reason, the lowest forming temperature of the linear low density polyethylene base film, 150-160 ° C., was selected as the optimal forming temperature of the aliphatic polyester filled biodegradable blown film.

The step 1 biodegradable mixture manufacturing process can be extended to the process of adding and melting and mixing various types of resins and various fillers as needed, and the mixing process is excellent, but the manufacturing process is generally simple and easy to use as a practical process. .

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the scope of the present invention is not limited thereto.

Examples 1-7

The matrix resin, the biodegradable filler, and the auto-oxide were mixed at a ratio so as to have the composition of Table 2 as the raw material of Table 1, and then kneaded for 30 minutes in a kneader (FIG. 1) at 120 ° C. in a nitrogen atmosphere to melt the components. After mixing, the resulting reactants were processed into melt-extruded pellets using a biaxial feeder and a single screw extruder (FIG. 2), and then dried in an oven at 60 ° C. for 12 hours. The dried material was transferred to a 50? Blown film forming machine (screw length to diameter ratio = 24, die gap; 1.5 mm, screen; # 80-40, processing temperature; 150-160 ° C., screw speed; 50-60 rpm). Film molding having a thickness of 40 μm was performed. The tensile strength, which is the mechanical property of the processed aliphatic polyester filled biodegradable film, was measured according to KS-M3001 and the tear strength according to ASTM D1004.

Comparative Examples 1 to 3

As a raw material of Table 1, a matrix resin, a biodegradable filler, and an autooxide were mixed at a predetermined ratio to have the same composition as in Comparative Example of Table 2, and then kneaded in a Henschel mixer for 30 minutes, and then the same 50 ψ as in Example In a new film forming machine, the film was formed under the same processing conditions and the physical properties thereof were analyzed.

As a result of the experiment, compared to Comparative Examples 1 to 3 using Henschel mixer, the physical properties of Examples 1 to 3 using a kneader, which is the method claimed in the present invention, the film formability and physical properties were significantly increased. In order to determine the degree of such physical property change, the physical property increase rate [Δ (%)] of the example was calculated. As a result of the calculation, the physical properties of the Example were increased in both the MD (Machine Direction) and the TD (Transverse Drection) directions, and in particular, the rate of increase of physical properties in the TD direction was remarkable. Among them, the increase rate of the physical properties of Example 2 based on LLDPE-A linear low density ethylene was the most remarkable.

In terms of the effect of the change of the copolymer monomer, in the case of the linear low density polyethylene alone base, Example 6 using the linear low density polyethylene in which the copolymer monomer is butene-1 was used as the matrix resin showed the best physical properties, but ethylene vinyl acetate (EVA) was used. At 10% addition, Example 2 using linear low density polyethylene in which octene-1 is a copolymerization monomer showed the best physical properties.

Example 8

Biodegradability test

Biodegradability tests were conducted according to ASTM G21-70.

The test method was sprayed with agar medium mixed aspergillus niger, penicillium funiculum and Trichoderma mixture mixed suspension of 4, after 4 weeks, divided into four stages according to the degree of mold cover.

0%: 0

10% or less: 1

10-30%: 2

30-60%: 3

60-100%: 4

The preparation method of the sample was the same as that of Example, and the composition and the degradability test results of the sample were as shown in Table 4.

As a result of the biodegradability test, as shown in Table 4, in the case of pure linear low density polyethylene film, no mold was generated, and it was found that as the amount of aliphatic polyester filling increased, the mold generation increased. Samples formulated with ethylene vinyl acetate in composition showed better biodegradability than samples packed with aliphatic polyester in pure low density polyethylene. It was found that biodegradable properties were decreased when oleic acid and ethyl oleate were not prescribed in the composition.

TABLE 1

Used raw materials

[표 2]

TABLE 2

Creation costs

TABLE 3

Properties

[표 4]

TABLE 4

Biodegradability test

According to the present invention, it is excellent in biodegradability, easy to form a film, and excellent in tensile strength and tear strength of the film after processing, which can be used for various uses such as various packaging materials, agricultural films and bags for separating and removing garbage. A sex film can be obtained.

1 is a kneader and mixing chamber used in the biodegradable film manufacturing process according to the present invention,

Figure 2 is a biaxial raw material feed port used in the biodegradable film manufacturing process of the present invention, a single screw extruder and pelletizing apparatus.

Claims (3)

30-90% by weight of linear low density polyethylene copolymerized using butene-1, hexene-1 or octene-1 as monomer, 10-40% by weight of aliphatic polyester and 0-30% by weight of ethylene vinyl acetate copolymer, and these resins A biodegradable film prepared by adding 0.01-0.3 parts by weight of fatty acids and fatty acid esters to a kneader, mixing the dough, extruding and pelletizing, and extruding in a blown film machine. The biodegradable film according to claim 1, wherein the aliphatic polyester is polyethylene succinate, polybutylene succinate or a mixture thereof. Linear low density polyethylene, aliphatic polyester, ethylene vinyl acetate copolymer, aliphatic polyester, ethylene vinyl acetate copolymer, fatty acid and fatty acid ester were added to the kneader, kneaded for 30 minutes at 120 ° C. under a nitrogen atmosphere, and pelletized by extrusion. The method for producing a biodegradable film according to claim 1 or 3, wherein the film is extruded in a blown film machine at 150 to 160 ° C.

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