KR20020006930A - High molecular weight degradable film containing crosslinked potato starch and process for preparation thereof - Google Patents

Abstract

PURPOSE: A degradable polymer film containing the cross-linked potato starch and its preparation method are provided, which film is improved in tensile strength, elongation and tensile energy, and is degraded by heat and a microorganism rapidly. CONSTITUTION: The method comprises the steps of cross-linking potato starch by using 0.1-2.0 % epichlorohydrin; mixing the cross-linked potato starch and a polymer film by the same amount to prepare a master batch; mixing the master batch, a linear low density polyethylene and a prooxidant by the amount of 1-20 wt% of potato starch, 80-96 wt% of the polyethylene and 2-10 wt% of the prooxidant, extruding the mixture at a barrel temperature of 140-160 deg.C and at a screw speed of 15-25 rpm to make a chip; and extruding the chip at a barrel temperature of 110-160 deg.C and a screw speed of 45-65 rpm to make a cast film. Preferably the polymer film is polyethylene, polypropylene or polystyrene.

Description

High molecular weight degradable film containing crosslinked potato starch and process for preparation etc.

The present invention relates to a degradable polymer film containing crosslinked potato starch and a method for producing the same. More specifically, the present invention relates to a polymer film having excellent mechanical strength as well as excellent thermal decomposition and biodegradability by containing crosslinked potato starch and a method for producing the same.

Synthetic plastics are widely used as packaging materials for various purposes because of their excellent corrosion resistance, water resistance, and biological stability. However, since they are hardly decomposed in the natural environment when they are landfilled after use, environmental pollution due to waste plastics is becoming more serious. With a raised environmental pollution caused by plastic waste research and development of a possible 'biodegradable plastics' decomposed in nature it began in the 1970s (Wei, S. and ZL Nikolov. 1992. Accelerated degradation studies of starch-filled polyethylene films. Ind Eng. Chem. Res ., 31 (10): 2332). Among them, starch, which is a representative material of the natural product polymer, is relatively easy to obtain in large quantities, and is highly suitable for use as a filler for biodegradable films because of its excellent biodegradability and low price. Starch-based film for degradable, as well as raw starch (Griffin, JL 1974. Biodegradable fillers in thermoplastic.Adv. Chem. Ser . 134: 159.), As well as luxury starches (Otey, FH, AM Mark, CL Mehltretter and CR Russell. 1974. agricultural mulch. Ind. Eng. Chem . Prod. Res. Dev., 13:90, Otey, FH, RP Westhoff and WM Doane. 1980. Starch-based blown films. Ind. Eng. Chem. Prod. Res. Dev. , 19:..... .. 592, Otey, FH and RP Westhoff 1984. Starch-based films Preliminary diffusion evaluation Ind Eng Chem Prod Res Dev, 23:.. 284, Otey, FH, RP Westhoff and WM Doane. Starch-based blown films. 2. Ind. Eng. Chem. Res ., 26: 1659), polyethylene oxide (Kim, M., AL Pometto III, KE Johnson and AR Fratzke. 1994. Degradation studies of novel degradable starch- polyethylene plastics containing oxidized polyethylene and prooxidant.J. Environ.Polym.Degrad , 2:27) have also been used as fillers to improve the biodegradability of plastics. However, in the biodegradable film produced using starch, the weakness of the film appears. Therefore, in order to increase the film strength, a method of chemically modifying the surface of starch particles to enhance the affinity between starch and synthetic polymers has been studied. Otey et al. (Otey, FH, RP Westhoff and CR Russell. 1977. Biodegradable films from starch and ethylene-acrylic acid copolymer.Ind . Eng. Chem.Prod.Res. Dev ., 16 (4): 305) To develop, polyvinyl alcohol (PVA) and modified starch were mixed and used, and Swanson et al. (Swanson, CL, RP Westhoff and WP Doane. 1988. Modified starches in plastic films.Proceedings of the corn utilization conference II, Columbus, OH. Corn Growers Association, St, Louis, Mo) studied the effects of corn modified starch to improve the mechanical properties of biodegradable films. However, starch has very different physicochemical properties from source to source, and thus, when they are mixed with high molecular materials to form a film, the influence on the film varies widely. Therefore, in starch biodegradable film, the influence of starch source and modified starch should be studied. Biodegradation occurs as a result of living organisms such as bacteria, fungi and their metabolic intermediates (Griffin, JL 1977. Synthetic resin sheet material. US Patent. 4,021,388).

It has been widely used to evaluate the extent of the biodegradable polymer film changes in the physical properties of the film, changing the chemical nature of the film, a method of measuring a change in biological activity (Maddever, WJ 1989. Modified starch- based biodegradable plastics. Plastics engineering . pp31-34).

Starch crosslinking is a modification that strengthens the hydrogen bonding of particles by chemical bonds that act as bridges between molecules. Starch particles retain their properties by chemical bridges and are not easily destroyed. It also increases the fission resistance to regulate the release of amylose in the swollen starch particles to provide improved film properties. Because of these properties, cross-linked starch is not only used in the food industry but also modified starch, which is used in various fields such as textiles, paper, coatings, ion exchange resins, and film's anti-blocking agents (Rutenberg, MW and D. Solarek. 1984.Starch derivatives: production and uses.In: Starch Chemistry and Technology , 2nd ed. By RL Whistler, JN Bemiller and EF Paschall (eds.). Academic Press, New York, NY pp324-331, Wurzburg, OB 1987.Cross linked starches.In: Modified starches , properties and uses, ed. by OBWurzburg (ed) .CRS Press, Frorida.pp46-51).

The present inventors crosslink this starch by using starch extracted from potatoes as a raw material to improve the mechanical properties and degradability of the biodegradable film, and then produce a degradable polyethylene film containing crosslinked potato starch. As a result of evaluating the mechanical properties and the degree of decomposition of the present invention, the present invention was completed by confirming that the mechanical strength is superior to that of the film prepared using untreated potato starch without crosslinking, and that the decomposition by heat and the degradation by microorganisms are superior.

Accordingly, it is an object of the present invention to provide a degradable polymer film having excellent mechanical strength as well as excellent thermal and biodegradability by containing crosslinked potato starch.

Another object of the present invention to provide a method for producing the degradable polymer film.

The object of the present invention is to prepare a cross-linked potato starch-polymer film by crosslinking potato starch and then crosslinking potato starch to a polymer film, and measuring the mechanical strength, thermal decomposition and biodegradability of the film, respectively. This was achieved by comparing the mechanical strength, thermal decomposition and biodegradability of the polymer film containing untreated potato starch that was not crosslinked with the resulting values.

Hereinafter, the configuration of the present invention will be described.

FIG. 1 shows the carbonyl index of the crosslinked potato starch-polyethylene film of the present invention heat treated at 70 ° C. for 12 weeks.

Figure 2 shows the carbonyl index of the cross-linked potato starch-polyethylene film of the present invention inoculated with Pseudomonas aeruginosa (KCTC 2651) strain for 4 weeks.

Figure 3 shows the mechanical properties of the cross-linked potato starch-polyethylene film of the present invention inoculated with Pseudomonas aeruginosa (KCTC 2651) strain for 4 weeks.

Figure 4 shows the results of observing the surface of the cross-linked potato starch-polyethylene film of the present invention incubated by inoculating Pseudomonas aeruginosa (KCTC 2651) strain for 4 weeks with a scanning electron microscope (× 2,000) .

The present invention comprises the steps of adding epichlorohydrin to potato starch and crosslinking under alkaline conditions; Measuring the reaction yield of starch and epichlorohydrin and the degree of crosslinking of starch by measuring the amount of epichlorohydrin that did not react during the crosslinking reaction of the potato starch; Preparing a crosslinked potato starch-polyethylene film by mixing crosslinked potato starch with different degree of crosslinking, linear low density polyethylene (LLDPE) and prooxydant, and preparing a polyethylene film containing untreated potato starch as a comparative group; When the polyethylene film containing the untreated potato starch and the crosslinked potato starch was heat treated, respectively, and the carbonyl index, tensile strength, elongation rate, and tensile energy were measured, the crosslinked potato starch-polyethylene film of the present invention contained untreated potato starch. Confirming the faster decomposition by heat treatment; And chemically sterilized polyethylene film containing untreated potato starch and crosslinked potato starch, inoculated with Pseudomonas aeruginosa (KCTC2651) strain and incubated for 4 weeks, followed by carbonyl index and tensile strength of the film. , Elongation and tensile energy were measured and the film form was observed under a scanning electron microscope to confirm that the polyethylene film containing the cross-linked potato starch of the present invention had better biodegradability than that containing untreated potato starch. .

The polymeric materials usable in the film production in the present invention are polystyrene, polypropylene, polyethylene, preferably polyethylene.

The crosslinked potato starch contained in the polymer film in the present invention is 1 to 20% by weight, preferably 5 to 10% by weight.

In the present invention, the prooxydant contained in the polymer film is 2 to 10% by weight, preferably 5% by weight.

In the present invention, the polymer material contained in the polymer film is 80 to 96% by weight, preferably 85 to 90% by weight.

The experimental results obtained in the present invention were statistically analyzed using a SAS program (version 6.12) (SAS Institute, Inc., 1995).

Hereinafter, the specific method of the present invention will be described in detail with reference to Examples, but the scope of the present invention is not limited only to these Examples and Experimental Examples.

Example 1 Inventive Degradable Crosslinked Potato Starch-Polyethylene Film Preparation

First Step: Preparation of Crosslinked Potato Starch

Potato starch was extracted using alkaline immersion method (Lee Shin-young, Perfume, Cho Yong-Yong, Ju-Hyun Yoo, Lee Sang-Kyu. 1984. Suspension of Rice Starch and Flow Behavior of Gelatinized Liquids. Korean Journal of Food Science and Technology, 16 (1)), and Jane et al. , T., A. Xu, M. Radosavljevic and PA Seib. 1992. Location of amylose in normal starch granules.I. Susceptibility of amylose and amylopectin to cross-linking reagents.Cereal Chem ., 69: 405). Crosslink (CL) potato starch was prepared. That is, 100 g of potato starch was suspended in 166 mL of distilled water, stirred at room temperature for 2 hours, and then 0.1%, 0.5%, 1%, and 2% epichlorohydrin of the potato starch was added. 1M NaOH solution was added thereto to adjust the pH to 10.5, and the crosslinking reaction proceeded while stirring at room temperature for 24 hours. This was adjusted to pH 5.5 using acetic acid and the Whatman No. 2 filtered with filter paper, washed twice with the same amount of distilled water, washed once with 95% ethanol. The crosslinked starch obtained was dried at 40 ° C. for 48 hours and then passed through a 100 mesh sieve.

Second Step: Determination of Crosslinking Degree

In this process, the crosslinking of potato starch in the first process is carried out according to the method of Hamerstrand et al. (Hamerstrand, GE, BT Hofretter and CL Mehltretter. 1960. Determination of the extent of reaction between epichlorohydrin and starch. Cereal Chem ., 37: 519). After the reaction, the amount of unreacted epichlorohydrin was measured to calculate the reaction yield of starch and epichlorohydrin and the degree of crosslinking of starch. In other words, the epichlorohydrin remaining without reaction in the cross-linking was oxidized with periodate, which was then developed with chromotropic acid, and the absorbance was measured and measured at 570 nm. From this, anhydroglucose units per crosslink (AGU / CL) and molar degree of crosslinking (MDC) were calculated to indicate the degree of crosslinking.

As a result, as shown in Table 1, the yield of crosslinking reaction between starch and epichlorohydrin was 85% in the range of 75% to 91%. The amount of epichlorohydrin consumed without forming crosslinks in starch particles is less than 5% of the amount of epichlorohydrin reacted, so this value was calculated in consideration of the crosslinking degree. The molar crosslinking degree (MDC) of potato starch is In proportion to the amount of epichlorohydrin used (r ² = 0.9992) it was confirmed that the crosslinking of the starch was properly made.

Reaction yield and crosslinking result in potato starch crosslinking reaction Starch type Applied Epichlorohydrin Unreacted Epichlorohydrin Reacted Epichlorohydrin Reacted Epichlorohydrin Reaction yield AGU ¹ ) / crosslinked Crosslinked / 100AGU G per 100 g of starch (dry basis) Moles / starch 100 g (%) (MDC ²⁾ ) 0.1CL 0.1 0.02469 0.07531 0.000814 75.31 732 0.137 0.5CL 0.5 0.05935 0.44065 0.004760 88.13 124 0.807 1.0CL 1.0 0.14972 0.85028 0.009185 85.03 64 1.563 2.0CL 2.0 0.16439 1.83561 0.019829 91.78 30 3.333 ¹⁾ Number of anhydrous glucose ²⁾ Moly crosslinking degree

Third Step: Preparation of Crosslinked Potato Starch-Polyethylene Film

The crosslinked potato starch prepared in the first step was mixed with a linear low density polyethylene (LLDPE) and a prooxidant (IR1025, Novon International, INC., NY, USA) and mixed with cast ( cast) films were prepared as shown in Table 2. After drying the cross-linked potato starch in a vacuum oven to 0.3% or less, the starch and PE were mixed in the same amount and 50% masterbatch was prepared using a kneader (Haake Rheomex 3000, Germany) at 150 ° C and 50 rpm. I created a master batch. The temperature of the barrel in Haake Rheocord 90 (Germany) equipped with a single screw extruder (Rheomex 254) by mixing the master batch with LLDPE and prooxydant to contain 5% of each other cross-linked potato starch. A 0.5 cm chip was produced at 140 to 160 ° C. and a screw speed of 15 to 25 rpm. Five kinds of cast films were prepared using a single screw extruder at a barrel temperature of 110 to 160 ° C. and a screw speed of 45 to 65 rpm. Films made from untreated potato starch were also prepared under the same conditions in order to compare with films made from crosslinked potato starch.

Composition of Crosslinked Potato Starch-Polyethylene Film Film form Epichlorohydrin concentration (%) Crosslinked starch content (g) Prooxydant (g) ¹⁾ Polyethylene Natural / PE 0 50 50 900 0.1CL / PE 0.1 50 50 900 0.5CL / PE 0.5 50 50 900 1.0CL / PE 1.0 50 50 900 2.0CL / PE 2.0 50 50 900 ¹⁾ Prooxydant containing natural starch (10%), unsaturated substance (8.0%) and transition metal compound (0.2%) in linear low density polyethylene

Experimental Example 1: Mechanical Properties of the Crosslinked Potato Starch-Polyethylene Film of the Present Invention

The film prepared from the untreated potato starch and the crosslinked potato starch prepared in Example 1 was cut into strips of 1 × 3 cm, and then the instron (Instron; AGS-500A, Shimadzu, Japan) was used to Tensile strength, percent elongation, and tensile energy were measured. For the operation of Instron, the load cell was 50 kgf, the load range was 5, and the speed was 100 mm / min. Before the measurement by Instron, the film was measured after holding at least 40 hours in a 25 ℃, 50% thermo-hygrostat.

As a result, as shown in Table 3, the tensile strength, which means the force per unit area required to break the film, was higher than that of the cross-linked potato starch film and that of 1.0 CL starch. Significantly higher in one film. The elongation was significantly higher than the film made of cross-linked starch except the film made of 1.0 CL starch. The tensile energy, which means the work required to bring the film to break point, is also significantly higher than that of a film made from cross-linked starch, so that the mechanical strength of the film is increased by crosslinking the starch. It can be seen that the improvement.

Mechanical Properties of Crosslinked Potato Starch-polyethylene Films Film form Tensile strength (kgf / mm ² ) Elongation (%) Tensile Energy (kgfmm) Natural / PE 1.0253 ± 0.04 ^b 200.42 ± 19.71 ^c 62.979 ± 8.34 ^b 0.1CL / PE 1.2320 ± 0.03 ^ab 230.62 ± 32.78 ^ab 89.975 ± 14.28 ^a 0.5CL / PE 1.0492 ± 0.03 ^b 252.95 ± 35.78 ^a 87.125 ± 13.41 ^a 1.0CL / PE 1.5831 ± 0.94 ^a 217.11 ± 20.07 ^bc 87.625 ± 8.77 ^a 2.0CL / PE 1.304 ± 0.05 ^ab 227.35 ± 21.55 ^b 91.418 ± 10.10 ^a NOTE The mean ± SEM angle is the average of 10 repeated experiments. ^ad Means with different superscripts in each mechanical property are significantly different (p <0.05).

Experimental Example 2: The thermal decomposition degree of the crosslinked potato starch-polyethylene film of the present invention

In this experimental example, first, the thermal decomposition property of the film by FT-IR was investigated.

The film prepared from the untreated potato starch and the oxidized potato starch prepared in Example 1 was cut into strips of 1 × 3 cm and then heat treated every week for 12 weeks in a 70 ° C. forced air dry oven. IR was measured and the carbonyl index was obtained by the following equation.

And the thermally decomposed properties of the film by mechanical properties by measuring the tensile strength, elongation rate, and tensile energy of the film heat-treated weekly in the Instron (Instron) by the same method as the thermal decomposition property measurement method of the film by the FT-IR . The operating conditions of Instron were the same as those when measuring the mechanical properties of the film in Experimental Example 1.

Experimental results of the thermal decomposition properties of the film by FT-IR show that the carbonyl index of the film prepared with untreated potato starch during the 12-week heat treatment shows little change, while it is 0.1 CL starch. The carbonyl index increased after 4 weeks, and the film made with 0.5 CL starch and 2.0 CL starch increased after 5 weeks and the film produced with 1.0 CL starch showed carbonyl index after 6 weeks. It started to increase. In addition, at 12 weeks of heat treatment, the carbonyl index of the film made from untreated potato starch was very different from the carbonyl index of the film made from crosslinked potato starch. It was shown that the oxidative decomposition was faster by heat treatment than the film made from powder.

In addition, as a result of investigating the thermal decomposition property of the film by mechanical properties, as shown in Tables 4, 5, and 6, the mechanical property changes of the film heat-treated at 70 ° C. showed the carbonyl index according to the FT-IR spectrum ( It is generally consistent with the change of carbonyl index). Tensile strength, elongation, and tensile energy of the untreated potato starch were significantly reduced after 11 weeks, whereas the films made of 0.1 CL starch and 2.0 CL starch had 0.5 CL starch after 5 weeks. Films made with 1.0 CL starch showed a significant decrease in mechanical properties after 7 weeks (p <0.05), indicating that pyrolysis of film made with crosslinked potato starch was faster than that made with untreated potato starch. It was. In particular, the film made from 0.1 CL starch was thermally degraded from 5 weeks due to thermal degradation, the mechanical strength was weakened from 7 weeks and the mechanical strength could not be measured. The case where the mechanical characteristic value does not appear in the table is when the film is thermally decomposed by heat treatment and thus the mechanical characteristic value is not measured as the film is broken. Films made from 0.5 CL and 1.0 CL starch were thermally decomposed to the extent that their mechanical strength was lost from 9 weeks after heat treatment.

Tensile Strength of Crosslinked Potato Starch-Polyethylene Film Heated at 70 ° C. for 12 Weeks week Film form Natural / PE 0.1CL / PE 0.5CL / PE 1.0CL / PE 2.0CL / PE 0 1.049 ^a 1.243 ^a 1.077 ^a 1.296 ^a 1.320 ^a One 1.114 ^a 1.135 ^ab 0.942 ^b 1.161 ^ab 1.113 ^b 2 1.041 ^a 1.149 ^ab 0.952 ^b 1.222 ^ab 1.098 ^b 3 1.071 ^a 1.056 ^b 0.870 ^b 1.069 ^b 1.032 ^b 4 1.031 ^a 1.112 ^b 0.895 ^b 1.200 ^ab 1.077 ^b 5 0.978 ^a 0.873 ^c 0.878 ^b 1.124 ^ab 0.895 ^c 6 0.933 ^a 0.619 ^d 0.862 ^b 1.162 ^ab 0.853 ^cd 7 0.989 ^a - 0.702 ^cd 0.887 ^c 0.590 ^e 8 1.041 ^a - 0.757 ^c 0.856 ^c 0.790 ^d 9 0.956 ^a - 0.728 ^cd 0.782 ^cd - 10 0.969 ^a - 0.623 ^d 0.647 ^d - 11 0.572 ^b - - - - 12 0.136 ^c - - - - [Note] Unit: kgf / mm ² Each value is the average of 4 replicates. ^ae The mean with different superscripts for each type of film is significantly different (p <0.05)

Elongation of Crosslinked Potato Starch-Polyethylene Film Heated at 70 ° C. for 12 Weeks week Film form Natural / PE 0.1CL / PE 0.5CL / PE 1.0CL / PE 2.0CL / PE 0 210.5 ^a 253.1 ^a 279.8 ^a 227.4 ^a 231.7 ^a One 197.2 ^a 186.1 ^b 211.2 ^b 196.0 ^bc 184.5 ^bc 2 198.2 ^a 192.6 ^b 179.9 ^b 210.9 ^ab 181.7 ^bc 3 183.6 ^a 192.2 ^b 188.5 ^b 171.6 ^c 199.2 ^b 4 178.7 ^a 206.0 ^b 196.0 ^b 193.1 ^bc 168.4 ^c 5 155.3 ^a 46.8 ^c 184.3 ^b 174.8 ^c 59.0 ^d 6 150.0 ^a 3.3 ^d 121.1 ^c 200.7 ^abc 15.3 ^e 7 148.2 ^a - 22.1 ^d 30.7 ^d 3.6 ^e 8 175.0 ^a - 7.6 ^d 9.4 ^d 6.4 ^e 9 157.5 ^a - 4.4 ^d 5.9 ^d - 10 145.1 ^a - 3.1 ^d 5.6 ^d - 11 19.9 ^b - - - - 12 3.5 ^b - - - - [Unit] units; % Each value is the average value repeated four times. ^ae The mean with different superscripts for each type of film was significantly different (p <0.05).

Tensile Energy of Crosslinked Potato Starch-Polyethylene Films Heat-treated at 70 ° C for 12 Weeks week Film form Natural / PE 0.1CL / PE 0.5CL / PE 1.0CL / PE 2.0CL / PE 0 67.5 ^a 99.3 ^a 97.8 ^a 92.5 ^a 95.8 ^a One 69.9 ^a 68.0 ^b 66.9 ^b 73.2 ^bc 65.0 ^b 2 67.0 ^a 72.2 ^b 57.7 ^b 83.0 ^ab 63.7 ^b 3 61.7 ^a 65.7 ^b 55.0 ^bc 58.3 ^d 65.5 ^b 4 58.5 ^a 73.7 ^b 58.9 ^b 74.3 ^bc 57.6 ^b 5 48.3 ^a 14.5 ^c 54.2 ^bc 63.1 ^cd 17.0 ^c 6 43.6 ^a 0.4 ^c 36.0 ^c 74.5 ^bc 3.7 ^d 7 47.0 ^a - 5.3 ^d 8.4 ^e 0.5 ^d 8 59.8 ^a - 1.7 ^d 2.0 ^e 1.2 ^d 9 52.0 ^a - 0.7 ^d 1.4 ^e - 10 48.2 ^a - 0.5 ^d 1.1 ^e - 11 3.5 ^b - - - - 12 2.6 ^b - - - - NOTES unit: kgf · mm ^ae from each kind of the film type with an average of different superscripts differ significantly (p <0.05).

Experimental Example 3: Biodegradability of Cross-linked Potato Starch-Polyethylene Film of the Present Invention

First Process: Chemical Sterilization of Film

The biodegradable film prepared from the untreated potato starch and the crosslinked potato starch prepared in Example 1 was cut into strips of 1 cm x 3 cm, respectively, and then, this was a universal disinfection solution (20 mL of bleach, 8 mL of sterilization). Tween 80, 972 mL sterile distilled water) was added and stirred for 1-2 hours. This was transferred to 1 L sterile distilled water using sterile tweezers and stirred for 1 hour. The film was washed successively with 95% ethanol, 70% ethanol and finally sterile distilled water.

Second Process: Inoculation and Cultivation of Pseudomonas aeruginosa

The film sterilized by the first process was placed in a Erlenmeyer flask containing sterilized nutrient broth and cultured for one day at 35 ° C. and 100 rpm to observe the sterilization degree of each film against microorganisms. That is, after culturing for 24 hours to confirm the sterile state of the film by observing the transparency of the nutrient broth (nutrient broth) of the flask containing the film, the flask was inoculated with Pseudomonas aeruginosa (KCTC 2651) strain. This was incubated for 4 weeks with stirring at 100 rpm in a 35 ℃ incubator. The control group was cultured through the same process without inoculating Pseudomonas aeruginosa (KCTC 2651) strain.

Third Process: Determination of Biodegradability of Film

In this process, first, the films incubated for 4 weeks by the second process were transferred to the sterile water from the Erlenmeyer flask, and then immersed in 70% ethanol for 30 minutes in order to measure the biodegradability of the film by FT-IR. . The film was transferred to petridish and dried in a 45 ° C. oven for 8 hours. The carbonyl index was determined by measuring the FT-IR spectrum on the dried film. In addition, in order to measure the biodegradability of the film by mechanical properties, the dried film was maintained for 40 hours at 50% relative humidity in the same manner as the method for measuring the decomposition of the film by FT-IR of Experimental Example 2, followed by Instron (Instron Tensile strength, elongation rate, and tensile energy were measured using. The operating conditions of the Instron were the same conditions as when measuring the mechanical properties of the film of Experimental Example 1.

As a result, as shown in FIG. 2, according to the biodegradation characteristic analysis of the film by FT-IR, the film prepared with untreated potato starch was treated with Pseudomonas aeruginosa (KCTC 2651) strain and Pseudomonas. Although there was little difference in the carbonyl index in the control film that was not treated with the Pseudomonas aeruginosa (KCTC 2651) strain, the film prepared with the crosslinked potato starch was obtained from Pseudomonas ae except 1.0 CL / PE film. Films treated with Pseudomonas aeruginosa (KCTC 2651) strains showed higher carbonyl indices than in control films. This means that the film made with cross-linked starch is more easily attacked by enzymes produced by microorganisms, and thus more carbonyl groups are produced by the decomposition of the Starch / PE film more easily.

The change in the mechanical properties of the film was consistent with the change in carbonyl index by the FT-IR spectrum as shown in FIG. 3. In other words, the film prepared with untreated potato starch showed little change in mechanical properties between Pseudomonas aeruginosa ( KCTC 2651) treated film and the control film, whereas most of the films made with cross-linked potato starch were Pseudomonas aeruginosa. Almost all mechanical properties of the film treated with Pseudomonas aeruginosa ( KCTC 2651) were lower than those of the control film. Particularly, in the film prepared with 0.1 CL starch and 1.0 CL starch, the film treated with Pseudomonas aeruginosa (KCTC 2651) strain showed significantly lower tensile strength, elongation rate and tensile energy than the control group, resulting in biodegradation of the film. Showed that it happened actively. These results indicate that the crosslinked starch provides more suitable environmental conditions for the metabolism of Pseudomonas aeruginosa (KCTC 2651) strain than untreated potato starch, making the film more readily biodegradable by the microorganism.

4th process: measuring the shape of a film

The form of the film incubated in the second step was observed at a magnification of 2,000 times using a scanning electron microscope (Hitachi S-4200, Japan).

As a result, as shown in Figure 4, the control film (A) was almost unchanged from the initial film form, but in the film treated with Pseudomonas aeruginosa (KCTC 2651) strain produced in the metabolic process of microorganisms The starch particles and film were slightly destroyed by the attack by the enzyme.

Most experiments, such as landfill, to measure the biodegradability of a film take 1 to 10 years under conditions of extreme changes in temperature and humidity.However, in this experiment, the biodegradability of a film can be measured within a short period of time under certain conditions. there was.

As described above, the degradable polymer film of the present invention prepared by containing 1 to 20% by weight of potato starch cross-linked with 0.1 to 2.0% epichlorohydrin, as described through the above Examples and Experimental Examples The mechanical properties such as tensile strength, elongation, and tensile energy are superior to polymer films prepared by containing powder, and they are not only rapidly decomposed by heat but also biodegraded by microorganisms to minimize environmental pollution. And it is a very useful invention in environmental conservation industry.

Claims (3)

(a) crosslinking potato starch with 0.1-2.0% epichlorohydrin; (b) preparing a master batch by mixing the same amount of crosslinked potato starch and the polymer film in the step (a); (c) In the step (b), the masterbatch and linear low density polyethylene and prooxydant are mixed to contain 1 to 20% by weight of crosslinked potato starch, 2 to 10% by weight of prooxydant and 80 to 96% by weight of polyethylene. Producing a chip by extrusion molding at a barrel temperature of 140 ° C. to 160 ° C. and a screw speed of 15 to 25 rpm; And (d) extruding the chips produced in the step (c) under conditions of a barrel temperature of 110 ° C. to 160 ° C. and a screw speed of 45 to 65 rpm. Method for producing a degradable polymer film. The method of claim 1, wherein the polymer material is polyethylene, polypropylene, or polystyrene. Degradable polymer film prepared by the method of claim 1.