KR100903885B1 - Aerobic biodegradable compound using poly lactic acid and method for producing it - Google Patents

Abstract

A biodegradable compound using a poly lactic acid is provided to prevent environmental contamination due to decomposition by ultraviolet irradiation or microorganism in application to plastic products and to maintain early strength before certain time is passed. A method for manufacturing a biodegradable compound using a poly lactic acid comprises the steps of: mixing poly lactic acid 10~55 weight%, ground calcium carbonate 7~15 weight%, aliphatic polyester 10~30 weight% and methylmethacrylate 1~7 weight% to produce a first substance; mixing powdered milk 10~20 weight%, biodegradable aid 1~5 weight% and photo-degrading agent 1~4 weight% to produce a second substance; mixing the lactose 3~10 weight% and ethyl acetate 1~5 weight% to produce a third substance; mixing the first substance, second substance, and third substance and then extracting the molded crystals; and cooling the extruded composition to produce biodegradable composition.

Description

Biodegradable composition using polylactic acid and its preparation method {Aerobic Biodegradable Compound using Poly Lactic Acid and Method for Producing it}

The present invention relates to a biodegradable composition of a plastic resin using polylactic acid, and in particular, it is possible to biodegrade not only the biodegradable composition itself but also the base polymer of thermoplastic synthetic resins. Environment-friendly biodegradable composition using polylactic acid that can prevent environmental pollution and maintain its initial strength until a certain time since it is decomposed by microorganisms in nature after exposure or after a certain time has elapsed, and its It relates to a manufacturing method.

Plastic products that are widely used in cases, mulching films, and toy products are made of various synthetic resins because of their excellent properties, convenience, productivity, and price.However, they are highly used due to the seriousness of environmental pollution and waste treatment. Because of social costs, its use is regulated as a law.

For this reason, biodegradable products in which synthetic resins such as polyethylene are used as base polymers and mixed with natural ingredients such as starch have been developed, but even these products may be capable of degrading natural ingredients, but biodegradation of the base polymer itself is impossible. Since the base polymer is not decomposed later, it still has the fundamental problem of causing environmental pollution.

In addition, even if the base polymer of the synthetic resin biodegradation, there was a problem that it is difficult to secure a minimum strength maintenance period to enable the biodegradable product itself to exhibit the original function.

In addition, polylactic acid has the characteristics of high melting point and excellent heat resistance compared to other biodegradable materials, while low melting viscosity and low crystallization rate, so that the production efficiency in injection molding is poor. In order to provide practical use, it is necessary to improve the melt viscosity and the improvement of the crystallization rate, as well as the physical properties such as tensile strength by itself.

The present invention has been made to solve the problems of the prior art,

An object of the present invention is a polylactic acid that can be widely used in various plastic products because it can be naturally decomposed by soil microorganisms, even when exposed to the outside or embedded in the soil by irradiation with ultraviolet rays when a predetermined amount is mixed with the base polymer It is to provide a biodegradable composition and a method for producing the same.

Another object of the present invention is to maintain the initial strength of the biodegradable product initially when applied to the biodegradable product, and to be fully decomposed after a certain time, to combine product performance and eco-friendliness It is to provide a biodegradable composition using a polylactic acid and a method for producing the same.

Still another object of the present invention is to use a polylactic acid, which is a biodegradable material, and to supplement mechanical properties such as tensile force and elongation rate, which are limited only by polylactic acid, and a biodegradable composition using polylactic acid, which can be applied to various biodegradable products. It is to provide a manufacturing method.

Another object of the present invention is to remove the odor peculiar to the plastic resin when used in mixing with the base polymer of the plastic resin, as well as biodegradability using polylactic acid that can suppress the generation of black smoke, especially during incineration It is to provide a composition and a method of producing the same.

The present invention is implemented by the embodiment having the following configuration in order to achieve the above object.

According to one embodiment of the present invention, the biodegradable composition using polylactic acid according to the present invention is polylactic acid, heavy calcium carbonate, aliphatic polyester, lactose, ethyl acetate, methyl methacrylate, milk powder, biodegradation aid, photodegradant Characterized in that made by mixing.

According to another embodiment of the present invention, the biodegradable composition using polylactic acid according to the present invention is 10 to 55% by weight of polylactic acid, 7 to 15% by weight of heavy calcium carbonate, 10 to 30% by weight of aliphatic polyester, 3 to lactose 10 wt%, ethyl acetate 1-5 wt%, methyl methacrylate 1-7 wt%, powdered milk 10-20 wt%, biodegradation aid 1-5 wt%, photodegradant 1-4 wt% do.

According to another embodiment of the present invention, the biodegradable composition using the polylactic acid according to the present invention is 44% by weight of polylactic acid, 10% by weight of heavy calcium carbonate, 15% by weight of aliphatic polyester, 5.5% by weight of lactose, ethyl acetate 2.5 Weight%, methyl methacrylate 3.5% by weight, powdered milk 14.5% by weight, biodegradation aid 3% by weight, characterized in that consisting of 2% by weight of a photodegradant.

According to another embodiment of the present invention, the method for producing a biodegradable composition using a polylactic acid according to the present invention is a mixture of polylactic acid, heavy calcium carbonate, aliphatic polyester and methyl methacrylate to produce a first material, Powdered milk, biodegradation aids and photodegradants are mixed to produce a second substance, lactose and ethyl acetate are mixed to form a third substance, and the first substance, crystals formed by mixing the second substance and the third substance And extruding the cooled, extruded composition to produce a biodegradable composition.

The present invention can obtain the following effects by the configuration, combination, and use relationship described above with the present embodiment.

According to the present invention, when a predetermined amount is mixed with the base polymer, polylactic acid that can be widely used in various plastic products can be naturally decomposed by microorganisms in the soil even when exposed to the outside by UV irradiation or embedded in the soil. Provided are biodegradable compositions and methods for their preparation.

The present invention is to maintain the initial strength of the biodegradable products initially when applied to biodegradable products, and after a certain period of time to be fully decomposed, polylactic acid to combine product performance and eco-friendliness It provides a biodegradable composition and a method for producing the same.

The present invention provides a biodegradable composition using polylactic acid that can be applied to various biodegradable products by using a polylactic acid, a biodegradable material, and supplementing mechanical properties such as tensile strength and elongation rate, which are limited only by polylactic acid. to provide.

The present invention provides a biodegradable composition using polylactic acid that can remove odors peculiar to plastic resins, and especially suppresses the generation of black smoke upon incineration when used in a mixture of plastic resin base polymers. Provide a method.

Applicants describe preferred embodiments of the present invention described below.

Biodegradable composition using a polylactic acid according to the present invention, the polylactic acid, heavy calcium carbonate, aliphatic polyester, lactose, ethyl acetate, methyl methacrylate, powdered milk, biodegradation aid, photodegrading agent mixed and extruded do.

Herein, polylactic acid (PLA) refers to a polymer of a low molecular weight compound (monomer) called lactic acid, and generally has a property of being hydrolyzed by water to lower molecular weight and then degraded by microorganisms. Heavy calcium carbonate is especially added to plastic resins to improve strength stability, improve fluidity and dispersibility, and make it easy to process. Aliphatic polyesters are usually biodegradable by replacing hydrocarbons in the molecular structure of non-biodegradable aromatic polyesters with hydrocarbons. They are characterized by high strength and excellent processability. Nate and the like can be used. Ethyl acetate is added as a processing additive to improve processability such as intermolecular binding, surface beauty. Lactose, methyl methacrylate and ground milk promote biodegradation of the base polymer. Biodegradation agent to facilitate biodegradation in contact with microorganisms such as bacteria, fungi, enzymes, etc. under natural conditions may be used (Bionyl), etc. of the subject can easily be used by those skilled in the art. The photodegrading agent concentrates ultraviolet rays to accelerate oxidation, and a photodegrading agent containing a photosensitive material and an ethylene / carbon monoxide polymer may be used. In addition, the plastic resin is mixed and processed into a biodegradable composition using a polylactic acid according to the present invention to produce a variety of products, wherein the plastic resin as a base polymer to secure the mechanical properties (tear strength, tensile strength, etc.) of the product To be added. The plastic resin is any one of LDPE, LLDPE, HDPE, LMPE, PP, PS, PE, or a predetermined amount thereof. Where LDPE stands for Low Density Polyethylene, low density polyethylene, HDPE stands for High Density Polyethylene, high density polyethylene, LLDPE stands for Linear Low Density Polyethylene, linear low density polyethylene, and LMPE stands for Low Molecular Polyethylene. PP stands for polypropylene, polypropylene stands for polypropylene, PS stands for polystyrene for polystyrene, and PE stands for polyethylene for polyethylene. General HDPE and LDPE have a molecular weight of 10,000 or more, but LMPE is formed at a low molecular weight of 2000 ~ 2500 to induce a smooth fusion operation such as CaCo ₃ when manufacturing a product, and the composition is made of polyethylene wax.

Hereinafter, look at the experimental example of the present embodiment.

Preparation of Sample

44% by weight of polylactic acid, 10% by weight of heavy calcium carbonate, 15% by weight of aliphatic polyester, and 3.5% by weight of methyl methacrylate were placed in a high-speed mixer (40KW, 1480 RPM) and mixed for 40 minutes under an internal temperature of 110 ° C. 14.5% by weight of powdered milk, 3% by weight of biodegradable adjuvant, 2% by weight of photodegradant were added to a high speed mixer and mixed at 40 ° C. for 30 minutes to produce a second substance, 5.5% by weight of lactose and 2.5% by weight of ethyl acetate. The mixture is placed in a mixer and mixed at 40 ° C. for 20 minutes to produce a third material.

Then, the first material, the second material and the third material are put in a high speed mixer (40KW, 1300RPM) and mixed at 90 ° C for 30 minutes, and after 60 minutes, the crystal obtained by opening the mixer is introduced into the extruder hopper (37KW). . Here, the extruder is a double-skew, the length / diameter ratio of 28: 1 or more, the heating bowl section 1 to 4 to 180 ℃, section 5 to 8 Up to 190 ° C and sections 9-12 to 210 ° C. In addition, a wire screen is installed horizontally at the rear end of the extruder ejection mold to remove foreign substances during the operation of the equipment so that they can be replaced once every 8 hours. The biodegradable composition is discharged through the dog's hold. The discharged biodegradable composition is cut into ellipses with a thickness of 0.3-0.5 mm by four rotary cutters and is transported 14 m through a duct 300 in diameter by the wind power of the blower. And it is cooled in the transport process to complete a biodegradable composition using polylactic acid.

Subsequently, 40 wt% of the above biodegradable composition was added to the extruder hopper together with 12 wt% of LDPE and 48 wt% of LLDPE as a base polymer, and a heating bowl of 180 to 190 ° C and a heating tee of 190 ° C to The biodegradable film (Test Example 1) having a thickness of 0.01 to 0.02 mm was prepared while maintaining 210 ° C and a heating top of 220 ° C.

In addition, the following samples were further prepared by varying the amount of the base polymer and the biodegradable composition.

(1) Test Example 2 to Comparative Example 2

PP film (Comparative Example 2) to which the present biodegradable composition was not added, and a film (Test Example 2) to which 5 wt% of the biodegradable composition was added were produced.

(2) Test Example 3 to Comparative Example 3

PS film (Comparative Example 3) to which the present biodegradable composition was not added (Comparative Example 3) and a film (Test Example 3) to which 7 wt% of the biodegradable composition was added were produced.

(3) Test Example 4 to Comparative Example 4

The PE film (Comparative Example 4) to which the present biodegradable composition was not added, and the film (Test Example 4) to which 5 wt% of the biodegradable composition was added were prepared.

* Experiment 1 : Aerobic Biodegradation Test of Plastics in Composting Conditions

Applicant requested the experiment from Korea Testing and Research Institute and summarizes the report as follows.

1. Material Composition Analysis

(1) Material test sample

Before conducting biodegradability test, elemental analysis (NCHO) was conducted on the sample to be tested, and the test sample was designated according to the Ministry of Environment's notification of biodegradable synthetic resin testing institute of 2004-110. By cutting the sample of Test Example 1 was prepared as shown in Figure 1 below.

<Picture 1>

(2) Material testing equipment and method

An element analyzer with model name EA1110 Element Analyes System (CE Instrumnets Co., Italy) is used.

N, C, H among the elemental components were analyzed by TCD detector after pyrolysis of 1mg of material test sample at 1800 ℃, and the remaining component O was analyzed by TCD detector after pyrolysis of 1mg of material test sample at 1000 ℃. do.

(3) Material test result

Test Items N C H O weight% 0.00 75.9 18.7 5.4

2. Biodegradation test

(1) Biodegradable city materials

   The sample of Test Example 1 was cut into 2 × 2 cm size to prepare a biodegradability test sample as shown in Figure 2 below.

<Picture 2>

(2) Test principle and method

The biodegradability test sample was measured by measuring the amount of carbon dioxide generated during the aerobic composting process according to the Korean Industrial Standard KSM 3100-1 "Measuring Aerobic Biodegradability and Disintegration Degree of Plastics in Composting Conditions". Measure

Here, compost is an organic substance that controls a soil composed of a mixture of vegetable residues obtained by biodegradation and other organic substances and certain inorganic components. And, composting means aerobic process for composting.

Principle of test is to put the sample and standard materials in the compost and fix it in the composting container. In addition, by measuring the amount of carbon dioxide generated during the composting process continuously or periodically, the degree of biodegradation is determined by the ratio of the theoretical maximum carbon dioxide generation amount and the actual carbon dioxide generation amount of the sample and the standard material. Here, the theoretical maximum carbon dioxide generation amount (ThCO ₂ ) is calculated from the total organic carbon content of the sample or standard material, the total organic carbon content is determined by the material component analysis described above, and the theoretical maximum carbon dioxide generation amount is determined by the following formula. It is calculated.

ThCO ₂ = M _TOT × C _TOT × 12/44

M _TOT : Total dry solids (g) of test substances added to the compost at the beginning of the test.

C _TOT : percentage of organic carbon in the total dry solids of the test substance (g / g)

44: molecular weight of carbon dioxide 12: molecular weight of carbon

In addition, the actual amount of carbon dioxide generated is measured by capturing carbon dioxide generated in a state of being directly connected to each composting vessel in a transparent glass tube containing potassium hydroxide and barium chloride mixed aqueous solution in a 1: 1 manner. All of these facts are described in detail in the above Korean Industrial Standards, and further explanations are omitted.

(mole 단위)

(mole unit)

(mg 단위)

in mg

And biodegradability is computed based on the following formula.

(CO ₂ ) Cumulative amount of carbon dioxide generated from a sample or standard during _t = t hours

(CO ₂ ) _b = the cumulative amount of carbon dioxide produced in the compost only container

D _t : Biodegradability during t hours

All the above descriptions are based on Korean Industrial Standard KSM 3100-1.

(3) Characterization of compost

Compost was prepared by Sangmyung University and prepared through a two-month composting period.

 division  Moisture (wt%)  pH   Solid content (wt%)    Elemental Analysis (wt%)     C / N ratio  Total dry solids  Volatile Solids  N  C   H   O    compost  48.2   8.2   62.5  6.5 0.00 21.0 1.8 20.6    30.2     Remarks Maintain about 50% during test period  Within 7.0 ~ 9.0  Within 60-65% of wet solids  Within 10% of wet solids            -   10-40 suitable    Test Methods Waste Process Test Act Deionized Water: Compost = 5: 1   Waste Process Test Method       Elemental analyzer   Fertilizer Test

Table 1: Composting Table

Here, the total dry solids is the amount of solids obtained after drying the compost to yield a constant amount at 105 ℃, volatile solids is the amount of solids obtained after subtracting the residue after incineration at 550 ℃ from the total dry solids. Volatile solids are an indicator of organic matter content.

As shown in the 'Remarks' column of the above table, since the compost content of water, acidity, solids, and C / N ratios are all within the standard range, it is considered to satisfy the compost requirements required by the Korean Industrial Standard.

(4) Determination of Biodegradability of Test Example 1 and Standards

Three samples of Test Example 1 described above were fixed together with gastric compost and placed in three composting containers, respectively, and observed for 59 days. In addition, TLC grade cellulose of 20 μm or less was used as a standard material, which was fixed with gastric compost and placed in a composting container for observation for 59 days. And, only the compost without the specimen or standard material was placed in the composting container and observed for 59 days. For each case, the mean value of the CO2 that is measurement of the carbon dioxide emissions daily occurred in three composting vessel (CO ₂₎ calculated on the basis of _Bmean in the formula above, and further calculates also the mean value (D _t) of the biodegradability of the The results are shown in the graph below.

                        <Graph 1 Carbon Dioxide>

                             <Graph 2 Biodegradation>

According to the above graph 1, it can be seen that the amount of carbon dioxide generated in the compost fixed in Test Example 1 was higher than that of the non-composted, and the carbon dioxide generation gradually increased with time, and then rapidly increased after a certain time, so that biodegradation was actively performed. I could see that it was in progress. In addition, according to Graph 2, although the amount of carbon dioxide generation or biodegradation was initially low compared to cellulose, which is a standard substance, the test example 1 is rapidly increasing with time as in cellulose, and thus biodegradation is in progress in the natural state as in cellulose. Able to know.

And, comparing the biodegradation of the standard material and the specimen at 59 days as shown in Table 2 below.

  division  Average biodegradation (%) calculated by carbon dioxide emissions   Test period         Observation   Test substance 52.2       59 days   There were no changes in compost status, moisture content, color, bacterial growth, or smell.   Standard material            72.8 Standard            71.7

Table 2: Comparison Table of Biodegradability at 59 Days

As confirmed in Table 2, Test Example 1 shows a rapid increase in biodegradability after a certain period of time, showing a biodegradability of 52.2% at 59 days, reaching 71.7% of cellulose as a reference material.

Experiment 2 : MITI method Biodegradation by

(1) Experimental method

After collecting from more than 10 sludge, compost and soil, and mixed with the culture medium once a day for 10 days or more were used as inoculation microorganisms.

In addition, the amount of oxygen consumed in the process of inoculating microorganisms during the decomposition of the polymer was measured using a respirometer.

In this experiment, the same cellulose as in Experiment 1 was used as the standard material.

(2) Experiment result

The oxygen consumption (mg / L) measured by the respirometer is summarized in Table 3 below.

Day Standard material (cellulose)   Comparative Example 2   Test Example 2   Comparative Example 3   Test Example 3   Comparative Example 4   Test Example 4     One    60     0     0     0     0     0     0     2   176.2     0    5.5     0     0     0     0     3   271.4     0    5.7    23.3   31.2     0     0     4   336.6    4.8    5.7    40.7   69.1     0     0     5   439.7    7.2    15.3    40.7   69.1     0     0     6   557.2    7.2    15.3    41.8   115.6     0     0     7   618.5    7.2    15.3    41.8   115.6     0     0     8   618.5    7.3     20    41.8   115.6     0    4.6     9   651.1    7.3     20    41.8   198.4     0    4.6    10   695.5    7.3     20    43.2   198.4    1.1   24.5    11   747.7    7.3    42.2    43.5   242.5    1.2   24.5    12   806.4    7.3    42.2    43.5   242.5    1.2   48.2    13   914.7    7.5    42.2    43.5   311.7    1.3   69.4    14   977.3    7.5    60.4    43.5   311.7    1.5   78.4    15   977.3    7.5    60.4    43.5   311.7    1.5   78.4

[Table 3: Oxygen consumption]

According to the above table, Test Examples 2 to 4, although the oxygen consumption is lower than the standard material, it was confirmed that significantly higher than Comparative Examples 2 to 4.

Experiment 3 : Measurement of biodegradation at outdoor sites

(1) Experimental method

After Comparative Examples 2 to 4 and Test Examples 1 to 4 were deposited in rivers and soils for 30 days, the degree of biodegradation was measured by weight loss rate, SEM and AFM, and the change in the surface of the sample was measured. A sample was taken and observed under a microscope to confirm the presence of bacteria.

(2) Experiment result

1) weight loss rate

In each case, the weight loss rate was calculated and the results are shown in Table 4 below.

division River soil Standard material 100 100 Comparative Example 2 0 0.2 Comparative Example 3 0 1.3 Comparative Example 4 0 0.1 Test Example 2 6.5 9.7 Test Example 3 9.2 14.2 Test Example 4 5.3 8.6 Test Example 1 39.4 42.4

[Table 4: Comparison of weight reduction rate]

As shown in Table 4 above, it was confirmed that the weight loss rate is higher than Comparative Examples 2 to 4 with the addition of the biodegradable compound was not added. In particular, Test Example 1 showed a high weight loss rate compared to Test Examples 2 to 4 because the ratio of the biodegradable compound is higher than Test Examples 2 to 3, it was easy to confirm that the biodegradation is in progress even with the naked eye.

2) change of surface roughness of sample through SEM and AFM

The surface roughness change was compared with only Comparative Example 2 and Test Example 2 for convenience, and the results are shown below.

AFM to  Measured Comparative Example 2 Of Test Example 2  3D surface shape

division Deposition soil River Comparative Example 2

Test Example 2

After 30 days of immersion, it can be seen that the sample surface of Test Example 2 is rougher than that of Comparative Example 2 in both soil and rivers.

AFM Measured on Comparative Example 2 Of Test Example 2 Average Roughness Value

division Deposition soil River Comparative Example 2 12.4 17.9 15.1 Test Example 2 10.0 73.2 72.8

After 30 days of immersion, it can be confirmed that the surface roughness value of Test Example 2 is higher than that of Comparative Example 2.

3) Microscopic observation of sample surface

As a result of microscopic observation of the bacteria present on the surface of the sample of Comparative Example 2 and Test Example 2, the sample deposited on the soil was found, compared to Comparative Example 2 on the surface of Test Example 2 as shown in the figure below. It can be seen that bacteria inhabit the biofilm.

      <Comparative Example 2> <Test Example 2>

Experiment 4 : Measurement of physical properties at outdoor sites

(1) Experiment Method

Tensile strength and elongation after 8 weeks were measured in the state that Test Example 1 and Comparative Example 2 were exposed to sunlight (ultraviolet) as it was outdoors.

(2) experimental results

division Tensile Strength (Mpa) Elongation (%) Comparative Example 2 48.9 298.8 Test Example 1 20.14 38.0

As can be seen from the table showing the experimental results, in the case of Test Example 1, the biodegradation progressed after 8 weeks, it can be seen that the tensile strength is 41% compared to the tensile strength of Comparative Example 2, the biodegradation hardly occurred, elongation rate In addition, it can be seen that the biodegradation of the comparative example 2, the level of 13% compared to the elongation rate, the biodegradation of Experimental Example 1 was actively progressed.

As confirmed in the above Experiments 1 to 4, Experimental Examples 1 to 4 was confirmed experimentally that the carbon dioxide generation amount, oxygen consumption amount, surface roughness or the degree of habitat of bacteria is higher than Comparative Examples 2 to 3. In particular, in the case of Test Example 1, the biodegradability is close to about 52.2% in 59 days, which is a remarkable result compared to Comparative Examples 2 to 4 that do not decompose in the natural state.

Claims (4)

delete 10 to 55% by weight of polylactic acid, 7 to 15% by weight of heavy calcium carbonate, 10 to 30% by weight of aliphatic polyester, 3 to 10% by weight of lactose, 1 to 5% by weight of ethyl acetate, 1 to 7% by weight of methyl methacrylate Biodegradable composition using a polylactic acid, characterized in that 10 to 20% by weight of powdered milk, 1 to 5% by weight of biodegradation aid, 1 to 4% by weight of photodegradant. According to claim 2, wherein the biodegradable composition using polylactic acid is 44% by weight polylactic acid, 10% by weight heavy calcium carbonate, 15% by weight aliphatic polyester, 5.5% by weight lactose, 2.5% by weight ethyl acetate, methyl methacrylate Biodegradable composition using a polylactic acid, characterized in that consisting of 3.5% by weight, milk powder 14.5% by weight, biodegradation aid 3% by weight, photodegradant 2% by weight. 10 to 55% by weight of polylactic acid, 7 to 15% by weight of heavy calcium carbonate, 10 to 30% by weight of aliphatic polyester and 1 to 7% by weight of methyl methacrylate are mixed to form a first substance, and 10 to 20 powdered milk By weight, 1-5% by weight of biodegradable adjuvant and 1-4% by weight of photodegradant to produce a second material, 3 to 10% by weight of lactose and 1 to 5% by weight of ethyl acetate to produce a third material And extruding the formed crystals by mixing the first material, the second material, and the third material, and cooling the extruded composition to produce a biodegradable composition. .