KR20210095004A - Biodegradable pla screw cap having improved translucency, gas-barrier, impact-resistance and sealing performance, and method of manufacturing the same - Google Patents

Abstract

Provided are a biodegradable PLA screw cap with improved translucency, penetration barrier, impact resistance, and sealing properties, and a manufacturing method thereof. The biodegradable PLA screw cap contains: 43 to 87 wt% of polylactic acid (PLA); 5 to 20 wt% of polyhydroxyalkanoate (PHA); 5 to 20 wt% of a non-toxic plasticizer; 1 to 5 wt% of silica; 1 to 5 wt% of a dispersant; 0.5 to 5 wt% of a slip agent; and 0.1 to 2 wt% of an antioxidant.

Description

BIODEGRADABLE PLA SCREW CAP HAVING IMPROVED TRANSLUCENCY, GAS-BARRIER, IMPACT-RESISTANCE AND SEALING PERFORMANCE, AND METHOD OF MANUFACTURING THE SAME }

The present invention relates to a biodegradable PLA screw cap having improved translucency, penetration barrier, impact resistance and sealability, and a method for manufacturing the same.

Plastics such as PET (Poly Ethylene Terephthalate) and HDPE (High Density Polyethylene) have become common and are being mass-produced and used for various purposes such as beverage bottles, cosmetic bottles, and household goods bottles. However, due to global warming, environmental pollution of plastics, which are recently becoming issues around the world, accumulation in animals, and microplastic problems, the rejection of conventional plastics such as PET is growing. Therefore, there is a growing demand for biodegradable bio-resin produced from renewable plant resources.

In general, as raw materials for biodegradable resins, natural polymers such as polylactic acid (PLA), polyhydroxybutyrate (PHB), cellulose (Cellulose), starch (Starch), chitin (Chitin), chitosan (Chitosan) There are also PBS, PBSA, PBAT, and PCL from petroleum. Among them, PLA is a biodegradable and biocompatible polymer that can be obtained from renewable raw materials such as starch and sugar cane, and has excellent mechanical strength and transparency, so that it is being developed for use in food containers. Because PLA is composed of lactic acid, a biometabolite, it is completely metabolized when decomposed (KFDA: Guide for Evaluation of Mechanical Properties, Physicochemical and Biological Safety (2009), Korea Institute of Science and Technology Information 2002: PLA is a drug release agent. Biocompatible resin being used, FCN=food contact notification NO178 certified).

However, PLA, as a semi-crystalline polymer, has brittleness, a slow crystallization rate and a long molding time, so the productivity is poor, and the gas barrier is low. Therefore, in order to make bottled water or beverage bottles from PLA, it is important to have a degree of crystallinity, crystal grain size, penetration barrier, mechanical properties, transparency, etc. suitable for the purpose.

On the other hand, the primary structure of the polymer resin is a structure determined by chemical bonds having various structural arrangements according to polymerization conditions. It is an aggregate of molecular chains and has crystalline and amorphous structures. The crystal structure affects the primary and secondary structures, and the degree of crystallinity of polymer resins depends on the primary structure. The agglomeration structure of the crystal depends on the conditions of crystallization, such as the molten state, pressure, and temperature. The bonds between the polymer resin chains are affected by the external environment and are affected by the degree of polymerization of the polymer resin, the shape and three-dimensional structure of the chain, the chemical structure of the repeating unit, and the intramolecular attraction. Therefore, the degree of crystallinity, crystal grain size, penetration barrier, mechanical properties, and transparency vary depending on the processing conditions by heat, pressure, etc. according to polymerization of polymer resin and compound manufacturing. For example, the penetration barrier property largely depends on the primary structure, which is a structure determined by the chemical bonding of the polymer resin, and also depends on the secondary structure, which is the molecular structure of the solid. In this case, the solid structure means a degree of crystallinity and a degree of molecular orientation. As such, the structure and properties of polymer resins may vary greatly depending on molding or processing conditions, and in particular, it is more difficult to prepare a resin having desired properties using PLA, which has weak penetration barrier properties.

Korean Patent Publication No. 10-2007-7005578, a related prior document, discloses a liner material coated with a penetration barrier resin containing PLA and PBS Blend on paper or foam, but in this case, when opening and closing the cap, the liner There is a problem in that fine powder may be generated due to the ash grinding phenomenon.

Korean Patent Office Laid-Open Patent Publication No. 10-2007-7005578

An object of the present invention to solve this problem is to provide a biodegradable PLA screw cap that can be used for a suitable purpose for sealing a bottle or container by improving impact resistance, sealing property, etc. while having appropriate translucency and flexibility. .

Another object of the present invention for solving the above problem is to provide a method for manufacturing such a biodegradable PLA screw cap.

The problems of the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

A biodegradable PLA screw cap according to an embodiment of the present invention for solving the above problems is polylactic acid (PLA) 43-87 wt%, polyhydroxyalkanoate (PHA) 5-20 wt% , 5-20 wt% of a non-toxic plasticizer, 1-5 wt% of silica, 1-5 wt% of a dispersant, 0.5-5 wt% of a slip agent and 0.1-2 wt% of an antioxidant.

In addition, it may have one or more of the following characteristics (1) to (4).

(1) Tensile strength: 50 MPa or more

(2) Elongation: more than 100%

(3) Impact strength: 60 J/m ² or more

(4) Biodegradability: more than 90% for 180 days

Meanwhile, the PHA is P3HB-4HB (P(3-hydroxybutyrate)-(4-hydroxybutyrate)), the non-toxic plasticizer is polyethylene glycol, the slip agent is erucamide, and/or the dispersant is ethylenebis(stearic acid amide) ) (Ethylenebis(stearamide); EBS).

The method of manufacturing a biodegradable PLA screw cap according to an embodiment of the present invention for solving the above other problems is PLA 43-87 wt%, PHA 5-20 wt%, non-toxic plasticizer 5-20 wt%, silica 1-5 Putting wt%, 1-5 wt% of a dispersant, 0.5-5 wt% of a slip agent, and 0.1-2 wt% of an antioxidant into an extruder at 160-200° C., making pellets from the extrudate extruded from the die of the extruder and manufacturing the screw cap by molding the pellets with an injection machine having an injection temperature of 170-190 ℃ and a mold temperature of 20-30 ℃.

In addition, one or more of the following methods (a) and (b) may be satisfied.

(a) the non-toxic plasticizer is introduced in the middle part of the extruder

(b) preparing the pellets by quenching the extrudate

The details of other embodiments are included in the detailed description.

The biodegradable PLA screw cap according to the embodiments of the present invention has a suitable translucency and flexibility while greatly improving impact resistance, sealing properties, etc., so it can be used for a suitable purpose for sealing a bottle or container.

In addition, according to other embodiments of the present invention, it is possible to manufacture a biodegradable PLA screw cap having the above characteristics.

Effects according to the embodiments of the present invention are not limited by the contents exemplified above, and more various effects are included in the present specification.

1 is a flowchart showing an apparatus and a process for manufacturing a biodegradable PLA screw cap according to an embodiment of the present invention.

Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. In adding reference numerals to components in each drawing, it should be noted that the same components are given the same reference numerals as much as possible even though they are indicated in different drawings.

In the description of the embodiment of the present invention, if it is determined that a detailed description of a related known configuration or function interferes with the understanding of the embodiment of the present invention, the detailed description thereof will be omitted.

In addition, in describing the components of the embodiment of the present invention, terms such as first, second, A, B, (a), (b), etc. may be used. These terms are only for distinguishing the components from other components, and the essence, order, or order of the components are not limited by the terms.

The terminology used herein is for the purpose of describing the embodiments and is not intended to limit the present invention. In this specification, 'and/or' includes each and every combination of one or more of the mentioned items. The singular also includes the plural, unless the phrase specifically states otherwise.

As used herein, 'comprises' and/or 'comprising' does not exclude the presence or addition of one or more other components in addition to the stated components. Numerical ranges indicated using 'to' or '-' indicate numerical ranges including the values stated before and after them as the lower and upper limits, respectively. 'About' or 'approximately' means a value or numerical range within 20% of the value or numerical range recited thereafter.

As used herein, 'penetration barrier' means a property that does not penetrate or permeate gas (gas) or moisture, and has substantially the same meaning as gas barrier and/or water barrier properties. have

Hereinafter, the present invention will be described in detail.

The biodegradable PLA screw cap according to an embodiment of the present invention contains 43-87 wt% of polylactic acid (PLA), 5-20 wt% of polyhydroxyalkanoate (PHA), and 5-20 non-toxic plasticizers. wt%, 1-5 wt% silica, 1-5 wt% dispersant, 0.5-5 wt% slip agent and 0.1-2 wt% antioxidant.

In the present specification, that the PLA screw cap includes the above components means that the components or a composition thereof are manufactured into a PLA screw cap through steps such as mixing, melting, extrusion, injection and/or molding.

The PLA screw cap of the present invention may be suitable for use in opening/closing or closing the inlet/outlet of a bottle or container.

PLA (Polylactic acid)

PLA is a main component for manufacturing the biodegradable PLA screw cap of the present invention, and is a biodegradable natural polymer that can be obtained from starch, sugar cane, and the like. PLA has excellent mechanical strength and transparency, but it has a brittleness and a slow crystallization rate, so the molding time is long and productivity is low. In addition, PLA itself does not have good gas barrier properties, which can be represented by water permeability or oxygen permeability. Therefore, it is important to improve the weak properties while maintaining excellent properties by mixing with appropriate PHA, non-toxic plasticizer, nucleating agent, and dispersing agent in an appropriate amount.

Such PLA may be included in 43-87 wt%, preferably in 50-80 wt%.

PHA (Polyhydroxyalkanoate, Polyhydroxyalkanoate)

PHA is added to improve the easily brittle properties of the aforementioned PLA. By mixing PHA, a biodegradable raw material, it is possible to improve the impact resistance of PLA resin while maintaining its biodegradability and transparency.

PHA may be included in 5-20 wt%, preferably in 10-15 wt%. In addition, the weight ratio of PLA and PHA may be 8:1 to 4:1. If the weight ratio is greater than 8:1, the impact resistance improvement may be insignificant, and if it is less than 4:1, the reduction in elongation compared to the impact resistance improvement effect is can be large

These PHAs include polyhydroxybutyrate (PHB), polyhydroxyvalerate (PHV), polyhydroxyhexanoate (PHH), polyhydroxyoctanoate (PHO) and their It may include one or more selected from the group consisting of copolymers.

Preferably, the PHA comprises at least one selected from the group consisting of poly-3-hydroxybutyrate (P3HB) and poly-4-hydroxybutyrate (P4HB). It may be PHB.

More preferably, the PHA may be P3HB-4HB (P(3-hydroxybutyrate)-(4-hydroxybutyrate)), which is a copolymer obtained by copolymerizing P4HB with a homopolymer of P3HB. Since P3HB has the property of being easily broken like PLA, it is possible to supplement impact resistance, flexibility, elongation, tensile strength/elongation, and formability by copolymerizing P4HB with elasticity.

Non-toxic plasticizer

Non-toxic plasticizers can impart flexibility and stretchability to PLA resin. In addition, since the crystallization rate is increased by dropping the glass transition temperature, melting temperature, and crystallization temperature of PLA, while not affecting the crystallinity, transparency can be maintained while improving moldability. In addition, it is possible to prevent loss of transparency by using a plasticizer with low migration that can prevent the whitening of PLA resin.

The non-toxic plasticizer may be included in an amount of 5-20 wt%, preferably, it may be included in an amount of 10-15 wt%. If the non-toxic plasticizer is less than 5 wt%, the effect of improving flexibility, stretchability and/or moldability may be insignificant, and if it exceeds 20 wt%, transparency may be affected.

The non-toxic plasticizer may include one or more of a polyol and a citric acid ester. In an exemplary embodiment, the polyol may be selected from the group consisting of ethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, trimethylolpropane, and pentaerythritol. and the citric acid ester may be selected from the group consisting of Triethyl citrate (TEC), Acetyl triethyl citrate (ATEC), Tributyl citrate (TBC), Acetyl tributyl citrate (ATBC) and Acetyl tris(2-ethylhexyl) citrate (ATEHC). there is.

silica

Silica provides slip properties to PLA resin to prevent blocking, and also acts as a nucleating agent to increase crystallization rate and crystallinity without impairing transparency, thereby improving penetration barrier properties. The smaller the silica particle size, the better the crystallinity.

Silica may be included in 1-5 wt%, preferably in 1-3 wt%. If the content of silica is less than 1 wt%, the effect of providing slip properties and preventing blocking may be insignificant, and if the content of silica is more than 5 wt%, stretchability, transparency, etc. may be deteriorated.

As silica it is possible to use commercially available silica powders such ^{as Sylobloc ®} , Sylosiv ^® , Shieldex ^® , Perkasil ^® or Sylowhite ^{® .} However, the present invention is not limited thereto.

dispersant

The dispersant has polarity and is mixed with PLA to maintain transparency, and is not mixed with water to improve penetration barrier properties.

These dispersants may be included in 1-5 wt%, preferably in 1-3 wt%. If the content of the dispersant is less than 1 wt%, the penetration barrier effect may be small, and if it exceeds 5 wt%, impact resistance may be deteriorated. In particular, when the content of the dispersant is within the range of 1-5 wt%, the penetration barrier improvement efficiency may be the best compared to the impact resistance reduction.

As a dispersant, an amide-based wax such as ethylenebis(stearamide) (EBS) may be used. In addition, it may include a metallic fatty acid, specifically, calcium stearate, zinc stearate, magnesium stearate, aluminum stearate, calcium oleate, zinc oleate, magnesium oleate, aluminum oleate, calcium palmitate, zinc palmitate, magnesium palmitate and It may include one or more selected from the group consisting of aluminum palmitate.

slip agent

A slip agent is added to provide slip properties so that the PLA screw cap can be opened and closed smoothly. As the slip agent is added, the coefficient of friction decreases, so that it is possible to prevent the generation of fine powder due to friction when opening and closing the PLA screw cap.

The slip agent may be included in 0.5-5 wt%, preferably 0.5-3 wt%. If the content of the slip agent is less than 0.5 wt%, the slip property improvement may be insignificant, and if it exceeds 5 wt%, stretchability, transparency, etc. may be deteriorated.

The slip agent may include an amide-based compound such as oleamide or erucamide (Erucamide or Erucic amide).

antioxidant

Antioxidants are added to prevent decomposition or yellowing of the PLA resin or the composition during PLA resin production by heat.

The antioxidant may include at least one selected from the group consisting of phenolic antioxidants, phosphorus antioxidants, amine antioxidants, and thio antioxidants. Specifically, phosphoric acid such as phosphoric acid, trimethyl phosphate or triethyl phosphate; 2,6-di-t-butyl-p-cresol, octadecyl-3-(4-hydroxy-3,5-di-t-butylphenyl)propionate, tetrabis[methylene-3-(3, 5-di-t-butyl-4-hydroxyphenyl)propionate]methane or bis[3,3-bis-(4'-hydroxy-3'-tert-butylphenyl)butanoic acid]glycol ester hindered phenol type; amines such as phenyl-α-naphthylamine, N,N′-diphenyl-p-phenylenediamine or N,N′-di-β-naphthyl-p-phenylenediamine; and thio antioxidants such as dilauryl disulfide, dilauryl thiopropionate, distearyl thiopropionate or tetramethylthiuram disulfide tetrabis[methylene-3-(laurylthio)propionate]methane; can be heard In an exemplary embodiment, Songnox 1010 (Songwon Industries) may be used as the phenolic antioxidant, and Songnox 1680 (Songwon Industries) may be used as the phosphorus antioxidant, but is not limited thereto.

These antioxidants may be included in 0.1-2 wt%, preferably 0.1-1 wt%. In an exemplary embodiment, as the antioxidant, the phenolic antioxidant and the phosphorus antioxidant may be included in an amount of 0.1-1 wt%, preferably 0.1-0.5 wt%, respectively, but is not limited thereto.

nucleating agent

A nucleating agent may be additionally included to affect the crystallinity of the PLA resin to improve penetration barrier properties. On the other hand, PLA has an L-stereoisomer and a D-stereoisomer. In general, since the L-stereoisomer is 98.5 wt% or more, it may have a high degree of crystallinity, and thus whitening may occur and transparency may be lost. Therefore, it is important to control the degree of crystallinity to a level having optimum penetration barrier properties while having appropriate transparency for the purpose of the PLA resin (preferably a PLA bottle containing beverages such as water). The degree of crystallinity is preferably 15% or more, particularly 30% or more in order to have adequate penetration barrier properties.

The nucleating agent may be included in an amount of 1-5 wt%, and more preferably, it may be included in an amount of 1-3 wt%. If the nucleating agent is included in an amount of less than 1 wt%, the crystallinity may be too low and penetration barrier properties may be deteriorated.

In particular, when the content of the nucleating agent is in the range of 1-5 wt%, the improvement effect of penetration barrier is large compared to the degree of decrease in transparency, so the efficiency may be the best. When the content of the nucleating agent is 1-5 wt%, The relationship between transparency and penetration barrier properties can be expressed as in Equation 1 below.

[Equation 1]

In the above formula, Haze represents the transparency of the PLA resin as turbidity, and OTR represents the penetration barrier property of the PLA resin as the oxygen permeability.

The nucleating agent is N,N'-Ethylenebis(stearic acid amide) (N,N'-Ethylenebis(stearamide); EBS), N,N'-ethylenebis(12-hydroxystearic acid amide)(N,N' -Ethylenebis(12-hydroxystearamide)), zinc phenyl phosphate, and Nissan chemical's Ecopromote ^® -TF may include one or more selected from the group consisting of.

Nanocellulose

Nanocellulose may be additionally included to improve the penetration barrier properties of the PLA resin. However, nanocellulose is very difficult to disperse, and when it is well dispersed, the penetration barrier property is greatly improved, but when the dispersion is poor, agglomeration occurs, which can worsen mechanical properties, transparency, and penetration barrier properties.

In order to uniformly disperse the nanocellulose, a kneading block element of an extruder may be used. The kneading block elements may be continuously arranged in the axial direction of the screw of the extruder and kneaded while transferring the raw material. In particular, by configuring 1-2 melting zones and 1-3 mixing zones with a plurality of kneading block elements and optimizing the screw design, PLA resin raw materials including nanocellulose are melted and uniformly dispersed , it is possible to prevent thermal decomposition while mixing. In an exemplary embodiment, the extruder having such a kneading block element may be one having a high degree of kneading as two co-rotating intermeshed type twin screw extruders. In another exemplary embodiment, PLA and additives can be uniformly mixed using a kneading block with a narrow disc width for melt and distribution kneading, and a kneading block with a wide disc width for dispersion kneading is used to provide a strong force to evenly It can be dispersed by dispersing and pulverizing the particles into small pieces.

Nanocellulose may be included in 0.1-10 wt%, preferably in 0.1-5 wt%, more preferably in 0.1-2 wt%. If the content of nanocellulose is less than 0.1 wt%, the penetration blocking effect may be insignificant, and if it exceeds 10 wt%, mechanical properties or transparency may deteriorate.

Nanocellulose may include one or more of CNCs (Cellulose NanoCrystals) and CNFs (Cellulose NanoFibrils), and the CNCs and/or CNFs are preferably used as a powder after complete drying.

compatibilizer

A compatibilizer may be added to improve the mechanical properties of PLA and PHA by improving the bonding strength. The compatibilizer may increase molecular weight by acting as a chain extender, increase melt viscosity, and improve moldability such as stretchability.

The compatibilizer may be included in an amount of 0.1-5 wt%, preferably 0.2-2 wt%. If the content of the compatibilizer is less than 0.1 wt%, the effect of improving mechanical properties is insignificant, and if it exceeds 5 wt%, transparency and penetration barrier properties may be deteriorated.

The compatibilizer may include one or more selected from the group consisting of MAH-graft-PLA and Joncryl 4468C.

1 is a flowchart showing an apparatus and a process for manufacturing a biodegradable PLA screw cap of the present invention. Hereinafter, a method of manufacturing a biodegradable PLA screw cap according to another embodiment of the present invention will be described in detail with reference to FIG. 1 .

First, 43-87 wt% PLA, 5-20 wt% PHA, 1-5 wt% silica, 1-5 wt% dispersant, 0.5-5 wt% slip agent and 0.1-2 wt% antioxidant were mixed in a supermixer (10 ), etc., and then put into the main hopper 21 of the extruder 20 maintained at 160-200 ℃.

5-20 wt% of non-toxic plasticizer can also be mixed with PLA and the like and put into the main hopper 21, but it is preferable to put it into the side feeder 22 connected to the middle of the extruder to prevent thermal decomposition of the non-toxic plasticizer. . When non-toxic plasticizers are thermally decomposed, mechanical properties such as flexibility and penetration barrier properties of PLA resin may be deteriorated. To this end, the side feeder 22 is preferably connected at the rear end of the melting zone of the extruder 20, but is not limited thereto.

The raw materials pass through the extruder 20 and are melted, kneaded, dispersed, etc., and unreacted substances and gases are removed from the vacuum vent 23 . The raw material mixture that has undergone this process is extruded from the die 24 of the extruder 20 . This extrudate is quenched by passing it through a water tank 30 containing cooling water, and moisture and the like are removed to prepare pellets (1). At this time, if the extrudate is not quenched with cooling water or the like, the degree of crystallinity and crystal size may become excessively large, which may deteriorate transparency.

PLA screw caps are manufactured by molding the prepared pellets 1 with an injection machine 40 having an injection temperature of 170-190 ℃ and a mold temperature of 20-30 ℃.

Figure 1 shows the case of manufacturing the PLA screw cap, but is not limited thereto, and it can be applied to other types of PLA resins that require substantially similar properties or molding process to the PLA screw cap.

The biodegradable PLA screw cap of the present invention comprising the above components may satisfy one or more of the following characteristics.

(1) Tensile strength: 50 MPa or more, preferably 65 MPa or more

(2) Elongation: 100% or more, preferably 130% or more

(3) Impact strength: 60 J/m ² or more, preferably 80 J/m ² or more

(4) biodegradability: 90% or more for 180 days, preferably 92% or more for 180 days

Hereinafter, embodiments of the present invention will be described in more detail through specific preparation examples and experimental examples. However, the following Preparation Examples and Experimental Examples are only for illustrating the present invention, and the scope of the present invention is not limited thereto.

Manufacturing Example: PLA Bottle Manufacturing

77.3 wt% PLA (Total Corbion), 10 wt% P3HB-4HB (CJ Cheiljedang), 1 wt% Sylobloc ^® (Grace division), 1 wt% EBS (Leochem), 0.5 wt% erucamide (Kao), 0.1 wt% Songnox 1010 (Songwon Industries) and 0.1 wt% Songnox 1680 (Songwon Industries) were put into a super mixer, mixed for 2-5 minutes, and then put into the main hopper of the extruder maintaining a temperature of 160-200 °C.

10 wt% of polyethylene glycol 400 (Lotte Chemical) 9.8 wt% and joncryl 4368C 0.2 wt% is supplied to the side feeder connected to the middle part of the extruder using a liquid injection pump to make it uniform with other components in the extruder After mixing, unreacted substances and gases were removed through a vacuum vent. After the extrudate extruded from the die was quenched in a water bath, it was put into a dehumidifying dryer and dried to obtain a moisture content of 0.02-0.03 wt% to prepare PLA pellets.

PLA screw caps were prepared by injection molding the prepared PLA pellets in an injection machine with an injection temperature of 170-190 ℃ and a mold temperature of 20-30 ℃.

Experimental Example 1: Comparison of physical properties of PLA screw cap and HDPE cap

Physical properties such as tensile strength and impact strength of the PLA screw cap of the present invention and the conventional HDPE cap were compared in the following way. First, PLA pellets prepared in the same manner as in Preparation Example were molded into ASTM standard specimens to prepare PLA cap specimens (Example 1). In addition, the pellets made of 100% HDPE were similarly molded into ASTM standard specimens to prepare PET cap specimens (Comparative Example).

The physical properties of the prepared PLA cap specimen and PET cap specimen were measured according to the following method, and the results are shown in Table 1 below.

- Tensile strength and elongation: ASTM D638

- Impact strength: ASTM D256

- Sealability: SANSU-M (Cap the screw cap with a predetermined torque on the bottle containing the dye, lay it down and leave it at room temperature (25 ℃) for 24 hours, then open the cap and let the pigment come into contact with the cap and the tip of the bottle mouth.) In the case of penetrating to the screw part of the cap or the screw part of the bottle, the sealing property is judged to be poor. judged to have good sealing properties)

- Biodegradability: ISO14855, ASTM D5338, KS M 3100-1

Properties Example 1 comparative example Tensile strength (MPa) 40 25 Elongation (%) 150 250 Impact strength (J/m ² ) 85 128 hermeticity Good Good biodegradability 92% or more in 180 days not biodegradable

As shown in Table 1, the PLA cap of the present invention is a biodegradable resin that decomposes 92% or more within 180 days, but has similar physical properties to the HDPE cap and has good sealing properties, so it is not decomposable like conventional HDPE caps. It can be seen that it can be used as an eco-friendly multi-purpose resin replacing resin.

Experimental Example 2: Comparison of physical properties and moldability according to the time of addition of non-toxic plasticizer

In order to investigate the difference in the physical properties and moldability of PLA screw caps according to the addition time of the non-toxic plasticizer, 9.8 wt% of polyethylene glycol 400 and 0.2 wt% of Joncryl 4368 C, which are non-toxic plasticizers, were added to the supermixer and main hopper together with PLA, etc. A PLA screw cap was prepared in the same manner as in Preparation Example except for (Example 2). Table 2 below shows the results of measuring the tensile strength and elongation of the manufactured cap and comparing it with the cap of Example 1, and Table 3 below shows the time taken for molding the cap compared with the time taken for Example 1 It is the result.

Example Tensile strength (MPa) Elongation (%) Example 2 28 101 Example 1 40 150

Example time taken Example 2 about 60 seconds Example 1 about 25 seconds

As shown in Tables 2 and 3, it can be seen that when polyethylene glycol 400, a non-toxic plasticizer, is mixed with components such as PLA from the beginning, tensile strength and elongation are somewhat decreased and molding time is also long, which is polyethylene glycol 400 This suggests that if a low-molecular-weight non-toxic plasticizer is introduced from the front end of the extruder, it may be decomposed by receiving excessive heat history.

Experimental Example 3: Confirmation of ease of opening and closing according to the content of slip agent and silica

In order to find out the ease of opening and closing the PLA screw cap according to the content of the slip agent and silica, the PLA screw cap was prepared in the same manner as in the Preparation Example by varying the contents of the ^{slip agent erucamide and the silica Sylobloc ® as shown in Table 4 below.} prepared (Examples 3-1 to 3-4). Table 4 below shows the results of confirming the ease of opening and closing while capping the prepared cap at the mouth of the plastic bottle and opening it.

Example Erucamide (wt%) Sylobloc ^® (wt%) Easy to open and close Example 3-1 0.1 One × Example 3-2 0.5 One ◎ Example 3-3 One 0.5 × Example 3-4 3 0.1 △

◎: Easy to open and close, △: Not easy to open and close ×: Not easy to open or close, or the cap or bottle is crushed when opening and closing, resulting in powder

As shown in Table 4, it can be seen that the opening and closing of the PLA screw cap was easy when the content of the slip agent and silica was at least 0.5 wt% and 1 wt% or more, respectively.

Experimental Example 4: Comparison of physical properties according to weight ratio of PLA and PHA

In order to investigate the change in the physical properties of the PLA screw cap according to the weight ratio of PLA and PHA, the PLA screw cap was prepared in the same manner as in the Preparation Example by varying the content ratio by weight of PLA and PHA as shown in Table 5 below (Execution) Examples 4-1 to 4-4). Impact strength and elongation were measured for the prepared caps, and the results are shown in Table 6 below.

Example PLA content (wt%): PHA content (wt%) Example 4-1 10:1 Example 4-2 8:1 Example 4-3 4:1 Example 4-4 2:1

Example Impact strength (J/m ² ) Elongation (%) Example 4-1 65 150 Example 4-2 80 140 Example 4-3 86 130 Example 4-4 91 115

As shown in Table 8, it can be seen that the higher the ratio of PHA to PLA, the better the impact strength is, while the elongation tends to decrease, and the content ratio of PLA and PHA is in the range of about 8:1 to 4:1. It can be seen that the effect of improving the impact strength in consideration of the reduction in elongation is the best tomorrow. Although the embodiments of the present invention have been mainly described above, these are merely examples and do not limit the present invention. Those of skill in the art will know that various modifications and applications not exemplified above are possible without departing from the essential characteristics of the embodiments of the present invention.

Therefore, it should be understood that the scope of the present invention includes changes, equivalents or substitutes of the technical ideas exemplified above. For example, each component specifically shown in the embodiment of the present invention may be implemented by modification. And differences related to such modifications and applications should be construed as being included in the scope of the present invention defined in the appended claims.

Claims (5)

Polylactic acid (PLA) 43-87 wt%;
Polyhydroxyalkanoate (PHA) 5-20 wt%;
5-20 wt% of a non-toxic plasticizer;
1-5 wt% of silica;
1-5 wt% dispersant;
0.5-5 wt% of slip agent; and
Biodegradable PLA screw caps containing 0.1-2 wt % of antioxidants. According to claim 1,
A biodegradable PLA screw cap having at least one of the following properties (1) to (4).
(1) Tensile strength: 50 MPa or more
(2) Elongation: more than 100%
(3) Impact strength: 60 J/m ² or more
(4) Biodegradability: more than 90% for 180 days According to claim 1,
The PHA is P3HB-4HB (P(3-hydroxybutyrate)-(4-hydroxybutyrate)),
The non-toxic plasticizer is polyethylene glycol,
The slip agent is erucamide, and/or
The dispersant is ethylenebis (stearic acid amide) (Ethylenebis (stearamide); EBS) biodegradable PLA screw cap. PLA 43-87 wt%, PHA 5-20 wt%, non-toxic plasticizer 5-20 wt%, silica 1-5 wt%, dispersant 1-5 wt%, slip agent 0.5-5 wt% and antioxidant 0.1-2 wt% % into the extruder at 160-200 °C;
preparing pellets from the extrudate extruded from the die of the extruder; and
A method of manufacturing a biodegradable PLA screw cap comprising the step of manufacturing the screw cap by molding the pellet with an injection machine having an injection temperature of 170-190 ℃ and a mold temperature of 20-30 ℃. 5. The method of claim 4,
A method for producing a biodegradable PLA screw cap satisfying one or more of the following methods (a) and (b).
(a) the non-toxic plasticizer is introduced in the middle part of the extruder
(b) preparing the pellets by quenching the extrudate

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