KR100900251B1 - Polymer composition of polylactic acid, foam sheet using the same, manufacturing method thereof and use of foam-molding product thereby - Google Patents

Abstract

The present invention relates to a polylactic acid polymer composition having excellent foamability and molding stability, a foam sheet using the same, a method for producing the same, and the use of a foam sheet molded article produced therefrom.

In the polylactic acid polymer composition of the present invention, by mixing amorphous polylactic acid with crystalline polylactic acid, by mixing the content of amorphous polylactic acid less than crystalline polylactic acid, the impact resistance of the crystalline polylactic acid polymer and It exhibits heat resistance and imparts flexibility by the amorphous polylactic acid polymer, improves the foamability and molding stability in the mold of the polylactic acid resin, improves thermal stability, and increases the molecular weight of the polylactic acid resin. It is useful as food packaging materials or industrial packaging materials such as trays, cups, cup noodle containers, lunch boxes, etc. by increasing the properties, manufacturing foam sheets by controlling the crystallization rate and melt index during molding, and providing the foam sheet molded articles produced therefrom. Can be utilized.

Foaming Formability, Molding Stability, Thermal Stability, Crystalline Polylactic Acid, Amorphous Polylactic Acid, Foam Sheet

Description

POLYMER COMPOSITION OF POLYLACTIC ACID, FOAM SHEET USING THE SAME, MANUFACTURING METHOD THEREOF AND USE OF FOAM-MOLDING PRODUCT THEREBY}

The present invention relates to a polylactic acid polymer composition, a foam sheet using the same, a method for preparing the same, and a use of a foam sheet molded article prepared therefrom, and more particularly, in which amorphous polylactic acid is mixed with crystalline polylactic acid, By mixing the content of lactic acid less than crystalline polylactic acid, a polylactic acid polymer composition having improved thermal stability as well as foamability forming and molding stability, a foam sheet using the same, a method for producing the same, and the use of a foam sheet molded product prepared therefrom It is about.

Foams composed of general-purpose resins such as polyethylene resins, polypropylene resins, and polystyrene resins have been used in various fields because of their excellent lightness, heat insulation, and buffering properties.

On the other hand, as awareness of global environment has recently increased, and environmental problems such as depletion of petroleum resources have emerged, polylactic acid resins derived from plants have been attracting attention in place of the general-purpose resins using conventional petroleum resources.

The polylactic acid resin is an environmentally low-load thermoplastic resin that is made from a plant such as corn as a starting material and decomposes into carbon dioxide and water even after being left in the natural environment after use. Therefore, polylactic acid resin is expected to be used as a general purpose resin for foaming, which is an environmentally friendly plant that exhibits degradability under a natural environment, and studies on foams using polylactic acid resin as a raw material have been made. Development of the molded body is in progress.

Since the crystallinity of the polylactic acid-based resin to be used is high in the prior art regarding the foamed molded article made of polylactic acid, it is difficult to foam any more when crystallization occurs at the nozzle part of the extruder when molding the foam sheet. In addition, there is a problem that a special molding machine for high temperature is required when the food container or the industrial packaging material is molded at the high temperature of 141 to 161 ° C. Moreover, since the supply amount of energy required for molding in the mold is enormous, and the high-temperature energy is used when forming the foam sheet, the part obtained by heat-decomposing the part which is not crystallized by energy even though the crystallinity is high is obtained. The foamed molded body may shrink and cause irregularities on its surface.

In addition to these problems, polylactic acid has low heat resistance, and when storing or transporting a polylactic acid-based resin sheet and a molded article thereof, a high temperature does not reach a high temperature when the storage or the truck during transportation and the ship's interior reach summer. For this reason, problems such as deformation and fusion may occur. Moreover, polylactic acid-based polymers are vulnerable in form stability, and are difficult to be used in the form of sheets or the like. In addition, since the crystallization speed is high and the melt index is high, the molding conditions are largely limited, and thus productivity is reduced during molding.

As a conventional technique for solving such a problem, a method of crosslinking by adding a (meth) acrylic acid ester compound or a polyvalent isocyanate compound to a biodegradable polyester in order to improve heat resistance and productivity [Japanese Patent Laid-Open No. 2003-128901] Or a method using a biodegradable polyester and layered silicate in combination (Japanese Patent Laid-Open No. 2003-147182) has been proposed.

On the other hand, Japanese Patent Laid-Open No. 2001-261797 discloses a technique for improving heat resistance and hydrolysis resistance by blocking the carboxyl terminal of polylactic acid with a specific carbodiimide compound. However, although the heat resistance and moldability of polylactic acid are improved by crosslinking and the addition of layered silicate, the physical properties are not retained by hydrolysis of the resin during long-term storage or when used under severe moist heat, and thus the practicality is deteriorated under such conditions. Therefore, simply blocking the end of polylactic acid with a carbodiimide compound is not preferable as a molded article such as injection, extrusion, foaming or blow.

In addition, Japanese Patent Application Laid-Open No. 8-73628 discloses a blister sheet and a molded article excellent in transparency, impact resistance, and heat resistance by stretching a polylactic acid-based sheet biaxially and performing a predetermined orientation. I have reported it. Since polylactic acid requires crystallization in order to perform a predetermined orientation in the present invention, it is known to those skilled in the art that it does not exhibit crystallinity unless the composition occupies most of D form or L form. Polylactic acid having a / L ratio of 4 to 5/96 to 95 is used.

However, in the case of producing a thermoformed product using the polylactic acid disclosed in the present invention, in order to exhibit sufficient impact resistance and heat resistance, it is necessary to increase the thickness of the molded body, and thus a sheet made of the polylactic acid having a sufficient thickness is used. In the case of performing thermoforming by use, impact resistance and heat resistance are maintained, but the pressurization pressure in thermoforming becomes larger, resulting in problems in molding processability.

Accordingly, the present inventors have made efforts to improve the physical properties of polylactic acid and increase its utilization, by mixing amorphous polylactic acid with crystalline polylactic acid, by mixing the content of amorphous polylactic acid less than crystalline polylactic acid, It provides a polylactic acid-based polymer composition that improves the thermal stability, as well as foaming and molding stability in the mold of the polylactic acid-based resin, and increase the molecular weight of the polylactic acid-based resin to increase the crystallinity, crystallization rate and melting during molding The present invention has been completed by controlling the index to produce foam sheets and providing useful uses of the foam sheet moldings produced therefrom.

An object of the present invention is to provide a polylactic acid polymer composition having excellent foamability and molding stability.

Another object of the present invention is to provide a foam sheet using the polylactic acid polymer composition having excellent foamability and molding stability and a method of manufacturing the same.

Still another object of the present invention is to provide a use of the foamed molded article molded from the foamed sheet prepared from the above production method.

In order to achieve the above object, the present invention provides a polylactic acid polymer composition excellent in foamability and molding stability, consisting of 55 to 98% by weight of crystalline polylactic acid and 2 to 45% by weight of amorphous polylactic acid.

In addition, the present invention is foamed by mixing the foaming agent 0.05 to 4 parts by weight and the foaming nucleating agent 0.01 to 4 parts by weight with respect to 100 parts by weight of the polylactic acid-based polymer composition, polylactic acid excellent in foamability forming and molding stability Provided is a foam sheet using a polymer composition.

The chain extender is an epoxy compound selected from the group consisting of bisphenol A diglycidyl ether, terephthalic acid diglycidyl ether, trimethylolpropane diglycidyl ether, and 1,6-hexanediol diglycidyl ether. ; Or an isocyanate compound selected from the group consisting of hexamethylene diisocyanate, tolylene diisocyanate, xyylene diisocyanate, diphenylmethane diisocyanate and triisocyanate; Or an acryl-based compound; any one selected from the group consisting of: an epoxy compound is preferably used to apply to a food container.

In addition, with respect to 100 parts by weight of the polylactic acid-based polymer composition, 0.01 to single or mixed form selected from the group consisting of biodegradable aliphatic polyester, aliphatic / aromatic copolyester, polycaprolactone and polyhydroxyalkanoate It may contain 30 weight part further.

The biodegradable aliphatic polyester or aliphatic / aromatic copolyester may comprise at least one aliphatic diol selected from the group consisting of ethylene glycol, 1,4-butanediol and 1,4-cyclohexanedimethanol; And at least one aliphatic dicarboxylic acid selected from the group consisting of terephthalic acid, isoterephthalic acid, succinic acid and adipic acid; polycondensation of the above-mentioned aliphatic polyester or aliphatic / aromatic copolyester. It is further possible to add a single or mixed form selected from lactones or polyhydroxyalkanoates.

Specific examples of the biodegradable aliphatic polyester or aliphatic / aromatic copolyester include polybutylene succinate, polybutylene adipate, polybutylene succinate / terephthalate, polybutylene succinate / adipate / tere One or two or more polymer mixtures selected from the group consisting of phthalates, polybutylenesuccinates / adipates / isoterephthalates, polyethylenesuccinates / adipates / terephthalates and polyethylenesuccinates / adipates / isoterephthalates Can be used.

In addition, with respect to 100 parts by weight of the polylactic acid polymer composition, 0.01 to 2 parts by weight of carbodiimide-based stabilizer and 0.01 to 2 parts by weight of lubricant It may contain 2 parts by weight further.

In particular, when crosslinking a polymer with an epoxy compound, a carbodiimide stabilizer selected from N, N'-diisopropyl carbodiimide or N, N'-di-2,6-diisopropylphenyl carbodiimide It is more preferable to use the polymer because it stabilizes the melt viscosity of the polymer.

In addition, the lubricant may be used alone or a mixed form of the fatty acid amide-based compound and the fatty acid base.

In this case, the fatty acid amide-based compound is at least one selected from the group consisting of stearic acid amide, oleic acid amide, palmitic acid amide, lauric acid amide, ethylene bis stearic acid amide, ethylene bis oleic acid amide and ethylene bis lauric acid amide, The fatty acid base uses at least one member selected from the group consisting of aluminum stearate, magnesium stearate, zinc stearate, calcium stearate, magnesium oleate, zinc oleate, calcium oleate, magnesium palmitate, zinc palmate and calcium palmitate.

Furthermore, the present invention provides a method for producing the foam sheet. More specifically, with respect to 100 parts by weight of the polylactic acid polymer composition, 0.05 to 4 parts by weight of the chain extender, 0.01 to 4 parts by weight of the foaming nucleating agent and 1 to 30 parts by weight of the blowing agent are fed to the extruder, followed by heat melt kneading to melt kneading. Preparing water; Cooling the melt kneaded material; And extruding the cooled melt kneaded product.

In addition, in the method for preparing a foam sheet of the present invention, the step of preparing the melt kneaded product is performed by mixing 0.05-4 parts by weight of a chain extender and 0.01-4 parts by weight of a foaming nucleating agent with respect to 100 parts by weight of the polylactic acid polymer composition, After cutting the strand-like extrudate obtained by extruding the strand-like extrudate to obtain pellet-like polylactic acid resin particles, foaming agents 1 to 30 were applied to the polylactic acid resin particles and the polylactic acid polymer composition. The weight part may be fed to an extruder and melt-kneaded by heat to prepare a melt-kneaded product.

In the manufacturing method of the foam sheet of the present invention, the biodegradable aliphatic polyester, aliphatic / aromatic copolyester, polycaprolactone and polyhydroxy based on 100 parts by weight of the polylactic acid polymer composition in the step of preparing the melt kneaded product It may further contain 0.01 to 30 parts by weight of a single or mixed form selected from the group consisting of alkanoates.

In the above, the temperature of the extruder is based on the polylactic acid-based resin composition temperature, the melting point ± 40 ℃ at a maximum of 250 ℃, the temperature of the cooling step, based on the polylactic acid-based resin composition temperature, from 120 to 170 ℃ To perform.

Furthermore, the present invention provides a foamed molded article for food packaging or industrial packaging, in which the foamed sheet manufactured from the manufacturing method is molded.

The present invention mixes amorphous polylactic acid with crystalline polylactic acid, but mixes the content of amorphous polylactic acid less than crystalline polylactic acid, thereby improving foamability and molding stability, as well as polylactic acid polymer having improved thermal stability. A composition can be provided.

In addition, the present invention can provide a foam sheet having excellent thermal stability as well as foamability and molding stability by using the polylactic acid polymer composition.

Furthermore, the present invention may provide a foamed molded article that may be usefully used as a food packaging material or an industrial packaging material by molding the foam sheet.

Hereinafter, the present invention will be described in detail.

The present invention is composed of 55 to 98% by weight of crystalline polylactic acid and 2 to 45% by weight of amorphous polylactic acid, and provides a polylactic acid polymer composition having excellent foamability and molding stability.

Lactic acid, a raw material of polylactic acid, has a carbon atom array showing optical activity in its molecule, and thus has optical isomers of L-lactic acid and D-lactic acid. Furthermore, poly L-lactic acid (hereinafter referred to as "PLLA") and poly D-lactic acid (hereinafter referred to as "PDLA") are present.

As the polylactic acid in the present invention, crystalline polylactic acid and amorphous polylactic acid are mixed and used in a specific mixing ratio, but crystalline polylactic acid is mixed with 2 to 45% by weight of amorphous polylactic acid to form crystalline polylactic acid. In addition to exhibiting impact resistance and heat resistance of the polymer, the flexibility is provided by the amorphous polylactic acid polymer, thereby improving the foamability and molding stability of the polylactic acid resin. In particular, since the content of the amorphous polylactic acid is less mixed than the crystalline polylactic acid, the flex resistance is improved, and the shape change of the molded article due to heat can be minimized.

The crystalline polylactic acid used in the polylactic acid polymer composition of the present invention may use both PDLA or PLLA. At this time, when the amorphous polylactic acid is contained in less than 2% by weight, the effect by the amorphous polylactic acid-based polymer can not be expected, and when the amorphous polylactic acid is contained in excess of 45% by weight, the overall polylactic acid-based polymer composition Conversion to amorphous system nature results in a final morphology change. More preferably, by mixing 2 to 30% by weight of amorphous polylactic acid, most preferably 2.5 to 10% by weight of crystalline polylactic acid, not only the foamability of the polylactic acid resin and the molding stability in the mold, but also the heat resistance of the molded article Stability is imparted.

In the present invention, crystalline polylactic acid refers to a case where the ratio of L-lactic acid in PLLA and D-lactic acid in PDLA is high, that is, the optical purity is high, and the crystallinity is high, and the heat resistance and the mechanical properties are excellent. . On the other hand, amorphous polylactic acid is a copolymer having a relatively high ratio of L-lactic acid in PDLA and D-lactic acid in PLLA, and has low crystallinity and thermal stability and low mechanical properties.

The present invention is foamed by mixing 0.05 to 4 parts by weight of a chain extender and 0.01 to 4 parts by weight of a foaming nucleating agent with respect to 100 parts by weight of the polylactic acid polymer composition, and having excellent foamability and molding stability. Provided is a foam sheet using a polymer composition.

0.01 to 30 weight percent of a single or mixed form selected from the group consisting of biodegradable aliphatic polyester, aliphatic / aromatic copolyester, polycaprolactone and polyhydroxyalkanoate based on 100 parts by weight of the polylactic acid polymer composition It may contain more.

The polylactic acid used in the present invention has a low molecular weight even when the moisture is well dried, so it is difficult to carry out a post-process due to insufficient strength and breakage, so that the chain extender (chain extender) is for the purpose of increasing the molecular weight of the polylactic acid. ). In addition, it can be used for the purpose of lowering the high melt index of polylactic acid in order to satisfy the conditions of 4g / 10min or less, which is a suitable melt index for sheet extrusion.

Preferred examples of the chain extender used in the present invention include bisphenol A diglycidyl ether, terephthalic acid diglycidyl ether, trimethylolpropane diglycidyl ether, and 1,6-hexanediol diglycidyl ether. An epoxy compound selected from the group; Or isocyanate compounds selected from the group consisting of hexamethylene diisocyanate, tolylene diisocyanate, xyylene diisocyanate, diphenylmethane diisocyanate and triisocyanate; Or an acryl-based compound.

In particular, it is preferable to use an epoxy compound in view of the fact that the polymer is used in a food container. When using an epoxy chain extender, the high melt index of crystalline polylactic acid should be lowered to 4 g / 10 min or less to show excellent sheet formability.

When crosslinking the polymer with an epoxy compound, 0.01 to 2 parts by weight of a carbodiimide stabilizer and 0.01 to 2 parts by weight of a lubricant may be further contained with respect to 100 parts by weight of the polylactic acid polymer composition.

At this time, the carbodiimide stabilizer is selected from N, N'-diisopropyl carbodiimide or N, N'-di-2,6-diisopropylphenyl carbodiimide, and by using a carbodiimide stabilizer It is preferable because the melt viscosity of the polymer can be stabilized, and other metal complexes, polyvalent carboxylic acids or mixtures thereof can be used.

In addition, the polylactic acid polymer has a high degree of crystallinity, high Young's modulus at a temperature below the glass transition temperature, for example, at room temperature, and thus is hard in a solid state, which may interfere with the use of a polylactic acid molded article. In addition, when melt processing a polylactic acid polymer, a lubricant is used to improve melt flowability of the polymer.

The lubricant used in the present invention is preferably to use a fatty acid amide-based compound, more preferably, when using it together with a fatty acid base, the improvement effect is obvious.

At this time, the fatty acid amide may be added at least one selected from the group consisting of stearic acid amide, oleic acid amide, palmitic acid amide, lauric acid amide, ethylene bis stearic acid amide, ethylene bis oleic acid amide and ethylene bis lauric acid amide.

The fatty acid bases include aluminum stearate, magnesium stearate, zinc stearate, calcium stearate, magnesium oleate, zinc oleate, calcium oleate, magnesium palmitate, zinc palmitate, calcium palmitate, or a mixture of one or more of these. Product can be added. At this time, the addition amount of the lubricant is 0.01 to 2 parts by weight, preferably 0.05 to 1 part by weight based on 100 parts by weight of the polylactic acid polymer composition.

When the chain extender of the present invention is used in an amount of 0.05 to 4 parts by weight, more preferably 0.1 to 2 parts by weight, based on 100 parts by weight of the polylactic acid polymer composition, the effect of improving heat resistance is obvious.

At this time, if the content of the chain extender is less than 0.05 parts by weight, the effect of increasing the molecular weight is insufficient, it can not be produced in a sheet form, if it exceeds 4 parts by weight, the crystallinity and heat resistance is improved, but due to excessive crosslinking extruder There is a risk of clogging, causing process problems.

In addition to the polylactic acid polymer composition, based on 100 parts by weight of the polylactic acid polymer composition, solely selected from the group consisting of biodegradable aliphatic polyester, aliphatic / aromatic copolyester, polycaprolactone and polyhydroxyalkanoate Or it may further contain 0.01 to 30 parts by weight of the mixed form.

Since polylactic acid made of a single monomer has a too high crystallization rate, an appropriate foam cannot be obtained because crystallization occurs immediately when it is discharged onto a sheet from an extrusion die and foamed. Moreover, the cell wall thickness of the obtained foam becomes thin, and the crystallinity is high, the tensile elongation is low, so the wall is easily broken. Therefore, when the biodegradable aliphatic polyester polymer is mixed with the polylactic acid and extruded, the two polymers are randomly arranged by a trans esterification reaction without aggregation when they are melted in the extruder. Since the crystallization rate is lowered, the desired crystallization rate is exhibited when ejected from the extrusion die. Therefore, the foam which is not easily broken can be obtained by adjusting the cell thickness of the foam obtained.

Examples of the biodegradable polymers include aliphatic polyesters obtained by condensing aliphatic diols and aliphatic dicarboxylic acids, aliphatic polyesters which are ring-opened-polymerized with cyclic lactones, and synthetic aliphatic polyesters. As aliphatic polyester which ring-opened-polymerized the said cyclic lactones, epsilon -caprolactone, delta-valerolactone, (beta) -methyl- delta-valerolactone, etc. which are cyclic monomers are mentioned typically, One type from these is mentioned. It selects and polymerizes above.

In particular, the present invention provides at least one aliphatic diol selected from the group consisting of ethylene glycol, 1,4-butanediol (butylene glycol) and 1,4-cyclohexanedimethanol; And at least one aliphatic dicarboxylic acid selected from the group consisting of terephthalic acid, isoterephthalic acid, succinic acid and adipic acid; it is preferable to use a biodegradable aliphatic polyester prepared by condensation polymerization.

Specific examples of the biodegradable polyesters used in the present invention include polybutylene succinate, polybutylene adipate, polybutylene succinate / terephthalate, polybutylene succinate / adipate / terephthalate and polybutyl Any one or two or more polymer mixtures selected from the group consisting of lensuccinate / adipate / isoterephthalate may be used.

Furthermore, the present invention provides a method for producing a foam sheet using a polylactic acid polymer composition.

More specifically, in the manufacturing method of the foam sheet of the present invention, as a first preferred embodiment, 0.05 to 4 parts by weight of a chain extender and 0.01 to 4 parts by weight of the foaming nucleating agent with respect to 100 parts by weight of the polylactic acid polymer composition. Supplying 1 to 30 parts by weight of the blowing agent and the blowing agent to the extruder, followed by heat melt kneading to prepare a melt kneaded product;

Cooling the melt kneaded material; And

Extrusion cooling the cooled melt kneaded material;

In the manufacturing method of the foam sheet of this invention, as a 2nd preferable example, 0.05-4 weight part of chain extenders and 0.01-4 weight part of foaming nucleating agents are mixed with respect to 100 weight part of polylactic acid type polymer compositions, and it melt | dissolves After cutting the extrudate on the strand obtained by heating the extrudate on the strand to obtain pellet-like polylactic acid resin particles, 1 to 30 parts by weight of the blowing agent relative to the polylactic acid resin particles and the polylactic acid polymer composition were extruded. Feeding and heating melt kneading to produce a melt kneaded product;

Cooling the melt kneaded material; And

Extrusion cooling the cooled melt kneaded material;

At this time, it is preferable that the extruder uses a tandem extruder.

In the manufacturing method of the foam sheet of the present invention, in the step of preparing the melt-kneaded, with respect to 100 parts by weight of the polylactic acid-based polymer composition, biodegradable aliphatic polyester, aliphatic / aromatic copolyester, polycaprolactone and polyhydride It may further contain 0.01 to 30 parts by weight of a single or mixed form selected from the group consisting of oxyalkanoate.

In the method for producing a foam sheet using the polylactic acid polymer composition of the present invention, the polylactic acid polymer composition, chain extender and biodegradable aliphatic polyester contained in step 1 are the same as described above.

The foaming nucleating agent used in the step 1 may be selected from known materials, and examples thereof include inorganic foaming nucleating agents such as talc and silica or organic foaming nucleating agents such as calcium stearate. It can be added in batch form. At the time of preparation of the masterbatch, a dispersing agent may be further added to adjust the dispersibility of the foaming nucleating agent. In addition, instead of adding the dispersant together in the preparation of the masterbatch, a dispersant may be further added separately. At this time, a stearic acid amide etc. can be used as a dispersing agent.

The foaming nucleating agent preferably contains 0.01 to 4 parts by weight with respect to 100 parts by weight of the polylactic acid polymer composition, and in this case, when the content is too small at less than 0.01 parts by weight, the polylactic acid resin particles may be sufficiently foamed. If it is more than 4 parts by weight, no further function of the foaming nucleus agent can be expected, and there is a possibility that the expandability and adhesion at the time of molding the obtained foamed particles in the mold are insufficient.

The blowing agent is pressed together with the polylactic acid-based resin particles and the foaming nucleating agent described above in the extruder, and the content of the blowing agent is 1 to 30 parts by weight, preferably 3 to 20 parts by weight. In this case, as the blowing agent, propane, isobutane, n-butane, cyclobutane, isopentane, n-pentane, cyclopentane, isohexane, n-hexane, cyclohexane, trichlorofluoromethane, dichlorodifluoromethane and chlorofluoro Methane, trifluoromethane, 1,1,1,2-tetrafluoroethane, 1-chloro-1,1-difluoroethane, 1,1-difluoroethane, 1-chloro-1,2, Organic physical blowing agents such as 2,2-tetrafluoroethane and inorganic physical blowing agents such as nitrogen, carbon dioxide, argon, and air. Among them, inorganic physical blowing agents without destruction of the ozone layer and inexpensive inorganic foaming agents are preferable. Is preferably nitrogen, air or carbon dioxide. Moreover, carbon dioxide is preferable at the point which foamed particle | grains of a smaller external appearance density are obtained with respect to the usage-amount of a foaming agent. Moreover, like carbon dioxide and isobutane, you may use combining 2 or more types of blowing agents.

The temperature of the extruder is carried out at a melting point ± 40 ℃ at a maximum of 250 ℃ based on the polylactic acid-based resin particle temperature, by adjusting the residence time during extrusion, it can be produced in a sheet shape, the preferred residence time is 5 to 10 minutes.

If the temperature of the extruder is too low, it is difficult to melt kneading, if the temperature exceeds 250 ℃, the rigidity of the resin is sharply lowered and the molded body can not maintain a constant shape may cause sagging during extrusion.

In the cooling step of step 2, the molten kneaded material in the extruder is connected and then transferred into the extruder to undergo a cooling step, wherein the cooling temperature is performed within 120 to 170 ° C based on the polylactic acid resin particle temperature. It is preferable to be.

In step 3, after the cooling process, the melt exits the extruder and is extruded through the annular die to be extruded as an annular foam sheet, and when cut, a wide foam sheet can be obtained.

At this time, the preferred foaming ratio of the foam sheet of the present invention may vary depending on the application, the foaming ratio suitable for food packaging and industrial packaging material is 4 to 15 times, more preferably 6 to 10 times.

The cooling section is subjected to a cooling section during the extrusion through the annular die, but the cooling section is preferably longer than that of the styrenic foam sheet, but is not limited thereto.

The foam sheet thus obtained may further include a printing layer.

The present invention provides a use of the foamed molded article prepared by the thermoforming method of the foam sheet produced from the manufacturing method.

Specifically, the foam sheet may be obtained as a foamed molded article through a conventional processing method. As an example, the foamed sheet may be heat-softened, sandwiched between male and female, and heated using a mold shaped in a container or the like. The shaping | molding method is mentioned. Examples of the thermoforming method include a vacuum molding method, a pressure molding method, a plug assist molding method, and the like.

The foamed molded article can be applied to food packaging materials such as trays, cups, cup noodles containers, lunch boxes, etc., and can also be used as other industrial packaging materials.

Hereinafter, the present invention will be described in detail by way of examples.

The following examples are merely illustrative of the present invention, but the scope of the present invention is not limited to the following examples.

<Example 1>

A polylactic acid polymer composition was prepared by mixing 10% by weight of amorphous polylactic acid (manufactured by NatureWorks, trade name: PLA 2002D) with 90% by weight of crystalline polylactic acid (manufactured by NatureWorks, trade name: PLA 4032D).

10 parts by weight of polybutylene succinate (PBS) as a biodegradable aliphatic polyester and 2 parts by weight of an epoxy chain extender as a chain extender and N, N 'as a stabilizer based on 100 parts by weight of the polylactic acid polymer composition. 0.5 parts by weight of diisopropylcarbodiimide, 0.05 parts by weight of ethylenebisstearic acid amide and zinc stearate as lubricants, and 3 parts by weight of talc as foaming nuclei are mixed well using a general mixer such as a tumbling mixer, and then The foam sheet was manufactured as follows using the tandem type | mold extruder with which the 1st extruder and the 2nd extruder of internal diameter 120mm were connected. The polylactic acid resin particles were fed to the first extruder and kneaded with heat, and then 2.5 parts by weight of butane was pressed into the first extruder as a blowing agent to maintain a residence time of 10 minutes. At this time, the heating melting temperature was maintained at 170 to 230 ℃ based on the resin temperature. The temperature of the melt mixed reactant was then slightly reduced in the second extruder connected with the first extruder to bring the resin temperature to 120-150 ° C. Thereafter, the sheet was extruded from an annular die having a cylindrical slit having a diameter of 110 mm and a slit interval of 0.5 mm to be foamed in a cylindrical shape, and the foam was discharged in the printing and extrusion directions while cooling the cylindrical foam to obtain a foam sheet.

<Example 2>

A polylactic acid polymer composition was prepared by mixing 40 wt% of amorphous polylactic acid (manufactured by NatureWorks, trade name: PLA 2002D) with 60 wt% of crystalline polylactic acid (manufactured by NatureWorks, trade name: PLA 4032D).

Comparative Example 1

A polylactic acid polymer composition was prepared, consisting only of 100% by weight of crystalline polylactic acid (manufactured by NatureWorks, trade name: PLA 4032D).

Comparative Example 2

A polylactic acid polymer composition was prepared, consisting only of 100% by weight of amorphous polylactic acid (manufactured by NatureWorks, trade name: PLA 2002D).

Comparative Example 3

A polylactic acid polymer composition was prepared by mixing 80 wt% of amorphous polylactic acid (manufactured by NatureWorks, trade name: PLA 2002D) with 20 wt% of crystalline polylactic acid (manufactured by NatureWorks, trade name: PLA 4032D).

Experimental Example 1 Measurement of Physical Properties of Foam Sheet according to Polylactic Acid-based Polymerizable Composition

1. Heat resistance measurement

The foam sheet obtained from the polylactic acid polymer composition prepared in Examples 1 to 2 and Comparative Examples 1 to 3 was immersed in water at 70 ° C. for 3 minutes, and then observed a change in form and classified into the following criteria.

Very good: no shape change,

Good: Changes in form, but the container can be used at room temperature,

Poor: A condition that is severely changed and cannot be used as a container.

2. Measurement of glass transition temperature (Tg) and melting point (Tm)

Based on JIS-K-7121, the glass transition temperature (Tg) and melting point (Tm) of a sheet were measured by the differential scanning calorimetry (DSC) at the temperature increase rate of 10 degreeC / min, and it is shown in following Table 3 .

3. Determination of Crystallinity

Based on JIS-K-7121, the crystallinity attributable to polylactic acid-based resin in the sheet was measured by differential scanning calorimetry (DSC) at a rate of 20 ° C / min, and the results are shown in Table 1 and FIG. 1 . It was. For reference, in order to calculate the degree of crystallization of polylactic acid-based resin, the amount of heat of fusion (ΔHm) and the amount of heat of crystallization (ΔHc) are measured and calculated by the following formula.

Relative Crystallization Degree (%) = [(ΔHm-ΔHc) / ΔHm] × 100

Physical property measurement results of foam sheet according to polylactic acid polymer composition Glass transition temperature (Tg) Crystallization temperature (Tc) Melting temperature (Tm) Heat resistance Example 1 65 ℃ 119 ~ 129 ℃ 164 ℃ Very good Example 2 65 ℃ 119 ~ 129 ℃ - Good Comparative Example 1 65 ℃ Does not appear 164 ℃ Good Comparative Example 2 65 ℃ - - Bad Comparative Example 3 65 ℃ - - Bad

As shown in Table 1 and Figure 1, the foam sheet using the polylactic acid-based polymer composition prepared in Examples 1 to 2 by mixing amorphous polylactic acid with crystalline polylactic acid, to confirm a clear crystallization temperature (Tc) It was.

<Examples 3 to 5>

The chain extension was carried out in the same manner as in Example 2, except that it was changed as described in Table 2 .

<Comparative Example 4>

The same procedure as in Example 1 was carried out except that no chain extender was used.

Chain extender Content (parts by weight) Melt Index (g / 10min) Sheet formability Example 3 Epoxy compounds 2 1.0 Good Example 4 Isocyanate Compound 2 2.0 Good Example 5 Acrylic compound 2 3.0 usually Comparative Example 4 No addition 8 Sag in extruder die

<Examples 6-16>

The biodegradable aliphatic polyester was carried out in the same manner as in Example 2, except that it was changed as described in Table 3 .

At this time, the thickness of the cell of the prepared foam sheet was measured by using a scanning electron microscope, the sheet formability by molding a disposable ramen container, and classified according to the following criteria with the results.

(Circle): When formability is equal to the sheet | seat of polystyrene resin,

(Triangle | delta): When moldability is favorable but thickness and shrinkage are not uniform,

X: When there is no commercial property from the external appearance of the product shape | molded with the sheet | seat,

Comparative Example 5

The same procedure as in Example 1 was conducted except that no biodegradable aliphatic polyester was used.

Addition polymer Addition amount (part by weight) Cell thickness (μm) Sheet formability Example 6 PET 10 2 × Example 7 PBT 10 4 △ Example 8 PETiT 10 4 ○ Example 9 PBS 5 3 ~ 6 △ Example 10 PBS 10 3 ~ 7 ○ Example 11 PBA 10 2 ~ 8 △ Example 12 PBST 10 1-6 ○ Example 13 PBAT 10 3 ~ 10 ○ Example 14 PBSAT 10 3 ~ 7 ○ Example 15 PCL 10 2 to 10 ○ Example 16 PBSATiT 20 5-10 ○ Comparative Example 5 No addition 1 to 3 × ~ △

E: Ethylene Glycol

B: Butylene Glycol

T: terephthalic acid

iT: Isoterephthalic Acid

S: Succinic acid

A: adipic acid

PCL: Polycaprolactone

As described above, the present invention

First, by mixing amorphous polylactic acid with crystalline polylactic acid, but less content of amorphous polylactic acid than crystalline polylactic acid, polylactic acid-based polymer composition improved not only foamability and molding stability, but also thermal stability Provided,

Second, by mixing a chain extender and a biodegradable aliphatic polyester in the polylactic acid-based polymer composition, by increasing the molecular weight of the polylactic acid to increase the crystallinity, by controlling the crystallization rate and melt index during molding, as well as foamability and molding stability , Prepared a foam sheet with excellent thermal stability,

Third, the foamed molded article produced by molding the foam sheet can be usefully used as a food packaging material or an industrial packaging material such as a tray, a cup, a cup ramen container, a lunch box, etc., thereby providing a use thereof.

While the invention has been described in detail only with respect to the described embodiments, it will be apparent to those skilled in the art that various modifications and variations are possible within the scope of the invention, and such modifications and variations belong to the appended claims.

1 is a DSC result of the foam sheet using the polylactic acid polymer composition of the present invention.

Claims (18)

delete To 100 parts by weight of the polylactic acid polymer composition consisting of 55 to 98% by weight of crystalline polylactic acid and 2 to 45% by weight of amorphous polylactic acid, 0.05 to 4 parts by weight of a chain extender and 0.01 to 4 parts by weight of a foaming nucleating agent are mixed. Foam sheet using a polylactic acid polymer composition, characterized in that the foam. According to claim 2, Alkali or mixed selected from the group consisting of biodegradable aliphatic polyester, aliphatic / aromatic copolyester, polycaprolactone and polyhydroxyalkanoate with respect to 100 parts by weight of the polylactic acid polymer composition A foam sheet using the polylactic acid-based polymer composition, characterized in that it further comprises 0.01 to 30 parts by weight of the form. The carbodiimide-based stabilizer according to claim 2, wherein the carbodiimide-based stabilizer is 0.01 to 100 parts by weight of the polylactic acid-based polymer composition. To 2 parts by weight and lubricant from 0.01 to A foam sheet using the polylactic acid polymer composition, characterized in that it further contains 2 parts by weight. The method according to claim 2, wherein the chain extender is selected from the group consisting of bisphenol A diglycidyl ether, terephthalic acid diglycidyl ether, trimethylolpropane diglycidyl ether, and 1,6-hexanediol diglycidyl ether Epoxy-based compound; Or an isocyanate compound selected from the group consisting of hexamethylene diisocyanate, tolylene diisocyanate, xyylene diisocyanate, diphenylmethane diisocyanate and triisocyanate; Or an acrylic compound; foam sheet using the polylactic acid-based polymer composition, characterized in that any one selected from. According to claim 3, wherein the biodegradable aliphatic polyester is at least one aliphatic diol selected from the group consisting of ethylene glycol, 1,4-butanediol and 1,4-cyclohexanedimethanol; And at least one or more aliphatic dicarboxylic acids selected from the group consisting of terephthalic acid, isoterephthalic acid, succinic acid and adipic acid; and foamed sheet using the polylactic acid polymer composition. The method of claim 6 wherein the biodegradable aliphatic polyester is polybutylene succinate, polybutylene adipate, polybutylene succinate / terephthalate, polybutylene succinate / adipate / terephthalate and polybutylene succinate. Foam sheet using the polylactic acid-based polymer composition, characterized in that any one selected from the group consisting of nate / adipate / isoterephthalate. The polycarbide according to claim 4, wherein the carbodiimide-based stabilizer is N, N'-diisopropyl carbodiimide or N, N'-di-2,6-diisopropylphenyl carbodiimide. Foam sheet using lactic acid polymer composition. The foam sheet using the polylactic acid polymer composition according to claim 4, wherein the lubricant is in the form of a fatty acid amide compound alone or a mixture of the fatty acid amide compound and a fatty acid base. 10. The compound according to claim 9, wherein the fatty acid amide compound is selected from the group consisting of stearic acid amide, oleic acid amide, palmitic acid amide, lauric acid amide, ethylene bis stearic acid amide, ethylene bis oleic acid amide and ethylene bis lauric acid amide. Foam sheet using the polylactic acid-based polymer composition, characterized in that more than. 10. The method according to claim 9, wherein the fatty acid base is at least one selected from the group consisting of aluminum stearate, magnesium stearate, zinc stearate, calcium stearate, magnesium oleate, zinc oleate, calcium oleate, magnesium palmate, zinc palmate and calcium palmitate. Foam sheet using the polylactic acid polymer composition. 0.05 to 4 parts by weight of chain extender, 0.01 to 4 parts by weight of foaming nucleating agent and foaming agent based on 100 parts by weight of polylactic acid polymer composition comprising 55 to 98% by weight of crystalline polylactic acid and 2 to 45% by weight of amorphous polylactic acid. Supplying 1 to 30 parts by weight to an extruder, followed by hot melt kneading to prepare a melt kneaded product; Cooling the melt kneaded material; And Extruding and foaming the cooled melt kneaded product. The method according to claim 12, wherein the step of preparing the melt kneaded product is a strand obtained by mixing 0.05 to 4 parts by weight of a chain extender and 0.01 to 4 parts by weight of the foaming nucleating agent with respect to 100 parts by weight of the polylactic acid polymer composition, and melting and heating. After cutting the extrudate of the phase to obtain pellet-like polylactic acid-based resin particles, 1 to 30 parts by weight of the blowing agent is supplied to the extruder based on 100 parts by weight of the polylactic acid-based resin particles and the polylactic acid-based polymer composition, followed by hot melt kneading. Method for producing a foam sheet using the polylactic acid polymer composition, characterized in that to prepare a melt kneaded. The biodegradable aliphatic polyester, aliphatic / aromatic copolyester, polycaprolactone and polyhydride according to claim 12 or 13, in the step of preparing the melt kneaded product, based on 100 parts by weight of the polylactic acid polymer composition. Method for producing a foam sheet using the polylactic acid-based polymer composition, characterized in that it further comprises 0.01 to 30 parts by weight of a single or mixed form selected from the group consisting of oxyalkanoate. The foam sheet using the polylactic acid polymer composition according to claim 12 or 13, wherein the temperature of the extruder is up to 250 ° C at a melting point of ± 40 ° C based on the polylactic acid resin particle temperature. Manufacturing method. The method of claim 12, wherein the temperature of the cooling step is 120 to 170 ° C based on the temperature of the polylactic acid-based resin particles. The chain extender according to claim 12 or 13, wherein the chain extender is selected from bisphenol A diglycidyl ether, terephthalic acid diglycidyl ether, trimethylolpropane diglycidyl ether, and 1,6-hexanediol diglycidyl ether. An epoxy compound selected from the group consisting of; Or an isocyanate compound selected from the group consisting of hexamethylene diisocyanate, tolylene diisocyanate, xyylene diisocyanate, diphenylmethane diisocyanate and triisocyanate; Or an acrylic compound; a method for producing a foam sheet using the polylactic acid polymer composition, characterized in that any one selected from. Molded foam for food packaging material or industrial packaging material, characterized in that the molded molded foam sheet produced from the manufacturing method of claim 12 or 13.

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