JP2009007039A - Polylactic acid resin container provided with gas barrier property - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biodegradable polylactic acid resin container with an improved gas barrier property. <P>SOLUTION: At least either the inside surface or the outside surface of a container main body is provided with a thin gas barrier film. The main body of the container is made of a resin obtained by blending a functional filler to a poly-L-lactic acid resin. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a polylactic acid resin container, and more particularly to a polylactic acid resin container that is biodegradable and has excellent gas barrier properties.

  PET bottles are widely used all over the world so as to be said to be a container revolution, and soy sauce, edible water, drinking water, light drinks, and even beer are widely used, contributing greatly to civic life and distribution. The development of plastics such as PET bottles has greatly contributed to human life and industrial activities, but in recent years it has also attracted attention as a factor that causes environmental problems such as depletion of petroleum resources and global warming. It is becoming.

  One solution to this problem is the development of plastic from plant resources, which are renewable resources. Among them, polylactic acid resin is a kind of biodegradable resin obtained from renewable raw materials such as corn and potato. It has excellent transparency and hardness and is widely used in polystyrene, which is currently widely used in food containers. Has similar physical properties.

  On the other hand, when the container is made of a resin such as polylactic acid resin, the container is more permeable to oxygen gas and carbon dioxide gas than a glass container, so the period during which the quality of the contents can be maintained, so-called There is a concern that the shell life will be shortened. On the other hand, for example, a packaging material made of a degradable plastic has been proposed in which a thin film layer of an inorganic substance is formed on a degradable plastic layer to give gas barrier properties (Patent Document 1).

Japanese Patent No. 2917576

  In recent years, in order to achieve stable maintenance of the quality of contents over a long period of time in resin containers, further improvement in gas barrier properties has been demanded, and containers made of biodegradable resins such as polylactic acid resins have been required. In practical use, improvement of the gas barrier property of the container is one of the important issues.

  Accordingly, an object of the present invention is to improve gas barrier properties in a container made of a biodegradable polylactic acid resin.

  As a result of intensive studies to solve the above problems, the inventors of the present invention constituted a container body with a resin obtained by adding a functional filler containing D-lactic acid to a resin made of poly-L-lactic acid, It has been found that the gas barrier property can be improved by forming a gas barrier thin film on at least one of the inner surface and the outer surface of the container body, and the present invention has been completed.

That is, the container of the present invention comprises a gas barrier thin film on at least one of the inner surface or the outer surface of the container body,
The container body is made of a resin in which a functional filler is blended with a resin made of poly-L-lactic acid.

  In a preferred example of the container of the present invention, the poly L-lactic acid has a number average molecular weight of 60,000 to 80,000.

  In another preferred embodiment of the container of the present invention, the functional filler is obtained by graft-polymerizing 1 to 100 molecules of D-lactic acid on a compound having 2 to 4 hydroxyl groups.

  In another preferred embodiment of the container of the present invention, the compound is a saccharide selected from polysaccharides or oligosaccharides. Here, the oligosaccharide is preferably a pentose.

  In another preferred embodiment of the container of the present invention, the compound is a silicon compound.

  In another preferred embodiment of the container of the present invention, the compound is an organic compound selected from polyethylene glycol, trimethylolpropane, or pentaerythritol.

  In another preferred embodiment of the container according to the present invention, 30 to 50 molecules of the D-lactic acid are graft-polymerized in the functional filler.

  Another preferred embodiment of the container of the present invention is characterized in that 50 molecules of D-lactic acid are graft polymerized with pentaerythritol having 4 hydroxyl groups.

  In another preferred embodiment of the container of the present invention, the amount of the functional filler is 5 to 20% by mass based on the poly L-lactic acid. Here, it is preferable that the compounding quantity of the said functional filler is 10 mass% with respect to the said poly L-lactic acid.

  In another preferred embodiment of the container of the present invention, the gas barrier thin film is provided on the inner surface of the container body.

  In another preferred embodiment of the container of the present invention, the gas barrier thin film is made of a material selected from a silicon oxide compound, an organic silicon compound, or amorphous carbon.

  According to the present invention, there is an advantageous effect that a container made of a polylactic acid resin that is biodegradable and has an excellent gas barrier property can be provided.

  Hereinafter, the container of the present invention will be described in detail. The container of the present invention comprises a gas barrier thin film on at least one of the inner surface and the outer surface of the container body, and the container body is made of a resin in which a functional filler is blended with a resin made of poly-L-lactic acid. To do. The container body is made of a resin made of poly-L-lactic acid containing a functional filler, and a gas barrier film is provided on at least one of the inner or outer surface of the container body, thereby improving the gas barrier property of the container. be able to.

  In the container of the present invention, the container body is made of a resin in which a functional filler is blended with a resin made of poly-L-lactic acid, as described above. In the present invention, the poly L-lactic acid preferably has a number average molecular weight of 60,000 to 80,000. By using poly L-lactic acid having a number average molecular weight in the above range, a hollow molded product such as a bottle can be suitably molded. Here, as a resin made of polylactic acid, a commercially available resin can be used, for example, Lacia H100, H440 and Lacia H400 manufactured by Mitsui Chemicals, NatureWorks 7000D and 7032D manufactured by NatureWorks, etc. However, it is not particularly limited.

  In the present invention, the functional filler is preferably one obtained by graft-polymerizing 1 to 100 molecules of D-lactic acid on a compound having 2 to 4 hydroxyl groups. If the amount of graft polymerization of D-lactic acid is 1 molecule or less, good gas barrier properties may not be obtained, and if it is 100 molecules or more, the container tends to be opaque. From the viewpoint of achieving both good gas barrier properties and transparency of the container, the functional filler is more preferably a compound obtained by grafting 30 to 50 molecules of D-lactic acid to the compound, and 50 molecules of graft polymerization. It is most preferred that

  In the present invention, the compound having 2 to 4 hydroxyl groups in the functional filler is, for example, a saccharide selected from polysaccharides or oligosaccharides, a silicon compound, polyethylene glycol, trimethylolpropane or pentaerythritol. Compounds.

  Specific examples of the saccharide include monosaccharides such as glucose and fructose, disaccharides such as sucrose, and polysaccharides such as starch and dextrin. When the functional filler is an oligosaccharide, it is preferably a pentose.

  Specific examples of the silicon compound include Aerosil silica (manufactured by Nippon Aerosil Co., Ltd.), tetraethoxysilane, hexamethyldisiloxane and the like.

  Moreover, when the said compound is polyethyleneglycol, it is preferable that the molecular weight of polyethyleneglycol exists in the range of 200-1000.

  In this invention, it is preferable that the compounding quantity of the said functional filler is 5-20 mass% with respect to the said poly L-lactic acid, and it is especially preferable that it is 10 mass%. If the blending amount of the functional filler is 5% or less, sufficient gas barrier properties may not be obtained. If it is 30% by mass or more, the viscosity at the time of injection molding becomes low, and there is a problem in workability of secondary molding. May occur.

  The container body according to the present invention is obtained by first extruding, compressing or injection-molding a resin obtained by blending the above functional filler with the above-mentioned resin made of poly-L-lactic acid, which is known in this technical field. A reform can be manufactured and the preform can be blow molded in a mold. As a blow molding method, a biaxial stretch blow molding method is preferably used, but is not limited thereto.

  Further, the container body may be formed by laminating by a known method using one or more resins made of poly-L lactic acid containing the above functional filler, or one or more kinds of resins may be formed. Laminated using the above functional filler blended poly-L lactic acid resin and one or more of the resins used in conventional containers such as polyethylene terephthalate (PET), ethylene-vinyl alcohol copolymer, nylon, polyolefin, etc. May be formed. Further, two or more kinds of the above resins may be blended to form a container body, or one or two or more kinds of the above resins and one or more kinds of resins used in the above conventional containers. May be blended to form a container body.

  Next, the gas barrier thin film in the container of the present invention will be described in detail. In the container of the present invention, the gas barrier thin film is formed on at least one of the inner surface and the outer surface of the container body. From the viewpoint of further improving the gas barrier property, it is preferable that a gas barrier thin film is formed on the inner surface of the container body. In addition, a single thin film may be formed on at least one of the inner surface and the outer surface of the container body, or one or more thin films may be laminated.

  The substance constituting the gas barrier thin film may be a substance that is conventionally known to impart gas barrier properties to the thin film, and is not particularly limited, but may be selected from a silicon oxide compound, an organic silicon compound, or amorphous carbon. preferable. By selecting the types of substances that make up the thin film, it is possible to increase the barrier properties against various gases such as oxygen, carbon dioxide, and water vapor. It is also possible to select the type of compound constituting.

  First, the case where a thin film made of a silicon oxide compound or an organic silicon compound is formed as a gas barrier thin film will be described in detail. A thin film made of the silicon oxide compound (hereinafter referred to as a silicon oxide compound thin film) contains a compound having a Si—O bond as a main component, and in addition, one or two of carbon, hydrogen, silicon and oxygen are used. There are compounds composed of more than one element. In addition, a thin film made of the organosilicon compound (hereinafter referred to as an organosilicon compound thin film) contains a compound composed of one or more elements selected from carbon, hydrogen, silicon and oxygen as a main component.

  Examples of the compound composed of one or more elements among carbon, hydrogen, silicon and oxygen include, for example, a compound having a C—H bond, a compound having a Si—H bond, a compound having a C—O bond, When the compound having an Si—C bond or the simple carbon is in the form of graphite, diamond, or fullerene, it may further contain a raw material organosilicon compound or a derivative thereof.

  Specific examples include hydrocarbons having alkyl groups such as methyl groups and methylene groups, hydroxycarbons containing hydroxyl groups and ketone groups, hydrosilicas having silyl groups and silylene groups, and hydroxyl groups such as silanols. There are derivatives. In addition to the above, the type and amount of the compound contained in the gas barrier thin film can be controlled by changing the composition of the source gas and the deposition conditions.

  The silicon oxide compound thin film and the organic silicon compound thin film can be manufactured using, for example, a known chemical vapor deposition (CVD) method typified by a CVD method, a thermal CVD method, a plasma CVD method, or the like. it can. Further, for example, it is manufactured using a known physical vapor deposition (PVD) method represented by a reactive sputtering method, an ion plating method, an arc vapor deposition method, an ion vapor deposition method, a plasma ion implantation method, or the like. You can also. Here, the thickness of the formed thin film is preferably 10 to 100 nm from the viewpoint of barrier properties and film flexibility.

  Examples of source gases for the silicon oxide compound thin film and the organosilicon compound thin film include silanes such as silane, alkylsilane, dialkylsilane, and trialkylsilane, alkoxysilanes such as monoalkoxysilane, dialkoxysilane, and trialkoxysilane, In addition to siloxanes such as tetraalkyldisiloxane and hexaalkyldisiloxane, silazanes such as hexamethyldisilazane, and the like, gases of organic silicon compounds known per se can be used. In the present invention, it is preferable to use hexamethyldisiloxane (HMDSO) as the gas of the organosilicon compound from the viewpoint of safety during raw material handling and raw material price.

  The raw material gases may be used alone or as a mixture of two or more as necessary, and oxygen gas is preferably mixed and used at an appropriate ratio. Note that a silicon oxide compound thin film can be formed by increasing the proportion of oxygen in the source gas, and an organosilicon compound thin film can be formed by decreasing the proportion of oxygen. When an organic silicon compound having a high carbon content is used as the source gas, it is preferable to increase the mixing ratio of oxygen gas in order to remove carbon as carbon dioxide. The source gas may be diluted with a rare gas such as argon or helium.

Next, the case where a thin film made of amorphous carbon is formed as the gas barrier thin film will be described in detail. In the present invention, a thin film made of amorphous carbon (hereinafter referred to as an amorphous carbon thin film) includes a diamond component (carbon atom bond is SP ³ bond), a graphite component (carbon atom bond is SP ² bond), a polymer component ( It is a carbon thin film having an amorphous structure in which carbon atom bonds are SP ¹ bonds). The amorphous carbon thin film refers to a thin film including a hard carbon film and a soft carbon thin film, the hardness of which changes due to the change in the abundance ratio of the bonding component of each carbon atom. The hard carbon thin film also includes an amorphous DLC (Diamond Like Carbon) thin film mainly composed of SP ³ bonds.

  For the amorphous carbon thin film, a known chemical vapor deposition method (CVD method) and physical vapor deposition method (PVD method) can be used as in the formation of the silicon oxide compound thin film. Here, the thickness of the formed thin film is preferably 10 to 100 nm from the viewpoint of barrier properties and film flexibility.

  The raw material gas used to form a thin film made of amorphous carbon includes aliphatic unsaturated hydrocarbon compounds such as acetylene, ethylene, and propylene, aliphatic saturated hydrocarbon compounds such as methane, ethane, and propane, and alicyclic carbonization such as cyclohexane. Examples thereof include carbon-containing compounds such as hydrogen compounds, aromatic hydrocarbon compounds such as benzene, toluene and xylene. The source gas may be used alone or as a mixture of two or more as required. A small amount of hydrogen, an organosilicon compound, and other film-forming organic compounds are used in combination as a film modifier. Also good. The source gas may be diluted with a rare gas such as argon or helium.

  From the viewpoint of forming an amorphous carbon thin film excellent in gas barrier properties in a shorter time, it is suitable that the source gas is substantially acetylene, and is 60% by volume or more, preferably 80% by volume or more of the source gas. Is preferably acetylene. In addition, when the said source gas consists of acetylene substantially, this acetylene may contain the unavoidable impurity mixed in a manufacturing process etc.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

Example 1
Injection molding is performed by adding 10% by mass of polylactic acid resin (PLA) (Lacia H400 manufactured by Mitsui Chemicals) to which 50 molecules of D-lactic acid is graft-polymerized with pentaerythritol having four functional groups as a functional filler. Thus, a preform was produced. The obtained preform was blow-molded in a mold having a temperature of 120 ° C. to produce a 180 mL capacity blow bottle.

On the inner surface of the obtained bottle, a silica (SiO _x ) vapor deposition film having a thickness of 36.6 nm is formed by plasma CVD using high frequency pulses using hexamethyldisiloxane (HMDSO) and oxygen as source gases. did. The film forming conditions are as follows: RF output is 330 W, film forming time is 14 sec (0.1 sec pulse film forming), film forming pressure is 22 Pa, HMDSO gas flow rate is 5 sccm, and oxygen gas flow rate is 20 sccm. Here, “sccm” is the amount of gas (cc) flowing per minute at 0 ° C. and 1 atm.

(Example 2)
In the same manner as in Example 1 except that polylactic acid resin (PLA) (Laissia H100 manufactured by Mitsui Chemicals, Inc.) was used instead of polylactic acid resin (PLA) (Laissia H400 manufactured by Mitsui Chemicals, Inc.), a silica vapor deposited film was formed. A 180 mL capacity blow bottle provided on the inner surface of the container was prepared.

(Example 3)
A 180 mL capacity blow bottle having a silica vapor deposition film on the inner surface of the container was produced in the same manner as in Example 1 except that the mold temperature for blow molding was changed to 20 ° C.

(Comparative Example 1)
A 180 mL capacity blow bottle having a silica vapor deposition film on the inner surface of the container was prepared in the same manner as in Example 1 except that the functional filler was not added to PLA.

(Comparative Example 2)
A 180 mL capacity blow bottle was produced in the same manner as in Example 1 except that the silica vapor deposition film was not formed.

(Comparative Example 3)
A 180 mL capacity blow bottle having a silica vapor deposition film on the inner surface of the container was prepared in the same manner as in Example 2 except that the functional filler was not added to PLA.

(Comparative Example 4)
A 180 mL capacity blow bottle having a silica vapor deposition film on the inner surface of the container was prepared in the same manner as in Example 3 except that the functional filler was not added to PLA.

(Conventional example 1)
A blow bottle with a capacity of 180 mL was produced in the same manner as in Example 1 except that the functional filler was not added to PLA and a silica vapor deposition film was not formed.

(Conventional example 2)
A 180 mL capacity blow bottle was produced in the same manner as in Example 2 except that the functional filler was not added to PLA and the silica vapor deposition film was not formed.

(Conventional example 3)
A 180 mL capacity blow bottle was produced in the same manner as in Example 3 except that the functional filler was not added to PLA and a silica vapor deposition film was not formed.

About the bottle of each Example, a comparative example, and a conventional example, the oxygen permeation amount per day (OX-TRAN 2/20 manufactured by MOCON, Inc. Measurement conditions: oxygen partial pressure 21%, bottle outer side 23 ° C.-55% RH, The inside of the bottle (23 ° C.-90% RH) was measured, and the barrier improvement factor (Barrier Improvement Factor, BIF) compared with Conventional Examples 1 to 3 without filler and without coating was calculated by the following formula. The results are shown in Tables 1-3.
Formula: BIF = [Oxygen Permeation of Conventional Example] / [Oxygen Permeation of Examples and Comparative Examples]

  From Table 1, Example 1 in which a polylactic acid resin with a functional filler added to the container body was applied and a silica vapor deposition film was formed on the inner surface of the container was applied with a polylactic acid resin to which no functional filler was added. Compared to Conventional Example 1 in which no deposited film was formed, the gas barrier properties were greatly improved.

  On the other hand, the polylactic acid resin to which the functional filler is not added is applied, and the comparative example 1 in which the silica vapor deposition film is formed and the polylactic acid resin to which the functional filler is added are applied, and the silica vapor deposition film is not formed. In Comparative Example 2, although the gas barrier property was slightly improved as compared with Conventional Example 1, no significant improvement as in Example 1 was observed.

  From Tables 2 and 3, when polylactic acid resin (PLA) (Laissia H100 manufactured by Mitsui Chemicals) is used instead of polylactic acid resin (PLA) (Laisia H400 manufactured by Mitsui Chemicals), and for blow molding Even when the mold temperature was changed to 20 ° C., the same tendency as the above results was observed.

Claims (13)

A gas barrier thin film is provided on at least one of the inner surface and the outer surface of the container body,
A container characterized in that the container body is made of a resin in which a functional filler is blended with a resin made of poly-L-lactic acid.   The container according to claim 1, wherein the poly-L-lactic acid has a number average molecular weight of 60,000 to 80,000.   The container according to claim 1 or 2, wherein the functional filler is obtained by graft-polymerizing 1 to 100 molecules of D-lactic acid to a compound having 2 to 4 hydroxyl groups.   4. A container according to claim 3, wherein the compound is a saccharide selected from polysaccharides or oligosaccharides.   The container according to claim 5, wherein the oligosaccharide is pentose.   The container according to claim 3, wherein the compound is a silicon compound.   The container according to claim 3, wherein the compound is an organic compound selected from polyethylene glycol, trimethylolpropane, or pentaerythritol. The container according to any one of claims 3 to 7, wherein 30 to 50 molecules of the D-lactic acid are graft-polymerized in the functional filler.
3. The container according to 3.   The container according to claim 3, wherein the functional filler is obtained by graft-polymerizing 50 molecules of D-lactic acid to pentaerythritol having four hydroxyl groups.   The container according to any one of claims 1 to 9, wherein a blending amount of the functional filler is 5 to 20% by mass with respect to the poly-L-lactic acid.   The container according to claim 10, wherein the amount of the functional filler is 10% by mass with respect to the poly-L-lactic acid.   The container according to any one of claims 1 to 11, wherein the gas barrier thin film is provided on an inner surface of the container main body.   The container according to any one of claims 1 to 12, wherein the gas barrier thin film is made of a material selected from a silicon oxide compound, an organic silicon compound, or amorphous carbon.