JP5007623B2 - Freshness preservation material - Google Patents

Description

  The present invention relates to a freshness-keeping material used for packaging films, packaging containers, and the like that can maintain the freshness of meat, fish, vegetables, fruits, florets and the like.

  Various packaging materials have been studied in the past to maintain freshness when storing meat, fish, vegetables, fruits, flowers, etc. from the production area to the consumer and until they are consumed for a certain period of time. Has been. For example, a film made of a mixed resin of an ethylene-octene copolymer and a polypropylene-ethylene copolymer was used (Patent Document 1), or a biodegradable resin was used (Patent Document 2). Moreover, it was necessary to make it a multilayer film, and it was necessary to enclose a desiccant and a freshness keeping material.

  However, if a multilayer film is used or a freshness-holding material is included, it is too costly and the productivity is lowered, which is not practical. In addition, since the ethylene-based packaging material has a low water vapor permeability, the humidity inside the packaging material is increased, and mold generation, oxidation, pest generation, and discoloration are likely to occur. At the time of disposal, there is a problem of carbon dioxide generation when incinerated, and the problem of insufficient landfill in urban areas when reclaimed is becoming more serious.

On the other hand, in biodegradable films, polylactic acid, polybutylene succinate, polybutylene terephthalate adipate, polycaprolactone, etc. are common, but polylactic acid is not suitable as a packaging film because it lacks flexibility. In addition, when used as a packaging material, there is a drawback that heat sealability is poor. In addition, polybutylene terephthalate adipate and polycaprolactone have problems due to being too flexible, such as being too flexible and difficult to process into a bag. In addition, since polybutylene succinate has been conventionally difficult to achieve high molecular weight, it is chain extended with a chain extender such as hexamethylene diisocyanate. There was a problem with safety to use.
JP 2003-169598 A JP 2006-051982 A

  The present invention has been made in view of the above-mentioned background art, and the problem is that the meat, vegetables, fruits, flowers, etc. are transported or stored, the freshness is maintained, the water is resistant, and the waste An object of the present invention is to provide a freshness-keeping material as a packaging resin material that uses only raw materials that contribute to solving problems and are not problematic for food applications.

  As a result of intensive studies to solve the above problems, the present inventors can maintain the freshness of fresh food products and the like by containing a specific aliphatic polyester, and the specific aliphatic In order to complete the present invention, it has been found that it is possible to provide a safer freshness-retaining material by refining the polyester without using a harmful organic solvent to remove impurities. It came.

That is, the present invention is an aliphatic polyester containing an aliphatic dicarboxylic acid unit and an aliphatic and / or alicyclic diol unit,
(1) The water vapor permeability measured at 40 ° C. and 90% RH of the 25 μm-thick film of the aliphatic polyester alone is 100 [cm ³ / (m ² · day · atm)] or more,
(2) The organic compound not derived from the raw material of the aliphatic polyester contains 10 mass% to 100 mass% of an aliphatic polyester having a content of 10 ppm or less with respect to the entire aliphatic polyester. A freshness maintaining material is provided.

  According to the present invention, “organic compounds not derived from aliphatic polyester raw materials” such as organic solvents and impurities are low in concentration, which is particularly suitable for food packaging applications, biodegradable, heat-resistant Since the sealing property is good, the material is flexible, and has good gas permeability, it is possible to provide a freshness-holding material that exhibits excellent freshness-keeping performance. Further, according to the present invention, since it has biodegradability and does not contain harmful substances, it is possible to provide a freshness maintaining material suitable for environmental protection and safe.

  Hereinafter, the freshness-keeping material of the present invention, the aliphatic polyester contained therein, and the like will be described in detail, but the present invention is not limited to the following specific forms, and is arbitrary within the technical scope of the invention. Can be transformed into

<Aliphatic dicarboxylic acid unit>
The freshness-keeping material of the present invention contains an aliphatic polyester containing an aliphatic dicarboxylic acid unit and an aliphatic and / or alicyclic diol unit. Specific examples of the aliphatic dicarboxylic acid constituting the aliphatic dicarboxylic acid unit in the aliphatic polyester contained in the freshness-keeping material of the present invention are not particularly limited. For example, oxalic acid, succinic acid, glutaric acid, Examples include adipic acid, sebacic acid, dodecanedioic acid, 1,6-cyclohexanedicarboxylic acid, and the like. These acid anhydrides may also be used. Furthermore, “aliphatic dicarboxylic acid derivatives” such as lower alkyl esters of these aliphatic dicarboxylic acids may be used.

  Among these, specifically, succinic acid, glutaric acid, sebacic acid, dimer acid, dodecanedioic acid, acid anhydrides thereof, lower alkyl (for example, alkyl having 1 to 4 carbon atoms) ester derivatives, and the like Succinic acid, succinic anhydride, lower alkyl (preferably alkyl having 1 to 4 carbon atoms) ester derivatives of succinic acid, adipic acid and the like are more preferable, and succinic acid and adipic acid are particularly preferable. These may be used alone or in combination of two or more.

<Aliphatic and / or alicyclic diol units>
The “aliphatic and / or alicyclic diol” constituting the “aliphatic and / or alicyclic diol unit” of the aliphatic polyester contained in the freshness-keeping material of the present invention is not particularly limited. , Ethylene glycol, diethylene glycol, triethylene glycol, 1,3-propanediol, 1,2-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexane Examples include diol and 1,4-cyclohexanedimethanol. Among these, 1,4-butanediol, ethylene glycol or 1,3-propanediol is preferable, and 1,4-butanediol or ethylene glycol is more preferable from the viewpoint of the physical properties of the obtained aliphatic polyester. 1,4-butanediol is particularly preferred. These may be used alone or in combination of two or more.

  The content of the “aliphatic and / or alicyclic diol” in the aliphatic polyester is usually substantially equimolar to the dicarboxylic acid unit.

<Other components that may be copolymerized>
The aliphatic polyester contained in the freshness-keeping material of the present invention contains an aliphatic dicarboxylic acid unit and an aliphatic and / or alicyclic diol unit as main components, but may contain a hydroxycarboxylic acid unit. . The lower limit of the ratio of hydroxycarboxylic acid units to all components is usually 0 mol% or more, preferably 0.01 mol% or more, more preferably 0.1 mol% or more, and particularly preferably 1 mol% or more. is there. Moreover, an upper limit is 50 mol% or less normally, Preferably it is 30 mol% or less, More preferably, it is 10 mol% or less, Most preferably, it is 5 mol% or less. When there are more than 50 mol% of hydroxycarboxylic acid units, heat resistance and moldability may be reduced, and when less than 0.01 mol%, mechanical properties may be inferior.

  Examples of the hydroxycarboxylic acids constituting the hydroxycarboxylic acid unit include hydroxycarboxylic acids and hydroxycarboxylic acid derivatives, and in particular, any compound or derivative thereof having one hydroxyl group and one carboxyl group in the molecule. It is not limited. Specific examples of the hydroxycarboxylic acid and derivatives thereof include, for example, lactic acid, glycolic acid, 2-hydroxy-n-butyric acid, 2-hydroxycaproic acid, 6-hydroxycaproic acid, 2-hydroxy3,3-dimethylbutyric acid, 2 -Hydroxy-3-methylbutyric acid, 2-hydroxyisocaproic acid, mandelic acid, salicylic acid, their ester compounds, their acid chlorides, their acid anhydrides and the like. These may be used alone or in combination of two or more.

  When an optical isomer exists in hydroxycarboxylic acids, any of D-form, L-form and racemic form may be used, and the form may be any of solid, liquid or aqueous solution. Among these, lactic acid, glycolic acid, or caprolactone is particularly preferable because of the remarkable increase in the polymerization rate during use and easy availability. As a form as these raw materials, an aqueous solution of 30 to 95% by mass is preferable because it can be easily obtained.

<Constitutional unit having 3 or more ester-forming groups in the molecule>
The aliphatic polyester of the present invention may contain a constitutional unit having 3 or more ester-forming groups (hereinafter sometimes abbreviated as “functional group”) in the molecule. As a compound having three or more functional groups (hereinafter sometimes abbreviated as “trifunctional or higher”), a trifunctional or higher polyhydric alcohol; a trifunctional or higher polyvalent carboxylic acid, its anhydride, acid Examples thereof include at least one “trifunctional or higher compound” selected from the group consisting of chloride, ester compound; trifunctional or higher functional hydroxycarboxylic acid, its anhydride, acid chloride, and ester compound.

  Specific examples of the trifunctional or higher polyhydric alcohol include glycerin, trimethylolpropane, pentaerythritol and the like. These may be used alone or in combination of two or more.

  Specific examples of the trifunctional or higher polyvalent carboxylic acid or anhydride thereof include, for example, trimesic acid, propanetricarboxylic acid, trimellitic anhydride, pyromellitic anhydride, benzophenonetetracarboxylic anhydride, cyclopentatetracarboxylic acid. An anhydride etc. are mentioned. These may be used alone or in combination of two or more.

  Specific examples of the tri- or higher functional hydroxycarboxylic acids include malic acid, hydroxyglutaric acid, hydroxymethylglutaric acid, tartaric acid, citric acid, hydroxyisophthalic acid, and hydroxyterephthalic acid. These may be used alone or in combination of two or more. Of these, malic acid, tartaric acid or citric acid is particularly preferred because of its availability.

  The content ratio of the tri- or higher functional compound is the total of all the structural units constituting the aliphatic polyester of the present invention, and the lower limit is usually 0.0001 mol% or more, preferably 0.001 mol% or more. More preferably, it is 0.005 mol% or more, and particularly preferably 0.01 mol% or more. Further, the upper limit is generally 4 mol% or less, preferably 3 mol% or less, particularly preferably 1 mol% or less. When the content ratio of the trifunctional or higher functional compound in the aliphatic polyester is higher than the above upper limit, the crosslinking of the polymer proceeds excessively, the strand cannot be stably extracted, the moldability deteriorates, various physical properties are impaired, etc. May cause problems. In addition, when the content of the trifunctional or higher functional compound in the aliphatic polyester is less than the above lower limit, the purification of the aliphatic polyester is overloaded and the cost is increased, and the reactivity of the polymerization reaction may decrease. is there.

<Other structural units in aliphatic polyester>
In the present invention, in order to increase the hydrophilicity of the aliphatic polyester, a compound having a hydrophilic group such as a sulfone group, a phosphoric acid group, an amino group, or a nitric acid group is used at the time of production, and these hydrophilic groups are introduced. May be. Examples of the compound for that purpose include 4-sulfonated-2,6-isophthalic acid.

  In addition, chain extenders such as carbonate compounds, dioxazolines, silicate esters, and diisocyanates may be used. In particular, when carbonate compounds such as diphenyl carbonate are used, the carbonate compound is used as the total component of the aliphatic polyester. On the other hand, it is preferable to add 20 mol% or less, particularly preferably 10 mol% or less, to obtain a polyester carbonate.

  Specific examples of the carbonate compound in this case include diphenyl carbonate, ditolyl carbonate, bis (chlorophenyl) carbonate, m-cresyl carbonate, dinaphthyl carbonate, dimethyl carbonate, diethyl carbonate, dibutyl carbonate, ethylene carbonate, dia Examples include mill carbonate and dicyclohexyl carbonate. In addition, carbonate compounds composed of the same or different hydroxy compounds derived from hydroxy compounds such as phenols and alcohols can also be used.

  Specific examples of the diisocyanate compound include 2,4-tolylene diisocyanate, a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, diphenylmethane diisocyanate, and 1,5-naphthylene diisocyanate. And known diisocyanates such as xylylene diisocyanate, hydrogenated xylylene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate. However, since the present invention relates to a freshness-keeping material and is used as a packaging material for foods and the like, it is preferable from the viewpoint of safety that no diisocyanate compound is used. That is, it is preferable that the aliphatic polyester contained in the freshness-keeping agent of the present invention does not substantially contain a urethane bond generated by a reaction between a diisocyanate compound and a hydroxyl group.

  Specific examples of the silicate ester include tetramethoxysilane, dimethoxydiphenylsilane, dimethoxydimethylsilane, and diphenyldihydroxysilane.

  Further, a small amount of an organic peroxide may be blended in order to increase the melt tension. Any of these may be used alone or in combination of two or more.

  Moreover, in this invention, you may seal the polyester terminal group of aliphatic polyester with a carbodiimide, an epoxy compound, monofunctional alcohol, or carboxylic acid. In this case, examples of the carbodiimide compound include compounds having one or more carbodiimide groups in the molecule (including polycarbodiimide compounds). Specifically, as the monocarbodiimide compound, dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, Examples include diisobutyl carbodiimide, dioctyl carbodiimide, t-butyl isopropyl carbodiimide, diphenyl carbodiimide, di-t-butyl carbodiimide, di-β-naphthyl carbodiimide, N, N′-di-2,6-diisopropylphenyl carbodiimide. These may be used alone or in combination of two or more.

<Compounds contained in aliphatic polyester>
In the aliphatic polyester contained in the freshness-keeping material of the present invention, it is essential that the organic compound not derived from the raw material of the aliphatic polyester contains 10 ppm or less with respect to the entire aliphatic polyester. is there. Examples of the “organic compound not derived from the aliphatic polyester raw material” include an organic solvent that performs a treatment such as washing and dipping on the aliphatic polyester. Such an organic solvent is not particularly limited, and examples thereof include acetone and tetrahydrofuran. These contents are preferably 5 ppm or less, and particularly preferably 1 ppm or less. If the content of the organic solvent is too large, problems such as odor, hygiene, and safety due to contamination with food may occur. If the aliphatic polyester is treated not with an organic compound such as an organic solvent but with an alkaline aqueous solution as will be described later, the content of the organic compound can be reduced to the above content or less.

  For example, when the aliphatic polyester is polybutylene succinate, the cyclic dimer contained in the aliphatic polyester is a cyclic ester in which two units of succinic acid and 1,4-butanediol are alternately ester-bonded. is there. In the present invention, the content of the cyclic dimer in the aliphatic polyester is preferably 5000 ppm or less, more preferably 3000 ppm or less, and particularly preferably 1000 ppm or less. When there are too many cyclic dimers, a cyclic dimer may bleed out from a molded article, or it may adhere to foodstuffs etc. The method for reducing the content of the cyclic dimer is not particularly limited, and examples thereof include a method of treating with an alkaline aqueous solution as described later.

  The content of the metal contained in the aliphatic polyester is preferably 300 ppm or less, more preferably 200 ppm or less, and particularly preferably 100 ppm or less. If the metal content is too high, problems may arise in terms of safety problems when used in food, thermal deterioration during molding, coloring, long-term stability of the material, and the like.

  Aliphatic polyesters have anti-blocking agents, slip agents, anti-fogging agents, heat stabilizers, antioxidants, and hydrolysis inhibitors as long as the properties and safety are not impaired and as long as the above requirements are satisfied. An agent, a crystal nucleating agent, a flame retardant, an antistatic agent, a release agent, an ultraviolet absorber, an organic or inorganic reinforcing agent, an extender, and the like may be blended.

  These may be added to the reaction apparatus before the polymerization reaction, may be added to the conveying apparatus from the start of the polymerization reaction to the end of the polymerization reaction, or may be added before the product is withdrawn after the completion of the polymerization reaction. Also good. Moreover, you may add to the aliphatic polyester after extraction.

<Method for producing aliphatic polyester>
As the method for producing the aliphatic polyester of the present invention, known methods relating to the production of polyester can be employed. Moreover, the polycondensation reaction in this case can set the appropriate conditions conventionally employ | adopted, and is not restrict | limited in particular. After the esterification reaction is advanced, the degree of polymerization can be further increased by performing a decompression operation.

  The amount of the aliphatic and / or alicyclic diol used is substantially equimolar with respect to the total number of moles of the dicarboxylic acid component, but in general, since there is distillation during the esterification reaction, 1 to It is used in an excess of 100 mol%, preferably 5 to 80 mol%, more preferably 10 to 60 mol%.

  When using the aforementioned hydroxycarboxylic acids, the timing and method of adding the hydroxycarboxylic acid component is not particularly limited as long as it is before the end of the polycondensation reaction. For example, (1) the catalyst is previously dissolved in the hydroxycarboxylic acid solution. And (2) a method of adding the catalyst at the same time as adding the catalyst at the time of charging the raw materials.

  In addition, when using the above-mentioned trifunctional or higher compound, the addition time may be any of before the other raw materials are charged, at the time of charging, after the charging, before the polymerization reaction, from the start of the polymerization reaction to the end of the reaction, It is preferable from the point of simplification of the process to charge simultaneously with other monomers.

  The aliphatic polyester in the present invention is produced in the presence of a catalyst. As such a catalyst, any catalyst that can be used for the production of polyester can be selected, but germanium, titanium, zirconium, hafnium, antimony, tin, magnesium, calcium, zinc, aluminum, cobalt, lead, cesium, Metal compounds such as manganese, lithium, potassium, sodium, copper, barium and cadmium are suitable. Among these, germanium compounds, titanium compounds, magnesium compounds, zinc compounds, and lead compounds are preferable, and germanium compounds, titanium compounds, and magnesium compounds are particularly preferable.

  As magnesium compounds, germanium oxide, germanium lactate, germanium formate, germanium acetate, germanium propionate, germanium n-butyrate, germanium n-valerate, germanium n-caproate, germanium n-caprate, germanium stearate, germanium oxide, etc. However, germanium oxide, germanium formate, germanium acetate, and germanium propionate are more preferable, and germanium oxide and germanium acetate are more preferably used.

  The titanium compound is not particularly limited, and preferred examples include organic titanium compounds such as tetraalkoxytitanium such as tetrapropyl titanate, tetrabutyl titanate, tetraethyl titanate, tetrahydroxyethyl titanate, and tetraphenyl titanate. Among these, tetrapropyl titanate, tetrabutyl titanate and the like are preferable from the viewpoint of price and availability, and the most preferable catalyst is tetrabutyl titanate.

  As the magnesium compound, magnesium formate, magnesium acetate, magnesium propionate, magnesium n-butyrate, magnesium n-valerate, magnesium n-caproate, magnesium n-caprate, magnesium stearate, magnesium oxide, etc. are preferred. Preferably, magnesium formate, magnesium acetate, magnesium propionate, and more preferably magnesium acetate is used.

  These catalysts may be used individually by 1 type, and may mix and use 2 or more types. Moreover, unless the objective of this invention is impaired, combined use of another catalyst is not prevented. As the catalyst, a combination of tetraalkoxytitanium and a magnesium compound is particularly preferable because of high activity, and a combination of tetrabutyltitanate and magnesium acetate is most preferable.

  The amount of the catalyst used is a metal equivalent amount in the catalyst with respect to the total amount of monomers to be subjected to the reaction, and the lower limit is preferably 0.0001% by mass or more, more preferably 0.001% by mass or more, and particularly preferably 0.00. It is 003 mass% or more. The upper limit is preferably 3% by mass or less, more preferably 1% by mass or less, particularly preferably 0.1% by mass or less, and still more preferably 0.05% by mass or less. If the amount of the catalyst used is less than the above lower limit value, the reaction rate of the polymerization reaction is too slow, which is not preferable for production, and if it exceeds the above upper limit value, the production cost becomes too high, and an aliphatic system from which a catalyst residue can be obtained. May adversely affect the stability of the polyester.

  The catalyst addition time is not particularly limited as long as it is before the start of the pressure reduction reaction, and it may be added at the time of charging the raw materials or may be added at the time of the start of pressure reduction.

About conditions, such as reaction temperature at the time of manufacturing the aliphatic polyester contained in the freshness-keeping material of this invention, polymerization time, and pressure, about 150-260 degreeC is preferable about temperature, and the range of 180-250 degreeC is especially preferable. preferable. About polymerization time, 1 hour or more is preferable and the range of 4 to 15 hours is especially preferable. As for the pressure, the final degree of decompression is preferably 1.33 × 10 ³ Pa or less, particularly preferably 0.27 × 10 ³ Pa or less.

<Physical properties of aliphatic polyester>
The aliphatic polyester contained in the freshness-keeping material of the present invention has a water vapor permeability of 100 [cm ³ / (m) measured at 40 ° C. and 90% RH of a 25 μm thick film of the aliphatic polyester alone. ² · day · atm)] or more. It is preferably 500 [cm ³ / (m ² · day · atm)] or more, and particularly preferably 1000 [cm ³ / (m ² · day · atm)] or more. In a freshness-keeping material containing an aliphatic polyester having a water vapor permeability of less than 100 [cm ³ / (m ² · day · atm)] under the above measurement conditions, the humidity inside the packaging material using the freshness-keeping material It becomes high and the inside of the packaging material may condense.

For the aliphatic polyester contained in the freshness-keeping material of the present invention, the oxygen permeability (A) measured at 23 ° C. and 50% RH of the 25 μm thick film of the aliphatic polyester alone is 100 [cm. ³ / (m ² · day · atm)] or more, more preferably 500 [cm ³ / (m ² · day · atm)] or more, and 1000 [cm ³ / (m ² · day). -Atm)] or more is particularly preferable. If the oxygen permeability (A) is too low, the freshness of the foods to be packaged may be quickly reduced.

Regarding the aliphatic polyester contained in the freshness-keeping material of the present invention, the carbon dioxide permeability (B) measured under an absolutely dry condition at 23 ° C. of a 25 μm thick film of the aliphatic polyester alone is 50,000. preferably ^{[cm 3 / (m 2 ·} day · atm)] or ^less, more preferably ^{30000 [cm 3 / (m 2} · day · atm)] or ^{less, 18000 [cm 3 / (m} 2 · Day · atm)] or less, particularly preferably 13000 [cm ³ / (m ² · day · atm)] or less. When the carbon dioxide permeability (B) is too high, the freshness of foods to be packaged may be rapidly reduced.

  In the aliphatic polyester contained in the freshness-keeping material of the present invention, the carbon dioxide permeability (B) measured at 23 ° C. under absolutely dry conditions of a 25 μm thick film of the aliphatic polyester alone The value of (B / A), which is the ratio of oxygen permeability (A) at 23 ° C. and 50% RH, is preferably 20 or less. More preferably, it is 15 or less, Most preferably, it is 10 or less. If the value of (B / A) is too large, the carbon dioxide concentration inside the packaging material is low, the oxygen concentration is high, and the freshness reduction of foods to be packaged may be accelerated. That the value of (B / A) is preferably a certain value or less means that even if the oxygen permeability (A) is large to some extent, but the carbon dioxide permeability (B) is larger than that, the packaging This means that the freshness of the foods to be used may be quickly reduced.

Regarding the aliphatic polyester contained in the freshness-keeping material of the present invention, the ethylene gas permeability measured at 23 ° C. under absolutely dry conditions of a 25 μm-thick film of the aliphatic polyester is 1000 [cm ³ / (M ² · day · atm)] or more, preferably 1500 [cm ³ / (m ² · day · atm)] or more, and 2000 [cm ³ / (m ² · day · atm)] or more. )] It is particularly preferable that the above be present. ^Also, 20000 is preferably ^{[cm 3 / (m 2 ·} day · atm)] or ^less, more preferably at most ^{10000 [cm 3 / (m 2} · day · atm)], 8000 [cm 3 / (M ² · day · atm)] or less is particularly preferable. If the ethylene gas permeability is too low, the freshness of the food to be packaged may decrease rapidly, and if the ethylene gas permeability is too high, the moisture of the packaged food may decrease, which may be undesirable.

  It has the gas permeability as described above, and further has the above-mentioned requirement, that is, the requirement that the content of the organic compound not derived from the raw material of the aliphatic polyester is 10 ppm or less with respect to the entire aliphatic polyester. The combined aliphatic polyester suppresses a decrease in freshness and moisture of packaged foods and the like, and does not contain harmful substances, so that it can be a main component of a safe freshness retaining material.

  About the aliphatic polyester contained in the freshness-keeping material of the present invention, the production method of the “film having a thickness of 25 μm” for measuring the gas permeability is the method described in the examples. Moreover, the measuring method of the transmittance | permeability shall also be the method as described in an Example. In addition, the gas permeability defines the physical properties of the aliphatic polyester itself contained in the freshness-keeping material of the present invention, and does not define the physical properties of the freshness-keeping material.

  The production method of the aliphatic polyester having gas permeability as described above is not particularly limited, but after the aliphatic polyester is obtained by polymerization, the method of treating with an alkaline aqueous solution, the method of treating with hot water, and alcohol. Examples thereof include a method of adjusting the treatment temperature to an appropriate temperature during the washing treatment and devising a relationship with the treatment time, a method of adjusting the enzyme concentration during the enzyme treatment, and the like. Preferably, the aliphatic polyester is obtained by polymerization and then treated with an alkaline aqueous solution or washed with hot water.

  The alkaline aqueous solution is not particularly limited as long as it has a pH of 7.5 to 9.0, and examples thereof include hydroxides, carbonates, hydrogen carbonates, sulfates, hydrogen sulfates, sulfonates, and phosphates. Of these, hydrogen carbonate is preferable in terms of weak alkalinity, easy pH control, no toxicity, odorlessness, and easy removal after treatment. The counter anion is not particularly limited, but is preferably an alkali metal, and particularly preferably sodium.

  The method for the treatment is not particularly limited, and examples thereof include a method in which pellets, powders, fibrous materials, and strands are immersed in an aqueous solution. In the case of an alkaline salt such as sodium hydrogen carbonate (sodium bicarbonate), the concentration is preferably from 0.1 to 10% by mass, particularly preferably from 0.2 to 5% by mass. The immersion temperature is preferably 15 ° C to 98 ° C, particularly preferably 50 to 90 ° C, and the immersion time is preferably 1 to 100 hours, particularly preferably 5 to 50 hours. After the treatment, it is filtered and dried according to a conventional method.

  The aliphatic polyester contained in the freshness-keeping material of the present invention preferably has a reduced viscosity (ηsp / c) of 1.4 or more, more preferably 1.6 or more, particularly preferably 1.8 or more. is there. Further, the reduced viscosity (ηsp / c) of the aliphatic polyester is usually 5.0 or less, preferably 3.5 or less, more preferably 3.2 or less. If the reduced viscosity is less than 1.4, the mechanical properties may be lowered, and if it exceeds 5.0, molding may be difficult.

  The reduced viscosity (ηsp / c) of the aliphatic polyester was determined from the solution viscosity measured at 30 ° C. at an aliphatic polyester concentration of 0.5 dL / g in phenol / tetrachloroethane (1: 1 mass ratio). Is.

  The aliphatic polyester contained in the freshness-keeping material of the present invention usually has an MFR (melt flow rate) of 0.1 or more and 100 or less, but a preferred lower limit is 0.5, and a more preferred lower limit is 1.0. is there. The upper limit of the MFR of the aliphatic polyester is preferably 50, more preferably 20 or less, and particularly preferably 10 or less. If the MFR is greater than 100, the mechanical properties may decrease, and if it is less than 0.1, the fluidity may be poor and molding may be difficult. The MFR is a value measured at 190 ° C. and a 2.19 kg load.

  The freshness-keeping material of the present invention contains the above aliphatic polyester in an amount of 10% to 100% by weight based on the whole freshness-keeping material, but the lower limit of the content of the aliphatic polyester is preferably 50% by weight. More preferably, it is 70 mass%, Most preferably, it is 80 mass%. The upper limit of the content is preferably 99% by mass, more preferably 95% by mass, and particularly preferably 90% by mass. If the content is less than 10% by mass, the biodegradability may be reduced, or the effect of maintaining freshness may not be obtained.

<Freshness preservation material>
[Other polyesters in freshness-keeping materials]
The freshness-keeping material of the present invention preferably further contains an aliphatic aromatic polyester in addition to the aliphatic polyester described above. “Aliphatic aromatic polyester” is an aromatic dicarboxylic acid unit, “aliphatic and / or alicyclic dicarboxylic acid unit”, and “aliphatic and / or alicyclic diol unit” as constituent units. Polyester containing. The aliphatic aromatic polyester is preferably contained in the range of 5% by mass to 90% by mass and more preferably in the range of 10% by mass to 70% by mass with respect to the whole freshness-keeping material. Preferably, it is contained in the range of 20% by mass to 50% by mass. If the content of the aliphatic aromatic polyester in the freshness-keeping material of the present invention is too large, the biodegradability may be inferior, the rigidity may be inferior, whereas if it is too small, the flexibility is inferior, The strength may decrease.

  Hereinafter, the aliphatic aromatic polyester that is suitably mixed with the aliphatic polyester will be described.

  Specific examples of aromatic dicarboxylic acid units that are constituents of aliphatic aromatic polyesters that can be used in combination with aliphatic polyesters include terephthalic acid units, isophthalic acid units, trimellitic acid units, pyrrole. A merit acid unit, a benzophenone tetracarboxylic acid unit, a phenyl succinic acid unit, a 1,4-phenylenediacetic acid unit, a naphthalenedicarboxylic acid unit, a diphenyldicarboxylic acid unit, and the like can be given. These may be acid anhydrides. Examples of the aromatic dicarboxylic acid derivatives include lower alkyl esters of these aromatic dicarboxylic acids. Among these, terephthalic acid and isophthalic acid, and lower alkyl (for example, alkyl having 1 to 4 carbon atoms) ester derivatives thereof are preferable, and methyl ester derivatives of terephthalic acid and terephthalic acid, or a mixture thereof are particularly preferable. These may be used alone or in combination of two or more.

  Specific examples of “aliphatic and / or alicyclic dicarboxylic acid units” constituting the aliphatic aromatic polyester include succinic acid units, oxalic acid units, malonic acid units, glutaric acid units, adipic acid units, and pimelic acid units. , Suberic acid units, azelaic acid units, sebacic acid units, undecanedioic acid units, dodecanedioic acid units, 1,4-cyclohexanedicarboxylic acid units, and the like. Preferred is succinic acid or adipic acid, and particularly preferred is adipic acid. These may be used alone or in combination of two or more.

  Specific examples of the “aliphatic and / or alicyclic diol unit” that is a constituent unit of the aliphatic aromatic polyester include, for example, an ethylene glycol unit, a diethylene glycol unit, a triethylene glycol unit, a polyethylene glycol unit, and a propylene glycol unit. , Dipropylene glycol unit, 1,3-butanediol unit, 1,4-butanediol unit, 3-methyl-1,5-pentanediol unit, 1,6-hexanediol unit, 1,9-nonanediol Units, neopentyl glycol units, polytetramethylene glycol units, 1,4-cyclohexanedimethanol units and the like can be mentioned. 1,4-butanediol or ethylene glycol is preferable, and 1,4-butanediol is particularly preferable. These may be used alone or in combination of two or more.

  The ratio of the aromatic dicarboxylic acid unit constituting the aliphatic aromatic polyester to the total constituent components is usually 50 mol% to 99 mol%, preferably 50 mol% to 90%, particularly preferably 50 mol. % To 80%. In addition, a urethane bond, an amide bond, a carbonate bond, an ether bond, a ketone bond, or the like may be introduced into the aliphatic aromatic polyester within a range that does not affect biodegradability and safety. However, since introduction of these bonds may use a material having a safety problem, it is preferable that these bonds, particularly urethane bonds, carbonate bonds, and the like are not introduced.

  The aliphatic aromatic polyester may be a polyester whose molecular weight is increased or crosslinked using, for example, an isocyanate compound, an epoxy compound, an oxazoline compound, an acid anhydride, or a peroxide. Furthermore, the terminal group may be sealed with carbodiimide, epoxy compound, monofunctional alcohol or carboxylic acid. However, it is preferable not to use an isocyanate compound, a carbodiimide, or the like because a substance having a safety problem may be used when trying to introduce these bonds.

  The freshness-keeping material of the present invention preferably further contains an aliphatic hydroxycarboxylic acid polymer comprising an aliphatic hydroxycarboxylic acid or a derivative unit thereof in addition to the above-described aliphatic polyester.

  Examples of the hydroxycarboxylic acid and its derivative units include glycolic acid units, L-lactic acid units, L-lactides, D-lactic acid units, D-lactides, 3-hydroxybutyric acid units, 4-hydroxybutyric acid units, and 4-hydroxyalkyl units. Examples include herbal acid units, 5-hydroxyvaleric acid units, 6-hydroxycaproic acid units, and caprolactone units. In particular, L-lactic acid is preferable in terms of availability and physical properties. These may be used alone or in combination of two or more. Most preferably, it is poly L-lactic acid, but a small amount of D-lactic acid may be contained as long as its properties are not impaired.

  When an aliphatic hydroxycarboxylic acid polymer comprising hydroxycarboxylic acid units is used by mixing with the freshness-keeping material of the present invention, the content of the aliphatic hydroxycarboxylic acid polymer is 0 with respect to the whole freshness-keeping material. Although it can be used in the range of ˜99% by mass, it is preferably 1 to 90% by mass, more preferably 5 to 80% by mass, and particularly preferably 10 to 50% by mass. If the content of the aliphatic hydroxycarboxylic acid polymer in the freshness-keeping material of the present invention is too large, the flexibility may be impaired or the biodegradability may be reduced, while if too little, Stiffness may be impaired.

[Additives in freshness-keeping materials]
In the freshness-keeping material of the present invention, various additives such as anti-blocking agent, slip agent, anti-fogging agent, reinforcing agent, extender, inorganic filler, organic, as long as the characteristics and safety are not impaired. Fillers, heat stabilizers, antioxidants, hydrolysis inhibitors, crystal nucleating agents, flame retardants, antistatic agents, mold release agents, UV absorbers, light fasteners, plasticizers, colorants, surface wetting improvers, pigments Further, a lubricant, a dispersion aid, a surfactant, a freshness-preserving agent, an antibacterial agent, and the like may be blended. In particular, it is preferable to contain at least one selected from the group consisting of an antiblocking agent, a slip agent and an antifogging agent.

  Examples of the anti-blocking agent include saturated fatty acid amides having 6 to 30 carbon atoms, saturated fatty acid bisamides, methylol amides, ethanol amides, natural silicas, synthetic silicas, synthetic zelites, and talc, preferably talc and silica. .

  Examples of the slip agent include unsaturated fatty acid amides and unsaturated fatty acid bisamides consisting of unsaturated fatty acids having 6 to 30 carbon atoms, preferably erucic acid derivatives, and particularly preferably erucic acid amide.

  As the antifogging agent, specifically, an ester surfactant of a saturated or unsaturated aliphatic carboxylic acid having 4 to 20 carbon atoms and a polyhydric alcohol is preferably used, and glycerin monoester is more preferably used. . The antifogging agent may be kneaded into the polyester in advance, or may be added to the freshness retaining material, or may be applied to the surface of the molded product after molding.

  The addition amount of these additives is 0.001-20 mass% normally as content in a resin composition. The lower limit of the addition amount is preferably 0.01% by mass, more preferably 0.1% by mass. The upper limit of the addition amount is preferably 10% by mass, more preferably 5% by mass.

In addition, as reinforcing agents and extenders, glass fibers, carbon fibers, titanium whiskers, mica, talc, CaCO ₃ , TiO ₂ , silica, starch, rice flour, wood flour, bamboo flour, paper flour, cellulose, etc. May be.

  Inorganic fillers include anhydrous silica, mica, talc, titanium oxide, calcium carbonate, diatomaceous earth, allophane, bentonite, potassium titanate, zeolite, sepiolite, smectite, kaolin, kaolinite, glass, limestone, carbon, wollastonite. , Calcinated perlite, silicates such as calcium silicate and sodium silicate, hydroxides such as aluminum oxide, magnesium carbonate and calcium hydroxide, salts such as ferric carbonate, zinc oxide, iron oxide, aluminum phosphate and barium sulfate Is mentioned. These may be used alone or in combination of two or more.

  The content of the inorganic filler in the freshness-keeping material of the present invention is usually 1 to 80% by mass, preferably 3 to 70% by mass, and more preferably 5 to 60% by mass.

  Some inorganic fillers, such as calcium carbonate and limestone, have properties of soil improvers. If a freshness-keeping material containing a large amount of these inorganic fillers is dumped into the soil, the freshness-keeping material The inorganic filler after biodegradation of this remains and functions as a soil conditioner. When dumping in soil, the usefulness of the freshness-keeping material of the present invention is enhanced.

  Examples of the organic filler include raw starch, modified starch, pulp, chitin / chitosan, coconut shell powder, bamboo powder, bark powder, and powders such as kenaf and straw. These may be used alone or in combination of two or more. The content of the organic filler in the freshness-keeping material of the present invention is preferably less than 40% by mass.

  These additives may be added to the reaction apparatus before the polymerization reaction, may be added to the conveying apparatus from the start of the polymerization reaction to the end of the polymerization reaction, or after the completion of the polymerization reaction, before the product is withdrawn. You may add and you may add after extraction.

<Kneading method>
In preparing the freshness-keeping material of the present invention, conventionally known mixing / kneading techniques can be applied. As the mixer, a horizontal cylindrical type, V-shaped, double-cone type mixer, a blender such as a ribbon blender or a super mixer, various continuous mixers, or the like can be used. Moreover, as a kneading machine, a batch type kneading machine such as a roll or an internal mixer, a one-stage type, a two-stage type continuous kneading machine, a twin screw extruder, a single screw extruder, or the like can be used. As a kneading method, aliphatic polyester and / or other polyester is heated and melted, and various additives and fillers are added and blended. A method of mixing a master batch mixed with an aliphatic polyester with an aliphatic polyester resin, a method of charging resin pellets at the time of molding, or a method of charging a resin pellet and a master batch can be used. At this time, blending oil or the like can also be used for the purpose of uniformly dispersing the various additives.

<Molding method>
The freshness-keeping material of the present invention can be used for molding by various molding methods applied to general-purpose plastics. Examples of the molding method include compression molding (compression molding, lamination molding, stampable molding), injection molding, extrusion molding, and co-extrusion molding (film molding by inflation method and T-die method, laminate molding, pipe molding, electric wire / cable molding. , Profile molding), hollow molding (various blow molding), calendar molding, foam molding (melt foam molding, solid phase foam molding), solid molding (uniaxial stretching molding, biaxial stretching molding, roll rolling molding, stretch oriented nonwoven fabric Examples thereof include molding, thermoforming (vacuum molding, pressure molding, plastic working), powder molding (rotary molding), various nonwoven fabric molding (dry method, adhesion method, entanglement method, spunbond method, etc.). Of these, inflation molding, T-die molding, vacuum molding, pressure molding, and injection molding are particularly preferably used.

  The molding temperature is preferably 140 ° C to 250 ° C, but a more preferable lower limit of the molding temperature is 150 ° C, and a particularly preferable lower limit is 160 ° C. A more preferable upper limit of the molding temperature is 230 ° C, and a particularly preferable upper limit is 220 ° C.

  In particular, the freshness-keeping material of the present invention is preferably applied to an injection-molded body, a foam-molded body, a hollow molded body, and a specific shape such as a film, a container, and a fiber.

  In addition, these molded products are provided with chemical functions, electrical functions, magnetic functions, mechanical functions, friction / wear / lubrication functions, optical functions, thermal functions, surface functions such as biocompatibility, etc. For this purpose, it is also possible to perform various purposeful secondary processing. Examples of secondary processing include embossing, painting, adhesion, printing, metalizing (plating, etc.), machining, surface treatment (antistatic treatment, corona discharge treatment, plasma treatment, photochromism treatment, physical vapor deposition, chemical vapor deposition, Coating) and the like.

<Film>
When the freshness-retaining material of the present invention is used as a film, the production method thereof is a normal thermoplastic resin molding method, for example, inflation molding, extrusion molding, compression molding, vacuum molding, injection molding, hollow molding, rotational molding. Etc., and further, a method of applying a secondary molding method such as thermoforming, stretch molding, foam molding, etc. can be applied to them, and in particular, in film molding, inflation molding, T-die molding, injection molding are preferred, Inflation molding is most preferred.

  As a molding method for inflation molding, a general molding method is used, and the molding temperature is the portion closest to the resin inlet (C1) in the temperature control zone of the molding machine, which is usually 80 ° C. or higher, preferably 100 ° C. or higher. Most preferably, it is 110 ° C. or higher. The control temperature of C1 is usually 180 ° C. or lower, preferably 160 ° C. or lower, more preferably 140 ° C. or lower. The lower limit of the cylinder temperature of the molding machine other than C1 is usually 120 ° C., preferably 140 ° C., more preferably 150 ° C. Moreover, an upper limit is 230 degreeC normally, Preferably it is 210 degreeC, More preferably, it is 200 degreeC. The lower limit of the temperature of the head portion of the molding machine is usually 130 ° C., preferably 140 ° C., more preferably 150 ° C. Moreover, an upper limit is 230 degreeC normally, Preferably it is 210 degreeC, More preferably, it is 200 degreeC. The lower limit of the temperature of the die portion of the molding machine is usually 130 ° C., preferably 140 ° C., more preferably 150 ° C. Moreover, an upper limit is 230 degreeC normally, Preferably it is 220 degreeC, More preferably, it is 210 degreeC. The upper limit of the blow ratio is usually 10.0, preferably 5.0, and more preferably 4.0. The lower limit of the blow ratio is usually 1.5, preferably 2.0, more preferably 2.5.

  When the freshness-retaining material of the present invention is used as a film, the thickness of the film is usually 5 μm to 1000 μm, but a preferred lower limit is 10 μm, a particularly preferred lower limit is 20 μm, a preferred upper limit is 500 μm, and a particularly preferred upper limit is 200 μm. .

<Application>
Examples of the use of the freshness-keeping material of the present invention include broccoli, shiitake mushrooms, nameko, shimeji, enoki, eringi, maitake, matsutake, komatsuna, nabana, edamame, corn, tomato, sweet pea, green beans, sudachi, kabosu, spinach, komatsuna , Chrysanthemum, leek, leek, leek, parsley, mizuna, bell pepper, cucumber, tomato, bitter melon, eggplant, green asparagus, white asparagus, ginger, spruce, silkworm, cypress, chestnut, herbs, lettuce, cabbage, cabbage, Carrots, pumpkins, paprika, onions, potatoes, radish, turnips, potatoes, and other fruits and vegetables -Fruits such as berry, watermelon, rose, carnation, chrysanthemum, color, lily, cherry blossom, peach, plum, freesia, almeria, sweet pea, hydrangea, safinia, dahlia, etc. Sea bream, sea bream, bandit, sea bream, sea bream, sword fish, sword fish, flying fish, conger, sea bream, etc. It can be used for packaging materials such as meat, and packaging containers. Among them, it is preferably used for fruits and vegetables, and particularly preferably used for packaging materials and packaging containers such as broccoli and shiitake.

  Specific forms of the packaging materials and packaging containers are food trays, packaging films, supermarkets, fast food containers, food bags, containers for transportation from producers to retailers, producers and stores. Box or container, food storage container at home, food packaging film, food packaging bag and the like.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples as long as the gist thereof is not exceeded.

<Measurement method of permeability of various gases>
[Method of molding a 25 μm thick film of aliphatic polyester alone for measuring transmittance]
Molded by inflation molding. That is, the pellets of aliphatic polyester were put into an inflation molding machine having an extruder size of 30φ, and the temperature setting of the extruder and the die was 160 ° C., the blow ratio was 2.5, and the film thickness was 25 μm.

[Oxygen permeability (A)]
Based on JIS K7126-2, using OX-TRAN 2/21, measurement was performed at a film thickness of 25 μm under conditions of 23 ° C. and humidity of 50%.

[Carbon dioxide permeability (B)]
In accordance with JIS K7126-1, measurement was performed at 23 ° C. and absolutely dry conditions using a differential pressure type gas permeation tester MC-3 at a film thickness of 25 μm.

[Water vapor permeability]
In accordance with JIS K7129B, measurement was performed at a film thickness of 25 μm using PERMATRAN-W 3/31 at 40 ° C. and a humidity of 90%.

[Ethylene gas permeability]
In accordance with JIS K7126-1, measurement was performed at 23 ° C. and absolutely dry conditions with a film thickness of 25 μm using a differential pressure type gas / vapor permeability measuring device (GTR-30XAD2, G2700T · F).

Example 1
100 parts by mass of GS Pla (AZ91TN) pellets manufactured by Mitsubishi Chemical Corporation were immersed in 500 parts by mass of an aqueous sodium bicarbonate solution (concentration: 1% by mass) at 80 ° C. for 24 hours, and then filtered to remove the oligomer components and the like. It collect | recovered and it dried for 8 hours under 80 degreeC and nitrogen circulation. Since the content of the cyclic dimer contained in this pellet was 1600 ppm and the organic solvent was 10 ppm or less, it was not detected.

The oxygen permeability is 1100 [cm ³ / (m ² · day · atm)], the carbon dioxide permeability is 8000 [cm ³ / (m ² · day · atm)], and the water vapor permeability is 1200 [cm. ³ / (m ² · day · atm)]. A bag was made of a film having a thickness of 25 μm used for measurement of gas permeability, and broccoli was placed therein and heat sealed. The appearance after storage in a constant temperature room at 23 ° C. and 50% RH after 7 days was observed, but no change in appearance was observed.

Example 2
GS Pla (AD92WN) pellets manufactured by Mitsubishi Chemical Corporation were immersed in an aqueous sodium bicarbonate solution (concentration: 1% by mass) at 60 ° C. for 30 hours to remove and purify oligomer components, and dried at 70 ° C. under nitrogen flow for 8 hours. Since the content of the cyclic dimer contained in this pellet was 1700 ppm and the organic solvent was 10 ppm or less, it was not detected.

The oxygen permeability is 2500 [cm ³ / (m ² · day · atm)], the carbon dioxide permeability is 17000 [cm ³ / (m ² · day · atm)], and the water vapor permeability is 2200 [cm. ³ / (m ² · day · atm)]. A bag was made of a film having a thickness of 25 μm used for measurement of gas permeability, and broccoli was placed therein and heat sealed. The appearance after storage in a constant temperature room at 23 ° C. and 50% RH after 7 days was observed, but no change in appearance was observed.

Example 3
“GS Pla (AZ91TN) pellets made by Mitsubishi Chemical Co., Ltd. washed and dried with an aqueous sodium bicarbonate solution” used in Example 1 and “GS Pla (AD92WN made by Mitsubishi Chemical Corp. washed and dried with an aqueous sodium bicarbonate solution) used in Example 2 ) Pellets "were blended with AZ91TN / AD92WN = 8/2 (mass ratio) and then kneaded using a twin screw extruder. This pellet was blown to produce a film having a thickness of 25 μm.

The oxygen permeability measured using this film is 1800 [cm ³ / (m ² · day · atm)], and the carbon dioxide permeability is 12000 [cm ³ / (m ² · day · atm)]. The water vapor transmission rate was 1600 [cm ³ / (m ² · day · atm)]. A bag was made of this film alone, and broccoli was put inside and heat sealed. The appearance after storage in a constant temperature room at 23 ° C. and 50% RH after 7 days was observed, but no change in appearance was observed.

Example 4
In Example 1, instead of 100 parts by mass of the purified and dried pellets used in Example 1, 70 parts by mass of the purified and dried AZ91TN pellets and 30 parts by mass of BASF aliphatic aromatic polyester resin Ecoflex A film was molded and gas permeability was measured in the same manner as in Example 1 except for using a part. The results are shown in Table 2. Moreover, the bag was created with this film alone, broccoli was put in, and it heat-sealed. The appearance after storage in a constant temperature room at 23 ° C. and 50% RH after 7 days was observed, but no change in appearance was observed.

Example 5
In Example 1, instead of 100 parts by mass of the purified and dried pellets used in Example 1, 70 parts by mass of AZ91TN purified and dried pellets, 30 parts by mass of BASF Ecoflex and 2 parts by mass of talc PKP53 were used. When the film was molded in the same manner as in Example 1, the moldability was improved. The gas permeability was measured using this film. The results are shown in Table 2. A bag was made of this film alone, and broccoli was put inside and heat sealed. The appearance after storage in a constant temperature room at 23 ° C. and 50% RH after 7 days was observed, but no change in appearance was observed.

Example 6
In Example 1, instead of 100 parts by mass of the pellets after purification and drying used in Example 1, 70 parts by mass of the pellets after purification and drying of AZ91TN, 30 parts by mass of BASF Ecoflex, and stearic acid monoglyceride as an antifogging agent When a film was molded in the same manner as in Example 1 except that 0.5 part by mass was used, the moldability was improved. The gas permeability was measured using this film. The results are shown in Table 2. A bag was made of this film alone, and broccoli was put inside and heat sealed. The appearance after storage in a constant temperature room at 23 ° C. and 50% RH after 7 days was observed, but no change in appearance was observed.

Comparative Example 1
LLDPE (Novatech LLUF420) manufactured by Mitsubishi Chemical Corporation was blown to produce a film having a thickness of 25 μm. The oxygen permeability is 4000 [cm ³ / (m ² · day · atm)], the carbon dioxide permeability is 19000 [cm ³ / (m ² · day · atm)], and the water vapor permeability is 20 [cm. ³ / (m ² · day · atm)]. A bag was made of this film alone, and broccoli was put inside and heat sealed. When the appearance after storage in a thermostatic chamber at 23 ° C. and 50% RH after 7 days was observed, the color partly changed to yellow and cloudiness was seen on the inner surface of the bag.

Comparative Example 2
The oligomer component was removed and purified by immersing 100 parts by mass of GS Pla (AZ91TN) pellets manufactured by Mitsubishi Chemical Corporation in 200 parts by mass of acetone at 30 ° C. for 24 hours, and drying for 8 hours at 80 ° C. under nitrogen flow. The content of the cyclic dimer contained in this pellet was 1200 ppm, but 1500 ppm of acetone was detected, and the odor of acetone was detected, which could not be used as a food packaging material.

The raw material compositions, processing methods, and drying conditions of Examples 1 to 6 and Comparative Examples 1 and 2 are summarized in Table 1. In addition, Table 2 summarizes gas permeability, cyclic dimer content, organic solvent content, broccoli appearance, and bag appearance. In Table 2, all units of gas permeability are [cm ³ / (m ² · day · atm)]. In Table 2, since the cyclic dimer of Comparative Example 1 does not exist in the first place, it is described as “−”, and “−” in the appearance of Comparative Example 2 indicates that it was not molded because of the smell of acetone.

  Packaging materials and packaging containers using the freshness-keeping material of the present invention are excellent in safety and biodegradable because the content of organic compounds, cyclic dimers, metals, etc. not derived from polyester raw materials is low. In addition, since it has good heat sealability, is flexible, and has good gas permeability, it is widely used for packaging materials and packaging containers such as meat, fish, vegetables, fruits, and florets.

Claims (14)

An aliphatic polyester comprising an aliphatic dicarboxylic acid unit and an aliphatic and / or alicyclic diol unit,
(1) The water vapor permeability measured at 40 ° C. and 90% RH of the 25 μm-thick film of the aliphatic polyester alone is 100 [cm ³ / (m ² · day · atm)] or more,
(2) The organic compound not derived from the raw material of the aliphatic polyester contains 10 mass% to 100 mass% of an aliphatic polyester having a content of 10 ppm or less with respect to the entire aliphatic polyester. Freshness preservation material. 2. The oxygen permeability (A) measured at 23 ° C. and 50% RH of a 25 μm thick film of the aliphatic polyester alone is 100 [cm ³ / (m ² · day · atm)] or more. The freshness retaining material described. Carbon dioxide permeability (B) measured at 23 ° C. under absolutely dry conditions of a 25 μm thick film of the aliphatic polyester alone is 18000 [cm ³ / (m ² · day · atm)] or less. Item 3. The freshness-keeping material according to item 1 or 2.   Ratio of carbon dioxide permeability (B) measured at 23 ° C. under absolutely dry conditions and oxygen permeability (A) at 23 ° C. and 50% RH of a 25 μm thick film of the aliphatic polyester alone (B The freshness-keeping material according to any one of claims 1 to 3, wherein / A) is 20 or less. The ethylene gas permeability measured at 23 ° C. under absolutely dry conditions of a 25 μm thick film of the aliphatic polyester alone is 1000 to 10,000 [cm ³ / (m ² · day · atm)]. The freshness-keeping material according to any one of claims 4 to 4.   The freshness-keeping material according to any one of claims 1 to 5, wherein the aliphatic polyester has substantially no urethane bond in the molecule.   The freshness-keeping material according to any one of claims 1 to 6, wherein the content of the cyclic dimer contained in the aliphatic polyester is 5000 ppm or less with respect to the entire aliphatic polyester.   The freshness-keeping material according to any one of claims 1 to 7, wherein a content of a metal contained in the aliphatic polyester is 300 ppm or less with respect to the entire aliphatic polyester.   The freshness-keeping material according to any one of claims 1 to 8, wherein the aliphatic polyester is treated with an alkaline aqueous solution.   The freshness-keeping material according to any one of claims 1 to 9, further comprising an aliphatic aromatic polyester in an amount of 5% to 90% by weight based on the whole freshness-keeping material.   The freshness-keeping material according to any one of claims 1 to 10, further comprising an aliphatic hydroxycarboxylic acid polymer in an amount of 1 to 90% by weight based on the whole freshness-keeping material.   The freshness-keeping material according to any one of claims 1 to 11, further comprising at least one selected from the group consisting of an antiblocking agent, a slip agent, and an antifogging agent.   The freshness-keeping material according to any one of claims 1 to 12, wherein a molding temperature when molding the freshness-keeping material is 140 ° C or higher and 250 ° C or lower.   The freshness-keeping material according to any one of claims 1 to 13, which is a film having a thickness of 10 to 500 µm.