JP2008019418A - Biodegradable resin composition and molded article by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biodegradable resin having transparency, and improved with flexibility and barrier property. <P>SOLUTION: This biodegradable resin composition is provided by containing 100 pts.mass polylactic acid and 1 to 50 pts.mass polyesterpolyol. The polyester polyol consists of a multivalent carboxylic acid with a polyhydric alcohol and has 250 to 6,000 average molecular weight. The hydroxy value of the biodegradable polyester polyol is 20 to 800 mgKOH/g, and its acid value is ≤3 mgKOH/g. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a biodegradable resin composition excellent in transparency, flexibility, and barrier properties, and a molded article obtained therefrom.

  In recent years, biodegradable resins such as polylactic acid, particularly plant-derived resins, have attracted attention from the viewpoint of reducing environmental burden and preventing oil depletion. Among the biodegradable resins, polylactic acid is one of the most transparent and most heat-resistant resins, and it can be mass-produced from plant-derived raw materials such as corn and sweet potato. It is highly useful because it can contribute to reducing the amount. However, polylactic acid has poor flexibility and barrier properties, and has not yet been satisfactory as a container or packaging material that requires them.

  For example, Patent Document 1 presents a flexible film mainly composed of a resin composition composed of polylactic acid and polyethylene glycol in order to impart flexibility. However, it is described that flexibility is imparted by adding or copolymerizing polyethylene glycol, but the gas barrier property is deteriorated 3 to 4 times.

  As a method for enhancing the gas barrier performance of a biodegradable resin, Patent Document 2 discloses a method of coating a biodegradable plastic with a metal oxide such as silicon oxide by a chemical vapor deposition method. However, although this method is excellent in gas barrier properties, it cannot be said that it is sufficient in terms of transparency, reduction of environmental burden, and degree of plant material origin.

JP 2005-219487 A JP 2002-068201 A

  Accordingly, an object of the present invention is to provide a biodegradable resin composition that maintains the transparency of polylactic acid and has improved flexibility and barrier properties.

  As a result of intensive studies to solve the above problems, the present inventors have found that by adding a polyester polyol to polylactic acid, transparency is maintained and flexibility and barrier properties are improved. The present invention has been reached based on this finding.

That is, the gist of the present invention is as follows.
(1) A biodegradable resin composition containing 100 parts by mass of polylactic acid and 1 to 50 parts by mass of polyester polyol.
(2) The biodegradable resin composition according to (1), wherein the polyester polyol is composed of a polyvalent carboxylic acid and a polyhydric alcohol and has an average molecular weight of 250 to 6,000.
(3) The polyvalent carboxylic acid is at least one selected from the group consisting of terephthalic acid, isophthalic acid, adipic acid and succinic acid, and the polyhydric alcohol is selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol and glycerin. The biodegradable resin composition according to (2), which is at least one selected.
(4) The biodegradable resin composition according to any one of (1) to (3), wherein the polyester polyol has a hydroxyl value of 20 to 800 mgKOH / g and an acid value of 3 mgKOH / g or less.
(5) The biodegradable resin according to any one of (1) to (4), wherein an oxygen permeability coefficient at 20 ° C. and 90% relative humidity is 150 ml · mm / m ² / day / MPa or less. Composition.
(6) The biodegradable resin composition according to any one of (1) to (4), wherein the haze at a thickness of 1 mm is 15% or less.
(7) The biodegradable resin composition according to any one of (1) to (4), wherein the glass transition temperature measured with a differential scanning calorimeter (DSC) is 55 ° C. or lower.
(8) The biodegradation according to any one of (1) to (4), wherein the bending fracture strength measured at 23 ° C. according to ASTM-D790 is 100 MPa or less and the flexural modulus is 3.6 GPa or less. Resin composition.
(9) The biodegradability according to any one of (1) to (4), wherein the tensile strength measured at 23 ° C. according to ASTM-D638 is 60 MPa or less and the tensile modulus is 2.5 GPa or less. Resin composition.
(10) A molded article comprising the biodegradable resin composition according to any one of (1) to (9).
(11) When producing the biodegradable resin composition according to any one of (1) to (9), a polyester polyol is added to polylactic acid at the time of melt-kneading or molding. A method for producing the composition.

  According to the present invention, a biodegradable resin composition that is transparent and excellent in flexibility and barrier properties is provided, and can be suitably used as a container or a packaging material. Further, the molded body made of this resin composition can be composted when discarded, and the amount of waste can be reduced and reused as a fertilizer. In addition, the use of polylactic acid, which is a plant-derived raw material, increases the ratio of plant-derived materials as a whole resin composition, which can greatly contribute to prevention of the depletion of petroleum resources and reduce the burden on the environment. It becomes a gentle material.

  Hereinafter, the present invention will be described in detail.

  As the polylactic acid in the present invention, any of a homopolymer composed only of L-lactic acid or D-lactic acid, a copolymer of L-lactic acid and D-lactic acid, or a polymer generally called a stereocomplex may be used. They may be used as a mixture. Although the content ratio of L-lactic acid / D-lactic acid in polylactic acid is not particularly limited, (L-lactic acid / D-lactic acid) = 0.2 / 99.8 to 99.8 / 0 is commercially available. .2 (mol%) range, and can be used without limitation.

  As a method for producing polylactic acid, a two-stage lactide method in which L-lactic acid, D-lactic acid, and DL-lactic acid (racemic) are used as raw materials to once generate lactide, which is a cyclic dimer, and then perform ring-opening polymerization. A one-step direct polymerization method in which the raw material is directly subjected to dehydration condensation in a solvent is known. The polylactic acid used in the present invention may be obtained by any production method. Alternatively, if necessary, a solid phase polymerization method may be used in combination.

  The molecular weight of polylactic acid is not particularly limited, but considering the strength of the molded article, at least the weight average molecular weight (Mw) is preferably 50,000 or more, more preferably in the range of 70,000 to 400,000, most preferably Is in the range of 80,000-250,000. The weight average molecular weight (Mw) here is measured at 40 ° C. using a gel permeation chromatography apparatus (GPC) equipped with a differential refractive index detector and tetrahydrofuran (THF) as an eluent. It is the value calculated | required in polystyrene conversion when doing.

  When the melt flow index (MFI) is used as an index of the molecular weight of polylactic acid, it can be used preferably if the MFI at 190 ° C. and 2.16 kg is in the range of 0.1 to 50 g / 10 min, more preferably The range is 0.2 to 40 g / 10 min.

  The polylactic acid used in the present invention may be partially crosslinked. Moreover, it may be modified with an epoxy compound or the like. For the purpose of increasing the molecular weight of polylactic acid, chain extenders such as diisocyanate compounds, polyepoxy compounds, and acid anhydrides may be used. Although the addition amount is not particularly limited, it is preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the resin.

  In order to improve the durability of polylactic acid, a terminal blocking agent can be added to block the terminal of the resin. Examples of the terminal blocking agent include carbodiimide compounds, epoxy compounds, oxazoline compounds, isocyanate compounds and the like. Although the addition amount is not particularly limited, it is preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the resin.

  Examples of the polyvalent carboxylic acid constituting the polyester polyol include aromatic polyvalent carboxylic acids and aliphatic polyvalent carboxylic acids. Specifically, examples of the aromatic carboxylic acid component include terephthalic acid, isophthalic acid, orthophthalic acid, trimesic acid, trimellitic acid, 2,6-naphthalenedicarboxylic acid, biphenyldicarboxylic acid, and 5-sulfoisophthalic acid. These may be anhydrous. Among the above-mentioned aromatic carboxylic acid components, terephthalic acid and isophthalic acid are preferable from the viewpoint of versatility. Aliphatic carboxylic acids include oxalic acid, malonic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, aicosanedioic acid, hydrogenated dimer acid, etc. Unsaturated aliphatic dicarboxylic acids such as acid, maleic acid, itaconic acid, mesaconic acid, citraconic acid and dimer acid and their anhydrides, and 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1, Also included are alicyclic dicarboxylic acids such as 2-cyclohexanedicarboxylic acid, 2,5-norbornene dicarboxylic acid, and tetrahydrophthalic acid. Among these, adipic acid, succinic acid, and sebacic acid are preferable from the viewpoint of biodegradability, and succinic acid and adipic acid are particularly preferable.

  Examples of the polyhydric alcohol constituting the polyester polyol include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2 -Methyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-amino-2-ethyl-1,3-propanediol, 2-amino-2-methyl-1,3- Propanediol, 2-ethyl-2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 1, 5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,15-pentadecanediol, 1,16-hexadecanediol, Aliphatic glycols such as 1,17-heptadecanediol, 1,18-octadecanediol, 1,19-nonadecanediol, 1,20-eicosanediol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, Ethylene oxide or propylene oxide adducts of bisphenols such as 2,2-bis (4-hydroxyethoxyphenyl) propane, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cycl Alicyclic glycols such as hexane dimethanol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and the like. Examples of the trifunctional or higher functional alcohol include glycerol, trimethylolpropane, trimethylolethane, pentaerythritol, α-methylglucose, mannitol, sorbitol, and the like. Among these, ethylene glycol, diethylene glycol, triethylene glycol, and glycerin are particularly preferable.

  The average molecular weight of the polyester polyol is preferably 250 to 6,000, more preferably 300 to 4,000, and most preferably 500 to 2, considering compatibility for maintaining good transparency. 500. The average molecular weight here is a value measured according to JIS-K1601 method.

In order to obtain the barrier property and flexibility improving effect of the present invention, the hydroxyl value of the polyester polyol is preferably 20 to 800 mgKOH / g, more preferably 40 to 600 mgKOH / g, and most preferably 50 to 500 mg KOH / g.
Similarly, the acid value of the polyester polyol is preferably 3 mgKOH / g or less, more preferably 2 mgKOH / g, and most preferably 1.5 mgKOH / g.

  The content of the polyester polyol is required to be 1 to 50 parts by mass with respect to 100 parts by mass of polylactic acid, preferably 2 to 30 parts by mass, and more preferably 5 to 15 parts by mass. If the amount is less than 1 part by mass, the intended flexibility and barrier properties of the present invention cannot be obtained. If the amount exceeds 50 parts by mass, the physical properties of the resin composition deteriorate, poor molding, poor kneading, and the like occur.

  The polyester polyol can be produced by a known method. Examples of production are described in, for example, JP-A-5-70573, JP-A-8-41179, JP-A-11-13049, JP-A-11-255878, JP-A-2002-105183, and the like. Yes. Moreover, a commercial item can also be used for the polyester polyol, and MAXIMOL SDP-163, RDP-133, RDP-141, RMP-342, RFP-556 etc. by Kawasaki Kasei Kogyo Co., Ltd. are mentioned.

The resin composition of the present invention preferably has an oxygen permeability coefficient at 20 ° C. and 90% relative humidity of 150 ml · mm / m ² / day / MPa or less. It is preferably 120 ml · mm / m ² / day / MPa or less, and more preferably 100 ml · mm / m ² / day / MPa or less. The oxygen permeation coefficient here is a value specific to the composition having no thickness dependency, calculated by multiplying the oxygen permeability by the thickness of the sample. This value is an index of gas barrier properties, and the smaller the value, the better the gas barrier properties.

  Furthermore, the resin composition of the present invention is excellent in transparency, and a haze is 15% or less in a molded product having a thickness of 1 mm. If the haze value is larger than this value, the transparency is insufficient. In addition, the haze value here means the turbidity measured with a turbidimeter. The larger the haze, the stronger the turbidity, and the smaller the haze, the weaker the turbidity, indicating that it is transparent. A molded body having a thickness of 1 mm, preferably having a haze of 15% or less, more preferably having a haze of 12% or less, and most preferably having a haze of 10% or less.

  The resin composition of the present invention has physical properties with improved flexibility as follows.

  The glass transition temperature (Tg) of the resin composition is preferably 55 ° C. or lower. When it exceeds 55 ° C., the flexibility tends to decrease.

  The bending rupture strength of the resin composition measured at 23 ° C. according to ASTM-D790 is preferably 100 MPa or less, more preferably 90 MPa or less, and most preferably 80 MPa or less. When it exceeds 100 MPa, the molded product becomes hard and the desired flexibility tends not to be obtained.

  The flexural modulus of the resin composition is preferably 3.6 GPa or less, more preferably 3.2 GPa or less, and most preferably 3.0 GPa or less. If it exceeds 3.6 GPa, the molded product becomes hard, and the bending resistance tends to decrease, or the desired flexibility tends not to be obtained.

  The tensile strength of the resin composition measured at 23 ° C. according to ASTM-D638 is preferably 60 MPa or less, more preferably 55 MPa or less, and most preferably 50 MPa or less. When it exceeds 60 MPa, the molded product becomes hard and the desired flexibility tends not to be obtained.

  The tensile elastic modulus of the resin composition is preferably 2.5 GPa or less, more preferably 2.2 GPa or less, and most preferably 2.0 GPa or less. If it exceeds 2.5 GPa, the molded product becomes hard and the desired flexibility tends not to be obtained.

  In the production of the biodegradable resin composition of the present invention, examples of the method for adding the polyester polyol include a method of adding at the time of polymerization of the biodegradable polyester resin, a method of adding at the time of melt kneading, and a method of adding at the time of molding. It is preferable to add at the time of melt-kneading or molding. In addition, when adding at the time of melt kneading or molding, after blending with the resin in advance, a method of supplying to a general kneader or molding machine, if using solid, using a side feeder, or liquid If so, there may be mentioned a method of adding from the middle of kneading using a constant supply pump. When the liquid is more viscous, a method of lowering the viscosity by warming the liquid itself is easy to supply and effective in operation.

  In melt kneading, a general kneader such as a single screw extruder, a twin screw extruder, a roll kneader, or a Brabender can be used. In order to improve the dispersibility of additives, a twin screw extruder is used. It is preferable to use it.

  The biodegradable resin composition of the present invention includes a heat stabilizer, an antioxidant, a pigment, a weathering agent, a flame retardant, a plasticizer, a lubricant, a mold release agent, and an antistatic agent, as long as the effects of the present invention are not impaired. , Fillers, dispersants and the like may be added. Examples of heat stabilizers and antioxidants include phosphite organic compounds, hindered phenol compounds, benzotriazole compounds, triazine compounds, hindered amine compounds, sulfur compounds, copper compounds, alkali metal halides, or these. Mixtures can be used. These additives are generally added during melt-kneading or polymerization. Inorganic fillers include talc, mica, montmorillonite, layered silicate, calcium carbonate, zinc carbonate, wollastonite, silica, alumina, magnesium oxide, calcium silicate, sodium aluminate, calcium aluminate, sodium aluminosilicate, silicic acid Examples include magnesium, glass balloon, carbon black, zinc oxide, antimony trioxide, zeolite, hydrotalcite, metal fiber, metal whisker, ceramic whisker, potassium titanate, boron nitride, graphite, glass fiber, and carbon fiber. Examples of the organic filler include naturally occurring polymers such as starch, cellulose fine particles, wood flour, okara, fir shell, bran and kenaf, and modified products thereof.

  In addition, the biodegradable resin composition of the present invention includes an aliphatic polyester mainly composed of α- and / or β-hydroxycarboxylic acid units other than lactic acid and a dicarboxylic acid component, as long as the effects of the present invention are not impaired. And a polyester comprising a diol component may be included as a mixture or a copolymer. Examples of α- and / or β-hydroxycarboxylic acid units include glycolic acid, 3-hydroxybutyric acid, 3-hydroxyvaleric acid, 3-hydroxycaproic acid, and the like, and mixtures and copolymers thereof. Examples of the dicarboxylic acid include succinic acid, succinic anhydride, adipic acid, suberic acid, sebacic acid, dodecanoic acid, terephthalic acid, isophthalic acid, or a lower alkyl ester compound or acid anhydride as a derivative thereof. it can. Examples of the diol include ethylene glycol, polyethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol and the like. Polyamide (nylon), polyethylene, polypropylene, polybutadiene, polystyrene, AS resin, ABS resin, poly (acrylic acid), poly (acrylic acid ester), poly (methacrylic acid), poly (methacrylic acid ester), polybutylene terephthalate Further, non-biodegradable resins such as polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polyarylate, and copolymers thereof can be added.

  The biodegradable resin composition of the present invention can be formed into various molded articles by known molding methods such as injection molding, blow molding, and extrusion molding.

  As an injection molding method, in addition to a general injection molding method, gas injection molding, injection press molding, or the like can be adopted. The cylinder temperature at the time of injection molding needs to be equal to or higher than the melting point (Tm) of polylactic acid or the flow start temperature, and is preferably in the range of 180 to 230 ° C, more preferably 190 to 220 ° C. If the molding temperature is too low, the fluidity of the resin is reduced, which tends to cause molding defects or overload of the apparatus. Conversely, when the molding temperature is too high, polylactic acid is decomposed, and problems such as a decrease in strength and coloring of the molded product occur. On the other hand, the mold temperature is preferably (Tg−10 ° C.) or less when it is set to Tg or less of the biodegradable resin composition. Further, in order to promote crystallization for the purpose of improving strength, heat resistance and barrier property, it can be set to Tg or higher and (Tm-30) ° C. or lower, or heat treatment is performed at a temperature of Tg or higher and Tm or lower after molding. You can also.

  Examples of the blow molding method include a direct blow method in which molding is performed directly from raw material pellets, and an injection blow molding method (stretch blow molding method) in which blow molding is performed after molding a preform (bottomed parison) by injection molding. Can be mentioned. In addition, any of a hot parison method in which blow molding is continuously performed after molding of a preformed body, and a cold parison method in which blow molding is performed by once cooling and taking out the preformed body and then performing blow molding can be employed. For the purpose of improving strength, heat resistance and barrier properties, in order to promote crystallization, the blow mold temperature can be molded at Tg or more and (Tm-30) ° C. or less, and after molding, Tg or more and Tm or less. Heat treatment can also be performed at a temperature of

  As the extrusion molding method, a T-die method, a round die method, or the like can be applied. The extrusion temperature must be equal to or higher than the melting point (Tm) of the raw polylactic acid or the flow start temperature, and is preferably in the range of 180 to 230 ° C, more preferably 190 to 220 ° C. If the molding temperature is too low, the operation becomes unstable or easily overloaded. On the other hand, if the molding temperature is too high, the polylactic acid component decomposes, causing problems such as reduced strength and coloration of the extruded product. It is not preferable. A film, a sheet, a pipe or the like can be produced by extrusion.

  Specific applications of films, sheets, or pipes obtained by the extrusion method include wrap films, garbage bags, compost bags, flexible films for agriculture and horticulture, raw sheets for deep drawing, and raw materials for batch foaming. Sheets, cards such as credit cards, underlays, clear files, straws, soft pipes for agriculture and horticulture, and the like. The film can be used as an unstretched film in the form of a film or slit, and the unstretched film can be processed into various shapes by vacuum forming or the like. Further, an unstretched film can be uniaxially or biaxially stretched using a roll stretching method, a tenter method, a tubular method, or the like and used for various applications. Further, the sheet is further subjected to deep drawing such as vacuum forming, pressure forming, and vacuum / pressure forming to produce food containers, agricultural / horticultural containers, blister pack containers, press-through pack containers, and the like. be able to. The deep drawing temperature and the heat treatment temperature are preferably (Tg + 20 ° C.) to (Tg + 100 ° C.). If the deep drawing temperature is less than (Tg + 20 ° C), deep drawing becomes difficult. Conversely, if the deep drawing temperature exceeds (Tg + 100 ° C), polylactic acid will decompose and uneven thickness will occur, or orientation will be lost and impact resistance will be reduced. There is a case to do. In addition, for the purpose of improving the strength, heat resistance, and barrier properties of the molded container, heat treatment may be performed at a temperature of Tg to Tm in order to promote crystallization. The form of the food container, the agricultural / horticultural container, the blister pack container, and the press-through pack container is not particularly limited, but is deeply drawn to a depth of 2 mm or more in order to accommodate food, articles, medicines, and the like. It is preferable. Although the thickness of a container is not specifically limited, From a strong point, it is preferable that it is 50 micrometers or more, and it is more preferable that it is 150-500 micrometers. Specific examples of food containers include fresh food trays, instant food containers, fast food containers, lunch boxes and the like. Specific examples of the agricultural / horticultural containers include seedling pots. Specific examples of blister pack containers include packaging containers for various product groups such as office supplies, toys, and dry batteries in addition to food.

  Other molded articles produced using the biodegradable resin composition of the present invention include dishes such as dishes, bowls, bowls, chopsticks, spoons, forks, knives, containers for fluids, caps for containers, rulers, Office supplies such as writing instruments, clear cases, CD cases, triangular corners for kitchens, trash cans, washbasins, toothbrushes, combs, hangers and other daily necessities, agricultural and horticultural materials such as flower pots and nursery pots, various toys such as plastic models, Examples include resin parts for electrical appliances such as air conditioner panels and various cases, and resin parts for automobiles such as bumpers, instrument panels, and door trims. In addition, although the form of the container for fluid is not specifically limited, In order to accommodate a fluid, it is preferable to shape | mold to 20 mm or more in depth. Although the thickness of a container is not specifically limited, From a strong point, it is preferable that it is 0.1 mm or more, and it is more preferable that it is 0.1-5 mm. Specific examples of fluid containers include beverage cups and beverage bottles for dairy products, soft drinks and alcoholic beverages, soy sauce, sauces, mayonnaise, ketchup, containers for condiments such as cooking oil, shampoos and rinses Containers, cosmetic containers, agricultural chemical containers, and the like.

  The biodegradable resin composition of the present invention may be a fiber. The production method is not particularly limited, but a method of melt spinning and stretching is preferred. The melt spinning temperature is preferably 160 ° C to 260 ° C. If it is less than 160 ° C., melt extrusion tends to be difficult. On the other hand, if it exceeds 250 ° C., decomposition tends to be remarkable, and it becomes difficult to obtain high-strength fibers. The melt-spun fiber yarn may be drawn at a temperature of Tg or higher so as to have a target fiber diameter. Further, after stretching, heat treatment may be performed for the purpose of relaxing internal strain, preventing shrinkage, promoting crystallization, and stabilizing strength. As a heat treatment method, a known method such as contacting with a heating plate or passing through a heating medium under tension or no tension can be appropriately employed.

  The fibers obtained by the above method are used as clothing fibers, industrial material fibers, short fiber nonwoven fabrics, and the like.

  The biodegradable resin composition of the present invention can also be developed into a long fiber nonwoven fabric. Although the production method is not particularly limited, the resin composition can be obtained by depositing fibers by a high-speed spinning method, then forming a web, and further forming a fabric using a means such as hot pressing.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited only to an Example.

(1) Acid value (mgKOH / g) and hydroxyl value (mgKOH / g) of polyester polyol
It was determined in accordance with JIS-K1557 (polyurethane polyether test method).

(2) Average molecular weight of polyester polyol It calculated | required from the following formula according to JIS-K1601 (polyether diol 2000 for polyurethanes).
X = 56.1 × N × 1000 / (OHV + AV)
X: Average molecular weight (g / mol)
N: number of terminal groups (number of functional groups) in the molecule. In the case of a linear polyol composed of a dicarboxylic acid and a diol, N = 2.
OHV: hydroxyl value of polyester polyol (mgKOH / g)
AV: Acid value of the polyester polyol (mgKOH / g)

(3) Glass transition temperature (Tg) and melting point (Tm)
Using a DSC apparatus (DSC7 manufactured by PerkinElmer Co., Ltd.), the temperature was raised from 20 ° C. to 200 ° C. at + 20 ° C./min and held for 5 minutes, then cooled from 200 ° C. to −50 ° C. at −20 ° C./min for 5 minutes. Retained. Furthermore, the glass transition temperature in the process (2nd Scan) in which the temperature was raised again from −50 ° C. to 200 ° C. at + 20 ° C./min was defined as Tg of the resin composition. Similarly, the peak top temperature of the crystal melting peak observed with 2nd Scan was defined as Tm.

(4) Haze:
In accordance with JIS-K7136, measurement was performed on a press sheet having a thickness of 1 mm. That is, using a desktop test press machine manufactured by Tester Sangyo Co., Ltd., the resin composition pellets were pressed at 190 ° C. for about 3 minutes, and then rapidly cooled to produce a 1 mm thick press sheet as a molded body. About this press sheet, it measured using the Nippon Denshoku Industries Co., Ltd. NDH-2000 type turbidity / cloudiness meter.

(5) YI (yellowness):
A color difference meter Z-Σ90 manufactured by Nippon Denshoku Industries Co., Ltd. was used. A 1.5 mm × 3 mm square pellet was filled into a 12 mm × 30 mmφ glass cell and measured.

(6) Oxygen permeability coefficient:
Oxygen permeation by a differential pressure method using a differential pressure type gas / gas permeability measuring device (Yanaco, GTR-30XAU) for a heat-pressed sheet previously conditioned at 20 ° C. and a relative humidity of 90% The degree was measured. The oxygen permeability coefficient is (oxygen permeability coefficient) = (oxygen permeability) x (sample thickness)
Calculated from This value is an index of gas barrier properties, and the smaller the value, the better the gas barrier properties.
The hot press sheet was produced by the same method as (4) so that the thickness was 200 to 300 μm.

(7) Bending strength and flexural modulus:
The resin composition was injection-molded to obtain a molded piece of (5 inches) × (1/2 inch) × (1/8 inch). A load was applied at a deformation rate of 1 mm / min according to the method of ASTM-D790, and the bending fracture strength and the flexural modulus were measured at 23 ° C. The preparation conditions of the test piece are as follows.
Injection molding conditions: using an injection molding machine (IS-80G type manufactured by Toshiba Machine Co., Ltd.), cylinder temperature 190-170 ° C, mold temperature 15 ° C, injection pressure 60%, injection time 20 seconds, cooling time 20 seconds, interval 2 It was performed by using a mold for ASTM standard 1/8 inch three-point bending / dumbbell test piece.

(8) Tensile modulus and tensile strength ASTM standard dumbbell-shaped injection molded pieces were molded in the same manner as in (7) and evaluated at 23 ° C. according to the method of ASTM-D693.

[material]
Various raw materials used in Examples and Comparative Examples are shown.

(1) Polylactic acid resin A: 4032D (Nature Works, Nature Works), L-form / D-form = 98.6 / 1.4 (mol%), weight average molecular weight (MW) = 190,000, melting point 170 ° C. , MFI = 2.5 g / 10 min (190 ° C., load 2.16 kg)

(2) Polyester polyol additive B: MAXIMOL SDP-163 (manufactured by Kawasaki Kasei Kogyo Co., Ltd.), aliphatic, hydroxyl value 163 mgKOH / g, acid value 0.69 mgKOH / g, average molecular weight 685, viscosity (25 ° C.) 1, 400 mPa · s, functional group number 2.0, flash point 236 ° C., specific gravity 1.18, refractive index 1.472
Additive C: MAXIMOL SDP-145 (manufactured by Kawasaki Kasei Kogyo Co., Ltd.), aliphatic, hydroxyl value 98 mgKOH / g, acid value 0.89 mgKOH / g, average molecular weight 1135, viscosity (25 ° C.) 9,180 mPa · s, sensory Radix 2.0, flash point 252 ° C, specific gravity 1.23, refractive index 1.474
Additive D: MAXIMOL RDP-133 (manufactured by Kawasaki Kasei Kogyo Co., Ltd.), hydroxyl value 315 mgKOH / g, acid value 0.40 mgKOH / g, average molecular weight 356, viscosity (25 ° C.) 2,600 mPa · s, functional group number 2.0 , Flash point 178 ° C, specific gravity 1.24, refractive index 1.517
Additive E: MAXIMOL RMP-342 (manufactured by Kawasaki Kasei Kogyo Co., Ltd.), polyfunctional, hydroxyl value 420 mgKOH / g, acid value 1.59 mgKOH / g, average molecular weight 319, viscosity (25 ° C.) 3,720 mPa · s, sensory Radix 2.4, Flash point 194 ° C, Specific gravity 1.24, Refractive index 1.517
Additive F: MAXIMOL RFP-556 (manufactured by Kawasaki Kasei Kogyo Co., Ltd.), aromatic, hydroxyl value 247 mgKOH / g, acid value 0.19 mgKOH / g, average molecular weight 454, viscosity (25 ° C.) 1,820 mPa · s, functional Cardinal number 2.0, flash point 192 ° C., specific gravity 1.19, refractive index 1.506

[Example 1]
Using a PCM-30 type twin screw extruder (screw diameter is 30 mmφ, average groove depth is 2.5 mm) made by Ikegai Co., Ltd. with 100 parts by mass of resin A and 5 parts by mass of additive B, screw rotation is performed at 190 ° C. Melt kneading was performed at several 150 rpm (= 2.5 rps) and a discharge rate of 100 g / min, extruded, and processed into pellets. Since additive B used was a highly viscous liquid, it was added simultaneously with the resin from the supply port of the extruder with a metering feed pump while warming to 90 ° C. in a warm bath. The obtained pellets were dried to obtain a resin composition 1.

  Tg and YI of the obtained resin composition 1 were measured. In addition, press molding was performed to evaluate haze and oxygen permeability coefficient. Furthermore, the resin composition was injection-molded, ASTM standard bending and dumbbell test pieces were molded, and mechanical strength was evaluated. All the results are shown in Table 1.

[Examples 2 to 8]
As shown in Table 1, resin compositions 2 to 8 were prepared in the same manner as in Example 1 except that the type and amount of polyester polyol were changed, and Tg and YI of the resin composition were measured. Furthermore, physical properties of the molded product were evaluated by injection molding and press molding. All the results are shown in Table 1.

[Comparative Example 1]
In Example 1, the resin A was kneaded without adding the additive B to produce a resin composition 9 and evaluated in the same manner. The results are shown in Table 1.

The resin compositions obtained in Examples 1 to 8 all had low haze, transparency, and improved flexibility and barrier properties.
On the other hand, since the resin composition obtained in Comparative Example 1 did not contain polyester polyol, the resin composition was poor in flexibility and barrier properties were not good.

Claims (11)

  A biodegradable resin composition containing 100 parts by mass of polylactic acid and 1 to 50 parts by mass of polyester polyol.   The biodegradable resin composition according to claim 1, wherein the polyester polyol is composed of a polyvalent carboxylic acid and a polyhydric alcohol, and has an average molecular weight of 250 to 6,000.   The polyvalent carboxylic acid is at least one selected from the group consisting of terephthalic acid, isophthalic acid, adipic acid and succinic acid, and the polyhydric alcohol is at least selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol and glycerin. It is 1 type, The biodegradable resin composition of Claim 2 characterized by the above-mentioned.   The biodegradable resin composition according to any one of claims 1 to 3, wherein the polyester polyol has a hydroxyl value of 20 to 800 mgKOH / g and an acid value of 3 mgKOH / g or less. 5. The biodegradable resin composition according to claim 1, wherein an oxygen permeability coefficient at 20 ° C. and 90% relative humidity is 150 ml · mm / m ² / day / MPa or less.   The biodegradable resin composition according to any one of claims 1 to 4, wherein a haze at a thickness of 1 mm is 15% or less.   The biodegradable resin composition according to any one of claims 1 to 4, wherein the glass transition temperature measured with a differential scanning calorimeter (DSC) is 55 ° C or lower.   The biodegradable resin composition according to any one of claims 1 to 4, having a bending breaking strength measured at 23 ° C according to ASTM-D790 of 100 MPa or less and a flexural modulus of 3.6 GPa or less.   The biodegradable resin composition according to any one of claims 1 to 4, having a tensile strength measured at 23 ° C according to ASTM-D638 of 60 MPa or less and a tensile elastic modulus of 2.5 GPa or less.   The molded object which consists of a biodegradable resin composition in any one of Claims 1-9.   A method for producing a biodegradable resin composition, wherein a polyester polyol is added to polylactic acid during melt-kneading or molding in producing the biodegradable resin composition according to any one of claims 1 to 9. .