JP2018062573A - Polylactic acid resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polylactic acid resin composition which is excellent in hydrolysis resistance and suppresses generation of foreign odor and foreign matter during molding, and a thermoforming sheet containing the polylactic acid resin composition.SOLUTION: The polylactic acid resin composition contains: (A) a polylactic acid resin; (B) an ester of an aliphatic alcohol having a C9-30 alkyl group and a C4-12 dicarboxylic acid, preferably an ester of an aliphatic alcohol having a C9-20 alkyl group and a C4-12 dicarboxylic acid; and (C) an organic nucleating agent. The sheet for thermoforming comprises the polylactic acid resin composition.SELECTED DRAWING: None

Description

  The present invention relates to a polylactic acid resin composition. More specifically, the present invention relates to a polylactic acid resin composition that can be suitably used as a material for molded articles such as packs and trays of daily necessities, cosmetics, home appliances, and the like, and a thermoforming sheet comprising the polylactic acid resin composition.

  Polylactic acid resin is inexpensive because L-lactic acid as a raw material is produced by fermentation using sugar extracted from corn, straw, etc., and the carbon dioxide emission is extremely low because the raw material is derived from plants. In addition, due to the characteristics of the resin such as high rigidity and high transparency, its use is currently expected.

  For example, in Patent Document 1, by blending a specific plasticizer and a crystal nucleating agent with a polylactic acid resin, it is possible to reduce the environmental burden and obtain a molded article having excellent transparency and heat resistance. It is possible and excellent in moldability, and 0.1 to 3 parts by mass of an adipate ester plasticizer and 0.1 to 2 amide crystal nucleating agent having a hydroxyl group with respect to 100 parts by mass of the polylactic acid resin. A polylactic acid-based resin composition containing parts by mass is disclosed.

  Patent Document 2 discloses that a polylactic acid resin has a plasticizer of 0.5 to 3.5 parts by mass and an organic crystal nucleating agent of 0.15 to 0.45 parts by mass with respect to 100 parts by mass of the polylactic acid resin. It is reported that the thermoforming sheet comprising the polylactic acid resin composition contained is excellent without deterioration of thermoformability even after storage at a relatively high temperature (30-40 ° C) in summer. doing.

JP2015-113442A JP2015-165016A

  The present invention relates to a polylactic acid resin composition that is excellent in hydrolysis resistance and suppresses the generation of off-flavors and foreign substances during molding, and a thermoforming sheet containing the polylactic acid resin composition.

The present invention relates to the following [1] to [3].
[1] A polylactic acid resin composition comprising the following (A), (B), and (C).
(A) Polylactic acid resin (B) An ester of an aliphatic alcohol having an alkyl group having 9 to 30 carbon atoms and a dicarboxylic acid having 4 to 12 carbon atoms (C) Organic crystal nucleating agent [2] [1] ] The sheet | seat for thermoforming containing the polylactic acid resin composition of description.
[3] Use of the polylactic acid resin composition according to [1] as a thermoforming sheet.

  The polylactic acid resin composition of the present invention is excellent in hydrolysis resistance and has an excellent effect of suppressing the generation of off-flavors and foreign matters during molding.

  In the production of a polylactic acid resin composition, it is conventionally known that a carbodiimide compound is blended as a terminal blocking agent for a polylactic acid resin. However, when a polylactic acid resin composition having such a composition is molded, a odor and foreign matter derived from a carbodiimide compound may be generated during molding. Therefore, when an ester compound having a more hydrophobic specific structure is used as a plasticizer, hydrolysis resistance is improved without using a carbodiimide compound, and the occurrence of off-flavors and foreign substances can be suppressed. It was found that a composition was obtained. This is presumably because the use of a hydrophobic plasticizer prevents water from entering the resin matrix and improves the hydrolysis resistance of polylactic acid. However, these assumptions do not limit the present invention.

[Polylactic acid resin composition]
The polylactic acid resin composition of the present invention contains a polylactic acid resin, an ester having a specific structure, and an organic crystal nucleating agent.

[(A) Polylactic acid resin]
Examples of the polylactic acid resin include commercially available polylactic acid resins such as those manufactured by Nature Works: Nature Works PLA / NW3001D, NW4032D (N-4000), 2500HP, and Toyota Motor Corporation: Eco Plastic U'z S-09. In addition to S-12, S-17, and the like, polylactic acid resin synthesized from lactic acid or lactide can be used. These can be used alone or in combination of two or more.

  The optical purity of the polylactic acid resin is preferably 90% or more, more preferably 95% or more, still more preferably 98% or more, preferably 100% or less, more preferably from the viewpoint of molding speed and availability of raw materials. Is substantially 100% or less, more preferably 99% or less. Here, “substantially 100%” means a case in which a trace amount of impurities is inevitably included. The optical purity of polylactic acid resin is the D-form content described in “Voluntary Standard for Food Containers and Packaging Made of Synthetic Resins such as Polyolefins, Third Edition, Revised June 2004, Part 3 Sanitation Test Method P12-13”. It can be determined according to the measurement method. Specifically, it is measured by the method described in Examples described later.

  The weight average molecular weight of the polylactic acid resin is preferably 100,000 or more, more preferably 150,000 or more from the viewpoint of improving hydrolysis resistance, and from the same viewpoint, preferably 400,000 or less, more preferably 350,000. It is as follows. The weight average molecular weight of the polylactic acid resin was measured by gel permeation chromatography (GPC), chloroform as the solvent, Tosoh Corporation column, high temperature SEC column (GMHHR-H series), flow rate 1.0 mL / min, column The temperature can be calculated by using a differential refractive index detector (RI) as a detector at a temperature of 40 ° C. and polystyrene having a known molecular weight as a reference.

  In the present invention, from the viewpoint of the strength and transparency of the polylactic acid resin composition, as the polylactic acid resin, a stereocomplex comprising two types of polylactic acid obtained by using lactic acid components mainly composed of different isomers. Polylactic acid resin may be used.

  In addition, the polylactic acid resin in the present invention may contain a biodegradable polyester resin other than the polylactic acid resin or a non-biodegradable resin such as polypropylene as a polymer alloy by blending with the polylactic acid resin. In the present specification, “biodegradable” means a property that can be decomposed into a low molecular weight compound by a microorganism in nature. Specifically, JIS K6953 (ISO 14855) “controlled aerobic composting conditions”. This means biodegradability based on the “Aerobic and Ultimate Biodegradation and Disintegration Test”.

  In the polylactic acid resin composition, the content of the polylactic acid resin is preferably 70% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more, from the viewpoints of peelability, transparency, and biodegradability. . Moreover, from a moldability viewpoint, Preferably it is 99.5 mass% or less, More preferably, it is 99 mass% or less.

[(B) Ester]
The ester used in the present invention is characterized by being an ester compound of an aliphatic alcohol having an alkyl group having 9 to 30 carbon atoms and a dicarboxylic acid having 4 to 12 carbon atoms.

  The aliphatic alcohol has an alkyl group having 9 to 30 carbon atoms. The alkyl group may be linear or branched, but is preferably branched from the viewpoint of hydrolysis resistance. The number of carbon atoms of the alkyl group is 9 or more, preferably 10 or more, more preferably 11 or more, still more preferably 12 or more, from the viewpoint of hydrolysis resistance, and 30 or less from the viewpoint of compatibility with the resin. Preferably it is 20 or less, More preferably, it is 15 or less, More preferably, it is 10 or less. The carbon number of the alkyl group of the aliphatic alcohol is 9 or more and 30 or less, preferably 9 or more and 20 or less, more preferably 9 or more and 15 from the viewpoint of hydrolysis resistance and compatibility with the resin. Or less, more preferably 9 or more and 10 or less.

  Specific examples of the aliphatic alcohol having an alkyl chain having 9 to 30 carbon atoms include isononyl alcohol, decanol, lauryl alcohol, cetyl alcohol, isotridecanol, hexyl decanol, stearyl alcohol, octyldodecanol, and isodecyl. Examples include alcohol, undecanol, and isostearyl alcohol.

  Examples of the dicarboxylic acid include saturated or unsaturated ones, but saturated ones are preferable from the viewpoint of heat resistance. The total number of carbon atoms of the dicarboxylic acid is 4 or more, preferably 5 or more from the viewpoint of hydrolysis resistance, and 12 or less, preferably 8 or less, more preferably 7 or less, from the viewpoint of compatibility with the resin. is there.

  Specific examples of the dicarboxylic acid having 4 to 12 carbon atoms include succinic acid, glutaric acid, adipic acid, phthalic acid, isophthalic acid, terephthalic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid. .

  A combination of the aliphatic alcohol and the dicarboxylic acid is not particularly limited as long as the above-described compound is used. For example, a combination of an aliphatic alcohol having an alkyl group having 9 to 20 carbon atoms and a dicarboxylic acid having 4 to 12 carbon atoms. And a combination of an aliphatic alcohol having an alkyl group having 9 to 15 carbon atoms and a dicarboxylic acid having 4 to 8 carbon atoms.

  Specific examples of the ester include a diester of an aliphatic alcohol having an alkyl group having 9 to 20 carbon atoms and a dicarboxylic acid having 4 to 12 carbon atoms. These compounds may be commercially available or synthesized according to a known production method. The ester is not limited to the diester of an aliphatic alcohol having an alkyl group having 9 to 20 carbon atoms and a dicarboxylic acid having 4 to 12 carbon atoms, as long as the effects of the present invention are not impaired. An ester mixture containing the ester may be used.

  From the viewpoint of hydrolysis resistance, the content of the ester is preferably 0.5 parts by mass or more, more preferably 0.7 parts by mass or more, and 1.0 part by mass or more with respect to 100 parts by mass of the polylactic acid resin. More preferably, 1.2 parts by mass or more is even more preferable. Further, from the viewpoint of compatibility with the resin and transparency, 5.0 parts by mass or less is preferable, 4.0 parts by mass or less is more preferable, 3.0 parts by mass or less is further preferable, and 2.0 parts by mass or less is preferable. Even more preferred. In the present invention, the ester content means the content of the mixture in the case of the ester mixture described above.

  In addition, the content of the ester in the polylactic acid resin composition is preferably 0.5% by mass or more, more preferably 0.7% by mass or more, and further preferably 1.0% by mass or more from the viewpoint of hydrolysis resistance. Preferably, 1.2% by mass or more is more preferable, and from the viewpoint of compatibility with the resin and transparency, 5.0% by mass or less is preferable, 4.0% by mass or less is more preferable, and 3.0% by mass or less. Is more preferable, and 2.0 mass% or less is still more preferable.

[(C) Organic crystal nucleating agent]
The organic crystal nucleating agent in this invention is not specifically limited, The organic crystal nucleating agent used for general biodegradable resin can be used. Among them, from the viewpoint of transparency and thermoformability, the organic crystal nucleating agent molecule has an aliphatic group having two or more groups selected from the group consisting of an ester group, a hydroxyl group, and an amide group. A compound is preferable, and an aliphatic compound having two or more of one or two groups selected from the group consisting of a hydroxyl group and an amide group is preferable. Examples of the aliphatic compound include an aliphatic compound having two or more ester groups, an aliphatic compound having two or more hydroxyl groups, an aliphatic compound having two or more amide groups, and one each of an ester group and a hydroxyl group. Aliphatic compound, aliphatic compound having one ester group and one amide group, aliphatic compound having one hydroxyl group and one amide group, fat having one or more ester groups and two or more amide groups An aliphatic compound having at least one hydroxyl group and having at least two amide groups, an aliphatic compound having at least one ester group and having at least two hydroxyl groups, one amide group An aliphatic compound having two or more hydroxyl groups, an aliphatic compound having one or more hydroxyl groups and two or more ester groups, one or more amide groups, and an ester group Aliphatic compound having two or more thereof.

  Specific examples include alkylene bis fatty acid amides, alkylene bis hydroxy fatty acid amides, and the like, and hydroxy fatty acid monoamides such as 12-hydroxy stearic acid monoethanolamide; methylene bis 12-hydroxy stearic acid amide, ethylene bis 12-hydroxy stearin. Examples thereof include hydroxy fatty acid bisamides such as acid amides and hexamethylene bis 12-hydroxystearic acid amides; and fatty acid bisamides such as ethylene bisstearic acid amides, ethylene bisoleic acid amides, and ethylene bislauric acid amides.

  The content of the organic crystal nucleating agent is preferably 0.2 parts by mass or more, more preferably 0.3 parts by mass or more, with respect to 100 parts by mass of the polylactic acid resin, from the viewpoint of molding speed and transparency. More preferred is part by mass or more. Moreover, from the same viewpoint, 0.6 mass part or less is preferable and 0.5 mass part or less is more preferable.

  The content of the organic crystal nucleating agent in the polylactic acid resin composition is preferably 0.2% by mass or more, more preferably 0.3% by mass or more, and 0.4% by mass or more from the viewpoint of molding speed and transparency. From the same viewpoint, it is preferably 1.0% by mass or less, more preferably 0.7% by mass or less, and further preferably 0.5% by mass or less.

  The content ratio of the ester to the organic crystal nucleating agent (ester / organic crystal nucleating agent) is preferably 1 or more, more preferably 1.5 or more, and still more preferably 2.0, from the viewpoint of molding speed and transparency. From the same viewpoint, it is preferably 10 or less, more preferably 6 or less, and still more preferably 4 or less.

  The polylactic acid resin composition of the present invention includes, as components other than those described above, (B) known plasticizers other than esters; inorganic crystal nucleating agents; fillers (inorganic fillers, organic fillers); hydrolysis inhibitors Flame retardants; antioxidants; lubricants that are hydrocarbon waxes and anionic surfactants; UV absorbers; antistatic agents; antifogging agents; light stabilizers; pigments; Surfactants; polysaccharides such as starches and alginic acids; natural proteins such as gelatin, glue and casein; inorganic compounds such as tannins, zeolites, ceramics and metal powders; fragrances; flow regulators; leveling agents; An ultraviolet dispersant; a deodorant and the like can be contained within a range not impairing the effects of the present invention. In addition, other polymer materials and other resin compositions can be added within a range that does not impair the effects of the present invention. As a content ratio of an arbitrary additive, it may be appropriately contained within a range in which the effects of the present invention are not impaired. For example, the resin composition is preferably 20% by mass or less, more preferably about 10% by mass or less, More preferably, it is about 5% by mass or less.

  The polylactic acid resin composition of the present invention can be prepared without particular limitation as long as it contains the above-mentioned polylactic acid resin, a specific ester, and an organic crystal nucleating agent. Thus, a raw material containing various additives can be prepared by melt-kneading using a known kneader such as a closed kneader, a uniaxial or biaxial extruder, or an open roll kneader. The raw materials can be subjected to melt kneading after being uniformly mixed in advance using a Henschel mixer, a super mixer, or the like. In preparing the polylactic acid resin composition, in order to promote the plasticity of the polylactic acid resin, it may be melt-mixed in the presence of a supercritical gas. After the melt-kneading, the melt-kneaded product may be dried according to a known method.

  The melt kneading temperature is preferably 170 ° C. or higher, more preferably 175 ° C. or higher, further preferably 180 ° C. or higher, preferably 240 ° C. or lower, from the viewpoint of improving the moldability and prevention of deterioration of the polylactic acid resin composition. More preferably, it is 220 degrees C or less, More preferably, it is 210 degrees C or less. The melt-kneading time cannot be generally determined depending on the melt-kneading temperature and the type of the kneader, but is preferably 15 seconds or more and 900 seconds or less.

  Since the polylactic acid resin composition of the present invention thus obtained is excellent in transparency and thermoformability, it can be molded into a primary processed product comprising the polylactic acid resin composition, that is, the thermoforming sheet of the present invention. it can.

[Thermoforming sheet]
The thermoforming sheet of the present invention is not particularly limited as long as the polylactic acid resin composition is used, and can be prepared by extrusion molding, injection molding, or press molding.

  Specifically, in the extrusion molding, the polylactic acid resin composition filled in a heated extruder is melted and then extruded from a T die to obtain a sheet-like molded product (also referred to as a sheet molded product). be able to. The sheet molded product is immediately brought into contact with a cooling roll, cooled, separated from the cooling roll, and then wound up with a winding roll, whereby the thermoforming sheet of the present invention can be obtained. In addition, when filling the extruder, the raw material constituting the polylactic acid resin composition, for example, the raw material containing polylactic acid resin, specific ester, organic crystal nucleating agent, and various additives as necessary is filled as it is. Then, it may be melt-kneaded, or the melt-kneaded in advance may be filled in the extruder.

  The temperature of the extruder is preferably 170 ° C. or higher, preferably 240 ° C. or lower, more preferably 220 ° C. or lower, from the viewpoint of uniformly mixing the polylactic acid resin composition and preventing deterioration of the polylactic acid resin. is there. In the present invention, the temperature of the extruder means the barrel set temperature of the extruder. Further, the residence time in the extruder cannot be defined unconditionally because it depends on the thickness, width, and winding speed of the sheet, but is preferably about 30 seconds to several minutes from the viewpoint of avoiding deterioration due to heat.

The temperature of the cooling roll is preferably set to be less than Tg of the polylactic acid resin composition from the viewpoint of obtaining a sheet in an amorphous state or a semi-crystalline state, specifically, preferably less than 40 ° C., and preferably 30 ° C. or less. More preferably, 20 degrees C or less is further more preferable. In this specification, the amorphous state and the semi-crystalline state are an amorphous state and a relative crystallinity of 60% or more and 80% when the relative crystallinity obtained by the following formula is less than 60%. The case where it is less than that is defined as a semi-crystalline state. Therefore, an amorphous or semi-crystalline sheet means a sheet having a relative crystallinity of less than 80%.
Relative crystallinity (%) = {(ΔHm−ΔHcc) / ΔHm} × 100
Specifically, the relative crystallinity was raised from 20 ° C. to 200 ° C. at a rate of temperature increase of 20 ° C./min using a DSC apparatus (Diamond DSC manufactured by PerkinElmer Co., Ltd.) at a rate of temperature increase of 20 ° C./min. After holding, the temperature was lowered from 200 ° C. to 20 ° C. at a temperature drop rate of −20 ° C./min, held at 20 ° C. for 1 minute, and then further increased from 20 ° C. to 200 ° C. at a temperature rising rate of 20 ° C./min as 2ndRUN. The absolute value ΔHcc of the cold crystallization enthalpy of the polylactic acid resin observed at 1st RUN and the crystal melting enthalpy ΔHm observed at 2nd RUN can be used.

  The time for contact with the cooling roll is not necessarily specified because it varies depending on the set temperature of the cooling roll, the number of cooling rolls, the extrusion speed, and the sheet winding speed. For example, the sheet in an amorphous or semi-crystalline state can be efficiently used. From the viewpoint of obtaining the above, it is preferably 0.1 seconds or longer, more preferably 0.5 seconds or longer, further preferably 0.8 seconds or longer, preferably 50 seconds or shorter, more preferably 10 seconds or shorter, still more preferably 5 seconds. Less than a second. Further, from the same viewpoint, the sheet winding speed is preferably 0.1 m / min or more, more preferably 0.5 m / min or more, further preferably 1 m / min or more, preferably 50 m / min or less, More preferably, it is 30 m / min or less, More preferably, it is 20 m / min or less.

  When molding the thermoforming sheet of the present invention by injection molding, specifically, from the viewpoint of uniform mixing and molecular weight suppression, the polylactic acid resin composition preferably has a cylinder temperature of 180 ° C or higher, preferably Can be filled into a mold having a desired shape using an injection molding machine set at 220 ° C. or lower, more preferably 210 ° C. or lower, and molded into a sheet.

  When the thermoforming sheet of the present invention is formed by press molding, specifically, the polylactic acid resin composition is surrounded by a frame having a desired sheet shape and press-molded to form the thermoforming sheet of the present invention. Can be obtained.

  The press molding temperature and pressure are preferably 170 to 240 ° C. and 5 to 30 MPa, more preferably 175 to 220 ° C. and 10 to 25 MPa, more preferably, from the viewpoint of uniform mixing and molecular weight suppression. It is preferable to press under conditions of 180 to 210 ° C. and 10 to 20 MPa. Although the press time cannot be determined unconditionally depending on the temperature and pressure of the press, it is preferably 1 minute or more, preferably 10 minutes or less, more preferably 7 minutes or less, and still more preferably, from the viewpoint of uniform mixing. 5 minutes or less.

  Also, immediately after pressing under the above conditions, preferably 0 to 40 ° C., 0.1 to 20 MPa, more preferably 10 to 30 ° C., 0.1 to 10 MPa, further preferably 10 to 20 ° C., It is preferable to press and cool under conditions of 0.1 to 5 MPa. By pressing under this temperature condition, the polylactic acid resin composition of the present invention can be cooled to below its Tg to maintain an amorphous state or a semi-crystalline state. Although the press time cannot be determined unconditionally depending on the temperature and pressure of the press, from the viewpoint of cooling efficiency and productivity, it is preferably 1 minute or more, preferably 10 minutes or less, more preferably 7 minutes or less, More preferably, it is 5 minutes or less.

  Thus, the thermoforming sheet of the present invention is obtained. In the thermoforming sheet of the present invention, by using a specific ester compound without using a carbodiimide compound, generation of off-flavors and foreign matters during production is suppressed while hydrolysis is suppressed.

  In addition, since it contains an ester compound having a specific structure, the crystallization speed of the thermoforming sheet of the present invention is improved, so that the molding speed is improved and the thermoformability is improved. The body will be obtained.

  In addition, the thermoforming sheet of the present invention is not particularly limited with respect to its crystallinity, but it is preferable to cool the sheet at the time of forming to form an amorphous or semi-crystalline sheet. The thermoforming sheet of the present invention obtained by cooling has a relative crystallinity calculated by the above formula of preferably less than 80%, more preferably less than 60%, and even more preferably less than 50%. The lower limit is not particularly set, but may be 0% or more.

  The thickness of the thermoforming sheet of the present invention is preferably 0.1 mm or more, more preferably 0.2 mm or more, preferably 1.5 mm or less, more preferably 1.4 mm or less, and further preferably 1.2 mm. It is as follows.

  Since the thermoforming sheet of the present invention thus obtained has good thermoformability, it is used in various applications, for example, packaging materials for daily necessities, cosmetics, home appliances, blister packs, trays, lunch box lids, etc. It can be thermoformed into food containers, industrial trays used for transportation and protection of industrial parts.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example. The parts in the examples are parts by mass unless otherwise specified. “Normal pressure” indicates 101.3 kPa, and “normal temperature (room temperature)” indicates 25 ° C.

[Optical purity of polylactic acid resin]
The optical purity of polylactic acid resin is measured by the D-body content measurement method described in “Voluntary Standards for Food Containers and Packaging Made of Synthetic Resins such as Polyolefins, Third Edition, Revised June 2004, Part 3 Sanitation Test Method P12-13” Can be asked according to.

First, sodium hydroxide / methanol is added to precisely weighed polylactic acid, set in a water bath shaker set at 65 ° C., and hydrolyzed until the resin content becomes a homogeneous solution. The solution is neutralized by adding dilute hydrochloric acid, and the decomposition solution is dissolved in pure water, and then a predetermined volume is separated into a volumetric flask and diluted with a high-performance liquid chromatography (HPLC) mobile phase solution. The volumetric flask is adjusted to a range of 7, and the volumetric flask is quantitatively filtered through a membrane filter (0.45 μm). The optical purity of the polylactic acid resin is determined by quantifying D-lactic acid and L-lactic acid in this adjusted solution by HPLC under the measurement conditions shown below.
<Measurement conditions>
Column: Sumichiral OA6100 (46 mmφ × 150 mm, 5 μm), pre-column manufactured by Sumika Chemical Analysis Co., Ltd .: Sumichiral QA6100 (4 mmφ × 10 mm, 5 μm), Column temperature manufactured by Sumika Chemical Analysis Center Co., Ltd .: 25 ° C.
Mobile phase: 2.5% methanol-containing 1.5 mM aqueous copper sulfate mobile phase flow rate: 1.0 mL / min Detector: UV detector (UV254 nm)
Injection volume: 20 μL

[Weight average molecular weight of polylactic acid resin]
The weight average molecular weight of the polylactic acid resin was determined by using gel permeation chromatography (GPC), chloroform as the solvent, Tosoh Corporation column, high temperature SEC column (GMHHR-H series), flow rate 1.0 mL / min, column temperature 40 Calculated by using a differential refractive index detector (RI) as a detector and polystyrene having a known molecular weight as a reference.

Plasticizer Production Example 1 (Methyltriglycol succinic acid diester)
A four-necked flask (with a stirrer, thermometer, dropping funnel, distillation tube and nitrogen blowing tube) was charged with 363 g (3.42 mol) of diethylene glycol and 6.6 g of a methanol solution containing 28% by weight sodium methoxide as a catalyst (sodium methoxide 0). 0.034 mol) was added, and methanol was distilled off while stirring at normal pressure and 120 ° C. for 0.5 hour. Thereafter, 1000 g (6.84 mol) of dimethyl succinate (manufactured by Wako Pure Chemical Industries, Ltd.) was added dropwise over 3 hours, and methanol produced by the reaction was distilled off at normal pressure and 120 ° C. Next, the mixture was cooled to 75 ° C., and the pressure was gradually reduced from normal pressure to 6.7 kPa over 1.5 hours to distill off methanol, and then returned to normal pressure. Further, 28% by mass sodium methoxide as a catalyst was obtained. A methanol solution containing 5.8 g (sodium methoxide 0.030 mol) was added, and the pressure was gradually reduced from normal pressure to 2.9 kPa over 2 hours at 100 ° C. to distill methanol. Then, after cooling to 80 ° C., 18 g of KYOWARD 600S (manufactured by Kyowa Chemical Industry Co., Ltd.) was added and stirred at a pressure of 4.0 kPa and 80 ° C. for 1 hour, followed by filtration under reduced pressure. The filtrate was pressured at 0.3 kPa and the temperature was raised from 70 ° C. to 190 ° C. over 1 hour to distill off the remaining dimethyl succinate to obtain a room temperature yellow liquid. In addition, the usage-amount of the catalyst was 0.94 mol with respect to 100 mol of dicarboxylic acid ester.

Examples 1-11 and Comparative Examples 1-8
As a polylactic acid resin composition, using the composition raw materials shown in Tables 1 and 2 using a twin screw extruder (Perker, HK25D, cylinder diameter 25.2 mm, rotation speed 100 rpm, discharge rate 8 kg / h), Melt-kneading was performed at a melt-kneading temperature of 180 to 190 ° C. for 1 minute, and strand cutting was performed to obtain pellets of a polylactic acid resin composition. The obtained pellets were dried at 110 ° C. under reduced pressure for 2 hours, and the water content was adjusted to 500 ppm or less.

Preparation of sheet for thermoforming The obtained pellet was formed into a sheet having a width of 400 mm under the following conditions using a T-die extruder (500 mm T-die manufactured by Plastic Engineering Laboratory Co., Ltd.).
<Extrusion conditions>
Cylinder temperature of biaxial kneading part: 180 ° C
T-die (outlet) temperature: 180 ° C
Extrusion speed: 8kg / h (Cooling roll contact time is 34 seconds)
Cooling roll surface temperature: 25 ° C
Sheet thickness: 0.4 mm

Preparation of Thermoformed Body Using the single vacuum / pressure forming machine “FVS-500P WAKITEC” (manufactured by Wakisaka Seisakusho Co., Ltd.), the obtained thermoforming sheet was attached to a guide and heated to 80 ° C. using a heater. Thereafter, vacuum forming was performed using an upper mold in which the heated thermoforming sheet was set at 115 ° C., and then air was blown from the nozzle attached to the apparatus to the molded body to cool the molded body, thereby obtaining a sample.

  The characteristics of the obtained polylactic acid resin composition, the thermoforming sheet, and the thermoformed article were evaluated according to Test Examples 1 to 5 below. The results are shown in Tables 1-2.

Test Example 1 <Hydrolysis resistance>
Three thermoforming sheets (70 mm x 20 mm x 0.25 mm) are placed in a 60 ° C / 75% RH constant temperature and humidity machine (Platinum K series PL-3KPH, manufactured by Espec) every 24 hours after storage When the center of the 70 mm side (35 mm from the end) of the thermoforming sheet is bent parallel to the 20 mm side and the 20 mm sides are brought close to each other, one or more of the three sheets will crack. The number of days until was measured, and the longer the number of days, the better the durability.

Test Example 2 <Odor during Compound Production>
When the resin composition was melt-kneaded at 200 ° C. for 5 minutes, it was determined by sensory evaluation by one expert panel whether or not the measurer felt an isocyanate odor. When no isocyanate odor was felt, “No” was assigned, and when an isocyanate odor was felt, “Yes”.

Test Example 3 <Foreign matter on sheet>
After 30 minutes from the start of sheet forming, the sheet was cut into a size of 400 × 1500 mm, and the number of foreign matters (discolored matter) contained in the sheet was measured using an optical microscope (VHX-1000 Keyence). The smaller the number of discolored items, the better.

Test Example 4 <Production speed>
When the molded body was prepared, the time required for obtaining the same sample as the standard product of the molded body and the mold holding time and cooling time were calculated as the production rate. The production rate was evaluated to be preferably 13 seconds or less.

Test Example 5 <Transparency>
About the molded body, the haze value was measured using an integrating sphere type light transmittance measuring device (HM-150 Murakami Color Research Laboratory) defined in JIS-K7105. When the value of the Haze value is small, it indicates that the transparency is good, and 7% or less was judged to be acceptable.

In addition, the raw material in Tables 1-2 is as follows.
<Polylactic acid>
N-4000: manufactured by Nature Works, poly-L-lactic acid NatureWorks 4032D, optical purity 98.6%, weight average molecular weight 180000
2500HP: manufactured by Nature Works, poly-L-lactic acid NatureWorks 2500HP, optical purity 99.5% or more, weight average molecular weight 190000
<Plasticizer>
DINA: isononyl adipate, Taoka Chemical Co., Ltd. 610A: adipate n- _{(alkyl: n-C 6 H 13,} n-C 8 H 17, n-C 10 H 21), Taoka Chemical Co., Ltd. A-1010 : Compound prepared in Production Example 1 of plasticizer DAIFATTY-101: Ester of adipic acid and benzyl alcohol and methyl diglycol, Daihachi Chemical Industries, Ltd. ATBC: Tributyl acetylcitrate, Taoka Chemical Co., Ltd. <Organic crystal nucleating agent >
SLIPAX H: 12-hydroxy stearic acid ethylene bisamide, Nippon Kasei Co., Ltd. KAOWAX EB-FF: stearic acid ethylene bisamide, manufactured by Kao Corporation <hydrolysis inhibitor>
LA-1: aliphatic polycarbodiimide compound, manufactured by Nisshinbo Chemical Co., Ltd.

  From Tables 1 and 2, the polylactic acid resin compositions of the examples have good hydrolysis resistance even when no carbodiimide compound is blended, and the effect of suppressing the generation of off-flavors and foreign matters during preparation is also obtained. Is. Further, it can be seen that by using a specific ester compound, a molded body having improved thermoformability, improved production speed, and excellent transparency can be obtained.

  The polylactic acid resin composition of the present invention can be suitably used for various industrial applications such as household goods, household appliance parts, automobile parts and the like.

Claims (8)

A polylactic acid resin composition comprising the following (A), (B), and (C).
(A) Polylactic acid resin (B) An ester of an aliphatic alcohol having an alkyl group having 9 to 30 carbon atoms and a dicarboxylic acid having 4 to 12 carbon atoms (C) Organic crystal nucleating agent   The polylactic acid resin composition according to claim 1, wherein the ester (B) is an ester of an aliphatic alcohol having an alkyl group having 9 to 20 carbon atoms and a dicarboxylic acid having 4 to 12 carbon atoms.   (B) The polylactic acid resin composition according to claim 1 or 2, wherein the ester is an ester of an aliphatic alcohol having an alkyl group having 9 to 15 carbon atoms and a dicarboxylic acid having 4 to 8 carbon atoms. .   (B) Polylactic acid resin in any one of Claims 1-3 whose content of ester is 0.5 to 5.0 mass parts with respect to 100 mass parts of (A) polylactic acid resin. Composition.   (C) Content of an organic crystal nucleating agent is 0.2 mass part or more and 0.6 mass part or less with respect to 100 mass parts of (A) polylactic acid resin, Any one of Claims 1-4. Polylactic acid resin composition.   (C) The organic crystal nucleating agent contains an aliphatic compound having two or more groups selected from the group consisting of an ester group, a hydroxyl group, and an amide group in the molecule. The polylactic acid resin composition in any one of these.   The sheet | seat for thermoforming containing the polylactic acid resin composition in any one of Claims 1-6.   Use of the polylactic acid resin composition according to any one of claims 1 to 6 as a thermoforming sheet.