JP2008138102A - Polylactic acid-based resin composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polylactic acid resin-based composition which contains a polylactic acid which is modified and yet attains suppressed long-term change and excellent moldability and processability. <P>SOLUTION: The polylactic acid resin-based composition comprises a polylactic acid (A) and a polylactic acid block copolymer (B) and is characterized by having an acid value of 10-60 [eq./t] as measured by the method defined in the text and a melt volume flow rate (MVR) of 5-20 [cm<SP>3</SP>/10 min] as measured according to JIS K7210. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a polylactic acid-based resin composition that is excellent in moldability and processability while suppressing changes with time while modifying polylactic acid.

  Conventionally widely used resins include polyethylene, polypropylene, polyethylene terephthalate, polyvinyl chloride, and polycarbonate, which are processed into various molded products such as various containers and used in various situations. However, since these general-purpose resins are made from petroleum, they are not decomposed even if they are buried, and remain in the ground semipermanently.

  In recent years, attention has been focused on resins having excellent biodegradability in plant raw materials due to problems of plastic waste disposal and environmental problems. These resins are materials that do not require petroleum and are degraded by microorganisms in the soil, so that they have very little impact on the environment.

  Examples of such biodegradable resins include polylactic acid and polyhydroxybutyric acid. In particular, polylactic acid has the highest glass transition temperature among these resins and has transparency. The use for materials is attracting attention.

  However, it is difficult to use polylactic acid alone as an alternative to conventional general-purpose resins because it has a hard and brittle nature, and resin compositions blended with other resins have been developed to compensate for such properties. It has been broken. Among them, research and patent applications (see Patent Document 1) regarding resin compositions with polyalkylene ethers have been actively conducted because of transparency and compatibility with polylactic acid.

  However, it is difficult to say that these resin compositions have sufficient performance in terms of processability and handleability, and they are difficult to use as a general-purpose resin because they decompose too quickly except for special applications. Therefore, there is a problem of suppressing decomposition, that is, improving stability over time.

  With respect to the stability over time, an acid component derived from a monomer (lactide) or the like is involved in polymer chain scission in polylactic acid, which is one factor that decreases the stability over time of molded products made of polylactic acid. (See Patent Documents 4 and 5).

  In addition, the composition of polylactic acid and polyalkylene ether has been developed in many ways to suppress the occurrence of bleeding out (extraction) of the polyalkylene ether component. A technique (see Patent Document 3) that improves the compatibility of the base polylactic acid and suppresses bleed-out by copolymerizing the segments is known.

  However, a resin composition obtained by blending these copolymers with polylactic acid may have a decreased melt viscosity. When the molecular weight of the polyalkylene ether to be used is low, there is a problem in that the viscosity is significantly decreased as the molding process is difficult. there were.

  In order to prevent such a decrease in viscosity and obtain a composition having a high viscosity and a low acid value, it is necessary to deactivate or reduce the activity of the catalyst used during copolymerization at the end of the polymerization. Techniques using active phosphorus compounds (see Patent Documents 4 and 5) are known.

  In addition, when paying attention to the phosphorus compound in the polymer, the purpose is completely different, but for the purpose of imparting flame retardancy and thermal stability, a technique for adding a phosphorus compound as a flame retardant in polylactic acid (patent document) 2 and 6).

However, they have not been investigated for viscosity or deterioration with time when a polymer, a synthetic product or a flame retardant having been subjected to catalyst deactivation is used for blending with a polymer.
Japanese Patent Laid-Open No. 2003-41142 JP 2005-162871 A JP 2005-146274 A Japanese Patent No. 3513972 Japanese Patent No. 3487388 JP 2003-119276 A

  In view of the background of such prior art, the present invention aims to provide a polylactic acid-based resin composition that is excellent in molding and processability while suppressing changes with time while modifying polylactic acid.

In order to solve the above problems, the present invention employs the following means. That is, the polylactic acid composition of the present invention is a resin composition containing polylactic acid (A) and a polylactic acid block copolymer (B), and is measured by the method described later. that the acid value of the resin composition is not more than 60 [eq / t], and wherein the melt volume flow rate to be measured by the method described later (MVR) is ²⁰ [cm 3 / 10min] or less It is.

  According to the present invention, a polylactic acid resin composition excellent in processability, which has not been achieved by the prior art, improves transparency while maintaining rigidity and brittleness, suppresses changes with time. Can be provided. Moreover, the composition by this invention can be provided for uses, such as a packaging use, such as a sheet | seat and a film, an injection molded body, and a lamination.

The present invention has been intensively studied on the above-mentioned problem, that is, a polylactic acid-based resin composition that is excellent in molding and processability, while suppressing the change with time while modifying polylactic acid, and the resin composition is polylactic acid (A ) And the polylactic acid block copolymer (B), the acid value of the resin composition measured by the method described later is 60 [equivalent / t] or less, and by melt volume flow rate is measured according to JIS-K7210 (MVR) is a polylactic acid resin composition which is a 5~20 ^[cm 3 / 10min], such a problem all at once It has been investigated to solve.

  The present invention is described in detail below.

  Polylactic acid is a biodegradable resin, which is decomposed after a certain period of time by molecular chains being cleaved by hydrolysis or bacteria. The degradation rate is caused by the acid terminal in the polylactic acid. When there are many acid terminals in the composition, the chain breakage is promoted and the physical properties are lowered at an early stage.

  The acid end can be measured by neutralization titration, and the acid end amount is called an acid value, and is handled in units of chemical equivalent per 1 t [equivalent / t].

  In the present invention, the acid value is preferably in the range of 0 to 60 [equivalent / t] from the viewpoint of suppressing breakage of the polymer molecular chain and suppressing change with time. When the acid value exceeds 60 [equivalent / t], the molecular chain is rapidly cut and the change with time may be promoted. A more preferable range is 0 to 50 [equivalent / t], particularly preferably 0 to 30 [equivalent / t]. The lower the acid value, the better. However, since the acid value of polylactic acid itself is 10 [equivalent / t], the practical lower limit of the acid value is 10 [equivalent / t].

  The acid terminal present in the polylactic acid-based resin composition may be caused by lactic acid generated by hydrolysis of lactide remaining as a monomer. Therefore, in order to reduce the acid value, it is preferable to sufficiently remove the remaining monomer (lactide) before becoming lactic acid by hydrolysis.

  Examples of the method for removing lactide include a method using a solvent and a method using devolatilization, but removal by devolatilization is widely used from the viewpoint of good productivity. The removal method by devolatilization is also an effective method from the viewpoint that lactide has sublimability. Moreover, since lactic acid produced by hydrolysis of lactide is poor in sublimability, it is difficult to remove by devolatilization.

  It is preferable that the unreacted monomer (lactide) is sufficiently removed from both the polylactic acid (A) and the polylactic acid block copolymer (B) constituting the polylactic acid resin composition. In the case where the polylactic acid block copolymer (B) is produced by ring-opening polymerization of lactide, if the activity of the polymerization catalyst remains, unreacted monomer (lactide) is generated by depolymerization. Is preferably reduced.

  When a lactide ring-opening polymerization catalyst is used to polymerize lactide to obtain polylactic acid, the reaction becomes an equilibrium reaction between polymerization and depolymerization. The catalyst has a function to lower the activation energy, but when the monomer (lactide) is removed out of the system by devolatilization, depolymerization is promoted to maintain the equilibrium, and the amount of monomer (lactide) is below the equilibrium value. In some cases, it may be difficult to reduce it.

  Therefore, it is preferable to add a catalyst activity reducing agent for the purpose of reducing the activity of the catalyst. Since the activity of the polymerization catalyst is reduced by the catalyst activity reducing agent and the activation energy of the equilibrium reaction is increased, depolymerization can be suppressed. The amount of unreacted monomer (lactide) can be further reduced by removing the monomer (lactide) by devolatilization after adding a catalyst activity reducing agent to suppress depolymerization. Therefore, it is preferable to add a catalyst activity reducing agent to the composition of the present invention.

  Here, sufficiently removing means that no peak derived from a monomer (lactide) is produced when 10 mg each of polylactic acid (A) and polylactic acid block copolymer (B) is measured by NMR.

Further, it is excellent in order to have workability, 170 ° C., which is measured in accordance with JIS-K7210, the melt volume rate under a load of 2.16 kg (MVR) is 0~20 ^[cm 3 / 10min] Is preferred. Viscosity is greater than ²⁰ [cm 3 / 10min], sometimes molded to too low viscosity may become difficult. For example, when performing such top-blown Inflation, MVR can be used more favorably if 0~10 ^[cm 3 / 10min]. Also no lower limit on the viscosity, is preferably as low as possible, in practice a value of less than 5 [cm 3 ^/ 10min] is difficult to achieve.

In general, it viscosity when blended copolymer of the modifying purposes, such as polylactic acid polylactic acid block copolymer is liable to decrease, which may MVR may exceed the 20 [cm 3 ^/ 10min]. The main factor is that a polylactic acid block copolymer having a low molecular weight is blended with polylactic acid.
Therefore, in the present invention, the polylactic acid block copolymer (B) contained in the polylactic acid (A) preferably has a molecular weight of 8000 or more. When the molecular weight is extremely increased, it may be difficult to obtain a sufficient modification effect, and 10,000 to 20,000 is more preferably used.

  The polylactic acid block copolymer (B) is a block copolymer comprising a polylactic acid segment and a polyalkylene ether as a copolymerization component. The copolymer component includes polyalkylene ethers, glycol derivatives, dialkylacetic acid. , Hydroxybutyric acid, ε-caprolactone, and the like, but polyalkylene ethers are preferably used, and most preferably polyethylene glycol is used to impart flexibility while imparting transparency to polylactic acid. preferable. At that time, the molecular weight of the polyalkylene ether used is preferably 5000 or more and 15000 or less.

  Further, in order to impart affinity with polylactic acid or impart bleed resistance, it is preferable to have a polylactic acid segment having a crystallinity with a molecular weight of 1500 or more mainly composed of L-lactide or D-lactide. The polylactic acid segment exhibits bleed-out resistance by co-crystallizing with polylactic acid (A). In order to improve the modification effect and moldability, the molecular weight of the polylactic acid segment is more preferably 1500 or more and 3500 or less.

  The polylactic acid block copolymer (B) is a block obtained by copolymerizing with a polyalkylene ether with a lactide ring-opening polymerization catalyst and then reducing the catalytic activity with a catalytic activity reducing agent such as a phosphorus acidic compound. A copolymer is preferred. The catalyst activity reducing agent varies depending on the polymerization catalyst used in the polymerization reaction, and generally includes a compound having one or more phosphoric acid or phosphoric acid esters, such as phosphoric acid, phosphorous acid alone or the number of carbon atoms. Phosphate esters having one or two alkyl chains of 1 or more and 20 or less are preferably used, and a mixture thereof can also be used. Of these, a phosphoric acid compound is particularly preferred because it suppresses breakage of the polymer chain, has a good hue, and efficiently binds to the catalyst.

  Moreover, it is preferable that content of a catalyst activity reducing agent is contained in the polylactic acid-type resin composition in the range of 70-350 ppm in the quantity of a phosphorus atom. If it is less than 70 ppm, the activity of the catalyst may not be sufficiently reduced. If the catalytic activity is not reduced, the heat during processing of the resin composition of the present invention accelerates the depolymerization reaction, resulting in molecular chain scission or generation of a large amount of monomer (lactide), resulting in odor The MVR may increase, or the acid value may increase. If it exceeds 350 ppm, the activity reducing agent tends to be excessive with respect to the catalyst. Phosphorus acidic compounds that were not involved in the reduction of the catalytic activity acted on the molecular chain scission as an acid end in the same manner as lactic acid hydrolyzed by lactide, which may cause an increase in MVR due to an increase in acid value or a decrease in molecular weight. When melt processing is performed with an extruder or the like, the workability may be reduced.

  Similarly, the polylactic acid (A) preferably has a high molecular weight and a high viscosity, and is preferably a polylactic acid having a weight average molecular weight of 50,000 or more obtained by ring-opening polymerization of lactide or dehydration condensation of lactic acid. In addition, since the polylactic acid block copolymer (B) exhibits bleed-out resistance by co-crystallizing a polylactic acid segment in the polylactic acid (A) crystal, the polylactic acid (A) is crystalline. It is preferable to have

  The polylactic acid-based resin composition contains 15 to 60% by weight of the polylactic acid-based block copolymer (B) having the above characteristics in the polylactic acid (A) having the above characteristics from the viewpoint of the modification effect and molding processability. It is preferable that it is the structure which carried out. If the content of the polylactic acid block copolymer (B) is less than 15% by weight, the intended modification effect may not be obtained, and the content of the polylactic acid block copolymer (B) is 60. If it exceeds wt%, molding processability may be lowered due to a decrease in viscosity or the like.

Examples of the kneading of the polylactic acid (A) and the polylactic acid block copolymer (B) include use of a twin screw extruder, a ball mill, an autoclave, a reaction kettle used for polymerization, and the like. (A) and (B) are a method in which a predetermined amount is measured in advance and charged into the kneader, a method in which (B) is added in a predetermined amount after synthesis in (B), Examples thereof include a method in which both are charged into another kettle after polymerization of (B) in a separate reaction kettle. From the viewpoint of good handleability, accuracy of the mixing ratio, etc., it is useful to measure a predetermined amount of (A) and (B) in advance and put them into the kneader.
The molding method is to cast from a T-shaped die and create an unstretched film, and then stretch the film in the width direction (TD) and the film longitudinal direction (MD), or from a circular die to a cylindrical film A method in which the inside is pressurized with air or nitrogen and the TD / MD is stretched at the same time, or the melted polylactic acid resin composition of the present invention is pressed with a press to obtain an unstretched sheet. And then stretching.

  The polylactic acid-based resin composition of the present invention is a polylactic acid resin that has not been able to be achieved by the prior art, has improved transparency, improves hardness and brittleness, suppresses changes with time, and has excellent processability. A lactic acid resin composition can be provided. Moreover, the composition by this invention can be provided for uses, such as a packaging use, such as a sheet | seat and a film, an injection molded body, and a lamination.

  In addition, a lubricant, particles, an antioxidant for the purpose of preventing coloring due to oxidation, and the like can be used for the purpose of improving the slippage between films within the range not impairing the effects of the present invention.

The present invention will be described more specifically with reference to the following examples and comparative examples, but the present invention is not limited to the following examples. The physical properties and evaluation were measured and evaluated by the following methods.
(1) Composition analysis of polylactic acid block copolymer The success or failure of the copolymerization reaction was analyzed using ¹ H-NMR (nuclear magnetic resonance apparatus). Since a peak derived from a portion where the polylactic acid segment and the polyether are bonded appears, it was determined whether or not the copolymerization was performed.

  The crystallinity of the polylactic acid segment is a crystal derived from the polylactic acid component when the composition is once crystallized under heating and then subjected to DSC (Differential Scanning Calorimetry) measurement in an appropriate temperature range. Judgment was made based on whether heat of fusion was observed.

  The number average molecular weight of the polylactic acid segment of the resin composition of the present invention and the number average molecular weight of the polyether component can be calculated from the integrated intensity of NMR and GPC. The number average molecular weight of the polyether used for the synthesis is known, and the number average molecular weight of the polylactic acid segment can be determined by comparison with a sample obtained by copolymerizing the polylactic acid segment. Even when the number average molecular weight of the polyether is unknown, if the GPC of the entire composition is measured and the total number average molecular weight is measured, it can be determined from the number average molecular weight of the PLA segment calculated by NMR.

Mn [PLA] = {72 × H (e) × ∫ (PL) × Mn [E]} / {∫ (E) × Mn [e]}
Actual value = Mn [PLA] + Mn [E] +6500
However,
Mn [PLA]: Number average molecular weight of PLA segment H (e): Number of protons per polyether unit molecule ∫ (PL): Integral intensity of PLA segment Mn [E]: Polyether number average molecular weight ∫ (E): Poly Integral strength of ether M [e]: Unit molecular weight of polyether.
(2) Measuring method of content of polylactic acid block copolymer 5 ° C. of resin composition crystallized by heat treatment at 120 ° C. for 2 hours at a heating rate of 20 ° C./min with DSC (Differential Scanning Calorimetry) The measurement is performed from −20 ° C. to 200 ° C., and the DSC of polylactic acid is also measured in the same manner.

  At that time, if the heat of crystal melting at a melting point of 170 ° C. derived from polylactic acid is ΔHms and ΔHm, respectively, it can be calculated from the following equations.

Content (% by weight) = ΔHms / ΔHm × 100
However,
ΔHms = heat of crystal melting of the resin composition ΔHm = heat of crystal melting of polylactic acid.
(3) Acid value It measured using the neutralization titration method described below.

  First, an indicator was dropped into chloroform. This chloroform solution was titrated with a 0.02 mol / L ethanolic potassium hydroxide solution, and the titration at that time was designated as B (blank titration (ml)).

  Subsequently, 0.2 g of the resin composition as a sample was weighed and dissolved in fresh chloroform, and then an indicator was dropped. The chloroform solution was titrated with a 0.02 mol / L ethanolic potassium hydroxide solution, and the titration at that time was designated as A (sample titration (ml)).

It calculated from the numerical value of A and B using the following formula.
[KOHmg / g] = {(A−B) × f × 1/25 × 56.11} / W
Acid value [equivalent / t] = [KOH mg / g] × 1000 / 56.11
However,
f: Potency of ethanolic potassium hydroxide solution W: Sample collection amount (g)
(4) MVR (melt volume flow rate)
Based on JIS-K7210, it measured by 170 degreeC and the load 2.16kg (B method) (unit [cm < ³ > / 10min]).
(5) P amount (phosphorus amount)
The amount of phosphorus atom in the present invention was measured using fluorescent X-ray FL-X.

First, a sample piece was prepared by melt-molding 6 g of a polylactic acid resin composition into a plate shape. With respect to this sample piece, the intensity of the fluorescent X-ray was measured with a fluorescent X-ray apparatus (model number 3270) manufactured by Rigaku Corporation. Using this calibration curve prepared in advance with a sample with a known content, the amount of heavy metal element and the amount of phosphorus element were each quantified.
(6) Stability over time Judgment was made based on whether or not there was a decrease in molecular weight and an increase in acid value after standing in a refrigerator at 5 ° C. for 1 month.
A: The molecular weight decrease is less than 10%, and the acid value increase is less than 10%.
B: Molecular weight decrease is less than 10%, and acid value increase is 10% or more and less than 50%.
C: Molecular weight reduction is 10% or more and less than 20%, and acid value increase is 10% or more and less than 50%.
D: The molecular weight decrease is 20% or more, or the acid value increase is 50% or more.

  A, B, and C were judged to have good stability over time, and D was judged to be poor.

The molecular weight was measured in terms of polystyrene using GPC (gel permeation chromatography) by dissolving the sample in a THF (tetrahydrofuran) solution at 1 mg / cc. The instrument is LC-10A series manufactured by Shimadzu Corporation, the solvent is THF (for high performance liquid chromatography), the detector is RI detector (RID-10A), the column is Shodex (trademark) KF-806L and KF- manufactured by Showa Denko KK 804L (each 300 mm × 8 mmφ) was used in series. The column temperature is 30 ° C., and the flow rate is 1.0 ml / min (on-line deaeration system with He). The polystyrene used as a standard is a polystyrene standard manufactured by Shodex (trademark). No. Used S-6850, S-1190, S-205, S-52.4, S-13.9, and S-1.31. These were measured by drawing a calibration curve by cubic approximation.
(7) Workability The polylactic acid resin composition obtained by the present invention was dried at 100 ° C. under reduced pressure for 3 hours, and then extruded at 30 mm in diameter, L / D = 35, and 160 ° C. to 190 ° C. Inflation film formation was performed by melting and discharging from a circular die having a diameter of 20 mm and a lip width of 1.5 mm from the machine and winding the tube upward.
A: A tube can be easily formed, and winding is stable.
B: Polylactic acid cannot be sufficiently modified and film formation is impossible.
C: Due to insufficient viscosity, the tube cannot be formed and cannot be wound.
A was judged as good workability, and B and C were judged as poor workability.
[Example 1]
A block copolymer (B) was synthesized using a catalyst for L-lactide (manufactured by PURAC) and polyethylene glycol (manufactured by Sanyo Chemical Co., Ltd., molecular weight 8,300). After completion of the synthesis, 0.15% by weight of phosphoric acid (manufactured by Aldrich) was added as a catalyst deactivator, and after stirring, the monomer (lactide) was removed by devolatilization.

  Polylactic acid (A) (manufactured by Nature Works) 85% by weight and 15% by weight of the previously synthesized block copolymer (B) were kneaded while being devolatilized using a vented twin screw extruder, A pellet of the resin composition was obtained.

The acid value of the obtained pellets, MVR, was measured the amount of P, an acid value of 10 [eq / t], MVR is ⁵ [cm 3 / 10min], the amount of P was 71 ppm.

When the blown blown film was formed using the pellets, the processability was good and the stability of the resulting film with time was good.
[Example 2]
A block copolymer (B) was synthesized using D-lactide (manufactured by PURAC) and polyethylene glycol (molecular weight 8,300) as a catalyst. After completion of synthesis, 0.2% by weight of phosphoric acid was added as a catalyst deactivator and stirred, and then the monomer (lactide) was removed by devolatilization.

70% by weight of polylactic acid (A) and 30% by weight of the previously synthesized block copolymer (B) were kneaded while devolatilized using a twin-screw extruder with a vent, and pellets of the polylactic acid resin composition were obtained. Obtained.
The acid value of the obtained pellets, MVR, was measured the amount of P, an acid value of 18 [eq / t], MVR is ⁷ [cm 3 / 10min], the amount of P was 140 ppm.

When the top blown inflation film formation was performed using the pellets, the film forming property was good, and the stability of the obtained film was good.
Example 3
A block copolymer (B) was synthesized using a catalyst for L-lactide and polyethylene glycol (molecular weight 8300). After completion of synthesis, 0.2% by weight of phosphoric acid was added as a catalyst deactivator and stirred, and then the monomer (lactide) was removed by devolatilization.

  64% by weight of polylactic acid (A) and 36% by weight of the previously synthesized block copolymer (B) were kneaded while devolatilized using a twin-screw extruder with a vent, and pellets of the polylactic acid resin composition were obtained. Obtained.

The acid value of the obtained pellets, MVR, was measured the amount of P, an acid value of 23 [eq / t], MVR is ⁹ [cm 3 / 10min], the amount of P was 190 ppm.

When the top blown inflation film formation was performed using the pellets, the film forming property was good, and the stability of the obtained film was good.
Example 4
A block copolymer (B) was synthesized using a catalyst for L-lactide and polyethylene glycol (molecular weight 10,000). After completion of the synthesis, 0.15% by weight of phosphoric acid was added as a catalyst deactivator and stirred, and then the monomer (lactide) was removed by devolatilization.

  40% by weight of polylactic acid (A) and 60% by weight of the previously synthesized block copolymer (B) were kneaded while devolatilized using a twin-screw extruder with a vent, and pellets of the polylactic acid resin composition were obtained. Obtained.

The acid value of the obtained pellets, MVR, was measured the amount of P, an acid value of 54 [eq / t], MVR is ²⁰ [cm 3 / 10min], the amount of P was 350 ppm.

When the top blown inflation film formation was performed using the pellets, the film forming property was good, and the stability of the obtained film was good.
[Comparative Example 1]
A block copolymer (B) was synthesized using a catalyst for L-lactide and polyethylene glycol (molecular weight 8,300). After completion of the synthesis, 0.15% by weight of phosphoric acid was added as a catalyst deactivator and stirred, and then the monomer (lactide) was removed by devolatilization.

  90% by weight of polylactic acid (A) and 10% by weight of the previously synthesized block copolymer (B) were kneaded while devolatilized using a vented twin-screw extruder, and pellets of the polylactic acid resin composition were obtained. Obtained.

The acid value of the obtained pellets, MVR, was measured the amount of P, an acid value of 9 [eq / t], MVR is ³ [cm ³ / 10min], the amount of P was 47 ppm.

When the top blown inflation film was formed using the pellet, the hardness and brittleness of polylactic acid were not improved, and tearing and bursting occurred repeatedly.
[Comparative Example 2]
A block copolymer (B) was synthesized using a catalyst for L-lactide and polyethylene glycol (molecular weight 10,000). After completion of synthesis, 0.2% by weight of phosphoric acid was added as a catalyst deactivator and stirred, and then the monomer (lactide) was removed by devolatilization.

  30% by weight of polylactic acid (A) and 70% by weight of the previously synthesized block copolymer (B) were kneaded while devolatilized using a twin-screw extruder with a vent, and pellets of the polylactic acid resin composition were obtained. Obtained.

The acid value of the obtained pellets, MVR, was measured the amount of P, an acid value of 75 [eq / t], MVR is ⁵⁰ [cm 3 / 10min], the amount of P was 440 ppm.

  When top blown inflation film formation was performed using the pellets, the viscosity was too low to form bubbles, making film formation impossible.

  The compositions prepared in Examples and Comparative Examples are shown in Table 1 below.

  If the acid value and the amount of P are in the preferred ranges, the stability over time is good, and if the MVR is in the preferred range, the viscosity is sufficient and the workability is good.

If the content of the block copolymer is within a preferable range, the polylactic acid is sufficiently modified and the processability is good.
In the comparative example, since the acid value and the amount of P are not in the preferred ranges, the stability over time is poor, and the contents of MVR and the block copolymer are not in the preferred ranges, so the workability is poor.

  By using the resin composition provided by the present invention, it is possible to provide a resin composition that improves the hardness and brittleness of polylactic acid, suppresses changes over time, and has excellent processability. In particular, it can be suitably used for processing sheets, films and the like.

Claims (5)

A resin composition comprising polylactic acid (A) and a polylactic acid block copolymer (B), and the acid value of the resin composition measured by the method defined in the specification is 60 eq / t] or less, and polylactic acid resin composition, wherein the melt volume flow rate is measured according to JIS-K7210 (MVR) is ²⁰ [cm 3 / 10min] or less object.   2. The polylactic acid resin composition according to claim 1, wherein the polylactic acid block copolymer (B) is a block copolymer with a polyalkylene ether having a polylactic acid segment having a molecular weight of 1500 or more. .   The polylactic acid resin composition according to claim 1 or 2, wherein the polylactic acid resin composition contains 15 to 60 wt% of the polylactic acid block copolymer (B).   The polylactic acid resin composition according to any one of claims 1 to 3, wherein the polylactic acid block copolymer (B) contains a phosphorus acid compound as a catalyst activity reducing agent.   The polylactic acid resin composition according to claim 4, wherein the polylactic acid resin composition contains phosphorus atoms in a range of 70 ppm to 350 ppm.