JP2005239932A - Polylactic acid resin composition and molded article using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a polylactic acid resin composition without reduction in molecular weight and generation of gel, or the like, and with rheological properties advantageous for molding a direct blow molded article, an inflation molded article, an expansion molded article and an extrusion molded article, or the like, and to provide a molded article using the same. <P>SOLUTION: The polylactic acid resin composition comprises a polylactic acid resin (A) component and a vinyl copolymer (B) component containing a monomer unit, as a structural unit, with a functional group having reactivity with carboxyl group and/or hydroxyl group. The resin composition has strain of 0.1% at 200°C and shearing viscosity of 800-2,000 Pa s at a frequency of 100 rad/s. The resin composition has a degree of strain hardening λ of uniaxial stretching viscosity of 0.4-0.8 at a uniaxial stretching rate of 1.0 sec<SP>-1</SP>and a uniaxial stretching strain of 1.0-4.0. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a polylactic acid-based resin composition, and more specifically, a polylactic acid-based resin composition having rheological properties advantageous for molding such as a direct blow molded article, an inflation molded article, a foamed molded article, and an extruded molded article, and The present invention relates to a molded product using the same.

  Plastics are now pervasive in every field of life and industry, with annual production of around 100 million tons worldwide. On the other hand, however, the problem of processing used plastics is increasing in proportion to the production volume.

  Conventionally, most used plastics have been disposed of by landfill or the like, but plastics are generally stable in nature for a long period of time, and the bulk specific gravity is small, so the life of landfills is becoming shorter. For this reason, various problems, such as a natural scenery and the living environment of a wild plant being impaired, have arisen.

  In recent years, the effective use of depleting resources has become more important due to the growing environmental problems, and biodegradable resins that do not adversely affect the natural environment, that is, decay and decomposition progress due to hydrolysis in soil and water However, biodegradable resins that eventually become harmless degradation products due to the action of microorganisms have attracted attention.

  Examples of biodegradable resins that have begun to be put into practical use include polylactic acid resins, aliphatic polyesters, modified polyvinyl alcohol, cellulose ester compounds, modified starches, and blends thereof.

  Among them, polylactic acid-based resins are made from lactic acid obtained by fermentation of starch and can be mass-produced in the chemical industry, and because they are excellent in transparency, rigidity, heat resistance, etc., polystyrene and polyethylene terephthalate It is particularly attracting attention as an alternative material.

  However, the polylactic acid-based resin has a problem that the shear viscosity at the time of molding is low, the strain curability is poor, and the moldability is poor. For example, bubbles are not stable in blown film molding, hot parison is drawn down in direct blow molding, cell shape is not stable in foam molding, and many bubbles are broken. was there.

  In order to improve the shear viscosity and strain hardenability at the time of melting, generally, a method of adding a high molecular weight resin or a method of using a resin having a long chain branch is considered effective for these problems. However, in order to obtain a high molecular weight resin, it takes a long time for the polymerization and not only the production efficiency is deteriorated, but also coloration and decomposition due to a long thermal history are observed. For example, the weight average molecular weight is 500,000. The above polylactic acid resin has not been put into practical use.

  Thus, for example, Patent Document 1 discloses a method for producing a branched polylactic acid resin by adding a polyfunctional initiator during polymerization. Patent Document 2 discloses a method of causing crosslinking by melt-kneading an organic peroxide and a compound having an unsaturated bond. However, these methods have problems such as unstable operation due to generation of gels and the like. Patent Document 3 discloses a method of causing crosslinking by melt kneading with a polyvalent isocyanate. However, this method has a problem in that the molecular weight tends to decrease at the time of remelting or the safety during operation.

JP 2000-136256 A JP-A-10-324766 JP 2000-17037 A

  That is, the object of the present invention is a polylactic acid-based resin composition having less rheological properties advantageous for molding of direct blow molded products, inflation molded products, foamed molded products, extruded molded products, etc., with less molecular weight reduction and generation of gels, etc. And providing a molded article using the same.

  In view of the current situation, the present inventors have made extensive studies and, as a result, can solve the above problems by using a polylactic acid resin composition having a specific composition and having a specific strain hardening property. The headline and the present invention were completed.

That is, the present invention
(1) A polylactic acid-based resin composition containing the following components (A) and (B), having a strain of 0.1% at 200 ° C. and a shear viscosity of 800 to 2000 Pa · s at a frequency of 100 rad / s. And a strain hardening degree λ of a uniaxial elongation viscosity at a uniaxial elongation rate of 1.0 sec ⁻¹ and a uniaxial elongation strain of 1.0 to 4.0 is 0.4 to 0.8. Composition,
(A) Polylactic acid-based resin (B) Vinyl polymer containing a monomer unit having a functional group having reactivity with a carboxyl group and / or a hydroxyl group as a constituent unit (2) The carboxyl group of component (B) and / or Or the functional group having reactivity with a hydroxyl group is an epoxy group, the polylactic acid-based resin composition according to the above (1),
(3) A molded article using the polylactic acid resin composition according to (1) or (2) above,
Is to provide.

  According to the present invention, a polylactic acid-based resin composition having less rheological properties advantageous for molding a direct blow molded article, an inflation molded article, a foam molded article, an extruded molded article, and the like, with less generation of molecular weight reduction and gel, and the like. A molded product using can be provided.

  Hereinafter, the present invention will be described in detail, but the scope of the present invention is not limited to the embodiments described below.

The polylactic acid-type resin composition of this invention contains the following (A) component and (B) component.
(A) Polylactic acid resin (B) Vinyl polymer containing a monomer unit having a functional group having reactivity with a carboxyl group and / or a hydroxyl group as a constituent unit

  Here, the polylactic acid-based resin which is the component (A) used in the present invention includes poly (L-lactic acid) whose structural unit is L-lactic acid, poly (D-lactic acid) whose structural unit is D-lactic acid, and structure. Poly (DL-lactic acid) whose units are L-lactic acid and D-lactic acid, and mixtures thereof.

  The composition ratio of D-lactic acid (D-form) and L-lactic acid (L-form) in the polylactic acid resin is L-form: D-form = 100: 0 to 90:10, or L-form: D-form = 0: 100- 10:90 is preferable, and L-form: D-form = 100: 0 to 94: 6, or L-form: D-form = 0: 100 to 6:94 is more preferable. When the composition ratio of the D body and the L body is out of this range, the heat resistance of the obtained molded product is low, and the application may be limited.

  In the present invention, polylactic acid resins having different copolymerization ratios of L-form and D-form may be blended. In this case, the average value of the copolymerization ratios of the L-form and D-form of a plurality of polylactic acid-based resins may be set within the above range. By blending the L and D homopolymers and the copolymer, it is possible to balance the difficulty of bleeding and the development of heat resistance.

As a polymerization method for the polylactic acid-based resin, known methods such as a condensation polymerization method and a ring-opening polymerization method can be employed. For example, in the condensation polymerization method, a polylactic acid resin having an arbitrary composition can be obtained by directly dehydrating condensation polymerization of L-lactic acid, D-lactic acid, or a mixture thereof.
In the ring-opening polymerization method (lactide method), lactide, which is a cyclic dimer of lactic acid, has an arbitrary composition and crystallinity using an appropriate catalyst while using a polymerization regulator or the like as necessary. A polylactic acid resin can be obtained. Lactide includes L-lactide, which is a dimer of L-lactic acid, D-lactide, which is a dimer of D-lactic acid, and DL-lactide composed of L-lactic acid and D-lactic acid. Accordingly, by mixing and polymerizing, a polylactic acid resin having an arbitrary composition and crystallinity can be obtained.

  Furthermore, the polylactic acid resin used in the present invention can be added with a small amount of a copolymer component according to the necessity for improving heat resistance, etc., and non-aliphatic dicarboxylic acid such as terephthalic acid and / or bisphenol A. Non-aliphatic diols such as ethylene oxide adducts can also be used.

  Even if the polylactic acid-based resin is a copolymer with other hydroxycarboxylic acid units such as lactic acid and / or α-hydroxycarboxylic acid other than lactic acid, A copolymer may also be used.

  Here, as other hydroxy-carboxylic acid units, optical isomers of lactic acid (D-lactic acid for L-lactic acid, L-lactic acid for D-lactic acid), glycolic acid, 3-hydroxybutyric acid, Bifunctional aliphatic hydroxy such as 4-hydroxybutyric acid, 2-hydroxy-n-butyric acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-methyllactic acid, 2-hydroxycaproic acid Examples thereof include lactones such as carboxylic acid, caprolactone, butyrolactone, and valerolactone.

  Examples of the aliphatic diol copolymerized with the polylactic acid resin include ethylene glycol, 1,4-butanediol, and 1,4-cyclohexanedimethanol. Examples of the aliphatic dicarboxylic acid include succinic acid, adipic acid, suberic acid, sebacic acid, and dodecanedioic acid.

  The polylactic acid resin used in the present invention preferably has a weight average molecular weight in the range of 50,000 to 400,000, more preferably in the range of 100,000 to 250,000. When the weight average molecular weight of the polylactic acid resin is less than 50,000, practical physical properties such as mechanical properties and heat resistance are hardly expressed, and when it is more than 400,000, the melt viscosity becomes too high and the molding processability may be inferior. .

  As the polylactic acid resin preferably used in the present invention, trade name “Lacty” series manufactured by Shimadzu Corporation, trade name “Lacia” series manufactured by Mitsui Chemicals, Inc., trade name manufactured by Cargill Dow The "Nature Works" series is commercially available.

  Moreover, in this invention, you may mix the aliphatic polyester resin and / or aliphatic aromatic polyester resin whose glass transition temperature (Tg) is 0 degrees C or less with said polylactic acid-type resin. By further mixing these resins, it can be expected to improve the impact resistance and cold resistance in addition to the improvement of the molding processability of the polylactic acid resin, which is the gist of the present invention.

  Here, as the aliphatic polyester resin, aliphatic polyester obtained by condensation of aliphatic diol and aliphatic dicarboxylic acid, aliphatic polyester obtained by ring-opening polymerization of cyclic lactones, aliphatic obtained by ring-opening polymerization of cyclic lactones Examples thereof include polyester and synthetic aliphatic polyester.

  Aliphatic polyesters obtained by condensing the above aliphatic diols and aliphatic dicarboxylic acids are aliphatic glycols such as ethylene glycol, 1,4-butanediol and 1,4-cyclohexanedimethanol, and aliphatic dicarboxylic acids. It can be obtained by condensation polymerization by selecting one or more of succinic acid, adipic acid, suberic acid, sebacic acid and dodecanoic acid. Moreover, a desired resin can be obtained by a chain extension reaction with an isocyanate compound or the like as required. Specifically, the trade name “Bionore” manufactured by Showa Polymer Co., Ltd. is commercially available.

  Typical examples of the aliphatic polyester obtained by ring-opening polymerization of the above cyclic lactones include cyclic monomers such as ε-caprolactone, δ-valerolactone, β-methyl-δ-valerolactone, and the like. Selected and polymerized. Examples of the synthetic aliphatic polyester include cyclic acid anhydrides and oxiranes, such as copolymers of succinic anhydride with ethylene oxide, propylene oxide, and the like.

  Next, the aliphatic aromatic polyester is a resin obtained by copolymerizing 50 mol% or less of an aromatic monomer component such as terephthalic acid as a dicarboxylic acid component in order to improve heat resistance and mechanical strength. Specifically, the product name “Easter Bio” manufactured by Eastman Chemical Co., Ltd., the product name “Eco-Flex” manufactured by BASF, and the like are commercially available.

  Next, a vinyl polymer containing a monomer unit having a functional group having reactivity with a carboxyl group and / or a hydroxyl group as the component (B) will be described.

  Here, examples of the monomer having a functional group having reactivity with a carboxyl group and / or a hydroxyl group include an acid anhydride group, an epoxy group, and an oxazoline group. In the present invention, an epoxy group is particularly preferable. The monomer which has is preferable. In the case of a monomer having an epoxy group, the reaction with the carboxyl group can be facilitated moderately, and strain hardening characteristics are manifested by chain extension or grafting reaction of the polylactic acid resin as component (A). For this reason, the effect of improving the moldability is imparted. Furthermore, it is preferable because it also has an effect of suppressing a decrease in molecular weight due to hydrolysis during extrusion melting. Specific examples of the monomer having an epoxy group include glycidyl methacrylate, glycidyl acrylate, (3,4-epoxycyclohexyl) methyl methacrylate, and the like.

  The amount of the monomer unit having a functional group having reactivity with a carboxyl group and / or a hydroxyl group is preferably in the range of 5 to 95% by weight of all the structural units of the component (B). The vinyl polymer as the component (B) may contain a monomer unit other than the monomer unit having a functional group having reactivity with a carboxyl group and / or a hydroxyl group as a constituent unit.

  Specific examples of other monomers include monomers having an aromatic ring such as styrene and α-methylstyrene, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, and methyl methacrylate. , Ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate and the like.

  The vinyl polymer constituted as described above is obtained by polymerizing a monomer having a functional group having reactivity with a carboxyl group and / or a hydroxyl group and, if necessary, other monomers by a known method. Manufactured by. As a preferable method for producing the vinyl polymer, there is a method by high-temperature continuous polymerization disclosed in JP-A-57-502171, JP-A-59-6207, and JP-A-60-215007. That is, it is a method in which a mixture of the above monomers is continuously supplied into a reactor set at a predetermined temperature and pressure at a constant supply rate, and an amount of reaction liquid corresponding to the supply amount is withdrawn. Specifically, it is commercially available from Toagosei Co., Ltd. under the trade name “ARUFON UG series and XG series”.

Next, the polylactic acid-based resin composition of the present invention has a strain of 0.1% at 200 ° C., a shear viscosity of 800 to 2000 Pa · s at a frequency of 100 rad / s, and a uniaxial elongation rate of 1.0 sec ⁻¹ . It is important that the strain hardening degree λ of the uniaxial elongation viscosity at uniaxial elongation strain of 1.0 to 4.0 is 0.4 to 0.8.

  Here, if the shear viscosity is less than 800 Pa · s, there is a problem that moldability, for example, drawdown tends to be large at the time of direct blow molding, which is not preferable. On the other hand, if it exceeds 2000 Pa · s, the swell becomes large. In addition, since the torque (extrusion load) increases during melt extrusion, molding processability tends to decrease, which is not preferable.

  Further, when the strain hardening degree λ of the uniaxial elongation viscosity is within the above range, good moldability is obtained in inflation molding, direct blow molding, and the like.

  By having such characteristics, for example, (1) Bubble formation is stabilized in inflation molding, (2) Neck-down during extrusion casting is prevented in sheet molding, (3) Draw during preheating in sheet molding (4) In foam sheet molding and in-mold foam products, the cell structure is made uniform and dense to prevent bubble breakage. (5) In direct blow molding, parison's thickness distribution is improved. In order to prevent drawdown and improve the thickness distribution of the molded product, (6) fiber molding is expected to have an effect of improving the spinnability during spinning and preventing yarn breakage.

Here, the strain hardening degree λ of the uniaxial extensional viscosity is the increase in the uniaxial extensional strain (ε) after the start of measurement in the transient response of the uniaxial extensional viscosity measured by the uniaxial extensional viscometer as shown in FIG. Accordingly, the region (nonlinear region) where the uniaxial elongation strain (ε) rises from the region where the uniaxial elongation viscosity gradually increases (linear region) (in the plot of the uniaxial elongation rate of 1.0 sec ^{−1 in} FIG. (Ε) is an index representing the degree of increase in uniaxial elongational viscosity in the region of 1.0 or more, and is measured as follows.

First, using a uniaxial extension viscometer (for example, TA Instrument Co., Ltd. (formerly Rheometric Scientific F.E., product name: RME)) at a measurement temperature of 200 ° C., a uniaxial extension rate of 1 Measure transient response of uniaxial elongational viscosity at 0.0 sec ⁻¹ and 0.01 sec ⁻¹ . The uniaxial extension viscosities at the uniaxial extension speeds of 1.0 sec ⁻¹ and 0.01 sec ⁻¹ are η ₁ and η ₂ , respectively. Then, the uniaxial extension distortion of the eta ₁ / eta ₂ of the natural logarithm _{(ln (η 1 / η 2} )) at a uniaxial extension rate of 1.0 sec ^-1 is plotted determined in 1.0 to 4.0 in FIG. 2 Such a relationship is obtained.

Note that the uniaxial elongation strains (ε) 1.0, 2.0, 3.0, and 4.0 at the uniaxial elongation rate of 1.0 sec ⁻¹ are 2.0 seconds after the start of measurement, and 2.0 The distortion is after 3.0 seconds, after 4.0 seconds, and after 4.0 seconds. With respect to this plot (FIG. 2), the slope of the straight line is obtained by the least square method, and the strain hardening degree λ of the uniaxial elongational viscosity is obtained. Such strain hardening degree of uniaxial elongation viscosity and the measuring method thereof are described in, for example, Kiyamato Koyama, Journal of Japanese Rheological Society, vol. 19, pages 174 to 180 (1991).

  It is important that the polylactic acid-based resin composition of the present invention has the strain hardening characteristics described above, and the reaction between the (A) component polylactic acid-based resin and the (B) component carboxyl group and / or hydroxyl group. The mixing weight ratio of the vinyl polymer containing a monomer unit having a functional group having a property as a constituent unit is not particularly limited, but it is usually preferable to mix as follows.

  The content of the component (A) and the component (B) is 0.5 to 20 parts by weight, preferably 1 to 10 parts by weight, more preferably 100 parts by weight of the component (A). 2 to 8 parts by weight. Here, when the content of the component (B) is less than 0.5 parts by weight, the effect of improving the molding processability of the polylactic acid-based resin is not remarkable. On the other hand, when the content exceeds 20 parts by weight, the entire resin is crosslinked and molded. It is not preferable because workability is lowered and heat resistance is easily lowered.

  Next, a method for producing the polylactic acid resin composition of the present invention will be described. Usually, a method of melting and kneading the component (A) and the component (B) while heating to about 130 to 240 ° C. with an extruder such as a co-directional twin screw extruder or a batch kneader is used. For example, a method of melt-kneading at a relatively low temperature of about 130 ° C. and then reheating in a hot air oven or the like can be used.

  The polylactic acid-based resin composition of the present invention can be obtained by the various methods described above. At this time, the reaction of the component (A) in terms of polystyrene determined by gel permeation chromatography measurement with the component (B). When the previous polydispersity is D1 and the post-reaction polydispersity is D2, it is preferable to control D2 / D1 = 1.2 to 3.0, preferably 1.3 to 2.5.

  Here, the polydispersity is a value obtained by dividing the weight average molecular weight by the number average molecular weight. When D2 / D1 is less than 1.2, the effect of improving the molding processability of the polylactic acid resin is not significant. On the other hand, if it exceeds 3.0, the entire resin is cross-linked and the molding processability is lowered, the mechanical properties are lowered, and even if the shear viscosity is increased, the strain hardening degree is lowered and the oligomer bleed is reduced. Problems such as occurrence are likely to occur and are not preferable.

  In order to control the strain hardening degree λ and D2 / D1 of the uniaxial elongation viscosity described above, the type and addition amount of the component (B) to be mixed with the component (A) are important. Since it is also affected by the heating temperature, heating time, shear rate, moisture content, presence of the specific metal, etc., it is preferable to adjust appropriately.

  For example, D2 / D1 tends to increase when heating for a long time during melt kneading, when the presence of water or acidity is high, and D2 / D1 when high shearing and heating in a short time. Tend to be smaller.

  The polylactic acid-based resin composition of the present invention has a flame retardant, a weather resistance stabilizer, and a heat resistant stability for the purpose of improving and adjusting the molding processability and physical properties of the molded product within a range that does not significantly impair the effects of the present invention. Agent, hydrolysis inhibitor (carbodiimide compound monomer or polymer, etc.), antistatic agent, antiblocking agent, crosslinking agent, lubricant, nucleating agent, plasticizer, anti-aging agent, antioxidant, colorant, pigment Additives such as inorganic fillers and chemical foaming agents may be added as appropriate.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. In addition, various measured values and evaluations of the polylactic acid resin composition and the molded product displayed in this specification were performed as follows.

(1) Strain hardening degree of uniaxial extensional viscosity (λ)
The pellet made of the obtained polylactic acid-based resin composition was pressed for 10 minutes at a set temperature of 200 ° C. using a 100 t press machine, and then cooled to prepare a 1.5 mm thick plate. Next, a test piece having a width of 7 mm, a length of 55 mm, and a thickness of 1.5 mm was cut out from the plate. This test piece was measured using a uniaxial extension viscometer (TA Instruments Co., Ltd. (formerly Rheometric Scientific F.E.), trade name: RME) at a measurement temperature of 200 ° C. and a uniaxial extension rate of 1. Transient responsiveness of uniaxial elongational viscosity was measured at 0 sec ⁻¹ and 0.01 sec ⁻¹ . Uniaxial extensional viscosity eta ₁ of the uniaxial elongation rate 1.0 sec ^-1 of from 1.0 seconds after the start of measurement until after 4.0 seconds, the uniaxial elongation viscosity eta ₂ of the uniaxial elongation rate 0.01 sec ^-1 A linear gradient in the relationship between the natural logarithm ln (η ₁ / η ₂ ) of the ratio η ₁ / η ₂ and the uniaxial elongation strain (ε) was obtained by the least square method, and the strain hardening degree λ of the uniaxial elongation viscosity was obtained.

(2) Shear viscosity A cylindrical test piece having a diameter of 40 mm was cut from the 1.5 mm-thick press plate obtained in (1). This test piece was measured using a shear viscometer (TA Instruments Co., Ltd. (formerly Rheometric Scientific F.E., product name: ARES), measuring temperature 200 ° C., strain 0.1%, The shear viscosity at a frequency of 100 rad / s was measured.

(3) D2 / D1
Tosoh Co., Ltd. Gel Permeation Chromatography HLC-8120GPC is equipped with Shimadzu Corporation chromatographic column Shim-Pack series GPC-800CP, solvent: chloroform, solution concentration: 0.2 wt / vol%, solution Injection volume: 200 μl, solvent flow rate: 1.0 ml / min, solvent temperature: 40 ° C. The number average molecular weight (Mn) and the weight average molecular weight (Mw) of the polylactic acid resin before and after the reaction were calculated in terms of polystyrene (average value of 10 samples was calculated, and the number less than 100 was rounded down). The weight average molecular weights of the standard polystyrene used are 2,000,000, 670,000, 110,000, 35,000, 10,000, 4,000, 600. The value obtained by dividing the weight average molecular weight (Mw) by the number average molecular weight (Mn) is the polydispersity, and D2 / D1 was calculated by setting the polydispersity before the reaction as D1 and the polydispersity after the reaction as D2.

(4) Neck-in rate Using a 30 mmφ single-screw extruder (L / D = 22) equipped with a kneading zone, pellets obtained from the polylactic acid-based resin composition were extruded at a set temperature of 200 ° C. and a rotational speed of 30 rpm. Sheet extrusion was carried out from a T-die having an amount of 3 kg / h, a width of 200 mm, and a lip gap of 1 mm. When the take-up speed is adjusted and the sheet thickness is 100 μm (take-off speed: 4 m / min), the sheet width immediately after the T-die exit is L1, and the sheet width 20 cm away from the T-die is L2. The rate was calculated by the following formula. In general sheet extrusion, the neck-in rate is preferably 10% or less.
Neck-in rate (%) = {(L1-L2) / L1} X100

(5) Foamed cell diameter A 30 mmφ single-screw extruder (L) equipped with a kneading zone is prepared by adding 1 part by weight of ADCA (azodicarbonamide) as a foaming agent to 100 parts by weight of pellets made of the obtained polylactic acid resin composition. / D = 22), a sheet having a thickness of 500 μm was obtained from a T die having a setting temperature of 190 ° C., a rotation speed of 30 rpm, an extrusion rate of 3 kg / hr, a width of 200 mm, and a lip gap of 1 mm. Next, the extruded sheet was cut with a cutter in the flow direction and observed with an optical microscope, and the diameter of 10 foamed cells in the field of view was measured.

(Example 1)
As shown in Table 1, as a component (A), NatureWorks 4032D (manufactured by Cargill Dow, L-lactic acid: D-lactic acid = 98.6: 1.4) as a sufficiently dried polylactic acid resin , Simply abbreviated as PLA), as component (B), ARUFON UG-4030 (manufactured by Toa Gosei Co., Ltd., catalog value; Mw = 11,000, Tg = 52 ° C., epoxy value = 1. 8 meq / g, property: solid, styrene / acrylic copolymer) (hereinafter abbreviated as B-1) 2.5 parts by weight of resin composition, φ25 mm twin screw extruder (L / D = 40) Was melt-kneaded at 230 ° C. and 200 rpm, the strand was extruded, quenched in a water bath, and then cut into strands to obtain pellets. The results of evaluation using this pellet are shown in Table 1.

(Example 2)
As shown in Table 1, instead of B-1 used as the component (B) in Example 1, ARUFON XG-4050 (manufactured by Toa Gosei Co., Ltd., catalog value; Mw = 9,000, Tg = 70 ° C.) , Epoxy value = 0.7 meq / g, properties: solid, styrene / acrylic copolymer) (hereinafter abbreviated as B-2), pellets were obtained in the same manner as in Example 1. The results of evaluation using this pellet are shown in Table 1.

(Comparative Example 1)
As shown in Table 1, pellets were obtained in the same manner as in Example 1 except that the amount of PLA and B-1 in Example 1 was changed to 100% by weight / 0% by weight. The results of evaluation using this pellet are shown in Table 1.

  From Table 1, a vinyl copolymer (B) containing a monomer unit having a functional group having reactivity with a polylactic acid resin (A) component and a carboxyl group and / or a hydroxyl group as defined in the present invention as a constituent unit. The polylactic acid-based resin composition containing the components does not cause a decrease in molecular weight and generates less gel. Further, the strain hardening degree λ of the uniaxial elongation viscosity was high, the neck-in rate was small during extrusion sheet molding, and the foam cell diameter was relatively uniform during extrusion foam molding. (Example 1, Example 2). On the other hand, in the case of only the polylactic acid-based resin, the neck-in rate was large at the time of extrusion sheet molding, the foam cell diameter was varied at the time of foam molding, and there were many foam breaking cells (Comparative Example 1). ).

2 is a graph obtained by measuring transient response of uniaxial elongational viscosity in Example 1. FIG. 6 is a graph obtained by determining the strain hardening degree λ of the uniaxial elongation viscosity of Example 1 by the least square method.

Claims (3)

It is a polylactic acid-based resin composition containing the following components (A) and (B), the strain at 200 ° C. is 0.1%, the shear viscosity at a frequency of 100 rad / s is 800 to 2000 Pa · s, and A polylactic acid-based resin composition having a uniaxial elongation viscosity of 1.0 sec ⁻¹ and a uniaxial elongation viscosity strain hardening λ of 0.4 to 0.8 at a uniaxial elongation strain of 1.0 to 4.0.
(A) Polylactic acid resin (B) Vinyl polymer containing a monomer unit having a functional group having reactivity with a carboxyl group and / or a hydroxyl group as a constituent unit The polylactic acid resin composition according to claim 1, wherein the functional group having reactivity with the carboxyl group and / or hydroxyl group of component (B) is an epoxy group. A molded article using the polylactic acid resin composition according to claim 1.

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