JP2016172787A - Polylactic acid composition and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polylactic acid composition having excellent impact strength.SOLUTION: A polylactic acid composition comprises (A) polylactic acid, and (B) untreated laminar silicate uniformly dispersed in the (A) component, and a content ratio of these components is (B) component 21-30 pts.mass to (A) component 100 pts.mass.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a polylactic acid composition and a method for producing the same.

  Conventionally, layered silicates typified by clay have been mixed and dispersed in polymers to improve properties such as strength and heat resistance, but the polymer and layered silicate have affinity or binding. Due to its low power, various improvements have been taken. In addition, various polymer nanocomposites having more excellent characteristics have been proposed by dispersing layered silicate in a polymer on the nano order.

  For example, a method of obtaining a composite by organizing a layered silicate to form an organized layered silicate and adding it to a polyamide together with a swelling agent and a dispersing agent (see, for example, Patent Document 1), water or proton donor A method for obtaining a composite by preparing a solvent containing a solvent, an organically modified layered silicate, a dispersant, and a thermoplastic resin, and mixing them at a temperature equal to or higher than the melting temperature of the thermoplastic resin (for example, Patent Documents) 2).

However, in the above-described prior art, when obtaining a polylactic acid composition containing a layered silicate, it is necessary to make the layered silicate organic using an alkylammonium salt or the like. Moreover, in order to disperse | distribute to a polymer in nano order, it was necessary to use the organic-ized layered silicate which processed the layered silicate with the alkylammonium salt, and substituted the alkylammonium salt between layers.
In addition, products using these resins have a disadvantage of good durability at the stage of disposal after being used, and are inferior in degradability in nature, which may affect the ecosystem.

In order to solve such problems, biodegradable polyesters starting from renewable resources, represented by polylactic acid, which is a thermoplastic resin and biodegradable, are currently being widely developed.
For example, a ring-opening polymerizable monomer, a compressive fluid, a nucleating agent (a nucleating agent for increasing the crystallization speed and crystallinity of the polylactic acid composition), and preferably a crystallization accelerator are mixed. Thus, a method for obtaining a polylactic acid polymer by ring-opening polymerization of the ring-opening polymerizable monomer in the presence of a catalyst has been proposed (see, for example, Patent Document 3).
However, the impact strength of the polylactic acid polymer produced in this way has not reached the level desired by the present inventors.

  The object of the present invention is that the layered silicate is not treated with an organic treatment (and therefore does not contain an organic treatment agent and does not cause coloration) and has a good impact strength with respect to the above-described conventional technology. It is an object of the present invention to provide a polylactic acid composition (layered silicate and polymer nanocomposite) containing layered silicate.

  The polylactic acid composition according to the present invention for solving the above problems includes (A) polylactic acid, and (B) an untreated layered silicate that is uniformly dispersed in the component (A). And the content rate of these components is 21-30 mass parts of (B) component with respect to 100 mass parts of (A) component, It is characterized by the above-mentioned.

  According to the present invention, it is possible to provide a polylactic acid composition which is not particularly colored and has excellent impact strength.

It is a phase diagram which shows the state of the substance with respect to temperature and pressure. It is a phase diagram for defining the range of compressible fluid. It is a systematic diagram which shows an example of a batch type polymerization process.

As a result of intensive studies, the inventors have found that a specific amount of untreated layered silicate (hereinafter also referred to as “untreated layered silicate”) is present in the polylactic acid composition. It has been found that a polylactic acid resin composition having impact strength can be obtained. The present invention has been made based on these findings.
That is, the present invention includes (A) polylactic acid and (B) untreated layered silicate uniformly dispersed in the component (A), and the content ratio of these components is (A) component 100. (B) component is 21-30 mass parts with respect to a mass part, It is a polylactic acid composition characterized by the above-mentioned. In the present invention, “untreated layered silicate” means a layered silicate that has not been subjected to organic treatment or other chemical treatment.

  Hereinafter, the polylactic acid composition and the method for producing the same according to the present invention will be described in more detail. Although the embodiments described below are preferred embodiments of the present invention, various technically preferred limitations are given, but the scope of the present invention is intended to limit the present invention in the following description. As long as there is no description, it is not restricted to these aspects.

(Polylactic acid composition)
The polylactic acid composition of the present invention contains at least polylactic acid, contains 21 to 30 parts by mass of untreated layered silicate with respect to 100 parts by mass of polylactic acid, and further contains other components as necessary. Do it.

The polylactic acid is a kind of aliphatic polyester having lactic acid as a basic unit and a plurality of lactic acids connected to have a high molecular weight.
Examples of polylactic acid include poly-L-lactic acid (PLLA), poly-D-lactic acid (PDLA), a random copolymer of L-lactic acid and D-lactic acid, and a stereocomplex of L-lactic acid and D-lactic acid. And other copolymerization components may be further included as necessary. These may be used alone or in combination of two or more.
Among these, it is preferable to use polylactic acid having a high optical purity of the lactic acid component, and among the total lactic acid components of polylactic acid, it is preferable that the L-form is contained in 80% or more, or the D-form is contained in 80% or more. .
The polylactic acid is not particularly limited and can be appropriately selected according to the purpose. The polylactic acid can be synthesized by ring-opening polymerization from lactic acid through a cyclic dimer lactide in the presence of a catalyst, which will be described later. It can be produced by a method for producing a polylactic acid composition.

  The polylactic acid composition of the present invention does not contain an ammonium component because ammonia, ammonium salts, and other compounds containing nitrogen atoms are not used in the production process. Since the ammonium component is not contained, the polylactic acid composition of the present invention has an advantage of preventing a decrease in heat resistance such as coloring due to heating.

  The polylactic acid composition of the present invention has a polystyrene-based weight average molecular weight (Mw) measured by gel permeation chromatography of 100,000 or more, preferably 150,000 or more, more preferably 200,000 or more. When the weight average molecular weight is less than 100,000, the mechanical strength becomes insufficient. The upper limit of the weight average molecular weight (Mw) is not particularly limited, but is preferably 600,000 or less, and more preferably 300,000 or less, from the viewpoint of moldability. If the weight average molecular weight exceeds 600,000, a high temperature condition is required at the time of molding, which causes a decrease in molecular weight. Examples of the method for measuring the weight average molecular weight in the polylactic acid composition include the methods described in Examples below.

  The molecular weight distribution (Mw / Mn) obtained by dividing the weight average molecular weight (Mw) of the polylactic acid composition by the number average molecular weight (Mn) is not particularly limited and may be appropriately selected depending on the intended purpose. 1.0 to 2.5 is preferable, and 1.2 to 2.0 is more preferable. When the molecular weight distribution (Mw / Mn) exceeds 2.5, the low molecular weight component increases and the mechanical strength may decrease. Examples of the method for measuring the molecular weight distribution in the polylactic acid composition include the methods described in Examples below.

  The polylactic acid composition may or may not contain an organic solvent. The organic solvent is an organic solvent used as a reaction field that is liquid at normal temperature and does not chemically react with a solute. When the polylactic acid composition is polylactic acid obtained by a ring-opening polymerization reaction, examples of the organic solvent include chloroform, methylene chloride, toluene, tetrahydrofuran, and the like. “Substantially free of organic solvent” means that the content of the organic solvent in the polylactic acid composition is specifically less than the detection limit (5 ppm). It is preferable to use a compressive fluid (for example, supercritical carbon dioxide) alone as a solvent without using the organic solvent, from the viewpoint of safety and stability. However, the organic solvent as an entrainer and supercritical dioxide are preferable. Carbon can also be used in combination.

  The untreated layered silicate in the polylactic acid composition of the present invention is a silicate mineral having a layered structure, such as mica, fluorinated mica, montmorillonite, smectite, kaolin, hectorite, bentonite, vermiculite, Examples include halloysite and saponite. These untreated layered silicates can be used alone or in combination.

The volume average particle diameter (D50) of the untreated layered silicate is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 0.005 μm to 100 μm, more preferably 0.01 μm to 20 μm. .
The volume average particle diameter (D50) can be measured by, for example, a laser scattering / diffraction type particle diameter measuring apparatus (LA-920, manufactured by Horiba, Ltd.).
The amount of the untreated layered silicate is 21 to 30 parts by mass, preferably 23 to 28 parts by mass with respect to 100 parts by mass of polylactic acid. If it is less than 21 parts by mass with respect to 100 parts by mass of polylactic acid, the impact strength becomes insufficient, and if it exceeds 30 parts by mass, the mixing of layered silicate with lactide or polylactic acid becomes incomplete, and molding is impossible. There is a problem that it cannot be done.

  The yellow index (YI) value of the polylactic acid composition of the present invention is not particularly limited and can be appropriately selected according to the purpose, but is preferably 15 or less, more preferably 10 or less, and still more preferably 5 or less. When the YI value exceeds 15, not only the appearance may be impaired when the polymer product is used for food packaging containers or the like, but the physical properties of the polylactic acid composition such as strength reduction due to thermal deterioration are poor. May have an impact.

(Production method of polylactic acid composition)
The method for producing a polylactic acid composition of the present invention is characterized in that lactide is subjected to ring-opening polymerization in a compressive fluid atmosphere in the presence of an untreated layered silicate. According to this production method, a polylactic acid composition having good impact strength can be obtained. This is because the ring-opening polymerization of lactide is performed in a state where the untreated layered silicate is dispersed in lactide. This is probably because the untreated layered silicate is well dispersed.
In addition, although the manufacturing method of the polylactic acid composition of this invention includes a superposition | polymerization process at least, it may also include the other process as needed. Further, since the polylactic acid composition has a high molecular weight, when the polylactic acid composition is produced, the polymer product can be smoothly produced by using an extrusion means in the production apparatus for producing the polylactic acid composition. (Polylactic acid composition) can be taken out.

In the polymerization step, the lactide is subjected to ring-opening polymerization by bringing at least an initiator (polyfunctional initiator), an untreated layered silicate, lactide, and a compressive fluid into contact with each other.
Here, carbon dioxide is preferably used as the compressive fluid because it can easily create a supercritical state.

〔raw materials〕
First, the ring-opening polymerizable monomer, raw material such as untreated layered silicate and initiator used for the production of the polymer product, and components such as a catalyst will be described. In the present embodiment, the raw material is a material from which the polymer is produced, and includes a ring-opening polymerizable monomer, an untreated layered silicate, and an initiator, and, if necessary, optional components such as additives. including.
Here, the compressible fluid is also described.

<Ring-opening polymerizable monomer>
The ring-opening polymerizable monomer used in this embodiment preferably has an ester bond in the ring. Examples of such ring-opening polymerizable monomers include cyclic esters and cyclic carbonates.

Although it does not specifically limit as cyclic ester, The cyclic dimer obtained by dehydrating condensation of the L-form and / or D-form of the compound represented by following General formula (1) is used suitably.
R—C * —H (—OH) (— COOH) General formula (1)
(In general formula (1), R represents an alkyl group having 1 to 10 carbon atoms. In general formula (1), “*” represents an asymmetric carbon.)

  Specific examples of the compound represented by the general formula (1) include an enantiomer of lactic acid, an enantiomer of 2-hydroxybutanoic acid, an enantiomer of 2-hydroxypentanoic acid, and an enantiomer of 2-hydroxyhexanoic acid. , 2-hydroxyheptanoic acid enantiomer, 2-hydroxyoctanoic acid enantiomer, 2-hydroxynonanoic acid enantiomer, 2-hydroxydecanoic acid enantiomer, 2-hydroxyundecanoic acid enantiomer And enantiomers of 2-hydroxydodecanoic acid. Among these, enantiomers of lactic acid are particularly preferable from the viewpoint of reactivity or availability. These cyclic dimers can be used alone or in admixture of several kinds.

  Examples of cyclic esters other than the general formula (1) include β-propiolactone, β-butyrolactone, γ-butyrolactone, γ-hexanolactone, γ-octanolactone, δ-valerolactone, and δ-hexalanolactone. , Δ-octanolactone, ε-caprolactone, δ-dodecanolactone, α-methyl-γ-butyrolactone, β-methyl-δ-valerolactone, glycolide, lactide, and the like. In particular, ε-caprolactone is preferable from the viewpoint of reactivity and availability. Moreover, although it does not specifically limit as cyclic carbonate, Ethylene carbonate, propylene carbonate, etc. are mentioned. These ring-opening polymerizable monomers may be used alone or in combination of two or more.

<Layered silicate>
The untreated layered silicate used in the production method of the present embodiment is a silicate mineral having a layered structure, such as mica, fluorinated mica, montmorillonite, smectite, kaolin, hectorite, bentonite, vermiculite. , Halloysite, saponite, and the like, and mica, smectite, and kaolin are particularly preferable. These untreated layered silicates can be used alone or in combination.
21-30 mass parts is preferable with respect to 100 mass parts of ring-opening polymerizable monomers, and, as for the quantity of these untreated layered silicate, 23-28 mass parts is more preferable.

<Initiator>
In this embodiment, an initiator is preferably used to control the molecular weight of the polymer obtained. As the initiator, known ones can be used, and any alcoholic mono-, di- or polyhydric alcohol may be used, and either saturated or unsaturated may be used.
Specific examples of the initiator include monoalcohols such as methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, nonanol, decanol, lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol; ethylene glycol, 1,2 -Dialcohols such as propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, hexanediol, nonanediol, tetramethylene glycol, polyethylene glycol; glycerol, sorbitol, xylitol, ribitol, And polyhydric alcohols such as erythritol and triethanolamine; and methyl lactate and ethyl lactate.
Further, a polymer having an alcohol residue at the terminal, such as polycaprolactone diol or polytetramethylene glycol, can be used as an initiator. Thereby, a diblock or triblock copolymer is synthesized.

  What is necessary is just to adjust suitably the usage-amount of an initiator according to the target molecular weight, Preferably it is 0.05 mol% or more and 5 mol% or less with respect to 100 mol% of monomers. In order to prevent the polymerization from starting unevenly, it is desirable that the initiator is well mixed with the monomer in advance before the monomer contacts the polymerization catalyst.

<Other ingredients>
There is no restriction | limiting in particular as another component used when manufacturing the said polymer product, According to the objective, it can select suitably, For example, a catalyst, an additive, etc. are mentioned.

-Catalyst-
There is no restriction | limiting in particular as said catalyst, According to the objective, it can select suitably, A metal catalyst is used preferably.

--Metal catalyst--
The metal catalyst used in the production method of the present embodiment is an organic catalyst containing a metal atom. Such a metal catalyst is not particularly limited, and tin compounds such as tin octylate and tin dibutylate, aluminum compounds such as aluminum acetylacetonate and aluminum acetate, titanium compounds such as tetraisopropyl titanate and tetrabutyl titanate Known compounds such as compounds, zirconium compounds such as zirconium isoprooxide, and antimony compounds such as antimony trioxide are used.

  What is necessary is just to adjust the addition amount of a metal catalyst suitably according to a metal catalyst seed | species, a ring-opening polymerization monomer seed | species, etc. For example, when ring-opening polymerization of lactide using tin octylate, 0.005 to 0.5 mol%, preferably 0.01 to 0.2 mol% of tin octylate is used with respect to 100 mol% of lactide. It is preferable.

-Additives-
In the ring-opening polymerization, an additive may be added as necessary. Examples of additives include surfactants, antioxidants, stabilizers, antifogging agents, ultraviolet absorbers, pigments, colorants, inorganic particles, various fillers, thermal stabilizers, flame retardants, crystal nucleating agents, antistatic agents Agents, surface wetting improvers, incineration aids, lubricants, natural products, mold release agents, plasticizers, and the like. If necessary, a polymerization terminator (benzoic acid, hydrochloric acid, phosphoric acid, metaphosphoric acid, acetic acid, lactic acid, etc.) can be used after the polymerization reaction.
The compounding amount of these additives varies depending on the purpose of addition and the type of additive, but is preferably 0 part by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the polymer composition.

  As the surfactant, those which are soluble in the compressive fluid and have an affinity for both the compressive fluid and the ring-opening polymerizable monomer are suitably used. By using such a surfactant, the polymerization reaction can be promoted uniformly, and effects such as narrowing the molecular weight distribution of the product and obtaining a particulate polymer can be expected. When using a surfactant, it may be added to the compressive fluid or to the ring-opening polymerizable monomer. For example, when carbon dioxide is used as the compressive fluid, a surfactant having a parent carbon dioxide group and a parent monomer group in the molecule is used. Examples of such surfactants include fluorine-based surfactants and silicon-based surfactants.

As the stabilizer, epoxidized soybean oil, carbodiimide and the like are used. As the antioxidant, 2,6-di-t-butyl-4-methylphenol, butylhydroxyanisole and the like are used.
As the antifogging agent, glycerin fatty acid ester, monostearyl citrate and the like are used.
As the filler, an ultraviolet absorber, a heat stabilizer, a flame retardant, an internal mold release agent, clay having an effect as a crystal nucleating agent, talc, silica, or the like is used.
As the pigment, titanium oxide, carbon black, ultramarine blue and the like are used.

<Compressive fluid>
The compressive fluid will be described with reference to FIGS. 1 and 2. FIG. 1 is a phase diagram showing the state of a substance with respect to temperature and pressure. FIG. 2 is a phase diagram for defining the range of the compressible fluid.
The “compressible fluid” is a fluid in the phase diagram shown in FIG. 1 when it exists in any of the regions (1), (2), and (3) shown in FIG. Means.

  In such a region, it is known that the substance has a very high density and behaves differently from that at normal temperature and pressure. In addition, when a substance exists in the area | region of (1), it becomes a supercritical fluid. A supercritical fluid is a fluid that exists as a non-condensable high-density fluid in a temperature and pressure region that exceeds the limit (critical point) at which gas and liquid can coexist, and does not condense even when compressed. Further, when the substance is present in the region (2), it becomes a liquid, but in the present invention, it is obtained by compressing a substance that is in a gaseous state at normal temperature (25 ° C.) and normal pressure (1 atm). Represents liquefied gas. Further, when the substance is present in the region (3), it is in a gaseous state, but in the present invention, it represents a high-pressure gas whose pressure is 1/2 (1/2 Pc) or more of the critical pressure (Pc).

  Examples of substances that can be used in the state of a compressive fluid include carbon monoxide, carbon dioxide, dinitrogen monoxide, nitrogen, methane, ethane, propane, 2,3-dimethylbutane, and ethylene. Among these, carbon dioxide is preferable in that it has a critical pressure of about 7.4 MPa and a critical temperature of about 31 ° C., can easily create a supercritical state, and is nonflammable and easy to handle. These compressive fluids may be used alone or in combination of two or more.

[Batch polymerization reactor]
Next, an example of a batch-type polymerization reaction apparatus used for producing the polymer product (polylactic acid composition) will be described with reference to FIG. FIG. 3 is a system diagram showing an example of a polymerization process.

  The polymerization reaction apparatus 400 shown in FIG. 3 has a tank 121, a metering pump 122, an addition pot 125, a reaction vessel 127, and valves (123, 124, 126, 128, 129). Each of the above devices is connected as shown in FIG. The pipe 130 is provided with joints (130a, 130b).

  The tank 121 stores a compressible fluid. The tank 121 may store a gas (gas) or a solid that becomes a compressible fluid by being heated and pressurized in a supply path supplied to the reaction vessel 127 or in the reaction vessel 127. In this case, the gas or solid stored in the tank 121 is heated or pressurized to be in the state (1), (2), or (3) in the phase diagram of FIG. .

  The metering pump 122 supplies the compressive fluid stored in the tank 121 to the reaction vessel 127 at a constant pressure and flow rate. The addition pot 125 stores the catalyst added to the raw material in the reaction vessel 127. The valves (123, 124, 126, 129) are opened and closed so that the compressive fluid stored in the tank 121 is supplied to the reaction vessel 127 via the addition pot 125 and the addition pot 125. The route for supplying to the reaction vessel 127 without passing through is switched.

  The reaction vessel 127 previously contains a ring-opening polymerizable monomer, an initiator, an untreated layered silicate, and a catalyst before starting the polymerization. The reaction vessel 127 brings the ring-opening polymerizable monomer and the initiator, the untreated layered silicate, the compressive fluid supplied from the tank 121, and the catalyst supplied from the addition pot 125 into contact with each other. And a pressure-resistant container for polymerizing the ring-opening polymerizable monomer. The catalyst can also be charged in the reaction vessel 127 in advance. In addition, the reaction vessel 127 may be provided with a gas outlet for removing evaporated substances. In addition, the reaction vessel 127 has a heater for heating the raw materials and the compressive fluid. Furthermore, the reaction vessel 127 has a stirring device for stirring the raw materials and the compressive fluid. When the density difference between the raw material and the produced polymer product occurs, the settling of the produced polymer product can be suppressed by adding the stirring of the stirring device, so that the polymerization reaction can proceed more uniformly and quantitatively. After completion of the reaction, the valve 130 installed at the top of the reaction vessel 127 was opened at a rate of 0.1 MPa / min or less at a rate of 0.1 MPa / min or less, and maintained at normal pressure. Open and discharge the polymer product P in the reaction vessel 127. In the case of this method, since the valve 130 is installed at the upper part of the reaction vessel 127, the polymer in the reaction vessel 127 will foam violently and cause clogging unless it is slowly depressurized. Therefore, in addition to the valve 130, a plurality of valves may be further provided to secure the depressurization location.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to these examples.

[Example 1-1]
Ring-opening polymerization of L-lactide and a D-lactide mixture (L-lactide / D-lactide = 90/10 (mass ratio)) was performed using a batch polymerization reactor 400 shown in FIG. The structure of the polymerization reaction apparatus 400 is shown below.
Tank 121: Carbon dioxide gas cylinder Reaction vessel 127: Lactide in a liquid state (L-lactide and D-lactide mixture (mass ratio 90/10) (mass ratio 90/10) as a ring-opening polymerizable monomer in a 500 mL SUS316 pressure vessel 100 parts by mass, melting point: 100 ° C., and 25 parts by mass of untreated mica (manufactured by Co-op Chemical Co., Ltd., Somasif ME-100) were added and charged with carbon dioxide to 10 MPa. After stirring for 1 hour, lactide and non-organic mica were mixed, and then 0.02 parts by mass of 2-ethylhexanoate was added as a catalyst and 0.07 mol% of 1-hexanol was added as a reaction initiator. The temperature was raised to 180 ° C. The polymerization reaction was carried out at 180 ° C. and 10 MPa for 2 hours, and the temperature and pressure were returned to room temperature and normal pressure. A polylactic acid composition containing an iodate was obtained.
Table 1 shows the results of measuring the weight average molecular weight, YI value, and impact strength evaluation results of the obtained polylactic acid composition.

[Example 1-2]
A polylactic acid composition containing an untreated layered silicate was obtained in the same manner as in Example 1-1 except that the amount of untreated mica was changed from 25 parts by mass to 23 parts by mass. Table 1 shows the results of measuring the weight average molecular weight, YI value, and impact strength evaluation results of the obtained polylactic acid composition.

[Example 1-3]
A polylactic acid composition containing an untreated layered silicate was obtained in the same manner as in Example 1-1 except that the amount of untreated mica was changed from 25 parts by mass to 28 parts by mass. Table 1 shows the results of measuring the weight average molecular weight, YI value, and impact strength evaluation results of the obtained polylactic acid composition.

[Example 2]
A polylactic acid composition containing an untreated layered silicate was obtained in the same manner as in Example 1-1 except that untreated smectite (manufactured by Corp Chemical Co., Lucentite SWN) was used instead of untreated mica. It was. Table 2 shows the results of measuring the weight average molecular weight and YI value of the obtained polylactic acid composition, and the impact strength evaluation results.

Example 3
A polylactic acid composition containing an untreated layered silicate was obtained in the same manner as in Example 1-1 except that untreated kaolin (manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of untreated mica. Table 2 shows the results of measuring the weight average molecular weight and YI value of the obtained polylactic acid composition, and the impact strength evaluation results.

Example 4
A polylactic acid composition containing an untreated layered silicate in the same manner as in Example 1-1 except that the amount of 1-hexanol (reaction initiator) was changed from 0.07 mol% to 0.045 mol%. Got. Table 2 shows the results of measuring the weight average molecular weight and YI value of the obtained polylactic acid composition, and the impact strength evaluation results.

[Comparative Example 1]
A batch type polymerization reaction apparatus 400 shown in FIG. 3 was used.
As a ring-opening polymerizable monomer, lactide in a liquid state (L-lactide and D-lactide mixture (mass ratio 90/10) (manufactured by Pulac Co., Ltd., melting point: 100 ° C.) 100 parts by mass; (Somasif MEE), 25 parts by mass, were charged with carbon dioxide at normal pressure, heated to 110 ° C., stirred for 1 hour, and mixed with lactide and organically treated mica. 0.02 part by mass of tin 2-ethylhexanoate, 0.07 mol% of 1-hexanol as a reaction initiator was added, and the temperature was raised to 180 ° C. The polymerization reaction was performed at 180 ° C. and normal pressure for 2 hours, The temperature and pressure were returned to room temperature and normal pressure to obtain a polylactic acid composition containing an organically treated layered silicate.
Table 3 shows the results of measuring the weight average molecular weight and YI value of the resulting polylactic acid composition, and the evaluation results of impact strength.

[Comparative Example 2-1]
A polylactic acid composition containing an untreated layered silicate was obtained in the same manner as in Example 1-1 except that the amount of untreated mica was changed from 25 parts by mass to 19 parts by mass. Table 3 shows the results of measuring the weight average molecular weight and YI value of the resulting polylactic acid composition, and the evaluation results of impact strength.

[Comparative Example 2-2]
A polylactic acid composition containing an untreated layered silicate was obtained in the same manner as in Example 1-1 except that the amount of untreated mica was changed from 25 parts by mass to 40 parts by mass. Table 3 shows the results of measuring the weight average molecular weight and YI value of the resulting polylactic acid composition, and the evaluation results of impact strength.

  The physical properties and evaluation of the polymer product (polylactic acid) were performed as follows.

<Weight average molecular weight of polymer product>
It measured on the following conditions by the gel permeation chromatography (GPC).
-Equipment: GPC-8020 (manufactured by Tosoh Corporation)
Column: TSK G2000HXL and G4000HXL (manufactured by Tosoh Corporation)
・ Temperature: 40 ℃
-Solvent: Chloroform-Flow rate: 1.0 mL / min 1 mL of a sample with a concentration of 0.5% by mass was injected, and from the molecular weight distribution of the polymer product (polylactic acid composition) measured under the above conditions, a monodisperse polystyrene standard sample Was used to calculate the number average molecular weight (Mn) and the weight average molecular weight (Mw) of the polymer product. The molecular weight distribution is a value obtained by dividing Mw by Mn.

<Yellow Index (YI value)>
About the obtained polymer product (polylactic acid composition), a resin pellet having a thickness of 2 mm was prepared and measured according to JIS-K7103 using an SM color computer (manufactured by Suga Test Instruments Co., Ltd.) to obtain a YI value.

<Impact strength>
The impact strength was evaluated by the following method.
The obtained polymer product (polylactic acid composition) is made into a sheet having a thickness of 0.4 mm, a 200 g weight is dropped, the maximum height at which the test piece is not broken is measured, and the impact strength is evaluated according to the following criteria. did.
〔Evaluation criteria〕
◎: 300 mm or more ○: 150 mm or more and less than 300 mm △: 50 mm or more and less than 150 mm

In Table 3, “-” indicates that measurement is impossible because molding is difficult.
As seen in Tables 1 to 3, the polylactic acid composition of the present invention is excellent in YI value and impact strength.

121 tank 127 reaction vessel 400 polymerization reactor
P polymer product (polylactic acid composition)

Japanese Patent Publication No. 7-47644 Japanese Patent No. 3296317 JP 2014-145007 A

Claims (8)

  (A) polylactic acid and (B) untreated layered silicate uniformly dispersed in the component (A), and the content ratio of these components is 100 parts by mass of the component (A) (B) A component is 21-30 mass parts, The polylactic acid composition characterized by the above-mentioned.   2. The polylactic acid composition according to claim 1, which does not contain an ammonium component.   The polylactic acid composition according to claim 1 or 2, wherein the untreated layered silicate is mica, smectite, or kaolin.   The polylactic acid composition according to any one of claims 1 to 3, wherein the polystyrene-based weight average molecular weight measured by gel permeation chromatography is 100,000 to 600,000.   The polylactic acid composition according to any one of claims 1 to 4, wherein the YI value is 15 or less. A method for producing the polylactic acid composition according to any one of claims 1 to 5,
A method for producing a polylactic acid composition, wherein lactide is subjected to ring-opening polymerization in a compressive fluid atmosphere in the presence of an untreated layered silicate.   The method for producing a polylactic acid composition according to claim 6, wherein the ring-opening polymerizable monomer is subjected to ring-opening polymerization after the lactide and the untreated layered silicate are brought into contact with the compressive fluid. The method for producing a polylactic acid composition according to claim 6 or 7, wherein the compressive fluid is carbon dioxide.

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