JP2005248117A - Polylactic acid resin composition and method for producing the same - Google Patents

Abstract

【Task】
The problem to be solved by the present invention is to provide a polylactic acid resin composition which is excellent in impact resistance and transparency, and also excellent in biodegradability.
[Solution]
The present invention provides a polylactic acid (A) and a polyhydroxycarboxylic acid copolymer (B) having a polyhydroxycarboxylic acid structural unit (I) and a polyester structural unit (II) derived from a diol and a dicarboxylic acid. A polylactic acid resin composition comprising the polylactic acid (A) and the polyhydroxycarboxylic acid copolymer (B) having a weight composition (A) / (B) of 97/3 to 30/70. The polyhydroxycarboxylic acid copolymer (B) has a microphase separation structure having domains in the matrix of the polylactic acid (A), and 85% or more of the domains are 0.10 μm to 1%. The present invention relates to a polylactic acid resin composition characterized by being a domain having a domain diameter in the range of 0.000 μm.
[Selection figure] None

Description

  The present invention relates to a polylactic acid resin composition having excellent impact resistance, transparency, and biodegradability.

  In recent years, products in the biodegradable plastics field have attracted attention as materials that contribute to the realization of a sustainable society, centering on polylactic acid derived from biomass. In particular, polylactic acid is made from reproducible plant materials such as corn, and does not increase carbon dioxide gas even when burned. Therefore, it can contribute to saving limited fossil resources and preventing global warming. Furthermore, demand is increasing due to the start of large-scale production of polylactic acid, and it is expected to become one of the large chemical products within a few years. However, since polylactic acid is very brittle, its use is limited, and modification has been attempted by various methods. However, there has been a problem that a sufficient modification effect cannot be obtained.

  As methods for modifying polylactic acid, attempts have been made to blend polylactic acid with other resins and the like, and copolymerize polylactic acid with other resins and the like.

  Examples of the method of blending polylactic acid with other resins and the like include a method of melt blending polylactic acid, aliphatic polyester composed of diol and dicarboxylic acid, and polycaprolactone (for example, see Non-patent Document 1). . However, in order to express sufficient impact resistance and flexibility by this method, it is necessary to add a large amount of other resins, and as a result, the transparency and heat resistance inherent to polylactic acid may be reduced, There was a problem of causing bleed-out and the like because the compatibility between other resins and polylactic acid was not good.

  Examples of the method of copolymerizing other resins with polylactic acid include a method of ring-opening copolymerization of lactide, which is a cyclic dimer of lactic acid, and polyester in the presence of a catalyst. The resulting lactic acid-based copolymer polyester Have been reported to be excellent in toughness and the like (see, for example, Patent Document 1). However, the lactic acid-based copolymer polyester obtained is not yet sufficient in terms of characteristics such as impact resistance and bleeding.

  On the other hand, a high molecular weight polyhydroxycarboxylic acid copolymer composition obtained by melt-kneading polyhydroxycarboxylic acid, an aliphatic polyester and a high molecular weight agent without using a cyclic dimer such as lactide is provided. It has been reported that it is excellent in flexibility and heat resistance (for example, see Patent Document 2).

  However, in order to further expand the applications where polylactic acid can be used from the industrial world, there is a demand for the development of a superior impact resistance. In such a situation, the polyhydroxycarboxylic acid copolymer composition is required. Things are still not sufficient in terms of impact resistance and transparency.

A. Je. AJ Domb, “Journal Polymer Science Polymer Chemical Edition”. 31, 1973 (1993) JP 07-173266 A (Claim 1, paragraph “0244”) JP-A-9-95603 (Claim 1, paragraph "0163")

  The problem to be solved by the present invention is to provide a polylactic acid resin composition which is excellent in impact resistance and transparency, and also excellent in biodegradability.

  In the course of diligent research to solve the above problems, the present inventors have obtained polyhydroxycarboxylic acid obtained by using polylactic acid, polyester derived from diol and dicarboxylic acid, and polyhydroxycarboxylic acid. In a polylactic acid resin composition comprising a copolymer, in order to maximize the imparting of impact resistance to polylactic acid, the form of polyhydroxycarboxylic acid copolymer dispersed in polylactic acid (morphology) ) Led to the idea that control is important.

  Specifically, in order to develop excellent impact resistance, biodegradability, and transparency, a polyhydroxycarboxylic acid copolymer is dispersed in a matrix formed by polylactic acid to form a domain, and We thought that it was important that the domain had a domain diameter within a specific range, and conducted extensive research. As a result, the σ / ρ value of the polyester in the polyhydroxycarboxylic acid copolymer (where σ represents the solubility parameter value of the polyester and ρ represents the density of the polyester) and the weight average molecular weight are within a specific range. In combination, the polylactic acid resin composition having the above-described microphase separation structure is obtained. According to the polylactic acid resin composition, when an external stress is applied to the polylactic acid resin composition after molding. The present inventors have found that external stress is uniformly dispersed by domains, can suppress irregular reflection of light transmission, and can exhibit excellent impact resistance and transparency.

  That is, the present invention relates to polylactic acid (A) and polyhydroxycarboxylic acid copolymer (B) having polyhydroxycarboxylic acid structural unit (I) and polyester structural unit (II) derived from diol and dicarboxylic acid. A polylactic acid resin composition comprising the polylactic acid (A) and the polyhydroxycarboxylic acid copolymer (B) having a weight composition (A) / (B) of 97/3 to 30 / 70, and the polyhydroxycarboxylic acid copolymer (B) has a microphase separation structure having domains in the polylactic acid (A) matrix, and 85% or more of the domains are from 0.10 μm to The present invention relates to a polylactic acid resin composition having a domain diameter in the range of 1.00 μm.

  Moreover, this invention has the hydroxyl group which contributes to esterification in the one terminal or both terminals obtained by making the said polyhydroxycarboxylic acid (D), diol, and dicarboxylic acid react, and a weight average molecular weight is 40,000- Having a range of 200,000 and a σ / ρ value of 8.30 ≦ σ / ρ <9.20 (where σ represents a solubility parameter value of the polyester (Ca), and ρ represents the polyester (Ca) Polyester (Ca) having a range of density) and polyester (Cb) having a hydroxyl group at the terminal obtained by reacting diol and dicarboxylic acid and having a weight average molecular weight of 10,000 to 40,000. ), The difference between the weight average molecular weight of the polyester (Ca) and the weight average molecular weight of the polyester (Cb) is 20,000-1 In the presence of a polymerization catalyst, the molten mixture is in the range of 90,000 and the weight composition (Ca) / (Cb) of the polyester (Ca) and the polyester (Cb) is in the range of 95/5 to 60/40. The reaction product was esterified under reduced pressure conditions, and the obtained reaction product was measured with a rotary rheometer at a frequency of 1 Hz and a temperature within the range of the melting point to the melting point + 50 ° C. When the storage elastic modulus G ′ (M%) of the strain M% (1 <M ≦ 80) is in the range of 90 to 100% of the storage elastic modulus G ′ (1%) of the strain 1%. The polyhydroxycarboxylic acid copolymer (B) obtained by continuing the esterification reaction until melted and mixed with the polylactic acid (A), and a method for producing a polylactic acid resin composition, Preferably the polyhydroxy Carboxylic acid (D) is a method of manufacturing a polylactic acid resin composition is one having a range of weight average molecular weight 10,000 to 400,000.

  According to the present invention, a polylactic acid resin composition having excellent impact resistance, transparency and biodegradability can be obtained.

  Below, the polylactic acid resin composition obtained by this invention is demonstrated in detail.

  The polylactic acid resin composition of the present invention comprises polylactic acid (A) and a polyhydroxycarboxylic acid copolymer (B), and a polyhydroxycarboxylic acid copolymer is contained in a matrix formed by the polylactic acid (A). The union (B) is dispersed to form a domain, and the domain has a microphase separation structure having a domain diameter in a specific range.

  The polylactic acid resin composition of the present invention has a form in which domains of a polyhydroxycarboxylic acid copolymer (B) are dispersed in a matrix of polylactic acid (A), and the domain diameter ranges from 0.1 μm to 1.0 μm. The number of domains of the polyhydroxycarboxylic acid copolymer (B) it has occupies 85% or more of the total number of domains in the polylactic acid resin composition.

  The domain diameter of the domain comprising the polyhydroxycarboxylic acid copolymer (B) is particularly preferably in the range of 0.3 μm to 0.8 μm, and from the polylactic acid resin composition obtained by adjusting to such a range. When an impact is applied to a molded product or the like, the uniformly dispersed domains can uniformly disperse the impact, and thus the impact resistance can be improved.

  In the polylactic acid resin composition of the present invention, it is necessary that the number of domains having the domain diameter is 85% or more, and 90% or more is included with respect to the total number of domains in the polylactic acid resin composition. Are particularly preferred.

  In particular, when a domain composed of a polyhydroxycarboxylic acid copolymer (B) having a domain diameter of less than 0.1 μm is present in the polylactic acid resin composition, the impact resistance of the polylactic acid resin composition is remarkably inferior, If there are many domains having a domain diameter exceeding 1 μm in the polylactic acid resin composition, it becomes difficult to maintain the transparency of the polylactic acid resin composition. Therefore, when the domain deviating from the domain diameter range is less than 85% with respect to the total number of domains in the polylactic acid resin composition, a polylactic acid resin composition having insufficient impact resistance and transparency can be obtained. .

  The microphase-separated structure of the polylactic acid resin composition of the present invention is prepared by performing pretreatment for observation using a transmission electron microscope (hereinafter abbreviated as TEM; JEM-200CX, manufactured by JEOL Datum). , TEM observation can be performed.

  As an observation method using TEM, for example, a polylactic acid resin composition is formed into a 200 μm-thick sample piece, cut into an appropriate size, and embedded in a visible light curable resin. Thereafter, the sample piece is dyed for 1 to 2 hours using ruthenium tetroxide or osmium tetroxide as a staining agent, and then left in liquid nitrogen overnight or longer. Thereafter, an ultrathin section of a sample piece is prepared with an ultramicrotome, and TEM observation is performed. In addition to this, an example of a method of observing the form of the polylactic acid resin composition includes a method of observing the softness of the surface using an atomic force microscope.

  In the microphase-separated structure observed using TEM, the domain diameter of the polyhydroxycarboxylic acid copolymer (B) is, for example, the long axis and short axis of a plurality of domains seen in a photograph observed at a magnification of 5,000 times. It is obtained by measuring the axes and averaging them. In the present invention, the average value of the major axis and the minor axis of the domain is defined as the domain diameter. Based on the domain diameter obtained by the above method, the ratio of domains having a domain diameter in the range of 0.10 μm to 1.00 μm is calculated with respect to the total number of domains seen in the photograph observed using TEM. it can.

  The polylactic acid (A) used in the present invention can be synthesized by a known and usual method, has an asymmetric carbon in the repeating unit, and has optical isomers such as L-form and D-form. Is not particularly limited. The weight average molecular weight of the polylactic acid (A) is preferably in the range of 100,000 to 400,000 in order to have molding processing characteristics and mechanical characteristics.

  The polyhydroxycarboxylic acid copolymer (B) used in the present invention is a block copolymer having a polyhydroxycarboxylic acid structural unit (I) and a polyester structural unit (II).

  More specifically, the chemical structure of the polyhydroxycarboxylic acid copolymer (B) when the polyhydroxycarboxylic acid structural unit (I) is X and the polyester structural unit (II) is Y is the raw material charge ratio and For example, XY type block copolymer, XYX type block copolymer, random block copolymer, and a mixture thereof may be mentioned, although it varies depending on the molecular weight.

  The weight composition (I) / (II) of the polyhydroxycarboxylic acid structural unit (I) and the polyester structural unit (II) is preferably in the range of 95/5 to 20/80. In particular, in order to increase the compatibility between the polylactic acid (A) and the polyhydroxycarboxylic acid copolymer (B), the weight composition (I) / (II) is in the range of 80/20 to 30/70. In order to impart excellent impact resistance to the polylactic acid (A), it is preferably in the range of 60/40 to 30/70.

  The polyhydroxycarboxylic acid copolymer (B) is strained using a rotary rheometer at a frequency of 1 Hz and at a temperature within the range of the melting point to the melting point + 50 ° C. of the polyhydroxycarboxylic acid copolymer (B). When the amount is changed from 1 to 80%, the ratio of the change with the arbitrary storage elastic modulus G ′ in the range to the storage elastic modulus (G ′ (1%)) of 1% strain is in the range of 90 to 103%. It is characterized by that.

  Although it does not specifically limit as said rotation type rheometer, For example, the ARE instrument viscoelasticity measuring apparatus by a TA instrument company can be mentioned preferably.

  The measurement is preferably performed under the following measurement conditions. That is, frequency: 1 Hz, temperature: the range of the melting point of the polyhydroxycarboxylic acid copolymer to the melting point + 50 ° C. is preferable, and when the viscosity after the melting point of the polyhydroxycarboxylic acid copolymer is low, the polyhydroxycarboxylic acid copolymer The range of the melting point to the melting point + 30 ° C. is more preferable. Although it will not restrict | limit especially if it is in the range of parallel plate: 25mm (phi) and a gap (distance between parallel plates): 0.5-2.0mm, 0.5-1.0mm is especially preferable.

  Under the above conditions, a curve showing the relationship with the storage elastic modulus (G ′) when the strain amount is changed is measured. When the amount of strain is changed from 1 to 80%, the polyhydroxycarboxylic acid copolymer has an arbitrary storage elastic modulus G ′ within the above range relative to a storage elastic modulus (G ′ (1%)) of 1% strain. The rate of change is preferably in the range of 90 to 103%, particularly preferably in the range of 95 to 101%. For the sake of clarity, the storage elastic modulus G ′ (80%) at a strain of 80% is read for convenience, and the ratio between G ′ (80%) and G ′ (1%) (G ′ (100%)) / G ′ (1%)) is calculated and may be within the range of 90 to 103%. It should be noted that the ratio of G ′ (80%) to G ′ (1%) G ′ (80%) / G ′ (1%) in the range of 100% to 103% is substantially within the measurement error range. Even if it is regarded as 100%, there is no problem.

  The polyhydroxycarboxylic acid copolymer (B) includes, for example, a polyhydroxycarboxylic acid (D) constituting the polyhydroxycarboxylic acid structural unit (I) and a polyester (C) constituting the polyester structural unit (II). It can be produced by an esterification reaction.

  The polyester (C) has a weight average molecular weight in the range of 40,000 to 200,000, and a σ / ρ value of 8.30 ≦ σ / ρ <9.20 (where σ is a polyester ( The solubility parameter value of Ca) is represented, and ρ represents the density of the polyester (Ca). The polyester (Ca) is a polyester (Cb) having a weight average molecular weight of 10,000 to 40,000. The difference between the weight average molecular weight of the polyester (Ca) and the weight average molecular weight of the polyester (Cb) is in the range of 20,000 to 190,000, and the polyester (Ca) and the polyester (Cb) It is necessary to use the one whose weight composition (Ca) / (Cb) is in the range of 95/5 to 60/40. By producing the polyhydroxycarboxylic acid copolymer (B) using such a polyester (C), the polylactic acid resin composition can obtain a microphase-separated structure having a domain diameter in the specific range described above. .

  The polyester (Ca) and the polyester (Cb) are obtained by using a diol and a dicarboxylic acid as raw materials. For example, an aliphatic polyester or an aliphatic polyester obtained by using an aliphatic dicarboxylic acid and an aliphatic diol. An aliphatic / aromatic polyester obtained by using a dicarboxylic acid, an aromatic dicarboxylic acid and an aliphatic diol is preferable, and these can be produced by a known and usual esterification reaction.

  Any diol may be used as long as it has two hydroxyl groups. Among them, an aliphatic diol is preferably used. Examples of the aliphatic diol include those having a chain hydrocarbon side chain and an alicyclic hydrocarbon side chain, and an aliphatic diol having 2 to 45 carbon atoms is more preferable. Specifically, ethylene glycol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,4-cyclohexanedimethanol, Propylene glycol, neopentyl glycol, 3,3-diethyl-1,3-propanediol, 3,3-dibutyl-1,3-propanedi 1,2-pentanediol, 1,3-pentanediol, 2,3-pentanediol, 2,4-pentanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,5-pentane Diol, 1,4-pentanediol, 1,2-hexanediol, 1,3-hexanediol, 1,4-hexanediol, 1,5-hexanediol, n-butoxyethylene glycol, cyclohexanedimethanol, hydrogenated bisphenol A, dimer diol, diethylene glycol, dipropylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, hexylylene glycol, phenylethylene glycol and the like.

  As said diol, these can also be used together 2 or more types, for example, are combined use of propylene glycol and polyethyleneglycol, combined use of ethylene glycol and 1, 4- butanediol, etc. Furthermore, in the present invention, an EO addition product or PO addition product of bisphenol A, which also includes an aromatic ring, which is considered to be an aliphatic diol, can be used as the aliphatic diol.

  The diol can be used in combination with a hydroxyl group-containing compound other than the diol within the range of achieving the object of the present invention, and examples thereof include glycerin, trimethylolpropane, polyglycerin, pentaerythritol and the like.

  As the dicarboxylic acid, any kind can be used as long as it is an aliphatic dicarboxylic acid having a chain hydrocarbon side chain, an alicyclic hydrocarbon side chain, or an aromatic dicarboxylic acid having an aromatic ring. Of these, aliphatic dicarboxylic acids having 4 to 45 carbon atoms or aromatic dicarboxylic acids having 8 to 45 carbon atoms are preferable, and specifically, succinic acid, glutaric acid, adipic acid, pimelic acid, and suberic acid. , Azelaic acid, sebacic acid, decanedicarboxylic acid, cyclohexanedicarboxylic acid, aliphatic dicarboxylic acid such as dimer acid, unsaturated aliphatic dicarboxylic acid such as fumaric acid, etc., and aromatic dicarboxylic acid includes phthalic acid, Examples include terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid. Two or more of these dicarboxylic acids can be used in combination, for example, a combination of terephthalic acid and adipic acid, a combination of sebacic acid and dimer acid, or the like.

  Among the diols, as the diol used when producing the polyester (Ca), a diol having an alkyl group in the side chain is preferably used. For example, propylene glycol, 1,2-butanediol, 1,3- Butanediol, neopentyl glycol, 3,3-diethyl-1,3-propanediol, 3,3-dibutyl-1,3-propanediol, 1,2-pentanediol, 1,3-pentanediol, 2,3 -Pentanediol, 2,4-pentanediol, 2-methyl-2,4-pentanediol, 1,4-pentanediol, 3-methyl-1,5-pentanediol, 1,2-hexanediol, 1,3- Hexanediol, 1,4-hexanediol, 1,5-hexanediol, n-butoxyethylene glycol, Softimage ol, and the like preferably. Among the dicarboxylic acids, the dicarboxylic acid used for producing the polyester (Ca) is preferably an aliphatic dicarboxylic acid having 6 or more carbon atoms, adipic acid, pimelic acid, suberic acid, Examples include azelaic acid, sebacic acid, decanedicarboxylic acid, cyclohexanedicarboxylic acid, and dimer acid. By using the polyester (Ca) obtained by combining the diol and the dicarboxylic acid, the polylactic acid resin composition of the present invention can exhibit excellent impact resistance.

  The melting point of the polyester (C) obtained using the diol and the dicarboxylic acid is preferably 150 ° C. or less from the viewpoint of maintaining the molding processing characteristics of the polylactic acid (A). Examples of the melting point of polyester (C) include polyethylene succinate of about 102 ° C., polypropylene succinate of about −2 ° C., polybutylene succinate of about 113 ° C., polyethylene adipate of about 44 ° C., and polypropylene adipate of about 58 ° C. Polybutylene adipate is about 58 ° C, polyethylene sebacate is about 63 ° C, polypropylene sebacate is about -41 ° C, polybutylene adipate / terephthalate (feeding molar ratio; adipic acid: terephthalic acid = 1: 1) is about 120 ° C. Etc., and these can be preferably used as the polyester (C).

  The polyester (C) used in the present invention can be produced, for example, by a known and usual esterification reaction using the above-mentioned diol and dicarboxylic acid with a polymerization catalyst. At that time, in order to suppress coloring of the polyester (C), an antioxidant such as a phosphite compound may be added and used in the range of 10 to 2000 ppm with respect to the total amount of the diol and the dicarboxylic acid. preferable.

  Moreover, when using the polyester (C) used by this invention as a raw material of the polyhydroxycarboxylic acid copolymer (B) mentioned later, it is preferable to have a hydroxyl group at the terminal. Polyester having hydroxyl groups that contribute to esterification at both ends or one end can be produced, for example, by adding an excessive amount of diol to dicarboxylic acid and carrying out an esterification reaction. Specifically, charging of diol and dicarboxylic acid The molar ratio is preferably 1.0 / 1.0 <diol / dicarboxylic acid ≦ 1.4 / 1.0, and 1.0 / 1.0 <diol / dicarboxylic acid ≦ 1.2 / 1.0. It is more preferable that

  As the polymerization catalyst that can be used in the esterification reaction of the diol and the dicarboxylic acid, those made of at least one metal or metal compound selected from the group consisting of Groups 2, 3, and 4 of the periodic table are preferable. As such a polymerization catalyst comprising a metal or a metal compound, for example, a polymerization catalyst comprising a metal such as Ti, Sn, Zn, Al, Zr, Mg, Hf, Ge, or a metal compound is preferable. Isopropoxide, titanium tetrabutoxide, titanium oxyacetylacetonate, tin octoate, 2-ethylhexanetin, acetylacetonate zinc, zirconium tetrachloride, zirconium tetrachloride tetrahydrofuran complex, hafnium tetrachloride, hafnium tetrachloride tetrahydrofuran complex, oxidation Examples thereof include germanium and tetraethoxygermanium.

  The amount of the polymerization catalyst used is usually an amount that can control the esterification reaction and that can produce a polyester of good quality. For example, 10 to 1000 ppm is used with respect to the total amount of diol and dicarboxylic acid. It is more preferable to use 20 to 800 ppm, and it is particularly preferable to use 30 to 500 ppm in order to reduce coloring of the resulting polyester (C).

  The polymerization catalyst remaining in the polyester (C) is preferably deactivated in advance before producing the polyhydroxycarboxylic acid copolymer (B).

  In the present invention, it is extremely important for the polyester (C) to deactivate the polymerization catalyst contained in the polyester (C) after completion of the reaction. If the polymerization catalyst deactivation step is not performed, when the polyhydroxycarboxylic acid (D) and the polyester (C) are melt-mixed, the polymerization catalyst acts on the polyhydroxycarboxylic acid (D) to cause a depolymerization reaction. Therefore, it is difficult to produce a polyhydroxycarboxylic acid copolymer having a reduced molecular weight and a stable hue, and the transparency and molding processability are extremely inferior.

  Examples of the method for deactivating the polymerization catalyst include a method of adding a deactivator after the production of the polyester (C). In such a method, the addition amount of the deactivator for deactivating the polymerization catalyst is not particularly limited as long as the polymerization catalyst used for the polyester (C) is substantially deactivated.

  Examples of the deactivator include chelating agents, and known and commonly used organic chelating agents or inorganic chelating agents can be used. Examples of organic chelating agents include amino acids, phenols, hydroxycarboxylic acids, diketones, amines, oximes, phenanthrolines, pyridine compounds, dithio compounds, diazo compounds, thiols, porphyrins, and N as a coordination atom. Preferred examples thereof include phenols and carboxylic acids. Moreover, as an inorganic chelating agent, phosphorus compounds, such as phosphoric acid, phosphoric ester, phosphorous acid, and phosphite, are preferable, for example.

  The polyester (Ca) has a weight average molecular weight in the range of 40,000 to 200,000, and the σ / ρ value is 8.30 ≦ σ / ρ <9.20 (where σ is the value of the polyester (Ca)). The solubility parameter value is represented, and ρ represents the density of the polyester (Ca).) The polylactic acid resin composition obtained in such a range can exhibit excellent impact resistance.

  Here, the σ / ρ value will be described. The solubility parameter σ can be easily calculated according to the calculation method proposed by Fedors. By dividing this by the density of the known polymer, the desired numerical value can be obtained, but it is difficult to know the density at the molecular design stage of the polymer. Therefore, according to the formula proposed by Hoy, which is often used for the evaluation of the solubility parameter σ, the substituent constant is converted to the heat of molar dissolution per unit volume, so the σ / ρ value can be easily calculated. Hoy's formula is (D. Earl Paul, Seamall Newman, "Polymer Blend", Volume 1, Academic Press, pp. 46-47 (1978) (English title; DRPAUL and SEYMOUR NEWMAN, POLYMER BLENDS, Vol.1 , ACADEMIC PRESS, p.46-47 (1978))).

  More specifically, it is a value obtained by calculating the substituent constant determined by the Hoy equation as a numerical value per repeating unit of the polymer and dividing this by the molecular weight per repeating unit. That is, σ / ρ = ΣFi / M (where Fi is a substituent constant and M is a molar molecular weight per repeating unit). Table 1 shows calculation examples of substituent constants.

For example, polyester (hereinafter referred to as EG-SuA) obtained by esterifying ethylene glycol (hereinafter abbreviated as EG) and succinic acid (hereinafter abbreviated as SuA) is specifically described. A calculation method will be described. The repeating unit of EG-SuA is represented by — (CH ₂ —CH ₂ —COO—CH ₂ —CH ₂ —COO) —, and includes four substituents — (CH ₂ ) — and two substituents —COO. To have

  ΣFi = (131.5 × 4 + 326.58 × 2) = 1179.16. On the other hand, since the molar molecular weight (M) per repeating unit is 144.13, a value of σ / ρ = 1179.16 / 144.13 = 8.18 is obtained. Some examples are shown in the right column of Table 1.

The abbreviations in Table 1 described in the present invention mean the following.
EG; ethylene glycol SuA; succinic acid EG-SuA; polyester DA obtained by reacting ethylene glycol and succinic acid; dimer acid EG-DA; polyester obtained by reacting ethylene glycol and dimer acid PLA: polylactic acid

  Of the polyester (C) thus obtained, polyester (Cb) having a weight average molecular weight in the range of 10,000 to 40,000 can be used.

  In the present invention, it is necessary to combine those in which the difference between the weight average molecular weight of the polyester (Ca) and the weight average molecular weight of the polyester (Cb) is in the range of 20,000 to 190,000. The difference is preferably in the range of 40,000 to 190,000. The polylactic acid resin composition thus obtained has a microphase separation structure having a domain diameter in the specific range described above.

  The weight composition (Ca) / (Cb) of the polyester (Ca) and the polyester (Cb) is preferably in the range of 95/5 to 60/40, more preferably in the range of 97/3 to 20/80. . In order to make the polylactic acid resin composition having particularly excellent impact resistance, the range of 95/5 to 20/80 is preferable, and in order to maintain the transparency of the polylactic acid resin composition, 97/3 to 3/3. A range of 70/30 is preferred. Moreover, if it is in this range, it becomes a micro phase separation structure in which domains of the polyhydroxycarboxylic acid copolymer (B) are dispersed in the matrix of the polylactic acid (A), and the domain diameter is 0.10 μm to 1.00 μm. In the range, a polylactic acid resin composition in which 85% or more of the domains have domains having a domain diameter of 0.10 μm to 1.00 μm can be formed.

  The polyhydroxycarboxylic acid (D) that can be used when producing the polyhydroxycarboxylic acid copolymer (B) has a repeating unit of aliphatic carboxylic acids having a hydroxyl group in the molecule, for example, Examples include polylactic acid, polycaprolactone, polyglycolic acid, polyhydroxybutyrate, polyhydroxyvalylate, polylactic acid / glycolic acid copolymer, polyhydroxybutyrate / valerate copolymer, etc. Good. Moreover, when it has asymmetric carbon in a repeating unit like polylactic acid, any of L-form, D-form, the mixture of L-form and D-form (a mixing ratio is not specifically limited), and a racemate may be sufficient.

  As the polyhydroxycarboxylic acid (D), it is preferable to use polylactic acid. When polylactic acid and other polyhydroxycarboxylic acid are used in combination, the content of polylactic acid is 50% by mass or more. It is preferable that it is 60 mass% or more. Within such a range, a polyhydroxycarboxylic acid copolymer (B) excellent in compatibility with polylactic acid (A) can be obtained, and transparency is maintained when formed into a molded product such as a film or sheet. The obtained polylactic acid resin composition can be obtained.

  The weight average molecular weight of the polyhydroxycarboxylic acid (D) is preferably in the range of 10,000 to 400,000, more preferably in the range of 10,000 to 300,000, and 15,000 to 250. More preferred are those in the range of 1,000. By having such a weight average molecular weight, a polylactic acid resin composition excellent in transparency, melt moldability, rigidity, and the like can be obtained.

  The polyhydroxycarboxylic acid copolymer (B), for example, supplies the polyhydroxycarboxylic acid (D) and the polyester (C) to a reactor, and preferably has a temperature of 150 to 230 ° C. in an inert gas atmosphere. It can be produced by melting under conditions and esterification reaction. Within such a temperature range, the polyhydroxycarboxylic acid (D) is easily melted and is hardly thermally decomposed. In addition, it is preferable that the polyhydroxycarboxylic acid (D) is sufficiently dried in advance, so that the viscosity is not reduced by hydrolysis and the resin is not colored during melting, so that an excellent molten mixture is obtained. The esterification reaction referred to in the present invention is not only a reaction for obtaining an ester by dehydration reaction of an acid and an alcohol, but also causes an alcohol, acid or other ester to act on the ester to cause an acid group or an alkyl group to be exchanged. It includes a reaction for generating another type of ester (transesterification reaction) and the like.

  As the reactor that can be used in the esterification reaction, a vertical or horizontal tank reactor corresponding to a high vacuum and a batch type or a continuous type is preferable. Further, the blade used in the reactor is not particularly limited, but may be appropriately selected according to the viscosity or molecular weight of the produced polyhydroxycarboxylic acid copolymer (B). As the shape of the wing, as the blade of the vertical reactor, for example, paddle type, anchor type, helical type, other large wings, etc. As the wing of the horizontal reactor, for example, lattice type, glasses type, rib type Etc. are preferred. In addition, when producing polyester (C) in one reactor and then producing polyhydroxycarboxylic acid copolymer (B), blades with excellent surface renewability corresponding to the low viscosity to high viscosity region can be obtained. Preferably mentioned.

  The method for melting the polyhydroxycarboxylic acid (D) and the polyester (C) is not particularly limited, but it is preferably performed in an inert gas atmosphere. For example, both may be simultaneously supplied to the reactor under an inert gas atmosphere such as nitrogen or argon, and when the polyester (C) is in a liquid state, the polyester (C) is charged into the reactor in advance, Polyhydroxycarboxylic acid (D) may be added to the reactor, or polyhydroxycarboxylic acid (D) and polyester (C) may be melt-mixed using an extruder or the like and then added to the reactor.

  The reaction temperature of the esterification reaction is not particularly limited as long as it is a melting temperature of the polyhydroxycarboxylic acid (D) and the polyester (C), but the reaction rate of the esterification reaction and the thermal decomposition of the polyhydroxycarboxylic acid (D) Is preferably in the range of 150 to 230 ° C, more preferably in the range of 160 to 220 ° C, and particularly preferably in the range of 170 to 220 ° C.

  The degree of reduced pressure of the esterification reaction is preferably 5,000 Pa or less, more preferably 2,000 Pa or less, and particularly preferably 500 Pa or less. Moreover, regarding the lower limit value of the degree of vacuum, although it varies depending on the performance of the machine to be used, a range of 5 to 30 Pa can usually be set as the lower limit value of the degree of vacuum.

  The end point of the reaction for producing the polyhydroxycarboxylic acid copolymer (B) is not particularly limited, but when the esterification reaction in producing the polyhydroxycarboxylic acid copolymer (B) reaches the rate-limiting step, the polyhydroxycarboxylic acid Since the depolymerization reaction of the copolymer (B) proceeds, it is preferable to stop at the stage where the depolymerization reaction is suppressed as much as possible. At this time, since a sublimation product is generated by the depolymerization reaction of the polyhydroxycarboxylic acid (D), phenomena such as a decrease in the degree of reduced pressure in the reaction system and coloring of the polyhydroxycarboxylic acid copolymer are observed. On the other hand, if the esterification reaction is not sufficient, the properties such as impact resistance and transparency of the polyhydroxycarboxylic acid copolymer (B) and the polylactic acid resin composition are impaired. Therefore, as a means for confirming the end point of the reaction, a determination method using a rotary rheometer can be proposed. That is, when the strain amount was changed from 1% to 100% under the measurement conditions of the frequency of 1 Hz and the temperature within the range of the melting point of the polyhydroxycarboxylic acid copolymer to the melting point + 50 ° C., the storage elastic modulus (G ′ ( The reaction may be carried out until the ratio of change from the arbitrary storage elastic modulus G ′ in the range to 1%)) is in the range of 90 to 105%.

  Furthermore, if the reaction time can be specified by the above method, the melt viscosity ratio between the initial melt mixture of polyhydroxycarboxylic acid (D) and polyester (C) and the product is measured using a flow tester or a melt flow rate measuring device. Or the molecular weight measurement by gel permeation chromatography (hereinafter abbreviated as GPC), the polyhydroxycarboxylic acid (D) and the polyester (C) are separate peaks and become a single peak. It is possible to propose a simple method or the like until it is recognized (referred to as “single peak”).

  Here, in the case of a melt blend of polyhydroxycarboxylic acid (D) and polyester (C) derived from diol and dicarboxylic acid, the reaction of polyhydroxycarboxylic acid copolymer (B) was insufficient. In the case of a copolymer obtained by ring-opening copolymerization reaction of a cyclic dimer such as lactide and a polyester (C) obtained by using a diol and a dicarboxylic acid in the presence of a polymerization catalyst, The ratio of (80%) / G ′ (1%) deviates from the above range. The storage elastic modulus (G ′) indicates the degree of elasticity, but the polyhydroxycarboxylic acid copolymer (B) of the present invention has a characteristic that the elastic behavior is almost constant even when strain is applied. .

  The melt residence time of the molten mixture of polyhydroxycarboxylic acid (D) and polyester (C) is not particularly limited, but avoids nonspecific esterification reaction between polyhydroxycarboxylic acid (D) and polyester (C). Therefore, immediately after melting, an esterification catalyst is added to the molten mixture of polyhydroxycarboxylic acid (D) and polyester (C), the reaction temperature is in the range of 150 to 230 ° C., the degree of vacuum is 5,000 Pascals (hereinafter referred to as Pa The following esterification reaction is preferably carried out.

  The polyhydroxycarboxylic acid copolymer (B) obtained by the production method of the present invention is obtained by removing the remaining monomers and esterification catalyst by a conventionally known method and deactivating the esterification catalyst. The storage stability of the hydroxycarboxylic acid copolymer can be further improved.

  As a method for removing the remaining monomer, for example, it may be removed by vacuum devolatilization after the catalyst deactivation treatment. In addition, as a method for removing the esterification catalyst, for example, a polyhydroxycarboxylic acid copolymer is immersed in a methanol / hydrochloric acid aqueous solution, an acetone / hydrochloric acid aqueous solution, or a mixed solution thereof as a solvent, or a polyhydroxycarboxylic acid copolymer is used. Examples include a method in which the coalescence is mixed with the above solution in a solution state and washed while the polymer is precipitated. By such a method, a trace amount of residual monomer, oligomer, etc. can be simultaneously removed by washing.

  Examples of the method for deactivating the esterification catalyst used in the present invention include a method of adding a chelating agent after completion of the esterification reaction. In such a method, the addition amount of the deactivator of the esterification reaction catalyst (D) is not particularly limited as long as it is an amount that substantially deactivates the esterification catalyst used in the production of the polyhydroxycarboxylic acid copolymer. It is not something. More specifically, in terms of mass, the esterification catalyst is preferably used in an amount of 0.001 to 10 parts by mass with respect to 1 part by mass, more preferably 0.1 to 5 parts by mass, and more preferably 0.5 to It is particularly preferable to use 2 parts by mass. Here, examples of the chelating agent include known and commonly used organic chelating agents and inorganic chelating agents. Examples of organic chelating agents include amino acids, phenols, hydroxycarboxylic acids, diketones, amines, oximes, phenanthrolines, pyridine compounds, dithio compounds, diazo compounds, thiols, porphyrins, and N as a coordination atom. Containing phenols and carboxylic acids are preferred. Moreover, as an inorganic chelating agent, phosphorus compounds, such as phosphoric acid, phosphoric ester, phosphorous acid, and phosphite, are preferable, for example.

  The polyhydroxycarboxylic acid copolymer (B) thus obtained preferably has a weight average molecular weight in the range of 10,000 to 400,000, more preferably in the range of 10,000 to 300,000, A range of 50,000 to 250,000 is particularly preferable.

  The polylactic acid resin composition of the present invention contains the polyhydroxycarboxylic acid copolymer (B) and polylactic acid (A).

  The polylactic acid resin composition of the present invention may be produced by, for example, melt-kneading the polylactic acid (A) and the polyhydroxycarboxylic acid copolymer (B), It can also be used as a master batch blended with a polyhydroxycarboxylic acid copolymer (B) at a concentration.

  The mixing ratio of the polylactic acid (A) and the polyhydroxycarboxylic acid copolymer (B) in the polylactic acid resin composition of the present invention is such that the polylactic acid (A) and the polyhydroxycarboxylic acid copolymer (B ) And the weight composition (A) / (B) is in the range of 97/3 to 30/70, and the range of 97/3 to 70/30 is preferable in order to maintain the transparency of the polylactic acid (A). . If it is outside the above-mentioned range, the impact resistance is inferior or the transparency is remarkably impaired due to the reverse plasticizing effect.

  The polylactic acid resin composition of the present invention can be processed into a molded product or a film. When the molded product or film (10 cm × 10 cm square, 250 μm thickness) is left in a constant temperature and humidity chamber at 35 ° C. and a humidity of 80%, these Bleed material is not generated from the surface of the molded product for 200 days or more. In addition, it has good degradability and is subject to degradation due to hydrolysis, biodegradation, etc. even when dumped in the sea. In seawater, it can be disassembled without keeping its outer shape within a few months. In addition, when compost is used, it is biodegraded before it remains in its original form in a shorter period of time, and no toxic gases or toxic substances are emitted even when incinerated.

  The polylactic acid resin composition of the present invention comprises various molded products, packaging materials, paint resins, ink resins, toner resins, emulsion resins, adhesive resins, sanitary materials, medical materials, textile materials, agriculture. Materials, fishery materials, materials for paper lamination, foamed resin materials, reactive resins, powder coating resins, powder slush polyhydroxycarboxylic acid copolymers, dot adhesive resins, synthetic leather resins, coating resins It is useful as a primer resin, a foam coating resin, and the like.

  More specifically, for example, as various molded products, trays, cups, dishes, blisters, blow molded products, shampoo bottles, OA cases, cosmetic bottles, beverage bottles, oil containers, injection molded products (golf tees, cotton swab cores) Candy sticks, brushes, toothbrushes, helmets, syringes, dishes, cups, combs, razor handles, tape cassettes and cases, disposable spoons, forks, stationery such as ballpoint pens, etc.). Packaging materials include sheet materials, film materials, and more specifically shrink film, vapor deposition film, wrap film, food packaging, other general packaging, garbage bags, plastic bags, general standard bags, heavy bags, etc. Bags, hygiene materials such as disposable diapers, sanitary products, medical materials such as wound dressings and sutures, textile materials such as woven and knitted fabrics, lace, braids, nets, felts, non-woven fabrics, and other agricultural materials As germination film, seed string, agricultural multi-film, slow-release agricultural chemical and fertilizer coating agent, bird net, curing film, seedling pot, etc. as fishing materials, fishing net, nori culture net, fishing line, ship bottom paint, etc. In addition, paper lamination products include trays, cups, dishes, megaphones, etc., as well as tie tapes (tie bands), prepaid cards, balloons, panties A wide range of processing aids during molding, including tocking, hair caps, sponges, cellophane tape, umbrellas, goggles, plastic gloves, hair caps, ropes, tubes, foam trays, foam cushioning materials, cushioning materials, packing materials, cigarette filters, etc. There are a wide range of uses.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. In the examples, “parts” or “%” are based on mass unless otherwise specified. Various characteristics were measured by the methods described below.

[Method of measuring number average molecular weight (Mn) and weight average molecular weight (Mw)]
Using a gel permeation chromatography measuring apparatus (hereinafter abbreviated as GPC) “HLC-8020” manufactured by Tosoh Corporation, tetrahydrofuran was used as a developing solvent, and the measurement was performed in comparison with standard polystyrene.

[Measurement method of proton nuclear magnetic resonance ( ¹ H-NMR)]
^{Using a 1} H-NMR apparatus (manufactured by JEOL Ltd., JNM-LA300), the weight composition ratio of the polyhydroxycarboxylic acid (D) and the polyester (C) in the polyhydroxycarboxylic acid copolymer (B) is determined. Therefore, it was measured as a solution of chloroform-d (CDCl ₃ ).

[Measurement method of transparency]
A 200 μm-thick polylactic acid resin composition film was cut into a 5 cm × 5 cm square, and haze measurement was performed with a turbidimeter (ND-1001DP manufactured by Nippon Denshoku Industries Co., Ltd.).

[DuPont impact strength test method]
Using a DuPont impact strength measurement device, the weight of a constant weight was changed and dropped, and the 50% fracture energy of the previously obtained film was determined according to the presence or absence of breakage (conforms to JIS K 5400). .

[Observation with transmission electron microscope]
A sample film having a thickness of 200 μm was embedded in a visible light curable resin, dyed with ruthenium tetroxide for 1 to 2 hours, and then allowed to stand overnight in liquid nitrogen. Thereafter, an ultrathin section of a sample piece was prepared with an ultramicrotome and observed with a transmission electron microscope (hereinafter abbreviated as TEM; JEM-200CX, manufactured by JEOL Datum). The ratio of the domain diameter is calculated as follows. That is, based on TEM observation, all domain diameters observed in a photograph observed at a magnification of 5,000 times are measured. Here, the average value of the major axis and the minor axis of the domain was defined as the domain diameter. Subsequently, the ratio of the domain which has a domain diameter of the range of 0.10 micrometer-1.00 micrometer among the measured domain diameters was computed.

  The methods for producing polyesters (C-1) to (C-4) are shown in << Reference Example 1 >> and << Reference Example 2 >>.

<< Reference Example 1 >> Production of Aliphatic Polyesters (C-1) and (C-2) One mole equivalent of sebacic acid (hereinafter abbreviated as SeA) and propylene glycol (hereinafter abbreviated as PG) are added to the reactor. ) Was added in an amount of 1.4 molar equivalents, the temperature was increased from 150 ° C. to 10 ° C. per hour under a nitrogen stream, and the esterification reaction was performed by heating and stirring to 230 ° C. while distilling off the generated water. Two hours later, titanium tetraisopropoxide was charged as a polymerization catalyst, 60 ppm was added to the amount of raw material, and the pressure was reduced to 200 Pa, followed by stirring with heating. After 5 hours of decompression, aliphatic polyester (C-1) having a number average molecular weight (hereinafter abbreviated as Mn) of 12,000 and a weight average molecular weight (hereinafter abbreviated as Mw) of 20,000. Obtained. As a result of further continuing the reaction for 6 hours with respect to the obtained (C-1), an aliphatic polyester (C-2) having an Mn of 35,000 and an Mw of 62,000 was obtained. The obtained aliphatic polyesters (C-1) and (C-2) were melted by heating to 200 ° C., and 70 ppm of 2-ethylhexanoic acid phosphate was added as a deactivator for the polymerization catalyst with respect to each amount. . The σ / ρ value of (C-1) and (C-2) was 8.59.

Reference Example 2 Production of Aliphatic Polyesters (C-3) and (C-4) A reactor was charged with 1 molar equivalent of succinic acid (hereinafter abbreviated as SuA) and 1.4 molar equivalent of PG, and nitrogen. The temperature was raised from 150 ° C. to 10 ° C. per hour under an air stream, and the esterification reaction was carried out by heating and stirring to 230 ° C. while distilling off the generated water. Two hours later, titanium tetraisopropoxide was charged as a polymerization catalyst, 100 ppm was added to the amount of the raw material, the pressure was reduced to 133 Pa, and the reaction was continued for 8 hours. After completion of the reaction, 110 ppm of 2-ethylhexanoic acid phosphate was added to the aliphatic polyester as a deactivator for the polymerization catalyst, and the pressure was reduced to 333 Pa, followed by stirring at 220 ° C. for 1 hour. As a result, an aliphatic polyester (C-3) having Mn of 17,000 and Mw of 28,000 was obtained. The obtained (C-3) was heated to 190 ° C., and then 800 ppm of hexamethylene diisocyanate was added to (C-3) and subjected to a melt reaction for 30 minutes. As a result, an aliphatic polyester (C-4) having an Mn of 34,000 and an Mw of 84,000 was obtained. The σ / ρ value of (C-3) and (C-4) was 8.12.

  Production methods of polyhydroxycarboxylic acid copolymers (B-1) to (B-4) are shown in << Reference Example 3 >> to << Reference Example 6 >>.

<< Reference Example 3 >> Production of Polyhydroxycarboxylic Acid Copolymer (B-1) 10 parts of aliphatic polyester (C-1) obtained in Reference Example 1 and 40 aliphatic polyester (C-2) were prepared in a reactor. The mixture was melted and mixed at a jacket temperature of 210 ° C. in a nitrogen atmosphere. Thereafter, polylactic acid [Mn is 92,000, Mw is 170,000, L isomer: D isomer = 98.5: 1.5 (molar ratio); hereinafter, abbreviated as PLA1. ] Was added and melt-mixed. After visually confirming that the above mixture was melt-mixed uniformly, the molecular weight was measured. As a result, Mn was 58,000 and Mw was 111,000. Further, the mixture was melt-mixed for 2 hours and the molecular weight was measured. As a result, a melt mixture having Mn of 57,000 and Mw of 110,000 was obtained. Thereafter, 150 ppm of titanium tetrabutoxide as an esterification catalyst was added to the molten mixture and reacted at a reduced pressure of 80 Pa for 4 hours. After completion of the reaction, 500 ppm of 2-ethylhexanoic acid phosphate as a deactivator for the esterification catalyst is added to the reaction product, and a polyhydroxycarboxylic acid copolymer (B) with Mn of 65,000 and Mw of 123,000. -1) was obtained. The obtained (B-1) had a higher molecular weight than the molecular weight after melting, and the property was solid. Moreover, the GPC spectrum measurement showed unimodality, and the ratio of G ′ (80%) / G ′ (1%) was 100%.

Reference Example 4 Production of Polyhydroxycarboxylic Acid Copolymer (B-2) 40 parts of aliphatic polyester (C-2) obtained in Reference Example 1 and 10 aliphatic polyester (C-3) were added to a reactor. The mixture was melted and mixed at a jacket temperature of 205 ° C. in a nitrogen atmosphere. Thereafter, 50 parts of PLA1 was added and melt mixed. After visually confirming that the above mixture was uniformly melt-mixed, the molecular weight was measured to find that Mn was 47,000 and Mw was 102,000. Further, the mixture was melt-mixed for 2 hours and the molecular weight was measured. As a result, a melt mixture having Mn of 47,000 and Mw of 101,000 was obtained. Thereafter, 200 ppm of zirconium tetrachloride as an esterification catalyst was added to the molten mixture and reacted at a reduced pressure of 133 Pa for 3 hours. After completion of the reaction, 500 ppm of 2-ethylhexanoic acid phosphate as a deactivator for the esterification catalyst is added to the reaction product, and a polyhydroxycarboxylic acid copolymer (B) with Mn of 70,000 and Mw of 126,000. -2) was obtained. The obtained (B-2) had a higher molecular weight than the molecular weight after melting, and the property was solid. Moreover, the GPC spectrum measurement showed unimodality, and the ratio of G ′ (80%) / G ′ (1%) was 95%.

Reference Example 5 Production of Polyhydroxycarboxylic Acid Copolymer (B-3) 50 parts of the aliphatic polyester (C-2) obtained in Reference Example 2 was charged into a reactor, and the jacket temperature was 205 ° C. in a nitrogen atmosphere. Heated. Thereafter, 50 parts of PLA1 was added and melt mixed. After visually confirming that (C-2) and PLA1 were uniformly melt-mixed, the molecular weight was measured to find that Mn was 47,000 and Mw was 102,000. Further, the mixture was melt-mixed for 2 hours and the molecular weight was measured. As a result, a melt mixture having Mn of 47,000 and Mw of 101,000 was obtained. Thereafter, 100 ppm of titanium tetrabutoxide as an esterification catalyst was added to the molten mixture and reacted at a reduced pressure of 133 Pa for 4 hours. After completion of the reaction, 500 ppm of 2-ethylhexanoic acid phosphate as a deactivator for the esterification catalyst is added to the reaction product, and a polyhydroxycarboxylic acid copolymer (B) with Mn of 70,000 and Mw of 126,000. -3) was obtained. The obtained (B-3) had a higher molecular weight than the molecular weight after melting, and the property was solid. Moreover, the GPC spectrum measurement showed unimodality, and the ratio of G ′ (80%) / G ′ (1%) was 98%.

Reference Example 6 Production of Polyhydroxycarboxylic Acid Copolymer (B-4) 35 parts of aliphatic polyester (C-4) obtained in Reference Example 2 and 15 aliphatic polyester (C-1) were added to a reactor. The mixture was melted and mixed at a jacket temperature of 205 ° C. in a nitrogen atmosphere. Thereafter, 50 parts of PLA1 was added and melt mixed. After visually confirming that the above mixture was uniformly melted and mixed, the molecular weight was measured. As a result, Mn was 56,000 and Mw was 142,000. Further, the mixture was melt-mixed for 2 hours and the molecular weight was measured. As a result, a melt mixture having Mn of 56,000 and Mw of 141,000 was obtained. Thereafter, 100 ppm of titanium tetraisopropoxide as an esterification catalyst was added to the molten mixture and reacted at a reduced pressure of 133 Pa for 4.5 hours. After completion of the reaction, 500 ppm of 2-ethylhexanoic acid phosphate as a deactivator for the esterification catalyst is added to the reaction product, and a polyhydroxycarboxylic acid copolymer (B) with Mn of 68,000 and Mw of 175,000. -4) was obtained. The obtained (B-4) had a higher molecular weight than the molecular weight after melting, and the properties were solid. Moreover, the GPC spectrum measurement showed unimodality, and the ratio of G ′ (80%) / G ′ (1%) was 100%.

As described above, (B-1) to (B-4) obtained in Reference Examples 3 to 6 are polyhydroxycarboxylic acid structures in a polyhydroxycarboxylic acid copolymer using a ¹ H-NMR measuring apparatus. When the weight composition ratio of the unit and the polyester structural unit was measured, it was almost the same as the charged composition ratio.

Example 1 Polylactic acid resin composition (P-1) and film production thereof PLA1 and (B-1) obtained in Reference Example 3 were dried under reduced pressure at 60 ° C. for 3 hours, and then Table 1 The polylactic acid resin composition (P-1) was obtained by melting and kneading at 190 ° C. for 10 minutes using a lab plast mill mixer manufactured by Toyo Seiki Co., Ltd. The obtained (P-1) was dried under reduced pressure at 80 ° C. for 3 hours, and then a film having a thickness of 200 μm was produced at 195 ° C.
<< Example 2 >>, << Example 3 >>, << Comparative Example 1 >> to << Comparative Example 3 >> Production of Polylactic Acid Resin Compositions (P-2) to (P-6) and Films thereof << Example 1 >> Similarly, a film having a thickness of 200 μm was prepared from the polylactic acid resin compositions (P-2) to (P-6).

Comparative Example 4 Production of PLA1 Film PLA1 was dried under reduced pressure at 80 ° C. for 3 hours, and then a film having a thickness of 200 μm was produced at 195 ° C.

Table 2 shows the results of haze measurement, Dupont impact strength measurement, and bleed-out evaluation for the films obtained in Examples 1 to 3 and Comparative Examples 1 to 3.

  Note 1) In Table 2, when a polylactic acid resin composition was observed with a TEM, a microphase-separated structure in which domains of polyhydroxycarboxylic acid copolymer were dispersed in a polylactic acid matrix was observed. "What could not be observed was written as" nothing ".

  Note 2) In Table 2, the ratio of domains having a specific domain diameter is a domain diameter in the range of 0.10 μm to 1.00 μm with respect to the domain seen in the photograph observed at a magnification of 5,000 times using TEM. Indicates the percentage of domains with.

  According to the present invention, it was possible to produce a polylactic acid resin composition having a microphase separation structure having 85% or more of domains having a domain diameter in the range of 0.10 μm to 1.00 μm.

  The polylactic acid resin composition having the specific microphase separation structure described above did not impair the heat resistance of polylactic acid and had excellent transparency.

  When the 200-micrometer-thick film of the polylactic acid resin composition (P-1) to (P-6) is kept in a constant temperature and humidity chamber PR-2F manufactured by Tabay Espec Co., Ltd. while maintaining the conditions of 40 ° C. and 90% humidity. No bleed out was observed after 200 days.

  Using the polylactic acid resin compositions (P-1) and (P-2) obtained in Example 1 and Example 2, (P-4) obtained in Comparative Example 1, and a film having a thickness of 200 μm, TEM Observations were made.

  The TEM observation result of the polylactic acid resin composition (P-1), (P-2), and (P-4) was shown in FIGS. The domain of the polyhydroxycarboxylic acid copolymer (B-1) can be observed by TEM observation of the film made of the polylactic acid resin composition (P-1) in FIG. The domain in the range of 30 to 1.00 μm is present in 92% or more. By TEM observation of the film made of the polylactic acid resin composition (P-2) in FIG. 2, the polyhydroxycarboxylic acid copolymer (B-2) Domains could be observed, and the microphase separation structure in which PLA1 formed a matrix with 88% or more of domains having a domain diameter in the range of 0.30 to 1.00 μm was observed with respect to the total number of domains.

  Moreover, the domain of the polyhydroxycarboxylic acid copolymer (B-3) can be observed by TEM observation of the film made of the polylactic acid resin composition (P-4) in FIG. 3, and the domain diameter is 0.06 to 3.50 μm. A domain having a domain diameter in the range of 0.10 μm to 1.00 μm with respect to the total number of domains was able to be observed.

The TEM observation photograph of the film obtained using a polylactic acid resin composition (P-1) is shown. The black part in a TEM photograph (FIG. 1) shows the polyhydroxycarboxylic acid copolymer (B-1), and the white part shows polylactic acid (PLA1). The TEM observation photograph of the film obtained using a polylactic acid resin composition (P-2) is shown. The black part in a TEM photograph (FIG. 2) shows the polyhydroxycarboxylic acid copolymer (B-2), and the white part shows polylactic acid (PLA1). The TEM observation photograph of the film obtained using a polylactic acid resin composition (P-4) is shown. A black part in a TEM photograph (FIG. 3) shows a polyhydroxycarboxylic acid copolymer (B-3), and a white part shows polylactic acid (PLA1).

Claims (2)

Containing polylactic acid (A) and polyhydroxycarboxylic acid copolymer (B) having polyhydroxycarboxylic acid structural unit (I) and polyester structural unit (II) derived from diol and dicarboxylic acid A polylactic acid resin composition, wherein the weight composition (A) / (B) of the polylactic acid (A) and the polyhydroxycarboxylic acid copolymer (B) is in the range of 97/3 to 30/70. And the polyhydroxycarboxylic acid copolymer (B) has a microphase separation structure in which a domain is formed in a matrix formed by the polylactic acid (A), and 85% or more of the domains are from 0.10 μm to A polylactic acid resin composition having a domain diameter in the range of 1.00 μm. The terminal obtained by reacting polyhydroxycarboxylic acid (D) with diol and dicarboxylic acid has a hydroxyl group and a weight average molecular weight in the range of 40,000 to 200,000, and the σ / ρ value is 8.30 ≦ Reaction between polyester (Ca) having σ / ρ <9.20 (where σ represents the solubility parameter value of polyester (Ca) and ρ represents the density of polyester (Ca)), diol and dicarboxylic acid Among the molten mixture with the polyester (Cb) having a hydroxyl group at the terminal obtained and having a weight average molecular weight of 10,000 to 40,000, the weight average molecular weight of the polyester (Ca) and the polyester (Cb ) With a weight average molecular weight of 20,000 to 190,000, the polyester (Ca) and the polyester (Cb) A molten mixture having a weight composition (Ca) / (Cb) in the range of 95/5 to 60/40 is subjected to an esterification reaction in the presence of a polymerization catalyst under reduced pressure conditions, and the obtained reaction product is subjected to a rotary rheometer. When the strain was changed from 1 to 80% under the measurement conditions in which the frequency was 1 Hz and the temperature was within the range of the melting point of the reactant to the melting point + 50 ° C., the storage stability G of strain M% (1 <M ≦ 80) The polyhydroxycarboxylic acid copolymer (B) obtained by continuing the esterification reaction until '(M%) is in the range of 90 to 100% of the storage elastic modulus G' (1%) of 1% strain ) And polylactic acid (A) are melt-kneaded, and the method for producing a polylactic acid resin composition according to claim 1.

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