JP2007161801A - Polyester composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biodegradable polyester composition having excellent impact resistance. <P>SOLUTION: This invention relates a polyester composition that comprises (A) a block copolymer having a polyhydroxy-carboxylic acid structure unit (I) and a polyester structure unit (II) obtained by reaction between dicarboxylic acid and diol, (B) polylactic acid and (C) particulated calcium carbonate, wherein the micro-phase separation structure that forming the domain with the polyester structure unit (II) originating from the block copolymer (A) is formed in the matrix formed by (B) the polylactic acid, and 70 mass% to 100 mass% of calcium carbonate (c1) based on the total calcium (C) come into existence in the domain. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a polyester composition that can be used in various applications such as automobile parts and home appliance parts that require impact resistance.

  Biodegradable resins are beginning to be applied to various environmentally friendly products from the standpoint of environmental protection in recent years. In particular, polylactic acid is attracting attention as a material capable of reducing the environmental load because it can be produced using corn, potatoes and the like as raw materials. In addition, polylactic acid is expected to be used for packaging materials and the like because it is excellent in mechanical properties, heat resistance, and transparency as compared with other aliphatic polyesters. On the other hand, since polylactic acid has a major drawback of being hard and brittle, it has been difficult to use it for industrial materials that require characteristics such as high impact resistance.

Known industrial materials that require high impact resistance include, for example, automobile bumpers and exterior parts of home appliances. In such applications, acrylonitrile butadiene styrene resin (ABS resin), polycarbonate resin, and the like, which are conventionally known as having high impact resistance, are used.
However, since ABS resin or the like is not a biodegradable resin, it is difficult to say that it is preferable to use a large amount of ABS resin or the like from the viewpoint of recent environmental protection promotion.
Therefore, development of a resin composition having good biodegradability and characteristics such as a level of impact resistance that can be used as a substitute for ABS resin or the like has been demanded by the industry.

Various resin compositions having good biodegradability and high impact resistance have been studied in the past. For example, crystalline polylactic acid and at least one selected from natural rubber and polyisoprene are used. It has been reported that the polylactic acid resin composition contained therein is excellent in biodegradability, moldability and impact resistance (see, for example, Patent Document 1).
The polylactic acid-based resin composition has good impact resistance as compared with known polylactic acid resin compositions, but requires a higher level of impact resistance. It was still difficult to use for applications.

  On the other hand, studies on biodegradable modifiers that can impart impact resistance and the like to the polylactic acid and are excellent in compatibility with polylactic acid are also underway. For example, polyhydroxycarboxylic acid A block copolymer having a structural unit and a polyester structural unit obtained by reacting a dicarboxylic acid and a diol in a specific range of proportions, forming a so-called sea-island microphase separation structure, is a biodegradation unique to polylactic acid. It has been reported that excellent flexibility and impact resistance can be imparted to polylactic acid without impairing the properties and transparency (see, for example, Patent Document 2).

  Although the polyester composition containing the block copolymer and the polylactic acid has an impact resistance of about 2 to 4 times that of polylactic acid alone, it is still not suitable for use in applications requiring high impact resistance. It was not enough.

  As described above, in applications requiring high impact resistance, it has a level of impact resistance that can be used as an alternative to the conventionally used ABS resin and the like, and is favorable from the viewpoint of promoting environmental protection. At present, no biodegradable resin composition has yet been found.

JP 2003-183488 A JP 2004-250663 A

  The problem to be solved by the present invention is to provide a biodegradable polyester composition excellent in impact resistance.

The inventors of the present invention have made studies based on the use of inorganic particles that are generally used for improving heat resistance and the like. Specifically, various properties of a composition obtained by mixing polylactic acid and general calcium carbonate as inorganic particles were examined, but the above-described high level of impact resistance could not be expressed. .
The inventors further studied, and as a modifier component of polylactic acid, a block copolymer having a polyhydroxycarboxylic acid structural unit and a polyester structural unit obtained by reacting a dicarboxylic acid and a diol, A polyester composition containing calcium carbonate and polylactic acid as inorganic particles, and having a microphase-separated structure in which the block copolymer (A) forms a domain in a matrix formed by the polylactic acid. And a polyester composition in which the calcium carbonate is present in a specific amount in the domain, in other words, a polyester composition having a form (morphology) in which a specific amount of the particulate calcium carbonate is encapsulated by the domain. , And it can be seen that the impact resistance can be greatly improved without impairing the moldability. It was.

That is, the present invention provides a block copolymer (A) having a polyhydroxycarboxylic acid structural unit (I) and a polyester structural unit (II) obtained by reacting a dicarboxylic acid and a diol, and polylactic acid (B). And containing particulate calcium carbonate (C),
In the matrix formed by the polylactic acid (B), the polyester structural unit (II) derived from the block copolymer (A) has a microphase separation structure in which a domain is formed,
In addition, the present invention relates to a polyester composition characterized in that 70% by mass to 100% by mass of calcium carbonate (c1) in the total amount of the calcium carbonate (C) is present in the domain.

  Since the polyester composition of the present invention is excellent in impact resistance and molding processability, it is practically useful for use in applications such as miscellaneous goods, home appliance parts, housings, and automobile parts.

  The polyester composition of the present invention comprises a polyhydroxycarboxylic acid structural unit (I), a block copolymer (A) having a polyester structural unit (II) obtained by reacting a dicarboxylic acid and a diol, polylactic acid ( B), particulate calcium carbonate (C), and other additives as required.

  The polyester composition of the present invention has a so-called sea-island microphase separation structure in which the block copolymer (A) is dispersed in a matrix formed by the polylactic acid (B). Such a structure is confirmed by the method described later based on the fact that the polyester structural unit (II) derived from the block copolymer (A) forms a domain in the matrix formed by the polylactic acid (B). be able to.

  First, the block copolymer (A) used in the present invention will be described in detail below. The block copolymer used in the present invention has a polyhydroxycarboxylic acid structural unit (I) and a polyester structural unit (II) obtained by reacting a dicarboxylic acid and a diol.

  More specifically, the block copolymer (A) when the polyhydroxycarboxylic acid structural unit (I) is X and the polyester structural unit (II) obtained by reacting a dicarboxylic acid and a diol is Y. The form of the XY-type block copolymer, XYX-type block copolymer, random block copolymer, and these varies depending on the charging ratio and molecular weight of the raw materials used when the block copolymer (A) is produced. And the like. Moreover, as long as the characteristic of a block copolymer (A) is not impaired, these may contain polyhydroxycarboxylic acid, polyester, etc. which are mentioned later as an unreacted substance.

  The mass ratio (I) / (II) of the polyhydroxycarboxylic acid structural unit (I) and the polyester structural unit (II) is in the range of 95/5 to 10/90. In particular, when the block copolymer (A) is added to the polylactic acid (B), in order to increase the compatibility between the polylactic acid (B) and the block copolymer (A), the mass ratio (I) / ( II) is preferably 20/80 to 70/30, and particularly preferably 30/70 to 60/40 in order to impart impact resistance to polylactic acid (B).

  In the block copolymer (A) used in the present invention, the other structural unit is a domain in a matrix formed by one of the structural units of the polyhydroxycarboxylic acid structural unit (I) and the polyester structural unit (II). Having a microphase-separated structure.

  Specifically describing the microphase separation structure, the block copolymer (A) can be roughly divided into the following three forms. These are determined by the composition ratio (mass ratio) of the polyhydroxycarboxylic acid structural unit (I) and the polyester structural unit (II).

  The first form is a block copolymer in which the polyhydroxycarboxylic acid structural unit (I) is phase-separated as a sea phase and the polyester structural unit (II) is an island phase, and the second form is a polyhydroxycarboxylic acid structural unit (I). Is a block copolymer in which a polyester structural unit (II) is an island phase, and a polyhydroxycarboxylic acid structural unit (I) is further phase-separated as an island phase, and a third form is a polyhydroxycarboxylic acid This is a block copolymer in which the acid structural unit (I) is phase-separated as an island phase and the polyester structural unit (II) is a sea phase.

The average domain diameter of the polyester structural unit (II) constituting the block copolymer (A) is preferably in the range of 0.08 to 5.0 μm, more preferably the average domain diameter of the island phase is 0.1 to 4. The range is 0 μm, and even more preferably, the average domain diameter of the island phase is in the range of 0.1 to 3.5 μm.
The polyester composition of the present invention having a specific microphase separation structure having an average domain diameter in the above range can exhibit unprecedented excellent flexibility and impact resistance, and has excellent transparency that polylactic acid (B) has The property is also maintained without being impaired.

  The block copolymer (A) and the form (morphology) of the polyester composition of the present invention are abbreviated as transmission electron microscope (hereinafter referred to as TEM. For example, JEM-200CX manufactured by JEOL Datum Co., Ltd. may be used. Can be observed.

  As an example of an observation method using TEM, a block copolymer (A) and a polyester composition are formed into a film sample piece having a thickness of 200 μm, and then cut into an appropriate size. Embed in 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 for one night or more. Thereafter, an ultrathin section of a sample piece is prepared with an ultramicrotome, and TEM observation is performed.

  Next, the manufacturing method of the said block copolymer (A) is demonstrated. As a method for producing the block copolymer (A), a molten mixture (II ′) of polyhydroxycarboxylic acid (I ′) and polyester having hydroxyl groups at both ends obtained by reacting dicarboxylic acid and diol is prepared. The reaction product is subjected to esterification reaction under reduced pressure in the presence of an esterification catalyst, and the reaction product is measured using a rotary rheometer at a frequency of 1 Hz and a temperature within the range of the melting point of the reaction product to the melting point + 50 ° C. When the strain is changed from 1 to 60%, the storage elastic modulus G ′ (M%) of the strain M% (1 <M ≦ 60) is 90 to the storage elastic modulus G ′ (1%) of the strain 1%. There is a method in which the esterification reaction is continued until the point of time reaches 100%.

  First, polyester (II ') having hydroxyl groups at both ends obtained by reacting polyhydroxycarboxylic acid (I') with dicarboxylic acid and diol used in the present invention will be described.

  The polyhydroxycarboxylic acid (I ′) used in the present invention only needs to be composed of a repeating unit of an aliphatic carboxylic acid having a hydroxyl group in the molecule. For example, polylactic acid, polycaprolactone, polyglycolic acid, Examples thereof include polyhydroxybutyrate, polyhydroxyvalerate, polylactic acid / glycolic acid copolymer, polyhydroxybutyrate / valerate copolymer, and the like, and a mixture thereof may be used. Of these polyhydroxycarboxylic acids (I), polylactic acid is particularly preferred. 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.

  In addition, the polyhydroxycarboxylic acid (I ′) used in the present invention is such that the resulting block copolymer (A) imparts excellent properties such as transparency, melt moldability, and rigidity to the polylactic acid (B). From the viewpoint that the weight average molecular weight is preferably in the range of 5,000 to 400,000, more preferably in the range of 10,000 to 400,000, and particularly preferably in the range of 10,000 to 300,000. Most preferably, it is in the range of 15,000 to 250,000.

  Furthermore, the content of polylactic acid based on the whole polyhydroxycarboxylic acid (I ′) is preferably 50% by mass or more, and more preferably 60% by mass or more. If the content of polylactic acid in the polyhydroxycarboxylic acid (I ′) is within such a range, compatibility with polylactic acid (B) described later is improved. Further, when the polyhydroxycarboxylic acid (I ′) is polylactic acid, it is particularly preferable when it is formed into a molded product such as a film or a sheet because the transparency is improved.

  The polyester (II ′) that reacts with the polyhydroxycarboxylic acid (I ′) is obtained by an esterification reaction of a dicarboxylic acid and a diol, and has hydroxyl groups at both ends of the molecule, and preferably has a weight average molecular weight. It is in the range of 5,000 to 200,000, more preferably in the range of 10,000 to 200,000, and particularly preferably in the range of 15,000 to 200,000.

  Examples of the polyester (II ′) include an aliphatic polyester obtained by reacting an aliphatic dicarboxylic acid and an aliphatic diol, or an aliphatic / aromatic dicarboxylic acid in which an aliphatic dicarboxylic acid and an aromatic dicarboxylic acid are used in combination. It is preferable to use an aliphatic / aromatic polyester obtained by reacting with an aliphatic diol. In particular, the polyester (II ′) having 8 to 22 carbon atoms is used so that the polyester structural unit (II) constituting the block copolymer (A) is a domain in the polylactic acid (B). As a result, the impact resistance of the polyester composition can be improved, which is preferable.

  The aliphatic diol may be an aliphatic diol having a chain hydrocarbon chain or an alicyclic hydrocarbon chain, such as ethylene glycol, 1,3-propanediol, 1,2-butanediol, , 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-propanediol, 1,2-pentanediol, 1,3-pentanediol, 2,3- Nthanediol, 2,4-pentanediol, 2-methyl-2,4-pentanediol, 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, xylylene glycol, phenyl Aliphatic diols having 2 to 45 carbon atoms such as ethylene glycol can be used, and it is more preferable to use propylene glycol among them.

  Two or more of these diols can be used in combination, for example, a combination of propylene glycol and polyethylene glycol, a combination of ethylene glycol and 1,4-butanediol, and the like. Furthermore, in the present invention, an EO addition product of bisphenol A or a PO addition product of bisphenol A, which contains an aromatic ring but is considered to be an aliphatic diol, can be used as the aliphatic diol.

  As the dicarboxylic acid, any aliphatic dicarboxylic acid or aromatic dicarboxylic acid can be used. Among them, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid. It is preferable to use an acid, cyclohexanedicarboxylic acid, aliphatic dicarboxylic acid such as dimer acid or fumaric acid, and it is more preferable to use sebacic acid.

  As said polyester structural unit (II), it is preferable to use what has 8-22 carbon atoms. Specifically, it is possible to use calcium carbonate (c1) obtained by esterifying propylene glycol (3 carbon atoms) as the diol and sebacic acid (10 carbon atoms) as the dicarboxylic acid. ), And as a result, the impact resistance of the polyester composition can be dramatically improved.

  The melting point of the polyester (II ′) is preferably 150 ° C. or less. Examples of the melting point of the polyester include: polyethylene succinate at about 102 ° C., polypropylene succinate at about −2 ° C., polybutylene succinate at about 113 ° C., polyethylene adipate at about 44 ° C., polypropylene adipate at about 58 ° C. About 58 ° C for butylene adipate, about 63 ° C for polyethylene sebacate, about -41 ° C for polypropylene sebacate, about 120 ° C for polybutylene adipate / terephthalate (feeding molar ratio; adipic acid: terephthalic acid = 1: 1) These can be preferably used as the polyester (II ′).

  The method for producing the polyester (II ′) used in the present invention is not particularly limited, and for example, the polyester (II ′) can be produced by esterification by a known and usual esterification reaction using the above diol, dicarboxylic acid, and polymerization catalyst. it can. In that case, in order to suppress coloring of polyester (II '), you may add antioxidants, such as a phosphite compound, preferably 10-2000 ppm with respect to the total amount of diol and dicarboxylic acid.

  The polyester (II ′) has hydroxyl groups at both ends, and an excessive amount of diol may be charged with respect to the dicarboxylic acid. Specifically, the molar ratio of diol and dicarboxylic acid is adjusted to the diol. : Dicarboxylic acid = 1.4: 1.0 to 1.0 (excluding 1.0): 1.0 molar ratio is preferable, 1.2: 1.0 to 1.0 (provided 1.0 is Not included): 1.0 molar ratio is more preferable.

  As said polymerization catalyst, it is preferable to use what consists of at least 1 type of metal or metal compound chosen from the group which consists of periodic table 2 group, 3 group, 4 group. As the polymerization catalyst (D) comprising such a metal or metal compound, for example, a polymerization catalyst (D) comprising a metal such as Ti, Sn, Zn, Al, Zr, Mg, Hf, Ge, or a metal compound is preferred. Specifically, titanium tetraisopropoxide, titanium tetrabutoxide, titanium oxyacetylacetonate, tin octoate, 2-ethylhexanetin, acetylacetonate zinc, zirconium tetrachloride, zirconium tetrachloride tetrahydrofuran complex, hafnium chloride, 4 Examples include hafnium chloride tetrahydrofuran complex, germanium oxide, and tetraethoxygermanium.

  In addition, the amount of the polymerization catalyst used in the production of the polyester (II ′) is usually an amount that can control the reaction and that gives a copolymer of good quality. Preferably it is the range of 10-1000 ppm with respect to the total amount with an acid, More preferably, it is the range of 20-800 ppm, and the range of 30-500 ppm is especially in order to reduce the coloring of polyester (II '). preferable.

  When producing the block copolymer (A) used in the present invention, the polyhydroxycarboxylic acid (I ′) and the polyester (II ′), which are raw materials, are esterified with a predetermined molecular weight. However, from this point of view, it is preferable to deactivate the polymerization catalyst used in the production of each raw material before the esterification reaction.

  It is extremely effective to deactivate the polymerization catalyst contained in the polyester (II ') after the synthesis reaction of the polyester (II'). When the polymerization catalyst is not deactivated, when the polyhydroxycarboxylic acid (I ′) and the polyester (II ′) are melt-mixed, the polymerization catalyst acts on the polyhydroxycarboxylic acid (I ′) to cause a depolymerization reaction. Therefore, it is difficult to produce a stable molecular weight and hue of the target block copolymer (A), and the transparency and molding processability may be extremely inferior.

  Examples of the method for deactivating the polymerization catalyst when the polyester (II ′) contains a polymerization catalyst include a method of adding a chelating agent after the reaction of the polyester (II ′). In such a method, the addition amount of the deactivator for deactivating the polymerization catalyst is not particularly limited as long as it is an amount that substantially deactivates the polymerization catalyst used for the polyester (II ′).

  As the chelating agent which is such a deactivator, a known and commonly used organic chelating agent or inorganic chelating agent 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.

  In addition, before and after the addition of the polymerization catalyst deactivator, the polyester (II ′) is reacted with an acid anhydride or a polyvalent isocyanate by a known and conventional method to make the chemical structure branched and further increase the molecular weight. You can also.

  Next, a method for melting and mixing the polyhydroxycarboxylic acid (I ′) and the polyester (II ′) will be described.

  Here, the raw material polyhydroxycarboxylic acid (I ′) and polyester (II ′) are supplied to the reactor and melted in an inert gas atmosphere, preferably at a temperature of 150 to 230 ° C. Within such a temperature range, the polyhydroxycarboxylic acid (I ′) is easily melted and is hardly thermally decomposed. The polyhydroxycarboxylic acid (I ′) is preferably sufficiently dried in advance, so that the viscosity is not reduced by hydrolysis and the block copolymer is not colored during melting, so that an excellent molten mixture is obtained.

  Next, the reactor is preferably a vertical or horizontal tank reactor corresponding to high vacuum and batch type or continuous type. The blade used in the reactor is not particularly limited, but may be appropriately selected according to the viscosity or molecular weight of the block copolymer to be produced. As the shape of the wing, the vertical reactor wing includes, for example, a paddle type, anchor type, helical type, large wing, etc., and the horizontal reactor wing includes, for example, a lattice type, glasses type, rib type, etc. preferable. Moreover, when manufacturing polyester (II ') by one reactor and manufacturing block copolymer after that, the blade | wing excellent in the surface renewability corresponding to a low viscosity to a high viscosity area | region is mentioned preferably.

  The method for melting the polyhydroxycarboxylic acid (I ′) and the polyester (II ′) 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. When the polyester (II ′) is in a liquid state, the polyester (II ′) is charged into the reactor in advance. Thereafter, polyhydroxycarboxylic acid (I ′) is added to the reactor, or polyhydroxycarboxylic acid (I ′) and polyester (II ′) are melted using an extruder or the like and then added to the reactor. Also good.

  To the obtained polyhydroxycarboxylic acid (I ′) and polyester (II ′) molten mixture, an esterification catalyst is added, and the esterification reaction is performed under reduced pressure conditions. When the strain was changed from 1 to 60% 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 elastic modulus G ′ of strain M% (1 <M ≦ 60) The target block copolymer (A) is obtained by continuing the esterification reaction until the point (M%) is in the range of 90 to 100% of the storage elastic modulus G ′ (1%) with a strain of 1%. Obtainable.

  The melt residence time of the molten mixture of polyhydroxycarboxylic acid (I ′) and polyester (II ′) is not particularly limited, but the melt of polyhydroxycarboxylic acid (I ′) and polyester (II ′) immediately after melting An esterification catalyst is added to the mixture, and the esterification reaction is preferably carried out at a reaction temperature in the range of 150 to 230 ° C. and a reduced pressure of 5,000 Pascal (hereinafter abbreviated as Pa).

  Here, the esterification reaction referred to in the present invention is a reaction for obtaining an ester by dehydration of an acid and an alcohol, and an alcohol, an acid or another ester is allowed to act on the ester to cause an exchange of an acid group or an alkyl group, It includes a reaction for generating another type of ester (transesterification reaction) and the like.

Examples of the esterification catalyst used in the present invention include one or more elements belonging to any one of groups 2 to 4 of the periodic table or compounds containing the elements. Examples of elements belonging to groups 2 to 4 of the periodic table include For example, Ti, Zr, Hf, Al, Sn, Zn, Mg and the like are preferable. A compound containing Ti, Zr, Hf, Al or the like is more preferable from the viewpoint of suppressing the depolymerization reaction of the polyhydroxycarboxylic acid (A), although it varies depending on the reaction temperature, reaction time, and catalyst amount. _{, Ti (OC n H 2n +} 1) 4 [wherein n, an integer of 1 to _8], ZrCl _4, ZrCl 4 · 2 tetrahydrofuran (hereinafter, abbreviated as THF) _complex, HfCl _4, HfCl ₄ · 2THF Complexes etc. are mentioned, More specifically, titanium tetraisopropoxide, titanium tetrabutoxide, etc. are mentioned.

  The amount of the esterification catalyst used varies depending on the reaction conditions in the esterification reaction process shown below, that is, reaction temperature, reaction time, degree of reduced pressure, etc., but polyhydroxycarboxylic acid (I ′) and polyester (II ′ ), Preferably in the range of 10 to 800 ppm, more preferably in the range of 20 to 500 ppm, and particularly preferably in the range of 30 to 300 ppm. If the amount of the esterification catalyst used is within such a range, the resulting block copolymer can be colored and the progress of the depolymerization reaction can be minimized.

  The reaction temperature of the esterification reaction carried out in the present invention is not particularly limited as long as it is a melting temperature of the above polyhydroxycarboxylic acid (I ′) and polyester (II ′). Considering the thermal decomposition of the hydroxycarboxylic acid (I ′), it 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 performed in the present invention 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.

  In the method for producing the block copolymer (A), when the esterification reaction reaches a rate-determining step, the depolymerization reaction of the polyhydroxycarboxylic acid structural unit (I) of the block copolymer as a reaction product is performed. Sublimates are generated because it is promoted. At this time, phenomena such as a decrease in the degree of vacuum in the reaction system and coloring of the reaction product are observed. For this reason, it is preferable to stop at a stage where the depolymerization reaction of the polyhydroxycarboxylic acid structural unit (I) is suppressed as much as possible. On the other hand, the properties such as flexibility, transparency and impact resistance of the block copolymer and the polyester composition obtained when the esterification reaction is not sufficient are impaired.

Next, a method for determining the end point of the esterification reaction between the polyhydroxycarboxylic acid (I ′) and the polyester (II ′) will be described.
In order to obtain the target block copolymer (A), the reaction product in the esterification reaction is rotated at a frequency of 1 Hz and the temperature is within the range of the melting point of the reaction product to the melting point + 50 ° C. When the strain is changed from 1 to 60% under the measurement conditions, the storage elastic modulus G ′ (M%) of the strain M% (1 <M ≦ 60) is the storage elastic modulus G ′ (1%) of the strain 1%. What is necessary is just to continue the said esterification reaction until the time of becoming the range of 90 to 100%.

  In addition, it is important to determine the end point of the esterification reaction between the polyhydroxycarboxylic acid (I ′) and the polyester (II ′) using the above-described method. That is, by determining the end point of the esterification reaction, in addition to providing stable production of the resulting block copolymer, the resulting block copolymer has the above-described microphase separation structure, and has excellent resistance to resistance. When it is used as a block copolymer, it exhibits impact resistance, flexibility, bleed out resistance, and the like, which are excellent in polylactic acid described later.

  The block copolymer obtained by the production method of the present invention is obtained by removing the remaining monomer and esterification catalyst by a conventionally known method, and deactivating the esterification catalyst, thereby preserving the storage stability of the obtained block copolymer. The property can be further improved.

  As a method for removing the remaining monomer, for example, it may be removed by decompression after the catalyst deactivation treatment. In addition, as a method for removing the esterification catalyst, for example, a block 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 the block copolymer is in a solution state as described above. Examples of the method include washing in a solution while precipitating the polymer. By such a method, a trace amount of residual monomer, oligomer, etc. can be simultaneously removed by washing.

  Examples of the method of deactivating the esterification catalyst that can be 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 deactivation agent for the esterification catalyst is not particularly limited as long as it is an amount that substantially deactivates the esterification catalyst used for the production of the block copolymer. More specifically, in terms of mass, it is preferable to use 0.001 to 10 parts, more preferably 0.1 to 5 parts, and 0.5 to 2 parts to 1 part of the esterification catalyst. It is particularly preferred.

  Here, as the chelating agent, those similar to the chelating agents exemplified as those that can be used as the deactivator of the polymerization catalyst can be used.

  The block copolymer (A) can be used by mixing with polylactic acid. At this time, the block copolymer (A) can be used alone or in combination of two or more, improving the impact resistance and flexibility of the polylactic acid, maintaining the heat resistance and transparency, and further generating bleed out Can be suppressed.

  The block copolymer (A) has a weight average molecular weight of 10,000 or more, more specifically, maintains transparency, suppresses bleed out, and provides excellent impact resistance and flexibility. The weight average molecular weight is preferably in the range of 10,000 to 400,000, more preferably in the range of 10,000 to 300,000, and in the range of 15,000 to 250,000. Particularly preferred.

  Further, as will be described later, when the block copolymer (A) and calcium carbonate are previously melt-mixed to form a so-called masterbatch, the block copolymer (A) is 70,000 to 400. It is preferable to use those having a weight average molecular weight in the range of 1,000.

  The block copolymer (A) is a glass transition temperature (hereinafter abbreviated as Tg) measured using a differential scanning calorimeter (DSC220C manufactured by Seiko Denshi Kogyo Co., Ltd.) at a temperature rising rate of 10 ° C./min. ) Is preferably in the range of -70 to 65 ° C, more preferably in the range of -65 to 65 ° C.

  The weight average molecular weight of the polylactic acid (B) used in the polyester composition of the present invention is preferably 10,000 or more, more preferably in the range of 50,000 to 400,000, and 100,000 to 300,000. A range is particularly preferred. If the polylactic acid (B) used for the polyester composition of the present invention has a weight average molecular weight in such a range, it has excellent mechanical strength.

  In addition, calcium carbonate (C) used in the present invention is inexpensive and highly safe, is abundant in nature, and is useful for resources, so it is used in various applications. As calcium carbonate (C) used in the present invention, heavy calcium carbonate obtained by pulverizing limestone by a dry method or a wet method, light calcium carbonate artificially synthesized by reacting carbon dioxide with slaked lime, etc. Can be used.

  The calcium carbonate (C) is surface-treated with a fatty acid, a silane coupling agent or the like for the purpose of improving dispersibility in the block copolymer (A) or polylactic acid (B). Also good. By improving the dispersibility of calcium carbonate (C), the impact resistance of the resulting polyester composition can be further improved.

  Examples of the fatty acids include saturated fatty acids such as butyric acid, caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid and stearic acid, unsaturated fatty acids such as oleic acid, linoleic acid, linolenic acid and ricinolenic acid, Rosin acid, lignic acid, etc. can be used.

  As the calcium carbonate (C) used in the present invention, those having an average particle diameter in the range of 0.03 μm to 3 μm are preferably used, and those having a range of 0.1 μm to 2 μm are more preferably used. It is more preferable to use one having a range of 0.1 μm to 1.5 μm. The “average particle size” as used in the present invention is a particle size distribution created based on the particle size obtained by a light scattering diffraction method using a laser as a light source, and calculated based on the particle size distribution. Is the average value.

  In general, there is a relationship represented by the formula d = 6 / (p · S) between the particle diameter (d) and the specific surface area (S) (wherein p represents the density of the particles). Therefore, it is considered that the calcium carbonate (C) also has a larger specific surface area as its average particle size is smaller. Since calcium carbonate (C) having a large specific surface area can finely disperse the impact (load) applied to the composition in the polyester composition of the present invention, the impact resistance of the composition is remarkably increased. It is thought to improve. The specific surface area is the total surface area of the calcium carbonate particles contained in the unit mass.

The polyester composition of the present invention can be produced by melt-mixing the block copolymer (A), the polylactic acid (B), and the calcium carbonate (C).
Specifically, for example, the affinity between the block copolymer (A) and the calcium carbonate (C) is increased by previously melt-mixing the block copolymer (A) and the calcium carbonate (C), Subsequently, it is preferable to manufacture by the method of melt-mixing them and polylactic acid (B). By the production by the above method, the calcium carbonate (C) forms a polyester or structural unit (II ′) derived from the block copolymer (A) rather than in the matrix composed of the polylactic acid (B). It becomes easy to exist excessively in the domain, and as a result, a polyester composition having excellent impact resistance can be obtained. In addition, you may mix calcium carbonate (C) in the middle of manufacture of a block copolymer (A).

As a mixer that can be used when the block copolymer (A), the polylactic acid (B), and the calcium carbonate (C) are heated and melted and mixed, for example, a single-screw extruder or a twin-screw extruder is used. Although it can be used, it is preferable to use a twin-screw extruder having high kneadability.
The temperature at the time of melt mixing is preferably in the range of a low value to 260 ° C among the melting points of the block copolymer (A) and the polylactic acid (B), but is usually 180 ° C to 250 ° C. It is preferable to melt and mix.

  The block copolymer (A) contained in the polyester composition is 5 to 30 parts by mass, the polylactic acid (B) is 40 to 90 parts by mass, and the calcium carbonate (C) is 5 to 30 parts by mass. It is preferable that it is the range of these. Within such a range, a polyester composition having excellent impact resistance and molding processability can be obtained.

  The polyester composition of the present invention obtained by the method as described above has a form (morphology) in which the block copolymer (A) is dispersed in a matrix formed by the polylactic acid (B). The dispersion of the block copolymer (A) can be confirmed by various methods. For example, the polyester structure of the block copolymer (A) is formed in the matrix formed by the polylactic acid (B) by the method described later. It can be confirmed based on the fact that a domain derived from the unit (II) is formed and a so-called sea-island type microphase separation structure is formed.

  The block copolymer (A) is dispersed, for example, by embedding part of the polyester composition in a visible light curable resin and dyeing with ruthenium tetroxide for 1 to 2 hours, and then in liquid nitrogen overnight. It can confirm by observing using the transmission electron microscope (The JEOL datum company make, JEM-200CX) the test piece obtained by leaving to stand and then ultra-thinning using an ultramicrotome. The polyhydroxycarboxylic acid structural unit (I) constituting the polylactic acid (B) and the block copolymer (A) is not dyed, but the polyester structural unit (II) constituting the block copolymer (A) is gray. Stained. The average domain diameter of the domain formed by the polyester structural unit (II) can be obtained by measuring the major axis and the minor axis of a certain number of particles of the domain dyed in gray and averaging all of them.

The average domain diameter of the domains formed by the polyester structural unit (II) that can be confirmed by the above method is preferably in the range of 0.05 μm to 5 μm. When the average domain diameter of such domains is within the above range, it is possible to efficiently disperse the impact (load) applied to the polyester composition of the present invention, and as a result, the impact resistance can be improved. Can not.

  In addition, the calcium carbonate (C) contained in the polyester composition of the present invention is present in the domain more than in the matrix. Specifically, 70% by mass to 100% by mass of calcium carbonate (c1) based on the total amount of calcium carbonate (C) to be used is present in the domain formed by the polyester structural unit (II) constituting the domain. This is a state in which the calcium carbonate (c1) is encapsulated by the polyester structural unit (II) forming the domain. Among them, the presence of calcium carbonate in the range of 90% by mass to 100% by mass of the total amount of the calcium carbonate (C) in the domain provides a polyester composition capable of exhibiting excellent impact resistance. Is preferable.

  The form (morphology) in which the calcium carbonate is encapsulated in the polyester structural unit (II) is observed by the same method as the method for observing the dispersion of the block copolymer (A) in the polylactic acid (B). can do. Calcium carbonate (C) is stained black when observed by this method.

  Various additives can be used in the polyester composition of the present invention as necessary. Examples of the additive include organic fillers other than calcium carbonate (C), inorganic fillers, antioxidants, ultraviolet absorbers, stabilizers, lubricants, antiblocking agents, surfactants, colorants, foaming agents, plasticizers, and the like. Can be used.

  The polyester composition of the present invention can be formed into a film, sheet, or the like under known and usual conditions by an injection molding method, an extrusion molding method, a vacuum / pressure forming method, a vacuum forming method, or the like.

  The polyester composition of the present invention uses the crystallinity of the block copolymer (A) or polylactic acid (B), and when it is molded by the above-described method, for the purpose of improving heat resistance and the like. A crystallization treatment may be performed. For example, when the polyester composition is molded by an injection molding method, a temperature higher than a mold temperature (approximately 30 to 40 ° C.) in a normal injection molding method (crystallization treatment temperature: approximately 70 ° C. to approximately It can be crystallized by injecting the polyester composition using a mold adjusted to 120 ° C.

In addition, when the polyester composition is molded by a thermoforming method such as a vacuum forming method, the polyester composition heated and softened in a shaping mold adjusted in advance to a crystallization treatment temperature (70 ° C to 120 ° C). It can crystallize by sticking the film or sheet which consists of a thing.

  The molded product obtained by molding the polyester composition of the present invention can be used for applications requiring high impact resistance, such as Sunday sundries, home appliance parts, housings, and automobile parts. .

<< Production Example 1 >> Production Example of Polyester (II-1) A reactor is charged with 1 molar equivalent of sebacic acid (hereinafter abbreviated as SeA) and 1.4 molar equivalent of propylene glycol (hereinafter abbreviated as PG). The temperature was raised from 150 ° C. to 230 ° C. in an nitrogen stream at 10 ° C. per hour, and the mixture was stirred while distilling off the generated water to conduct an esterification reaction. After reacting at 230 ° C. for 2 hours, 100 ppm of titanium tetraisopropoxide as a polymerization catalyst was added to the total amount of SeA and PG, and reacted at 200 Pa for 8 hours.
After completion of the reaction, 110 ppm of 2-ethylhexanoic acid phosphate as a deactivator for the polymerization catalyst was added to the total amount of SeA and PG, and the mixture was stirred at 333 Pa and 220 ° C. for 1 hour, whereby the number average molecular weight was 35. Polyester (II-1) having a weight average molecular weight of 63,000 was obtained.

<< Production Example 2 >> Production Example of Block Copolymer (A-1) A reactor was charged with 50 g of the polyester (II-1) obtained in Production Example 1, and heated at a jacket temperature of 200 ° C. in a nitrogen atmosphere. Thereafter, 50 g of polylactic acid (B-1) [number average molecular weight 92,000, weight average molecular weight 170,000, L form: D form = 98.5: 1.5 (molar ratio)] was added and melted. Mixed. After visually confirming that the polyester (II-1) and the polylactic acid (B-1) were uniformly melt-mixed, the mixture was further melt-mixed for 2 hours. Subsequently, 200 ppm of titanium tetrabutoxide was added as an esterification catalyst with respect to the total amount of the molten mixture, and reacted at a reduced pressure of 80 Pa for 4 hours. Next, as a deactivator for the esterification catalyst after completion of the reaction, 500 ppm of 2-ethylhexanoic acid phosphate is added to the total amount of the reaction product, and the number average molecular weight is 58,000 and the weight average molecular weight is 125,000. A copolymer (A-1) was obtained.

(Example 1) Polyester composition 1.06 kg of block copolymer (A-1), 4.27 kg of polylactic acid (B-1), calcium carbonate (C-1) having an average particle size of 0.15 μm (Shiraishi After dry blending 1.33 kg of CALSHITEC Vigot-15) manufactured by Calcium Co., Ltd., they were melt-mixed and pelletized using a twin screw extruder (manufactured by Toyo Seiki Seisakusho Co., Ltd.) having a cylinder temperature of 220 ° C.

  Next, using a 1 oz vertical injection molding machine (manufactured by Yamashiro Seiki Seisakusho Co., Ltd.) with a cylinder temperature of 185 ° C. and a mold temperature of 30 ° C., a No. 2 test piece for Izod impact test in the test standard JIS K 7110 Produced. Next, using a notching machine (manufactured by Techno Supply Co., Ltd.), the No. 2 test piece was notched so as to have the shape of No. 2 A in the test standard JIS K 7110.

The Izod impact value of the test piece obtained by the above method was measured using a universal impact tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.) according to the test standard JIS K7110. Impact resistance required of the polyester composition of the present invention, i.e., the Izod impact value is different depending on the application being used, it is preferably approximately 6 kJ / m ² or more, more preferably 10 kJ / m ² or more .

A portion of the test piece notched by the above method was embedded in a visible light curable resin (D-800, JEOL Datum Co., Ltd.), stained with ruthenium tetroxide for 1 to 2 hours, and then liquid nitrogen. Left in it overnight. Whether or not they form a microphase-separated structure by observing what was ultra-thinned using an ultramicrotome using a transmission electron microscope (JEM-200CX, manufactured by JEOL Datum). Was confirmed visually.
Although the polyhydroxycarboxylic acid structural unit constituting the polylactic acid (B-1) and the block copolymer (A-1) is not dyed, the polyester structural unit (II-1 constituting the block copolymer (A-1)) is not dyed. ) Is dyed gray and calcium carbonate is dyed black so that they can be distinguished.

The average domain diameter of the domain formed by the polyester structural unit encapsulating the calcium carbonate is obtained by measuring the major and minor axes of a certain number of particles of the domain dyed in gray and averaging all of them. Asked. If the domain contains calcium carbonate, measure the domain diameter in the encapsulated state. If the domain does not contain calcium carbonate, measure the domain diameter in the unencapsulated state. It was measured.
The mass ratio of calcium carbonate present in the domain to the total amount of calcium carbonate was calculated based on the occupied area shown in the photograph taken using the transmission electron microscope.

(Example 2) Polyester composition 0.8 kg of block copolymer (A-1) and 1 kg of calcium carbonate (C-1) were melt-kneaded using the same twin-screw extruder as in Example 1. A master batch was prepared by pelletization. The temperature of the twin screw extruder was 190 ° C. Next, the master batch and 3.2 kg of polylactic acid (B-1) were melt kneaded and pelletized using the same twin screw extruder as described above. Using the obtained pellet, a test piece was prepared in the same manner as in Example 1, and the Izod impact value of the test piece was measured in the same manner as in Example 1.

(Example 3) Polyester composition Implemented except that calcium carbonate (C-2) (average particle size 0.05 μm, white gloss flower CC manufactured by Shiraishi Calcium Co., Ltd.) was used instead of calcium carbonate (C-1). Pellets were produced in the same manner as in Example 1. Using the obtained pellet, a test piece was prepared in the same manner as in Example 1, and the Izod impact value of the test piece was measured in the same manner as in Example 1.

(Example 4) Polyester composition Instead of calcium carbonate (C-1), calcium carbonate (C-3) (average particle size 1.2 μm, PO-220-B-10 manufactured by Shiraishi Calcium Co., Ltd.) is used. Except that, pellets were produced in the same manner as in Example 1. Using the obtained pellet, a test piece was prepared in the same manner as in Example 1, and the Izod impact value of the test piece was measured in the same manner as in Example 1.

(Example 5) Polyester composition Instead of calcium carbonate (C-1), calcium carbonate (C-4) (average particle size 2.3 μm, PO-180-B-10 manufactured by Shiroishi Calcium Co., Ltd.) was used. Except that, pellets were produced in the same manner as in Example 1. Using the obtained pellet, a test piece was prepared in the same manner as in Example 1, and the Izod impact value of the test piece was measured in the same manner as in Example 1.

(Comparative example 1) Polyester composition Polylactic acid (B-1) is similar to Example 1 using a 1 oz vertical injection molding machine (manufactured by Yamashiro Seiki Co., Ltd.) having a cylinder temperature of 210 ° C and a mold temperature of 30 ° C. A test piece was prepared by the method described above, and the Izod impact value of the test piece was measured in the same manner as in Example 1.

(Comparative example 2) Polyester composition Except not using a calcium carbonate (C-1), a pellet is produced by the method similar to Example 1, and a test piece is used by the method similar to Example 1 using this pellet. Was made. The Izod impact value of the test piece was measured in the same manner as in Example 1.

(Comparative Example 3) Other than not using the polyester composition block copolymer (A-1) and changing the cylinder temperature of the 1 oz vertical injection molding machine (manufactured by Yamashiro Seiki Seisakusho Co., Ltd.) to 210 ° C. Prepared a test piece by the same method as in Example 1, and measured the Izod impact value of the test piece by the same method as in Example 1.

(Comparative Example 4) Polyester Composition A twin-screw extruder similar to Example 1 (Co., Ltd.) such that polylactic acid (B-1) has a blending ratio of 3.2 kg and calcium carbonate (C-1) of 1 kg. A master batch was prepared by pelletizing by melt kneading using Toyo Seiki Seisakusho. The cylinder temperature of the twin screw extruder was 220 ° C. Next, the master batch and 0.8 kg of the block copolymer (A-1) were melt-kneaded using a twin screw extruder to produce pellets. Using the obtained pellets, test pieces were prepared in the same manner as in Example 1, and the Izod impact value to the test was measured in the same manner as in Example 1.

Claims (6)

Block copolymer (A) having polyhydroxycarboxylic acid structural unit (I) and polyester structural unit (II) obtained by reacting dicarboxylic acid and diol, polylactic acid (B), and particulate carbonic acid Containing calcium (C),
In the matrix formed by the polylactic acid (B), the polyester structural unit (II) derived from the block copolymer (A) has a microphase separation structure in which a domain is formed,
And the polyester composition characterized by 70 mass%-100 mass% calcium carbonate (c1) of the said calcium carbonate (C) whole quantity exist in the said domain. The polyester composition according to claim 1, wherein the polyester structural unit (II) has 8 to 24 carbon atoms. The polyester composition according to claim 1, wherein the polyester structural unit (II) is derived from a polyester obtained by an esterification reaction of propylene glycol and sebacic acid. The polyester composition according to claim 1, wherein the particulate calcium carbonate (C) has an average particle diameter in the range of 0.03 to 3 μm. The block copolymer (A) is 5 to 30% by mass, the polylactic acid (B) is 40 to 90% by mass, and the calcium carbonate (C) is 5 to 30% by mass. Polyester composition. A method for producing a polyester composition, comprising melt-kneading a mixture containing the block copolymer (A) and the calcium carbonate (C) and the polylactic acid (B) under heating.