JP2008101032A - Lactic acid-oxalate block copolymer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a lactic acid-oxalate block copolymer having toughness superior to that of polylactic acid. <P>SOLUTION: (1) The lactic acid-oxalate block copolymer comprises a polylactic acid block and a polyoxalate block each having a number-average molecular weight of 2,000-50,000 respectively. (2) The crystalline lactic acid-oxalate block copolymer according to the copolymer (1) comprises a polylactic acid block and a polyoxalate block each having an average number of blocks of 0.1-9, respectively. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a lactic acid-oxalate copolymer, more particularly to a lactic acid-oxalate block copolymer, and more particularly to a lactic acid-oxalate block copolymer having a controlled molecular structure.

  Polylactic acid has excellent characteristics as a biodegradable resin, but is not always satisfactory in terms of toughness and impact resistance. For improving the physical properties of such polylactic acid, for example, a copolymer of lactide and ethylene oxalate is disclosed (Patent Document 1), but its mechanical strength is specifically disclosed. No block copolymer was specifically disclosed.

  In addition, an aliphatic polyester obtained by polycondensation reaction of an aliphatic hydroxycarboxylic acid polymer (polylactic acid or the like) with an aliphatic polycarboxylic acid and an aliphatic polyhydric alcohol polymer (polyester) (Patent Document 2) In addition, a lactic acid-based polyester (Patent Document 3) obtained by copolymerization of a lactic acid component and a polyester component has been proposed. However, as for the oxalate-based copolymer, oxalic acid is only exemplified as the aliphatic dicarboxylic acid constituting the polyester component, and the corresponding copolymer (lactic acid-oxalate copolymer) has physical properties and the like. There was no specific description including

Furthermore, aliphatic block copolyesters obtained by polycondensation reaction of polylactic acid and aliphatic polyesters are also known (Patent Document 4). For oxalate-based copolymers, fats constituting the aliphatic polyesters are known. As one of the group dicarboxylic acids, oxalic acid is only exemplified in the same manner as in the above document, and the corresponding copolymer (lactic acid-oxalate copolymer) is not specifically described including physical properties and the like. It was.
JP-A-9-316181 Japanese Patent Laid-Open No. 10-12076 JP 2002-167497 A JP-A-10-120773

  An object of the present invention is to provide a lactic acid-oxalate copolymer having toughness compared to polylactic acid.

  As a result of intensive studies to solve the above problems, the present inventors can obtain a lactic acid-oxalate block copolymer having a controlled molecular structure by using a lactic acid-oxalate copolymer as a block copolymer. The lactic acid-oxalate block copolymer was found to have toughness compared to polylactic acid, and the present invention was completed.

That is, the subject of this invention is solved by the following invention.
1) A lactic acid-oxalate block copolymer composed of a polylactic acid block and a polyoxalate block, wherein the polylactic acid block and the polyoxalate block each have a number average molecular weight in the range of 2000 to 50000.
2) The lactic acid-oxalate block copolymer of 1) above, wherein the average number of blocks of the polylactic acid block and the polyoxalate block is in the range of 0.1 to 9, respectively.
3) The lactic acid-oxalate block copolymer of 1) above, wherein the number average molecular weight is in the range of 18,000 to 70000.

4) The lactic acid according to 1) above, wherein the ratio (lactic acid / oxalate) of the lactic acid structural unit constituting the polylactic acid block to the oxalate structural unit constituting the polyoxalate block is in the range of 5/95 to 95/5 on a weight basis. An oxalate block copolymer.
5) The lactic acid-oxa of any one of 1) to 4) above, wherein the block copolymer forms a microphase-separated structure comprising a polylactic acid block aggregate, a polyoxalate block aggregate, and an intermediate phase. Rate block copolymer.
6) The lactic acid-oxalate block copolymer according to 5), wherein any one of the polylactic acid block aggregate part and the polyoxalate block aggregate part is a dispersed phase and has a size of 0.5 to 5 microns.
7) The lactic acid-oxalate block copolymer according to any one of 1) to 6), wherein a crystal melting peak is observed in differential scanning calorimetry.

8) The lactic acid-oxalate block copolymer according to any one of 1) to 7), wherein the polylactic acid block is represented by the formula (1) and the polyoxalate block is represented by the formula (2).
(In the formula, m is a positive number representing the average number of repeating lactic acid structural units and corresponds to the number average molecular weight of the polylactic acid block. N is a positive number representing the average number of repeating oxalate structural units; (It corresponds to the number average molecular weight of the oxalate block. A represents an alkylene group having 3 to 12 carbon atoms in the main chain, which may contain a branched structure or an alicyclic structure.)

Furthermore, the present invention also includes the following inventions.
9) A polylactic acid composition comprising the lactic acid-oxalate block copolymer according to any one of 1) to 8) above and polylactic acid.
10) The polylactic acid composition according to 9), further comprising a polyoxalate.

  According to the present invention, a lactic acid-oxalate copolymer having toughness compared to polylactic acid can be provided. That is, the lactic acid-oxalate block copolymer of the present invention has a higher melting point (has heat resistance) than the known (patent document 1) lactic acid-oxalate copolymer, and also has a higher melting point than polylactic acid. The elongation is remarkably large without greatly reducing the elastic modulus and strength, and the hydrolysis resistance is further improved. Moreover, when it mix | blends with polylactic acid individually or together with polyoxalate, the low elongation characteristic which is a fault of polylactic acid can also be improved. As a result, a novel lactic acid-based resin (lactic acid-oxalate copolymer and polylactic acid composition) that can make use of the characteristics of polylactic acid and make up for its drawbacks in various applications where it has been difficult to use polylactic acid. ) Can be provided.

[Polyoxalate]
The polyoxalate used in the present invention is preferably represented by the formula (3). In the formula, p is a positive number representing the average number of repeating oxalate structural units (—A—O—CO—COO—) corresponding to the number average molecular weight of polyoxalate, and A is the same as described above. The number average molecular weight of the polyoxalate is preferably in the range of 20000-100,000 in order to satisfy both the mechanical strength of the molded product and the viscosity at the time of melt molding, but is preferably 20000-80000, more preferably 20000-75000. In particular, the range of 20000 to 70000 is more preferable. If the number average molecular weight is less than 20,000, the mechanical strength of the molded product is low, and if it exceeds 100,000, the melt viscosity becomes high and the molding process becomes difficult. The weight average molecular weight of the polyoxalate is preferably in the range of 30,000 to 200,000, and the molecular weight distribution defined by the ratio of the weight average molecular weight to the number average molecular weight is preferably in the range of 1 to 5.

  The aliphatic diol unit of the polyoxalate is defined by the alkylene group A of the above formula. If the carbon chain of A is too short, the polyoxalate will be hard and brittle, and if the carbon chain of A is too long, the polyoxalate will become hydrophobic and the chemical affinity with polylactic acid will decrease. The alkylene group A in the formula preferably has 3 to 12 carbon atoms in the main chain. The alkylene group A may have an even or odd number of carbon atoms in the main chain, and is not limited to a straight chain structure, and may include a branched structure or an alicyclic structure.

  As the aliphatic diol unit source, one or more aliphatic diols having 3 to 12 carbon atoms in the main chain of the alkylene group A are preferably used. Examples of such aliphatic diols include 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, and 1,8-octanediol. 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, neopentyl glycol, trans (or cis) -1,4-cyclohexanedimethanol, 2,4 -Diethyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, 2-ethyl-2-butyl-1,3-propanediol, 2,2,4-trimethyl-1,3-propanediol 2,2-diethyl-1,3-propanediol, 2-ethyl-1,3-hexanediol and the like.

  Since the structure of the aliphatic diol unit significantly affects the melting point and crystallization speed of the polyoxalate, an appropriate aliphatic diol is selected according to the melt processing conditions or the use temperature of the molded product. Among the aliphatic diols, those capable of obtaining a polyoxalate having a melting point close to that of polylactic acid are preferable. For example, 1,4-cyclohexanedimethanol is preferable.

  If necessary, the aliphatic diol may contain a part of a polyhydric alcohol compound (excluding the aliphatic diol) for the purpose of improving the melt processability of the polyoxalate or the mechanical properties of the molded product. Good. Examples of such polyhydric alcohol compounds include glycerol and 1,2,6-hexanetriol. However, the content ratio of the polyhydric alcohol compound is within a range that does not impair the effects of the invention. For example, it is preferably 30 mol% or less, more preferably 10 mol% or less of the aliphatic diol. Too much polyhydric alcohol compound is not preferred because it may cause gelation during polymerization or molding.

  Further, the aliphatic diol may partially contain an aromatic diol as desired, for example, to increase the heat resistance of the polyoxalate. Examples of such aromatic diols include bisphenol A, p-xylylene glycol, and hydroquinone. However, the content ratio of the aromatic diol is in a range that does not impair the effects of the invention, and is, for example, less than 50 mol% of the aliphatic diol. If the amount of aromatic diol is too large, the melting point becomes high, and the molding process temperature rises and molding may become difficult, which is not preferable.

  As the oxalic acid source of the polyoxalate used in the present invention, dialkyl oxalate (dimethyl oxalate, diethyl oxalate, dibutyl oxalate, etc.), diaryl oxalate (diphenyl oxalate, di-p-tolyl oxalate, etc.) And oxalic acid, among which dialkyl oxalate and diaryl oxalate are preferred.

  Furthermore, the oxalic acid source may contain a part of an aromatic dicarboxylic acid diester such as dimethyl terephthalate or a carbonic acid ester such as diphenyl carbonate as desired to increase the heat resistance of the polyoxalate. However, the content of these esters is less than 50 mol% of the oxalic acid source.

  The polyoxalate used in the present invention is produced from an oxalic acid source and an aliphatic diol by a generally well-known polycondensation reaction (preferably melt polymerization). For example, it can be produced by charging the oxalic acid source and the aliphatic diol together with a catalyst into a reactor and subjecting them to a polycondensation reaction under suitable polymerization conditions. At this time, the polycondensation reaction is preferably performed by a pre-polycondensation step and a post-polycondensation step as described in JP-A-2004-143400.

  As the catalyst, compounds such as P, Ti, Ge, Zn, Fe, Sn, Mn, Co, Zr, V, Ir, La, Ce, Li, Ca, and Hf are preferable. In particular, organic titanium compounds and organotin compounds are preferable. For example, titanium alkoxide (titanium tetrabutoxide, titanium tetraisopropoxide, etc.), distanoxane compound (1-hydroxy-3-isothiocyanate-1,1,3,3-tetra) Butyl distanoxane, etc.), tin acetate, dibutyltin dilaurate, butyltin hydroxide hydrate and the like are preferred because of their high activity.

  In the polycondensation reaction, when dialkyl oxalate is used as the oxalic acid source, in order to increase the molecular weight of polyoxalate, dialkyl oxalate is used excessively with respect to the aliphatic diol, and the water concentration in the raw material It is necessary to control (weight basis) to less than 2000 ppm. That is, the ratio of use of dialkyl oxalate and aliphatic diol (feeding molar ratio) is 0.5 ≦ OL / OX <1, where OX is the number of moles of dialkyl oxalate and OL is the number of moles of aliphatic diol. The range is preferably 0.6 ≦ OL / OX <1, more preferably 0.7 ≦ OL / OX <1, and particularly preferably 0.8 ≦ OL / OX <1. The water concentration in the reaction raw material is controlled to less than 2000 ppm, preferably 10 to 2000 ppm.

  On the other hand, when diaryl oxalate is used as the oxalic acid source, it is preferable to use an aliphatic diol in an amount of 0.95 to 1.05 times mol with respect to the diaryl oxalate, and the water concentration (weight basis) in the reaction raw material is It is necessary to control to less than 1000 ppm. This reaction raw material contains a catalyst in addition to dialkyl oxalate or diaryl oxalate and an aliphatic diol. Dialkyl oxalate and diaryl oxalate may contain a catalyst (aromatic carboxylic acid ester, carbonate ester). ) And aliphatic diols (polyhydric alcohol compounds and aromatic diols) that may be contained therein.

  In the polycondensation reaction, a known reactor can be used. However, in order to advance the reaction efficiently, it is necessary to facilitate the evaporation of the alcohol generated during the reaction. What can ensure a wide gas-liquid contact surface is preferable. For example, if it is a vertical reactor, a flask equipped with a stirrer or a reaction kettle can be used. Instead of a stirrer, a reactor equipped with a device capable of bubbling an inert gas such as nitrogen into the reaction solution can also be used. it can. In the horizontal reactor, a kneading apparatus having one or two stirring blades is preferable because the surface area can be efficiently increased. The reactor is preferably for high viscosity. In the polycondensation reaction, a heat-resistant agent may be added if necessary to prevent thermal degradation. Further, a catalyst deactivator such as a phosphate ester compound (such as phosphate ester) may be added after the reaction to deactivate or reduce the activity of the catalyst.

  The polyoxalate thus obtained is represented by the above formula (3) and has either an alkyl group, an aryl group, a hydroxyl group or a formate group at the terminal. That is, in this polyoxalate, the structural unit is —A—O—CO—COO— and the end groups are as follows (where A is the same as described above, and R is dialkyl oxalate or oxalic acid): An alkyl group or an aryl group derived from diaryl), and the number average molecular weight is preferably within the above range.

(I) When the terminal group bonded to the molecular terminal on the alkylene group (-A-) side of the structural unit is HO-: The terminal group bonded to the molecular terminal on the other oxycarbonyl group (-COO-) side is: One of -R, -AOH, and -AOCHO.
(B) When the terminal group bonded to the molecular terminal on the alkylene group (-A-) side of the structural unit is ROCOCOO- or OHCO-: the terminal bonded to the molecular terminal on the other oxycarbonyl group (-COO-) side The group is —R or —AOCHO.

In this _polyoxalate , the terminal hydroxyl group concentration [OH] _POX , the terminal alkoxy or terminal aryloxy group concentration [OR] _POX , and the terminal formate group concentration [OCHO] _POX expressed in units of eq / g, 0.1 ≦ ([OR] _POX + [OCHO] _POX ) / ([OH] _POX + [OR] _POX + [OCHO] _POX ) ≦ 1.0, and further 0.15 ≦ ([OR] _POX + [OCHO] _POX ) / ([OH] _POX + [OR] _POX + [OCHO] _POX ) ≦ 1.0 is more preferable in terms of color tone. [OR] _POX is preferably 1.5 × 10 ^{−5 to} 8.0 × 10 ⁻⁵ eq / g, and [OH] _POX is 4.0 × 10 ⁻⁵ eq / g or less. Is preferred.

[Polylactic acid]
The polylactic acid used in the present invention may be represented by the formula (4) and may have a sufficiently high molecular weight showing practical strength, but the number average molecular weight is 20,000 to 500,000, and further 50,000 to 200,000. Are preferred. In the formula, q is a positive number representing the average number of repeating lactic acid structural units (—CH (CH ₃ ) COO—) corresponding to the number average molecular weight of polylactic acid. As polylactic acid, a commercially available product that is most commonly produced from L-lactic acid and lactide, which is a cyclic dimer thereof, can be used. In addition, polylactic acid may be produced by any method such as ring-opening polymerization method or direct polymerization method, and in the same manner as polyoxalate, a catalyst deactivator is added to deactivate or reduce the activity of the catalyst. Also good.

[Lactic acid-oxalate block copolymer]
The lactic acid-oxalate block copolymer of the present invention is a polylactic acid block in which the number average molecular weight (M _PLA ) of the polylactic acid block and the number average molecular weight (M _POX ) of the polyoxalate block are in the range of 2000 to 50000, respectively. And a block copolymer composed of polyoxalate blocks. In this block copolymer, the average number of blocks of the polylactic acid block and the polyoxalate block is preferably in the range of 0.1 to 9, and the number average molecular weight is preferably in the range of 18000 to 70000.

  When the average block number or the number average molecular weight is out of the above range, the block property is lowered and the crystallinity is not exhibited, so the toughness improving effect is lowered. Further, when the number average molecular weight is less than 18,000, the mechanical properties are not preferable, and when it is more than 70000, the workability is not preferable. The polylactic acid block can be represented by the formula (1), and the polyoxalate block is preferably represented by the formula (2).

  Furthermore, in the block copolymer of the present invention, the ratio of lactic acid structural units constituting the polylactic acid block and oxalate structural units constituting the polyoxalate block (lactic acid / oxalate) is 5/95 to 95/5 on a weight basis. Further, it is preferably in the range of 20/80 to 80/20. If this ratio exceeds 95/5, the effect of the present invention cannot be expected. Conversely, if the ratio is less than 5/95, the original characteristics of polylactic acid are lost.

  And, according to the microstructure observation, the block copolymer of the present invention has a polylactic acid block aggregate part (domain mainly composed of polylactic acid), a polyoxalate block aggregate part (domain mainly composed of polyoxalate), And it is preferable to form the micro phase separation structure which consists of three phases of an intermediate phase (interface phase; domain comprised from both components of polylactic acid and polyoxalate). In this microphase-separated structure, either the polylactic acid aggregate part or the polyoxalate aggregate part is a continuous phase and the other is a dispersed phase, but the size (diameter) of the dispersed phase is about 0.5 to 5 microns. It is preferable that If the average number of blocks and the number average molecular weight are out of the above ranges, the block property is lowered and a clear microphase separation structure is not formed, and a more homogeneous structure than the phase separation structure is formed. It does not appear and the toughness improving effect is reduced.

  That is, the lactic acid-oxalate block copolymer of the present invention is composed of a polylactic acid block and a polyoxalate block whose number average molecular weight is in the above range, and the average number of blocks, the number average of the copolymer Particularly preferred are those in which the molecular weight and the ratio of the lactic acid structural unit to the oxalate structural unit are in the above range. Such a block copolymer of the present invention forms the above-described microphase separation structure, and either one of the polylactic acid aggregate part and the polyoxalate aggregate part becomes a dispersed phase (the other is a continuous phase) and is large in size. The diameter (diameter) is about 0.5 to 5 microns, and a crystal melting peak (melting point) is clearly recognized in differential scanning calorimetry (DSC; temperature rising from room temperature at 10 ° C./min).

  The lactic acid-oxalate block copolymer of the present invention is produced by transesterifying the polyoxalate and polylactic acid. Specifically, it can be produced, for example, by melt-mixing polyoxalate and polylactic acid batchwise or continuously in the operation shown below, and transesterification in the presence of a transesterification catalyst under reduced pressure. .

  That is, after polyoxalate and polylactic acid are charged into a reactor and the inside of the reactor is replaced with an inert gas (nitrogen or the like), the temperature is gradually raised to a temperature not lower than the melting point and lower than the thermal decomposition temperature (for example, 170 In the range of ˜230 ° C., and then, while stirring and / or inert gas bubbling, the contents are uniformly mixed and gradually reduced in pressure so as not to bump (start the reaction), By controlling the final pressure and reaction time according to the reaction temperature and the amount of catalyst, the number average molecular weight of the polylactic acid block and the polyoxalate block, and preferably the average number of these blocks is within the above range. The lactic acid-oxalate block copolymer of the invention can be produced.

  At this time, the reaction time is the number average molecular weight of the polylactic acid block and the polyoxalate block, and preferably the average number of these blocks is in the above range, depending on the final ultimate pressure, the catalyst concentration, the reaction temperature, and the raw material charge amount. It is preferable to control as described above. The final ultimate pressure is preferably lower than 5.0 mmHg (667 Pa), more preferably 0.1 mmHg (13.3 Pa) or higher and lower than 3.0 mmHg (400 Pa) because the reaction time can be shortened. Depending on the amount of catalyst and the reaction time, only the normal pressure may be used instead of the reduced pressure, and a lactic acid-oxalate block copolymer that does not impair the effects of the present invention can be obtained.

  Specifically, for example, the raw material charge amount is 40 g in total (polylactic acid 20 g, polyoxalate 20 g), the catalyst concentration is about 1000 ppm, and the final ultimate pressure is 0.5 mmHg (with respect to the total amount of polylactic acid and polyoxalate). If the reaction temperature is 200 ° C., the desired product can be obtained in a reaction time of about 0.5 hours. The polyoxalate and polylactic acid are preferably melt-mixed under an inert gas stream, but the pressure at that time may be normal pressure.

  The charge ratio of polyoxalate and polylactic acid (polylactic acid / polyoxalate) is 5/95 to 95/5 on a weight basis, as is the ratio of lactic acid structural units to oxalate structural units in the block copolymer of the present invention. Furthermore, it may be in the range of 20/80 to 80/20, and the amount of the transesterification catalyst used is not particularly limited as long as it substantially accelerates the reaction. However, since the coloring and depolymerization may be promoted when the amount of the catalyst used is too large, the amount of the catalyst used is 10 to 2000 ppm, more preferably 20 to 1500 ppm on a weight basis with respect to the total amount of polyoxalate and polylactic acid. It is preferable that it is the range of these. The reaction temperature is not particularly limited as long as it is higher than the melting point of polyoxalate and polylactic acid and lower than the thermal decomposition temperature. However, since the melting point of polylactic acid is about 167 ° C, it is preferably 170 ° C to 230 ° C, more preferably 180 ° C. It is the range of -220 degreeC.

  The same transesterification catalyst as in the production of polyoxalate can be used, and an organic titanium compound and an organic tin compound are likewise preferred. The addition timing is not particularly limited as long as the reaction rate is not significantly reduced, and may be any of charging, melting, homogeneous mixing, and transesterification. In addition, when the transesterification catalyst contained in polyoxalate or polylactic acid is not deactivated or the activity is not lowered, it can be used as it is (without newly adding a catalyst). The reactor may be the same as that used in the production of polyoxalate.

  The lactic acid-oxalate block copolymer used in the present invention can be used alone, but if necessary, other components (additives, other polymers, etc.) may be blended alone or in combination. It can also be used as a composition (a material comprising a lactic acid-polyoxalate block copolymer; powder, chip, beads, etc.). Examples of additives include hydrolysis inhibitors, crystal nucleating agents, pigments, dyes, heat-resistant agents, anti-coloring agents, antioxidants, weathering agents, lubricants, antistatic agents, stabilizers, fillers (talc, clay, Montmorillonite, mica, zeolite, zonotlite, calcium carbonate, carbon black, silica powder, alumina powder, titanium oxide powder, etc.), reinforcement (glass fiber, carbon fiber, silica fiber, cellulose fiber, etc.), flame retardant, plasticizer, waterproof Agents (wax, silicone oil, higher alcohol, lanolin and the like) and the like, and can be added within a range not impairing the effects of the present invention.

  Moreover, natural or synthetic polymer is mentioned as another polymer. Examples of the natural polymer include starch, cellulose, chitosan, alginic acid, and natural rubber. Examples of the synthetic polymer include polycaprolactone or a copolymer thereof, polyglycolic acid, polysuccinic acid ester, and succinic acid. Acid / adipic acid copolyester, succinic acid / terephthalic acid copolyester, poly (3-hydroxybutanoic acid), (3-hydroxybutanoic acid / 4-hydroxybutanoic acid) copolymer, polyvinyl alcohol, polyethylene, polyethylene terephthalate, Polybutylene terephthalate, polyvinyl acetate, polyvinyl chloride, polystyrene, polyglutamic acid ester, polyester rubber, polyamide rubber, styrene-butadiene-styrene block copolymer (SBS), rubber or elastomer such as hydrogenated SBS, etc. It can be mentioned.

  The lactic acid-oxalate block copolymer of the present invention thus obtained can further improve the thermal stability by deactivating or reducing the activity of the transesterification catalyst contained therein. The catalyst deactivation can be performed by a known method. For example, a method of adding a known catalyst deactivator (chelating agent, acidic phosphate ester, etc.) may be used.

[Polylactic acid composition]
Although the lactic acid-oxalate block copolymer of the present invention can be used alone, it can also be used as a polylactic acid composition containing it. This polylactic acid composition comprises a lactic acid-oxalate block copolymer and polylactic acid, and the ratio of both components is not particularly limited, but in order not to impair the characteristics of polylactic acid, The proportion is preferably 50 to 5% of the combined polymer and 50 to 95% of the polylactic acid. In addition, the polylactic acid composition may further contain polyoxalate, and in that case, the proportion of the block copolymer is 5 to 30%, polylactic acid is 35 to 85%, and polyoxalate is 10 to 45%. It is preferable. All these ranges are based on weight. Furthermore, other components (additives, other polymers, etc.) can be blended in the polylactic acid composition singly or in the same manner as in the lactic acid-oxalate block copolymer. The components that can be blended are the same as in the case of the copolymer.

  The polylactic acid composition is generally produced by a melt kneading method. For example, the block copolymer of the present invention and polylactic acid (and polyoxalate) are produced by melt-mixing in the above-described proportions (and blending the other components as necessary) by a known method. For example, it can be dry blended using a solid mixer such as a tumbler, but the most common method is a continuous kneading apparatus such as a single screw extruder, a twin screw extruder, a twin screw rotor kneader, or an open roll. These are kneaded and melt kneaded using a batch kneader such as a kneader or Banbury mixer, and there are no particular restrictions on the kneading method and conditions. In addition, a solution blend method using a solvent may be used.

  The lactic acid-polyoxalate block copolymer and the polylactic acid composition of the present invention can be formed into molded products such as films or sheets, various molded products, and textile products by various molding methods. The film or sheet can be obtained by a known method such as an extrusion method (T-die method, inflation method, etc.), a press method, a calendar roll method. The resulting film or sheet can be stretched (uniaxially stretched or biaxially stretched), and a laminate with other polymer, metal, paper or the like can be produced.

  Examples of the various molded products include injection molded products, hollow molded products, thermoformed products (vacuum molded products, compressed air molded products, etc.), foam molded products, and press molded products. Examples of the fiber product include monofilaments, multifilaments, chops, and nonwoven fabrics, and other processed products such as ropes, nets, felts, and woven fabrics.

  The molded product obtained from the lactic acid-polyoxalate block copolymer and the polylactic acid composition of the present invention can be used for a wide variety of known uses. Applications of films or sheets include agricultural materials (multi-films for agriculture and horticulture, seed tape, pesticide bags, etc.), food waste bags (compostable garbage bags, garbage bags, etc.), office supplies (paper resource recovery) Coated paper, printed laminate, card cover, window frame envelope, printing paper cover film, etc.), general packaging applications (paper diaper pack sheet, laundry bag, foam sheet, shrinkage film for miscellaneous goods, retort food pack, food packaging film) , Wrap film, etc.), shopping bags, disposable gloves and the like.

  Various molded products can be used for food (food trays, food containers, food or beverage bottles, fresh food boxes, tableware, etc.), daily goods (cosmetics containers, detergent containers, shampoo containers, toiletries, etc.), Agricultural / horticultural relations (nurturing materials, pots, planters, etc.), office supplies, sports / leisure supplies, medical equipment, electrical / electronic parts, computer / information equipment parts, automotive parts, etc.

  In addition, the use of textile products includes various nets (fish nets, insect nets, etc.), various ropes (agricultural ropes, tree ropes, etc.), various threads (fishing lines, sutures, etc.), various non-woven products (paper diapers, Sanitary and hygiene products), filters, clothes, and the like.

  Next, the present invention will be specifically described with reference to examples and comparative examples. In addition, characterization, structural analysis, physical property evaluation, etc. were performed as follows.

1. Characterization of polyoxalate (1) Number average molecular weight (M _n ): Calculated by the following formula based on the signal intensity obtained from ¹ H-NMR spectrum. ¹ H-NMR was measured using JNM-EX400WB (manufactured by JEOL Ltd.) under the conditions of solvent CDCl ₃ , 32 times of accumulation, and sample concentration of 5% by weight.

An example of using dimethyl oxalate as the dialkyl oxalate is shown below.
_{M n = n p × M p} + n OH × (M DOL -17) + n OCHO × 45.02 + n OCH3 × 103.06

However, each term in the formula is defined as follows.
N _p = N _p / [(N _OH + N _OCHO + N _{OCH 3} ) / 2]
N _OH = N _OH / [(N _OH + N _OCHO + N _{OCH 3} ) / 2]
N _OCHO = N _OCHO / [(N _OH + N _OCHO + N _{OCH 3} ) / 2]
N _OCH3 = N _CCH3 / [(N _OH + N _OCHO + N _{OCH 3} ) / 2]
N _p = {S _p / s _p −1} / s _p
・ N _OH = S _OH / s _OH
・ N _OCHO = S _OCHO / s _OCHO
・ N _OCH3 = S _OCH3 / s _OCH3

Here, each term has the following meaning.
· N _p: Total oxalate structural units excluding the terminal oxalate structural units.
N _p : number of oxalate structural units per molecule S _p : integral value of signal based on arbitrary hydrogen in oxalate structural units excluding terminal oxalate structural units (for example, in the case of 1,4-cyclohexanedimethanol) Is the integrated value of the 3.95 to 4.42 ppm signal based on its methylene protons).
· S _p: The number of hydrogens counted in the integration value S _p (e.g., in the case of 1,4-cyclohexanedimethanol 2).

-N _OH : Total number of terminal hydroxyl groups.
N _OH : number of terminal hydroxyl groups per molecule.
S _OH : an integrated value of a signal based on any hydrogen that can identify the terminal hydroxyl group (for example, in the case of 1,4-cyclohexanedimethanol, an integrated value of a signal of 3.40 to 3.60 ppm based on the methylene proton).
S _OH : Number of hydrogens counted in the integral value S _OH (for example, 2 for 1,4-cyclohexanedimethanol).

-N _OCHO : total number of terminal formate groups.
N _OCHO : number of terminal formate groups per molecule.
S _OCHO : The integral value of the signal based on any hydrogen that can identify the terminal formate group (for example, in the case of 1,4-cyclohexanedimethanol, the integral value of the signal of 8.10 ppm based on the formyl proton).
S _OCHO : Number of hydrogens counted in the integral value S _OCHO (= 1).

-N _OCH3 : Total number of terminal methoxy groups.
N _OCH3 : number of terminal methoxy groups per molecule.
S _OCH3 : The integral value of the signal based on any hydrogen that can identify the terminal methoxy group (for example, in the case of 1,4-cyclohexanedimethanol, the integral value of the signal of 3.90 ppm based on the methyl proton).
S _OCH3 : Number of hydrogens counted in the integral value S _OCH3 (= 3).

M _DOL : Molecular weight of the aliphatic diol constituting the oxalate structural unit.
· M _p: oxalate molecular weight of the structural units.

(2) End group concentration: The end group concentration was determined from the ¹ H-NMR spectrum. An example of using dimethyl oxalate as the dialkyl oxalate is shown below. The measurement conditions for n _OH , n _OCHO , n _{OCH 3} , M _n and ¹ H-NMR are the same as described above.
(I) Terminal hydroxyl group concentration [OH] = n _OH / M _n
(Ii) Terminal formate group concentration [OCHO] = n _OCHO / M _n
(Iii) terminal methoxy group concentration _{[OCH 3] = n OCH3 /} M n

2. Structural analysis of lactic acid-oxalate block copolymer (1) Number average molecular weight (M _n ): Calculated by the following formula based on the signal intensity obtained from ¹ H-NMR spectrum. An example of using polycyclohexylene dimethylene oxalate obtained from dimethyl oxalate and 1,4-cyclohexanedimethanol as a polyoxalate block is shown below. The measurement conditions of ¹ H-NMR are the same except that the model used is changed to XWIN-NMR500 (manufactured by Bruker).
M _n = M _(POX-OMe) + M _(PLA-OMe) + M _OCHO + M _(POX-OH) + M _(PLA-OH) + M _POX + M _PLA + M _{(POX-OCO-PLA)} + M _{(POX-COCOO-PLA)}

However, each term in the formula is defined as follows.
・ M _(POX-OMe) = n _(POX-OMe) x 31
・ M _(PLA-OMe) = n _(PLA-OMe) x 31
・ M _OCHO = n _OCHO × 29
・ M _(POX-OH) = n _(POX-OH) x 143
・ M _(PLA-OH) = n _(PLA-OH) x73
・ M _POX = n _POX × 198
・ M _PLA = n _PLA × 72
・ M _{(POX-OCO-PLA)} = n _{(POX-OCO-PLA)} x 126
・ M _{(POX-COCOO-PLA)} = n _{(POX-COCOO-PLA)} x 72

Here, each term has the following meaning.
M _(POX-OMe) : Molecular weight per molecule of a methoxy group at the oxalate terminal.
N _(POX-OMe) : Number of methoxy groups at the oxalate terminal per molecule.
M _(PLA-OMe) : molecular weight per molecule of a methoxy group at the lactic acid end.
N _(PLA-OMe) : Number of methoxy groups at the lactic acid terminal per molecule.

M _OCHO : molecular weight of the terminal formate group per molecule.
N _OCHO : number of terminal formate groups per molecule.
M _(POX-OH) : molecular weight per molecule of the HOCH ₂ C ₆ H ₁₀ CH ₂ O— group at the oxalate terminal.
N _(POX-OH) : Number of HOCH ₂ C ₆ H ₁₀ CH ₂ O— groups at the oxalate terminal per molecule.
M _(PLA-OH) : molecular weight per molecule of HOCH (CH ₃ ) CO— group at the lactic acid terminal.
N _(PLA-OH) : Number of HOCH (CH ₃ ) CO— groups at the lactic acid terminal per molecule.

M _POX : molecular weight of oxalate structural units per molecule.
N _POX : number of oxalate structural units per molecule.
M _PLA : Molecular weight of lactic acid structural unit per molecule.
N _PLA : number of lactic acid structural units per molecule.

M _{(POX-OCO-PLA)} : molecular weight per molecule of the OCH ₂ C ₆ H ₁₀ CH ₂ — group in the oxalate structural unit adjacent to the ester group portion of the lactic acid structural unit.
N _{(POX-OCO-PLA)} : The number per molecule of —OCH ₂ C ₆ H ₁₀ CH ₂ — groups in the oxalate structural unit adjacent to the ester group portion of the lactic acid structural unit.
M _{(POX-COCOO-PLA)} : molecular weight per molecule of —OCH (CH ₃ ) CO— group in the lactic acid structural unit adjacent to the ester group portion of the oxalate structural unit.
N _{(POX-COCOO-PLA)} : The number per molecule of —OCH (CH ₃ ) CO— groups in the lactic acid structural unit adjacent to the ester group portion of the oxalate structural unit.

Further, each term in the above formula is defined as follows.
N _(POX-OMe) = (s _(POX-OMe) / 3) / [(s _(POX-OMe) / 3 + s _(PLA-OMe) / 3 + s _OCHO + s _(POX-OH) / 2 + s _(PLA-OH) ) / 2]
・ N _(PLA-OMe) = (s _(PLA-OMe) / 3) / [(s _(POX-OMe) / 3 + s _(PLA-OMe) / 3 + s _OCHO + s _(POX-OH) / 2 + s _(PLA-OH) ) / 2]
N _OCHO = s _OCHO / [(s _(POX-OMe) / 3 + s _(PLA-OMe) / 3 + s _OCHO + s _(POX-OH) / 2 + s _(PLA-OH) ) / 2]
N _(POX-OH) = (s _(POX-OH) / 2) / [(s _(POX-OMe) / 3 + s _(PLA-OMe) / 3 + s _OCHO + s _(POX-OH) / 2 + s _(PLA-OH) ) / 2]
N _(PLA-OH) = s _(PLA-OH) / [(s _(POX-OMe) / 3 + s _(PLA-OMe) / 3 + s _OCHO + s _(POX-OH) / 2 + s _(PLA-OH) ) / 2]

N _POX = (s _POX / 4-s _(POX-OH) / 2-s _{(POX-OCO-PLA)} / 2) / [(s _(POX-OMe) / 3 + s _(PLA-OMe) / 3 + s _OCHO + s _(POX-OH) / 2 + s _(PLA-OH) ) / 2]
・ N _PLA = s _PLA / [(s _(POX-OMe) / 3 + s _(PLA-OMe) / 3 + s _OCHO + s _(POX-OH) / 2 + s _(PLA-OH) ) / 2]
・ N _{(POX-OCO-PLA)} = (s _{(POX-OCO-PLA)} / 2) / [(s _(POX-OMe) / 3 + s _(PLA-OMe) / 3 + s _OCHO + s _(POX-OH) / 2 + s _{( PLA-OH)} ) / 2]
・ N _{(POX-COCOO-PLA)} = (s _{(POX-COCOO-PLA)} / 4) / [(s _(POX-OMe) / 3 + s _(PLA-OMe) / 3 + s _OCHO + s _(POX-OH) / 2 + s _{( PLA-OH)} ) / 2]

Here, each term has the following meaning.
S _POX : integrated value of 4.15 ppm signal based on methylene protons of oxalate structural units. Hereinafter, this value was set to 100,000.
S _(POX-OMe) : the integrated value of the 3.91 ppm signal based on the methyl proton of the methoxy group at the oxalate end.
S _(PLA-OMe) : integrated value of 3.75 ppm signal based on the methyl proton of the methoxy group at the lactic acid end.
S _OCHO : the integrated value of the signal of 8.05 ppm based on the proton of the formate group at the oxalate terminal.
S _(POX-OH) : integrated value of a signal of 3.5 ppm based on the methylene proton of the HOCH ₂ C ₆ H ₁₀ CH ₂ O— group at the oxalate terminal.
S _(PLA-OH) : integrated value of 4.35 ppm signal based on the methine proton of the HOCH (CH ₃ ) CO— group at the lactic acid end.
S _PLA : integrated value of 5.18 ppm signal based on methine proton of lactic acid structural unit.
S _{(POX-OCO-PLA)} : an integrated value of a signal of 3.97 ppm based on the methylene proton of the —OCH ₂ C ₆ H ₁₀ CH ₂ — group in the oxalate structural unit adjacent to the ester group portion of the lactic acid structural unit.

(2) Number average molecular weight of polylactic acid block and polyoxalate block (i) Number average molecular weight of polylactic acid block (M _PLA ): Calculated according to the following formula based on signal intensity obtained from ¹ H-NMR spectrum. The measurement conditions for ¹ H-NMR are the same as in the case of the block copolymer.
M _PLA = N _PLA × 72

However, N _PLA represents the number average degree of polymerization of the polylactic acid block, and is defined as follows.
(A) When n _(TE-INT) is an odd number: N _PLA = n _PLA / [(n _(TE-INT) +1) / 2] × W _(TE-INT) + {n _PLA / [(n _{(TE -INT)} +2) / 2] + n _PLA / 2} × W _{(TE-INT + 1)}
(B) When n _(TE-INT) is an even number: N _PLA = {n _PLA / [(n _(TE-INT) +1) / 2] + n _PLA } / 2 × W _(TE-INT) + n _PLA / [ (N _(TE-INT) +2) / 2] × W _{(TE-INT + 1)}

Here, each term in the above formula has the following meaning and is defined as follows.
N _PLA : number of lactic acid structural units per molecule.
· N _(TE-INT): integer truncation the fractional part of n _TE. However, n _TE is the number of transesterification points per molecule in the lactic acid-polyoxalate block copolymer produced by transesterification of polylactic acid and polyoxalate.
W _(TE-INT) : The ratio of the lactic acid-oxalate block copolymer in which the number of transesterification points per molecule is n _(TE-INT) .
W _{(TE-INT + 1)} : ratio of lactic acid-oxalate block copolymer in which the number of transesterification points per molecule is n _(TE-INT) +1.

・ W _(TE-INT) = 1- (n _TE -n _(TE-INT) )
・ W _{(TE-INT + 1)} = n _TE −n _(TE-INT)
・ N _TE = n _{(POX-OCO-PLA)} + n _{(POX-COCOO-PLA)}

(Ii) Number average molecular weight of _polyoxalate block (M _POX ): Calculated by the following formula based on the signal intensity obtained from the ¹ H-NMR spectrum. The measurement conditions of ¹ H-NMR are the same as in the case of the block copolymer.
M _POX = N _POX × 198

However, N _PLA represents the number average degree of polymerization of the polyoxalate block, and is defined as follows. In the following formula, n _POX represents the number of oxalate structural units per molecule, and the others are the same as described above.

(A) When n _(TE-INT) is an odd number • N _POX = n _POX / [(n _(TE-INT) +1) / 2] × W _(TE-INT) + {n _POX / [(n _{(TE -INT)} +2) / 2] + n _POX / 2} × W _{(TE-INT + 1)}
(B) When n _(TE-INT) is an even number • N _POX = {n _POX / [(n _(TE-INT) +1) / 2] + n _POX } / 2 × W _(TE-INT) + n _POX / [ (N _(TE-INT) +2) / 2] × W _{(TE-INT + 1)}

(3) Average number of polylactic acid blocks = M _n × [M _PLA / (M _PLA + M _POX )] / M _PLA
(4) Average number of _polyoxalate blocks = M _n × [M _POX / (M _PLA + M _POX )] / M _POX
(5) Lactic acid / oxalate weight ratio (LA / OX)
= [M _PLA / (M _PLA + M _POX ) × 100] / [M _POX / (M _PLA + M _POX ) × 100]

3. Production of polylactic acid composition Using a batch-type melt kneader, lactic acid-oxalate block copolymer and polylactic acid (and polyoxalate) are melted for 5 minutes at a temperature of 200 ° C. and a rotor rotation speed of 60 rpm in a nitrogen stream. It was produced by kneading.

4). Production of a press sheet Using a hot press (manufactured by Shinto Metal Industry), from a lactic acid-oxalate block copolymer or a polylactic acid composition, a temperature of 200 ° C., a preheating of 4 minutes, a pressure of 2.94 MPa, a pressing time of 1 minute, A hot press sheet (100 mm square, thickness about 0.4 mm) was produced under the molding conditions of a cooling temperature of 15 ° C. and a cooling time of 3 minutes.

5. Lactic - oxalate Characterization of the block copolymer and the polylactic acid composition (1) the thermal melting point (T _m) and glass transition temperature (T _g): was determined from the second heating process in a differential scanning calorimetry (DSC). In the measurement, DSC-7 (manufactured by PerkinElmer) was used, and in the first temperature raising process, the temperature was raised from room temperature to the melting point (set by the sample) or more at a temperature rising rate of 10 ° C./min and held for 5 minutes. In the first temperature lowering process, the temperature is lowered from the melting point (set by the sample) to −100 ° C. at a temperature lowering rate of 10 ° C./min and held for 5 minutes. The temperature was raised from −100 ° C. to the melting point (set by the sample) or more in minutes.

(2) Microstructure observation An ultrathin section stained with RuO _{4 in the} cross section of the press sheet was prepared and observed at an acceleration voltage of 100 KV using a transmission electron microscope (JEM-200CX manufactured by JEOL).

(3) Tensile properties: Tensilon (manufactured by Orientec) was used, and a JIS No. 3 tensile test piece was measured at a tensile speed of 5 mm / min, 23 ° C., and 50% RH.

(4) Hydrolysis resistance From a press sheet, a test piece having a width of 25 mm and a length of 100 mm was cut out and immersed in warm water (pure water) at 50 ° C., taken out after a predetermined time, and the reduced viscosity was measured. The retention rate (%) with respect to the reduced viscosity of was determined. The reduced viscosity was measured at 25 ° C. using a 0.5 g / dl chloroform solution.

[Reference Example 1]
In a 5 L internal pressure vessel equipped with a stirrer, thermometer, pressure gauge, nitrogen gas inlet, pressure relief outlet, and polymer outlet, dimethyl oxalate 2025.0 g (17.148 mol), cyclohexanedimethanol 2288 .7 g (15.878 mol), 1.8 g of butyltin hydroxide hydrate (0.05 mol% of dimethyl oxalate) and 21.6 g of heat-resistant irgaphos 168 (manufactured by Ciba Specialty Chemicals) (5000 ppm of the raw material) The inside was replaced with nitrogen. Next, a polycondensation reaction was performed as follows. The water concentration in dimethyl oxalate was 478 ppm, and the water concentration in cyclohexanedimethanol was 200 ppm.

(I) Pre-polycondensation step: The temperature in the pressure vessel was raised from room temperature to 100 ° C. over 1.25 hours. After confirming that the melt was uniform, the reaction was carried out while raising the temperature to 150 ° C. over 2 hours. The amount of methanol distilled during this temperature raising process was 393.9 g. Subsequently, it was made to react further, heating up to 190 degreeC over 2 hours. The total amount of methanol distilled was 430.5 g.

(II) Post-polycondensation step: Depressurization was started while maintaining the temperature in the pressure vessel at 190 ° C., the pressure was reduced to 300 mmHg (39.9 kPa) in 0.75 hours, and 100 mmHg (13.3 kPa) in 1 hour. The reaction was performed under reduced pressure. During this time, the total amount of methanol distilled was 484.5 g. Next, the temperature in the pressure vessel is increased to 207 ° C. over 1.5 hours, and gradually decreased to 5 mmHg (665 Pa) after 1.25 hours while gradually reducing the pressure, and further to 0.8 mmHg (106 Pa) after 4 hours. The reaction was carried out. Thereafter, the stirring was stopped, and the melted contents were drawn out from the polymer outlet through a string, cooled with water, and pelletized.

The obtained polycyclohexylenedimethylene oxalate (2440 g; POX-1) had M _n = 24000, T _g = 40 ° C., T _m = 174 ° C., and terminal hydroxyl group concentration [OH] = 0.96 × 10 ^−5. eq / g, terminal methoxy group concentration [OMe] = 6.98 × 10 ⁻⁵ eq / g, terminal formate group concentration [OCHO] = 0.46 × 10 ⁻⁵ eq / g. POX-1 contained about 530 ppm of a transesterification catalyst on a weight basis (the same applies hereinafter).

[Reference Example 2]
The same as Reference Example 1 except that the amount of cyclohexanedimethanol charged was changed to 2312.0 g (16.032 mol) and the amount of butyltin hydroxide hydrate was changed to 3.6 g (0.100 mol% of dimethyl oxalate). Went to. However, the amount of distilled methanol in the pre-polycondensation step was 394.5 g, and the total amount of distilled methanol was 434.5 g.

Next, with respect to 100 parts by weight of the obtained pellets, 0.32 parts by weight of the heat-resistant agent Irgaphos 168, 0.25 parts by weight of the same Irganox 1010 (both manufactured by Ciba Specialty Chemicals), and the hydrolysis inhibitor Carbodilite HMV- 0.1 parts by weight of 8CA and 1 part by weight of Carbodilite LA-1 (both manufactured by Nisshinbo) were dry blended and compounded using a twin screw extruder. The barrel temperature was set to 190 ° C. The obtained compound pellet (POX-2) contains about 1060 ppm of a transesterification catalyst, Mn = 29000, terminal hydroxyl group concentration [OH] = 3.96 × 10 ⁻⁵ eq / g, terminal methoxy group concentration [OMe] = The concentration was 1.84 × 10 ⁻⁵ eq / g and the terminal formate group concentration [OCHO] = 1.10 × 10 ⁻⁵ eq / g.

[Example 1]
In a 300 mL separable flask equipped with a mechanical stirrer and a nitrogen introduction tube, 20 g of polylactic acid (PLA-1; M _n = 90,000, T _m = 167 ° C.) and the polyoxalate (POX-1) obtained in Reference Example 1 were used. ) 20 g was added, and the bath temperature was raised to 200 ° C. under normal pressure and a nitrogen stream (50 mL / min). Stirring was started when melting of the contents was started and melt mixing was confirmed. Then, 20 mg of tin 2-ethylhexanoate (500 ppm with respect to the total amount of PLA-1 and POX-1; butyltin in POX-1) A total of 1030 ppm of hydroxide oxide hydrate was added. After stirring for about 5 minutes at normal pressure, pressure reduction was started (this time is set as the start of reaction), and reached 2 mmHg (267 Pa) in about 5 minutes. The final pressure reached was 0.5 mmHg (67 Pa). It was. After 0.5 hours from the start of the reaction, nitrogen gas was introduced to complete the reaction. About the obtained lactic acid-oxalate block copolymer, M _n , number average molecular weight of polylactic acid block (M _PLA ), average number of blocks of polylactic acid block, number average molecular weight of polyoxalate block (M _POX ), poly Table 1 shows the average number of oxalate blocks, lactic acid / oxalate weight ratio (LA / OX), T _g , and T _m . This block copolymer showed a crystal melting peak (melting point) and had crystallinity.

[Example 2]
PLA-1 usage was changed to 40 g and POX-1 usage was changed to 40 g, tin 2-ethylhexanoate was not added (only by transesterification catalyst contained in POX-1), and final ultimate pressure was 500 mmHg (67 kPa). The reaction was carried out in the same manner as in Example 1 except that the reaction time was changed to 1 hour. The physical properties of the obtained lactic acid-oxalate block copolymer are similarly shown in Table 1. This block copolymer showed a crystal melting peak (melting point) and had crystallinity.

Example 3
After melting only POX-1 (40 g), 0.2 g of monostearyl acid phosphate / distearyl acid phosphate mixture (2500 ppm relative to the total amount of POX-1 and PLA-1) was added as a catalyst deactivator. Stir at atmospheric pressure for 0.5 hours. Subsequently, it carried out like Example 2 except having added PLA-1 (40g) and making it react for 6 hours with a normal pressure. The physical properties of the obtained lactic acid-oxalate block copolymer are similarly shown in Table 1. This block copolymer showed a crystal melting peak (melting point) and had crystallinity.

Example 4
Replace POX-1 with POX-2 (40 g), change the addition amount of catalyst deactivator to 0.4 g (5000 ppm with respect to the total amount of POX-1 and PLA-1), and supply PLA-1 (40 g) The reaction was performed in the same manner as in Example 3 except that the reaction was performed later at 500 mmHg (67 kPa). Various physical properties of the obtained lactic acid-oxalate block copolymer are similarly shown in Table 1. This block copolymer showed a crystal melting peak (melting point) and had crystallinity.

[Comparative Example 1]
The same procedure as in Example 2 was performed except that the final ultimate pressure was 100 mmHg (13.4 kPa). Various physical properties of the obtained lactic acid-oxalate block copolymer are similarly shown in Table 1. As apparent from Table 1, this block copolymer did not exhibit a melting point and did not have crystallinity.

[Comparative Example 2]
The reaction vessel was replaced with a 5 L volume, the PLA-1 usage was changed to 1.25 kg and the POX-1 usage was changed to 1.25 kg, respectively, and 0.5 mmHg ( 67 Pa) and the same procedure as in Example 1 was performed except that the reaction time was changed to 1 hour. Various physical properties of the obtained lactic acid-oxalate block copolymer are similarly shown in Table 1. As apparent from Table 1, this block copolymer did not exhibit a melting point and did not have crystallinity.

Example 5
The same procedure as in Example 4 was conducted except that POX-1 was replaced with POX-1, and the amount of POX-1 used was changed to 32 g and the amount of PLA-1 used was changed to 48 g. Various physical properties of the obtained lactic acid-oxalate block copolymer are similarly shown in Table 1. This block copolymer showed a crystal melting peak (melting point) and had crystallinity.

Example 6
The same procedure as in Example 1 was conducted except that the amount of POX-1 used was changed to 24 g and the amount of PLA-1 used was changed to 56 g. Various physical properties of the obtained lactic acid-oxalate block copolymer are similarly shown in Table 1. This block copolymer showed a crystal melting peak (melting point) and had crystallinity.

Example 7
The same procedure as in Example 1 was conducted except that the amount of POX-1 used was changed to 16 g and the amount of PLA-1 used was changed to 64 g. Various physical properties of the obtained lactic acid-oxalate block copolymer are similarly shown in Table 1. This block copolymer showed a crystal melting peak (melting point) and had crystallinity.

[Examples 8 to 14, Comparative Examples 3 to 5]
The lactic acid-oxalate block copolymers obtained in Examples 1 to 7 and the lactic acid-oxalate copolymer press sheets obtained in Comparative Examples 1 and 2 were respectively molded to give tensile properties (elastic modulus, maximum strength, (Elongation at break) was examined. The results are shown in Table 2. The tensile properties of PLA-1 are also shown in Table 2 as Comparative Example 5. In addition, Table 3 shows the evaluation results of hydrolysis resistance of the lactic acid-oxalate block copolymer (press sheet) obtained in Example 8 and the lactic acid-oxalate copolymer (press sheet) obtained in Comparative Example 3. And transmission electron micrographs are shown in FIGS. 1 and 2, respectively.

Example 15
Using the lactic acid-oxalate block copolymer obtained in Example 1 and polylactic acid (PLA-1) in the composition ratio shown in Table 4, a polylactic acid composition (polylactic acid / lactic acid-oxalate block copolymer) was used. The combined composition) was manufactured, the press sheet was prepared, and the tensile properties (elastic modulus, maximum strength, elongation at break) were examined. The results are shown in Table 4.

Example 16
Using the lactic acid-oxalate block copolymer, polylactic acid (PLA-1) and polyoxalate (POX-1) obtained in Example 2 in the composition ratios shown in Table 4, a polylactic acid composition (poly A lactic acid / lactic acid-oxalate block copolymer / polyoxalate composition) was produced, and a press sheet was produced to examine tensile properties (elastic modulus, maximum strength, elongation at break). The results are shown in Table 4.

Example 17
Using the lactic acid-oxalate block copolymer, polylactic acid (PLA-1) and polyoxalate (POX-1) obtained in Example 1 in the composition ratios shown in Table 4, a polylactic acid composition (poly A lactic acid / lactic acid-oxalate block copolymer / polyoxalate composition) was produced, and a press sheet was produced to examine tensile properties (elastic modulus, maximum strength, elongation at break). The results are shown in Table 4.

[Comparative Example 6]
Using polylactic acid (PLA-1) and polyoxalate (POX-1) in the composition ratios shown in Table 4, a polylactic acid composition (polylactic acid / polyoxalate composition) was produced, and the press sheet was Fabrication and tensile properties (elastic modulus, maximum strength, elongation at break) were examined. The results are shown in Table 4.

  The lactic acid-oxalate block copolymer of the present invention has a high melting point and is tougher than polylactic acid, and can also be used as a modifier of polylactic acid. Therefore, it cannot be used with polylactic acid. In addition, it can be used for various purposes by supplementing the drawbacks of polylactic acid.

The microstructure observation result (an electron micrograph; magnification 30000 times) of the lactic acid-oxalate block copolymer (press sheet) obtained in Example 8 is represented. This copolymer forms a microphase separation structure composed of a polylactic acid block aggregate part, a polyoxalate block aggregate part, and an intermediate part. The microstructure observation result (electron micrograph; magnification 30000 times) of the lactic acid-oxalate copolymer (press sheet) obtained in Comparative Example 3 is shown. This copolymer does not form a microphase separation structure at all.

Claims (10)

A lactic acid-oxalate block copolymer composed of a polylactic acid block and a polyoxalate block, wherein the polylactic acid block and the polyoxalate block each have a number average molecular weight in the range of 2000 to 50000. The lactic acid-oxalate block copolymer according to claim 1, wherein the average number of blocks of the polylactic acid block and the polyoxalate block is in the range of 0.1 to 9, respectively. The lactic acid-oxalate block copolymer according to claim 1, wherein the number average molecular weight is in the range of 18,000 to 70,000. The lactic acid- according to claim 1, wherein the ratio of lactic acid structural units constituting the polylactic acid block to oxalate structural units constituting the polyoxalate block (lactic acid / oxalate) is in the range of 5/95 to 95/5 on a weight basis. Oxalate block copolymer. The lactic acid-oxalate block according to any one of claims 1 to 4, wherein the block copolymer forms a microphase-separated structure composed of a polylactic acid block aggregate part, a polyoxalate block aggregate part, and an intermediate phase. Copolymer. The lactic acid-oxalate block copolymer according to claim 5, wherein any one of the polylactic acid block aggregate part and the polyoxalate block aggregate part becomes a dispersed phase and has a size of 0.5 to 5 microns. The lactic acid-oxalate block copolymer according to any one of claims 1 to 6, wherein a crystal melting peak is observed in differential scanning calorimetry. The lactic acid-oxalate block copolymer according to any one of claims 1 to 7, wherein the polylactic acid block is represented by the formula (1) and the polyoxalate block is represented by the formula (2).
(In the formula, m is a positive number representing the average number of repeating lactic acid structural units and corresponds to the number average molecular weight of the polylactic acid block. N is a positive number representing the average number of repeating oxalate structural units; (It corresponds to the number average molecular weight of the oxalate block. A represents an alkylene group having 3 to 12 carbon atoms in the main chain, which may contain a branched structure or an alicyclic structure.)

A polylactic acid composition comprising the lactic acid-oxalate block copolymer according to claim 1 and polylactic acid. The polylactic acid composition according to claim 9, further comprising a polyoxalate.

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