JP6119608B2 - Process for producing block copolymer - Google Patents

Description

  The present invention relates to a block copolymer composed of a polylactic acid-based resin and a resin having at least one hydroxyl group in the molecule, as production conditions thereof, a polylactic acid-based resin, a resin having at least one hydroxyl group in the molecule, and The transesterification catalyst is melted at normal pressure.

  In recent years, due to increasing environmental awareness, there are concerns about soil pollution problems caused by the disposal of plastic products and global warming problems caused by increased carbon dioxide caused by incineration of the products. As a countermeasure against the former, biodegradable resin that is completely decomposed into carbon dioxide molecules and water molecules under the environment in the soil, and as a countermeasure against the latter, synthesized from biological raw materials such as plants and incinerated Research and development on biomass resins that do not impose a new carbon dioxide load in the atmosphere are being actively conducted.

  Attention to polylactic acid-based resins is increasing as it is compatible with both of them and is relatively advantageous in terms of cost. When using polylactic acid resin alone, the flexibility is insufficient. For example, in applications such as agricultural multi-films, shopping bags, packaging wrap films and stretch films, use of polylactic acid copolymers and addition of plasticizers Flexibility by is being considered.

  The polylactic acid-based block copolymer can be used as a flexible resin by mixing it alone or with a polylactic acid-based resin. In particular, when mixed with a polylactic acid resin, the block copolymer can function as a plasticizer. For example, a plasticizer made of a polylactic acid-polyether block copolymer described in Patent Document 1 has a conventional polylactic acid because the polylactic acid segment contributes to preventing exudation and the polyether segment contributes to plasticization of polylactic acid. Compared to plasticizers for plastic resins, it has a feature of excellent bleed-out resistance.

  As disclosed in Patent Document 1, these polylactic acid block copolymers are produced by opening lactide, which is a cyclic dimer of lactic acid, starting from a hydroxyl group of a resin having at least one hydroxyl group in the molecule. Those that polymerize are common. As another method, as disclosed in Patent Document 2, a polylactic acid resin and a resin having at least one hydroxyl group in the molecule are melted, and then a transesterification catalyst is added and transesterification is performed under reduced pressure. A known method for producing a polylactic acid block copolymer is known.

Japanese Patent No. 4363325 JP 2004-231773 A

  In the lactide ring-opening polymerization method described in Patent Document 1, contamination of the reactor due to accumulation of sublimated lactide during polymerization, and some unreacted lactide remains in the obtained polylactic acid block copolymer There are problems such as generation of lactide odor of the resin and deterioration of hydrolysis resistance. Further, in the method described in Patent Document 2, since the reaction is performed under reduced pressure, the generation of lactide by the intramolecular transesterification reaction of the polylactic acid resin is promoted, and the same problem as described above occurs.

  The present invention solves this conventional problem, and thereby obtains a method for producing a specific block copolymer with little residual lactide.

In order to solve the above problems, the present invention proposes the following manufacturing method. That is:
(1) polylactic acid resin, a resin having at least one hydroxyl group in the molecule (hereinafter, the resin having at least one hydroxyl group in the molecule, the resin (A) hereinafter) as a polyether-based resin, and as a transesterification catalyst organic acid salts and / or metal halide salt of the metal, twin-screw extruder (hereinafter, the twin-screw extruder, a twin that screw extruder 1) melted at atmospheric pressure at a (hereinafter, normal pressure A block copolymer of a polylactic acid resin and a resin (A) (hereinafter referred to as polylactic acid type), characterized by carrying out a transesterification reaction under normal pressure. A block copolymer of a resin and a resin (A) is referred to as a block copolymer) .
(2)
The method for producing a block copolymer according to (1) , wherein the resin (A) is a polyalkylene glycol resin .
(3)
The block copolymer produced by the method described in (1) is directly introduced from the twin-screw extruder 1 into another twin-screw extruder and mixed with a polylactic acid resin. For producing a mixture of a resin and a block copolymer.
(4)
The block copolymer produced by the method described in (1) is charged with a polylactic acid resin from the side feeder of the same twin-screw extruder that produced the block copolymer, A method for producing a mixture of a polylactic acid resin and a block copolymer, wherein the block copolymer and the polylactic acid resin are mixed in the same twin-screw extruder as that produced the copolymer.

  By using the normal pressure / melting step, which is a feature of the present invention, a block copolymer with little residual lactide can be obtained. The block copolymer obtained by the present invention can be used as a flexible resin for molded articles such as films, alone or mixed with a polylactic acid resin, and a plasticizer having bleed-out resistance for a polylactic acid resin. Can also be suitably used.

  The present invention relates to a polylactic acid-based resin, a resin having at least one hydroxyl group in the molecule (hereinafter, a resin having at least one hydroxyl group in the molecule is referred to as a resin (A)), and a transesterification catalyst at normal pressure. Block copolymer of polylactic acid resin and resin (A) (hereinafter referred to as polylactic acid resin), characterized by melting at a normal pressure (hereinafter referred to as normal pressure / melting step) And a resin (A) block copolymer is referred to as a block copolymer).

  Hereinafter, the manufacturing method of the block copolymer of this invention is demonstrated.

(Polylactic acid resin)
In the present invention, a polylactic acid resin is used as a raw material for producing the block copolymer. The polylactic acid-based resin is a polymer mainly composed of an L-lactic acid unit and / or a D-lactic acid unit. Here, the main component means that the ratio of lactic acid units is the maximum in 100 mol% of all monomer units in the polymer, and preferably 70% of lactic acid units in 100 mol% of all monomer units. ˜100 mol%.

  The poly L-lactic acid in the present invention refers to those having a content ratio of L-lactic acid units exceeding 50 mol% and not more than 100 mol% in 100 mol% of all lactic acid units in the polymer. On the other hand, the poly D-lactic acid in the present invention refers to those having a D-lactic acid unit content of more than 50 mol% and not more than 100 mol% in 100 mol% of all lactic acid units in the polymer.

  However, the polylactic acid resin in the present invention does not include those obtained by block copolymerization of the resin (A). In addition, when resin (A) and polylactic acid-type resin are copolymerized, this is called a block copolymer.

  In poly L-lactic acid, the crystallinity of the resin itself varies depending on the content ratio of the D-lactic acid unit. That is, if the content ratio of the D-lactic acid unit in the poly-L-lactic acid increases, the crystallinity of the poly-L-lactic acid becomes lower and becomes closer to an amorphous state, and conversely, the content ratio of the D-lactic acid unit in the poly-L-lactic acid. As the amount decreases, the crystallinity of poly-L-lactic acid increases. Similarly, in poly D-lactic acid, the crystallinity of the resin itself changes depending on the content ratio of the L-lactic acid unit. That is, if the content ratio of the L-lactic acid unit in the poly-D-lactic acid increases, the crystallinity of the poly-D-lactic acid becomes low and approaches an amorphous state. Conversely, the content ratio of the L-lactic acid unit in the poly-D-lactic acid. As the amount decreases, the crystallinity of poly-D-lactic acid increases.

  The content ratio of the L-lactic acid unit in the poly L-lactic acid used in the present invention or the content ratio of the D-lactic acid unit in the poly D-lactic acid used in the present invention can be arbitrarily adjusted. When the block copolymer obtained in the present invention is formed into a molded product requiring mechanical strength, the L-lactic acid unit is 90 to 100 mol% or the D-lactic acid unit is 90 to 100 mol% in 100 mol% of all lactic acid units. Preferably, the L-lactic acid unit is 95 to 100 mol%, or the D-lactic acid unit is 95 to 100 mol%. When the block copolymer obtained in the present invention is used as a plasticizer for a crystalline polylactic acid resin, a co-crystal is formed between the polylactic acid resin and the polylactic acid segment of the block copolymer. In order to suppress bleed out of the block copolymer, the content ratios of L-lactic acid and D-lactic acid are preferably the same as described above. Conversely, when a block copolymer obtained in the present invention or a polylactic acid resin containing the block copolymer obtained in the present invention as a plasticizer is used for a heat seal layer of a film, the resin is low. Since it is preferably crystalline or amorphous, L-lactic acid units and D-lactic acid units are preferably 10 to 90 mol% in 100 mol% of all lactic acid units.

  The crystalline polylactic acid resin in the present invention is measured with a differential scanning calorimeter (DSC) at a temperature rising rate of 20 ° C./min after leaving the polylactic acid resin to stand for 1 hour under heating at 100 ° C. In this case, it means a polylactic acid resin in which the heat of crystal melting derived from the polylactic acid component is observed.

  On the other hand, the amorphous polylactic acid-based resin referred to in the present invention refers to a polylactic acid-based resin that does not exhibit a melting point when measured in the same manner.

  The polylactic acid resin used in the present invention may randomly copolymerize other monomer units other than lactic acid. Other monomers include ethylene glycol, propylene glycol, butanediol, heptanediol, hexanediol, octanediol, nonanediol, decanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, glycerin, pentane. Glycol compounds such as erythritol, bisphenol A, polyethylene glycol, polypropylene glycol and polytetramethylene glycol, oxalic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, malonic acid, glutaric acid, cyclohexanedicarboxylic acid, terephthalic acid , Isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, bis (p-carboxyphenyl) methane, anthracene dicarboxylic acid, 4,4′-diphenyl ether dicarboxylic acid, -Dicarboxylic acids such as sodium sulfoisophthalic acid, 5-tetrabutylphosphonium isophthalic acid, glycolic acid, hydroxypropionic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, hydroxybenzoic acid and other hydroxycarboxylic acids, caprolactone, valerolactone, Examples include lactones such as propiolactone, undecalactone, and 1,5-oxepan-2-one. The copolymerization amount of the other monomer units as described above is preferably 0 to 30 mol% with respect to 100 mol% of the whole monomer units in the polymer of the polylactic acid resin, and is 0 to 10 mol%. More preferably. In addition, it is preferable to select the component which has biodegradability among the above-mentioned monomer units according to a use.

  The mass average molecular weight of the polylactic acid resin used in the present invention is preferably 5,000 to 1,000,000 from the viewpoint of the molecular weight of the block copolymer after the reaction and the handleability at the time of melting. It is more preferable that it is 1,000-500,000, and it is most preferable that it is 100,000-300,000. In addition, the mass average molecular weight in this invention means the molecular weight which measured with the good solvent, such as hexafluoroisopropanol, by gel permeation chromatography (GPC), and was calculated by the polymethylmethacrylate conversion method.

  The polylactic acid resin used in the present invention can be obtained by a method of directly dehydrating condensation of lactic acid and other raw materials, or a method of ring-opening polymerization of lactide and other cyclic ester intermediates. For example, in the case of producing by direct dehydration condensation, lactic acid or lactic acid and hydroxycarboxylic acid are preferably subjected to azeotropic dehydration condensation in the presence of an organic solvent, particularly a phenyl ether solvent, and particularly preferably a solvent distilled by azeotropic distillation. A polymer having a high molecular weight can be obtained by polymerizing by a method in which water is removed from the solvent and the solvent is brought into a substantially anhydrous state and returned to the reaction system.

  It is also known that a high molecular weight polymer can be obtained by subjecting a cyclic ester intermediate such as lactide to ring-opening polymerization under reduced pressure using a catalyst such as tin octoate. At this time, a method for adjusting the conditions for removing moisture and low molecular weight compounds during heating and refluxing in an organic solvent, a method for suppressing the depolymerization reaction by deactivating the catalyst after completion of the polymerization reaction, and a method for heat-treating the produced polymer Can be used to obtain a polymer with a small amount of lactide.

(Resin having at least one hydroxyl group in the molecule (resin (A)))
In this invention, resin (A) is used as a manufacturing raw material of a block copolymer. In the present invention, since the ester exchange reaction proceeds from the hydroxyl group of the resin (A) to the ester bond between the lactic acid unit and the lactic acid unit in the polylactic acid resin, at least one resin (A) is present in the molecule. It is important that the resin has two hydroxyl groups. However, the resin (A) is a resin having at least one hydroxyl group in the molecule other than the polylactic acid resin. In addition, it is preferable to select resin (A) which has biodegradability depending on a use.

  Examples of the resin (A) include a polyester resin other than a polylactic acid resin, a polyether resin, a polyacetal resin, and the like as a resin containing a hydroxyl group at a molecular terminal. Moreover, as a resin containing a hydroxyl group in the side chain, polyvinyl alcohol resin, ethylene-vinyl alcohol copolymer resin, polysaccharide, esterified polysaccharide, etherified polysaccharide, deoxyhalogenated polysaccharide, polysaccharide Examples thereof include oxides and hydroxyl group-modified polyolefin resins. In order to impart flexibility to the polylactic acid-based resin, the glass transition temperature of the resin (A) is preferably −70 to 50 ° C., and more preferably −70 to 40 ° C.

  Among these, since the effect of increasing the flexibility of the polylactic acid-based resin is high and the compatibility with the polylactic acid-based resin is high, the resin (A) is a polyester-based resin other than the polylactic acid-based resin and / or poly It is preferably an ether resin, more preferably a polyether resin, and further preferably a polyalkylene glycol resin.

  Particularly preferred as the polyalkylene glycol resin as the resin (A) is polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyethylene glycol / polypropylene glycol copolymer, and among these, polyethylene glycol is most preferred. Since polyethylene glycol is flexible and has high affinity with the polylactic acid resin, the block copolymer of the polylactic acid resin and polyethylene glycol is excellent in flexibility and plasticization efficiency of the polylactic acid resin.

  The mass average molecular weight of the resin (A) used in the present invention is 1,000 to 1,000,000 from the viewpoint of the molecular weight and flexibility of the block copolymer after the reaction, and the handling property at the time of melting. Is preferably 5,000 to 500,000, more preferably 5,000 to 100,000, and most preferably 5,000 to 30,000.

(Transesterification catalyst)
In the present invention, it is important to melt the polylactic acid resin, the resin (A), and the transesterification catalyst at normal pressure. That is, in the present invention, the block copolymer is produced by a transesterification method, and it is important to use a transesterification catalyst at that time.

  The transesterification catalyst in the present invention is not particularly limited, and examples thereof include metals, metal salts, sulfur acids, and nitrogen-containing basic compounds.

  Examples of metals include manganese, magnesium, titanium, zinc, iron, aluminum, cerium, calcium, barium, cobalt, lithium, sodium, potassium, cesium, lead, strontium, tin, antimony, germanium, yttrium, lanthanum, indium, Zirconium etc. are mentioned.

  Examples of the metal salt include metal organic acid salt, metal nitrate, metal phosphate, metal borate, metal halide salt, metal hydroxide salt and the like. In addition, as a metal used for a metal salt, the thing similar to the example of said metal is mentioned. Examples of organic acids include carboxylic acid, sulfur acid, carbonic acid, phenol and the like.

  Examples of sulfur acids include sulfuric acid, sulfonic acid compounds, sulfinic acid compounds, and sulfenic acid compounds.

  Examples of the nitrogen-containing basic compound include quaternary amine salts, tertiary amines, secondary amines, primary amines, pyridines, imidazoles, ammonia and the like.

  Among these, the transesterification catalyst in the present invention is preferably a metal salt from the viewpoint of dispersibility in the resin, the degree of decomposition and molecular weight reduction of the resin, and the effect as a catalyst, and the metal organic acid salt and / or metal More preferred is a halide salt. In particular, from the viewpoint of selecting a polymer kettle and an extruder having low corrosiveness, a high transesterification catalytic ability per mass, and a material that hardly causes bleed out from a resin, organic acid salts of metals and / or metals The halide salt is preferably a salt of an organic acid and a metal having an alkyl group having 0 to 10 carbon atoms (metal organic acid salt) and / or a metal halide salt. In the present invention, an alkyl group having 0 carbon atoms means that there is no alkyl group in the molecule.

  Further, the block copolymer obtained in the present invention is an ester used in the present invention, considering the possibility of being used for agricultural and forestry applications and applications requiring biodegradability such as garbage bags and compost bags. The exchange catalyst is preferably one that is highly safe to living organisms. In addition, when the ability as a transesterification catalyst is selected together, the transesterification catalyst is preferably a metal organic acid salt and / or a metal halide salt. Examples thereof include salts of organic acids having 0 to 10 alkyl groups with metals (metal organic acid salts) or metal halide salts shown below.

  A specific example of a salt of an organic acid having an alkyl group having 0 to 10 carbon atoms and a metal, which is particularly preferable as a metal organic acid salt, is, for example, a carboxylic acid having 1 to 10 carbon atoms having no hydroxyl group. And a salt made of a metal selected from magnesium, titanium, tin, zinc, iron, aluminum, calcium, and potassium. Specific examples of particularly preferred metal halide salts are metal halides selected from, for example, magnesium, titanium, tin, zinc, iron, aluminum, calcium, and potassium.

  In the present invention, two or more different transesterification catalysts can be used in combination.

(Method for producing block copolymer of polylactic acid resin and resin (A))
In the method for producing a block copolymer of the present invention, a raw material polylactic acid resin, resin (A), and transesterification catalyst are supplied to a reactor and melted at normal pressure (through a normal pressure / melting step). ).

  In the present invention, a block copolymer is produced by a transesterification reaction between the polylactic acid resin and the resin (A). The transesterification referred to here means that a hydroxyl group, a carboxylic acid group, or another ester bond is allowed to act on a certain ester bond to cause an exchange with a hydroxyl group or a carboxylic acid group in the ester bond. Is a reaction that forms another type of ester bond. In particular, the main object of the present invention is to introduce an ester bond between the polylactic acid resin and the resin (A) by allowing the hydroxyl group of the resin (A) to act on the ester bond of the polylactic acid resin. To do.

  The melting temperature in the normal pressure / melting process varies depending on the type of reactor, the melting point of the polylactic acid resin, the melting point of the resin (A), the viscosity of the polylactic acid resin, and the viscosity of the resin (A). Considering the melting point and thermal decomposition temperature of the resin, the temperature in the normal pressure / melting step is preferably 150 to 250 ° C, more preferably 180 to 240 ° C. Moreover, in order to prevent the hydrolysis and coloring at the time of a fusion | melting, the polylactic acid-type resin and resin (A) to be used are fully dried beforehand and it is preferable to reduce a moisture content. The water content of both the polylactic acid resin and the resin (A) is preferably 1,200 ppm (mass basis) or less, more preferably 500 ppm (mass basis) or less, and 200 ppm (mass basis) or less. Is more preferable.

  The charging mass ratio between the polylactic acid-based resin and the resin (A) is not particularly limited, but a preferable range is 95: 5 to 5:95 by mass ratio. In particular, when the product block copolymer is used as the main component of the molded body as a flexible resin, the charged mass ratio of the polylactic acid resin and the resin (A) is 95: 5 to 50:50. It is preferably 90:10 to 60:40, and more preferably 90:10 to 60:40. Moreover, when using a block copolymer as a plasticizer of polylactic acid-type resin, it is preferable that preparation mass ratio of polylactic acid-type resin and resin (A) is 80: 20-5: 95, 75: It is more preferably 25 to 10:90, and further preferably 70:30 to 30:70.

  The addition amount of the transesterification catalyst varies depending on the type of reactor, reaction temperature, reaction time, reaction atmosphere, and the like, but is 0.001 to 5 with respect to 100 parts by mass of the total of the polylactic acid resin and the resin (A). The range is preferably in the range of parts by mass, and more preferably in the range of 0.005 to 1 part by mass. If the addition amount of the transesterification catalyst is in the range of 0.001 to 5 parts by mass with respect to 100 parts by mass in total of the polylactic acid resin and the resin (A), the resulting block copolymer is colored and the molecular weight is decreased. And the generation of lactide can be kept to a minimum.

In the present invention, in order to suppress the generation of lactide during the transesterification reaction, it is important to perform the normal pressure / melting step at normal pressure. The normal pressure in the present invention means that the atmospheric pressure in the normal pressure / melting step is within the range of 5 × 10 ^{4 to} 1.5 × 10 ⁵ Pa, and is 7 × 10 ^{4 to} 1.3 × 10 ⁵ Pa. Is preferable, and it is further more preferable that it is 9 * 10 < ⁴ > -1.1 * 10 < ⁵ > Pa. In this normal pressure / melting step, the reactor is preferably placed in an inert gas atmosphere in order to suppress hydrolysis and oxidative degradation of the resin.

  The reactor used for the normal pressure / melting process is not particularly limited, and examples of the batch reactor include a test tube with a stirrer, a vertical or horizontal tank reactor, or a kneader. Examples of the continuous reactor include a single screw extruder, a twin screw extruder, and other multi-screw extruders. In a multi-screw extruder of two or more axes, the screw rotation direction may be the same or different.

  Among them, from the viewpoint of shortening the reaction time and operability, the reactor for the normal pressure / melting step is preferably a continuous reactor, and more preferably a twin screw extruder. That is, the normal pressure / melting step is preferably performed in a continuous reactor, particularly in a twin-screw extruder. In the twin-screw extruder, not only the melting of the polylactic acid resin and the resin (A) proceeds rapidly, but also the distribution mixing and dispersion mixing of the resins proceed efficiently, so the ester bond of the polylactic acid resin and the resin (A) The probability of collision with a hydroxyl group increases, and as a result, their transesterification proceeds in a short time.

  As described above, the normal pressure / melting step is preferably performed in a twin-screw extruder, but the screw configuration of such a twin-screw extruder is to ensure the resin residence time and kneading force necessary for the reaction. It is preferable to use a kneading disk having an opposite direction, the screw diameter is preferably 10 to 400 mm, and the L / D is preferably 20 to 200.

  If the reactor is a twin screw extruder, the atmospheric pressure is measured at the vent hole.

  The time required for the normal pressure / melting step is preferably 30 minutes to 5 hours when a batch reactor having low kneadability is used. On the other hand, in the case of a continuous reactor represented by a twin screw extruder, the normal pressure / melting process time corresponds to the residence time of the resin in the reactor, and it is preferably 5 to 30 minutes. More preferably, it is 5 to 15 minutes.

  The block copolymer obtained by the production method of the present invention can further improve its storage stability by deactivating the remaining transesterification catalyst. Examples of the quenching agent used for such purposes include amino acids, phenols, hydroxycarboxylic acids, diketones, amines, oximes, phenanthrolines, pyridine compounds, dithio compounds, diazo compounds, thiols, porphyrins, Examples of the coordination atom include nitrogen-containing phenols and phosphorus compounds such as carboxylic acid, phosphoric acid, phosphoric acid ester, phosphoric acid metal salt, phosphorous acid, phosphorous acid ester, and phosphorous acid metal salt. These deactivators can be used alone or in combination. Among these deactivators, phosphorus compounds are more preferable, and phosphoric acid crystals or phosphorous acid crystals having a purity of 98% by mass or more are more preferable from the viewpoint of hydrolysis resistance of the polylactic acid resin.

  As a method of adding a deactivator, in the case of a batch type reactor, there is a method of once stopping the reactor after completion of the transesterification reaction, and operating the reactor again after adding the deactivator. In the case of a continuous reactor represented by a twin screw extruder, there is a method of adding a quencher from a side feeder of the extruder.

  The addition amount of the deactivator is preferably 0.01 to 10 parts by mass, and more preferably 0.1 to 5 parts by mass with respect to 1 part by mass of the transesterification catalyst added in the production process.

  Regarding the mass average molecular weight of the block copolymer obtained in the present invention, in the case where the present block copolymer is the main component of the molded product, in order to satisfy practical mechanical properties, its mass average molecular weight Is preferably 10,000 to 1,000,000, and more preferably 50,000 to 500,000. Further, when the present block copolymer is used as an additive such as a plasticizer, the mass average molecular weight is preferably 1,000 to 500,000 in order to develop softening and bleed-out resistance. 5,000 to 100,000, more preferably 5,000 to 50,000.

(Mixture of block copolymer and polylactic acid resin)
The block copolymer obtained in the present invention can be used in combination with a polylactic acid resin. The block copolymer in this case can also function as a plasticizer for the polylactic acid resin. Thus, when the block copolymer obtained in the present invention is used as a plasticizer for a polylactic acid resin, in order to disperse the block copolymer in the polylactic acid resin, the polylactic acid resin and the block copolymer are used. The polymer may be melt-kneaded, or the polylactic acid resin and the block copolymer may be dissolved in a good solvent such as chloroform, and the resin may be volatilized or the resin precipitated in a poor solvent.

  When a block copolymer is used as a plasticizer for a polylactic acid resin, the content ratio of the polylactic acid resin and the block copolymer is 100% by mass in total of the block copolymer and the polylactic acid resin. The polymer is preferably contained in an amount of 3 to 70% by mass, more preferably 5 to 60% by mass, and further preferably 5 to 50% by mass. If the content rate of a block copolymer is in said range, the softness | flexibility and impact resistance of a polylactic acid-type resin will improve, and the bleed-out of a block copolymer can be suppressed.

  When the block copolymer is used as a plasticizer for a polylactic acid-based resin, in addition to the polylactic acid-based resin and the block copolymer, other thermoplastic resins, general particles and additives are contained in the resin composition. You may mix.

  The normal pressure / melting step for producing the block copolymer is preferably performed in a twin screw extruder (hereinafter, the twin screw extruder is referred to as the twin screw extruder 1) as described above. Furthermore, when producing a mixture of a polylactic acid resin and a block copolymer, such as using a block copolymer as a plasticizer for a polylactic acid resin, the block copolymer produced in the twin screw extruder 1 is used. The coalescence is directly introduced from the twin-screw extruder 1 into another twin-screw extruder (hereinafter, the other twin-screw extruder is referred to as the twin-screw extruder 2), A method for producing a mixture of a polylactic acid resin and a block copolymer, which is characterized by mixing with a polylactic acid resin, is preferred. That is, when producing a mixture of a polylactic acid-based resin and a block copolymer, the block copolymer produced by the twin-screw extruder 1 is used in a twin-screw extruder 2 using a polymer tube or the like in a molten state. It is preferable to introduce it directly into the middle by a method such as side feed and mix with the polylactic acid resin in the twin-screw extruder 2. Here, the term “directly” means that when the block copolymer is introduced from the twin-screw extruder 1 into the twin-screw extruder 2, the block polymer is kept in the twin-screw extruder 1 from the twin-screw extruder 1 while maintaining the glass transition temperature or higher. It means introducing into the extruder 2. For example, when the block copolymer is taken out from the twin-screw extruder 1 and introduced into the twin-screw extruder 2 in a state where the block copolymer is at a glass transition temperature or lower, it is directly referred to here. Is not understood. In addition, when the block copolymer has a plurality of glass transition temperatures, the introduction of the block copolymer from the twin screw extruder 1 into the twin screw extruder 2 while maintaining the highest glass transition temperature or more directly That's it.

  When producing a mixture of a block copolymer and a polylactic acid resin, the mass average molecular weight of the block copolymer may be small and the glass transition temperature may be low, and such a block copolymer is difficult to chip. There is a possibility. In such a case, it is necessary to cool and solidify the obtained block copolymer once, and then to perform pulverization. On the other hand, if the block copolymer obtained by using the twin screw extruder 1 is directly introduced into the twin screw extruder 2 and mixed with the polylactic acid resin in the twin screw extruder 2, The cooling and pulverization time and labor described above are omitted, which is preferable.

  The screw configuration, screw diameter, L / D, and residence time of the twin screw extruder 1 and the twin screw extruder 2 are the same as the preferred screw configuration, screw diameter, L / D, and residence time of the twin screw extruder described above. It is preferable. Moreover, the twin screw extruder 1 and the twin screw extruder 2 may have the same configuration.

  Note that the twin-screw extruder 1 in which the block copolymer is produced needs to be at normal pressure for the reasons described above. The range of normal pressure is the same as described above. On the other hand, since the twin screw extruder 2 does not contribute to the production of the block copolymer in the present method, the pressure in the twin screw extruder 2 does not necessarily need to be a normal pressure, and can be reduced.

  In addition, as a method for producing a mixture of a polylactic acid resin and a block copolymer, the same biaxial extrusion as that in which the block copolymer was produced is performed on the block copolymer produced by a twin screw extruder. The block copolymer and the polylactic acid resin are mixed in the same twin-screw extruder as that produced the block copolymer by introducing the polylactic acid resin from the side feeder of the machine. There is also a method for producing a mixture of a polylactic acid resin and a block copolymer. This method is preferable because the time and labor for cooling and pulverizing the block copolymer can be omitted in the same manner as described above, and only one twin-screw extruder is required, and the apparatus configuration can be simplified.

  A preferable screw configuration of the twin-screw extruder used in the present method is that a kneading disk is placed in front of a side feeder into which a polylactic acid resin is introduced. The screw diameter, L / D and residence time are preferably the same as the preferred screw diameter, L / D and residence time of the twin screw extruder described above. The extrusion temperature is preferably 200 to 280 ° C. near the kneading disk, and the catalyst amount is preferably 0.05 to 5 parts by mass. This is because the block copolymer is mainly produced in this method from the point of the main feeder of the twin screw extruder to the point of the side feeder into which the polylactic acid resin is put, that is, a part of the twin screw extruder. This is because it is necessary to efficiently advance the reaction in this portion. Moreover, it is preferable to add a deactivator at the same time when putting the polylactic acid resin from the side feeder.

  In this method, the block copolymer is mainly produced from the point of the main feeder of the twin-screw extruder to the point of the side feeder into which the polylactic acid resin is put. For reasons it is necessary to carry out the reaction at normal pressure. The range of normal pressure is the same as described above. On the other hand, after the side feeder point, it hardly contributes to the formation of the block copolymer. Therefore, the atmospheric pressure is not necessarily a normal pressure in the section, and can be reduced.

  The polylactic acid resin used in the mixture of the polylactic acid resin and the block copolymer can be the same resin as the polylactic acid resin described above as a raw material for the block copolymer.

  The composition containing the block copolymer obtained in the present invention includes known antioxidants, crystal nucleating agents, UV stabilizers, anti-coloring agents, matting agents, deodorants, flame retardants, weathering agents, charging agents. Additives such as inhibitors, ion exchangers, tackifiers, antifoaming agents, color pigments, dyes, lubricants, foaming agents, and other resins may be used as necessary. The addition amount of these additives is not particularly limited as long as the effects achieved in the present invention are not impaired, but the additive is added to 100% by mass of the composition containing the block copolymer. Is preferably 0.01 to 30% by mass, more preferably 0.01 to 20% by mass, and still more preferably 0.01 to 10% by mass.

  From the viewpoint of odor and hydrolysis resistance, the block copolymer obtained in the present invention preferably has a residual lactide content of 1.00% by mass or less, more preferably 0.70% by mass or less. More preferably, it is 0.50% by mass or less.

  Moreover, since it is preferable that the polylactic acid-type resin and resin (A) which are raw materials do not remain, the block copolymer obtained by this invention has one peak derived from a polymer in the GPC elution curve. Is preferably present (unimodal). When the polylactic acid-based resin and the resin (A) remain, there are two (bimodal) peaks derived from the polymer in the GPC elution curve.

  Moreover, it is preferable that the resin (A) which is a raw material does not remain in the block copolymer obtained by the present invention. Therefore, for TmA0 and TmA defined below, TmA0-TmA is preferably 7.0 ° C. or higher, and more preferably 9.0 ° C. or higher.

  TmA0: Melting peak temperature derived from the resin (A), read from the chart of the DSC temperature rising process of the resin (A) alone.

  TmA: Melting peak temperature derived from the resin (A) segment, read from the DSC temperature rising chart of the block copolymer.

  In addition, when the mixture of the block copolymer and the polylactic acid resin obtained in the present invention is formed into a sheet, the resulting sheet has a tensile elastic modulus of 100 to 1,000 MPa in order to exhibit sufficient flexibility. It is preferable. The tensile elastic modulus is more preferably 100 to 950 MPa, and further preferably 100 to 900 MPa.

  In addition, the sheet containing the block copolymer and the polylactic acid resin needs to prevent the block copolymer from coming out of the polylactic acid resin, that is, its bleed-out resistance. As an index of bleed-out resistance, the hot water extraction rate of the sheet is preferably in the following range. That is, the mass reduction rate when the sheet is treated for 1 hour in distilled water boiled at 1 atm is preferably 5.0% or less, and more preferably 3.0% or less.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited thereto.
[Measurement and evaluation method]
Measurements and evaluations shown in the examples were performed under the following conditions.

(1) Elastic modulus (MPa)
Stress-strain measurement was performed using TENSILON UCT-100 manufactured by Orientec Co., Ltd. Using the first linear part of the stress-strain curve, the stress difference between the two points on the straight line was the same as the strain difference between the two points. And the tensile modulus was calculated. Specifically, a strip sample having a length of 150 mm and a width of 10 mm is cut out from a breath sheet, and measured according to the method defined in JIS K 7127 (1999) at an initial tensile chuck distance of 50 mm and a tensile speed of 200 mm / min. It was. Moreover, the measurement was performed 5 times and the average value was calculated.

(2) The amount of lactide produced was dissolved in methylene chloride, the concentration was adjusted to 1 g / 20 ml, 60 ml of acetone was added, and 320 ml of cyclohexane was added dropwise with ultrasonic stirring to precipitate a polymer component. The precipitate was removed by centrifugation and a PTFE filter having a pore diameter of 0.45 μm to prepare a sample solution. Using this sample liquid, gas chromatograph GC-17A (manufactured by Shimadzu Corporation), column: DB-17MS type (manufactured by J & W), column temperature: 80-250 ° C., 10 ° C./min, carrier gas: He Analysis was performed under conditions. In addition, a calibration curve was prepared using a sample solution of lactide alone, the concentration of which was changed in advance, and the lactide amount (% by mass) of the sample was determined using this calibration curve.

(3) Hot water extraction rate The hot water extraction rate was measured as an index of bleed-out resistance. The mass before processing was measured for a press sheet that had been conditioned for 1 day or more in an atmosphere of a temperature of 23 ° C. and a humidity of 65% RH. Next, the sheet was immersed in distilled water boiled at 1 atm for 1 hour, and after conditioning again under the same conditions as before the treatment, the mass after the treatment was measured. And the hot water extraction rate was computed by the following formula.
Hot water extraction rate (mass%) = (mass before treatment−mass after treatment) × 100 / mass before treatment (4) GPC
The mass average molecular weight was measured by gel permeation chromatography (GPC) and calculated by a polymethyl methacrylate conversion method. The calculation of the mass average molecular weight is performed only when there is only one polymer-derived peak in the elution curve of the obtained sample (unimodal), and it is derived from the polylactic acid resin and the resin (A). This was not carried out in the case of having peaks derived from two polymers (bimodal) or having peaks derived from more polymers. GPC measurement is performed using a Waters 2695 type, a WATERS differential refractometer 2414 type is used as a detector, a WATERS MODEL 510 is used as a pump, and two Shodex HFIP-806M are connected in series to a column. Used. Measurement conditions were a flow rate of 0.5 mL / min, a column temperature of 40 ° C., hexafluoroisopropanol added with 5 mM sodium trifluoroacetate as a solvent, and 0.2 mL of a solution having a sample concentration of 0.1% by mass was injected.

(5) DSC
Using a differential scanning calorimeter RDC220 manufactured by Seiko Instruments Inc., 5 mg of the generated sample was set in an aluminum pan, heated from 25 ° C. to 220 ° C. at a heating rate of 20 ° C./min, and kept at 220 ° C. for 5 minutes. After melting and holding, it was rapidly cooled to 25 ° C. And the melting peak temperature TmA (degreeC) derived from the resin (A) segment was read from the chart about the temperature rising process. Further, with the unreacted resin (A) as a sample, the melting peak temperature TmA0 (° C.) of the resin (A) was determined by the same method as described above, and TmA0-TmA was calculated.

[Polylactic acid resin]
(4032D)
Poly L-lactic acid, “4032D” manufactured by Natureworks, mass-average molecular weight 200,000, D-form content 1.4 mol%, melting point 166 ° C. A product dried in advance at 100 ° C. for 5 hours while reducing the pressure in a vacuum oven was used.

(4060D)
Poly L-lactic acid, “4060D” manufactured by Natureworks, mass average molecular weight 200,000, D-form content 12.0 mol%, no melting point. What was previously dried under the conditions of 50 ° C. and 7 hours while reducing the pressure in a vacuum oven was used.

  The mass average molecular weight was measured by using Waters 2695 manufactured by Japan Waters Co., Ltd., using polymethyl methacrylate as a standard, a column temperature of 40 ° C., and a hexafluoroisopropanol solvent.

[Resin (A)]
(PEG6000S)
Polyethylene glycol, “PEG6000S” manufactured by Sanyo Chemical Industries, mass average molecular weight 8,000, TmA0 is 64.0 ° C. A product dried in advance in a vacuum oven under reduced pressure at 30 ° C. for 7 hours was used.

(Ecoflex)
Polybutylene adipate terephthalate, “Ecoflex F Blend C1200” manufactured by BASF, mass average molecular weight 60,000, TmA0 is 120.2 ° C. What was previously dried under conditions of 80 ° C. and 7 hours while reducing the pressure in a vacuum oven was used.

[Transesterification catalyst]
(Mg acetate)
Magnesium acetate tetrahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) was used as a metal salt (metal organic acid salt).

(Mg chloride)
Magnesium chloride hexahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) was used as the metal salt (metal halide salt).

(Octanoic acid Sn)
As the metal salt (metal organic acid salt), tin (II) 2-ethylhexanoate (manufactured by Wako Pure Chemical Industries, Ltd.) was used.

(P-TSA)
As the sulfur acid, p-toluenesulfonic acid (manufactured by Wako Pure Chemical Industries, Ltd.) was used.

( Reference Example 1 )
40 parts by mass of 4032D, 60 parts by mass of PEG6000S and 0.5 parts by mass of Mg chloride were added to a test tube equipped with a stirrer and stirred at 200 ° C. in a nitrogen atmosphere at a pressure of 1.0 × 10 ⁵ Pa. The sample A was melted for 4 hours, cooled and solidified. The obtained sample A was subjected to lactide content, mass average molecular weight, and DSC measurement.

Further, 30 parts by mass of sample A, 20 parts by mass of 4032D, and 50 parts by mass of 4060D were weighed and added to a test tube equipped with a stirrer, and stirred at 240 ° C. in a nitrogen atmosphere at a pressure of 1.0 × 10 ⁵ Pa. The sample B was melted for 1 hour, cooled and solidified. The obtained sample B was pulverized, dried in a vacuum oven under reduced pressure at 50 ° C. for 7 hours, and pressurized at 220 ° C. to obtain an isotropic press sheet having a thickness of 200 μm. The elastic modulus and hot water extraction rate of the obtained press sheet were measured.

In Reference Example 2 and Comparative Example 1, samples were obtained in the same manner as in Reference Example 1 except that the composition and melting temperature of the raw materials charged into the test tube were changed as shown in Tables 1 and 2.

Further, in Comparative Examples 2 to 3, the composition and melting temperature of the raw material charged into the test tube were changed as shown in Table 2, and when obtaining Sample A, the air pressure in the test tube was changed to 1.0 × using a vacuum pump. A sample was obtained in the same manner as in Reference Example 1 except that 10 ³ Pa was used.

( Example 1 )
40 parts by mass of 4032D, 60 parts by mass of PEG6000S and 0.5 parts by mass of Mg chloride were weighed and blended, and charged into a twin screw extruder TEX30α (L / D = 35, screw diameter = 30 mm) manufactured by Nippon Steel Works. Then, the sample was melted and kneaded at a screw speed of 200 rpm and a feed rate of 10 kg / h, discharged from the die, cooled and solidified to obtain sample A. The temperature setting of TEX30α was 80 ° C. from the lower part of the hopper to the front of the first kneading part (the point of L / D = 25 as measured from the screw tip), and 200 ° C. after the first kneading part. Moreover, the vent hole which exists in the point of L / D = 20 measured from the screw front-end | tip was made into the open state. The atmospheric pressure at the point was 1.0 × 10 ⁵ Pa. The obtained sample A was subjected to lactide content, mass average molecular weight, and DSC measurement.

Further, 30 parts by mass of sample A, 20 parts by mass of 4032D, and 50 parts by mass of 4060D were weighed and added to a test tube equipped with a stirrer, and stirred at 240 ° C. in a nitrogen atmosphere at 1.0 × 10 ⁵ Pa. The sample B was melted for 1 hour, cooled and solidified. The obtained sample B was pulverized, dried in a vacuum oven under reduced pressure at 50 ° C. for 7 hours, and pressurized at 220 ° C. to obtain an isotropic press sheet having a thickness of 200 μm. The elastic modulus and hot water extraction rate of the obtained press sheet were measured.

Moreover, Examples 2-7 and Comparative Examples 4-7 obtained the sample similarly to Example 1 except having changed the composition and extrusion temperature of the raw material thrown into TEX30 (alpha) as Table 1 and Table 2. FIG. .

Further, in Comparative Example 8, after changing the composition of the raw material to be introduced into TEX30α and the extrusion temperature as shown in Table 2, the vent hole existing at the point of L / D = 20 as measured from the screw tip of TEX30α was vacuumed. A sample was obtained in the same manner as in Example 1 except that it was connected to a pump and the pressure at the point was set to 3.0 × 10 ³ Pa.

  The physical properties of the obtained samples are shown in Tables 1 and 2.

( Example 8 )
TEX30α (L / D = 35, screw diameter = 30 mm) manufactured by Nippon Steel Works is used as the twin screw extruder 1, and TEX44α (L / D = 38, screw diameter = 44 mm) manufactured by Nippon Steel Works is used as the twin screw extruder 2. The apparatus was configured such that the resin discharged from the twin-screw extruder 1 was side-fed in the middle of the twin-screw extruder 2 (measured from the screw tip and at a point of L / D = 18).

4032 parts of 4032D, 60 parts by weight of PEG6000S, and 0.5 parts by weight of Mg chloride are weighed and blended, put into the twin screw extruder 1 and melted and kneaded at a screw speed of 200 rpm and a feed rate of 10 kg / h. did. The temperature of the twin-screw extruder 1 was set to 80 ° C. from the lower part of the hopper to the front of the first kneading part (measured from the tip of the screw, the point of L / D = 25), and 200 ° C. after the first kneading part. . Moreover, the vent hole which exists in the point of L / D = 20 measured from the screw front-end | tip of the twin-screw extruder 1 was made into the open state. The atmospheric pressure at the point was 1.0 × 10 ⁵ Pa.

Further, 67 parts by mass of 4032D and 167 parts by mass of 4060D were weighed and blended, and charged into the twin-screw extruder 2 and melted and kneaded at a screw rotational speed of 200 rpm and a feed amount of 23.3 kg / h. The temperature setting of the twin-screw extruder 2 was 150 ° C. from the lower part of the hopper to the front of the first kneading part (the point of L / D = 28 measured from the screw tip), and 220 ° C. after the first kneading part. . Moreover, the vent hole which exists in the point of L / D = 20 measured from the screw front-end | tip of the twin-screw extruder 2 was made into the open state. The atmospheric pressure at the point was 1.0 × 10 ⁵ Pa. Sample C was obtained by cooling and solidifying the resin discharged from the die of the twin screw extruder 2. The obtained sample C was pulverized, dried in a vacuum oven under reduced pressure at 50 ° C. for 7 hours, and pressurized at 220 ° C. to obtain an isotropic press sheet having a thickness of 200 μm. The elastic modulus and hot water extraction rate of the obtained press sheet were measured.

In Example 9 and Comparative Example 9, samples were obtained in the same manner as in Example 8 except that the composition of the raw materials charged into the twin screw extruders 1 and 2 was changed as shown in Table 3.
The physical properties of the obtained sample are shown in Table 3.

( Example 10 )
TEX30α (L / D = 35, screw diameter = 30mm) manufactured by Nippon Steel Works is used as a twin screw extruder, and the side feeder is in the middle of the twin screw extruder (point of L / D = 18 as measured from the screw tip). Was installed.

4032D, 40 parts by weight of PEG6000S, 60 parts by weight of PEG6000S, and 0.5 parts by weight of Mg chloride are weighed and blended, put into the main hopper of a twin screw extruder and melted at a screw speed of 200 rpm and a feed rate of 10 kg / h. -Kneaded. The temperature setting of the twin-screw extruder 1 is 80 ° C. from the lower part of the hopper to the front of the first kneading part (the point of L / D = 25 as measured from the screw tip), and 240 from the first kneading part to the side feeder. C. Moreover, the vent hole which exists in the point of L / D = 20 measured from the screw front-end | tip of the twin-screw extruder 1 was made into the open state. The atmospheric pressure at the point was 1.0 × 10 ⁵ Pa.

  Further, 67 parts by mass of 4032D and 167 parts by mass of 4060D were weighed and blended, put into a side feeder, and melted and kneaded. The temperature setting after the side feeder was 200 ° C. Further, the resin discharged from the die of the twin screw extruder was cooled and solidified to obtain Sample D. The obtained sample D was pulverized, dried in a vacuum oven under reduced pressure at 50 ° C. for 7 hours, and pressurized at 220 ° C. to obtain an isotropic press sheet having a thickness of 200 μm. The elastic modulus and hot water extraction rate of the obtained press sheet were measured.

Moreover, Examples 11-12 and Comparative Examples 10-11 obtained the sample similarly to Example 10 except having changed the composition of the raw material thrown into a twin-screw extruder as Table 4.
The physical properties of the obtained sample are shown in Table 4.

( Example 13 )
4032D 40 parts by mass, PEG6000S 60 parts by mass, Mg chloride 0.5 parts by mass weighed and blended, single-screw extruder GT-40 (L / D = 28, screw diameter = 40 mm) manufactured by Plastic Engineering Laboratory The sample A was melted and kneaded at a screw speed of 50 rpm and a feed rate of 10 kg / h, discharged from the die, cooled and solidified to obtain sample A. In addition, the temperature setting of GT-40 was 80 degreeC in the lower part of the hopper, and 200 degreeC after that. The vent hole in the middle was opened. The atmospheric pressure at the point was 1.0 × 10 ⁵ Pa. The obtained sample A was subjected to lactide content, mass average molecular weight, and DSC measurement.

Further, 30 parts by mass of sample A, 20 parts by mass of 4032D, and 50 parts by mass of 4060D were weighed and added to a test tube equipped with a stirrer, and stirred at 240 ° C. in a nitrogen atmosphere at a pressure of 1.0 × 10 ⁵ Pa. The sample B was melted for 1 hour, cooled and solidified. The obtained sample B was pulverized, dried in a vacuum oven under reduced pressure at 50 ° C. for 7 hours, and pressurized at 220 ° C. to obtain an isotropic press sheet having a thickness of 200 μm. The elastic modulus and hot water extraction rate of the obtained press sheet were measured.

Moreover, the comparative example 12 obtained the sample like Example 13 except having changed the composition of the raw material thrown into GT-40 as Table 5. FIG.

Further, in Comparative Example 13, a sample was obtained in the same manner as in Example 13 except that the vent hole of GT-40 was connected to a vacuum pump and the atmospheric pressure at the point was set to 3.0 × 10 ³ Pa.

  The physical properties of the obtained sample are shown in Table 5.

By using the normal pressure / melting step, which is a feature of the present invention, a block copolymer with little residual lactide can be obtained. The block copolymer obtained by the present invention can be used as a flexible resin for molded articles such as films, alone or mixed with a polylactic acid resin, and a plasticizer having bleed-out resistance for a polylactic acid resin. Can also be suitably used.

Claims (4)

Polylactic acid resins, resins having at least one hydroxyl group in the molecule (hereinafter, resins having at least one hydroxyl group in the molecule are referred to as resins (A)), polyether resins, and metal organics as transesterification catalysts salt and / or a metal halide salt, twin-screw extruder (hereinafter, the twin-screw extruder, a twin that screw extruder 1) melted at atmospheric pressure at a (hereinafter, the melt under atmospheric pressure A block copolymer of a polylactic acid resin and a resin (A) (hereinafter referred to as a polylactic acid resin and a resin), characterized by carrying out a transesterification reaction under normal pressure. (A) A block copolymer is referred to as a block copolymer). The method for producing a block copolymer according to claim 1, wherein the resin (A) is a polyalkylene glycol resin .   A block copolymer produced by the method according to claim 1 is directly introduced from a twin screw extruder 1 into another twin screw extruder and mixed with a polylactic acid resin. For producing a mixture of a resin and a block copolymer.   The block copolymer produced by the method according to claim 1 is charged with a polylactic acid resin from a side feeder of the same twin-screw extruder that produced the block copolymer. A method for producing a mixture of a polylactic acid resin and a block copolymer, wherein the block copolymer and the polylactic acid resin are mixed in the same twin-screw extruder as that produced the copolymer.