JPWO2002006400A1 - Lactic acid-based resin composition and molded body made thereof - Google Patents

Abstract

(57) [Abstract] The present invention provides a lactic acid-based resin composition comprising a mixture (A) of polylactic acid (a1) and aliphatic polyester (a2) and a mixture (B) of an aliphatic block copolyester having polylactic acid segments and aliphatic polyester segments, wherein the aliphatic block copolyester (B) (1) contains 20 to 80 wt % of a lactic acid component in terms of monomers, (2) has a weight-average molecular weight of 1,000 to less than 60,000, and (3) the weight-average molecular weight of the polylactic acid segments is 500 to 55,000, and the weight-average molecular weight of the aliphatic polyester segments is 500 to 55,000.

Description

Detailed Description of the Invention

TECHNICAL FIELD The present invention relates to a lactic acid-based resin composition and a molded article thereof. More specifically,
This invention relates to a lactic acid-based resin composition that is excellent in moldability, flexibility, and safety, and furthermore, easily decomposes in nature after use, and molded articles thereof. Background Art Generally, resins with excellent flexibility, heat resistance, and water resistance include polyethylene, polypropylene, soft polyvinyl chloride, polyethylene terephthalate, and the like, and are used for garbage bags, packaging bags, and the like. However, when these resins are discarded after use, they increase the amount of waste, and since they are hardly decomposed in the natural environment, even if buried, they remain in the ground semi-permanently. Furthermore, dumped plastics cause problems such as landscape damage and destruction of the living environment of marine life. In response to this, biodegradable thermoplastic polymers have been developed, such as polyhydroxycarboxylic acids such as polylactic acid, and aliphatic polyesters derived from aliphatic polyhydric alcohols and aliphatic polycarboxylic acids. These polymers are 100% biodegradable in the animal body within several months to one year, and
Alternatively, when placed in soil or seawater, it begins to decompose in a few weeks in a humid environment and disappears within about one to several years. Furthermore, the decomposition products are lactic acid, carbon dioxide, and water, which are harmless to the human body. In particular, polylactic acid is expected to be used in a wider range of fields due to the recent trend toward mass-produced, inexpensive production of its raw material, L-lactic acid, through fermentation, its rapid decomposition rate in compost, its mold resistance, and its resistance to odor and discoloration in food. However, polylactic acid has high rigidity and is not suitable for applications requiring flexibility, such as films and packaging materials. Blending a flexible polymer is generally known as a method for softening a resin. However, blending a flexible general-purpose resin, such as polyethylene, polypropylene, or polyvinyl chloride, with polylactic acid does not achieve the development of a biodegradable and flexible lactic acid-based resin composition, which is the subject of the present invention, as described below.
Therefore, the only polymer blends that can impart flexibility to polylactic acid are soft biodegradable resins. Examples of such resins include polybutylene succinate, polyethylene succinate, polyhydroxybutyric acid, polyhydroxyvaleric acid, polycaprolactone, and copolymers and mixtures thereof.
These soft resins are disclosed in Japanese Patent Application Laid-Open No. 245866 and Japanese Patent Application Laid-Open No. 9-111107. However, these soft resins are not very compatible with polylactic acid, and simply melt-mixing them poses several practical problems when producing films, filaments, etc. For example, when forming films or filaments, even if they are heated and melt-mixed in an extruder, they do not disperse sufficiently uniformly, resulting in uneven viscosity, uneven film thickness and non-uniform fiber diameter, and even film or fiber breakage, making stable molding difficult. Furthermore, even if a film or fiber is obtained, when it is subsequently stretched and oriented to improve physical properties such as heat resistance and strength, the resin is prone to breakage during stretching, cannot be stretched stably, or cannot be stretched to a sufficient ratio, resulting in insufficient improvement in heat resistance and strength, and practically usable films or fibers cannot be obtained. Japanese Patent Application Laid-Open No. 10-262474 discloses a method for producing crystalline polylactic acid (
A), an aliphatic polyester (B) containing a chain diol and an aliphatic dicarboxylic acid as main components and having a melting point of 140°C or less, and a mixture of the polylactic acid (A) and the aliphatic polyester (B)
The publication also discloses an agricultural sheet comprising a mixture of a block copolymer (C) of polylactic acid, a chain diol, and an aliphatic dicarboxylic acid, and fibers. It also describes that this mixture has improved flowability and moldability compared to a simple mixture of an aliphatic polyester of polylactic acid, a chain diol, and an aliphatic dicarboxylic acid. However, no specific examples are given, and in particular, the molecular weight of the block copolymer (C) is unclear from the descriptions of other examples.
It is estimated that the molecular weight is several hundred thousand. However, when a block polymer having such a large molecular weight is used, the effects of improving fluidity and moldability are not fully realized, as will be apparent from the comparative examples described below. Thus, simply blending polylactic acid with a soft biodegradable resin does not substantially enable stable and productive production of molded articles such as films and filaments that have been imparted with flexibility. Furthermore, conventional techniques have been virtually unable to improve physical properties such as heat resistance and strength through stretch-oriented crystallization. The objectives of the present invention are: 1) a technology for efficiently dispersing polylactic acid and a soft biodegradable resin; 2) the development of a flexible lactic acid-based resin composition; 3) molded articles such as films and filaments obtained from the flexible lactic acid-based resin composition; and 4) the development of a technology for efficiently producing molded articles from polylactic acid that are highly endowed with practical physical properties such as strength, heat resistance, and flexibility. Disclosure of the Invention In order to solve the problems of the present invention, the present inventors have designed and searched for compounds to improve the compatibility between polylactic acid and soft biodegradable resins. As a result, they have found a compound that has a substantially sufficient compatibilizing effect even in small amounts and satisfies the above-mentioned problems, and have completed the present invention. That is, the present invention is characterized by the following features [1] to [12]. [1] A lactic acid-based resin composition comprising a mixture (A) of polylactic acid (a1) and an aliphatic polyester (a2) and a mixture (B) of an aliphatic block copolyester having a polylactic acid segment and an aliphatic polyester segment, wherein the aliphatic block copolyester (B) satisfies all of the following conditions (1) to (3): (1) Contains 20 to 80 wt% of lactic acid components in terms of monomers. (2) Has a weight-average molecular weight of 1,000 to less than 60,000. (3) The weight-average molecular weight of the polylactic acid segment is 500 to 55,000, and the weight-average molecular weight of the aliphatic polyester segment is 500 to 55,000. [2] The composition ratio of the mixture (A) to the aliphatic block copolyester (B) is 0.
[3] The lactic acid resin composition according to [1], wherein the aliphatic polyester (a2) has an elastic modulus of 2,500 MPa or less as measured by the test method of JIS K6732. [4] The lactic acid resin composition according to any one of [1] to [3], wherein the blend (A) of polylactic acid (a1) and aliphatic polyester (a2) has a mixing ratio of 20 to 80 parts by weight of polylactic acid (a1) to 80 to 20 parts by weight of aliphatic polyester (a2). [5] The lactic acid resin composition according to any one of [1] to [4], wherein the aliphatic polyester (a2) is polybutylene succinate and/or polycaprolactone. [6] A molded article made from the lactic acid resin composition according to any one of [1] to [5]. [7] The molded article according to [6], wherein the molded article is stretched 1.1 to 15 times in at least one axial direction. [8] The molded article according to [6] or [7], wherein the molded article is a film or sheet. [9] The molded article according to [6] or [7], wherein the molded article is a tape yarn. [10] The molded article according to [6] or [7], wherein the molded article is a monofilament or multifilament. [11] The molded article according to [6] or [7], wherein the molded article is a nonwoven fabric. [12] A method for producing a block copolymer of aliphatic block copolyester (B) having a polylactic acid segment and an aliphatic polyester segment with polylactic acid (a1) and aliphatic polyester (a2).
), a lactic acid-based resin composition comprising the mixture with an aliphatic block copolyester (B), characterized in that the aliphatic block copolyester (B) satisfies all of the following conditions (1) to (3): (1) containing 20 to 80 wt% of a lactic acid component in terms of monomers; (2) having a weight-average molecular weight of 1,000 to less than 60,000; and (3) having a weight-average molecular weight of 500 to 55,000 of the polylactic acid segment and a weight-average molecular weight of 500 to 55,000 of the aliphatic polyester segment. BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. In the present invention, the mixture (A) of polylactic acid (a1) and other aliphatic polyester (a2) comprises 20 to 80 parts by weight of polylactic acid (a1) and other aliphatic polyester (a2).
a2) 80 to 20 parts by weight. [Polylactic acid (a1)] Lactic acid used as a raw material for polylactic acid in the present invention includes L-lactic acid, D-lactic acid,
Specific examples of the method for producing polylactic acid used in the present invention include: 1) a method of direct dehydration polycondensation using lactic acid as a raw material (e.g., a method described in USP 5,310
1) a method for producing a polyester polymer by dehydration polycondensation of lactic acid in the presence of a catalyst, in which solid-state polymerization is carried out in at least a part of the steps. However, the production method is not particularly limited. Furthermore, copolymerization may be carried out in the presence of a small amount of aliphatic polyhydric alcohols such as trimethylolpropane and glycerin, aliphatic polybasic acids such as butanetetracarboxylic acid, polysaccharides, or other polyhydric alcohols. Furthermore, a binder (polymer chain extender) such as a diisocyanate compound may be used to increase the molecular weight. [Aliphatic Polyester (a2)] The soft aliphatic polyester (a2) used in the present invention is a polyester polymer containing an aliphatic hydroxycarboxylic acid, an aliphatic dihydric alcohol, and an aliphatic dibasic acid, as described below.
It is a biodegradable polymer that can be produced by combining various
The elastic modulus measured by the test method of IS K6732 is 2500 MPa or less, more preferably 1 to 1500 MPa, even more preferably 5 to 1000 MPa, even more preferably 5 to 750 MPa, and most preferably 5 to 500 MPa. If the elastic modulus is greater than 2500 MPa, the softening effect when mixed with polylactic acid is reduced. Preferred soft aliphatic polyesters in this invention include, for example, polyethylene succinate, polybutylene succinate, polybutylene succinate adipate, polyhydroxybutyric acid, polyhydroxyvaleric acid, copolymers of β-hydroxybutyric acid and β-hydroxyvaleric acid, polycaprolactone, etc. In particular, polybutylene succinate, polybutylene succinate adipate, and polycaprolactone are preferred in terms of their elastic modulus and because they are readily available and inexpensive. These aliphatic polyesters may have their polymer chains extended with a binder such as diisocyanate, or may be copolymerized in the presence of a small amount of aliphatic polyhydric alcohols such as trimethylolpropane or glycerin, aliphatic polybasic acids such as butanetetracarboxylic acid, or polyhydric alcohols such as polysaccharides, and may further be crosslinked by electron beam. The aliphatic polyesters may be produced by methods similar to those used for producing polylactic acid, but are not limited to these methods. [Aliphatic Hydroxycarboxylic Acids] Specific examples of aliphatic hydroxycarboxylic acids used in the soft aliphatic polyesters of the present invention include glycolic acid, lactic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxyvaleric acid, 4-hydroxyvaleric acid, and 6-hydroxycaproic acid. Furthermore, cyclic esters of aliphatic hydroxycarboxylic acids, such as glycolide, a dimer of glycolic acid, and ε-caprolactone, a cyclic ester of 6-hydroxycaproic acid, may be used. These may be used alone or in combination.

Specific examples of the aliphatic dihydric alcohol used in the flexible aliphatic polyester of the present invention include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, neopentyl glycol, polytetramethylene glycol, 1,4-
cyclohexanedimethanol, etc. These can be used alone or in combination of two or more. [Aliphatic dibasic acids] Specific examples of aliphatic dibasic acids used in the soft aliphatic polyester of the present invention include oxalic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, phenylsuccinic acid, etc. These can be used alone or in combination of two or more. [Molecular weights of polylactic acid (a1) and aliphatic polyester (a2)] The weight average molecular weights (M
The weight average molecular weight (Mw) and molecular weight distribution are not particularly limited as long as they are substantially moldable. The weight average molecular weights of the polylactic acid (a1) and aliphatic polyester (a2) used in the present invention are not particularly limited as long as they exhibit substantially sufficient mechanical properties, but generally, the weight average molecular weight (Mw) is preferably 60,000 to 1,000,000, more preferably 80,000 to 500,000, and most preferably 100,000 to 300,000.
If the molecular weight is less than 60,000, the mechanical properties of the molded article obtained by molding the resin composition may be insufficient, and conversely, if the molecular weight exceeds 1,000,000, the melt viscosity during molding may become extremely high, making handling difficult and uneconomical in production. [Aliphatic Block Copolyester (B)] The aliphatic block copolyester (B) used in the present invention is a block copolymer comprising lactic acid and the above-mentioned [aliphatic dibasic acid], [aliphatic dihydric alcohol], and [aliphatic hydroxycarboxylic acid], and contains 20 to 80% lactic acid component in terms of monomers.
The aliphatic block copolyester (B) according to the present invention can be produced by applying, for example, the method of direct dehydration condensation of lactic acid seen in the above-mentioned example of polylactic acid, or the method of ring-opening polymerization of lactide, a cyclic dimer of lactic acid, and examples thereof include: 1) a method of ring-opening polymerization of a monomer to polymerize it, and then ring-opening polymerization addition of another monomer component to the polymer, wherein at least one of the monomer components is lactide; and 2) a method of mixing a polylactic acid component obtained by direct dehydration polycondensation or ring-opening polymerization with an aliphatic polyester component obtained by a similar method, and carrying out dehydration polycondensation addition in the presence or absence of a catalyst and/or an organic solvent. More specifically, examples include: 1) a method (two-stage ring-opening polymerization) in which caprolactone is first subjected to ring-opening polymerization in the presence of a catalyst and an aliphatic alcohol to obtain a polymer, and then lactide is added and polymerized, as shown in Production Example 5-1; and 2) a method (two-stage dehydration polycondensation) in which polylactic acid obtained by direct dehydration polycondensation is mixed with another aliphatic polyester and dehydration polycondensed in the presence of a catalyst and an organic solvent, as shown in Production Example 5-10. In the present invention, it is necessary to control the molecular weight of the aliphatic block copolyester (B) and the molecular weight of each block unit within a specific range. Examples of such methods include a method of appropriately changing reaction conditions such as reaction temperature and time during polymerization to monitor the progress of the polymerization degree, and a method of adding a terminal terminator. In particular, in the case of ring-opening polymerization, the method of adding a terminal terminator is particularly preferred because it has a high polymerization rate. Examples of terminal terminators that can be used in the present invention include compounds having a hydroxyl group or a carboxyl group, such as monofunctional compounds such as aliphatic alcohols, aliphatic carboxylic acids, and their anhydrides. Examples of the aliphatic alcohol include saturated, unsaturated, straight-chain, and
Branched aliphatic alcohols include methanol, ethanol, propanol,
Examples of the aliphatic carboxylic acids and their acid anhydrides include isopropanol, butanol, isobutanol, tert-butanol, heptanol, isoheptanol, hexanol, octanol, lauryl alcohol, palmityl alcohol, myristyl alcohol, stearyl alcohol, oleyl alcohol, etc.
Examples of the terminal terminator include saturated, unsaturated, straight-chain, and branched aliphatic carboxylic acids, such as acetic acid, propanoic acid, isopropanoic acid, butanoic acid, isobutanoic acid, tert-butanoic acid, heptanoic acid, isoheptanoic acid, pentanoic acid, octanoic acid, lauric acid, palmitic acid, stearic acid, oleic acid, erucic acid, and behinic acid. Ethanol, lauryl alcohol, palmityl alcohol, myristyl alcohol, stearyl alcohol, and oleyl alcohol are particularly preferred for use as the terminal terminator in the present invention. The amount of terminal terminator added is preferably 0.05 to 5 mol%, more preferably 0.1 to 3 mol%, and more preferably 0.2 to 2 mol%, based on the total number of moles of monomer units constituting the aliphatic block copolyester. If the amount is less than 0.05 mol%, the molecular weight of the aliphatic block copolyester increases, which may result in the compatibilizing effect not being exerted. On the other hand, if it is more than 5 mol %, the molecular weight of the aliphatic block copolyester will be small, and when the composition of the present invention is prepared, not only will the compatibilizing effect not be achieved but the mechanical strength may also be reduced. The molecular weight of the aliphatic block copolyester (B) is particularly important, and the weight average molecular weight is 1,000 to less than 60,000, preferably 1,000 to 50,000, more preferably 3,000 to 40,000, and even more preferably 5,000 to 30,000.
If it is less than 1,000, the effect as a compatibilizer is lost. Conversely, if it is more than 60,000, the effect of addition is not exhibited. Furthermore, the repeating unit of lactic acid, which is an essential component of the block copolymer, should have a weight-average molecular weight of 500 to 55,000, preferably 1,500 to 50,000, more preferably 3,000 to 40,000, and even more preferably 5,000 to 30,000. On the other hand, the repeating unit of other aliphatic polyesters should have a weight-average molecular weight of 500 to 55
000, preferably 1500 to 50000, more preferably 3000 to 4
[Amount of Aliphatic Block Copolyester (B)] The amount of aliphatic block copolyester (B) added is 0.05 to 100 parts by weight of the mixture (A) of polylactic acid (a1) and other aliphatic polyester (a2).
The range is 10 parts by weight, preferably 0.1 to 7 parts by weight, more preferably 0.2
The preferred amount of the aliphatic block copolyester (B) is 0.05 to 5 parts by weight, more preferably 0.3 to 3 parts by weight. If the amount of the aliphatic block copolyester (B) added is less than 0.05 parts by weight, the compatibilizing effect may be insufficient. If the amount exceeds 10 parts by weight, the melting point and molecular weight of the aliphatic block copolyester (B) may be relatively low, resulting in a decrease in the heat resistance of the lactic acid-based resin composition and a decrease in the strength of the resulting molded article. The aliphatic block copolyester (B) of the present invention exhibits excellent compatibilizing effect when mixed with polylactic acid (a1) and aliphatic polyester (a2). For example, when pellets obtained by simply melt-kneading a mixture of polylactic acid and polybutylene succinate are heated, melted, and then cooled, an exothermic peak due to crystallization of the polybutylene succinate component is observed in thermal analysis by DSC. However, by adding the aliphatic block copolyester (B) of the present invention to the mixture, this exothermic peak disappears. That is, the addition of the aliphatic block copolyester (B) of the present invention is thought to suppress separation and rearrangement of the polybutylene succinate component in the mixture during melt cooling, thereby delaying crystallization of the polybutylene succinate component, thereby providing an excellent compatibilizing effect. As a result, in molded articles obtained by injection molding or the like, the polybutylene succinate component is efficiently dispersed in the mixture, and even when a relatively small amount of the aliphatic block copolyester (B) is added, the resulting molded article can exhibit a higher elongation percentage. Furthermore, in stretch-oriented molded articles such as yarns and filament nonwoven fabrics, the addition of the aliphatic block copolyester (B) reduces unevenness in the concentration and thickness of each component in the molded article before stretching, enabling more uniform and higher stretching, resulting in a molded article with high strength. [Other Additives] The lactic acid-based resin composition of the present invention can be further supplemented with other additives to achieve the desired properties (e.g., moldability, secondary processability, degradability,
Depending on the purpose of improving tensile strength, heat resistance, storage stability, weather resistance, etc., various additives (plasticizers, antioxidants, UV absorbers, heat stabilizers, flame retardants, internal mold release agents, inorganic additives, antistatic agents, surface wetting improvers, incineration aids, pigments, lubricants, natural products, etc.) can be added. For example, in inflation molding and T-die extrusion molding, inorganic additives and lubricants (aliphatic carboxylic acid amides, aliphatic carboxylic acid bisamides, etc.) can be added to prevent blocking and improve the slip properties of films and sheets. Examples of inorganic additives include silica, calcium carbonate, talc, kaolin, kaolinite, carbon, titanium oxide, zinc oxide, etc., with silica and calcium carbonate being particularly preferred. These additives can be used alone or in combination. Examples of organic additives include starch and derivatives thereof, cellulose and derivatives thereof, pulp and derivatives thereof, paper and derivatives thereof, wheat flour, soybean pulp refuse, bran, coconut shells, coffee grounds, and protein. These may be used alone or in a mixture of two or more. [Method for producing a lactic acid based resin composition] The lactic acid based resin composition of the present invention is a mixture of polylactic acid (a1) and other aliphatic polyesters (
a2) and the aliphatic block copolyester (B), and, if necessary, other additives are mixed and kneaded to obtain the copolymer.
For example, a method of uniformly mixing using a high-speed or low-speed agitator, etc., followed by melt-kneading in a single-screw or multi-screw extruder with sufficient kneading capacity, or a method of mixing and kneading during melting can be adopted. The lactic acid based resin composition of the present invention is preferably in the form of pellets, rods, powder, etc. [Molded Product and Method for Producing the Same] The lactic acid based resin composition of the present invention is a suitable material that can be applied to known and commonly used molding methods, and the obtained molded product is not particularly limited, but can be, for example, a film/sheet, monofilament, multifilament such as fiber or nonwoven fabric, injection molded product, blow molded product,
Examples of suitable thermoformed articles include laminates, foams, and vacuum-formed articles. The lactic acid-based resin composition of the present invention has good moldability when subjected to stretch-oriented crystallization,
In this case, the effects of the present invention are significantly exhibited, and the composition is suitable for producing films and sheets obtained by stretching, tape yarns, stretch-blow molded articles, (mono- and multi-) filaments, and nonwoven fabrics. Molding methods for molded articles obtained from the lactic acid-based resin composition of the present invention include injection molding, blow molding (injection stretch-blow, extrusion stretch-blow, and direct blow), and
Examples of suitable molding methods include balloon molding, inflation molding, coextrusion, calendaring, hot pressing, solvent casting, (stretching) extrusion molding, extrusion lamination with paper or aluminum, profile extrusion molding, thermoforming such as vacuum (compressed air) molding, melt spinning (monofilament, multifilament, spunbonding, meltblown, fiberization, etc.), foam molding, and compression molding. In particular, molding methods including stretching, orientation, and crystallization steps such as extrusion molding and melt spinning are more preferred because they can improve the practical strength and appearance of the resulting molded article, such as strength, heat resistance, impact resistance, and transparency. Molded articles obtained from the lactic acid-based resin composition of the present invention include, for example, molded articles obtained by known or commonly used molding methods, and are not limited in terms of shape, size, thickness, design, etc. [Specific Uses] Molded articles obtained by molding the lactic acid-based resin composition of the present invention using the above molding method include bottles, films or sheets, hollow tubes, laminates, vacuum (compressed air) molded containers, (mono- and multi-)filaments, nonwoven fabrics, foams, shopping bags, paper bags, shrink films, garbage bags, compost bags, lunch boxes, containers for prepared foods, food and confectionery packaging films, food wrap films, cosmetic and fragrance wrap films, diapers, sanitary napkins, pharmaceutical wrap films, pharmaceutical wrap films, surgical patches used for stiff shoulders, sprains, etc. The film can be suitably used as a wide range of materials, including medicinal wrap films, agricultural and horticultural films, pesticide wrap films, greenhouse films, fertilizer bags, packaging bands, packaging films for magnetic tape cassettes such as video and audio products, floppy disk packaging films, plate-making films, adhesive tapes, tapes, yarns, seedling pots, waterproof sheets, sandbags, construction films, weed control sheets, vegetation nets, and various other packaging films for food, electronics, medical care, pharmaceuticals, cosmetics, etc., as well as materials used in the agricultural, civil engineering, and fisheries fields. Examples The present invention will be specifically explained below using examples, but is not limited thereto as long as it does not exceed the technical scope of the present invention. The weight-average molecular weight (Mw) and physical properties shown in the Production Examples, Examples, and Comparative Examples were measured by the following methods. 1) Weight-average molecular weight (Mw): Measured by gel permeation chromatography (GPC) using polystyrene as a standard.
) at a column temperature of 40°C using chloroform as a solvent. 2) Strength, modulus of elasticity (flexibility), and elongation of film: These were determined in accordance with JIS K6732. A flexible film in the present invention has a modulus of elasticity in the range of 2500 MPa. 3) Tensile strength, elongation, flexural strength, and flexural modulus of dumbbell specimen: Test specimens obtained by injection molding were evaluated in accordance with ASTM D-790. 4) Strength and elongation of filament: These were determined in accordance with JIS L1095. 5) Folding endurance: These were determined in accordance with JIS P8115. 6) Haze: These were measured using a Tokyo Denshoku Haze Meter in accordance with JIS K-6714. 7) Drop impact test: A 1000 ml container was filled with 800 ml of water and the specimen was dropped for 1 minute at an ambient temperature of 20°C.
The container was dropped onto a concrete floor from a height of 0.5 m, and the number of times until the container broke was determined. The number of drops was repeated up to 10 times. Production Example 1 (Production of Polylactic Acid) 400 kg of L-lactide, 0.04 kg of stannous octanoate, and 0.12 kg of lauryl alcohol were sealed in a thick-walled cylindrical stainless steel polymerization vessel equipped with a stirrer, and degassed in vacuum for 2 hours. After replacing with nitrogen gas, the vessel was heated at 200°C/10 m.
The mixture was heated and stirred at 1000 kJ/cmHg for 2 hours. After the reaction was completed, the molten polylactic acid was extracted from the outlet at the bottom, cooled in air, and cut into pellets using a pelletizer. The polylactic acid thus obtained was found to be in a yield of 340 kg and 85%.
The weight average molecular weight (Mw) was 138,000. Production Example 2 (Production of Polylactic Acid) 100 kJ of 90% L-lactic acid was added to a reactor equipped with a Dien-Stark trap.
450 g of tin powder was charged, and water was distilled off while stirring at 150°C/50 mmHg for 3 hours, and then the mixture was further stirred at 150°C/30 mmHg for 2 hours to oligomerize. 210 kg of diphenyl ether was added to the oligomer, and the mixture was further stirred at 150°C/35 mmHg.
The azeotropic dehydration reaction was carried out under 1000 sq. mHg, and the distilled water and solvent were separated using a water separator, and only the solvent was returned to the reactor. After 2 hours, the organic solvent to be returned to the reactor was passed through a column packed with 46 kg of molecular sieves 3A before being returned to the reactor.
The reaction was carried out at 20 mmHg for 20 hours to obtain a polylactic acid solution having a weight average molecular weight (Mw) of 150,000. 440 kg of dehydrated diphenyl ether was added to the solution to dilute it, and then the solution was cooled to 40°C, and the precipitated crystals were filtered. 0.5N-HCl was added to the crystals.
120 kg of 1,4-butanediol and 120 kg of ethanol were added, stirred at 35°C for 1 hour, filtered, and dried at 60°C/50 mmHg to obtain 61 kg of polylactic acid powder (yield 85%). This powder was melted and pelletized in an extruder to obtain polylactic acid pellets. The weight average molecular weight (Mw) of this polymer was 147,000. Production Example 3 (Production of Polybutylene Succinate) 293.0 kg of diphenyl ether and 2.02 kg of metallic tin were added to 50.5 kg of 1,4-butanediol and 66.5 kg of succinic acid, and the mixture was heated at 130°C/140 mmHg.
The mixture was heated and stirred at 400°C for 7 hours while distilling water out of the system to cause oligomerization.
An n-Stark trap was attached, and azeotropic dehydration was carried out at 140°C/30 mmHg for 8 hours. After that, a tube filled with 40 kg of molecular sieve 3A was attached, and the distilled solvent was returned to the reactor through the molecular sieve tube.
The reaction mass was dissolved in 600 liters of chloroform, added to 4 kiloliters of acetone for reprecipitation, and then diluted with a 0.5% solution of HCl in isopropyl alcohol (hereinafter abbreviated as IPA) (HCl concentration: 0.7 wt%).
The resulting cake was washed with IPA and then filtered under reduced pressure for 6 hours.
The mixture was dried at 0° C. for 6 hours to obtain polybutylene succinate (hereinafter abbreviated as PSB).
The molecular weight of this polymer was 140,000, and the yield was 92%. Production Example 4 (Production of polyhydroxycaproic acid) A reaction was carried out in the same manner as in Production Example 2, except that 6-hydroxycaproic acid was used instead of lactic acid. As a result, polyhydroxycaproic acid (weight average molecular weight (Mw) 1
50,000, yield 90%). Production Example 5 (Production of Aliphatic Block Copolyester (B)) Production Example 5-1 (Production of Block Copolymer of Polycaprolactone and Polylactic Acid) In a 1-liter autoclave, 80 g of caprolactone and 1.6 g of ethanol were added.
After the reactor was charged with 0.56 g of tin laurate (divalent), and the atmosphere inside the reactor was fully purged with nitrogen, the reactor was heated at a temperature of 90 to 100°C for 8 hours to obtain polycaprolactone (PCL) with a weight average molecular weight (Mw) of 8,000. After charging 101 g of lactide, 0.56 g of tin laurate (divalent), and 20 g of toluene into the autoclave, the atmosphere inside the reaction system was purged with nitrogen, and the temperature was raised to 100 to 110°C.
The mixture was heated at 0°C for an additional 8 hours. During this time, the reaction mass in the reactor gradually solidified into a block. After the reaction was completed and the mixture was cooled, 400 ml of chloroform was added to the reaction mass, which was dissolved and added dropwise to 4 liters of stirred methanol to precipitate a polymer. This polymer was filtered, washed with hexane, and then dried. The resulting polymer was a block copolymer of polycaprolactone (PCL) and polylactic acid (PLA), with a weight-average molecular weight of 23,000 and a yield of 92%.
Differential scanning calorimetry (DSC) of this block copolymer showed a melting point derived from the PCL segment and the PLA segment. Production Example 5-2 (Production of a random polymer of caprolactone and lactic acid) Production Example 5-1 was repeated except that the raw materials were charged all at once, resulting in a random copolymer of caprolactone and lactic acid. The yield was 87%, and the weight-average molecular weight was 25,000. DSC analysis of this polymer also showed that the PCL block and the PLA segment were the melting points.
No melting point derived from the A block was observed. Production Examples 5-3 to 5-8 Production was carried out in the same manner as in Production Example 5-1 except that the amounts of ethanol (EtOH) and lactide (LTD) were changed. The results are shown in Table 1. Production Example 5-9 (Production of Block Copolymer of Polybutylene Succinate and Polylactic Acid) 293.0 g of diphenyl ether and 2.02 g of metallic tin were added to 50.5 g of 1,4-butanediol and 66.5 g of succinic acid, and the mixture was heated and stirred at 130°C/140 mmHg for 7 hours while distilling water out of the system to oligomerize. The weight-average molecular weight was 10,000. The resulting polybutylene succinate reaction mass was mixed with 50.0 g of polylactic acid (weight-average molecular weight: 8,600) obtained in the same manner as in Production Example 2 and 0.7 g of metallic tin, and the dehydration condensation reaction was again carried out at 130°C/17 mmHg for 8 hours. After completion of the reaction, post-treatment was carried out in the same manner as in Production Example 2, yielding 89.7 g of a block copolymer of polybutylene succinate and polylactic acid. The weight-average molecular weight of this block copolymer was 22,000. Production Example 5-10 (Production of Block Copolymer of Polyhydroxycaproic Acid and Polylactic Acid) 100 g of 90% L-lactic acid was placed in a reactor equipped with a Dien-Stark trap.
450 mg of tin powder was added, and the mixture was stirred at 150°C/35 mmHg for 3 hours to distill off water, and then further stirred at 150°C/30 mmHg for 2 hours to oligomerize the mixture. 210 g of diphenyl ether was added to the oligomer, and the mixture was stirred at 150°C/35 mmHg for 2 hours to oligomerize the mixture.
The azeotropic dehydration reaction was carried out at 1000 Hg/4 Hr, and the distilled water and solvent were separated using a water separator, and only the solvent was returned to the reactor. The weight-average molecular weight of polylactic acid in the reaction mass was 7,500. On the other hand, oligomerization and further azeotropic dehydration were carried out in the same manner using 100 g of 6-hydroxycarboxylic acid instead of 90% L-lactic acid, resulting in a reaction mass of polyhydroxycaproic acid with a weight-average molecular weight of 12,000. 150 g of the reaction mass of polylactic acid was added to 150 g of the reaction mass of polyhydroxycaproic acid.
The mixture was charged into a reactor and subjected to an azeotropic dehydration reaction at 150°C/35 mmHg/4 hours. A block copolymer of polylactic acid and polyhydroxycaproic acid was obtained in the reaction mass. The weight-average molecular weight was 27,000. 440 g of dehydrated diphenyl ether was added to this solution to dilute it, and then cooled to 40°C, and the precipitated crystals were filtered. 120 g of 0.5N HCl and 120 g of ethanol were added to the crystals, and after stirring at 35°C for 1 hour, the mixture was filtered and then cooled to 60°C/50 mmHg.
The mixture was dried at 80°C for 10 hours and then passed through a 65 mm spinning machine (die diameter 40 mm).
The undrawn yarn was spun at 200-220°C using a nozzle (90 nozzle holes) and stretched in a first water bath at 70-80°C and a second water bath at 90-100°C (total stretch ratio: 7.2 times), and then heat-treated in an atmosphere at 100-120°C. The spinnability was stable and good. The obtained yarn had a thickness of 500d and a strength of 4.
The elongation was 22±3% and the elongation was 78±0.15 g/d. The results are shown in Table 2. Examples 1-2 to 1-6 The same procedure as in Example 1-1 was repeated, except that a block copolyester produced under different production conditions was used instead of the block copolyester of polylactic acid and polycaprolactone obtained in Production Example 5-1 used in Example 1-1. The spinnability, draw ratio, and physical properties of the obtained yarn are shown in Table 2. Comparative Example 1-1 The same procedure as in Example 1-1 was repeated except that the addition of the block copolyester used in Example 1-1 was omitted.
The spinning was carried out in the same manner as in Example 1-1. The spinning was unstable, with occasional breakage of the yarn. The draw ratio was 5.8 times. The obtained yarn had a thickness of 500d and a strength of 2.
The elongation was 25±6%. The results are shown in Table 3. Comparative Examples 1-2 to 1-5 The same procedure as in Example 1-1 was repeated except that other block copolyesters were used instead of the block copolyester used in Example 1-1. The spinnability, draw ratio, and physical properties of the obtained yarn are shown in Table 3. Example 2 (Injection Molding) 60 parts by weight of the polylactic acid obtained in Production Example 1, 40 parts by weight of Celgreen PH-7 (trade name, manufactured by Daicel Chemical Industries, Ltd.) as polycaprolactone, and the mixture of Production Example 5-
The mixture was mixed with 0.5 parts by weight of the block copolyester obtained in 10, and pelletized at 190°C using a twin-screw extruder. The pellets obtained were dried at 80°C for 8 hours. The pellets were then extruded at a cylinder temperature of 14°C using an injection molding machine equipped with a dehumidifying dryer.
The dumbbell pieces were injection molded at 0-220°C and a die temperature of 170-190°C in a mold set at 10-30°C to obtain tensile and bending dumbbell pieces. The resulting dumbbell pieces had a bending strength of 65 MPa, a bending modulus of 2200 MPa, a tensile strength of 55 MPa, and an elongation of 220%. Comparative Example 2 (Injection Molding) The same procedure as in Example 2 was performed except that no block copolyester was used. The resulting dumbbell pieces had a bending strength of 67 MPa and a bending modulus of 2300 MPa.
The tensile strength was 57 MPa and the elongation was 25%. Example 3 (Spinning (production of multifilament)) 70 parts by weight of the polylactic acid obtained in Production Example 2,
40 parts by weight of Bionolle 1001 (trade name, manufactured by Showa Polymer Co., Ltd.)
The mixture was mixed with 0.5 parts by weight of the block copolyester obtained in -1 and pelletized at 190°C using a twin-screw extruder. The resulting pellets were dried at 80°C for 8 hours. The pellets were spun at 230°C using a dry spinning machine equipped with a dehumidifying dryer using a die with 20 holes and a hole diameter of 0.2 mm to obtain a semi-drawn yarn. The spinning process was satisfactory without any breakage. The resulting yarn was stretched at 80 to 100°C and heat-set at 120 to 140°C. The resulting fiber had a diameter of 5 d and a tenacity of 4.85±0.17 g/d. Comparative Example 3 (Spinning (Production of Multifilaments)) Pellets were obtained in the same manner as in Example 3, except that the block copolyester was not added, and the pellets were spun at a die temperature of 230°C. Spinning during molding occasionally resulted in breakage, and the spinning and drawing process was not satisfactory. The obtained fiber had a thread diameter of 5d and a strength of 3.00±0.41 g/d. Example 4 (Paper lamination molding) 60 parts by weight of the polylactic acid obtained in Production Example 2, 40 parts by weight of the polybutylene succinate obtained in Production Example 3, and 1.5 parts by weight of the block copolyester obtained in Example 5-1 were mixed.
0 parts by weight were mixed and pelletized at 190°C using a twin-screw extruder.
The pellets were dried for 8 hours. A dehumidifying dryer was installed on the pellets, and the pellets were dried in a 1300 mm wide container with a lip width of 0.8 m.
The mixture was kneaded and melted at 235°C using an extruder equipped with a 100mm T-die, and extruded onto kraft paper (basis weight 75g/ ^m2 ) at a take-up speed of 120m/min. The film-forming properties were good with no film breakage. The resin layer of the resulting paper laminated product had a thickness of 20±2µm, and the thickness precision was good. Comparative Example 4 (Paper Lamination Molding) Pellets were obtained in the same manner as in Example 4, except that no block copolyester was used, and extruded at a die temperature of 235°C. The film-forming properties were such that film breakage sometimes occurred and stable molding was not possible. The resin layer of the resulting paper laminated product had a thickness of 23±7µm
Example 5 (Stretch Blow Molding) 60 parts by weight of the polylactic acid obtained in Production Example 2, 40 parts by weight of the polybutylene succinate obtained in Production Example 3, and 1.5 parts by weight of the block copolyester obtained in Example 5-1 were mixed.
0 parts by weight were mixed and pelletized at 190°C using a twin-screw extruder.
The pellets were melted in an injection stretch blow molding machine at a cylinder temperature of 140 to 250°C and injection molded into a mold set at 0 to 50°C to obtain a cold parison weighing 40g. The obtained parison was heated to 100°C to soften it, then transferred to a bottle-shaped mold and compressed air of 1 MPa was blown into it to form a 3-inch parison.
. 5 times and 3 times the width, the diameter is 75 mm, the height is 100 mm, and the internal volume is 100
A cylindrical bottle with a volume of 100 ml was obtained. The wall thickness was 0.2 mm and the haze was 2.6%. 800 ml of water was filled into the blown container and the bottle was heated to 1.5 m under the condition of an ambient temperature of 20° C.
The bottle was dropped ten times from a height of 100 mm onto a concrete floor without any breakage. Comparative Example 5 (Stretch Blow Molding) The procedure of Example 5 was repeated except that the block copolyester was omitted. A bottle with an internal volume of 1000 ml was produced as a result of which a cylindrical bottle with a mouth diameter of 75 mm, a height of 100 mm, and an internal volume of 1000 ml was obtained. The wall thickness was 0.2 mm and the haze was 20.
The blown container was filled with 800 ml of water and heated to 1.5 m under the condition of an atmospheric temperature of 20°C.
When the sample was repeatedly dropped onto a concrete floor from a height of 100 mm, it broke on the third drop. Example 6 (Extrusion stretch molding) A mixture of 60 parts by weight of the polylactic acid obtained in Production Example 1, 40 parts by weight of the polybutylene succinate obtained in Production Example 3, and 0.5 parts by weight of the block copolyester obtained in Example 5-1 was used.
5 parts by weight were mixed and pelletized at 190°C using a twin-screw extruder. The obtained pellets were dried at 80°C for 8 hours. Using these pellets, a film having a thickness of 200 μm was formed using an extruder equipped with a dehumidifying dryer. This film was dried at a temperature of 65°C.
The film was stretched 2.5 times longitudinally and 2.5 times transversely in an oven set at a temperature of 65 to 70°C. The obtained film had a thickness of 30 μm, a tensile strength of 45 MPa, a tensile modulus of 1200 MPa, an elongation of 300%, a haze of 2.3%, and a folding endurance of 5000 times or more. Comparative Example 6 (Extrusion Stretching) The same procedure as in Example 6 was performed except that the block copolyester was omitted, resulting in a film with a thickness of 200 μm. This film was stretched 2.5 times longitudinally and 2.5 times transversely in an oven set at a temperature of 65 to 70°C. The obtained film had a thickness of 30 μm, a tensile strength of 43 MPa, a tensile modulus of 1300 MPa, an elongation of 20 to 280%, a haze of 6.1%, and a folding endurance of 15 to 280%.
Example 7 (Tape Yarn Molding) 70 parts by weight of the polylactic acid obtained in Production Example 1, 30 parts by weight of the polybutylene succinate obtained in Production Example 3, and 0.00 to 5,000 times the block copolyester obtained in Example 5-1 were mixed.
5 parts by weight of the mixture was mixed and pelletized at 190°C using a twin-screw extruder. The pellets obtained were dried at 80°C for 8 hours. These pellets were used to extrude 150 ml of the mixture in a 90 mm extruder with a die width of 1200 mm and a lip gap of 0.8 mm, equipped with a dehumidifying dryer.
The film was then slit into a 6 mm width, stretched 5 times at a temperature of 65 to 80°C using a hot plate stretcher, and then stretched 10 times.
The tape was heat-set using a hot plate at 0 to 120°C. The obtained tape had a width of 3.5 mm, a thickness of 30 µm, and a strength of 5.10 ± 0.13 g/d. Comparative Example 7 (Tape Yarn Forming) The same procedure as in Example 7 was carried out except that the block copolyester was omitted, resulting in a tape having a width of 3.6 mm and a thickness of 35 µm. The obtained tape had a strength of 2.8
Example 8 (molding of nonwoven fabric) 70 parts by weight of polylactic acid obtained in Production Example 2, 30 parts by weight of polybutylene succinate obtained in Production Example 3, and 0.9±0.47 g/d of the block copolyester obtained in Example 5-1 were mixed.
5 parts by weight of the mixture was mixed and pelletized at 190°C using a twin-screw extruder. The pellets obtained were dried at 80°C for 8 hours. The pellets were melted at 210°C and extruded into pellets with a pore size of 0.
The melt was spun through a spinneret having a 35 mm spinning hole, and the melt was spun from the spinneret face to 13 mm.
The nonwoven fabric was then heat-sealed using an air sucker placed 00 mm below the surface of the nonwoven fabric, and deposited on a moving collecting surface to form a web. The take-up speed was approximately 3,500 m/min. The resulting web was then passed between a metal embossing roll heated to 80-100°C and a smooth metal roll heated to the same temperature, resulting in heat fusion and a nonwoven fabric. The staple fiber strength of the resulting nonwoven fabric was 2.5 d, and the basis weight of the nonwoven fabric was 30 g/ ^m2 . This nonwoven fabric was then treated in an oven at 90°C for 60 seconds, and the shrinkage rate calculated from the dimensional change before and after treatment was 5.8%. Comparative Example 8: Pellets were obtained in the same manner as in Example 8, except that the block copolyester was omitted.
The melt spinning was carried out at 210°C. During the molding, the spinning property was such that the yarn sometimes broke and the take-up speed was 3500 mm/s.
In the case of 1000 mm, spinning was not successful. Next, the take-up speed was reduced to about 2600 m/min. As a result, spinning became possible without thread breakage, and a nonwoven fabric with a staple strength of 3.0 d and a basis weight of 30 g/ ^m2 was obtained. However, the shrinkage rate after heat treatment for 60 seconds in an oven at 90°C was as high as 17%. Industrial Applicability The lactic acid-based resin composition according to the present invention has transparency and flexibility because each component resin is efficiently dispersed. Furthermore, molded articles made from it have good moldability, and in particular, stretched, oriented, and crystallized molded articles such as films, sheets, and filaments have excellent mechanical properties and heat resistance in addition to the above physical properties, and therefore are suitable for use in a wide range of applications, including food, electronics, medical, and other industries.
It can be suitably used in a wide range of applications, such as packaging materials for medicines, cosmetics, etc., agricultural, civil engineering and construction, fisheries, composting, etc. After use, it will not accumulate as industrial or household waste when discarded.

───────────────────────────────────────────────────────── Continued from the front page (51) Int.Cl. ⁷ Identification Code FI D01F 6/92 307 D01F 6/92 307A (72) Inventor Kitahara Yasuhiro 580-32 Nagaura, Sodegaura City, Chiba Prefecture (Note) This publication is based on the gazette published internationally by the International Bureau of International Trade (WIPO). The effect of the international publication of the Japanese patent application (Japanese utility model registration application) related to this publication arises pursuant to Article 184-10, Paragraph 1 of the Patent Act (Article 48-13, Paragraph 2 of the Utility Model Act) and is unrelated to this publication.

Claims (12)

[Claims] 1. A mixture (A) of polylactic acid (a1) and aliphatic polyester (a2).
and an aliphatic block copolyester (B) having a polylactic acid segment and an aliphatic polyester segment, wherein the aliphatic block copolyester (B) satisfies all of the following conditions (1) to (3): (1) the content of a lactic acid component is 20 to 80 wt % in terms of monomers, (2) the weight-average molecular weight is 1,000 to less than 60,000, and (3) the weight-average molecular weight of the polylactic acid segment is 500 to 55,000, and the weight-average molecular weight of the aliphatic polyester segment is 500 to 55,000. 2. The composition ratio of the mixture (A) to the aliphatic block copolyester (B) is:
Based on 100 parts by weight of the mixture (A),
2. The lactic acid-based resin composition according to claim 1, wherein the amount of the lactic acid-based resin is 0.05 to 10 parts by weight. 3. A lactic acid-based resin composition according to claim 1, wherein the aliphatic polyester (a2) has an elastic modulus of 2500 MPa or less as measured by the test method of JIS K6732. 4. A mixture (A) of polylactic acid (a1) and aliphatic polyester (a2).
The mixing ratio is 20 to 80 parts by weight of polylactic acid (a1) and 10 to 15 parts by weight of aliphatic polyester (
a2) 80 to 20 parts by weight of the lactic acid-based resin composition according to any one of claims 1 to 3. 5. A lactic acid-based resin composition according to claim 1, wherein the aliphatic polyester (a2) is polybutylene succinate and/or polycaprolactone. 6. A molded article made from the lactic acid-based resin composition according to any one of claims 1 to 5. 7. The molded article according to claim 6, which is stretched 1.1 to 15 times in at least one axial direction. 8. The molded article according to claim 6 or 7, which is a film or sheet. 9. The molded article according to claim 6 or 7, which is a tape yarn. 10. The molded article according to claim 6 or 7, which is a monofilament or multifilament. 11. The molded article according to claim 6 or 7, which is a nonwoven fabric. 12. A method for using an aliphatic block copolyester (B) having polylactic acid segments and aliphatic polyester segments as a compatibilizer for a mixture (A) of polylactic acid (a1) and aliphatic polyester (a2), characterized in that the resulting mixture is a lactic acid-based resin composition, wherein the aliphatic block copolyester (B) satisfies all of the following conditions (1) to (3): (1) it contains 20 to 80 wt % of a lactic acid component in terms of monomers, (2) it has a weight-average molecular weight of 1,000 to less than 60,000, and (3) the weight-average molecular weight of the polylactic acid segments is 500 to 55,000, and the weight-average molecular weight of the aliphatic polyester segments is 500 to 55,000.