JP2000072961A - Polylactic acid resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resin compsn. which is soft and safe by incorporating a polylactic acid resin and an acetylricinolic ester, each in a specified amt., into the same. SOLUTION: This compsn. comprises 100 pts.wt. polylactic acid resin, 1-50 pts.wt. acetylricinolic ester, and if necessary a plasticizer, an antioxidant, a heat stabilizer, a flame retardant, an inorg. filler, an antistatic agent, etc. The compsn., after being mixed e.g. with a stirrer, is melt kneaded and pelletized e.g. with a multiscrew extruder, and then is formed into a film e.g. by inflation. The resin is a polymer having a wt. average mol.wt. of 10,000-1,000,000 and a content of lactic acid component of 50 wt.% or higher, examples being polylactic acid, a copolymer of lactic acid and another aliph. hydroxycarboxylic acid, and a copolymer of lactic acid, an aliph. polyhydric alcohol and an aliph. polybasic acid. Examples of the acetylricilolic ester are methyl acetylricinolate, butyl acetylricinolate and phenyl acetylricinolate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a polylactic acid resin composition and a molded product thereof. More specifically, the present invention relates to a lactic acid-based resin composition having excellent flexibility and safety, and further having excellent decomposability after use, and a molded product thereof.

[0002]

2. Description of the Related Art In general, resins having excellent flexibility, heat resistance and water resistance include resins such as polyethylene, polypropylene, soft polyvinyl chloride and polyethylene terephthalate, and are used for garbage bags, packaging bags and the like. Have been. However, when these resins are discarded after use,
In addition to increasing the amount of garbage, it is hardly decomposed in the natural environment, so it remains semi-permanently even when buried.
In addition, abandoned plastics have caused problems such as spoiling the landscape and destroying the living environment of marine life.

On the other hand, as a biodegradable polymer of a thermoplastic resin, polylactic acid, a copolymer of lactic acid with another aliphatic hydroxycarboxylic acid, an aliphatic polyhydric alcohol and an aliphatic polycarboxylic acid are used. Polyester and the like have been developed.

[0004] These polymers are 100% biodegradable in the body of animals within months to a year, or, when placed in soil or seawater, begin to degrade in a few weeks in a humid environment, with about 1 It disappears in a few years from the year. Furthermore, the decomposition products have the property of becoming lactic acid, carbon dioxide, and water that are harmless to the human body.

[0005] In particular, polylactic acid, in particular, has recently been able to produce L-lactic acid as a raw material in large quantities and inexpensively by a fermentation method, has a high decomposition rate in compost, has resistance to mold, and has a high resistance to food. Due to its excellent characteristics such as odor resistance and coloring resistance, it is expected that its field of use will be expanded.

[0006] However, polylactic acid has high rigidity and cannot be said to be a suitable resin for applications requiring flexibility such as films and packaging materials.

Generally, as a technique for softening a resin,
Methods such as addition of a plasticizer, copolymerization, and blending of a soft polymer are known. However, in the method, even if sufficient flexibility can be imparted, the glass transition temperature of the resin composition decreases, and as a result, a change in physical properties such as crystallization or hardening due to normal environmental temperature occurs. In the case of adding a plasticizer, the plasticizer further bleeds, so that there are practically several problems for practical use.

Furthermore, some plasticizers have insufficient safety, and in particular, there are many cases where the use as food packaging materials is limited. Polylactic acid has a limited amount of compatible plasticizers compared to vinyl chloride resin, such as tributyl acetyl citrate.However, the plasticizing effect on the amount of polylactic acid is not sufficient, and the safety is also high. May be limited depending on the application.

On the other hand, in the above method, considering the biodegradability, which is one of the problems, the resin to be blended is limited to a biodegradable resin having flexibility. Such resins include, for example, polybutylene succinate, polyethylene succinate, polycaprolactone, and the like, and have already been described in JP-A Nos. 8-245866 and 9-1.
No. 11107 discloses this. However, in this method, it is necessary to add a large amount (for example, in the case of polybutylene succinate, 60 wt% or more) in order to impart sufficient flexibility (elastic modulus of 1000 MPa or less) to the polylactic acid-based resin composition. As a result, the above-mentioned characteristics of polylactic acid are impaired. As described above, it has not been possible to improve flexibility without impairing the characteristics of polylactic acid by using the conventional technology.

[0010]

One of the problems to be solved by the present invention is to provide a polylactic acid resin composition having both flexibility and safety.

One of the problems to be solved by the present invention is as follows.
An object of the present invention is to provide a film or sheet comprising a polylactic acid-based resin composition having both flexibility and safety.

One of the problems to be solved by the present invention is:
An object of the present invention is to provide a molded product made of a polylactic acid-based resin composition having both flexibility and safety.

An object of the present invention is to develop a polylactic acid-based resin composition having flexibility without impairing the characteristics of polylactic acid, and a film obtained therefrom. More specifically, it has flexibility (elastic modulus of 200 to 1000 MPa) and heat resistance (heat resistant temperature of 60 to 120 ° C.), such as polypropylene, polyethylene and polyvinyl chloride used for garbage bags and packaging materials. It is an object of the present invention to develop a polylactic acid-based resin composition and a film and a sheet comprising the same.

[0014]

Means for Solving the Problems As a result of intensive studies on polylactic acid, the present inventors have found that by using a specific plasticizer having good compatibility with polylactic acid, a sufficient plasticizing effect can be obtained with a small amount. The present inventors have found a polylactic acid-based resin composition satisfying the above-mentioned problem and having excellent safety, and have completed the present invention. That is, the present invention provides the following [1] to
It is specified by the items described in [4].

[1] A polylactic acid-based resin composition comprising 100 parts by weight of a polylactic acid-based resin and 1 to 50 parts by weight of an acetyl ricinoleate. [2] The polylactic acid-based resin composition according to [1], wherein the acetyl ricinoleate is methyl acetyl ricinoleate.

[3] A film or sheet comprising the polylactic acid-based resin composition according to [1] or [2]. [4] A molded article comprising the polylactic acid-based resin composition according to [1] or [2].

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

[Polylactic acid-based resin] In the present invention, the polylactic acid-based resin includes a polymer containing 50% by weight or more of a lactic acid component in terms of the weight of a monomer to be subjected to polymerization. Specific examples thereof include, for example, polylactic acid, a copolymer of lactic acid and another aliphatic hydroxycarboxylic acid, lactic acid, a copolymer of an aliphatic polyhydric alcohol and an aliphatic polybasic acid, a mixture of any combination of the following, And the like.

[Polylactic acid] In the present invention, specific examples of lactic acid which is a raw material of polylactic acid include L-lactic acid, D-lactic acid, DL-lactic acid or a mixture thereof, or a cyclic dimer of lactic acid. Lactide can be mentioned. However,
When the obtained polylactic acid is used by mixing L-lactic acid and D-lactic acid, it is necessary that either L-lactic acid or D-lactic acid is 75% by weight or more.

Specific examples of the method for producing polylactic acid used in the present invention include, for example, a method in which lactic acid or a mixture of lactic acid and an aliphatic hydroxycarboxylic acid is used as a raw material for direct dehydration polycondensation (for example, U.S. Pat.
SP 5,310,865), a ring-opening polymerization method for melt-polymerizing a cyclic dimer of lactic acid (lactide) (for example, a production method disclosed in US Pat. No. 2,758,987). Method), cyclic dimer of lactic acid and aliphatic hydroxycarboxylic acid,
For example, a ring-opening polymerization method in which lactide or glycolide and ε-caprolactone are melt-polymerized in the presence of a catalyst (for example, a production method disclosed in US Pat. No. 4,057,537),

A method of directly dehydrating and polycondensing a mixture of lactic acid, an aliphatic dihydric alcohol and an aliphatic dibasic acid (for example, a production method disclosed in US Pat. No. 5,428,126), polylactic acid and fat A method of condensing a polymer of an aliphatic dihydric alcohol and an aliphatic dibasic acid in the presence of an organic solvent (for example, a production method disclosed in European Patent Publication No. 0712880 A2), and the like. The method is not particularly limited. Further, a small amount of an aliphatic polyhydric alcohol such as glycerin, an aliphatic polybasic acid such as butanetetracarboxylic acid, and a polyhydric alcohol such as a polysaccharide may coexist and may be copolymerized. The molecular weight may be increased by using a binder (polymer chain extender) such as a diisocyanate compound.

[Aliphatic polyester] In the present invention, a blend with an aliphatic polyester having biodegradability and a copolymer of a polylactic acid component and an aliphatic polyester component may be used as long as the object of the invention is not impaired. .

[Aliphatic polyester] An aliphatic polyester is a biodegradable polymer that can be produced by various combinations of an aliphatic hydroxycarboxylic acid, an aliphatic dihydric alcohol and an aliphatic dibasic acid. As a method for producing the aliphatic polyester, a method similar to the method for producing polylactic acid can be used, but the method is not limited thereto.

[Aliphatic hydroxycarboxylic acid] Specific examples of the aliphatic hydroxycarboxylic acid include glycolic acid,
Examples thereof include 3-hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxyvaleric acid, 4-hydroxyvaleric acid, and 6-hydroxycaproic acid. Further, cyclic esters of aliphatic hydroxycarboxylic acids, for example, glycolic acid Examples include glycolide which is a dimer and ε-caprolactone which is a cyclic ester of 6-hydroxycaproic acid. These can be used alone or in combination of two or more.

[Aliphatic dihydric alcohol] Specific examples of the aliphatic dihydric alcohol include ethylene glycol, diethylene glycol, triethylene glycol, and the like.
Polyethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,4
-Butanediol, 3-methyl-1,5-pentaneddiol, 1,6-hexanediol, 1,9-nonanediol, neopentyl glycol, polytetramethylene glycol, 1,4-cyclohexanedimethanol, 1,
4-benzenedimethanol and the like. They are,
They can be used alone or in combination of two or more.

[Aliphatic dibasic acid] Specific examples of the aliphatic dibasic acid include, for example, succinic acid, oxalic acid, malonic acid,
Glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecandioic acid, dodecandioic acid, phenylsuccinic acid, 1,4-phenylenediacetic acid, and the like. These can be used alone or in combination of two or more.

In the present invention, the aliphatic polyester is
There is no limitation as long as it is a biodegradable aliphatic polyester having a melting point of 40 ° C. to 250 ° C. that can be produced by variously combining the above-described aliphatic hydroxycarboxylic acid, aliphatic dihydric alcohol and aliphatic dibasic acid. . Particularly, a soft aliphatic polyester having crystallinity is preferable. When the melting point of the aliphatic polyester is lower than 40 ° C., the heat resistance of the resulting polylactic acid-based resin composition decreases, and
If the temperature is higher than 0 ° C., the melting temperature at the time of pelletization becomes high, so that the polylactic acid component tends to be deteriorated or colored, which is not preferable. Preferred aliphatic polyesters include polyethylene oxalate, polybutylene oxalate, polyneopentyl glycol oxalate, polyethylene succinate, polybutylene succinate, polyhydroxybutyric acid and a copolymer of β-hydroxybutyric acid and β-hydroxyvaleric acid, Polycaprolactone and the like are mentioned, and polyethylene succinate and polybutylene succinate are particularly preferred.

These aliphatic polyesters may have a polymer chain extended by a binder such as diisocyanate, or may be a small amount of an aliphatic polyhydric alcohol such as glycerin or butanetetracarboxylic acid. Polyhydric alcohols such as aliphatic polybasic acids and polysaccharides may coexist and be copolymerized.

[Molecular weight of polylactic acid-based resin] The weight-average molecular weight (Mw) and molecular weight distribution of the polylactic acid-based resin are not particularly limited as long as they can be molded substantially. The weight average molecular weight of the polylactic acid-based resin used in the present invention is not particularly limited as long as it shows substantially sufficient mechanical properties, but is generally 1 to 10 in weight average molecular weight (Mw).
Preferably it is 100,000, more preferably 30,000 to 500,000, and 5 to 30
Much more preferred. Generally, the weight average molecular weight (M
When w) is less than 10,000, mechanical properties are not sufficient, and when the molecular weight exceeds 1,000,000, handling may be difficult or uneconomical.

[Types of acetyl ricinoleate]
Examples of the acetyl ricinoleate used in the present invention include methyl acetyl ricinoleate, ethyl acetyl ricinoleate, propyl acetyl ricinoleate, butyl acetyl ricinoleate, and phenyl acetyl ricinoleate. Among them, methyl acetyl ricinoleate is particularly preferred.

[Addition amount of acetyl ricinoleate] The addition amount of acetyl ricinoleate is in the range of 1 to 50 parts by weight based on 100 parts by weight of the polylactic acid resin. Preferably 3 to 30 parts by weight, more preferably 5 to 30 parts by weight
20 parts by weight is good. If the amount of the acetyl ricinoleate is less than 1 part by weight, the flexibility may not be sufficient. If the amount exceeds 50 parts by weight, the heat resistance of the composition may be poor or acetyl ricinoleate may bleed out.

[Additives] Various additives (plasticizers, antioxidants, etc.) may be added to the polylactic acid resin composition according to the present invention in accordance with the purpose (for example, improvement in tensile strength, heat resistance, weather resistance, etc.). UV absorbers, heat stabilizers, flame retardants, internal release agents, inorganic additives, antistatic agents, surface wetting improvers, incineration aids, lubricants such as pigments, natural products) and the like can be added. For example, in inflation molding and T-die extrusion molding, a film,
In order to improve the anti-blocking property and the sliding property of the sheet, an inorganic additive and a lubricant (aliphatic carboxylic acid amide) can be added.

Examples of the inorganic additives include silica, calcium carbonate, talc, kaolin, kaolinite, and zinc oxide, and silica is particularly preferred. These can be used as one kind or as a mixture of two or more kinds.

[Polylactic acid-based resin composition] As a method for producing the polylactic acid-based resin composition, a polylactic acid-based resin and acetyl ricinoleic acid ester and, if necessary, other additives are mixed with a high-speed stirrer or a low-speed stirrer. After that, a method of melt-kneading with a single-screw or multi-screw extruder having sufficient kneading ability can be adopted. In general, the shape of the polylactic acid-based resin composition according to the present invention is preferably a pellet, a rod, a powder, or the like.

[Production and Film Production of Film and Sheet] The polylactic acid-based resin composition according to the present invention is a material suitable for production of a film or sheet. Examples of the method for forming a film, sheet, or plate-like molded body according to the present invention include inflation molding, T-die molding, and thermoforming, but the method is not particularly limited. The films and sheets of the present invention include, for example, films and sheets obtained by known and publicly-known molding methods, and there are no restrictions on the shape, size, thickness, design, and the like.

[Manufacturing technology] Films and sheets made of the resin composition according to the present invention can be obtained by a known or publicly used extrusion method, coextrusion method, calendering method, hot pressing method, solvent casting method, inflation method, balloon method, tenter, etc. It can be manufactured by a technique such as a method.

[Methodology of Extrusion Method or Coextrusion Method] In the extrusion method or coextrusion method, a T die, an inflation die (circular die), a flat die, a feed block / single manifold die or a combination of several feed blocks is used. Known and public dies such as a manifold die can be used. In the coextrusion method, a multilayer film can be produced by using a plurality of the polymers having different properties and / or other kinds of polymers.

When the inflation method is adopted, it is possible to perform biaxial simultaneous stretching, to produce at a relatively low cost with higher productivity, and because the shape is a bag-like (seamless) shape, a carry-out bag for a supermarket. It is suitable for the production of bags and bags such as bags, compost bags, etc., for preventing water condensing on low-temperature food packs such as frozen foods and meats from wetting the surroundings. By combining with a coextrusion method, a multilayer film can be manufactured with high productivity using a plurality of resin compositions and / or other kinds of polymers according to the present invention having different properties. The inflation method and the coextrusion method can be combined. Film or sheet comprising the resin composition according to the present invention, by setting the process conditions according to the purpose, roll shape, tape shape,
It can be manufactured in cut sheet form, plate form, bag form (seamless form).

[Secondary processing] The film or sheet made of the resin composition according to the present invention may be further subjected to a secondary or three-dimensional shape imparting a two-dimensional or three-dimensional shape such as stretching, blowing and vacuum forming. It is a material suitable for processing.

[Specific Examples of Use] The film or sheet comprising the resin composition according to the present invention may be used for shopping bags,
Garbage bags, compost bags, food / confectionery packaging films, food wrap films, cosmetic / cosmetic wrap films, pharmaceutical wrap films, herbal medicine wrap films Surgical patch wrap films applied to shoulder stiffness, sprains, etc. Agricultural / horticultural film, agricultural chemical wrap film, greenhouse film, fertilizer bag, film for magnetic tape cassette products such as video and audio, film for floppy disk packaging, film for plate making, adhesive tape, tape, waterproof It can be suitably used as a sheet, a sandbag bag, or the like.

The film or sheet, which is one embodiment of the molded article of the present invention, can be suitably used particularly in applications where degradability is required by utilizing its properties. By using a film or sheet, which is one embodiment of the molded article according to the present invention, as a packaging material as a food / confectionery bag, at the time of sealing the food / confectionery, by putting an oxygen absorber in the bag. In addition, the storage period and the shelf life can be greatly extended.

[0042]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the scope of the present invention. Polylactic acid weight average molecular weight (M
w) The flexibility in the examples was measured by the following method.

Weight average molecular weight (Mw) Measured by gel permeation chromatography (GPC) using a polystyrene standard as a column temperature of 40 ° C. and a chloroform solvent. Flexibility The modulus of elasticity of the film obtained in the examples is JIS K67.
32. The flexible film described in the present invention has the elastic modulus in the range of 200 to 1000 MPa. Safety RTECS of plasticizer used (Acute oral toxicity LD50)
Was described.

Production Example 1 400 g of L-lactide and stannous octoate
04 g and lauryl alcohol 0.12 g were sealed in a thick cylindrical stainless steel polymerization vessel equipped with a stirrer and degassed under vacuum for 2 hours. After replacing with nitrogen gas, 200 ℃
The mixture was heated and stirred at / 10 mmHg for 2 hours. After completion of the reaction, a melt of polylactic acid was extracted from the lower outlet, air-cooled, and cut with a pelletizer. The resulting polylactic acid had a yield of 340 g, a yield of 85%, and a weight average molecular weight (M
w) 138,000.

Production Example 2 9 was added to a reactor equipped with a Dien-Stark trap.
10 kg of 0% L-lactic acid and 45 g of tin powder are charged, and 150 ° C.
After distilling water while stirring at / 50 mmHg for 3 hours, the mixture was stirred at 150 ° C / 30 mmHg for 2 hours to oligomerize. 21.1 kg of diphenyl ether was added to this oligomer, and an azeotropic dehydration reaction at 150 ° C./35 mmHg was performed. The distilled water and the solvent were separated by a water separator, and only the solvent was returned to the reactor. Two hours later, the organic solvent to be returned to the reactor was passed through a column packed with 4.6 kg of molecular sieve 3A, and then returned to the reactor.
The reaction was carried out at 17 mmHg for 20 hours to obtain a polylactic acid solution having a weight average molecular weight (Mw) of 150,000. 44 kg of dehydrated diphenyl ether was added to this solution to dilute it, and then cooled to 40 ° C., and the precipitated crystals were filtered. 12 kg of 0.5 N HCl and 12 k of ethanol
g, and the mixture was stirred at 35 ° C. for 1 hour, and then filtered.
Drying at 50 mmHg yielded 6.1 kg of polylactic acid powder (85% yield). This powder was melted and pelletized by an extruder to obtain polylactic acid. The weight average molecular weight (Mw) of this polymer was 1470,000.

Examples 1-4 The polylactic acid and acetyl ricinoleate obtained in Production Examples 1 and 2 were mixed in a Henschel mixer at the ratios shown in Table 1 [Table 1], and then the extruder cylinder temperature was set. 160 ~
Pellets were formed at 210 ° C. 6 pellets
After drying at 0 ° C. for 10 hours, the temperature was 160 to 17 with a 40 mm inflation molding machine (die diameter: 40 mm).
Molding was performed at 0 ° C., and an inflation film having a folding diameter of 150 mm and a thickness of 30 μm was formed and wound. The flexibility of the obtained film was measured. The results are shown in Table 1 [Table 1].

Comparative Examples 1 to 5 The polylactic acid, acetyl ricinoleate and other plasticizers obtained in Production Examples 1 and 2 were mixed in a Henschel mixer in the proportions shown in Table 2 [Table 2]. The extruder was pelletized under the conditions of a cylinder set temperature of 160 to 210 ° C. After drying the pellets at 60 ° C. for 10 hours, they were molded at a temperature of 160 to 170 ° C. with a 40 mm inflation molding machine (die diameter: 40 mm), and a 30 μm thick blown film was formed and wound up. The flexibility of the obtained film was measured. The results are shown in Table 2 [Table 2].

[0048]

[Table 1] [Legend] “←” means “same as left”.

[0049]

[Table 2] [Legend] “←” means “same as left”.

[0050]

The polylactic acid-based resin composition according to the present invention comprises:
It is a composition imparted with flexibility, and is a composition suitable for T-die molding and inflation molding. Flexibility can be imparted with a smaller amount of addition than conventional products,
Also, safety is improved.

Continuing from the front page (72) Inventor Takayuki Watanabe 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Inside Mitsui Chemicals Co., Ltd. Person Tomoyuki Nakata 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture F-term (reference) 4F073 AA32 BA23 BA42 BB01 EA73 4J002 CF181 EH076 FD020 GA01 GE00 GG02 GS00

Claims (4)

[Claims] 1. A polylactic acid-based resin composition comprising 100 parts by weight of a polylactic acid-based resin and 1 to 50 parts by weight of an acetyl ricinoleate. 2. The polylactic acid-based resin composition according to claim 1, wherein the acetyl ricinoleate is methyl acetyl ricinoleate. 3. A film or sheet comprising the polylactic acid-based resin composition according to claim 1. 4. A molded article comprising the polylactic acid-based resin composition according to claim 1.