JP3105020B2 - Thermoplastic decomposable polymer composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a decomposable thermoplastic resin used for packaging materials and the like. More specifically, flexible L-lactide containing a plasticizer, D
A thermoplastic degradable polymer obtained from lactide, D, L-lactide or mixtures thereof. These thermoplastic decomposable polymers have recently attracted attention as packaging materials and medical materials.

[0002]

2. Description of the Related Art In recent years, the amount of plastic used for packaging has been increasing due to the problems of aesthetics, hygiene and packing and transportation of prizes. Along with this, the amount of garbage discarded from homes and factories has increased rapidly, and the shortage of land to bury has become a serious problem around large cities.

Conventionally, polyethylene, polypropylene, polystyrene, polyethylene terephthalate, vinyl chloride and the like have been used as such packaging plastics. However, when they are disposed of in the natural environment, they remain without decomposition due to their stability,
It causes problems such as spoiling the landscape and polluting the living environment of marine life.

[0004] Many researches and developments have been made to use degradable polymers that do not cause these problems as packaging materials. For example, there has been an attempt to impart degradability by blending materials such as polyethylene, polypropylene, and polystyrene with starch.

[0005] In this method, however, it is said that the starch decomposes and the resin itself disintegrates, but the non-decomposable polymer itself remains as it is, thus promoting environmental pollution.

As a thermoplastic and degradable polymer,
Lactic acid and its copolymers are known. This lactic acid polymer is 100% biodegradable in the body of animals in months to years. In addition, when placed in soil or seawater, it decomposes in a few weeks in a humid environment and disappears in about one year. The decomposition products are all harmless with lactic acid, carbon dioxide and water.

[0007] Lactic acid as a raw material is obtained from fermentation of inexpensive raw materials such as corn starch and corn syrup, and also from petrochemical raw materials such as ethylene.

US Pat. No. 1,995,970,2,36
2,511,2,683,136 show a process for the polymerization of lactic acid, lactide or mixtures thereof. Lactic acid polymers are synthesized from a cyclic dimer of lactic acid, commonly called lactide. When a polymer is directly synthesized from lactic acid by dehydration condensation, a high molecular weight polymer cannot be obtained even over a long period of time. On the other hand, a linear polyester synthesized by ring-opening polymerization using lactide as a raw material has a high molecular weight.

[0009] The lactic acid polymer thus obtained is
Processed into yarns and molded products and used for biomedical sustained-release materials, bone plates, screws and the like. However, these applications require strong and hard polymer properties, but not flexibility.

However, when a lactide polymer is used as a film material, it is brittle and hard to use because of lack of flexibility.

US Patents 3,736,646 and 3,98
No. 2,543 discloses using a volatile solvent as a plasticizer in order to obtain the flexibility of a lactide copolymer. However, when a solvent is used as a plasticizer, the solvent gradually evaporates during storage or use of a product such as a film, and the effect is lost. Further, there is a problem with respect to foods and products for medical use in terms of the safety of these solvents.

[0012] PCT International Application 90000151 includes L-
Lactide, D-lactide, meso-lactide,
When polymerizing in the presence of a catalyst, the polymerization is stopped to such an extent that a small amount of lactide remains, and the remaining lactide, lactide oligomer, and lactic acid oligomer act as a plasticizer to give the polymer flexibility. . This patent also discloses a method of adding lactide, lactic acid oligomer, and lactide oligomer after the polymerization is completed.

However, in this method, it is difficult to stop the polymerization reaction at a polymerization degree that indicates the physical properties of the target polymer, which requires a special technique industrially and has sufficient flexibility. When the content of lactide, lactic acid oligomer, lactide oligomer, etc. is increased, the lactide crystallizes and loses transparency over time after forming into a film or the like.

As described above, a flexible polymer composition containing polylactic acid as a main component which can be used for films, yarns, packaging materials and the like, especially for food packaging or medical use has not been known. .

[0015]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a film, a yarn, a packaging material, etc., which overcomes the above-mentioned disadvantages, and has a flexibility mainly composed of polylactic acid which can be used for food packaging or medical use. An object of the present invention is to provide a polymer composition.

The present inventors have conducted intensive studies in order to solve the above problems, and as a result, dehydrated or condensed L-lactic acid, D-lactic acid or a mixture thereof, or obtained L-lactide (L-LTD), D-lactide (D-LTD), D,
A polymer obtained by subjecting L-lactide (DL-LTD), meso-lactide (meso-LTD) or a mixture thereof to ring-opening polymerization and having a residual monomer content of 0.9% or less.
By adding a plasticizer to the limer, it is possible to impart flexibility to the polymer, and even if the addition amount is increased by an amount that gives sufficient flexibility, a transparent polymer molded product can be obtained, and the present invention is completed. did.

The polymer used in the present invention is a mixture of polylactic acid and a polymer of another hydroxycarboxylic acid, or a copolymer of lactic acid and another hydroxycarboxylic acid. As other hydroxycarboxylic acids, glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 4-hydroxyvaleric acid, 5-hydroxyvaleric acid, 6-hydroxycaproic acid and the like are used.

These polymers may be those synthesized by direct dehydration polycondensation from lactic acid or other hydroxycarboxylic acids, or lactide, glycolide (GLD), ε-caprolactone (CL), or a mixture thereof. A product obtained by ring-opening polymerization of the mixture may be used. Alternatively, a copolymer synthesized by subjecting a polymer of polylactic acid and another hydroxycarboxylic acid to a transesterification reaction at a high temperature may be used. The lactic acid constituting the polymer may be L-lactic acid, D-lactic acid or a mixture thereof.

The polymerization method may be a method using a solvent or a method without using a solvent.
Industrially, bulk polymerization without using a solvent is preferred.

As the catalyst for the ring-opening polymerization, zinc chloride, tin chloride or carboxylate is generally used, but is not particularly limited. When used for biocompatible materials and foods, toxicity must be considered.

The polymerization temperature varies depending on the catalyst, but is usually from 95 to 180 ° C. The polymerization time is determined by the type and temperature of the catalyst, and can be determined while measuring the amount of lactide remaining during the reaction.

The end point of the polymerization is when the amount of the remaining raw material lactide monomer becomes 5% or less. If the remaining lactide exceeds this, the physical properties of the obtained thermoplastic resin are affected. It is difficult to obtain the desired physical properties along.

The degree of polymerization of the polymer is from 150 to 20,000
0 is preferred. If the degree of polymerization is lower than this, the strength when formed into a molded product such as a film is small and is not suitable for practical use.

On the other hand, when the degree of polymerization is higher than this, the viscosity in a state of being melted by heating is high, and the moldability is poor.

The plasticizer to be added (however, glycolic acid
Rigomers (degree of polymerization 1-30), lactic acid oligomers (degree of polymerization
1-30), glycolic acid-lactic acid co-oligomer (degree of polymerization
1-30), excluding glycolide and lactide. ] Are preferably safe even when used for food packaging containers and the like. For example, phthalic acid esters such as diethyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, di-1-butyl adipate, di-adipate Aliphatic dibasic acid esters such as n-octyl, di-n-butyl sebacate, di-2-ethylhexyl azelate, phosphate esters such as diphenyl-2-ethylhexyl phosphate, diphenyloctyl phosphate, and acetyl citrate Hydroxy polycarboxylic acid esters such as tributyl citrate, acetyl tri-2-ethylhexyl and tributyl citrate, fatty acid esters such as methyl acetyl ricinoleate and amyl stearate, glycerin triacetate, triethylene glycol dicaprylate Such as polyhydric alcohol Ether, epoxidized soybean oil, epoxy-based plasticizers such as epoxy stearic octyl, polypropylene glycol adipate, polyester plasticizers such as polypropylene glycol sebacic acid ester was prepared in which glycolic acid oligomer (polymerization degree 1
30), lactic acid oligomer (degree of polymerization 1-30) and
Excluding cholic acid-lactic acid co-oligomer (degree of polymerization 1-30)
Good. And the like.

Additives are usually added to the polymer composition in an amount of 5%.
To 50% by weight. Particularly preferably, it is 5 to 20% by weight. As a method for adding these plasticizers, they may be added to polylactic acid in a state of being dissolved in a solvent, or may be added in a molten state.

Further, the polymer composition of the present invention may contain other additives such as a stabilizer, an antioxidant, an ultraviolet absorber and a coloring agent in addition to the plasticizer.

The plasticized polymer composition can be processed by, for example, pouring it into an extrusion mold at the time of heating. Also, a method of dissolving in a solvent and forming a film in a film form can be used. In order to use a molded product such as a film processed as described above as a packaging material or the like, it is necessary to have an appropriate elastic modulus. Usually, this value is preferably 10 to 100 kg / mm ² . If it is larger than this, it is hard and easily cracks due to external force. If it is smaller than this, it is easily deformed by a small force and is not practical.

[0029]

The method of the present invention will be specifically described below with reference to examples and comparative examples.

Examples 1 to 7 A monomer was charged into a glass polymerization tube, and 150 mg of stannous octoate was added as a catalyst. A degassing cock was attached to the polymerization tube, and after degassing and drying for several hours, the cock was closed and the polymerization tube was sealed while keeping the vacuum. Then at 180 ° C 2
Polymerization was carried out for 0 hour to obtain a resin composition as a reaction product.
After termination of the polymerization reaction, the reaction product is dissolved in methylene chloride,
The residual monomer was quantified by gas chromatography.

Further, the polymer was dissolved in chloroform, and the weight average molecular weight was calculated by gel permeation chromatography (GPC).

The obtained resin composition was dissolved in chloroform (concentration: 5% by weight), and an additive was added. These were cast on a Teflon flat dish, and the solvent was slowly evaporated at room temperature to form a film. Further decompression (3
The film was dried at 50 ° C. for 24 hours under the same pressure (mmHg), and it was confirmed that there was no solvent remaining in the film by measuring the infrared absorption spectrum of the film.

A test piece having a width of 10 mm and a length of 50 mm was prepared from the obtained film, and measured using a tensile tester at a chuck width of 20 mm and a tensile speed of 50 mm / min. Table 1 shows the results of the hydrolysis test in hot water at 60 ° C.
It was shown to.

The obtained results are summarized in Table 1 shown in (Table 1), (Table 2) and (Table 3). All films had good flexibility.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

[Table 3]

Comparative Examples 1 to 4 Films were prepared without adding additives to the reaction products obtained in the same manner as in Examples 1 to 4. These were clearly less flexible than those with additives.

[0039]

According to the present invention, a thermoplastic resin composition containing polylactic acid as a main component having good flexibility and hydrolyzability can be obtained.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hosei Masaru 2-1 Tangodori, Minami-ku, Nagoya-shi, Aichi Mitsui East Pressure Chemical Co., Ltd. (56) References JP-A-4-283227 (JP, A) Table 6-500818 (JP, A) U.S. Patent No. 4057537 (US, A) Journal of Biomedical Materials Research, Vol. 13, p. 497 (1979) (58) Field surveyed (Int. Cl. ⁷ , DB name) C08L 67/04 C08K 5/10-5/12 CA (STN)

Claims (4)

(57) [Claims] (1) polylactic acid, or lactic acid and a hydro-acid other than lactic acid;
Copolymer of xycarboxylic acid or polylactic acid and lactic acid or less
Based on a mixture of outer hydroxycarboxylic acid polymers
And the remaining monomers of these polymers or copolymers
At a ratio of 0.9% or less to the main component, and a plasticizer
[However, glycolic acid oligomer (polymerization degree 1 to 30),
Lactic acid oligomer (degree of polymerization 1-30), glycolic acid-milk
Acid oligomers (degree of polymerization 1-30), glycolide and lactide
Excludes Cutide. Excellent flexibility and transparency
A plastically decomposable polymer composition. 2. A plasticizer wherein glycolic acid oligomer (polymerization degree 1 to 30), lactic acid oligomer (polymerization degree 1 to 3)
0), glycolic acid-lactic acid oligomers (degree of polymerization 1-3)
0), excluding glycolide and lactide. ] Is a phthalic acid ester, a fatty acid dibasic acid ester, a phosphoric acid ester, a hydroxy polycarboxylic acid ester, an aliphatic ester, a polyhydric alcohol ester, an epoxy plasticizer, a polyester plasticizer [provided that glycolic acid oligomer (polymerized Degree 1-30), lactic acid oligomer (polymerization degree 1-30),
Excluding glycolic acid-lactic acid oligomers (degree of polymerization 1-30), glycolide and lactide. Or a mixture thereof. 3. The composition according to claim 1, wherein the polylactic acid is obtained from L-lactic acid, D-lactic acid, or a mixture thereof. 4. Hydroxycarboxylic acids other than lactic acid are glycolic acid, 3-hydroxybutyric acid, 3-hydroxyvaleric acid,
2. The composition according to claim 1, wherein the composition is 6-hydroxycaproic acid. ".