JP2004204195A - Biodegradable molding and preparation process therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biodegradable molding with excellent mechanical strengths, heat resistance, durability and capable of sterilization in a short period of time, and a process for preparing the same. <P>SOLUTION: The molding has characteristic features prepared from a crosslinked product of a biodegradable polymer and a polyfunctional triazine compound at 0.01-20 wt.% to that of the polymer. The process for its preparation has a characteristic feature of molding the composition containing the biodegradable polymer and the polyfunctional triazine compound at 0.01-20 wt.% to that of the biodegradable polymer followed by ra irradiation. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a molded article made of a biodegradable polymer. The molded article of the present invention can be suitably used, for example, in the medical field, food field, clothing field, agriculture field, civil engineering field, academic research field, and other general industrial fields. The present invention also belongs to a method for producing a molded product made of a biodegradable polymer.
[0002]
[Prior art]
The biodegradable polymer is a polymer that can be decomposed by an action of an enzyme in a living body, an action of a soil bacterium, hydrolysis, or the like, and can be absorbed into a living body or soil. Therefore, molded articles made of the biodegradable polymer are expected to be used as surgical sutures, fracture joining members, clothes, food containers, food packaging films, and the like.
[0003]
However, conventional molded articles made of biodegradable polymers are weak to heat and have low mechanical strength. Furthermore, since it is easily disintegrated by moisture, durability is low. Therefore, the use of the conventional biodegradable molded product is limited.
[0004]
The method of increasing the mechanical strength is not for biodegradable polymers, but for example, a method of blending hydrogenated rosin methyl ester with polypropylene for radiation crosslinking (for example, see Patent Document 1), a method of adding a styrene resin to polypropylene. There are known a method of mixing and radiation-crosslinking (for example, see Patent Document 2), a method of mixing radiation-crosslinking by blending an appropriate crosslinking agent with polyethylene, and the like.
[0005]
However, these methods are not very effective because free radicals are generated by irradiation, and the free radicals break the polymer chains. Even more, the biodegradable polymer is easily broken down, so severe cleavage by free radicals occurs, and as a result, mechanical strength is rather lowered. Therefore, the above method cannot be immediately applied to a biodegradable polymer.
[0006]
Further, molded articles used in the medical field and the food field, such as surgical sutures and food containers, need to be sterilized. As a sterilization method, a method using an autoclave or a method of irradiating radiation is generally used. However, these methods cannot be adopted because conventional biodegradable molded articles have low heat resistance and easily disintegrate. Therefore, a sterilization method using ethylene oxide gas (EOG) is employed. However, this method requires three days and has a problem of toxicity due to residual EOG.
[0007]
Furthermore, food packaging films such as wraps are required to have sufficient heat resistance so that they can be used in a microwave oven and also have flexibility to wrap food. However, a film satisfying these conditions and using a biodegradable polymer as a material has not been hitherto known.
[0008]
[Patent Document 1] JP-A-61-213243 [Patent Document 2] JP-A-7-157922
[Problems to be solved by the invention]
An object of the present invention is to provide a biodegradable molded article having excellent mechanical strength, heat resistance and durability, which can be sterilized in a short time, and a method for producing the same.
[0010]
[Means for Solving the Problems]
The molded article of the present invention is characterized by comprising a material containing a biodegradable polymer and a polyfunctional triazine compound in an amount of 0.01 to 20% by weight based on the polymer and cross-linked.
[0011]
According to the molded article of the present invention, heat resistance is improved, and durability or water resistance to moisture is improved. Further, since the mechanical strength is also improved, the range of use is wider than before. Furthermore, since the molded article of the present invention can be sterilized by radiation, it can be sterilized in a short time, and is safe because it has no toxicity. In addition, in the molded article of the present invention, when radiation is applied during cross-linking, cross-linking treatment and sterilization treatment can be performed simultaneously.
[0012]
In the molded article of the present invention, the biodegradable polymer is preferably poly-DL-lactic acid, poly-L-lactic acid, poly-D-lactic acid, polyglycolic acid, polycaprolactone, polydioxanone, or polytrimethylene carbonate. Microbial aliphatic polyesters such as polyhydroxybutyrate are also preferred. In addition, aliphatic polyesters such as polyamide, polyurethane, polyethylene succinate and polybutylene succinate are also preferable. Further, a copolymer or a blend thereof may be used. As the copolymer, glycolide / caprolactone copolymer, L-lactic acid / caprolactone copolymer, L-lactic acid / dioxanone copolymer, and glucolide / trimethylene carbonate copolymer are particularly preferable. In order to impart flexibility to the molded article of the present invention, an L-lactic acid / caprolactone copolymer is suitable.
[0013]
In addition, collagen, gelatin, chitin, chitosan, silk, cellulose, hyaluronic acid, albumin, dextran, polyglutamic acid, polydepsipeptide, polyphosphazene, polybutylene succinate, or a copolymer thereof can be used. . The biodegradable polymer may be a natural polymer or a synthetic polymer.
The weight average molecular weight of the biodegradable polymer is preferably from 100,000 to 600,000, and particularly preferably from 120,000 to 450,000.
[0014]
As the polyfunctional triazine compound in the molded article of the present invention, triallyl isocyanurate or a derivative thereof is preferable. Derivatives include trimetaallyl isocyanurate, tri (2,3-dibromopropyl) isocyanurate and the like.
The concentration of the polyfunctional triazine compound is from 0.01 to 20% by weight based on the biodegradable polymer, and the preferred concentration is from 0.5 to 6.0% by weight, particularly preferably from 1.0 to 1.0% by weight. ~ 3.5% by weight.
[0015]
The degree of crosslinking in the molded article of the present invention is preferably such that the gel fraction is 30% by weight or more, and more preferably 50% by weight or more.
The molded article of the present invention may contain, if necessary, antioxidants such as vitamin E, vitamin C, and catechins, heat stabilizers, ultraviolet absorbers, light stabilizers, coloring agents, antistatic agents, lubricants, nuclei. Agents, flame retardants, fillers and the like may be added. It is also possible to form a composite in which an inorganic substance, for example, a layered silicate, ceramics, silica glass fiber, carbon fiber or the like is blended in order to improve heat resistance and durability.
[0016]
The shape of the molded product of the present invention is not particularly limited, and the most preferable shape may be selected according to the application. Examples include fibrous, thread-like, rod-like, sheet-like, film-like, bag-like, petri-dish, container-like, needle-like, tube-like, pipe-like, molded, foamed, sponge-like, and porous bodies.
[0017]
The use of the molded article of the present invention can be applied in the medical field, food field, clothing field, agricultural field, civil engineering field, academic field, and other general industrial fields.
In the medical field, surgical sutures, artificial blood vessels, fracture bonding materials, dental materials, wound dressings, artificial skin, contact lenses, intraocular lenses, artificial ligaments, artificial valves, artificial joint movement members, meshes, medical nonwoven fabrics , Stent, clip, stapler, artificial dura, tissue regeneration scaffold, anti-healing material, anastomotic splint, disposable syringe, catheter, infusion tube, blood bag, tube, surgical gloves, gown, sheets, filter, feeding Examples include a tube, a balloon catheter, a clean tube, a sheet, a blood collection tube, an infusion tube, a blood collection needle, a denture base, an artificial tooth, a urine bag, an ostomy, an infusion circuit, and a frozen bag for storing blood components.
[0018]
The food field includes packaging films such as wraps, packaging bags, food containers and the like. In addition, clothes, mulch, fertilizer bags, cold gauze, sandbags, tree protection nets, planting pots, slope protection sheets, garbage bags, test tubes, cell culture instruments, petri dishes, tissue culture bags, three-way cocks, It can be applied to injection needles, wing needles, liquid guide needles, automobile parts, information medium packaging materials, golf balls, and the like.
[0019]
A desirable method for producing the molded article of the present invention is to form a composition containing a biodegradable polymer and 0.01 to 20% by weight of the polyfunctional triazine compound with respect to the polymer, and then irradiate the composition with radiation. It is characterized by the following.
[0020]
In this manufacturing method, the crosslinking treatment by irradiation also serves as a sterilization treatment. Therefore, it is possible to improve the properties of the material of the molded product and at the same time to sterilize the material, thereby increasing the production efficiency.
[0021]
In the method for producing a molded article according to the present invention, the molding method is not particularly limited, and an appropriate method may be employed depending on the shape and application. Examples include melt spinning, injection molding, extrusion molding, press molding, hollow molding, thermoforming, compression molding, FRP molding, roll molding, and the like.
[0022]
Types of radiation to be irradiated include α-rays, β-rays, γ-rays, neutron rays, and x-rays. Particularly preferred are gamma rays and electron beams from cobalt 60. The radiation dose is preferably about 10 to 50 kGy, and the irradiation time is preferably several seconds to several hours.
[0023]
【Example】
The present invention will be described in detail with reference to the following examples, but the present invention is not limited thereto.
[0024]
[Example 1]
A pellet of sufficiently dried polydioxanone having a weight average molecular weight of about 180,000 (intrinsic viscosity at 25 ° C. in a 0.1 g / dl solution of hexafluoroisopropanol (HFIP) at 2.5 ° C.) was added in an amount of 2.5% by weight based on the polydioxanone. After the addition of triallyl isocyanurate, spinning, drawing and annealing were performed with a simple melt spinning machine to obtain a monofilament. After the monofilament was packed in an aluminum / polyethylene laminate bag by nitrogen replacement, it was sterilized by irradiation with an electron beam at 25 kGy.
[0025]
When the monofilament irradiated with the electron beam was immersed in HFIP, it did not dissolve therein but swelled, and its gel fraction was about 77% by weight. Further, the tensile strength and elongation of the monofilament before and after electron beam irradiation were measured. The tensile strength test is performed in accordance with JIS-L1017, and is measured using an Autograph 100 type tensile tester manufactured by Shimadzu Corporation in a 25 ° C., 65% RH constant temperature and humidity chamber at a sample length of 250 mm and a tensile speed of 300 mm / min. did. As a result, the tensile strength and elongation of the monofilament before electron beam irradiation were 4.3 g / d and 36%, respectively, but were 4.8 g / d and 35% after irradiation.
[0026]
For comparison, polydioxanone was spun, stretched and annealed in the same manner as described above except that triallyl isocyanurate was not added. Then, the obtained monofilament was similarly packed and irradiated with an electron beam. The monofilament after this irradiation was dissolved in HFIP, and the gel fraction was 0% by weight. Further, the tensile strength and elongation of the monofilament after irradiation were reduced to 3.1 g / d and 22%, respectively.
[0027]
[Example 2]
To a sufficiently dried pellet of poly-L-lactic acid (PLLA) having a weight average molecular weight of about 340,000, 1.0% by weight of triallyl isocyanurate based on poly-L-lactic acid was added, and then the mixture was injected with an injection molding machine. It was formed into a rod shape having a diameter of 10 mm and a length of 10 cm. Further, the rod was subjected to solid extrusion at an extrusion ratio of 4 at 140 ° C. by an isostatic extruder. This molded product was packed in an aluminum / polyethylene laminate bag purged with nitrogen, and then sterilized by irradiation with cobalt 60γ rays at 25 kGy.
[0028]
When the molded product after the γ-ray irradiation was immersed in methylene chloride, it did not dissolve therein but swelled, and the gel fraction was about 67% by weight. The three-point compressive bending strength of the molded product before and after irradiation was measured in accordance with JIS K7171 and found to be 250 MPa before irradiation and 260 MPa after irradiation. Also, when the compression bending elastic modulus was measured, it was 6.2 GPa before irradiation, but improved to 8.5 GPa after irradiation.
[0029]
For comparison, PLLA was injection-molded in the same manner as described above except that triallyl isocyanurate was not added, and the obtained rod was further subjected to solid extrusion molding. This molded product was packed in the same manner and irradiated with cobalt 60γ rays at 25 kGy. The molded product after the γ-ray irradiation was dissolved in methylene chloride, and the gel fraction was 0% by weight. In addition, the three-point compression bending strength of the molded article after irradiation was 180 MPa, and the compression bending elastic modulus was greatly reduced to 4.3 GPa.
[0030]
[Example 3]
A pellet of sufficiently dried polyglycolic acid having a weight average molecular weight of about 120,000 (ηsp / c 1.4 at 170 ° C. in a mixed solvent of phenol and 2.4.6 trichlorophenol in a 10/7 (weight ratio) solvent) was added After adding 3.0% by weight of triallyl isocyanurate to glycolic acid, the mixture was spun, stretched and annealed by a simple melt spinning machine to obtain a multifilament. The multifilament was packed in an aluminum / polyethylene laminate bag with a nitrogen purge, and then sterilized by irradiation with an electron beam at 25 kGy.
[0031]
When the multifilament after the electron beam irradiation was immersed in a mixed solvent of phenol / 2.4.6 trichlorophenol (10/7 (weight ratio)) at 170 ° C., the multifilament swelled without being dissolved therein. The gel fraction was about 58% by weight. The tensile strength and elongation of the multifilament before and after irradiation were measured in the same manner as in Example 1. As a result, the tensile strength and elongation before irradiation were 7.6 g / d and 25%, respectively, but their values hardly changed after irradiation.
[0032]
For comparison, polyglycolic acid was spun, stretched and annealed in the same manner as above, except that triallyl isocyanurate was not added. Then, the obtained multifilament was similarly packed and irradiated with an electron beam. When the multifilament after the irradiation was immersed in a mixed solvent of phenol / 2,4,6, trichlorophenol (10/7 (weight ratio)) at 170 ° C., the whole was dissolved. Also, the tensile strength and elongation of this multifilament were reduced to 3.8 g / d and 17%, respectively.
[0033]
[Example 4]
A sufficiently dried pellet of an L-lactic acid / caprolactone copolymer having a weight average molecular weight of about 420,000 was mixed with 1.8% by weight of triallyl isocyanurate and 0.2% by weight based on the L-lactic acid / caprolactone copolymer. Was added, and the mixture was spun, stretched and annealed by a simple melt spinning machine to obtain a monofilament. After the monofilament was packed in an aluminum / polyethylene laminate bag by nitrogen replacement, it was sterilized by irradiation with an electron beam at 25 kGy.
[0034]
When the monofilament after this irradiation was immersed in chloroform, it did not dissolve therein and swelled, and its gel fraction was about 63% by weight. Further, the tensile strength and elongation of the monofilament before and after irradiation were measured in the same manner as in Example 1. As a result, the tensile strength and elongation before irradiation were 5.9 g / d and 32%, respectively, but their values hardly changed after irradiation.
[0035]
For comparison, an L-lactic acid / caprolactone copolymer was spun, drawn, and annealed in the same manner as described above except that triallyl isocyanurate was not added. Then, the obtained monofilament was similarly packed and irradiated with an electron beam. When the irradiated monofilament was immersed in chloroform, it was completely dissolved. Also, the tensile strength and elongation of this monofilament were reduced to 2.9 g / d and 21%, respectively.
[0036]
[Example 5]
To a sufficiently dried pellet of poly-L-lactic acid having a weight-average molecular weight of about 260,000, 3.0% by weight of triallyl isocyanurate based on poly-L-lactic acid was added, and then a thickness of 1 wt. A sheet of 0.0 mm was formed. After the sheet was packed under reduced pressure, the sheet was irradiated with 50 kGy of electron beam in the air and sterilized.
[0037]
When the sheet after irradiation was immersed in chloroform, it did not dissolve therein and swelled, and its gel fraction was about 100% by weight. Further, the sheet after irradiation did not soften even at a glass transition point of 60 ° C. or higher, and maintained its shape up to 300 ° C., thus improving heat resistance. When the tensile strength was measured before and after irradiation, it was 80 MPa before irradiation and was 83 MPa after irradiation. Further, when a hydrolysis experiment was performed at 37 ° C., cracks occurred in two months before irradiation and the intensity became 0, but no cracks occurred in 2 months after irradiation, and the intensity became 0 in 3 months. Was.
[0038]
[Example 6]
A sufficiently dried pellet of an L-lactic acid / caprolactone copolymer having a weight-average molecular weight of about 380,000 (copolymer composition ratio (mol ratio) 70/30) was added in an amount of 3.0 to the L-lactic acid / caprolactone copolymer. After adding wt% triallyl isocyanurate and 2.0 wt% vitamin E, a 100 μm thick film was formed by a melt film forming machine. The film was irradiated with 30 kGy of electron beam in air to sterilize it.
[0039]
When the film after the irradiation was immersed in chloroform, it did not dissolve therein and swelled, and its gel fraction was about 79% by weight. In addition, the frozen food was wrapped with the irradiated film and thawed in a household microwave oven. As a result, there was no change in the shape of the film, and heat resistance was observed.
[0040]
[Example 7]
To a sufficiently dried poly-L-lactic acid pellet having a weight average molecular weight of about 260,000, 1.5% by weight of triallyl isocyanurate with respect to poly-L-lactic acid was added, and then used for cell culture using an injection molding machine. A petri dish was formed. After the petri dish was packed under reduced pressure, it was irradiated with 30 KGy of electron beam and sterilized.
[0041]
When this petri dish was used for culturing fibroblasts, the cell growth ability was equivalent to that of a conventional styrene petri dish, but it was stronger and more durable than a polystyrene petri dish.
[0042]
Example 8
After adding 2.0% by weight of triallyl isocyanurate to poly-L-lactic acid to a sufficiently dried poly-L-lactic acid pellet having a weight average molecular weight of about 240,000, a multifilament is formed by a melt spinning machine. Obtained. Thereafter, it was hot stretched 6 times. The drawn multifilament was irradiated with an electron beam at 25 KGy.
[0043]
When the multifilament after the irradiation was immersed in chloroform, it did not dissolve therein and swelled, and its gel fraction was about 100% by weight. Was the tensile strength was measured in before and after irradiation, before irradiation was the 68kgf / mm ^2, after the irradiation was 71kgf / mm ^2. In addition, when the hydrolyzability at 50 ° C. was examined, the intensity was reduced to 0 in one month before irradiation, but was maintained for 1 month after irradiation, and then reduced to 0 after 1.5 months. became.
[0044]
[Example 9]
To a sufficiently dried poly-L-lactic acid pellet having a weight average molecular weight of about 280,000, 1.8% by weight of triallyl isocyanurate with respect to poly-L-lactic acid was added, and the T-die was formed using an extruder. After forming a 500 μm film, a biaxially stretched poly-L-lactic acid film was obtained by a sequential method. Thereafter, the film was irradiated with an electron beam at 20 KGy to obtain a crosslinked film.
[0045]
The biaxially stretched film exhibited transparency even after irradiation. When the tensile strength of the film was measured before and after irradiation, it was 35 kgf / mm ² before irradiation, but was 38 kgf / mm ² after irradiation. Further, heat resistance and hot water resistance were also improved.
[0046]
【The invention's effect】
According to the present invention, the mechanical strength, heat resistance and durability of a biodegradable molded product can be improved. Further, the sterilization can be performed in a short time, and the production efficiency can be improved.

Claims (7)

A molded article comprising a material containing a biodegradable polymer and a polyfunctional triazine compound in an amount of 0.01 to 20% by weight based on the polymer and cross-linked. The biodegradable polymer is poly-DL-lactic acid, poly-L-lactic acid, poly-D-lactic acid, polyglycolic acid, polycaprolactone, polydioxanone, polytrimethylene carbonate, microorganism-produced aliphatic polyester, polyamide, polyurethane, The molded article according to claim 1, which is an aliphatic polyester such as polyethylene succinate or polybutylene succinate, or a copolymer or blend thereof. The molded article according to claim 1, wherein the polyfunctional triazine compound is triallyl isocyanurate or a derivative thereof. The molded product according to any one of claims 1 to 3, wherein the range of the polyfunctional triazine compound is 0.5 to 6.0% by weight based on the biodegradable polymer. The molded article according to any one of claims 1 to 4, wherein the gel fraction is 30% by weight or more. The molded product according to any one of claims 1 to 5, wherein the molded product is in the form of a fiber, a thread, a sheet, a molded body, a porous body, a foam, or a film. A method for producing a molded product, comprising: molding a composition containing a biodegradable polymer and 0.01 to 20% by weight of a polyfunctional triazine compound with respect to the polymer, followed by irradiation with radiation.