JP3371012B2 - Composition - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a specific ethylene-vinyl alcohol-based copolymer and a poly (3-hydroxybutyrate) -based polymer. The present invention relates to a composition having excellent transparency, gas barrier properties and biodegradability. 2. Description of the Related Art Since many synthetic polymers are stable in the ocean, seabed or soil, there is a problem in that they remain semi-permanently and continue to affect the environment in various ways. In recent years, biodegradable materials that are easily decomposed by the action of microorganisms have been actively studied from the viewpoint of global environmental protection. Conventionally, natural polymers derived from plants and animals such as cellulose, which have been widely used, are expected to occupy an important position as a biodegradable material in the future. Therefore, it cannot be said that it has sufficient performance. Therefore, a new biodegradable material has been developed for a long time by blending these natural polymers and synthetic polymers. However, these natural polymers and synthetic polymers are inherently incompatible, so that even if they are modified by polymer reaction or copolymerization, sufficient biodegradability cannot be obtained, or materials cannot be obtained. There is a problem that the characteristics are significantly reduced. [0004] Poly (3-hydroxybutyrate) (hereinafter sometimes abbreviated as PHB) has been available since 1925.
Since being discovered by emogyne, it has been drawing attention and researching as a biodegradable material. However, poly (3
-Hydroxybutyrate) had high crystallinity and had disadvantages of being hard and brittle. To make up for this shortcoming,
A copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate (manufactured by ICI, trade name: Biopol) has been developed and put to practical use as a flexible biodegradable material with improved impact resistance. However, there was a problem that the strength was still low. [0005] In order to improve the mechanical properties of poly (3-hydroxybutyrate), blends with other polymers have been widely studied, and poly (3-hydroxybutyrate) is used in combination with polyvinyl acetate and polyethylene oxide. It is known to be compatible. However, since polyvinyl acetate and polyethylene oxide are not biodegradable, the above composition was insufficient as a biodegradable material. Conventional atactic ethylene-vinyl alcohol copolymers (hereinafter sometimes abbreviated as EVOH) are excellent in gas barrier properties and mechanical properties, and are therefore used in various packaging such as foods. Known as materials and molding materials. However, the atactic ethylene-vinyl alcohol copolymer has insufficient biodegradability. In order to improve the biodegradability of an atactic ethylene-vinyl alcohol copolymer, poly (3-
(Hydroxybutyrate) is being studied (JP-A-4-139248). However, the conventional composition of an atactic ethylene-vinyl alcohol copolymer and poly (3-hydroxybutyrate) has low compatibility, is opaque, has poor water resistance, and still has biodegradability. It was not enough. [0008] Under such circumstances, an object of the present invention is to provide a specific ethylene-vinyl alcohol-based copolymer and a poly (3-hydroxybutyrate) -based polymer, An object of the present invention is to provide a composition having excellent mechanical properties, water resistance and biodegradability. The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, surprisingly,
An ethylene-vinyl alcohol copolymer having a syndiotacticity of 55% or more as indicated by dyad and poly (3
(Hydroxybutyrate) -based polymer was found to exhibit high compatibility, and the present invention was completed. Hereinafter, the present invention will be described in more detail. The ethylene-vinyl alcohol copolymer used in the present invention needs to have a high syndiotacticity in a stereoregular manner, and the syndiotacticity by diad display must be 55% or more. , 57% or more, more preferably 60% or more. In addition, the syndiotacticity referred to herein is a method in which an ethylene-vinyl alcohol copolymer is dissolved in deuterated dimethyl sulfoxide, and a hydroxyl group peak (T.
Moritani et al. , Macromole
cules, 5,577, (1972). ) Syndiotacticity by diad display obtained from the above. When the syndiotacticity is less than 55%, as in a conventional atactic ethylene-vinyl alcohol copolymer (syndiotacticity: 53%), poly (3-
The compatibility with the (hydroxybutyrate) polymer is low, and the effect of the present invention is not exhibited. The ethylene content of the ethylene-vinyl alcohol copolymer of the present invention is preferably from 10 to 65 mol%, more preferably from 20 to 55 mol%. If the ethylene content is less than 10 mol%, the melt moldability is reduced, and the ethylene content is 65 mol%.
If it exceeds, the gas barrier properties decrease. The molecular weight of the ethylene-vinyl alcohol copolymer of the present invention is the intrinsic viscosity measured at 30 ° C. in a water / phenol (15/85: weight ratio) mixed solvent of the ethylene-vinyl alcohol copolymer. Expressing 0.3 to 5.0
dl / g is preferred, 0.5-3.0 dl / g is more preferred, and 0.7-2.0 dl / g is even more preferred. When the intrinsic viscosity is less than 0.3 dl / g, the mechanical properties of the composition are low, and when the intrinsic viscosity is more than 5.0 dl / g, moldability is reduced due to high viscosity. The degree of saponification of the ethylene-vinyl alcohol copolymer of the present invention is not particularly limited, but is preferably at least 10 mol%, more preferably at least 30 mol%, and particularly, mechanical properties and gas barrier properties are required. In this case, it is preferably at least 60 mol%, more preferably at least 90 mol%,
98 mol% or more is even more preferred. The ethylene-vinyl alcohol copolymer of the present invention can be prepared by, for example, a method described in JP-A-4-227905 (a method of copolymerizing ethylene and a vinyl ester and then saponifying with an alkali catalyst in the absence of oxygen). It is manufactured by The ethylene-vinyl alcohol copolymer of the present invention may contain units other than ethylene units, vinyl alcohol units and vinyl ester units, as long as the effects of the present invention are not impaired. Examples of such a unit include olefins such as propylene, 1-butene and isobutene; acrylic acid and its salts; acrylic esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate and i-propyl acrylate. Methacrylic acid and salts thereof; methacrylic esters such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate; acrylamide; acrylamide derivatives such as N-methylacrylamide and N-ethylacrylamide; Amide;
Methacrylamide derivatives such as N-methyl methacrylamide and N-ethyl methacrylamide; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether and i-propyl vinyl ether; nitriles such as acrylonitrile and methacrylonitrile; vinyl chloride; Vinyl halides such as vinylidene chloride, vinyl fluoride, and vinylidene fluoride; allyl acetate;
Allyl compounds such as allyl chloride; maleic acid, its salts or esters; itaconic acid, its salts or esters; vinylsilyl compounds such as vinyltrimethoxysilane; isopropenyl acetate; The content of these units is preferably at most 10 mol%, more preferably at most 5 mol%, even more preferably at most 3 mol%. The poly (3-hydroxybutyrate) -based polymer used in the present invention includes, in addition to a homopolymer composed of 3-hydroxybutyrate units, other hydroxyalkanoate units within a range not to impair the purpose of the present invention. May be used. Examples of such a copolymerizable unit include 3-hydroxypropionate,
3-hydroxyvalerate, 3-hydroxycaprolate, 3-hydroxyheptanoate, 3-hydroxyoctanoate, ω-fluoro-3-hydroxyheptanoate, ω-fluoro-3-hydroxynonanoate,
3-hydroxyalkanoates such as ω-chloro-3-hydroxyoctanoate; polyglycolic acid, polylactic acid, poly (2-hydroxybutyrate), poly (2-hydroxyisobutyrate), poly (2-hydroxy- 2
-Methylbutyrate), poly (2-hydroxyvalerate), poly (2-hydroxycaproate), poly (2
-Hydroxy-2-ethyl butyrate) and the like; 4-hydroxybutyrate and the like;
-Hydroxyalkanoates; 5-hydroxyalkanoates such as 5-hydroxyvalerate;
The content of these units is not particularly limited as long as the content of the present invention is not impaired, but is preferably 50 mol% or less, more preferably 30 mol% or less, even more preferably 10 mol% or less. The molecular weight of the poly (3-hydroxybutyrate) polymer used in the present invention is preferably 1,000 to 10,000,000, and 5,000 to 3 from the viewpoint of mechanical properties and moldability. More preferably 1,000,000, and still more preferably 10,000 to 1,000,000. When the molecular weight is less than 1,000, the mechanical properties decrease, and when the molecular weight is more than 10,000,000, the moldability decreases. Here, the molecular weight is a weight average molecular weight in terms of polystyrene obtained by gel permeation chromatography of a chloroform solution. The method for producing the poly (3-hydroxybutyrate) polymer is not particularly limited. For example, the poly (3-hydroxybutyrate) polymer is synthesized by a fermentation method using a known microorganism such as Alcaligenes eutrophus, and extracted with chloroform or hypochlorous acid. There is a method of taking out the cells by acid treatment. The blending ratio of the ethylene-vinyl alcohol-based copolymer and the poly (3-hydroxybutyrate) -based polymer (hereinafter referred to as a weight-based blending ratio) is not particularly limited, but is 5/95 to 98. / 2 is preferred, and 30/70 to 9
5/5 is more preferable, 40/60 to 90/10 is still more preferable, and 60/40 to 85/15 is particularly preferable. When the blending ratio of the ethylene-vinyl alcohol-based copolymer is less than 5/95, the mechanical properties are low and 98/2
If it is larger, the biodegradation rate will be slow. The method for obtaining the composition of the present invention is not particularly limited, but may be a method of dry blending the two and molding as it is, or more preferably a Banbury mixer, a single screw extruder or a twin screw extruder. After pelletizing with a machine or the like, a method of drying may be mentioned. Further, to the resin composition of the present invention, after adding a single solvent or a mixed solvent selected according to the blending ratio, and melting or dissolving by heating, (1) a dry molding method of evaporating and removing the solvent after molding, 2) A wet molding method in which the polymer is extruded into a solvent that does not dissolve and solidify by extrusion, and (3) a gel molding method in which the solvent is extracted and removed after solidification by gelation, and the like can also be used. At the time of dry blending or pelletizing, in order to suppress the generation of gels and lumps and to eliminate cracks and unevenness of the molded product, use an extruder with a high kneading degree, seal the hopper port with nitrogen, and It is preferable to extrude with. When dry blending or pelletizing, other additives (plasticizers, heat stabilizers, ultraviolet absorbers, antioxidants, coloring agents, fillers, other resins, etc.) may be used. It does not matter as long as the gist of the present invention is not impaired. In particular, as a measure for preventing gel formation, one or more of a hydrotalcite-based compound, a hindered phenol-based, a hindered amine-based heat stabilizer, and a metal salt of a higher aliphatic carboxylic acid (for example, calcium stearate) are used in an amount of 0.01%. It is preferable to add 〜1% by weight. When the composition of the present invention is molded using a solvent, the solvent used is dimethylsulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, water, phenol, hexafluoroisopropanol, alcohol, polyhydric alcohol. , Chloroform, dichloromethane, 1,2-dichloroethane and the like are used alone or in combination. In addition, an aqueous solution of an inorganic salt such as lithium chloride, calcium chloride, and sodium hypochlorite may be used alone or as a mixture with the solvent. Among them, water, dimethyl sulfoxide, phenol, hexafluoroisopropanol, glycerin, ethylene glycol, propanol, chloroform and the like are preferably used alone or in combination. As a method of forming the composition of the present invention into a fiber, the composition is formed into a fiber by the above-mentioned method, and then, if necessary, is stretched under moist heat or dry heat. The stretching temperature varies depending on the stretching method, but is in the range of 20 to 300C, preferably 20 to 250C. The stretching ratio is selected from the range of 2 to 30 times according to the purpose. The stretching operation is performed in air, in nitrogen gas, or in an oil bath, and is performed in one stage or two or more stages. Also, micro-area heating stretching (so-called zone stretching) is applied. In addition, additives such as various antioxidants and surfactants can be mixed within a range that does not impair the purpose of the present invention. As a method of forming the composition of the present invention into a film, after forming into a film by the above method,
Drawing is performed under moist heat or dry heat as required. The stretching temperature varies depending on the stretching method, but is in the range of 20 to 300C, preferably 20 to 250C. Stretch ratio is 1.1
It is selected from the range of 10 to 10 times according to the purpose. So-called biaxial stretching, which stretches in two orthogonal directions, is also applied. The stretching operation is performed in air, in nitrogen gas, or in an oil bath, and is performed in one stage or two or more stages. In addition, additives such as various antioxidants and surfactants can be mixed within a range that does not impair the purpose of the present invention. The composition of the present invention is used in the form of a film, sheet, fiber, molded product, etc., for example, used for food packaging, agriculture, civil engineering, fisheries, medical care, sanitary goods and the like. Can be EXAMPLES Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to these Examples. “Parts” and “%” in the following examples represent “parts by weight” and “% by weight”, respectively, unless otherwise specified. In addition, various physical property values in the examples were measured by the following methods. [Mechanical properties] The tensile strength, elongation, and initial elastic modulus of the film were measured using an Autograph DCS10 manufactured by Shimadzu Corporation.
It was measured at 20 ° C. and 65% RH using type 0. The film was measured at a sample length between the clamps of 20 mm and a pulling speed of 100% / min. [Swelling magnification] The weight (W1) when immersed in water at 40 ° C. for 16 hours and the dry weight (W0) when the same sample was dried at 105 ° C. for 2 hours were obtained by the following equation. Swelling ratio = W1 / W0 [Transparency] The transparency of the film was visually evaluated. The evaluation results are shown in Table 1 using the following symbols. Transparent: ○ Opaque: × Example 1 Ethylene content 31 mol%, syndiotacticity 61
%, Saponification degree 99.9 mol%, water / phenol (15 /
85: weight ratio) in a mixed solvent having an intrinsic viscosity at 30 ° C. of 1.
0.80 parts of an ethylene-vinyl alcohol copolymer having a weight ratio of 52 dl / g and 0.20 parts of poly (3-hydroxybutyrate) having a molecular weight of 800,000 were placed in a twin screw type vented 40φ extruder, and the mixture was placed under nitrogen. , 200
Extrusion pelletization was performed at ° C. Pellets 40
It was placed in a φ extruder and formed into a single layer at 200 ° C. under nitrogen to obtain a film having a thickness of 100 μm. Table 1 shows the physical property values of the obtained film. Comparative Example 1 Syndiotacticity 53, ethylene content 32 mol%
%, Saponification degree 99.9 mol%, water / phenol (15 /
85: weight ratio) in a mixed solvent having an intrinsic viscosity at 30 ° C. of 1.
A 100 μm thick film was prepared in the same manner as in Example 1 using 0.80 parts of an ethylene-vinyl alcohol copolymer having a weight ratio of 10 dl / g and 0.20 parts of poly (3-hydroxybutyrate) having a molecular weight of 800,000. Obtained. Table 1 shows the physical property values of the obtained film. [Table 1] The film formed using the composition of the present invention is excellent in mechanical properties, water resistance, transparency, gas barrier properties and biodegradability, and thus is industrially useful. High in nature.

Claims (1)

(1) A composition comprising an ethylene-vinyl alcohol-based copolymer and a poly (3-hydroxybutyrate) -based polymer having a syndiotacticity of 55% or more as indicated by dyads. .