JP2002060545A - Biodegradable film or sheet, and molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biodegradable film or sheet mainly composed of cellulose acetate, excellent in a melt extruding porperty and moisture resistance, having low smell and biodegradability, and excellent in transparency. SOLUTION: The biodegradable film or sheet has the following properties; it is mainly composed of cellulose acetate having an acetyl group substitution degree of 2.3-2.7 and a biodegradable plasticizer; it has a pulling elastic modulus of >=100 kg/mm2 at 23 deg.C and 0% RH; and a pulling elastic modulus at 23 deg.C and 60% RH is >=80% of that at 23 deg.C and 0% RH; and the biodegradable plasticizer comprises a combination of one or more kinds selected from the group consisting of compounds expressed by general formula (1) and compounds described in (2). (1) H5C3(OH)3-n(OOCCH3)n 0<n<=3 (2) Glycerin alkylates (the number of carbons of the alkyl group is 2-20, and it may contain a hydroxyl residue), ethylene glycol alkylates, polyethylene glycol alkylates and others.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a biodegradable film or sheet which can be widely used in the field of packaging materials and the like.
The present invention relates to a biodegradable multilayer film or sheet using such a film or sheet, and a thermoformed product comprising such a film or sheet.

[0002]

2. Description of the Related Art Plastic films or sheets made of polyethylene, polypropylene, polystyrene, polyvinyl chloride and the like, and thermoformed products thereof (collectively,
(May be referred to simply as film or film product)
Means that millions of tons are produced every year in Japan,
It is used in all industrial fields including food packaging. And the convenience and economics they bring are indispensable to our daily lives and to economic activities in a broader sense. On the other hand, although these plastic film products are partially recovered and reused, many cases immediately become waste after fulfilling the mission of packaging, which is the original purpose. Film products are often landfilled as waste.However, their stability and bulkiness shorten the life of landfills. It has caused problems such as impairing the living environment of animals and plants.

[0003] Attention is now focused on biodegradable plastic materials. It is known that biodegradable plastics gradually disintegrate and decompose in soil or water due to hydrolysis or biodegradation, and eventually become harmless decomposition products due to the action of microorganisms. Biodegradable plastics that have begun to be put into practical use are roughly classified into aliphatic polyesters, modified PVA, modified starch, and blends thereof. Examples of the aliphatic polyester include poly (hydroxybutyric acid / valeric acid) as a microorganism-producing polymer, polycaprolactone or a condensate of an aliphatic dicarboxylic acid and an aliphatic diol as a synthetic polymer, and a semi-synthetic polymer. Polylactic acid is typically known as a polymer. Each of these biodegradable plastics has a unique characteristic, and application development corresponding to the characteristic is considered.

[0004] On the other hand, cellulose acetate marketed in the United Kingdom around 1922 was used by Reese in the Ind.
Eng. Chem. , 49, 89 (1957) are known to be biodegradable.
Cellulose acetate is widely used today in tobacco filters, photographic base films and the like, but its development history has focused more on how to prevent hydrolysis and biodegradability. Attempts to actively use biodegradability as a function have only recently begun to be studied.

[0005]

Cellulose acetate as a biodegradable material is disclosed in JP-A-4-142344 and JP-A-6-49275. Compared with film products, there were some problems in industrial production, wide use as packaging materials, and biodegradability as a new function. These materials have remarkably inferior melt extrusion characteristics compared to general-purpose plastic raw materials, have low elastic modulus due to the effect of humidity in the air after processing into films, are not stable in quality, and have a strong odor of acetic acid. However, the biodegradable raw material or film product could not be said to be practically satisfactory because of the odor transfer and the extremely low biodegradation rate.
Further, thermoformed products of cellulose acetate sheet have not been practically used until now.

[0006]

Means for Solving the Problems In view of such a situation, the present inventors have made intensive studies, and as a result, using a specific cellulose acetate and a specific plasticizer, an index indicating the properties of the whole material. The biodegradation is excellent in other properties such as melt extrudability, moisture resistance, low odor, biodegradability and transparency by adjusting Film or sheet, furthermore, biodegradable multilayer film or sheet using these films or sheets
And a thermoformed product were obtained, and the present invention was completed.

A first gist of the present invention is that cellulose acetate having a degree of acetyl group substitution of 2.3 to 2.7 and a biodegradable plasticizer are used as main components, and at 23 ° C. and 0% The tensile elastic modulus at RH is 100 kg / mm ² or more,
Tensile modulus at 3 ° C and 60% RH is 23 ° C and 0%
80% or more of the tensile modulus in RH, and
The biodegradable plasticizer comprises one or a combination of two or more compounds selected from the group consisting of a compound represented by the following general formula (1) and a compound represented by the following (2): In a film or sheet. _{(1) H 5 C 3 (} OH) 3-n (OOCCH 3) n 0
<N ≦ 3 (2) glycerin alkylate (the alkyl group may have 2 to 20 carbon atoms and may have a hydroxyl residue), ethylene glycol alkylate (the alkyl group has 1 to 20 carbon atoms,
A hydroxyl group residue may be present), polyethylene glycol alkylate having an ethylene repeating unit of 5 or less (an alkyl group has 1 to 20 carbon atoms and a hydroxyl group residue may be present), aliphatic monocarboxylic acid Alkyl ester (alkyl group has 1 to 20 carbon atoms), aliphatic dicarboxylic acid alkyl ester (alkyl group has 1 to 20 carbon atoms, and may have a carboxyl group residue), aliphatic tricarboxylic acid alkyl ester (alkyl group Has 1 to 20 carbon atoms and may have a carboxyl group residue).

Another aspect of the present invention is as follows.
The present invention resides in a molded article thermoformed from the film or sheet of the first aspect.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. Cellulose acetate in the present invention is a purified cotton linter.
Alternatively, high-purity wood pulp is used as a raw material and produced by any of well-known industrial production methods called a mixed acid method, a methylene chloride method, and a benzene method. The mixed acid method is most widely used, in which cellulose acetate is obtained from cellulose as a starting material through the following steps. A drying step of reducing the water content to 5% or less, a pretreatment step of moistening acetic acid, acetylation with acetic acid, acetic anhydride and sulfuric acid,
That is, an acetylation step, a ripening (hydrolysis, hydrolysis) step of deacetylation by the action of added water and catalytic sulfuric acid,
Precipitation, stabilization, dehydration, and drying steps for washing stabilization. To obtain cellulose acetate with the desired degree of acetylation,
In the aging step of deacetylating cellulose triacetate in which all hydroxyl groups have been acetylated in the acetylation step, the hydrolysis conditions may be adjusted.

In the present invention, it is important that the acetyl group substitution degree of cellulose acetate is in the range of 2.3 to 2.7. If the value is below the range, the film,
If the elasticity decreases due to the influence of the humidity in the air after processing into a product, and the quality is not stable, and if the quality is higher, on the contrary, the biodegradation rate becomes extremely slow and it is practically hard to say that it is biodegradable. The degree of polymerization is
The average degree of polymerization of cellulose acetate is preferably in the range of 80 to 400, although it depends on the degree of polymerization of the starting cellulose and the degree of reduction in the degree of polymerization in the subsequent steps. If the amount is less than the above range, the physical properties are not exhibited. If the amount exceeds the range, the melt moldability is inferior even if a plasticizer described later is added.

Cellulose acetate has a melting point of 280-290 ° C.
Is higher than the decomposition temperature and the melt viscosity is high, so that melt extrusion is difficult. Therefore, it is necessary to add a plasticizer in order to lower the melting point and the melt viscosity to enable melt extrusion. Examples of the plasticizer for cellulose acetate include phthalate plasticizers such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate and dimethoxyethyl phthalate, ethyl phthalyl ethyl glycolate and methyl phthalyl ethyl. Phthalyl glycolate-based plasticizers such as glycolate and butylphthalylbutyl glycolate; phosphate ester-based plasticizers such as tricresyl phosphate and triphenyl phosphate; Tolueneethylsulfonamide and the like are used because of their good compatibility, but they are not biodegradable and are not preferred as the main components of the biodegradable material in the present invention.

In the present invention, compounds that can be used as suitable biodegradable plasticizers include compounds represented by the following general formula (1) and compounds represented by the following (2):
These can be used alone or in combination of two or more.

(1) H ₅ C ₃ (OH) _3-n (OOCC
H ₃ ) _n 0 <n ≦ 3 (2) Glycerin alkylate (the alkyl group has 2 carbon atoms)
-20, there may be a hydroxyl residue), for example, glycerin tripropionate, glycerin tributyrate;
Ethylene glycol alkylate (the alkyl group may have 1 to 20 carbon atoms and may have a hydroxyl residue) such as ethylene glycol diacetate;
The following polyethylene glycol alkylates (the alkyl group may have 1 to 20 carbon atoms and may have a hydroxyl residue), for example, diethylene glycol monoacetate, diethylene glycol diacetate; alkyl esters of aliphatic monocarboxylic acids (alkyl The group has 1 to 20 carbon atoms) such as butyl stearate; an alkyl ester of an aliphatic dicarboxylic acid (the alkyl group may have 1 to 20 carbon atoms and a residue of a carboxyl group) such as di (2-ethylhexyl) adipate G, di (2-ethylhexyl) azelate; an alkyl ester of an aliphatic tricarboxylic acid (the alkyl group may have 1 to 20 carbon atoms and a residue of a carboxyl group), for example, trimethyl citrate.

The compounds represented by the above formula (1) are mono-, di- and tri-acetates of glycerin, which may be a mixture. In the film of the present invention, triacetate or a material mainly composed of triacetate, which is called triacetin, is preferable from the viewpoint of compatibility (plasticizing effect) and elastic modulus and humidity dependency.

The above-described plasticizer has biodegradability even when used alone, and does not inhibit the biodegradability of the composition when added to cellulose acetate at an arbitrary ratio. The amount is from 5 to 50 based on the total amount of cellulose acetate and plasticizer.
It is preferred to be in the range of weight%. If it is below this range, the melting point or melt viscosity is not sufficiently reduced and the melt extrudability is not developed.If it is higher, the melt viscosity is too low or the plasticizer is separated from the reduced compatibility. This makes it difficult to take out the extruded sheet while maintaining the flatness and appearance of the sheet. However, the extrudability is related not only to the amount of the plasticizer added but also to the degree of polymerization of cellulose acetate. Therefore, the melt viscosity is used as an index as an addition of the actions of both. In the present invention, at 220 ° C. and a shear rate of 100
The melt viscosity as measured in seconds ^-1 is (1.0-100)
It is important that it is × 10 ³ poise. Outside this range, even if the extrusion temperature is adjusted for the reasons described above,
Extrusion suitability cannot be obtained.

With respect to the composition of cellulose acetate and plasticizer,
Furthermore, other polymer materials, particularly biodegradable plastics, may be blended as long as the effects of the present invention are not impaired. Addition of plasticizers, lubricants, inorganic fillers, stabilizers, ultraviolet absorbers, flame retardants, antifogging agents, antifungal agents, pigments, fluorescent agents, etc. for the purpose of adjusting moldability and film properties. It is also possible to add agents and modifiers. In the present invention, such a cellulose acetate composition (hereinafter sometimes simply referred to as cellulose acetate) is melt-extruded to form a sheet.
And film form. The cellulose acetate film is generally produced by a solution method (the same as the casting method and the wet method). In the solution method, a relatively thick sheet suitable for thermoforming as described later is used. It cannot be made, and a laminate cannot be obtained at the same time as forming a film or sheet. Furthermore, it is disadvantageous in manufacturing cost.

The extruder may be of any type commonly used for extruding plastics. When adding a plasticizer or performing polymer blending, a co-rotating twin screw extruder is preferred over a single screw extruder. The set temperature of the extruder is appropriately determined depending on the melt viscosity of cellulose acetate, but is preferably in the range of 180 to 240 ° C. Outside this range, it is not only difficult to obtain the melt viscosity specified in the present invention, but also phase separation and thermal decomposition may occur. Cellulose acetate melted in the extruder is a T-die,
It is extruded from an I die, a round die, etc., and formed into a film or sheet. When extruded from a round die, inflation is performed subsequently, and one or more locations are slit in the flow direction to obtain a so-called inflation film.
In either case, the film may be uniaxially or biaxially stretched by a roll method, a tenter method or a tuber method, if necessary. Etc. are not so large. When performing stretching for the purpose of thinning or the like, the operation is performed at a film temperature of 100 to 150 ° C. and a stretching magnification of 2.5 times or less. The thickness of the film or sheet is in the range of 5 μm to 1 mm and is determined according to the application.

The thus obtained film or sheet is biodegradable, transparent, and has a tensile modulus of 1%.
As a polypropylene-like material having a rigidity (lumbar) of not less than 00 kg / mm ² (measured at 23 ° C. and 0% RH), it can be used in a wide range of fields mainly for general packaging materials. The conventional cellulose acetate film has a serious disadvantage in practical use.
That is, the water in the atmosphere is adsorbed, and as a result, the water acts as a plasticizer, and the elastic modulus of the film decreases with time or changes in accordance with humidity, so that the quality is not stable. As a result, usable applications are limited. In the cellulose acetate of the present invention, since the degree of acetyl group substitution is specified, the elastic modulus is hardly reduced by adsorbed water, and the tensile modulus at 23 ° C. and 60% RH is 23%.
80% or more of the tensile modulus at 0 ° C. and 0% RH.

However, the cellulose acetate film of the present invention also has problems. It means that there is an odor of acetic acid remaining in the manufacturing process or produced by hydrolysis after the film is extruded or formed into a film product. In the solution method, not only the heat history during processing is small and the amount of newly generated acetic acid is small, but also the acetic acid derived from the raw material is dissolved in the solution, so that the acetic acid odor of the film product is relatively small. On the contrary, it is remarkable in the melt extrusion method. Since the acetic acid odor is an unpleasant odor, it is not practically preferable that the acetic acid odor is present in the film product even if it is slight. Therefore, in the present invention, in order to prevent the acetic acid odor, a multilayer biodegradable film based on two or three layers comprising an cellulose acetate film or sheet as an inner layer and an aliphatic polyester as an outer layer is used. It is a sheet. The aliphatic polyester is not particularly limited as long as it has an alkylene bond and an ester bond as a basic skeleton. Urethane bonds, amide bonds, ether bonds and the like can be introduced within a range that does not substantially affect biodegradability.

Specifically, a polymer obtained by first condensing an aliphatic diol and an aliphatic dicarboxylic acid is exemplified.
As aliphatic diols, ethylene glycol, 1,4
-Butanediol and 1,4-cyclohexanedimethanol are typical examples. Representative examples of the aliphatic dicarboxylic acid include succinic acid, adipic acid, suberic acid, sebacic acid, and dodecane diacid. From among these, one or more kinds are each selected and subjected to condensation polymerization, and then, if necessary, a molecular chain extender such as an isocyanate compound is added, and the polymer that jumps up to a weight average molecular weight of 50,000 or more is usually 60 to 60. It has a melting temperature of 110 ° C and relatively excellent basic properties similar to polyethylene. Next, there is a series of aliphatic polyesters obtained by ring-opening polymerization of cyclic lactones using an organic metal catalyst. Examples of the monomer include ε-caprolactone, δ-valerolactone, β-methyl-δ-valerolactone, β-propiolactone, pivalolactone, β-butyrolactone, γ-butyrolactone, and the like. One or more kinds are selected from these, including lactide and glycolide, and polymerization is carried out under conditions so that the weight average molecular weight is 30,000 or more.

Further, there is a polymer of α-hydroxycarboxylic acid represented by polylactic acid. Lactic acid includes L-lactic acid and D-lactic acid, and other hydroxycarboxylic acids include glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxyvaleric acid, 4-hydroxyvaleric acid, Typical examples include 6-hydroxycaproic acid. As these polymerization methods, any known methods such as a condensation polymerization method and a ring-opening polymerization method from a cyclic dimer can be adopted. The weight average molecular weight of the polymer is preferably in the range of 60,000 to 1,000,000. Further, other synthetic aliphatic polyesters include cyclic anhydrides and oxiranes, for example, polymers of succinic anhydride and ethylene oxide, propylene oxide or allyl glycidyl ether, and ethylene and cyclic ketene acetate.
A radical polymer with 2-methylene-1,3-dioxolane or 2-methylene-1,3-dioxepane.

In cells such as alkaligenes eutrophus, acetyl coenzyme A (acetyl C
Aliphatic polyesters biosynthesized by oA) are known. This aliphatic polyester is mainly poly-β-hydroxybutyric acid (poly 3HB), but in order to improve the practical properties as a plastic, a fermentation process is devised and a valeric acid unit (HV) is usually copolymerized. It is industrially advantageous to use a poly (3HB-Co-3HV) copolymer. The HV copolymerization ratio is generally 0 to 40%, and the melting temperature is 130 to 165 ° C in this range.
Investigations have been made to copolymerize 4HB instead of HV or further copolymerize a long-chain hydroxyalkanoate, but any of them can be used as the aliphatic polyester of the present invention.

As a method for laminating the cellulose acetate film and the aliphatic polyester film, any method for producing a laminated film can be usually employed. For example, a plurality of extruders are connected to one die, so-called co-extrusion, an aliphatic polyester film is coated on an unwound cellulose acetate film, or a plurality of types of films at an appropriate temperature are rolled. Typical examples include a method of thermocompression bonding with a tool or a press machine, or a method of bonding films together using an adhesive. As an adhesive for performing so-called dry lamination or wet lamination, vinyl-based, acrylic-based, polyamide-based, polyester-based, rubber-based, and urethane-based adhesives are generally used, and the adhesive is also biodegradable. In the case of making, polysaccharides such as starch, amylose and amylopectin, proteins and polypeptides such as glue, gelatin, casein, zein and collagen, unvulcanized natural rubber, or low molecular weight aliphatic Polyester and the like are preferably employed.
By forming a laminated film based on two or three layers as described above, the acetic acid odor of the inner cellulose acetate layer is blocked by the aliphatic polyester layer, and the acetic acid odor is not substantially eliminated in the whole film. Further, by laminating, not only does odor of acetic acid disappear, but also processability such as stretchability and inflation suitability, and surface characteristics such as surface lubricity, heat sealability and printability are improved. Therefore, a wider range of applications can be developed.

Next, a thermoformed product from a cellulose acetate film or a sheet (hereinafter simply referred to as a sheet) will be described. Thermoformed articles from cellulose acetate sheets have not been practically used until now. The reason for this is that the rigidity of the product is required in the use of thermoformed products, but cellulose acetate is reduced in elastic modulus due to water absorption and cannot maintain an appropriate rigidity. In addition, in a system in which a plasticizer is not added, the glass transition temperature is significantly higher than that of a general-purpose resin at 150 ° C. or more, and therefore, there is a relationship that a system cannot be processed by a general-purpose vacuum / pressure molding machine. Cellulose acetate of the present invention is less likely to cause a decrease in elastic modulus due to water absorption,
Further, the glass transition temperature is also 80 to 13 by adding a plasticizer.
Since the temperature is reduced to 0 ° C., thermoforming processing and application development are easy.

The thickness of the sheet suitable for thermoforming is not particularly limited, but is preferably 50 μm to 1 mm
Is preferably used. The method of thermoforming includes any known method of thermoforming a sheet, for example, vacuum forming,
Pneumatic molding, vacuum pneumatic molding, male and female mold molding, plug assist vacuum molding, CD (Cuspension Dilatio)
n: tip extension) It can be arbitrarily adopted from molding or the like. The sheet temperature during molding is determined in the temperature range of 80 to 170 ° C. depending on the glass transition temperature of the sheet, while the mold temperature is preferably 80 ° C. or lower. Although deep drawing is somewhat difficult due to the characteristics of the raw material, it can be easily formed if the area forming magnification is 4 times or less.

[0026]

The present invention is not limited by the following examples. The measured values shown in the examples were calculated under the following conditions. (1) Degree of acetyl group substitution Based on JIS L1013, acetic acid produced by saponification with an alkali was titrated to determine the degree of acetylation of cellulose acetate, and the degree of acetyl group substitution was calculated. The degree of acetyl group substitution is 0 if no hydroxyl group of cellulose is substituted with an acetyl group, and 3.0 (acetylation degree: 62.5%) if the hydroxyl group is completely substituted.
It is. (2) Melt Viscosity A 1 mmφ × 10 mmL nozzle was attached to a flow tester-CFT-500C manufactured by Shimadzu Corporation, and the sample was measured for 22 minutes.
After preheating at 0 ° C. for 5 minutes, the mixture was extruded at a constant load and a shear rate of
The apparent viscosity at 0 sec ^-1 (poise) was defined as the melt viscosity in the present invention.

(3) Tensile Modulus and Humidity Dependence of Tensile Modulus A sample was cut into a strip having a width of 5 mm, left in an atmosphere conditioned at 23 ° C. for 2 days, and then Tensilon II manufactured by Toyo Seiki Co., Ltd. Using a die machine, 25mm between chucks, 5m pulling speed
A tensile test was performed at m / min, and a strong elongation of の of the yield strength was obtained from the obtained stress-strain curve, and the elastic modulus was calculated by dividing the strength by the elongation. The unit is kg / mm ² . The humidity dependency of the elastic modulus was defined as a percentage (%) by dividing the tensile elastic modulus at 23 ° C. and 60% RH by the tensile elastic modulus at 23 ° C. and 0% RH.

(4) Biodegradability A film sample having a thickness of 100 μm was prepared by subjecting a film sample having a width of 25 mm × length 13
A 0 mm strip was cut out and buried in the ground in Kawasaki-cho, Nagahama-shi, Shiga Prefecture in accordance with the soil field test method of the Society for Biodegradable Plastics (BPS). After standing for 5 months, the sample was dug up and the weight retention (%) of each sample was measured. The weight retention rate (%) is the value obtained by retrieving as small as possible a small visible piece in a dug sample and measuring the weight.
Percentage (%) divided by the weight of the film sample before embedding. Thus, the weight loss portion is the sum of fine powder, decomposition products up to the molecular level, and water and carbon dioxide.

Examples 1-2 and Comparative Examples 1-2 The average degree of polymerization was in the range of 100-300, and various cellulose acetates in which the degree of acetyl group substitution was changed from 2.1 to 2.9 were used. Triacetin was added as a plasticizer in an amount of 30% by weight based on the total weight of cellulose acetate and triacetin, and pelletized at 220 ° C. using a 40 mmφ twin screw extruder. These pellets were extruded using a 40 mmφ single screw extruder at a temperature of 220 ° C. using a T-die to obtain
A film of 00 μm was obtained. The lower the degree of acetyl group substitution, the lower the extrudability tended to be, but all were able to be formed into films. Table 1 shows the results of evaluating the tensile modulus and biodegradability of these films.

[0030]

[Table 1]

Examples 3-5 and Comparative Examples 3-4 Various plasticizers were added to cellulose acetate having an average degree of polymerization of 180 and a degree of acetyl group substitution of 2.4 based on the total weight of cellulose acetate and plasticizer. Example 1
A film was obtained in the same manner as described above. Film formation was possible from any of the raw materials. Table 2 shows the results of evaluating the biodegradability of these films.

[0032]

[Table 2]

Examples 7 to 9 and Comparative Examples 5 to 7 For cellulose acetate having an average polymerization degree of 180 and an acetyl group substitution degree of 2.6, triacetin was added to the total amount of cellulose acetate and triacetin. And the mixture was stirred with a Henschel mixer and allowed to penetrate into the granules.
Extrude the T-die with a 0mmφ single screw extruder to obtain a thickness of 100μ.
Table 3 shows the results of evaluating the extrudability and the melt viscosity when a film having a film thickness of m was obtained. The extrudability and the film formability were evaluated at 220 ° C., and in the case of failure, the temperature was changed in a direction to improve the failure.

[0034]

[Table 3]

Examples 10 to 11 and Comparative Example 8 To cellulose acetate having an average degree of polymerization of 180 and an acetyl group substitution degree of 2.6, triacetin was used as a plasticizer in an amount of 30 to the total amount of cellulose acetate and triacetin. % By weight and pelletized using a 40 mmφ co-rotating twin screw extruder. Next, co-extrusion was performed using a two-type, three-layer T-die die so that the melt from the 50 mmφ single-screw extruder became the inner layer and the melt from the 30 mmφ single-screw extruder became both outer layers. Done. The thickness ratio of the outer layer / the inner layer / the outer layer was adjusted to 1/8/1 to obtain a film having a total thickness of 100 μm. As the inner layer, the above cellulose acetate is
As an outer layer, an aliphatic polyester, Bionole 1010 manufactured by Showa Polymer Co., Ltd. (melting temperature = 114 ° C.),
And, BioPole D300G (melting temperature = 162 ° C.) manufactured by Zeneca Corporation was used.

The bionole 1010 is a compound obtained by chain-extending a copolymer of succinic acid and 1,4-butanediol with hexamethylene diisocyanate. -A composition in which a plasticizer and a nucleating agent are added to a copolymer of hydroxybutyric acid and 3-hydroxyvaleric acid. As Comparative Example 8, using this device,
A substantially monolayer film in which both the inner and outer layers were the cellulose acetate was also obtained. Table 4 shows the results of evaluating the odor (acetic acid odor) and biodegradability of the film surface of these films.

[0037]

[Table 4]

Example 12 To cellulose acetate having an average degree of polymerization of 180 and a degree of acetyl substitution of 2.6, triacetin was used as a plasticizer at a ratio of 30% by weight to the total amount of cellulose acetate and triacetin. The mixture was added and pelletized using a 40 mmφ co-directional twin screw extruder. Furthermore, a T-die was extruded with a 40 mmφ single screw extruder, and a sheet having a thickness of 450 μm was collected.
Compressed air molding machine FKS-03-410 manufactured by CDK Co., Ltd. in which a sheet cut to 100 mm is set with an aluminum mold.
After heating the hot plate to 125 ° C, air pressure 1.5kg
/ Cm ^{2 at} a mold temperature of 45 ° C. to obtain a good molded product. This molded article is a cup-shaped container having an open upper edge of 5 cm on a side, a height of 3 cm and a cup-like shape which is narrowing toward the bottom surface.

[0039]

According to the present invention, by using a specific cellulose acetate and a specific plasticizer, an index indicating the properties of the whole material is adjusted to a specific range, and the melt extrudability, moisture resistance, and low odor property are obtained. A biodegradable film or sheet having good biodegradability and transparency can be obtained.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shigenori Terada 5-8 Mitsuya-cho, Nagahama-shi, Shiga Pref. Inside Nagahama Plant of Mitsubishi Plastics Co., Ltd. (72) Inventor Hiroya Kobayashi 5-8, Nishimitabi-cho, Suita-shi, Osaka F-term in Nippon Shokubai Co., Ltd. (reference) 4F071 AA09 AA51 AA88 AC10 AF52 BA01 BB06 BC01 4J002 AB021 CH052 EH036 EH046 EH056 EH096 FD022 FD026

Claims (5)

[Claims] 1. A cellulose acetate having a degree of acetyl group substitution of 2.3 to 2.7 and a biodegradable plasticizer as main components.
Tensile modulus at 3 ° C. and 0% RH is 100 kg / m
m ² or more, and the tensile modulus at 23 ° C. and 60% RH is 80% of the tensile modulus at 23 ° C. and 0% RH.
And the biodegradable plasticizer comprises the following (1)
A biodegradable film or sheet comprising one or a combination of two or more compounds selected from the group consisting of a compound represented by the general formula: and a compound represented by the following (2): _{(1) H 5 C 3 (} OH) 3-n (OOCCH 3) n 0
<N ≦ 3 (2) glycerin alkylate (the alkyl group may have 2 to 20 carbon atoms and may have a hydroxyl residue), ethylene glycol alkylate (the alkyl group has 1 to 20 carbon atoms,
A hydroxyl group residue may be present), polyethylene glycol alkylate having an ethylene repeating unit of 5 or less (an alkyl group has 1 to 20 carbon atoms and a hydroxyl group residue may be present), aliphatic monocarboxylic acid Alkyl ester (alkyl group has 1 to 20 carbon atoms), aliphatic dicarboxylic acid alkyl ester (alkyl group has 1 to 20 carbon atoms, and may have a carboxyl group residue), aliphatic tricarboxylic acid alkyl ester (alkyl group Has 1 to 20 carbon atoms and may have a carboxyl group residue). 2. The biodegradable plasticizer is mixed with cellulose acetate at a ratio of 5 to 50% by weight based on the total weight of cellulose acetate and biodegradable plasticizer. A biodegradable film or sheet according to claim 1. 3. The biodegradation according to claim 1, wherein the melt viscosity is (1.0 to 100) × 10 ³ poise when measured at 220 ° C. and a shear rate of 100 sec ^−1. Film or sheet. 4. The biodegradable film or sheet according to claim 1, which is obtained by melt extrusion. 5. A molded article obtained by thermoforming the biodegradable film or sheet according to any one of claims 1 to 4.