JP3593661B2 - Biodegradable resin composition - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a biodegradable resin composition. More specifically, the present invention relates to a biodegradable resin composition obtained by heating and melting a mixture containing raw starch and a thermoplastic biodegradable resin (biodegradable polymer) as essential components.
[0002]
[Prior art]
In recent years, from the viewpoint of global environmental protection, the field of biodegradable plastics using natural polymers has attracted attention. Several inventions have also been made on biodegradable compositions in which starch, which is a natural polymer, and other synthetic resins are complexed.
[0003]
When a starch and another synthetic resin are compounded (blended), usually, a mixture of the starch and the synthetic resin is heated and melted, and if necessary, water is added and the compound is formed using an extruder or the like. Often. However, the method using an extruder has a problem that it is difficult to obtain a high-quality compound due to the influence of steam generated during heating.
[0004]
That is, in order to obtain a uniform compound, it is necessary to heat to a temperature at which the starch and the resin are sufficiently dispersed or compatible. The melting temperature of the raw starch is as high as about 120 ° C. or higher. Therefore, at the melting temperature of the resin, steam is generated, and the extrudability is deteriorated by the steam pressure against the extrusion pressure of the extruder. In addition, bubbles are mixed into the molded article due to the generated water vapor.
[0005]
Therefore, conventionally, there has been proposed a method for solving the above problem by minimizing the amount of water added. For example, a method of obtaining a biodegradable resin composition using a denatured starch having a low water content and a specific biodegradable resin without adding water (see JP-A-11-228736), There has been proposed a method of obtaining a biodegradable resin composition by adding a denaturant such as urea and a plasticizer instead of water (see JP-A-11-335401).
[0006]
[Problems to be solved by the invention]
However, in the methods described in the above publications, the resulting biodegradable resin compositions were low in transparency because of low water content. Furthermore, since the melt has a low water content, it has a high viscosity and is difficult to uniformly dissolve or disperse (homogenize).
[0007]
In addition, since it is impossible to completely remove water from the system, it has not been possible to completely solve the problems of pressure increase and air bubble mixing.
[0008]
The reason why water cannot be completely eliminated from the system is as follows. It is said that the starch granules are not a cluster of molecules randomly but have a microcrystalline structure in which a partially fine crystalline structure is developed. It is considered that the starch molecules are stabilized by hydrogen bonding with each other or hydrogen bonding with water molecules.
[0009]
Due to the above structure, starch granules have a property of controlling their own water content by a strong nucleus due to hydrogen bonding. For this reason, even dry starch usually contains a certain amount of water molecules as equilibrium water.
[0010]
The present invention can be homogenized with a general-purpose biodegradable resin without using a denaturing agent or a modified starch, and can provide a high-quality biodegradable resin regardless of the amount of water in the system. It is an object to provide a composition and to provide a biodegradable resin production plant capable of producing the biodegradable resin composition.
[0011]
[Means for Solving the Problems]
Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have intensively researched and developed a biodegradable resin composition and a biodegradable resin manufacturing plant having the following configurations.
[0012]
The biodegradable resin composition of the present invention is obtained by heating and melting a mixture containing raw starch and a biodegradable resin having thermoplasticity as essential components,
The mixture is heated and melted by using a shear extruder having a vent hole and a flight (screw) capable of imparting a mechanical shearing force. It is characterized by applying a shearing force to break the intermolecular hydrogen bonds of the raw starch to make it uniform.
[0013]
In the above configuration, the mass composition ratio of the mixture is80/100 <raw starch (based on dry starch) / aliphatic polyester ≦ 70/30AndFor a total amount of 100% of the raw starch and the aliphatic polyester,Plasticizer having a boiling point above the melting temperature of the mixture: 5~ 20%, lubricant: 0１1%.
[0014]
As the above plasticizerhandUse polyhydric alcohol. As polyhydric alcohol,, Glycerin, ethylene glycol, propylene glycol, trimethylene glycol, tetramethylene glycol, polyethylene glycol, polypropylene glycol, erythrit, arabbit, sorbit alone or can be selected from two or more,Especially for glycerin,Good quality compounds can be obtained.
[0015]
As the above lubricanthand,Fatty acid amide (fatty acid amide)useUseYou.In particular, when stearic acid amide is used, a high quality compound can be obtained.
[0016]
Further, the biodegradable resin production plant of the present invention is used for producing the biodegradable resin composition,
A raw starch and a Henschel mixer capable of uniformly mixing a mixture containing a biodegradable resin having thermoplasticity as an essential component,
A shear extruder having a vent hole and a flight capable of imparting a mechanical shear force, which is used for kneading and shearing the mixture;
A pellet forming machine that pelletizes the biodegradable resin composition extruded from the shear extruder,
A pellet sorter for sorting the size of the pellets formed by the pellet forming machine,
It is characterized by comprising.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail. In this specification, "%" representing the blending ratio indicates "% by mass" unless otherwise specified. Further, the moisture means a moisture content-based moisture content: w [kg / kg (wet stock)].
[0018]
The biodegradable resin composition of the present invention is a compound and can be used for various biodegradable resin products.
[0019]
Here, the compound refers to "a synthetic resin or rubber is added with various compounding agents such as a plasticizer, a curing agent, a filler, a coloring agent, a stabilizer, and a reinforcing agent, if necessary, and the mixture is molded as it is. Material that can be processed "(" Illustrated Plastic Glossary Dictionary 2nd Edition "Nikkan Kogyo Shimbun (1994) p.297), which is in the form of powder, granules, pellets, pastes, and granules. The shape may be any shape such as small spherical shape.
[0020]
The biodegradable resin composition of the present invention is a biodegradable resin composition obtained by heating and melting a mixture containing raw starch and a biodegradable resin having thermoplasticity as essential components. Is the basic feature.
[0021]
The raw starch is a natural starch that is present in a plant itself and is not modified.
[0022]
In addition, (1) another monomer is added to the main raw material to copolymerize or co-condensate, or a certain polymer compound is bonded to another polymer compound (block copolymerization, graft copolymerization). Modification by mixing: so-called chemical denaturation, and (2) a physical treatment such as heating or the like, in which a unique three-dimensional structure held by intramolecular non-covalent bonds such as ionic bonds, hydrogen bonds, hydrophobic bonds, etc. Denaturation that undergoes little chemical composition change, which is cleaved by a chemical treatment such as a change in pH, etc .: There is a so-called physical denaturation (“Illustration Plastic Terminology Dictionary 2nd Edition” Nikkan Kogyo Shimbun (1994) p. 741).
[0023]
As the raw starch, all starches of natural or vegetable origin, consisting essentially of amylose and / or amylopectin, can be suitably used. Specifically, corn starch, potato starch, rice starch, tapioca starch, starch derived from cereals (rye, oats, wheat, etc.) and the like can be exemplified, and alone or two or more types can be selected from these. Can be used. Particularly, corn starch (corn starch) is desirable because it is easily available.
[0024]
The raw starch can be used without limitation of the moisture content, and can be used from a dry starch (containing about 13.5% or less as equilibrium moisture (RH: 81%)) in a wet state. Can be used up to starch. The use of dry raw starch can reduce the generation of steam during heating, as described below. On the other hand, if the raw starch having a high water content is used, the transparency of the biodegradable resin composition becomes good. Therefore, the water content can be appropriately set according to the target. The upper limit of the water content is not particularly defined, but the effect (with respect to transparency) is saturated at about 60%.
[0025]
In addition, the equilibrium water content of the raw dry starch after purification using corn starch as a raw material is about 12 to 13% when the RH is about 81%.
[0026]
On the other hand, as the biodegradable resin, any commercially available biodegradable resin can be suitably used as long as it has thermoplasticity. If a resin having high compatibility with starch is used, a uniformly degradable biodegradable resin composition can be obtained, and even if the resin has low compatibility with starch, a uniformly dispersed biodegradable resin can be obtained. It is possible to obtain a resin composition.
[0027]
For example, cellulose acetate, (chitosan / cellulose / starch) polymerization system, (starch / chemically synthesized green plastic (R)) polymerization system, (aliphatic polyester / aromatic polyester) polymerization system (copolymer of aliphatic and aromatic polyester) and the like. Those derived from natural polymers, polylactic acid, polycaprolactone, polybutylene succinate, poly (butylene succinate / adipate), poly (butylene succinate / carbonate), polyethylene succinate, poly (butylene succinate / terephthalate), Synthetic polymers such as polyvinyl alcohol, poly (glycol / dicarboxylic acid) (Glycols and dicarboxylic acid), poly (hydroxybutyrate / hydroxyvalidate) From the microorganism-produced polymers such like alone or selected to be used.
[0028]
More specifically, "Bionole (R)" (manufactured by Showa Kobunshi Co., Ltd. and Showa Denko KK), "Cell Green (R) PH" (commercially available as Chemical Synthetic Green Plastic (R)) Daicel Chemical Industries, Ltd.), "Lacty (R)" (manufactured by Shimadzu Corporation), "Terramac (R)" (manufactured by Unitika), "Upec (R)" (Mitsubishi Gas Chemical Co., Ltd.) )), "Lacia (R)" (manufactured by Mitsui Chemicals, Inc.), "Ecoflex (R)" (manufactured by BASF Japan Ltd.), "Empol (TM)" (manufactured by IRe CHEMICAL), etc. are used. It is possible.
[0029]
Here, green plastic (R) is a biodegradable plastic that is basically composed of only materials that have been confirmed to have biodegradability and safety above a certain standard value without harmful heavy metals and the like. It is a generic term (registered trademark No. 3364196). The biodegradable resin composition using GreenPla (R) and starch has very good biodegradability.
[0030]
In addition, other additives can be added to the mixture, although not necessarily. For example, a plasticizer having a boiling point equal to or higher than the melting temperature of the mixture can be added to improve the plasticity. The melting temperature of starch is about 120 ° C. or higher for corn starch.
[0031]
As the above plasticizerhand,Use polyhydric alcoholYou.Specifically, glycerin (bp. 290 ° C.), ethylene glycol (bp. 197.7 ° C.), propylene glycol (bp. 188.2 ° C.), trimethylene glycol (bp. 214.2 ° C.), tetramethylene glycol (Bp. 235 ° C.), polyethylene glycol, polypropylene glycol, erythritol (bp. 329-331 ° C.), arabbit, and sorbit, which can be used alone or in combination of two or more (“Chemical Handbook Basic Edition I”, Nihon Kagaku) (See S.41.9.25) Maruzen).Of these, glycerin is particularly desirable.
[0032]
Further, a lubricant may be added to the mixture to improve the melting rate, the melt viscosity, the stability, and the like.
[0033]
Examples of the lubricant include fatty acid amide type, fatty acid type, alcohol type, fatty acid ester type, hydrocarbon type, metal soap type, etc.here, Fatty acid amides based on the resin useduse.
[0034]
Fatty acid amide-based lubricants include stearamide, lauric amide, palmitic amide, benzoic amide, methylene-bis-stearamide, ethylene-bis-stearamide, ethylene-bis-hydroxy-stearamide, hydroxystearamide, methylolamide , Erucic acid amide, lecithin-mono-alkyl phosphate, lecithin-di-alkyl phosphate and the like, and in particular, stearic acid amide can be suitably used.
[0035]
The above mixture further contains additives other than lubricants, such as ultraviolet stabilizers such as carbon black, flame retardants, crosslinkers such as formaldehyde and paraformaldehyde, antibacterial agents, herbicides, antioxidants, fertilizers, opacifiers, and stabilizers. And the like.
[0036]
And the mass composition ratio of the mixture is, for example,80/100 <raw starch (based on dry starch) / aliphatic polyester ≦ 70/30 (preferably 60/40).More preferablyRaw starch (based on dry starch) / aliphatic polyester @ 50/50And In the above,For a total amount of raw starch and aliphatic polyester of 100%,Plasticizer having a boiling point above the melting temperature of the mixture(Polyhydric alcohol): 5~ 20%, lubricant (fatty acid amide): 0When it is set to １1%, a biodegradable resin composition utilizing both characteristics of starch and biodegradable resin can be obtained.
[0037]
Various design changes other than the above-mentioned mass composition ratio are possible. That is, the mixing ratio between the raw starch and the biodegradable resin is arbitrary, and the raw starch may be based on the biodegradable resin. Naturally, if the relative amount of the raw starch increases, the characteristics of the raw starch increase, and if the relative amount of the biodegradable resin increases, the characteristics of the biodegradable resin appear strongly.
[0038]
If the mixing ratio of the plasticizer is too large, the amounts of the biodegradable resin and the raw starch relatively decrease, which is not desirable. Further, if the mixing ratio of the lubricant is too large, no further effect can be expected and the effect is saturated. Plasticizers and lubricants are not essential components as described above.
[0039]
It is desirable that the mixture is uniformly mixed. This is because a more uniform biodegradable resin composition can be obtained during heating and melting in a later step. The mixing may be performed manually, but as described later, a Henschel mixer, a flash mixer, or the like used for normal mixing can be used.
[0040]
By heating and melting the mixture using a shear extruder having a vent hole and a flight (screw) capable of applying a mechanical shear force, the mixture is removed while removing water vapor generated from the mixture. The greatest feature of the present invention is to apply a mechanical shearing force to break and homogenize intermolecular hydrogen bonds of the raw starch.
[0041]
The water vapor is removed when the mixture is heated and agitated using a shear extruder, in order to prevent a steam pressure against the extrusion pressure of the shear extruder from being applied, and the water vapor is used to remove the biodegradable resin. This is for preventing air bubbles from being mixed into the composition.
[0042]
As described above, at the time of heating, even in a dry starch containing only equilibrium moisture, the moisture contained in the starch evaporates. Therefore, even when dry starch is used, it is necessary to remove water vapor.
[0043]
The water vapor may be removed by providing a vent hole in the middle of the shearing extruder or the like to open to the atmosphere, or, if the amount of generated water vapor is large, may be removed by suction (vacuum suction or the like) as necessary.
[0044]
As described above, since the steam is removed at the time of heating and melting, there is no necessity to use a starch having a low water content from the beginning. Therefore, even if water is separately added to impart transparency to the biodegradable resin composition, the extrudability is not reduced. Therefore, pretreatment of starch and addition of a modifier can be omitted, and the process is simplified.
[0045]
The reason why a mechanical shearing force is applied when the mixture is heated and melted is to at least partially break hydrogen bonds between the raw starch molecules. If the hydrogen bond is broken by mechanical shearing force, the starch granules can be finely divided and the biodegradable resin and the starch can be uniformly dissolved or dispersed.
[0046]
Under conditions of no mechanical shearing force, despite the heating, the starch molecules have strong hydrogen bonds despite heating, so that undestructed starch particles remain in the raw material and cannot be uniformly dispersed or compatible.
[0047]
The mixture after heating and melting is highly viscous, but is efficiently dispersed and compatible by the action of mechanical shearing force. That is, it is possible to obtain a biodegradable resin composition which is uniformly dispersed and compatible without using a modified starch having a low viscosity or a low melting point or adding a modifying agent.
[0048]
The mechanical shearing force can be applied using a shear extruder using a shear extruder having a flight (screw) capable of imparting shear deformation to a dull mage type. The flight refers to an outer surface portion of a helical ridge left after processing the screw groove.
[0049]
FIG. 1 shows a model diagram of a shear extruder that can be used for producing the biodegradable resin composition of the present invention. The shear extruder 12 in FIG. 1 is a single-shaft type shear extruder provided with a heating means (not shown). A screw 16 is provided inside the cylinder 14, and the cylinder 14 is provided with a first vent hole 18a and a second vent hole 18b. Each of the first vent hole 18a and the second vent hole 18b can be connected to a vacuum pump or the like, so that steam generated from the raw material can be efficiently removed from the outside of the shear extruder.
[0050]
The specific screw shape is as shown in FIG.
[0051]
In the case of a 130 mm extruder (cylinder inner diameter 130 mm), the vent hole diameter can be, for example, a square vent hole of 40 mm × 90 mm. Further, the number of vent holes may be up to three.
[0052]
A flight 20 and a groove 22 are formed in the screw 16. The raw material supplied from the raw material input port 24 on the input side of the shear extruder moves through the groove 22 of the screw 16 in the direction indicated by the black arrow and is discharged from the shear extruder 12, and the granulator provided on the discharge port side. 26 and the like.
[0053]
The raw material exists in a semi-molten state in a section from the first vent hole 18a to the second vent hole 18b, and this section is effective for shearing and kneading.
[0054]
The discharge port side of the flight 20 has a configuration in which a transparent space is provided so that the raw material in the molten state retreats and pulsates. This is because the raw material can be extruded while repeating the shearing and kneading many times while the raw material retreats, so that the kneading property is improved and more uniform mixing becomes possible.
[0055]
FIG. 4 shows a shear extruder 112 with granulation means 126 at the tip of a preferred embodiment. Here, as for the corresponding parts in FIG. 1, a two-digit graphic code is prefixed with "1" to give a three-digit graphic code, and all or part of the description thereof will be omitted.
[0056]
The screw 116 has a first vent hole (Water suction hole: Water vapor removal holeA first shearing / compression kneading section is formed before ()) 118a. This first shearing / compression kneading section extends over a plurality of (three in the example in the figure) valleys (grooves) 122 and is at a predetermined angle (60 to 180) from both sides of the thread.°)A plurality of kneading ridges (lower than the screw thread) 123a and 123b which are started by being displaced back are formed. The presence of the kneading ridges 123a, 123b reduces the cross-sectional area between the valleys and causes a compression action, and the displacement between the kneading ridges 123a, 123b causes the valley 122 to return to the molten raw material. As a result, the molten material is partially moved back and forth (flow), and the flow phenomenon of compression and shearing occurs. Thus, even if the raw material is semi-molten, the raw material as a whole moves forward by the main body screw while receiving the compression / shearing action. The first shearing / compression kneading section is a section in which the raw material is in a semi-molten state and compression / shear kneading is most effective. The kneading raised portion 123 is formed so as to gradually increase from the bottom surface of the valley portion 122.
[0057]
Also, the second vent hole (Water suction hole: Water vapor removal holeA second kneading promoting section B is formed just before) 118b. In the example shown,PointIt is formed as a multi-threaded portion (four in the illustrated example) by being displaced back by a predetermined angle (60 to 120 °: 90 ° in the illustrated example).
[0058]
The molten material undergoes compression / shear flow phenomena while repeating a partial back-and-forth movement (flow) between the displaced threads (flights) 120b of the multi-threaded portion. The molten raw material moves forward by the main body screw as a whole while being kneaded by compression and shearing.
[0059]
Further, in the illustrated example, a cutter 129 that is rotated and driven by a motor 127 at predetermined time intervals is provided facing the extrusion die 125 so that granulation can be performed. The pellets thus granulated fall from a pellet outlet 131 into a collection container (not shown). 133 in the figure is a screen mesh.
[0060]
The biodegradable resin composition of the present invention is produced, for example, according to the process diagram shown in FIG. That is, the raw materials are mixed by a Henschel mixer or the like, and then kneaded and sheared by using the above-described shear extruder 12 to perform granulation such as pellet molding.
[0061]
At this time, a manufacturing plant shown in FIG. 3 including the shear extruder 12 can be used.
[0062]
The production plant in FIG. 3 includes a Henschel mixer 28 capable of uniformly mixing a mixture containing raw starch and a biodegradable resin having thermoplasticity as essential components,
A shear extruder 12 having a vent hole 18 and a flight 20 capable of applying a mechanical shearing force, which is used for kneading and shearing the mixture,
A granulator (pellet molding machine) 26 for pelletizing the biodegradable resin composition extruded from the shear extruder;
And a pellet sorter 30 for sorting the size of the pellets formed by the pellet forming machine.
[0063]
Hereinafter, the manufacturing plant will be described along the flow of the raw material (workpiece) with reference to FIG. The production of the biodegradable resin of the present invention is not limited to the following production plant.
[0064]
First, powder materials such as biodegradable resin and raw starch are mixed by the blender 32. The blender 32 is provided with powder inlets 34, 34 at the upper part, and performs high-speed rotation of a rotary tank 36 on a gantry 38 by a motor or the like to perform powder mixing. A blender generally used for powder mixing can be used, and examples thereof include a drum blender and a bucket blender. The mixed powder is supplied into the mixing tank 48 of the Henschel mixer 28 by a fixed amount via the powder quantitative feeder 40.
[0065]
On the other hand, although not an essential component, a liquid raw material such as glycerin or water is pumped from liquid tanks 42, 42 by liquid pumps 43, 43, and passed through liquid flow meters 44, 44. Supplied within.
[0066]
Other necessary additives are similarly supplied into the mixing tank 48 of the Henschel mixer 28 using the additive feeding conveyor 46.
[0067]
In the Henschel mixer 28, the above materials are mixed. The Henschel mixer is a type of high-speed mixer of the propeller mixer type, and is widely used mainly for uniform mixing of powders and granules, plastic raw materials, coloring agents and additives, coloring, etc. 2nd Edition ", Nikkan Kogyo Shimbun (1994), p. 741). In this plant, a general-purpose Henschel mixer can be suitably used.
[0068]
Usually, a propeller (stirring blade) provided in the mixing tank 48 is rotated by a V-belt 52 connected to a drive motor 50 to perform uniform mixing.
[0069]
The uniformly mixed mixture is discharged from the mixture discharge port 54 by its own weight, and is carried into a preheating extruder 58 via a feeder 56. As the feeder 56, it is desirable to use a propeller type feeder that can supply a fixed amount.
[0070]
In the preheating extruder 58, the mixture is heated to the target melting temperature and conveyed to the above-described shear extruder 12 in the next step. As the preheating extruder 58, for example, a triaxial screw can be used. In FIG. 3, the supply from the preheating extruder 58 to the shear extruder 12 is performed by forcible pushing using a vertical screw in the supply device 60.
[0071]
The screw 16 having the special flight 20 described above is provided in the shearing extruder 12, and the shearing and kneading is performed efficiently. Since the structure of the shear extruder 12 has already been described, a detailed description is omitted here.
[0072]
The kneaded resin discharged from the shear extruder 12 is pelletized by a granulator (pellet forming machine) 26. In the pellet molding machine 26, a general-purpose pellet molding machine usually used for resin molding can be used. In FIG. 3, a hot-cut pellet molding machine that cuts the resin at the outlet of the shear extruder 12 is used, but other pellet-forming machines such as a cold cut system, an underwater cut system, and a sheet cut system are used. (Pelletizer) can also be used.
[0073]
The formed pellet is cooled in a pellet cooling tank 62. Cooling can be easily performed by water cooling, air cooling, or the like. In FIG. 3, since the pellets are cooled by water cooling, the pellets are dried by a pellet dryer 64 and then conveyed to a pellet sorter 30.
[0074]
The pellet dryer 64 is provided with a general-purpose hot air blowing means and the like. The pellet dryer 64 supplies the pellets and the hot air to perform a flash drying, and is pneumatically conveyed to a collector 66 provided at an upper portion to be collected. The collected pellets are sorted by size in a pellet sorter 30.
[0075]
As the pellet sorter 30, a general-purpose product can be used. Specifically, a vibrating sorter or the like that sorts the size by passing the pellets on a vibrating screen formed of a punching plate, a mesh, or the like can be suitably used.
[0076]
The selected pellets are transported to the upper pellet storage tank 70 by air transport using a blower 68 or the like. Thereafter, the pellets are supplied from a pellet discharge port 72 into a finished product stock tank 74 arranged on an automatic weighing device 76, packaged by a vacuum automatic sealer 78 or the like, turned into a product, and transported by a finished product transport conveyor 79 or the like.
[0077]
As described above, by using the biodegradable resin production plant of the present invention, it becomes possible to realize complete automation in biodegradable resin production.
[0078]
The production conditions of the biodegradable resin composition described above include an extrusion pressure of about 60 kg / cm.²As described above, the extrusion temperature is set to about 130 to 160 ° C. If the extrusion temperature is too low, the melting temperature of the starch or the biodegradable resin will not be reached, and the resin will remain without melting and cannot be plasticized. On the other hand, if the extrusion temperature is too high, depolymerization of the starch and the biodegradable resin occurs, and the properties are lost.
[0079]
After the heating and melting treatment, the unmodified starch is thermally denatured to become pregelatinized starch. The raw starch is insoluble in cold water. The starch which is pulverized by applying a mechanical shearing force in a molten state becomes slightly soluble in water and slightly better in solubility.
[0080]
In the above description, the description has been made on the premise that raw starch is used, but this description does not exclude the use of modified starch. The present invention merely shows that a modified starch having a low melting point and a low viscosity or a modified starch having a low water content can be directly used without using a modified starch having a low moisture content. Naturally, the modified starch is used. It is also possible.
[0081]
Examples of the modified starch that can be used include dextrin, an acid-treated starch, an oxidized starch, a crosslinked starch that is a derivative of a raw starch, a starch ester, a starch ether, a graft copolymer, which is a decomposition product of a raw starch. .
[0082]
For example, acetylated starch is an example of a starch ester. By using acetylated starch, aging resistance and transparency of the starch can be improved. Acetylation simply requires adding an acetylating agent such as acetic anhydride, acetic acid, itaconic anhydride, vinyl acetate, acetyl chloride, ketene, etc. to the above-described mixture of the present invention. The addition amount of the acetylating agent may be, for example, about 0.05 to 1% of the whole mixture.
[0083]
【The invention's effect】
The biodegradable resin composition of the present invention is characterized in that during heating and melting of a mixture as a raw material, a mechanical shearing force is applied to the mixture while removing water vapor generated, thereby breaking intermolecular hydrogen bonds of raw starch. The homogenization made it possible to homogenize the general-purpose biodegradable resin and the starch without using a denaturing agent or a modified starch as in the related art. Further, it became possible to provide a high-quality biodegradable resin composition regardless of the amount of water in the system.
[0084]
【Example】
Hereinafter, examples performed to confirm the effects of the present invention will be described. The starting materials used in the mixtures and the amounts mixed in the examples are described.
[0085]
-Corn starch (raw starch: American yellow dent (horse)): about 45%
・ Biodegradable resin (MFR: 1.4 g / 10 min (190 ° C., 2.16 kg load): about 40%
Glycerin (plasticizer: purity 98.5% or more): about 15%
・ Stearic acid amide (lubricant: 98% or more in purity): about 0.5%
Using each of the above-mentioned raw materials, a heating temperature: 138 ° C. in the die part, 140 ° C. other, extrusion pressure: 60 kg / cm 2, diameter of screw for shearing: 129 by the biodegradable resin production plant described in the detailed description of the invention. It was extruded under the conditions of 0.8 mm and cylinder inner diameter: 130 mm to produce pellets. Vent holes were provided at the shear start and end portions of the shear extruder to remove water vapor. The removal of water vapor was performed using a vacuum pump.
[0086]
As a result, it was confirmed that a biodegradable resin in which corn starch and the biodegradable resin were uniformly dispersed was obtained, and the extrusion moldability was also good.
[Brief description of the drawings]
FIG. 1 is a model diagram of a shear extruder that can be used for producing the biodegradable resin composition of the present invention.
FIG. 2 is a production process diagram of the biodegradable resin composition of the present invention.
FIG. 3 is a diagram of a biodegradable resin production plant of the present invention including the shear extruder of FIG.
FIG. 4 is a schematic sectional view showing an example of a shear extruder used for producing the biodegradable resin composition of the present invention.
[Explanation of symbols]
12 ... Shearing extruder
14 ... Cylinder
16. Screw
18a, 18b ... vent hole
20: Flight (screw thread)
22 ... groove
26 ... Granulator
28 ... Henschel mixer
30 ... Pellet sorting machine
62 ... Pellet cooling tank
64 ... Pellet dryer

Claims (4)

In a biodegradable resin composition obtained by heating and melting a mixture containing raw starch and a biodegradable resin having thermoplasticity as essential components,
The mass composition ratio of the mixture is 80/100 <raw starch (based on dry starch) / aliphatic polyester ≦ 70/30, and based on 100% of the total amount of the raw starch and the aliphatic polyester, And a polyhydric alcohol having a boiling point equal to or higher than the melting temperature of the mixture: 5 to 20%, and a fatty acid amide: 0 to 1%. The biodegradable resin composition according to claim 1, wherein the aliphatic polyester is polybutylene succinate. The biodegradable resin composition according to claim 1, wherein the polyhydric alcohol is glycerin. 4. The biodegradable resin composition according to claim 1 , wherein the fatty acid amide is stearic acid amide.

Images