JP2009292875A - Moisture-proof starch composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a moisture-proof starch composition of a starch resin composition containing a starch bio-degradable or disintegrable in a short time when subjected to disposal treatment, especially useful for various uses such as a container for food and drink, various packaging materials such as a sheet and a film, a shock absorbing material, livingware and agricultural goods, and having moisture-proof functions. <P>SOLUTION: The moisture-proof starch composition contains 3-20 pts.wt. calcium oxide added thereto based on 100 pts.wt. starch to enable the composition to exhibit the moisture-proof effects. The composition holds the moisture-absorbed water strongly without causing the risk of re-release at a molding processing temperature. The composition is inexpensive, hardly forms a pinhole, exhibits the high moisture-proof effects of the starch, and stably maintains the moisture-proof effects for a long period. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a starch resin composition mainly composed of starch that biodegrades or disintegrates in a short period of time when it is disposed of, and in particular, food and drink containers, various packaging materials such as sheets and films, cushioning materials, The present invention relates to a moisture-proof starch composition having a moisture-proof function, which is useful for various uses such as household goods and agricultural products.

Conventional plastic molded products are difficult to decompose in the natural environment when discarded, and are a factor that pollutes the environment. Therefore, in recent years, it has been studied to use a molded product made of a material that can be decomposed in a natural environment, and is actually used. Various types of biodegradable resins such as polylactic acid and modified starch are known as resin materials that can be decomposed in such a natural environment. Since these biodegradable resins are finally decomposed by microorganisms in the natural environment and do not adversely affect the environment even if discarded, they are environmentally friendly resin materials.
Starch, one of these biodegradable resins, is a plant-derived natural polymer that is absorbed by the original plant (starch) during the growth process, based on the amount of carbon dioxide emitted during combustion. It is a so-called carbon neutral material that has the same amount of carbon dioxide. However, starch itself is a high molecular weight material, and if it remains as starch, it lacks fluidity during molding and has difficulties in molding processability. Starch that has been plasticized by chemical modification such as etherification is used.

On the other hand, it is also handled by additives, and considering that it is biodegradable and environmentally friendly, the additive added to the starch composition is preferably a natural product as much as possible.
Since additives for petroleum plastics are often used to improve physical properties and processability (Patent Documents 1 and 2), when producing molded products using starch compositions as environmentally friendly materials, The amount added should be considered to be minimal.

  Conventional starch compositions include starch, plasticizers such as glycerin, ethylene glycol, propylene glycol and sorbitol, hydrophilic polymers such as polyvinyl alcohol and carboxymethyl cellulose, lubricants such as glycerin esters and fatty acids, polypropylene and polyethylene, etc. In addition, fillers such as petroleum plastics, talc and clay, and coloring materials such as dyes and pigments are used.

  In addition, such starch compositions are produced by various molding methods such as extrusion molding, T-die extrusion molding, injection molding, vacuum pressure forming, etc., and various packaging materials and disposable products such as shopping bags and garbage collection bags. , Disposable lunch boxes, cups, food trays, knives, forks, spoons, toothbrushes, combs and agricultural products such as agricultural bags, seedling pots, cultivation sets, compost bags and cushions, food and beverage containers, etc. In recent years, such starch molded products have begun to be partially used as environmentally friendly molded products in place of petroleum-based plastic molded products.

  However, among these biodegradable resins, starch is a material that easily absorbs moisture. For example, if a sheet-formed product by a T-die extruder is left at room temperature for several days and then containers are formed by a vacuum / pneumatic machine, Pinholes are generated in the container due to the influence of moisture, which is a problem. Also, extruded pellets that have been left in a simple packaging that is easy to come into contact with air for a long time will absorb moisture from the pellets into the film, resulting in moisture absorbed during inflation molding. The problem is that bubbles are generated.

  Therefore, moisture-proofing has been achieved by forming a petroleum-based plastic skin layer on the surface of molded products by mixing olefin-based resins such as polypropylene and polyethylene, which are petroleum-based plastics, and other petroleum-based plastics with starch. As a result, the moisture absorption of starch tends to be slightly reduced, but it is not sufficient.

  In this way, in the starch composition, as a characteristic property of the starch itself, since it usually contains 10 to 20% as the moisture content, pinholes are likely to be generated by moisture during the molding process, and the use of starch for various purposes is required. There is a possibility that it may be suppressed or the value as a molded product may be impaired, and it is required to improve the moisture absorption property of starch.

By the way, the surface of a hygroscopic petroleum-based plastic molded product is improved with moisture vapor-impermeable petroleum-based plastic, for example, to improve moisture resistance. Even if the method is applied to starch, the physical properties and the like are different between starch and petroleum-based plastics, and the moisture-proofing treatment only on the surface of the molded product cannot be expected to have a continuous moisture-proofing effect.
JP 2001-64458 A JP 2004-155842 A

  The present invention, when using a starch composition in various fields of application, focuses on the above-mentioned environmental friendliness, and forms moldings for food and drink containers, various packaging materials, cushioning materials, agricultural products, daily necessities, etc. It is an object of the present invention to provide a moisture-proof starch composition that is useful as a material, is inexpensive, has a high moisture-proof effect on starch, and can stably obtain a moisture-proof effect for a long period of time.

  As a result of intensive investigations to solve the above problems, the present inventors surprisingly, in the present invention, surprisingly, by adding a predetermined amount of calcium oxide as a moisture-proof component to starch, the moisture absorbed is strongly strengthened. At the molding temperature, there is no risk of re-release, pinholes are not formed, they can be obtained at low cost, and are friendly to the natural environment even after being discarded. It can be set as the moisture-proof starch composition which exhibits an effect, and came to solve the said subject.

  In order to solve the problems of the present invention, the first of the present invention is a moisture-proof starch composition excellent in moisture-proof effect, characterized by adding 3 to 20 parts by weight of calcium oxide to 100 parts by weight of starch. is there.

  The second of the present invention is a moisture-proof starch composition, wherein the starch used in the moisture-proof starch composition is raw starch.

  The third one of the present invention is a moisture-proof starch composition, wherein the starch used in the moisture-proof starch composition is a physically modified starch.

A fourth aspect of the present invention is a moisture-proof starch composition characterized in that the starch used in the moisture-proof starch composition is a chemically modified starch.
By using these moisture-proof starch compositions, the present invention has been completed.

  The moisture-proof starch composition in which a predetermined amount of calcium oxide is added to the starch of the present invention strongly retains moisture absorbed, there is no risk of releasing it again at the molding temperature, pinholes are not formed, and excellent moisture-proof It has an effect. Moreover, it is suitable for molding such as extrusion molding, T-die extrusion molding, inflation molding, calendar molding, and the like, and can be manufactured as an environmentally friendly mold having excellent molding processability and excellent moisture resistance.

  For this reason, the moisture-proof starch composition of the present invention is a more suitable environment-friendly composition as an alternative to petroleum-based plastics, such as various food and drink containers, packaging materials, cushioning materials, household goods, agricultural products, etc. Can be applied sufficiently.

The present invention will be described in more detail below.
First, regarding the constitution of the moisture-proof starch composition according to the present invention, raw starch is used as the starch used in the moisture-proof starch composition excellent in moisture resistance according to the present invention, for example, corn starch, bean starch, tapioca starch, Examples thereof include potato starch, wheat starch, rice starch, black mackerel starch, castor starch, lotus starch, sago starch, bracken starch, and waste starch.

  Physically modified starch can also be used, and examples include alpha starch and wet heat starch.

  Furthermore, starch chemically modified to such an extent that it does not affect biodegradability can also be used, for example, acetoacetate esterified starch, acetate esterified starch, hydroxymethyl etherified starch, hydroxypropyl ether starch, carboxymethyl etherified starch, Allyl etherified starch, methyl etherified starch, succinate esterified starch, xanthogen acetate esterified starch, nitrate esterified starch, urea phosphate esterified starch, phosphate esterified starch, phosphate crosslinked starch, formaldehyde crosslinked starch, acrolein Crosslinked starch, epichlorohydrin crosslinked starch, etc. can be mentioned.

  In the present invention, the starch can be used alone or in combination of two or more from raw starch, physically modified starch or chemically modified starch.

  In the present invention, an essential component of the moisture-proof starch composition is a moisture-proof agent, and the moisture-proof agent is calcium oxide. Calcium oxide is also called quicklime, and is produced by heating calcium carbonate to 900 ° C. or higher and releasing carbon dioxide. The calcium oxide used in the present invention preferably has a small particle size, has a large moisture absorption capacity, and is advantageous for the moisture-proof effect. However, if the particle size becomes too small, the powder will be agglomerated and the powder will become lumpy, it will be difficult to mix uniformly as a moisture-proof starch composition, the moisture-proof effect will be uneven, and the molded product will not be moisture-proofed efficiently. It is not preferable.

In the present invention, if the particle size of the calcium oxide used is too large, the dispersibility in the molded product is inferior to that of a small particle size, and also causes pinhole formation, resulting in poor moisture-proof effect. In addition, the physical properties and the appearance of the product are also inferior.
In consideration of the dispersibility during the molding process of calcium oxide, those obtained by treating the surface of calcium oxide with a fatty acid such as stearic acid can also be used. As such a product, there is CML # 31 manufactured by Omi Chemical Industry Co., Ltd., which can be suitably used. Further, when a master batch in which polyethylene or the like and calcium oxide are mixed from polypropylene is used and the master batch is used for molding a molded product, the calcium oxide itself absorbs less moisture, is safe in storage, and can be suitably used. Examples include Omi Chemical Industry Co., Ltd .: Bell-CML-P and Bell-CML-EM.

In the present invention, it is appropriate that the starch composition is added with 3 to 20 parts by weight of calcium oxide with respect to 100 parts by weight of starch in order to exert a moisture-proof effect. If the amount is less than 3 parts by weight, the moisture-proof effect is poor and the original purpose cannot be achieved. If the amount exceeds 20 parts by weight, the physical properties such as tensile strength, elongation rate, tearing force and the like are fragile and are not preferable. It becomes unbearable, and the product application is limited. Furthermore, workability is inferior, for example, it becomes difficult to form a sheet by a T-die extruder.
In addition, the specific gravity of calcium oxide is as large as 3.35, and the product weight increases as the addition amount increases, which is a practical problem.

  In the present invention, it can be suitably used for food and drink containers, packaging materials such as sheets and films, cushioning materials, daily necessities, agricultural products, and the like. In addition to the above, various additives may be selected according to various uses and required physical properties and functions, and one or two or more kinds may be added in combination as long as the object of the present invention is not impaired.

  As an additive used in the moisture-proof starch composition of the present invention, specifically, sorbitol, mannitol, D-glucose, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol as a plasticizer, Polypropylene glycol, trimethylolpropane, pentaerythritol and the like can be mentioned.

  A filler may be added to the moisture-proof starch composition of the present invention in order to adjust the mechanical strength and reduce the blending cost. Suitable fillers include calcium carbonate, talc, clay, mica and the like. Examples of the lubricant include glycerin ester, fatty acid, fatty acid metal salt, paraffin, and polyethylene wax. Furthermore, in order to improve the molding processability and physical properties, petroleum plastics such as polyethylene, polypropylene, polystyrene, polyamide, polyester, ethylene / vinyl acetate copolymer, alkylene / acrylate or methacrylate copolymer, Cellulose derivatives such as methylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxyethylmethylcellulose, hydroxypropylmethylcellulose, hydroxybutylmethylcellulose, hydrophilic polymer materials such as polyvinyl alcohol, carboxymethylcellulose, polyacrylic acid polymer, polyacrylamide, NBR, SBR, natural rubber, latex such as chloroprene, various acrylates, ethylene / acetic acid Cycloalkenyl copolymer emulsion such as polyurethane, various kinds of synthetic rubber, natural rubber, polymer materials such as biodegradable resins such as polylactic acid, water and the like may also be added. If necessary, colorants such as titanium oxide, carbon black, dyes, and pigments can also be used. In order to improve the mechanical strength, natural fibers such as kenaf and hemp, synthetic fibers such as polyester and polyamide, and reinforcing materials such as various whiskers and glass fibers can be used.

  In addition, chemical foaming agents such as azodicarbonamide, p, p'-oxybisbenzenesulfonyl hydrazide, N, N'-dinitrosopentamethylenetetramine, carbon dioxide, nitrogen gas and butane are used to reduce weight and improve heat insulation. Hydrocarbon foaming agents such as pentane and propane, inorganic foaming agents such as sodium bicarbonate, and hollow bodies such as shirasu balloons, glass balloons and organic balloons can also be added.

  For the purpose of flame retardancy, bromine compound flame retardants such as pentabromodiphenyl, octabromodiphenyl ether, decabromodiphenyl ether, phosphate ester flame retardants such as triphenyl phosphate, antimony compounds such as antimony trioxide and antimony pentoxide Flame retardants, metal hydroxide flame retardants such as aluminum hydroxide and magnesium hydroxide can be added. In addition, additives such as an antioxidant, a crosslinking agent, and a compatibilizing agent can be appropriately added as necessary.

For the production of the molded article of the present invention, a usual petroleum-based plastic molding technique can be applied.
For example, starch, calcium oxide and other additives are mixed in a mixer such as a Henschel mixer, tumbler mixer, barbary mixer, kneader mixer, etc. It is possible to employ a molding processing technique and a molding processing machine such as manufacturing of a sheet by using an inflation molding machine, manufacturing a film by an inflation molding machine, manufacturing a sheet by a calendar molding machine, and manufacturing a molded product by an injection molding machine.

  Also, instead of kneading, mixing and molding the raw moisture-proof starch composition as it is, after mixing with a mixer, produce pellets with a uniaxial or biaxial extruder, and use the pellets as master pellets It is also possible to carry out a molding process such as production of a product by each of the above-mentioned molding machines or production of a molded product by a vacuum pressure machine.

  When manufacturing pellets, cutting the strands extruded from the strand die is considered to cause product defects (such as pinholes) because starch is hygroscopic when cut after cooling in a water bath. Hot cutting is preferred.

  When producing the molded product with the same composition of the moisture-proof starch composition of the present invention, the molding temperature range employed is generally 160 for extrusion molding, T-die extrusion molding, injection molding, inflation molding and the like. It is the range of -220 degreeC. When the molding temperature exceeds 220 ° C., burns and decomposition occur. In extreme cases, the color changes to brown or black, and the molding machine is damaged by seizure in the cylinder. Moreover, in the molding temperature range below 160 ° C., the moisture-proof starch composition is discharged in an unmelted state, which is not preferable. In a remarkable case, the shearing force between the cylinder and the screw is increased, which causes a trouble with an increase in pressure.

  Also, when the residence time in the cylinder is long, the moisture-proof starch composition is burned and decomposed. Although depending on the molding temperature and the discharge speed, the residence time in the cylinder is preferably within 5 minutes at the maximum.

  Further, the purging operation after molding is important, and if there is a residue, foreign matter is mixed into the subsequent molded product, causing defective products. In particular, injection molding requires caution. For example, starch may be unstable due to moisture content. This is because the starch-containing water in the cylinder becomes water vapor, and the screw is returned to the vapor pressure. As a result, the screw backs up at the timing when the pressure is changed from the holding pressure, and in the case of remarkable, the set value may be exceeded and measurement may become impossible. Accordingly, the moisture-proof starch composition is set to a high back pressure so that a constant amount can be supplied during measurement, and the screw rotation speed is set to be slow. Further, if the rotational speed is increased too much, it causes burns and decomposition.

Moreover, the sheet | seat shape | molded and extruded by the T-die extruder was set to the temperature of a take-up roll at 60 degrees C or less, the sheet | seat shape | molded by predetermined thickness was cooled, taken up, and wound up.
EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not restrict | limited to a following example, unless the summary is exceeded.

  About the obtained moisture-proof starch composition, in order to evaluate a moisture-proof effect, the moisture-proof effect was confirmed by the presence or absence of the pinhole which generate | occur | produces in the shape | molded container. The evaluation method was performed as follows.

<Evaluation by pinhole counting>
Specifically, a 0.7 mm-thick sheet prepared by a T-die extruder was left in an atmosphere of 20 ° C. × 70% RH for 30 days, and then a container was manufactured by a vacuum pressure machine. Examine the manufactured container for pinholes.
<Evaluation criteria>
If a total of 3 or more pinholes occurred for 10 molded containers, the moisture-proof effect was confirmed by judging that there was a pinhole. Specifically, if there are 3 or more pinholes in one container, this sheet is judged to have pinholes without checking the presence or absence of pinholes for the remaining 9 and it is judged that the moisture-proof performance is poor To do.

The raw materials used and the sample preparation methods in the examples and comparative examples of the present invention are as follows.
For the raw materials used, in order to blend the moisture-proof starch composition of the present invention Starch: Nippon Cornstarch Co., Ltd., Amilok No. 1A (pregelatinized cornstarch)
Calcium oxide: made by Mined Hengyo Co., Ltd., Moistop # 20 Average particle size 2μm
Glycerin: Showa Chemical Co., Ltd., reagent grade 1 Stearic acid: Showa Chemical Co., Ltd., reagent grade 1 Sorbitol: Showa Chemical Co., Ltd., reagent grade 1 Polypropylene: Prime Polymer Co., Ltd., E-150GK, block type Polyvinyl alcohol: Nippon Vinegar Polymer Co., Ltd., JP-18S
The raw materials were used. A moisture-proof starch composition was prepared for each of the raw materials described above according to the blending ratios in Table 1.

A test sample was prepared as follows using the moisture-proof starch composition of the present invention.
(1) Mixing 25 L Henschel mixer was used for mixing each raw material mix | blended with the moisture-proof starch composition of this invention. The mixing conditions are 500 rpm × 3 minutes and 1000 rpm × 5 minutes. In addition, L is a unit and means a liter. The same applies below.
(2) Preparation of pellets The method for producing the pellets of the moisture-proof starch composition of the present invention is a method of producing a moisture-proof starch composition prepared by the above mixing process by using a single screw extruder with a vent port: screw; 50φ, L / D = 28. Each set temperature of the heating zone of the extruder of the single screw extruder was set to an operating temperature in the range of 180 to 200 ° C., extruded from the nozzle in a strand shape, and hot cut to obtain pellets of a predetermined size.
(3) Preparation of sheet A method for producing a sheet from the moisture-proof starch composition of the present invention is as follows. Pellets prepared by the above mixing treatment were prepared by a T-die single screw extruder (manufactured by LAB TECH Engineering Co., Ltd., with vent port): Die opening Part width: 300mm, Screw: 25φ, L / D = 30, Revolution 88rpm, Extruded in sheet form with each set temperature of uniaxial extruder heating zone set to operating temperature within the range of 175-195 ° C The temperature of the take-up roll was set to 55 ° C., and the sheet formed to a predetermined thickness of 0.7 mm was cooled, taken up and wound up.
(4) Molding of container In order to confirm the moldability of the above-mentioned sheet produced from the moisture-proof starch composition of the present invention, the sheet after being stored for 30 days was subjected to a vacuum / pneumatic machine; FVS, manufactured by Wakisaka Engineering Co., Ltd. -Using a 500P mold, after heating at 400 ° C for 35 seconds, use a vacuum / pneumatic machine to form a conical cup with container size: upper outer diameter: 80φ, bottom outer diameter: 60φ, height: 55mm Molded by vacuum pressure.

  Evaluation by pinhole counting in order to confirm the moisture-proof effect using a test sample obtained by molding the moisture-proof starch composition to which calcium oxide is added according to the blending ratio described in Table 1 of the present invention as in the above sample preparation method. The moldability of the sheet was also evaluated by molding the test sample. Regarding the formability of the sheet, it was also evaluated whether the sheet could be formed with the above-mentioned T-die extruder, whether the formed sheet was vacuum-pressurized with a vacuum pressure machine, and the container could be formed with an injection molding machine. did.

[Example 1]
100 parts (parts by weight, the same shall apply hereinafter) of pregelatinized corn starch (manufactured by Nippon Corn Starch Co., Ltd., Amylok No. 1A) as starch, and calcium oxide as a moisture-proofing agent (Moystop Co., Ltd., Moistop # 20) 3 parts of an average particle size of 2 μm, 5 parts of glycerin (made by Showa Chemical Co., Ltd., reagent grade 1) as plasticizer, 5 parts of sorbitol (made by Showa Chemical Co., Ltd., reagent grade 1), stearic acid as a lubricant 0.5 parts (manufactured by Showa Chemical Co., Ltd., first grade reagent), and 1 part polyvinyl alcohol (Nippon Acetate Polymer Co., Ltd., JP-18S) to further improve molding processability and physical properties, Each was compounded, put into a 25 L Henschel mixer, and mixed with mixing conditions: 500 rpm × 3 minutes, 1000 rpm × 5 minutes, and a moisture-proof starch composition prepared by a single screw extruder with a vent port: screw; 50φ, L / D = 28 Supplied, each set temperature of the heating zones of the extruder of single-screw extruder set at operating temperatures in the range of 180 to 200 ° C., extruded from a nozzle into a strand, was then hot cut into pellets of a predetermined size.

  T-die uniaxial extruder (manufactured by LAB TECH Engineering Co., Ltd., with vent opening): Dies opening width: 300 mm, rotating at 88 rpm, each set temperature of heating zone of uniaxial extruder is 175-195 ° C Extruded into a sheet with the operating temperature set within the range of, the temperature of the take-up roll was set to 55 ° C., the sheet formed to a predetermined thickness of 0.7 mm was cooled, taken up and wound up . A 0.7 mm thick sheet prepared by a T-die single screw extruder was stored in an atmosphere of 20 ° C. × 70% RH and left for 30 days.

The sheet after being prepared for confirming the formability of the sheet and stored for 30 days is formed by using a vacuum / pneumatic machine; FVS-500P type manufactured by Wakisaka Engineering Co., Ltd., molding condition: 400 ° C. × 35 seconds. After heating, the container was molded by vacuum pressure using a vacuum pressure machine so as to form a conical cup having a container size: upper outer diameter: 80φ, bottom outer diameter: 60φ, and height: 55 mm.
About the manufactured container, the presence or absence of the pinhole in the container manufactured like the said evaluation method was investigated. The results are shown in Table 1.

[Examples 2 and 3]
In Examples 2 and 3, of the composition of the moisture-proof starch composition used in Example 1, the composition as shown in Table 1 except that the amount of calcium oxide as a moisture-proofing agent was changed to 6 parts and 20 parts. A moisture-proof starch composition of composition was obtained. From the obtained moisture-proof starch composition, pellets and sheets were produced in the same manner as in Example 1, and the sheets after being stored for 30 days were formed into a container having the same dimensions as in Example 1 with a vacuum / pressure device. The same evaluation as Example 1 was performed about the obtained container. The results are shown in Table 1.

[Comparative Examples 1-3]
In Comparative Example 1, a moisture-proof starch composition having the same composition as Example 1 was prepared except that calcium oxide as a moisture-proof agent was not added. In Comparative Example 2 and Comparative Example 3, the addition amount of calcium oxide, which is a moisture-proofing agent, is 1 part and 30 parts, respectively, outside the scope of the present invention. In Comparative Example 3, the conventional starch moldability is further improved. A moisture-proof starch composition was obtained by blending 10 parts of polypropylene used for quality. The obtained moisture-proof starch composition was molded into a sheet and a container in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The results are shown in Table 1.

  As the result of Table 1, the thing of the compounding composition concerning which the calcium oxide of Example 1-3 is applied to the moisture-proof starch composition of this invention does not find a pinhole by evaluation by pinhole count, and the moisture-proof effect by moisture absorption It is understood that the moisture-proof effect is excellent. Further, as can be seen from Comparative Example 2, when the amount of calcium oxide added is as small as 1 part by weight, the occurrence of pinholes is recognized and a moisture-proof effect cannot be expected, and as shown in Comparative Example 3, it is as large as 30 parts by weight. And although polypropylene is added, it turns out that sheet | seat shaping | molding by a T-die extruder is impossible, and workability is inhibited by the increase in calcium oxide.

Claims (4)

  A moisture-proof starch composition having excellent moisture resistance, wherein 3 to 20 parts by weight of calcium oxide is added as an essential component to 100 parts by weight of starch.   The moisture-proof starch composition according to claim 1, wherein the starch is raw starch.   The moisture-proof starch composition according to claim 1, wherein the starch is a physically modified starch.   The moisture-proof starch composition according to claim 1, wherein the starch is a chemically modified starch.