JP2006328405A - Biodegradable sheet and process for producing the same, biodegradable molded article comprising the sheet, and process for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biodegradable molded article which has excellent biodegradability and has good in formability and mechanical strength, and has excellent in air permeability and water retentivity, and to provide an economical process for easily producing the article. <P>SOLUTION: The biodegradable molded article is characterized in that it contains ≥70% by weight of a starchy substance and in that it is obtained by melting a starch resin mainly comprising an olefin resin at a temperature of 120-180°C, forming the starch resin into a sheetlike shape with a cooled roller and rolling up the resultant sheet in a roll cooled to ≤60°C. Preferably, the olefin resin contains polyethylene or polypropylene. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a biodegradable molded article and a method for producing the same, and particularly, a biodegradable molded article that does not generate harmful substances such as dioxin even when burned and is excellent in biodegradability and is effective for environmental problems, and its It relates to a manufacturing method.

  Currently, plastic products that are widely used are difficult to decompose in nature when discarded, and usually 200 to 400 years are required for decomposition. When incinerated, dioxins and other toxic gases were generated, causing air and soil contamination.

  On the other hand, a material that can be decomposed by living organisms in nature and an alternative to a conventional plastic product and a molded product using the material are desired.

In JP-A-6-32386, attention is paid to starch having excellent biodegradability, and in order to improve heat insulation and water resistance, grains, starch, vegetable protein, and fibrous powder, the powder A method for producing a biodegradable foamed container, wherein a raw material comprising at least one selected from a granulated product and a grain is placed in a closed mold, heated, depressurized and bound into a container shape Is disclosed.
JP-A-6-32386

Moreover, as starch resin which mixed resin, such as starch and plastics, in Unexamined-Japanese-Patent No. 9-296076, corn starch or potato starch or other starch 40-80%, fat 5-15%, water 0.5- 2%, polypropylene or polyethylene or other plastics 3-10%, glycerin 1-5%, protein 2-8%, and ethylene methacrylic acid or ethylene acrylic acid 10-25% A starch resin is disclosed. Further, as a method for producing a molded product such as a container, a method of direct injection molding has been proposed.
JP-A-9-296076

  However, a molded product such as a container obtained from a raw material containing a large amount of starch as in JP-A-6-32386 has a weak binding force between starches compared with plastics and obtains sufficient mechanical strength. For this purpose, the thickness of the container increases and the amount of material used increases, so that the cost becomes expensive.

  In addition, in order to mold a raw material containing a large amount of starch directly into a closed mold, it contains a large amount of starch, so the viscosity is high, and discoloration and foaming occur at high temperatures, resulting in a stable molded product. It has the disadvantage that it is difficult to do.

  When using starch resin as disclosed in JP-A-9-296076, when molding a container or the like by injection molding, it is necessary to suppress the starch quality to about 50% by weight in order to maintain strength. However, a decrease in starch content reduces the degradation rate in nature and causes problems such as an increase in the amount of dioxin generated when incinerated and an increase in incineration temperature. In addition, since starch is contained, temperature control during injection molding is difficult and viscosity is increased, leading to problems such as high production cost and difficulty in mass production.

  The problem of the present invention is to solve the above-mentioned problems, and the starch content is as high as 70% by weight or higher, preferably 75 to 90% by weight or higher, and has excellent biodegradability and good moldability. It is to provide a biodegradable molded article using an adhesive sheet and to provide a simple and economical manufacturing method.

  Another object of the present invention is to provide a biodegradable molded article using a biodegradable sheet having good mechanical strength and excellent breathability and water retention.

  In order to solve the above-mentioned problems, an invention according to claim 1 is a roller in which starch resin containing 70% by weight or more of starch and olefin resin as a main component is melted at a temperature of 120 to 180 ° C. and cooled. A biodegradable molded product obtained by molding a biodegradable sheet obtained by molding into a sheet and cooling to 60 ° C. or lower and winding into a roll.

  Preferably, as in the invention according to claim 2, in the biodegradable molded product according to claim 1, the olefin resin contains either polyethylene or polypropylene.

Further, as in the invention according to claim 3, in the biodegradable molded product according to claim 1 or 2, the biodegradable sheet is obtained by heating and vacuum forming or pressure forming. To do.
In particular, as in the invention according to claim 4, in the biodegradable molded article according to any one of claims 1 to 3, the thickness of the biodegradable sheet is 0.2 to 0.8 mm. Features.

  Moreover, as in the invention according to claim 5, in the biodegradable molded product according to any one of claims 1 to 4, the molded product is provided with grooves and / or protrusions for increasing mechanical strength. It is characterized by.

  Preferably, as in the invention according to claim 6, in the biodegradable molded article according to any one of claims 1 to 5, the biodegradable molded article contains a fungus having starch as a nutrient. It is a container for storing food.

  The invention according to claim 7 is a method comprising melting starch resin containing 70% by weight or more of starch and containing olefin resin as a main component at a temperature of 120 to 180 ° C., and forming it into a sheet with a cooled roller. It is a method for producing a biodegradable molded product that obtains a biodegradable molded product by molding a biodegradable sheet obtained by cooling to 60 ° C. or lower and winding it into a roll.

  Preferably, as in the invention according to claim 8, in the method for producing a biodegradable molded article according to claim 7, the starch resin contains starch and starch so that the starch content is 70% by weight or more. The olefin resin is kneaded, the kneaded product is extruded, and then cut to form raw material pellets, and the raw material pellets are dried.

  And, preferably, as in the invention according to claim 9, in the method for producing a biodegradable molded product according to claim 8, the water content in the raw material pellet is 2% by weight or less, preferably 0.2 to It is characterized by drying to 0.4% by weight.

  The invention according to claim 10 is the method for producing a biodegradable molded product according to any one of claims 7 to 9, wherein at least one biodegradable sheet is laminated, and the sheet is heated to be softened. And then forming a biodegradable molded product by vacuum-die-cutting or pressure-pneumatic die-cutting of the softened sheet. In this invention, in the method for producing a biodegradable molded article according to claim 10, the temperature of the female mold used for the die cutting is set to 20 to 70 ° C.

  As in the invention according to claim 1, since starch is contained in an amount of 70% by weight or more, preferably 75% by weight to 90% by weight, the biodegradability is very good, and the raw material is 120 to 180 ° C., preferably 150%. ~ 170 ° C, more preferably melted while being held at around 165 ° C, molded into a sheet with a cooled roller, and cooled to 60 ° C or lower and wound into a roll, so that the starch is thermally denatured It is possible to obtain a uniform sheet by suppressing discoloration and foaming due to.

Moreover, since it contains olefin resin in addition to starch, especially polyethylene or polypropylene as in claim 2, it is possible to ensure proper fluidity during molding and binding after molding. It becomes.
Furthermore, since the sheet is molded to obtain a biodegradable molded article, it is possible to provide a biodegradable molded article using a biodegradable sheet that has good mechanical strength and excellent air permeability and water retention. it can.

  As in the invention according to claim 3, even if the raw material contains a large amount of starch and has high viscosity and is difficult to control the temperature, it can be heated from the biodegradable sheet and vacuum molded or compressed air molded, A homogeneous molded product can be easily obtained by using a heat vacuum molding machine or a heating / pressure forming machine which is widely used.

  Further, in order to form a molded product from the biodegradable sheet, even when compared with a closed mold insertion / compression molding, injection molding, etc., as in the invention according to claim 4, it is 0.2 to 0.8 mm. Since a thin sheet can be stretched and formed, consumption of raw materials can be suppressed and cost reduction can be achieved.

  Moreover, in order to reinforce the mechanical strength that becomes brittle by reducing the thickness of the molded product, it is possible to easily increase the strength by providing grooves or protrusions as in the invention according to claim 5. Become.

  Furthermore, since it contains a large amount of starch as a raw material, it has higher air permeability and water retention than conventional plastic molded products, and it is possible to supply starch as nutrients. By using it as a container for containing foods that contain the bacterium with the characteristics of nutrients such as natto as nutrients and taking in the starch, it can be used for a longer period of time than plastic molded products. It is possible to provide food that contains live bacteria.

  As in claim 7, the starch resin containing 70% by weight or more of starch and containing olefin resin as a main component is melted at a temperature of 120 to 180 ° C. and molded into a sheet with a cooled roller, and 60 ° C. Since the biodegradable sheet obtained by cooling to below and winding in roll shape is shape | molded, it becomes possible to suppress discoloration and foaming by the thermal modification | denaturation of starchy substance, and to obtain a uniform sheet | seat. Moreover, since an olefin resin is contained in addition to the starchy substance, it is possible to ensure an appropriate fluidity during molding and a binding property after molding. Furthermore, since the sheet is molded to obtain a biodegradable molded article, a method for producing a biodegradable molded article using a biodegradable sheet having good mechanical strength and excellent air permeability and water retention is provided. be able to.

  As in the invention according to claim 8, the starch resin is formed by forming a raw material containing starch, into a pellet form, and melting the pellet to form a sheet. Since the processes to be performed can be separated, the management of each process becomes easy, and the manufacturing bases can be decentralized. Therefore, it is possible to improve productivity, disperse manufacturing risks, and reduce manufacturing costs. Further, for example, the sheet-like molding can be performed using a biaxial stirrer, and the thickness of the obtained sheet can be kept uniform.

  In addition, in the raw material pellets, starch and plastic are uniformly mixed, and even if the production amount of the sheet fluctuates, it is possible to always produce a homogeneous sheet by adjusting the supply amount of the raw material pellets. . Moreover, as in the invention according to claim 9, the moisture content can be adjusted by passing through the step of drying the raw material pellets, and the characteristics are stabilized in combination with the characteristics of the binder added at the time of melting as necessary. A biodegradable sheet can be produced.

  According to the invention of claim 10, by stacking one or more biodegradable sheets until a desired thickness, and heating to a temperature at which the sheet softens, by vacuum die cutting or pneumatic die cutting, It becomes possible to process into a required shape while maintaining a uniform thickness. In addition, as in the invention according to claim 11, by setting the temperature of the female die used for die cutting to 20 to 70 ° C., it is possible to maintain the sheet formability and mold release property well. It becomes. In particular, when the temperature of the female mold is less than 20 ° C., the extensibility of the sheet is lowered and the moldability is deteriorated. Moreover, when it exceeds 70 degreeC, the mold release property from the metal mold | die of a molded article will fall.

Hereinafter, the present invention will be described in detail using preferred examples.
As the starchy substance used in the present invention, the biodegradable molded product according to the present invention may be used as a food-related product. Therefore, from the viewpoint of user safety, it is derived from a natural product. Starch is desirable, but processed (modified) starch and mixtures thereof can be used if desired. As raw materials for starch, corn, potato, sweet potato, wheat, rice, tapioca, sago, cassava, beans, kuzu, bracken, lotus, castor, etc. can be used. Is more preferable.

  Processed starch includes natural starch that has been subjected to various physical modifications, such as α-starch, fractionated amylose, wet heat-treated starch, natural starch that has been subjected to various enzyme modifications, such as hydrolyzed dextrin , Enzyme-degraded dextrin, amylose-degraded starch, amylopectin-degraded starch, etc. that have been subjected to various chemical treatments, such as acid-treated starch, hypochlorous acid-oxidized starch, oxidized dicarboxylic acid starch, acylated Acetylated starch, other chemically modified starch derivatives such as esterified starch, etherified starch, crosslinked starch treated with a crosslinking agent, aminated with 2-dimethylaminoethyl chloride Such as cationized starch. As esterified starch, acetate esterified starch, succinate esterified starch, urea phosphate esterified starch, xanthate esterified starch, acetoacetate esterified starch, etc. As etherified starch, allyl etherified starch, methyl ether As cationized starches such as starch starch, carboxymethyl etherified starch, hydroxyethyl etherified starch, hydroxypropyl etherified starch, etc., the reaction product of starch and 2-dimethylaminoethyl chloride or 2-diethylaminoethyl chloride, starch and 2, Examples of the crosslinked starch such as a reaction product of 3-epoxypropyltrimethylammonium chloride include formaldehyde crosslinked starch, aldehyde crosslinked starch, dialdehyde crosslinked starch, epichlorohydrin crosslinked starch, phosphate crosslinked starch, and acrolein crosslinked starch.

  In the present invention, a so-called starch resin obtained by mixing starch and a resin such as plastic is used as a raw material. This is to be mixed in order to further impart water resistance, heat resistance, mechanical strength, fluidity at the time of thermoforming, etc. to the starch-only raw material, preferably 10 to 30% by weight in the raw material More preferably, it is mixed so as to be 15 to 25% by weight.

  Plastics to be mixed with starch include polyethylene resins, polypropylene resins, polybutylene resins, polyvinyl chloride resins, polyacrylic or polymethacrylic resins, polyacrylonitrile resins, polystyrene resins, styrene-acrylonitrile copolymers. Styrene-butadiene-acrylonitrile copolymer, polycarbonate resin, polyester resin or recycled polyester resin, polyamide resin, polyacetal resin, etc. Can be used. In the present invention, in particular, an olefin resin such as polyethylene or polypropylene can be suitably used in order to increase the strength during molding.

  Next, it is possible to manufacture a biodegradable sheet or a biodegradable molded product directly from the raw materials such as starch and plastic, but the biodegradable sheet or molded product according to the present invention has a starch quality of 70. In order to reduce the production cost because it is contained by weight%, preferably 75 to 90% by weight, and from the viewpoint of reusing the conventional production line for plastic sheets and containers, the raw materials are first added. Uniformly mixed raw material pellets are manufactured, and the raw material pellets are melted by a necessary amount to form a biodegradable sheet.

  In addition, for biodegradable molded products, it is possible to melt and pelletize raw material pellets, but because of the raw material having a high concentration of starch, it is difficult to control temperature and has a high viscosity. In order to obtain a thin and homogeneous molded product, a method of once processing into a sheet shape, then softening the sheet, and then performing vacuum die cutting or pneumatic die punching molding is possible at a low cost and with good quality. You can get a product.

  In addition, the manufacturing process is separated into multiple processes, such as manufacturing raw material pellets from raw materials, then using the raw material pellets to produce biodegradable sheets, and using the biodegradable sheets to produce biodegradable molded products. As a result, the management of the manufacturing process becomes easy and the manufacturing bases can be decentralized, so that productivity can be improved, manufacturing risk can be distributed, and manufacturing costs can be reduced.

  The raw material pellet manufacturing method is a method in which the raw material starch and plastics are uniformly mixed, and the manufactured raw material pellet can maintain its shape and characteristics even in normal storage and transport conditions. If there is, a known mixing method by kneading or melting can be used.

  However, a method utilizing a kneading machine that can easily control the temperature of an extruder or the like is more desirable from the viewpoint of appropriately controlling the temperature of starch.

  A preferred example of a method for producing raw material pellets using an extruder will be described. A production machine uses a biaxial extruder that pivots inward with respect to each other, and has at least one, preferably two or more, raw material supply tanks. Place in the direction of. For example, starch is supplied from the first supply tank and plastic is supplied from the second supply tank, and the raw material is conveyed in the axial direction while being pulverized and kneaded by a biaxial extruder. Moreover, each supply tank is temperature-controlled, starch substance is hold | maintained at atmospheric temperature, and plastics are hold | maintained at about 100-160 degreeC. The amount of raw material supplied per hour is such that the proportion of the raw material in the viscous raw material mixture extruded from one end of the extruder is 70% by weight or more of starch, preferably 75 to 90% by weight of starch, The supply amount of each supply tank is adjusted to be in the range of 10 to 25% by weight.

  The viscous raw material mixture extruded from the extruder is cooled and cut into a predetermined length to form raw material pellets.

  Next, a preferred example of the method for producing a starchy biodegradable sheet will be described.

  In addition, the starchy substance contains moisture or is contained in the air when preparing the starchy substance from the raw material for producing the starchy substance such as corn, when producing the raw material pellets, and when storing it. Since starch has a property of easily containing moisture, such as absorbing moisture, the raw material pellets are dried. As a drying method, a known technique such as hot air drying can be used. Preferably, drying is performed so that the moisture content in the raw material pellets is 2% by weight or less, preferably 0.2 to 0.4% by weight, that is, the moisture content is reduced as much as possible. Is desirable.

  Next, the dried raw material pellets are melted, preferably melted at a temperature of about 180 ° C., and the temperature of the melt is 120 to 180 ° C., preferably 150 to 170 ° C., more preferably 165 while cooling with air. The sheet is formed in a sheet shape by using a biaxial roller while maintaining the temperature in the vicinity of ° C. It is also possible to form the sheet into a sheet while cooling the roller with water. Thereafter, the sheet is cooled by air or natural cooling, preferably 60 ° C. or lower, and wound into a roll. The stretching roller at the time of sheet formation can be a uniaxial roller, but in the case of a uniaxial roller, the load on the driving roller is large and the temperature rises, which may cause foaming and discoloration of the biodegradable sheet, It is preferable to use a biaxial roller. If the temperature at the time of melting exceeds 200 ° C., particularly 220 ° C., the starch is cured and foamed in the melting container, and it becomes difficult to form a homogeneous sheet. Further, when the temperature at the time of forming the sheet exceeds 180 ° C., the generation of bubbles is conspicuous in the formed sheet, and when the temperature once decreases and rises again, discoloration is likely to occur. Furthermore, at a temperature lower than 120 ° C., the melted raw material has a high viscosity, and a sheet having a uniform thickness and density cannot be formed. In addition, when the temperature is in the preferable range of 150 to 170 ° C., and more preferable in the vicinity of 165 ° C., the generation of a strange odor during sheet production can be prevented, the foaming phenomenon can be effectively suppressed, and a high-quality sheet can be obtained and produced. Since the time is shortened, the production cost is reduced, which is desirable.

  The obtained sheet is considered not to be in a state in which the starchy substance and the plastic are completely bonded, and is porous, has good air permeability, and excellent water retention.

  Furthermore, if necessary, a binder may be added at the time of melting the raw material pellets. The binder is used for the purpose of enhancing the binding performance between the starches or between the starch and the plastic when formed into a sheet, and improving the shape retention. By adding such a binder, the mechanical strength such as tensile strength after sheet forming increases, handling of the biodegradable sheet, and transport in the manufacturing process when reprocessing into a biodegradable molded product. Work and the like can be performed stably, and long-term storage in a sheet state is also possible.

  As such a binder, the same polymer resin as the plastic contained in the raw material pellets can be used, but polypropylene is preferably used from the viewpoint of increasing the molding strength. Moreover, extensibility can be improved by adding polyethylene.

  In addition, various additives can be added for the purpose of water resistance and moisture absorption prevention of the biodegradable sheet and discoloration prevention during storage. The amount of the binder or additive added can be arbitrarily adjusted as long as the starch content in the sheet is 70% by weight or more, preferably 75 to 90% by weight when formed into a sheet. However, it is desirable to add an amount corresponding to the amount of water reduced in the drying process from the raw material pellets.

  By such a manufacturing method, a highly versatile homogeneous biodegradable sheet of 1 mm or less can be formed, and in particular, it is confirmed that a homogeneous biodegradable sheet can be formed up to about 0.005 mm. Yes. Moreover, as a thing utilized for the biodegradable molded article mentioned later, the thickness of a biodegradable sheet | seat is preferable about 0.2-0.8 mm.

  Next, a method for producing a biodegradable molded product will be described with reference to a suitable example.

  When the biodegradable sheet is conveyed through the heater, it is warmed and softened, and preferably heated up to near the softening point temperature of the sheet to be raised. Die-cut with a mold. In particular, when producing a molded product that requires a uniform thickness such as a container, vacuum punching or pressure forming is preferable. In the case of vacuum punching, vacuum suction is applied to the female die, The male die fitted with the female die is subjected to die cutting and rapidly cooled to a temperature in the range of 20 to 70 ° C. while adsorbed on the female die.

  The temperature of the female mold at this time is desirably maintained at 20 to 70 ° C., because this is a temperature suitable for releasing the molded product from the moldability of the sheet and the mold. That is, when the temperature is less than 20 ° C., the extensibility of the sheet is lowered and the formability is deteriorated. Moreover, when it exceeds 70 degreeC, the mold release property from the metal mold | die of a molded article will fall.

  However, in order to improve the releasability, it is possible to apply a release agent to improve the releasability. For example, when polyethylene or polypropylene is included in the raw material, it is possible to produce a molded product by using a material in which the female mold temperature is raised to about 80 ° C. and a release agent is applied to the sheet surface. It is.

  When the sheet is softened and die cut, the environmental conditions for softening the sheet can be changed according to the die cutting shot time. For example, the shot time (time per die cutting) is 9 to 10 seconds. In this case, the heater temperature for heating the sheet is 380 to 400 ° C., when the shot time is 11 to 14 seconds, it is 280 to 300 ° C., and when the shot time is 15 to 20 seconds, 180 to It is preferable to set the heater temperature and the passage time of the sheet in the heater space so that the sheet is adjusted to 220 ° C. and the sheet is maintained in an optimum softened state when being punched. Thus, by performing temperature management at the time of container forming in relation to the die-cutting time (shot time), the manufacturing cost can be significantly reduced.

The degree of vacuum during vacuum forming is stamped is not particularly limited as long embodiment, for example, when representing the degree in the suction of the female, it 40 m 3 ^/ h 200 m 3 is when ^/ it can. Further, a female mold is disposed above the sheet and a male mold is disposed below, and the female mold is configured to suck air and blow air from the male mold side. Thus, the sheet is pushed up while air is blown onto the softened sheet, the sheet is adsorbed on the wall surface of the female mold by the suction force of the female mold, and a container having a uniform thickness is formed while appropriately stretching the sheet.

  According to said manufacturing method, when the depth of a container is about 10-60 mm, for example, it is 1 mm or less, Preferably it is 0.2-0.8 mm, More preferably, it is 0.4-0.5 mm By using a biodegradable sheet of a certain thickness, it is possible to easily form a homogeneous container.

  In the case of pressure forming, for example, when the depth of the container to be formed is about 2 cm or less, it is possible to form using a pressure forming machine. The temperature conditions for die cutting in the case of pressure forming are the same as in the case of the above vacuum forming.

  The obtained molded article is considered not to be in a state in which the starch and the plastic are completely bonded, and is porous, has good air permeability, and excellent water retention.

  In the above description, the method of using a biodegradable sheet in one layer has been described. However, two or more layers of the sheet are laminated, heated to the softening point of the sheet, and die-cut molded in the same manner as described above. Is also possible.

  Furthermore, the burrs remaining after die cutting during molding of the molded product can be used as a raw material for the recyclable decomposable sheet by melting, so it is reduced to the biodegradable sheet manufacturing process and reused. It is also possible.

  The softening point temperature of the biodegradable sheet when forming a molded product will be described. FIG. 1 shows the measured softening point temperature of the biodegradable sheet according to the present invention.

  The biodegradable sheet used in the experiment had a starch content of 70% by weight, a polypropylene content of 28% by weight, and a 2% by weight polypropylene as a binder added as necessary. 5 mm.

  As a measuring method, a differential scanning calorimetry method (DSC3100; manufactured by MAC SCICEE) is used, and a change in the endothermic rate per second is measured while increasing the temperature at 1 ° C. per minute.

  As the graph of FIG. 1 shows, the softening point exists in the vicinity of 116 to 124 ° C., and the biodegradable sheet containing a large amount of starch according to the present invention has a softening point mainly at 115 to 125 ° C.

  In addition, the biodegradable sheet according to the present invention has a heat absorption rate at the softening point that is about 1.5 times higher than that of polypropylene or the like, and therefore more stringent temperature control compared to the production of ordinary plastic molded products. Is understood to be necessary.

  The biodegradable molded product can also be used as a disposable container used for packaging foods, tableware such as disposable forks and spoons, space materials and cushion materials used for various packaging. It is also possible to form a garbage bag, a packaging bag, a disposable garment, etc. by thinly forming a biodegradable sheet and utilizing heat fusion or the like.

  In a biodegradable molded product having a small thickness and requiring a three-dimensional shape, as described above, once the biodegradable sheet is formed, the sheet is heated, and then subjected to vacuum die cutting or pneumatic die cutting. It becomes possible to obtain a molded product having a uniform thickness over the entire molded product. In particular, by forming a thin container, the consumption of raw materials can be reduced and costs can be reduced, and even when discarded, the volume of waste is reduced and the speed of biodegradation is increased, resulting in extremely useful effects. be able to.

  FIG. 2 is a view showing a disposable container which is one of the biodegradable molded products according to the present invention.

  FIG. 2A is a view as seen from above the container, and FIG. 2B shows a cross-sectional shape taken along one-dot chain lines A and B in FIG.

  When the thickness of the container is reduced, the mechanical strength on the side surface of the container is reduced, so that it becomes difficult to handle the container as in the case of a conventional plastic container. For this reason, in order to increase mechanical strength, it is preferable to form a groove or a protrusion on the side surface of the container.

  FIG. 2 shows a container 1 having a length and width of about 80 to 100 mm and a depth of about 30 mm. The container 1 is formed by forming a biodegradable sheet of 0.5 to 1 mm by heating vacuum die cutting and width. As shown in FIG. 2 (a), grooves having a depth of about 1 to 2 mm and a depth of about 1 mm are formed on the side surface and bottom surface of the container 1 as indicated by reference numerals 2 to 4, so that a normal plastic (polypropylene) is made. The mechanical strength equivalent to that of the container was secured.

  The groove can be expected to improve to some extent by forming it on the surface where the mechanical strength should be strengthened, but in order to prevent deformation of the three-dimensional shape of the container, it is at least continuous as shown in FIG. It is preferable to form common grooves 2 to 4 across the two surfaces. Further, by crossing the grooves as indicated by reference numeral 3, it is possible to increase the mechanical coupling force between the grooves, and a higher strength container can be formed. Furthermore, by forming the protrusion 5 having a shape higher or wider than the groove at the intersection of the grooves, it is possible to further strengthen the connection between the grooves.

  The biodegradable sheet and biodegradable molded product according to the present invention are naturally decomposed even when discarded, and are useful for reducing the burden on the environment, but themselves contain a large amount of starch, Since air permeability and water retention are good, it is possible to circulate and store bacteria in a living state by packaging food containing bacteria containing starch as nutrients in the biodegradable container described above. Become.

  For example, natto bacteria, baker's yeast, lactic acid bacteria, koji molds, and other foods that need to keep bacteria alive not only in the food production process, but also in the distribution process, such as natto, bread dough, lactic acid food, and alcoholic beverages. In particular, the biodegradable container according to the present invention has a high utility value.

  Examples according to the present invention will be described below.

Example 1
As raw materials, 70% by weight of corn starch and 30% by weight of polyethylene were kneaded by a biaxial extruder, and the raw material mixture extruded from the extruder was cut into a length of 0.5 to 5 mm to form raw material pellets. .

  The raw material pellets were dried with hot air until the water content was 0.2% by weight. Polypropylene as a binder is added to the dried raw material pellets so that the total weight of the polyethylene is 30% by weight, melted at 180 ° C., and the molten raw material is brought to around 165 ° C. while cooling with air. The biodegradable sheet having a thickness of 0.5 mm was formed by a biaxial roller.

(Material and dissolution test)
About the sample of Example 1, the material test and the elution test were implemented based on the "synthetic resin instrument or container packaging specification test (polyethylene)" (Ministry of Health and Welfare Notification No. 20). The results are as follows, and it can be seen that the sample of Example 1 conforms to the above standard.
・ Material test Cadmium ・ ・ ・ less than 1ppm (standard standard 100ppm or less)
Lead .... Less than 10ppm (100ppm or less)
・ Elution test Heavy metal (as Pb): Less than 1 ppm (1 ppm or less)
Potassium permanganate consumption: 1.5 ppm or less (10 ppm or less)
Evaporation residue (n-heptane leaching): 84 ppm or less (150 ppm or less)
Same (20% ethanol leaching) ・ ・ 9ppm or less (30ppm or less)
Same (water leaching): 11 ppm or less (30 ppm or less)
Same (4% acetic acid leaching) ... 11ppm or less (30ppm or less)

(Physical property test of biodegradable sheet)
The biodegradable sheet of Example 1 was tested based on “polyethylene degradable base film sheet” (Q / 12XT3832-99). The test results are shown in Table 1.

  Tensile strength and tear elongation rate are average values obtained by testing five samples with a sample formed into an iron array mold, width 10 mm, effective length 40 mm, sample total length 120 mm, test speed 500 ± 50 mm / min. Is shown.

  Further, in the test in which cracks were made at right angles, the test speed was set to 200 ± 20 mm / min, and the maximum value at break was measured.

(Degradation performance test of biodegradable sheet)
When producing a biodegradable sheet in the same manner as in Example 1, the content of starch was changed in the range of 0 to 80% by weight, and a test specimen molded so as to have a sheet thickness of 0.5 mm was prepared. The test was performed based on “determination of plastic and microbial activity” (ISO846). The test results are shown in Table 2.

However, the test period is 30 days, and the bacteria used are black-cured bacteria.
The relationship between the breeding area of bacteria and the breeding level is as follows.
Breeding level 0: No breeding Same level 1: Visible under the microscope.
Same level 2: Breeding area that can be confirmed visually is less than 25% Same level 3: Breeding area that can be visually confirmed is less than 50% Same level 4: Breeding area that can be confirmed to breed clearly is more than 50% Same level 5: Mass With 100% breeding area

From the above test results, it can be seen that the biodegradable sheet according to the present invention is extremely hygienic and safe. In addition, it is understood that the mechanical properties are equal to or higher than those of the polyethylene sheet and the biodegradability is excellent.
In particular, in terms of biodegradability, it can be confirmed that in those containing 60% by weight or more of starchy substance, the bacterial growth area covers the whole and exhibits extremely good biodegradability.

(Example 2)
Next, a biodegradable sheet having a thickness of 0.5 mm was formed by the same production method as in Example 1 except that polyethylene was replaced with polypropylene, the sheet was heated and softened, and vacuum die cutting was performed. A biodegradable container as shown in FIG. 2 was molded.

(Strength test of biodegradable containers, etc.)
When the biodegradable container of Example 2 was used in a natto production line (a production line in which natto was placed in a container and the top surface of the container was sealed with a film) instead of a polypropylene container, There was no occurrence of dents, scratches, cracks, dents, etc., and it was confirmed that they had the same mechanical strength as compared to conventional polypropylene containers.

  And when the dynamic viscoelasticity measurement was performed with respect to the biodegradable sheet | seat utilized in Example 2, and a polypropylene sheet, the biodegradable sheet | seat of this invention is equal to or more than a polypropylene sheet also at -30 degreeC. It was confirmed that it has characteristics and is suitable as a container for frozen foods.

(Preservation test of bacteria-containing foods in biodegradable containers)
Moreover, the natto food was put into the biodegradable container of Example 2 and a normal polyethylene container, respectively, sealed with a film, and the storage state at room temperature was confirmed.

  In a polyethylene container, natto turns black in 2 weeks, and it is confirmed that most of the natto bacteria have been killed. However, in a biodegradable container, natto bacteria are It was confirmed that the animal was alive and sticky, and that the fungus was growing.

  ADVANTAGE OF THE INVENTION According to this invention, while being excellent in biodegradability, it becomes possible to provide the biodegradable sheet | seat which is excellent in moldability, and the biodegradable molded article using this sheet | seat at low cost.

  That is, in a biodegradable molded product that is thin and requires a three-dimensional shape, as described above, once the biodegradable sheet is formed and the sheet is heated and vacuum-molded, the entire molded product is obtained. A molded product having a uniform thickness can be obtained. In particular, by forming a thin container, the consumption of raw materials can be reduced and costs can be reduced, and even when discarded, the volume of waste is reduced and the speed of biodegradation is increased, resulting in extremely useful effects. be able to.

  In addition, the biodegradable sheet and biodegradable molded product according to the present invention have sufficient strength, and even if discarded, natural decomposition is decomposed in, for example, 6 months to 1 year, which is useful for reducing the burden on the environment. However, since it itself contains a large amount of starch, it can be distributed and stored in a living state by packaging the food containing bacteria with nutrients from starch in the biodegradable container described above. It becomes possible to do.

  According to the production method of the present invention, the biodegradable sheet of the present invention and the biodegradable molded article using the sheet are made of plastic containers used in the market without requiring a large capital investment. An existing apparatus to be manufactured can be used, and a method that can be mass-produced easily and extremely economically in large quantities can be provided.

  Since the biodegradable sheet and the biodegradable molded product according to the present invention contain a large amount of starch, the food containing the fungus containing the starch as nutrients can be used with the biodegradable sheet or the biodegradable container of the present invention. By packaging, it becomes possible to distribute and store bacteria in a live state.

  For example, natto bacteria, baker's yeast, lactic acid bacteria, koji molds, and other foods that need to keep bacteria alive not only in the food production process, but also in the distribution process, such as natto, bread dough, lactic acid food, and alcoholic beverages. In particular, the present invention has high utility value.

  Furthermore, as a biodegradable molded product, it can be used as a disposable container used for packaging foods, tableware such as disposable forks and spoons, space materials and cushion materials used for various packaging. It is also possible to form a garbage bag, a packaging bag, a disposable garment, etc. by thinly forming a biodegradable sheet and utilizing heat fusion or the like.

It is a diagram which shows the endothermic speed change of the biodegradable sheet which concerns on this invention. It is the top view (a) and sectional drawing (b) of an example of the biodegradable container which concerns on this invention.

Claims (11)

  A starch resin containing 70% by weight or more of starch and containing an olefin resin as a main component is melted at a temperature of 120 to 180 ° C., molded into a sheet shape with a cooled roller, and cooled to a temperature of 60 ° C. or lower to form a roll. A biodegradable molded article, which is obtained by molding a biodegradable sheet obtained by winding the sheet on.   2. The biodegradable molded article according to claim 1, wherein the olefin resin contains either polyethylene or polypropylene.   The biodegradable molded article according to claim 1 or 2, wherein the biodegradable molded article is obtained by heating and vacuum forming or pressure forming the biodegradable sheet.   The biodegradable molded article according to any one of claims 1 to 3, wherein the biodegradable sheet has a thickness of 0.2 to 0.8 mm.   The biodegradable molded article according to any one of claims 1 to 4, wherein the molded article is provided with grooves and / or protrusions for increasing mechanical strength. Goods.   The biodegradable molded product according to any one of claims 1 to 5, wherein the biodegradable molded product is a container that contains a food containing a fungus containing starch as a nutrient. Sex molded product.   A starch resin containing 70% by weight or more of starch and containing an olefin resin as a main component is melted at a temperature of 120 to 180 ° C., molded into a sheet shape with a cooled roller, and cooled to a temperature of 60 ° C. or lower to form a roll. A method for producing a biodegradable molded product, characterized in that a biodegradable molded product is obtained by molding a biodegradable sheet obtained by winding the product into a roll.   8. The method for producing a biodegradable molded article according to claim 7, wherein the starch resin is obtained by kneading the starch and olefin resin so that the starch quality becomes 70% by weight or more, and extruding the kneaded product. A method for producing a biodegradable molded product, characterized in that a raw material pellet is formed by cutting and the raw material pellet is dried.   9. The method for producing a biodegradable molded product according to claim 8, wherein the raw material pellets are dried so that the moisture content of the raw material pellets is 2% by weight or less. Product manufacturing method.   The method for producing a biodegradable molded product according to any one of claims 7 to 9, wherein at least one biodegradable sheet is laminated, the sheet is heated and softened, and then the softened sheet is vacuumed. A method for producing a biodegradable molded product, wherein the biodegradable molded product is formed by performing die cutting or compressed air die cutting. The method for producing a biodegradable molded article according to claim 10, wherein the temperature of the female die used for vacuum die cutting or pressure die cutting is set to 20 to 70 ° C. Manufacturing method of molded products.

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