JP6830302B1 - Starch-blended polyethylene resin composition and packaging materials using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biodegradable resin composition which can substitute a commercially available general-purpose plastic by using starch, and a packaging material such as a film using the biodegradable resin composition. SOLUTION: The above-mentioned problem is that the amount of starch is 120 parts by mass or less and 10 parts by mass or more with respect to 100 parts by mass of total polyethylene resin, and 30 to 90 parts by mass of a modified polyethylene resin in which an internal carboxyl group of the total polyethylene resin is introduced, polyfunctional Melt a mixture consisting of 0.1 to 5 parts by mass of a compound having an epoxy group, 10 to 60 parts by mass of a polyhydric alcohol-based plasticizer with respect to 100 parts by mass of starch, and 0 to 30 parts by mass of water with respect to 100 parts by mass of starch. It is solved by a polyethylene resin composition containing a starch obtained by kneading and dehydrating the water under reduced pressure in the final stage. [Selection diagram] None

Description

The present invention relates to a resin composition in which starch, which is a naturally derived substance, is combined with polyethylene resin, which is a general-purpose packaging material, and a packaging material using the resin composition.

In recent years, it has become a social problem that the residue of waste plastic called "microplastic" which is shredded by chemical decomposition or the like is deposited in seawater or soil and adversely affects the ecosystem and food chain. Furthermore, plastics derived from petroleum resources emit a large amount of carbon dioxide over the life cycle from raw materials to disposal, which is one of the causes of global warming.

For the purpose of reducing these environmental loads, various aliphatic polyester resins that are biodegraded by bacteria in soil or seawater have been devised and put into practical use. Typical biodegradable aliphatic polyester resins are succinic acid, adipic acid and terephthalic acid as dicarboxylic acid monomers, and dehydration polycondensation of ethylene glycol and 1,4-butanediol as diol monomers, carboxyl groups and hydroxyls. Examples thereof include a dehydration-condensation polymer of a glycolic acid having a group, and a polylactic acid obtained by polymerizing a lactide obtained by heat-decomposing a heat-dehydration polymer of lactic acid under reduced pressure under a metal catalyst. These and other aliphatic polyester resins are commercially available as low environmental load materials, and films and sheets have also been put into practical use.

However, biodegradable aliphatic polyester resins are not only more expensive than general-purpose aromatic polyester resins and polyolefin resins, but also have no level of strength and properties that can replace conventional general-purpose resins. is there. Therefore, various ideas have been made and put into practical use in order to reduce the manufacturing cost of films and sheets.

The invention of Patent Document 1 is an invention relating to a composition of a biodegradable aliphatic polyester resin and starch, in which some glucose units in the starch are cleaved between C-2 and C-3, and the ends thereof are cleaved. It is characterized by being a gelatinized product (less than 50%) of oxidized starch modified with a carboxyl group.

The present inventors have also been worried about such deterioration of the global environment and have been working on the development of materials using starch. Then, by combining starch with a biodegradable aliphatic polyester resin and blending it with a water-soluble polymer, the hydroxyl groups and acryloyl groups thereof have an affinity between the hydroxyl group ends and carboxyl group ends of the polyester resin and the hydroxyl groups of starch. A patent application was filed for improving the properties of starch so that it can be sufficiently mixed with a polyester resin to produce a film or the like (Patent Document 2). Since starch tends to turn brown when a film or the like is produced, the problem of browning is further solved by adding an antioxidant, and a patent application has also been filed (Patent Document 3).

Japanese Unexamined Patent Publication No. 2007-277353 Japanese Unexamined Patent Publication No. 2018-53165 JP-A-2018-188574

However, Patent Document 1 is more expensive than general-purpose starch because it is necessary to oxidize the starch through a complicated process using a special oxidized starch that is not a general-purpose product or an aqueous solution of sodium hypochlorite. , There is concern that the processing cost of the resin composition will rise. Furthermore, in the unlikely event that sodium hypochlorite remains, contact with the human mucosa may cause a symptom called "anaphylactic shock".

This is solved because starch has a low affinity for polyester resin, and by converting it into oxidized starch, the carboxyl group is significantly increased.

Patent Documents 2 and 3 solve these problems and can be mixed stably and uniformly using general-purpose starch that can be easily and inexpensively obtained. , Aliphatic polyester resins are expensive, and even if starch is added to reduce the cost, it is not easy to replace commercially available general-purpose plastics.

An object of the present invention is to provide a biodegradable resin composition that can replace a commercially available general-purpose plastic by using starch, and a packaging material such as a film using the biodegradable resin composition.

The present inventor has made diligent studies to solve the above problems, and focused on polyethylene resin, which is a packaging material having low-cost and practical strength physical properties. Then, first, water was added to the starch to form a gelatinized paste, and polyethylene resin pellets were added to form a compound. However, when gelatinization in water decreased due to evaporation or vaporization, hydrogen bonds between starch molecules occurred again, and the starch molecules became hard and brittle dry noodles, and aggregated and phase-separated again. Therefore, a polyhydric alcohol-based plasticizer such as glycerin or monoglyced that does not easily evaporate and water within a range that does not impair the physical characteristics of the material are blended. On the other hand, polyethylene resin having no polar group has no affinity for starch. Therefore, a modified polyethylene resin obtained by grafting a carboxylic acid anhydride on polyethylene was added. As a result, the acid anhydride group of the modified polyethylene resin was ester-bonded with the hydroxyl group of the starch, and the affinity between the two phases could be enhanced. When a compound having an epoxy group reactive with the above-mentioned polar group (particularly an acid anhydride group) is added to this to cause polymerization due to partial molecular bond to form a film or the like. The strength of the epoxide can be increased, and the present invention has been completed.

That is, the present invention provides a modified polyethylene resin having 120 parts by mass or less and 10 parts by mass or more, 30 to 90 parts by mass of a modified polyethylene resin having a carboxyl group introduced therein, and a polyfunctional epoxy group with respect to 100 parts by mass of the total polyethylene resin. A mixture containing 0.1 to 5 parts by mass of the compound, 10 to 60 parts by mass of the polyhydric alcohol-based plasticizer with respect to 100 parts by mass of starch, and 0 to 30 parts by mass of water with respect to 100 parts by mass of starch was melt-kneaded. The present invention provides a polyethylene resin composition containing a starch obtained by dehydrating water under reduced pressure in the final stage.

Even if the above resin composition is used, hot browning due to oxidation of starch is likely to occur during the process from melt kneading to molding. Therefore, by adding an antioxidant to this resin composition, browning of starch can be prevented. Therefore, the present invention provides the above-mentioned starch-blended polyethylene resin composition in which 0.1 to 0.8 parts by mass of an antioxidant is further blended.

When the resin composition of the present invention is discarded, starch and polyhydric alcohol-based plasticizers are biodegraded, which can contribute to reduction of environmental load. Further, by blending this resin composition with an oxidative decomposition agent that lowers the molecular weight of polyethylene after a desired practical period, the decomposition of polyethylene in the resin composition is promoted to reduce the molecular weight so that it is decomposed by microorganisms and the like. become. Therefore, the present invention may be provided as the above-mentioned starch-blended polyethylene resin composition in which 0.1 to 3 parts by mass of an oxidative decomposition agent that lowers the molecular weight of the polyethylene resin is further blended.

Further, when a naturally-derived cellulose fiber is blended with the resin composition of the present invention, its strength can be increased while maintaining the biodegradability of the composition. Therefore, the present invention provides the above-mentioned starch-blended polyethylene resin composition in which 1 to 10 parts by mass of cellulose fibers are further blended with respect to 100 parts by mass of starch.

If the polyethylene used in the resin composition of the present invention is manufactured from a naturally derived raw material, it becomes "carbon neutral", which means that the carbon cycle amount is environmentally neutral, which helps prevent global warming. .. Therefore, the present invention provides the starch-blended polyethylene resin composition according to any one of the above, wherein the polyethylene resin is obtained from a naturally derived raw material.

Then, if such a resin composition is used to produce a melt-extruded laminate, a blow bottle, an injection molded product or the like on a substrate such as a film, a sheet, a paper or a film or a metal foil, even if they are discarded. It is biodegraded. Therefore, the present invention provides a film, a sheet, a blow bottle, an injection molded product, and a laminate obtained by melt-extruding and laminating the above resin composition on a paper base material, which comprises the above resin composition. ..

In the resin composition of the present invention, when all the components are mixed at once, a uniformly dispersed one cannot be obtained, and the starch needs to be uniformly mixed and plasticized by adding a polyhydric alcohol-based plasticizer and water in advance. Therefore, in the present invention, a polyhydric alcohol-based plasticizer and water are added to starch and mixed uniformly with stirring, and a polyethylene resin, a modified polyethylene resin and a compound having a polyfunctional epoxy group are added to this mixture and mixed uniformly with stirring. The present invention provides a method for producing the above-mentioned polyethylene resin composition containing starch, which is obtained by melt-kneading the mixture and dehydrating the water under reduced pressure at the final stage.

The resin composition of the present invention is inexpensive and has excellent strength using a general-purpose material as a main material, and is also highly biodegradable because starch is one of the main materials. Further, if an oxidative decomposition agent that lowers the molecular weight of polyethylene is further added, polyethylene is also molecularly cleaved and biodegradation is promoted, so that the polyethylene is biodegraded as a whole and the problem of environmental pollution can be solved.

First, the polyethylene resin used in the resin composition of the present invention will be described. The polyethylene resin may be any kind, and high-density polyethylene, low-density polyethylene, linear low-density polyethylene and the like can be used. For the purpose of the present invention, the polyethylene resin is preferably one obtained from a naturally derived raw material, for example, a polyethylene resin produced from ethanol obtained by fermenting sugar cane called biomass or the like as a raw material. In order to make the polyethylene resin uniformly compatible with starch, it is particularly preferable that the polyethylene resin has an MFR (at 190 ° C.) of about 0.1 to 20 g / 10 minutes. A suitable MFR may be arbitrarily selected depending on the molding method and composition.

Next, the starch used in the resin composition of the present invention will be described.

There are no particular restrictions on starch, and commercially available products can be used. For example, grain starch such as corn starch, wheat starch, rice starch, morokoshi starch, potato starch such as sweet potato starch, horse bell starch, tapioca starch, bean starch such as green bean starch, kudzu starch, kataguri starch, and wild grasses such as 蕨 starch. Starch can be mentioned. As these starches, raw starch without any chemical modification can be used, but chemically modified starch can also be used. Examples of chemically modified starch include oxidized starch, acetylated starch, etherified starch, crosslinked starch and the like.

The mixing ratio of the starch in the resin composition of the present invention is 120 parts by mass or less, 10 parts by mass or more, preferably 100 parts by mass or less, 30 parts by mass or more, more preferably 100 parts by mass or more, based on 100 parts by mass of the total polyethylene resin. It is 50 parts by mass or less and 50 parts by mass or more. If it exceeds 120 parts by mass, the reaggregation of starch tends to make the kneading of the resin composition non-uniform, and the strength of the film or sheet obtained by using the same tends to be significantly reduced, which is not preferable in practice. On the other hand, if it is less than 10 parts by mass, the effect of significantly reducing the environmental load due to biodegradability cannot be expected.
In addition, "100 parts by mass of total polyethylene resin" in this specification is the total amount of polyethylene resin and modified polyethylene resin, and total polyethylene resin also includes an oxidative decomposition agent master batch which is a polyethylene resin composition.

The polyhydric alcohol-based plasticizer used in the present invention will be described. The polyhydric alcohol-based plasticizer is used as a plasticizer for starch, and it is preferable that the polyhydric alcohol-based plasticizer is hard to evaporate and remains even after molding into a film or the like. Specifically, it is preferred to have a boiling point and high flash point which is not vaporized at melt-kneading temperature, by way of example, glycerin, glycerides, grayed recall, polyvinyl alcohol, ethylene - polyvinyl alcohol copolymer, sorbitol, And so on. Examples of glycerides include monoglycerides and diglycerides, and examples of glycols include ethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, and the like. Of these, glycerin is particularly preferred.

The blending ratio of the polyhydric alcohol-based plasticizer is about 10 to 60 parts by mass, preferably about 20 to 50 parts by mass with respect to 100 parts by mass of starch. If it is less than 10 parts by mass, the plasticization of starch becomes insufficient, and the starches tend to reaggregate during melt-kneading and subsequent film formation and molding, and the physical strength of that portion locally decreases, which is not preferable. On the other hand, if it exceeds 60 parts by mass, the excess polyhydric alcohol-based plasticizer that does not participate in plasticization has a side effect as a lubricant in the extruder that performs melt kneading and film formation / molding, and it is preferable that kneading with a screw is hindered. Absent. It is more preferable to add 0 to 30 parts by mass of water when blending the polyhydric alcohol-based plasticizer. Water promotes gelatinization of starch during melt kneading in the next step. Since pregelatinized starch has strong stickiness and excellent transparency, it contributes to improvement of the strength physical characteristics and transparency of the resin composition of the present invention. However, pregelatinized starch is known to retransfer (age) to betaized starch over a long period of time, and the aged starch deteriorates various physical properties of the resin composition of the present invention. Rapid dehydration is known as a method for suppressing aging, and in order to obtain the good resin composition of the present invention, it is preferable to dehydrate under reduced pressure with a vent during melt-kneading.

A modified polyethylene resin having a carboxyl group introduced will be described. The modified polyethylene resin is preferably a graft copolymer obtained by graft-polymerizing an unsaturated dicarboxylic acid anhydride or an unsaturated carboxylic acid on low-density, linear low-density or high-density polyethylene. Examples of unsaturated dicarboxylic acid anhydrides include maleic anhydride, phthalic anhydride, itaconic anhydride, citraconic anhydride, mesaconic anhydride, fumaric anhydride, and the like. Examples of unsaturated carboxylic acids include maleic anhydride. Acrylic acid, methacrylic acid and the like can be mentioned, and among them, maleic anhydride and phthalic anhydride, which are commonly used from the viewpoint of ease of handling, heat resistance and the like, are preferable. The ratio of graft copolymerization is preferably about 0.01 to 5 parts by mass, preferably about 0.05 to 3 parts by mass of unsaturated dicarboxylic acid anhydride with respect to 100 parts by mass of polyethylene. If it is less than 0.01 parts by mass, the compatibility between the starch phase and the polyethylene phase becomes poor. The modified polyethylene resin may be graft-modified by the above formulation, or a commercially available one may be used.

The modified polyethylene having an MFR (at 190 ° C.) of 0.1 to 20 g / 10 minutes is preferable for the above-mentioned reason.

The blending ratio of the modified polyethylene resin is about 30 to 90 parts by mass out of 100 parts by mass of the total polyethylene resin. If it is less than 30 parts by mass, the polar group having an affinity for the starch phase is insufficient, macro-phase separation occurs in the obtained film-forming and molded product, and its appearance and physical strength are significantly deteriorated. On the other hand, if it exceeds 90 parts by mass, it does not adversely affect the obtained film-forming or molded product, but the commercially available resin is expensive and puts pressure on the manufacturing cost, which is not preferable.

The compound having a polyfunctional epoxy group and / or the compound having a carbodiimide used in the present invention will be described. Here, polyfunctional means having a plurality of epoxy groups. The compound has an epoxy group that reacts with a carboxyl group of modified polyethylene or a hydroxyl group of starch glucose to form a hydrogen bond to increase the affinity.

Preferable examples of the compound include methyl styrene- (meth) acrylate-glycidyl methacrylate copolymer, glycidyl methacrylate homopolymer, and ethylene-glycidyl methacrylate copolymer. Other good examples of the compound include epoxidized higher fatty acid esters such as epoxidized soybean oil and epoxidized linseed oil. The epoxy value measured by the method of ASTM-D 1652 is preferably 0.5 to 2.5 meq / g. A more preferred epoxy value is 1.0 to 4.0 meq / g. If the epoxy value is less than 0.5 meq / g, the compatibility of the resin composition becomes insufficient, and not only the appearance is deteriorated but also the physical strength cannot be expected to be improved. On the other hand, if it exceeds 4.0 meq / g, the cross-linking reaction between the molecules proceeds excessively, which causes problems such as frequent occurrence of gel foreign substances during molding, which is not preferable. Examples of the methyl styrene- (meth) acrylate-glycidyl methacrylate copolymer are described in JP-A-2005-154690, for example, John Krill of BASF Japan Ltd., Alfon of Toa Synthetic Co., Ltd., etc. Is commercially available. The styrene-methyl (meth) acrylate-glycidyl methacrylate copolymer may be used alone or in combination of two or more.

The compounding ratio of the compound having a polyfunctional epoxy group and / or the compound having a carbodiimide is about 0.1 to 5 parts by mass with respect to 100 parts by mass of the total polyethylene resin. If it is less than 0.1 part by mass, the bonding and affinity between the two phases will be insufficient, macro-phase separation will occur in the obtained film-forming and molded products, and the appearance and physical strength thereof will be significantly deteriorated. On the other hand, if it exceeds 5 parts by mass, an excessive bond is generated between both phases, and the viscosity of the resin composition increases remarkably. Therefore, in the worst case, a film-forming or molded product cannot be obtained.

The antioxidant used in the present invention will be described. The antioxidant is preferably formulated in order to reduce the oxidation reaction called "browning" that occurs when the starch contained in the resin composition is melt-kneaded or molded. The preferable blending ratio is 0.1 to 0.8 parts by mass with respect to 100 parts by mass of the total polyethylene resin. If it is less than 0.1 part by mass, a sufficient effect of suppressing browning cannot be obtained, while if it exceeds 0.8 parts by mass, the manufacturing cost is unnecessarily increased, which is not preferable. Suitable antioxidants include phenolic antioxidants, phosphorus-based antioxidants, tocopherols and ascorbic acid. It is effective to use one or more of these groups alone or in combination. It is most preferable to prescribe a combination of phenol and phosphorus.

The oxidative decomposition agent used in the present invention for reducing the molecular weight of polyethylene will be described. It is composed of, for example, a thermoplastic polymer, an oxidizing component that breaks a carbon-carbon bond between a directly biodegradable component and a thermoplastic component such as a fatty acid, a transition metal component, and hindered phenol (Patent No. 2961138). No.), sold by Novon Japan Co., Ltd. under the trade name of "Degranobon" (registered trademark). In addition, some products are sold by P-Life Japan, Inc. under the brand name of "P-Life". By blending an oxidative decomposition agent that lowers the molecular weight of polyethylene with polyethylene, polyethylene is oxidatively deteriorated to reduce its molecular weight by utilizing ultraviolet rays, temperature, oxygen, microorganisms, etc., and finally water, carbon dioxide, and biomass. Can be.

The amount of the oxidative decomposition agent that reduces the molecular weight of polyethylene is about 0.1 to 3 parts by mass, preferably about 0.2 to 2 parts by mass, based on 100 parts by mass of the total polyethylene resin. If it is less than 0.1 parts by mass, the generation of radicals, which is an oxidation initiation reaction, is insufficient, and it is almost the same as the deterioration over time when polyethylene is naturally left outdoors, and the appeal as an addition effect is poor. On the other hand, if it exceeds 3 parts by mass, the oxidation reaction is rapid, which is effective from the viewpoint of biodegradation, but the period during which the obtained resin composition should maintain its shape as a product (for example, the expiration date in the case of food packaging). There is a risk that collapse or decomposition will begin before. All of the above-mentioned commercially available products are commercially available as master batches in which an oxidative decomposition agent is dispersed in a polyethylene resin. This masterbatch will also be part of the total polyethylene resin.

Next, a cellulose fiber that may be blended in the present invention as a strengthening component of physical strength will be described. Cellulose nanofibers are also suitable in terms of physical properties, but are expensive. Specifically, the most suitable powder is a finely divided powder of natural cellulose, which is widely used in foods, cosmetics, resin fillers, etc., and is an inexpensive cellulose powder. The preferable blending amount of the cellulose fiber is 1 to 10 parts by weight with respect to 100 parts by mass of starch. If it exceeds 10 parts by mass, the tip of the extruder that performs melt kneading, film formation, and molding is equipped with a film called a screen mesh that removes foreign substances and deteriorated substances. Excess cellulose fibers are found on this screen mesh. It is not appropriate because it may cause clogging and make continuous operation for a long time difficult. By adding the cellulose fiber, the strength of the film or sheet of the present invention can be increased, and in particular, the tensile strength in the longitudinal direction corresponding to the molding direction can be increased.

Additives may be added to the resin composition of the present invention if necessary for physical characteristics. For example, calcium stearate, oleic acid amide, erucic acid amide, etc., which are commonly used as lubricants for films, fine particle synthetic zeolite, which is commonly used as anti-blocking agents for films, titanium oxide particles as coloring pigments, carbon black, etc. Be done.

Subsequently, a method for producing the resin composition of the present invention will be described.

The production process is also important because the resin composition of the present invention does not become uniformly dispersed when all the components are mixed at once, and for example, even if a film is produced, it becomes unsightly.

Therefore, first, the starch is made into a wet powder by adding a required amount of a polyhydric alcohol-based plasticizer and, if necessary, water, and stirring and mixing the starch uniformly at room temperature. If a polyhydric alcohol-based plasticizer or water is mixed in one place of the starch at a time, it tends to cause "lumps", so it is desirable to spread it over the entire starch. When adding cellulose fibers, it is preferable to add them in this step. As the mixer, a Henschel mixer, a mixer for noodle making machines, and other continuous mixers can be used. It is important that this mixing device is a mixing mechanism that is easily stirred up, down, left and right.

Then, other components such as polyethylene resin are further added thereto, and the mixture is stirred and melt-kneaded. Antioxidants, compounds with polyfunctional epoxy groups and / or compounds with carbodiimides, and polyethylene oxidative decomposition agents to be added as needed may also be added here. The polyethylene resin or the modified polyethylene resin may be in the form of pellets or may be in the form of powder called fluff.

The modified polyethylene resin is melted by adding an unsaturated dicarboxylic acid anhydride and / or a radical generator such as an unsaturated carboxylic acid and an organic peroxide to polyethylene and kneading the modified polyethylene resin. It can also be produced in the kneading process.

The melt-kneading extruder may be a single-screw extruder, but from the viewpoint of kneading property, a twin-screw extruder is preferable, and one having a vent mechanism capable of suction and exhaust during kneading is preferable. The kneading temperature is preferably 100 ° C. to 170 ° C., but since the starch tends to turn brown when the temperature is high, it is preferable to carry out the kneading at a low temperature within the range where kneading is possible.

The resin composition extruded into a string from the extruder may be molded into a film or the like as it is, but usually, it is cooled and pelletized with a pelletizer. Cooling may be either water cooling or air cooling, but in the case of water cooling, moisture is absorbed by the pellets and foams when they are molded into a film or the like, so the obtained pellets need to be dried before molding. Air cooling is preferable.

The obtained resin composition can be molded into a film, a sheet, a laminate formed by extruding and laminating on a paper base material, a blow bottle, an injection molded product, or the like.
Although this resin composition contains a large amount of starch, it has sufficient water resistance to withstand rainwater and the like. After boiling the film obtained in the present invention in hot water at 90 ° C. for 30 minutes, the dry weight of the film taken out was reduced by about 3%, but no change in the appearance of the film was observed. That is, the amount of starch that fell off due to water content or immersion was very small, and the water resistance was not a problem in practical use.

When making a film or a sheet, a casting method using a T-die or the like, an inflation method, or a calendar method can be used. A suitable film forming temperature is 100 to 165 ° C. The thickness of the film or sheet is not limited, but is, for example, about 20 to 400 μm, usually about 30 to 100 μm. The film or sheet can be extruded in multiple layers, in which case polyethylene layers can be provided on one or both adjacent sides. Since the film or sheet formed of the resin composition of the present invention has a slight starch odor, the starch odor can be shielded by providing a polyethylene layer on the surface. Moreover, since the strength is not as high as that of the polyethylene film, it can be supplemented. Further, when laminating, it is preferable that the laminated surface is smooth, so that it can be supplemented by the multilayer. The thickness of the polyethylene layer may be about 20 to 50% of the total thickness. These polyethylene layers are finally decomposed by a chain transfer reaction of radicals generated from the polyethylene oxidative decomposition agent blended in the resin composition of the adjacent layer.

The thickness of the laminate layer in the case of extrusion laminating on a paper base material is about 10 to 60 μm, usually about 15 to 50 μm. The type of paper base material is not limited, but is, for example, corrugated board, paperboard for paper containers, miscellaneous paperboard, and the like.

The present invention will be described in more detail with reference to examples.

The materials used are as follows.

Polyethylene resin LLDPE
"Harmorex NH745N" Japan Polyethylene Corporation product,
Density = 0.913g / cm ³ , MFR = 8.0g / 10 minutes "Evolu SP1071C" Prime Polymer Co., Ltd.,
Density = 0.910 g / cm ³ , MFR = 10.0 g / 10 minutes Bio-LDPE
"Braschem SBC818" manufactured by Toyota Tsusho Corporation,
Density = 0.918 g / cm ³ , MFR = 8.3 g / 10 minutes Starch (raw)
Cornstarch Oji Cornstarch Co., Ltd. Product name: Raw starch Cellulose fiber Cellulose powder KC Flock Nippon Paper Industries Co., Ltd. Product name: W-50
Polyalcohol-based plasticizer Glycerin Wako Pure Chemical Co., Ltd. Monoglyceride "Rikemar" RIKEN Vitamin Co., Ltd. Organic peroxide "Kayahexa AD" Kayaku Akzo Corporation Modified polyethylene resin Maleic anhydride Graft polyethylene "Modic M545" Mitsubishi Chemical Made by Co., Ltd.
Density = 0.900 g / cm ³ , MFR = 6.0 g / 10 minutes gPE
Maleic anhydride graft polyethylene prepared in the reference example Compound having polyfunctional epoxy group JC: Styrene- (meth) methyl acrylate-glycidyl methacrylate copolymer, manufactured by BASF Japan Co., Ltd. "IRGANOX 1010"
Ciba Specialty Chemicals Irg168: Phosphorus-based Antioxidant "IRGAFOS168"
Made by BASF Japan Co., Ltd. Oxidizing agent "Degranobon" Made by Novon Japan Co., Ltd. (Masterbatch in which 5% by mass of oxidative decomposition agent is dispersed in polyethylene resin)
"P-LIFE GREEN 20" manufactured by P-Life Japan, Inc. (masterbatch in which 20% by mass of oxidative decomposition agent is dispersed in polyethylene resin)

Stirrer used Henschel mixer FM20C type manufactured by Nippon Coke Industries Co., Ltd. Capacity 20L

Extruder used Biaxial extruder with vent mechanism manufactured by Japan Steel Works, Ltd. 44mmΦ L / D30

T-die film forming machine used Tanabe Plastics Machinery Co., Ltd., feed block type two-layer die,
Lip length = 370 mm, lip spacing = 2 mm

Inflation film forming machine used First extruder equipped with a circular die with a diameter of 300 mmΦ and a screw with a diameter of 55 mmΦ and L / D = 25.
Second extruder with a screw with diameter = 65 mmΦ, L / D = 28,
Third extruder with screws with diameter = 55 mmΦ, L / D = 25,
3-layer air-cooled inflation film-making machine consisting of

Extruded laminating machine used Laminating machine consisting of an extruder equipped with a T-die with a lip surface length of 2000 mm and a screw with a diameter of 120 mmΦ and L / D = 32.

Preparation of Resin Composition A predetermined amount of raw starch was placed in a tank of a Henschel mixer, a predetermined amount of glycerin or monoglyceride was added dropwise with stirring, and the mixture was further stirred for 5 minutes or more to obtain a wet powder. Then, while stirring again, a predetermined amount of polyethylene resin, modified polyethylene resin, methyl styrene- (meth) acrylate-glycidyl methacrylate copolymer, antioxidant and oxidative decomposition agent are added and stirred for 10 minutes to obtain a wet powder. And pellets were mixed to obtain each resin composition shown in Table 1.
In Table 1, 100 parts by mass of the total polyethylene resin is the total amount of the master batch of the polyethylene resin, the modified polytylene resin and the oxidative decomposition agent. In addition, polyhydric alcohol-based plasticizers
Reference example: Production of maleic anhydride grafted polyethylene An extruder (above) prepared by 100 parts by mass of Bio-LDPE, 1 part by mass of maleic anhydride, 0.03 parts by mass of Kayahexa AD, and 0.47 parts by mass of solvent methanol. A modified polyethylene resin was produced by putting it in a twin-screw extruder with a vent mechanism manufactured by Japan Steel Works, Ltd. and melt-kneading it. The melt kneading was carried out at set temperatures of 110 ° C., 120 ° C., 130 ° C. and 140 ° C. in order from the upstream portion of the cylinder by operating the vent. The denaturation temperature was set to 140 ° C. from the half decomposition temperature of Kayahexa AD and the graft efficiency. The reason for operating the vent is to remove unreacted maleic anhydride because it inhibits compatibilization.

Examples 1-7
A resin composition obtained by mixing a total polyethylene resin, starch, a polyhydric alcohol-based plasticizer, a compound having a polyfunctional epoxy group, and an antioxidant shown in Table 1 in a henshell is placed in an extruder and melted at 140 ° C. while operating a vent. The mixture was kneaded and extruded with a residence time of about 5 minutes, and air-cooled at room temperature to 30 ° C. to obtain pellets of a polyethylene resin composition containing starch. Then, each of the obtained pellets was formed with the above-mentioned T-die film forming machine to prepare a cast film. At that time, the T-die film forming machine was set to 100 ° C., 130 ° C., 150 ° C., 155 ° C., and 165 ° C. in order from the upstream portion of the cylinder, and the die temperature was set to 165 ° C.

Example 8
Using the inflation film forming machine described above, the same starch-blended polyethylene resin composition as in Example 3 of Table 1 was charged into a three-layer extruder, and the melt extrusion temperature from the die was 155 ° C., and the blow ratio was 2.7. A single-layer inflation film having a total thickness of 70 μm was prepared at a film forming speed of 23 m / min.

Example 9
The same starch-blended polyethylene resin composition as in Example 3 of Table 1 was put into the extrusion laminating machine, and the melt extrusion temperature was 160 ° C. and the thickness was 25 μm on bleached kraft paper having a basis weight of 50 g / m ^2. Laminated.

Example 10
In Example 3, without using Modic M545, Evolu SP1071C, which is the main polyethylene resin, was blended with maleic anhydride and Kayahexa AD dissolved in methanol, and a modified polyethylene resin was simultaneously prepared during melt-kneading to obtain a starch blend. The pellets of the polyethylene resin composition were film-formed with the above-mentioned T-die film-forming machine to prepare a cast film. At that time, the T-die film forming machine was set to 100 ° C., 130 ° C., 150 ° C., 155 ° C., and 165 ° C. in order from the upstream portion of the cylinder, and the die temperature was set to 165 ° C.

Example 11
The amount of glycerin in the composition of Example 3 in Table 1 was reduced to 75%, and the remaining 25% was obtained by forming pellets of the starch-containing polyethylene resin composition obtained as water with the above-mentioned T-die film forming machine to obtain a cast film. Made. At that time, the T-die film forming machine was set to 100 ° C., 130 ° C., 150 ° C., 155 ° C., and 165 ° C. in order from the upstream portion of the cylinder, and the die temperature was set to 165 ° C.

Evaluation Methods of Examples 1 to 8, 10 and 11 The tensile strength of each of the obtained films was measured with JIS K-6760 at a sample width of 15 mm, a tensile strength of 200 mm / min, and a chuck distance of 100 mm.

The vertical and horizontal elongation rates were also measured by JIS K-6760.

For the biodegradability evaluation, a cast film whose dry weight was measured in advance was embedded in activated sludge at 25 ° C. and allowed to stand. After 180 days, it was taken out, washed and dried, and its weight was measured, and the weight loss rate (%) before and after standing was used as an index.

Evaluation Results Examples 1-8, 10 and 11
The pellets in Examples 1-8, 10 and 11 were not browned and were pale yellow. Each cast film and inflation film were also pale yellow, but the starch grains were not visible and were mixed uniformly, and the surface was smooth. Table 1 shows the thickness, tensile strength, elongation, and biodegradability of each cast film or inflation film.

An attempt was made to prepare pellets of the samples of Comparative Examples 1 to 3, but the tension in the molten state was insufficient and granulation was difficult. It has been found that even if any of the modified polyethylene, the polyhydric alcohol-based plasticizer, and the polyfunctional epoxy compound constituting the resin composition of the present invention is missing, the desired resin composition cannot be obtained.

Example 9
The laminate of the example extruded and laminated on bleached kraft paper was at a practical level in terms of appearance and strength and physical characteristics as a commonly used paper container.

The product of the packaging material using the resin composition of the present invention has good biodegradability and does not cause a problem of environmental pollution, so that it can replace various packaging materials such as polyethylene which are conventionally used.

Claims (12)

A polymer containing 120 parts by mass or less of starch, 10 parts by mass or more of starch, 30 to 90 parts by mass of a modified polyethylene resin having a carboxyl group introduced therein, and glycidyl methacrylate as constituents with respect to 100 parts by mass of total polyethylene resin. and / or compounds from 0.1 to 5 parts by mass with carbodiimide, Rana Ru or 10 to 60 parts by weight to 100 parts by weight polyol plasticizer starch starch blended polyethylene resin composition. The starch-blended polyethylene resin composition according to claim 1, wherein the antioxidant is further blended by 0.1 to 0.8 parts by mass with respect to 100 parts by mass of the total polyethylene resin. The starch-blended polyethylene resin composition according to claim 1 or 2, wherein an oxidative decomposition agent that lowers the molecular weight of the polyethylene resin is further blended by 0.1 to 3 parts by mass with respect to 100 parts by mass of the total polyethylene resin. The starch-blended polyethylene resin composition according to any one of claims 1 to 3, further comprising 1 to 10 parts by mass of cellulose fibers with respect to 100 parts by mass of starch. The starch-blended polyethylene resin composition according to any one of claims 1 to 4, wherein the polyethylene resin is obtained from a naturally derived raw material. A film or sheet comprising the resin composition according to any one of claims 1 to 5. A multilayer film or sheet in which a polyethylene resin layer is laminated on one side or both sides of the film or sheet of claim 6. A laminate in which the resin composition according to any one of claims 1 to 5 is melt-extruded and laminated on a paper substrate. A blow bottle comprising the resin composition according to any one of claims 1 to 5. An injection molded product comprising the resin composition according to any one of claims 1 to 5. A polyhydric alcohol-based plasticizer, or a polyhydric alcohol-based plasticizer and water are added to starch and mixed uniformly with stirring, and a polymer containing a polyethylene resin, a modified polyethylene resin and glycidyl methacrylate as constituents in this mixture. and / or by adding a compound having a carbodiimide were melt-kneaded uniformly stirred and mixed mixture, you vacuum dehydration of moisture in the final stage, a manufacturing method of claim 1 starch blended polyethylene resin composition. The starch-blended polyethylene resin composition according to claim 11, wherein the modified polyethylene resin is produced by melt-kneading polyethylene with an unsaturated dicarboxylic acid anhydride and / or an unsaturated carboxylic acid and a radical generator on the spot. How to make things.