JPH0892419A - Biodegradable composite plastic composition - Google Patents

Abstract

PURPOSE: To obtain a biodegradable composite plastic composition excellent in the gate of degradation and mechanical properties by mixing a modified starch obtained by allowing starch to adsorb fat, oil or the like and aging the product with a biodegradable resin. CONSTITUTION: Starch is allowed to adsorb at least one member selected from among fat and oil (e.g. soybean oil), an analogue of fat and oil (e.g. soybean lecithin), a fatty acid and a fatty acid derivative (e.g. an ester of amyl alcohol with a fatty acid), and the product is heated to produce a modified starch. The modified starch and a biodegradable resin are kneaded at e.g. 60-220 deg.C for about 10-60min to obtain a biodegradable composite plastic composition. Suitable examples of the biodegradable resins used include aliphatic polyester, polycaprolactone, polylactic acid and polyvinyl alcohol, and the mixing ratio is suitably such that 20-70wt.% modified starch is mixed with 80-30wt.% biodegradable resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention prevents the deterioration of physical properties due to the incorporation of starch in the biodegradable resin by compounding the starch with oil and fat processing, can reduce the production cost, and can improve the biodegradability of the biodegradable resin. A biodegradable composite plastic composition that can be accelerated.

[0002]

2. Description of the Related Art Recently, the development of biodegradable resins has become active from the viewpoint of protecting the global environment. These resins are divided into chemical synthetic systems such as aliphatic polyester, polycaprolactone, polylactic acid, and polyvinyl alcohol, microbial systems such as polyhydroxybutyrate / vallate copolymer, and natural product utilization systems such as acetylcellulose. There is. Further, it has been proposed that starch is blended with these resins to reduce costs and improve biodegradability, and some of them have been put into practical use.

For example, a composite of starch and non-biodegradable resin such as polyethylene or polypropylene and starch is disclosed in JP-B-52-21530 and JP-B-52-42187, and a composite of polyethylene and starch is eco-friendly. It is marketed as Star (Ogihara Industry Co., Ltd.). However, in this complex, the starch was decomposed and the shape of the product was destroyed, but the resin was not decomposed and remained as it was, and it was still not a solution to environmental pollution. Further, a composite of polylactic acid, which itself has biodegradability, and starch and / or modified starch is disclosed in JP-A-5-39381. By compounding polylactic acid with starch and / or modified starch, the decomposition rate is improved and the hardness of the resin composition is adjusted to improve the processability. However, although the biodegradability and the like are improved by blending the starch with the resin as described above, there is a problem in that mechanical properties such as strength and elongation rate are significantly reduced and the resin becomes brittle. Therefore, practically, the amount of starch added to the resin was also limited.

[0004]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a biodegradable resin composition such as polylactic acid which has an improved decomposition rate and mechanical properties which are the same as those of the resin alone. , To provide an excellent biodegradable resin composition. The present inventor has found that the above object can be achieved by compounding the starch processed with oil and fat with a resin having biodegradability. Incidentally, the above-mentioned JP-A-5-3938.
Japanese Unexamined Patent Publication No. 1 discloses a composite of polylactic acid and modified starch. However, neither oil nor fat-modified starch is described or suggested as the modified starch. Furthermore, the solubilized starch, carboxymethylated starch, and acetylated starch described in the examples of this publication were unable to maintain the mechanical properties of the resin as in the case of using the oil-processed starch. .

[0005]

SUMMARY OF THE INVENTION The present invention relates to a biodegradable composite plastic composition comprising a fat-and-oil modified starch and a biodegradable resin. The present invention will be described in detail below.

The oil-and-fat processed starch used in the present invention is conventionally known. For example, a fat-and-oil-processed starch obtained by over-drying and processing the fat and oil and starch can be mentioned [JP-B-45-32878]. This oil-and-fat-processed starch is obtained by adsorbing one or a mixture of two or more kinds of oils and fats, oil-and-fat analogues, fatty acids or their derivatives on starch, and further aging it by heating it.
The fats and oils may be vegetable oils or animal oils, and examples thereof include soybean oil, rapeseed oil, linseed oil, olive oil, lard, and fish fat. Examples of the oil and fat analogs are phospholipids such as soybean lecithin, monoglycerides, diglycerides and the like. The fatty acid is not particularly limited as long as it is a fatty acid which is a constituent of fats and oils.

The fatty acid derivatives are esters, amides and salts of fatty acids which are generally synthetic products, and the fatty acid esters are, for example, esters of methyl alcohol, ethyl alcohol, amyl alcohol and the like with fatty acids. . The amides of fatty acids are amides of the above fatty acids and amides of fatty acids and amino acids. The salts of fatty acids are salts of fatty acids such as alkali metals such as sodium and potassium, alkaline earth metals such as calcium and magnesium, and ammonium.

[0008] Furthermore, oil-and-fat processed starch using liver oil as the oil and fat can be exemplified [JP-A-53-11582].
No. 6]. The oil-and-fat-processed starch using liver oil can be obtained by adding liver oil, which is one of fats and oils, to starch powder, and mixing and adsorbing it sufficiently. Here, "liver oil" means cod liver oil,
In addition to fatty oils obtained from fish livers such as shark liver oils, fish oils such as squid oils, whale liver oils and sardine oils are also included, and one kind or a mixture of two or more kinds can be used.

Further, an oil-and-fat-processed starch using an oil and fat having an iodine value of 130 or more can be exemplified [JP-A-54-1].
No. 1247]. In addition to the above-mentioned liver oil, oil-and-fat-modified starch obtained by mixing and adsorbing oil and fat having a high iodine value with starch can also be used in the present invention. As the oil and fat having an iodine value of 130 or more, animal oil or vegetable oil can be used. Such fats and oils include safflower oil (iodine value 122 to 15).
0), perilla oil (iodine value 162 to 208), linseed oil (iodine value 187 to 197), hemp seed oil (iodine value 14)
1-175), sardine oil (iodine number 163-195),
Mackerel oil (iodine value 136-178) etc. can be illustrated.

Further, an oil-and-fat modified starch using soybean meal as an oil and fat can be exemplified [JP-A-56-7857].
No. 2]. The oil-processed starch using soybean meal as the oil is a mixture of raw soybean flour and starch in an amount of 0.1 to 20% by weight, preferably 0.3 to 3% by weight, and 100 ° C or less, particularly 60 to It can be obtained by heating in the temperature range of 80 ° C. for 3 to 6 hours.

The raw material starch used as the raw material of the oil-and-fat processed starch is not particularly limited. For example, subterranean starch such as potato starch, sweet potato starch, tapioca starch, and above-ground starch such as wheat starch, corn starch, sago starch, rice starch and the like can be used. Further, the state thereof may be any of powdery starch, slurry, cake starch and the like. The amount of fats and oils added to starch can be appropriately changed depending on the types of starch and fats and oils. For example, it is 0.
It is suitable to set the range of 1 to 5.0 parts by weight, preferably 0.5 to 2.0 parts by weight.

The oils and fats can be processed into oil-and-fat processed starch by admixing the starch and oil with the starch and adsorbing the starch to the starch, and then aging the oil and fat if necessary. For example, in the case of starch cakes and powders, oils and fats are dissolved or dispersed in water or an organic solvent and sprayed, and in the case of starch slurry, the oils and fats are dissolved or dispersed in the slurry and stirred to dissolve the oils and fats into starch. Can be adsorbed on. Depending on the type of fats and oils, it can be used as a fat-and-oil modified starch without aging by heating. The heat aging is, for example, 30 to 18
It can be performed at a temperature of 0 ° C. for 1 hour to 10 days. Further, the heat aging and the drying of the starch having adsorbed the fats and oils by the wet method can be simultaneously performed. The drying can be carried out by using a drier such as a band dryer or a flash dryer which is usually used for drying starch so that the equilibrium water content of the starch is reached, so that fats and oils can be uniformly mixed and adsorbed to the starch. However, when mixed with a resin, the water content of the oil-and-fat-processed starch is appropriately 1% or less.

The biodegradable resin used in the resin composition of the present invention is not particularly limited. Any resin that has biodegradability itself may be used, and thermoplastic resin is suitable in consideration of moldability. For example, aliphatic polyester,
Examples thereof include chemically synthesized resins such as polycaprolactone, polylactic acid, and polyvinyl alcohol, microbial resins such as polyhydroxybutyrate / valylate copolymer, and natural product utilization resins such as acetyl cellulose. More specifically, in consideration of biodegradability, an aliphatic polyester having an average molecular weight of 30,000 to 40,000, a polycaprolactone having an average molecular weight of 40,000 to 70,000, and an average molecular weight of 80,000 to 120,000 are used. Polylactic acid, polyvinyl alcohol having an average molecular weight of 20,000 to 90,000, polyhydroxybutyrate / valerate copolymer having a hydroxyvalerate fraction of 0 to 40 mol%, acetyl cellulose having an acetic acidity of 43 to 55%, and methoxy. It is preferable to use methyl cellulose having a rate of 27.5 to 31.5% and ethyl cellulose having an ethoxy content of 47.5 to 49.0%.

The blending amount of each component is, for example, 10 to 70% by weight of oil-and-fat processed starch, preferably 30 to 50% by weight, and 90 to 10% by weight of biodegradable resin, preferably 70 to 50%.
It is appropriate to set it as a weight%. When the blending ratio of the oil-and-fat modified starch is 10% by weight or more, the effect of promoting the degradability by the starch becomes remarkable, and when it is 70% by weight or less, the molding of the composite can be performed in the same manner as in the case of using only a normal resin. it can. The oil-and-fat processed starch and the biodegradable resin are, for example, 60 ° C to 22 ° C.
A composite can be obtained by heating and kneading at a temperature in the range of 0 ° C. for 10 to 60 minutes. The complex of the present invention uses oil-and-fat modified starch. Therefore, the composite is thermoformed,
The film or sheet obtained by inflation molding or blow molding has less deterioration in mechanical properties as compared with the case of using unprocessed starch. In particular, the tensile strength is maintained at the same level as that of the resin alone, and the elastic modulus is higher than that of the resin alone.

[0015]

INDUSTRIAL APPLICABILITY According to the present invention, an oil-processed starch obtained by lightly and inexpensively processing starch is used to improve the compatibility with biodegradable resin and the interfacial adhesion and to improve the mechanical properties. While preventing the decrease, it enables to increase the blending ratio of starch,
A biodegradable resin composition having good moldability can be obtained. Biodegradable resins are more expensive than general-purpose thermoplastic resins, and it will be difficult to achieve a price comparable to general-purpose resins in the future. According to the present invention, it is possible to reduce the price of biodegradable plastics by adding inexpensive starch to form a composite, and also to promote biodegradability, so that the range of application can be expanded to that of general-purpose resins. Becomes

[0016]

EXAMPLES The present invention will be further described below with reference to examples. Example 1 2 parts by weight of safflower oil was added to 100 parts by weight of corn starch, and the mixture was uniformly mixed using a Henschel mixer (manufactured by Mitsui Miike Kakoki Co., Ltd.), and the product moisture was changed by a box dryer heated to 120 ° C. It was dried to 0.3% or less to obtain safflower oil-processed corn starch. After mixing this safflower oil-processed corn starch and a commercially available aliphatic polyester-based biodegradable resin [Bionole # 1000, Showa High Polymer Co., Ltd., number average molecular weight 35,000] at a weight ratio of 30:70,
1 in Brabender plastograph heated to 180 ℃
A composite was prepared by kneading for 5 minutes.

The composite thus obtained was tested at 180 ° C. and 100 kgf / cm using a test bench press (Toyo Seiki Seisakusho).
² Formed under heat and pressure to obtain a sheet having a thickness of about 0.4 mm.
A strip-shaped test piece having a width of 5 mm and a length of 80 mm was cut out from the sheet, and the mechanical properties were examined using a tensile tester (Orientec). The measurement conditions were a load cell of 100 kgf, a span length of 40 mm, and a crosshead speed of 5 mm / min. Each mechanical property was calculated from the tensile test results by the following formulas.・ Tensile strength (kgf / cm ² ) = breaking load (kg
f) / Cross-sectional area (cm ² ) -Fracture elongation rate (%) = {(Fracture elongation-Span length) / Span length} × 100-Elastic modulus (kgf / cm ² ) = Proportional source stress / strain Shown in.

Comparative Example 1 A composite was prepared by the same preparation method as in Example 1 except that the cornstarch processed with safflower oil was replaced with an unprocessed cornstarch having a water content of 0.3% or less, and the same test was conducted to perform the test. I investigated the physical properties. The results are shown in Table 1. Comparative Example 2 A sheet was obtained only with a commercially available aliphatic polyester-based biodegradable resin without using safflower oil-treated corn starch, and the same test as in Example 1 was conducted to examine the mechanical properties. The results are shown in Table 1.

[0019]

[Table 1]

As shown in Table 1, the sheet of Example 1 in which the oil-and-fat modified starch was used showed less decrease in tensile strength and breaking elongation rate than the sheet in which unprocessed starch was used.

The composites prepared in Example 1 and Comparative Example 1,
Furthermore, the thermal properties of the aliphatic polyester-based biodegradable resin were examined by a temperature raising method and a constant temperature method using a flow tester (CFT500C manufactured by Shimadzu Corporation). As a measuring method, a die having a length of 2 mm and a diameter of 1 mm was used in both measuring methods, but in the temperature raising method, the load was 5 kg / m at 10 kgf.
in. The heating rate was measured in the range of 50 ° C to 200 ° C. In the constant temperature method, the load was 5 kgf and the measurement was performed at a melting temperature of 190 ° C. The heat softening temperature and the heat fluidizing temperature were determined by the temperature raising method, and the melt viscosity, the shear rate, and the flow rate were determined by the constant temperature method. The results are shown in Table 2.

[0022]

[Table 2]

As shown in Table 2, the thermal properties of the composite of Example 1 were not significantly different from those of Comparative Example 2 consisting of resin only, and the composite was molded under the same molding conditions as used for conventional resins. It was recognized that it was possible.

The strip-shaped test piece of the composite prepared in Example 1 was subjected to an activated sludge test and a soil burial test. Low-density polyethylene (made by Idemitsu Kosan) was used as a comparative sample. The results are shown in Table 3. It is considered that the complex of the present invention containing the oil-and-fat-processed starch is preferentially decomposed by microorganisms and enzymes, and as a result, becomes porous and accelerates the biodegradation of the aliphatic polyester chain.

[0025]

[Table 3]

Example 2 4 parts by weight of soybean meal was added to 100 parts by weight of starch solids in a tapioca starch wet cake containing about 40% water, and uniformly mixed with a kneader (DS1 type manufactured by Moriyama Seisakusho Co., Ltd.).
Preliminary drying was performed for 30 minutes using a box dryer heated to ℃. Then, it was dried to a product moisture of 0.3% or less using a box dryer heated to 120 ° C. to obtain soybean meal-processed tapioca starch. After blending the soybean meal-processed tapioca starch and a commercially available polyhydroxybutyrate-valerate copolymer [Biopol D410G manufactured by Zeneca, hydroxyvalerate fraction 8 mol%] at a weight ratio of 50:50, the mixture is heated at 170 ° C. for 15 minutes. The mixture was kneaded to prepare a composite.

Comparative Example 3 The same preparation method as in Example 2 was used except that tapioca starch having a water content of 0.3% or less was used in place of the soybean meal-processed tapioca starch.
A complex was obtained. The resulting composite was evaluated for mechanical properties as in Example 2. The results are shown in Table 4.

Comparative Example 4 A sample was obtained in the same manner as in Example 2 except that the soybean meal-processed tapioca starch was not used and only the copolymer of commercially available polyhydroxybutyrate and valilate was used. However, the evaluation method of the sheet was the same as in Example 1 except that the pressing temperature was 180 ° C. The results are shown in Table 4.

As shown in Table 4, the composite composition of the present invention, Example 2, is a comparative example 3 using unmodified starch.
It has excellent mechanical properties as compared with. Further, it can be seen that Example 2 which is the composite composition of the present invention has substantially the same mechanical properties as Comparative Example 4 in which only the resin is used.

[0030]

[Table 4]

Example 3 To 100 parts by weight of corn starch, 2 parts by weight of soybean oil was added and uniformly mixed using a super mixer (manufactured by Kawada Seisakusho Co., Ltd.). To obtain a soybean oil-processed cornstarch, the cornstarch was overdried so that the cornstarch content was not more than%. This soybean oil-processed cornstarch and polycaprolactone having a molecular weight of 40,000 [Placcel H4 manufactured by Daicel Chemical]
Was blended in a ratio of 40:60, and then a uniform cylindrical pellet having a diameter of 3 mm was obtained using a twin screw extruder having a screw diameter of 20 mm and L / D25 heated to 100 ° C. The sheet was manufactured in the same manner as in Example 1 except that the pressing temperature was 100 ° C. The mechanical properties of the obtained sheet were determined in the same manner as in Example 1, and the results are shown in Table 5. When the obtained sheet was buried in the soil 15 cm below the surface of the earth, the shape of the sheet disappeared after 2 months.

Comparative Example 5 A composite was obtained by the same preparation method as in Example 3 except that cornstarch was used instead of cornstarch processed with soybean oil.
The results of mechanical properties are shown in Table 5. Comparative Example 6 A sheet was obtained in the same manner as in Example 3 except that the soybean oil-processed corn starch was not used and the sheet was produced only with the polycaprolactone resin. The results of mechanical properties of the obtained sheet are shown in Table 5.

[0033]

[Table 5]

Example 4 1 part by weight of linseed oil was added to 100 parts by weight of corn starch, and the mixture was uniformly mixed using a plain mixer (manufactured by Takara Machine Co., Ltd.), and then a box type dryer heated to 100 ° C. was used. It was dried so that the product water content was 0.3% or less, and linseed oil-processed corn starch was obtained. This linseed oil-processed corn starch and polylactic acid having an average molecular weight of 120,000 (manufactured by Shimadzu Corporation) were mixed at a ratio of 30:70, and then homogenized using a Lapoplast mill (manufactured by Toyo Seiki Seisakusho) heated to 180 ° C. A cylindrical pellet having a diameter of 3 mm was obtained. The sheet was manufactured in the same manner as in Example 1 except that the pressing temperature was 180 ° C. The mechanical properties of the obtained sheet are shown in Example 1.
The results are shown in Table 6.

Comparative Example 7 A composite was obtained by the same preparation method as in Example 4 except that corn starch was used instead of maani oil-processed corn starch. The results of mechanical properties are shown in Table 6. Comparative Example 8 A sheet was obtained in the same manner as in Example 4 except that a sheet made of only a polylactic acid resin was used without using linseed oil-processed corn starch. The results of mechanical properties are shown in Table 6.

[0036]

[Table 6]

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Claims (4)

[Claims] 1. A biodegradable composite plastic composition comprising a fat-and-oil modified starch and a biodegradable resin. 2. The processed fat-and-oil starch is obtained by adsorbing one or more compounds selected from the group consisting of fats and oils, analogs of fats and oils, fatty acids and fatty acid derivatives, and aging. The composition according to 1. 3. The biodegradable resin is an aliphatic polyester,
The composition according to claim 1 or 2, which is a resin selected from the group consisting of polycaprolactone, polylactic acid, polyvinyl alcohol, polyhydroxybutyrate-valerate copolymer, and acetylcellulose. 4. The blended amount of the oil-and-fat modified starch is in the range of 20 to 70% by weight, and the blended amount of the biodegradable resin is in the range of 80 to 30% by weight. The composition as described.