CN100340579C - Hydrolyzed polycondensed starch, method for producing same, and molded article made of hydrolyzed polycondensed starch - Google Patents

Abstract

The invention provides a starch prepared by hydrolysis polycondensation which has thermoplasticity, flexibility, practical strength and elongation and is economical and a method for producing the same. Involves introducing soft linear organic groups into at least a portion of the starch backbone, e.g., -O- (C ═ O) -O-, - ((O-R) into at least a portion of the starch backbone¹)_x-(O-(C＝O)-R²)_y)_m-O_z-or-CH₂-(C＝O)-CHR³-O-based hydrolytic polycondensation starch. In the formulae, R¹And R²Is represented by C₁Alkylene group above or C₆The arylene group above; x, y and z represent 0 or 1; x + y is 1 or 2; m represents an integer of 1 to 3100; r³Represents a hydrogen atom, C₁Alkyl group of the above, C₆Aryl radicals above or C₁The above alkoxy group.

Description

Hydrolyzed polycondensed starch, method for producing same, and molded article made of hydrolyzed polycondensed starch

Technical field

The present invention relates to hydrolyzed polycondensed starch, its production method, and fiber products, film or sheet-shaped molded products and molded products made of the hydrolyzed polycondensed starch. The hydrolyzed polycondensed starch of the present invention is used, for example, as a thickener for cosmetics, a thickener for food, glutinous rice paper, edible materials, and extruded products such as fiber products, films, sheets, pipes, rods, etc., molded Used as raw material for molded products and injection molded products.

Background technique

Non-thermoplastic starch is an economical polymer, but it cannot be used in general polymer applications such as films, fibers, and molded products. There have been many proposals to use starch to produce thermoplastic articles.

Such modified starches include hydroxyalkyl starches, acetate starches, or carbamate starches. These modified starches are produced by reacting the methylol groups of the starch with urea, epoxides, carbamate or isocyanate forming substances and the like. However, the chemical starch produced by this type of denaturation method is not economical, and is generally not used for the aforementioned purposes.

Starch has branched chains formed by amylopectin and does not exhibit thermoplasticity due to being a bulky polymer. Moreover, the hydrogen bond between the methyl hydroxyl groups and the like hinders thermoplasticity. By reacting the methyl hydroxyl groups of starch, denaturing and losing the hydrogen bonding force, starch becomes thermoplastic.

On the other hand, starch forms α-starch when heated and reverts to β-starch when cooled. Lotus root starch is an example of starch that turns into a paste when heated in the presence of water, and can appear thermoplastic in appearance. Japanese Patent Publication No. 7-74241 describes adding water to starch, producing hydrolyzed starch at high temperature, and producing a melt prepared by drying. However, it is not described that the polycondensation is continued after hydrolysis.

In addition, JP-A-7-57827 describes a method of mixing starch with a biodegradable resin. It is a method of adding water to starch, producing hydrolyzed starch at high temperature, and producing a dry prepared melt.

That is, starch is hydrolyzed by adding water to produce hydrolyzed starch. It is described that this hydrolyzed starch exhibits thermoplasticity. It is also recorded that the molecular weight of hydrolyzed starch is reduced from 1/2 of the initial stage to 1/5000, showing thermoplasticity. This is technically questionable since the absolute value of the molecular weight is not specified.

In addition, it is described that the hydrolyzed starch is made to absorb 18% by weight of moisture, mixed with other resins, and a dumbbell-shaped test piece is trial-produced using an injection molding machine. The test piece has little moisture absorption deformation. However, 18% by weight is a considerably large value compared with ordinary plastics, and it is not a general value.

There have been many reports on the method of hydrolyzing starch in a tank under the supercritical state of carbon dioxide-water system. For example, JP-A-11-92501 proposes the denaturation of polysaccharides in densified fluids. However, this proposal only discloses a method of hydrolyzing the giant macromolecules of starch into molecules lower than oligomers in a carbon dioxide-water supercritical state in a tank, and how to efficiently hydrolyze them into low-molecular compounds is the main issue . Therefore, there is no description of a method of hydrolyzing high-molecular starch and continuously polycondensing the resulting low-molecular weight.

In addition, Japanese Patent Laid-Open No. 2001-253967 proposes a regeneration method of a cross-linked polymer material. It describes a method in which a crosslinked polymer material and water are supplied to a single-screw or twin-screw extruder, and the water is hydrolyzed under the condition that the water becomes supercritical water or subcritical water in the extruder to cut off the crosslinked portion. There is no description of a method using carbon dioxide supercritical or subcritical in a carbon dioxide-water system. In addition, there is no description of a method of further polycondensing the cut crosslinked portion.

Generally, thermoplastic polymers have the property of being easily melt-adhesive at high temperatures above the softening point. Therefore, in order to prevent such sticking, quenching is usually performed. It is well known that, for example, when producing pellets such as nylon and polyester, the molten polymer is extruded from a nozzle into slices, quenched in cold water, and cut with a knife when the temperature drops below the softening point to prevent the pellets from sticking . However, the use of water cooling requires drying before remelting, which is economically disadvantageous. A method for preventing sticking above the softening point of thermoplastic resins has not been reported.

The object of the present invention is to provide novel hydrolyzed polycondensed starch and its cheap manufacturing method.

An object of the present invention is to provide thermoplastic, flexible, and practically sufficient mechanical properties, and to provide inexpensive hydrolyzed polycondensed starch and its production method, especially hydrolyzed polycondensed starch and its production method which are less sticky even above the softening point.

An object of the present invention is to provide inexpensive and biodegradable fiber products, film and sheet molded products, and molded molded products having sufficient usage characteristics.

Contents of invention

The present invention relates to a part of the introduction formula (1): -O-(C=O)-O-, formula (2): -((OR ¹ ) _x -(O-(C= At least one group selected from the group consisting of a group represented by O)-R ² ) _m -O _z - and a group represented by formula (3): -CH ₂ -(C=O)-CHR ³ -O- Hydrolyzed polycondensed starch. ^R1 represents an alkylene group above _C1 or an arylene group above _C6 . ^R2 represents an alkylene group above _C1 or an arylene group above _C6 . x represents 0 or 1. y Represents 0 or 1. x+y is 1 or 2. m represents an integer from 1 to 3100, z represents 1 or 2. R ³ represents a hydrogen atom, an alkyl group with C ₁ or higher, an aryl group with C ₆ or higher, or a C _{1 or} higher of alkoxy.

The present invention relates to the aforementioned hydrolyzed polycondensed starches which are crosslinked.

The hydrolyzed polycondensed starch of the present invention is preferably placed for 24 hours at a temperature of 20°C and a relative humidity of 60%, and the moisture content that actually reaches a constant equilibrium is 1 to 6% by weight. The hydrolyzed polycondensed starch of the present invention preferably has a swelling rate of 150 to 400% after being immersed in water at a temperature of 25° C. for 1 hour. The hydrolyzed polycondensed starch of the present invention preferably exhibits melt denaturation.

The hydrolyzed polycondensed starch of the present invention, for example, can be formed by making starch and the compound that forms the group represented by formula (1), the compound that forms the group represented by formula (2) and the compound that forms the group represented by formula (3) The selected at least one compound is produced by reacting in the presence of water at 100 to 350°C, or in the presence of water and carbon dioxide gas under the condition that the carbon dioxide gas is in a supercritical state or a subcritical state.

The manufacture method of the hydrolyzed polycondensation starch of the present invention, preferably in the group consisting of starch and the compound that forms the group shown in formula (1), the compound that forms the group shown in formula (2) and the compound that forms the group shown in formula (3) In the reaction of at least one compound selected from among them, an extruder is used to extrude at a pressure in front of the nozzle of 100 to 250 kg/cm ² (=9.8 to 24.5 MPa).

The hydrolyzed polycondensed starch of the present invention is used as a material for forming fibrous products, film or sheet shaped products and molded shaped products.

The hydrolyzed polycondensed starch of the present invention is thermoplastic, hardly sticks even at a temperature above the softening point, and preferably exhibits thixotropy. The hydrolyzed and polycondensed starch of the present invention can be regarded as having a soft linear organic group represented by formula (1), formula (2) or formula (3) in a part of the main chain of the starch, which improves the obvious hygroscopicity. The disadvantage of starch is thermoplastic and soft starch. That is, by introducing a group represented by formula (1), formula (2) or formula (3), part of the starch main chain composed of rigid glucose chains has a hinge-like soft part, and the main chain becomes soft. The main chain with increased flexibility tends to become a small silk ball. The main chain that has become a silk ball is less entangled with other main chains, and as a result, the main chains can slide. This phenomenon is considered to be the reason why the hydrolyzed polycondensed starch of the present invention exhibits thermoplasticity.

By making starch react with the compound shown in formula (1), formula (2) or formula (3) under the conditions as mentioned above, starch produces hydrolysis reaction, and the starch of hydrolysis forms formula (1), formula (2) ) or a compound represented by formula (3) undergoes dehydration polycondensation to generate the hydrolyzed polycondensed starch of the present invention.

A brief description of the drawings

Fig. 1 is a graph showing the results of measuring the hydrolyzed polycondensed starch produced in Example 1 of the present invention using a Fourier transform infrared spectrophotometer.

Fig. 2 is a graph showing the measurement results of the hydrolyzed polycondensed starch produced in Example 1 of the present invention and the cornstarch used as raw material using a Fourier transform infrared spectrophotometer.

                                    

The hydrolyzed polycondensed starch of the present invention has a structure in which a group represented by formula (1), formula (2) or formula (3) is introduced into a part of the starch main chain. The hydrolyzed polycondensed starch of the present invention has a repeating unit represented by formula (10): -GM _n -. G represents a divalent group except the 1-position and 4-position hydroxyl groups of glucose. M represents a group represented by formula (1), formula (2) or formula (3). n represents an integer of 1 or more. When n is an integer of 2 or more, a plurality of M may be the same as or different from each other.

R ¹ in formula (2) includes, for example, linear alkylene groups with C ₁ or more (usually 12 or less) such as 1,2-ethylene, 1,3-propylene, and 1,4-butylene. ; C ₆ or more (usually 15 or less) arylene groups such as phenylene, biphenylene, biphenylene alkylene (for example, biphenylene methylene, 2,2-biphenylene propylene) .

As R ² in formula (2), there are, for example, 1,1-ethylene, 1,1-propylene, 1,2-propylene, 1,1-butylene, 1,2-butylene, 1,3-butylene and other alkylene groups having C ₁ or more (usually 12 or less) alkyl groups; phenylene, biphenylene alkylene (such as biphenylene methylene, 2,2-biphenylene Propyl) and other C ₆ or more (usually 15 or less) arylene groups.

The hydrolyzed polycondensed starch in which ^R2 is an alkylene group tends to have higher flexibility and biodegradability than the hydrolyzed polycondensed starch represented by an arylene group.

As the group represented by the formula (2), there are the groups represented by the formula (4): -(O-(C=O)-R ² ) _m - (x=0, y=1, z=0), the formula (5 ): -(O-(C=O)-R ² ) _m -O-represented group (x=0, y=1, z=1), formula (6): -(OR ¹ ) _m - Group (x=1, y=0, z=0), formula (7): -(OR ¹ -O-(C=O)-R ² ) _m - represents the group (x=1, y=1, z=0), formula (8): -(OR ¹ ) _m -O- group (x=1, y=0, z=1) and formula (9): -(OR ¹ )-O-( A group represented by C=O)-R ² ) _m -O- (x=1, y=1, z=1).

As the group represented by formula (4), there are aliphatic ester groups (R ² is an alkylene group), aromatic ester groups (R ² is an arylene group), monoester groups (m=1), diester groups (m=2), triester group (m=3), polyester group (m is an integer of 2 to 3100, especially an integer of 4 to 3100).

As the group represented by formula (5), there are aliphatic ester ether groups (R ² is an alkylene group), aromatic ester ether groups (R ² is an arylene group), monoester ether groups (m=1), di Ester ether group (m=2), triester ether group (m=3), polyester ether group (m is an integer of 2 to 3100, especially an integer of 4 to 3100).

As the group represented by formula (6), there are monoalkyl ether group (R ¹ is an alkylene group, m=1), dialkyl ether group (R ¹ is an alkylene group, m=2), trialkyl ether group (R ¹ is an alkylene group, m=3), a polyalkylene ether group (R ¹ is an alkylene group, m is an integer of 2 to 3100, especially an integer of 4 to 3100), a single aryl ether group ( R ¹ is an arylene group, m=1), a diaryl ether group (R ¹ is an arylene group, m=2), a triaryl ether group (R ¹ is an arylene group, m=3), a polyaryl group Ether group (R ¹ is an arylene group, m is an integer of 2 to 3100, especially an integer of 4 to 3100).

As the group represented by the formula (7), there are monoalkylene ester group (R ¹ is an alkylene group, m=1), a dialkylene ester group (R ¹ is an alkylene group, m=2), trialkylene ester group Ester group (R ¹ is an alkylene group, m=3), polyalkylene ester group (R ¹ is an alkylene group, m is an integer from 2 to 3100, especially an integer from 4 to 3100), monoarylene Base ester group (R ¹ is an arylene group, m=1), a diarylene ester group (R ¹ is an arylene group, m=2), a triarylene ester group (R ¹ is an arylene group, m=2) 3), polyarylene ester group (R ¹ is an arylene group, m is an integer of 2 to 3100, especially an integer of 4 to 3100).

As the group represented by formula (8), there are monoalkyl diether group (R ¹ is an alkylene group, m=1), dialkyl diether group (R ¹ is an alkylene group, m=2), trioxane Diether group (R ¹ is an alkylene group, m=3), polyalkyl diether group (R ¹ is an alkylene group, m is an integer from 2 to 3100, especially an integer from 4 to 3100), monoaryl Diether group (R ¹ is an arylene group, m=1), a diaryl diether group (R ¹ is an arylene group, m=2), a triaryl diether group (R ¹ is an arylene group, m=2) 3) Polyaryl diether group (R ¹ is an arylene group, m is an integer of 2 to 3100, especially an integer of 4 to 3100).

As the group represented by the formula (9), there are monoalkylene ester ether groups (R ¹ is an alkylene group, m=1), a dialkylene ester ether group (R ¹ is an alkylene group, m=2), Trialkylene ester ether group (R ¹ is an alkylene group, m=3), polyalkylene ester ether group (R ¹ is an alkylene group, m is an integer of 2 to 3100, especially an integer of 4 to 3100), Monoarylene ester ether group (R ¹ is an arylene group, m=1), diarylene ester ether group (R ¹ is an arylene group, m=2), triarylene ester ether group (R ¹ is Arylene, m=3). Polyarylene ester ether group (R ¹ is an arylene group, m is an integer of 2 to 3100, especially an integer of 4 to 3100).

As R ³ in formula (3), for example, there are hydrogen atoms; methyl, ethyl, n-propyl, isopropyl and other C ₁ or more (usually 3 or less) alkyl groups; phenyl and other C ₆ (usually 8 aryl group of the following); methoxy, ethoxy, n-propoxy, isopropoxy and other C ₁ or more (usually 3 or less) alkoxy groups. As the group represented by formula (3), for example, there are dimethyl ketone group (R ³ is a hydrogen atom), ethyl methyl ketone group (R ³ is a methyl group), methyl methoxymethyl ketone group (R ³ for methoxy).

In the hydrolyzed polycondensed starch of the present invention, one or more groups represented by formula (1), formula (2) or formula (3) may be introduced into a part of the starch main chain. As two or more hydrolyzed polycondensed starches that introduce groups represented by formula (1), formula (2) or formula (3), there are groups represented by formula (1) and groups represented by formula (2) or groups represented by formula (3) The hydrolyzed polycondensed starch of the group shown in the formula; the hydrolyzed polycondensed starch with the group shown in the formula (2) and the group shown in the formula (3); the hydrolyzed polycondensed starch with two or more groups shown in the formula (2); (3) The hydrolyzed polycondensed starch of more than two kinds of bases; there are hydrolyzed polycondensed starches with the bases represented by the formula (1), the bases represented by the formula (2) and the bases represented by the formula (3).

A part of the starch main chain is introduced with the group represented by formula (1), which can be measured by infrared spectrophotometer through measuring the characteristic CO stretching vibration of the carbonic acid group that starch does not have ^. The absorption band was confirmed.

A part of the introduction of the group (y=1) shown in formula (4), formula (5), formula (7) and formula (9) in the starch main chain, this is obtained from the After extracting unreacted compounds (for example, polylactic acid) that form groups represented by formula (4), formula (5), formula (7) and formula (9) in hydrolyzed polycondensed starch, adopt infrared spectrophotometer to measure, can pass The absorption band at 1730 to 1740 cm ^-1 due to CO stretching vibration unique to the measurement of ester groups that starch does not have was confirmed. In addition, when ^R3 is 1,1-ethylene (for example, when using polyα-hydroxypropionic acid as a compound forming the group represented by the aforementioned formula (5), unreacted polycondensate is extracted from the obtained hydrolyzed polycondensed starch. After α-hydroxypropionic acid, it can be confirmed by NMR measurement by measuring a characteristic peak of the methyl group of poly α-hydroxypropionic acid.

A part of the introduction of the base (x=1) shown in formula (6), formula (7), formula (8) or formula (9) in the starch backbone, which can be obtained from the obtained solvent (for example, boiling water) After extracting unreacted compounds (for example, n-propanol) that form groups represented by formula (6), formula (7), formula (8) and formula (9) in the hydrolyzed polycondensed starch, in the NMR measurement, for example, R When ¹ is a 1,3-propylene group, a peak unique to the measurement of the methylene group of propanol, which is not present in starch, was confirmed.

A part of the starch main chain is introduced into the group shown in formula (3), which can be measured by measuring the characteristic CO stretching vibration of the group shown in formula (3) when using an infrared spectrophotometer ^. The absorption band was confirmed. There is no such absorption band for starch and compounds forming groups of formula (3) (eg, glycerol).

From the perspective of thermoplasticity of hydrolyzed polycondensed starch, the group represented by formula (1), formula (2) or formula (3) is preferably 50 to 100, especially 70, based on the total chemical formula amount relative to 100 moles of glucose units of starch. Imported at a ratio of ~100. When the introduction amount of the group represented by formula (1), formula (2) and formula (3) is small, the thermoplasticity of the hydrolyzed polycondensed starch is low, and when the introduction amount is large, it forms the group shown in formula (1), formula (2) or formula (3). Base compounds sometimes precipitate out of the final product.

Even if the amount of the group represented by formula (1), formula (2) or formula (3) introduced into the main chain of hydrolyzed polycondensed starch is a small amount observed with an infrared spectrophotometer, that is, even a few percent, this phenomenon occurs. Effect. Photometers with low sensitivity are sometimes observed as shoulders. As the introduction amount of groups represented by formula (1), formula (2) or formula (3) into the main chain increases, the thermoplasticity of the hydrolyzed polycondensed starch increases. When the amount of groups represented by formula (1), formula (2) and formula (3) is small, the hydrolyzed polycondensed starch becomes hard, and when the amount is large, it tends to become soft.

The hydrolyzed polycondensed starch of the present invention can be formed by making starch and the compound that forms the base shown in formula (1), the compound that forms the base shown in formula (2) (forming formula (4), formula (5), formula (6), formula (7), the compound of the group represented by the formula (8) or the formula (9)) or the compound reaction forming the group represented by the formula (3) is produced.

Generally used starch can be used as a main raw material starch. For example, it is produced from cereals such as barley, rye, rye, wheat, rice and corn, potatoes and tapioca. The type of raw material starch in the present invention is not particularly limited. However, cornstarch is preferably used in view of economic efficiency.

The molecular weight of starch is very large, for example, about 20,000,000, depending on the type of starch.

As the group represented by the formula (1), i.e., a compound that forms a carbonic acid group, carbon dioxide, or sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, calcium carbonate, calcium bicarbonate, etc., which emit carbon dioxide by heating, etc. .

As the compound forming the group represented by the formula (4), for example, there is the compound represented by the formula (11): H-(C=O)-R ³ -(O-(C=O)-R ³ ) _m-1 -OH compound.

Among the groups represented by the formula (4), as the compound forming an aliphatic monoester group (R ³ is an alkylene group, m=1), for example, there are hydroxyalkanes such as glycolaldehyde, glycolaldehyde, hydroxybutyraldehyde, glyceraldehyde, etc. Aldehydes. Among the groups represented by the formula (4), compounds that form an aromatic monoester group (R ³ is an arylene group, m=1) include, for example, hydroxymethylbenzylaldehyde, hydroxyethylbenzylaldehyde, hydroxypropyl Hydroxyalkylaryl aldehydes such as benzylaldehyde.

Among the groups represented by the formula (4), as a diester group (m=2), a triester group (m=3), a polyester group (m is an integer of 2 to 3100, especially an integer of 4 to 3100), etc. Examples of compounds include esters of hydroxyalkylaldehydes and aliphatic carboxylic acids such as glycolaldehyde monolactate, glycolaldehyde dilactate, glycolaldehyde trilactate, and glycolaldehyde multilactate.

As the compound forming the group represented by the formula (5), for example, there is a compound represented by the formula (12): H-(O-(C=O)-R ³ ) _m -OH. Among the groups represented by formula (5), examples of compounds forming aliphatic ester ether groups ( ^R is an alkylene group) include α-hydroxypropionic acid (lactic acid), β-hydroxypropionic acid, α-hydroxybutyric acid , β-hydroxybutyric acid, γ-hydroxybutyric acid and other hydroxyalkylcarboxylic acids and polycondensates thereof (for example, poly α-hydroxypropionic acid). Among the groups represented by the formula (5), as compounds forming an aromatic monoester ether group (R ³ is an arylene group), for example, there are hydroxymethylbenzylcarboxylic acid, hydroxyethylbenzylcarboxylic acid, hydroxypropyl hydroxyalkylaryl carboxylic acids such as benzyl carboxylic acid.

As the compound forming the group represented by the formula (6), for example, there is a compound represented by the formula (13): H-(OR ¹ ) _m -H. Among the groups represented by the formula (6), examples of compounds forming an alkyl ether group (R ¹ is an alkylene group, m=1) include methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, and Alcohols such as alcohol, octanol, and nonanol.

Examples of the compound forming the group represented by the formula (7) include compounds represented by the formula (14): H-(R ¹ -O-(C=O)-R ³ ) _m -OH.

In the group represented by the formula (7), as an alkyl ester ether group (R ¹ is an alkylene group, m=1), a dialkyl ester ether group (R ¹ is an alkylene group, m=2), a trialkyl group Ester ether group (R ¹ is an alkylene group, m=3), polyalkyl ester ether group (R ¹ is an alkylene group, m is an integer of 2 to 3100, especially when an integer of 4 to 3100), for example, Ethyl Lactate, Ethyl Dilactate, Ethyl Trilactate, Ethyl Polylactate, Propyl Lactate, Propyl Dilactate, Propyl Trilactate, Propyl Polylactate, Butyl Lactate, Butyl Dilactate, Trilactate Butyl ester, butyl polylactate, ethyl alpha-hydroxybutyrate, ethyl di-alpha-hydroxybutyrate, ethyl tri-alpha-hydroxybutyrate, ethyl poly-alpha-hydroxybutyrate, propyl alpha-hydroxybutyrate , Diα-hydroxybutyrate propyl ester, triα-hydroxybutyrate propyl ester, polyα-hydroxybutyrate propyl ester, α-hydroxybutyrate butyl ester, diα-hydroxybutyrate butyl ester, triα-hydroxybutyrate Alkyl esters of hydroxy acids such as butyl butyrate and poly-α-hydroxybutyrate.

Examples of compounds forming groups represented by formula (8) include compounds represented by formula (15): HR ⁴ -(C=O)-OH and formula (16): H-(OR ¹ ) _m -OH. -R ⁴ -CH ₂ - corresponds to R ¹ . As the group represented by the formula (8), that is, the compound forming an alkyl ether group, there are, for example, propionic acid, butyric acid (butyric acid, isobutyric acid), valeric acid, caproic acid, lauric acid, oleic acid, stearic acid Aliphatic carboxylic acids such as; ethylene glycol, propylene glycol, butylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, ethylene glycol-propylene glycol copolymer.

Examples of the compound forming the group represented by the formula (9) include compounds represented by the formula (17): HR ¹ -O-(C=O)-R ⁵ -(C=O)-OH. R ⁵ , -R ⁵ -CH ₂ - corresponds to R ³ in formula (2). As the compound forming the group represented by the formula (9), for example, there are monoethyl maleate, monopropyl maleate, monobutyl maleate, ethyl succinate, propyl succinate, butyl succinate , Ethyl fumarate, propyl fumarate, butyric fumarate, ethyl adipate, propyl adipate, butyl adipate and other dicarboxylic acid alkyl esters.

Examples of the compound forming the group represented by the formula (3) include compounds represented by the formula (18): XO-CH ₂ -CH(OH)-CHR ³ -OY (X and Y each represent a hydrogen atom or an acyl group). Examples of the compound forming the group represented by the formula (3) include glycerin, 1-alkylglycerin such as 1-methylglycerin, 1-alkoxyglycerin such as 1-methoxyglycerin, or esters thereof. Glycerin or its esters are partially introduced into the starch main chain to form dimethyl ketone (R ³ in formula (3) is a hydrogen atom). 1-Alkylglycerol and its esters are introduced into the starch main chain to form an α-alkylmethyl ketone group ( ^R3 in formula (3) is an alkyl group). 1-alkoxyglycerol and its esters are introduced into the main chain of starch to form alkoxymethyl ketone groups (R in formula ( ³ ) is an alkoxy group). Examples of esters include glycerin esters (monoglycerides, diglycerides, etc.) of aliphatic organic acids such as lauric acid, stearic acid, oleic acid, and linoleic acid. When esters are used, it is preferable that the free organic acid (especially low molecular weight organic acid) does not adversely affect the properties of the final product.

As the compound forming the group represented by formula (1), formula (2) or formula (3), by using ingredients present in natural food, it is possible to obtain hydrolyzed polycondensed starch with good safety and environmental friendliness.

By reacting starch with a compound that forms a group represented by formula (1), formula (2) or formula (3), in the presence of water, 100-350 ° C, preferably 135-155 ° C, can be in the starch main chain Part of the introduction of the group represented by formula (1), formula (2) or formula (3). When the reaction temperature is too low, the reaction rate decreases, and when the reaction temperature is too high, the resulting hydrolyzed polycondensed starch may sometimes be colored, and the molecular weight is obviously reduced and brittle.

By making starch and the compound that forms the group represented by formula (1), formula (2) or formula (3), in the presence of water and carbon dioxide gas, carbon dioxide gas becomes under the condition of supercritical state or subcritical state (for example, The temperature is 100-350°C, preferably 135-155°C, and the maximum reaction pressure is 7.48-29.4MPa, preferably 15.7-23.5MPa) to carry out the reaction, and a part of the starch main chain can be introduced into formula (1), formula (2) Or the group represented by formula (3). The carbon dioxide present also serves to form the compound of the formula (1). Carbon dioxide is in a supercritical state at a temperature of 31.1°C or higher and a pressure of 7.48MPa or higher, and at a temperature of 31.1°C or higher and a pressure of less than 7.48MPa or at a temperature of less than 31.1°C. It is a subcritical state under the condition of pressure above 7.48MPa. Carbon dioxide in a supercritical or subcritical state promotes the hydrolysis reaction of starch, and at the same time facilitates the dehydration polycondensation reaction between the hydrolyzed starch and the compound forming the group represented by formula (1), and acts as a crosslinking agent to facilitate the crosslinking reaction. The amount of carbon dioxide used is, for example, preferably 0.1 to 3% by weight based on water. Since carbon dioxide acts as a catalyst when starch is decomposed, it is effective even in a small amount.

The highest reaction pressure can be, for example, 76-300 kg/cm ² (=7.5-29.4 MPa), preferably 160-240 kg/cm ² (=15.7-23.5 MPa). The reaction rate decreases when the pressure is too low. When the pressure is too high, the resulting hydrolyzed polycondensed starch may sometimes be colored, the molecular weight will be significantly reduced, and the starch will be brittle. The reaction time may be, for example, 1 to 10 minutes, preferably 3 to 5 minutes. When the time is too long, the resulting hydrolyzed polycondensed starch may sometimes be colored, the molecular weight will be significantly reduced, and the starch will be brittle. When the time is too short, the reaction rate decreases, and hydrolyzed polycondensed starch having sufficient properties may not be obtained.

The amount of water used is, for example, 30 to 80 parts by weight, preferably 50 to 70 parts by weight, based on 100 parts by weight of starch (excluding water), and the water contained in starch (usually 12 to 13% by weight). When the amount of water used is small, the reaction rate of starch decreases. When the amount of water used is too large, the dehydration polycondensation reaction rate decreases, the recovery of the molecular weight is small, and the molecular weight of the obtained hydrolyzed polycondensed starch tends to decrease. In addition, the energy required for dehydration to recover the hydrolyzed polycondensed starch increases, which is not economical.

By making starch react with a compound that forms a group represented by formula (1), formula (2) or formula (3) under the aforementioned conditions, the hydrolysis reaction of the main chain of starch and the hydrolysis of the starch and the formation of formula (1) are carried out continuously. , the dehydration polycondensation reaction of the compound represented by the formula (2) or the formula (3), and a part of the starch main chain introduces the group represented by the formula (1), the formula (2) or the formula (3). It is considered that the branched chain of starch is cut off with the hydrolysis reaction of the main chain of starch, the molecular weight of starch decreases, and the starch is close to straight chain at the same time. In addition, by introducing the group represented by formula (1), formula (2) or formula (3), Imparting hydrophobicity and softness, hydrolyzed polycondensed starch exhibits thermoplasticity.

A part of the compound that forms the group represented by formula (1), formula (2) or formula (3) undergoes dehydration reaction with the hydroxyl group of the glucose unit, especially with the hydroxyl group of the methylol group, to form a side chain, which improves the thermoplasticity of the hydrolyzed polycondensed starch .

The reaction rate of starch and the compound that forms the group represented by formula (1), formula (2) or formula (3) can be measured by TGA, DSC analysis of the reduction rate and moisture content of hydrolyzed polycondensed starch, and calculate the unreacted The amount of the base compound formed by formula (1), formula (2) or formula (3) is estimated.

Starch can be hydrolyzed by heating in the presence of water under high pressure and high shear. In order to hydrolyze the starch in a short period of time under high pressure, and then carry out the dehydration polycondensation reaction, the starch reacts with the compound represented by the formula (1), formula (2) or formula (3), preferably using a dehydration exhaust extrusion A continuous reaction machine of the discharge type. As the reaction machine, it is preferable to use an extruder, for example, a 2-vent extruder or a 3-vent extruder. The used screw is preferably a twin screw so that only the supply portion can be fed well, and then the machine head is constituted by a single screw. For example, a 3-vent extruder is preferably composed of a screw supply section, a shear mixing compression section, an open exhaust section, a kneading compression section, a vacuum pump suction exhaust section, a kneading compression section, and a suction and exhaust section of a vacuum pump. Department, mixing and compression department.

When using an extruder as a reaction machine, for example, it is preferable to extrude under a pressure before the nozzle of 100 to 250 kg/cm ² (=9.8 to 24.5 MPa).

The hydrolyzed polycondensed starch of the present invention can be crosslinked using a crosslinking agent. By intercrosslinking the hydroxymethyl groups of the hydrolyzed polycondensed starch, water swelling property can be suppressed and water resistance can be improved. Even if the degree of crosslinking is small, the effect of sufficiently suppressing water swelling is exhibited. Water swelling decreases with increasing crosslinking. The water swelling rate can be calculated, for example, by measuring the weight before and after being immersed in water at normal temperature (for example, 25° C.) for 1 hour to swell, and the absolute dry weight.

As the crosslinking agent, for example, phosphoric acid, polycarboxylic acids, hydroxycarboxylic acids, epoxides, acid anhydrides, isocyanates, silanized compounds and the like can be used. As the crosslinking agent, there are, for example, phosphates such as sodium tripolyphosphate; polycarboxylic acids such as oxalic acid, maleic acid, adipic acid, phthalic acid, and succinic acid; calcium adipate, calcium oxalate, maleic acid, etc. Polycarboxylates of calcium, calcium phthalate, calcium succinate, etc.; hydroxycarboxylic acids such as lactic acid; hydroxycarboxylates of calcium lactate, etc.; carbon dioxide; Epoxides such as glycidyl ether; acid anhydrides such as succinic anhydride and maleic anhydride; isocyanates such as hexamethylene diisocyanate and toluene-2,4-diisocyanate; silylates such as vinyltrimethylsilane; Hydrogen-1,3,5-triacryloyl-s-triazine. A crosslinking agent can be used individually by 1 type, or in mixture of 2 or more types.

The hydrolyzed polycondensed starch can be crosslinked by adding a crosslinking agent to the hydrolyzed polycondensed starch and kneading by heating (for example, 100 to 180° C.). The amount of the crosslinking agent added is preferably 0.01 to 3% by weight based on the hydrolyzed polycondensed starch before crosslinking. When the addition amount of the crosslinking agent is small, the effect of suppressing the water swelling of the hydrolyzed polycondensed starch and improving the water resistance tends to be small, and the hydrolyzed polycondensed starch dissolves in water, and the water swelling property may be infinitely increased. When the amount of the crosslinking agent added is too large, the thermoplasticity and fluidity of the hydrolyzed polycondensed starch may decrease, and the processability may decrease.

When using an extruder, starch is reacted with a compound (for example, carbon dioxide gas) that forms a group represented by formula (1) in the presence of water, and starch is reacted with a compound that forms a group represented by formula (2) or When the compound of the group represented by formula (3) is reacted, for example, the pressure in front of the nozzle is maintained at 160kg/cm ² (=15.7MPa) or more, and rapid dehydration is caused by instantaneous extrusion in the atmosphere, so that the glucose unit can be The intermethylol moiety causes crosslinking of carbon dioxide. Due to the carbonic acid crosslinking of this part, the hydrolyzed polycondensed starch with sufficient crosslink density and thixotropy above the softening point can be obtained. Since this cross-linking reaction is a cross-linking reaction caused by dehydration between methylol groups, the faster the dehydration, that is, the faster the decompression from a higher pressure, the higher the cross-linking density of the hydrolyzed polycondensed starch, The lower the water swelling, the higher the water resistance, and the harder it is for the hydrolyzed polycondensed starch to stick.

For example, the pellets of cross-linked hydrolyzed polycondensed starch obtained are cut off with a hot knife in contact with the head of the extruder, and dropped while spraying some air, for example, even if they are stopped in a receiving pan set at a height of 1 m. , Since it is not sticky, it can be directly delivered by a pressure delivery jet machine. In addition, in film production using such pellets with a blown film device, for example, the bubble-shaped film at a distance of 1 m behind the machine head will not stick even if it is pressed tightly from both sides. The cross-linked hydrolyzed polycondensed starch is difficult to stick, which is presumably due to the reversible thixotropy of cross-linking.

The hydrolyzed polycondensed starch of the present invention, for example, may have a weight average molecular weight of 30,000 to 500,000, preferably 50,000 to 200,000. Hydrolyzed polycondensed starch with a low molecular weight tends to have low mechanical properties, and hydrolyzed polycondensed starch with a high molecular weight may have low fluidity and may be difficult to mold.

The molecular weight of the hydrolyzed polycondensed starch tends to decrease due to the increase of the reaction temperature when the starch reacts with the compound represented by the formula (1), formula (2) or formula (3), or due to the increase of the reaction pressure.

The hydrolyzed polycondensed starch of the present invention is preferably placed for 24 hours at a temperature of 20° C. and a relative humidity of 60%, and the moisture content that actually reaches a constant equilibrium is 1 to 6% by weight.

The hydrolyzed polycondensed starch of the present invention preferably has a swelling rate of 150 to 400% after immersion in water at 25° C. for 1 hour. A hydrolyzed polycondensed starch with too high a swelling ratio has low water resistance and tends to stick pellets easily, and a hydrolyzed polycondensed starch with too low a swelling ratio tends to have low fluidity. For example, the aforementioned swelling ratio can be reduced by crosslinking the hydroxymethyl groups of the hydrolyzed polycondensed starch glucose unit.

The hydrolyzed polycondensed starch of the present invention preferably has thixotropy. For example, cross-linked hydrolyzed polycondensed starch exhibits reversible thixotropy. The cross-linked hydrolyzed polycondensed starch is only heated above the softening point, because the cross-links are not broken, and the surface tension is small, so it becomes spherical and maintains the original shape, but it is easy to flow and deform when a slight load is applied in this state. Remains deformed when the load is removed, exhibiting reversible thixotropy.

The hydrolyzed polycondensed starch of the present invention has good transparency because the starch does not exist in particles. The hydrolyzed polycondensed starch of the present invention has, for example, an excellent value of 30 or less in haze measured on a sheet having a thickness of 1 mm produced by hot pressing using a spectrophotometer. For haze, for example, Tt (total light transmittance (%) and Td (diffuse transmittance (%)) are measured using HGM-2DP manufactured by Suga Testing Instrument Co., Ltd., and can be calculated as haze (%)=Td÷Tt×100 When the sheet of hydrolyzed polycondensed starch of the present invention is immersed in water, due to the difference in partial swelling, a partial difference in refractive index occurs, causing light scattering, and gradually becomes cloudy, but after drying, the local difference in refractive index disappears , becomes transparent again.

Generally used additives for polymers may be added to the hydrolyzed polycondensed starch of the present invention. Examples of these additives include additives such as colorants (pigments, dyes), antibacterial agents, deodorants, preservatives, insect repellents, antistatic agents, light-resistant agents, heat-resistant agents, and anti-blocking agents. These additives may be used alone or in combination of two or more. The use of these additives should be considered in accordance with the intended use so that there is no adverse effect on the properties as food, properties as pharmaceuticals, biodegradability at the time of disposal, etc.

Thermoplasticity can be improved by adding plasticizers such as aliphatic organic acids and glycerides to the hydrolyzed polycondensed starch of the present invention. Thermoplasticity can be further improved by increasing the compounding amount of plasticizer.

Form the reaction rate of the compound represented by formula (1), formula (2) or formula (3), can use TGA, DSC analysis to measure the decrement of obtained hydrolyzed polycondensed starch to estimate. For example, mix 70% by weight of starch and 30% by weight of glycerin, and carry out a constant rate reduction at a certain speed on the obtained hydrolyzed polycondensed starch until the temperature (about 270° C.) begins to decompose. The weight loss rate is about 15% by weight including the water weight loss rate. Because the moisture content of the hydrolyzed polycondensed starch to achieve a constant balance is 4 to 5% by weight, it is estimated that about 10% by weight of unreacted glycerin remains, and the remaining about 20% by weight of glycerol reacts and is introduced into a part of the starch main chain, or forms a side chain. chain.

The hydrolyzed polycondensed starch of the present invention can be used as fiber products, films, sheets, etc. Used as raw materials for extruded products, molded products and injection molded products such as materials, pipes and rods.

The hydrolyzed polycondensed starch of the present invention can be spun by, for example, melt spinning. That is, the hydrolyzed polycondensed starch is melted and kneaded using an extruder, spun from a jet weaving head while metering with a gear pump, oiled, and wound to obtain a filament. Various fiber products can be obtained by stretching the filaments, or blending them with other fibers, or performing false twisting processing, or cross-twisting processing, etc.

As a material for melt spinning, hydrolyzed polycondensed starch having a melt viscosity of 10-500 is preferable, and 200-400 is more preferable. The melt viscosity of the hydrolyzed polycondensed starch can be determined by the outflow amount (g) flowing out from an orifice with a diameter of 2 mm for 10 minutes under the conditions of a temperature of 190° C. and a load of 2.16 kg. A hydrolyzed polycondensed starch having a melt viscosity of less than 100 or more than 500 has low spinnability when producing fiber products.

For example, when the spun yarn is cooled by a rectified air flow (air), slow cooling tends to have better spinnability than rapid cooling. The moisture contained in the hydrolyzed polycondensed starch is removed by air flow. Stretching may also be performed simultaneously with spinning or after spinning. The tensile breaking strength of the undrawn yarn is, for example, about 0.2 g/d, and the tensile breaking elongation is, for example, about 530%. Fiber strength can be increased by drawing the undrawn yarn. From the viewpoint of increasing the fiber strength, it is preferable to stretch the unstretched yarn at a temperature equal to or higher than the glass transition temperature of the hydrolyzed polycondensed starch. By drawing the undrawn yarn, it is possible to obtain, for example, a fiber with a tensile breaking strength of 2 g/d or more, and depending on the drawing conditions, it is possible to obtain a fiber of 3 g/d or more.

After the hydrolyzed polycondensed starch of the present invention is spun, bundled into fiber bundles, oiled, wound and cut after thermal stretching, short fibers can be obtained. Cut staple fibers are usually packaged immediately after cutting. Short fibers can be blended with other fibers.

The spun yarn using the hydrolyzed polycondensed starch fiber of the present invention can be used by intertwisting or paralleling other yarns. The fiber of the hydrolyzed polycondensed starch of the present invention can be used to produce a knitted fabric similarly to general filaments or spun yarns. The short fibers of the hydrolyzed polycondensed starch of the present invention can be used in the manufacture of nonwoven fabrics by needle punching, air-laying, spunlace, or paper-making, similarly to general short fibers.

Film and sheet moldings can be produced using the hydrolyzed polycondensed starch of the present invention. For example, films and sheets can be produced by extruding the hydrolyzed polycondensed starch of the present invention with a T-shaped die. When using the T-shaped head method to manufacture film or sheet, the thickness of the obtained film or sheet can be controlled by adjusting the extrusion volume and pulling speed. The film and sheet of the hydrolyzed polycondensed starch of the present invention can also be manufactured by blow molding. When blow molding is used to produce film or sheet, it is preferable to use hydrolyzed polycondensed starch with a viscosity of 1-10, especially 1-5, in operation.

When producing the hydrolyzed polycondensed starch film or sheet of the present invention, the extrusion temperature of the hydrolyzed polycondensed starch is preferably within the range of 20°C above and below the melting point of the hydrolyzed polycondensed starch, for example, preferably 140 to 180°C.

Stretched film or stretched sheet can be produced by stretching the hydrolyzed polycondensed starch film or sheet of the present invention produced by T-shaped die or blow molding method. The temperature for stretching the hydrolyzed polycondensed starch film and sheet of the present invention is preferably in the range of not less than the glass transition temperature and 30°C higher than the temperature.

The hydrolyzed polycondensed starch unstretched sheet of the present invention can be produced, for example, by vacuum molding. For example, use an infrared heater to heat a sheet with a thickness of 0.2 to 2mm to above the glass transition temperature, move it to a vacuum molding mold, and process the sheet into the shape of the mold by sucking the mold.

Polylactic acid is a well-known biodegradable resin. The tensile elongation at break in the unstretched state is very small, 2 to 3% at room temperature, and it is brittle and not durable. In addition, even if it is vacuum molded, although the deformation is large The part is stretched, but the part at the edge of the mold is hardly stretched, so the unstretched part remains, which is brittle and not durable. On the other hand, the hydrolyzed polycondensed starch unstretched sheet of the present invention has a tensile elongation at break of 20% or more at room temperature (eg, 25° C.), and the unstretched portion has mechanical properties that are acceptable for practical use.

Hereinafter, the present invention will be described in detail using examples.

Embodiment 1: have the hydrolyzed polycondensed starch of base shown in formula (3)

Mix 100 parts by weight of cornstarch, 70 parts by weight of ion-exchanged water, 50 parts by weight of glycerin, and 10 parts by weight of butanediol with 12 to 13 percent by weight of water usually contained in starch, and supply it to a 45 mm three-stage Vented single screw extruder. Dehydration is carried out from the exhaust port by using an open water seal pump and an oil diffusion pump. The screw of the extruder is designed to go through the process of feeding, mixing, compressing, dehydrating from the exhaust port, mixing, dehydrating from the exhaust port, mixing, dehydrating from the exhaust port, and compressing, and can obtain no less than the usual The effect of a twin-screw extruder.

The kneading effect of the screw was confirmed by mixing 2 parts by weight of polyethylene containing carbon black into 100 parts by weight of colorless transparent polypropylene, and observing and comparing the presence of carbon black with a microscope after kneading. It was confirmed with an optical microscope that polyethylene was uniformly dispersed in polypropylene with a size of about 30 micrometers.

Under the conditions of the highest heating temperature of 150°C and the pressure of 230kg/cm ² (=22.5MPa), the starch is hydrolyzed, and then the hydrolyzed starch and glycerol are rapidly dehydrated and polycondensed. The total residence time was 3 minutes and the raw material feed rate was 50 kg/hour. The generated hydrolyzed polycondensed starch was filtered through a 100-mesh filter, extruded from a nozzle with a diameter of 1 mm, and processed into pellets with a hot knife. The MI value (180°C) of the prepared hydrolyzed polycondensed starch pellets was 5, showing good thermoplasticity.

A film was made from the obtained hydrolyzed and polycondensed starch pellets, and FT-IR measurement was carried out using a Fourier transform infrared spectrometer, and the 1724.9 cm ^-1 absorption band formed by the CO stretching vibration peculiar to the group represented by the formula (3) that starch did not have was confirmed. . Fig. 1 shows the measurement results of FT-IR measurement with an infrared spectrophotometer. For the sake of comparison, the measured results of the FT-IR measurement of the obtained hydrolyzed polycondensed starch are compared with the measurement results of the FT-IR measurement of the cornstarch used as a raw material with a Fourier transform infrared spectrophotometer and are shown in figure 2.

In Figure 1 and Figure 2, the absorption of hydrolyzed polycondensed starch at 3294cm ^-1 represents the OH of the hydrogen bond, the absorption of 2929cm ^-1 represents the CH of _{the CH2} group, and the absorption of 1724.9cm ^-1 represents the C=O of the dimethyl ketone group, The absorption at 1646 cm ^-1 indicates the presence of water of crystallization. In Fig. 2, the absorption of 3295 cm ⁻¹ of cornstarch indicates the OH of the hydrogen bond, the absorption of 2929 cm ⁻¹ represents the CH of the _CH2 group, and the absorption of 1645 cm ⁻¹ indicates the presence of crystallization water. Corn starch has no absorption near 1724.9 cm ^-1 indicating the presence of C=O of the dimethyl ketone group.

For the FT-IR measurement, a Fourier transform infrared spectrophotometer manufactured by Perkin Elma Co., Ltd. was used.

Embodiment 2 and 3: have the hydrolyzed polycondensation starch of group shown in formula (3)

Except that the residence time is 3 minutes (Example 2) and 5 minutes (Example 3), the others are processed into pellets in the same manner as Example 1. The result is the same as Example 1. It is confirmed that it has thermoplasticity and introduces formula (3) The hydrolyzed polycondensed starch of the base shown.

<Forming of sheet>

A T-shaped head extrusion device with a gap of 0.5 mm was used to extrude at a head temperature of 160° C. to obtain an unstretched sheet with a film thickness of about 400 microns. The tensile breaking strength and tensile breaking elongation of the obtained sheet are shown below, showing a practical strength. The constant moisture content after standing at a temperature of 20°C and a relative humidity of 60% for 24 hours is shown below. Tensile breaking strength Tensile elongation at break Moisture rate Example 1 0.5N/ ^mm2 125% 6% Example 2 0.8N/ ^mm2 88% 5% Example 3 1.1N/ ^mm2 71% 4%

<Molding of film>

The unstretched sheet of Example 3 was stretched 4 times at a heating chamber temperature of 90°C to produce a uniaxially stretched film with a film thickness of 100 µm. The obtained film had a tensile strength at break of 9.9 N/mm ² and a tensile elongation at break of 25%, showing a practical strength.

Embodiment 4: have the hydrolyzed polycondensed starch of base shown in formula (1)

Except using 10 parts by weight of sodium bicarbonate which generates carbon dioxide instead of glycerol, it carried out similarly to Example 1. When the obtained hydrolyzed polycondensed starch is measured by an infrared spectrophotometer, due to the newly discovered absorption band of 1745-1755 cm ^-1 formed by the unique CO stretching vibration of the carbonic acid group, it can be confirmed that a part of the starch main chain has been introduced into the formula (1):- A group represented by O-(C=O)-O-. Starches do not have this absorption band. The MI value of the resulting hydrolyzed polycondensed starch was 23.

Embodiment 5: have the hydrolyzed polycondensation starch of base shown in formula (5)

The reaction was carried out in the same manner as in Example 1, except that polyα-hydroxypropionic acid equivalent to equivalent moles in terms of monomer units was used instead of glycerin. After using o-cresol to extract unreacted poly-alpha-hydroxypropionic acid from the resulting hydrolyzed polycondensed starch, use an infrared spectrophotometer to measure the 1730-1740cm ^-1 absorption band formed by the newly discovered CO stretching vibration unique to the ester group. It was confirmed that a group represented by (O-(C=O)-CH(CH ₃ )) _m -O- had been introduced into a part of the starch main chain. Starch does not have this absorption band. In addition, after extraction of unreacted poly-α-hydroxypropionic acid from the obtained hydrolyzed polycondensed starch, NMR analysis detected a peak indicating the presence of a methyl group of poly-α-hydroxypropionic acid.

Embodiment 6: have the hydrolyzed polycondensed starch of base shown in formula (6)

The reaction was carried out in the same manner as in Example 1, except that equimolar n-propanol was used instead of glycerin for the reaction. After extracting unreacted n-propanol from the resulting hydrolyzed and polycondensed starch with boiling water, NMR analysis detected a peak indicating the presence of methylene groups of n-propanol that starch does not have, and it was confirmed that a part of the n-propanol in the main chain of starch was present. A group represented by O-CH ₂ -CH ₂ -CH ₂ - has been introduced.

Embodiment 7: have the hydrolyzed polycondensation starch of formula (5) and the base represented by formula (6)

The reaction was carried out in the same manner as in Example 1, except that half the mole of n-propanol was used, and polyα-hydroxypropionic acid equivalent to half the mole of monomer units was used instead of glycerin. Use boiling water to extract unreacted n-propanol from the resulting hydrolyzed and polycondensed starch, and then use o-cresol to extract unreacted poly-alpha-hydroxypropionic acid. After NMR analysis, it is detected that there is no n-propanol in the starch. It can be confirmed that a group represented by O-CH ₂ -CH ₂ -CH ₂ - has been partially introduced into the starch main chain. In addition, the obtained hydrolyzed and polycondensed starch was measured by an infrared spectrophotometer. Due to the newly discovered absorption band of 1730 to 1740 cm ^-1 formed by the CO stretching vibration unique to the ester group, it can be confirmed that a part of the starch main chain has been introduced (O- A group represented by (C=O)-CH(CH ₃ )) _m -O-.

Embodiment 8～11: cross-linking

To the hydrolyzed polycondensed starch produced in Example 1, sodium tripolyphosphate was added in varying amounts, kneaded at 130°C using a single-screw kneading extruder, and pellets were produced with a dry cutter. The measurement results of the water-swellability of the obtained pellets are as follows. The less water-swellable the pellets are, the less sticky they will be when granulated with hot knives. In addition, a sheet was produced in the same manner as in Example 1. Addition amount of sodium tripolyphosphate water swelling Example 8 0.03% by weight dissolved, infinity Example 9 0.05% by weight 630% Example 10 1% by weight 160% Example 11 3% by weight 20%

<Manufacture of molded products>

Use the hydrolyzed polycondensation starch of Example 8 to produce an unstretched sheet with a thickness of 1mm, heat it to 90°C (above the glass transition temperature) with an infrared heater, move it to a vacuum molding mold at room temperature, and use a vacuum pump from the bottom of the mold Suction makes the sheet into the same shape as the mold, trims the mold with a knife, and produces molded products. The shape of the mold is that the corner R of the bottom edge and the opening part is 5mm, the opening surface is 5cm on each side, and the bottom edge is 3cm on each side. Use three molds with depths of 2cm, 4cm, and 6cm side by side at 1cm intervals. Judging whether the different depths are well formed, it turns out that any depth will do. The sheet was free from cracks and extremely thin-walled portions, and had good formability.

Embodiment 12: have the hydrolyzed polycondensed starch of group shown in formula (8)

It carried out similarly to Example 1 except having used the n-butanediol of equimole number instead of glycerin. Unreacted n-butylene glycol was extracted from the resulting hydrolyzed polycondensed starch using boiling water, and a peak indicating the presence of methylene groups of n-butylene glycol, which is not present in starch, was detected by NMR analysis, confirming that a part of the starch main chain was introduced. A group represented by O-CH ₂ -CH ₂ -CH ₂ -CH ₂ -O-.

<Softening point, destruction temperature>

As a result of analyzing the hydrolyzed polycondensed starches obtained in Examples 1 to 12 using DSC6200 manufactured by Seiko Denshi Co., Ltd. and SSC5200 manufactured by Seiko Denshi Co., Ltd., the softening point was 42 to 80°C and the destruction temperature was 278 to 299°C.

<Biodegradability>

The sheets obtained in Examples 1 to 12 were put into a commercially available household mixer, and a part of the samples were periodically taken every 8 hours to measure the reduction of the samples. The biodegradability of the sheet was evaluated using this weight reduction rate. The mixing treatment temperature is kept at 40-50° C., and wheat flour is used as the nutrient for the mixed inoculum. None of the samples could become hydrolyzed polycondensed starch samples after 48 hours, showing good biodegradability.

Embodiment 13: the manufacture of fiber product

Using an extruder to melt the hydrolyzed polycondensed starch with an MI value of 32 manufactured in Example 12, use a circular spinneret to carry out spinning and oiling at a nozzle temperature of 180°C while metering with a gear pump to produce a circular unfinished product. stretched wire. Evaporation of water was observed during spinning, but had no adverse effect on spinning. Then, the stretched yarn of the fiber 250D/16F of the present invention was produced under the conditions of a draw ratio of 4.4 times and a heating plate temperature of 90°C. The fiber exhibited no melting point as determined by DSC in a nitrogen ambient atmosphere. The tensile breaking strength of this fiber was 1.8 g/d, and the tensile breaking elongation was 22%.

Possibility of Industrial Utilization

Unlike starch, the hydrolyzed polycondensed starch of the present invention is thermoplastic, so it can be used as a substitute material for conventional thermoplastic resins, for example, as a material for manufacturing various molded products. Unlike starch, the hydrolyzed polycondensed starch of the present invention is economical because it does not require drying when used as a material for producing various molded articles. Since the hydrolyzed polycondensed starch of the present invention has biodegradability similarly to starch, it can be easily biodegraded during mixing.

Claims (13)

1. Hydrolyzed polycondensed starch, which is to introduce the group represented by formula (1): -O-(C=O)-O- and formula (3): -CH ₂ -(C=O)-CHR into the main chain of starch The hydrolyzed polycondensed starch of at least one base selected from the group consisting of groups represented by ³ -O-, with respect to 100 moles of glucose units of the starch, the base represented by formula (1) or formula (3) is based on the total chemical formula amount Imported at a ratio of 50 to 100 moles, Wherein, in formula (3), R ³ represents a hydrogen atom, an alkyl group with C ₁ to C ₃ , an aryl group with C ₆ to C ₈ , or an alkoxy group with C ₁ to C ₃ . 2. The hydrolyzed polycondensed starch according to claim 1, wherein only groups represented by formula (1) are introduced. 3. The hydrolyzed polycondensed starch according to claim 1, wherein only groups represented by formula (3) are introduced. 4. the hydrolyzed polycondensed starch described in claim 1, 2 or 3 of crosslinking. 5. The hydrolyzed and polycondensed starch according to claim 1, 2 or 3, wherein the moisture content that actually reaches a constant equilibrium is 1 to 6% by weight when placed at a temperature of 20° C. and a relative humidity of 60% for 24 hours. 6. The hydrolyzed polycondensed starch according to claim 1, 2 or 3, wherein the swelling rate after immersion in water at a temperature of 25° C. for 1 hour is 150 to 400%. 7. The hydrolyzed polycondensed starch according to claim 1, 2 or 3 showing thixotropy. 8. the manufacture method of hydrolyzed polycondensation starch described in claim 1 is to make starch and from forming formula (1):-O-(C=O)-O-compound shown in base and form formula (3): Production of hydrolyzed polycondensed starch in which at least one compound selected from the group consisting of compounds represented by groups represented by -CH ₂ -(C=O)-CHR ³ -O- reacts at 100 to 350°C in the presence of water method, Wherein, in formula (3), R ³ represents a hydrogen atom, an alkyl group with C ₁ to C ₃ , an aryl group with C ₆ to C ₈ , or an alkoxy group with C ₁ to C ₃ . 9. the manufacture method of hydrolyzed polycondensation starch described in claim 1 is to make starch and from forming formula (1):-O-(C=O)-O-compound shown in base and form formula (3): -CH ₂ -(C=O)-CHR ³ -O- is at least one compound selected from the group consisting of compounds representing a radical, and in the presence of water and carbon dioxide gas, the carbon dioxide gas is in a supercritical state or a subcritical state The manufacture method of the hydrolyzed polycondensed starch that reacts under the condition, Wherein, in formula (3), R ³ represents a hydrogen atom, an alkyl group with C ₁ to C ₃ , an aryl group with C ₆ to C ₈ , or an alkoxy group with C ₁ to C ₃ . 10. the manufacture method of the hydrolyzed polycondensation starch described in claim 8 or 9, wherein, starch is selected from the group that forms the compound shown in the base shown in formula (1) and the compound that forms the base shown in formula (3) In the reaction of at least one compound, extruder is used to extrude under the pressure in front of the nozzle of 100-250kg/cm ² . 11. A fiber product made from the hydrolyzed polycondensed starch according to claim 1, 2 or 3. 12. A film or sheet shaped product made of the hydrolyzed polycondensed starch according to claim 1, 2 or 3. 13. A molded product made of the hydrolyzed polycondensed starch according to claim 1, 2 or 3.

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