JP2003261598A - Modified soy protein, method for producing the same, and molded article using the same - Google Patents

Abstract

(57) [Problem] To provide a flexible soybean protein which has a good balance between tensile strength and elongation. SOLUTION: The modified soybean protein having a repeating unit composed of an alkylene oxide chain in the molecule, wherein the repeating unit composed of the alkylene oxide chain bonded to the denatured site of the modified soybean protein has a general formula (1) and / or The present invention relates to a modified soybean protein represented by the general formula (2), a method for producing the same, and a molded article using the same. _{- (CH 2 CH 2 O)} m- (1) ## STR1 ## [In the general formulas (1) and (2), m is an integer of 3 or more, and n is an integer of 3 to 8. ]

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a modified soybean protein, a method for producing the same, and a molded article using the same, which has improved water resistance and flexibility.

[0002]

BACKGROUND OF THE INVENTION Soybean protein is used as a main component of tofu, miso, soy sauce, natto and soybean protein isolate in domestic food applications, and is used overseas mainly as soybean meal for feed applications. Is a useful protein resource. However, it is still underutilized for non-food applications. The reason is that, in general, soybean proteins have poor water resistance because they are hydrophilic, and they are composed of many kinds of amino acids, have many functional groups, and have an average molecular weight of several hundred thousand. It is believed that the resulting article is hard and brittle because it has a nitrogen-containing polymer compound.

Therefore, if the water resistance can be improved and the performance can be improved so as to impart flexibility to the huge soybean protein, it can be expected that the inexpensive soybean protein can be more effectively used for non-food applications.

Soy protein is a hydrophilic protein by nature, and in order to improve its water resistance, for example, a cross-linking agent having a functional group capable of reacting with a functional group contained in the molecule is reacted with soy protein. A method has been proposed (Japanese Patent Laid-Open No. H11-11)
-49962 publication). However, in the above method, unless a plasticizer such as glycerin is used together, the soybean protein becomes harder due to denaturation, or the fluidity deteriorates,
As a result of the lack of flexibility, it is difficult to process into films, sheets and other molded articles. Further, softening of soybean protein is usually achieved by adding a plasticizer such as glycerin. In that case, although the elongation is increased, the mechanical strength (tensile strength) inherent to soybean protein is reduced. ,
It has been difficult to obtain soybean protein that maintains a good balance between mechanical strength and elongation. On the other hand, since water-soluble glycerin is water-soluble, there is a problem that the water resistance of the plasticized soybean protein is reduced.

The modification of soybean protein with a compound containing an epoxy group is disclosed in JP-A-7-237233 and JP-A-9-237233.
As disclosed in JP-A-124796, the soybean protein modified with these epoxy group-containing compounds cannot give sufficient flexibility to the molded article. Further, JP-A 2000-109562 discloses the use of a monoepoxy compound for soybean protein, but although the solubility in water or a solvent and the compatibility with a synthetic resin are improved, the flexibility of a molded article is improved. There was a problem that sex was not enough.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides a soybean protein having a flexible modification which can be expected to be expanded to non-food applications by improving the water resistance of soybean protein and maintaining tensile strength and elongation in a well-balanced manner. The object is to provide soybean protein, a method for producing the same, and a molded article using the same.

[0007]

[Means for Solving the Problems] As a result of intensive studies, the present inventors have obtained a flexible soybean protein which retains the effects of a plasticizer such as glycerin and has a well-balanced tensile strength and elongation. The inventors have found that the use of a modified soybean protein having a specific structure is effective in improving the performance, and have completed the present invention.

That is, the present invention is a modified soybean protein having a repeating unit composed of an alkylene oxide chain in the molecule, wherein the repeating unit composed of an alkylene oxide chain bonded to the modified site of the modified soybean protein has the following general structure: Disclosed is a modified soybean protein represented by the formula (1) and / or the general formula (2). _{- (CH 2 CH 2 O)} m- (1)

[Chemical 3] [In general formula (1) and general formula (2), m is an integer greater than or equal to 3, and n is an integer of 3-8. ]

The present invention also relates to a soybean protein (A) and a polyfunctional epoxy compound (B) having an alkylene oxide chain represented by the general formula (1) and / or the general formula (2) in the molecule as a cross-linking agent. The present invention provides a method for producing a modified soybean protein, which comprises reacting _{- (CH 2 CH 2 O)} m- (1)

[Chemical 4] [In general formula (1) and general formula (2), m and n are the same as the above. ]

Further, the present invention provides a molded article using the modified soybean protein.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION First, the modified soybean protein of the present invention will be described in detail. The modified soybean protein of the present invention is a modified soybean protein having a repeating unit composed of an alkylene oxide chain in the molecule, and has a structure in which soybean proteins are linked to each other by a repeating unit composed of an alkylene oxide chain.

The modified soybean protein of the present invention has the following general formula (1) and /
Alternatively, it has a repeating unit composed of an alkylene oxide chain represented by the general formula (2). _{- (CH 2 CH 2 O)} m- (1)

[Chemical 5] In the general formulas (1) and (2), m is an integer of 3 or more. When m and n are less than 3, the flexibility of the molded product becomes insufficient, and when n exceeds 8, the water solubility decreases. In addition, m is preferably an integer of 8 or less in order to impart flexibility while maintaining good water resistance, depending on the application.

Examples of the repeating unit of the alkylene oxide chain include those represented by the above general formulas (1) and (2). Of these, the water-soluble point in the alkylene oxide Those containing 50 mol% or more of the repeating unit represented by the general formula (1) are preferable.

The soybean protein used in the present invention is a known soybean protein and is not particularly limited as long as it contains at least a soybean protein component. Examples of such soybean protein include full-fat soybean, defatted soybean, soymilk, concentrated soybean protein, isolated soybean protein and the like. The amount of the protein component in these soybean proteins is preferably 90% by weight or more from the viewpoint of the transparency of the produced film. The structure of soybean protein purified from soybean is usually a macromolecule composed of about 20 kinds of polyamino acids, the average molecular weight of which is about 350,000, and about 1,000 carboxyl groups and about 300 carboxyl groups per molecule. It has an amino group, about 30 thiol groups and a small amount of hydroxyphenyl groups. It is also known that by heating the soybean protein, etc., several macromolecules or several tens of macromolecules are bound to each other. The modified soybean protein of the present invention has a structure in which soybean proteins are bound to each other via a specific binding unit.

Next, the method for producing the modified soybean protein of the present invention will be described. The modified soybean protein of the present invention is a polyfunctional epoxy compound (B) having a repeating unit composed of an alkylene oxide chain represented by the general formula (1) and / or the general formula (2) in the molecule of the soybean protein (A). It is obtained by reacting with a crosslinking agent consisting of

-(CH ₂ CH ₂ O) m- (1)

[Chemical 6] [In general formula (1) and general formula (2), m and n are the same as the above. ]

The polyfunctional epoxy compound (B) is preferably a diepoxy compound in that the crosslink density does not become too high and flexibility can be imparted.

Examples of diepoxy compounds used in the present invention include triethylene glycol diglycidyl ether and polyethylene glycol diglycidyl ether having a higher molecular weight, tripropylene glycol diglycidyl ether and polypropylene glycol diglycidyl having a higher molecular weight. Examples thereof include ether and poly (oxyethylene / oxypropylene) copolymer [random type or block type] diglycidyl ether. Of these, when particularly high flexibility is required, the polyfunctional epoxy compound is preferably a high molecular weight polyethylene glycol diglycidyl ether from the viewpoint of maintaining water resistance.

Further, a trifunctional or higher functional epoxy compound may be used in combination with the diepoxy compound within an allowable range of imparting water solubility and flexibility. Examples of the trifunctional or higher functional epoxy compound include triglycidyl ether of an ethylene oxide adduct of glycerin, triglycidyl ether of a propylene oxide adduct of glycerin, and the like.

The polyfunctional epoxy compound has a molecular weight of 250.
The above is preferable. This molecular weight has a meaning for imparting flexibility to the soy protein which is originally hard and brittle. Further, a diepoxy compound having a molecular weight of 250 or more can be used in combination with a diepoxy compound having a molecular weight of less than 250, if necessary.

That is, when the molecular weight of the polyfunctional epoxy compound is less than 250, the flexible modified soybean protein of the present invention cannot be obtained and a hard one with little elongation can be obtained, which is not preferable. However, a polyfunctional epoxy compound having a molecular weight of 250 or more can be used in combination with a polyfunctional epoxy compound having a molecular weight of 250 or more within a range not impairing the object of the present invention.

Of the diepoxy compounds mentioned above, water-soluble diepoxy compounds are preferred when the modified soybean grain of the present invention is produced in an aqueous medium. The water-soluble diepoxy compound means a compound having a dissolution rate of 50% or more when added to water at room temperature so as to have a concentration of 10% by weight.

The reaction between the soybean protein and the polyfunctional epoxy compound is not particularly limited, but usually, the soybean protein and the polyfunctional epoxy compound are mixed in water adjusted to an appropriate pH range at room temperature to 100 ° C., preferably at room temperature. It is carried out by stirring and mixing at -80 ° C in the absence of a catalyst or, if necessary, in the presence of a catalyst. Usually, when soybean protein is dispersed in an acidic aqueous solution, strict pH control is required to stabilize the dispersion system, and it is difficult to secure stability. Therefore, it is preferable to disperse soybean protein in an alkaline aqueous solution. In this case, destabilization of the dispersion system due to pH change is small.

The amount of the polyfunctional epoxy compound used with respect to the soybean protein is not particularly limited, but it depends on the flexibility required for the molded product of the modified soybean protein and the amino group, carboxyl group and thiol contained in the soybean protein. Although it is determined depending on the total number of moles of the group, it is usually used in an amount of 1 to 80% by weight, preferably 5 to 60% by weight.

When the soybean protein and the polyfunctional epoxy compound are reacted, various additives can be added as required. Examples of the additives include stabilizers such as antioxidants, lubricants, pigments, fillers and antistatic agents.

Next, the modified soybean protein molded article of the present invention will be described. Since the modified soybean protein is obtained in an aqueous medium, the shape of the molded article obtained from this is, for example, a sheet shape, a film shape, a fibrous shape or the like. Of these shapes, the molded article of the present invention has both water resistance and flexibility, and in order to make full use of these characteristics, it is preferable to mold into a film shape. Molded articles having these shapes can be obtained by molding the modified soybean protein obtained above by a casting method or a heat calendar method.

The modified soybean protein obtained by the present invention is
It has water resistance and flexibility that cannot be obtained with the original hard and brittle soybean protein, and can be applied to applications such as agricultural films, horticultural films, and packaging films.

[0028]

EXAMPLES The present invention will now be described with reference to specific examples, but the present invention is not limited to these examples.
Parts and% in the examples relate to weight unless otherwise specified.

<Measurement Method of Physical Properties of Film and Evaluation Criterion> 1) Flexibility The films obtained in Examples and Comparative Examples described later were subjected to relative humidity of 6
At 5 ± 3%, the degree of cracking when bent 90 degrees at a corner of 1 mm in diameter was observed. It was evaluated as − when it was cracked, ++ when it was bendable, and ++ when it was partially broken.

2) Tensile Strength and Elongation The films obtained in Examples and Comparative Examples described below were conditioned for a whole day at a relative humidity of 65 ± 3%,
5 strip-shaped test pieces with a width of 10 mm and a length between marked lines of 20 mm
This was prepared, and the breaking strength (MPa) and the maximum elongation (%) when stretched at a tension rate of 200 mm / min were measured using an autograph (tensile tester) manufactured by Shimadzu Corporation.

3) Degree of water swelling A strip-shaped film test piece similar to that used in 2) above was immersed in water at room temperature for 65 hours, and the thickness, width and length of the test piece were measured and tested. The volume of the piece was calculated, and the volume expansion rate (%) was calculated from this volume and the volume before swelling that was measured in advance.

Example 1 Fuji Pro-F [isolated soybean protein (hereinafter referred to as SPI), moisture 5.8%; Fuji Oil Co., Ltd.] 10.65 g was added to deionized water 100 ml in a commercially available juicer mixer. Then, after uniformly dispersing at room temperature, the reaction system was adjusted to pH 9 by adding a 1.5 mol / l caustic soda aqueous solution, and further dispersed and mixed. 3.0 g of Denacol EX-821 (polyethylene glycol diglycidyl ether, 4 ethylene oxide units, molecular weight of about 306, solubility in 100% concentration aqueous solution; Nagase Kasei) was added to the obtained dispersion. 30 with SPI
%) And uniformly mixed, and then cast on a polyethylene terephthalate (hereinafter referred to as PET) sheet coated with a release agent and dried at room temperature. When the obtained film was heat treated at 80 ° C. for 15 minutes, the physical properties of the obtained film (thickness: 63 μ) were as shown in Table 1.

[Example 2] In Example 1, instead of Denacol EX-821, Denacol EX-830
(Polyethylene glycol diglycidyl ether, 9 ethylene oxide units, molecular weight of about 526, dissolution rate in 10% concentration aqueous solution is 100%; manufactured by Nagase Kasei)
Example 1 except that g (30% with respect to SPI) was added.
Similarly to the above, a dry film was prepared at room temperature by casting. When the produced film was heat-treated at 80 ° C. for 15 minutes, the physical properties of the obtained film (thickness: 61 μ) were as shown in Table 1.

[Example 3] In Example 1, instead of Denacol EX-821, Denacol EX-861
(Polyethylene glycol diglycidyl ether, 22 ethylene oxide units, molecular weight about 1100, 10%
A dry film was prepared at room temperature by casting in the same manner as in Example 1 except that 3.0 g (made by Nagase Kasei Co., Ltd.) having a dissolution rate of 100% in a concentrated aqueous solution; When the produced film was heat-treated at 80 ° C. for 15 minutes, the physical properties of the obtained film (thickness: 59 μ) were as shown in Table 1.

[Example 4] The amount of Denacol EX-830 used in Example 2 was 5.0 g (versus SPI: 50).
%), A dry film was prepared at room temperature by casting in the same manner as in Example 2. When the produced film was heated at 80 ° C. for 15 minutes, the physical properties of the obtained film (thickness: 68 μ) were as shown in Table 1.

[Embodiment 5] In Embodiment 2, the amount of Denacol EX-830 used was 1.5 g (versus SPI: 15 g).
%), A dry film was prepared at room temperature by casting in the same manner as in Example 2. When the produced film was heated at 80 ° C. for 15 minutes, the physical properties of the obtained film (thickness: 55 μ) were as shown in Table 1.

[Example 6] In Example 1, instead of Denacol EX-821, Denacol EX-920
(Polypropylene glycol diglycidyl ether, 3 propylene oxide units, molecular weight 304, 10%
A dry film was prepared at room temperature by casting in the same manner as in Example 1 except that 3.0 g (made by Nagase Kasei Co., Ltd.) having a dissolution rate of 100% in a concentrated aqueous solution; When the produced film was heat-treated at 80 ° C. for 15 minutes, the physical properties of the obtained film (thickness: 64 μ) were as shown in Table 1.

[Example 7] Before adding Denacol EX-861 in Example 3, 0.1 g of NaHSO3 (1.0% by SPI) was added to the dispersion liquid adjusted to pH 9, and the mixture was cooled to room temperature. A dried film was prepared at room temperature by casting the finally obtained dispersion liquid in the same manner as in Example 3 except that the mixture was further mixed for a certain period of time. When the produced film was heat-treated at 80 ° C. for 15 minutes, the physical properties of the obtained film (thickness: 51 μ) were as shown in Table 1.

[Example 8] In Example 1, instead of Fujipro-F as soybean protein, New Fujipro-1 was used.
200 (water content 5.8%; made by Fuji Oil Co., Ltd.)
In the same manner as in Example 1, a dry film was prepared by casting at room temperature. The produced film was heat-treated at 80 ° C. for 15 minutes, and the obtained film (thickness: 58 μ)
The physical properties of are shown in Table 1.

Comparative Example 1 In a commercially available juicer mixer, 10.65 g of Fujipro-F and 3.0 g of glycerin (30% based on SPI) were added to 100 ml of deionized water and uniformly dispersed at room temperature. After that, the reaction system was adjusted to pH 9 by adding a 1.5 mol / l caustic soda aqueous solution, and further dispersed and mixed. The obtained dispersion was cast on a PET sheet coated with a release agent and dried at room temperature. When the produced film was heat treated at 80 ° C. for 15 minutes,
The physical properties of the obtained film (thickness: 60 μ) are shown in Table 1.

Comparative Example 2 Fuji Pro-F 10.65 g was added to deionized water 100 ml in a commercially available juicer mixer.
After adding to the inside and uniformly dispersing at room temperature, 1.5 mol /
The reaction system was adjusted to pH 9 by the addition of 1 L of an aqueous solution of caustic soda, and further dispersed and mixed. To the obtained dispersion, 3.0 g of Denacol EX-810 (ethylene glycol diglycidyl ether, molecular weight: 174, dissolution rate in 10% concentration aqueous solution: 100%; manufactured by Nagase Kasei) was used (3% by SPI).
0%) was added and uniformly mixed, and then cast on a PET sheet coated with a release agent and dried at room temperature. When the produced film was heated at 80 ° C. for 15 minutes, the physical properties of the obtained film (thickness: 58 μ) were as shown in Table 1.

COMPARATIVE EXAMPLE 3 In a commercially available juicer mixer, 10.65 g of Fujipro-F and 3.0 g of glycerin (30% based on SPI) were added to 100 ml of deionized water and uniformly dispersed at room temperature. After that, the reaction system was adjusted to pH 9 by adding a 1.5 mol / l caustic soda aqueous solution, and further dispersed and mixed. Denacol EX- was added to the obtained dispersion.
1.0 g of 810 (10% with respect to SPI) was added and uniformly mixed, and then cast on a PET sheet coated with a release agent and dried at room temperature. Produced film 1 at 80 ℃
After heat treatment for 5 minutes, the obtained film (thickness: 65
The physical properties of () were as shown in Table 1.

[Comparative Example 4] In Comparative Example 2, in the obtained dispersion liquid, instead of Denacol EX-810, Denacol EX-313 (glycerin polyglycidyl ether, molecular weight: 260, dissolution rate in 10% concentration aqueous solution) Is 9
9%; made by Nagase Kasei) 3.0 g (30% of SPI)
It was dried at room temperature by casting in the same manner as in Comparative Example 2 except that it was added. Produced film 1 at 80 ℃
After heat treatment for 5 minutes, the obtained film (thickness: 52
The physical properties of () were as shown in Table 1.

As is clear from Table 1, by modifying soybean protein with the specific polyfunctional epoxy compound constituting the present invention, modified soybean protein excellent in water resistance and flexibility can be obtained. It can be seen that a processed product having excellent water resistance and flexibility can be obtained by processing into a molded product such as a film or a sheet.

[0045]

[Table 1]

* Gly: glycerin EX-821: Denacol EX-821, polyethylene glycol diglycidyl ether, 4 ethylene oxide units, MW = 306, dissolution rate in 10% aqueous solution = 1
00%) EX-830: Denacol EX-830, polyethylene glycol diglycidyl ether, 9 ethylene oxide units, MW = 526, dissolution rate in 10% aqueous solution = 1
00%) EX-861: Denacol EX-861, polyethylene glycol diglycidyl ether, 22 ethylene oxide units, MW = 1100, dissolution rate in 100% aqueous solution = 100%) EX-920: Denacol EX-920, polypropylene glycol Diglycidyl ether, 3 propylene oxide units, MW = 304, dissolution rate in 10% aqueous solution = 100%) EX-810: Denacol EX-810 (ethylene glycol diglycidyl ether, 1 ethylene oxide unit, MW = 174, Dissolution rate in 10% aqueous solution = 100
%) EX-313: Denacol EX-313, glycerin polyglycidyl ether, MW = 260, dissolution rate in 10% aqueous solution = 99%)

[0047]

EFFECTS OF THE INVENTION The modified soybean protein of the present invention can be molded to obtain a molded product such as a film or sheet having excellent water resistance and excellent flexibility with a balanced balance between tensile strength and elongation. .

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Claims (6)

[Claims] 1. A modified soybean protein having a repeating unit composed of an alkylene oxide chain in the molecule, wherein the repeating unit composed of an alkylene oxide chain bonded to a modified site of the modified soybean protein has the general formula (1) and / or Alternatively, a modified soybean protein represented by the general formula (2). _{- (CH 2 CH 2 O)} m- (1) ## STR1 ## [In general formula (1) and general formula (2), m is an integer greater than or equal to 3, and n is an integer of 3-8. ] 2. The repeating unit represented by the general formula (1) is 50 in the repeating unit consisting of an alkylene oxide chain.
The modified soybean protein according to claim 1, which is at least mol%. _{- (CH 2 CH 2 O)} m- (1) 3. A soybean protein (A) and a polyfunctional epoxy compound (B) having a repeating unit composed of an alkylene oxide chain represented by the general formula (1) and / or the general formula (2) in the molecule as a cross-linking agent. A method for producing a denatured soybean protein, which comprises reacting with and in an aqueous medium. _{- (CH 2 CH 2 O)} m- (1) ## STR2 ## [In general formula (1) and general formula (2), m is an integer greater than or equal to 3, and n is an integer of 3-8. ] 4. The method for producing a modified soybean protein according to claim 3, wherein the polyfunctional epoxy compound (B) has a molecular weight of 250 or more. 5. The method for producing a modified soybean protein according to claim 3, wherein the polyfunctional epoxy compound (B) is a diepoxy compound. 6. A molded product obtained by molding the modified soybean protein according to claim 1 or 2.