FIELD OF THE INVENTION

This invention relates to novel carboxymethyl-

etherified starch derivatives and its manufacturing method

and more particularly, to the novel carboxymethyl-

etherified starch derivatives and its manufacturing method,

wherein its viscosity in 5S> aqueous solution is 15-600 cps,

when measured by a viscometer in Ha e rotary type ,

permeability in 0.1& aqueous solution shows more than 95%

in 625 nm, when measured by UV spectrophotometer ; viscosity

values at the maximum temperature of 95 ^C C and at the

temperature cooled to 50 , are 6-304 Bϋ and 6-720 Bϋ,

respectively when measured by Brabender viscometer.

DESCRIPTION OF THE RELATED ART

In general, etherified or esterified starch

derivatives have been used as an enhancer and stabilizer

for viscosity in the foods industry ; a carrier designed to

manufacture dyestuff and dyeing agents in the crude dyeing

industry. Further said derivatives are being widely used in

other industries such as papers, pharmaceuticals, etc. The

starch derivatives include methylated starch, ethylated

starch, hydroxyethyl starch, hydroxypropyl starch,

carboxymethyl starch, formic acid starch, acetic acid

starch, hydroxypropylpropionic acid starch, and butylic

acid starch. Said starch derivatives, showing a relatively

high viscosity in 10 to 20% aqueous solution have a poor

transparency and when exposed at room temperature, their

weak resistance to microorganisms may give rise to the

formation of mold. In addition, since there are a wide gap

of viscosities between the maximum temperature of 95°C and

cooled temperature of 50t, when measured by Brabender

viscometer, said starch derivatives is a weak resistance to

the aging when they are cooled after the increase of the

temperature.

In U.S. Pat. No. 4837314 a method of manufacturing

hydroxypropyl starch with low viscosity of less than

15,000 cps (Brookfield viscometer, 20 rpm) at relatively high

concentration (10% aqueous solution) has been disclosed.

However, since highly inflammable propylene oxide have to

be employed as an etherifing agent in the manufacturing

process, special care should be exercised for the

prevention of explosion in the actual production.

In the Japanese Kokai Patent Nos. 91-146502 and

91-146503 which refer to the manufacture of carboxymethyl-

etherified salts of starch having the average degree of

substitution of more than 0.2 through the reaction of sweet

potato or corn starch with alkali in the presence of

aqueous solution of etherifing agent, another method of

manufacturing carboxymethyl-etherified salts of sweet

potato starch having the average degree of substitution of

more than 0.2 has been also disclosed. According to said

conventional method, more than 7 moles of water as reaction

medium should be used to 1 mole of sweet potato starch. Even

though the degree of substitution is good, larger facility

should be established due to requirement of a lot of water

in the manufacturing process and with more complicated

re-processes involved in pulverizing, neutralizing and

purifying the molding, the transparency proves to be poor.

SUMMARY OF THE INVENTION

To be free from the aforementioned shortcomings, the

object of this invention is to provide cool water-soluble

carboxymethyl-etherified starch derivatives, characterized

in that ; said starch derivatives in 10 to 20% aqueous

solution may have low viscosity, said starch derivatives

in low concentration may have high viscosity, the

transparency of said starch derivatives in 0.1% aqueous

solution has more than 95%, when measured by UV

spectrophotometer, said starch derivatives have a

resistance to microorganisms, said starch derivatives, in

heating and cooling, have a strong resistance to the aging.

According to this invention, the cool water-soluble

carboxymethyl-etherified starch derivatives are prepared

in the following steps : Some starches (e.g., corn, potato,

wheat and rice) as main materials are dissolved in organic

solvents such as lower alcohol without hydrolysis, or

hydrolyzed in the presence of inorganic acids such as

hydrochloric acid or sulfuric acid at 25 to 75'C for 30

minutes to 72 hours. Then, with the addition of etherifing

agent in the presence of alkali, some organic solvent such

as lower alcohol was further added to the mixture for

reaction thereof. The reactant was neutralized, purified

with organic solvents and dried to give the cool

water-soluble carboxymethyletherified starch derivatives.

According to this invention, the lower alcohol

presents lower alcohols of C1-3, includes methanol, ethanol

or isopropyl alcohol while using caustic soda (NaOH) or KOH

as alkali. The etherifing agent presents etherifing agents

having one functional group, includes lower alkylhalides of

C1-4, lower alkyldisulfates of C1-4, lower alkylene oxides,

halogenated lower carboxylic acids and its salts. Further

more specifically, said halides include methyl chloride or

ethyl chloride, disulfates include dimethylsulfate or

diethylsulfate, oxides include ethylene oxide or propylene

oxide, carboxylic acid or its salts include

monochloroacetic acid, bromoacetic acid or its alkali metal

salts. Among them, monochloroacetic acid is the most

preferable in embodying this invention.

Hence, the reaction temperature for etherification is

20-75 ^* 0 and the reaction time is 30 minutes to 3 hours. For

the etherification reaction, some alkali materials

including alkali metal oxide or its hydroxide or ammonium

hydroxide may be employed together with etherifing agent.

Among them, caustic soda (sodium hydroxide) is preferably

used for better etherification reaction and said reaction

may be efficiently conducted in approx. 20-70% aqueous

solution, preferably in 30—60% aqueous solution. In a water

system containing less than 20% in alkali concentration,

half amounts of added monochloroacetic acid is hydrolyzed

and this may affect the yield thereto. In case of exceeding

70% in alkali concentration, starches are sparsingly

soluble to water so that reaction cannot be conducted

homogeneously.

After etherification reaction is completed, the

reactant during purification should not be made in the form

of paste or gelatination and its desalting process is

performed with common methods such as inclination,

filtration and centrifuge.

The cool water-soluble carboxymethyl-etherified

starch derivatives manufactured in accordance with this

invention are characterized in that;- In case of 0.1%

aqueous solution of said derivatives measured by UV

spectrophotometer in 625 nm, its permeability shows more

than 95%, - In case of 5% aqueous solution of said

derivatives measured by a viscometer in Hakke rotary type,

its viscosity ranges 15-600 cps, and when measured by

Brabender viscometer, the viscosity is 6-304 BU at the

maximum temperature of 95 ^° C and 6-720 BU at the cooled

temperature, - In case of 5—20% aqueous solution of said

derivatives, its long-term storage testing at room

temperature (25 ^* C) for 6 months revealed the resistance

against bacteria.

Compared with the conventional carboxymethyl¬

etherified starch derivatives, therefore, it is well

understood that the carboxymethyl-etherified starch

derivatives of this invention is superior in terms of

transparency, viscosity, bacteria-resistance and aging.

This invention is explained in more detail by the

following examples.

EXAMPLE 1

500 g of potato starch was dissolved in 755 ml of

methanol and with the addition of 248.2 g of

monochloroacetic acid (CICH2COOH), the mixture was stirred

for one hour. Then, a solution containing 312 g of caustic

soda dissolved in 428.5 g of water was added to said mixture

and stirred at 37 ^° C for 50 minutes. The reactant was

neutralized, purified with 85% methanol and dried to give a

dried product (1).

As shown in Fig. 1, the test results of 0.1% aqueous

solution of said dried product(1), so prepared, revealed

that transparency measured by UV spectophotometer was 96.5%

in 625 nm. Further the test results of 5% aqueous solution

were as follows : - Viscosity was 500 cps at the shear rate

of 150 sec ^"1 , when measured by a viscometer in Hakke rotary

type ; - Formation of bacteria was not detected from the

long-term storage testing at room temperature (25 ^* C) for 6

months ; - Viscosities at the maximum temperature of 95 ^C C

and at a temperature cooled to 50 ^° C were 304 BU and 430 BU,

respectively when measured by Brabender viscometer.

The test conditions and their evaluation of Fig.1 are

as follows :

1) Test conditions

Moisture : 18.0 [%] Correction : 14.0 [%]

Corr. to 14% : 20.0 [g] Sample weight : 20.0 [g]

Corr. to 14% : 399.1 [ml] Water : 400.0 [ml]

Speed 70 [r/min] Meas. range : 1000 [cmg]

Start temp. : 30 [°C] Heat/cool rate : 1.5 [°C/min]

Max. temp. : 95 [TJ] Up. hold time : 15 [min]

End temp. 50 [IC] Fin. hold time : 15 [min]

2) Evaluation

EXAMPLE 2

500 g of corn starch was hydrolyzed with 0.5N-

hydrochloric acid at 25"C for 30 minutes and with the

addition of 205 g of monochloroacetic acid and 1180 ml of

methanol as solvent, the mixture was stirred for one hour.

Then, a solution of caustic soda containing 189 ml of

caustic soda dissolved in 400 ml of water was added to said

mixture and stirred at 50°C for 2.5 hours. The reactant was

neutralized, purified with 90% methanol and dried to give a

dried product (2).

0.1% aqueous solution of said dried product (2) was

prepared and its transparency measured based upon the same

method as described in Example 1 was 95.1% in 625 nm. Further

the test results of 5% aqueous solution which was left for

6 months revealed that there was no formation of bacteria.

EXAMPLE 3

500 g of potato starch was hydrolyzed with 4N-

hydrochloric acid at 50 ^° C for 45 minutes and with the

addition of 250 g of monochloroacetic acid and 1328 ml of

ethanol as solvent, the mixture was stirred for one hour

and twenty minutes. Then, 245 g of caustic soda was added to

said mixture and stirred at room temperature for 3 hours.

The reactant was neutralized, purified with 75% methanol

and dried to give a dried product (3).

0.1% aqueous solution of said dried product (3) was

prepared and its transparency measured based upon the same

method as described in Example 1 was 95.6% in 625 nm. Further

the test results of 5% aqueous solution which was left for

6 months revealed that there was no formation of bacteria.

EXAMPLE 4

500 g of potato starch was hydrolyzed with 3N-

hydrochloric acid at 25T: for 30 minutes and with the

addition of 248 g of monochloroacetic acid and 1250 ml of

ethanol as solvent, the mixture was stirred for 1.5 hours.

Then, a solution of caustic soda containing 275 g of caustic

soda dissolved in 612 ml of water was added to said mixture

and stirred at 60°C for 2 hours. The reactant was

neutralized, purified with 90% methanol and dried to give a

dried product (4).

As shown in Fig. 2, the test results of 0.1% aqueous

solution of said dried product(4), so prepared, revealed

that transparency based upon the same method as described

in Example 1 was 98.2%. Further the test results of 5%

aqueous solution were as follows : - Viscosity was 500 cps

at the shear rate of 150 sec ^"1 , when measured by a viscometer

in Hakke rotary type ; - Formation of bacteria was not

detected from the long-term storage testing at room

temperature (25"O for 6 months ; - Viscosity values at 30°C,

95°C and at a temperature cooled again to 50"C were 562 BU,

207.0 BU and 254 BU, respectively when measured by Brabender

viscometer.

The test conditions and their evaluation of Fig.2 are

as follows:

1) Test conditions

Moisture : 18.0 [%] Correction : 14.0 [%]

Corr. to 14% : 15.7 [g] Sample weight : 15.0 [g]

Corr. to 14% : 299.2 [ml] Water 300.0 [ml]

Speed : 70 [r/min] Meas. range : 1000 [cmg]

Start temp. : 30 [TJ] Heat/cool rate : 1.5 [T /min]

Max. temp. 95 TC] Up. hold time : 15 [min]

End temp. 50 [TJ] Fin. hold time : 15 [min]

2) Evaluation

EXAMPLE 5

500 g of potato starch was hydrolyzed with 5N-

hydrochloric acid at room temperature for 72 hours and with

the addition of 248 g of monochloroacetic acid and 1280 ml

of ethanol as solvent, the mixture was stirred for 1 hour.

Then, 200 g of caustic soda was added to said mixture and

stirred at 45°C for 2 hours. The reactant was neutralized,

purified with 80% methanol and dried to give a dried

product (5).

As shown in Fig. 3, the test results of 0.1% aqueous

solution of said dried product (5), so prepared, revealed

that transparency based upon the same method as described

in Example 1 was 96.9%. Further the test results of 5%

aqueous solution were as follows : - Formation of bacteria

was not detected from the long-term storage testing for 6

months ; - Viscosity values at 30TJ, 95TJ and 50Tj were 23 BU,

7 BU and 6 BU, respectively when measured by Brabender

viscometer.

The test conditions and their evaluation of Fig.3 are

as follows:

1) Test conditions

Moisture : 18.0 [%] Correction : 14.0 [%]

Corr. to 14% : 15.7 [g] Sample weight : 15.0 [g]

Corr. to 14% 299.2 [ml] Water 300.0 [ml]

Speed 70 [r/min] Meas. range : 1000 [cmg]

Start temp. 30 [Tj] Heat/cool rate : 1.5 [TJ/min]

Max. temp. 95 [TJ] Up. hold time : 10 [min]

End temp. 50 [TJ] Fin. hold time : 20 [min]

2) Evaluation

EXAMPLE 6

500 g of potato starch was hydrolyzed with 2.8N-

hydrochloric acid at 40TJ for 40 minutes and with the

addition of 355 g of monochloroacetic acid and 2500 ml of

ethanol as solvent, the mixture was stirred for one hour

and 25 minutes. Then, a solution of caustic soda containing

295 g of caustic soda dissolved in 613 ml of water was added

to said mixture and stirred at 70'C for 2 hours. The

reactant was neutralized, purified with 90% methanol and

S dried to give a dried product (6).

As shown in table 4, the test results of 0.1% aqueous

solution of said dried product (6), so prepared, revealed

that transparency based upon the same method as described

0 in Example 1 was 96.S%. Further the test results of 20%

aqueous solution were as follows : - Formation of bacteria

was not detected from the long-term storage testing for 6

months ; - Viscosity values at 30TJ, 95TJ and 50TJ were 18 BU,

8 BU and 6 BU, respectively when measured by Brabender

viscometer. The difference of viscosity from 95TJ to 50TJ is

2 BU.

The test conditions and their evaluation of Fig.4 are

as follows:

1) Test conditions

Moisture : 18.0 [%] Correction : 14.0 [%]

Corr. to 14% : 15.7 [g] Sample weight : 15.0 [g]

Corr. to 14% : 299.2 [ml] Water : 300.0 [ml]

Speed : 70 [r/min] Meas. range : 1000 [cmg]

Start temp. : 30 [TJ] Heat/cool rate : 1.5 [TJ/min]

Max. temp. : 95 [TJ] Up. hold time : 15 [min]

End temp. 50 [T ] Fin. hold time : 15 [min]

2) Evaluation

COMPARATIVE EXAMPLE 1

As shown in Fig. 5, the viscosity values of Pullulan

(Hayashibara, Japan) containing non-carboxymethyl starch

derivatives, which was purchased from the local market,

were measured by Brabender viscometer ; 10 BU at the initial

temperature of 30TJ, 78 Bϋ at 95TJ and 6 BU at 80TJ.

The test conditions and their evaluation of Fig.5 are

^s as follows:

1) Test conditions

Moisture : 18.0 [%] Correction 14.0 [%]

Corr. to 14% : 20.9 [g] Sample weight : 20.0 [g]

] J> Corr. to 14% : 399.1 [ml] Water : 400.0 [ml]

Speed : 70 [r/min] Meas. range : 1000 [cmg]

Start temp. : 30 [Tj] Heat/cool rate : 1.5 [Tj/min]

Max. temp. 95 [T ] Up. hold time : 15 [min]

15 End temp. 50 [T ] Fin. hold time : 15 [min]

2)Evaluation

0

COMPARATIVE EXAMPLE 2

As shown in Fig. 6, the viscosity values of potato

starch raw materials, which were purchased from the local

market, were measured by Brabender viscometer; 243 BU at 95°C

and 419 BU at 80TJ.

The test conditions and their evaluation of Fig.6 are

as follows:

1) Test conditions

Moisture : 18.0 [%] Correction 14.0 [%]

Corr. to 14% : 20.9 [g] Sample weight : 20.0 [g]

Corr. to 14% : 399.1 [ml] Water : 400.0 [ml]

Speed : 70 [r/min] Meas. range : 1000 [cmg]

Start temp. : 30 [T ] Heat/cool rate : 1.5 [Tj/min]

Max. temp. 95 [TJ] Up. hold time : 15 [min]

End temp. 50 [TJ] Fin. hold time : 15 [min]

2) Evaluation

For reference Fig.7 is a viscograph showing the test

results on Examples 1, 4, 5, 6 of this invention and Pullulan

of comparative example 1 in 5% aqueous solution, which

measured by a viscometer in Hakke rotary type.

From the aforementioned tests, it is well understood

that the cool water-soluble carboxymethyl-etherified

starch derivatives manufactured in accordance with this

invention are characterized in that ; - In case of 0.1%

aqueous solution of said derivatives measured by UV

spectrophotometer in 625 nm, its permeability shows more

than 95%, - In case of 5% aqueous solution of said

derivatives measured by a viscometer in Hakke rotary type,

its viscosity ranges 15-600 cps, and when measured by

Brabender viscometer, the viscosity is 6-304 BU at the

maximum temperature of 95TJ and 6-720 BU at the cooled

temperature of 50TJ, - In case of 5-20% aqueous solution of

said derivatives, its long-term storage testing at room

temperature (25TJ) for 6 months revealed the resistance

against bacteria.

Now that the carboxymethyl-etherified starch

derivatives of this invention in relatively high

concentration of 10-20% aqueous solution may be freely

controlled in any level of viscosity, that is, from the high

concentration and low viscosity to the low concentration

and high viscosity. Various kinds of starch derivatives of

the invention having the extended solubilities of 1%, 5%,

10%, 20% and 30% and having a property of from the

relatively low concentration and high viscosity to the

high concentration and low viscosity, may be widely applied

in the industrial fields involved.

BREIF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a viscograph in which starch derivatives,

manufactured according to Example 1 of this invention, are

measured by Brabender viscometer,

Fig. 2 is a viscograph in which starch derivatives,

manufactured according to Example 4 of this invention, are

measured by Brabender viscometer,

Fig. 3 is a viscograph in which starch derivatives,

manufactured according to Example 5 of this invention, are

measured by Brabender viscometer,

Fig. 4 is a viscograph in which starch derivatives,

manufactured according to Example 6 of this invention, are

measured by Brabender viscometer,

Fig.5 is a viscograph in which Pullulan, a well-known

substance, is measured by Brabender viscometer,

Fig. 6 is a viscograph in which potato starch is

measured by Brabender viscometer,

Fig. 7 is a viscograph showing the test results on

Examples 1, 4, 5, 6 of this invention and Pullulan of

comparative example 1 in 5% aqueous solution, when measured

by a viscometer in Hakke rotary type