JP3440233B2 - Method for producing polyamino acid - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polyamino acid excellent in biodegradability and a method for producing the polyamino acid.

[0002]

2. Description of the Related Art Conventional polyaspartic acid is manufactured by a dehydration method in which aspartic acid solid is heated to remove water, and it is used in the presence of an acid catalyst by using various dryers, kneading heating devices, ovens and the like (US Pat. , US5457
176, US 5830985), in the absence (US 539).
1764, US Pat. No. 5,319,145), a method of heating dehydration condensation of aspartic acid solid at around 200 ° C., a method of heating in an organic solvent having a high boiling point, and azeotropically removing water released by the condensation (US5380817, US54).
84945, US5756595) and the like have been proposed.

In the above-mentioned method, when using sulfuric acid, phosphoric acid or boric acid as the acid catalyst, the polymerization is carried out while removing the water produced during the polymerization, or the acid catalyst is uniformly mixed with aspartic acid. A method using water is disclosed. However, in these methods, even if water is present in the initial stage of the reaction, water is removed by decompression, a nitrogen stream, azeotropic distillation, or the like during polymerization to obtain a substantially dry solid polymer.

[0004] In these methods, solids may become agglomerates during the polymerization, so it was necessary to disintegrate during the polymerization. In particular, when an acid catalyst was used, candy-like lumps were formed during the polymerization, and it was necessary to disintegrate them.

Further, in these methods, the product obtained by heating aspartic acid is solid polysuccinimide which is an intermediate of polyaspartic acid, and the polyaspartic acid salt is further hydrolyzed with a base. Is obtained.

[0006]

An object of the present invention is to directly obtain an acid-type polyamino acid by a method that does not form a lump when a polyamino acid is obtained by condensing an amino acid that requires aspartic acid. is there.

Another object of the present invention is to provide a novel polyaspartic acid.

In the conventional method, the polymerization is carried out while removing the water produced by the polymerization. Surprisingly, when an amino acid containing aspartic acid as an essential component is suspended in water and heated, Polyamino acid is produced even in the presence of the polymer, the polymer yield is 80% or more, and the produced polymer is obtained in a state of being dissolved in water. The polymer is an acid type polyamino acid-based polymer. The inventors have found that there is and have completed the present invention.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to prepare a pressure resistant mixture of an amino acid containing aspartic acid as an essential component and water .
The method for producing a polyamino acid is characterized in that it is heated in a closed container or under pressure feeding of the mixture .

[0010]

The technical scope of the present invention is not limited to the language described in each of the claims, but extends to a range easily replaced by those skilled in the art.

[0012]

DETAILED DESCRIPTION OF THE INVENTION Polyaspartic acid as used herein also includes salts of polyaspartic acid. Counterions for polyaspartic acid include, but are not limited to, alkali and alkaline earth metals, specifically sodium, potassium, magnesium, calcium, strontium, and ammonium cations. A polyamino acid obtained from an amino acid that requires aspartic acid is also referred to as polyaspartic acid.

In the present invention, an amino acid which essentially contains aspartic acid is used as a raw material. As aspartic acid, L-form, D-form, or a mixture thereof can be used. In addition to aspartic acid, up to 100% by weight of one or more other amino acids may be mixed and polymerized with respect to the weight of aspartic acid. As the amino acid copolymerized with aspartic acid,
Glycine, alanine, asparagine, glutamic acid, lysine, valine, leucine, isoleucine, phenylalanine, methionine, histidine, proline, serine, threonine, cysteine, etc., among them, are inexpensive amino acids, and water-soluble polymerized products L-glutamic acid, L-alanine and L-lysine are preferred because of their high properties. Among the polyamino acids, polyaspartic acid is most preferable from the viewpoint of biodegradability.

In the present invention, polyaspartic acid can be obtained by heating an amino acid containing aspartic acid as an essential component (hereinafter, also simply referred to as aspartic acid) in the presence of water.

The amount of water used for polymerizing aspartic acid by heating is not particularly limited with respect to the weight of amino acids mainly consisting of aspartic acid, but the lower limit is usually 0.2 times or more, preferably 0. 0.5 times or more, more preferably 1 time or more, while the upper limit is 40 times or less, preferably 20 times or less, more preferably 10 times or less. That is, the amount of water is 0.2 to 40 times, preferably 0.5 to 20 times, the weight of amino acids mainly containing aspartic acid.
A double range is desirable. If it is less than 0.2 times, the polymer obtained by the polymerization becomes bulky, which is not preferable. Also, 4
When it exceeds 0 times, the concentration of the resulting polymer aqueous solution becomes low, which is not economically preferable.

The heating temperature is not particularly limited, but the lower limit is usually 140 ° C. or higher, preferably 150 ° C. or higher, more preferably 160 ° C. or higher, while the lower limit is 300.
℃ or less, preferably 250 ℃ or less, more preferably 2
It is 20 ° C or lower. That is, the heating temperature is 140 to 30.
It is desirable that the temperature is 0 ° C, preferably 150 to 250 ° C.
When the temperature is lower than 100 ° C, the yield of the polymer obtained by the polymerization is low, which is not preferable. On the other hand, if the temperature exceeds 300 ° C., the biodegradability, which is one of the characteristics of the polymer obtained, may deteriorate, which is not preferable.

Therefore, the reaction is usually carried out in a pressure-proof closed container, and the internal pressure at that time is 0.3 MPa or more, preferably 0.5 to 4 MPa.

An acid catalyst is preferably added during the polymerization, but it is preferable to use an organic or inorganic acid having a pKa value lower than that of aspartic acid. As the inorganic acid, orthophosphoric acid, metaphosphoric acid, phosphoric acid such as polyphosphoric acid, phosphonic acid, phosphinic acid, sulfuric acid, sulfurous acid,
Examples include pyrosulfuric acid, boric acid, trifluoromethanesulfonic acid and the like. As the organic acid, acidic phosphoric acid esters such as methyl phosphoric acid, ethyl phosphoric acid, and phenyl phosphoric acid,
Examples thereof include phosphonic acid esters such as methylphosphonic acid, ethylphosphonic acid, butylphosphonic acid, laurylphosphonic acid, stearylphosphonic acid, and phenylphosphonic acid, methanesulfonic acid, and paratoluenesulfonic acid.
Hydrogen salts of these acids can likewise be used. Examples of hydrogen salts of acids include MH ₂ PO ₄ , M ₂ HPO ₄ (provided that
(Wherein M is sodium, potassium, calcium) or the like, hydrogen phosphate such as potassium hydrogen sulfate, sodium hydrogen sulfate, nitrosyl hydrogen sulfate or hydrazinium hydrogen sulfate, and the like. Among these, inorganic acids are preferable, and sulfuric acid, phosphoric acid, and boric acid are particularly preferable.

The lower limit of the amount of the acid catalyst used is 0.001 times or more, preferably 0.01 times or more, more preferably 0.05 times or more, with respect to the weight of the amino acid mainly containing aspartic acid. On the other hand, the upper limit is 10 times or less, preferably 2 times or less, more preferably 1 time or less. That is, the amount of the acid catalyst used is 0.001 to 10 relative to the weight of the amino acid mainly containing aspartic acid.
The range is preferably double, preferably 0.01 to 2 times. 0.
If it is less than 001 times, the effect as an acid catalyst cannot be sufficiently obtained, which is not preferable. On the other hand, if it exceeds 10 times,
A large amount of the acid catalyst remains in the polymer aqueous solution, and the cost for treating the acid catalyst is further required, which is not preferable.

As the polymerization method, either a batch method or a continuous method can be adopted. In the case of the batch type, a reactor such as a stirring tank and a horizontal mixer which can withstand the vapor pressure of water at the polymerization temperature can be used. Further, in the case of the continuous type, a method of continuously feeding the slurry of aspartic acid as a raw material into a reactor used in a batch type and continuously withdrawing after a certain retention time, a single tube type, a multi-tube type As long as it can withstand the vapor pressure of water at the polymerization temperature and can hold heating at a pressure equal to or higher than the vapor pressure for a certain period of time, such as a method using various heat exchangers such as plate type and plate type , Any of which can be suitably used. Of these, a line mixer and the like are particularly preferable, and pressure can be applied by a back pressure valve, heating with a jacket and attachment to a heating medium tank for heating to continuously polymerize.

In the case of the single pipe type, for example, a unit for heating the coiled stainless pipe and a unit for cooling the coiled stainless pipe are connected in series, and a back pressure valve is attached to the heating unit and the cooling unit. Use a device that applies back pressure. The heating unit is a unit that provides the temperature required for the polymerization, and the lower limit is usually 1
40 ° C or higher, preferably 150 ° C or higher, more preferably 160 ° C or higher, while the lower limit is set to 300 ° C or lower, preferably 280 ° C or lower, more preferably 260 ° C or lower, a heating jacket, an oil bath. Etc. through the pipe. The residence time of the liquid is usually 1 minute to 1
0 hours, preferably 2 minutes to 5 hours, more preferably 5 minutes
The range of minutes to 2 hours is desirable. The length of the pipe is determined by the residence time, speed, temperature of the liquid, etc.
m or more, preferably 0.5 to 100 m. The cooling unit is a unit that is subjected to cooling treatment up to room temperature or around 25 ° C. by air cooling of pipes, water cooling using a water tank or the like, because it is difficult to handle high-temperature products as they are. The length of the pipe is determined depending on the residence time, speed, temperature, etc. of the liquid, but is usually 0.1 m or more, preferably 0.5 to 100 m. In addition, back pressure is applied to the heating and cooling units, typically 0.8
It is not less than MPa, preferably in the range of 1 to 3 MPa. The inner diameter of the pipe used depends on the residence time of the liquid, the speed, etc., but is usually 1 mm or more, preferably 2 mm to 1 m.
Is the range. A mixture of an amino acid containing aspartic acid as an essential component and water is pressure-fed by a pump such as a slurry pump, but is not particularly limited as long as it satisfies the above conditions, but usually a rate of 1 ml / min to 10 L / min. Is.
These conditions are applicable when using other devices such as a multi-tube type.

A horizontal kneader is particularly preferable because the viscosity increases when the amount of water used is small. It is not necessary to remove water during the polymerization, but if the concentration of the polymer is low or if you want to concentrate it, remove some of the water up to 0.2 times the weight of the amino acid mainly containing aspartic acid. be able to. However, if the amount of water is too small, a strong lump will be formed, so it is not preferable in terms of operation to make the concentration too high.

In the method of the present invention, an amino acid mainly composed of aspartic acid is heated in the presence of water to obtain the acid-type polyaspartic acid polymer in an aqueous solution. At this time, when an acid catalyst is used, the biodegradability of the obtained polymer becomes high.

It is desirable that the polyaspartic acid obtained by using the acid catalyst has a biodegradability of BOD 7 days of 45% or more, preferably 47% or more, more preferably 50% or more.

Generally, the biodegradation rate by BOD is usually 60%.
If it is above, it is easily decomposable, and it is said that it is completely decomposed at about 70%. In the present invention, polyaspartic acid obtained by using an acid catalyst has a very good initial decomposability, and is characterized in that more than half of it is decomposed within one week after the decomposition test.

The weight average molecular weight of the obtained polyaspartic acid is usually in the range of 2000 to 3600.

The polymer obtained by the above-mentioned method is in a state from a viscous to an aqueous solution having a low viscosity at high temperature, but is cooled to a state from a candy to an aqueous solution. The polymer obtained at this time can be heated again as necessary, or can be neutralized to form a salt.

For example, by subjecting the polymer obtained in an aqueous solution state to spray drying, it is separated as an acid-type polyaspartic acid solid, or the solidified polymer is again solidified in the range of 100 ° C. to 300 ° C. A polysuccinimide polymer can be formed by heating. Also, a polyaspartic acid-based polymer salt can be obtained by adding a base to an acid-type polyaspartic acid-based polymer to neutralize it. Examples of the base used for neutralization include hydroxides of alkali metals such as sodium, potassium and lithium, and alkaline earth metals such as calcium, magnesium and strontium, cetylamine, pentadecylamine, tetradecylamine, tridecylamine and dodecyl. Primary organic amines such as amine, undecylamine, decylamine, nonylamine and octylamine, secondary organic amines such as dibutylamine and diamylamine, ammonium and the like can be used.
As the alkali metal hydroxide, sodium hydroxide, potassium hydroxide and the like are particularly preferable.

Further, various amines and amino acids are added to the acid-type polyaspartic acid-based polymer obtained by the polymerization and heated to obtain an amine-amino acid-modified polyaspartic acid-based polymer (polyaspartic acid derivative). You can also

Furthermore, we have found that by concentrating the resulting aqueous polymer solution, the molecular weight of the polymer is increased. The concentration method is not particularly limited as long as it is a method of reducing the water content from the aqueous polymer solution, for example, a method of heating the aqueous solution of the polymer to evaporate the water, a method of depressurizing the aqueous solution of the polymer to remove the water. Alternatively, after completion of the reaction in the autoclave, a method of discharging steam while maintaining a predetermined temperature can be adopted. Specifically, in the case of the heating method, the temperature is usually maintained at 90 to 160 ° C. for 0.1 to 10 hours. In the case of the depressurizing method, the pressure is usually 66 to 666 hPa and the pressure is 0.1 to 1
Hold for 0 hours. In the case of the steam discharging method, the method of discharging steam by reducing the pressure in the autoclave while maintaining the temperature of 100 to 160 ° C. can be usually adopted. The degree of concentration is almost proportional to the degree of concentration, and the molecular weight of the polymer increases. Therefore, the concentration is adjusted according to the purpose.
It is preferred to concentrate to 0%, preferably 95%. After concentration, it may be recovered as it is, or when the polymer is solidified, it may be recovered after being diluted with water or after being diluted with a weakly basic aqueous solution.
As the base, the above bases can be used.

As described above, the polymer obtained by further concentration usually has a weight average molecular weight of 3800 or more, preferably in the range of 4000 to 6500, and when comparing before and after the concentration, an apparent increase in the molecular weight is observed. To be

The molecular weight of the polyaspartic acid salt is, for example, Shodex OHp manufactured by Showa Denko KK using a standard polyethylene glycol (PEG) having a known molecular weight as a standard.
It can be measured by gel permeation chromatography (GPC) analysis using an ak column. The measurement results are expressed in terms of PEG.

The biodegradability of polyaspartic acid can be measured, for example, by the modified MITI test of the OECD test guideline.

The polyaspartic acid produced according to the present invention can be used as a detergent additive excellent in biodegradability, a dispersion stabilizer, a scale inhibitor, a moisturizer, a fertilizer and the like.

[0035]

The preferred embodiments of the present invention will be specifically described below. However, it is needless to say that the present invention is not limited to these examples by that.

(Biodegradability of polyaspartic acid) The biodegradability of polyaspartic acid was measured according to the modified MITI test except that the returned sludge of the municipal sewer was used. That is, polyaspartic acid as a test substance was added to 200 ml of a basic culture solution as a composition solution specified in the section of biochemical oxygen consumption in JIS K-0102 so as to be 100 ppm, and activated sludge was added at 30 ppm. Was added. Then, the basal culture solution was kept at 25 ° C. in the dark and stirred with stirring at 28 ° C.
Cultured for days. Then, during the culturing period, the amount of oxygen consumed by the activated sludge is periodically measured to obtain a biochemical oxygen demand (BOD: Biochemical Oxygen Deman).
d) The curve was determined.

The biodegradation rate (%) is the biochemical oxygen demand A (mg) of the test substance obtained from the above BOD curve.
And the blank consumption obtained from the BOD curve, that is, the oxygen consumption B (mg) of the basal culture solution and the total oxygen demand (TOD: Theoretical Ox) required for complete oxidation of the test substance.
ygen Demand) C (mg), and calculated according to the ratio of the following equation and the theoretical oxygen demand (TOD) of the test substance.

Biodegradation rate (%) = {(A−B) / C} × 100 In addition, the reduction of the total organic carbon content (TOC) in the test solution is T
It measured using the OC measuring device (the Shimadzu make, TOC-500). The TOC removal rate was calculated according to the following formula.

TOC removal rate (%) = {(C ₀ -C _B0 )-
(C ₂₈ -C _B28 ) / (C ₀ -C _B0 )} × 100 where C ₀ : TOC (mg / L) in the test solution at the start of the test C ₂₈ : in the test solution after 28 days TOC (mg / L) C _B0 : TOC (mg / L) C _B28 at the start of the test of the system (blank test solution) containing no test substance 28 days after the system (blank test solution) containing no test substance TOC (mg / L).

(Conversion rate to polymer) After the reaction, the amount of L-aspartic acid as a raw material remaining was measured by liquid chromatography and calculated as a ratio to the raw material.

(Example 1) 15 g of L-aspartic acid,
50m by mixing ion-exchanged water 15g and phosphoric acid 1.5g
It was put into a 1-volume autoclave and heated to 180 ° C.
When the internal temperature reached 180 ° C., the pressure in the autoclave was 1.1 MPa. After 1 hour, the contents were taken out by cooling, and an evenly dissolved syrup-like polymer aqueous solution was obtained. The pH of the aqueous solution of this polymer is 3.2.
(25 ° C). When the molecular weight of this polymer was measured, the weight average molecular weight MW was 3,300. When this solution was left at room temperature, a large amount of polyaspartic acid was precipitated. Water was added to the liquid in which the insoluble matter had been precipitated, and the solution was diluted 5 times to obtain a uniform solution. The conversion rate to the polymer is L
-89% by weight of aspartic acid.

The biodegradability of this polymer was measured according to the modified MITI method, and was 58.
The biodegradability was 9%, 71.2% on the 14th day, and 70.2% on the 28th day.

GPC analysis of the polyaspartic acid in the liquid after the biodegradation test revealed that the initial polyaspartic acid had completely disappeared.

Separately, the obtained polyaspartaraginic acid was added to 100 ml of water and stirred, and 5N sodium hydroxide aqueous solution was added little by little to dissolve it, and the pH was adjusted to 9.5 to obtain sodium polyaspartate. Got
The solution was freeze-dried, and the NMR spectroscopic analysis results of the sodium polyaspartate powder were as follows (assignment of each signal was carried out based on Makromol. Chem. 194, 1095 (1993)).

¹ H-NMR (D ₂ O): δ = 4.68 (C
(Α) H, α-peptide, 4.49 (C (α) H, β-p
eptide), 2.77 (2H, C (β) H, H ′) ¹³ C-NMR (D ₂ O): δ = 177.81 (C═O, β
-peptide), 177.37 (C = O, α-peptide), 1
72.72 (CONH, α-peptide), 172.62
(CONH, α-peptide), 172.02 (CONH,
β-peptide), 171.89 (CONH, β-peptid
e), 51.83 (C (α), β-peptide), 51.3
8 (C (α), α-peptide), 39.00 (C (β),
α-peptide), 37.69 (C (β), β-peptide) (Example 2) L-aspartic acid 15 g, ion-exchanged water 15 g, and sulfuric acid 1.5 g were mixed and put into a 50 ml autoclave, Heated to 180 ° C. Internal temperature is 180 ℃
When, the autoclave pressure was 1.1 MPa. After 1 hour, the contents were taken out by cooling, and an evenly dissolved syrup-like polymer aqueous solution was obtained. The aqueous solution of this polymer had a pH of 3.2 (25 ° C.). When the molecular weight of this polymer was measured, the weight average molecular weight MW was 3,400. When this solution was left at room temperature, a large amount of polyaspartic acid was precipitated. Water was added to the liquid in which the insoluble matter had been precipitated, and the solution was diluted 5 times to obtain a uniform solution. The conversion rate to a polymer was 85% based on the weight of L-aspartic acid.

The biodegradability of this polymer was measured according to the modified MITI method.
Biodegradability was 1%, 77.4% on day 14 and 83.5% on day 28.

GPC analysis of the polyaspartic acid in the liquid after the biodegradation test revealed that the initial polyaspartic acid had completely disappeared.

(Example 3) 15 g of L-aspartic acid,
50m by mixing ion-exchanged water 15g and boric acid 1.5g
It was put into a 1-volume autoclave and heated to 180 ° C.
When the internal temperature reached 180 ° C., the pressure in the autoclave was 1.1 MPa. After 1 hour, the contents were taken out by cooling, and an evenly dissolved syrup-like polymer aqueous solution was obtained. The pH of the aqueous solution of this polymer is 3.2.
(25 ° C). When this solution was left at room temperature, a large amount of polyaspartic acid was precipitated. Water was added to the liquid in which the insoluble matter had been precipitated, and the solution was diluted 5 times to obtain a uniform solution. The conversion rate to the polymer was 88% based on the weight of L-aspartic acid.

When the molecular weight of this polymer was measured, the weight average molecular weight MW was 3,600. When the biodegradability of this polymer was measured according to the modified MITI method, it was 57.9% on the 7th day from the start of the test and 72.
The biodegradability was 2% and 78.9% at 28 days.

Example 4 15 g of L-aspartic acid,
50m by mixing ion-exchanged water 15g and phosphoric acid 1.5g
It was put into a 1-volume autoclave and heated to 180 ° C.
When the internal temperature reached 180 ° C., the pressure in the autoclave was 1.1 MPa. After 30 minutes, it was cooled and the contents were taken out. As a result, an evenly dissolved syrup-like polymer aqueous solution was obtained. The pH of the aqueous solution of this polymer is 3.2.
(25 ° C). When the molecular weight of this polymer was measured, the weight average molecular weight MW was 3,400. When this solution was left at room temperature, a large amount of polyaspartic acid was precipitated. Water was added to the liquid in which the insoluble matter had been precipitated, and the solution was diluted 5 times to obtain a uniform solution. The conversion rate to the polymer is L
-89% by weight of aspartic acid.

The biodegradability of this polymer was measured according to the modified MITI method.
The biodegradability was 7%, 64.0% on the 14th day, and 72.2% on the 28th day.

GPC analysis of the polyaspartic acid in the liquid after the biodegradation test revealed that the initial polyaspartic acid had completely disappeared.

(Example 5) L-aspartic acid 7.5
g, L-glutamic acid (7.5 g) and ion-exchanged water (15 g) were mixed and put into a 50 ml autoclave.
Heated to ° C. When the internal temperature reached 180 ° C., the pressure in the autoclave was 1.1 MPa. After 1 hour, the contents were taken out by cooling, and an evenly dissolved syrup-like polymer aqueous solution was obtained. The weight average molecular weight of this polymer was 2,300.

Even when this solution was left at room temperature for 1 day, it was in a uniform solution state.

(Example 6) L-aspartic acid 7.5
g, L-glutamic acid 7.5 g, ion-exchanged water 15 g,
Phosphoric acid (1.5 g) was mixed and put into a 50 ml autoclave and heated to 180 ° C. When the internal temperature reached 180 ° C., the pressure in the autoclave was 1.1 MPa. After 1 hour, the contents were taken out by cooling, and an evenly dissolved syrup-like polymer aqueous solution was obtained.

Even when this solution was allowed to stand at room temperature for 1 day, it was in a uniform solution state.

(Example 7) L-aspartic acid 7.5
g, L-alanine 7.5 g, ion-exchanged water 15 g and phosphoric acid 1.5 g were mixed and put into a 50 ml autoclave and heated to 180 ° C. When the internal temperature reached 180 ° C., the pressure in the autoclave was 1.1 MPa. 1
After a lapse of time, the contents were taken out by cooling, and an evenly dissolved syrup-like polymer aqueous solution was obtained.

Even when this solution was allowed to stand at room temperature for 1 day, it was in a uniform solution state.

(Example 8) 15 g of L-aspartic acid,
L-lysine 1.5 g, ion-exchanged water 15 g, phosphoric acid 1.
Mix 5g and put into a 50ml autoclave,
Heated to 180 ° C. When the internal temperature reached 180 ° C., the pressure in the autoclave was 1.1 MPa. After 1 hour, the contents were taken out by cooling, and an evenly dissolved syrup-like polymer aqueous solution was obtained.

Even when this solution was allowed to stand at room temperature for 1 day, it was in a uniform solution state.

(Example 9) 15 g of L-aspartic acid,
50m by mixing 1.5g phosphoric acid and 15g ion-exchanged water
It was put into a 1-volume autoclave and heated to 180 ° C.
When the internal temperature reached 180 ° C., the pressure in the autoclave was 1.1 MPa. When cooled after 1 hour, the content was in the form of a syrup in which the contents were uniformly dissolved.

1.28 g of cysteamine hydrochloride was added.
Was added, mixed and heated at 180 ° C. for an additional hour.
After cooling, the contents were taken out and found to contain some insoluble matter. 4 g of sodium hydroxide was added to this solution for neutralization to obtain a polyaspartic acid derivative aqueous solution modified with cysteamine.

Example 10 L-Aspartic acid 15
5g, phosphoric acid 1.5g, ion-exchanged water 15g
It was put into a 0 ml autoclave and heated to 180 ° C. After cooling for 1 hour, the contents were uniformly dissolved. The solution was frozen in liquid nitrogen and dried in a lyophilizer to give a pale yellow solid.

When this solid was dissolved in heavy water and analyzed by ¹ H-NMR, an NMR spectrum of polyaspartic acid was obtained. From this, it was confirmed that polyaspartic acid was produced without neutralization with a base.

Example 11 The procedure of Example 10 was repeated to obtain a pale yellow solid. The solid was spread on a stainless steel vat and dried in a drier at 140 ° C. for 4 hours. The solid matter after drying was insoluble in water. 60 ml of a 2N sodium hydroxide aqueous solution was added to this solid substance, and it was uniformly dissolved by stirring.

This solution was freeze-dried, the obtained solid was dissolved in heavy water and analyzed by ¹ H-NMR, and an NMR spectrum of polyaspartic acid was obtained. From this, it was confirmed that when the solid polyaspartic acid solid was heated, it could be made into polysuccinimide insoluble in water.

(Example 12) L-aspartic acid 15
g and ion-exchanged water 15 g were mixed and put into a 50 ml autoclave and heated to 180 ° C. Internal temperature is 180
When the temperature reaches ℃, the autoclave pressure is 1.1 MPa
Met. After 1 hour, the contents were taken out by cooling, and an evenly dissolved syrup-like polymer aqueous solution was obtained. The pH of the aqueous solution of this polymer was 3.5 (25 ° C.). When the molecular weight of this polymer was measured, the weight average molecular weight MW was 3,400. When this solution was left at room temperature, a large amount of polyaspartic acid was precipitated. Water was added to the liquid in which the insoluble matter had been precipitated, and the solution was diluted 5 times to obtain a uniform solution. The conversion rate to the polymer was 90% based on the weight of L-aspartic acid.

The biodegradability of this polymer was measured according to the modified MITI method.
The biodegradability was 0%, 52.3% on day 14, and 56.4% on day 28.

(Comparative Example 1) 98 g of maleic anhydride was dissolved in 100 ml of deionized water to prepare a solution of 68% of 25% ammonia water.
g was added to neutralize. This solution was freeze-dried to prepare a monoammonium maleate salt.

Obtained maleic acid monoammonium salt 6
6 g was spread on a stainless steel vat, put in a hot air dryer set at 180 ° C., heat-treated for 7 hours, and then cooled to obtain 53 g of polysuccinimide. To this polysuccinimide, 300 ml of water was added, 20 g of sodium hydroxide was added to hydrolyze the polysuccinimide, and water was added to prepare a 10% sodium polyaspartic acid salt aqueous solution.

A biodegradability test was carried out using this aqueous solution of sodium polyaspartate, 10.8% on the 7th day from the start of the test and 37.6% on the 14th day.
On day 28, it was 45.6% biodegradable.

(Comparative Example 2) L-aspartic acid powder 6
6.5 g of the product was spread on a stainless steel vat, put in a warm air dryer set at 200 ° C., heat-treated for 12 hours, and then cooled to obtain 57 g of polysuccinimide. Add 300 ml of water to this polysuccinimide and add sodium hydroxide 2
0 g was added to hydrolyze the polysuccinimide, and water was added to give a 10% sodium polyaspartate aqueous solution.

A biodegradability test was conducted using this aqueous solution of sodium polyaspartic acid salt. The results were 7.4% on the 7th day from the start of the test, 33.4% on the 14th day, and 2%.
On day 8 it was 44.9% biodegradable.

(Comparative Example 3) L-aspartic acid powder 6
6.5 g and orthophosphoric acid 14 g were mixed well, spread on a stainless steel vat, put in a hot air dryer set at 200 ° C., and heated for 6 hours. After 6 hours, the mass was taken out from the warm air dryer, the lumps were crushed, and the mixture was heated for 6 hours and then cooled to obtain 65 g of polysuccinimide.

300 ml of water was added to this polysuccinimide, 20 g of sodium hydroxide was added to hydrolyze the polysuccinimide, and water was added to prepare a 10% sodium polyaspartate sodium salt aqueous solution. A biodegradability test was conducted using this polyaspartic acid sodium salt aqueous solution.
As a result, the biodegradability was 9.9% on the 7th day from the start of the test, 67.3% on the 14th day, and 74.0% on the 28th day.

Comparative Example 4 A biodegradability test was carried out using sodium poly-L-aspartate (manufactured by Sigma, product number P5387, weight average molecular weight: 12000). As a result, the biodegradability was 41.7% on the 7th day from the start of the test, 71.5% on the 14th day, and 72.0% on the 28th day.

Comparative Example 5 Poly-D. A biodegradability test was performed using L-sodium aspartate (manufactured by Sigma, product number P3418, weight average molecular weight: 5800). As a result, the biodegradability was 36.0% on the 7th day from the start of the test, 73.2% on the 14th day, and 73.0% on the 28th day.

(Example 13) L-aspartic acid 50
g, ion-exchanged water 50 g, sulfuric acid 5 g are mixed to 200 m
It was put into a 1-liter autoclave equipped with a stirrer and heated to 180 ° C. The internal temperature was kept at 180 ° C for 30 minutes and after cooling to 90 ° C, the contents were taken out. The content taken out was a syrup-like polymer aqueous solution. When the polymer was diluted and neutralized and the molecular weight was measured, the weight average molecular weight MW was 3,400. The conversion rate to the polymer is
It was 85% based on the weight of L-aspartic acid.

(Example 14) L-aspartic acid 50
g, ion-exchanged water 50 g, sulfuric acid 5 g are mixed to 200 m
It was put into a 1-liter autoclave equipped with a stirrer and heated to 180 ° C. The internal temperature was kept at 180 ° C. for 30 minutes, the valve attached to the upper part of the autoclave was slightly opened, and steam was discharged while the temperature was kept at 120 ° C. or higher to concentrate the contents. The discharged water vapor was condensed by a cooling pipe and collected. When the amount of condensed water reaches 32 ml, close the valve and
It cooled to 0 degreeC and took out the content. The contents taken out were candy-like. When this candy was diluted and neutralized to measure the molecular weight, the weight average molecular weight MW was 4000.

(Example 15) L-aspartic acid 50
g, ion-exchanged water 50 g, sulfuric acid 5 g are mixed to 200 m
It was put into a 1-liter autoclave equipped with a stirrer and heated to 180 ° C. The internal temperature was kept at 180 ° C. for 30 minutes, the valve attached to the upper part of the autoclave was slightly opened, and steam was discharged while the temperature was kept at 120 ° C. or higher to concentrate the contents. The discharged water vapor was condensed by a cooling pipe and collected. When the amount of condensed water reaches 41 ml, close the valve and
It cooled to 0 degreeC and took out the content. The contents taken out were candy-like. When the molecular weight was measured by diluting and neutralizing this candy, the weight average molecular weight MW was 5,300.

(Example 16) L-aspartic acid 50
g, ion-exchanged water 50 g, sulfuric acid 5 g are mixed to 200 m
It was put into a 1-liter autoclave equipped with a stirrer and heated to 180 ° C. The internal temperature was kept at 180 ° C. for 30 minutes, the valve attached to the upper part of the autoclave was slightly opened, and steam was discharged while the temperature was kept at 120 ° C. or higher to concentrate the contents. The discharged water vapor was condensed by a cooling pipe and collected. When the amount of condensed water reaches 42 ml, close the valve and
It cooled to 0 degreeC and took out the content. The contents taken out were candy-like. When this candy was diluted and neutralized to measure the molecular weight, the weight average molecular weight MW was 5,600.

(Example 17) L-aspartic acid 50
g, ion-exchanged water 50 g, sulfuric acid 5 g are mixed to 200 m
It was put into a 1-liter autoclave equipped with a stirrer and heated to 180 ° C. The internal temperature was kept at 180 ° C. for 30 minutes, the valve attached to the upper part of the autoclave was slightly opened, and steam was discharged while the temperature was kept at 120 ° C. or higher to concentrate the contents. The discharged water vapor was condensed by a cooling pipe and collected. When the amount of condensed water reaches 45 ml, close the valve and
It cooled to 0 degreeC and took out the content. The contents taken out were candy-like. When this candy was diluted and neutralized to measure the molecular weight, the weight average molecular weight MW was 6150.

(Example 18) L-aspartic acid 50
g, ion-exchanged water 50 g, sulfuric acid 5 g are mixed to 200 m
It was put into a 1-liter autoclave equipped with a stirrer and heated to 180 ° C. The internal temperature was kept at 180 ° C. for 30 minutes, the valve attached to the upper part of the autoclave was slightly opened, and steam was discharged while the temperature was kept at 120 ° C. or higher to concentrate the contents. The discharged water vapor was condensed by a cooling pipe and collected. When the amount of condensed water reaches 46 ml, close the valve and
It cooled to 0 degreeC and took out the content. The contents taken out were candy-like. When this candy was diluted and neutralized to measure the molecular weight, the weight average molecular weight MW was 6,500.

(Example 19) A unit for heating a coiled stainless pipe by heating it in an oil bath and a unit for cooling a coiled stainless pipe in a water tank were connected in series, and a back pressure valve was attached to the heating unit. And the apparatus which applies a back pressure of 1.5 MPa to the cooling unit was prepared. The stainless steel pipe had a diameter of 1/4 inch, the heating unit had a length of 10 m, and the cooling unit had a length of 3 m. The temperature of the oil bath was set to 250 ° C.

L-aspartic acid (5 kg), water (5 kg) and sulfuric acid (0.5 kg) were mixed, and 1 was added to the above apparatus by a monomer pump.
A continuous polymerization reaction was carried out by pressure-feeding at a rate of 25 ml per minute. The residence time in the heating unit was 2.8 minutes. A syrup-like polymer aqueous solution was obtained from the back pressure valve. When the molecular weight of this polymer was measured, the weight average molecular weight was 3
It was 400.

In the examples, the obtained polymer solution was a uniform solution having a slight yellow or brown coloration. A polymer having a weight average molecular weight of 2000 to 6500 was obtained.

[0087]

According to the production method of the present invention, a polyamino acid excellent in biodegradability can be obtained by an extremely simple method.

The polyamino acid of the present invention is particularly excellent in biodegradability.

Since it is excellent in biodegradability, the polyamino acid of the present invention is effective as a detergent additive, a dispersion stabilizer, a scale inhibitor, a moisturizer and a fertilizer.

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Claims (4)

(57) [Claims] 1. A method for producing a polyamino acid, which comprises mixing an amino acid containing aspartic acid as an essential component and water and heating the mixture in a pressure-resistant closed container or while feeding the mixture under pressure. 2. The method according to claim 1, wherein the amount of water to be added is in the range of 0.2 to 40 times the weight of the amino acid containing aspartic acid as an essential component. 3. The method according to claim 1, further comprising adding an acid catalyst. 4. The method according to claim 1, wherein the polymer obtained by heating is concentrated.