JPH04251845A - Bleaching bath - Google Patents

Abstract

PURPOSE: To particularly prevent contamination of the environment. CONSTITUTION: An iron (III) complex expressed by formula I is contained in >=20mol%, preferably >=80mol% of a complexing agent and is controlled to pH >=4.5 to <6.0. The bleaching bath contains a thiosulfate in some cases but it is preferable to contain further smaller quantity of the thiosulfate than the insufficient quantity to fix an undeveloping silver halide. Particularly the quantity of the thiosulfate is preferably 0.3mol/l and it is most preferable to contain no thiosulfate. Residual <=80mol% complexing agent is composed of a usual complexing agent such as ethylene diamine tetra-acetate, propylene diamine tetra-acetate. The iron complexing agent is used in the ratio of 0.005-1.0mol/l.

Description

[Detailed description of the invention]

The present invention relates to a bleaching bath suitable for processing halogen silver color photographic materials, which is characterized in particular by its environmental friendliness.

Iron complex salts of aminopolycarboxylic acids, such as the iron ammonium complex of ethylenediaminetetraacetic acid, are widely used for bleaching silver produced by the development of color photographic materials. This series of complexing agents biodegrades very slowly.

If a bleaching bath containing an iron complex of a biodegradable complexing agent such as nitrilotriacetic acid is used for bleaching color photographic materials under normal conditions of pH 6-8, its bleaching power is insufficient. It is.

The object of the present invention is to provide a bleaching bath suitable for processing halogen silver color photographic materials, which is characterized by containing biodegradable components and having sufficient bleaching power.

This problem is solved by (1) 20 mol % or more, preferably 80 mol % or more of the complexing agent having the following formula I

[0006]

[Chemical formula 2] (HOOC-CH2)2-N-C
The problem was solved by a bleaching bath characterized by containing an iron (III) complex represented by H2-CH2-COOH (I) and (2) having a pH adjusted to 4.5 or more and less than 6.0.

[0007] The bleach bath may also contain thiosulfate. Preferably, the bleach bath contains an amount of thiosulfate that is less than an amount insufficient to fix undeveloped silver halide. In particular, the amount of thiosulfate is preferably 0.03 mol/l. Most preferably, the bleach bath is completely free of thiosulfates.

The remaining 80 mol% or less of the complexing agent, preferably 20 mol% or less of the complexing agent, is, for example, ethylenediaminetetraacetic acid, propylenediaminetetraacetic acid, nitrilotriacetic acid, nitrilodipropionic acid monoacetic acid, or any of these. of conventional complexing agents, such as mixtures of compounds. It is preferable that the composition consists only of the complexing agent of the present invention.

[0009] This iron complex is preferably 0.005-1.
It is used at a rate of 0 mol/l.

[0010] In addition to the components according to the invention, the bleaching bath contains a halogen compound for rehalogenating the silver.

[0011] The halogen compounds used in this bleaching bath are inter alia the chlorides and bromides of sodium, potassium and ammonium.

[0012] This bleach bath has a 0.05-2.0
Contains mol/l of halogen compounds.

[0013] This bleaching bath has a 1-1 content based on the iron complex.
Preferably, it contains an excess of free complexing agent of 20 mol%, preferably 5-20 mol%.

The bleaching bath according to the invention is particularly suitable for halogen silver color photographic recording materials, characterized in that the halogen silver emulsion consists primarily of AgBr, AgBrI, AgBrCl or AgCl. This color photographic material consists of at least one layer of a blue-sensitive silver halide emulsion coated on an opaque or transparent support (such as paper coated on both sides with polyethylene or cellulose triacetate film), at least one layer of a green-light-sensitive silver halide emulsion. layer,
and at least one red-sensitive emulsion layer, each of which in turn comprises at least one yellow coupler, at least one magenta coupler, and at least one cyan coupler. There is.

This bleaching bath is used in the conventional processing of halogen silver color photographic materials and is suitable for bleaching all known halogen silver color photographic materials, such as negative color film, negative color photographic paper, reversal color film, and reversal color photographic paper. suitable for

The treatment can also be carried out continuously, with constant replenishment of the individual treatment baths.

The bleaching baths described in the Examples were tested for their bleaching power (residual silver in the treated material).

Measurement of residual silver: Silver remaining in the black image area of the step wedge of the color photographic material processed after exposure as described above was measured using an infrared silver detector PM8030 manufactured by Photomatic (Denmark).

[0019]

EXAMPLES Example 1 (Invention) A color photographic recording material was prepared by applying the following layers in the following order to a paper support coated with polyethylene on both sides. All quantities mentioned below are per square meter. The coating amount of silver halide is expressed in terms of the corresponding amount of AgNO3.

Layer arrangement First layer (subbing layer) Gelatin 0.2g Second layer (blue light sensitive layer) Silver halide emulsion sensitive to blue light prepared from 0.63g AgNO3 (99.5 mol% chloride) , bromide 0.
5 mol%, average particle size 0.8 μm) Gelatin 1.38 g Yellow coupler Y 0.95 g Tricresyl phosphate (TCP) 0.29 g Third layer (protective layer) Gelatin 1.1 g 2,5-dioctylhydroquinone 0 .06g dibutyl phthalate (DBP) 0.06g Fourth layer (green-sensitive layer) A silver halide emulsion sensitive to green light prepared from 0.45g of AgNO3 (99.5 mol% chloride, 0.06g bromide).
5 mol%, average particle size 0.6 μm) Gelatin 1.08 g Magenta coupler M 0.41 g 2,5-dioctylhydroquinone 0.08 g DB
P 0.34g TCP 0.04g Fifth layer (ultraviolet protection layer) Gelatin 1.15g Ultraviolet absorber corresponding to the following formula 0.6g

[0021]

[Chemical formula 3]

2,5-dioctylhydroquinone 0.045gT
CP 0.04g Sixth layer (red-sensitive layer) Silver halide emulsion sensitive to red light prepared from 0.3g of AgNO3 (chloride 99.5 mol%, bromide 0.5
(mol%, average particle size 0.5μm) Gelatin 0.75g Cyan coupler C 0.36g TCP 0.36g Seventh layer (ultraviolet protection layer) Gelatin 0.35g Ultraviolet absorber used in fifth layer 0.15g TCP
0.2g Eighth layer (protective layer) Gelatin 0.9g Hardening agent H corresponding to the following formula 0.3g

[0023]

[C4]

The coupler used here is represented by the following formula:

[0025]

[C5]

The photographic recording material described above was exposed to reflected light by overlapping step wedges and processed as follows: Development 45 seconds 35
℃ water washing 22 seconds <
Bleach at 20℃ for 90 seconds
Wash with water at 35℃ for 45 seconds
Fixed at 30℃ 45
seconds 35℃ water washing
Drying for 90 seconds at approximately 30°C Each processing bath had the following composition: Developing bath: Water
9
00ml ethylenediaminetetraacetic acid (EDTA)
2g 60% by weight hydroxyethane diphosphonic acid (HEDP)
0.5ml sodium chloride
2gN,N-diethylhydroxylamine (85% by weight) 5m
l4-(N-Ethyl-N-2-methanesulfonylaminoethyl)-2-methylphenylenediamine-1/2 sulfate monohydrate (CD3) (50% by weight)
8ml potassium carbonate

Adjust pH to 10 with 25 ml KOH or H2SO4.

Add water to make up to 1 liter.

Bleach bath A water
8
00ml iron(III) nitrate・9H2O
40g nitrilodiacetic acid monopropionic acid
25g ammonia water (25% by weight)
* Approximately 35ml ammonium bromide
40
g Add water to make 1 liter.

*Adjust pH to 5.0.

Fixing bath water
9
00ml sodium sulfite
10
gAmmonium thiosulfate
Adjust the pH to 7 with 100 g ammonia water or acetic acid.

Add water to make up to 1 liter.

See Table 1 for the measurement results of residual silver.

Example 2 (Comparative Example) Exposure and processing were carried out in the same manner as in Example 1. The developing bath had the same composition as in Example 1.

Bleach bath B water
8
00ml iron(III) nitrate・9H2O
40g nitrilodiacetic acid monopropionic acid
25g ammonia water (25% by weight)
* Approximately 40ml ammonium bromide
40
g Add water to make 1 liter.

*Adjust pH to 6.0.

The fixing bath was the same as in Example 1.

See Table 1 for the measurement results of residual silver.

Example 3 (Comparative Example) Exposure and processing were carried out in the same manner as in Example 1. The developing bath had the same composition as in Example 1.

Bleach bath C water
8
00ml EDTA ammonium-iron(III)
50g EDTA

5g ammonium bromide
Adjust the pH to 6.0 with 80g ammonia water or acetic acid.

Add water to make up to 1 liter.

The fixing bath was the same as in Example 1.

See Table 1 for the measurement results of residual silver.

[0043]

[Table 1] Table 1 Bleach bath Silver detector reading* A 4 B 　　　　　　　9 　C　　　　　　　　　4 *A value of 6 or more indicates the presence of residual silver.

Table 1 shows the excellent bleaching effect of bleach bath A containing the biodegradable complexing agent according to the invention. Its bleaching power is comparable to that of conventional bleaching bath C, which contains EDTA, which is difficult to biodegrade. Bleach bath B has substantially the same composition as bleach bath A, but is in the pH range of the EDTA bleach bath.
Insufficient bleaching power.

Example 4 (Invention) A transparent support of cellulose triacetate was coated with the following layers in the following order:

All quantities mentioned below are per square meter. The coating amount of silver halide is expressed in terms of the corresponding amount of AgNO3.

All silver halide emulsions are AgNO31
It is stabilized by 0.1 g of 4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene per 00 g.

Layer arrangement First layer (antihalation layer) Black colloidal silver 0.2g Gelatin 1.2g Ultraviolet absorber UV-1 0.1g Ultraviolet absorber U
V-2 0.2g tricresyl phosphate 0.02g dibutyl phthalate 0
．． 03g second layer (Micrato intermediate layer) Micrato Ag prepared from 0.25g AgNO3
(Br, I) Emulsion: average particle size φ=0.07 μm, iodide 0.5 mol% gelatin 1.0 g color coupler RM-1 0.05 g tricresyl phosphate 0.10 g third layer (low sensitivity) red light layer) Silver halide emulsion sensitive to red light prepared from 2.2 g of AgNO3 (4 mol% iodide, average grain size 0.4
5μm) Gelatin 2.0g Colorless cyan coupler C-1 emulsified in tricresyl phosphate (TCP) 0.5g 0.6g
Colored cyan coupler RM-1 50mgTCP
DIR coupler emulsified to 20mg DIR-
1 30 mg Fourth layer (high sensitivity red light layer) Silver halide emulsion sensitive to red light prepared from 2.8 g of AgNO3 (iodide 8.5 mol%, average particle size 0.8 μm) Gelatin 1.8 g Dibutyl Colorless cyan coupler C-2 emulsified with phthalate (DBP) 0.15g 0.15
g Fifth layer (separation layer) 0.7 g gelatin 0.2 g 2,5-diisooctylhydroquinone emulsified with 0.15 g DBP Sixth layer (low sensitivity green light layer) Prepared from 1.8 g AgNO3 Ag (Br, I) emulsion sensitive to green light (iodide 4.5 mol%, average particle size 0.4 μm) Gelatin 1.6 g Magenta coupler M-1 (latex coupler) 0.6 g Emulsified in TCP 50 mg Masking coupler YM-1 50mg DIR coupler emulsified with DBP 20mg
DIR-2 30mg DIR coupler emulsified in TCP 60mg
DIR-3 80mg Seventh layer (high sensitivity green light layer) Silver halide emulsion sensitive to green light prepared from 2.2g of AgNO3 (7 mol% iodide, average grain size 0.
7μm) Gelatin 1.4g Magenta coupler M-2 emulsified in 0.45g TCP 0.15g Masking coupler used in the 6th layer emulsified with 30mg TCP 30mg 8th layer (separation layer) Gelatin 0.5g DBP 0 .08g 2,5-diisooctylhydroquinone emulsified with 0.1g Ninth layer (yellow filter layer) Ag (yellow colloidal silver sol) 0.2g gelatin
0.2 g of 2,5-diisooctylhydroquinone emulsified with 0.9 g of DBP 0.16 g Tenth layer (low sensitivity blue-light layer) Silver halogen emulsion sensitive to blue light prepared from 0.6 g of AgNO3 ( Iodide 4.9 mol%, average particle size 0.
45μm) Yellow coupler Y emulsified in gelatin 0.85g TCP 0.7g
-1 0.7g DIR coupler emulsified in 0.5g TCP
DIR-3 0.5g 11th layer (high sensitivity blue light layer) Silver halide emulsion sensitive to blue light prepared from 1.0g of AgNO3 (9.0 mol% iodide, average grain size 0.
9 μm) Gelatin 0.85 g Same yellow coupler as layer 10 emulsified in 0.3 g TCP 0.3 g Layer 12 (protective and hardening layer) Micrato Ag (prepared from 0.5 g AgNO3)
Br, I) emulsion (iodide 0.5 mol%, average grain size 0.
07μm) Gelatin 1.2g Hardening agent corresponding to the following formula 0.4g

[0049]

embedded image (CH2=CH-SO2-CH2-CONH-CH2-
) Formaldehyde scavenger of the following formula 1.0g

0
050]

[C7]

The compound used here is represented by the following formula: Ultraviolet absorber UV-1

[0052]

[Chemical formula 8]

[0053] Weight ratio x:y=7:3

[0054]

[Chemical formula 9]

[0055]

[Chemical formula 10]

[0056]

[Chemical formula 11]

The photographic recording material described above was exposed to reflected light by stacking step wedges and then processed as follows: Developing bath 3 minutes 15 seconds 37.8°C
Bleach bath 4 minutes 20 seconds 38℃
Washing with water 1 minute 05 seconds 38
°C fixing bath 4 minutes 20 seconds 38
℃ water washing 3 minutes 15 seconds 3
8℃ finishing bath 1 minute 05 seconds 3
Each processing bath at 8°C had the following composition: Development bath: Water
800ml potassium carbonate

37.5g sodium sulfite
4.25g potassium iodide
1.2mg sodium bromide

1.3g hydroxylamine sulfate
2.0g diethylenetriaminepentaacetic acid 2.0g
4-(N-ethyl-N-β-hydroxyethylamino)
-2-Methylaniline sulfate 4.
75g pH adjusted to 10.

Add water to make up to 1 liter.

Bleach bath D water
600ml iron nitrilodiacetic acid monopropionate 7
0g nitrilodiacetic acid monopropionic acid
5.5g ammonium bromide
150g ammonium nitrate
1
6g acetic acid (80% by weight)
pH 5 with about 10ml ammonia water
．． Adjust to 0.

Add water to make 1 liter.

Fixing bath water
800ml ammonium thiosulfate solution (58% by weight) 162ml
l ethylenediaminetetraacetic acid
1.3g sodium sulfite
13g sodium hydroxide

2.4g Adjust pH to 6.5.

Add water to make up to 1 liter.

0063 Finishing bath water
800ml formalin (37% by weight)
3ml polyoxyethylene-p-monononylphenyl ether
Add 0.5g water to make 1 liter.

The residual silver results are shown in Table 2 below. The color image formed had excellent reproducibility.

Example 5 (Comparative Example) Exposure and processing were carried out in the same manner as in Example 4. The developing bath, fixing bath and finishing bath had the same composition as in Example 4.

Bleach bath E water
600ml iron nitrilodiacetic acid monopropionate 7
0g nitrilodiacetic acid monopropionic acid
5.5g ammonium bromide
150g ammonium nitrate
1
6g acetic acid
Adjust the pH to 6.0 with about 10 ml of aqueous ammonia.

Add water to make up to 1 liter.

The measurement results for residual silver are shown in Table 2 below.

Example 6 (Comparative Example) Exposure and processing were carried out in the same manner as in Example 4. The developing bath, fixing bath and finishing bath had the same composition as in Example 4.

Bleach bath F water
600ml EDTA
Ammonium iron (III) 9
9g acetic acid (80% by weight)
Approximately 10ml ammonium bromide
1
50g ammonium nitrate
p with 16g ammonia water
Adjust to H6.0.

Add water to make up to 1 liter.

The measurement results for residual silver are shown in Table 2 below.

[0073]

[Table 2] Table 2 Bleaching bath Silver detector reading *D
4E
9F
A value of 4*6 or more indicates the presence of residual silver.

As shown in Table 2, the bleaching power of the bleaching bath D according to the present invention containing a biologically degradable complexing agent is higher than that of the conventional bleaching bath F containing an EDTA complexing agent that is difficult to biologically decompose. equal to the bleaching power of On the other hand, bleach bath E, which has substantially the same composition as bleach bath D but has the same pH as the EDTA bleach bath, has insufficient bleaching power. As a result of the bleaching tests carried out, the bleaching bath D according to the invention does not lead to the formation of leucocyan dye, whereas a conventional bleaching bath containing EDTA at the corresponding pH loses a considerable amount of cyan dye.

Example 7 (Invention) A color photographic recording material for reversal processing was prepared by applying the following layers in the following order to a support of cellulose triacetate coated with an adhesive layer.

Layer arrangement first layer (antihalation layer) Black colloidal silver sol
0.2g gelatin
1.2g UV absorber UV-
1 0.10g Ultraviolet absorber UV-2 0.
20g tricresyl phosphate (TCP) 0
．． 02g dibutyl phthalate (DBP)
0.03g second layer (Micrato intermediate layer) Micrato Ag prepared from 0.25g AgNO3
(Br, I) emulsion: iodide 0.5 mol%, average grain size 0.07 μm, gelatin 1.0 g TCP 0.10 g, 70 g gelatin, 60 g silver (96 mol% of which is bromide and 4 mol per kg of third layer) % iodide) and a red light sensitive silver halide emulsion (average grain size 0.5 μm) containing 55 g of cyan coupler BG.The amount of silver coated per 1 m2 is 2.5 g in terms of silver nitrate.

Fourth layer: A 2% by weight aqueous gelatin solution containing 4g of polymeric white coupler W per 1kg is coated at 60g/m2.

Fifth layer: green light sensitive silver halide emulsion (average grain size 0.45 μm) containing 70 g of gelatin, 60 g of silver (of which 96 mol % is bromide and 4 mol % iodide) and 60 g of magenta coupler PP per kg of fifth layer. ) The amount of silver applied per 1 m2 is 2.8 g in terms of silver nitrate.

[0079] Sixth layer: 1.8 g of silver and gelatin 12 in terms of silver nitrate per 1 kg
A yellow silver dispersion containing g. The color density of this yellow filter layer measured through the blue filter is 0.6;
The amount of silver coated per m2 was 70 g of gelatin per kg of the seventh layer corresponding to 0.2 g of silver nitrate, 60 g of silver (of which 95 mol% bromide and 5 mol% iodide) and 140 g of the yellow coupler GB. The amount of silver coated per 1 m2 of the halogen silver emulsion (average grain size 0.6 μm) is as follows:
It is 1.5 g in terms of silver nitrate.

60 g of a 1% by weight aqueous gelatin solution was applied per 1 m 2 of the eighth layer.

60 g of a 1% by weight aqueous solution of curing agent H was applied per 1 m 2 of the ninth layer.

The compound used here is represented by the following formula:

[
0083

[Chemical formula 12]

[0084]

[Chemical formula 13]

The samples produced by these methods were exposed using step wedges and then processed as follows: First developing bath 6 minutes 38°C water washing 2 minutes 38°C
Inversion bath 2 minutes 38
°C color development 6 minutes 38 °C
Conditioning bath 2 minutes 38
°C bleach bath 6 minutes 3
8℃ fixing bath 4 minutes
Wash with water at 38℃ for 4 minutes
38℃ finishing bath 1 minute
Each processing bath at 38°C had the following composition: First developing bath: water
50
0ml Pentasodium Nitrilotrimethylenephosphonate
2.0g potassium diethylenetriaminepentaacetate 2.0g potassium sulfite
30.0g Potassium hydroquinone sulfonate 22.0
g potassium carbonate
33.0g1-phenyl-4-methyl-4-hydroxy methyl-3-
Pyrazolidone
1.4g sodium bromide

2.2g Sodium thiocyanate
1.0g potassium iodide
Adjust pH to 9.60 with 4.5 mg KOH or H2SO4.

Add water to make up to 1 liter.

Inversion bath water
8
00ml pentasodium nitrilotrimethylenephosphonate 3.0g tin chloride

1.6gp-aminophenol

10.0mg sodium hydroxide
5
．． 0g propionic acid
12.0m
l Adjust pH to 6.0 with HCl or NaOH.

Add water to make up to 1 liter.

Color developing bath water
800
ml Pentasodium nitrilotrimethylenephosphonate
2.0g sodium sulfite
7.
0g phosphoric acid (85%)
8.7ml potassium bromide
1.0g potassium iodide
30.0mg potassium hydroxide (45% solution) 40.0m
l Citrazic acid
1.25gN-
Ethyl-N-(2-methanesulfonamidoethyl)-
2-Methyl-1,4-phenylenediamine 1/2 sulfate
11.0g3,6-dithiooctane-1,8
-Diol 1.0gKOH
Or adjust pH to 11.75 with H2SO4.

Add water to make up to 1 liter.

Adjustment solution water
800
ml ethylenediaminetetraacetic acid
8.0g sodium sulfite
12.0g thioglycerol

Adjust pH to 6.15 with 0.4 ml KOH or H2SO4.

Add water to make 1 liter.

Bleach bath G water
500
ml iron(III) nitrilodiacetic acid monopropionate
88.0g Nitrilodiacetic acid monopropionic acid 7.0g
potassium bromide
78.0g hydrobromic acid (48% by weight)
33.0ml potassium nitrate

25.0g Adjust pH to 5.0 with aqueous ammonia or HBr. Add water to make 1 liter.

Fixing bath water
500
ml ammonium thiosulfate solution (58% by weight)
94.0ml ethylenediaminetetraacetic acid
0.8g sodium sulfite
Adjust pH to 7.2 with 8.0 g aqueous ammonia or H2SO4.

Add water to make up to 1 liter.

Stabilized bath water
900
ml formalin (37% by weight)
6.0ml polyoxyethylene-p-monononyl phenyl ether
Add 0.5ml water to make 1 liter.

The residual silver results are shown in Table 3 below.

Example 8 (Comparative Example) Exposure and processing were carried out in the same manner as in Example 7. All treatment baths except the bleach bath had the same composition as in Example 7.

Bleach bath H water
5
00ml Nitrilodiacetic acid monopropionate iron(III)
88.0g Nitrilodiacetic monopropionic acid
7.0g potassium bromide

78.0g hydrobromic acid (48% by weight)
33.0ml potassium nitrate
25.0g Adjust pH to 6.0 with aqueous ammonia or HBr. Add water to make 1 liter.

The measurement results for residual silver are shown in Table 3 below.

Example 9 (Comparative Example) Exposure and processing were carried out in the same manner as in Example 7. All treatment baths except the bleach bath had the same composition as in Example 7.

Bleach bath I water
5
00ml EDTA ammonium iron(III)
124.0g ethylenediaminetetraacetic acid (EDTA)
10.0g potassium bromide
7
8.0g hydrobromic acid (48% by weight)
33.0ml potassium nitrate
25.0g Adjust pH to 5.7 with aqueous ammonia or HBr. Add water to make 1 liter.

The measurement results for residual silver are shown in Table 3 below.

[0104]

[Table 3] Table 3 Bleaching bath Silver detector reading *G
4H
9I
A value of 4*6 or more indicates the presence of residual silver.

As shown in Table 3, the bleaching power of the bleaching bath G according to the invention containing a biologically degradable complexing agent is higher than that of the conventional bleaching bath I containing an EDTA complexing agent that is difficult to biologically decompose. equal to the bleaching power of However, bleach bath H, which has substantially the same composition as bleach bath G but has the same pH as the EDTA bleach bath, has insufficient bleaching power.

The main features and aspects of the present invention are as follows.

1. (1) 20 mol% or more of the complexing agent is of the following formula I

[0108]

embedded image (HOOC-CH2)2-N-CH2
-CH2-COOH (I) containing an iron(III) complex represented by (2) a pH of 4.
A bleaching bath characterized by being adjusted to 5 or more and less than 6.0.

2. Bleaching bath according to claim 1, characterized in that at least 80 mol % of the complexing agent is represented by formula I.

3. 2. The bleaching bath according to item 1, characterized in that the free complexing agent is contained in an excess of 1 to 120 mol %.

4. 1 above, characterized in that it contains an insufficient amount of thiosulfate to fix undeveloped silver halide.
The bleaching bath described in.

5. 2. The bleaching bath according to item 1 above, characterized in that it does not contain any thiosulfate.

Claims (1)

[Claims] Claim 1: (1) at least 20 mol% of the complexing agent.
is the following formula I: (HOOC-CH2)2-N-C
A bleaching bath comprising an iron (III) complex represented by H2-CH2-COOH (I), and (2) having a pH adjusted to 4.5 or more and less than 6.0.