WO2000022930A1 - Method for preventing aqueous slurry containing polysaccharide thickener from putrefaction - Google Patents

Abstract

A method whereby an aqueous slurry containing a water soluble polysaccharide thickener (carboxymethyl cellulose, natural rubber, etc.) can be prevented from putrefaction and a high storage stability over a long time can be imparted thereto. This method comprises adding an alkali metal salt or zinc salt of 2-pyridinethiol-1-oxide optionally combined with a formaldehyde-liberating compound to an aqueous slurry containing a polysaccharide thickener.

Description

 Description Preservative method for aqueous slurry containing polysaccharide thickener

 The present invention relates to a novel method of preserving an aqueous slurry containing a polysaccharide thickener. More specifically, polysaccharide thickeners such as carboxymethylcellulose (hereinafter abbreviated as CMC) and various natural gums are used in civil engineering work involving drilling of oil wells and soil, or in the manufacturing process of various industrial materials. The present invention relates to a novel preservative method capable of preventing decay and deterioration of an aqueous slurry which has been added and thickened, and which can impart long-term storage stability to the slurry. Background art

 Excavated mud generated in civil works, construction works, dredging works, etc. has a high water content and is often in a slurry state, so it is difficult to handle it in a solid form like solid materials. After excavation of such mud, it is often very difficult to carry out and transport it using ordinary dump trucks and trucks. For this reason, handling has been conventionally performed by adding a consolidation agent such as lime or cement, or by adding a water-soluble polymer compound or a superabsorbent resin to increase the consistency. . For example, in the conventional earth pressure shielding method applied to soft ground in tunnel excavation work, excavated earth and sand generated by various types of force turtles is once received in a chamber behind the power turret and then The soil is discharged from the screw conveyor. A large amount of sand or muddy water is generated In tunnel excavation work, sand is not efficiently discharged due to low water retention and plastic fluidity, and only muddy water is discharged by the screw conveyor to leave solid sediment The problem is that the work efficiency is reduced due to this.

To solve this problem, add a water-soluble polysaccharide thickener such as xanthan gum or CMC to the excavated sediment taken into the chamber to increase the consistency, water retention and plastic fluidity of the excavated sediment To improve the discharge efficiency of conveyors (See JP-A-5-44394 and JP-A-1-121396). Generally, water-soluble polymer compounds including natural water-soluble polymer compounds, semi-synthetic water-soluble polymer compounds and synthetic water-soluble polymer compounds are used as modifiers to reduce the fluidity of excavated mud. A substance is added and dissolved (see JP-A-8-283717).

 With regard to such additives for improving the consistency, water retention and plastic fluidity of excavated soil, emphasis has been placed on consideration for environmental protection and ensuring safety for the human body. In recent years, natural gums such as guar gum, xanthan gum and the like, and thickening polysaccharide compounds such as CMC are increasingly used. This is because such thickening polysaccharide compounds are derived from natural products, and it has been confirmed that there is no problem in safety even when used as a food additive. You.

 However, such a thickening polysaccharide compound derived from a natural product rots in an aqueous solution in a short period of time due to the action of microorganisms, and therefore has the effect of improving the viscosity, water retention, and plastic fluidity of the aqueous slurry. The mud to which such additives are added quickly has a serious problem that the working environment is remarkably deteriorated due to the bad odor that is generated unless it is immediately carried out.

 Furthermore, natural gums may contain endogenous microorganisms in their own right, and when used as an aqueous solution, the endogenous microorganisms immediately start growing and reduce the viscosity of the aqueous solution. As time passes, the viscosity drops sharply. Since there is a certain correlation between the growth of endogenous microorganisms and the decrease in viscosity, the use of gums in civil engineering and various industrial material manufacturing processes as described above is avoided. Absent.

In order to solve such problems, an aqueous slurry of formalin, ie, formaldehyde, which has a bactericidal action, is added to an aqueous slurry containing CMC and natural gums. However, when formalin is used, it is effective against a wide range of microbial spectrum, but has a very low effect on inhibiting the growth of molds and yeasts. In addition, although there is an advantage that the sterilizing effect is instantaneously exerted, on the other hand, it is not possible to prevent the decay of the slurry for a long period of time. To be lost Become. In addition, products made using such altered slurries are also susceptible to spoilage. Disclosure of the invention

 Under such circumstances, the present invention prevents the spoilage deterioration of an aqueous slurry containing a water-soluble polysaccharide compound such as CMC and natural gums as a thickener, and improves the viscosity and water retention of the slurry. Preservation method for aqueous slurries that can maintain performance such as fluidity and plastic fluidity, does not generate putrefaction odor, maintains its rot effect over a long period of time, and does not adversely affect the environment. It is intended to provide.

 The present inventors have conducted various studies to develop an antiseptic method for the aqueous slurry containing the thickening polysaccharide compound, which does not have the above-mentioned problems. As a result, the alkali metal salt of 2-pyridinethiol-1-oxide or Zinc salts (hereinafter sometimes referred to as antimicrobial compounds) or, if desired, a combination of these and a formaldehyde-releasing compound are added to an aqueous slurry to effectively prevent decay thereof. The present inventors have found that the slurries can be produced and that the rot preventing effect can be maintained for a long period of time without deteriorating the preferable properties of the slurry, and based on this finding, the present invention has been completed.

 That is, the method for preventing spoilage of an aqueous slurry provided by the present invention comprises a polysaccharide thickener containing an antimicrobial compound selected from alkali metal salts and zinc salts of 2-pyridinthiol-1-oxide as an antiseptic active ingredient. A preservative method characterized by being added to an aqueous slurry containing a polysaccharide thickener as a composite antiseptic active ingredient, wherein the combination of the antimicrobial compound and a formaldehyde releasing compound is added to an aqueous slurry containing An antiseptic method characterized by being added. BEST MODE FOR CARRYING OUT THE INVENTION

The alkali metal salt of 2-pyridinethiol-1-oxide used as an antimicrobial compound in the preservative method of the present invention has a general formula: Οι (.

O

(M in the formula is a metal atom)

Wherein the zinc salt of 2-pyridinethiol-1-oxide is represented by the formula

で表わされる構造を有する化合物である。 0 → Ζ η— Ο

Is a compound having a structure represented by

 The alkali metal represented by Μ in the above general formula (I) includes sodium, potassium, lithium and the like, and sodium is preferred industrially.

 In the method of the present invention, one of the alkali metal salt and zinc salt of 2-pyridinethiol-1-oxide may be used alone, or two or more thereof may be used in combination.

 In the preservative method of the present invention, only the metal salt or zinc salt of 2-pyridinethiol-1-oxide may be added to the aqueous slurry as a preservative active ingredient, but the polysaccharide thickener may be added. In order to further improve the long-term storage stability of the aqueous slurry to be produced, a combination of the above-mentioned alkali metal salt or zinc salt of 2-pyridinethiol-1-oxide and a formaldehyde releasing compound should be added as a composite active ingredient. Is desirable.

Here, as the formaldehyde-releasing compound, for example, 13-dimethylolone-5,5-dimethylhydantoin, 1- (3-chloroallyl) -3,57-triaza-1-azoniaadamantank Do, 2-bromo-2-dipropanol -1,3-Diol, N, N "-methylenebis [Ν '-[1- (hydroxymethyl) -2,5-dioxo-4-imidazolidinyl] urea], Ν- (hydroxymethyl) -Ν- (1,3-Dihydroxymethyl-2,5-dioxo-4-imidazolinyl) -N '-(Hydroxymethyl) urea, Ν, Ν', Ν "-Trishydroxyxexetil Hexahydro-sym-triazine Can be One of these formaldehyde releasing compounds may be used alone, or two or more thereof may be used in combination.

 When the antimicrobial compound and the formaldehyde-releasing compound are used in combination, the mixing ratio thereof is not particularly limited and may be appropriately selected depending on the situation. 10: 1 to 1:50, preferably 10: 1 to 1:15. If the proportion of the formaldehyde-releasing compound is less than this range, the long-lasting effect of the preservative action will not be sufficiently exerted. If the proportion of the formaldehyde-releasing compound is greater than this range, the viscosity of the slurry, ρ Η It is not preferable because physical properties such as appearance are adversely affected.

 It should be noted that the amount of the above-mentioned antiseptic active ingredient to be added to the aqueous slurry in the preservative method of the present invention should be appropriately selected according to conditions such as the type of the target aqueous slurry, the use, the type of microorganism, and the density of the microorganism. Of course, in general, the amount of the antiseptic active ingredient is generally 0.002 to 2% by weight, preferably 0.01 to 1% by weight based on the total amount of the aqueous slurry containing the polysaccharide thickener. It is good to choose so that it becomes weight%. For example, when the polysaccharide thickener-containing aqueous slurry to which the preservative method of the present invention is applied is related to civil engineering work such as mud slurry, the concentration of the active ingredient is from 0.1 to 0.1% by weight. It may be added so that the concentration of the active ingredient is 0.1 to 0.5% by weight when it relates to a general industrial material production process. Needless to say, if the amount of the preservative active ingredient is too small, the desired preservative effect is not sufficiently exhibited, but if it is too large, various metals contained as impurities in the 2-pyridinethiol-1-oxide salt and slurry. In some cases, a colored chelate compound is formed between the components and the aqueous slurry is colored, thereby deteriorating the appearance or not obtaining the desired consistency or ρ Η.

Polysaccharide that can be contained in an aqueous slurry to which the preservative method of the present invention is applied 增 Examples of the thickener include natural gums such as CMC, guar gum, glucone gum, xanthan gum, and arabia gum, but these may contain only one kind or two or more kinds at the same time. It may be contained. The concentration of these polysaccharide thickeners in the slurry is not particularly limited, and may be an appropriate amount depending on the use of the aqueous slurry.

 Next, the preservative method of the present invention will be described in more detail based on examples and comparative examples, but the present invention is not limited to these examples.

 In the following description, compound names are abbreviated as follows.

 Z PT: 2-pyridinethiol-1-zinc oxide

 DMDMH: 1,3-Dimethylol-5,5-dimethylhydantoin

 Dowicil 75 (trademark of Dow Chemical Company): 1- (3-chloroallyl)

-3, 5, 7-Triaza-1-Azoniadamanthan chloride

 BNP: 2-Bromo-2-nitropropane-1,3-diol

Example 1 Preservative effect of ZPT on CMC aqueous solution

巿 100 parts by weight of water and 0.2 parts by weight of CMC were placed in a beaker and sufficiently stirred with a homogenizer to prepare a homogeneous aqueous solution. 0.01 wt% to the aqueous solution, 0.02 wt% and 0.05 wt% of Z PT ones were added and their respective 300 of an aqueous solution with no additive g, so that to the 10 ⁶ NZM 1 10 ⁵ Density spoilage bacteria Was inoculated. This spoilage bacterium was separated from spoiled CMC aqueous solution prepared separately. Each aqueous solution inoculated with the spoilage bacteria was kept in a thermostat at 35 ° C for 21 days, during which the viscosity, pH and the number of microorganisms were measured. Table 1 shows the measurement results of the aqueous solution viscosity, and Table 2 shows the measurement results of the pH.

 The conditions for measuring the viscosity are as follows. In other words, after shaking for 5 minutes, the sample aqueous solution was allowed to stand for 24 hours at a measurement temperature of 30 ° C, and the rotor was rotated using a rotary viscometer (No. 3 ports, rotation speed: 12 rpm). The viscosity after 2 minutes of rotation was read.

The measurement result of the microorganism density did not reach 1 ONZm 1 in all the measurements for the viper, but did not reach 10 N / m 1 in the whole measurement for the bacteria when ZPT was added. 1, 8, 14 and After 21 they were 3.1 x 10 ⁵ , 6.4 x 10 1.4xl ⁰⁹ and 7.7 x 10 ⁷ N / m 1 respectively.

これらの測定結果からわかるように、 Z PTを添加しなかった CMC水溶液で はバクテリア数の増加 （14曰以後は減少に転じる） ならびに粘度および pHの 著しい低下が確認されたが、 Z PTを添加した水溶液では、 バクテリア数の増加 はなく、 粘度、 pHともにその低下が顕著に抑制されることが確認された。 実施例 2 ベントナイ トスラリーに対する防腐効果

As can be seen from these measurement results, in the CMC aqueous solution to which ZPT was not added, the bacterial count increased (after 14), the viscosity and pH decreased significantly, but ZPT was added. It was confirmed that there was no increase in the bacterial count in the aqueous solution, and the decrease in both viscosity and pH was significantly suppressed. Example 2 Antiseptic effect on bentonite slurry

An aqueous slurry of bentonite was prepared as the equivalent of a drilling mat. That is, 100 parts by weight of water, 6 parts by weight of bentonite, 0.2 parts by weight of CMC, and 0.1 parts by weight of sodium humate as a dispersant were placed in a beaker, and the mixture was homogenized. The mixture was sufficiently stirred to obtain a homogeneous bentonite slurry. For this slurry

The inoculum was inoculated in the same manner as in Example 1 to each of the slurry containing 0.01, 0.02, and 0.05% by weight of ZPT and the slurry to which no ZPT was added, and then kept at 35 ° C for 21 days. , PH and microbial count were measured. To clarify the persistence of the preservative effect, the bacteria were re-inoculated after 7 days and 14 days later. Table 3 shows changes in viscosity of these slurries, and Table 4 shows changes in pH. As can be seen from these measurement results, the effect of preventing the decrease in viscosity and pH for bentonite slurry was almost the same as in the case of the CMC aqueous solution.

Regarding the density of microorganisms in the slurry, the density of power locomotives did not reach 10 NZ ml in all measurements, but for bacteria, the suppression effect was somewhat insufficient when the amount of ZPT added was 0.01 or 0.02% by weight. , the 15 days and 21曰後, both in 0.01 wt% 1. becomes 6x l 0 ⁷ N / ml, in 0.02% by weight respectively were 1.0 X 10 ² or ^{1. 7x 10 2 N / m 1} . Bacteria densities in the absence of additives were 1, Ox 10 ³ , 1.0 x 10 ⁶ , 1.7 x 10 ⁶ and 1.0 x 10 ⁸ NZm 1, respectively. Table 3 Viscosity (cps)

 1 after 8 after 15 after 21 after

 Z P T 0 3 485 300 150 150 Addition amount 0.01 3415 2715 2830 2800

 (% By weight) 0.02 3495 2820 2740 2900

0.05 3530 2960 2715 2915 Table 4

実施例 3 ZPTとホルムアルデヒ ド放出性化合物の併用効果

Example 3 Combined effect of ZPT and formaldehyde releasing compound

 The experimental conditions were largely the same as in Example 2 above, except that the use of ZPT alone was replaced by 0.001 or 0.005% by weight of ZPT and 0.009 or 0.005% by weight of formaldehyde releasing compounds (DMDMH, Dowicil 75 and BNP). Combinations (all in total 0.01% by weight) were used.

Table 5 shows the change in viscosity of the bentonite slurry up to the date of 21 and Table 6 shows the change in pH.

 Table 5 Amount of preservative added Viscosity (cps)

 (% By weight) 1 after 8 after 15 after 21 after

 Z PT (0.001)

 3340 2815 2800 2415 DMDMH (0.009)

 ZPT (0.005)

 3350 2875 2550 2200 DMDMH (0.005)

 Z PT (0.001)

 3380 2350 2300 2200 Dowicil 75 (0.009)

 ZPT (0.005)

 3480 2500 2300 2150 Dowicil 75 (0.005)

 ZPT (0.001)

 3490 2450 2175 2100 BNP (0.009)

 ZPT (0.005)

3380 2450 2100 2240 BNP (0.005) Table 6

As can be seen from the comparison between these measurement results and Tables 3 and 4, the combined effect of ZPT and formaldehyde-releasing compounds is almost the same in preventing pH reduction despite the small amount of ZPT used. there were. However, the effect of preventing the viscosity from decreasing is somewhat inferior.

Microbial density measurement results did not reach 10 NZm1 for all tests on power vines, but for bacteria, ZPT (0.005%) + DMDMH (0.005%), ZPT (0.005%) + Dowicil 75 (0.005%), ZPT (0.001%) + BNP (0.009%) and the combination of ZPT (0.005%) + BNP (0.005%), the measured results after 21 were 3.2 X 10 1.3xl 0 ² , respectively. Except for 2.0 × 10 ³ and 3.8 × 10 ⁶ NZm 1, it did not reach 10 NZm 1 in all measurements. 1

Comparative Example 1 Preservative effect of adding only formaldehyde releasing compound

 The experimental conditions were almost the same as in Example 2 above, except that only DMD MH, Dowicil 75 or BNP as a formaldehyde releasing compound was used in place of ZPT so that the concentration was 0.01% by weight, respectively. It was added to the bentonite slurry. Table 7 shows the change in viscosity of the slurry, and Table 8 shows the change in pH. Table 7

Table 8

これらの測定結果からわかるように、 スラリ一の粘度の低下および p Hの低下 を防止する効果は同量の Z P Tと比較して明らかに劣るものであった。

As can be seen from these measurement results, the effect of preventing the viscosity of the slurry from decreasing and the pH from decreasing was clearly inferior to that of the same amount of ZPT.

Microbial density was measured for bacteria and molds, and the results are shown in Table 9. As can be seen, the effect of inhibiting the growth of both bacteria and fungi is lost relatively quickly. Table 9

Example 4 and Comparative Example 2 Antiseptic effect on xanthan gum aqueous solution

 ZPT was used under almost the same conditions as in Example 1 except that a homogeneous aqueous solution prepared from 100 parts by weight of city water and 1.7 parts by weight of xanthan gum was used instead of the CMC aqueous solution.

Experiments were performed on a combination of DMDMH. ZPT and Dowicil 75, and a combination of ZPT and BNP. However, in order to clarify the persistence of the preservative effect, putrefactive bacteria are re-inoculated after 7 days and 14 days, and viscosity measurement using a rotational viscometer should be performed using a No. 4 rotor.

 Table 10 shows the change in viscosity up to and after, and Table 11 shows the change in pH. These tables also show the results when only DMDMH was added at 0.1% or 0.2% for comparison, and when no preservative was added as a control.

The change in microbial density was measured for bacteria and bacteria, and when ZPT was used in combination with a formaldehyde-releasing compound, the bacterial density after one day was increased when 0.01% ZPT and 0.09% Dowicil 75 were used together. Except for 1.5 × 10 ² N ml, 1 ONZml was not reached in all measurements. Table 12 shows the change in microbial density when only DMDMH was added and when no preservative was added.

As can be seen from the measurement results of the change in microbial density, the preservative method of the present invention It is clear that even when the gum is a water-soluble polysaccharide thickener, an extremely excellent preservative effect can be obtained as compared with the use of a formaldehyde-releasing compound alone.

 Table 10

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 V T

SS8eO / 66 «If / XDd 0C6ZZ / 00 OW Table 1 2

Industrial applicability

 The preservative method of the present invention, characterized in that ZPT or the like is added as a preservative, is applied to an aqueous slurry containing a perishable polysaccharide thickener to reduce the odor of the slurry and the odor associated with the putrefaction. Generation can be prevented and a decrease in slurry viscosity can be suppressed. Therefore, it is possible to improve the work efficiency of civil engineering work, especially work involving excavation of mud. In particular, when a formaldehyde-releasing compound is used as a preservative in combination with, for example, Ζ Ρ, it is possible to impart long-term storage stability to a slurry containing a polysaccharide thickener.

Claims

Claims  A method for preserving an aqueous slurry containing a polysaccharide thickener, comprising adding an antimicrobial compound selected from the group consisting of alkali metal salts and zinc salts of 12-pyridinethiol-1-oxide. 2. The preservative method according to claim 1, wherein the amount of the antimicrobial compound added is in the range of 0.002 to 2% by weight based on the total amount of the aqueous slurry containing the polysaccharide thickener. 3. The preservative method according to claim 1, wherein the antimicrobial compound is a zinc salt of 2-pyridinethiol-1-oxide.  An aqueous slurry containing a polysaccharide thickener characterized by adding a combination of an antimicrobial compound selected from the group consisting of alkali metal salts and zinc salts of 42-pyridinethiol-1-oxide and a formaldehyde releasing compound. Preservative method. 5. The method according to claim 4, wherein the total amount of the antimicrobial compound and the formaldehyde releasing compound is in the range of 0.002 to 2% by weight based on the total amount of the aqueous slurry containing the polysaccharide thickener. Preservative method. 6. The preservative method according to claim 4, wherein the ratio of the microorganism compound to the formaldehyde-releasing compound is in the range of 10: 1 to 1:50 by weight. 7. The preservative method according to claim 4, wherein the antimicrobial compound is a zinc salt of 2-pyridinethiol-1-oxide.  8 The formaldehyde-releasing compound is 1,3-dimethylol-5,5-dimethylhydantoin, 1- (3-chloroallyl) -3,5,7-triaza-1-azonia adamantank lid , 2-Bromo-2-nitropropane-1,3-diol, N, N "-methylenebis [Ν '-[1- (hydroxymethyl) -2,5-dioxo-4-imidazolidinyl] urea], Ν- (Hydroxymethyl)-Ν-(1,3-Dihydroxymethyl-2,5-dioxo-4-imidazolinyl) -N '-(Hydroxymethyl) urea and Ν, Ν', Ν〃-Tris-hydroxixylhexa Hydro- The preservative method according to claim 4, which is selected from the group consisting of sym-triazine. 9 2 -Pyridinethiol-1-oxide An antimicrobial compound selected from the group consisting of an alkali metal salt and a zinc salt and a formaldehyde-releasing compound in a weight ratio of 10 : A preservative composition containing the composition in a ratio of 1 to 1:50.  10. The preservative composition according to claim 9, wherein the antimicrobial compound is a zinc salt of 2-pyridinethiol-1-oxide.  11 The formaldehyde-releasing compound is 1,3-dimethylol-5,5-dimethylhydantoin, 1- (3-chloroallyl) -3,5,7-triaza-1_azoniadamantank, 2-bromo-2-nitropropane-1,3-diol, N, N "-methylenebis [Ν '-[1- (hydroxymethyl) -2,5-dioxo-4-imidazolidinyl] urea], Ν- ( (Hydroxymethyl)-Ν-(1,3-Dihydroxymethyl-2,5-dioxo-4-imidazolinyl)-N '-(Hydroxymethyl) Urea and, Ν', Ν "-Tris-hydroxyhexyl hexyl hydro-sym -The preservative composition according to claim 9, which is selected from the group consisting of triazines.