JPS6121168B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a zeolite slurry with good suspension stability, and in particular to a zeolite slurry with good suspension stability and whose flow characteristics hardly change depending on temperature conditions. Generally, zeolites have the formula xM ₂ O・Al ₂ O ₃・ySiO ₂・zH ₂ O (where
M represents a monovalent metal or a polyvalent metal equivalent thereto, x is 0.5 to 1.5, y is 1.5 to 50, z is 0 to
It is a general term for aluminosilicates with the chemical composition and unique three-dimensional structure shown in 6). Various zeolites are known due to differences in their component composition and crystal structure, and there are zeolite-specific They are used for various purposes based on their performance such as ion exchangeability, filling ability, adsorption ability, and catalytic ability. On the other hand, all industrially used zeolites consist of fine primary particles with a particle size of about 0.1 to 50 μm, so in most cases they are bulky and easily turn into dust when transported, stored, or used. It has the disadvantage that handling is inefficient and it tends to harm the working environment. Therefore, in order to improve the drawbacks of powdered zeolite, slurry-like or granulated zeolite has come to be used, especially as a builder for detergents, water treatment agents, pigments for coated paper, paints, etc. For applications that require the handling of multiple zeolites, such as seed fillers, it is convenient to use them in the form of an aqueous slurry in which zeolite particles are dispersed and suspended in water, and the zeolite manufacturing process is also streamlined. It also has the advantage of being However, a simple aqueous slurry of zeolite is originally a physically unstable system, and as the suspended zeolite particles eventually settle, the separated zeolite particles settle at the bottom of the container, forming a hard cake. Moreover, once formed, such a hard cake exhibits significant dilatancy against externally applied forces, making it difficult to redisperse it into a homogeneous slurry state. Therefore, it has been proposed to stabilize the aqueous slurry of zeolites by adding various substances to the slurry. For example, in JP-A No. 51-91898, and others, polymers containing carboxyl and/or hydroxyl groups, phosphonic acid phosphate alkyl ester emulsifiers, nonionic surfactants, surface-active sulfonic acids are used as dispersion aids in zeolite aqueous slurries. It has been proposed to improve the fluidity of the slurry by adding about 0.5 to 6% by weight of at least one of salts, swellable insoluble silicates, etc. However, these additive methods are associated with a number of drawbacks and are not always rational or advantageous. In other words, while water-soluble polymers exhibit high viscosity in small amounts, the physical and chemical properties of water-soluble polymers are unstable, easily affected by temperature and mechanical stirring, and change significantly over time, which can cause trouble when storing or transporting slurry over long periods of time. may occur. In addition, when using a surfactant, there are problems such as an increase in volume due to air entrainment during stirring or pumping, and foam scattering due to foaming.Also, since swellable insoluble silicates are mainly natural products, It lacks stability in quality and is generally dark gray, which has disadvantages such as impairing the appearance of the product. In addition, the fluidity properties, especially the viscosity, of the zeolite slurries obtained by these conventionally proposed methods differ significantly depending on the temperature, and may vary depending on the seasonal fluctuations of summer and winter and the temperature conditions during use. It is not uncommon for this to cause serious trouble during transportation, storage, processing, etc., and in order to avoid such trouble, special measures are taken to keep the slurry temperature constant through heating and cooling. This method has the serious disadvantage of requiring equipment, energy, labor, etc. In addition, Japanese Patent Publication No. 55-84533 proposes adding an organic coagulant, but this method involves adding 0.01 to 5. Weight% especially 0.05-2% by weight
By including the slurry, the purpose is to mainly utilize the high viscosity of the medium to obtain a slurry in which the zeolite particles are difficult to settle. Not only does it require a large amount of energy to transport, but it also acts as a glue when drying, which can impair the solubility and dispersibility of synthetic detergent powders made using it in water. The disadvantage is that serious troubles can easily occur. On the other hand, the present inventors previously found that in a zeolite slurry consisting of zeolite and an electrolyte aqueous solution, the suspension stability of the slurry is closely related to the electrical conductivity of the slurry, and the electrical conductivity of the slurry was appropriately adjusted. We have developed a zeolite slurry with good suspension stability based on adjusting the value to a certain range (Japanese Patent Application No. 142011/1982). However, although zeolite slurries characterized by the presence of such electrolytes have good suspension stability, they often have the disadvantage of extremely high viscosity values at low temperatures, and they also tend to aggregate into granules when left to stand for long periods of time. In other words, a new problem may arise: the formation of small bumpy lumps (hereinafter simply referred to as bumps). This phenomenon of formation of two particles is a unique phenomenon that is often observed in the case of high-performance zeolite with high purity, high crystallinity, and uniform particle size distribution. This can be easily observed by the large number of small pieces attached to the glass rod when the glass rod is inserted and pulled up. These particles are generally easily redispersed and disappear with mild agitation or vibration, but if left as is, they will not flow out completely even if the container is tilted, and the characteristics of the zeolite slurry as a virtually perfect fluid will be significantly impaired. It turns out. The present inventors have conducted various experiments to solve the new problem of improving the viscosity versus temperature characteristics of zeolite slurry and the formation of lumps, and as a result, we have developed a method of adding polyethylene oxide, which has stringability, to an aqueous zeolite slurry. By adjusting the electrolyte concentration so that it is present in a very small amount and the conductivity of the slurry is within a specific range,
The present invention was completed after discovering the surprising fact that a high-performance zeolite slurry with good suspension stability, no tendency to form particles, high fluidity, and whose fluidity hardly changes depending on temperature conditions can be obtained. That is, the present invention provides an aqueous slurry of zeolite whose main components are zeolite having a uniform particle size distribution in which the particle size portion of 6 μm or less accounts for 85% or more and an aqueous electrolyte solution at 25°C.
0.01 to 0.5 of polyethylene oxide having a stringability of at least 5 cm in a 0.2% by weight aqueous solution.
% by weight, and the electrolyticity of the slurry at 25° C. is 0.025Ω ⁻¹ ·cm ⁻¹ or less as a specific conductivity, and has good suspension stability. According to the study results of the present inventors, the electrical conductivity of an aqueous slurry consisting of zeolite and an aqueous electrolyte solution generally varies significantly depending on the particle state of the zeolite, the slurry concentration, the type and concentration of the dissolved electrolyte, etc. , detergent builder, water treatment agent,
In the case of zeolite having a particle size suitable for applications such as coated paper pigments, the specific conductivity of the slurry at 25°C is 0.006 to 0.1 Ω ^-1 cm ^-1 , almost regardless of the slurry concentration or the type of dissolved electrolyte. Favorable suspension stability is obtained only when a critical amount of electrolyte is present such that the value of then 5
The viscosity is extremely high in the low-temperature range around ℃, and noticeable lumps are often formed after being left standing for a long time.
When present at 0.01 to 0.5% by weight, the slurry at 25°C
In the presence of a small amount of electrolyte with a specific conductivity of 0.025Ω ^-1 cm ^-1 or less, suspension stability is good, there is no tendency to form lumps, and the fluidity is high.
Moreover, a high-performance zeolite slurry whose fluidity hardly changes depending on temperature conditions can be obtained. If the amount of stringable polyethylene oxide is less than 0.01% by weight, the effect of addition will be insufficient, while if it exceeds 0.5% by weight, the viscosity of the slurry will generally increase significantly and the fluidity will deteriorate. As this decreases, the cost also increases economically. In addition, if the specific conductivity of the zeolite slurry at 25°C is greater than 0.025Ω ^-1 cm ^-1 , the viscosity of the slurry in the low temperature range becomes extremely high regardless of the amount of polyethylene oxide present, resulting in insufficient fluidity. becomes. The polyethylene oxide used in the zeolite slurry according to the present invention has unique rheological properties in which an aqueous solution thereof is characterized by remarkable stringiness. The stringiness referred to here refers to a phenomenon in which, for example, when one end of a glass rod is dipped in a dilute solution and pulled up, it stretches like a string like starch syrup, and the cause and mechanism of this are still not completely understood. However, since high viscosity solutions do not necessarily exhibit great stringiness, stringiness does not simply depend on the degree of polymerization, but is based on the unique structure of the dissolved polymer or the highly uniform degree of polymerization. It is considered a thing. In general, polyethylene oxide is obtained by subjecting ethylene oxide to a polymerization reaction in the presence of a catalyst, but polymers with a high degree of polymerization with a molecular weight of about 1 million or more and a uniform degree of polymerization have a remarkable aqueous solution. It is said to exhibit stringiness. For the purpose of the present invention, the test method described below
It is useful that a 0.2% by weight aqueous solution exhibits stringiness of at least about 5 cm or more, and particularly preferred is one that exhibits stringiness of 10 cm or more. On the other hand, polyethylene oxide, the aqueous solution of which exhibits almost no stringiness, does not exhibit a dispersing effect on zeolite particles, and may even have the opposite effect of aggregating the particles. When using polyethylene oxide having stringability, it is practical to form an aqueous solution of about 0.2 to 1% by weight in advance and add the required amount to the zeolite slurry. Although the details of the mechanism of action of polyethylene oxide having the above-mentioned stringiness in the present invention are not necessarily clear, it is adsorbed to the surface of zeolite particles in an aqueous medium, exhibiting an aggregation prevention effect as a kind of protective colloid, and becoming suspended. It is presumed that it improves the fluidity of the slurry by ensuring stability and preventing the formation of bumps, and also by imparting unique viscoelasticity to the aqueous medium, making it itself a type of lubricant. The present invention is based on new findings of such remarkable fact. The zeolite used in the zeolite slurry according to the present invention may be any type of zeolite, whether natural or synthetic, and can be appropriately selected depending on the purpose of use. For example, type A zeolite with high Ca ion exchange capacity is particularly suitable for detergent builders.
Spherical and fine A-type zeolite is suitable for coating paper pigments, and A-type, X-type, and
Synthetic zeolites such as Y type and natural zeolites such as mordenite and clinoptilolite can be used.
In the case of any zeolite, a zeolite having a fine and uniform particle size distribution in which the particle size distribution is 85% or more with a particle size of 6 μm or less is particularly suitable. Generalite, which has a non-uniform particle size distribution that contains many coarse particles with a particle size of 6 μm or more, quickly settles and separates from the slurry state, and the particles that settle at the bottom of the vessel form a harder cake, making redispersion more difficult. Not only this, but also the final product made using zeolite is likely to suffer from various troubles due to coarse agglomerated particles. The particle size distribution of zeolite can be measured, for example, by a particle size distribution measuring device based on a sedimentation method. Various concentrations of zeolite can be applied to the zeolite slurry of the present invention.
A content other than 20 to 60% by weight is unfavorable from the viewpoint of production, handling, and efficiency in use. The electrolytes used in the zeolite slurry of the present invention include carbonates, sulfates, silicates, phosphates, borates, hydroxides, chlorides, nitrates of sodium, potassium, ammonium, lithium, magnesium, calcium, etc., respectively; Sulfites, thiosulfates, hypochlorites, percarbonates, polymerized phosphates, perborates, imidobissulfates, formates, acetates, oxalates, citrates, nitrilotriacetates, etc. (However, (excluding those insoluble in water), but compounds other than those listed above can also be used as long as they are soluble in water and exhibit conductivity by dissociating into ions in a solution. Among these electrolytes, particularly sodium carbonate, sodium silicate, sodium sulfate, sodium borate, sodium polyphosphate, sodium imidobis sulfate, sodium citrate,
Salts such as sodium nitrilotriacetate, sodium percarbonate, and sodium perborate are often practical, and it is preferable to use one or more of them. The preparation of the zeolite slurry according to the present invention can usually be carried out as follows, but the mode of preparation is not limited thereto. That is, in the case of synthetic zeolite, a well-washed overcake or powder of zeolite having the above-mentioned particle state produced by wet reaction is dispersed in an appropriate amount of water to form an aqueous slurry, and the conductivity is adjusted to a predetermined value. After adjusting the salt concentration and PH as described above, a predetermined amount of an aqueous solution of polyethylene oxide having the above-mentioned stringiness is added to the solution, and the overcake or powder of the above-mentioned zeolite is added to a predetermined amount of the polyethylene oxide having the stringability. Examples include a method of dispersing and suspending the salt in a dilute aqueous solution containing the salt to form a slurry, and adjusting the salt concentration so that the conductivity finally reaches a predetermined value. In the case of natural zeolite, the particle size is adjusted by grinding, classification, etc., and then a uniform zeolite slurry is prepared in the same manner as in the case of synthetic zeolite. In addition, the zeolite slurry according to the present invention is
It goes without saying that one or more of various salts, water-soluble polymers, surfactants, chelating agents, colorants, fragrances, etc. can be added as appropriate depending on the final purpose of use. The zeolite slurry according to the present invention generally has excellent fluidity and suspension stability, and in particular, not only is the redispersibility of sedimented particles that occur when the slurry is left standing for a long period of time very good, but also The viscosity remains almost constant even when temperature conditions change, and it always shows good flow characteristics even when there are seasonal changes in summer or winter or temperature changes during use, so there is no need for special insulation equipment or energy. , its storage;
It has the revolutionary advantage of being extremely easy to transport and handle during use. In addition, the zeolite slurry according to the present invention does not require the addition of large amounts of dispersants or stabilizers, and it is possible to obtain a slurry with high fluidity. It is also possible to prepare For example, in the case of zeolite slurry for detergents, it is mainly used as a builder for low-phosphorus or no-phosphorus synthetic detergents, but the zeolite slurry according to the present invention always maintains fluidity despite fluctuations in seasonal and process temperature conditions. Not only does it have excellent suspension stability and is easy to transport and store, but it can also be blended into other detergent raw materials in place of conventional sodium tripolyphosphate at detergent manufacturing plants without making major changes to conventional equipment or processes. Moreover, the detergent obtained by blending this zeolite slurry does not cause powder to adhere to or remain on contaminated cloth when it is washed, and there is extremely little risk of causing problems such as so-called cloth adhesion. Furthermore, synthetic detergents are generally manufactured by spray-drying a thick formulation slurry obtained by mixing various raw materials such as surfactant aqueous solution, sodium silicate, soda ash, polymerized phosphate or zeolite, Glauber's salt, and carboxymethyl cellulose. Therefore, from the viewpoint of saving water evaporation energy in the spray drying process, efforts are desired to avoid mixing of water accompanying the raw materials as much as possible. However, the zeolite slurry for detergents according to the present invention It is also possible to make a very thick slurry with a slurry concentration of about 50 to 60% by weight, and the increase in water content due to the addition of zeolite to the precursor can be kept to a minimum. In addition, in the case of zeolite slurry for coated paper, it is mainly used for coated paper, art paper, etc., but the zeolite slurry according to the present invention always maintains fluidity and suspension stability almost unaffected by temperature conditions. In addition to being easy to transport, store, and handle, the zeolite particles can be used as the main or secondary raw material for slurry-like coated paper compositions, imparting high gloss and whiteness to coated paper, and improving printability. Demonstrates excellent performance in improving the In this case as well, a zeolite slurry with a high slurry concentration has the advantage of being able to efficiently coat paper and helping to save energy in the process. The present invention will be explained below with reference to Examples and Comparative Examples. However, the characteristic values of the zeolites shown in the Examples and the various performances of the zeolite slurries prepared using these zeolites were measured or evaluated by the following test methods. [Threadability] When the tip of a glass rod with a diameter of 5 mm is immersed to a depth of approximately 1 cm in a 0.2% by weight aqueous solution (25°C) of the sample polymer and the rod is pulled up vertically at a speed of 5 cm per second, the solution is Measure the length (cm) until it stretches like a thread and eventually breaks. [Ca ion exchange capacity] Calcium chloride solution (300mg/ as CaO) 1
1 g of zeolite sample (calculated as anhydride) was added to the solution, stirred at 25°C to react, and after 15 minutes, the zeolite was quickly overseparated, the concentration of calcium (CaO) in the solution was analyzed, and the concentration of calcium (CaO) dissolved in the solution was determined. Calculate the amount of decrease in calcium and use this as the Ca ion exchange capacity. [Particle size distribution] Approximately 0.5 g of zeolite sample was added to 500 ml of 0.01% sodium hexametaphosphate solution, and stirred thoroughly to form a uniform suspension using a light transmission particle size distribution analyzer (manufactured by Seishin Enterprise Co., Ltd.). Create a sedimentation curve at 25°C using [Viscosity] Using a B8H type viscometer manufactured by Tokyo Keiki Seisakusho Co., Ltd.,
The viscosity of the zeolite slurry sample at 5 to 45°C is measured under the measurement conditions of rotor No. 2 and 20 rpm. [Electrical conductivity] The electrical conductivity of the zeolite slurry sample at 25°C is measured using a conductivity meter CM-20E model manufactured by Toa Denpa Kogyo Co., Ltd. [Suspension stability] 700 to 800 g of a zeolite slurry sample was placed in a 500 ml plastic bottle and left to stand. After 3 days, a glass rod was inserted into the sample and the sedimentation status of the zeolite at the bottom of the container was evaluated by feeling with the glass rod. , No sedimentation is observed as ○, Slight sedimentation is observed as △, and hard or sticky deposits are observed on the bottom of the container as x. [Vibration stability] A zeolite slurry sample prepared in the same manner as in the suspension stability test was
VIBRATORY PACKER (50 cycles/sec) and vibrated for 10 hours, a glass rod was inserted into the sample, and the suspension stability was evaluated using the same scale as the suspension stability described above. indicate. [Supernatant production rate] A zeolite slurry sample was placed in a 50 ml sedimentation tube and left to stand at room temperature, and the supernatant production rate after 72 hours was determined from the position of the sedimentation interface. Examples 1 to 4 and Comparative Examples 1 to 2 Type A zeolite was synthesized using a sodium aluminate aqueous solution and a sodium silicate aqueous solution, and after the reaction was completed, the mother liquor was separated by operations such as filtration and water washing, and the zeolite concentration was 71.0% (water content). A filtration cake was obtained.
A part of this filter cake was dried and pulverized, and its particle state and Ca ion exchange capacity were examined, and the various values shown in Table 1 were obtained.

[Table] On the other hand, using the above supercake as an intermediate raw material, water was added to it and repulped to prepare a slurry, and the pH was adjusted by introducing carbon dioxide gas and an aqueous solution of polyethylene oxide was added. A homogeneous zeolite slurry shown in was prepared. However, it is the second largest polyethylene oxide.
The materials shown in the table were used.

[Table] Polyethylene oxide A and B are manufactured by Tetsuko Kagaku Kogyo.
It is commercially available under the registered trademark "PEO" manufactured by Co., Ltd. Table 3 shows the composition and properties of each zeolite slurry.

[Table] From Tables 2 and 3, it can be seen that a zeolite slurry whose main components are zeolite and an electrolyte aqueous solution, which has a uniform particle size distribution with a particle size of 6 μm or less reaching 98%, has stringability. Contains 0.05-0.10% by weight of polyethylene oxide,
In Examples 1 to 4, in which the specific gravity conductivity was 0.010 to 0.011 Ω ^-1 cm ^-1, the supernatant formation rate was small and the suspension stability was good when left standing for 3 days or shaken for 10 hours. One thing is clear. On the other hand, in Comparative Example 2, which used polyethylene oxide without stringiness, the supernatant formation rate was high, similar to Comparative Example 1 in which no polyethylene oxide was added, and in particular, the vibration stability against vibration was insufficient. I understand. Examples 5 to 6 and Comparative Example 3 An aqueous slurry of zeolite was prepared in the same manner as in Example 1, and the pH was adjusted by introducing carbon dioxide gas and the conductivity was adjusted by adding various amounts of soda carbonate. Zeolite slurries having different electrical conductivities were prepared by adding polyethylene oxide A having stringability. The composition and properties of each zeolite slurry are shown in Table 4, and the temperature versus viscosity curve is shown in FIG.

[Table] From Table 4 and Figure 1, it is clear that a zeolite slurry whose main components are zeolite with a uniform particle size distribution and an aqueous electrode solution contains 0.05% by weight of polyethylene oxide with spinnability and has a specific conductivity. In Examples 5 and 6, in which the temperature is 0.010 to 0.018 Ω ^-1 cm ^-1 , the suspension stability is good, and the viscosity value is 10 poise or less over a wide temperature range and has excellent fluidity. it is obvious. On the other hand, even if the same amount of polyethylene oxide with stringiness is contained, the specific conductivity is 0.027Ω.
^-1・cm ^-1 Comparative Example 3 has good suspension stability, but the viscosity value is 12 poise or more at any temperature and has poor fluidity, making it difficult to transport by tank truck or piping. .

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between temperature and viscosity of each zeolite slurry of Example 5, Example 6, and Comparative Example 3.

Claims (1)

[Scope of Claims] 1. A 0.2 wt% aqueous solution at 25°C in an aqueous slurry of zeolite whose main components are zeolite having a uniform particle size distribution such that the particle size portion of 6 μm or less is 85% or more and an aqueous electrolyte solution. contains 0.01 to 0.5% by weight of polyethylene oxide having a stringability of at least 5 cm, and
A zeolite slurry with good suspension stability, characterized in that the electrical conductivity of the slurry at 25°C is 0.025Ω ^-1 ·cm ^-1 or less as a specific electrical conductivity. 2 Zeolite concentration in slurry is 20 to 60% by weight
A zeolite slurry with good suspension stability according to claim 1. 3. The zeolite slurry with good suspension stability according to claim 1 or 2, wherein the zeolite is type A zeolite.