JP5335289B2 - Collection method of inorganic powder - Google Patents

Description

  The present invention relates to a method for recovering inorganic powder from a dispersion liquid (including a suspension) in which the inorganic powder is dispersed in a dispersion medium.

  In recent years, with the development and diversification of industries, many waste liquids containing inorganic powder are generated in media such as water and organic solvents in various fields. These effluents are often discarded because it is difficult to separate the inorganic powder from a medium such as water or an organic solvent, and it is difficult to distill due to the presence of the inorganic powder. On the other hand, due to environmental problems and the like, it is desired that the medium such as water and oil in the drainage liquid and the inorganic powder be separated and reused.

  Examples of the drainage include drainage containing silicon powder. For example, when a silicon crystal ingot is used as a silicon wafer, the drainage containing silicon powder usually includes a slicing step and / or a polishing step, and silicon powder is generated as cutting waste or the like derived from the slicing step. Together with the lubricating oil used in the slicing step and the abrasive grains used in the polishing step, the silicon powder is removed by the cleaning agent, resulting in the result. As the cleaning agent, a hydrocarbon solvent such as kerosene is mainly used.

  As a treatment method for the waste liquid containing the silicon powder, for example, the waste water contains an inorganic flocculant composed of silica sol-water-soluble metal salt so as to have a predetermined concentration, and then an organic polymer flocculant is added. A method to do this has been proposed (Patent Document 1).

JP 2007-185647 A

  However, the treatment method of Patent Document 1 contains an inorganic flocculant so as to have a predetermined concentration, and further adds an organic polymer flocculant, so that the treatment operation is complicated by using a plurality of materials. In addition, it is difficult to perform a processing operation such as setting the ratio of the inorganic flocculant to a predetermined concentration. Moreover, since the processing method of patent document 1 makes the wastewater containing silicon powder the process object, when the hydrocarbon-type solvent is used as a cleaning agent after the slicing processes, such as a silicon wafer, the concerned It cannot be applied to the drainage of cleaning agents (hydrocarbon solvents).

  An object of this invention is to provide the method of collect | recovering inorganic powder by the simple method from the drainage containing inorganic powder, such as silicon powder.

That is, the present invention includes a step (1) of adding an inorganic powder separation promoter composition (P) containing an alkyl glycoside and water to a dispersion in which the inorganic powder is dispersed in a dispersion medium
A step (2) of subjecting the dispersion to which the separation accelerator composition (P) has been added to a dispersion means to separate the layer (x) mainly containing the dispersion medium and the layer (y) containing the inorganic powder. And a step (3) of taking out the layer (y) containing the separated inorganic powder, and a method for recovering the inorganic powder.

  In the inorganic powder recovery method of the present invention, an inorganic powder separation accelerator composition (P) containing an alkyl glycoside and water is used. According to the separation accelerator composition (P), the separation accelerator composition (P) is added to a waste liquid such as a dispersion containing inorganic powder, stirred, mixed, and then allowed to stand. The dispersion can be easily separated into a layer (x) mainly containing a dispersion medium and a layer (y) containing an inorganic powder. In the present invention, by applying a centrifugal separation means as the stirring and mixing means, the layer (x) mainly containing the dispersion medium and the layer (y) containing the inorganic powder are rapidly separated. The inorganic powder can be easily taken out and collected from the layer (y) containing the inorganic powder thus separated. The inorganic powder recovered as described above can be reused. For example, when the inorganic powder is silicon powder, a silicon crystal ingot can be produced again from the collected silicon powder.

  For example, when a hydrocarbon solvent (eg kerosene) is used as a cleaning agent after a slicing process for silicon wafers, etc., a layer containing kerosene and silicon powder are contained from the drainage of the cleaning agent (eg kerosene). The layer to be separated can be separated, and the silicon powder can be taken out and collected from the layer containing the silicon powder.

  In the inorganic powder recovery method of the present invention, the step (1) of adding the inorganic powder separation accelerator composition (P) containing alkylglycoside and water to the dispersion liquid in which the inorganic powder is dispersed in the dispersion medium is performed. .

  The separation accelerator composition (P) of the present invention used in the step (1) can be used, for example, as an aqueous solution containing an alkyl glycoside and water. The alkyl glycoside used in the present invention can promote separation of the inorganic powder and the dispersion medium in the drainage by stirring and standing in addition to the dispersion such as the drainage in which the inorganic powder is dispersed. it can.

Examples of the alkyl glycoside used in the present invention include the following general formula (1):
R ¹ (OR ² ) _x G _y (1)
[Wherein, R ¹ represents a linear or branched alkyl group having 8 to 18 carbon atoms, an alkenyl group, or an alkylphenyl group, R ² represents an alkylene group having 2 to 4 carbon atoms, and G represents a carbon number. The residue derived from the reducing sugar which has 5-6 is shown, x (average value) shows 0-5, y (average value) shows 1-5].

In the formula, x is preferably 0 to 2, more preferably 0. y is preferably 1 to 1.5, more preferably 1 to 1.4. R ¹ preferably has 9 to 16 carbon atoms, and more preferably 10 to 14 carbon atoms. R ² is preferably an ethylene group. The structure of G is determined by a reducing sugar such as a monosaccharide or polysaccharide used as a raw material. Examples of the monosaccharide include glucose, galactose, xylose, mannose, lyxose, arabinose, and mixtures thereof. Examples of the polysaccharide include maltose, xylobiose, isomaltose, cellobiose, gentibiose, lactose, sucrose, nigerose, tulanose, raffinose, gentianose, melezitose, and mixtures thereof. Among these, as the monosaccharide, glucose or fructose is preferable from the viewpoint of availability and low cost, and maltose or sucrose is preferable as the polysaccharide. X and y are determined by proton ( ¹ H) NMR.

  The alkyl glycoside is not particularly limited as long as it satisfies the general formula (1). For example, alkyl polyglucoside is preferable, and decyl polyglucoside, dodecyl polyglucoside, myristyl polyglucoside, and the like are more preferable.

  Here, the alkylpolyglucoside refers to an alkyl glycoside in which G is a residue derived from glucose and y is 1 or more in the general formula (1), and includes, for example, a monosaccharide or a polysaccharide as its structure. Things.

  The separation accelerator composition (P) of the present invention is prepared by blending water with an alkyl glycoside. The separation accelerator composition (P) of the present invention is prepared such that the ratio of the alkyl glycoside to the total amount of the alkyl glycoside and water in the composition (P) is usually 0.01 to 50% by weight. Is done. The proportion is preferably 0.05 to 30% by weight, more preferably 0.1 to 20% by weight. By containing the alkyl glycoside at the above ratio, separation of inorganic powder, particularly silicon powder, can be promoted.

  There is no limitation in particular as water used for this invention, Ion exchange water, a pure water, deionized water, etc. are mentioned, Ion exchange water is preferable.

  The separation accelerator composition (P) of the present invention can further contain glyceryl ether. By containing glyceryl ether, separation of inorganic powder, particularly silicon powder, can be further promoted, and as a result, recovery of inorganic powder such as silicon powder can be facilitated.

  As the glyceryl ether used in the present invention, separation from inorganic powder, particularly silicon powder, can be promoted, and from the viewpoint of easy recovery of inorganic powder, for example, linear or branched chain having 4 to 12 carbon atoms. Examples thereof include those having an alkyl group or an alkenyl group, such as n-butyl group, isobutyl group, n-pentyl group, isopentyl group, n-hexyl group, isohexyl group, n-heptyl group, n-octyl group, 2-ethylhexyl. A group having an alkyl group having 4 to 12 carbon atoms such as a group, an n-nonyl group, and an n-decyl group is preferable, and one or two alkyl groups having 5 to 10 carbon atoms and further 5 to 8 carbon atoms, particularly 1 It is more preferable to have one. Furthermore, as the glyceryl ether used in the present invention, it is possible to promote separation of inorganic powder, particularly silicon powder, and from the viewpoint of facilitating recovery of the inorganic powder, the number of glyceryl groups is preferably 2 or more, preferably 2 to 3 A monoalkyl diglyceryl ether or a monoalkyl polyglyceryl ether in which glyceryl groups are connected by an ether bond can be used.

  When glyceryl ether is used in combination with alkylglycoside and water, glyceryl ether is used with respect to 100 parts by weight of the total amount of alkylglycoside and water from the viewpoint of promoting precipitation by precipitating inorganic powder in the dispersion medium, particularly silicon powder. Preferably it is 0.0001-1000 weight part, More preferably, it is 0.0005-500 weight part, More preferably, it is 0.005-100 weight part.

  As a preferable combination of the alkyl glycoside and glyceryl ether, the alkyl glycoside is decyl polyglucoside and / or dodecyl polyglucoside, and the glyceryl ether is 2-ethylhexyl glyceryl ether and / or hexyl glyceryl ether.

  The separation promoter composition (P) of the present invention can further contain any additive as long as the effects of the present invention are not impaired. Additives may include organic or inorganic acids, hydrocarbons, alkali agents, antifoaming agents, other surfactants, preservatives, rust inhibitors, and the like.

  The target of the inorganic powder recovery method of the present invention is a dispersion liquid in which inorganic powder is dispersed in a dispersion medium. Examples of the inorganic powder include metal powder such as silicon powder, silica powder, silicon carbide powder, alumina and ceria, or these metal oxide powders, mineral powder such as bentonite, etc., but the separation promoter of the present invention. Among these, the composition is preferably applied to silicon powder. The inorganic powder usually has an average particle size of 0.1 to 10 μm. The said average particle diameter is based on the measuring method described in the Example.

  Examples of the dispersion medium of the dispersion in which the inorganic powder is dispersed include various solvents, and examples thereof include organic solvents such as water, hydrocarbons, and glycol ethers.

  The hydrocarbon used as the dispersion medium of the dispersion in which the inorganic powder is dispersed is preferably, for example, kerosene, olefinic hydrocarbon and / or paraffinic hydrocarbon from the viewpoint of preferably exhibiting the separation promoting effect of the present invention. Kerosene is more preferred. As the olefinic hydrocarbon and paraffinic hydrocarbon, compounds having 10 to 18 carbon atoms, preferably 10 to 14 carbon atoms are preferable. For example, decane, dodecane, tetradecane, hexadecane, octadecane, decene, dodecene, tetradecene, hexadecene, octadecene, etc. Straight chain or branched chain saturated or unsaturated hydrocarbons; cycloaliphatic hydrocarbons such as cyclo compounds such as cyclodecane and cyclododecene, and the like.

  Examples of hydrocarbons other than the above include aromatic hydrocarbon solvents such as alkylbenzenes such as nonylbenzene and dodecylbenzene, and naphthalene compounds such as methylnaphthalene and dimethylnaphthalene. The aromatic hydrocarbon solvent can be used in addition to the olefin hydrocarbon and paraffin hydrocarbon.

  As a specific example of the dispersion liquid, for example, when a silicon crystal ingot is made into a silicon wafer, drainage is performed by a cleaning process using a cleaning agent, which is performed after a slicing process or a polishing process. The cleaning agent drainage contains silicon powder as inorganic powder in the cleaning agent (water-based cleaning agent or kerosene is used), lubricating oil (processing oil), thickener, abrasive grains, etc. Containing. Examples of the dispersion medium for the dispersion include water, hydrocarbons such as kerosene, organic solvents such as glycol ether, preferably hydrocarbons such as kerosene, and more preferably kerosene.

  In the said process (1), although the said separation promoter composition (P) is added to the dispersion liquid containing inorganic powder which is a process target, it is separated from a viewpoint which can accelerate | stimulate isolation | separation with respect to inorganic powder. In the accelerator composition (P), the alkyl glycoside in the separation accelerator composition (P) is usually preferably 0.0001 to 1000 parts by weight, more preferably 100 parts by weight of the dispersion medium in the dispersion. 0.001 to 100 parts by weight, more preferably 0.001 to 10 parts by weight, further preferably 0.001 to 1 part by weight, and further preferably 0.001 to 0.1 parts by weight. preferable.

  Step (1) of adding the separation accelerator composition (P) when the dispersion in which the inorganic powder is dispersed in the dispersion medium is a dispersion containing two or more kinds of inorganic powders having different specific gravities. Step (A) in which the dispersion is subjected to centrifugal separation to separate the layer (a) mainly containing inorganic powder having a large specific gravity and the layer (b) mainly containing inorganic powder having a low specific gravity (A) ), And then adding the separation accelerator composition (P) to the dispersion, which is the layer (b) mainly dispersed in the inorganic powder having a small specific gravity, separated in the step (A). It is preferable to apply (1). In the layer (a) and the layer (b), “mainly” means that the inorganic powder having a large specific gravity and the inorganic powder having a small specific gravity are separated from each other as long as they can be distinguished by the naked eye. ing. In the layer (b), the inorganic powder having a small specific gravity is usually dispersed, while in the layer (a), the inorganic powder having a large specific gravity is usually separated in a precipitated state, but the layer (a ), The inorganic powder having a large specific gravity may be separated in a dispersed state.

  The dispersion containing two or more kinds of inorganic powders having different specific gravities mainly contains inorganic powder having a large specific gravity by applying a centrifugal separation means without adding the separation accelerator composition (P) of the present invention. In some cases, the layer (a) can be separated into a layer (b) in which inorganic powder having a small specific gravity is mainly dispersed. In particular, the step (A) is effective when the specific gravity difference between two or more kinds of inorganic powders is 0.2 or more, and further 0.5 or more. Applying the step (A) before the step (1) means that the dispersion added with the separation accelerator composition (P) can be more efficiently dispersed in the centrifugation step (2) described later. It is preferable when separating into a layer (x) mainly containing a medium and a layer (y) containing an inorganic powder. In addition, the means and conditions similar to a process (2) can be employ | adopted for the centrifugation means and conditions of a process (A).

  In the inorganic powder recovery method of the present invention, after the step (1), as a step (2), a centrifugal separator is applied to the dispersion to which the separation accelerator composition (P) is added. By applying the centrifugal separation means, the dispersion is separated into a layer (x) mainly containing a dispersion medium and a layer (y) containing an inorganic powder.

  The layer (x) separated by centrifugation mainly contains the dispersion medium of the dispersion. On the other hand, it is considered that the layer (y) contains the separation promoter composition (P) as a main medium and the inorganic powder is dispersed or aggregated. Accordingly, whether the layer (x) and the layer (y) are separated into the upper layer or the lower layer can be determined by using the specific gravity of the dispersion medium and the component of the separation accelerator composition (P) as an index. . For example, when the specific gravity of the separation accelerator composition (P) is larger than the specific gravity of the dispersion medium, a layer (y) containing the lower inorganic powder and a layer (x) mainly containing the upper dispersion medium Can be separated. On the other hand, when the specific gravity of the dispersion medium is larger than the specific gravity of the separation accelerator composition (P), the layer (y) containing the upper inorganic powder and the layer mainly containing the lower dispersion medium are separated. Can do. In the layer (x), “mainly” means that the layer (x) is separated from the layer related to the dispersion medium and the layer (y) is separated from the layer related to the inorganic powder by the naked eye. In the layer (x), the concentration of the dispersion medium in the medium is preferably 80% by weight or more, more preferably 90% by weight or more, and still more preferably 95% by weight or more. In y), the concentration of the separation accelerator composition (P) in the medium is preferably 80% by weight or more, more preferably 90% by weight or more, and still more preferably 95% by weight or more. Usually, the layer (x) may be transparent to the naked eye and may contain a small amount of inorganic powder, while the layer (y) is separated with the inorganic powder containing a dispersion medium. May be.

  A known device can be used as the centrifuge. The conditions for centrifugation are usually a rotation speed of 100 to 25000 rpm, preferably 500 to 10000 rpm, 1 to 180 minutes, preferably 1 to 120 minutes, more preferably 1 to 60 minutes, more preferably 1 to 1 minute. It is preferable to carry out under conditions of 30 minutes, more preferably 2 to 10 minutes. In addition, the temperature at the time of centrifugation is usually preferably 25 to 60 ° C, and more preferably 25 to 40 ° C. The conditions for centrifugation can be appropriately set according to the concentration of the inorganic powder and other impurities in the dispersion and the component concentration in the separation accelerator composition (P).

  In the inorganic powder recovery method of the present invention, the layer (x) mainly containing the upper or lower dispersion medium separated by the step (2) and the layer (y) containing the lower or upper layer inorganic powder, In step (3), the layer (y) containing inorganic powder is taken out and collected.

  For example, when the layer (y) containing the inorganic powder is separated as an upper layer, the layer (y) containing the inorganic powder can be taken out and recovered by extracting the separated upper layer from above. . When the separation is performed using a separatory funnel, the lower layer containing the dispersion medium is extracted from the lower side of the separatory funnel, and the layer (y) containing the upper inorganic powder is taken out and collected. be able to. When the layer (y) containing the inorganic powder is separated as a lower layer, the lower layer of the inorganic powder can be taken out and recovered by extracting from the lower side of the separatory funnel.

  The layer (y) containing the inorganic powder recovered by the take-out step (3) as described above usually contains a separation accelerator composition. Therefore, the process (4) which takes out inorganic powder from a layer (y) can be given with respect to the said layer (y). The separation promoter composition contained in the layer (y) is appropriately removed by the step (4) of taking out the inorganic powder, and the inorganic powder can be reused. Moreover, the layer (y) containing the collect | recovered inorganic powder can be dried suitably, and can be used for reuse of inorganic powder.

  For the layer (y) containing the inorganic powder recovered from the dispersion in which the inorganic powder is dispersed in the dispersion medium after the steps (1) to (3) are applied, the centrifugal separation is further performed. The step (2 ′) and the removal step (3 ′) can be performed at least once. For the centrifugation step (2 ') and the removal step (3'), the same method as the centrifugation step (2) and the removal step (3) can be employed. By repeating the centrifugation step (2 ') and the removal step (3'), the recovery rate of the inorganic powder can be further improved. The step (4) of taking out the inorganic powder from the layer (y) similar to the above can also be applied to the layer (y) containing the inorganic powder recovered by the taking out step (3 ').

  Further, in the centrifugation step (2 ′) and the extraction step (3 ′), before the centrifugation step (2 ′), the inorganic separated and extracted from the layer (x) mainly containing the dispersion medium. A step (1 ′) of adding a separation accelerator composition (P ′) containing an alkyl glycoside and water can be applied to the layer (y) containing the powder. The separation accelerator composition (P ′) can be the same as the separation accelerator composition (P), and the step (1 ′) of adding the separation accelerator composition (P ′) A method similar to the step (1) of adding the separation accelerator composition (P) can be employed. By the step (1 ′) of adding the separation accelerator composition (P ′), the recovery rate of the inorganic powder can be further improved. In particular, it is effective when the layer (y) containing inorganic powder recovered in steps (1) to (3) is recovered as a dispersion containing a dispersion medium.

Example 1
<Preparation of separation accelerator composition (P)>
Alkyl polyglucoside (R ¹ = linear alkyl group having an average carbon number of 11.3, x = 0, y = 1.3, G = glucose residue in the general formula (1)), 2-ethylhexyl glyceryl ether and Water was sequentially mixed so that the weight of each component was 0.31 g, 0.09 g, and 19.61 g to prepare a separation accelerator composition (P).

  In Table 1, alkyl glycoside is abbreviated as AG. Table 1 shows the amount (g) of each component in the separation accelerator composition (P) and the ratio of AG to the total amount of AG and water (in Table 1, [AG / (AG + water)] × 100 (%) Table 1 shows the ratio (parts by weight) of glyceryl ether to 100 parts by weight of the total amount of AG and water.

<Object to be treated: Dispersion>
Oil-soluble cutting oil composition containing 25% by weight of SiC (average particle size in the range of 5 to 15 μm) and 20% by weight of silicon powder (average particle size in the range of 0.1 to 1 μm) as cutting abrasive grains I prepared something. Furthermore, the oil-soluble cutting oil composition (20 parts by weight) was added to 100 parts by weight (67 g) of kerosene to prepare a dispersion. The specific gravity of SiC, which is a cutting abrasive grain, is 3.2, and the specific gravity of silicon powder is 2.3.

  In addition, the average particle diameter of SiC as cutting abrasive grains and silicon powder as inorganic powder is a spherical casting sand randomly oriented from a projected particle section of SiC in a single field of view of 50 μm × 50 μm with an optical microscope at a magnification of 2000 times. The major axis diameter (μm) and minor axis diameter (μm) of the particles are measured to determine (major axis diameter + minor axis diameter) / 2. The average particle diameter (μm) is obtained by averaging the values obtained for a total of 20 SiCs, which are arbitrary 10 from the visual field and arbitrary 10 from other visual fields. The major axis diameter and the minor axis diameter are defined as follows. When the particle is stabilized on a plane and the projected image of the particle on the plane is sandwiched between two parallel lines, the width of the particle that minimizes the distance between the parallel lines is called the minor axis diameter. The distance when a particle is sandwiched between two parallel lines in a direction perpendicular to the line is called the major axis diameter. The same applies to other inorganic powders. However, in this example, it was easily confirmed visually that the average particle diameter of SiC found in the visual field was 5 to 15 μm and the average particle diameter of silicon powder was 0.1 to 1 μm.

<Separation of layer (precipitation layer) containing silicon powder after centrifugation>
10 g of a dispersion containing the oil-soluble cutting oil composition (100 parts by weight of kerosene and 20 parts by weight of cutting oil) is centrifuged at 1000 rpm for 5 minutes in a high-speed centrifuge (manufactured by SIGMA, 3K30C) to form the upper layer. By removing the dispersion layer (upper layer) containing silicon powder, cutting oil composition and kerosene, SiC abrasive grains precipitated in the lower layer were recovered. Further, with respect to the kerosene standard (this is defined as 100 parts by weight) in the removed dispersion layer, the above-described separation accelerator composition (30 parts by weight based on 100 parts by weight of the kerosene standard) is added. In addition, after centrifuging at 1000 rpm for 10 minutes in the centrifugal separator, the kerosene layer (upper layer) separated transparently and the layer containing silicon powder (layer where the silicon powder is precipitated; lower layer) The presence or absence was confirmed.

<Recovery of inorganic powder>
As for the silicon powder in the dispersion, the above-described transparently separated kerosene layer was extracted from above, and then the layer (precipitated layer) containing the remaining silicon powder was recovered. After removing components other than water of the separation accelerator composition (P) from the layer containing the collected silicon powder (layer where silicon powder is precipitated: lower layer), and filtering the residue containing the obtained silicon powder, The silicon powder was recovered by drying at room temperature.

Examples 2-4
In Example 1, a separation accelerator composition (P) was prepared in the same manner as in Example 1 except that the blending ratio of each component of the separation accelerator composition (P) was changed as shown in Table 1. Except having used the said separation promoter composition (P), operation similar to Example 1 was performed and inorganic powder (silicon powder) was collect | recovered. The results are shown in Table 1.

Comparative Example 1
In Example 1, the dispersion was centrifuged without adding the separation accelerator composition, but the silicon powder was dispersed in the dispersion and did not settle.

  In the examples, as a result of adding the separation accelerator composition to the dispersion of the processing object, the lower layer containing silicon powder (precipitate layer) is separated from the transparent kerosene layer as an upper layer, and is taken out and collected. I was able to. In particular, when glyceryl ether is used together with alkylglycoside as the separation accelerator composition as in Examples 1 to 3, the separation promotion effect is large. On the other hand, as in Comparative Example 1, when only kerosene was used instead of the separation accelerator composition, the dispersion liquid was only diluted, and the silicon powder was not settled while being dispersed in the dispersion liquid. became.

Claims (3)

Adding a silicon powder separation accelerator composition (P) containing alkylglycoside and water to a dispersion in which silicon powder is dispersed in a hydrocarbon solvent (1),
A step of subjecting the dispersion to which the separation accelerator composition (P) has been added to a dispersion means to separate it into a layer (x) mainly containing a hydrocarbon solvent and a layer (y) containing silicon powder ( 2) and a step (3) of taking out the separated layer (y) containing silicon powder, and a method for recovering silicon powder. The method for recovering silicon powder according to claim 1, wherein the separation accelerator composition (P) further contains glyceryl ether. For the layer (y) containing silicon powder separated and extracted from the layer (x) mainly containing the hydrocarbon solvent, the centrifugation step (2) and the extraction step (3) Performing the same centrifugation step (2 ′) and removal step (3 ′) at least once, and
In the centrifugation step (2 ′) and the extraction step (3 ′), before the centrifugation step (2 ′), the silicon powder separated and extracted from the layer (x) mainly containing a hydrocarbon solvent. The step (1 ') of adding a separation accelerator composition (P') containing alkylglycoside, glyceryl ether and water to the layer (y) containing Collection method.