Method of packing silicon and packing body

Abstract

When packing a polycrystalline silicon with a two-layer structured packing body comprising an inner bag (1a) and an outer bag (1b), there are used the inner bag (1a) and the outer bag (1b) having bottom sections (4a, 4b) provided with a pair of tucked sections, the shape of which is substantially a triangle in plan view, formed by inward-folding the portions continued from both of rectangular side face sections (3a, 3b), and when storing the inner bag (1a) that stores the polycrystalline silicon therein into the outer bag (1b), the bottom sections (4a, 4b) are superimposed with the respective tucked sections (6a, 6b) of the inner bag (1a) and the outer bag (1b) displaced from each other by 90 so that they do not overlap on each other.

Claims

1. A multiple-layer packing body for silicon consisting of: a plurality of packing bags consisting of an inner bag and an outer bag, the inner bag being superposed in the outer bag, wherein each packing bag is made of: a substantially square bottom section; a bottom sealed section; and four side face sections, each bottom section is made of: tucked sections each consisting of three sheets each having a substantially isosceles triangle shape in plan view; and non-tucked sections between the tucked sections each consisting of a sheet each having a substantially isosceles triangle shape in plan view, the tucked sections of one of the plurality of packing bags and the non-tucked sections of the other packing bag are stacked and constitute an entire bottom section of the packing body with four sheets, each packing bag has a margin section of an upper end section to form a strip shape by overlapping both opposing side face sections and folding several times, the strip-shaped folded sections of the respective packing bags are arranged in parallel to the bottom sealed section, and a top section of the packing body is configured to include: a first region including the strip-shaped folded section of the inner bag; a second region including the strip-shaped folded section of the outer bag which longitudinal direction of the strip shape is orthogonally arranged to a longitudinal direction of the strip shape of the strip-shaped folded section of the inner bag; and a third region where the strip-shaped folded sections of the respective packing bags are overlapped on each other.

2. A method of packing silicon with a multiple-layer packing body using a plurality of packing bags, said method comprising: providing a multiple-layer packing body for silicon consisting of: a plurality of packing bags consisting of an inner bag and an outer bag, the inner bag being superposed in the outer bag, wherein each packing bag is made of: a substantially square bottom section; a bottom sealed section; and four side face sections, each bottom section is made of: tucked sections each consisting of three sheets each having a substantially isosceles triangle shape in plan view; and non-tucked sections between the tucked sections each consisting of a sheet each having a substantially isosceles triangle shape in plan view, where the tucked sections of one of the plurality of packing bags and the non-tucked sections of the other packing bag are stacked and constitute an entire bottom section of the packing body with four sheets, each packing bag has a margin section of an upper end section to form a plate shape by overlapping both opposing side face sections and folding several times, the strip-shaped folded sections of the respective packing bags are arranged in parallel to the bottom sealed section, and a top section of the packing body is configured to include: a first region including the strip-shaped folded section of the inner bag; a second region including the strip-shaped folded section of the outer bag; and a third region where the strip-shaped folded sections of the respective packing bags are overlapped on each other; and packing silicon in the inner bag of the plurality of packing bags, whereby a high level of shock absorbing property can be attained on the entire bottom section, impacts and vibrations transmitted to the silicon stored inside can be uniformly distributed and absorbed, rubbing between the silicon and the packing bag can be prevented, and the generation of fine powder can be suppressed.

3. The method of packing silicon according claim 2, wherein the inner bag and the outer bag are superimposed and displaced from each other by 90.

4. A multiple-layer packing body for silicon consisting of: a plurality of transparent packing bags consisting of an inner bag and an outer bag, the inner bag being superposed in the outer bag, wherein each packing bag is made of: a substantially square bottom section; a bottom sealed section; a margin section at an upper end; and four side face sections, each bottom section is made of: tucked sections each consisting of three sheets each having a substantially isosceles triangle shape in plan view; and non-tucked sections between the tucked sections each consisting of a sheet each having a substantially isosceles triangle shape in plan view, the tucked sections of one of the plurality of packing bags and the non-tucked sections of the other packing bag are stacked and constitute an entire bottom section of the packing body with four sheets, each margin section forms a strip-shaped folded section by overlapping both opposing side face sections and folding several times, a longitudinal direction of the strip-shaped folded section of the outer bag is orthogonally arranged to that of the inner bag, and the strip-shaped folded sections of the respective packing bags are overlapped on each other in parallel to the bottom sealed section.

5. The multiple-layer packing body according claim 1, wherein an outer diameter of the outer bag is slightly greater than that of the inner bag.

6. The multiple-layer packing body according claim 1, wherein a constituent material of the outer bag contains a slip material.

7. The multiple-layer packing body according claim 1, wherein respective tucked sections of the inner bag and the outer bag are superimposed and displaced from each other by 90.

8. The multiple-layer packing body according claim 1, wherein with the side face sections of the inner bag having no fold lines thereon and the side face sections of the outer bag having fold lines thereon overlapped on each other, and the side face sections of the inner bag having fold lines thereon and the side face sections of the outer bag having no fold lines thereon overlapped on each other, whereby each tucked section and each non-tucked section in the respective bottom sections make a pair and overlap on each other.

9. The multiple-layer packing body according claim 1, wherein each packing body that internally stores polycrystalline silicon lump is stored in a transport case having a number of storage spaces which are further internally layered in a plurality of levels.

10. The multiple-layer packing body according claim 1, wherein a fine powder is trapped in a folded part of the tucked section and the fine powder is held inside the inner bag, thereby the fine powder can be effectively removed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a perspective view of a packing bag.

(2) FIG. 2 is a plan view of a bottom section of the packing bag.

(3) FIG. 3 is a sectional view of the bottom section taken along the A-A line in FIG. 2.

(4) FIG. 4 is a drawing for describing a sequence when storing lump of polycrystalline silicon in an inner bag.

(5) FIG. 5 is an explanatory drawing for describing when storing the inner bag into an outer bag.

(6) FIG. 6 is a plan view showing the bottom section of a packing body having a two-layer structure comprising the inner bag and the outer bag.

(7) FIG. 7 is a perspective view of the packing body having the two-layer structure with the inner bag and the outer bag.

(8) FIG. 8 is a drawing showing a transport case.

DETAILED DESCRIPTION

(9) Hereunder, a method of packing silicon and a packing body according to an embodiment of the present invention is described, with reference to the accompanying drawings. FIG. 1 is a perspective view of a packing bag to be used as an inner bag or an outer bag of the present embodiment. A packing bag 1 is formed for example from a transparent film such as polyethylene resin, and has a cross-sectionally substantially square bottomed bag shape with four side face sections 2 and 3 and a bottom section 4. Among the four side face sections 2 and 3, each of a pair of the opposing side face sections 2 has a substantially planar state. In another pair of the opposing side face sections 3, there are provided inward fold lines, which are for valley-folding, along the longitudinal direction to allow the packing bag 1 to be folded into a small size. The packing bag 1 is folded along these fold lines into a small size when not in use, and is expanded into a bag shape when used.

(10) In this packing bag 1, the bottom section 4 is formed as described below. First, the side face sections 3 with the fold lines are valley-folded, of the transparent film of a tubular body. On one end of the transparent film, inside faces of end portions of portions P, which are continued from the pair of side face sections 2, are approximated so as to fit together, therefore, between the end portions, the other end portions of portions Q, which are continued from the other pair of side face sections 3 with the fold lines thereon, are intervened in valley-fold state. Then, these end portions are thermally sealed by a sealing device, and a bottom sealed section 5 is thereby formed. Then both of the side face sections 3 having the fold lines thereon are unfold in a planer state, a tubular structure is thereby formed with another pair of side face sections 2. As a result, above the bottom sealed section 5, the portions Q continued from both of the side face sections 3 having the fold lines thereon are tucked inward, and a pair of tucked sections 6 is thereby formed. Thus, in the plan view shown in FIG. 2, each of the tucked sections 6 becomes an isosceles triangle shape, with the respective ridge lines of the bottom section 4 and the side face sections 3 having the fold line thereon, as one side, and the vertex formed substantially in the center of the bottom section 4.

(11) As shown in FIG. 3, each of the tucked sections 6 is formed by superimposing three layers namely: a layer L1 (which is formed by the portions P continued from both of the side face sections 2) positioned on the bottom surface of the bottom section 4 on which the bottom sealed section 5 is provided; a layer L2 formed with each of the inward-peak-folded portions Q continued from the side face sections 3 having the fold lines thereon; and a layer L3 formed by the layer L2 being valley-folded inside the tucked section 6 to fold back. That is to say, on the bottom section 6, each of the isosceles triangle shaped tucked sections 6 in FIG. 2 has a transparent film three-layer structure, and other portions are of a single layered section 7 having a single transparent film layer.

(12) Moreover, in the present embodiment, lump of polycrystalline silicon W which is the raw material for the single crystal silicon, is the primary packing object. This polycrystalline silicon lump W is used as a material in the CZ method which is one of methods for manufacturing single crystal silicon, and can be obtained by cutting and crushing a polycrystalline silicon rod. In the CZ method, single crystal silicon is manufactured by; placing this polycrystalline silicon lump W in a quartz crucible and melting in a furnace, contacting the silicon melt with a wire-suspended seed crystal (silicon single crystal), and pulling out the silicon single crystal gradually while rotating, to grow a silicon single crystal.

(13) Next, a specific sequence of the silicon packing method is described. With the packing bag 1 formed as described above serving as an inner bag 1a, then as shown in part (a) of FIG. 4, at first the polycrystalline silicon lump W is stored in the inner bag 1a. Subsequently, as shown in part (b) of FIG. 4, in an opening section on the top end of the inner bag 1a, the inside faces of a pair of side faces 2a having no fold lines thereon are approximated so as to fit together, therefore, between the end portions of the side faces 2a, the other end portions of the side face sections 3a with the fold lines thereon, are intervened in valley-fold state. These end portions are overlapped with each other to form a margin section 8a, and the margin section 8a is sealed. Then, as shown in part (c) of FIG. 4, this margin section 8a is folded several times to thereby form a strip-shaped folded section 9a, and the sequence of storing the polycrystalline silicon lump W into the inner bag 1a is complete.

(14) Then, as shown in FIG. 5, the inner bag 1a having the polycrystalline silicon lump W enclosed therein, is stored into an outer bag 1b. The outer bag 1b also, as with the inner bag 1a, has a shape the same as that of the packing bag 1. However, the outer diameter is slightly greater than that of the inner bag 1a. Furthermore, a transparent film which is a constituent material of the outer bag 1b, contains a slip material, and as a result the outer bag 1b is one in which the surface has a high level of lubricity.

(15) When storing the inner bag 1a into the outer bag 1b, these are stored so that the sides of the cross-sectional square are aligned. At this time, a bottom section 4a of the inner bag 1a and a bottom section 4b of the outer bag 1b are superimposed with the respective tucked sections 6a and 6b displaced from each other by 90 degrees so that they do not overlap on each other, that is to say, with the side face sections 2a of the inner bag 1a having no fold lines thereon and the side face sections 3b of the outer bag 1b having fold lines thereon overlapped on each other, and the side face sections 3a of the inner bag having fold lines thereon and the side face sections 2b of the outer bag 1b having no fold lines thereon overlapped on each other. Consequently, each of the tucked sections 6a and 6b and each of single layered sections 7a and 7b in the respective bottom sections 4a and 4b make a pair and overlap on each other. As shown in FIG. 6, in a bottom section 11 of a two-layer structured packing body 10 comprising the inner bag 1a and the outer bag 1b, the three-layered tucked sections 6a and 6b and the single layered sections 7a and 7b form a four-layered structure of the transparent film in the entire area of the bottom section 11.

(16) The outer bag 1b that stores the inner bag 1a therein as described above encloses the inner bag 1a therein such that, as with the inner bag 1a, the pair of side face sections 2b having no fold lines thereon are approximated so as to fit together in the opening section on the upper end of the outer bag 1b, therefore, between the end portions of the side faces 2b, the other end portions of the side face sections 3b with the fold lines thereon, are intervened in valley-fold state. These end portions are overlapped with each other so as to form a margin section 8b and the margin section 8b is sealed. Then a strip shaped folded section 9b is formed by further folding this margin section 8b several times. Each two-layer structured packing body 10 that internally stores the polycrystalline silicon lump W packed in the above sequence is stored in a transport case 20 shown in FIG. 8 having a number of storage spaces which are further internally layered in a plurality of levels, and is shipped to a single crystal silicon manufacturing factory.

(17) The polycrystalline silicon lump W, which is the packing object of the silicon packing method and the packing body according to the present embodiment, is a brittle material, and hence the edges of the cut surfaces and the edges of the crushed surfaces are often sharp.

(18) Therefore, when transporting in a state of being packed in the packing bag 1 made of polyethylene resin or the like, if vibrations are transmitted to the polycrystalline silicon lump W, the polycrystalline silicon lump W and the surface of the packing bag 1 rub against each other, and the polycrystalline silicon lump W and the packing bag become pulverized. If fine powder of such a polycrystalline silicon lump W and polyethylene resin or the like is brought into a quartz crucible together with the polycrystalline silicon lump W, it causes crystal defects in the single crystal silicon produced after being pulled out of the quartz crucible, and consequently causes a reduction in the quality of the silicon single crystal.

(19) For example, in the case where the polycrystalline silicon lump W is packed in a single packing bag 1, then as for the polycrystalline silicon lump W positioned above the tucked sections 6 of the packing bag 1, each of the tucked sections 6 has a three-layer structure and a high level of shock absorbing property and therefore acts as a cushion so as to absorb vibrations that occur in transport. As a result it is possible to suppress rubbing between the polycrystalline silicon lump W positioned above the tucked sections 6 and the packing bag 1, and hence pulverization of the polycrystalline silicon lump W and the packing bag 1 is suppressed. However, for the polycrystalline silicon lump W positioned above the single layered section 7, since the vibrations are directly transmitted thereto, the polycrystalline silicon lump W and the packing bag 1 rub against each other, and fine powder of the polycrystalline silicon lump W or the packing bag 1 is generated. This powder emerges on the bottom section 4, as contamination that only occurs at the area of the single layered section 7.

(20) On the other hand, in the present embodiment, as described above, by superimposing the bottom sections 4a and 4b with the respective tucked sections 6a and 6b of the inner bag 1a and the outer bag 1b displaced by 90 so that they do not overlap on each other, it is possible to form, on the entire bottom section 11 of the two-layer structured packing body 10 comprising the inner bag 1a and the outer bag 1b, a four-layered structure of the transparent film from the three-layered tucked sections 6a and 6b and the single layered sections 7a and 7b.

(21) In other words, in the embodiment, the packing body 10 is a multiple-layer packing body for silicon that comprises: a plurality of packing bags (sheet bags) 1a, 1b respectively having bottom sections 4a, 4b being superimposed on each other, at least one sheet stack section (i.e., the tucked sections 6a, 6b) being partially provided at each of the bottom sections 4a, 4b, wherein the sheet stack sections (6a) of one of the packing bags 1a, 1b are displaced from the sheet stack sections (6b) of another one of the packing bags (1a, 1b). The sheet stack sections (i.e., the tucked sections 6a, 6b) of the packing bags 1a, 1b are generally disposed over (or cover) the entire bottom section 11 of packing body 10.

(22) In the present embodiment, the sheet stack sections (6a) of one of the packing bags 1a, 1b are shifted from the sheet stack sections (6b) of another one of the packing bags 1a, 1b about a point. Alternatively or also, the sheet stack section(s) of one of the packing bags may shift from the sheet stack section(s) of another one of the packing bags along a line. In the present embodiment, the total number of stacked sheets is substantially the same over the substantially entire area of the superimposed bottom section 4a, 4b. In the present embodiment, each of the bottom sections 4a, 4b comprises: a first region (6a, 6b) in which at least one of the sheet stack section is formed; and a second region (7a, 7b) in which no sheet stack section (or sheet stack section with less stacked sheets) is formed, and the first region (6a, 6b) of one of the packing bags 1a, 1b is superimposed on the second region (7b, 7a) of another one of the packing bags 1a, 1b. The first region (6a, 6b) has a similar shape to the second region (7a, 7b). Both the first region (6a, 6b) and the second region (7a, 7b) comprise substantially polygonal shapes (triangle shapes). The first region (6a, 6b) has a nearly equal size as the second region (7a, 7b), or the first region (6a, 6b) has a small size than the size of the second region (7a, 7b). Each of the bottom sections 4a, 4b comprises a plurality of the first regions (6a, 6b) and a plurality of the second regions (7a, 7b), and the first regions (6a, 6b) and the second regions (7a, 7b) are alternately disposed in the circumferential direction about a point. Each of the bottom sections 4a, 4b has a substantially polygonal shape, and one of the first regions (6a, 6b) or one of the second regions (7a, 7b) is arranged corresponding to each one side of the polygonal shape of each of the bottom sections 4a, 4b. In the present embodiment, the sheet stack sections (6a, 6b) can comprise a gusset section of the packing body 1a, 1b.

(23) As a result a high level of shock absorbing property can be given to the entire bottom section 11. Therefore it is possible to disperse and absorb impacts and vibrations transmitted to the internally stored polycrystalline silicon lump W, and rubbing between the polycrystalline silicon lump W and the inner bag 1a can be suppressed. Consequently it is possible to further reduce the occurrence of fine powder from the polycrystalline silicon lump W and the inner bag 1a, and to prevent a reduction in the quality of the polycrystalline silicon lump W.

(24) Moreover, with use of the previously utilized packing bag 1, it is possible with such a simple method described above, to reliably suppress vibrations received by the polycrystalline silicon lump W. Therefore, without the special need for an additional facility, it is possible to easily avoid a reduction in the quality of the polycrystalline silicon lump W. Furthermore, in transport, it is possible to suppress vibrations without use of an excessive amount of polystyrene foam (expanded polystyrene) as a shock absorbing material, and therefore there is no cost for processing polystyrene foam, and no negative impact on the environment.

(25) Furthermore, even in the case where fine powder of the polycrystalline silicon lump W and the inner bag 1a is generated inside the inner bag 1a, when taking the polycrystalline silicon lump W out of the inner bag 1a, the fine powder is trapped in the folded section of the tucked section 6a and the fine powder is held inside the inner bag 1a, and thereby the fine powder can be effectively removed. Therefore, it is possible to suppress the fine powder entering the quartz crucible for performing the CZ method, and to maintain the quality of the single crystal silicon to be produced.

(26) Moreover, in the present embodiment, in the case of packing the polycrystalline silicon lump W with the two-layer structured packing body 10 comprising the inner bag 1a and the outer bag 1b, then as shown in FIG. 7, the respective folded sections 9a and 9b on the upper end section of both bags 1a and 1b intersect with each other at a 90 angle. Therefore, a high level of shock absorbing property on the upper end section can be attained, and it is possible to desirably absorb vibrations or impacts from the upper side.

(27) Furthermore, as described above, the outer bag 1b of the packing bag 1 for polycrystalline silicon according to the present invention contains a slip agent. Therefore it is possible to smoothly push the inner bag 1a into the outer bag 1b and thus facilitate the operation during two-layer packing. Moreover, when external vibrations are transmitted to the outer bag, the surface of the inner bag 1a and the inside face of the outer bag 1b slip on each other, so that even if the outer bag 1b vibrates, it is possible to reduce transmission of these vibrations to the inner bag 1a. As a result it is possible to further reduce vibrations transmitted to the polycrystalline silicon lump W, and generation of the fine powder can be further effectively suppressed.

(28) In order to confirm the effectiveness of the packing bag according to the present embodiment, a transportation test was conducted. In this test, five hundred first packing bags and five hundred second packing bags were provided and were packed in corrugated boxes. Lump of polycrystalline silicon, which was packed in each one of the first and second packing bags, has a length of 5-60 mm and has a total weight of 5 kg lump. In each of the first packing bags, the tucked section of the inner bag was superimposed with the tucked section of the outer bag. In each of the second packing bags, the tucked sections of the inner bag and the outer bag were displaced from each other by 90 so that they do not overlap on each other. A truck on which the corrugated boxes were loaded runs 500 km, for reproducing the vibration in transport condition. After the running, in the first packing bags (the tucked sections of the inner bag and the outer bag were superimposed with each other), the controversial powder on the bottom section was substantially confirmed. On the contrary, in the second packing bags (the tucked sections of the inner bag and the outer bag were displaced from each other), the adherence fine powder on the bottom section was not confirmed.

(29) The method of packing silicon and the packing body that are an embodiment of the present invention have been described. However, the present invention is not to be considered limited to this embodiment, and may be appropriately modified without departing from the technical scope of the invention. For example, in the present embodiment, for each of the inner bag 1a and the outer bag 1b, the margin sections 8a and 8b are formed by overlapping the side face sections 2a and 2b having no fold lines thereon on each other, and these margin sections are folded several times to form the folded sections 9a and 9b. However, the margin sections may be formed by overlapping the side face sections 3a and 3b having the fold lines thereon on each other, and the folded sections may thereby be formed.

(30) In the present embodiment, there has been described a case where the polycrystalline silicon lump W is packed in a two-layer structure. However, it is not limited to this, and may be packed in a structure of three or more layers. Moreover, the shape of the packing bag 1 is not limited to the shape of the present embodiment, as long as there are formed tucked sections. That is to say, with any shape of the packing bag, the intent of the present invention is to displace and superimpose the bottom sections of the respective packing bags, and arrange the tucked sections in the entire area of the bottom section of the packing body, and includes any embodiment as long as this intent is satisfied.

(31) Furthermore, in the present embodiment, the polycrystalline silicon lump W is taken as the object of packing. However, the object of packing is not limited to this, and for example, even in the case of packing cut-rods cut from a polycrystalline silicon rod or packing single crystal silicon, the present method of packing silicon and the packing body can be applied.