EP3022119A1

EP3022119A1 - Packaging of polycrystalline silicon

Info

Publication number: EP3022119A1
Application number: EP14734445.1A
Authority: EP
Inventors: Bruno Lichtenegger; Reiner Pech; Matthias Vietz
Original assignee: Wacker Chemie AG
Current assignee: Wacker Chemie AG
Priority date: 2013-07-18
Filing date: 2014-06-26
Publication date: 2016-05-25
Also published as: JP6321161B2; CA2918118A1; CN105593120B; KR20180082645A; KR20160034963A; MY172361A; CA2918118C; US20160167862A1; WO2015007490A1; DE102013214099A1; TW201504117A; US9981796B2; CN105593120A; TWI508904B; JP2016531049A; KR102037570B1

Abstract

A transport container containing at least two plastics bags, in each of which polycrystalline silicon fragments are provided, characterized by a packing density of greater than 500 kg/m³.

Description

Packaging of polycrystalline silicon

The invention relates to the packaging of polycrystalline silicon. Polycrystalline silicon (polysilicon) is predominantly deposited by means of the Siemens process from halosilanes such as trichlorosilane and then comminuted as little as possible in contamination into polycrystalline silicon fragments.

For applications in the semiconductor and solar industries, the least possible contamination of polysilicon is desired. Therefore, the material should also be packed with low contamination before it is transported to the customer.

Usually, the polysilicon fragments are packaged in single or multiple plastic bags. Mostly the packaging is done in double bags.

The bags are then placed in a bulk package, e.g. a cardboard box, and transported to the customer.

When Polysiliciumbruch is a sharp-edged, z.T. not pourable bulk material. Therefore, it must be ensured during packaging that the material does not puncture the usual plastic bags during filling, or even completely destroyed in the worst case.

In order to avoid this, various measures are proposed in the prior art.

In US 20100154357 A1 it is proposed to suck the air out of the bag during the closure until a vacuum of 10 to 700 mbar is produced. US 20120198793 A1 discloses sucking the air out of the bag before welding until a flat, air-poor bag is formed.

However, it has been found that these measures are not suitable to avoid piercing. US 20100154357 A1 provides an energy absorber within the plastic bag during packaging which is intended to prevent punctures.

Penetration of the bag, however, can occur not only during packaging but also during transport to the customer. Polysilicon is sharp-edged, so that when unfavorable orientation of the fragments in the bag by relative movement or pressure of the fragments to or on the bag film this is cut or pierced. Fragments sticking out of the pouch packaging can be directly through surrounding materials, internal fragments through inflowing

Ambient air are unacceptably contaminated.

In addition, unwanted post-shredding occurs during transport of packaged silicon fragments by relative movement and collisions or by edge breakouts and abrasion.

This is undesirable, in particular, since the resulting fine fraction demonstrably leads to a lower process performance for the customer. This has the consequence that prior to further processing at the customer's fines must be screened again, which is disadvantageous.

This problem applies equally to broken and classified, purified and unpurified silicon, regardless of the size of the packaging (usually bags with 5 or 10 kg of polysilicon).

It has been shown that the risk of bag injuries increases in proportion to the fragment mass. A conceivable way in principle to reduce the puncture rate by reinforcing the bag film, has proved to be less practicable, especially since such a less flexible film would be difficult to handle and more expensive. The main reason for these punctures and post-shredding lies in the too large "freedom of movement" of the bags during transport During transport (truck, air, sea and rail, loading, etc.) there are a variety of loads on the packaging unit.

Investigations have shown that the most detrimental influence in the constant vibrations, as e.g. mainly caused by the truck transport, is to be sought. From this problem, the task of the invention resulted.

The object of the invention is solved by the claims.

Surprisingly, both the piercings and the formation of fines during transport could be minimized by the invention. At the same time cost advantages could be realized.

The inventors have recognized that the more freedom a vibration / vibration has, the more latitude a packaged polysilicon bag will have in a secondary packaging unit, such as e.g. has a carton. Too narrow a packaging leads to an increase in piercings, too loose packaging can also lead to piercings and significantly more fines.

The invention therefore provides for a targeted reduction of the clearance (empty space) in the secondary packaging unit (cardboard), thereby avoiding or considerably reducing unwanted secondary shredding or puncturing of the packaging film. By a targeted arrangement of the bags in the carton, such as by the defined horizontal superimposing or by special deposits, it is possible to avoid the fines / penetration.

This applies equally to broken u. Classified, purified and unrefined silicon in packaging of 5 u. 10 kg, or units of similar magnitude. These are used especially for Sillicium fracture with a typical edge length between 0.1 mm and 250 mm. The invention relates to a transport container containing at least two plastic bags, each containing polycrystalline silicon fragments, characterized by a packing density of greater than 500 kg / m ³ .

The packing density is defined in the context of the invention as the weight of the weighing in on polycrystalline silicon fragments in relation to the internal volume of the transport container.

Preferably, the packing density is more than 650 kg / m ³ . Particularly preferred is a packing density of greater than 800 kg / m ³ . The packing density should not exceed 950 kg / m ³ .

The invention also provides for securing a plurality of transport containers according to the invention on a pallet. The invention also relates to a method for transporting polycrystalline silicon fragments by means of a transport container according to the invention, wherein after completion of the transport, the penetration rate of the plastic bags is less than 20%. Preferably, the puncture rate is less than 10%, more preferably less than 5%. Ideally, no punctures occur.

Piercing is within the scope of the invention as a proportion of bags with at least one visually visible hole, i. a hole with a linear expansion greater than or equal to 0.3 mm, defined with respect to all bags in the transport container.

Preferably, the Si fines content formed during transport is <100 ppmw, preferably <50 ppmw. Ideally, no fines are produced. In the following, for fraction sizes 3 to 5, all fragments or particles of silicon which have a size such that they can be separated by means of a mesh screen with square meshes of a size of 8 mm × 8 mm are referred to as fine particles. For the fraction sizes 0 to 2, the same definition applies, whereby the mesh size here is defined as 1 mm x 1 mm.

The size class is defined as the longest distance of two points on the surface of a silicon fragment (= maximum length):

Breaking size (BG) 0 [mm] 0.1 to 5

Break size 1 [mm] 3 to 15

Break size 2 [mm] 10 to 40

Breaking size 3 [mm] 20 to 60

Breakage size 4 [mm] 45 to 120

Breakage size 5 [mm] 100 to 250

In each case, at least 90% by weight of the fracture fraction are within the stated size ranges.

Preferably, the residual volume present in the transport container (= carton volume - volume of all bags) is reduced by special inserts, such as e.g. Foam, cardboard inserts greater than 70%, particularly preferably filled to 100%. Preferably, mold-forming elements made of PU, polyester or expandable polystyrene or another plastic are additionally introduced.

It is preferred if the bags are arranged horizontally in the transport container. By this is meant that the filled bags rest with their longer side on the cardboard bottom. By contrast, a vertical arrangement would mean placing the filled bags in the carton.

The bags may overlap in a horizontal arrangement, ie a bag may partially rest on another bag. The preferred horizontal arrangement of the bags in the carton is shown below with reference to FIG.

Fig. 1 shows a carton with 8 filled bags.

reference numeral

1 carton

2 polysilicon fragments

3 bags

4 deposits

In box 1 eight bags 3, each filled with polysilicon fragments 2, introduced. There are a total of four levels, each with two bags 3 available. In some cases, inserts 4 are introduced between the levels. The bags 3 are arranged horizontally, the elongated side of the bag 3 is approximately parallel to the plane of the cardboard bottom.

Separating layers between the bags such as inner cartons, web sets or separating layers made of cardboard are preferred, but not mandatory for safe transport.

For example, 8 bags each containing 10 kg of polysilicon fragments may be placed horizontally in a transport container. In this case, the transport container is filled with 80 kg of polysilicon.

The transport containers are preferably fastened on a pallet, particularly preferably lashed. For example, 6 transport containers each with 80 kg of polysilicon can be mounted on a pallet.

The transport container is preferably a bulk packaging such as a carton. Preferably, the total volume of a plastic bag in relation to the volume of the fragments 2.4 to 3.0.

This is accomplished by removing the air therein after filling the fragments into the plastic bag prior to closing the plastic bag.

Preferably, the plastic bag is a double bag comprising first and second plastic bags and polysilicon in the form of debris located in the first plastic bag, the first plastic bag being plugged into the second plastic bag, both plastic bags being closed Total volume of the double bag in relation to the volume of the fragments is 2.4 to 3.0. Preferably, the total volume of the first bag relative to the volume of the fragments is 2.0 to 2.7.

Preferably, the first bag is dimensioned so that the plastic films fit snugly against the silicon fragments. As a result, relative movements between the fragments can be avoided.

The plastic bags are preferably made of a high purity plastic. These are preferably polyethylene (PE) polyethylene terephthalate (PET) or polypropylene (PP) or composite films. A composite film is a multilayer packaging film from which flexible packaging is made. The individual film layers are usually extruded or laminated or laminated.

The plastic bag preferably has a thickness of 10 to 1000 μηη, more preferably a thickness of 100 to 300 μηη.

The closing of the plastic bag can be done for example by means of welding, gluing, sewing or positive locking. Preferably, it is done by welding. To determine the volume of the packaged bag, it is immersed in a pool of water.

The displaced water corresponds to the total volume of the bag.

The volume of the silicon was determined by weighing the silicon with the constant density of hyperpure silicon (2.336 g / cm ³ ).

Alternatively, the volume of silicon could also be determined by the dipping method.

The air can be removed from a silicon-filled plastic bag by various methods: - manual pressing and subsequent welding

Clamping or stamping device and subsequent welding

Suction device u. subsequent welding

Vacuum chamber u. subsequent welding The ambient conditions during packaging are preferably a temperature of 18-25 ° C. The relative humidity is preferably 30-70%.

It has been shown that this condensation can be avoided. Preferably, the packaging also takes place in the vicinity of filtered air.

Examples

Determination of fines

To determine the fines content of the fractional sizes 3 to 5, a mesh screen with 8 mm square mesh or 1 mm square mesh for smaller fracture sizes, and vibration motors are used. The sieved fines were quantified gravimetrically. example 1

Transport simulation (worst case): typical loads of transport vibrations on truck bed 800 km, transport lorries 2 to 6 g (gravitational acceleration), horizontal impacts when handling the loading unit and overseas transport.

Table 1 shows an overview of the examined boxes.

In the test examples, the poly fragments in PE double bags (290μη "ΐ) are arranged in the cardboard as follows:

Table 1

The total volume of each plastic double bag relative to the volume of fragments therein was in the range of 2.4 to 3.0.

Table 2 shows packing density, fines and penetration for the fifth box tested. Per test run 960 kg were evaluated. The puncture rate refers to punctures of the outer bag. Table 2

Packing density in kg / m ³ fines in ppm penetration

Carton 1

Test Run 1 675 150 19.79%

Test Run 2 675 300 15.63%

Test Run 3 675 200 18.75%

Test Run 4 675 250 19.79%

Test Run 5 675 250 18.75%

Carton 2

Test Run 1 588 250 19.79%

Test Run 2 588 150 18.75%

Test Run 3 588 50 12.50%

Test Run 4 588 200 14.06%

Test Run 5 588 250 16.67%

Carton 3

Test Run 1 675 50 14.58%

Test Run 2 675 100 15.63%

Test Run 3 675 50 12.50%

Test Run 4 675 100 0.00%

Test Run 5,675 0 6.25%

Carton 4

Test Run 1 702 0 0.00%

Test Run 2 702 100 15.63%

Test Run 3 702 50 13.54%

Test Run 4 702 50 8.33%

Test Run 5 702 0 6.25%

Carton 5

Test Run 1 702 0 4.17%

Test Run 2 702 50 0.00%

Test Run 3 702 100 6.25%

Test Run 4 702 0 0.00%

Test Run 5 702 50 4.17% Example 2

1000 km truck journey with loading and unloading

Again, the boxes 1-5 were examined according to Table 1.

Table 3 shows packing density, fines and penetration for the five boxes tested. Per test run 960 kg were evaluated.

If the packing density is less than 500 kg / m ³ , more than 400 ppmw fines are generated during transportation and the throughput rate is greater than 25%, regardless of the bag arrangement in the container (horizontal / vertical).

Table 3

Packing density kg / m ³ fines in ppm penetration

Carton 1

Test Run 1 675 350 15.63%

Test Run 2 675 150 1 1, 46%

Test Run 3 675 150 9.38%

Test Run 4,675 200 9.38%

Test Run 5 675 250 14.58%

Carton 2

Test Run 1 588 250 10.42%

Test Run 2 588 100 5.21%

Test Run 3 588 150 7.29%

Test Run 4 588 100 5.73%

Test Run 5 588 200 8.85%

Carton 3

Test Run 1 675 50 4.17%

Test Run 2 675 80 4.17%

Test Run 3 675 0 5.21%

Test Run 4,675 70 10.42%

Test Run 5 675 0 0.00% Carton 4

Test Run 1 702 0 2.08%

Test Run 2 702 0 0.00%

Test Run 3 702 50 10.42%

Test Run 4 702 100 5.21%

Test Run 5 702 0 6.25%

Carton 5

Test Run 1 702 50 2.08%

Test Run 2 702 50 3.13%

Test Run 3 702 0 2.08%

Test Run 4 702 0 0.00%

Test Run 5 702 0 0.00%

Claims

claims

1. Transport container, comprising at least two plastic bags, in each of which polycrystalline silicon fragments are, characterized by a packing density of greater than or equal to 500 kg / m ³ .

2. Transport container according to claim 1, with a packing density greater than or equal to 650 kg / m ³ .

3. Transport container according to claim 2, with a packing density of greater than 800 kg / m ³ .

4. Transport container according to one of claims 1 to 3, wherein the residual volume present in the transport container (= cardboard volume - volume of all bags) by deposits of foam or mold-forming elements of PU, polyester, an expandable polystyrene or other plastic, to more than 70% is completed.

5. Transport container according to one of claims 1 to 4, wherein the Kunststoffbeu- tel are arranged horizontally in the transport container.

6. Transport container according to one of claims 1 to 5, wherein the total volume of each plastic bag in relation to the volume of the fragments therein is 2.4 to 3.0.

7. pallet on which a plurality of transport containers are attached according to one of claims 1 to 6.

8. A method for transporting polycrystalline silicon fragments in a transport container according to one of claims 1 to 6 or on a pallet

Claim 7, wherein after completion of the transport, a penetration rate of the plastic bag is less than 20%.

The method of claim 8, wherein the puncture rate is less than 10%.

10. The method of claim 8 or claim 9, wherein a fine fraction of silicon formed during transport is in the range of 0 to 350 ppmw.