Packing of polysilicon

Abstract

A bag contains polysilicon, has been welded and includes at least one weld seam and a polyethylene film having: a thickness of 150-900 μm; a stiffness at a flexural modulus F.sub.max of 300-2000 mN and F.sub.t of 100-1300 mN; a fracture force F determined by dynamic penetration testing of 200-1500 N; a fracture energy Ws of 2-30 J; a penetration energy W.sub.tot of 2.2-30 J; a film tensile stress at 15% longitudinal and transverse elongation of 9-50 MPa; an Elmendorf longitudinal film tear resistance of 10-60 cN; an Elmendorf transverse film tear resistance of 18-60 cN; a longitudinal film elongation at break of 300-2000%; a transverse film elongation at break of 450-3000%; and a weld seam strength of 25-150 N/15 mm. A method includes filling a bag with polysilicon, and welding by pulse sealing with contact pressure greater than 0.01 N/mm.sup.2 to obtain a 25-150 N/15 mm weld seam strength.

Claims

1. A method for packing polysilicon into a plastic bag from a PE film with a thickness of 150-900 μm, a stiffness at a flexural modulus F.sub.max of 300-2000 mN and F.sub.t of 100-1300 mN, having a fracture force F determined by dynamic penetration testing of 200-1500 N, a fracture energy W.sub.s of 2-30 J and a penetration energy W.sub.tot of 2.2-30 J, having a film tensile stress at 15% longitudinal and transverse elongation of 9-50 MPa, having an Elmendorf longitudinal film tear resistance of 10-60 cN and an Elmendorf transverse film tear resistance of 18-60 cN, having a longitudinal film elongation at break of 300-2000% and having a transverse film elongation at break of 450-3000, and is produced by means of an extruder from a tubular PE film, comprising production of the bag, sealing the PE film prior to filling the bag, filling the bag with polysilicon and welding the bag after filling the bag, wherein the sealing and welding steps are effected by time-controlled, temperature regulated pulse sealing with a contact pressure by means of welding jaws greater than 0.01 N/mm.sup.2, resulting in a weld seam having a weld seam strength of 25-150 N/15 mm, wherein in each sealing and welding operation, the sealing and welding temperatures are detected without a sensor through electrical resistance measurement of a metallic seal wire that is sheathed in a nonmetallic material and regulated, in order to ensure reproducible sealing results and a homogeneous sealing quality, especially in prolonged operation with high frequency.

2. The method of claim 1, wherein prior to the welding, air is sucked out of the bag until a flat bag containing little air arises.

3. The method of claim 2, wherein before packing, the polysilicon is first portioned and weighed.

4. The method of claim 3, comprising fold-free shaping of a second plastic bag from a PE film by means of tubular preforms or air injection or film spreaders or through a combination thereof, and introducing a first already closed polysilicon-filled PE bag horizontally into the second plastic bag by means of a conveying channel or other suitable transport units and welding of the second plastic bag by means of two welding jaws.

5. The method of claim 1, wherein before packing, the polysilicon is first portioned and weighed.

6. The method of claim 5, comprising fold-free shaping of a second plastic bag from a PE film by means of tubular preforms or air injection or film spreaders or through a combination thereof, and introducing a first already closed polysilicon-filled PE bag horizontally into the second plastic bag by means of a conveying channel or other suitable transport units and welding of the second plastic bag by means of two welding jaws.

7. The method of claim 6, comprising introducing a first already closed polysilicon-filled PE bag horizontally into a second plastic bag of tubular PE film by means of a conveying channel or other suitable transport units and welding of the second plastic bag by means of two welding jaws, wherein the conveying channel or the transport unit is lowered to such an extent that the first bag can slide within the second plastic bag as far as the weld seam already produced so that the tubular film is pulled over the edge of the welding jaw and a fold-free weld seam arises.

8. The method of claim 1, comprising fold-free shaping of a second plastic bag from a PE film by means of tubular preforms or air injection or film spreaders or through a combination thereof, and introducing a first already closed polysilicon-filled PE bag horizontally into the second plastic bag by means of a conveying channel or other suitable transport units and welding of the second plastic bag by means of two welding jaws.

9. The method of claim 8, comprising introducing a first already closed polysilicon-filled PE bag horizontally into a second plastic bag of tubular PE film by means of a conveying channel or other suitable transport units and welding of the second plastic bag by means of two welding jaws, wherein the conveying channel or the transport unit is lowered to such an extent that the first bag can slide within the second plastic bag as far as the weld seam already produced so that the tubular film is pulled over the edge of the welding jaw and a fold-free weld seam arises.

10. The method of claim 1, comprising introducing a first already closed polysilicon-filled PE bag horizontally into a second plastic bag of tubular PE film by means of a conveying channel or other suitable transport units and welding of the second plastic bag by means of two welding jaws, wherein the conveying channel or the transport unit is lowered to such an extent that the first bag can slide within the second plastic bag as far as the weld seam already produced so that the tubular film is pulled over the edge of the welding jaw and a fold-free weld seam arises.

11. The method of claim 1, wherein prior to the welding, air is sucked out of the bag until a flat bag containing little air arises.

Description

EXAMPLES

Comparative Example 1

(1) Packing in a Flat PE Bag with the Following Film Properties:

(2) Thickness of the film: 100 μm

(3) Stiffness at the flexural modulus: F.sub.max=100 mN; F.sub.t=50 mN

(4) Dynamic penetration testing: Fracture force F=100 N Fracture energy Ws=1 J Penetration energy W.sub.tot=1 J

(5) Longitudinal film tensile stress at 15% elongation=6 MPa

(6) Transverse film tensile stress at 15% elongation=5 MPa

(7) Elmendorf longitudinal film tear resistance=5 cN

(8) Elmendorf transverse film tear resistance=5 cN

(9) Longitudinal film elongation at break: =100 percent

(10) Transverse film elongation at break: =150 percent

(11) This PE film was used to produce 60 PE bags which were filled with 5 kg of chunk poly with chunk size 4 having an edge length of from 60 to 150 mm.

(12) The welding was effected by time-controlled temperature-regulated pulse sealing:

(13) Temperature: 200 degrees

(14) Sealing time: 2 seconds

(15) Contact pressure through the welding jaws: 0.01 N/mm.sup.2

(16) Mean weld seam strength: =20 N/15 mm

(17) 6 bags each were introduced into one cardboard box. The 10 cardboard boxes were driven for 2000 km through Germany on a truck.

(18) After transport, the bags were checked visually for damaged weld seams and, with the aid of the water dip method, for punctures.

(19) The water dip method involves dipping the air-filled, emptied bag into a water-filled basin. Leaks in the PE bag are recognized immediately by ascending gas bubbles.

(20) 20% of the weld seams came open during transport.

(21) 50% of the bags were no longer leakproof after transport.

Example 1

(22) Packing into a Flat PE Bag Having the Following Film Properties:

(23) Thickness of the film: 300 μm

(24) Stiffness at the flexural modulus: F.sub.max=500 mN; F.sub.t=200 mN

(25) Dynamic penetration testing: Fracture force F=300 N Fracture energy Ws=4 J Penetration energy W.sub.tot=4.5 J

(26) Longitudinal film tensile stress at 15% elongation=12 MPa

(27) Transverse film tensile stress at 15% elongation=13 MPa

(28) Elmendorf longitudinal film tear resistance=15 cN

(29) Elmendorf transverse film tear resistance=25 cN

(30) Longitudinal film elongation at break: =500 percent

(31) Transverse film elongation at break: =700 percent

(32) This PE film was used to produce 60 PE bags which were filled with 5 kg of chunk poly with chunk size 4 having an edge length of 60 to 150 mm.

(33) The welding was effected by time-controlled temperature-regulated pulse sealing:

(34) Temperature: 240 degrees

(35) Sealing time: 4 seconds

(36) Contact pressure through the welding jaws: 0.02 N/mm.sup.2

(37) Mean weld seam strength: =45 N/15 mm

(38) The weld seam strength for the 60 PE bags has a scatter of +/−15% with respect to the mean.

(39) 6 bags each were introduced into one cardboard box. The 10 cardboard boxes were driven for 2000 km through Germany on a truck.

(40) After transport, the bags were checked visually for damaged weld seams and, with the aid of the water dip method, for punctures.

(41) 0% of the weld seams came open during transport.

(42) 0% of the bags were no longer leakproof after transport.

Example 2

(43) Packing into a Flat PE Bag Having the Following Film Properties:

(44) Thickness of the film: 300 μm

(45) Stiffness at the flexural modulus: F.sub.max=500 mN; F.sub.t=200 mN

(46) Dynamic penetration testing: Fracture force F=300 N Fracture energy Ws=4 J Penetration energy W.sub.tot=4.5 J

(47) Longitudinal film tensile stress at 15% elongation=12 MPa

(48) Transverse film tensile stress at 15% elongation=13 MPa

(49) Elmendorf longitudinal film tear resistance=15 cN

(50) Elmendorf transverse film tear resistance=25 cN

(51) Longitudinal film elongation at break: =500 percent

(52) Transverse film elongation at break: =700 percent

(53) This PE film was used to produce 60 PE bags which were filled with 5 kg of chunk poly with chunk size 4 having an edge length of 60 to 150 mm.

(54) The welding was effected by time-controlled pulse sealing without temperature regulation:

(55) Sealing time: 4 seconds

(56) Contact pressure through the welding jaws: 0.02 N/mm.sup.2

(57) Weld seam strength: =45 N/15 mm

(58) The weld seam strength for the 60 PE bags has a scatter of +/−30% with respect to the mean.

(59) 6 bags each were introduced into one cardboard box. The 10 cardboard boxes were driven for 2000 km through Germany on a truck.

(60) After transport, the bags were checked visually for damaged weld seams and, with the aid of the water dip method, for punctures.

(61) 5% of the weld seams came open during transport.

(62) 25% of the bags were no longer leakproof after transport.

(63) Examples 1 and 2 show a distinct improvement over the comparative example. These improvements are attributable to the altered properties of the film and to the altered weld seam strength.

(64) Example 1 shows the advantages of temperature-regulated pulse sealing. This makes it possible to provide bags of chunk polysilicon which show no leaks or breaking-open of the weld seam whatsoever after transport.