Process for making a polymeric film

Patent metadata

Field	Value
Publication number	US-10384408-B2
Application number	US-201214131104-A
Country	US
Kind code	B2
Filing date	Jun 29, 2012
Priority date	Jul 7, 2011
Publication date	Aug 20, 2019
Grant date	Aug 20, 2019

Abstract

The invention relates to a process to make films and tapes from ultrahigh molecular weight polyethylene (UHMWPE) in the solid state. The films and tapes according to the invention have an improved thickness whereby the coefficient of variation of the thickness of the film of at most 6%.

First claim

The invention claimed is:

1. A process for the manufacturing of an ultrahigh molecular weight polyethylene (UHMWPE) film, comprising in sequence the steps of:
(a) providing a bed of UHMWPE powder;
(b) applying a compression pressure on the bed of UHMWPE powder at a compression temperature below a melting temperature of the UHMWPE powder to obtain a compressed bed;
(c) forming a film by compacting the compressed bed in a smoothing unit comprising two compacting surfaces providing a non-constant line of pressure and a gap having a gap-thickness dimension and a gap length dimension between the two compacting surfaces, at a compacting temperature below the melting temperature of the UHMWPE powder, the non-constant line of pressure being achieved by establishing a substantially constant gap-thickness dimension which has a variation over time between a minimum gap thickness and a maximum gap-thickness (Δ compaction ) of at most 20%, and wherein
the film formed by step (c) exhibits a reduced variation in thickness along its width and/or length as determined by a plurality of tapes slit from the film each having an average thickness (T) such that a plurality of the tapes has a coefficient of variation in thickness (CV thickness ) of less than 2% as determined by the following formula using the average thickness (T) of a number of five representative tape lengths each corresponding to a different randomly chosen tape from the plurality of tapes slit from the film:

CV
THICKNESS

=

∑

i
=
1

n

⁢

(

x
i

-

x
_

)

2

n
-
1

×

1

x
_

×
100

,

wherein
x i is the average thickness of any one of the representative tape lengths and x is the averaged value over the n=5 measured average thicknesses, where each measured average thickness is an average of at least 10 thickness measurements carried out at randomly chosen locations of the representative tape lengths.

2. The process of claim 1 , further comprising a step of:
(d) calendaring the film obtained at step (c) and/or uniaxially drawing the film.

3. The process of claim 1 , wherein the bed of the UHMWPE powder has a width of at least 100 mm.

4. The process of claim 1 , wherein the bed of the UHMWPE powder has a thickness of at least 0.3 mm.

5. The process of claim 1 , wherein the UHMWPE powder comprises particles having D50 sizes of at most 1000 micron.

6. The process of claim 1 wherein the compressed bed has a width of at least 100 mm.

7. The process of claim 1 , wherein the gap-length dimension has a variation (Δ length ) of at most 10%.

8. The process of claim 1 , wherein step (c) comprises a smoothing unit having two rotating rolls respectively comprising the two compacting surfaces, wherein the gap between the two compacting surface of the rolls is controlled by providing the rolls with actuators and a feedback mechanism controlling the actuators.

Assignees

• Steeman Reinard Jozef Maria
• Jongedijk Marcel
• Dsm Ip Assets Bv

Inventors

• Steeman Reinard Jozef Maria
• Jongedijk Marcel

Classifications

• C08J2323/06

  Polyethene · CPC title

• C08J5/18 Primary

  Manufacture of films or sheets · CPC title

• B29C43/228

  using endless belts feeding the material between non-rotating pressure members, e.g. vibrating pressure members · CPC title

• B29C43/003

  characterised by the choice of material · CPC title

• Y10T428/269

  including synthetic resin or polymer layer or component · CPC title