Molding thermotropic liquid crystalline polymers

Patent metadata

Field	Value
Publication number	US-9339956-B2
Application number	US-201013516270-A
Country	US
Kind code	B2
Filing date	Dec 16, 2010
Priority date	Dec 18, 2009
Publication date	May 17, 2016
Grant date	May 17, 2016

Abstract

A method of molding a composition comprising a thermotropic liquid crystalline polymer (TLCP) comprising mesogens; providing a mold having a mold cavity, with a feature cavity ( 43 ) comprising a fine feature chamber; heating the composition to form molten composition; filling the fine feature chamber with molten composition moving at a flow velocity that causes flow alignment of at least a portion of the mesogens in the molten TLCP filling the fine feature chamber ( 49 ), relative to a flow direction of the moving molten composition; and solidifying the molten composition such that mesogens of at least the solidified TLCP in the fine feature chamber maintain their flow alignment. A molded article comprising a body and a 3-dimensional structural feature protruding out from the body and comprising a fine feature element having a minor dimension, with TLCP mesogens across the minor dimension being in a flow aligned state.

First claim

What is claimed is:

1. A method of molding an article, said method comprising:
providing a composition comprising at least one thermotropic liquid crystalline polymer (TLCP), with the TLCP comprising a plurality of mesogens;
providing a mold comprising a mold cavity, with the mold cavity comprising at least one feature cavity, and each feature cavity comprising at least one fine feature chamber having a minor dimension up to 100 micrometers;
heating the composition so as to form molten composition comprising molten TLCP;
filling the mold cavity and the at least one feature cavity with a desired amount of the molten composition such that the molten composition filling a body cavity is moving at a first flow velocity that causes at least some flow tumbling of mesogens in the corresponding molten TLCP, and the molten composition filling the at least one fine feature chamber is moving at a second flow velocity that is faster than the first flow velocity and that causes flow alignment of at least a portion of the mesogens in the corresponding molten TLCP relative to a flow direction of the moving molten composition; and
solidifying the molten composition such that mesogens of at least the solidified TLCP in the at least one fine feature chamber substantially maintain their flow alignment.

2. The method of claim 1 , wherein the first flow velocity of the molten composition filling the body cavity is less than or equal to 108 mm/s.

3. The method of claim 1 , wherein the flow velocity of the molten composition filling the at least one fine feature chamber is at least 51 mm/s.

4. The method of claim 1 , wherein the at least one fine feature chamber has a minor feature dimension in the range of from 100 nm up to and including 20 microns.

5. The method of claim 1 , wherein the difference between the first flow velocity and the second flow velocity is at least 12.7 mm/s.

6. The method of claim 1 , wherein the mesogens of the TLCP solidified in the at least one fine feature chamber are molecularly aligned, relative to the flow direction of the moving molten composition filling the at least one fine feature chamber, by an anisotropy factor in the range of from greater than 0.4 up to 1.0.

7. The method of claim 1 , wherein the molded article comprises a body and at least one 3-dimensional structural feature integral with and protruding out from said body, said at least one structural feature comprising at least one fine feature element having a minor dimension up to 100 micrometers, and said at least one structural feature comprising at least one thermotropic liquid crystalline polymer (TLCP) having a plurality of mesogens, with at least a portion of the mesogens across said minor dimension being in a flow aligned state.

8. The method of claim 7 , wherein for the article, at least 30% of the TLCP mesogens across the minor dimension of each fine feature element are flow aligned.

9. The method of claim 7 , wherein for the article, the TLCP mesogens in each fine feature element exhibit an average anisotropy factor in the range of from at least 0.3 up to and less than 1.0.

10. The method of claim 7 , wherein for the article, the flow aligned TLCP mesogens across the minor dimension of each fine feature element exhibit an average anisotropy factor in the range of from at least 0.5 up to and less than 1.0.

11. The method of 7 , wherein for the article, at least 10% of the TLCP mesogens in each structural feature are flow aligned, with the remainder of the TLCP mesogens in each structural feature having a relatively isotropic orientation state.

12. The method of claim 7 , wherein for the article, the minor dimension of said at least one fine feature element is less than or equal to 500 μm.

13. The method of claim 7 , wherein for the article, the minor dimension of said at least one fine feature element is in the range of from 90 nm up to and including 20 microns.

14. The method of claim 7 , wherein a core of the TLCP mesogens in said body have an isotropic orientation state compared to that of said structural feature.

15. The method of claim 7 , wherein for the article, all of the TLCP mesogens in the body have an isotropic orientation state compared to that of said fine feature element.

16. The method of claim 7 , wherein for the article, the TLCP mesogens in said body are in a flow tumbled state.

17. The method of claim 7 , wherein for the article, said 3-dimensional structural feature is a cube, rib, ridge, solid needle, hollow needle, pin, fin, gear, channel, socket, bobbin, pump, chip carrier or switch.

18. The method of claim 17 , wherein for the article, said fine feature element comprises a leading edge or tip of said 3-dimensional structural feature.

19. The method of claim 18 , wherein for the article, said fine feature element is a tip of said hollow needle, a tip of said solid needle, a tip of said pin, a gear tooth of said gear, opposite edges defining an opening of said channel, or a bore of said hollow needle.

20. The method of claim 1 , wherein the mesogens of the TLCP solidified in the at least one fine feature chamber are molecularly aligned, relative to the flow direction of the moving molten composition filling the at least one fine feature chamber, by an anisotropy factor in the range of from greater than 0.6 up to 1.0.

Assignees

• Rendon Stanley
• 3M Innovative Properties Co

Inventors

• Rendon Stanley

Classifications

• B29K2105/16

  Fillers · CPC title

• B29K2995/0082

  Flexural strength; Flexion stiffness · CPC title

• B29C45/77 Primary

  of velocity or pressure of moulding material · CPC title

• B29C33/0088

  Multi-face stack moulds · CPC title

• B29K2509/08

  Glass · CPC title