Method for impregnating natural fibres with a polymer in aqueous dispersion and use of said fibres in composite materials

Patent metadata

Field	Value
Publication number	US-10287410-B2
Application number	US-201515310463-A
Country	US
Kind code	B2
Filing date	May 7, 2015
Priority date	May 12, 2014
Publication date	May 14, 2019
Grant date	May 14, 2019

Abstract

A method for impregnating strands or strips of natural fibers, using the following successive steps: i) the impregnation of the strands or strips by immersion in a bath containing a fine aqueous polymer dispersion; followed by ii) the drying of the strands or strips using a heating system, with the progressive elimination of the water and the gradual melting of the polymer, and the coating of the strands or strips and the molten polymer incorporated into the core of the strands or strips as a binder between the fibers; iii) optionally, the forming of the treated strands or strips into their final shape; and iv) the cooling of the treated strands or strips. The aqueous polymer dispersion comprises at least one semi-crystalline or amorphous polymer and, in the case of an amorphous polymer, has a Tg varying between 50° C. and 175° C.

First claim

The invention claimed is:

1. A process for impregnating, on line, rovings or ribbons of natural fibers, wherein the process comprises at least the following successive steps:
i) impregnating said rovings or said ribbons of said fibers by immersing in a bath containing a fine aqueous polymer dispersion or by spraying said aqueous dispersion, said impregnating being followed by
ii) drying said rovings or said ribbons by means of a heating system, with, during said drying, the gradual elimination of the water and the melting of said polymer as said drying advances, the coating of said rovings or ribbons with said molten polymer incorporated into the core of the bundle of fibers of said rovings or of said ribbons binding said fibers to one another,
iii) optionally, final forming of said rovings or ribbons thus treated, of unidirectional ribbons or of rovings with a cylindrical cross section or in the form of pre-impregnated fabrics or in the form of an assembly of ribbons,
iv) cooling said rovings or said ribbons thus treated,
with said aqueous polymer dispersion comprising at least one amorphous or semi-crystalline polymer and, in the case of an amorphous polymer, said polymer having a Tg ranging from 50° C. to 175° C., and, in the case of a semi-crystalline polymer, said polymer having a melting point ranging from 70° C. to less than 220° C., said dispersion comprising a content by weight of said polymer ranging from 5% to 50% with particles in dispersion having a number-average size of less than 10 000 nm, wherein said polymer is a polyurethane formed from a polyisocyanate prepolymer comprising an ionic group, dispersed in water with chain extension in an aqueous medium or a copolyamide.

2. The process of claim 1 , wherein said polymer is dispersible (or dispersed) in powder form in an aqueous medium without surfactant.

3. The process of claim 1 , wherein said copolyamide bears amine groups.

4. The process of claim 1 , wherein said copolyamide bears carboxy groups which are neutralized in salt form by a base.

5. The process of claim 1 , wherein said copolyamide is semi-crystalline with a melting point of less than or equal to 150° C.

6. The process of claim 1 , wherein said copolyamide comprises at least one of the following units: 5.9, 5.10, 5.12, 5.13, 5.14, 5.16, 5.18, 5.36, 6, 6.9, 6.10, 6.12, 6.13, 6.14, 6.16, 6.18, 6.36, 9, 10.6, 10.9, 10.10, 10.12, 10.13, 10.14, 10.16, 10.18, 10.36, 11, 12, 12.6, 12.9, 12.10, 12.12, 12.13, 12.14, 12.16, 12.18, 12.36, 6.6/6, 11/10.10 and mixtures thereof.

7. The process of claim 1 , wherein said polymer is a copolyamide chosen from: PA 6/6.6/12, PA 6/6.6/11/12, PA 6/12, PA 6.9/12, PA Pip.9/Pip.12/11, PA 6/1PD.6/12, PA IPD.9/12, PA6/MPMD.12/12, PA 6/6.12/12, PA 6/6.10/12, PA 6/Pip.12/12, PA 6/6.6/6.10/6.I, PA 6.10/Pip.10/Pip.12, PA 6/11/12, PA Pip.12/12, PA IPD.10/12, PA Pip.10/12, PA 6/11, PA Pip.10/11/Pip.9, PA 6/6.6/6.10, PA 6/6.10/6.12 and mixtures thereof.

8. The process of claim 1 , wherein said polyamide is semi-aromatic amorphous and corresponds to the following formulae:
6.I, 8.I, 9.I, 10.I, 11.I, 12.I, 6.I/9.I, 9.I/10.I, 9.I/11.I, 9.I/12.I, 9/6.I, 10/6.I, 11/6.I, 12:6.I, 10/9.I, 10/10.I, 10/11.I, 10/12.I, 11/9.I, 11/10.I, 11/11.I, 11/12.I, 12/9.I, 12/10.I, 12/11.I, 12/12.I, 6.10/6.I, 6.12/6.I, 9.10/6.I, 9.12/6.I, 10.10/6.I, 10.12/6.I, 6.10/9.I, 6.12/9.I, 10.I/6.I, 10.10/9.I, 10.12/9.I, 6.10/10.I, 6.12/10.I, 9.10/10.I, 9.12/10.I, 10.10/10.I, 10.12/10.I, 6.10/12.I, 6.12/12.I, 9.10/12.I, 9.12/12.I, 10.10/12.I, 11/6.I/9.I, 11/6.I/10.I, 11/6.I/11.I, 11/6.I/12.I, 11/9.I/10.I, 11/9.I/11.I, 11/9.I/12.I, 11/10.I/11.I, 11/10.I/12.I, 11/11.I/12.I, 6.I/10.I, 6.I/11.I, 6.I/12.I, 10.I/11.I, 10.I/12.I, 11.I/12.I, 12/6.I/10.I, 12/6.I/11.I, 12/6.I/12.I, 12/9.I/10.I, 12/9.I/11.I, 12.9.I/12.I, 12/10.I/11.I, 12/10.I12.I, 12/11.I/12.I, 12/11.I/12.I,
the preceding terpolymer polyamides with 12/ replaced with 9/, 10/, 6.10/, 6.12/, 10.6/, 10.10/, 10.12/, 9.10/ and 9.12/,
all the preceding polyamides, with isophthalic (I) partially replaced up to 40 mol % with terephthalic (T), naphthalene-2,6-dicarboxylic and/or with 1,3- or 1,4-CHDA (cyclohexanedicarboxylic acid), with all or some of the linear aliphatic diamines possibly being replaced with branched aliphatic diamines,
all the preceding polyamides, wherein isophthalic (I) is partially or totally replaced with a linear or branched C6 to C18 aliphatic diacid and at the same time with total or partial replacement of the aliphatic diamine with a cycloaliphatic diamine among BMACM, BACM and/or IPD.

9. The process of claim 1 , wherein said polymer is semi-crystalline with a melting point Mp greater than 90° C., and wherein the particles of said dispersion have a number-average size ranging from 50 to 5000 nm.

10. The process of claim 1 , wherein the content by dry weight of said polymer relative to the dry weight of said fibers ranges from 0.5% to less than 50%.

11. The process of claim 10 , wherein said content by weight ranges from 0.5% to 10%, and wherein said impregnation is limited to the consolidation of said fibers to one another, in addition to sizing.

12. The process of claim 10 , wherein said content is greater than 25% and less than 50%, and wherein said impregnation in addition to said consolidation results in a prepreg of said fibers that is used or can be used separately or successively in the manufacture of composite materials.

13. The process of claim 1 , wherein the viscosity of said dispersion at 23° C. ranges from 10 to 1000 mPa·s.

14. The process of claim 1 , wherein said polymer is biobased.

15. The process of claim 1 , wherein said fibers are long flax fibers with L/D>2000.

16. The process of claim 1 , wherein said rovings or ribbons are based on flax fibers having a tex ranging from 10 to 10 000.

17. The process of claim 1 , wherein the process comprises at least one additional series of steps of impregnating according to i) and of drying according to ii) after a first series of steps of impregnating according to i) and of drying according to ii), with a polymer dispersion different than that of the preceding series.

18. The process of claim 1 , wherein the process comprises at least one additional series of steps of impregnating according to i) and of drying according to ii) after a first series of steps of impregnating according to i) and of drying according to ii), wherein said dispersion remains the same, passing in at least one loop in the same impregnation bath or in the same spraying device and in the same drying system of the first series of steps.

19. The process of claim 11 , wherein the process further comprises an additional step of impregnating and of coating in the molten state, after said drying step ii), with a polymer in the molten state, said polymer being different than but compatible with said polymer of said aqueous dispersion and said polymer is deposited in the molten state by passing said rovings or said ribbons through an extruder die, with optionally, after cooling according to step iv), passing through a system for reducing the size of said fibers thus treated.

20. The process of claim 1 , wherein said heating means of said drying step ii) are chosen from: infrared (IR) radiation, microwaves, induction or by an oven with water extraction, pulsed-air oven or by calendering on heating rolls.

21. The process of claim 1 , wherein said process comprises a step of forming said fibers in the shape of a ribbon with a width of less than 2000 mm.

22. The process of claim 1

Assignees

• Arkema France
• Dehondt Tech
• Akrema France

Inventors

• Pineau Quentin
• Hochstetter Gilles
• Audenaert Marc
• Dehondt Guy
• Philippe Edouard

Classifications

• C08J2377/00

  Characterised by the use of polyamides obtained by reactions forming a carboxylic amide link in the main chain; Derivatives of such polymers · CPC title

• D06M15/263

  of unsaturated carboxylic acids; Salts or esters thereof · CPC title

• B29B15/125

  by dipping · CPC title

• D06M15/227 Primary

  of hydrocarbons, or reaction products thereof, e.g. afterhalogenated or sulfochlorinated · CPC title

• D06M15/564 Primary

  Polyureas, polyurethanes or other polymers having ureide or urethane links; Precondensation products forming them · CPC title