PRODUCTION OF FIBER COMPOSITE MATERIALS

Abstract

The invention relates to a process for the production of fiber composite materials via specific application of monomer mixtures to a surface of a fiber material and subsequently polymerization.

Claims

1. A process for the production of a fiber composite material, the process comprising: a) applying to the surface of a fiber material: a1) droplets of a first monomer mixture that is liquid at the application temperature, the first monomer mixture comprising a cyclic amide and an activator, and a2) droplets of a second monomer mixture that is liquid at the application temperature, the second monomer mixture comprising a cyclic amide and a catalyst, at a temperature above the melting point, and b) polymerizing the monomer mixtures in a) at a temperature of 120 to 300 C., wherein the average droplet size of the droplets of the respective monomer mixtures a1) and a2) is less than 500 m.

2. The process for the production of the fiber composite material as claimed in claim 1, wherein the cyclic amide is laurolactam, caprolactam or a mixture of these.

3. The process for the production of a fiber composite material as claimed in claim 1, wherein the activator comprises at least one compound selected from the group of the isocyanates, uretdiones, carbodiimides, anhydrides, acyl halides, and reaction products of these with the monomer.

4. The process for the production of a fiber composite material as claimed in claim 1, wherein the catalyst comprises at least one compound selected from the group consisting of sodium caprolactamate, potassium caprolactamate, magnesium bromide caprolactamate, magnesium chloride caprolactamate, magnesium biscaprolactamate, sodium hydride, sodium, sodium hydroxide, sodium methanolate, sodium ethanolate, sodium propanolate, sodium butanolate, potassium hydride, potassium hydroxide, potassium methanolate, potassium ethanolate, potassium propanolate and potassium butanolate.

5. The process for the production of a fiber composite material as claimed in claim 1, characterized in that the fiber material is selected from the group of the woven fabrics, laid scrims inclusive of multiaxial laid scrims, knitted fabrics, braided fabrics, nonwoven fabrics, felts, and mats.

6. The process for the production of fiber composite material as claimed in claim 1, when the droplets of the monomer mixtures are applied by means of a three-fluid nozzle.

7. The process for the production of a fiber composite material as claimed in claim 1, wherein the fiber material comprises a plurality of plies of fiber material, superposed on one another with an uppermost ply, and the process further comprises: i) treating the surface of the uppermost ply in step a) with the monomer mixtures a1) and a2) before step b) follows, or ii) individually treating each of the plurality of plies of fiber material in step a) with the monomer mixtures, and placing the treated plies into contact with one another before step b) follows.

8. The process for the production of the fiber composite material as claimed in claim 1, wherein the average droplet size of the droplets of the respective monomer mixtures a1) and a2) is less than 200 m.

9. The process for the production of the fiber composite material as claimed in claim 1, wherein the average droplet size of the droplets of the respective monomer mixtures a1) and a2) is 10 to 100 m.

10. The process for the production of the fiber composite material as claimed in claim 1, wherein: the cyclic amide is laurolactam, caprolactam or a mixture of these; the activator comprises at least one compound selected from the group of the isocyanates, uretdiones, carbodiimides, anhydrides, acyl halides, and reaction products of these with the monomer; and the catalyst comprises at least one compound selected from the group consisting of sodium caprolactamate, potassium caprolactamate, magnesium bromide caprolactamate, magnesium chloride caprolactamate, magnesium biscaprolactamate, sodium hydride, sodium, sodium hydroxide, sodium methanolate, sodium ethanolate, sodium propanolate, sodium butanolate, potassium hydride, potassium hydroxide, potassium methanolate, potassium ethanolate, potassium propanolate and potassium butanolate.

11. The process for the production of the fiber composite material as claimed in claim 10, wherein: the catalyst comprises at least one of sodium hydride, sodium and sodium caprolactamate; the fiber material comprises a plurality of layers of fiber material and the fiber material is selected from the group of the woven fabrics, laid scrims inclusive of multiaxial laid scrims, knitted fabrics, braided fabrics, nonwoven fabrics, felts, and mats; and the average droplet size of the droplets of the respective monomer mixtures a1) and a2) is 10 to 100 m.

Description

[0093] FIG. 1 depicts a preferred arrangement of a continuously operated system for the operation of the process of the invention.

ELEMENTS OF FIG. 1

[0094] (1) Fiber material (supply from a roller) [0095] (2) Hot air for the predrying procedure [0096] (3) Perforated metal sheets for air ingress [0097] (4) Hot dry air in circulation [0098] (5) Preheated nitrogen [0099] (6) Three-fluid nozzle [0100] (7) Dome structure (spray-zone housing) [0101] (8) Teflon transport belt [0102] (9) Opposing rollers to compress fiber material [0103] (A) Caprolactam with activator [0104] (B) Caprolaciam with catalyst

EXAMPLES

[0105] 1. Experiments relating to the effect of melt-application procedure and of droplet size:

[0106] a1)

[0107] 100 g of -caprolactam and 6.5 g of Addonyl Kat NL (Rhein Chemie Rheinau GmbH) catalyst were weighed into a three-necked flask. Addonyl Kat NL is a commercially available mixture of 18.5% by weight of sodium caprolactamate (CAS No.: 2123-24-2) in monomeric caprolactam.

[0108] a2)

[0109] 100 g of -caprolactam and 3.5 g of Addonyl 8120 (likewise from Rhein Chemie Rheinau GmbH) were charged to a second three-necked flask. Addonyl 8120 is a bilaterally caprolactam-blocked hexamethylene diisocyanate, specifically N,N-hexane-1,6-diylbis(hexahydro-2-oxo-1H-azepine-1-carboxamid), CAS No.: 5888-87-9.

[0110] The contents of the two flasks were melted separately in oil baths preheated to 135 C. Vacuum was then applied at this temperature for 10 minutes. The two flasks were then blanketed with nitrogen, and the oil baths were removed.

[0111] The melts a1) and a2) were respectively cooled until the temperature of melts was 100 C.

[0112] The experiments were carried out by hotplate, which was enclosed with foil for inertization and the internal cavity of which was blanketed with nitrogen. Specifically, the dry nitrogen was charged to the internal cavity and the temperature of the hotplate was controlled to 160 C.

[0113] A woven glassfiber fabric (P-D Interglas Technologies, Erbach, type 92152 with weight per unit area 290 g/m.sup.2) was predried in an oven at 80 C. for 12h.

[0114] The desired fiber content by volume of the fiber composite material in the experiments was 40%. The textile plies used for the experiments were first weighed, in order to permit calculation of the volume of melt required to achieve the 40% fiber ratio by volume.

[0115] In order to improve heat conduction, an iron plate (mass: 2.0 kg) likewise controlled to a temperature of 160 C. was placed from above onto the impregnated woven fabric after melt application. In order to avoid direct contact between the melt and the iron plate, the woven glassfiber fabric was covered with a polyimide foil (Kaptan HN from DuPont) after melt application.

[0116] Polymerization time was 5 minutes in all cases.

Comparative Example 1

[0117] The two prepared caprolactam melts a1) and a2) were combined and mixed, and then a preheated PE pipette was used to apply the quantity calculated to achieve 40% fiber content by volume.

[0118] The residual monomer content of the PA 6 Matrix after polymerization was 1.9% by weight.

Comparative Example 2

[0119] The two prepared caprolactam melts a1) and a2) were not combined, but instead two preheated PE pipettes were used to apply equal volumes thereof separately to the woven glassfiber fabric. Droplets of the two melts were applied here simultaneously, and the droplets were applied in the immediate vicinity of the respective other component in order to achieve the best possible mixing.

[0120] The average mass of an individual droplet formed here under the influence of gravitational force was 20 mg.

[0121] The residual monomer content of the PA 6 Matrix after polymerization was 80% by weight, and it was therefore composed mainly of unreacted monomer, which could be leached out of the composite sheet by warm water.

Comparative Example 3

[0122] The procedure was as in comparative example 2, but after application of the two melts a1) and a2) the woven fabric was covered with a polyimide foil and rolled, i.e. pounded, by a single roller for 5 seconds.

[0123] The residual monomer content of the PA 6 Matrix after polymerization was 50% by weight, and it was therefore still composed mainly of unreacted monomer.

Example 1 (of the Invention)

[0124] In this case, the two melts were applied at identical volume flow rates by way of a 946 S1 three-fluid nozzle from Schlick. In order to avoid solidification of the caprolactam melts, the temperature of the nozzle was controlled in advance to 120 C. in an oven, the materials were metered at identical volume flow rates by way of two preheated PE spray devices, and atomization achieved via a current of nitrogen (30% by weight of nitrogen, based on the total quantity of melt metered).

[0125] This method can achieve droplet diameters <100 m. Average droplet mass was therefore about 1/1000.sup.th of that in the variant described in comparative example 2.

[0126] The residual monomer content of the PA 6 Matrix after polymerization was only 2.5% by weight. In addition to this, no problematic polymer deposits were discernible.