Polyurethane prepregs with controllable tack

Patent metadata

Field	Value
Publication number	US-10428193-B2
Application number	US-201615336922-A
Country	US
Kind code	B2
Filing date	Oct 28, 2016
Priority date	Oct 30, 2015
Publication date	Oct 1, 2019
Grant date	Oct 1, 2019

Abstract

The invention relates to a process for producing a prepreg based on polyurethane, which is notable for high storage stability at room temperature, a two-stage reaction mechanism, and adjustable adhesion on metal surfaces. It is based on the problem of making the surface tack of the prepregs controllable during processing. The solution is to assemble the PU mixture from which the matrix originates at a later stage such that the glass transition temperature of the thermoplastic polymer is above 30° C. For this purpose, the invention proposes two basically independent but certainly synergistic measures, namely:
i) use of a polyol compound or a mixture of a number of polyol compounds as binder, the OH number or mean OH number of which is above 300 mg KOH/g, ii) choice of the proportion of hardener corresponding to the co-binder in the reactive composition at greater than 2% by weight, based on the total solids content of the reactive composition.

First claim

What is claimed is:

1. Process for producing a laminate, comprising the steps of:
a) providing a reactive composition comprising at least the following constituents:
at least one blocked isocyanate hardener,
at least one binder which is a polyol compound having an OH functionality of 3 to 6 and which has at least one polar functional group selected from an ester, carbonate, amide, urethane, urea, thioester or thiocarbonate functionality;
at least one co-binder which is an epoxy resin,
at least one hardener which corresponds to the co-binder and is selected from the group comprising the following substance classes: aliphatic polyamines, cycloaliphatic polyamines, polyetheramines, polymercaptans or polyamidoamines, polycarboxylic acids, polycarboxylic anhydrides;

b) providing fibres;
c) coating the fibres with the reactive composition;
d) exposing at least the reactive composition to heat to perform a first crosslinking reaction, in the course of which hardener and binder are converted to a thermoplastic polymer, the fibres being embedded into the thermoplastic polymer;
e) obtaining a prepreg comprising the thermoplastic polymer with the fibres embedded therein,
characterized in that
the reactive composition is provided in such a way that the glass transition temperature of the thermoplastic polymer measured in the second heating curve at 10 K/min according to the DSC method as defined in DIN 53765 is above 30° C., through

i) use of a polyol compound or a mixture of a number of polyol compounds as binder, the OH number measured according to DIN 53 240-2 or mean OH number of which is above 300 mg KOH/g,
and/or
ii) choice of the proportion of hardener which corresponds to the co-binder in the reactive composition at greater than 2% by weight, based on the total solids content of the reactive composition,
characterized in that the fibres are provided continuously from a roll as a textile fabric, in that the textile fabric is coated continuously with the reactive composition, and in that the textile fabric coated with the reactive composition is exposed continuously to heat to perform the first crosslinking reaction, such that the thermoplastic polymer with the fibres embedded therein forms a continuous prepreg in the form of a strip which is cut into individual sections and the individual sections are layered in a stack and pressed to form a laminate.

2. Process according to claim 1 , characterized in that hardeners used are uretdiones which are free of blocking agents and are prepared from at least one of the following substances: isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), diisocyanatodicyclohexylmethane (H12MDI), 2-methylpentane diisocyanate (MPDI), mixtures of 2,2,4-trimethylhexamethylene diisocyanate and 2,4,4-trimethylhexamethylene diisocyanate (TMDI), and norbornane diisocyanate (NBDI).

3. Process according to claim 1 characterized in that the binder used is at least one polyester polyol having an OH number measured according to DIN 53 240-2 between 20 mg KOH/g and 500 mg KOH/g and having an acid number measured according to DIN EN ISO 2114 of not more than 2 mg KOH/g.

4. Process according to claim 1 , characterized in that the binder used is at least one polycaprolactone having an OH number measured according to DIN 53 240-2 between 20 mg KOH/g and 1000 mg KOH/g and having an acid number measured according to DIN EN ISO 2114 of not more than 2 mg KOH/g.

5. Process according to claim 1 , characterized in that co-binders used are epoxy resins selected from the group comprising epoxy resins based on bisphenol A diglycidyl ether, epoxy resins based on bisphenol F diglycidyl ether and cycloaliphatic types.

6. Process according to claim 1 , characterized in that the composition comprises, as further component, at least one additive, selected from the group consisting of a rheology modifier, a wetting agent, a colour pigment, a defoamer, a release agent, a filler, a deaerator, an impact modifier, a flow auxiliary, a levelling auxiliary, and a flame retardant.

7. Process according to claim 1 , characterized in that the composition is provided as a dry powder, and so the coating of the fibres with the composition is effected by scattering and/or melting the powder onto the fibres.

8. Process according to claim 1 , characterized in that the composition is provided in a liquid solvent, the constituents of the composition being dissolved and/or suspended and/or dispersed in the solvent, such that the fibres are coated with the composition by impregnating the fibres with the solvent and the constituents dissolved/suspended/dispersed therein, and in that the solvent is at least partly evaporated out of the fibres in the course of performance of the first crosslinking reaction.

9. Process according to claim 8 , characterized in that the solvent is an ester or a ketone or a mixture comprising at least one ester and/or at least one ketone.

10. Process according to claim 8 , characterized in that the solids content of the solution is between 30% by weight and 80% by weight, based on the total weight of the solution.

11. Process according to claim 1 , characterized in that the nonvolatile constituents present in the reactive composition are
between 30% by weight and 70% by weight of hardener
between 30% by weight and 70% by weight of binder
more than 0% by weight and up to 20% by weight of co-binder
more than 0% by weight and up to 20% by weight of corresponding hardener
between 0% by weight and 5% by weight of additives, where the nonvolatile constituents present add up to 100% by weight.

12. Process according to claim 11 , characterized in that the reactive composition comprises
as hardener 40% by weight to 60% by weight of a uretdione or a mixture of two or more uretdiones based on isophorone diisocyanate (IPDI);
as binder 25% by weight to 50% by weight of a polycaprolactone or a mixture of two or more polycaprolactones;
as co-binder 5% by weight to 15% by weight of an epoxy resin selected from the group comprising epoxy resins based on bisphenol A diglycidyl ether, epoxy resins based on bisphenol F diglycidyl ether and cycloaliphatic types;
as corresponding hardener between 2% by weight and 5% by weight of a polycarboxylic acid and/or a polycarboxylic anhydride;
as additive between 0% by weight and 1% by weight of a wetting agent; where the nonvolatile constituents present add up to 100% by weight.

13. Process according to claim 8 , characterized in that at least 98% by weight of the solvent has evaporated out of the fibres.

14. A method of producing a hybrid component, comprising producing a laminate according to the process of claim 1 , handling the laminate at a temperature between 15° C. and 25° C., and then pressing the laminate onto a metallic workpiece at a temperature of 50° C. to 100° C. without using an additional adhesive, such that the laminate sticks to the workpiece.

15. The method of claim 14 , further comprising exposing the laminate that is stuck to the workpiece to heat within a temperature range from 160° C. to 220° C., in the course of which the thermoplastic polymer is converted to a thermoset polymer.

16. Process for producing a hybrid component, comprising the steps of:
a. providing a reactive composition comprising the following constituents:
i. at least one blocked isocyanate hardener,
ii. at least one binder which is a polyol compound having an OH functionality of 3 to 6 and which has at least one polar functional group selected from an ester, carbonate, amide, urethane, urea, thioester or thiocarbonate functionality,
iii. at lea

Assignees

• Evonik Degussa Gmbh

Inventors

• Stapperfenne Uwe
• Schmidt Marina-Elena
• Gutmann Tobias
• Cron Christina
• Reemers Sandra

Classifications

• C08G18/4676

  containing sulfur · CPC title

• C08G18/42 Primary

  Polycondensates having carboxylic or carbonic ester groups in the main chain · CPC title

• B32B27/40 Primary

  comprising polyurethanes · CPC title

• C08G59/42

  Polycarboxylic acids; Anhydrides, halides or low molecular weight esters thereof · CPC title

• C08J2375/06

  from polyesters · CPC title