DE4321938A1 - Use of a novolak melt for impregnating glass fibres - Google Patents

Abstract

The invention relates to a novolak melt for impregnating glass fibres formed from a multiplicity of individual filaments. It is expediently provided that the melt comprises a novolak with a low degree of condensation and has a melting range of 50-120 DEG C (preferably 60-100 DEG C) and a melt viscosity of 0.1-150 Pa.s/130 DEG C (preferably 1-50 Pa.s/130 DEG C) and a flow distance (at a content of 10% of hexamethylene tetramine) of at least 20 mm (preferably 40-120 mm). Hitherto, such glass fibres, which are widely used for reinforcing mouldings, such as, for example, winding discs or brake and clutch linings, have been impregnated with a phenolic resin solution. The use of a novolak melt gives considerable advantages over this.

Description

Phenolic resin bonded glass fabrics are widely used to reinforce kung of moldings used, for. B. in grinding wheels or in clutch and Brake pads.

The impregnation of the fabric is usually carried out by dip impregnation nierung with solvent-based phenolic resins and subsequent drying at 80-160 ° C, wherein the resin content of the fabric adjusted to 30-40% becomes. The for the production of z. As grinding wheels required round blanks are made from sheet-shaped prepregs by punching (art Stoff-Handbuch, Vol. 10, 1988, pp. 908-910). However, fol disadvantages:

• 1st cut when punching up to 35%.
• 2. Workplace exposure to solvents and free phenol (up to 5%) from the commonly used resins.
• 3. Environmental impact of emissions when drying the pre pregs.

The disadvantage of the waste, which is disposed of as hazardous waste can be eliminated by placing the round blank by placing a single a plurality of individual filaments (eg up to 1200 filaments at a Thread of about 1 mm diameter) formed glass thread in the desired  Geometry is made, the glass thread before laying with the Phe nolharzlösung is impregnated. However, the disadvantages remain 2 and 3 exist.

Surprisingly, it has now been found that these remaining To avoid disadvantages by the fact that the impregnation of the glass thread by means of a suitable novolak melt. Accordingly, he is in the use of a novolak melt for the impregnation of glass threads, which are formed from a multiplicity of single filaments.

The invention provides the following advantages:

• 1. The resin is solvent-free.
• 2. Your free phenol content can be reduced to below 1% become.
• 3. The impregnated fabric is tack-free to produce.
• 4. An embrittlement of tissue occurs over time not a.

Important in this melt impregnation is that the individual filaments of the glass thread are optimally impregnated. This should be the novolak melt during the impregnation process the lowest possible viscosity and Surface tension and after impregnation a precisely tuned Curing course have. Accordingly, in a preferred embodiment the invention provided that the novolak melt from a low kon condensed novolak exists and a melting range of 50-120 ° C. (preferably 60-100 ° C) and a melt viscosity of 0.1-150 Pa · s / 130 ° C. (Preferably 1-50 Pa.s / 130 ° C and a flow path (at a content of 10% hexamethylenetetramine) of at least 20 mm (preferred wise 40-120 mm) has. The measurement of these values takes place after standardized methods, which in DIN 16 916-02A for the flow path (the one Measure of the hardening process), in DIN 53 229 for the melt viscosity and DIN 53 181 for the melting range.

The novolaks suitable for the purposes of the invention can be leached conventional methods and can with the usual Modifizie such as hardening accelerators, elastification and plastification  be provided.

The curing of novolaks in the impregnated glass threads is done by Addition of the usual curing agent, eg. For example hexamethylenetetramine. This herd can

• - be applied in advance to the thread
• - Are added in the melt
• - be taken from the resin used to make the reinforcing molding is used.

The following are examples of novolacs, for the Purpose of the invention are suitable, explained in more detail.

Novolac A

In a stirrer were 563 kg of phenol and 9 kg of phthalic anhydride before placed. The mixture was brought to 90 ° C. Then within 4 Hours continuously fed 270 kg of 37% formalin, the Tempe temperature was maintained at 90 ° C. Subsequently, to completion the reaction is recondensed for a further 2 hours at reflux temperature. The Working up of the reaction mixture was carried out by conventional methods, and obtained about 400 kg of a novolak with the following characteristics:

Melting range | 70-95 ° C Melt viscosity 4.5 Pa · s / 130 ° C flow path 52 mm

Novolak B

In a stirrer 992 kg of phenol and 2 kg of oxalic acid were submitted. The Mixture was brought to 85 ° C. Then, within 1 hour kon continuously added 598 kg of 37% formalin, the temperature on 100 ° C rose. Subsequently, to complete the reaction 5 hours the condensed at reflux temperature until the content of free form aldehyde was less than 0.3%. The workup of the reaction mixture he Followed by the usual methods, and you got about 910 kg of a Novo laks with the following characteristics:  

Melting range | 74-79 ° C Melt viscosity 14 Pa · s / 130 ° C flow path 90 mm

Novolac C

In a stirrer 992 kg of phenol and 8.3 kg of oxalic acid were submitted. The Mixture was brought to 85 ° C. Then it was confiscated within 3 hours continuously added 667 kg of 37% formalin, with the temperature on 100 ° C rose and was held there. Subsequently, the completion was Nachkondensiert tion of the reaction for 3 hours at reflux temperature until the Free formaldehyde content was less than 0.2%. The workup of the Reaction mixture was carried out by the customary methods, and about 950 kg of a novolak with the following characteristics:

Melting range | 94-103 ° C Melt viscosity 95 Pa · s / 130 ° C flow path 48 mm

Claims (2)

1. Use of a novolak melt for the impregnation of Glasfä those formed from a variety of individual filaments. 2. Use of a novolak melt for the purposes of claim 1, wherein the melt consists of a low-condensed novolak and a melting range of 50-120 ° C (preferably 60-100 ° C) and a melt viscosity of 0.1-150 Pa · s / 130 ° C (preferably 1-50 Pa · s / 130) and a flow path (at a content of 10% He xamethylenetetramine) of at least 20 mm (preferably 40-120 mm) has.