CH639766A5 - Method for the rapid determination of the thickener content and the thickening behaviour of thickenable resins - Google Patents

Description

The invention relates to a method for quickly determining the thickener content and the thickening behavior of thickenable, polar resins or resin systems by heating and measuring a viscosity.

Various resins show after adding small amounts of metal oxides or hydroxides - such as Magnesium oxide - an increase in viscosity over time. This thickening behavior is used in the manufacture of resin mats, which are used, among other things, in the manufacture of car bumpers, electrical device housings, etc. To control the production and also to develop new products, it is important to determine the behavior of the resin when it is thickened in advance.

] There are quantitative chemical analyzes to determine the thickener content of thickenable resins.

These analyzes are time-consuming due to the rather complex substance mixtures of the thickenable resin systems. Furthermore, they also require certain chemical knowledge from the executors and are therefore generally excluded from production control in the company.

Another possibility is to measure the change in viscosity during thickening. For this purpose, a thickening agent present in pasty form is added to the substance to be examined. After intensive mixing, the sample is then stored at a defined temperature. The viscosity is measured at predetermined intervals, and depending on the temperature specification (23, 50, 80 ° C), the total test time can be only a few hours to several days.

Due to the mostly very poor heat conduction of the substances in question, the heating takes a long time and leads to falsifications of the measurement results due to the strong temperature gradient to the core during the heating. Each measuring point is individually measured, evaluated and entered in coordinate systems. The process is therefore labor and time consuming. Since a reliable statement is only possible after hours or days, this method is not suitable for a production control in a continuously operating company. Furthermore, the discontinuous reading does not record the changes in viscosity that occur between the individual measurements. This method is therefore unsuitable for the investigation of new types of substances. Automation of the measurement process is difficult due to the equipment used in these methods.

A method can be found which allows the thickener content of resin systems and the thickening behavior of resins after addition of a thickener to be ascertained with sufficient accuracy in a short-term experiment, whereby the measuring process must be able to be automated.

This object is achieved according to the invention in that a resin or resin system is heated homogeneously by a high-frequency or ultra-high-frequency field in less than 300 s, preferably 20-30 s, and in that the increase in viscosity is measured continuously.

It was surprising to those skilled in the art that with homogeneous heating the viscosity of resin or resin systems, e.g. from UP resin, epoxy resin, etc., large, reproducible differences are shown, which allow reliable statements about the thickening behavior of the individual resins and resin systems during processing (e.g. during the production of 20 resin mats). It is particularly advantageous with this method that sufficiently precise comparison values can be determined in a short time and at low cost. That is why it can also be used in general, such as in studies of delivery quality, storage stability and to characterize new products.

The measuring device used is simple in construction and reliable. Automation is possible without major technical difficulties, so that savings in labor are possible while at the same time better control of product quality.

In a special implementation of the method, the viscosity is read off 1-3 s after the start of heating for the purpose of determining the thickener content with the aid of a calibration curve.

35 The thickening that occurs spontaneously as a result of the rapid HF or UHF heating causes large differences in viscosity immediately after heating, depending on the concentration of thickener, so that the concentration of thickener can be inferred immediately using a calibration curve. 4o In a further implementation of the method according to claim 1, the resin or resin system is heated to a temperature of 30-150 ° C, preferably 50-100 ° C.

Using a high temperature causes rapid thickening.

An exemplary embodiment of the invention is described in more detail below, the dependence of the viscosity on time being shown in one figure.

UP resin, hardener, stabilizer, filler and release agent are filled in a glass vessel (0 = 50 mm, h = 85 mm) and homogenized using a stirrer (n = 4660 min-1). Then the homogeneous mixture is heated in a UHF heating cabinet with the following electrical values: mains connection: 220 V, 50 Hz power consumption: 2.6 kW 55 output power: 1400 watts frequency: 2.45 GHz in 20 s to 80 ° C. After pouring into a measuring vessel preheated to 80 ° C (0 = 15 mm, h = 59 mm), using a rotary viscometer with metal spin-60 del 0 = 7.5 mm, h = 26 mm) at a speed of n = 55, 5 min-1 the current viscosity value measured.

The concentration of thickener is determined on the basis of a calibration curve, which was generally determined beforehand for the substances used.

65 The further recording of the viscosity indicates the slope of the viscosity curve and the values of the function r | = f (t) practical values of thickening behavior that can be used in practice.

example

To create calibration values, 255.56 g of master batch, consisting of

100

Parts by weight

UP resin

1.5

Parts by weight

Harder

0.06

Parts by weight

stabilizer

150

Parts by weight

filler

4th

Parts by weight

Release agent,

different amounts of thickener weighed. After mixing the samples with a high-speed mixer, the samples are heated to 80 ° C in 20 s in the HF or UHF field. The viscosity value which arises immediately thereafter is determined by means of a rotary viscometer. The values resulting from these measurements are summarized in the table below and can be used to create a calibration curve.

Weight display on

Thickening agent rotary viscometer

(g) (divisions)

3,639,766

The substances to be tested are now examined under the same conditions, of which it is only known that the same type of thickener is present. It was found by comparison with the calibration curve:

Findings g thickener / 255.56 g base stock

3.40 6.30

15 The increase in viscosity of the resin system is shown in the figure for various thickener contents (0.1, 25.2.5 ... g) in the case of a test time of more than 12 minutes.

The initial viscosities at time t = 0 (after heating) correspond to the specified thickener content. The 20 curve rise and the function r] = f (t) characterize the thickening behavior.

Weigh-in (foreign) g thickener /

3.35 6.04

0.00 1.25 2.50 3.75 5.00 7.50

2.0 5.0 13.0 20.0 26.0 45.0

25th

G

1 sheet of drawings

Claims (4)

639 766 1. A method for quickly determining the thickener content and the thickening behavior of thickenable, polar resins or resin systems by heating and measuring a viscosity, characterized in that a resin or resin system is heated homogeneously by a high-frequency or ultra-high-frequency field in less than 300 s and that the increase in viscosity is measured continuously. 2. The method according to claim 1, characterized in that the viscosity is read 1-3 s after the start of heating for the purpose of determining the thickener content with the aid of a calibration curve. 2nd PATENT CLAIMS 3. The method according to claim 1, characterized in that the resin or resin system is heated to a temperature of 30-150 ° C, preferably 50-100 ° C. 4. The method according to claim 1, characterized in that a resin or resin system is heated homogeneously by a high-frequency or ultra-high frequency field in less than 20-30 s.