DE1778824B1 - PROCESS FOR MANUFACTURING OBJECTS FROM PRESSABLE HEAT-CURABLE MATERIALS - Google Patents

Description

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The invention relates to a method for producing the impedance curve at a kink and rising again of articles made of pressable thermosetting. This kink indicates the point in time at which the

Materials. maximum pressure can be effective. It is

The first step in the production of indicated, 5 to 10 seconds the maximum pressure laminates usually consists of the impregnation 5 to shorten the effect so that the whole stack

of the starting materials, ζ. B. of paper and glass has reached a gel-like state. The required

fiber fabric with a thermosetting resin, ζ. B. borrowed delay depends on the thickness of the stack and

with phenolic, epoxy and polyester resin. The resin depends on the nature of the resin.

is cured to such an extent that the panels can be stored. The stack is placed in the press. Usually

are. This storable condition is called »Condition B« io a hydraulic press is used. At a

and the plates from which all volatile steam-heated press can already be used after pressing the

Substances that have evaporated are called prepregs. The molding can be cooled by passing through the press platens

They are generally dry and not sticky. cold water is passed. The press is taking

When heated, the resin liquefies and the contact pressure is closed. Contact pressure is that

then turns into a gel-like state and solidifies 15 pressure that is required to apply the individual layers

finally completely. pressed together so tightly that a good heat

The resin that has hardened to this point is no longer conductive again through the stack. The test elec-

available. electrodes are connected to an external power source

If the pressure is already in the liquid state with the interposition of an impedance measuring

abandoned, the liquid resin mass swells out of the 20 device, z. B. a registration voltmeter. Will with

Laminate, creating cavities. If the resin is measured alternating current, it is advisable to use less

already from the gel-like to the solid state, to work as 1 megahertz, because at higher frequencies

it no longer has enough adhesive strength for a good zen an exact determination of the impedance with one

Binding. It is therefore necessary that the resin is not possible in simple measuring methods. Preferably

to be pressed in a lined condition. For the prior art 25, however, direct current at a voltage of about

includes a procedure in which a thermocouple is used in 3 volts. Depending on the type of press, the

the laminate is embedded and the pressing process is heated after the material to be laminated has been inserted

controls. This procedure is not completely satisfactory; it can be started, or the press can already be

because the temperature at which the resin heats to gel is already a temperature slightly below

begins, is not fixed. It depends on the type and the solidification temperature you have.

Manufacturing process of the »prepregs«. Therefore, the impedance curve is made with measuring electrodes

this method can only be detected by a trained professional who is connected to a differential amplifier

be performed. are, and a storage device and a

The invention is based on the object of providing a switching arrangement for determining comparison values

To find a method of the type mentioned at the outset, the pressing process is controlled automatically. This becomes a

in which the gelation time of the thermosetting is automatic - always constant quality of the end product

resin is detected and the signal for the achieved and the pressing process extraordinarily

There is pressing of the molding with maximum pressure. and regardless of the skills of the press

To solve this problem, operators are made according to the invention.

It has been suggested that the state of heat- 40 The following are some manufacturing examples

hardenable material-dependent electrical impedance according to the invention explained in more detail,
course of the thermosetting material measured and

then the pressing process is controlled so that about example
the maximum pressure at the beginning of gelation

is abandoned. 45 A multilayer circuit should be made by pressing a

In a further embodiment of the invention, the stack is formed from five layers with the production of laminates so proceed that there is conductor elements, between which each the stack to be pressed together with measuring electrodes are two layers of a glass fabric, which with is brought between the plates of a press that epoxy resin is soaked and dried, so yourself then the press plates are moved together so far 5 ° in the B-state. To determine the impedance, that the heat transfer from these plates is used on a polytetrafluoroethylene course Stack ensures that the plates and thus foil applied measuring electrode arrangement, the the stack are heated and at the same time, for example, in the middle of the stack Impedance is determined across the measuring electrodes that is attached.

the point of the impedance curve is determined at 55 The stack is between the plates of a steam-soft the impedance value brought after going through heated hydraulic press, and this a minimum begins to rise, and that about is closed so far that the heat transfer from this point the stack the maximum pressure between the press plates and the stack and in this is exposed. is guaranteed. The measuring electrodes are connected to a pre-60 current source used to determine the impedance, preferably a direct current source, direction is built into the molding press. The electrical e.g. of 1.5 V, and a writing measuring instru-impedance is the total resistance associated with a element opposed to the measured counter-electric current. It includes status history records. So then the press ends ohmic resistance, the capacitive and the heating switched on and the resistance recording inductive Resistance. 65 observed. The resulting values The impedance is measured during the heating are as an example in the table below. It first sinks while the resin wears off. As can be seen from this, the epoxy begins to liquefy. Once the resin begins to gel, resin will begin to gel after 9 minutes and 10 seconds.

I 778

Since the line in the stack is not uniform, the full pressure of 17 atm only takes 20 seconds abandoned this point.

Time Seconds Tempe
rature Impedance comment Minutes 30th (Celsius) (Ohm) O 50 82 ° 100 · 10 ⁶ O 10 105 ° 35 · 10 ⁶ T-H 30th 111 ° 26 · 10 ⁶ 1 00 115 ° 18 · 10 ⁶ 2 20th 121 ° 16 · 10 ⁶ 2 40 124 ° 14 · 10 ⁶ 2 10 127 ° 12 · 10 ⁶ 3 40 128 ° 10.5 · 10 ⁶ 3 10 132 ° 9.5 · 10 ⁶ 4th 40 133 ° 9.0 · 10 ⁶ 4th 05 135 ° 8.5 · 10 ⁶ 5 40 136 ° 8.0 · 10 ⁶ 5 00 137 ° 7.4 · 10 ⁶ 6th 30th 138 ° 7.0 · 10 ⁶ 6th 05 139 ° 6.7 · 10 ⁶ 7th 40 139.5 ° 6.4 · 10 ⁶ 7th 05 139.5 ° 6.4 · 10 ⁶ 8th 40 139.5 ° 6.4 · 10 ⁶ 8th 10 139.5 ° 6.4 · 10 ⁶ 9 30th 140.0 ° 6.5 · 10 ⁶ beginning of 9 45 140.5 ° 6.6 · 10 ⁶ »Gelzu- 9 30th 141.0 ° 6.7 · 10 ⁶ status « 10 142.0 ° 7.0 · 10 ⁶ turn on of the full Pressing pressure

Claims (2)

Patent claims: 1. A method for producing objects, in particular laminates, from pressable thermosetting materials, characterized in that the state of the thermosetting material dependent electrical impedance curve of the thermosetting material measured and then the pressing process is controlled so that about the beginning of gelling of the maximum pressure is given up. 2. The method according to claim 1 for producing laminates, characterized in that brought the stack to be pressed together with measuring electrodes between the plates of a press is that then the press plates are moved together so far that the heat transfer from These plates to the stack it is ensured that the plates and thus the stack are heated and at the same time the impedance is determined via the measuring electrodes that the point of the impedance curve it is determined at which the impedance value should rise after passing through a minimum begins, and that about this point the stack is subjected to the maximum pressure.