CS240489B1 - Cold-insulated electro-insulating laminate - Google Patents

Abstract

The invention relates to the problem of electrotechnical laminated materials, especially hardened papers. The problem of producing hardened papers with a surface compatible with applied resistive layers and with sufficient flexibility of the plates even at thicknesses below 1 mm is solved. The principle of the invention is that the reinforcement is impregnated with a drying oil-modified phenolic resin, the phenolic base of the resin being a mixture of phenols and alkyl-substituted phenols. To increase the flexibility of the reinforcement, it is covered on both sides with another impregnated or non-impregnated organic or inorganic fabric. The invention can be used for the production of lacquer-based resistor plates and strips for potentiometers, as well as for the production of printed circuit boards.

Description

240489

BACKGROUND OF THE INVENTION The present invention relates to a composition of laminated insulating materials suitable for use in the electrical industry. These insulators are based on organic or inorganic reinforcements, especially cold-shearable papers, with a surface resilient to the applied resistive layer.

Electroinsulating hardened papers produced by pressing and curing the laminated, thermally reactive bituminous impregnated papers are subject to the requirements of the invention. Complexity and specificity. applications of individual types of materials, as well as economic reasons, exclude the possibility of producing universal layered insulations in.

Paper is required for the manufacture of lauter resistance resistances for layered potentiometers, characterized by low water absorption, good shear and cold good insulating properties and some special properties which are critical in practical use.

One of such properties is to produce a perfectly smooth surface of pressed hardened paper (max. 0.2 roughness), resistant to the action of organic solvents such as trichlorethylene and ethyl acetate, but with some, its breakage even after prior heat treatment. needed to anchor a water-based lacquer. Important for the formation of such a surface, that the impregnant used after curing exhibits adhesion to the resist layer, i.e., the lacquer-based paste based on phenolic or epoxy resin filled with conductive and non-conductive pigments, the surface interference being related to the extractable fraction in acetone.

The unmodified phenolic or epoxide resins commonly used for the production of hardened paper do not allow the above-mentioned special properties to be achieved after hardening. The current state of comparable products is characterized by inadequate, respectively. fluctuating values of decisive processing properties due to the aceto extract, surface adhesion to the abrasive layers as well as the manufacturing difficulties caused by the thinness of the thin plates to 0.7 mm.

The drawbacks of the prior art are the fact that the layered insulator is formed from an inorganic or organic reinforcement, preferably a cotton or alpha-cellulosic paper, impregnated with a proportion of 30-60% by weight of a phenolic resin binder modified with alkyl substituted phenols. a ratio of 0.1 to 1 mole: 1 mole of phenol-modified resin and containing 2 to 20% by weight of a drying oil, preferably wood, partially incorporated into the resin structure, prior to impregnation being treated to a workable consistency by adding a solvent which may be toluene, xylene, acetone, methyl ethyl ketone, preferably methanol, ethanol or mixtures thereof Naim-coated papers after drying at 130-180 cc and laminated to the desired ridge and compressed to a laminate at a curing temperature of 130-170 ° C and pressure of 3 to 10 MPa. The laminate obtained has a smooth glossy finish the top resistant to organic solvents, but due to the limited proportion of acetone extractable ingredients, with the surface resistive to the applied resist layer. The material is cold-shearable and has a high resilience, which is particularly advantageous in the manufacture of 1 mm laminated sheet. The material is coated with a cotton, glass, polyamide or polyester fabric.

The following examples demonstrate the preparation of a laminated electro-insulating material, with no particular requirements for use: In Example 1, a low absorbency laminate is shown, the paper reinforcement of which is pre-impregnated with phenolalcohols or methylolfenols. Example 1 Bituminous solutions prepared in Examples 1 to 3 in MS. No. 240,490 is impregnated with cotton or cellulosic paper which has been treated with aqueous solution of methylolfenols butomethylolmelamines to 15-25% by weight in a prior art operation so that the total resin content, calculated on the net paper weight, is about 50% ( 100 to 110% deposition). The rate of flow rate and temperature in the drying tunnel are adjusted to impregnate 100 x 100 mm at 160 ° C and 1.5 MPa for 5 minutes when the test plate is pressed from the five sheets, for 5 minutes. up to 8% by weight.

The paper reinforcement for surface, so-called cover sheets is impregnated in a similar manner, but using a bituminous binder of the examples 1 to 3 above with the addition of 0.15% by weight of montan wax.

The sheets of impregnated paper, stitched to the required size, are stacked differently, covered with a cover sheet from both sides, and the prepared bales are placed between the stainless steel sheets in a hydraulic tray press where they cure at 150 ° C and a pressure of 6, 5 MPa over 50 to 90 minutes per ridge. After cooling at a temperature of 30 ° C, hardened papers are obtained with the following properties.

Thickness (mm) 1.0

Absorption: after 24 h in water (mg) 24.0 after 96 h in water (mg) 45.0

Shear at 23 ° C according to ČSN 640 891 (grade) 6.0 240489

Acetone extract according to ČSN 640 234 (%) 1,8

Flexural strength (MPa) 100.0

Insulation resistance, in supply condition (ohm) 1012 for 24 h in water (ohm) 1011

Dimensional stability (%) - after 100 ° C, 4 days - 0.03 - after 100 ° C, 10 days. —0.05 - after air conditioning 40 ° C and 95% rh 4 days --j-0.3 - after air conditioning 40 ° C and 95% rh 10 days 4-0.5 where the layered reinforcement is clad in one or both sides. The material is suitable for printed circuit boards where the etched surface of the dock is required to be adhered to the gypsum paste. EXAMPLE 2 Bituminous solutions prepared according to Example 1 or 2 of the above MS. AO is mixed with an aqueous solution of methylolefin or methylolmelamines having an average molecular weight of 150 to 300 so that about 1000 g of an approximately 50% solution of the oil-modified resin is a proportion of 250 g of an approximately 40% solution of methyl phenol or methylol melamine. The reinforcing material is impregnated with the bituminous mixture obtained without pretreatment. Next, papers impregnated with a binder content of 50% by weight are extruded together with the copper foil at 150 ° C, 6 MPa for 90 minutes. The coated material obtained has a temperature resistance to bonding at 260 DEG C. for 15 to 20 seconds. In Examples 3 and 4, there are provided combinations of impregnated reinforcement with one or more layers of cotton, glass, a polyester or polyamide fabric which can be impregnated with a resinous composition or not impregnated. Laminates with higher elasticity and mechanical strength are obtained and hence the prior art difficulty in breaking thin slabs up to 1 mm when removing pressed bales is removed. Example 3

It is particularly advantageous when pressing the crest plates of less than 1 millimeter, if the primed papers are as described in Example 1 and FIG. 2 are combined with a non-impregnated layered corrugated, glass, polyester or polyamide fabric having a basis weight of 20 to 60 g / m 2 in the following order of layering: a) 1 layer of the cover sheet prepared by the example of Example 1 with the addition of montanose; b) 1 to 3 layers of paper of Example 1 , respectively. 2, c) 1 layer of non-impregnated fabric, which dimensions can exceed the dimensions of the other layers by 10 to 20 mm, d) 1 to 3 layers of paper according to Example 1, respectively. 2, e) 1 layer of the cover sheet of Example 1.

The laminate is cured in a known manner, penetrating the resin of the impregnated paper into a non-impregnated fabric. The composition thus created is the object of the invented solution. The laminates obtained have similar properties to the hardened paper of Example 1, which exceeds the mechanical strength values, which is particularly advantageous in that it does not break thin slabs when taking pressed bales. Attaches

Glass or cotton fabric weighing 50 to 150 g / m 2 is impregnated with heat prepared according to Examples 1 to 3 of the above MS. AO so that, after drying in the drying tunnel of the impregnating machine, the prepreg with a resin content of about 40% is obtained.

The cotton, alphacellular or sulfate paper is impregnated as described in Examples 1 or 2. The method of folding the layers before molding the laminate is as follows: a) 1 layer of a cover sheet according to Example 1 or a separation sheet; b) 1 to 2 layers of paper of Example 1 and 2, respectively; 2, c) 1 layer of impregnated fabric according to Example 4, d) 1 to 2 layers of paper of Example 1 and 2, respectively; 2, e) 1 layer of the cover sheet according to example 1 or a separation sheet.

The combination of points b) to d) may be repeated several times over the desired laminate ridge.

After pressing at a temperature of 155 ° C and a pressure of 5 MPa, a composite composite laminate with a higher mechanical strength is obtained compared to hardened papers. It is an object of the present invention to provide a cold-cured material with high adhesion to the applied resistive layers and with sufficient elasticity even at the depths below 1 mm, which is used for the manufacture of potentiometer cartridges and printed circuit boards.

Claims (2)

CLAIMS 1. Electro-insulating, cold-shearing composite material, also suitable for clad with a metal foil having a surface resistant to the resistive layer and limited in resistance to organic solvents, characterized in that it consists of an organic or inorganic reinforcement, preferably of cotton or alfacelulose up to 60% by weight of phenolic resin modified with alkylsubstituted phenols in an amount of 0.1 to 1 mol per 1 mol of phenol modified resin containing 2 to 20% by weight of a drying oil, preferably wood, partially incorporated into the resin structure. 2. The electro-insulating layered material of claim 1, characterized in that it is coated with a cotton, glass, polyamide or polyester impregnated or non-impregnated fabric.