DD250934A1 - METHOD FOR PRODUCING A LONG-TERM PROCESSIBLE, HEAT-CERTAIN MASS - Google Patents

Abstract

The invention relates to a thermosettable mass based on cyanic esters and oxiranes, which is converted by thermal treatment in a crosslinked polymer with a high heat and moisture resistance and good electrical properties. The aim of producing a heat-treatable mass which is processable over the long term and free of additional hardening catalysts is achieved according to the invention by means of a two-stage process, in which case the cyanic acid ester is first precultured in a targeted manner and then mixed with the oxirane. The thermo-massable composition produced according to the invention is applicable, for example, as a laminating resin, potting compound or adhesive in microelectronics, electrical engineering / electronics, in building construction or in the automotive industry.

Description

Characteristic of the known technical solutions

It is known that can be produced by thermal curing of combinations of di- and polyfunctional cyanic esters and di- and polyfunctional oxiranes moisture and heat-resistant polymers with good electrical properties (DE-PS 1720663). According to this method, the oxiranes are mixed with the cyanic acid esters in an equivalent ratio of 0.5 to 2: 1 and reacted by heating to 50 to 200 ⁰ C with each other. Although it is possible to interrupt the reaction briefly, if it is necessary for the technological process of the application area. However, this means an extra effort. In addition, these systems, which is also set out in DD-WP 210405, are not very stable on storage owing to the effect of the oxirane groups catalyzing the reaction. Furthermore, combinations of polyfunctional oxiranes, optionally additionally monofunctional oxiranes, cyanic acid esters or their prepolymers and different catalysts, are specified for the preparation of thermally stable crosslinked polymers. Thus, these combinations contain typical cyclotrimerization catalysts such as zinc octoate (JP 76-39770, DE-OS 2442780) or quaternary ammonium salts (JP 85-26031), which are special curing catalysts. Due to the proportion of catalyst, these mixtures have a high reactivity. Thus, JP 80-43130 gelling times of a maximum of 50 minutes at 15O ⁰ C are given in the invention. Due to their high reactivity, however, these combinations can be stored for only a short time. Another disadvantage is that the ionic catalysts used here severely limit the possible uses of the thermally curable combinations as electrical insulating materials, especially when exposed to moisture. For applications in which a tack-free of the thermosetting mixture at room temperature is required and in which a flow (eg from the adhesive joint or the prepreg) is to be avoided, the combinations described must be so far hardened that they are difficult to melt and are very difficult to dissolve in common solvents such as acetone and methyl ethyl ketone, so that their processing is strongly adversely affected or is no longer possible.

Object of the invention

It is the object of the invention to provide a process which, on the basis of cyanic acid esters and oxiranes, leads, by long-term processing by thermal curing without additional curing catalysts, to polymers having a high moisture and temperature resistance and good electrical properties.

Explanation of the essence of the invention

The object is inventively achieved in that the thermosetting mass is prepared in two stages by in the first stage, a di- or polyfunctional cyanic acid ester is heated to 120 to 220 ⁰ C, preferably to 140 to 18O ⁰ C, until the Gel point is almost reached and the cyanate prepolymer formed in the second stage in the equivalent ratio of 1: 0.1 to 2.3 is mixed with a di- or polyfunctional oxirane.

The mixing takes place in a simple manner by jointly melting or dissolving the component in a common solvent.

Suitable solvents for blending are acetone> methyl ethyl ketone, N-methylpyrrolidone, and the like, with preference given to the more volatile because of their ease of removability.

The cyanate ester prepolymers usually have an OCN conversion of 45 to 48% shortly before reaching the gel point. The process can easily be interrupted after the first stage, since both the cyanate ester prepolymer thus obtained and the di- or polyfunctional oxiranes can be stored for a long time. The storage times are at least 18 months at room temperature.

Suitable di- or polyfunctional cyanic acid esters are, for example, 1,4-dicyanatobenzene, 1,3-dicyanatobenzene, 2,2-bis (4-cyanatophenyl) propane.

The di- or polyfunctional oxiranes are i.a. those compounds which are obtainable by reacting 2,2-bis (4-hydroxyphenyl (propane or low molecular weight novolaks with epichlorohydrin therein) are preferably di- or polyfunctional oxiranes having an epoxide equivalent of 170 to 210 g / equivalent.

The processing of the thermosetting mixture prepared according to the erfindungsg ermäßen two-stage process can be carried out according to the application - for example, as an adhesive, laminating resin, casting resin - according to different technologies. The required processing temperature is between 150 and 29O ⁰ C. The curing times are usually 10 to minutes.

The process according to the invention is characterized by easy reproducibility and a simple procedure. After thermal curing, it leads to polymers with good electrical properties and, surprisingly, to improved resistance to aggressive media, increased heat resistance and an increase in adhesive force.

embodiments example 1

1st stage ·

2,2-bis (4-cyanatophenyl) propane (diandicyanate, DDC) with a gel time of 20 hours at 160 ⁰ C is prepolymerized up to an OCN conversion of 45% at 16O ⁰ C (within about 18 hours) and cooled to room temperature. The pulverulent DDC prepolymer thus obtained has a shelf life of 18 months (at room temperature).

2nd stage

A 30% (in terms of solid resin) acetone solution of the prepolymer obtained in the 1st step and a 60% (in terms of solid resin) acetone solution of a bis-glycidyl ether of 2,2-bis (4-hydroxyphenyl) propane (DBGE), epoxide equivalent: 210) continuously added in a ratio of 2: 1 to a laminating resin pan, the metering speed corresponding to the laminating speed of the glass fabric. After removal of the solvent in the dry well (at 160 ⁰ C approx.

15 min), the resulting tack-free prepregs are stacked in eight layers and pressed with a 35 / xm Cu film at 18O ⁰ C and 10 MPa within 100 min. The properties of the laminate are summarized in Table 1.

Example 2

300 g of DDC prepolymer from the 1st stage of Example 1 are mixed with 700 g of novolak polyglycidyl ether (NPGE, epoxide equivalent: 189) and used as a melt to impregnate a glass fabric. The B-time of the mixture is 7min at 160 ⁰ C. After leaving the drying shaft (about 160 ⁰ C, 17 min), the tack-free prepregs are stacked in eight layers and pressed with 35 / xm Cu film for 50min at 2MPa and 18O ⁰ C. , The properties of the resulting laminates are summarized in Table 1.

Table 1

Properties of laminates (o.

-without complaints)

example 1 Example 2

Resin content (%)

Flammability after TGL

stress test

Mini surge test

Copper adhesion at 260 ° C (N / mm) Glass transition temperature (from TMA) (° C) Pressure cooker test

Acetone uptake after 2 h (%)

Durchkontaktierbarkeit

Breakdown voltage

after water treatment (kV)

dielectric loss factor

permittivity

39

if.

if.

if.

1.7

222

if.

0.1

if.

68

39

if.

if.

if.

200

3-7-10 " ³ (at 20-180 ⁰ C and 1 kHz) 4.3-4.4 (at 20-180 ⁰ C and 1 kHz)

Comparative Example 1

50 g of DDC and 50 g of DBGE (epoxide equivalent: 210) are reacted to the point where a B time of 5 to 10 minutes at 160 ⁰ C is reached. The reaction product obtained is only very difficult to dissolve in acetone (several days standing at room temperature, which already gel fractions are formed) and only with gelation melted, whereby further processing was no longer possible.

Examples 3 to 5

For the production of molding materials, diandicyanate prepolymer from the 1st stage of Example 1 is mixed in the stoichiometric ratios indicated in Table 2 by melting with dianbisglycidyl ether, poured into silicone rubber molds and cured until the maximum achievable glass transition temperature is reached. The shaped articles thus obtained and characterized by the glass transition temperature are stored for 14 days at room temperature in a 10% strength NaOH solution and the glass transition temperature is determined again. The results are summarized in Table 2.

For comparison DDC and Dianbisglycidether based on DDC (Comparative Examples 2 to 4) are prepared in such a way that DDC and DBGE mixed in the stoichiometric ratios shown in Table 2, melted and cast analogously to Examples 3 to 5 in silicone rubber molds and then be hardened. The characterization of the molding materials is carried out analogously to Examples 3 to 5.

Table 2

Composition, hardening and properties of the moldings

example

composition

DDC prepolymer according to Example 1% by mass

Comparative Example DDC

Wt .-%

23 51 86

DBGE

(Epoxidäquivalent210)

Wt .-%

Cure cycle glass transition temperature

(TMA)

before NaOH to NaOH

Storage ° C Storage ⁰ C

3 23 77 ? 15h, 150 ° C 176 175 4 51 49 [5h, 18O ⁰ C 214 216 5 86 14 J 5 h, 220 ^° C 242 243

DBGE

Epoxidäquivalent210

Wt .-%

77 49 14

15h, 120 15h ⁰ C, 15O ⁰ C 5h, 18O ⁰ C for 5 h, 220 ⁰ C.

171 ·

215

230

167 195 202

Example 6

The thermosetting material composition of Example 4 (Table 2) is used for bonding aluminum sheets by being applied as a melt on the aluminum sheets, these aluminum sheets are positioned by means of terminal block and stored for 2 hours at 180 ⁰ C in the oven.

Tensile shear strengths for the resulting composites are 15.4 ± 1.9MPa, while for composites made with a composition in the stoichiometric composition of Comparative Example 3 (Table 2) in an analogous manner only tensile shear strengths of 12.2 ± 1, 4MPa be obtained.

Analogous results are obtained if the bonding takes place within 10 min at 280 ⁰ C.

Claims (1)

A process for the preparation of a long-time workable, thermosetting mass based on cyanic acid esters and oxiranes, characterized in that the thermosetting mass is prepared in two stages, by in the first stage, a di- or polyfunctional cyanic acid ester at 120 to 220 ⁰ C, preferably is heated to 140 to 180 ° C until the gel point is almost reached and the cyanate prepolymer thus formed in the second stage in the equivalent ratio of 1: 0.1 to 2.3 is mixed with a di- or polyfunctional oxirane. Field of application of the invention The invention relates to a process for the preparation of a long-time workable, thermosetting mass based on cyanic acid esters and oxiranes, which leads by thermal curing to a crosslinked polymer with a high heat resistance and moisture resistance and good electrical properties and as a laminating resin, potting compound, coating, molding compound or adhesive can be used in microelectronics, electrical engineering / electronics, in device construction or the automotive industry.