DD218376A1 - METHOD FOR PRODUCING STORAGE STILTS, HOT-HOLDING EPOXY RESIN COMPOSITIONS - Google Patents

Abstract

The purpose of the invention is the production of an epoxy resin molding compound for wrapping electrotechnical and electronic components, which is stable in storage as powder or granules and is flowable on heating, can deform and aushaertet at elevated temperature to form a thermoset. The preparation is carried out by homogenization of powder mixtures of epoxy resins, novolak halides, accelerators and optionally further additives at elevated temperatures, wherein in the molding compound, an accelerator is incorporated, which has a softening point, either pure or as a blend with novolak, between the homogenization and the processing temperature of Epoxy molding compound is such that it is retained during the homogenization of the epoxy molding compound in particle form.

Description

YSB Leuna-Werke Leuna,

"Walter Ulbricht"

LP 8311

Title of the invention

Process for the preparation of storage-stable, thermosetting Epoxidharzformmassen

Field of application of the invention

Epoxy resin molding compounds are increasingly being used to encase electrotechnical and electronic components in order to protect them from environmental influences and to ensure their puncture resistance under extreme stress.

Epoxy resin molding compounds are pulverulent or granulated substances which become fluid when heated and can be easily deformed by pressing or spraying before they thermoset-harden. The final curing is achieved by heating for several hours at elevated temperature. ·:

'inw i ⁰ '" ¹ ° · *. ' ^y \\) Ss'->'

  , : ·. '- 2 - ·' 'characteristic of the known technical solutions

Epoxy molding compositions are known and consist of an epoxy resin-containing binder ¹ , fillers, pigments, lubricants, flame retardants and optionally other additives.

The binder comprises, in addition to epoxy resin, a curing agent which, in the presence of accelerators, causes the thermoset curing. As epoxy resins are preferably solid, semi-liquid and liquid Produkte.wie glycidyl ether of bisphenol !, phenolic or cresol novolacs, polyphenols and cycloaliphatic compounds use. Particularly suitable curing components are novolaks which have been prepared by acid condensation of phenol or cresols and formaldehyde and are present in a particularly pure form with a low content of volatile substances due to the selection of the preparation conditions.

The processing properties of the epoxy molding compounds are largely determined by the reactivity of the binder system. Since epoxy resins are thermosetting with ITovolaks relatively slowly, the addition of low accelerator quantities necessitates the adjustment of the curing rate. Nitrogen compounds, such as amines, have proven particularly suitable. _ Imidazoles and ammonium salts, further phosphines, arsines and their derivatives, boron trifluoride complexes, inter alia,

The main component of the epoxy molding compounds form fillers in proportions of 50 to 80% such as silica, alumina, glass fibers, titanium dioxide u. a., Which by intensive mixing with the binder system and subsequent homogenization by extrusion,: kneading or rolling give a usable Epoxidharzformmässe.

The most essential processing properties of the epoxy molding compound are determined by the Bp Oxide Hardener Accelerator binder. Due to its composition, it provides a reactive mixture is to be taken by the "feature to leave the one hand, under the processing conditions (eg. B. molding at 150 to 180 ⁰ G) within a few minutes deform and thermoset cure on the other hand without changing these properties as long as possible to be stored at room temperature.

In the interest of a uniform quality of the epoxy molding compound are simple powder mixtures of all components, as described in GB-A 869 459 and DE-AS 1 151 934, for most applications, especially those of electronics, not usable,.

Uniform epoxy resin molding compounds are prepared from powder masterbatches by homogenization by means of an extruder, kneader or rolling mill. This process involves thermal and mechanical stress on the epoxy molding compound, with the reactive binder in danger of causing uncontrolled curing operations and making the epoxy molding compound difficult or unworkable. * ''

The use of accelerators which become effective during the processing of the epoxy resin molding material, that is to say by thermal influence, by means of chemical modification, is described in a large number of inventions. So z. In DE-OS 2 247 512 quaternary phosphonium salts, DE-AS 2 416 4O8 tetraphenylborates of imidazole, DE-OS 2 300 489 heavy metal imidazolates, DE-OS 2 019 816 acetylacetone metal complexes and boron trifluoride complex in the DE -OS 1 495 259 proposed as a latent-acting accelerator. '

Adducts of imidazole and its. Derivatives ζ. B. with isocyanuric acid (DE-OS 2,811,764), acid anhydrides (DE-OS 2 418 754), monoglycidyl compounds (DE-AS 1 910 758) are also called as accelerators ·

Lifting imidazole-based accelerators are other basic nitrogen compounds such as alkylamidinopyridines (DE-OS 1 808 670), half-esters of polycarboxylic acids and tertiary aminoalcohols (DE-OS 2 716 593), amides of dicarboxylic acid anhydrides and melamine or triazine (DE-AS 1 645 206).

All of these systems have the disadvantage that they are added to the sputtered resin premix and selected. Homogenization already initiate the hardening process. As a result, inconsistent Spoxidharzformmassen arise with deviating plunger-hardening behavior. '' ·· ''.

• '*

This fact was countered by the fact that epoxy molding compounds were homogenized with reduced accelerator content at the lowest possible temperature and subjected to subsequent maturation (DE-AS

1 061 067) or very short homogenization times for. Were applied (US Patent No. 3,063,965).

By mixing prereacted products with resin or hardener excess in a 2-component system (DE-OS

2 228 583) or multiple interrupted pre-reaction until shortly before the B-state (DE-AS 1 545 191) or use of anreagierten epoxy resin (DS-OS 2 235 440) should also be storable ¹ Epoxidharzformmassen produced.

By use of pre-reaction products of the accelerator with the epoxy resin (DE-AS 1 645 193 and DE-OS 2 230 653) storable epoxy molding compounds

· 3Ί ~ \ Ί U

be produced. ·

It has been described several times to add the accelerator in the form of a homogeneous hardener-accelerator mixture prior to homogenization in the case of novolak-cured spatter resin molding compositions (US Pat. No. 3,838,094, DE-OS No. 1 645 556 and German Pat. No. 225,485). By the accelerator can thus come into effect only in an attenuated concentration, the molding material is better storable.

All these methods are associated with disadvantages that affect the processing properties of Epoixidharzformmasse, their uniform structure and the technical implementation of the production process.

• \

Object of the invention

With the present invention, the aim is to produce a storable Epozidharzformmasse in a technologically simple manner, which contains all the necessary ingredients and is suitable for coating microelectronic devices.

Presentation of 7 / esens the invention

The invention solves the problem of producing a reactive, EpoXidharzformmasse that changes only slightly after the manufacturing process to processing by the user their processing properties as a function of storage time and storage temperature.

This object is achieved by a process for the production of epoxy molding compounds by homogenization of powder mixtures of epoxy resin, lovolak hardening, accelerating

ι υ η fs

niger and optionally further additives at elevated temperatures according to the invention achieved in that an accelerator is incorporated in the molding compound, which has a softening 'pure or mixed with iJovolakhärter, which is between the homogenization temperature in the manufacturing process and the processing temperature, so that whose original particle shape is maintained during homogenization. If accelerators, by their chemical nature, do not possess this property, they can find use as a homogeneous mixture with a softening or hardening component suitable for the softening point. Particularly suitable are high-melting mixture components to increase the softening point, since usually a very good miscibility with the loading. faster exists. In addition to the effect of the high softening point, mixtures of a reduced local accelerator concentration also become effective.

The term "homogenization" was retained as a common technical term, although the goal is to obtain the accelerator particulate.

The temperatures of the homogenization of epoxy resin molding powder premixes, which already contain all components in heterogeneous form _? As a function of the Yiscosity properties of the epoxy resins and hardeners used are usually in the temperature range from 333 K to 403 K. If the accelerator or its mixture are retained as particles in the epoxy molding compound, its softening point must be well above that of resin and hardener or over Furthermore, the homogenization process is to be carried out so that melting of the particles is avoided by the operation of the homogenization unit. Estru- ders, kneaders and rolling mills proved to be suitable apparatuses. "

η λ vinii -1Π

The accelerator is added in powder form to the epoxy resin masterbatch powder masterbatch in an amount that meets the processing requirements and the eposid. resin molding material gives the necessary flow-curing behavior during the transfer molding process. The binder is usually made of pulverformigem epoxy resin and hardener or resin / hardener Gernischen. In the epoxy molding compound powder masterbatch, the binder components are present in heterogeneous form with fillers, lubricants, pigments, flame retardants and adhesion promoters. Liquid epoxy resins can find direct application if they are used to prepare all the powdered ingredients into a heterogeneous free-flowing agglomerate instead of the epoxy molding compound powder masterbatch.

In all these cases, it has been found that sputtered resin molding compositions whose accelerator has a softening point which is above the homogenization temperature and below the processing temperature have a good shelf life, because at optimum. Homogenization of the accelerator in the epoxy molding compound in particle form is largely retained and only fully distributed under the processing conditions in the mass and thus -effective.

Due to their nearly constant flow-hardening behavior, epoxy resin molding compositions prepared in this way can be processed even after prolonged storage, under uniform transfer molding conditions, the EMMI splitting length decrease is only slight, and the thermal, mechanical and electrical properties of the compacts remain constant.

ÄusfUhrungsbeispiele

example 1

In 3 experiments, spozid resin molding powder-powder mixtures were prepared which contained accelerators of the same composition with different softening points. -

Composition:

, 30 g accelerator of various softening points (imidazole / tetrahydrophthalic anhydride / Krosolnovolak, 50%) -

570 g mixture of 2 parts by weight of liquid phenol-1O-volak-epoxy resin and 1 part by weight of phenol-liovolak hardener, softening point 337 K 1346 g of fused silica 20 g of stearic acid

4 g of carbon black r30 g of antimony trioxide

The components were mixed in a 2.5 liter planetary mixer and at 352 K with an average residence time of 1.5. Homogenized in a twin-screw extruder of the type Brabender DSE 35 / 7D. ,.

The extruded epoxy molding compound was rapidly cooled to room temperature and stored at 298K. The EMMI flow length was tested at 449 K with the following results:

verse , 1 verse , 2 Verse. 3. Benefit point 363 K 381 K 403 K Flow length (EMU) 43 inch 39 inch 38 Inch·' läartenstemperatur 424 K 428 κ 428 K flexural strength 167 MPa 170 MPa 174 IIPA

18 % 13 ct / 0  5 41 % 21 % 9 58 fo 32 fo 16 67 % 42 % 25

Shelf life in % Drop in spiral flow length after

7 days / 298 K

14 days / 298 K

21 days / 298 K

28 days / 298 K

Sa is to recognize that the Spoxidharzformmassen in Ab-

Depending on the softening point of the accelerator have different storage capabilities, the thermal and mechanical properties remain unchanged.

_fl

Example 2

Sine Eposid resin molding powder powder mixture of composition:

1.2 g accelerator corresponds to example 1, softening point

400 K 15.5 g cresol-Hovolak epoxide resin, softening point 353 K

7.3 g Phenol Hovolak hardener, softening point 370 K 54.0 g fused silica flour

0.7 g of stearic acid

0.05 g of benzoic acid

0.16 g of carbon black

1.2. g antimony trioxide

was kneaded in an internal mixer with 50 ml void volume for 2 minutes, at a melt temperature of 355 K and then cooled to room temperature. The test was carried out as in Example 1.

38 inch 440 K, 162 MPa 4 % 9 % 13 % 21 - %

Flow length (EMMI) Martens temperature flexural strength

Shelf life in % Loss of flow length after

7 days / 298 K

H days / 2 98 K

21 days / 298 K

28 days / 2 98 IC -

Example 3 ·. , <

An epoxy resin forramasaen powder yorin blend of composition:

120 g benzimidazole / cresol novolak spreader mixture, 7.5 / öig, softening point 398 K

1,600 g of a mixture of 2 parts by weight of liquid phenol-o-voiak spoxide resin and 1 part by weight of phenol-1-octanolamine.

Hardener, calibration point 337 K 3700 g- fumed silica 50 g stearic acid 20 g carbon black 100 g antimony triozide

was mixed in a mixer and homogenized at a roll temperature of 358 K with a mean residence time of 3 minutes, cooled to room temperature and tested.

Flow length (EMII),. 49 inches. 'Marten temperature 428 K

Flexural strength 167 MPa

Shelf life in% Waste of plunger length after,

7 days / 298 K 2.5 %

14 days / 298 K 10.0 % 21 days / 29S K 13.5%

Claims (6)

- 12 claim for invention 1. A process for the preparation of storage-stable, thermosetting Epoxidharzformmassen by homogenization of 'powder mixtures of epoxy resins, Bovolakhärtern, Be. accelerated and optionally further additives at elevated temperatures, characterized in that in the molding material, an accelerator is incorporated, which has a pure or as blending with novolak a Verwei-chungspunkt between the homogenization • and the processing temperature of the epoxy molding compound, so that this obtained in the homogenization of Epos id resin molding compound in particle form. 2. The method according to item 1, characterized in that the homogenization takes place by Estruder, kneader or rolling mill. · 3. The method according to item 1 to 2, characterized in that as we.itere additives fillers, lubricants, flame retardants, pigments, adhesion promoters are used. 4. The method according to item T to 3, characterized in that are used as / epoxy resins solid or liquid JTovolakeposidharze. · - '. " 5. The method according to item 1 to 4, characterized in that solid mixtures of liquid or semi-solid sposid resin and JFovolakhärter be used. 6. The method according to item 1 to 5, characterized in that using powdered epoxy resin all powdered constituents of the epoxy molding compound before homogenization ver to a free-flowing agglomerate . be agreed. - '. ,