DD233118A1 - METHOD FOR PRODUCING INJECTION MOLDING MEASURES - Google Patents

Abstract

The invention relates to injection molding compositions which can be processed at temperatures below 150C with injection pressures below 30 MPa. Such injection molding compositions consist of a preformed ceramic powder mixed with organic binders. Sedimentation phenomena should be avoided, however, the dimensional stability of the bodies should be high. According to the invention, the organic binder with surface-active compounds which are characterized by a polarity in both the hydrophobic and in the hydrophilic part of the molecule for multivalent adaptation and are cation surfactants and / or nonionic surfactants in which the hydrophobic molecular part of siloxanylalkyl, alkylphenyl, alkenyl Alkyl, cycloalkenyl and / or cycloalkyl radicals and the hydrophilic molecular moiety of oxyethylene and / or oxypropylene residues of 2 to 40 and / or -NR3 groups, mixed at temperatures up to 150C in the ratio of 10: 0.1 to 2.0 and Thereafter, the over a period of 1 to 3 h between 200 and 800C thermally pretreated ceramic powder with a specific surface area less than 20 m2 / g of the binder mixture at a temperature between 80 and 150C and a pressure of 5 Torr gradually added. The invention can be applied to ceramic powders in the broadest sense (oxides, nitrides, carbides).

Description

P 1099

IPK: C 04 B, 35/00

06/12/1984

Title of the invention

Process for the production of injection molding compounds

Field of application of the invention

The invention relates to the shaping of ceramic bodies, for example. For electrical engineering and electronics, for engine and mechanical engineering or for medical applications by the low-pressure transfer method, injection molding of a preformed ceramic powder in the mixture with organic binders at temperatures below 150 ⁰ C with injection pressures be processed below 30 MPa.

Characteristic of the known technical solutions

It is known to produce ceramic masses for complicated moldings by mixing organic plasticizers with fine ceramic powders. In addition to poly-

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meren substances such as polystyrene (DE 2 904 707) and polypropylene (DE 1 817 588) surfactants such. As stearic acid, added to palmitic acid. The use of plasticizers such as paraffin mixtures, naphthalene, camphor and waxes for the production of ceramic materials is also known. These ceramic materials are processed at high temperatures (above 150 ⁰ C) and with large injection pressures (above 30 MPa) and require a high expenditure on equipment. The injection molding compositions produced using hard paraffin as plasticizer and surfactants in the form of saturated and unsaturated carboxylic acids are relatively thin with minimal binder proportions (DD 139 397) Thus, although complicated ceramic moldings can be produced by the Nlederdruckwarmspritzverfahrens, but the ceramic moldings after the thermal treatment for Exhaustion of organic substances due to the theological properties of the mass often deformations. In addition, such spraying the Nach-, part, that occur during processing segregation phenomena that have a negative effect on the injection molding properties and the dimensional stability of the ceramic moldings.

Object of the invention

The aim of the invention is to produce injection molding compounds for the low-pressure hot-spraying process, which show no disturbing sedimentation during processing and the required expulsion of the organic components have a high dimensional stability, so that a special embedding of the ceramic molded body is unnecessary in this operation.

Explanation of the essence of the invention

The invention is therefore based on the object of providing a process for the production of injection molding compounds from a preformed ceramic powder in the mixture with organic binder.

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which have a yield value * l and which behave like solid bodies in the range of shear stresses smaller than tT, but exhibit pseudoplastic flow behavior in the region of greater t . According to the solution of this problem as set out in the invention claim.

The preparation of the injection molding material is carried out in special aggregates by physical-chemical reactions of the surface-active compounds with targeted elimination of the adulteration negatively influencing parameters. The ratio of the amounts of said compounds to binder depends on both the specific surface area of the powders and the compound used. The ratio is 0.1 to 2.0: 10. The powder is introduced stepwise into the present binder mixture in order to maintain constant flow properties throughout the treatment process. In the liquid phase is carried out at a temperature of 80 ° to 150 ⁰ C, the adsorption of multivalent to the powder and the binder adapted surface active compounds via a polar group, both in the hydrophobic, as well as in the hydrophilic moiety and / or a reactive group in Molecule of the compound used.

In this way, an extensive automated production of ceramic moldings of different geometry can be performed.

embodiment

By some examples, the invention will be explained in more detail:

Example 1

Starting material for the production of the injection molding material is sintered material of a 96% AIpO ^ -Versatzes, the

was dry-ground to a specific surface ^ 2.5 m ² / g and annealed at 450 ⁰ C _ + 5 ⁰ C. In a mixing unit at a temperature of 110 ⁰ C and under vacuum (^ 5 Torr), the powder is mixed in three steps after every 2 h with the binder mixture (15.75 parts by weight per 100 parts by weight of powder) and homogenized , The binder mixture is previously prepared in the treatment unit by 14.0 parts by weight of paraffin and 1.75 parts by weight of tris (trimethylsilylpropyl) -ammonium acetate are mixed at the processing temperature (110 ⁰ C). The total duration of the mixing process is 6 h. The solidified spray mass is melted before the Pormgebungsprozeß, degassed at - 5 Torr and processed with a spray pressure = 60OkPa in a pneumatic spraying machine to basic bodies of dimension 60 χ 15 x 3.0 for microelectronic devices.

The expelling of the binder takes place in a continuous ventilated unit with a max. Temperature of 300 ⁰ C for a total throughput time of 4 to 6 h. The handling-resistant articles are fed to the sintering process.

Example 2

Starting material for the production of the injection molding compound is a single-phase Alp0 ~ powder with a specific surface area of 15 m ² / g _ + 0.5 m ² / g. After annealing the powder at 400 ° C and -2. h- the injection molding compound is processed in a mixing unit at a temperature of 110 ⁰ C in a vacuum (- 5 Torr). The powder mixture is mixed in three steps, each after 2 hours, with the binder mixture (20 parts by weight per 100 parts by weight of powder) and homogenized. The binder mixture is prepared beforehand in the processing unit by mixing 17 parts by weight of paraffin, 2.0 parts by weight of dodecanol polyglycol ether and 1.0 part by weight of siloxanyl polyglycol ether at the processing temperature. The total duration of the mixing process is S h. The solidified injection molding compound is melted before the forming process at ^ 5 Torr degassed and with an injection pressure = 6O0kPa to articles of wear ceramic (needle guide and

Crucible of dimensions 20 χ 15 with a wall thickness of 0.5 mm) and processed into articles of bioceramics (anchor implants of dimensions 22 χ 17 χ 3). The process of expelling the binder takes place in discontinuous, ventilated aggregates with a max. Temperature of 300 ⁰ C in a total cycle time of 12h. The articles are embedded in absorbent powders, preferably finely dispersed Al 2 O 3, powder. The handling-resistant articles are fed to the sintering process.

Example 3

For the preparation of the injection molding compound of an offset consisting of Al ₂ O ₃ (94% by weight, SiO ₃ , CaO and MgO, single-phase oxides and mixed oxides are the starting materials.) The specific surface area is 4.5 m ² / g +, 0.5 mVg . The. powder is heated at 400 ⁰ C for 2 h annealed. In a mixing unit, a binder mixture consisting of 90 parts by weight of paraffin wax and 10 parts by weight of alkylphenol polyglycol ether (alkyl chain of 6 to 12, 2 to 20 ethoxy groups), at a temperature of 90 ⁰ C prepared. after mixing and homogenization of the single-phase oxide (AIPO.,) with the binder mixture, after 3 hours, the addition of the mixed oxides. the total addition of the binder mixture is 13 parts by weight per 100 parts by weight of powder The total duration of the mixing process is a maximum of 6 hours.

The solidified injection molding composition, prior to the molding process molten at £ 5 Torr degassed and processed with an injection pressure = 1.2 MPa to caps of the dimensions 50 χ 25 x 10 with a wall thickness of 2 mm and structural pedestals measuring 40 χ 35 x 15 °. The expulsion of the binder is carried out in a continuous unit with a max. Tempei- of 300 ⁰ C at a total cycle time of 6 h = ature. The handling-resistant articles are fed to the sintering process.

In principle, the invention for all ceramic powders in the broadest sense, esp. But for oxides, carbides and nitrides, are applied.

Claims (1)

- 6 - P 1099 invention claim A process for the production of injection molding compounds from a preformed ceramic powder mixed with organic binders, characterized in that first the organic binder with surface-active compounds which are characterized by a polarity in both the hydrophobic and in the hydrophilic moiety for multivalent fitting and cation surfactants and / or nonionic Represent surfactants in which the hydrophobic moiety consists of siloxanylalkyl, alkylphenyl, alkenyl-alkyl, cycloalkenyl and / or cycloalkyl radicals and the hydrophilic moiety of qxyethylene and / or oxypropylene radicals has from 2 to 40 and / or -NR-3 groups, is mixed at temperatures up to 150 ⁰ C in the ratio of 10: 0.1 to 2.0 and then over a period of 1 to 3 h between 200 and 800 ⁰ C thermally pretreated ceramic powder having a specific surface area less than 20 m ² / g the binder mixture at a temperature between 80 and 150 ⁰ C and a Pressure - 5 torr mixed gradually.