DD233117A1 - 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 is first of all compounded with compounds of the general formula RX in which R is alkyl, alkylphenyl, alkenyl, cycloalkenyl, siloxanylalkyl, siloxanylalkenyl and / or aryl radicals and X reactive groups, such as -COCl 2, -SO 2 Cl, -POCl 2 and Me3SiY3-n, where n1 and 2 may be and the Y halides, such as chlorine and bromine and / or alkoxy groups, at temperatures up to 150C and in amounts that can reach a monomolecular coverage, in particular in the ratio (binder to the Compounds of 10: 0.1 to 2.0 are mixed and thereafter, over a period of 1 to 3 hours between 200 and 800C thermally pretreated ceramic powder having a specific surface area less than 10 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 1098

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 compositions is also known. These ceramic materials are processed at high temperatures (above 150 ⁰ C) and with large injection pressures (above 30 AiPa) and require a high expenditure on equipment. The injection molding compositions produced using hard paraffin as a plasticizer and surfactants in the form of saturated and unsaturated carboxylic acids are relatively thin with minimal binder contents (DD 139 397) Thus, although complicated ceramic moldings can be produced by the low-pressure hot-spraying method, however, the ceramic moldings after the thermal treatment Exhaustion of organic substances due to the theological properties of the mass often deformations. In addition, such sprays have the disadvantage that segregation phenomena occur during processing, which have a negative effect on the injection molding properties and dimensional accuracy 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 Sedimentationserscheinungen in 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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developing means having a yield point X, and which behave in the range of shear stresses smaller C as solid bodies, but show greater in the region * { "pseudoplastic flow behavior. According to the invention the solution of this problem as set forth in the invention of claim.

It may be advantageous if, as stated in point 2 of the claim, mixtures of binders with reactive and those with adsorption effect are used. The pretreatment of the ceramic powders initiates chemical reactions of the compounds used with the powder surface and the organic binder, which lead to a targeted concentration of OH groups on the powder surface and thus to the desired properties of the injection molding compound. The ratio of organic binder to the compounds used depends on both the specific surface area of the powders and the type of compound used. In order to ensure consistent properties during the entire treatment process, the powder is introduced stepwise into the treated binder mixture, and mixtures of the compounds mentioned with compounds which exhibit adsorption effects have synergistic effects on the plasticizing behavior, the shaping process and the baking behavior capable of processing ceramic powders with specific surface areas of 10 mVg with the same amount of surfactants in connection with hard paraffin, guaranteeing as far as possible an automatic production of molded ceramic parts of different geometries.

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% AlpOo offset , which was prepared by dry grinding to a specific surface ^ 2.5 mVg and heated at 200 ⁰ G + 5 ⁰ C 2 h. 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 (14.25 parts by weight per 100 parts by weight of powder) and homogenized. The binder mixture is previously prepared in the treatment unit, in which at a temperature of 110 ⁰ C 12.5 parts by weight of paraffin and 1.75 parts by weight

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Tetrasaurechlorid be mixed. The said compound causes a covalent bond between Al-O-CO with elimination of HCl. After the addition of the last portion of the powder, 0.5 part by weight of triethylamine is added to neutralize the resulting reaction products. The total duration of the mixing process is max. 6 h. The solidified spray mass is melted before the forming process, degassed at - 5 Torr and processed at an injection pressure = 60 kPa in automatic operation to basic bodies of dimension 70 χ 20 χ 2.5 for microelectronic circuits.

The expulsion of the binder takes place in a continuous, ventilated aggregate with a meax. Temperature of 300 ⁰ C for a total throughput time of 4 to 6 h. The manageable articles are fed to the sintering process.

Example 2

Starting materials for the production of the injection molding compound are in addition to the single-phase oxide Al ₂ O.-, still 6 % of mixed oxides, \ ile SiOp, CaO, MgO and Cr ₂ Oo with a specific surface area? * 8 mVg. The material is annealed at 200 ⁰ C for 2 h and prepared in a mixing unit at a temperature of 110 ⁰ C in a vacuum (* 5 Torr). The powder mixture is mixed with the binder in three steps after every 2 hours.

mixed (18.2 parts by weight per 100 parts by weight of powder) and homogenized. The binder mixture is previously prepared in the treatment unit by mixing at the processing temperature 16 parts by weight paraffin and 2.2 parts by weight Oktadecylphosphonsäuredichlorid. The said compound causes a covalent bond between Al-O-PO with elimination of HCl. After the addition of the last portion of the powder, 1.1 parts by weight of triethylamine is added to neutralize the resulting reaction products. The total duration of the mixing process is max. 6 h. The solidified Spritzgießmasse is melted before the molding process, degassed at ^ 5 torr and processed with an injection pressure = 600 kPa in a pneumatic spraying machine to support bodies for hybrid housing. The expulsion of the binder mixture takes place in a continuous, ventilated unit with a max. Temperature of 300 ⁰ C with a total cycle time of -8h. The handling-resistant articles are fed to the sintering process

Example 3

Starting material for the production of the injection molding compound is the single-phase oxide AlpOq with a specific surface ^ 6 mVg. The material is annealed at 200 ⁰ C _ + 5 ⁰ C and processed in a mixing unit at a temperature of 110 ⁰ C in a vacuum ^ 5 Torr. The powder is mixed in three steps after every 2 hours with the binder mixture (16.5 parts by weight per 100 parts by weight of powder) and homogenized. The binder mixture is previously prepared in the processing unit by mixing 15 parts by weight of paraffin and 1.5 parts by weight of octadecylmethyl 2-thoxysilane at the processing temperature. The compound used causes a covalent bond between Al-O-Si with elimination of ethanol. The total duration of the mixing process is max. 6 h. The solidified spray mass is melted before the shaping process at - 5 Torr degassed and processed with a spray pressure = 60OkPa in a pneumatic injection molding machine to human implants of maxillofacial surgery. The expulsion of the binder mixture takes place in a discontinuous,

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ventilated unit with a max. Temperature of 300 ^° C. for a total throughput time = 12 h. The handling-resistant articles are fed to the sintering process

Other possible applications arise in principle for all ceramic powders, in particular. Oxides, nitrides and carbides.

Claims (2)

-V- r ί uyo invention claim 1. A process for the preparation of injection molding compounds a preformed ceramic powder in the mixture with organic binders, characterized in that first the organic binder with compounds of the general formula RX in which R is alkyl, alkylphenyl, alkenyl, cycloalkenyl, siloxanylalkyl, siloxanylalkenyl and / or aryl radicals and X reactive groups, such as -COCl ₂ , -SOpCl, -POCl ₂ and -Me-, SiY_, in which η = 1 and 2 and the Y halides, such as chlorine and bromine and / or alkoxy represent, at temperatures up to 150 ⁰ C. and in amounts that can reach a monomolecular coverage, esp. In the ratio (binder to said compounds) of 10: 0.1 to 2.0 is mixed and then over a period of 1 to 3 h between 200 and 800 ^0th C thermally pretreated ceramic powder having a specific surface area less than 10 m ^a / g of the binder mixture at a temperature between 80 and 150 ⁰ C and a pressure - 5 torr is gradually added. 2. The method according to item 1, characterized in that the binder mixture nor surface-active compounds are added, which are characterized by a polarity in both the hydrophobic and in the hydrophilic moiety for multivalent fitting and cationic surfactants and / or nonionic surfactants, in which the hydrophobic moiety from siloxanylalkyl, alkylphenyl, alkenylalkyl, cycloalkenyl and / or cycloalkyl radicals and the hydrophilic moiety of oxyethylene and / or oxyprophylene radicals of 1 to 40 and / or -NR ^, - groups.