DEP0048318DA - Process for the production of core sand mixtures for foundry purposes - Google Patents

Description

1 .G.Farbenindustrie Aktiengesellschaft · ρ <\ Q (\ "In dissolution" {A OO

■ P / -48518 · YI a / 3 Ic Our reference; O. Z-. 15 543 "

Y Ludwigshafen a / Hh », July 7th, 1949 ·

Kü / l-It

-Process .for the production of cores $ / uot ___ _νΎ ... , for foundry purposes. · / ■ · ■■■ 'f ■■ i "

- It is known to use cores for G-iesseroi purposes from Sana t SiI, uara condensation product QEf from urea and formaldehyde al

among others

Kernbind emit teJL ite-reusireTbl-e-n. ' To harden, the urine to ff -form- ' Aldehyde condensation products became acids or ammonium salts. used from which free by reaction with formaldehyde. Acid is formed. " But there is the inner bond of the sand unsatisfactory and in the formation of the cores is the danger of breaking given »Only after the kernels have dried out is achieved a certain strength.

It has now been found that excellent mold cores are obtained using urea-formaldehyde condensation products if hydrolytically decomposable salts such as iron chloride, aluminum sulfate / alum and "dejpffl. As hardeners" are used as hardening agents.

The invention is based on the knowledge that the types of sand commonly used in foundries have a relatively strong alkalinity. This prevents the acidic hardening agents from being effective. Even very quartz-rich sands, such as sea sand or / ^ silver sand, show the same appearance »Condensation products made of urea and formaldehyde to which the usual amount of hardener has been added immediately show a neutral reaction after being applied to the sand and do not harden at normal temperature» Also, increasing the amount of hardener does not lead becomes self objectives set when a sand previously washed free of alkali with dilute hydrochloric acid or even the hydrogen ion concentration of a slurry of sand with dilute hydrochloric acid to p _H 4? 5 _s. A sand treated in this way consumes the acidic hardening agent after drying, without it being hardened.

the urea ^ formaldehyde condensation products come " /

It pst surprising that according to the

Invention to use hydrolytically decomposable metal salts the effect of the acid released is retained and consequently the urea-formaldehyde condensation products in normal Cure way.

Ea has been found to be beneficial that

hydrolyzable metal salt in dry form the dry Sana First to mix in, and then the aqueous solution of the urea-formaldehyde condensation producta and mix the whole thing thoroughly. In this way of working, the core attains in the form-nsjieh about 1 hour a "such firmness" that ;;. he ^ can be shaped »In the air it then hardens quickly as it dries.,

The dwell time of the core in the mold can still be reduced quite considerably, ¹ so that the core

immediately after the sand is pressed into the mold;

.. ■■ - (. ■ ^: '■ ■' ■ ■ '· ■' ■. · ■. ■ -. Can, if the -mixture of sand ₉ hydrolytically decomposable metal salt and aqueous solution of the urea-formaldehyde, condensation product is left to stand for a certain period of time before it is introduced into the mold. At the same time, the condensation product becomes tangled, which considerably increases its stickiness and cohesiveness =

If the water is avoided, out

this mixture before introduction into the mold can escape, lets s ^ i the time within which this mixture is now processed must be extended to about 2-3 hours = except for the fast Cores produced in this way have the advantage «that they can be molded easily detach themselves from the Eormwandung «, which is the case with the cores, which are made immediately after mixing the individual ingredients, is not always the case =

Around the gelation time, i.e. the time from

Mixing the individual ¹ constituents until they are introduced into the core mold, it is advisable to add a small amount of swellable water-binding colloids, ZoBo water-soluble starch, when mixing the molding sand with the hydrolytically decomposable metal salt that serves as a hardener

If no hardening of the molding in the mold is required and more emphasis is placed on working as long as possible

Claims (1)

■■ 804: barireit of, harüimprägßiertea molding sand gel «gt _s then are mixed advantageously oriented © 'he sals® and dee Harnst ^ ff-formaldehyde Köndensatioiisprodukteg sum sand suer adding the hard t the mixture 15 after"' ~ 20 minutes until 1fr eic hung a good Klebefähigksit and buffers ansohliessend the acidic sais nor j by adding ammonia or also urea, possibly in aqueous solution "! ₀ 'this achieves ₉ dag" the Weitergeliei ^ ung been seriously delayed and aussäendem de ^ "when processing is abspaltend ® formaldehyde is bound. ,, On this leis ^ produced "Κβτη.® are then ^{nachgehlrteto at 60-100 0} IGOO parts sifted, washed, and dried =. ' neter ^ IuSsand are first filed with 21 files of an & emic ' from potash alum and wela flour in the ratio 1§1 and then with 25 Share a 65 = 70% aqueous solution of a. Kondenaatiöna product from urea and formaldehyde mixed. “BasG-emic process in the usual quiet on mold cores? 1000 parts of washed and dried /% il "b © rsand \ be 4 _P 5 ropes potash alum and then with 55 • filed the mentioned in Example 1 Kondens & tionsproduktec urea and formaldehyde mixed" You can this mixture ■ temperature about ZO ■ = 30 minutes at ordinary! stand obm before it can be formed ia DI® form etsmpfto the setting of 'sand in © j? orm occurs within? 2-5 hours on "Will & di © @ @ τά directly laughing filling d @ r" © ym so one through them 3 «^ ch the size. Brhit ^ en on,? Twa SO ^ iOO ⁰ in a few linmt © n to about 1 gtua.de thru hair ο Yerfahren sur production voué core ent for application dead made of urea and for mal'd ehjd al® marked _s that m & n, as a hardening agent for the sation product © hydrolytically splittable metal! s © 2o - ^^ s ^ vhrwa ^ ffOTEir-n-ßys' Y experience according to claim; If: characterized in that the hardening agent is mixed with the dry molding sand, and this mixture is then replaced with the aqueous solution of the condensation product of urea and formaldehyde ν 3ο ^ Mxs £ üfew * s ^ si ^ m ^ ä- ^ f procedure gsm-äiiV ^ · ^ * ^ \ v ^; Claim 2 _f characterized in -that main 'before the mixture. : \? Bringing it into the mold for some time. for the purpose of · -Vorgel ieerung- des Kon- ;;.> / ^: ". ·; densationsproduktes &. © Αε · - & 3Φτ ^ 4ι» θ »-αα: & ^ ^« jäW- f ^ i-vi- ^ m, 4-0 AWsf'tihrO: 'ng'S "fO" ria - "- de'0 ^# Procedure ^ according to * ^ ■■■■' -. <' ■■ - ₍ ■ ■ ■' ■■■ '■. < ■ '. ■ ■ ■ </ *' · '■ ·. ■ Claim 1, characterized in that the adhesive state > 4 of the impregnated molding sand / is stabilized by adding: ■ ammonia or mixtures of ammonia and urea BADISGHE .AHIiIH & SODA FABBIK