SU914168A1 - Method of producing binding for manufacturing casting sheel moulds and cores in heated equipment - Google Patents

Description

The invention relates to foundry, and in particular to methods for producing binders for molding and core mixtures used in the manufacture of shell or bulk molds and cores, cured in a heated snap.

A known method of producing a casting binder, which consists in combining oligomers of furyl alcohol and phenol alcohols or furyl alcohol, phenol alcohols and urea resins. The binder has a high heat resistance [1].

However, molds and rods made from mixtures based on a phenolofuran binder have low elastic properties at high temperatures, which leads to reject casting and brittle fracture of molds and rods during transportation and storage.

The closest to the proposed technical essence and achievable result 2 is a method of producing a binder for the manufacture of foundry shell molds and cores in a heated tool, consisting in the mechanical combination of phenol ⁵ formaldehyde oligomer novolac type and rosin ester. Shell molds and rods, obtained on the basis of this binder, are characterized by increased heat resistance, ⁰ which allows eliminating casting rejects due to underfilling due to cracking of molds and rods during pouring and crystallization of metal (2].

However, the efficiency of lysis steps ⁵ termostabi rosin ester in the case of a mechanical mixture of the ingredients of the binder depends on the thoroughness of the mixing of sand and resin mixture in the process of plating ⁱⁿ sand. A uniform distribution of the components throughout the volume of the mixture is difficult to achieve with cladding. since it leads to a lengthening of the technological cycle of mixture preparation. In addition, a binder obtained by mechanically combining Phenolic 'novolak and ether: tnifoli _; characterized by the absence of chemical interaction between these ingredients, which leads to reduced thermomechanical elastic properties of the binder -l leads to reduced thermomechanical characteristics of the molds and rods.

The purpose of the invention is the improvement of thermal characteristics of molds and rods.

This goal is achieved by the fact that according to the method of producing a binder for the manufacture of foundry shell or three-dimensional molds and cores in a heated snap-in, including combining a phenol-formaldehyde oligomer with glycerol or glycol unsaturated rosin ester, 50-98 weight parts. The phenol-formaldehyde oligomer and 2-50 parts by weight of glycerol or glycol unsaturated rosin ester are condensed by heating their composition at a temperature of 95-230 ° C for 0.5 ~ 5.0 hours.

Moreover, the phenol-formaldehyde oligomer of the novolac type and said rosin ester are condensed by heating their composition at a temperature of 180-230 ° C. for 1-5 hours.

Furthermore, phenol-formaldehyde resol type oligomer and said rosin ester is condensed by heating the composition at a temperature of ^_ 95 11P ° C for 0.5 "2,5ch.

Unsaturated rosin ester enters into chemical interaction with a phenolic resin, while the melting point of the interaction product increases significantly (by 10-20, depending on the molecular weight of the resin and its degree of interaction with ether). The increase in the melting temperature is explained by the formation of higher molecular weight compounds, which provides increased heat resistance of the binder.

When the binder is cured, the phenolic nuclei are bound by elastic long links due to which the proposed binder is characterized by a low bending modulus with a high value

68 4 deflection, which indicates increased elastic properties of the binder.

High thermomechanical properties of the binder cause the appearance of small thermal stresses and contribute to the production of castings with high surface cleanliness.

As the phenol-formaldehyde 10 oligomer, the usual phenol-formaldehyde resin of the resol or novolac type or modified phenolic resins phenol-furan, phenol-urea 15 and others can be used.

Gum rosin esters, as well as esters based on various types of modified caniofol Fole (polymerized, disproportionated, hydrogenated, etc.) can be used as rosin esters.

The esters of polymerized gum rosin contribute to a greater increase in the heat resistance of the binder, compared with the ether of unpolymerized rosin, due to the higher molecular weight of the products of their interaction with the phenolic resin.

The esters of a disproportionate cani ₃ 0 foli narrow the temperature range of softening the binder, causing the occurrence of small thermal stresses during hardening of the binder,. which leads to a decrease in cracking marriage ₃₅ when pouring molds and cores.

The esters of hydrogenated rosin contribute to the production of a binder with increased elasticity, since a different composition of the acid base leads to an increase in the size of crosslinking bridges, which contributes to an increase in the flexibility of the macromolecules of the formed polymer.

When rosin ester is introduced with its content below the lower stipulated limit, the effect of increasing the thermomechanical properties of the binder is not observed, and when it is introduced with the content above the upper stipulated limit, the strength of the molds and rods in the hot state sharply decreases.

The optimal temperature range for the interaction of the phenol-formaldehyde oligomer of the novolac type with rosin ether 180-230 ° C, the optimal process time is 1 ^to 5 hours.

^'91

When the heating temperature is less than 180 ° C and the duration of the process is less than 1 h, the novolac phenol-formaldehyde oligomer does not interact with rosin ether. Therefore, the effect of enhancing the thermomechanical properties of _a binder is insignificant.

At a heating temperature of more than 23 ° C and a duration of more than 5 hours, the degree of interaction of rosin ester with novolac phenol-formaldehyde oligomer is excessively high. This reduces the fluidity of the reaction product, due to the high molecular weight of the modified binder, which leads to an increased consumption of it in the mixture to provide the necessary strength.

The optimal temperature range for the interaction of the phenol-formaldehyde oligomer of the resol type with rosin ester is 95'110 ° С, the optimal process duration is 0.5 ~ 2.5 hours. At temperatures above 110 ° С and the process duration is more than 2.5 hours, the resin autocondensates, which limits the possibility of a reaction of its interaction with rosin ester. At a temperature of less than 95 ° C and a duration of the process of less than 0.5 h, the reaction rate of the interaction of the ether with the phenol-formaldehyde oligomer of the resol type is insufficient to achieve the desired effect.

Example. To obtain a binder, the novolac resin is treated with rosin ether at an elevated temperature of ΐ8θ-230 ° C for 1- £ h. The resole resin is condensed with rosin ether at 95 “1 ° C for 0.52 hours.

It is also possible to obtain a binder, according to which rosin ester is introduced at the stage of synthesis of a pre-treated or rezol resin. In this case, phenol, formaldehyde and rosin ester are mixed and heated in the presence of an appropriate catalyst at the boiling point until most of the formaldehyde is bound, then water is distilled off, the reaction temperature is raised to 180-230 ° and heated for 1-5 hours (in the case of novolac type resin) or up to 95 * 110 ° С with a heating duration of 0.5–2.5 h (in the case of resole type resin).

In the table. 1 shows the characteristics of the used rosin esters,

6 a in table. 2 - compositions and modes of preparation of the proposed (1-8) and known (9) binder compositions.

Given in the table. 2 phenolic resins are commercially available products:

Sf-260-Tu 6-05-231 -114-77; SF-015-GOST 18694-73; SF-3042-.

TU 6-05-1826-77; SF-411-TU 6-05-031516-75

In the table. Figure 3 shows some basic properties of the binder compositions (1-9), the compositions and modes of synthesis of which are indicated in Table. 2.

Compositions 1-9 are used in the compositions of sand-resin mixtures in combination with the following hardeners: urotropin (1-4 and 9), oxalic acid (5) and M 2 (6-8).

The elastic properties of the binder are evaluated by the values of the bending elastic modulus and the corresponding deflection measured on a flat rectangular sample 6x25x100 mm from the molding sand.

The molding mixture is prepared on sand 2Κ016Λ and contains 3 / (by weight) resin binder and hardener in the amount of 10-25% by weight of the resin (10% for clad mixtures, 25% for hot cure mixtures).

In a box heated to 220-2 ° C, samples are held for 180 s, after which they are tested. The bending strength test is carried out at room temperature on three samples according to standard methods. To calculate the modulus of elasticity, a load of 90% of the breaking load is used, and the specimen deflection corresponding to this load.

The heat resistance of the binder is estimated by the value of the relative weight loss (%). Thermograms are obtained by heating weighed portions of the pre-cured binder to 800 ° C for 15 minutes.

Thermomechanical properties of clad mixtures are presented in table. four.

From the results given in table. 4, it follows that mixtures with a binder obtained by the proposed method are characterized by a reduced modulus of elasticity in bending, an increased amount of deflection with equal or greater bending strength.

This indicates increased elasticity with a high margin of safety for mixtures obtained using a binder prepared according to the proposed method.

At the same time, from the data in Table 3 it follows that the binder obtained by the proposed method has a higher heat resistance, which is expressed in a reduced rate of relative weight loss when piercing.

The totality of the achieved advantages allows us to conclude that the thermomechanical characteristics of the molds and cores of mixtures with a binder !, improved by the proposed method, are improved.

Table 1

^ Polymerized glycerin ester

gum rosin HEPFA TU0P81- -05-96- -79 90-95 one eighteen 1400 Trading mark ECA110 Tall oil rosin glycerin ester GETK - 45-51 fifteen 800 Experienced sample Hydrogenated gum rosin triethylene glycol ether TEGHK - Viscous fourteen 7Y Experienced sample Disproportionate Rosin glycerin ester (Harpius ester) - OST 81-26-78 65-70 12 - Trademark rosin ester Extraction rosin diethylene glycol ether DEEK Viscous 24 670 Experienced sample T a blitz 2 Compositions and modes of preparation those who know ---------- Binders ---- _g _ __ _g ..:..one. 2 | 3 gp OO phenolic resin novolak type. the weight.% SF-260 69 90 69 SF-015 - 90 90 - -

Compositions and modes of preparation of binders 1 ________________ ·; ___ 0В2Д ° false _ΙΒ§ · Βδ _?

Binders ρ ::] Ζί'Ρ'ΤΡ''Τ'ί

Phenolic resin of rezol type, weight. %

SF-3042 - - - 90 • - • SF-411 - -  - - 98 fifty 97 Rosin ether, wt.% HEPFA 31 10 10 31 TEGHK - - - 10 - - -90 3 -; getk - 10 - - - 2 - - - Temperature, ^ С 180. 230 180 200 110 110 one hundred 95 Mecha Duration, h one four 5 four 0.6 0.5 2 2.5 nical.

mixing

one T a e l and a 3 Properties bind- Indicators properties -u - for binding t t composition one . ’ of composition one 2 3 I AND 5 ⁶ 7 8 9 known , ____ .one....... naya

Mass fraction,%: free phenol 4.48 4.49 4,5 ^ free formaldehyde - - - Melting point, ° С 106 94 120 The viscosity of a 50% alcohol solution according to VZ ^- 4, s 102 92 97 * Fluidity, mm 78 80 80 Dry residue,% but*** but but Relative mass loss during calcination,% 31 29th 31

4.07 15.9 6.82 4.74 5.96 5.77 - 1,5 2,8 1.94 2.68 125 _ l * ^** Viscous Viscous Viscous Viscous 92 99 76 84 92 83 92 75 82 86 78 84 96 but 77 72 82 72. but thirty 35 38 . 33 33 41

* It is determined on the device. Ubellode ** Practically means that the melting point is less than 20 ° С.

* n / a - c _e is determined. ·.

Table 4

Thermomechanical properties

I -------, ------------- | ------.- d .------ _G ---- Property indicators for mixtures with binders

-P ΤΊΎ —L _____ (famous

Flexural modulus, kn / cm ^

Sample deflection, mm

Bending strength, kgf / cm *

1 53.5 1 17.0 137.0 123,2 144.5 127.4143.2 111.5 182.0 0.40 0.45 0.38 0.42 0.32 0.30 0.34 0.39 0.24 75.8 65.1 64.7 63.9 55.3 57.2 60.1 53.7 54.0

of the invention, the novolac type dehydrated oligomer and said rosin ester condensate

Claims (3)

1. A method of producing a binder for the manufacture of foundry shell or three-dimensional molds and cores in a heated tooling, comprising combining a phenol-formaldehyde oligomer with glycerol or glycol unsaturated rosin ester, characterized in that, 25, in order to improve the thermomechanical characteristics of the molds and cores, 5098 weight parts phenol-formaldehyde oligomer and 2 ~ 50 parts by weight The glycerol or glycol unsaturated rosin ester condenses by heating their composition at 95,230 ° C for 0.5 “ 5.0 hours 2. The method according to the fifth and second. 1, distinct - _{35 that} phenol-formalized by heating their composition at a temperature of 180-230 ° C for 1-5 hours 3. The method of pop. 1, characterized in that the phenol-formaldehyde oligomer of the resol type and said rosin ester are condensed by heating their composition at a temperature of 95-1 ° C for 0.5 ^- 2.5 hours.