DE2353642A1 - Binding agent for heat-hardenable moulding compsns - contg phenol-formaldehyde prods and amino acids - Google Patents

Abstract

Binding agent based on phenol-formaldehyde condensation prods., optionally contg. resoles and modifying agents, and having a content of hardener, and also contg. amino-carboxylic acids or aminosulphonic acids. Pref. the binder contains 2-6 mol. phenol per mol. of aminocarboxylic acid or amino-sulphonic acid, and 0.5-1 mol, pref. 0.6-0.. mol, HCHO per mol. of the total of phenol and amino acid. Suitable amino acids are glycine, sarcosine, alanine, beta-alanine, glutamic acid, aspargic acid, leucine or proline; and also taurine, methyltaurine, sulphanilic acid or aminopropyl sulphonic acid. The binders are useful in heat hardenable moulding compsns,esp. in foundry moulding compsns or for coating granular, fire-resistant materials in soln. Pref. the molar ratio of phenol:HCHO:aminoacid ranges from 5-4 : 4-3 : 1. Condensation of the components takes place without catalyst, or with addn. of alkali cpds., pref. 1 mol. alkali per mol amino acid being used. The condensation takes place at raised temp. yielding a product similar to a Novolak, although it is not acid catalysed. The prod. can be isolated as solid prod. or be dissolved in water and alkali. Hardening of the binder can be effected with hexamethylene tetramine.

Description

EIKENBERG 8t BRÜMMERSTEDT

PATENT LAWYERS IN HANOVER.

Hüttenes-Albertus 380/32

Chemical ¥ erke GmTaH

Binders for use in thermosetting molding compounds

The invention relates to a binder based on phenol-formaldehyde condensation products, if necessary. with additives of resols and modifiers, and with a content of hardeners, for use in hot-curing molding compounds, especially in foundry molding compounds using the shell molding process.

In the mask molding process, also known as the Groning process, the molding compound is a dry, free-flowing powder, which consists of a granular refractory material, such as sand, coated with a thermosetting binder. The binder is usually a resin

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Form of a phenol-formaldehyde condensation product from ITovolak-'i'yp that still has to adjust its properties with additives of resols or madifying agents, such as root resin or salicylic acid, and that contains a formaldehyde donor, in particular hexamethylenetetramine, as hardener.

The granular refractory material can be coated with the binder in two different ways, with somewhat different types of resins being deposited in each case. In one procedure, the "coating in solution", the resin, if necessary. together with the additions of resols and modifiers, dissolved in organic solvents, e.g. lower alcohols, and then the solution is mixed with the sand (or other granular refractory material). While mixing, the hardener is added and then the solvent is evaporated off in the heat, usually by blowing hot air, leaving a granular sand coated with the binder. The other procedure, the "coating with solid resin", is based on a solid resin in granular form, for example in the form of lozenges _t flakes or sticks. This solid resin is, if necessary. together with the additions of resols and modifiers, mixed with the sand previously heated to a higher temperature (or another granular refractory material), whereby the resin melts and envelops the sand grains. Then the hardener is added (e.g. in an aqueous solution), mixed briefly and then quickly cooled, which is usually done by adding water.

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The method of encasing in solution is generally considered to be more favorable in practice than encasing with solid resin, although the molding compounds encased with solid resin also adhere to their practical areas of application the sand must be heated high enough to ensure proper melting of the resin, but on the other hand the temperature of the resin ^{should not be above 120 °} C. when the hardener is added so that the resin does not harden during the coating. In addition, the conversion of the solid resins into the. The granular shape necessary for a favorable melting behavior is difficult, so that overall the coating with solid resin requires complex equipment and careful implementation. In addition, the known solid resins> which are produced slightly differently and also have a slightly different composition than those in solution resins used, consistently have a higher melting point and that the solid resins cannot be modified to any extent, for example by Eesols, which limits the range of their application possibilities.

The resins to be used in solution have one name of the disadvantages that the solid resins do not have. In solution, they can be modified in practically any way with eesols and other additives, excessive temperatures do not need to be used in the encapsulation, and furthermore they have Resins consistently have a lower melting point, which is different Reasons are sought, for example because the lower the melting point, the higher the cold bending strength. This one However, advantages are offset by the fact that also with

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technological problems perceivable in solution of the envelope available. The solvent vapors released during the wrapping are namely, flammable and especially They are in a mixture with hot air, even explosive, so that in this respect again great care and considerable expenditure for safety-related measures are required.

There is thus a need for binders which avoid the disadvantages of the binders known to date. Accordingly, the invention is intended to provide a binder for use in thermosetting molding compositions, in particular in foundry molding compositions are created according to the mask molding process, which has the properties necessary for coating in solution, but used in aqueous solution can be, and which can also be used as a solid resin for sheathing.

Starting with a binder based on phenol-Iformaldehyde condensation products, possibly with additives of eesols and modifiers, and with a content of hardeners, this goal is achieved according to the invention by that the phenol-formaldehyde condensation product has an additional content of aminocarboxylic acids or aminosulfonic acids having.

In the case of the amino acids used in the context of the invention (including here both the aminocarboxylic acids and the aminosulfonic acids are also to be understood) are at least one, but preferably both, hydrogen atoms of the amino group are unsubstituted. It has been found to be aminocarboxylic acids for example G-lycocoll, sarcosine, alanine, ß-alanine, Glutamic acid, aspartic acid, leucine or proline proven to be suitable and as aminosulfonic acids for example

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wise taurine, methyl taurine, sulfanilic acid or aminopropyl sulfonic acid. Different amino acids can also be used in a mixture with one another.

It can be assumed (although this has not yet been definitively confirmed) that in the case of the binder according to the invention the amino acids via their amino groups into the phenol-formaldehyde condensation product are incorporated, while the carboxyl groups remain free, because the corresponding Equivalents of carboxyl groups can still be found to be largely present after the condensation of the resin prove. Accordingly, the resins resulting from the condensation of phenol, formaldehyde and amino acids are soluble in water, preferably in an alkaline solution, with inorganic bases such as NaOH, KOH or HH-r » if necessary, however, organic bases such as amines or amino alcohols can also be used.

Preferably, two to six moles of phenol are used per mole of amino acid and phenol per mole of the total + Amino acid about 0.5 to 1 mol, preferably 0.6 to 0.9 mol of formaldehyde. In practice, there are molar ratios Phenol: formaldehyde: amino acid from 5 to 4: 4 to 3: 1 has been tried and tested. These preferred limits for the content of Amino acids, however, can also go up and down are exceeded, but if the content of amino acids is too low, the. Solubility of the resin in alkaline solution can become too low. In that case, the aqueous alkaline solution of the resin can be smaller Amounts of organic solvent can be added to improve solubility.

Surprisingly, it was found that the condensation of the resin without the addition of the acidic ones customary for iTovolaks Condensation agent can be done. This condensation is running rather, without catalysts or with the addition of alkaline ones

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Compounds from, with expediently less than 1 mole of alkali per mole of amino acid is used. The condensation is carried out at elevated temperature !!, wherein the components can be condensed together in one approach, but just as well a ^r J? Eil precondensed and the rest of the components may be later added to the batch. The condensation conditions are not critical, in any EaIl obtained as the condensation product of a resin which is similar to the novolaks products in themselves, although it is not condensed sour.

The condensation product, i.e. the resin, can either be isolated as a solid resin or with water and alkali Solution, with Pail less than in the latter 1 mole of alkali per mole of condensed amino acid, i.e. a substoichiometric amount, is used. This will it is ensured that when the solvent (i.e. the water) has evaporated, there is no free Alkali remains in the binder.

The binder according to the invention is hardened As with the known binders with formaldehyde donors, preference is given to hexamethylenetetramine. Furthermore can the binder according to the invention just like the known binders for the purpose of varying the application technology Properties can be mixed with resols, or the other known additives, such as root resin or salicylic acid, be added, which is expediently done before the resin is completed.

In terms of their properties, the binders according to the invention are similar to the binders known for coating in solution, however, they have the advantage that they can be used in aqueous solution, hence the Disadvantage of the fire hazard or the risk of explosion is eliminated. & was required when wrapping in watery

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Solution the evaporation of the water a slightly larger amount of heat compared to the evaporation of an organic solvent, but this larger amount of heat can, if it cannot be provided by hot air alone, very easily by preheating the sand (or the other granular refractory) Materials). Preheating the sand does not cause any problems in this pail, because the resin does not need to melt and the sand very quickly due to the used heat of evaporation of the water. completely unproblematic temperatures are cooled down before the hardener is added.

The same "binders" that are used for the coating in solution can, however, also be used as solid resin can be used for coating with solid resin. So there is no need for different types of for both procedures Resins to be manufactured, so that the previous qualitative differences between solid resins and in solution to resins used, e.g. with regard to the melting point, disappear. That has an effect when used as a plague resin as an advantage.

The invention is illustrated below by means of examples explained in more detail. .

Example 1:

A mixture of 620 g phenol 91 $ ig »390 g aqueous 37% formaldehyde solution and 100 g Glycocoll (corresponding to a molar ratio of 4.5 moles of phenol: 3.6 moles of formaldehyde : 1 mole of amino acid) was within 30 minutes to the Heated to reflux and then refluxed for 3 hours.

ο Subsequently, up to an internal temperature of 130

distilled and finally excess phenol drawn off in a water jet ^by P ^enva ku ^um .

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The condensation product was obtained as plague resin. It was crushed and z. i '. as such, ζ. ΐ. in alkaline Aqueous solution for coating quartz sand of type P 32 used. The coating took place in a laboratory mixer.

The heated quartz sand was poured into the preheated mixer for coating with plague resin. The Pestharz was at about 150 ° sand temperature in an amount of 3 $ ₄ based on the sand, was added .. Uach one minute mixing time by the addition of aqueous hexamethylenetetramine solution corresponding to 10 io Hexamenthylentetramin, based on the Pestharz, as a curing agent, and then of 5 ^ Calcium stearate, "also based on the plague resin, as a separating agent. When the mixture was complete, the coated sand was sieved and, after it had cooled down completely, used for further tests.

The coating in solution was first determined the Peststojgf ton the solution by drying for one hour at 130 ° C. To coat the resin solution was the etv on / a 180 - 200 C heated sand added, namely in an amount of 3 f »Peststoff on the sand. To. The hexamethylenetetramine was added as a powder for 1 minute.

Finally, the sand encased by both methods was tested for flexural strength and sintering point. The preparation of the bending test (dimensions according DIlT 52404 design) was carried in to 280 ⁰ C heated model cans followed by 5-minute baking in the "warm oven at 280 ⁰ G. The corresponding DIIT 52404 design specific bending strength was obtained as the average of 3 samples. The sintering points the covered sands were determined on a Kofler melting bench.

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It turned out:

a) when coated with solid resin:

Flexural strength 98 kp / cm ^: sintering point 91 ⁰ C

b) "when wrapped in solution with a 2.5 η

■ aqueous ammonia produced

Resin solution of 58 ° C content ί flexural strength 92 kp / cm sintering point 91 ⁰ C

Example 2: '■

A mixture of 620 g Phenol 91- $ ig, 433 g aqueous formaldehyde solution 37 $ ig and 100 g G-lycocoll (corresponding to a Molar ratio 4.5 moles phenol: 4.0 moles formaldehyde: 1 mole Amino acid) was refluxed in 30 minutes, after 3 hours reflux "distilled to 115 ° G, one hour at 115 C and then under vacuum to a final temperature distilled from 150 C.

The further processing of the resin obtained and the encased sands were tested as in the example

It turned out:

a) when coated with plague resin:

Flexural strength 89 kp / cm sintering point 94 ⁰ C

b) when coated in solution with an aqueous resin solution of 55.3 % solids content prepared with 1.7 mmol ammonia per gram of solid content:

Flexural strength 99 kp / cm ² . Sintering point 90 ⁰ C

c) when coated in solution with a 0.85 minol

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ITaOIJ per gram of pest resin produced aqueous resin solution of 55.3 ί ° pesticide content:

Flexural strength 104 kgf / cm ²

Sintering point 95 ⁰ C

Example 5t

300 g of the Pestharzeö according to Example 2 were dissolved after the addition of 50 ml of 5 η KaOH and 150 pil of water with heating in a water bath. 460 g of the solution, the Peststoffgehalt was 56.7 ^, were mixed with 112.5 g of a resol mixed, which had been prepared as follows: 414 g of phenol 406 g of aqueous Pox naldehydlÖsung ^ 37 / '- ig and 5 S 2 of calcium hydroxide were Hours of 50 ⁰ C and L hours at SO ⁰ G kept. J5e.i decreased. Pressure was removed from 275 ml of distillate. The Ilesol's pesticide content was $ 77.1.

The mixture of resin solution and resol, the one The pesticide content of 59 »8 ^ was used in the example 1 for the coating in the solution described manner 'further process The coated sand was also tested according to Example 1.

It turned out:

Flexural strength 104 kgf / cm

Sintering point 80 ⁰ C

It should be noted that curing is faster than in Example 2.

Example 4:

A mixture of 465 g phenol 91% 284 g aqueous formaldehyde solution 37 g and 147 g of glutamic acid (corresponding to a molar ratio of 4.5 hol phenol: 3 »5 hol formaldehyde : 1 hol amino acid) together with 16 g NaOH (0.4 mol) heated to reflux within 30 minutes and refluxed for 3 hours. Then the easy ones became

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Ingredients "up to" an internal temperature of 140 ⁰ G distilled off. ·

The further processing of the resin obtained and the like, the testing of the encased sands was carried out as in Example 1

It turned out: Solid resin: kp / cm a) when wrapped with 75 ⁰ C Flexural strength 94 Sintering point

Coating in solution with an aqueous resin solution with a solids content of 50.7% made with 1.7 mmoles of ammonia per gram of solid content:

Flexural strength 110 kp / cm

Sintering point 93 ⁰ C

Example 5:.

A mixture of ^> ^ β g phenol 91 $ ig> 341 g of aqueous 37 Forrnaldehydlösung successfully and 125 g of taurine (corresponding to a molar ratio of 5.0 moles of phenol: 4.2 mol of formaldehyde to 1 mole of amino acid) were ZIAM within 30 minutes of reflux heated. Tray 3 hours of reflux, the reaction mixture was subjected to a temperature of 115 G bis'zu distillation, held for one hour at 115 C and then heated with distillation at 150 ⁰ C.

The further processing of the resin obtained and the encased sands were tested as in the example

It turned out:

a) when coated with solid resin:

Flexural strength 91 kg / cm ² "· - ■

Sintering point 107 ⁰ C '

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b) when wrapped in solution with a 1.7-umiol Ammonia per gram of solid resin produced aqueous resin solution of $ 58.7 pesticide content:

Flexibility S9 lcp / cm sintering point 100 ⁰ C

c) In the case of wrapping in solution with a solution prepared with 0.85 per inmo.1 UaOH Grainn Pes'tharz aqueous resin solution of 58.7 $ Eeststoffgehalt: Flexural strength 98 kgf / cm sintering point 106 ° 0

- Expectations -

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Claims (1)

- 13. - ■ '■ A η s Ό r ν cbe 1. Binder based on phenol-iOrmaldehyd'-condensation products, if necessary This is indicated by the fact that the phenol-formaldehyde-dehydrogenation product has an additional content of arainocarl-donic acids or aninosulphonic acids. 2. binder nacii Ansprucih _$ 1 characterized in that per mol of aminocarboxylic acid or aminosulfonic acid 2 to 6 moles of phenol per and- Kai of the sum of phenol and amino carboxylic acid or, amino sMlfonsäure 0.5 -Ms HoI 1 ₁ is preferably O "6-0 ·· _Γ tion product 9 Hol Foraaldehyd in the Elondensa-; is included .. 5.Binder according to claims: h 1 or claim 2 _J; through this.' characterized: ,, DA® at dex wrapping physi- nig; _eB; refractory materials an aqueous alkaline solution of the co <mdensatio; nsprodiuktesi is used, which contains less / than 1 mole of base per mole of incorporated AmiBoearbonisIuore or Aminoisulfonsauare; " KEEß / Εΐι