WO1997004899A1

WO1997004899A1 - Glance coal producing agent for foundry sand

Info

Publication number: WO1997004899A1
Application number: PCT/DE1996/001328
Authority: WO
Inventors: Franz Baumgartner; Eckhard Mekus; Siegfried Steinke
Original assignee: Hüttenes-Albertus Chemische Werke GmbH; Hüttenes-Albertus France S.A.R.L.
Priority date: 1995-07-28
Filing date: 1996-07-19
Publication date: 1997-02-13
Also published as: DE19529030A1; DE19680623D2; EP0783387A1; AU6610596A

Abstract

A glance coal producing agent consists substantially of a residue from bisphenol production set to a softening temperature of at least 70 °C by separating low-boiling components. It is preferably set to a softening temperature of at least 90 °C by a subsequent distillative and/or reactive treatment. This glance coal producing agent yields more than 40 % by weight glance coal, can be very easily crushed and stored in silos. It may be used alone or mixed with other glance coal producing agent. In a particularly appropriate manner, it is molten with polystyrene and crushed after cooling down.

Description

Glossy carbon former for foundry sands

Glossy carbon formers are carbonaceous substances that are added to the foundry molding mixture in order to develop hydrocarbonaceous gases in the casting heat, which create a reducing atmosphere and create a glossy carbon film on the molding material particles, which has a favorable effect on the casting surface.

A typical carbon luster is hard coal dust, which, however, only forms about 10% by weight of carbon luster and, because of its risk of explosion, also gives rise to storage problems. Other substances such as coal tar pitch, bitumen or synthetic resins have a higher ability to form lustrous carbon, but are difficult to grind and / or are too expensive. Mixtures of various glossy carbon formers are therefore often used as a compromise in practice.

DE-A 3830463 describes a step in the direction of an inexpensive carbon luster. This carbon luster is based on a processed residue of phenol synthesis, has a softening temperature of 80-110 ° C. and forms 30-40% by weight carbon luster. However, working up the residue of the phenol synthesis is quite complex and, after distillation to remove low-boiling components, requires an aftertreatment to increase the yield of glossy carbon. This aftertreatment consists in mixing the destination residue with a high-boiling aromatic oil and a reflux distillation at temperatures between 320 and 360 ° C under a pressure of at least 300 mbar for 5 to 24 hours.

The aim of the invention is to provide the foundry technology with a particularly inexpensive bright carbon former which has a high ability to form bright carbon without the need for post-treatment to increase the yield of bright carbon. This object is er¬ sufficient that the lustrous carbon consists essentially of a residue of the bisphenol production, low-boiling by separation Komponen¬ th to a softening temperature of at least 70 ^* C is set.

It has been found that the residues from bisphenol production, in particular from the production of bisphenol-A, are outstandingly suitable as glossy carbon formers and can form more than 40% by weight of glossy carbon without any aftertreatment to increase the Yield of shiny carbon is required. This is surprising and was not to be expected in view of the close relationship between phenol and bisphenol.

The elimination of aftertreatment considerably reduces the expenditure for the production of the glossy carbon former and has an effect on the price of the product. But what is also important here is that the starting material is also extremely inexpensively available as a waste product. In the technical production of e.g. Bisphenol-A accumulates primary distillation residues on a large scale. These primary residues still contain significant amounts of low-boiling components, especially phenol and bisphenol, and are therefore often worked up for the recovery of phenol by being subjected to a cracking and distillation process in which the bisphenols are at least partially added Phenols are split back and these phenols are at least partially distilled off. However, even when this process is used, which is typically catalyzed by substances such as dodecylsulfonic acid or the like, there are still considerable residues to be disposed of (also called secondary residues) which have so far been of no further use, and were mainly eliminated by burning.

In addition to the advantages of the good yield of glossy carbon and the inexpensive nature, there is also a considerable environmental aspect. The situation described for the primary and secondary residues of bisphe- Production of nol was understood, for a long time, from an ecological and economic point of view by the affected branches of the chemical industry as unsatisfactory, but without realizable concepts for improving the situation being recognized. It is to the merit of the invention that it has now shown a way in which the residue of technical bisphenol production is completely converted into a useful product. The term "residue" includes both primary, untreated residues and processed secondary residues and their fractions.

The setting of the residues, be they primary or secondary Rückstän¬ de, a softening temperature of at least 70 ^* C is preferably done by AbdestiHation of low-boiling components, that is in the first place of phenol. The softening temperature has practically no effect on the yield of glossy carbon, but primarily affects the physical manageability of the product. Softening temperatures below 70 ° C are not excluded in principle, but are unsuitable because then the product can hardly be milled and no longer remains free-flowing during storage.

If problems arise during the grinding and storage of the residue, auxiliaries such as bentonite and / or hard coal dust can be added to the residue in order to improve the grindability and storage stability. However, these auxiliaries have to be used in increasing quantities as the reaching temperature drops and can possibly make up up to 90% by weight of the product, as a result of which the yield of bright coal formed is correspondingly reduced. It is therefore much more advantageous to set the softening temperature of the residues to values of at least 90 ° C., as a result of which the grindability and storability is ensured even without the addition of auxiliaries.

A softening temperature of 90 ° C and higher can be achieved in different ways. The possibility of subjecting the residues to vacuum distillation, by means of which the softening temperature can be increased to up to 130 ° C., depending on the procedure, is particularly simple and inexpensive. It is also very effective to treat the residues oxidatively or to implement them with an epoxy. This generally leads to an increase in the softening temperature of up to 30 ° compared to an initial value of around 70 ° C. The addition of non-oxidative salts such as sodium carbonate or basic substances W ^yy Ov ^j 9 ^y 7 ^/ / ^/ 0u4 * 8 »9 ^y 9 ^y PCT / DE96 / 01328

- 4 - gives a corresponding increase in the softening temperature, and finally all of these methods can also be used in combination with one another.

With the increase in the softening temperature, there is not only the advantage of improved grindability and storage stability, but also the advantage of an improvement in odor. The residues of bisphenol production have a strong, unpleasant odor due to a content of sulfur-containing reaction products (including sulfonated organic compounds, mercaptans, mercapto acids, thiols and the like) from the production process, which also one of the reasons for this is that the residues have so far not been able to be used effectively. This odor is reduced to a greater or lesser extent even by vacuum distillation, and this odor can be largely eliminated by oxidation, reaction with epoxides or addition of salts / bases. Although modern molding plants are completely encapsulated from the environment, so that the question of the smell is not necessarily in the foreground there, but not all foundries work with such closed molding plants, so that the question of the smell cannot be neglected either.

The preferred way to set an elevated softening temperature is vacuum distillation, which can be carried out at temperatures between 150 and 300 ^* C and pressures in the range of 15 mbar and normally requires distillation times of only 1-2 hours. If a further improvement in odor (in combination with a further increase in the softening temperature) is then desired, oxidation, reaction with an epoxy and / or addition of salts / bases can take place in a second stage.

All customary oxidizing agents are suitable as oxidizing agents, air oxidations and oxidations using metal ions capable of changing valence have in many cases led to particularly good results, ecologically harmless, particularly easy to carry out and highly effective, the oxidation with a peroxo or peroxy compound, preferably a percarbonate. Peroxo and peroxy compounds are generally excellent oxidizing agents, percarbonate acts simultaneously as an oxidizing agent and as a basic substance and is therefore probably particularly well suited.

All common compounds can also be considered as epoxies. All in general, it can be stated that higher molecular weight epoxides are easier to handle than low molecular weight epoxides and that their physiological effect is also less harmful. Low molecular weight epoxides such as ethylene oxide or epichlorohydrin, on the other hand, have the advantage that even small additions bring great success, but this requires a comparatively high outlay on equipment. Polyfunctional epoxides such as bisphenol A diglycidyl ether or triglyddyl isocyanurate are therefore preferably used.

The mechanism of the processes involved in the oxidation or reaction with epoxides has not yet been clarified. Apparently, first of all the odor-intensive components of the residues which reach or boil at low temperatures are converted into more odorless substances with a higher boiling temperature or softening temperature. The addition of salts or bases is likely to have a similar effect, as a result of which probably odor-intensive acidic constituents pass into their complementary, odorless salt (e.g. phenol in phenolates) or are precipitated.

The bright carbon former according to the invention can be used on its own as the only bright carbon former or in a mixture with other shiny carbon former. An addition of polystyrene has proven to be particularly advantageous, since it also has an increasing effect on the softening temperature and the yield of bright coal.

The invention is explained in more detail below on the basis of exemplary embodiments.

Example 1: Residue of bisphenol A production as the base material

A residue of bisphenol A production is adjusted to a softening temperature of 77 ° C. by the processes described at the beginning for removing low-boiling components. This product, also referred to below as the "base material", has a phenol content of 11% by weight and a strong odor. It pyrolyzes very uniformly over a wide temperature range and forms 43% by weight of glossy carbon, and in this respect represents an inexpensive and highly effective glossy carbon former. However, the softening temperature of 77 ° C requires careful avoidance of heat during the grinding and can also result in problems with the storage of the ground product, because in practice temperatures in the range of up to 50 ° C can occur in the storage silos can lead to clumping.

B.

The difficulties in grinding and storing the product according to Example 1A can be reduced or eliminated entirely by adding auxiliaries. Bentonite is a suitable additive in this sense. For example, a mixture of 30% by weight of the product according to Example 1A and 70% by weight of bentonite is easy to grind and also easy to ensilage.

Example 2: Vacuum distillation of the base material

A.

The base material according to Example 1A was refluxed at a temperature of 165 ° C. for 15 minutes and then subjected to vacuum distillation at this temperature (for 1 to 2 hours at 14 mbar). The residue treated in this way had a reduced but still clearly perceptible odor. His Phenol¬ salary had dropped from 11 wt.% To 0.34 wt.% And increased its softening vonn 77 ° C to 104 ^* C. He was easy to grind, the ground Zu¬ was readily at temperatures in the range of 50 ^* C stock and formed still 43 wt.% Gloss coal.

In addition to phenol, the residue also contained bisphenol, which can cleave back to phenol. In order to demonstrate this, a little sulfuric acid was added to the residue after the vacuum distillation and the mixture was heat-treated in a closed vessel at 170 ° C. for 24 hours. After the tempering, the softening temperature and the yield of bright coal had practically not changed, but the phenol content had risen from 0.94% by weight to just over 2% by weight as a result of bisphenol cleavage.

A low (residual) phenol content of the residue does not hinder the use as a glossy carbon former, especially when the molding sands are regenerated. When dumping old sands, however, higher phenol contents must be observed because phenol is a water poison. B.

The base material according to Example 1A was again subjected to vacuum distillation under the conditions described in Example 2A, but at a temperature of 230 ° C. instead of 165 ° C. The residue treated in this way had a softening temperature of 128 ° C., formed (unchanged) 43% by weight of glossy carbon and no longer contained any free phenol, and no further cleavage of bisphenol (heating for 24 hours, 170 ° C.) took place, and the phenol content remained at 0.0% by weight after the heating The smell of the residue was greatly reduced and barely perceptible, and grindability and shelf life (silage capacity) were very good.

Example 3: Oxidation plus epoxidation of the base material

A.

100 parts by mass (about 1 kg) of the base material according to Example 1A with a Er¬ softening temperature of about 77 ° C ^* C were heated and thereby liquefied in a heated vessel at about 130th A mass portion of sodium percarbonate was then added and the mixture was further heated to a temperature of approximately 180 ° C., with foaming of the reaction mixture being observed from a temperature of approximately 150 ° C. A sample was taken from the oxidation product formed at 180 ° C. and cooled. As softening temperature of this sample 94 ^* C were determined. The sample was then slurried in ten times the amount of water and the pH of this slurry was determined to be 8.6. In comparison, the pH of a correspondingly slurried sample of the base material was 5.9, so the weakly acidic base material was converted into a weakly basic oxidation product. The smell of the oxidation product at 180 ° C was greatly reduced compared to the base material.

The oxidation product was then at 180 ^* C for the purpose of epoxidation zusätz¬ Lich converted to glycidyl ether of bisphenol A with three parts by weight. After about half an hour, the softening point was determined for a sample of the epoxidation product formed, a value of 95 ° C. being obtained. A smell of the epoxidation product was no longer detectable at 180 ° C. The yield of glossy carbon was 43% by weight. This also applies to the following examples 3B and 3C, 4A and 4B and 5A, 5B, 5C and 5D. B.

The procedure is as in Example 2A, but with the addition of 1.75 parts by weight of sodium percarbonate to 100 parts by weight of the liquefied base material.

The softening temperature of the oxidized product was 91 ^* C and the product epoxi¬-founded at 92 ^* C. The pH was 8.9 after the oxidation. The smell of the oxidized product was low and could no longer be detected in the epoxidized product.

C.

The procedure is also as in Example 3A, but with the addition of 2.5 parts by weight of sodium percarbonate to 100 parts by weight of the liquefied base material.

The softening temperature of the oxidized product was 86 ^* C and the epoxi¬-founded product at 88 ° C. The pH was 9.0 after the oxidation. The smell of the oxidized product was low and could no longer be detected in the epoxidized product.

Example 4: Sodium carbonate addition plus epoxidation

A.

Carried out as in Example 3A, but instead of adding sodium percarbonate, adding a mass part of sodium carbonate (soda) to 100 ml mass parts of the liquefied base material.

The base material was not oxidized by the addition of soda, but only converted into a basic material. This corresponds to an increase in pH from 5.9 (base material slurry) to 10.4. Foaming of the reaction mixture of base material and soda was not observed when heating to 180 ^° C. The smell of the reaction product was almost unchanged compared to the base material, ie still very strong, the softening temperature was 91 ^* C.

Dienachfolgende treatment with three parts by weight of bisphenol-A-bis-glycidyl ether at 180 "C resulted in a significant reduction in odor. The Erweichungstem¬ temperature slightly dropped to 89 ^* C. B.

Carried out as in Example 4A, but with the addition of 1.5 parts by mass of soda to 100 parts by mass of base material. The smell of the reaction product with soda was still strong. The pH was 10.7, and the softening temperature was 97 ^* C. After the epoxidation of the smell was significantly reduced and the Er¬ softening temperature slightly dropped to 96 ^* C.

Example 5: Epoxidation without / with previous distillation

A.

Carried out analogously to previous Examples 3 and 4, but no addition of sodium percarbonate or soda to the base material. Instead, direct addition of three parts by mass of bisphenol-A-bis-glycidyl ether at 180 ° C. to 100 parts by mass of the base material. The smell of the resulting product was significantly reduced compared to the base material. The softening point of the product was determined to be 93 ° C.

B.

Carried out as in Example 5A, but with the direct addition of 5 parts by mass of bisphenol A bis-glycidyl ether to 100 parts by mass of the base material. This addition led to a particularly strong reduction in the smell, but had no effect on the softening temperature. As in Example 5A, this was 93 ° C.

C.

Carried out as in Examples 5A and 5B, but with the direct addition of 11 parts by mass of bisphenol-A-bis-glycidyl ether. Similar to Example 5B, a particularly strong reduction in odor was found. The softening temperature was again 93 ° C.

D.

After vacuum distillation, 100 parts by mass of the product according to Example 2A were mixed with 5 parts by mass of bisphenol-A-bis-glycidyl ether analogously to Example 5B. The smell decreased and the softening temperature rose by 6 °. Example 6: Combination with polystyrene

A.

The bright carbon former according to the invention according to one of the preceding examples can be easily combined with other bright carbon former, for example hard coal dust and in particular polystyrene. The substances can be milled and mixed together. In the case of polystyrene, however, it is more advantageous to fuse the product according to the invention with polystyrene analogously to the process described in DE-C 33 05 745 at temperatures above 150 ^° C. and to grind it after cooling.

A mixture of 30 parts by mass of regenerated polystyrene and 70 parts by mass of the product according to the invention was prepared by stirring the polystyrene into the still warm residue after the vacuum distillation according to Example 2A. After cooling, a product was obtained which was very easy to grind and ensilage. As a result of the high ability of polystyrene to form glossy carbon, the product gave a glossy carbon yield of 48% by weight. The softening temperature had risen to 126 ° C.

B.

Analogously to Example 6A, the product distilled at higher temperatures was fused with polystyrene according to Example 2B and ground after cooling. The yield of glossy carbon increased in accordance with the contributions made by the individual components (polystyrene alone provides 60-80% by weight of polystyrene), and the softening temperature increased as follows:

With 15% by weight addition of polystyrene to 140 ° C With 20% by weight addition of polystyrene to 145 ° C With 25% by weight addition of polystyrene to 148 ^* C

2.5 kg of the product mixed with 20% by weight of polystyrene were mixed with 100 kg of quartz sand of fineness AFS 50 and 9 kg of bentonite and rolled to 45% compactibility in the pan mill. A mold was stamped from the molding sand thus produced and a coreless casting with a sand / iron ratio of 4: 1 was produced in this mold. For this purpose, cast with gray cast iron at a temperature of 1430 ° C. No unpleasant smells occurred during the production of the casting. The finished casting had a good surface.

Claims

Expectations

1.) carbon luster for foundry sands, characterized in that it consists essentially of a residue of bisphenol production, which is adjusted to a softening temperature of at least 70 ° C by separating low-boiling components.

2.) carbon luster according to claim 1, characterized in that the residue is adjusted by distillation and / or reactive aftertreatment to a softening temperature of at least 90 ° C.

3.) carbon luster according to claim 2, characterized in that the distillative aftertreatment consists in a vacuum distillation of the residue at temperatures above 140 ° C.

4.) carbon luster according to claim 2 or 3, characterized in that the residue for reactive aftertreatment is subjected to an oxidative treatment below its combustion temperature and / or is reacted with an epoxy.

5.) carbon luster according to one of claims 2, 3 or 4, characterized in that the reactive aftertreatment is carried out with a peroxo or peroxy compound, preferably a percarbonate.

6.) carbon luster according to one of claims 2, 3 or 4, characterized in that the reactive aftertreatment is carried out with a polyfunctional epoxy.

7.) carbon luster according to one of claims 2 to 6, characterized in that the residue is reacted with a salt or a basic substance.

8.) carbon luster according to one of claims 2 to 7, characterized in that the residue is first treated by distillation and then reactive.

9.) A process for producing a lustrous carbon agent for Gießerei¬ sands, characterized in that a residue of the bisphenol is the preparation adjusted by removal of low boiling components to a softening temperature of at least 70 ^* C, if necessary., The softening temperature by distillation and / or reactive Nach¬ Treatment is increased to at least 90 ^* C and the product is then melted with polystyrene and ground.

10.) Use of a residue of bisphenol production, aftertreatment and / or reactively aftertreated, if necessary, as bright carbon former for foundry sands, possibly in a mixture with other bright carbon former.