DE4020855A1 - Purifying technical grade camphor prodn. - by melt crystallisation with at least one reheating step once initial crystallisation has ceased - Google Patents

Abstract

Impurities are sepd. from technical grade (at least 50%) camphor (I) by melting the (I), and then cooling to allow pure (I) to crystallise out. The crystallisation process which initially sets in and continues practically to a standstill, is set in motion against at least once by a heating step. Pref., 1-4 heating steps are employed. USE/ADVANTAGE - This method gives pure (I) without the need for solvent recrystallisation (and consequently drying), so avoids loss of both product and solvent. Pure (I) is used as a plasticiser for cellulose nitrate (in prepn. of celluloid and nitrocellulose lacquer) or cellulose propionate. It is also useful as a pharmaceutical (antiseptic or cardiac stimulant);perfume component; clothes moth repellent; in smokeless gunpowder or primers, and as fumigant. (4pp Dwg.No.0/0)

Description

That in the manufacture of synthetic camphor α-pinene via the reaction steps: pinene rearrangement, Acetoxylation of camphene, saponification of isobornyl acetate and catalytic dehydrogenation of isorborneol Reaction product contains a variety of bothersome By-products that generally belong to the substance classes of Terpene hydrocarbons (camphene, tricyclic, dipentene and Isomers), terpene alcohols and terpene ketones belong.

To use this mixture as a camphor Plasticizer for cellulose nitrate in the manufacture of Celluloid and nitrocellulose varnishes or for that To win plasticization of cellulose propionate Campher from the raw mixture in general Distillation and sublimation separated. These However, cleaning operations are far from sufficient if the purity of the camphor, as in medicine, higher demands are made. Here, Camphor z. B. as a cardiac stimulant or as an antiseptic (Camphor alcohol, ointment formulations) used. To the provided in many pharmacopoeias To meet purity requirements, it is essential the camphor additionally from solvents, mainly Ethanol to recrystallize once or twice. This requires an additional effort for solvents and annoying Mother liquor processing, combined with camphor and Solvent losses, as well as an energy-intensive Drying the end product.

It has now surprisingly been found that this Disadvantages can be avoided if one instead of Recrystallization using solvents  technical camphor of crystallization from the melt submits. However, certain conditions must be met be respected. The attempt at crystallization only due to constant cooling of the melt Deposition of a fraction of crystalline camphor quickly to a standstill. The invention relates to a Process for separating contaminants from technical, at least 50% camphor, thereby characterized that you melt the technical camphor. and then camphor cleaned by cooling can crystallize out, whereby the one which starts first and then largely coming to a standstill again Crystallization at least once through a heating period gets going again.

So you melt the technical camphor, and then cool one to crystallize until the cleaned camphor begins. It is advisable to carry out a preliminary test Melting point of the technical camphor to be cleaned determine so that you have an orientation when the technical camphor will be completely melted and when to cool down with the start of crystallization to calculate. One cools down as long as essential Crystallize amounts of camphor. When about 30 to 50 % By weight of the camphor present has crystallized out, the crystallization generally comes to a large extent Standstill, d. H. it becomes so slow that it becomes technical cleaning process becomes uninteresting. According to the invention, the mixture is heated such that the Crystallization gets going again without essential parts of the already crystallized purified Melt camphers again. Generally one is Warming by about 2 to 5 ° C for 3-10 minutes for this Suitable purpose. You can also do a preliminary test in one Glass jar for the specified technical camphor best suitable values for temperature and duration determine. When crystallization got going again , you stop heating and continue to cool down as long as  crystallize significant amounts of camphor. If the crystallization essentially stopped again has come, you can either cancel it or cancel it start again by briefly warming up again. In general, the crystallization becomes 1 to 4 times start again by briefly warming up; preferably you will only do this 1 to 2 times, especially if you are looking for very high purity of the Crystallizing Camphers value, for example medical purposes because of the risk that the Contaminants sometimes also become solid the higher you try, the camphor is quantitative or crystallize out almost quantitatively.

With the help of the method according to the invention, the Technical camphers melt into one convert cohesive, porous crystal block into where the impurities are still in liquid form and also a more or less large remnant Campher is in liquid form, depending on when you take the Crystallization has stopped. By subsequent Opening the crystallizer at the bottom and slight increase in temperature - generally around about 2-5 ° C - can then remove the liquid contaminants and the also liquid remaining camphor from the Drain and sweat the coherent crystals. The cleaning process according to the invention can, if necessary, be repeated if the technical camphor used was very impure, or the end product should be particularly pure should. In many cases, however, it is also sufficient for medical purposes Purposes a one-time cleaning, preferably not more than 1 to 2 times the crystallization by short Warming is started again, as already above mentioned.

It is special to get the best possible yield advantageous, the resulting from the crystallization, strong  contaminated liquid residues to sublimation subject and usually more than 60 wt .-% Sublimate containing camphor in the inventive Crystallization process attributed.

The cleaning process according to the invention can be both static in tube crystallizers (so-called drip devices) such as Sie in Winnacker-Küchler, Chemical Technology, 4th ed. Vol. 6, 1982, p. 148, or to Cooling coils as in Example 2 of this application specified, or also dynamically in an apparatus, as in the US-PS 36 21 664 described can be performed.

Purified camphor is a valuable product. He is used as a plasticizer for cellulose nitrate irreplaceable of celluloid and nitrocellulose varnishes. He has also been used in the plasticization of Proven cellulose propionate. Campher continues to be Formulation of pharmaceutical preparations (e.g. as Camphor alcohol), as a fragrance component, for Odor improvement and as a repellent against clothes moths used. It is also used for the production of smokeless Gunpowder and primers. Another important one Field of application for camphor is the use as Incense for ritual use. The invention Process is illustrated by the following examples. The Percentages are percentages by weight. The refer to the specified temperatures for cooling and heating always refer to the cooling or heating medium of the thermostat.

example 1

In a tube crystallizer, its heating and cooling jacket connected to a thermostat, 312.5 g of one technical camphers (purity 89.4% by weight) as a solid filled and at a heating temperature of 180 ° C. completely melted. With the constant presence of  The homogeneous melt became inert nitrogen as long as the following cooling and heating program Subjected to crystallization until it becomes a porous block was frozen:

• - Cooling from 180 ° C to 167 ° C within 30 minutes
• - Heating from 167 ° C to 170 ° within 4 minutes
• - Cooling from 170 ° C to 165 ° C within 30 minutes
• - Heating from 165 ° C to 168 ° C within 5 minutes
• - Cooling from 168 ° C to 161 ° C within 60 minutes
• - Heating from 161 ° C to 165 ° C within 4 minutes
• - Cooling from 165 ° C to 151.5 ° C within 120 minutes.

When crystallization was complete, opening the Bodenhahns collected a residual melt of 44 g, one Camphor content of 51.3 wt .-% had. After that the Heating medium temperature within 18 hours from Increased 151.5 to 160 ° C, with a camphor sweat fraction of 52 g with a content of 90.3 wt .-% was separated. Eventually the crystals that remained in the apparatus melted and isolated: The amount of camphor purified was 216 g with one Pure content of 97% by weight.

Example 2

In a tube crystallizer as in Example 1 152.1 g of a technical camphor were described (84.2% by weight) as a solid and a heating temperature of 180 ° C completely melted. In the presence of inert argon the homogeneous melt with a few camphor crystals vaccinated and as long as the following program Subjected to crystallization until it becomes a porous block was frozen:

• - Cooling from 156 ° C to 129 ° C within 120 minutes
• - Heating from 129 ° C to 132 ° C within 5 minutes  
• - Cooling from 132 ° C to 122 ° C within 120 minutes
• - Heating from 122 ° C to 126 ° C within 4 minutes
• - Cooling from 126 ° C to 116 ° C within 120 minutes.

After crystallization was complete, the bottom tap of the Crystallizer opened and the temperature of the heating medium Increased from 116 ° C to 135 ° C within 25 hours. Here, a fraction of 71 g with a Camphor content of 78.5% collected. Then the remaining crystals melted and isolated. The amount of camphor purified was 80 g with one Pure content of 90% by weight. The so obtained Crystals can be recrystallized further enrich their camphor content.

Example 3

In a crystallizer that consists of all sides thermally insulated stainless steel container of dimensions 600 mm length × 600 mm width × 700 mm height existed and in the four oil-flowed, serpentine arranged 4-inch heat exchange register for heating and cooling were installed, 100 kg camphor (89.4%) as Filled solid and under argon as a protective gas 185 ° C completely melted. Then the homogeneous Melt according to the following cooling and heating program subjecting a thermostat to crystallization as long as until it solidified into a porous block:

• - Cooling from 185 ° C to 167 ° C (speed 1.8 ° C / min)
• - cooling from 167 ° C to 161 ° C (speed 0.1 ° C / min)
• - Heating from 161 ° C to 164 ° C (speed 0.5 ° C / min)
• - Cooling from 164 ° C to 157 ° C (speed 0.1 ° C / min)
• - Heating from 157 ° C to 160 ° C (speed 0.5 ° C / min)
• - Cooling from 160 ° C to 155 ° C (speed 0.1 ° C / min).

At 155 ° C internal temperature, the heated at 185 ° C Bottom tap of the crystallizer opened and one  Drained liquid fraction of 25 kg (70.5%). After that the temperature rose to 155 with the drain tap open 161 ° C with a heating rate of 0.1 ° C / min increased (sweating), taking 10 kg of a second fraction (93%) expired, the next approach directly again can be used. Finally at 161 ° C Drain tap closed and that in the crystallizer remaining camphor completely at 185 ° C melted. The result was 65 kg of cleaned camphor a purity of 96.1% by weight.

Claims (4)

1. Process for removing contaminants from technical, at least 50% camphor, thereby characterized that you melt the technical camphor and then camphor cleaned by cooling can crystallize out, the first beginning and then largely to a standstill coming crystallization at least once by a Starts the heating-up period again. 2. The method according to claim 1, characterized in that one to four times by one Starts the heating-up period again. 3. The method according to claim 1 and 2, characterized in that the technical camphor is 80 to 95% by weight. 4. The method according to any one of claims 1 to 3, characterized characterized in that the crystallization subjecting the residue obtained to sublimation and the sublimate obtained here into the invention Procedure.