DE19503437A1 - Propylene glycol mono:alkyl:ether ester(s) - Google Patents

Abstract

Propylene glycol monoalkylether esters of formula R<1>-O-CH2-CH(Me)-O-C(O)-R<2> (I) are new, where R<1> = ethyl or propyl; and R<2> = methyl or ethyl. (I) are prepd. by reacting a propylene glycol monoalkyl ether (II) with acetic acid or propionic acid at above 80 deg C in the presence of an acid catalyst and an azeotropic agent to cause esterification with formation of the crude (I), followed by sepn. of the unreacted acid and water by distn. to yield (I) of high purity. Pref. the mol. ratio (II)/organic acid is 0.6-3.0, the acid catalyst is chosen from H2SO4, p-toluenesulphonic acid and methanesulphonic acid, and the azeotropic agent is chosen from benzene, toluene, xylene and cyclohexane, used in an amt. of 6-30 vol.% w.r.t. the sum of the vol. of (II) and the organic acid.

Description

The invention relates to propylene glycol monoalkyl ethers and a process for their preparation.

Organic ester compounds are good solvents, which in significant quantities in the resin processing Industry are needed, for example, for paints, Paints, inks, adhesives, detergents and the like chen. At present, ether compounds are mainly used in two categories, d. H. an E series and a P series divided up. The E series of ether compounds are off obtained during the synthesis of alcohol and ethylene oxide the P series of ether compounds from the syntheses of Alcohols and propylene oxide are obtained. In the ver In recent years it has been discovered that the E series of Ethhers and their acetate ester compound on inhalation by humans probably to Alkoxyessigsäureether be broken down, which in turn causes the Ery Throcythen become abnormal, rendering them toxic to the Sexual organs become. In contrast, cause the P-series does not do this damage. There is currently a part the propylene glycol monomethyl ether acetates of the P series regarding the solubility of unsaturated polyesters or polyurethane resins worse, as well as in terms the drying ability of existing Beschich obligations. Therefore, it is urgently necessary, a Lö to develop a kind of agent that is not just an  characterized solubility and drying ability, but which is also little toxic.

To meet these requirements of the market, have the applicants of this application in DE-A-43 25 149.8 a new propylene glycol monomethyl ether propionate compound and a process for their preparation described and in DE-A-44 16 661.3 another propylene glycol monomials methyl ether butyrate and isomers and a process for their use Production explained. Following this, the sub This area has been greatly expanded so that new Connections were successfully developed.

A main object of the present invention is in the creation of a novel propylene monoalkyl ether ester ver Compound with the general structural formula:

wherein R₁ represents an ethyl or propyl group and R₂ a methyl or ethyl group generated by the reaction between propylene glycol monoalkyl ether and acetic acid or Propionic acid was obtained as starting material. in this connection are among the new connections that are made by the general ne structural formula is represented, propylene glycol mono ethyl ether acetate (PGEA), propylene glycol monoethyl ether propionate (PGEP), propylene glycol monopropyl ether acetate (PGPA) and propylene glycol monopropyl ether propionate (PGPP).

Another object of this invention is in Creation of a method of producing the present novel propylene glycol monoalkyl ether ester compounds which represented by the above-mentioned general formula where either the reaction of Propylene glycol monoethyl ether (PGE) obtained by the synthesis  of ethanol and propylene oxide, with vinegar or Propionic acid in the presence of an acidic catalyst and an azeotropic agent to propylene glycol monoethyl ether acetate (PGEA) or propionate (PGEP), or the reaction of propylene glycol monopropyl ether (PGP), the obtained by the synthesis of propanol and propylene oxide was reacted with acetic or propionic acid in the presence of a acid catalyst and an azeotropic agent, propylene glycol monopropyl ether acetate (PGPA) or Pro to form pionate (PGPP).

Furthermore, it is an object of the invention is that Use of the currently new propylene glycol monoal kyhletheresterverbindungen as a solvent, in particular in the range of paints and inks, inks and adhesives as well as with cleaning agents, inter alia in the field electronic manufacturing and dry cleaning specify.

In the drawing, embodiments of the counter standes of the invention shown. Show it:

Figures 1 and 2 NMR'H and mass spectra of PGEA, which was obtained according to Example 1 of the description of the figures ten;

FIGS. 3 and 4 NMR'H- or mass spectra of PGEP, produced in accordance with Example 3 of the description of the figures;

FIGS. 5 and 6 NMR'H- or mass spectra of PGPA generated according to FIG. 5, the description of the figures and

Fig. 7 and 8 NMR'H and mass spectra of PGPP, which was produced according to Example 7 of the figure description.

The process of making the new propyhlen Glycol monoalkyl ether ester compounds include both batch processes as well as continuous processes. If that Water generated during the reaction is not removed In general, the reaction system will easily reach a state of equilibrium, a productivity growth impeded and thus detrimental to the industriel le production is. Therefore, in the invention appropriate procedures, whether a batch process or a continuous process is used, to the Reak tion system added aromatic compounds, as in For example, benzene, toluene, xylene and cyclohexane as azeotropic agents. The thus added azeotropic com Component must be incompatible and water show an azeotropic effect. Aromatic compounds meet these conditions well.

In the batch process, the reactants and the azeotropic agent is added to a reactor to the To stir reaction at the azeotropic temperature while the water is removed and the azeotropic agent recy celt. At the end of the reaction, the product and the azeotropic agent separated by fractional distillation, to obtain products with high purity. At the continu On the one hand, the initial process becomes the starting material fed with a given flow rate and others on the other hand, the water is continuously at the top of the Fractionator withdrawn during the reaction process. The azeotropic agent is recycled while the reaction system containing the products (PGEA, PGEP, PGPA or PGPP) in contains a predetermined concentration and in the Reactor is included in a rectification tower over will carry around with a fractional distillation continue, so a small proportion of unresponsive ten ethers and acids is removed. This will be a Obtained product of high purity.

In the manufacturing process for the new Propy  Glycol monoalkyl ether ester compounds are allowed to Starting materials, such as PGE or PGP and vinegar or Propionic acid at an elevated temperature above 80 ° C in the presence of an acid catalyst and a Azeotropic agent react, thus an esterification takes place to generate crude PGEA, PGEP, PGPA or PGPP. The products are then separated by rectification, to remove unreacted acids and the water produced to provide PGEA, PGEP, PGPA or PGPP with high purity receive.

For the starting materials, the molar behavior is of PGE or PGP to acetic or propionic acid in all common in the range between 0.6 to 3.0, preferably in the range Range between 1.1 to 1.5, being opposite to PGE or PGP the acetic or propionic acid is present in excess. If the molar ratio is less than 0.6 or greater than Is 3.0, generates a portion of the reaction system after the reaction has expired, to a great extent remains, that did not react, so not only a bigger one Energy consumption required in the rectification process is necessary, but also the required rectification time is increased, which reduces productivity. If the excess of acetic or propionic acid is too large, namely, the molar ratio is less than 0.6 drops the reaction rate significantly. The reason here for is not clear, however, it is believed that the acidic Catalyst is subject to buffering.

The catalysts of the invention include organic acids such as sulfuric acid, hydrochloric acid and Phosphoric acid and organic acids such as oxalic acid, Citric acid, p-toluenesulfonic acid, methanesulfolic acid where the strong acids, such as sulfuric acid, p- Toluene sulfonic acid and methanesulfonic acid are preferred. The boiling points of the propylene glycol monoalkyl ether ester ver compounds obtained according to the present invention are at 155 ° C for PGEA, 170 ° C for PGEP, 175 ° C  for PGPA and 190 ° C for PGPP.

The metabolic substances of the invention obtained products show a lower toxicity for the genitals. The NOEL (No Observal Effect Le vel) as defined by the Environment Protection Agency of USA is published for the E and P series the ester at Karnickeln 30 or 3000 ppm. The invention proper ester compounds belong to the P series and very rarely affect the sexual organs.

Furthermore, the new products show a better Lös for different resins. For example, has übli Propylene glycol monomethyl ether ether acetate a limit Solubility of 70% for alkyd resins, while the new ones Products have a solution limit of over 90%, which means excellent solvent is available.

In the method according to the invention, if the Reaction is complete, the reaction system one be subjected to double rectification. The first Rectification consists in a dehydration process and a deacetification process. To increase the effect To save energy, it becomes an azeotrope Agent in the form of an aromatic organic solution by means such as benzene, toluene, xylene or cyclohexane in in an amount between 6% and 30% based on the mixed Starting material added to the azeotropic temperature to decrease in rectification. For the second Rectification are just two components of ether and Ester remained, due to the different Boiling temperatures of both components readily full can be continuously fractionally distilled, creating a Product with very high purity is obtained.

The invention will now be described with reference to the following Examples are described in detail.

example 1

Into the reactor with a volume of 3 liters were Added 1392 ml of PGE and 572 ml of acetic acid. After passing through 200 ml of xylene and 10 g of p-toluenesulfonic acid are mixed added. Then the temperature on the Refluxtempe temperature of 140 ° C brought to the reaction for five hours to drain long. During this period finds the dehydration at the same time in favor of the reaction step instead. The reaction solution was by gas analyzed and it became the following composition:

PGEA | 65.49% PGE 20.46% acetic acid 5.35% xylene 8.21% water 0.49%

This solution was still a double rectification and it became PGEA with a purity of better obtained as 99.9%.

This PGEA compound was characterized by NMR'H spectrum as shown in Fig. 1 and by mass spectrograph as shown in Fig. 2, from which the chemical structure was determined as follows.

Example 2

Into the reactor with a volume of 3 liters were Added 1392 ml of PGE and 572 ml of acetic acid. After passing through  10 g of p-toluenesulfonic acid were added. thereupon the temperature was raised to the reflux temperature of 98.5 ° C brought to expire the reaction for five hours to let. It was not possible to turn off the aqueous layer because no azeotropic agent was added so that soon a state of equilibrium was reached. The Reak mixture was analyzed by gas chromatograph and the following composition resulted:

PGEA | 41.27% PGE 37.74% acetic acid 15.32% water 5.67%

Example 3

Into the reactor with a volume of 3 liters were Added 1392 ml of PGE and 746 ml of propionic acid. After Mixing was 200 ml of xylene and 10 g of p-toluenesulfone added acid. Then the temperature was on the Reflux temperature of 145 ° C brought to the reaction five Expire for hours. During this time found the dehydration at the same time in favor of progress in the reaction instead. The reaction mixture was washed with Gas chromatograph analyzed and it was the after standing composition determined:

PGEA | 64.78% PGE 19.53% propionic 6.58% xylene 8.57% water 0.54%

This solution was additionally a double rectifika PGEP with a purity better than 99.9% was obtained.  

This PGEP compound was characterized by NMR'H spectrum as shown in Fig. 3 and mass spectrum as shown in Fig. 4, whereby the chemical structure was determined as follows.

Example 4

Into the reactor with a volume of 3 liters were Added 1392 ml of PGE and 746 ml of propionic acid. After By mixing, 10 g of p-toluenesulfonic acid was added. Then the temperature was added to the reflux temperature the azeotropic temperature of 103.5 ° C for water and Propionic acid brought to the reaction for five hours to expire. It was impossible, the aqueous layer to separate, since no azeotropic agent was added, so that a state of equilibrium was easily reached. The Reaction mixture was analyzed by gas chromatography analy and the following constituents were determined:

PGPA | 40.58% PGE 36.39% propionic 18.45% water 4.58%

Example 5

Into the reactor with a volume of 3 liters were Added 1600 ml of PGP and 572 ml of acetic acid. After the through Mixture were 200 ml of xylene and 10 g of p-toluenesulfonic acid added. Then the temperature was on the reflux temperature of 147 ° C brought to the reaction five hours to drain the long. During this period  The dehydration was always in favor of the reaction step instead. The reaction mixture was by gas analyzed and it became the following composition:

PGPA | 64.45% PGP 21.35% acetic acid 5.03% xylene 8.6% water 0.57%

This solution was additionally supplemented by 2-fold rectifika treats PGPA with a purity better than 99.9% was obtained.

This PGPA compound was characterized by a NMR'H spectrum as shown in Fig. 5 and a mass spectrogram as shown in Fig. 6, whereby the chemical structure could be determined as follows.

Example 6

Into the reactor with a volume of 3 liters were Added 1600 ml of PGP and 572 ml of acetic acid. After the through Mixture 10 g of p-toluenesulfonic acid were added. thereupon the temperature was raised to the reflux temperature of 107.5 ° C brought to expire the reaction for five hours to let. It was impossible to remove the aqueous layer because no azeotropic agent was added so that easily a state of equilibrium has been reached. The reaction mixture was analyzed by gas chromatography and it the following components were determined:

PGPA | 40.60% PGP 40.29% acetic acid 14.54% water 4.57%

Example 7

Into the reactor with a volume of 3 liters were Added 1600 ml of PGP and 746 ml of propionic acid. After Mixing was 200 ml of xylene and 10 g of p-toluenesulfone acid added. Then the temperature was raised to the Re temp temperature of 150 ° C brought to the reaction five Expire for hours. During this period found the dehydration at the same time in favor of the reaction progress. The reaction solution was by gas analyzed and it became the following Components determined:

PGPP | 63.80% PGP 20.67% propionic 6.28% xylene 8.65% water 0.60%

This solution was additionally supplemented by 2-fold rectifika tion, which PGPP with a purity of better was obtained as 99.9%.

This PGPP compound was characterized by NMR'H spectrum as shown in Fig. 7 and by mass spectrogram as shown in Fig. 8, thus determining the chemical structure as follows.

Example 8

Into the reactor with a volume of 3 liters were Added 1600 ml of PGP and 746 ml of propionic acid. After Mixing 10 g of p-toluenesulfonic were added ben. Then the temperature was at the reflux temperature at the azeotropic temperature of 103.5 ° C for water and Propionic acid brought to the reaction for five hours to expire. It was impossible, the aqueous layer to separate, since no azeotropic agent was added, so that a state of equilibrium was easily reached. The Reaction mixture was analyzed by gas chromatography analy and the following constituents were determined:

PGPP | 40.47% PGP 37.96% propionic 16.97% water 4.60%

Claims (9)

1. Propylene glycol monoalkyl ether ester compounds having the general formula: wherein R₁ represents an ethyl or propyl group and R₂ represents a methyl or ethyl group. 2. Propylene glycol monoalkyl ether ester compounds according to claim 1, characterized by the reaction between Propy glycol monoalkyl ethers and an organic acid which is selected from a group, containing acetic acid and propionic acid. 3. A process for the preparation of propylene glycol monoalkyl ether ester compounds according to claim 1, comprising the steps of:
it is propylene glycol monoalkyl ether and the organic acid at an elevated temperature above 80 ° C him presence of an acidic catalyst and azeo tropic agent to promote the esterification react to produce crude propylene glycol monoalkylesteretherver compounds and
the unreacted acid and water are removed by distillation to obtain propylene glycol monoalkyl ether ester compounds of high purity. 4. The method of claim 3, wherein the molar Ratio between propylene glycol monoalkyl ether and the organic acid is in the range between 0.6 to 3.0. 5. The method of claim 3, wherein the catalyst  a strong acid is selected from a group is the sulfuric acid, p-toluenesulfonic acid and methanesul Contains fonic acid. 6. The method of claim 3, wherein the azeotropic Benzene, toluene, xylene and cyclohexane. 7. The method of claim 6, wherein the azeotropic Agent in an amount between 6% by volume and 30% Volume percent based on the sum of the propylene glycol monoalkyl ester ether compounds and the organic acid is used. 8. Use of propylene glycol monoalkyl ethers Sterverbindungen according to claim 1 as a solvent. 9. Use according to claim 8 as a solvent for Paints, paints, inks, adhesives, detergents and like.