|Title of Invention||
"PROCESS FOR PRODUCING LIQUID DIBENZOATE ESTER"
|Abstract||The present invention relates to a process for the preparation of diethylene glycol dibenzoate, which is liquid at ambient temperature having high dibenzoate content and less than 10% of monobenzoate. The process comprises reacting diethylene glycol and benzoic acid in presence of an organometalhc catalyst and an azeotrope former. The use of the prepared liquid diethylene glycol dibenzoate at ambient temperature is also disclosed.|
|Full Text||FIELD OF THE INVENTION
This invention in general relates to the process of preparing a dibenzoate ester. More specifically, but without restriction to the particular embodiments hereinafter described in accordance with the best mode of practice, this invention relates to an improved process for preparation of diethylene glycol dibenzoate that is liquid at ambient temperature.
BACKGROUND OF THE INVENTION
Dibenzoate esters are widely used as a plastcizers in diversified applications such as plastics, coatings, adhesives, sealants, rubber articles etc. Plastcizers enter into a physical interaction with the polymers without reacting chemically, preferably by way of their solvent and swelling capabilities. This forms a homogeneous system resulting in optimization of mechanical properties and reduction of hardness.
In order to service a wide range of applications, plasticizers should meet a series of criteria which include requirements like the material be easily dispensable, colourless, odourless, stable to light, not degrade within reasonable storage conditions of heat and cold, and have a low volatility.
Liquid plasticizers are advantageous compared to solid ones because liquids are easier to transport and process. Their physical nature also eliminates the necessity to heat the aqueous polymer composition during or following addition of the plasticizer to ensure uniform distribution of plasticizer throughout the polymer composition and absorption of the plasticizer by the emulsified polymer particles.
Diethylene glycol dibenzoate solidifies at 28°C, which creates problems in transportation and end-use applications carried out at or below this temperature. A number of prior art publications and patents have disclosed the process for preparing such a dibenzoate ester and its blends in different ways so as to provide dibenzoate ester in a liquid form and facilitate its applications in diverse fields.
British patent No. GB 915570 issued to Raymond et al. on January 16, 1963 discloses a process of making polyalkylene glycol dibenzoates and resinous composition plasticized
therewith. The process consists of heating polyalkylene glycol (DEG, DPG, PEG) with benzoyl hahde or chlorine substituted benzoyl halide at 80-150°C and after the glycol is completely esterified, washing the ester with aqueous alkali to remove any unreacted residue. The dibenzoate ester so produced acts as a plasticizer for variety of polymeric materials like polyvinyl chloride, polyvinyl acetate, vinyl chloride-acetate copolymers, polyisobutylene, polystyrene, butadiene-styrene copolymers, polymethyl methacrylate, etc.
British Patent No. GB 1323478 pubhshed on December 16, 1970 discloses a process of preparing polyalkyleneglycol dibenzoates from benzoic acid and polyalkylene glycol, which are suitable for use as plasticizers for processing of polyvinyl chloride and polyvinyl acetate. Polyalkyleneglycol dibenzoates is obtained by reacting a glycol with benzoic acid in the presence of an acid catalyst under nitrogen atmosphere at 210-250°C. However the product is coloured and unsuitable for use as plasticizer. This invention also describes an effective process for colour removal by treating the product with acidic or basic potassium permanganate solution.
U.S. Patent No. 4112240 issued to Hulsmann et al. on September 5, 1978 discloses a process for production of dipropyleneglycol dibenzoate isomer mixture. A crude methyl benzoate containing at least 80 wt.% methylbenzoate, which is a by-product in the production of dimethylterephthalate by catalytic oxidation of p-xylene or methyl-p-toluate and esterification of the resulting acids with methanol, is contacted with dipropylene glycol commercial isomer mixture in the presence of aluminum alkoxide or an aluminum silicon alkoxide catalyst containing the group Al O Si. The product is obtained in good yield, has good color, and is useful as plasticizer for PVC.
U.S. Patent No. 4444933 issued to Columbus et al. on April 24, 1984 discloses a cyanoacrylate-based adhesive composition containing a plasticizer with reduced adhesion to skin. The plasticizer is selected from dipropylene glycol dibenzoate, diethylene glycol dibenzoate, a mixture of these two compounds, butyl benzyl phthalate, dibutyl phthalate, etc. Phthalates are undesirable because of their high volatility, hitroduction of plasticizer into the composition improves the adhesion to flexible substrate and impact resistance when bond to rigid substrate. This composition has additional advantages of easier clean up, lower cost, comparative bond strength, greater alkali & boiling water resistance.
U.S. Patent No. 5006585 issued to Debella on April 9, 1991 discloses a process for preparation of a stain resistant plasticizer composition. Esters of 2,2,4-trimethyl-l,3-pentanediol (TMPD) and benzoic acid are useful plasticizers for polyvinyl chloride and other polymers, particularly for imparting improved stain resistance to plasticized compositions. One interesting aspect of this invention is the use of basic catalysts instead of usual acidic catalysts. Base catalyzed transesterification are preferred method for preparation of TMPD dibenzoates in high yield and excellent selectivities. The transesterification is carried out to a yield of above 90% diester preferably using a combination catalyst system. This invention also reveals a comparative yield of mono and dibenzoates using several different basic catalyst systems.
U.S. Patent No. 5039728 issued to Debella on August 13, 1991 discloses a stain resistant plasticized composition comprising of at least one polymer and at least one plasticizer, wherein the plasticizer comprises from about 60% to 100% by weight of compounds selected from the group consisting of 2,2,4-trimethyl-l,3-pentanediol dibenzoate, the diester of 2,2,4-trimethyl-l,3-pentanediol and benzoic acids having from 1 to 4 alkyl substituents each containing from 1 to 4 carbon atoms, and mixtures thereof, and from 0% to about 40% by weight of compounds selected from the group consisting of monobenzoate esters of 2,2,4-trimethyl-l,3-pentanediol, mono-esters of benzoic acids having from 1 to 4 alkyl substituents each containing from 1 to 4 carbon atoms and 2,2,4-trimethyl-l,3-pentanediol, and mixtures thereof. The polymer is selected from homopolymers of vinyl chloride and copolymers of vinyl chloride and at least one mono- or di-olefinically unsaturated monomer copolymerizable therewith.
U.S. Patent No. 5153342 issued to Debella on October 6, 1992 discloses a process for preparation of a stain resistant plasticizer composition using 2,2,4-trimethyl-l,3-pentanediol (TMPD) and benzoic acid or alkyl substituted benzoic acid using one or more basic catalysts selected from the group consisting of the glycolates, amides and hydrides of the alkali and alkaline earth (excluding magnesium) metals, quaternary ammonium hydroxides and alkoxides, and combinations of sodium methoxide with glycolates, amides or hydrides of the alkali and alkaline earth (excluding magnesium) metals. The products are used as stain-resistant plasticizers for poly (vinyl chloride) and especially for poly (vinyl chloride) based floor covering compositions. Chinese patent No. CN 1158842 issued to Shungcheng et al on October 9, 1997 discloses a method of preparation of dipropylene glycol dibenzoate from dipropylene glycol (DPG) and benzoic acid in the molar ratio of 1 to 20-22 and methylbenzene amount of 8-15% as main material reflux-react at 180-220°C and in the presence of B2OH catalyst of 0.1-0.3 mol % of benzoic acid and certain amount of water for 8 hour, and then the product is distilled under reduced pressure (666.6 Pa) to extract the fraction of 210-223°C and to obtain the dipropylene glycol dibenzoate (DPGDB). Said method has high yield and purity of DPGDB, and the product is superior to common plasticizer and may be widely used in plastics and rubber industry.
U.S. Patent No. 5676742 issued to Arendt et al. on October 14, 1997 discloses mono and dibenzoate ester blends as caulk plasticizers that are bioresistant to fungal growth. This invention disclosed the relation that the addition of monobenzoate ester to a dibenzoate makes the blend fungal growth resistant and applied these blends in latex caulk, adhesive and floor polish.
U.S. Patent No. 5939239 issued to Lundy et al. on August 17, 1999 discloses a photoimageable composition containing photopolymerizable urethane oligomers and dibenzoate plasticizers which includes dipropylene glycol dibenzoate, diethylene glycol dibenzoate, polypropylene glycol dibenzoate and polyethylene glycol dibenzoate etc that is used 2-6% of the formulation and the composition thus produced shows a significant improvement in tenting strength, adhesion and stripping. It is believed that the addition of dibenzoates contributes to lower the glass transition temperature thus allowing better flow.
U.S. Patent No. 5990214 issued to Arendt et al. on November 23, 1999 discloses liquid glycol benzoate ester blends containing the di- and triethylene glycol esters of benzoic and toluic (methylbenzoic) acids, which are liquids below the freezing point of the individual constituent esters. When the present blends are used as plasticizers they can optionally include at least one additional ester that is a liquid at 25"C and is conventionally used as a plasticizer for organic polymers.
U.S. Patent No. 6184278 issued to Arendt et al. on February 6, 2001 describes liquid glycol benzoate ester blends and a polymer composition containing the same said compositions comprising mixtures of esters derived from diethylene glycol and triethylene glycol with
benzoic or toluic acid, wherein the freezing point of the ester blend is below the freezing points of the constituent esters. A third plasticizer selected from the group consisting of di(2-ethylhexyl) adipate, di(2-ethylhexyl) phthalate and dipropylene glycol dibenzoate acts as a freeze point depressant for the two solid esters and extends the useful range of the present compositions. The present liquid ester compositions are used in polyvin>'l chloride resilient flooring, latex adhesive and latex caulk applications.
PCT application No. WO03020814 issued to Arendt et al. on March 13, 2003 discloses the addition of at least 20 weight percent of a specified class of monobenzoate to a dibenzoate that freeze at 28°C or above results in a mixture that is both a liquid at this temperature and an unexpectedly effective plasticizer for many organic polymers. The plasticized polymer compositions are useful in various end use applications including adhesives and caulks.
U.S. Patent No. 6583207 issued to Arendt et al. on June 24, 2003 discloses the addition of at least about 30 weight percent of diethylene glycol monobenzoate or dipropylene glycol monobenzoate to diethylene glycol dibenzoate, which is a solid at 28^0 results in a mixture that is unexpectedly a liquid at this temperature. The resultant mixtures are effective plasticizers for aqueous polymer compositions including adhesives and caulks.
The present invention provides an improved process to prepare dibenzoate ester, which is liquid at ambient temperature having high dibenzoate content that can effectively be used as a plasticizer at ambient temperature. Furthermore the preparation process is simple, meets ecological requirements and avoids the formation of hazardous byproduct.
STATEMENT OF THE INVENTION
The Present invention provides a process for producing a liquid dibenzoate ester comprising reacting dialkylene glycol and benzoic acid in the presence of an organometallic catalyst and an azeotrope former, wherein the dibenzoate ester has a liquid consistency at less than 28°C.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to improve upon limitations in the prior art. These and other objects are attained in accordance with the present invention wherein there is
provided an improved process for preparation of diethylene glycol dibenzoate which has a liquid consistency below 28°C.
It is the principal aspect of the present invention to provide a process for preparation of liquid diethylene glycol dibenzoate, wherein the prepared liquid comprises less than 10% monobenzoate to make the resultant dibenzoate liquid at ambient temperature.
It is another aspect of the invention to provide a process for preparation of liquid diethylene glycol dibenzoate, wherein the process comprises, reacting diethylene glycol and benzoic acid in presence of an organometallic catalyst and an azeotrope former.
It is yet another aspect of the invention to provide a process for preparation of liquid diethylene glycol dibenzoate, wherein the liquid comprises at least 85% of diethylene glycol dibenzoate.
It is still another aspect of the invention to provide a process for preparation of liquid diethylene glycol dibenzoate, which is liquid below 28°C and applicable as an effective plasticizer in water based adhesive comprised of poly (vinyl acetate) as main binder.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a process for the preparation of liquid dialkylene glycol dibenzoate, which is liquid at ambient temperature having high dibenzoate content that can effectively be used as a plasticizer at ambient temperature. The process disclosed herein is simple, meets ecological requirements and avoids the formation of hazardous by-products.
A specific class of ester plasticizers comprises diols or ether diols, namely ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol etc. as alcohol component. In addition of reaction of an alcohol and acid in presence or absence of an acid catalyst, further processes include reaction of diols with acid halides, transesterification of a carboxylic acid with diol and addition of ethylene oxide with carboxylic acids (ethoxylation).
The choice of catalyst and method of water removal are very important process features of this reaction, as these influence the optical properties of the final products. The structure of
the starting materials e.g. alcohol and acid influence the mechanical and thermal properties of the plasticizers. Various methods of removing the water of reaction formed by the reaction of ethylene glycol (and oligomers) and carboxylic acids are known, however preference is given to the process. The process comprises azeotropic distillation in presence of a water immiscible solvent, heating the reaction mixture while passing an inert gas through it and finally reacting the glycol and acid under reduced pressure.
The process disclosed in the present invention provides a process for preparing liquid dibenzoate ester composition for use as a plasticizer by reacting dialkylene glycol and benzoic acid in presence of an entrainer for removal of water formed during the reaction as an azeotropic mixture. The reactor also contains a catalyst and an antioxidant. Antioxidant prevents the oxidation and colour generation of the final product. All the reactants are initially mixed under nitrogen atmosphere at 70°-90*'C, temperature is then gradually raised and reactants are allowed to reflux-react up to a temperature of 225°C. The progress of the reaction is monitored by measuring both the acid value of the reaction mixture and the volume of condensed water. The reaction is then continued under vacuum until the desired acid and hydroxyl value is reached.
The said dialkylene glycol is selected from diethylene glycol, dipropylene glycol or a mixture thereof and the entrainer used is xylene, toluene or a mixture thereof The catalyst used in the present process is an organometallic compound based on tin, lead, arsenic, titanium, zirconium or aluminum as the metal component and phosphorus or nitrogen or oxygen containing compounds as the organic component. The antioxidant is selected from the group consisting of triphenyl phosphate or cobalt acetate depending on the specific catalyst used.
The examples mentioned below explain the aspects of the present invention. The examples are given to illustrate the details of the invention and should not be construed to limit the scope of the present invention.
Preparation of diethylene glycol dibenzoate
A round bottom four-necked flask equipped with a variable drive agitator, a thermometer and
a reflux condenser contains diethylene glycol and benzoic acid in a molar ratio of 0.52:1. The
flask also contains 11 wt % of xylene as an azeotrope former based on the total charge of diethylene glycol and benzoic acid. A dean-stark apparatus is fitted with the flask to facilitate the removal of water formed during the reaction. Triphenyl phosphate is added in the flask along with an organotin catalyst. Both of these additives are present 0.05% by weight based on total weight of diethylene glycol and benzoic acid. Nitrogen is purged in the flask to maintain an inert atmosphere. All the ingredients are allowed to mix at a temperature of 70-90°C for 2-3 hours. The temperature is then slowly raised to 225°C in 24 hours time. The progress of reaction is monitored periodically measuring both the acid value of the reaction mixture and the volume of condensed water collected in the trap. The mass is allowed to react at this temperature for 4-6 hours and reaction is continued under 690-730 mm Hg pressure until the desired acid value and hydroxyl value is reached. The acid value of the final dibenzoate ester composition is found to be 1.2 and hydroxyl value is 1.1.
Application in latex adhesives
This example demonstrates the application of the liquid dibenzoate ester composition prepared above as a plasticizer in water based adhesive comprised of poly (vinyl acetate) as the main binder.
A latex adhesive is used to adhere a porous substrate to a porous or non porous substrate. The adhesive may consist of a homopolymer or a copolymer as the main binder and used for diversified applications. A plasticizer performs several fiinctions in a latex adhesive system. These include thickening of base emulsion, increase in flexibility, reduction in Glass transition temperature, improved adhesion & performance at low temperature.
Preparation of emulsion: 6.5% partially hydrolyzed poly (vinyl alcohol) solution in water is prepared in a beaker. 10% of vinyl acetate monomer is taken in a four necked reactor. Freshly prepared polyvinyl alcohol solution is added in the reactor along with a non-ionic emulsifier (1% by wt. of monomer), a defoamer (0.05% by wt. of monomer) and the pH of the mixture is adjusted to 8-8.5 by adding sodium bicarbonate solution along with one third of the total quantity of potassium persulphate initiator (5% solution in water). The reactor is fitted with a stirrer, a reflux condenser and a feeding funnel. The reactor is placed in v/ater bath and is heated to maintain a temperature of 74-80°C. with Continous addition of test of the monomer
and intermittent addition of initiator. The feeding time is 5-6 hours. After the addition is completed, temperature is maintained at 81-82°C for 1 hour. The material is allowed to cool below 60°C. Benzoate plasticizer (2%) and coalescing agents e.g. n-butanol (1%), 2 ethyl hexanol (1%) are added in the emulsion and finally formalin is added as a preservative. Several tests of this emulsion are performed.
Appearance: The material is swirl in the container and the colour of the product is examined visually.
Film clarity: A small amount of emulsion is taken on a glass plate and applied on it by a 150° applicator. The film is then allowed to dry at room temperature. After complete drying the film clarity is checked.
meter. The pH meter is standardized by using standard buffer solution at 25°C. The pH of the
pH: The pH of the emulsion is determined by using standard glass electrode attached to a pH meter. The pH meter is standardized by using standard bufj emulsion is tested by dipping the electrode in the emulsion.
Non-volatile content: 1-2 gram of emulsion is accurately weighed in an aluminum foil. The foil is kept in an oven maintained at 105°C for 3 hours. It is then taken out, allowed to cool to room temperature in a dessicator. The foil is then re weighed and nonvolatile content is calculated.
Viscosity: The viscosity of the emulsion is measured by using a Brookfield viscometer (RVT) at 25°C using spindle No. 7 at 20 rpm.
Bond strength: The adhesive is coated on 2 cm X 2 cm area on one end of two teak wood pieces of size 10 cm X 2 cm X 0.4 cm. The surface to be coated is smoothen using sand paper of grid number 50. The pieces are joined at the coated end, uncoated ends remaining in opposite direction. The coated ends are clamped for 24 hours at 25°C. The clamp is then removed and strength is checked using tensile testing machine, which is operated at 50 mm/minute. An average of 30 samples are checked.
%Wood failure: A pair of shisum wood pieces of size 25 cm X 5 cm X 5 cm is selected and one side of the wood is smoothen by using sand paper (grid number 50). Adhesive is then
applied on the smooth side of both the pieces. The coated ends are then clamped for 24 hours.
The joined surfaces are then separated using a chisel and the area of wood failure to total
coated area is measured. An average of 30 samples are tested. The results of all the above
tests are given below.
Appearance : white viscous emulsion
Film clarity : clear
pH : 4.35
Non-volatile content : 43
Viscosity(poise) : 330
Bond strength : 250 kg/inch2
%Wood failure : 5%
Those who are skilled in this art would recognize that the use of the plasticizer of present invention can be extended to other applications, including but not limited to poly (vinyl chloride), cyanoacrylate adhesive, vinyl acetate based latex adhesive, latex caulks, neoprene and nitrile rubber based compounds.
Certain modifications and improvements of the disclosed invention will occur to those skilled in the art without departing from the scope of invention, which is limited only by the appended claims.
1. A process for producing a liquid dibenzoate ester comprising reacting dialkylene glycol and benzoic acid in the presence of an organometallic catalyst and an azeotrope former, wherein the dibenzoate ester has a liquid consistency at less than 28°C.
2. The process according to claim 1, wherein the dibenzoate ester is dialkylene glycol dibenzoate.
3. The process according to claim 1, wherein the dialkylene glycol is diethylene glycol or dipropylene glycol or any mixture thereof.
4. The process according to claim 1, wherein the organometallic catalyst used is based on arsenic, tin, lead, titanium, zirconium or alum.inum as the metal component and phosphorus or nitrogen or oxygen containing groups as the organic component.
5. The process according to claim 1, wherein the azeotrope former is selected from a group comprising toluene, o-xylene, m-xylene, p-xylene or a mixture thereof
6. The process according to claim 1, wherein the liquid dibenzoate ester comprises less than 10% monobenzoate.
7. The process according to claim 1, wherein the liquid dibenzoate ester comprises more than 85% dibenzoate.
8. The use of liquid dibenzoate ester prepared by the process according to claim 1 as a plasticizer for poly (vinyl chloride), cyanoacrylate adhesive, vinyl acetate based latex adhesive and textile finishing agent, latex caulks, neoprene rubber and nitrile rubber.
9. A process for producing a liquid dibenzoate ester as substantially herein described with reference to the examples.
|Indian Patent Application Number||2178/DEL/2004|
|PG Journal Number||47/2010|
|Date of Filing||01-Nov-2004|
|Name of Patentee||JUBILANT ORGANOSYS LIMITED|
|Applicant Address||PLOT 1A, SECTOR 16A, NOIDA-201 301, U.P., INDIA.|
|PCT International Classification Number||C07C 069/78|
|PCT International Application Number||N/A|
|PCT International Filing date|