WO2000075252A1

WO2000075252A1 - Process for producing light color dimer acids from the dimerization of unsaturated fatty acids

Info

Publication number: WO2000075252A1
Application number: PCT/US2000/014911
Authority: WO
Inventors: Michael D. Sublett; C William Blewitt
Original assignee: Cognis Corp
Current assignee: Cognis Corp
Priority date: 1999-06-04
Filing date: 2000-05-31
Publication date: 2000-12-14
Anticipated expiration: 2001-12-04
Also published as: AU5306200A

Abstract

It has been found that producing dimer acid by carrying out the dimerization reaction with an initial starting pressure above atmospheric pressure, with the initial pressure being created by the use of an inert gas, produces lighter colored product as compared to conventional methods of producing dimer acid. The present invention is a process for making dimer acid by reacting unsaturated fatty acids in a reaction zone where the initial starting pressure of the reaction zone is above atmospheric pressure before initiating the oligomerization of the unsaturated acids, with this initial pressure being created by the use of an inert gas. The process consists of providing a mixture of unsaturated fatty acid and an effective amount of dimerization catalyst and other optional reactants in a reaction zone, removing air, pressurizing the reaction zone with an inert gas to a pressure above atmospheric and then carrying out the dimerization of the fatty acid.

Description

PROCESS FOR PRODUCING LIGHT COLOR DIMER ACIDS FROM THE DIMERIZATION OF UNSATURATED FATTY ACIDS

BACKGROUND OF THE INVENTION Field of the Invention

This invention relates to a process for producing a light colored dimer acid

by carrying out the dimerization reaction in a pressured inert gas atmosphere.

DESCRIPTION OF RELATED ART

Dimer acid, and preparation thereof has been known for some time.

Processes for dimerizing monounsaturated fatty acids, such as oleic acid and

polyunsatu rated acids, such as linoleic and linolenic, a mixture of which with

oleic acid is found in tall oil acids, have been described in U.S. Patent No.

2,793,219, the disclosure of which is hereby incorporated by reference, and U.S.

Patent No. 2,793,220, the disclosure of which is hereby incorporated by

reference.

Dimer acids are used in a wide variety of products, such as surface

coatings, unsaturated polyesters, elastomers, lubricants and greases,

plasticizers and epoxy resins. For many uses of dimer acid a light colored

product is preferred. A lighter color dimer acid will not impart undesired color to

the end product. Standard methods for making dimer acids are well known.

These methods produce dimer acids that vary in the color of the product. Dimer

acids are discussed in Encyclopedia of Polymer Science and Technology, vol.

11 , pp. 476-489, (John Wiley & Sons, Inc. N.Y., N.Y., 1988), the disclosure of

which is incorporated herein by reference. Dimer acids are also described in

detail in U.S. Patent No. 5,138,027, the disclosure of which is incorporated herein by reference. The first step in the production of dimer acids is the

oligomerization of the unsaturated acids producing a mixture referred to as the

"Total Product". The "Total Product" is a blend of monomer acids, dibasic acids,

and polybasic acids. Monomer acids are a mixture of unreacted saturated acids,

isomerized unsaturated acids, and isomerized saturated acids. The monomer

acids are separated from the dimer acids by distillation. The dimer acid collected

from this distillation is a blend consisting mainly of dibasic acids and a small

amount of polybasic acids, usually in the ratio of 5 - 7:1 , respectively. Known

methods of production often require a bleaching step to reduce the color of the

dimer acid to an acceptable level. Additional steps such as bleaching add to the

overall time and cost of manufacturing. It is therefore desirable to produce a

dimer acid with a light color with minimal need for color lightening steps.

SUMMARY OF THE INVENTION

It has surprisingly been found that producing dimer acid by carrying out

the dimerization reaction with an initial starting pressure above atmospheric

pressure, with the initial pressure being created by the use of an inert gas,

produces lighter colored product as compared to conventional methods of

producing dimer acid. The present invention is a process for making dimer acid

by reacting unsaturated fatty acids in a reaction zone, where the initial starting

pressure of the reaction zone is above atmospheric pressure before initiating the

oligomerization of the unsaturated acids, with this initial pressure being created

by the use of an inert gas. The process consists of providing a mixture of

unsaturated fatty acid and an effective amount of dimerization catalyst and other optional reactants in a reaction zone, removing air, pressurizing the reaction

zone with an inert gas to a pressure above atmospheric and then carrying out

the dimerization of the fatty acid.

DESCRIPTION OF THE INVENTION

Except in the claims and the operating examples, or where otherwise

expressly indicated, all numerical quantities in this description indicating amounts

of material or conditions of reaction and/or use are to be understood as modified

by the word "about" in describing the broadest scope of the invention. Practice

within the numerical limits stated is generally preferred. Also, throughout this

description, unless expressly stated to the contrary, percent, "parts" of, and ratio

values are by weight; the description of a group or class of materials as suitable

or preferred for a given purpose in connection with the invention implies that

mixtures of any two or more of the members of the group or class are equally

suitable or preferred; description of constituents in chemical terms refers to the

constituents at the time of addition to any combination specified in the

description or of generation in situ by chemical reactions specified in the

description, and does not necessarily preclude other chemical interactions

among the constituents of a mixture once mixed.

It is understood that dimer acid as produced by the oligomerization of C₁₈

unsaturated fatty acids refers to a substantially C_3β aliphatic, dibasic acid. Dimer

acid is a mixture of many isomers, and four major structural types have been

identified: acyclic, cyclic, bicyclic and aromatic. In addition to the C₃₆ dibasic

acids, minor amounts of C_M+ polybasic acids are also commonly present as well as small amounts of monomer acids.

An unsaturated fatty acid is a carboxylic acid having at least one double

bond and having at least six carbon atoms. It is understood that a carboxylic

acid is any compound containing one or more carboxyl groups.

A Gardner color unit, denoted as G, is a measure of color. The higher the

Gardner number the darker or more color the substance has.

The process, according to the invention, consists of providing a mixture

of unsaturated fatty acid and an effective amount of dimerization catalyst and

other optional reactants in a reaction zone, removing air, pressurizing the

reaction zone with an inert gas to a pressure above atmospheric and then

carrying out the dimerization of the fatty acid. It is understood that a reaction

zone is the space in which the reaction takes place, example of which include

but are not limited to vessels, pipes, inline mixers or any type of containment

used to hold the reactants while the reaction proceeds to completion. The

dimerization reaction results in a mixture of monomer acids, dibasic acids and

tribasic acids and other various side products. The product of the dimerization

reaction can be enriched in dimer acid by standard separation methods,

examples of which include but are not limited to distillation and recrystallization.

After the product is enriched in dimer acid via a separation method the enriched

product can optionally be bleached to further reduce the color of the product.

The reagents are typically added to the reaction zone at ambient

temperature. The unsaturated fatty acid added is from about 85% to about 99%

of the total reactants in the reaction zone. Any source of C₁₈ unsaturated fatty

acid is within the scope of the invention. The unsaturated fatty acids can be derived from a variety of sources, examples include but are not limited to lard,

beef tallow, castor oil, canola oil, corn oil, cottonseed oil, linseed oil, palm oil, rice

bran oil, soybean oil. Particularly preferred unsaturated fatty acids are tall oil

fatty acids, oleic acid, soya fatty acid, linoleic acid and linolenic acid. Although

other unsaturated fatty acids can be used, such as C₁₆ unsaturated fatty acids,

the preferred unsaturated fatty acids are typically C₁₈ fatty acids. A typical C₁₈

fatty acid composition comprises 0.14% C₁₄, 6.97% C_1β, 0.27% C_{16 1}, 3.22 C₁₈,

49.71% C_{1β 1}, 28.56% C₁₈₂, 7.34% C₁₈₃, 0.56% C₂₀, 1.15% C₂₀₁, 0.29% C₂₂ and

0.18% C_{22 1}. The fatty acids can be mono-unsaturated, di-unsaturated or poly-

unsaturated fatty acids.

Many catalysts are well known. Examples of clay catalysts are described

in U.S. Patent 2,793,219 and US Patent 2,793,220. Other examples of

catalysts include but are not limited to lithium salt-acetic anhydride stabilized

clay, described in U.S. Patent 3,412,039, the entire contents of which are herein

incorporated by reference, synthetic magnesium silicate described in U.S. Patent

3,444,220, the entire contents of which are herein incorporated by reference and

neutral Alabama bentonite described in U.S. Patent 3,732,263, the entire

contents of which are herein incorporated by reference. Typically, the

dimerization reaction is carried out using an effective catalytic amount of a

natural acidic clay as the catalyst to bring the reaction to a desired yield. A

particularly preferred acidic clay is calcium bentonite clay. The percent of natural

acidic clay added is typically from about 1 % to about 15%, preferably from about

3% to about 7%, and even more preferably from about 3% to about 6% by

weight of the total reactants. In addition to the unsaturated fatty acid and catalyst other reagents are

optionally added. The performance of the clay catalyst can be enhanced by

adjusting the acidity of the clay. For example, an alkali has been added as a

reagent as disclosed in U.S. patent 2,955,121 , the entire contents of which are

herein incorporated by reference. Examples of bases used to adjust the acidity

of the clay catalyst include, but are not limited to, hydroxides such as sodium

hydroxide and calcium hydroxide, alkali metal salts, preferably lithium, calcium

or potassium salts. A preferred alkali metal salt is lithium carbonate (Li₂CO₃).

The addition of Li₂CO₃ to the reaction mixture improves the effectiveness of the

catalyst resulting in increased yield of dimer acid. The percent Li₂CO₃ is from 0%

to about 1.0%, preferably from about 0.03% to about 0.30%, and even more

preferably from about 0.04% to about 0.25% by weight of the total reactants.

Water is also optionally added. The percent H₂O added is from 0.0% to about

5.0%, preferably from 0.0% to about 3.5%, and even more preferably from 0%

to about 3.0% by weight of the total reactants.

The process, according to the invention, consists of providing a mixture

of unsaturated fatty acid and an effective amount of dimerization catalyst and

other optional reactants in a reaction zone, removing air, pressurizing the

reaction zone with an inert gas and then carrying out the dimerization of the fatty

acid. Air can either be removed by reducing pressure to form a vacuum or by

purging the system with an inert gas before beginning the reaction or a

combination of vacuum followed by use of an inert gas. Any gas that does not

interact with the dimerization reaction, the reactants or products of the

dimerization can be considered an inert gas for the purposes of the invention and is within the scope of the invention. Examples of the inert gas include, but

are not limited to, H₂, N₂, Helium, Argon and CO₂. The preferred inert gases are

nitrogen and H₂. When using an inert gas, the pressure in the reaction zone can

be adjusted to the desired initial starting pressure using the inert gas. The initial

pressure is typically in the range of 3 psig to about 150 psig. A preferred initial

pressure range is from about 10 psig to about 70 psig, an even more preferred

range is from about 15 psig to about 35 psig.

To carry out the dimerization reaction of the fatty acids, heat is applied

and the temperature of the reactants is increased to the dimerization reaction

temperature. The temperature is maintained in the desired range until the

desired conversion of the starting unsaturated fatty acids is reached. The %

conversion of the starting unsaturated fatty acid is determined by multiplying the

% unsaturated acid in the monomer fraction, as determined by GLC analysis,

times the % monomer collected from the distillation of the "Total Product" divided

by the % unsaturates in the feed times 100. The "Total Product" is the blend of

fatty acids initially obtained from the dimerization reaction before the isolation of

the dibasic acids. The preferred reaction temperature range is from about 220°C

to about 280°C, and even more preferably about 220°C to about 270°C.

After the dimerization reaction has been carried out to its desired level,

the crude reaction product mixture, "Total Product", can optionally be further

treated to convert soaps formed during the dimerization reaction to their

respective acids, to remove insoluble material and side products.

One method for converting the soaps formed to their respective acid is as

follows. After completion of the dimerization reaction, the reaction mixture is cooled and the pressure in the system is decreased while agitation is

maintained. The preferred cooling temperature range is from about 80°C to

about 120°C, and more preferably about 90°C to about 110°C. The pressure is

preferably reduced to less than about 10 psig. Water and a strong acid, such as

H₃PO₄, HCI, or sulfuric acid are added to the dimer mixture. When the water and

the acid for the soap conversion is added, heat is applied for a suitable amount

of time to promote the conversion. The preferred temperature range for the

conversion is from about 120°C to about 180°C, and more preferably about

140°C to about 160°C. The mixture is then cooled and filtered. The filtration

removes insolubles such as the calcium salts formed when the calcium soap was

converted to its respective acid, the clay catalyst, and any other insolubles. The

dimer acid can be optionally heated to a temperature of from about 60°C to

about 120°C preferably from about 80°C to about 100°C, to reduce viscosity of

the dimer acid thereby increasing filtration rate, and decreasing the filtration time.

The crude reaction product, "Total Product" is a mixture of monomer and

dibasic acids. Separation procedures can be performed on the crude reaction

product to separate the monomer acids and dimer acid. The separation

procedures are typically carried out until a desired amount of monomer acids are

removed. Typical methods include, but are not limited to, wiped film evaporation

and distillation. Typically, distillation is done under high vacuum, while heat and

agitation are applied. The distillation is continued until the desired removal of

monomer acids from the desired product is achieved. The monomer acids are

more volatile than the dimer acids and therefore distill off leaving the dimer acid

behind. The dimer acid product is in the distillation residue. A bleaching step can optionally be used to further lighten the color of the

dimer acid. Any method that removes color from dimer acid can be used,

generally any standard fatty acid color reduction technique can be used and is

within the scope of the invention. Examples of bleaching agents include, but are

not limited to, peroxide, sodium hypochlorite and bleaching clay. The preferred

bleaching agent is a bleaching clay such as acid-activated montmorillonite, an

example of which is GRADE 1 FILTROL™ (Engelhard Corporation, Iselin, NJ).

A typical procedure for bleaching the dimer is as follows. The distillation residue

(dimer mixture) is purged with nitrogen, while heat and agitation are applied to

remove oxygen. A strong acid, such as 75% H₃PO₄, HCI or sulfuric acid, is

added when the temperature reaches a desired level to catalyze the hydrolysis

of any anhydride to the acid form. The acid addition is followed by the addition

of a bleaching agent. The distillation residue (dimer mixture) is held at a desired

temperature for a time sufficient to reduce the color of the dimer and is then

filtered to remove insolubles. The dimer acid can be optionally heated to a

temperature of from about 70°C to about 120°C, preferably from about 90°C to

about 110°C to facilitate the filtering step. The heating reduces viscosity of the

dimer acid thereby increasing filtration rate, and decreasing the filtration time.

The following examples are meant to illustrate but not to limit the scope

of invention. Examples 1 and 2 are not within the scope of the invention and are

to be used as comparative examples. Examples 3 through 5 are illustrative of

the invention. EXAMPLE 1: COMPARATIVE EXAMPLE

DIMERIZATION:

A 1- liter autoclave was used to run the dimerization process. The C₁₈

unsaturated fatty acid (500g, 93% of total reactants) was added to the autoclave.

The composition of the C₁₈ fatty acid consisted essentially of 0.14% C₁₄, 6.97%

C₁₆, 0.27% C_{1β 1}, 3.22 C₁₈, 49.71% C₁₈₁, 28.56% C₁₈₂, 7.34% C₁₈₃, 0.56% C₂₀,

1.15% C₂₀₁, 0.29% C₂₂ and 0.18% C₂₂₁. To the C₁₈ fatty acid was added calcium

bentonite clay (22.5g, 4.5%), Li₂CO₃ (0.4g, 0.08%) and H₂O (13g, 2.6%).

Agitation was applied. The temperature was 28°C.

The initial pressure was 0 psig and heat was applied. When the pressure

reached 20 psig, the pressure was reduced to 10 psig to remove air. The

pressure was allowed to build to 80 psig and then released down to 75 psig.

Heat was applied until the temperature reached 250°C. The temperature was

maintained at 250°C for four hours.

The temperature and pressure were reduced to 150°C and less than 10

psig respectively. At 110°C, 75% H₃PO₄ (3.0ml) and H₂O (0.5ml) was added to

the autoclave. The temperature was increased to 150°C and held for 5 minutes.

The mixture was then cooled to 90°C and the contents were filtered in a heated

filter at 110°C. The resulting mixture was analyzed. The resulting product had

an acid value of 193.8 and a color of 5.2 G.

DISTILLATION:

The mixture was added to a 4-neck flask. Three of the necks contained two stoppers and a thermocouple. The fourth neck contained a Claisen

distillation head that was connected to a condenser, 90° vacuum adapter, and

a receiver, respectively. This set-up is referred to as a "monomer distillation set¬

up". The system was placed under high vacuum, and heat and stirring were

applied. The distillation was continued until the pot temperature reached 290°C.

The system was then allowed to cool under vacuum until the dimer temperature

was less then 60°C. 226.28 g of dimer acid was collected. The dimer acid had

an acid value of 194.2 and a color of 6.8 G. The dibasic to polybasic ratio was

6.6.

BLEACHING:

The dimer mixture (123.14 g) was added to a 250 ml, 4-neck flask. A

thermometer, stirrer, N₂ inlet and outlet were attached to the flask. The system

was purged with N₂, heat and stirring were applied. When the mixture reached

a temperature of 90°C, 75% H₃PO₄ (0.12g) was added. When the mixture

reached a temperature of 110°C, GRADE 1 FILTROL®, a Trademark of

Engelhard Corp., a bleaching clay (3.08g) was added. The mixture was stirred

for 30 min at 110°C. The mixture was then filtered in a heated funnel (110°C).

The resulting product had an acid value of 192.3 and a color of 6.4 G. The

dibasic to polybasic ratio was 6.4.

EXAMPLE 2: COMPARATIVE EXAMPLE

DIMERIZATION:

A 1 -liter autoclave is used to run the dimerization process. The C₁₈

unsaturated fatty acid (500 g, 94%) was added to the autoclave. The composition of the C₁₈ fatty acid consisted essentially of 0.14% C₁₄, 6.97% C₁₆,

0.27% C₁₆₁, 3.22 C₁₈, 49.71% C_{1β 1l} 28.56% C₁₈₂, 7.34% C₁₈₃, 0.56% C₂₀, 1.15%

C₂₀₁, 0.29% C₂₂ and 0.18% C₂₂₁. To the C₁₈ unsaturated fatty acid was added

calcium bentonite clay (22.5g, 4.5%), Li₂CO₃ (0.4g, 0.08%) and H₂O (13g, 2.6%).

Agitation was applied. The temperature was 22°C. The system was purged

with nitrogen gas for fifteen minutes.

The initial pressure was 0 psig and heat was applied. When the pressure

reached 20 psig, the pressure was reduced to 10 psig. The pressure was

allowed to build to 80 psig and then released down to 75 psig. Heat was applied

until the temperature reached 250°C. The temperature was maintained at 250°C

for four hours. The maximum pressure reached was 105 psig.

The temperature was then reduced to 150°C, and the pressure was

reduced to less than 10 psig. The reactants were then cooled to 100°C and 4.0

ml of 75% H₃PO₄ and 0.7 ml of H₂O were added to the autoclave.

The temperature was increased to 150°C and held for 5 minutes. The

mixture was then cooled to 90°C and the contents were then filtered. The

resulting mixture was analyzed. The mixture had an acid value of 192.5 and a

color of 5.3 G. The mixture was 54.0% dimer acid before distillation.

DISTILLATION:

The mixture (380 g) was added to a 4-neck flask and a monomer

distillation set-up was prepared. The system was placed under high vacuum,

heat and stirring were applied. The distillation was continued until the pot

temperature reached 290°C. The system was then allowed to cool under vacuum until the dimer temperature was less then 60°C. The dimer acid had an

acid value of 194.4 and a color of 6.7 G. The dibasic to polybasic ratio was 5.8.

BLEACHING:

The dimer mixture (121 g) was added to a 250ml, 4-neck flask. A

was purged with N₂, heat and stirring were applied. At 90°C, 75% H₃PO₄ (0.12g)

was added. At 110°C, GRADE 1 FILTROL™ (Engelhard Corporation, Iselin,

NJ), a bleaching clay, (3.03 g) was added. The mixture was stirred for 30 min

at 110°C. The mixture was then filtered. The resulting product had an acid

value of 194.8 and a color of 6.6 G. The dibasic to polybasic ratio was 6.0. The

resulting product was 81.3% dibasic acid after bleaching.

EXAMPLE 3

DIMERIZATION:

A 1 -liter autoclave is used to run the dimerization process. The C₁₈

unsaturated fatty acid (660g, 94%) was added to the autoclave. The

composition of the C₁₈ fatty acid consisted essentially of 0.14% C₁₄, 6.97% C₁₆,

0.27% C_1β:1, 3.22 C₁₈, 49.71% C_18:1, 28.56% C_18:2, 7.34% C_18:3, 0.56% C₂₀, 1.15%

C_20:1, 0.29% C₂₂ and 0.18% C_22:1. To the C₁₈ unsaturated fatty acid was added

calcium bentonite clay (29.7g, 4.5%), Li₂CO₃ (0.53g, 0.08%) and H₂0 (7.9g,

1.2%). Agitation was applied. The temperature was adjusted to 25°C. The

system was purged three times with 50-psig hydrogen gas.

The initial pressure was adjusted to 125 psig with the hydrogen gas and

heat was applied to increase the temperature to 250°C. The temperature was maintained at 250°C for four hours. The maximum pressure reached was 300

psig.

The temperature was then reduced to 150°C and the pressure was

reduced to less than 10 psig. The reactants were then cooled to 100°C and 4.0

ml of 75% H₃PO₄ and 0.7 ml of H₂O was added to the autoclave.

The temperature was increased to 150°C and held for 5 minutes. The

mixture was then cooled to 90°C and the contents were then filtered. The

resulting mixture was analyzed. The mixture had an acid value of 191.2 and a

color of 4.3 G. The mixture was 51.2% dimer acid before distillation.

DISTILLATION:

The mixture (428 g) was added to a 4-neck flask and a monomer

distillation set-up was prepared as described in example 1. The system was

placed under high vacuum, heat and stirring were applied. The distillation was

continued until the pot temperature reached 290°C. The system was then

allowed to cool under vacuum until the dimer temperature was less then 60°C.

The dimer acid had an acid value of 191.8 and a color of 6.0 G. The dibasic to

polybasic ratio was 7.0.

BLEACHING:

The dimer mixture (125 g) was added to a 250 ml, 4-neck flask. A

was added. At 110°C, GRADE 1 FILTROL™ (Engelhard Corporation, Iselin, NJ), a bleaching clay, (3.12 g) was added. The mixture was stirred for 30 min

at 110°C. The mixture was then filtered. The resulting product had an acid

value of 191.3 and a color of 5.4 G. The dibasic to polybasic ratio was 7.0. The

resulting product was 80.8% dibasic acid after bleaching.

EXAMPLE 4

DIMERIZATION:

A 1 -liter autoclave is used to run the dimerization process. The C₁₈

unsaturated fatty acid (660 g, 94%) was added to the autoclave. The

0.27% C₁₆₁, 3.22 C₁₈, 49.71% C_{18 1}, 28.56% C₁₈₂, 7.34% C₁₈₃, 0.56% C₂₀, 1.15%

calcium bentonite clay (29.7g, 4.5%), Li₂CO₃ (0.53g, 0.08%) and H₂O (7.9g,

1.2%). Agitation was applied. The temperature was adjusted to 25°C. The

system was purged three times with 50-psig nitrogen gas.

The initial pressure was adjusted to 125 psig with the nitrogen gas and

heat was applied to increase the temperature to 250°C. The temperature was

maintained at 250°C for four hours. The maximum pressure reached was 300

psig.

The temperature was then reduced to 150°C and the pressure was

reduced to less than 10 psig. The reactants were then cooled to 100°C and 4.0

ml of 75% H₃PO₄ and 0.7 ml of H₂O was added to the autoclave.

The temperature was increased to 150°C and held for 5 minutes. The mixture

was then cooled to 90°C and the contents were then filtered. The resulting mixture was analyzed. The mixture had an acid value of 192.9 and a color of 3.7

G. The mixture was 50.5% dimer acid before distillation.

DISTILLATION:

The mixture (435 g) was added to a 4-neck flask and a monomer

distillation set-up was prepared. The system was placed under high vacuum,

heat and stirring were applied. The distillation was continued until the pot

temperature reached 290°C. The system was then allowed to cool under

vacuum until the dimer temperature was less then 60°C. The dimer acid had an

acid value of 192.3 and a color of 5.6 G. The dibasic to polybasic ratio was 7.2.

BLEACHING:

The dimer mixture (128g) was added to a 250ml, 4-neck flask. A

was added. At 110°C, GRADE 1 FILTROL™ (Engelhard Corporation, Iselin,

NJ), a bleaching clay, (3.20 g) was added. The mixture was stirred for 30 min

at 110°C. The mixture was then filtered. The resulting product had an acid

value of 190.7 and a color of 4.8 G. The dibasic to polybasic ratio was 7.0. The

resulting product was 80.3% dibasic acid after bleaching.

EXAMPLE 5

DIMERIZATION:

A 1 -liter autoclave is used to run the dimerization process. The C₁₈ unsaturated fatty acid (660 g, 94%) was added to the autoclave. The

0.27% C_{1β 1>} 3.22 C₁₈, 49.71% C_{18 1}, 28.56% C₁₈₂, 7.34% C_{1β 3>} 0.56% C₂₀, 1.15%

C_{20 1}, 0.29% C₂₂ and 0.18% C_{22 1}. To the C₁₈ unsaturated fatty acid was added

calcium bentonite clay (29.7g, 4.5%), Li₂CO₃ (0.462g, 0.07%) and H₂O (6.6g,

1.0%). Agitation was applied. The temperature was adjusted to 25°C. The

system was purged three times with 50-psig nitrogen gas.

The initial pressure was adjusted to 30 psig with the nitrogen gas and

heat was applied to increase the temperature to 254°C. The temperature was

maintained at 254°C for four hours. The maximum pressure reached was 219

psig.

The temperature was then reduced to 150°C and the pressure was

reduced to less than 10 psig. The reactants were then cooled to 100°C and 4.0

ml of 75% H₃PO₄ and 0.7 ml of H₂0 was added to the autoclave.

The temperature was increased to 150°C and held for 5 minutes. The

mixture was then cooled to 90°C and the contents were then filtered. The

resulting mixture was analyzed. The mixture had an acid value of 192.0 and a

color of 3.8 G. The mixture was 50.5% dimer acid before distillation.

DISTILLATION:

The mixture (521 g) was added to a 4-neck flask and a monomer

distillation set-up was prepared. The system was placed under high vacuum,

heat and stirring were applied. The distillation was continued until the pot

acid value of 194.0 and a color of 5.7 G. The dibasic to polybasic ratio was 7.1.

BLEACHING:

The dimer mixture (143g) was added to a 250ml, 4-neck flask. A

was added. At 110°C, GRADE 1 FILTROL™ (Engelhard Corporation, Iselin,

NJ), a bleaching clay, (3.57 g) was added. The mixture was stirred for 30 min.

at 110°C. The mixture was then filtered. The resulting product had an acid

value of 192.6 and a color of 4.8 G. The dibasic to polybasic ratio was 6.7. The

resulting product was 83.1% dibasic acid after bleaching.

Claims

What is claimed is:

1. A process comprising the steps of

a) providing a mixture comprised of an unsaturated fatty acid and an

effective amount of a dimerization catalyst in an reaction zone;

b) removing air from the reaction zone and then raising the pressure in

the reaction zone above one atmosphere by pressurizing with an

inert gas;

c) carrying out the reaction to produce a product comprised of dimer

acid.

2. The process of claim 1 wherein the unsaturated fatty acid comprises C₁₈

unsaturated fatty acid.

3. The process of claim 1 wherein the unsaturated fatty acid is selected from

the group consisting of tall oil fatty acid, oleic acid, soya fatty acid, linoleic

acid, linolenic acid, acids derived from lard, beef tallow, castor oil, canola

oil, corn oil, cottonseed oil, linseed oil, palm oil, rice bran oil, soybean oil

and combinations thereof.

4. The process of claim 1 wherein the catalyst is a natural acidic clay.

5. The process of claim 4 wherein the catalyst is calcium bentonite clay.

6. The process of claim 1 wherein the temperature of the reaction is from

about 220°C to about 280°C.

7. The process of claim 5 wherein the temperature is from about 220°C to

about 270°C.

8. The process of claim 1 wherein the initial pressure of the reaction zone

is from about 3 psig to about 150 psig.

9. The process of claim 1 wherein the inert gas is selected from the group

consisting of nitrogen, hydrogen, carbon dioxide, helium argon, and

combinations thereof.

10. The process of claim 1 further comprising the step of filtering the reaction

product.

11. The process of claim 10 wherein the reaction product is heated from

about 70°C to about 120°C to facilitate the filtering step.

12. The process of claim 1 further comprising the step of distilling the reaction

product. 13. The process of claim 12 further comprising the step of bleaching the

distillation residue.

14. The process of claim 13 further comprising the step of filtering the product

of the bleaching step wherein the filtering step is carried out at from about

60°C to about 120°C.

15. The product of the process of claim 1.

16. A process comprising the steps of

a) providing a mixture comprised of a C₁₈ unsaturated fatty acid and an

effective amount of a dimerization catalyst in an reaction zone;

b) removing air from the reaction zone and then raising the pressure in

the reaction zone above one atmosphere by pressurizing with an

inert gas, wherein the inert gas is selected from the group consisting

of hydrogen, nitrogen or combinations thereof;

c) carrying out the reaction to produce a product comprised of dimer

acid.

7. The process claim 16 wherein the catalyst is calcium bentonite clay.