Low color tall oil rosin

Abstract

The present invention is directed to tall oil rosin in solid, crystalline form. The tall oil rosin according to the present invention has a very low color, i.e. it is essentially color-less. The present invention is also directed to a process for producing the tall oil rosin and to the use of the tall oil rosin according to the present invention.

Description

[0001] LOW COLOR TALL OIL ROSIN

[0002] Field of the invention

[0003] The present invention is directed to tall oil rosin in solid, crystalline form. The tall oil rosin according to the present invention has a very low color, i.e. it is essentially color-less. The present invention is also directed to a process for producing the tall oil rosin and to the use of the tall oil rosin according to the present invention.

[0004] Background

[0005] During production of Kraft pulp, black liquor is formed and removed from the produced pulp. The removed black liquor comprises soap which needs to be separated from the black liquor since the soap comprises valuable wood extractives. The black liquor is concentrated by evaporation and the black liquor soap is skimmed off and acidulated to make crude tall oil (CTO). Another reason to separate the soap from the black liquor is that the soap may cause problems during subsequent treatment steps of the black liquor.

[0006] The separated soap comprises extractives, water, lignin, inorganic compounds, fibers and some black liquor. The fatty and rosin acids of crude tall oil (CTO) are in the form of sodium salts in the soap. The amount of each component in the soap depends on the raw material, as well as seasonal variations thereof, used pulping process and on the process in which the soap is separated from the black liquor, i.e. the soap skimming process. The CTO is mainly composed of fatty acids (TOFA), rosin acids (TOR) and unsaponifiables.

[0007] Currently tall oil rosin (TOR) is produced in high-temperature vacuum distillation of crude tall oil (CTO). Typical products are heads, tall oil fatty acids (TOFA), distilled tall oil (DTO), tall oil rosin (TOR), and tall oil pitch (TOP). During a CTO distillation a large fraction of TOP is produced.

[0008] There are several parameters to grade TOR, including color, softening point, acid number and fatty acid content. The color is often the most important parameter, and it is desirable for the TOR to have as little the color as possible. A low color corresponds to a high quality of the rosin. Currently, the only viable way of impacting the color of rosin is to take out a smaller, cleaner TOR fraction during the vacuum distillation and thereby enlarge the pitch fraction that is taken out from the bottom of the distillation column. This will lower the yield of the rosin, but even in the case of bleeding some of the rosin into the pitch fraction, the color of the rosin is still yellowish at best. The topgrade TOR has a color value between 3-5 on the Gardner scale.

[0009] Bulk TOR is currently delivered either in liquid form in heated containers or as solidified material in metal drums. Delivering in heated containers over great distances induces cost and while kept hot the material slowly picks up more color. On the other hand, metal drums need to be peeled off and the solid block of rosin needs to be crushed and melted, which will also initiate the color increase. The logistics of bulk volumes of high-grade rosin is cumbersome.

[0010] There is a need for higher-quality rosin, ideally in a form that allows for easier storage and transportation.

[0011] Summary of the invention

[0012] It has surprisingly been found that higher-quality rosin, in crystalline form, can be obtained. By fractionating a purified crude tall oil having a high acid number by vacuum distillation, followed by re-crystallizing the rosin fraction, a colorless rosin in solid crystalline form can be obtained. The rosin crystals are stable when stored and can be transported without heating. The rosin can be used for example in lubricating compositions, adhesives, for paper sizing, in paint and in printing inks. Rosin can also be used as a glazing agent for pharmaceutical formulations and as an additive in chewing gum.

[0013] Thus, the present invention is directed to tall oil rosin in crystalline form having a softening point in a range of from 80°C to 90°C and / or having Gardner Color Number of 2 or less, determined by comparing a sample of the tall oil rosin to standards for Gardner Color scale.

[0014] The present invention is also directed to a use of the tall oil rosin in crystalline form in the preparation of lubricating compositions, adhesives, compositions for paper sizing, paint and printing inks. The present invention is also directed to a use of the tall oil rosin in crystalline form as a glazing agent for pharmaceutical formulations and as an additive in chewing gum.

[0015] The present invention is also directed to a process for preparing tall oil rosin in crystalline form comprising the steps of a) providing tall oil having an acid number of at least 175; b) subjecting the tall oil from step a), or a derivative of the tall oil from step a), to distillation; c) recovering at least one rosin fraction from step b); d) subjecting the rosin fraction from step c) to re-crystallization from a mixture of an alcohol and water, to obtain tall oil rosin in crystalline form, wherein the tall oil rosin in crystalline form has a softening point in a range of from 80°C to 90°C and / or has a Gardner Color Number of 2 or less, determined by comparing a sample of the tall oil rosin to standards for Gardner Color scale. Detailed description

[0016] Tall oil having an acid number of at least 175 can be produced according to methods known in the art, such as through methods disclosed in WO 2022 / 269449 A1. The tall oil has an acid number of at least 175, preferably at least 180 or at least 185 or at least 188. The tall oil acid number can be determined using methods known in the art. The acid number corresponds to the amount of potassium hydroxide in milligrams needed to neutralize 1 g of tall oil.

[0017] The tall oil having an acid number of at least 175 can optionally be derivatised or chemically modified before the distillation step. Such derivatisation or chemical modification can for example be hydrogenation or esterification. Preferably, the tall oil is not subjected to derivatisation or chemical modification before the distillation step. Thus, the tall oil rosin according to the present invention is preferably not chemically modified, i.e. it is not in hydrogenated form or esterified.

[0018] The distillation of the tall oil having an acid number of at least 175, or a derivative of the tall oil having an acid number of at least 175, can be carried out using methods known in the art. Preferably, the distillation can be carried out as vacuum distillation, i.e. distillation under reduced pressure.

[0019] At least one rosin fraction is recovered as a product from the distillation. The product can be collected from the distillation using methods known in the art, such as vacuum distillation.

[0020] The rosin fraction is subjected to re-crystallization using a mixture of an alcohol and water. The alcohol is preferably methanol, ethanol and / or isopropanol. Most preferably, the alcohol is methanol. The mixture of rosin and alcohol preferably comprises 0.1 weight-% to 25 weight-% water, such as 0.1- 10 weight-% or 1-10 weight-% water or 5-10 weight-% water, based on the total weight of the mixture. The rosin crystallization can be performed using methods known in the art, including cooling, concentration by removing some of the solvent by distillation, evaporation to dryness followed by introduction of a solvent or solvent mixture in which the rosin only dissolves at elevated temperature followed by cooling or through seeding with rosin crystals or by adding antisolvent. The precipitation or crystallization may occur after a step of evaporating, such as distilling off, some of or all of said solvent. Alternatively, another solvent, such as an anti-solvent, may be added to facilitate precipitation or crystallization of the rosin, optionally in combination with seeding.

[0021] Preferably, the re-crystallization is carried out by mixing the rosin fraction from step b) with the mixture of alcohol and water and heating the mixture until the rosin fraction is dissolved. Preferably, the mixture of the rosin fraction from step b) and the mixture of alcohol and water is heated to a temperature in the range of from 40°C to 90°, more preferably to a temperature in the range of from 50°C to 80°C. When the rosin fraction has been dissolved, the temperature of the mixture is reduced, preferably to a temperature in the range of from 1°C to 15°C, such as from 1 °C to 10°C until crystals are formed. Typically, the crystal formation may take from 30 minutes to 10 hours, such as from 2 hours to 5 hours. The solid crystals can then be removed from the liquid by methods known in the art, such as by filtration or centrifugation, and then preferably washed and dried.

[0022] The tall oil rosin in crystalline form has a Gardner Color Number of 2 or less, determined by comparing a sample of the tall oil rosin to standards for Gardner Color scale. The comparison can be carried out using a BYK instrument. Preferably, the tall oil rosin in crystalline form has a Gardner Color Number of 1 or less.

[0023] Typically, the tall oil rosin comprises abietic acid in an amount of from 45 weight-% to 65 weight-%, dehydroabietic acid in an amount of from 15 weight-% to 27 weight-%, palustric acid in an amount of from 8 weight-% to 20 weight-%, isopimaric acid in an amount of from 4 weight-% to 8 weight-%, pimaric acid in an amount of from 0.8 weight-% to 2.4 weight-%, neoabietic acid in an amount of from 0.5 weight-% to 3 weight-%, and sandaracopimaric acid in an amount of from 0.4 weight-% to 0.9 weight-%, based on the total weight of the tall oil rosin. Preferably, the tall oil rosin comprises less than 1.0 weight-% of components other than abietic acid, dehydroabietic acid, palustric acid, isopimaric acid, pimaric acid, neoabietic acid, and sandaracopimaric acid. Thus, the combined amount of abietic acid, dehydroabietic acid, palustric acid, isopimaric acid, pimaric acid, neoabietic acid, and sandaracopimaric acid in the tall oil rosin is preferably at least 99.0 weight-%, preferably at least 99.5 weight-%.

[0024] The tall oil rosin in crystalline form according to the present invention has a softening point in a range of from 80°C to 90°C, such as in a range of from 82°C to 89°C or in a range of from 84°C to 88°C or about 86°C. The softening point can be determined using a Mettler Toledo DP70 instrument, with the following parameters: start temperature 50°C, heating rate 2°C / min, end temperature 100°C, detection length 19 mm.

[0025] The process according to the present invention may be carried out as a batch process or continuously.

[0026] The rosin is useful for example in lubricating compositions, adhesives, paint and printing inks. Thus, the present invention is also directed to lubricating compositions, adhesives, paint and printing inks comprising the tall oil rosin according to the present invention. Example 1

[0027] Tall oil having an acid number of more than 175 was prepared as disclosed in WO 2022 / 269449 A1. The tall oil was subjected to vacuum distillation. From the vacuum distillation, a rosin fraction was collected.

[0028] The rosin fraction (9:1 rosin acids / fatty acids, by weight) (8.3g), methanol (23.75 ml) and water (1.25 ml) were added to a round bottle flask. The mixture was heated until all solids had been dissolved, at a temperature of 65°C. The solution was then cooled to 5 °C during 3 h.

[0029] The solid thus formed was filtered off using a pressure filter and washed with cold methanol with 5 %-v / v water (4 ml). The solid was dried by flushing with N2. Yield: 55% (4.55 g) white solid.

[0030] The solid had a Gardner Color Number of 0.5, determined according to ASTM D1544-04. The solid was in crystalline form.

[0031] The solid had the following composition: abietic acid 51.8 weight-%, dehydroabietic 22.7 weight-%, palustric acid 16.5 weight-%, isopimaric acid 6.0 weight-%, pimaric acid 1.4 weight-%, neoabietic acid 0.7 weight-%, and sandaracopimaric acid 0.7 weight-%.

[0032] The softening temperature was determined using a Mettler Toledo DP70 instrument, with the following parameters: start temperature 50°C, heating rate 2°C / min, end temperature 100°C, detection length 19 mm. It was found that the softening temperature was 86.1 °C.

[0033] In view of the above detailed description of the present invention, other modifications and variations will become apparent to those skilled in the art. However, it should be apparent that such other modifications and variations may be affected without departing from the spirit and scope of the invention.

Claims

Claims1. Tall oil rosin in crystalline form having a softening point in a range of from 80°C to 90°C and / or having Gardner Color Number of 2 or less, determined by comparing a sample of the tall oil rosin to standards for Gardner Color scale.

2. Tall oil rosin according to claim 1 , having a softening point in a range of from 80°C to 90°C.

3. Tall oil rosin according to claim 2, having a softening point in a range of from 82°C to 89°C.

4. Tall oil rosin according to claim 1 , having Gardner Color Number of 1 or less, determined by comparing a sample of the tall oil rosin to standards for Gardner Color scale.

5. Tall oil rosin according to any one of claims 1-4, wherein the amount of abietic acid in the tall oil rosin is from 45 weight-% to 65 weight-%, based on the total weight of the tall oil rosin.

6. Tall oil rosin according to any one of claims 1-5, wherein the amount of dehydroabietic acid in the tall oil rosin is in an amount of from 15 weight-% to 27 weight-%, based on the total weight of the tall oil rosin.

7. Tall oil rosin composition according to any one of claims 1-6, wherein the amount of palustric acid in the tall oil rosin is in an amount of from 8 weight-% to 20 weight-%, based on the total weight of the tall oil rosin.

8. Tall oil rosin composition according to any one of claims 1-7, wherein the amount of isopimaric acid in the tall oil rosin is in an amount of from 4 weight-% to 8 weight-%, based on the total weight of the tall oil rosin.

9. Lubricating composition, adhesive, composition for paper sizing, paint, printing ink, glazing agent for pharmaceutical formulations,or chewing gum comprising tall oil rosin according to any one of claims 1-8.

10. A process for preparing tall oil rosin in crystalline form comprising the steps of a) providing tall oil having an acid number of at least 175; b) subjecting the tall oil from step a), or a derivative of the tall oil from step a), to distillation; c) recovering at least one rosin fraction from step b) d) re-crystallizing the rosin fraction from c) from a mixture of an alcohol and water, to obtain tall oil rosin in crystalline form, wherein the tall oil rosin in crystalline form has a softening point in a range of from 80°C to 90°C and / or has a Gardner Color Number of 2 or less, determined by comparing a sample of the tall oil rosin to standards for Gardner Color scale.

11. A process according to claim 10, wherein step d) is carried out using a mixture of an alcohol and water.

12. A process according to claim 11 , wherein the alcohol is methanol.

13. A process according to claim 12, wherein step d) is carried out by mixing the rosin fraction from step c) with the mixture of methanol and water and heating the mixture to a temperature in a range of from 40°C to 90°C until the rosin fraction is dissolved, followed by reducing the temperature of the mixture to a temperature in the range of from 1 °C to 15°C, until tall oil rosin crystals are formed.