CA2060043A1 - Surfactants as kraft pulping additives for reject reduction and yield increase - Google Patents
Surfactants as kraft pulping additives for reject reduction and yield increaseInfo
- Publication number
- CA2060043A1 CA2060043A1 CA 2060043 CA2060043A CA2060043A1 CA 2060043 A1 CA2060043 A1 CA 2060043A1 CA 2060043 CA2060043 CA 2060043 CA 2060043 A CA2060043 A CA 2060043A CA 2060043 A1 CA2060043 A1 CA 2060043A1
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- Prior art keywords
- ethoxylated
- cooking liquor
- wood chips
- recited
- penetration
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Abstract
ABSTRACT
A composition and method for enhancing the penetration of cooking liquor into wood chips in the Kraft pulping process are disclosed. The composition comprises an amount, effective for the intended purpose of an ethoxylated isostearyl alcohol and an ethoxylated oleyl alcohol, or alternatively two ethoxy-lated dialkylphenols of different molecular weight. The method comprises administering a sufficient amount of the combined treat-ment to a sample of wood chips for which treatment is desired.
A composition and method for enhancing the penetration of cooking liquor into wood chips in the Kraft pulping process are disclosed. The composition comprises an amount, effective for the intended purpose of an ethoxylated isostearyl alcohol and an ethoxylated oleyl alcohol, or alternatively two ethoxy-lated dialkylphenols of different molecular weight. The method comprises administering a sufficient amount of the combined treat-ment to a sample of wood chips for which treatment is desired.
Description
L-h72 SURFACTANTS AS KRAFT PULPING ADDITIVES FOR
REJECT REDUCTION AND YIELD INCREASE
BACKGROUND OF THE INVENTION
In the papermaking process known as Kraft pulping, the pulp yield and reject level are a function of the degree of delignification. The lignin in wood chips is chemically attacked and split into fragments by the hydroxyl (OH-) and hydrosulfide (SH-) ions present in the pulping liquor. The lignin fragments are then dissolved as phenolate or carboxylate ;ons. This chemical reaction is known as delignificat;on.
It is believed that penetration and diffusion are two major functions involved in the delignification process. In many cases, insufficient penetration causes higher rejects and a lower degree of cooking because the cooking liquor moves much more rapidly in the longitudinal direction (by penetration) than in the transverse direction (by diffusion) of the fibers. Therefore, the reject reduction and total yield can be improved by enhancement of penetration of cooking liquor into the wood chips. Three parameters are responsible for the function of penetration. They are~
interfacial tension, (2) surface tension, and (3) contact angle.
REJECT REDUCTION AND YIELD INCREASE
BACKGROUND OF THE INVENTION
In the papermaking process known as Kraft pulping, the pulp yield and reject level are a function of the degree of delignification. The lignin in wood chips is chemically attacked and split into fragments by the hydroxyl (OH-) and hydrosulfide (SH-) ions present in the pulping liquor. The lignin fragments are then dissolved as phenolate or carboxylate ;ons. This chemical reaction is known as delignificat;on.
It is believed that penetration and diffusion are two major functions involved in the delignification process. In many cases, insufficient penetration causes higher rejects and a lower degree of cooking because the cooking liquor moves much more rapidly in the longitudinal direction (by penetration) than in the transverse direction (by diffusion) of the fibers. Therefore, the reject reduction and total yield can be improved by enhancement of penetration of cooking liquor into the wood chips. Three parameters are responsible for the function of penetration. They are~
interfacial tension, (2) surface tension, and (3) contact angle.
2~ 3 Interfacial tension may be defined as the work required to increase the unit area of an interface at constant temperature, pressure and composition. Surface tension is the interfacial tension between the liquid and the air or the solid and the air, and contact angle is defined as the angle formed by a droplet in contact with a solid surface, measured from within the droplet.
The interfacial tension between the cooking liquor and resin must be dramatically decreased in order to increase the penetration rate of cooking liquor into the wood chips. Two mechanisms are involved with the lowering of interfacial tension: deformation of resin and formation of an emulsion or microemulsion.
Low interfacial tension reduces the work of deformation necessary for resin droplets to emerge from the narrow necks of pores. A very low liquor/resin interfacial tension allows resin to move easily through the necks of pores. This mechanism can assist in the penetration of liquor into the chips.
Alternatively, a very low interfacial tension is required to form an emulsion or microemulsion of` resin in the cooking liquor.
If resin, which blocks the pores, can be emulsified by a surfactant, the cooking l;quor can pass easily through the pores. This leads to improved liquor penetration.
The increased wettability of a chip surface by a surfact~nt also creates more favorable conditions for cooking liquor pene-tratiorl. The spreading of cooking liquor on the chip surface ;s ~ 3~3 governed by the surface tension of the cooking liquor, the surface tension of the chip, and the interfacial tension between the cooking liquor and the chip. In general, the lower the surface tension of the cooking liquor, the easier spreading occurs. Ease of spreading can be accomplished by adding the proper surfactant to the cooking liquor.
SUMMARY OF THE INVENTION
The components of the present invention comprise 1) an ethoxylated isostearyl alcohol and 2) an ethoxylated oleyl alcohol, or alternatively, a combination of two ethoxylated dialkylphenols of different molecular weight. These constituents are all commercially available.
Although all of the prev;ously listed compounds are known surfactants, the effects of increasing yield and decreasing reject level upon combination of the various components have not been previously disclosed.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention consists of the addition of specific types of surfactants to the cooking liquor in order to enhance the penetration of cooking liquor into the chips, the wettability of the chips, and to prevent the redeposition of dissolved materials back onto the fibers. The advantages of adding these pulping additives are to reduce rejects and increase yield.
~ 3 The chemical structures of these surfactants are as follows:
Etho,x,,ylated Oleyl Alcohol CH3(CH2)7C=c(cH2)8~(cH2cH20)2oH
Molecular Weight - 1148 Etho,xvlated Tsoste.. a.rvl Alcohol CH3 - CH(cH2)lso(cH2cH2o) Molecular Weight = 712 EthoxY~ated DialkY.lPhenol "A".
R~ ---- 0(CH2CH20)nH
n=15 R = Nonyl group Molecular Weight = 994 Ethoxylated Dialkvlphenol "B'' R~ ~- O(CH2CH20)nH
n = 24 R = Nonyl group Molecular Weight = 1402 ~q'~
For the application of Kraft pulping additives, the effective molecular weight and effective HLB of these surfactants is in the range of 500-3000 and 8-20, respectively. It is believed that any surfactant with a similar chemical structure, molecular weight (500-3000), HLB (8-20), and possessing the function of mechanisms mentioned above will work as a Kraft pulping additive. It is also believed that the aforementioned pulping additives can be applied to sulfite pulping and semichemical pulping.
In the laboratory procedure, wood chips are first collected from a paper mill source. A sample of the wood chips to be cooked is oven dried to determine the moisture content. The amount of wood chips fed to the cooking vessel or digester is selected to provide a predetermined weight ratio of chips (dry weight) to cooking liquor.
A laboratory scale digester, equipped with temperature and pressure monitoring devices and having a capacity of 6 liters, is charged with the wood chips, alkali cooking liquor and optional surface active agent additive. The digester is heated by electricity until the target cooking temperature is achieved. The wood chips are cooked with the liquor at the temperature indicated in the closed digester.
After cooking is completed, the pressure in the digester is released.
A sample of the chips is rinsed to remove residual alkali, and the rinsed chips are allowed to drain for one hour. The ch;ps are mech-an;cally agitated in a laboratory blender to simulate the process of blowing the charge of the digester into a blow tank as practiced on a mill scale. The cooked pulp is then screened using a sieve (26/1000 inch sieve size screen) and the percentage of rejects is determined. The rejects are the material retained on the screen.
The rejects percentage is determined by drying the material retained on the screen and utilizing that weight in conjunction with the dry weight of chips added to the digester to establish the weight percentage of material rejected.
The total active alkali consists substantially of bisodium oxide (Na20) with active alkali of 18% of the dry weight of wood chips, and a sulfidity of about 25 percent. The liquor to wood ratio is approximately 5.6:1, and the optimal cooking temperature is 170C. The chips are cooked for 90 minutes until the temperature reaches 170C, and are then cooked at this temperature for 36 minutes. The concentration of additive is approximately 0.05%, based on the dry weight of the chips.
It is believed that a range of conking temperatures from 160-180C and a concentration of additive of about 0.01 - 1%
(based on dry weight of chips) would be effective in this invention. Furthermore, a liquor to wood ratio of 2.5:1 to 6:1, active alkali of 10-30% as Na20 and a sulfidity of 10-40% are believed to be effective ranges.
The following laboratory results demonstrate the effectiveness of these surfactants on the wettability of chips, emulsification of resin, and the reduction of rejects.
Surface Contact Inter-1 Tension Angle on facial Tur-CMC* at CMC Aged Chips Tension* bidity #
SampleHLB (~e ) (dYnes/cm) (degrees) (dYnes/cm) (NTU) Water ---- --- ---- 133 18.0 ---1. Ethoxylated 12.0 180 30.6 34 4.7 220 Isostearyl Alcohol 2. Ethoxy1ated 11.3 160 40.5 32 3.0 20 Oleyl Alcohol 3. Ethoxylated 13.0 140 29.3 34 3.2 300 Dialkylphenol A
The interfacial tension between the cooking liquor and resin must be dramatically decreased in order to increase the penetration rate of cooking liquor into the wood chips. Two mechanisms are involved with the lowering of interfacial tension: deformation of resin and formation of an emulsion or microemulsion.
Low interfacial tension reduces the work of deformation necessary for resin droplets to emerge from the narrow necks of pores. A very low liquor/resin interfacial tension allows resin to move easily through the necks of pores. This mechanism can assist in the penetration of liquor into the chips.
Alternatively, a very low interfacial tension is required to form an emulsion or microemulsion of` resin in the cooking liquor.
If resin, which blocks the pores, can be emulsified by a surfactant, the cooking l;quor can pass easily through the pores. This leads to improved liquor penetration.
The increased wettability of a chip surface by a surfact~nt also creates more favorable conditions for cooking liquor pene-tratiorl. The spreading of cooking liquor on the chip surface ;s ~ 3~3 governed by the surface tension of the cooking liquor, the surface tension of the chip, and the interfacial tension between the cooking liquor and the chip. In general, the lower the surface tension of the cooking liquor, the easier spreading occurs. Ease of spreading can be accomplished by adding the proper surfactant to the cooking liquor.
SUMMARY OF THE INVENTION
The components of the present invention comprise 1) an ethoxylated isostearyl alcohol and 2) an ethoxylated oleyl alcohol, or alternatively, a combination of two ethoxylated dialkylphenols of different molecular weight. These constituents are all commercially available.
Although all of the prev;ously listed compounds are known surfactants, the effects of increasing yield and decreasing reject level upon combination of the various components have not been previously disclosed.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention consists of the addition of specific types of surfactants to the cooking liquor in order to enhance the penetration of cooking liquor into the chips, the wettability of the chips, and to prevent the redeposition of dissolved materials back onto the fibers. The advantages of adding these pulping additives are to reduce rejects and increase yield.
~ 3 The chemical structures of these surfactants are as follows:
Etho,x,,ylated Oleyl Alcohol CH3(CH2)7C=c(cH2)8~(cH2cH20)2oH
Molecular Weight - 1148 Etho,xvlated Tsoste.. a.rvl Alcohol CH3 - CH(cH2)lso(cH2cH2o) Molecular Weight = 712 EthoxY~ated DialkY.lPhenol "A".
R~ ---- 0(CH2CH20)nH
n=15 R = Nonyl group Molecular Weight = 994 Ethoxylated Dialkvlphenol "B'' R~ ~- O(CH2CH20)nH
n = 24 R = Nonyl group Molecular Weight = 1402 ~q'~
For the application of Kraft pulping additives, the effective molecular weight and effective HLB of these surfactants is in the range of 500-3000 and 8-20, respectively. It is believed that any surfactant with a similar chemical structure, molecular weight (500-3000), HLB (8-20), and possessing the function of mechanisms mentioned above will work as a Kraft pulping additive. It is also believed that the aforementioned pulping additives can be applied to sulfite pulping and semichemical pulping.
In the laboratory procedure, wood chips are first collected from a paper mill source. A sample of the wood chips to be cooked is oven dried to determine the moisture content. The amount of wood chips fed to the cooking vessel or digester is selected to provide a predetermined weight ratio of chips (dry weight) to cooking liquor.
A laboratory scale digester, equipped with temperature and pressure monitoring devices and having a capacity of 6 liters, is charged with the wood chips, alkali cooking liquor and optional surface active agent additive. The digester is heated by electricity until the target cooking temperature is achieved. The wood chips are cooked with the liquor at the temperature indicated in the closed digester.
After cooking is completed, the pressure in the digester is released.
A sample of the chips is rinsed to remove residual alkali, and the rinsed chips are allowed to drain for one hour. The ch;ps are mech-an;cally agitated in a laboratory blender to simulate the process of blowing the charge of the digester into a blow tank as practiced on a mill scale. The cooked pulp is then screened using a sieve (26/1000 inch sieve size screen) and the percentage of rejects is determined. The rejects are the material retained on the screen.
The rejects percentage is determined by drying the material retained on the screen and utilizing that weight in conjunction with the dry weight of chips added to the digester to establish the weight percentage of material rejected.
The total active alkali consists substantially of bisodium oxide (Na20) with active alkali of 18% of the dry weight of wood chips, and a sulfidity of about 25 percent. The liquor to wood ratio is approximately 5.6:1, and the optimal cooking temperature is 170C. The chips are cooked for 90 minutes until the temperature reaches 170C, and are then cooked at this temperature for 36 minutes. The concentration of additive is approximately 0.05%, based on the dry weight of the chips.
It is believed that a range of conking temperatures from 160-180C and a concentration of additive of about 0.01 - 1%
(based on dry weight of chips) would be effective in this invention. Furthermore, a liquor to wood ratio of 2.5:1 to 6:1, active alkali of 10-30% as Na20 and a sulfidity of 10-40% are believed to be effective ranges.
The following laboratory results demonstrate the effectiveness of these surfactants on the wettability of chips, emulsification of resin, and the reduction of rejects.
Surface Contact Inter-1 Tension Angle on facial Tur-CMC* at CMC Aged Chips Tension* bidity #
SampleHLB (~e ) (dYnes/cm) (degrees) (dYnes/cm) (NTU) Water ---- --- ---- 133 18.0 ---1. Ethoxylated 12.0 180 30.6 34 4.7 220 Isostearyl Alcohol 2. Ethoxy1ated 11.3 160 40.5 32 3.0 20 Oleyl Alcohol 3. Ethoxylated 13.0 140 29.3 34 3.2 300 Dialkylphenol A
4. Ethoxylated 15.1 120 31.7 30 2.6 70 Dialkylphenol B
1 ~ 2 ---- --- ---- 32 3.8 7**
3 ~ 4 ---- --- ---- 30 2.9 4**
* 1CMC - critical micelle concentration - that concentration in which the aggregation of surfactant molecules into large units begins. These units are known as micelles.
* Interfacial -tension between surfactant solution ~0.33%) and turpentine consisting of pine sap and abietic acid (10%).
# Turbidity of the emulsions consisting of surfactants, pine sap, abietic acid and alkali solution.
** Microemulsion was formed.
Pulping Conditions: Active Alkali = 18% as Na20 Sulfidity = 25%
Liquor to Wood Ratio = 5.6/1 Cooking Tem~erature = 170~C
Time to 170 C = 90 minutes Time at 170C Y 36 minutes Dosage = 0.05% (based on chip dry weight) When the ethoxylated isostearyl alcohol and the ethoxylated oleyl alcohol are added in a 1:1 ratio in the pulping process, an unexpPcted increase in yields and a decrease in reject levels are obtained:
Accepts (Weiqht %) Re.iects (Weiqht %) Untreated 42.8 14.1 Treated 46.3 11. 3 Similar unexpected results are achieved when the ethoxylated dialkylphenols are added together in a l:l ratio:
Accepts (Weiqht %) Re~iects (Weiqht %) Untreated 37.9 18.6 Treated 45.0 12.6 It is believed that weight ratios for both sets of components of from about 1:9 to 9:1 would be effectiYe in this invention.
While this invention has been described with respect to particular embodiments thereof, it is apparènt that numerous other forms and modifications of this invention will be obvious to those skilled in the art. The appended claims and this invention generally should be construed to cover all such obvious forms and modifications which are within the true spirit and scope of the present invention.
1 ~ 2 ---- --- ---- 32 3.8 7**
3 ~ 4 ---- --- ---- 30 2.9 4**
* 1CMC - critical micelle concentration - that concentration in which the aggregation of surfactant molecules into large units begins. These units are known as micelles.
* Interfacial -tension between surfactant solution ~0.33%) and turpentine consisting of pine sap and abietic acid (10%).
# Turbidity of the emulsions consisting of surfactants, pine sap, abietic acid and alkali solution.
** Microemulsion was formed.
Pulping Conditions: Active Alkali = 18% as Na20 Sulfidity = 25%
Liquor to Wood Ratio = 5.6/1 Cooking Tem~erature = 170~C
Time to 170 C = 90 minutes Time at 170C Y 36 minutes Dosage = 0.05% (based on chip dry weight) When the ethoxylated isostearyl alcohol and the ethoxylated oleyl alcohol are added in a 1:1 ratio in the pulping process, an unexpPcted increase in yields and a decrease in reject levels are obtained:
Accepts (Weiqht %) Re.iects (Weiqht %) Untreated 42.8 14.1 Treated 46.3 11. 3 Similar unexpected results are achieved when the ethoxylated dialkylphenols are added together in a l:l ratio:
Accepts (Weiqht %) Re~iects (Weiqht %) Untreated 37.9 18.6 Treated 45.0 12.6 It is believed that weight ratios for both sets of components of from about 1:9 to 9:1 would be effectiYe in this invention.
While this invention has been described with respect to particular embodiments thereof, it is apparènt that numerous other forms and modifications of this invention will be obvious to those skilled in the art. The appended claims and this invention generally should be construed to cover all such obvious forms and modifications which are within the true spirit and scope of the present invention.
Claims (17)
1. In the process of Kraft pulping, a method for enhancing the penetration of cooking liquor into wood chips which comprises adding to the cooking liquor an effective amount for the purpose of a combination of (a) an ethoxylated isostearyl alcohol and (b) an ethoxylated oleyl alcohol.
2. The method as recited in claim 1 wherein the weight ratio of (a):(b) is from about 1:9 to 9:1.
3. The method as recited in claim 1 wherein the weight ratio of (a):(b) is about 1:1.
4. The method as recited in claim 1 wherein said combination is added to the cooking liquor in an amount of about 0.01 - 1%
based on the dried weight of wood chips.
based on the dried weight of wood chips.
5. In the process of Kraft pulping, a method for enhancing the penetration of cooking liquor into wood chips which comprises adding to the cooking liquor an effective amount for the purpose of a combination of two ethoxylated dialkylphenols.
6. The method as recited in claim 5 wherein the weight ratio of the two ethoxylated dialkylphenols is from about 1:9 to 9:1.
7. The method as recited in claim 5 wherein the weight ratio of the two ethoxylated dialkylphenols is about 1:1.
8. The method as recited in claim 5 wherein said combination is added to the cooking liquor in an amount of about 0.01 - 1%
based on the dried weight of wood chips.
based on the dried weight of wood chips.
9. A composition for enhancing the penetration of cooking liquor into wood chips comprising a combination of (a) an ethoxy-lated isostearyl alcohol and (b) an ethoxylated oleyl alcohol.
10. The composition as recited in claim 9 wherein the weight ratio of (a):(b) is from about 1:9 to 9:1.
11. The composition as recited in claim 9 wherein the weight ratio of (a):(b) is about 1:1.
12. A composition for enhancing the penetration of cooking liquor into wood chips comprising a combination of two ethoxylated dialkylphenols.
13. The composition as recited in claim 12 wherein the weight ratio of the two ethoxylated dialkylphenols is from about 1:9 to 9:1.
14. The composition as recited in claim 12 wherein the weight ratio of the two ethoxylated dialkylphenols is about 1:1.
15. In the process of Kraft pulping, a method for enhancing the penetration of cooking liquor into wood chips which comprises adding to the cooking liquor an effective amount for the purpose of an additive selected from the group consisting of (1) a combination of an ethoxylated isostearyl alcohol and an ethoxylated oleyl alcohol, or (2) a combination of two ethoxylated dialkylphenols.
16. The method as recited in claim 15 wherein said additive is added to the cooking liquor in an amount of about 0.01 - 1%
based on the dried weight of wood chips.
based on the dried weight of wood chips.
17. A composition for enhancing the penetration of cooking liquor into wood chips selected from the group consisting of (1) a combination of an ethoxylated isostearyl alcohol and an ethoxylated oleyl alcohol, or (2) a combination of two ethoxylated dialkylphenols.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US65790591A | 1991-02-20 | 1991-02-20 | |
| US07/657,905 | 1991-02-20 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2060043A1 true CA2060043A1 (en) | 1992-08-21 |
Family
ID=24639130
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2060043 Abandoned CA2060043A1 (en) | 1991-02-20 | 1992-01-24 | Surfactants as kraft pulping additives for reject reduction and yield increase |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2060043A1 (en) |
-
1992
- 1992-01-24 CA CA 2060043 patent/CA2060043A1/en not_active Abandoned
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