CA2096277C - 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
- CA2096277C CA2096277C CA 2096277 CA2096277A CA2096277C CA 2096277 C CA2096277 C CA 2096277C CA 2096277 CA2096277 CA 2096277 CA 2096277 A CA2096277 A CA 2096277A CA 2096277 C CA2096277 C CA 2096277C
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- Prior art keywords
- surfactants
- liquor
- cooking
- cooking liquor
- chips
- Prior art date
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- Expired - Lifetime
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Abstract
The present invention relates to a method for enhancing the penetration of cooking liquor into wood chips to form a Kraft pulp which comprises adding to the cooking liquor specific surfactants such as ethoxylated dialkylphenols and ethoxylated alcohols.
Description
- 2 ~ 7 ~1 SURFACTANTS AS KRAFT PULPING ADDITIVES FOR
REJECT REDUCTION AND YIELD INCREASE
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 chem;cally 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 ions. This chemical reaction is known as delignification.
. ~ .
It is bel;eved that penetration and diffus;on are two ma~or 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 dlrection (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: (1) interfacial tension, (2) surface tension, and (3) contact angle.
Interfacial tension may be defined as the work required to increase the unit area of an interface at constant tempera-ture, pressure and composition. Surface tension is the inter-facial tension between the liquid and the air or ~he solid and the air, and contac~ 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 lowerin~ of in~erfacial tension:
deformation of resin and formation of an emulsion or micro-emulsion.
Low in~erfacial tension reduces the work of deformation necessary for re~in droplets to emerge from the narrow necks of pores. A very low liquor/resin interfacial tension allows resin to mo~e easily through the necks of pores. Thls mechanism can ass~st in the penetration of liquor into the chips.
.
.
.
:
_3_ 2 ~ ~ ~ 2 77 Alternat;vely, a very low ;nterfacial tension is required to form an emulsion or microemulsion of r~sin in the cooking liquor. If resin, which blo~ks the pores, can be emulsi~ied by a surfactant, the cooking liquor can pass easily through the pores.
This leads to improved liquor penetration.
The increased wettabili~y of a chip surface by a sur-factant also creates more favorable conditions for cooking liquor penetration. The spreading of cooking liquor on the chip surface is governed by the surfaee ~ension of the cooking liquor, the the surface tension of the chip, and the interfacial tension between the cooking liquor and the chip. The tendency of spreading cooking liquor on the chip surface is indicated by measuring the contaot angle of the liquid on the chip surf~ce.
In general, the lower the contact angle of the cooking liquor, the easier spreading occurs. Ease of spreading can be accomp-l;shed by adding the proper surfactan~ to the cooking liquor.
Prior art references teach the use of ethoxylated alkyl-phenols (U.S. Patent 4,9529277) and ethylene oxlde-propylene oxidc block copolymers (U.S. Patent 4,906,331) as Kraft pulping additives. ,~
SUMMARY OF THE INVENTION
The present invention relates to a method for enhancing the penetration of caoking liquor into wood chips to form a Kraft . - ~ . . . ... .
:. ~ . ' . ' ., '~:, .
..
- , . ~ .
~9~277 pulp which comprises adding to the cooking liquor specific surfactants, (surface active agents) such as ethoxylated dialkylphenols and ethoxylated alcohols.
. 5 The present invention comprises the addition of speci~ic types of surfactants to the cooking liquor ln 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.
The chemical structures of these surfactants are as follows:
Ethoxvlated Alcohols R - O(CH2CH20)nH
R = Alkyl or alkenyl group n = 1 - 50 (n - 10 - 20 preferred) EthoxYlated DialkYlphenols R ~ ~- O(cH2cH2o)nH
R
R ~ Nonyl group n = 1 - 50 (n = 15 - 24 preferred) .
' ' ': .
'.
5209~277 Preferred ethoxylated alcohols include ethoxylated oleyl alcohols (R of CH3(CH2)7 CH - CH(CH2)8) and ethoxylated isostearyl alcohols (R of CH3 - CH(CH2)15) I
. CH3 For the application of Kraft pulping additives, the effective HLB of these surfactants is in the range 6-20. It is believed that any surfactant with a similar chemical structure7 ~LB (6-20), and possessing the function of mechanisms mentioned above will work as a Kraft pulping additive. It is also believed th~t the aforementioned pulping additives can be applied to sulfite pulp;ng and semichemical pulping.
In the labnratory 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 ;s selected to provide a predetermined weight ratio of chips (dry weight) to cooking liquor. A laboratory scale digester, equipped with ~emperature and pressure monitoring devices and having a capac,7ty of 6 liters, is charged with the wood chips, . 20 alkali cooking liquor and optional surface active agent addit~e. The digester is heated by electricity until the targ~t 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 - ..... ~ . . ... .
.
.
.
.. . . . ..
2~9~277 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 chips are mechanically 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 mater;al reta;ned on the screen. Th~
rejects percentage is determined by drying the material retained on the screen and util;z;ng 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 th~n 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 cooking 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. Furth~rmore, 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.
.
"
7 20~277 The following laboratory results demonstrate the effec-tiveness of these surfactants on the emulsification of resin and the reduction of rejects. Interfacial tension measurements were conducted using a system of 930 ppm Na2S, 2660 ppm NaOH and - 5 1330 ppm surfactant. As shown in Tables 1 and 2, the blends of alcohol ethoxylates are superior to ethylene oxide propylene oxide block copolymers such as Pluronic~ F-108, F-88, etc. By the same token, the dialkylphenol ethoxylates are more effective than alkylphenol ethoxylates (Surfoni ~ N-95, N-1203~
, .
. .
,: , .
- . . . .
- . .
209~277 EthoxYlated Alcohols Interfacial Tension Turbidity #
Sample (10-~ dynes/cm) (NTU) Ethoxylated 24.37 220 Isostearyl Alcohol (A) Molecular Weight = 712 Ethoxylated 14.61 20 Oleyl Alcohol (B) Molecular Weight = 1148 lA:4B 11.56 10*
2A:3B 14.14 14*
lA:lB 8.96 7*
3A:2B 15.56 15*
4A:lB 18.70 18*
Pluronic: F-108 24.75 F- 88 27.07 ----P-123 11.70 3~0 L-122 25.60 ----.
Turbidity of the emulsions containing surfactants, pine sap, abietio acid~and alkali solution.
* Mlcroemulsion was formed.
---- These surfactants are not good emulsifiers for pine sap 25 and abietic acid. Therefore, turbidity measurement is not appl i cabl e .
, , ~ , .
, ' . , : :
, .
2~277 g EthoxYlated DialkYlphenols Interfacial Tens~on Turbidity #
Sample (10- dynes/cm) (NTU) Ethoxylated 11.05 300 Dialkylphenol A (C) Molecular Weight = 994 Ethoxylated 5.86 70 lO Dialkylphenol B (D) Molecular Weight = 1402 lC:4D 8.63 5*
2C:3D 7.98 4*
lC:lD 7.99 ~*
3C:2D 8.42 7*
4C:lD 9.36 13*
Surfonic: N-95 9.21 290 N-120 14.13 350 # Turbidity o~ the emulsions containing surfactants, pine sap, abietic acid and alkali solution.
* Microemulsi~ was formed.
.. .. , ,, .: , ' , '' ' ,, ~ ' .
- . : ' - ~ ,' ': . . .
.. . . . . .
,. . . . . , . ::. . :.
~9~277 Laboratory Kra~t Pulping Study A laboratory pulping study was conducted under the following pulping conditions:
Active Alkali = 18% as Na20 Sulf;dity = 25%
Liquor to Wood Ratio = 5.6/1 ` Cooking Temperature = 170C
Time to 170C 8 90 minutes Time at 170C = 36 minutes Dosage = 0.05% (based on chip dry weight) When the ethoxylated isostearyl alcohol and the ethoxylated oleyl alcohol from Table I are added in a 1:1 ratio in the pulping process, an unexpected increase in yields and a decrease in reject levels are obtained:
Accepts (Weiqht %) Re.iects tWeight %) Untr~ated 42.8 14.1 Treated 46 . 3 11. g - - . . .: .. : . . .
.. . . .
. . ~ , . .. ~. . ~ :
- . : , . . . .
- .
, :,: ' -:, ,: ,:: . , ' , :
~q~`277 Similar unexpected results are achieved when the ethoxylated dialkylphenols from Table II are added together ;n a l:l rat;o:
AcceDts (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 effective in this invention.
While this invention has been described with respect to particular embodiments thereof, it is apparent 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 arc within the trUe spirit and scope of the present invention.
;
.
- . . - - , . . . . .. . . . .
.- - ' . . -: .- ..... . . .
. .
. . . . - . . ., - . . . . . .
,..... , ,: :
- : . .
. . - .. . . . .
", '' '' ' ~ ' .
... . ' .
REJECT REDUCTION AND YIELD INCREASE
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 chem;cally 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 ions. This chemical reaction is known as delignification.
. ~ .
It is bel;eved that penetration and diffus;on are two ma~or 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 dlrection (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: (1) interfacial tension, (2) surface tension, and (3) contact angle.
Interfacial tension may be defined as the work required to increase the unit area of an interface at constant tempera-ture, pressure and composition. Surface tension is the inter-facial tension between the liquid and the air or ~he solid and the air, and contac~ 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 lowerin~ of in~erfacial tension:
deformation of resin and formation of an emulsion or micro-emulsion.
Low in~erfacial tension reduces the work of deformation necessary for re~in droplets to emerge from the narrow necks of pores. A very low liquor/resin interfacial tension allows resin to mo~e easily through the necks of pores. Thls mechanism can ass~st in the penetration of liquor into the chips.
.
.
.
:
_3_ 2 ~ ~ ~ 2 77 Alternat;vely, a very low ;nterfacial tension is required to form an emulsion or microemulsion of r~sin in the cooking liquor. If resin, which blo~ks the pores, can be emulsi~ied by a surfactant, the cooking liquor can pass easily through the pores.
This leads to improved liquor penetration.
The increased wettabili~y of a chip surface by a sur-factant also creates more favorable conditions for cooking liquor penetration. The spreading of cooking liquor on the chip surface is governed by the surfaee ~ension of the cooking liquor, the the surface tension of the chip, and the interfacial tension between the cooking liquor and the chip. The tendency of spreading cooking liquor on the chip surface is indicated by measuring the contaot angle of the liquid on the chip surf~ce.
In general, the lower the contact angle of the cooking liquor, the easier spreading occurs. Ease of spreading can be accomp-l;shed by adding the proper surfactan~ to the cooking liquor.
Prior art references teach the use of ethoxylated alkyl-phenols (U.S. Patent 4,9529277) and ethylene oxlde-propylene oxidc block copolymers (U.S. Patent 4,906,331) as Kraft pulping additives. ,~
SUMMARY OF THE INVENTION
The present invention relates to a method for enhancing the penetration of caoking liquor into wood chips to form a Kraft . - ~ . . . ... .
:. ~ . ' . ' ., '~:, .
..
- , . ~ .
~9~277 pulp which comprises adding to the cooking liquor specific surfactants, (surface active agents) such as ethoxylated dialkylphenols and ethoxylated alcohols.
. 5 The present invention comprises the addition of speci~ic types of surfactants to the cooking liquor ln 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.
The chemical structures of these surfactants are as follows:
Ethoxvlated Alcohols R - O(CH2CH20)nH
R = Alkyl or alkenyl group n = 1 - 50 (n - 10 - 20 preferred) EthoxYlated DialkYlphenols R ~ ~- O(cH2cH2o)nH
R
R ~ Nonyl group n = 1 - 50 (n = 15 - 24 preferred) .
' ' ': .
'.
5209~277 Preferred ethoxylated alcohols include ethoxylated oleyl alcohols (R of CH3(CH2)7 CH - CH(CH2)8) and ethoxylated isostearyl alcohols (R of CH3 - CH(CH2)15) I
. CH3 For the application of Kraft pulping additives, the effective HLB of these surfactants is in the range 6-20. It is believed that any surfactant with a similar chemical structure7 ~LB (6-20), and possessing the function of mechanisms mentioned above will work as a Kraft pulping additive. It is also believed th~t the aforementioned pulping additives can be applied to sulfite pulp;ng and semichemical pulping.
In the labnratory 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 ;s selected to provide a predetermined weight ratio of chips (dry weight) to cooking liquor. A laboratory scale digester, equipped with ~emperature and pressure monitoring devices and having a capac,7ty of 6 liters, is charged with the wood chips, . 20 alkali cooking liquor and optional surface active agent addit~e. The digester is heated by electricity until the targ~t 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 - ..... ~ . . ... .
.
.
.
.. . . . ..
2~9~277 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 chips are mechanically 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 mater;al reta;ned on the screen. Th~
rejects percentage is determined by drying the material retained on the screen and util;z;ng 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 th~n 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 cooking 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. Furth~rmore, 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.
.
"
7 20~277 The following laboratory results demonstrate the effec-tiveness of these surfactants on the emulsification of resin and the reduction of rejects. Interfacial tension measurements were conducted using a system of 930 ppm Na2S, 2660 ppm NaOH and - 5 1330 ppm surfactant. As shown in Tables 1 and 2, the blends of alcohol ethoxylates are superior to ethylene oxide propylene oxide block copolymers such as Pluronic~ F-108, F-88, etc. By the same token, the dialkylphenol ethoxylates are more effective than alkylphenol ethoxylates (Surfoni ~ N-95, N-1203~
, .
. .
,: , .
- . . . .
- . .
209~277 EthoxYlated Alcohols Interfacial Tension Turbidity #
Sample (10-~ dynes/cm) (NTU) Ethoxylated 24.37 220 Isostearyl Alcohol (A) Molecular Weight = 712 Ethoxylated 14.61 20 Oleyl Alcohol (B) Molecular Weight = 1148 lA:4B 11.56 10*
2A:3B 14.14 14*
lA:lB 8.96 7*
3A:2B 15.56 15*
4A:lB 18.70 18*
Pluronic: F-108 24.75 F- 88 27.07 ----P-123 11.70 3~0 L-122 25.60 ----.
Turbidity of the emulsions containing surfactants, pine sap, abietio acid~and alkali solution.
* Mlcroemulsion was formed.
---- These surfactants are not good emulsifiers for pine sap 25 and abietic acid. Therefore, turbidity measurement is not appl i cabl e .
, , ~ , .
, ' . , : :
, .
2~277 g EthoxYlated DialkYlphenols Interfacial Tens~on Turbidity #
Sample (10- dynes/cm) (NTU) Ethoxylated 11.05 300 Dialkylphenol A (C) Molecular Weight = 994 Ethoxylated 5.86 70 lO Dialkylphenol B (D) Molecular Weight = 1402 lC:4D 8.63 5*
2C:3D 7.98 4*
lC:lD 7.99 ~*
3C:2D 8.42 7*
4C:lD 9.36 13*
Surfonic: N-95 9.21 290 N-120 14.13 350 # Turbidity o~ the emulsions containing surfactants, pine sap, abietic acid and alkali solution.
* Microemulsi~ was formed.
.. .. , ,, .: , ' , '' ' ,, ~ ' .
- . : ' - ~ ,' ': . . .
.. . . . . .
,. . . . . , . ::. . :.
~9~277 Laboratory Kra~t Pulping Study A laboratory pulping study was conducted under the following pulping conditions:
Active Alkali = 18% as Na20 Sulf;dity = 25%
Liquor to Wood Ratio = 5.6/1 ` Cooking Temperature = 170C
Time to 170C 8 90 minutes Time at 170C = 36 minutes Dosage = 0.05% (based on chip dry weight) When the ethoxylated isostearyl alcohol and the ethoxylated oleyl alcohol from Table I are added in a 1:1 ratio in the pulping process, an unexpected increase in yields and a decrease in reject levels are obtained:
Accepts (Weiqht %) Re.iects tWeight %) Untr~ated 42.8 14.1 Treated 46 . 3 11. g - - . . .: .. : . . .
.. . . .
. . ~ , . .. ~. . ~ :
- . : , . . . .
- .
, :,: ' -:, ,: ,:: . , ' , :
~q~`277 Similar unexpected results are achieved when the ethoxylated dialkylphenols from Table II are added together ;n a l:l rat;o:
AcceDts (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 effective in this invention.
While this invention has been described with respect to particular embodiments thereof, it is apparent 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 arc within the trUe spirit and scope of the present invention.
;
.
- . . - - , . . . . .. . . . .
.- - ' . . -: .- ..... . . .
. .
. . . . - . . ., - . . . . . .
,..... , ,: :
- : . .
. . - .. . . . .
", '' '' ' ~ ' .
... . ' .
Claims (8)
1. A method of enhancing the penetration of cooking liquor into wood chips, the method comprising cooking wood chips in a Kraft liquor to form a Kraft pulp and including at least two surfactants having the general formula R-O(CH2CH2O)nH
where n is an integer from 1 to 50 and R is oleyl in at least one of said surfactants, and R is isostearyl in at least one other of said surfactants, said method resulting in the formation of a microemulsion, an increase in pulp yield and a decrease in reject levels.
where n is an integer from 1 to 50 and R is oleyl in at least one of said surfactants, and R is isostearyl in at least one other of said surfactants, said method resulting in the formation of a microemulsion, an increase in pulp yield and a decrease in reject levels.
2. The method as recited in claim 1 wherein n is an integer from 10 to 20.
3. The method as recited in claim 1 wherein said surfactants are added to the cooking liquor in an amount of about 0.01-1% based on the dried weight of the chips.
4. A method for enhancing the penetration of cooking liquor into wood chips, the method comprising cooking wood chips in a Kraft liquor to form a Kraft pulp and including at least two surfactants having the general formula:
where n is an integer from 1 to 50 an R is nonyl in each of said surfactants, said method resulting in the formation of a microemulsion, an increase in pulp yield and a decrease in reject levels.
where n is an integer from 1 to 50 an R is nonyl in each of said surfactants, said method resulting in the formation of a microemulsion, an increase in pulp yield and a decrease in reject levels.
5. The method as recited in claim 4 wherein n is an integer from 15 to 24.
6. The method as recited in claim 4 wherein said surfactants are added to the cooking liquor in an amount of about 0.01-1% based on the dried weight of the chips.
7. A composition for enhancing the penetration of cooking liquor into wood chips in Kraft pulping comprising a combination of (a) an ethoxylated isostearyl alcohol and (b) an ethoxylated oleyl alcohol, the weight ratio of (a):(b) being from about 1:9 to 9:1.
8. The composition as recited in claim 7 wherein the weight ratio of (a):(b) is about 1:1.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/913,519 US5250152A (en) | 1991-02-20 | 1992-07-14 | Ethoxylated alcohol and dialkylphenol surfactants as Kraft pulping additives for reject reduction and yield increase |
| US913,519 | 1992-07-14 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2096277A1 CA2096277A1 (en) | 1994-01-15 |
| CA2096277C true CA2096277C (en) | 1997-08-26 |
Family
ID=25433353
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2096277 Expired - Lifetime CA2096277C (en) | 1992-07-14 | 1993-05-14 | Surfactants as kraft pulping additives for reject reduction and yield increase |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2096277C (en) |
-
1993
- 1993-05-14 CA CA 2096277 patent/CA2096277C/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| CA2096277A1 (en) | 1994-01-15 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |
Effective date: 20130514 |
|
| MKEC | Expiry (correction) |
Effective date: 20131009 |