CA2259970C - Process for improving printing papers - Google Patents
Process for improving printing papers Download PDFInfo
- Publication number
- CA2259970C CA2259970C CA002259970A CA2259970A CA2259970C CA 2259970 C CA2259970 C CA 2259970C CA 002259970 A CA002259970 A CA 002259970A CA 2259970 A CA2259970 A CA 2259970A CA 2259970 C CA2259970 C CA 2259970C
- Authority
- CA
- Canada
- Prior art keywords
- retention agent
- additional retention
- paper
- fiber
- additional
- 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.)
- Expired - Fee Related
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Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
- D21H21/06—Paper forming aids
- D21H21/10—Retention agents or drainage improvers
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
- D21H23/76—Processes or apparatus for adding material to the pulp or to the paper characterised by choice of auxiliary compounds which are added separately from at least one other compound, e.g. to improve the incorporation of the latter or to obtain an enhanced combined effect
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
- D21H17/20—Macromolecular organic compounds
- D21H17/21—Macromolecular organic compounds of natural origin; Derivatives thereof
- D21H17/24—Polysaccharides
- D21H17/28—Starch
- D21H17/29—Starch cationic
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
- D21H17/20—Macromolecular organic compounds
- D21H17/21—Macromolecular organic compounds of natural origin; Derivatives thereof
- D21H17/24—Polysaccharides
- D21H17/31—Gums
- D21H17/32—Guar or other polygalactomannan gum
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
- D21H17/20—Macromolecular organic compounds
- D21H17/33—Synthetic macromolecular compounds
- D21H17/34—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
- D21H17/37—Polymers of unsaturated acids or derivatives thereof, e.g. polyacrylates
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
- D21H17/20—Macromolecular organic compounds
- D21H17/33—Synthetic macromolecular compounds
- D21H17/46—Synthetic macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
- D21H17/54—Synthetic macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen
- D21H17/55—Polyamides; Polyaminoamides; Polyester-amides
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
- D21H17/20—Macromolecular organic compounds
- D21H17/33—Synthetic macromolecular compounds
- D21H17/46—Synthetic macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
- D21H17/54—Synthetic macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen
- D21H17/56—Polyamines; Polyimines; Polyester-imides
Landscapes
- Paper (AREA)
Abstract
The invention relates to a process for improving the capacity of gravure printing and offset printing for printing paper. To increase the filler proportion in the paper web before or during formation, the outer layers of the material suspension forming the web are provided with an additional retention agent.
Description
2 "" .~ ~-'- 1 , PCT/EP97/0597 Process for Improving Printing Papers The invention relates to a process for improving the gravure and offset printability of coated and uncoated printing papers by increasing the filler share in these papers on the top and bottom sides or in the outer layers of the paper web by the use of retention agents.
According to the prior art, so-called SC and LWC rotary printing papers, which must meet higher standards for printing results, are used for large print jobs. The term "SC papers" refers to rotary printing papers that contain up to 35% mineral filler and have high gloss and smoothness due to post-treatment in a super-calendar. The abbreviation "SC"
stands for "super-calendared."
The term "LWC papers" refers to rotary printing papers that contain up to 15%
mineral filler by mass and are provided inside or outside the paper-making machine with a pigmented surface coating, the coat, on both sides. After being coated, these printing papers are also treated with a super-calendar to attain high gloss and smoothness. The abbreviation LWC stands for "light-weight coated."
SC and LWC printing papers were initially produced on so-called endless-wire paper-making machines. These papers have the disadvantage known as "two-sidedness," i.e., due to one-sided dewatering on the wire, filler and fine material were washed out on the bottom side, so that the wire side of the paper was always rougher than the top side, and the paper web, seen in the Z-direction, had an irregular or skewed ash cross-section. Varying filler or ash contents inevitably lead to irregular printing results on the top and wire sides, so that such papers no longer satisfy modern requirements.
To avoid such disadvantages, wire devices with two-sided dewatering, known as hybrid formers, were therefore developed.
The German publication "Paper Fabrication Weekly" [" Wochenblatt fur Papierfabrikation"], 1987, pages 461 through 478, provides an overview of modern sheet formation systems, consisting of flow box and sheet formation devices. Section 3, in particular, describes hybrid and twin-wire formers and their advantages compared with the classic endless-wire models.
In addition, the "Paper Fabrication Weekly" [" Wochenblatt fur Papierfabrikation"], 1987, pages 662 through 667, describes multi-layer printing papers formed by means of multi-layer flow box devices and twin-wire formers. The same reference also discloses that it is possible to deliberately influence the distribution of filler in the outer layers of the paper web by adding filler to the outer channels of a multi-layer flow box.
Finally, DE 42 37 309 discloses a process for producing a fibrous web, wherein a fiber-bearing liquid is evenly distributed, with the help of a flow box, on a wire or between two wires. To avoid fluctuations in the area weight cross-section, the retention of fiber-bearing liquid on the wire is sectionally influenced by the sectional dosing of retention agent in the flow box.
Modern twin-wire formers for producing SC and LWC papers are operated at working speeds of up to 1,500 m/min. Known SC papers produced with these devices have filler shares of up to 34% with very even distribution in the Z-direction. These SC printing papers currently constitute the highest paper class with respect to printability.
Continued increases in production speed, including in twin-wire formers, are urgently needed to increase profitability. However, this raises the problem of intensifying the dewatering of the fiber-bearing liquid between the two wires along a given distance. This is done by applying a higher vacuum to individual dewatering elements, which engage with the upper and lower wires. However, the increased water extraction and the higher flow speed that accompanies it inevitably create the disadvantage that more filler is applied in the Z-direction of the formed wet paper web. This results in filler impoverishment on the outer sides, and thus in a substantial deterioration in printability.
DE 37 20 618 A1 attempts to offer an improvement by providing a process to improve the filler retention. The fiber-bearing liquid is supplied to a multi-layer flow box after first being divided by fractionation into a long-fiber portion and a short-fiber portion, which also contains all fillers. The long-fiber portion is subjected to additional fibrillation by beating and, after dilution and the simultaneous addition of retention agent, is supplied to the outer channels of a mufti-layer flow box in front of the pulp pump by means of the pulp pump. The portion containing short fibers and filler is supplied to the middle or inner channels of the 5 mufti-layer flow box. Upon subsequent dewatering, the long fibrillated fibers of a fine network are formed between the two wires of a twin-wire former. The fine network, as a filter layer, serves to retain the filler and fine material of the middle layer and results in an increase in filler.
It is disadvantageous in this process that the anchoring of the outer layer containing the long fibers is impaired by the increased filler and fine material content of the middle layer, so that the Z-strength is decreased. The paper tends to split when stressed in the Z-direction, e.g., during offset printing.
In one process aspect, the invention provides a process for improving gravure and offset printability of coated and uncoated printing papers, comprising the steps of:
increasing filler share in the paper on top and bottom sides or in outer layers of a paper web using a retention agent;
and, providing outer layers of fiber-bearing liquid forming the paper web with additional retention agent one of before and during sheet formation one of on and between wires of a paper-making machine, the step of providing additional retention agent including injecting the additional retention agent in a flow box downstream from a turbulence generator, across a width of a suspension flow in top and bottom boundary layers of the suspension flow.
In a further process aspect, the invention provides a process for improving gravure and offset printability of coated and uncoated printing papers, comprising the steps of: increasing filler share in the paper on top and bottom 5a sides or in outer layers of a paper web using a retention agent; and, providing outer layers of fiber-bearing liquid forming the paper web with additional retention agent one of before and during sheet formation one of on and between wires of a paper-making machine, the step of providing additional retention agent including spraying the additional retention agent onto a wire gauze in a twin-wire former in a returning drum of top and bottom wires downstream of a turbulence generator.
Suitably, the step of providing additional retention agent includes providing a retention agent having a high positive charge. The additional retention agent may have a charge opposite to that of the retention agent already present in the fiber-bearing liquid. The additional retention agent may consist of at least one of the group consisting of polyethylene imines, polyacrylamides, epichlorhydrine resins, and polyvinylamines. The additional retention agent may consist of cationic hydrocolloids, cationic starch or cationic guar. Suitably, the step of providing additional retention agent includes injecting the additional retention agent in a flow box with a multi-layer device, into the top and bottom layers.
The process for improving the gravure and offset printability of coated and uncoated printing papers by increasing the filler share in these papers on their top and bottom sides or in the pouter layers of the paper web by the use of retention agents is characterized by the fact that, before or during sheet formation on the wires or between the wires of a paper-making machine, the outer layers of the fiber-bearing liquid forming the paper web are provided with additional retention agent.
The use of retention agents in producing paper has long been known and permits good filler and fibrous material retention on the sheet formation wire. Such retention agents are generally added to the fiber-bearing liquid before a mixing organ, e.g., the flow box pump, so that the fiber-bearing liquid is mixed evenly with the retention agent before emerging from the lip or nozzle of the flow box. Starting from the recognition that the inner layer of a paper web, due to the filter effect, already has sufficient retention for filler and fine materials, the inventors realized that an enrichment of the retention agent in the outer layer is advantageous. The problem was thus solved by the additional dosing of retention agent.
Depending on the paper type, retention agents with cationic or anionic charges of various strengths can be used. Although strongly charged retention agents improve the retention of filler and fine materials, such agents can, depending on their reaction time with the fiber-bearing liquid, form large fiber flocks, which negatively affect the fibrous formation in the formed paper sheet. This is known as a cloudy look-through.
However, it has been recognized that this negative effect can be suppressed by shortening the reaction time. Therefore, in an advantageous embodiment of the process according to the invention, a retention agent having a high cationic charge is used.
In addition, so-called dual retention systems are known. In these, the fiber-bearing liquid is provided with a first retention agent, e.g., a cationic agent, before the flow box, and mixed well. Subsequently, but still before the flow box, a second retention agent, in this case, an anionic agent, is added to the fiber-bearing liquid and mixed. The retention agents with opposite charges react with each other and with the fibers, the filler and the fine materials of the fiber-bearing liquid, and contribute to substantially better overall retention. In a further advantageous embodiment of the invention, the charge of the additional retention agent is opposite to that of the retention agent already present in the fiber-bearing liquid supplied to the flow box.
The following known retention agents can be added individually or in mixtures:
polyethylene imines, polyacrylamides, epichlorhydrine resins and/or polyvinylamines.
According to the prior art, so-called SC and LWC rotary printing papers, which must meet higher standards for printing results, are used for large print jobs. The term "SC papers" refers to rotary printing papers that contain up to 35% mineral filler and have high gloss and smoothness due to post-treatment in a super-calendar. The abbreviation "SC"
stands for "super-calendared."
The term "LWC papers" refers to rotary printing papers that contain up to 15%
mineral filler by mass and are provided inside or outside the paper-making machine with a pigmented surface coating, the coat, on both sides. After being coated, these printing papers are also treated with a super-calendar to attain high gloss and smoothness. The abbreviation LWC stands for "light-weight coated."
SC and LWC printing papers were initially produced on so-called endless-wire paper-making machines. These papers have the disadvantage known as "two-sidedness," i.e., due to one-sided dewatering on the wire, filler and fine material were washed out on the bottom side, so that the wire side of the paper was always rougher than the top side, and the paper web, seen in the Z-direction, had an irregular or skewed ash cross-section. Varying filler or ash contents inevitably lead to irregular printing results on the top and wire sides, so that such papers no longer satisfy modern requirements.
To avoid such disadvantages, wire devices with two-sided dewatering, known as hybrid formers, were therefore developed.
The German publication "Paper Fabrication Weekly" [" Wochenblatt fur Papierfabrikation"], 1987, pages 461 through 478, provides an overview of modern sheet formation systems, consisting of flow box and sheet formation devices. Section 3, in particular, describes hybrid and twin-wire formers and their advantages compared with the classic endless-wire models.
In addition, the "Paper Fabrication Weekly" [" Wochenblatt fur Papierfabrikation"], 1987, pages 662 through 667, describes multi-layer printing papers formed by means of multi-layer flow box devices and twin-wire formers. The same reference also discloses that it is possible to deliberately influence the distribution of filler in the outer layers of the paper web by adding filler to the outer channels of a multi-layer flow box.
Finally, DE 42 37 309 discloses a process for producing a fibrous web, wherein a fiber-bearing liquid is evenly distributed, with the help of a flow box, on a wire or between two wires. To avoid fluctuations in the area weight cross-section, the retention of fiber-bearing liquid on the wire is sectionally influenced by the sectional dosing of retention agent in the flow box.
Modern twin-wire formers for producing SC and LWC papers are operated at working speeds of up to 1,500 m/min. Known SC papers produced with these devices have filler shares of up to 34% with very even distribution in the Z-direction. These SC printing papers currently constitute the highest paper class with respect to printability.
Continued increases in production speed, including in twin-wire formers, are urgently needed to increase profitability. However, this raises the problem of intensifying the dewatering of the fiber-bearing liquid between the two wires along a given distance. This is done by applying a higher vacuum to individual dewatering elements, which engage with the upper and lower wires. However, the increased water extraction and the higher flow speed that accompanies it inevitably create the disadvantage that more filler is applied in the Z-direction of the formed wet paper web. This results in filler impoverishment on the outer sides, and thus in a substantial deterioration in printability.
DE 37 20 618 A1 attempts to offer an improvement by providing a process to improve the filler retention. The fiber-bearing liquid is supplied to a multi-layer flow box after first being divided by fractionation into a long-fiber portion and a short-fiber portion, which also contains all fillers. The long-fiber portion is subjected to additional fibrillation by beating and, after dilution and the simultaneous addition of retention agent, is supplied to the outer channels of a mufti-layer flow box in front of the pulp pump by means of the pulp pump. The portion containing short fibers and filler is supplied to the middle or inner channels of the 5 mufti-layer flow box. Upon subsequent dewatering, the long fibrillated fibers of a fine network are formed between the two wires of a twin-wire former. The fine network, as a filter layer, serves to retain the filler and fine material of the middle layer and results in an increase in filler.
It is disadvantageous in this process that the anchoring of the outer layer containing the long fibers is impaired by the increased filler and fine material content of the middle layer, so that the Z-strength is decreased. The paper tends to split when stressed in the Z-direction, e.g., during offset printing.
In one process aspect, the invention provides a process for improving gravure and offset printability of coated and uncoated printing papers, comprising the steps of:
increasing filler share in the paper on top and bottom sides or in outer layers of a paper web using a retention agent;
and, providing outer layers of fiber-bearing liquid forming the paper web with additional retention agent one of before and during sheet formation one of on and between wires of a paper-making machine, the step of providing additional retention agent including injecting the additional retention agent in a flow box downstream from a turbulence generator, across a width of a suspension flow in top and bottom boundary layers of the suspension flow.
In a further process aspect, the invention provides a process for improving gravure and offset printability of coated and uncoated printing papers, comprising the steps of: increasing filler share in the paper on top and bottom 5a sides or in outer layers of a paper web using a retention agent; and, providing outer layers of fiber-bearing liquid forming the paper web with additional retention agent one of before and during sheet formation one of on and between wires of a paper-making machine, the step of providing additional retention agent including spraying the additional retention agent onto a wire gauze in a twin-wire former in a returning drum of top and bottom wires downstream of a turbulence generator.
Suitably, the step of providing additional retention agent includes providing a retention agent having a high positive charge. The additional retention agent may have a charge opposite to that of the retention agent already present in the fiber-bearing liquid. The additional retention agent may consist of at least one of the group consisting of polyethylene imines, polyacrylamides, epichlorhydrine resins, and polyvinylamines. The additional retention agent may consist of cationic hydrocolloids, cationic starch or cationic guar. Suitably, the step of providing additional retention agent includes injecting the additional retention agent in a flow box with a multi-layer device, into the top and bottom layers.
The process for improving the gravure and offset printability of coated and uncoated printing papers by increasing the filler share in these papers on their top and bottom sides or in the pouter layers of the paper web by the use of retention agents is characterized by the fact that, before or during sheet formation on the wires or between the wires of a paper-making machine, the outer layers of the fiber-bearing liquid forming the paper web are provided with additional retention agent.
The use of retention agents in producing paper has long been known and permits good filler and fibrous material retention on the sheet formation wire. Such retention agents are generally added to the fiber-bearing liquid before a mixing organ, e.g., the flow box pump, so that the fiber-bearing liquid is mixed evenly with the retention agent before emerging from the lip or nozzle of the flow box. Starting from the recognition that the inner layer of a paper web, due to the filter effect, already has sufficient retention for filler and fine materials, the inventors realized that an enrichment of the retention agent in the outer layer is advantageous. The problem was thus solved by the additional dosing of retention agent.
Depending on the paper type, retention agents with cationic or anionic charges of various strengths can be used. Although strongly charged retention agents improve the retention of filler and fine materials, such agents can, depending on their reaction time with the fiber-bearing liquid, form large fiber flocks, which negatively affect the fibrous formation in the formed paper sheet. This is known as a cloudy look-through.
However, it has been recognized that this negative effect can be suppressed by shortening the reaction time. Therefore, in an advantageous embodiment of the process according to the invention, a retention agent having a high cationic charge is used.
In addition, so-called dual retention systems are known. In these, the fiber-bearing liquid is provided with a first retention agent, e.g., a cationic agent, before the flow box, and mixed well. Subsequently, but still before the flow box, a second retention agent, in this case, an anionic agent, is added to the fiber-bearing liquid and mixed. The retention agents with opposite charges react with each other and with the fibers, the filler and the fine materials of the fiber-bearing liquid, and contribute to substantially better overall retention. In a further advantageous embodiment of the invention, the charge of the additional retention agent is opposite to that of the retention agent already present in the fiber-bearing liquid supplied to the flow box.
The following known retention agents can be added individually or in mixtures:
polyethylene imines, polyacrylamides, epichlorhydrine resins and/or polyvinylamines.
Cationic hydrocolloids can also be advantageously used. These can consist of cationic starch or cationized guar. When cationic starch or guar is used, it is also possible to influence the charge and network formation via the degree of cationization and the chain length of the starch or guar.
In an advantageous process for providing the outer layers of the fiber-bearing liquid forming the paper web with additional retention agent, the retention agent is injected into a flow box downstream from the turbulence generator across the width of the fiber-bearing liquid flow in its upper or bottom boundary layer. Such a one-layer flow box is called a step diffusor.
In a further advantageous process, the additional retention agent is injected, in a flow box with a mufti-layer device, into the chamber for the top and bottom layers.
In a further advantageous process, when a twin-wire former with a gap device is used, the additional retention agent is sprayed onto the wire gauze in the returning drum of the upper and lower wires.
In an advantageous process for providing the outer layers of the fiber-bearing liquid forming the paper web with additional retention agent, the retention agent is injected into a flow box downstream from the turbulence generator across the width of the fiber-bearing liquid flow in its upper or bottom boundary layer. Such a one-layer flow box is called a step diffusor.
In a further advantageous process, the additional retention agent is injected, in a flow box with a mufti-layer device, into the chamber for the top and bottom layers.
In a further advantageous process, when a twin-wire former with a gap device is used, the additional retention agent is sprayed onto the wire gauze in the returning drum of the upper and lower wires.
A flow box to implement the process according to the invention has, at a right angle to the flow direction of the fiber-bearing liquid, devices for the even dosing of the additional retention agent. In the simplest case, these devices comprise borings arranged in the flow box in a line that extends at a right angle to the flow direction, which borings have inflow devices for the retention agent.
A further device, especially for a mufti-layer flow box with three layers and step diffusors, has borings for injecting retention agent that are located upstream from the respective step diffusors of the top and bottom layers.
A further device, especially for a mufti-layer flow box with three layers and step diffusors, has borings for injecting retention agent that are located upstream from the respective step diffusors of the top and bottom layers.
Claims (9)
1. A process for improving gravure and offset printability of coated and uncoated printing papers, comprising the steps of: increasing filler share in the paper on top and bottom sides or in outer layers of a paper web using a retention agent; and, providing outer layers of fiber-bearing liquid forming the paper web with additional retention agent one of before and during sheet formation one of on and between wires of a paper-making machine, the step of providing additional retention agent including injecting the additional retention agent in a flow box downstream from a turbulence generator, across a width of a suspension flow in top and bottom boundary layers of the suspension flow.
2. A process for improving gravure and offset printability of coated and uncoated printing papers, comprising the steps of: increasing filler share in the paper on top and bottom sides or in outer layers of a paper web using a retention agent; and, providing outer layers of fiber-bearing liquid forming the paper web with additional retention agent one of before and during sheet formation one of on and between wires of a paper-making machine, the step of providing additional retention agent including spraying the additional retention agent onto a wire gauze in a twin-wire former in a returning drum of top and bottom wires downstream of a turbulence generator.
3. A process as defined in claim 1 or 2, wherein the additional retention agent has a high positive charge.
4. A process as defined in claim 1 or 2, wherein the additional retention agent has a charge opposite to that of the retention agent already present in the fiber-bearing liquid.
5. A process as defined in claim 1 or 2, wherein the additional retention agent is selected from the group consisting of polyethylene imines, polyacrylamides, epichlorhydrine resins, and polyvinylamines.
6. A process as defined in claim 1 or 2, wherein the additional retention agent consists of cationic hydrocolloids.
7. A process as defined in claim 1 or 2, wherein the additional retention agent consists of cationic starch.
8. A process as defined in claim 1 or 2, wherein the additional retention agent consists of cationic guar.
9. A process as defined in claim 1 or 2, wherein the step of providing additional retention agent includes injecting the additional retention agent in the flow box with a multi-layer device, into the top and bottom layers.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19627669A DE19627669C2 (en) | 1996-07-10 | 1996-07-10 | Process for improving printing paper |
| DE19627669.1 | 1996-07-10 | ||
| PCT/EP1997/003597 WO1998001622A1 (en) | 1996-07-10 | 1997-07-08 | Process for improving printing paper |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2259970A1 CA2259970A1 (en) | 1998-01-15 |
| CA2259970C true CA2259970C (en) | 2006-10-31 |
Family
ID=37395840
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002259970A Expired - Fee Related CA2259970C (en) | 1996-07-10 | 1997-07-08 | Process for improving printing papers |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2259970C (en) |
-
1997
- 1997-07-08 CA CA002259970A patent/CA2259970C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CA2259970A1 (en) | 1998-01-15 |
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|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |