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
  • D21H21/14—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 characterised by function or properties in or on the paper
  • D21H21/16—Sizing or water-repelling agents
• • 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
  • D21H17/03—Non-macromolecular organic compounds
  • D21H17/05—Non-macromolecular organic compounds containing elements other than carbon and hydrogen only
  • D21H17/17—Ketenes, e.g. ketene dimers
• • 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
  • D21H23/02—Processes or apparatus for adding material to the pulp or to the paper characterised by the manner in which substances are added

Definitions

• the present invention relates to a method defined in the preambles of the independent claims set forth below for a paper making process or other corresponding process, such as board production process or paper converting process, in order to treat the web to be manufactured in the process by an adhesive mixture containing alkyl ketene dimer (AKD) wax.
• the invention also relates to the use of said method.
• AKD size has been used in paper and board production ever since the 1950'ies.
• AKD size can be used as a stock size, in which case the size brought in the paper making process is fed into the stock, for instance to the stock chest or to the short circulation of the mill immediately prior to feeding the stock onto the wire of a paper or board machine.
• AKD size can also be used in surface sizing, in which case the size can be fed for instance together with spray starch onto the web that is being created, or by a size press together with starch onto an at least partly dried web.
• AKD size can also be used in coating the web, in which case the size is fed onto the web to be coated in an on-line or an off-line coating unit, for instance together with coating paste.
• the size can also be brought in the process as a non-diluted product.
• a regular AKD size has proved to be an extremely efficient adhesive that increases the hydrophobicity of paper or board web.
• the use of AKD size has been considered troublesome owing to the technical problems caused by it.
• stickies in various devices of paper or board machines there have occurred stickies in various devices of paper or board machines.
• the decrease of friction in the paper or board web when using large amounts of adhesive may constitute a problem for certain products.
• a common and generally used AKD wax is made of a fatty acid mixture mainly containing palmitinic acid (Ci ⁇ ) and stearic acid (Cis) roughly in the proportion 1:1.
• the melting point of this type of AKD wax is about 50 °C.
• the melting point of another regular and commonly used AKD wax that is formed of a fatty acid mixture mainly containing stearic acid, melting point is about 62 °C.
• the melting of these AKD waxes already begins at a temperature that is 10 - 15 °C lower than said melting point, which means that the melting of AKD waxes generally takes place within the range 40 - 60 °C.
• the process temperatures in the wet end of paper and board machines are within the range 40 - 60 °C, i.e. in the same area where conventional AKD sizes melt.
• the AKD size fed into a paper or board machine already starts melting in the wet section of the machine, immediately after the size gets into contact with the web to be created, in the wet end of the machine, in the wire and press section.
• Said partial melting of the wax starting in the wet end results in the creation of wax-originated stickies both in the stock chest and in the headbox, as well as in the wire section and press section surfaces.
• stickies cause runability problems, production interruptions and extra washing of the machine, i.e. production losses, in addition to which the quality of the manufactured product is weakened for instance by holes created in the paper.
• AKD size dispersion temperature must be kept as low as possible, and that after manufacturing, AKD wax must according to instructions be stored in a cool environment.
• the melting point of AKD wax affects the formation of stickies in the devices in paper or board production processes. Lately it has particularly been found that the formation of stickies is all the more active, the nearer to the mass temperature the melting point of the AKD wax used in each case is. Hence it has often been necessary to choose the ADK wax for the adhesive mixture according to the paper making process temperature, i.e. there has been chosen an AKD wax with a suitable melting temperature - which, however, is not necessarily the AKD wax with the best adhesive capacity.
• AKD size often is weaker than conventional AKD sizes, which results in larger size additions in the process and consequently in higher expenses.
• a method where AKD size has been manufactured of a mixture of several different fatty acids or by adding other adhesive agents to the AKD size mixture in order to achieve a suitable melting point has also brought more difficulties to the size production.
• the object of the present invention is to realize a new improved method for treating the web created in the manufacturing process of paper, board or other corresponding product by an adhesive mixture containing AKD wax.
• the object is to realize an improved method where the above mentioned problems are minimized.
• a particular object of the invention is to realize a method where the sticking of the size in the process equipment is minimized.
• Another object is to realize a method that enables the use of one and the same AKD size dispersion in several different production processes.
• the adhesive mixture is fed in the process as an adhesive dispersion containing solid AKD wax particles,
• the temperature of the adhesive mixture brought in the process is raised at least up to the melting point of the AKD wax contained in the adhesive mixture in order to melt the AKD wax particles contained in the adhesive mixture,
• the thus heated adhesive mixture is fed onto the web to be made by feeding the adhesive mixture into the stock creating the web, onto a web that is being created or has already been created,
• the feeding takes place at a temperature where the AKD wax contained in the adhesive mixture is in a molten state.
• the temperature of the adhesive dispersion brought in the process is first raised at least up to the melting point of the AKD wax contained in the adhesive dispersion in order to bring the wax particles to a molten state. Only after this the adhesive dispersion is fed onto the web to be made, at a temperature that is higher than the crystallization point of the AKD wax contained in the adhesive dispersion. Consequently, in this typical method according to the invention, the following realizations have been utilized:
• the adhesive mixture is thus brought in the process as an adhesive dispersion containing solid AKD wax particles.
• the temperature of the adhesive mixture is kept above the crystallization point of AKD wax, in order to enable the feeding of AKD wax in a molten state onto the web to be made. Therefore it may be necessary to heat the adhesive mixture both in order to melt the wax particles and in order to maintain the temperature of the dispersion containing molten wax on the desired level, if the adhesive mixture tends to cool off too much, i.e. under the crystallization point, before feeding it onto the web to be made.
• the temperature of the adhesive mixture is maintained at a temperature that is higher than the melting point of the wax particles.
• the melting point of the AKD waxes contained in most conventional adhesive dispersions is > 35 °C, even > 60 °C, typically within the range 40 - 60 °C.
• the temperature of the adhesive mixture is typically raised in the melting step of the wax particles up to a temperature that is 1 - 20 °C, typically 5 - 15 °C, over the melting point of the solid AKD wax particles contained in the adhesive mixture.
• the melting point is typically higher than the process temperature, or very near to the process temperature, i.e. near to the stock temperature in the stock chest or to the temperature of the created web in the wet end of the machine and/or in the press section, the temperature of which is generally within the range 40 - 60 °C.
• AKD wax remains molten, even if the temperature thereafter decreases for several degrees. AKD wax remains molten even if the temperature decreases under the wax melting point, because the wax crystalhzation point is about 15
• AKD wax is not sensitive to form stickies near the AKD wax melting point, i.e. in conditions that were earlier considered as risky with respect to the formation of stickies.
• the temperature of the adhesive mixture generally has no time to drop below the AKD wax crystallization point before feeding the adhesive mixture onto the web to be made.
• the adhesive mixture is fed ⁇ 60 seconds, typically ⁇ 10 seconds, even ⁇ 5 seconds after preheating onto the web to be made.
• the adhesive dispersion can be fed directly onto the web to be made, or for example to the water circulation in the wet end of the machine, and further onto the web as diluted with water.
• the temperature of the adhesive mixture can be raised in many different ways.
• the adhesive mixture temperature can be raised by mixing the adhesive mixture with some other processing agent circulation to be mixed onto the web to be made, such as to the pulp starch circulation, or to some hot water circulation, such as water circulation used for diluting the stock, the temperature of which circulations is normally higher or has in the process in question raised higher than the melting point of the AKD wax contained in the adhesive mixture.
• the temperature of the pulp starch circulation is about 60 °C, which is sufficient for raising the temperature of the adhesive dispersion very rapidly over the AKD wax melting point or to maintain the AKD wax contained in the adhesive mixture in a molten state.
• pulp starch serves in the adhesive mixture as an auxiliary protection colloid, thus also improving the functionality of the AKD adhesive mixture.
• the AKD adhesive dispersion can be diluted with hot water in order to raise or maintain the temperature.
• the employed diluting water must be so hot that it is capable of raising the AKD wax temperature up to the desired temperature within the same period of time during which the diluted adhesive mixture proceeds up to the adhesive feeding point, i.e. typically in a few seconds.
• the adhesive mixture can also be fed in another substance circulation that can be fed onto the web to be made.
• the adhesive mixture temperature can also be raised by means of a heat exchanger or by heating the adhesive mixture by electric heating or by some other means, for instance in a pipe through which the adhesive mixture is fed onto the web to be made.
• the adhesive mixture temperature can advantageously be raised in a period of less than 60 seconds, typically ⁇ 10 seconds, most typically ⁇ 5 seconds, before feeding the adhesive mixture into the stock that creates the web.
• the AKD size is very rapidly attached to the web after the temperature rise, and it has no time to be harmfully hydrolyzed before it.
• the invention can also be applied so that the AKD wax is molten already when the adhesive mixture is brought in the process, and that the adhesive mixture is maintained at a temperature that is higher than the crystallization point of AKD wax, until the adhesive mixture is fed onto the web to be made.
• R is hydrogen or a hydrocarbon chain and R', R" and R" ' are hydrocarbon chains.
• the hydrocarbon chains R' , R" and R' ' ' can be same or different hydrocarbon chains, mainly containing 12 - 22 carbon atoms. Generally the major part, i.e. > 80 % or typically > 90 % of the hydrocarbon chain is derived from palmitinic and or stearic fatty acids.
• a fatty acid mixture where the amount of fatty acids is as follows, in percentages by weight:
• the adhesive mixture is chosen so that the crystallization point Ti of the AKD wax contained therein is lower, preferably 1 - 10 °C lower, than the temperature T2 of the web to be made.
• the adhesive mixture constituting the adhesive may include other stock size components, such as water, stabilizing agents, protective colloid, typically starch, emulsifying agent, other surface active agents, pH adjusting agent, biocide and/or other adhesive, such as alkenyl succinic acid anhydride (ASA) size, styren maleic acid anhydride (SMA) size, or other polymer, resin or paraffin size.
• ASA alkenyl succinic acid anhydride
• SMA styren maleic acid anhydride
• the feeding of the adhesive mixture means, unless otherwise stated, the feeding of the adhesive mixture into contact with the main part of the web to be made.
• a paper or board making process such as the web making process, the surface treatment process or the finishing process, such as the coating process,
• the arrangement according to the invention can advantageously be used in the making of paper and/or board containing wood or pulp fibers or other corresponding fibers, typically in their stock sizing, web surface sizing and/or coating.
• the invention can also be utilized in the making and refining of webs containing synthetic fibers, such as nonwoven webs.
• the invention can advantageously be applied in the surface sizing and coating of paper or board, also because the molten AKD wax is distributed better and more evenly on the paper or board surface than solid wax particles.
• the invented simple method enables the use of solid AKD wax sizes in paper and board machines without weakening the machine runability or the product quality.
• any harmful melting of the AKD size is essentially eliminated in the wet end of paper and board machines proper, and also elsewhere stickies caused by melting are clearly diminished or altogether eliminated.
• the sizing efficiency remains high, because it is not necessary to make the prior art changes in the composition of the AKD wax in order to adjust the melting temperature.
• the invention enables a simpler use of the AKD wax and a simpler adhesive dispersion production.
• the size it is no more necessary to take into account the process temperature, because the size is made to function in a process where the process temperature is within the range of the size melting temperature.
• the size can be chosen fairly freely according to the desired composition of the process adhesive or other criteria, not according to the functionality in the process.
• the advantage achieved by the invention can also be described as follows: Earlier paper or board manufacturers had to choose such an AKD wax type that was in each case suited to the process conditions at hand. Thus it has not been possible for example to choose an AKD wax where the contained fatty acids are mainly derived from stearic acids, if said AKD wax causes serious stickies. Instead, it has been necessary to choose an AKD wax with a lower melting temperature, in order to ensure good runability. However, in this case the achieved sizing efficiency has been poorer. Owing to the present invention, the making of this choice is no more necessary. Now an AKD wax that in normal process conditions would be solid is heated prior to feeding it into the process, and it is maintained in this non-harmful state, so that a good runability and an efficient sizing result can be ensured.
• the arrangement according to the invention can also be used in cases where the melting point of the AKD wax is higher or on the same level as the process temperature in the wet end of the paper or board machine where the AKD wax is used for sizing. In that case, however, the process temperature is advantageously higher than the crystallization point of the AKD wax.
• Figure 1 illustrates the melting and crystallization diagram of an AKD wax
• Figure 2 illustrates the melting and crystallization diagram of another AKD wax
• Figure 3 illustrates the melting and crystallization diagram of a third AKD wax
• Figure 4 is a schematical illustration of the wet end of a paper machine, where different possibilities for the feeding points of AKD wax are marked by way of example.
• Figure 1 illustrates the melting diagram A and the crystallization diagram B of an AKD wax, according to the Perkin Elmer Thermal Analysis 10° C/min.
• the melting diagram A of Figure 1 it can be seen that the melting of AKD wax already starts below the temperature of 30 °C and continues up to the temperature of somewhat over 50 °C.
• this wax is being fed without first melting it as is suggested in the invention, into a paper making process having the temperature of about 40 °C, i.e. to a process where the temperature is in the middle region of the wax melting range, the result is that the AKD wax shall be present in the process both in a molten and solid form. Practice has shown that in that case the wax tends to create stickies.
• this wax is, according to method of the present invention, first melted before it is fed in the process, i.e. the wax temperature is raised up to the melting point, to a temperature of about 48 °C or slightly higher, i.e. when the wax is melted completely or nearly completely, the molten wax will, as can be seen in the crystallization diagram B, remain in a molten state as long as the wax is cooled off to a temperature under 35 °C, i.e. until its temperature is lower than the process temperature (40 °C). Consequently, this wax does not cause stickies in the process.
• Figure 2 respectively illustrates the melting and crystallization diagrams A and B of another AKD wax.
• the melting of this wax takes place mainly in the temperature range 50 - 65 °C.
• this wax would remain solid in processes where the temperature is 40 °C, if the prior art sizing methods would be applied. In that case, the advantages provided by molten wax would not be reached.
• this wax When this wax is, according to the invention, heated up to a temperature that is over 65 °C, the wax starts to melt. According to diagram B, the wax is only crystallized at the temperature of about 40 °C. According to the invention, the wax is suited to be used in processes where the temperature is somewhat over 40 °C.
• Figure 3 respectively illustrates the melting and crystallization diagrams A and B of another AKD wax.
• the melting of this wax is mainly carried out within the temperature range 30 - 45 °C.
• this wax would appear both in molten and solid form, like the wax illustrated in Figure 1.
• the wax is according to the invention heated before feeding it into the process, up to a temperature of over 45 °C, the wax is completely melted and thus the runability problems caused by solid wax can be avoided.
• the diagrams A and B in Figures 1 - 3 show that in these cases, there is a difference of about 20 degrees between the temperature required for melting the wax and the wax crystallization point. This difference makes it possible for the wax to remain molten, even if its temperature drops below the melting point.
• melting point and crystallization point mean the peak points of the above described diagrams A and B.
• melting temperature means the temperature where the major part, typically > 90 % of the wax has melted.
• Figure 4 illustrates the wet end of a paper machine 10, including a headbox 12 and a wire 14, a wire pit 16, a white water tank 18, stock cleaning 20 and stock chest 22.
• Stock feeding pipes 24, 26 convey the stock by pumps 28, 30 from the stock chest 22 to the stock cleaning 20 and further to the headbox 12.
• Figure 4 also illustrates white water pipes 32, 34, 36 for conveying the white water from the white water tank 18 to the stock feeding pipe 24, to stock cleaning 20 and to the stock feeding pipe 26.
• the adhesive dispersion containing AKD wax can for instance be conveyed by a conduit 38 to a line 40 that conveys the pulp starch into the stock chest 22, when the temperature of the pulp starch is suitable for melting said AKD wax.
• the adhesive dispersion containing AKD wax can be fed through the pipe 42 or 44 to a white water pipe 32 or 36 supplying the dilution water, when the water temperature is suitable for melting said AKD wax.
• the AKD wax dispersion can also be brought through the pipe 46 directly for instance to the stock feeding pipe 26 without first mixing the- dispersion in the starch or stock circulation.
• the temperature of the AKD wax dispersion can prior to feeding into the stock feeding pipe 26 be raised for example in a heat exchanger 48.
• the temperature of the AKD wax dispersion can also be raised by means of other suitable means.
• Figure 4 illustrates various possibilities for bringing the AKD wax dispersion into the process and into the wet end of a paper making process, so that the AKD wax can be heated and fed in a molten state in the headbox.
• the adhesive mixture is brought in the process through the pipes 38, 42, 44 and/or 46'. Thereafter the adhesive mixture with a raised temperature is fed into contact with the web to be made through the pipes 40, 32, 36 and/or 46.
• the AKD wax can in a paper machine or other corresponding machine be fed onto the web that is being created and/or has been created, such as

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• Adhesives Or Adhesive Processes (AREA)

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Family Applications (1)

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Citations (4)

• 2002
  • 2002-07-15 FI FI20021387A patent/FI20021387A0/fi unknown
• 2003
  • 2003-07-15 AU AU2003246746A patent/AU2003246746A1/en not_active Abandoned
  • 2003-07-15 WO PCT/FI2003/000566 patent/WO2004007840A1/en not_active Application Discontinuation

Patent Citations (4)

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