MXPA99010624A - Absorbent and soft paper product containing cethane dimero agents off - Google Patents

Abstract

The present invention relates to new and improved methods related to increasing the softness of paper sheets, without affecting the wettability. The increased softness, without the loss of wettability is obtained by adding ketene dimer predispersing agents inactivated

Description

ABSORBENT AND SOFT PAPER PRODUCT CONTAINING CETENA DIMER AGENTS DISABLED BACKGROUND OF THE INVENTION The use of ketene dimer based agents in the paper industry to impart sizing or water resistivity to paper products is well known. Such agents are commercially available from Hercules, Ine, of Wilmington Delaware under the trade names AQUAPEL® and HERCON®. The patents that describe the compositions, variations and uses of these types of agents are: Inventor No. Patent Publication Date Aldrich, and others 3,922,243 November 25, 1975 Anderson 3, 957,574 May 18, 1976 Aldrich, and others 3,990,939 November 9, 1976 Aldrich 4,017,431 April 12, 1977 Aldrich, and others 4,087,395 May 2, 1978 Dumas 4,240,935 December 23, 1980 Dumas 4,243,481 January 6, 1981 Dumas 4,279,794 July 21, 1981 Dumas 4,295,931 October 20, 1981 Bankert, and others 4,407,994 October 4, 1983 Bankert, and others 4,478,682 October 23, 1984 Edwards, and others 4,861,376 August 29, 1989 Cenisio, and others 4, 919,724 April 24, 1990 Walkden 4,927,496 May 22, 1990 Nolan, and others 5,484,952 January 16, 1996 Zhang 5,525,738 June 11, 1996 The descriptions of which are incorporated herein by reference, These sizing agents when added to the wet end of the paper making machine, in the sizing press or to the finished product in an application outside the machine impart water resistivity to the paper, by decreasing the hydrophilicity of the sheet. The use of these prepping agents in writing paper, in the liner board, in the grocery bags and in the milk boxes is well known, since all these paper products require sizing.

These types of prepping agents are well known because they produce a very hard material (with high resistivity to wetting) such as a milk box. The use of these dressing agents in tissue and towels, although not unknown, has been very limited, because water resistivity is not desirable in these products. On the contrary, it has been a long-standing goal in the tissue and towel industry to increase rather than decrease the rate at which the product is moistened and the total amount of water that the product can absorb. For example, however, the use of ketene dimer precuring agents in tissue and towel products to increase water resistivity is found in European patent application number 0 144 658 in the name of Dan Endres, assigned Kimberly-Clark Corporation.

It has been found that the use of the keten dimer deactivating agents in the tissue and towels increases the softness of these products while not materially affecting the absorbency of water or hydrophilicity.

SYNTHESIS OF THE INVENTION In an embodiment of this invention, there is provided a soft absorbent tissue product comprising long and short papermaking fibers and having a hydrolyzed ketene dimer agent. A soft absorbent paper product comprising papermaking fibers and at least about 1 pound per tonne of a hydrolyzed ketene dimer agent, is further provided with the tissue having an absorbance rate test of less than about 50 seconds. .

In a further embodiment of the invention, there is provided a soft absorbent tissue sheet comprising a first layer and a second layer with the first layer comprising predominantly long papermaking fibers and the second layer comprising predominantly short papermaking fibers . At least one of these layers further comprises a ketene dimer and this layer is easily wettable in water. This soft tissue can be creped or dried continuously. This can also have an absorbance rate test of less than about 10 seconds.

In still another embodiment of the invention, there is provided a soft paper product having papermaking fibers and at least about 1 pound per tonne of ketene dimer sizing agent fibers that has been neutralized so that the product has a Absorbency test of less than about 40 seconds.

In still another embodiment of the invention, a sheet of paper having an improved smoothness comprising a first sheet surface and a second sheet surface and having a layer comprising paper fibers has been provided. The layer has a surface that corresponds to the surface of the sheet for making paper. The surface of the layer has a ketene dimer-trapping agent deactivated therein so that the wettability of the sheet is equivalent to that of a sheet of similar composition but which does not have therein the deactivated ketene dimer-prescribing agent. This sheet of paper can be a bath tissue having a second layer comprising fibers for making paper or a towel product. This sheet can also be a facial tissue with two or more layers comprising fibers for making paper. This sheet can also be a three layer sheet.

A further embodiment of the present invention is a sheet of paper having an improved softness comprising fibers for making cellulose paper and a hydrolyzed ketene dimer agent in which the sizing of the sheet is not greater than about three times the sizing of a sheet of a similar composition but not having the hydrolyzed ketene dimer agent.

In an alternate embodiment of the invention, there is provided a method for making an absorbent and soft paper sheet product having improved smoothness. This method comprises forming in a pulp reducer an aqueous solution comprising papermaking fibers, hydrolyzing a ketene dimer-sizing agent, combining the hydrolyzing product of the ketene dimer-sizing agent with the papermaking fibers, and removing the water from the aqueous solution to form a sheet of paper. In this method, the product of hydrolyzing the ketene dimer can be combined with the fibers to make paper either before, or during or after the removal of the water from the solution.

In still another embodiment of the invention there is provided a highly absorbent and soft mixed base sheet having a ketene dimer deactivating agent deactivated. This mixed base sheet can have long and short paper fibers.

DRAWINGS Figure 1 is a schematic process flow diagram generally showing the manufacture of paper products.

DETAILED DESCRIPTION OF THE CURRENTLY PREFERRED INCORPORATIONS OF THE INVENTION The ketene dimers used in the paper industry to impart sizing, or paper resistivity to water, generally have the chemical structure: R1-CH = C-CH-R2 I! 0-C = 0 in which R! and R2 can be a wide range of carbon column structures. Known structures and methods for making these products are described in the above-mentioned patents which are incorporated herein by reference.

When such a sizing agent is used to impart water resistivity, it is speculated that the four-membered ring consisting of one oxygen and three carbon atoms, also known as the lactone ring, is primarily responsible for the formation of a covalent bond to cellulose fiber. It is also speculated that the lactone ring undergoes a reaction with the hydrophilic group on cellulose. Once this reaction is completed the R groups are then reoriented, through the application of heat, air flow or pressure out of the cellulose fiber. Therefore, they in effect create a hydrophobic monomolecular layer on the outer surface of the cellulose fiber. It is speculated that it is this outer hydrophobic surface layer that provides the water resistivity to the paper product that is observed when these sizing agents are used.

When a ketene dimer-priming agent is hydrolyzed before being contacted with the cellulose fiber, its ability to prepare the sheet, for example, imparting water resistivity is greatly reduced, if not eliminated. As such, the addition to the paper machine formation of this hydrolyzed agent has been avoided for some time. It has surprisingly been found, however, that the addition of such hydrolyzed ketene dimer-preparing agents to the tissue and towel products increases the softness, while allowing the product to remain hydrophilic. Therefore, the absorbency of water (both rate and total volume) is not materially affected.

Referring to Figure 1, which is a schematic process flow diagram of a process for making paper, the cellulose fibers are prepared in a pulp reducer (not shown) to form an aqueous solution of water fibers which is mentioned as a supply or a supply solution. The supply is pumped to the box 1, which can be mentioned as a draining box. From the emptying box the supply is pumped to another holding box 2, which can be mentioned as a machine chest. From the machine chest the supply is pumped by the ventilation pump 3 to the head box 4 of the paper making machine 5. On or before the fan pump, the supply is diluted with water. Usually and preferably, the dilution is made with return water, referred to as white water from the paper making machine. The flow of white water is shown by lines 6 and 7. Prior to dilution the supply is referred to as a thick supply, and after dilution and supply is referred to as a water supply.

The water supply is then dewatered by the forming section 8 of the paper making machine to form embryonic tissue of wet cellulose fibers. The wet fabric is then transferred to a dryer 9, which removes the water from the wet tissue that forms a sheet of paper. The paper sheet then leaves the dryer and rolls onto the cart 10.

It should be understood that Figure 1 is a general description of the process for making paper and is meant to illustrate that process and in no way limits the scope of the present invention. Many variations in the process and in the equipment are known to those skilled in the art of papermaking. For example, various types of dryers can be used including dryers through air, dryers with and without creping, tunnel driers and can dryers or any combination of these. Although the scheme generally shows a twin wire type forming section, other forming sections known in the art may be used. The additional components can also be added or removed from the process. For example, grids, filters and refiners, which are not illustrated, can typically be placed between the pulp reducer and the headbox. The transfer section 11 of the paper making machine may not be present or may be expanded to include additional water removal devices. Additional steps can also be added to the machine after the dryer and before the reel, such as calendering and the use of the size press, even when additional drying is usually required after the press application is used. of sizing The calendering and coating operations can also be carried out outside the machine.

Paper sheets can be made of long paper fibers (soft wood), short paper fibers (hardwood), secondary fibers, other natural fibers, synthetic fibers or any combination of these or other fibers known to those skilled in the art of papermaking as being useful in the manufacture of such paper. The long papermaking fibers are generally understood to have a length of about 2 millimeters or greater. Particularly suitable hardwood fibers include eucalyptus and maple fibers. As used herein, the term "paper fibers" refers to any and all of the above mentioned.

As used herein, and unless otherwise specified, the term "sheet" generally refers to any type of sheet of paper, eg, tissue, face towel, bath tissue or heavier weight basis product, creped or non-creped, blended, multilayer or single layer and multiple layer or single layer.

The deactivation or neutralization of the ketene dimer sizing agent can be achieved by hydrolyzing the agent. The formation of the hydrolyzed ketene dimer agent was achieved by combining a ketene dimer sizing agent with water and then heating. This can be more easily achieved by heating the raw ketene dimer-sizing agent in the presence of water. It is believed that this reaction is best carried out before the agent is added to the papermaking system, but can be removed performed in the papermaking system if that system is such that the reaction can be essentially completed before the agent comes in contact with enough fibers so that the agent does not tighten the sheet.

The hydrolyzed ketene dimer agent can be added at the wet end of the paper making machine to any thick or watery supply. For wet end applications the hydrolyzed agent will preferably be formed in an emulsion and will have an added promotion agent thereto as well. Such promoters will include organic or inorganic retention aids such as polyaminoamides, polyamines, polyethylene imine resin, polychlorinated dialkyldimethylammonium polymers or copolymers, cationic starch, amphoteric starch, gums and any other natural and synthetic polyelectrolytes and their derivatives. In addition to the wet end addition, the hydrolyzed ketene dimer agent can be added to the embryonic tissue, the partially dried leaf or the dried leaf. This can be sprayed or applied by roller application either as an application on the machine or machine strength. The method and the optimum application point will depend on the particular paper type and the machine, however, it should be selected to optimize the distribution of the hydrolyzed agent in or on the sheet, minimizing the effect on the run of the machine, such as for reduce the amount of foam, and maximize the increase in softness for the amount of agent used.

The types of ketene dimers that are available to form the hydrolyzed ketene dimer agent can vary greatly. The hydrolyzed ketene dimer can be derived from either plant and animal fatty acids, which can have branched or unbranched, saturated or unsaturated R groups. In addition, at least one group R can be substituted with one H. The currently preferred chain extensions for these R groups vary from C6 to C24 and can optionally vary from about C8 to about C22 and furthermore can optionally vary from C8 to C18.

The amount of hydrolyzed ketene dimer agent that is added to the paper will depend on the ketene dimer being used, the type and composition of the paper being made, and the manner and point in the papermaking process in which the hydrolyzed agent is added. Currently it can be used between about 0.5 to about 5 pounds per ton of paper (dry basis weight) of hydrolysed agent. Even when depending on the application, the benefits of this invention can be seen with lower and higher amounts. From about 0.5 to about pounds per ton they can be used optimally for the wet end addition. The practical upper limits for the amount of the thihydrolyzed agent used mainly will be controlled by the run of the machine, the absorbency of the leaf and the cost.

The addition of hydrolyzed ketene dimer to the leaf does not materially affect the wettability of the sheet, for example, it does not impart sizing to the leaf. Therefore, the rate of water absorption and the total amount of water that a softened sheet can absorb with a hydrolyzed ketene dimer agent is materially different from an equivalent sheet that does not have the hydrolyzed agent. These sheets can have as much as one to two times the increase in sizing compared to a sheet without the hydrolyzed agent, and still exhibit a sufficient hydrophilicity.

The wettability of the sheet, or the amount of sizing, can be measured in several ways. Afterwards, all samples must be aged and tested according to the TAPPI standards.

The Absorbency Test Rate - The absorbency rate is the time it takes for a product to become completely saturated in the distilled water. Samples are prepared as 2 and a half inch squares composed of 2 sheets of finished product using a matrix press (eg TMI DGHD from Testing Machines Incorporated Inc., Amityville, New York, 11701). The stratum of a finished product dictates the number of individual sheets: 1-stratum: 20 individual sheets 2 -stratum: 40 individual sheets 3 -stratus: 60 individual sheets When soft rolls are tested (single layer of tissue coming out of the tissue machine before playing on the rewinder), 40 individual soft roll sheets are used per sample.

Samples are stapled at all four corners using Swingline S.F. speed point staples. 4 (the staples are half an inch wide with legs a quarter inch long). The samples are tested in a constant temperature water bath at a depth of at least 4 inches (maintained through the test) maintaining the distilled water at 30 +/- 1 degree celsius. The sample is kept close to the surface of the water (the tips of the staples in the downward position) and then pulled flat on the surface of the water. A timing is started (readable at 0.1 s) when the sample hits the water. When the sample is completely saturated, the stopwatch stops and the absorbing rate is recorded. A minimum of five samples were tested.

All tests were carried out in a standard laboratory atmosphere of 23 +/- 1 degrees Celsius and 50 +/- 2% RH. All samples were stored in a laboratory at least 4 hours before the test. All samples are aged and tested at TAPPI conditions.

Hercules Stencil Test (HST) - A small volume of ink was placed on the paper sample to be tested. The sample amount is typically one to five layers of paper. A photoelectric eye then measures the time that is required for the reflectance of the sample to fall to a specific level from its original point. This test is typically used for bleached paperboard, cup supply, fine paper and linerboard grades. This test can be used to measure readiness in facial tissue classes.

Flotation Tests - A paper sample is floated on an aqueous solution. The test is timed and reaches its completion when the sample has been completely saturated with the test solution. The type of solution use will depend on the final use of the paper. The typical solutions used are water, ink, fluorescent dye and ammonium solutions. The use of flotation tests is usually limited to the types of thin paper. Linerboard, gypsum board and cup supply are typically not tested with this method due to the excessive time required to saturate the sample. A water bath saturation test can be used to measure sizing in facial tissue classes.

Boiling Pot - This test measures the time required for a sample of paper in the form of "pot" to be completely saturated in boiling water. This test is typically used for highly prepared classes such as plasterboard and linerboard.

Valley Fill Test - A paper sample is connected to each end by an electrode. The sample is immersed in a water solution and the conductivity of the paper sample, after a predetermined period of time was measured. The use of this test is typically limited to the "cyliner" paper classes.

Carrier - Sizing is measured by the time necessary for a paper sample, soaked in an aqueous fluid, to complete an electrical circuit. This test has become very popular in use in lining carton classes.

Immersion Test - A paper sample is weighed and then soaked in a water bath for a predetermined period of time. Sizing is measured by the weight of water that has been absorbed during the test. This test is frequently used for fine paper classes.

Edgewick - A sample of paper is submerged on this edge in a liquid sample of lactic acid, peroxide, coffee, etc. This test measures the amount of liquid that is taken by the paper over a defined period of time. This test is exclusively used for food packaging classes such as milk cartons and other liquids for packaging applications.

Klemm - The end of the paper sample is immersed in a liquid bath. Sizing was measured by the amount of time it takes the liquid to rise up the sample to a predetermined point. This test is very flexible and can be used for many classes booked.

Typically, the tissue made without the use of dressing agents showed an absorbance test rate of from about 1 second to about 10 seconds. The towel made without grooming agents typically shows an absorbency rate of about 1 to about 50 seconds. When a tissue and a towel are primed with a ketene dimer-priming agent it can be anticipated that the levels of sizing, or water resistivity will be substantially increased with the tests of absorbance rate of as much as 25 seconds or longer occurring in for example the tissue The tissue having an improved softness of the use of hydrolyzed keten dimer agents remains hydrophilic, having a very low resistance to wetting, for example, these are not prepared and therefore are easily moistened. The water absorbency rate test for such softened sheets are from about 1 to about 4 seconds, but may be about 10 seconds or more depending on the type of paper, the basis weight and other physical characteristics of the sheet . For tissue and paper towel products the water absorbency test results in less than 40 seconds and is believed to show that the sheet is essentially hydrophilic and is seen as low or insignificant levels of sizing.

The prepping agents can typically exhibit a threshold effect on the development of water resistivity. Thus, for example, the initial one quarter to 2 pounds / tonne of sizing agent may develop little or no increased water resistivity. But at any higher amounts the increase in water resistivity can be substantial. This threshold level will vary from the type of paper to the type of paper and from the sizing agent to the sizing agent. By using a deactivated spreading agent, the addition of this agent above the sizing threshold level is thus allowed to have smoothed benefits without experiencing a dramatic loss of hydrophilicity.

This is described below as an example of a single-end delivery system which can be used in the manufacture of tissue having a deactivating dressing agent. A divided supply system with several chests can be used for the storage of an aqueous suspension of papermaking fibers. From these chests, water fiber suspensions can enter separate boxes used to maintain a constant pressure head. A divided delivery system has the advantage of being able to selectively apply the chemicals to certain fibers and layered these fibers during the forming process. Alternatively, a single current supply system can be used with a hood, a box and a fan pump.

A part of the output current from the box can be pulled out as a separate current and sent to a fan pump while the remaining part can be recirculated back to the top of the box.

Alternatively, the complete outlet of the box can be sent to the fan pump.

The deactivating preparation agents produced by hydrolyzing the alkyl ketene dimer (Hercon) in hot water can be added at any point in the process. This agent can be added only, with the help of retention or with any other chemicals that help the distribution and retention of the agent on the fibers. Other functional chemicals such as dry strength resins and wet strength resins can also be added. Additionally, the supply can be passed through the refiners. The papermaking fibers treated with deactivated preparation agents can be supplied to all or some of the headbox layers. In order to achieve the target wetting time for a product, the absorbency rate or wetting time can be controlled by varying the dose level of the deactivating dresser agent or by varying the percent or degree of deactivation of the dressing agent. Therefore, by way of illustration the agent agent can be 80% deactivated rather than 100% deactivated. Some sizing or delayed wetting can be beneficial for certain products. Therefore, the absorbency or controlled wetting time of the final product or any layer or stratum within the final product can be achieved. This can be particularly useful to create moisture barriers in some layers of the paper product that will maintain the absorbency in other layers. layers.

Deactivating wetting agents can be applied to the dry fabric by spraying an aqueous solution through a spray distributor bar or dryer section. Similarly, disabled dealers can be sprayed in off-line wrapping operations by using a similar spreader bar or other off-line application methods used in papermaking.

Example The eucalyptus fibers are pulped for 30 minutes and placed in a draining chest which feeds a machine chest. In a similar way, it was reduced to pulp by minutes a mixture at 72% kraft of soft northern wood and 28% kraft of hardwoods from the north and was placed in a draining chest which feeds another machine chest. The eucalyptus fibers enter a section of a multilayer tow box and exit through a stream. No chemical addition is made to this stream. The mixture of soft northern wood fiber / northern hardwood in the machine chest is supplied to another section of the multi-layer supply box. The Hercon 79 deactivated (Hercon 79 is available from Hercules Incorporated) and fed at the outlet of the packing box at an addition rate of 1.25 pounds / tonne of solids by weight of total sheet. A commercially available wet strength agent is added in the amount of 0.82 pounds / ton of active solids per total leaf weight. The final sheet has the following fiber composition: 50% eucalyptus, 36% kraft softwood from the north and 14% kraft from the northern hardwood. This sheet is soft and highly absorbent.

Claims (21)

R E I V I ND I C A C I O N S

1. A soft, highly absorbent tissue product comprising long and short papermaking fibers and a hydrolyzed ketene dimer agent.

2. A soft absorbent paper product comprising papermaking fibers and at least about pound per ton of hydrolyzed ketene dimer agent, and tissue having an absorbance rate test of less than about 50 seconds.

3. The paper product as claimed in clause 2, characterized in that the product also comprises a three-layer base sheet.

4. An absorbent and soft tissue sheet comprising: a first layer and a second layer; the first cap comprises predominantly long papermaking fibers and the second layer comprises predominantly short papermaking fibers; at least one of the layers further comprises a ketene dimmer; and the layer comprising a ketene dimer is easily wettable by water.

5. The soft tissue sheet as claimed in clause 4, characterized in that the sheet is creped.

6. The soft tissue sheet as claimed in clause 4 characterized in that the sheet is dried continuously.

7. The soft tissue sheet as claimed in clause 4 characterized in that the absorbance rate test is less than about 10 seconds.

8. The soft tissue as claimed in clause 4 further characterized in that it comprises a third layer.

9. A soft paper product having papermaking fibers and at least about 2 pounds per tonne of ketene dimer sizing agent fiber that has been neutralized; The product has a test of absorbency rate of less than about 40 seconds.

10. A sheet of paper having an improved smoothness comprising: a first sheet surface and a second sheet surface; a layer comprising fibers for making paper; the layer has a surface; the surface of the layer corresponds to a surface of the paper sheet; the surface of the layer has a ketene dimer primer agent deactivated there; and the wettability of the sheet is equivalent to a sheet of a similar composition but not having the ketene dimer-prescribing agent deactivated therein.

11. The sheet of paper as claimed in clause 10 characterized in that the sheet is a bath tissue.

12. The sheet of paper as claimed in clause 11 characterized in that the bath tissue has a second layer comprising fibers for making paper.

13. The sheet of paper as claimed in clause 10 characterized in that the sheet is a towel product.

14. The sheet of paper as claimed in clause 13 characterized in that the towel product has a second layer comprising fibers for making paper.

15. The sheet of paper as claimed in clause 10 characterized in that the sheet is a facial tissue.

16. The sheet of paper as claimed in clause 15 characterized in that the facial tissue sheet has a second layer comprising fibers for making paper.

17. A sheet of paper having an improved softness comprising: fibers for making cellulose paper and a hydrolyzed ketene dimer agent; the sheet finisher being no greater than about three times the dresser of a sheet of a similar composition but not having the hydrolyzed ketene dimer agent.

18. A method for making an absorbent paper sheet product having improved softness comprising: (a) forming an aqueous solution comprising fibers for making paper in a pulp reducer; (b) hydrolyzing a ketene dimer-sizing agent; (c) combining the hydrolyzing product of ketene dimer sizing agent with papermaking fibers; (d) remove the water from the aqueous solution.

19. The method as claimed in clause 18 characterized in that the product of the hydrolyzation of the ketene dimer is combined with the fibers to make paper before the removal of water from the solution.

20. The method as claimed in clause 18 characterized in that the product of the hydrolyzation of the ketene dimer is combined with the fibers to make pape after the removal of the water from the aqueous solution.

21. A high-absorbent papermaking product comprising a mixed base sheet and a ketene dimer deactivating agent; said mixed bas leaf comprises long and short papermaking fibers. R E U M N New and improved methods are described related to increasing the softness of paper sheets, if they affect wettability. The increased softness, without the loss of wettability is obtained by adding ketene dimer deactivating agent deactivated to the sheet.