MXPA96001666A - Method for designing paper of dese - Google Patents

Abstract

The present invention relates to a method for deinking waste paper fibers, comprising the steps of: disintegrating the waste paper into an aqueous alkaline solution containing sodium sulfite and sodium carbonate without other bleaching agents and without caustic soda added to form a pulpafibrosa that has a ph of at least about 7.5, separate the ink from the paper fibers in the pulp, and remove the ink separated from the pulp

Description

METHOD FOR THE DISPOSAL OF WASTE PAPER FIELD OF THE INVENTION The invention relates to a method for destining printed waste paper, and with the use of a deinking agent, to produce a recycled pulp that can be processed into paper products.

BACKGROUND OF THE INVENTION Waste paper has long served as a source of raw material for use in papermaking but, normally, recycled waste paper is used to manufacture low quality paper and pressed cardboard products. Currently, as consumers have become ecologically more aware, the demand for a higher content of recycled paper in higher quality paper has increased. Due to its quantity, waste newspaper is a particularly important source. It is necessary to eliminate the ink from these waste paper papers, so that they can be used in the production of high quality products. In a conventional waste paper recovery process, the deinking methods include: disintegrating the waste paper or "raw material" to give a pulp or pulp in an alkaline aqueous de-inking solution that P1125 / 96MX contains the deinking agents; wash and then whiten the dough. The physical agitation of the paper fibers causes some ink separation. Caustic soda is normally used to provide the alkalinity necessary to promote the swelling of the fiber which results in the remaining ink separating from the paper fibers. A surfactant is added to prevent the ink from re-adhering to the fibers. The surfactant also acts as a foaming agent to remove the ink when the fibers are washed in flotation cells. To whiten and brighten the pulp to the appropriate end-use requirements, hydrogen peroxide or other bleaching agents are added. Metallic silicates are added to stabilize the bleaching agents. Caustic soda and bleaching agents can have deleterious effects on paper fibers. At the high pH levels necessary for the caustic soda to promote ink-fiber separation, the strong alkalinity can weaken the fibers and cause alkaline dimming. Although the bleaching agents counteract the darkening, these agents can further weaken the fibers. Therefore, there is a need for a waste paper deinking process that reduces the amount of chemical compounds that are required and simplifies the P1125 / 96MX process, and achieve brighter and more flexible fibers.

SUMMARY OF THE INVENTION The present invention provides a method of deinking recycled fibers by disintegrating the waste paper in an alkaline aqueous solution containing sodium sulfite and sodium carbonate, to produce a fibrous pulp having a pH of at least approximately 7.5; separating the ink from the fibers and removing or eliminating the ink from the pulp. This process advantageously provides the alkalinity necessary to separate the ink without imparting brittleness or darkening the fibers. In another embodiment, a composition used to promote the ink-fiber separation consisting of sodium sulfite and sodium carbonate in a ratio between about 95: 5 and 50:50, and a surfactant is provided. The use of this invention can produce recycled pulp of the desired brilliance, so that additional bleaching is totally eliminated or greatly reduced. Additional advantages and benefits will be apparent from the detailed description of the invention.

P1125 / 96MX DETAILED DESCRIPTION OF CURRENTLY PREFERRED MODALITIES The present invention includes a waste paper deinking process in which the waste paper load disintegrates in an aqueous alkaline solution containing sodium sulfite and sodium carbonate., and preferably, a surfactant, to produce a fibrous pulp. These chemical compounds separate the ink from the waste paper fibers and prevent the ink from being re-adhered to the fibers. The pulp is then washed by a sieve wash, or by flotation, to remove or remove the ink from the pulp. The pulp in the pulp has good properties, such as refining and brilliance, so that it can then be pressed into paper or used as a raw material for other high quality paper products. The invention is applicable to the deinking of common stocks of waste paper, such as newsprint, books, files, magazines, xerographic paper and mixed office waste. The loading of waste paper for the process is also known as "raw material". The chemical requirements of the process may vary depending on the raw material. Since different papers are made from different processes, such as the acid-sulfite process, the kraft process, the defibrated wood process, the thermomechanical chemical process, etc., the raw material of waste paper exhibits different characteristics P1125 / 96MX depending on the combination of papers used to constitute the raw material. Moreover, even the character of the homogeneous raw material can vary depending on the original source of paper. For example, newsprint made from southern conifers through a papermaking process can result in raw material characteristics very different from newsprint made from conifers in the Pacific Northwest. Thus, the optimum amount of chemical compounds and the combination and optimum proportion of the chemical compounds required by the process may vary depending on the raw material used when practicing this invention. However, the optimum amount of chemical compounds can be easily determined by someone skilled in the art without undue experimentation. The process, according to this invention, is carried out by placing the raw material in a disintegrator with water and the deinking agent. The disintegrator physically reduces the raw material in individual fibers. This step can be completed using any of the various conventional equipment designed for this purpose. For example, either a disintegrator or a hydrodisgregator can be used. This equipment reduces the raw material and its content in a fibrous pulp or pulp. It is preferred that the raw material is disintegrated in an alkaline environment P1125 / 96MX so that the deinking agents and the mechanical forces cooperate to more effectively separate the ink from the fibers. However, it is possible to carry out the invention by first producing a pulp and then adding the deinking chemicals. Depending on the raw material used and the requirements of the pulp to be produced, sufficient sodium sulfite and sodium carbonate must be used to obtain a pH in the pulp of between approximately 7.5 and 10.5. It is considered important to control the pH of the pulp after the raw material has disintegrated. Therefore, an acid raw material will require more sodium sulfite and sodium carbonate to obtain the desired final pH, it will then be an alkaline raw material. Preferably, sufficient deinking agent is used to obtain a pulp pH of between about 8 and about 10, more preferably, between about 9 and about 10. Typically, the invention will require sodium sulfite and sodium carbonate in a total amount between about 0.5% by weight and about 12% by weight, calculated as a percentage of the dry weight of the raw material. For example, in the de-inking of waste newspaper supplied by the southeastern United States, adding, a total amount of sodium sulfite and P1125 / 96MX sodium carbonate of between about 1% and about 7.5% by weight of the dry raw material, a pH of between about 9 and about 10 can be obtained in a pulp with 3% consistency. For this example, the proportion of sodium sulfite is preferably from about 70% to about 30% sodium carbonate. In this manner, from about 0.7% to about 5.0% sodium sulfite and from about 0.3% to about 2.5% sodium carbonate can be used. Preferably, between about 2.1% and about 5.0% sodium sulfite is used and between about 0.9% and about 2.5% sodium carbonate. A pH of about 9.5 can be obtained by using about 3.5% sodium sulfite and about 1.5% sodium carbonate by weight of the dry raw material in a pulp with 3% consistency. In practice, the waste paper can be de-inked by preparing a pulp with a consistency of between about 3% and about 15%. By consistency should be understood as the weight of dry raw material on the total weight of the pulp. This consistency is based on the condition of the pulp during disintegration and before it is diluted for washing and removal of the separated ink. The optimum pH and the optimum amount of sulfite P1125 / 96MX sodium and sodium carbonate will vary depending on the consistency of the pulp. Generally, it is believed that the desirable pH of the pulp will decrease at higher consistencies. In the same way, because sodium sulfite and sodium carbonate are measured based on the dry weight of the raw material, with this base smaller quantities will be necessary to obtain the same aqueous concentrations with pulps of higher consistencies. Correspondingly, to obtain the same or lower pH with higher consistency pulps, smaller quantities of sodium sulfite and sodium carbonate will be necessary, based on the dry weight of the raw material. Although there is probably no direct linear correlation, a person having ordinary skill in the art can easily determine the optimum pH and the required amount of deinking agent from the above mentioned and without undue experimentation. The invention can be effected using a waste paper deinking composition that includes relative proportions of between about 50-95% sodium sulfite and about 5-50% sodium carbonate. Also, the deinking agent can include up to an equal amount of surfactant. Preferably, the deinking composition contains relative proportions of between about 60-80% sodium sulfite and from P1125 / 96MX approximately 20-40% sodium carbonate. More preferably, the deinking composition contains relative proportions of about 70% and about 30% sodium carbonate. Preferably, the surfactant may be added in a proportion to the sodium sulfite and sodium carbonate combined between about 1: 1 and about 1: 1000. More preferably, the relative proportion of the surfactant can be of the order of magnitude between about 1:10 and about 1: 100. Due to the superior results obtained by this invention, the need for additional bleaching will be eliminated or greatly reduced. In this way, the need to use other bleaching agents, stabilizers, etc., together with the deinking composition is totally eliminated or greatly reduced. Of course, the optimum composition will vary depending on the conditions of operation intended for the pulp and the characteristics of the raw material, among other factors, such as whether an increase in refining or pulp brilliance is more desirable. In general, the processing of the pulp can be carried out at temperatures between about 20 ° C and about 100 ° C. It has been found that the invention is particularly effective at a temperature between about 30 ° C and 75 ° C, is preferred P1125 / 96MX more than operate half of this interval. For the purposes of this invention, the contact time of the deinking composition and the waste paper raw material is not critical. From the point of view of deinking performance, a contact time greater than about 5 minutes is preferred. It is considered that a contact time in the range from about 15 minutes to about 45 minutes will provide more efficient deinking performances. This, of course, depends on the size of the equipment used, the volumes and the desired production. After the prescribed contact time period, the separated ink is removed or removed from the pulp. Typically, flotation methods can be used in which a stream of air or gas is bubbled through the pulp. The bubbles rise to the surface, dragging the ink particles with them and generating a foam that traps the ink particles. The foam is then removed or removed. For flotation methods, the use of a surfactant is required, either as part of the deinking agent or as a separate additive.

As is well known to one skilled in the art, any surfactant suitable for operating under alkaline conditions can be used with the invention. Alternatively, washing methods can be used to remove or remove the ink particles P1125 / 96MX separated from the fibrous pulp. Any number of washing methods practiced commercially would be adequate for this purpose.

EXAMPLES A raw material of 100% waste newspaper from the southeastern United States was established. The raw material was disintegrated in a standard British disintegrator using 33 grams of newspaper air-dried in 1 liter of water from the municipal network at approximately 55 ° C. Sodium sulfite and / or sodium carbonate was added to the blender in the amounts shown in Table 1 calculated as a percentage of the dry waste paper load. Sodium hydroxide was used as a control reference. The blaster was then operated for 15 minutes. The pH of the resulting pulp was measured at the end of the disintegration run. Generally, the temperature decreased to approximately 40 ° C at the end of the disintegration run. The pulp was transferred to the tank of a laboratory flotation cell (laboratory flotation machine with agitator brand emco Model 71260-01, 2 liters) and diluted to a total volume of 3 liters with water from the municipal network to 55 ° C. The agitator was started from the flotation cell at 900 r.p.m. and 2 ml of a surfactant was added P1125 / 96MX (DI-600, from Kao Chemicals) equivalent to 0.35% by weight of the dry waste paper load. An air flow of 10 liters / min was introduced into the pulp. and continued for 10 minutes while the foam spill was captured on a side mounted tray. A sample of the deinked pulp was taken and its consistency and the Canadian standard refining were tested. With the remaining pulp, standard test sheets were manufactured, conditioned overnight and various properties were tested including brightness and strength. The results are shown in Table 1. As the data show, the use of sodium sulfite alone showed some slight improvement in brightness with respect to the control. However, the brightness increased significantly when sodium sulfite was used in combination with sodium carbonate. The optimum brightness was reached in Example 8 with the addition of 3.0% sodium sulfite and 1.5% sodium carbonate. For some recycled waste paper plants, refining is an important feature. Optimum refining of the pulp was obtained in Example 9. However, in all cases, the raffinate was greater than that obtained by the control in Example 1, which typifies the normal caustic soda technology.

P1125 / 96MX TABLE 1 X As can be seen, this invention offers the advantage of deinking waste paper stocks and achieving superior gloss characteristics, whereby the need for additional bleaching is totally eliminated or greatly reduced. Compared with the use of caustic soda, this invention produces fibers with greater flexibility that achieve a pulp with higher fat, which results in a paper product with improved smoothness. The economic advantages are easily evident from the elimination or reduction of the use of additional chemical compounds, and the operational and quality advantages obtained. Therefore, it is intended that the above detailed description be considered as illustrative rather than limiting, and that it be understood that the following claims, including all their equivalents, define the scope of the invention.

P1125 / 96MX

Claims (7)

1. NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and, therefore, the content of the following CLAIMS is claimed as property; A method for deinking waste paper fibers, characterized in that it comprises the steps of: disintegrating the waste paper in an aqueous alkaline solution containing sodium sulfite and sodium carbonate to form a fibrous pulp having a pH of at least about 7.5; separating the ink from the paper fibers; and remove or remove the ink separated from the pulp. The method according to claim 1, characterized in that the sodium sulfite and the sodium carbonate are in a proportion of between about 95 to 5 and about 50 to 50 by weight. The method according to claim 1, characterized in that to the waste paper is added sodium sulfite in at least about 0.7% by weight of the dry paper filler, and sodium carbonate in at least about 0.3% by weight of the dry paper loading. The method according to claim 3, characterized in that sodium sulfite is added at P1125 / 96MX minus about 5% by weight of the dry paper load, and the sodium carbonate is added by at least about 2.5% of the dry paper load. The method according to claim 1, characterized in that the pH of the pulp is between about 7.5 and about 10.5. The method according to claim 1, characterized in that the disintegration is carried out at a temperature between 30 ° C and about 75 ° C. The method according to claim 1, characterized in that it also comprises the addition of a surfactant to aid in the removal of the displaced ink. The method according to claim 1, characterized in that the sodium sulfite and the sodium carbonate are added before disintegrating the waste paper. The method according to claim 1, characterized in that the sodium sulfite and the sodium carbonate are added without any other alkali, deinking agent or bleaching agent. 10. A composition used to destin waste paper characterized in that it contains: a relative proportion of sodium sulfite to sodium carbonate of between about 95: 5 and about 50:50; and a surfactant. 11. The composition according to claim 10, P1125 / 96MX characterized in that the relative ratio of sodium sulfite to sodium carbonate is between about 80:20 and about 60:40. The composition according to claim 10, characterized in that the ratio of surfactant to the total amount of sodium sulfite and sodium carbonate is between about 1: 1 and about 1: 1000. The composition according to claim 12, characterized in that the ratio of surfactant to the total amount of sodium sulfite and sodium carbonate is between about 1:10 and about 1: 100. 1 . An aqueous pulp of waste paper characterized in that it comprises: waste newspaper disintegrated; and a deinking composition containing a relative proportion of sodium sulfite to sodium carbonate of between about 95.5 and about 50:50; and a surfactant, wherein the pulp is at a pH of between about 8 and about 10. P1125 / 96MX METHOD FOR DETERMINATION OF WASTE PAPER SUMMARY OF THE INVENTION This invention is a method for deinking waste paper by disintegrating the waste paper in an aqueous carbonate solution containing sodium sulfite and sodium carbonate to produce a fibrous pulp having a pH of at least 7.5; the separation of the ink from the fibers and elimination or removal of the ink from the pulp. A useful composition for fiber deinking consists of a relative proportion of sodium sulfite to sodium carbonate of between about 95: 5 and about 50:50, and a surfactant. P1125 / 96MX