CA2061940A1 - Aluminum hydroxychloride as pitch control agent - Google Patents

Abstract

ABSTRACT

This invention comprises a process for treating wood based pulp with aluminum hydroxychloride to reduce or eliminate pitch problems associated with making and processing such pulp. Aluminum hydroxychloride having a basisity of at least 70 percent is added to wood based pulp in an amount of up to 5 percent by weight (based on the weight of ovendry pulp) at one or more points in the pulp and/or paper processes and at a system pH within the range of from about 3 to about 8. The use of this invention results in paper products which retain more of their brightness than pulp processed with other known aluminum containing products.

Description

206~9~0 AL~XIN~M ~YDROXYC~L4RIDE as PITC~ CON~RO~ AGEX$
BAC~GRO~ND OF ~E IN~2N~ION

The art of wood pulp processing and papermaking spans a variety of topics and chemistries. One of the concerns of pulp processors is pitch control. It has now been found that aluminum hydroxychloride, such as in the form of an aluminum hydroxychloride complex, can be used as an lo effective pitch control agent with less brightness loss of the pulp.
There are a number of definitions of pitch. Pitch is generally considered to be a mixture oS fatty acids, resin acids9 and unsaponifiable organic deposits of widely varying composition originating in the extractive fraction of wood. Pitch ~sometimes called resins or pitch resins) is a term used for the organic ~aterials that can be extracted from wood or wood pulp with an organic solvent such as ether. These hydrophobic extractables are usually dissolved or dispersed in the water phase of a pulp slurry;
however, under certain process conditions, these dispersions or solutions will destabilize and form pitch deposits. Pit~h deposits may contain more that just the naturally occurring resins, however. They may include a combination of (a) organic compounds (naturally occurring or produced by the digestion process, for examplQ, fatty and rosin acids and salts thereof, lignins and unsaponifiable materials); (b) insoluble mineral salts or " 20619~0 soaps (for example, calcium car~onate, calcium salts and fatty a~ids); and/or (c) organic and inorganic ~aterials present in papermaking additives tfor exa~ple, fatty acids or hydrocarbon oils found in many defoamers).
Some people classify pitch into two major types based on whether one i5 discussing naturally occurring pitch from virgin pulp (pitch) or pitch comprising additives from previous processing where these additives are found in pulp or paper which is being reprocessed (white pitch). White pitches may inc}ude lattices and/or organic polymers from coating compositions and organiC retaining material from preceding papermaking processes.
Pitch problems are both paper and pulp related. They are particularly evident in sulfite and groundwood (mechanical pulps) mills, where the solubilizing action ef the alkaline kraft proce5s is not present. Pitch problems manifest themselves in various ways, but the most common are dark, tacky, layered deposits on eguipment and sticky balls floating in pulp slurries. Pitch is a ma;or problem because it (l) agglomerates and also occludes other matter to form visible "dirt" in the final paper; (2~ plates out and collects on pulp and paper processing equipment such as screens, filters, refining equipment, pulp washers, and the paper machine: and (3) reduces pulp brightness and brightness stability. Once pitch becomes attached to the machine parts, the only way it can be r~moved is by scrubbing with organic solvents or special cleaning 20~1940 compounds. The down time associated with such procedures reduces the productivity of the plant.
~ he research in this area is made difficult because of the complex and reactive nature of this fraction of materials, because they often have been subjected to many chemical reactions during pulping and bleaching, and because the resin fraction is mixed with other wood components and materials added during the paper-making process. Additionally, changes in operating variables such as temperature, electrolyte content (for example, calcium and magnesium content) or pH can cause agglomeration and precipitation of pitch deposits.
A number of approaches have been tried either alone or in combination to reduce the presence of pitch and/or the problems associated with processing ~ulp and paper containing pitch. These approaches include seasoning wood, storing wood as chips, using kraft pulping methods rather than sulfite processes, controlling the types and amounts of wash aids and defoamers used in system processing, using a bleaching process, and using pitch absorbants such as talc and clay. Still other methods that have been tried include the a~dition of surfactants, chelating agents, crystal modifiers or dispersants, dispersants followed by fixatives, and controlling system parameters such as size of equipment.
In solving the problems associated with the presence of pitch in wood based pulp as it is being processed either as wood pulp and/or paper pulp one approach has been the 2~ 9~

use of a~uminum sul~ate, also callea alum or papermakers~
alum (Note that papermaker's alum is usually represented by the for.-ula Al2(SO~)3 14H20, whereas other types of alum may be represented with a different nu-~er of waters, for example Al2(SO4)3 18H20). Alum can be added to the mill system at many different times and locations. In a papermaking apparatus it may be added into the headbox at dosages ranging up to 4 percent on a dry fiber weight basis (4 percent equals 80 pounds of alum content per ton of dry fiber). ~n a wood pulp mill alu~ may be added at any place ~rom the pulpers, refiners and/or grinders through to the paper machine blend chest. Pulp mill applications can range in dosages up to 4 percent (80 pounds per ton) in the final dry fiber.
While it is not known exactly how alum works to reduce pitch in the pulping process, it is believed that alum fixes the pitch on the fibers of pulp. There are problems associated with the use of alum, however; these include the fact that the pitch particles are fixed to the pulp fibers, difficulties in handling and disposing of sulfate residues, and slime and deposit problems stemming from the use of sulfate-reducing bacteria. Additionally, loss of pulp brightness caused by the addition of alum is a major problem.
There have been several attempts to replace alum. One of these efforts has resulted in product(s) known as Gen+IonT~ (General Chemical Corporation), a proprietary polyaluminum hydroxychloride-based material having a 20~1940 cationic charge and designed for paper machines operating in the pH range of 6.0 to 7.5.
None of these approaches has resulted in a totally satisfactory solut-on to the problem of alum replacement.
There still remains a need for a product to replace alum as a pitch control agent, wherein the product can reduce or eliminate the pitch contaminants with less brightness losses. There also remains a need for a product to replace known aluminum containing products such as alum as a pitch control agent where the product can be used at acid pH's.
Thus, it is an object of this invention to provide a material to use as a substitute for known aluminum containing products as a pitch control agent in the processing of pulp which gives products that have less lS brightness losses. It is a further object of this invention to provide a material which i5 useful in the control of pitch and which can be used at acidic pH's.

~MMARY OF ~EE INVENTION

This invention comprises a process for treating wood based pulp with aluminum hydroxychloride to reduce or eliminate pitch problems associated with making and processing such pulp. Aluminum hydroxychloride having a basisity of at least 70 percent is added to wooc based pulp in an amount of up to S percent by weight (based on the weight of ovendrv pulp) at one or more points in the pu' and/or paper processes and at a system pH within t.;e ranse 20619~0 of from aDout 3 to about 8. The use of this invention results in paper products which retain more of their brightness (that is have less brightness reversion or less loss of brightness) than pulp processed with other known aluminum containing products such as alum.

DE~AILE3 DESCRIPTION OF T~E INVENTION

It has been found that aluminum hydroxychloride (Al2(OH)5Cl2) is useful in treating wood and/or paper pulp to reduce problems associated with the presence of pitch.
For purposes of this invention, this aluminum hydroxychoride is also called aluminum hydroxychloride complex (AHC), for example in its trihydrate form. The AHC
used in this invention must have a basici~y of at least 7-0 percent. A particular value for the basicity is from about 70 percent to about 90 percent; a more particular value is from about 80 percent to about 90 percent, and an even more particular value is from anout 80 percent to about 85 percent. The percent basicity of the AHC's used in this invention corresponds to the percentage of OH groups in the species Al(OH)43.
The processes of this invention may be used at pH's in the range of about 3 to about 8, especially in the range of about 4 to about 8, and ~ore particularly in the range of about 4.5 to about 8. In contrast to other aluminum hydroxychloride materials used as pitch control agents (such as Gen+IonT~ material), this invention may be 206~9~0 practiced at acidic pH's such as in the range of about 3 to about 6.
An example of an AHC which is useful in this invention is LocronT~ aluminum hydroxychloride complex. LocronT~ AHC
is an inorganic polymeric compound. Unlike other aluminum compounds, Locront~ AHC is believed to exist as a highly charged species, All~O4(OH)24(HzO) 12) ~7~ in solution. LocronT~
AHC may be supplied as a solid (LocronT~ S, a trihydrate form) or as a liquid (LocronT~ L, a solution of AHC
containing about 50 percent solids by weight) and is easy to handle and use. LocronT~ L is a clear, odorless and colorless material with a specific gravity of about 1.35 (at 20 degrees C) and a pH of about 3.6.
This invention may be used with all types of pulps.
These include 1) mechanical wood pulp, 2) alkaline process derived pulps and 3) paper pulp. Mechan~cal wood pulp is a pulp manufactured wholly or in part by a mechanical process, including stone-ground wood,. chemigroundwood and chip mechanical pulp. Uses include newsprint papers, specialty papers, tissue, toweling, paperboard and wallboard. Mechanical wood pulp is sometimes subdivided into three types:

a) thermomechanical pulp (TMP):
A high-yield pulp produced by a thermomechanical process in which wood particles are softened by pre-heating under pressure prior to a pressurized ~19~0 pri~ary refining stage. ~o~e that refining stages are frequently don~ as two or three ~tepsO~ TMP usually replaces or reduces the ch~mical pulp componen~ ~n newsprint or groundwood papers, b) refiner groundwood~ A variety of paper~
with substantial proportions of mechanical wood pulp processed in a reiner; and c) groundwood pulp: A mechanical wood pulp ~ :
produced by pressing a barked log against a pulpstone and reducing the wood to a mass of relat:ively short fibers.
.jj, Paper pulp is the pulp used as the starting material in papermaking. Paper pulp can contain virgin wood pulp and/or secondary stock. Secondary stock is a term for fibers which have previously been used i~ the papermaking process. The term includes paper stock reclaimed from a recycling of pre~iously used paper pulp products ~for example, newsp~pers) as well as wet or dry broke. It appears to be the general case that paper reclai~ed from a recycling o~ previously used paper is ~urned into pulp in separa.e mi'ls as recycled paper pulp to be us~ in secondary stocX. BroXe is paper being reprocessed ~or recycled from the paper making apparatus~ because it ~as 20~19~

not dried completely in the papermaking apparatus, was off specification, et cetera. Broke is repulped and can be mixed with virgin pulp to use in the headbox.
For a description of various types of pulps and methods for their preparation, see PU1D and p~per Manufaçture, Volume 2, Mechanical Pulping, Edited by Ray A.
Leask (third edition, 1987, prepared under Joint Textbook Committee of Paper Industry, Technical Association of the Pulp and Paper Industry (TAPPI) and Canadian Paper and Pulp Association, incorporated by reference herein. (See particularly Chapter VII).
For purposes of this invention wood based pulp is defined to mean wood pulp (both mechanical and alkaline process derived) and paper pulp. For purposes of the examples recited herein, thermomechanical pulps made from pine were used. ~
In practicing the processes of this invention, the aluminum hydroxychloride may be added to one or both of wood pulp and paper pulp at various points in the processing of these pulps. Wood pulp and paper pulp are manufactured and processed on a continuous basis and the AHC may be added at the beginning of a process or at one or more later stages when a pitch problem is observed. In the case of wood pulp, AHC may be added, for example, after the refining stage(s). For groundwood, AHC may be added, for example, in the grinder shower water. For TMP's and wood pulp processed in re~iner mills, AHC may be added, for example, at the discharge side of the latency chest. In a 20~1940 papermaking ~achine, AHC may be a~dea, for example, to t~e material in the headbox. It is preferred that AHC be added at the point in the particular process where a pitch problem is observed. Thus, treating the pulp means that the pulp is exposed to aluminum hydroxychloride in sufficient amount to reduce or eliminate problems caused by the presence of pitch.
In practicing the processes of this invention, aluminum hydroxychloride is added to the pulp at one or more points in the pulp or papermaking process as described above in an amount(s) such that the final aluminum hydroxychloride content of the pulp or paper is any amount up to 5 percent by weight, and more perferably any amount up to 2 percent by weight, based on the ovendry weight of pulp or paper. (It i5 to be noted that if the pulp is used to make paper, the terms pulp and paper are essentially the same.) Aluminum hydroxychloride may be added as a solid or in the form of a liquid, such as an aqueous solution to a pulp slurry. Dilution of the aluminum hydroxychloride in a solution, such as a water solution, before addition to ~he wood or paper pulp makes small dose application easier although it is not required. It will be appreciated by those skilled in the art that the concentrations of AHC in such liquids may vary and that one would add a quantity o~
a particular concentration of ~C which is appropriate to substantially reduce the degree of pitch problem observed.

20619~0 The levels of addition describeu for this invention are based on ovendry weight. Ovendry means containing practically no moisture. A paper or pulp is said to be ovendry when it has been dried in an oven at 105 ~ 3 degrees Centiqrade until its weight has become constant within about 0.1 percent. Ovendry is considered a more accurate term than airdry, because airdry can contain as much a 10 percent moisture.
A sample calculation to determine the amount of aluminum hydroxychloride which must be added to a wood pulp or paper pulp slurry to achieve a described aluminum hydroxychloride content may be made as follows. For a quantity of 250 tons of pulp with a 4 percent consistency, one would add at least 0.3 tons of alu~inum hydroxychloride to achieve an AHC content of about 3 percent. Two hundred fifty (250) tons (2000 pounds per ton) of a pulp stock having 4 percent consistency would mean the stock contained 10 tons of solids. (Note that the term consistency is generally defined to be the percentage by weight of airdry or ovendry fibrous material in a stock or stock suspension.
It is sometimes called density or concentration, and is used interchangeably with weight percent.) To obtain a loading of 3 ~percent aluminum hydroxychloride or. the ovendry product, one would need to add a_ least 0.3 tons (10 tons x .03) of aluminum hydroxychloride (mixed in whatever volume of water desired) to achieve the 3 percent loading.

20~ 9~

For purposes of the examples contained herein, the wood pulp was preconditioned to simulate conditions found in thermomechanical pulp mills. This ~equired heating the thermomechanical pulp stoc~ (pine) to about 71 degrees Centigrade and adjusting its consistency to about 3 percent by the addition of deionized water. The use of this highly basic alu~inum hydroxychloride (of which LocronT~ is one example) is believed to be suita~le for all pulp and paper raw material (also called wood based pulp herein) including, in particular, those systems which use a large percentage of recycled material or coating line waste.
While it is not known precisely how the invention works, it is believed that highly basic aluminum hydroxychlorides, such PS those with a minimum basicity of about 70%, act as a contaminant binder and~sizing agent for fine organic and inorganic particles such as resins, polymers from binders, pitc~es and white pitch.
It is believed that the high level of external cationic charge of the precipitation product neutralizes and/or binds anionically charged particles in such a ~ay with the pulp that they no longer burden the water system.
This precipitaqion product has an isoelectric point of about 8. This invention may be used in a pH range of from about 3 to about 8, and preferably in a range of from about 4 to about 8, and more particularly in a range of from about ~.5 to about 8. The acidic pH range ~here the invention may be used is from about 3 to 6. The pH a~
~hich the invention is utilized will depend on a varie~y o factors. For example, with bleaching materials such as V-BriteT~ bleach (from Hoechst Celanese Corporation) a pH in the acidic range of about 5.2 is generally preferr2d. IP
calcium carbonate is used as a filler, a neutral pH is preferred. The cationicity is stable and effective over a prolonged period of time, so that the highly basic aluminu~
hydroxychloride can be added even at the very beginning of the paper process without loss of activity over the course of time. In the paper process the high cationicity of the precipitation product stabilizes cationically charged organic additives such as retaining materials and cationized starch which are protected from being discharged and lost, and are thu~ preserved to the full extent of their effectiveness in stabilizing the system. The precipitation product surrounds organic ~polymers such as pitches and cationizes them so that they lose their adhesiveness. Since their external charges are now all about the same, the particles repel each other and are prevented from agglomerating.
For the practice of this invention it is contemplated that the usual and most convenient way of combining or mixing AHC and~pulp is by adding AHC (either in d~y form or as an aqueous solution) to the pulp. It is also within .he spirit anc scope of this invention to a d AHC and pulp to the process container or process system at about the same time or to add wood based pulp after the AHC is present in the con.ainer or process syste~.

206194~

~ t has also been found that additional benefits, especially in the acidic pH range, from the practice of this invention include reduction in the amount of fine fibers (those particles less than 1 m~ in size) and waste products or organic additives in the water system;
decreased need for cationic materials: increased machine capacity because of faster dewatering; better retent_on with a higher degree of filler retention, whether naturally anionically or cationically precharged; reduction or elimination of pH shift at concentrations of up to about 5 percent (by weight) (equal to about lO0 pounds per ton of ovendry pulp) aluminum hydroxychloride; prevention of gypsum forma'ion due to absence of aluminum sulfate; and reduction or elimination of defects resulting from formation of carbon dioxide present in other systems.

E~AMPLES

Eor purposes of these Examples, the pulp used was South American Pine thermomechanical pulp. As explained above, mechanical wood pulps are any wood pulp5 manufactured wholly or in part by a mechanical process;
stone groundwood, chemigroundwood, refiner ~echanical, and thermomechanical. The pulp used in this work was a mechanical pulp manufactured by a high yield thermomechanical process. The pulp was o~tained from a mill and required no further treatments other than diluting it to 3% consistency with the addition of deionize water and heating it to its normal mill te~erature of about 71 degrees Centigrade. A HunterLab D25-PC2 ~rightness Meter was used to measure brightness.
Unless otherwise noted, chemical abbreviations and symbols have their regular and customary meeting, 0 for oxygen, H for hydrogen, ml for milliliter, N for normal, C
for Centigrade, lb for pound(s), et cetera.

EgAMP~ES 1-~8 The general laboratory procedure used for Examples 1-48 was as follows. A 500 milliliter Erlenmeyer flask for each example was equipped with a stirrer and a constant temperature water bath i~itially set at a temperature of 71 degrees C. A pulp sample (15 grams, dry weight of thermomechanical pine pulp) was placed in, each of the 500 ml Erlenmeyer flasks and diluted with deionized water to a consistency of 3.25 percent (by weight) to facilitate mixing. The initial pH of the pulp samples in each of the flasks was 4.8. The pH was adjusted to about 5.2 using O.lN sodium carbonate. (A p~ of 5.2 was selected because it is believed to be within the optimal range of bleach response for this pulp, thus allowing for any effect on brightness by the other additives to be more readily observed.) The pulp samples were initially heated to 71 degrees C using a microwave oven (Whirlpool Model MW8650XR:
1.3 cubic feet; 700 watt) equipped with a temperature probe. The Erlenmeyer flasks containing the pulp were then -2061~40 sealed witn a rubber stopper and plao~d in the water bath to maintain the desired temperature prior to bleaching.
Additives to be added to each of the flasks were prepared.
These additives included solutions of each of the following: I,ocronTM S aluminum hydroxychloride complex (Hoechst AG), and reagent grade alum (octahydrate of alum;num sulfate Al2(50~)3 18H20) (Fisher Certified ACS).
The AHC additive was prepared as a 2 percent (weight/volume) solution of its respective non-water components. The alum was diluted until its specific gravity matched that of a 2 percent solution. (This dilution was 11 ml of the alum sample into 210 ml of deionized water). The additive indicated in Table I was then added with mixing to the particular flas~ in the amount shown in the table, and the flasks were resealed and placed back in the water bath for one hour. Af'er equilibrating in the water bath for one hour at 71 degrees C, the pulp samples were then deaerated by alternately pulling a vacuum (to about 0.9 bar pressure) using a standard laboratory vacuum pump followed by applying nitrogen at about 1.1 bar pressure. The deaeration/nitrogen addi~ion procedure was done three times on each sam ~ e. (The ceaeration/nitrogen addition procedures are believed to be necessary (at least in laboratory procedures) because the oxygen present in the pulp will decompose the sodium hydrosulfite. Bleach (-'-BriteT~ B, a proprietary blend of sodium hydrosulfite, sequestering agents and stabi:izers from Hoechst Celanese 206~0 Corp.) was added with agitation un~er an atmosphere of nitrogen (about 1.1 bar pressure) and the flask was resealed and placed in the water bath to allow for one hour retention at 71 degrees C. After this hour in the water bath, a 2.5 gram (dry weight) pulp sample was removed from each flask and diluted with deionized water to a consistency of about 0.5 percent. ~he pH of the resulting material (also called a furnish) was adjusted with sufficient O.lN sulfuric acid or O.lN sodium carbonate to get each sample to a pH of about 4.S + 0.1. A handsheet of 2.S grams and 15 cm diameter was formed on a Buchner funnel from the contents of each flasX using the method described in the Technical Association of the Pulp and Paper Industry (TAPPI~ Test Method T 218 om-83, incorporated by reference herein. Each handsheet was then air dried at ambient temperature (about 22 degrees C) and 50% relative humidity for approximately 16 hours.
Table I lists the amounts of additives used in each of the Examples. Since 15 grams of ovendry pulp were used for each example, the actual amount of additive can be calculated by multiplying the weight percent value in the Table times 15 and dividing by 100. Thus, Example 2 contained 15 x 0.385 . 100 grams of AHC; this equals .05775 or about .058 grams of AHC.

-`-` 20619~0 TAB~ I

,.
Example V-BriteTM LocronT~ Alum Number Bleach A~C(weight (weight (weightpercent) percent) percent) .
1 0.00 0.000 0.00 2 o.oo 0.385 o.oo 3 O.oo 0.770 o.oo 4 0.00 0.770 0.00 0.25 O.JOO 0.00 6 0.25 0.385 0.00 7 0.25 0.770 ~0.00 8 0.25 0.770 0.00 ~ 0.50 0.000 0.00 0.50 0.385 0.00 11 0.50 0.770 o. oa 12 O.5o 0.770 O.Oo 13 0.75 o.ooo o.oO
1 14 0.75 0.385 0.00 0.75 0.770 0.00 1 16 0.75 0.770 0.00 206~94~
.

~ 1.00 0.000 0.00-18 1.00 0.385 0.00 19 1.00 0.770 0.00 I _ 1.00 0.770 0.00 21 1.25 0.000 0.00 22 1.25 0.385 .

23 1.25 0.770 0.00 24 1.25 0.770 0.00 0.00 0.000 0.00 . I
26 0.00 0.000 0.50 27 0.00 0,000 ~ 1.00 28 0. 00 0. 000 1. 00 ..
29 0.25 0.000 0.00 . .. _ .... _ 0.25 0.000 0.50 131 0 . 25 0. 000 1 . 00 _ . 0 . 25 0 . 000 1 .

33 0.50 0.000 0.00 34 0.50 0.000 0.50 __ _ ~
0.50 0.000 1.00 36 0 . 50 0. 000 1 . 00 206194~

_ 0.75 0.000 0.00 38 0.75 0.000 0.50 39 0.75 0.000 1.00 _ .
0.75 0.000 l.Oo .
41 1.0~ 0.000 O.00 _ _ 1.00 0.000 0.50 44 1.00 0.000 1.00 ..
1.25 0.000 0.00 __ 1.25 0.000 0.50 47 1.25 0.000 1.00 . .
48 1.25 O.Ooo 1.00 Example 43 is not reported. Flask broke.

EZA~P~E8 1~A-48A

Examples lA through 48A were done to evaluate t~e brightness of the handsheets prepared in Examples 1-~8.
For these examples, the handsheet made from Example 1 was evaluated as Example lA, and so on. Each of the handshee~s made in Examples 1-48 was evaluated for briahtness by usin7 the procedure described in the Technical Association of the Pulp and Paper Incustry (TAPPI), Method I 452 o~.-87, ~06ts~a incorporated by reference herein and ~he Hunter apparatus listed above.
The data for these examples is found in Table II.

TA~LE Il I - ..... _ . - ,_, ¦Example pH After Value Change in Effect~2 ¦Number Retention Measured Brightness by TAPPI (Gain) Method ~ _ ¦ lA 5.1 52.7 0.0 na I
2A 4.5 51.3 -1.4 -1.4 I
l 3A 4.2 49.8 -2.9 -2.9 ,~
l 4A 5.5 50.4 -2.3 -2.3 ._ , l 5A 5.3 57.0 4.3 na . _ 6A 4.5 56.6 3.9 ¦ -o.~
.... .... .... _ _ _ , _ 4.5 56.2 3.5 -0.8 l 8A 5.5 55.2 2.5 -1.8 . __ . _ I
l 9A ~ 5.4 60.1 7.4 na l .. _ . , lOA 4.9 60.2 7.5 0.1 l ._ _ .
11~ 4.6 58.7 6.0 12A 5.7 58.1 5.4 -2.0 I

13A ¦ 5.7 61.9 9.2 na 20~1940 ... . .. . .. .

14A 5.0 61.1 ~ 8.4 15A 4.9 58.6 5~9 -~ .3 . I
l 16A 5.8 60.0 7.3 -1.9 _ _ .. .... _ l 17A 5.8 63.3 10.6 na ¦ 18A S.1 62.0 9.3 -1.3 ._ ...... ~ . ...... _.__ ._ ._ l9A 5.1 60.8 8.1 -2.5 ..... _ ._ .. _ 20A 5.5 60.6 _. - 1.4 2 lA 5.9 63.6 10.9 na 22A 5.3 60.5 7. a -3.1 ¦ 23A 5.2 61.9 9.2 -1.7 .
l 24A 6.8 61.0 8.3 -2.6 ...____ l 25A 5.1 52.7 0.0 na ...... _ _ . .
l 26A 3.5 49.6 -3.1 -3.1 I
¦ 27A 3.2 47.6 - 5.1 -5.1 l .
¦ 28A 5.4 48.8 -3.9 -3.9 I _ . ... . . .. .
¦ 29A 5.3 57.0 4.3 n e ¦ 30A ~ 3.5 52.9 0.2 -4.1 ¦ 31A 3.2 52.2 - 0.5 - 4.8 ¦ 32A 5.5 52.7 0.0 -4.3 I ._ 33A 5.4 60.1 7.4 ¦ na 20~1940 _ _ . _ ~ ~
34A 3.654.8¦ 2.1 -5.3 , _ ~ , . ._ 35A 3.353.8 1.1 -6~3 _ _ 1 36A 5.656.3 3.6 -3.8 l l ._ ¦ 37A 5.761.9 9.2 ~a l I . .. _ .
¦ 38A 3.7 56.9 4.2 -5.0 l I
¦ 39A 3.3 S4.4 1.7 -7.5 ¦ 40A 5.7 57.7 5.0 -4.2 4lA 5.8 63.3 10.6 na . . .. I
42A 3.9 57.8 5.1 -5.5 10 ¦ 44A 3.3 54.4 1.7 -8.9 .
l 45A 5.9 63.6 10.9 na . ~
46A 4.2 58.0 5.3 -5.6 47A 3.5 55.5 2.8 -8.1 48A S.9 58.7 6.0 -4.9 _ _ 20~'~9l~

lna means not applicable.
2This column provides data calculate~ by taking t}.e difference in the Change in Brightness column minus its corresponding untreated sample or blank for each set of experiments. For example, comparing Locronr~ AHC treated E~ample 22 to the alum treated Example 46 tboth of which were bleached at 1.25 percent V-BriteT~ bleach and treated with the corresponding pitch control products at equivalent aluminum ion concentration) shows that the ~ocronl~ AHC
treated Example 22 lost 3.1 points of brightness (10.9-7.8), while the alum treated sample lost 5.6 points of brightness (10.9-5.3). Thus, the LocronT~ AHC treated example yielded less brightness loss. Note: 0.385 percent LocronT~ A~C addition is equal to about o.5 percent alum addition, and 0.77 percent LocronT~ AHC addition is equal to about 1.0 percent alum addition on an equivalent aluminum ion basis.
E2~HP~E~ ~9-5O
COMPARAIIVE EXAMPTT'S
2~
Examples 49-55 were run to compare the brightness retention of handsheets made with Gen+IonT~ material to handsheets made in accordance with this invention using aluminum hydroxychloride. These materials were added on an equivalent aluminum ion basis.
Oven dried unbleached pine stock (210 grams) (weight basis as determined by drying in an oven at 105 degrees C
until weight equilibration was reached) prepared according 2~9~

to the method of Example 1 was placed in a 10 Liter buc~et and dilutGd with ~eic.nize3 ~ater to a con3istency of about 3 percent. The p~ of the re~ultins ~ateria; was then adjusted to about 5.2 by adding sufficient amounts of dilute (O.lN) sodium carbonate. After adjusting the pH to about 5.2, the sample was divided into 7 equal portions each containing approximately 30 grams of ovendry stock.
Each of the samples weighed about lOG0 grams. Each of the 7 samples was placed in a water bath maintained at about 71 degrees C until the temperature of the sample had equilibrated to the bath temperature (about 30 minutes).
Dilutions of the additives to be added to the samples were prepared as follows: Additive LL was made by mixing 20 grams of aluminum hydroxychloride complex ~LocronT~ S) with 500 ml of deionized water. ~dditive G3 w~s made by mixin~
20.0 grams of Gen+IonT~ 9023C with 500 ml of deionized water. Additive G6 was ~ade by mixing 20.0 grams of Gen+IonT~ 9026C with 500 ml of deionized water. After equilibration of the samples, the additives listed in Table III were added as indicated. Note that weight percen~ of Al~3 added can be calculated for each example by dividing the value liste~d in the last column by 20.

,~,; _, . . . .. . .

T~

. .. _ ~. ~
Example Sample ~dditive Amount of ~mount of Number Number Additive Al+3 added Added (~1) (lb./ton of stocX) 49 1 LL 5.8 1.4 2 L~ 11.8 2.88 51 _ 3 _ G3 15.2 1.~4 52 _ 4 G3 30.4 2.88 53 5 G6 13.1 1.44 54 6 G6 26.2 2.88 7 . NoneNone None All of the samples were then returned to the constant temperature bath (retention bath) at 71 degrees C and kept in the bath for about one hour. After the hour in the retention bath, the pH of each sample was ~easured and then adjusted to a pH of about 4.5 by adding up to 1 milliliter of O.lN ~zSO~ or O.lN sodium carbonate. Two handshee~s were made with the contents of each sample flask using the procedure described in the Technical Assoc-ation of the Pulp and Paper Industry, Method T 452 om-83, incorporated by reference herein. The brightness of each of the handsheets mad~ was measured using a Hunter D25-PC2 Brishtness Meter, and using the procedure described in the Technical Association of the Pulp and Paper Indust~ , Method T 452 om-87, incorporated by reference herein. Four measurements were taken for each han~sheet. The average of the four values is recorded in Table IV. For ea-h example 20~19~0 the aver-~e of Sheet A and Sheet B and the value for Effect (see the first sentence of note 2 under Table II) are recorded in Table V; note that the value for the blank (Example 55) is 62.0- Table ~ shows thaS the ~amples 'reat~d with AHC retair,ed ~.ore of their brightness.

~AB~ IV

Sheet Number Br.aht~ess .
Example Sample Sheet Average Number Number of 4 _ _ _ Readlngs = = = 6 2 B 61.0 52 4 A 58.8 52 4 B 58.8 53 5 A S9.2 53 5 B 59.3 54 6 A 58.0 54 B 58.0 7 A 62.0 7 B 62.2 lSheet lost.

~ ~,~. ~,~ ~ ~ ~ ~ ~ ~ _ 2 0~6 1.9 4 0 V

Esriqhrne ;s " __ _ ~ _ Example Number Average of Sheets Æffect I .
49 62.0 - 0.1 l I
61.1 - 1.0 l I _ I
~ 5~ 7 54 58.0 - 4.1 . I
. 55 62.1 Blank l _ _

Claims (24)

1. A process for treating wood based pulp to reduce the problems associated with pitch, wherein said process comprises mixing aluminum hydroxychloride having a basicity of at least 70 percent with said pulp in an amount sufficient to form pulp or paper containing up to 5 percent by weight of aluminum hydroxychloride based on an ovendry weight of said pulp or said paper, and wherein said process is performed at a pH selected from a range of from about 3 to about 8.

2. A process as claimed in Claim 1, wherein said aluminum hydroxychloride is in the form of an aqueous solution.

3. A process as claimed in Claim 1 wherein said pH is in a range from about 4 to about 8.

4. A process as claimed in Claim 3 wherein said pH is in a range from about 4.5 to about 8.

5. A process as claimed in Claim 1 wherein said pH is in the range from about 3 to about 6.

6. A process 25 claimed in Claim 1, wherein said wood based pulp is wood pulp.

7. A process as claimed in Claim 6, wherein said wood pulp is thermomechanical wood pulp.

8. A process as claimed in Claim 6, wherein said wood pulp is refiner groundwood.

9. A process as claimed in Claim 6, wherein said wood pulp is groundwood pulp.

10. A process as claimed in Claim 6 wherein said mixing is done after refining stage(s) of said pulp.

11. A process as claimed in Claim 6 wherein said pH is in the range from about 3 to about 6.

12. A process as claimed in Claim 1 wherein said wood based pulp is paper pulp.

13. A process as claimed in Claim 1 or Claim 12, wherein said mixing is done at a headbox of a papermaking apparatus.

14. A process as claimed in Claim 1, wherein said amount of aluminum hydroxychloride in said pulp or said paper is an amount up to 2 percent.

15. A process as claimed in claim 12 wherein said pH is in a range from about 3 to about 6.

16. A process for producing paper having reduced loss of brightness, wherein said process comprises mixing aluminum hydroxychloride having a basicity of at least 70 percent with at least one of wood pulp or paper pulp used in forming said paper in an amount sufficient to form a paper containing up to 5 percent by weight of aluminum hydroxychloride based on an ovendry weight of said paper, and wherein said process is performed at a pH selected in a range from about 3 to about 8.

17. A process as claimed in Claim 16, wherein the pH is in a range of from about 4 to about 8.

18. A process as claimed in Claim 17, wherein the pH is in a range from about 4.5 to about 8.

19. A process is claimed in claim 16, wherein the pH is in a range from about 3 to about 6.

20. A process as claimed in Claim 16, wherein the process comprises mixing wood pulp and aluminum hydroxychloride.

21. A process as claimed in Claim 16, wherein the process comprises mixing paper pulp and aluminum hydroxychloride.

22. A process as claimed in Claim 20, wherein said amount of aluminum hydroxychloride is an amount up to 2 percent by weight.

23. A process as claimed in Claim 21, wherein said amount of aluminum hydroxychloride is an amount up to 2 percent by weight.

24. Paper made by any of the processes claimed in any one of Claims 16, 17, 18, 19, 20, 21, 22 or 23.