CA1230525A - Starch distribution by rotary applicator in paper or board manufacture - Google Patents
Starch distribution by rotary applicator in paper or board manufactureInfo
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- CA1230525A CA1230525A CA000471075A CA471075A CA1230525A CA 1230525 A CA1230525 A CA 1230525A CA 000471075 A CA000471075 A CA 000471075A CA 471075 A CA471075 A CA 471075A CA 1230525 A CA1230525 A CA 1230525A
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Abstract
ABSTRACT OF THE DISCLOSURE
Suspensions and solutions of substances in liquids, especially aqueous suspensions of starch which have been stabilised by addition of a minor amount of a hydrophilic polymeric viscosity-increasing agent such as xanthan gum, are applied to paper or board during manufacture, by using a rotary atomiser and allowing the spray discharged there-from to fall on the surface of the paper or board moving relatively to the atomiser.
Suspensions and solutions of substances in liquids, especially aqueous suspensions of starch which have been stabilised by addition of a minor amount of a hydrophilic polymeric viscosity-increasing agent such as xanthan gum, are applied to paper or board during manufacture, by using a rotary atomiser and allowing the spray discharged there-from to fall on the surface of the paper or board moving relatively to the atomiser.
Description
~l~3~ S
IMPRo ~ MæNTs IN PAPER AND B ARD MANUFACTURE
This invention relates to paper or board manufacture. More especially, it relates to a method of paper or board manufacture in which an organic polysaccharide is added to the mixture or applied ~o the web of fibre~ during the process of manufacturing the paper or board. In particular it relates to paper of improved streng~h or ~urface characteristics manufactured according to such a method. An improved additive material also constitute~ a feature of the present invention.
~ is well known to add during the early ~tages of paper OI board manufacture one or more additive6 ~o as tD
increa~e the int0r-fibre bonding and thus the ~trengtA
of the eventual paper or board. The additives are u~ually polysaccharides including starche~ and cellulo~e and their chemical derivative~ as well as other organic ~ubstances capable of forming chemical links with the cellulose which forms the ba~iE of the paper or board web. Thi~ latter cellulo6e may have been modified by - the paper or board manufacturer in order to assi~ the web formation during the early stage6 of manufacture preceding the web formation.
Additives as described in the application can be added to the pulp its~lf, or to the early ~t~ges in the formation~of tha paper web ~wet-end addition"), i.e.
when the water content is reduced from a~out 99% to about 30%. The additives are in ~uch cases dis~ributed more or less uniformly throughout the ~hickness of the paper or board. It i6 also knswn, for convenience, to apply ~he additive to the formed web, on one or both surfaces thereof in ztages of manufacture 6ubsequen~ to web formation, as the water content is reduced to 2% ~o 20% by weight of the web.
"Size-Press Addition" named after the relevant part of the paper-making machine, is an example of a ~nown proces~; application of additives may be effected a~
this stage using solutions or dispersions of the additives, or foamed liquids, or dry powders. It i~
known that, whilst the size press process i5 a useful method of applying substances to paper or board, the equipment is expensive to buy and install; it also consumes large amounts of energy to drive the machinery and to carry out the extra drying operations consequent on the use of a size pres~.
Since the application of substances at the size pre~s is carried out using sollltions or dispersions in water, it i~ neces&ary to arrange for extra drying equipment to be installed in addition to that used to dry the paper or board before it .is passed through the size press. This extra drying reguire6 up to 30~ extr~
drying equipment and repre&ents a further 30% increase in energy consumed during the manufacture of the paper or board.
The present invention is concerned with the transfer, handling and subseguent behaviour on heating of t~ese dispe.rsions or solutions of polysaccharide additives~ and i~ based on a consideration of the flow characteristics thereof.
When dispersions of starch in water are subjected to high rates of shear, e.g. high rates of flo~ through restricted orifices such as those which are normally used to produce sprays, they exhibit considerable dilatancy. i.e. ~he apparent viscosity or resistance to flow increases as the rate of shear increases. The result of such increases is to restrict or stop flow.
Dilatancy is particularly noticeable in suspensions of ~tarch where the starch represents 5% or more of the total ~luid. This stoppage is familiar to ~hose users of starch who wish to spray suspen6ions of raw or processed starch as aids to ~arious industrial processes including application to paper and board during and subseguent to manufacture.
Aqueous dispersion~ of starch al~o tend to form sediment6 owing to the effect ~ gravity or inertial forces on ~he particulate matter suspended in the water~ Such s~diments are the cause of much failure of equipment. In order to pre~ent o~ reduce the occurrence of sedimentation, it has hitherto been cu~tomary to increase the viscosity of the su6pension by raising the temperature of the starch above the tempera~ure at which the individual particles rupture; the process is generally referred to as "cooking". This enables the starch to hydrate, forming a gel which, by increasing the fluid viscosity, reduces the tendency of the starch particles to sediment. Alternatively, it is customary to add ~ubstances which, by raising the viscosity of the aqueous phase of the ~uspension, reduce the sedimenta~ion process. Such viscosi~y-increasing substances include col~-water ~oluble deriva~ive~ of starch or of cellulose and many high molecular weight polyhydric substancQs such as polyethylene oxide ethers, polyvinyl alcohols as well as "swelling clays" such as bentonite, attapulgite, Laponite and the like which are capable of raising the viscosity of the dispersion of ~tarch in cold wa~er.
However, such procedures a6 described above lead to ~l~3~
poor ~pray formation since the fluids require high pumping pressures in order to achieve a suEficiently high degree of turbulence at the spray head ~o produce the fine droplets tha~ are desirable for a,pplication as herein described. Such high pumping pre~sures frequently lead to failure of equipment due to the inherent ~endency of starch ~uspensions to become dilatant. The present invention has discovered a method of paper or board manufacture in which one or more further additives are presen~ in the streng~h-affecting starch suspension.
According to this invention there is provided an agueous suspension of starch characterised in that it contains minor amount of a hydrophilic polymeric visco~ity increasing agent whereby the settlement of suspended starch particles is prevented. There is also provided a me~hod of applying a viscous trea~ing agent in the manufacture of paper or board, characterised in that the agent is applied by means of a rotary atomiser.
The in~ention can be ~een to comprise three a~pect~.
In one aspect, the invention provides a method for the manufacture of paper or board in which an aqueous ~, suspension~starch is applied to the paper web during or ~....
~2 ~ J~
af~er it8 formation; wherein there is present in the . ~uspension a hydra~able polymer in an amount such that : the rheology of the suspen~ion is altered so as to render the suspension more pseudoplastic whereby application to the web is facilitated since p~eudopl~stic (alternatively known as visco-elastic or shear-thinning) fluids as described in this invention are capable of having sufficient vi~cosity to prevent sedimentation of dispersed particles such as s~arch under the low ra~es of shear experienced during storage or whil~t being transported; yet, when subjected to high rates of shear such as occur when a fluid-is expelled from a narrow orifice such as the nozzle of a spray jet, the same fluids exhibit sufficiently low viscosi~y to permit the formation of droplets suitable for the application of solutions or suspensions tO paper or board during the early ~ages of manufacture.
In another aspect ~he invention provides a method for the manufacture of paper or board in which an agueous solution of a hydratable polymer is applied to the paper web during or after formation; wherein there is present in the solution a water-soluble polymeric sub6tance capable of forming a continuous film at or near the surface of the paper or board. This polymer may be applied alone utilising the advantages of the atomi6ing distributor described in this invention;
7 ~3~t5 alternatively, it may be applied together with the starch and rheology-modifying polymer described above.
In each of the above aspects, the hydratable polymer is nonionic or ionic, preferably anionic. It may be the sodium, potassium or ammonium salt of a polycarboxylic acid in which the carhoxylic units are attached to long-chain polyhydroxyl polymers, e.g. polysaccharides, whereo~ ~he polymers are based on glucose, mannose, galactose, pyranose, amylose and ths like and their hybrid derivatives including such acids as glucuronic acid. Typical polymers include the sodium, potassium and ammonium salts of carboxyme~hylcellulose and the complex polymer obtained by fermenta~ion of a suitable sugar-based medium by the organism Xanthomonas lS ampestris and commonly known as xanthan gum. It may also be one of the water-soluble salts of polyacrylic acid, polymethacrylic acid and their homologuesO the actual polysaccharides and their derivatives most preferred will depend on which aspect of the invention is of major importance~
In another aspect the invention provides a method for the manufacture of paper or board in which suspensions or solutions of 6ubstances in wa~er or other li~uids are applied by means o~ a rotary atomiser.
Although the aqueous uspensiOnS and solutions described .
~ 5 in this invention may be applied to the surface of the paper by conventional, high-pressure sprays, it is pre-ferred to use the ro~.ary a~omiser which has hitherto n~t been used in the manufac~ure of paper although well known in the agricultural art. The atomiser is availabl~ in several similar forms including devices sold under several registered trade marks including those of "~ICRON MICROMAX"
and "LELY HYDRASPIN". Such an atomiser is described in detail in GB Patents 2,004,204B, 2,004,205B and 2,004,206B
and defined in claim 1 of those patents. These atomisers and other similar devices comprise a truncated hollow con-ical shell set t~ spin on its vertical axis with the narrow end downwards.
An illustration of the configuration of the atomiser 15 i6 ~hown in the accompanying drawing, which consists of a sectional view of a twin-cone sys~em. The atomi~er comprises a fixed inner cone 1 surrounded by an outer cone 2 mounted on a bottom bearing 3 si~uated at the end of a central ~haft 4. A central nozzle 5 is 20 arranged to supply incoming fluid. The outer cone 2 is provided at the top with a top bearing 6 and drive means comprising a belt driven pulley system 7,8 coupled with an electric motor 9. The upper outer edge of the outer cone 2 is provided with teeth lO and a circumferen~ial 25 protecting ring~! The fluid to be atomised is pumped through one or more port6 into the interior of the spinning cone 2 and i~ sub6equently carried upwards and outwards across the inner surface of the ~pinning cone 2 ~3~)~25 until it leave6 the cone tangentially at it~ wide~t, upper circumferance. The ~ize of khe droplet6 generated by this ~ovement of ~he fluid is par~ly con~rolled ~y arranging for the upper edge of the cone to be serrated in the form of teeth 10 arranged radially around its upper surface. The cone may be driven by an electric or air or hydraulic motor through a suitable drive and with suitable bear;ngs to support the cone rigidly on its moun~ing. In the ca~e of a hydraulic motor, the driving energy may be ~ransferred to the motor by means of a conventional hydraulic generator pump and specialised so-called "hydraulic fluid"; alternatively, the driving energy may be transferred by arranging for the agueous starch suspension or other fluid, intended to be applied to the paper, to drive a turbine connected to the spinning cone.
For a given atomiser and a liquid of given rheological properties and set spinning at a given speed of rotation, droplet~ of uniform size are genera~ed. It follows that droplet size can be selected by choosing an appropriate combination of atomiser geometry, fluid rheology and 6peed of rotation in order to meet the particular reguirements of the user. Each of the parameters governing droplet size may be adjusted independently of the others and also independently of ~L~3~
the rate of flow of the ~uspen~ion or solution being applied to the paper 6urface, whereas with a conventional spray nozzle as previously used in the art.
the droplet iZe i~ dependent on the pressure drop acros~ the nozzle which, in turn, governs the ra~e of flow. Since the droplets produced by the at~miser are of virtually uniform fiize, they follow similar trajec~ories thu~ permi~ting a remarkably close degree of control of the pattern laid down on the paper surface and hence, uniformity of application. If the droplets are ejected from the rotating atomiser 6et ~o spin on a vertical axis, they will travel in a horizontal trajectory; it therefore follows that they will each travel along a path determined by the resultant of the horizon~al forces produced by ~he tangential motion and the force of gravity. If the body of the atomiser is placed so that the ba~e of the cone is close to the surface to which the fluid is to be applied, it follows that the droplets will travel approximately 20 centimetre~ in the vertical direction under the force of gravity and so will be travelling very much more slowly than would similar droplets ejected at high velocity from a conventional pres~ure-operated spray nozzle.
This i6 particularly advantageous when the fluid is to be applied to the surface o~ paper or board during the early state~ of manufacture when the water content of the paper i~ high and the strength of the paper con~equsntly low.
One or more atomiser~ may be fixed to a boom 8et 80 as ~o allow the fluid to be applied to th~ upper or lower side~ of the paper or board a~ it pas~es through the paper machine. If desired, part of the circumference of ~he spinning cone may be surrounded by a shield so a~ to res~rict the passage of drople~s ~o the space diametrically opposite the shield: this permits directional application of fluids ~o be made as and when reguired by the user. Fluid collected by the 6hield can be resurned to the holding tank or into the fluid circulating system as may be convenient.
The fir~t aspec~ o~ the invention i~ concerned with the rheology of the suspension. It i6 well known that : 15 ~he velocity of a liguid at which is changes from laminar or quiescent flow to turbulent flow is defined by the Reynolds Equation expressed as follows:-NR = d v.r .K
~L~3~
where Nr = the ReynoldG number of the fluid d = the density of the fluid v _ the velocity of the fluid r = Fadius of the pipe or orifice through which the fluid is ~lowing K = a proportionality constant V = the viscosity of the fluid If the above parameters are expressed in cgs units, it is known that turbulence occurs when the Reynold~
Number exceeds 2000. It can be ~een ~hat if the value of V tthe vi~cosi~y~ for a particular fluid is low, the Reynolds Number will be high and so turbulence will occur in conditions in which a fluid of higher viscosity would flow in a laminar manner: additionally, the low viscosity wiIl enable the fluid to flow at a higher velocity under given circumstances and 80 fur~her increase the Reynolds Number and, hence, the turbulence of the fluid.
It i~ well known that, for optimum e~ficiency of a spray o~ atomising system, it is necessary for the fluid to be in a state of turbulence at the point at which break-up into droplet6 occurs; in other words, optimum droplet formation occur6 when the fluid visco~i~y is low. It therefore follows tha~, if two fluids of different viscositie~ are compared under ~imilar .~ 5 conditions of flow as defined by the parameter~ used in the Reynolds Equation, better spray efficiency will bs obtained in the fluid wi~h ~he lower viscosity.
- Fur~her consideration of the ~ir~t aspect, ie. the rheology of the ~u~pension of s~arch, reguires tha~ the viscosity or re~istance to deformation within the fluid should be as high as possible when the fluid is at or virtually at rest, i.e. under conditions of low rates of shear. Prior art teaches ~hat a starsh or ~imilar suspension could be stabilised if the fluid visco~i~y is raised by cooking at least par~ of the starch or by the addition of a ~oluble polymeric substance a~ defined earlier, i.e. the 6tarch particles are prevented from setting out undex the forces of gravity or inertia.
Stokes' Law illustra~es this by calculating that thc forces exerted on suspended particle~ by external forces are inversely proportional to the viscosity of the fluid. However, such treatments give rise to high viscosities which are detrimental to the eficiency o~
the ~praying eguipment. It follows, therefore, that ~he rheology of the fluid in which the starch is &uspended ~hould exhibit a high visco~ity at low rates of ~hear in order to prevent settlement of the starch particles; at the ~ame time it ~hould exhibit low visoc~ity at high ra~e~ of 6hear in order to ensure sufficient trubulence to form droplet~ of optimum ~ize and particle size ~3~
di~tribution.
lt i& well known that the vi~cosi~y of solutions of ~ome polymeric substance6 fall6 off more rapidly than others as the rate of shear or ~he rate of flow through a given orifice i~ increa~ed. Thifi is illustrated in the following Table in which ~he viscosities in water of ~eYeral well-known high viscosity polymeric substances are compared over a ~ange of rate~ of ~hear; the respective viscosities and rates of ~hear were measured wi~h a Brookfield Viscometer fitted with a concentric bob and cylinder attachment sold under the designation Sc4 Small Sample Adapter:-.:
Shear Rate PolYmer~ Vi6co~itY (centiPoise~) @ 20 deq C _ C~C18000 13~00 ~4006000 4300 3000 1900 14~0 HEC~000 6500 50003800 2700 1900 1100 UC660 550 4804~0 400 340 260 210 . . _ . .
The present in~ention ha~ di~covered that if a minor proportion of a 6ub~tance capable of providingaqueou~ solution~ of high p~eudoplasticity i~ added to starch powder or incorporated into a ~u~pension of i2~
lS
~tarch, it renders the starch capable of being stored for prolonged periods in aqueou~ suspension; of being capable of being transported through restricted~orifices without giving rise to dilatancy; and itz suspensions of being readily ~ran~formed into drople~s of sufficiently small size to enable them to be used as a means of applying ~arch uni~ormly to surfaces includi~g sur~aces of paper during manufacture.
Preferred polymers for the rheology-affec~ing purpose are xanthan gum and similar polysaccharides capable o~ dissolving in water to produce solutions possessing very high vi8cosity at low rates of shear compared with other commerically available polymers but a relatively low viscosity at high rate of shear; this i~ illustrated in Table 1. Solu~ions of xanthan gum ~how little varia~ion in their physic 1 properties, including rheology, over temperature ranges normally experienced in paper mills and other closed industrial premises: these properties also show neglible variations when ionic and other dissolved substances are present with the xanthan gum. This is especially important when water of unknown compo6ition is used to prepare the ~tarch suspensions e.g. when recycled water of differing degree6 of hardnes~ or with differing salt contents and at varying temperature is used in such preparations.
. .
16 ~ ?~
The rheology-af~ecting propertie~ of xanthan gum are of par~icular importance if it i~ desired ~o apply ~tarch in the form of a suspension or slurry in water since the presence of the xanthan gum in the 6uspension greatly reduces the tendency of starch particles to settle QUt or form intractable sediments. The presence of xanthan gum in a fitarch suspension as described in this inventio~ allow~ users to store such suspension~
for prolonged periods and enables users to transport the starch in the form o slurry to its eventual destination without the nece~sity to in~all ~pecial agitation equipment in the slurly container~ used for transport and storage of the slurry. The convenience of being able to transport and ~tore starch suspensions by the addition of xanthan gum i~ particularly important in that ~uch suspen6ion~ are available a6 residue~ produced in ce~tain food-manufacturing proces6e~; it i~
economically advantageous to be able to supply the starch in the su~pen~ion or slurry form in which it is produced rather than to extract and dry the s~arch and sub6equently have to ~e-form the suspension before use.
p~o~i e5 ~, Thi8 invention ~c~ide~ an economic me~hod of storing and tran6porting ~uch starch suspen~ions or ~lurries to the benefit of the ~tarch and paper industxie~.
Thi~ in~ention has also discovered that the presence of xanthan gum in ~tarch su~pensions al60 overcome~ tAe tendency of ~uch ~uspen~ion~ ~o exhibit ~he phenomenon of dilatancy wh.ich can best be de~cribed as a rise in vi~cosity sr re6istance to flow a~ the rate of ~hear increases. Dilatancy i~ a condition to be avoided in handling tarch and other suspen~ions ~ince dilatant fluid~ tend to cease flowing under conditions of high rates of ~hear such as occur in~ide pumps and control valves, re~trictions and bends in pipes and in the nozzles of conventional spraying eguipment. Therefore, the presenc~ of xanthan gum in such suspensions ~erves ~o pre~ent the well-known and ~rouble~ome ~endency of suspension6 to cause blockages in the equipment u~ed to carry them and, particularly, in the nozzles of conventional spray equipment.
The amount of weight of xanthan gum can vary between 0.025% and 1.0% of the water used to prepare the starch su6pen~ion6: in the ca6e of suspen~ions prepared from dried, powder ~tarch, the xanthan gum can be incorporated in the ~tarch powder together wi~h ~uch other polymeric substance~ as may be desired ~o as to be present in the a~oremen~ioned proportions in the 61urry during u5e. In the ca6e of ~tarch already prepared in ~u~pen~ion form as previou61y de6cribed, it i6 conYenient to add the xanthan gum at an early stage in order to facilitate tran~port and prolonged storage.
~3C~
The 6econd aspect of thi~ invention is concerned with the film-forming propertie~ of certain polymer~
when di~601ved or otherwi~e disper~ed in water and applied in droplet form in a manner similar to that already describ~d for ~he application of starch suspension~ ~o paper or board during manufacture. ~he preferred polymers are polysaccharide8 ~uch a~ the alkali metal salts of carboxymethyl starches or of carboxymethyl celluloses or of alginic acid or of polyacrylic acid and their homologue~, or lmore preferably) the sodium salt of carboxymethyl cellulo~e commonly known as SCMC or CMC. The polymer~ may be applied with or without ~tarch as herein de~cribed in order to provide different benefit~ ~o sllit the requirements of user~.
The carboxymethyl celluloses can have a degree of carboxymethylation of from 0.35 to 1.4 ~i.e. related to the three labile hydroxy group~ ~heoretically available for sub~titution in each an~ydroglucose ring wi~hin the cellulose molecule chain) and total molecular weight~
from 15,000 to 800,000, preferably 50,000 to Z50,000.
It ha~ been di~covered in this invention that the presence o~ SCMC or the other polymers de~cribed in an aqueous starch disper~ion ha~ the effect of reducing the tempera~ure at which ~tarch particles rupture and form a >~
1~
gel (the gelation Temperature~ as exemplified by a rapid increase in vi~cosity. For ex~mple, ~ part6 of SCMC of molecular weight approximately 100,000 and degree of carboxymethylation of 0.85 were added to 16 parts of wheat ~tarch~ The effec~ wa~ to reduce ~he gelation temperature of a 20~ by weight ~tarch ~uspen~ion from 64 degreees Celsius to 5g degrees Celsius. This reduction in gelation temperature is important in the paper or board making processes in that it is known tha~ low temperature gelation of starch improves the beneficial effects of adding starch to cellulose. Thus, the addition of such SCMC to star~h is an important and hitherto unexpected method of improving the economy of operating the paper or board manufacturing proces~es.
The amount of these polymers, or mixture~ thereof, can vary up to 10% of the weight of the water used to carry the additive~ through a conventional spray or the atomi~ing distributor as herein described, but is more usually O.Z5~ to 7.5%.
The pre~ence of xanthan gum as part of the agueou~
dispersion of ~tarch or other water-soluble polymers ~uch as SCMC increases the resi6tance to flow of the di~persion and thus serves to control the rate at which the dispe~sion penetrate6 the paper after application.
It follows, therefore, that the presence of xanthan gum ~3~
will keep the di~persion at or clo~e ~o the ~urfac~ Of the paper even when the paper contains high propor~ions ~of wa~er such a~ occur6 during the early 6tage6 of paper manufacture.
In the method of the inven~ion it is envi~aged that starch may be applied to paper or board by the methods described herein so as to represent from 0.5% to 10% of the weight of the dried paper. It is also envi~aged that a rheology-affecti~g material, e.g. xanthan gum, may be present in sufficient quantity to prevent the starch settling out or it~ disper~isns becoming dilatant and thus un~uitable for transportation throuyh re~tric~ed orifice6. It i6 also envisaged that ~o-called water-~oluble polymers as de6cribed above may be applied to paper or board by the methods de~cribed herein in order to provide improYements to the paper or board or to augment the benef its of applying ~tarch. It is envisaged that the starch and polymers may be blended together in the dry f orm; or by mixing together their re6pective di~persions or solutions and then applying ~he resultant mixture br the method~ herein described;
or by arranging for dispe{ion~ or 601utions of the respectiYe materials to be applied severally through two or more atomi6ing di6tributors ~et so as to apply the respective material~ at the mo~t appropriate points of the paper- or board-making proce~.
.
Whil~ the invention ha~ been defined above as a method of manufacture of pape.r or board, it will be apprecia~ed that the paper or board ~o manufactured i~ a further aspect of the invention. Such paper or board has heen ~hown ~o have increased ~trength and improved surface ~u~lities, a~ described b~low in the Examples ~i given. which make it a more ~ commodity.
.1'~, 'f~
The invention also extend~ to intima~e particula~e mixture~ of starch and one or more of the additive~ as 5et forth above, capable of being jointly zuspended or hydrated for use in the method. The ~tarch/xanthan gum mixture i6 capable of long-term ~orage and reliable pa~age through application equipmen~ de~cribed above and the SCMC ~olution~ u~ed alone or jointly with starch are particularly valuable.
The invention will be further de6cribed with reference to the following Examples:
.
la) Prior Ar$
100 gram~ of wheat ~tarch were di~per6ed in 1000 ml water to form a ~lurry containing 10~ ~tarch ~olid~ at room temperature.
8 ml of the above ~luLry were placed in the cylindriaal container of a ~rookfield SC-4 Adapter fitted with the appropria~e bob which wa~ ~et to rotate at 20 revolution~ per minute (rpm) and the tempera~ure to ri~e from 20 degree~ Celsius at a rate of 2 degree~
per minute by mean~ of a ~hermostatically controlled water circula~or. Dial reading~ were ~aken continuously until t~e viscosity of the ~u~pension had undergone a rapid ri~e indicating gelation. The dial readings were plotted on yraph paper. By extrapolation, the gela~ion temperature was judged to be 64 degrees Celsius.
tb) Addition of SCMC fl ow DS
To 250 ml of the starch ~lurry prepared for the above were added 1.25 grammes of SCMC of molecular weight approximt~ly 100,000 and degree o~ carboxymethyl ~ub6titu~ion 0.65, representing 5% by weight of the starch ~olid~ and 0.5% the total slurry~solution ~ombination. The mixture was ~tirred mechanisally for one hour. 8 ml of the mixture were placed in the cylinder of the Brookfield SC-4 and the procedure de~cribed above wa~ repeated. The extrapolated gelation temperature wa~ judged to be 60 degree~ C.
' tc) Addition o~ SC'MC of hiqher DS
To a further 250 ml of the original starch slurry were added 1.25 gramme~ of SCMC of ~imilar molecular . .
~3~ 5 weight to ~he SCMC used in Example (b) but with a degree of ~ub~titution of 0.8 and the experiment repeated. In this case the ext~apolated gelation temperature was judged to be 53 degrees C.
(d) Addit on of extra SCMC
To a ~urthe~ 250 ml of ~he original starch slurry were added 2.5 gr~mme~ of the SCMC used in Example (c), repre~enting 10% by weight of the 6tarch ~olid~ and 1.0%
of the total dispersion. The experiment was repea~ed and the gelation temperature judged to be 58 degrees C.
The above experiments ha~e indicated an unexpected reduction in the gela~ion temperature or s~arch ~u~pen~ions as exemplified by the rapid rise in viscosity over a narrow range of temperature. This is interpreted as a form of co-solvency which is more apparent when the SCMC ha~ a greater degree of substitution and 80 po~se~es a greater affinity for 20 water. Thus, when water plu8 such SCMC enter6 6tarch granule6 during the early 6tages of granule rupture, the natural tendency of SCMC molecules to uncoil and expand as6i~ts the rupture of the granules at lower temperatures than would happen if SCMC were not present.
~23
IMPRo ~ MæNTs IN PAPER AND B ARD MANUFACTURE
This invention relates to paper or board manufacture. More especially, it relates to a method of paper or board manufacture in which an organic polysaccharide is added to the mixture or applied ~o the web of fibre~ during the process of manufacturing the paper or board. In particular it relates to paper of improved streng~h or ~urface characteristics manufactured according to such a method. An improved additive material also constitute~ a feature of the present invention.
~ is well known to add during the early ~tages of paper OI board manufacture one or more additive6 ~o as tD
increa~e the int0r-fibre bonding and thus the ~trengtA
of the eventual paper or board. The additives are u~ually polysaccharides including starche~ and cellulo~e and their chemical derivative~ as well as other organic ~ubstances capable of forming chemical links with the cellulose which forms the ba~iE of the paper or board web. Thi~ latter cellulo6e may have been modified by - the paper or board manufacturer in order to assi~ the web formation during the early stage6 of manufacture preceding the web formation.
Additives as described in the application can be added to the pulp its~lf, or to the early ~t~ges in the formation~of tha paper web ~wet-end addition"), i.e.
when the water content is reduced from a~out 99% to about 30%. The additives are in ~uch cases dis~ributed more or less uniformly throughout the ~hickness of the paper or board. It i6 also knswn, for convenience, to apply ~he additive to the formed web, on one or both surfaces thereof in ztages of manufacture 6ubsequen~ to web formation, as the water content is reduced to 2% ~o 20% by weight of the web.
"Size-Press Addition" named after the relevant part of the paper-making machine, is an example of a ~nown proces~; application of additives may be effected a~
this stage using solutions or dispersions of the additives, or foamed liquids, or dry powders. It i~
known that, whilst the size press process i5 a useful method of applying substances to paper or board, the equipment is expensive to buy and install; it also consumes large amounts of energy to drive the machinery and to carry out the extra drying operations consequent on the use of a size pres~.
Since the application of substances at the size pre~s is carried out using sollltions or dispersions in water, it i~ neces&ary to arrange for extra drying equipment to be installed in addition to that used to dry the paper or board before it .is passed through the size press. This extra drying reguire6 up to 30~ extr~
drying equipment and repre&ents a further 30% increase in energy consumed during the manufacture of the paper or board.
The present invention is concerned with the transfer, handling and subseguent behaviour on heating of t~ese dispe.rsions or solutions of polysaccharide additives~ and i~ based on a consideration of the flow characteristics thereof.
When dispersions of starch in water are subjected to high rates of shear, e.g. high rates of flo~ through restricted orifices such as those which are normally used to produce sprays, they exhibit considerable dilatancy. i.e. ~he apparent viscosity or resistance to flow increases as the rate of shear increases. The result of such increases is to restrict or stop flow.
Dilatancy is particularly noticeable in suspensions of ~tarch where the starch represents 5% or more of the total ~luid. This stoppage is familiar to ~hose users of starch who wish to spray suspen6ions of raw or processed starch as aids to ~arious industrial processes including application to paper and board during and subseguent to manufacture.
Aqueous dispersion~ of starch al~o tend to form sediment6 owing to the effect ~ gravity or inertial forces on ~he particulate matter suspended in the water~ Such s~diments are the cause of much failure of equipment. In order to pre~ent o~ reduce the occurrence of sedimentation, it has hitherto been cu~tomary to increase the viscosity of the su6pension by raising the temperature of the starch above the tempera~ure at which the individual particles rupture; the process is generally referred to as "cooking". This enables the starch to hydrate, forming a gel which, by increasing the fluid viscosity, reduces the tendency of the starch particles to sediment. Alternatively, it is customary to add ~ubstances which, by raising the viscosity of the aqueous phase of the ~uspension, reduce the sedimenta~ion process. Such viscosi~y-increasing substances include col~-water ~oluble deriva~ive~ of starch or of cellulose and many high molecular weight polyhydric substancQs such as polyethylene oxide ethers, polyvinyl alcohols as well as "swelling clays" such as bentonite, attapulgite, Laponite and the like which are capable of raising the viscosity of the dispersion of ~tarch in cold wa~er.
However, such procedures a6 described above lead to ~l~3~
poor ~pray formation since the fluids require high pumping pressures in order to achieve a suEficiently high degree of turbulence at the spray head ~o produce the fine droplets tha~ are desirable for a,pplication as herein described. Such high pumping pre~sures frequently lead to failure of equipment due to the inherent ~endency of starch ~uspensions to become dilatant. The present invention has discovered a method of paper or board manufacture in which one or more further additives are presen~ in the streng~h-affecting starch suspension.
According to this invention there is provided an agueous suspension of starch characterised in that it contains minor amount of a hydrophilic polymeric visco~ity increasing agent whereby the settlement of suspended starch particles is prevented. There is also provided a me~hod of applying a viscous trea~ing agent in the manufacture of paper or board, characterised in that the agent is applied by means of a rotary atomiser.
The in~ention can be ~een to comprise three a~pect~.
In one aspect, the invention provides a method for the manufacture of paper or board in which an aqueous ~, suspension~starch is applied to the paper web during or ~....
~2 ~ J~
af~er it8 formation; wherein there is present in the . ~uspension a hydra~able polymer in an amount such that : the rheology of the suspen~ion is altered so as to render the suspension more pseudoplastic whereby application to the web is facilitated since p~eudopl~stic (alternatively known as visco-elastic or shear-thinning) fluids as described in this invention are capable of having sufficient vi~cosity to prevent sedimentation of dispersed particles such as s~arch under the low ra~es of shear experienced during storage or whil~t being transported; yet, when subjected to high rates of shear such as occur when a fluid-is expelled from a narrow orifice such as the nozzle of a spray jet, the same fluids exhibit sufficiently low viscosi~y to permit the formation of droplets suitable for the application of solutions or suspensions tO paper or board during the early ~ages of manufacture.
In another aspect ~he invention provides a method for the manufacture of paper or board in which an agueous solution of a hydratable polymer is applied to the paper web during or after formation; wherein there is present in the solution a water-soluble polymeric sub6tance capable of forming a continuous film at or near the surface of the paper or board. This polymer may be applied alone utilising the advantages of the atomi6ing distributor described in this invention;
7 ~3~t5 alternatively, it may be applied together with the starch and rheology-modifying polymer described above.
In each of the above aspects, the hydratable polymer is nonionic or ionic, preferably anionic. It may be the sodium, potassium or ammonium salt of a polycarboxylic acid in which the carhoxylic units are attached to long-chain polyhydroxyl polymers, e.g. polysaccharides, whereo~ ~he polymers are based on glucose, mannose, galactose, pyranose, amylose and ths like and their hybrid derivatives including such acids as glucuronic acid. Typical polymers include the sodium, potassium and ammonium salts of carboxyme~hylcellulose and the complex polymer obtained by fermenta~ion of a suitable sugar-based medium by the organism Xanthomonas lS ampestris and commonly known as xanthan gum. It may also be one of the water-soluble salts of polyacrylic acid, polymethacrylic acid and their homologuesO the actual polysaccharides and their derivatives most preferred will depend on which aspect of the invention is of major importance~
In another aspect the invention provides a method for the manufacture of paper or board in which suspensions or solutions of 6ubstances in wa~er or other li~uids are applied by means o~ a rotary atomiser.
Although the aqueous uspensiOnS and solutions described .
~ 5 in this invention may be applied to the surface of the paper by conventional, high-pressure sprays, it is pre-ferred to use the ro~.ary a~omiser which has hitherto n~t been used in the manufac~ure of paper although well known in the agricultural art. The atomiser is availabl~ in several similar forms including devices sold under several registered trade marks including those of "~ICRON MICROMAX"
and "LELY HYDRASPIN". Such an atomiser is described in detail in GB Patents 2,004,204B, 2,004,205B and 2,004,206B
and defined in claim 1 of those patents. These atomisers and other similar devices comprise a truncated hollow con-ical shell set t~ spin on its vertical axis with the narrow end downwards.
An illustration of the configuration of the atomiser 15 i6 ~hown in the accompanying drawing, which consists of a sectional view of a twin-cone sys~em. The atomi~er comprises a fixed inner cone 1 surrounded by an outer cone 2 mounted on a bottom bearing 3 si~uated at the end of a central ~haft 4. A central nozzle 5 is 20 arranged to supply incoming fluid. The outer cone 2 is provided at the top with a top bearing 6 and drive means comprising a belt driven pulley system 7,8 coupled with an electric motor 9. The upper outer edge of the outer cone 2 is provided with teeth lO and a circumferen~ial 25 protecting ring~! The fluid to be atomised is pumped through one or more port6 into the interior of the spinning cone 2 and i~ sub6equently carried upwards and outwards across the inner surface of the ~pinning cone 2 ~3~)~25 until it leave6 the cone tangentially at it~ wide~t, upper circumferance. The ~ize of khe droplet6 generated by this ~ovement of ~he fluid is par~ly con~rolled ~y arranging for the upper edge of the cone to be serrated in the form of teeth 10 arranged radially around its upper surface. The cone may be driven by an electric or air or hydraulic motor through a suitable drive and with suitable bear;ngs to support the cone rigidly on its moun~ing. In the ca~e of a hydraulic motor, the driving energy may be ~ransferred to the motor by means of a conventional hydraulic generator pump and specialised so-called "hydraulic fluid"; alternatively, the driving energy may be transferred by arranging for the agueous starch suspension or other fluid, intended to be applied to the paper, to drive a turbine connected to the spinning cone.
For a given atomiser and a liquid of given rheological properties and set spinning at a given speed of rotation, droplet~ of uniform size are genera~ed. It follows that droplet size can be selected by choosing an appropriate combination of atomiser geometry, fluid rheology and 6peed of rotation in order to meet the particular reguirements of the user. Each of the parameters governing droplet size may be adjusted independently of the others and also independently of ~L~3~
the rate of flow of the ~uspen~ion or solution being applied to the paper 6urface, whereas with a conventional spray nozzle as previously used in the art.
the droplet iZe i~ dependent on the pressure drop acros~ the nozzle which, in turn, governs the ra~e of flow. Since the droplets produced by the at~miser are of virtually uniform fiize, they follow similar trajec~ories thu~ permi~ting a remarkably close degree of control of the pattern laid down on the paper surface and hence, uniformity of application. If the droplets are ejected from the rotating atomiser 6et ~o spin on a vertical axis, they will travel in a horizontal trajectory; it therefore follows that they will each travel along a path determined by the resultant of the horizon~al forces produced by ~he tangential motion and the force of gravity. If the body of the atomiser is placed so that the ba~e of the cone is close to the surface to which the fluid is to be applied, it follows that the droplets will travel approximately 20 centimetre~ in the vertical direction under the force of gravity and so will be travelling very much more slowly than would similar droplets ejected at high velocity from a conventional pres~ure-operated spray nozzle.
This i6 particularly advantageous when the fluid is to be applied to the surface o~ paper or board during the early state~ of manufacture when the water content of the paper i~ high and the strength of the paper con~equsntly low.
One or more atomiser~ may be fixed to a boom 8et 80 as ~o allow the fluid to be applied to th~ upper or lower side~ of the paper or board a~ it pas~es through the paper machine. If desired, part of the circumference of ~he spinning cone may be surrounded by a shield so a~ to res~rict the passage of drople~s ~o the space diametrically opposite the shield: this permits directional application of fluids ~o be made as and when reguired by the user. Fluid collected by the 6hield can be resurned to the holding tank or into the fluid circulating system as may be convenient.
The fir~t aspec~ o~ the invention i~ concerned with the rheology of the suspension. It i6 well known that : 15 ~he velocity of a liguid at which is changes from laminar or quiescent flow to turbulent flow is defined by the Reynolds Equation expressed as follows:-NR = d v.r .K
~L~3~
where Nr = the ReynoldG number of the fluid d = the density of the fluid v _ the velocity of the fluid r = Fadius of the pipe or orifice through which the fluid is ~lowing K = a proportionality constant V = the viscosity of the fluid If the above parameters are expressed in cgs units, it is known that turbulence occurs when the Reynold~
Number exceeds 2000. It can be ~een ~hat if the value of V tthe vi~cosi~y~ for a particular fluid is low, the Reynolds Number will be high and so turbulence will occur in conditions in which a fluid of higher viscosity would flow in a laminar manner: additionally, the low viscosity wiIl enable the fluid to flow at a higher velocity under given circumstances and 80 fur~her increase the Reynolds Number and, hence, the turbulence of the fluid.
It i~ well known that, for optimum e~ficiency of a spray o~ atomising system, it is necessary for the fluid to be in a state of turbulence at the point at which break-up into droplet6 occurs; in other words, optimum droplet formation occur6 when the fluid visco~i~y is low. It therefore follows tha~, if two fluids of different viscositie~ are compared under ~imilar .~ 5 conditions of flow as defined by the parameter~ used in the Reynolds Equation, better spray efficiency will bs obtained in the fluid wi~h ~he lower viscosity.
- Fur~her consideration of the ~ir~t aspect, ie. the rheology of the ~u~pension of s~arch, reguires tha~ the viscosity or re~istance to deformation within the fluid should be as high as possible when the fluid is at or virtually at rest, i.e. under conditions of low rates of shear. Prior art teaches ~hat a starsh or ~imilar suspension could be stabilised if the fluid visco~i~y is raised by cooking at least par~ of the starch or by the addition of a ~oluble polymeric substance a~ defined earlier, i.e. the 6tarch particles are prevented from setting out undex the forces of gravity or inertia.
Stokes' Law illustra~es this by calculating that thc forces exerted on suspended particle~ by external forces are inversely proportional to the viscosity of the fluid. However, such treatments give rise to high viscosities which are detrimental to the eficiency o~
the ~praying eguipment. It follows, therefore, that ~he rheology of the fluid in which the starch is &uspended ~hould exhibit a high visco~ity at low rates of ~hear in order to prevent settlement of the starch particles; at the ~ame time it ~hould exhibit low visoc~ity at high ra~e~ of 6hear in order to ensure sufficient trubulence to form droplet~ of optimum ~ize and particle size ~3~
di~tribution.
lt i& well known that the vi~cosi~y of solutions of ~ome polymeric substance6 fall6 off more rapidly than others as the rate of shear or ~he rate of flow through a given orifice i~ increa~ed. Thifi is illustrated in the following Table in which ~he viscosities in water of ~eYeral well-known high viscosity polymeric substances are compared over a ~ange of rate~ of ~hear; the respective viscosities and rates of ~hear were measured wi~h a Brookfield Viscometer fitted with a concentric bob and cylinder attachment sold under the designation Sc4 Small Sample Adapter:-.:
Shear Rate PolYmer~ Vi6co~itY (centiPoise~) @ 20 deq C _ C~C18000 13~00 ~4006000 4300 3000 1900 14~0 HEC~000 6500 50003800 2700 1900 1100 UC660 550 4804~0 400 340 260 210 . . _ . .
The present in~ention ha~ di~covered that if a minor proportion of a 6ub~tance capable of providingaqueou~ solution~ of high p~eudoplasticity i~ added to starch powder or incorporated into a ~u~pension of i2~
lS
~tarch, it renders the starch capable of being stored for prolonged periods in aqueou~ suspension; of being capable of being transported through restricted~orifices without giving rise to dilatancy; and itz suspensions of being readily ~ran~formed into drople~s of sufficiently small size to enable them to be used as a means of applying ~arch uni~ormly to surfaces includi~g sur~aces of paper during manufacture.
Preferred polymers for the rheology-affec~ing purpose are xanthan gum and similar polysaccharides capable o~ dissolving in water to produce solutions possessing very high vi8cosity at low rates of shear compared with other commerically available polymers but a relatively low viscosity at high rate of shear; this i~ illustrated in Table 1. Solu~ions of xanthan gum ~how little varia~ion in their physic 1 properties, including rheology, over temperature ranges normally experienced in paper mills and other closed industrial premises: these properties also show neglible variations when ionic and other dissolved substances are present with the xanthan gum. This is especially important when water of unknown compo6ition is used to prepare the ~tarch suspensions e.g. when recycled water of differing degree6 of hardnes~ or with differing salt contents and at varying temperature is used in such preparations.
. .
16 ~ ?~
The rheology-af~ecting propertie~ of xanthan gum are of par~icular importance if it i~ desired ~o apply ~tarch in the form of a suspension or slurry in water since the presence of the xanthan gum in the 6uspension greatly reduces the tendency of starch particles to settle QUt or form intractable sediments. The presence of xanthan gum in a fitarch suspension as described in this inventio~ allow~ users to store such suspension~
for prolonged periods and enables users to transport the starch in the form o slurry to its eventual destination without the nece~sity to in~all ~pecial agitation equipment in the slurly container~ used for transport and storage of the slurry. The convenience of being able to transport and ~tore starch suspensions by the addition of xanthan gum i~ particularly important in that ~uch suspen6ion~ are available a6 residue~ produced in ce~tain food-manufacturing proces6e~; it i~
economically advantageous to be able to supply the starch in the su~pen~ion or slurry form in which it is produced rather than to extract and dry the s~arch and sub6equently have to ~e-form the suspension before use.
p~o~i e5 ~, Thi8 invention ~c~ide~ an economic me~hod of storing and tran6porting ~uch starch suspen~ions or ~lurries to the benefit of the ~tarch and paper industxie~.
Thi~ in~ention has also discovered that the presence of xanthan gum in ~tarch su~pensions al60 overcome~ tAe tendency of ~uch ~uspen~ion~ ~o exhibit ~he phenomenon of dilatancy wh.ich can best be de~cribed as a rise in vi~cosity sr re6istance to flow a~ the rate of ~hear increases. Dilatancy i~ a condition to be avoided in handling tarch and other suspen~ions ~ince dilatant fluid~ tend to cease flowing under conditions of high rates of ~hear such as occur in~ide pumps and control valves, re~trictions and bends in pipes and in the nozzles of conventional spraying eguipment. Therefore, the presenc~ of xanthan gum in such suspensions ~erves ~o pre~ent the well-known and ~rouble~ome ~endency of suspension6 to cause blockages in the equipment u~ed to carry them and, particularly, in the nozzles of conventional spray equipment.
The amount of weight of xanthan gum can vary between 0.025% and 1.0% of the water used to prepare the starch su6pen~ion6: in the ca6e of suspen~ions prepared from dried, powder ~tarch, the xanthan gum can be incorporated in the ~tarch powder together wi~h ~uch other polymeric substance~ as may be desired ~o as to be present in the a~oremen~ioned proportions in the 61urry during u5e. In the ca6e of ~tarch already prepared in ~u~pen~ion form as previou61y de6cribed, it i6 conYenient to add the xanthan gum at an early stage in order to facilitate tran~port and prolonged storage.
~3C~
The 6econd aspect of thi~ invention is concerned with the film-forming propertie~ of certain polymer~
when di~601ved or otherwi~e disper~ed in water and applied in droplet form in a manner similar to that already describ~d for ~he application of starch suspension~ ~o paper or board during manufacture. ~he preferred polymers are polysaccharide8 ~uch a~ the alkali metal salts of carboxymethyl starches or of carboxymethyl celluloses or of alginic acid or of polyacrylic acid and their homologue~, or lmore preferably) the sodium salt of carboxymethyl cellulo~e commonly known as SCMC or CMC. The polymer~ may be applied with or without ~tarch as herein de~cribed in order to provide different benefit~ ~o sllit the requirements of user~.
The carboxymethyl celluloses can have a degree of carboxymethylation of from 0.35 to 1.4 ~i.e. related to the three labile hydroxy group~ ~heoretically available for sub~titution in each an~ydroglucose ring wi~hin the cellulose molecule chain) and total molecular weight~
from 15,000 to 800,000, preferably 50,000 to Z50,000.
It ha~ been di~covered in this invention that the presence o~ SCMC or the other polymers de~cribed in an aqueous starch disper~ion ha~ the effect of reducing the tempera~ure at which ~tarch particles rupture and form a >~
1~
gel (the gelation Temperature~ as exemplified by a rapid increase in vi~cosity. For ex~mple, ~ part6 of SCMC of molecular weight approximately 100,000 and degree of carboxymethylation of 0.85 were added to 16 parts of wheat ~tarch~ The effec~ wa~ to reduce ~he gelation temperature of a 20~ by weight ~tarch ~uspen~ion from 64 degreees Celsius to 5g degrees Celsius. This reduction in gelation temperature is important in the paper or board making processes in that it is known tha~ low temperature gelation of starch improves the beneficial effects of adding starch to cellulose. Thus, the addition of such SCMC to star~h is an important and hitherto unexpected method of improving the economy of operating the paper or board manufacturing proces~es.
The amount of these polymers, or mixture~ thereof, can vary up to 10% of the weight of the water used to carry the additive~ through a conventional spray or the atomi~ing distributor as herein described, but is more usually O.Z5~ to 7.5%.
The pre~ence of xanthan gum as part of the agueou~
dispersion of ~tarch or other water-soluble polymers ~uch as SCMC increases the resi6tance to flow of the di~persion and thus serves to control the rate at which the dispe~sion penetrate6 the paper after application.
It follows, therefore, that the presence of xanthan gum ~3~
will keep the di~persion at or clo~e ~o the ~urfac~ Of the paper even when the paper contains high propor~ions ~of wa~er such a~ occur6 during the early 6tage6 of paper manufacture.
In the method of the inven~ion it is envi~aged that starch may be applied to paper or board by the methods described herein so as to represent from 0.5% to 10% of the weight of the dried paper. It is also envi~aged that a rheology-affecti~g material, e.g. xanthan gum, may be present in sufficient quantity to prevent the starch settling out or it~ disper~isns becoming dilatant and thus un~uitable for transportation throuyh re~tric~ed orifice6. It i6 also envisaged that ~o-called water-~oluble polymers as de6cribed above may be applied to paper or board by the methods de~cribed herein in order to provide improYements to the paper or board or to augment the benef its of applying ~tarch. It is envisaged that the starch and polymers may be blended together in the dry f orm; or by mixing together their re6pective di~persions or solutions and then applying ~he resultant mixture br the method~ herein described;
or by arranging for dispe{ion~ or 601utions of the respectiYe materials to be applied severally through two or more atomi6ing di6tributors ~et so as to apply the respective material~ at the mo~t appropriate points of the paper- or board-making proce~.
.
Whil~ the invention ha~ been defined above as a method of manufacture of pape.r or board, it will be apprecia~ed that the paper or board ~o manufactured i~ a further aspect of the invention. Such paper or board has heen ~hown ~o have increased ~trength and improved surface ~u~lities, a~ described b~low in the Examples ~i given. which make it a more ~ commodity.
.1'~, 'f~
The invention also extend~ to intima~e particula~e mixture~ of starch and one or more of the additive~ as 5et forth above, capable of being jointly zuspended or hydrated for use in the method. The ~tarch/xanthan gum mixture i6 capable of long-term ~orage and reliable pa~age through application equipmen~ de~cribed above and the SCMC ~olution~ u~ed alone or jointly with starch are particularly valuable.
The invention will be further de6cribed with reference to the following Examples:
.
la) Prior Ar$
100 gram~ of wheat ~tarch were di~per6ed in 1000 ml water to form a ~lurry containing 10~ ~tarch ~olid~ at room temperature.
8 ml of the above ~luLry were placed in the cylindriaal container of a ~rookfield SC-4 Adapter fitted with the appropria~e bob which wa~ ~et to rotate at 20 revolution~ per minute (rpm) and the tempera~ure to ri~e from 20 degree~ Celsius at a rate of 2 degree~
per minute by mean~ of a ~hermostatically controlled water circula~or. Dial reading~ were ~aken continuously until t~e viscosity of the ~u~pension had undergone a rapid ri~e indicating gelation. The dial readings were plotted on yraph paper. By extrapolation, the gela~ion temperature was judged to be 64 degrees Celsius.
tb) Addition of SCMC fl ow DS
To 250 ml of the starch ~lurry prepared for the above were added 1.25 grammes of SCMC of molecular weight approximt~ly 100,000 and degree o~ carboxymethyl ~ub6titu~ion 0.65, representing 5% by weight of the starch ~olid~ and 0.5% the total slurry~solution ~ombination. The mixture was ~tirred mechanisally for one hour. 8 ml of the mixture were placed in the cylinder of the Brookfield SC-4 and the procedure de~cribed above wa~ repeated. The extrapolated gelation temperature wa~ judged to be 60 degree~ C.
' tc) Addition o~ SC'MC of hiqher DS
To a further 250 ml of the original starch slurry were added 1.25 gramme~ of SCMC of ~imilar molecular . .
~3~ 5 weight to ~he SCMC used in Example (b) but with a degree of ~ub~titution of 0.8 and the experiment repeated. In this case the ext~apolated gelation temperature was judged to be 53 degrees C.
(d) Addit on of extra SCMC
To a ~urthe~ 250 ml of ~he original starch slurry were added 2.5 gr~mme~ of the SCMC used in Example (c), repre~enting 10% by weight of the 6tarch ~olid~ and 1.0%
of the total dispersion. The experiment was repea~ed and the gelation temperature judged to be 58 degrees C.
The above experiments ha~e indicated an unexpected reduction in the gela~ion temperature or s~arch ~u~pen~ions as exemplified by the rapid rise in viscosity over a narrow range of temperature. This is interpreted as a form of co-solvency which is more apparent when the SCMC ha~ a greater degree of substitution and 80 po~se~es a greater affinity for 20 water. Thus, when water plu8 such SCMC enter6 6tarch granule6 during the early 6tages of granule rupture, the natural tendency of SCMC molecules to uncoil and expand as6i~ts the rupture of the granules at lower temperatures than would happen if SCMC were not present.
~23
2~
A ~eauctlo~ ~n the ~emp~r~tur~ ~t which starcl ~els alla 80 i6 r~ndered capable o~ form~ng a ~ore or less eon~inuo~ fil~ ~ithi~ the ~tructure of the p~p~r ~eb i8 ~ benef~t to t~o~e making paper 6ince it i6 to ,b~
S exp~cted t~at ~e heat energy reguired ~o atta~n gela~ion ~ill be reduced: additiona~ly, the g~lation ~ill take place at an e~rlier st~ge in the dryin~
s~etion o~ the ~aper-~aking proce~6, thu6 allowing ~re t~e for th~ ~enefi~al interactions be~ween ~arsh and c~llulo6e ibre~ to take pla~.
xa~le ?
heolo~ic~l Effect of Xant~an Gum (Su~pen6ion Stability) (a) 38% Star~h So~id6 SlurrY
- 250 ~1 qua~titie6 o~ a com~er~ial ~tarch ~lurry marketed under the trade mark Tenstar AB by Ranks Hovis MacDougall Ltd.~ by wet-milling of wheat and constituting a never-dried starch slurry containing 38% by welght of wheat starch solids were treated w~th several addi~ions o xanthan gum. The amount o settlement or sediment~tion of the starch was judged by noting the volume of clear liquid appearing in the upper part of the fluid whe~ stored in 2S0 ml graduated glass cylinders over periods of several days. The results ~ere noted and shown in Table 2 below.
Table 2 38~ Ten~tar Starch Slurry Per cent xanthan gum Volume of Clear Liguid (ml) (on total volumel 1 daY 3_day~ _ 7 davs 14_days __ 0.0 0 5 10 25 0.10 0 0 5 10 0.15 o o 0 o 0.20 0 0 0 r =: . _____.__ _ .. __ _____ .
(b) 18%_5tarch Sol d6 Slurrv The procedure de~cribed in Example 2(a) wa~ repeated with another never-dried commercial starch slurry known as Staper Starch obtained by wet-milling cereals and contain-ing 18% starch solids. The results are shown in Table 3.
Table 3 .
Per cent ~anthan Gum Volume of Clear Liguid (ml) 15 ton total volume) _1 day3 days _ 7 days 14 days 0.0 120 140 170 180 0.10 50 70 11~ 150 0.15 20 ~o 60 70 ~.2~ 0 0 0 0 _ (Note: The ~lurrie~ u6ed in the above experimen~ were treated with 0.2% dichlorophen in order to prevent microbiological interference with the starch and polymer dispersions).
The re6ult6 of the above experiment~ indicate that xanthan gum addition to commercial slurrie6 of ~tarch 1~3~
has ~he beneficial effect of preventing settlement of the ~tarch particle~ and 60 provîde~ the benefit of long-term storage without the nece~ity for continuous agitation as is the case of the prior art.
ExamPle 3 a) Effe~t on Strenqth of Hand Made PaPer Blends of starch combined with sodium carboxymethyl cellulose and/or xanthan gum were prepared as ~hown in Table q.
10 Table fl BLEND Starch SCMC 0.65 SCMC DS 0.85 ~anthan Gum B 96 4 o o C 96 0 4 o 15 D 99.5 0 0 0.4 E 95.6 0 4 0.4 F 95.6 4 o 0.4 250 Gramme~ of each blend were mixed into 750 ml water ~o a~ to form 25% w/v slurries whiCh were used to spray on to hand-made paper as it was being formed. The ~pray was arranged 80 as ~o deliver 0.7 ml on each occa~ion which, on paper sheets of nominal 3.7 gramme~
dry weight, is equivalent to 4.7% add-on of dry starch or blend to dry paper.
- ~x~ s The paper furni~h was bleached kraft With neutral ca~ioni~ retention aid. After drying and calendering, the sheet6 were ~e~ted for burst ~trength wi~h a ~ullen Te6ter. Th~ mean of 10 test~ was recorded and compared with un~rea~ed paper made a~ the same time but sprayed with water in place of the ~tarch slurry.
Table 5 Bleached kraft; 3.7 gramme ~heets; 4.7% ~t~rch add-on __ _ _ _ T . _ . _ _________ __ _ . _ . ______ _____ __ _ BLEND Mullen Bur~t (p8i~ ~ Chanqe lo NIL 14.2 0.0 ~ 1~.7 110.5 ) B - 16.5 +16.5 C 17.0 +19.7 D 17.0 +19.7 E 17.2 ~21.1 F 17.5 +23.2 2~ ~
The re~ult~ of the experiments ~hown in Table 5 illu~trate the beneficial effects of increasing the bursting 6trength of paper by adding starch; they îur~her ~how ~he additional benef its derived ~rom the addition of small proportion~ of polymers as described in this invention ~o the ~tarch. The additional cos~s of making these additions are greatly outweighed by ~he commercial advantages to be gained by paper-maker~
making u~e of this invention.
Example 4 USE OF ATOMISING DISTRIBUTOR
An atomi6er as de~cribed in thi~ inventisn was ~et above ~he wire par~ of a Foudrinier paper-making machine so a~ to di~tribute a ~lurry prepared by dilution of a commercial star~h slurry into which had been introduced SMCM and xanthan gum immediately following manufac~ure of the slurry a~ a by-produc$ o a proce~s to extract other component6 of milled wheat. The proportions of materials used in this Example were:
20 Starch Slurry Wheat ~tarch solids 380 Kg SCMC 18 Xg ~anthan gum 2 Kg Water 600 Kg . ~
The paper-making machine had been ~et to produce 40 Kg of paper of a weight of 35 grammes per square metre per minute at a speed of 400 me~re6 per minute. Th~
paper-making machine furni~h contained 1.5% dry ba~is of a commercial cationic sta~ch acting partly as a m~thod of providing the reguired bur~t s~rength and par~ly to aid drainage as well aS re~ention of ~ibre~ on the wire part of the machine. Slurry of the above compo~ition was pumped ~hrough a flowmeter at 1.5 litre~ per minu~e, representing 0.57 Xg 6~arch ~olids per minute, i.e. 1.~%
of the paper dry weîght. The slurry passed through an in-line diluter in which it was mixed with wate~
separately pumped at 5 litres per minute. The resultant 6.5 litre~ per minute of diluted ~lurry wa~ pas~ed through an atomiser a~ herein described driven by an air motor ~et to run at 5000 revolutions per minute producing droplets of 500 microme~re~ mean diameter.
The ~lurry was applied to the paper over a 30 hour period, ~ample~ being taken at approximately hourly intervals. During the period, the cationic ~tarch addition to the furni~h wa~ progressively reduced to zero in order to make a compari~on of this invention with a well-known and hitherto acceptable method of improving paper quali~y by the addition of a ~a~ch-ba~ed product to the paper-making machine furnish. Random result~ of thi~ experiment are ~hown in ?~S
Table 6.
Table ~ Selected wa~e ~ ~leached kraft 50 gramme~/~g.
metre: 1.4% ~tarch add-on SAMPLE MULLEN BURST % CH~NGE TENS I LE: STRENGTH % CH~NGE
P~ATIO~ (PE;i ) ~ ;psi cationic ~tarch 1.5%
Blank2.80 0.0 56 . 0.0 A3.20 ~14 57 ~1.8 cationic ~tarch reduced ~o 0.8%
B3.41 +22 60 +6.7 C3.36 ~0 62 ~9.7 D3.33 ~19 59 ~5.
Cationi~ ~tarch reduced to zero E3.46 +24 56 o.o F3.52 ~Z6 56 o.o , * The parameter "Mullen Bur~t Rat;o" (MBR) i~ define~
a~:-
A ~eauctlo~ ~n the ~emp~r~tur~ ~t which starcl ~els alla 80 i6 r~ndered capable o~ form~ng a ~ore or less eon~inuo~ fil~ ~ithi~ the ~tructure of the p~p~r ~eb i8 ~ benef~t to t~o~e making paper 6ince it i6 to ,b~
S exp~cted t~at ~e heat energy reguired ~o atta~n gela~ion ~ill be reduced: additiona~ly, the g~lation ~ill take place at an e~rlier st~ge in the dryin~
s~etion o~ the ~aper-~aking proce~6, thu6 allowing ~re t~e for th~ ~enefi~al interactions be~ween ~arsh and c~llulo6e ibre~ to take pla~.
xa~le ?
heolo~ic~l Effect of Xant~an Gum (Su~pen6ion Stability) (a) 38% Star~h So~id6 SlurrY
- 250 ~1 qua~titie6 o~ a com~er~ial ~tarch ~lurry marketed under the trade mark Tenstar AB by Ranks Hovis MacDougall Ltd.~ by wet-milling of wheat and constituting a never-dried starch slurry containing 38% by welght of wheat starch solids were treated w~th several addi~ions o xanthan gum. The amount o settlement or sediment~tion of the starch was judged by noting the volume of clear liquid appearing in the upper part of the fluid whe~ stored in 2S0 ml graduated glass cylinders over periods of several days. The results ~ere noted and shown in Table 2 below.
Table 2 38~ Ten~tar Starch Slurry Per cent xanthan gum Volume of Clear Liguid (ml) (on total volumel 1 daY 3_day~ _ 7 davs 14_days __ 0.0 0 5 10 25 0.10 0 0 5 10 0.15 o o 0 o 0.20 0 0 0 r =: . _____.__ _ .. __ _____ .
(b) 18%_5tarch Sol d6 Slurrv The procedure de~cribed in Example 2(a) wa~ repeated with another never-dried commercial starch slurry known as Staper Starch obtained by wet-milling cereals and contain-ing 18% starch solids. The results are shown in Table 3.
Table 3 .
Per cent ~anthan Gum Volume of Clear Liguid (ml) 15 ton total volume) _1 day3 days _ 7 days 14 days 0.0 120 140 170 180 0.10 50 70 11~ 150 0.15 20 ~o 60 70 ~.2~ 0 0 0 0 _ (Note: The ~lurrie~ u6ed in the above experimen~ were treated with 0.2% dichlorophen in order to prevent microbiological interference with the starch and polymer dispersions).
The re6ult6 of the above experiment~ indicate that xanthan gum addition to commercial slurrie6 of ~tarch 1~3~
has ~he beneficial effect of preventing settlement of the ~tarch particle~ and 60 provîde~ the benefit of long-term storage without the nece~ity for continuous agitation as is the case of the prior art.
ExamPle 3 a) Effe~t on Strenqth of Hand Made PaPer Blends of starch combined with sodium carboxymethyl cellulose and/or xanthan gum were prepared as ~hown in Table q.
10 Table fl BLEND Starch SCMC 0.65 SCMC DS 0.85 ~anthan Gum B 96 4 o o C 96 0 4 o 15 D 99.5 0 0 0.4 E 95.6 0 4 0.4 F 95.6 4 o 0.4 250 Gramme~ of each blend were mixed into 750 ml water ~o a~ to form 25% w/v slurries whiCh were used to spray on to hand-made paper as it was being formed. The ~pray was arranged 80 as ~o deliver 0.7 ml on each occa~ion which, on paper sheets of nominal 3.7 gramme~
dry weight, is equivalent to 4.7% add-on of dry starch or blend to dry paper.
- ~x~ s The paper furni~h was bleached kraft With neutral ca~ioni~ retention aid. After drying and calendering, the sheet6 were ~e~ted for burst ~trength wi~h a ~ullen Te6ter. Th~ mean of 10 test~ was recorded and compared with un~rea~ed paper made a~ the same time but sprayed with water in place of the ~tarch slurry.
Table 5 Bleached kraft; 3.7 gramme ~heets; 4.7% ~t~rch add-on __ _ _ _ T . _ . _ _________ __ _ . _ . ______ _____ __ _ BLEND Mullen Bur~t (p8i~ ~ Chanqe lo NIL 14.2 0.0 ~ 1~.7 110.5 ) B - 16.5 +16.5 C 17.0 +19.7 D 17.0 +19.7 E 17.2 ~21.1 F 17.5 +23.2 2~ ~
The re~ult~ of the experiments ~hown in Table 5 illu~trate the beneficial effects of increasing the bursting 6trength of paper by adding starch; they îur~her ~how ~he additional benef its derived ~rom the addition of small proportion~ of polymers as described in this invention ~o the ~tarch. The additional cos~s of making these additions are greatly outweighed by ~he commercial advantages to be gained by paper-maker~
making u~e of this invention.
Example 4 USE OF ATOMISING DISTRIBUTOR
An atomi6er as de~cribed in thi~ inventisn was ~et above ~he wire par~ of a Foudrinier paper-making machine so a~ to di~tribute a ~lurry prepared by dilution of a commercial star~h slurry into which had been introduced SMCM and xanthan gum immediately following manufac~ure of the slurry a~ a by-produc$ o a proce~s to extract other component6 of milled wheat. The proportions of materials used in this Example were:
20 Starch Slurry Wheat ~tarch solids 380 Kg SCMC 18 Xg ~anthan gum 2 Kg Water 600 Kg . ~
The paper-making machine had been ~et to produce 40 Kg of paper of a weight of 35 grammes per square metre per minute at a speed of 400 me~re6 per minute. Th~
paper-making machine furni~h contained 1.5% dry ba~is of a commercial cationic sta~ch acting partly as a m~thod of providing the reguired bur~t s~rength and par~ly to aid drainage as well aS re~ention of ~ibre~ on the wire part of the machine. Slurry of the above compo~ition was pumped ~hrough a flowmeter at 1.5 litre~ per minu~e, representing 0.57 Xg 6~arch ~olids per minute, i.e. 1.~%
of the paper dry weîght. The slurry passed through an in-line diluter in which it was mixed with wate~
separately pumped at 5 litres per minute. The resultant 6.5 litre~ per minute of diluted ~lurry wa~ pas~ed through an atomiser a~ herein described driven by an air motor ~et to run at 5000 revolutions per minute producing droplets of 500 microme~re~ mean diameter.
The ~lurry was applied to the paper over a 30 hour period, ~ample~ being taken at approximately hourly intervals. During the period, the cationic ~tarch addition to the furni~h wa~ progressively reduced to zero in order to make a compari~on of this invention with a well-known and hitherto acceptable method of improving paper quali~y by the addition of a ~a~ch-ba~ed product to the paper-making machine furnish. Random result~ of thi~ experiment are ~hown in ?~S
Table 6.
Table ~ Selected wa~e ~ ~leached kraft 50 gramme~/~g.
metre: 1.4% ~tarch add-on SAMPLE MULLEN BURST % CH~NGE TENS I LE: STRENGTH % CH~NGE
P~ATIO~ (PE;i ) ~ ;psi cationic ~tarch 1.5%
Blank2.80 0.0 56 . 0.0 A3.20 ~14 57 ~1.8 cationic ~tarch reduced ~o 0.8%
B3.41 +22 60 +6.7 C3.36 ~0 62 ~9.7 D3.33 ~19 59 ~5.
Cationi~ ~tarch reduced to zero E3.46 +24 56 o.o F3.52 ~Z6 56 o.o , * The parameter "Mullen Bur~t Rat;o" (MBR) i~ define~
a~:-
3~ 5 MB
GS1~5 where: MB = the pre~sure in pounds per square inchrequired ~o bur6t a ~ample of paper i~ the well-k~o~n 5 Mullen Te~ter u~ed throughout the paper-making indu~try;
GS2q = the weiyh* in granune~ of ~ne ~quare metre of paper .
Thu~, the ~Mulle~ Bur~c Ratio~ can be u~ed to eliminate minor variation~ in paper weight which would o~her~ise af~ec~ ~he re~ult~ of the bur~t ~est, The result~ show that the addition of ~tarch increased the ~urst ~trength of paper already containi~g a fitrength-increa~ing additive; furthermore, the Mullen Burst Strength Ratio i~creased still further a~ the previou~ly u~ed 6trength-in~rea~ing additive wa~
progres6ively reduced to zero. Therefole, the addition of 6tarch modified as de~cribed in thi~ inyention and applied in the ~orm o~ ~mall droplet6 to paper during produc~ion on a paper-making machine ~an produce be~ter re~ults than another type o~ starch hitherto regarded as accepta~le by tho6e 6kllled in the ar~ of manufacturing paper.
32 ~3~ 5 The results also show that the addition of starch modified as described above and applied to paper during the eaLly stage~ o~ manufacture enhances the ~en~ile ~treng~h of paper to which had already been added a tensile ~trengtA incrasing additive, i.e. cationic s~arch.
Example 5 ~ddition of SC~C to Pa~er durinq manufacture usina the atomiser A dispersion of SCMC was applied to paper ufiing the atomiser and flowmetering eguipment described in Example
GS1~5 where: MB = the pre~sure in pounds per square inchrequired ~o bur6t a ~ample of paper i~ the well-k~o~n 5 Mullen Te~ter u~ed throughout the paper-making indu~try;
GS2q = the weiyh* in granune~ of ~ne ~quare metre of paper .
Thu~, the ~Mulle~ Bur~c Ratio~ can be u~ed to eliminate minor variation~ in paper weight which would o~her~ise af~ec~ ~he re~ult~ of the bur~t ~est, The result~ show that the addition of ~tarch increased the ~urst ~trength of paper already containi~g a fitrength-increa~ing additive; furthermore, the Mullen Burst Strength Ratio i~creased still further a~ the previou~ly u~ed 6trength-in~rea~ing additive wa~
progres6ively reduced to zero. Therefole, the addition of 6tarch modified as de~cribed in thi~ inyention and applied in the ~orm o~ ~mall droplet6 to paper during produc~ion on a paper-making machine ~an produce be~ter re~ults than another type o~ starch hitherto regarded as accepta~le by tho6e 6kllled in the ar~ of manufacturing paper.
32 ~3~ 5 The results also show that the addition of starch modified as described above and applied to paper during the eaLly stage~ o~ manufacture enhances the ~en~ile ~treng~h of paper to which had already been added a tensile ~trengtA incrasing additive, i.e. cationic s~arch.
Example 5 ~ddition of SC~C to Pa~er durinq manufacture usina the atomiser A dispersion of SCMC was applied to paper ufiing the atomiser and flowmetering eguipment described in Example
4. In thi~ Example the modified starch slurry u~ed in Example 4 was replaced by an agueous solution of SCMC of molecular weight approxima~ely 100,000 and degree of carboxymethyl ~ubstitution of 0.85, con~aining 20 gramme6 of dry SCMC per litre of solution. As in Example 4~ the paper-making machine was set to produce 40 Kg of dry paper per minute. The rate of flow of the SC~C solution was adjusted to 5 litres per minute, representing an addition rate of 0.25% of SCMC to the dry paper produced.
Results of thi~ experiment are shown in Table 7:-33 ~L~3t)~
Table 7 ~ ' Selectea wast~ ~ ble~hed kraft; 50 grammes/sq. metre;
0.25% SCMC add-on: no ~tarch SCMC MULLEN BURST RATI0 % CH~NGE TENSILE STRENGTH %CHU~NGE
Results of thi~ experiment are shown in Table 7:-33 ~L~3t)~
Table 7 ~ ' Selectea wast~ ~ ble~hed kraft; 50 grammes/sq. metre;
0.25% SCMC add-on: no ~tarch SCMC MULLEN BURST RATI0 % CH~NGE TENSILE STRENGTH %CHU~NGE
5 % (P~i) (psil 0.0 2.80 0.0 56 0.0 0.25 3.46 +23.6 57 +l.e The results shown in Table 7 illustrate the benefits of applying as little as 0.25% SC~C of relatively low molecular weight and high degree of carboxymethyl ~ubstltut~on to paper by means of the atomi~er herein de~cribed during the early ~tage~ of manufacture.
V~ri~u~ t~ dfid ~Iddltl~ m~y b~ m~de to the invention as defined above.
For example, the incorporation of the special atomi~er~ into the mach;nery u~ed in the manufacture of paper or board (as de6cribed above in relation to the spraying of ~tarch suspensions and ~olutions ~uch as 34 ~ 2~
those of SCMC~ give6 the pO~ibility of the operation of the machinery by the selective or additional u~e of ~uch atomisers in re~pect of o~her ~uspen6ion~ or ~olution~.
For example, such atomiser~ may be u~ed with ~izing agents whether in the form of solution~, emulsion~ or su pensions. They may also be u6ed with colouring material~ whether in ~he ~orm of soluble dye~ o~
in~oluble pigment suspen~ions. They may al~o be used with oily material~, e.g. as applied to waterproof or otherwise modify the paper. They may also be used with liquid forms of reactive re~in~ a~ added to paper in order to increa~e the wet strength or re~i~tance to water of the dried paper; in thi~ a~pect the u~e of two or more atomi6er~ arranged above the wire part of a paper-ma~ing machine permit~ the application of ~everal materials which may, by phy6ical or chemical interaction with each other and the paper to which they are applied, provide further benef it6 .
By adjusting the po~ition of the atomi~er along the 20 wire part of the paper-making machine it i~ envi~aged that the degree of penetration of the applied material may be controlled. For example, applying the material at po~ition~ where the water content of the paper ~
high allows ~uch materials to penetrate the body of the paper and ~o become an integral part of the paper;
3~
3~
conversely, application at point~ where the water content has been reduced by drainage, suction or the application of heat allows the materials ~o be held at the surface of the paper and so become concentrated at or near the ~urface.
It is also envi~aged that the atomifier~ may be u~ed to apply coa~ings to paper aft~r ~he end of ~he drying part of the p~ocess: in thi~ case, the atomi~er~ could form part of the ~pecialised machinery used to apply pigment6, resins, waxes, colouring matter or ~arious solutions to the surface of the paper.
The advantage of 6~parating ~he ~ize of droplets from the rate of flow. once incorporated into the machinery i~ respect of the starch ~uspen6ion~ and SCMC
solutions as described, is of g-eneral utility throughout the process of making paper of commercial value. It is envisaged that the atomi~ers in question will either be connected for selective al~ernative u~e, or tha~ a ~uccession of atomisers will be provided at differen~
points of the flo~ path in paper production and that the necessary solutions or 6u~pen~ions will be in permanent communication with ~uch atomisers for instant use when desired.
V~ri~u~ t~ dfid ~Iddltl~ m~y b~ m~de to the invention as defined above.
For example, the incorporation of the special atomi~er~ into the mach;nery u~ed in the manufacture of paper or board (as de6cribed above in relation to the spraying of ~tarch suspensions and ~olutions ~uch as 34 ~ 2~
those of SCMC~ give6 the pO~ibility of the operation of the machinery by the selective or additional u~e of ~uch atomisers in re~pect of o~her ~uspen6ion~ or ~olution~.
For example, such atomiser~ may be u~ed with ~izing agents whether in the form of solution~, emulsion~ or su pensions. They may also be u6ed with colouring material~ whether in ~he ~orm of soluble dye~ o~
in~oluble pigment suspen~ions. They may al~o be used with oily material~, e.g. as applied to waterproof or otherwise modify the paper. They may also be used with liquid forms of reactive re~in~ a~ added to paper in order to increa~e the wet strength or re~i~tance to water of the dried paper; in thi~ a~pect the u~e of two or more atomi6er~ arranged above the wire part of a paper-ma~ing machine permit~ the application of ~everal materials which may, by phy6ical or chemical interaction with each other and the paper to which they are applied, provide further benef it6 .
By adjusting the po~ition of the atomi~er along the 20 wire part of the paper-making machine it i~ envi~aged that the degree of penetration of the applied material may be controlled. For example, applying the material at po~ition~ where the water content of the paper ~
high allows ~uch materials to penetrate the body of the paper and ~o become an integral part of the paper;
3~
3~
conversely, application at point~ where the water content has been reduced by drainage, suction or the application of heat allows the materials ~o be held at the surface of the paper and so become concentrated at or near the ~urface.
It is also envi~aged that the atomifier~ may be u~ed to apply coa~ings to paper aft~r ~he end of ~he drying part of the p~ocess: in thi~ case, the atomi~er~ could form part of the ~pecialised machinery used to apply pigment6, resins, waxes, colouring matter or ~arious solutions to the surface of the paper.
The advantage of 6~parating ~he ~ize of droplets from the rate of flow. once incorporated into the machinery i~ respect of the starch ~uspen6ion~ and SCMC
solutions as described, is of g-eneral utility throughout the process of making paper of commercial value. It is envisaged that the atomi~ers in question will either be connected for selective al~ernative u~e, or tha~ a ~uccession of atomisers will be provided at differen~
points of the flo~ path in paper production and that the necessary solutions or 6u~pen~ions will be in permanent communication with ~uch atomisers for instant use when desired.
Claims (16)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for the manufacture of paper or board in which a suspension of starch is applied to the surface of a web during manufacture by being allowed to fall onto said surface as said web travels in a substantially horizontal path, said process being characterised by the steps of a) supplying said suspension to the surface of a rotatable member of a spinning atomiser mounted above the web surface in sufficiently large volume that the starch will represent about 0.5% to 10% of the weight of the dried paper or board, b) moving said web surface beneath said rotatable member at paper or board making speed, c) rotating said rotatable member to cause said suspension to be discharged as droplets in a substantially horizontal trajectory from an outer edge thereof and thereafter to follow a path influenced by the resultant of the force on said droplets produced by the rotation of said rotatable member and the force of gravity, but excluding any electrical forces, until they impinge on said web, d) surrounding part of the circumference of the spinning atomiser with a shield so as to make directional application of the suspension, and e) maintaining the atomiser close to the surface to which the suspension is to be applied.
2. A process according to claim 1 including the steps of arranging said spinning atomiser sufficiently close to said web so that the droplets travel vertically through not more than approximately 20 cm under the force of gravity onto the web surface.
3. A process according to claim 1 including the steps of disposing across the web path a plurality of spinning atomisers and supplying the same or different suspension(s) or solution(s) to said spinning atomisers in that the web receives adjacent or overlapping longitudinal stripes of the suspension(s) or solution(s) from the atomisers.
4. A process according to claim 1 wherein said rotatable member comprises a truncated hollow conical shell and said process includes the steps of mounting said rotatable member with its narrow end at the bottom, and close to said web, and driving said rotatable member from the top.
5. A process according to claim 1 in which an aqueous starch suspension containing a minor amount of dissolved xanthan gum to stabilise the suspension is sprayed onto a paper or board web by said spinning atomiser.
6. A process according to claim 1 in which said aqueous starch suspension contains a minor amount of sodium carboxy methyl cellulose.
7. The process according to claim 4 in which said sus-pension is supplied to the lower portion of the inner surface of said conical shell.
8. The process according to claim 7 in which the upper cylindrical edge of said conical shell is serrated in the form of teeth.
9. A process according to claim 1 in which a plurality of said atomisers supplied with the same or different suspension(s) or solution(s) is employed, the atomisers being disposed longitudinally of the papermaking or boardmaking machine so that the paper or board travelling through the machine receives sequential sprays of the suspension(s) or solution(s) from the atomisers.
10. A process according to claim 1 in which the liquid is water.
11. A process according to claim 3 or 9 in which a viscous suspension or solution of a substance required to penetrate the paper or board is applied at an early stage in the papermaking or boardmaking process.
12. A process according to claim 5 in which the starch is granular.
13. A process according to claim 1 in which the suspension further includes one or more of a sizing agent, a colouring material, a reactive resin and a film forming material.
14. A process according to claim 1 in which the suspension is sprayed onto the paper or board after the drying part of the process, in order to produce a surface effect.
15. A process according to claim 14 in which the suspension further includes a wax, an adhesive, a pigment, a dye or a film-forming material.
16. A process as claimed in claim 1, in which the suspension is a viscous suspension required to penetrate the paper and is applied early in the manufacturing process.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000471075A CA1230525A (en) | 1984-12-27 | 1984-12-27 | Starch distribution by rotary applicator in paper or board manufacture |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000471075A CA1230525A (en) | 1984-12-27 | 1984-12-27 | Starch distribution by rotary applicator in paper or board manufacture |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1230525A true CA1230525A (en) | 1987-12-22 |
Family
ID=4129465
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000471075A Expired CA1230525A (en) | 1984-12-27 | 1984-12-27 | Starch distribution by rotary applicator in paper or board manufacture |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1230525A (en) |
-
1984
- 1984-12-27 CA CA000471075A patent/CA1230525A/en not_active Expired
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