MXPA98006823A - Pa gluing - Google Patents

Abstract

The present invention relates to dispersions for glueing liquid reactive glue by dispersing the reactive glue as a pure liquid in a dispersion of bentonite or other anionic microparticulate material in water. These dispersions can be used for internal sizing, for example where the dispersion is used as the anionic microparticulate stage in a microparticulate papermaking process or can be used in external sizing

Description

PAPER FINISHING DESCRIPTION OF THE INVENTION This invention relates to sizing compositions which can be used for internal gluing of paper or external sizing of paper, and relates especially to processes for manufacturing glued paper using these compositions. The glued paper is generally manufactured internally by incorporating an aqueous emulsion of the glue into a cellulosic light-supply suspension, draining the suspension through a screen to form a sheet and then drying the sheet. Externally sized paper is generally manufactured by coating a cellulosic sheet with an aqueous emulsion of the glue, and drying the sheet. The external sizing operation is often integrated with the production of the paper, such that a typical process comprises providing a suspension of cellulosic light supply, draining the suspension of light supply through a screen to form a sheet, drying the sheet , coat the dry sheet with the dispersion of the glue and then re-dry the sheet. Although non-reactive adhesives have traditionally been used, there are many cases where it is preferred to use a reactive glue as part of the total glue which is on or on the paper. Since the reactive glues are insoluble in water, they have to be predispersed before use, that is, before incorporation into the light supply or before coating the sheet. The resulting dispersion (often referred to more accurately as an emulsion) has to be sufficiently stable since it decomposes before use. The formation of a stable emulsion of the glue in water is usually achieved by emulsifying the glue in the presence of emulsifying surfactant and / or cationic polyelectrolyte such as cationic starch. The use of the cationic polyelectrolyte, and / or cationic emulsifying surfactant has been considered advantageous since it is thought to promote the substantivity of the glue on the cellulosic fibers, especially when used for internal sizing. When an emulsifying surfactant is being used as the sole emulsifier, ie, without cationic polyelectrolyte, it is usually necessary to use enough amounts of the emulsifier in order to form a stable emulsion, typically up to 7 or 8% in dry weight based on the weight of the emulsion. glue. If cationic polyelectrolyte is included then smaller amounts of the emulsifier may be sufficient, for example below 2%. Even when low amount of the emulsifying surfactant is included to facilitate the formation of the emulsion, even this amount tends to detract from the performance of gluing and therefore there are many purposes for attempting to reduce the amount of emulsifying surfactant in the glue. However, if the amount is reduced too much, generally the resulting dispersion or emulsion is very unstable which is not obtained and no adequate results are obtained. Accordingly, despite efforts to the contrary, it is always necessary in conventional processes to use significant amounts of the surfactant to promote the formation of a stable dispersion or emulsion. It may be desirable to be able to produce sizing compositions which are suitably stable for use and which do not have the disadvantage of necessarily including significant amounts of the emulsifying surfactant. Emulsions are usually manufactured for gluing by homogenizing the glue in water, possibly using prolonged homogenization. When the glue is solid at room temperature (20 ° C) it is common to perform the homogenization at an elevated temperature at which the glue is fused. Since the anhydride glues tend to be unstable, it is generally necessary that homogenization and emulsification of anhydride glues are performed in the laminator. It may be desirable to be able to simplify the production of the composition for gluing, and in particular to be able to reduce the amount of homogenization that is required when the anhydride or other glue is being emulsified for use in the laminator. Since the anhydride glues are, unfortunately, capable of undergoing hydrolysis in water, the act of pre-emulsification and the handling of the emulsion before its use may result in some hydrolysis and formation of stickiness that originate from the glue. When the use of the emulsion involves the introduction of the dispersion into the light supply, the risk of stickiness due to the risk of contaminating the screen and the risk of contaminating the other components of the apparatus by handling the cellulosic suspension is undesirable. When the emulsion of the glue is applied as an external glue during the manufacture of the sheet, for example in a gluing press, it is conventional to apply hot (for example above 40 ° C) and recycle the excess emulsion. The dispersed glue is exposed in this way to hot hydrolysis conditions for prolonged periods and it is particularly likely that the formation of stickiness and other undesirable hydrolysis effects occur. It may therefore be desirable to be able to place anhydride or other glue in a more stable form where there is less tendency for tack formation to occur during the preparation and use of the emulsified glue.

There is always a desire to improve the gluing operation which is obtained by internal or external gluing compositions. In some cases it is desirable to achieve this improvement in a general aspect, for example by obtaining an improved (ie, lower) Cobb value. In other cases it is desirable to obtain improved sizing operation with respect to some particular use. For example, externally sized paper can be used for inkjet printing wherein the black color is a composite black which is generated by the ink jet printing, and it is then desirable to have a maximum optical density for this composite black. It may be desirable to be able to improve the gluing operation. The manufacture of glued paper internally or externally necessarily involves a significant number of process steps and chemical additions, and it may be desirable to be able to combine two of these additions into a single addition which gives approximately equivalent performance or, preferably, better performance than which is obtained when the additions are made separately. Sizing compositions are usually cationic since it is conventional to assume that a cationic sizing composition will be more substantive to the paper substrate, especially when used as an internal glue. Accordingly, it is conventional to include a cationic poly-electrolyte in the composition for internal sizing and another composition. However, it is known to use anionic or nonionic emulsifying surfactants to give anionic or non-ionic dispersions or emulsions. EP-A-499,448 discloses a process using a microparticulate retention system where the reactive glue in the form of a nonionic or anionic emulsion is added to the cellulosic suspension after flocculating the suspension by the addition of retention aid cationic A preferred way to perform this process is by providing an emulsion of anhydride glue or other glue by emulsifying the glue using anionic and / or nonionic emulsifying surfactants and injecting this emulsion into the dispersion of bentonite or other microparticulate anionic material as soon as that dispersion flows towards the point at which it is added to the cellulose suspension. This process requires pre-emulsification of the glue. This also suffers from the problem that the emulsifying surfactant is necessarily introduced (with the consequential potential reduction in the functioning of the encoldo) and there is opportunity for potential hydrolysis of the anhydride glue with formation of sticky deposits. Another description is found for using an anionic dispersion of reactive glue in 096/17127 (published after the priority date of this application).

The anionic adhesive dispersion is manufactured by emulsifying a reactive glue (preferably a ketene dimer glue) in water to form a dispersion, and mixing this dispersion with a sol of colloidal anionic aluminum modified aluminum particles. This technique therefore involves conventional pre-emulsification of the glue in water, followed by mixing the glue by emulsifying with the aluminum-modified silica sol. Apparently unmodified silica sol does not provide useful stability in this process since it is established that modification with aluminum improves stability. The resulting suspension is said, in one example, to be stable for one week. In the example, the suspension is added in the light cellulose supply followed by the addition of cationic starch. It is mentioned elsewhere that the dispersion for gluing can be added before, between, after or simultaneously with the addition of cationic polymers. Also described are anionic dimer keying compositions in EP-A-418, 015. They are made by emulsifying the ketene dimer glue., while melting, in water in the presence of anionic dispersant or emulsifier. It is established that the anionic charge density of the emulsified composition can be increased by the addition of anionic components such as anionic polyacrylamide, anionic starch or colloidal silica. The examples show that, in broad terms, the internal sizing using the anionic compositions gives results (as measured by fluid intake) approximately equal as or in some cases slightly worse than when the cationic compositions are used. Additionally, the results show that increasing the anionic charge density does not improve the operation but, instead, generally makes it worse. For example, the relevant liquid intake of glued sheets with the silica-containing anionic composition shows to be much higher (worse) than the corresponding anionic composition free of silica (examples 11 and 13). Other data (the case of example 19) also show poor results under the same conditions. It is also known from U.S. Patent 5,433,776 to form an emulsion of ketene dimer with emulsifier and various cationic materials, including cationic colloidal silica. Again this involves the essential use of an emulsifier, and again produces a cationic composition. Many users consider that anhydride glues offer better performance than ketene dimer glues, but handling and hydrolysis difficulties are a disadvantage. It may be desirable to be able to reduce or eliminate these. It may be desirable to be able to incorporate a reactive glue as an internal or external glue with reduced need for the presence of emulsifying surfactant and therefore potentially improved sizing properties. It may be desirable to be able to incorporate the reactive glue, such as an internal glue, as part of another addition which is being made to the process, to minimize the number of addition points that are required. It may be desirable to be able to reduce the risk of hydrolysis, especially of the anhydride glues and thereby reduce tack contamination both during internal sizing and external sizing, especially when there is recycling of the aqueous reactive glue. It may be desirable to achieve these objectives using simple materials and simple mixing apparatus so that they can be achieved in the mill without additional complications in the papermaking process. According to the invention, a glue composition of a reactive glue which is liquid at room temperature is made by a process which comprises dispersing the reactive glue as a pure liquid in a dispersion of anionic microparticulate material in water. The resulting dispersion is a novel material and includes a size dispersion which is a water dispersion of a reactive glue (preferably ASA or other anhydride glue) which is liquid at room temperature and anionic microparticulate material which stabilizes the dispersion. Accordingly, the dispersion may contain little or nothing of the emulsifying surfactant. The invention also provides a process for sizing paper which comprises providing the novel dispersion and / or forming a sizing dispersion by a method which comprises the defined process, and gluing the paper with the sizing dispersion. The invention includes internal sizing processes wherein the paper is internally sized by incorporating the dispersion into a cellulosic light-supply suspension and then draining the suspension through a screen to form a sheet and drying the sheet. The invention also includes external sizing processes which involve coating a paper sheet with a sizing dispersion manufactured by a process comprising a process as defined above. As a result of the formation of the sizing dispersion in the presence of the anionic microparticulate material, it is possible to obtain a useful spreading dispersion using much less emulsifier than the required one. The same glue is dispersed in the same water in the absence of the anionic microparticulate material. Therefore the invention allows elimination or reduction of the emulsifier, and thus allows to improve the gluing operation.

It is possible, by the invention, not only to obtain improved physical stability but also improved chemical stability and in this way it is possible to produce anhydride and other dispersions of reactive glue which have less tendency to hydrolysis. Since the dispersions of the invention contain two essential components (glue and microparticulate material) each of which can give beneficial performance results in the papermaking or paper coating process, the dispersions make it possible to obtain beneficial results using a single addition, whereas previously two separate additions might be required. An additional advantage of the dispersions is that, despite the fact that they contain little or none of the emulsifier, they can generally be manufactured using less homogenization energy than is required when the same glue is emulsified in the same water using a conventional emulsifier. instead of the microparticulate material. The dispersion for sizing which is manufactured and used in the invention must have sufficient stability which is useful for gluing. In this way it must remain substantially homogeneous without significant separation or decomposition for sufficient time to allow convenient handling of dispersion between manufacture and use. Therefore it should generally be stable for at least about a quarter of an hour and it is often appropriate to maintain the dispersion for a mean to two hours, or sometimes longer, before use, and therefore it should be stable throughout this period. It is often advantageous to maintain the dispersion before use. However, it is not essential that the dispersion has long-term storage stability (eg, more than a week) and is suitable for most purposes to be stable against separation or decomposition for at least one hour and preferably at least minus five hours. The reactive glue that is used in the invention must be one which is liquid at room temperature, that is, 20 ° C. In this way, conventional, high-melting cetene dimer adhesives can not be used and instead the glue is a liquid ketene dimer glue or, preferably, a liquid anhydride glue. Therefore the glue is preferably a liquid ketene dimer glue such as ketene oleyl dimer glue or any of the conventional anhydride glues, since most or all of them are liquid at room temperature. The preferred anhydride glue is the succinic alkenyl anhydride (ASA) glue. The glue can be provided by the manufacturer either substantially pure or in combination with an emulsifying surfactant. In the invention, the amount of the surfactant required to make a stable dispersion, for use in the invention, can be much less than what is required in normal processes. Accordingly it is possible, in the invention, to use glues which are provided with less than the normal amount of the emulsifying surfactant and, preferably, to use glues which are provided with zero emulsifying surfactant. The amount, if any, of the surfactant which needs to be added to optimize the formation of the dispersion can then be selected by the laminator operator. Although it is possible in the invention to include some of the surfactant in the dispersion, the presence of the surfactant increases costs and causes technical problems, such as bottom gluing and therefore the amount of the surfactant is usually kept at zero or as low as practical. , consistent with obtaining a properly stable dispersion. In practice, the amount of the surfactant which can be incorporated into the dispersion is generally substantially less than that which is required to form a stable emulsion in the absence of the microparticulate material using such a surfactant or mixture of surfactants. Generally the amount of the surfactant is less than half the amount required to make a stable emulsion of that glue in the same water in the absence of the microparticulate material. For example if (as is common) it is necessary to include at least 5% (based on the reactive glue) by weight of a surfactant or mixture of surfactants in order to make a stable emulsion of that glue in that water, then in the invention the amount of that glue must be less than 2%. Accordingly, if the surfactant is present, the selected surfactant and its amount is preferably such that a stable emulsion is not formed using that glue in that water twice, and preferably 3 or 4 times, the amount of the surfactant. Generally the total amount of the surfactant is below 2% based on the weight of the glue and is preferably less than 1%, usually less than 0.5%. The best results are usually obtained in the absence of the surfactant. If the surfactant is present, it is usually selected from nonionic and anionic surfactants. Accordingly, the dispersions for sizing of the invention are usually anionic. Traditionally, it is normally considered necessary, for internal gluing, to apply the glue in combination with a cationic polyelectrolyte, for example to improve substantivity on the fibers when the glue is being used as an internal glue. However, in the invention this is not necessary and may indeed be undesirable. Therefore preferably the dispersion is also substantially free of cationic polyelectrolyte, such as cationic starch or a synthetic cationic polymer. Therefore, the amount of the cationic polyelectrolyte is generally zero, although trivial, non-interfering quantities can be incorporated and, in fact, can be present in small amounts due to recycling deposits in the mill. However such materials are best avoided. As a generality, if the emulsifier or other additives are present for the reactive glue in the dispersion, its quantity must be insufficient to make an emulsion of the same reactive glue in the same water in the absence of the microparticulate material and which is stable, in the same sense that it is stable for several hours. Additionally, the quantity must be insufficient to manufacture such an emulsion which is semi-stable, that is, in such a way that it decomposes even within five minutes of initial manufacture. By saying herein that pure liquid reactive glue is dispersed with water and anionic particulate material it is understood that the glue is dispersed while in liquid, non-emulsified form and is substantially pure, ie does not contain large amounts of the surfactant, water or another diluent but is, in turn, generally the substantially pure material as it is initially manufactured and which, prior to the invention, is normally emulsified in water using emulsifying surfactant. If any diluent or other additive is present during the manufacture of the dispersion, it is preferably one which does not detract from the dispersion properties. The process involves dispersing the reactive glue as a pure liquid within a dispersion of anionic microparticulate material in water. This dispersion of the microparticulate material in water is usually preformed, and thus the preferred method of the invention involves forming a dispersion of the microparticulate material in water, for example by stirring the material in water, and then dispersing the reactive glue in the resulting dispersion. However, the invention also includes processes in which the dispersion of the microparticle material in water is formed at substantially the same time as the reactive glue is dispersed in that dispersion. In this way, for example, the microparticulate material, the reactive glue and the water can be provided separately to a dispersion apparatus of the microparticulate material in water and the dispersion of the reactive glue therein. The invention does not include processes in which the glue is first formed as a stable dispersion in water since the invention depends primarily on the microparticulate material to provide stability to the dispersion.

Naturally it is possible to combine the pure reactive glue and water in a single feed for a dispersion apparatus in which the anionic microparticulate material is introduced since the water and the glue would not then form a dispersion (in the absence of the microparticulate material) but in instead the reactive glue will only be dispersed in water in the presence of the microparticulate material. However, generally this is not convenient and it is usually better to pre-disperse the microparticulate material and then disperse the reactive glue therein. An advantage of the invention is that it is not necessary to apply as much homogenization energy as is normally required to make a dispersion of the reactive glue in water using traditional techniques. In this way it is not required and, in its place, it is usually sufficient to apply mixing. Generally vigorous mixing, such as by a high shear mixer, is sufficient for a reasonably short period (for example less than 10 minutes and often less than 5 or even 2 minutes) in order to obtain satisfactory dispersion. The amount of microparticulate material in the final dispersion is generally in the range of 0.03 to 10% by weight of the dispersion, often 0.5 to 2% or 3%. Although it is satisfactory to add the glue to a microparticulate dispersion having the desired final content of the microparticulate material, it is observed that better results are obtained by adding the glue to a dispersion having a higher concentration of the microparticulate material than is finally desired and then diluting the resulting dispersion. For example the glue is typically mixed in a dispersion of at least 0.5%, typically up to 5%, of the microencapsulated material and this dispersion is then diluted 2 to 20 times, often about 10 times, for the desired solids content. . The water that is used in the dispersion is preferably relatively "soft" since it is easier to obtain satisfactory dispersions for sizing by the invention in the absence or substantial absence of the emulsifier when the water is soft than when it is hard. In this way when the dispersion for gluing is being made in process water of the laminator which contains interfering substances, it may be necessary to use more emulsifying surfactant than when using other water to form the dispersion. The water to be used may be subjected to an ion exchange softening process before use, but it is particularly preferred to include a sequestering agent in the water that is used to form the dispersion of the glue and microparticulate material, preferably in the water which is used to form the dispersion of the microparticulate material and in which the reactive glue is then added. The sequestering agent, alternatively known as a chelating agent, presumably interacts with hardness salts and, especially, polyvalent metal ions in the water. The sequestering agent is preferably an aminocarboxylic acid sequestrant such as ethylenediaminetetraacetic acid or nitriloacetyl acid, hydroxycarboxylic acid sequestering agents or polycarboxylic acid which are known to be suitable for sequestering divalent or trivalent metal ions such as calcium, magnesium, iron and aluminum. The amount of the glue will be selected taking into account the quality of the paper and the degree of gluing that is required. Usually the amount is 0.1 to 10 parts, often 0.3 to 3 parts per part by dry weight of the anionic particulate material. Often the amount of the glue is at least 1.1 parts per part of the anionic material. The optimum amount of each, to obtain a satisfactorily stable adhesive dispersion, can be determined by routine experimentation. Typically the dispersion contains 0.05 to 2%, generally 0.07 to 0.3 or 0.5%, by weight of each of the glues and the anionic microparticulate material. The anionic particulate material which is used in the invention to form the dispersion (and optionally also as a microparticulate retention aid) can be selected from those inorganic and organic microparticulate materials which are suitable for use as microparticle retention materials. This must be anionic and usually has a maximum dimension of below 3 μm, usually below 1 μm, in at least 90% by weight of the particles. Preferred microparticulate materials for use in the invention are swellable clays. In this way, the microparticulate material is preferably an inflatable clay of montmorillonite or smectite. It is usually an inflatable clay of the type which is usually referred to colloquially as bentonite. In this way the microparticulate material useful for incorporation into the dispersions of the adhesive of the invention can be one of the bentonite or other inflatable clays conventionally used in papermaking, for example in the papermaking process with retention of the microparticulate Hydrocol ( Brand) as described in EP-A-235,893 and EP-A-335, 575. Such materials, in use, can be separated into lamellae or other structures having a maximum dimension of less than 1 μm, for example about or less than 0.5 μm,. The minimum dimension can be as low as 0.001 μm (1 nm) or less. The inflatable clay is preferably activated before use, in a conventional manner, to replace some or all of the calcium, magnesium or other polyvalent metal ions which are exposed with sodium, potassium or other suitable ions. Thus, the preferred microparticulate material for use in the invention is activated bentonite of the type that is conventionally used in Hydrocol processes and another papermaking process. Instead of using an inflatable clay, a microparticulate synthetic silica compound can be used. Preferred materials of this type are the polysilicic acid microgels, polysilicate microgels and polyaluminosilicate microgels as described in U.S. Patent Nos. 4,927,498, 4,954,220, 5,176,891 or 5,279,807 and the use of the which in the manufacture of paper is marketed under the brand Particol by Dupont and Allied Colloids. The microgels typically have a surface area of 1200 to 1700 m2 / g or more. Instead of using these microgels, it is possible to use silica sols in which the silica particles typically exhibit a surface area in the range of 200 to 800 m2 / g. Processes using silica sols are described as the microparticulate retention aid in the Patent of the States No. 4,388,150 and WO86 / 05826 and are marketed under the trademark Composil, and other processes using silica sols are described in EP 308,752 and marketed under the trademark Posite. Although it is preferred to use an inorganic microparticulate material, especially an inflatable clay or a siliceous material having a surface area of 200 to 1700 m2 / g or more, organic microparticulate polymeric materials such as the microparticulate material are also of potential use, e.g. materials described in U.S. Patents No. 5,167,766 and No. 5,274,055 and used in the retention process of the microparticulate marketed under the Polyflex brand. The organic polymer particles may have a size below 1 μm, often below the average size 0.5 μm. The dispersion for internal sizing can be used, in this case it is optional if the paper is externally sized and, if this is, by a reactive glue or a non-reactive glue. When the dispersion is being used for internal sizing, the dispersion for sizing which is added to the light supply is usually the material which is formed by the defined process and thus is usually free substantially free of cationic polyelectrolyte, surfactant or other additives, all as described above. When the dispersion for gluing is to be used in external gluing, the paper is often also glued internally, and is optional if the internal gluing is with reactive glue or a non-reactive glue. The dispersion for gluing may have other components mixed before it is used as a dispersion for external sizing, for example a viscosity modifier, coating aids, binders and other materials which are conventional for the particular coating operation in which it is the dispersion is used. Naturally these materials must be chosen to avoid the destabilization of the dispersion. When the dispersion for gluing is being used common internal glue, this can be incorporated into the light supply at any convenient place and pot rate can be incorporated into the coarse supply which is then diluted. Generally this is added to the light provision. Preferably, the paper sized internally is manufactured by a retention process of the microparticulate in which the dispersion provides part or all of the retention material of the microparticulate. The microparticulate retention processes comprise, as is well known, incorporating a polymeric retention aid in the light supply and then mixing the microparticulate retention material in the light supply, generally after sufficient shear stress degrades the flocs formed by the microparticulate. addition of the retention aid. In this way the dispersion of the glue can be used in any of the microparticulate retention processes mentioned above or described in the patents given above. Accordingly, a preferred process according to the invention for making internally sized paper is a microparticulate retention process and comprises incorporating a polymeric retention aid into the polymeric light supply and then mixing the aqueous dispersion of the reactive glue and the anionic microparticulate material in the suspension where that microparticulate material acts as microparticulate retention material, and then drain the suspension. In particular, a preferred process of the invention for manufacturing the sized paper from a cellulosic suspension utilizes a microparticulate retention system comprising a polymeric retention aid and a microparticulate anionic material, and the process comprises providing a cellulosic suspension containing the auxiliary polymeric retention, then mix in the suspension a dispersion which is made of water and which contains the microparticulate anionic material and the water-insoluble reactive glue, liquid, drain the suspension to form a sheet and dry the sheet, and in this process the dispersion in water contains the microparticulate material and the reactive glue is substantially free of emulsifying additives for the reactive glue. In such processes the dispersion can provide all the microparticulate material that is required, or it can be aggregated simultaneously or sequentially material for additional microparticulate retention. In the preferred processes, the polymeric retention aid is added to the light supply, the light supply is then subjected to vigorous turbulence or mixed with high shear and then the dispersion and optionally another anionic microparticulate material is added, usually after the last point. of high shear stress, for example, just before or in the upper compartment. Although the process may be using a single addition of the polymeric retention aid, often two or more different polymers are added beforehand to the microparticulate material. For example, a cationic coagulant followed by a polymeric retention aid can first be added. The coagulant can be inorganic such as alum or another polyvalent metal inorganic coagulant or it can be a low molecular weight, highly charged, cationic polymer. In these processes, the retention aid is often cationic but can be anionic or non-ionic (and can be amphoteric). If a separate addition of the microparticulate is being made in the process, the microparticulate material used for that may be the same or different from the microparticulate material in the dispersion. It is usually the same.

In these embodiments of the invention, there is therefore a significant advantage that the same addition is used both to provide internal sizing and to provide retention of the microparticulate. Additionally the retention of the microparticulate can be improved as a result of the presence of the glue in some cases, and the ability to form the dispersion to glue in the substantial absence of the emulsifier means that improved sizing operation can be obtained. The sizing dispersions of the invention can be incorporated into the light supply (or thick supply) in a wide variety of other papermaking processes, i.e., processes that depend on other retention systems. For examples these can be added beforehand to a polymeric retention aid. In this way, in other preferred processes of the invention, the dispersion for gluing in the light supply (or thick supply) is added and the polymer retention aid is subsequently added. (often cationic), for example on or after the last point of high shear stress. In this way, the dispersion can be added for gluing before the centriscreen or the retention aid after centriscreeing, for example in the path to the upper compartment or in the upper compartment. In other processes, the dispersion may be added instead of the known use of bentonite or other microparticulate material. For example, the dispersion for gluing as replacement of part or all of the bentonite or other microparticulate material which is used as a pretreatment for a light supply or coarse supply to which a substantially non-ionic polymeric retention aid or a cationic polymeric retention aid or an anionic polymeric retention aid. This is of particular value when the supply is relatively dirty and the polymer is preferably of low ionicity, for example, 0-10% by weight of the ionic monomer and 90 to 100% of the nonionic monomer although higher cationic polymers (or anionic). In all the previously described processes of the invention which involve the use of a retention aid, this material can be cationic starch but is preferably a high molecular weight synthetic polymer, which typically has the intrinsic viscosity above 4 dl / g. The VI values are measured in the present by a suspended level viscometer at 20 ° C in 1 N sodium chloride buffered to pH 7. The viscosity is generally above 6 or 8 dl / g. When the polymer is cationic, the VI is typically in the range of 8 to 18 dl / g but when the polymer is nonionic or anionic the VI is typically in the range of 10 to 30 dl / g.

When the polymeric retention aid is substantially non-ionic, it may be of polyethylene oxide, but usually the retention aid is a polymer formed of ethylenically unsaturated monomers. The polymeric retention aid is usually a substantially water-soluble polymer formed by polymerization of a monomer or mixture of water-soluble ethylenically unsaturated monomers. The polymer can be anionic, nonionic, cationic (including amphoteric), and will be chosen according to conventional criteria. Suitable nonionic monomers include acrylamide. Suitable cationic monomers include diallyldimethylammonium chloride and dialkylaminoalkyl (meth) acrylates and acrylamides (generally as quaternary ammonium or acid addition salts). Dimethylaminoethyl acrylate or methacrylate or a quaternary ammonium salt is often particularly preferred. Suitable anionic monomers include acrylic acid, methacrylic acid, acrylamidomethylpropanesulfonic acid and other carboxylic and sulphonic monomers. Preferred anionic and cationic polymers are generally copolymers of 3 to 70 (often 5 to 50) weight percent of ionic monomer and 97 to 30 weight percent of acrylamide or other nonionic monomer. High molecular weight polymers can be branched or lightly crosslinked, for example as described in EP 202,780. When the process involves the use of a lower molecular weight, high charge density polymer, it is usually a homopolymer of recurring cationic groups or a copolymer of at least 80% by weight of the cationic monomer and 0 to 20% by weight of the cationic monomer. acrylamide or other non-ionic monomer. The cationic groups can be derived from any of the cationic monomers mentioned above. Alternatively, the low molecular weight cationic polymer can be a condensation polymer such as a dicyandiamide polymer, a polyamine or a polyethyleneimine. Inorganic coagulants (such as alumni) can be used. The dispersions for gluing of the invention can also be used in processes in which the retention system comprises a phenolsulfone resin followed by polyethylene oxide. In these processes the dispersion can be added to glue at any stage in the process, and in this way it can be added before or after the addition of the polyethylene oxide, but usually after the phenolsulfone resin. Suitable processes of this type are described in EP 693,146. Other suitable papermaking processes to which the invention can be applied are described in, for example, European Patent 235, 893, U.S. Patent 4,927,498, U.S. Patent 4,954,220, U.S. Patent 5,176,891, U.S. Pat. United States 5,279,807, United States Patent 5,167,766, United States Patent 5,264,055 and European Patent 698,986 (including the patents mentioned therein): The cellulosic suspension can be any suitable suspension for manufacturing sized paper. This may include recycled paper. This may be filled or unfilled and may therefore contain any of the conventional fillers. The invention is of particular value when the suspension contains at least 10% filler, for example up to 50%. The preparation of the suspension and the details of the papermaking process can be conventional except for the incorporation of the internal and / or external glue in the form of the dispersions described. As indicated in the patent specifications mentioned above, some of the processes described are of particular value when the suspension is dirty, for example as a result of prolonged recycling of white water and / or the use of at least 25% mechanical pulp. or semi-mechanics and / or de-inked pulp. The amount of the retention polymer which will be used will be selected from conventional doses and is generally in the range of 0.01 to 0.5%, often around 0.03 to 0.1% based on the dry weight of the paper. The amount of the microparticulate material, when the retention process is a microparticulate retention process, is usually in the range of 0.03 to 3% based on the dry weight of the paper. Thus, in preferred processes, at least 100 grams of the polymer and at least 300 grams of bentonite or other microparticulate material per tonne of dry weight of the paper are added. When the invention is applied to the production of externally sized paper, the dispersion can be applied as a gluing composition to preformed paper. In this way paper can be manufactured and wound in the conventional manner and then coated with the size dispersion of the invention, optionally containing other additives. The invention also includes processes in which external sizing is part of the entire papermaking process, in which case the paper is made glued by a process that comprises incorporating a polymeric retention aid in a light cellulosic supply, draining the supply lightly to form a leaf, dry the leaf, apply the aqueous dispersion to the dry leaf and re-dry the leaf. Accordingly, the glue dispersion can be added in a conventional manner in the conventional papermaking position. In practice paper is usually made on a papermaking machine in which the suspension is fed to a screen by a top compartment, it is pressed to eliminate water and it is passed through dryers and then to a presna of glue. In this way the papermaking machine generally includes a gluing press and the dispersion is preferably applied in the gluing press with the excess dispersion that is recovered and recycled. In this way the invention includes processes in which the excess of the dispersion is applied hot, for example at a temperature above 40 ° C, to the sheet and the excess dispersion is recovered and recycled. Since the normal manufacturing process is carried out continuously with recycling of the excess glue composition, this allows the glue composition to be maintained at a high temperature for extended periods. This temperature is usually at least 50 ° C and can be up to 70 to 80 ° C, often around 60 ° C. These conditions have tended, prior to the invention, to increase the hydrolysis of anhydride glues with the consequent formation of tackiness, but in the invention the undesirable formation of tackiness is avoided or reduced. Thus, for the first time, it is possible to use an ASA or anhydride glue on the size press without significant stickiness and without the need for other modifications of the size press conditions. The external glue composition can be applied to a wet sheet which is then dried but the sheet is usually completely or partially dry before application of the glue dispersion of the invention. Thus, when external gluing is performed during papermaking on a paper machine, the sheet is usually dry down, a or towards the ambient moisture content before the application of the adhesive dispersion of the invention for surface bonding. . The process typically comprises draining the light supply through the sieve, pressing, drying completely or partially, applying the dispersion and then re-drying. When the glue dispersion of the invention is being used for external sizing, the paper will usually have been glued internally by the incorporation of a reactive glue or non-reactive glue in the light supply. In this way the non-reactive or other adhesive may be incorporated in the light supply (optionally including in the coarse supply from which the light supply is formed) in a conventional manner or internal gluing may have been carried out in accordance with the invention. The paper that will be glued externally may have been formed in any conventional manner. It is therefore usually manufactured using a retention system. In this way the total process comprises generally incorporating a polymeric retention aid in the cellulosic light supply, draining the light supply to form the sheet, drying the sheet, applying the aqueous dispersion to the sheet and re-drying the sheet. The polymeric retention aid may be the only material that is added to promote retention or a plurality of materials such as the retention system may be used. For example, the retention system may be a microparticulate system, as described above. If so, the microparticulate retention material which is used may be the same or different from the microparticulate material which is present in the dispersion that is applied to the sheet. It is usually the same. In this way, preferably, bentonite or other swellable clay is used as part of the microparticulate retention system and as the microparticulate material for the dispersion for external sizing. Instead of using a microparticulate retention system, the papermaking system which is externally sized may consist of a single polymer retention polymer or a multiple dose system comprising counterionic polymers. In this way the process may comprise adding a cationic polymeric retention aid followed by an anionic polymeric retention aid or other organic anionic polymer. If desired, the process can include a pretreatment, for example with bentonite or other microparticulate material or a low molecular weight cationic polymer or inorganic coagulant. Any of these processes can also be used in the internal sizing processes of the invention, for example as indicated above. The amount of the ASA or other glue in the glue dispersion that is used for external sizing is generally in the same ranges as discussed above for internal sizing, typically 0.05 to 5% glue and 0.05 to 10% particulate, based on to the total weight of the composition. The weight of the total dry coating provided by the surface sizing, that is, the dry weight of the glue and particulate material and any other material that is included is generally in the range of 0.07 g / m2 to 65 g / m2. Although it is generally preferred, for internal sizing systems, that the dispersion be free of polyelectrolyte or other additive, the preferred external sizing compositions of the invention may contain conventional sizing components and in particular conventional sizing binder. Thus, although the size dispersion of the invention is generally manufactured in the presence of little or no surfactant, a binder such as starch or other suitable polymer may be included. The starch can be gelatinized and can be unmodified or modified, for example cationic starch. The dry weight of the starch to the reactive glue is generally in the range of 5: 1 to 40: 1, ie, which corresponds to the general proportions of starch and glue conventionally applied when glued in size press. The optimal quantity will depend on other conditions, for example the degree (if any) to which the sheet is already glued internally. The amount of the starch or other binder that is applied in the external sizing coating is usually in the range of 0 to 40 g / m2. When binder, viscosity modifier or other additives are included, they are usually mixed into the size dispersion of the invention after it is manufactured in the substantial absence of additives, as described above. It appears that the drying applied after internal or external sizing can contribute to the success of the sizing of the invention, perhaps as a result of the migration of the glue away from the microparticulate material with which it is associated in the dispersion and on the adjacent paper fibers. . The drying can be carried out at conventional temperatures. The advantages of using the sizing dispersions in external sizing involve the ability to bond externally with ASA in processes where this may have been previously countered due to the excessive instability of the ASA glue. Other advantages arise from the benefits of the particular sizing that are obtained (for example in the determination of sizing of the composite black for inkjet printing), and the benefit of having bentonite or other microparticulate coating in the outer glue coating. This gives desirable properties for the coating and, by the invention it is possible to obtain both this and the benefits of incorporating the ASA glue and another liquid. For optimal results it seems desirable that the microparticulate material should interact closely with the exposed surfaces of glue particles that are formed in the dispersion. For example, photographic examination of preferred compositions of the invention (using an anhydride and bentonite glue or other swellable clay) made in the presence of mild water shows that many or substantially all of the surfaces of the glue particles are covered by and apparently associated with with lamellae of inflatable clay. However in compositions which are less satisfactory (such as those which are only marginally stable and have been manufactured in the presence of hard water and with inadequate emulsifier to compensate for hardness) there are significant exposed surfaces of glue particles, apparently without association between these exposed surfaces and the microparticulate material. Whatever the mechanism, it is found in the present that there is a close interaction between the glue and the microparticulate material with the result that the simple extraction of the dispersion with an organic solvent can result in the extraction of none, or mostly only a small proportion, of the glue from the dispersion. The preferred microparticulate materials are those which, in the processes of the invention, can be shown under photographic examination (by optical microscope) to show close association between the microparticulate material and the glue. It is not clear if the association is due to the ionic interaction (perhaps with partially hydrolyzed groups on the surfaces of the glue particles) or if it is due to some physical interaction. The following are examples. Example 1 Paper is made in accordance with the Hydrocol process as described in EP-A-235,893, by mixing an appropriate amount (usually in the range of 300 to 800 g / t) of cationic polymeric retention aid. soluble in water having a VI above 6 dl / g followed by mixing with shear stress in the normal papermaking apparatus followed by the addition of an activated aqueous dispersion of bentonite. The dry weight of the paper is around 165 g / m2. The glue Asa is emulsified in hard water in the presence of 5% (based on the glue) of emulsifier to form a stable emulsion. This is then added to the bentonite dispersion in a dose of 2 kg / t (based on the final paper). When the manufacturing water is very hard, the Cobb value of the final paper is 35 but when the manufacturing water is soft the Cobb value is 30. When the process is repeated using pure glue containing 1% of the direct homogenized surfactant in the bentonite suspension, the corresponding Cobb values are 30 and 27. It is not possible to form a stable emulsion of the ASA glue containing this amount of emulsifier in the absence of the bentonite, either in hard water or in hard water. The reduced Cobb values show the benefit of performing the process of the invention in either hard water or mild water with less emulsifier than is required to form a stable emulsion of the glue in water. When the process is repeated using an AA glue in the total absence of the surfactant, it is difficult to obtain a properly stable dispersion of the microparticulate material and glue in hard water, but in mild water a stable dispersion is formed and the Cobb value of the final paper is 26 This demonstrates the additional advantage that is obtained by performing the process in the absence of emulsifying surfactant. This demonstrates that, although a satisfactory dispersion can be elaborated in the presence of 5% emulsifier, better results are obtained with low or zero amounts of the surfactant. Example 2 0.65 parts of pure ASA (free of emulsifier or other additives) are mixed in a dispersion of 1 part of activated bentonite in 99 parts of water. When the water of the dispersion of the bentonite is hard, it can be observed that the resulting dispersion has an oily tendency. When the water of the bentonite dispersion is soft, the resulting dispersion appears less oily. When 0.2 parts salt of sodium EDTA is included in the water of the bentonite dispersion before dispersing the bentonite therein, the resulting dispersion containing the ASA glue appears very uniform and stable and gives improved sizing performance, both internal sizing or external gluing. In each of these tests the mixing is by means of a few seconds of homogenization using a mixer Silverson. Example 3 This is an example of a process similar to Example 1 except that the dispersion of the invention is made using ASA and 1% of the direct homogenized surfactant in an aqueous dispersion of colloidal silica BMA. The values of Cobb are as follows. Table 1 Example 4 The process of Example 1 is repeated using pure ASA emulsified in a 44% bentonite suspension. The results are obtained in Tables 2. Table 2 Example 5 Pure ASA is dispersed in aqueous bentonite as in Example 1. In process A the dispersion is mixed to glue in a water-based cellulosic feed followed by a substantially non-ionic polymer after four inversions. In process B the polymer retention aid is added, the system is stirred, and the dispersion is then added for sizing and mixed using four inversions. In process C, the dispersion for gluing is added and mixed with four inversions, but no retention aid is added. The results are shown in Table 3. Table 3 EXAMPLE 6 In this, and other examples of bentonite, the bentonite suspension is subjected to shear stress using a Silverston high shear mixer at 1200 rpm and ASA is injected into it and the shear stress is continued for approximately 30 seconds. The present example reproduces the process of Example 1 using such dispersions formed with and without surfactant. In process C, pure ASA is dispersed in the sizing composition in the absence of the surfactant. In the process D is dispersed in the presence of 1% surfactant. The results are shown in Table 4. Table 4 Example 7 In this process a 5% bentonite dispersion batch is prepared using demineralized water and then mixed with pure ASA shear stress therein, as above, in the absence of an emulsifier. 100 g / t of a phenolsulfone resin is mixed in the waste supply followed by 100 g / t of polyethylene oxide followed by binder dispersion with bentonite and ASA. The results are shown in Table 5. Table 5 ASA (kg / T) Cobb (gsm) (60 seconds) 6 34 8 27 Example 8 100 ml of a suspension of 0.1% bentonite in water is subjected to shear stress using an emulsifier Silverson. After 5 seconds, 1 ml of pure Asa glue is added and the resulting dispersion is subjected to shear stress for an additional 30 seconds. A coating board having a Cobb value of 60 seconds uncoated of about 200 gsm is coated with this dispersion using a K No. 7 bar. The treated liner board is dried on a rotary glass drier at 60 ° C. 4 minutes The sheet is further dried in an oven at 11 ° C for 30 minutes. After conditioning overnight, the value Cobb's 60 seconds is 20.0 gsm. Example 9 Pure Asa is emulsified in water containing varying amounts of bentonite to form a size dispersion which immediately coats substantially the white printing / writing paper which has been previously internally sized. The coating with the Asa sizing dispersion of the invention results in external sizing to provide a substrate for inkjet printing. This is subjected to evaluation of black composed of standard Hewlett Packard and the minimum optical density for each composition is recorded. The results are shown in Table 6. Table 6 It will be appreciated in all of these examples that the best gluing results are demonstrated by the lowest Cobb value and that, in Table 6, the best coating quality is indicated by the highest optical density value. In this way the various examples demonstrate the gluing benefits of the invention and that these benefits are maximized when the surfactant is omitted.

Claims (22)

1. CLAIMS 1. A process for manufacturing a glue dispersion of a reactive glue which is liquid at room temperature by a process characterized in that it comprises dispersing the reactive glue as a pure liquid in a dispersion of anionic microparticulate material in water.
2. 2. The process according to claim 1 characterized in that the glue is a reactive anhydride glue.
3. 3. The process according to claim 1 or claim 2 characterized in that the anionic microparticulate material is selected from castable clays, polysilicic acid, polysilicate microgel and polyaluminosilicate microgel.
4. 4. The process according to claim 1 or claim 2 characterized in that the microparticulate material is bentonite.
5. 5. The process according to any of the preceding claims characterized in that the water is soft.
6. 6. The process according to any preceding claim characterized in that the dispersion is formed in the substantial absence of cationic materials.
7. The process according to any preceding claim characterized in that the dispersion is formed in the substantial absence of an additive selected from cationic polyerytrolytes and surfactants.
8. 8. The process according to claim 7, characterized in that the dispersion is formed in the absence of cationic poly-electrolytes and in the absence of emulsifying surfactant or in the presence of not more than 2% (by weight based on the weight of the reactive glue) of the surfactant.
9. 9. The process according to claim 8, characterized in that the dispersion is formed in the absence of surfactant or in the presence of not more than 1% of the surfactant, and wherein the surfactant is selected from nonionic and anionic surfactants.
10. The process according to any preceding claim characterized in that it comprises providing a stable dispersion of the anionic microparticulate material and then stirring the glue therein.
11. 11. The process according to any preceding claim characterized in that the water is softened in the presence of sequestering agent.
12. 12. A sizing dispersion characterized in that it comprises a dispersion in water of a reactive glue which is liquid at room temperature and anionic microparticulate material which stabilizes the dispersion and in which the dispersion is substantially free of cationic polyelectrolyte and is free of surfactant or contains not more than 2%, preferably not more than 1%, of surfactant.
13. A process for gluing paper characterized in that it comprises forming a dispersion by a process according to any of claims 1 to 11 providing a sizing dispersion according to claim 12 and gluing the paper with the sizing dispersion.
14. The process according to claim 12, characterized in that the paper is internally sized by incorporating the dispersion into a suspension of light cellulosic supply and then draining the suspension through a screen to form a sheet and drying the sheet.
15. 15. The process in accordance with the claim Characterized in that it comprises incorporating a polymeric retention aid in the light cellulosic supply and then mixing the aqueous dispersion of reactive glue and anionic microparticulate material in the light supply as a microparticulate retention material and then draining the suspension.
16. 16. The process in accordance with the claim Characterized in that the dispersion which is incorporated into the light cellulosic supply has been processed by a process according to any of claims 7 to 0 or is a dispersion according to claim 12 and is substantially free of additives selected from cationic polyelectrolytes. and surfactants.
17. 17. The process in accordance with the claim 14 for making glued paper from a cellulosic suspension using a microparticulate retention system comprising a polymeric retention aid and a microparticulate anionic material, the process comprising providing a cellulosic suspension containing the polymeric retention aid, and then mixing in the suspension a dispersion which is in water and which contains the microparticulate anionic material and the water-insoluble reactive glue, drain the suspension to form a sheet and dry the sheet, characterized in that the dispersion in the manufacturing water contains the material microparticulate and the reactive glue and is substantially free of additives selected from polyerytrolytes and cationic surfactants.
18. 18. The process according to claim 14 characterized in that the dispersion is incorporated in the cellulosic suspension and then the polymeric retention aid is added.
19. 19. The process according to claim 14, characterized in that a phenolsulfone resin is incorporated in the suspension followed by a polyethylene oxide resin as a retention system and the dispersion is added to the suspension before or after the addition of the oxide. of polyethylene.
20. 20. The process according to claim 13 characterized in that the paper is externally glued by coating the paper with the dispersion.
21. 21. The process according to claim 20, characterized in that viscosity modifiers and / or coating components are included in the dispersion before coating the paper with the dispersion.
22. 22. The process according to claim 20 or claim 21 for manufacturing externally sized paper characterized in that it comprises incorporating a polymeric retention aid in a light cellulose supply, draining the light supply to form a sheet, drying the sheet, applying the aqueous dispersion to the leaf and dry the leaf again.