Paper making and fiber liberation – Processes and products – Non-fiber additive
Patent
1998-08-19
2000-12-12
Chin, Peter
Paper making and fiber liberation
Processes and products
Non-fiber additive
162175, 162179, 1062151, 1062152, 1062153, 1062154, 10628723, 10628724, D21H 2116
Patent
active
061593397
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a paper size consisting essentially of an alkyl ketene dimer (AKD) and/or alkenyl succinic acid anhydride (ASA) sizing agent, a cationic starch emulsifier and water. Further the invention relates to a paper sizing process using a paper size which is essentially composed of an alkyl ketene dimer and/or alkenyl succinic acid anhydride sizing agent, a cationic starch emulsifier and water.
AKD and ASA sizes are widely used in the production of paper and cardboard. For good sizing efficiency it is required that the sizing agent is applied in the form of very small particles. Thus, AKD sizes are currently supplied to paper and cardboard manufacturers as fully formulated size dispersions or emulsions. However, such dispersions and emulsions have several disadavantages. For example, they often have to be transported over considerable distances to the paper plant which is uneconomical since such transport includes the transport of great amounts of water. Further, stability of AKD dispersions and emulsions is a problem. Accordingly such AKD size formulations include adjuvants like protective colloids, emulsifiers, surfactants etc. Such ingredients are not necessarily required for good sizing. To the contrary it is known that surfactants, particularly anionic surfactants, will not assist the deposition of AKD particles onto anionically charged fibers and will tend to reduce the performance of the sizing composition. Finally, during transport and storage the AKD may react with the aforementioned ingredients. Again this impairs the efficiency of the AKD size.
To avoid these disadvantages of AKD dispersions and emulsions it has already been proposed in the past to prepare the AKD sizing composition directly at the place of application, namely the paper plant. However, the problem is that emulsifying AKD is not easy and requires considerable know-how and expensive mixing equipment, namely high pressure homogenisers. It is not realistic and would be highly uneconomical to supply every paper plant with a high pressure homogeniser.
Therefore there have been several proposals in the past for economically feasible on-site processes for producing AKD and ASA sizes. However, it is not known that any of these proposals has gained commercial importance with regard to AKD sizes, while ASA sizes are mostly produced on-site.
DE-AS 25 33 411 includes a detailed discussion of the above outlined problems and discloses a process for sizing paper products using an aqueous emulsion containing AKD and an emulsifier selected from specific polyoxyalkylenealkyl or polyoxyalkylenealkylaryl ethers or corresponding mono- or diesters. It is reported that emusification only requires stirring or passing the mixture through a mixing valve or an aspirator. It is even claimed that particularly selected mixtures can be used in sizing without a prior emulsification step.
Other proposals for on-site preparation of AKD and ASA sizes are disclosed in DE-OS 24 39 026, PCT-Application WO 94/13883, GB-A-2 252 984, EP-B-0 220 941 and EP-B-0 228 576.
It has now been surprisingly found that AKD and/or ASA sizes can be produced on-site at a paper plant in a simple manner by using a specific cationic starch emulsifier.
Thus the present invention relates to a paper size consisting essentially of
a) alkyl ketene dimer and/or alkenyl succinic acid anhydride, to 3.5 meqv/g, a degree of substitution of more than 0.25 and a viscosity of less than 10000 cps (30% by weight solution in water at 25.degree. C.), and
Further the invention relates to a process for making paper products in which a paper size is added to the pulp which is essentially, composed of to 3.5 meqv/g, a degree of substitution of more than 0.25 and a viscosity of less than 10000 cps (30% by weight solution in water at 25.degree. C.), and
Preferred embodiments of the present invention will become apparent from the following description and the claims.
Useful alkyl ketone dimers are those of the formula (RCH=C=O).sub.2 wherein R is selected from saturated or unsaturated al
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Hassler Thord G.
Schuetz Jurgen F.
Smith Bryan C.
BetzDearborn Inc.
Chin Peter
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