Compositions: coating or plastic – Coating or plastic compositions – O-containing organic compound
Reexamination Certificate
1999-12-16
2002-09-03
Chin, Peter (Department: 1731)
Compositions: coating or plastic
Coating or plastic compositions
O-containing organic compound
C106S287240, C162S158000, C162S168100, C162S179000
Reexamination Certificate
active
06444024
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to sizing of paper and paperboard products. More specifically, the invention relates to a substantially water-free sizing composition and an aqueous sizing dispersion comprising a cellulose reactive sizing agent and a copolymer prepared from a monomer mixture comprising olefins and derivatives of unsaturated carboxylic acids.
BACKGROUND OF THE INVENTION
Cellulose-reactive sizing agents have long been used in conjunction with paper and paperboard production in order to introduce water repellence. By nature the cellulose-reactive sizing agents are hydrophobic in their character, hence, they are not easily soluble in polar solvents such as water. In order to achieve adequate sizing of the cellulose material the hydrophobic cellulose-reactive sizing agent must be finely dispersed in an aqueous medium before the sizing agent is added to the paper or paperboard wet stock.
Cellulose-reactive sizing agents derived from 2-oxetanone sizing agents are usually prepared as dispersions which are fairly stable. However, cellulose-reactive sizing agents derived from the reaction product of acid anhydrides or dicarboxylic acids and unsaturated hydrocarbons, commonly referred to as ASA sizing agents, are highly reactive, thus, they have to be prepared at the mill. As a consequence of the reactivity of the ASA sizing compounds the stability of a prepared emulsion is very limited. Another drawbacks linked to the preparation of dispersions of cellulose-reactive sizing agents are the introduction of shear forces in order to achieve finely divided/dispersed particles or droplets of the sizing agent in the aqueous phase. Shear forces are often applied by using high pressure equipment which, is cumbersome and costly.
Accordingly, one object of the present invention is to overcome the above mentioned drawbacks. Specifically, the present invention provides a sizing composition which practically is self-emulsifiable or needs low shear forces in order to obtain proper size distribution of the sizing agent in the aqueous phase.
Another object with the present invention is to further improve the dispersibility i.e. smaller particle size, of storage stable substantially water-free sizing compositions.
A still further object of the invention is to provide a storage stable substantially water-free sizing composition.
Yet another object of the present invention is to further improve the dispersability of sizing compositions comprising liquid cellulose-reactive sizing agents.
SUMMARY OF THE INVENTION
The present invention relates to a substantially water-free sizing composition, an aqueous sizing dispersion and a process for the production of paper and paperboard according to the claims. More specifically, the invention relates to a substantially water-free sizing composition and an aqueous sizing dispersion comprising a cellulose-reactive sizing agent and a copolymer prepared from a monomer mixture comprising one or more olefins and one or more derivatives of unsaturated carboxylic acids.
Cellulose-reactive sizing agents in general and especially substituted succinic anhydride sizing agents, often referred to as ASA, are unstable due to hydrolysis. Thus, aqueous dispersion comprising ASA have to be prepared close to the location of the intended use. By providing substantially water-free sizing compositions storage stability is obtained. Furthermore, substantially water-free compositions can be transported over longer distances not only due to improved stability but due to the exclusion of water. Substantially water-free sizing compositions comprising ASA or 2-oxetanone sizing agents are further more resistant to temperature changes than aqueous dispersions.
U.S. Pat. No. 4,695,401 and U.S. Pat. No. 4,915,786 refer to an ASA composition containing an emulsifier formed by the reaction of ASA and a nonionic water soluble compound having from 1 to 3 reactive polar groups. The latter compounds are exemplified particularly by polyethylene glycols or polypropylene glycols which may be capped at one end by an alkyl group. The product formed are esters, where polyalkylene glycols are linked to 1 to 3 ASA compounds.
DETAILED DESCRIPTION OF THE INVENTION
According to one preferred embodiment of the invention the cellulose-reactive sizing agent is selected among any cellulose-reactive sizing agents known in the art. The cellulose-reacive sizing agents are selected from the groups comprising 2-oxetanone sizing compounds and/or substituted succinic anhydrides, commonly referred to as ASA. and mixtures thereof, ASA being especially preferred.
Preferred 2-oxetanone sizing agents are mixtures of 2-oxetanore sizing compounds having at least one reactive 2-oxetanone group and pendant hydrophobic hydrocarbon groups. The mixture of 2-oxetanone compounds is suitably not so:id at 35° C. Preferably, the mixture of 2-oxetanone compounds is not solid at 25° C., more preferably even at 20° C. Even more preferably, the sizing agent is liquid at 35° C., more preferably at 25° C., and most preferably at 20° C. The term “liquid” apply to the sizing agent per se and not to a composition or a dispersion. The preferred structure of 2-oxetanone sizing agents is as follows:
wherein n can be from 0 to 6, more preferably 0 to 3, and most preferably 0. R and R″, which may be the same or different, are selected from the group of straight or branched alkyl or alkenyl chains. If n=0, then suitably not all are straight alkyl chains. Preferably, at least 25% by weight of the sizing agent consists of the 2-oxetanone structure in which at leastone of R and R″ is not straight chain alkyl. R and R″ can be substantially hydrophobic in nature, are suitably acyclic, and are preferably at least 6 carbon atoms in length, more preferably from 8 up to 36, most preferably from 12 up to 20 carbon atoms in length. When n>0 the sizing agents are termed 2-oxetanone multimers. R′ is preferably straight chain alkyl, more preferably a straight chain alkyl containing from 6 to 16 carbon atoms, most preferably containing from 8 to 20 carbon atoms. Preferably, the 2-oxetanone sizing agent is made from fatty acids or fatty acid chlorides containing irregularities such as double bonds and chain branching. Preferred fatty acid are selected from the group comprising oleic, linoleic, linoleic, palmitoleic, dodecenoic, tetradecenoic (myristoleic), hexadecenoic (palmitoleic), octadecadienoic (linoelaidic), octadecatrienoic (linolenic), eicosenoic (gadoleic), eicosatetraenoic (archidionic), docosenoic (erucic), docosenoic (brassidic) and docosapentaenoic (clupanodinic) acids or mixtures thereof.
Suitable acid anhydrides can be characterized by the general formula (II) below, wherein R
A
and R
B
can be identical or different and represent saturated or unsaturated hydrocarbon groups suitably containing from 8 to 30 carbon atoms, or R
A
and R
B
together with the —C—O—C— moiety can form a 5 to 6 membered ring, optionally being further substituted with hydrocarbon groups containing up to 30 carbon atoms. Examples of acid anhydrides which are used commercially include alkyl and alkenyl succinic anhydrides and particularly isooctadecenyl succinic anhydride. Further examples are: iso-octadecyl succininc anhydride, n-hexadecenyl succinic anhydride, dodecenyl succinic anhydride, decenyl succininc anhydride, octenyl succinic anhydride, triisobytenyl succinic anhydride, 1-octyl-2-decenyl-succinic anhydride and 1-hexyl-2-octenyl-succinic anhydride.
Suitable ketene dimers and acid anhydrides include the compounds disclosed in U.S. Pat. No. 4,522,686, U.S. Pat. No. 3,102,064, U.S. Pat. No. 3,821,069, U.S. Pat. No. 3,968,005 which are hereby incorporated by reference.
The copolymer used as an emulsifier in the present invention is a copolymer prepared from a monomer mixture comprising one or more olefins and one or more derivatives of unsaturated carboxylic acids, suitably the copolymer is prepared from a monomer mixture comprising one or more olefins and one or more esterified unsaturated dicarboxylic acids. Suit
Hoffmann Jochen
Krückel Ralf
Mills Robert J.
Van Den Berg Albert
Akzo Nobel NV
Chin Peter
Mancini Ralph J.
Parker Lainie E.
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