Sizing agent

A sizing agent is provided which has at least a self-emulsifiable property, which is stable for long period of time as well being effective in low concentrations.

BACKGROUND OF THE INVENTION 
The present invention relates to a sizing agent for use in cellulosic 
paper-making. 
Heretofore a wide variety of sizing agents for use in paper-making have 
been proposed such as rosin-based, wax-based, alkylketene dimer based, 
polymer based, alkenylsuccinic anhydride based ones and the like and they 
have all been actually employed commercially. Since many of these 
conventional sizing agents are inherently water-insoluble, it is 
impossible to use them along as such so it is usually necessary to 
disperse and/or emulsify them in water with the aid of an emulsifying 
agent. However, the emulsifying operation has such drawbacks that it is 
only achieved with difficulty and that said operation requires additional 
costs therefor. 
The alkenylsuccinic anhydride based sizing agents in particular undergo 
hydrolysis with time due to their inherent nature if they are kept in 
contact with water for a short period of time, thereby losing their sizing 
effect. 
Due to the poor stability in water of said alkenylsuccinic anhydrides based 
sizing agents, they have the serious limitation that the sizing treatment 
should be finished in a short period of time and this has been the 
greatest drawback for applying them commercially, in spite of such 
excellent effects that they exert adequate sizing effect in lower 
concentrations, thus providing greater economical benefits as compared to 
that of rosin based, alkenylketene dimer based, wax based sizing agents 
and the like. 
The inventor has carried out a wide variety of investigations on the sizing 
effect of alkenylsuccinic acids and their derivatives having various 
structures, and as a result he has found that unsaturated hydrocarbyl 
partial esters of alkenylsuccinic acids and the salts thereof are at least 
self-emulsifiable with water and provide an excellent sizing effect. 
For example, unsaturated hydrocarbyl diesters of alkenylsuccinic acids not 
only entail significant difficulties in their synthesis but they also 
require troublesome procedures for emulsifying similar to conventional 
sizing agents and further they require additional auxiliaries such as an 
activator. In addition, they are inferior to unsaturated monohydrocarbyl 
esters in sizing effect, which makes them useless commercially. 
Further, saturated partial(mono)- and di- hydrocarbyl esters of 
alkenylsuccinic acids have substantially no sizing effect, thus they 
cannot be used as a sizing agent. This is due to the fact that saturated 
hydrocarbyl mono- and di-esters of alkenylsuccinic acids are not 
substantially absorbed by paper and also they can only impart poor 
repellancy to paper. Contrary to the saturated hydrocarbyl mono- or 
di-esters, alkenylsuccinic anhydrides per se are readily absorbed by paper 
and make the resultant paper water repellent thereby exhibiting a sizing 
effect. However, once the anhydrides have been hydrolyzed to the 
corresponding dicarboxylic acids, the resulting dicarboxylic acids are not 
readily absorbed, thus losing their sizing effect. In this way, 
alkenylsuccinic anhydrides have drawbacks in that they drastically change 
their identity in water with time, thereby requiring a adequate care. 
He has also found that if unsaturated hydrocarbyl partial esters of 
alkenylsuccinic acids or the water-soluble salt thereof are employed in 
combination with an acid catalyst, a further improved sizing effect can be 
obtained. 
SUMMARY OF THE INVENTION 
The object of the present invention is to provide a sizing agent which is 
at least self-emulsifiable and stable in water for a long period of time 
and which is effective in lower concentration. 
Another object of the present invention is to provide a sizing agent which 
can be prepared without any difficulties. 
Further objects of the present invention will become apparent from the 
descriptions hereinafter referred to. 
Thus, the present invention relates to a sizing agent for use in 
paper-making comprising at least one unsaturated hydrocarbyl partial ester 
of alkenylsuccinic acid of the general formula: 
##STR1## 
wherein R represents an unsaturated hydrocarbyl group having at least six 
carbon atoms and R' represents an unsaturated hydrocarbyl group having 3 
to 18 carbon atoms, and a water-soluble salt thereof as an active 
component. 
The present invention further relates to a sizing agent comprising at least 
one unsaturated hydrocarbyl partial ester of alkenylsuccinic acid set 
forth above and/or at least one water-soluble salt thereof together with 
at least one acid catalyst. 
DETAILED DESCRIPTION OF THE INVENTION 
It was generally known that compounds having an unsaturated group or groups 
are strongly absorbed by paper and render the paper more hydrophobic than 
saturated compounds. The sizing agent of the present invention supports 
the above fact. Therefore, in contrast to saturated esters of 
alkenylsuccinic acids which are only poorly absorbent by paper, thus 
having no sizing effect, unsaturated hydrocarbyl partial esters of 
alkenylsuccinic acids have surprisingly been found to be strongly absorbed 
by paper, making the paper significantly water-repellant, thereby 
providing an excellent sizing effect along with the advantages that they 
are not hydrolyzed by water, so that they can maintain their identity as a 
stable solution or dispersion in water for a long period of time. The 
unsaturated hydrocarbyl partial esters of alkenylsuccinic acids not only 
exhibit strong absorbability towards paper, but they also show no 
discoloring, and indicate a sustained stable sizing effect over a long 
period of time. Moreover, the unsaturated hydrocarbyl partial esters of 
the present invention provides consistently stable sized paper sheets even 
if said paper is treated with the agent in a low concentration. 
The alkenylsuccinic anhydride or corresponding acid employed comprises all 
the alkenylsuccinic acid or anhydride in which the substituting side chain 
contains six or more than six carbon atoms and these include, for example, 
hexenyl-, octenyl-, decenyl-, octadecenyl-, dococenyl-, triancotenyl-, 
eicocenyl-succinic acid and the like and corresponding anhydrides. As the 
unsaturated alcohols, there may be mentioned all the unsaturated alcohols 
having 3 to 18 carbon atoms such as allyl-, propargyl-, butenyl-, butyn-, 
pentenyl-, hexenyl-, octenyl-, decenyl-, laurenyl-, oleyl-alcohols and the 
like. 
The unsaturated partial esters of the present invention can be converted to 
water-soluble products or at least self-emulsifiable products by 
converting the remaining free carboxyl groups into a salt with alkaline 
metals or water-soluble amine whereby a stable aqueous solution or 
dispersion can be obtained by adding it to water. Upon use, it is 
preferably to use it with a cationic starch, as alkyleneoxide adduct based 
activator and the like as is conventionally employed in the art to fully 
assure the benefit of the sizing agent, although such use of an activator 
is not essential. 
The unsaturated hydrocarbyl partial estersof alkenylsuccinic acids can be 
easily synthesized by a conventional esterification technique. Thus, an 
alkenylsuccinic anhydride or the corresponding acids and unsaturated 
alcohol are heated together to cause a reaction between them in the 
presence or absence of a catalyst through a ring opening in the case of 
anhydride, while in the case of acid through a dehydration to form an 
unsaturated partial ester. The ration between the acidic starting material 
to the unsaturated alcohol is such that the amount of the alcohol is 
sufficient to esterify only one of the carboxyl groups of the acid. 
The unsaturated hydrocarbyl partial esters of alkenylsuccinic acids of the 
present invention may be added to paper material in an amount of 0.0001 to 
10 parts by weight per 100 parts by weight of paper material (dry base) 
and preferably 0.01 to 2.0 parts by weight per 100 parts by weight of 
paper material. 
The use of the above catalyst can significantly reduce the amount of 
unsaturated hydrocarbyl partial ester and thus provide great economical 
advantages. 
Although this increase in the sizing effect achievable by the use of acid 
catalyst cannot be fully understood at present, the following assumption 
may be induced, although this should not be regarded as binding to any 
particular theory. An acid catalyst such as sulfonic acid, organic 
phosphoric acid, inorganic acid or Lewis acid excites the unsaturated 
linkage in the unsaturated hydrocarbyl partial esters, thereby bringing 
about a state where the double or triple unsaturated bond can be readily 
broken, so as to promote the etherification reaction with hydroxyl groups 
contained in cellulose or the esterification reaction by dehydration and 
that as a result the fixing of the sizing agent to paper is more fully 
effected in a short period of time. 
As the acid catalyst, there may be mentioned sulfonic acid, organic 
phosphoric acid, inorganic acid, such as phosphoric acid, phosphorous 
acid, hypophosphorous acid, sulfuric acid, nitric acid, hydrochloric acid 
or the like, a Lewis acid such as boron fluoride, zinc chloride, aluminum 
chloride, ferric chloride and the like. These acid catalysts can be used 
alone or two or more in combination. 
Among the sulfonic acid catalysts are included benzenesulfonic acid, 
toluene sulfonic acid, dimethylbenzene sulfonic acid, ethylbenzene 
sulfonic acid, diethylbenzene sulfonic acid, triethylbenzene sulfonic 
acid, styrene sulfonic acid, dichlorobenzene sulfonic acid, 
dichlorotoluene sulfonic acid, aniline sulfonic acid, aminotoluene 
sulfonic acid, dimethylaniline sulfonic acid, diaminobenzene sulfonic 
acid, diaminotoluene sulfonic acid, aniline disulfonic acid, 
anilinetrisulfonic acid, diaminobenzene disulfonic acid, ethyltoluidine 
sulfonic acid, diethylaniline sulfonic acid, chloroaniline sulfonic acid, 
aminochlorotoluene sulfonic acid, dichloroaniline sulfonic acid, 
nitrobenzenesulfonic acid, nitrotoluene sulfonic acid, dinitrobenzene 
sulfonic acid, dinitrostyrene sulfonic acid, nitrochlorobenzene sulfonic 
acid, chloronitrotoluene sulfonic acid, dinitrochlorobenzene sulfonic 
acid, nitroaniline sulfonic acid, phenylhydrazine sulfonic acid, 
methylphenylhydrazine sulfonic acid, phenol sulfonic acid, cresolsulfonic 
acid, dihydroxybenzene sulfonic acid, methacryloxybenzene sulfonic acid, 
aminophenol sulfonic acid, aminomethoxybenzene sulfonic acid, 
dimethoxyaniline sulfonic acid, chloroaminohydroxybenzene sulfonic acid, 
nitroaminohydroxybenzene sulfonic acid, butylbenzene sulfonic acid, 
naphthalene sulfonic acid, naphthalene disulfonic acid, methylnaphthyl 
sulfonic acid, ethylnaphthyl sulfonic aid, propylnaphthyl sulfonic acid, 
butylnaphthyl sulfonic acid, lignin sulfonic acid, naphthalene disulfonic 
acid, naphthalene trisulfonic acid, naphthylamine sulfonic acid, 
naphthylaminedisulfonic acid, naphthylamine trisulfonic acid, 
nitronaphthalene sulfonic acid, nitronaphthalene disulfonic acid, 
nitronaphthalene trisulfonic acid, naphthol sulfonic acid, 
dihydroxynaphthalene sulfonic acid, naphtholdisulfonic acid, 
aminonaphtholsulfonic acid, aminonaphtholdisulfonic acid, 
1-(4'-amino-2'-chlorobenzoylamino)-8-naphthtol-3,6-disulfonic acid, 
1-(4'-nitrobenzene)amino-8-naphthol-3,6-disulfonic and nitronaphthol 
sulfonic acid, anthracene sulfonic acid, anthraquinone sulfonic acid, 
anthraquinone, disulfonic acid, aminoanthraquinone sulfonic acid, 
diaminoanthraquinone disulfonic acid, nitroanthraquinone sulfonic acid, 
dihydroanthraquinone sulfonic acid, diaminodioxyanthraquinone sulfonic 
acid, bromoethane sulfonic acid, 3-fluoromethanesulfonic acid, 
perchlorooctane sulfonic acid, aminoethane sulfonic acid, hydroxyheptane 
sulfonic acid, dodecyloxybutane sulfonic acid, propargyloxypropyl sulfonic 
acid, acetone disulfonic acid, bis[octylsulfonic acid 
substituted]-sulfonic acid, dihydroxyethane sulfonic acid, mercaptopropane 
sulfonic acid, methane sulfonic acid, and .alpha.-olefine sulfonic acid. 
Among the organic phosphoric acid or esters thereof include 
nitrilotrimethylphosphoric acid, aminodimethylphosphonomonoethylphosphoric 
acid, ethylenediaminethtramethylphosphoric acid, 
diethlenetriaminepentamethylphosphoric acid, 
triethylenetetraminehexamethylphosphoric acid, 
hydroxyethylidenediphosphoric acid, hydroxypropylidenediphosphoric acid, 
1,2,4-tricarboxybutane-2-phosphoric acid, 1,2-dicarboxybutane-2-phosphoric 
acid,1,2,4-tricarboxyhexane-1-phosphoric acid, 
.beta.-chloroethylacidphosphate, 
bis[(2-hydroxyethyl)-methacrylate]acidphosphate,2-ethylhexylacidphosphate, 
methylacidphosphate, ethylacidphosphate, propylacedphosphate, 
butylacidphosphate, octylacidphosphate, decylacidphosphate, 
laurylacidphosphate, stearylacidphosphate, dibutylacidphosphate, 
di-(.beta.-chloroethyl)acidphosphate, di(2-ethylhexyl)acidphosphte, 
dimethylacidphosphate, diethylacidphosphate, dipropylacidphosphate, 
dioctylacidphosphate, didecylacidphosphate, dilaurylacidphosphate, 
distearylacidphosphate, tributylphosphite, tris(2-ethylhexyl)phosphite, 
tridecylphosphite, tristearylphosphite, tris(nonylphenyl)phosphite, 
trisphenylphosphite, trislauryltrithiophosphite, 
tris(2,3-dichloropropyl)phosphite, diphenyldecylphosphite, 
diphenyltridecylphosphite, trimethylphosphite, triethylphosphite, 
trioctylphosphite, trilaurylphosphite, dilaurylhydrogenphosphite, 
diphenylhydrogenphosphite, demethylhydrogenphosphite, 
diethylhydrogenphosphite, depropylhydrogenphosphite, 
dibutylhydrogenphosphite, dioctylhydrogenphosphite, 
didecylhydrogenphosphite, distearylhydrogenphosphite. These acid catalysts 
only named few, not limiting thereto. 
The amount of acid catalyst to be used in the sizing agent is 0.0001 to 
10.0 parts by weight, preferably 0.001 to 1 parts by weight of the acid 
catalyst per 100 parts by weight of the sizing agent.