Note: Descriptions are shown in the official language in which they were submitted.
~ 1325~0
PAPER SIZING MET~IODS AND COMPOSITIONS
The present invention relates to paper sizing
methods and is more particularly concerned with the
sizing of paper using rosin-based sizing compositions
5 at relatively high pH values. The invention also
relates to sizing compositions per se, for use in
carrying out such methods, and the resultant sized
paper products.
Conventional paper sizing methods, using rosin
10 in either its emulsified or soaped forms, involve the
separate addition to one or more selected points in the
paper machine wet-end of the rosin-based sizing
composition and of an aluminium salt. This technique
; operates satisfactorily at pH values lying generally in
15 the range from 4 to 6. When the pH is higher than
about 6, to any significant extent, fox example in the
case where chalk is added to the paper pulp, sizing by
this technique becomes erratic and very difficult to
control. In view of these difficulties, when
20 attempting to make sized paper or to surface size paper
already made, using a pH value above the normal 4 to 6
range, it is common practice to resort to the use of
non-rosin sizes, such as those based on alkyl ketene
dimers.
Attempts to size generally at neutral or
alkaline pH values or to use specific aluminium salts
(e.g. polyaluminium chloride) in the two-shot mode in
the presence of chalk have only given very poor
results.
It is also known that if a one-shot mode of
operation is used, namely a method involving use of a
pre-mix of rosin and aluminium salt, made a
considerable time before addit.ion of the pre-mix to the
machine, again only spasmodic control of sizing in an
35 alkaline environment is obtainable. Such one-shot
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systems, operated so as to avoid these difficulties,
are disclosed for instance in our pending Application
No. ~8304405.9 (Publication Number EP-A-0293119) and
- also in US-A-4333795.
It has now surprisingly been found that if a
pre-mix of a rosin-based size and an aluminium salt is
made, on an in-line basis just before its addition to
the paper machine, much better and more controlled
sizing is obtained with rosin, when the stock contains
10 chalk or otherwise has a neutral or alkaline pH value.
'~ Thus, the present invention is based upon the
; unexpected discovery of a difference in behaviour if a
pre-mix of rosin and an aluminium salt is made when or
just before it i5 in fact used, as compared with known
15 methods where it is made a considerable time before its
use.
According to one aspect of the present
invention therefore, a paper sizing method is provided,
in which paper is made from a pulp system containing
20 chalk or otherwise havir,g a neutral or alkaline and
therefore high pH, in which a pre-blended composition
containing a rosin-based size and an aluminium compound
is used or the rosin-based sizing composition and the
aluminium compound are added separately but
25 simultaneously and are pre-mixed just prior to addition
at an appropriate selected point in the paper machine
wet-end.
According to another aspect of the present
invention, a pre-blended paper sizing composi~ion,
30 comprising a rosin-based size and an aluminium compound
and suitable for u~e on or immediately after its
formulation, is also provided. Particular optional but
preferred features of the proposed one-shot paper
sizing composition of the present invention may include
35 the incorporation into the composition of a higher than
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normal amount of aluminium salt, a higher than normal
amount of the rosin-based size or the inclusion of at
;` least one polyelectrolyte.
According to a further preferred feature of
5 the method and the composition of the invention, the
; weight ratio of the rosin size to the aluminium
compound, used in carrying out the method and
accordingly present in the one-shot composition, on a
dry basis, lies in the ratio 1:0.01 to 5. According to
10 a further preferred feature of the invention, the
ingredients added to the paper machine wet-end in
' carrying out the method of the invention, either during
!.' operation or as a one-shot pre-mix, include at least
one urea-based extender.
.ti~ 15 In addition to the stock sizing of paper,
according to the invention, another aspect consists in
~; the use of pre-mixed compositions and techniques, of
the kind indicated above, in the surface sizing of
paper which has already been manufactured, whether or
20 not a rosin-based sizing composition has been used in
its manufacture up to that stage. A further aspect of
the present invention consists of any paper or paper-
like product made by a method according to the present
invention or made using a paper-sizing composition
.
25 according to the invention.
In accordance with a preferred embodiment of
the invention, a pre-mixed rosin-based sizing
composition for use in carrying out the present
invention may contain, in addition to the rosin and the
30 aluminium compound, one or more other additives useful
in the making of paper, for instance for optimising the
sizing function of the rosin-based component per se.
; Such additional and optional additives include cationic
and anionic polyelectrolytes, and also cationic
; 35 starches. For example, the pre-mix can contain one or
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more of cationic and anionic polyacrylamides,
polyethyleneimine, polydialkyl dimethyl ammonium
chloride (DADMAC) or polyamide/epichlorohydrin
condensates, as well as dicyandiamide/formaldehyde
5 condensation products. ;
According to a further aspect of the
invention, despite the fact that pre-mixed one-shot
sizing products, such as are available commercially, in
the form of products made and supplied by chemical
-10 companies, are difficult to use, particularly in
neutral or alkaline pH circumstances, it is possible
according to another aspect of the invention to effect
modification of the in-line mixing technique indicated
above, optionally with the addition of further
15 aluminium salt and/or polymers, so that such pre-mixed
commercial products can also be employed, in accordance
with the principles of the present invention, whereby
greater control and effectiveness than has previously
been possible with such one-shot products.
In order to carry out the method of the
invention in practical terms, it is necessary to employ
some form of mixing device, so as to control the degree
of dispersion of the aluminium salt and the rosin size,
which in turn affects its distribution amongst the
25 paper fibres, with optimisation of sizing efficiency.
The mixing device is suitably associated with the wet-
end of the paper machine and its proper use ensures
that the dispersion serves to control the degree of
agglomeration of the fibres in the pulp. ~-
In carrying out the invention, the rosin-based
size component employed, by being formulated into a
pre-mix with an aluminium compound, can be based on
rosin or rosin modifications, prior to conversion into
a stable emulsion form. Thus, use can be made for this ;
35 purpose of gum rosin, ~ormaldehyde-treated gum rosin or
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tall oil rosin, fumaric acid-treated gum rosin or tall
- oil rosin, disproportionated rosin, maleic anhydride-
- treated gum rosin or tall oil rosin such as the
compounds or any combination of untreated or treated
5 rosin, such as the compounds of the kinds just
mentioned. In addition, esters or part esters of any
of any of the above-mentioned forms of rosin, formed
with straight chain or polyhydric alcohols, can also be
used. A third possibility is to use any appropriate
10 mixture of any of the aforementioned untreated or
;i treated forms of rosin, including disproportionated
rosin and tall oil rosin, together with any one or more
of the esters or part esters just described.
~ As a further aspect of the invention, it is
;~ 15 possible to use resinous materials other than rosin per
se or chemically-modified rosin compounds. For
example, hydrocarbon resins, both of the aromatic and
aliphatic varieties, can be used when suitably
formulated, in order to carry out the paper-making
20 methods of the present invention.
Paraffin waxes and microcrystalline waxes may
be used in con~unction with any of the above-mentioned
rosin or resin-based types of sizing compositions, the
particular use of one or other of the possible waxes
25 depending largely upon the properties which may be
required ln the eventual paper product.
Furthermore, any appropriate rosin-based
sizing emulsion, derived from any one or more of the
above-mentioned materials, may incorporate one or more
30 extenders. By way of example, urea-based extenders may
be employed for this purpose. Such extenders are
disclosed for example in US-A-4022634, 4093779,
i 4141750, 4025354, 4437894 and 4605445. Any appropriate
rosln emulsion may al50 be extended with emulsions of
35 alkyl ketene dimers, prior to or subsequent to pre-
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6mixing with the aluminium compound. The alkyl ketene
dimer emulsions may be stabilised with either cationic
starch or cationic or anionic polymers.
According to another aspect of the invention,
S the aluminium compound incorporated in the one-shot
pre-mix of the invention or otherwise employed in
carrying out paper sizing methods according to the
present invention is selected from polyaluminium
chlorides, aluminium chlorohydrate, aluminium sulphate
10 (paper makers alum) and any mixture of two or more of
the foregoing.
In putting the invention into practice, it is
desirable to incorporate in the paper sizing
composition, when made up in a one-shot form, at least
1i one stabilising agent, which may take the form of one
or more surface active agents or surfactants. Mixtures
of stabilising agents or surfactants also can be used.
A very wide range of possibilities is available as to
the nature of such materials, which can be anionic,
20 non-ionic, cationic or amphoteric.
One particular class of stabilised emulsion
comprises essentially a rosin soap and a protective
colloid. The rosin-based component, namely the rosin
soap, can be a sodium, potassium or ammonium soap of
25 rosin or of a modified rosin, together with amine salts
of rosins or modified rosins, for instance the amine
salts formed with mono-, di- or triethanolamine. These ~;
stabilisers can be added separately or formed in situ
when making up the rosin-based emulsion composition.
30 Colloids which can be used to stabilise the resultant
product include casein, starch, soya protein and
cellulo~e derivatives, the former being the most
preferred, as well as certain polymers, such as
polyvinyl pyrrolidone or polyvinyl alcohol (PVA). A
35 preferred form of ~tabilised emulsion consists
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. essentially of the potassium or sodium soap of the
rosin or rosin derivative and casein as the stabilising
: colloid.
According to a further feature of the
5 invention, surface active agents or surfactants which
. can be used in formulating the compositions of this
invention include: .
(i) salts of sulphonic acids having the general
i ~ormula:
(R')m - ~ - O(C2H40)n -CH2-CH-CH2-S03M
" X
where R' represents a hydrocarbon residue having from
4-18 carbon atoms, m is an integer having a value of 1
or 2, n is an integer having a value of 4 to 25, X
15 represents a hydrogren atom or a hydroxyl group and M
represents a monovalent cation and~
(ii) salts of sulphuric acid half esters having
the general formula:
[R2 _ ~ - A]2 - 0(c2H4o)pso3Q
20 wherein R2 represents a hydrogen atom or an alkyl
group having from 1 to 4 carbon atoms, A re~resents a
straight chain or branch chain alkylene group having 2
or 3 carbon atoms, p is an integer having a value of 4
to 25 and Q is a monovalent cation, including all those .
25 compounds described in US-A-4309388. -:
(iii) alkyl-benzene sulphonates wherein the alkyl
substituent comprises from 8 to 24 carbon atoms,
including all those compounds described in US-A-
4157982.
(iv) ~ulphosuccinate half esters of fortified
rosin having the formula:
H(3_m). R- [(cH2cH2o)n - OC.C2H3S03Na.- COONa]m :-
wherein R is a fortified rosin acid tricarboxylate
~ group, m has an average value of 1.5 to 3 and n has an
¦ 35 average value from 4.5 to 25 including all those
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: 8
described in EP-A-159794.
(v) compounds having one or other of the
: formulae:
~ ~ (CH2CH2)n~S3 M+
and
LR O(CH CH O) SO ~ M+
1 0
wherein ~ represents an alkyl group comprising from 4 ~:~
to 18 carbon atoms, and R' represents an alkyl or -:
alkenyl group comprising from 4 to 18 carbon atoms and
n is an integer having a value of 4 to 25, including
15 all those described in US-A-4199367.
(vi) sulphosuccinate salts of ethylene oxide
condensates having the general formula~
l 1l ~:
~ O(CH2CH20)n C - ~CH CH2
wherein R represents an al~yl group comprising from 4
to 18 carbon atoms and n is an integer having a value
of 4 to 25 including all those compounds described in :: -
US-A-4203776. ~.
(vii) organic phosphate esters having one or other
of the general formulae: .
R.O.(CH2-cH2 )n~
o-x / ~o-x '~ ..
30 and .:
E~.O. (CH2--CH2~0)n, ,~0
, ~"~o-x '''.' '
R (CH2-CH2 )n
35 and mixtures thereof,
. ...
.
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wherein R represents an alkyl or an alkyl~phenol~
alkenyl or alkaryl group comprising from 5 to 20 carbon
atoms, n has a value of 5 to 20 and X represents a
monovalent cation or hydrogen.
Cationic resin dispersant systems may also be
used to stabilise the rosin dispersions of this
invention. Examples of suitable materials include
water-soluble polyaminopolyamide/epichlorohydrin
r e s i n s , w a t e r - s o l u b l e a l k y l e n e -
10 polyamine/ephichlorohydrin resins and poly~diallyl-
amine)/epichlorohydrin resins.
In order that the present invention may be
fully understood and appreciated, the following
examples of use of the paper sizing methods and
15 compositions of the present invention are given, by way
', of illustration only. In the examples, all amounts are
gi~en as percentages hy weight, unless otherwise
indicated. In example 1, part A represents use of the
invention, while part B represents use according to the
20 prior art.
Example_1
Part 1
A pilot Fourdrinier paper machine was used
which was operated to produce paper of 85 gsm at 16 kg
25 per hour from softwood/hardwood Rraft furnish loaded
with 10~ chalk.
Pre-mixes of the rosin size and aluminium salt
were made using a laboratory mixer and were metered
just prior to the flow box.
- 30 The following results were obta = -
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! Polyaluminium l l l
Rosin Size `, chloride (as I 1 min Cobb ' pH at Flow ,
Solids/fibre i received) I gsm , Box
% I !
, 1.0 0.5 , 68 , 7.8
.0 l.o 1 29 1 7.6
.0 1.5 1 29 1 7.6
1 o
Part B
For comparison with the practice exemplified
in Part A, sheets were made using Rraft pulp containing
10% of chalk. The size and the PAC were added : :
,15 separately to the pulp and held for 30 minutes before :
sheets were made. ~-
The following results w~,~re obtained:-
~'Rosin size Polyaluminium
20 Solids/fibre chloride (as I 1 min Cobb pH at Flow ! - :-~
% . received) I gsm Box
1.0 O.S 146 , 7.4
. 1.0 ' 1.0 , 156 7.2 . - -
1.0 1.5 1 154 7.3
2.0 0.5 154 7-4 ' ~
2.0 1.0 , 144 , 7.3 ` .
2.0 1.5 137 7.2 ~ -
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1 1
Example 2
A commercial paper machine producing envelope
paper at the rate of 6.8 tonnes per hour with a chalk
content varying from 5.8 to 7.8 per cent was sized by
5 pre-blending free rosin size and alum and adding the
pre-mix to the forward side of the thick stock head-
box. Throughout the run, the amount of size used (dry
basis) was 0.45% and the amount of alum us~od (dry
basis) was 1.93%.
Time L~ Min Cobb I Flow Box pH
i 12.30 1 26 1 8.0
s 12.45 i 20 1 8.0
' 13.45 1 20 1 8.0
13.50 1 22 1 7.5
t4.25 1 21 1 7.7
.~ 14.59 ~ 21 1 7.6
15.34 ~ 21 1 7.7
~---- ~;~ ~ ~_
Referring to example 1 above, it will be noted
that, in part B, the Cobb values indicate that the
sheets were close to saturation. Referring to the
3 last three results in part B of example 1, double the
25 amount of rosin size on a percent solid/fibre basis was
used, as compared with the first ~hree, but this made
very little difference to the Cobb values obtained and
none of those obtained in part B came anywhere near the
much better results in terms of levels of ~izing
30 achieved in carrying out the invention, according to
part A of example 1. A very satlsfactory range of
3izing is given b~ the last two results of example 1
part A in particular and throughout example 2. In
these examples, "as received" in relation to the
35 polyalumlnium chloride means that it contained 10
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percent A1203.
The invention thus represents a substantial
and surprising advance on previous paper sizing methods
and compositions.
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