Note: Descriptions are shown in the official language in which they were submitted.
~5,~689
A PROCESS FOR THE ANTI~ICROBIAL FINISHING OF PAPER
This invention relates to a process for the antimicrobial finishing
of paper.
The antimicrobial finishing of paper material, for example hand
towels, pocket handkerchiefs, napkins ant wrapping paper for moist articles,
is of considerable interest. Replacement of the widely used textile hand
towel, for example by the paper hand towel which is discarded after only ono
use, is only sensible if the paper hand towel is hygienically satisfactory. `~
Unfortunately, the starting material from which paper is produced, for example ~ -
old paper, is generally full of germs. Similarly, the aqueous material guide
system, in which the water is largely circulated, is a good breeding ground
for microbes Although the number of germs is automatically reduced during
drying of the paper, the number of germs on the paper can multiply during
subsequent further processing.
The packaging of moist articles, for example, soap, in paper gives
rise to further problems because moist paper goes mouldy particularly easily.
Accordingly~ any means of microbicidally and, ~ore especially, fungicidally
finishing pàpsr would be desirable and atvantageous.
Well-known, thoroughly tested microbicides include phenol deriva-
tives, such as dichlorinated, tetrachlorinated and hexachlorinated 2,2'-dihy-
droxy diphenyl methanes, 2-phenyl phenol, 3-methyl-4-chlorophenol and penta-
chlorophenol. These microbicides are already used for finishing cellulose-
containing materials, such as textile and paper. Since they are largely
insoluble in water, they have to be applied to the material from organic
solvents. Unfortunately, the technique involved is over-elaborate and, hence,
is in need of improv~ment.
Although phenol derivatives of the kind in question form readily
water~soluble alkali salts, the alkaline solutions show a marked tendency
towards discoloration. In addition, the application of aquoous solutions to
; 30 paper necessitates additional drying capacities or slower machine speeds. Add-
ed to this is the fact that certain papers, such as tissue papers, are unable
to withstand treatment with aqueous solutions without some damage through
~o5"~689
lack of strength.
Although the addition of aqueous alkaline solutions of these
phenol derivatives to neutral or acid pulp dilutions results in the precip-
itation on the pulp of the active phenol derivatives with their free phen-
olic hydroxyl group, the active material content of the paper is neither un-
iform nor complete. In addition, the water solubility and volatility of
the compounds gives rise to pollution problems both in regard to the efflu-
ent and especially when the paper is dried, in regard to the waste air.
Accordingly, there is still a need to be able to apply chlorinated
phenol derivatives of the kind in question to the paper without any additio-
nal outlay in terms of apparatus. It would be particularly desirable to
be able to add the chlorinated phenol derivatives to the aqueous pulp sus-
pension in a form in which they are absorbed into the paper as uniformly
and as completely as possible.
It has now been found that microbicidally active phenol deriva-
tives corresponding to the general formula
:: R Rl
1~3~011 (1)
~ R4 R5
~her~in
Rlm R2, R3, ~ and R5 which may be the same or different represent hydrogen,
- 20 halogen or a lower alkyl radical, in addition to which Rl can also represent
the group
R R3 t
2~R4
OH 5
R
~os,~ sg
whereln `~
R2, R3 , R4 and R5 which may be the same or different represent hydrogen
halogen or a lower alkyl radical, R3 may also represent the carboxyl group
(-COOH) and R5 may also represent phenyl, may be applied to the paper from
the pulp suspension uniformly and in a substantially quantitative yield,
providing they are added to the aqueous pulp suspension in the form of their :~
phenolate salts with quaternary ammonium ions in an organic solvent prefer-
ably miscible with water.
In the context of this invention, halogens are chlorine, bromine,
and iodine, especially chlorine.
Lower alkyl radicals are straight-chain and branched-chain alkyl
radicals with up to 8 carbon atoms, preferably with up to 4 carbon atoms
and, more especially, with l or 2 carbon atoms, for example butyl, isobutyl,
tert.-butyl propyl, isopropyl, and ethyl, preferably methyl.
Solvents suitable for use in the process according to the invention
are alcohols, esters such as acetic acid esters and glycolic acid esters of
the aforementioned alcohols, ketones such as acetone, methyl ethyl ketone,
and ethers such as glycol ether, dioxan. It is preferred to use solvents
of this kind which are partly or completely miscible with water.
Examples of suitable alcohols are methanol, ethanol, propanol,
isopropanol, butanol, isobutanol, tert.-butanol and amyl alcohol. However,
it is preferred to use ethanol and isopropanol.
The content of the quaternary ammonium salt of the phenol der-
ivative of general formula I in the solution used in accordance with the
invention in one of or in a mixture of several of the aforementioned sol-
vents, is not a critical parameter in the process according to the invention
The most suitable content can readily be determined through one or more t
preliminary tests. In general, it amounts to between about 10 and about
70% by weight, preferably to between 15 and 40% by weight and, in part-
icular, to between about 15 and 25~ by weight.
The quaternary ammonium 5alts of the phenol derivatives of
general formula I, which may be used, in the process according to the inven-
.
_3_
105'~689
tion, are known or may readily be obtained by reacting the phenol deriv-
atives of general formula I with corresponding ammonium salts in an organic
solvent. In this connection, it may be advantageous to use as the solvent
the same solvent which is to be used for preparing the solution of the
quaternary ammonium salt of the phenol derivative of general formula I
which is to be added to the pulp suspension in the process according to
the invention.
The phenol derivative of general formula I may be reacted with
the corresponding ammonium salt at temperatures in the range from about
20 C up to the reflux temperature of the solvent. Although the reaction
temperature is generally not an important parameter, it can have an affect
upon the reaction time. In most cases, the reaction is carried out under
normal pressure, although it is also possible to apply reduced or ele-
vated pressure.
In general, one mol of the phenol derivative of general formula
I is reacted with one mol of the corresponding ammonium salt. However,
it is also possible to use an excess of phenol derivative of general form-
ula I or an excess of the quaternary ammonium salt.
This excess does not have to be removed after the reaction, in-
stead it may remain in the solution of the quaternary ammonium salt of the
phenol derivative of general formula I used in accordance with the inven-
tion. An excess of the phenol derivative or ammonium salt may even be
advantageous because the phenol derivatives of general formula I and also
the ammonium salts preferably used are microbicidally active, as shown
hereinafter, so that their presence in the pulp suspension can be desirable.
However, the excess is not a critical parameter of the process according
to the invention, because it is only the quater~ary ammonium salts of the
phenol derivatives of general formula I which are absorbed uniformly into
the paper in the high yields according to the invention.
In principle, any quaternary ammonium salts with any anion, is
suitable for use in the preparation of the quaternary ammonium salt of the
phenol derivative of general formula I. However, since the anion reacts
105'~f~89
with the proton of the phenolic hydroxyl group to form the corresponding
acid, it is best to use quaternary ammonium salts with a simple anion of
the kind which are formed by quaternising the corresponding amines. Accord-
ingly, the preferred anlon is chloride or bromide.
It is preferred to use quaternary ammonium salts of the ~ind which
are commonly used as cationic microbicides, for example benzyl dimethyl
dodecyl ammonium chloride, 3,4-dichlorobenzyl dimethyl dodecyl ammonium
chloride, benzyl dimethyl tetradecyl ammonium chloride, benzyl di-(~-hydroxy
ethyl)-dodecyl ammonium chloride, cetyl pyridinium chloride, (diisobutyl
phenoxy ethoxy ethyl)-dimethyl benzyl ammonium chloride, dodecyl trimethyl
ammonium chloride and cetyl trimethyl ammonium bromide, lauryl trimethyl
ammonium chloride and myristyl tri~ethyl ammonium chloride.
By using these cationic microbicides, it is also possible to
obtain an improvement in the ancimicrobial activity of the phenol deriv- -
atives of general formula I, and in particular to broaden their range of
activity.
In general, the process according to the invention is carried
::.
out as follows:
The solution of the quaternary ammonium salt of the phenol der-
ivative obtained by reacting the selected phenol derivative with the selec-
ted quanternary ammonium salt is added to the pulp suspension continuously
or in batches in a quantity corresponding to the selected content of the
quanternary ammonium salt of the phenol derivative, based on absolutely dry
pulp .
In the context of the invention, absolutely dry pulp is the pulp
~-~ obtained after the drying stage of paper production.
The quaternary ammonium salt of the phenol derivative of general
formula I is added in a quantity of from 0.01 to 1% by weight, preferably
in a quantity of from 0.05 to 0.5% by weight and more especially in a quan-
tity of from 0.1 to 0.3% by weight, based on absolutely dry pulp. There-
after the volume of the solution of said quaternary ammonium salt, added
~; to the aqueous pulp suspension, depends from the before mentioned quantity
. .
~o5'~689
to be added; the volume of 8 for example 20% solution according to the
invention of the quaternary ammonium salt of the phenol derivative of
general formula I may amount ta between 0.05 and S~, preferably to between
0.25 and 2.5% and, more especially, to between 0.5 and 1.5~ (volume/weight)
based on absolutely dry pulp as before mentioned, provided that the density
of the solution is 1. The volume of solutions with different contents of
said quaternary ammonium salt is calculated correspondingly.
When the solution of the quaternary ammonium salt of the phenol
derivative of general formula I is added to the pulp suspension, this
solution may form an emulsion with the pulp suspension or a suspension of
the quaternary ammonium salt of the phenol derivative of general formula
I in the pulp suspension depending upon the miscibility of the solvent
used with water. In either case, the quaternary ammonium salt of the
phenol derivative of general formula I is uniformly absorbed into the pulp
in a substantially quantitative yield from the emulsion or suspension
formed.
Although the production of an antimicrobially finished paper
for hand towels is described in the following Examples, other types of
antimicrobially finished paper intended for other applications may be
similarly produced.
EXAMPLE 1
A hand-towel paper was produced in ap~p,~l~making machine using
. 25% of semi-bleached cellulose and 75% of waste (old paper and rotary
printing paper). The diluted pulp suspension had a pH-value of 4.2. The
paper weighed 60 g/m . 2% by volume, based on absolutely dry pulp, of a
. 22% solution in isopropanol of the reaction product of (2,2-dihydroxy-5,
S'-dichloro)-diphenyl methane and benzyl dimethyl dodecyl ammonium chloride
(molar ratio 1:0.6), were added to the 2% diluted pulp suspension. The pulp
had a density of 0.4% on reaching the breast box. The addition of the
active-material formulation did not lnterfere with paper production in any
way. The finished paper contained the active material in a yield of 80 to
100%. The concentrations of active material in the effluent were correspond
--6--
~05;~689
ingly lower.
The paper produced with an addition of 2% by volume of the above
active-material formulation, based on absolutely dry pulp, was tested as
follows for its antimi~robial activity:
a) Circular paper samples (diameter 2 cm) were placed on a sterile agar
nutrient medium in a Petri dish and subsequently covered with an agar nut-
rient medium which had previously been infected with Staphylococcus aureus.
After 2 days at 37C, samples of paper without the active ingredient are
completely overrun by the test microbes, whilst the samples of paper con-
taining the active ingredient have a 6 to 10 mm inhibition zone unaffected
by microbe growth.
b) Samples of paper (15 mg) antimicrobially finished in the same way as
described above were introduced into 20 ml of sterile nutrient broth. After
storage for 4 days at 37C, the nutrient solutions are still clear,whereas
nutrient solutions containing corresponding quantities of paper without
the active ingredient are clouded by microbe growth over the same period.
EXAMPLE 2
A hand towel paper was produced in the same way as described in
Example 1. However, the active-material formulation mentioned in Example 1
was added in a concentration of 4% by volume, based on completely dry paper.
This dose did not interfere with paper production either.
The paper was tested for its antimicrobial activity in the same
way as described in Example la), but using Bacterium coli and Trichoplyton
pedis as test organisms. 2 mm inhibition zones were obtained.
The effluent from the paper machine was found to contain 1.102
germs per ml. No slime was formed. When the paper was produced in the
absence of the active material, the number of germs in the effluent rose
quickly to 1.107 to 1.108 germs per ml. The increase in the number of germs
; was associated with troublesome slime formation in the production system.
EXAMPLE 3 (Comparison Example)
In the prod~lction of wrappi~g paper, 1% by weight of sodium pen-
~achlorophenola~e, based on completely dry paper, was introduced into the
_7_
1()5'~689
pulper for mould-proof finishing. E~cessive pollution of the drying section
occurred during production on account of volatilising pentachloropenol.
The finished paper only contained 50% of the quantity of active material
originally used. The losses of active material totalling 50% broke down
as follows: 27% in the effluent (as determined by analysis) and hence 23%
of losses in the drying section.
The effluent from the paper machine could only be discharged after
heavy dilution in a biological treatment plant. The effluent could not have
been discharged without biological treatment for reasons of pollution control.
EXAMPLE 4
By contrast, the addition of a 24% solution in isopropanol of
the reaction product of pentachlorophenol and benzyl dimethyl dodecyl am-
monium chloride (molar ratio 1:0.7) to the 4% diluted pulp suspension in
a concentration of 2% by volume, based on completely dry paper, instead
of sodium pentachlorophenolate, did not give rise to any pollution in the
drying section during paper production in accordance with Example 3. The
yield of active material in the paper amounted to between 80 and 100%.
The paper produced under tbese conditions proved to be antimicrobial and,
. ~
in particular, highly mould-resistant in tests carried out in accordance
~ith Example la~ but additionally using Chaetonium globsum,Trichoderma
viride and Aspergillus niger as test organisms.
-,
',
, .
i' .
''''
-8-
