Method for deinking

A deinking method for obtaining regenerated pulp of high brightness is provided. One or more of deinking agents selected from (a-1) to (a-2) given below are used, and a deinking step is carried out, in which a washing step is carried out at treating temperatures from 40 to 80.degree. C.; PA1 (a-1) : a compound represented by the general formula (a-1) given below, EQU R.sub.1 --O--(AO).sub.p --H (a-1) where R.sub.1 is an alkyl group or an alkenyl group having 14 to 24 carbon atoms, AO is specific quantities of EO and PO, and p is a number to satisfy the specific quantities, PA1 (a-2): a compound represented by the general formula (a-2) given below, EQU R.sub.2 [--COO--(AO).sub.m --R.sub.3 ].sub.n (a-2) where n is an integer of one or more, R.sub.2 is a residue of carboxylic acid having 14 to 24 carbon atoms in total, R.sub.3 is hydrogen atom or an alkyl group having 1 to 20 carbon atoms and the like, AO is specific quantities of EO and PO, and m is a number to satisfy the specific quantities.

FIELD OF THE INVENTION 
This invention relates to a method for deinking of waste papers of 
magazines, newspapers and the like, and more particularly to a method for 
deinking by which regenerated pulp of high brightness and high quality can 
be obtained when obtaining the regenerated pulp from printed waste papers 
of magazines, newspapers and the like by means of a flotation process. 
PRIOR ART 
Although reclamation or recycling of newspapers, magazines, etc. has been 
conventionally carried out, an apparatus or method for accelerating 
deinking more effectively and rapidly has been required for current waste 
papers because of changes in printing technique and printing process, 
alteration of compositions of printing ink, reclamation of waste papers 
which has not been conventionally recovered for reclamation and the like. 
As chemical agents which have been conventionally used for separating and 
removing impurities such as ink etc. from waste papers, anion activators 
such as alkylbenzensulfonate, sulfuric ester of higher alcohol, 
.alpha.-olefin sulfonate, dialkylsulfosuccinate and the like, nonionic 
activators such as adduct of ethylene oxide with higher alcohol, 
alkylphenol and fatty acid, alkanolamides and the like have been used as 
deinking agents independently or in combination of these two or more along 
with alkaline agents such as caustic soda (sodium hydroxide), sodium 
silicate, sodium carbonate, sodium phosphate and the like, bleaching 
agents such as hydrogen peroxide, hyposulfite, hypochlorous acid and the 
like, sequestering agent such as EDTA, DTPA and the like. 
In the deinking method currently employed, nonionic surfactants, 
particularly nonionic surfactants of type of an adduct of ethylene oxide 
with higher alcohol etc. are widely used as a deinking agent. This is 
because that while the deinking agent used in, for example, a flotation 
method requires a balance between ink removing power for removing ink from 
waste papers as raw materials and frothing power for capturing removed ink 
in the flotation step, the ethylene oxide adduct-type nonionic surfactant 
can be easily changed in its property by alkyl chain length, number of 
moles of added ethylene oxide, etc. and can impart the ink removing power 
and frothing power depending on the objective. 
There is, however, a limitation for obtaining regenerated pulp of 
sufficient brightness only by using such the ethylene oxide adduct-type 
nonionic surfactant, and hence it has been becoming increasingly difficult 
to obtain regenerated pulp of high quality in parallel with 
diversification of waste papers as raw materials. 
JP-A 6-287878 and JP-A 7-3681 describe an adduct of alkylene oxide with 
special blocked carboxylic acid and an adduct of alkylene oxide with 
alcohol, but do not describe the temperature at the washing step. 
JP-A 7-305287 an adduct of alkylene oxide with fat and oil, but does not 
describe the temperature at the washing step. 
DISCLOSURE OF THE INVENTION 
The inventors of this invention have studied devotedly in order to solve 
the aforesaid problems. As a result, the present inventors found that 
regenerated pulp of more high quality can be obtained without a lowering 
of deinking effect by using a deinking agent containing an adduct of 
alkylene oxide with specific higher alcohol or adduct of alkylene oxide 
with higher fatty acid or ester thereof and by setting the temperature at 
the washing step in the range from 40 to 80.degree. C., and achieved this 
invention. 
That is to say, this invention provides a method for deinking comprising a 
step for removing ink from waste papers as raw materials in the presence 
of one or more of deinking agent selected from (a-1) to (a-2) described 
below, and a step for carrying out washing of pulp after completion of 
deinking at temperatures in the range from 40 to 80.degree. C.; 
(a-1): a compound represented by the following general formula 
EQU R.sub.1 --O--(AO).sub.p --H (a-1) 
wherein R.sub.1 is an alkyl group or an alkenyl group having 14 to 24 
carbon atoms or an alkylphenyl group having an alkyl group having 8 to 14 
carbon atoms, AO is an oxyethylene group (EO) or an oxypropylene group 
(PO), an average number of moles of added EO is in the range from 20 to 
300, a mole ratio of added EO to added PO is in the range from 1 to 7, and 
p is such a number that EO and PO satisfy the aforesaid relations. 
(a-2): a compound represented by the following general formula 
EQU R.sub.2 [--COO--(AO).sub.m --R.sub.3 ].sub.n (a- 2) 
wherein n is an integer of one or more, R.sub.2 is a residue of carboxylic 
acid having n's --COOH groups and 14 to 24 carbon atoms in total, from 
which all the --COOH groups are removed, R.sub.3 is hydrogen atom or an 
alkyl or an alkenyl group of 1-20 carbon atoms, AO is an oxyethylene group 
(EO) or an oxypropylene group (PO), an average number of moles of added EO 
is in the range from 20 to 300, a mole ratio of added EO to added PO is in 
the range from 1 to 7, and m is such a number that EO and PO satisfy the 
aforesaid relations. 
The deinking agents (a-1).about.(a-2) used in this invention, in which the 
alkyl chain length, the number of moles of added alkylene oxide, etc. fall 
in the range defined in this invention may be preferably used since they 
are excellent in deinking performance. 
It is preferable in AO of formula (a-1) or (a-2) that the average number of 
moles of added EO is in the range from 50 to 90 and the mole ratio of 
added EO to added PO is in the range from 1.7 to 3. 
The method for deinking of this invention comprises a dissociation step of 
waste papers, a high concentration bleaching step, a pre-flotation step, a 
flotation step, and a washing step, and in which the deinking agent (a) 
may be preferably added before the flotation step and the washing step may 
be preferably carried out at temperatures in the range from 50 to 
60.degree. C. 
DETAILED DESCRIPTION OF THE INVENTION 
In the case where R.sub.1 of the general formula (a-1) is an alkyl group or 
an alkenyl group, when the number of carbon atoms contained therein is not 
more than 14, since ink flocculating power is weak due to too poor 
hydrophobic nature, and efficiency of removing ink at the flotation step 
lowers, and, particularly efficiency of washing at high temperature lowers 
because of low dispersion force, deinked pulp of high brightness can not 
be obtained, on the contrary, when the number of R1 exceeds 24, since the 
property for removing ink from cellulose is low due to too strong 
hydrophobic nature and residues of unremoved ink increase and the load 
applied at the washing step is increased, and, particularly the efficiency 
of washing at high temperature lowers, only deinked pulp of poor quality 
can be obtained. In the case where R1 of the general formula (a-1) is an 
alkylphenyl group, when the number of carbon atoms contained in the 
substituted alkyl group is not more than 8, since particularly the 
efficiency of washing decreases, deinked pulp of high brightness can not 
be obtained, and when the number of carbon atoms of the substituted alkyl 
group exceeds 14, since particularly the efficiency of washing lowers 
likewise, nothing but deinked pulp of poor quality can be obtained. 
The compound represented by the general formula (a-1) may be produced by 
adding EO and PO to alcohol according to the methods conventionally 
publicly known. Alcohol used for preparing the compounds represented by 
the general formula (a-1) may be one having an alkyl group or an alkenyl 
group of 14.about.24 carbon atoms, or an alkylphenyl group having an alkyl 
group of 8.about.14 carbon atoms, and may be illustrated by 
1-tetradecanol, 1-pentadecanol, 1-hexadecanol, 1-heptadecanol, 
1-octadecanol (stearyl alcohol), 1-nonadecanol, 1-eicosanol, 
1-heneicosanol, 1-docosanol, 1-tricosanol, 1-tetracosanol, 2-tetradecanol, 
2-pentadecanol, 2-hexadecanol, 2-heptadecanol, 2-octadecanol, 
2-nonadecanol, 2-eicosanol, 2-tetradecene-1-ol, 2-pentadecene-1-ol, 
2-hexadecene-1-ol, 2-octadecene-1-ol, 13-tetradecene-1-ol, 
15-hexadecene-1-ol, oleic alcohol, elaidyl alcohol, linoleyl alcohol, 
linolenyl alcohol, eleostearil alcohol, ricinoyl alcohol, 
cyclotetradecanol, cyclopentadecanol, cyclohexadecanol, cycloheptadecanol, 
cyclooctadecanol, cyclononadecanol, cyclocosanol, octylphenol, 
nonylphenol, etc. These alcohols may be, of course, used in combination 
with two or more. 
Of these alcohols, alcohol having an alkyl group or an alkenyl group of 
14.about.24 carbon atoms may be preferable, and alcohol having an alkyl 
group or an alkenyl group of 16.about.18 carbon atoms may be more 
preferable, and alcohol having an alkyl group of 16.about.18 carbon atoms 
may be particularly preferable. 
In the general formula (a-1), AO is a mixture of an oxyethylene group (EO) 
with an oxypropylene group (PO), and the average number of moles of added 
EO may be in the range from 20 to 300, preferably in the range from 30 to 
160, particularly preferably in the range from 50 to 90. The mole ratio of 
added EO to added PO may be in the range from 1 to 7, preferably in the 
range from 1.5 to 4.5, particularly preferably in the range from 1.7 to 3. 
If the average number of moles of added EO and the mole ratio of added EO 
to added PO do not fall in these ranges, regenerated pulp with excellent 
brightness can not be obtained. In the general formula (a-1), an addition 
of EO and PO may be random addition or blocked addition. Random adducts 
and blocked adducts in which EO is added to alcohol and then PO is added 
thereto may be preferable, and random addition may be further preferable. 
Next, an explanation on the deinking agent of the general formula (a-2) is 
given below. The compound represented by the general formula (a-2) may be 
produced according to the method conventionally publicly known by adding 
EO and PO to n's-hydric carboxylic acid having 14 to 24 carbon atoms in 
total or esters thereof (complete esters are not required in the case of 
esters of polyhydric carboxylic acid). Similarly to the compound 
represented by the general formula (a-1), it is necessary that the average 
number of moles of added EO and the mole ratio of added EO to added PO 
fall in the specific range defined by this invention. That is to say, in 
the general formula (a-2), AO is a mixture of an oxyethylene group (EO) 
with an oxypropylene group (PO), and the average number of moles of added 
EO may be in the range from 20 to 300, preferably in the range from 30 to 
160, particularly preferably in the range from 50 to 90. The mole ratio of 
added EO to added PO may be in the range from 1 to 7, preferably in the 
range from 1.5 to 4.5, particularly preferably in the range from 1.7 to 3. 
If the average number of moles of added EO and the mole ratio of added EO 
to added PO do not fall in these ranges, regenerated pulp with excellent 
brightness can not be obtained. In the general formula (a-2), an addition 
of EO and PO may be random addition or blocked addition. Random adducts 
and blocked adducts in which EO is added to carboxylic acid and then PO is 
added thereto may be preferable, and random adducts may be more 
preferably. 
R.sub.2 in the compound represented by the general formula (a-2) is a 
residue of carboxylic acid having n's --COOH groups and 14 to 24 carbon 
atoms in total, from which all the --COOH groups are removed. In the case 
where the total number of carbon atoms of the carboxylic acid is less than 
14, deinked pulp of high brightness can not be obtained because of low ink 
flocculating power, and when the total number of carbon atoms of the 
carboxylic acid exceeds 24, the residues of unremoved ink increase for 
reason that effectiveness of removing ink from cellulose is lowered. And, 
deinked pulp of high sticking and low quality can be obtained. 
The carboxylic acid used for preparing the compound represented by the 
general formula (a-2) may be one having 13 to 23 carbon atoms for R.sub.2, 
and exemplified by myristic acid, pentadecanoic acid, palmitic acid, 
margaric acid, stearic acid, oleic acid, elaidic acid, linoleic acid, 
linolenic acid, stearolic acid, ricinoleic acid, ricinoelaidic acid, 
nonadecanoic acid, arachidinic acid, heneicosanoic acid, behenic acid, 
brassidic acid, erucic acid, tricosanoic acid, tetracosanoic acid, beef 
tallow fatty acid, rape oil fatty acid, fish oil fatty acid, tall oil 
fatty acid and the like. 
In the compound represented by the general formula (a-2), R.sub.2 may be a 
residue of alkyl polyhydric carboxylic acid. In this case, R.sub.2 derives 
from the corresponding alkyl polyhydric carboxylic acid, and includes 
dimer acid and/or polymer acid of higher fatty acid having 14 to 20 carbon 
atoms. The dimer acid and/or polymer acid as used herein may be 
synthesized by a method in which a monomer of monoene-acid or dimer acid 
illustratively stated by unsaturated fatty acid such as oleic acid, 
linoleic acid, linolenic acid and the like is reacted by thermal 
polymerization, for example, Diels-Alder reaction or by other reaction 
methods. As used herein the term "polymer acid" is intended refer to 
polycarboxylic acid having not less than three carboxylic groups in a 
molecule and does not include dimer acid. It may be not objectionable that 
an unreacted monomer acid remains in dimer acid and/or polymer acid 
produced to such an extent that the effects of this invention is not 
damaged. And, it is not objectionable that the compounds represented by 
the general formula (a-2) is those prepared by mixing two kinds of fatty 
acids or polyhydric alkyl carboxylic acids. 
R.sub.2 in the general formula (a-2) may be preferably a residue of 
monocarboxylic acid having 14 to 24 carbon atoms in total, more preferably 
a residue of monocarboxylic acid having 18 to 24 carbon atoms. 
In the compound represented by the general formula (a-2), R.sub.3 may be 
hydrogen atom or an alkyl group or an akenyl group having 1 to 20 carbon 
atoms. These may be straight chain or branched chain. The alkyl group or 
alkenyl group having 1 to 20 carbon atoms may be exemplified by methyl 
group, ethyl group, propyl group, butyl group, t-butyl group, pentyl 
group, hexyl group, 2-etylhexyl group, isopentyl group, octyl group, nonyl 
group, decyl group, isopropyl group, propenyl group, butenyl group, 
hexenyl group, octenyl group, lauryl group, myristyl group, cetyl group, 
stearyl group and the like. 
In the case where R.sub.2 of the compound represented by the general 
formula (a-2) is an alkyl group or an alkenyl group having 1 to 20 carbon 
atoms, when the total number of the carbon atoms exceeds 20, the residue 
of unreacted ink increases, since the power for removing ink from 
cellulose is lowered. 
R.sub.3 of the compound represented by the general formula (a-2) may be 
preferably a hydrogen atom or an alkyl group or an alkenyl group having 6 
to 18 carbon atoms, and more preferably a hydrogen atom or an alkyl group 
having 12 to 18 carbon atoms. 
In the deinking method of this invention, the component (a) may be added in 
any of the steps of this invention insofar as the objective removal of ink 
can be achieved, and, specifically, may be added in at least one of steps 
in the deinking method, that is, a step for dissociating waste papers, a 
high concentration bleaching step, a pre-flotation step, etc. and more 
preferably may be added in the step for dissociating waste papers. The 
amount of the component (a) added may be preferably in the range from 0.03 
to 1.0 weight percent to waste papers as raw materials. In the case where 
the component (a) is added at the pre-flotation step, an addition thereof 
is carried out by putting it in a tank before entering the flotation step. 
In this invention, washing of pulp after completion of deinking is carried 
out at temperatures ranging from 40 to 80.degree. C., preferably from 50 
to 70.degree. C., and more preferably from 50 to 60.degree. C. When the 
treating temperature at the washing step is less than 40.degree. C., the 
efficiency of washing ink is poor, since the hydrophilic nature of 
deinking agent is too strong. On the contrary, when the treating 
temperature at the washing step exceeds 80.degree. C., an affinity of 
deinking agent for ink is too strong, and as a result, the efficiency of 
washing decreases and regenerated pulp of good appearance can not be 
obtained. 
In this invention, the washing step of pulp after deinking is a step of 
removing minute ink after removal of ink from waste papers as raw 
materials, followed by removal of ink by means of flotation etc. The main 
deinking methods may be a flotation method and a washing method, and such 
a washing step may be carried out in each of methods. Although, in the 
flotation method, the washing step is carried out usually after the 
flotation step, it is not objectionable that when the general deinking 
step includes a washing step or concentration step of pulp slurry, the 
washing step may be carried out in the washing step or concentration step 
included in the deinking step. For example, this invention is effective in 
the concentration step after pulping or before kneading or bleaching. In 
the case where there are plural washing steps or plural concentration 
steps in the general deinking step, this invention is also effective in 
either of these plural steps or all the washing steps or concentration 
steps. This invention may be, of course, applied to the conventional 
washing method or washing or concentration step. Specifically, in this 
invention, the washing step may be carried out by concentrating pulp by 
removing some of the water by making use of a screen having a proper 
screen mesh after the pulping or the flotation, or preferably by adding an 
additional washing water to wash the pulp slurry, by dispersing remaining 
removed ink in the water and then by removing the washing water in the 
same manner as mentioned above to concentrate the pulp slurry. 
In this invention, although a deinking effect can be obtained by using a 
deinking agent containing a component (a) independently, it can be used in 
combination with conventional deinking agents. The conventional deinking 
agents may be exemplified by higher alcohol sulfates, polyoxyalkylene 
higher alcohol sulfates, alkylbenzenesulfonates, fatty acids or salts 
thereof, adducts of alkylene oxide with higher alcohol or alkylphenol, 
adducts of alkylene oxide with fatty acid, adducts of alkylene oxide with 
mono-, di-, or tri-glyceride, adducts of alkylene oxide with partial or 
complete ester of polyhydric alcohol (except ones corresponding to 
component (a) of this invention) and the like. More excellent deinking 
effect can be obtained by using the fatty acids or salts thereof in 
combination with the other deinking agents. The fatty acids or salts 
thereof may be fatty acids having 8 to 24 carbon atoms or salts thereof 
and exemplified by caprylic acid, capric acid, lauric acid, palmitic acid, 
stearic acid, oleic acid, behenic acid and the like, coconut oil fatty 
acid, soybean oil fatty acid, rape oil fatty acid, tall oil fatty acid, 
castor oil fatty acid, tallow oil fatty acid, palm oil fatty acid, fish 
oil fatty acid and the like containing the above mentioned fatty acids, 
and fatty acids obtained from natural products of hydrogenated products of 
the above mentioned fatty acids and synthetic fatty acids. The salts of 
the fatty acids may be preferably sodium salt or potassium salt. The 
weight ratio of component (a) to fatty acid or salt thereof (component 
(a)/fatty acid or salt thereof (weight ratio)) may be preferably in the 
range from 30/70 to 70/30. 
The deinking method of this invention is described by taking a flotation 
method as an example. The waste papers as raw materials are cut, and then 
put in a dissociating apparatus into which alkaline component bleaching 
component such as sodium hydroxide, sodium silicate, hydrogen peroxide and 
the like and water are added to dissociate (dissociation step). If 
necessary, dehydration (a dehydration step) or chemical mixing is carried 
out, and aging is carried out. Thereafter, water is added to dilute the 
concentration of pulp and a flotation treatment is carried out (a 
flotation step). It is not objectionable to set a kneading step 
(dispersing) or a refining step between the aging step and the flotation 
step. Washing of pulp after the deinking is carried out by concentrating 
pulp slurry after the flotation by means of a screen having proper screen 
size (washing step). In this invention, the temperature of the pulp slurry 
at this step is maintained in the range from 40 to 80.degree. C. And, the 
washing step may be carried out twice or more. The subsequent steps are 
carried out according to conventional deinking methods.

EXAMPLES 
While this invention is described in more detail with reference to 
examples, it should be understood that this invention is not limited 
thereto. In the following examples, "%" is on the basis of weight, unless 
otherwise noted. 
Deinking agents used in Examples 1 and 2 are indicated in Table 1. R.sub.1 
and R.sub.2 in Table 1 are alcohol or carboxylic acid as raw materials. 
The forms of addition are explained in block. P is a propylene oxide 
block. E is an ethylene oxide block. R is R.sub.1 O-- of alcohol or 
R.sub.2 COO-- of carboxylic acid. 
TABLE 1 
__________________________________________________________________________ 
(a) Component EO/PO 
Deinking 
General Alkylene Oxide 
The forms of 
agent No. 
formula 
R1 R2 R3 EO addition 
__________________________________________________________________________ 
product of the 
present invention 
1 a-1 stearyl alcohol 
-- -- 63 2.3 
random 
2 a-2 -- palmitic acid 
hydrogen 
34 2 random 
3 a-2 -- stearic acid 
stearyl 
65 2.4 
random 
4 a-1 2-pentadecanol 
-- -- 20 2 R-P-E block 
5 a-2 -- linoleic acid 
hydrogen 
81 1.8 
R-E-P block 
6 a-2 -- trimer acid 
lauryl 
24 1 R-P-E block 
7 a-1 oleic alcohol 
-- -- 40 2.3 
R-E-P block 
8 a-2 -- fish oil 
2-ethylhexyl 
34 4 random 
fatty acid 
9 a-2 -- myristic acid 
lauryl 
26 5 random 
10 a-1 nonylphenol 
-- -- 23 3.5 
random 
11 a-2 -- dimer acid 
hydrogen 
43 4.5 
R-E-P block 
12 a-2 -- tall oil 
lauryl 
150 3 random 
fatty acid 
13 a-1 2-hexadecene- 
-- -- 220 4 R-P-E block 
1-ol 
Comparative 
product 
14 a-1 stearyl alcohol 
-- -- 63 0.8 
random 
15 a-2 -- palmitic acid 
hydrogen 
10 2 random 
16 a-2 -- rape oil 
methyl 
17 6 random 
fatty acid 
17 a-1 2-hexadecanol 
-- -- 12 7 R-E-P block 
18 a-2 -- stearic acid 
myristyl 
148 0.8 
R-E-P block 
19 a-2 -- dimer acid 
octyl 43 0.5 
R-P-E block 
20 a-1 lauric alcohol 
-- -- 360 4 R-P-E block 
21 a-2 -- lauric acid 
glycerine 
80 2 random 
residue 
__________________________________________________________________________ 
Example 1 
Deinking treatment was carried out in a manner described below by the use 
of waste papers as raw materials comprising magazines and newspapers in 
weight ratio of the former to the latter of 20:80 
(magazines/newspapers=20/80 (weight ratio)). The waste papers as raw 
materials contain 8% of mixed office waste papers. 
Waste papers as raw materials were cut to an enormous of pieces of paper in 
size of 2.times.5 cm and put in a desk-top dissociating machine, then into 
which 1% sodium hydroxide (to the waste papers as raw materials), 3% 
sodium silicate (to the waste papers as raw materials), 3% hydrogen 
peroxide of 30% in concentration (to the waste papers as raw materials), 
0.4% deinking agent indicated in Table 1 (to the waste papers as raw 
materials), and water were added, and dissociation was carried out in 
concentration of pulp of 5% at a temperature of 50 for ten minutes. After 
aging at a temperature of 50.degree. C. for 60 minutes, water was added to 
lower the concentration of pulp to 1%, and a flotation treatment was 
carried out at a temperature of 50.degree. C. for ten minutes (flotation 
step). The pulp slurry after flotation was concentrated to 10% by means of 
a screen of 80 screen mesh (washing step at a temperature of 50.degree. 
C.), and thereafter water of 50.degree. C. was added to return the 
concentration to 1%, and a pulp sheet was prepared by means of a tapping 
sheeting machine while the washing step was carrying out. In this Example, 
the washing step according to this invention was carried out twice in this 
sample. 
The brightness of the pulp sheet after the flotation and that after the 
washing were measured respectively. The difference in brightness of the 
pulp between after the flotation and after the washing was evaluated for 
washing efficiency (%). Results obtained were shown in Table 2. 
TABLE 2 
______________________________________ 
Brightness (%) 
Washing 
Deinking after the after the 
efficiency 
agent No. flotation washing (%) 
______________________________________ 
Product of the 
present invention 
1 48.3 55.5 7.2 
2 48.9 55.7 6.8 
3 48.5 56.2 7.7 
4 48.6 54.3 5.7 
5 48.3 55.6 7.3 
6 48.5 53.7 5.2 
7 48.1 54.8 6.7 
8 48.2 54.3 6.1 
9 47.9 53.6 5.7 
10 47.6 53.4 5.8 
11 48.5 54.5 6.0 
12 48.6 55.1 6.5 
13 49.0 54.1 5.1 
Comparative 
product 
14 47.8 50.3 2.5 
15 47.9 48.9 1.0 
16 47.5 49.0 1.5 
17 47.8 49.0 1.2 
18 46.5 48.1 1.6 
19 45.9 47.4 1.5 
20 46.0 47.0 1.0 
21 47.4 48.7 1.3 
______________________________________ 
As can be seen from Table 2, the brightness of pulp after the washing is 
improved and washing efficiency is increased in the product of this 
invention compared with comparative product. 
Example 2 
Waste papers as raw materials ((magazines/papers 30/70 (weight ratio)) were 
cut to an enormous of pieces of paper in size 2.times.5 cm and put in a 
desk-top dissociating machine, then into which 1% sodium hydroxide (to the 
waste papers as raw materials), 3% sodium silicate (to the waste papers as 
raw materials), 3% hydrogen peroxide of 30% in concentration (to the waste 
papers as raw materials), 0.35% several kinds of deinking agents used in 
Example 1 (to the waste papers as raw materials), and water were added, 
and dissociation was carried out in the concentration of pulp of 5% at a 
temperature of 50.degree. C. for ten minutes. After aging at a temperature 
of 60.degree. C. for 60 minutes, water was added to lower the 
concentration of pulp to 1%, and a flotation treatment was carried out at 
a temperature of 45.degree. C. for ten minutes (flotation step). The pulp 
slurries after the flotation were concentrated to 10% with changing the 
temperature of the slurries at 30.degree. C., 40.degree. C., 50.degree. 
C., 60.degree. C. and 80.degree. C. (concentration step), and thereafter 
water of 20.degree. C. was added to return the concentration to 1%, and a 
pulp sheet was prepared by means of a tapping sheeting machine. In this 
Example, the washing step of this invention was carried out once. 
Evaluations similar to that of Example 1 were carried out for this 
Example. Results obtained were shown in Table 3. 
TABLE 3 
______________________________________ 
Brightness (%) 
Washing 
Washing Deinking after the 
after the 
efficiency 
temperature 
agent No. flotation 
washing 
(%) 
______________________________________ 
Example of the present invention 
Product of the 
present invention 
40.degree. C. 
1 47.8 52.7 4.9 
50.degree. C. 
1 47.5 53.8 6.3 
60.degree. C. 
1 47.8 54.4 6.6 
60.degree. C. 
3 48.1 55.0 6.9 
60.degree. C. 
5 48.0 54.5 6.5 
Comparative example 
Comparative 
product 
60.degree. C. 
14 47.5 48.4 0.9 
16 47.2 48.2 1.0 
Product of the 
present invention 
30.degree. C. 
1 48.0 49.6 1.6 
3 48.2 49.6 1.4 
5 48.1 49.7 1.6 
Comparative 
product 
14 47.7 48.7 1.0 
16 47.5 47.8 1.2 
Product of the 
present invention 
85.degree. C. 
1 47.4 48.7 1.3 
3 47.6 48.9 1.3 
5 47.6 49.0 1.4 
Comparative 
product 
14 47.1 48.1 1.0 
16 47.3 48.2 0.9 
______________________________________ 
As can be seen from Table 3, the brightness of pulp after the washing is 
improved and washing efficiency is increased in this Example of this 
invention compared with comparative Example. On the other hand, 
improvement in washing efficiency can be hardly observed when using 
comparative deinking agents, even if the washing step is carried out at a 
temperature of 60.degree. C.