ECOFATTING Deliverable D5 Action 1-2

Transcription

INESCOP
STUDY ON
FATLIQUORING
AGENTS
ENVIRONMENTAL
IMPACT
ACTION 1-2
DELIVERABLE 5
January 2012–March 2013
LIFE ECOFATTING PROJECT
LIFE10 ENV/IT/000364
ENVIRONMENTALLY
FRIENDLY NATURAL
PRODUCTS INSTEAD OF
CLOROPARAFFINS IN THE
FATTING PHASE OF THE
TANNING CYCLE
Prepared by INESCOP
1
Study on the fatliquoring agents environmental impact
LIFE10 /ENV/IT/000364
TABLE OF CONTENTS
1. INTRODUCTION....................................................................................................................1
2. SELECTION OF LEATHER FAT-LIQUORING PRODUCT FAMILIES ........................1
3. DEFINITION OF PARAMETERS TO BE ANALYSED ......................................................2
4. DESCRIPTION OF LABORATORY, SEMI-INDUSTRIAL AND INDUSTRIAL SCALE
TRIALS. .......................................................................................................................................4
4.1. Laboratory scale trials. .................................................................................................4
4.2. Semi-industrial scale trials. ..........................................................................................6
4.3. Industrial scale trials. ...................................................................................................7
5. ENVIRONMENTAL IMPACT OF DIFFERENT FAT-LIQUORING AGENTS................8
5.1. Analysis of fat-liquoring products ................................................................................8
5.2. Characterization of fat-liquoring residual baths ...........................................................9
5.3. Characterization of fat-liquoring leathers ...................................................................13
5.3.1. Organoleptic Tests.......................................................................................13
5.3.2. Physical Resistance Tests.............................................................................14
5.3.3. Chemical Tests on leather ............................................................................16
6. CONCLUSIONS ....................................................................................................................18
7. PHOTO GALLERY...............................................................................................................19
2
1. INTRODUCTION
This report presents the results of the assessment of fat-liquoring products of different
chemical nature from the point of view of their environmental performance. For this, different
types of hides have been fat-liquored employing several products by carrying out trials at
laboratory, semi-industrial and industrial level.
In these trials, INESCOP has carried out the following tasks:
− Selection of leather fat-liquoring product families
− Definition of parameters to be analysed
− Description of laboratory, semi-industrial and industrial scale trials
− Analysis of fat-liquoring products
− Characterisation of fat-liquoring residual baths
− Analysis of leather: physical tests, chemical tests and organoleptic properties
The results obtained have been used as a standard against which the improvement of the
environmental impact of the natural fats developed is to be compared.
2. SELECTION OF LEATHER FAT-LIQUORING PRODUCT FAMILIES
Traditionally, the process of fat-liquoring tanned leathers is carried out by either coating the
hide with crude oil or by mixing this with soaps during the natural drying phase. Later, with
the emergence of surfactants and the ability to produce fat emulsions, fat-liquoring began to
be conducted by bathing the materials inside drums or paddle vats.
Fat-liquoring products are formulated from a variety of different raw materials, such as
vegetable oil trioleins, alcohol and fatty acids, fish oil, paraffins, lanolin, lecithin, etc. Then,
different polar groups are added by sulphation, sulphonation, phosphatisation, chlorination,
etc. in order to make them emulsifiable in water and to enable them to properly penetrate
leather. Thus, this makes it possible to synthesise a large variety of fat-liquoring products.
Nowadays, the fat-liquoring process carried out inside drums uses mixtures of fat-liquoring
products of differing chemical natures, which transfer certain specific properties to the
leather. However, efforts have been made to test the different products independently in order
to properly evaluate each of their individual environmental impacts.
Concerning the selection of the fat-liquoring product families most commonly used in EU
tanneries, the tested families of fat-liquoring products are:
1
2
3
4
5
Sulphated olein
Sulphonated olein
Sulphited olein
Sulphited fish oil
Sulphated lecithin
6
7
8
9
10
Sulphated ester
Phosphoric ester
Sulphochlorinated paraffin
Synthetic oils
Fat-liquoring polymer
Table 1. Selected fat-liquoring products families
1
Figure 1. Selected fat-liquoring products.
In commercial products, greases are mixed with water or emulsifiers with an active ingredient
concentration of 65-80%. For this reason, the percentage of the commercial product added is
recalculated for each fat-liquoring product so as to ensure the addition of the same amount of
grease to all leathers.
3. DEFINITION OF PARAMETERS TO BE ANALYSED
INESCOP has defined the parameters to be analysed, as much in fat-liquoring products and
the wastewater produced in the fat-liquoring stage as in the leather obtained. Table 2 shows
the parameters analysed for assessing the environmental impact of fat-liquoring products:
Tests on fat-liquoring products (heavy metals)
As (mg/l)
Cd (mg/l)
Pb (mg/l)
Wastewater parameters
pH
Conductivity at 25 º C (µS/cm)
BOD5 (mg O2/l)
COD (mg O2/l)
Biodegradability (BOD/COD)
Cr (III) (mg/l)
Oils and fats (mg/l)
Leather parameters
Touch / Softness
Colour
Organoleptic
Grain firmness
Fullness
Shrinkage temperature (ºC)
Tear resistance (N)
Physical
Tensile strength (N/mm2)
Elongation at break (%)
Extractable substance by using CH2Cl2 (% m.s.)
Chemical
Cr (VI)
Table 2. Assessment of the environmental impact of fat-liquoring products;
parameters to be analysed.
2
The tests were monitored by means of control sheets for tests & results, which contain
information about:
− Test type
− Type of fat-liquoring product and characteristics
− Type of skin and treatment
− Fat-liquoring products analysis
− Leather analysis: physical tests - chemical tests and organoleptic properties
− Wastewater analysis
Figure 2. Control sheets for tests & results.
3
4. DESCRIPTION OF LABORATORY, SEMI-INDUSTRIAL AND INDUSTRIAL
SCALE TRIALS.
4.1. Laboratory scale trials.
The laboratory-scale leather fat-liquoring trials were conducted at INESCOP-U.T Vall d’Uixó
facilities using the selected products. The trials were carried out in rotating stainless steel
tanning drums measuring 300 mm in diameter and 150 mm in width respectively, featuring
systems for automation, control and dosage of water and reactants.
Figure 3. Laboratory-scale rotating drums at INESCOP-UT Vall d’Uixó facilities.
Figure 4. Detail of laboratory-scale trials at INESCOP-UT Vall d’Uixó facilities.
In each test with the calf hides, 1 sq. foot pieces of wet-blue shaved hides with a thickness of
1.5 mm were processed. These pieces of wet-blue cattle hides had been prepared for the fatliquoring operation by means of a standard process of neutralisation, retanning and dyeing.
The formulations used in these tests are shown in Table 3 where it is indicated, for the
different operations, the product used, the percentage by weight with respect to the wet-blue
leather introduced into the tanning drum, temperature, rotating time and checks to be
performed.
4
% by
wet-blue
weight
Tª
(ºC)
Rinse with water
200
40
Acetic Acid
0’2
Degreasing surfactant
0’2
PROCESS/PRODUCTS
Time
(min.)
pH
Remarks
4’1
Check pH
4’5
Check pH
45’
4’6
Check through section
30’
3’8
Check pH
RETANNNG
20’
Drain and wash
Water
100
Synthetic Chromium
5
Sodium Formiate
1
40
30’
Drain
NEUTRALISATION
Water
200
40
Synthetic buffered solution
2
Sodium Formiate
1
40’
Sodium bicarbonate
1
15’
Acrylic Resin
5
60’
Drain and wash
DYEING
Water
50
Synthetic Phenol
5
Filler
5
Dispersing Agent
1
Powdered dye
1
Water
200
Formic Acid
0’5
25
20’
60
Drain and wash
Table 3. Description of the retanning, neautralisation, and dyeing processes.
5
Once the hides had been retanned, neutralised and dyed, the fat-liquoring stage was
performed, according to the process described in Table 4:
PROCESS/PRODUCTS
% by
wet-blue
weight
Tª
(ºC)
5000
45-50
Time
(min.)
pH
Remarks
FAT-LIQUORING
Water
1
Fat-liquoring product
8
Formic acid (1:10 dilution)
3
90’
20’
Check pH
Wash, drain drum, take bath sample and remove leather
Air dry
Table 4. Description of the leather fat-liquoring process.
Once this operation was completed, a sample of the waste fat-liquoring bath and a sample of
each one of the obtained leathers were taken for the determination of the parameters showed
in Table 2.
In Annex 1, there are images of the trials being carried out in laboratory conditions and also
of the resulting leather.
4.2. Semi-industrial scale trials.
The semi-industrial scale leather fat-liquoring trials were conducted at INESCOP-U.T Vall
d’Uixó facilities using the selected products. The trials were carried out in rotating tanning
drums measuring 900 and 1,200 mm in diameter respectively and 450 mm in width, made of
bolondo wood and featuring systems for automation, control and dosage of water and
reactants.
Figure 5. Semi-industrial scale rotating drums at INESCOP-UT Vall d’Uixó facilities.
1
In commercial products, greases are mixed with water or emulsifiers with an active ingredient concentration of
65-80%. For this reason, the percentage of the commercial product added is recalculated for each fat-liquoring
product so as to ensure the addition of the same amount of grease to all leathers.
6
In each test with the calf hides, wet-blue shaved hides with a thickness of 1.5 mm divided into
sides (half hide) were processed.
The formulations used in these tests are the same as the ones employed during the laboratory
trials which are shown above in Table 3, where it indicates, the product used, the percentage
by weight with respect to the wet-blue leather introduced into the tanning drum, temperature,
rotating time and checks to be performed during each process.
Then, adhering to the process described above in Table 4, fat-liquoring was performed, on the
retanned, neutralised and dyed hides.
in Table 2.
In Annex 2, there are images of the trials being carried out on a pre-industrial scale and also
of the resulting leather.
4.3. Industrial scale trials.
The industrial scale leather fat-liquoring trials were conducted at INESCOP-U.T. Vall d’Uixó
facilities using the selected products. The trials were carried out on rotating tanning drum of
1,600 mm diameter respectively and 1,100 mm width, made of bolondo wood and featuring
systems for automation, control and dosage of water and reactants
The trials were carried out in this tannery in an industrial rotating tanning drums, as show in
Figure 6:
Figure 6. Pre-industrial scale rotating drums at INESCOP-UT Vall d’Uixó facilities.
7
In each test with the calf hides, wet-blue shaved hides with a thickness of 1.5 mm divided into
sides (half hide) were processed.
The formulations used in these trials are the same that employed at laboratory scale trials
which are shown in previous Table 3, where it is indicated, for the different operations, the
product used, the percentage by weight with respect to the wet-blue leather introduced into
the tanning drum, temperature, rotating time and checks to be performed.
Then, on the hides retanned, neutralised and dyed, the fat-liquoring stage was performed,
according to the process described in previous Table 4.
in Table 2.
In Annex 3, there are images of the tests being carried out on a pre-industrial scale and also of
the resulting leather.
5. ENVIRONMENTAL IMPACT OF DIFFERENT FAT-LIQUORING AGENTS
In all trials carried out, the obtained leathers have good physical strength and adequate
smoothness, softness, fullness and flexibility, and no significant difference between the
different fatliquoring agents has been detected.
The environmental evaluation of the results of the carried out tests is done through:
− the analysis of fat-liquoring products
− the characterization of fat-liquoring residual baths
− the analysis of leather: physical tests, chemical tests and organoleptic properties
5.1. Analysis of fat-liquoring products
The evaluation of the characteristics possessed by the fatliquoring products chosen to be used
in the tests was carried out by determining the levels of arsenic, cadmium, and lead contained
in the products, in order to prevent these substances from being present in leather in
accordance with the criteria of the European Eco-label for footwear (Decision 2009/563/EC).
The determination of the chemical parameters of the fatliquoring products showed its
conformity to the limits established in the European Eco-label for footwear, since the findings
of the analysis showed results that were less than the aforementioned limit for all of the
products:
Arsenic:
Cadmium:
Lead:
< 60 ppm *
< 6 ppm *
< 8 ppm*
* Limit of detection of the analysis technique employed
8
5.2. Characterisation of fat-liquoring residual baths
The evaluation of the impact of the fat-liquoring on wastewater was achieved by the
characterisation of the fat-liquoring waste-baths obtained in the different tests carried out,
determining the most significant parameters in accordance with international standards. The
table below shows the selected control parameters and the testing standards used:
PARAMETER
pH
Conductivity
COD
STANDARD
--UNE-EN 27888:1994. Determination of electrical conductivity. (ISO
7888:1985).
UNE 77004:2002. Determination of the chemical oxygen demand (COD).
BOD5
UNE-EN 1899-1:1998 Determination of biochemical oxygen demand after n
days (BODn).
Total Cr
UNE 77061:2002 Chromium determination.
Oils & Fats
Standard Methods for the Examination of Water and Wastewater_SM 5520 B
Table 4. Standards used in the characterization of tanning wastewater.
Below, shown in graph form are the results of the analyses on fatliquoring residual baths,
where the different impact of each fatliquoring product can be compared for each parameter.
The graphs show the results obtained for each parameter in laboratory tests (in blue colour) on
a semi-industrial scale (in pink colour) and on pre-industrial test (in white colour). In general,
it can be seen that the growing mechanical effect entails a greater fixation of fatliquoring
products and, therefore, a lower level of contamination in the residual baths.
pH
The pH value of waste water resulting from fatliquoring baths plays an important role in the
process, since both the cross of leather (which depends on neutralisation) and the stability of
the fatliquoring emulsion depend on pH levels.
Furthermore, fatliquoring products can possess diverse ionic natures (anionic, cationic, and
non-ionic), though usually they tend to be anionic. Moreover, the ionic characteristics of
leather depend on pH levels, with fatliquors of an anionic nature attaching to cationic leather
and vice versa. Amongst the various products that have been tested, all of them presented
anionic characteristics, the only exceptions being the sulphated lecithin and sulphonated olein,
both of which are non-ionic.
In order to evaluate this parameter, pH levels in the residual baths were measured when the
fatliquoring process had ended. Values between 3.3 and 4 were obtained, typical for this type
of bath, which is used to carry out the fixation of fats through the addition of formic acid at
the end of the stage in question. Figure 7 displays the values obtained during the laboratoryscale tests, and also the tests carried out on a semi-industrial and pre-industrial scale.
9
4,00
1. Sulphated olein
2. Sulphonated olein
3. Sulphited olein
4. Sulphited fish oil
5. Oxidised lecithin
6. Sulphated ester
7. Phosphoric ester
8. Sulphochlorinated paraffin
9. Synthetic oil
10. Fatliquoring polymer
3,80
3,60
3,40
3,20
Laboratory test
3,00
1
2
3
4
5
6
7
8
9
10
pH
Semi-industrial test
Pre-industrial test
Figure 7. Measuring the pH of the residual baths used in fatliquoring.
Conductivity
Regarding COD values present in the residual baths used in fatliquoring, the results obtained
show a large variability in relation to the fatliquor used.
As can be seen in figure 8, conductivity in the fatliquoring baths is less than 3000 µS/cm,
except in the bath where sulphochlorinated paraffin was used, whose values are a lot higher
than the mean. This is due to doubly ionic characteristics of this product, owing to the content
of chlorine and other groups of sulphonated substances, whilst the other products only
presented a sole ionic group each (a sulphated, sulphonated, sulphited or phosphatised group).
5.000
1. Sulphated olein
3. Sulphited olein
6. Sulphated ester
7. Phosphoric ester
9. Synthetic oil
4.000
3.000
2.000
1.000
Laboratory test
0
1
2
3
4
5
6
7
8
9
10
Conductivity (µs/cm )
Pre-industrial test
Figure 8. Measuring the conductivity of fatliquoring baths.
With regard to conductivity, the environmental impact of fatliquoring agents is not very
significant compared to other products and stages of the tanning process. Sulphochlorinated
paraffins are the fats with the greatest impact on conductivity and Sulphonated olein,
Sulphited olein and Oxidised lecithin are the fats with the lowest impact on it.
10
Chemical Oxygen Demand (COD)
Regarding COD values present in the residual baths used in fatliquoring, the results obtained
show a large variability in relation to the fatliquor used. In all cases, the COD of these
residual baths exceeded established limits for wastewater discharged into the sewers in Spain
(< 1,500 mg/l). However, the wastewater from these baths is not discharged directly into the
sewer, but it is mixed with the other water from the tannery, and as a result accounts for
approximately 6% of the total volume of water discharge, and thus there is a factor of dilution
with the remainder of the water used throughout the process.
Figure 9 shows the values obtained in the laboratory, semi-industrial and pre-industrial tests.
20.000
1. Sulphated olein
3. Sulphited olein
6. Sulphated ester
7. Phosphoric ester
9. Synthetic oil
15.000
10.000
5.000
Laboratory test
0
1
2
3
4
5
6
7
8
9
10
Pre-industrial test
COD (m g/L)
Figure 9. Determining COD in the residual baths used in fatliquoring.
Biodegradability relationship (BOD/COD)
The biodegradability of the fatliquoring residual baths is determined by analysing the
relationship between BOD and COD. In terms of wastewater, effluents are classified in the
following fashion:
BOD/COD < 0.2
0.2 < BOD/COD < 0.7
0.7 < BOD/COD < 0.8
BOD/COD > 0.8
Non-biodegradable
Slightly biodegradable
Biodegradable
Highly biodegradable
The results obtained (as shown in figure 10) demonstrate that in general, fatliquoring baths do
not, in themselves, tend to be particularly biodegradable. However, the phosphoric esters and
the fatliquoring polymer are the two substances that proved to be the least biodegradable
when transferred to water.
11
0,60
1. Sulphated olein
3. Sulphited olein
6. Sulphated ester
7. Phosphoric ester
9. Synthetic oil
0,50
0,40
0,30
0,20
0,10
Laboratory test
0,00
1
2
3
4
5
6
7
8
9
10
Biodegradability
Pre-industrial test
Figure 10. Comparing levels of biodegradability in the fatliquoring baths.
Cromium (III)
The determination of this parameter is carried out in order to verify the incidence of the
fatliquoring product in the release of trivalent chromium of leather.
The results obtained, (as shown in Figure 11) demonstrated that, in general, fatliquoring baths
do not cause the discharge of vast quantities of leather, the fatliquoring polymer being the one
with the lowest capacity for the solubilisation of chromium from leather, owing to the lack of
any reactive groups (sulphated, sulphonated, sulphited, phosphatised, or chlorinated groups
etc.), which are present in the remainder of the products that were tested.
6,0
1. Sulphated olein
3. Sulphited olein
6. Sulphated ester
7. Phosphoric ester
9. Synthetic oil
5,0
4,0
3,0
2,0
1,0
Laboratory test
0,0
1
2
3
4
5
6
7
Chrom ium (III) (m g/L)
8
9
10
Pre-industrial test
Figure 11. Comparison of the content of trivalent Chromium in fatliquoring baths
12
Oils and fats
The determination of this parameter was carried out in order to test the fixation of fatliquoring
products on leather. The extraction of fats from the residual baths was conducted with a
mixture of two solvents (hexane and tert-butyl methyl ether, at a ratio of 80:20).
The results obtained (shown in Figure 12) demonstrate that, in general, fats fix adequately to
leather and fatliquoring baths do not present a high content of non-fixed oils and fats.
2.500
1. Sulphated olein
3. Sulphited olein
6. Sulphated ester
7. Phosphoric ester
9. Synthetic oil
2.000
1.500
1.000
500
Laboratory test
0
1
2
3
4
5
6
7
8
9
10
Oils/Fats (m g/L)
Pre-industrial test
Figure 12. Analysis of levels of oils/fats in fatliquoring baths.
5.3. Characterisation of fat-liquoring leathers
The characterisation of fatliquored leather was conducted from three points of
consideration::
- Organoleptic tests.
- Physical resistance tests.
- Chemical tests.
5.3.1. Organoleptic tests
The parameters considered in the organoleptic tests were: touch, colour, and firmness factors.
Regarding the touch of the leathers tested, this was graded on the level of softness obtained,
assigning a value of 1 for the lowest level of softness and 5 for the highest. In table 5 the
results of this test are displayed, observing an adequate level of leather softness in all leather
hides (3-5), except those subjected to the fatliquoring process using sulphited fish oil, which
demonstrated a lower level of softness (2).
13
No. of
Sample
1
2
3
4
5
6
7
8
9
10
Type of fat
Touch (1-5)
Sulphated olein
Sulphonated olein
Sulphited olein
Sulphited fish oil
Sulphated lecithin
Sulphated ester
Phosphoric ester
Sulphochlorinated paraffin
Synthetic oils (*)
Fatliquoring polymer
3
5
4
2
5
4
4
3
5
4
Table 5. Touch test on fatliquored leather hides.
In reference to the firmness of the leather, continuous flexing of the leather was carried out to
test the degree of adhesion of the grain. Loose grain is an undesirable effect in leather, since
during use as part of finished products (e.g. shoes, leather garments, etc.), wrinkles begin to
form in areas where flexing movements take place. With all of the fatliquors that were tested,
none produced leather with loose grain characteristics; all of the resulting leather possessed
adequate levels of firmness.
Finally, regarding colour, differences in final leather colour tone were observed upon the use
of the various fatliquors, but no significant differences were present.
5.3.2. Physical resistance tests
The quality assessment on the production of fatliquoring hides is done through physical
validations in accordance with accepted standards (EN, ISO, etc.). The table below shows the
selected control parameters and the testing standards used:
PARAMETER
STANDARD
Thickness
(mm)
ISO 2589:2002 (IULTCS/IUP 4)
Determination of thickness
Tear strength
(N)
ISO 3377-2:2002 (IULTCS/IUP 8)
Determination of tear load -- Part 2: Double edge tear
Tensile strength
(N/mm2)
Determination of tensile strength and percentage extension
Elongation at break
(%)
Determination of tensile strength and percentage extension
Grain burst
(mm)
Determination of distension and strength of grain -- Ball burst test
Table 6. Standards used in the physical validations of fatliquoring hides.
14
The determinations of physical parameters of the leathers have shown to be compliant with
the limits required for footwear manufacture.
Tear resistance (N):
We can see in figure 13 that all the fatliquored leathers comply with the minimum tear
resistance requirements of 50 N for articles being used in the manufacture of footwear.
1. Sulphated olein
3. Sulphited olein
6. Sulphated ester
7. Phosphoric ester
9. Synthetic oil
25
20
15
10
5
0
1
2
3
4
5
6
7
8
9
10
Laboratory test
Te nsile strength (N/m m 2)
Pre-industrial test
Figure 13. Tear resistance of fatliquored leather.
Tensile strength (N/mm2)
In all cases, the fatliquored leather hides comply with the minimum tensile strength
requirements of 15 N/mm2 for articles being used in the manufacture of footwear and in the
leather goods industry (figure 14).
350
1. Sulphated olein
3. Sulphited olein
6. Sulphated ester
7. Phosphoric ester
9. Synthetic oil
300
250
200
150
100
50
Laboratory test
0
1
2
3
4
5
6
7
8
9
10
Tear resistance (N)
Pre-industrial test
Figure 14. Tensile strength of fatliquored leather.
15
Through the use of this test, the elasticity of leather is evaluated, measuring the maximum
elongation reached before breaking the leather. The minimum level of elongation required for
the manufacture of footwear and other leather goods is 40%, this being extensively fulfilled
by each of the fatliquored leathers (see Figure 15).
120
1. Sulphated olein
3. Sulphited olein
6. Sulphated ester
7. Phosphoric ester
9. Synthetic oil
100
80
60
40
20
Laboratory test
0
1
2
3
4
5
6
7
8
9
10
Pre-industrial test
Figure 15. Elongation at break of the fatliquored leather.
Grain burst (mm)
The testing of this parameter verifies if the grain layer of the leather breaks upon being folded,
which would indicate a low level of elasticity deriving from the poor fatliquoring of the
leather. The minimum grain burst requirement for the manufacture of footwear is 7 mm, this
value being fulfilled in all cases.
5.3.3. Chemical tests on leather
The quality assessment on the production of fatliquoring hides is done through physical
validations in accordance with accepted standards (EN, ISO, etc.). The table below shows the
selected control parameters and the testing standards used:
PARAMETER
Matter soluble in
dichloromethane (%)
Chromium(VI)
(mg/kg)
STANDARD
ISO 4048:2008
Leather - Chemical tests - Determination of matter soluble in
dichloromethane
ISO 17075:2007
Leather - Chemical tests - Determination of chromium(VI) content
16
Matter soluble in dichloromethane
This parameter enables the evaluation of the level of fatliquor fixation in the leather in a way
that has a direct relationship with its physical behaviour in terms of grain burst, tear
resistance, tensile strength, elongation at break, and touch, etc.
The quantity of fat that is required to be fixed in the fatliquoring process, as well as the level
of penetration into the leather that will take place, largely depend on the type of fat used. So,
although fatliquored leather hides generally present amounts of fat accounting for between 3
and 9% of total content, certain fatliquors may result in amounts being less than 3%. On the
whole, levels accounting for less than 3% tend to result in leathers that are not significantly
fatliquored and their mechanical characteristics are not adequate for use in the manufacture of
garments. Above 9% proves that the fatliquoring has been excessive, impeding the subsequent
finishing, bonding, or vulcanisation processes taking place during the latter stages of the
assembly of footwear.
8,0
1. Sulphated olein
3. Sulphited olein
6. Sulphated ester
7. Phosphoric ester
9. Synthetic oil
7,0
6,0
5,0
4,0
3,0
2,0
1,0
Laboratory test
0,0
1
2
3
4
5
6
7
8
9
10
Fat (%m .s.)
Pre-industrial test
Figure 16. Measuring the % of fat present in the leather.
According to figure 16, during the tests a level of fat fixation higher than 3% was reached in
all samples except for products 8, 9, and 10. In the example shown by product 8, this product
being a sulphochlorinated paraffin, two polar groups are present in its composition, so the
level of leather fixation is at very high levels. Therefore, it is not entirely extracted with
dichloromethane, a solvent employed in the test measuring the percentages of fat present. On
the other hand, the synthetic oils and fatliquoring polymers are not fats as per se like the
others, so with lesser quantities fixed onto the leather, the results of the fatliquoring process
are of a higher quality and differences are not observed in the properties of the leather hides.
Chromium (VI)
By conducting this test, it has been possible to evaluate the influence of each fatliquoring
agent on the formation of Chromium VI, derived from the Chromium III fixed to the leather
during tanning. Hence, before and after the fatliquoring process, leather hides were subjected
to an aggressive ageing process, prompting the appearance of hexavalent chromium.
17
The formation of Chromium VI is owed to the free radicals that emerge after the breakdown
of the double bonds in the fats. However, the various commercial products, despite being part
of the same family (e.g. sulphated olein), can present very distinctive chain lengths and
degrees of instauration.
During the previous ageing tests, there were no detections of cases where hexavalent
chromium was present in the fatliquored leathers, complying with the requirements
established by the Eco-label for footwear.
However, after ageing, hexavalent chromium was determined to be present in all of the
leather. As can be seen in figure 17, two ranges of chromium VI were observed: a range of
between 13 and 23% was seen in products 3, 4, 5, and 7, and between 5 and 10% for products
6, 8, 9, and 10. In particular, product 2 (sulphited olein) obtained the lowest level of
Chromium VI in the resulting leather.
25
1. Sulphated olein
3. Sulphited olein
6. Sulphated ester
7. Phosphoric ester
9. Synthetic oil
20
15
10
5
Laboratory test
0
1
2
3
4
5
6
Cr VI (ppm)
7
8
9
10
Pre-industrial test
Figure 17. The formation of Chromium VI in fatliquored leathers after ageing.
6. CONCLUSIONS
The results obtained show that none of the families of commercial fatliquoring agents that
have been evaluated stand out in terms of their environmental performance. Instead several
products have been highlighted as having a reduced contribution to COD, but, on the other
hand, they have also shown to have a high level of conductivity or a high tendency for the
formation of hexavalent chromium.
Therefore, in order to allow a better comparison of the results obtained, tables 7 and 8 show
the minimum, maximum and average results collected; these will be used as reference values
during the evaluation of the natural fats developed by SERICHIM.
18
Laboratory test
Minimum
Maximum
Average
pH
3,54
3,98
3,81
Conductivity
(µs/cm)
1.900
5.000
2.750
COD
(mg/l)
12.700
18.300
15.360
BOD
(mg/l)
2.570
8.850
6.291
Biodegradability Total Cr
(mg/l)
0,17
0,7
0,59
5,4
0,41
3,0
Oils & Fats
(mg/l)
65
2380
991,5
Conductivity
(µs/cm)
1.100
3.900
2.130
COD
(mg/l)
8.200
17.100
12.000
BOD
(mg/l)
1.310
5.130
3.611
(mg/l)
0,11
0,4
0,48
4,0
0,31
2,2
Oils & Fats
(mg/l)
27
980
348,4
Conductivity
(µs/cm)
800
3.700
1.982
COD
(mg/l)
7.500
16.700
11.500
BOD
(mg/l)
1.130
4.192
2.844
(mg/l)
0,10
0,9
0,48
3,5
0,27
2,0
Oils & Fats
(mg/l)
31
684
230
Minimum
Maximum
Average
pH
3,42
3,76
3,66
Pre-industrial test
Minimum
Maximum
Average
pH
3,37
3,71
3,56
Table 7. Minimum, maximum and average results of
fatliquoiring residual baths characterization
Laboratory test
Tear strength
(N)
Minimum
132
Maximum
211
Average
155,6
Tear strength
(N)
Minimum
55
Maximum
314
Average
211,8
Pre-industrial-test
Tear strength
(N)
Minimum
67
Maximum
343
Average
229,9
Tensile strength
(N/mm2)
15,2
19
16,95
Elongation at
break (%)
59,9
84,6
72,32
Matter soluble in
Cl2CH2 (% m.s.)
1,6
8
4,42
Chromium
(VI) (mg/kg)
7,8
22
14,3
Tensile strength
(N/mm2)
Elongation at
break (%)
Matter soluble in
Cl2CH2 (% m.s.)
Chromium
(VI) (mg/kg)
15,2
67,8
0,9
6,7
18,9
103,1
4
20,4
17,39
85,92
2,67
12,97
Tensile strength
(N/mm2)
Elongation at
break (%)
Matter soluble in
Cl2CH2 (% m.s.)
Chromium
(VI) (mg/kg)
15,4
67
0,8
4,1
20,4
93
3,5
17,8
18,08
82,5
2,37
10,7
Table 8. Minimum, maximum and average results
of physical-chemical leather analisys
19
7. PHOTO GALLERY
The images that have been collected show the tests (those carried out in the laboratory, and on
a semi-industrial, and pre-industrial scale) conducted during the different stages of the
fatliquoring process: the pH control of the leather in the neutralising stage, colour penetration,
fat fixing, and the draining of the leather hides by hanging them on horses, etc.
Ensayos escala laboratorio: emulsión engrase
Ensayos escala laboratorio: dosificación reactivos
20
Ensayos escala semi-industrial: neutralización
Ensayos escala semi-industrial: tintura y engrase de las pieles.
21
Ensayos escala semi-industrial: aspecto pieles engrasadas
Ensayos escala semi-industrial: aspecto final de las pieles
22
Ensayos escala pre-industrial: control pH
Ensayos escala pre-industrial: dosificación reactivos
23
Ensayos escala pre-industrial: tintura y engrase de las pieles.
24

ECOFATTING Deliverable D5 Action 1-2

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