Vegetable tanning
With the industrial application of chrome tannage rapidly advancing since the end of the last century vegetable tannage has been ousted from its predominant position into second place. Moreover synthetic tanning agents were invented by the condensation of phenols with formaldehyde and further developed with great number of aromatics. In the past decades syntans having very particular properties have been produced. In many cases they improved the vegetable tanning agents in term of tanning techanique and were sometimes even superior. This led to a great number of combinations of vegeatable tanning agents with syntans which modified the tanning methods and also the properties of the leather.
vegetable tanning materials
barks ; momosa mangroves acacia negra eucalyptus pine
wood; Quebracho , chestnut, oak
fruit ; Myrobalans , valonea
leaves; Sumac , gambir
learn online leather production process,leather news and technology .All kind of leather from Pakistan leather hand gloves, leather garments and finish leather in very attractive price. To get working leather gloves made from cow split and fashion hand gloves made from sheep !Contact us irfan_gil@hotmail.com garalaboy86@gmail.com
Saturday, September 12, 2009
Thursday, September 10, 2009
lime stain, lime blast
deposits of insoluble calcium compounds on the skin. Which is caused when skin left carelessly in the open air for too long or indequately covered by the lime liquor. use of water with bicarbonate hardness or free carbonic acid. This problem in leateher causing industrial pollutions.
First an East African update. In early August Burundi introduced an overnight export ban on raw hides and skins with the provision that anyone who builds a tannery will get an export license. The Burundi Ministry of Industry guaranteed only one year ago that it would not repeat the same Rwandan mistake! So much for promises and verbal guarantees but East African countries are notorious for that and recognised as less than reliable up to the inner circles of the EU in Brussels. So in Burundi we now have the same situation as in Rwanda, for exactly the same reasons. The tannery in Burundi was formerly owned by a European company and could theoretically transform all domestic raw hides and skins. It was forced to close in the 1990s due to lack of raw materials. Hence this export ban could secure supplies for the tannery if able to process the available supply. However, like in Rwanda, the local tannery is (as yet) not capable of transforming the available quantity of raw hides and skins. Hence smugglers will have a great time. The sector strategy of these countries makes one wonder where they get their advice from and how much money changes hands in order to get these strategies approved?
During the G8 conference in Japan, the world’s eight most industrialised countries announced that they had agreed to a 50% reduction of atmospheric pollution by 2050. Even if time flies, 2050 is far away and I won’t be around to check.
In a demonstration of democracy G8 also invited Brazil, China and India, recognising those countries that have industrialised tremendously during the last thirty or so years and can, therefore, no longer be considered ‘third world’ or ‘underdeveloped’. All three countries are contributing to a very large extent to global pollution. It is good to remind ourselves that these countries have benefited from massive financial and political help from the West, part of which enabled them to build strategic nuclear capabilities. It is true that in colonial times these countries were robbed blind but the West has paid for this over and again and is still paying in many ways. We invented the General System of Preference which allows entry of processed commodities into the industrialised world without being burdened by an import tax, whereas the same countries were allowed to levy an import tax on Western produced goods. A large number of countries, India, Brazil and China included, levy an export tax on raw materials. We have transferred technology and we have transferred production.
In the leather sector the industrialists in developed countries thought they were clever and ducked the severe effluent laws by doing all the dirty work in developing countries which did not have effluent laws and thus no effluent treatment costs. The developing countries were happy because this created jobs but most of all this created wealth. In fact tanneries in India produce more leather than all of Europe together. This production transfer created also massive pollution and not only in the leather industry. At first everybody was happy and pollution was not an issue. Now it is, and all governments have taken serious and important steps to curb pollution.
Twenty-five or thirty years ago, combating pollution was considered an expensive burden. Now our way of thinking has changed and we are about pollution and accept the costs involved in reducing it. The developed world has achieved a lot. In Germany the Ruhrgebiet, the heart of the country’s heavy industry, was in a similar condition 30-40 years ago to Beijing now. You could hardly see the next block due to the smog. Germany cleaned up its act. So has the whole developed world with only the USA lagging behind because of their sacred bottom line, which does not allow for environmental sacrifices, particularly in an election year. If the US people have started to drive more fuel-efficient cars it is because the petrol price went up, not because they pollute less…. In general however, our mentality has changed over the years. We have smoking bans because we understand that smoking, apart from being dangerous for one’s health, is also an offensive habit to those who don’t smoke. In short we look around ourselves rather than just ahead. Gradually the environment is helped by important new laws, which were unthinkable ten years ago. We know that what pollutes Chinese rivers today will, after some time, pollute the seas 10,000 km away, where we catch our fish. Pollution is not a local problem but a global problem. The radioactive cloud from the Chernobyl accident did not stop at the Ukrainian borders. It went around the globe many times.
We must keep a vigilant eye on what’s going on in other parts of the world and what we see is that ex developing countries are polluting even if, in all fairness, all of them are trying to curb pollution as much as possible, though not willing to make sacrifices in order not to slow down their economies. That’s why India, Brazil, China and others were invited to the G8 conference in Tokyo. I can’t understand why they are not willing to join the G8 anti-pollution recommendations and make the planet a better place to live. Do we have to pay again? Is only the west supposed to make sacrifices and come up (again) with funds to finance effluent plants in developing countries, which take decades to develop and build?
Authorities in Bangladesh, Egypt, Syria and several others have been deciding for years to close existing heavily polluting tannery clusters in their countries and shift the tanneries to newly designated industrial areas. But it’s all talk. No effective action is being taken. Nevertheless the West buys the leather and leathergoods produced in these areas without sanctions, on the contrary, with subsidies in favour of the exporters. That means that the governments in question are in no hurry to clean up their act or, better, the pollution. In present circumstances, therefore, nothing changes for developed developing countries whether they pollute or don’t pollute. Whether they adhere to G8 or not. The developed world pours billions into the developing world. Let’s ask for something in return and not just cheap leather products that kill our homegrown industries.
What I propose is that imports from countries that do not subscribe to the Kyoto Protocol and subsequent amendments should be burdened with an eco tax, which should cover the difference in price between an ecologically responsible manufactured product and the same or similar product without environmental provisions. It will reduce the unfair price difference, and make the product less competitive, hence reduce production and thus pollution. Once pollution is brought under control, then the tax should be reduced in the same proportion as pollution is reduced.
First an East African update. In early August Burundi introduced an overnight export ban on raw hides and skins with the provision that anyone who builds a tannery will get an export license. The Burundi Ministry of Industry guaranteed only one year ago that it would not repeat the same Rwandan mistake! So much for promises and verbal guarantees but East African countries are notorious for that and recognised as less than reliable up to the inner circles of the EU in Brussels. So in Burundi we now have the same situation as in Rwanda, for exactly the same reasons. The tannery in Burundi was formerly owned by a European company and could theoretically transform all domestic raw hides and skins. It was forced to close in the 1990s due to lack of raw materials. Hence this export ban could secure supplies for the tannery if able to process the available supply. However, like in Rwanda, the local tannery is (as yet) not capable of transforming the available quantity of raw hides and skins. Hence smugglers will have a great time. The sector strategy of these countries makes one wonder where they get their advice from and how much money changes hands in order to get these strategies approved?
During the G8 conference in Japan, the world’s eight most industrialised countries announced that they had agreed to a 50% reduction of atmospheric pollution by 2050. Even if time flies, 2050 is far away and I won’t be around to check.
In a demonstration of democracy G8 also invited Brazil, China and India, recognising those countries that have industrialised tremendously during the last thirty or so years and can, therefore, no longer be considered ‘third world’ or ‘underdeveloped’. All three countries are contributing to a very large extent to global pollution. It is good to remind ourselves that these countries have benefited from massive financial and political help from the West, part of which enabled them to build strategic nuclear capabilities. It is true that in colonial times these countries were robbed blind but the West has paid for this over and again and is still paying in many ways. We invented the General System of Preference which allows entry of processed commodities into the industrialised world without being burdened by an import tax, whereas the same countries were allowed to levy an import tax on Western produced goods. A large number of countries, India, Brazil and China included, levy an export tax on raw materials. We have transferred technology and we have transferred production.
In the leather sector the industrialists in developed countries thought they were clever and ducked the severe effluent laws by doing all the dirty work in developing countries which did not have effluent laws and thus no effluent treatment costs. The developing countries were happy because this created jobs but most of all this created wealth. In fact tanneries in India produce more leather than all of Europe together. This production transfer created also massive pollution and not only in the leather industry. At first everybody was happy and pollution was not an issue. Now it is, and all governments have taken serious and important steps to curb pollution.
Twenty-five or thirty years ago, combating pollution was considered an expensive burden. Now our way of thinking has changed and we are about pollution and accept the costs involved in reducing it. The developed world has achieved a lot. In Germany the Ruhrgebiet, the heart of the country’s heavy industry, was in a similar condition 30-40 years ago to Beijing now. You could hardly see the next block due to the smog. Germany cleaned up its act. So has the whole developed world with only the USA lagging behind because of their sacred bottom line, which does not allow for environmental sacrifices, particularly in an election year. If the US people have started to drive more fuel-efficient cars it is because the petrol price went up, not because they pollute less…. In general however, our mentality has changed over the years. We have smoking bans because we understand that smoking, apart from being dangerous for one’s health, is also an offensive habit to those who don’t smoke. In short we look around ourselves rather than just ahead. Gradually the environment is helped by important new laws, which were unthinkable ten years ago. We know that what pollutes Chinese rivers today will, after some time, pollute the seas 10,000 km away, where we catch our fish. Pollution is not a local problem but a global problem. The radioactive cloud from the Chernobyl accident did not stop at the Ukrainian borders. It went around the globe many times.
We must keep a vigilant eye on what’s going on in other parts of the world and what we see is that ex developing countries are polluting even if, in all fairness, all of them are trying to curb pollution as much as possible, though not willing to make sacrifices in order not to slow down their economies. That’s why India, Brazil, China and others were invited to the G8 conference in Tokyo. I can’t understand why they are not willing to join the G8 anti-pollution recommendations and make the planet a better place to live. Do we have to pay again? Is only the west supposed to make sacrifices and come up (again) with funds to finance effluent plants in developing countries, which take decades to develop and build?
Authorities in Bangladesh, Egypt, Syria and several others have been deciding for years to close existing heavily polluting tannery clusters in their countries and shift the tanneries to newly designated industrial areas. But it’s all talk. No effective action is being taken. Nevertheless the West buys the leather and leathergoods produced in these areas without sanctions, on the contrary, with subsidies in favour of the exporters. That means that the governments in question are in no hurry to clean up their act or, better, the pollution. In present circumstances, therefore, nothing changes for developed developing countries whether they pollute or don’t pollute. Whether they adhere to G8 or not. The developed world pours billions into the developing world. Let’s ask for something in return and not just cheap leather products that kill our homegrown industries.
What I propose is that imports from countries that do not subscribe to the Kyoto Protocol and subsequent amendments should be burdened with an eco tax, which should cover the difference in price between an ecologically responsible manufactured product and the same or similar product without environmental provisions. It will reduce the unfair price difference, and make the product less competitive, hence reduce production and thus pollution. Once pollution is brought under control, then the tax should be reduced in the same proportion as pollution is reduced.
Tuesday, September 8, 2009
unic issue social and envirenment decree
The Italian tanners' association UNIC issued a statement at the beginning of September committing their members to social and environmental responsibilities drawn up by the EU to trade unions.
The social and environmental commitment of UNIC (Unione Nazionale Industria Conciaria) Italian tannery members have subscribed to a European agreement with the employee trade unions concerning the respect of human rights in the workplace and the responsible use of natural and environmental resources.
This ‘declaration of social and environmental commitment' is considered as an element of excellence towards consumers in the international market.
Since 1999 UNIC members adopted their own ethical code and they have acquired many certifications for leather quality, environmental and product processing.
Monday, September 7, 2009
color matching control
The appearance of a product has a great deal of influence on the consumer's decision to purchase. A consumer or professional buyer will expect the article and its different components to be homogeneous in their overall appearance. Colour management is a delicate process and requires reliable tools and constants in order to meet the quality levels demanded. In a strong position due to their expertise in vision technology, CTC studied the best performing colorimetric measurement systems for leather and have developed a mechanism/device to automate the batching of pieces of leather for leathergoods.
The pitfalls of colour in leathergoods
Colour is very difficult to pin down: what we see is not always what we think we see; however, what we think we see can be measured. Also, during the manufacture of leather products such as wallets, the management of pieces of the same colour is a delicate stage.
Currently, production workers carry out a visual control of the pieces and samples coming from the cut: the various parts of the neck and body for, say, credit card holders, taking the different substances into consideration.
They ensure that perceived colours match, in order to reassemble the pieces by batch. Over a hundred pieces can be treated at the same time. One must recognise the colour differences between them, ensuring that:
pieces match from one skin to another
pieces from a single skin can be used together
Colour matching in leathergoods is an essential procedure. If pieces have not been matched exactly, a repair may be necessary after assembling the article. This would involve searching the stock for a piece in the appropriate colour.
Furthermore, it can be interesting to control the colour of pieces made in different materials (leather, textile etc) so that once assembled, a multi-material product appears uniform in colour.
Limitations of current controls
This operation is currently carried out manually and by the same person throughout the working day. This control has several limitations:
perception of colour varies between individuals
the human being has poor colour memory
the difficulty of communication on the subject of colour
colour varies according to the light
perception of colour deteriorates with fatigue
Objectives of the project
The project, led by CTC, aimed to validate a method of colorimetric analysis, and then an automatic tool capable of matching pieces of leather or other material, which are to be assembled into one single product.
This system is capable of analysing colour and brilliance of different materials by generating a ‘harlequin' effect1, as well as controlling the presence of metamerism2. This tool is objective, fast, precise and constantly reliable.
Optimal batching for leathergoods
In order to correctly analyse the colour of a leather, CTC opted for a spectrocolorimeter equipped with a sphere of diffusion capable of setting itself free of the texture of the leather and only extracting the information which pertains to the characteristics of colour, which allows the control of different types of materials in a single batch.
The data supplied by the spectrocolorimeter (reflection curve) are not usable in this state to characterise the perceived colour of the sample, so CTC decided to develop two systems which meet differing objectives and costs. A choice can be made between a validation of manual sorting and an automatic batching.
Validation of manual batching: control via CMC sorting
This control is carried out with the help of a portable spectrometer with an integrated sorting programme. This control is traced through the provision of an existing visual control which the operator has introduced a priori to the control. The operator chooses a sample from among a ‘population' which will be referenced as ‘standard' from the batch of pieces which will make up a single product.
Automatically, the system will define an ellipse of acceptability around a point measured in the 3D HSL space (HSL = hue, saturation, luminosity). This space allows us to more easily describe colour using intelligible data.
This ellipse is measureable according to the colorimetric distance tolerated by the client and standardised by the International Commission on Illumination (CIE).
Furthermore, it adapts automatically to the analysed colour as human vision is more sensitive to green than black for example.
The ellipse will be narrower around the point in the green and the tolerance will be more important in the black. Straight away, the operator analyses a second sample which he deems suitable for the batch, and the system indicates whether the sample is in fact acceptable, ie that it is located within the ellipse of acceptability: if so the system displays ‘Good'. If not, it indicates ‘Poor'. The operator repeats this process until a complete batch is obtained.
Furthermore, this method allows us to resolve the problem of a potential repair after the product has been assembled. Even if it is just one piece that has to be replaced, the operator can simply analyse a neighbouring piece from the product and analyse a replacement piece or a skin from the stock which falls within the defined colorimetric distance. Due to the system's portability, this stage is easy to carry out.
Automatic control
In this method, the operator will measure the set of parts of the same colour and the apparatus will automatically sort batches of parts according to the colour parameter. Thus the operator will be able to assemble parts from the same batch without worrying about the colour. The visual matching should be carried out only according to the grain and the brilliance.
a. Optimal method
After having been ‘flashed' with the spectrocolorimetry, all the data on the samples desired are transferred to a computer. The treatment is carried out with a colorimetric software programme developed by CTC, allowing batching of samples according to the number of samples per batch, the light, the colorimetric colour distance parameters tolerated by the client and standardised by the CIE with a management of the harlequins.
This method is awkward because it requires handling samples without automating the station. CTC opted instead for the sorting 555 method which allows the user to obtain a code for each sample after each measurement.
b. Sorting 555
Sorting 555 is a partition of colour distance in a box whose dimensions correspond closely to the colours tolerated by the company. All the samples present in this box are accepted and receive the same colour code.
This method is well suited to the challenges of automatic batching, because the sample's classification code is obtained directly after measurement and thus the colour category of the sample is directly affected. Moreover, by using this method to finish batches we carry out regroupings of boxes, and have a perfect command of the error induced according to the components of bringing together L and a or b.
Promising results
This system also allows us to take into consideration the phenomenon of metamerism which is present on certain leathers, according to the acceptable colour distance under the primary source of light defined by the user (for example D65 ‘daylight'). The system also calculates the colour distance between two samples under a secondary light source (eg F11 flourescent tube') and defines the metamerism as the colour distance under the secondary light source, having restored the colour distance under the primary light source to zero.
The user specifies a variation value of the colour distance between the two defined light sources. A batch may be acceptable under one light source but rejected if the notion of metamerism is taken into account.
The system perfected by CTC allows them to improve the reliability (unchanging to visual fatigue, calibrated daily against a reference slide and integrating all types of lighting into one measure) and the productivity of batching in leathergoods (less than one second for the analysis of a piece).
Understanding colour
A small theoretical detour is essential to understanding what is at stake in the control of colour.
In a human being, the notion of colour is intuitive: it's a phenomenon which is interpreted by the brain of the observer, of an image perceived by the eye. Hence the subjectivity of judgements and the difficulties in communicating about colour. In perceiving a colour, one must analyse three parameters:
The light source
The angle of light source and observer
The object
The observer/receiver
The light source causes colour to vary considerably: fluorescent light in production, daylight, shop lighting...
The object absorbs, diffuses, reflects, diffracts and refracts the light. According to its texture, its relief, its colour and its capacity to reflect, it will resend a spectre of light to the viewer. The viewer or observer picks up this light: it must be calibrated according to the source of light in the scene being observed. And in this case, the calibration of the measuring apparatus will always be easier than that of the human cortex...
Colour is deceptive: subject to interpretation, it varies constantly.
Furthermore, colorimetry provides elements for analysis with the goal of specifying colour, from the starting point of its three constituent parts.
Footnotes
1 The management of harlequins consists in establishing an order of positioning of the samples in a batch according to the increasing colour distance
2 With metamerism, two samples of which the colorimetric distance is acceptable under a given light source (natural light for example) and is not greater under another light source such as a fluorescent tube
Restricted formalin harmful chemical
Formaldehyde is a colorless gas bp -21 degree c. It has an irritating odour. It is extremely soluble in water. Formaldehyde is sold as 40 % aqueous solution under the name FORMALIN and is used in this form for most purposes. Formalin is used as a jeneral aniseptic. In leather industry for good fastness (physical fastness ) property.
Formaldehyde is a chemical compound (also known as methanal) that is widely used in many industries. It is the simplest aldehyde chemically with the formula H2CO. Formaldehyde is a gas at room temperature but it is also readily soluble in water (and is often sold as an aqueous solution).
Areas of application include adhesives, textile processing, as a preservative in some paints, coating products and also in some cosmetics. Formaldehyde is also used in the production of some polymers. When combined with phenol, urea or melamine, formaldehyde produces a hard thermoset resin. It is also used during embalming processes to preserve corpses.
Potential exposure routes for formaldehyde are as wide ranging as smog, cigarettes and tobacco smoke and some household sources such as fibreglass, carpets, foam in cushions, permanent press fabrics, paper products, household cleaners, shampoos, bubble bath, medicines and disinfectants.
Restricted?Why is it
The use of formaldehyde in many construction materials means that it is a common indoor air pollutant. At concentrations above 0.1ppm in air, inhaled formaldehyde can irritate the eyes and mucous membranes, potentially resulting in watery eyes, headache, a burning sensation in the throat, and difficulty breathing. Formaldehyde is also classified as a carcinogen.
How is it relevant to leather?
Historically, formaldehyde has been used as a tanning agent due to its ability to crosslink proteins such as collagen. In addition, it has been used (again historically) to crosslink protein finishes such as casein.
Formaldehyde or materials that are formaldehyde release agents may, however, be used in some areas of tanning, specifically in the production of wet-white, to allow stabilisation prior to splitting or shaving and in the production of syntans.
In modern processing, formaldehyde can be used in the manufacture of certain polymeric-based synthetic tanning agents. Its presence in leather may be as a result of the condensation residue from some synthetic tanning agents.
Theoretically, formaldehyde should be fixed to the collagen during processing (considering that formalin is used as a preservative because of its reactivity with protein). However, some of the reactions used in the preparation of syntans are reversible (eg production of melamine formaldehyde resins). This means that, under certain conditions, it is possible that formaldehyde is liberated. Also oxidisation of oils/fats can result in formaldehyde formation.
Practical advice on avoiding formaldehyde formation (as determined by the current industry test methods) includes:
Careful management of formaldehyde releasing compounds, for example:
- Aldehyde tanning agents
- Formaldehyde resin retannages
- Preservatives (formaldehyde can sometimes be used as a preservative in processing chemicals)
The use of oxidisable oils should be carefully controlled as these can oxidise on exposure to air, moisture and heat, resulting in possible formaldehyde formation.
Adding reducing agents to the float (such as sodium metabisulfite) may help avoid formaldehyde liberation.
What is the legislation?
Restricted substance legislation is highly variable depending upon the final application of the leather in the product and the target user. Also there are considerable variations in legislation depending on the country where the leather or product is manufactured or sold. It is one of the key examples of how variable the restrictions can be.
Within Europe there is no general legislation that limits the presence of formaldehyde in leather. There are some individual countries that have restrictions on its presence in consumer products and formaldehyde is restricted within the recently published EN71-9 Toy standard. Various Eco-labels require that levels of formaldehyde are determined and the automotive industry tends to have quite strict limits on formaldehyde release from car interior materials. Table 1 lists some of the limits currently in place for formaldehyde. In addition to these restrictions on the extractable levels of formaldehyde present in leather, there are also some Eco-labels (Blue Angel for example) that have restrictions on the volatile formaldehyde released from leather and products.
BLC guidelines state that leathers should contain no more than 200ppm of formaldehyde for articles in general use. If the item is in direct skin contact this should be 75ppm, and 20ppm for items used by babies (<36>Methods of analysis
There are three separate methods used in the leather industry for the analysis of formaldehyde. Their application depends on the final use of the product along with the technical level of the laboratory carrying out the analysis. The most commonly used methods for analysis are described in CEN ISO TS 17226. This has two parts: a colorimetric method and an HPLC method.
Colorimetric method: This involves a colorimetric determination of the extractable formaldehyde. The leather is extracted at 40°C, after which the extract is treated with acetyl acetone. A yellow compound (3,5-diacetyl-1,4-dihydrolutin) is formed in the presence of formaldehyde, which is quantified photometrically at 412nm. Within this method there is a check to determine the presence of other compounds that may result in a coloured compound when reacted with acetylacetone. This involves addition of Dimedone to the extract prior to addition of the acetylacetone. If the resulting solution has an absorbance in excess of 0.025 (for a 1cm cell) there is the possibility of a false positive result being obtained.
HPLC method: This is based on determining the extractable formaldehyde using high performance liquid chromatography (HPLC). The formaldehyde is extracted at 40°C, after which the extract is reacted with 2,4-dinitrophenylhydrazine (DNPH). The resulting extract is then separated using HPLC, with UV detection at 350nm.
The CEN and ISO committees responsible for these methods are currently in the process of converting them to become full standards. When complete they will be referenced as EN ISO 17226-1 and EN ISO 17226-2. Part 1 is the HPLC method and will include a statement to the effect that this is the more reliable technique to be used in any case of dispute. This is due to the potential for interference and false positive results that may occur with a colorimetric analysis.
Also used in the leather industry but to a lesser extent is the Japanese method JIS L 1041 - 1983 (revised 1994). This is similar to the colorimetric method listed in CEN ISO TS 17226, with some modifications to the extraction procedure.
In addition, the automotive industry uses a separate analysis based on a headspace extraction technique. Within this method the sample is suspended in a sealed container over a defined amount of water. After heating, any formaldehyde liberated by the leather should be dissolved in the water. This resulting solution is then analysed colorimetrically. Acceptable limits as analysed by this method are typically 10ppm.
Conclusions
Testing of formaldehyde in consumer products is not straightforward. Even within a single material, such as leather, there are several testing methods that can be applied. Different materials (such as wood, cosmetics and textiles) will also have their own test methods that are appropriate. In addition to the complexity of the testing, there is also the variability in legislation and regulations that affect the products. BLC is able to offer support and advice to customers who have concerns about the presence of formaldehyde in their products
Formaldehyde is a chemical compound (also known as methanal) that is widely used in many industries. It is the simplest aldehyde chemically with the formula H2CO. Formaldehyde is a gas at room temperature but it is also readily soluble in water (and is often sold as an aqueous solution).
Areas of application include adhesives, textile processing, as a preservative in some paints, coating products and also in some cosmetics. Formaldehyde is also used in the production of some polymers. When combined with phenol, urea or melamine, formaldehyde produces a hard thermoset resin. It is also used during embalming processes to preserve corpses.
Potential exposure routes for formaldehyde are as wide ranging as smog, cigarettes and tobacco smoke and some household sources such as fibreglass, carpets, foam in cushions, permanent press fabrics, paper products, household cleaners, shampoos, bubble bath, medicines and disinfectants.
Restricted?Why is it
The use of formaldehyde in many construction materials means that it is a common indoor air pollutant. At concentrations above 0.1ppm in air, inhaled formaldehyde can irritate the eyes and mucous membranes, potentially resulting in watery eyes, headache, a burning sensation in the throat, and difficulty breathing. Formaldehyde is also classified as a carcinogen.
How is it relevant to leather?
Historically, formaldehyde has been used as a tanning agent due to its ability to crosslink proteins such as collagen. In addition, it has been used (again historically) to crosslink protein finishes such as casein.
Formaldehyde or materials that are formaldehyde release agents may, however, be used in some areas of tanning, specifically in the production of wet-white, to allow stabilisation prior to splitting or shaving and in the production of syntans.
In modern processing, formaldehyde can be used in the manufacture of certain polymeric-based synthetic tanning agents. Its presence in leather may be as a result of the condensation residue from some synthetic tanning agents.
Theoretically, formaldehyde should be fixed to the collagen during processing (considering that formalin is used as a preservative because of its reactivity with protein). However, some of the reactions used in the preparation of syntans are reversible (eg production of melamine formaldehyde resins). This means that, under certain conditions, it is possible that formaldehyde is liberated. Also oxidisation of oils/fats can result in formaldehyde formation.
Practical advice on avoiding formaldehyde formation (as determined by the current industry test methods) includes:
Careful management of formaldehyde releasing compounds, for example:
- Aldehyde tanning agents
- Formaldehyde resin retannages
- Preservatives (formaldehyde can sometimes be used as a preservative in processing chemicals)
The use of oxidisable oils should be carefully controlled as these can oxidise on exposure to air, moisture and heat, resulting in possible formaldehyde formation.
Adding reducing agents to the float (such as sodium metabisulfite) may help avoid formaldehyde liberation.
What is the legislation?
Restricted substance legislation is highly variable depending upon the final application of the leather in the product and the target user. Also there are considerable variations in legislation depending on the country where the leather or product is manufactured or sold. It is one of the key examples of how variable the restrictions can be.
Within Europe there is no general legislation that limits the presence of formaldehyde in leather. There are some individual countries that have restrictions on its presence in consumer products and formaldehyde is restricted within the recently published EN71-9 Toy standard. Various Eco-labels require that levels of formaldehyde are determined and the automotive industry tends to have quite strict limits on formaldehyde release from car interior materials. Table 1 lists some of the limits currently in place for formaldehyde. In addition to these restrictions on the extractable levels of formaldehyde present in leather, there are also some Eco-labels (Blue Angel for example) that have restrictions on the volatile formaldehyde released from leather and products.
BLC guidelines state that leathers should contain no more than 200ppm of formaldehyde for articles in general use. If the item is in direct skin contact this should be 75ppm, and 20ppm for items used by babies (<36>Methods of analysis
There are three separate methods used in the leather industry for the analysis of formaldehyde. Their application depends on the final use of the product along with the technical level of the laboratory carrying out the analysis. The most commonly used methods for analysis are described in CEN ISO TS 17226. This has two parts: a colorimetric method and an HPLC method.
Colorimetric method: This involves a colorimetric determination of the extractable formaldehyde. The leather is extracted at 40°C, after which the extract is treated with acetyl acetone. A yellow compound (3,5-diacetyl-1,4-dihydrolutin) is formed in the presence of formaldehyde, which is quantified photometrically at 412nm. Within this method there is a check to determine the presence of other compounds that may result in a coloured compound when reacted with acetylacetone. This involves addition of Dimedone to the extract prior to addition of the acetylacetone. If the resulting solution has an absorbance in excess of 0.025 (for a 1cm cell) there is the possibility of a false positive result being obtained.
HPLC method: This is based on determining the extractable formaldehyde using high performance liquid chromatography (HPLC). The formaldehyde is extracted at 40°C, after which the extract is reacted with 2,4-dinitrophenylhydrazine (DNPH). The resulting extract is then separated using HPLC, with UV detection at 350nm.
The CEN and ISO committees responsible for these methods are currently in the process of converting them to become full standards. When complete they will be referenced as EN ISO 17226-1 and EN ISO 17226-2. Part 1 is the HPLC method and will include a statement to the effect that this is the more reliable technique to be used in any case of dispute. This is due to the potential for interference and false positive results that may occur with a colorimetric analysis.
Also used in the leather industry but to a lesser extent is the Japanese method JIS L 1041 - 1983 (revised 1994). This is similar to the colorimetric method listed in CEN ISO TS 17226, with some modifications to the extraction procedure.
In addition, the automotive industry uses a separate analysis based on a headspace extraction technique. Within this method the sample is suspended in a sealed container over a defined amount of water. After heating, any formaldehyde liberated by the leather should be dissolved in the water. This resulting solution is then analysed colorimetrically. Acceptable limits as analysed by this method are typically 10ppm.
Conclusions
Testing of formaldehyde in consumer products is not straightforward. Even within a single material, such as leather, there are several testing methods that can be applied. Different materials (such as wood, cosmetics and textiles) will also have their own test methods that are appropriate. In addition to the complexity of the testing, there is also the variability in legislation and regulations that affect the products. BLC is able to offer support and advice to customers who have concerns about the presence of formaldehyde in their products
sweaty foot fill gap footwear comfort
one of the most important requirment of leather footwear is its resistance to sweatif it is sweatless it become comfortableAs part of its comprehensive comfort testing programme (which includes advanced moisture management test AMMT, and whole shoe thermal insulation test WSTIT), Satra Technology Centre, located in the UK, have designed and created a new small size 'sweating foot' component to meet growing demand to test women's and children's footwear for breathability and comfort.
The new moulded foot is based on a UK size four foot and considerably enhances the testing facility. Since introducing the comfort testing programme, it has been used continually to help manufacturers across the world develop footwear that remains dry and performs at a comfortable temperature.
By using a heated and 'breathing' foot form to simulate a realistic in-shoe environment, AMMT effectively creates a picture of how much sweat has been absorbed into each part of the footwear system and how much has permeated to the atmosphere. Based on the results, a manufacturer is better placed to make a decision on whether or not to make adjustments to footwear design and the materials used in production.
Satra's comfort testing equipment has been using foot forms in UK sizes seven and nine to arrive at findings to cover most of the adult market; the new size four foot will allow clearer insight for product aimed at the children's and part of the women's market.
Data from testing can be used to monitor and improve sweat management and thermal properties in all types of footwear including sports, performance, outdoor and industrial, as well as everyday shoes. Satra also uses its own climate chambers for the testing of performance and comfort properties of footwear.
Saturday, September 5, 2009
leather from Pakistan cheap and good quality leather
we are the producer of gloves leather of all kind. Working gloves and winter wearing gloves in all color range and also in pure white crust. Leather garment of all quality and fashion range available here.
To purchase our product or get sample for check contact us
we will provide you complete information about our products
Subscribe to:
Posts (Atom)