July 16, 2018

Basic tanners process

In order to have a beautiful leather product, skilled tanning workers need to go through a lot of complicated stages. 


Products such as leather handbags, leather belts, leather shoes, leather clothes, etc., have to go through hundreds of stages of processing from raw materials to finished production. However, for tanning, it is divided into 3 main stages as follows: 

+ Prepare 

+ Tanning 

+ Edit and finish


1- Preparation: 

It is the first stage in the tanning process. At this step the goal is to type all the excess components (unnecessary) when giving a skin product, which are connective tissue, epidermis, substances that can easily be decomposed by bacteria ..., create a link between tanning with collagen fibers during tanning stages. 


All skin before tanning must be classified carefully according to categories, mass size, own nature ... to have preservation methods and processing mode suitable for each type. 


Steps in tanning preparation may vary, depending on raw materials, preservation methods and finished skin use purposes. 


Basic stages to prepare include: humidifier, soaking lime, hair removal, liming, softening by acidification are applied to all methods. If the skin is used in industry, softening and acidification stages do not perform or perform at a mild level. 


a. Moisture (fresh recovery):


- The purpose of moisture is to restore the amount of water in the skin lost due to the preservation process (from 35-45% to 60-70% for salt preserved by salt and reduced to 18% -50 % for skin preserved drying), which means making skin fiber structure back to the almost original state. 


-With leather preserved by drying method, it's more difficult to make suitable moisture than salt methods. Therefore, the humidifier is mainly sensory, satisfactory when fur is soft enough. 


-The fresh recovery time will make bacteria grow and cause skin damage due to a part of collagen in the skin to be decomposed, so pay attention to the time during this period. 


- In addition, temperatures in this stage are very important to prevent bacteria, preferably 26-27 degrees C.


b. Hairy, soaking lime: 


- Purpose: Remove fur, epidermis and subcutaneous fat. This stage is quite complicated, lime hair removal chemicals have the effect of destroying the pores and epidermis on the skin simultaneously making skin blooming, so it is necessary to have strict control of the use of chemicals, water, temperature, time. 


- In the process of hair removal, soaking lime, sunfuanaturi alkaline solution plays an important role to clean hair and pores. Conventional pH is 12 - 13. 


- Today with modern tanning techniques, soaking lime is conducted in foulons at a speed of 3-4 rpms / minute, time is 12-18 hours and needs to be every 10 minutes / hour so that the skin absorbs solutions. 


- Washing skin with water will create on the skin surface of the CaCO3 layer into a poor quality skin, so when washing it requires an additional 0.5% of the amount of lime compared to the amount of skin to avoid reducing skin quality.  


- Lime-soaked hair: performed in foulons, water weight and chemicals calculated according to the appropriate amount of skin, turned during 12 hours-24h 


c. Slim thin: 


- Thin leathers are done on a dedicated sawn machine for an equal thickness according to the required use. 


For example, the skin after soaking lime with a thermal thickness is 4 mm, the following is 2.8 mm, after the cell is 2.6 mm and the skin is 2.3 mm thickness. 


d. Lime, softening: 

After removing lime hair, alkaline chemicals in the skin should be removed, otherwise they will affect the quality of the skin (chromium and even herbs). 


- Cleaning lime and softening is usually conducted in foulons, the softening process is conducted after removing lime removes alkaline chemicals in the skin, increasing skin quality. 


- Foulons are currently often used to higher speeds of rotary barrels to recover fresh and remove, to improve the bleaching. Depending on the item, lime removal can use different components. 


- Softening: is to create a smooth skin. Softening components will work on unstructured collagen such as elastic fibers that increase the softness, the elasticity of the surface, this is useful for chromium leather - leather belt, leather wallet , leather bags, leather bags, gloves, cushioning; But do not be applied to skin types for shoe base, skin used for industry. 


-The softening process is done in the same foulons used to remove lime and in a tank of lime eraser. Temperature and time factors are important for softening, an optimal process of 37 degrees Celsius, because this temperature is suitable for ferment; The pH also plays an important role, the optimal pH is 8.3. The softening time must be suitable, if too long will reduce the durability of the skin.


- Methods to check the softeneration process by folding the skin and squeezing to let the air bubbles go through. 


2 - Tannery: 

Tanning is the process through which animal skin is transformed into leather with its optimal characteristics such as high temperature resistance, not rotting when exposed to water and other environments, withstanding the effectiveness of microorganisms and has high air permeability. 


Potassium Bicrome (K2CR207): is commonly used chemicals for tanning 


- People use different neutralization components, their alkali-aliensurist effects increase slowly such as mogrigan mog, dolomite minerals. 


-Next steps, we need to check the penetration of acidification, test temperature and pH. 


For alum skin, it is necessary to use anti-landmarks to room, usually 0.3-0.5% Preventol WB. 


3 - Editing and finishing the skin: Leather after moisture is very high 60-65%, therefore it is not flexible, rough surface and water absorption. So after it is necessarily through the processing stage. 


This is the stage of skin modifying, grooming to finished skin, quality, satisfactory, for the right use. 


After completing the stages from the production facility, the skin is taken to the leather shoe processing factory, leather belts, leather wallets, leather clothes, pairs of leather bags ... to create products that meet market needs . 


Source: Captuida.vn


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