Dyeing and Finishing - Testex

testextextile — Tue, 23 Jan 2024 03:25:28 +0000

Have you ever stared confused at an ingredient list on a clothing tag wondering what cryptic chemical is used to achieve that vibrant red? Or scoured the labels trying to figure out why some tees retain their color season after season while others fade to pale remnants after a few washes? Well, I’m about to decode the secrets clothing makers use to work their color magic so they withstand the test of time. In this article, we infiltrate the hidden world inside textile dyeing laboratories where shades are born before they hit retail stores. I’ll be your top-secret guide into this obscure, high-security facility few outsiders ever witness first-hand, especially the working process of dyeing labs. We’ll uncover complex industrial techniques even insider chemists find bewildering like spectral fingerprinting, computer predictive modeling, and ingenious chemical tweaks that trick fibers into absorbing more color than should be possible! So let’s sneak a peak into the color science transforming textile manufacturing as we know it! This shadowy field could redefine fashion as fundamentally as the loom and spinning wheel did in their era.

Chapter 1: Critical Role of a Dyeing Facility

While apparel design studios and fashion runways bask in the spotlight, few recognize the silent partner that transforms their imaginative creations into wearable reality. Yes, I’m referring to the dyeing facility which specialty colors yards of fabric based on a designer’s vision. Let’s briefly touch upon 5 key roles played by a textile dyeing lab:

Optimizing Dye Use

Carefully engineering the optimum combination of dyes, chemicals, and auxiliaries for reproducing a color with minimal processing costs

Upscaling New Shade Recipes

Taking a lab color recipe and adapting practices to seamlessly transfer onto factory floor bulk machinery

Ensuring Consistent Quality

Implementing process controls and testing protocols so that production runs deliver uniform coloring meeting all specifications

Validating Eco Compliance

Testing and certifying that colorant chemistry and effluents meet stringent quality, safety, and environmental norms

Building Process Knowledge

Accumulating technical knowhow on dye selection, application procedures, and issue resolution for continuous improvement net As you can see, a dyeing facility is the bridge between inspiration and production. Balancing creativity on one end and quality compliance on the other involves considerable behind-the-scenes effort. Now that we know why dyeing labs matter, let’s get into specifics of their workspace and tools of the trade!

Chapter 2: Key Areas and Equipment in a Dyeing Lab

A large dyeing facility comprises multiple specialized zones such as:

Incoming Material Inspection

Here, suppliers�?deliveries of fabrics and dyes undergo tests to ensure they meet trade quality standards related to composition, strength, color, etc.

Computer Color Matching

The heart of the facility contains software tools, spectrophotometers, and scientific techniques for predicting dye mixes to match color targets and tolerance checks after trials.

Wet Processing Hall

Where substrate preparation, continuous fabric dyeing at longer lengths, and post-treatment happen with the aid of specialized high-production machinery to mimic factory environments.

Sample Dyeing Room

Smaller instruments that handle yarn, fabric swatches, and tests related to lab dip color matching, fastness properties evaluation, and physical and chemical testing. Among the diverse equipment found here, let me call out some interesting ones:

GYROWASH �?a high-speed instrument that performs wash, rinse, and drying cycles on fabric specimens as per apparel/home laundering conditions CROCKMETER �?employs a rubbing action on dyed fabrics to assess the potential for color loss during everyday friction/abrasion

SPECTRA LIGHT BOOTH �?contains special lights spanning the solar spectrum for color matching with illumination representing consumer usage

INKJET PRINTER �?directly prints dye or pigment-based colors onto substrate offering flexibility of design compared to conventional dyeing

GSM CUTTER �?accurately cuts fabric swatches of specified area for determining key properties like grams per square meter or ends per inch

Now that we know the landscape and tools, we’re ready to immerse in the actual dyeing workflow. Let’s get our hands dirty!

Chapter 3: Step-by-Step Workflow in a Dyeing Lab

Each assignment in the lab flows through a sequential procedure personalized to the customer’s needs:

Step 1 – Substrate Analysis

Incoming fabric properties like fiber type (wool, cotton, polyester, etc), yarn thickness, construction style (knitted, woven, non-woven), weight, weave pattern, and pre-treatment are assessed.

Step 2 – Dye Selection

Based on substrate and fastness expectations (crocking, light exposure, etc), the appropriate dye type and application class is chosen �?sulfur, azoic, reactive, disperse, cationic, etc.

Step 3 – Recipe Prediction

A small fabric swatch is analyzed using spectral data and sensor techniques to generate a putative dye/chemical formula for achieving the same color.

Step 4: Lab Trial

The computer-suggested recipe is manually prepared, applied on the substrate via a suitable dyeing machine, and assessed after post-treatment through visual examination and instrument verification.

Step 5 – Batch Creation

If the lab trial clears all quality checks, bulk quantities of selected dyes, auxiliaries, and substrates are weighed/set up on factory floor machinery for larger production.

Step 6 �?Continual Monitoring

During extended runs, parameters like liquor temperature, pH, flow rate, mechanical agitation, etc are monitored to minimize color variation across thousands of meters. As evident, transitioning a color inspiration into a consistently reproducible reality involves considerable science and artisanship. Both human expertise and automation combine for a results synthesis that balances creativity with compliance. Now that you know the method, let me share a real-world dye selection scenario our colorists handle.

Chapter 4: Expert Technique – Judicious Dye Selection

While common perception associates dyeing with creativity, considerable logical thinking goes into choosing the right colorant type. Let me illustrate with two examples:

Polyester Dyeing Scenario

For coloring polyester fabrics, dispersed dyes get selected due to polarized structure enabling desired migration and bonding. Comparatively, reactive or sulfur dyes lack substantive power leading to unsatisfactory shade depth despite higher application concentrations.

Wool Dyeing Situation

The isotropic wool fiber matrix allows both acidic and reactive dye classes to deliver vibrant colors. But factors like lightfastness, penetration kinetics and batch-to-batch reproducibility make acid dyes the prudent primer choice before considering next-gen variants. I share these real-world dye selection stories to highlight that while the end objectives of a textile technologist and fashion designer converge, the underlying thought process differs significantly. Imagination guides initial creation whereas scientific rigor transforms those nascent ideas into practicality! Let me give you a peek into an even more intricate procedure �?computer color matching.

Chapter 5: Computer Color Matching System

Among recent advancements that enhanced precision, automation, and objectivity, computer color matching (CCM) systems stand tall. The high-tech color measurement and formulation techniques not only improve reproducibility but also eliminate human errors and subjective bias that inevitably creep in during visual color matching. But how does CCM work? Let’s dive deeper. The core principle lies in quantifying colors based on their unique visible light reflectance signature or fingerprint. It comprises these key steps:

Step 1: Data Acquisition

The spectrophotometer captures the spectral reflectance curve of the fabric swatch target color and converts light signals into digital readings across wavelength bands.

Step 2: Prediction Logic

Complex software models containing calibration data on dye absorption behavior calculate a putative recipe that theoretically matches standard sample readings when combined.

Step 3: Lab Trial

The computer-suggested formulations are physically dyed on specified material at pilot scale for creating the test color sample.

Step 4: Result Comparison

Reflectance data of lab-dyed and original standard fabric are statistically analyzed with permissible ΔE divergence.

Step 5: Iteration or Batch Release

If the difference metric exceeds the cut-off, the recipe gets further optimized. For confirmation batches, bulk production gets approved. While seemingly straightforward, considerable mathematics, physics, and chemistry manifest delivering this digital mimicry. Let’s look at an example highlighting its benefits.

CCM Benefits

Shifting from manual color matching to a CCM system for evaluating polyester lab dips yields some insightful outcomes: – Objective repeatability improved as human biases were eliminated – Enhanced color differentiation led to matching shades earlier deemed impossible – 15-20% savings in dyestuff and auxiliaries translated into a better environmental footprint The merits of scientific pigmentation shine through here! With CCM adoption expanding, I foresee dyeing labs transforming from experience-driven facilities to data-powered think tanks shortly!

The Future of Textile Dyeing Labs

We covered tremendous ground unpacking the workings of modern textile dyeing laboratories. Before we sign off, here is my projection on upcoming technologies and trends likely to reshape this color-critical industry:

Artificial Intelligence

AI-based cognitive models will take the baton from existing CCM systems reaching new heights in predictive accuracy.

Automation

Human-free robotic dye selection, preparation, dispensing, and quality testing will manifest through advanced AI and mechanical engineering working in tandem.

Augmented Reality

AR tools enabling real-time remote color collaboration between designers, dyeing technicians, and factory personnel will emerge as the new normal. I can envisage these innovations enabling customization, hyper-flexibility, and democratization at a scale unimaginable in today’s ecosystem.

If you found this behind-the-scenes dyeing lab expedition insightful, stay tuned for more as I track exciting developments from the cutting edge of textile science innovation. Until next time, take care!

The post The Working Process of Dyeing Lab first appeared on Testex.

The post The Working Process of Dyeing Lab appeared first on Testex.

Dyeing and Finishing - Testex

testextextile — Tue, 16 May 2023 07:09:50 +0000

The textile industry heavily relies on dyeing processes to add vibrant colours and patterns to various fabrics. Dyeing machines play a crucial role in achieving consistent and high-quality results. Among the different types of dyeing machines available, infrared (IR) lab dyeing machines have gained popularity due to their efficiency and versatility. In this article, we will explore the factors to consider when selecting an IR lab dyeing machine, their advantages and limitations, common applications, maintenance tips, and cost considerations.

Introduction
Dyeing machines are essential equipment in textile laboratories and production facilities, enabling efficient and controlled dyeing processes. IR lab dyeing machines, in particular, utilise infrared radiation to transfer heat energy and enhance the dye absorption by the fabric or yarn. By understanding the key factors to consider when choosing an IR lab dyeing machine, textile professionals can make informed decisions to optimise their dyeing processes.

How does an IR dyeing machine work?
The working principle of an IR dyeing machine is based on the use of infrared radiation to facilitate the dyeing process. IR radiation, with its longer wavelength, is capable of penetrating the fabric and transferring heat to the dye bath. This heat transfer helps activate the dye molecules, resulting in a faster and more efficient dyeing process compared to conventional methods.

Factors to Consider When Choosing an IR Lab Dyeing Machine Capacity and Sample Size: Determine the volume of fabric you will be dyeing and ensure the machine can handle the required capacity. Consider the sample size options available to meet your specific needs. Temperature and Pressure Control: Look for an IR lab dyeing machine that offers accurate temperature and pressure control. This ensures optimal dye penetration and colour consistency throughout the fabric. Material Compatibility: Different fabrics may require specific dyeing conditions. Ensure the machine can accommodate the materials you work with, such as natural fibres, synthetic fibres, or blends. Programmability and automation: Opt for a machine that provides programmable features and automation options. This allows for precise control over dyeing parameters and reduces human error. Energy Efficiency: Consider the energy consumption of the machine. Energy-efficient models can help minimise operating costs and reduce environmental impacts. Ease of Use and Maintenance: Choose a machine that is user-friendly and easy to maintain. Look for features like intuitive interfaces and easily accessible components for hassle-free operation and upkeep. Available Features and Accessories: Evaluate the additional features and accessories offered by the machine. Features like pre-wash cycles, dosing systems, and customizable dyeing programmes can enhance efficiency and flexibility. Reputation and Support from the Manufacturer: Research the manufacturer’s reputation in the industry. Look for a company known for producing reliable and durable equipment along with excellent customer support. Top 3 IR Lab Dyeing Machines RHS series IR lab dyeing machine

Introduction
IR lab dyeing machine stands for infrared laboratory sample dyeing machine. The machine got its name due to the use of infrared heating for heat transmission. It’s suitable for dyeing knitted fabric, woven fabric, yarn, cotton, fibre, zippers, shoes, and so on. The machine is not only suitable for high-temperature dyeing but also works for washing fastness tests. This can be said to be very practical dye lab equipment.

Feature
Used for textile dyeing samples at laboratory scale.
Used to determine the standard of colorfastness to washing.
Heater infrared system.
Removable dye temperature sensor for ease of use.
High temperature accuracy requires a minimal dyeing temperature set of not less than 135°C.
Programmable microprocessor controller to set parameters such as temperature and time (with capacity to store such parameters).
touch-screen LCD monitor that displays conditions or parameters such as desired dyeing parameters, programmed temperature, actual parameters during the process, a graphical representation of temperature, and dyeing process duration.
There is a mounting bracket for the dye cylinders that rotates around the main horizontal shaft of the machine. The brackets must be able to accommodate 24 cylinders of 150 ml, 6 cylinders of 300 ml, and 6 cylinders of 500 ml (without changing mounting apparatus).
Air cooling circulation system.
There is a container (basket) for cylinders for proper storage.
The machine must be made of non-corrosive, non-scratchable, non-corrosive material. The door must be transparent so the dyeing process can be observed.
Wheels attached to the machine for mobility.
There is a safety sensor to stop the machine or process when the machine door is open.
There is an automatic warning system and an alarm when the process is completed.

ACCDYER series lab dyeing machines This type of lab dyeing machine has “built-in electric heating” and “built-in oil heat conduction” equipment with a number of patents. It has all the advantages of “oil thermal conductivity”, but also has the characteristics of simple operation, energy savings, accurate temperature control, a very low bath ratio, and the ability to dye large volume samples. The labrotory sample dyeing machine has been recognised as a really perfect and practical piece of dyeing lab equipment by the majority of users since its birth.

Characteristic
Energy savings and environmental protection

The maximum power consumption is 2 KW, and air cooling is used for cooling. Strong and durable The whole machine is made of stainless steel. More over, it has a self-return cup buckle that can be operated with one hand. Accurate temperature control Built-in oil thermal conductivity to achieve an accurate temperature control effect with very good consistency and reproducibility. Unlimited test Different bath ratios and different bath quantities can be tested in the same batch or separately at any time. All-in-one Temperature control ranges from room temperature to 135 °C, which is common at room temperature and high temperatures. What’s more, it can do constant temperature samples and temperature control tests. Low bath does not spend Bath ratio can be low to 1:5, and it is also not easy to colour flower. Dye up to a 50-gramme sample (500 CC dye cup). Simple installation Connect to a household single-phase 220V power supply for use. Security Double overtemperature protection. Specifically, computer overtemperature alarms and overtemperature power off protection Good compatibility Optional dosing cup lid for multiple dosing Implement accurate process tests. Intelligent centralised control The computer can be connected to centralised dyeing control. So that it can be used to realise intelligent and informationized dyeing of sample samples. TesTex- IR Lab Dyeing Machine TD130 The TD130 Lab Dyeing Machine, also known as the Sample Dyeing Machine TD130, is specifically designed for conducting high-temperature sample dyeing tests on various materials such as knitted fabric, woven fabric, yarn, cotton, fiber, zipper, and shoe material mesh fabric. The use of this laboratory sample dyeing machine in textile workshops helps improve the success rate of dyeing, which directly impacts three crucial factors: factory efficiency, quality, and cost. TESTEX, a lab dyeing machine manufacturer with over 10 years of experience, has established strong partnerships with dyeing labs in 42 countries. We currently offer a range of sample dyeing machines for sale. Key Features of the TD130 IR Lab Dyeing Machine: Effective color consistency: The machine utilizes specific wavelength infrared heating to ensure even warming of the dyeing solution in the test cup, thereby eliminating color discrepancies caused by temperature variations in traditional small infrared sample dyeing machines.

Enhanced dyeing accuracy: Equipped with a precision heating system and fully automatic computer control, the machine allows clockwise and anticlockwise rotation of the cup, with adjustable speed, resulting in more precise sample dyeing.
Significant energy savings: The machine consumes low power, eliminating the need to purchase glycerin and reducing costs. Additionally, it operates without producing oil or smoke, making it energy-efficient and environmentally friendly.
Simultaneous multiple staining: The machine offers 24 positions, enabling the application of multiple staining solutions at the same time.
Programmable computer system: The dyeing process is controlled by a programmable computer system, capable of saving up to 99 different processes. It displays important parameters such as temperature, time, process number, and temperature curve. The system also features an imported high-precision PT-100 temperature probe, which directly monitors the actual temperature of the dyeing liquor, enabling automatic heating and cooling.

Applications of the TD130 IR Lab Dyeing Machine: A sampling machine for dyeing is designed to quickly create dyeing samples at a reduced cost. Textile manufacturers require lab dyeing machines to minimize dyeing errors before carrying out large-scale production. Additionally, fabric dyeing laboratories utilize these machines for research purposes. To obtain accurate dyeing results, dyeing lab testers often need to add auxiliaries when the temperature reaches 80 degrees. Many IR sample yarn dyeing machine systems use syringes to add liquid quickly, which can lead to inaccuracies. However, the TESTEX TD130 IR high-temperature laboratory dyeing machine offers a different approach. It allows users to slowly add liquid to the assistant beaker located on top of the lid. The liquid then gradually flows through small holes in the lid into the main beaker, simulating the actual dyeing process. This controlled liquid addition method ensures accurate simulation of the dyeing process in textile labs.

Types of IR Lab Dyeing Machines
There are different types of IR lab dyeing machines available, each utilising a specific range of infrared radiation. Understanding these types can help in selecting the most suitable machine for your specific dyeing requirements.

Infrared Dyeing Machines
Infrared dyeing machines use a broad spectrum of infrared radiation to heat the samples. They are versatile and can be used for a wide range of fabric types. These machines provide uniform heating and efficient dye penetration, resulting in vibrant and even colours.

Near-Infrared Dyeing Machines
Near-infrared dyeing machines utilise a specific range of near-infrared radiation for heating purposes. They are known for their fast heating capabilities, reducing the overall dyeing time. Near-infrared radiation is absorbed by water molecules, making these machines particularly efficient for water-based dyeing processes.

Far-infrared dyeing machines
Far-infrared dyeing machines utilise far-infrared radiation for heating. They offer gentle and controlled heating, making them suitable for delicate fabrics and heat-sensitive materials. Far-infrared radiation promotes deep dye penetration while minimising the risk of damage to the fibres.

Advantages of IR Lab Dyeing Machines
IR lab dyeing machines offer several advantages over traditional dyeing methods. Understanding these benefits can help justify the investment and improve overall dyeing efficiency.

Faster Dyeing Process
IR lab dyeing machines provide faster dyeing processes compared to conventional methods. The efficient transfer of heat energy through infrared radiation speeds up dye absorption, reducing the overall processing time. This allows textile professionals to increase productivity and meet tight deadlines.

Energy Efficiency
Energy efficiency is a significant advantage of IR lab dyeing machines. By utilising targeted heat transfer through infrared radiation, these machines minimise heat loss and reduce energy consumption. This not only saves operational costs but also contributes to sustainability by reducing the carbon footprint.

Improved Dye Penetration
IR lab dyeing machines promote better dye penetration into the fabric or yarn. The infrared radiation penetrates the material, enhancing the absorption of dye molecules. This results in vibrant and long-lasting colours with excellent colorfastness properties.

Reduced water consumption
Traditional dyeing methods often require a significant amount of water for rinsing and washing processes. IR lab dyeing machines, on the other hand, can minimise water consumption. The efficient heat transfer reduces the need for excessive rinsing, leading to water savings and environmental benefits.

Common Applications of IR Lab Dyeing Machines
IR lab dyeing machines find applications in various dyeing processes across the textile industry. Here are some common areas where these machines are utilised:

Yarn Dyeing
IR lab dyeing machines are commonly used for dyeing yarns. Whether it’s natural fibres like cotton or synthetic fibres like polyester, these machines offer efficient and uniform dye penetration, resulting in vibrant and evenly coloured yarns.

Fabric Dyeing
Fabric dyeing is another prominent application of IR lab dyeing machines. From woven fabrics to knits, these machines provide precise temperature control and dye distribution, ensuring consistent and high-quality dyeing results.

Garment Dyeing
IR lab dyeing machines are also employed in garment dyeing processes. They allow for efficient and controlled dyeing of finished garments, providing vibrant and durable colours. Garment manufacturers can achieve desired colour effects and meet customer demands using these machines.

Maintenance and Care Tips for IR Lab Dyeing Machines
To ensure the longevity and optimal performance of IR lab dyeing machines, proper maintenance and care are essential. Here are some tips to follow:

Regular cleaning and inspection
Regularly clean the machine’s interior and remove any accumulated dye residues or impurities. Inspect the heating elements, sensors, and controls for any signs of wear or damage. Promptly address any maintenance issues to prevent further complications.

Proper chemical handling
Follow proper chemical handling procedures when preparing dyes and chemicals for the dyeing process. Incorrect handling or mixing of chemicals can damage the machine components or compromise the dyeing results. Adhere to safety guidelines and use appropriate protective equipment.

Calibration and Adjustment
Periodically calibrate and adjust the machine’s temperature sensors and controls to ensure accurate temperature readings. This helps maintain precise and consistent dyeing conditions. Consult the manufacturer’s guidelines for calibration procedures or seek professional assistance if needed.

Cost considerations and return on investment
When considering an IR lab dyeing machine, it’s important to evaluate the associated costs and potential return on investment. Here are some factors to consider:

Initial Investment Cost
The cost of an IR lab dyeing machine varies depending on its features, capacity, and brand. Consider your budget and compare prices from different suppliers. Additionally, evaluate the long-term benefits and potential cost savings associated with energy efficiency and reduced water consumption.

Operational Expenses
Factor in the operational expenses, including energy consumption, maintenance, and chemical costs. Energy-efficient machines may result in lower operational expenses over time. Assess the expected usage and calculate the potential savings.

Long-Term Benefits
Evaluate the long-term benefits of using an IR lab dyeing machine. Faster dyeing processes, reduced water consumption, and improved dye penetration can lead to increased productivity, a lower environmental impact, and enhanced customer satisfaction. Consider the overall value and potential competitive advantage gained through the use of such machines.

How long does it take to dye a sample using an IR lab dyeing machine?
The dyeing time can vary depending on factors such as the type of fabric, desired colour intensity, and the specific machine used. However, IR lab dyeing machines are designed to significantly reduce dyeing time compared to traditional methods. On average, the dyeing process can take anywhere from a few minutes to a couple of hours.

Can different types of fabrics be dyed using the same machine?
Yes, IR lab dyeing machines are versatile and can handle a wide range of fabrics, including natural fibres like cotton and wool as well as synthetic fibres such as polyester and nylon. However, it’s always recommended to check the machine specifications and guidelines to ensure compatibility with specific fabric types.

Are IR lab dyeing machines suitable for small-scale production?
Yes, IR lab dyeing machines can be used for small-scale production. Their efficient and precise dyeing capabilities make them suitable for both small and large-scale operations. However, it’s important to consider the machine’s capacity and throughput to ensure it aligns with your production requirements.

How often should an IR lab dyeing machine be serviced?
Regular maintenance is crucial to ensuring the optimal performance and longevity of an IR lab dyeing machine. It is recommended to follow the manufacturer’s guidelines for maintenance, which may include routine cleaning, inspection of heating elements, calibration of temperature controls, and lubrication of moving parts. The frequency of servicing may vary depending on the intensity of machine usage and the specific recommendations provided by the manufacturer.

Are IR lab dyeing machines energy-efficient?
Yes, IR lab dyeing machines are known for their energy efficiency. By utilising infrared radiation for heating, these machines require less energy compared to traditional dyeing methods that rely on extensive water heating. The precise temperature control and shorter dyeing time further contribute to energy savings. Investing in an energy-efficient IR lab dyeing machine not only reduces operational costs but also aligns with sustainable practises.

Conclusion
IR lab dyeing machines offer efficient, energy-saving, and precise dyeing processes for various textile materials. By considering the factors outlined in this guide, such as capacity, heating and cooling mechanisms, control systems, material compatibility, and energy efficiency, textile professionals can select the most suitable

The post IR Lab Dyeing Machine Selection Guide first appeared on Testex.

The post IR Lab Dyeing Machine Selection Guide appeared first on Testex.

Dyeing and Finishing - Testex

Alaric Vaughn — Thu, 10 Nov 2022 03:56:03 +0000

What is textile sample dyeing in the dyeing lab?

Based on the colour requirement and design requirement of the incoming sample, design the dyeing process, select the appropriate dyes or paints and dyeing until obtain confirmation. Textile sample dyeing can also be called color matching, usually with a single colour or a combination of colours to achieve the colour requirements.

For example, if a customer sends in a sample, the operator starts to make a sample dyeing. The colour should be the same as the colour of the sample sent in by the customer. However, in order to give the customer a choice, the proofreader will usually send 2 or 3 samples of a similar shade to the customer for confirmation. If the customer confirms a sample, it is ready for mass production, if the customer does not confirm it, a new sample dyeing is required. Textile sample dyeing is an important preparation before dyeing production. The timing and accuracy of the sample dyeing in the deying lab will directly affect the smooth running of mass production.

Textile sample dyeing process in the dyeing lab

As far as textile materials are concerned, the range of fibres is constantly increasing and blends and composite fibres are used in large numbers. As far as customer requirements are concerned, there is a high degree of colour and light conformity, small colour grade differences, fast proofing and short production lead times. All this places higher demands on textile sample dyeing. In general, textile sample dyeing is divided into 4 steps: analysis of incoming sample, confirmation of the dyeing recipe, sample dyeing and color matching after dyeing.

1 Analysis of incoming sample

Choose the right combination of dyestuffs according to the fabric composition and specification requirements of the incoming material. The composition of the fabric is directly related to which dyestuff is used? Common relationships are listed in the table below.

Composition	Dyestuffs
Cotton, linen, viscose	Reactive dyes, reduction dyes, sulphide dyes, direct dyes.
Wool, silk	Acid dyes, alternatively, reactive dyes, direct dyes.
Polyester	Disperse dyestuffs
Nylons	Acid dyes, alternatively, reactive dyes, direct dyes or disperse dyes.

Specification requirements: according to the colour, thread density, yarn thickness, colour fastness requirements, shrinkage rate, moisture absorption and perspiration and other requirements of the fabric, combined with previous dyeing experience, choose the appropriate dyestuff.

2 Confirmation of the dyeing recipe

Based on the colour matching principles and the experience of the operator, the proofers confirm a set of dyeing recipes in advance. In addition, with the development of computer technology, it is now possible to make recipe predictions directly with a computer colour matching system. It is important to note that computer colour matching systems play an auxiliary role and do not replace manual colour matching. This is because environmental changes, colour variations, material variations etc. may cause the computer colour matching system to be inaccurate.

3 Sample dyeing: dip dyeing and pad dyeing

There are two main dyeing methods for sample dyeing of textiles: dip dyeing and pad dyeing.

Dip dyeing is a dyeing method in which the dyed fabric is impregnated in a dyeing solution and the dye is circulated and spreads and fixes on the fibres through the relative movement of the dyeing solution and the dyed material.

Dip dyeing method is suitable for all forms of textiles and factors such as dyestuff. Factors such as dyestuff, auxiliaries, temperature, concentration, bath ratio and relative movement can affect the uniformity of the dyeing. The temperature of the dyeing solution and the concentration of the dyestuff and auxiliaries must be uniform in all places, and the temperature of the dyed material must also be uniform in all places, otherwise the dyeing will be uneven, and secondly the bath ratio is too small, which is likely to cause uneven dyeing. At present, the commonly used sample dip dyeing machine, the IR lab dyeing machine TD130, has obvious advantages over traditional dip dyeing machine and is the first choice for dyeing in the lab.

IR Lab Dyeing Machine TD130

Advantages of the dip dyeing machine: IR lab dyeing machine TD130

Automatic reversal of the dyeing cup, even dyeing, no sticking or stringing of colours.
More precise temperature measurement and control.
Easy to operate and high working efficiency.
Stable machine performance, good reproducibility of dyeing results.
Using special infrared heating method, no pollution to the environment.
All dyeing cups are made of stainless steel, resistant to salt, acid and alkali, no stagnation of dyestuff.

Pad dyeing is the process of impregnating the fabric in the dye solution for a short period of time (usually a few seconds or tens of seconds) and then rolling it with a roller. After rolling, the dye enters the fabric’s tissues and voids, so that the dye is evenly distributed on the fabric. The dyeing is done later in the process of steaming or baking.

The pad dyeing concentration is expressed in a different way to dip dyeing, it is usually expressed in g/L, i.e. the number of grams (g) of dye contained in 1L of dye solution. Pad dyeing is suitable for continuous mass production and has a high production efficiency, but the dyed fabric is generally under greater tension and is usually used for dyeing woven fabrics, sometimes also for dyeing silk bundles and yarns.

Lab Padder TD122

The commonly used pad dyeing machine is the TD122 lab padder.

4 Colour matching of samples

When matching colours, the background of the object being observed, the size and shape of the object, the distance and angle of observation can all cause people to have an illusion of colour. Therefore, the following points need to be noted.

The light source must be sufficiently bright: an inadequate light source will affect the tonal effect, especially with dark and dull colours.
The material grain must be in the same direction: if the material grain is in a different direction when color matching, the colour intensity and colour light may be misjudged.
The background colour must be the same: when color matching, the colour samples should be placed in the centre of the same background colour.
The light source must be fixed, the distance between the eye and the sample must be fixed, the angle at which the sample is viewed must be fixed and the brightness of the light source must be fixed.
In addition, after a long period of colour matching, pay attention to the effects of residual images.

The post How does Textile Sample Dyeing Work in the Dyeing Lab? first appeared on Testex.

The post How does Textile Sample Dyeing Work in the Dyeing Lab? appeared first on Testex.

Dyeing and Finishing - Testex

testextextile — Fri, 27 May 2022 06:11:31 +0000

What is the dyeing of textiles?

Dyeing is the application of dyes or pigments on textile materials such as fibers, yarns, and fabrics to achieve color with desired color fastness through physical or chemical action. Textile dyeing is to be able to select and use dyes reasonably, make the dyeing process correctly for dyeing processing and obtain high-quality dyeing products.

Dyeing Methods of Textiles

On the one hand, based on the requirements of production cost and product quality of textiles, on the other hand, with the consumer’s demand for individualization and fashion of garment products. The dyeing methods of textiles are diversified and can be dyed in 2 different ways, in 5 steps of production, thus giving different colors, styles, and forms of expression to the products.

InfraDye Infrared Lab Dyeing Machine

1 According to the way of dyeing, it can be divided into two kinds: dip dyeing and padding.

1.1 Dip dyeing: this dyeing refers to dipping textiles in a dyeing solution for a certain period, the fabric and dye are in contact with each other so that the dye is fixed in the fiber. This dyeing method is suitable for all kinds of textiles (loose fiber, yarn, small-batch fabric, silk fabric, wool fabric, etc.). It is characterized by intermittent production, low production efficiency, simple equipment, and easy operation. 1.2 Padding: padding is a dyeing method this way, after a brief dip in the dye solution, press the textile with a roll to squeeze the dyeing solution into the tissue gap of the fabric, and remove the excess dye solution so that the dye is evenly distributed on the fabric, then steam or hot melt, etc. This is a continuous dyeing process, with high production efficiency, suitable for a large number of textile fabric dyeing, but the dyed material subjected to high tension, is usually used for woven fabric dyeing, sometimes silk bundles and yarns are dyed with padding.

No matter what kind of dyeing method, it is necessary to perform color matching with dyeing/finishing testing machines before the batch dyeing to ensure the quality of the dyeing.

2 According to the production and processing links, it can be divided into 5 steps: solution-dyed, fiber dyeing, top dyeing, yarn dyeing, piece dyed, and garment dyed.

Whether woven fabric or knitted fabric, most of them are dyed with piece dyed, yarn dyeing is the second, and other dyeing methods reflect each other, together deducing colorful fashion.

2.1 Solution dyed

When chemical fiber (man-made fiber and synthetic fiber) is made, the spinning solution should be prepared first. Generally, the original solution is colorless or white, and the fiber is also white. To meet certain needs, we could add colored substances (such as color masterbatch) into the original liquid or pre-spinning coloring, after full mixing and spinning, all kinds of colored fibers can be obtained, either short fiber or filament.

The colored fibers obtained by the solution dyed are stable in hue, good in color fastness, and low in production cost, but the batch is large, which increases the cleaning burden of spinning equipment. As a result, only more common colors, such as blue, black, and group textiles (such as army), are generally produced, while it is difficult to apply for small batch production with a rapid change of market demand.

2.2 Fiber dyeing

2.2.1 Dyeing of loose fiber To enrich the color of the product, reduce the color difference of yarn, and increase the hazy effect of the product, we can carry on loose fiber dyeing, such as wool fiber dyeing, cotton fiber dyeing, and so on. The dyeing way is generally dip dyeing, but also the padding method. By spinning and weaving after dyeing loose fiber, we can obtain the color spinning and color fabric. In addition, whether it’s man-made fiber or synthetic fiber, both of them are first made of tow and then cut into staple fibers, so that the tow can also be dyed. By this method, the dyeing batch is small and the color phase can be specified at will, the cleaning of a large number of equipment in the two processes of spinning is saved. The dyeing of the tows can be padding and dip dyeing, but the application is less. 2.2.2 top dyeing In the process of spinning (cotton mix, carding, drawing, roving, spun yarn) after the dyeing of loose fiber, there will be a small number of color fibers remaining in the equipment, which will cause inconvenience for the subsequent cleaning work, so there is the top dyeing. This process has been matured and applied in wool spinning. In recent years, this process has been used in cotton spinning to produce color spinning. The top dyeing also belongs to the fiber dyeing before the fiber is spun, and is the same as the purpose of dyeing the loose fiber, to obtain a soft color mixing effect. The top dyeing can not only get the rich color level of the yarn but also reduce the “Flos Lonicerae” to the minimum. The top dyeing is generally used for combing the wool yarn and the wool fabric.

2.3 yarn dyeing

Yarn dyeing is mainly based on dip dyeing, but also by padding (such as denim warp yarn). Yarn dyeing is generally used in yarn-dyed textile fabrics, sweaters, or indirect use of yarns (sewing thread, etc.). Yarn-dyed products (woven, knitted, woven) are obtained by dyeing yarn first and then weaving different color warp and weft yarns according to a certain rule. The products have a unique style.

Yarn dyeing is the basis of dyeing and weaving, and there are three ways.
2.3.1 Hank dyeing: Soaking loose yarn in a special dyeing tank, is a costly dyeing method.
2.3.2 Cone dyeing: Load the cylinder with yarn into the dyeing cylinder, and the dyeing solution is circulating. The fluffy effect and softness are not as good as those of twisted yarn.
2.3.3 Slasher dyeing: It is a kind of large-scale roll dyeing, which is most suitable for common colors and dyed woven fabrics.

2.4 Piece dyed

Piece dyeing refers to a method for dyeing the woven fabric blank, and the common methods are in the form of rope-like dyeing, jet dyeing, roll-dyeing, padding, and slasher dyeing, and only the piece dyeing of the fabric is introduced here.

In the current textile, piece dyeing of fabric is the most important dyeing method. In addition to dyeing in the same color, it can also be dyed in different colors, such as printing, sandwich dyeing, hair tip dyeing, and so on. Fabric dyeing can be dyed with flat width or rope, or by dip dyeing, padding, gas-phase transfer dyeing, and so on.

2.5 Garment dyed

To meet the market demand and to respond quickly, or to obtain a special style, before the dyeing or printing, the fabric should be pre-treated to make the garment. The garment is dyed by dip dyeing, both woven and knitted fabrics can be dyed. Garment dyeing is mostly suitable for knitted socks, T-shirts, other knitted clothing, sweaters, pants, shirts, and other simple ready-to-wear.

In general, the dyeing cost will be lower at the beginning of the dyeing process, any color can be repaired in the back production, but the market reaction speed is slow, and the amount of bonus of colored semi-product is large. At the later dyeing process, not only the amount of semi-product bonus can be reduced, but also the rapid response can be made according to the market demand, but the requirement of the dyeing uniformity, the dye, and the processing process is high.

Looking back on the development history of textile dyeing, we can see that textile dyeing is developing towards ecological dyeing, new fiber, and multicomponent dyeing. In addition, new fibers and new materials will appear faster, water-saving dyeing will be more mature, the organic combination of the bionic coloring, the multifunctional dyeing, the coloring of the pigment, and the structure chromophore can greatly improve the current dyeing effect and improve the dyeing level of the textile.

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Dyeing and Finishing - Testex

testextextile — Wed, 30 Mar 2022 02:23:04 +0000

The fiber, yarn, or fabric without dyeing and finishing process contains a certain amount of impurities, common impurities include natural impurities and artificial impurities. Natural impurities are impurities that exist in natural textile fibers, such as waxes, pectin, pigments, and nitrogenous substances on cotton and linen fibers, silk gum on silk, sheep fat sheep sweat on wool, etc. Artificial impurities are additives that contaminate foreign impurities in the textile process, such as slurry, oil grease, etc.

The presence of these impurities not only makes textiles rough to the touch and of low whiteness but also has poor water absorption. The most important task of textile pretreatment is to remove these impurities by scouring and bleaching for their subsequent processing. In addition to scouring and bleaching, the pretreatment process also includes several processes that are aimed at improving the quality of textiles and must be completed before other dyeing and finishing processes, such as singeing, mercerizing, heat setting, wool washing, degumming, etc. There are many different kinds of textiles and different forms, so the pretreatment processes are also different.

The types of textiles covered in this article are cotton woven fabrics, cotton knitted fabrics, ramie fabrics, wool fabrics, silk fabrics, chemical fiber fabrics…

The pretreatment processes covered in this article are: singeing, desizing, scouring, bleaching, mercerizing, heat setting, wool washing, carbonizing, alkali decrement, degumming…

Pretreatment of cotton woven fabrics: singeing, de-sizing, scouring, bleaching, mercerizing

Cotton woven fabrics mainly refer to pure cotton fabrics and polyester-cotton blended, dimensional-cotton blended fabrics. These fabrics contain cotton fiber components, so more natural impurities, the pretreatment process is more complex, and the basic content mainly includes singeing, de-sizing, scouring, bleaching, mercerizing, etc.

1 Singeing

Cotton woven fabric is made of short fibers, and the surface will form nap of varying lengths, not only affecting the fabric’s finish but also the subsequent processing cause defects. Therefore, this layer of nap must be removed by singeing, singeing is carried out on the singeing machine, and the most commonly used machine is the gas singeing machine.

The degree of nap removal is used to determine the effect of singeing, the specific method is to put the fabric after singeing in a better light and visually inspect the rating. The general fabric should reach 3~4 grade, high-quality requirements should reach more than 4 grade, and thin fabric up to 3 grade.

Grade 1: The gray cloth is not singeing
Grade 2: Less long nap
Grade 3: Basically no long nap
Grade 4: Only short nap, and neater
Grade 5: Singeing clean

2 Desizing

The purpose of designing is to remove the pulp and some of the natural impurities from the gray cloth for subsequent scouring and bleaching. The warp yarns of cotton woven fabrics are usually sized before weaving, and then appropriate de-sizing methods should be used according to the type of pulp and impurities. Commonly used desizing methods are enzyme desizing, alkali de-sizing, acid de-sizing, oxidizer de-sizing, and plasma de-sizing.

Desizing quality assessment: In production, it is generally required that the desizing rate is above 80% or the residual pulp is below 1% relative to the cloth weight, and the remaining pulp can be further removed in the scouring process.

3 Scouring

Fabric after de-sizing, has removed most of the pulp and part of the natural impurities, but most of the natural impurities such as cottonseed shells, waxy substances, pectin, etc. remain on the fabric, and must be completely removed after the scouring process. Caustic soda is mainly used for scouring, and the common additives include surfactants, sodium silicate, and sodium bisulfite. Caustic soda has a strong ability to remove impurities. It can dissolve and disintegrate cottonseed hulls at high temperatures, it can hydrolyze nitrogenous substances and pectin into soluble substances, and it can saponify fatty acids on fibers and then emulsify and remove wax-like substances. The Surfactants can help wet the fabric and improve the effect of debridement. Sodium silicate is mainly used to adsorb iron and other impurities in the practice solution to prevent embroidery stains and deposition of impurities on the surface of the fabric and to improve the water absorption and whiteness of the fabric. Effect assessment method: The purpose of scouring is to enhance the wetting performance and permeability of the fabric. Immerse one end of the fabric vertically into the water and measure the height of the water rising within 30 minutes, the general requirement is 8~10cm in 30min.

4 Bleaching

After scouring, a large number of impurities are removed, but pigments are still present and the appearance is not white enough. The purpose of bleaching is to remove pigments and give the fabric the necessary and stable whiteness without damaging the fiber.

The natural pigment on cotton fiber and its coloring system can be destroyed by the oxidizing agent to achieve the purpose of decolorization. Therefore, bleaching mainly uses oxidants, and the commonly used bleaching oxidants for cotton-type fabrics are sodium hypochlorite, hydrogen peroxide, and sodium chlorite.

5 Mercerizing

When natural cellulose fibers interact with highly concentrated (12.5%) caustic soda solution, irreversible swelling occurs, the molecular structure changes and the adsorption capacity for water and dyes increases. If proper tension is applied to the fiber during the swelling process, the fiber morphology changes and shows regular reflection to light, which can improve the luster of the fabric. This process is called mercerizing.

SmartPull Tensile Tester

In addition to mercerizing with caustic soda, cotton fabrics can also be treated with liquid ammonia for the mercerizing process. The temperature of liquid ammonia is -33�? which can penetrate the fiber quickly and the treatment effect is uniform, especially suitable for high twist and compact fabrics. At present, the research and application of this kind of technology are still relatively small, Germany Monfort already has the relevant equipment and process.

Pretreatment of cotton knitted fabrics: scouring, bleaching, alkali decrement

The voids between the yarns of knitted fabrics are larger and the yarns are not sized before weaving, so the pretreatment is easier. The requirements for scouring and bleaching of knitted fabrics vary with the varieties and uses. For example, cotton sweaters are mostly natural or dark in color, so they simply need scouring, not bleaching. In addition to scouring and bleaching, cotton knitted fabrics often need to do alkali decrement treatment, which refers to treating the fabric with concentrated caustic soda solution in a relaxed state to cause free shrinkage of fiber yarns to increase the density and elasticity of the fabric.

After scouring and bleaching, the grease and wax on the knitted fabric fibers are removed, and the fibers do not slide easily when sewing and are easily broken by the needle, resulting in the dispersion of the loops, so it is often necessary to carry out soft treatment, i.e. dewatering and then dipping and rolling paraffin emulsion and drying.

Pretreatment of ramie textiles: degumming, singeing, scouring and bleaching

Compared with cotton textiles, in addition to pectin and oil wax, ramie has a large amount of sugar gum and a small amount of lignin, which makes pretreatment relatively difficult. Ramie contains a large amount of sugar gum, which is removed before spinning, commonly known as degumming. After degumming, ramie is made into fabric, due to the rigidity of ramie fibers, there is much hairiness after yarn formation, and there is a prickly feeling when wearing ramie, so it is necessary to singeing, in addition, the ramie fabric should have proper scouring and bleaching.

Pretreatment of wool textiles: wool washing, carbonization, bleaching

Wool contains a large amount of impurities, mainly sheep fat and sweat, as well as some foreign dust and debris, so wool washing is the main process to remove the sheep fat, sweat, and dust. The most common process of wool washing is the soap alkaline method, using a washing solution containing soap and soda ash to treat the wool. The wool-washing process requires strict control of temperature, pH, and time to avoid damage to the wool.

For impurities such as branches, leaves, and grass seed fragments in wool, hydrolysis in strong inorganic acids, i.e. carbonization, is required. For example, if wool is treated with sulfuric acid, the impurities in the wool become fragile hydrolyzed cellulose at high temperatures. Wool is more resistant to acid than cellulose and will not be significantly damaged as long as the carbonization conditions are right. In addition, for wool fabrics with high whiteness requirements, bleaching is required.

Pretreatment of silk textiles: degumming, bleaching

Raw silk is mainly composed of fibroin and sericin, as well as impurities such as fat waxes, inorganic substances, and pigments, which can affect the feel and luster of silk. In addition, oil, pulp, and coloring dyes have adhered during the weaving process, these natural and foreign impurities must be removed by pretreatment. The pretreatment of silk includes two aspects: degumming and bleaching. The purpose of degumming is to remove sericin. For textile products with high whiteness requirements, a small amount of reducing or oxidizing agent can be added to the refining for bleaching without a separate bleaching process.

Pretreatment of chemical fiber textiles

Chemical fibers have very few impurities and the purpose of pretreatment is mainly to remove the sizing and oil stains added during the weaving process, so the process is not complicated.

1 Pretreatment of artificial fiber: singeing, de-sizing, scouring, bleaching

The pretreatment of viscose fiber is usually composed of several processes of singeing, de-sizing, and bleaching. Desizing commonly used synthetic detergent, the scouring process can be omitted, and the bleaching process is not necessary, if necessary, an available oxidation bleaching process.

It should be noted that viscose fibers have a relaxed structure, high chemical sensitivity, and low wet strength, so strong chemical action and mechanical tension should be avoided during processing, and milder process conditions and non-tension equipment should be used for processing.

2 Pretreatment of synthetic fiber pretreatment: alkali decrement, heat setting

The scouring and bleaching of synthetic fiber are relatively simple, desizing can use hot water, scouring commonly used soda ash, and surfactants for medium and high-temperature treatment, generally do not need bleaching. Most synthetic fibers are thermoplastic fibers, and they produce wrinkles that are difficult to eliminate under hot and humid conditions and cause dimensional changes in the fabric due to shrinkage, so the heat setting process must be used to improve this defect.

Heat-setting is the process of making the fabric under proper tension, maintaining a certain size, treating it with high temperature for a certain time, and then cooling it at a proper speed. Heat setting can eliminate wrinkles, improve heat stability performance, and improve the strength, hand feel, and dyeability of the fabric to a certain extent.

InfraDye Infrared Lab Dyeing Machine

The heat setting process varies with fabric variety, structure, cleanliness, dyeing method, and factory conditions, and commonly includes gray cloth setting, pre-dyeing setting, and post-dyeing setting.

The above is the content of the pretreatment process of common textiles, about each step, there is no detailed introduction here, if you want to know the textile industry-related information, please save or subscribe to the ChiuVention Blog, here will continue to update for you.

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Dyeing and Finishing - Testex

testextextile — Thu, 11 Nov 2021 06:33:34 +0000

Textile dyeing is an essential process for textile processing. Mastering the basic knowledge of textile dyeing and understanding the properties and of common dyestuffs and dyeing methods can help us to select and use dyestuff reasonably, develop the dyeing process correctly for dyeing processing and obtain high-quality dyed textiles.

Textile Dyeing Basics

1 What is textile dyeing?

Textile dyeing is the process of dyeing textiles products into colored objects by using physical or chemical methods to allow dyes to bond with fibers. Dyeing requirements: uniform dyeing with good color fastness.

2 Dyeing principle: color properties of dyes

Dyes have chromophore and autochrome in their molecular structure, which selectively absorb visible light. When the chromophore and the autochrome are different, the dyes absorb light differently, and therefore, different dyes have different colors. In addition to differences in hue, the colors of dyes also differ in brightness and saturation. Hue indicates the type of color and depends on the state of absorption of visible light by the dye molecules. Brightness reflects the degree of brightness perceived by the human eye and depends on the reflectance of the dye molecules to incident light. Saturation is equivalent to purity and indicates the magnitude of the ratio between colored and non-colored colors at the same brightness.

Although there are many kinds of colors of dyes, the most basic tricolor are cyan, magenta and yellow, i.e. any color can be obtained by mixing the tricolor in a certain ratio with appropriate proportions. In production, the method of visual color discrimination is often used to repeatedly test color matching. In recent years, the technology of computer color matching system has been increasingly widely used.

3 The three stages of dyeing

Absorbing

The dyestuff is adsorbed by the fibers in solution due to intermolecular forces and electrostatic gravitational forces between ions.

Diffusing and penetrating

The adsorbed dyestuff diffuses and penetrates from the fiber surface to the fiber interior under certain conditions until the concentration of dyestuff reaches equilibrium in the dye solution, on the fiber surface, and inside the fiber.

Fixing

The dye entering the amorphous region of the fiber is connected to the fiber macromolecules by chemical forces (ionic or covalent bonds) intermolecular gravitational forces (van der Waals forces) and hydrogen bonds to obtain a certain dyeing fastness. In the actual dyeing process, the above three stages cannot be clearly distinguished. For different dyestuffs, different fibers, and different dyeing processes, the dyeing process is also different.

4 Terms related to dye

Affinity
When a certain dye can automatically dye fiber in solution, we say that the dye has an affinity or directness for this fiber. The faster the dyeing velocity and the higher the percentage of the dye, the higher the affinity or directness, which indicates the size of the dyeing ability.

Dye strike rate
When the dyeing reaches equilibrium, the ratio of the amount of dye that has been dyed on the fiber to the amount of dye originally present in the dye solution, often expressed as a percentage, is called the dye strike rate.

Dyeing velocity
The rate at which the fibers absorb the dye and dye the color, dyeing too fast, easy to cause uneven dyeing, dyeing too slow, will prolong the dyeing time.

Dye migration
Dye migration refers to the ability of a dye that has been absorbed by the fiber to desorb from the fiber, re-enter the dye solution, and then dye other parts of the fiber. Dyestuff with good dye migration can continuously desorb from places with high dye concentration and dye in places with low concentration until the concentration difference disappears throughout the fabric, thus achieving uniform dyeing.

Colorfastness
After dyeing, textiles are constantly subjected to various external factors during use or processing, which will result in different degrees of fading. The ability of textiles to resist fading is expressed by color fastness or dyeing fastness. If you want to know more about color fastness, please refer to this article: Color Fastness: The Ultimate Guide

5 Dyeing equipment

According to the different dyeing objects, dyeing equipment can be divided into fiber dyeing equipment, yarn dyeing equipment, and fabric dyeing equipment.
According to the different dyeing temperatures and pressure, dyeing equipment can be divided into atmospheric pressure dyeing equipment and high temperature and high-pressure dyeing equipment.
According to the different dyeing methods, the dyeing equipment can be divided into dip dyeing equipment and pad dyeing equipment.
Lab dyeing machine for improving production and operation efficiency quickly, which is convenient.

Dyeing properties and dyeing methods of common dyestuffs

According to the different forms of textiles, there are various dyeing processes such as fabric dyeing, yarn dyeing, fiber dyeing, and garment dyeing, etc. The most common application is fabric dyeing. Dyeing is mainly divided into two methods: dip dyeing and pad dyeing. Dip dyeing is to impregnate the textile in the dyeing solution so that the dyeing solution is in constant contact with the textile to complete the dyeing process. This dyeing method is used for fibers, yarns, and small batches of fabrics, and garments. Pad dyeing is suitable for continuous dyeing processing of high-volume fabrics. When dyeing, the fabric is first impregnated with the dye solution for a short time, and then the dye solution is rolled evenly into the inside of the fabric by pressing the rollers, and then the dye is fixed on the fiber by steam or high-temperature baking. The color of the dyed products should match with the standard sample or the sample from customers and should be uniform and have good color fastness. The quality of textile dyeing is related to many factors, including fiber type, dyestuff characteristics, dyeing method, dyeing process conditions, and dyeing equipment. Only on the basis of mastering the nature of fiber and dyestuff, choosing suitable equipment and process, and strictly controlling the conditions, can we obtain dyeing products with color compound requirements, uniform color, and sufficient color fastness.

1 Dyeing properties and dye types of common dyestuffs

types	properties	applicable fibers	color fastness
types	properties	applicable fibers	light	washing	dry rubbing
direct dyestuff	water-soluble non-bright-color	cotton, hemp, viscose, copper ammonia, silk, polyvinyl acetals	poor / good	poor	good
acid dyestuff	water-soluble bright color	wool, silk, nylon	poor / good	poor / good	good
cationic dyestuff	water-soluble very bright color	acrylic	good	good	good
neutral dyestuff 1:2 metal complex dyes	water-soluble non-bright-color	wool, silk, spandex	good	good	good
acid mordant dyestuff	water-soluble non-bright-color	wool	good	good	poor / good
sulfur dyestuff	water-soluble non-bright-color	cotton, hemp, viscose, copper ammonia, polyvinyl acetals	good	good	poor / good
insoluble azo dyestuff	non-water-soluble bright color	cotton, hemp, viscose, copper ammonia	good	good	poor
vat dyestuff	non-water-soluble bright color	cotton, hemp, viscose, copper ammonia	good	good	poor / good
soluble reductive dyestuff	water-soluble bright color	cotton, wool, viscose, copper ammonia, silk, polyvinyl acetals, hemp, nylon	good	good	poor / good
disperse dyestuff	non-water-soluble bright color	acetate polyester	poor / good good	poor / good good	good good
reactive dyestuff	water-soluble bright color	cotton, wool, viscose, copper ammonia, silk, polyvinyl acetals, hemp, nylon	poor / good	good	good
pigments	non-water-soluble bright color	all fibers	good	good	poor

2 Dyeing methods of common dyestuff

Dyeing with direct dyestuff

Direct dyestuff can be used for dyeing various cotton products and viscose products. When dyeing, the textile is first wetted with water, added to the dyeing solution, heated to 95�? and neutral salt is added to promote dyeing, dyeing for 60min. Wash after dyeing, and add color fixing agent treatment if necessary to improve dyeing fastness. Silk dyeing often uses direct dyes with a high dyeing strike rate and good color fastness to supplement the lack of acidic dye chromatography, mainly brown, black, dark green, and other divine colors. Dyeing can be carried out in neutral or slightly acidic baths, often with salt to promote dyeing, and after dyeing to improve the feel, it can be treated in dilute acetic acid baths for a period of time.

Dyeing with vat dyestuff

Vat dyestuffs are high-grade dyes for dyeing cellulose fibers because of their bright color, complete color spectrum, and good color fastness. There are two different processes for dyeing with vat dyestuffs: leuco dip dyeing and suspension pad dyeing. In the case of leuco dip dyeing, the dyestuff is first treated with insurance powder (a strong reducing agent) and caustic soda to reduce it to leuco body dissolved in the soda solution, and then put into the dyeing material, control the temperature and adjust the amount of salt to ensure the dye strike rate. After dyeing, oxidation treatment must be carried out to fix the leuco body on the fibers, and finally soaping is carried out to improve the color light of the dyed products and increase the color fastness. In suspension pad dyeing, the dyestuff is not reduced, formulated as a dispersion of fine particles in suspension, dipped and padded on the fabric, then dried and further dipped and padded in an alkaline reducing solution containing insurance powder, and then entered into a closed steamer to promote the reduction, dissolution, diffusion and penetration of the dye, and finally oxidation and soaping. At present, the most applied vat dyestuff is indigo, which is mainly used in the processing of denim fabrics and garments.

Dyeing with sulfur dyestuff

Sulfur dyestuff is commonly used for dyeing cotton textiles with deep intense black and blue. The dyeing method is similar to that of vat dyestuff, where the dyestuff is first reduced and then dissolved, and then oxidized for color development after dyeing. Here the reducing agent is often sodium sulfide, which is more easily oxidized than the vat dyestuff. In the case of cotton roll dyeing, for example, the fabric is dyed for a period of time at a high temperature in a solution of the dye cryptophore, then washed and oxidized, and finally treated with sodium acetate for anti-brittle.

Dyeing with insoluble azo dyestuff

Insoluble azo dyes consist of two parts: the color phenol and the color base, and the dyeing process is actually the reaction of two water-soluble components on the fiber to produce insoluble color precipitates. When dyeing, the fabric is first dipped and rolled with an alkaline solution of color phenol, commonly known as “priming”, then dried at low temperature, then dipped and rolled with a solution of color base for color development, then washed and soaped after a certain period of time by air or steam, and finally washed with water. The dye can also be dyed by the dip-dyeing method, also through the priming and color development in two steps.

Dyeing with reactive dyestuff

Reactive dyestuff contains reactive groups in their molecules, which can react with certain groups on fibers to generate covalent bonding, resulting in high color fastness to washing and rubbing, and can be used for dyeing cellulose fibers, wool, silk, and nylon. Dyeing of cellulose fibers: In the process of dip dyeing and pad dyeing, the fabric is usually treated with a dyeing solution without alkali first, then alkali is added to the dyeing solution or alkali is applied to the fabric to make the dye react with the fiber, and finally, fully washed, soaped and boiled to remove the floating color. Wool, silk, and nylon dyeing: Wool dyeing is usually done under acidic conditions, with acetic acid to adjust the PH, with yuanming powder as retarding agent, neutralization, and washing after dyeing. Silk can be dyed by different processes in weak acidic and neutral dyeing or alkaline conditions, or by dyeing in a weakly acidic or neutral bath first and then fixing in an alkaline bath. Nylon has fewer reactive groups than wool and silk, so it is difficult to dye dark colors with reactive dyes, and its dyeing process is similar to that of silk.

Acid dyes, acid mordant dyes, and acid mordant-containing dyes for dyeing

These three dyes are water-soluble and specialized for wool, silk, and nylon, but they have certain differences in structure, performance, and application range. Acid dyes have a simple structure and can be divided into two categories, strong acid dyes, and weak acid dyes, depending on the size of the molecular structure. Strong acid dyes can dye the wool in a strongly acidic medium with bright color and good uniformity, while weak acid dyes can dye wool, silk, and nylon in a neutral or weak acidic medium with high color fastness, but less uniformity and vividness than strong acid dyes. Acid mordant dyes have the basic structure of acid dyes, but also contain groups that can create complexes with mordant chromium ions. These dyes are mainly used for wool dyeing and have better color fastness in washing and sunlight than acid dyes but are darker in color. Dyeing is often done by dip dyeing, and after dyeing, potassium dichromate is used as a mordant for a certain period of time. Acidic mordant-containing dyestuffs are easy to apply as they do not require mordant treatment for dyeing. When chromium ions and dye molecules are complexed in 1:1, the dyeing effect is similar to that of strong acid dyes, mainly used for wool, and when chromium ions and dye molecules are complexed in 1:2, the dyeing fastness is higher, but the color is darker, and it is often used for neutral bath dyeing of wool, silk, and nylon.

Disperse dyestuff for dyeing

Disperse dyestuff are the main dyes for dyeing synthetic fibers, especially polyester fibers, and has good dyeing performance on polyester with high color fastness. Disperse dyes do not contain ionized genes in their structure and are non-ionic hydrophobic dyes, which are insoluble in water and can only be dispersed as particles in suspension in the dye solution. Disperse dyes have a simple structure and small molecules, which have an affinity for the hydrophobic polyester fibers with a tight structure and can diffuse into the interior of the fibers and have a high dyeing rate. Disperse dyestuff has a simple structure with small molecules and has an affinity for the hydrophobic, tightly structured polyester fibers, allowing them to diffuse into the interior of the fiber and have a high dyeing strike rate. When dyeing polyester with dispersing dyestuff, high-temperature conditions above 120�?are necessary because only at high temperatures is the degree of thermal movement of polyester macromolecular chains sufficient to produce the gaps needed for dye diffusion. There are three types of dispersing dyestuff for dyeing polyester: carrier method, HTHP method, and hot-melt method. The high-temperature and high-pressure (HTHP) method is the most commonly used method. The dyeing is carried out in a closed high-pressure container at a temperature of up to 130�? with a high dyeing strike rate, and acetic acid and leveling agent can be added to assist the dyeing in order to control the color light and the uniformity of the dyeing.

Cationic dyestuff for dyeing

Cationic dyestuff is the main dye for dyeing acrylic fiber, which not only has bright color and high dyeing strike rate but also has good color fastness. Since the macromolecules of acrylic fiber contain acidic groups, which are negatively charged after ionization in water, they have high adsorption power to cationic dyes, fast dyeing speed, and high dyeing rate. Cationic dyestuff has poor dye migration on acrylics. Due to the fast dyeing velocity, uneven dyeing can easily occur, so the dyeing process must be strictly controlled and dyeing agents must be used. Commonly used dyeing migration agents include acetic acid, methenamine powder, and cationic surfactants. Dyeing is generally done by dip-dyeing method, adjusting the dyeing solution PH=4.5 with acetic acid, etc., and adding the dyeing migration agent, starting from room temperature, and strictly controlling the speed of temperature rise, continuing to dye for a certain time after boiling, and then slowly cooling and washing. At present, there are also modified polyester fibers that can be dyed with cationic dyestuff.

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The post Basic Knowledge and Common Dyestuffs of Textile Dyeing first appeared on Testex.

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