The origins of knitting are recorded as dating back to the 5th and 6th centuries BC, when knitting techniques emerged among both the Central Asian Turks and the Egyptians.

The development of mechanical knitting accelerated in the 19th century. Matthew Townsend invented the latch needle in 1853, the first knitting machine equipped with this needle was produced in 1867, and the first circular knitting machine using the same element was developed in 1878.

Following the First World War, the rapid development of synthetic fibres and yarns contributed to major advances in knitting machines, knitting methods and fabric structures. After the Second World War, further developments in mechanical and electronic technologies accelerated this transformation, eventually leading to highly advanced automated and electronically controlled knitting systems.

Over the last decade, fully electronic circular knitting machines have gained increasing popularity in the market. This development has encouraged knitting machine manufacturers to adopt new technologies and produce machines capable of operating at increasingly higher speeds.

In terms of product groups, knitted fabric exports account for 15.2% of textile and raw material exports, following fibre, yarn and woven fabric exports.

Performance Requirements for Needle and Sinker Oils

Among the most important requirements for needle and sinker oils are that they must not damage machine paint or plastic components, increase machine temperatures, damage power cable coatings or interfere with control systems. They must also provide corrosion protection and high lubrication performance while maintaining excellent washability.

Carefully selected specialty oils not only help ensure maximum operating reliability but can also reduce maintenance costs. When selecting an appropriate lubricant, all technical and operational parameters should be considered, including machine type, required product quality and price-performance expectations.

The additive package responsible for the quality and washability characteristics of knitting and sinker oils represents one of the most important cost factors in a knitting oil. Differences in the effectiveness and performance of these additives can therefore result in significant differences in product cost.

A properly selected oil, combined with conventional washing liquors used during subsequent finishing processes, should allow oil stains created during knitting to be removed from the fabric effectively.

Lubrication Under Demanding Operating Conditions

A lubricant must be correctly designed for components exposed to water, steam, acidic and alkaline solutions, as well as high speeds, temperatures and vibration. Greater efficiency requires longer equipment life or reduced lubricant consumption.

A lubricant developed specifically for its intended application will generally create fewer operational problems. Every movement between machine components inevitably causes wear. Selecting and using a lubricant capable of minimizing this wear helps reduce costs while improving overall efficiency.

Washability and Water Compatibility

For needle oils to provide washability, they must be capable of mixing with water. The additives that provide this capability are emulsifiers, which reduce the surface tension of the oil and allow it to mix with water. The use of this type of water-miscible oil is particularly important for manufacturers producing cotton-blend knitted fabrics.

Higher-performance oils are especially important for minimizing problems in the production of fabrics containing Lycra. Knitting oil transferred onto the fabric can adversely affect its Lycra properties. Removing the oil may require washing the fabric at high temperatures, an undesirable process that can further affect the fabric and lead to production and time losses.

Insufficient lubrication performance can also result in frequent needle and sinker replacement, creating additional problems in terms of production efficiency, time and cost.

What Is Expected from a Knitting Oil?

• Long-lasting and high lubrication performance
• Stable viscosity across different operating temperatures
• Resistance to resin formation
• Continuous cleaning of needle channels
• Reduction of machine vibration and noise
• Reduction of heat generated by friction
• Resistance to rust and corrosion
• Effective rust-preventive additives
• Compatibility with machine paint and plastic components
• Reduced wear on machine components
• Effective spreading and adhesion on metal surfaces
• Compatibility with different lubrication systems
• No harmful physiological or environmental effects during production
• Protection against wear to extend the service life of needles and sinkers and reduce maintenance costs
• Reduced energy and operating costs through low friction resistance
• Compatibility with electronic control systems, elastane fibres, commonly used sealing materials and plastics

How Can High Machine Protection and Washability Be Achieved at the Same Time?

Achieving all of these characteristics in a single knitting oil requires careful selection of suitable raw materials. The formulation must provide effective machine protection and lubrication while also allowing the oil to be removed from the fabric through washing without leaving stains.

Suitable Raw Materials

• An additive such as Triaryl phosphorothionate / Triphenyl phosphorothionate (TPPT) should be used to provide extreme-pressure and anti-wear performance without leaving ash or carbon deposits. It should offer high thermal stability and, unlike sulphur-containing extreme-pressure additives, remain neutral toward yellow metals.
• An ashless raw material based on an amine phosphate mixture should be used to provide extreme-pressure, anti-wear and rust-preventive properties.
• A phenolic antioxidant such as 2,6-Di-tert-butyl-4-methylphenol (BHT) should be used.
• For effective washability, an amphiphilic oleic acid derivative should be used as a water-in-oil emulsifier and corrosion inhibitor.
• A non-ferrous metal deactivator containing dimercaptothiadiazole and effective in non-polar base oils should be used.
• A half ester of succinic acid with excellent demulsifying properties should be selected as an effective corrosion-inhibiting additive.

To maintain a homogeneous mixture containing these different raw materials while also allowing components with different chemistries to be removed easily from the fabric, an additional key raw material is required.

An emulsifier with hard-water stability, high solubility during washing and low skin irritation should be selected. It should be plant-based and biodegradable, based on fatty alcohol ethoxylate (2EO), and provide low-temperature performance. For water-miscible metalworking fluid concentrates, it should also provide low-foaming and hydrophobic emulsification characteristics.

Tayfun Yılmaz

General Manager / Senior Engineer — Vario Engineering and Production Technologies Inc.