What Is Fabric Finishing?

Polyurethane coating adhesive (Polyurethane referred to as PU)

Polyurethane, which is called polycarbamate, is a high molecular compound containing NHCOO - unit in the molecular structure. The unit is formed by reaction of isocyanate group and hydroxyl group.

- N=C=O + HO NH-COO -

In 1970s, Otto Bayer of Germany first synthesized PU.

Before and after 1950, PU appeared as a textile finishing agent in Europe, but most of them were solvent based products for dry coating finishing.

In 1960s, due to the enhancement of people's awareness of environmental protection and the introduction of government environmental regulations, the PU coating of water system came into being.

Since 70s, PU coating has developed rapidly, and PU coated fabrics have been widely used.

Since 80s, breakthroughs have been made in PU's research and application technology.

Compared with foreign countries, domestic research on PU textile finishing agent is relatively late.

Polyurethane coating agent is the main type of development nowadays. Its advantages lie in:

The coating is soft and elastic.

The coating has good strength and can be used for very thin coating.

The coating has porosity, moisture permeability and aeration performance.

Wear resistance, moisture resistance and dry cleaning.

Its shortcomings lie in:

Higher cost;

Poor climate tolerance;

Water, heat and alkali must be hydrolyzed.

PU coating agents are classified according to their composition: Polyester system polyurethane, polyether polyurethane, aromatic isocyanate polyurethane, aliphatic isocyanate polyurethane.

According to the medium used, it can be divided into solvent and water type [2].

1.1 solvent type

Solvent PU has good strength and water resistance, but it is highly toxic and easy to burn.

In terms of composition, it is also divided into two groups and one group.

The two-component product is composed of prepolymer and crosslinking agent. The prepolymer is a prepolymer with a hydroxyl terminated terminal formed by reaction of isocyanate with oligomeric polyols.

The cross linker is a compound containing more than three isocyanate groups.

When coating is finished, the prepolymer is reacted with the crosslinking agent to form thermosetting reticular film, which endows the textile with excellent performance.

This product is Crisvon7367 SL of the big Japanese ink company.

The single component products are linear structures, amorphous regions and crystalline regions, which are thermoplastic.

The single component product is made by chain extension of the terminal isocyanate group (NCO) prepolymer.

Products such as domestic AR-1401, foreign large Japanese ink company's Crisvon2016 EL, 2116EL.

Impranil series of Bayer company.

Solvent based PU coating mostly uses DMF, or a mixture of toluene and isopropanol as solvent.

In order to achieve the effect of waterproof and moisture permeation, solvent coating finishing agents usually use wet coating process to process fabrics.

1.2 water based PU coating adhesive

The drainage system is divided into two types: water soluble and water dispersive type.

The water system PU is widely used in fabric finishing, such as Japan's Superflex series and Germany's Imperanil water dispersive series.

The water system PU has good film-forming property and good water repellency.

Elastron CT-7 and C-52 are water systems PU for waterproof and moisture permeable coatings.

Water dispersible PU can be made into nonionic, anionic and cationic dispersions.

Water dispersive PU is sensitive to acid and alkali. In the presence of acid, anion PU will coagulate, while cation PU is not alkali resistant.

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Water based PU coating was initially prepared by phase change emulsification, but the product contained emulsifiers, which had adverse effects on adhesiveness, strength and toughness and water resistance.

In order to solve this problem, in the late 1980s, the self emulsifying coating system increased gradually. Its main principle was to introduce appropriate hydrophilic groups onto the polymer chain, and spontaneously disperse into emulsion under certain conditions.

Water PU coating adhesive is usually used for dry coating.

In order to improve the water resistance, softness and durability of coating products, pre and post waterproof finishing should be carried out.

PU macromolecules contain a large number of polar groups. The intermolecular force is very strong, leading to its excellent film-forming ability. It can form tough and durable film on the fabric. It has good water repellency and has a certain moisture permeability.

The reason is: on the one hand, polar groups or hydrophilic groups in PU, such as OH, NHCOO -, SO3H - COOH, and so on, act as "chemical step stone" [9], so that water vapor molecules migrate from the high humidity side to the low humidity side along the ladder; on the other hand, PU is formed by soft segments and hard segments, forming the non qualitative and crystalline regions in the structure respectively, because the molecular chains of the undetermined region are relatively loose.

The crosslinking agent SC-100 is a 100% functional multi functional nitropropane cross linking agent.

The addition of waterborne acrylic emulsion or polyurethane dispersions by 1-3% can obviously improve its water resistance, chemical resistance, high temperature resistance and adhesion on special substrates.

Crosslinking agent SC-100 is used for cross-linking reaction at room temperature, but it can also be used for warm spraying or baking process.

Typical characteristics:

Type: multi functional nitropropidium crosslinking agent

Appearance: yellow, clear liquid.

Solid content (1%w/w): 99.

Viscosity Brookfield (25 C): 200mPas

PH (25 C):8-9

Density (20 C):1.08kg/l

Stability (20 C): six months.

Water resistance (20 C): 100%.

Solubility: completely dissolved in acetone, xylene, isopropanol, N- butyl nitrate, ketone and butyl ketone.

Suggested end use:

increase

It can improve water resistance, alcohol resistance, washability, chemical resistance and abrasion resistance in waterborne wood floor varnish, waterborne plastic paint and waterborne metallic paint.

It can improve water resistance, alcohol resistance and viscosity resistance in waterborne industrial wood coatings.

In vinyl coatings, migration of plasticizers can be reduced and pollution resistance improved.

The wear resistance of water-based cement sealants is improved.

The adhesion of waterborne systems to porous materials can be generally improved.

Improve water resistance and washability of waterborne printing inks;

Improve the tolerance of solvent based polymers;

It is suitable for pad dyeing of polyester cotton, medium cotton and medium length fiber.

Improve the water resistance, viscosity resistance and high temperature resistance of waterborne printing coating.

Formula suggestion:

The crosslinking agent SC-100 is a three functional crosslinking agent which can react with the carboxyl group of the polymer (equivalent number 166). In most cases, the best reaction can be obtained if the carboxyl group and the 0.6 equivalent SC-100 react with each other. However, some systems require equivalent equivalent crosslinking agent to react with it. In general, cross-linking of all acrylic or polyurethane dispersions requires 2% or 3% SC-100 (weight), and SC-100 should be added before varnish, coating and printing ink. Because of its excellent compatibility, it can be stirred by hand. The best method is to mix SC-100 with water 1:1 first and then join the system.

Use storage:

Handle with care, avoid contact with skin and eyes. Use inhalation of mouth and nose while wearing special mask. Store in cool, dry and dark places.

1. fastness, you can see it with your fingernail.

2. the thickness should be uniform. The sides should be thicker and thinner.

3 water pressure, according to requirements

4. when the shape is fixed, the width of the door should be set wider, because the width of the door should be reduced by 7,8 cm during rolling.

5. beat the roll and prevent the cloth from wrinkling.

6. prevent colloidal particles from occurring.