TEXTILE COURSE,Singeing,RAKUTO KASEI INDUSTRIAL Co.,Ltd.

TEXTILE COURSE

| Introduction | Pretreatment of Cotton Fabric 1 2 3 | Methods for Size Analysis 1 2 3 4 5 6 |

Cotton is a fiber growing in seeds <of plants in Gossypium in Malvaceae> that have been planted by human hands in the tropics and subtropics. Cotton accounts for 45% of the major fiber production in the world (Cotton: 1,900 ton, in 1995), and is the most popular fiber of all. Also, cotton is a valuable fiber to the earth in view that cotton trees are photosynthetic.

1) Singeing

Singeing is a finishing method for smoothing surfaces of fabrics by burning and removing fuzz thereon, and visualizing fabric textures. A gas-singeing machine is normally employed. The gas-singeing machine is typically equipped with four burners, and is capable of singeing one or both surfaces of the fabrics. A water-cooled roller is provided at a location opposite to the burners, thereby enabling singeing to be performed without undermining the strength of even thin fabrics. It is important to set a drain temperature of the water-cooled roller in a range of 50 to 55 C. Cautions are required because a dew-point is generated when the water-cooled roller is cooled down too much, and results in increased amount of remaining fuzz or adhered carbon. The fabric feed speed is preferably set at around 100 to 150m/minute.

(Tip)

Adding an enzymatic desizing agent into a fire-extinguishing bath will prevent dirtying of water in the bath as well as help desize starches.
(Recipe) RACTASE IDN-200 2g/L

2) Desizing

Cotton fabrics contain primary and secondary impurities as shown in tables below, and the purpose of desizing and scouring is to remove these impurities.

Primary impurities
Pectic substance	2-3%
Cotton wax, Cottonseed oil	0.3%
Protein	0.3-0.4%
Ash pigment	0.01-0.03%

Secondary impurities
Starch	4-6%
PVA	3-5%
Acrylic size	0.5-1.0%
Wax	0.2-0.5%
After-wax	0.5%

The purpose of a desizing process is to remove sizes that have been attached to warp yarns during a weaving process. Prior to the desizing process, therefore, the size analysis should be performed in order to set desizing conditions suitable for the sizes.

<Sizes>

Starch
Starches have conventionally been used for sizing warp yarns. There are various types of starches. Cornstarch, flour, and modified starch are mainly used for this purpose.

PVA
Polyvinyl alcohol (poval) is produced by polymerizing vinyl acetate to generate polyvinyl acetate and saponifying the polyvinyl acetate. PVA is an epoch-making sizing agent soluble at high temperatures. However, if a fabric is dried with insufficient desizing of PVA, a film is formed on the fabric, which makes desizing difficult.

Acrylic Size
Acrylic size is used when a single use of PVA does not provide enough adhesive property and warp yarns are a little too hard. The acrylic size is soluble in alkali, but has a drawback of reacting with calcium magnesium and precipitating.

Wax
The purposes of using wax are to

provide warp yarns with flexibility
smooth the surfaces of warp yarns
make a sizing agent penetrated easily
provide electric property
provide moderate hygroscopicity

It should be noted that the excessive use of wax might cause troubles in after-tr

eatment and undermine dyeing property.

<Methods for Size Analysis>
1) Qualitative Analysis for Starch
A drop of an N/50 iodine solution is applied onto a fabric

Fabric	Fabric

Starch detected	Starch not detected

2) Qualitative Analysis for PVA
A drop of an N/50 boric iodine solution is applied onto a fabric.

Fabric	Fabric

PVA detected	PVA not detected

3) Qualitative Analysis for Acrylic Size
Rhodamine dye method
i) Acrylic size present

Original fabric	Completely desized fabric

ii) Acrylic size not present

Original fabric	Completely desized fabric

If you want to study more about sizes, go to
Methods for Size Analysis

1)	Method for detecting starch and PVA
2)	Method for detecting acrylic size
3)	Method for determining total size amount
4)	Method for Determining Starch Amount
5)	Method for determining wax amount
6)	Method for iodine coloration and boric iodine coloration

<Desizing Agent>
Desizing agents are roughly divided into enzymatic desizing agents, oxidative desizing agents, and others.

Enzymatic desizing agent
An enzymatic desizing agent is mainly composed of amylase.

Characteristics
1)	Quickly degrades starches
2)	Treatable in the neutral pH range (cannot be used together with NaOH)
3)	Gentle to the earth
4)	Removal of PVA and an acrylic size is made possible only with the assistance of high temperatures or a surfactant.

Product Name

Mid-temperature enzymatic desizing agent
(treated at 70 to 80 C)

RACTOSE RCS CONC	...	mid-temperature amylase
RACTOSE L CONC	...	mid-temperature amylase; and PVA dispersing agent

ii)

Heat-stable enzymatic desizing agent (treated at 90 to 100 C)

RACTOSE IDN-200	...	heat-stable amylase
PAS-600 ECO	...	heat-stable amylase; PVA dispersing agent; acrylic size dispersing agent; and pH buffer

Product Name
i)	RACTOGEN KS Used together with NaOH, a surfactant, and a chelating agent.
ii)	RACTOGEN KWC CONC Provides better desizing effects when used together with NaOH. Also produces bleaching effects. Note that desizing effects are inferior to RACTOGEN KS.

Other desizing agents
Other desizing agents are mainly composed of an alkaline agent and a surfactant.

Product Name
i)	DESCO AP CONC Suitable for removing PVA and acrylic size
ii)	DESCO VS Suitable for removing PVA