Choice of Size Receipe

Choice of Size Receipe

The suitability of size receipe for the type of yarn should take into account, fabric construction, and end use as follows:

1. Cotton Yarn- Starch Based
Polyester etc.- Polyvinyl Alcohol (PVA) based

2. Fine and Superfine cotton- thin boiling Starches
Coarse Count- ordinary starch

3. Heavy Fabrics- Modified starches
Light and Medium- Ordinary starches

4. conventional sizing Machines- Low viscosity starch
High speed sizing machines- High viscosity starches

5. Unlbleached calendered sort of fabrics- More weighting agents, antiseptic softners etc. are used.
Bleached sorts- ordinary starches

6. Finer Counts and Heavier Constructions- More size pickups
Coarse counts- Less size pickups

7. Plied yarns- low size pick up or nil even

Ingredients for water Based Sizes

1. Adhesives- Potato starch, starch from cereals ( corn, wheat, rice etc0, carboxy methyl cellulose (CMC), Polyviny alcohol (PVA), Polyviny Chloride (PVC)

2. Lubricants- Mineral Waxes, vegetable waxes, animal fats, mineral oils, vegetable oils

3. Additives- Salicylic Acid, Zinc Chloride, Chloride emulsifiers.

Suggested Size Receipe

Ordinary starch=100
Gum= 2
Mutton tallow= 7.5

Preparation of Size Receipe

1. Ingredients

Water= 18.5"
Modified Starch = 50 kg
CMC= 5 kg
PVA= 10 kg
Gum = 1.5 kg
Softner= 1.2 kg
Antistat= 0.8 kg

Mixing: Took 17" water. Added Starch, Gum, CMC and PVA slowly and one by one as the slurry is stirred. Softner and antistat added in storage kettle.

Cooking

1. cold stirring at 50 rpm = 12 min
2. Transfer into pressure cooker through sieve=== 45 deg C
3. Stirrer rpm in cooker== 55
4. Close lid, open steam inlet, open air vent
5. Close air vent valve when steam is seen escaping through it, temperature = 96 deg C, Pressure = 10 PSI
6. time between point 3 and 4 == 15 min
7. Cooking starts, steam continued till temperature = 130 deg c, Pressure = 40 PSI
8. Time for getting 130 deg C after closing air vent valve = 25 min
9. Stem in-let closed
10. 10 minutes after closing steam, Temp= 124 deg C, Pressure = 32 PSI
11. Total cooking time after getting 130 deg C= 35 min
12. Flow time of paste taken through sample valve= 24 seconds
13. Transferred to storage beck
14. Final volume = 18.5 "
15. Stirrer RPM in storage beck = 20
16. Temperature after 10 min. of transfer = 100 deg C
17. Refrectometer reading= 16

Lab Data

1. Size add on = 18 %
2. Increase in strength % = 5.2
3. Elongation at break % os sized yarn = 6.8%

Process Control in Sizing-1

Sizing

The process consists of laying warp yarn parallel and sizing the yarn with a mixture to strengthen it to withstand the rigours of weaving.

Warp yarn is withdrawn in sheet from from warp beams which are placed at the back of the sizing machine. The yarn is then passed through sow box. Size solution is applied by immersion. After removing surplus solution that occurs at this state, the yarn is dried and arranged on a loom beam.

The objective of sizing is RESISTANCE to ABRASION

This objective is achieved by applying on the yarn a unifrom and smooth protective film of suitable sizing material.

We also want that in the sized yarn there should be

- Some increase in tensile strength in the yarn
- Minimum loss of extensibility in yarn ( about 4.4-4.6% elongation at break is required for cotton)
-Required moisture content ( 8-10% of cotton)
- Good quality of sized beam (neither too soft nor too firm + free from yarn defects)
- Good productivity and efficiency
- Reduced Cost

Process Control in Sizing

The process control programme in sizing should, therefore, comprise of the following aspects:

1. Selecting the correct size receipe and size pick -up level
2. Ensuring correct preparatio of size paste
3. Control of
- size pick up
- stretch
-moisture content
-quality of beam
-machine speed
-machine efficiency
-a method to calculate the expected level of productivity

Cost of Warping

Warping process is required exclusively for preparing warp yarn for weaving. Hence warping cost should be calculated for warp yarn.

Unit costs in this section can be developed on weight basis or on length basis.

Weight Basis

Warping cost per piece length of fabric= weight of warp yarn per length x cost per unit weight.

If unit costs are developed on length basis, they are expressed with reference to specific number of ends (generally 400-500 ends). It follows , therefore, that about four to eight beams ( some time even more) would be required to made one beam for weaving.

In other words, unit cost in terms of length will have to be multiplied by the number of warp beams required per weaving beam. Then warping cost per piece length of a fabric can be calculated as shown:

warping cost per piece length of fabric = cost per meter x tape length x no of warp beams per weaving beam.

If the warp beam is partly colored and partly greige, warping cost should be calculated for greige warp yarn and coloured warp yarn. Generally coloured yarn is processed on slow speed warping frame. Hence cost of color warping usually works out higher as compared to the cost of greige warping.

control of end breaks in warping

Minimising end breaks in warping involves four steps namely:

1. Control of tension in the yarn
2. Satisfactory maintenance of those machines
3. Minimising the defects on packages produced at winding
4. A regular check on the end breakage rate for comparison with the norm.

1. conrol of tension in the yarn

On the warping machine, there are two types of variation in yarn tension
1. Between different stages of unwinding of a package. This can be detected after the first thread guide.
2. Between ends. It can be detected at the head stock.

The tension variation that occurs during the unwinding of a package can be minimised if you design the creel such that the distance between the package and the first thread guide is shortest, it will avoid the yarn balloon rubbing the nose of the package.

The tension variation between the ends at the headstock is minimised if the groups of neighbouring ends on the beam are taken from the same column of packages in the creel.

2. Condition of Machine

a. Alignment of the package at the creel

Non alignment of the creel package with respect to the first guide is often seen to be a cause of high end breakage rate at warping. This alignment is done with the help of a gauge.

b. Eccentric Guide rollers

On machines with mechanical stop motions, there are several guide rollers at the headstock which are positioned very near to one another. Eccentricity in those rollers can introduce short term tension variations of high amplitude.

c. Thread Guides

Deep cuts in thread guides can significantly increase yarn tension and hence deteriorate warping performance. If found dirty, the thread guides should be cleaned with CCl4.

d. Relative humidity and temperature

For satisfactory working at warping, about 60% RH should be maintained. The dry bulb temperature should be kept at about 29 o C (84 o F). Lower humidity may increase yarn hairiness, end breaks and liberation of fluff. The fluff ultimately passes to the beam and given difficulty during sizing. Higher humidity is unnecessary; in fact relative humidity higher than 70% may increase end breakage rate.