The production of black polyester fibers is extremely sensitive to the various cost variables that have a direct impact on the overall process (raw materials, Central Polymer Filtration System, spin-pack, etc). Moreover, the production of black fine-denier polyester fibers requires premium black pigments with high level of physical cleanliness in order to optimize all these costs.

Cabot has developed a fiber model that can simulate the total cost of producing black polyester fibers. This model shows that the use of a premium black pigment over a standard fiber pigment is, for the polyester fiber producer, a cost-effective solution.

The production of a black polyester fiber and the successive variables considered in the model are represented in the picture below:


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The model calculates, for a regular fiber pigment and a premium black pigment (BLACK PEARLS 4560i or BLACK PEARLS 5560), the costs that are related to each of these four steps. The majority of the fields included in the model are open. In other words, the figures in these fields can be changed in order to allow the user to simulate at the best his own operating conditions*. In this article, some of the figures are not shown on purpose in order to preserve the divulgation of confidential data.

1. Polymerization/Compounding: In this first stage, the model is calculating the total compounding costs per year, taking into account the prices of the polyester and the black pigment as well as the related manufacturing costs.

2. Central Polymer Filtration System (CPF): The Central Polymer Filtration system or CPF is a key variable in the evaluation of the costs related to black polyester fiber production. In fact, because of its principle, it consists of two alternating canisters each filled with metal candles. The model hence takes into account the following variables:

• the average cost per candle;
• the candle cleaning, which is an operation than can be done in house or externally (more expensive);
• the number of days of operation before the cleaning of the candles is required;
• the number of cleanings that can be operated before removing the candles from the canister and invest in new ones.

A premium pigment has a high level of physical cleanliness and therefore reduces the plugging of the candles filters. As a consequence, the number of running days before cleaning and the total number of cleanings on a yearly basis are much lower than the ones observed for a regular fiber pigment.

3. Screen Pack and Labor Costs
This section of the model calculates the costs related to the spin-pack filter system. The latter, which is very often a metal powder pack, is installed immediately in front of the spinneret. The contaminants present in the black pigment will lead to the plugging of the screen pack. The immediate consequence is a pressure build up that will, overtime, require the change of the screen. The cleaner the black pigment, the lower the frequency of screen changing and the lower the costs will be.

The number of changes/year takes into account the number of positions as well as the frequency of change (see section 4).

4. Spinning Costs and Fiber Value: This is most probably the most complex part to analyze. In this section, the following variables are considered:

• the time lost to change screen pack;
• the number of positions;
• the production rate.

In a second step, the model calculates the actual loss of production time and volume due to the pack changes (on a yearly basis and in function of the number of positions). A premium pigment will definitely limit these losses over a regular fiber pigment.

Finally, the total annual fiber value is estimated by subtracting:

The Fiber Revenue (price/kg * production rate * number of positions) with:

• the total annual fiber cost;
• the total value of lost production/yr;
• the total CPF cost/yr.

The higher this number the better as it represents the net profit (loss) generated. From the inputs used in this article, one can see that premium pigments such as BLACK PEARLS 4560i or BLACK PEARLS 5560 can generate a benefit of more than 300 k$/yr for the fiber producers. These two grades have been developed in order to ensure an optimum cost/performance ratio for the entire polyester fiber value chain. BLACK PEARLS 5560 has an improved color strength and blue tone over BLACK PEARLS 4560i and is therefore suitable for applications where high color performance is required.

Moreover, Cabot has developed a Fine Screen Delta P (FSDP) test method (165 X 1400 mesh size screen) in order to accurately predict the filterability and spinability of the black polyester fibers. BLACK PEARLS 4560i and BLACK PEARLS 5560 are specified in FSDP (reported on the certificate of analysis). They consequently both have low and consistent values from lot-to-lot.