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Developing a turnkey nonwovens spunbond line: identifying the process.

Developing A Turnkey Nonwovens Spunbond Line: Part II - Identifying The Process

a complete list of process parameters must be determined at this stage; process trials and materials samples are also two necessities

ABC has determined that the company will develop a turnkey spunbond line for producing filtration media. The type of process has been defined, but the process parameters have not.

The consultant's first responsibility is to prepare a list of knowns and unknowns for resolution. By compiling this list, the company will be able to analyze and target specific process questions.

At the top of the list will be the type of polymer to be used. The management team has already targeted reclaimed polyester as the primary source of raw material. There also exists other types of polymers that should be considered, including nylon and polypropylene.

Concentrating on polyester as the first option for defining the process parameters, items that must be considered as the core for achieving success are:

*The average melt index of the reclaimed material.

*The percentage of virgin PET that can/will/is to be mixed with the reclaimed material.

*What special additives should be used to improve upon the existing properties of the reclaimed polymer?

*What colors will mix well with this material?

*How much debris is mixed within the material?

*What special post extruder filtering requirements are needed? This list will continue to grow. The concept is to begin to accumulate this information prior to beginning the process trials. What other information is needed? The following partial list serves as an example:

*Polymers: Type, properties, melt index, percentages, additive types, color types, drying requirements, contaminants, continuous heating requirements, degradation constants

*Weight: anticipated basis weight, variations of

*Filament properties: diameter, deposition, feel (hand)

*Material: color, varieties, tensile strength, direction of fibers

*Extruder: Number of temperature zones, screw type, screw material, precision of heat control, heating profile, cooling requirements, pressure requirements, burst (rupture) disk types, pre-filtering requirements, feed rates

*Filtering equipment: number of filters, screen size, back pressure monitoring, temperature control and requirements

*Polymer delivery: heated jacketed tubing, thermal fluids available, heating control, material type

*Spin pumps: type to be used, disk filter types, configuration of polymer path, metering rates, heating zones, seals

*Spin plates: material, hole diameter, hole quantities, seals, size, finish

*Filament delivery: type - Lurgi, Reicofil, other, none

*Quench air requirements: temperature, volume, velocity

*Other air requirements: to be evaluated

*Web former: type of wire, pre-compaction requirements

*Below wire exhaust: volume, vacuum settings

*Calendering: need, type of, temperature, method of heating, patterns if required

*Post treatment: need, requirements, chemical types

This again represents a partial list. It will help clarify lab equipment and process equipment as the work continues.

Running Process Trials

ABC has conducted extensive research into identifying the process variables to be incorporated into the new spunbond line. Unfortunately, it does not presently have a pilot line with which to test the process.

Investigation of process variables is required prior to starting the engineering portion of the project. Not all spunbond processes are alike. The equipment utilized within a spunbond operation may be quite similar to that of the other manufacturers, but the processes employed can be radically different.

In order to narrow the variables and to isolate/define the exact parameters that make up those variables, test runs of the product must be made to confirm any assumptions. Unlike buying a car, ABC is about to invest several million dollars on specialized machinery. To minimize the financial risk posed by the project, and to protect the company, process trials must be conducted.

The process trials will assist in the determination of the exact chemical properties of the fabric. ABC will be able to test whether it has the additives in the correct percentages imperative to having a saleable product. Color mixing will also be accomplished during this phase of the project.

The post chemical treatments of the cloth can generally be processed off-site and away from the pilot facility. In some instances this may be advantageous when attempting to maintain secrecy.

Besides testing the chemical composition of the fabric, at this point work will also be done on refining several known parameters and defining those that are open to question. A partial list of process variables are shown in Table 1.

Table : PROCESS VARIABLES metering rates screen filtering disk filtering for linear elongation of

the fibers at the spin pumps thermal (heating) constants air quench temperatures and velocity

other air variables unique mechanical configurations below wire vacuum requirements spin plate hole diameters and

configuration mechanical formation chambers material basis weights web formation speeds compaction/fiber compression

requirements calendering/thermal bonding

temperatures calendering fabric profiles based on

temperatures fabric texture (hand)

While management has been obtaining the appropriations requests, the marketing team should have, by this time, generated interest in the project with several potential clients. A side benefit of the process trial phase is that sample material can now be sent to potential clients. ABC will need the client's input and response about the material to make improvement upon the fabric.

The process staff will also receive valuable training in anticipation for actual startup. Future operations staff should be present during this portion of the project. What operations learns from working with the machinery will help them in constructing operation guidelines.

Minimum Requirements Of A Pilot Line

For the purposes of defining, conducting tests and improving upon the proposed material, the leased facility must be able to produce fabric a minimum of one foot wide. The mission of the pilot line is not to manufacture fullsize material. The aim of the pilot line is to test our variables.

The pilot line will have at a minimum:

* Pellet handling equipment. For ABC's purposes it may have to blend the reclaimed material off-site and then transport it to the facility.

* Extruder with multiple (five optimum) temperature zones, filter screens and an accessible spin pump. The facility should provide information on the spin pump filter disks so that these can be tested as needed. It may also need to add an additional screen filter for filtering the reclaimed material. These questions will be answered during the trials.

*Spin plate and beam that can be diassembled with ease.

*Compressed air system with chiller unit.

*Mechanical conveying chamber from the spin plate to the web former (collector).

*Web former (collector) unit.

*Under wire, high vacuum system.

*Thermal calender


*Data gathering via distributed control system if available.

There will be additional costs to the company other than the rental of the facility for development time. The purpose of the project is to come as close as possible to the process conditions that it will experience on a production line.

The development facility will permit modifications to its equipment if the costs are absorbed by the client. ABC's process team will have to work closely with the pilot facility owners. Most reasonable demands will be met as long as the burden of supplementary engineering costs is paid by the company.

The use of reclaimed polyester will require that ABC purchase an additional screen filter. This will require modifications to the existing equipment as well as impose extra heating loads. The spin plate may also not be adequate for its purposes. The process team will be responsible for obtaining the template dimensions of the plate and having outside machining performed on an as needed basis.

In this second part of a three-part series, Mr. Harmon takes a look at the steps of identifying the process and running process trials to test and improve the product. The previous section, published in the January issue of nonwovens industry, determined the direction of ABC Nonwovens' entry into new markets using a spunbond material. The consultant devised a strategic plan and is currently advising marketing in the development of a customer base using the new fabric.

About the author: Mr. Harmon is a senior partner at HSJ Group, Alpharetta, GA. He had been previously employed with Johnson & Johnson and Dow Chemical. HSJ Group is an engineering consulting firm specializing in the nonwovens business.
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Title Annotation:part 2
Author:Harmon, Jerry
Publication:Nonwovens Industry
Date:Feb 1, 1992
Previous Article:Getting to the point of needlepunch technology.
Next Article:Oil sorbent producer starts melt blown line.

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