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Pub Health 4310 Health Hazards in Industry

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Textile Fibers Cotton and Rayon. 11/11/09. PH 4310 - Health Hazards in ... the textile plant, it is first opened so that compressed fibers can be loosened ... – PowerPoint PPT presentation

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Title: Pub Health 4310 Health Hazards in Industry


1
Pub Health 4310Health Hazards in Industry
  • John Flores
  • Lecture 26
  • Mills and Textiles

2
Lecture 26Mills and Textiles
  • Chapters 33-34
  • Mills and Textiles
  • Pulp and Paper
  • Textile Fibers Cotton and Rayon

3
Mills and Textiles Pulp and Paper
  • Introduction
  • The major producers of pulp are the US, Canada,
    Japan, Sweden, and Finland
  • Although wood pulp was originally only used for
    paper it is now used in a variety of chemical
    processes
  • The US workforce in pulp, paper, and paperboard
    is about 160,000 strong
  • Pulp production in dominated by
  • the sulfate (Kraft) process (60),
  • the sulfite process (10),
  • and 40 of other techniques including the ground
    wood processing
  • Discussion will be based on the sulfate and
    sulfite processes as they make up about 70 of
    the industry and represent the bulk of the
    occupation health challenges
  • Although only a few comprehensive studies have
    been done within this profession it appears that
    paper dust and working in pulp and paper has an
    impact on lung capacity and that it is possible
    that this industry may cause restrictive or
    obstructive lung disease

4
Mills and Textiles Pulp and Paper
  • Chemical Pulping
  • Pulp can be produced by mechanical and chemical
    processes
  • The chemical process produces more than 70 of
    the pulp used today
  • Exposures in chemical pulping are much more
    serious than those of the mechanical pulping, so
    we will discuss chemical pulping
  • The sulfate (Kraft) process
  • Chipped wood is digested with steam in tanks
    using a solution of sodium sulfide and sodium
    hydroxide (white liquor)
  • The digestion builds gases, so must be
    periodically vented off
  • When digestion is complete, the load is dumped to
    the blow tank and any gases will vent from the
    pulp and digestion liquid
  • The spent cooking liquid (black liquor) is
    drained off to the evaporators, and the pulp is
    washed, screened, and bleached
  • The black liquor is processed through
    multiple-effect evaporators to concentrate
    chemicals
  • Salt cake (sodium sulfate) and the recovered
    chemicals are sprayed into a recovery furnace
    where water is removed, the liquor is burned, and
    chemicals are recovered
  • Recovered chemicals are dissolved in a smelt
    tank, quicklime is added to convert the sodium
    carbonate to sodium hydroxide and leave calcium
    carbonate
  • The calcium carbonate is converted to calcium
    oxide in the lime kiln, then slaked with water to
    produce calcium hydroxide which is used in the
    caustic tank (part of process to produce white
    liquor)

5
Mills and Textiles Pulp and Paper
  • Chemical Pulping (cont.)
  • Soda pulp process
  • Is the original chemical pulp process, of which
    the Kraft process is an advance of this
  • Similar to the Kraft (sulfate) process except
    that sodium carbonate is the chemical used in the
    furnace to make sodium hydroxide
  • Unlike the Kraft process, only sodium hydroxide
    cooking liquor is used in the digester
  • Sulfite process
  • This process is often called the acid sulfite
    process because it uses high-acid cooking liquor
    and requires a substantial chemical plant and
    recovery process for the sulfur dioxide released
  • The digester liquor is an aqueous solution of
    sulfurous acid mixed with lime or another base to
    form bisulfites
  • Sulfur dioxide is obtained either as a compressed
    gas, from the burning of sulfur, or from the
    roasting of pyrite ores
  • The relief gases from the digester contain high
    concentrations of sulfur dioxide, which must be
    recovered for air quality reasons
  • The sulfur dioxide is processed using a
    combination of separators and coolers

6
Mills and Textiles Pulp and Paper
  • Paper Production
  • The paper making process usually occurs at a site
    adjacent to the pulp mill
  • The process starts with bleaching of the pulp
  • Pulp bleaching is done by
  • Mixing the pulp with chlorine to remove colored
    degradation products
  • Extracting it and mixing it with sodium
    hydroxide, then exposing it to calcium or sodium
    hypochlorite to remove any remaining lignin, and
    a chlorine dioxide final treatment to brighten
    the pulp
  • Exposures from the pulp bleaching process include
    chloride hydrates which form when gaseous
    chlorine mixes in the vat and seeps to the
    surface releasing chlorine byproducts
  • Generally the chlorine is well controlled with
    local exhaust ventilation
  • After the pulp is bleached, it goes through a
    series of beating and refining steps, additives
    are blended with the pulp which is determined by
    paper end use
  • Chemicals that make up the additives are
    extensive but fall into 7 major categories
  • Filler pigments
  • Lubricants, plasticizers, and flow modifiers
  • Humectants and viscosity modifiers
  • Barrier coatings
  • Coating pigments
  • Sizes
  • Foam Controls

7
Mills and Textiles Pulp and Paper
  • Paper Production (cont.)
  • The paper making process (cont.)
  • The pulp consistency is adjusted by adding water,
    this pulp slurry is then pumped to a wire sieve
    where some of the water is drained away
  • The pulp leaves the sieve and processes through a
    press to increase solids content
  • A heated cylinder is then used on the pulp to
    reduce the water content to 5-8
  • The paper may be coated with clay, mica, talc,
    casein, soda ash, dyes, plastics, gums,
    varnishes, linseed oil, and organic solvents
  • Exposures
  • Principle exposures occur during operations in
    which acrlolein and other aldehydes are formed
    from the oxidation of linseed oil and solvent
    vapors from coating and drying operations

8
Mills and Textiles Pulp and Paper
  • Exposure Profile
  • The principle exposures to operators in the pulp
    and paper industry include
  • Raw wood preparation exposes employees to
  • Wood volatiles
  • Wood dusts
  • Spores and Fungi
  • Sulfate (Kraft) and soda process digester
    preparation
  • Lime
  • During Kraft pulping, opening the digester and
    dumping the product releases the following gases
  • Hydrogen sulfide,
  • Methyl mercaptan
  • Dimethyl sulfide
  • Dimethyl disulfide,
  • Sulfur dioxide
  • From operation of the recovery furnaces, effluent
    contains
  • Organic mercaptans and sulfides
  • Hydrogen sulfide, and
  • Sulfur dioxide

9
Mills and Textiles Pulp and Paper
  • Exposure Profile (cont.)
  • The principle exposures to operators in the pulp
    and paper industry (cont.)
  • Bleaching operations exposures include
  • Chlorine
  • Chlorine dioxide
  • Boron compounds
  • Neoabietic acids
  • Paper rolling, sizing, dying, drying, glazing,
    coating exposures include
  • Urea and melamine formaldehyde
  • Paper dust
  • Coating and pigment dusts
  • Maintenance
  • General plant exposures

10
Mills and Textiles Pulp and Paper
  • Controls
  • Worker exposure controls
  • Lime exposures can be excessive in both the
    sulfate (Kraft) and soda processes so handling
    practices to limit dust and inhalation exposures
    may be necessary
  • Digestion pits should be ventilated to remove and
    control sulfur dioxide, hydrogen sulfide, and
    mercaptans
  • Serious exposures to sulfur dioxide can be
    released through out the entire sulfate process,
    so controlling emissions at the sulfur burners
    provides the best control since this also puts
    the rest of the system under negative pressure
  • Ventilation provided to the digester controls
    build-up of gases which removes most of them
    prior to opening the digester
  • Remote operation of blow down valves allows for
    the operation to occur without the worker being
    president
  • Air pollution control
  • Most significant effort to control air emission
    involves the oxidation of the black liquor (used
    liquor) before it enters the multiple-effect
    evaporators, this occurs by
  • Sulfur compounds are oxidized which reduces their
    volatility
  • Incineration of sulfur off-gases has also been
    effective, this is done by
  • The gases are collected in a gas holder then
    burned off in the furnace

11
Mills and Textiles Textile Fibers
  • Introduction
  • There are many natural and artificial fibers that
    are able to be used in the textile industry
  • Natural
  • Cotton (plant)
  • Silk (silkworm)
  • Wool (sheep)
  • Linen (flax plant)
  • Hemp (plant)
  • Artificial
  • Rayon (cellulose treated with various chemicals)
  • Nylon (diamines and dicarboxylic acids)
  • Polyester (ethylene glycol and terephthalic acid)
  • Vinyl (ethylene)
  • Polyacrylonitrile (from natural gas, oxygen, and
    nitrogen)
  • For discussion purposes, only the natural fiber,
    cotton, and the artificial fiber, rayon will be
    discussed
  • Both of these materials have a range of
    manufacturing processes and health hazards that
    span the textile industry

12
Mills and Textiles Textile Fibers
  • Cotton
  • First of all, concerning cotton, there is disease
    related to the cotton textile industry
  • Byssinosis is a disease characterized by
    shortness of breath, coughing, and a tight chest
  • This disease occurs in workers handling cotton,
    but is also found in workers handling other
    organic fibers such as flax and hemp
  • Symptoms occur when returning to shift from
    extended time away, such as returning to work on
    a Monday after a weekend off
  • Symptoms are strongest at beginning of shift and
    subside as the week moves on, then returns upon
    returning to work
  • Since the disease is prevalent in the cotton
    industry, OSHA has a standard for cotton dust
  • Extracts of cotton dust and specific cotton
    components cause bronchoconstriction (asthma) and
    are contaminated with gram-negative bacterial
    endotoxin that can cause acute respiratory
    symptoms and pulmonary decrement
  • Prior to entering the cotton mill it must be
    picked
  • Cotton is now picked almost entirely by machine
    in the US
  • Seed cotton is processed a local cotton gins in
    which the seed and trash are separated from the
    cotton lint (fiber)
  • After ginning, the cotton lint is cleaned and
    baled
  • Biologically active materials are still present
    in the cotton bales , which are sent to the
    textile plant

13
Mills and Textiles Textile Fibers
  • Cotton (cont.)
  • Cotton processing operations
  • The processing of cotton into textiles involves a
    large number of specific operations common to
    textile plants, understanding these operations is
    necessary to understand
  • Opening
  • When cotton reaches the textile plant, it is
    first opened so that compressed fibers can be
    loosened
  • Heavy and bulky impurities are removed making the
    cotton fiber suitable for processing
  • Dust producing equipment includes
  • Bale breaker
  • Automatic feeders
  • Separators and openers
  • Mechanical conveyors
  • Dust producing equipment are enclosed and
    supplied with local exhaust to control dust
    emissions
  • Picking
  • A picker includes a feed hopper, beaters, screen
    sections, and calendar roll section
  • This equipment opens and cleans cotton and forms
    a continuous web (lap) for the carding machine
  • This equipment creates a lot of dust so should be
    equipped with an exhausted enclosure

14
Mills and Textiles Textile Fibers
  • Cotton (cont.)
  • Carding
  • The cards are a major source of dust because they
    handle the cotton in such a way that dust,
    debris, and trash are released from the fibers,
    generally the machine is enclosed and ventilated
  • The lap formed by the picker is a loosely bound
    layer of cotton that consists of unopened tufts
    and tangled fibers which the card is designed to
    remove
  • This lap contains a large amount of trash or
    non-lint material that must be removed
  • The lower the quality of cotton, the higher
    amounts of trash and debris
  • Along with removing unwanted debris, the card
    also takes the cotton lap and forms it into a
    thin lacy mat with parallel fibers that will
    eventually be converted to a continuous filament
  • The card process
  • The lap (mat) is positioned on the feed roll and
    fed between the lickerin (small cylinder
    covered with wire teeth) and the feed roll
  • The rotating lickerin finger the lap to open
    the tufts of cotton releasing trash out of the
    lap (dusty work)
  • The continuous mat is processed across a rapidly
    rotating card cylinder which is covered with wire
    teeth
  • Flats contain a wire cloth which slowly passes
    over the card cylinder moving in the opposite
    direction to open and straighten the cotton
    passing between them and the cylinder (dusty
    work)
  • The fibrous mat is removed from the card cylinder
    by the doffer (small cylinder with needle
    surface)
  • The web is then compressed by rolls and fed
    through a round opening to transform the 100 cm
    (39 in) wide web into a 2.5-cm (1-in) diameter
    rope-like sliver which is coiled into a can for
    the next operation

15
Mills and Textiles Textile Fibers
  • Cotton (cont.)
  • Drawing and Roving
  • The drawing process consists of feeding several
    cotton slivers into a drawing frame which
    compresses them into one dense sliver that is
    coiled again for the next operation
  • This process pulls the fibers together and
    orients them all in the same direction and
    improves the uniformity of the sliver
  • Although this operation is usually enclosed and
    ventilated it does not generate a lot of dust
  • Roving involves combining many slivers into one
    sliver, again providing additional uniformity to
    the cotton product
  • During continuous roving, the product is also
    given a twist that improves the product strength
  • The roving process is also not a major source of
    dust
  • After drawing and roving the sliver is wound on a
    bobbin for spinning
  • Spinning and Winding
  • Spinning takes the large diameter roving and
    processes it into a small-diameter twisted yarn
  • Since the spinning process occurs at high speeds,
    any trash left in the cotton will be released
  • To provide long yarn lengths, cotton is removed
    from small bobbins and spun onto cones or tubes
    at high speeds which can become dusty
  • By the time the cotton is ready for weaving,
    little trash or dust is left in the cotton so
    additional hazards are minimal

16
Mills and Textiles Textile Fibers
  • Cotton (cont.)
  • Control
  • NIOSH (1975) recommends the following controls
  • Treat raw cotton to remove or minimize the
    offending agents
  • Change the process that is the source of dust
  • Remove dust from the workplace air
  • Ventilation continues to be the principle measure
  • A study of airborne cotton dust in a large
    textile plant showed much of the re-circulated
    air contained respirable cotton dust (Hammad and
    Corn, 1971), requiring the following
    recommendations
  • Re-circulated air must be curtailed or use of
    better filtering be implemented
  • Local exhaust ventilation should be used with
    enclosures
  • Better work procedures and housekeeping to remove
    settled dust
  • A major source of cotton dust is due to blowdown
    by air lines or blowers
  • This is done to remove deposited lint and dust
    which can become a fire hazard and must be
    removed
  • Vacuuming is considered inadequate to remove the
    lint and dust, so blowdown tasks in conjunction
    with the use of respiratory equipment is
    recommended

17
Mills and Textiles Textile Fibers
  • Rayon
  • Rayon making process
  • Pads or sheets of cellulose made from wood pulp
    are soaked in sodium hydroxide to form a soda
    cellulose
  • The sheet material is then shredded, aged, and
    mixed with carbon disulfide in an xanthating
    churn (mixer with xanthic acid)
  • The mixture becomes a cellulose xanthate, which
    is a brown syrupy liquid known as viscose
  • After filtration, aging, and deaeration, the
    viscose if forced through small holes in a nozzle
    (spinnerette) submerged in a sulfuric acid bath
  • When the stream of viscose contacts the bath, the
    cellulose is regenerated into a continuous fiber
  • Tension (stretching) on the fiber is controlled
    with godgets which operate at slightly
    different speeds to orient the yarn fibers

18
Mills and Textiles Textile Fibers
  • Rayon
  • Exposure and controls
  • Exposures to carbon disulfide are widespread in
    this industry
  • Carbon disulfide has a range of toxic effects
    that are very serious
  • Overexposures can lead to a Parkinsonism like
    syndrome, psychosis, and suicide
  • Repeated exposures have been linked to coronary
    heart disease
  • Has a wide explosive range and can autoignite at
    120 ºC (250 ºF), about the surface temperature of
    a light bulb
  • Potential vapor exposures occur during
  • The xanthation process
  • Can usually be controlled because it is an
    enclosed operation
  • Spinning process
  • The open spinning baths release carbon disulfide
    and hydrogen sulfide and should be monitored and
    controlled with ventilation
  • Godget and cutter operations
  • During the stretching of the fiber, carbon
    disulfide is released, if the fiber breaks, it
    must be pulled by hand to get it started again,
    exposing the employee to the off-gasing carbon
    disulfide
  • This operation must be controlled by local
    exhaust ventilation with an enclosing hood
  • Complete range of controls must be utilized to
    protect employees from overexposure
  • If engineering and procedural controls are not
    adequate, a complete respiratory program is needed
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