[0001] , This invention relates to the sizing or dressing , of yarns whether of spun or
continuous filament type, to render them amenable to textile operations, for example,
twisting, doubling, weaving, knitting, braiding and so forth. It is particularly concerned
with sizes of the removable type which are adapted to be applied to hydrophobic yarns,
such as polyester or nylon yarns, and especially yarns for use in water jet looms.
[0002] Various water-soluble 'or highly water dispersible polymeric colloidal substances,
such as starch, polyvinyl alcohol and'acid rich 'acrylic copolymers have been used
for the sizing of yarns including moderately hydrophobic yarns such as nylon yarn,
but such materials generally show insufficient adhesion to the more hydrophobic yarns
such as polyester. This lack of adhesion requires the application of excessive 'amounts
of sizing material to protect the filaments or fibers or to compensate for the tendency
for the size to rub off on guides and other surfaces of the textile fabricating machinery.
A suitable polymeric size must not be so hard or brittle as to shed particles during
passage through the textile fabricating machinery nor may it adhere to the metal in
preference to the fiber or yarn and in this way lead to deposits of size materials
being left on metal drives or drying drums during the processing. Sizing of yarns
for use in water jet looms presents particular problems because the shed opening on
the looms is very small and electronic controls may be so fine that fuzzy yarns either
transfer with the jets or tend to trip the stop motion in electronically cont-rolled
units which then stop the loom abruptly.
[0003] The acrylic copolymer size 'of the instant invention has excellent adhesion to a
wide range of hydrophobic yarns and does not require extremely stringent drying conditions
in order to develop good water resistance.- De ite being highly hydrophobic, the polymer
is readily removable with a mild alklaine scour and thus is an excellent warp size
for yarns to be woven on a conventional shuttled or shuttless loom or preferably on
a water jet loom. Additionally, the polymer is tack-free in film form and, being a
latex emulsion as prepared, is readily amenable to dilution and dries easily under
moderate conditions to a water-resistant tack-free polymer.
[0004] In one aspect the present invention provides a method of sizing hydrophobic yarns
for weaving which comprises applying to the yarn an acidic latex of a free radical
initiated vinyl polymer having a . weight average molecular weight between about 300,000
and about 2,500,000. Said polymer, in dried film form, is hydrophobic and is not redispersible
in an aqueous solution at a low pH, such as from about 2 to about 5 or preferably
even to 7, and is redispersible in an alkaline aqueous medium. The polymer is a polymer
of monomers having a volume average solubility parameter (S.P.) between about 9.0
and about 9.5; the monomers comprising about 8% to about 14% α-β-ethylenically unsaturated
acid. The glass transition temperature (T ) of the polymer is between about -20°C
and 20°C.
[0005] In other aspects the invention provides.a method of weaving hydrophobic fibers which
have been sized by the method described, the woven fabrics thus obtained, and the
sizing compositions themselves.
[0006] The polymer latex of the instant invention is made, preferably by a gradual addition
thermal process, at about 30% to 60% solids following conventional emulsion polymerization
procedures such as taught in the books entitled Emulsion Polymerization by D.C.Blackley
(Wiley, 1975) and by S.A.Bovey et al (Interscience Publishers, 1965) and Applications
of Synthetic Resin Emulsions by H.Warson (E.Benn,Ltd., 1972) and Emulsion Polymerization
of Acrylic Monomers (Rohm and Haas Co.bulletin CM104A/cf) all herein incorporated
by reference. The polymer is preferably a linear polymer free of crosslinks and branch
points. In one desirable embodiment, the polymer is prepared from monomers consisting
essentially of, by weight, 45-65% butyl acrylate, 28-45% styrene or methyl methacrylate
or a mixture thereof, 8-14% acrylic acid or methacrylic acid or a mixture thereof;.preferably
the monomers consist essentially of 50-60% butyl acrylate, 28-40% styrene and'10-13%
acrylic acid or methacrylic acid. The polymer has a weight average molecular weight
of from about 300,000 to about 2,5.00,000 with 500,000 to about 2,000,000 being preferred
and 600,000 to 1,500,000 being most preferred.
[0007] The polymer latex size forms a film on a hydrophobic yarn, preferably a polyester
such as polyethylene terephalate or a nylon such as nylon 66, or nylon 6. The film
has excellent adhesion and flexibility thus providing a hard, tough.protective film
unaffected by the abrasive action of looms, particularly water jet looms, and by humidities
up to 100%. ' The polymer is easily. removed by scouring with dilute aqueous solutions
of alkaline materials.
[0008] The hydrophobic yarn of this invention comprises fibers which exhibit moderate to
little uptake of water upon immersion in water or exposure to high humidity. This
property is often measured by adsorption of water
'by a.polymer film having a composition corresponding to that of the fiber or by. the
moisture regain or-uptake of dehydrated fibers when held in an atmosphere of fixed
relative humidity. Sources of such data are J. R. Scott and W. J. Roff, et al., Handbook
of Common Polymers CRC Press, Cleveland, Ohio, 1971; E. Sutermeister, Chemistry of
Pulp and Paper Making, John Wiley & Sons, New York, 1941; and the periodical Textile
World, McGraw-Hill Publications, Atlanta, Georgia. The following table is abstracted
from the 1978 Textile World Man-Made Fibers Chart, herein included by references on
page 51 et seq. of the August 1978 Textile World.
[0009] Hydrophobic fibers are fibers wherein the moisture . regain is about 5% or less,
preferably between about 4._5%,
'and . about 0.1% and most preferably between about 3% and 0.2% of the fiber weight
at 70° F and 65% R. H. The yarn of the present invention preferably comprises at least
about 50% by weight of such hydrophobic fibers; more preferably the yarn consists
essentially of hydrophobic fibers and most preferably entirely of hydrophobic fibers,
especially 100% polyester fibers, such as poly(ethylene terephthalate), and 100% nylon
fibers.
[0010] The amount of copolymer applied to the textile material may vary from about 1 to
'about 20% by weight of yarn depending on the purpose for which the application is
intended and on whether or not auxilliary conditioning or sizing agents are included
in the composition'when it is applied to the textile. The latex may be applied by
spraying, dipping, padding, by sizing-rolls, transfer rolls or the like; An entire
warp may be passed through a conventional slasher or a yarn may be individually treated
in a single end sizer. The latex may have a concentration of 1-25% by weight solids
in the aqueous system and excess may be removed, such as by squeeze rolls or wipers,
and the treated yarn may then be dried. 'Drying may be effected by any suitable means
such as by heated air or drying cans. Drying may be effected at a wide range of temperatures
such as 70-120°C. The aqueous latex may be applied at room temperature or at elevated
temperatures such as up to about 80°C. For warp - sizing of spun yarns the preferred
proportion of polymer applied to the yarn is from 5-15% by weight of the initial _
weight of the yarn. For the sizing of continuous filament yarns, including water jet
loom sizing, the preferred pro- portion is from about 1% to about 10% copolymer on
the weight of the yarn. The higher amount of size is needed for fine (low) denier
zero or low twist yarn.
[0011] . The copolymer of this invention may be applied to modify their properties and especially
to render them more amenable to textile processing operation. Although not necessary,
auxiliary materials may be incorporated into the latex such as surfactants or water
dispersible lubricants, including sulfonated oils, self-dispersible waxes, swelling
or plasticizing agents for the yarn, etc.
[0012] The article obtained, after application of the sizing composition to the yarn and
drying, is essentially free from the disadvantage of developing static charges and
loss of sizing material by transfer to guides or by shedding. Surprisingly, the sizing
material is readily removed by common scouring operations because of the ready solubility
in aqueous alkaline medium despite its marked hydrophobicity, affinity for hydrophobic
fibers and insolubility in'acid medium. Even mildly alkaline scour solutions, such
as 0.15% soda ash, are completely effective in removal of this polymer. Such mildly
alkaline solutions may have a pH about 11.,
[0013] Various tests
.are employed to gauge the suitability of the polymer latex for use in sizing polyester
yarn. The test methods are described below; in the examples there are data comparing
polymers of the instant invention with materials of the prior art and with examples
of polymer latices outside the bounds of the instant invention.
[0014] The adhesion of the polymer to the yarn as measured by the Sand Tumble Test, described
below, guages how well a yarn bundle will resist abrasion on the loom. Run under dry
conditions the test relates to performance on a stan- . 'dard loom and run under wet
conditions the test relates to performance on a water jet loom. A value of 50 is considered
acceptable although 75 is preferred and values about 100 are most preferred.
[0015] The Adhesion to Mylar® Test is indicative of adhesion, especially to a polyester
substrate since Mylar is a polyester substrate. The Crinkle Test gives the tendency
of the polymer to flake from the substrate under flexing, thus simulating a yarn going
over a roller or a guide. Flaking under such conditions would cause a weak spot in
the yarn and thus lead to breaks in the yarn on the loom. The Scrape Test is to simulate
the action at drop wires or a reed in the loom and also gives a gauge of the film
toughness which property is required for runability in a mill.
[0016] . Water Resistance Tests measure a property needed for good performance in a water
jet loom. Low water resistance is indicative of high swelling which leads to a markedly
'weaker film and thus to a weak sized yarn. The Moisture Regain measure, being at
95% relative humidity, additionally indicates the stability of the sized yarn to changes
in ambient conditions such as seasonal or from dry day to humid day.
[0017] Tack Test measures the ability of the sized and dried yarn to be rolled on a beam
while warm and then be unrolled from the beam without sticking.
[0018] Removability of the size is, of course, essential with the final test of removability
from the sized yarn being most important. The size should be completely removable
from the yarn.
[0019] . The polymer of the instant invention is applied to. the yarn in the form of a latex
of particles usually about 0.07 to about 0.25 microns diameter, with 0.10 to 0.18
being pre- ferred and about 0.14, or a range within about 0.02 of that value, being
most preferred. Polymerization procedures useful' in producing polymers of the desired
particle size and molecular. weight are given in the books referred to above. This
highly hydrophobic polymer composition is applied at acid_ pH and is scoured at basic
pH thus the polymer is intrinsically stronger, as a size, than a solution polymer
would be in this application. The solution polymer would have to be at least partially
neutralized to be'in aqueous solution and thus would be highly swollen and weaker
than the very hydrophobic latex polymer at low pH, of the instant invention. If attempts
are made to have the solution polymer be more hydrophobic, and thus marginally soluble,
then the difficulty of scouring increases. A further advantage of utilizing a latex
versus an alkaline solution or dispersion of a polymer is that less severe drying
conditions' are .required for the latex, a particularly significant energy saving.
[0020] Alternative embodiments of the instant invention may employ other ethylenically unsaturated
monomers in the pre- paration of the polymer latex..In alternative embodiments it
is preferred that the acid content and identity be the same as in the above-described
embodiments altho other α - β ethylenically unsaturated acids, such as itaconic acid,
may be used: The acid level remains at 8% to 14% with 10% to i3% ' .being preferred.
Replacements for the butyl acrylate, styrene and methyl methacrylate are made on the
basis that the range of glass transition temperatures, (Tg), calculated for a high
; molecular weight polymer, and S. P. are to remain within the range implicit in the
compositigpal range for the embodiments taught above. Likewise preferred and more
preferred are ranges of Tg and S. P. corresponding to the preferred and more preferred
compositional ranges recited above.
[0021] - Polymer Handbook, 2nd Edition, J. Brandrup and E. H. Immergut, editors (John Wiley
& Sons, New York, 1975) section IV, part 15, entitled "Solubility Parameter Values"
by H. Burrell, on pages IV-337 to IV-359, herein incorporated by reference, defines
S. P., describes how it is determined or calculated, contains tables of S. P. and
gives further references to scientific literature on S. P. Table I on pages IV 341
to 344 lists the S. P. of solvents, including many monomers thereunder. In this specification
numerical values of S. P. have the dimensions (calories per cubic centimeter)to the
one half power, i,e (cal./cc.)0.5. The S. P. is the square root of the cohesive energy
density which in turn is the numerical value of the potential energy of 1 cc of material,
the potential resulting from the Van der Waals at.traction forces between the molecules
of a liquid or solid. Burrell describes a number of ways of calculating S. P. from
experimentally determined physical constants and two ways of calculating them from
the structural formula of a molecule. The structural formula methods are normally
used when the data for the calculation from physical constants are not available or
are considered particularly unreliable. Calculation
'from the structural formula utilizes tables of group , molar attraction constants
such as those given on pages IV-339. The table of Small is preferred. The S. P. concept
may be considered an extension of the old rule "Like dissolves like." recognized .
since the early days of chemistry.
[0022] . ' . As tables of the .solubility parameter of monomers are' available, as noted
above, it is convenient to
'define a polymer in terms of the solubility parameter of the monomers employed in
its polymerization. The effective solubility parameter of a mixture is the sum, over
the (i) components of the mixture, of the product of the volume 'fraction of the component
(vi) times its S. P., i.e., S. P. (mixture) = ΣVi (S. P.) i according to Scott and
Magatt (See Encyclopedia of Polymer Science and Teclinology, Vol. 3, John Wiley, 1965,
.page 856). The volume-fraction of each
' component is calculated from the weight fraction and the known density of the component
of the monomer mixture assuming no changes in volume on mixing. Densities of the monomers
are available in the usual sources such as The Polymer Handbook, The Encyclopedia
of Polymer Science and Technology, and the . manufacturers of the various monomers.
-The range of S. P. of the monomers employed in the polymers of the instant invention
is from about 9.0 to about 9.5 with the range 9.1 to 9.4 being preferred...
[0023] The calculated Tg of a polymer is determined by the equation of T. G. Fox, Bull.
Am. Physics Soc. 1, 3, page 123 (1956) based on the Tg of homopolymers of the individual
monomers in the copolymer. Tables of the Tg of homopolymers are given in "Polymer
Handbook", section III, part 2, by W. A. Lee and R. A. Rutherford herein incorporated
by reference. Tg values referred to herein are calculated Tg values for high molecular
weight polymers. The polymers of this invention have a Tg from about -20° C. to about
200 C. with the range -10
0 C. to +10° C.'
being preferred.
.
[0024] Other monomers which can be used in these alternative embodiments are preferably
vinyl aromatic hydrocarbons, such as vinyl toluene and alpha methyl styrene; alkyl
acrylates wherein the alkyl group has 1 to 8 carbon atoms, such as ethyl acrylate,
propyl acrylate, and 2-ethylhexyl acrylate; alkyl methacrylates having 2 to 4 carbon
atoms, such as ethyl methacrylate and isobutyl methacrylate and acrylonitrile.
[0025] The vinyl polymer used in the present invention is made as an aqueous dispersion
of an emulsion polymer at about 40% to 60% by weight of polymer solids. Monomers can
be . selected from the group consisting of C
2-C
18 alkyl acrylates, C
2-C
18 alkyl methacrylates, vinyl aromatic compounds, vinyl halides, vinylidene halides,
vinyl esters of saturated carboxylic acids, other polymerizable ethylenically unsaturated
mono- carboxylic and dicarboxylic acids and esters thereof, acrylonitrile,: methacrylonitrile
and alpha-olefins. Examples of the C
2-C
18 alkyl groups of the esters of acrylic and meth- acrylic acids which are useful in
forming the polymers of this invention include methyl, ethyl, n-butyl, i
-butyl, sec-butyl, t-butyl the various isomeric pentyl, hexyl, heptyl, and octyl (especially
2-ethylhexyl), isobornyl, decyl,lauryl, cetyl, . stearyl and like groups. Examples
of useful vinyl aromatic compounds include styrene and derivatives thereof such asvinyl
toluene and alpha-methyl styrene; of vinyl and vinylidene halides are the corresponding
chloride compounds; of vinyl esters of saturated carboxylic acids include vinyl acetate
and vinyl propionate; of polymerizable ethylenically unsaturated monocarboxylic and
dicarboxylic acids include acrylic acid, methacrylic acid, itaconic acid and crotonic
acid; and of alpha-olefins include ethylene, propylene, and butylene.
[0026] In the following examples parts and percentages are by weight and temperature in
degrees Celsius'unless otherwise indicated. The examples illustrate the invention
and are not to be construed as limiting the invention thereto. As given below, a general
method was followed in the preparation of yarns and films. - The method was followed
throughout the examples unless an exception is noted in a given example. The same
is true of the general test methods given below. .
Preparation of Materials:
[0027] Sized Yarns: The latex, at a pH of ca. 2.0 to 2.5 as prepared, or at a higher acid
pH such as about 4 or 5, is diluted to 8% resin solids with water and applied to polyester
or nylon filament yarn at room temperature on a laboratory size single end slasher.
The slasher employs a double squeeze and consists of an immersion bath followed by
a metal drum and two Teflon-coated drums, the first squeeze being between the metal
drum and the first Teflon coated drum and the second squeeze between the two Teflon
coated drums. The slasher is run at 4M/min and the sized yarn is dried 15 seconds
through a tube dryer set at 115°C. All sized yarn is conditioned one day at 21°C.
and 60% R.H. before testing.
[0028] Film Preparation: 20 mil films are prepared by diluting the latex with water to the
necessary solids content per volume. The diluted latex is then poured into a polypropylene
culture dish, placed in a dust free area on a level surface, and air dried for 4 days
or until a clear film is obtained. Thinner films (about 0.2 mils) are prepared by
pouring a 15% solids latex, obtained by dilution with warm water (54
0C), onto a two mil Mylar sheet. The films are room dried overnight, then oven dried
for one minute at 110°C.
Test Methods:
[0029] Adhesion by Sand Tumble Test: The sized yarns are evaluated for wet and dry adhesion
using laboratory sand tumble tests. Dry-Duplicate 3 yd. skeins of the sized yarn are
placed in an 8 oz. jar containing 150g of coarse sand, rotated for 30 minutes on an
Atlas .Launder-ometer®, removed and rated for % of the fiber bundle remaining intact.
Wet - The same procedure is .
-followed except the jar now contains 50g of sand and 150g water. Ratings are made
the same way.
[0030] Adhesion to Mylar: The adhesion of the thin film is determined by two methods, scrape
and crinkle. The scrape test -consists- of scraping the film with a razor blade and
counting the number of strokes required to remove the polymer film from the polyester
sheet. The . - crinkle test is designed to measure.the film adhesion to polyester
sheet by crumbling the sheet by hand and flat-.tening it, noting any film separation
from the Mylar. In the scrape test the results are classed as follows: Poor 1-2, Fair
3-4, Good 5 and Excellent -
'6 or more strokes. Crinkle test results are judged: Excellent - no change or Fair
- cracks and slight film removal.
[0031] Water Resistance: The wet sand tumble test, previously noted, is a preliminary screen
test of the water resis- - .-tance. All additional testing of this property is conducted
on the polymer films, either free or on Mylar, as follows: One inch squares of both
the free and Mylar films are placed in 30°C water for 30 minutes and evaluated for
any change in clarity, toughness, adhesion, and size using the following ratings:
Excellent = no change; Good = film swelling and Fair = swelling and loss of toughness.
The 20 mil (0.5mm) free film is also evaluated .for moisture-regain when first bone
dried and then subjected to 95% RH in a constant humidity chamber; the film is -also
observed for degree of haze developed.
[0032] Tack. The tackiness of_the'polymer is evaluated, . immediately following one minute
drying at 110°C, on the film cast on Mylar. For this evaluation, two films on Mylar
are pressed film/film and then opened to gauge adhesion.
[0033] Removeability of the Size: This property is evaluated by two methods, alkali solubility
of the film, and an actual scouring of sized yarn. Solubility of the film is determined
by placing of a 3/4" (2cm) square of the 20 mil free film in a 1% Na
2C0
3 solution at 70°C and .recording the time it takes to dissolve up to 20 min. at which
time the level of incomplete solution is gauged. The sized yarn is evaluated for size
removal by scouring the yarn at 70-74°C for 30 minutes in a 1.0% Na
2CO
3 and 0.1% surfactant (Triton®-X-100) bath with mild agita-
-' - . tion. The yarns are rinsed five minutes in warm water (54°C) and then cold water.
The degree of removeability is determined by dyeing scoured and control yarns in Basic
Red #14 at 60°C and observing the dye pickup.
[0034] The following abbreviations are used in the examples below: BA butyl acrylate, St
styrene, AA acrylic acid, MMA methyl methacrylate, MAA methacrylic acid, EA-ethyl
acrylate, EGDMA ethyleneglycol dimethacrylate, iBMA. isobutyl methacrylate, VT vinyl
toluene, .
MeST α-methyl styrene, AN acrylonitrile, 2- EHA 2-ethylhexyl acrylate, PMA propyl methacrylate,
and EMA ethyl methacrylste.
Example 1 - Copolymers Containing 12% Acrylic Acid
[0035] Film and yarn are prepared using acrylic copolymer latex samples described in Table
I below. The yarn being sized is Milliken textured polyester yarn, Saluda 373, 70
Denier, 33 filament, 1 twist. The test results, in Table I below, show that the samples
varying in butyl acrylate content from 45% to 50.5% are all suitable sizing polymers
compared to two commercial materials
. (1D, IE). All of the examples exhibited no tack, except 1D which had slight tack
when hot. The viscosity average molecular weight of the polymer of Example 1A is about
1.2 to 1.3 million.
Example 2 - Copolymers of 12% Methacrylic Acid
[0036] Using the same yarn as in Example 1 methacrylic . acid containing polymers having
55-60% butyl acrylate are tested with the results found in Table II. An additional
observation made is that the methacrylic acid samples produced less foam in the bath
and during handling than the corresponding acrylic acid samples. All of the examples
exhibited no tack.' The weight average molecular weight of the polymer in Example
2C is about 600,000 to 700,000.
Example 3 - Compositional Variations
[0037] Polymer latexes of various compositions, as reported in Table III below, are used
to prepare films and size yarns as in Example
1. The results in Table III indicate that the polymer based on ethyl acrylate (3C) has
low adhesion, both by the sand tumble test and the two adhesion to Mylar tests, is
high in moisture
' regain and produces a hazy film when tested for water resistance of a thin film on
Mylar. Example 3D, having 4% acid in the copolymer, exhibits an insoluble film and
less than complete removability from the yarn upon scouring and slightly hazy thin
film on Mylar in the water resistance test. Example 3E, having 16% acid in the copolymer,
also shows less than complete removability . from the yarn on scouring and in addition
has limited . water resistance shown by both the 20 mill (0.5mm) film and the thin
film results. The only examples, in this group, exhibiting tack are 3C which has some
tack when hot and .3D which has some tack even when cooled to room temperature.
Example 4 - Utilization of other Monomers
[0038] Using the same yarn as in Example 1 other polymers are tested resulting in the data
in Table IV. All of the examples are suitable for use in the water jet loom although
Example 4A appears to be somewhat less so than the others.
. Example 5 - Nylon Yarn
[0039] The procedure of Example 1 is followed with nylon yarn being substituted for the
polyester yarn of Example 1. The' nylon yarn employed is DuPont 70 denier, 34 filament,
0 twist yarn. The test results, in Table V below, show that the polymer of Example
4D compares favorably with materials commercially available. The nylon employed is
identified as 70-34-R25 295 M. D. pirn 13073.
Example 6 - Other Compositions
[0040] Polymer latexes of a number of different compo- sitions applied to the yarn of Example
1 and films prepared from the latex have wet and dried adhesion which are acceptable
as is the adhesion to Mylar by scrape and crinkle, the water-resistance of the film,
the moisture regain, tack, solubility of the film, and removability of the polymer
from the yarn. Polymer compositions, calculated Tg values and solubility parameter
values are given in Table VI.
1. A method of sizing hydrophobia synthetic fibers which comprises' applying to the fibers
an -acidic latex of a vinyl polymer prepared from monomers having a solubility parameter
in the range 9.0 to 9.5 and comprising 8-14% by weight of an α,β-unsaturated carboxylic
acid, said polymer having a weight average molecular weight in the range 300,000 to
2,500,000 and a.glass transition temperature in the range -20°C to + 20°C,said polymer
in dried film form being redispersible in aqueous alkali media but essentially non-redispersible
in acid media, and drying the treated fiber.
2. A method according to Claim 1 in which the latex comprises a polymer prepared from
a monomer charge consisting of monomers selected from the following: butyl acrylate,
styrene,' acrylic acid, methacrylic acid, ethyl acrylate, 2-ethyl hexylacrylate, propyl
acrylate, methyl acrylate, vinyl toluene, a-methyl styrene, acrylonitrile,' ethyl
methacrylate, butyl methacrylate and propyl methacrylate.
3. A method according to Claim 1 in which the latex comprises a polymer prepared from
a monomer charge consisting of, by weight, 45-65% butyl acrylate, 28-45% styrene and/or
methyl methacrylate and 8-14% acrylic and/or methacrylic acid.
4. A method according to Claim 3 in which the latex comprises a polymer prepared from
45-65% butyl acrylate, 28-45% styrene and 8-14% acrylic and/or methacrylic acid.
5. A method according to Claim 3, in which the latex comprises a polymer prepared
from 50-60% butyl acrylate, 28-40% styrene and 10-13% acrylic acid or methacrylic
acid.
6. A method according to any'one of Claims 1 to 5 wherein the yarn is a nylon or polyester
yarn,
7. A method according to Claim 6, wherein the yarn is a polyester yarn and the sizing
composition is a composition according to any one of Claims 3 to 5.
8. A method of weaving hydrophobic, synthetic yarn characterised in that before weaving
the yarn is sized by a method claimed in any one of the preceding claims and, after
weaving, the size is removed from the woven fabric by alkaline scouring.
9. A method according to Claim 8, wherein the yarn is woven in a water jet loom.
10. A sizing composition for sizing hydrophobic synthetic fibers prior to weaving
comprising an acidic latex of a free radical initiated vinyl polymer prepared from
a monomer having a solubility parameter in the range 9.0 to 9.5 and comprising from
8 to 14% by weight of an α,β-unsaturated carboxylic acid, said polymer having a weight
average molecular weight in the range 300,000 to 2,500,000 and glass transition temperature
in the range -20°C to + 20°C, said polymer in dried film form being redisperislbe
in aqueous alkaline media but essentially non-redispersible in acid media.
11. A composition according to Claim 10, wherein the polymer is as" defined in Claims
3,4 or 5.