FR2482613A1 - COATING COMPOSITION FOR FIBROUS POLYOLEFIN SHEETS - Google Patents

Abstract

THE INVENTION RELATES TO COATING COMPOSITIONS. IT CONCERNS AN IMPROVED COATING COMPOSITION IN THE FORM OF A WATER-BASED DISPERSION WHICH CONTAINS 10 TO 40 BY WEIGHT OF SOLID MATERIALS, WHICH SOLID MATERIALS INCLUDE EFFECTIVE QUANTITIES OF A WAX INSOLUBLE IN WATER, AN ANTISTATIC AGENT, D 'A NON-IONIC SURFACTANT AND A WATER INSOLUBLE RESIN, CHARACTERIZED IN THAT THE COMPOSITION INCLUDES AN EFFECTIVE AMOUNT OF FINE PARTICLES OF POLYTETRAFLUOROETHYLENE. USE, IN THE FIELD OF SURGICAL CLOTHING, FOR COATING FIBROUS POLYOLEFIN SHEETS WITH A VIEW TO CONFIRMING THEIR PROPERTIES OF WATERPROOFING IN THE BLOOD.

Description

The present invention relates to an improved coating composition which

  provides superior water-impermeability properties as well as advantageous water-proof, anti-static and anti-slip characteristics to a sheet

  fibrous polyolefin which is coated therewith. In particular

  The invention relates to such a coating composition which contains polytetrafluoroethylene powder, processes for preparing the

  coating and fibrous sheets of polyolefin

  clad in the coating composition.

  The U.S. Patent No. 4,082,887 discloses a coating composition which advantageously provides good water impermeability properties; slip and anti-static to a fibrous sheet of polyolefin which is coated therewith. Such coated sheets have been used for gowns and drapes in hospital operating rooms. The

  coating composition of U.S. Patent

  No. 4,082,887 is in the form of an aqueous dispersion

  which contains 10 to 40% by weight of

  solid. Solids consist essentially of

  and effective amounts of (a) water insoluble wax, (b) an antistatic agent, (c) a nonionic surfactant and (d) a water-insoluble binder resin. Example 5 of the patent describes such a composition which also contains an aqueous anionic dispersion of a fluoropolymer

  useful as an alcohol repelling agent. This composition

  When it is applied to a non-woven polyolefin fibrous sheet and then dried, it is said to give the coated sheet good water-proof, anti-static, anti-slip properties.

  and impermeability to alcohol. However, the request

  deresse has found that improvements are needed regarding the blood impermeability properties of

these coated sheets.

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  The present invention relates to an improved coating composition which, when applied to a polyolefin fibrous sheet and subsequently dried, provides the coated sheet with improved blood impermeability properties, as well as advantageous waterproofing properties. water, antistatic and anti-slip. The coating composition is of the general type described in U.S. No. 4,082,887. The composition is in the form of an aqueous dispersion which contains from 10 to 90% by weight of solids. Solid materials

  include effective amounts of an insoluble wax

  luble in water, an antistatic agent, an agent

  nonionic surfactant and a non-ionic resin binder

  luble in the water. The improvement according to the present

  invention includes inclusion in this

  coating of an effective amount of fine polytetrafluoroethylene particles giving the coated and dried sheet improved blood impermeability characteristics. Usually, the amount of polytetrafluoroethylene in the coating composition is at least 10% based on dry solid materials; the preferred quantity is included

between 10 and 35%.

  The present invention also relates to a

  fibrous sheet of polyolefin coated with the

  improved coating, dried. Preferably, the sheet is a nonwoven sheet made of polyolefin film fibrils, in particular

  fibrils of polyethylene film.

  The invention also relates to novel processes for preparing the coating composition described above. According to one embodiment, the method comprises the steps of (a) forming a molten mixture of the water insoluble wax and the nonionic surfactant, (b) dispersing the fine particles of polytetrafluoroethylene in the mix

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  melted, (c) add water vapor and then

  the liquid water with dispersion thus prepared from

  in the molten mixture to form an aqueous dispersion, (d) adding the water-insoluble resinous binder to the aqueous dispersion, and (e) adding the antistatic agent. A preferred method for preparing the coating composition comprises the steps of (a) forming a molten mixture of

  water-insoluble wax and surfactant

  nonionic active agent, (b) preparing a slurry of the polytetrafluoroethylene fine particles in an aqueous mixture of the water-insoluble resinous binder, (c) dispersing the slurry in the molten mixture while adding water vapor and then the water

  liquid and (d) add the antistatic agent.

  Except as regards the presence of fines

  polytetrafluoroethylene particles in the

  improved coating conditions of the present invention.

  tion, the present compositions are substantially

  the same as those described in the patent

  United States of America NI 4,082,887. Thus, the present

  The coating composition is in the form of an aqueous dispersion containing from 10 to 40% by weight solids, the polytetrafluoroethylene particles being from 10 to 35% by dry weight of the solids of the coating composition. The other ingredients of the present coating composition include the known effective amounts of a water insoluble wax, an antistatic agent, a nonionic surfactant, a binder resin, and the like.

  insoluble in water and the required amount of water.

  Particulate polytetrafluoroethylene

  use in the coating composition of the invention

  are introduced in an amount effective to significantly improve the blood impermeability properties of the polyolefin fibrous sheet coated therewith. This improvement is observed by

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  compared to similar compositions in which the polytetrafluoroethylene particles are not

  not present. Polytetrafluoro particles

  ethylene usable include those sold under the names DLX-6000 and "Teflon" 7A, both sold by E.I. from Pont de Nemours and Company of Wilmington, Delaware, U.S.A. The DLX-6000 product has a density of 2.3 g / cm3, a melting range of 320 to 34000 C, and an average

  particles of less than 1 micron, although the

  These may agglomerate into loose aggregates having sizes of about 150 microns. The product "Teflon" 7A has a particle size of about microns, a density of about 2.2 g / cm3

  and a melting point of about 327 C.

  As in the coating composition of U.S. No. 4,082,887, the water-insoluble wax for use in the coating composition according to the invention is capable of being dispersed in water at a concentration of 10%, based on the total weight of wax and water. For its dispersion in water, the water-insoluble wax requires only a nonionic surfactant or a mixture of two or more of these surfactants in a proportion of 15 to 100% by weight relative to the amount of wax. The nonionic surfactant has a balance

  hydrophilic-lipophilic (abbreviated EHI) from about 6 to 10.

  The term "wax" as used herein means a substance that meets the modern-use definition given on page 721 of the "Hackh's Chemical Dictionary",

  4th Edition, McGraw-IIill Co., N.Y., 1969.

  A preferred wax for the composition according to the invention is an ethylene diamine bisamide wax, such as that called "Kenamide" W-5, sold by Hnmko-Sheffield of Memphis, Tennessee, USA, or that called "Advawax" - 225, sold by Cincinnati Milacron Chemicals, Inc. of New Brunswick, New Jersey,

  USA. These waxes are known to be useful as lubricants.

  for thermoplastic or thermo-resins

  hardenable and pocket mutual adhesion between sheets, confer antistatic properties and reduce stickiness. However, the level of antistatic properties provided by the wax, when used in a coating composition of the type described here without another

  antistatic agent, is of an order of magnitude insufficient

  compared to what is necessary for the applications

  envisaged sheets of the coated sheets according to the present invention. Other waxes that can be used in the composition according to the invention are, in particular, the following: "Advawax" 140 and "Advawax" 240, products of Cincinnati Nilacron Chemicals, Inc .; "Mooreflake" 160, a product of Moore and Munger, Inc .; and "Mobilwax" 150 and "Mobilwax" 2505, products of the Mobil Oil Company. The wax is present in the composition according to the invention in an amount effective so that when the composition is applied to a nonwoven polyolefin sheet

  at a desired coating weight and dried,

  Impermeability to water is imparted to the leaf. Suitable wax concentrations are from about 15 to about 40% by weight

  relative to the amount of resin in the composition.

  The antistatic agent of the coating composition according to the invention is described in U.S. No. 4,082,887 and has the formula M R nPO, wherein M is selected from lithium, sodium, potassium and ammonium ions; R represents an alkyl group containing 3 to 5 carbon atoms and n is selected from the integers 1 and 2. A preferred antistatic agent is a mixture of approximately equimolar amounts of potassium dibutylphosphate and dipotassium butylphosphate. The anti-static agent is present in an amount of 246t13 effective as it gives antistatic properties

  to the fibrous polyolefin sheet when the composition

  tion is applied on it is dried. Quantities

  Antistatic agents are usually included.

  between 0.034 and 0.17 g / m2 (dry weight)

  relative to the surface of the sheet. Like, usually

  the antistatic agent is commercially available in the form of an aqueous solution, the amount of antistatic agent used will depend on

  the concentration of the solution. Too much

  The antistatic agent in the composition will cause a loss of waterproofing properties and will result in incompatibility with the dispersion.

of binder.

  The coating composition according to the invention contains a nonionic surfactant as described in U.S. Pat. No. 4,082,887. The surfactant has a hydrophilic-lipophilic balance (EEL) of about 6 to 10. An EEL of less than 6 results in an uneven application of the coating while

  that a value greater than 10 causes a loss of resistance

  water. EEL is defined as the percentage by weight of the hydrophilic portion of a nonionic emulsifier molecule and is described in "The Atlas System", 4th Edition, edited and reprinted from Chemmunique, a publication of Atlas Chemical. Industries, Inc. The surfactant should not coagulate the binder resin dispersion. Among the commercially available nonionic surfactants which can be used, mention may be made of the

  "Spans", which are mixtures of mono-type esters

  laurate, monooleate and monostearate and "Tweens", which are the polyoxyethylene derivatives of these esters. "Spans" and "Tweens" are products of Atlas Powder Company. A mixture containing 83% by weight of "Span" 80 and 17% by weight of "Twain" 80 will give an EHL of 6. A mixture containing 46% by weight of "Span" 80 and 54% by weight of "Tween" 80 will give an EHL of 100 The surfactant is used at the rate of

  to 10% by weight, based on the amount of wax.

  If a quantity of surfactant substantially greater than the maximum specified above is used, foaming of the coating composition and degradation of the water-proofing properties of the formed coating may result. of the composition. It is preferable that the amount of surfactant is just sufficient

  to carry out the dispersion of the wax in the water.

  The coating composition according to the present invention contains, as well as the coating composition of U.S. NI 4,082,887, a water-insoluble binder resin that is capable of

  wet the polyolefin sheet (oleophilic).

  Whether or not a particular binder resin has the oleophilicity required for the purposes of the present invention is determined by a test in which an aqueous dispersion of the particular binder resin is diluted to 25% solids and then

  a rule of Mayer NI 16, a thin layer of the disc

  diluted resin persion is spread on a medium to try. If the resulting wet film is smooth

  and continues and remains intact after drying, for example

  for three minutes in air at 1100C, the binder resin meets the "wetting" criterion as used herein. In addition, the binder resin

  not possess an excessive degree of oleophilia, ie

  to say that it should not impregnate the support in

  the conditions of the test described above.

  Other requirements for the binder resins useful in the present coating composition are that the resin should not impart stickiness or stickiness, brittleness or poor adhesion to coatings formed therewith. Resins

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  having a glass transition temperature Tg included

  between 20 and 50% C are usually used.

  ble. In addition, the binder resin dispersions used

  Readable in the present invention should not coagulate in the presence of the antistatic agent. We

  can perform a test to determine whether a dis-

  Particular binder resin persion possesses this coagulation property by diluting the dispersion of the particular binder resin to 25% by weight solids, mixing about 70 parts by weight of the dilute resin dispersion and about 2 parts by weight of the aqueous antistatic agent and then observing if coagulation occurs

or not.

  The proportion of binder resin used in the composition according to the invention is not critical

  and will depend on the particular binder resin used.

  In a preferred embodiment, the binder resin is present in an amount of about 35 to about 80 percent by weight, based on the weight of the coating composition when dried. Suitable aqueous dispersions of resins include a copolymer dispersion

  ethylene / vinyl acetate and a dispersion of

  ethylene / methacrylic acid as described in U.S. NI 3 487 036; a crosslinked terpolymer dispersion of ethyl acrylate / styrene / acrylonitrile having a Tg of 200C; a crosslinked terpolymer dispersion of ethyl acrylate / styrene / acrylonitrile having a Tg of 335C; and a dispersion of a copolymer of 85 parts of ethylene / 15 parts

  of methacrylic acid which has been partially neutralized

  made with potassium hydroxide as described in U.S. No. 3,264,272. The product "Rhoplex" P-310 from Rohm and Haas, an acrylic compound / vinyl acetate copolymer dispersion having a Tg of 25 ° C. is also usable. These resin dispersions are usually marketed at a

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  solids content of about 5% by weight.

  Preferred resins for use in the

  position are the two terpolymer compositions.

mentioned above.

  The coating composition according to the invention

  may also contain one or more pigments, usually

  in an amount of about 1 to about 10% by weight based on the weight of the coating composition when it is dried. Both organic and inorganic pigments are usable. Examples of such pigments are those produced by the Applicant under the designations of Yellow "Dalasmar", Blue "N'onastral" and Red "Monastral", which have solids contents of about 29, 37 and 19 / o

by weight, respectively.

  The total solids content of the

  composition according to the invention is usually understood

  approximately 10 to 40% by weight. Solid contents of less than about 10% w / w are generally to be avoided because they often make it difficult to form dispersions.

  stable and require excessive drying times.

  Compositions with a solids content greater than 40% / are usually of high viscosity and are difficult to uniformly

a technique with an air gap.

  Special novel processes are required to form the aqueous dispersions of the coating compositions according to the present invention containing

  polytetrafluoroethylene particles dispersed.

  A process for preparing the coating composition is described in Example 1 hereinafter. The method comprises the steps of:

  (a) a molten mixture of the insoluble wax is

  luble in water and nonionic surfactant;

  (b) the fine particles of poly-

  tetrafluoroethylene in the molten mixture; (c) adding live steam and then liquid water to the molten mixture containing the polytetrafluoroethylene particles to form an aqueous dispersion; (d) adding the water-insoluble resinous binder to the aqueous dispersion; and

(e) adding the antistatic agent.

  A preferred method by which the coating composition according to the invention can be prepared is described in detail in Example 2 below and comprises the following steps: (a) a molten mixture of the water-insoluble wax is formed; nonionic surfactant;

  (b) a slurry of the fine particles

  polytetrafluoroethylene capsules in an aqueous mixture of the water insoluble resin; (c) dispersing the slurry in the melt while adding live steam and then liquid water; and

(d) adding the antistatic agent.

  In each of the processes described above, a molten mixture of the wax and the surfactant is prepared. In the first described process, the polytetrafluoroethylene particles are dispersed directly into the melt blends. This results in the formation of a very thick viscous paste. A strong mixer is required to mix and mix the peat to evenly disperse the particles. As the viscosity of the pftte increases with the content of polytetrafluoroethylene, this method limits the proportion of polytetrafluoroethylene in the final coating composition prepared

  by this process to not more than about 16% by dry weight.

  In the dispersion step itself, the polytetrafluoroethylene content of the resulting mixture prior to step (c) of addition of water and water vapor is usually limited to no more than about 60%. , by

  relative to the total weight of the mixture (before step (c)).

  In contrast, in the preferred method described above,

  the combination of the porridge particles

  Fluoroethylene / resinous binder with the molten mixture gives viscosities which are relatively low (compared to those of the pulp of the first process) and are kept at this low level by the simultaneous addition of water vapor while combining the boiled and melted mixture. As a result, the proportion of polytetrafluoroethylene particles in the final coating compositions prepared by this preferred method can be 35% or more, by weight based on the final coating composition.

once dried.

  The coating compositions described above can be applied to fibrous polyolefin sheets in various known ways

  to give coated sheets according to the invention.

  For example, the coating composition may be applied to a polyolefin fibrous support by air knife coating techniques, Meyer's rule, gravure roll, roller

  licker, etc. The technique is preferred to the air knife.

  When the coating composition is applied to a nonwoven sheet of polyethylene film fibril elements, it is preferred that the weight of the coating, in dry weight, be included

  between 1.7 and 3.4 g / m 2. After the application of the coating

  The coated support is dried at a high temperature, as in a hot air oven. During drying, evaporation of the liquid from the coating composition, coalescence and hardening of the binder and even spreading of the binder, polytetrafluoroethylene particles and

  wax on the surface of the support.

  It should be noted that in the past the dispersion of polytetrafluoroethylene particles in water posed daunting problems, due in large measure to the extreme hydrophobicity and high density of the polymer. Previous processes

  to disperse such particles

  generally come from large quantities of surfactants

  powerful assets. However, these surfactants

  assets also had the effect of canceling

  the desired hydrophobic effects of polytetrafluoro

  ethylene in the dried coating. In fact, some of the commercially available aqueous polytetrafluoroethylene dispersions contained such a large amount of surfactant that the dried coatings became

  makes hydrophilic. In addition to these difficulties,

  the high density of polytetrafluorocarbon particles

  fluoroethylene accelerated the sedimentation of

  in water, rendering the dispersions unusable

  for practical coating operations.

  On the contrary, in the dispersions of the compositions according to the present invention, the solids remain well dispersed for many hours.

  and are easily redispersed by a simple operation

  mixing without requiring excessive amounts

  and undesirable potent surfactants.

  Fibrous sheets of polyolefins

  may be reproduced from this composition

  take non-woven sheets of linear polyethylene, mixtures of linear polyethylene and minor proportions of branched polyethylene,

  polypropylene, polybutene and polyisobutylene.

  The nonwoven sheet may be continuous filaments, staple fibers or fibrillated films. A preferred medium is a non-paper

  woven elements of fibrils of poly-film

  olefin, in particular of linear polyethylene. -Of

  nonwoven sheets of film fibril elements

  polyolefin can be prepared by the

  method of the U.S. Patent N 3 169 899. The sheets

  coated according to the invention comprising non-woven sheets of fibrils elements of

  polyethylene coated with the composition according to the invention.

  have good impermeability properties

  blood, in addition to advantageous waterproofing properties.

  water resistance, anti-static, anti-slip,

  softness and aesthetics, which makes the leaves revive

  very useful kills for making blouses

  for hospital operating rooms.

  Antistatic protection can be determined

  provided by a coating prepared from a

  according to the invention by submitting a sample

  It is coated, which has been conditioned for at least 24 hours at 23.90 C / 55% relative humidity, in the US National Fire Protection Association (NFPA) Test Code 56A, Section 25433, Part A, Part 3. The result is reported as "Log R" with values of 10.5 or less representing acceptable antistatic properties and a value of about 9.5 being preferred. The value of "Log R" is determined as the average of measurements for several different portions of the coated sample. The impermeability to water of a coated sample is measured by the "hydrostatic head" test, ABSM standard D-583, paragraph 53A, method II. The term "good waterproofness" as used herein means a "hydrostatic head" of at least 63.5 cm as measured by

this test.

  We can measure the impermeability to blood

  by the following test of "blood permeability". We use

  in this test a resistance measuring device

  modified AATCC (American Association of Textile Chemists and Colorists) friction. The head of the unit is equipped with two rubber rollers and weighed 500 grams. A piece of foam rubber is covered with a plastic film and attached to the bed with adhesive tape to form a pad. A blotter (or folded paper towel) is placed on the pad. A sample, with the top coated side, is then placed on the pad. 1 cc of synthetic blood is applied to the coated surface of the sample. The apparatus is then operated for 20 cycles at a rate of 1 cycle per second, while the weighted rubber rollers force the synthetic blood into

  the sample. The blood that passes through the sample

  tillon is absorbed on the blotter. By determining the weight of the blotter, before and after the test, a measure of the amount of blood passed through the sample is obtained. Synthetic blood, which has about the same surface tension as real blood, consists of 10 grams of "Pontamine" Fast Red 8 BLI (a dye sold by the Applicant) and grams of nAcrysol "G110 (an agent surfactant sold by Rohm and Haas of Philadelphia, Pennsylvania, USA), added to enough distilled water to provide

1 liter of solution.

  The following nonlimiting examples illustrate

  invention and show the advantageous characteristics

  blood impregnated ticks of coated sheets according to the invention. Unless otherwise specified, the weights indicated for the quantities of resinous binder and pigment added to the coating composition

  relate to aqueous dispersions of these ingredients.

  ents. Quantities of the various ingredients used in each example and comparative experiment

  are summarized in Tables I, II and III.

EXEPLE 1:

  A mixture of nonionic surfactants consisting of 680 g "Span" 80 and 374 g Tween "

  is mixed with 3207 g of ethyl bisamide wax

  Lenin diamine "Advawax" 240 and heated to a temperature between 115 and 120 C. The wax-surfactant mixture melts and forms a homogeneous liquid of amber color. With the temperature of the mixture maintained at 115.degree.-120.degree. C. and stirring being effected by a mixer with two helicoidal mixers, 5.348 kg of

  micronized polytetrafluoroethylene DLX 6000. The result is

  a viscous mass. The heating is then stopped and a total of 64.18 kg of water is added, initially in the form of live steam and then in the form of liquid water, each time at about C. The resulting aqueous dispersion of tetrafluoroethylene particles is then cooled and provides a base for the remainder of the coating composition. To the cooled aqueous dispersion was added 3.688 kg of "Polywax 2000" micronized polyethylene powder (a product of Petrolite Corp. Bareco Division, Wayne, Pennsylvania, U.A.) while performing an intense shear mixing. Then, mixing at low shear, 66.34 kg is added

  of aqueous latex of ethylene-methacrylic acid copolymer

  "Surlyn" 56220, 726 g of "Dowfax" 2A-I surfactant stabilizer (a product of Dow Chemical Company of Midland, Michigan, USA), 451 g of "Nopco" antifoaming agent 267A (a product Diamond Shamrock of Morristown, New Jersey, E.UoA.), 7-4 g of "Chemcor" 973-A polyethylene binder (a product of Chemical Corp. of America of East Rutherford, New Jersey, USA) and 24, 2 kg of water, together with pigments consisting of 7.854 kg of "Super Imperse" Blue X2688 (a product of Ciba-Geigy of Arkysley, New York, USA), 7.289 kg of "Monastral" Red

  RW 768P and 0.934 kg of Yellow "Dalmar" YW768P.

  Just before getting a support from the com-

  As described above, 2,268 kg of a 3% aqueous solution of potassium "Zelec" TY antistatic butyl phosphate agent (a product of the Applicant) which was added to the composition was added to the composition to complete the coating composition. has been adjusted to pH 9.5 by

addition of ammonium hydroxide.

  The coating composition is applied at a rate of 1.7 g / m 2, dry weight, to a non-woven fibrous film of weakly bound polyethylene film fibrils (ie, Tyvek spunbonded olefin sheet). a product of the Applicant) weighing 42.4 g / m2. The coated sheet has a much better impermeability to blood than other sheets "Tyvek" coated with compositions

  similar not containing polytetrafluoroethyl.

EXAMPLE 2

  A slurry was formed from 303 kg of "Surlyn" latex resin 56220, 84.03 kg of polytetrafluoroethylene "Teflon" particles 7A and 1.68 kg of acetylenic glycol surfactant "Surfynol" 104 (a product of Air Products of Allentown, Pennsylvania, USA) mixing these ingredients

  at a high speed and with intense shear.

  In a separate container, a molten mixture is formed at a temperature of 115 to 120 C from 7.044 kg of "Span" 80, 3.81 kg of "Tween" 80 and 32.89 kg of bisamide wax. Kenamide "W-5. The slurry is then added over a period of 10 minutes to the melt while simultaneously adding 101.6 kg of

  water vapor and mixing the mass with a

  propeller "Lightenin". The conditions of the mixing operation are then modified using a high shear sawtooth mixer blade. The following materials are then added: 3.35 kg of "Nopco" 267A, 5.366 kg of "Dowfax" 2A-1, 54.4 kg of "Chemcor" 973A, 584.7 kg of water, 17.1 kg of "Blue Super Imperse" X2668, 17.5 kg of Red "Monastral" RW68P and 2.27 kg of Yellow "Dalamar" YW718P. Finally, 27.22 kg of the XZelec ™ TY solution of Example I was added just prior to using the application composition on a polyolefin fibrous sheet, and then the coating composition was applied using the technique. with air gap

  on olefin sheet spun and bonded "Tyvek" weakly

  bound and dried in such a way as to obtain a

  added weight (dry) of about 1.7 g / m2.

  By way of comparison, a compound is prepared

  according to the prior art and applied to a similar "Tyvek" sheet. A copolymer of

  parts of ethylene / 15 parts of methacrylic acid

  that (partially neutralized by hydro-

  potassium hydroxide as described in U.S. No. 3,264,272) is used as a binder resin in the form of an aqueous dispersion of 30% solids. Although this dispersion as received may coagulate upon addition of "Zelec"

  TY, it is stabilized by addition of a surfactant

  appropriate nonionic active and using a suitable mixing technique. The binder resin "as received" is stabilized by addition to 20 g of this dispersion of a solution of 0.5 g of a surfactant consisting of 65% "Span" 80 and 35% "Tween. "80 in 20 g of water. The resulting mixture is stirred at a moderate rate. After 10 minutes, a solution of 2 g of "Zelec" TY and 30 g of water is added dropwise to the mixture. Once the bill

  of the "Zelec" solution completed, we add success-

  the following ingredients: 0.7 g of "Monastral" Blue; 1.4 g of "Monastral" Red B; 0.4 g of yellow "Dalamar"; 10 g of "Zepel" 2373B (unedispersion)

  anionic aqueous solution at 22% solids of a poly-

  fluorinated mother sold by the applicant); and 20 g of a wax emulsion prepared as described in U.S. No. 4,082,887, column 6, lines 49 to 58, from "Advawax" 225 and "Span" and "Tween" surfactants 80. This coating is applied in the same manner as the coating according to US Pat. as shown above in the present example. The comparative sample and a sample coated with the coating according to the invention (as shown in this example) are tested for "blood permeability". The sample coated with the product containing polytetrafluoroethylene prepared according to the invention has a permeability of 0.029 g instead of

  0.155 g for the comparison sample.

TABLE I

  Coating Composition of Example I Quantities Included T t Ingredients *

* Polytetrafluoroethylene powder

  Ethylene DLX 6000 Water-insoluble wax "Advawax" 240 "Zelec" antistatic agent TY Non-ionic surfactant II "Span" 80 "" Tween "80 Water-insoluble resin latex" Surlyn "56220 Pigments Red" Monastral "Yellow" Dalamar "Blue" Super Imperse "

they that

  kg, 348 3,207 2,268 0,680 0,374 66,34 7,289 0,934 7,584 A dry kg%

, 348 12.8

3.207 7.69

0.680 1.63

0.680 1.63

0.374 0.90

, 897 50.10

  1,399 0,271 2,154 3,35 0.65, 16 Other Water 88.38 "Nopco" 267A 0.431 "Chemcor" 973A 7.4 "Polywax" 2000 3.688 "tDowfax" 2A-I 0.726 * Note - All of the specified ingredients 0.431 2.220 0.363 by names

  mercials are defined in the text.

1.03, 32 8.84 0.87

TABLE II

  Coating Composition of Example 2 Quantities

Such as

Ingredients * kg tees

Polytetra-

  Fluoroethylene DLX "Teflon" 7A 84.03 Water-insoluble wax "Kenamide" W-5 32.89 "Zelec" antistatic agent TY 27.22 "Span" nonionic surfactants 80 7.044 "Tween" 80 3, 81 "Surfonyl" 104 1.68 Water-insoluble resin latex "Surlyn" 56220 303.0 Pigments Red "Monastral" 17.5 Yellow "Dalamar" 2.27 Blue "Super Imperse" 17.1 Other Water 686, 3 "Nopco" 267A 5,35 "Ohemcor" 975-A 54,4 "Dowfax" 2A-1 5,366 * Note All ingredients indicated by commercial are defined in the dry section.

84.05 31.8

52.89 12.4

8,166 5,09

7.044, 81 1.68 2.67 0.64

, 445 56.1.1

335.56

  0,658 4,856 o, 55 16,32 2,683 The names exte. 1.27 0.25 o 1.27 6.17 1.02

TABLE III

  Comparative Composition of Example 2 Quantities Included Ingredients *

Such as

g -

  "Zepel" aqueous fluoropolymer dispersion 2373B "Advawax" water-insoluble wax 225 "Zelec" antistatic agent TY "Span" non-ionic surfactant l 80 "Tween" 80 Bonding resin latex Pigments "Mionastral" red yellow "Dalamar" Blue "Monastral" Water, 0 1.71 52.0 1.065 0, 575, 0 1.4 0.4 0.7 37.1

2.2 16.67

1.71 12.96

1,002 7.59

1,065 8.08

0.575 4.36

6.0 45.48

0.269 2.04

0.116 0.88

0.257 1.95

0 0

  * Note - All ingredients indicated by trade names are defined in the text To Dry

Claims (7)

  An improved coating composition in the form of an aqueous dispersion which contains from 10 to 40% by weight of solids, which solids comprise effective amounts of a water-insoluble wax, an antistatic agent, a nonionic surfactant and a resin   insoluble in water, characterized in that the composition   tion comprises an effective amount of fine particles   polytetrafluoroethylene fibers imparting to a fibrous polyolefin sheet on which the composition   coating is applied and dried   improved ticks for blood impermeability.   2. Coating composition according to the   cation 1, characterized in that the polytetrafluoroethylene particles constitute from 10 to 35% by weight of the coating composition, relative to to dry solids.   3. Coating composition according to the claim   1, characterized in that   (a) Water-insoluble wax is dispersed   in water at a concentration of 10% by weight relative to the total amount of wax and water, and requires for its dispersion in water only a nonionic surfactant or a mixture of two non-ionic surfactants or more in an amount of not less than 15% and not more than 100%, by weight of the amount of wax; (b) the antistatic agent has the formula M R P0O wherein M is selected from n 3-n4 lithium, sodium, potassium and ammonium ions, R represents an alkyl group containing from 3 to 5 carbon atoms and n is I or 2.   (c) the nonionic surfactant has a hydrophilic-lipophilic balance of from about 6 to about 10 and is present at about 15 to about 100% by weight based on the amount of wax; (d) the water-insoluble binder is capable of wetting a polyolefin fibrous sheet and, in the form of an aqueous dispersion, does not coagulate in the presence of the antistatic agent; and (e) the polytetrafluoroethylene particles constitute from 15 to 35% by weight of the composition of coating in the dry state.   Fibrous sheet of polyolefin, characterized in that it is coated with a composition according to   any of claims 1 to 3 and dried.   5. Sheet according to claim 4, characterized in that it is a nonwoven sheet of elements   fibrils of polyethylene film.   A process for the preparation of a coating composition as defined in any one of   Claims 1 to 3, characterized in that   takes the steps of forming a molten mixture   water-insoluble wax and surfactant   nonionic active, to disperse the fine particles of polytetrafluoroethylene in the molten mixture, to add water vapor and then liquid water   to the melted mixture containing the polytetrafluorocarbon particles   to form an aqueous dispersion, to add the water-insoluble resinous binder to the aqueous dispersion, and to then add the antistatic agent.   7. Process for the preparation of a composition   coating as defined in any one   one of claims 1 to 3, characterized in that   it comprises the steps of forming a molten mixture of the water insoluble wax and the nonionic surfactant, preparing a slurry of the polytetrafluoroethylene fine particles in an aqueous mixture of the insoluble resin in the water. water, to disperse the slurry in the melt while adding water vapor and then liquid water to the mixture, and then adding the antistatic agent.