US 3245942 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
United States Patent ()filice 3,245,942 Patented Apr. 12,1966
3245 942 VAPOR PEaMnAnLE, witrnnrnoor COATINGS CoNTAINING PIGMENTS, isocYANArn AND VINYL 'rERPoLYMEn George Limperos, Lancaster Village, Wilmington, DeL,
This invention relates to novel coating compositions, coated sheet materials suitable for use in portable protective shelters and for other purposes, and to processes for coating synthetic fabrics.
The requirements of protective sheeting materials for tents, temporary buildings, domes, tarpaulins, wrappings, protective covers, clothing and the like are many and appear to be incompatible, so that no material is known which is completely satisfactory. The products of this invention provide substantially complete protection against rain while permitting sufficient permeability to water vapor to prevent the development of condensation of moisture on the inner Walls of the protective sheet. They are also highly resistant to ultra-violet degradation.
For many years protective sheetings have been based on woven cotton fabrics. Such fabrics have many deficiencies and Without special treatments have now only limited acceptance. Although they have good aesthetic properties and permeability to water vapor, they are easily penetrated by water when wet, are heavy and bulky, and are subject to practically all kinds of environmental deterioration. Many types of finishes have been proposed to produce a hydrophobic surface on such fabrics to reduce water penetration. These are useful for limited and occasional service, but the hydrophobic surface is easily destroyed by soiling, abrasion, and other deteriorating influences. Other types of finishes incorporating waxes, chlorinated hydrocarbons, flame-resistant pigments, and specific compounds to resist microbiological attack have had more acceptance. However, when used in efiective amounts, such finishes add greatly to the weight of the fabric and reduce the water vapor permeability. The finish is usually somewhat tacky, easily soiled, and rubbed off by light abrasion. The odor of such finishes is frequently highly offensive and irritant.
Cotton fabrics having continuous coatings of elastomer or resin compositions are in common use. When new, or after only slight exposure such continuous coatings do provide excellent protection against the elements, but they suffer from the serious defect of having little or no permeability to water vapor. Furthermore, the coating adds considerably to the already heavy weight of cotton fabrics and causes a serious reduction in tear strength. The coated fabrics are generally not resistant to mildew or to fire.
The use of synthetic fiber fabrics, and particularly those made from continuous filament yarns, to replace cotton base fabrics results in a very substantial improvement in tensile and tear strength permitting reduction in over-all weight. However, such fabrics introduce a very serious problem of obtaining adequate adhesion of the film to the fabric and contribute nothing toward improving the almost complete lack of moisture vapor permeability.
In fabric coatings, which is the field of this invention, resistance to folding, flexing, vibration, distortion, scrubhing, abrasion and to stiffening and cracking at low tem peratures is of paramount functional importance. All of these properties are known to be adversely affected by the presence of pigments. Highly pigmented films are said to be cheesy. Consequently, the best practice has been to keep the amount of pigment to a minimum. For primer coats used to insure good adhesion, clear coatings with little or no pigment are preferred. In top coats, pigments of high covering power and light protective properties are preferred and are used in the minimum amounts permitted. In vinyl resin films which are used unsupported for protective coverings or are laminated to fabrics, it is common practice to achieve coloring by means of dyes and light stability by means of resin-solubie stabilizers to avoid the deleterious effects of pigments such as reduction in tensile strength, elongation, toughness and abrasion resistance.
it is an object of this invention to provide a protective sheet material having an excellent combination of properties which overcome the deficiences outlined above to a degree superior to any known prior art material including the property of transmitting water vapor to the extent necessary to maintain comfortable conditions within a covered structure. A further object is to provide novel coating compositions for the preparation of such a sheet material. Other objects will appear hereinafter.
These objects are achieved in coated fabrics comprising a base material of synthetic organic polymer fibers which may be woven or non-woven, coated on at least one side with a composition comprising a synthetic polymer composition selected from the class consisting of (1) chlorosulfonated polyethylene elastomers or (2) vinyl copolymers having free carboxyl groups in combination with at least one polyfunctional isocyanate compound capable of reaction with the said free carboxyl groups and at least an equal amount by weight based on the weight of synthetic polymer, of an inorganic pigment selected from titanium and antimony oxides. Such coated fabrics are unique in that they have throughout the coating film numerous minute pores of such size that they permit passage of water vapor but resist the passage of liquid Water.
The coated fabrics are obtained by applying to the fabric base a coating formulation containing the inorganic pigment and the synthetic resin dispersed in a volatile solvent and then immediately, and without substantial evaporation of the solvent, introducing the coated fabric into a heated atmosphere at a temperature substantially above the boiling point of the solvent, maintaining the coated fabric at elevated temperature for a time sufiicient to remove the solvent, and then cooling the coated fabric. When the synthetic resin coating composition contains a polyfunctional isocyanate compound, the time in removing the solvent is also sufficient to bring about reaction of the isocyanate material with its coreactant group to cause setting up and curing of the resin. For those resin compositions which employ chlorosulfonated polyethylene elastomer material, the curing process occurs by virtue of accelerators present in the formulation.
The use of chlorosulfonated polyethylene elastomer compositions is Well known. The preparation of such polymers and their desirable properties are described in Kelly, US. Patent 2,914,496. The use of polymers and copolymers of vinyl chloride in a Wide variety of finishes and coatings, both alone and in combination with plas-- ticizers and pigments is also well known. However, it has not heretofore been recognized that these polymeric materials could be employed in the preparation of highly pigmented breathable coated fabrics. Furthermore, it has not been recognized that the unique combination of polymer and pigment could impart to a fabric the desirable qualities described here.
Especially useful for the purpose of this invention, are chlorosulfonated polyethylene resins containing from 25 to 50% by weight of chlorine, and 0.4 to 3.0% by Weight of sulfur. These may be used with any of the conventional curing agents in the indicated proportions, all as described in the aforementioned Kelly patent.
The vinyl copolymers which may be used in the practice of this invention are those comprising b'etweeen about 70-97 mol percent vinyl chloride, 3-20 mol percent of vinyl esters of aliphatic carboxylic acids, or lower alkyl esters of acrylic or methacrylic acid; and 0.2-15 mol percent of an alpha, beta-olefinically unsaturated carboxylic acid such as maleic, fumaric, itaconic, crotonic, acrylic and methacrylic acid or their derivatives having free carboxy-l groups. Preferably the co-polyrners contain between 70-90 mol percent of vinyl chloride, 5-20 mol percent of vinyl esters and 0.5 mol percent of the acid. An example is the resin known as vinyl resin VMCH available from the Bakelite Corporation. This resin which is a copolymer on a Weight basis of about 86% of vinyl chloride, 13% of vinyl acetate and about 1.0% of maleic acid, is used in some of the examples to follow. Such resins are used in combination with polyisocyanates as adhesives and primer coatings, and the heating of such combinations brings about improved adhesion. Such a process is described in a copending application Serial No. 709,465, now U.S. Patent No. 3,067,085. 7
Titanium dioxide T10 and antimony oxide (Sb O and mixtures thereof, are the pigments required to obtain the advantages of the invention. Small amounts of other pigments may be used as a filler, i.e., calcium carbonate or for tinting purposes, for example, phthalocyanine green or blue. The amount of titanium or antimony oxide pigment which is used as well as its particle size is critical to obtaining the pore formation necessary for moisture vapor permeability as well as sunlight resistance and fire resistance. In the practice of the present invention, there is employed between 100 parts and 250 parts and preferably between 100 parts and 200 parts by weight of such pigments per 100 parts of resin and the pigment particles pass through a 325-mesh sieve. As the amount is reduced below 100 parts, the pores become smaller and fewer in number and the vapor permeability is reduced. Above 250 parts the physical properties of the film such as abrasion resistance and continuity begin to deteriorate. The preferred compositions comprise mixtures of titanium dioxide and antimony oxide. Titanium dioxide contributes excellent light durability and antimony oxide gives resistance to fire. Combinations such as 100 parts of titanium dioxide and 50 parts of antimony oxide give a superior combination of properties.
. The kind and amount of solvent used is critical in the process of this invention. The solvent components should have boiling points within a range of C. and the midpoint of the range should be below about 100 C. It has proven entirely satisfactory to use only a single solvent, although mixed solvents may be used for economic reasons. Methyl-ethyl ket-one, which has a boiling point of 796 C. is used as the principal solvent in some of the examples to follow. The amount of solvent used should be between l50 parts and 450 parts by weight per 100 parts of resin and 200 to 400 parts are preferred. When the amount of solvent is reduced below 200 parts, the size and number of pores formed during drying are reduced, and below 150 parts of solvent the water vapor permeability becomes too low to be characteristic of the invention. As the solvent content is increased, the total amount of wet coating composition must be increased to obtain the desired dry coating on the finished fabric. At the same time, the coating composition becomes more dilute and less viscous and consequenetly more difficult to control in applying the required increased amounts. These difiiculties become serious for amounts of solvent above 400 parts and above 450 parts it has been impractical to achieve the desired thickness of dried coating in the required single coating operation. Furthermore, the use of more than the required amount of solvent is expensive and wasteful.
Plasticizers are desirably used in combination with the vinyl resins. trioctyl phosphate, and tricresyl phosphate are preferred. Of these, dioctyl phthalate appears to give the best retention of pliability after long exposure although it is some what inferior in fire resistance. In geneeral, mixed plasticizers will be used, and in this connection other plasticizers such as dioctyl sebac-ate, dioctyl adipate, and other types available under the trade names of Drapex and Paraplex are satisfactory. The amount of plas-ticizer by weight may vary from about 50 parts to about 70 parts and the preferred amount is about 60 parts per parts of resin. It is generally not necessary to use a plasticizer for the chlorosulfonated polyethylene resin.
The polyisocyanate compound used with the vinyl resins may be methylene bis(4-phenyl) isocyanate (designated hereinafter as MDI) or any equivalent polyfunctional isocyanate, for example, hexamethylene diisocyanate, decarnethylene diisocyanate, methaphenylene diisocyanate, 2,4-toluene diisocyanate, mixed isomers of toluene diisocyanate, polymethylene polyphenylisocyanate, triphenylmethane-4,4'4"-triisocyanate, or the like. More than one isocyanate may be used if desired. Any isocyanate monomer containing at least two -N=C=O groups may be used. The isocyanate compound is used in molar amounts equal to the number of free carboxyl groups in the resin. This ratio can be varied by about 20% in either direction. The isocyanate compound is dissolved in a portion of the solvent and added to the otherwise complete vinyl-resin coating composition shortly before use. A 50% solution of MDI, which is a convenient and effective form, is used in the examples.
The fabrics used as the base in the products of this invention may be woven fabrics or non-woven fabrics comprising man-made fibers and preferably fibers made of Wholly synthetic polymers such as polyesters, polyamides, acrylic polymers, polyhydrocarbons, and others although ceramic fibers and glass fibers may be used. Such fibers have inherent resistance to chemical and microbiological attack and can be made to have the high strength desired to resist mechanical abuse. Fabrics made from high strength continuous filament yarns are preferred although this it not required in the case of woven fabrics.
Continuous filament woven fabrics ranging in weight from 2.0 ounces to 10 ounces per square yard are suitable, and for most of the described uses, fabrics of 2 to 5 ounces per square yard have suitable strength and are preferred. Plain weave fabrics and simple modification of of this weave are satisfactory but the invention is not limited to such weaves. Any fabric having a suitable surface may be used.
Of the non-woven fabrics, those comprising continuous filaments are preferred because of their superior physical properties and their smooth surface characteristics. Particularly suitable fabrics of this class are those in which 7 individual separated filaments are disposed uniformly in a random loopy configuration, and are bonded at filament intersections by mechanical entanglement or other suitable binding means. Other non-woven fabrics including those combining continuous and staple fibers and As primary plasticizers, dioctyl phthalate, I
those in which binding is achieved by needle-punching are also suitable.
In preparing the coated fabrics of this invention the coating composition is made up by grinding the pigments with all or a portion of the resin component and the plasticizers, if there is one. Intimate separation and Wetting of the pigment particles by the resin formulations is the desired goal of this grinding. To that end the precise grinding conditions should be selected in such a way as to promote this mixing. Solvent may be added or omitted at this stage. After grinding, the other components of the formulation may be added with additional mixing. When a vinyl resin is employed and a polyfunctional isocyanate coreactant is to be added, the latter should be added shortly before the composition is used. The fabric is coated with the composition and the excess is removed by conventional means. Without substantial delay the fabric bearing its wet coating is then passed into a heating chamber having a temperature at least 50 C. higher than the midpoint of boiling point range of the solvent. Preferably a temperature between 120 C. and 200 C. is employed. During the very rapid heating and evaporation of the solvent, minute pores are formed in the coating layer. The coated fabric is maintained in the heating chamber for a brief period of time to complete the evaporation of the solvent and the curing of the polymer composition. After the evaporation and curing have been completed, the coated fabric is then cooled to room temperature.
In the practice of applying organic polymer resins compositions to fabrics from organic solvent solutions or dispersions, precautions must generally be taken to prevent the formation of blisters. If the solids content is too high or the layer of coating too thick, or if the rate of solvent evaporation is too high, blisters are generally formed and their presence destroys the utility of the coated fabric. The usual practice is to use a solids content of about 20% and to restrict the amount of wet coating applied in a single pass to about 2 ounce per square yard. Solvents are blended or balanced, being mixtures of components having different boiling points and evaporation rates, and drying temperatures are carefully controlled to prevent sudden loss of solvent with consequent blistering. Multiple successive coating operations are commonly required to build up the thickness of coating required in the final product. This practice is very expensive.
In practicing the present invention, it has been found that higher solids content and thicker coatings can be employed without blistering. In accordance with the present invention, it is possible and necessary to complete the coating on any one side of the fabric in a single pass.
The application of the coating composition to the fabric is preferably accomplished by dipping the fabric through a reservoir of the composition and removing the excess by scraping or by doctor blades, thus coating both sides of the fabric. Other means such as knife coating or roller coating may also be used to obtain this result. It is not necessary that the same amount of coating remain on the twosides of the fabric. The relative amounts may be controlled by the means for removal of excess or the means for application or both.
It will be obvious that the total desired amount of coating must be applied to the fabric in a single operation. Any subsequent coating would cover over the pores formed in the first coating and thereby destroy the water vapor permeability of the product. The present invention thus differs radically from the conventional methods of solution coating by building up successive thin coatings to achieve the desired total. The success of the present invention in producing highly durable coated fabrics without blisters or other processing imperfections depends on the novel and critical elements in both the coating composition and its application.
The amount of coating composition required per square yard of fabric is not directly related to the weight of the fabric, although heavier fabrics would normally be chosen only for more severe service or to obtain longer life and it would be appropriate to use heavier coatings for the same reason and also to allow for the greater amount of coating buried within the body of heavier fabrics. To obtain the properties described in woven fabrics of 2 to 5 ounces per square yard a total dry coating weight of 1.5 to 4.0 ounce per square yard distributed between the two sides is adequate and 2.5 to 3.5 ounce per square yard is preferred. With only 1.5 ounce per square yard, the initial measured properties are good but the coated fabric is not sufficiently durable for other than light service. If this amount is primarily on one side, that surface will have good properties and be durable. A preferred product has a total of 3.0 ounce per square yard evenly distributed between the two sides. When nonwoven fabrics are used, larger amounts of coating material have been found desirable. These fabrics are more bulky and open than woven fabrics and are substantially impregnated with the wet coating so that a higher proportion of the coating material is buried within the fabric \and a lower proportion is present in the surface coating. In such cases, the total dry coating material may be 5 or 6 ounce per square yard. It is also practical to use coating compositions having higher solids content and lower amounts of solvent in coating such non-woven fabrics.
The pores in the coating which permit the transmission of water vapor are neither as small nor as uniformly distributed throughout the coating material as those which result from including very fine particles of blowing agents or soluble materials in the composition which are later removed. On the contrary, they appear to be discrete channels which penetrate substantally through the thickness of the film. They are haphazardly distributed across the surface of the fabric and are varying in diameter. The diameter of these pores is of the order of 30 to 120 microns. Pores of this size strongly resist the passage of liquid water. A hydrostatic pressure in excess of 20 cm. of water is required for any penetration. The products of the invention successfully resist water penetration during heavy rain.
It is surprising to find that if the same amount of coating per square yard is applied to woven fabrics weighing 2.3 to 3.9 ounces per square yard, the heavier fabric generally has the higher moisture vapor permeability. It is believed that in such cases the pores in the coatings of one side do not connect with those of the other side, but both connect with an unimpregnated or incompletely impregnated space in the center of the fabric. In the heavier and thicker fabric, it is thought that this central space is more open and provides easier access from one side to the other. It is also to be noted that in general non-Woven fabrics when coated with the same amounts of coating are more permeable to moisture vapor than woven fabrics. In such cases, it is believed that these fabrics are thoroughly impregnated with coating and thus capable of having continuous pores extruding throughout the fabric as a whole.
EXAMPLE I A coating composition is prepared in the following manner, all parts being by weight. parts of VMCH vinyl terpolymer resin, 200 parts of antimony oxide pigment, 60 parts of tricresyl phosphate, 5 parts of Drapex 4.4 plasticizer and 2.0 parts of phthalocyanine green tinting pigment are milled together on a two-roll rubber mill until a uniform mixture is obtained, which is taken from the mill in sheets and cut to chips. The chips are steeped in 400 parts of methyl-ethyl ketone and dispersed therein with a propeller type high speed mixer. Just before use, 10 parts of methylene bis-(4-phenyl isocyanate) dissolved in a like amount of monochlorobenzeneis added and thoroughly mixed.
A continuous filament nylon fabric having 40 warp and 40 filling ends per inch of 210 denier yarns, and weigh ing 2.3 ounces per square yard is dipped through the above composition, passed between coating bars to remove the excess composition, and without delay passed into a circulating air oven at an air temperature of about 175 C. The fabric remains in the oven for two minutes and then is removed, cooled to room temperature and collected on a roll. Its weight is 6.3 ozs./yd
The resulting coated fabric is strong, flexible, light weight, has an attractive smooth surface without blisters, is an attractive light green color, and is eminently suitable for use in light weight tentage. Microscopic observations show that both coated surfaces have numerous small pores of the order of 80 to 120 microns in diameter. The fabric is permeable to moisture vapor but highly resistant to rain. It will not support combustion. It retains its initial properties to a high degree after severe exposure both in a laboratory weatherometer and in actual outdoor exposure in Florida. Certain detailed properties are shown .in Table I.
To demonstrate the effectiveness of the water vapor permeability of this coated fabric in preventing excessive humidity and condensation of moisture within tents, a complete wall tent 6.5' x 6.5 in floor plan with 6' center height and sewn-in floor is constructed from it. A commercial treated cotton tent of about the same dimensions is used as a control. The cotton tent weighs 25.4 pounds compared with 14.0 pounds for the coated nylon tent. The two tents were pitched in the open side by-side for a period from April to August and frequent comparative measurements of temperature and relative humidity made within the tents. Conditions within the two tents changed in a similar pattern with large changes in ambient'conditions. However, the relative humidity within the nylon tent was generally somewhat lower than in the cotton tent. Of even more significance is the fact that on 12 occasions conditions within the cotton tent were 100% relative humidity whereas this never occurred in the coated nylon tent. The water vapor permeability values for the coated fabric of the invention, while not being as high as for the cotton fabric, still represents entirely satisfactory and adequate levels. At no time was the condensation'of liquid water observed within the tent of this invention. It is well known that this does occur and is highy objectionable in prior art coated fabric tents.
Table I Coated fabric, Cotton tent Example I fabric 12 weeks 12 weeks Initial exposure Initial exposure in Florida in Florida Wt. z./sq. vd.:
Fini hed 6.3 12.0 T G g u t 8) ens e s reng warp s rip, lbs 145 95. 3 82 55 Tear strength, tongue 7. 6 4. 6 Hydrostatic pres, cm. (Hydrostatic pres. test AATCO Method).. 56 37 Rain test, grns. penetrating (Slowinske and Pope- Am. Dyestufi Reptr. 36, pgs. 108-121 (1947)) 0.15 3. 0 6. 0 12 Water vapor permeability, grns/rnfi/24 hrs. (Water vapor permeabi1ity- ASTM E96-53'1 procedure B) 38. 2 35. 415 386 Flammability V 1 Does not support combustion 2 All samples burned. EXAMPLE II A coating composition containing by weight 100 parts VMCH resin, 30 parts dioctylphthalate, 30 parts dioctyl sebacate, parts titanium dioxide pigment, 12 parts of phthalocyanine green pigment, 10 parts of MDI (dissolved in 10 parts of monochlorobenzene), and 400 parts of methyl-ethyl ketone is prepared as in Example I. A plain weave continuous filament nylon fabric weighing 3.9 ounces per square yard is coated on both sides by dipping through said composition, the excess coating composition being removed by doctor blades, and the fabric is passed without delay into an air oven at 175 C. for two minutes. The total pick-up of dry solid coating composition is 3.8 oZs./ sq. yd.
The resulting coated fabric has a warp tensile strengt of 230 lbs./in., a tongue tear strength of 18.5 lbs., a hydrostatic pressure resistance of 60 cm. and a water vapor permeability exceeding gms./m. /24 hrs. A commercial treated cotton fabric tarpaulin control has a weight of 13.5 ozs./yd. a warp tensile strength of 107 lbs./in., a tongue tear strength of 8.6 lbs., a hydrostatic pressure of 42 cm. and a water vapor permeability of 420 gms./m. /24 hrs.
EXAMPLE III Non woven fabrics are made from continuous filaments of polyamides by separating the individual fila- 'rnents by electrostatic means, collecting the filaments in swirls, coils and convolutions on av receiving surface to form a uniform sheet, and calendering the sheet as shown in Example 4 of copending and coassigned application Serial No. 859,614. Such sheets weighing 3.0
to 4.5 ounces per square yard are dip-coated on both sides with a vinyl resin composition as in Example I except that the pigment used is 100 parts of TiO 50 parts of Sb O and 12 parts of phthalocyanine green pigment and the plasticizer is 30 parts of trioctylphosphate and 30 parts of Paraplex (fr-62, per 100 parts of vinyl resin terpolymer. The Wet coated fabric is immediately placed in an oven at C. for two minutes. The amount of coating solids applied in the series varies from 3.5 to 5.6 ounces per square yard. All the coated fabrics contain pores visible under the low power microscope. The hydrostatic pressure resistance is from 22 to 35 cm. of water. The amount of water penetrating the fabrics in the rain test at 7 feet head is a minimum of 0.0, a maximum of 0.5 and an average of 0.15 grams. The Water vapor permeability is from 130 to 230 and averages about 200 gms./m. 24 hrs.
A specimen of the above coated fabric is subjected to laboratory exposure to the weatherometer for 500 hours. 74% of its original tensile strength is retained. An uncoated' specimen of the same fabric loses its tensile strength completely during such exposure. Other uncoated specimens of this fabric laminated to a 3 mil black polyethylene film and to a 4 mil clear vinyl film retain only 48% and 52% of their original tensile strength respectively. Two cotton tent fabrics treated with a wax finish and weighing 12 ounces and 15 ounces per square yard retain only 32% and 59% of their initial tensile strength respectively after this exposure.
EXAMPLE IV A non-woven fabric as shown in Example 7 of the aforementioned application, Serial No. 859,614, comprising continuous individual polyester filaments distri- 7 Parts by Weight VMCH resin 100 Dioctyl phthalate 3O 'Tricresylphosphate 3 0 Ti0 5O Sb 0 L 50 Phthalocyanine blue pigment 6 MDI 20 Methyl-ethyl ketone 200 The amount of dry solids deposited on the fabric is 3.4 ounce per square yard giving a total finished weight of 6.3 ounce per square yard. The coated fabric is strong and flexible with a smooth attractive surface. Its water repellency determined by the hydrostatic pressure test is 61 cm. and its water vapor permeability is 300 grams/ m. /24 hrs. Neither the tensile strength nor the hyrostatic pressure rating are affected by exposure to 500 hours in the weatherometer.
The behavior and properties of commercial treated cotton fabrics considered to be permeable to moisture vapor have been shown above for comparison with the products of this invention. It is well known that there is no typical fabric of this class. The fabric weights vary from 6.5 to 18.0 ounces per square yard, the hydrostatic pressure resistance may vary from 20 to over 100 cm. and the water vapor permeability from 35 to over 400 grams/m. /24 hours. The comparisons given clearly indicate that the products of this invention in water resistance and water vapor permeability are entirely adequate and in portability, durability, and aesthetic prop erties are far superior to those of the prior art.
EXAMPLE V A series of experiments were performed in which nonwoven fabric base materials were prepared and coated with resin formulations based on chlorosulfonated polyethylene. The base fabrics were prepared in accordance with the teachings of copending and coassigned application Serial No. 859,614, now abandoned. Continuous filament polyethylene terephthalate fibers were deposited together with copolyester binder fibers giving a nonwoven fabric of continuous filaments in which the individual filaments were randomly and individually disposed with essentially no parallelism between the individual filament components. A number of these fabrics were prepared in difierent basis weights as shown in the accompanying tables. Webs were consolidated and heated to fuse the binder filaments giving strong cohesive integral non-woven sheet materials.
Three different resin formulations all based on chlorosulfonated polyethylene were prepared using different proportions of solvents and pigments, all within the scope of the present invention. By pigment is meant solely titanium dioxide and antimony oxide. Other pigments do not yield the desired results as seen with formulation No. 1 below. Table II describes the preparation of the coating formulations. The first formulation which contained only 60 parts of pigment per 100 parts of resin was not within the scope of this invention and as the second table shows the breathability of this material was unsatisfactory. However, formulations 2 and 3 were within the scope of this invention and had adequate water vapor permeability. As explained earlier, it is preferable to employ between 200 and 400 parts of solvent and to select a solvent whose boiling point is at least 50 C. and preferably 60-100 C. lower than the drying and curing temperature necessary for the treatment of the resin formulation. This insures that during the curing and drying treatment there takes place adequate formation of pores in the coating to give breathability.
When a chlorosulfonated polyethylene resin is employed an aromatic solvent such as toluene or xylene is generally used. Mineral spirits are not required and a low boiling ketone can be used in the place of that solvent. As the formulations show, isopropyl alcohol is included in the mix. Isopropyl alcohol or other alcohols of similar molecular weight and volatility are not included for solvency but rather to provide a temporary stopping agent for the curing of the polymer while in solution.
The resin formulations of Table II were applied to the different fabrics in the amounts indicated in Table III and 10 then the coated fabric was dried and cured at 150 C. to complete the formation of the coated fabric.
The coated fabrics obtained in accordance with this teaching are strong and flexible and have a smooth attractive surface. As the results of Table III show, these coatings have excellent water repellency and, when the teachings indicated are followed, a very satisfactory level of water vapor permeability. These fabrics are found to be entirely the equivalent of the similar constructions shown in Example I and in fact the vapor permeability is somewhat higher. This improvement can provide increased comfort for example, in tents.
Table lI.Resin formulations Formulation Item No. 1 No. 2 No. 3
INGREDIENTS Part ASoluti0n, pts./wt:
Chlorosultonated polyethylene resin 90 90 90 Toluene 135 135 Xylene 200 65 65 Isopropyl alcohol (99%) 3O 30 30 Silicone flowing agent 2 2 2 Part B-Pigment mix, ptsJwt Tribasic lead maleate 40 40 40 Tetramethyl thiuram di lfide 0.5 0.5 0.5 2-benzothiazolyl disulfide 1 1 1 Calcium carbonate (York Whiting) 60 60 Talc 60 Titanium dioxide (Ti-Pure R-SlO) 60 150 100 Antimony trioxide 50 Phthaloeyanine green pigment 1 9 9 Hydrogenated wood resin 3 3 3 Xylene 80 120 115 Mineral spirits... 15 4-5 Isopropyl alcohol (997 30 30 30 Synthetic dispersing agent 2 3 3 Part C-Dispersion additive, pts./Wt.:
Chlorosulfonated polyethylene resin 10 10 10 oluene 15 15 Xylene 40 25 1 Resin of the type described in [7.8. 2,914,496, which are made containing 25 to chlorine and 0.4 to 3.0% sulfur.
Table III.-Fabric properties Wt. of Vapor Fabric Resin uncoated Wt. of Water permeitem formula fabric, coating, repellency, ability,
tion N o. or../yd. oz./yd. cm. gin/24 hrs./
1 Measured hydrostatic pressure. 2 Formulation diluted with parts methyl-ethyl ketone.
What is claimed is:
1. A coated farbic bearing from 1.5-6 oz. per square yard of fabric, of a composition consisting essentially of a vinyl terpolymer of about by weight of vinyl chloride, about 13% by weight of vinyl acetate, and about 1.0% by weight of maleic acid and from about -250 parts by weight of a pigment selected from the group consisting of titanium dioxide and antimony oxide per 100 parts of resin, said pigment particles being under 325 mesh, a molar amount of methylene bis (4 phenylisocyanate) equal to the number of free carboxyl groups in the resin, the surface of said polymer coating having pores of a diameter between 30 and microns.
2. The fabric of claim 1 wherein the base material is non-woven.
3. A composition consisting essentially of a terpolymer of vinyl chloride, vinyl acetate and maleic acid in about an 86/ 13/ 1 weight ratio, from about 100 to 250 parts by Weight of a pigment per 100 parts of resin, said pig merit being selected from the group consisting of titanium dioxide and antimony oxide having a particle size of under 325 mesh, a molar amount of methylene bis(4- phenylisocyanate) equal to the number of free carboxyl groups in the resin and from about 150 to 450 parts by Weight of methyl-ethyl ketone per 100 parts of resin.
References Cited by the Examiner UNITED STATES PATENTS McCarthy 260-41 Habeck 26041 Greenhoe. Wilhelm. Roche 117-135.5
MORRIS LIEBMAN, Primary Examiner. 10 LEON J. BERCOVITZ, Examiner.