GB2036822A - Water Impervious Fabric - Google Patents

Abstract

A water impervious fabric suitable for use as a lining material for liquid- containing structures is produced by coating or impregnating a woven or non-woven polyester fabric with a plasticised sulphur composition in a molten state, the plasticised sulphur composition containing from 50 to 98 weight percent of sulphur, based on the sulphur and plasticiser content of the composition. The sulphur composition advantageously contains an inorganic filler such as mica. The polyester fabric is preferably one formed from polyethylene terephthalate fibre.

Description

SPECIFICATION Water Impervious Fabric This invention relates to a polyester fabric treated with a plasticized sulfur composition, as by coating or impregnation, suitable as a lining material for liquid-containing structures.

Plasticized sulfur compositions have been disclosed, for example by J. I. Jin in "Chemistry of Plasticized Sulfur", Petroleum Division, A.C.S.

Symposium, Vol. 19, No. 2, March 1974, pp.

234-241. An exemplary patent is U.S. Patent No. 4,026,719 entitled "Sulfur Composition With Mica". Plasticized sulfur compositions as suchhave been used as coatings for earthen structures. In many such applications, very heavy or thick coatings are required to give satisfactory strength and impermeability and to protect the basic structure from liquid seepage.

It is known to line a lake with a sulfur-asphalt impregnated polypropylene fabric [Sulfur Research and Development, Volume 1, page 18 (1978) and Belgian Patent 834,456 of April 13, 1976]. In this process, an emulsion of sulfur-inasphalt is prepared in the weight ratio-of 30 to 70. A non-woven polypropylene fabric is then dipped into this emulsion and the resulting impregnated product is laid over pregraded soil surfaces to form the bottom and sides of the containment pond. The sulfur remains as finely dispersed particles in an asphalt matrix.

Further, as described in the book New Uses of Sulfur--ll, Dougias J. Bourne, Ed., Advances in Chemistry Series 165, ACs, Washington, D.C.

(1978), pp. 26-30, plasticized sulfur-fiber composites have been proposed for use in the fields of civil engineering and building construction, such as roofing materials and liners for ponas, canals, and irrigation ditches. The fibers mentioned are polypropylene and glass. The plasticizer recommended for the sulfur are myrcene, alloocimene, and cycloocta-1 ,3-diene.

Polyester fiber composites consisting of polyester fabric bonded to a butyl rubber membrane have also been suggested for use as liners for ponds, canals and irrigation ditches.

However, as compared with the prior art products, the plasticized sulfur structures or composites herein contemplated have superior properties. The plasticized sulfur composites of the present invention have greater resistance to deformation and as a result are more resistant to mechanical damage, such as by draglines and punctures caused by animal traffic. This strength is especially desirable when the sulfur composites are used in lining structures required to have loadbearing strength. It is a result of utilizing polyester fiber in contrast to polypropylene or nylon fibers, the polyester having a higher modulus of elasticity, less creep and less elongation under load than the other fibers.While composites of glass fiber and plasticized sulfur may also possess the foregoing high resistance to deformation and have the desirable strength above-mentioned, the use of glass fiber increases the cost of the composite and, because of the higher density of the fiber, produces an undesirably heavier composite.

A further advantage of the composites of the present invention is that, because of the higher melting point of the polyester as compared with polypropylene, the process of their preparation is not as temperature-sensitive, and hence higher temperatures may be employed without shrinkage of the fabric.

Finally, as a further advantage of the present composites there may be mentioned the superior surface bonding or adhesion between polyester fabric and plasticized sulfur.

Summary of the Invention By way of summary, the present invention is concerned with an article of manufacture comprising a polyester fabric, woven or nonwoven, coated or impregnated with a plasticized sulfur composition, in which the sulfur is present in an amount of 50-98 weight percent based on sulfur and plasticizer. Optionally, the plasticized sulfur composition may contain fillers.

Detailed Description of the Invention and Examples It has been discovered that a superior covering material or lining material can be prepared by treating a polyester fabric with molten plasticized sulfur. By proper control of the treating or contacting operation or selection of polyester fabric of different structures, the molten plasticized sulfur composition may merely surface-coat the fabric or deeply impregnate it.

The composite of this invention characterized by high strength, waterproofness, varying flexibility and light weight can be used in numerous applications. It is especially useful in lining earthen structures intended for the containment of water or other liquids, such as reservoirs, canals, basins, ponds, swimming pools, etc. It can be installed as a lining material on the sides and banks of streams and rivers to prevent weed growth, erosion, and seepage in the channel. It is also useful as a protective lining or membrane for structures susceptible to corrosive attack by acids, salt solutions, and other aggressive media. Examples of such structures are concrete and masonry constructed tanks, vats, conduits, pedestals, colums, piers, floors and supports. Another application of the article of the present invention is the use of it as a roof for housing.

The plasticized sulfur compositions for coating or impregnating the polyester fabric to form the article of this invention is prepared by heating a mixture of sulfur and a plasticizing agent at a temperature above the melting point of the mixtures. Temperatures in the range of 11 00C to 1 800C, preferably 1 250C to 1 500C, can be employed for this purpose. As is known, the plasticizer for the sulfur may be inorganic or organic compounds. Preferred organic sulfur plasticizers are aromatic and aliphatic polysulfides.Sulfur is the major ingredient of the compositions and is present as total sulfur in an amount above about 50%, usually from 60% to 98%, and the plasticizer, in an amount from 0.5% to 10%, usually 2% to 7%, the foregoing percentages being by weight and being based on sulfur and plasticizer.

Plasticized sulfur usually has a slightly lower melting point than elemental sulfur. Furthermore, plasticized sulfur requires a longer time to crystallize, i.e., the rate of crystallization of plasticized sulfur is slower than that of elemental sulfur. One useful way to measure the rate of crystallization is as follows: the test material (0.040 g) is melted on a microscope slide at 1 300C and is then covered with a square microscope slide cover slip. The slide is transferred to a hot plate and is kept at a temperature of 780i20C, as measured on the glass slide using a surface pyrometer. One corner of the melt is seeded with a crystal of test material. The time required for complete crystallization is measured.Plasticized sulfur, then, is sulfur containing an additive which increases the crystallization time within experimental error, i.e., the average crystallization time of the plasticized sulfur is greater than the average crystallization time of the elemental sulfur feedstock. For the present application, plasticizers are those substances which, when added to molten elemental sulfur, cause an increase in crystallization time in reference to the elemental sulfur itself.

As noted, inorganic and organic materials may be used to plasticize sulfur. Inorganic plasticizers include iron, arsenic and phosphorus sulfides, but the particularly preferred sulfur plasticizers are organic compounds which contain sulfur or which react with sulfur to give sulfur-containing materials. As used herein, sulfur plasticizer means a compound that plasticizes sulfur or results in plasticized sulfur.

Sulfur plasticizers which are suitable include aliphatic polysulfides, aromatic polysulfides, dioctylphthalate, and the reaction products of sulfur with styrene, cyclooctadiene, dicyclopentadiene, acrylic acid, epoxidized soybean oil, triglycerides, and tail oil fatty acids.

One class of preferred plasticizers is the alicyclic polysulfides, particularly those that will not form cross-linking. Thus butadiene is not a preferred constituent to form the aliphatic polysulfide, as it may form cross-linking sulfur bonds, whereas dicyclopentadiene is a preferred compound for forming the alicyclic polysulfide useful as the sulfur plasticizer. with molten sulfur, dicyclopentadiene forms an extremely satisfactory alicyclic polysulfide.

Another class of preferred plasticizers for use in the composition of the present invention are aromatic polysulfides formed by reacting one mol of an aromatic carbocyclic or heterocyclic compound, substituted by at least one functional group of the class -OH or -NHR in which R is H or lower alkyl with at least two mols of sulfur.

Suitable aromatic compounds of this type include: phenol, aniline, N-methyl aniline 3hydroxy thiophene, 4-hydroxy pyridine, paminophenol, hydroquinone, resorcinol metacresol, thymol, 4,4'-dihydroxy bi-phenyl, 2,2-di(phydroxyphenyl) propane, di(p-hydroxyphenyl) methane, p-phenylene diamine, methylene dianiline, etc. Phenol is an especially preferred aromatic compound to form the aromatic polysulfide.

The aromatic polysulfides are generally prepared by heating sulfur and the aromatic compound at a temperature in the range of 1200 to 1 7O0C for 1 to 12 hours, usually in the presence of a base catalyst such as sodium hydroxide. (See for example, Angew. Chem. V.70, No. 12,pages35l-67 (1958) for the preparation of a phenol-sulfur adduct). The polysulfide product made in this way has a mol ratio of aromatic compound:sulfur of 1:2 to 1:10, preferably from 1:3 to 1:7. Upon completion of the reaction, the caustic catalyst is preferably neutralized with an acid such as phosphoric or sulfuric acid. Organic acids may also be used for this purpose. The resulting aromatic polysulfide may be used immediately or it may be cooled and stored for future use.

Another type of aliphatic polysulfide useful as a piasticizer for this invention are the linear aliphatic polysulfides. Although these polysulfides may be used alone as the sulfur plasticizer, it is preferred to use them in combination with either (a) the dicyclopentadiene sulfur reaction product or (b) the aromatic polysulfides described above, especially with the phenol-sulfur adduct. In this connection, the preferred plasticizer mixtures contain from 5 to 60% linear aliphatic polysulfide by weight based on total plasticizer, preferably about 10 to 30 weight percent.

These aliphatic polysulfides may have branching indicated as follows:

wherein x is an integer of from 2 to 6 and wherein B is H, alkyl, aryl, halogen, nitrile, ester acid, or amide group. Thus in this connection, the aliphatic polysulfide is preferably a linear polysulfide. The chain with the sulfur preferably is linear, but it can have side groups as indicated by B above. Also, this side group B may be aromatic.

Thus, styrene can be used to form a phenylsubstituted linear aliphatic polysulfide. The preferred aliphatic polysulfides of this type are both linear and non-branched.

Unbranched linear aliphatic polyether polysulfides include those such as those sold under the trade-name of Thiokol LP-3 which contain an ether linkage and have the recurring unit: SxCH2CH20CH2OCH2CH2Sx wherein x has an average value of about 4. The ether constituent of this aliphatic polysulfide is relatively inert to reaction. Other suitable aliphatic polysulfides have the following recurring units: Sx(CH2.)vSx from reaction of alpha, omegadihaloalkanes and sodium polysulfide -S,-(-CH,CH,-S-CH,CH,-)-S,- from reaction of alpha, omega-dihalosulfides and sodium polysulfide -S2-(-CH2CH2-O-CH2CH 2)x from reaction of alpha, omega-dihaloesters and sodium polysulfide wherein x is an integer of 2 to 5; and y is an integer of 2 to 10.

Any one or combinations of these plasticizers may be used in the present invention. For instance, the plasticizer may consist of a mixture of a phenol-sulphur adduct, an unbranched linear aliphatic polyether polysuiphide and cyclooctadiene.

Optionally, the plasticized sulfur composition may contain a filler material, as indicated in the aforesaid U.S. Patent No. 4,026,719. Typical fillers include talc, mica, glass fibers, asbestos, silica and the like. The preferred filler is mica.

When used, fillers are present in an amount from 1% to 25%, preferably 5% to 1 5%, by weight, based on the total composition. Inorganic or organic fillers acting as fire retardants are also included. Examples are hydrated alumina, antimony oxide, and the halogenated compounds, such as tetrabromophthalic anhydride and perchlorodicyclopentadiene.

The fabric or cloth for use in the present invention is made from a polyester fiber. Polyester fibers are made from polyester polymers having a molecular weight in excess of 2000, preferably in the range of 5000 to 10,000. The polymer is extruded through an orifice to form a fiber which is further improved by orientation in the longitudinal direction. Polyester polymers are made by the self-condensation of a hydroxy acid or by the condensation polymerization of equal molar quantities of dihydric alcohols and dibasic acids. Among the satisfactory hydroxy acids that may be used singly or in mixtures are phydroxybenzoic acid, glycolic acid, and the like.

Among the satisfactory dihydric alcohols that may be used singly or in mixtures are ethylene glycol, diethylene glycol, butane-1,4-diol, propane-1,2diol, cyclohexane-i ,4-diol, 1 ,4- dimethylolcyclohexane, hydroquinone, and the like.

The preferred dihydric alcohols have two primary hydroxy groups. Among the satisfactory dibasic acids that may be used singly or in mixtures are terephthalic acid, isophthalic acid, adipic acid, oxalic acid, succinic acid, and the like. The preferred acid is terephthalic acid. The preferred fiber is that made from poly(ethyleneterephthalate) or poly(cyclohexane 1 ,4-dimethyleneterephthalate). The fiber used herein may be monofilament or polyfilament in structure.

The fabric made from the polyester fiber may be loosely or tightly woven or non-woven. The non-woven fabrics may be needle-punched, heatsealed, or point-contact-glued to give additional fabric dimensional stability. Preferabiy, the fabric is a needle-punched non-woven mat.

The polyester fabric for use herein may be of varying thickness, strength, weight, and compactness. Generally, the fabric is 1 to 1000 mils, preferably 10 to 500 mils, and most preferably 50 to 200 mils in thickness. Tensile strengths (ASTM D-1 682) are preferably above 100 pounds; The fabric weight will be a function of the fiber size, chemical nature, and tightness of the fibers. However, a fabric having a weight in excess of about 2 ounces per square yard is satisfactory. Preferably the weight is about 5 to 1 5 ounces per square yard. Fabric porosity will depend on whether the fabric is tightly woven or is a very loose matting. Porosity may be measured by amount of water that flows through a square foot in one minute under a head of 5 inches.

Fabrics of low porosity are useful for giving structures having a surface layer of plasticized sulfur, whereas a highporosity fabric results in a composite or structure which is highly penetrated by, or impregnated with, the plasticized sulfur.

Polyester fabrics having a water flow rate of about 100 to 1000 gallons per minute per square foot are preferred.

The composites of the present invention are made by contacting the polyester fabric with molten plasticized sulfur. This contacting may be carried out in several ways. In one method of preparation, the polyester fabric is dipped into a vat or tank of the molten material and then laid in place before solidification takes place. This operation may be carried out either batchwise or continuously. After dipping, the plasticized sulfurimpregnated fabric may be contacted by metering devices such as squeeze rolls or scraper bars to remove excess liquid.

Another method of preparing the structures of this invention involves laying the polyester fabric in place and then spraying it with molten plasticized sulfur. As will occur to those skilled in the art, the velocity of the spray and the temperature-viscosity relationship of the plasticized sulfur will affect the degree of penetration into the fabric. A similar method involves painting or brushing molten plasticized sulfur onto previously laid fabric. The preferred method is to spray molten plasticized sulfur on the fabric already in place.

Another embodiment involves coating two or more separate pieces of polyester fabric and then, while the plasticized sulfur is still molten, pressing each coated fabric face-to-face with the other coated fabrics to form a multiple laminate with plasticized sulfur cores.

Regardless of the method, sufficient plasticized sulfur is added to the polyester fabric to produce a continuous sulfur-containing body which is essentially water-proof, i.e., it has a negligible water flow rate. The minimum quantity of plasticized sulfur necessary to obtain this degree of coverage will range from 0.1 to about 10 pounds per square foot, preferably 0.5 to 5 pounds per square foot. Additional coverage may be applied to improve mechanical properties, increase weight, or provide additional thickness.

Example 1 A piece of non-woven mat prepared from a poly(ethylene terephthalate) polyester of at least 99.7% purity (sold under the Monsanto tradename of "Bidim"), 24 in. by 36 in. was laid on the top of a work bench. This mat was 90 mils thick, weighed 8 ounces per square yard, had a grab tensile strength of 234 pounds as measured by ASTM D-1 682 method, and had a water flow rate of 380 gallons of water per minute per square foot under 5-inches of head.

A molten plasticized sulfur composition, comprising 84 parts of sulfur, 2 parts of a phenolsulfur adduct (about 30% phenol), 1 part of an unbranched linear aliphatic polyether polysulfide (Thiokol LP-3), 1 part of cyclooctadiene, and 12 parts of mica, at 2750F was sprayed at a vessel pressure of 75 psi onto the Bidim from a distance of 4-inches and at a rate of 0.75 gallon per minute while moving the spray nozzle across the fabric at a rate of 0.5 feet per second. After cooling, the covering material was found to be deeply impregnated by the plasticized sulfur and to contain an average of about 0.75 pound of plastticized sulfur per square foot. Under a 5-inch head of water, the resulting material was impervious and did not leak. A 6-inch square piece of this product was fixed several times through almost 3600 without cracking or crumbling.This flexing test was repeated with a second 6-inch square of this material soaked in water with the same results.

Example 2 This example was carried out essentiaily the same as Example 1, except that two pieces of Bidim, about 6 inches square, were sprayed.

While still molten, the sulfur coated side of one was pressed firmly against the sulfur coated side of the other to form a laminate. This laminate contained a core of plasticized sulfur and weighed 2 pounds per square foot and was very strong and inflexible.

Example 3 Two separate sites on an earthen water canal were provided with a composite of a Bidim polyester fabric and plasticized sulfur, one site being 1 7 feet by 500 feet and the other, 1 7 feet by 450 feet. The polyester fabric had a thickness of 90 mils and weighed 8 ounces per square yard.

At each site the polyester fabric was laid over the bare earth on the outer bank of the canal. Slope of the banks ranged from 1.5:1 to 3.0:1. The polyester fabric was cut into several sections and overlapped to fit the shape of the bend in the canal. The polyester fabric was anchored at the top and bottom edges of the bank by keying it into a two foot deep trench. Afterwards the trenches were filled with earth and compacted.

Plasticized sulfur having the composition described in Example 1 was applied by spray to the polyester fabric at a rate of 0.75-1.00 lb/ft2.

Only one spray pass was required to saturate the fabric, using a nozzle with a 500 spray angle and a rated capacity of 1.5 gallon per minute of water at 40 psi. A plasticized sulfur spraying vessel of 500 gallons capacity was used. A pressure of 100--1 10 psi was maintained in the vessel to allow for pressure drop in the 1-inch, 100 foot long hose and adequate velocity through the nozzle to penetrate the fabric. The temperature of the plasticized sulfur was maintained at 270 28O0F during its application to the fabric.

The canal was then subjected to water flow for several days, and then drained for inspection. The treated sections were intact, whereas adjacent untreated banks were severely eroded and undermined by the flowing water.

Claims (10)

Claims

1. An article of manufacture impervious to water, comprising a polyester fabric which has been coated or impregnated with a plasticized sulphur composition in which the sulphur is present in an amount of from 50 to 98 weight percent, based on sulphur and plasticiser.

2. An article as claimed in Claim 1, the plasticised sulphur composition having been applied to the polyester fabric whilst the composition is in a molten state.

3. An article as claimed in Claim 1 or 2, wherein the plasticised sulphur composition contains an inorganic filler in an amount of from 1 to 25 weight percent, based on the total composition.

4. An article as claimed in Claim 3, wherein the inorganic filler is mica.

5. An article as claimed in Claim 1, 2, 3 or 4, wherein the plasticiser for the sulphur of the plasticised sulphur composition is an aromatic polysulphide, an aliphatic polysulphide, an alicyclic polysulphide, or a mixture of two or more thereof.

6. An article as claimed in Claim 5, wherein the plasticiser is a mixture of a phenol-sulphur adduct, an unbranched linear aliphatic polyether polysulphide and cyclooctadiene.

7. An article as claimed in any preceding claim, wherein the polyester fabric is a non-woven polyethylene terephthalate polyester fibre fabric.

8. An article as claimed in Claim 7, wherein the coated or impregnated fabric comprises from 0.1 to 10 pounds per square foot of the plasticised sulphur composition.

9. An article as claimed in Claim 8, wherein the coated or impregnated fabric comprises from 0.5 to 5 pounds per square foot of the plasticised sulphur composition.

10. An article in accordance with Claim 1, substantially as described in any one of the foregoing examples.