IN SITU POLYMERIZATION FOR HYDROPHOBIC TEXTILES

Cross Reference to Related Applications

tool] Priority is claimed from United States Provisional Patent

Application 61 /455,407, filed 10/20/2010, which is hereby incorporated by reference

Background

[002] Hydrophobic fabrics and textiles have useful application for sporting goods, sportswear, other garments, carpets, cordage (rope), restaurant linens, and in many other applications where water repellency would be desirable.

Summary

[003] In situ polymerization of hydrophobic monomers in aqueous solution is used to create hydrophobic coatings on textiles. A reactive emulsion of hydrophobic monomers is produced, and the textile being treated is contacted with the liquid emulsion. The emulsion and textile are then heated to a sufficient temperature for a sufficient length of time to activate an initiator in mixture, which causes reaction of the monomers and creation of a hydrophobic surface on the textile.

[004] By "textiles" is meant any woven or nonwoven material generally characterized as a network of natural and/or artificial fibers or it may mean the fibers themselves. These include any suitable textile and fabric materials, such as, for example, synthetic polymers, such as acrylics, nylons, polyesters, aramid synthetics (Kevlar™, Nomex™), polyolefins (polyethylenes, polypropylene, and other polyolefins), polycarbonates, polystyrenes, and copolymers of these with each other and with other monomers. Also included are blends of any of these materials in the same textile, or composites of these materials with fibers or other materials, such as carbon fiber

composites. Also contemplated are natural materials such as vegetable fibers or materials (e.g, cellulosic, ligninous, cotton, hemp), animal fibers or materials (e.g. wool, hair, silk, feather, leather). The textile materials can be in any suitable form, such as fiber, yarn, bulk cloth, film, sheet, or bulk form.

[005] The treated textiles include suitable textiles and anything made thereof. The textile can be treated, for example, in the form of fibers, finished or unfinished cloth, or manufactured textile goods and articles. These include, but are not limited to, apparel and other textile articles such as water-resistant outerwear (coats, jackets, liners, pants, gloves, footwear, socks, hats), stain resistant clothing, clothing (formal, casual, work, medical, athletic), carpeting and rugs, zipper fasteners, rope/cordage, camping equipment (tents, footprints, sleeping bags, sleeping pads, rain flies, screens, backpacks, dry bags, canopies), filters, upholstery, medical gowns, bedding (sheets, pillows, comforters, blankets, pillow cases, mattress pads, mattress covers, mattresses), Geotextiles, water sport apparel (swimming suits, wet suits, dry suits, skull caps, booties, gloves), protective wear (chemical suites, bullet proof vests, firefighting apparel, helmets), and covers (pool covers, awnings, boat covers, protective covers).

[006] The hydrophobic textiles are produced by first forming a reaction mixture of one or more of hydrophobic monomer(s), initiator(s), and surfactant(s). The mixture is formed in aqueous solution and is an emulsion of the hydrophobic monomer in the solution. Without being bound to any theory, it is believed that the initiator activates or reacts with the textile surface to form sites that are reactive to the hydrophobic monomers. Accordingly, as the monomers react and polymerize the reaction product is incorporated as part of and is bound to the surface. Because of the hydrophobic portions from the hydrophobic monomers, a hydrophobic property is thereby imparted to the surface of the textile.

[007] Monomer

[008] Suitable monomers include one of or a mixture of hydrophobic monomers. There are monomers with a reactive polymerizable group and a hydrophobic group. The reactive group enables polymer forming reactions and the hydrophobic group imparts hydrophobic properties to the treated textile. This includes a wide variety of monomers, and includes, for example, methacrylates, acrylates, styrenics, vinyl ethers, and acrylamide-based monomers. The hydrophobic group can be any suitable hydrophobic group and functions to impart the suitable hydrophobic properties to the final product. It has been found that perfluorinated groups are suitable. Monomers with alkyl groups may also be used where a milder hydrophobic property is desired, or can be used in mixture with monomers with perfluorinated groups. Exemplary monomers include, but are not limited to, 2-perfluorohexyl ethyl methacrylate, lauryl methacrylate, stearyl methacrylate, palmitoyl

methacrylate, 2-perfluorohexyl ethyl acrylate, lauryl acrylate, and 2- perfluorobutyl ethyl methacrylate. The monomers included in the reaction mixture may include other hydrophobic polymers, or any other monomer that does not materially compromise the hydrophobic property of the final product.

[009] The monomers may be chosen to impart properties in addition to or in place of a hydrophobic property. For example, monomers may be chosen to impart an oleophilic property.

[0010] Initiator

loon] One of or a mixture of thermal activated radical initiators are included in the reaction mixture. Any suitable initiator is contemplated.

Without being bound to any theory, it is believed that water soluble initiators may be more effective in creating reactions sites on the textile surface and reacting the monomers with these sites. In contrast, an oleophilic initiator may react the hydrophobic monomers within emulsion micels, rather that promoting reaction of the monomers at or near the textile surface.

[0012] Examples of water soluble radical initiators include sodium persulfate, potassium persulfate, and 4,4'-Azobis(4-cyanovaleric acid). In general, organic peroxides that produce oxygen centered radicals are suitable, such acyloxy- or peroxy- compounds (for example benzoyl peroxide, and di-tert-butyl peroxide).

[0013] Surfactant

[0014] Surfactants are employed to emulsify the generally water- insoluble monomers to create an emulsion of the hydrophobic monomers in water. Without being limited by theory, it is believed that the emulsion is required for the hydrophobic monomers to become activated and react with the initiator and the textile surface. The surfactant may be ionic or non-ionic, and may be any one or a mixture of many suitable surfactants available on the market. For example, sodium dodecyl sulfate can be used. Other possible surfactants might include surfactant product families available under the trade names Triton, Brij, and Zonyl.

tools] Without being limited by theory, it is believed the surfactant plays a role of lowering the surface tension of the solution so that it better wets the fabric surface. However, one or more wetting agents may also be added to the formulation for this purpose. Wetting agents are commonly used in solutions that contact textiles. Other common components of textile formulations, such as antibacterial agents may also be added.

[0016] Optional Components in the Reaction Mixture

Cross/inker

[0017] One or more crosslinkers may be added to the reaction mixture. Crosslinkers can be used to increase to durability and/or brittleness of the hydrophobic surface on the textile, or otherwise improve properties of the surface. Suitable crosslinkers are any such compound compatible with the monomers that will not materially compromise the hydrophobic nature of the textile or other desired property. Crosslinkers are molecules that contain at least two polymerizable groups that are compatible with the monomers, such as, for example, dimethacrylates, diacrylates. The crosslinker may have suitable bridge between its polymerizable groups or reactive parts, for example, an aliphatic bridge, an aromatic bridge, or a fluorinated alkyl or aryl bridge.

Examples of crosslinkers, include, but are not limited to 1 ,4-butanediol dimethacrylate, 1 ,4-butanediol diacrylate, 1 ,12-dodecanediol diacrylate, and 1 ,12-dodecanediol dimethacrylate.

[0018] Chain Transfer Agents [0019] Chain transfer agents might also be employed to help control the molecular weight of the final polymers (macromolecules). Chain transfer agents are known, and suitable chain transfer agents include those

compatible with the monomer and polymerization chemistry. Examples of suitable chain transfer agents include thiols, such as dodecane thiol.

[0020] Reaction

[0021] The reaction emulsion is then reacted with the fabric to be treated by contacting the fabric with the emulsion, and initializing a

polymerization reaction by heating the emulsion to a temperature sufficiently high and for sufficient long time to activate the initiator. The temperature required and the length of the contacting time depend on the properties of the initiator, such as the activation temperature and half life. Finding a suitable temperature and time can be determined by reference to the properties of the initiator and routine experimentation.

[0022] A suitable method for contacting the fabric with the emulsion is to place the textile in the bath container of the emulsion. Contact time may involve several minutes so soaking the textile in heated baths of the emulsion is suitable. Equipment for treating textiles with solutions in known, and such can be adapted. Both continuous and batch methods are contemplated, depending upon the requirements.

[0023] In an aspect the reaction is carried out by first mixing the hydrophobic monomer(s), crosslinker(s), surfactant(s), and initiator(s) are into water to form a homogeneous solution or emulsion. The solution is degassed and a textile is added to the mixture. (Degassing may not always be necessary.) The temperature of the mixture and textile is then raised so that the initiator decomposes and polymerization takes place. This process leads to the formation of a hydrophobic finish on the fabric or textile.

[0024] Under some circumstances, it may be advantageous to employ methacrylates instead of acrylates in this process because of their higher glass transition temperatures. In some cases, the crosslinker may not be necessary in the reaction. It may be advantageous for the initiator to be water soluble. [0025] Suitable results have been obtained with a mixture of a perfluorinated methacrylate and an alkyl methacrylate, or the perfluorinated methacrylate alone.

[0026] For textiles that have been previously dyed, the reaction conditions may be adjusted to decrease the solubility of the dye to retain the dye in the fabric. As an example, it may be advantageous to raise the pH of the solution using a weak base, such as sodium bicarbonate or sodium carbonate, because many textile dyes contain aromatic amine groups, which are less soluble in water when they are deprotonated. It may also be advantageous to employ an initiator that decomposes at low temperature, such as 2,2'- azobis(2-methylpropionamidine)dihydrochloride and 2,2'-azobis[2-(2- imidazolin-2-yl)propane]dihydrochloride. The addition of certain reactive monomers, such as glycidyl methacrylate, may also improve the durability of the finish and reduce the tendency for the dye to escape from the fabric and textile during this finishing.

[0027] Another possible method for keeping the dye in the fabric is to use a non ionic surfactant. Such non ionic surfactants, such as those known by the trade names Zonyl and Brij, do not appreciably affect the stability of dye in fabrics.

[0028] In another aspect of the invention, the processes of deposition a hydrophobic surface and dying may be combined into a single step. This will require some measure of compatibility between the conditions used for dyeing and those used for deposition of the hydrophobic coating, such that either process or the properties of the product are materially compromised. In this deposition process, the dye and hydrophobic coating are deposited on the fabrics simultaneously. If it is not possible to do every part in the dyeing and hydrophobic coating processes simultaneously, it is be possible to merge a fraction of the steps. The first advantage of this approach is the cost savings it represents. Because two processes become one, the original cost for the second process and the pretreatment will be cut. Suitable conventional equipment can be adapted to apply this combined finish or either separately, as for example a jet dyer. Brief Description of Drawings

[0029] FIG. 1 is a spray pattern rating chart.

Detailed Description

[0030] In the following examples, to test hydrophobicity of the samples, wetting tests similar to the Dupont Water Drop Test LS & CO Method 42 were conducted with water/isopropyl alcohol (I PA) mixtures. For example, 98/2 means a mixture of 98% water and 2% I PA.

[0031] In addition, water spray tests were performed in accordance with the AATCC Test Method 22-2005, Water Repellency: Spray Test. The spray patterns were evaluated by comparison to a rating chart, which is shown in FIG. 1 , and with reference to Table 1 .

Table 1

Spray Test Evaluation

Example 1

[0039] The aqueous solution contained (based on weight) 1000 parts of water, 7.2 parts of 2-perfluorohexyl ethyl methacrylate, 2.8 parts of lauryl methacrylate, 0.094 parts of 1 ,4-butanediol dimethacrylate, 0.33 parts of sodium persulfate, and 3 parts of sodium dodecyl sulfate. The aqueous solution was stirred for 30 minutes to disperse the monomers into water homogeneously. Then, 18 parts of knit polyester was added into the aqueous solution and the solution was degassed with nitrogen for 1 hour. The solution was heated to 80 °C for 2.5 hours. Finally, the knit polyester was washed with water three times and dried. [0040] The coated polyester showed good water repellency. Initially, the dry fabric passed a 40/60 water/isopropyl alcohol test mixture and its spray test rating was 95. The durability of this finish was excellent: after 25 home launderings, it still had a spray rating of 95, and it passed a 50/50 water/isopropyl alcohol test mixture.

Example 2

[0041] The aqueous solution contained (based on weight) 1000 parts of water, 6.3 parts of 2-perfluorohexyl ethyl methacrylate, 3.7 parts of lauryl methacrylate, 0.07 parts of 1 ,4-butanediol dimethacrylate, 0.16 parts of 4,4'- azobis(4-cyanovaleric acid), 1 part of sodium dodecyl sulfate, and 1 part of Zonyl FS 300 (HLB 14). The aqueous solution was stirred for 30 minutes to disperse the monomers into water homogeneously. Then, 18 parts of knit polyester was added into the aqueous solution and the solution was degassed with nitrogen for 1 hour. The solution was heated to 70 °C for 20 hours. Finally, the knit polyester was washed with water three times and dried.

[0042] The coated polyester showed good water repellency. Initially, the dry fabric passed a 40/60 water/isopropyl alcohol test mixture and its spray test rating was 95.

Example 3

[0043] The aqueous solution contained (based on weight) 1000 parts of water, 6.3 parts of 2-perfluorohexyl ethyl methacrylate, 3.7 parts of lauryl methacrylate, 0.094 parts of 1 ,4-butanediol dimethacrylate, 0.39 parts of potassium persulfate, and 3 parts of sodium dodecyl sulfate. The aqueous solution was stirred for 30 minutes to disperse the monomers into water homogeneously, but not degassed. Then, 18 parts of knit polyester was added into the aqueous solution and the solution was heated to 80 °C for 2.5 hours. Finally, the knit polyester was washed with water three times and dried. [0044] The coated polyester showed good water repellency. Initially, the dry fabric passed a 50/50 water/isopropyl alcohol test mixture and its spray test rating was 95.

Example 4

[0045] The aqueous solution contained of (based on weight) 1000 parts of water, 10 parts of lauryl methacrylate, 0.094 parts of 1 ,4-butanediol dimethacrylate, 0.33 parts of sodium persulfate, and 3 parts of sodium dodecyl sulfate. The aqueous solution was stirred for 30 minutes to disperse the monomers into water homogeneously. Then, 18 parts of knit polyester was added into the aqueous solution and the solution was degassed with nitrogen for 1 hour. The solution was heated to 80 °C for 2.5 hours. Finally, the knit polyester was washed with water three times and dried.

[0046] Initially, the dry fabric passed an 80/20 water/isopropyl alcohol test mixture and its spray test rating was 60. Example 5

[0047] The aqueous solution contained (based on weight) 1000 parts of water, 10 parts of 2-perfluorohexyl ethyl methacrylate, 0.094 parts of 1 ,4- butanediol dimethacrylate, 0.33 parts of sodium persulfate, and 3 parts of sodium dodecyl sulfate. The aqueous solution was stirred for 30 minutes to disperse the monomers into water homogeneously. Then, 18 parts of knit polyester was added into the aqueous solution and the solution was degassed with nitrogen for 1 hour. The solution was heated to 80 °C for 2.5 hours. Finally, the knit polyester was washed with water three times and dried.

[0048] The coated polyester showed good water repellency. Initially, the dry fabric passed a 40/60 water/isopropyl alcohol test mixture and its spray test rating was 90.

[0049] While this invention has been described with reference to certain specific embodiments and examples, it will be recognized by those skilled in the art that many variations are possible without departing from the scope and spirit of this invention, and that the invention, as described by the claims, is intended to cover all changes and modifications of the invention which do not depart from the spirit of the invention.