METHOD FOR MAKING AN ARTICLE HYDROPHOBIC AND OLEOPHOBIC AS WELL AS ARTICLES MADE THEREFROM AND THEIR USE

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

BACKGROUND OF THE INVENTION

[0001] In as much as additional references, articles, journals and the like

are mentioned or cited herein, each such item is expressly incorporated herein by reference in its entirety as if it were set forth herein explicitly.

1. Field of the Invention

[0002] The present invention relates in general to a method and variations thereof for making an article, such as cloth, water repellent and/or water

resistant (i.e. hydrophobic) as well as oil repellent (i.e. oleophobic). In

particular, the method involves the process of providing a thin-layer polymer

coating on the article thereby rendering the article water repellent and/or water

resistant. Articles made according to the method of the present invention are

also disclosed and claimed herein as are the treated articles use.

2. Brief Description of the Related Art

[0003] The formation of thin films on solid surfaces has been the subject

of many studies by persons of ordinary skill in the art because of the wide

variety of differing films and their individual and unique applications. The

preparation of very thin polymer films in adsorbed surfactant bilayers has also

been under study, but the results of such studies have oftentimes been

inconclusive or unsatisfactory.

[0004] Thin film polymerization is carried out in a multi-step process based

on the formation of micelle-like aggregates of physically adsorbed surfactants at a solid-solution interface. Such surface aggregates are termed admicelles

or hemimicelles. Polymerization of monomers adsolubilized in the admicelles leads to the formation of a thin film on the solid substrate. This technique, which is called admicellar polymerization, is quite versatile and is applicable to

a variety of surfaces. Various potential applications have been proposed for thin

films formed by this technique such as in the microelectronic industry,

particularly for the manufacture of miniaturized circuit patterns on silicon

wafers. Other uses include solid lubrication, corrosion inhibition, optical

coatings, and surface-modified electrodes.

[0005] The present invention is generally directed to a method for

producing a hydrophobic and oleophobic article (such as wool or cotton fabric)

wherein this hydrophobic and oleophobic article includes a surface coated with

a very thin film of fluroalkyl polymer, such as Poly (perfluoroalkylethyl

methacrylate) ("PFMA") using a unique admicellar polymerization methodology. By using such a methodology, the hydrophobic and oleophobic article retains

air permeability thereby allowing for production of an article, such as a wool or

cotton fabric, that can be used to produce water and oil repellent garments

which are also comfortable to wear and easy to maintain/clean.

[0006] Production of water and oil repellent textiles has developed from a

traditional art to a highly specialized branch of technology during the past

century. In the case of cotton, which is a hydrophilic fiber, water repellency is generally imparted by treating the surface of the fabric with a hydrophobic

material. Examples of hydrophobic materials used includes wax, silicone, and

fluorochemicals. Such a treatment usually involves the pad-and-dry process. To improve the breathability of the fabric, Formasa Taffeta Co. Ltd. in Taiwan

developed a process employing a porous polyurethane coating to allow air and

moisture to pass through the coated fabric. This water-repellent cotton had

good air permeability due to the coating of a porous resin on the fabric with

specially designed, tightly woven, cloth construction. However, this process

resulted in a fabric which was much thicker and heavier than the original fabric.

The present invention offers a new method for coating a thin film on an article

or substrate, such as cotton or wool, which provides a water and oil repellant

and/or water or oil resistant fabric that is easily handled and has superior air

permeability without creating a thicker than original substrate or article - for

example; a cotton or wool textile.

[0007] The effects of counterion on surfactant adsorption are known in the

art. It has been shown that the counterion giving the highest adsorption of

surfactant, at a given surfactant and added electrolyte concentration, depends

on both pH and fractional surface coverage. The results have suggested that

any Region II/Region III transition in the adsorption of surfactant does not

occur near the completion of the monolayer coverage nor as a result of

electrostatic repulsion of surfactant ions from the mineral surface due to

reversal of the net surface charge.

[0008] Wu et al. coated polystyrene on alumina surface by using sodium dodecyl sulfate (SDS) as the surfactant in a water/ethanol solution. The treated alumina was analyzed in two parts. The first part was analyzed by FTIR (KBr

pellets) and the other one was extracted by tetrahydrofuran (THF) and analyzed by UV spectrophotometer. The results confirmed that admicellar polymerization

occurred. Wu et al. also found that the polymerization of styrene in the

admicelle followed the case IB model in the Smith-Ewart theory. After that, Wu

et al. characterized the alumina surface coated with polystyrene. Film thickness

ranged from 1.8 to 0.4 nm while BET surface area decreased from 94.7 to 57.8

m ² /g- The alumina surface changed from hydrophilic to hydrophobic while

retaining the basic pore structure.

[0009] Esumi et al. studied polymerization on alumina powder by using

sodium 10-undecenoate, which is a polymerizable surfactant. Esumi et al. formed a bilayer of surfactant and polymerized this layer through UV radiation.

The dispersion of the alumina particles was studied by looking at mean particle

size. Because hydrophiiic groups of the surfactant in the second layer were in

contact with the aqueous solution, the alumina particles were dispersed due to

electrostatic repulsion. The results also showed that purging with nitrogen gas

enhanced polymerization.

[0010] The incorporation of alcohols into admicelles is also known in the

art. It has been found that the surfactant adsorption over most of the isotherm is enhanced dramatically by the presence of alcohol. As the chain length of alcohol is increased, the surfactant adsorption at regions of lower surfactant adsorption was enhanced. A two-site adsolubilization model has been proposed

to interpret this complicated system. One of the alcohol sites was the same as in micelles, at the region between the headgroups of the surfactant. The other

was a site not present in micelles, the hydrophobic perimeter arising from

patchwise adsorption of the disk-shaped admicelle. This model was used to

explain: (i) very high ratios of alcohol to surfactant adsorption at lower

coverage, (ii) increase of surfactant adsorption below the CMC, and (iii) a slight

decrease of plateau adsorption.

[0011] Coated polystyrene on precipitated silica is also known in the art.

beverai types of surfactants consisting of cationic surfactant (CTAB), nonionic

surfactant (MACOL), and water-insoluble surfactant (ADOGEN) have been used. Two kinds of polymerization were tested: First, thermal polymerization, and

secondly, REDOX polymerization. Due to the effect of head group packing

density and length of alkyl chain, the results showed that CTAB adsorbed less

than SDS and ADOGEN but greater than MACOL on this substrate. When using AIBN as an initiator, the ratio of initiator to monomer was necessarily high. It

has been proposed that the ethanol used to dissolve AIBN consumed many of the radicals formed. For the REDOX system, as the ratio was lower, the reaction

took longer to complete. The reduction in the molecular weight of the

extractable polymer, as well as the increase in dispersity, was expected. As the chain length of the polymer increases it become more entangled in the surface and more difficult to extract.

[0012] Formation of polytetrafluoroethylene (PTFE) on aluminum oxide by admicellar polymerization is also known in the art. In these experiments,

ammonium persulfate was used as the initiator. Sodium bisulfate (NaHSO ₄ ) and

ferrous sulfate (FeSO ₄ ) were used as initiator regulators thereby improving the

initiator effectiveness at low temperature. The results showed that pressure was

the main factor in the control of adsolubilization of the gaseous monomer

tetrafluoroethylene into surfactant bilayers. The concentration of the initiator

also affected polymerization indicating the analysis of kinetic data must take

Into account such as the concentration of the initiator. Polytetrafluoroethylene

was successfully coated on both aluminum oxide powder and chips. Frictional behavior seemed to be related with film thickness and continuity.

[0013] The formation of thin polystyrene films on glass fiber surface has

been attempted is known in the art as well. These experiments used the

cationic surfactants dodecyl trimethylammonium bromide (DTAB) and

cetylpyridinium chloride (CPC). The concentration of styrene used and testing

method of treated fiber were tested the same as in the work of Wu et al., except that treated fiber was examined by SEM. The results showed that

polystyrene can be coated on glass fiber surface but the SEM micrographs

revealed a nonuniform coating on the surface. These experiments showed that polymerization was not restricted to the admicelles and that some polymerization occurred in the supernatant.

SUMMARY OF THE INVENTION

[0014] The present invention discloses and claims a method for providing a sheet of material having a hydrophobic and oleophobic polymer coating on at

least one surface thereof. In one embodiment, the method comprises the

following steps: (1) providing a sheet of material having a first surface and a

second surface and possibly the sheet of material may also have a plurality of

porous internal surfaces; (2) providing an aqueous hydrophobic and oleophobic

„ _, coating composition containing a surfactant and a monomer of a hydrophobic

and oleophobic polymer providing an initiator; (3) coating at least one of the first and second surfaces of the sheet of material with the aqueous hydrophobic

and oleophobic coating composition; (4) introducing the initiator into the

hydrophobic and oleophobic coating composition disposed on at least one of the

first and second surfaces of the sheet of material; and (5) initiating a reaction

on the sheet of material coated with the aqueous hydrophobic and oleophobic

coating composition and the initiator for a predetermined period of time such that a hydrophobic and oleophobic polymer coating forms on at least one

surface of the sheet of material.

[0015] In a preferred embodiment, the sheet of material is selected from

the group consisting of cloth, wool, burlap, natural and synthetic polymer films, polyesters, paper, cardboard and combinations thereof. In this embodiment

and/or other embodiments, the surfactant is selected from the group consisting of fluoralkyl compounds and, more preferably, poly (perfluoralkylethyl

methacrylate) ("PFMA"). In this same embodiment and/or other embodiments the initiator may be either 2, 2'-Azobis (2-m e t h y l p r o p i o n a m i d i n e )

dihydrochloride, sodium persulfate, or AIBN and it may be introduced

concurrently with the surfactant and monomer or at any later stage.

Additionally, the initiation may include heat, alone or in combination with any

additional compound, as well as any other polymer initiating methodology or

technology, such as sonic waves, IR and UV ra aton, ec.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0016] FIG. 1 is a schematic flow diagram view of the methodology of the

present invention.

[0017] FIG. 2 is a representative view of aggregations of surfactant on a

surface.

[0018] FIG. 3 is a graph view of an adsorption isotherm of a surfactant

used in the present invention.

[0019] FIGS. 4 A-C are a diagrammatic representation of the steps of

admicellic polymerization.

[0020] FIG. 5 is a diagrammatic representation of the chemical structure

of cellulose.

[0021] FIG. 6 is a panel of SEM micorgraphs showing fiber surfaces treated according to the methodology of the presently claimed and disclosed

invention.

[0022] FIG. 7 is a graphical representation of contract angles of water drops

on treated cotton fabric at varying monomer concentration.

[0023] FIG. 8 is a graphical representation of contract angles of n-

hexadecane drops on treated cotton fabric at varying monomer concentration.

DETAILED DESCRIPTION OF THE INVENTION

[0024] Before explaining in detail at least one embodiment of the invention in detail by way of exemplary drawings experimentation and results, it is to be

understood that the invention is not limited in its application to the details of

construction and the arrangement of the components set forth in the following

description, experimental results, or illustrated in the drawings. The invention

is capable of other embodiments or of being practiced or carried out in various

ways. Also, it is to be understood that the phraseology and terminology employed herein is for purpose of description and should not be regarded as

limiting.

[0025] The present invention encompasses a method for making an article, such as cloth, water repellent and/or waterproof. In general, the method includes the following steps (shown generally in FIG. 1): (1) providing 10 a

sheet of material having a first surface and a second surface; (2) providing 20 an aqueous hydrophobic and oleophobic coating composition containing a

surfactant and at least one monomer of a hydrophobic and oleophobic polymer

(such as PFMA); (3) providing 30 an initiator; (4) coating 40 at least one of the

first and second surfaces of the sheet of material with the aqueous

hydrophobic and oleophobic coating composition; (5) introducing 50 the

initiator into the hydrophobic and oleophobic coating composition disposed on

at least one of the first and second surfaces of the sheet of material; and (6)

initiating 60 a reaction on the sheet of material coated with the aqueous

hydrophobic and oleophobic coating composition and the initiator for a predetermined period of time such that a hydrophobic and oleophobic polymer

coating forms on at least one surface of the sheet of material.

[0026] Surfactants are substances that are widely used for cleaning,

enhanced oil recovery, construction, and pharmaceutical formulations.

Surfactants tend to migrate to interfaces or form structures to create new

molecular surfaces. A surfactant molecule consists of two parts, a head group

62 and a tail group 64 (as shown in FIG. 2). The head group 62 of a typical surfactant is hydrophilic or lipophobic, which is water-loving or oil-hating. The

head group 62 is an ionic or highly polar group. In contrast, the tail group 64

is water hating or oil loving, which is called hydrophobic or lipophilic. The tail group 64 is usually a long-chain hydrocarbon. Depending on the nature of the

hydrophilic group, surfactants are classified into four types. Surfactants having

a negative or positive charge on the hydrophilic group are called anionic or cationic, respectively. Surfactants with both a positive and negative charge are

called zwitterionic. The last type consists of surfactant molecules with no

apparent charge on the hydrophilic group. They are called nonionic surfactants.

[0027] Surfactant aggregation in solution has many forms. The most well

known form is a micelle 70 as shown in FIG. 2. Micelles 70 are suspended in

solution 80. Surfactants can also adsorb onto a surface 90 of a substrate 100

Dy means or electrostatic attraction. They can adsorb with or without

aggregation. If the aggregation on the surface 90 of the substrate 100 consists of only one layer, it is called a hemimicelle 110. If it consists of two layers, it

has been called an admϊcelle 120.

[0028] One parameter that determines the aggregation of surfactant is the

surfactant concentration as shown in FIG. 3, an adsorption isotherm. The

adsorption isotherm shown in FIG. 3 is the plot between log of surfactant

concentration and log of surfactant adsorbed onto the surface 90 of the

substrate 100. The adsorption isotherm shown in FIG. 3 can be divided into

four regions. In Region 1 130, the surfactant adsorbs onto the surface 90 mainly by ion exchange without aggregation. In Region II 140, there is a sharp

increase in adsorption, resulting from interaction of the hydrophobic chains of oncoming surfactant with those of previously adsorbed surfactant. The concentration at which the isotherm moves from Region 1 130 to Region II 140

is called the critical admϊcelle concentration (CAC) 135. In Region III 150 the

slope of the isotherm is reduced because the surface of the substrate 100 is

becoming saturated and, thus, further adsorption must overcome electrostatic

repulsion between the oncoming surfactant and the similarly charged solid. In

Region IV 160, any further increase in the surfactant concentration will lead to

micelle formation in the solution 80 with no further adsorption on the substrate

100 and the isotherm remains constant. The concentration at which the

isotherm moves from the Region III 150 to Region IV 160 is called the critical

micelle concentration (CMC) 155.

[0029] Admicellar polymerization consists of three main steps to produce

a thin-film of polymer and is shown in FIGS. 4 A-C. Step 1, as shown in FIG.

4A, consists of admicelle 120 formation by adsorption of surfactant 85 from the

aqueous solution 80 to the surface 90 of the substrate 100. The aggregation of

surfactant 85 depends on several parameters. One parameter that determines

the aggregation of surfactant 85 is surfactant concentration. The initial feed

concentration of surfactant is generally chosen close to but below the critical

micelle concentration (CMC) 155 to avoid emulsion polymerization in micelles 70 and to maximize admicelle 120 formation. The choice of surfactant is

influenced by the point of zero charge (PZC) of the surface. The surface becomes positive at pH values below the PZC, but negative above the PZC.

Consequently, anionic surfactants adsorb better below the PZC and cationic surfactants above the PZC. Thus, surfactant molecular structure also effects

adsorption. The addition of salt reduces the repulsion between head groups 62 of the surfactants 85 and causes the surfactant molecules to come closer

together.

[0030] Step 2, as shown in FIG. 4B ₇ is the solubilization of a monomer 170

into the micelle 70. Step 2 is called adsolubilization. The monomers 170, which

are nearly insoluble in water, diffuse from aqueous solution 80 and solubilize

in the hydrophobic interior 180 of the admicelle 120. Formally, adsolubilizatϊon

is defined as the excess concentration of a species at an interface in the

presence of the admicelle 120 that would not exist in the absence of the

admicelle 120.

[0031] Step 3, as shown in FIG. 4C, is the in situ polymerization of the

monomer 170. Once an initiator 190 is added, the polymerization reaction

starts in the admicelles 120, which act as a reaction site or a two-dimensional

reaction solvent for polymerization. The polymerization mechanism is similar

to those that occur in conventional emulsion techniques. [0032] After the formation of a polymer, excess surfactant 85 may be

removed by washing. This leaves a thin polymer film 210 exposed over the

surface 90 of the substrate 100.

[0033] Cotton is a natural fiber from the seeds of a plant in the genus

Gossypium. It has an average diameter of 20 μm and an average length of 1-

1.5 inches. In its natural state, cotton consists mainly of cellulose with about 10-20% other substances such as, wax, pectin, hemicellulose, seed husks, and

others. Normally, these impurities have to be removed prior to the dyeing

process to improve the wettability and uniformity of fabric properties. Cleaned

cotton usually consists of over 99% cellulose. The cellulose molecules in cotton

mainly gathered in bundles in the form of fibrils which spiral around the fiber

surface. The molecular structure of cellulose is shown in FIG. 5.

, _,

[0034] Cellulose ^" contains extensive hydroxyl groups making it highly

hydrophilic in its raw form. In making cotton water resistant and/or water

repellant, normally a film of wax, silicone, or fluorocarbon, is coated on the

fabric. This conventional treatment process consists of padding the fabric in a

solution containing waterproofing agent followed by drying. This results in a

thick film on the coated fibers making the fabric stiff. Furthermore, the coating

reduces air permeability of the fabric thus making it unsuitable for use as

clothing. Cotton treated according to the methodology of the present invention becomes water resistant and/or water repellant without such disadvantages of

the methodology known in the art.

Overview of the Process According to the Presently Disclosed and Claimed Invention

[0035] Poly(perfluoroalkylethyl methacrylate) (PFMA) was applied to cotton

fabric to obtain a hydrophobic/oleophobic surface by the admicellar polymerization technique. The increase in the hydrophobicity and oleophobicity

of the treated fabric surface was evaluated by the drop test with water and oil,

and water- and oil-repellency ratings were determined. The results show that

satisfactory evenness of coating and repellency on fabric was obtained after 24

hr of polymerization. Water and oil repellency of the treated fabric increased

with increasing monomer concentration in the range of 2.4-24.0 mM. At the

FMA:DBSA (dodecylbenzenesulfonic acid) molar ratio of 6: 1 (or FMA

concentration of 7.2 mM), the treated fabric can resist wetting by both water

and n-hexadecane droplets for longer than 30 min. Water contact angles of

136-151° and n-hexadecane contact angles of 121-127° were obtained.

[0036] Surface treatment of fibers to achieve water and oil repellency as a

way to produce soil-resistant fabric has long been a subject of great interest.

The wettability of a material is dependent on the chemical composition of the

surface layer with surfaces having lower surface energy typically exhibiting

poorer wetting. Many fabrics have been commercially treated with water- and oil-repellent agents for use in various fields such as rainwear, sports and leisure

wear, curtains, upholstery fabrics, carpet goods, restaurant uniforms, and aprons.

[0037] Fluorinated polymers represent a well-known group of low surface energy materials having both hydrophobic and oleophobϊc character. A very low energy surface is obtained when the surface is uniformly coated with a trifluoromethyl (-CF ₃ ) group. Various water-repellent agents containing

fluoroalkyl compounds have been developed since 1950. These fluorine-based

agents, which also show oil-repellency, do not affect the texture of the fibers

because a small amount is very effective. For these reasons, the fluoroalkyl

compounds remain the most important water- and oil-repellent treatments.

Most of the fluoroalkyl compounds used for the above purposes are long-chain

perfluoroalkyl-acrylate or methacrylate-based polymers, containing

perfluoroalkyl groups (R _f group: ^: "(CF ₂ CF ₂ ) _n F) e.g. poly(perfluoroalkylethyl

acrylate) and poly(perfluoroalkylethyl methacrylate).

[0038] Various techniques have been used to deposit fluorocarbon compounds onto different kinds of fiber and textile to enhance oil and water

repellency and also soil release property. Some of these methods, for example

padding and dipping are the most common in treating the fabric. The use of

admicellar polymerization to coat fluorocarbon compounds on fabrics , as

disclosed and claimed herein, is a novel and non-obvious approach to produce

articles (such as fabrics) that are hydrophobic and oleophobic.

[0039] Admicellar polymerization is a relatively new method for application

of a thin film coating. In this method, a suitable monomer is induced to undergo a polymerization reaction in a surfactant bilayer adsorbed on the

substrate surface. The polymerization is conducted in the liquid phase with no special equipment needed, while the monomer may be a gas, liquid, or solid. Because the reaction only occurs on the substrate surface, there is no risk of

blocking the interstices between fibers and yarns; hence, good air permeability

of the fabrics remains. As discussed hereinabove, the process of admicellar

polymerization has been characterized as occurring in four distinct steps. In the

first step, surfactants are adsorbed on the substrate surface to form a bilayer

structure or admicelle. The surfactant concentration is chosen to be close or

equal to the critical micelle concentration (CMC) to obtain maximum admicelle

formation with no micelle in the solution to avoid emulsion polymerization.

Admicelle formation is controlled by the electrochemical nature of the substrate,

the type of surfactant molecule, the pH of solution, and added counterion. In step two, a known amount of monomer is added to the solution. Due to its

hydrophobicity, the monomer will concentrate in the hydrophobic interior of the

admicelle. Then the initiator is introduced into the solution to initiate the

polymerization of the monomer in the admicelle to form the thin polymeric film

on the surface substrate. In the final step, surfactant is removed by washing

with water, exposing the polymer film on substrate.

[0040] As also discussed hereinabove, thin film coating by admicellar

polymerization has been successfully prepared in various systems. Examples

are poly(tetrafluoroethylene) on alumina, polystyrene on cotton, polystyrene on glass fibers, poly(methylmethacrylate) on cellulosic fibers and sodium styrene sulphonate on cotton. In one specific and particularly useful

embodiment of the presently disclosed and claimed invention, cotton fabric was coated with poly(perfluoroalkylethyl methacrylate) by such an admicellar

polymerization process thereby imparting hydrophobic and oleophobic

characteristics to the material.

Materials

[0041] Perfluoroalkylethyl methacrylate (ZONYL (TM), Aldrich), which is

abbreviated as FMA, was heated to 5O ⁰ C and stirred before use to ensure

uniformity. 2, 2'-Azobis (2-methylpropionamidine) dihydrochloride (97%,

Aldrich) was used as the initiator. Dodecylbenzenesulfonic acid (DBSA), sodium

salt, tech., used as the surfactant, was purchased from Aldrich. Methyl ethyl

ketone, which is abbreviated as MEK, (Carlo Erba Reagenti) was used as

received. Plain weave bleached cotton (fabric weight 165 g/sq.m) was washed

several times in a washing machine at 95 ⁰ C until it was free from any

remaining surfactant prior to use. Concentrated hydrochloric acid (37%) and

sodium chloride were acquired from Carlo Erba Reagenti. Isopropanol was

supplied by JT. Baker, while paraffin oil (Nujol), n-Octane >99% and n-

Heptane 99.7% all came from Carlo Erba Reagenti. Other alkanes which

included n-Hexadecane 99%, tetradecane 99%, dodecane 99%, and decane

99+% were purchased from Acros Organics.

Admicellar Polymerization of Monomer on Fabric

[0042] Polymerization of FMA on cotton was carried out using 1.2 mM DBSA

and 0.15M NaCI with the desired FMA:DBSA and FMA:V50 molar ratios.

Solution of DBSA, NaCI and initiator were prepared using pH 4 distilled water

(adjusted by using concentrated hydrochloric acid 37%) and a stock solution of

120 mM monomer was prepared using MEK. The stock solution was used to

prepare monomer solutions of desired concentrations that covered the

concentration range of 2.4-12.0 mM to give FMA: DBSA ratios in the range of

2:1, 4: 1, 6: 1, 8: 1, to 10: 1. FMA:V50 ratio of 1 : 1 was used. Polymerization

time was varied from Vz ₁ 1, 2, 4, 5, 6, 8, 10 to 24 hr. The 5.5 x 5.5 cm ² fabric

__ was placed in a 24-mL vial containing 20 mL solution of DBSA, NaCI, monomer

and initiator. The vial was then sealed with aluminium foil and the lid was screwed on and sealed with paraffin film. The vial was placed in the shaker

bath at 3O ⁰ C for 15 hr, then the temperature was raised to 75°C to initiate the

polymerization. After polymerization, the fabric was taken out from the vial and

washed in water at 80 ⁰ C for 30 min, 3 times to remove the outer layer of

DBSA. Finally it was dried in the oven at 65°C overnight. Oleophobicϊty Testing

[0043] For evaluation of oleophobic properties of the treated fabrics, four drops of n-hexadecane, which is AATCC oil test grade liquid No.3 representing

moderate oil repellency grade according to AATCC test method 118-1984, were

placed on the inner surface of the fabric in different parts and three drops on the outer surface. The time required for the droplets to disappear from the

surface of the fabric was measured up to a maximum of 30 min. The AATCC

Oil Repellency: Hydrocarbon Resistance Test method 118-1984, with a scale

from 0 (no oil repellency) to 8 (extremely high oil repellency), was applied to

evaluate oil repellency rating. In this test, five pieces of 5.5x5.5 cm ² treated

cotton fabric were used for a set of testing. 0.05 mL of test liquid drops were

placed on each test specimen and observed for 30±2 seconds. If three (or

more) of the five drops applied show clear well-rounded drop or rounded drop

with partial darkening of the fabric, the next higher-numbered test liquid drops

were p ace on e a ric an aga n o serve or secon s. i repe ency

rating of a fabric is the highest numbered test liquid that does not wet the fabric.

Hydrophobϊcity Testing

[0044] The hydrophobicity of the fabric was determined by placing five drops

of water in different parts of the surface on both sides to observe the time for

the water droplet to disappear up to a maximum of 30 min. Water repeliency ratings were determined according to the scale given in 3M Water Repeliency

Test: Water/Alcohol Drop Test. This test was carried out with the same

procedure and consideration as oil repeliency rating evaluation. The repeliency

rating was given on a spectrum of 0 to 10, where 0 is pure water and 10 is pure isopropanol. The rating for the fabric was based on the most concentrated aqueous liquid that does not penetrate the fabric within a period of 30±2

seconds. Both oleophobicity and hydrophobicity tests were carried out with untreated and treated fabric. Test liquids were prepared and numbered

according to Table 1.

.

¹ VoB^ isopropanol in distilled water ² In n-hexadecane

Contact angle measurement

[0045] Static contact angles with water and oil were measured for both front

and back sides of the fabric at 3O ⁰ C using sessile drop method on a DSAlO

contact angle measuring instrument (KRUSS Gmbh Germany). For each

sample, a total of ten drops of water and seven drops of n-hexadecane were

placed on different parts of the sample on both sides. Contact angle at every

1 min was measured for a period of 5 min. The average value of all

measurements was then calculated.

Surface morphology of the treated fabric

, - _e , _, _^ ,

[0046] Surface morphology of the treated fabric was studied Dy Joel SEM

model JSM 2590+. Specimens were sampled at random from different fabric

locations and sputter coated with gold prior to observation. Magnification used was in the range of 750-2000 times.

Effect of polymerization time

[0047] Effect of polymerization time on the hydrophobicity and oleophobicity

of the treated fabrics was determined by varying polymerization time from Vi,

I ₁ 2, 4, 5, 6, 8, 10 to 24 hr using FMA:DBSA molar ratio of 10: 1 and FMA:V50 molar ratio of 1: 1. Table 2 compares the wetting time of water and oil of

treated cotton at varying polymerization time. The results for untreated cotton

were also presented which show that untreated cotton was completely and instantly wetted by both water and oil. The wetting time ranges indicated in Table 2 show the time taken for complete wetting by the first drop and for

complete wetting by the last drop of the test liquids on each test specimen.

NP-no penetration or wetting of fabric by test droplets throughout the test period of 30 τm ^' n. ( ) Number of positions on fabric that is not wetted in one sample.

[0048] In instances where no penetration or wetting of the fabric by the test

liquid droplets occurred during the observation period, the wetting time is

labelled as "no penetration or NP." Where penetration without complete

disappearance of the droplet occurred during 30 min, the wetting time is

labelled as being "greater than 30 min."

[0049] The results in Table 2 show that the longer the polymerization time,

the better the evenness of coating and the repellency to test liquids of treated

cotton fabrics. At the polymerization time of Vi hr, the treated fabrics were

non-repe en an ere was i e improvemen w en e po ymerization time

was extended to 1 to 4 hr. After the polymerization time of 5 hr, the repellency

of treated fabrics increased rapidly until the polymerization time of 24 hr when

fully hydrophobic and oleophobic cotton was achieved. Therefore, in order to

obtain satisfactory evenness of coating and repellency on cotton fabrics, the

polymerization time was chosen to be 24 hr.

Effect of monomer concentration

[0050] In this work DBSA concentration, NaCI concentration and the

FMA:V50 molar ratio were fixed at 1.2 mM, 0.15 M and 1:1, respectively. After

adsorption and adsolubilization for 15 hr, the temperature was raised to 75 ⁰ C and polymerization reaction was carried out for 24 hr. Effect of FMA monomer concentration on the repellency of the cotton fabric was investigated by varying FMA concentration from 2.4-12 mM to give a FMA: DBSA molar ratio in the

range 2: 1-10:1.

[0051] The results in Table 3 show that higher amount of monomer added

enhanced the evenness of coating as can be seen in the decrease in the

difference between the time taken for complete wetting by the first and the last

drops of test liquid. Water and oil repellency of the treated fabric increased

with increasing monomer concentration. At a FMA:DBSA ratio of 2: 1, little

improvement in the hydrophobicity of treated cotton fabric was observed in

compar son w un rea e co on. or a : ra o o : , some

penetration without complete disappearance of droplets occurred whereas at the ratio of 6:1 to 8:1, all the water droplets remained on the fabric after 30

min. Some of these water droplets still showed slight penetration. Fully

hydrophobic cotton was obtained at a ratio of 10:1. In case of oil repellency,

some oil drops remained on the fabric without penetration even at a FMA: DBSA

ratio of 2:1 but fully oleophobic cotton was achieved from a ratio of 6:1. The

results show that, at the same amount of FMA coating, cotton fabric showed

better oil repellency than water repellency.

Table 3 Time required for test liquids to penetrate treated cotton fabric with different monomer concentrations

NP-no penetration or wetting of fabric by test droplets throughout the test period of 30 min. ( ) Number of positions on fabric that is not wetted in one sample.

. _ n a i ion, microgr p s o rea e i er sur ace s own in .

3 show that each individual fiber of coated fabric was covered with a thin film of PFMA produced by admicellar polymerization. At high monomer

concentration, there were also some PFMA particle depositions. These particles

may come from solution polymerization of the monomer and initiator in the

aqueous phase. The SEM micrographs confirm that PFMA was successfully

coated on the fiber surface by admicellar polymerization.

Effect of Coating Methodology

[0053] A standard admicellar polymerization process, which is a four-step

process consisting of admicelle formation, monomer adsolubilization,

polymerization and surfactant removal, has been adapted for PFMA coating. Since FMA is an oil-soluble monomer, it helps to dissolve them separately in MEK before adding to the surfactant solution. In order to save time and facilitate monomer adsolubilization, the monomer can be added at admicelle

formation step to perform admicelle formation and monomer adsolubilization

concurrently.

[0054] Effect of coating procedure on the repellency and surface morphology

of treated cotton fabric was investigated by using two types of admicellar

polymerization process; (1) standard process (4-step), (2) adapted process (3-

step), and solution polymerization. The FMA concentration was varied from

2.4-12 mM to give a FMArDBSA ratio in the range of 2: 1-10: 1. Solution

po ymerization or on co on was earne ou in e same way as a m ce ar

polymerization but only monomer and initiator were added with no surfactant and the washing step was not done. Standard admicellar polymerization was

also conducted as described in admicellar polymerization of monomer on fabric

section but the combined adsorption/adsolubilization step was separated and

both steps were set for a period of 15 hr each.

[0055] As shown in Table 4, at the same FMA: DBSA ratio, water and oil

repellency of treated cotton obtained from adapted process was better than that

of the samples obtained from standard process except at a FMA: DBSA ratio of

10:1, water repellency of treated cotton obtained from both processes was the same. According to SEM micrographs (FIG. 6), combining adsorption with

adsolubilization step facilitates monomer adsolubilization (more monomer concentrated in the admicelle) resulting in more even polymer film formed on the fabric. In case of cotton fabric treated by solution polymerization, fully

hydrophobic/oleophobic cotton was achieved from a FMA: DBSA ratio of 4: 1

showing that PFMA particles from solution polymerization can deposit well on

the cotton fabric. The results show that, the repellency of solution

polymerization treated cotton was better than admicellar polymerization

samples because solution polymerization samples were not washed as in the

case of admicellar polymerization samples and some PFMA may have been

removed during the washing step. In addition, SEM micrographs of treated

. _ i er surrace in ι- . s ow a sou ion poymeriza ion coa e a ric was

covered with a thick layer of PFMA particles and the coating was uneven

whereas each individual fiber of coated fabric by admicellar polymerization was

covered with a thin film of PFMA and the coating was more even.

Table 4 Time required for test liquids to penetrate treated cotton with different coating procedures

NP-no penetration or wetting of fabric by test droplets throughout the test period of 30 min. ( ) Number of positions on fabric that is not wetted in one sample.

_ on ac ang es o wa er an oi n- exa ecane rops on rea e a ric surface

[0056] Contact angles of both water and oil droplets on treated cotton

surface were measured at varying monomer concentration. As shown in FIGS.

7and 8, when greater amount of monomer was charged to the reactor, the

contact angle of water and oil drops increased corresponding to the

improvement in the hydrophobicity and oleophobicity of treated cotton fabric.

After 5 min, contact angle of both test liquids decreased a little at the low

concentrations of monomer but stayed nearly the same at high concentrations of monomer. Contact angles of all water droplets on treated cotton fabric are

greater than 135° whereas contact angles of n-hexadecane droplets are greater

than 120° showing the excellent water and oil repellency of treated cotton. For homo-PFMA, water contact angle of 113.6° was previously observed in the literature. The results show that in the present work, higher contact angles

were obtained on treated fabric surface. Similar results were also reported by

Sherman et al. (1969) for a fluorochemical finishing cotton, polyester, and

polyester/cotton blend fabrics treated by a padding process.

Water- and Oil-Repellency Rating

[0057] According to the drop test results, the cotton fabric treated according

to the presently disclosed and claimed methodology can resist wetting by both

water and oil (n-hexadecane) droplets for longer than 30 min from a FMA: DBSA

ra io o : so rea e co on a a ra o o : , : , an : were se ec e o evaluate their water- and oil-repellency rating.

[0058] The ratings of water and oil repellency tests reported in Table 5 are

in good agreement with the wetting time results discussed with respect to the

effect of monomer concentration hereinabove. All samples obtained high

water-repellency rating (6 to 7 rating) and moderate oil-repellency rating (3

rating). Water- and oil-repellency ratings of other fluorocarbon-treated fabrics

were also determined by other authors. Cotton fabric coated with commercial

water borne fluorinated resin by pad-cure method has a water-repellency rating of 5 and an oil repellency rating of 4. Cotton fabric coated with polymer having

the polyfluoro-octyl side chain obtained a rating of 3 for both water and oil

repellency.

Table 5 Water-and oil-repellency ratings determined for untreated and treated cotton fabrics with different monomer concentrations

Water-repellency rating scale is 0-10 Oil-repellency rating scale is 0-8

i c ry venness o coa ing an repe ency o o wa er an oi

on fabric was obtained at 24 hr of polymerization. An increase in monomer

concentration resulted in higher hydrophobicity and oleophobicity of treated

fabric as shown by drop test and contact angle measurements. At the

FMA: DBSA molar ratio of 6: 1 (or FMA concentration of 7.2 mM), the treated

fabric can resist wetting by both water and n-hexadecane droplets for longer

than 30 min whereas water-repellency rating of 6 and oil-repellency rating of

3 were obtained. In the presently disclosed and claimed methodology,

combining adsorption with adsolubilization step was found to be the way to save time and facilitate monomer adsolubilization resulting in more even PFMA

film on the fabric. Water contact angles of 136-153° and n-hexadecane contact angles of 121-130° were obtained showing the excellent repellency properties of treated cotton. SEM micrographs of the treated surface show film-like

coating of PFMA together with PFMA particles deposition that increases with increase in monomer concentration. The presently claimed and disclosed

methodology is useful for polymer formation by admicellar polymerization that

is capable of producing cotton and polyester fabrics with good water- and oil-

repellency properties.

[0060] Thus, in accordance with the present invention, there has been

provided a method for making an article, such as cloth or wool, water repellent

and/or waterproof and oil repellent and/or oil proof that fully satisfies the

o jecives an a vanages se o a ove. oug e i v i

described in conjunction with the specific drawings and language set forth above, it is evident that many alternatives, modifications, and variations will be

apparent to those skilled in the art. Accordingly, it is intended to embrace all

such alternatives, modifications and variations that fall within the spirit and

broad scope of the invention.

[0061] The following references, to the extent that they provide exemplary procedural or other details supplementary to those set forth herein, are specifically incorporated herein by reference in their entirety as though set forth herein particular.

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