KR100444367B1 - Sulfonated Polymers and Methods of Sulfonating Polymers - Google Patents

Abstract

Provided is a method for sulfonating a polymer. One method of sulfonating a polymer involves exposing sulfur dioxide and oxygen to energy yielding free radicals and contacting the polymer with the product of the preceding step. Preferably, the steps of exposing sulfur dioxide and oxygen to energy producing free radicals and contacting the polymer with this product are carried out under reduced pressure. Another method of sulfonating a polymer includes contacting the polymer with sulfur dioxide and oxygen and exposing the contacted polymer to energy that yields contacted free radicals. The polymer may be contacted with a mixture of sulfur dioxide and oxygen or separately contacted with sulfur dioxide and oxygen. When the polymer is contacted separately with sulfur dioxide and oxygen, the polymer may be contacted first with sulfur dioxide and then with oxygen. Sources of energy producing free radicals can be ultraviolet light, electron beams, inert gas radio frequency plasma, corona discharges or gamma radiation.

Description

Sulfonated Polymers and Methods of Sulfonating Polymers

As generally known, the surface of certain polymers, such as thermoplastic polymers, is inherently non-wetting or hydrophobic. It is also generally known that thermoplastic polymers such as, for example, polyolefin polymers can be formed from fibers. Such polyolefin fibers are used in a variety of commercial applications. In some commercial applications such as absorbent products, disposable absorbent products, disposable nonwoven absorbent products, the inherent hydrophobic nature of such polymers is a disadvantage. As such, it is necessary to change the hydrophobic nature of this polymer before it can be used in absorbent articles.

One method of changing the hydrophobic nature of such polymers, such as shaped polymers, is sulfonation. The term "molded polymer" or "molded polymers" as used herein means a polymer in any solid form as opposed to a polymer in gaseous, liquid or solution phase. Thus, the molded polymer may be in particulate form such as powder or granules or chips, shaped bodies, extruded shapes, fibers, woven or nonwovens, films, foams and the like. The term "sulfonation" as used herein refers to a method of forming a compound comprising a sulfonic acid, -SO ₂ O group. Such methods include, for example, the conversion of organic compounds to sulfonic acid or sulfonic acid salts containing the structural groups C-SO ₂ -O or optionally N-SO ₂ -O.

In many cases, however, traditional sulfonation methods require the use and / or storage of materials that raise concerns for both health and safety. Examples of such materials include, for example, sulfur trioxide, concentrated sulfuric acid, oleum and chlorosulfuric acid. In addition, in many cases, undesired surface discoloration may occur when a polymer such as the surface of a polyolefin nonwoven web is carried out by traditional sulfonation methods. For example, fibers formed from undyed polymers such as polyolefin fibers and preferably polypropylene fibers are generally translucent. After treatment with traditional sulfonation methods, the surface color of the fibers changes so that the fibers usually appear yellow, brown or black. As mentioned above, such polymers may have use as absorbent articles. In such cases, in some instances, discoloration of the polymer fibers is generally undesirable, especially when such polymer fibers are contained in personal absorbent articles such as diapers, feminine sanitary napkins, adult incontinence articles.

Therefore, there is a need for an improved sulfonation method that avoids the disadvantages of traditional sulfonation processes. The present invention provides such improved sulfonation methods and products by the methods, which will become more apparent as the specification is read.

Summary of the Invention

For the above problems encountered by those skilled in the art, the present invention provides a method for sulfonating a polymer that does not require storage of large amounts of sulfur trioxide, concentrated sulfuric acid, oleum, or chlorosulfuric acid. The process of the present invention also provides a method of avoiding undesirable discoloration, particularly undesirable browning pigmentation inherent in traditional sulfonation processes.

In one preferred embodiment of the present invention, the method of sulfonating a polymer exposes sulfur dioxide and one oxygen source to energy which yields free radicals to form a product, and the polymer is contacted with the product of the preceding step. It involves making. Preferably, exposing the sulfur dioxide and oxygen source to energy yielding free radicals and contacting the resulting product with the polymer are carried out under reduced pressure. Sources of energy producing free radicals may be ultraviolet light, gamma radiation, electron beams, inert gas radio frequency (rf) plasma or corona discharges. The oxygen source can be oxygen, an oxygen donor gas, or a combination thereof.

In another embodiment, a method of sulfonating a polymer comprises contacting the polymer with sulfur dioxide and an oxygen source and exposing the contacted polymer to energy yielding free radicals. In this embodiment, the polymer may be contacted with a mixture of sulfur dioxide and an oxygen source or the polymer may be contacted separately with a sulfur dioxide and oxygen source. When the polymer is contacted separately with sulfur dioxide and an oxygen source, the polymer may be contacted first with sulfur dioxide and then with an oxygen source. Preferably the contacting and exposing steps are generally carried out under reduced pressure, i.e. under 1 atmosphere. In this embodiment, the source of energy that produces the free radicals may also be ultraviolet light, gamma radiation, electron beams, inert gas radio frequency plasma or corona discharges. The oxygen source can be oxygen, an oxygen donor gas, or a combination thereof.

Another embodiment of the present invention provides a method of imparting hydrophilic properties to the molded polymer. This method involves exposing the sulfur dioxide and oxygen source to energy producing free radicals and contacting the polymer with the product of the preceding step. Preferably, the contacting and exposing step takes place in a reduced pressure environment. In this embodiment, the source of energy that produces the free radicals may be ultraviolet light, gamma radiation, electron beams, inert gas radio frequency plasma or corona discharge. The oxygen source may comprise oxygen, an oxygen donating gas or a combination thereof.

Another method of imparting hydrophilic properties to the molded polymer includes contacting the polymer with sulfur dioxide and some oxygen source and exposing the contacted polymer to energy that yields free radicals. Preferably, the contacting and exposing step takes place in a reduced pressure environment. The source of energy for producing free radicals can also be ultraviolet radiation, gamma radiation, electron beams, inert gas radio frequency plasma or corona discharges. The oxygen source may comprise oxygen, an oxygen donating gas or a combination thereof.

The present invention relates to surface modified polymers. More particularly, the present invention relates to sulfonated polymers. Even more particularly, the present invention relates to gaseous sulfonation of polymers.

1 is a schematic diagram of a reaction chamber.

The term "oxygen donor gas" or "oxygen source" as used herein means either di-oxygen or a gas capable of supplying oxygen atoms or oxygen radicals.

As used herein, the term "energy to produce radicals" refers to any energy that causes isotropic or heterolytic decomposition of at least two covalent atoms.

The term "hydrophilic" or "hydrophilic properties" as used herein refers to a water contact angle (deionized, distilled water) of water droplets placed on the surface of such a material when it relates to a material such as, for example, a polymer or shaped polymer, which is less than 90 degrees. Means that.

The term "hydrophobic" as used herein means that the water contact angle (deionized, distilled water) of the water droplets placed on the surface of such a material, for example when it relates to a material such as a polymer, is greater than 90 degrees.

The term "polymer" as used herein may mean both synthetic and natural polymers. Examples of natural polymeric materials include cotton, silk, wool and cellulose, by way of example.

The synthetic polymer can then be thermoset or thermoplastic, with thermoplastic being more common. Examples of thermosetting polymers include, by way of example, alkyd resins such as phthalic anhydride-glycerol resins, maleic acid-glycerol resins, adipic acid-glycerol resins and phthalic anhydride-pentaerythritol resins; Allyl resins in which monomers such as diallyl phthalate, diallyl isophthalate, diallyl maleate and diallyl chloride are used as nonvolatile crosslinkers in polyester compounds; Amino resins such as aniline-formaldehyde resins, ethylene urea-formaldehyde resins, dicyandiamide-formaldehyde resins, melamine-formaldehyde resins, sulfonamide-formaldehyde resins and urea-formaldehyde resins; Epoxy resins such as crosslinked epichlorohydrin-bisphenol A resins; Phenol resins such as phenol-formaldehyde resins, including Novolac and Resol; And thermosetting polyesters, silicones and urethanes.

Examples of thermoplastic polymers include, by way of example, poly (oxymethylene) or polyformaldehyde, poly (trichloroacetaldehyde), poly ( n -valeraldehyde), poly (acetaldehyde), poly (propionaldehyde), and the like. Capped polyacetals; Acrylic polymers such as polyacrylamide, poly (acrylic acid), poly (methacrylic acid), poly (ethyl acrylate), poly (methyl methacrylate), and the like; Poly (tetrafluoroethylene), perfluorinated ethylene-propylene copolymer, ethylene-tetrafluoroethylene copolymer, poly (chlorotrifluoroethylene), ethylene-chlorotrifluoroethylene copolymer, poly (vinyl fluoride) Fluorocarbon polymers such as leaden), poly (vinylidene fluoride), and the like; Polyamides such as poly (6-aminocaproic acid) or poly (ε-caprolactam), poly (hexamethylene adipamide), poly (hexamethylene sebacamide), poly (11-aminoundecanoic acid) and the like; Polyaramids such as poly (imino-1,3-phenyleneiminoisophthaloyl) or poly ( m -phenylene isophthalamide); Parylene such as poly- p -xylylene, poly (chloro- p -xylylene) and the like; poly (oxy-2,6-dimethyl-1,4-phenylene) or poly ( p -phenylene oxide) and the like Polyaryl ethers such as; Poly (oxy-1,4-phenylenesulfonyl-1,4-phenyleneoxy-1,4-phenylene-isopropylidene-1,4-phenylene), poly (sulfonyl-1,4-phenylene Polyaryl sulfones such as oxy-1,4-phenylenesulfonyl-4,4'-biphenylene); Polycarbonates such as poly (bisphenol A) or poly (carbonyldioxy-1,4-phenyleneisopropylidene-1,4-phenylene) and the like; Poly (ethylene terephthalate), poly (tetramethylene terephthalate), poly (cyclohexylene-1,4-dimethylene terephthalate) or poly (oxymethylene-1,4-cyclohexylenemethyleneoxyterephthaloyl) and the like Same polyester; Polyaryl sulfides such as poly ( p -phenylene sulfide) or poly (thio-1,4-phenylene) and the like; Polyimides such as poly (pyromellitimido-1,4-phenylene) and the like; Polyethylene, polypropylene, poly (1-butene), poly (2-butene), poly (1-pentene), poly (2-pentene), poly (3-methyl-1-pentene), poly (4-methyl- 1-pentene), 1,2-poly-1,3-butadiene, 1,4-poly-1,3-butadiene, polyisoprene, polychloroprene, polyacrylonitrile, poly (vinyl acetate), poly (vinyl chloride) Polyolefins such as leadene), polystyrene, and the like; Copolymers such as acrylonitrile-butadiene-styrene (ABS) copolymers and the like.

The term "molded polymer" or "molded polymers" as used herein means a polymer in any solid form as opposed to a polymer in gaseous or liquid or solution phase. Thus, the molded polymer may be in particulate form such as powder or granules or chips, shaped bodies, extruded shapes, fibers, woven or nonwovens, films, foams and the like.

The term "sulfonation" as used herein means a method of converting an organic compound to a sulfonic acid or sulfonate containing the structural group C-SO ₂ -O or optionally N-SO ₂ -O. Sulfonation of molded polymers is useful, for example, in modifying the surface properties of the molded polymers. For example, the properties of the surface may be modified such that the modified surface becomes hydrophobic, making it more suitable and / or printable for the adhesive to be placed thereon.

As used herein, the term "nonwoven fabric" refers to a fabric having a structure that is interposed with each other in a manner other than the repetitive manner that each fiber or filament can identify.

As used herein, the term "spunbond fiber" refers to a filament in which molten thermoplastic is extruded into filaments from a number of fine and often circular spherical capillaries, such as Appel et al., Incorporated herein by reference. US Patent No. 3,692,618 to Dorschner et al., US Pat. No. 3,802,817 to Matsuki et al., US Patent Nos. 3,338,992, 3,341,394 to Kinney, and Levy. By US Pat. Nos. 3,502,763, 3,909,009 and Dobo et al., US Pat. No. 3,542,615 refers to fibers formed by rapidly reducing the diameter of the extruded filaments.

The term " meltblown fiber " as used herein refers to a molten thermoplastic or filament that melts the molten thermoplastic material through a plurality of fine, often circular die capillaries that taper the filaments of the molten thermoplastic material. By fiber, it is usually formed by extruding into a heated stream of high speed gas (eg air) to reduce its diameter. Thereafter, the meltblown fibers are carried by the high velocity gas stream and placed over the gathering surface to form a fabric of irregularly distributed meltblown fibers. Meltblowing is described, for example, in US Pat. No. 3,849,241 to Buntin, US Pat. No. 4,307,143 to Meitner et al. And US Pat. No. 4,663,220 to Wisneski et al. It is described in.

The sulfonation process of the present invention avoids the need to use or store large amounts of materials, such as sulfur trioxide, concentrated sulfuric acid, oleum and chlorosulfuric acid, which are typically required for its disclosure in traditional sulfonation processes. The process of the present invention also avoids the inherent brown coloration that occurs in many traditional sulfonation processes.

In one embodiment of the present invention, the method of sulfonating a polymer comprises exposing a sulfur dioxide and oxygen source to energy that yields free radicals and contacting the polymer with the product in a previous step. Preferably, exposing the sulfur dioxide and oxygen source to energy producing free radicals and contacting the resulting product with the polymer in a reduced pressure environment. Sources of energy for producing free radicals may be ultraviolet light, gamma radiation, electron beams, inert gas radio frequency plasma or corona discharges. The oxygen source can be oxygen, an oxygen donor gas, or a combination thereof, described in more detail below.

In another embodiment, a method of sulfonating a polymer includes contacting the polymer with sulfur dioxide and an oxygen source and exposing the contacted polymer to energy that yields free radicals. In this embodiment, the polymer may be contacted with a mixture of sulfur dioxide and an oxygen source or the polymer may be contacted separately with a sulfur dioxide and oxygen source. When the polymer is contacted separately with sulfur dioxide and an oxygen source, the polymer may be contacted first with sulfur dioxide and then with an oxygen source. Preferably, the contacting and exposing steps are carried out in a reduced pressure environment. The source of energy for producing free radicals can also be ultraviolet radiation, gamma radiation, electron beams, inert gas radio frequency plasma or corona discharge. The oxygen source can be oxygen, an oxygen donor gas, or a combination thereof.

Another embodiment of the present invention provides a method of imparting hydrophilic properties to the molded polymer. This method involves exposing the sulfur dioxide and oxygen source to energy producing free radicals and contacting the polymer with the product of the preceding step. Preferably, the contacting and exposing steps are performed in a reduced pressure environment. Sources of energy for producing free radicals may be ultraviolet light, gamma radiation, electron beams, inert gas radio frequency plasma or corona discharges. The oxygen source can be oxygen, an oxygen donor gas, or a combination thereof.

Another method of imparting hydrophilic properties to the molded polymer includes contacting the polymer with sulfur dioxide and an oxygen source and exposing the contacted polymer to energy that yields free radicals. Preferably, the contacting and exposing steps are carried out in a reduced pressure environment. The source of energy for producing free radicals can also be ultraviolet radiation, gamma radiation, electron beams, inert gas radio frequency plasma or corona discharge. The oxygen park may be oxygen, an oxygen donor gas, or a combination thereof.

In this embodiment, the concentrations of sulfur dioxide and oxygen are not critical if the concentration is sufficient to impart the desired degree of sulfonation and / or hydrophilicity properties to the polymer. In general, if the amount of sulfur dioxide is greater than the amount of oxygen or if the concentrations of sulfur dioxide and oxygen are stoichiometric, the concentrations of sulfur dioxide and oxygen (O ₂ ) are sufficient. In another case, in the reaction environment during the sulfonation reaction, it is preferable to avoid the excessive presence of oxygen, that is, the amount of oxygen than the stoichiometric amount.

In addition, the reaction environment may be anhydrous or considerably or relatively free of water. In a recent example, small amounts of residual water can be removed by forming sulfur trioxide during the reaction. Sulfur trioxide reacts with water to produce sulfuric acid. If sufficient sulfur dioxide and oxygen are present in the reaction environment to dehydrate the reaction environment and sulfonate the polymer substrate, the presence of residual water may not affect the result of the sulfonation reaction.

The relative ratio of sulfur dioxide to oxygen for carrying out the process of the invention can be expressed in molar ratios. The minimum molar ratio of sulfur dioxide to oxygen for the sulfonation process of the present invention is 2: 1 (ie, exactly stoichiometric). Preferably, the molar ratio can be expressed in whole numbers. Moreover, at a molar ratio of sulfur dioxide to oxygen of 2: 1, the sulfonation reaction will generally succeed in producing sulfonated polymers that are free of yellowing or decolorization. Preferably, the molar ratio of sulfur dioxide to oxygen can range from 2: 1 to 5: 1.

In addition, an oxygen donor gas may be used in place of all or part of the oxygen required for the blend of sulfur dioxide and oxygen. For example, in the sulfonation process, all or part of the oxygen required can be replaced with nitric oxide, one of the oxygen donating gases. Other oxygen donating gases may include, for example, halogen dioxide, such as nitrogen dioxide and chlorine dioxide. It will be further understood that one or more oxygen donor gases, with or without oxygen, may be used if the overall stoichiometry of sulfur dioxide relative to other oxygen and / or oxygen donor gases depends on the molar ratio of sulfur dioxide to oxygen expressed above.

Inert gas may also be used in the sulfonation method of the present invention. In one embodiment of the low pressure gas phase sulfonation process, the inert gas may be blended with sulfur dioxide and oxygen and / or oxygen donor gas (es). Alternatively, an inert gas may be used to flush less desirable gases, such as air, from the reaction environment and / or material, such as a porous or fibrous web, prior to starting the sulfonation reaction. In an example in which an inert gas is used to flush such a reaction environment and / or material, the pressure of the reaction environment may be less than one atmosphere (decompression) or one atmosphere or more than one atmosphere. Examples of inert gases include nitrogen, argon, helium and krypton. Among these inert gases, argon can exclude oxygen because of its atomic weight and density.

In other embodiments, argon gas may be used in a continuous sulfonation process. In this example, a material such as a fibrous web is purged with an argon gas stream to remove the air contained therein. A web which is completely free of air for irradiation and sulfonation can then be passed through a UV chamber with a blend of sulfur dioxide, oxygen (or other oxygen source) and argon.

The amounts of sulfur dioxide and oxygen are best expressed in mole fractions. This provides flexibility without limiting the size of the reaction environment. Thus, when the polymer is contacted separately with sulfur dioxide and oxygen, the mole fraction range in the total gas present as sulfur dioxide is from about 0.83 to about 0.2. In particular, when the polymer is contacted separately with sulfur dioxide and oxygen, the mole fraction in the total gas present as sulfur dioxide can be about 0.83, preferably about 0.8, more preferably about 0.75 and most preferably 0.67. The corresponding mole fraction range of oxygen is about 0.17 to about 0.33. In particular, the mole fraction of oxygen may be about 0.17, preferably 0.2, more preferably 0.25, most preferably 0.33. If another oxidizing gas replaces oxygen, the mole fraction in that gas will be determined by the stoichiometry of the reaction leading to the production of sulfur trioxide.

Polymers, preferably molded polymers, more preferably fabrics produced from polymer fibers, are useful in the practice of the present invention. Such polymeric fabrics may be woven or nonwoven. Nonwovens include, but are not limited to, air laying processes, wet laid processes, entanglement processes, spunbonding, meltblowing, staple fiber carding, and bonding processes and solution spinning. Can be prepared from various processes. The fibers themselves can be made from a variety of polymeric materials, including but not limited to polyesters, polyolefins, nylons, and copolymers thereof. The fibers may be relatively short, staple length fibers, typically less than 7.62 cm (3 inches), or longer, more continuous fibers such as those typically produced in spunbonding processes. However, it should be noted that molded polymers other than woven or nonwoven can be used. Examples of such other shaped polymers include films, foams / film laminates, and combinations thereof, with or without wovens or nonwovens.

Moreover, such fabrics can be produced in single or multiple layers. In the case of multiple layers, the layers are generally placed in a juxtaposition or surface-to-surface relationship and all or a portion of the layer may be joined to adjacent layers. An example of a nonwoven produced from such a fabric is a polypropylene nonwoven produced by Kimberly-Clark Corporation, a registered assignee.

The following examples are provided to illustrate the nature of the invention.

<Background>

The quartz reactor 10 shown in FIG. 1 was used to sulfonate the samples described in Examples 1-5. The quartz reactor 10 is made from an optical grade fused quartz product of Technical Glass Products, Inc., Ohio, USA. The quartz reactor 10 includes a reactor mold 12 having separable tops and bottoms 14 and 16, respectively, for selectively positioning and removing specimens within the reactor mold 12. The upper portion 14 is a vacuum port 18 connected to the vacuum source 20 by a valve 22, a gas port 24 connected to a gas source 26 by a valve 28, and It further comprises a sphere 30 connected by a valve 34 to a pressure sensor 32 such as a capacitance manometer model number CM100 manufactured by Leybold Inficon, Inc., NY, USA.

Surface analysis

All ESCA (chemical analytical electron spectroscopy) data was collected on a Surface Science Instruments M-Probe ESCA spectrometer. Spectroscopic collection was performed with monochromatic aluminum X-ray excitation of the 800 micron region for each sample. Differential charging of the specimens was compensated using a low energy (one electron volt) electron flow generated from an electron flood gun.

Surface tension for wetting

Surface tension for wetting was measured with a wet tension test kit, Model STT 11-1 from Pillar Technologies, Inc., Heartland, Wisconsin. Surface tension for wetting was considered to be the surface tension of the fluid spontaneously absorbed into the fibrous nonwoven substrate. Wet tension kits follow ATSM standard D2578-67.

Contact angle

Contact angles were measured using a Rame-Hart model 100-06 NRL contact angle goniometer. The contact angle is considered to be the line which borders the edge of the fluid drop in contact with the substrate surface. Contact angle values were derived by averaging observations taken from at least 3 drops. Two observations were taken from each drop.

<Example 1>

Sulfonation of polypropylene meltblown

A sample of polypropylene meltblown (PP MB) material of 17 g / m ² (ozy per 0.5 yard) was placed in the quartz reactor 10 shown in FIG. The sample was placed in the lower part 16 and the reactor mold 12 was emptied through the vacuum port 18 to less than the total pressure 1 × 10 ⁻³ Torr. After 5 minutes, reactor frame 12 was refilled with inert gas (nitrogen or argon) through gas sphere 24 to a pressure of 760 Torr. Then reactor frame 12 was emptied again. The filling and emptying cycle was repeated three times and the reactor mold 12 was finally emptied to less than 1 × 10 ⁻³ Torr overall pressure. Finally, after the emptying, a mixture of sulfur dioxide and oxygen gas was injected into the reactor mold 12 through the gas sphere 24 to a total pressure of 200 Torr. The partial pressure ratio of sulfur dioxide to oxygen in the gas mixture was 2: 1. The reactor was then placed in a cyclic ultraviolet reactor (Rayonet photochemical reactor, The Southern New England Ultraviolet Company) equipped with 16 low pressure mercury lamps. Each lamp had a main emission wavelength of 254 nm. The total power of all 16 lamps measured in the center of the reactor chamber was 6 milliwatts per square centimeter (mW / cm ² ).

UV irradiation time (response time) for each PP MB sample varied from 5 to 15 minutes. The reactor was purged with inert gas (nitrogen or argon) through gas sphere 24 to remove residual sulfur dioxide or sulfur trioxide following ultraviolet irradiation.

Response time 5 minutes

The PP MB material was white and could be wetted with a surface tension of 56 dyne / cm in the test aqueous solution. The PP MB control could be wetted with a surface tension of 35 dyne / cm in the test solution. Surface analysis of the sulfonated meltblown PP using ESCA revealed the following surface atomic composition: 88.3 atomic% carbon, 9.2 atomic% oxygen and 2.5 atomic% sulfur.

Response time 10 minutes

The PP MB material was white and could be wetted with 72 dyne / cm surface tension (ie, equivalent to water) in the test aqueous solution. Surface analysis of the sulfonated meltblown PP using ESCA revealed the following surface atomic composition: 88.5 atomic% carbon, 9.2 atomic% oxygen and 2.3 atomic% sulfur.

Response time 15 minutes

The PP MB material was very light brown and could be wetted with 72 dyne / cm surface tension (ie, equivalent to water) in the test aqueous solution. Surface analysis of this sulfonated meltblown using ESCA revealed the following surface atomic composition: 84.9 atomic% carbon, 12.1 atomic% oxygen and 3.0 atomic% sulfur.

Compared to the meltblown polypropylene control, a material was produced with a significant change in surface properties with each reaction time. ESCA data obtained from each sample provide evidence of sulfur incorporation on the surface of each material. Sulfur is in the form of sulfonic acid. This indicates that the bond between carbon and sulfur is formed in the sulfonation reaction leading to the formation of R-SO ₃ H groups.

<Example 2>

Sulfonation of polyethylene meltblown

The experimental method used to sulfonate polyethylene meltblown (PE MB) was the same as outlined in Example 1. In this example, 204 g / m ² (6 osy) PE MB specimens were irradiated in a sulfur dioxide / oxygen environment for 5 minutes.

After sulfonation, the PE MB material was white in appearance. The material could be wetted in a test aqueous solution with a surface tension of 72 dyne / cm (ie, equivalent to water). In contrast, the unsulfonated PE MB control could only be wetted with 36 dyne / cm test solution. Surface analysis of PE MB using ESCA revealed the following surface composition: 95.4 atomic% carbon, 3.5 atomic% oxygen and 1.1 atomic% sulfur. The appearance of sulfur on the surface indicates the inclusion of sulfur on the surface of the material. Sulfur is in the form of sulfonic acid.

<Example 3>

Sulfonation of cellulose

The experimental method used to sulfonate cellulose was the same as outlined in Example 1. The cellulose substrate was Whatman Type 1 filter paper. In this example, cellulose samples were examined in a sulfur dioxide / oxygen environment for 10 minutes.

After sulfonation the cellulose substrate was white. Comparing the surface tension for wetting did not show any difference in the cellulose substrate before and after sulfonation. The sulfonated cellulose had a slight sulfur odor. This odor was effectively removed by washing with deionized water and drying at 80 degrees Celsius.

The surface composition (ESCA) of unsulfonated cellulose control, sulfonated cellulose and sulfonated cellulose washed with water is summarized in Table 1.

Table 1

Surface Atomic Composition of Cellulose Percent Atom Composition (Atom%) specimen carbon Oxygen sulfur Fluoride Unsulfonated Cellulose Control 59.0 40.2 0.0 0.8 Sulfonated 59.2 38.2 0.9 1.8 Washed after being sulfonated 57.2 39.4 1.2 2.2

ESCA analysis of cellulose specimens clearly shows the incorporation of sulfur on the cellulose surface. Sulfur appears to be in the form of sulfonic acids. The presence of fluorine may be due to the fluorine chemicals present in the Whatman filter paper or the high vacuum grease used to seal the quartz reactor tube (see FIG. 1).

<Example 4>

Sulfonation of Polyethylene Terephthalate Fiber

The experimental method used to sulfonate polyethylene terephthalate (PET) fibers was the same as outlined in Example 1. PET fibers were irradiated for 10 minutes in the sulfur dioxide / oxygen environment described in Example 1.

The sulfonated PET fibers were white. The sulfonated PET fibers could be wetted in the test aqueous solution with a surface tension of 72 dyne / cm (ie equivalent to water). In contrast, unsulfonated control PET fibers could be wetted in aqueous solution with a surface tension of 56 dyne / cm and a water contact angle was observed to be greater than 90 degrees. The water contact angle on sulfonated fibers could not be measured due to the spontaneous absorption of water droplets. Washing sulfonated PET fibers and drying them at 80 degrees Celsius did not change their wettability.

The surface composition (ESCA) of PET fibers is summarized in Table 2.

TABLE 2

Surface atomic composition of PET Percent Atom Composition (Atom%) specimen carbon Oxygen sulfur Fluoride Contrast PET Fiber 75.2 24.8 0.0 0.0 Sulfonated PET fibers 66.0 28.2 2.5 3.3 Washed Sulfonated PET Fiber 70.2 26.8 1.5 1.6

ESCA analysis clearly shows the incorporation of sulfur on the surface of PET fibers. Sulfur is in the form of sulfonic acid. The fluorine present on sulfonated and washed sulfonated fibers is due to the high vacuum grease used to seal the stone tube reactor.

Example 5

Sulfonation of polystyrene

The experimental method used to sulfonate the polystyrene (PS) film was the same as outlined in Example 1. PS film was irradiated for 10 minutes in a sulfur dioxide / oxygen environment.

The sulfonated PS film was noticeable yellow compared to the unsulfonated control. The water contact angle on the sulfonated PS film was effectively 0 degrees and water droplets spontaneously spread on the film. The water contact angle on the unsulfonated PS film was 92 degrees. Washing the sulfonated PS film did not change its water wettability.

The surface composition (ESCA) of the sulfonated PS film is summarized in Table 3.

TABLE 3

Surface atomic composition of PS Percent Atom Composition (Atom%) specimen carbon Oxygen sulfur Fluoride Contrast PS film 95.7 2.6 ^a 0.0 0.0 Sulfonated PS film 66.5 22.2 7.6 3.7 Washed Sulfonated PS Film 69.0 20.6 7.8 2.6

^a 1.12 atomic% silicon and 0.6 atomic% chlorine are also measured

Ideally, the control PS film should have a surface composition of about 100 atomic% carbon. Silicon, chlorine and oxygen observed in the control are present due to the manipulation of the film specimen. The significant increase in the atomic composition percentages of oxygen and sulfur in the sulfonated PS film is clear evidence that sulfonation has greatly changed the PS surface. Sulfur is present in the form of sulfonic acid groups. Again, fluorine is due to surface contamination by the high vacuum grease used in the quartz tube reactor.

While the present invention has been described in detail herein with reference to specific embodiments thereof, it will be appreciated that variations, modifications, and equivalents thereof may be readily made by those skilled in the art upon understanding the foregoing. something to do.

Claims (9)

Contacting the gaseous mixture with a polymer which contains essentially no gaseous chlorine and consists essentially of sulfur dioxide and an oxygen donor gas and whose molar ratio of sulfur dioxide to the oxygen donor gas is stoichiometric, Continuously exposing the polymer and gaseous mixture to ultraviolet light while the polymer is in contact with the gaseous mixture, Wherein the contacting and exposing is carried out at a pressure of less than 1 atmosphere and the oxygen donating gas is nitrogen oxide, nitrogen dioxide or halogen dioxide, Sulfonation of polymers. The method of claim 1 wherein the gaseous mixture is anhydride. The method of claim 1, wherein said ultraviolet light has a dominant wavelength of 254 nm. Continuously exposing to a UV light a gaseous mixture which is essentially free of sulfur dioxide and an oxygen donor gas and whose molar ratio of sulfur dioxide to the oxygen donor gas is a stoichiometric ratio, Contacting the polymer with the exposed gaseous mixture, Wherein said exposing and contacting is carried out at a pressure of less than 1 atm, continuous exposure is carried out while said exposed gaseous mixture is in contact with said polymer, and said oxygen donating gas is nitric oxide, nitrogen dioxide or halogen dioxide, Sulfonation of polymers. 5. The method of claim 4, wherein said gaseous mixture is anhydride. The method of claim 4, wherein said ultraviolet light has a dominant wavelength of 254 nm. Contacting the molded polymer with a molded polymer which contains gaseous chlorine and which consists essentially of sulfur dioxide and an oxygen donating gas and whose molar ratio of sulfur dioxide to the oxygen donating gas is stoichiometric, Continuously exposing the molded polymer and gaseous mixture to ultraviolet light while the molded article is in contact with the gaseous mixture, Wherein the contacting and exposing is carried out at a pressure of less than 1 atmosphere and the oxygen donating gas is nitrogen oxide, nitrogen dioxide or halogen dioxide, A method of imparting hydrophilic properties to shaped polymers. 8. The method of claim 7, wherein said gaseous mixture is anhydride. 8. The method of claim 7, wherein said ultraviolet light has a dominant wavelength of 254 nm.