Patent Application
20140283323
The present disclosure relates to a cleaning surface with a reactivatable adhesive. In particular, the present disclosure relates to a cleaning surface with a reactivatable adhesive and spacing elements.
Cloths, wipes, mops are used to wipe and clean surfaces covered with dirt, dust, and debris. Typically, most cloths, wipes, and mops do not have the ability to effectively capture and retain small and large particles of dirt and debris. Cleaning sheets such as shown in U.S. Pat. No. 7,691,760 have been developed that include an adhesive on the working surface of the cleaning sheet to help in retaining particles of dirt and debris. Another design of a floor cleaning system, such as shown in U.S. Pat. No. 7,757,334, includes a stack of adhesive sheets, which help in retaining particles of dirt and debris, with an overlying frame to allow for spacing of the adhesive sheets from the surface being cleaning. However, for both designs, once the adhesive is loaded the sheet is no longer able to retain particles and is discarded.
The disclosed cleaning surface includes a reactivatable adhesive to capture and hold dirt, dust, and debris and a spacing element to allow for the cleaning surface to glide over a surface to be cleaned. The reactivatable adhesive can be washed clean, but once dry, it regains the ability to capture and hold dirt, dust, and debris, so that the cleaning surface is reusable. The disclosed cleaning surface combines the ability of using adhesive to greatly enhance the capture of dirt, dust, and debris, while also being reusable.
In one embodiment, the cleaning surface comprises raised portions comprising a spacer and recessed portions comprising a reactivatable pressure sensitive adhesive. The reactivatable pressure sensitive adhesive is a polymerized precursor comprising a monomer component which contains one or more alkyl acrylates, the alkyl groups of which have an average of 4-14 C atoms, at least about 2.0 phr of hydrophobic silica, one or more polymerization initiators, one or more crosslinker compounds, and which is essentially free from polar comonomers.
In one embodiment, the spacer comprises an apertured cleaning sheet overlying the reactivatable pressure sensitive adhesive. In one embodiment, the cleaning surface comprises a cleaning wipe comprising the raised portions and recessed portions comprising the reactivatable pressure sensitive adhesive. In one embodiment the cleaning surface is a portion of a cleaning tool comprising the raised portions and recessed portions comprising the reactivatable pressure sensitive adhesive. In one embodiment
the spacer is removable from the reactivatable pressure sensitive adhesive. In one embodiment, the reactivatable pressure sensitive adhesive can be washed clean, but once dry, regains the ability to capture and hold dirt, dust, and debris. In one embodiment, the reactivatable pressure sensitive adhesive contains between 4 and 25 phr of hydrophobic silica. In one embodiment, the concentration of the alkyl acrylates with respect to the mass of the precursor of the adhesive is 75% wt or more. In one embodiment, the crosslinker compound is in a concentration resulting in a crosslink density obtainable by using tripropyleneglycoldiacrylate as a reference crosslinker compound in a concentration of 0.15 phr or more. In one embodiment, the raised portion comprise at least 25% of the cleaning surface area. In one embodiment, the raised portions extend at least 1 mm from the recessed portions.
While the above-identified drawings and figures set forth embodiments of the invention, other embodiments are also contemplated, as noted in the discussion. In all cases, this disclosure presents the invention by way of representation and not limitation. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art, which fall within the scope and spirit of this invention.
The figures may not be drawn to scale.
A cleaning surface 10 comprises raised portions 12 comprising a spacer 30 and recessed portions 14 comprising a reactivatable pressure sensitive adhesive 20.
The cleaning surface 10 is the surface intended to come into contact with the surface to be cleaned and is capable of capturing and retaining dirt, dust, and debris. The cleaning surface 10 may be a portion of an assembly for a cleaning tool 40, such as shown and described in
The spacer 30 on the cleaning surface 10 provides distance between the surface to be cleaned and the portion of the cleaning surface 10 containing the adhesive 20. If the adhesive 20 completely contacts the surface to be cleaned, then the cleaning surface 10 with adhere too aggressively to the surface being cleaned and will not glide. The spacer 30 can help to prevent total contact of the adhesive 20 with the surface to be cleaned. Further, the spacer 30 generally lifts the entire cleaning surface 10 from the surface to be cleaned thereby exposing more area, and especially more area containing adhesive, of the cleaning surface 10 for picking up dirt and debris.
There is at least one spacer 30. However, in some embodiments, there is a plurality of spacers 30. The spacer 30 can be arranged on the cleaning surface 10 in any number of ways. The spacer 30 may be an interconnected network across the entire cleaning surface 10, such as depicted in
The spacer 30 can be removably connected to the cleaning surface 10, such as shown with
Becasue the spacer 30 is in direct contact with the surface to be cleaned, preferably the spacer is of a material that will not damage the surface to be cleaned. For cleaning hard surfaces, the spacer 30 is typically a compliant, open material that itself may capture and retain dirt and debris and allow for gliding over a hard surface. For cleaning soft, fabric-like surfaces like carpet, then the spacer should be a smooth, low-friction surface to allow for a smooth glide on the surface to be cleaned.
Examples of materials that may be used for the spacer 30 are nonwoven fabric, woven fabric, knitted fabric, foams, sponges, yarn, rows of bristles, extruded polymers. For an extruded strand, suitable materials include polypropylene, polyethylene or olefin copolymers and other thermoplastics. The cross section of the spacer may be shaped such as round, oval, rectangular.
The reactivatable pressure sensitive adhesive 20 at the cleaning surface 10 is tacky to capture and retain dirt, dust, and debris from the surface to be cleaned. The pressure sensitive adhesive 20 is reactivatable, meaning that the adhesive can be washed clean, but once dry, it regains the ability to capture and retain dirt, dust, and debris. Therefore, the reactivatable pressure sensitive adhesive 20 can be reused. Suitable adhesives 20 are disclosed in European Patent 0736585, the disclosure of which is herein in corporate by reference, and portions of which are below. A suitable reactivatable pressure sensitive adhesive is used in Scotch™ Mounting Squares available from 3M Company, St. Paul Minn.
The adhesive 20 is obtained by the polymerizing of a precursor which contains one or more alkyl acrylate, the alkyl groups of which have an average of 4-14 C atoms, and which is essentially free from strongly polar comonomers, said precursor further comprises at least about 2 phr of hydrophobic silica, or one or more polymerization initiators and one or more crosslinking compounds in a concentration resulting in a crosslinking density which is obtainable by using tripropyleneglycoldiacrylate as a reference crosslinker in a concentration of 0.15 phr or more. The term phr or pph means parts per hundred resin and gives the mass ratio of, for example, the crosslinking component (or of another component) with respect to the mass of the polymerizable monomer component.
The precursor of the removable PSA material comprises one or more alkyl acrylates the alkyl groups of which have an average of 4-14 C atoms. The term average of 4-14 C atoms means that with respect to the mass of the alkyl acrylate component, in one embodiment is between 4-14 and, in another embodiment is between 4-12 C atoms.
Useful alkyl acrylates (i.e., acrylic acid alkyl ester monomers) include linear or branched monofunctional unsaturated acrylates or methacrylates or non-tertiary alkyl alcohols, the alkyl groups of which have from 4 to 14 and, in particular, from 4 to 12 carbon atoms. Examples of these lower alkyl acrylates include but are not limited to, n-butyl acrylate, isobutyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, n-octyl acrylate, n-octyl methacrylate, 2-methylbutyl acrylate, isononyl acrylate, n-nonyl acrylate, isoamylacrylate, n-decyl acrylate, iso-decyl acrylate, isodecyl methacrylate, isobornyl acrylate, 4-methyl-2-pentyl acrylate and dodecyl acrylate.
The precursor contains up to 5 and, in particular, 1-4 alkyl acrylates. The average number of carbon atoms in the alkyl groups of the alkyl acrylates as defined, above, is in one embodiment between 4-14, in another embodiment between 4-12, and in another embodiment between 5-10. The concentration of the alkyl acrylate component with respect to the mass of the precursor of the PSA is in one embodiment at least 75% wt. and in another embodiment at least 85% wt.
The presence of polar comonomers is usually detrimental to the resistance of the PSA against water and organic solvents and limits its removability and reactivatability.
The term polar monomers include both moderately polar and strongly polar monomers. Polarity (i.e., hydrogen-bonding ability) is frequently described by the use of terms such as ‘strongly,’ ‘moderately,’ and ‘poorly.’ Examples of strongly polar monomers are acrylic acid, methacrylic acid and acrylamides while N-vinyl lactams such as, for example, N-vinyl pyrrolidone, N-vinyl caprolactam, acrylonitrile and dimethyl amino-propyl methacrylate are typical examples of moderately polar monomers.
Typically, the PSA contain no polar comonomers. A superior balance of tack, peel strength, cohesive strength, shear strength, resistance against water and organic solvents, reactivatability and optical transparency can be obtained without adding polar monomers. Adding polar comonomer component typically distinctly decreases the resistance against water and organic solvents and especially the reactivatability which adversely affects the desired mix is properties of the removable PSA to an undesirable or even unacceptable degree. In some cases however, like, for example, for PSA materials exhibiting a high crosslink density (TPGDA concentration >1 phr, expecially >2 phr), high values of static shear and low values of adhesion, a small amount of polar comonomers might be added in order to improve the abrasion resistance of the PSA material. The concentration of the strongly polar comonomer should not exceed, however, 0.5 phr, and in one embodiment should be less than 0.25 phr, and in one embodiment should be less than 0.1 phr. A slightly higher amount of moderately polar comonomers of up to 1.0 phr, might be used. The amount of the moderately polar comonomer is, however, typically less than 0.5 phr and in one embodiment less than 0.25 phr.
The precursor of the PSA also contains a filler component comprising in one embodiment at least 2.0 phr, in another embodiment at least 3.0 phr, and in another embodiment at least 4.0 phr of hydrophobic silica. In one embodiment, the amount of the hydrophobic silica is between 5-25 phr. In another embodiment, the amount of the hydrophobic silica is between 5-20 phr, on in particular 5-15 phr.
Hydrophobic silica is commercially available, for example, from Degussa, Hanau as “Aerosil” R972, R974 or R976; from Cabot Cab-O-Sil Division, Tuscola, Ill. as TS-720. In U.S. Pat. No. 2,859,198 (Sears et al.) it is proposed that the surface of finely-divided inorganic solid silicon-containing materials, such as silica, can be rendered hydrophobic by treating the material with an organi-siloxane material. According to U.S. Pat. No. 4,136,081 (Schultz), silica “can be treated with organosilicon materials such as chlorosilanes, silazanes, alkoxysilanes and cyclic siloxanes to produce hydrophobic surfaces.” (col. 6, lns. 47-52).
The enumeration of hydrophobic silica materials given above, and the description of some selected methods for preparing hydrophobic silica materials is illustrative and not to be limiting. In one embodiment, the hydrophobic silica used to prepare the PSA materials exhibits as surface areas of at least 10 m2/g and especially at least 50 m2/g. In one embodiment, the surface area of the hydrophobic silica is between 50 to 400 m2/g (B.E.T. surface area).
The specific selection of hydrophobic silica in combination with the other components of the precursor of the PSA materials results in an outstanding and advantageous balance of properties. Substituting hydrophobic silica in the precursor with:
*hydrophilic silica, results in a PSA materials exhibiting disadvantageous values of the peel and a relatively poor reactivatability, especially after contamination with finely divided or powdered particles such as dust. When mixing hydrophilic silica with the other components of the precursor of the PSA, uniform and useful dispersions are obtained only up to loadings of about 4 phr while hydrophobic silica allows concentrations of up to 25 phr or even more. The limited range of concentration accessibly with hydrophilic silica, results in a lower mechanical strength of the PSA materials and restricts the possibilities of the formulator to control the properties of the PSA material.
*polysaccharide fillers such as cellulose fibers, starch fibers or cotton fibers, yield PSA materials with limited reactivatability, especially after contamination with finely divided or powdered particles such as dust. Mixing polysaccharide fillers with the other components of the precursor results in PSA materials which exhibit on smooth surfaces such as, for example, stainless steel or glass a decrease of shear strength with increasing crosslinker concentration while the preferred PSA materials show the opposite benavior. PSA materials containing cellulose fillers, are furthermore white-opaque.
*other inorganic fillers such as, for example, finely divided iron oxide, titanium oxide, calcium carbones or carbon black adversely affect adhesion, static shear, optical clarity, viscosity, and/or coatability of the resulting PSA material.
*other organic fillers such as, for example, polymeric microspheres often adversely affect the adhesion and/or optical properties of the resulting PSA material.
The filler component of the PSA materials mainly consist of one or more hydrophobic silicas which may differ with respect to their surface area and/or the method of preparation used. The filler component typically contains at least 75% wt., in one embodiment at least 85% wt., and in one embodiment 100% wt. of one or more hydrophobic silicas with respect to the mass of the filler component.
The precursor contains a crosslinker component to increase the cohesive strength and the tensile strength of the resulting PSA material. Useful crosslinkers include benzaldehyde, acetaldehyde, anthraquinone, various benzophenone-type and vinyl-halomethyl-s-triazine type compounds such as, for example, 2,4-bis(trichloromethyl)-6-p-methoxylstyryl-s-triazine. Preferred are polyacrylic-functional monomers such as, for example, trimethylolpropane triacrylate, pentaerythritol, 1,2-ethylene glycol diacrylate, tripropyleneglycoldiacrylate, 1,6-hexanediol diacrylate or 1,12-dodecanediol diacrylate. The compounds listed above, which can be substituted or unsubstituted, are intended to be illustrative and by no means limiting.
The crosslinking component typically contains 1-5, in one embodiment 1-3, and in one embodiment 1-2 crosslinker components. In one embodiment, the crosslinker compounds are 1,6-hexanedioldiacrylate and tripropyleneglucoldiacrylate.
The crosslink density is reported with respect to the crosslink density which is obtainable by using variable amount of tripropyleneglycol diacrylate (TPGDA) as a reference crosslinker component under standardized reaction conditions (bulk photopolymerization, photoinitiator: Irgacure 651, supplied by Ciba Geigy, in a concentration of 0.24 phr; UV irradiation with an exposure of 900-1500 mJ/cm2 from a UV lamp, 90% emissions of which are between 300 and 400 nm, with a maximum at 351 nm; room temperature; normal pressure; exclusion of oxygen).
The precursor contains one or more crosslinker compounds in a concentration to give a crosslink density obtainable by using TPGDA as a reference crosslinking compound in an otherwise identical precursor under identical external conditions, in a concentration of 0.15 phr or more and preferably of 0.30 phr or more. For lower crosslinker concentrations, the mechanical strength, the removability and the reactivatability are insufficient and do not meet all practical requirement especially in case the loading with hydrophobic silica is less than 5 and, in particular, less than 3 phr. The precursor preferably exhibits a crosslink density obtainable by using TPGDA in a concentration of not more than 5.0 phr because above this value, the shear strength on most surface, even on smooth surface, such as, for example, glossy paper or polyester film, tends to become too low.
In one embodiment, the precursor contains one or more crosslinker compounds in a concentration to give a crosslink density obtainable by using TPGDA in a concentration between 0.3-4.5 phr. The concentration of TPGDA is one embodiment is between 0.4 to 4.0 phr. In one embodiment, the concentration of TPGDA preferably is 1.0 phr or more and in one embodiment between 1.0 and 4.5 phr.
The PSA materials can be obtained by applying generally known polymerization methods such as bulk, solution, emulsion or suspension polymerization. Due to environmental reasons bulk polymerization is often preferred in order to avoid using organic solvents.
The polymerization reaction is preferably started by means of a polymerization initiator and preferably proceeds via a radical polymerization mechanism. Useful examples of polymerization initiators include photoactivatable initiators such as, for example, benzoin ethers (e.g., benzoinmethykl ether, benzoin isopropyl ether, substituted benzoin ethers such as anisoin methykl ether), acetophenones (e.g., 2,2-diethoxyacetophenone) or alpha-ketols (e.g., 2-methyl-2-hydroxy-propiophenone), and/or thermally activatable initiators such as, for example, organic peroxides (e.g., benxoyl peroxide and lauryl peroxide) and 2,2-azobis(isobutyronitrile). In one embodiment, the initiator component comprises between 1-3 and, in one embodiment, between 1-2 initiator compounds. In one embodiment, the initiator component containly only one photoinitiator. In one embodiment, the initiator component is present in an amount of 0.012 phr, in one embodiment between 0.05-1.00 phr, and in one embodiment 0.1-0.5 phr.
In one embodiment, a part of the initiator component is added to the alkyl acrylate component which is partly polymerized to a degree of typically 2-30% to form a syrup of coatable viscosity of, for example, 300-20,000 cps (Brookfield) at ordinary room temperature. The viscosity of the syrup is adjusted to the amount of hydrophobic silica to be added. For high loadings with hydrophobic silica of, for example, 15 phr or more, the viscosity of the syrup is typically not more than 1,000 cps and in one embodiment between 25 and 1,000 cps. For lower loadings with hydrophobic silica, the viscosity typically is not less than 1,500 cps and, in one embodiment 1,750 cps or more. The viscosity of the precursor can also be adjusted by adding a small amount of typically less than 5 phr of a polymeric additive which typically is a phtotpolymerizable polyacrylate as is described, for example, in WO94/000,052. The polymerization typically proceeds as photopolymerization which is described, for example, in U.S. Pat. No. 4,181,752. In one embodiment, the polymerization is carried out with UV black lights having over 60 percent and preferably over 75 percent of their emission spectra between 280 to 400 nm, with an intensity between about 0.1 to about 25 mW/cm2. The exposure is typically between 900-1,500 mJ/cm2. The polymerization may be stopped either by removal of the radiation or heat source and/or introduction of, for example, radical scavenging oxygen.
The filler component comprising hydrophobic silica, is subsequently added to the prepolymerized syrup. When the amount of the hydrophobic silica exceeds about 8 phr, a high shear mixer such as a paint mill is used to obtain uniform dispersion. By doing so and by properly adjusting the viscosity of the pre-polymerized syrup, useful and essentially uniform dispersion can be obtained for loadings as high as about 25 phr.
The dispersion obtained is mixed with the remaining part of the initiator component and, optionally, with other adjuvants such as, for example, chain transfer agents, polymer additives like, for example, those described in EP0349216 or EP0352901, solvents, fire retardants, pigments, colorants, odor masking agents, and/or other adjuvents known in the tape art.
To produce PSA films, the above dispersion or mixture obtained is coated onto a backing, a carrier web, or a release liner and polymerized in an inert, i.e., oxygen free atmosphere, for example a nitrogen atmosphere. Above and below, the term film is used to describe a structure whose thickness is substantially less than either its length or width and which has two, essentially parallel opposed surfaces. As used herein, the term film includes, for example, sheets, ribbons, tapes and discs.
The cohesive strength, tensile strength, elongation, shear strength and peel adhesion are interrelated and are mainly influenced by the crosslink density, loading with filler, and the thickness of the adhesive layer. The PSA material is reactivatable and/or exhibits a low sensitivity towards contamination. Even after heavy contamination with dust, dirt or organic compounds, etc., the surface of the PSA materials can be cleaned by applying, for example, an aqueous solution, lower alcohols like methanol or ethanol or acetone. The PSA layer can be rinsed with water and dried. The adhesion recovers even after several cycles of contamination and reactivation to a substantive, to a high, or to a very high percentage with respect to the adhesion of the fresh and uncontaminated PSA layer.
In the range of low cross link density, the following combination of parameters was found to be especially useful:
*crosslink density obtainable by using a concentration of TPGDA between 0.15 and 0.5 phr
*hydrophobic silica between 10-25 phr
*layer of thickness between 50-1,000 μm
The spacer 30 forms the raised portion 12 and extends from the recessed portion 14, which includes the adhesive 20. Depending on the arrangement of the spacer 30, there may be one or more raised portions 12 and one or more recessed portions 14. In one embodiment, the raised portion 12 extends at least 1 mm from the recessed portion 14. In one embodiment, the raised portion 12 extends at least 5 mm from the recessed portion 14. In one embodiment, the raised portion 12 covers at least 10% of the area of the cleaning surface. In one embodiment, the raised portion covers at least 25% of the area of the cleaning surface. In one embodiment, the raised portion is essentially free of adhesive.
To clean a surface, the cleaning sheet 50 is applied over the adhesive 20 of the cleaning tool 40. The cleaning surface 10 contacts the surface to be cleaned. Dirt, dust and debris are captured and contained in the cleaning sheet 50 as well as adhered to the adhesive 20 through the apertures 54 in the cleaning sheet 50. When finished cleaning, the cleaning sheet 50 is removed and either washed for later use or discarded. The adhesive 20 is washed removing the dirt, dust and debris. Once dry, the adhesive 20 regains the ability to capture and hold dirt, dust, and debris, so that the cleaning surface can be used again.
To clean a surface, the cleaning sheet 50 is used independently to clean a surface. In another embodiment, the cleaning sheet 50 is applied over the cleaning tool 40. The cleaning sheet 50 can be removably secured to the cleaning tool 40 is a number of know ways such as mechanical or adhesive securement. The cleaning surface 10 contacts the surface to be cleaned. Dirt, dust and debris are captured and retained by the adhesive 20. Depending on the material used for the spacer 30, the spacer 30 can also capture and retain material. When finished cleaning, the cleaning sheet 50 is removed and either washed for later use or discarded. The adhesive 20 is washed removing the dirt, dust and debris. Once dry, the adhesive 20 regains the ability to capture and hold dirt, dust, and debris, so that the cleaning surface 10 can be used again.
To clean a surface, an overlying cleaning sheet may or may not be used. The cleaning tool 40 contacts the surface to be cleaned. Dirt, dust and debris are captured and contained by the adhesive 20 either through apertures in an overlying cleaning sheet or by direct contact with the surface. The spacer 30, with or without an overlying cleaning sheet 50 provide for gliding of the cleaning tool 40. When finished cleaning, the cleaning sheet 50, if included, is removed and either washed for later use or discarded. Also, the cleaning tool 40, which includes the adhesive 20 is washed removing the dirt, dust and debris. Once dry, the adhesive 20 regains the ability to capture and hold dirt, dust, and debris, so that the cleaning tool 40 can be used again.
Although specific embodiments have been shown and described herein, it is understood that these embodiments are merely illustrative of the many possible specific arrangements that can be devised in application of the principles of the invention. Numerous and varies other arrangements can be devised in accordance with these principles by those of ordinary skill in the art without departing from the sprit and scope of the invention. Thu, the scope of the present invention should not be limited to the structures described in this application, but only by the structures described by the language of the claims and the equivalents of those structures.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US12/63317 | 11/2/2012 | WO | 00 | 4/28/2014 |
| Number | Date | Country | |
|---|---|---|---|
| 61558558 | Nov 2011 | US |
