Patent Application
20180263316
The present application claims the benefit of priority to European. Application No. 17161447.2, filed Mar. 16, 2017, which is incorporated herein by reference in it's entirety.
The protective gloves for process industries (e.g., petrochemical, chemical, food, beverage, and pharmaceutical) have a very robust technology, able to assure people safety under harsh chemical, mechanical and electrical conditions. Glove suppliers provide a large catalog of products, where different types of gloves are recommended for different type of chemicals to be handled with. This means that depending on the application and chemical products to which they are exposed, the gloves have a different type of material and a different thickness of the layers from which they are made of. These gloves have to pass mechanical (EN 388), thermal (EN511) and chemical European standards (EN 374-2, EN 374-3) before they are sent to the market.
In addition to these standards, the gloves should comply with the standard EN 420, which specifies general criteria for comfort, size, dexterity, labeling, and heavy metal content and pH content. Each standard defines exact test and acceptance conditions for the gloves exposed to critical mechanical, thermal, chemical agents. For each standard there are up to five levels of performance, where the first level specifies the test and acceptance conditions for the least aggressive value of the externally applied agent and the highest level (4 or 5) is associated with the most aggressive value of the externally applied agent.
For example, the standard EN-374-2 characterizes the permeability features of the gloves and it specifies a method for testing the protective gloves resistance to permeation of chemical products (penetration). The standard EN374-3 includes the standard EN 374-2 requirements, and in addition, it requires that the protective glove to pass the performance level 2 of chemical resistance for at least three chemical products, like methanol, sulphuric acid 96%, 40% sodium hydroxide, tetrahydrofuran, acetone, carbon disulphide, ethyl acetate, etc. This performance level 2 for chemical resistance means that the permeation time (test made according to the standard) should be higher than or equal to 30 minutes, when the glove is exposed continuously to that chemical.
Typical gloves for chemical protection during handling of acids and alkalis, for example, include latex gloves that can be used in harsh applications for food and beverage industry where cleaning with high concentrated cleaning agents are the most used. Such latex gloves meet the above standard and they are also accompanied by a wide list of permeation data.
Use of gloves in the field usually is not accompanied by evidence of the time of use during their lifetime, and so in many cases the gloves should be used for a much shorter time with respect to their designed lifetime. On the other hand, the suppliers themselves may be conservative in specifying the level of performance, which means that even if the real level of performance may be 4, the supplier would specify 3.
The present invention provides gloves and methods for estimating the remaining time of glove operation before removing the glove, or what is termed “near-end of service life indication” (NESLI). The invention provides for this purposes a NESLI protective glove that very rapidly indicates the remaining service time by means of colorimetric principles based on the use of a “sealed” or protected colorimetric (indicator) layer with high water solubility. Such an indicator layer contains a pH indicator. The organic solutions that are used for the fabrication of gloves made of nitrile or latex, for instance, have a pH of about 10. Thus, in this context the protective layers insulate the indicator layer during glove fabrication so as to prevent the pH indicators in the indicator layer from reacting to the organic solutions during the fabrication process. After a certain period of time of use in harsh chemicals, the outer surface of a completed glove shows immediate color change with respect to its background color. Such an event can signify, for example, that the remaining lifetime for operation is equal to about 10% of its entire life.
The invention thus provides in one embodiment, optionally in combination with any other embodiment, at least one inner layer (230) having a thickness a top surface, and a bottom surface, the bottom surface facing a hand of a user when wearing the glove; at least one inner protective layer (225) having a thickness tip, a top surface, and a bottom surface, the bottom surface abutting the top surface of the inner layer (230); an outer layer (210) having a thickness to, a top surface, and a bottom surface, the bottom surface facing a hand of a user when wearing the glove; at least one outer protective layer (215) having a thickness top, a top surface, and a bottom surface, the top surface abutting the bottom surface of the outer layer (210); and at least one indicator layer (220) having a thickness tc and that is disposed between the top surface of the inner protective layer (225) and the bottom surface of the outer protective layer (215), wherein the indicator layer comprises at least one pH indicator that generates a color visible at the top surface of the outer layer when the indicator layer is exposed to an aqueous medium. The sum of to, each top, each tip, each tc, and each ti defines a total thickness T.
In another embodiment, optionally in combination with any other embodiment, the invention provides a method of forming a multilayer glove. The method comprises the steps of (a) dip coating a hand shaped former into a bath to form an outer layer (210) having a thickness to; (b) forming an outer protective layer (215) having a thickness top on the outer layer (210); (c) forming an indicator layer (220) having a thickness tc on the outer protective layer (215), wherein the indicator layer comprises at least one pH indicator that generates a color when the indicator layer is exposed to an aqueous medium; (d) forming an inner protective layer (225) having a thickness tip on the indicator layer (220); and (e) dip coating the product of step (d) into a bath to form an inner layer (230) having a thickness ti, wherein the sum of ti, tip, tc, and top is less than to.
In the following description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments which may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural, logical and electrical changes may be made without departing from the scope of the present invention. The following description of example embodiments is, therefore, not to be taken in a limited sense, and the scope of the present invention is defined by the appended claims.
The diffusion coefficient of the pH indicator through the liquid-filled nanopores of the gloves is strongly dependent on the size of the molecule. More specifically, one advantage of the indicator layer is that small molecule pH indicators have a high diffusion coefficient in the liquid state, and thus the time elapsed between the permeation of the outer 210 and outer protective 215 layers of the glove by liquid and the visualization of the color on the top surface of the multilayer glove 100 by the operator is minimum. Such a minimum response time of the indicator layer 220 is important for the safety of the operator. In accordance with some embodiments, the multilayer glove 100 is exposed to the liquid medium for a time equal to or exceeding the time required for the liquid medium to diffuse through the outer 210 and outer protective 215 layers and contact the indicator layer 220.
One example of a universal pH indicator is bromophenol blue. When bromophenol blue is exposed to a liquid, a yellow color is obtained for pH smaller than 3, multiple colors for pH between 3 and 4.6 (real pH indicator in this pH range), and blue color for pH greater than 4.6. The advantage of bromophenol blue is that it has the largest change in color hue, when the concentration of the observed sample increases or decreases.
In another example, if one needs a pH indicator for use of the multilayer glove 100 in only acid baths, then the indicator layer 220 can be based on methyl orange (C14H14N3NaO3S) because it indicates the presence of acids (pH between 0 and 6), indicating very well the strength of the acid. For other applications, where only bases are handled, the indicator layer can be based on phenolphthalein, which is colorless below 8.2 and pink above that value up to a pH of about 13. In even stronger basic solutions, the phenolphthalein becomes colorless.
Other examples of an indicator layer 220 are based upon mixtures of pH indicators. For instance, a first example of such an indicator layer is based on phenolphthalein (PPT) and methyl red (MR). Another example of mixed pH indicators are PPT and methyl orange (MO). Another example is PPT and neutral red (NR).
On the one hand, an indicator layer 220 based only on PPT will change in color from colorless to pink-fuchsia, when pH of a solution in contact with the layer increases from low pH values (acidic) to basic values with a pH transition region from 8.2 to 10, while for pH values higher than 12 it will become colorless, again. On the other hand, an indicator layer 220 based only on MR will change from red to yellow when the pH is increased from small pH value (acidic) to basic with a transition region from red to yellow in the pH range from 4 up to 6.4. Thus, by mixing two low molecule size pH indicators like PPT with MR, the indicator layer 220 will expose to an operator a red color in the acidic range and yellow to fuchsia in the basic range, which will thus eliminate the lack of color of PPT in the acidic medium, and thus being able to indicate by colorimetric principle that the glove consumed a portion of its lifetime a predetermined by the percentage to/T.
Another example of an indicator layer 220 combines PPT with NR. NR has a pH transition region between 6.8 and 8, i.e., at the transition between an acidic and basic medium.
The bottom layer 220 of the inner glove, which is in contact with the skin, is made of a chemically resistant material like latex, butyl, CSM/neoprene, neoprene, etc.
The inner protective 225 and outer protective 215 layers protect the indicator layer 220 by sealing it against exposure to aqueous media during fabrication of the glove 100. In this manner, basic baths that are used to form inner 230 and outer 210 layers do not prompt reaction with pH indicators in the indicator layer 220. For this purpose, the inner protective 225 and outer protective 215 layers are chosen from polymers that are water-soluble, wherein aqueous solutions of the polymers substantially maintain neutral pH, i.e., pH 7. In addition, water solubility of the inner protective 225 and outer protective 215 layers in a manufactured glove 100 ensures rapid diffusion of acid or basic liquid media to the indicator layers 220, thereby preserving the ability of the glove to rapidly indicate remaining glove life to a user of the glove. For these purposes, a wide variety of water-soluble polymers and combinations thereof are used for the inner protective 225 and outer protective 215 layers. According to various embodiments, water-soluble polymers include polyvinyl alcohols (PVA); cellulose-derived polymers such as methylcellulose, hydroxypropyl cellulose (HPC), hydroxypropyl methylcellulose (HPMC), and the like; and polyvinylpyrrolidones (PVP). In some embodiments, the inner protective 225 and outer protective 215 layers further comprise a plasticizer that is also water-soluble. Examples of water-soluble plasticizers include those described herein, such as polyalkylene glycols. For instance, the plasticizer is a polyethylene glycol (PEG), such as PEG-400, and combinations of various PEGs known to those who are skilled in the art are contemplated as well.
According to various embodiments, the indicator layer 220 is formed not by dip coating, but by direct printing onto an inner protective layer 225, or if the glove 100 is formed by creating the outer layer 210 first, then the indicator layer 220 can be direct-printed onto the outer protective layer 215. In this manner, precise patterns of pH indicators and mixtures thereof are affixed to the inner protective layer 225. Thus, for instance, an inner layer 230 with an inner protective layer 225 with tip, and outer protective layer 215 with top can support an indicator layer 220 with tc and bearing alphanumeric text such as “10% left,”, where ti, tip, top, and tc in combination represent 10% of total thickness T as a notification to the user of the glove. Hence, when the outer layer 210 with to representing 90% of the total thickness T is compromised or worn away by a liquid medium, the indicator layer 220 is exposed to the liquid medium and immediately reacts, thereby showing the predetermined text or pattern to the glove user.
Some embodiments provide for multiple sets of inner 230, inner protective 225, indicator 220, and outer protective 215 layers, wherein each indicator layer 220 is located at a depth in the glove as determined by the cumulative thicknesses ti, tip, tc, and top that, in the aggregate, are present below a given indicator layer 220. In this manner, indicator layers residing at multiple depths in the glove that are direct-printed can be configured into certain patterns or alphanumeric text signaling remaining glove life to a user of the glove.
In some embodiments, each inner layer 230 bears the same thickness wherein the indicator layer 220 direct-printed onto a given inner protective layer 225 bears a pattern or alphanumeric text corresponding to the depth of that inner protective layer 225. Examples include (ti+tip+tc+top)/T ratios of 10%, 20%, 25%, and 50%. Thus, in one example, a glove 100 can have an outer layer 210 with a thickness to representing 50% T, and two sets of inner 230, inner protective 225, and outer protective 215 layers, each set having a cumulative thickness (ti+tip+tc+top) of 25% of T, wherein the outermost indicator layer 220 can be direct-printed to read “50% left”, and the innermost indicator layer 220 can be direct-printed to read “25% left.”
In other embodiments, the glove 100 has multiple sets of inner 230, inner protective 225, and outer protective 215 layers with different thicknesses ti in each set, wherein each indicator layer 220 that is direct-printed onto an inner layer 230 within each set is configured to convey to a user of the glove the percentage of remaining glove life. Thus, in one example of a glove 100, an innermost inner layer 230 and its corresponding inner protective 225, outer protective 215, and corresponding indicator 220 layers have a cumulative thickness (ti+tip+tc+top) that is 10% of total thickness T, wherein the indicator layer 220 that is direct-printed onto that inner layer 230 reads “10% left.” The next innermost inner layer 230 and its corresponding inner protective 225, outer protective 215, and corresponding indicator 220 layers have a cumulative thickness (ti+tip+tc+top) that is 40% of total thickness T; hence, an indicator layer 220 direct-printed onto that inner layer 230 would read, for example, “50% left.” In this example, the outer layer 210 would have a thickness to equal to 50% of the total thickness T.
In the embodiments described above, an indicator layer 220 can be direct-printed with a pattern that is unique to that layer's depth in the glove. For instance, the pattern can be cross-hatches, dots, stripes, and the like. Alternatively, alphanumeric text can be direct-printed as a pattern so as to be visible to a user of the glove irrespective of the orientation of the glove.
One advantage of multiple sets of inner 230, inner protective 225, outer protective 215, and indicator 220 layers as described herein is useful indication to a user the remaining lifetime of various parts of the glove 100. For instance, layers of the glove 100 that are most often exposed to a harsh liquid medium and/or subject to most abrasion, such as fingertips and palm regions, can become compromised earlier than other regions of the glove. Hence, multiple sets of inner 230, inner protective 225, outer protective 215, and indicator 220 layers, each indicator layer 220 having a unique direct-printed pattern, can convey accurate and unambiguous information to a glove user on the remaining glove 100 lifetime for a particular region of the glove.
As described herein, various materials can be chosen for the inner and outer layers, and the skilled person can select various colors of those materials. In general, the colors of inner and outer layers are chosen to maximize the appearance of the indicator layer to a user of the glove. Thus, high contrast color schemes are most useful for this purpose. Examples of colors include white, yellow, and pastel shades of various other colors, so long as a user can discern the color produced, the pattern or alphanumeric text that appears, when an indicator layer is exposed to a liquid medium.
In general, the dip coating fabrication process of an exemplary protective glove consists of full immersion of a hand-shaped former (HSF) in multiple baths where the liquid state of the future layers are present. Different HSFs may be used for each hand and multiple HSFs may be used of varying sizes corresponding to different sizes of hands and protective gloves.
After each dip coating, a thermal treatment is applied for the solid state consolidation of the film, such as by passing the HSF through a furnace. At the end of the manufacturing process, the gloves are peeled off the HSF, and thus the last deposited layer on the glove will be the layer in contact with the skin. In some embodiments, the glove is not reversed when peeling it off from the HSF, or the glove may be turned inside out after peeling off. This allows an inner layer 230 to be formed first followed by inner protective 225 and indicator 220 layers.
Indicator layers 220 that are direct-printed can be achieved by various methods known to the skilled person. For instance, according to some embodiments, direct-printing can be achieved by a 3D printer.
In the embodiments described herein, one or more dip-coating steps in the manufacturing process can be replaced by direct-printing. In some embodiments, all steps for making the multilayer glove 100 are achieved by direct-printing, such as with a 3D printer. An advantage to direct-printing is the avoidance of material waste that is left over by dip-coating baths. Hence, direct-printing achieves essentially 100% efficiency in the use of glove material(s).
The indicator layer 220 can be made from a composition comprising one or more pH indicators, as illustrated in the examples below. In general, the pH indicators are dissolved in a mixture of water and a branched or straight (C1-5)-alkyl alcohol, such as methanol or ethanol, and mixtures of such alcohols.
One or more water-soluble binders is added to the pH indicator solution. Suitable binders include polyvinylalcohols, starches, carboxymethylcellulose, methylcellulose, hydroxypropyl methylcellulose, dextrin, polyethylene glycols, lignosulfates, and polyacrylates. An exemplary binder is methylcellulose.
The pH indicator composition also comprises one or more water soluble plasticizers useful to increase the fluidity of the composition. Examples of plasticizers include glycerins, polyethylene glycols, polyethylene glycol monomethyl ethers, propylene glycols, sorbitol and sorbitan.
The pH indicator composition is stirred to obtain a homogeneous and viscous solution. The composition thus prepared is suitable as a bath for the dip-coating manufacturing process described below. Alternatively, according to some embodiments, the composition can be used in a direct-printing process for applying the indicator layer. In these embodiments, viscosity of the pH indicator composition is readily adjusted so as to promote even coverage of the pH indicator(s) throughout the indicator layer.
This example illustrates a process for making a solution of small molecule pH indicators useful in subsequent procedures for making an indicator layer in a multilayer glove.
Phenolphthalein and methyl red are dissolved in ethanol. Optionally, the resulting solution is combined and mixed with a solution of polyvinylalcohol in warm water. To the resulting solution, a plasticizer such as polyethylene glycol and, optionally, a binder such as methylcellulose are added. The final mixture is then stirred to obtain a homogeneous and viscous solution of phenolphthalein and methyl red
An example of a standard all-dip-coating fabrication process of a smart latex glove containing a single color change layer indicating 10% lifetime left before removal (NESLI indicator) is as follows:
As an alternative, the outer layer, the indicator layer, the inner protective and outer protective layers, and the inner layer can be deposited in the sequence described above, but a single thermal treatment is made at the end.
This example demonstrates the manufacture of a multilayer glove in which an indicator layer is direct-printed to reveal a desired pattern, such as alphanumeric characters, as a service life indicator. The procedure is analogous to that in Example 2, except that step 6 is replaced by direct printing of an indicator layer solution such as from Example 1 on selective areas of the HSF from step 5 for creating the text “10% LEFT.”
1. A multilayer glove (100) comprising:
2. The multilayer glove (100) according to example 1, wherein the indicator layer (220) comprises two or more different pH indicators, each indicator being responsive to different ranges of pH, respectively.
3. The multilayer glove (100) according to example 1 or 2, wherein each ti is less than to.
4. The multilayer glove (100) according to any one of examples 1-3, wherein the pH indicator is selected from the group consisting of bromophenol blue, bromothymol blue, phenolphthalein, methyl red, methyl orange, neutral red, and combinations thereof.
5. The multilayer glove (100) according to any one of examples 1-4, wherein the outer layer and each inner layer independently comprise at least one member selected from the group consisting of latex, nitrile, chlorosulphonated polyethylene, butyl rubber, and neoprene.
6. The multilayer glove (100) according to any one of examples 1-5, wherein each inner protective layer and each outer protective layer independently comprise one or more of polyvinyl alcohol and polyethylene glycol.
7. The multilayer glove (100) according to any one of examples 1-6, further comprising one or more additional sets of inner (230), inner protective (225), indicator (220), and outer protective (215) layers, each indicator layer (220) being disposed between the top surface of its corresponding inner protective layer (225) and the bottom surface of its corresponding outer protective layer (215).
8. The multilayer glove (100) according to any one of examples 1-7, wherein the glove comprises two to four sets of inner (230), inner protective (225), indicator (220), and outer protective (215) layers.
9. The multilayer glove (100) according to example 7 or 8, wherein each indicator layer (220) comprises a pH indicator or combination of pH indicators that is different than pH indicators in other indicator layers.
10. The multilayer glove (100) according to any one of examples 7-9, wherein the sum of each ti, tip, tc, and top is 10 to 15% of T.
11. The multilayer glove (100) according to example 1, wherein the pH indicator in each indicator layer (220) is present as alphanumeric text corresponding to the sum of remaining sums of thicknesses ti, tip, tc, and top expressed as a percentage of T.
12. The multilayer glove (100) according to example 1, wherein each outer layer (210) and inner layer (230) consists of latex, nitrile, chlorosulphonated polyethylene, butyl rubber, or neoprene; each inner protective layer (225) and outer protective layer (215) consists of polyvinyl alcohol and polyethylene glycol; and the pH indicator is a combination of phenolphthalein and methyl red.
13. A method of forming a multilayer glove (100), the method comprising
14. The method according to example 13, wherein the forming of an indicator layer (220) on the outer protective layer (215) comprises dip coating the hand shaped former having the outer protective layer (215) into a composition comprising the pH indicator to form the indicator layer (220).
15. The method according to example 13 or 14, wherein the composition further comprises an alcohol, water, a binder, and a plasticizer.
16. The method according to example 15 wherein the alcohol is a (C1-C5) branched or straight alkyl alcohol.
17. The method according to example 15 or 16 wherein the alcohol is methanol or ethanol.
18. The method according to any one of examples 13-17, wherein steps (b), (c), (d), and (e) are repeated to form successive sets of outer protective (215), indicator (220), inner protective (225), and inner (230) layers.
19. The method according to any one of examples 13-18, wherein steps (b), (c), (d), and (e) are repeated to form two to four successive sets of outer protective (215), indicator (220), inner protective (225), and inner (230) layers.
20. The method according to any one of examples 13-19, wherein the baths in steps (a) and (e) comprise latex, nitrile, chlorosulphonated polyethylene, butyl rubber, or neoprene; and the indicator layer comprises phenolphthalein and methyl red
Although some embodiments have been described in detail above, other modifications are possible. For example, the logic flows depicted in the figures do not require the particular order shown, or sequential order, to achieve desirable results. Other steps may be provided, or steps may be eliminated, from the described flows, and other components may be added to, or removed from, the described systems. Other embodiments may be within the scope of the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 17161447.2 | Mar 2017 | EM | regional |
