Patent Description:
PSAs are known to provide instantaneous adhesion to the substrate when subjected to pressure. PSAs are generally easy to handle in solid form and have a long shelf-life, so they are widely used for the manufacture of, for example, self-adhesive labels. However, labeling low-temperature articles, such as blood packages that have been kept at ultra-low temperature of less than -<NUM>, has been challenging due to the stringent requirements for these applications. For example, the labels must be able to be affixed to frozen blood packages and their tubings under these ultra-low temperatures. The labeled packages also need to be stored under ultra-low temperature for a long period. In use, these blood packages need to be pre-thawed under relatively low temperature, e.g., <NUM>-<NUM> (the pre-thaw stage) and then thawed at <NUM> (the thawing stage) e.g., by being submerged in a warm water bath. These procedures subject the labels to a wide range of temperatures, including harsh, ultra-low temperatures, and to adverse environment of being underwater. During these procedures, the labels often become loose and detach from the packages.

Although efforts have been made in the industry to create adhesives that can be functional under these conditions, the results are still far from ideal. For example, these adhesives have to be produced in a way to keep them very soft, in order to maintain their ability to attach to the packages under ultra-low temperatures. As a result, the adhesive often overflows after being applied to substrates, which adversely affects printing quality. During the pre-thawing and thawing stages, the labels on the tubing of the packages often stretch out and become detached from the package. In addition, the application of labels under ultra-low temperatures is also burdensome in that the frozen icy layer on the substrate must be first removed from the package before the label can be affixed. Thus, a need remains to produce a PSA that can perform to its intended purposes despite of these adverse conditions.

<FIG> shows a blood package with labels comprising the PSA of the invention. The arrows indicate the labels that have been attached to the package and the tubing.

This disclosure provides a pressure sensitive adhesive comprising: a polyacrylate base polymer having a glass transition temperature, a polyacrylate tackifier having a glass transition temperature, and a metal chelating crosslinker, wherein both the glass transition temperature of the polyacrylate tackifier and the glass transition temperature of the polyacrylate base polymer are lower than <NUM>, and wherein the glass transition temperature of the polyacrylate base polymer is lower than the glass transition temperature of the polyacrylate tackifier, wherein the glass transition temperature of the polyacrylate base polymer ranges from -<NUM> to -<NUM> and wherein the glass transition temperature of the polyacrylate tackifier is greater than -<NUM>.

In some embodiments, the pressure sensitive adhesive is a solvent-borne PSA. In some embodiments, the glass transition temperature of the polyacrylate base polymer ranges from -<NUM> to -<NUM>. In some embodiments, the Tg of the polyacrylate base polymer is <NUM> to <NUM> lower than that of the polyacrylate tackifier.

In some embodiments, the molecular weight of the polyacrylate base polymer is greater than the molecular weight of the polyacrylate tackifier. In some embodiments, the polyacrylate base polymer has a Mw (weight average molecular weight) ranging from <NUM>,<NUM>~<NUM>,<NUM>,<NUM>/mol.

In some embodiments, the polyacrylate base polymer is present in an amount ranging from <NUM> wt. % to <NUM> wt. %, based on the total solid weight of the pressure sensitive adhesive.

In some embodiments, the polyacrylate base polymer is selected from the group consisting of <NUM>-<NUM>,<NUM>,<NUM>, and 3462A from Taizhou Yade Adhesive company; BPS <NUM> ,BPS5330W, BPS5448 from Toyo Ink; Etrac <NUM>, Etrac <NUM> from Eternal; Ultra Reclo 109A, Ultral Reclo 236A from Henkel; and Y-<NUM>, and Y-180314X from YASUSA.

In some embodiments, the polyacrylate tackifier has a weight average molecular weight ranging from <NUM>,<NUM> to <NUM>,<NUM>/mol. In some embodiments, the polyacrylate tackifier is present in an amount ranging from <NUM> wt. % to <NUM> wt. %, based on the total solid weight of the pressure sensitive adhesive. In some embodiments, the polyacrylate base polymer comprises less than <NUM> wt. % rosin resin, aziridine, or epoxy or combinations thereof. In some embodiments, pressure sensitive adhesive demonstrates a peel strength greater than <NUM>. 5N/inch on polyvinyl chloride, as measured by FINAT Test Method <NUM> (<NUM>).

In some embodiments, the pressure sensitive adhesive demonstrates a shear greater than <NUM>,<NUM> minutes (e.g. greater than <NUM>,<NUM> minutes) on stainless steel according to FINAT <NUM>. In some embodiments, the pressure sensitive adhesive has a peel strength on polyvinyl chloride ranging from <NUM> N/mm (<NUM> N/inch) to <NUM> N/mm (<NUM> N/inch). In some embodiments, the pressure sensitive adhesive is capable of remaining attached to a substrate when the pressure sensitive adhesive has been subjected to a temperature ranging from -<NUM> to -<NUM> for a period of <NUM> month to <NUM> years. In some embodiments, the pressure sensitive adhesive is capable of remaining attached to a substrate when the pressure sensitive adhesive has been subjected to a temperature ranging from <NUM> to <NUM> for a period of <NUM> hours to <NUM> hours. In some embodiments, the pressure sensitive adhesive is capable of remaining attached to a substrate when the pressure sensitive adhesive has been in contact with water for a period of <NUM> hour to <NUM> hours.

In some embodiments, the metal chelating agent is a triple aluminum comprising the structure of the formula below:
<CHM>.

In some embodiments, the metal chelating agent is present in an amount ranging from <NUM> wt. % to <NUM> wt. %, based on the total solid weight of the pressure sensitive adhesive.

In some embodiments, the glass transition temperature of the polyacrylate base polymer ranges from -<NUM> to -<NUM> and the molecular weight of the polyacrylate base polymer ranges from <NUM>,<NUM>/mol to <NUM>,<NUM>/mol, and wherein the glass transition temperature of the polyacrylate tackifier ranges from -<NUM> to <NUM> and the molecular weight of the polyacrylate tackifier ranges from <NUM>,<NUM>/mol to <NUM>,<NUM>/mol.

In some embodiments, the glass transition temperature of the polyacrylate base polymer ranges from -<NUM> to -<NUM> and the molecular weight of the polyacrylate base polymer ranges from <NUM>,<NUM>/mol to <NUM>,<NUM>,<NUM>/mol wherein the polyacrylate base polymer is present in an amount ranging from <NUM> wt. % to <NUM> wt. %, based on the total solid weight of the pressure sensitive adhesive; wherein the glass transition temperature of the polyacrylate tackifier ranges from -<NUM> to -<NUM> and the molecular weight of the polyacrylate tackifier ranges from <NUM>,<NUM>/mol to <NUM>,<NUM>/mol, wherein the polyacrylate tackifier is present in an amount ranging from <NUM> wt. % to <NUM> wt. % based on the solid weight of the pressure sensitive adhesive; and wherein the metal chelating crosslinker is present in an amount of <NUM> wt. % to <NUM> wt.

In some embodiments, the glass transition temperature of the polyacrylate base polymer ranges from -<NUM> to -<NUM> and the molecular weight of the polyacrylate base polymer ranges from <NUM>,<NUM>/mol to <NUM>,<NUM>/mol; wherein the polyacrylate base polymer is present in an amount ranging from <NUM> wt. % to <NUM> wt. %, based on the total solid weight of the pressure sensitive adhesive; wherein the glass transition temperature of the polyacrylate tackifier ranges from -<NUM> to <NUM> and the molecular weight of the polyacrylate tackifier ranges from <NUM>,<NUM>/mol to <NUM>,<NUM>/mol, (e.g., <NUM>,<NUM>/mol to <NUM>,<NUM>/mol); wherein the polyacrylate tackifier is present in an amount ranging from <NUM> wt. % to <NUM> wt. % based on the solid weight of the pressure sensitive adhesive; wherein the metal chelating crosslinker is present in an amount ranging from <NUM> wt. % to <NUM> wt. %; and wherein the pressure sensitive adhesive demonstrates a peel strength of at least <NUM> N/mm (<NUM> N/inch) to <NUM> N/mm (<NUM> N/inch) on polyvinyl chloride, as measured by FINAT-<NUM> (<NUM>) and a static shear on stainless steel of <NUM>,<NUM> minutes to <NUM>,<NUM> minutes, as measured by FINAT-<NUM> (<NUM>).

In some embodiments, wherein the glass transition temperature of the polyacrylate base polymer ranges from -<NUM> to -<NUM> and the molecular weight of the polyacrylate base polymer ranges from <NUM>,<NUM>/mol to <NUM>,<NUM>/mol; wherein the polyacrylate base polymer is present in an amount ranging from <NUM> wt. % to <NUM> wt. %, based on the total solid weight of the pressure sensitive adhesive; wherein the glass transition temperature of the polyacrylate tackifier ranges from -<NUM> to <NUM> (e.g., from -<NUM> to -<NUM>) and the molecular weight of the polyacrylate tackifier ranges from <NUM>,<NUM>/mol to <NUM>,<NUM>/mol (e.g.,<NUM>,<NUM>/mol to <NUM>,<NUM>/mol); wherein the polyacrylate tackifier is present in an amount ranging from <NUM> wt. % to <NUM> wt. % based on the solid weight of the pressure sensitive adhesive; wherein the metal chelating crosslinker is present in an amount ranging from <NUM> wt. % to <NUM> wt. %; and wherein the pressure sensitive adhesive demonstrates a peel strength of at least <NUM> N/mm (<NUM> N/inch) to <NUM> N/mm (<NUM> N/inch) on polyvinyl chloride, as measured by FINAT-<NUM> (<NUM>) and a static shear on stainless steel of greater than <NUM>,<NUM> minutes, as measured by FINAT-<NUM> (<NUM>); wherein the pressure sensitive adhesive is capable of remaining attached to a substrate when the pressure sensitive adhesive has been subjected to a temperature ranging from -<NUM> to <NUM> for a period of <NUM> hour to <NUM> years(e.g., at -<NUM> to <NUM> for <NUM> years); and wherein the pressure sensitive adhesive is capable of remaining attached to a substrate when the pressure sensitive adhesive is has been in contact with water for a period of <NUM> hour to <NUM> month, e.g., a period of <NUM> hour to <NUM> week, a period of <NUM> hour to <NUM> days.

This disclosure provides a laminate composition comprising a facestock layer and a pressure sensitive adhesive layer comprising the pressure sensitive adhesive of any one of pressure sensitive adhesive as disclosed above. In some embodiments, the pressure sensitive adhesive layer has a thickness ranging from <NUM> to <NUM>.

In some embodiments, the facestock layer is a film comprising one or more resins selected from the group consisting of polyester, polypropylene(PP) , PP synthesis paper, polyvinyl chloride (PVC) ,ABS, polyacrylate, polycarbonate (PC), polyamide, polyimide (PI), polyamidoimide, polyacetal, polyphenylene oxide (PPO), polysulfone, polyethersulfone (PES), polyphenylene sulfide, polyether ether ketone (PEEK), polyetherimide (PEl), metallized polyethylene terephthalate (PET), polyvinyl fluoride (PVF), polyethylene ether (PEE), fluorinated ethylene propylene (FEP), polyurethane (PUR), liquid crystal polymers (LCPs, class of aromatic polyester), polyvinylidene fluoride (PVDF), aramid fibers, DIALAMY, (polymer alloys), polyethylene naphthalate (PEN), ethylene/tetrafluoroethylene, (E/TFE), polyphenyl sulfone (PPSU). In some embodiments, the laminate further comprises a topcoat layer disposed on top of the facestock layer.

Also provided is a label comprising the pressure sensitive adhesive described above or the laminate composition described above.

Also provided is a process for producing a pressure sensitive adhesive, the process comprising: dissolving in a solvent a) a polyacrylate base polymer; b) a polyacrylate tackifier; and c) a metal chelating crosslinker to form a pressure sensitive adhesive solution. In some embodiments, the solvent is selected from the group consisting of toluene, ethyl acetate, isopropanol, xylene, n-hexane, n-heptane, methyl cyclohexane, butyl acetate, acetone, butanone, and <NUM>-Acetoxy-<NUM>-methoxypropane. In some embodiments, the method further comprises the step of coating a facestock with the pressure sensitive adhesive solution, and drying the pressure sensitive adhesive solution to produce a label.

In some embodiments, the method further comprises applying the label to an article to produce a labeled article, wherein the label is capable of remaining attached to the article after the labeled article has been kept under a temperature that ranges from -<NUM> to <NUM> for a period at least <NUM> hours and/or the label is capable of remaining attached to the article after the label has been in contact with water for a period of at least <NUM> hour.

Also provided is a process for applying a pressure sensitive adhesive to an article, the process comprising applying the label produced in any of the processes above to the article at an application temperature equal to or less than -<NUM>. In some embodiments, the article is a frozen blood product package.

In some embodiments, the glass transition temperature of the polyacrylate base polymer is less than the application temperature.

In some embodiments, the pressure sensitive adhesive demonstrates a peel strength of at least <NUM> N/mm (<NUM> N/inch) to <NUM> N/mm (<NUM> N/inch) on polyvinyl chloride, as measured by FINAT Test Method <NUM> (<NUM>) and a static shear on stainless steel of greater than <NUM> minutes.

In some embodiments, the pressure sensitive adhesive remains attached to the article after subjecting to a temperature ranging from -<NUM> to <NUM>.

In some embodiments, the pressure sensitive adhesive remains attached to the substrate after contact with water for a period of <NUM> hour to <NUM> month.

Also provided is a pressure sensitive adhesive solution comprises the components of any of the pressure sensitive adhesive as described above, and a solvent. In some embodiments, the polyacrylate base polymer solution is present in an amount ranging from 30wt. % to <NUM> wt. % (e.g. <NUM> wt% to <NUM> wt. %) based on the total weight of the pressure sensitive adhesive solution. In some embodiments, the solvent is present in an amount ranging from <NUM> wt. % to <NUM> wt. % based on the total weight of the pressure sensitive adhesive solution.

The present invention relates generally to pressure sensitive adhesives (PSAs). The PSAs of this disclosure comprise two different acrylate polymers and a metal chelating agent and can be effectively used under a broad range of working temperatures, e.g., from -<NUM> to <NUM> or from - <NUM> to <NUM>. As some benefits, these PSAs demonstrate optimal tack and cohesiveness and/or resistance to warm water bath, when affixed to substrates.

As noted herein, a variety of conventional PSAs are known in the art. Many of these adhesives, however, do not demonstrate desired performance for labeling low temperature substrates or desired water resistance.

<CIT> discloses a PSA that comprises two polyacrylate polymers L and H, however the polymer H has a high glass transition temperature, i.e., in the range of between <NUM> and <NUM>. Thus the PSA is not suitable for use under ultra-low temperatures.

<CIT> discloses a PSA, comprising a copolymer having a low glass transition temperature in the range of -<NUM> to -<NUM> and another copolymer having a high glass transition temperature in the range of <NUM> to <NUM>. However, the PSA is a hot melt PSA, not a solvent-borne PSA. In addition, the PSA does not contain metal chelating crosslinker. These differences render the PSA, unlike the claimed PSA, unable to perform well under ultra-low temperatures or after being exposed to warm water-bath.

<CIT> and <CIT> also relate to PSA compositions based on different polyacrylate base polymers and oligomers.

The inventors have found that the unique combination of specific components - a particular polyacrylate base polymer, a polyacrylate tackifier, and a metal chelating agent crosslinker - surprisingly demonstrate a synergistic balance of high peel strength and static shear. Importantly, it has been discovered that when the glass transition temperatures ("Tg") of both polyacrylate base polymer and a polyacrylate tackifier are lower than <NUM> and the glass transition temperature of the polyacrylate base polymer is less than the glass transition temperature of the tackifier, the PSAs show good performance under ultra-low temperature and/or excellent resistance to warm water bath, which was previously unattainable with existing PSAs.

Without being bound by theory, it is postulated that the lower Tg (and optionally higher molecular weight) polyacrylate provides for low temperature attachment, while the higher Tg (and optionally lower molecular weight) polyacrylate may serve as a tackifier and thus provide for a surprising increase in tack performance. Importantly, due to the synergies of the components, the presence of the higher Tg polyacrylate allows the use of lesser amounts thereof, which provides processing and economic benefits. It also provides the unexpected benefit of reducing or eliminating the need for rosin resin, which has been found to create problems associated hardening of the PSA, which impairs the ability of attaching to the substrate under ultra-low temperature and the poor resistance to warm water bath. In addition, it has been found that the use of the aforementioned higher Tg polyacrylate, also unexpectedly improves water resistance in the PSA, without sacrificing other performance characteristics. It is believed that the specific higher Tg polyacrylate may have a higher degree of cohesiveness, which contributes to the water resistance improvements. Further, the use of specific crosslinkers has been found to significantly increase both cohesiveness of the polymer and resistance to warm water bath. Importantly, the use of these particular crosslinkers also surprisingly has minimal, if any negative impact on the PSA's low temperature adhesion. The increase in the cohesiveness also reduces the problem of overflow of the adhesive and eases die cutting.

All ranges and limits referenced in this disclosure include end points.

The PSA disclosed herein comprises two polyacrylate polymers, one polyacrylate polymer is more abundant, referred to herein as the "polyacrylate base polymer;" the other polyacrylate polymer is present in a lesser amount and may serve as a tackifier, referred to herein as the "polyacrylate tackifier. " In some embodiments, the polyacrylate base polymer used herein typically has a molecular weight greater than that of the polyacrylate tackifier. The polyacrylate base polymer may also have Tg lower than that of the polyacrylate tackifier. As discussed above, the use of the polyacrylate polymers has been found to contribute to the benefits mentioned above. In some embodiments, both the Tg of the polyacrylate base polymer and the Tg of the polyacrylate tackifier are lower than <NUM>, e.g., lower than <NUM>, lower than <NUM>, lower than <NUM>, or lower than -<NUM>.

The average molecular weight of the polyacrylate base polymer may vary widely. In some embodiments, the average molecular weight may range from <NUM>,<NUM>/mol to <NUM>,<NUM>,<NUM>/mol, e.g., from <NUM>,<NUM>/mol to <NUM>,<NUM>,<NUM>/mol, from <NUM>,<NUM>/mol to <NUM>,<NUM>/mol, from <NUM>,<NUM>/mol to <NUM>,<NUM>/mol, from <NUM>,<NUM>/mol to <NUM>,<NUM>/mol, from <NUM>,<NUM>/mol to <NUM>,<NUM>/mol or about <NUM>,<NUM>/mol. In terms of upper limits, the polyacrylate base polymer can have an average molecular weight of less than <NUM>,<NUM>,<NUM>/mol, e.g., less than <NUM>,<NUM>,<NUM>/mol, less than <NUM>,<NUM>/mol, less than <NUM>,<NUM>/mol, less than <NUM>,<NUM>/mol. In terms of lower limits, the polyacrylate base polymer can have an average molecular weight of greater than <NUM>,<NUM>/mol, e.g., greater than <NUM>,<NUM>/mol, or greater than <NUM>,<NUM>/mol.

The polyacrylate base polymer, in some embodiments, has a Tg within particular ranges and/or limits. The Tg defines the region where the polymer transitions from a hard, glassy material to a soft, rubbery material. In some embodiments, the polyacrylate base polymer has a Tg ranging from - <NUM> to -<NUM>, e.g., from -<NUM> to -<NUM>, from -<NUM> to -<NUM>, from -<NUM> to -<NUM>, from -<NUM> to -<NUM>, or about -<NUM>. In terms of lower limits, the Tg of the polyacrylate base polymer is higher than -<NUM>, e.g., higher than -<NUM> or higher than -<NUM>. In terms of upper limits, the Tg of the polyacrylate base polymer is lower than -<NUM>, e.g., lower than -<NUM>, or lower than -<NUM>. The glass transition temperature of the polyacrylate base polymer is typically lower than that of the polyacrylate tackifier. In some embodiments, the Tg of the polyacrylate base polymer is <NUM> -<NUM> C° lower than that of the polyacrylate tackifier, e.g., <NUM> -<NUM> lower, <NUM> -<NUM> lower, <NUM> -<NUM> lower, or <NUM> lower.

In some embodiments, the PSA comprises polyacrylate base polymer in an amount that ranges from <NUM> wt. % to <NUM> wt. %, e.g., <NUM> wt. % to <NUM> wt. %, <NUM> wt. % to <NUM> wt. %, <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, e.g., about <NUM> wt. %, based on the total dry weight of the PSA. In terms of upper limits, the polyacrylate base polymer is present in an amount less than <NUM> wt. %, less than <NUM> wt. In terms of lower limits, the polyacrylate base polymer is present in an amount greater than <NUM> wt. %, e.g., greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, or greater than <NUM> wt.

Suitable commercially available polyacrylate base polymers include, but are not limited to, <NUM>-<NUM>, <NUM>, <NUM>, and 3462A from Taizhou Yade Adhesive company (Zhejiang, P. China); BPS5296 ,BPS5330W, BPS5448 from Toyo Ink (Tokyo, Japan); Etrac <NUM>, Etrac <NUM> from Eternal (Taiwan); Ultra Reclo 109A, Ultral Reclo 236A from Henkel (Diisseldorf, Germany); and Y-<NUM> and Y-180314X from YASUSA (JiaXing, P. These polyacrylate base polymers are typically available in solution, for example, <NUM>-<NUM> has a solid content about <NUM> wt. % and a solvent content about <NUM> wt.

Unlike conventional PSAs, which typically use low molecular weight tackifiers, e.g., rosin, the PSA disclosed herein uses a specific polyacrylate to serve as tackifiers. The inventors have found that polyacrylates have higher molecular weight than rosin and that the use of the higher molecular weight tackifier surprisingly confers the PSA increased resistance to water. This is particular useful for applications such as PSA-labeled packages, e.g., blood packages, which must be immersed in warm water bath to thaw before use. In addition, polyacrylate polymers are closer in structure to the base polymer than rosin is; which advantageously allows them to minimize the negative impact of conventional tackifiers on the cohesiveness of the PSA, which is also beneficial for its function when exposed to water.

The average molecular weight of the polyacrylate tackifier may vary. In some cases, the average molecular weight may range from <NUM>,<NUM>/mol to <NUM>,<NUM>/mol, e.g., from <NUM>,<NUM>/mol to <NUM>,<NUM>/mole, from <NUM>,<NUM>/mol to <NUM>,<NUM>/mole, from <NUM>,<NUM>/mol to <NUM>,<NUM>/mol, from <NUM>,<NUM>/mol to <NUM>,<NUM>/mol or about <NUM>,<NUM>/mol. In terms of upper limits, the polyacrylate base polymer can have an average molecular weight of less than <NUM>,<NUM>/mol, e.g., less than <NUM>,<NUM>/mol, less than <NUM>,<NUM>/mol. In terms of lower limits, the polyacrylate base polymer can have an average molecular weight of greater than <NUM>,<NUM>/mol, e.g., greater than <NUM>,<NUM>/mol, greater than <NUM>,<NUM>/mol, greater than <NUM>,<NUM>/mol.

The polyacrylate tackifier in the PSA has a Tg that is higher than the glass transition temperature of the polyacrylate base polymer. As noted above, the inventors have found that the use of the higher Tg polyacrylate also contributes to the increased cohesiveness of the PSA and thus increased water resistance. The Tg of the polyacrylate tackifier used in the PSA typically ranges from -<NUM> to <NUM>, e.g., from -<NUM> to <NUM>, from -<NUM> to <NUM>, from -<NUM> to <NUM>, from -<NUM> to -<NUM>, from -<NUM> to -<NUM>, from -<NUM> to -<NUM>, e.g., -<NUM>. In terms of lower limits, the Tg of the polyacrylate base polymer is higher than -<NUM>, e.g., higher than -<NUM>, or higher than -<NUM>. In terms of upper limits, the Tg of the polyacrylate base polymer is lower than <NUM>, e.g., lower than <NUM>, or lower than <NUM>.

The polyacrylate tackifier is present in the PSA in an amount ranging from <NUM> wt. % to <NUM> wt. %, e.g., from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, e.g., about <NUM> wt. %, based on the total dry weight of the PSA. In terms of upper limits, the polyacrylate base polymer is present in an amount less than <NUM> wt. %, less than <NUM> wt. %, or less than <NUM> wt. %, based on the total solid weight of the PSA. In terms of lower limits, the polyacrylate base polymer is present in an amount greater than <NUM> wt. %, e.g., greater than <NUM> wt. %, greater than <NUM> wt. %, or greater than <NUM> wt.

Exemplary commercially available tackifiers that are suitable for use in the PSA disclosed herein include ZHP-<NUM>,ZHP-<NUM>,ZHP-<NUM>, <NUM>-<NUM> From DIC (Japan),Neocryl ® B-<NUM>, from DSM NeoResins, Aroset TM PS6033, <NUM>,<NUM> from Ashland, STS <NUM> from Toyo, Ultra Reclo 247A from Henkel,BM66, BM24E from Pioneer.

Various monomers can be used to produce the polyacrylate base polymer or polyacrylate tackifier, so long as the polymers produced have the desired glass transition temperatures as disclosed above. In some embodiments, the polyacrylate base polymer or polyacrylate tackifier may comprise acrylate monomers that also include alkyl chains. These alkyl chains may vary widely, e.g., linear, branched, cyclical, aliphatic, aromatic, saturated, or unsaturated. The number of carbon atoms in the alkyl chain(s) of the acrylate monomer may vary, ranging from <NUM> to <NUM> carbon atoms, e.g., from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM> carbons. In preferred embodiments, these alkyl chains comprise no more than <NUM> carbon atoms, e.g., no more than <NUM> carbon atoms, no more than <NUM> carbon atoms, no more than <NUM> carbon atoms, no more than <NUM> carbon atoms, no more than <NUM> carbon atoms, or no more than <NUM> carbon atoms. In preferred embodiments these alkyl chains comprise greater than <NUM> carbon atom, e.g., greater than <NUM>, greater than <NUM>, greater than <NUM>, or greater than <NUM> carbon atoms. In some embodiments, the polyacrylate base polymer or polyacrylate tackifier may comprise a single type of acrylate monomer, while in other cases, the polyacrylate base polymer or polyacrylate tackifier may comprise a combination of different acrylate monomers. In some embodiments, the polyacrylate base polymer or polyacrylate tackifier may include acrylic acid (AA), methyl acrylate (MA), butyl acrylate (BA), <NUM>-ethyl hexyl acrylate (<NUM>-EHA), hydroxyethylacrylate (HEA), or combinations thereof. In some embodiments, the polyacrylate base polymer or polyacrylate tackifier do not comprise iso-butyl methyl acetate (IBMA), ethyl acrylate (EA), Vinylic monomers, or combinations thereof.

The PSA of the present invention comprises one or more particular crosslinkers. These one or more crosslinkers functionally link one polymer chain to another. In some embodiments, the one or more crosslinkers are metal chelating agents. Unlike conventional crosslinkers, such as aziridine and epoxy, metal chelating agents can unexpectedly promote the ability of the PSA to affix to the substrate under ultra-low temperatures as well as increasing the water resistance of the PSA.

In some embodiments, the metal chelating crosslinker is a metal acetylacetonate, a metal alkoxide, or an alkoxy-metal acetylacetonate. A metal acetylacetonate for the purposes of this invention is a metal chelating with the enolate anion of acetylacetone as ligand. The IUPAC name for acetylacetone is pentane-<NUM>,<NUM>-dione. A metal alkoxide for the purposes of the invention is a metal alcoholate, in other words a compound composed of a metal cation and an alcoholate anion. Examples of alcoholates frequently used industrially are methanolate, ethanolate, isopropanolate, tert-butanolate. An alkoxy-metal acetylacetonate means a complex compound composed of a metal cation and at least two different ligands, one of the ligands being an alcoholate anion and another ligand being the enolate anion of acetylacetone. Synonyms for an alkoxy-metal acetylacetonate are metal alkoxide acetylacetonate or metal acetylacetone alkoxide. All of the stated metal compounds may carry additional, further ligands, without departing the concept of the invention. Preferred metals are titanium, aluminum, zirconium, zinc, and iron. In some embodiments, the metal chelating crosslinker is a triple aluminum chelating agent. In some embodiments, the metal chelating reagent comprises the following structure:
<CHM>.

Suitable commercially available metal chelating crosslinkers include, but are not limited to ETERAC EC-<NUM> available from Eternal Chemical ( China) Ltd. , LD-<NUM> available from Yangzhou Lida ( Yangzhou, China) company, A-<NUM> available from TCI (Shanghai) company.

The PSA may comprise from <NUM>-<NUM> wt. % of the metal chelating crosslinker, e.g., from <NUM> to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, or about <NUM> wt. %, based on the total dry weight of the PSA. In terms of upper limits, the PSA comprises epoxy in an amount of less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, and less than <NUM> wt. %, based on the total dry weight of the PSA. In terms of lower limits, the PSA comprises epoxy in an amount of greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. %, greater than <NUM> wt. % based on the total dry weight of the PSA.

In some embodiments, the PSA comprises less than <NUM> wt. %, e.g., less than <NUM> wt. %, less than <NUM> wt. %, less than. %, or less than <NUM> wt. % rosin resin, aziridine, or epoxy or combinations thereof. As noted above, the reduction of rosin resin in the PSA reduces/eliminattes problems associated hardening of the PSA, which impair the ability of attaching to the substrate under ultra-low temperature and the poor resistance to warm water bath.

As noted above, the combination of the unique polyacrylate base polymer, polyacrylate tackifier, and/or metal chelating crosslinkers, as described above, provides for the surprising results that the PSA is able to remain attached to substrate under ultra-low temperatures (-<NUM> or lower) and/or when the PSA is in contact with water, e.g., submerged in a water bath of a temperature range of <NUM> to <NUM>, e.g., <NUM>.

In some specific cases, the glass transition temperature of the polyacrylate base polymer may range from -<NUM> to -<NUM>, and the molecular weight of the polyacrylate base polymer may range from <NUM>,<NUM>/mol to <NUM>,<NUM>/mol. The polyacrylate base polymer may be present in an amount ranging from <NUM> wt. % to <NUM> wt. %, based on the total solid weight of the pressure sensitive adhesive.

In another embodiment, the glass transition temperature of the polyacrylate tackifier ranges from -<NUM> to <NUM> and the molecular weight of the polyacrylate tackifier ranges from <NUM>,<NUM>/mol to <NUM>,<NUM>/mol (e.g., <NUM>,<NUM>/mol to <NUM>,<NUM>/mol); and the polyacrylate tackifier may be present in an amount ranging from <NUM> wt. % to <NUM> wt. % based on the solid weight of the pressure sensitive adhesive; the metal chelating crosslinker may be present in an amount ranging from <NUM> wt. % to <NUM> wt.

The PSA having the aforementioned ingredients shows optimal tack and shear. In some embodiments, the PSA demonstrates a peel strength of at least <NUM> N/mm (<NUM> N/inch) to <NUM> N/mm (<NUM> N/inch) on polyvinyl chloride, measured after the PSA has been attached to the polyvinyl chloride plate for <NUM> minute according to FINAT-<NUM> (<NUM>), and a static shear on stainless steel of <NUM>,<NUM> minutes to <NUM>,<NUM> minutes, as measured by FINAT-<NUM> (<NUM>) under ambient temperatures.

The PSA is capable of remaining attached to a substrate when the pressure sensitive adhesive has been in exposed to water for a period of <NUM> hour to <NUM> day, e. g, <NUM> hour to <NUM> hours, <NUM> hour to <NUM> hours.

In some embodiments, the PSA has a number of features, which, in combination, contribute to the excellent ultra-low temperature performance and water resistance: the glass transition temperature of the polyacrylate base polymer ranges from -<NUM> to -<NUM>; the molecular weight of the polyacrylate base polymer ranges from <NUM>,<NUM>/mol to <NUM>,<NUM>,<NUM>/mol (e.g., from to <NUM>,<NUM>/mol to <NUM>,<NUM>,<NUM>/mol); the polyacrylate base polymer is present in an amount ranging from <NUM> wt. % to <NUM> wt. %, based on the total solid weight of the pressure sensitive adhesive; the glass transition temperature of the polyacrylate tackifier ranges from -<NUM> to -<NUM>; the molecular weight of the polyacrylate tackifier ranges from <NUM>,<NUM>/mol to <NUM>,<NUM>/mol; the polyacrylate tackifier is present in an amount ranging from <NUM> wt. % to <NUM> wt. % based on the solid weight of the pressure sensitive adhesive; and the metal chelating crosslinker is present in an amount of <NUM> wt. % to <NUM> wt.

In some embodiments, the glass transition temperature of the polyacrylate base polymer ranges from -<NUM> to -<NUM>; the molecular weight of the polyacrylate base polymer ranges from <NUM>,<NUM>/mol to <NUM>,<NUM>/mol; the polyacrylate base polymer is present in an amount ranging from <NUM> wt. % to <NUM> wt. %, based on the total solid weight of the pressure sensitive adhesive; the glass transition temperature of the polyacrylate tackifier ranges from -<NUM> to -<NUM> and the molecular weight of the polyacrylate tackifier ranges from <NUM>,<NUM>/mol to <NUM>,<NUM>/mol; the polyacrylate tackifier is present in an amount ranging from <NUM> wt. % to <NUM> wt. % based on the solid weight of the pressure sensitive adhesive; the metal chelating crosslinker is present in an amount ranging from <NUM> wt. % to <NUM> wt. %; and the pressure sensitive adhesive demonstrates a peel strength of at least <NUM> N/mm (<NUM> N/inch) to <NUM> N/mm (<NUM> N/inch) on polyvinyl chloride, as measured by FINAT-<NUM> (<NUM>) and a static shear on stainless steel greater than <NUM> minutes (e.g., greater than <NUM>,<NUM> minutes), as measured by FINAT-<NUM> (<NUM>).

In some embodiments, the glass transition temperature of the polyacrylate base polymer ranges from -<NUM> to -<NUM>; the molecular weight of the polyacrylate base polymer ranges from <NUM>,<NUM>/mol to <NUM>,<NUM>/mol; the polyacrylate base polymer is present in an amount ranging from <NUM> wt. % to <NUM> wt. %, based on the total solid weight of the pressure sensitive adhesive; the glass transition temperature of the polyacrylate tackifier ranges from -<NUM> to -<NUM>; the molecular weight of the polyacrylate tackifier ranges from <NUM>,<NUM>/mol to <NUM>,<NUM>/mol (e.g., <NUM>,<NUM>/mol to <NUM>,<NUM>/mol); the polyacrylate tackifier is present in an amount ranging from <NUM> wt. % to <NUM> wt. % based on the solid weight of the pressure sensitive adhesive; the metal chelating crosslinker is present in an amount ranging from <NUM> wt. % to <NUM> wt. %; and the pressure sensitive adhesive demonstrates a peel strength of at least <NUM> N/mm (<NUM> N/inch) to <NUM> N/mm (<NUM> N/inch) on polyvinyl chloride, as measured by FINAT-<NUM> (<NUM>), and a static shear on stainless steel greater than <NUM>,<NUM> minutes, as measured by FINAT-<NUM> (<NUM>); the pressure sensitive adhesive is capable of remaining attached to a substrate when the pressure sensitive adhesive has been subjected to a temperature ranging from -<NUM> to <NUM> for a period of <NUM> hour to <NUM> years; and the pressure sensitive adhesive is capable of remaining attached to a substrate when the pressure sensitive adhesive has been in contact with water for a period of <NUM> hour to <NUM> week.

The disclosure also provides a laminate composition that comprises any of the PSAs disclosed above. The laminate composition may comprise a facestock layer and an adhesive layer comprising the PSA as disclosed herein. In some cases, the laminate composition further comprises a topcoat layer disposed on the top of the facestock layer. In some cases, the laminate composition further comprises one or more primer layers and/or a liner, as further described below. The disclosure also contemplates labels that comprise the laminate compositions.

The laminate composition may have one or more facestock layers. In one embodiment, from the perspective of looking downward to the substrate, the facestock layer is on the top surface of the label, exposed to the environment and is configured to receive printable information, such as barcode or alphanumeric characters.

In some embodiments, the pressure sensitive adhesive is disposed in the form of a flat layer (optionally as a layer in the laminate composition). The flat layer has a thickness (wherein <NUM> microns = <NUM>) in the range of <NUM>-<NUM> microns, e.g., from <NUM> to <NUM> microns, from <NUM> to <NUM> microns, from <NUM>-<NUM> microns, from <NUM>-<NUM> microns, or from <NUM> to <NUM> microns, or other ranges in the foregoing amounts. In terms of lower limits, the PSA layer may have a thickness of at least <NUM> micron, e.g., at least <NUM> microns, at least <NUM> microns, or at least <NUM> micros. In terms of upper limits, the polyolefin films may have a thickness less than <NUM> microns, e.g., less than <NUM> microns, less than <NUM> microns, or less than <NUM> microns.

The facestock layer can include, for example, glassine, kraft, and polyesters, such as polyethylene terephthalate (PET), polyamides (PA), polyethylene naphthalate (PEN), cotton, tissue, paper, fiberglass, synthetic textiles, and polyolefins, such as polypropylene (PP), Polyvinyl chloride (PVC),ethylene-propylene copolymers, polyethylene (PE), and combinations thereof. Other polymeric film materials include urethane based polymers such as polyether urethane and polyester urethane; amide based polymers including polyether polyamide copolymers; acrylic based polymers including a polyacrylate, and ethylene/vinyl acetate copolymer; polyester based polymers including a polyether polyester; a vinyl chloride; a vinylidene chloride; a polystyrene; a polyacrylonitrile; a polycarbonate; a polyimide; ABS; polyacrylate; polycarbonate (PC); polyamide; polyimide (PI); polyamidoimide; polyacetal; polyphenylene oxide (PPO); polysulfone, polyethersulfone (PES); polyphenylene sulfide; polyether ether ketone (PEEK); polyetherimide (PEl); metallized polyethylene terephthalate (PET); polyvinyl fluoride (PVF); polyethylene ether (PEE); fluorinated ethylene propylene (FEP); polyurethane (PUR); liquid crystal polymers (LCPs, class of aromatic polyester); polyvinylidene fluoride (PVDF); aramid fibers; DIALAMY, (polymer alloys); polyethylene naphthalate (PEN); ethylene/tetrafluoroethylene; (E/TFE); polyphenyl sulfone (PPSU); and polymers or polymer alloys containing one or more of these materials.

The thickness or coating weight of the facestock layer may vary depending on the stiffness of the label desired for particular applications. The facestock layer according to certain embodiments of the present invention may comprise a thickness (wherein <NUM> microns = <NUM>) ranging from <NUM> microns to <NUM>,<NUM> microns, e.g., from <NUM> microns to <NUM> microns, from <NUM> microns to <NUM> microns, from <NUM> microns -<NUM> microns, or from <NUM> microns to <NUM> microns, or other ranges in the foregoing amounts. In terms of lower limits, the facestock layer may have a thickness of at least <NUM> microns, e.g., at least <NUM> microns, at least <NUM> microns, or at least <NUM> microns. In terms of upper limits, the polyolefin films may have a thickness less than <NUM> microns, e.g., less than <NUM> microns, less than <NUM> microns, less than <NUM> microns, or less than <NUM> microns. In some embodiments, the facestock layer is <NUM> microns.

In some embodiments, the laminate composition comprises a topcoat layer disposed on the top of the facestock layer. The topcoat may enhance printing performance, durability and/or chemical resistance. In one embodiment, the topcoat layer of the label typically comprises a resin. Non-limiting examples of the resins that are suitable for use as topcoat include polyester-amino resin and a phenoxy resin, polyester-isocyanate, polyurethane, and polyacrylate. In some embodiments, the topcoat may possess one or more additional properties such as UV-resistance and anti-scratch property.

In some embodiments, the topcoat layer may also be configured to be receptive to printing. For example, the topcoat layer may comprise one or more printable layers containing an ink-receptive composition that is utilized to form the printable information. A variety of such compositions are known in the art, and these compositions generally include a binder and a pigment, such as silica or talc, dispersed in the binder. Optionally, the printable layer comprises a crosslinker CX-<NUM> (DSM's polyfunctional aziridine liquid crosslinker). A number of such ink-receptive compositions are described in <CIT>. Printable information can be deposited on the facestock layer using various printing techniques, such as screen printing, dot-matrix, ink jet, laser printing, laser marking, thermal transfer, and so on. In some cases, the facestock layer is receptive to thermal transfer printing.

The inks used for printing on the topcoat layer may vary widely and may include commercially available water-based, solvent-based or radiation-curable inks. Examples of these inks include Sun Sheen (a product of Sun Chemical identified as an alcohol dilutable polyamide ink), SUNTEX® MP (a product of Sun Chemical identified as a solvent-based ink formulated for surface printing acrylic coated substrates, PVDC coated substrates and polyolefin films), X-Cel (a product of Water Ink Technologies identified as a water-based film ink for printing film substrates), Uvilith AR-<NUM> Rubine Red (a product of Daw Ink identified as a UV ink) and CLA91598F (a product of Sun Chemical identified as a multibond black solvent-based ink).

In some cases, the printable layer may be a layer that utilizes activatable inks, e.g., stimulus-activatable inks, such as (for example) laser-activated, pressure-activated, or temperature-activated inks.

The topcoat layer, in accordance with certain embodiments of the present invention, may be applied onto the facestock portion of the facestock layer by any known techniques in the art, such as spray, roll, brush, or other techniques. The printable layer can be formed by depositing, by gravure printing or the like, on the topcoat layer, with the bottom surface in contact with the top surface of the topcoat layer.

In some cases, the PSAs, facestock layer, topcoat layer, or primer layer may optionally include one or more fillers, antioxidants, UV-absorbers, photo-stabilizers, and/or fillers. These additives may be incorporated into the adhesive in conventional quantities using conventional equipment and techniques. For example, representative fillers can include tale, calcium carbonate, organo-clay, glass fibers, marble dust, cement dust, feldspar, silica or glass, fumed silica, silicates, alumina, various phosphorus compounds, ammonium bromide, titanium dioxide, antimony trioxide, antimony trioxide, zinc oxide, zinc borate, barium sulfate, silicones, aluminum silicate, calcium silicate, glass microspheres, chalk, mica, clays, wollastonite, ammonium octamolybdate, intumescent compounds and mixtures of two or more of these materials. The fillers may also carry or contain various surface coatings or treatments, such as silanes, fatty acids, and the like. Still other fillers can include flame-retardant agents, such as the halogenated organic compounds. In certain embodiments, the topcoat layer may include one or more thermoplastic elastomers that are compatible with the other constituents of the layer, such as etherified melamine, hydroxylated polyester, polyester-melamine, and other suitable elastomers.

Optionally, the label disclosed herein comprises one or more primer layers and the one or more primer layers may be situated between the facestock layer and the adhesive layer.

In some embodiments, the label further includes a liner deposited on the opposite side of the surface of the reactive adhesive layer that contacts the facestock layer. A releasable liner can be positioned adjacent to the reactive adhesive layer such that the reactive adhesive layer is disposed, or sandwiched, directly or indirectly between the bottom surface of facestock layer and the releasable liner. The releasable liner may function as a protective cover such that the release liner remains in place until the label is ready for attachment to an object. If a liner or release liner is included in the label, a wide array of materials and configurations can be used for the liner. In many embodiments, the liner is a paper or paper-based material. In many other embodiments, the liner is a polymeric film of one or more polymeric materials. Typically, at least one face of the liner is coated with a release material such as a silicone or silicone-based material. As will be appreciated, the release material-coated face of the liner is placed in contact with the otherwise exposed face of the adhesive layer. Prior to application of the label to a surface of interest, the liner is removed to thereby expose the adhesive face of the label. The liner can be in the form of a single sheet. Alternatively, the liner can be in the form of multiple sections or panels.

The liner used in the label may have a thickness (wherein <NUM> microns = <NUM>) ranging from <NUM> microns to <NUM> microns, e.g., from <NUM> microns to <NUM> microns, from <NUM> microns to <NUM> microns, or from <NUM> microns to <NUM> microns. In terms of upper limits, the thickness of the label is less than <NUM> micron, e.g., less than <NUM> microns, or less than <NUM> microns. In terms of lower limits, the thickness of the label is greater than <NUM> microns, e.g., greater than <NUM> microns, or greater than <NUM> microns.

Various additives can also be added to one or more of the facestock layer, the primer layer, the adhesive layer, or liner layers to obtain a certain desired characteristic. These additives can include, for example, one or more waxes, surfactants, talc, powdered silicates, filler agents, defoamers, colorants, antioxidants, UV stabilizers, luminescents, crosslinkers, buffer agents, anti-blocking agents, wetting agents, matting agents, antistatic agents, acid scavengers, flame retardants, processing aids, extrusion aids, and others.

The PSA of the disclosure demonstrates good mechanical performance, for example, a high peel strength, indicating that it has excellent tack. Peel strength is the average force required to remove an adhesive laminated under specified conditions on a substrate, from the substrate at constant speed and at a specified angle. Peel strength can be assessed using methods well known in the art. In some embodiments, peel strength evaluations are performed according to the FINAT Test Method <NUM> (<NUM>) ("FINAT-<NUM>"). The specimen comprising the PSA to be tested are prepared by cutting into strips of dimensions suitable for testing. For example, the strips may has a width of <NUM> and a length of <NUM>. The backing material, if present, is removed before adhering the strips to a clean test plate using a roller. Typically at least three strips from each sample are tested <NUM> minutes after the PSA has been attached to the plate or <NUM> hours after the PSA has been attached. In some embodiments, the test plate is positioned relative to the measuring device in a way such that the angle of peel is <NUM>. The test plate can be of any material suitable for evaluating peel strength of the PSA. In some embodiments, the test plate comprises polyvinyl chloride. The peeling force is recorded when the strips are peeled off the test plate at a predetermined speed, e.g., <NUM> per minute. Typically, a minimum of five readings at <NUM> intervals from the center section of each of the strips are recorded.

In some cases, when the PSA has been attached to the polyvinyl chloride test plate for <NUM> minutes, the PSA may demonstrate a peel strength (wherein <NUM> N/in = <NUM> N/cm) from <NUM> N/inch to <NUM> N/inch on according to the FINAT-<NUM> (<NUM>), e.g., from <NUM> N/inch to <NUM> N/inch, from <NUM> N/inch to <NUM> N/inch, from <NUM> N/inch to <NUM> N/inch, e.g., about <NUM> N/inch. In terms of upper limits, the PSA demonstrated a peel strength of less than <NUM> N/inch, less than <NUM> N/inch, less than <NUM> N/inch, or less than <NUM> N/inch on stainless steel substrate. In terms of lower limits, the PSA demonstrated peel strength of greater than <NUM> N/inch, greater than <NUM> N/inch, greater than <NUM> N/inch, or greater than <NUM> N/inch.

The PSA of this disclosure also shows high static shear, indicating excellent cohesiveness. Static shear can be tested using methods well known in the art. The test specimen comprising the PSA is centered on test panel, and is applied without added pressure to cover an area on the test panel, e.g., an area of <NUM> x <NUM>. The test panel can be produced from any material suitable for the static shear testing. In one embodiment, the test panel is a stainless steel panel. Typically, the test specimen is adhered to the steel panel at ambient temperature for one day before a load of <NUM> is applied to the specimen. The weight of the load will gradually pull the specimen off the test panel. The duration of specimen while it remains on the test panel can be recorded. The longer the time the specimen remains on the panel, the greater the static shear the specimen possesses.

In some cases, the PSA demonstrates a static shear that ranges from <NUM>,<NUM> minutes to <NUM>,<NUM> minutes, e.g., from <NUM>,<NUM> minutes to <NUM>,<NUM> minutes, from <NUM>,<NUM> minutes to <NUM>,<NUM> minutes, or from <NUM>,<NUM> minutes to <NUM>,<NUM> minutes, or about <NUM>,<NUM> minutes, when tested on stainless steel under the ambient temperature. In terms of lower limits, the static shear is greater than <NUM>,<NUM> minutes, greater than <NUM>,<NUM> minutes, greater than <NUM>,<NUM> minutes, or greater than <NUM>,<NUM> minutes. In terms of upper limits, the static shear is lower than <NUM>,<NUM> minutes, lower than <NUM>,<NUM> minutes, or lower than <NUM>,<NUM> minutes. In some cases, using a polyacrylate tackifier as opposed to using a non-polyacrylate tackifer can increase cohesiveness as reflected in that static shear measured using FINAT-<NUM> (<NUM>) of the PSA having polyacrylate tackifier is at least 2x, at least 5x, at least 10x, at least 100x higher than that of the PSA having non-polyacrylate tackifier.

As noted above, without being limited to a particular theory, it is believed that using polyacrylate polymers as tackifiers in the PSA can significantly increase both the tack and cohesiveness of the PSA. In some cases the molecular weight of polyacrylate tackifiers is much higher than that of the traditional tackifiers. The polyacrylate tackifier itself can also be used as adhesive, thus using the acrylate as tackifier can minimize the negative impact on the cohesiveness of the PSA and increase the PSA's static shear and resistance to water. In some embodiments, as shown in Example <NUM>, using a polyacrylate tackifier as opposed to using a non-polyacrylate tackifer, such as rosin, can increase tack by <NUM>% to <NUM>%, when other components of the PSA are the same. In some embodiments, the increase of tack is between <NUM>% to <NUM>%, e.g., between <NUM>% to <NUM>%, or about <NUM>%. In terms of upper limits, the increase is less than <NUM>%, e.g., less than <NUM>%, or less than <NUM>%. In terms of lower limits, the increase is greater than <NUM>%, greater than <NUM>%, or greater than <NUM>%.

In some embodiments, the pressure sensitive adhesive of the invention, having the unique combination of a polyacrylate base polymer, a polyacrylate tackifier, and/or a metal chelating crosslinker above, is capable of remaining attached to a substrate when the PSA has been in contact in water for a period of <NUM> hour to <NUM> week, e.g., <NUM> hour to <NUM> hours, <NUM> hour to <NUM> hours, e.g. about <NUM> hours. In some embodiments, the water is at a temperature of <NUM> to <NUM>, for example, about <NUM>. In some embodiments, the PSA is able to remain attached to the substrate under a temperature of -<NUM> or lower. In some embodiments, the PSA is capable of remaining attached to a substrate when the PSA has been subjected to a temperature ranging from -<NUM> to -<NUM>, e.g., from -<NUM> to -<NUM>, or from -<NUM> to -<NUM>.

This disclosure also provides an adhesive solution which comprises a solvent, a polyacrylate base polymer (typically in solution form, e.g., a polyacryate base polymer <NUM>-<NUM> may comprise <NUM> wt. % of solid content), a polyacrylate tackifier (also typically in solution form, e.g., a polyacrylate tackifier 247A may comprise <NUM> wt. % of solid content), a metal chelating crosslinker as disclosed above. The glass transition temperature of the polyacrylate base polymer is lower than the glass transition temperature of the polyacrylate tackifier. Both the glass transition temperature of the polyacrylate tackifier and the glass transition temperature of the polyacrylate base polymer are lower than <NUM>.

The solvent that can be used to produce the PSA disclosed herein may be one or more solvents selected from the group consisting of toluene, ethyl acetate, isopropanol, xylene, n-hexane, n-heptane, methyl cyclohexane, butyl acetate, acetone, butanone, and <NUM>-Acetoxy-<NUM>-methoxypropane.

In some embodiments, the polyacrylate base polymer solution comprises from <NUM> wt. % to <NUM> wt. %, e.g., <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, or about <NUM> wt. % of solid content of polyacrylate base polymer. In terms of upper limits, the polyacrylate base polymer solution comprises less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, or less than <NUM> wt. % of the solid content of polyacrylate base polymer. In terms of lower limits, the polyacrylate base polymer solution comprises greater than <NUM> wt. %, e.g., greater than <NUM> wt. %, or greater than <NUM> wt. % of solid content of polyacrylate base polymer. In some embodiments the polyacrylate base polymer solution is present in the PSA solution in an amount ranging from <NUM> wt. % to <NUM> wt. %, e.g., from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, e.g., about <NUM> wt. %, based on the total weight of the pressure sensitive adhesive solution. In terms of upper limits, the PSA solution comprises polyacrylate base polymer solution in an amount of less than <NUM> wt. %, less than <NUM> wt. %, based on the total weight of the PSA solution. In terms of lower limits, the PSA solution comprises polyacrylate base polymer solution in an amount of greater than <NUM> wt. %, e.g., greater than <NUM> wt. %, based on the total weight of the PSA solution. In some embodiments, the polyacrylate base polymer solution is <NUM>-<NUM>, which comprises <NUM> wt. % solid content of <NUM>-<NUM> (TaiZhou Yade Adhesive company, Taizhou, P.

In some embodiments, the polyacrylate tackifier solution comprises from <NUM> wt. % to <NUM> wt. %, e.g., from <NUM> wt. % to <NUM> wt. %, or about <NUM> wt. % of solid content. The polyacrylate tackifier solution may be present in an amount ranging from <NUM> wt. % to <NUM> wt. %, e.g., from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, e.g., about <NUM> wt. %, based on the total weight of the pressure sensitive adhesive solution. In terms of upper limits, the PSA solution comprises polyacrylate tackifier solution in an amount of less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, based on the total weight of the PSA solution. In terms of lower limits, the PSA solution comprises polyacrylate tackifier solution in an amount of greater than <NUM> wt. %, e.g., greater than <NUM> wt. %, based on the total weight of the PSA solution. In some embodiments, the polyacrylate tackifier solution is 247A from Henkel (Diisseldorf, Germany), which comprises <NUM> wt. % solid content.

The amount of solvent(s) used for producing the adhesive solution may vary depending on the desired viscosity that is suitable for coating on the substrate or other layers. Typically, the solvent is present in the adhesive solution in an amount ranging from <NUM> wt. % to <NUM> wt. %, e.g., <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, from <NUM> wt. % to <NUM> wt. %, e.g., about <NUM> wt. In terms of lower limits, the solvent is present in an amount of greater than <NUM> wt. %, e.g., greater than <NUM> wt. %, greater than <NUM> wt. %, or greater than <NUM> wt. %, or greater than <NUM> wt. %, based on the total weight of the adhesive solution. In terms of upper limits, the solvent is present in an amount of less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, less than <NUM> wt. %, or less than <NUM> wt. %, based on the total weight of the adhesive solution.

The present invention also relates to methods of producing a PSA. The methods include dissolving in a solvent, a polyacrylate base polymer, a polyacrylate tackifier, a metal chelating crosslinker to form an adhesive solution. Any of the aforementioned embodiments of the polyacrylate base polymer, a polyacrylate tackifier, the metal chelating cross-linker can be used to produce an adhesive solution. An exemplary PSA solution is prepared using components shown in Table <NUM>. This process is commonly referred to as compounding. The compounding can occur under a temperature less than <NUM>, e.g., between <NUM> and <NUM>, or between <NUM> and <NUM>.

A variety of solvents can be used to dissolve the components of the PSA. Suitable solvents include those that demonstrate proper evaporation rate and in which the various components show good solubility. In preferred embodiments, the solvent is a petroleum-based solvent. Suitable solvents include but are not limited to, aromatic solvents, aliphatic solvents, ester solvents, xylene, ethyl benzene, isopropyl alcohol, and combinations thereof. Examples of aromatic solvents include aromatic rings with alkyl substitution (e.g. toluene). Examples of ester solvents include esters of <NUM> or more carbon atoms (e.g. methyl acetate, or ethyl acetate). In some embodiments, two or more solvents can be used to dissolve various components above to produce the adhesive solution.

The adhesive solution, as prepared above, has good coatability with a typical viscosity (<NUM> cps = <NUM> mPA. s) from <NUM> to <NUM>,<NUM> cps, e.g., from <NUM> to <NUM>,<NUM> cps, from <NUM> to <NUM>,<NUM> cps, from <NUM> to <NUM>,<NUM> cps, from <NUM> to <NUM> cps, or about <NUM> cps. In terms of lower limits, the viscosity is greater than <NUM>, e.g., greater than <NUM> cps, greater than <NUM> cps, or greater than <NUM> cps. In terms of upper limits, the viscosity is less than <NUM>,<NUM>, less than <NUM>,<NUM> cps, less than <NUM>,<NUM> cps, less than <NUM>,<NUM> cps. Methods for measuring viscosity are well known, for example using the Brookfield Viscometer method, testing the flow resistance of the fluid by low and medium rate rotation.

The adhesive solution can be coated to a facestock using methods that are well known for solvent based adhesives, for example, as disclosed in Manufacturing Pressure-Sensitive Adhesive Products: A Coating and Laminating Process, available at adhesivesmag. com/articles/<NUM>-manufacturing-pressure-sensitive-adhesive-products-a-coating-and-laminating-process.

In some embodiments, the coating is performed by direct coating, in which the pressure-sensitive adhesive is coated directly onto the facestock or backing material and dried to produce a label. In some embodiments, the coating is performed by transfer coating, in which the adhesive is first coated onto a release liner (as described above), and dried. The dried adhesive/liner is then laminated with a facestock.

In some embodiments, the adhesive solution as produced above can then be coated onto a facestock or a release liner using a solvent coater by knife over roll, slot die, or comma coating. The solution may be coated to form an adhesive layer having a coat weight of at least <NUM> grams per square meter (gsm), e.g., at least <NUM> gsm or at least <NUM> gsm. In terms of upper limits, the solution may be coated to form an adhesive layer having a coat weight of <NUM> gsm or less, e.g., <NUM> gsm or less, or <NUM> gsm or less. In terms of ranges, the solution may be coated to form an adhesive layer having a coat weight from <NUM> gsm to <NUM> gsm, e.g., from <NUM> gsm to <NUM> gsm or from <NUM> gsm to <NUM> gsm, depending on the end use of the adhesive layer. The facestock/liner coated with the solution above then can be dried as further described below and processed into labels. In some cases, it is used as a transfer adhesive without being associated with a facestock.

The coating process is typically performed in an oven having multiple temperature zones, e.g., at least <NUM> zones, at least <NUM> zones, at least four zones, at least five zones, or at least six zones. The temperature zones may range from <NUM> to <NUM>, e.g., from <NUM> to <NUM> or from <NUM> to <NUM>. The temperature may increase from the first to last zone, though multiple zones may be at the same temperature.

Once coated, the adhesive may be dried in an oven, for a predetermined drying time. The drying oven can have a temperature of greater than <NUM>. The rate of solvent evaporation increases with temperature. The drying time can be at least <NUM> minutes, at least <NUM> minutes, at least <NUM> minutes, at least <NUM> minutes, at least <NUM> minutes, at least <NUM> minutes, at least <NUM> minutes, at least <NUM> minutes, at least <NUM> minutes, at least <NUM> minutes, at least <NUM> minutes, or at least <NUM> hour.

The present invention also relates to methods of applying a label comprising the PSA to an article (also referred to as a substrate). The present invention also provides labeled articles. The methods include providing an article defining an outer surface, and a label in accordance with an embodiment. The methods further include affixing the label to the outer surface of the article, thereby applying the label to the article.

The labels can be affixed to the articles in a batch, continuous, or semi-continuous fashion. Prior to application, one or more liners can be removed from the labels to thereby expose the adhesive face of the labels. The adhesive face and label is then contacted with the container(s) or article(s) and the labels applied thereto. Adhering may also include one or more operations of pressing or otherwise applying a pressing force against the label to promote contact and/or adhesion with the container; activating and/or curing of the adhesive such as by heating and/or exposure to UV light; and/or drying operations.

In some embodiments, the article to be labeled is an article that has a temperature of -<NUM> or lower. In some embodiments, the article is one that, after being labeled with the PSA in this invention, is to be placed in warm water bath having a temperature of <NUM> to <NUM>, for example, about <NUM>. In some embodiments, the article is a blood package. In some embodiments, the label is affixed to e.g., the surface of the blood package. In some embodiments, the label is attached to the tubings attached to the blood product package.

Typically, when in storage, the solution containing the polyacrylate base polymer, optionally also the polyacrylate tackifier, is kept separate from the metal chelating crosslinkers to prevent undesired crosslinking. The crosslinkers can be added to the solution containing the polyacrylate base polymer immediately prior to the producing of the adhesive and/or the labels. Thus, also provided is an adhesive system comprising: a) a polycrylate base polymer; b) a metal crosslinker; the crosslinker is separate from the polyacrylate base polymer.

The materials in the adhesive system may be present in the amounts such that the PSAs produced have the properties described in this disclosure.

This invention is illustrated by the appended claims <NUM> to <NUM>.

The following examples are offered to illustrate, but not to limit the claimed invention.

Three exemplary PSA solutions having the ingredients as listed in Table <NUM> were prepared. The values in Table <NUM> represent the weight percentages of the individual components based on the total weight of the PSA solution. The numbers in parentheses in the first column represent the percentages of the solid content in each component, which can be used to calculate the solid weight percentages of the components based on the solid weight of the PSA.

Each of the PSA solutions was coated on a liner to dry. After drying, the liner/PSA is laminated with a facestock layer to form a laminate comprising the liner, the PSA, and the facestock, with the PSA being coated with the liner on one surface and with the facestock layer on the opposite surface (i.e., a laminate of liner/PSA adhesive/facestock).

The peel strength and static shear of the laminate comprising the PSA, the ability to adhere to blood packaged under ultra-low temperature, and the resistance of the PSA to warm water bath were tested according to methods as described below.

To test peel strength, the laminate comprising the PSA was cut into strips of <NUM> wide by <NUM> long. The release liners were peeled off the strips. The strips were bonded to the test plate by a single back-and-forth pass with a <NUM> roller. Twenty minutes after attachment, the peel strength (N/-<NUM> wide) was measured following FINAT-<NUM> test protocol at ambient temperature and a relative humidity of <NUM>%. The measurements were obtained by using a tensile strength testing machine at a pull rate of <NUM>/min and a pull angle of <NUM>. The peel force at a minimum of five readings at <NUM> intervals from the center of the each strip was recorded. The average of the five readings were reported as the peel strength for the PSA.

The static shear of the examples was evaluated as follows.

Resistance to warm water bath is performed by submerging the labeled blood packages in <NUM> water bath for <NUM> hours At the end of the <NUM>-minute period, the blood packages were retrieved from the water bath and the labels thereon were inspected. If the label did not come off or lift off, the PSA was determined to be resistant to warm water bath (or performed well when in contact with warm water bath) and accorded a status of "pass".

The ability to label at ultra-low temperatures was tested on blood packages that has been stored in -<NUM> C for at least one day. In one set of experiments, the blood packages were taken out, the frozen icy layer was first wiped off the surface, and the label comprising the PSA was applied to the surface of the blood package. In another set of experiments, the blood packages were taken out, without wiping, the label comprising the PSA was applied directly to the surface of the blood packages. In either set of experiments, if the labels did not come off or move relative to the blood package, the label is accorded a status of "pass".

The results for peel strength and shear were obtained from tests performed according to FINAT-<NUM> (<NUM>) and FINAT-<NUM> (<NUM>), respectively. "Pass" for labeling of the blood package under - <NUM> means the label did not lift off the package or slipped while labeling. "Pass" for the <NUM> water bath, means that the label fixed onto blood bag did not come off or lift off, the label affixed to tubings on the blood packages do not stretch out or come off.

The results (see Table <NUM>) show that the PSA of Examples <NUM>-<NUM> comprising 247A, BM-<NUM>, and a combination of BM-<NUM> and polyacrylate tackifer Neocryl® B-<NUM> as tackifiers, showed excellent performance in both labeling the surface of substrate under ultra-low temperatures, e.g., -<NUM> or less, as well as in <NUM> water bath. 247A, BM-<NUM>, and Neocryl® B-<NUM> are all polycrylate tackifiers, with glass transition temperatures being -<NUM>, <NUM>, and <NUM>, respectively. The PSA additionally showed a peel on PVC of <NUM> N/inch after a <NUM>-minute attachment to the polyvinyl chloride test plate and a shear on stainless steel of greater than <NUM> on stainless steel at ambient temperature. The Comparative examples showed lower peel values and "no pass" for the water bath test. This indicates that having a polyacrylate as the tackifier in the PSA greatly increases the tack and the cohesiveness when the PSA is under ultra-low temperatures or in contact with water. These advantageous properties allow the use of the PSA in labeling articles (e.g., blood packages) which are used under both ultra-low temperatures and warm water bath, under which conditions conventional PSAs often fail to deliver good results.

Two additional comparative examples, Comp. C and Comp. D, were prepared from ingredients listed in Table <NUM> as described in Procedure II. The values in Table <NUM> represent the weight percentages of the individual components based on the total weight of the PSA solution. The numbers in parentheses in the first column represent the solid content in each component. Each of the PSA solutions was coated on a liner to dry. After dying, the liner was peeled off, and the dry PSA was transferred to a facestock to form a laminate. The peel strength and static shear of the laminate comprising the PSA, the ability to adhere to blood packaged under ultra-low temperature, and the resistance of the PSA to warm water bath was tested according to methods as described above. The results are shown in Table <NUM>.

Claim 1:
A pressure sensitive adhesive comprising:
a polyacrylate base polymer having a glass transition temperature,
a polyacrylate tackifier having a glass transition temperature, and
a metal chelating crosslinker,
wherein both the glass transition temperature of the polyacrylate tackifier and the glass transition temperature of the polyacrylate base polymer are lower than <NUM>, and
wherein the glass transition temperature of the polyacrylate base polymer is lower than the glass transition temperature of the polyacrylate tackifier,
wherein the glass transition temperature of the polyacrylate base polymer ranges from -<NUM> to -<NUM> and wherein the glass transition temperature of the polyacrylate tackifier is greater than -<NUM>.