TW201837150A - Hotmelt pressure sensitive adhesive for clear on clear labels - Google Patents

Abstract

A hotmelt pressure sensitive adhesive comprising a low diblock grade SIS as base polymer, low viscosity and molecular weight hydrogenated cycloaliphatic hydrocarbon resin as tackifier, high viscosity and molecular weight paraffin oil with high molecular weight as plasticizer, and polyethylene wax. The adhesive can achieve performance characteristics that include clear on clear labeling for beverage bottles, transparency, water-whitening resistance, repositionability within the first 4 to 8 hours after label application, low swelling for film facestock, low viscosity for processibility of compounding and coating, low odor, and light color.

Description

Hot melt pressure sensitive adhesive for clear to clear labels

The present invention relates generally to compositions for pressure sensitive adhesives, and more particularly to improved adhesives that provide higher quality labels while maintaining good performance in a method that includes compounding and coating the improved adhesive Workability.

Adhesive labels and tapes are well known. In a typical label structure, one or more layers of adhesive are coated or otherwise applied to a release liner and then laminated to a face material such as paper, polymer film, or other ink-absorbing flexible material. In a typical tape structure, a polymer film or woven paper is coated with an adhesive on one surface and then is wound on itself. Adhesives used in tapes and labels include rubber-based and acrylic-based pressure-sensitive adhesives (PSA). PSA can be applied from an organic solvent, an aqueous dispersion or a hot melt to a release liner or facestock. Hot melt PSA (HMPSA) provides a convenient and economical way to label consumer and industrial goods such as glass, metal and plastic containers. HMPSAs are easy to handle in solid form, they quickly form adhesive bonds without any auxiliary processing, and they usually have a long shelf life. Moreover, because HMPSA does not contain solvents, it is generally environmentally friendly and cost effective. An example of HMPSA can be found in U.S. Patent No. 5,942,569, which describes a polymer composition in the form of a pellet comprising a viscous hot-melt composition comprising a) from about 5 to about 90% by weight of a thermoplastic polymer, b) from about 0% to about 65% by weight of a tackifying resin, c) from about 0% to about 50% by weight of a plasticizer, d) up to about 2% by weight of an antioxidant, and a granulation aid, wherein The viscous hot-melt composition has some minimum amount of tackifier or plasticizer, and is a pressure-sensitive adhesive having a storage modulus G 'of less than about 5 x 10 ⁶ dyne / cm ² at about 25 ° C. And each pellet has a substantially non-sticky surface. The disclosure further includes polymer compositions in the form of pellets suitable for use in molded articles. The composition comprises a viscous hot-melt composition comprising at least one high molecular weight triblock copolymer of the general configuration ABA and a plasticizer and a granulation aid. The granulation aid substantially surrounds the viscous composition so that the molded article is substantially free of surface tack. A method of forming pellets is also disclosed. HMPSA of U.S. Patent No. 7,595,365 discloses the use of poly-alpha-olefin oil or a combination of poly-alpha-olefin oils to modify the softening point characteristics of tackifiers. The disclosure also includes compositions containing a tackifier and a poly alpha olefin oil. U.S. Patent No. 8,076,422 discloses a hot-melt adhesive for resealable packaging comprising 30 to 90% by weight of at least one copolymer based on ethylene and / or propylene and C ₄ -C ₁₂ α-olefins, which It can be obtained by metallocene-catalyzed polymerization with a melt index of 5-100 g / 10 minutes (DIN ISO 1133). The adhesive further comprises 5-50% by weight of a tackifier resin having a softening point of 80-140 ° C, 0-15% by weight of a wax having a melting point of 120-170 ° C, and 0.1-20% by weight of additives and auxiliaries. . The viscosity of the adhesive at a temperature of 170-190 ° C is 25,000-250,000 mPas. Other HMPSA compositions are also provided by US Patent Nos. 9,242,437; US Patent Application Publication Nos. US2005 / 0013996, US2006 / 0251890, US2010 / 0193127 and US2016 / 0272856; and International Patent Application Publication Nos. WO2002 / 074837 and WO2006 / 107763. Even in light of these references, there is a need to provide high-performance HMPSA with improved performance characteristics, such as water whitening resistance, repositionability, and / or optical clarity.

In a specific embodiment, the invention relates to a hot-melt pressure-sensitive adhesive. The binder comprises a base polymer, wherein the base polymer comprises a styrene-isoprene copolymer. The base polymer preferably has a diblock fraction of less than 30% by weight. The adhesive also contains a tackifier, wherein the tackifier comprises a hydrogenated alicyclic hydrocarbon resin. Preferably, the weight average molecular weight of the tackifier is in the range of 300-800. The adhesive also contains a plasticizer, wherein the plasticizer includes a paraffin oil having a kinematic viscosity of 400-1000 mm ² / s at 40 ° C. The number average molecular weight of the preferred plasticizer is 400-1000, and the kinematic viscosity at 40 ° C is 400-700 mm ² / second. The adhesive may further include polyethylene wax. Preferably, the polyethylene wax has a dynamic viscosity at 140 ° C of 150-500 centipoise and a pour point of greater than 100 ° C. In another specific embodiment, the invention relates to a label. The label includes a facestock layer for receiving printed indicia. According to a specific embodiment, the label further includes a hot-melt pressure-sensitive adhesive layer. In another specific embodiment, the invention relates to a labeled container. Labeled containers include containers that define an outer surface. The labeled container also includes a label according to a specific embodiment adhered to the outer surface of the container. In another specific embodiment, the invention relates to a method of applying a label to a container. The method includes providing a container defining an outer surface. The method also includes providing a tag according to a specific embodiment. The method also includes adhering the label to the outer surface of the container, thereby applying the label to the container.

The present invention relates generally to hot-melt pressure-sensitive adhesives (HMPSA), which when used in label applications provide an advantageous combination of performance characteristics while maintaining good processability. For example, for adhesives exposed to moist or humid environments, it is beneficial to have a high level of water whitening resistance. This wet condition is common for adhesive labels on glass or plastic bottles used to hold beverages, personal care products or other items. It is also useful that the label is removable and / or repositionable without leaving significant adhesive residue on the bottle or other container from which the label was removed. This feature is especially important for containers to be reused or recycled. In addition, an optically clear or transparent adhesive may allow visual labeling through similarly clear or transparent containers, such as glass bottles. The ability of the adhesive to be easily processed is also a better characteristic, which allows the adhesive to better form a high-quality coating on a label or other article. However, it is difficult for HMPSA to display all of the above characteristics at the same time. One reason is that components that improve one characteristic often have an adverse effect on another. For example, the desired characteristics of low water whitening and repositionability may be associated with the use of an adhesive component having a high molecular weight and high viscosity. However, using an adhesive component having a high molecular weight and a high viscosity tends to adversely affect the ease of compounding and high-quality coating properties. The inventors have now found that a particular combination of components, optionally used in a particular amount, surprisingly provides a high performance HMPSA that exhibits highly desirable performance characteristics such as water whitening resistance, repositionability and / Or a combination of optical clarity. Advantageously, these HMPSAs also show improvements in processability during adhesive and label manufacturing and application, as well as good adhesion and label quality in end-user products. In particular, it has been found that HMPSA compositions comprising: a plasticizer comprising a paraffin oil; and a tackifier comprising a hydrogenated alicyclic hydrocarbon resin; each optionally having a molecular weight and viscosity within a specific range, Surprisingly, HMPSA is provided with a combination of the aforementioned performance characteristics. For example, adhesives can be used to produce labels with good transparency, repositionability, and resistance to whitening, oil migration, swelling, or wrinkling, while still being easy to use in standard compounding and coating applications. Without being bound by a particular theory, it is believed that paraffin oil has good compatibility with the SIS block copolymer which is the basis of HMPSA, because both the paraffin oil and the SIS block copolymer have a linear molecular structure. The internal interactions of these components of the adhesive layer can serve, for example, to limit oil migration and control swelling and wrinkling of the polymer-structured film facestock that is bonded. In addition, the low molecular weight of the hydrogenated alicyclic hydrocarbon resin relative to the linear aliphatic hydrocarbon resin can make the hydrogenated alicyclic resin increase the processability of HMPSA without adversely affecting its softening point. Since the HMPSA composition is generally hydrophobic, water whitening of the adhesive is also minimized. In a specific embodiment, HMPSA includes a base polymer, a tackifier, and a plasticizer. In some embodiments, HMPSA also includes polyethylene wax. In some embodiments, the base polymer comprises a styrene-isoprene-styrene (SIS) copolymer, the tackifier comprises a hydrogenated alicyclic hydrocarbon resin, and the plasticizer comprises a paraffin oil. In a preferred embodiment, the kinematic viscosity of the plasticizer at 400C is 400-1000mm. ² Per second. HMPSA's base polymers include SIS block copolymers, where "S" represents the polymeric segment or "block" of the styrene monomer, and "I" represents the polymeric segment or "block" of the isoprene monomer . The SIS block copolymer may be a pure triblock copolymer without SI diblock, or may contain a certain percentage of SI diblock. It has been found that higher diblock content may be related to increased viscosity of the SIS block copolymer, and lower diblock content may be related to increased elasticity of the copolymer. The diblock content of the HMPSA base polymer can be in the range of 0-50% by weight, such as 0-30% by weight, 5-35% by weight, 10-40% by weight, 15-45% by weight, or 20-50% by weight . In terms of the upper limit, the diblock content may be less than 50% by weight, such as less than 45% by weight, less than 40% by weight, less than 35% by weight, less than 30% by weight, less than 25% by weight, less than 20% by weight, and less than 15% by weight. , Less than 10% by weight or less than 5% by weight. In terms of the lower limit, the diblock content may be at least 5 wt%, at least 10 wt%, at least 15 wt%, at least 20 wt%, at least 25 wt%, at least 30 wt%, at least 35 wt%, at least 40 wt% Or at least 45% by weight. In some embodiments, the base polymer has a diblock fraction of less than 30% by weight. The styrene content of the SIS block copolymer can also affect the performance characteristics of the base polymer. It has been found that a specific styrene content and a specific diblock content can give the base polymer the desired properties of a high melt flow index (greater than 20 grams per 10 minutes at 190 ° C) and low viscosity. These properties together make the polymer more suitable for compounding and coating processes. The styrene content of the base polymer may be in the range of 0-50% by weight, such as 0-30% by weight, 5-35% by weight, 10-40% by weight, 15-45% by weight, or 20-50% by weight. In terms of the upper limit, the styrene content may be less than 50% by weight, for example, less than 45% by weight, less than 40% by weight, less than 35% by weight, less than 30% by weight, less than 25% by weight, less than 20% by weight, and less than 15% by weight. Less than 10% by weight or less than 5% by weight. In terms of the lower limit, the styrene content may be at least 5 wt%, at least 10 wt%, at least 15 wt%, at least 20 wt%, at least 25 wt%, at least 30 wt%, at least 35 wt%, at least 40 wt% or At least 45% by weight. In some embodiments, the base polymer has a styrene content of less than 25% by weight. The amount of the SIS block copolymer in the HMPSA composition may be in the range of 15-65% by weight, such as 15-45, 20-50, 25-55, 30-60, or 35-65% by weight. The amount of the SIS block copolymer in the HMPSA composition may be in the range of 30-50% by weight, such as 30-42, 32-44, 34-46, 36-48, or 38-50% by weight. In terms of upper limits, the amount of SIS block copolymer in the HMPSA composition may be less than 70, less than 65, less than 60, less than 55, less than 50, less than 45, or less than 40% by weight. In terms of a lower limit, the amount of the SIS block copolymer in the HMPSA composition may be at least 10, at least 15, at least 20, at least 25, at least 30, at least 35, or at least 40% by weight. Suitable commercially available linear SIS block copolymers include, for example, SIS 1220 available from Shandong Ju Sage Technology Company LTD. (Shandong, China); Quintac 3433 and Quintac 3421, available from Nippon Zeon Company, Ltd. (Louisville, KY) ; Vector DPX 559, Vector 4111 and Vector 4113, available from Dexco, a partnership of Exxon Chemical Co. (Houston, Texas) and Dow Chemical Co. (Midland Mich); and KRATON ™, rubber, for example from Shell Chemical Co. (Houston, Texas) Kraton 604x, Kraton D-1117, Kraton D-1107, and Kraton D-1113. In a specific embodiment, the plasticizer, such as a paraffin oil plasticizer, is a high molecular weight paraffin oil. It has been found that the use of such high molecular weight plasticizers offers many advantages for adhesives, which are not observed with conventional HMPSA compositions. For example, the resulting adhesive has improved repositioning capabilities after first application to a substrate. More specifically, in some embodiments, within the first 12 hours after the initial application (e.g., the first 11 hours, 10 hours, 9 hours, 8 hours, 7 hours, 6 hours, 5 hours, or 4 hours) (Inside) above 5 ^o At a temperature of C, the label using the adhesive can be removed substantially completely, for example, substantially completely from a substrate such as polyethylene terephthalate (PET) or a glass bottle and then applied to the substrate Examples are polyethylene terephthalate (PET) or glass bottles. FIG. 1 shows an example of such a labeled bottle 100 in which a label 101 is applied to an outer surface 102 of the bottle 100. Due to the specific HMPSA composition, this label can also be removed cleanly over a longer period of time, thereby removing the adhesive substantially completely from the outer surface of the glass or PET container. The term "substantially completely removed" is used herein to refer to at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96% at least 97%, at least 98% or At least 99% of the adhesive is held with the label and not with the outer surface of the container to which the label is applied. Another advantage of high molecular weight paraffin oil is that the adhesive can be used to make labels with greater structural integrity. For example, a label containing the HMPSA may exhibit reduced wrinkling and swelling. Reduced swelling may indicate a dimensional change of less than 5%, less than 4%, less than 3%, less than 2%, or less than 1% over a predetermined measurement period. The swelling and wrinkling measurement period can be greater than 3 days, greater than 4 days, greater than 5 days, greater than 6 days, greater than 7 days, greater than 8 days, greater than 9 days or greater than 10 days. Above 45 ° C, Above 50 ° C, Above 55 ° C, Above 60 ° C, Above 65 ^o During storage at C or above 70 ° C, reduced swelling and wrinkling can be observed. Reduced swelling and wrinkling can be observed during storage with relative humidity greater than 80%, greater than 82%, greater than 84%, greater than 86%, greater than 88%, or greater than 90%. In some embodiments, after storage at 85% relative humidity for 4 days at greater than 65 ° C or for 7 days at greater than 50 ° C, the HMPSA-containing label does not change in size or in various dimensions (e.g., machine direction) And lateral). Moreover, it was surprisingly found that these paraffin oils can improve the stability of the label, while the migration of oil within and between the layers of the label is less, and there is less adhesive leakage beyond the original occupied area of the bonded label. These improvements not only increase the effectiveness of the label in attaching items and anchoring and retaining printed instructions, but also increase the visual presentation of the label from the perspective of the end user. Because labels are often used to present important information or to increase the visibility or appeal of consumer products, these improvements can significantly increase the value of labels. The amount of the paraffin oil plasticizer in the HMPSA composition may be in the range of 5-35 wt%, such as 5-23, 8-26, 11-29, 14-32, or 17-35 wt%. The amount of the paraffin oil plasticizer in the HMPSA composition may be in the range of 14-26% by weight, such as 14-21.2, 15.2-22.4, 16.2-23.6, 17.6-24.8, or 18.8-26% by weight. In terms of upper limits, the amount of paraffin oil plasticizer in the HMPSA composition may be less than 38, less than 35, less than 32, less than 29, less than 26, less than 23, or less than 20% by weight. In terms of a lower limit, the amount of the paraffin oil plasticizer in the HMPSA composition may be at least 2, at least 5, at least 8, at least 11, at least 14, at least 17, or at least 20% by weight. Paraffin oil plasticizers can have 400-1000, such as 400-700, 500-800, 600-900, 700-1000, 400-500, 500-600, 600-700, 700-800, 800-900, or 900- Number average molecular weight of 1,000. In terms of upper limits, the plasticizer may have a number average molecular weight of less than 1,000, such as less than 900, less than 800, less than 700, less than 600, or less than 500. In terms of a lower limit, the plasticizer may have a number average molecular weight of at least 400, such as at least 500, at least 600, at least 700, at least 800, or at least 900. Paraffinic oil plasticizers can also have high viscosity. Kinematic viscosity can be measured, for example, using the program of Chinese Standard BG / T 265-1988. The paraffin oil plasticizer can have the following kinematic viscosity at 40 ° C: 400mm-1000mm ² Per second, for example 400-700mm ² Per second, 500-800mm ² Per second, 600-900mm ² Per second, 700-1000mm ² Per second, 400-500mm ² Per second, 500-600mm ² Per second, 600-700mm ² Per second, 700-800mm ² Per second, 800-900mm ² Per second or 900-1000mm ² /second. In terms of upper limits, plasticizers can have less than 1000mm ² Per second, for example less than 900mm ² / S, less than 800mm ² / Second, less than 700mm ² / S, less than 600mm ² / Second, or less than 500mm ² Kinematic viscosity per second. As far as the lower limit is concerned, the kinematic viscosity of the plasticizer can be greater than 400mm ² Per second, such as greater than 500mm ² / S, greater than 600mm ² / Second, more than 700mm ² Per second, more than 800mm ² / Second, or greater than 900mm ² /second. It has been found that the use of tackifiers with low molecular weight and viscosity advantageously (partially) counteracts the high molecular weight and viscosity of the plasticizer. The inventors have found that if the total viscosity of HMPSA is too high, the workability of the adhesive may be impaired. Specifically, adhesives with higher viscosity may be more difficult to use in standard compounding and coating processes related to the production of adhesive labels. Generally, as the viscosity of the adhesive decreases, the processability of the adhesive improves, and the resulting adhesive coating is more uniform and consistent. Many common linear aliphatic hydrocarbon tackifiers have a weight average molecular weight in the range of 1000-4000. The inventors have discovered that by using alicyclic hydrocarbon tackifier resins in HMPSA, high molecular weight linear aliphatic hydrocarbons can be advantageously avoided. Alicyclic hydrocarbon tackifiers may have a lower weight average molecular weight, which is in the range of 300-1000 or 300-800, such as 300-600, 400-700, 500-800, 300-400, 400-500, 500-600 , 600-700 or 700-800. In terms of upper limits, the tackifier may have a weight average molecular weight of less than 800, such as less than 700, less than 600, less than 500, or less than 400. In terms of a lower limit, the tackifier may have a weight average molecular weight of at least 300, such as at least 400, at least 500, at least 600, or at least 700. As a further benefit, the relatively high polar and steric effects of the alicyclic hydrocarbon chemical structure can also be used to reduce oil migration within and between the relevant label layers. Moreover, the hydrogenation of the resin produces adhesive layers and labels with reduced color, odor, and coke particles. The amount of the alicyclic hydrocarbon tackifier in the HMPSA composition may be in the range of 15-65% by weight, such as 15-45, 20-50, 25-55, 30-60, or 35-65% by weight. The amount of alicyclic hydrocarbon tackifier in the HMPSA composition may be in the range of 30-50% by weight, such as 30-42, 32-44, 34-46, 36-48, or 38-50% by weight. In terms of upper limits, the amount of alicyclic hydrocarbon tackifier in the HMPSA composition may be less than 70, less than 65, less than 60, less than 55, less than 50, less than 45, or less than 40% by weight. In terms of the lower limit, the amount of alicyclic hydrocarbon tackifier in the HMPSA composition may be at least 10, at least 15, at least 20, at least 25, at least 30, at least 35, or at least 40% by weight. HMPSA may optionally contain polyethylene wax. HMPSA's optional polyethylene wax can increase the hydrophobicity of the adhesive. This increased hydrophobicity can help increase the adhesive's resistance to water whitening and its ability to be cleanly removed or repositioned. Specific polyethylene waxes can also be selected to further reduce the overall viscosity of HMPSA and have minimal impact on the transparency of the adhesive. The polyethylene wax can be selected to have a specific hardness value. The hardness value can be measured using, for example, a penetration test in the ASTM D5 standard procedure. The hardness in this program is defined as the distance in tenths of a millimeter that a standard needle penetrates a sample of the material under test. Polyethylene waxes can have 3-10, such as 3-6, 4-7, 5-8, 6-9, 7-10, 3-4, 4-5, 5-6, 6-7, 7-8, Hardness values in the range 8-9 or 9-10. In terms of the upper limit, the polyethylene wax may have a hardness value of less than 10, such as less than 9, less than 8, less than 7, less than 6, less than 5 or less than 4. In terms of a lower limit, the polyethylene wax may have a hardness value of at least 3, such as at least 4, at least 5, at least 6, at least 7, at least 8, or at least 9. Polyethylene waxes can have relatively low viscosities, such as dynamic viscosities as measured by a Brookfield viscometer. Polyethylene waxes can have 150-500 centipoise (cps) at 140 ° C, such as 150-300 centipoise, 250-400 centipoise, 350-500 centipoise, 150-200 centipoise, 200-250cps, 250-300cps , 300-350cps or 350-400cps dynamic viscosity. In terms of upper limit, the dynamic viscosity of polyethylene wax at 140 ° C can be less than 500 cps, less than 450 cps, less than 400 cps, less than 350 cps, less than 300 cps, less than 250 cps or less than 200 cps. In terms of the lower limit, the polyethylene wax may have a dynamic viscosity at 140 ° C. of at least 150 cps, such as at least 200 cps, at least 250 cps, at least 300 cps, at least 350 cps, at least 400 cps, or at least 450 cps. Polyethylene waxes can also be selected to have a specific pour point measured by the standard formula ASTM D5949. Pour point is defined as the temperature at which a liquid becomes semi-solid and loses its flow characteristics. The pour point of polyethylene wax can be greater than 90 ° C, greater than 91 ° C, greater than 92 ° C, greater than 93 ° C, greater than 94 ° C, greater than 95 ° C, greater than 96 ° C, greater than 97 ° C, greater than 98 ° C, greater than 99 ° C, and greater than 100 ° C. , Greater than 101 ° C, greater than 102 ° C, greater than 103 ° C, greater than 104 ° C, greater than 105 ° C, greater than 106 ° C, greater than 107 ° C, greater than 108ºC, greater than 109ºC, or greater than 110ºC. In some embodiments, the pour point of the polyethylene wax is greater than 100 ° C. The amount of polyethylene wax in the HMPSA composition may be in the range of 0-5 wt%, such as 0-3, 0.5-3.5, 1-4, 1.5-4.5 or 2-5 wt%. The amount of polyethylene wax in the HMPSA composition may be in the range of 0-2% by weight, such as 0-1.2, 0.2-1.4, 0.4-1.6, 0.6-1.8, or 0.8-2% by weight. In terms of upper limits, the amount of polyethylene wax in the HMPSA composition may be less than 5, less than 4, less than 3, less than 2, less than 1.5, less than 1 or less than 0.5% by weight. In terms of a lower limit, the amount of polyethylene wax in the HMPSA composition may be zero or at least 0.5, at least 1, at least 1.5, at least 2 or at least 2.5% by weight. The overall viscosity of HMPSA can make the dynamic viscosity of the adhesive at 140 ° C measured by Brookfield viscometer at 10,000-20,000 cps, such as 10,000-14,000 cps, 12,000-16,000 centipoise, 14,000-18,000 centipoise, 16,000-20,000 In the range of centipoise, 10,000-12,000 centipoise, 12,000-14,000 centipoise, 14,000-16,000 centipoise, 16,000-18,000 centipoise, or 18,000-20,000 centipoise. In terms of upper limits, HMPSA may have a dynamic viscosity at 140 ° C of less than 20,000 cps, such as less than 18,000 cps, less than 16,000 cps, less than 14,000 cps, or less than 12,000 cps. In terms of the lower limit, HMPSA may have a dynamic viscosity at 140 ° C of at least 10,000, such as at least 12,000 cps, at least 14,000 cps, at least 16,000 cps, or at least 18,000 cps. HMPSA can be formulated as above to have a slightly white or colorless appearance. HMPSA can also be formulated with high definition clarity and transparency. This can provide benefits for adhesives or related labels in applications where a clear or transparent adhesive or label is required. For example, clear labels can be used with a variety of different attachment surfaces or materials to allow the color or texture of these attachment surfaces to remain visible through the label. Clear or transparent adhesives or labels can also be used for clear or transparent containers. For example, such "clear on clear" labels are common in the beverage industry using glass or plastic bottles. In clear-to-clear labels, any printed matter on the label tends to behave as if printed directly on the container itself, in part due to the transparency and lack of color of the adhesive. To produce adhesives with the desired lack of color, tackifier resins, plasticizer oils, waxes, fillers, and other ingredients are each selected to have light to no coloration and / or good in the adhesive composition. Solubility. The clarity and transparency of HMPSA can be measured according to the standard agreement ASTM D1003 as a haze value or according to the opacity contrast ratio of the standard agreement ASTM D2805. The haze value is defined as the percentage of transmitted light that is scattered by the sample, which is the cause of the above reduction by its observation. The HMPSA haze value may be, for example, less than 10, less than 9, less than 8, less than 7, less than 6, less than 5, less than 4, less than 3, less than 2 or less than 1. In some embodiments, the HMPSA has a haze value of less than 5. The opacity contrast ratio is defined as the ratio of the reflectance of a film on a black substrate to the same film on a white substrate. The HMPSA opacity ratio value may be, for example, less than 40, less than 35, less than 30, less than 25, less than 20, less than 15, less than 10, or less than 5. In some embodiments, the opacity contrast ratio of HMPSA is less than 20. Another advantage of HMPSA formulations is that whitening, clarity and transparency are not significantly affected by changes in temperature or humidity. For example, when the adhesive is heated to 65 ° C and after 1 hour, the haze value and the opacity ratio can be independently changed less than 30%, less than 28%, less than 26%, less than 24%, less than 22%, less than 20 %, Less than 18%, less than 16%, less than 14%, less than 12%, less than 10%, less than 8%, less than 6%, less than 4% or less than 2%. Heating may include contacting the adhesive with water heated to 65 ° C. Heating may include immersing the adhesive in 65ºC water. The components of the HMPSA composition can be selected to meet food contact requirements and are generally classified as food safe. For example, the use of hydrogenated tackifiers and food-grade paraffin oils can make HMPSA a food-safe adhesive. The present invention also relates to a label comprising the hot-melt pressure-sensitive adhesive of the present invention. The label includes a facestock layer for receiving a printed mark and a hot-melt pressure-sensitive adhesive layer having a composition as described above. The label may also include one or more facestock layers, one or more optional printed layers, one or more adhesive layers, and an optional backing layer. This subject matter can be used in unprinted labels, but in many specific embodiments, the label includes one or more printed areas. Figure 2 shows a multilayer label according to a specific embodiment. The label 200 shown includes a facestock layer 201, a HMPSA layer 202, and a backing layer 203. The HMPSA layer is disposed on the surface 204 of the facestock layer closer to the backing layer. The opposite surface 205 of the facestock layer may be configured to receive a printed mark. The optional mark may be printed directly on surface 205; embedded in any of the layers 201, 202, or 203; or printed on any other surface of the label 200. The layers shown in FIG. 2 may be positioned directly next to each other as shown, or may have one or more additional layers between them. Additional layers may include, for example, one or more coatings, support layers, printed layers, reflective layers, laminated layers, and the like. Any one or more of the layers shown may also include two or more sub-layers, each of which has a different composition, construction, and function. The face material may include, for example, a paper face material, a cardboard face material, a plastic face material, a multilayer laminated face material including a paper layer and a plastic layer, or any other material commonly used in the industry. The multilayer laminated facestock may include a paper layer overlying a plastic layer. The plastic layer of the multilayer laminated facestock can be extruded or coated onto a paper layer. The paper layer may include, for example, glossy paper, semi-gloss paper, lithographic paper or electronic data processing (EDP) paper; and may be configured for, for example, multi-color printing, typewriter printing, or inkjet printing. The plastic layer may include, for example, polyester, such as PET; polyolefins such as polypropylene (PP), ethylene-propylene copolymer, polyethylene (PE); and other materials. Other polymer film materials include polyurethane-based polymers, such as polyether polyurethanes and polyester polyurethanes; amido-based polymers, including polyether-polyamine copolymers; acrylic-based polymers, including polyacrylates and ethylene / vinyl acetate Copolymers; polyester-based polymers, including polyether polyesters; vinyl chloride; vinylidene chloride; polystyrene; polyacrylonitrile; polycarbonate; polyimide; or similar materials. The face material may include a flexible face material. The facestock may include a transparent polymer film. In certain applications, it may be useful to use a "shrink" film or an orientation film as a facestock layer. The subject matter of the present invention includes, for example, a biaxially oriented film such as PET as a facestock layer. In some embodiments, the label further includes a print disposed on the facestock layer. The print may include layers or areas of ink, dye, pigment or similar material. It will be understood that "dye" and similar terms refer to visible light absorbing compounds in molecularly dispersed or dissolved form. "Pigment" and similar terms refer to a visible light absorbing material or compound in a non-molecularly dispersed or particulate form. "Ink" and like terms refer to a coatable or printable formulation containing dyes and / or pigments. Although the subject matter is primarily directed to labels that include visually perceptible prints, it is contemplated that the labels may include only or primarily prints indicated under UV light or other conditions. The HMPSA layer can be directly applied to and in contact with the surface material. There may be an intermediate layer between the HMPSA layer and the face material. The label may include two or more layers of HMPSA and / or facestock. The HMPSA layer of the label can be applied to the facestock at a coating weight of, for example, 5-30 grams per square meter (gsm). The coating weight of the adhesive layer may be 6-20 gsm, 8-20 gsm, 22-30 gsm, 16-40 gsm. In some embodiments, the adhesive layer coating weight is in the range of 5-40 gsm. In terms of the upper limit, the coating weight of the adhesive layer may be less than 40 gsm, for example, less than 35 gsm, less than 30 gsm, less than 25 gsm, less than 20 gsm, less than 15 gsm, or less than 10 gsm. In terms of the lower limit, the adhesive layer coating weight may be at least 5 gsm, such as at least 10 gsm, at least 15 gsm, at least 20 gsm, at least 25 gsm, at least 30 gsm, or at least 35 gsm. The subject matter can include introducing one or more clear or transparent layers into any of the label constructions described herein. The subject matter may also include introducing one or more metal layers or foils into any of the label constructions described herein. It is also conceivable that the label structure may further include a combination of one or more transparent layers and one or more metal layers. In some embodiments, the label is a clear-to-clear label having a laminated composition including a transparent biaxially oriented polypropylene (BOPP) film, a transparent HMPSA layer, and a transparent PET liner. In some embodiments, the label further includes a liner disposed on the HMPSA layer. The releasable liner may be positioned adjacent to the adhesive layer such that the adhesive layer is disposed or sandwiched directly or indirectly between the bottom surface of the facestock and the releasable liner. The releasable liner can be used as a protective cover so that the release liner remains in place until the label is ready to attach to the object. If the label contains a liner or release liner, a variety of materials and structures can be used as the liner. In many specific embodiments, the liner is paper or a paper-based material. In many other specific embodiments, the liner is a polymer film of one or more polymer materials. Typically, at least one side of the liner is coated with a release material such as a polysiloxane or polysiloxane material. It is understood that the release-coated side of the liner is placed in contact with the other exposed side of the adhesive layer. Before applying the label to the surface of interest, the liner is removed, exposing the adhesive side of the label. The liner may be in the form of a single piece. Alternatively, the liner may be in the form of multiple sections or panels. Other additives may be added to one or more of the HMPSA, facestock, or backing layers to obtain certain desired characteristics. These additives may include, for example, one or more waxes, surfactants, talc, silicate powders, fillers, defoamers, colorants, antioxidants, UV stabilizers, luminescent agents, crosslinkers, buffers, anti-oxidants Caking agents, wetting agents, matting agents, antistatic agents, acid scavengers, flame retardants, processing aids, extrusion aids, etc. The invention also relates to a labelled container comprising the hot-melt pressure-sensitive adhesive of the invention. The labeled container includes a container defining an outer surface, and the above-mentioned label adhered to the outer surface of the container. In some embodiments, the container is a bottle. The outer surface to which HMPSA is bonded can include a wide range of substrates. The outer surface can include glass, plastic, wood, metal, combinations of these and other materials. In some embodiments, the outer surface of the container includes glass. In some embodiments, the outer surface of the container includes plastic. The outer surface may include or be formed from any suitable polymer or mixture of polymers. The polymer or polymer mixture may include, for example, PET, recycled polyethylene terephthalate (rPET), high density polyethylene (HDPE), polyvinyl chloride (PVC), polylactic acid (PLA), cellulose, Biopolymer film, low density polyethylene (LDPE), PP, polystyrene (PS), polyester or other types of polymers or plastics. In some embodiments, the plastic includes PET. Although the label can usually be removed from the container, the outer surface of the container can retain a portion of the adhesive used to adhere the label to the container. This adhesive residue may contaminate or interfere with subsequent container operations, such as later washing, relabeling, or container recycling. In some embodiments, the provided label can be removed from the outer surface, while substantially all of the adhesive remains with the label and / or remains, rather than remaining on the outer surface. The invention also relates to a method of applying a label to a container. The method includes providing a container defining an outer surface and a label according to a specific embodiment. The method also includes adhering the label to the outer surface of the container, thereby applying the label to the container. Labels can be bonded to one or more containers or articles in a batch, continuous or semi-continuous manner. Before use, one or more liners can be removed from the label to expose the adhesive side of the label. The adhesive side and label are then contacted with the container or article and the label is applied thereto. Adhesion may also include one or more operations, i.e. pressing or otherwise applying pressure on the label to promote contact and / or adhesion to the container; for example, activation and / or curing by heating and / or exposure to UV light Adhesives; and / or drying operations. Consider the following specific embodiments. All combinations of features and specific embodiments are also contemplated. Specific Example 1: A hot-melt pressure-sensitive adhesive comprising: a styrene-isoprene-styrene copolymer; a tackifier containing a hydrogenated alicyclic hydrocarbon resin; a plasticizer containing 40 ° C Kinematic viscosity at 400-1000mm ² Paraffin oil in the range per second; and less than 5 weight percent polyethylene wax. Specific embodiment 2: A specific embodiment of specific embodiment 1, wherein the tackifier has a weight average molecular weight in the range of 300-1000. Specific embodiment 3: A specific embodiment of any one of specific embodiments 1 or 2, wherein the plasticizer has a number average molecular weight in a range of 400-1000. Specific embodiment 4: A specific embodiment of specific embodiment 3, wherein the weight average molecular weight of the tackifier is within 10% of the number average molecular weight of the plasticizer. Specific embodiment 5: Specific embodiment of any one of the specific embodiments 1-4, wherein the concentration of the styrene-isoprene-styrene copolymer in the hot-melt pressure-sensitive adhesive is 15-65 weight %, Where the concentration of the tackifier in the hot-melt pressure-sensitive adhesive is in the range of 15-65% by weight, and where the concentration of the plasticizer in the hot-melt pressure-sensitive adhesive is 5-35% by weight %In the range. Specific embodiment 6: Specific embodiment of any one of specific embodiments 1-4, wherein the concentration of the styrene-isoprene-styrene copolymer in the hot-melt pressure-sensitive adhesive is 25-55 weight %, Wherein the concentration of the tackifier in the hot-melt pressure-sensitive adhesive is in the range of 25-55 wt%, and the concentration of the plasticizer in the hot-melt pressure-sensitive adhesive is 15-25% by weight Range, and where the concentration of polyethylene wax in the hot-melt pressure-sensitive adhesive is less than 2% by weight. Specific embodiment 7: A specific embodiment of any one of specific embodiments 1-6, wherein the styrene-isoprene-styrene copolymer has a diblock fraction of less than 30% by weight. Specific embodiment 8: A specific embodiment of any one of specific embodiments 1-7, wherein the styrene-isoprene-styrene copolymer has a styrene content of less than 25% by weight. Specific embodiment 9: Specific embodiment of any one of the specific embodiments 1-8, wherein the kinematic viscosity of the plasticizer at 40 ° C is 400-700mm ² Per second. Specific embodiment 10: A specific embodiment of any one of the specific embodiments 1-9, wherein the polyethylene wax has a dynamic viscosity of 150-500 cps at 140 ° C. Specific embodiment 11: A specific embodiment of any one of the specific embodiments 1-10, wherein the pour point of the polyethylene wax is greater than 100 ° C. Specific embodiment 12: A specific embodiment of any one of the specific embodiments 1-11, wherein the hot-melt pressure-sensitive adhesive has a haze value of less than 5. Specific Embodiment 13: A specific embodiment of any one of the specific embodiments 1-12, wherein the hot-melt pressure-sensitive adhesive has an opacity contrast ratio of less than 20. Specific embodiment 14: A specific embodiment of specific embodiment 12, wherein after the hot-melt pressure-sensitive adhesive is heated to 65 ° C. for 1 hour, the change in the haze value is less than 20%. Specific embodiment 15: A specific embodiment according to specific embodiment 13, wherein after the hot-melt pressure-sensitive adhesive is heated to 65 ° C. for 1 hour, the opacity contrast ratio changes by less than 20%. Specific embodiment 16: A specific embodiment of any one of the specific embodiments 1-15, wherein the dynamic viscosity of the hot-melt pressure-sensitive adhesive at 140 ° C is in the range of 10,000-20,000 centipoise. Specific embodiment 17: A label comprising a face material capable of receiving a printed mark; and the hot-melt pressure-sensitive adhesive of the hot-melt pressure-sensitive adhesive of any one of the specific embodiments 1-16. Specific embodiment 18: A specific embodiment of specific embodiment 17, further comprising a liner disposed on the hot-melt pressure-sensitive adhesive layer. Specific Embodiment 19: A specific embodiment of any one of the specific embodiments 17 or 18, wherein the label has a longitudinal length and a lateral length, and wherein the label is stored vertically for more than 65 ° C and 85% relative humidity for four days in the vertical The length and lateral lengths each vary by less than 2%. Specific embodiment 20: A labelled container including a container having an outer surface; and the label of any one of the specific embodiments 17-19 of the specific embodiments 17-19 adhered to the outer surface of the container. Specific embodiment 21: A specific embodiment of specific embodiment 20, wherein the outer surface of the container includes glass, polyethylene terephthalate or other plastics. Specific embodiment 22: A specific embodiment of any one of the specific embodiments 20 or 21, wherein the container is a bottle. Specific embodiment 23: A specific embodiment of any one of the specific embodiments 20-22, wherein the label can be substantially completely removed from the container by peeling. Specific embodiment 24: A method of applying a label to a container, the method comprising providing a container defining an outer surface; providing the label of any of the specific embodiments 17-19; and adhering the label to the outside of the container Surface to apply the label to the container. Specific embodiment 25: A specific embodiment of specific embodiment 24, wherein the outer surface of the container comprises glass, polyethylene terephthalate or other plastic. Specific embodiment 26: A specific embodiment of any one of specific embodiments 24 or 25, wherein the label can be substantially completely removed from the container at a temperature greater than 5 ° C within the first 8 hours after bonding and then Apply to container. The invention will be better understood in view of the following non-limiting examples. Examples Eight HMPSA compositions were prepared according to the formulations listed in Table 1 below. Test HMPSA for physical and performance characteristics such as swelling, dynamic viscosity, and processability. The results are also provided in Table 1. The labels were prepared using Comparative Examples A and B and HMPSA of Example 1, and tested for swelling. The labels using HMPSA of Example 1 (and those using Comparative Examples A and B) showed very good swelling results. As described above, adhesives with reduced swelling have greater structural integrity and may also exhibit less oil migration than adhesives with a greater tendency to swell. The tag using the HMPSA of Example 1 also exhibited an excellent combination of performance characteristics, such as water whitening resistance, repositionability, and / or optical clarity. Importantly, the HMPSA of Example 1 has a lower viscosity, is easier to process, and results in higher quality labels. In contrast, the HMPSAs of Comparative Examples A and B exhibited much higher viscosities, which resulted in difficult processing and poorer quality labels. As shown in Table 1, the formulations of Examples 1-4 and 8 have a kinematic viscosity of 400-1000 mm at 40 ° C. ² Plasticizer in the range per second. These formulations especially provide a hot-melt PSA with an advantageous combination of performance characteristics and excellent processability. These example adhesives have high levels of whitening resistance, good removability, optical clarity and low swelling and oil migration. It is important that Examples 1-4 exhibit low dynamic viscosity, for example in the range of 10,000-20000 centipoise, which provides the formation of a high-quality coating, that is, excellent processability. In contrast, Comparative Example AD exhibited a much higher dynamic viscosity (well above 20,000 centipoise, and in some cases greater than 80,000 centipoise). These comparative examples exhibit poor processability due at least in part to high viscosity plasticizers. In addition, as shown in Table 1, the HMPSA formulations of Examples 1-4 each contained a tackifier with a molecular weight within a preferred range of 300-800. These relatively low molecular weight viscosifiers can be used to partially offset the number average molecular weight of the plasticizer, which further helps to reduce the overall dynamic viscosity, for example, in the favorable range of 10,000 to 20,000 centipoise. In contrast, the formulation of Comparative Example AD uses a tackifier with a number average molecular weight greater than 1000. The resulting HMPSA has a much higher dynamic viscosity, for example greater than 35,000 centipoise, which makes processing steps such as compounding and coating difficult. Therefore, Examples 1-4 and Comparative Example AD demonstrate the combination of a low weight average molecular weight tackifier with a high number average molecular weight plasticizer to formulate a bond that meets the required properties of low swelling, low oil migration, and low viscosity The importance of agents. In summary, the data in Table 1 show that the formulations of the comparative examples used high viscosity plasticizers (and optional plasticizers and / or tackifiers) outside the viscosity and / or molecular weight ranges discussed herein. These comparative examples have undesired physical and / or performance characteristics. These data show the importance and criticality of the above combination. Although the present invention has been described in detail, modifications within the spirit and scope of the invention will be apparent to those skilled in the art. In view of the above discussion, the relevant knowledge in the art and the references discussed above in connection with the background and detailed description, the disclosures of which are all incorporated herein by reference. In addition, it should be understood that various aspects of the invention and portions of various specific embodiments and various features described below and / or described in the appended claims may be combined or interchanged in whole or in part. In the foregoing description of various specific embodiments, those specific embodiments referring to another specific embodiment may be appropriately combined with other specific embodiments, as will be understood by those skilled in the art. Moreover, those of ordinary skill in the art will understand that the foregoing description is merely an example and is not intended to limit the present invention.

100‧‧‧ bottles

101‧‧‧ tags

102‧‧‧ outer surface of bottle 100

200‧‧‧ tags

201‧‧‧ surface material layer

202‧‧‧HMPSA layer

203‧‧‧lining layer

204‧‧‧ Surface of the liner

Opposite surface of 205‧‧‧ facing material layer

The present invention is described in detail below with reference to the drawings, in which the same reference numerals denote similar parts. FIG. 1 is a schematic diagram of a labeled container (such as a bottle) according to a specific embodiment of the present invention. 2 is a schematic diagram of a cross-sectional view of a label having a facestock layer, a hot-melt pressure-sensitive adhesive layer, and a liner according to a specific embodiment of the present invention.

Claims (26)

A hot-melt pressure-sensitive adhesive, comprising: a styrene-isoprene-styrene copolymer; a tackifier containing a hydrogenated alicyclic hydrocarbon resin; and a plasticizer containing a kinematic viscosity at 40 ° C at Paraffin oil in the range of 400-1000 mm ² / s; and polyethylene waxes of less than 5% by weight. The hot-melt pressure-sensitive adhesive according to claim 1, wherein the tackifier has a weight average molecular weight in a range of 300-1000. The hot-melt pressure-sensitive adhesive according to claim 1, wherein the plasticizer has a number average molecular weight in a range of 400-1000. The hot-melt pressure-sensitive adhesive according to claim 3, wherein the weight average molecular weight of the tackifier is within 10% of the number average molecular weight of the plasticizer. The hot-melt pressure-sensitive adhesive according to any one of claims 1-4, wherein the concentration of the styrene-isoprene-styrene copolymer in the hot-melt pressure-sensitive adhesive ranges from 15 to 65% by weight Inside, where the concentration of the tackifier in the hot-melt pressure-sensitive adhesive is in the range of 15-65% by weight, and where the concentration of the plasticizer in the hot-melt pressure-sensitive adhesive is in the range of 5-35% by weight Inside. The hot-melt pressure-sensitive adhesive according to any one of claims 1-4, wherein the concentration of the styrene-isoprene-styrene copolymer in the hot-melt pressure-sensitive adhesive is in a range of 25 to 55% by weight Inside, wherein the concentration of the tackifier in the hot-melt pressure-sensitive adhesive is in the range of 25-55 wt%, and the concentration of the plasticizer in the hot-melt pressure-sensitive adhesive is in the range of 15-25% by weight , And wherein the concentration of polyethylene wax in the hot-melt pressure-sensitive adhesive is less than 2% by weight. The hot-melt pressure-sensitive adhesive according to any one of claims 1-4, wherein the styrene-isoprene-styrene copolymer has a diblock fraction of less than 30% by weight. The hot-melt pressure-sensitive adhesive according to any one of claims 1-4, wherein the styrene-isoprene-styrene copolymer has a styrene content of less than 25% by weight. The hot-melt pressure-sensitive adhesive according to any one of claims 1-4, wherein the kinematic viscosity of the plasticizer at 40 ° C is in a range of 400-700 mm ² / second. The hot-melt pressure-sensitive adhesive according to any one of claims 1-4, wherein the polyethylene wax has a dynamic viscosity of 150-500 cps at 140 ° C. The hot-melt pressure-sensitive adhesive according to any one of claims 1-4, wherein the pour point of the polyethylene wax is greater than 100 ° C. The hot-melt pressure-sensitive adhesive according to any one of claims 1-4, wherein the hot-melt pressure-sensitive adhesive has a haze value of less than 5. The hot-melt pressure-sensitive adhesive according to claim 12, wherein after the hot-melt pressure-sensitive adhesive is heated to 65 ° C and after 1 hour, the change in the haze value is less than 20%. The hot-melt pressure-sensitive adhesive according to any one of claims 1-4, wherein the hot-melt pressure-sensitive adhesive has an opacity contrast ratio of less than 20. The hot-melt pressure-sensitive adhesive according to claim 14, wherein after the hot-melt pressure-sensitive adhesive is heated to 65 ° C and after 1 hour, the opacity contrast ratio changes by less than 20%. The hot-melt pressure-sensitive adhesive according to any one of claims 1-4, wherein the hot-melt pressure-sensitive adhesive has a dynamic viscosity at 140 ° C in a range of 10,000-20,000 centipoise. A label comprising: a face material capable of receiving a printed mark; and a hot-melt pressure-sensitive adhesive including the hot-melt pressure-sensitive adhesive of any one of claims 1-16. The label according to claim 17, further comprising: a liner provided on the hot-melt pressure-sensitive adhesive layer. A label according to claim 17 or 18, wherein the label has a longitudinal length and a lateral length, and wherein the vertical and lateral lengths each change by less than 2% when the label is stored at more than 65 ° C and 85% relative humidity for four days. A labeled container comprising: a container having an outer surface; and a label as claimed in any one of claims 17-19, adhered to the outer surface of the container. A labeled container according to claim 20, wherein the outer surface of the container comprises glass, polyethylene terephthalate or other plastic. A labeled container according to claim 20 or 21, wherein the container is a bottle. A labeled container according to claim 20 or 21, wherein the label can be removed substantially completely from the container by peeling. A method of applying a label to a container, the method comprising: providing a container defining an outer surface; providing the label as in any of claims 17-19; and adhering the label to the outer surface of the container to apply the label To the container. The method according to claim 24, wherein the outer surface of the container comprises glass, polyethylene terephthalate or other plastic. The method according to claim 24 or 25, wherein the label can be substantially completely removed from the container and reapplied to the container within a first 8 hours after bonding at a temperature greater than 5 ° C.