CN108690540B

CN108690540B - Ultra-removable hot melt adhesive and label comprising same

Info

Publication number: CN108690540B
Application number: CN201810287836.2A
Authority: CN
Inventors: 潘晓明; 王少华; 邢新雨; 王敏
Original assignee: Avery Dennison Corp
Current assignee: Avery Dennison Corp
Priority date: 2017-04-07
Filing date: 2018-04-03
Publication date: 2022-04-19
Anticipated expiration: 2038-04-03
Also published as: WO2018184198A1; CN108690540A; TW201900820A; AR111147A1

Abstract

A hot melt adhesive comprising 15 to 65 wt% of a styrene-isoprene-styrene copolymer, a tackifier having a softening point below 150 ℃, 1 to 15 wt% of a wax having a high needle penetration greater than 8dmm as measured by ASTM D5(2016), and a plasticizer. The adhesive has a stainless steel peel strength of 0.5N/inch to 20N/inch as measured by FINAT test method 2 (2016).

Description

Ultra-removable hot melt adhesive and label comprising same

Technical Field

The present application relates generally to hot melt adhesives and, in particular, to improved hot melt adhesives that provide high removability. The present application also relates to labels comprising the improved hot melt adhesives.

Background

Hot melt pressure sensitive adhesives (PSAs or HMPSAs) are known to provide tack or tackiness (when applied at room temperature) to a variety of substrates. This tack provides instantaneous adhesion to the substrate upon extrusion. PSAs are readily handled in solid form, quickly forming bonds without significant additional processing. And PSAs typically have a long shelf life. PSAs are known to generally provide a convenient and economical way of labeling glass, metal, and plastic containers for commercial products such as consumer and industrial products. In particular, PSAs are widely used to produce self-adhesive labels that are affixed to articles for presentation of information (e.g., bar codes, instructions, prices) and/or decorative purposes.

In some applications, it is desirable to remove and/or rearrange the articles adhered with the PSA. For example, after their contents are removed, the labeled packages and/or containers are subjected to a washing (or recycling) process to reuse them or, after destruction, to recover their constituent materials. Such treatments typically require complete separation of the label from the article to which it is affixed without leaving adhesive residue on the surface of the article in order to make the recycling process easier. In other cases, the container may use a repositionable or re-attachable closure to open and close the container multiple times, such as a tissue box closure label. In other applications, removable PSAs may be used to adhere loose items to appliances such as refrigerators during transport. As another example, children's books may use re-attachable adhesives to combine the pictures with the corresponding text, thus enhancing the learning experience. In these applications, PSAs having a particular combination of tack, cohesive strength, removability, and/or repositionability are desirable.

U.S. publication No.2005/0013996 discloses a Hot Melt Pressure Sensitive Adhesive (HMPSA) obtained by combining: linear a-B-a block copolymers wherein the B component is polyisoprene and the a component is polystyrene (S-I-S), at least one compatible tackifying resin, at least one plasticizer, antioxidant and stabilizer, and optionally a wax. The A-B-A block copolymer contains 0 to 10 weight percent residual A-B diblock. HMPSA are suitable as positioning adhesives for disposable articles such as plasters, bandages, sanitary napkins such as sanitary napkins, adult incontinence pads or diapers. The HMPSA has a viscosity of 3,500 to 25,000mPas at 140 ℃ and exhibits a tack value of 1.0 to 3.0N/cm at a coating weight of 10 to 25 grams per square meter.

U.S. publication No.2010/0193127 discloses a Hot Melt Pressure Sensitive Adhesive (HMPSA) composition comprising 25-50% of a styrenic block copolymer selected from SIS, SIBS, SEBS, and SEPS block copolymers; 35-75% of a compatible tackifying resin having a softening temperature of 80-150 ℃ and an acid number of less than 20; and 0.5-20% of one or more carboxylic acids, the hydrocarbon chain of which comprises 6-54 carbon atoms.

U.S. patent No.9,242,437 discloses a Hot Melt Pressure Sensitive Adhesive (HMPSA) composition comprising: (a) 25-50% of one or more styrene block copolymers SBS, SIS, SIBS, SEBS or SEPS; (b) 35-75% of one or more compatible tackifying resins that are liquid or have a softening temperature below 150 ℃; and (c) 1-20% of one or more supramolecular polymers obtained by reacting 1- (2-aminoethyl) -2-imidazolidinone with a fatty acid composition comprising 51-100% of one or more fatty acid dimers and/or trimers and 0-49% of one or more fatty acid monomers. Also provided is a multilayer system comprising a HMPSA, an adjacent printable carrier layer made of paper or a polymer film, and an adjacent protective layer. The multi-layer system can be used in self-adhesive labels.

Chinese application No.103849100A discloses the preparation of a carrier styrene-isoprene block copolymer composition and an adhesive for plasters or patches. The composition comprises the following components in percentage by weight: 80% -90% of a styrene-isoprene-styrene triblock, i.e. S-I-S, and 10% -20% of a styrene-isoprene diblock, i.e. S-I. The block ratio S: I of the styrene-isoprene-styrene triblock is (14-17) to (83-86). The molecular weight is 110000 to 140000. The block ratio S: I of the styrene-isoprene diblock was (8-12) to (88-92). The molecular weight is 55000 to 75000. The plaster or patch carrier hot melt pressure sensitive adhesive is prepared by adopting 100 parts of SIS composition, 70-80 parts of plasticizer and 140-150 parts of tackifying resin, and has high drug loading capacity, low drug adding temperature, lower peeling force and good retention.

Chinese application No.104694047A discloses hot melt pressure sensitive adhesives and methods of making hot melt pressure sensitive adhesives. Hot melt pressure sensitive adhesive belongs to the field of waterproof coiled material technology. The problem to be solved is that the waterproofing roll is not suitable for winter or frozen ground because the conventional pre-laying anti-adhesion structure can be performed only in a climate environment of-4 ℃ or higher. The disclosed hot melt pressure sensitive adhesive is prepared from raw materials comprising: an elastomer, polyisobutylene, a first C5 petroleum resin and a second C5 petroleum resin, wherein the first C5 petroleum resin refers to a solid alicyclic hydrocarbon hydrogenated petroleum resin and has a softening point of 80 to 127 ℃; the second C5 petroleum resin refers to a liquid petroleum resin and has a softening point of less than or equal to 1 ℃. According to the hot melt pressure sensitive adhesive disclosed by the invention, the high-density polyethylene self-adhesive film waterproof coiled material can be firmly lapped at the temperature of minus 10 ℃, and the hot melt pressure sensitive adhesive can be used for sealing glue, double faced adhesive tape and the like.

Chinese application No.103602295A discloses a high stretch resistant hot melt pressure sensitive adhesive and a method of making the same. The high stretch resistant hot melt pressure sensitive adhesive is characterized by comprising 25 to 40 wt.% of an elastomer SIS (styrene isoprene styrene block copolymer), 50 to 65 wt.% of a synthetic resin, 4 to 10 wt.% of a synthetic wax, 5 to 10 wt.% of a rubber plasticizer, and 0.3 to 1 wt.% of an antioxidant. The preparation method comprises the following steps: adding an elastomer SIS, a rubber plasticizer and an antioxidant into a stainless steel reactor in parts; slowly heating to 140-175 ℃, stirring until all materials are molten, and stably reacting for 5-20 minutes; the remaining other materials were added in portions under stirring and continuously stirred for 5 to 30 minutes and cooled, and molding treatment was carried out so as to obtain the desired hot melt type pressure sensitive adhesive. The high elastic resistance hot melt pressure sensitive adhesive prepared by the method has the following advantages: high instantaneous adhesive strength, high thermal adhesive strength, high peel force, strong and fast adhesion, ease of use and no bounce. It is very suitable for producing mattresses, sofas or cushions.

Chinese application No.102660219A discloses the preparation of low temperature resistant hot melt pressure sensitive adhesives. The low temperature resistant hot melt pressure sensitive adhesive is characterized by comprising the following components in percent by weight: 12-25% of elastomer SIS, 30-50% of tackifying resin, 10-25% of synthetic liquid rubber, 2-12% of synthetic wax, 25-35% of rubber plasticizer and 0.2-0.5% of antioxidant. The method comprises the following steps: during preparation, elastomer SIS, synthetic liquid rubber, synthetic wax, plasticizer and antioxidant are put into a stainless steel reactor according to a certain proportion; slowly heating to 130-160 ℃; stirring until all materials are molten; stably reacting for 5-20 minutes; adding other residual raw materials while stirring; continuously stirring for 5-30 minutes; and cooling and molding to obtain the desired low temperature resistant hot melt pressure sensitive adhesive product. The adhesive product produced by the method has the following advantages: low temperature resistance, high peel strength and strong adhesion, and are well suited for sealing LDPE (low density polyethylene) film plastic bags.

Even in view of these references, there is a need to provide hot melt PSAs with improved performance characteristics, particularly removability and repositionability.

Summary of The Invention

In one embodiment, the present invention relates to a hot melt adhesive comprising: 15 to 65 wt% of a styrene-isoprene-styrene copolymer, a tackifier having a softening point below 150 ℃, 1 to 15 wt% of a wax having a high needle penetration of greater than 8dmm, and a plasticizer. The adhesive has a stainless steel peel strength of 0.5 to 20N/inch, preferably 0.5 to 5N/inch, as measured by FINAT test method 2 (2016). The styrene-isoprene-styrene copolymer comprises less than 35 wt% polymerized styrene monomer and/or less than 60 wt% SI diblock, optionally, the styrene-isoprene-styrene copolymer comprising less than 60 wt% SI diblock is present in an amount of 15 wt% to 65 wt%. The tackifier may have a molecular weight of less than 1180 and/or may comprise a hydrogenated (cycloaliphatic) hydrocarbon resin. The wax may have a melting point above 60 ℃ and/or may have a dynamic viscosity of 150-500cps at 140 ℃ as measured by a brookfield viscometer. Preferably, the wax has a melting point above 60 ℃ and the tackifier has a molecular weight of less than 1180. The plasticizer may have a molecular weight of at least 200 and/or may have a molecular weight of at least 175mm at 40 ℃ as measured by Chinese Standard BG/T265 (1988)²Viscosity per second. The plasticizer may be selected from the group consisting of polyisobutylene, naphthenic oil, paraffinic oil, liquid polyisoprene, liquid white mineral oil, and combinations thereof. The weight ratio of plasticizer to tackifier may be at least 0.05:1, and/or may be from 0.05:1 to 2: 1. The weight ratio of the wax and plasticizer combination to the tackifier may be at least 0.05:1 and/or the weight ratio of the wax to tackifier may be at least 0.05: 1. The hot melt adhesive may comprise from 15 wt% to 45 wt% tackifier; and/or 5 to 35 wt% plasticizer. The invention also relates to a label comprising a facestock suitable for print marking and a hot melt adhesive. The present invention also relates to a method of producing a hot melt adhesive, the method comprising the steps of: providing a styrene-isoprene-styrene copolymer; a tackifier; a wax; and a plasticizer; determining a required peeling strength range; determining a weight ratio of plasticizer to tackifier based on the desired peel strength; and mixing styrene-isoprene-a styrene copolymer, a tackifier, a wax and a plasticizer in combination to form a hot melt adhesive. The plasticizer and tackifier are present in a determined plasticizer to tackifier weight ratio and wherein the stainless steel peel strength of the hot melt adhesive is within the desired peel strength range.

Detailed Description

The present invention relates generally to hot melt Pressure Sensitive Adhesives (PSAs) that provide advantageous performance characteristics, particularly improved removability and repositionability without leaving significant adhesive residue on the bottle or other container from which the label is removed. This characteristic is particularly important when the PSA is used in a repositionable or re-attachable closure or for adhering labels to containers to be reused or recycled.

As noted herein, several conventional hot melt PSAs are known. However, many of these hot melt adhesives were developed for applications where high adhesive strength is preferred. In these cases, removability and redeployability are not desirable features. In fact, the components used to contribute to improved adhesion typically have a deleterious effect on removability/repositionability. In other applications, conventional (non-permanent) hot melt PSAs fail to provide sufficient removability/repositionability without forming or leaving a significant amount of residue on the substrate.

The inventors have now found that a particular combination of components, optionally used in specific amounts, surprisingly provides high performance PSAs that demonstrate highly desirable performance characteristics, such as sufficient adhesive/cohesive strength in combination with high levels of removability and/or repositionability, and optionally low levels, if any, of cohesive failure and low adhesive transfer (strong matrix anchoring). Advantageously, these PSAs also exhibit improved processability during adhesive and label production and application and good adhesive and label quality in end-user products.

In particular, it has been found that hot melt adhesives, such as hot melt PSAs comprising (low diblock content) styrene-isoprene-styrene (SIS) copolymers, tackifiers, (soft) waxes, and plasticizers unexpectedly provide hot melt PSAs having the above-described combination of performance characteristics. For example when using e.g. a di having less than 60 wt. -%A block content of a low diblock content SIS copolymer, a soft wax, e.g., a wax having a high degree of needle penetration greater than 8dmm, optionally a tackifier and/or a high viscosity plasticizer having a softening point below 150 ℃ (e.g., at least 175mm at 40 ℃), and²second), the resulting hot melt PSA surprisingly demonstrates a stainless steel peel strength of 0.5N/inch to 20N/inch as measured by FINAT test method 2(FTM 2) (2016). In some cases, this range of peel strengths represents a hot melt PSA that provides the desired combination of adhesive strength and removability/repositionability. Hot melt PSAs thus prepared exhibit other advantageous performance characteristics, such as lack of cohesive failure, low adhesive transfer, and/or improved oil migration performance. In some cases, hot melt PSAs can be used to produce labels that have good removability, repositionability, and oil migration, while still being easily used in standard compounding and coating applications. If not otherwise mentioned, all test methods are presented as a 2016 version.

Additionally, without being bound by theory, it is believed that many typical hot melt formulations comprise smaller molecular components that deleteriously become rigid after only minor aging. In addition, it has been found that these small molecule components tend to migrate out of the hot melt adhesive and onto the substrates where the molecules form undesirable residues on the respective substrates. The hot melt PSAs described herein comprise a specific combination of components having limited amounts of these smaller molecules. Thus, the hot melt PSAs of the present invention are capable of providing a combination of the above performance characteristics. In addition, the internal interaction of the components of the hot melt adhesive can be used, for example, to limit or minimize oil migration if in fact it begins to occur. Additionally, in a preferred embodiment, the tackifier comprises a hydrogenated (cycloaliphatic) resin. Hydrogenated resins have lower polarity and lower adhesion than non-hydrogenated resins. The use of such hydrogenated resins and the resulting adhesion inhibition advantageously allows for the use of lower amounts of oil for hot melt PSAs, which can be used to control adhesion for removability and repositionability. In addition, it is believed that the use of lower molecular weight (and/or low viscosity) tackifiers allows for the use of higher molecular weight plasticizers, which provide a synergistic balance of larger molecular components.

In particular, the inventors have found that the weight ratio of plasticizer to tackifier and the weight ratio of the wax and plasticizer combination to tackifier each have a surprising relationship with, inter alia, peel strength and adhesive failure mode. Ranges and limits on these ratios and other component ratios are discussed herein. In particular, when the weight ratio of plasticizer to tackifier is at least 0.05:1 and/or optionally when the weight ratio of wax and plasticizer (combination) to tackifier is at least 0.05:1, for example, a desirable peel strength, elimination or reduction of cohesive failure mode, and/or elimination or reduction of anchor failure is achieved. Anchoring failure may involve locations where there is adhesive competition between the facestock and the substrate; if the adhesive has a stronger adhesion to the substrate than to the facestock, the adhesive is deleteriously transferred from the facestock to the substrate. This phenomenon may also be referred to as adhesive transfer. Preferably, the hot melt PSA has greater adhesion (anchoring) to the substrate than to the substrate, and the substrate remains clean when the label or tape (with the hot melt PSA) is peeled from the substrate.

In one embodiment, the SIS copolymer has a diblock content of less than 60 wt.%, the tackifier has a softening point below 150 ℃, the wax is a soft wax, e.g., a wax having a high needle penetration of greater than 20dmm, and the plasticizer has a high viscosity of at least 175mm at 40 ℃, as measured, for example, by chinese standard BG/T265 (1988)²A/sec, and/or a high molecular weight, e.g., at least 200. Due to the combination of these components, the resulting hot melt PSA has a melt flow rate as measured by FTM 2 of from 0.5N/inch to 20N/inch, such as from 0.5N/inch to 15N/inch; 0.5N/inch to 10N/inch, 0.5N/inch to 5N/inch, 1.0N/inch to 10N/inch, 1N/inch to 7N/inch, 1N/inch to 5N/inch.

With respect to the lower limit, the hot melt PSA has a stainless steel peel strength of at least 0.5N/inch, such as at least 1.0N/inch, at least 1.5N/inch, at least 2.0N/inch, at least 2.5N/inch, at least 3.0N/inch, at least 3.5N/inch, at least 4.0N/inch, at least 4.5N/inch, or at least 5.0N/inch. With respect to the upper limit, the hot melt PSA has a stainless steel peel strength of less than 20N/inch, such as less than 15N/inch, less than 10N/inch, less than 7N/inch, less than 5N/inch, less than 4.5N/inch, less than 4.0N/inch, less than 3.5N/inch, less than 3.0N/inch, less than 2.5N/inch, less than 2.0N/inch, less than 1.5N/inch, or less than 1.0N/inch. These particular peel strength ranges/limits represent highly desirable levels of removability and repositionability. Lower peel strengths do not provide sufficient tack or adhesion, while higher peel strengths make removal or rearrangement difficult, if not impossible, without disruption of the facestock tear, matrix tear, or adhesion.

In one embodiment, a lower range of peel strengths is contemplated ("ultra low tack solution"). For example, hot melt PSAs have a stainless steel peel strength of 0.5N/inch to 2.0N/inch, such as 0.5N/inch to 1.5N/inch, 0.5N/inch to 1.0N/inch, or 0.5N/inch to 0.75N/inch.

In one embodiment, the peel strength is focused on the low-to-medium range ("low tack protocol"). For example, the hot melt PSA has a stainless steel peel strength of 0.5N/inch to 3.0N/inch, such as 0.5N/inch to 2.5N/inch, 1.0N/inch to 3.0N/inch, 1.0N/inch to 2.5N/inch, 1.0N/inch to 2.0N/inch, or 1.2N/inch to 2.3N/inch. Low tack applications involve washi paper.

In one embodiment, a medium range is contemplated for peel strength ("medium tack protocol"). For example, hot melt PSAs have a stainless steel peel strength of 1.5N/inch to 4.5N/inch, such as 1.5N/inch to 4.0N/inch, 2.0N/inch to 4.0N/inch, or 2.5N/inch to 3.5N/inch. A medium solution may for example be suitable for containers that open and close the container multiple times using a repositionable or re-attachable closure, such as a tissue box closure label and for some washi paper applications.

In one embodiment, a higher range is contemplated for peel strength ("high tack solution"). For example, hot melt PSAs have a stainless steel peel strength of 4.5N/inch to 20.0N/inch, such as 5.0N/inch to 15.0N/inch, 5.0N/inch to 10.0N/inch, 4.5N/inch to 10.0N/inch, or 7.0N/inch to 9.0N/inch. The high-tack solution may, for example, be suitable for adhering loose items to an appliance, such as a refrigerator, during transport.

The compositional makeup of these schemes is discussed further herein. The above upper and lower limits may also be applied to these solutions, if appropriate. For example, low tack hot melt PSAs have a stainless steel peel strength of at least 0.5N/inch, such as at least 1.0N/inch.

Polymer and method of making same

The polymers of hot melt PSAs comprise styrene-isoprene-styrene copolymers (SIS block copolymers), where "S" represents a polymeric segment or "block" of styrene monomer, and "I" represents a polymeric segment or "block" of isoprene. The SIS block copolymer can be a pure triblock copolymer that does not contain SI diblock or can contain a weight percentage of SI diblock. In some cases, a single SIS block copolymer may be used, while in other cases, a combination of SIS block copolymers may be used. The SIS copolymer may comprise a mixture of copolymer products. The structure of the SIS copolymer can vary widely, for example, linear, branched, radial, asymmetric radial, or combinations thereof. Preferably, the SIS copolymer has a linear or radial structure.

In some embodiments, the copolymer can comprise other blocks in addition to the SIS blocks. Different types of polymers can be mixed with the SIS blocks. Examples include, but are not limited to, SBS, SIBS, SEBS, and mixtures thereof.

It was found that higher diblock content (SI, SB or combinations thereof) (in SIs copolymers) can be associated with an excessive increase in stickiness of the SIs block copolymer. Advantageously, lower SI diblock content was found to be associated with increased copolymer elasticity and improved removability and rearrangeability. The SI diblock content of the SIS copolymer can be 0 wt% to 60 wt%, e.g., 1 wt% to 60 wt%, 1 wt% to 55 wt%, 3 wt% to 55 wt%, 15 wt% to 53 wt%, 20 wt% to 53 wt%, 10 wt% to 30 wt%, 22 wt% to 53 wt%, or 25 wt% to 50 wt%. With respect to the upper limit, the SI diblock content of the SIS copolymer can be less than 60 wt%, such as less than 55 wt%, less than 53 wt%, less than 50 wt%, less than 35 wt% less than 30 wt%, less than 25 wt%, or less than 20 wt%. With respect to the lower limit, the SI diblock content of the SIS copolymer can be at least 5 wt%, at least 10 wt%, at least 15 wt%, at least 20 wt%, at least 22 wt%, at least 25 wt%, or at least 30 wt%, and in some embodiments the base polymer is substantially free of, e.g., comprises, e.g., less than 10 wt%, less than 5 wt%, less than 3 wt%, or less than 1 wt% SI diblock, e.g., is free of SI diblock. In some cases, SIS block copolymers can have lower SB diblock (and/or low SB and SI diblock) content. The weight percentages mentioned herein for the SI diblock also apply to the SB diblock content and the total diblock (e.g., SB and SI) content.

The styrene content of the SIS copolymer can also affect the performance characteristics of the base polymer. It was found that specific styrene contents, as well as specific diblock contents, can impart the desired properties of high melt flow index (greater than 20g/10 min at 190 ℃) and low viscosity to the base polymer. Together, these properties make the polymer more suitable for compounding and coating processes. The styrene content of the base polymer may be from 0 to 35 wt%, such as from 5 to 30 wt%, from 10 to 25 wt%, from 15 to 30 wt%, from 15 to 25 wt%, from 15 to 20 wt%, or from 25 to 30 wt%. With respect to the upper limit, the styrene content can be less than 35 wt%, such as less than 30 wt%, less than 25 wt%, less than 20 wt%, less than 15 wt%, less than 10 wt%, or less than 5 wt%. With respect to the lower limit, the styrene content may be at least 5 wt.%, such as at least 10 wt.%, at least 15 wt.%, at least 20 wt.%, at least 25 wt.%, at least 30 wt.%, or at least 35 wt.%.

The amount of (solid) SIS copolymer in the hot melt PSA composition can be from 15% to 65%, for example from 15% to 45%, from 20% to 50%, from 25% to 55%, from 30% to 60%, or from 35% to 65%. The amount of SIS copolymer in the hot melt PSA composition can be 30% to 50%, for example 30% to 42%, 32% to 44%, 34% to 46%, 36% to 48%, or 38% to 50%. With respect to the upper limit, the amount of SIS copolymer in the hot melt PSA composition can be less than 70%, less than 65%, less than 60%, less than 55%, less than 50%, less than 45%, or less than 40%. With respect to the lower limit, the amount of SIS block copolymer in the hot melt PSA composition can be at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, or at least 40%.

In some cases, the copolymer may have a lower molecular weight. As an example of a linear copolymer, the molecular weight of the copolymer may be 50000-300000, such as 65000-275000, 80000-250000, or 100000-200000. With respect to the lower limit, the linear copolymer may have a molecular weight of at least 50000, for example at least 65000, at least 80000, or at least 100000. With respect to the upper limit, the linear copolymer can have a molecular weight of less than 300000, such as less than 275000, less than 250000, or less than 200000. The molecular weight of the radial copolymer depends on the number of branches. For example, the molecular weight of the copolymer may be 200000-. With respect to the lower limit, the radial copolymer may have a molecular weight of at least 200000, for example at least 300000, at least 400000, or at least 500000. With respect to the upper limit, the radial copolymer may have a molecular weight of less than 1200000, such as less than 1000000, less than 900000, or less than 800000.

Suitable commercial SIS copolymers include, but are not limited to, SIS 1220, SIS 1100, SIS 1300, SIS 1250; SIS 4019, Balin yueyayang Sinopec; quintac 3421 available from Nippon Zeon Company, ltd. (US sales of louis ville, Ky.); vector 4293, Vector 4230 and Vector 4111 available from Dexco/TSRC, and rubber available from Kraton Polymers (Houston, Texas).

Tackifier

The tackifiers used in hot melt formulations can vary widely. In some embodiments, tackifiers with low softening points are preferred. For example, the tackifier may have a softening point of 150 ℃ or less, e.g., 140 ℃ or less, 130 ℃ or less, 120 ℃ or less, 110 ℃ or less, 105 ℃ or less, 100 ℃ or less, 95 ℃ or less, 90 ℃ or less, 85 ℃ or less, or 80 ℃ or less. With respect to ranges, the tackifier may have a softening point of 60 ℃ to 140 ℃, e.g., 80 ℃ to 150 ℃, 90 ℃ to 130 ℃, or 90 ℃ to 110 ℃.

In some cases, the tackifier may comprise a single tackifier. In other cases, the tackifier may comprise a mixture of multiple tackifier products.

In some embodiments, the tackifier has a low molecular weight (number average molecular weight may be suitable for the molecular weight discussed herein). For example, the tackifier may have a molecular weight of less than 1700, such as less than 1500, less than 1200, less than 1180, less than 1000, less than 900, less than 800, less than 700, or less than 650. The tackifier may have a molecular weight greater than 300, such as greater than 400, greater than 500, greater than 550, greater than 600, greater than 650, greater than 700, greater than 750, or greater than 800. With respect to ranges, the tackifier may have a molecular weight of 500-. Without being bound by theory, it is believed that the use of lower molecular weight (and/or low viscosity) tackifiers allows for the use of specific higher molecular weight plasticizers that provide a synergistic improvement in oil migration performance.

In a preferred embodiment, the tackifier comprises a hydrogenated (hydrocarbon) resin. In some (but not all) cases, the hydrogenated resin may generally have a lower polarity than the non-hydrogenated resin. Lower polarity results in lower adhesion in hot melt PSAs, which is advantageous for applications requiring removability and/or repositionability. In some cases, the tackifier comprises a (hydrogenated) alicyclic hydrocarbon resin. Oils are commonly used in hot melt formulations to control adhesion. The use of hydrogenated resins and the resulting adhesion inhibition advantageously allows for the use of lower amounts of oil for hot melt PSAs.

As another benefit, hydrogenation of the resin produces adhesive layers and labels with reduced color, odor, and carbon particles.

Suitable commercial tackifiers include, but are not limited to, for example, hydrogenated DCPD resins such as HD1100, HD1120 from Luhua, or E5400 from Exxon Mobil. Other suitable hydrogenated resins include fully hydrogenated resins such as Regalite S1100, R1090, R1100, C100R and C100W from Eastman, and fully hydrogenated C9 resins such as QM-100A and QM-115A from Hebei Qiming. E5400 and HD1100 are hydrogenated cycloaliphatic DCPD resins.

In one embodiment, a hot melt PSA composition comprises a (solid) tackifier in an amount from 15 to 45 wt%, from 15 to 40 wt%, from 20 to 35 wt%, or from 25 to 35 wt%. With respect to the upper limit, the amount of tackifier in the hot melt PSA composition may be less than 45 wt%, such as less than 40 wt%, less than 35 wt%, less than 30 wt%, less than 25 wt%, less than 20 wt%, or less than 15 wt%. With respect to the lower limit, the amount of tackifier in the hot melt PSA composition may be 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 wt%.

Wax

Hot melt PSAs may use soft wax. In some embodiments, the soft wax has a high needle penetration, e.g., a needle penetration greater than 8dmm, e.g., greater than 10, greater than 12, greater than 15, greater than 17, greater than 20, or greater than 25dmm, greater than 30dmm, or greater than 35dmm, as measured by ASTM D5 (2016). With respect to ranges, the soft wax has a needle penetration of from 8dmm to 40dmm, for example from 10dmm to 40dmm, from 10dmm to 35dmm, from 10dmm to 30dmm, from 15dmm to 40dmm, from 15dmm to 30dmm or from 15dmm to 25 dmm. The inventors have found that the use of a harder wax results in high stiffness, which results in very low initial tack and a high level of "easy tear" (zipping) when peeled from the substrate. Tearability is associated with the rapid removal of the hot melt adhesive (or a label containing the hot melt adhesive) from the substrate. Labels that peel quickly and produce a high peel sound are considered to have a high level of tearability. And tearability is a negative quality, especially from the end user's point of view. It has been found that soft waxes advantageously provide hot melt PSAs with long-term softness, which yields the benefits of improved tack (relative to hard waxes) and smooth, less prone to tearing off.

In some cases, the wax may comprise a single wax. In other cases, the wax may comprise a mixture of multiple wax products.

The wax may have a higher molecular weight. The inventors have found that higher molecular weight waxes can advantageously improve oil migration.

In some preferred embodiments, exemplary waxes include microcrystalline waxes, paraffin waxes, hydrocarbon waxes, and combinations thereof.

In some cases, the wax is a polyethylene wax. Polyethylene waxes can be used to increase the hydrophobicity of the adhesive. This increased hydrophobicity may help improve the resistance of the adhesive to water whitening and the ability of the adhesive to be cleanly removed or rearranged. The specific polyethylene wax may also be selected to further reduce the overall viscosity of the hot melt PSA and to have minimal effect on the clarity of the adhesive.

In some embodiments, the wax has a high melting point. For example, the wax may have a melting point of 60 ℃ or greater, e.g., 65 ℃ or greater, 70 ℃ or greater, 75 ℃ or greater, 80 ℃ or greater, or 85 ℃ or greater. With respect to ranges, the wax may have a melting point of 60 ℃ to 125 ℃, e.g., 65 ℃ to 115 ℃, 65 ℃ to 100 ℃, 70 ℃ to 90 ℃, or 75 ℃ to 85 ℃. The wax may have a melting point of 150 ℃ or less, e.g., 125 ℃ or less, 100 ℃ or less, 95 ℃ or less, 90 ℃ or less, or 85 ℃ or less. The use of these waxes was found to surprisingly reduce oil migration, especially during storage and transportation. In addition, it was found that the use of a wax with a higher melting point unexpectedly provides better aging performance at higher temperatures. Without being bound by theory, it is believed that the use of higher melting point waxes helps the resulting adhesive to soften at much higher temperatures. Thus, better cohesive strength is shown for a much wider (higher) temperature range.

The wax may have a relatively low viscosity, such as a dynamic viscosity as measured by a brookfield viscometer. The polyethylene wax can have a dynamic viscosity of 150-500cps, such as 150-300cps, 250-400cps, 350-500cps, 150-200cps, 200-250cps, 250-300cps, 300-350cps, or 350-400cps at 140 ℃. With respect to the upper limit, the polyethylene wax can have a dynamic viscosity of less than 500cps, less than 450cps, less than 400cps, less than 350cps, less than 300cps, less than 250cps, or less than 200cps at 140 ℃. With respect to the lower limit, the polyethylene wax can have a dynamic viscosity of at least 150cps, such as at least 200cps, at least 250cps, at least 300cps, at least 350cps, at least 400cps, or at least 450cps at 140 ℃.

The wax may also be selected to have a particular pour point as measured by standard procedure ASTM D5949. Pour point is defined as the temperature at which a liquid becomes semi-solid and loses its flow characteristics. The polyethylene wax can have a pour point greater than 90 ℃, greater than 91 ℃, greater than 92 ℃, greater than 93 ℃, greater than 94 ℃, greater than 95 ℃, greater than 96 ℃, greater than 97 ℃, greater than 98 ℃, greater than 99 ℃, greater than 100 ℃, greater than 101 ℃, greater than 102 ℃, greater than 103 ℃, greater than 104 ℃, greater than 105 ℃, greater than 106 ℃, greater than 107 ℃, greater than 108 ℃, greater than 109 ℃, or greater than 110 ℃. In some embodiments, the polyethylene wax has a pour point of greater than 100 ℃.

The amount of wax in the hot melt adhesive is 1 to 15 wt%, such as 1 to 12 wt%, 2 to 10 wt%, 3 to 9 wt%, 2 to 8 wt%, or 3 to 8 wt%. With respect to the upper limit, the amount of wax in the hot melt adhesive can be less than 15 weight percent, less than 13 weight percent, less than 12 weight percent, less than 10 weight percent, less than 9 weight percent, less than 8 weight percent, less than 7 weight percent, or less than 5 weight percent. With respect to the lower limit, the amount of polyethylene wax in the hot melt PSA composition can be 0 or at least 1, at least 2, at least 3, at least 4, at least 5, at least 7, at least 10, or at least 12 weight percent.

Suitable commercial waxes include, but are not limited to, for example, Sasol wax 3971, 7835, 6403, 6805, and 1800 from Sasol; A-C1702, A-C6702, A-C5180 from Honeywell; microwax FG 7730 and Microwax FG 8113 from Parameter Specialty Materials (Suzhou) Co.Ltd.

Plasticizer

Hot melt PSAs contain a plasticizer. Plasticizers may vary widely. In some embodiments, the plasticizer has a high molecular weight and/or a high viscosity. The use of high molecular weight plasticizers has been found to provide many advantages to hot melt adhesives that are not observed with conventional hot melt PSA compositions. Without being bound by theory, high molecular weight plasticizers (especially in combination with low molecular weight tackifiers) inhibit or eliminate oil migration in hot melt PSAs, which contribute to the advantageous performance characteristics discussed herein.

In some cases, the plasticizer may comprise a single plasticizer. In other cases, the plasticizer may comprise a mixture of multiple plasticizer products.

In some embodiments, the plasticizer has a molecular weight of at least 200, such as at least 300, at least 400, at least 500, at least 700, at least 1000, at least 1200, or at least 1500. With respect to ranges, the plasticizer can have a molecular weight of 200-1500, such as 200-1000, 250-900, 400-800, 500-700, or 550-650. With respect to the upper limit, the plasticizer may have a molecular weight of less than 3000, such as less than 2000, less than 1000, less than 800, less than 650, or less than 600. The use of these plasticizers was found to surprisingly reduce oil migration and/or membrane facer swelling.

In some embodiments, the plasticizer may have a high viscosity. The kinematic viscosity can be measured, for example, using the procedure of China Standard BG/T265-. The plasticizer may have a thickness of 175mm at 40 ℃²Second to 1000mm²Per second, e.g. 300mm²Second to 1000mm²Second, 300-²Second, 400-²400-²650 mm/sec, 450-²Second, 475-²Second, or 500-²Kinematic viscosity per second. With respect to the upper limit, the plasticizer may have less than 1000mm²Per second, e.g. less than 900mm²Per second, less than 800mm²Per second, less than 700mm²Per second, less than 650mm²Second, less than 625mm²Per second, less than 600mm²Per second, or less than 500mm²Kinematic viscosity per second. With respect to the lower limit, the plasticizer may have a thickness of at least 175mm²Per second, e.g. at least 200mm²Per second, at least 300mm²Per second, at least 400mm²Per second, at least 450mm²At least 475mm per second²Per second, at least 500mm²Per second, at least 600mm²Per second, at least 700mm²Per second, at least 800mm²Per second, or at least 900mm²Kinematic viscosity per second.

In some cases, it is also contemplated to use a plasticizer having a lower molecular weight or viscosity, although higher molecular weights and viscosities are preferred.

In some embodiments, the plasticizer is a compound selected from the group consisting of polyisobutylene, naphthenic oil, paraffinic oil, liquid polyisoprene, liquid white mineral oil, and combinations thereof.

Suitable commercial plasticizers include, but are not limited to, for example, 300# white oil from Sinopec, KN4010 and KP6030, Claire F55 from Tianjin and F550 from Formosa Petrochemical Corp, as well as various polyisobutylene products.

Another advantage of high molecular weight plasticizers is that hot melt PSAs can be used to create labels with greater structural integrity. For example, labels comprising hot melt PSAs can exhibit reduced shrinkage and expansion. The 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 shrinking measurement period may 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. Reduced expansion and contraction can be observed during storage at temperatures greater than 45 ℃, greater than 50 ℃, greater than 55 ℃, greater than 60 ℃, greater than 65 ℃, or greater than 70 ℃. Reduced expansion and contraction may be observed during storage at a relative humidity of greater than 80%, greater than 82%, greater than 84%, greater than 86%, greater than 88%, or greater than 90%. In some embodiments, the label comprising a hot melt PSA has no dimensional change, or less than a 2% change in each dimension, when stored at 85% relative humidity for 4 days at greater than 65 ℃ or 7 days at greater than 50 ℃.

If the plasticizer comprises a paraffinic oil, it has surprisingly been found that these paraffinic oils enhance the stability of the label, have lower oil migration within and between the layers of the label, and little adhesive leaks under the original print of the adhered label. These improvements not only improve the effectiveness of the label in adhering to an article and anchoring and retaining printed indicia, but also improve the visual appearance of the label from the perspective of the end user. As tags are often used to present important information, or to enhance the visibility or appeal of consumer products, these improvements can significantly enhance the value of the tags.

The amount of plasticizer in the hot melt PSA composition can be from 5 wt% to 35 wt%, such as from 10 wt% to 30 wt%, from 12 wt% to 28 wt%, from 10 wt% to 25 wt%, from 15 wt% to 25 wt%, or from 18 wt% to 25 wt%. With respect to the upper limit, the amount of plasticizer in the hot melt PSA composition can be less than 35 weight percent, less than 30 weight percent, less than 28 weight percent, or less than 25 weight percent. With respect to the lower limit, the amount of plasticizer in the hot melt PSA composition may be at least 5 wt%, at least 10 wt%, at least 12 wt%, at least 15 wt%, or at least 18 wt%.

Component weight ratio/viscosity related protocol

In some embodiments, the weight ratio of soft wax to plasticizer is at least 0.05:1, such as at least 0.1:1, at least 0.15:1, at least 0.17:1, or at least 0.2: 1. With respect to ranges, the weight ratio of soft wax to plasticizer may be from 0.05:1 to 2:1, such as from 0.05:1 to 1.5:1, from 0.05:1 to 1:1, from 0.1:1 to 0.8:1, or from 0.1:1 to 0.6: 1. The weight ratio of soft wax to plasticizer may be less than 2:1, such as less than 1.5:1, less than 1:1, less than 0.8:1, less than 0.6:1, or less than 0.5: 1.

In some cases, the weight ratio of soft wax to tackifier in hot melt adhesives is high. The inventors have found that a particular balance of high molecular weight and low molecular weight tackifiers can balance the overall molecular weight of the hot melt composition, which has been found to inhibit oil migration. In some cases, the weight ratio of soft wax to tackifier is at least 0.05:1, such as at least 0.1:1, at least 0.15:1, at least 0.2:1, at least 0.3:1, at least 0.4:1, at least 0.5:1, or at least 1:1. With respect to ranges, the weight ratio of soft wax to tackifier may be from 0.05:1 to 2:1, such as from 0.05:1 to 1.5:1, from 0.05:1 to 1:1, from 0.1:1 to 0.8:1, or from 0.1:1 to 0.5: 1. The weight ratio of soft wax to tackifier may be less than 2:1, such as less than 1.5:1, less than 1:1, less than 0.8:1, less than 0.6:1, or less than 0.5: 1.

It was found that the use of a tackifier (having a low molecular weight and viscosity) advantageously (partially) compensates for or allows for the use of a higher molecular weight and viscosity plasticizer. This combination provides a significant improvement in the age staining, which is a measure of oil migration. In some cases, the weight ratio of plasticizer to tackifier is at least 0.05:1, such as at least 0.1:1, at least 0.15:1, at least 0.2:1, at least 0.3:1, at least 0.4:1, at least 0.5:1, or at least 1:1. With respect to ranges, the weight ratio of soft wax to tackifier may be from 0.05:1 to 2:1, such as from 0.05:1 to 1.5:1, from 0.2:1 to 2:1, from 0.2:1 to 1:1.1, or from 0.2:1 to 0.9: 1. The weight ratio of plasticizer to tackifier may be less than 2:1, such as less than 1.5:1, less than 1.1:1, less than 1:1, or less than 0.8: 1.

In some cases, the weight ratio of the soft wax and plasticizer combination to the tackifier in the hot melt adhesive is high. In some cases, the weight ratio of the soft wax and plasticizer combination to the tackifier is at least 0.05:1, such as at least 0.1:1, at least 0.15:1, at least 0.2:1, at least 0.3:1, at least 0.5:1, at least 0.7:1, or at least 1:1. With respect to ranges, the weight ratio of the soft wax and plasticizer combination to the tackifier may be from 0.05:1 to 3:1, such as from 0.1:1 to 3:1, from 0.2:1 to 2:1, from 0.3:1 to 1.5:1, or from 0.5:1 to 1.5: 1. The weight ratio of the soft wax and plasticizer combination to the tackifier may be less than 3:1, such as less than 2:1, less than 1.5:1, less than 1:1.4, less than 1.3:1, or less than 1:1.

In one embodiment, the high viscosity hot melt PSA comprises the weight percentages of styrene-isoprene-styrene copolymer, tackifier, and plasticizer (and optionally wax) described herein. In some embodiments, the high viscosity hot melt PSA does not include a wax component.

When no wax is used, the weight ratio may be similar to those described above, for example the weight ratio may vary by less than 20%, for example less than 15%, less than 10% or less than 5%. Where no wax is used, the weight percent of the components (copolymer, tackifier, and plasticizer) may be slightly higher than when a wax is used, e.g., less than 20%, less than 10%, or less than 5% higher.

The total viscosity of the hot melt PSA can be such that the dynamic viscosity of the adhesive at 170 ℃ is in the range of 10,000cps to 35,000cps, e.g., 10,000cps to 30,000cps, 12,000cps to 28,000cps, 12,000cps to 16,000cps, 14,000cps to 18,000cps, 16,000cps to 20,000cps, 10,000cps to 12,000cps, 12,000cps to 14,000cps, 14,000cps to 16,000cps, 16,000cps to 18,000cps, or 18,000cps to 20,000cps as measured by a brookfield viscometer. With respect to the upper limit, the hot melt PSA can have a dynamic viscosity of less than 35,000cps, e.g., less than 33,000cps, less than 30,000cps, less than 28,000cps, less than 25,000cps, less than 20,000cps, less than 18,000cps, less than 16,000cps, less than 14,000cps, or less than 12,000cps at 170 ℃. With respect to the lower limit, the hot melt PSA can have a dynamic viscosity of at least 10,000, such as at least 12,000, such as at least 14,000, at least 16,000, at least 18,000, at least 20,000, at least 22,000, or at least 25,000 at 170 ℃.

The total viscosity of the hot melt PSA can be such that the dynamic viscosity of the adhesive at 160 ℃ is in the range of 15,000cps to 50,000cps, e.g., 15,000cps to 48,000cps, 20,000cps to 48,000cps, 22,000cps to 48,000cps, 25,000cps to 46,000cps, 25,000cps to 40,000cps, 30,000cps to 40,000cps, or 32,000 to 38,000cps as measured by a brookfield viscometer. With respect to the upper limit, the hot melt PSA can have a dynamic viscosity of less than 50,000cps, such as less than 48,000cps, less than 46,000cps, less than 40,000cps, or less than 38,000cps at 160 ℃. With respect to the lower limit, the hot melt PSA can have a dynamic viscosity of at least 15,000, such as at least 20,000, at least 22,000, at least 30,000, or at least 32,000cps at 160 ℃.

Adjustability

As noted above, the inventors have found that the weight ratio of plasticizer to tackifier and the weight ratio of the wax and plasticizer combination to tackifier each have a surprising relationship to peel strength, especially of stainless steel. The invention further relates to a method for producing a hot melt adhesive based on the peel strength of stainless steel. In one embodiment, the method comprises the steps of: providing a styrene-isoprene-styrene copolymer; tackifiers, waxes, and plasticizers, and to determine the desired peel strength or range of peel strengths. Based on the desired peel strength range, a suitable plasticizer to tackifier weight ratio may be determined. The method further comprises the steps of: the components are combined to form a hot melt adhesive. Importantly, the plasticizer and tackifier are combined such that these components are present in a defined plasticizer to tackifier weight ratio. The resulting hot melt adhesive has a stainless steel peel strength within the desired peel strength range. In some preferred embodiments, the method further comprises the step of: the method further includes determining a weight ratio of the plasticizer and wax combination to the tackifier based on the desired peel strength, and combining the components such that the plasticizer, wax, and tackifier are combined such that the components are present in the determined weight ratio of the plasticizer and wax combination to the tackifier.

In some embodiments, other component relationships may be utilized to achieve the desired peel strength range. The method may further comprise the steps of: the weight ratio of one or more components to another is determined. For example, the weight ratios of the components for the ultra low, medium, and high viscosity regimes can be used in conjunction with the performance property ranges.

In one embodiment, the method may further comprise the step of: the weight ratio of wax to tackifier is determined based on the desired peel strength range. This determination may be made using the weight ratio ranges and peel strength ranges discussed herein.

In one embodiment, the method may further comprise the step of: the weight ratio of the wax and plasticizer combination to the tackifier is determined based on the desired peel strength range. This determination may be made using the weight ratio ranges and peel strength ranges discussed herein.

In one embodiment, the method may further comprise the step of: the weight ratio of wax to plasticizer is determined based on the desired peel strength range. This determination may be made using the weight ratio ranges and peel strength ranges discussed herein.

Label (R)

The invention also relates to a label comprising the above hot melt PSA and a facestock (suitable for printed marking). The facestock may include, for example, a paper facestock, a cardboard facestock, a plastic facestock, a multi-layer laminate facestock comprising a paper layer and a plastic layer, or any other material commonly used in the industry. The multilayer laminate facestock may include a paper layer overlying a plastic layer. The plastic layer of the multilayer laminate facestock may be extruded or coated onto the paper layer. The paper layer may include, for example, high gloss paper, semi-gloss paper, lithographic paper, or Electronic Data Processing (EDP) paper; and may be configured for multi-color printing, typewriter printing, or inkjet printing, for example. The plastic layer may comprise, for example, polyester, such as PET; polyolefins, such as polypropylene (PP), ethylene-propylene copolymers, Polyethylene (PE); and other materials. Other polymeric film materials include urethane-based polymers, such as polyether urethanes and polyester urethanes; amide-based polymers including polyether polyamide copolymers; acrylic-based polymers, including polyacrylates, and ethylene/vinyl acetate copolymers; polyester-based polymers, including polyether polyesters; vinyl chloride; vinylidene chloride; polystyrene; polyacrylonitrile; a polycarbonate; a polyimide; and the like. The facestock may comprise a flexible facestock. The facestock may comprise a transparent polymeric film. In certain applications, it may be useful to use "shrink" or oriented films as facestock layers. The inventive subject matter includes, for example, biaxially oriented films such as PET as facestock layers.

In some embodiments, the label further comprises a print disposed on the facestock layer. The print comprises a layer or area of ink, dye, pigment or similar material. It is understood that "dye" and similar terms mean a visible light absorbing compound that exists in a molecularly dispersed or dissolved form. "pigment" and like terms mean a visible light absorbing material or compound that is present in a non-molecularly dispersed or particulate form. "ink" and like terms mean a coatable or printable formulation comprising a dye and/or pigment. While the present subject matter is largely directed to labels containing visually-perceptible prints, it is contemplated that the labels may include prints that are displayed only or primarily under UV light or other conditions.

The hot melt PSA layer may be applied directly adjacent to or in contact with the facestock. An intermediate layer may be present between the hot melt PSA layer and the facestock. The label may include two or more layers of hot melt PSA and/or facestock. The hot melt PSA layer of the label may be applied to the facestock at a coat weight of, for example, 5 grams per square meter (gsm) to 30 gsm. The bond layer coat weight can be from 6gsm to 20gsm, from 8gsm to 20gsm, from 22gsm to 30gsm, from 16gsm to 40 gsm. In some embodiments, the adhesive layer coat weight is in the range of 5gsm to 40 gsm. With respect to the upper limit, the bond layer coat weight can be less than 40gsm, such as less than 35gsm, less than 30gsm, less than 25gsm, less than 20gsm, less than 15gsm, or less than 10 gsm. With respect to the lower limit, the adhesive layer coat weight may be at least 5gsm, such as at least 10gsm, at least 15gsm, at least 20gsm, at least 25gsm, at least 30gsm, or at least 35 gs.

The inventive subject matter may include the incorporation of one or more clear or transparent layers into any of the label structures described herein. The inventive subject matter also includes incorporating one or more metal layers or foils into any of the label structures described herein. It is also contemplated that the label structure may also include a combination of one or more transparent layers and one or more metal layers. In some embodiments, the label is a clear on clear (clear on clear) label having a laminate composition comprising a transparent biaxially oriented polypropylene (BOPP) film, a transparent hot melt PSA layer, and a transparent PET liner.

In some embodiments, the label further comprises a liner disposed on the hot melt PSA layer. The release liner may be disposed adjacent to the adhesive layer such that the adhesive layer is directly or indirectly interposed or sandwiched between the bottom surface of the facestock and the release liner. The release liner may act as a protective cover such that the release liner remains in place until the label is ready to be adhered to an object. If a liner or release liner is included in the label, a wide range of materials and structures can be used for the liner. In many embodiments, the liner is paper or a 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 releasable material, such as a silicone or silicone-based material. It is understood that the release-coated side of the liner is in contact with the otherwise exposed side of the adhesive layer. The liner is removed to expose the adhesive layer of the label before the label is applied to a surface of interest. The liner may be in the form of a single sheet. Alternatively, the pad may be in the form of multiple segments or plates.

Other additives may be added to one or more of the hot melt PSA, facestock or deposition layer to achieve certain desired properties. These additives may include, for example, one or more waxes, surfactants, talc, powdered silicates, filler agents, defoamers, colorants, antioxidants, UV stabilizers, luminescent agents, crosslinking agents, buffering agents, antiblocking agents, wetting agents, matting agents, antistatic agents, acid scavengers, flame retardants, processing aids, extrusion aids, and others.

The present invention also relates to labeled containers comprising the hot melt pressure sensitive adhesive of the present invention. The labeled container includes a container defining an outer surface and a label as described above adhered to the outer surface of the container. In some embodiments, the container is a bottle. The outer surface to which the hot melt PSA is adhered can comprise a wide range of substrates. The outer surface may comprise glass, plastic, wood, metal, combinations of these and other materials. In some embodiments, the outer surface of the container comprises glass.

In some embodiments, the outer surface of the container comprises plastic. The outer surface may comprise or be formed from any suitable polymer or polymer blend. The polymer or polymer blend 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 comprises PET.

Although the label is typically removable from the container, the outer surface of the container may retain a portion of the adhesive used to adhere the label to the container. This adhesive residue can contaminate or interfere with subsequent container operations, such as later washing, re-labeling or container recycling. In some embodiments, the provided labels may be removed from the outer surface while substantially all of the adhesive remains disposed of and/or retained with the label rather than with 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 exterior surface, and a label according to an embodiment. The method further comprises adhering the label to the outer surface of the container, thereby applying the label to the container.

The labels may be adhered to one or more containers or articles in a batch, continuous, or semi-continuous manner. One or more liners may be removed from the label prior to application, thereby exposing 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. Adhering may also include one or more operations of squeezing or applying a squeezing force to the label to facilitate contact and/or adhesion with the container; activating and/or curing the adhesive, for example by heating and/or exposure to UV light; and/or a drying operation.

Other applications for hot melt PSAs are contemplated. For example, one application involves adhesive sheets that do not include a facestock. Another application involves adhesive sheets using the composition on both sides of the facestock, such as double sided tape. Another application involves a self-adhesive (self-wind) adhesive with a hot melt PSA on one side of the facestock and any other adhesive composition on the other side. The structure may optionally include a liner or may be linerless.

Hot melt PSAs are useful in many markets. For example, in the electronics market, hot melt PSAs are useful in applications where good adhesion to glass and/or to a variety of engineering plastics is desired. The above removability and/or repositionability characteristics of hot melt PSAs can provide adequate adhesion to electronic device substrates and the ability to rework the product when problems arise in production. In particular, the ability to be cleanly removed can allow for recycling of the substrate from which the hot melt PSA is removed after use.

Hot melt PSAs are useful in situations where removability and/or repositionability characteristics are required in the building and construction market. Some examples include self-adhesive products, as discussed above, or masking tape, such as painter's tape.

In other markets, such as automobiles, hot melt PSAs are useful as adhesive skins for foam compositions, particularly in applications where one-sided removability is desired. In other cases, the ability to adhere to low surface energy materials such as engineering plastics, oleophobic coated glass, or painted metals can be advantageous because it is a low polarity design composition.

Among others, the following embodiments are contemplated. All combinations of features and embodiments are contemplated.

Embodiment 1: a hot melt adhesive comprising: a styrene-isoprene-styrene copolymer, optionally present in an amount of 15 wt% to 65 wt%; a tackifier having a softening point of 150 ℃ or lower; 1 to 15 wt% of a wax having a needle penetration greater than 8dmm as measured by ASTM D5(2016), optionally present in an amount of 1 to 15 wt%; a plasticizer, wherein the adhesive has a stainless steel peel strength of 0.5N/inch to 20N/inch as measured by FINAT test method 2 (2016).

Embodiment 2: the embodiment according to embodiment 1 wherein the adhesive has a stainless steel peel strength of 0.5N/inch to 5N/inch as measured by FINAT test method 2 (2016).

Embodiment 3: an embodiment according to embodiment 1 or 2, wherein the styrene-isoprene-styrene copolymer comprises less than 60 wt% SI diblock.

Embodiment 4: an embodiment according to any of embodiments 1-3, wherein the adhesive comprises 15 to 65 wt% of a styrene-isoprene-styrene copolymer containing less than 60 wt% SI diblock.

Embodiment 5: an embodiment according to any of embodiments 1 to 4, wherein the styrene-isoprene-styrene copolymer comprises less than 35 wt% polymerized styrene monomer and less than 60 wt% SI diblock.

Embodiment 6: an embodiment according to any one of embodiments 1 to 5 wherein the weight ratio of plasticizer to tackifier is at least 0.05: 1.

Embodiment 7: an embodiment according to any one of embodiments 1 to 6 wherein the weight ratio of plasticizer to tackifier is from 0.05:1 to 2: 1.

Embodiment 8: an embodiment according to any one of embodiments 1 to 7 wherein the weight ratio of the wax and plasticizer combination to tackifier is at least 0.05: 1.

Embodiment 9: an embodiment according to any one of embodiments 1 to 8 wherein the weight ratio of wax to tackifier is at least 0.05: 1.

Embodiment 10: an embodiment according to any of embodiments 1 to 9 wherein the viscosifier has a molecular weight of less than 1180.

Embodiment 11: an embodiment according to any of embodiments 1 to 10 wherein the tackifier comprises a hydrogenated hydrocarbon resin.

Embodiment 12: an embodiment according to any one of embodiments 1 to 11, wherein the wax has a melting point above 60 ℃.

Embodiment 13: an embodiment according to any of embodiments 1-12, wherein the wax has a melting point above 60 ℃ and the tackifier has a molecular weight of less than 1180.

Embodiment 14: the embodiment according to any one of embodiments 1 to 13, wherein has a dynamic viscosity of 150-500cps at 140 ℃ as measured by a Brookfield viscometer.

Embodiment 15: an embodiment according to any of embodiments 1 to 14, wherein the plasticizer has a molecular weight of at least 200.

Embodiment 16: an embodiment according to any one of embodiments 1 to 15, wherein the plasticizer has a viscosity of at least 175mm at 40 ℃ as measured by chinese standard BG/T265 (1988)²Viscosity per second.

Embodiment 17: an embodiment according to any of embodiments 1 to 16, wherein the plasticizer is a compound selected from the group consisting of polyisobutylene, naphthenic oil, paraffinic oil, liquid polyisoprene, liquid white mineral oil, and combinations thereof.

Embodiment 18: the embodiment according to any one of embodiments 1 to 17, wherein the hot melt adhesive comprises: 15 to 45 wt% tackifier; and 5 to 35 wt% of a plasticizer.

Embodiment 19: a label comprising a facestock suitable for printing indicia; and a hot melt adhesive according to any one of embodiments 1 to 18.

Embodiment 20: a method of producing a hot melt adhesive, the method comprising: providing a styrene-isoprene-styrene copolymer; a tackifier having a softening point of 150 ℃ or lower; waxes having a high needle penetration of greater than 8dmm as measured by ASTM D5 (2016); and a plasticizer; determining a required peeling strength range; determining a weight ratio of plasticizer to tackifier based on the desired peel strength; mixing styrene-isoprene-styrene copolymer; the tackifier, wax, and plasticizer combine to form a hot melt adhesive, wherein the plasticizer and tackifier are present in a determined plasticizer to tackifier weight ratio, and wherein the stainless steel peel strength of the hot melt adhesive is within a desired peel strength range.

Examples

Three removable hot melt PSAs were prepared according to the formulations listed in table 1 below.

Minor amounts of other additives include antioxidants.

As shown in Table 1, hot melt PSA examples 1-3 exhibit peel strengths of 1-5N/inch. These samples exhibited sufficient tack, high removability/repositionability, elimination or reduction of cohesive failure modes, low adhesive transfer, and little, if any, oil migration. The weight ratio of the plasticizer to the tackifier is 0.6-1. The weight ratio of the wax and oil combination to the tackifier is from 0.7 to 1.4. Examples 1-3 (and other examples) demonstrate the importance of using specific components, such as (low diblock content) polymers, (soft) waxes, plasticizers and tackifiers, at specific ratio/weight percentages.

Tables 2a and 2b show two formulations prepared using different waxes and the associated performance characteristics.

As shown in table 2b, the use of a soft wax improves the release, G', and ease of tearing, thus indicating the importance of the use of a high needle penetration wax (even if a higher molecular weight tackifier is used).

Table 3 shows hot melt PSA formulations using plasticizers with various viscosities.

Example 5 showed slight staining, but not as much as example 6, example 6 showed some staining. These examples show that these formulations provide hot melt PSAs with advantageous tack, removability, and repositionability. The examples also show the particular benefit of using high viscosity plasticizers, such as improvement in oil migration.

Table 4 shows the viscosities of hot melt PSA formulations using plasticizers with various viscosities and the resulting hot melt PSAs.

These examples show, inter alia, formulations that provide hot melt PSAs with advantageous tack, removability, and repositionability. In addition, the use of low molecular weight tackifiers allows the use of higher molecular weight plasticizers, such as KP6030 or KN4010, which provide the improvements described above. In addition to oil migration related benefits, higher viscosity plasticizers, when used with the above-described waxes and tackifiers, provide hot melt PSAs having viscosities that provide ease of processability, as well as other benefits. This example demonstrates the importance of the plasticizer to tackifier weight ratio and the plasticizer and wax (combination) to tackifier weight ratio.

Examples 7 and 8 show lower peel values, which is particularly advantageous in applications where greater removability and redeployability are desired, such as for label applications. The risk of adhesive transfer and/or face stock tearing is advantageously improved. Example 7 no low molecular weight adhesion promoter was used. In addition, this example shows the benefit of using an alicyclic hydrocarbon tackifier, such as HD1100, compared to a linear hydrocarbon resin, such as C100R.

Table 5 shows hot melt PSA formulations using polymers with varying amounts of diblock content. These hot melt PSAs were applied to various substrates, aged at 60 ℃ for 1 day, and tested for removability. Table 5 shows the results.

SIS 1250 comprised 50% SI diblock; SIS 1220 contains 25% diblock; solprene 1205 is a substantially pure SB diblock copolymer.

These examples show, inter alia, formulations that provide hot melt PSAs with advantageous tack, removability, and repositionability. In particular, when the SI diblock content (based on the total weight of the polymer) or the total SB and SI diblock content is reduced, the mode of failure is advantageously improved compared to the case where a higher SI diblock or higher total SB and SI diblock content is used. The SI diblock content of example 9 (in total polymer) was about 50%. The block content (of the total polymer) of example 10 was about 25% (of the total polymer). With respect to the SI and SB diblock, example 9 contains 10% SI diblock and 20% SB diblock (based on the total weight of all components), while example 10 contains only 10% SI diblock.

Although the present invention has been described in detail, modifications within the spirit and scope of the invention will be readily apparent to those skilled in the art. In view of the above discussion, the relevant knowledge in the art and in the references discussed above in connection with the background and detailed description, the disclosure of which is incorporated herein by reference in its entirety. Additionally, it should be understood that aspects of the invention and portions of the various embodiments and features described below and/or in the appended claims may be combined or interchanged either in whole or in part. In the above description of the various embodiments, those embodiments that refer to another embodiment may be suitably combined with other embodiments, as will be understood by those skilled in the art. Furthermore, those skilled in the art will appreciate that the foregoing description is by way of example only, and is not intended to limit the invention.

Claims

1. A hot melt adhesive comprising:

15 to 65 wt% of a styrene-isoprene-styrene copolymer;

a tackifier having a softening point of 150 ℃ or lower;

1 to 15% by weight of a wax having a needle penetration greater than 8dmm as measured by ASTM D5 (2016);

a plasticizer;

wherein the adhesive has a stainless steel peel strength of 0.5N/inch to 20N/inch as measured by FINAT test method 2 (2016).

2. The hot melt adhesive of claim 1 wherein the adhesive has a stainless steel peel strength of 0.5N/inch to 5N/inch as measured by FINAT test method 2 (2016).

3. The hot melt adhesive of claim 1 wherein the styrene-isoprene-styrene copolymer comprises less than 60 wt% SI diblock.

4. The hot melt adhesive of claim 2 wherein the styrene-isoprene-styrene copolymer comprises less than 60 wt% SI diblock.

5. The hot melt adhesive according to any one of claims 1 to 4, wherein the adhesive comprises from 15 to 65% by weight of a styrene-isoprene-styrene copolymer containing less than 60% by weight of SI diblock.

6. The hot melt adhesive according to any one of claims 1 to 4, wherein the styrene-isoprene-styrene copolymer comprises less than 35 wt% polymerized styrene monomer and less than 60 wt% SI diblock.

7. The hot melt adhesive of claim 5 wherein the styrene-isoprene-styrene copolymer comprises less than 35 wt% polymerized styrene monomer and less than 60 wt% SI diblock.

8. A hot melt adhesive according to any one of claims 1 to 4, wherein the weight ratio of plasticizer to tackifier is at least 0.05: 1.

9. The hot melt adhesive of claim 7 wherein the weight ratio of plasticizer to tackifier is at least 0.05: 1.

10. A hot melt adhesive according to any one of claims 1 to 4, wherein the weight ratio of plasticizer to tackifier is from 0.05:1 to 2: 1.

11. A hot melt adhesive according to any one of claims 1 to 4, wherein the weight ratio of the wax and plasticizer combination to the tackifier is at least 0.05: 1.

12. The hot melt adhesive of claim 9 wherein the weight ratio of the wax and plasticizer combination to tackifier is at least 0.05: 1.

13. A hot melt adhesive according to any one of claims 1 to 4, wherein the weight ratio of wax to tackifier is at least 0.05: 1.

14. The hot melt adhesive of claim 12 wherein the weight ratio of wax to tackifier is at least 0.05: 1.

15. The hot melt adhesive according to any one of claims 1 to 4, wherein the tackifier has a molecular weight of less than 1180.

16. The hot melt adhesive of claim 14 wherein the tackifier has a molecular weight of less than 1180.

17. The hot melt adhesive according to any one of claims 1 to 4, wherein the tackifier comprises a hydrogenated hydrocarbon resin.

18. The hot melt adhesive of claim 16 wherein the tackifier comprises a hydrogenated hydrocarbon resin.

19. A hot melt adhesive according to any one of claims 1 to 4, wherein the wax has a melting point of 60 ℃ or higher.

20. The hot melt adhesive of claim 18 wherein the wax has a melting point above 60 ℃.

21. The hot melt adhesive according to any one of claims 1 to 4, wherein the wax has a melting point of 60 ℃ or higher and the tackifier has a molecular weight of less than 1180.

22. The hot melt adhesive according to any one of claims 1 to 4, wherein the wax has a dynamic viscosity of 150-500cps at 140 ℃ as measured by a Brookfield viscometer.

23. The hot melt adhesive according to claim 20, wherein the wax has a dynamic viscosity of 150-500cps at 140 ℃ as measured by a brookfield viscometer.

24. A hot melt adhesive according to any one of claims 1 to 4, wherein the plasticizer has a molecular weight of at least 200.

25. The hot melt adhesive of claim 23 wherein the plasticizer has a molecular weight of at least 200.

26. The hot melt adhesive according to any one of claims 1 to 4, wherein the plasticizer has a general formula ofMeasured at least 175mm at 40 ℃ by China Standard BG/T265 (1988)²Viscosity per second.

27. A hot melt adhesive according to claim 25, wherein the plasticizer has a viscosity of at least 175mm at 40 ℃ as measured by chinese standard BG/T265 (1988)²Viscosity per second.

28. A hot melt adhesive according to any one of claims 1 to 4, wherein the plasticizer is a compound selected from the group consisting of polyisobutylene, naphthenic oil, paraffinic oil, liquid polyisoprene, liquid white mineral oil, and combinations thereof.

29. The hot melt adhesive according to claim 27, wherein the plasticizer is a compound selected from the group consisting of polyisobutylene, naphthenic oil, paraffinic oil, liquid polyisoprene, liquid white mineral oil, and combinations thereof.

30. The hot melt adhesive according to any one of claims 1 to 4, comprising:

15 to 45 wt% tackifier; and

5 to 35 wt% of a plasticizer.

31. The hot melt adhesive of claim 29 comprising:

15 to 45 wt% tackifier; and

5 to 35 wt% of a plasticizer.

32. A label, comprising:

a face stock adapted for printing indicia; and

a hot melt adhesive comprising:

15 to 65 wt% of a styrene-isoprene-styrene copolymer;

a tackifier having a softening point of 150 ℃ or lower;

1 to 15% by weight of a wax having a high needle penetration greater than 8dmm as measured by ASTM D5 (2016);

a plasticizer;

33. A method of producing a hot melt adhesive, the method comprising:

providing a styrene-isoprene-styrene copolymer; a tackifier having a softening point of 150 ℃ or lower; waxes having a high needle penetration of greater than 8dmm as measured by ASTM D5 (2016); and a plasticizer;

determining a required peeling strength range;

determining a weight ratio of plasticizer to tackifier based on the desired peel strength;

mixing styrene-isoprene-styrene copolymer; the tackifier, wax and plasticizer combine to form a hot melt adhesive,

wherein the plasticizer and tackifier are present in a defined plasticizer to tackifier weight ratio and wherein the stainless steel peel strength of the hot melt adhesive is within a desired peel strength range.