阅读说明：本技术 干湿表面粘合剂 (Dry and wet surface adhesives ) 是由 佐藤忍 工藤进平 格雷格·A·帕特诺德 于 2018-06-27 设计创作，主要内容包括：本发明公开了一种压敏粘合剂,所述压敏粘合剂包含反应混合物的聚合产物,所述反应混合物包含：(a1)一种或多种(甲基)丙烯酸酯单体；(a2)一种或多种亲水性单体；和(b)非反应性离子表面活性剂。还提出了包含此类粘合剂的制品以及用于制备此类粘合剂和此类制品的方法。(A pressure sensitive adhesive comprising the polymerization product of a reaction mixture comprising: (a1) one or more (meth) acrylate monomers; (a2) one or more hydrophilic monomers; and (b) a non-reactive ionic surfactant. Articles comprising such adhesives and methods for making such adhesives and such articles are also presented.)

1. A pressure sensitive adhesive comprising the reaction product of a reaction mixture comprising (a) polymerizable component (a1) one or more (meth) acrylate monomers which, when polymerized in the absence of other comonomers, yield T_gA polymer or copolymer at less than about 10 ℃; and (a2) one or more hydrophilic non-acidic comonomers or one or more hydrophilic acidic comonomers; (b) a orA plurality of non-reactive ionic surfactants;

wherein the one or more (meth) acrylate monomers and the one or more hydrophilic comonomers are present in a weight ratio of about 1:1 to about 1.5:1, and the surfactant is present from about 10 wt% to about 30 wt% based on the total weight of the surfactant plus (a1) (meth) acrylate monomer and (a2) hydrophilic comonomer.

2. The adhesive of claim 1 wherein the one or more (meth) acrylate ester monomers are selected from the group consisting of n-butyl acrylate, decyl acrylate, 2-ethylhexyl acrylate, hexyl acrylate, isoamyl acrylate, isodecyl acrylate, isononyl acrylate, isooctyl acrylate, lauryl acrylate, 2-methylbutyl acrylate, 4-methyl-2-pentyl acrylate, ethoxyethoxyethyl acrylate, 2-octyl acrylate, monomers comprising structural isomers of secondary alkyl (meth) acrylates, and mixtures thereof.

3. The adhesive of claim 1 wherein the one or more hydrophilic non-acidic comonomers are selected from the group consisting of N, N-dimethylacrylamide, N-diethylacrylamide, t-octylacrylamide, N-dimethylmethacrylamide, N-diethylmethacrylamide, N-octylacrylamide, and mixtures thereof.

4. The adhesive of claim 1 wherein the one or more hydrophilic acidic comonomers are selected from the group consisting of ethylenically unsaturated carboxylic acids, ethylenically unsaturated sulfonic acids, ethylenically unsaturated phosphonic acids, and mixtures thereof.

5. The adhesive of claim 1, wherein the surfactant is selected from the group consisting of ammonium or sodium sulfate salts and ammonium or sodium phosphate salts.

6. The adhesive of claim 1 wherein the reaction mixture further comprises one or more initiators selected from the group consisting of photoinitiators and thermal initiators.

7. The adhesive of claim 6, wherein the one or more initiators are selected from the group consisting of a benzoin ether, a substituted benzoin ether, an aromatic sulfonyl chloride, and a photoactive oxide.

8. The adhesive of claim 7 wherein the one or more initiators are selected from the group consisting of hydroperoxides and peroxides.

9. The adhesive of claim 7 wherein the amount of the one or more initiators is from about 0.005 wt% to about 1 wt% based on the weight of the copolymerizable monomer.

10. The adhesive of claim 1 wherein the reaction mixture further comprises one or more chain transfer agents selected from the group consisting of halogenated hydrocarbons, sulfur compounds, and mixtures thereof.

11. The adhesive of claim 10 wherein the reaction mixture comprises about 0 to about 10 parts by weight of chain transfer agent per 100 parts total monomers.

12. A hot melt pressure sensitive adhesive comprising a wet-stick pressure sensitive adhesive having a flow temperature and a thermoplastic encapsulating material encapsulating the wet-stick pressure sensitive adhesive, the thermoplastic encapsulating material having a melting temperature that is lower than the flow temperature of the wet-stick pressure sensitive adhesive, wherein the pressure sensitive adhesive comprises the reaction product of a reaction mixture comprising: (a) polymerizable component (a1) one or more (meth) acrylate monomers, when polymerized in the absence of other comonomers, to give T_gA polymer or copolymer at less than about 10 ℃; and (a2) one or more hydrophilic non-acidic comonomers or one or more hydrophilic comonomersAn acidic comonomer; and (b) one or more non-reactive ionic surfactants;

wherein the one or more (meth) acrylate monomers and the one or more hydrophilic comonomers are present in a weight ratio of about 1:1 to about 1.5:1, and the surfactant is present from about 10 wt% to about 30 wt% based on the total weight of the surfactant plus (a1) (meth) acrylate monomer and (a2) hydrophilic comonomer.

13. An article of manufacture, comprising: a substrate; and a hot melt pressure sensitive adhesive applied to the surface of the substrate, the hot melt pressure sensitive adhesive comprising a mixture of a pressure sensitive adhesive having a flow temperature and a thermoplastic having a melting temperature that is lower than the flow temperature of the pressure sensitive adhesive, the pressure sensitive adhesive comprising the reaction product of a reaction mixture comprising (a) a polymerizable component (a1) one or more (meth) acrylate monomers that, when polymerized in the absence of other comonomers, yield a T_gA polymer or copolymer at less than about 10 ℃; and (a2) one or more hydrophilic non-acidic comonomers or one or more hydrophilic acidic comonomers; and (b) one or more non-reactive ionic surfactants;

wherein the one or more (meth) acrylate monomers and the one or more hydrophilic comonomers are present in a weight ratio of about 1:1 to about 1.5:1, and the surfactant is present from about 10 wt% to about 30 wt% based on the total weight of the surfactant plus (a1) (meth) acrylate monomer and (a2) hydrophilic comonomer.

14. A method for preparing a pressure sensitive adhesive, the method comprising the steps of:

(1) preparing a solvent-free reaction mixture comprising (a) polymerizable component (a1) one or more (meth) acrylate monomers which, when polymerized in the absence of other comonomers, yield T_gPolymers or copolymerizations at less than about 10 ℃An agent; and (a2) one or more hydrophilic non-acidic comonomers or one or more hydrophilic acidic comonomers; and (b) one or more non-reactive ionic surfactants,

wherein the one or more (meth) acrylate monomers and the one or more hydrophilic comonomers are present in a weight ratio of about 1:1 to about 1.5:1, and the surfactant is present from about 10 wt% to about 30 wt%, based on the total weight of the surfactant plus (a1) (meth) acrylate monomer and (a2) hydrophilic comonomer; and

(2) reacting the reaction mixture to polymerize the polymerizable component to produce the pressure sensitive adhesive.

15. A method for preparing a hot melt pressure sensitive adhesive, the method comprising the steps of:

(1) preparing a solvent-free reaction mixture comprising (a) polymerizable component (a1) one or more (meth) acrylate monomers which, when polymerized in the absence of other comonomers, yield T_gA polymer or copolymer at less than about 10 ℃; and (a2) one or more hydrophilic non-acidic comonomers or one or more hydrophilic acidic comonomers; and (b) one or more non-reactive ionic surfactants,

wherein the one or more (meth) acrylate monomers and the one or more hydrophilic comonomers are present in a weight ratio of about 1:1 to about 1.5:1, and the surfactant is present from about 10 wt% to about 30 wt%, based on the total weight of the surfactant plus (a1) (meth) acrylate monomer and (a2) hydrophilic comonomer;

(2) encapsulating the polymerizable composition in a thermoplastic encapsulating material; and

(3) exposing the encapsulated polymerizable composition to radiation in an amount sufficient to polymerize the polymerizable component and form the pressure sensitive adhesive having a flow temperature,

wherein the thermoplastic packaging material has a melting temperature that is lower than the flow temperature of the pressure sensitive adhesive.

16. A method for preparing a hot melt pressure sensitive adhesive, the method comprising the steps of:

(1) preparing a prepolymer syrup comprising (a) polymerizable component (a1) one or more (meth) acrylate monomers which, when polymerized in the absence of other comonomers, yield T_gA polymer or copolymer at less than about 10 ℃; and (a2) one or more hydrophilic non-acidic comonomers or one or more hydrophilic acidic comonomers; (b) optionally, from about 10 wt% to about 30 wt% of a reactive ionic surfactant, based on the total weight of the prepolymer slurry; and (c) one or more photoinitiators;

wherein the one or more (meth) acrylate monomers and the one or more hydrophilic comonomers are present in a weight ratio of about 1:1 to about 1.5:1, the surfactant is present in about 10 wt% to about 30 wt% based on the total weight of the surfactant plus (a1) (meth) acrylate monomer and (a2) hydrophilic comonomer, and the photoinitiator is present in about 0.04 wt% based on the total weight of the reaction mixture;

(2) mixing the prepolymer slurry until the photoinitiator is dissolved;

(3) exposing the prepolymer paste to UV-a light having a spectrum comprising 350nm until the paste has a sufficient viscosity to be considered suitable for coating;

(4) if not added in step (1), adding an additional 0.1 weight percent of at least one photoinitiator and from about 10 to about 30 weight percent of a reactive ionic surfactant based on the total weight of the surfactant plus (a1) (meth) acrylate monomer and (a2) hydrophilic comonomer and mixing them until the photoinitiator is dissolved to produce a slurry;

(5) coating the resulting slurry between two release liners optionally comprising polyester, optionally using notched rods; and

(6) optionally exposing the coated slurry from both sides to UV-a light having a spectrum comprising 350nm, optionally providing an approximate total energy of at least 1440 mj/cm.

Technical Field

The present invention relates to pressure sensitive adhesives, and more particularly to non-emulsion, solventless acrylate-based pressure sensitive adhesives incorporating a hydrophilic comonomer and a non-reactive ionic surfactant in the polymer matrix. The adhesive exhibits the characteristics of good tack and strong adhesion to both wet and dry surfaces.

Background

Pressure sensitive adhesives that effectively adhere to wet or damp surfaces (so-called "wet-stick" adhesives) are useful in selected industrial, commercial, and consumer applications. In the medical and other medical fields, wet-stick adhesives are commonly used to attach articles such as tapes, bandages, dressings, and drapes to moist skin surfaces (such as wounds or body areas that are prone to becoming wet). Wet-stick adhesives may also be used in outdoor or exterior applications, such as coatings and surfaces for road surfaces (e.g., asphalt, cement, and concrete) and marine and automotive applications. Wet-stick adhesives are also used on labels for food containers and other products that are exposed to moisture (caused by condensation or exposure to water or ice immersion).

(meth) acrylate pressure sensitive adhesives are attractive materials for many tape and label applications. (meth) acrylates are known for their optical clarity, oxidation resistance and inherent tack properties. Inherently tacky (meth) acrylate pressure sensitive adhesives (i.e., materials that do not require additives such as tackifying resins to provide the desired tack) are typically formulated primarily from acrylate monomers other than tertiary alcohols. Examples of such monomers include n-butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, isononyl acrylate, isodecyl acrylate, and dodecyl acrylate. For applications requiring room temperature tack, it is common to use (meth) acrylate monomers that, when polymerized, yield polymers having glass transition temperatures (T) of less than about 0 ℃_g) A homopolymer of (a). However, such (meth) acrylate polymers are hydrophobic in nature (i.e., less than 1 wt% soluble with water) and are generally not suitable for use as wet-stick adhesives without modification.

One means of making the (meth) acrylate polymer more hydrophilic is to copolymerize the (meth) acrylate monomer with hydrophilic acidic comonomers (e.g., acrylic acid, methacrylic acid, β -carboxyethyl acrylate, itaconic acid, sulfoethyl acrylate, etc.) the addition of minor amounts of these hydrophilic acidic comonomers (e.g., about 1 to about 15 wt%, preferably 1 to 10 wt%) can also enhance the internal or cohesive strength of the resulting PSA.

U.S. patent 6,855,386(Daniels et al) discloses a wet-stick adhesive comprising the reaction product of a (meth) acrylate copolymer, a hydrophilic acidic comonomer, and a non-reactive, non-ionic plasticizer.

When preparing wet-stick adhesives based on (meth) acrylate copolymers with high levels of acidic or non-acidic comonomers, there is a need to provide a means to overcome the glassy nature of the adhesive. While such systems can produce adhesion in the presence of surface moisture, they have the following disadvantages: for relatively low viscosity systems, it takes some time to form a bond in the presence of water. The time required for such adhesives to bond in the presence of water is longer than the time required to apply the adhesive. In addition, these systems do not bond strongly or quickly in the absence of moisture. One means of addressing the stiffness of such adhesives is to incorporate non-reactive nonionic plasticizers, such as described in U.S. patent 6,855,386(Daniels et al). These systems have the following disadvantages: when immersed in water, the plasticizer may be removed from the adhesive. In addition, incorporating high levels of non-reactive plasticizers into the adhesive can dilute the adhesive polymer entanglements, resulting in an adhesive with inherently low shear strength.

Another approach to address the stiffness associated with high acid comonomer adhesives is to incorporate a reactant that will act as a plasticizer to lower the adhesive T_gU.S. Pat. No. 5,397,614(Patnode et al) discloses alkali dispersible pressure sensitive adhesive compositions based on a terpolymer system comprising a (meth) acrylate comonomer, β -carboxyethyl acrylate comonomer, and an ethylene oxide acrylate comonomer.

U.S. patent 8,030,395(Tseng et al) discloses an emulsion acrylate pressure sensitive adhesive utilizing from 0.1 parts to 2 parts of a reactive ionic surfactant in a latex binder. Low levels of reactive ionic surfactant are present to provide the ability to prepare emulsion acrylate adhesives. These adhesives do not have effective wet-stick properties.

There is a need for novel wet-stick pressure-sensitive adhesives having good dry and wet adhesion, good tack and stability. There is also a need for wet-stick compositions that use plasticizers that are inherently more stable in the adhesive matrix than the previously disclosed non-reactive nonionic plasticizers.

Disclosure of Invention

The present invention provides novel pressure sensitive adhesive compositions based on (meth) acrylate copolymers that provide surprising properties, articles comprising such adhesive formulations, and methods for preparing such adhesive formulations.

The adhesive composition of the present invention comprises the reaction product of a reaction mixture comprising: (a) selected polymerizable components (i.e., certain (meth) acrylate monomers and certain hydrophilic comonomers), (b) a high proportion of selected non-reactive surfactants, (c) optional initiators, and (d) optional chain transfer agents, all as described herein. The polymerizable component in the adhesives of the present invention comprises (a1) (meth) acrylate comonomer and (a2) a hydrophilic non-acidic or hydrophilic acidic monomer (e.g., N-dimethylacrylamide (nnDMA), acrylic acid, etc.), and, optionally, in some embodiments (a3) other comonomers. Useful surfactants include non-reactive ionic surfactants of the type used to produce emulsion acrylate adhesives.

It has been surprisingly found that if such polymerizable components (i.e., (a1) (meth) acrylate monomer and (a2) hydrophilic comonomer) when present in a weight ratio of (a1) to (a2) of about 1:1 to about 1.5:1, polymerization in the composition in the presence of a non-reactive ionic surfactant at a level of at least about 10 wt% (by weight based on the total weight of surfactant plus (a1) (meth) acrylate monomer and (a2) hydrophilic comonomer) to about 30 wt%, provides a stable adhesive composition having wet and dry adhesion as well as good tack. Thus, these novel compositions provide a heretofore unattained and surprising combination of performance characteristics, thereby achieving surprising and heretofore unattained advantages.

Briefly, in one aspect, the present invention is a pressure sensitive adhesive comprising the reaction product of a reaction mixture comprising (a) a polymerizable component (a1) one or more (meth) acrylate monomers when combined with a pressure sensitive adhesiveWhen polymerized in the absence of further comonomers, T is obtained_gA polymer or copolymer at less than about 10 ℃; and (a2) one or more hydrophilic non-acidic monomers or one or more hydrophilic acidic monomers; and (b) one or more non-reactive ionic surfactants;

wherein the one or more (meth) acrylate monomers and the one or more hydrophilic monomers are present in a weight ratio of about 1:1 to about 1.5:1 and the surfactant is present in a range of about 10 wt.% to about 30 wt.% (by weight based on the total weight of the surfactant plus (a1) (meth) acrylate monomers and (a2) hydrophilic comonomers). Such adhesive compositions have been found to adhere surprisingly well to wet substrate surfaces.

Advantageously, the pressure sensitive adhesives of the present invention have hydrophilic character but do not have the common problems commonly described in the art-low tack and poor adhesion to dry surfaces. The novel adhesives of the present invention provide fast tack, high tack, or acceptably good tack (i.e., ASTM D3121 rolling ball tack values of less than 60mm or less than 250mm, respectively) and high tack, or acceptably good adhesion (i.e., 90 ° peel adhesion to a surface of greater than 10N/25mm or greater than 5N/25mm, respectively) to both wet and dry surfaces.

In another aspect of the present invention, there is provided a hot melt pressure sensitive adhesive, wherein the hot melt pressure sensitive adhesive comprises a wet-stick pressure sensitive adhesive having a flow temperature and a thermoplastic encapsulating material encapsulating the wet-stick pressure sensitive adhesive, the thermoplastic encapsulating material having a melting temperature lower than the flow temperature of the wet-stick pressure sensitive adhesive, wherein the adhesive comprises the reaction product of a polymerizable composition comprising: (a) polymerizable component (a1) one or more hydrophobic (meth) acrylate monomers, when polymerized in the absence of other comonomers, yield T_gA polymer or copolymer at less than about 10 ℃; (a2) one or more hydrophilic acidic or hydrophilic non-acidic monomers; and (b) one or more non-reactive ionic surfactants;

wherein the one or more (meth) acrylate monomers and the one or more hydrophilic monomers are present in a weight ratio of about 1:1 to about 1.5:1 and the surfactant is present in a range of about 10 wt.% to about 30 wt.% (by weight based on the total weight of the surfactant plus (a1) (meth) acrylate monomers and (a2) hydrophilic comonomers).

In another aspect of the present invention, there is provided an article, wherein the article comprises: a substrate; and a hot melt pressure sensitive adhesive on at least a portion of the surface of the substrate, the hot melt adhesive comprising a mixture of a pressure sensitive adhesive having a flow temperature and a thermoplastic material having a melting temperature that is less than the flow temperature of the pressure sensitive adhesive, the pressure sensitive adhesive comprising the reaction product of a reaction mixture comprising (a) a polymerizable component (a1) one or more (meth) acrylate monomers that, when polymerized in the absence of other comonomers, yield a T_gA polymer or copolymer at less than about 10 ℃; and (a2) one or more hydrophilic acidic monomers or one or more hydrophilic non-acidic monomers; and (b) one or more non-reactive ionic surfactants;

wherein the one or more (meth) acrylate monomers and the one or more hydrophilic monomers are present in a weight ratio of about 1:1 to about 1.5:1 and the surfactant is present in a range of about 10 wt.% to about 30 wt.% (by weight based on the total weight of the surfactant plus (a1) (meth) acrylate monomers and (a2) hydrophilic comonomers).

In another aspect of the present invention, a method for preparing a pressure sensitive adhesive comprises the steps of:

(1) preparing a solvent-free reaction mixture comprising (a) polymerizable component (a1) one or more (meth) acrylate monomers which, when polymerized in the absence of other comonomers, yield T_gA polymer or copolymer at less than about 10 ℃; and (a2) one or more hydrophilic acidic or non-acidic monomers; and (b) one or more non-reactive ionic surfactants;

wherein the one or more (meth) acrylate monomers and the one or more hydrophilic monomers are present in a weight ratio of about 1:1 to about 1.5:1 and the surfactant is present in a range of about 10 wt.% to about 30 wt.% (by weight based on the total weight of the surfactant plus (a1) (meth) acrylate monomers and (a2) hydrophilic comonomers); and

(2) reacting the reaction mixture to polymerize the polymerizable component to produce the pressure sensitive adhesive.

In another aspect of the invention, a method for preparing a hot melt pressure sensitive adhesive comprises the steps of:

(1) preparing a solvent-free reaction mixture comprising (a) polymerizable component (a1) one or more (meth) acrylate monomers which, when polymerized in the absence of other comonomers, yield T_gA polymer or copolymer at less than about 10 ℃; and (a2) one or more hydrophilic acidic monomers or one or more non-acidic monomers; and (b) one or more non-reactive ionic surfactants;

wherein the one or more (meth) acrylate monomers and the one or more hydrophilic monomers are present in a weight ratio of about 1:1 to about 1.5:1 and the surfactant is present in a range of about 10 wt.% to about 30 wt.% (by weight based on the total weight of the surfactant plus (a1) (meth) acrylate monomers and (a2) hydrophilic comonomers); and

(2) encapsulating the polymerizable composition in a thermoplastic encapsulating material; and

(3) exposing the encapsulated polymerizable mixture to radiation in an amount sufficient to polymerize the polymerizable mixture and form a pressure sensitive adhesive that adheres well to both the wet and dry substrate surfaces, the pressure sensitive adhesive having a flow temperature,

wherein the thermoplastic packaging material has a melting temperature that is lower than the flow temperature of the pressure sensitive adhesive.

In another aspect of the invention, a method for preparing a hot melt pressure sensitive adhesive comprises the steps of:

(1) preparing a prepolymer syrup comprising (a) polymerizable component (a1) one or more (meth) acrylate monomers which, when polymerized in the absence of other comonomers, yield T_gLess than about 10A polymer or copolymer at DEG C; and (a2) one or more hydrophilic non-acidic comonomers or one or more hydrophilic acidic comonomers; (b) optionally from about 10 to about 30 wt% (by weight based on the total weight of the surfactant plus (a1) (meth) acrylate monomer and (a2) hydrophilic comonomer) of a reactive ionic surfactant; and (c) one or more photoinitiators;

wherein the one or more (meth) acrylate monomers and the one or more hydrophilic monomers are present in a weight ratio of about 1:1 to about 1.5:1, the surfactant is present in about 10 wt.% to about 30 wt.% (by weight based on the total weight of surfactant plus (a1) (meth) acrylate monomer and (a2) hydrophilic comonomer), and the photoinitiator is present in about 0.04 wt.%, based on the total weight of the reaction mixture;

(2) mixing the prepolymer slurry until the photoinitiator is dissolved;

(3) exposing the prepolymer paste to UV-a light having a spectrum comprising 350nm until the paste has a sufficient viscosity to be considered suitable for coating;

(4) if not added in step (1), adding an additional 0.1 weight percent of at least one photoinitiator and from about 10 to about 30 weight percent of a reactive ionic surfactant (by weight based on the total weight of surfactant plus (a1) (meth) acrylate monomer and (a2) hydrophilic comonomer) (e.g., to optimize chain transfer characteristics) and mixing them until the photoinitiator is dissolved and the reaction mixture is thoroughly mixed to produce a slurry;

(5) coating the resulting slurry between two release liners optionally comprising polyester, optionally using notched rods; and

(6) optionally exposing the coated slurry from both sides to UV-a light having a spectrum comprising 350nm, optionally providing an approximate total energy of at least 1440 mj/cm.

The adhesives and methods for forming them can be used to prepare a variety of useful adhesive articles, such as tapes, pavement markings, labels, patches, and the like.

Glossary

As used in this application, the following terms and acronyms have the meanings indicated.

"Pressure-sensitive adhesive" or "PSA" refers to a viscoelastic material having the following properties: (1) dry tack and permanent tack, (2) tack without exceeding finger pressure, and (3) ability to remain sufficiently on the substrate.

"wet-stick adhesive" refers to a material that exhibits pressure-sensitive adhesive properties when adhered to a substrate that has been flooded with water. Wet-stick adhesives may or may not typically exhibit pressure sensitive adhesive properties under dry conditions. The adhesives of the present invention are wet-stick adhesives and do exhibit pressure sensitive adhesive properties under dry conditions.

"Hot melt adhesive" refers to a material that is heated to room or above ambient temperature to increase the tendency to flow or wet the adherend, resulting in bonding when cooled to ambient temperature. Hot melt adhesives may or may not exhibit some degree of pressure sensitive characteristics.

"high tack" refers to an adhesive tack value of less than 60mm as measured by the ball test using ASTM D3121.

"good tack" refers to an adhesive tack value of less than 250mm as measured by the ball test using ASTM D3121.

"high adhesion" means a pair of NAKAICHI of greater than 10N/25mm as measured using a push-pull dynamometer model Aikoh Engineering RZ-100^TMPre Stone Mini Red concrete interlocking blocks 90 peel adhesion.

"good adhesion" means a para-NAKAICHI of greater than 5N/25mm as measured using a push-pull dynamometer model Aikoh Engineering RZ-100^TMPre Stone Mini Red concrete interlocking blocks 90 peel adhesion.

"(Meth) acrylate monomers" or "(Meth) acrylate ester monomers" are acrylic or methacrylic esters of non-tertiary alcohols, the alcohols preferably having from 4 to 12 carbon atoms, and any term beginning with "(Meth) acryloyl" is similarly intended to include both "acryloyl" and "methacryloyl".

A "hydrophilic acidic comonomer" or "hydrophilic non-acidic comonomer" is a water-soluble ethylenically unsaturated free radical reactive monomer having carboxylic, sulfonic, or phosphonic acid functionality, and is copolymerizable with a (meth) acrylate monomer.

"non-reactive ionic surfactant" refers to a compound having a hydrophilic group with an ionic functional group, a hydrophobic group, and optionally a polyalkylene oxide group.

Detailed Description

Generally, the wet-stick pressure-sensitive adhesives of the present disclosure comprise the reaction product of a reaction mixture comprising (a) polymerizable component (a1) one or more (meth) acrylate monomers that, when polymerized in the absence of other comonomers, yield T_gA polymer or copolymer at less than about 10 ℃; and (a2) one or more hydrophilic non-acidic monomers or one or more acidic comonomers; and (b) one or more non-reactive ionic surfactants;

wherein the one or more (meth) acrylate monomers and the one or more hydrophilic monomers are present in a weight ratio of about 1:1 to about 1.5:1 and the surfactant is present in a range of about 10 wt.% to about 30 wt.% (by weight based on the total weight of the surfactant plus (a1) (meth) acrylate monomers and (a2) hydrophilic comonomers).

In some embodiments, the adhesive will comprise the reaction product of a reaction mixture that further comprises one or both of (c) an optional initiator and (d) an optional chain transfer agent.

In some embodiments, the binder will comprise the reaction product of a reaction mixture consisting essentially of (a) such polymerizable compounds and (b) such surfactants. In some embodiments, the binder will comprise the reaction product of a reaction mixture consisting essentially of: (a) such polymerizable compounds, (b) such surfactants, (c) one or more optional initiators, and (d) one or more optional chain transfer agents.

(a) Polymerizable component

The adhesives of the invention are formed from a reaction mixture comprising selected polymerizable components including (a1) one or more (meth) acrylate monomers and (a2) one or more hydrophilic non-acidic comonomers or one or more hydrophilic acid comonomers. The polymerizable component is described in more detail.

(a1) (meth) acrylate ester monomer

The binder of the present invention comprises at least one unsaturated monomer selected from the group consisting of (meth) acrylic acid esters of non-tertiary alkyl alcohols, the alkyl group of which preferably comprises from 4 to 12, more preferably from 4 to 8 carbon atoms; and mixtures thereof. The (meth) acrylate monomers may contain a small proportion of di-or poly-functionality, but are preferably substantially fully mono-functional to minimize undesirable gelling or crosslinking.

Preferred (meth) acrylate monomers have the following general formula (I):

wherein R is¹Is H or CH₃The latter corresponds to the case where the (meth) acrylate monomer is a methacrylate monomer; r²Is broadly selected from linear or branched hydrocarbyl groups and may contain one or more heteroatoms, and the number of carbon atoms in the hydrocarbyl group is preferably from 4 to 12, and more preferably from 4 to 8.

Illustrative examples of (meth) acrylate monomers that may be used in the present invention include n-butyl acrylate, decyl acrylate, 2-ethylhexyl acrylate, hexyl acrylate, isoamyl acrylate, isodecyl acrylate, isononyl acrylate, isooctyl acrylate, lauryl acrylate, 2-methyl-butyl acrylate, 4-methyl-2-pentyl acrylate, ethoxyethoxyethyl acrylate, 2-octyl acrylate. Further suitable examples are monomers comprising structural isomers of secondary alkyl (meth) acrylates and mixtures thereof, as described in us patent 9,102,774 (clauper et al). Particularly preferred examples are n-butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, lauryl acrylate and mixtures thereof.

(a2) Hydrophilic comonomers

As known to those skilled in the art, comonomers are used to improve the cohesion of the resulting adhesive. Preferably, the (meth) acrylate monomer and hydrophilic comonomer are selected and used in proportions to produce a polymer having a T of about 20 ℃ or less, more preferably about 10 ℃ or less_gTo provide the desired dry adhesion. According to the invention, hydrophilic comonomers, usually non-acidic comonomers, are used to improve the water absorption properties of the resulting adhesive, to improve wet-stick adhesion, and to improve the compatibility of the ionic surfactant with the other components of the composition. Hydrophilic non-acidic comonomers are preferred when the adhesive can be exposed to surfaces containing metal cations (e.g., concrete), which can result in performance degradation when hydrophilic acidic comonomers are used.

Illustrative examples of useful hydrophilic non-acidic comonomers include, but are not limited to, N-dimethylacrylamide, N-diethylacrylamide, t-octylacrylamide, N-dimethylmethacrylamide, N-diethylmethacrylamide, and N-octylacrylamide.

Typically, the reaction mixture from which the adhesives of the invention are prepared comprises the (meth) acrylate monomer and the hydrophilic, non-acidic monomer in a weight ratio of from about 1:1 to about 1.5: 1.

In some embodiments, a hydrophilic acidic comonomer can be used in place of a hydrophilic non-acidic comonomer, particularly when the adhesive will not be exposed to a surface comprising metal cations.

The hydrophilic comonomer used may contain a small proportion of di-or poly-functionality, but is preferably substantially fully mono-functional to minimise undesirable gelling or cross-linking.

Illustrative examples of useful hydrophilic acidic comonomers include, but are not limited to, those selected from ethylenically unsaturated carboxylic acids, ethylenically unsaturated sulfonic acids, ethylenically unsaturated phosphonic acids, and mixtures thereof illustrative examples of such compounds include those selected from acrylic acid, methacrylic acid, itaconic acid, fumaric acid, crotonic acid, citraconic acid, maleic acid, β -carboxyethyl acrylate, 2-sulfoethyl methacrylate, styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, vinyl phosphonic acid, and the like, and mixtures thereof because of their availability and effectiveness in enhancing (meth) acrylate pressure sensitive adhesives, a particularly preferred hydrophilic acidic monomer is ethylenically unsaturated carboxylic acid β -carboxyethyl acrylate may be the preferred hydrophilic acidic comonomer.

A trace amount of monomer copolymerizable with the (meth) acrylate monomer and the hydrophilic acidic monomer may be used. Examples of such monomers include (meth) acrylamide, vinyl esters, and N-vinyl lactams.

(a3) Other comonomers

Another approach to address the stiffness associated with high acid comonomer adhesives is to incorporate a reactant that will act as a plasticizer to lower the adhesive T_gAnd modulus. The ethylene oxide acrylate monomer serves as a plasticizer that is incorporated into the polymer backbone. The polyalkylene glycol polyacrylate will also act to reduce the T of the polymer backbone_gAnd decrease T_gAnd the effect of modulus. Illustrative examples are:

MPE-550A methoxy polyethylene glycol polyacrylate: (Osaka organic chemical Industry)

(b) Non-reactive ionic surfactants

It has been found that when the polymerizable components as described above are polymerized in the presence of a non-reactive ionic surfactant, advantageous compositions are obtained which exhibit surprising properties.

Non-reactive ionic surfactants useful herein include compounds having a hydrophilic group and a hydrophobic group. Non-reactive ionic surfactants useful in the present invention include ionic surfactants having a poly (alkylene oxide) structure but substantially no vinyl functionality. Illustrative examples of useful ionic functional groups include ammonium or sodium salts of sulfuric and phosphoric acids. Some examples of materials useful in the present invention include HITENOL^TMLA-10, LA-12, LA-16, NF-08 and NF-17 ammonium poly (oxyethylene) alkylether sulfate obtained from first Industrial pharmaceutical Co., Ltd (Dai-ichi Kogyo Seiyaku Co., Ltd, Tokyo, Japan) and from PLYSURF^TMA208F was obtained from poly (oxyethylene) alkyl ether phosphate from first industrial pharmaceutical co. These non-reactive ionic surfactants are believed to have the following structure:

ammonium poly (oxyethylene) alkylether sulfate RO (CH)₂CH₂O)nSO₃M

M：Na，NH₄

Poly (oxyethylene) alkyl ether phosphates

The reaction mixture used in the present invention typically comprises from about 10 wt% to about 30 wt% (by weight based on the total weight of the surfactant plus (a1) (meth) acrylate monomer and (a2) hydrophilic comonomer) of one or more non-reactive ionic surfactants. In contrast, such materials are typically used in much lower proportions (e.g., 1 to 3 weight percent) in the art. If an excess proportion of surfactant is used in the reaction mixture, the resulting binder may tend to have more than a single homogeneous phase as desired.

The ratio and type of each comonomer in the wet-stick adhesive composition can be selected within the limits to optimize performance.

(c) Initiator

One or more free radical initiators are optionally added to aid in the copolymerization of the (a1) (meth) acrylate comonomer and the (a2) hydrophilic comonomer.

As will be appreciated by those skilled in the art, the choice of the available type of initiator used depends on the polymerization process. Photoinitiators useful for polymerizing the polymerizable mixture monomers include benzoin ethers, such as benzoin methyl ether or benzoin isopropyl ether; substituted benzoin ethers, such as 2-methyl-2-hydroxypropiophenone; aromatic sulfonyl chlorides such as 2-naphthalenesulfonyl chloride; and photoactive oxides, such as 1-phenyl-1, 1-propanedione-2- (o-ethoxycarbonyl) oxime. An example of a commercially available photoinitiator suitable for use in many embodiments is IRGACURE^TM651(2, 2-dimethoxy-1, 2-diphenylethan-1-one, available from Ciba-Geigy Corporation).

Illustrative examples of suitable thermal initiators include AIBN (i.e., 2' -azobis (isobutyronitrile)); hydroperoxides such as tert-butyl hydroperoxide; and peroxides such as benzoyl peroxide and cyclohexane peroxide.

Generally, the photoinitiator is present in an amount of about 0.005 wt% to about 1 wt%, based on the total weight of copolymerizable monomers in the reaction mixture.

(d) Chain transfer agent

Optionally, the composition may also include one or more chain transfer agents to control the molecular weight of the polymeric composition. Chain transfer agents are substances that regulate free radical polymerization and are generally known in the art. Illustrative examples of suitable chain transfer agents include: halogenated hydrocarbons such as carbon tetrabromide; sulfur compounds such as lauryl mercaptan, butyl mercaptan, ethyl mercaptan, isooctyl thioglycolate (IOTG), 2-ethylhexyl thioglycolate, 2-ethylhexyl mercaptopropionate, 2-mercaptoimidazole, 2-mercaptoethyl ether, and mixtures thereof.

The amount of chain transfer agent that can be used depends on the desired final molecular weight of the reaction product of the polymerization and the type of chain transfer agent. The chain transfer agent is generally used in an amount of about 0 to about 10 parts by weight, and preferably about 0 to about 0.5 parts by weight, per 100 parts of the total polymerizable components (i.e., (a1) (meth) acrylate monomer plus (a2) hydrophilic comonomer plus, if any, (a3) other monomer).

Solvent-free reaction method

Solventless polymerization processes such as the continuous free radical polymerization processes described in U.S. Pat. Nos. 4,619,979(Kotnour et al) and 4,843,134(Kotnour et al); a substantially adiabatic polymerization process using a batch reactor as described in U.S. Pat. No. 5,637,646 (Ellis); and the methods described for polymerizing the encapsulated polymerizable mixture described in U.S. Pat. No. 5,804,610(Hamer et al) can also be used to prepare the adhesives of the present invention.

In a preferred embodiment of this latter method, from about 0.1g to about 500g of the reaction mixture is completely surrounded by the encapsulating material. In some embodiments, about 3g to about 100g of the reaction mixture is surrounded by the encapsulating material. In other embodiments of the invention, the reaction mixture is substantially surrounded only by the encapsulating material. In still other embodiments, the reaction mixture is disposed on a surface of a sheet, or between a pair of two substantially parallel sheets of encapsulating material. In another embodiment of the invention, the polymerizable mixture is substantially or completely surrounded by a hollow profile of encapsulant material having a ratio of length to square root of cross-sectional area of at least about 30: 1.

The encapsulating material is made of a material that does not substantially adversely affect the desired adhesive properties when combined with the adhesive. In some embodiments, the encapsulating material is selected such that the resulting hot melt coated adhesive made from the mixture of the adhesive and the encapsulating material exhibits improved adhesive properties compared to a hot melt coated adhesive made from the adhesive alone.

The encapsulating material preferably melts at or below the processing temperature of the adhesive (i.e., the temperature or flow temperature at which the adhesive flows). The melting point or melting temperature of the encapsulating material is preferably about 200 ℃ or less, preferably about 170 ℃ or less. In a typical preferred embodiment, the melting point is in the range of about 90 ℃ to about 150 ℃. The encapsulating material may be a flexible thermoplastic polymer film. The encapsulating material is preferably selected from ethylene vinyl acetate film, ethylene acrylic acid film, polypropylene film, polyethylene film, polybutadiene film or ionomer film. In a preferred embodiment, the encapsulant is an ethylene-acrylic acid film or an ethylene-vinyl acetate film.

The amount of encapsulating material depends on the type of material and the desired final properties. The amount of encapsulating material typically ranges from about 0.5% to about 20% of the total weight of the reaction mixture and encapsulating material. Preferably, the amount of encapsulating material is from about 2 wt% to about 15 wt%, and more preferably from about 3 wt% to about 5 wt%. As will be appreciated, the encapsulating material may include plasticizers, stabilizers, dyes, fragrances, fillers, slip agents, antiblocking agents, flame retardants, antistatic agents, microwave acceptors, thermally conductive particles, electrically conductive particles, and/or other materials to improve the flexibility, handleability, visibility, or other useful properties of the film so long as they do not adversely affect the desired properties of the adhesive.

The encapsulating material should be suitable for the polymerization method used. For example, for photopolymerization, it is necessary to use a film material that is sufficiently transparent to ultraviolet radiation at the wavelength necessary for polymerization.

The transmitted energy may be selected from ultraviolet radiation, visible radiation, thermal radiation or thermal conduction. The transmitted energy is preferably ultraviolet radiation or thermal conduction. Preferably, at least about 80% of the pre-binder is converted to binder; more preferably, at least about 90% of the pre-adhesive is converted to adhesive.

Thermal polymerization can be achieved by immersing the encapsulated composition in a heat exchange medium at a temperature of about 40 ℃ to about 100 ℃ for a time sufficient to polymerize the composition. The heat exchange medium may be a forced or impinged gas or liquid, such as water, perfluorinated liquids, glycerol or propylene glycol. The heat required for thermal polymerization may also be provided by a metal platen, heated metal rollers, or microwave energy.

The temperature at which polymerization occurs depends on the activation temperature of the initiator. For example, VAZO, an initiator commercially available from DuPont Company (DuPont Company) is used^TMThe polymerization of 64 may be carried out at about 65 ℃ and is also available from VAZO of DuPont Company (DuPont Company)^TM52 may be used at about 45 c.

The polymerization is preferably carried out in a suitable liquid heat exchange medium at a controlled temperature. A suitable liquid heat exchange medium is water, heated to the desired reaction temperature. Commercially available heat transfer fluids may also be used. Additional information regarding Thermal polymerization can be found in PCT publication WO95/29770 entitled "Thermal Free-Radical Adhesives, Curing methods therefor, and articles Made therefrom".

Polymerization can also be achieved by exposure to Ultraviolet (UV) radiation as described in U.S. patent No. 4,181,752(Martens et al). In a preferred embodiment, the polymerization is carried out using UV black light having an emission spectrum of greater than 60% and preferably greater than 75% of the UV black light from about 280 to about 400nm at an intensity of about 0.1 to about 25mW/cm²。

During photopolymerization, it is advantageous to control the temperature by blowing cold air around the encapsulated polymerizable mixture, by running the encapsulated polymerizable mixture on a cooling plate, or by immersing the encapsulated polymerizable mixture in a water bath or heat transfer fluid during polymerization. Preferably, the encapsulated polymerizable mixture is immersed in a water bath having a water temperature of about 5 ℃ to 90 ℃, preferably less than about 30 ℃. Stirring the water or fluid helps to avoid hot spots during the reaction.

The packaged polymeric wet-stick adhesive composition can be used to prepare coatable hot-melt adhesives (prepared by introducing the adhesive and its packaging material into a container in which the adhesive and its packaging material are melted). The hot melt adhesive can be used to form a pressure sensitive adhesive sheet (formed by coating a molten adhesive and its encapsulating material onto a sheet material or another suitable substrate). The sheet material is preferably selected from a tape backing or a release liner. Preferably, the polymeric adhesive is hot melt coated by the following method: the packaged adhesive is placed in a hot melt coater at a temperature sufficient to melt the packaged adhesive and mix well to form a coatable mixture that is applied to a substrate. This step can be conveniently accomplished in a heated extruder, a collection tank melter, an on-demand instant melt apparatus, or a hand-held hot melt adhesive gun.

For any of these embodiments, the hot melt adhesive may be coated and then delivered from a film die, with the exiting adhesive then contacting a moving plastic web or other suitable substrate. A related coating method involves extrusion coating a hot melt adhesive and a coextruded backing material from a film die and cooling the laminate to form an adhesive tape. Other forming methods involve directly contacting the coatable hot melt adhesive to a rapidly moving plastic web or other suitable preformed substrate. By this method, the adhesive blend is applied to a moving preformed web using a die with flexible die lips (e.g., a rotary rod die). After being formed by any of these continuous processes, the resulting adhesive film or layer may be hardened by quenching using both direct methods (e.g., chill rolls or water baths) and indirect methods (e.g., air or gas jets).

The encapsulated adhesive composition may also include an effective amount of a crosslinking agent that can be activated (e.g., by exposure to actinic radiation such as ultraviolet light or an electron beam) to effect further reaction after the adhesive has been hot melt coated. Generally, the amount of the crosslinking agent ranges from about 0.01 to about 5.0 parts based on 100 parts of the (meth) acrylate monomer and the hydrophilic acidic comonomer. The crosslinking agent may be added to the polymerized adhesive before or during hot melt coating, or it may be added to the polymerizable mixture. The crosslinking agent may remain intact in the adhesive as a separate substance when added to the polymerizable mixture, or it may be copolymerized with the monomer. The crosslinking reaction is preferably initiated after hot melt coating, and is preferably initiated by ultraviolet radiation or ionizing radiation such as gamma radiation or electron beam radiation (in the case of ionizing radiation, the use of a separate crosslinking agent is optional). Preferred crosslinking agents that may be added after reaction and prior to hot melt coating include multifunctional (meth) acrylates such as 1, 6-hexanediol diacrylate and trimethylolpropane triacrylate and substituted triazines such as 2, 4-bis (trichloromethyl) -6- (4-methoxyphenyl) -s-triazine and 2, 4-bis (trichloromethyl) -6- (3, 4-dimethoxyphenyl) -s-triazine, as described in U.S. Pat. Nos. 4,329,384(Vesley et al) and 4,330,590 (Vesley). Another preferred class of crosslinking agents are copolymerizable monoethylenically unsaturated arone comonomers that do not contain ortho-aromatic hydroxyl groups, such as those disclosed in U.S. Pat. No. 4,737,559(Kellen et al). Specific examples include p-acryloxybenzophenone, p-acryloxyethoxybenzophenone, p-N- (methacryloyloxyethyl) -carbamoylethoxybenzophenone, p-acryloxyacetophenone, o-acrylamidoacetophenone, acrylated anthraquinones, and the like.

Another class of suitable crosslinkers are the multifunctional radiation activatable crosslinkers described in PCT patent publication WO 97/07161(Stark et al) and in U.S. Pat. No. 5,407,971 (Evererts et al). An example of such a crosslinking agent is 1, 5-bis (4-benzoyloxy) pentane. Also suitable are hydrogen abstraction-type carbonyl compounds (such as anthraquinones, benzophenones, and derivatives thereof), such as those disclosed in U.S. Pat. No. 4,181,752.

The acrylate copolymer may be crosslinked by exposure to ultraviolet radiation from, for example, a medium pressure mercury arc lamp. Preferably, the crosslinking agent activated by ultraviolet radiation is activated primarily by an energy wavelength different from that used for polymerization. For example, low intensity black light may be used for polymerization and mercury arc lamps may be used for subsequent crosslinking.

These steps may be performed in-line, that is, the polymerizable mixture may be surrounded with an encapsulating material, polymerized, hot melt coated to form a tape, and optionally crosslinked, or the steps may be performed individually at separate times and locations. For example, the encapsulated prepolymer mixture can be polymerized at one time and extruded and crosslinked at another time.

In another preferred bulk polymerization process, the wet-stick (meth) acrylate pressure sensitive adhesives of the present invention are prepared by a photo-initiated polymerization process of the technology described in U.S. Pat. No. 4,181,752. The (meth) acrylate monomer, the hydrophilic acidic comonomer, the plasticizer, and the photoinitiator are mixed together in the absence of solvent and partially polymerized to a viscosity in the range of about 500 centipoise to about 50,000 centipoise to obtain a coatable syrup. Alternatively, the (meth) acrylate monomer, hydrophilic acidic comonomer, plasticizer and thixotropic agent (e.g. fumed hydrophilic silica) may be mixed to achieve a coatable thickness. The crosslinker and any other ingredients are then added to the prepolymer slurry. Alternatively, these ingredients (except for the cross-linker) may be added directly to the monomer mixture prior to prepolymerization.

The resulting composition is coated onto a substrate that is transparent to ultraviolet radiation and polymerized by exposure to ultraviolet radiation in an inert (i.e., oxygen-free) atmosphere, such as a nitrogen atmosphere. Examples of suitable substrates include release liners (e.g., silicone release liners) and tape backings (which may be primed or unprimed paper or plastic). It is also possible to achieve a substantially inert atmosphere by covering the layer of polymerizable coating with a plastic film that is substantially transparent to ultraviolet radiation and irradiating the film through it in air using an ultraviolet lamp as described in the above-mentioned patents. Alternatively, instead of covering the polymerizable coating, an oxidizable tin compound may be added to the polymerizable paste to increase the resistance of the paste to oxygen, as described in U.S. Pat. No. 4,303,485. The 90% emission of the ultraviolet light source is preferably at about 280nm to about 400nm (more preferably at about 300nm to about 400 nm), with a maximum emission at about 351 nm.

The polymerizable mixture may also include a crosslinking agent or combination of crosslinking agents to enhance the shear strength of the adhesive. Useful crosslinking agents include substituted triazines such as 2, 4-bis (trichloromethyl) -6- (4-methoxyphenyl) -s-triazine, 2, 4-bis (trichloromethyl) -6- (3, 4-dimethoxyphenyl) -s-triazine, and chromophore substituted halo-s-triazines as disclosed in U.S. Pat. Nos. 4,329,384 and 4,330,590. Other useful crosslinking agents include multifunctional alkyl (meth) acrylate monomers such as trimethylolpropane triacrylate, pentaerythritol tetraacrylate, 1, 2-ethylene glycol diacrylate, 1, 4-butanediol diacrylate, 1, 6-hexanediol diacrylate, and 1, 12-dodecanol diacrylate. Various other crosslinkers having different molecular weights between the (meth) acrylate functions are also useful. Generally, the crosslinking agent is present in an amount of about 0.005 to about 1 weight percent based on the combined weight of the monomers.

Other additives

As will be appreciated, other additives may be included in the reaction mixture, or may be added to modify the properties of the adhesive when compounded or coated. Such additives or fillers include pigments, glass or polymer bubbles or beads (which may be expanded or non-expanded), fibers, reinforcing agents, hydrophobic or hydrophilic silica, toughening agents, flame retardants, antioxidants, finely ground polymer particles (such as polyester, nylon, and polypropylene), and stabilizers. The additives are added in amounts sufficient to achieve the desired final properties.

The wet-stick pressure-sensitive adhesives of the present invention that provide good tack and good adhesion to both wet and dry surfaces are useful in many industrial, commercial and consumer applications. For example, these adhesives that are well adherent to both wet and dry surfaces, as well as good adhesion, are useful in medical applications, such as tapes, bandages, dressings, and drapes that adhere to dry and moist skin surfaces (such as wounds or areas of the body that are prone to becoming wet). In addition, these adhesives that are well tacky and adhere well to both wet and dry surfaces can also be used in outdoor or exterior applications, for example, for road materials, e.g., road surfaces such as asphalt pavement, and for road marking tapes, traffic control signs, and marine or automotive coatings and surfaces. In addition, labels for food containers and other products that are exposed to moisture (caused by condensation or being subjected to water or ice immersion) may also be coated with adhesives that have good tack and good adhesion to both wet and dry surfaces.