CA2461425A1 - Printable release compositions for adhesive articles - Google Patents

Abstract

The present invention is directed to a printable release composition used for pressure sensitive labels and the like. The invention is also directed to an article, such as a label, that comprises a substrate such as paper, optionally a thermal transfer primer coating coated onto the substrate and a release layer coated onto the transfer primer coating or onto the substrate. The printable release composition of the present invention may be used with labels having permanent, repositionable or removable adhesives. The particular composition of the release layer depends on the type of adhesive that is appropriate for the desired end use.

Description

° 72049-168D

PRINTABLE RELEASE
Background of the Invention This is a divisional of Canadian patent application 2,177,847 filed January 20, 1995.
Field of the Invention The present invention relates to printable release compositions for pressure sensitive adhesive articles, such as labels, and to articles containing such release compositions.
Description of the Prior Art Many types of adhesive articles are known, such as labels, tapes, and note pads. Labels, in particular, are used for business forms, files, advertising, and the like.
Labels come in a variety of shapes and sizes, such as window labels, machine labels, integrated labels and the like.
Integrated labels are physically integrated, during manufacture, with business forms, mailings and the like.
The type of adhesive best suited for use with a particular article depends on the article's ultimate use.
The adhesive may be repositionable, permanent or removable.
For instance, it may be desirable for some applications to permanently affix an article to an object, for example, a label applied to a file folder. Such applications require a permanent adhesive. A repositionable adhesive, on the other hand, can be applied to an object, removed, and reapplied.
Pads of notes, for example, NoteStix or PostIt notes, are examples of articles using repositionable adhesives.
CleanTac is an example of a label having a repositionable adhesive. Finally, removable adhesives are appropriate when the article is to be removed after use, but is generally not la reusable. Removable adhesives may, however, also include adhesives which become permanent over time.
Regardless of their use, adhesive articles must be stored and readily available for use. Such articles may utilize a separate disposable liner in juxtaposed face-to-face contact with the adhesive substrate with a release material coated on the side of the liner in contact with the adhesive side of the adhesive substrate. Just prior to use, y CA 02461425 2004-04-06 , '.. ~....."

2 the liner is peeled away from the adhesive. Such an adhesive article is often referred to as a "linered" label.
Alternatively, the adhesive article may be a substrate coated on one side with a release material and boated on the opposite side with an adhesive material. Such a linerless label can be stored in pads or rolls.
The release coating facilitates either the removal of the adhesive-coated substrate from the liner or the pad or the unwinding the linerless label from the roll. The release coating needs to have sufficient adhesion to keep, for example, the linered label on its backing, or the linerless label on a pad or in a roll, but must have sufficient release properties to allow the label to be removed from the backing or pad or to be unwound from the roll, while maintaining its adhesive property.
For some time there have been problems in producing a release coating that possesses the above properties and that, additionally, contains printed matter. One problem relates to retaining the tenacity of the printed matter on the substrate so that the printed matter is not pulled off by the adhesive or wiped off by contact occasioned by someone rubbing against or applying the label. Another problem is "fill-in" of letters such as "o", "a", "e", etc.
Fill-in occurs when the porosity of the substrate is not sufficient to absorb the ink and the ink has a tendency to feather out. Wipe-off and related problems may occur if the porosity of the substrate is too low and the ink does not dry sufficiently.
As an example of the above-mentioned problems, a release coating may be used for the printing of Postnet barcodes and FIM codes for automated mail processing.
Postnet (Numerical 8ncoding Technique) is used to encode the ZIP code or ZIP+4 code on an envelope and is located in the lower right portion of a mail piece. FIMs (Facing Identification Marks) are used to identify Business Reply Mail and are a series of vertical bars printed in the upper middle portion of the mail piece just to the left of the .; ~~.

3.
postage indicia. flMs greatly facilitate the automated processing of the mail; thus the quality and placement of the barcodes is very critical to the success of automated processing techniques. for instance, in a linerless label application, the barge or bsrcodes are printed on the release surface of a substrate. If feathering or wipe off of the printed indicia occurs, then the information contained in the respective barcodea cannot be scanned.
This may result i~ the lose of the cheaper bulk~mailing rate. Standard postage for each piece must then be paid, increasing the cost to the customer, and the mail must be mechanically sorted, causing delay.
In the case of thermal transfer printing, not only is a high surface energy preferred, but the surface must be very smooth. Most thermal transfer substrates contain clay coatings with relatively high surface energy and bending properties to enhance ink transfer and anchorage. A release coating imparts a lower surface energy to the face of the label for better release characteristics; however, the porosity of the label is reduced, making printing much more difficult. Thus higher surface energy provides higher print quality, whereas lower surface energy provides for better release characteristics. Thus, there is a need for a printable release'coating having both a good quality print and good~release characteristics.
Summary of the Invention The present invention relates to printable release compositions for use with pressure sensitive adhesive articles, particularly labels. The release compositions provide appropriate release properties for the different adhesives: repositionable, permanent and removable.
The present invention is directed to a composition for use as a release layer for a permanent adhesive comprising a mixture of : .
(ay about 50 to about 95 parts by weight polyethylene;

~,,_,.~20~9-168

4 (b) about 5 to about 20 parts by weight silicone emulsion: and (c) a up to about 20 parts by taeight ethylene vinyl chloride copolymer.
The present invention is also directed to a composition for use as a release layer for a repositioaable adhesive comprising a mixture oft (a) a major amount of ethylene vinyl chloride copolymer; and ., (bj a minor amount of n polyethylene emulsion.
In another embodiment, the present invention is directed to a composition for use as a release layer for a repositionable adhesive comprising:
(a) about 10 to about 80 parts by weight of a surfactant;
and (bj about 20 to about 90 parts by weight of an acrylic golymsr.
In a further embodiment, the present invention is directed to an article comprising a substrate, a thermal transfer primer coating on the substrate, and a release layer on the thermal transfer primer coating wherein the thermal transfer primer coating comprises:
(aj about 20 to about 50 parts by w~ight of a latex;
and (b) about 50 to about 00 parts by weight pigment.
Add3.tional advantages of the invention Will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The advantages of the invention may be realized and obtained by means of the elements and combinations particularly pointed out in the claims.
It is to be understood that both the foregoing general description and the following detailed description are.
exemplary and explanatory only and are not restrictive of the present invention as claimed.

~/ 72049-1&8 Detailed Description of tie Preferred Embodiments The present invention is directed to an ink jet, video jet, and the likes printable release composition for use with pressure sensitive adhesives, such as labels and the like. The invention is also directed to an article, such as a label, that comprises a substrate such as paper, optionally a thermal transfer primer coating coated onto the substrate, and a release layer coated onto the thermal transfer primer coating or onto the substrate. The label nosy be either liaerless or linered. The p=intable release composition of the present invention may be used with labels having permanent, repositionable or removable adhesives.
The particular composition of the release layer depends on the type of adhesive that is appropriate for the desired end use.
In accordance with the preseat invention, as embodied and broadly described herein, a composition is provided for use as a release for ~ permanent adhesive. This composition comprises a mixture of:
(a) about 50 to about 95 parts by weight polyethylene;
and (b) about 5 to about 20 parts by weight silicon emulsion.
Preferably, the polyethylene has a melting point of 100'C or~higher. The polyethylene is preferably an emulsion and may be obtained from commercial sources such as MICxEM*
460, from Michelman, Inc., which is a polyethylene emulsion, having a density of 8.3, a pE of 10.1, a melting point of 11A'C, and a hardness of 1.5. Other emulsions that can be used include Michem 32535, 74040, 46025 and 6872 5, also ~rom Michelman, Inc. Preferably, the composition contains about 80 to about 95 parts by weight polyethylene.
The silicon emul$ion preferably contains an organopoly-s~iloxane, such as methylhydrogen polysiloxane, for example, SYLOFf 1171* available from Dow Corning Corporation, or dimethyl polysiloxane, for example, nPC-107" available from *Trade-mark __.;-2049-168 ~ , 6 i.
Rhone-Poulenc. Preferably, the composition contains about 5 parts by weight silicon emulsion.
The composition may further comprise up to about 20 parts by weight ethylene vinyl chloride copolymer. The ethylene vinyl chloride copolymer blend away be, for exampl~, vA~,COAT*';531 available from Air Products & Chemicals, Inc.
The composition may also contain other additives which do not adversely affect the desired properties bf the release, such as pigments, thickeners, binders and amphipathic materials.
Examples of pigments that can be included in the thermal transfer primer coating composition include, for example, B~1RGBS8 No. 28, available from Butgess Pigment, and SUPERMITE*~/aoailable from BCC International. An 8vA' thickener also may be used in the thermal transfer barrier coating composition of.the invention, such as A=RFLEX* 1650,, from Air Products. Examples of suitable binders that can be included in the thermah transfer barrier coating composition' include, for example, A=RF'LEX*~' 100 HS from Air Products Corp., CARGILL*~ 643.'L from Cargill, RRISTALEX~; 3070 from Hercules, RLICIiIiOLD~>68-010 from Reichhold Chemical, and UGAR* ' hATEX 376 from Union Carbide. Amphipathic materials that can be included in the release composition inchide ALIPAL*' CD-128 from GAIp Cosp. , FLURONIC*'L-101 from BASF Corp. , surfactant M-310 from Texaco, TEXAPHOR 963 from Henkel Corp., and TRITON*~~GR5M from Union Carbide and amphipathic surfactant AEROSOL*'22, C26$43NOlONa4'8' from American Cyanamid Co. The amphipathic materials increase the release and printing properties.
In accordance with the invention, as embodied and broadly described herein, a composition,is provided for use as a release for a repositionable adhesive which comprises a mixture of (a) a major amount of ethylene vinyl chloride copolymer; and (b) a minor amount of a polyethylene emulsion.
*Trade-mark '/:..:2049-I68 Polyethylene emulsions that can be used is the invention include, but are not limited to, MIC88M 460, 'tICHB~! 32535 MICHHM 68725, MICHBM 74040 and MICHHM 46025.
Breferably, the composition contains about 60 to about 90 parts by weiqht ethylene vinyl chloride copolymer, and most preferably about 7s parts by weight ethylene vinyl chloride copolymer.
Bthylene vinyl chloride copolymers that can be used in the invention include, but are not limited to, VAZCOAT 531.
Preferably, the compositioa contains about 10 to about 40 parts by e'sight polyethylene emulsion, and most preferably about 25 parts_by weight polyethyleas emulsion. .
The composition can also contain other additives which do not adversely affect the deeired properties of the release, such se the pigments, thickeners, binders end amphipathic materials dsscr3bed above.
In accordance with the invention, as embodied and broadly described herein, a release composition is provided which comprisess (a) about 10 to about 80 parts by wet weight of a surfactantf and .
(b) about 20 to about 90 parts by wet weight of an acrylic copolymer.
The surfactant may be selected from, for example, sulfosuccinamate compounds, preferably tetrasodium. R-(1,2-dicarbox~rethyl)-p-octadecy7, sulfosuccinamate. ether surfactants include StJRFACT*'M-310 ( Texaco j , ALIPAL CD-12 8 (GAF Corpj and TRITON GR5M (Union Carbido'. A particular sulfosuccinamats that may be used in the invention is ABROSOL 22, available from American Cyanamid Co. The release composition preferably contains about 20 to about 60 part8 by weight of a sn=factaat. The composition may also contain calcium stearat~, in a MICHBI~t 170 emulsion.
The acrylic copolymer may be selected from, for example, commercial formulations such as ACR7f90L ASB-60 from Robin and Haas Co. Another source is ALCOGt~M* ~-31, from Alco *Trade-mark Chemicals. The release composition preferably contains about 40 to about.80 parts by weight of an acrylic copolymer.
The release composition described above comprising a surfactant and an acrylic polymer is particularly suited for use as an ink-jet printable release. The release composition works well with the ink-jet to accept ink due to proper porosity and release. The ink is partially absorbed into the substrate so that it dries quickly and does not feather. Water based ink-jet, such as VideoJet, produces better print quality and drying times with formulas consisting of at least 50 parts of acrylic polymer. Better print quality and drying time for oil based ink-jet, such as Trident, require at least 60 parts of the acrylic polymer.
The release suited for use as an ink-jet printable release may also contain about 10 to about 20 parts by weight calcium stearate emulsion such as MICgEM.170 by Michelman, Inc. for enhanced edge definition.
The ink-jet printable release may be coated on substrates, preferably 20# or 24~ standard paper, such as 24# Union Camp Alkaline. The ink-jet release compositions are preferably coated at 0.37 - 1.8 gsm using a meyer rod, dahlgren, reverse roll, direct gravure, reverse gravure, direct and offset flexo. The release layer is printable with flexo, litho, gravure and dot matrix and laser.
Any of the release compositions described above may be coated on a substrate such as paper to obtain an article, preferably a label. The article may be prepared by coating the release composition onto at least a portion of one side of the substrate. A layer of a thermal transfer primer coating may be juxtaposed between the substrate and the release layer. , . _ The article may contain a permanent or repositionable adhesive depending on its intended use. The release layer composition should be selected accordingly. The adhesive is applied either on the side of the substrate opposite the release layer, e.g., a linerless label, or on at least a ~...J~49-168 portion of oae side of a different substrate, wherein the adhesive layer is in juxtaposed contact with the release layer, e.g., a linered label.
Improved image quality may be obtained on plain paper (e. g., Finch Fins 24~ stock) if the paper has been pre-coated with a thermial transfer primer coating. A thermal transfer primer coating provides for a smoother~contact surface between the pap~r sad the printhead. It also acts as an insulating layer or barrier by keeping the.heat generated during the priating operation from penetrating into the paper. Printing ribboas have a wax coating which melts to release the ink. By keeping the heat on the surfac~, the ink is forced to print on the release surface, improving the print quality and producing a superior image.
The thermal transfer primer coating also functions to bind the release coating to the substrate, enhancing the scratch and scuff resistance of'the release. .
Instead of a thermal transfer primer coating, a barrier coating may be provided between the substrate and the rel~ase, which may be, for example, vinyl acetate/ethylene copolymers such as AIRFh88 1650 by Air products.
In accordanc~ with th~ invention, as embodied and broadly described herein, an article is provided comprising a substrate, a thermal traasfer primer coating coated on the substrate, and a release layer coated on the thermal transfer primer coating. The thermal taansfer primer coating comprises:
(a) about 20 to about 50 parts by weight of a latex;
and (b) about 50 to about 80 parts by weight pigment:
The pigns~nt may be selected from, for example, ROpAQvB*
89, by Rohm and Haas Co. The pigment preferably has a small particle size to obftein a smooth coating. Preferably, the thermal transfer primer coating includes about 80 parts by weight of pigment.
The latex may be, for example, commercial formulations such as r~ATEx*; ~620.by Dow Chemical. Preferably, -the thermal *Trade-anark ', . . - .', ' 10 transfer primer coating includes about ZO parts by weight of a latex.
The substrates usable in the invention are preferably X24 or X20 paper. Commercial paper may be used such as 20~
Finch Fine, Consolidated, and other types of thermal transfer sheets commercially available. Other substrates include films, TYVEK, polyester, and the Like. The coating weight of the thermal transfer primer coating is preferably 2.5 to 4.0 gsm, and more preferably 2.8 gsm to 3.8 gsm. The coating weight of the release composition is preferably 5.0 gsm to 8.0 gsm, and more preferably 5.6 gsm to 7.5 gsm.
The substrate is'precoated with the thermal transfer primer coating, if desired, then a release composition is prepared and coated on the thermal transfer primer coating, or on the substrate if no thermal transfer primer coating is present, using a coater, such as a Meyer Rod coater. The coater can use a dahlgren, flexo, gravure blade or roll to roll. Preferably, a No. 28 meyer rod is used. A meyer rod is a coating rod or bar having different size diameters that can be selected for applying different amounts of coatings.
The release composition described above comprising a surfactant and an acrylic polymer is particularly suited for use as an ink-jet printable release.
Water based ink-jet, such as VideoJet, produces better print quality and dry times with formulas consisting of at least 50 parts of acrylic polymer. Better print quality and dry time for oil based ink-jet, such as Trident, require at least 60 parts of the acrylic polymer.
The ink-jet printable release may also contain 10 to 20 parts calcium stearate emulsion such as MICHEM 170 by Michelman, Inc, for enhanced edge definition.
The ink-jet printable release is coated on substrates, preferably 20~ or 24~ standard paper, such as 24~ union Camp Alkaline.
The ink-jet release compositions are preferably coated at 0.37 - 1.8 gsm using a meyer rod, dahlgren, reverse roll, direct gravure, reverse gravure, direct and offset flexo.

a CA 02461425 2004-04-06 ~_."w The release layer is printable with flexo, litho, gravure and dot matrix.
The following examples are illustrative, and are not intended to limit the scope of the present invention.
Examples Z and 2 are directed to release compositions for use with repositionable adhesives.

A substrate was prepared by precoating with a thermal transfer primer coating.
Substrate: 24# Finch Fine Paper Thermal transfer primer coating : 80 parts ROPAQUE 84 20 parts LATEX 620 Coat weight of 2.82 gsm A release composition was prepared and coated on the thermal transfer primer coating of the substrate using a Meyer Rod coater with a No. 28 meyer rod.
Release: 50 parts AEROSOL 22 Surfactant 50 parts ACRYSOL ASE 60 Coat weight of 5.64 gsm Two week accelerated aging (A.A) delamination values were in~the I.0 - 2.0 oz/in range. AA was performed under heated conditions of 120°F.

Substrate: 24# Consolidated Thermal Transfer Paper A release composition was prepared and coated on the substrate.
Release: 30 parts AEROSOL 22 70 parts ACRYSOL ASE-60 Coat weight 6.76 gsm Two week AA delamination values were in the I.0 - 2.0 oz/in range.
In examples 3-5, trials were conducted using the Meyer Rod coater to produce a permanent printable release for use with a permanent adhesive.

., CA 02461425 2004-04-06 _.
,.

A substrate was prepared by precoating with a thermal transfer primer coating.
Substrate: 24# Finch Fine paper Thermal transfer primer coating: 80 parts ROPAQUE 84 20 parts LAT$X 620 coat weight 3.76 gsm A release composition was prepared and coated on the thermal transfer primer coating.
Release: 75 parts - Polyethylene, MICEEM 460 Z5 parts - Ethylene Vinyl Chloride, vALCOAT 531 parts - Silicone Emulsion, PCL 107 coat weight 7.5 gsm A substrate was prepared by precoating with a thermal transfer primer coating.
Substrate: 24~ Finch Fine paper Thermal transfer primer coating: 80 parts ROPAQUE 84 parts LATEX 620 coat weight 2.82 -3.76 gsm A release composition was prepared and coated on the thermal transfer primer coating.
Release: 80 parts Polyethylene, (MICHEM 460) 10 parts VALCOAT 531 10 parts PCZ 107 coat weight 5.65 - 7.5 gsm A substrate was prepared by precoating with a barrier coating.
Substrate: 24~ Finch Fine paper Barrier: Vinyl Acetate/Ethylene Copolymer, AIRFIrEX 1650 coat weight 2.8 - 6.5 gsm A release composition was prepared and coated on the barrier coating.

. CA 02461425 2004-04-06 ' . f Release: 90 parts Polyethylene MICHEM 460 parts SYLOFF 1171 coat weight 5.6 - 7.5 gsm None of the materials alone meets all the requirements for a good printable release. However, proper blends offer acceptable print and release.
In examples 6-8, trials were conducted using dahlgren to produce an ink-jet printable release. After a 2 week accelerated aging test at 120°F, delamination values of less than 2.7 oz/in were obtained.
EXAMPLE 6 ~ ' A substrate was coated with a release composition.
Substrate: 24# Union Camp Alkaline Release: 50 parts AEROSOL 22 50 parts ASE-60 coat weight 1.5 gsm ' A substrate was coated with a release composition.
Substrate: 24~ Union Camp Alkaline Release: 20 parts AEROSOL 22 80 parts ASE-60 coat weight 1.3 gsm A substrate was coated with a release composition.
Substrate 24~ Union Camp Alkaline Release: l8~pa.rts AEROSOL 22 72 parts ASS-60 10 parts MICHBM 170 coat weight 1.3 gsm Examples 6-8 exhibited good drying time, good dot uniformity and contrast and a good print contrast ratio greater than 75.
It will be apparent to those skilled in the art that various modifications and variations can be made in the compositions and methods of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and'variations of this invention provided they come within the scope of the appended claims and their equivalents.

Claims (2)

CLAIMS:

1. An article comprising a substrate, a thermal transfer primer coating coated onto at least a portion of the substrate, and a release layer coated on the thermal transfer primer coating, wherein the thermal transfer primer coating comprises:
(a) about 20 to about 50 parts by weight of a latex; and (b) about 50 to about 80 parts by weight pigment.

2. The article of claim 1, wherein the thermal transfer primer coating comprises:
(a) about 20 parts by weight of a latex; and (b) about 80 parts by weight pigment.