GB2211759A

GB2211759A - Pressure sensitive adhesive products

Info

Publication number: GB2211759A
Application number: GB8725579A
Authority: GB
Inventors: David John Bebbington; Patrick Mark Clinton Branigan
Original assignee: Wiggins Teape Group Ltd
Current assignee: Wiggins Teape Group Ltd
Priority date: 1987-10-31
Filing date: 1987-10-31
Publication date: 1989-07-12
Also published as: GB8725579D0

Abstract

Peelable adhesive coated sheets, especially labels, comprise a substrate, especially paper, a primer coating and a peelable adhesive coating in which both the primer and peelable adhesive coatings include a contact cement and the adhesive coating is in the form of a discontinuous coating of discrete dots. The contact cement serves to ensure good bonding between the primer and adhesive and the dot coating enables greater flexibility in the choice of adhesive whilst preserving good peelability.

Description

PRESSURE SENSITIVE ADHESIVE PRODUCTS Pressure sensitive adhesives are adhesives which do not require specific activation in order to render them adhesive to the target substrate. Typical examples include pressure sensitive adhesive label materials.

Because the pressure sensitive adhesive will form an adhesive bond to a substrate without activation, the adhesive coated label is normally protected from premature adhesion by being beld in contact with a release surface, typically of a silicone polymer on a backing substrate.

Pressure sensitive adhesives are also sometimes referred to as "self-adhesives".

Pressure sensitive adhesive coated materials can be functionally divided into two broad classes. The first of these is represented by the so-called "permanent" materials in which the properties of the pressure sensitive adhesive are selected so as to form an adhesive bond with the target substrate which is strong and (apart from deterioration) does not weaken significantly with time. Many varieties of pressure sensitive adhesive labels are "permanent" in this sense.The second broad class is of "removable" or "peelable" pressure sensitive adhesive coated materials, particularly labels, in which the pressure sensitive adhesive forms an adhesive bond of functionally adequate strength with the target substrate but which, after an extended period of adhesion typically from days to months, can be peeled away from the target substrate, ideally, without damaging the substrate and without leaving pressure sensitive adhesive on the target substrate or with the adhesive coated material itself tearing. The present invention relates to this second broad class of pressure sensitive adhesive coated materials.

The term "removable" and "peelable" are used in the art as being substantially synonymous but for convenience and because it is suitably descriptive, the term "peelable" will be used herein. These terms do not relate to the removal of pressure sensitive adhesive coated materials from specific release surfaces because this is determined by the designed release properties of the release surface.

To be peelable a pressure sensitive adhesive coated material requires a combination of properties. The pressure sensitive adhesive must form a bond of adequate strength with the target substrate but one in which the bond does not subsequently either dramatically weaken, in which case the adhesive coated material might fall away from the target substrate, or significantly increase in strength as this would tend to limit peelability. From this it is clear that the adhesive should have adequate cohesive strength so as to minimise any tendency of the adhesive film itself to rupture and should bond strongly to the substrate onto which the adhesive is coated. It is plain that, at least in part, these requirements are in conflict.In particular the formation of a strong bond between the pressure sensitive adhesive and its coating substrate and a relatively much weaker bond between the adhesive and the target substrate are in conflict. Many of the "peelable" pressure sensitive adhesive coated products currently on the market do not fully resolve this technical conflict and are, effectively, only less permanent than typical "permanent" pressure sensitive adhesive coated materials.

Our copending European Patent Application No 87305610.5 (Publication No.csl,t A) the content of which is incorporated herein by reference is directed to an improved form of peelable pressure sensitive adhesive coated sheet product in which strong adhesion between the substrate and the adhesive coating is achieved by first coating the substrate with a primer containing a contact cement and then coating with the adhesive which also contains a contact cement. The presence of the contact cement in the primer and adhesive coatings serves to bond the adhesive firmly to the base. This substantially enhances the overall performance, as peelable pressure sensitive adhesives, of the adhesives used.That application is primarily concerned with improving otherwise conventional peelable adhesive products and, therefore describes the invention in the context of having a continuous adhesive coating over the surface of the substrate. This is satisfactory when typical peelable adhesives (otherwise than containing contact cement) are used. The present invention is based on the finding that the advantageous use of contact cements in primer coatings and adhesive coatings extends to adhesive coatings which are discontinuous and in particular take the form of an array of dots.

Accordingly, the present invention provides a peelable pressure sensitive adhesive coated substrate comprising a sheet substrate having on one surface thereof a primer coating, including a contact cement, firmly bonded to the sheet substrate, and, overlying the primer coating, a coating of a peelable pressure sensitive adhesive, including a contact cement, in the form of a discontinuous coating of discrete dots of the adhesive, the contact cement(s) serving to firmly bond the primer coating and the adhesive coating together.

The invention is particularly applicable to labels in which the substrate is a flexible sheet material and, as an industrial product, will normally be held, prior to use, on a backing sheet having a release surface.

Thus, the invention includes a peelable pressure sensitive adhesive coated label, as converted labelling or unconverted label stock, comprising a backing substrate having a release surface and releasably laminated thereto the pressure sensitive adhesive coated side of a peelable pressure sensitive adhesive label which comprises a flexible sheet label substrate and on one side thereof a primer coating, including a contact cement, firmly bonded to the sheet substrate, and, overlying the primer coating, a coating of a peelable pressure sensitive adhesive including a contact cement, in the form of a discontinuous coating of discrete dots of the adhesive, the contact cement(s) serving to firmly bond the primer coating and the adhesive coating together.

The invention further includes the peelable pressure sensitive adhesive coated sheet substrate of the invention, particularly in the form of a label, in use, peelably adhered to a target substrate.

In this invention the coating of peelable pressure sensitive adhesive is provided on the primed substrate in the form of discrete dots so that each dot of adhesive adheres to the primed substrate and is separate from and not adhered to adjacent dots. The best way of doing this is to use a substantially regular array of dots of the adhesive and the use of such regular arrays of adhesive dots forms a particular feature of the invention. Square, offset square and hexagonal arrays of dots are particularly preferred. It is desirable, within the limits of obtaining adequate coatweight, that the average dot diameter is at least 0.1 mm and not more than 1 mm.

Usually it will be in the range 0.3 to 0.8 and especially about 0.5 mm. "Diameter" refers to the diameter of a circle having the same area as the dot. Typically, this will be a representative measure as the dots will be approximately circular.

To give satisfactory adhesive properties, the coatweight of peelable pressure sensitive adhesive will typically be at least 3, commonly, in the range 5 to 25, and more usually 10 to 15, g m-2. As is described below, the use of dot coatings can permit a somewhat wider choice of adhesive than when the adhesive coating is continuous and uniform coatings at lower coatweights is possible.

The product of the invention has a primer coating containing a contact cement and includes a contact cement in the pressure sensitive adhesive. Contact cements are adhesives which exhibit high cohesive strength and a ready tendency for two surfaces of the adhesive to cohere when placed in contact. Examples include the commercially available "impact" adhesives and so-called "self-seal" coatings as are now common on envelopes. Examples of polymers which can be used as contact cements include polymers of isoprene, including natural rubber (unvulcanized), synthetic cis-polyisoprene and polychloroprene, and a class of acrylic polymers. A property common to polymers which can be used in contact cements is a low glass transition temperature.We believe that the limits on the nature of the contact cement are provided by process requirements (discussed below), compatibility of the contact cement with the pressure sensitive adhesive, adherence of the primer to the coating substrate and effectiveness of the polymers used in their function as contact cement in the product.

The requirement of compatibility is effectively that on coating, the pressure sensitive adhesive composition including the contact cement shall not undergo phase separation. With normal care in formulation, we would not expect this to be a major difficulty for those skilled in this art. Adherence of the primer coating to the coating substrate is referred to below. Isoprene polymers are generally superior as contact cements in the invention to the acrylic polymers referred to above.

Polychloroprene, such as that sold under the trade mark Neoprene by Du Pont, is particularly good. Unvulcanized natural rubber is technically good but is susceptible to oxidation and in practice it will probably be necessary to include an antioxidant in it (see below). Within the invention, provided the functional requirements are met, the contact cement used in the primer coating can be the same as or different to that used in the pressure sensitive adhesive coating.

The primer coat on the coating substrate can be substantially entirely of the contact cement polymer.

However, we have found that diluent polymers can be included in the primer coat which may improve the performance of the primer coat. Any such diluent polymer should be a film former and should not interfere significantly either with the bonding of the primer coat to the coating substrate or with the desired properties of the contact cement polymer. Apart from beneficial economic effects, the inclusion of a diluent polymer can assist in filling the surface of the coating substrate, if this is rough for example as it will be with paper, it may aid in forming a barrier, which can be important if the adhesive coating contained materials which may migrate, it may act to improve the bonding of the primer coat to the coating substrate and may provide beneficial mechanical properties in the primer coat. Styrene butadiene rubber (SBR) is particularly useful as a diluent in the primer coat.The SBR used is preferably a relatively "soft" SBR polymer i.e. one including a relatively high proportion of butadiene typically between 50 and 80%, especially around 70% of butadiene by weight. Even higher proportions of butadiene may be used, although we have not found any particular advantage in this. The particular proportion chosen will typically represent a balance between ensuring that the SBR is flexible enough so as to conform with the coating substrate in use and have a high enough styrene content so as to enhance bonding to the coating substrate.

The diluent SBR can be a carboxylated SBR. The carboxylation is included mainly because the source material is an SBR latex and appears not to adversely affects its use as a diluent. (See below in the discussion on the process.) As the contact cements typically include diene polymers we have found it beneficial to include small quantities, typically up to 1.0% and most usually from 0.3 to 0.6% by weight on the total dry polymer weight of the primer coat, of an antioxidant. The main reason for this is to inhibit discolouration which may otherwise occur. The inclusion of an antioxidant may also have a beneficial effect on performance e.g. after long term storage.

Antioxidants known for use with the polymer types used as contact cements, especially for the polydiene polymers will be chosen. Small quantities of filler may be included within the primer coat if desired but incorporation of more than about 5.0% is likely to have a deleterious effect on the desired properties.

The primer coat will typically present on the substrate at a coatweight of from 2 to 20, particularly 5 to 10 g m2. In principle, the primer could be coated as dots with the adhesive being dot coated in register.

However, the precision of coating required for this is high, and likely to be expensive. Accordingly, the primer coating will usually be coated uniformly on the substrate. The practical lower limit is that to obtain a good uniform coating pattern and the upper limit is economic.

The peelable pressure sensitive adhesive can be a conventional peelable pressure sensitive adhesive and the type of adhesive used in our Eurpoean Patent Application No. 87305610.5 can be used in this invention. However, we have found that the peelability of adhesive coated in dot form tends to be superior to that of the same adhesive coated continuously. Thus, it is now possible to use adhesives which would otherwise be considered too permantent for peelable use. This broadening of the type of adhesive which can be used is practically significant in offering greater operational flexibility. As indicated the broad criteria for selection of the adhesive are similar to those in our earlier European Application No. 87305610.5.

Typically, peelable adhesive polymers are available based on acrylic polymers, styrene butadiene rubbers and isoprene polymers. Typical acrylic peelable adhesives include a high proportion of alkyl e.g. butyl or 2-ehylhexyl, acrylate monomer units. Styrene butadiene rubbers will typically have a relatively high proportion of butadiene, so that they are relatively soft, typically greater than 60; by weight butadiene but not usually more than 80cm; as polymers with such low proportions of styrene tend to behave more like polybutadiene which is very soft and not itself a pressure sensitive adhesive. Styrene butadiene rubbers can be carboxylated or uncarboxylated types. The choice between these will primarily be determined by the coating method used. Thus, for aqueous coatings, carboxylated styrene butadiene rubbers, as latices, will be preferred. Isoprene polymers for example unvulcanized natural rubber and polychloroprene can be formulated into pressure sensitive adhesives by incorporating tackifiers with them. For these polymers tackifiers are needed as the polymers do not themselves form pressure sensitive adhesive films. Where the polymer is an isoprene polymer then part of this polymer may function as the contact cement present in the peelable pressure sensitive adhesive coating and, therefore it may not be necessary to add a separate contact cement component.

When present, tackifiers for the peelable pressure sensitive adhesive will typically be rosin esters where the main polymer is an acrylic polymer or a styrene butadiene rubber or a hydrocarbon resin where the main polymer is a polyisoprene or a styrene butadiene rubber.

For acrylic polymers and styrene butadiene rubber tackifiers may not be necessary but for polyisoprene polymers such as natural rubber they will be present in at least 5% by weight on the solid weight of adhesive. The amount of tackifier used will be selected to give sufficient tack for the desired properties of the adhesive but not significabntly more, as increasing the tack beyond this level will tend to make the adhesive less peelable.

Use of more than about 25% by weight on the total adhesive of tackifier will usually and more than 50 will almost invariably lead to the adhesive being non-peelable even if dot coated and, when used, typical amounts of plasticizer will be from 5 to 10 but possibly up to 20% by weight on the solid adhesive.

Plasticizers may be incorporated in the peelable pressure sensitive adhesive coating to soften the adhesive and thus improve peelability. However, care may be needed as some plasticisers can have a tackifying effect on adhesive polymers and this may limit the amount used. Typical plasticizers include phthalate esters and polyoxyakylene ether derivatives of phenols, the principal requirement being compatibility with the main adhesive polymer and the tackifier so as to avoid or minimise migration of the plasticizer. It is possible to use quite large quantities of plasticizer even up to 50% by weight on the solid adhesive. However, more usually, when plasticizers are present they will be used in an amount of from 10 to 20% by weight on the solid adhesive.

The chemical nature of the contact cement included in the adhesive layer has been mentioned above. When the contact cement component is added to the adhesive it will typically be present in at least 5 by weight of the solid adhesive as less than 5; has proved ineffective and usually the minimum amount will be about 7%. Typically the proportion will be from 10 to 20; by weight on the solid adhesive but higher amounts for example up to 50; work. However, as the best contact cement we have found is polychloroprene which is more expensive than the other polymers used there is an economic incentive to limit the amount used to that necessary to achieve the purpose.As is briefly noted above, where the main polymer of the adhesive is an isoprene polymer then the proportion of this polymer may represent the proportion of contact cement as that part of it adjacent to the primer coat will provide this function.

The nature of the coating substrate will be determined by the intended end use. Typically it will be a sheet of paper, polymeric film, foil or similar material. Usually it will have a substance (mass per unit area of sheet) of at least 50 g m-2, although for paper it will typically be at least 70 g m'2, as lower substances will make it difficult to provide the necessary strength to enable it to be peeled from the target substrate.

There is no specific functional upper limit of substance for the coating substrate but paper would not usually have a substance greater than 100 g m-2 and films and foils probably not more than about 150 g m'2 on a cost basis although where "fancy" sheets of pressure sensitive adhesive material are being produced the effective substance can be higher.

Where a separate backing substrate having a release surface is included in the product the backing substrate itself will typically be of paper, polymeric film, foil, polymer coated paper or similar material. The presence of this backing substrate is determined essentially by its function and this will determine its substance, but typically it will be from 60 to 100 g m'2, Lower substances tend not to be strong enough and higher substances relatively expensive. The release surface will normally, as is conventional in the art, be provided by a coating of a silicone polymer or a material providing similar release properties coated on the backing substrate. However, where the backing substrate is of a relatively hard polymeric film having a gloss surface it may not be necessary to provide a separate release coating to achieve adequate release.Where a coating of a silicone polymer is used to achieve the release surface its coatweight will typically be from 0.5 to 10 g m'2 but usually not more than 2 g m2. Backing substrates having release surfaces such as are commonly used in the art may be used in the present invention.

The primer coat of the product of the invention can be provided by conventional adhesive coating methods.

Because of the ease of operation at high speed provided by using aqueous coating mixes, we have used this method successfully to coat both the primer coating and the peelable pressure sensitive adhesive coating in making products of this invention.

To coat the primer coating onto the coating substrate an aqueous coating mix is made up in which the components of the primer coating are finely dispersed and which typically takes the form of a latex. Process aids such as defaomers and wetting aids may be added and the overall solids content adjusted, if necessary by adding further water, so as to achieve a satisfactory viscosity for coating, the coating mixes coated onto the substrate and dried to provide the primer coating. Thereafter the adhesive coating is coated onto the primed substrate either by coating it directly with the aqueous adhesive coating mix or indirectly by coating the aqueous adhesive mix onto a release surface, drying it on that surface and subsequently laminating the adhesive dot coating with the primed substrate. The method of dot coating the adhesive coating is described below.As will be recognised the release surface will usually be the release surface of the backing sheet when this is present.

The application of the discontinuous, dot, coating of the adhesive can be carried out by screen coating i.e. by coating through a perforated screen c.f. screen printing.

The screen is usually formed by a fine mesh/stencil combination or is a perforated sheet optionally with a stencil. In practice, a continuous rotary screen will be used to coat the primed substrate. Typically, the dot size spacing and pattern for the adhesive dots matches the scale perforations in conventional continuous rotary screens so it is not necessary to use stencils.

The equipment used to carry out continuous rotary screen coating typically comprises a driven cylindrical screen, usually a perforated, thin walled metal cylinder, and a driven backing roll. The web to be coated passes over or round the backing roll and through the "nip" between the screen and backing roll. Although the term "nip" is used the contact pressure is usually only adequate to maintain suitable contact between web and screen. A flexible squeegee blade, usually with a metal tip, is fitted inside the screen, with the blade tip pressed against the inside surface of the screen adjacent the length of the nip.

Coating mix is introduced inside the screen to form a puddle between the squeegee blade and the inside of the screen. Rotation of the screen pushes the coating mix against the squeegee and screen and pushes it through the screen with the squeegee blade acting to meter the amount.

The squeegee is adjustable to change the pressure applied to the blade and thus the force at the tip. An increase of pressure increases the amount of mix pushed through the screen and thus the coatweight applied to the web.

Movement of the blade tip in relation to the nip can also affect coatweight. The flexibility and size of the squeegee blade can also be changed but this, as is the choice of screen, is more a matter of setting up than adjustment. We have also found that coatweight and dot size also tend to increase with increasing line speed.

As is mentioned above it is possible to vary the coatweight applied to the paper web using a particular combination of screen and adhesive coating mix by adjusting the operating conditions. This coatweight variation will usually be reflected in a corresponding chnange of dot size. Care may be needed when trying to increase the coatweight to avoid undue increase in dot size as might lead to filming of the adhesive coating.

Aqueous pressure sensitive adhesive coating mixes can be made up to meet the particular operational requirements of screen coating. Thus the mix should be fairly viscous typically 1500 to 5000 cP Brookfield (No. 7 spindle, 100 rpm) and moderately shear thinning. The discontinuous nature of latices makes them particularly good for this method of coating as the phase boundaries inhibit spinning.

The invention includes various methods of making the adhesive coated sheet product of the invention.

Accordingly, the invention provides a method of making a peelable pressure sensitive adhesive coated sheet product which method comprises coating a substrate with a first aqueous coating mix including dispersed therein a contact cement, removing water from the coating so as to provide a primer coat on the substrate and subsequently screen coating the primed substrate with a discontinuous coating of discrete dots of an aqueous coating mix of a peelable pressure sensitive adhesive composition including a contact cement and removing water from the adhesive so as to give a discontinuous dot coating of the adhesive.

The invention further includes a method of making a peelable pressure sensitive adhesive coated label laminated to the release surface of a backing substrate which comprises applying a first aqueous coating mix having dispersed therein a contact cement material to one side of the label substrate, removing water from the coating so as to form a primer coating on the label substrate, screen coating the release surface of the backing substrate with a discontinuous coating of discrete dots of an aqueous coating mix comprising a dispersion of a peelable pressure sensitive adhesive including thererein a contact cement, removing water from the coating on the backing substrate so as to form a discontinuous coating of a peelable pressure sensitive adhesive on the backing substrate and subsequently laminating the primer coating face of the label substrate to the adhesive coated face of the backing substrate.

The following Examples illustrate the invention. All parts and percentages are by weight unless otherwise stated.

Test Methods Peel Strength Test A sample of pressure sensitive adhesive coated sheet substrate 1 inch (2.54 cm) wide and about 4 inches (ca. 10 cm) long is adhered to a target substrate (glass unless otherwise stated) surface. One end of the adhesive coated sheet is peeled off the target substrate and held in a plane perpendicular to the target substrate.

The target substrate is restrained in its initial plane.

The coated sheet is pulled away from the target substrate at a constant linear rate of 300 mm mien~1 and so that the angle at which the coated sheet is peeled from the target substrate is held at 90". The force needed to peel the coated sheet from the target substrate is measured. The instrument used provides a numerical readout which is the numerical result quoted below.

Nominally this readout has the dimensions: grams force per linear inch (1 gf in-l = ca.0.39 No~1). The behaviour of the test sample and the adhesive coating during peeling and the state of the test sample and the target substrate after peeling are also noted.

The test is usually carried out in duplicate and unless otherwise stated quoted results are the means of such duplicates.

Materials Used in Examples Trade Name Source Description Neoprene 115 Du Pont Polychloroprene latex (50% solids) Revinex 76 D 41 Doverstrand Carboxylated SBR latex (47% solids 70s butadiene) Acronal DS A120 BASF Acrylic polymer latex (used to be known as Acronal DS3342) (50% solids) Plastilit 3060 BASF Polypropylene glycol alkylphenyl ether plasticizer Collacryl VL BASF Acrylic thickener and stabilizer Naugawhite SL ~ Antioxidant Example 1 The following primer formulation was made up: Material Parts (dry) Parts (wet) Revinex 76 D 41 30 63.8 Neoprene 115 70 140 Naugawhite S.E. 2 2 Antifoam 22 Water to 45; solids This primer mix was coated onto 70 g m'2 labelstock paper using a Meyer bar coater to give a dry coatweight of 5 g m~2.

The following adhesive formulation was made up: Material Parts (dry) Parts (wet) Acronal DS A120 61.5 123 Plastilit 3060 41.1 41.1 Neoprene 115 38.5 82.3 Collacral VL 0.3 0.3 Naugawhite S.E. 2.0 2 Water to 50% solids This adhesive coating was dot screen coated onto the primed labelstock using a laboratory hand screen. The screen was a 110 mesh polyester fibre screen with dot raster stenciles of either 50 or 25 dots to the inch (20 or 10 dots to the cm). Various coatweights and areas of coverage were achieved by choice of stencil and, as necessary using multiple passes.The adhesive dot coated labelstock was laminated onto conventional silicone coated paper release base to give a label laminate. (Direct adhesive dot coating onto the labelstock was used as a convenience in the laboratory - generally in commercial operation the adhesive would be dot coated onto the release base and subsequently laminated with the primed labelstock to give a structurally substantially identical product.) The adhesive dot coated labelstock was peel strength tested against a glass target substrate. The results are set out in Table 1 below. Coverage figures are calculated from the geometry of the stencil.

Table No. 1 Sample Raster % Coverage Coatweight Peel Strength No. (%) (g m-2) (gf in -1) 1 25 50 14 24 2 25 5C 10 20 3 25 50 8 15 4 40 40 16 18 5 40 40 12 11 6 40 40 7 5 Comparison - 100 13 100

Claims

Claims 1. A peelable pressure sensitive adhesive coated substrate comprising a sheet substrate having on one surface thereof a primer coating, including a contact cement, firmly bonded to the sheet substrate, and, overlying the primer coating, a coating of a peelable pressure sensitive adhesive, including a contact cement, in the form of a discontinuous coating of discrete dots of the adhesive, the contact cements serving to firmly bond the primer coating and the adhesive coating together.
2. A peelable pressure sensitive adhesive coated label, as converted labelling or unconverted label stock, comprising a backing substrate having a release surface and releasably laminated thereto the pressure sensitive adhesive coated side of a peelable pressure sensitive adhesive label which comprises a flexible sheet label substrate and on one side thereof a primer coating, including a contact cement, firmly bonded to the sheet substrate, and, overlying the primer coating, a coating of a peelable pressure sensitive adhesive including a contact cement, in the form of a discontinuous coating of discrete dots of the adhesive, the contact cement(s) serving to firmly bond the primer coating and the adhesive coating together.
3. A pressure sensitive adhesive product as claimed in either claim 1 or claim 2 wherein the dots are arranged in a regular array of dots having an average diameter of 0.3 to 0.8 mm.
4. A pressure sensitive adhesive product as claimed in any one of claims 1 to 3 wherein the adhesive coatweight is from 5 to 25 g m2.
5. A pressure sensitive adhesive product as claimed in any one of claims 1 to 4 wherein the contact cement(s) in the primer and adhesive is(are) selected from natural rubber, synthetic cis-polyisoprene or polychloroprene.
6. A pressure sensitive adhesive product as claimed in any one of claims 1 to 5 wherein the primer comprises a blend of contact cement and styrene butadiene rubber.
7. A pressure sensitive adhesive product as claimed in any one of claims 1 to 6 wherein the primer has a coatweight of 5 to 10 g m2.
8. A pressure sensitive adhesive product as claimed in any one of claims 1 to 9 pee lab ly adhered to a target substrate.
9. A method of making a peelable pressure sensitive adhesive coated sheet product which method comprises coating a substrate with a first aqueous coating mix including dispersed therein a contact cement, removing water from the coating so as to provide a primer coat on the substrate and subsequently screen coating the primed substrate with a discontinuous coating of discrete dots of an aqueous coating mix of a peelable pressure sensitive adhesive composition including a contact cement and removing water from the adhesive so as to give a discontinuous dot coating of the adhesive.
10.A method of making a peelable pressure sensitive adhesive coated label laminated to the release surface of a backing substrate which comprises applying a first aqueous coating mix having dispersed therein a contact cement material to one side of the label substrate, removing water from the coating so as to form a primer coating on the label substrate, screen coating the release surface of the backing substrate with a discontinuous coating of discrete dots of an aqueous coating mix comprising a dispersion of a peelable pressure sensitive adhesive including thererein a contact cement, removing water from the coating on the backing substrate so as to form a discontinuous coating of a peelable pressure sensitive adhesive on the backing substrate and subsequently laminating the primer coating face of the label substrate to the adhesive coated face of the backing substrate.