WO2007041599A1

WO2007041599A1 - Laminate articles and preparations thereof

Info

Publication number: WO2007041599A1
Application number: PCT/US2006/038685
Authority: WO
Inventors: Richard F. Swinnerton; Marie Jewkes
Original assignee: 3M Innovative Properties Company
Priority date: 2005-10-03
Filing date: 2006-10-03
Publication date: 2007-04-12
Also published as: GB0520127D0

Abstract

A laminated article comprising a base substrate having one or more edges defining a major surface which bears a layer of pressure-sensitive adhesive covered by a liner, the liner comprising a liner substrate having a major surface coated with at least a first release agent to provide areas on the liner surface of higher release characteristics and areas of lower release characteristics, characterised in that at least part of at least one of said one or more edges coincides with an area of higher release characteristics for a sufficient distance to accommodate a finger to facilitate removal of the liner from the base substrate.

Description

LAMINATE ARTICLES AND PREPARATIONS THEREOF

TECHNICAL FIELD

This invention relates to laminate articles and to their preparation. In particular, the invention relates to laminate articles comprising a substrate coated with a pressure- sensitive adhesive layer covered by a liner sheet which is intended to be removed when the article is used.

BACKGROUND

Numerous articles comprise a substrate bearing a pressure-sensitive layer protected by a liner. Examples of such articles include adhesive tape (e.g. diaper tapes, foam weather striping tapes etc), adhesive transfer tapes, double-coated tapes, abrasive articles, bandages etc. The pressure-sensitive adhesive layer is protected by a liner to prevent contaminants from contacting the adhesive and to prevent the adhesive layer unintentionally adhering to a surface. The liner generally comprises a paper, plastics film or metallic substrate which may be coated with a release layer. The release layer comprises a non-adhesive material which will allow the liner to be temporarily adhered to the pressure-sensitive adhesive layer but allow the liner to be readily peeled therefrom without leaving any deposit. Thus, the bond strength between the pressure-sensitive adhesive and the release layer is less than the bond between the substrate and the pressures-sensitive adhesive layer and less than the bond strength between the release layer and the liner substrate. Examples of release agents include silicones.

One of the problems associated with the use of a liner sheet is that it may be difficult to initiate peeling of the liner sheet when the article is used. It is common practice to provide tabs or some other form of finger-lift to enable the user to separate the liner sheet from the substrates coated with the pressure-sensitive adhesive layer. However, the use of tabs tends to complicate the manufacturing process. For example, the incorporation of separate tabs (i.e. tabs that are separately applied to the liner sheet) is an expensive and labour intensive step in the manufacturing process, while the provision of an integral tab in the liner sheet requires the inclusion of a kiss-cutting operation in the manufacturing process. It is also known to provide a tab or finger lift by folding the liner, US2006/038685

by applying the liner as two separate overlapping sheets, or simply by forming a slit in the liner but those alternatives also add complexity to the manufacturing process.

It is an object of the present invention to provide a laminated article comprising a substrate coated with the pressure-sensitive adhesive layer protected by a liner in which the liner may be readily removed without the provision of tabs.

SUMMARY

According to one aspect of the present invention as provided in a laminated article comprising a base substrate having one or more edges defining a major surface which bears a layer of pressure-sensitive adhesive covered by a liner, the liner comprises a liner substrate having a major surface coated with at least a first release agent to provide, on the liner surface, areas of higher release characteristics and areas of lower release characteristics, characterised in that at least part of at least one of said one or more edges coincides with an area of higher release characteristics for a sufficient distance to accommodate a finger to facilitate removal of the liner from the base substrate.

According to a further aspect of the invention there is provided a method of manufacturing a laminated article comprising the steps of:

1) producing a base substrate having a major surface coated with a pressure- sensitive adhesive,

2) providing a liner sheet comprising a liner substrate having a major surface coated with at least a first release agent, to provide on the liner surface areas of higher release characteristics and areas of lower release characteristics,

3) laminating said base substrate to said liner sheet so that the pressure- sensitive adhesive contacts the release agent(s) and

4) cutting the resulting laminate to provide a laminated article having one or more edges wherein at least part of at least one of said one or more edges coincides with an area of higher release characteristics on the liner for a sufficient distance to accommodate a finger to facilitate removal of the liner from the base substrate. DETAILED DESCRIPTION

The invention provides a simple and effective means of facilitating removal of the liner from the base substrate. While release liners having areas of different release characteristics are known, e.g. US 3503782 (Ayres), US 5061535 (Kreckel et al.) and US 2002/0000718 (Schwarzbauer); it has never been suggested to provide at the edge of an article, an area of higher release characteristics of a sufficient size to accommodate a finger to facilitate removal of the liner.

The invention is particularly suitable for laminated articles in which the base substrate is co-extensive with the liner sheet. Examples of such articles include adhesively-backed stationary items, surface coverings, coated abrasives, structured abrasives, packaging for DVDs, clear adhesive sheets in photograph albums, adhesive wall charts, adhesive tapes, transfer tapes, medical products e.g. sticking plasters or other products for sticking to the human body, etc.

Coated and structured abrasives comprise a backing substrate having an abrasive composition on one of its major surface. In the case of a coated abrasive, for example, that major surface is coated with an adhesive which secures a plurality of abrasive grains. The adhesive may comprise several layers e.g. a make layer, size layer, super size etc. A coated or structured abrasive may be provided in the form of sheets of a variety of size and shape e.g. square, rectangular, circular, triangular, deltoid etc. In use, the abrasive sheets are often mounted on a backup pad to facilitate handling of the coated abrasive during hand-held applications or to facilitate attachment to a machine. One method of attaching coated abrasive to a backup pad is to coat the backside of the coated abrasive with a pressure-sensitive adhesive layer. While it is possible to stack a series of such coated abrasives on top of each other or to form a roll from an elongate length of such adhesive, such that the abrasive grains in any layer are in contact with the pressure sensitive adhesive of an adjacent layer, it is known to use a liner sheet to protect the adhesive surface of the coated abrasive from contamination during shipment and particularly in the environment where it will be used. It will be appreciated that in the environment where such products are used e.g. car-body repair shop, workshop etc it is desirable that the user can quickly and easily remove the liner and dispose of it before using the coated abrasive on the appliance such as a power tool. The present invention enables the operator to remove the liner from the coated abrasive, possibly even when wearing gloves.

The liner sheet used in an embodiment of the invention comprises a liner substrate which is coated with at least a first release agent at least over part of its surface. Generally, the liner substrate comprises a low cost material such as paper, plastics film e.g. high density polyethylene film. The substrate will generally have a basis weight in the range 30 to 60g/m² and/or a thickness of 25 to 100 micron. If the liner substrate inherently has little bonding affinity to the pressure-sensitive adhesive the liner substrate may be coated in areas with a single release agent to provide surface areas having different release characteristics to that of the liner substrate. The liner substrate may be coated with two different release agents covering the entire surface, one having higher release characteristics than the other. The release agents may be coated on different areas of the surface of the liner substrate. Alternatively, the entire surface of the liner substrate may be coated with a first release agent and then areas of the resulting surface may be coated with a second release agent. Suitable release agents are well known in the art and include silicones, such as aery late functional dimethyl siloxanes. Preferably, areas of the liner substrate having different release characteristics are produced using different coating weights of release agent on the liner. An effective level of silicone for easy release is about 1 gram per square metre of liner. The release characteristics of a coating may be adjusted by suitable selection of release agent and coating thickness. Liners that are easier to peel have been achieved when the peel force values of some areas are below 0.1 N per 25 mm, whilst other areas have peel force values between 0.2 and 0.5 N per 25 mm. In some cases, the higher release areas may have a peel force of zero.

In environments such as car-body repair shops, workshops etc., it has been found that surfaces for painting that may be contacted by discarded liners are not deleteriously affected by transfer of release agent, despite a higher coating weight being applied in examples of the invention. Such surfaces that are prepared for painting using abrasive disks must be substantially free of release agent to obtain a uniform coat of paint.

The precise shape and area of the liner surface which is coated by the release agent to provide areas of higher release characteristics is not important providing that at the edge of the article there is an area of higher release characteristics for a sufficient distance to accommodate a finger to facilitate removal of the liner from the substrate. Preferably the area of higher release characteristics extends along the edge for at least 15mm, more preferably at least 20mm, generally from 25 to 45mm. It has been found a length of about 38mm will accommodate the largest fingers, even when wearing gloves.

It is convenient that the areas of higher release characteristics should be readily discernable from the areas of lower release characteristics at the edge of the article. This may be readily achieved, particularly when the liner substrate is transparent or translucent, by employing a first release agent of a darker shade or different colour from the second release agent and/or liner substrate. In this way, the user can readily determine where an area of higher release characteristics is positioned at the edge of the article and grip that area of the liner for removal.

In general, the articles of the invention will be made by laminating a web of a base substrate (such as a coated abrasive), having a layer of pressure-sensitive adhesive thereon with a web of liner sheet bearing the release agent, such that the release agent contacts the pressure sensitive adhesive. The two webs may be laminated under pressure e.g. by passing through nip rollers, generally at room temperature.

The individual laminated articles may then be cut from the laminate webs by any suitable technique for example the articles may be cut on a flat bed -press that operates on the web by repeatedly descending on the web, or by using a rotary die that cuts into the web as it passes through. The die may cut any suitable shape and will be sized and positioned to minimise the waste due to cut-offs. The areas of higher release on the web may advantageously be co-ordinated with areas of articles to be cut out. Thus, the web width per cut article could be set to equal an integer number of widths of pairs of stripes of lower and higher release; so that all of the cut articles have their areas of higher release in the same places. For example, stripes may be arranged on the liners of cut abrasive disks so that the user finds a higher release stripe in the same place for each disk used. The production process is simple and effective since the provision of tabs is unnecessary. In the case of coated abrasives, the articles may be square, rectangular, circular, deltoid etc. Holes in the article used for dust extraction may be cut simultaneously as the article is cut.

The web of liner sheet may be prepared by any suitable process. The printing of the release coat or coats may be carried out in a single printing step by any suitable printing technique. For example, the pattern may be coated on a roll-coater having a plurality of transfer rolls equipped with feed devices which meter the release agent in accurately defined weights onto the outer roll surface of the coater roll. The coater rolls are fitted with an embossed outer surface corresponding to the pattern to be printed onto the substrate. The release coat may be applied in a solvent system or in a solvent-free system e.g. UV-curable material.

In the case where the liner substrate is a polymeric material, such as polypropylene, the surface of the material may be modified by corona treatment or flame treatment to improve the adhesion of the release coating to the liner substrate.

The invention will now be described with reference to the accompanying drawings in which:

Figure 1 represents a side view on an enlarged scale of a coated abrasive in accordance with the invention

Figures 2 to 4 represent plan views of sections of a laminated web from which circular disks in accordance with the invention are cut.

Figure 1 shows a side view of a coated abrasive article comprising a base substrate (2) of paper, cloth, plastics film, non- woven material, etc having one major surface coated with an adhesive layer (4), or make coat, which bonds abrasive grains (6) to the base substrate (2). The abrasive coating may comprise additional layers e.g. size, and super- size layers etc. Processes for preparing coated abrasive products are well known in the art.

The backside of the base substrate (2) is coated with a layer of pressure-sensitive adhesive (8). The pressure-sensitive adhesive may be hot-melt adhesive or solvent coated adhesive. Suitable adhesives are well known in the art. A liner sheet, generally shown at (10), is laminated to the adhesive layer (8). The liner sheet comprises a liner substrate (12) which is generally formed of paper or plastics material. The liner substrate is coated in some areas with a first release agent (14) and in other areas with a second release agent (16). The areas of release agent (14) have higher release characteristics than the areas of release agent (16). The release agents are of contrasting colour such that areas of each release agent are readily discernable from the side view. If the liner sheet is transparent or translucent, the areas of different release agent will be readily discernable through the liner.

In use, the operator grasps the article and inserts one or more fingers in one of the areas (14) where the release agent has higher release characteristics. In this region the liner will readily begin to separate from the adhesive layer (8) allowing the operator to grip the liner between thumb and finger (s) to enable the liner sheet to be peeled smoothly away from the pressure-sensitive adhesive layer. The coated abrasive may then be attached to a backup pad by applying the pressure sensitive adhesive layer (8) to the backup pad. >

Figures 2 to 5 show a plan view of sections of a web comprising a coated abrasive laminated to a liner in a similar manner to that shown in Figure 1. The liner substrate (12) is transparent translucent and it is readily possible to discern areas (14) of a first release agent having higher release characteristics and areas of a second release agent (16) having areas of lower release characteristics.

The figures show the perimeter (20) of a disk which is cut from the web e.g. by a die stamp. It will be noted that in each case, the perimeter of the disk coincides with areas (14) of release agent having high release characteristics. These areas facilitate removal of the liner from the coated abrasive in the manner described with reference to Figure 1. It will be noted that it is readily possible to achieve such areas at the edge of a disk regardless of whether the web is coated with areas of release agent having lower release characteristics in the form of diagonal stripes (Figure 2) horizontal stripes (Figure 3) circular dots (Figure 4) squares or diamonds (Figure 5).

The invention will now be illustrated by the following Example. EXAMPLE

1. A roll 1430mm wide of HDPE liner substrate 60 microns thick supplied by API Group pic, Poynton Industrial Estate, Poynton, Cheshire, SKl 2 IND, having release lining stripes of clear Acrylate functional dimethyl siloxane release agent in 38mm stripes and higher release (blue) stripes of blue-tinted Acrylate functional dimethyl siloxane release agent in 38mm stripes was prepared, using a gravure roller to apply the different release agents in different loadings.

2. A roll of 333U Pl 80 (commercially available from 3M Company) lined abrasive sheet was made on a production coater, and taken up onto a roll.

3. After allowing time to cool the pressure-sensitive adhesive on the backside of the abrasive sheet, the abrasive sheet was delaminated to remove the liner, and then laminated with striped liner from the roll described in step 1. To achieve this, the delaminated abrasive sheet and striped liner were fed together under tension around a guide roller to a take-up roller, while the original liner was taken up on another roll upstream of the guide roller.

4. 150mm discs were cut from the newly produced laminate using a Die Press machine positioned between the guide roller and the take-up roller, cutting down onto the laminate which was liner side up.

5. The resulting samples were subject to finger peel tests by a panel which included the use of gloves. The panel were instructed to peel the product at the blue stripe (the higher release stripe). The liners were readily peelable from the abrasive discs and were easier to peel than the 333U Pl 80 standard commercial product.

6. Peel forces were measured for sample stripes cut from the liners, against the adhesive on the abrasive disks, as follows.

TEST METHOD

1. Remove the liner from the disk. 2. Section liner to produce strips of higher and lower release of 25mm width and as long as the disk will allow, typically 150mm.

3. Apply these strips to the adhesive face of the abrasive disk and roll down using a 2Kg roller of BS 3924 specification.

4. Blank the regions of exposed adhesive to improve ease of handling.

5. Cover samples with a glass plate.

6. Apply masses equivalent to 70g/cm²

7. Dwell the samples at 23 °C/50%RH for 20 hours.

8. At the end of dwell remove masses, glass plates and condition in the lab at 23°C/50%RH for 4 hours.

9. Use IMASS peel tester (supplied by Imass Inc., Box 134, Accord, MA02018, USA) and measure the average peel force over a 10 second time period using a test speed of 305mm/min.

RESULTS

Claims

1. A laminated article comprising a base substrate having one or more edges defining a major surface which bears a layer of pressure-sensitive adhesive covered by a liner, the liner comprising a liner substrate having a major surface coated with at least a first release agent to provide areas on the liner surface of higher release characteristics and areas of lower release characteristics, characterised in that at least part of at least one of said one or more edges coincides with an area of higher release characteristics for a sufficient distance to accommodate a finger to facilitate removal of the liner from the base substrate.

2. A laminated article as claimed in Claim 1 wherein the said major surface of the liner is coated with a first release agent over part of its surface and a second release agent over the remainder of its surface, the first release agent having higher release characteristics than the second release agent.

3. A laminated article as claimed in Claim 1 or Claim 2 in which the first release agent is coated in the form of a repeat pattern.

4. A laminated article as claimed in Claim 3 in which the first release agent is coated in the form of a pattern selected from lines, dots, rectangles, diamonds, and a grid.

5. A laminated article as claimed in any preceding claim in which the first release agent has a contrasting tone or different colour to the liner substrate and/or a second release agent.

6. A laminated article as claimed in any preceding claim in which at least a part of an edge of the article coincides with an area of higher release characteristics for a distance of at least 15mm.

7. A laminated article as claimed in Claim 6, in which at least a part of an edge of the article coincides with an area of higher release characteristics for a distance of at least 20mm.

8. A laminated article as claimed in Claim 6, in which at least a part of an edge of the article coincides with an area of higher release characteristics for a distance of from 25 to 45mm.

9. A laminated article as claimed in any preceding claim in which the liner sheet is co-extensive with the base substrate.

10. A laminated article as claimed in any preceding claim which is in the form of a coated abrasive.

11. A laminated article as claimed in Claims 1 to 9 in which the laminated article is selected from adhesively-backed stationary items, surface coverings, structured abrasives, packaging for DVD's, clear adhesive sheets in photograph albums, adhesive wall charts, adhesive tapes, transfer tapes, sticking plasters or other products for sticking to the human body.

12. A method of manufacturing a laminated article comprising the steps of:

2) providing a liner sheet comprising a liner substrate having a major surface coated with at least a first release agent to provide areas on the liner surface of higher release characteristics and areas of lower release characteristics,

4) cutting the resulting laminate to provide a laminated article having one or more edges wherein at least part of at least one of said one or more edges coincides with an area of higher release characteristics on the liner for a sufficient distance to accommodate a finger to facilitate removal of the liner from the base substrate.

13. A method as claimed in Claim 12 in which the said major surface of the liner substrate is coated with a first release agent over part of its surface and a second release agent over the remainder of its surface, the first release agent having higher release characteristics than the second release agent.

14. A method as claimed in Claim 12 in which the first release agent is coated in the form of a repeat pattern.

15. A method as claimed in Claim 14 in which the first release agent is coated in the form of a pattern selected from lines, dots, rectangles, diamonds, and a grid.

16. A method as claimed in any one of Claims 12 to 15 in which the first release agent has a contrasting tone or different colour to the liner substrate and/or a second release agent.

17. A method as claimed in any one of Claims 12 to 16 in which at least a part of an edge of the article coincides with an area of higher release characteristics for a distance of at least 15mm.

18. A method as claimed in claim 12 in which at least a part of an edge of the article coincides with an area of higher release characteristics for a distance of at least 30mm.

19. A method as claimed in Claim 18 in which at least a part of an edge of the article coincides with an area of higher release characteristics for a distance from 25 to 45mm.

20. A method as claimed in any one of Claims 12 to 19 in which the liner sheet is coextensive with the base substrate.

21. A method as claimed in any one of Claims 12 to 20 in which the laminated article is selected from adhesively-backed stationary items, surface coverings, structured abrasives, packaging for DVD's, clear adhesive sheets in photograph albums, adhesive wall charts, adhesive tapes, transfer tapes, sticking plasters or other products for sticking to the human body.

22. A method as claimed in any one of Claims 12 to 20 in which the base substrate is in the form of a coated abrasive.

23. A method as claimed in any one of Claims 12 to 22 in which the laminate is cut by die stamping.

24. A method as claimed in Claim 23 in which the laminate is cut to provide a laminated article having a circular, rectangular or deltoid shape.