CH660373A5 - PROTECTIVE MATERIAL FOR ADHESIVE SURFACES AND MANUFACTURING METHOD THEREOF. - Google Patents

Description

The present invention relates to a protective material for adhesive surfaces intended to advantageously replace papers coated with silicone resins.

There are many articles in common use which have adhesive surfaces by which they are applied to a support for their use. Mention will be made, by way of examples, of hygiene products such as the protections which serve to absorb physiological fluids, in particular periodical pads and dressings; complete baby diapers, which are closed with two adhesive strips; the alèzes which often include at least one adhesive strip allowing them to remain flat on the bedding. We can also cite examples in the household sector: air fresheners and hooks 40 hangers are especially provided with sticky pads by which they are affixed to the walls of living quarters.

All the articles listed above and still others therefore comprise at least one adhesive surface, the geometry and dimensions of which vary from one article to another depending on the destination of these. These adhesive surfaces are protected, before the use of the articles, by materials, generally papers, cut to the dimensions of said adhesive surfaces and coated, on their face intended to come into contact with the adhesive surfaces, with a silicone resin.

50 These protective materials, which allow the adhesive not to fulfill its role during storage before use, must meet the following two essential conditions:

- at the time of use of the article, the protective material must be able to "peel", that is to say remove quickly by being

55 detached by an area of its border, and

- it must not diminish the qualities of the adhesive before using the article.

Until now, silicone adhesive has been the only adhesive protective material that meets these two requirements; however, its application on an industrial scale on strips of continuously moving paper is a very delicate operation and the silicone resins are themselves relatively expensive substances, so that silicone paper represents a significant part of the price of returns articles, in particular hygiene products which are consumer products; it follows that the manufacturers of these articles tend to limit the extent of the adhesive surfaces of said articles to the detriment of the correct maintenance of the latter when they are in the position of use.

3

660,373

The present invention aims to provide replacement materials for these silicone papers, less expensive than these and capable of being manufactured by very simple processes, these new protective materials also being as easily "pe-lables" as silicone papers and, in the same way as these, also not reducing, during storage, the tackiness of the adhesive. According to the invention, the protective material consists either of a film obtained from an extrudable polymer / metal soap mixture, or else of a support whose face intended to come into contact with the adhesive surface is hot coated with the aforementioned mixture. This therefore constitutes, in this second case, the active agent for replacing conventional silicone resins intended to make the protective material easily "peelable".

The present invention therefore firstly relates to the new industrial product which constitutes a protective material for adhesive surfaces, characterized in that it comprises a film comprising from 50 to 85% by weight of at least one polymer chosen from the group formed by low density polyethylene, high density polyethylene, polypropylene, polyamides, polyvinyl acetate, polyvinyl alcohol and 100% complement of at least one metallic soap.

The preferred polymer for the blend is low density polyethylene. It is also possible to use high density polyethylene and polypropylene. The latter is satisfactory by its polyolefinic nature, but it is more difficult to use than polyethylene because of its higher melting point. Mention may also be made of polyvinyl acetate, polyamide 11 and also polyvinyl alcohol such as that sold under the brand MOWIOL 488.

The metallic soap of the mixture is preferably an alkyl carboxylate, containing 12 to 24 carbon atoms in the alkyl chain. Examples of alkyl carboxylates that may be mentioned include laurate, palmitate, stearate, behenate and cirates. The metal used in the formula for metallic soap is advantageously chosen from the group formed by aluminum, calcium, magnesium and zinc. The preferred metallic soap is aluminum stearate.

According to a particularly preferred embodiment of the present invention, the film is obtained from a mixture of approximately 75% by weight of low density polyethylene and of 25% by weight approximately of aluminum stearate. The two constituents of this particular mixture are, on the one hand, compatible with each other and, on the other hand, readily available on the market for a relatively low purchase price. This formulation has been found to be very satisfactory after aging for 6 months at room temperature.

Furthermore, the percentages indicated are the optimal percentages. Experience has shown that if a film formed from a mixture of 50% by weight of low density polyethylene and 50% by weight of aluminum stearate is used, a significant loss of adhesiveness of the adhesive surface protected by this protective material. Furthermore, the cost price of the protective material is higher, aluminum stearate being more expensive than polyethylene. The value of 50% by weight for aluminum stearate therefore constitutes an upper limit not to be exceeded, the value of 25% being the optimum value.

In accordance with the present invention, a third constituent can also be provided for the constituent mixture of the film, this third constituent being at least one nonionic surfactant, used in particular at a rate of 2 to 15% by weight relative to the weight total of (or) polymer (s) and (or) metal soap (s).

Examples of nonionic surfactants which can be used in accordance with the present invention include po-lyoxyethylenated fatty alcohols, polyglycerolated fatty alcohols, sorbitol esters such as laurate, palmitate, sorbitol stearate, and the same polyoxyethylenated esters comprising from 3 to 40 moles of ethylene oxide.

According to a first alternative embodiment of the present invention, the film constitutes a coating layer deposited on a support. The latter is constituted in particular by paper or cellulose wadding. Preferably, the film forming the coating layer of the support is applied directly hot to the latter.

According to a second alternative embodiment of the present invention, the film is self-supporting and alone constitutes the protective material.

The present invention also relates to a method of manufacturing the protective material for adhesive surfaces defined above. This process is characterized by the fact that intimately mixing at least one powdered polymer, at least one metallic soap and optionally at least one surfactant. the definitions and the proportions of these constituents being those indicated above, the mixture thus obtained is heated to obtain a homogeneous paste, the extrusion of said paste is carried out so as to form a film, and that cools said film to ensure its solidification.

In the case where the material according to the invention is in the form of a support coated on one of its faces with a layer giving it the desired properties of protection of adhesive surfaces. the extruded mixture is applied hot to one face of a support material to form a film constituting a coating layer.

In the case where the mixture consists of approximately 75% by weight of low density polyethylene and approximately 25% by weight of aluminum stearate, in order to obtain a homogeneous paste, said mixture is brought to a temperature of the order of 200 ° C. .

In accordance with a particular embodiment of the process intended for the manufacture of a protective material in the form of a coated support, the molten mixture forming a homogeneous paste is extruded so as to obtain a film, which is, from its output from the extruder, deposited on a strip of continuously moving support material. In a preferred embodiment, a strip of support material stored in the form of a roll is continuously unrolled, it is passed between a pressure cylinder and a cooled cylinder, an extruder delivering the hot mixture intended for forming the coating layer, in line with the calendering zone located between the two aforementioned cylinders, the strip of support material is driven having thus received a thin layer of the hot mixture while keeping it in contact with the cooled cylinder over a sufficient angular sector of the latter to solidify said layer on the support material, and the strip of support material thus coated is then wound.

After the film has solidified and before the strip obtained is wound, the strip can be cut by passing it over a cylinder above which there are cutting blades placed side by side.

To better understand the object of the present invention, a description will be given in more detail below of the properties of the protective material for adhesive surfaces according to the present invention, as well as a process for manufacturing this protective material, with reference to the drawing. Annex.

On this drawing:

- Figures 1 and 2 each represent a device for studying, in the laboratory, the behavior of the protective material according to the invention;

- Figure 3 illustrates, schematically, an apparatus for implementing a manufacturing process, on an industrial scale, the protective material according to the invention;

FIG. 3a shows, in perspective and schematically, an element of the apparatus of FIG. 3.

The devices shown diagrammatically in FIGS. 1 and 2 are intended to carry out tests showing the ability of the protective material according to the invention, respectively, to be removed by "peeling" from the adhesive surface on which it is placed, and to maintain the qualities of the adhesive it protects. In both cases. comparing the results obtained with protective materials in accordance with the present invention and with those obtained with paper

5

10

15

20

25

30

35

40

45

50

55

60

65

660,373

4

commercial silicone protector. We know that it gives full satisfaction with regard to the properties sought for this type of material.

To carry out the first test, one uses, on the one hand, a strip 1 of paper or the like, on one face of which is deposited an adhesive layer la of 2 cm wide, and, on the other hand, a strip 2 of protective paper, one side of which is coated with a film 2a of the coating agent which is being studied, the film 2a having at least the same width as the layer la. The two strips 1 and 2 are applied to each other by rolling with a weight of 1 kg (5 back and forth), the face of the strip 1 carrying the adhesive layer being in contact with one end folded over it even over a length Lj (5 cm) of the strip 2 carrying the film 2a of the coating agent studied, so that the film 2a is in contact with the adhesive layer la. The free end of the strip 1 is placed in the clamp 3 of a dynamometer, and the free end of the strip 2 is placed in the other clamp 4 of the dynamometer. The force necessary for the "peeling" of strip 2 is recorded.

This test was carried out, each time under the same conditions, with the use of a commercial silicone protective paper which constitutes the reference product and then, successively, with papers coated with various films (polymer / soap) according to the invention. and with a self-supporting protective film according to the invention. The results which have been obtained are shown in Table I below:

TABLE I Test of the ability of the protective material to be removed

Protective material used

Force required for "peeling" (in cN)

Commercial silicone protective paper (50 g / m2)

70 to 85

Paper from 20 to 50 g / m2 coated at a rate of 5 to 50 g / m2 by means of the formulation: Low density polyethylene 75% by weight Aluminum stearate:

25% by weight or Self-supporting film of 20 to 50 g / m2 obtained by extruding a mixture before this formulation

40 to 170

Paper from 20 to 50 g / m2 coated at a rate of 5 to 50 g / m2 by means of the formulation:

Polyvinyl alcohol 65% by weight Aluminum stearate 25% by weight

Polyoxyethylenated sorbitol monolaurate containing 20 moles of ethylene oxide 10% by weight

20 to 100

It can therefore be seen that, with the formulations in accordance with the present invention, the forces necessary for the "peeling" of the protective paper are within entirely acceptable ranges of values.

To carry out the second test, use is made, on the one hand, of a strip 5 of paper or the like on one face of which an adhesive layer 5a is deposited, this adhesive layer 5a having been protected by the protective material whose behavior is studied and which has been removed, and, on the other hand, a strip 6 of a cotton fabric fixed flat on a rigid support 7. The two strips 5 and 6 are applied to each other by rolling a weight of 1 kg (5 back and forth), the face of the strip 5 carrying the adhesive layer 5a being in contact with the cotton fabric 6, the two strips 5 and 6 being however offset from one another longitudinally so that they only overlap over a defined length L2 (5 cm). The free end of the strip 5 is placed in the clamp 8 of the dynamometer, and the free end of the strip 6, on its support 7, is placed in the other clamp 9 5 of the dynamometer. The force required to detach the strip 6 is recorded. This test was carried out, each time under the same conditions, using strips 5 having been protected, either by a commercial silicone protective paper, or by a paper coated with a film (polymer / soap). in accordance with the present in-vention, or by a self-supporting protective film according to the invention, these strips having been stored for 60 days at 20 ° C and 50% relative humidity. The results obtained are shown in Table II below:

TABLE II Test of the ability of the protective material to retain the properties of the adhesive

Protective material having protected the adhesive layer

Force required for strip 6 to come off from strip 5 (in cN)

Commercial silicone protective paper (50 g / m2)

1500 to 2700

Paper from 20 to 50 g / m2 coated at a rate of 5 to 50 g / m2 by means of the formulation: Low density polyethylene 75% by weight Aluminum stearate:

25% by weight or Self-supporting film of 20 to 50 g / m2 obtained by extruding a mixture before this formulation

1900 to 2600

Paper from 20 to 50 g / m2 coated at a rate of 5 to 50 g / m2 by means of the formulation:

Polyvinyl alcohol 65% by weight Aluminum stearate 25% by weight

Polyoxyethylenated sorbitol monolaurate containing 20 moles of ethylene oxide 10% by weight

1500 to 2700

50 The values which have been found for the adhesive layer protected by a paper coated with the formulations according to the invention are equivalent or lie within the range which is given for the adhesive layer protected by a commercial silicone paper, of which we know that it has acceptable characteristics 55 tables.

A particular embodiment of the adhesive protective material according to the invention is described with reference to FIGS. 3 and 3a which show, schematically, an apparatus intended for manufacturing protective strips of adhesive layers put in place 60 on periodic towels. It can be seen that a strip 10 of a support material, consisting of paper, is stored in the form of a roll 11 and unrolled continuously from the latter. This strip 10 has a width L multiple of the width 1 which the protective strips for the periodic towels must have. The strip 10 of support material is passed 65 between a pressure cylinder 12 and a cooled cylinder 15; an extruder 13 delivers the particular homogeneous mixture used (polymer / soap, possibly surfactant), this mixture leaving continuously in the form of a fine

30

5

660,373

tablecloth or film 14; the ply 14 is extruded just in line with the calendering zone situated between the two cylinders 12 and 15 and is thus applied to the support strip 10. The support strip 10 thus coated is driven by the cylinder 15 and is held against that -ci on an angular sector between 90 ° and 180 °, so that the coating agent layer solidifies quickly by joining with the support strip. Then, the latter, having received its coating agent, passes over a cylinder 16 above which are arranged cutting blades 16a (FIG. 3), which aim is to perform the longitudinal cutting of the strip 10 in order to form strips of the desired width 1. These are wound side by side on a winding roller 17.

It is understood that the examples of composition and the embodiments and implementation of the invention described above are in no way limiting and may give rise to any desirable modifications, without departing from the scope of the invention; the protective material according to the invention can in particular consist of a self-supporting film not associated with a support material and obtained from a mixture (polymer / metallic soap with io optionally a surfactant), for example by extrusion .

R

1 sheet of drawings

Claims (20)

660,373 1. Protective material for adhesive surfaces, characterized in that it comprises a film comprising from 50 to 85% by weight of at least one polymer chosen from the group formed by low density polyethylene, high density polyethylene, polypropylene, polyamides, polyvinyl acetate, polyvinyl alcohol and 100% complement of at least one metallic soap. 2. Protective material according to claim 1, characterized in that the polymer of the mixture is a low density polyethylene. 2 3. Protective material according to one of claims 1 and 2, characterized in that the metal soap of the mixture is a metal alkyl carboxylate containing from 12 to 24 carbon atoms in the alkyl chain. 4. Protective material according to claim 3, characterized in that the alkyl carboxylate is chosen from the group formed by laurate, palmitate, stearate, behenate and cirates. 5 support (10) continuously scrolling. 5. Protective material according to one of claims 1 to 4, characterized in that the metal used in the formula of the metallic soap is chosen from the group formed by aluminum, calcium, magnesium and zinc. 6. Protective material according to one of claims 1 to 5, characterized in that the metallic soap is aluminum stearate. "" 7. Protective material according to claims 2 and 6 taken simultaneously, characterized in that the film comprises approximately 75% by weight of low density polyethylene and approximately 25% by weight of aluminum stearate. 8. Protective material according to one of claims 1 to 7, characterized in that the constituent mixture of the film comprises, in addition, at least one nonionic surfactant, in an amount of 2 to 15% by weight per relative to the total weight of the polymer (s) and the metal soap (s). 9. Protective material according to claim 8, characterized in that the nonionic surfactant is chosen from the group formed by polyoxyethylenated fatty alcohols, polygly-cerolated fatty alcohols, sorbitol esters and sorbito esters ! polyoxyethylenated comprising from 3 to 40 moles of ethylene oxide. 10. Protective material according to one of claims 1 to 9, characterized in that the film (14) constitutes a coating layer deposited on a support (10). 11. Protective material according to claim 10, characterized in that the support (10) consists of paper or of cellulose wadding. 12. Protective material according to one of claims 1 to 9, characterized in that the film is self-supporting and constitutes in itself the protective material. 13. A method of manufacturing the protective material for adhesive surfaces according to one of claims 1 to 12, characterized in that intimately mixed at least one polymer powder, and at least one metallic soap, which is heated mixture thus obtained to obtain a homogeneous paste, which is carried out the extrusion of said paste so as to form a film and that said film is cooled to ensure its solidification. 14. Method according to claim 13, characterized in that the mixture also comprises at least one surfactant. 15 thereof to solidify said layer on the support material, and that is then carried out the winding of the strip of support material thus coated. 15. Method according to one of claims 13 or 14 intended for the manufacture of a protective material for adhesive surfaces as defined in one of claims 10 or 11, characterized in that the mixture is applied hot extruded on one side of a support material (10) to form a film (14) constituting a coating layer. 16. Method according to one of claims 13 to 15, in which the film is formed from a mixture of approximately 75% by weight of low density polyethylene and approximately 25% by weight of aluminum stearate, characterized in that the said mixture is brought to a temperature of the order of 200 ° C to obtain a homogeneous paste. 17. Method according to one of claims 15 or 16, characterized in that the molten mixture forming a homogeneous paste is extruded so as to obtain a film (14), which is, as soon as it leaves the extruder (13) , deposited on a strip of material- 18. The method of claim 17, characterized in that one continuously unrolls a strip (10) of support material stored in the form of a roll (11), that it is passed between a pressure cylinder (12) and a cooled cylinder (15), an extruder (13) io delivering the hot mixture, intended to form the coating layer, in line with the calendering zone located between the two aforementioned cylinders, which the strip of support material (10) is driven, having thus received a thin layer of the mixture hot by keeping it in contact with the cooled cylinder (15) over a sufficient angular sector 19. Method according to one of claims 13 to 18, characterized in that after the solidification of the film (14) and before the bo- 20 hoeing of the strip obtained, said strip is cut by passing it over a cylinder (16) above which there are cutting blades (16a) arranged side by side.