AU2019202692B2

AU2019202692B2 - Kneadable adhesive element

Info

Publication number: AU2019202692B2
Application number: AU2019202692A
Authority: AU
Inventors: Fasih Abbas; Christian Hanf; Timo HERRLICH; Tim Holtkamp; Marie Rapp; Bernd Zimmer
Original assignee: UHU GmbH and Co KG
Current assignee: UHU GmbH and Co KG
Priority date: 2018-04-23
Filing date: 2019-04-17
Publication date: 2023-04-13
Anticipated expiration: 2039-04-17
Also published as: DE102018109732A1; PT3561017T; EP3561017A1; ES2913412T3; EP3561017B1; AU2019202692A1; DE102018109732B4

Abstract

A kneadable adhesive element for reversibly fixing an object to a support, the adhe sive element comprising at least the following components: a) at least one synthetic type of rubber based on polybutene and/or polyisobutene and/or isoprene and/or derivatives thereof; b) at least one styrenic block copolymer; c) paraffin oil; d) inorganic fillers.

Description

Kneadable adhesive element

The present invention relates to a kneadable adhesive element for reversibly fixing an object to a support, such as a wall.

Adhesive elements of this kind are known from the state of the art. They are typically slightly kneaded prior to use and then pressed onto the object to be fixed. The adhesive element adheres to the element to be fixed. Subsequently, the object to be fixed is fixed to a support by pressing the adhesive element positioned on the object onto the support. The advantage of these adhesive elements is that attachment is reversible, meaning that it is possible for the mounted object to be separated from the support without the support sustaining damage. In this, adhesive elements of this kind, which are made of pressure-sensitive adhesive compounds, significantly differ from conventional adhe sives or glues, which generally result in a type of mounting that is irreversible or that the user wishes to be indestructible.

The first kneadable pressure-sensitive adhesive was developed in 1969 by Alan Hol loway (Ralli Bondite) as he was trying to produce a new sealant on the basis of chalk, rubber and oil. While the developed product was not particularly useful as a sealant, the company Ralli Bondite, which specialized in sealants, failed to recognize its potential as a kneadable pressure-sensitive adhesive compound. Later, the company Bostik intro duced this formulation-now coloured blue so as to not be mistaken for chewing gum as a reusable kneadable pressure-sensitive adhesive compound under the name Blu Tack. The basic ingredients chalk, polyisobutene rubber and paraffin oil are still used today in all kneadable pressure-sensitive adhesive compounds available in the market. All kneadable pressure-sensitive adhesive compounds available in the market share the trait that they become more difficult to remove the longer they are in use. Non destructive removal from sensitive surfaces, such as wallpaper, in particular woodchip wallpaper, and from posters is very tricky and, in some cases, is impossible. Another disadvantage of known pressure-sensitive adhesives is a distinct and temperature dependent tendency toward creep. While this creeping behaviour is partially reduced by the use of anisotropic fillers in modern developments, it is not fully suppressed. With continued use, the creeping behaviour makes the adhesive compound permeate in particular microporous or finely structured surfaces, which impairs its removability. Moreover, creep contributes to a loss in cohesion and thus to undesired rupture of the adhesive connection.

In EP0874876, pressure-sensitive removable adhesive pastes are described. The document proposes using an increased amount of anisotropic fillers to improve cohesion and thus creep behaviour. Moreover, the use of up to 12 wt% of an adhesion-promoting resin is recommended, which is clearly at odds with clean removability.

DE10317788 describes an object whose removability is based on the resilience of a polyurethane-based elastic adhesive film which has a pressure-sensitive adhesive on one or both sides. The polyurethane has been chemically crosslinked in order to provide the adhesive film with resilience. The dissolution of the adhesive connection is based on the effect that the adhesive film constricts when being pulled. On the one hand, this approach requires smooth surfaces; on the other hand, in order for it to be removable, part of the adhesive has to stick out from behind the connected surfaces so that it can be pulled when it is to be removed at a later point. The user cannot see the removal process behind the connected parts. Pulling too quickly may cause damage to wallpaper, for example.

The object of the present invention is to overcome the disadvantages of the pressure sensitive adhesive compounds known from the state of the art. In particular, the object of the invention is to provide a fixing means in the form of an adhesive element that exhibits improved removability from surfaces such as woodchip wallpapers, non-woven wallpapers or posters, while ideally also exhibiting reduced creep behaviour.

According to the invention, this object is attained by an adhesive element having the features of claim 1.

As impressively demonstrated by the application examples given below, the inventors surprisingly found that significantly improved removal behaviour can be achieved with an adhesive element having the combination of components indicated in claim 1. Equally surprisingly, it was found that it is especially the combination of styrenic block copolymer with the synthetic rubber and the paraffin oil that provides the desired properties. A combination of this kind has not been known so far in any of the known pressure-sensitive adhesive compounds for temporarily fixing an object on a support.

In a preferred embodiment of the adhesive element according to the invention, compo nent a) is contained in an amount of 2 to 15 wt%, preferably 4 to11 wt%, component b) is contained in an amount of 0.2 to 8 wt%, preferably 0.5 to 5 wt%, component c) is contained in an amount of 7 to 15 wt%, preferably 10 to 13 wt%, and component d) is contained in an amount of 60 to 85 wt%, preferably 75 to 80 wt%.

It was found that in particular a content of styrenic block copolymer of 0.2 to 8 wt% yields the desired properties mentioned above. Especially good results can be achieved with a content of styrenic block copolymer of 0.5 to 5 wt%.

Advantageously, polyisobutene, preferably at a molecular weight between 73,000 and 2,700,000, in particular between 400,000 and 2,000,000, is used as component a), a mean molecular weight preferably being between 65,000 and 3,000,000, in particular 330,000 to 2,600,000.

If the molecular weights are selected greater than the indicated values, the adhesive element becomes too hard and can no longer be satisfactorily kneaded and used for fixing.

In a preferred embodiment of the adhesive element according to the invention, compo nent b) is at least one from the group of SEBS, SEPS, SBS and SIS. The block copoly mers mentioned are known from the state of the art. For instance, SEBS is a styrene block copolymer which consists of two styrene end blocks (hard component) and a soft ethene-butene mid-block. Butadiene can be used as an alternative to butene. In a styrene block copolymer SEPS, propylene is used instead of butene. SIS comprises two styrene end blocks and an isoprene mid-block.

In a particularly preferred embodiment of the adhesive element according to the invention, the styrenic block copolymer is a hydrogenated triblock copolymer, either consisting of the monomers styrene, ethene, butene and styrene (SEBS), preferably with a styrene content of 25 to 35 wt% and a viscosity in toluene of 200 to 2,000 cP, preferably of 250 to 550 cP, or consisting of the monomers styrene, ethene, butadiene and styrene with a styrene content of 25 to 35 wt% and a viscosity in toluene of 200 to 2,000 cP, preferably of 250 to 550 cP.

It has been found that a block copolymer of this kind in the adhesive element according to the invention shows particularly advantageous removal behaviour from the support or from an object to be fixed.

Advantageously, component c) is at least one from the group of mineral oil-based paraffinic raffinates and/or solvates, technical white oils, hydrocracked oils and full synthetic paraffin oils, in particular obtained from a gas-to-liquid process.

With oils of this kind, a particularly advantageous kneading behaviour of the adhesive element according to the invention is achieved.

Advantageously, the paraffin oil (component c)) has a carbon distribution (paraffin ic/naphthenic, S-corr.)> 65 % and a kinematic viscosity at 20 °C of 90 to 150 mm 2 /s.

Component d) is preferably at least one from the group consisting of chalk, dolomite, baryte, talc, kaolin, clay, glass, glass powder, quartz, titanium dioxide, zinc oxide and carbon black.

The adhesive element according to the invention typically contains other additives from the group of resins, pigments, light stabilisers, antioxidants, flame retardants, processing aids, waxes and lubricants, preferably at a content of up to 5 wt%.

The present invention further relates to the use of an adhesive element according to the invention for temporarily fixing objects to each other or to a support.

In a preferred variation of the use according to the invention, the objects to be fixed are made of paper, wood, plastic, glass, stone and/or metal, the support preferably having an absorbent or non-absorbent surface.

The present invention and its advantages are illustrated in more detail by way of the following examples.

Examples:

Application-related tests:

Removability (see figure 1):

To determine the removability, poster strips (100 mm x 50 mm, 130 g/m2 ) are affixed to different surfaces (woodchip wallpaper, non-woven wallpaper, vinyl wallpaper) by hand. To do so, portions of 1.00 g to 1.05 g of the kneadable pressure-sensitive adhesive compound to be tested are weighed out. Each portion corresponds to one adhesive element to be tested. Each portion is kneaded 10 x (picture 2) and shaped into a ball and then pressed onto the surface together with the poster strip for 5 s (pictures 3 and 4). After 4 weeks, removability is tested. To do so, the poster is peeled off the adhesive and off the respective test wall (picture 5). The test criteria are residue-free and non destructive removal from the respective surfaces (poster strip and test wall).

Thermal stability under load:

To determine the durability of an adhesive connection using a kneadable pressure sensitive adhesive compound to be tested, the latter is tested under static load in a so called thermal stability test under load (creep rupture test).

To this end, portions of 1.00 g to 1.05 g of the kneadable pressure-sensitive adhesive compound to be tested are weighed out and each portion is kneaded 10 x and shaped into a ball. The ball is lightly pressed onto a clean aluminium test body (80 mm x 25 mm x 1.5 mm). Then, a second aluminium test body (30 mm x 20 mm x 1.5 mm) is placed thereon in an overlapping manner and the two test bodies are mechanically pressed together for 5 s at 5 bar. The thus compressed aluminium test bodies are then hung in a thermal stability test cabinet at 40 °C and loaded with 320 g or 500 g. The time until the adhesive connection breaks is electronically monitored. Once the re quirement criteria of 1000 h are reached, the measurement ends and is considered passed. Note: When a holding duration of 1000 h is reached, sufficient creep resistance can be assumed. Each formulation is tested 5 x in parallel.

Kneadability:

To determine the kneadability, the pressure-sensitive adhesive compound to be tested is kneaded between thumb and index finger for 1 min. Kneadability is assessed qualita tively based on the comparison with reference samples [very easy (1), easy (2), medium (3), hard (4), very hard (5)]. Sample composition 1 serves as reference for sample compositions 2 to 6. Sample composition 7 serves as reference for sample compositions 8 to 10 (see table below). The gradation of the reference samples in terms of kneadabil ity is the result of a concentration series with paraffin oil. Formulation 1 (Comp.)= easy (2). By adding + 1 wt% paraffin oil (= very easy (1)) and by leaving out paraffin oil (- 1 wt%: medium (3), - 2 wt% oil: hard (4), etc.) in the formulation, the kneadability of the other reference samples is set.

Formulations: 1 2 3 4 5 6 (Comp.) (Inv.) (Inv.) (Inv.) (Inv.) (Inv.) Rubber(PIB) 10.5 9.9 7.1 6.4 6.4 4.7 Thermoplastic elastomer (SEBS) - 0.6 2.4 3.0 3.0 4.7 Paraffin oil 11 11 12 12 12 12.3 Chalk 66.2 66.2 66.2 66.3 70.3 66 Kaolin 10 10 10 10 6 10 Additives 2.3 2.3 2.3 2.3 2.3 2.3

7 (Comp.) 8 (Inv.) 9 (Inv.) 10 (Inv.) Rubber(PIB) 11 10.4 7.7 4.7 Thermoplastic elastomer (SEBS) - 0.6 2.5 4.7 Paraffin oil 13 13 14 14 Chalk 48.7 48.7 48.5 49.3 Kaolin 26 26 26 26 Additives 1.3 1.3 1.3 1.3

Tests:

1 (Comp.) 2 (Inv.) 3 (Inv.) 4 (Inv.) 5 (Inv.) 6 (Inv.) Kneadability: easy (2) easy (2) easy (2) easy easy (2) easy (2) (2-3) Removability after 4 reference: better signifi- signifi- signifi- signifi weeks: some remova- cantly cantly cantly cantly Assessment criteria: residue bility better better better better - residue-free and remova- remova- remova- remova - without damage to damage to bility bility bility bility the wallpaper the wallpaper Thermal stability: 3 of 5 5 of 5 5 of 5 5 of 5 5 of 5 5 of 5 1000 h/40 °C/320 g passed passed passed passed passed passed

7 (Comp.) 8 (Inv.) 9 (Inv.) 10 (Inv.) Kneadability: medium (3) medium (3) medium (3) medium (3) Removability after 4 reference: better significantly significantly weeks: some residue removability better better Assessment criteria: and damage removability removability - residue-free to the - without damage to the wallpaper wallpaper Thermal stability: 4 of 5 5 of 5 5 of 5 5 of 5 1000 h/40 °C/500 g passed passed passed passed

State of the art 1 State of the art 2 State of the art 3 Rubber (PIB) 10 10 10 Thermoplastic elasto- 0 0 0 mer (SEBS) Paraffin oil 12 12 12 Chalk 65 67 65 Kaolin 10 0 0 Additives 3 11 13

State of the art 1 State of the art 2 State of the art 3

Kneadability: medium (2) medium (2) medium (2) Removability after 4 some residue and some residue and some residue and weeks: damage to the damage to the damage to the Assessment criteria: wallpaper wallpaper wallpaper - residue-free - without damage to the wallpaper Thermal stability: 3 of 5 0 of 5 2 of 5 1000 h/40 °C/320 g passed passed passed

As the tables impressively illustrate, the sample compositions that have a styrenic block copolymer (thermoplastic elastomer) exhibit significantly improved removability. In the samples that do not contain styrene block copolymer, some residue remains on the object to be fixed or on the support and the objects to be fixed sustain damage when the adhesive element is removed. This impressively demonstrates the advantageous effect of the styrene block copolymer in the adhesive element according to the invention.

The adhesive element according to the invention can be present in its defined size and/or shape (such as in the form of small rectangular tablets) from the start. However, the adhesive element according to the invention can initially also be present as an undefined larger mass, in which case it will be obtained from the original mass by being separated therefrom.

8a

In the specification the term "comprising" shall be understood to have a broad meaning similar to the term "including" and will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. This definition also applies to variations on the term "comprising" such as "comprise" and "comprises". The reference to any prior art in this specification is not, and should not be taken as an acknowledgement or any form of suggestion that the referenced prior art forms part of the common general knowledge in Australia.

Claims

1. A kneadable adhesive element for reversibly fixing an object to a support, the adhesive element comprising at least the following components: a) at least one synthetic type of rubber based on polybutene and/or polyisobutene and/or isoprene and/or derivatives thereof; t0ob) at least one block copolymer comprising styrene; c) paraffin oil; d) inorganic fillers, wherein component a) is contained in an amount of 2 to 15 wt%, component b) is contained in an amount of 0.2 to 8 wt%, component c) is contained in an amount of 7 to 15 wt%, and component d) is contained in an amount of 60 to 85 wt%.

[5 2. The adhesive element according to claim 1, wherein component a) is contained in an amount of 4 to 11 wt%, component b) is contained in an amount of 0.5 to 5 wt%, com ponent c) is contained in an amount of 10 to 13 wt%, and component d) is contained in an amount of 75 to 80 wt%.

3. The adhesive element according to any one of claims 1 or 2, wherein polyisobutene is !o used as component a).

4. The adhesive element according to any one of the preceding claims, wherein component b) is at least one from the group of SEBS, SEPS, SBS and SIS.

5. The adhesive element according to any one of the preceding claims, wherein component c) is at least one from the group of mineral oil-based paraffinic raffinates and/or solvates, technical white oils, hydrocracked oils and fully synthetic paraffin oils, in particular ob tained from a gas-to-liquid process.

6. The adhesive element according to claim 5, wherein the paraffin oil (component c)) has a carbon distribution (paraffinic/naphthenic, S-corr.) > 65 % and a kinematic viscosity at 20 °C of 90 to 150 mm2 /s.

1u

7. The adhesive element according to claim 1, wherein at least one from the group consist ing of chalk, dolomite, baryte, talc, kaolin, clay, glass, glass powder, quartz, titanium dioxide, zinc oxide, and carbon black is contained as component d).

8. The adhesive element according to any one of the preceding claims, wherein other additives, which are selected from the group of resins, pigments, light stabilisers, antiox idants, flame retardants, processing aids, waxes and lubricants, are preferably contained in an amount of up to 5 wt%.

9. A use of an adhesive element according to any one of claims 1 to 8, for temporarily fixing objects to each other or to a support.

10. The use according to claim 9, wherein the objects to be fixed are made of paper, wood, plastic, glass, stone and/or metal, the support preferably having an absorbent or non absorbent surface.