WO2004003286A1 - Activatable adhesive layer - Google Patents

Abstract

The invention relates to a method for applying an adhesive layer, which can be activated by water, onto strip-shaped decorative materials, particularly onto strips of wallpaper. During the production process of the wallpaper strip, powder adhesives provided in the form of at least one granular starch, which is insoluble in cold water, are applied to the damp strip and dried. According to a preferred embodiment, an excess of applied powder adhesive is collected and recycled.

Description

 Activatable adhesive layer

The invention relates to a method for _. Production of an activatable adhesive layer on a web-shaped wall decoration material, on the use of suitable starches for this and on web-shaped decorative materials, in particular wallpapers, obtained by this process.

State of the art

The application of decorative, web-shaped wall coverings made of various materials such as: paper wallpaper, woodchip wallpaper, textile wallpaper, glass fiber wallpaper is one of the oldest ways of decorating wall surfaces in the interior of buildings.

Numerous adhesives are used to fasten the various wallpapers, starting with the simplest starch paste to modern wallpaper paste based on modified starch carboxymethyl ether and modified cellulose carboxymethyl ether, with the admixture of various auxiliaries, such as adhesive strength-enhancing plastic dispersions or synthetic resin powder.

These adhesives are mixed in powder form or as concentrated pastes with appropriate amounts of water to the ready-to-use paste and applied to the wallpaper strips. In industrial practice, machine paste application is preferred to manual application. After the required swelling time of the wallpaper in the folded state, the wallpaper webs are laminated onto the walls. The adhesives are designed in such a way that the paths on the wall can be corrected by moving them slightly for a certain time. The wallpapering process described is very time-consuming and requires careful handling of the adhesives, since otherwise the wallpaper strips are easily slip or become dirty. Depending on the weather, the drying process takes considerable time.

The production of self-adhesive wallpapers with glue already applied has therefore been the goal of numerous works to optimize the wallpapering process using a variety of concepts.

International application WO 98/14655 describes a glass fabric wallpaper which is coated with a thermoplastic adhesive. However, the wallpapering process for wallpapers finished in this way is difficult, since it is no longer possible to subsequently correct the wallpaper web on the wall and therefore differs significantly from the processing habits of the wallpaperers. The processing of these wallpapers in commercial practice is therefore almost impossible. In addition, wallpapers equipped in this way must also be equipped with a release film in order to protect the permanently sticky layer from premature sticking of the wallpaper roll in the delivery form. The effort is considerable and causes significantly higher costs compared to processing with conventional aqueous wallpaper paste. There are significant amounts of packaging material that can no longer be used. The application of the thermoplastic adhesive layer is only possible with flat, flat and completely closed wallpaper strips, which is rarely feasible, especially with textile wallpapers and glass fiber wallpapers. The fabric level or the interstices between the warp and weft threads are often not completely closed. An application of a thermoplastic adhesive would lead to incorrect bonding during manufacture, since the adhesive passes through these holes. The hardened adhesive residues would additionally contaminate the decorative wallpaper side and the subsequent processing steps such as Overpainting due to different adhesion of the colors makes it difficult.

Finally, the removal of the wallpaper after its use is due to the use of water-insoluble, thermo- plastic adhesives very tedious and often only possible using aggressive chemicals. The remaining adhesive residue destroys the flat wall subsurface, which is why it has to be renewed or repaired. DE 198 11 152 also proposes a permanently sticky coating on the wallpaper, which can only be removed from the masonry after the period of use with the aid of chemicals, has all the disadvantages described above in processing and is therefore only of very limited use.

In DE 198 48 693 the adhesive is not applied to the wallpaper as is customary in commercial practice, but first the substrate is coated with the adhesive and then the wallpaper is inserted into the adhesive. In this case, the risk of contamination of the wallpaper is lower, but very soft wallpapers with low restoring forces are required for this type of processing, as otherwise the shaping of corners and edges is impossible.

EP 0 909 850 describes a wallpaper with multicolored printing and a self-adhesive layer of adhesive. Although the wallpapers described can be removed from the substrate with virtually no residue due to their pure adhesive properties, the wallpapering process differs considerably from normal practice and is therefore not used with preference. The manufacturing cost of such, with

Wallpaper coated with pressure sensitive adhesives is considerable. The necessary systems for the production of the wallpapers differ in many points from the state of the art at the producers. The retrofitting would therefore cause enormous investment costs in the production lines, which is why these wallpapers are rare

Cases would apply.

EP 1 162 306 describes a process for the production of glass fiber wallpapers which are equipped with a latently sticky coating with the customary adhesives which are otherwise used as paste. It is made in a two-stage process in the first step from the glass fiber fabric with the aid of finishing liquors which are well known to the person skilled in the art, which are made from customary cold water-soluble modified potato starch derivatives or cold water-soluble modified corn starch derivatives or cold water-soluble carboxymethyl celluloses, from polymer latices, for example ethylene-vinyl acetate dispersions -Butadiene dispersions, styrene-acrylate dispersions and other customary polymeric film formers such as polyvinyl acetates, from crosslinking inorganic or organic active ingredients, such as various zirconium salts, aluminum salts, urea-formaldehyde resins or glyoxal derivatives, from pigments and hydrophobizing agents such as, for example Paraffin wax emulsions exist, and a stabilized glass fiber wallpaper is produced using the usual methods by pad application or application by means of transfer rollers as described in EP 1 162 306 or EP 1 143 064.

In a defined and delimited second process step, a customary aqueous wallpaper paste made from modified, cold water-soluble starch adhesives and / or cold water-soluble carboxymethyl celluloses is applied to the prefabricated wallpaper web with suitable application systems and then again dried in a drying section to form a latently sticky coating on the wallpaper. To improve the rewetability, salts, e.g. Sodium nitrate, also used on loan.

In the described process, the glass fiber wallpapers are thus produced and dried in a manner known per se using impregnation liquors which are well known to the person skilled in the art. After the first step, the wallpaper is available in a large roll.

Only in the second step is a known wallpaper paste composition applied in liquid form to the wallpaper web and dried again.

With this method too, the applicability is restricted to almost completely closed textile wallpapers, otherwise the adhesive would contaminate the decorative side of the wallpaper and would make the subsequent wallpapering process as difficult as the previously customary processing with liquid wallpaper paste. The two-stage process described is therefore limited to selected, completely closed wallpaper qualities, which currently only make up 10-20% of the total processed qualities, and, due to the two-time coating and drying, causes high manufacturing costs in addition to high drying energy expenditure. The wallpaper produced cannot be moistened by machine application, as is customary in commercial practice, but must be sprayed with water, since otherwise the applied adhesive would detach from the wallpaper when it was moistened. The adhesive layer must therefore also have an accelerated water absorption capacity, since otherwise the water absorption would only be too low by spraying, so that the adhesive can develop optimally. This is achieved through the additional use of wetting salts such as inorganic salts (sodium nitrate). However, this compromise also causes a deterioration in the adhesion of the wallpaper applied and dried on the substrate. As is known to the starch expert, ionic additions to starches soluble in cold water bring about increased solubility of the dried starch films and due to reactions of the monovalent cations with the hydroxyl groups of the starch molecules

Due to the reduced surface tension of the wetting solvent water, moisture penetration is faster. When you rewet the wallpaper on the wall, which also. normal behavior of the users of the rooms can occur again and again, the adhesive layer loosens too quickly. The wallpaper comes off especially in the critical edge area and when overlapping. Repeated reworking and touching up the wallpapering is the result.

Aim of the invention From the previously known prior art for the production of sheet-like decoration material for walls, which is coated with an activatable adhesive, there is a need for a correspondingly coated wallpaper which does not have the disadvantages described above.

The wallpaper should be able to be produced with the slightest modifications in the plants of the producers, change the production processes to the smallest extent and thus have the least possible increase in manufacturing costs.

The wallpaper produced should be processable with the usual, commercially applied work steps.

Regardless of the degree of closure of the wallpaper in the case of textile wallpapers and especially glass fiber wallpapers, the method should generally be applicable to all decorative wallpapers.

The adhesive system used in the process should be able to be activated with water using the equipment used by commercial upholsterers and the holding force should not differ significantly from previous experience with modern wallpaper paste.

The manufactured wallpaper should be removable from the surface without the use of additional, aggressive chemicals in accordance with the previous habits, but should be able to withstand the normal exposure of the decorated walls to moisture without damage, without the need for reworking.

Description of the invention

The goals described above can be achieved through a one-step

Manufacturing process can be achieved. The fabric webs are coated with the well-known impregnation liquors and with the respective coating process of the manufacturer and shortly before drying in the drying section with the heated drying cylinders or other drying processes sprinkled with fine-grained, powdery adhesives. Common powder spreading systems that are already used in the production of nonwovens can be used for this.

A sufficient amount of the powder is applied homogeneously across the entire web width. Between 10 g / m ² and 100 g / m ² powder are sprinkled in such a way that there is no dust pollution in the surrounding atmosphere.

The adhesive powder only adheres to the areas with a closed film, in those areas where no film has formed due to the limited film formation capacity of the impregnation liquor or the fabric level remains open, the powder falls through the web and is preferably just below the web is collected in a suitable device and returned for reuse. This achieves the efficient and economical consumption of the adhesive powder. Likewise, this does not result in any contamination of the underside of the web, which subsequently results in the decorative side of the wallpaper. Defects in the decorative surface of the wallpaper are therefore excluded. The web sprinkled with powder adhesive then arrives in the drying section on the drying cylinders. The heat energy acts on the one hand to completely film and dry the impregnation liquor to form a stable wallpaper, and on the other hand to ensure that the adhesive powder is adequately bonded to the back of the wallpaper.

The adhesive powders used can be the state-of-the-art modified, starch-soluble cold starches made from a wide variety of raw materials, for example potato starch, corn starch, rice starch, tapioca starch or other cereal starches such as wheat or rye starches in sufficiently fine grinding, or else mixtures of these starches with one another or the customary cellulose ethers , such as carboxymethyl celluloses or other cellulose ethers, or their mixtures with the starch products. Surprisingly, it is also possible to use starches of the raw materials mentioned which are not soluble in cold water, but which can be modified by partial acid hydrolysis or oxidative degradation, or mixtures thereof. These granular starches, which are only soluble at higher temperatures under the hydrating effect of solvents, such as water, have no adhesive power in the undigested state. As a result, there is no sticking to the spreading device during the spreading process. Surprisingly, however, it turns out that the heat transfer and the relatively short contact time in the drying section with the already evaporating water from the impregnation liquor are completely sufficient to convert the so-called cooking starches into their cold-water-soluble form and thus only prepare them for use as wallpaper glue. At the same time, the impregnation liquor is filmed as usual to form a stable coating around the textile fabric, so that after passing the drying section, a finished wallpaper with excellent properties coated on one side with a suitable adhesive is obtained.

This process is particularly suitable for all textile wallpapers, regardless of the degree of closure. This means that the coating process with the adhesive is generally applicable regardless of the actual impregnation liquor composition and its filming properties.

The impregnation systems only need to be expanded with a powder spreader for this process. The production processes in the manufacture of the wallpaper are hardly influenced, ^■ since the amount of water that has to be dried is not increased. The production speed hardly changes in comparison to the production of the wallpaper without an adhesive coating. The production costs of a wallpaper coated with adhesive are therefore only marginally higher than the production costs of a conventional wallpaper without an adhesive coating. This surprising possibility of using non-cold water-soluble starches in granular form and the possibility of digestion directly in the drying section results in a substantial reduction in raw material costs. In all the wallpapering methods used to date, either with liquid wallpaper paste in the method most frequently used up to now, or with the wallpaper known to date with an adhesive based on modified starches soluble in cold water, starches soluble in cold water are already used. These starch products are either produced by the producer of the starch products in a complex roll drying process, which is associated with cost-intensive investments, or in an extrusion process from the non-cold water-soluble granular starches and processed into the powdery adhesives.

The subject method is preferred in one

Form this production step of the first digestion carried out directly on the wallpaper web. As a result, significantly cheaper adhesive raw materials can be used to produce the adhesive coating on the wallpaper.

Another surprising property of the adhesive layer in question is its swelling behavior towards water. As is well known to the starch expert, a differently intensive digestion process leads to pronounced changes in the viscosity and rheology of the digested starches as soon as they are dissolved in water.

Because the digestion process is carried out only once in the process in question, starch adhesives with exceptional properties are obtained which make them particularly suitable for use as wallpaper adhesives.

The digestion in the dry section does not lead to the complete dissolution of the native molecular structures in the star grains, but still leaves clear residual structures of the native starch grains. , .

These residual structures have the ability to absorb water exceptionally quickly. On the other hand, these residual grain structures have a lubricating effect when the moistened wallpaper web is applied to the surface, comparable to a ball bearing effect. An open time is created, which is quite comparable to the processing of the liquid wallpaper paste previously used, although overall significantly less water has to be used to activate the adhesive layer. The necessary drying time of the wallpaper on the wall until the next processing step is significantly reduced.

The moistening step of the wallpaper web according to the invention does not necessarily differ from the process previously followed. As before, the wallpaper web can be moistened with a paste application machine. It is also possible to moisten the wallpaper with a water mist by spraying it on. It has also surprisingly been found that the coating according to the invention is only exceptionally firmly bonded to the wallpaper web with only partially digested starch, so that only very small amounts of the adhesive dissolve into the dampening water, which was not the case with the previously known wallpapers coated with adhesive , It is also possible to beat up the wallpaper strips so that the

Wallpaper, if necessary, lose its elasticity due to moisture so that it can be easily processed over corners and edges.

After passing the drying section, the wallpaper strips are cut into commercial sizes of 50 running meters and packed. In this form, the wallpapers can be processed by commercial or private consumers without the use of an additional wallpaper adhesive, without having to accept significant changes in the workflow. Examples

Example 1: Production of the impregnated wallpaper

A typical, loose glass fiber fabric with a basis weight of 100 g with wide mirrors in 60 by 60 cm pieces was finished with an impregnation liquor which had a dry substance concentration of 10% in water. The composition of the liquor corresponded to a typical and mostly used formulation of a potato starch ether, dissolved in water (25% of the dry matter), a styrene-acrylate dispersion (TG 6 ° C) (50% of the dry matter), a crosslinker based on an ammonium zirconium carbonate solution in water (12.5% of the dry substance) and a water repellent based on an aqueous paraffin emulsion (12.5% of the dry substance).

The liquor was finished on the fabric pieces so that a dry coating of 40 g / m ^{2 was} obtained.

Example 2: Coating with Metylan TT instant

A sufficient amount of the commercially available product Metylan TT instant was ground in a laboratory impact mill to a powder with a maximum grain size of less than 200 micrometers. This powder was applied via a suitable sieve to the still moist, impregnated piece of wallpaper from Example 1 in an amount corresponding to an application of 35 g / m ² .

The test specimen was dried on an aluminum plate with a Teflon coating at a temperature of 200 ° C within 1 minute, the side of the test surface not coated with adhesive resting on the heating plate. Several test specimens were cut from the center of the piece of wallpaper produced from the finished test specimen. The test specimens were soaked in water for 1 minute, folded up, stored for 10 minutes and then glued to a non-impregnated plasterboard. Example 3: Coating with a modified, roller-dried potato starch

A sufficient amount of the commercially available product Metylan TT instant was ground in a laboratory impact mill to a powder with a maximum grain size of less than 200 micrometers. This powder was applied to the still moist, impregnated wallpaper piece from Example 1 in a quantity corresponding to an application of 35 g / m ² via a suitable sieve.

The test specimen was dried on an aluminum plate with a Teflon coating at a temperature of 200 ° C. within 1 minute, the side of the test surface not coated with adhesive resting on the heating plate. Several test specimens were cut from the center of the piece of wallpaper produced from the finished test specimen. The test specimens were soaked in water for 1 minute, folded up, stored for 10 minutes and then glued to a non-impregnated plasterboard.

Example 4: Coating with a granular, technical potato starch

The finely powdered potato starch was applied via a suitable sieve to the still moist, impregnated piece of wallpaper from Example 1 in an amount corresponding to an application of 35 g / m ² .

The test specimen was dried on an aluminum plate with a Teflon coating at a temperature of 200 ° C. within 30 seconds, the side of the test surface not coated with adhesive resting on the heating plate. Several test specimens were cut from the center of the piece of wallpaper produced from the finished test specimen. The test specimens were soaked in water for 1 minute, folded, 10 mi grooves stored and then glued to a non-impregnated plasterboard.

Example 5: Coating with granular, technical corn starch

The finely powdered corn starch was applied via a suitable sieve to the still moist, impregnated piece of wallpaper from Example 1 in an amount corresponding to an application of 35 g / m ² . The test specimen was dried on an aluminum plate with a Teflon coating at a temperature of 200 ° C. within 30 seconds, the side of the test surface not coated with adhesive resting on the heating plate. Several test specimens were cut from the center of the piece of wallpaper produced from the finished test specimen. The test specimens were soaked in water for 1 minute, folded up, stored for 10 minutes and then glued to a non-impregnated plasterboard.

Example 6: Coating with a mixture of granular, technical corn starch and granular, technical potato starch in a ratio of 1: 1

The finely powdered starch mixture was applied via a suitable sieve to the still moist, impregnated piece of wallpaper from Example 1 in an amount corresponding to an application of 35 g / m ² .

The test specimen was dried on an aluminum plate with a Teflon coating at a temperature of 200 ° C. within 30 seconds, the side of the test surface not coated with adhesive resting on the heating plate. Several test specimens were cut from the center of the piece of wallpaper produced from the finished test specimen. The test specimens were soaked in water for 1 minute, folded up, Stored for 10 minutes and then glued to a non-impregnated plasterboard.

Example 7: Bonding a sample from example 1 with oval lit.

A sample from Example 1 was glued to a non-impregnated plasterboard with Ovalit T.

Example 8: Gluing a sample from example 1 with a ready-to-use, aqueous solution from Metylan TT instant

A sample from example 1 was coated with the wallpaper paste Metylan TT instant and glued to a non-impregnated plasterboard.

Experiment evaluation:

The comparison of the adhesive force of the test specimens in the bonding tests after drying completely showed no differences. In all cases, the test specimens could only be removed from the surface mechanically by destroying the wallpaper.

The comparison of the adhesive strength of the test specimens in the adhesive tests after the complete drying and a renewed storage of the adhesive samples in water for 30 minutes showed only slight differences. In all cases, the test objects could be detached mechanically from the surface with little effort. Patterns 2, 3, 7 and 8 clearly left adhesive residues on the surface. With patterns 4, 5 and 6, all of the adhesive remained on the wallpaper.

The comparison of the moistened adhesive layer showed for samples 2 and 3 a significantly more intensive swelling to a thicker adhesive layer than in Examples 4, .5 and 6. The swollen adhesive layers from Examples 2 and 3 were much easier to remove from the wallpaper surface than in Examples 4, 5 and 6.

Claims

Claims: 1. A method for applying a water-activatable adhesive layer to web-shaped decorative materials, in particular wallpaper webs, characterized in that during the manufacturing process of the wallpaper web powdery adhesives in the form of at least one granular, non-cold water-soluble starch are applied to the wet web and dried, preferably an excess on the applied powdered adhesive is collected and returned. 2. The method according to claim 1, characterized in that it is carried out in one stage. 3. The method according to claim 1 or 2, characterized in that a textile wallpaper is used as wallpaper web. 4. The method according to claim 3, characterized in that a glass fiber textile wallpaper is used as the textile wallpaper. 5. The method according to any one of claims 1 to 4, characterized in that a mixture of granular, not cold water-soluble starches is used as the powdery adhesive. 6. The method according to claim 5, characterized in that a mixture of granular potato starch and granular corn starch is used. 7. The method according to any one of claims 1 to 4, characterized in that modified, granular, not cold water-soluble starches or mixtures thereof are used as the powdery adhesive. 8. sheet-like decorative materials provided with powdered adhesives, obtainable by the process of one of claims 1 to 7. 9. Textile wallpapers provided with powdery adhesives, in particular glass fiber textile wallpapers, obtainable by the process of one of claims 1 to 7.