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US-12624263-B2 - Dimensionally stable, wipe-on, modified-polyether-polyurethane-based adhesive compound

US12624263B2US 12624263 B2US12624263 B2US 12624263B2US-12624263-B2

Abstract

The present invention relates to a dimensionally stable adhesive compound which is formulated so as to be largely water- and solvent-free and can be brought into contact with the substrate to be bonded by being wiped on in the form of a thin adhesive film that is suitable in particular for bonding materials obtained from plant fibers. The organic constituent of the adhesive compound according to the invention consists predominantly of a mixture of polyether polyurethanes which are end-capped with at least two monohydric aliphatic alcohols of different chain lengths. The invention also relates to a method for applying a tacky film to a planar substrate, preferably to paper, by wiping the adhesive compound onto the point of contact with the substrate.

Inventors

  • Adrian Brandt
  • Jennifer Schmidt
  • Horst Beck
  • Alexander Kux
  • Kerstin Schroeder
  • Christoph Lohr
  • Andrea Brenger
  • Nils Hellwig
  • Mathias Schriefers
  • Anna kaulisch

Assignees

  • HENKEL AG & CO., KGAA

Dates

Publication Date
20260512
Application Date
20220614
Priority Date
20191216

Claims (20)

  1. 1 . An adhesive compound comprising: an organic constituent comprising a mixture of polyether polyurethanes that are based on polyether polyols and that are end-capped with a first monohydric aliphatic alcohol having 4 to 8 carbon atoms and a second monohydric aliphatic alcohol having 16 to 22 carbon atoms, wherein the ratio of isocyanate groups to hydroxyl groups of the polyether polyols is from 2.5:1 to 4.0:1; an inorganic constituent; and water.
  2. 2 . The adhesive compound of claim 1 , wherein the first monohydric aliphatic alcohol is a linear, primary monohydric aliphatic alcohol, and the second monohydric aliphatic alcohol is a linear, primary monohydric aliphatic alcohol.
  3. 3 . The adhesive compound of claim 1 , wherein the ether functions of the polyether polyols are bridged to one another via aliphatic divalent groups having 4 to 8 carbon atoms in the main chain.
  4. 4 . The adhesive compound of claim 1 , wherein the polyether polyols have a hydroxyl number of from 30 to 200 mg KOH/g, based on the entirety of the polyether polyols.
  5. 5 . The adhesive compound of claim 1 , wherein the molar ratio of the first monohydric aliphatic alcohol to the second monohydric aliphatic alcohol is from 1:2 to 3:1.
  6. 6 . The adhesive compound of claim 1 , wherein the mixture of the polyether polyurethanes is prepared by: adding at least one trifunctional isocyanate selected from the group consisting of trimers of hexamethylene diisocyanate and pentamethylene diisocyanate to the polyether polyols; and end-capping with the first monohydric aliphatic alcohol and the second monohydric aliphatic alcohol.
  7. 7 . The adhesive compound of claim 1 , wherein the mixture of polyether polyurethanes has a dynamic Brookfield viscosity (spindle 27) at 80° C. from 2,000 to 140,000 mPas.
  8. 8 . The adhesive compound of claim 1 , wherein the mixture of the polyether polyurethanes that are end-capped with the first monohydric aliphatic alcohol and the second monohydric aliphatic alcohol, based on the total weight of polyether polyurethanes, is at least 80 wt. %.
  9. 9 . The adhesive compound of claim 1 , wherein the mixture of polyether polyurethanes that are end-capped with the first monohydric aliphatic alcohol and the second monohydric aliphatic alcohol, based on the total weight of organic constituent of the adhesive compound, is greater than 50 wt. %.
  10. 10 . The adhesive compound of claim 1 , wherein the polyether polyols are semi-crystalline polyester polyols, which are prepared by the polycondensation reaction of: dicarboxylic acids that are both saturated linear and aliphatic and have an even number of at least 8 methylene groups, and one or more diols selected from terminal diols that are both saturated linear and aliphatic and have at least one ether function.
  11. 11 . The adhesive compound of claim 10 , wherein the mixture of the polyether polyurethanes are prepared by adding at least trifunctional isocyanates to the semi-crystalline polyester polyols, and then end-capping with the first monohydric aliphatic alcohol and the second monohydric aliphatic alcohol.
  12. 12 . The adhesive compound of claim 1 , wherein the organic constituent is present in an amount of at least 70 wt. %, based on the total weight of the adhesive compound.
  13. 13 . The adhesive compound of claim 1 , wherein the water is present in an amount of less than 5 wt. %, based on the total weight of the adhesive compound.
  14. 14 . The adhesive compound of claim 1 , wherein: A. up to 80 wt. %, based on the total weight of the adhesive compound, of the organic constituent comprises: a) at least 40 wt. %, based on the total weight of the organic constituent, of the mixture of the polyether polyurethanes that are end-capped with the first monohydric aliphatic alcohol having 4 to 8 carbon atoms and the second monohydric aliphatic alcohol having 16 to 22 carbon atoms; b) up to 50 wt. %, based on the total weight of the organic constituent, of polyester polyurethanes; c) up to 20 wt. %, based on the total weight of the organic constituent, of polyolefin waxes; d) up to 5 wt. %, based on the total weight of the organic constituent, of tackifiers; and e) up to 5 wt. %, based on the total weight of the organic constituent, of polyalkoxylated C12-C22 fatty alcohols; B. up to 20 wt. %, based on total weight the adhesive compound, of the inorganic constituent selected from the group consisting of pigments, fillers, salts, and any combination thereof; and C. up to 5 wt. %, based on the total weight of the adhesive compound, of the water.
  15. 15 . A method for applying a tacky film to a planar paper substrate, the method comprising: pressing the adhesive compound of claim 1 onto the planar paper substrate; and subsequently changing the relative position of the tacky film while maintaining a contact pressure perpendicular to the surface normal to the planar paper substrate.
  16. 16 . The adhesive compound of claim 1 , wherein the softening point temperature of the adhesive compound is from 60° C. to 150° C.
  17. 17 . The adhesive compound of claim 1 , wherein the ratio of isocyanate groups to hydroxyl groups of the polyether polyols is from 2.5:1 to 3.5:1.
  18. 18 . The adhesive compound of claim 1 , further comprising a non-ionic surfactant.
  19. 19 . The adhesive compound of claim 1 , further comprising a polyalkoxylated C12-C22 fatty alcohol present in an amount of from 0.5 to 5 wt %, based on the total weight of the adhesive compound.
  20. 20 . The adhesive compound of claim 1 , wherein the mixture of polyether polyurethanes has a number-average molar mass of less than 6,000 g/mol.

Description

The present invention relates to a dimensionally stable adhesive compound which is formulated so as to be largely water- and solvent-free and can be brought into contact with the substrate to be bonded by being wiped on in the form of a thin adhesive film that is suitable in particular for bonding materials obtained from plant fibers. The organic constituent of the adhesive compound according to the invention consists predominantly of a mixture of polyether polyurethanes which are end-capped with at least two monohydric aliphatic alcohols of different chain lengths. The invention also relates to a method for applying a tacky film to a planar substrate, preferably to paper, by wiping the adhesive compound onto the point of contact with the substrate. Dimensionally stable adhesive compounds, which are used in such a way that a thin film of the adhesive compound is transferred to the substrate by being wiped onto the point of contact, are known in the prior art and have long been implemented, for example in glue sticks for bonding paper. WO 99/51699 A1 describes glue sticks that can be smoothly wiped on but are dimensionally stable, consisting of an aqueous preparation of starch ethers and sucrose as the adhesive component and a soap gel as the shaping builder substance and, if desired, further auxiliaries. After a thin film has been wiped on, such adhesive compounds set solely through the loss of water and thus in a purely physical manner. In order to ensure the applicability of such an adhesive compound over a longer period of time, it is necessary to prevent the adhesive compound from drying out, which is made possible by the selection of a suitable, largely water-vapor-impermeable packaging means. The packaging means is often at the same time an applicator which, as a rigid structure into which the adhesive compound is filled, is also dimensionally stabilizing, so that there is also greater latitude in the formulation of the dimensionally stable adhesive compound. DE 10047069 A1 describes such an applicator for a water-based, dimensionally stable glue stick. In contrast, water-free, dimensionally stable adhesive compounds are also known which are likewise formulated to be able to be wiped on. WO 96/37566 A1 describes semi-crystalline, dimensionally stable adhesive compounds based on polyether polyurethanes of which the semi-crystalline structure is broken up by the heat released with friction on a substrate surface, such that a thin adhesive film can be applied which, after a short time, forms semi-crystalline regions again and in this way sets and is able to bond the substrate. In said document, various additives which modify the crystallinity or increase tackiness or which are pigments, fillers, plasticizers, dyes, antioxidants and preservatives are added to such adhesive compounds to improve the property profile. In principle, the adhesive compounds disclosed in the WO publication are already suitable for being placed on the market largely without packaging and for being applied manually to substrates, in particular paper, without a special applicator. Such a largely water- and solvent-free, dimensionally stable adhesive compound must, however, satisfy a complex requirement profile that includes application-specific, consumer-specific and environmental hygiene aspects. For this purpose, the property profile of dimensionally stable adhesive compounds which can be activated by friction must be further improved in order to be able to establish packaging-free sales units in the consumer market. In this context, it is important to find formulations that can be easily wiped on in the form of a tacky film on flat substrates, have sufficient initial tackiness that flat substrates can be fixed in their relative position with respect to one another via the adhesive film, and set in a short time in a precisely positioned manner and in the process form a cohesive bond that is as long-lasting as possible. Ideally, the adhesive compound is suitable for bonding materials obtained from plant fibers. This property profile is also intended to be retained even after the adhesive compound is stored in a way that is customary in trade and typical for use. On the part of the consumer, it is also expected that a dimensionally stable adhesive compound which can be wiped onto the substrate directly by hand without an applicator has no tackiness, that the skin is not soiled with adhesive compound and that skin compatibility is ensured. It is also expected by the consumer that such an adhesive compound, in the form of a stick, can be guided over the substrate like a wax crayon when in use, and a continuous adhesive film can be applied in the process. Wiping the adhesive compound on a flat substrate must be possible with little effort, so that flexible thin substrates such as paper are not warped or torn when the adhesive is applied. Overall, the present invention thus addresses the problem of providing a dimensionally stable, wip