Use of Cellulose Ethers Having 3-Azido-Hydroxyalkyl Groups in Insoluble Adhesives

Abstract

The invention relates to the use of non-ionic, insoluble cellulose ethers having 3-azido-2-hydroxypropyl (AHP) groups, which are linked to the cellulose via an ether link, wherein the molar substitution degree MSAHP is in the region of 0.001 to 0.30, for the production of insoluble, solid adhesives. The cellulose ethers substituted by AHP groups are reacted in the presence of a copper or ruthenium catalyst with alkine compounds, such as phenylacetylene, propargyl alcohol, propiolic acid or heterocyclic compounds, which have a substituent with a terminal alkine group. The reaction of the azide with the alkine occurs as a 1,3-dipolar cyclcoaddition reaction at room temperature within a few seconds, and an insoluble, solid adhesive is obtained. The adhesive is suitable in particular for adhering paper, cardboard or wood.

Claims

1. Water-insoluble, solid adhesives for adhesively bonding paper, paperboard, wood or other materials based on cellulose or comprising cellulose, said adhesives comprising, nonionic, water-soluble cellulose ethers with 3-azido-2-hydroxypropyl groups, joined to the cellulose via an ether bond, the cellulose having a degree of molar substitution MS.sub.AHP being in the range from 0.001 to 0.30, the cellulose ethers being reacted with an alkyne, and catalyzed by a copper compound and/or ruthenium compound.

2. The adhesives as claimed in claim 1, wherein the cellulose ethers have alkyl and/or hydroxyalkyl groups as well as 3-azido-2-hydroxypronyl groups.

3. The adhesives as claimed in claim 2, wherein the alkyl groups are straight-chain (C1-C6)alkyl groups preferably methyl or ethyl groups.

4. The adhesives as claimed in claim 2, wherein the hydroxyalkyl groups are 2-hydroxyethyl or 2-hydroxypropyl groups.

5. The adhesives as claimed in claim 1, wherein the MS.sub.AHP is in the range from 0.05 to 0.25.

6. The adhesives as claimed in claim 2, wherein in the case of alkylhydroxyalkylcelluloses with 3-azido-2-hydroxypropyl groups, the DS(alkyl) is in the range from 1.0 to 2.5, and the MS (HE and/or HP) is in the range from 0.01 to 1.0.

7. The adhesives as claimed in claim 2, wherein in the case of hydroxyalkylcelluloses with 3-azido-2-hydroxypropyl groups, the MS(hydroxyalkyl) is in the range from 1.0 to 4.0.

8. The adhesives as claimed in claim 1, wherein the cellulose ether substituted by AHP groups has an average degree of polymerization DPn of 50 to 4000.

9. The adhesives as claimed in claim 8, wherein the alkyne a) is a compound of the formula HCCR.sup.4, where R.sup.4 is a straight-chain or branched (C.sub.1-C.sub.18)alkyl radical, an alkenyl radical of the formula [CH.sub.2]mCHCH.sub.2, where m is an integer from 1 to 8, a substituted alkyl radical of the formula [CH.sub.2].sub.nCX.sub.2Y, where n is an integer from 0 to 8, X is hydrogen, fluorine or chlorine, and Y is hydrogen, fluorine, chlorine, NH.sub.2, OH, OCH.sub.3, CO.sub.2H or CO.sub.2CH.sub.3, with the proviso that X and Y are not both a hydrogen atom, a polyoxyalkylene radical of the formula [CH.sub.2CH.sub.2O].sub.pCH.sub.2Z, where p is an integer from 1 to 8 and Z is a hydrogen atom or a methyl group, an aromatic radical, a substituted aromatic radical, the substituents bonded to aromatic carbon atoms being identical or different and selected from the group consisting of H, F, Cl, NH.sub.2, CH.sub.3 or OCH.sub.3, with the proviso that not all the substituents are a hydrogen atom; or is a heterocyclic radical; or b) is a diyne of the formula HCCR.sup.5CCH, where R.sup.5 is a divalent aromatic radical or a substituted divalent aromatic radical, the substituents bonded to aromatic carbon atoms being identical or different and selected from the group consisting of H, F, Cl, NH.sub.2, CH.sub.3 or OCH.sub.3, with the proviso that not all the substituents are a hydrogen atom.

10. The adhesives as claimed in claim 8, wherein the alkyne is phenylacetylene, propargyl alcohol, propiolic acid or propargyl 1H-imidazole-1-carboxylate.

11. The adhesives as claimed in claim 3, wherein the alkyl groups are methyl or ethyl groups.

12. The adhesives as claimed in claim 6, wherein the DS(alkyl) is in the range from 1.2 to 2.1, and the MS (HE and/or HP) is in the range from 0.05 to 0.8.

13. The adhesives as claimed in claim 6, wherein the DS(alkyl) is in the range from 1.4 to 1.9, and the MS (HE and/or HP) is in the range 0.05 to 0.6.

14. The adhesives as claimed in claim 7, wherein the MS(hydroxyalkyl) is in the range from 1.5 to 3.5.

15. The adhesives as claimed in claim 8, wherein the cellulose ether substituted by AHP groups has an average degree of polymerization DP.sub.n of 100 to 2000.

16. The adhesives as claimed in claim 8, wherein the cellulose ether substituted by AHP groups has an average degree of polymerization DP.sub.n of 600 to 1400.

17. The adhesives as claimed in claim 9, wherein the aromatic radical is a phenyl group, biphenyl or naphthyl group, and the divalent aromatic radical is ortho-, meta- or para-phenylene biphenyl-4,4-diyl or naphthalene-1,4-diyl.

Description

EXAMPLE 1

Copper-Catalyzed Coupling of Azidohydroxypropyl-Hydroxyethylcellulose (AHP-HEC) with Phenylacetylene and Cu Catalysis for the Bonding of Wood

[0038] 10.0 g of AHP-HEC (5% water content, MS(HE)=1.1, MS(GA)=0.15) were stirred into 1000 ml of cold drinking water and dissolved at room temperature by stirring. The clear solution had a viscosity of about 250 mPa s (Brookfield, LV). Added thereto with stirring were 2.0 g of phenylacetylene, causing no measurable change to the viscosity. A portion (approximately 50 ml) of this low-mobility, slightly turbid mixture was then applied by brush to two smooth, dry spruce-wood surfaces. After waiting for around 5 minutes for partial retreat of the solution into the pores in the wood, one of the two wood surfaces was sprayed, using a commercial spray bottle, with a solution consisting of 10.0 g of copper sulfate pentahydrate and 18.0 g of ascorbic acid in 60 ml of degassed, demineralized water, and immediately the other wood surface, likewise coated with glue, was pressed on by gentle rubbing movements and fixed, as is also carried out in the art in the conventional gluing of wood.

[0039] The next day, the bond had dried and the wooden pieces could not be moved relative to one another or removed from one another. Immersion of the bonded wooden plates in water over a period of 1.8 hours did not noticeably affect the bonding, and, while it was possible to break the bond with considerable application of force, fibers were torn from the other workpiece in each case.

EXAMPLE 2

Bonding of Wood as Described above but Without Catalyst Influence

[0040] The procedure described above in example 1 was followed completely analogously except for the spraying of the aqueous catalyst solution. The two wooden workpieces were similarly assembled and fixed overnight while pressed together. Here again, after a dry storage period of around 18 hours, the bond formed between the two pieces of wood could be parted again with a certain application of manual force, but without fibers being torn out.

[0041] A repeat experiment in which, instead of the application of force to part the bond, the bonded workpiece was first immersed in water for around 6 hours showed complete dissolution of the glued bond.

EXAMPLE 3

Copper-Catalyzed Coupling of Azidohydroxypropylhydroxyethylcellulose (AHP-HEC) with 1,4-diethynylbenzene and Cu Catalysis for the Bonding of Wood

[0042] 1.0 g of AHP-HEC (5% WC, MS(HE)=1.1, MS(GA)=0.15) were stirred into 1000 ml of cold drinking water and dissolved at room temperature by stirring. The clear solution had a viscosity of about 250 mPa s (Brookfield, LV). Added thereto with stirring were 2.0 g of diethynylbenzene [935-14-8], causing no measurable change to the viscosity. A portion (approximately 50 ml) of this low-mobility, slightly turbid mixture was then applied by brush to two smooth, dry spruce-wood surfaces. After waiting for around 5 minutes for partial retreat of the solution in the pores in the wood, one of the two wood surfaces was sprayed, using a commercial spray bottle, with a solution consisting of 10.0 g of copper sulfate pentahydrate and 18.0 g of ascorbic acid in 50 ml of degassed, demineralized water, and immediately the other wood surface, likewise coated with glue, was pressed on by gentle rubbing movements and fixed, as is also carried out in the art in the conventional gluing of wood.

[0043] The next day, the bond had dried and the wooden pieces could not be moved relative to one another or removed from one another. Immersion of the bonded wooden plates in water over a period of 18 hours did not noticeably affect the bonding, and, while it was possible to break the bond with considerable application of force, fibers were torn from the other workplace in each case.