FORMALDEHYDE-FREE BINDER COMPOSITION

Abstract

An aqueous binder composition. The aqueous binder composition is obtainable by radically initiated polymerization of vinyl acetate and ethylene, in the presence of polyvinyl alcohol in an aqueous medium, wherein (a) 50 to 94 wt % of vinyl acetate, (b) 5 to 40 wt % of ethylene, (c) 0.2 to 5 wt % of acrylamide and/or methacrylamide, and (d) 0.2 to 5 wt % of maleic anhydride and/or maleic acid are copolymerized in the presence of a polyvinyl alcohol having a degree of hydrolysis of 80 to 99 mol %. The amounts in wt % are each based on the total weight of the comonomers and add up in each case to 100 wt %.

Claims

1-11. (canceled)

12. An aqueous binder composition for fiber binding, comprising: an aqueous binder composition obtainable by radically initiated polymerization of vinyl acetate and ethylene, in the presence of polyvinyl alcohol in an aqueous medium, wherein a) 50 to 94 wt % of vinyl acetate, b) 5 to 40 wt % of ethylene, c) 0.2 to 5 wt % of acrylamide and/or methacrylamide, and d) 0.2 to 5 wt % of maleic anhydride and/or maleic acid, are copolymerized in the presence of a polyvinyl alcohol having a degree of hydrolysis of 80 to 99 mol %, and wherein the amounts in wt % are each based on the total weight of the comonomers and add up in each case to 100 wt %.

13. The composition of claim 12, wherein the comonomer a) 70 to 85 wt % of vinyl acetate is copolymerized, based on the total weight of the comonomers.

14. The composition of claim 12, wherein the comonomer b) 15 to 28 wt % of ethylene is copolymerized, based on the total weight of the comonomers.

15. The composition of claim 12, wherein the comonomer c) 0.5 to 2 wt % of acrylamide is copolymerized, based on the total weight of the comonomers.

16. The composition of claim 12, wherein the comonomer d) 0.2 to 2 wt % of maleic anhydride is copolymerized, based on the total weight of the comonomers.

17. The composition of claim 12, wherein the comonomers c) and d) are replaced wholly or partly by maleamic acid.

18. The composition of claim 12, wherein no acrylic acid and/or methacrylic acid are copolymerized.

19. The composition of claim 12, wherein copolymerization takes place in the presence of one or more polyvinyl alcohols having a degree of hydrolysis of 80 to 99 mol % and a Höppler viscosity in 4% aqueous solution of 2 to 15 mPas (Höppler method at 20° C., DIN 53015).

20. The composition of claim 12, wherein the aqueous binder is used for producing textile sheet products.

21. The composition of claim 20, wherein fibers are contacted with the aqueous binder composition and subsequently dried.

22. The composition of claim 20, wherein there are no catalysts in the aqueous binder composition.

Description

[0033] The examples hereinbelow serve for further illustration of the invention:

[0034] Binder composition:

[0035] For testing, aqueous dispersions of vinyl acetate-ethylene copolymer dispersions with a solids content of around 55% were prepared.

[0036] Preparation took place by emulsion polymerization of 76 to 78 wt % of vinyl acetate, 21 to 22 wt % of ethylene, and the amounts in wt %, as specified in table 1, of acrylamide (AA), acrylic acid (AS), maleic anhydride (MSA) and N-methylolacrylamide (NMA).

[0037] Each polymerization took place in a pressure-rated reactor in a temperature range from 40 to 75° C. under a pressure of up to 85 bar.

[0038] Polymerization was carried out in the presence of 10 wt %, based on the total wt % of the comonomers, of a polyvinyl alcohol (PVOH) having a Höppler viscosity of 5 mPas (4% aqueous solution) and a degree of hydrolysis of 88 mol %. Initiation was carried out using hydrogen peroxide and Brüggolith FF6.

TABLE-US-00001 TABLE 1 AA AAc MAm NMA Example (%) (%) (%) (%) Stabilization Inv. ex. 1 1 0 1 0 PVOH Inv. ex. 2 1 0 2 0 PVOH Comp. ex. 1 0 0 0 0 PVOH Comp. ex. 2 0 0 0.5 0 PVOH Comp. ex. 3 1 1 0 0 PVOH Comp. ex. 4 0 0 0 1 PVOH Comp. ex. 5 1 1 0 0 Emulsifier Comp. ex. 6 1 1 0.5 0 Emulsifier

[0039] Determination of wet strength values for airlaid nonwovens:

[0040] A thermally prebonded airlaid web (75 g/m.sup.2; 88% fluff pulp and 12% PP/PE bicomponent fibers; 0.85 mm thickness) was sprayed homogeneously on both sides with the polymer dispersion of the respective (comparative or inventive) example, diluted to a solids content of 20% with water, using a spray liquor and a semi-automatic spraying assembly, by the airless method (Unijet 8001 E slot dies; 5 bar), and then dried in a laboratory through-air dryer (Mathis LTF; Mathis/CH) at 160° C. for 3 min (application quantity: 20 wt % of polymer based on total weight of polymer and web).

[0041] For each breaking strength test, 10 web strips (20 cm clamped length; 5 cm clamped length) were prepared in the cross direction to the machine production direction. For measurement of the wet breaking strengths, the strip samples were each stored in water for 1 min prior to measurement.

[0042] The wet breaking strengths were determined in analogy to DIN EN 29073 (Part 3: Test methods for nonwovens, 1992) and the measurement samples underwent an ultimate tensile force measurement on a Zwick® 1445 testing machine (100 N load cell) using TestXpert® Software Version 11.02 (from Zwick Roell), with a clamped length of 100±1 mm, a clamped width of 15±1 mm and a deformation rate of 150 mm/min.

[0043] The results of the testing are summarized in table 2.

TABLE-US-00002 TABLE 2 AA AAc MAm NMA Wet strength Example (%) (%) (%) (%) (N/5 cm)* Inv. ex. 1 1 0 1 0 1032/—  Inv. ex. 2 1 0 2 0 1381/—  Comp. ex. 1 0 0 0 0 361/— Comp. ex. 2 0 0 0.5 0 861/— Comp. ex. 3 1 1 0 0  556/609 Comp. ex. 4 0 0 0 1  1020/1570 Comp. ex. 5 1 1 0 0 149/— Comp. ex. 6 1 1 0.5 0  383/415 *= no catalyst/1% citric acid, — = not measured

[0044] Inventive examples 1 and 2 show that high wet breaking strengths are obtained with the binder composition of the invention, even without addition of catalyst. In NMA-containing binder compositions, such as that of comparative example 4, lower values are obtained, with the further disadvantage of release of formaldehyde.

[0045] In contrast to the polyvinyl alcohol-stabilized binder composition in inventive examples 1 and 2, the values obtained with the emulsifier-stabilized binder composition of comparative examples 5 and 6 were inadequate.