Vulcanizable composition comprising HXNBR latex and polyfunctional epoxide

Abstract

The present invention relates to vulcanizable compositions comprising HXNBR latex and polyfunctional epoxide, to processes for vulcanization of vulcanizable compositions and to mouldings composed of HXNBR vulcanizates.

Claims

1. A composition comprising: (a) hydrogenated carboxylated nitrile rubber latex (HXNBR latex), (b) polyfunctional epoxide, and (c) optionally a pH adjusting agent, wherein the composition has a pH of 9 to less than 11.

2. The composition of claim 1, wherein the hydrogenated carboxylated nitrile rubber latex has been hydrogenated at least 50%.

3. The composition of claim 1, wherein the hydrogenated carboxylated nitrile rubber latex includes 0.1% to 50% by weight, of nitrile monomer units, based on the total amount of monomer units in the hydrogenated carboxylated nitrile rubber latex.

4. The composition of claim 1, wherein the hydrogenated carboxylated nitrile rubber latex includes from 0.1% to 30% by weight, of termonomer units containing carboxyl groups, based on the total amount of monomer units in the hydrogenated carboxylated nitrile rubber latex.

5. The composition of claim 1, wherein the polyfunctional epoxide (b) is a di- or trifunctional epoxide.

6. The composition of claim 1, wherein the composition contains (a) 100 parts by weight of HXNBR latex rubber, (b) 0.1 to 50 parts by weight, of polyfunctional epoxide and (c) 0 to 10 parts by weight of the pH adjusting agent, and, wherein the composition has a pH of 9 to less than 11.

7. The composition of claim 1, comprising (c) 0.1 to 5 parts by of the pH adjusting agent, based on 100 parts by weight of HXNBR latex solids.

8. The composition of claim 1, wherein the (c) pH adjusting agent is a base.

9. The composition of claim 1, wherein the HXNBR latex solids present in the composition is 5% to 65% by weight, based on the total weight of the composition.

10. A process of producing a composition according to claim 1, wherein the process occurs at a temperature in the range of 90 C. to 200 C.

11. Articles or coatings comprising a composition according to claim 1.

12. Articles or coatings formed by the process according to claim 10.

13. A composition of claim 1, wherein the composition comprises: (c) a pH adjusting agent.

14. The composition of claim 8, wherein the (c) pH adjusting agent is an inorganic base.

15. The composition of claim 2, wherein the hydrogenated carboxylated nitrile rubber latex has been hydrogenated at least 80%.

16. The composition of claim 15, wherein the hydrogenated carboxylated nitrile rubber latex has been hydrogenated at least 90%.

17. The composition of claim 3, wherein the hydrogenated carboxylated nitrile rubber latex includes 10% to 45% by weight of the nitrile monomer units.

18. The composition of claim 4, wherein the hydrogenated carboxylated nitrile rubber latex includes 1% to 20% by weight, of the of termonomer units containing carboxyl groups.

19. The composition of claim 5, wherein the polyfunctional epoxide (b) is a difunctional epoxide.

20. The process of claim 10, wherein the process occurs at a temperature in the range of 120 C. to 190.

Description

EXAMPLES

Materials Used

[0153]

TABLE-US-00001 Latex (a) Therban hydrogenated carboxylated secondary NBR latex; XT-Latex pH = 8.7; 40% by weight of solids; 33% by weight of acrylonitrile; 5% by weight of methacrylic acid; commercially available from ARLANXEO

TABLE-US-00002 Crosslinking agent (b) Polyfunctional EUDERM Fix GA-I (bisphenol A-epichlorohydrin epoxide epoxy resin with average molecular weight <700); available from LANXESS Resorcinol available from VWR Chemicals, 99.1% Formaldehyde available from VWR Chemicals, 36% Sulfur 50% colloidal sulfur dispersion, available from agrostulln GmbH

TABLE-US-00003 Auxiliaries ZDBC vulcanization accelerator; zinc dibutyldithiocarbamate dispersion; available from Aquaspersions, 50% ZnO zinc oxide; available from Aquaspersions, 50%

TABLE-US-00004 Coagulation solution Ca(NO.sub.3).sub.2*4 H.sub.2O calcium nitrate tetrahydrate; available from VWR Triton X-100 surfactant; available from Merck

TABLE-US-00005 pH adjuster NaOH sodium hydroxide; available from Merck, 99% KOH potassium hydroxide; available from VWR NH.sub.4OH ammonia solution; available from Merck, 28-30%

Measurement of Tensile Strength and Elongation

[0154] The measurement of the tensile strengths was conducted in a tensile tester from Zwick/Roell (model Z005, XForce HP load cell). For this purpose, four S2 tensile specimens (to DIN 53504:2009-10, adapted to ISO37-2005) were punched out of the latex film obtained and clamped into the jaws of the tensile tester. Subsequently, the jaws were pulled apart at a defined speed, and force and distance were recorded. The force at which the sample tears is determined as F.sub.max. The median over all four tensile tests is reported. The force is based on the width (4 mm) and the layer thickness of the tensile specimen measured, and is reported in MPa.

Measurement of M100

[0155] M100 is a measure of the wearing comfort and stiffness of mouldings, for example gloves. The lower the M100 value, the greater the wearing comfort. The force from the tensile test at which the S2 specimen has been extended by 100% is used as M100. The median over all four tensile tests is reported. The force is based on the width (4 mm) and the layer thickness of the tensile specimen measured, and is reported in MPa.

Procedure for the Dipping Experiments

[0156] Glass plates (1014 cm) were first dipped into a coagulation solution. The coagulation solution contained 22% by weight of calcium nitrate (Ca(NO.sub.3).sub.2), 0.025% by weight of Triton X-100 and surfactant. In a glass chamber, the dip-moulding latex composition was prepared. The glass plates were then dipped once into the dip-moulding latex composition for 3 minutes. The films produced in this way were dried at 25 C. for 3 minutes and then washed in a water bath at 40 C. for 3 minutes. After drying again at 130 C. for 10 minutes, the films obtained were vulcanized in an oven at elevated temperatures for 10 minutes. The latex films obtained were parted cautiously from the mould and the layer thickness was measured. The layer thicknesses of the films thus produced were between 0.19 and 0.42 mm.

1. Epoxide Crosslinker (Inventive):

Production of the Dip-Moulding Latex Composition

[0157] A beaker was charged with the HXNBR latex (a). The appropriate amount of epoxide (b) was added while stirring. It should be noted that the amounts of crosslinker stated are based on the mass of the crosslinker present in the overall dip-moulding latex composition and on the HXNBR solids dispersed in the dip-moulding latex composition. Subsequently, dilute KOH (10% by weight) was used to adjust the pH to the desired value. The dip-moulding latex compositions were then adjusted to a solids content of 35% with deionized water.

TABLE-US-00006 TABLE 1 Effect of the pH of the dip-moulding latex composition on the properties of the dip-moulded articles made from HXNBR latex with epoxide as crosslinking system V1 V2 V3 V4 V5 (a) HXNBR latex solids [parts by wt.] 100 100 100 100 100 (b) Euderm GA [parts by wt.] 3 3 3 3 3 pH 9 9.5 10 10.5 11 Solids content [%] 35 35 35 35 35 F.sub.max [MPa] 9 10 13 17 23 M100 [MPa] 1.00 1.09 1.28 1.80 3.14 Elongation [%] 681 619 505 407 331 Vulcanization time: 10 minutes; vulcanization temperature: 180 C.

[0158] The vulcanization and hence the properties of the vulcanized HXNBR latices, i.e. of the dip-moulded articles produced, are dependent on the pH of the dip-moulding latex composition. With falling pH, the dip-moulding composition turns yellowish to brownish. With rising pH, the viscosity of the formulation increases.

[0159] Dip-moulded articles that are produced from dip-moulding latex compositions having a pH of 9 to 10.5 have an exceptionally low and hence advantageous M100 value of less than 2.0 MPa.

TABLE-US-00007 TABLE 2 Effect of the vulcanization temperature on the properties of the dip-moulded articles made from HXNBR latex with polyfunctional epoxide as crosslinking system The vulcanizable compositions from experiment V4 were determined at different vulcanization temperatures and then the tensile strength was determined. V4.1 V4.2 Vulcanization temperature [ C.] 150 170 F.sub.max [MPa] 10 13 Vulcanization time: 10 minutes

[0160] Vulcanizates that have been crosslinked at an elevated vulcanization temperature above 170 C. have excellent tensile strengths (see also V4 in Table 1).

TABLE-US-00008 TABLE 3 Effect of the amount of crosslinker on the properties of the dip-moulded articles made from HXNBR latex with polyfunctional epoxide as crosslinking system V6 V4 V5 V7 V8 V9 (a) HXNBR latex solids [parts by wt.] 100 100 100 100 100 100 (b) Euderm GA [parts by wt.] 1 3 3 5 5 10 pH 11 10.5 11 10.5 11 11 Solids content [%] 35 35 35 35 35 35 F.sub.max [MPa] 19 17 23 17.5 24 19 Vulcanization time: 10 minutes; vulcanization temperature: 180 C.

[0161] At high pH values of 10.5 to 11, the addition of 5 parts by weight of polyfunctional epoxide based on 100 parts by weight of HXNBR latex solids leads to a slight improvement in tensile strength. In the case of elevated proportions of polyfunctional epoxide, a reduction in tensile strength can be observed.

2. RFL Crosslinker (Noninventive)

[0162] Resorcinol and formaldehyde are pre-condensed in water under basic conditions at room temperature overnight to give the premix.

TABLE-US-00009 TABLE 4 Premix composition Comparative Comparative experiment 1 experiment 2* Premix [parts by wt.] [parts by wt.] Resorcinol 11.0 11.0 Formaldehyde (37% solution) 16.2 8.1 Deionized water 235.8 194 NaOH (10% solution) 3.0 3.0

[0163] Thereafter, the dip-moulded latex composition is prepared by adding premix and further substances (NH.sub.4OH) to the HXNBR latex.

TABLE-US-00010 TABLE 5 Dip-moulding latex composition Comparative Comparative Dip-moulding latex experiment VV1 experiment VV2 composition [parts by wt.] [parts by wt.] HXNBR latex 244.sup.a 60.9.sup.b Premix 266 27.7 Water 60 11.4 NH.sub.4OH 11 0 (28% solution) .sup.a41% solution; .sup.b30% solution

[0164] The RFL formulation was dipped analogously to the epoxide-containing dip-moulding compositions according to the invention. It was not possible to obtain any films with the dip-moulding latex composition from comparative experiment 1. After drying, significant shrinkage and large cracks were observed, and so it was not possible to punch any suitable specimens for a tensile test out of the films.

[0165] With the same procedure as for the epoxide-containing dip-moulding latex compositions, it was possible to use the dip-moulding latex composition from comparative experiment 2 to obtain films, out of which it was possible to punch tensile specimens.

TABLE-US-00011 TABLE 6 Effect of the vulcanization temperature on the properties of the dip-moulded articles made from HXNBR latex with RFL as crosslinking system VV2.1 VV2.2 Vulcanization temperature [ C.] 120 170 F.sub.max [MPa] 17.5 21.4 M100 [MPa] 4.1 4.2 Elongation [%] 506 494

[0166] While the vulcanizates have good tensile strength coupled with high elongation, the M100 values obtained are too high for use as gloves.

3. Sulfur/ZnO Crosslinker (Noninventive)

[0167] A beaker was charged with the HXNBR latex. While stirring, the appropriate amount of sulfur, ZnO and ZDBC was added. It should be noted that the amounts of crosslinker stated are based on the mass of the crosslinker present in the overall dip-moulding latex composition and on the HXNBR solids dispersed in the dip-moulding latex composition. Subsequently, dilute KOH (10% by weight) was used to adjust the pH to the desired value. The dip-moulding latex compositions were then adjusted to a solids content of 35% with deionized water.

TABLE-US-00012 TABLE 7 Properties of the dip-moulded articles made from HXNBR latex with sulfur/ZnO as crosslinking system Comparative experiment VV3 HXNBR latex solids [parts by wt.] 100 Sulfur [parts by wt.] 0.5 ZnO [parts by wt.] 5.0 ZDBC [parts by wt.] 0.25 pH 9.0 Solids content [%] 35 F.sub.max [MPa] 37.2 M100 [MPa] 2.9 Elongation [%] 413.0 Vulcanization conditions: 20 minutes at 125 C.

[0168] Dip-moulded articles made from HXNBR latex with sulfur/ZnO crosslinking do have very high tensile strengths, but at the same time have much too high a M100 value of well over 2.0 MPa.

TABLE-US-00013 TABLE 8 Effect of the vulcanization temperature on the properties of the dip-moulded articles made from HXNBR latex with sulfur as crosslinking system VV3.1 VV3.2 Vulcanization temperature [ C.] 100 125 F.sub.max (median) [MPa] 10 37

[0169] In the case of a vulcanization temperature of 125 C., elevated tensile strength was measured in the HXNBR latex.