AQUEOUS DIPPING COMPOSITION

Abstract

The present invention relates to an aqueous dipping composition for coating a textile reinforcing material, comprising 4% to 40% by dry weight of at least one rubber latex, with the proviso that the rubber latex is no isoprene rubber latex, 0.1% to 10% by dry weight of at least one blocked isocyanate, 1% to 20% by dry weight of at least one isoprene rubber latex, and 0% to 6% by dry weight of at least one epoxy group-containing compound, wherein the amounts in % by dry weight are based on the total weight of the aqueous dipping composition. The composition is essentially free of resorcinol, resorcinol precondensates, formaldehyde and formaldehyde-releasing substances. The present invention relates to a use of such a composition, a process for coating a textile reinforcing material with this composition, a coated textile reinforcing material and a respective elastomeric article comprising the same.

Claims

1. An aqueous dipping composition for coating a textile reinforcing material, comprising 4% to 40% by dry weight of at least one rubber latex, with the proviso that the rubber latex is no isoprene rubber latex, 0.1% to 10% by dry weight of at least one blocked isocyanate, 1% to 20% by dry weight of at least one isoprene rubber latex, and 0% to 6% by dry weight of at least one epoxy group-containing compound, wherein the amounts in % by dry weight are based on the total weight of the aqueous dipping composition, and wherein the composition is essentially free of resorcinol, resorcinol precondensates, formaldehyde and formaldehyde-releasing substances.

2. The dipping composition according to claim 1, wherein the at least one rubber latex which is no isoprene rubber latex is selected from the group consisting of styrene-butadiene rubber latex, ethylene-propylene-diene rubber latex, butyl rubber latex, styrene-butadiene-vinylpyridine rubber latex, nitrile butadiene rubber latex, chloroprene rubber latex, butadiene rubber latex, functionalized rubber latex and combinations thereof.

3. The dipping composition according to claim 1, wherein the at least one blocked isocyanate comprises units selected from the group consisting of tetramethylene diisocyanate, hexamethylene diisocyanate, diphenylmethane 4,4′-diisocyanate, octamethylene diisocyanate, decamethylene diisocyanate, dodecamethylene diisocyanate, aromatic diisocyanates comprising toluene 2,4- or 2,6-diisocyanate, tetramethylxylylene diisocyanate, p-xylene diisocyanate, 2,4′- or 4,4′-diisocyanatodiphenylmethane, phenyl 1,3- or 1,4-diisocyanate, and combinations thereof.

4. The dipping composition according to claim 1, wherein the at least one isoprene rubber latex is selected from the group consisting of synthetic isoprene rubber latex (IR), natural isoprene rubber latex (NR) and combinations thereof.

5. The dipping composition according to claim 1, comprising 4.5% to 20% by dry weight of the at least one rubber latex which is no isoprene rubber latex, 0.2% to 4.5% by dry weight of the at least one blocked isocyanate, 2% to 15% by dry weight of the at least one isoprene rubber latex, and 0.2% to 4% by dry weight of the at least one epoxy group-containing compound selected from the group consisting of glycidyl-based glycerol, sorbitol-based epoxy compounds, phenol-based novolak epoxy compounds, cresol-based novolak epoxy compounds and combinations thereof, wherein the amounts in % by dry weight are based on the total weight of the aqueous dipping composition.

6. The dipping composition according to claim 1 which contains no epoxy group-containing compound.

7. The dipping composition according to claim 1, further comprising a base, preferably selected from the group consisting of ammonium hydroxide, sodium hydroxide and combinations thereof.

8. The dipping composition according to claim 1, further comprising an additive selected from the group consisting of waxes, colorants, polymers with carboxylic acid functional groups, catalysts of isocyanate deblocking or trimerization reactions, catalysts of reactions between isocyanate and an epoxy group-containing and/or hydroxyl group-containing compound or a polymer with carboxylic acid functional groups, catalysts of reactions between a polymer with carboxylic acid functional groups and an epoxy group-containing and/or hydroxyl group-containing compound, and combinations thereof, and/or a filler selected from the group consisting of silica, silicate, carbon black, graphite, graphene, fullerenes, carbon nanotubes, alkaline earth carbonates, alkaline earth oxides, zinc oxide, titanium dioxide, aluminum oxide, alkaline earth hydroxides, aluminum hydroxide and combinations thereof.

9. The dipping composition according to claim 1, having a solid content of 5 to 30% by dry weight, preferably 7 to 27% by dry weight.

10. The dipping composition according to claim 1, wherein the weight ratio of rubber latex to the sum of blocked isocyanate, epoxy-group containing compound and optional polymer with carboxylic acid functional groups is at least 2.

11. Use of the aqueous dipping composition according to claim 1 for coating a textile reinforcing material, preferably selected from the group consisting of polyesters, polyamides, polyurethanes, glass, carbon, celluloses, polycarbonates, polyketones and combinations thereof.

12. A process for coating a textile reinforcing material, comprising the steps of treating a textile reinforcing material with the dipping composition according to claim 1, preferably by dipping; and heat-treating the composition, preferably at a temperature in the range of from 60 to 260° C.

13. A coated textile reinforcing material obtained from the process according to claim 12.

14. An elastomeric article comprising (i) at least one elastomeric compound and (ii) the coated textile reinforcing material according to claim 13.

15. The elastomeric article according to claim 14 which comprises a rubber article.

16. The elastomeric article according to claim 15 in which the rubber article is selected from the group consisting of a tire, a belt, a conveyor belt, a transmission belt, a drive belt, a hose, a strip belt, a transport belt, and an air bellow.

17. An elastomeric article comprising (i) at least one elastomeric compound and (ii) a textile reinforcing material that is coated with a heat-treated dipping composition according to anyone of claim 1.

18. The elastomeric article according to claim 17 which comprises a rubber article.

19. The elastomeric article according to claim 18 in which the rubber article is selected from the group consisting of a tire, a belt, a conveyor belt, a transmission belt, a drive belt, a hose, a strip belt, a transport belt, and an air bellow.

Description

EXAMPLES

Examples 1 and 2

[0066] Examples 1 and 2 refer to experiments made in a lab dipping unit. Cords made from polyester (polyethylene terephthalate (PET), 2-plied, 1440 dtex, 375×375 twisted, non adhesive activated) were pretreated by dipping the cord into a pre-dip composition containing 95.26% by weight of water, 0.90% by weight of Denacol EX313 (an epoxy compound) and 3.84% by weight of Grilbond IL-6 (a polyisocyanate compound) and heat-treated at a temperature between 210 and 250° C. After treatment with the pre-dip composition, the cords were dipped with the aqueous dipping composition according to Example 1 (reference example) and Example 2 (according to the present invention), respectively. The dipping compositions of Examples 1 and 2 were prepared by adding the various components under stirring at ambient temperature in the amounts given in the following Table 1, in the following addition order (if one chemical is not part of the recipe according to Table 1, the subsequent component was added, and so on):

##STR00001##

[0067] The dipped cords were then passed through two additional furnaces. The temperature of the first furnace was kept between 170 and 220° C.; the temperature of the second furnace was kept between 200° C. and 250° C. It is noted that Table 1 provides the total amount (in parts by weight) of the added components and not the dry weight.

TABLE-US-00001 TABLE 1 Ex. 1 (Ref.) Ex. 2 VP latex.sup.a) 37.32 23.27 SBR latex.sup.b) 6.59 7.02 NR latex.sup.c) — 9.15 Isocyanate.sup.d) 4.71 4.71 Epoxy compound.sup.e) 1.67 1.67 Water 49.71 54.17 Total 100 100 Latex/resin 4.0 4.0 Dip solid % 22.5 23.0 .sup.a)Copolymer of butadiene, styrene and 2-vinylpyridine, containing approximately 15% per weight of vinylpyridine bound in the polymer, aqueous dispersion, 41% by weight; .sup.b)Styrene-butadiene copolymer, aqueous dispersion, 41% by weight; .sup.c)Centex HF: natural rubber latex, high filterability, high ammonia, aqueous dispersion, 60% by weight (CentroTrade); .sup.d)Grilbond IL-6: caprolactam-blocked 4,4′-methylene diphenyl diisocyanate, aqueous dispersion, 60% by weight (EMS-GRILTECH); .sup.e)Denacol EX313: glycerol-based polyglycidyl ether (Nagase Chemtex).

[0068] After dipping and subsequent hot-drawing, the strengthening members were each covered with a rubberizing mixture according to Table 2. A specimen including two plies of fabric bonded with rubber was produced, in order to measure the stripping force required to separate these two plies of fabric bonded with rubber. The cord density was 90 epdm (ends per decimeter). This composite material was then cured at 170° C. under pressure (7.5 bar) for 10 minutes to obtain the final reinforced material/strengthening member.

TABLE-US-00002 TABLE 2 Constituents of rubberizing mixture Amount, phr Natural rubber 70 SBR 30 N660 carbon black 50 Zinc oxide 4 Stearic acid 2 Oil 5 Penacolite (resorcinol-formaldehyde) 3 Hexamethoxymethyl melamine 2 2,2,4-Trimethyl-1,2-dihydroquinoline (TMQ) 1.8 Sulphur 2.5 2,2′-Dibenzothiazyl disulphide (MBTS) 0.8

[0069] For all the strengthening members described, a bonding test with the abovementioned rubberizing mixture was conducted according to ISO 36:2011. The vulcanized samples were heated to 120° C. for 30 min and the bonding test was conducted within 30 seconds after removal from the oven. The results are provided in Table 3, wherein the resultant force values are given in % relative to the initial force value of Reference Example 1 which has been normalized to 100%.

[0070] The assessment of the bonding force was conducted according to DIN ISO 6133:2004-05, procedure B. In addition, the separated areas of the test samples were assessed visually on a scale from 1 to 5 using the following coverage rating.

TABLE-US-00003 1 0% completely free of rubber 2 25% mainly free of rubber 3 50% half covered by rubber 4 75% mainly covered by rubber 5 100% completely covered by rubber

[0071] The side with the poorest coverage was used for the evaluation. In determining the coverage rating, half ratings (i.e., 3.5) were also permitted. For each example, the bonding force reported and the coverage reported are the mean value from three measurements in each case. The results are also provided in Table 3.

[0072] Furthermore, also the storage stability/shelf life stability of the textile reinforcing material being treated with the dipping composition according to the present invention was evaluated. As a test of the storage stability of the treated textile reinforcing material under real conditions, an accelerated ageing test was applied by ageing the treated textile reinforcing material at 60° C. for 72 hours in an air circulating oven. For the accelerated ageing test, the samples were put in the oven wound onto appropriate supports, avoiding stretching, twisting, untwisting or the formation of loops. The winding was loose enough that possible shrinkage could occur during drying without causing tension on the sample.

[0073] The aged treated textile reinforcing material was then tested in the same manner as the fresh textile reinforcing material treated with the dipping composition according to the present invention. The results are also provided in Table 3. Again, the resultant force values are given in % relative to the initial force value of Reference Example 1 (set to 100%).

TABLE-US-00004 TABLE 3 Ex. 1 (Ref.) Ex. 2 Initial adhesion force [%] 100.0 120.8 Initial coverage 3.5 4.5 Aged adhesion force (72 h) 64.8 129.5 Aged coverage (72 h) 1.5 4.7

[0074] As can be seen from Table 3, the textile reinforcing material being treated with the dipping composition according to the present invention (Example 2) shows improved initial bonding as well as aged coverage and bonding as compared to the prior art composition according to Reference Example 1.

Examples 3 and 4

[0075] Examples 3 and 4 refer to experiments made in a production dipping unit. Cords made from Rayon (2-plied, 2440 dtex, 340×340 twisted, weave made from the cords at 104 epdm (ends per decimeter; measure of the cord density in the textile ply)) were dipped with the aqueous dipping composition according to Example 3 (reference example) and Example 4 (according to the present invention), respectively, and passed through four furnaces. The dipping compositions of Examples 3 and 4 were prepared by adding the various components under stirring at ambient temperature in the amounts given in the following Table 4, in the following addition order (if one chemical is not part of the recipe according to Table 4, the subsequent component was added, and so on):

##STR00002##

[0076] The temperature of the first furnace was kept between 170 and 220° C.; the temperatures of the second, third and fourth furnace were independently kept between 200° C. and 250° C. It is noted that Table 4 provides the total amount (in parts by weight) of the added components and not the dry weight.

TABLE-US-00005 TABLE 4 Ex. 3 (Ref.) Ex. 4 VP latex.sup.a) 29.00 17.55 SBR latex.sup.f) 5.12 7.27 NR latex.sup.g) — 6.36 Isocyanate.sup.d) 3.40 3.40 Ammonia.sup.h) 0.60 0.60 Carboxylic resin.sup.i) 0.40 0.40 Epoxy compound.sup.j) 0.30 0.30 Water 61.18 64.12 Total 100 100 Latex/resin 6.0 6.3 Dip solid % 17.9 18.9 .sup.a) d)See above for examples 1 and 2; .sup.f)Styrene-butadiene copolymer, aqueous dispersion, 67% by weight; .sup.g)Natural rubber latex, high ammonia, aqueous dispersion, 60% by weight (Neoquimica); .sup.h)Ammonium hydroxide, aqueous solution, 25% by weight; .sup.i)Acrodur 950L: polyacrylate, aqueous solution, 50% by weight in water (BASF); .sup.j)Grilbond G1701: glycerol-based polyglycidyl ether (EMS-GRILTECH).

[0077] After dipping and subsequent hot-drawing, the strengthening members were each covered with a rubberizing mixture according to Table 2. The rayon material was oven dried according to ASTM D885 (1 h, 105° C.) prior to sample preparation. A specimen including two plies of fabric bonded with rubber was produced, in order to measure the stripping force required to separate these two plies of fabric bonded with rubber. The cord density was 90 epdm (ends per decimeter). This composite material was then cured at 170° C. under pressure (7.5 bar) for 10 minutes to obtain the final reinforced material/strengthening member.

[0078] The initial coverage and bonding of the obtained strengthening members were tested as described above for Examples 1 and 2. Moreover, also the storage stability/shelf life stability of the textile reinforcing material being treated with the dipping composition according to the present invention was evaluated. For testing the storage stability, the samples were kept in a closed moisture-proof dark bag at ambient temperature to protect the samples from light and atmospheric changes for 4 months and 12 months, respectively. The results are provided in Table 5, wherein the resultant force values are given in % relative to the initial force value of Reference Example 3 which has been normalized to 100%.

TABLE-US-00006 TABLE 5 Ex. 3 (Ref.) Ex. 4 Initial adhesion force [%] 100.0 109.4 Initial coverage 4.5 4.7 Aged adhesion force (4 months) 64.9 104.0 Aged coverage (4 months) 1.5 4.5 Aged adhesion force (12 months) n.d. 102.4 Aged coverage (12 months) n.d. 4.7 n.d.: non determined

[0079] As can be seen from Table 5, the textile reinforcing material being treated with the dipping composition according to the present invention shows improved initial and aged bonding and coverage (compare Reference Example 3 with Example 4).

Examples 5 to 7

[0080] Examples 5 to 7 refer to experiments made in a lab dipping unit. Cords made from Rayon (2-plied, 2440 dtex, 340×340 twisted) were dipped with the aqueous dipping composition according to Example 5 (reference example) and Examples 6 and 7 (according to the present invention), respectively (see Table 6), and passed through four furnaces. The dipping compositions of Examples 5 to 7 were prepared by adding the various components under stirring at ambient temperature in the amounts given in the following Table 6, in the following addition order (if one chemical is not part of the recipe according to Table 6, the subsequent component was added, and so on):

##STR00003##

[0081] The temperature of the first furnace was kept between 170 and 220° C.; the temperatures of the second, third and fourth furnace were independently kept between 200° C. and 250° C. It is noted that Table 6 provides the total amount (in parts by weight) of the added components and not the dry weight.

TABLE-US-00007 TABLE 6 Ex. 5 (Ref.) Ex. 6 Ex. 7 VP latex.sup.a) 29.00 17.55 17.55 SBR latex.sup.f) 5.12 7.27 7.27 NR latex.sup.g) — 6.36 6.36 Isocyanate.sup.d) 3.40 3.40 3.40 Ammonia.sup.h) 0.60 — — Carboxylic resin.sup.i) 0.40 — — Epoxy compound.sup.j) 1.20 1.20 — Water 60.28 64.22 65.42 Total 100 100 100 Latex/resin 4.5 4.9 7.8 Dip solid % 18.8 19.6 18.4 .sup.a) d) f) g) h) i) j) See above for examples 1 to 4.

[0082] After dipping and subsequent hot-drawing, the strengthening members were each covered with a rubberizing mixture according to Table 2. The rayon material was oven dried according to ASTM D885 (1 h, 105° C.) prior to sample preparation. A specimen including two plies of fabric bonded with rubber was produced, in order to measure the stripping force required to separate these two plies of fabric bonded with rubber. The cord density was 90 epdm (ends per decimeter). This composite material was then cured at 170° C. under pressure (7.5 bar) for 10 minutes to obtain the final reinforced material/strengthening member.

[0083] The obtained strengthening members were tested as described above for Examples 1 and 2. The results are provided in Table 7, wherein the resultant force values are given in % relative to the initial force value of Reference Example 5 which has been normalized to 100%.

TABLE-US-00008 TABLE 7 Ex. 5 (Ref.) Ex. 6 Ex. 7 Initial adhesion force [%] 100.0 105.9 108.1 Initial coverage 4.3 4.8 5.0 Aged adhesion force (72 h) 72.9 99.5 97.3 Aged coverage (72 h) 1.0 4.0 4.0

[0084] As can be seen from Table 7, the textile reinforcing material being treated with the dipping composition according to the present invention shows improved initial and aged bonding and coverage (compare Reference Example 5 with Examples 6 and 7).

[0085] Further disclosed herein are the following items: [0086] Item 1. An aqueous dipping composition for coating a textile reinforcing material, comprising [0087] 4% to 40% by weight (dry weight) of at least one rubber latex, with the proviso that the rubber latex is no isoprene rubber latex, [0088] 0.1% to 10% by weight (dry weight) of at least one blocked isocyanate, [0089] 1% to 20% by weight (dry weight) of at least one isoprene rubber latex, and [0090] 0% to 6% by weight (dry weight) of at least one epoxy group-containing compound, [0091] wherein the amounts in % by weight are based on the total weight of the aqueous dipping composition, and [0092] wherein the composition is essentially free of resorcinol, resorcinol precondensates, formaldehyde and formaldehyde-releasing substances. [0093] Item 2. The dipping composition according to item 1, wherein the at least one rubber latex which is no isoprene rubber latex is selected from the group consisting of styrene-butadiene rubber latex, ethylene-propylene-diene rubber latex, butyl rubber latex, styrene-butadiene-vinylpyridine rubber latex, nitrile butadiene rubber latex, chloroprene rubber latex, butadiene rubber latex, functionalized rubber latex and combinations thereof. [0094] Item 3. The dipping composition according to item 1 or 2, wherein the at least one blocked isocyanate comprises units selected from the group consisting of tetramethylene diisocyanate, hexamethylene diisocyanate, diphenylmethane 4,4′-diisocyanate, octamethylene diisocyanate, decamethylene diisocyanate, dodecamethylene diisocyanate, aromatic diisocyanates comprising toluene 2,4- or 2,6-diisocyanate, tetramethylxylylene diisocyanate, p-xylene diisocyanate, 2,4′- or 4,4′-diisocyanatodiphenylmethane, phenyl 1,3- or 1,4-diisocyanate, and combinations thereof. [0095] Item 4. The dipping composition according to anyone of items 1 to 3, wherein the at least one isoprene rubber latex is selected from the group consisting of synthetic isoprene rubber latex (IR), natural isoprene rubber latex (NR) and combinations thereof. [0096] Item 5. The dipping composition according to anyone of items 1 to 4, comprising [0097] 4.5% to 20% by weight (dry weight) of the at least one rubber latex which is no isoprene rubber latex, [0098] 0.2% to 4.5% by weight (dry weight) of the at least one blocked isocyanate, [0099] 2% to 15% by weight (dry weight) of the at least one isoprene rubber latex, and [0100] 0.2% to 4% by weight (dry weight) of the at least one epoxy group-containing compound selected from the group consisting of glycidyl-based glycerol, sorbitol-based epoxy compounds, phenol-based novolak epoxy compounds, cresol-based novolak epoxy compounds and combinations thereof, [0101] wherein the amounts in % by weight are based on the total weight of the aqueous dipping composition. [0102] Item 6. The dipping composition according to anyone of items 1 to 4 which contains no epoxy group-containing compound. [0103] Item 7. The dipping composition according to anyone of items 1 to 6, further comprising a base, preferably selected from the group consisting of ammonium hydroxide, sodium hydroxide and combinations thereof. [0104] Item 8. The dipping composition according to anyone of items 1 to 7, further comprising an additive selected from the group consisting of waxes, colorants, polymers with carboxylic acid functional groups, and combinations thereof, and/or a filler selected from the group consisting of silica, silicate, carbon black, graphite, graphene, fullerenes, carbon nanotubes, alkaline earth carbonates, alkaline earth oxides, zinc oxide, titanium dioxide, aluminum oxide, alkaline earth hydroxides, aluminum hydroxide and combinations thereof. [0105] Item 9. The dipping composition according to anyone of items 1 to 8, having a solid content of 5 to 30% by weight (dry weight), preferably 7 to 27% by weight. [0106] Item 10. The dipping composition according to anyone of items 1 to 9, wherein the weight ratio of rubber latex to the sum of blocked isocyanate, epoxy-group containing compound and optional polymer with carboxylic acid functional groups is at least 2. [0107] Item 11. Use of the aqueous dipping composition according to anyone of items 1 to 10 for coating a textile reinforcing material, preferably selected from the group consisting of polyesters, polyamides, polyurethanes, glass, carbon, celluloses, polycarbonates, polyketones and combinations thereof. [0108] Item 12. A process for coating a textile reinforcing material, comprising the steps of [0109] treating a textile reinforcing material with the dipping composition according to anyone of items 1 to 11, preferably by dipping; and [0110] heat-treating the composition, preferably at a temperature in the range of from 60 to 260° C. [0111] Item 13. A coated textile reinforcing material obtained from the process according to item 12. [0112] Item 14. An elastomeric article comprising (i) at least one elastomeric compound and (ii) the coated textile reinforcing material according to claim 13 or a textile reinforcing material that is coated with a heat-treated dipping composition according to anyone of items 1 to 10. [0113] Item 15. The elastomeric article according to item 14 which is a tire or a rubber article, such as a belt, a conveyor belt, a transmission belt, a drive belt, a hose, a strip belt, a transport belt, and an air bellow.