Dipping bath compositions for treating reinforcing inserts

Abstract

The present invention relates to an aqueous, solids-containing dipping bath composition for treating reinforcing inserts for rubber products comprising the following components or consisting of these components, (A) at least one blocked MDI mixture, the MDI mixture comprising MDI oligomers of formula (I), n being a whole number from 1 to 8, and MDI monomers; (B) at least one resorcinol-formaldehyde latex; and (C) possibly at least one additive, wherein the dipping bath composition is essentially free of epoxides. ##STR00001##

Claims

1. An aqueous, solids-containing dipping bath composition for treating reinforcing inserts for rubber products comprising the following components: (A) at least one blocked MDI mixture, the MDI mixture comprising MDI oligomers of formula (I), n being a whole number from 1 to 8, ##STR00004## and MDI monomers; (B) at least one resorcinol-formaldehyde latex; and (C) optionally at least one additive, wherein the dipping bath composition is essentially free of epoxides.

2. The aqueous, solids-containing dipping bath composition according to claim 1, wherein the proportion of the solids is 2 to 40% by weight relative to the total weight of the dipping bath composition.

3. The aqueous, solids-containing dipping bath composition according to claim 1, wherein the bath has the following composition, the parts by weight respectively relative to the total weight of the dipping bath composition: (A) 0.1 to 20 parts by weight, (B) 5 to 200 parts by weight, and (C) 0 to 20 parts by weight.

4. The aqueous, solids-containing dipping bath composition according to claim 1, wherein the blocked MDI mixture (A) comprises MDI derivatives selected from the group consisting of MDI uretdione, adducts of MDI, and MDI oligomers with other compounds.

5. The aqueous, solids-containing dipping bath composition according to claim 4, wherein the MDI is selected from the group consisting of 4,4-MDI, 2,4-MDI, 2,2-MDI and mixtures thereof, the proportion of 2,4-MDI and 2,2-MDI being less than 10% by weight, relative to the MDI mixture.

6. The aqueous, solids-containing dipping bath composition according to claim 1, wherein the MDI mixture has the following composition: (i) 25 to 60% by weight of MDI monomers; (ii) 40 to 75% by weight of MDI oligomers; and (iii) 0 to 9% by weight of MDI derivatives; the proportions of components (i) to (iii) adding up to 100% by weight.

7. The aqueous, solids-containing dipping bath composition according to claim 1, wherein: in the case of the at least one resorcinol-formaldehyde latex (B), the latex is selected from the group consisting of styrene-butadiene-vinylpyridine copolymer, styrene-butadiene-vinylpyridine copolymer modified with carboxylic acid, styrene-butadiene copolymer, styrene-butadiene copolymer modified with carboxylic acid, nitrile-butadiene copolymer, natural latex, chloroprene latex, and mixtures thereof.

8. The aqueous, solids-containing dipping bath composition according to claim 1, wherein the at least one additive (C) is selected from the group consisting of surfactants, defoamers, fillers, colourants, preservatives, thickening agents, acids, lyes, multivalent alcohols, and mixtures thereof.

9. The aqueous, solids-containing dipping bath composition according to claim 1, wherein the MDI mixture (A) is blocked with a compound which is selected from the group consisting of monophenols, lactams, oximes, enol-forming compounds, acetyl acetone, and mixtures thereof.

10. The aqueous, solids-containing dipping bath composition according to claim 1, wherein: the average particle diameter d.sub.50 of the blocked MDI mixture is at most 2 m; and/or the particle diameter d.sub.100 of the blocked MDI mixture is at most 6 m; and/or the blocked MDI mixture has a number-average molar mass M.sub.n in the range of 550 to 1,200 g/mol.

11. A method for producing an adhesive reinforcing insert which comprises at least the following steps: a) providing at least one reinforcing insert; b) dipping the reinforcing insert in at least one dipping bath composition according to claim 1; c) drying the reinforcing insert from step b) at 100 to 240 C.; and d) annealing the reinforcing insert from step c) at 200 to 250 C.

12. The method according to claim 11, wherein: the reinforcing insert is selected from the group consisting of polyamide 6, polyamide 66, polyethylene terephthalate, polyethylene naphthalate, rayon, aramide, cotton, basalt fibres, sisal, hemp, flax, coconut fibres, and mixtures thereof.

13. The method according to claim 11, wherein: the reinforcing insert is dipped, before step b), in an aqueous, solids-containing dipping bath composition which comprises at least one blocked MDI mixture or which comprises no other components besides the at least one blocked MDI mixture, the MDI mixture comprising MDI oligomers of formula (I), n being a whole number from 1 to 8, ##STR00005## and MDI monomers.

14. A method for producing a reinforced rubber product, which comprises the following steps: providing at least one layer of an adhesive reinforcing insert produced by the method according to claim 11; (ii) embedding at least one layer of an adhesive reinforcing insert from step (i) in a rubber matrix in a pressing mould; (iii) pressing the product from step (ii); (iv) vulcanising the product from step (iii) at 140 to 210 C. and 5 to 110 bar for 5 to 45 minutes; and (v) removing the reinforced rubber product from step (iv) from the pressing mould.

15. An adhesive reinforcing insert produced by the method according to claim 11.

16. A method of producing reinforced rubber products comprising utilizing the adhesive reinforcing insert according to claim 15.

17. A method for coating reinforcing inserts for rubber products comprising utilizing the aqueous, solids-containing dipping bath composition according to claim 1.

Description

1 Measuring Methods

(1) Within the scope of this application, the following measuring methods were used.

(2) Particle Diameter (d.sub.50 or d.sub.100 Value)

(3) The particle diameter was determined on a powder or on an aqueous dispersion according to ISO 13320 at 23 C. by means of laser diffraction. The laser measurements were implemented with a granulometer Cilas 1064 of Quantachrome GmbH (Germany).

(4) Peel Adhesion

(5) The peel adhesion was determined according to ASTM 4393. For this purpose, eight-layer test pieces with a symmetrical construction (2 layers of cord (=adhesive reinforcing insert)) and 6 layers of rubber, cf. FIG. 2, ASTM 4393) were produced. The tensile test was effected at a measuring temperature of 23 C. with a tensile speed of 20 mm/min. The tensile test was evaluated according to Option 1 of ASTM 4393. As rubber, the GB rubber of the company Wuxi Segen Rubber Tech. Co., Ltd, China (thickness 0.4 mm) was used. The vulcanisation was effected under three different conditions, 160 C., 100 bar for 12.5 minutes, 170 C., 100 bar for 15 minutes and 170 C., 100 bar for 30 minutes.

(6) Degree of Surface Covering

(7) The degree of surface covering after the peel adhesion test was determined by a visual examination by the corresponding tyre material being compared with internal patterns which had a covering of 0 to 100%. A covering of 0% means that the adhesive reinforcing insert has detached completely from the rubber after the peel adhesion test, i.e. the breakage was effected in the boundary layer between tyre cord and rubber. A covering of 100% means conversely that no detachment of the adhesive reinforcing insert from the rubber was effected, i.e. the breakage was effected in the rubber.

(8) Solids Content

(9) The solids content is determined by evaporation in a halogen drier (Mettler Halogen drier HR 73). For this purpose, approx. 3 g of the dipping bath composition is distributed uniformly on the shell base in an aluminium shell (diameter: 95 mm). The test duration is 25 minutes at 80 C. In the case of the type of display, the dry type dry content (100-0) is chosen. The average of three determinations is indicated.

(10) Number-Average Molar Mass (Mn)

(11) Determination of the number-average molar mass (Mn) is effected by means of GPC (gel permeation chromatography) with UV detection.

(12) For measurement, the samples are dissolved in THF (approx. 5 mg in 10 ml) and filtered into vials through disposable injection filters before filling.

(13) Device: Waters 2690 Alliance

(14) Software: Waters Millenium 32 GPC Module

(15) Column: PLgel 100 , particle size 3 m Length 30.0 cm Inner diameter 7.5 mm

(16) Wavelength UV detector: 254 nm

(17) Eluent: THF

(18) Flow rate: 1.0 ml/min

(19) The number-average molar mass (Mn) is determined with conventional calibration. The calibration is effected with polystyrene standards (masses 700, 1,100 and 2,000) and also laurinlactam (mass 197). Three determinations are implemented. The arithmetic mean of the molar mass is indicated in g/mol. The solvent THF with HPLC quality was obtained from EGT Chemie Switzerland. The disposable filters are obtainable at Macherey-Nagel GmbH & Co. KG, Germany, with the name Chromafil A-45/25 (pore size 0.45 m, filter diameter 25 mm). The disposable syringes are obtainable at VWR International GmbH, Germany.

2 Starting Materials

(20) The materials used in the examples and comparative examples are compiled in table 1.

(21) TABLE-US-00001 TABLE 1 Materials used in the examples and comparative examples CL-blocked MDI Aqueous dispersion of MDI mixture blocked with - mixture (A1) caprolactam and surfactant.sup.a) Solids content: 50% by weight Number-average molar mass M.sub.n of the MDI mixture blocked with -caprolactam: 740 g/mol Volume-average particle diameter: d.sub.50 = 1.2 m, d.sub.100 = 3.6 m Manufacturer: EMS-CHEMIE AG, Switzerland CL-blocked low- Aqueous dispersion of 4,4-diphenylmethane diisocyanate molecular blocked with -caprolactam and surfactant diisocyanate (A2) Solids content: 60% by weight Number-average molar mass of 4,4-diphenylmethane diisocyanate blocked with -caprolactam: 477 g/mol Volume-average particle diameter: d.sub.50 = 0.9 m, d.sub.100 = 3.0 m Manufacturer: EMS-CHEMIE AG, Switzerland RFL (B) Aqueous dispersion of resorcinol, formaldehyde, styrene- butadiene-vinylpyridine latex Weight ratio 1.0:0.6:9.2 Solids content: 20% by weight Manufacturer: EMS-CHEMIE AG, Switzerland Epoxide Glycerol triglycidyl ether, liquid Manufacturer: EMS-CHEMIE AG, Switzerland Defoamer Mineral oil-based defoamer, liquid Trade name: Surfynol DF-220 Manufacturer: Air Products and Chemicals Inc., USA .sup.a)The production of the blocked MDI mixture (A1) was effected by blocking the product Voronate M600 obtainable from DowDuPont with -caprolactam.

(22) A polyester cord (167012 dtex, ZS 380, 150) of the company Longlaville Performance Fibers SAS was used as substrate.

(23) As coating unit, a pilot unit of Mehler Engineering & Service GmbH, Fulda, Germany was used.

3 Examples and Comparative Examples

(24) In the following table 2, the results of the example and of the comparative examples according to the present invention are compiled.

(25) TABLE-US-00002 TABLE 2 Examples and comparative examples. Comparative Example examples Unit 1 2 3 Components CL-blocked MDI mixture (A1), Parts by 5 Solids content 50% by weight weight CL-blocked diisocyanate (A2), Parts by 4.2 4.2 Solids content 60% by weight weight RFL (B), Parts by 100 100 100 Solids content 20% by weight weight Epoxide, liquid Parts by 1.05 weight Defoamer, liquid Parts by 0.2 weight Water, deionised Parts by 95 95.8 94.55 weight Solids content of the dipping bath % by 11.3 11.3 11.9 composition weight Measurements Peel adhesion N/inch 160 C., 12.5 min, 100 bar 301 90 232 170 C., 15 min, 100 bar 242 75 191 170 C., 30 min, 100 bar 199 60 143 Degree of surface covering % 160 C., 12.5 min, 100 bar 20 0 7 170 C., 15 min, 100 bar 50 0 12 170 C., 30 min, 100 bar 38 0 7

4 Discussion of the Results

(26) The tyre cord according to the invention and illustrated in table 2 shows throughout a higher peel adhesion and a higher degree of surface covering than the tyre cords according to comparative examples 2 to 3 displayed in table 2. It is thereby noteworthy that, by using the dipping bath according to the invention, in fact even better adhesion properties and degrees of surface covering were achieved than was possible by the addition of epoxides.