Dipping solution for cord fabrics

Abstract

The present invention relates to a formaldehyde and resorcinol free dipping solution for cord fabrics and a production method thereof comprising the steps of adding acrylic polymer resin into water (11), adjusting pH value (12), adding epoxy to the composition (13), adding polyisocyanate to the composition (14), adding latex to the composition (15), obtaining the dipping material (16); enabling the synthetic fiber and the rubber used in cord fabric reinforced rubber materials production to be attached to each other by providing an interface between two said materials; not as hazardous as RFL for human health and also being environmentally friendly.

Claims

1. A method for producing dipping solution, free of resorcinol-formaldehyde, for cord fabrics, comprising the steps of: adding acrylic polymer resin, wherein functional acrylic resin comprising carboxylic acid is used, into water, adjusting the pH value until pH 5-11 by adding ammonium hydroxide, adding epoxy to the composition, adding polyisocyanate to the composition, adding latex, wherein the latex is a vinyl pyridine (VP) latex and/or a styrene-butadiene (SBR) latex, and wherein the solid amount inside the latex is between 40-45% by weight, obtaining the dipping solution, wherein the dipping solution comprises the acrylic polymer resin in an amount of 0.1-2% by weight, the epoxy in an amount of 0.1-2% by weight, the polyisocyanate in an amount of 0.7-3% by weight, and the latex in an amount of 6-21% by weight, the remainder being ammonium hydroxide used for pH adjustment and water, and with the proviso that oxazoline functionalized polymers are excluded.

2. The method according to claim 1, characterized by the step of adding acrylic resin (polymer) into the water wherein at least one of the monomers such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, cinnamic acid, maleic acid is used as carboxylic acid.

3. The method according to claim 1, characterized by the step of adding acrylic resin (polymer) into the water wherein the carboxylic monomer molar feed ratio with respect to monomers containing polymerizable ethylenic unit is in the range of 0.1-100%.

4. The method according to claim 1, characterized by the step of adding epoxy into the composition wherein epoxy material is used as water soluble or water based dispersion.

5. The method according to claim 1, characterized by the step of adding epoxy to the composition wherein at least one epoxy selected from the group consisting of glycidyl based glycerol, sorbitol epoxy, phenol epoxy, cresol epoxy and epoxy water dispersion, is used.

6. The method according to claim 1, characterized by the step of adding polyisocyanate into the composition wherein a water based blocked polyisocyanate or a water based polyurethane polymer containing blocked polyisocyanate groups is used.

7. The method according to claim 1, characterized by the step of adding polyisocyanate into the composition wherein at least one of tetramethylene diisocyanate, hexamethylene diisocyanate (1,6-diisocyanatohexane), diphenyl methane 4,4-diisocyanate, octamethylene diisocyanate, decamethylene diisocyanate, dodecamethylene diisocyanate, aromatic diisocyanates including 2,4- or 2,6-tolylene diisocyanate, tetramethylxylylene diisocyanate, p-xylene diisocyanate, 2,4- or 4-4-diisocyanatediphenylmethane, 1,3- or 1,4-phenylene diisocyanate is present as part of the polyisocyanate.

8. The method according to claim 1, characterized by using as VP and/or SBR latex at least one latex selected from the group consisting of vinylpyridine-styrene-butadiene, vinylpyridine-styrene-butadiene modified with carboxylic acid, styrene-butadiene, and styrene-butadiene modified with carboxylic acid.

9. A dipping solution for cord fabrics obtained by the method according to claim 1.

10. A dipping process characterized by the steps of heat treating a cord, dipped with the dipping solution according to claim 9, for 30-60 seconds at 180-210 C., then for 60-120 seconds at 180-240 C.

11. A fiber processed by the process of claim 10, wherein the fiber is selected from nylon 6,6, nylon 6, polyethylene terephthalate, polyethylene naphthalate, rayon or aramide cord.

Description

(1) The dipping material for cord fabrics and the production method thereof developed to fulfill the objective of the present invention is illustrated in the accompanying FIGURE, in which;

(2) FIG. 1 is a schematic flowchart illustrating the method according to the present invention.

(3) In general, the production method for the dipping solution for cord fabrics (10) comprises the steps of: adding acrylic resin (polymer) into water (11), adjusting pH value (12), adding epoxy to the composition (13), adding polyisocyanate to the composition (14), adding latex to the composition (15), obtaining the dipping material (16).

(4) In the production method for dipping material for cord fabrics (10) according to the present invention, first, a functional acrylic resin (polymer) material comprising carboxylic acid is added into the water (1). Regarding the functionality of the resin comprising carboxylic acid, at least one of the monomers such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, cinnamic acid, maleic acid is used. In a preferred embodiment of the invention, such carboxylic monomer molar feed ratio with respect to monomers containing polymerizable ethylenic unit is between 0.1-100%.

(5) In accordance with the present invention, the presence of oxazoline groups is excluded, i.e. oxazoline functionalized polymers are excluded.

(6) Exemplarily, the acrylic polymer is a self-crosslinking polycarboxylic acid which contains triethanolamine as crosslinking agent.

(7) In the final dipping solution material, the acrylic polymer represents a major reactive component which alters the final microstructure of the polymer network obtained after curing, i.e. in the subsequent process where the cords are prepared. In the absence of the polymer comprising carboxylic acid, the adhesive performance of the dip solution decreases.

(8) Then, the pH value of this composition comprising water and acrylic polymer is adjusted (2). According to the invention, ammonium hydroxide is added to the composition until the pH value of the composition is 5-11. In cases where pH is below 5, the homogeneity of the dipping solution is disturbed as observed in the form of local agglomerations.

(9) After the pH is adjusted to the desired level, epoxy is added into the composition (3). In a preferred embodiment of the invention, the epoxy which is used is water soluble or a water based dispersion. At least one of the materials such as glycidyl based glycerol, sorbitol epoxy, phenol novolac epoxy, cresol novolac epoxy is used as epoxy. However, the actual use is not limited to these. Any epoxy which is water soluble or can be prepared in dispersion can be used in this invention. When the dipping material composition does not contain the epoxy compound, the adhesion between the composition and the fiber cords decreases.

(10) Then, polyisocyanate is added to the composition (4). In a preferred embodiment of the invention, the polyisocyanate is water based and contains thermally dissociating blocked isocyanate groups, for example caprolactam blocked. At least one of tetramethylene diisocyanate, hexamethylene diisocyanate (1,6-diisocyanatohexane), diphenyl methane 4,4-diisocyanate, octamethylene diisocyanate, decamethylene diisocyanate, dodecamethylene diisocyanate, aromatic diisocyanates including 2,4- or 2,6-tolylene diisocyanate, tetramethylxylylene diisocyanate, p-xylene diisocyanate, 2,4- or 4-4-diisocyanatediphenylmethane, 1,3- or 1,4-phenylene diisocyanate is present as part of the polyisocyanate. In a preferred embodiment of the invention, the polyisocyanate is caprolactam-blocked 4,4-methylene diphenyl diisocyanate or a water based polyurethane prepolymer containing blocked isocyanate groups and having a molecular weight range of 1000-10000 g/mol, particularly between 1500-3000 g/mol. In the absence of a blocked isocyanate, the adhesive performance of the dipping solution decreases.

(11) After the addition of polyisocyanate, latex is added (5). The latex employed comprises butadiene, styrene, and optionally vinyl pyridine monomers. That is, it can be either but not limited to VP latex with monomer ratios of styrene (15%), butadiene (70%) and vinyl pyridine (15%) and/or SBR latex with monomer ratios of styrene, (25%) and butadiene (75%). The solid amount inside the latex is between 40-45% by weight.

(12) The dipping solution is obtained by adding all materials mentioned in the previous steps into the water at room temperature and stirring it (6). Thus, according to the present invention the four components (acrylic polymer, epoxy, polyisocyanate, latex) are employed at the same time, i.e. in a single step.

(13) According to the invention, the dipping solution comprises the acrylic polymer resin in an amount of 0.1-2% by weight, the epoxy in an amount of 0.1-2% by weight, the polyisocyanate in an amount of 1-3% by weight, and the latex in an amount of 6-21% by weight, the remainder being ammonium hydroxide used for pH adjustment and water.

(14) The dipping solution prepared by the inventive production method for cord fabrics (10) can be used for dipping cords such as nylon 6.6, nylon 6, polyethylene terephthalate, polyethylene naphthalate, rayon, aramide, and it is not limited to these. After the cords are prepared in certain constructions (ply number and twist), they are dipped into the inventive dipping material, then dried and cured at between 180-240 C. Subsequently, the dipped cords are pressed into the non-vulcanized (green) rubber composition in molds. This composite material is then cured typically at 170 C. under pressure for about 20 minutes to obtain the final cord.

(15) For exemplary purposes, different acrylic polymers, epoxies and polyisocyanates were used in different ratios and 8 compositions were prepared. The related table is given as Table 1. In said Table 1 below, the strip adhesion values of 8 different mixtures, the composition ratios of which are different, and one Resorcinol-Formaldehyde-Latex (RFL) adhesive solutions are compared.

(16) Table 2 herein below shows a table wherein the effects of resin (acrylic polymer, epoxy and polyisocyanate) composition, the absence of resin components (consequently, Examples 2, 3 and 4 in said Table 2 are not in accordance with the claimed invention), oven temperature and total exposure time of the cord in heat treatment ovens are shown and compared with RFL adhesive solution. The strip adhesion values are indexed according to strip adhesion value of Resorcinol-Formaldehyde-Latex (RFL) adhesive solution.

(17) In an exemplary embodiment of the composition, the amount of solid is determined as 15%, and pH is adjusted to 10 by adding ammonium hydroxide. The inventive dipping solution was used in dipping 2-plied, 1400 dtex value, 396396 twisted nylon 6.6 cords. The dipped cords were first heat treated for about 30-60 seconds at about 180-210 C., then for about 60-120 seconds at about 180-240 C., particularly at 220-240 C.

(18) Acrodur 950 and 3515 were used as aqueous acrylic functional polymer solution and dispersion, respectively. Both Acrodur 950 and 3515 comprise modified poly(acrylic acid) and polyalcohol with a final solid content of 50%.

(19) EX313 and EX614B were used as water-soluble epoxies. EX313 is a glycerol based glycidyl epoxy, and EX614B is a sorbitol based glycidyl epoxy resin.

(20) Grilbond IL-6 or BN-27 were used as blocked polyisocyanate. Grilbond IL-6 is a water based caprolactam blocked 4,4-methylene diphenyl diisocyanate with 60% solid content. BN-27 is a water-based, blocked isocyanate containing polyurethane prepolymer with 30% solid content.

(21) The solid contents of VP and SBR latexes are 41%, and their pH values are about 10-11.

(22) With the dipping solution production method according to the present invention, it is possible to obtain a RF free dipping solution for rubber composites by using environmentally friendly chemicals. Furthermore, this method provides opportunities such as cost and time saving. Since the final product is white, it is aesthetically appealing and also enables cord fabrics to be produced in various colors with pigment additives.

(23) Within the framework of these basic concepts, it is possible to develop various embodiments of the inventive dipping material for cord fabrics and a production method thereof. The invention cannot be limited to the examples described herein and it is essentially as defined in the claims.

(24) TABLE-US-00001 TABLE 1 Acrylic Examples of Functional polymer Epoxy Polyisocyanate Latex Strip adhesion compositions acrylic polymer Epoxy Polyisocyanate (%) (%) (%) (%) (indexed) 1 Acrodur 950 EX313 IL6 0.64 0.85 1.51 12.00 102 2 Acrodur 950 EX313 BN27 0.26 0.35 2.39 12.00 88 3 Acrodur 950 EX614 IL6 0.69 0.68 1.63 12.00 66 4 Acrodur 950 EX614 BN27 0.27 0.26 2.47 12.00 90 5 Acrodur 3515 EX313 IL6 1.06 0.70 1.24 12.00 91 6 Acrodur 3515 EX313 BN27 0.48 0.32 2.20 12.00 84 7 Acrodur 3515 EX614 IL6 1.13 0.55 1.32 12.00 93 8 Acrodur 3515 EX614 BN27 0.50 0.24 2.26 12.00 89 Control RFL 100 Amounts shown are the solid-based weight percent of each constituent, and the remainder is ammonium hydroxide used for pH adjustment and water.

(25) TABLE-US-00002 TABLE 2 Acrylic Examples of Functional polymer Epoxy Polyisocyanate Latex 1.sup.st Oven Exposure time Strip adhesion compositions acrylic polymer Epoxy Polyisocyanate (%) (%) (%) (%) ( C.).sup.a (sec).sup.b (indexed) 1 Acrodur 950 EX313 IL6 0.38 1.16 1.96 14.00 200 135 102 2 Acrodur 950 EX313 0.43 1.31 0.00 15.77 200 135 85 3 EX313 IL6 0.00 1.19 2.00 14.31 200 135 96 4 Acrodur 950 IL6 0.41 0.00 2.10 14.99 200 135 88 5 Acrodur 950 EX313 IL6 0.38 1.16 1.96 14.00 150 135 60 6 Acrodur 950 EX313 IL6 0.38 1.16 1.96 14.00 190 135 95 7 Acrodur 950 EX313 IL6 0.38 1.16 1.96 14.00 240 135 95 8 Acrodur 950 EX313 IL6 0.38 1.16 1.96 14.00 200 50 50 9 Acrodur 950 EX313 IL6 0.38 1.16 1.96 14.00 200 90 103 10 Acrodur 950 EX313 IL6 0.38 1.16 1.96 14.00 200 160 107 Control RFL 100 Amounts shown are the solid-based weight percent of each constituent, and the remainder is ammonium hydroxide used for pH adjustment and water. .sup.aThe temperatures of 2.sup.nd and 3.sup.rd oven are kept constant at 220-240 C. .sup.bTotal time the cord is exposed to heat.