WO2005080481A1

WO2005080481A1 - Resorcinol formaldehyde free dipping system

Info

Publication number: WO2005080481A1
Application number: PCT/EP2005/000673
Authority: WO
Inventors: Melchert Abbas; Michael Henricus Jacobus Van Den Tweel; Henri Willem Lion; Ronald Scholten
Original assignee: Diolen Industrial Fibers B.V.
Priority date: 2004-01-31
Filing date: 2005-01-25
Publication date: 2005-09-01

Abstract

The present invention relates to a resorcinol formaldehyde free dip composition used for adhering rubber to fibrous polyester material and to reinforcing elements carrying such a dip combination, wherein the dip composition is an aqueous dispersion of from 1 to 50 %, preferably from 1 to 20 %, by weight of solids consisting of (a) at least one rubbery latex component, (b) at least one water soluble or dispersible epoxide component, and (c) at least one water soluble or dispersible polyfunctional amine curing agent selected from primary, secondary and tertiary amines and mixtures of said amines. Further the dip compositions show a considerably longer shelf life. The invention is further directed to polyester reinforcing elements carrying resorcinol formaldehyde free dip composition and a process of making them. The resorcinol free dip offers the advantages of applying only a one-bath-dip process even to non-adhesive activated fibrous polyester materials and furthermore leads to better processibility and less deposit formation during processing in e.g. hose manufacturing.

Description

RESORCINOL FORMALDEHYDE FREE DIPPING SYSTEM

Description:

The present invention relates to a resorcinol formaldehyde free dip composition used for adhering rubber to fibrous polyester material and to reinforced elements carrying such a dip composition. The invention is further directed to a method for treating polyester reinforcing elements with such a resorcinol formaldehyde free dip composition.

In the context of this description the term "fibrous" refers to any embodiment having its origin from fibers in general. Examples are staple fibers or filaments, woven fabrics or nonwovens, twisted yarns or cords and so on.

When a fabric such as nylon, vinylon, rayon or polyester synthetic fibers is used as a reinforcing member for rubber articles such as pneumatic tires, belts, air cushions, hoses or rubber vibration insulators, it is necessary to firmly adhere rubber compounds to these synthetic fabric materials. The adhesive composition used for treating a large quantity of fabric materials is preferably non-inflammable and non-poisonous. From the above point of view, it is convenient and economical to use water as the medium for an adhesive composition. It is also desirable that the adhesive composition be durable and have a long shelf life. As the conventional adhesive composition for this purpose, there may be mentioned a mixture of a rubber latex and a condensed product obtained by the reaction of resorcinol with an aldehyde, particularly formaldehyde, in the presence of a catalyst such as an alkaline material or even an acid material (generally called "RFL"). This RFL has been and is widely used as an adhesive liquid suitable for mass production.

The difficulty in bonding polyester reinforcing elements, such as cords, to rubber is generally attributed to the presence of only hydroxyl (OH) and carboxyl (COOH) groups at the end of the polyester molecules, while in Nylon (for example) there is relatively high frequency of amide (CONH) groups along the macromolecular chain. Rayon and nylon are usually treated satisfactorily with a single step coating of an aqueous dispersion of an RFL, whereas simply dipping with an RFL system for polyester often is insufficient due to a low reactivity of polyester to resorcinol/formaldehyde.

To overcome this, so-called adhesive-activated polyesters are applied, which comprise a special adhesion promoting spin finish. As an alternative a comparable adhesion level can be obtained with the same RFL system as used for rayon and nylon, when applying a second dip step prior to the first dip. Such preceding activating step often involves application of water-insoluble reversibly blocked polyisocyanates (RBP) which, generally being solid, tend to precipitate in the baths in which the cord is dipcoated. An RBP is so termed because the reactive isocyanate (NCO) group is blocked against reaction at low temperature and then is regenerated when the temperature is raised, usually above 120 °C. The temperature at which a RBP will dissociate depends mostly on the blocking moiety (or substituting group).

In a typical two-step commercial process, polyester cord is dipped in a polyepoxide-containing first bath in which solid finely ground RBP is dispersed with the aid of a dispersing agent, excess RBP removed, dried and heat-set. Details of such a process are e.g. published in the U.S. Pat. No. 4,472,463.

The dips and dipping processes of the prior art suffer form various disadvantages, as to mention the instability of the polyisocyanates, the requirement of plural dips or the necessity to provide an adhesive-activated (pre-activated) fibrous material, in order to obtain sufficient adhesion. Further they suffer from a relatively short shelf life.

Moreover, the use of resorcinol formaldehyde (RF) containing dips often gives problems with deposit formation on braiding systems. This is due to a contamination by the RFL dip residues taking place during, e.g., the braiding of hoses.

The present invention seeks to resolve or at least to diminish these problems. Surprisingly, the object of the invention is achieved by a resorcinol formaldehyde free dip as described in the opening paragraph wherein the dip composition is an aqueous dispersion of from 1 to 50 %, preferably from 1 to 20 %, by weight of solids consisting of (a) at least one rubbery latex component, (b) at least one water soluble or dispersible epoxide component, and (c) at least one water soluble or dispersible polyfunctional amine curing agent selected from primary, secondary and tertiary amines and mixtures of said amines.

More preferably is a solid content from 4 to 13 % in the RF-free dip composition, an optimum with regard to some conventional rubbers, as outlined hereinafter is reached with a solid content between 4 and 7 % in the composition.

Although there are no isocyanates present in the composition according to the invention the adhesion to polyester is on a comparable level, even higher than with the conventional compositions both RF containing and RF-free. Remarkably, the adhesion level achieved when using non adhesive-activated PET fibrous material in connection with the RF-free dip composition according to the present invention is also comparable to the level obtained when applying the two- step process with the commonly used RFL dip respectively when using pre- activated PET. That means the second dip step and/or the pre-activation of the yarn can be saved without loosing adhesion capability, which is a significant advantage in terms of both time and money. For those skilled in the art it is clear that rubbery latex component used should be compatible with the rubber type to which adhesion is sought. To this end, it is preferred to use as rubbery latex component those latices that are based on vinyl pyridine (VP), ethylene propylene diene monomer (EPDM), butadiene acrylonitrile (NBR), chlorosulphonated ethylene (CSM), hydrogenated butadiene acrylonitrile (HNBR), chloroprene (CR), ethylene vinyl acetate (EVA), or blends or copolymers thereof.

The skilled person knows such components and he has no difficulties in choosing the right latex component for a specific rubber type. A detailed description of systems suitable for this purpose is given in T. Takeyama and J Matsui, Rubber Chem. Technol. 42, 159-256 (1969), which is incorporated herein by reference in its entirety.

In the frame of this invention it is especially preferred to use a copolymer based on butadiene, vinyl pyridine and styrene as rubbery latex component. An example of a suitable component is a copolymer consisting of 70% of butadiene, 15 % of vinylpyridine and 15% of styrene. Such component is e.g. offered under the trademark Pliocord® VP 106 by Eliokem, France.

For the epoxide component such components are very suitable that have an average of 2 or more epoxide groups per molecule. These components are also known to those skilled in the art. Examples for suitable epoxide components are triglycidyl isocyanurate; 1-epoxyethyl-3,4-epoxycyc!o-hexane; vinyl cyclohexene dioxide; ethylene glycol diglycidic ether; 1 ,2-propanediol diglycidic ether; 1 ,3- propanediol diglycidic ether; 2,3-butanediol diglycidic ether; and the glycidyl ethers of glycerol, erythritol, pentaerythritol, and sorbitol which contain two to three glycidic groups per molecule, for example, the diglycidyl ether of glycerol, the triglycidyl ether of hexanetriol and so forth. Still other epoxides can be used such as 3,4-epoxycyclohexyl methyl-3,4-epoxy cyclohexane carboxylate; 3-(3,4- epoxycyclohexane)-8,9-epoxy-2,4-dioxaspiro[5,5]-undecane; bis(2,3- epoxycyclopentyl)ether; bis(3,4-epoxy-6-methy!cyclohexyl methyl) adipate; the diglycidyl ether of polyethylene glycol 400; polyallyl glycidyl ether; the diglycidyl ether of bisphenol A; epoxy resorcinol ethers and the like. Further examples encompass the water soluble polyglycidyl ethers including the polyhydroxylated saturated aliphatic hydrocarbons of from 2 to 10 carbon atoms. Mixtures of these epoxides can be used. Preferred are the polyglycerin glycidyl ethers (CAS-No. 118549-88-5).

An example of a suitable epoxide component is a polymeric glycidyl ether which is offered under the naming GE 500 by Raschig, Germany.

The amine curing agents are well known to the art and are used as curing agents for the epoxides. Examples of such amines are polyfunctional primary and secondary amines and some tertiary amines including, for example, diethylene triamine, triethylene tetramine, dicyandiamide, melamine, pyridine, cyclohexylamine, benzyldimethylamine, benzylamine, diethylaniline, triethanolamine, piperidine, tetramethyl piperazine, N,N-dibutyl-1 ,3-propane diamine, N,N-diethyl-1 ,3-propane diamine, 1 ,2-diamino-2-methylpropane, 2,3- diamino-2-methylbutane, 2,4-diamino-2-methylpentane, 2-diamino-2,6- dimethyloctane, dibutylamine, dioctylamine, dinonylamine, distearylamine, diallyl amine, dioleylamine, dicyclohexylamine, methylethylamine, ethylcyclohexylamine, o-tolylnaphthylamine, pyrrolidine, 2-methylpyrrolidine, tetrahydropyridine, 2- methylpiperidine, 2,6-dimethylpiperidine, diaminopyridine, tetraethylene pentamine and metaphenylene diamine. Polyoxyalkyleneamines, also, can be used as well as polyethylenimines. Also effective in this invention are epoxide-curing agents such as diethylene triamine, triethylene tetramine, tetraethylene pentamine, polyethylene imine and m-phenylene diamine. Mixtures of said amines can be used. Particularly preferred is piperazine (synonym for diethylenediamine).

The dip composition according to the invention is easily prepared by mixing the above-mentioned components together in an aqueous medium. Usually the mixture is allowed to stand for about 12 hours at room temperature , i.e. undergoing a maturation phase. Afterwards it is ready to use and can be stored in a refrigerator. The shelf life is usually in the range from 4 to 10 days, but also much longer shelf lifes, up to 30 or even 60 days, have been witnessed. This fact leads to a considerable increase in comparison to the traditional RFL systems.

The ratios of the components relative to each other can be varied widely without departing from the scope of the invention.

It is, however, preferred, that the ratio by weight on a dry weight basis between the sum of the weights of the amine and epoxide components to the weight of the latex component is in a range from 0.1:1 to 3:1. A typical ratio reads 0.5:1.

As far as the overall amount of components is concerned, it is preferred that the amount of solids should be in the range from about 0.1 to about 50% by weight, preferably from about 1 to about 20% by weight, in the dispersion.

The present invention is further related to a polyester reinforcing element, carrying up to 20%, preferably up to 15 %, even more preferred from 0.1 to 10 %, by weight on a dry weight basis of said element of a heat cured or heat set adhesive composition, obtainable by treating a fibrous polyester material with a dip composition described above.

When dipcoating fibrous polyester materials, such as yarns, fabrics or cords with the claimed resorcinol formaldehyde free dip composition and subsequently adhering the coated material to rubber a rubbery polyester reinforcing element is obtained with peel adhesion values that are acceptable for a variety of end uses and mostly even come in the range of those obtained with the standard RFL dipping system, whereas the latter requires a two-dip system or a pre-activated yarn, in order to obtain the necessary adhesive-activation.

To this end the invention is also drawn to a process, which comprises treating a fibrous polyester material with a dip composition as described above. Although dipping is preferred, treating encompasses also other methods, known to the skilled person, to apply the composition according to the present invention to the fibrous polyester material, as e.g. spraying, brushing and kissing.

The selection of polyesters suitable for being treated by the dip according to the invention and present in the reinforcing elements are not restricted. On the other hand, it is preferred that the polyester is selected from a group consisting of polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene naphthalate or blends or copolymers therefrom. Usually the reinforcing elements are applied in rubber article, such as a pneumatic tire, a belt, an air cushion, a conveyor belt, a hose or a rubber vibration insulator.

The process according to the invention is also very suitable to be incorporated in standard fiber manufacturing processes, such as the well-known one-step spin- draw-winding processes, or the two-step processes, wherein spinning and drawing is separated. Drawing is for example performed by steam-draw-frames, hot plates or hot godets. The treatment of the fibrous polyester material in principle can be performed in any stage of such one- or two-step processes.

The invention is further outlined by the following non-limiting examples.

Table 1 provides an overview about various RF free dip compositions according to the invention.

Tab. 1 RF free dip compositions

Tab. 1 (cont'd.)

The dips listed in Tab. 1 were tested on different types of polyester yarns for adhesion to rubber.

The polyester yarns were Diolen® 855 T (non-adhesion activated) with a count of 1100 dtex, and Diolen® D890 (adhesion activated) with a count of 1100 dtex. Both polyester types were twisted in the construction 1100x3 Z130 and are commercially available from Diolen Industrial Fibers bv, the Netherlands.

After application of the dip solutions as described in Tab. 1 , the cords were dried for 120 s in a hot-air oven at a temperature of 110 °C and under a load of 7 N. This first drying step is followed by a curing step. This curing step is carried out in hot- air oven also, for 60 s at a temperature of 240 °C and under a load of 7 N.

As rubber types Dunlop® 5320, commercially available from Goodyear Dunlop Tires GmbH, Germany, and a natural rubber carcass compound were used. Adhesion performance was evaluated by measuring the strap peel adhesion force. The strap peel adhesion measurements of the rubber articles were performed according to ASTM D 4393-00 with the difference that the strip width is set to 20 mm instead of the 1" (= 25,4 mm) taken in the ASTM D 4393-00. This test method covers the determination of peel adhesion of reinforcing fabrics that are bonded to rubber compounds. In this peel test the force required to separate two fabrics vulcanized between thick rubber layers with a thin rubber layer in-between these fabrics (rubber thickness between 0.9 and 1.2 mm) is measured. This method is known to the skilled person.

The following tables 2 to 5 show the values obtained with the RF free dip composition. Note: S.D. stands for standard deviation. Tab. 2: Strap peel adhesion force (SPAF) with non-adhesion activated Diolen® 855T and adhesion activated Diolen® D 890 in Dunlop 5320

Tab. 3: Strap peel adhesion force (SPAF) with reference cord traditionally single bath RFL dipped: adhesion activated Diolen® 164S also commercially available from Diolen Industrial Fibers bv, 1100 dtex, x3 Z130 in Dunlop 5320

Tab. 4: Strap peel adhesion force (SPAF) with non-adhesion activated Diolen® 855T and adhesion activated Diolen® D 890 in a natural rubber carcass compound

Tab. 5: Strap peel adhesion force (SPAF) with reference cord traditionally single bath RFL dipped: adhesion activated Diolen® 164S, 1100 dtex, x3 Z130 in a natural rubber carcass compound

The deposit formation test on the braiding machine Herzog type 65330 was not done quantitatively. The deposit formation was judged by visual inspection of two guiding eyes. One at. the top of the baton support and one at the bottom/side of the baton support. The judgement of this visual inspection is give in table 6. Note that this inspection was done after 200 meters of braiding. The deposit formation on the braiding machine equipment was in all cases much lower than with the standard RFL dip composition.

Claims

Claims:

1. A resorcinol formaldehyde free dip composition for adhering rubber to fibrous polyester material, wherein the dip composition is an aqueous dispersion of from 1 to 50 %, preferably from 1 to 20 %, by weight of solids consisting of (a) at least one rubbery latex component, (b) at least one water soluble or dispersible epoxide component, and (c) at least one water soluble or dispersible polyfunctional amine curing agent selected from primary, secondary and tertiary amines and mixtures of said amines.

2. The dip composition according to claim 1 , wherein the ratio by weight on a dry weight basis between the sum of the weights of the amine and epoxide components to the weight of the latex component is in a range from 0.1 :1 to 3:1.

3. A process, which comprises treating a fibrous polyester material with a dip composition according to claims 1 or 2.

4. A polyester reinforcing element carrying up to 20%, preferably up to 15 %, by weight on a dry weight basis of said element of a heat cured or heat set adhesive composition, obtainable by treating a fibrous polyester material with a dip composition according to any one of the preceding claims 1 to 3.

5. The polyester reinforcing element of claim 4, wherein the polyester is selected from a group consisting of polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene naphthalate or blends or copolymers therefrom.

6. A rubber article, such as a pneumatic tire, a belt, an air cushion, a hose, a conveyor belt or a rubber vibration insulator, comprising a polyester reinforcing element according to claim 4 or 5.