CA2428327A1

CA2428327A1 - Impregnating and bonding agent for textiles

Info

Publication number: CA2428327A1
Application number: CA002428327A
Authority: CA
Inventors: Ralph Schaefer; Siegfried Wallenwein; Frank Scholl; Johann Wonner
Original assignee: Surface Specialties Germany GmbH and Co KG
Current assignee: Allnex Germany GmbH
Priority date: 2002-06-03
Filing date: 2003-05-08
Publication date: 2003-12-03
Also published as: PL360463A1; JP2004011090A; MXPA03004869A; RU2003116283A; US20040078900A1; KR20030093950A; BR0301585A

Abstract

Impregnating and bonding agent for textiles, comprising a mixture of a resorcinol-formaldehyde precondensate A, a rubber latex B and a melamine-formaldehyde resin C, impregnating process and reinforced rubber articles produced using the impregnates.

Description

Sclutia Germany GmbH & Co. KG
02/027 VDE - 1 - 04.14.2003 Dr.HD-ui Impregnating and bonding agent for textiles Field of the Invention This invention re1_ates to an impregnating and bonding agent for textiles, especially for reinforcing materials which are vulcanized into rubber.
Background of the Invention Textiles such as cords or fabrics based on rayon, polyamide, polyester, polyV.inyl alcohol, glass fiber and aramid fiber which are used as rein.forcemer_ts for rubber articles are customarily impregnated with latex baths which additionally contain resorcinol-formaldehyde resins.
Such baths are known as resorcinol-formaldehyde-latex or RFL dips. Impregnation serves to :impro~re the adhesion promotion between rubber and textile. ~'hus impregnated textil es have only i.n the outer edge zone (about 1%10-1/30 of the fiber or cord Cross section) a=~ impregnation layer which then promotes rubber adhesion during the vulcanizing operation. The interior of the fiber or cord is free of RFL impregnation, as a result of which the cord or fabric possesses good flexibility and has high fatigue resistance due to the preserved filamentary structure.
Textiles based on polyester or aramid, which by their chemical nature exhibit little adhesion to rubber, are customarily subjected to two-bath impregnations. The first impregnating step, which is likewise aqueous, is used to apply a small amount of an adhesion promoter such as blocked isocyana~es or epoxy resins to the textile structure. This is followed by the impregnation with a resorcinol-formaldehyde latex.

Sclutia Germany GmbH « Co. KG

RFL dips are frequently produced in-house by the processors from the ingredients. Resorcinol and formaldehyde are mixed in an. amount-of-substance ratio of 1:1.5 to 1:2; lifter about 6 hours of storage in an alkaline medium at room temperature, the resin solution formed is added to a latex containing natural rubber (NR} , styrene-butadiene rubber (SBR) or vinylpyridine copolymer rubber (VP) or a mixture thereof . After a further 12 to 24 hours of ~~ripening" at constant temperature, :,rhich is indispensable for uniform development of adhesion, the bath thus produced is used =or impregnating textiles.
Simpler handling is offered by precondensed resorcinol-formaldehyde resins, which are formulated together with i5 the rubber latex and acueous formaldehyde solution to form RFL baths, in that the ripening step can be omitted.
However, owing to their free formaldehyde content, neither type of bathldi~> is acceptable from. an occupational hygiene standpoint.
Summary of the Invention It is an object of the present invention to provide irnpreg:~ating agents which lead to similar results for the adhesion between rubber and textile reinforcements but contain little if any free forre~aldehyde.
This object is achieved by an impregnating and bonding agera which comprises a mixture of a resorcinol-formaldehyde precondensate, a rubber latex and a melamine-formaldehyde resin.
The present invention accordingly provides an impregnating and bonding agent for textiles for improving rubber adhesion, comprising a mixture of a resorcinol-Solutia Germany GmbH & Co. KG

formaldehyde precondensate A, a rubber latex B and a melamine-formaldehyde resin C.
The present invention further provides a process for producing a textile reinforcemer_t having enhanced adhesion to rubber, which comprises said textile reinforcement being treated with an impregnating and bonding agent comprising a mixture of a resorcinol-formaldehyde precondensate A, a rubber latex B and a melamine formaldehyde resin C and subsequently dried.
The present invention further provides rubber articles having enhanced adhesion between the textile reinforcement and the rubber, wherein sa'_d textile reinfcrcement has been impregnated with an impregnating and bonding agent comprising a mixture of a resorcinol-formaldehyde precondensate A, a rubber latex B and a melamine-formaldehyde resin_ C and has been vu~'~canized with a rubber mixture into a rubber article.
It is a further advantage of the invention that some of the costly resorcinol precondensate can be replaced by an inexpensive melamine resin. There is no longer any need to handle formaldehyde at all when making up the dips. It has also been determined that, surprisingly, the dips of the present invention Nave distinctly improved storage or aging stability compared with dips composed of resorcinol precondensates and rubber latex, bu.t not the melamine formaldehyde resin which is prese~:,t according to the present invention.
Detailed Description of the Preferred Embodiments The impregnating and bonding agent of the present invention is substantially free of formaldehyde. The mass fraction of free formaldehyde in the impregnating and Solutia Germany GmbH Fx Co. KG
bonding agent is preferably less than 0.5 0. The impregnating and bond;~ng agent preferably comprises resorcinol-formaldehyde precondensate A and melamine-formaldehyde resin C in a mass ratio (each based on solid resin) of 9:1 to 1:9, preferably 7:3 to 3:7 and more preferably 4:6 to 6:4. The ratio of the sum total of the masses of the solids of resins A ono. C to the mass of the solid of the rubber ir1 latex B (so7.ids mass fraction or rubber content about 35 to 45 cg/g; is preferably 1:1.5 to 1:15, more preferabl~,~ 1:1.7 to 1:10 and especially 1:2 to 1:9.
The resorcinol-formaldehyde precondensate A contains building blocks derived from formaldehyde and building blocks derived from resorcinol, the: amount-of-substance ratio of formaldehyde to resorcinol being 1:1.05 to 1:2, preferably 1:1.2 to 1:1.9 and especially 1:1.5 to 1_:1.8.
It is essentia,~ to maintain a stoichiometric deficiency of formaldehyde; this keeps the resin at low molecular weight and soluble. Optionally, up to 10 0 of the resorcinol can be replaced by other phenols, preferably dihydric phenols, provided the condensate prepared therefrom, remains soluble in water, ie when i g o.f resin is mixed with 100 g of water at room temperature no insoluble residue visible to the naked eye remains.
The latex B preferably contains a mass fraction of at least 5 °, in the solids fraction, of building blocks derived from 2-vir~ylpyridine. Copolymerized singly or multiply unsaturated comonomers furthe r include, in particular, styrene and butadiene. Lat_~ces of rubbers which contain building blocks of vinylpyridine are frequently known together as ~~vinylpyr idine latex" . Other monomers customary in rubber chemistry can be used as well, such as methylbutadiene, vinyltoluene, hexadiene and 5olutia Germany GmbH da Co. KG

also esters and other derivatives of acrylic acid.
According to the invention, it is possibl a to use mixtures of latices, provided at least one mass fraction of 10 is used of a latex which contains buildir_g blocks derived from vinylpyridine. Frequently, blends with natural rubber (NR) latex or styrene-butadiene rubber (SBR) latex are used. In general, however, it is also possible to use natural rubber 'latex, . SBR, CR or NBR l~~tex or su l table blends alone. Suitable lances are also commercially available from tire manufacturers or manufacturers of industrial rubber articles.
The melamine-formaldehyde -resin C is an unetherified condensate of formaldehyde and melamine, the amount-of-substance ratio between the building blocks derived from formaldehyde and melamine in the resin C preferably being between 1.5:1 to 6:1, nuore preferably between 1.8:1 to 3.8:1 and especially between 2.1:1 ~.rd 3.2:1. The resins C are preferably used as an aqueous :~clution of the pulverulent resins. Resins are referred to as unetherified when not more than 1p ~ of the N-methylol groups are etherified.
It is also possible for the reinforcements used in the rubber industry, for example fabrics or cords based on cotton, rayon, polyamides (nylon-6, n.ylon--6, 6) , polyester (polyethylene terephthalate?, aramid (m-phenyleneisophthalamide, p-phenylenet.erephthalamide) tc be coated with a pre-dip prior to the impregnation with the disclosed impregnating and bending agent which contains resorc-ono 1 resi:_, pre-dips customarily containing blocked isocyanates or epoxides in the form of aqueous dispersicns. The passage through each bath is followed by a thermal treatment (drying or curing). Combinations of 3~ epoxides and bloc'.~ed isocyanates are also effective.

Solutia Germar_y GmbH & Co. KG

Textile reinforcerments are, if necessary, impregnated with the above-described pre-dip solution by means of a suitable impregnating machine. The cord or fabric tension must here be adjusted such that good penetration of the impregnating solution into the cord or fabric structure is possible. Excess solut_on is removed by means of stripper devices cr_suction nozzles after passage through the impregnating bath. After the moist textiles have been dried, they are customarily subjected to a thermal treatment at 130 to 235 °C and p.referab.ly at 180 to 220 °C, in the course of which the to<~tiles are cptionally tensilized.
The optionally thus pretreated textiles are treated wish the above-described resorcinol-forma.ldeh~,~de rubber latex ;RFL; solution or dip in a second actual impregnating step, which can follow i~rmediately after '~~he pretreatment but may also be carried out after an intervening storage period.
The solids mass fraction of the RFL dip is in the range 10 to 35 o and pre-~erably 20 to 30 %. The choice of latex to be used should be made according to the solid rubber into which the impregnated textile is vulcanized. After passing through the impregnating- bath, the textile is initially dried in a drying zone and subsequently cured at 130 to 235 °C. The textile is then wound up and used for manufacturing the envisioned articles.
Thus impregnated reinforcements can be used for producing U-belts, spec_fically raw-edge V-bE:lts, transportation belts, hoses, membranes, automotive tires, in particular as a belt material. Cords which have been impregnated as described can further be subsequently processed into "cord _ ~ Solutia Germany GmbH & Co. KG

fabrics". The rubber articles produced using the thus prepared textiles can subsequently be cut to size, for example V-belts, transportation belts, hoses, membranes.
The inventi on will now be more particularly described with reference to examples. Hereinabove and hereinbelow, all gages are mass fractions (ratio of the mass of the substance in question to the mass of the mixture), unless otherwise stated. Concentrations in " o" are mass fractions of the dissolved substance in the solution (mass of the dissolved substance divided by the mass of the solution).
Examples Example 1(comparative) A conventional dip is prepared by mixing 200 g of a commercially available vinylpyridine latex (°Pliocord V 106 S, Goodyear Chemicals), 22.5 g of a resorcinol precondensate (~Penacolite Resin R 50, 50 o solution in water, Indspec Chemical Corporation), 6 ml of 25 % aqueous ammonia solution, 9 ml of 39 o aqueous formaldehyde solution and 255 ml of completely ion-frE:e water.
Example 2 (inventive) A dip according to the invention is prepared by mixing 200 g of a commercially available viny.lpyridine latex (°Pliocord V 106 S, Goodyear Chemicals),. 11.25 g of a resorcino~~ precondensate (°Penacolite Resir_ R 50, 50 0 solution in water, Indspec Chemical Corporation), 11.25 g of 50 o aqueous so",ution of an unetherified melamine resin having an amount-of-substance ratio of formalde~~yde to melamine of about 2.6:1, 6 ml of 25 o aqueous ammonia solution and 255 ml of completely ion-free water.

Sclutia Germany GmbH & Co. KG
_ g _ Example 3 (testing of adhesion to <~.ramid cord;
impregnation with unaged dips) A commercially available aramid cord (''JTwaron, 1680 1 2 2/S 250, Teijin Twaron BV) was impregnated with a dip as per example 1 and.a dip as per example 2. The loading (mass increase due~to~ impregnating agent, based on the mass of the impregnated cord after drying) was about r.5 0. The aramid cord was led through an impregnating tank, excess solution was stripped off_ and. the impregnated cord was dried in. a tubular oven at i00 °C in the course of a passage time of 1 minute; curing was carried out directly thereafter in a second tubular oven (residence time 2 minutes, 200 "C).
Example 4 (testing of adhesion to ag~amid cord;
impregnation with aged dips) Example 3 was repeated except that. the two dips were stored at room temperature (20 °C) for 14 days after preparation.
Adhesion testing:
The adhesion test was carried out as a T-test. An impregnated cord was placed between two rubber strips (composition see table 1) of equal thickness and the structure was vulcanized at 145 °C for 45 minutes. Before testing, the test specimens were stored at room temperature for 24 hours. A tensile tester was used to pull the cords our of the composite at ar. extension rage cf 300 mm/min. The results are summarizecin table 2.
The recipe of the rubber used was:

Solutia Germany GmbH s: Co. KG
-Table l: Rubber recipe Ingredients Mass in g per 100 g of rubber Natural rubber (NR) 100 Stearic acid 0.8 ~Vulkanox HS

(TMQ, 2,2,4-trimethyl-1,2- 0.8 dihydroquinoline, polymerized) ~Vulkanox 4010 NA

(IPPD; N-isopropyl-N'-phenyl- 0.6 p-phenylenediamine) Zinc oxide '7.0 Naftolen V 4055 (plasticizer oil) -7.0 Carbon black 43.0 Sulfur 2..8 "Rhenogran CTP 80 (N- 0.5 cyclohexylthiophthalimide) Vulkacit LDA (ZDEC, zinc 0.7 diethyldithiocarbamate) The measured result reported is the force per unit length at which yarn pullout was observed.

Solaria Germany GmbH & Co. KG

Table 2: Adhesion to aramid (length-specific pullout force E'~, in N/cm) Dip of example 1 2 m lil l09 FL (unaged) in N/c _ ~ X39 ~ _ _ 140 FT (aged) - in N/cm Whereas a conventional dip (resorcinol precondensate and formaldehyde together with vinylpyridine latex) gave ar._ acceptable adhesion value when freshly prepared, the adhesion value decreases by about 20 ~ to an unacceptable level after this dip has been stored for 14 days. In contrast, the dip according to the present invention, which starts from approximately the same fresh value, improved on storage by about 27 o in terms of adhesion performance. The dips according to the present invention can therefore remain in the baths even in the event of disruptior_s to the production process; the results do not deteriorate as a result. In the case of conventional dips, however, the baths have to be refilled after disruptions to the production process.
Example 5 Testing of adhesion to polyester cord Example 3 was repeated except that the aramid cord was replaced by a polyester cord. (1670 1 2 Z/S 340, KoSa GmbH & Co. KG). To test the stability in storage, a comparison was arranged as 1.n exampl.e 4 between freshly prepared dips (as per examples 1 and 2) and dips which, before the impregnating operation, were stored at room temperature for 14 days after preparation..
The predrying was carried out as above at 100 °C for 1 minute, and the caring was carried oui= at 230 °C for Solutia Germany GmbH s~ Co. KG

70 seconds. The results of the adhesion test, which was carried out as described above, are summarized in table 3.
Table 3: Adhesion to polyester (length-specific pullout force Fz in N/cm) Dip of example 1 2 F. (unaged) in N/cm 165 160 FT (aged) in N/cm 126 15~

There is no improvement in adhesion cn storage, but, within the margin of error, the adhesion. provided by the dip according to the present invention remains virtually unchanged (-4 0), while in the case of the conventional dip (example 1) the adhesion decrease's by about 24 o afters storage.
Example 6 (testing of aging at elevated temperature) The dip cf example 2 according to the present invention was used to carry out further aging ~est:7. The following adhesion values on polyester cord (as in example 5) were determined for v~he storage conditions specified in table 4:

Sclutia Germanv GmbH & Co. KG

Table 4: Adhesion to polyester (length-specific pullout force fL in N/cm) Storage _ Fr in N/cm directly after preparation 160 9 hours; 50 C 166 18 hours; 50 C 162 _ -~C? 153 _ i4 days; room temperature !20 9 hours; 50 C + 14 days; 20 C 142 18 hours; 50 C + 14 days; 2C C 140 It was found that the system according to the present invention provides advantages even on storage at comparatively high temperatures.

Claims

1. An impregnating and bonding agent for textiles, comprising a mixture of a resorcinol-formaldehyde precondensate A, a rubber latex B and a melamine-formaldehyde resin C.

2. The impregnating and bonding agent for textiles as is claimed in claim 1, wherein said resorcinol-formaldehyde precondensate A and said melamine-formaldehyde resin C are present in a mass ratio (each based on solid resin) of 9:1 to 1:9.

3. The impregnating and bonding agent for textiles as is claimed in claim 1, wherein the ratio of the sum total of the masses (solids fraction in each case) of said resins A and C to the mass of said rubber (solids fraction) in said latex B is 1:1.5 to 1:15.

4. The impregnating and bonding agent for textiles as is claimed in claim 1, wherein the amount-of-substance ratio in said resorcinol-formaldehyde precondensate A of the building blocks derived from formaldehyde and the building blocks derived from resorcinol is 1:1.05 to 1:2.

5. The impregnating and bonding agent for textiles as is claimed in claim 1, wherein the amount-of-substance ratio in said melamine-formaldehyde resin C of the building blocks derived from formaldehyde and these derived from melamine is between 1.5:1 to

6:1.

6. The impregnating and bonding agent for textiles as is claimed in claim 1, wherein said latex B contains a mass fraction of at least 5 %, in the solids fraction, of building blocks derived from 2-vinylpyridine.

7. The impregnating and bonding agent for textiles as is claimed in claim 1, wherein said latex B is a mixture of latices, at least one mass fraction of % being present of a latex which contains building blocks derived from vinylpyridine.

8. A process for producing a textile reinforcement having enhanced adhesion to rubber, which comprises said textile reinforcement being treated with the impregnating and bonding agent as claimed in claim 1 and subsequently dried.

9. A rubber article having enhanced adhesion between a textile reinforcement and said rubber, wherein said textile reinforcement has been impregnated with an impregnating and bonding agent comprising a mixture of a resorcinol-formaldehyde precondensate A, a rubber latex B and a melamine-formaldehyde resin C
and has been vulcanized with a rubber mixture into a rubber article.