DE1594006C - Improvement of the adhesion of rubber to reinforcement elements - Google Patents

Description

The lifespan of a rubber article reinforced with a natural or synthetic cord, z. B. a pneumatic tire, V-belt and the like., Depends on the bond strength between the cord and the rubber off ". The nature of the cord affects the durability of the bond, and it is like that Experience has shown that it is very difficult to connect a polyester cord to a rubber, especially when the reinforcing cord is to be used for the manufacture of pneumatic tires which . are subjected to extreme stresses at relatively high temperatures, as they are at high Speeds and the like can be developed.

It is known that polyisocyanates form a permanent adhesive bond between a polyester cord, for example and an associated rubber capable of producing. Polyisocyanates are however on Used in organic solvents because of their great sensitivity to water. at In the usual manufacture of pneumatic tires, it is more economical to use an aqueous adhesive system in contrast to a system that works with organic solvents. Thus, so far are polyisocyanates has only been used to a limited extent as a binder in the manufacture of pneumatic tires.

Polyisocyanates can be temporarily inactivated by the isocyanate group (- NCO) blocked with known blocking agents such as phenols and the like; yet such systems result not too high a bond strength. In addition, toxic by-products are formed when dealing with phenol blocked polyisocyanate is heated to regenerate the polyisocyanate.

It has been known to use a solution of a Bakelite-type resin crosslinked with a diisocyanate in a solvent for making coatings and forming a hard, paint-like film from a crosslinked resin. The crosslinking with diisocyanate takes place in order to form a water-resistant film with the specified properties. The film or product obtained in this way is attacked on the one hand at temperatures around 100 ^° C. and on the other hand undergoes no regression into the originally used polyisocyanate and resin, which was used to block the polyisocyanate at low temperatures, ^{at temperatures above about 100 ° C.} Generally speaking, this is a system that works with organic solvents (US Pat. No. 2,349,756).

The invention is now based on the object of creating a product that makes it possible due to its addition to conventional adhesives based on resorcinol and formaldehyde and rubber latex to overcome the particular difficulties that have hitherto been encountered with regard to permanent Bonding of rubber with reinforcing cords occurred especially with polyester cords.

The subject of the invention is the use of a water-dispersible addition product from a polyisocyanate and a water-soluble thermoplastic, made from an aldehyde and phenol, urea or melamine-made resin which has hydrogen reactive with the polyisocyanate, in addition to a common resorcinol formaldehyde rubber latex adhesive to improve adhesion of rubber on reinforcement elements.

In the case of the addition product used according to the invention, the polyisocyanate is protected, whereby the same received as a binding component and later brought into effect as soon as a with the Addition product covered reinforcing cord is heated together with a rubber for the purpose Connect the same. Furthermore, the addition product dispersible in water has due to its further conversion ability in the heat still the additional effect that there is a further reinforcement the bond of the cord to the rubber results, already made by the polyisocyanate -has been. Because of this double effect, there is a particularly strong and superior bond between the rubber and the polyester fibers or cords that are very difficult to permanently bond to achieved.

The polyisocyanates considered according to the invention are, for. B.

Polymethylene polyphenyl isocyanate,
Triphenyl methane triisocyanate,
2,4-tolylene diisocyanate,
■ 2,6-tolylene diisocyanate,
Bitolylene diisocyanate,
Dianisidine diisocyanate,
Hexamethylene diisocyanate,
m-phenylene diisocyanate,
1-alkylbenzene-2,4-diisocyanate,
l-alkylbenzene-2,5-diisocyanate,
2,6-dialkylbenzene-1,4-diisocyanate,
1-chlorobenzene-2,4-diisocyanate,
Dicyclohexylmethane diisocyanate,
3,3-dimethoxydiphenylmethane-4,4'-diisocyanate,
1-nitrobenzene-2,4-diisocyanate,
l-alkoxybenzene-2,4-diisocyanate,
l-alkylbenzene-2,6-diisocyanate,
m-xylylene diisocyanate,
1,3-dimethyl-4,6-bis (/ S-isocyanatethyl) -benzene-

diisocyanate,

Hexahydrobenzidine-4,4'-diisocyanate,
Ethylene diisocyanate,
Propylene-1,2-diisocyanate,
Cyclohexylene-1,2-diisocyanate,
S ^ '- DichloM ^' - biphenylene diisocyanate,
2,3-dimethyltetramethylene diisocyanate,
ρ, ρ'-diphenylene diisocyanate,
2-chlorotrimethylene diisocyanate,
Butane-1,2,2-triisocyanate,

Trimethylene diisocyanate,
Tetramethylene diisocyanate,
Butylene diisocyanate,
Ethylidene diisocyanate.

The second component of the addition product is made by reacting an aldehyde with urea, Phenol, preferably a polyhydric phenol such as resorcinol or especially phenolic resins, which are practically soluble in water. Suitable aldehydes for the formation of these resins are formaldehyde, Acrolein, glyoxal, furfural, crotonaldehyde, 'aldol and benzaldehyde. Suitable connections, which can be reacted with one of the aforementioned aldehydes are phenol, cresol, pyrocatechol, Phloroglucin, saligenin, di-ß-naphthol, xylenol, xylorcin, Hycroquinone, orcin, pyrogallol, ^ -naphthol, aminophenol, guaiac oil as well as urea and melamine.

In the production of the phenolic resin, it is advantageous if an excess of phenol is added during the reaction with the aldehyde. Characterized a Harzprödukt is obtained which causes at least in the reaction with the polyisocyanate a temporary blocking of the reaction ability of the polyisocyanate with water at temperatures of below 100 ⁰ C. In addition, this ensures the production of a resin that behaves chemically like an adhesive when the cord is bonded to rubber, here in conjunction with a rubber latex adhesive mixture when the polyisocyanate and the phenolic resin are regenerated by heating the blocked polyisocyanate.

A particularly preferred resin can be obtained by reacting resorcinol with formaldehyde at resorcinol-formaldehyde ratios from 1.0 / 0.25 to 1.0 / 1.0. In the manufacture of this particularly resinous formaldehyde-resorcinol blocking agent it is zv / square, a deficiency of formaldehyde, especially below 1, preferably between 0.5 and 0.75 to be used. The implementation of the resorcinol with the formaldehyde can either in a neutral or in a basic medium, e.g. B. with sodium hydroxide, as well as in an acidic medium, e.g. Using oxalic acid. It is beneficial to one To use resorcinol-formaldehyde resin, which is at a ratio of resorcinol to formaldehyde of 1.0: 0.7 in a neutral medium is.

In the following examples, the amounts are given in parts by weight, unless otherwise stated.

A. Preparation of the aldehyde resin

110 parts of resorcinol, 25 parts by volume of formalin (37% formaldehyde in methanol-water) and 20 parts by volume of water were reacted "in a vessel equipped with heating and cooling coils, a reflux condenser and a stirrer, the reaction vessel. The mixture was heated to reflux temperature (100 ⁰ C) and 15 At the end of this time, an additional 30 parts by volume of formalin was added continuously over 10 minutes, the mixture was refluxed for an additional 30 minutes and a resin formed in the reaction kettle which was allowed to cool to room temperature The result was a thick, syrupy resin (hereinafter referred to as resin A) with a solids content of 60%, a viscosity of 75OcP and a pH of 7. /

B. Production of an addition product from

Polymethylene polyphenyl isocyanate

20 parts of resin A, prepared according to Example 1, are with 6 parts of polymethylene polyphenyl isocyanate (PAPI) in a suitable reaction vessel as in Example 1 described type implemented 48 hours at 22 ° C.

Thereafter, the reaction mixture with a solution treated by 0.1 part of sodium hydroxide in 100 parts of water. The resulting neutralized blocked Polyisocyanate is referred to as Resin B in the following. After 8 hours of aging, a clear, protruding layer of the soluble blocked polyisocyanate, that of the less soluble blocked polyisocyanate Polyisocyanate existing precipitate can be separated.

C. Preparation of an addition product from

Triphenyl methane triisocyanate

20 parts of resin A were added to 3 parts of triphenylmethane triisocyanate. After that, the mixture became diluted with 100 parts of water. The reaction product Resin C does not need to be stirred. It is therefore directly as an adhesive component for • the production of an adhesive described in example 1 usable. Dilution with water can also be done by adding the water to the resin Addition of the polyisocyanate take place.

example 1
(Resorcinol formaldehyde rubber latex adhesive)

A commercially available cord adhesive that contains 20% solids is made using the following approach:.
R / F / L adhesive

Components Parts Resorcinol
Formaldehyde (37%)
Sodium hydroxide (10%)
Terpolymer rubber latex
Styrene / 1,3-butadiene / vinyl pyridine
15/70/15 (41%)
Mixed polymer rubber latex
Styrene / butadiene-1,3 (39%)
water 2.03
2.62
2.00
14.20
27.40
51.75

25 parts of resin B are added to 75 parts of the above resorcinol-formaldehyde rubber latex adhesive and the mixture is left to age at 22 ° C. for 4 hours. A reinforcing element made of commercially available polyester cord was treated with the adhesive described above by pulling the cord through the adhesive at such a rate that between 5 and 10% adhesive solids were deposited on the surface of the cord. This can be achieved by pulling the cord through the adhesive at a speed between about 1.50 to about 3 m per minute and then ^{drying the adhesive on the cord at a temperature of 218 °} C. for 2.5 minutes. The treated cord was embedded in a rubber material of the following composition:

Rubber material

Components Parts Natural rubber
zinc oxide
soot 100
3.00
29.80
2.00
7.00
1.25
3.00
0.15
1.00 Stearic acid
Pine resin
Mercaptobenzothiazole
sulfur
Diphenylguanidine
Phenyl-ß-naphthylamine

The heat was found to be 10.9 kg and the heat resistance to be 80 KC.

Example 3
(Resin B with R / F / L adhesive with excess aldehyde)

A resorcinol formaldehyde rubber latex adhesive was manufactured according to the following approach:

15th

The bond strength between the cord and the Kautsctmk was measured on a 0.634-cm "U" -probe at 121 ° C after curing of the rubber material 4minutigem at 204 ⁰ C; it was found to withstand a pull of 11.35 kg.

The O, 634 cm- 'U' test is defined as the dipped a measure of the binding strength between cord and rubber at 121 ° C (25O ⁰ F), wherein the two ends of a Kordschlaufe 0.634 cm in the rubber and for 15 minutes 154 ° C (310 ⁰ F) to be vulcanized. The force necessary to get the ends of the cord free from the rubber is reported as the hot U-strength value.

The heat resistance was measured by making a rubber tube made with reinforced a cord treated with the adhesive according to the invention in the manner described above had been. This pipe was subjected to a fatigue test set out in ASTM-D-885-59 T, Section 42 and U.S. Patent 2,412,524. It became a value of 200 KC found, compared to a bond strength of '5.45 kg and a value of 20KC that without the Using a resin-blocked polyisocyanate of the type used in the present invention.

One 840, / 2 nylon cord was used in place of the polyester and treated in a similar manner but dried for 3 minutes at 127 ° C and then at 210 ⁰ C 80 Sekünden. A "U" heat bond strength of 15.43 kg and a heat resistance of 600 KC were found, compared to the bond strength of 12.7 kg and a value of 440 KC for the same cord as that with the above R / F / L adhesive was treated without Resin B.

55

Example 2
(Blocked PAPI as a primer layer for cord)

A solution of the resin B was used as a primer coat for a polyester cord, the cord according to Example 1 being drawn through an immersion tank containing a 11% solid dispersion of the resin B and then the soaked cord directly into a second immersion tank, which is the usual R. / F / L adhesive of the type described in Example 1 with 20% solids content 'was drawn. The twice soaked cord was then dried ^{at 204 ° C. for 3 minutes.} The treated cord was then embedded in a rubber of the type described in Example 1. The bond strength in the

IO components

Resorcinol

Formaldehyde (37%)

Polymer rubber latex
Styrene / 1,3-butadiene / vinyl pyridine

'15 / 70/15 (41%)

water

Parts

98

53

1152
543

The R / F / L adhesive was prepared by dissolving 98 parts of resorcinol in 196 parts of water and then 53 parts of formaldehyde were added. The mixture was left to stand for 1 hour and then with 1152 parts of terpolymer rubber latex offset. The mixture was aged for 72 hours. After aging, the rest of the Added to water. To 65 parts of this R / F / L adhesive 35 parts of Resin B were added. The resulting adhesive mixture was aged for 24 hours calmly.

A reinforcement element made of a commercially available polyester cord M100 / 2 was used pulled through a dip tank containing the aged adhesive just described, and then Dried for 2.5 minutes at 227 ° C. The treated cord was incorporated into the rubber material of Example 4 embedded; it had a "U" bond strength of 11.8 kg in the heat and a heat resistance of 520 KC.

The phenol / aldehyde / synthetic rubber latex adhesive of Example 3 is deficient of formaldehyde, in contrast to the R / F / L adhesive of Example 1, in which an excess of formaldehyde was used. It was found that those with an adhesive in the example 3, the connection between cord and rubber produced better heat resistance values results. It thus follows that a compound with improved heat resistance is obtained, if an R / F / L adhesive is used in conjunction with an aldehyde resin-blocked polyisocyanate, whose ratio of formaldehyde to phenol is less than 1 and preferably in the range of 0.5 to 1.

Example 4

The conditions of Example 1 were repeated, only the resin C was used instead of the resin B, the tensile stress was found to be 14.75 kg.

Examples 5 to 10

The following table shows the O, 634 cm- 'U' -Klebefestigkeit at 121 ⁰ C, whereby the same curing of the material was made as in Example 1, at various resins with different to A using proportions of resorcinol and formaldehyde R / F resins produced are blocked.

Examples

7 8

Polyisocyanate

Resorcinol / CHjO ratio

1 / 0.25 series

1 / 0.50

1 / 0.70.

Solids

') Triphenylmethane triisocyanate.

² ) bitolylene diisocyanate.

³ ) 2,4-tolylene diisocyanate.

TMTI ¹ )

A 19.9

B 21.9

C 20.5

18th

TODI ²

16.7
20.5
21.5
13th

TDI ³ )

12.2
5

DADI ⁴ )

15.6
15.2
24.8
13th

Product M ⁵

16.0
15.4
19.0

PAPI ^b

18.9
21.0
18.1

⁴ ) dianisidine diisocyanate.

■ ⁵ ) reaction product of 1,2,3-trimelhylolpropane and 2.4-TDI.
^h ) polymethylene polyphenyl isocyanate.

Example 11

A conventional tubeless tire that consists of an open-bellied, hollow, annular body which is delimited by two spatially separated beads and is described in U.S. Pat. No. 2,987,094 is made by bonding several layers of polyester cord to the rubber were, the cord first impregnated with an R / F / L-blocked polyisocyanate adhesive of Example 1, dried at 204 ° C for 2.5 minutes and the dried cord a second time with a R / F / L adhesive of the type described in Example 1, but without the blocked polyisocyanate, impregnated and dried at 221 ° C for 1 minute.

The tire was tested by being inflated to a pressure of 10.9 kg and with 96.5 km each It was rolled against a wheel with a fixed axle for an hour, with a separation of layers after 8000 km. For comparison, the test was repeated with a tire using a rubber adhesive containing PAPI dissolved in toluene, with which the cord as the only adhesive soaked once before it was glued to the rubber in the manner described above; this tire held up only 4000 km stood.

The exceptional ones obtained using the blocked polyisocyanates mentioned in the examples Bond strength between rubber and a polyester cord is all the more surprising when consider that the same polyester cord used only with the traditional R / F / L adhesive that is used after Example 1 is used as the second soaking liquid, is soaked, has a tensile strength of only 5.5 kg and has a durability of only 25,000 revolutions.

209 682/189

Claims (2)

Patent claims: 1. Use of a water-dispersible addition product of a polyisocyanate and a water-soluble, thermoplastic, made of an aldehyde and phenol, urea or melamine produced resin, which has reactive hydrogen with the polyisocyanate, in addition to a common resorcinol formaldehyde rubber latex adhesive to improve adhesion of rubber on reinforcement elements. 2. Use according to claim 1, wherein the resin of resorcinol and formaldehyde in a molar ratio 1 / 0.25 to 1/1 has been made.