MXPA98006702A - Improved adhesion between chlorosulfonated polyethylene rubber compounds and a polyester cord treated with resorcinol-formaldehyde-la - Google Patents

Abstract

A method for improving the adhesion of alkylated chlorosulfonated polyethylene (ACSM) and chlorosulfonated polyethylene (CSM) compounds to a polyester reinforcement element treated with resorcinol lateformaldehyde (RFL) using lower heat setting temperatures than conventional ones, which comprises immersing the element in an RFL bath comprising chlorosulfonated polyethylene, drying the element, heat fixing the element at a temperature in the range of about 149 ° C (300 ° F) to about 218 ° C (425) §F) under tension, incorporate the element to rubber compounds, and cure the element and rubber compounds. In addition, add an amine functional polyacrylate to the RFL bath that prevents cord adhesion failure at start temperatures of approximately -40 ° C (-40 ° C).

Description

IMPROVED AiPHESLON BETWEEN CHLOROSULATED POLYETHYLENE RUBBER COMPOUNDS AND A POLYESTER CORD TREATED WITH RESORCINOL-FORMALDEHYDE - LATEX.

TECHNICAL FIELD The present invention relates to a method for improving the adhesion of alkylated chlorosulfonated polyethylene (ACSM) and molded chlorosul polyethylene (CSM) compounds to a polyester reinforcing element treated with a resorcinol-formaldehyde latex (RFL). , and more particularly, this invention relates to the use of lower setting temperatures than conventional heat to fix a polyester cord for use in conjunction with an ACSM or CSM polymer system. In order to attach a rubber to a reinforcement material in products such as energy transmission belts and other reinforced rubber products, the common practice is to treat the material with an RFL latex bath to improve the bonding of the rubber to the material. Typically, the RFL bath is prepared by mixing an RFL pre-polymer with a latex. The RFL pre-polymer provides adhesion to the reinforcement material and the latex provides adhesion to the rubber. When the surface reactivity of the reinforcing material is low, as is the case with polyester cords, the cord is usually pre-treated with a composition that improves its reactivity. The compositions that have been used for this purpose include epoxy resins and isocyanates. Conventionally, the bands are prepared by joining a double twisted cord to the rubber. The cord is immersed in an RFL bath, immersed in a neoprene latex bath, and transported through a vertical furnace, where it is heated under tension for a predetermined period of time. This causes the cord to lengthen and restructure the polyester. This procedure is known as "strain elongation" or "heat fixation". This process dries the adhesives that are placed as coatings on the cord. Common RFL bath systems have also been developed for general purpose causative compounds, such as natural rubber and rubber-butyl rubber. For these rubbers, the latex used in the RFL bath is usually a terpolymer based on styrene, butadiene and vinylpyridine. For less reactive rubber compounds, such as ACSM and CMS, common 'RFL' bath systems are not suitable.

BACKGROUND OF THE INVENTION In a more conventional polyester cord treatment, the polyester cord receives an initial poli pheny1 isocyanate treatment with a tension of 3.63 to 6.81 kg. (8 to 15 pounds), which is activated by heat at a temperature in the range of 149 ° to 218 ° C (300 ° F to 425 ° F) for 120 seconds to react the functional groups of pol i feni 1 i Soc ianate with the open binding sites in the cord. An RFL adhesive is coated on the reacted polyphenylisocyanate and dried, preferably in an oven for 120 seconds at a temperature in the range of 82 ° C to 135 ° C (180 ° F to 275 ° F) to evaporate the RFL water and protect the RFL from bursting before fixing by cord heat. Heat fixation of polyester at 238 ° C (460 ° F) for 60 seconds occurs after the adhesive is applied and, therefore, the adhesives are subjected to this elevated temperature. The normal polyester cord treatment temperatures are 243-246 ° C (470-475 ° F). These temperatures are designed to achieve proper heat fixation and, therefore, optimal cord properties. These temperatures are close to the melting point of the polyester cord, which is in the range of 248 ° C to 254 ° C (478 ° F to 490 ° F). Experience has shown that the alignment of the optimal molecular structure in the polyester is achieved at 238 ° C (460 ° F) at a tension of about 3.63 to 6.81 kg. (8 to 15 pounds). The adhesion of the polyester to ACSM and CSM rubber compounds is poor at the normal heat setting temperature of 238 ° C (460 ° F). In this way, there is a problem when using these normal heat setting temperatures when joining ACSM or CSM to a polyester cord treated with RFL. It has been found that the adhesion of the polyester cord to ACSM and CSM rubber compounds is greatly reduced at the normal heat setting temperature of the polyester cord, since the RFL reacts vigorously therewith resulting in a crosslink density It approaches a complete state of healing by little, if any, available sites for the union with rubber. The prior art methods for adhering CSM to polyester cord have included the use of neoprene latex and latex lixine latex in the latex bath of RFL. U.S. Patent No. 3,060,078 to Atwell teaches a method for joining polyester cord fibers to a CSM rubber compound by treating the cord with a resorcinol-formaldehyde-neoprene latex adhesive composition prior to heat setting. cord treated with the CSM rubber compound. United States Patent no. 3,325,333 to Kigane et al, teaches a method for adhering a polyester cord to a CSM rubber compound by treating the cord with an aqueous sticky composition containing methylolated blocked organic polyisocyanate with a vulcanizable organic polymer at conventional or normal polyester treatment temperatures . Accordingly, there is a need for a method for improving the adhesion between ACSM and CSM rubber compounds to an RFL-treated polyester cord at lower heat setting temperatures than conventional ones.

DESCRIPTION OF THE INVENTION The present invention relates to a method for improving the adhesion of ACSM and CSM rubber compounds to an RFL-treated polyester reinforcement element, preferably a polyester cord, using lower heat setting temperatures than conventional ones. In a particular embodiment, the method for adhering a polyester cord to the ACSM or CSM rubber compound comprises: immersing the cord in an inorganic formaldehyde latex bath comprising molded chlorosul polyethylene; dry the cord; heat setting the cord to a temperature in the range of about 149 ° C (300 ° F) to about 218 ° C (425 ° F) under tension; insorporate the cord in the rubber compounds of ACSM or CSM; and curing the cord and the ACSM or CSM compounds.

The invention improves the adhesion of the polyester cord treated with RFL to ACSM and CSM rubber compounds by heat setting the cord at a lower temperature than conventional. By heat fixing the cord at a lower temperature, the crosslinking of the RFL is controlled so that good adhesion of the cord and rubber is obtained. This allows sufficient open bonding sites in the cord for the ACSM and CSM rubber compounds to be bonded in the band. This has found that the polyester cord properties are not significantly affected if the heat setting temperature is reduced, while the tension applied to the cord is increased. The modulus properties of the cord are significantly unaffected until the heat fixation temperature is reduced to 149 ° C (300 ° F). Accordingly, the object of the invention is to improve the adhesion of a polyester cord treated with RFL to rubber compounds of ACSM and CSM. According to another embodiment of the invention, an amine functional polyacrylate is added to the RFL bath. At lower heat setting temperatures than conventional ones, the crosslink density of the RFL may not be sufficient resulting in a cohesive failure within the same RFL. The internal crosslink density of the RFL is such that the strength of the rubber is greater than the strength of the inner number of internal RFL crosslinking sites. Therefore, it is a further object of this invention to reduce the RFL failure present in the ACSM / RFL and CSM / RFL systems at lower heat setting temperatures than conventional ones by using an amine functional polyacrylate in the RFL bath. The amine functional polyacrylate, surprisingly avoids the failure of RFL at cooler start temperatures on the scale from about -18 ° C (0 ° F) to about -40 ° C (-40 ° F) increasing the crosslink density of the ACSM and CSM rubber compounds. It is believed that the amine functional polyacrylate cross-links the RFL and the pretreatment with epoxy or isocyanate and bonds to the ACSM and CSM rubber compounds completely that the rubber breaks before the RFL fails.

DESCRIPTION OF THE PREFERRED MODALITIES The invention improves the adhesion of a polyester reinforcement element treated with RFL to ACSM and CSM rubber compounds by heat setting the cord at a lower heat setting temperature than conventional. The method for improving the adhesion between ACSM and CSM rubber compounds and the RFL-treated polyester cord, according to the invention, provides unexpected good results in rubber breakage and adhesion strength. The polyester reinforcement element can be any polyester cord conventionally used to form rubber reinforced products. Examples of such cords include Dacron 52 available from DuPont Company, type 775T available from Akzo Chemicals Inc. or type 865 available from Hoescht Celanese Corporation. As a result of the low surface reactivity of the polyester cord, it is desirable to pre-treat the cord with a pre-bath composition in order to improve the surface reactivity of the polyester cord. The preferred pre-bath composition comprises an isocyanate selected from the group including NR69 from Akzo Chemicals, Inc.; Bayhydrol 116 from Bayer AG of Germany or polyimethylene partners such as PAPI. PAPI is commercially available under the trade name Mondur MR or Desmodur VK-18 from Bayer AG of Germany. The pre-bath composition can be applied to the polyester cord by spraying, brushing or by dipping, preferably dipping. In preparing the pre-bath composition, it is necessary to use a solvent, preferably toluene. Since toluene is the preferred solvent, those skilled in the art will appreciate that equivalent solvents can be substituted for toluene. In preparing the pre-bath composition, it is desirable that the pre-bath composition comprises from about 2% to about 15% by weight of an isocyanate, and from about 85% to about 98% by weight of toluene. Preferably, the cord is immersed in the pre-bath composition at a temperature from about 149 ° C (300 ° F) to about 238 ° C (460 ° F) for about 1 to 2 minutes under tension.

After pre-treating the polyester cord with the pre-bath composition, the cord is then immersed in an RFL bath. The RFL bath is preferably prepared by mixing water, sodium hydroxide, resorcinol and formaldehyde and forming a pre-polymer and subsequently adding chlorosullated polyethylene, resulting in the RFL bath. Preferably, the RF / CSM ratio in dry weight is from about 0.08 to about 0.66. The chlorosulfonated polyethylene is commercially available under the tradename Hypalon 605 from Burke-Palmason Chemical Company. It is desirable that the RFL bath further comprises an amine functional polyacrylate. The addition of an amine functional polyacrylate to the RFL bath prevents the failure of cord adhesion in a power transmission band or other reinforced rubber products at starting temperatures of about -40 ° C (-40 ° F). It is believed that the amine functional polyacrylate cross-links the RFL and the amine functional polyacrylate and binds the rubber compound of ACSM or CSM. Preferably, the amine functional polyacrylate has a molecular weight in the range of about 5,000 to about 20,000. It is preferred that the amine functional polyacrylate be present in an amount in the range of about 2% to about 20% based on the total solids content. The amine functional polyacrylate is preferably moderated in water soluble form and has a pH of about 5.5 to 7.0. Preferably, the amine functional polyacrylate is a mixture comprising 50% by weight of polyacrylate and 50% by weight of water. It is believed that the polyacrylate reaction occurs at the amide site. Examples of preferred amine functional polyacrylates include polyamine, polyacrylamide, hydrolyzed copolymers or copolymers thereof, polyacrylamide, n-methylol acrylamide, n-isobutoxy-meth acri-lamide. It is desired that the polyester cord be submerged in the RFL bath and then dried for about 2 minutes at about 107 ° C (225 ° F). After the polyester cord has been immersed in the RFL bath and dried, the polyester cord is then heat set at a temperature in the range of about 149 ° C (300 ° F) to about 218 ° C (425) ° F) under tension. Preferably, the heat setting process occurs for about 60 to about 180 seconds under a bead tension of about 3.63 to about 8. 17 kg. (8 to about 18 pounds). It is desired that the polyester cord be incorporated into the ACSM or CSM rubber compounds and cured in a conventional manner to produce rubber bodies such as the energy transmission band. For a more complete understanding of the invention, the following examples are presented to illustrate specific uses of the techniques taught.

Example 1 Pre-Bath Composition The pre-bath composition was prepared by mixing 5% by weight of isocyanate and 95% by weight of toluene. RFL Bath The RFL bath was prepared by mixing 88.6% by weight of water, 1.2% by weight of 10% sodium hydroxide, 4.2% by weight of a 100% solid resorcinol, and 6.0% by weight of a solution of 37% formalin. The dry weight of resorcinol - formaldehyde in this solution is 2.90 kg. for 45.4 kg. (6.4 to 100 pounds) of solution. The components were mixed in order and stirred in each addition until each component dissolved well and mixed. The resin was aged for 6 hours at room temperature, stirred occasionally, resulting in an RFL pre-polymer. An aqueous solution of chlorosullated polyethylene comprising 34.4% water and 65.6% of a 50% Hypalon 45 solution was prepared. The CSM latex was added to the water and stirred until homogeneous. The RFL pre-polymer was added slowly to the aqueous solution of CSM, while continuously stirring the resulting solution. Approximately equal wet weight amounts of CSM / water and pre-polymer of RFL were combined. The resulting mixture had an RFL / CSM ratio of dry weight of about 0.19. The resulting RFL bath was aged for 96 hours before being used. Several polyester cords were soaked in the pre-bath composition at 177 ° C (350 ° F) for 2 minutes under a 4.54 kg cord tension. (10 pounds). The pre-moistened cords were then immersed in the RFL bath and dried in an oven at 107 ° C (225 ° F) for 2 minutes. Finally, the cords were fixed by heat at various temperatures in the range of 149 ° C to 246 ° C (300 ° F to 475 ° F) for 60 seconds under a tension of 6.81 kg. (15 pounds). After heat setting, samples were prepared in accordance with ASTM D1871, method B, except that the heat setting polyester cord was wound in a closely spaced form against a first ACSM rubber fold across the width of the mandrel. . A second ACSM fold was applied to the outer periphery as shown in Method B. After cutting samples with a width of 2. 54 cm (one inch) of mandrel bead interleaving and tested according to method B; the results were recorded as peak peel strength (measured in kilograms per centimeter in width (pounds per inch in width), and the estimated percentage of rubber retention in the cord.) The results reflect the averages of 10 identical samples taken from the same. polyester cord treated with ACSM / RFL that was fixed by heat at various temperatures.

TABLE I FIXING TEMPERATURE LIFTING IN POUNDS OF HEAT ° C (° F) BY ASTM D1871, METHOD B (LBS) ... (KG.) 149 (300) 36 16.36 163 (325) 37 16.81 177 (350) 39 17.72 191 (375) 42 19.09 204 (400) 38 17.27 218 (425) 34 15.45 232 (450) 18 8.18 246 (475) 11 5 Example 2 Several polyester cords were prepared according to Example 1 above. However, the laces joined CSM. The final CSM / RFL treated polyester cords were then subjected to various release forces in ASTM D1871, Method B to evaluate the performance of CSM bonding to the RFL-treated polyester cord by determining the percentage of CSM rubber retained by the cord. . The results reflect the averages of 10 identical samples taken from the same polyester cords treated with CSM / RFL. TABLE II FASTENING TEMPERATURE HEAT POINTS DEPTH ° C (° F) IN ASTM DI871, METHOD B (LBS) (KG.) 149 (300) 35 15.90 163 (325) 34 15.45 177 (350) 35 15.90 191 (375) 36 16.36 204 (400) 34 15.45 218 (425) 30 13.63 232 (450) 23 10.45 246 (475) 11 5 Example 3 The same procedure of Example 1 was followed. Polyacrylamide, supplied by American Cyanamid Company, was also added to the RFL bath. The polyacrylamide was a 7% polyacrylamide mixture based on a total solids content and 50% by weight of water. Several polyester cords were treated with the pre-bath composition at 350 ° F (177 ° C) for 2 minutes under a 4.54 kg cord tension. (10 pounds). The treated cords were immersed in the adhesive composition and dried at 107 ° C (225 ° F) for 2 minutes. Finally, the treated cords were fixed by heat at various temperatures in the range of 177 ° C to 218 ° C (350 ° F to 425 ° F) for 60 seconds. The final ACSM / RFL treated polyester cords were subjected to several release stresses in ASTM D1871, Method B both at -18 ° C (0 ° F) and 22 ° C (72 ° F) to evaluate the performance of union of the ACSM to the polyester cord treated with RFL at lower temperatures. The results reflect the averages of 10 identical samples taken from the same polyester cords treated with ACSM / RFL.

TABLE III FIXING TEMPERATURE DETACHMENT HEAT DEPTH ° C (° F) 22 ° C (72 ° F) -18 ° C (0 ° F) (KG.) (LBS) (KG) (LBS) (KG.) 177 (350) 39 17.72 38 17.27 191 (375) 58 26.36 64 29.09 204 (400) 34 15.45 39 17.72 218 (425) 18 8.18 25 11.36 232 (450) 14 6.36 21 9.54 Having described the invention in detail and referring to its preferred embodiments, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims.

Claims (12)

1. A method for improving the adhesion of a polyester reinforcement element to a polyethylene crossover polyethylene rubber compound, characterized in that it comprises the steps of immersing the element in an inorganic formaldehyde latex bath comprising orosulfurized polyethylene; dry the element; heat setting the element at a temperature in the range of about 149 ° C (300 ° F) to about 218 ° C (425 ° F) under tension; incorporate the element to the rubber compound; and curing the element and the rubber compound.

2. The method of claim 1, characterized in that the polyester reinforcement element is a polyester cord.

3. The method of claim 1, characterized in that the element is pre-treated with a pre-bath composition, such as a pre-bath composition comprising about 2% to about 15% by weight of polyphenylene polyisocyanate and about 85% to about 98% by weight of toluene, and the pre-bath composition can be applied to the element at a temperature in the range of about 149 ° C (300 ° F) to about 238 ° C (460 ° F). ) for 1 to 2 minutes approximately, under tension.

4. The method of claim 1, characterized in that the resorcinol-formaldehyde latex comprises a resorc inol-formaldehyde pre-polymer; the ratio of chlorosulfonated polyethylene in the range of about 0.08 to about 0.66 in dry weight.

5. The method of claim 1, characterized in that the heat setting occurs for about 60 to about 180 seconds and may occur at a cord tension of about 3.63 to 8.17 kg. (8 to about 18 pounds).

6. The method of claim 1, characterized in that the molded chlorosul polyethylene rubber compound is a polyethylene c-lucosullated alkylated rubber compound.

7. A method for improving the adhesion of a polyester reinforcement element to a chlorosullated polyethylene rubber compound, characterized in that it comprises the steps of: immersing the element in a resorcinol-formaldehyde latex bath comprising chlorosulfonated polyethylene and a polyacrylate functional of amine; dry the element; heat setting the element at a temperature in the range of about 149 ° C (300 ° F) to about 218 ° C (425 ° F) under tension; incorporate the element to the rubber compound; and curing the element and the rubber compound.

8. The rei indication method 7, characterized in that the amine functional polyacrylate has a molecular weight of from about 5,000 to about 20,000.

9. The method of claim 7, characterized in that the amine functional polyacrylate is a mixture comprising about 50% by weight of amine functional polyacrylate and about 50% by weight of water, whereby the amine functional polyacrylate can be present in an amount in the range of about 2% to about 20% based on the total solids content.

10. The method of claim 7, characterized in that the cured polyethylene rubber compound is a compound of alkylated polyethylene c 1 orosul fondant.

11. A reinforced rubber body comprising a matrix of a cured polyethylene c 1 orosul cured rubber or alkylated polyethylene composite, reinforced with a polyester reinforcing element, prepared by the rei indication 1 method.

12. A method for improving the adhesion of a polyester reinforcement element to a molded chlorosul polyethylene rubber compound, characterized in that it comprises the step of applying an inholor-formal resorc latex comprising chlorosul polyethylene embedded in the element; heat setting the element at a temperature in the range of about 149 ° C (300 ° F) to about 2183 ° C (425 ° F) under tension; incorporate the element to the rubber compound; and curing the element and the rubber compound.