BRPI1103271A2 - adhesion process between at least one elastomer and at least one substrate and footwear comprising at least one elastomer and at least one substrate - Google Patents

Abstract

"Process of adhesion between at least one elastomer and at least one substrate, and footwear comprising at least one elastomer and at least one substrate". The present invention discloses an adhesion process between at least one elastomer and at least one substrate, characterized in that said adhesion is by applying pressure between said elastomer and said substrate, and wherein said elastomer comes from a pre-process. specific treatment. Additionally, the present invention relates to a process of manufacturing a footwear sole, preferably sneakers, by said innovative process.

Description

ADHERENCE PROCESS BETWEEN AT LEAST ONE ELASTOMER AND AT LEAST ONE SUBSTRATE, AND SHOE UNDERSTANDING AT LEAST ONE ELASTOMERO AND AT LEAST ONE SUBSTRATE

TECHNICAL SECTOR

The present patent application refers to a process

adhesive bonding of an elastomer and a substrate, particularly for the manufacture of footwear, more particularly sneakers.

BACKGROUND There are several processes in the art that propose the

union between an elastomer and a substrate. Among the most well-known processes we can mention the bonding of already vulcanized elastomers through adhesives, being called "post-vulcanization bonding". Another process that is widely known in the art is the bonding between an elastomer in contact with a substrate during vulcanization of the elastomer, this process being termed "bonding by vulcanization".

The post-vulcanization bond comprises an already vulcanized elastomer and an adhesive layer which has an interaction

20 between the surface of the elastomer and the surface of the

substrate to which the bond will occur. In this process, various types of adhesives can be used, with the possibility of optimizing several variables according to the manufacturer's needs. The adhesive may have additives / curing agents to facilitate interaction with any of the components of the assembly and there are almost a multitude of possible combinations of adhesive systems, substrates, elastomers.

The post-vulcanization bonding process through

3 0 Stickers Offers A Lot Of Benefits Over Others

joining processes of the technique, among the main ones: the realization of a homogeneous distribution of load throughout the joining area, invisibility within the joining, not disturbing the elastomer damping capacity, the possibility of joining even in complex shapes and the ability to optimize adhesive formulations to adapt to the most diverse contact surfaces.

Already the process of bonding by vulcanization is a

The process in which the bonding occurs during vulcanization and thus generates a specific chemical interaction between the substrate and the elastomer. The factors that lead to this interaction are mainly vulcanizing agents and the high temperature required by the process.

Such a process can provide a very strong bond when compared to other bonding processes and their costs are greatly reduced due to the reduction of steps required for bonding and the lack of specific bonding materials for bonding. The main disadvantage of this process is the lack of diversity between compatible types of elastomers and substrates and this process is often used for joining elastomers and metals or fibers only. 2 0 The ease of adhesive bonding will depend greatly

the surface characteristics of the elastomer during the moment of joining. Rubber follows a line of materials that generally require surface treatment prior to final bonding, mainly due to the presence of interaction with the vulcanization mold and plasticizers or extenders that may have migrated to the surface thereof. Among the main treatments used in the footwear sector today are chemical surface treatment (eg elastomeric surface halogenation),

roughness / abrasion or both.

Halogenation is the application of a halogenating solution, most often the base of trichloroisocyanuric chloroacid, in order to provide adequate chemical compatibility of the adhesive to be applied to the elastomer surface. Halogenation, however, eventually releases solvent vapors, and it is often desired that there be a process that can achieve proper adhesion, but without such waste emissions. Additionally, the present process entails an increase in the production costs of the sole, the need to be careful to avoid impregnation of the solvent inside the elastomer, and to be another step that must be performed on it. Another type of surface treatment is roughness,

where a mechanical abrasion (e.g. with steel brushes) of the elastomer surface occurs in order to prepare it for further interaction between the surface of said elastomer and the adhesive / primer and / or halogen groups incorporated through the halogenation process. This greater interaction occurs by removing oxidized impurities present on its surface and by opening "pores" in the elastomer, facilitating interaction with an adhesive layer. The asperation process, however, leads to problems such as a lack of homogeneity in the formation of reactive groups on the surface and the deposition of solid residues and particles from the asperation process, which requires a later step of their removal from the surface. of the elastomer with a solvent, ie one more residue. During both of these steps occurs the generation

solid waste and solvent vapors, as well as losses due to operational errors.

There are several proposals for performing a suitable process of joining an elastomer with a substrate through an adhesive among them:

US651203 9 discloses methods of attaching a curable peroxide elastomer to a metal surface comprising coating the substrate with an adhesive composition, drying the adhesive composition, applying a cured peroxide elastomer to the adhesive composition coating, and curing the assembly with heat and / or pressure. whereby the joining between the layers is performed during the vulcanization process of the assembly. However, the present document refers to the use of halogen-containing adhesives only, the substrates undergo abrasion prior to the application of adhesive and the process specifically refers to metal substrates. US5906872 describes the formation of a bond

between relatively elastic materials to relatively inelastic materials. Particularly between rubber (elastomers) and plastic materials. The document discloses relevant aspects regarding the adhesive bond between an elastomer and a shoe sole substrate.

US 6,328,840 describes a process which preferably uses a rubber composition for adhesion between the rubber layers to be bonded. Adhesion being achieved through vulcanization of the assembly. Document 20 further discloses that the adhesion rubber layer must have an amount of vulcanizing agent greater than the amount of vulcanizing agent of the rubbers which will be joined, thus there being an interaction between the layers during the vulcanization process. However, there is still a need for a

A process for the adhesive bonding between an elastomer and a substrate for all the particulars inherent in the needs of a shoe sole and which have the guarantees of bonding strength, abrasion resistance, flexural strength, gripp, recommended hardness, resistance to aging and light fastness. In addition, there is a need to find a process that can provide adequate adhesion for said purposes, avoiding or completely excluding elastomer pretreatment steps prior to bonding such as halogenation and grinding / abrasion, thus producing an environmentally improved process with respect to the technique.

BRIEF DESCRIPTION OF THE INVENTION

Thus the present invention aims to solve the problem of the technique of using the chlorination (halogenation) and / or roughing processes during the bonding process between an elastomer and a substrate and at the same time provide a process that can achieve a proper bond between a elastomer and an adhesive layer for successive bonding to a substrate, thus offering a low cost and environmentally friendly process. Particularly the said process aims at the production of footwear soles, mainly sneakers. The improved union between an elastomer and a layer

Adhesive is resolved by a pretreatment process of an unvulcanized elastomer with a uniform layer of adhesive according to an innovative process, followed by vulcanization of the elastomer and adhesive assembly. This last step allows a greater interaction between both layers and increasing the permeability of the adhesive in the elastomer as well as increasing the adhesion between them.

The present invention is generally defined as an adhesion process between at least one elastomer and at least one substrate, wherein said adhesion is by applying pressure between said elastomer and said substrate, and wherein said elastomer comes from the steps of :

heating an unvulcanized elastomer at a temperature between 40 and 50 ° C; 3 0 - application on said non-elastomer

vulcanized from a uniform layer of cross-linked polycaprolactone resin-based polyurethane adhesive between 0.1% and 5% of the aromatic polyisocyanate-based crosslinker; drying the non-vulcanized elastomer / adhesive assembly until said assembly is substantially solvent free;

vulcanization of the elastomer / adhesive assembly at a temperature between 60 and 180 seconds and a temperature between 150 and 190 ° C;

applying on the vulcanized elastomer / adhesive assembly a uniform layer of cross-linked polycaprolactone resin-based polyurethane adhesive between 0.1% and 5.0% of the aromatic polyisocyanate-based crosslinker;

elastomer assembly drying

vulcanized / adhesive until said assembly is substantially solvent free; and - heating of the assembly to temperatures between

50 ° C and 900 ° C.

DETAILED DESCRIPTION OF THE INVENTION In the context of the present patent application which reads "elastomer" it should be understood as a polymer capable of extending its length (deformation) several times and returning almost entirely to its original size.

In the context of the present patent application which reads "vulcanization" it is to be understood as a process consisting of promoting crosslinked bonds, i.e. a rubber crosslinking process which will be transformed from a thermoplastic to a thermoset.

In the context of this patent application which reads "substrate" it is to be understood as the component to which the elastomer will be further joined. 3 0 In the context of the present patent application where

"adhesive" is to be understood as a liquid or semi-liquid used to aid bonding / bonding between at least two components. In the context of the present patent application which reads "adhesive bond" is meant the same with a bond between at least two components where at the interface between the at least two components is an adhesive.

In the context of the present patent application where

reads "crosslinker" is to be understood the same as a chemical which when added to an adhesive provides a reaction of its molecules together, thus forming a large conglomerate of molecules pressed together through said crosslinker.

In the context of the present patent application which reads "pressure application" it is to be understood as applying pressure between at least two components in order to promote contact between them by any methods commonly found in the art and which are suitable. for the desired purpose.

When thinking about the adhesive bond between elastomers and an adhesive layer, one must first think about the interactions at the interface of both. Particularly the surface properties of the elastomer should be taken into account as they provide predictions of probable adhesion strength. The adhesive layer must effectively penetrate the elastomer surface and the thermodynamic relationship between penetration and surface energy of the elastomer is broadly defined according to the formula below:

>,> 7 for proper penetration to occur

Io (substrateJ '(adhesive) ^ r τ -a

Thus, mechanisms that act to alter one of the variables and increase the energy difference between both layers will increase the interaction and the adhesion force.

The present invention acts to enable

greater penetration of an adhesive layer on the surface of the elastomer. Such greater penetration occurs during vulcanization of a non-vulcanized elastomer which has been pretreated with a preheating process of an elastomeric blade followed by the application of an adhesive layer as described by the present invention. Thus, the combination of these specific factors surprisingly allows superior penetration of said adhesive layer into said elastomer surface and enhancing the interaction between them. This greater interaction acts to provide superior adhesion characteristics when compared to the technique and advantageous adhesion characteristics when thinking about the desirable factors for the manufacture of shoe soles, particularly sneakers.

The present invention is defined as an adhesion process between at least one elastomer and at least one substrate, wherein said adhesion is by applying pressure between said elastomer and said substrate, and wherein said elastomer comes from the steps of :

heating an unvulcanized elastomer at 20 to 40 to 50 ° C;

applying to said non-vulcanized elastomer a uniform layer of cross-linked polycaprolactone resin-based polyurethane adhesive between 0.1% and 5% of the aromatic polyisocyanate-based crosslinker; - drying of the elastomer assembly

vulcanized / adhesive until said assembly is substantially solvent free;

vulcanization of the elastomer / adhesive assembly at a temperature between 60 and 180 seconds and a temperature between 150 and 190 ° C;

applying on the vulcanized elastomer / adhesive assembly a uniform layer of cross-linked polycaprolactone resin-based polyurethane adhesive between 0.1% and 5.0% of the aromatic polyisocyanate-based crosslinker;

elastomer assembly drying

vulcanized / adhesive until said assembly is substantially solvent free; and

heating the assembly to temperatures between

50 ° C and 90 ° C.

In order for the process to proceed properly and deliver the beneficial results, it is preferable that all steps be performed as prescribed. However, the largest share for the increased physicochemical interaction between rubber and adhesive occurs at the vulcanization stage itself. At this stage there will be the "fusion" of the rubber adhesive χ set through the pressure and temperature resulting from the processes, ie, while the rubber vulcanization occurs, the adhesive will be penetrating the rubber and after complete vulcanization, a mechanical adhesion will occur, because part of the adhesive will be trapped inside the eraser.

In a preferred embodiment said elastomer is an elastomer selected from at least one of the group consisting of Natural Rubber, Nitrile Rubber, Butadiene Styrene Rubber Butadiene Rubber, Ethylene Propylene Diene Rubber, Polyisoprene Rubber, Styrene Butadiene Rubber and mixture mixed with at least one vulcanizing agent selected from the group consisting of Dicumila organic peroxide derivatives and sulfur derivatives and optionally containing suitable additives to achieve desired specific characteristics. Said additives preferably being 30 selected from at least one of the group consisting of flow aid, mixing aid, pigments, fillers, reinforcing fillers, lubricants and vulcanizing agent. In a preferred embodiment the first application of a uniform layer of adhesive to the elastomer is from a cross-linked Polycaprolactone resin-based polyurethane adhesive with (0.1% - 5%) aromatic polyisocyanate-based crosslinker. More preferably, said adhesive is crosslinked with 2.5 to 3.5% aromatic polyisocyanate based crosslinker. This adhesive is an adhesive prepared by adding by weight the crosslinker to the adhesive followed by mixing until complete homogenization. The addition of crosslinker over the adhesive is performed with the aid of an analytical balance and mixing is performed by a predetermined propeller agitation, rotation and time for the total and ideal homogenization. It is noteworthy that the shelf life after crosslinking is usually 2 - 6 hours. This adhesive in combination with the aforementioned elastomers and the innovative process act to achieve an improved interaction between the components as compared to the technique.

Said vulcanization is optimized such that preferably the elastomer achieves a degree of vulcanization between 80 to 95%, more preferably 90%. For purposes of the present invention, the non-vulcanized elastomer / adhesive assembly subjected to the vulcanization process will be subjected to a temperature between (60 and 180 seconds) and a temperature between (150 to 190 ° C). These temperatures have been found to be suitable so that the formulations tested so far can achieve the degree of vulcanization required for the advantageous characteristics of the present invention to be achieved, but other vulcanization parameters can be found for different formulations that may be of use. present knowledge disclosed herein.

In a preferred embodiment, the second application of a uniform layer of adhesive over the vulcanized elastomer / adhesive assembly is a cross-linked polycaprolactone resin-based polyurethane adhesive between 0.1% and 5.0% of the aromatic polyisocyanate based crosslinker. Preferably between 1.0% and 2.5% and more preferably between 1.25% and 1.75%.

Said drying of the assembly until it is

Finding substantially no solvent can occur by any method commonly known in the art. Preferably said first drying for the formulations and processes tested is a set drying between (3 and 15 minutes) and temperature between (35 and 70 ° C) carried out by a north-facing greenhouse.

In a preferred embodiment said substrate is a substrate selected from at least one of the group consisting of natural fabric, synthetic fabric, fibers, PU laminates, PVC, thermoplastic materials, thermoset materials and blends thereof.

In a preferred embodiment said applied pressure between the already prepared elastomer and the substrate is 80 to 100 Lb and can be performed by any mechanisms commonly found in the art for this purpose.

Final heating of the assembly prior to bonding with the substrate occurs in order to reactivate the adhesive and allow improved adhesion of the elastomer already treated with the substrate. Obviously, after this step, the two components must be quickly bonded together to prevent a significant temperature drop from the adhesive.

Additionally, the present invention is directed to the manufacture of shoe soles using a process of 30 according to the present invention. Particularly the present invention is directed to specific aspects of joining an elastomer and a substrate such that the elastomer is the sole and the substrate is the upper (tennis upper). Said elastomer, adhesive and substrate compositions will make the present joining process ideal for the desirable characteristics for resilient and flexible soles, where a firm joining that survives the weathering characteristics of a tennis sole for extended periods of time.

EXAMPLES

It is expected that the present invention will be better understood and visualized in light of the illustrative examples below which are not to be construed as limiting the teachings disclosed herein.

In a preferred embodiment the present process may be defined generically by the following steps:

- Prepare the rubber formulation according to the desired formula e.g.

Elastomers, BR (Natural Rubber), NR (Nitrile Rubber), SBR (Styrene Butadiene Rubber);

- Flow aid, aids in mixing (stearic acid and other fatty acids);

20 - Pigments (coloration);

- fillers (calcium carbonate);

- Reinforcement charges (Silicon dioxide, black

smoking);

- Lubricant, to decrease the hardness of the compound (mineral or vegetable oil); and

- Vulcanizing Agent (Organic Peroxide

Dicumila)

- Check with rheometer equipment the degree of vulcanization of the rubber so that it reaches 90% of

30 vulcanization;

- Roll rubber according to specification

desired; - Heat the still raw rubber laminated plate at a temperature of 40 to 50 ° C;

Using suitable equipment, apply a uniform layer of crosslinked Polycaprolactone resin polyurethane adhesive with 0.1% to 5% aromatic polyisocyanate based crosslinker;

- Dry 3 to 15 minutes in a north wind oven at a temperature of 35 to 700 ° C in order to enable solvent evaporation;

- Forward the rubber plate to the step of

cut according to desired model;

Vulcanize the elastomer / adhesive assembly into a suitable mold vulcanization press using a time of 60 to 180 seconds and a temperature of 150 to 190 ° C;

- Refill the parts of vulcanized rubbers of

according to standard procedure;

- Forward to the final pasting step;

- Apply, through appropriate equipment, a uniform layer of polyurethane resin-based adhesive.

Cross-linked polycaprolactone with 1.5% of the aromatic polyisocyanate-based crosslinker in the prepared soles and in the remaining parts;

- Dry the substrates in equipment suitable for solvent evaporation;

- Heat substrates for reactivation

proper chemistry of the adhesive film;

- Bond substrates and apply pressure to suitable equipment.

In accordance with the present case several

30 parameters were changed during the tests below and the respective bonding results were obtained. It can be seen from table 1 that there was a peak bond strength for test 3, which is the most preferred embodiment of the present invention.

The following bond opening tests aimed to evaluate the bonding process, the adhesive as well as the substrates used in the procedure and were performed according to the PFI standard (Germany). Samples were conditioned for at least 24 hours at 23 ° C and a dynamometer was used for measurement according to the following steps:

- Make the opening in the dynamometer of three bodies of

proves that we have the value of take-off without aging as follows:

- Set the height (distance) of the tweezers to 50

mm;

- Check the speed of the dynamometer, 100 mm per

minute;

- Turn on the dynamometer;

- Attach the ends of the specimen to the top and bottom clamps of the dynamometer, see figure 1;

- Activate the device;

- Verify the amount of force required to make the opening of the collage by averaging between the maximum and minimum peaks of the values obtained, when the material is leather or elastomeric compound; if it is textile material

average only the maximum peaks;

- Note the average in report or specimen.

Results were obtained by the formula X / L = R; where X = mean value found for each specimen, L = sum of specimen widths and R =

3 0 Result, kgF / cm.

Equipment used must be calibrated according to the TPM manual or internal procedure. The opening angle must be observed and respected, being 90 ° to the horizontal. Elastomeric compounds The opening procedure should be halved and restarted to eliminate material tension.

The results obtained are shown in table 1:

Table 1 - Variability of the parameters of

Processes Based on Pasting Results Obtained

(Test 1) Parameters Less than Ideal Process Condition (Test 2) Parameters Less than Ideal Process Condition (Test 3) Parameters under Ideal Process Condition (Test 4) Parameters Greater than Ideal Process Condition (Test 5) Parameters Greater than Ideal Process Condition Rubber Rheumatic Curve - Vulcanization Degree - (min: s) 2 2.8 3 3.2 3.8 Rubber Thickness (mm) 2 2.5 3.5 5 7 Raw Rubber Temperature (0C) 25 30 45 60 75 Adhesive / Primer Layer Weight (g / cm2) 0.025 0.05 0.1 0, 15 0.2 Adhesive / Primer Viscosity (cPs) 2000 2500 2800 3200 3500 Content Adhesive / primer solids (wt%) 12 15 18 20 22 Adhesive / primer crosslinker content (wt%) O 1.5 3.0 3, 5 5.0 Adhesive / primer Drying Time (min) 5 10 15 25 30 Vulcanization Time (S) 80 90 100 110 120 Vulcanization Vapor Pressure (Kgf / cm2) 7 8 9 10 11 Vulcanization Temperature (0C) 135 150 175 200 225 Adhesive Viscosity Final Adhesive (cPs) 2000 2500 2800 3200 3500 Final Adhesive Solid Content (% by weight) 12 15 18 20 22 Final Adhesive Crosslinker Content (% by weight) 0.1 1 1.5 2 5 Bonding Results ( Kg / cm) 4 4.3 4.5 4.2 4

Thus it can be noted that there is a peak of

bonding results for the parameters present in test 3, where there is believed to be a synergistic effect of the various steps of the present example and where there is a final product with superior adhesion characteristics between an elastomer and a substrate with a process. considered environmentally improved and economically viable mainly because there is no need to use halogenation and / or harsh pretreatment processes. Appropriate adhesions for the use of these components as tennis soles are thus achieved.

It should also be noted that while the invention has been described in relation to what is currently considered to be the most practical and preferred embodiment, it should be understood that the invention should not be limited to the presented embodiment, but rather lends itself to covering various modifications. and equivalent arrangements included within the character and scope of the appended claims. Accordingly, the scope of the appended claims should be in accordance with a broader interpretation to encompass all such similar modifications and adjustments.

Claims (9)

Adhesion process between at least one elastomer and at least one substrate, characterized in that said adhesion is by applying pressure between said elastomer and said substrate, and wherein said elastomer comes from the steps of: heating a non-elastomer vulcanized at a temperature between 40 and 50 ° C; applying to said non-vulcanized elastomer a uniform layer of cross-linked polycaprolactone resin-based polyurethane adhesive between 0.1% and 5% of the aromatic polyisocyanate-based crosslinker; drying the non-vulcanized elastomer / adhesive assembly until said assembly is substantially solvent free; vulcanization of the elastomer / adhesive assembly at a temperature between 60 and 180 seconds and a temperature between 150 and 190 ° C; applying on the vulcanized elastomer / adhesive assembly a uniform layer of cross-linked polycaprolactone resin-based polyurethane adhesive between 0.1% and 5.0% of the aromatic polyisocyanate-based crosslinker; drying the vulcanized elastomer / adhesive assembly until said assembly is substantially solvent free; and heating the assembly to temperatures between 50 ° C and 90 ° C. Process according to Claim 1, characterized in that said elastomer comprises at least one elastomer selected from the group consisting of Natural Rubber, Nitrile Rubber, Styrene Butadiene Rubber Butadiene Rubber, Ethylene-Propylene-Diene Rubber, Polyisoprene, Styrene Butadiene Rubber and mixtures thereof, mixed with at least one vulcanizing agent selected from the group consisting of organic dicumyl peroxide derivatives and sulfur derivatives. Process according to claim 2, characterized in that said elastomer comprises at least one additive selected from the group consisting of flow aid, mixing aid, pigments, fillers, reinforcement fillers and lubricants. Process according to Claim 1, characterized in that said substrate comprises at least one material selected from the group consisting of natural fabric, synthetic fabric, fibers, PU laminates, PVC, thermoplastic materials, thermoset materials and blends of the same. same. Process according to claim 1, characterized in that said application to said non-vulcanized elastomer of a uniform layer of adhesive is by means of a cross-linked polycaprolactone resin-based polyurethane adhesive preferably between 2.5 and 3, 5% of the aromatic polyisocyanate based crosslinker. Process according to Claim 1, characterized in that said application to said vulcanized elastomer / adhesive assembly of a uniform layer of adhesive is by means of a cross-linked polycaprolactone adhesive preferably between 1.25 and 1.75% of the crosslinker. based on aromatic polyisocyanate. Process according to Claim 1, characterized in that said pressure application is between 80 and 0 Lb. 8 Footwear comprising at least one elastomer and at least one substrate, characterized in that the adhesion between said elastomer and said substrate is by the process as defined in claim 1. Footwear according to claim 8, characterized in that said footwear is tennis shoes. Λ