GB2048897A - Improvements in shoe manufacture - Google Patents

Abstract

A primer for promoting adhesion to a rubber material e.g. shoe soles, the primer comprising in solution a reaction product of an SBS block copolymer and an organic halogen donor e.g trichloroisocyanuric acid. The solvent is preferably ethyl acetate, and the solution may also contain p-toluene sulphonamide.

Description

SPECIFICATION Improvements in shoe manufacture The present invention relates to a primer for mainly hydrocarbon rubber surfaces to improve the adhesion of adhesives including polyurethane and polychloroprene solvent adhesives, polyamide and polyester hot melt adhesives and aqueous dispersions of polar adhesives which would normally provide better adhesion to more polar surfaces such as urethane polymers, plasticised polyvinyl chloride (PVC) and leather. The use of such adhesives to bond rubbers to these more polar surfaces is thereby facilitated. The primer may also be used to promote the adhesion to the primed rubber surface of molten polar thermoplastics such as plasticised PVC, nylon etc. as well as reacted in-situ polymers such as urethanes and epoxide resins.It also relates to a process of adhering a rubber material to another material utilizing the primer, to the use of the process and treated rubber in the manufacture of footwear in particular and to a composite sole comprising a base rubber layer which has been treated with the primer.

It is known that the receptiveness of elastomeric soling material (e.g. natural rubber, styrenebutadiene rubber, nitrile rubber, and mixtures and blends of these), towards adhesives of, e.g.

polychloroprene and polyurethane types, and to polar thermoplastics materials is often unsatisfactory.

Modern methods of shoe-ma.kingfrequently employ stuck-on or directly moulded soles, as opposed to the traditional stitched-on leather sole and hence the problem of ensuring good adhesion of the sole to the upper is of considerable importance.

British Patent Specification 1,278,258 describes and claims a shoe-making process which comprises subjecting a sole unit of elastomeric soling material to a surface halogenation treatment, applying a solvent-based polyurethane or polychloroprene adhesive to the treated surface and then securing the shoe upper anctlor other shoe component to the adhesive-coated surface of the sole unit.

The preferred halogenation treatment described consists of dipping the material to be treated in an acidified hypochloric solution. Such solutions are subject to the disadvantage that the chlorine generated presents a hazard in shoe factories.

British Patent Specification 1,295,677 and British Patent Specification 1,293,842 describe an improvement in the halogenation technique in which an organic halogen donor is used instead of acidified hypochlorite. The preferred halogen donors are in general chlorine donors although the use of dibromodimethylhydantoin (DBH) is disclosed in British Patent Specification 1,295,677.

The treatment described in the latter patent specification consists of wiping or dipping the elastomeric sole material in a solution containing the halogen donor, after which the sole is dried and can be stored prior to attachment to the shoe upper. A sole may be precemented after such treatment and subsequently heat activated before securement.

British Patent Specification 1,293,842 and 1,458,007 disclose as an alternative process the incorporation of the halogen donor in the adhesive used for bonding the sole to the upper.

The organic chlorine donors mentioned liberate chlorine slowly which process is accelerated when heat and pressure are applied during the adhesion of the sole to the shoe. They have the advantage that they are relatively safe to handle in solution and so not liberate chlorine in the quantities sometimes found in inorganic hypochlorite solutions when these are exposed in opensdishes in relatively concentrated form.

One difficulty with the organic halogen donors Is that they present a certain hazard when misused. Thus the addition of water tends to liberate chlorine gas and the donors are strong oxidizing agents and when split and left to dry present a certain fire hazard. There has been a want of a primer which can be handled with greater safety under factory conditions.

At the same time the adhesion notably of thermoplastic rubbers of the SBS (styrene-butadienestyrene block co-polymer) type to more polar terminals such as PVC has always presented difficulty. For this purpose the most satisfactory primers up-to-date have included N-halogenated p-toluene sulfphonamide which is an unstable substance and difficult to prepare. A partial solution to this problem is presented in British Patent 1,500,296. However the primer therein disclosed is also subject to the safety hazard mentioned above.

We have surprisingly found that an essentially safe primer which is extremely effective in promoting the adhesion of vulcanized and thermoplastic rubbers to more polar materials can be prepared by halogenating an SBS block co-polymer in solution and utilizing this solution as a primer.

The effectiveness of this primer greatly exceeds that of the familiar chlorinated rubber of commerce which is available as a soluble product and chlorination of SBS random co-polymers in solution causes precipitation of the resulting product.

According to one aspect of the invention there is provided a primer for promoting adhesion to a rubber material, the primer comprising in solution a reaction product of an SBS block co-polymer and an organic holgen donor.

Preferably the solution has been prepared by mixing a first solution containing the SBS block copolymer and a second solution containing the organic halogen donor, both solutions containing the same solvent.

The preferred halogen donor comprises trichloroisocyanuric acid. However any of the organic halogen donors discussed in the aforementioned patents can be used.

The preferred solvent is ethyl acetate but limited success can also be achieved with nonflammable solvents such as dichloromethane. There are indications that non-flammable solvents are less effective with certain soling rubbers. A wide range of alternative solvents is permissible, including esters, ketones, aromatic and chlorinated aliphatic solvents. Solvents such as ketones which may not be used normally to prepare solutions of halogenating agents because of dangerous by-products are permitted in these formulations provided that the time between preparation of the organic halogen donor solution and its addition to the polymer solution is short, e.g. less than 1 hour.

The combined solution (i.e when mixed but prior to reaction) preferably contains from 1 to 4 wt. % of SBS co-polymer and from 0.2 to 2 wt. % of available halogen from an organic donor.

It is also preferred (especially where thermoplastic rubber substrates such as soles are being treated) to add to the solution of SBS block co-polymer a proportion of p-toluene sulphonamide. Thus preferably the first solution contains from 0.2 to 2 wt. % of p-toluene sulphonamide. The exact mechanism of reaction of the p-toluene sulphonamide is not clear. However as discussed in British Patent 1,500,296 the combination of p-toluene sulphonamide with trichloroisocyanuric acid, in particular, is effective in the pretreatment of thermoplastic rubbers, especially those containing low levels of polybutadiene, where pretreatment with trichloroisocyanuric acid alone is less effective. On the other hand when the polybutadiene content is high, trichloroisocyanuric acid is as effective.It is believed that the addition of the p-toluene sulphonamide allows for a wider choice of SBS block copolymer as used in the solution of the primer and also as selected and compounded for the base rubber material.

However the primer is also effective in improving the adhesion of polyurethane and polychloroprene adhesives and other thermoplastic materials to vulcanized rubbers.

The S8S co-polymer selected for the primer solution may be a linear, branched or radial block copolymer, but-a linear co-polymer is preferred.

In treating the surface to be primed, in the case of the thermoplastic rubbers which are soluble in the primer, the primer is preferably brushed on gently with a soft brush, whereas in the case of vulcanized rubbers, a stiff brush and scrubbing action are preferably used. The primer is generally allowed to dry for example for 15 minutes and the adhesive can be applied in the normal manner. The adhesive layer on the base rubber surface, e.g. a shoe sole, is then allowed to dry for e.g. 1 to 2 hours and may then be heat activated and bonded by pressure e.g. to an adhesive coated, lasted shoe upper.

Thus the invention includes as an aspect a process of adhering a rubber material to an adherend material receptive to a polyurethane, polychloroprene or polar hot melt adhesive which comprises treating a surface of the rubber material with a primer as described above and adhering the treated surface to a surface of the adherend material with the appropriate adhesive.

The invention also includes as an aspect a shoe comprising a rubber sole adhered to a shoe upper by a process as described above.

The primer and the process utilizing the primer are particularly suitable for bonding soles to plasticized PVC (polyvinyl chloride) ånd leather upper materials. However other suitable upper materials are polyamides, polyurethanes and polyesters.

The primer may also be used to modify the surface of thermoplastic rubber or vulcanized rubber prior to the injection onto the surface of a polar thermoplastic soling material of e.g. plasticized PVC, polyamides (nylon) polyesters (Hytrel, Trade Mark) and polyurethanes. In this way composite soling units can be prepared of e.g. vulcanized rubber as the wearing surface and plasticized PVC throughsoles. These composites may also be made by high frequency moulding the thermoplastic material onto the primed sole material. An extension of this principle lies in the attachment of rubber (vulcanized or thermoplastic) soles primed with the primer by the direct injection of an interlayer of thermoplastic material such as plasticized PVC between the sole and the adhesive coated lasted shoe upper.

Thus the invention includes as an aspect a composite sole comprising a base layer of thermoplastic or vulcanized rubber bonded to a layer of PVC, polyamide, polyurethane or polyester, the adhered surface of the base layer having been treated with a primer as described above.

It also includes as an aspect a process which comprises treating a surface of a rubber unit with a primer in accordance with the unit as defined above and moulding a thermoplastic material in contact wish said treated surface.

It further includes a shoe-making process which comprises the direct injection of an interlayer of a thermoplastic material between a rubber sole unit, the surface of which has been treated with a primer in accordance with the unit as defined above, and a shoe upper.

In addition to the above and other applications (such as lacquering) in the shoe industry, many other applications in other industries will be evident to those skilled in the art whereever it is desired to bond a rubber substrate to a more polar plastics material. Examples would be the production of garments, waterproofing material generally, and luggage and also upholstery and flooring materials e.g.

for motor vehicles.

The following Examples illustrate the invention. In the following Examples 1 to 10 the primer used was prepared as follows. 20 g of a linear SBS block co-polymer (Cariflex, Trade Mark, 1102) was dissolved in 800 ml ethyl acetate. 4 g p-toluene sulphonamide was added and allowed to dissolve.

There was then added a solution of 8 g trichloroisocyanuric acid dissolved in 200 ml ethyl acetate.

EXAMPLE 1 Sheets of different commerical soling compounds based on SBS block co-polymers with various additions were treated with the primer, using a soft brush and left for + hour. Then they were each coated with a polyurethane commercial adhesive (Unigrip, Trade Mark, BU 8300) and left for 2 hours in the open. A sheet of PVC upper material (a commercially available type having a 47 thou. thickness of PVC on Blakes SDI fabric) was wiped with ethyl acetate and left of b hour and then coated with the same polyurethane adhesive and left for 1 hour to dry. The prepared surfaces were bonded together by heat activating the adhesive on the thermoplastic rubber at 870C and then the two prepared surfaces were bonded together under a pressure of 5.6 kg cml for 1 5 seconds.

The various soling compounds contained different additives which are given below where they are known: A. added polystyrene B. added polyethylenevinylacetate C. added polyalphamethyl styrene D. unknown additives E. unknown additives F. unknown additives G. added polystyrene and polyalphamethyl styrene H. added polyalphamethylstyrene and toughened polystyrene I. added ethylenevinylacetate, polyalphamethyl styrene, toughened polystyrene and styrene butadiene resin J. added polystyrene and polyalphamethyl styrene K. added ethylenevinylacetate, styrene butadiene resin, and toughened polystyrene L. added polyalphamethylstyrene and toughened polystyrene M. added ethylenevinyiacetate, polyalphamethyl styrene and toughened polystyrene.

The bonds were subjected to peel testing using the SATRA Cantilever Tensiometer (STM 161) with a jaw separation rate of 10 cm/min. The results are given in Table 1.

Table I

Soling Compound # Load # Type of Failure Original Surface # kgf/cm A # 13,1 # 65R 35SR R Tore B 11.5 95SR/AR 5R C 10.8 100SR/AR D 11.9 95SR 5NC E 10.2 55SR/AR 40R 5NC F 6.5 100AR G 14.2 70SR/AR 30R UP Tore H 9.6 100AR I 15.6 70R 30AR J 9.6 95AR 5SR K 14.6 50AR 40R 5SR 5NC UP Tore L 13.4 80 20SR R Tore M 16.5 100R R Tore (Unheated surfaces had very low bond strength) Key to types of failure R - Rubber failure SR - Surface rubber failure SR/AR - Surface rubber/adhesion to rubber failure AR adhesion to rubber failure NC -Non-coalescence failure R Tore rubber tore UP Tore -Upper plastic tore AUM failure of adhesion to upper material SUM Surface of upper material failure SDL Surface delamination of soling SM/UM failure between sole and upper materials EXAMPLE 2 In this Example two types of vulcanized rubber were tested with the surface scoured and with the surface unscoured or original. The rubbers are identified below.

N. resin rubber No. SR4 from Long and Hambly 0. synthetic composition rubber No. S1 805 from Vitasole The sole surfaces were treated with the primer and bonded exactly as in Example 1 above except that a stiff brush was used to apply the primer.

The results of load at failure, with and without primer treatment, are given in Table 2.The same peel testing device was used in Example 1 and the key to the types of failure shown in Table 2 is the same as in Table 1. The adhesive was the same as in Example 1. Figures in brackets are controls. no primer treatment having been used.

Table 2

Rubber Load Type of failure kgf/cm N Original (0.3) 100AR Surface 3.1 55AR 45SR N Scoured (1.7) 95AR 5SR Surface 5.5 40AR 50SR 10NC O Original (0.4) 100AR Surface 5.4 45AR 40R 15SR O Scoured (2.2) 90AR 10SR Surface 8.4 100R EXAMPLE 3 In this Example two vulcanized rubbers and two thermoplastic rubbers were tested for response to the primer, utilizing a different polyurethane adhesive. The adhesive was Bayer No. 8066 which is an aqueous dispersion-of a urethane polymer.Rubber P was a commercial natural composition rubber, Sussex Mix No. 1 70. The other rubbers are as identified in Examples 1 and 2. The treatments were varied from the other Examples. The soles were treated with primer and left for + hour and then coated with the adhesive and left for 1 hour open. They were heat activated at 1OO0C. The upper material, which was the same as in Examples 1 and 2, was treated with two coats of adhesive, each coat being left + hour to dry. The load at failure was tested as in Examples 1 and 2. The results are given in Table 3, bracketed figures showing controls.

Table 3

Rubber Load Type of failure kgf/cm N Scoured (0.7) 100AR Surface 2.7 100AUM P Scoured (1.6) 60AR 40AUM Surface 2.3 100AUM F Original (0.1) 95AR 5NC Surface 6.9 90AR 10AUM I Original (0.3) 100AR Surface 4.3 65AUM 35NC EXAMPLE 4 In this Example the upper material was replaced by a pearl split leather (Steads). The adhesive used was a single polychloroprene adhesive, BU 6090. These materials were tested on vulcanized rubbers and thermoplastic rubbers which were primed and adhered as in Example 1 and 2. The leather upper was treated with two coats of the adhesive and left to dry for + hour and 1 hour with respective coats. The sole adhesive was reactivated as in Example 1. The results are given in Table 4, the key to types of failure being given in Example 1 The soling materials are identified in earlier Examples.

Bracketed figures show controls.

Table 4

Rubber Load Type of failure kgf/cm N Original (1.9) 95AR 5SR Surface 1.3 100AR N Scoured (5.5) 75AUM 15SUM 100SR Surface 6.8 40AUM 35SUM 20SR 5AR O Original (2.8) 100AR Surface 6.7 70R 10AR 15AUM 5SR O Scoured (6.8) 40AUM 25AR 15R 10SR 10SUM Surface 7.1 80R 10AUM 5SUM 5NC I Original (2.1) 100AR Surface 5.1 100AR F Original (3.2) 100AR Surface 7.1 100AR fital EXAMPLE 5 In this Example the primer was used to promote the adhesion of polyester hot melt adhesives between vulcanized rubber and thermoplastic rubber soling materials and the PVC coated fabric identified in Example 1. The hot melt adhesive was a polyester, Bostik HM 7242. This was applied at 230 to 2400 C. The rubbers are identified in earlier Examples. The upper material used was the PVC coated fabric identified in Example 1. This was merely wiped with ethyl acetate and left for X hour. The soles were treated with the primer and left for T hour. The results are given in Table 5, the load at failure being determined as described in Example 1, with control figures in brackets.

Table 5

Rubber Load Type of failure kgf/cm F Original (1.3) 80AR 20AUM Surface 2.5 85AR 5AUM 10SDL I Original (0.7) 75AR 25AUM Surface 2.8 90AR 10AUM N Scoured (0.7) tOOAUM Surface 4.5 30AR 55AUM 15PVC failure N Scoured (0.9) 5AR 95AUM Surface 2.0 25AR 75AUM EXAMPLE 6 In this Example vulcanized rubbers and thermoplastic rubbers were treated with the primer and adhered to the PVC coated fabric identified in Example 1 with a polyamide hot melt adhesive (Bostik 537). This was applied at its melting point of 200 to 210 C. The primer coatings were left for + hour.

Otherwise the conditions are as in Example 5. The results are given in Table 6, with control figures in brackets.

Table 6

Compound Load Type of Failure kgf/cm N Original (0.5) 90AR 10C Surface 1.5 45AR 40C 15AUM N Scoured (0.8) 75AR 20C 5AUM Surface 1.5 90AR 5C 5AUM O Original (0.5) 100AR Surface 0.5 100AR O Scoured (0.5) 85AR 15C Surface 1.0 20AR 45C 35AUM EXAMPLE 7 In this Example a nylon soling material was directly injection moulded onto a primer-treated soling material. Thermoplastic soling materials dhd vulcanized rubber soling materials were used.The nylon was identified by the No. L22N 1 50. The primer was applied and left to dry for - hour. The primertreated rubber soling materials were cut to shape and inserted into a conventional injection moulding machine and the nylon directly injected onto the treated surface. The load at failure is given in Example 1. Control results are given in brackets.

Table 7

Rubber Load d Type of Failure kgf/cm F Original (1.0) lOOSM/UM Surface 3.5 100SM/UM I Original (0.4) 100SM/UM Surface 3.0 lOOSM/UM 0 Scoured (0.6) 100SM/UM Surface 3.2 95SMtAJM 5SR N Scoured (2.5) 95SM /UM 5SR Surface 5.0 80SM/UM 10SR 10R N Original (1.5) 100SM/UM Surface 4.3 95SM.AJM 5SR EXAMPLE 28 In this Example another material was directly injected onto treated rubber soling materials as in Example 7. The injected material was a commercial polyester (Hytrel, Trade Mark, 5526). Other details are as in Example 7. The results of load at failure testing are given in Table 8, with control results in brackets.

Table 8

Rubber Load Type of Failure kgf/cm F Original (1.9) 100SM/UM Surface 3.4 100SM/UM I Original (0.8) 100SM/UM Surface 2.9 100SM/UM O Scoured (1.5) 80SM/UM 20SR Surface 5.4 100SR N Scoured (4.2) 60SM/UM 40SR Surface 7.5 100SR N Original (3.4) 90SM/UM 10SR Surface 7.9 100R EXAMPLE 9 In this Example a commercial polyurethane was injection moulded around an insert formed of a vulcanized or thermoplastic soling material, both surfaces of which had been treated with the primer as described above. The polyurethane material used was SATRA, Trade Mark, ref C(ELL 57DXX). The primer was left for T hour after being coated on. The failure at load was determined as described above and the results given in Table 9, with control results in brackets.

Table 9

Insert Load Type of Failure kgf/cm F Original (1.0) Separation at Interface Surface 3.3 Separation at Interface I Original (0.6) Separation at Interface Surface 3.5 Separation at Interface P Scoured (O) Separation at Interface Surfaces 1.3 Separation at Interface N Scoured (O) Separation at Interface Surfaces 0.4 Separation at Interface EXAMPLE 10 In this Example the primer already described in the foregoing Examples 1 to 9 was compared with a similar primer excluding the p-toluene suiphonamide. The tests were performed as in earlier Examples upon four different thermoplastic rubbers as identified in Example 1. The adhesive used and the PVC upper material used were as identified in Example 1 and the treatment was the same. The results are given in Table 10.

Table 10

Thermoplastic Primer Primer rubber -PTS +PTS Original Surface A 8.0 AR 13.1 R C 5.0 AR 10.8 SR!/AR F 3.9 AR 6.5 AR I 4.3 AR 15.6 R PTS = poluene sulphonamide It will be apparent from Table 10 that in the case of thermoplastic rubbers, acceptable results are obtained with the adhesive without the p-toluene sulphonamide, but significantly better results were obtained when the primer included this additive.

Claims (30)

1. A primer for promoting adhesion to a rubber material, the primer comprising in solution a reaction product of an SBS block co-polymer and an organic halogen donor.

2. A primer as claimed in claim 1 wherein the organic halogen donor comprises trichloroisocyanuric acid.

3. A primer as claimed in claim 1 or claim 2 wherein the solution has been prepared by mixing a first solution containing the SBS co-polymer and a second solution containing the organic halogen donor, both solutions containing the same solvent.

4. A primer as claimed in claim 2 or claim 3 wherein the solvent is ethyl acetate.

5. A primer as claimed in any of claims 2 to 4 wherein the first solution also contains p-toluene sulphonamide.

6. A primer as claimed in any of claims 2 to 5 wherein the combined solution contains from 1 to 4 wt.% of SBS block co-polymer and from 0.5 to 2 wt.% of organic halogen donor.

7. A primer as claimed in claim 6 wherein the first solution contains from 0.25 to 1 wit.% of ptoluene sulphonamide.

8. A primer according to claim 1 consisting substantially of, in wt./vol.% based on the volume of solvent: 2% SBS block co-polymer 0.4% p-toluene sulphonamide 0.8% trichloroisocyanuric acid.

9. A primer as claimed in claim 8 prepared substantially as described herein.

10. A process of adhering a rubber material to another material receptive to a polyurethane polychloroprene or polar hot melt adhesive which comprises treating a surface of the rubber material with a primer as claimed in any preceding claim and adhering the treated surface to a surface of the other material with the appropriate adhesive.

11. A process as claimed in claim 10 wherein the rubber material is a thermoplastic rubber.

12. A process as claimed in claim 10 wherein the rubber material is a vulcanized rubber.

13. A process as claimed in any of claims 10 to 12 wherein the other material is plasticized PVC.

1 4. A process as claimed in any of claims 10 to 12 wherein the other material is a fabric leather, a polyamide, a polyurethane or a polyester.

1 5. A process as claimed in claim 10 substantially as herein described with reference to any one of Examples 1 to 6.

1 6. A process which comprises treating a surface of a rubber unit with a primer as claimed in any of claims 1 to 9 and moulding a thermoplastic material in contact with said treated surface.

1 7. A process as claimed in claim 1 6 wherein the resulting moulding is of a shoe sole.

1 8. A process as claimed in claim 16 or claim 1 7 wherein the thermoplastic material is injection moulded.

1 9. A process as claimed in claim 16 or claim 17 wherein the thermoplastic material is highfrequency moulded.

20. A shoe making process which comprises the direct injection of an interlayer of a thermoplastic material between a rubber sole unit, the surface of which has been treated with a primer as claimed in any of claims 1 to 9, and a shoe upper.

21. A process as claimed in any of claims 16 to 20 wherein the rubber material is a thermoplastic rubber.

22. A process as claimed in any of claims 16 to 20 wherein the rubber material is a vulcanized rubber.

23. A process as claimed in any of claims 1 6 to 22 wherein said thermoplastic material is PVC.

24. A process as claimed in any of claims 1 6 to 22 wherein said thermoplastic material is a polyamide, polyurethane or a polyester.

25. A process as claimed in claim 16 substantially as disclosed herein with reference to Examples 7,8Or9.

26. A process which comprises treating a surface of a rubber unit with a primer as claimed in any of claims 1 to 9 and joining the treated surface to a layer of polymeric material by causing a polymerforming mix to react in place on the treated surface.

27. A process as claimed in claim 26 wherein the polymeric material is a polyurethane or epoxide resin.

28. A composite sole comprising a base layer of thermoplastic or vulcanized rubber bonded to a layer of PVC, polyamide, polyurethane or polyester, the adhered surface of the base layer having been treated with a primer according to any of claims 1 to 9.

29. A shoe comprising a rubber sole adhered to a shoe upper by a process as claimed in any of claims 10 to 15 or claim 20 or any of claims 21 to 25 as dependent on claim 20 or claim 26 or 27.

30. A shoe comprising a sole substantially as claimed in claim 26 or as prepared by a process as claimed in any of claims 16 to 19 or any of claims 21 to 25 as dependent on any of claims 16 to 19 or claim 26 or 27.