GB2025321A - Resilient composites - Google Patents

Abstract

The invention relates to resilient composites which may be useful as sports surfaces or flooring and to a method of making them. The composite comprises a plasticised vinyl chloride composition bonded without an adhesive interlayer to at least one component comprising a particulate vulcanized rubber in a matrix of a plasticised vinyl chloride polymer composition. The particulate vulcanised rubber is either nitrile rubber or a rubber which has been treated with either bromine, chlorine or an organic polyisocyanate. Bonding is effected by the application of heat. The aim of the invention is to provide a well-bonded resilient composite with minimal staining problems.

Description

SPECIFICATION Resilient composites This invention relates to novel resilient composites and to a method of producing them.

According to one aspect of the present invention there is provided a resilient composite of at least one component comprising a plasticised vinyl chloride polymer composition bonded without an adhesive interlayer to at least one component comprising a particulate vulcanised rubber selected from nitrile rubber and pretreated rubber as hereinafter defined in a matrix of a plasticised vinyl chloride polymer composition.

According to a further aspect of the present invention there is provided a method of producing a resilient composite by contacting at least one component comprising a particulate vulcanised rubber selected from nitrate rubber and pretreated rubber as hereinafter defined in a matrix of a plasticised vinyl chloride polymer composition with at least one component comprising a plasticised vinyl chloride polymer composition and applying heat to unite the assembly.

By "pretreated rubber" is meant rubber which has been treated with a treatment agent selected from bromide, chlorine and an organic polyisocyanate, and "pretreating" is to be construed accordingly.

If bromide or chloride is used as the treatment agent it may be in vapour form, in solution form, e.g. in water or a plasticiser, or in the form of a halogen-containing compound. The amount of halogen treatment agent used is such that the resulting halogen content of the particulate rubber is more than 1.5% by weight based on dry weight of rubber and preferably the action of the halogen treatment agent is to halogenate the rubber surface.Examples of organic polyisocyanates include 4,4'-diphenyl methane diisocyanate which is preferably modified to liquid form (e.g. as is available in about 55% concentration liquid form as Suprasec DND from ICI, as Isonate 143 available from Upjohn which contains 10% of higher molecular weight material consisting mainly of uretonimine groups, or as PBA 1042 from ICI which is a water-dispersable form and toluene diisocyanate (e.g. TDI which is a mixture of 2,4- and 2,6tolylene diisocyanates). When an isocyanate treatment agent is used the resulting isocyana.te content of the rubber is preferably more than 1.5%, more preferably at least 4.5% by weight based on the dry weight of rubber.If desired a compound e.g. dibutyl tin dilaurate, known to catalyse the reaction of an isocyanate with moisture in the air may be incorporated into the rubber in addition to the isocyanate.

The resilient composite of the present invention may be useful as surfacing materials (e.g. as sports surfaces or floqr tiles) or in belting or hose. Use of the selected class of rubbers as defined above may alleviate straining problems in the vinyl chloride polymer later adjacent the matrix, particularly when the treatment agent comprises an isocyanate, or when nitrile rubber is selected as the vulcanised rubber.

The term vinyl chloride polymer includes poly(vinyl chloride) homopolymers and copolymers (e.g.

random or block) of vinyl chloride with other monomers e.g. vinyl acetate, vinyl acetate/methacrylic acid or an acrylate. Examples of block copolymers include poly(vinyl chloride) with nitrile rubber, ethylene/propylene rubber or polyisobutylene. If desired a mixture of at least two vinyl chloride polymers may be used e.g. a preferred blend is 35 to 50% by weight poly(vinyl chloride) and 65 to 50% by weight vinyl chloride/vinyl acetate copolymer.

Either or both of the vinyl chloride polymer compositions may contain conventional additives e.g. a filler (e.g. whiting or a "plate-like" filler such as china clay) preferably in an amount up to 100 parts by weight, a fungicide and/or a pigment.

The particulate rubber may be cellular (closed or open-celled) or non-cellular and is usually vulcanised prior to incorporation in the vinyl chloride polymer composition. Preferably the pretreatment of the rubber is carried out when it is already in the vulcanised state. Alternatively, a liquid treatment agent may be "swollen" into the vulcanised rubber. Examples of rubbers include natural rubber, styrene/butadiene copolymer rubber (SBR), polybutadiene rubber and blends thereof. If desired, particles of tyres scrap e.g. whole tyre crumb (i.e. the vulcanised tyre rubber minus lint and bead wires) or tread crumb may be used.Usually whole tyre crumb and tread crumb are a mixture of synthetic rubber(s), natural rubber and additives e.g. carbon black, oil and filier. Preferably the particle size of the rubber is such thgt it will pass a B.S. No. 30 mesh sieve (nominal width of aperture is 500 microns).

Preferably the rubber is present in an amount of more than 30% by weight and more preferably in the range 40% to 60% by weight based on the total weight of rubber and its vinyl chloride polymer matrix.

Preferably, in order to minimise the risk of plasticiser migration, the amounts of plasticiser in the vinyl chloride polymer composition and in the plasticised vinyl chloride polymer composition matrix are about the same if the same plasticiser is used in each or if plasticisers of similar efficiency and chemical nature are used. Examples of "similar" plasticisers are dialphanyl phthalate (an ester based on C7 to C9 alcohols), dioctyl phthalate, di-iso-octyl phthalate, di-capryl phthalate and di-nonyl phthalate.

Examples of other plasticisers are phosphates, chioro-paraffins and epoxy materials.

Usually, for the production of resilient composites, the plasticised vinyl chloride polymer matrixforming composition and particulate rubber are initially in the form of a mixture which is consolidated by heat into a coherent composition e.g. a sheet and then contacted with a plasticised vinyl chloride polymer composition and heat applied to unite the assembly. In the manufacture of hose, plasticised vinyl chloride polymer matrix-forming composition and particulate rubber could be consolidated by heat into a tubular shape and then a plasticised vinyl chloride polymer composition extruded over it.

The composites of the present invention will now be illustrated by the following Examples in which all parts are by weight and in which the tests used are based upon British Standard tests.

EXAMPLE 1 Vinyl chloride polymer/nitrile rubber (NBR) mixtures having the formulations A, B, C, D and E given in the following Table were each poured onto a mill and passed through a nip at the temperatures shown in the Table to produce sheets. A portion of each sheet was then compression moulded at 1 650C and certain of its properties were then measured.

Another portion of each sheet was laminated with a vinyl chloride polymer surface layer consisting of a laminate of two sheets of 0.8 mmzplasticised vinyl chloride homopolymer composition containing 86 parts of dialphanyl phthalate, and other additives and having a Shore D hardness of 55 . This is the PVC surfacing layer referred to in the subsequent Examples. Certain properties of the composite were then measured and are given in the Table. Any of the resulting products would be suitable as a sports surface or flooring.

Vinyl chloride polymer/NBR blends A B C D E PVC homopolymer (Breon 125/12) 100 50 50 - Vinyl chloride/vinyl acetate copolymer (Breon AS70/42) - 50 50 100 100 Plasticlser (dialphanyl phthalate) 150 150 150 150 122 NBR 30 mesh crumb 200 200 200 200 200 China clay - - 50 - 100 Mark LC310 Liquid Ba/Cd stablliser (ex. Lankro Chemicals) 2 2 2 2 2 Mill sheeting temp. ( C) 165 145 145 145 145 Vinyl chloride Compression moulded 165 C homopolymer sheet * 100% modulus (MN/m2) 4.2 3.1 1.8 2.0 2.0 2.9 Tensile strength (MN/m2) 11.7 7.5 3.9 3.6 2.3 3.1 Elongation at break (%) 330 280 210 210 165 133 Hardness ( BS D') 56 48 37 42.5 30 51.5 Tripsometer Resilience (%) 52 54 53 47.5 42 25.5 Tear strength (N/test picee) 71.5 74 52 52 29 51 SG (g/cc) 1.278 1.198 1.195 1.270 * Average of 2 results.

Vinyl chloride polymer/NBR blends A B C E Laminated to vinyl chloride homopolymer sheet (PVC) at 170 C Thickness (mm) of vinyl chloride polymer rubber blend/PVC composite 4.3 3.7 3.6 5.5 Adhesion to PVC sheet very good very good very good fair BS D' hardness (PVC/vinyl chloride polymer-rubber blend) 45/41 48/41 47/37 49/48 - after 1 week 70 C 44/41 42/41 46/37 47/48 - after 2 weeks 70 C 44/40 47/42 46/39 48/49 Curling after 2 weeks 70 C slight none none none In the subsequent Examples the fomulations of tread crumb and whole tyre crumb used were as follows: Tread crumb: 50% rubber: 50% carbon black, oil, vulcanising agent etc.

42 parts natural rubber # 50 parts SBR # 8 parts polybutadiene rubber Whole tyre crumb: 55% rubber: 45% carbon black, oil, vulcanising agent etc.

60 to 70 parts SBR # 25 to 30 parts natural rubber # 10 parts polybutadiene rubber EXAMPLE II This Example gives the procedure for forming the base sheet of a sports-flooring composite using untreated tread crumb to provide a comparison with the subsequent Examples.

40 mesh tread crumb was mixed together with the following vinyl chloride polymer powders and plasticiser Parts Breon 125/1 2PVC homopolymer (BP Chemicals) 50 Breon AS70/42, vinyl chloride/vinyl acetate copolymer (BP Chemicals) 50 Dialphanyl phthalate (DAP) plasticiser 1 50 Mark LC-310 barium/cadmium complexstabiliser 2 Tread crumb 200 The mix was left overnight to allow partial absorption of the plasticiser and then was poured into a two-roll mill running at even speed and heated to 1450C. The material was processed until it had fused into a coherent sheet and then it was sheeted off hot at about 2.4 mm thickness A slab of the material was moulded in a positive compression-mould'at 1 650C for 10 min. to 1.6 mm using sufficient pressure to cause slight flashing of the material and the following properties at room temperature were obtained.

Tensile strength (MN/m2) 1.5 Elongation at break (%) 75 Tear strength (N/testpiece) 21 Hardness (OBS 'D') 42.5 Tripsometer resilience @ 50 C (%) 37 SG g/cc 1.171 A further portion of the base sheet was positive-compression moulded at 1 700C for 10 min.

against the PVC surfacing layer (see Example I). Sufficient moulding pressure was used to produce a small amount of flash from the mould. The composite was found to be poorly bonded, the base sheet tearing away easily from the surface sheet.

EXAMPLE Ill This Example iilustrates the improvement in physical properties and bond strength obtained by pretreating tread crumb with either bromine vapour or bromine dissolved in DAP prior to incorporation in a PVC matrix and then bonding to the PVC surfacing layer (see Example I).

Tread crumb was placed in a closed desiccator together with an open glass vessel containing log.

of liquid bromine per 1 00g of crumb. After 18 hours at ambient temperature all the bromine had volatilised and been absorbed by the crumb. This crumb was then compounded and formed into a test slab as in Example II. The properties obtained are given below under (a) for a sheetof 3 mm thickness.

A second experiment was carried out using 20g of liquid bromine dissolved in 1 50g of DAP plasticiser. This was mixed together with 2009 of tread crumb and left to stand at ambient temperature for 1 8 hours. After this time the remainder of the PVC formulation was added and processed as in Example II. The properties obtained were as (b) below for a sheet of 4.2 mm thickness.

(aJ (b) Tensile strength (MN/m2) 4.5 5.4 Elongation at break (%) 149 1 35 Tear strength (N/testpiece) 42.5 34 Hardness (OBS 'D') 44 51 Tripsometer resilience (%) 44 50 SG(g/cc) 1.185 1.204 Both these materials bonded well to the PVC surfacing layer (see Example I).

EXAMPLE IV This Example illustrates the beneficial effect obtained by treating tread crumb with a sufficient quantity of bromine water to give an analysed bromine content on the dry crumb of more than 1.5% by weight.

Batches of tread crumb were stirred into bromine water of various strengths and volumes as given in the following Table. These were left to stand at ambient temperature, for one hour, and then the crumb was filtered off, rinsed, and dried in a 700C air oven. Each crumb batch was then mixed and processed as in Example ll.

The results obtained are given in the Table below. Each sheet was approximately 2.7 mm thick.

Treatment for 100g crumb batch A B C D E * Saturated bromine water (g) 120 240 290 370 480 Diluting water (g) 360 240 720 750 Analysed bromine content weight (%) 0.73 0.67 1.99 2.9 1,59 Properties Tensile strength (MN/m2) . 1.2 1.4 2.5 4.7 2.1 Elongation at break (%) 94 101 143 163 116 Tear strength (N/Testpiece) 19 17 29 48 28 Hardness ("BS 'D) 37.5 35 - 46 37 Tripsometer resilience (%) 41.5 39 - 47 43 SG (g/cc) 1.147 1.145 1.150 - 1.148 (* Saturated bromine water contains 3.469 bromine/100g water at 20 C) Only the materials showing enhanced tear strength (i.e. C, D and E) bonded sufficiently well to the PVC surfacing layer (see Example I) to give a useful product. No detectable odour was noticed from these products.

EXAMPLE V This Example illustrates the benefit obtained by pretreating tread crumb with 5 parts of Suprasec DND isocyanate, the treated crumb being left to stand for a period before processing.

A batch of the tread crumb was placed in a Hobart planetary-action food-mixer and 59 per 1 00g of crumb of Suprasec DND (a crude liquid isocyanate supplied by ICI comprising about 55% 4,4'diphenylmethane diisocyanate with some 2,4-isomer, 25% triisocyanate and 20% polymeric isocyanate) containing 0.1% Stanclere DBTL (dibutyl tin dilaurate) was poured on and mixed with the crumb for 1 5 min.

This batch wds left to stand for one hour before being compounded and processed. A second batch was prepared in the same manner and left open to the air for one day before being mixed and processed. A third batch was left to stand open to the air for one month.

The properties obtained on 2.5 mm moulded sheets of the above materials were as follows.

Treated crumb standing time 1 hour 1 day 1 month Tensile strength (MN/m2) 2.3 2.8 1.8 Elongation at break (%) 78 95 82 Tear strength (N/testpiece) 32 36 20 Hardness ( BS'D) 47 49 44 Tripsometer resilience (oMO) ~ 47 SG (g/cc) 1.152 Thickness (mm) 2.4 2.5 3.1 The materials bonded reasonably well to the PVC surfacing layer (see Example I).

EXAMPLE VI This Example demonstrates the improved bond strengths obtained using 20 parts of Suprasec DND treatment on 100 parts of a) tread crumb and b) whole tyre crumb. Long storage time of the treated crumb had less effect than with a less concentrated pretreatment.

(a) 1 OOg of tread crumb was treated as in Example V using 20g of catalysed Suprasec DND.

Two batches were prepared, one was left to stand fbr one day and the other was left to stand for one month before compounding and processing as in Example II.

(b) 1 O0g of 40 mesh whole tyre crumb was treated as in Example V using 20g of catalysed Suprasec DND. The batch was left to stand for one day before being compounded and processed as in Example II.

The results are given in the following Table.

(a) (b) Crumb used Tread Crumb Whole Tyre Crumb Treated crumb standing time 1 day 1 month 1 day Tensile strength (MN/m2) 3.7 3.5 3.7 Elongation at break (%) 94 74 81 Tear strength (N/testpiece) 54 41 47 Hardness ("BS 'D) 59 64 61 Tri psometer resilience (%) 37 40 39 Thickness (mm) 2.8 3.1 2.6 The materials bonded well to the PVC surfacing layer (see Example I) EXAMPLE VII This Example shows the effect for three different storage periods of reducing the PVC content of the formulation in proportion to the degree of Suprasec DND treatment.

Separate 1 OOg batches of tread crumb were treated with both 1 Og and 20g of Suprasec DND as in Example V. A batch of each treatment level was left to stand for one hour, one day, and one week before mixing and processing as described in Example II, except tha the PVC content of the'formulation was reduced in proportion to the amount of Suprasec DND added. The formulations used and the physical properties obtained are given below.

109. Sup. DND/100g. 209. Sup. DND/100g. tread crumb tread crumb Formulation: Breon 125/12 46 42 Breon AS 70/42 46 42 DAP 138 126 Treated crumb 220 240 Standing time 1 hr 1 day 1 week 1 hr 1 day 1 week Properties:: Tensile strength (MN/m2) 2.6 3.7 3.7 5.0 5.0 5.6 Elongation at break ( /O) 60 88 100 85 68 75 Tear strength (N/testpiece) 38 43 41 58 60 53 Hardness (BS'D') 55 55 52 70 69 79 Tripsometer resilience (%) 45 45 46 38 36 32.5 Thickness (mm) 3.2 2.8 3.8 2.7 2.4 2.5

All the materials bonded very well to the PVC surfacing layer (see Example I).

EXAMPLE VIII This Example shows other types of polyisocyanate that may be used to treat tread crumb.

1 OOg batches of tread crumb were treated as in Example VI with 209 of each of the isocyanates given below. Each batch was left to stand for one day before mixing and processing as in Example II. TDI is a mixture of 2,4- and 2,6-tolylene diisocyanates. Isonate 1 43L (Upjohn) is a liquid grade of MDI containing about 10% of higher molecular weight material mainly consisting of uretonimine groups.

PBA 1042 (ICI) is a water-dispersible form of MDI and in one experiment this was mixed with water immediately before application to the crumb.

The results obtained are compared with the Suprasec DND treatment in the following Table.

Type of isocyanate used at Suprasec Ison. PBA PBA1042 209/1009 tread crumb DND 143L TDI 1042 2:1 water Tensile strength (MN/m2) 3.7 3.8 3.8 3.7 3.9 Elongation at break (O/o) 94 128 135 113 108 Tear strength (N/testpiece) 54 51 55 47 50 Hardness (BS'D) 59 58 61 53.5 59.5 Tripsometer resilience (%) 37 49 48.5 51.5 40.5 Thickness (mm) 2.8 3.8 4.2 4.4 3.1

Claims (24)

1. A resilient composite of at least one component comprising a plasticised vinyl chloride polymer composition bonded without an adhesive interlayer to at least one component comprising a particulate vulcanised rubber selected from nitrile rubber and pretreated rubber as hereinafter defined in a matrix of a plasticised vinyl chloride polymer composition.

2. A composite according to claim 1 wherein the surface of the rubber had been at least partially halogenated.

3. A composite according to claim 2 wherein the surface of the rubber had been at least partially brominated.

4. A composite according to claim 1 wherein the rubber had been treated with an organic polyisocyanate.

5. A composite according to claim 4 wherein the rubber had been treated with an organic polyisocyanate comprising 4,4'-diphenylmethane diisocyanate.

6. A composite according to claim 4 wherein the rubber had been treated with an organic polyisocyanate comprising toluene diisocyanate.

7. A composite according to claim 4, 5 or 6 wherein the rubber comprises more than 1.5% by weight based on the dry weight of rubber of isocyanate groups.

8. A composite according to claim 4, 5 or 6 wherein the rubber comprises at least 4.5% by weight of isocyanate groups based on the dry weight of rubber.

9. A composite according to any preceding claim wherein the rubber comprises particles of a size such that they will pass a B.S. 30 mesh sieve.

1 0. A composite according to any preceding claim wherein the rubber is present in an amount by weight of more than 30% based on the total weight of rubber and vinyl chloride polymer matrix.

1 A composite according to any of claims 1 to 9 wherein the amount of rubber is in the range 40% to 60% by weight based on the total weight of rubber and vinyl chloride polymer matrix.

12. A composite according to any preceding claim wherein the rubber is non-cellular.

13. A composite according to any preceding claim wherein the vinyl chloride polymer matrix comprises a mixture of poly(vinyl chloride) and a vinyl chloride/vinyl acetate copolymer.

14. A composite according to claim 1 and substantially as herein described with reference to any one of the Examples.

1 5. A method of producing a resilient composite by contacting at least one component comprising a particulate vulcanised rubber selected from nitrile rubber and pretreated rubber as hereinafter defined in a matrix of a plasticised vinyl chloride polymer composition with at least one component comprising a plasticised vinyl chloride polymer composition and applying heat to unite the assembly.

1 6. A method according to claim 1 5 wherein the rubber is pretreated with a liquid comprising 4,4'-diphenylmethane diisocyanate.

1 7. A method according to claim 1 5 wherein the rubber is pretreated with a liquid comprising toluene diisocyanate.

18. A method according to claim 1 5 wherein the pretreatment of rubber is by halogenation.

1 9. A method according to claim 18 wherein the pretreatment is by bromination.

20. A method according to any of claims 1 5 to 1 9 wherein the rubber is vulcanised prior to incorporation in the vinyl chloride polymer matrix.

21. A method according to any of claims 1 5 to 20 comprising the steps of i) pretreating a vulcanised particulate rubber, ii) mixing the pretreated vulcanised particulate rubber with a plasticised vinyl chloride polymer composition, iii) consolidating mixture (ii) with heat.

iv) contacting the resulting composition (iii) with a plasticised vinyl chloride polymer composition, and v) applying heat to unite the assembly (iv).

22. A method according to claim 1 5 having the feature defined in any one of claims 7 to 13.

23. A method according to claim 1 5 and substantially as herein described.

24. A method according to claim 1 5 and substantially as herein described with reference to any one of the Examples.