GB2072200A

GB2072200A - Moulding compositions comprising particulate elastomeric fillers

Info

Publication number: GB2072200A
Application number: GB8108863A
Authority: GB
Original assignee: VIK PLASTICS Ltd
Current assignee: VIK PLASTICS Ltd
Priority date: 1980-03-24
Filing date: 1981-03-20
Publication date: 1981-09-30
Also published as: IE800603L

Abstract

A moulding composition comprises a plasticized thermoplastic material and a particulate elastomeric material as a filler. The plasticized thermoplastic material is preferably a blend of polyvinylchloride (PVC) homopolymer with PVC copolymer combined with a plasticizer such as Di-octyl phthalate. The particulate elastomeric material may be rubber obtained from scrap motor vehicle tyres and ground to a particle size of 40 mesh. The moulding composition is used to manufacture articles such as shoe soles.

Description

SPECIFICATION Fillers for polymers The present invention relates to fillers for polymeric materials and in particular to fillers for thermoplastic materials such as polyvinyl chloride compounds.

It is weli known for polymeric materials to have particulate fillers added to them. These fillers generally comprise inorganic particles, added in amounts of up to 40% by weight; they are used primarily to reduce the cost of the material but they may also be added to modify the physical properties of the polymeric materials. With certain exceptions, such fillers generally serve to increase the stiffness and to decrease the tensile strength of the polymeric materials to which they are added.

Materials having elastic properties such as for example rubber have hitherto not been used as particulate fillers as they have been believed to be unsuitable for use in injection moulding. It was thought that each individual elastic particle would decrease in size under the pressure exerted during the injection moulding process and that upon release of the pressure, the particle would "relax", that is it would tend to regain its original size and shape, and that this relaxation could cause rupturing of the three dimensional matrix of polymeric material.

We have prepared a material comprising plasticized polyvinyl chloride homo- and co-polymers having particulate ground vulcanized rubber as a filler in which the polyvinyl chloride matrix, when molten, can fuse with the rubber filler and, when solidified, possesses good cohesion with the rubber and has sufficient flexibility to allow the rubber particles to behave elastically. We have found that the material may be used in injection moulding and may be formed into "chips" for that purpose and that the material has certain advantageous physical properties, in particular that it is highly resistant to wear, making it suitable for use in shoe soles, shock absorbers and other manufactured products requiring flexibility and wear resistance.

We believe that these advantageous physical properties are present because the rubber, due to its elastic properties, is able to absorb energy without permanent strain, and that when the material is stressed or flexed this energy of deformation is absorbed by the rubber particles thus lengthening the life of the material.

The invention accordingly provides a moulding composition including a filler, comprising a plasticized thermoplastic material in which the filler is a particular elastomeric material. Advantageously the thermoplastic material includes polyvinylchloride combined with a plasticizer and conveniently the material includes a blend of polyvinylchloride homopolymer with polyvinylchloride copolymer combined with a plasticizer. The particulate elastomeric material is ground rubber having a particle size less than size 20 mesh and preferably about size 40 mesh. Advantageously the ground rubber is obtained from scrap motor vehicle tyres.

The invention will now be described more particularly in the following three Examples which will show the developments leading to the preferred formulation given in Example 3.

EXAMPLE 1 A rubber filled polyvinyl chloride material was prepared having the following composition: Ingredients Parts by weight PVC homopolymer 100.0 Di-iso octyl Phthalate 60.0 Ground Rubber (20 mesh) 150.0 Calcium carbonate 50.0 Ceroclor S52 40.0 Lankro ED3 4.0 Manomet 459 2.0 The Di-iso octyl phthalate acts as a plasticizer for the homo-polymer and together they form the cohesive matrix in which the rubber particles are embedded. The calcium carbonate acts as an additional filler for the compound. Manomet 459 is a polyvinyl chloride stabilizer, that is it reacts with any chlorine that is evolved from the polyvinyl chloride. Lankro ED3 is an epoxidised oil which acts as an antioxidant and lubricant. Ceroclor S52 is a chlorinated paraffin and is used as an extender for the plasticizer.

This material was prepared by heating in a hot air circulation oven at 1 700C for eight minutes.

The material was found not to have sufficient cohesion between the rubber particles and the polyvinyl chloride homopolymer.

EXAMPLE 2 A further rubber filled polyvinyl chloride material was prepared having the following composition.

Ingredients Parts by weight PVC homopolymer 100.0 Di-iso octyl phthalate 60.0 Ceroclor S52 40.0 Butyl benzyl phthalate 30.0 Ground rubber (20 mesh) 150.0 Snowcal 7 ML 50.0 Lankro ED3 4.0 Manomet 459 2.0 Butyl benzyl phthalate is a plasticizer but is more volatile than Di-iso octyl phthalate.

Preparation of the material was as in Example 1.

The combination of two plasticizers produced a highly solvating plasticizer and dramatically improved the cohesion between the rubber and polyvinyl chloride. However the addition of Butyl benzyl phthalate introduced an undesirable degree of volatility into the material. To achieve this same degree of cohesion without introducing the volatility it is possible to use a combination of a polyvinyl chloride homopolymer and polyvinyl chloride copolymer.

EXAMPLE 3 A further rubber filled polyvinyl chloride material was prepared having the following eompositiont Ingredients Parts by weight PVC homopolymer (Norvinyl S3--68) 80.0 PVC copolymer (Vinnol E5-65C) 20.0 Di-octyl phthalate (Palatinol AH) 106.0 Ground rubber (40 mesh) 57.5 Calcium Carbonate (Snowcal 7ML) 3.0 Manomet 459 2.75 Lankro ED3 1.5 Monarch Black 800 Paste 0.4 Stearic Acid 0.15 271.30 The plasticizer used is Di-octyl phthalate, it being even more stable than Di-iso octyl phthalate.

Monarch Black 800 Paste is a carbon black pigment and the stearic acid is used as a stabilizer and lubricant. The rubber particles in Examples 1 and 2 gave excessive rebound due to their large size, so in this formulation particles of reduced size (40 mesh) were used and the percentage concentration was also reduced. The extender was removed and the calcium carbonate content was reduced to improve the fusion of the material.

The above material was prepared on a Werner plastificator/ pelletiser which produced the material in "Chip" form suitable for use in commercial injection moulding processes. The proportion of plasticizer may be varied approximately + 10% and the proportion of ground rubber may be varied approximately + 5% without affecting greatly the quality of the material.

In manufacturing articles by the injection moulding process, using this material, higher injection pressures must be used than for homogeneous polyvinyl chloride compounds, due to the back pressure developed by this material; and the cooling cycle in the mould may have to be longer to allow the polyvinyl chloride to orientate itself about the rubber particles as they relax.

This material was found to be highly wear resistant making it suitable for use in shoe soles, shock absorbers and other manufactured products requiring flexibility and wear resistance. Articles manufactured from the above material and in the above manner were lighter than articles made from conventional polyvinyl chloride, had a duller appearance or "finish", had better slip and abrasion resistance and were found to be free from cracking problems. A big advantage of this material is that the rubber filler may be obtained from scrap motor vehicle tyres and so fulfills the primary function of a filler1 which is to reduce the unit volume cost of the manufactured product.

The mesh sizes used for the rubber particles in the above Examples are the mesh sizes used in British Standards Institute Specifications for particle sizes.

In Example 3 a black colouring pigment is used. It is possible to use different colouring pigments so as to produce manufactured products of a different colour e.g. brown, beige or grey shoe soles.

Claims

1. A moulding composition including a filler, comprising a plasticized thermoplastic material in which the filler is a particulate elastomeric material.

2. A moulding composition according to Claim 1 in which the thermoplastic material includes a polyvinylchloride combined with a plasticizer.

3. A moulding composition according to Claim 1 or Claim 2 in which the thermoplastic material includes a blend of polyvinylchloride homopolymer with polyvinylchloride copolymer combined with a plasticizer.

4. A moulding composition according to any preceding claim in which the particulate elastomeric material is ground rubber.

5. A moulding composition according to Claim 4 in which the particle size of the ground rubber is less than 20 mesh.

6. A moulding composition according to Claim 4 in which the particle size of the ground rubber is 40 mesh.

7. A moulding composition according to Claim 4, 5 or 6 in which the ground rubber is obtained from scrap motor vehicle tyres.

8. A moulding composition according to any of Claims 1 to 6 which includes 100 parts by weight of a blend of polyvinylchloride homopolymer and polyvinylchloride copolymer, between 95 and 11 5 parts by weight of a plasticizer, such as Di-octyl phthalate and between 55 and 60 parts by weight of ground rubber.

9. A moulding composition according to Claim 7 which includes a colouring pigment.

10. A moulding composition according to Claim 1 substantially as herein described with reference to any of the Examples.

11. A moulding composition according to Claim 1 substantially as herein described with reference to Example 3.

12. A moulding composition which comprises a plasticized homopolymer or copolymer of vinylchloride forming a matrix in which particles of vulcanised natural or synthetic rubber are dispersed.

13. A shoe comprising a sole prepared from a moulding composition according to any preceding claim.

14. A manufactured product when prepared from a moulding composition claimed in any of claims 1 to 12.