GB1585260A - Flexible polyurethane moulded product - Google Patents

Description

(54) FLEXIBLE POLYURETHANE MOULDED PRODUCT (71) We, GENERAL FOAM PRODUCTS LIMITED, a British Company of West Chirton, North Shields, Northumberland, NE29 7UA, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to flexible and resilient moulded products composed predominantly of polyurethane resin.

In our Patent Specification No. 1,337,413 we have described a moulded product which comprises comminuted foam material, preferably polyurethane, having a particle size not exceeding 2 mm in a substantially non-cellular matrix of polyurethane resin, the product having a density in the range 10-60 lb/cu. ft. (160--960 kg/m3). Such a product is prepared by mixing together the comminuted foam material and a polyurethane precursor composition, and moulding and curing the mixture under pressure.

The preferred range specified for the density of the product in this prior specification is 25-40 lb/cu.ft and the formulation described in the Example therein falls within this range.

We have now surprisingly found that a moulded product of outstanding and distinctive properties can be obtained if a density between 50 and 60 or between 60 and 75 Ib/ cu.ft, preferably between 55 and 60 or between 60 and 65 Ib/cu.ft is selected.

Products with densities within this higher range have better wear-resistance than products specifically disclosed in Specification No. 1 337 413 and have other advantages.

Thus, for example, the moulded products of this invention exhibit enhanced resilience and readily regain their original shape after compression.

The improved properties of the moulded products having a density in the range 5075 Ib/cu.ft make them especially suited for use as shoe outer soles. It is to be noted however that this suitability found in practice is itself somewhat unexpected since sample soles may appear to show technical faults when subjected to conventional laboratory tests but appear highly satisfactory when tested in actual wear.

The invention also provides a method of making a moulded product suitable for the production of shoe soles which comprises mixing together comminuted foam material having a particle size not exceeding 2 mm.

and a polyurethane precursor composition, and moulding and curing the mixture under a pressure sufficient to give the product a density between 50 and 60 or between 60 and 75 Ib/cu.ft. As in Specification No.

1 337 413 the moulding mixture preferably contains a compatible solvent or carrier medium.

The comminuted foam material is preferably composed of polyurethane and preferably has a particle size in the range 0-1 to 2 mm. and a free density of 6 5 to 7-51 b/cu.ft.

Comminuted foam particles in this size range have little residual cellularity and are only slightly compressible individually. They are, however, distorted under pressure and tend to be flattened during moulding, with expulsion of interparticulate air, whereby a starting material of low bulk density can be accommodated in a product of relatively high density.

In estimating the particle size of the comminuted foam in the finished product, it is convenient to determine the mean value of particle diameter measured in two perpendicular directions in the matrix.

The techniques employed for preparing moulded products in accordance with the present invention can be similar to those described in Specification No. 1 337 413 though with some modification because of the higher densities involved. The foam material, preferably comminuted polyurethane, must still have a particle size not exceeding 2 mm, and the comminuted material still preferably represents the predominant constituent by weight in the finished product, but we have found it preferable to use 10 to 50% by weight polyurethane precursor composition in the moulding mixture, rather than the 7 to 30% expressed in Specification No. 1 337 413. The actual moulding process can be much the same as before though it is usually necessary to incorporate heat-treatment of the mixture.

This heat-treatment, which may be carried out during moulding or post-moulding (even after subdivision of the compressed mixture into, for example, sheets or boards) is desirable to facilitate a complete cure or to remove any residual solvent. As with the previous products, but more so because of the higher moulding pressures, the pressure in the mould largely suppresses the tendency of the polyurethane precursor to foam, and the product is thus substantially non-cellular.

That is to say, the binder or matrix in the product is not overtly cellular to the eye and behaves as it it were almost solid, but small voids or cells can be discernible on, for example, microscopic inspection.

The present invention will now be described further by way of illustration with reference to the following example, which relates to the manufacture of shoe soles.

Example A moulding formulation is made up as follows: Prepolymer of 4000 m.w.

polyol and toluyene di-isocyanate (Casa S8392- Trade Mark) 110.5 g Ground polyurethane foam powder (less than 2 mm.) 442 0 g Ethyl acetate 76-8 g The mixture was moulded under pressure to give a product with a density of 61 Ib/cu.ft.

The moulded product was then subdivided into sheet form and shoe soles cut therefrom.

In use over an extended trial period, such soles show little wear or marking.

The products of this invention differ from the materials specifically described in our Specification No. 1 337 413 in their utility as shoe outer wear-soles. The earlier described materials were suitable, for example, for insoles but were too absorptive and sensitive to notching for use as outer soles.

The materials of this invention tend to reject foreign bodies during wear, perhaps owing to an inbuilt high stress, and demonstrate high wear resistance.

WHAT WE CLAIM IS: 1. A moulded product suitable for the production of shoe soles and comprising comminuted foam material having a particle size not exceeding 2 mm. in a substantially non-cellular matrix of polyurethane, the product having a density between 50 and 60 or between 60 and 75 Ib/cu.ft.

2. A moulded product according to Claim 1 wherein the comminuted foam material is composed of polyurethane and is the pre dominant constituent of the product.

3. A moulded product according to Claim 1 or 2 having a density between 55 and 60 or between 60 and 65 Ib/cu.ft.

4. A method of making a moulded product suitable for the production of shoe soles which comprises mixing together com minuted foam material having a particle size not exceeding 2 mm. and a polyurethane precursor composition, and moulding and curing the mixture under a pressure sufficient to give the product a density between 50 and 60 or between 60 and 75 Ib/cu.ft.

5. A method according to Claim 4 wherein the moulding is conducted at a pressure giving a product density between 55 and 60 or between 60 and 65 Ib/cu.ft.

6. A method according to Claim 4 or 5 wherein the precursor composition constit utes from 10 to 50% by weight of the mould ing mixture.

7. A method according to Claim 4, 5 or 6 wherein the comminuted foam material is pulverized cellular polyurethane having a particle size in the range 0 1 to 2 mm and a free density of 6 5 to 7.5 Ib/cu.ft.

8. A method according to any of Claims 4 to 7 wherein the moulding mixture includes a compatible solvent or carrier medium.

9. A moulded product substantially as described with reference to the Example herein.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. represents the predominant constituent by weight in the finished product, but we have found it preferable to use 10 to 50% by weight polyurethane precursor composition in the moulding mixture, rather than the 7 to 30% expressed in Specification No. 1 337 413. The actual moulding process can be much the same as before though it is usually necessary to incorporate heat-treatment of the mixture. This heat-treatment, which may be carried out during moulding or post-moulding (even after subdivision of the compressed mixture into, for example, sheets or boards) is desirable to facilitate a complete cure or to remove any residual solvent. As with the previous products, but more so because of the higher moulding pressures, the pressure in the mould largely suppresses the tendency of the polyurethane precursor to foam, and the product is thus substantially non-cellular. That is to say, the binder or matrix in the product is not overtly cellular to the eye and behaves as it it were almost solid, but small voids or cells can be discernible on, for example, microscopic inspection. The present invention will now be described further by way of illustration with reference to the following example, which relates to the manufacture of shoe soles. Example A moulding formulation is made up as follows: Prepolymer of 4000 m.w. polyol and toluyene di-isocyanate (Casa S8392- Trade Mark) 110.5 g Ground polyurethane foam powder (less than 2 mm.) 442 0 g Ethyl acetate 76-8 g The mixture was moulded under pressure to give a product with a density of 61 Ib/cu.ft. The moulded product was then subdivided into sheet form and shoe soles cut therefrom. In use over an extended trial period, such soles show little wear or marking. The products of this invention differ from the materials specifically described in our Specification No. 1 337 413 in their utility as shoe outer wear-soles. The earlier described materials were suitable, for example, for insoles but were too absorptive and sensitive to notching for use as outer soles. The materials of this invention tend to reject foreign bodies during wear, perhaps owing to an inbuilt high stress, and demonstrate high wear resistance. WHAT WE CLAIM IS:

1. A moulded product suitable for the production of shoe soles and comprising comminuted foam material having a particle size not exceeding 2 mm. in a substantially non-cellular matrix of polyurethane, the product having a density between 50 and 60 or between 60 and 75 Ib/cu.ft.

2. A moulded product according to Claim 1 wherein the comminuted foam material is composed of polyurethane and is the pre dominant constituent of the product.

3. A moulded product according to Claim 1 or 2 having a density between 55 and 60 or between 60 and 65 Ib/cu.ft.

4. A method of making a moulded product suitable for the production of shoe soles which comprises mixing together com minuted foam material having a particle size not exceeding 2 mm. and a polyurethane precursor composition, and moulding and curing the mixture under a pressure sufficient to give the product a density between 50 and 60 or between 60 and 75 Ib/cu.ft.

5. A method according to Claim 4 wherein the moulding is conducted at a pressure giving a product density between 55 and 60 or between 60 and 65 Ib/cu.ft.

6. A method according to Claim 4 or 5 wherein the precursor composition constit utes from 10 to 50% by weight of the mould ing mixture.

7. A method according to Claim 4, 5 or 6 wherein the comminuted foam material is pulverized cellular polyurethane having a particle size in the range 0 1 to 2 mm and a free density of 6 5 to 7.5 Ib/cu.ft.

8. A method according to any of Claims 4 to 7 wherein the moulding mixture includes a compatible solvent or carrier medium.

9. A moulded product substantially as described with reference to the Example herein.