It is well know that plastic polymers are largely employed in the production of manufactured articles. Unfortunately plastic polymers require a hot molding procedure with high tonnage presses and costly steel molds.

Resin products capable of cold polymerization by means of appropriate catalysts are sometimes employed but their mechanical characteristics are very different from those of the above mentioned plastics and cannot replace them except in a very limited field of applications.

The general purpose of the present invention is to remedy the above mentioned shortcomings by making available a new plastic material which while having virtually the characteristics of a polymer such as for example polypropylene can be formed by cold techniques employed in cold hardening resins by means of an appropriate catalyst.

This allows the use for example of economical casting equipment in equally economical silicone molds or the like.

In view of this purpose it was sought to provide in accordance with the present invention a process for the production of cold molded plastic material comprising the steps of polymer particle production, dispersal thereof in a cold polymerizable resin in a quantity of at least 20% by weight of the total, and addition of a catalyst to the

resin to harden it.

Again in accordance with the present invention it was also sought to provide a plastic material comprising a cold polymerized resin containing as filler at least 20% by weight of dispersed polymer particles.

To clarify the explanation of the innovative principles of the present invention and its advantages compared to the prior art there is described below by way of example a possible embodiment applying said principles.

In a process in accordance with the present invention for the production of cold molded plastic articles one begins by producing polymer particles advantageously of polypropylene. Then these particles are dispersed cold in a polymerizable resin in an amount of at least 20% by weight of the total and preferably at least 35%. The product is then hardened in the desired form by the addition of an appropriate catalyst suitable for hardening of the resin employed. As the process takes place cold, costly presses and equally costly steel molds or the like are unnecessary and economical pour molding equipment is sufficient.

It has been found that infiltration of the resin as the antistripping agent into the crystal chain of the polymer particles with the polymers amalgamated and incorporated cold gives the finished product good mechanical characteristics for example satisfactorily similar to those of a hot molded polymer plastic product without the above mentioned disadvantages of hot molding.

It has been found particularly advantageous for the

qualitative characteristics of the product to use micronized polymer particles with grain size between 200pm and 500pm and preferably between 250pm and 450pm. It has been found indeed that particles with similar dimensions achieve very satisfactory cohesion between the polymer and the binder.

Among the possible forms of the micronized particles the spheroidal form has been identified as preferred. In addition the spheroidal particles can be advantageously produced with cavities distributed over the surface.

Indeed it has been found that the cavities receiving and incorporating the binder improve cohesion.

Among the employable resins polyester resin made up of unsaturated polymers with the addition of unsaturated monomers in a proportion of 25% to 50% and preferably 30% to 40% has been found particularly advantageous and capable of polymerizing with free radicals to give a reticulate copolymer as the result. The preferred unsaturated polymers have a molecular weight above 2000. It has been found that unsaturated polyester resins as the binder, being chemically inert with respect to polypropylene or the like, give the material good mechanical properties and chemical stability.

Various suitable catalysts can be used for cold hardening of the resin.

But it has been found particularly advantageous to use a catalyst made up of acetylacetone peroxide in a concentration between 0.5% and 5% by weight of the resin and in particular between 1% and 4% with the aid of a froth

promoter made up of Co-octane at 6% to 12% in variable concentration. The percentage of froth promoter can vary depending on the type of object it is desired to produce while its concentration depends on the thickness of the article and required hardening time. If thicknesses are relatively low it has been found advantageous to use a concentration between 2% and 3% and preferably around 2.5% by weight of the resin.

For very thick articles in which disposal of heat produced by the hardening reaction might be difficult it has been found more advantageous to use a catalyst made up of methylethylketone peroxide with percentages by weight of resin between 0.5% and 5% and in particular between 1% and 4% with the aid of an accelerating agent made up of Co salts in a percentage between 2% and 3% and preferably around 2.5% by weight of the resin.

If it is wished to produce articles with a light color or transparent, instead of using Co salts as the accelerating agent it has been found preferable to use an accelerating agent made up of N, N-diethylacetoacetamide in a concentration between 0.05% and 0.4% and preferably between 0.1% and 0.4% by weight of the resin.

Although the characteristics of the material produced by the cold process in accordance with the present invention proved to be surprisingly good even without the use of the known materials which necessitate hot processes it was found possible to further improve the mechanical characteristics if necessary by reinforcing the product by inserting dispersed glass fiber sheets or threads in the

mass before the resin hardens. This is quite feasable during pouring of the material into the mold.

It is now clear that the predetermined purposes have been achieved by making available a virtually cold process achieving with a material comprising a cold polymerized resin containing dispersed particles of a polymer as filler the advantages of production with cold hardening polyester resins or the like and at the same time mechanical and qualitative advantages peculiar to hot production using plastic polymers.

Naturally the above description of an embodiment applying the innovative principles of the present invention is given by way of non-limiting example of said principles within the scope of the exclusive right claimed here.