WO2014132184A1

WO2014132184A1 - Recycling method

Info

Publication number: WO2014132184A1
Application number: PCT/IB2014/059224
Authority: WO
Inventors: Emanuele BRAVO; Giovanni LUCCHESE; Franco Mioni
Original assignee: Gees Recycling Srl
Priority date: 2013-02-27
Filing date: 2014-02-25
Publication date: 2014-09-04

Abstract

The application relates to a recycling method for fiber-reinforced plastics materials comprising the steps of extruding a mixture formed by fragments of the material and an artificial resin in order to obtain a product in a solidified form, e.g. in granules, and subsequently to be able to feed producing machines, e.g. moulding machines with said product. Further it claims a granule (10) comprising an outer coating (20) of synthetic resin having at least one fragment (30) of fiberglass or fiber embedded in synthetic resin inside of it. Further the application claims an industrial plant for implementing the proposed method of recycling and a method for reprocessing the produced granules.

Description

RECYCLING METHOD

The invention mainly relates to a recycling method for plastic materials reinforced with fibers, particularly fiberglass here taken as an example, and/or to the product of the method.

For plastic materials reinforced with fibers, commonly referred to by the acronym FRP (Fibre Reinforced Polymers), it is meant here, and generally, those that incorporate inside them fiber e.g. made of Carbon (Carbon Fiber Reinforced Polymer) or glass, i.e. fiberglass (Glass Fiber Reinforced Polymer). They are particularly appreciated thanks to their chemical-physical and mechanical characteristics, and provide excellent corrosion resistance, good thermal insulation, high mechanical resistance and extreme lightness. In particular, the fiberglass is used in many products, such as boat hulls, bathtubs, silos and containers of various types. Its intense use determines the natural problem of disposal, made very difficult by the huge difficulty or impossibility of separating the fibrous elements from the polymer matrix.

A solution is present in US2008/0217811, which describes a process for the recycling of fiberglass. It consists in preparing a mixture comprising fragments of fiberglass, polyester resin, titanium dioxide, microspheres of thermoplastic material and benzoyl peroxide with a catalyst. The mixture is poured into a mold and then hot-pressed to form an object.

There are however several disadvantages. The preparation of the mixture requires the handling of milled fiberglass, which is very volatile and behaves as a toxic dust. Or one is equipped with expensive aspiration systems or the production of such molded articles is impossible, or at least unhealthy. Furthermore, for the same reason it is difficult to transport the milled fiberglass from one plant to another, which obliges to have dedicated molding sites thereby reducing the potential of recycling, on a global scale, of the system, thus requiring expensive ad hoc processing plants. In other applications glass microspheres are used as reinforcements to be added to the mixture to be molded. But the microspheres are expensive, and do not give rise to the fibrous filaments that so much boost the resistance of a material. To provide a method and/or a product that solves at least one of these problems is the main object of what is defined in claim 1, with the dependent claims defining advantageous variants.

The method involves recycling plastic material reinforced with fibers by the extrusion of a mixture formed by fragments of the material and an artificial resin. The mixture is brought into solidified form, in order to be able to feed then producing machines, e.g. molding machines. Preferably the mixture is reduced to granules, easily processable subsequently and a standard form of molding or extrusion material. Such granules can have any shape, regular or irregular, and can advantageously coincide, in shape and size, substantially with the granules commonly used in extruders or molding machines by the processing industry of plastic materials. Therefore, they are easy to process with and can replace or blend with the existing ones.

By artificial resin (or synthetic resin) it is defined here in general a material of polymeric nature capable of cold- or hot-hardening. Among the most common synthetic resins one can use phenolic resins, acrylic resins, epoxy resins, polyester resins, e.g. unsaturated (UPR, Unsaturated Polyester Resin), polyurethane resins, vinyl ester resins (VE), acrylonitrile-butadiene-styrene (ABS), or polypropylene. By fiberglass (or VTR) it is meant here in general a plastic reinforced with glass or glass fibers (and/or carbon, kevlar), impregnated with resins, e.g. thermosetting resins, or e.g. liquid resins and polyester-, vinylester- or epoxy-based resins (hardening due to catalysts or accelerators). The melting point of the resins preferably coincides with the temperatures of the known industrial extruders.

Fiberglass is also known as plastic reinforced with glass or GRP (from glass- reinforced plastic), glass fiber reinforced plastic or GFRP, GFK (from the German Glasfaserverstarkter Kunststoff), or fiberglass from the name of the material that constitutes it, together with the plastic matrix. The solidified product thus obtained is then used e.g.:

(i) directly, for hot-molding; or

(ii) for mixing and processing (gelatinization ) in dies or extruders for obtaining a final semimanufactured product (e.g. Granules or tapes ). The semifinished products have shape and size suitable for feeding subsequently producing machines of a finished object, e.g. machines for hot molding.

In other words, in addition to the solidified product (granules or balls of resin with fiber fragments dispersed inside, e.g. fiberglass, in random position - case (i) - semi-finished products can also be produced (e.g. in the form of cylinders, spheres, cubes or strips, in regular and/or predefined or irregular shapes) obtained by mixing and extruding together a portion of resin having inside the aforesaid fragments and at least another resin (case (ii)), in order to increase the total percentage of resin around the fibers.

In both cases, the great advantages are to incorporate in the resin the fiber fragments avoiding their dispersion in the environment and ease of manipulation within production cycles, especially standard cycles. Every pre-existing plant can use as raw (semi-finished) material the aforementioned solidified product, without modifications or special precautions, being able to produce, however, products made of recycled-fiber reinforced material that are cost-effective.

In case (i) the solidified product is produced directly with the mixture and in an appropriate form for feeding the packaging machines of the finished article.

In case (ii) the solidified product comprising recycled fiber (fiberglass) and resin (a semi-finished product altogether) is destined to mixing and re-processing by e.g. extrusion with other semi-finished products or raw materials. The solidified product is advantageously re-processed or re-processable via e.g. subsequent molding (for ease of processing), e.g. with one or more other resin. A semifinished product of desired shape and composition is obtained through e.g. further processing into granules. Here the solidified product can be combined with elements commonly defined "fillers", such as talc, calcium carbonate, titanium and the microspheres. Given that more resin is added later, it is preferable then to produce initially the solidified product with the maximum percentage of fiberglass or recycled fiber, limiting to a minimum the quantity of resin to the value just sufficient to hold the fibers incorporated (e.g. fibers of glass) and to give the solidified product predetermined shape and dimensions.

In the method before step (I) it is preferable a phase wherein the material is reduced to fragments, e.g. with size or average or maximum particle size of 2,5 mm. This size range has for benefits the reduced emissions of dust, a good mechanical compatibility with the dry-mixing systems of the processing plants, the correct proportion with respect to the average size of the granulized semifinished products that feed the processing machines for thermoplastic materials, and the conferment of mechanical properties to the finished product resulting from the lattice of the glass fibers. Or, by making use of dusters, the material is reduced to fragments, e.g. with size or maximum grain size of tenths of a millimeter, e.g. 0.5 mm. This size range has the advantage of limiting the visibility of the recycled fragment into the finished product, and of mixing and recovering even the smallest parts of fiberglass arising from industrial waste of fiberglass.

Note that preferably the said fragments are obtained by milling of a pre-existing object produced with fiberglass. Therefore the fragments are in turn composite elements or particles, formed by fibers of glass embedded or dispersed in the synthetic resin which formed the object that has been crushed or pulverized.

As another aspect of the invention, it is proposed a solidified product, e.g. in the form of granule/s, comprising an outer coating of synthetic resin inside which there is at least a fragment of fiberglass or fiber embedded in synthetic resin.

In the product the at least one fragment can have a diameter or maximum or average size of 2÷3 mm, or about a few tenths of a millimeter.

By weight the product or granule can be formed by 70% of outer coating and 30% for the at least one fragment. We point out these proportions as an example of average balance between synthetic resin and recycled fiberglass material in the finished product, where the structural and ecological advantages conferred by ground material of recycled fiberglass do not affect the aesthetic and elastic qualities of the pure synthetic resin. The average parameter can vary according to the synthetic resin used and the physical and chemical characteristics that it is intended to give the finished product.

As another aspect of the invention, it is proposed an industrial plant adapted to implement the method as defined above, as well as in one or more of the variants described.

As another aspect of the invention, it is proposed a method of processing, preferably molding or extrusion, in which a solidified product or granule as defined above, also in one or more of the variants described, is used and/or processed.

As another aspect of the invention, it is proposed the use of a solidified product or granule as defined above to produce an object, e.g. by molding or extrusion, as well as in one or more of the variants described.

The advantages of the invention will be more apparent from the following description of a preferred embodiment, making reference to the attached drawing in which

- Figure 1 shows a cross-section of a granule.

In figure 1 is visible a solidified product in the form of a granule 10 as obtainable by the recycling method.

On average, the granule 10 looks like a small sphere or ball 20 (or other shapes, e.g. a cylinder, cube, or ribbon) of synthetic resin inside which there is blended and incorporated at least one fragment 30 of fiberglass or fiber of glass. The fragment 30 is obtained by finely grinding an object made of fiberglass, e.g. an industrial waste or a ship hull. Therefore, the fragment 30 in turn ends up to be formed by glass fibers (usually with a 50%-60% percentage) embedded or dispersed in synthetic resin. The sphere/cylinder 20 naturally covers the fragment 30 when the milled fiberglass and the synthetic resin are mixed (e.g. by using mechanical dry- blending mixing) in the mixture of resin, which is then extruded (gelatinization and processing). In the mixture that occurs inside mixers and standard screw-dies, twin screw- dies, or pushing-dies the fragments are distributed chaotically in the resin, and Fig. 1 is only an ideal model. Each granule 10 can therefore include more than one fragment 30 and/or placed in even different position/s than the illustrated one. The dry-blending and gelatinization create a fusion amalgam (at the molecular level) that holds all the fiber fragments 30 inside the granule 10, so it is fairly certain that the fragment locates just in or near the center of the sphere/cylinder 20. The granules 10 are destined to molding or extrusion of fiber-reinforced plastic objects. Their composition can directly determine that of the final object, or can be modified, e.g. with the addition of granules of sole resin, to dilute the fibrous percentage. For example, granules were produced with satisfactory final results having e.g. diameter or maximum dimension of 2,5 mm, whose composition by weight is

10% fiberglass + 90% resin; or

20% fiberglass + 80% resin; or

50% fiberglass + 50% resin; or

70% fiberglass + 30% resin; or

80% fiberglass + 20% resin.

As a guideline it is good not to go down too much with the percentages of resin 20, because it is advantageous that it covers the fragment/s 30, in order to avoid blockages or jams during molding / extrusion.

If the granules 10 are to be mixed and re-processed by molding with other resins to obtain a semi-finished product of desired shape and composition through further processing in form of granules (also in combination with elements commonly defined fillers, such as talc, calcium carbonate, titanium and microspheres), they are preferably made with the highest percentage of recycled fiberglass limiting to the minimum the quantity of resin (just enough to retain embedded the fibers of glass and give the granule predetermined shape and dimensions). Otherwise the granule can be produced directly in the mixture and in an appropriate form for feeding the packaging machines of the finished item.

The fragments 30 are the result of grinding the material to be recycled. By several processing steps, e.g. in a series of mills, it is preferred to grind it as long as it reaches a diameter or size or maximum grain size of 2,5 mm, for the purpose of easily coating it with the resin 20, and/or

ensuring the passage through the injectors of the molding machines, which might otherwise become clogged, and/or

avoiding spontaneous combustion.

Note that to produce the granule 10 one can entirely use standard dry-blending installations (of various types) for the obtainment of the mechanical mixing, and then plants for gelatinization of the dry blend with cylinder mixers, closed mixers, extrusion screw-dies, twin screw-dies or pushing-dies, and cutting units upstream (water-bath units, liquid-ring units, dry units, by centrifugation or rotating blades, or in general any known unit of extruders with cutting units).

Extrusion tests have fully demonstrated the goodness of the granule.

As options, in the mixture for the granule one can insert:

- in percentages that can vary from 1 to 2%, a charge of "canceller essence", i.e. chemical additives in the form of masterbatches), which in the granule neutralizes any undesirable odors obtained from extrusion;

a charge of stearate zinc, e.g. 0.5%, which facilitates the flow of the mixture in the extruder ;

- a colored master or coloring agents, demonstrating the staining capacity of the material.

Better compatibilities of milled fiberglass with polyethylene were also seen, whose extrusion, tested on a model of twin-screw extruder, was more fluid (with extrusion temperatures below 180 °C) and with a greater hourly productivity with respect to the polypropylene (whose extrusion temperature was about 275 °C).

With the polyethylene e.g. the percentage of fiberglass in a mixture of 60 % with older machines was reached. With modern machines one can reach a percentage of 90 %>, allowing compositions as in the following table (by weight ) :

10% fiberglass + 88-89% resin + 1-2 %> essences and charges, or

20% fiberglass + 78-79 %> resin + 1-2 %> essences and charges or

50%) fiberglass + 48-49 %> resin; + 1-2 %> essences and positions, or

70%) fiberglass + 28-29 %> resin + 1-2 %> essences and charges, or

80%) fiberglass + 18-19%> resin + 1-2 %> essences and charges, or

90%) fiberglass + 8-9 %> resin + 1-2 %> essences and charges.

Other products with satisfactory final results were obtained with the previous composition.

In particular, it has been verified the ability to calibrate and/or vary in a wide range the mixtures with the goal of obtaining either a semi-finished product with a high concentration of fiberglass aimed to further mixing, or granules, whose composition and/or coloration is suitable to direct transformation into the finished product.

Claims

1. Recycling method of plastic fiber-reinforced material, comprising the step of (I) extruding a mixture formed by fragments of the material and an artificial resin in order to obtain a product in solidified form, e.g. in granules, to be able to feed then producing machines, e.g. molding machines.

2. Method according to claim 1, wherein before the step (I) there is a step

(la) wherein the material is reduced into fragments of maximum size or grain size of 2₁5 mm or a few tenths of millimeter.

3. Method according to claim 1 or 2, wherein the material is fiberglass.

4. Method according to claim 1 or 2 or 3, wherein the resin is polyester resin or acrylic resin or polyurethane resin or epoxy resin.

5. Method according to any one of the preceding claims, wherein the product or the granules are re-processed by molding with other resins.

6. Granule (10) comprising an outer coating (20) of synthetic resin inside which there is at least one fragment (30) of fiberglass or fiber embedded in synthetic resin.

7. Granule (10) according to claim 6, wherein the at least one fragment (30) has a maximum diameter or dimension of 2,3 mm or some tenths of mm up to 5 mm.

8. Granule (10) according to claim 6 or 7, having, by weight, 70% for the outer coating and 30% for the at least one fragment (30).

9. Industrial plant adapted to implement the method of any one of the preceding claims.

10. Method of processing, preferably molding or extrusion, wherein a solidified product or granule according to any one of the preceding claims is used and/or processed.