JPH06190830A - Production of sheets from polymer waste - Google Patents

Abstract

(57) [Abstract] [Purpose] Reuse of polymer waste in the production of reinforced composite sheets [Composition] Production of composite sheet material from recycled polymer waste of mixed raw materials which may contain up to 75% by weight of non-thermoplastic material The method is disclosed in which the waste is sintered and compressed onto a layer of fiber reinforcement, optionally with a thin film of polymer or metal laminated to one or both surfaces of the sheet.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to the reuse of polymer waste in the manufacture of reinforced composite sheets.

[0002]

BACKGROUND OF THE INVENTION Recycling and reuse of polymer waste is an important aspect of current industrial polymer waste management programs. For example, in addition to research on the recovery, separation and cleaning of polymeric materials from municipal waste,
It is important to develop an effective process for converting recycled waste into resellable goods. Several applications have already been developed for well-defined types of polymers, for example B.H. V. Wabin manufactures household bags made entirely from recycled polyethylene. However, when the polymer waste consists of a mixture of different polymers and generally contains various undefined contaminants, as is the case for polymer waste materials, articles of industrially acceptable quality, for example by extrusion or injection molding. Reprocessing is extremely difficult. Many attempts have been made to eliminate these problems, including placing granulated waste on a conveyor, passing it through an oven and then transporting it between compression rollers to produce a plate product. [For example, described in British Patent Nos. 1439353 and 2049540]. However, products of this kind generally exhibit various drawbacks in mechanical and aesthetic properties, limiting their degree of industrial application. The Applicant has now found that the incorporation of fiber reinforcement into sintered polymer waste results in a composite sheet of a quality that enables competent applications.

[0003]

SUMMARY OF THE INVENTION Accordingly, in one aspect, the present invention provides a method of making a composite sheet from recycled polymer waste, the method comprising depositing a particulate polymer waste containing at least 25% by weight of thermoplastic material on a support surface. Juxtaposed to the fiber reinforcement located at, heating the polymer waste coated reinforcement to a temperature sufficient to soften the thermoplastic material and compressing the heated and coated reinforcement, The composite sheet preferably consists of cooling under compression. Of course, a minimum level of thermoplastic component is required to achieve sufficient coverage of the fiber reinforcement, which, as stated above, effectively represents 25% by weight of total polymer waste.
And a higher proportion (ie, at least 40% by weight) of the thermoplastic component generally results in better wetting of the fiber reinforcement and therefore more uniform properties in the final composite sheet material. One of the important advantages of this method is that the polymer waste contains a significant amount of non-melting substances, which are in the form of ground particles and which are minerals such as sand or glass (fibers) or heat such as heat. It also works effectively when it is an organic material such as a curable resin (which generally contains inorganic fibers such as glass fibers), in fact the mechanical properties of the product are small Benefits from resins. Therefore, preferably the polymer waste contains from 5 to 25% by weight of thermosetting resin either initially or by the addition of supplements.

The actual chemistries of thermoplastic polymer waste and thermosetting resin components (if present) can vary widely, and the ability to process such a wide range of polymeric materials (its actual chemistry). (Almost independent of the physical properties and raw materials) is one of the significant advantages of the process according to the invention. The polymeric waste material is micronized by established techniques for comminuting the waste, such as cutting, grinding or granulating. Preferably the particle size is less than 10 mm, preferably about 3-5 mm, with flake-like particles providing particularly good properties.
Although any suitable fibrous material may be used for the reinforcement, glass fibers have been found to provide composite sheets with particularly attractive physical properties. However, it is also possible to use fiber materials of natural organic substances, which increase the environmental acceptability of the products obtained, examples of natural fiber materials of this type being flax and jute. The fiber material selected can be used in any convenient configuration. That is, it can be cut into relatively short fibers or can be relatively long (relative to the width of the composite sheet being formed). Furthermore, it can be placed as loose fibers on the surface of the support,
Alternatively, a non-woven fabric may be compressed or a woven fabric may be formed to form a self-supporting mat.

When the polymer waste contains a high proportion of thermoplastic material, the sheet forming conditions generally result in sufficient impregnation and wetting of the fiber reinforcement to produce an industrially useful product. However, the properties of this composite sheet can be improved by laminating (on one or both surfaces) a thin film of metal or polymer material, such laminating being such that polymer waste is not free flowing under sheet forming conditions. It is particularly advantageous if (for example as a result of a low thermoplastic content). The use of metal film laminates often requires adhesives to adhere the metal and polymer waste cores to each other (although the thermoplastic material itself often provides sufficient adhesion) and the resulting composite laminate sheet It goes without saying that both the physical and macroscopic properties of are altered. The use of polymer films also affects the macroscopic properties. However, another significant advantage derived from lamination is that the outer membrane acts to contain loose fibers and chemical or biological contaminants that may be present in the polymer waste. Because it is easy to operate,
Generally it is preferred to use a thermoplastic polymer (eg a polyolefin such as polypropylene or polyethylene) as the thin film material.

[0006] One modification of this method is the use of two fiber reinforcements.
Two layers (conveniently, but not necessarily the same material)
And sandwiching the particulate polymer waste between these two layers prior to heating and compression. In a preferred embodiment, this "two-layer" embodiment is used in combination with laminating a thin film (preferably thermoplastic) to the top, bottom or both surfaces of the polymer impregnated composite. The process of the present invention can be operated batchwise using a compression mold into which the desired ingredients are introduced in any suitable order.
For example, for a laminated "two-layer" composite sheet, the mold has (i) a thermoplastic film; (ii) a fiber reinforcement;
Filling with (iii) particulate polymer waste; (iv) second layer of fiber reinforcement; and (v) second thermoplastic film. The laminate assembly is then solidified by applying pressure and heating to a temperature sufficient to soften the thermoplastic components of the polymer waste.

However, a more convenient operation method is a (semi-) continuous method in which a fiber reinforced material on the surface of a support and a granular polymer waste arranged in parallel with the support surface are used for heating between a compression roller and a cooling zone. A belt to be conveyed through. The belt conveyor can be continuous or chained parts connected to each other and is generally made of steel but any other material that meets the requirements of flexibility / rigidity / heat resistance can be used. . In addition, it is often advantageous to provide a non-stick coating (eg, PTFE) on the upper surface of the belt to help release the composite sheet from the belt conveyor. The heating and compression steps do not have to be physically separated from each other and may be overlapping. Generally, the cooling of the composite sheet occurs while maintaining compression. This is because this reduces the tendency of the fiber reinforcement to expand (or "loft"). However, in some applications it is more convenient to cool without pressurization and then compression molding the composite sheet into a shaped article. Of course, this belt conveyor method allows a second layer of fiber reinforcement to be fed onto a layer of polymer waste placed on the first layer of fiber reinforcement to easily accommodate a "two-layer" configuration. it can. Similarly, if the adventitia is laminated onto the composite sheet, this can be done in an "in line" operation, with the film on the belt conveyor (if necessary to the bottom surface of the composite sheet) and / or the top surface. Directly before heating and compression. Alternatively, the laminating sheets can be applied in a separate "offline" laminating process.

The temperature of the heat treatment applied to the "layered" composite should be sufficient to soften the thermoplastic components of the polymer waste, thereby allowing it to flow around the reinforcement fibers and wet them. Should be. Of course, this temperature should not be so high as to cause significant thermal decomposition of the polymer. The exact temperature will, of course, depend on the components present in the polymeric waste material and can be ascertained by routine experimentation on the source of any selected waste material. Generally, a suitable temperature is 140-2.
20 ° C, with 180-200 ° C being generally preferred.
In general, higher pressures are effective in providing good polymer flow within the fiber reinforcement as well as improving fiber wetting and providing a smoother and more uniform sheet surface. However, operational and cost constraints generally limit the practical range, and the pressure used to solidify the heated composite of the fiber mat impregnated with the softening polymer is generally a few bar pressure, 3-5 bar. The pressure of is generally effective. In another aspect, the invention relates to an actual product formed by the above method, which is a composite sheet of fiber reinforcement impregnated with recycled polymer waste material containing at least 25% by weight of thermoplastic material. If necessary, a thin film of a metal or a thermoplastic polymer (preferably a polyolefin such as polypropylene or polyethylene) is laminated on one surface or both surfaces.

The present invention will be further described below with reference to the accompanying drawings. Referring to FIG. I, a belt conveyor 1, preferably made of steel, is moved by a transport roller 2 in the direction indicated by the arrow. A thin film 3 of thermoplastic polymer is fed onto a belt conveyor and a layer of fiber reinforcement 4 is fed onto this thin film 3. The particulate polymer waste stored in the hopper 5 is then loaded from this hopper 5 onto the layer of reinforcement 4 and then a second layer of fiber reinforcement is fed to the top surface of the polymer waste. Finally, a second thin film 7 of thermoplastic polymer is applied to the upper surface of the second layer 6 of reinforcing material, and the resulting layered product is passed by the belt 1 through the heating space 8 and the compression roller 9
And through the cooling zone 10. The resulting laminated composite sheet 11 is then removed from the belt conveyor 1 and either stored on reels or cut into individual sheets according to established procedures. The composite sheet can then be formed into molded articles by conventional stamping or molding methods. While the continuous process described above is generally the most economical technique for industrial production of reinforced composite sheets on a large scale, as mentioned above, reinforced composite laminated products are sequentially inserted into the compression molding press in a batch operation. Can also be manufactured by.

[0010]

The following is a non-limiting example of a batch-type process for making the composite laminate described above. Particles were made from a mixture of polymers selected to mimic a variety of different polymeric "waste" feedstocks, and also from commercial mixed plastic wastes with high or low polyolefin content. these,
A polypropylene membrane of glass fiber or flax was placed on a supported layer and covered with a second layer and a thin film of the same material. This laminate assembly is placed in a preheated forming press for 200
It was allowed to solidify for 10 minutes at 0 ° C. and a pressure of approximately 4 bar, then cooled to room temperature (without pressure release). In addition, an acrylic acid modified polypropylene (“Polybond” 1
A similar laminate was made with the 001) adhesive.
Flexural strength and flexural modulus were measured according to ASTM D-790M. The results of these tests are used to compare virgin polyethylene, polypropylene and "GM30" for comparison purposes.
It is shown in the table below with the corresponding properties of glass fiber reinforced polypropylene sheet commercially available from Simaruit as "PP".

In the table below, the different components of the polymer waste (as% by weight) are as follows: REPOIR 1: low density polyethylene 42.5% by weight polypropylene 34% by weight polystyrene 8.5% by weight sheet molding compound. (“SMC” thermosetting resin, from Citroen car bonnet) 15 wt% REG. 1: Coarse-cut, high-polyolefin content waste REG. 1B: REG. 1 + 15 wt% SMC Recycle: "Heavy fraction" waste from AKW; residue after granulation, cleaning and floating separation of domestic waste (mainly bottles); with low polyolefin content and mainly "flakes" Is.

[0012]

[Table 1]

[Brief description of drawings]

FIG. 1 is a schematic diagram of an embodiment in which particulate polymer waste is sandwiched between two layers of fiber reinforcement and the composite is laminated with a film of thermoplastic polymer on both the top and bottom surfaces.

[Explanation of symbols]

 1 Belt Conveyor 2 Transport Roller 3 Thermoplastic Polymer Thin Film 4 Fiber Reinforcer 5 Hopper 6 Fiber Reinforcer 7 Thermoplastic Polymer 8 Heating Space 9 Compression Roller 10 Cooling Zone 11 Composite Sheet

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Adrien Voueter van Blaen Netherlands 1031 C.M.Amsterdam, Bathoisuehi 3 (72) Inventor Josephs Heubertas van Deulsen Netherlands 1031 C.E. M Amsterdam, Bathouesuehi 3 (72) Inventor Petras Antonius Johannes Malia Hendricks The Netherlands 1031 Seem A. Amsterdam, Bathouesuehi 3

Claims (9)

[Claims] 1. In the production of composite sheets from recycled polymer waste, a particulate polymer waste containing at least 25% by weight of thermoplastic material is juxtaposed to a fiber reinforcement located on the surface of the support; polymer waste. Manufacture of a composite sheet characterized by heating the material-coated reinforcement to a temperature sufficient to soften the thermoplastic material; compressing the heated and coated reinforcement and cooling the resulting composite sheet Method. 2. The method according to claim 1, wherein the polymer waste contains thermosetting resins and / or inorganic materials in an amount of 5 to 25% by weight, either initially or via the addition of supplements. 3. The fiber reinforcement layer is glass fiber or flax or other naturally occurring fiber products.
The method described in. 4. The first layer of fiber reinforcement is placed on top of the polymer waste-coated reinforcement material.
The method described in. 5. The method according to claim 1, wherein a thin film of polymer or metal is laminated on at least one surface of the polymer-coated reinforcement. 6. The belt according to claim 1, wherein the surface of the support is a belt for transporting the fiber reinforcement and the polymer waste juxtaposed to the fiber reinforcement through the heating space, between the compression rollers and through the cooling zone. The method described. 7. The method according to claim 1, wherein the heating is carried out at a temperature of 140 to 220 ° C. for a time sufficient to soften the thermoplastic and the compression is carried out at a pressure of at least 3 bar. the method of. 8. A composite sheet of fiber reinforcement impregnated with recycled polymer waste material containing at least 25% by weight of thermoplastic material. 9. The composite sheet according to claim 8, further comprising an outer film of a thermoplastic polymer on both the upper surface and the lower surface.