Method of upgrading composite materials

<i>Introduction</i>

The present invention relates to a process for upgrading a composite material comprising fibrous materials and non-fibrous materials.

<i>State of the art</i>

The use of composite materials including fibrous and non-fibrous plastic materials is vast.

Such composite materials combining fibrous materials to non-fibrous plastic materials are commonly used in coatings of floors or walls. These composite materials may also serve as thermal and sonic insulation, for example in the field of construction or the automobile. For these applications, a felt is associated with a compact and / or expanded layer of non-fibrous plastic material. In other cases, the fibrous material is not ribbon, but grid associated to other layers.

Among the fibrous materials include, for example, textile sheets based on polyester, polyamide or polypropylene and in homopolymer or copolymer form, or non-woven products based on polyamide, polyester or polypropylene as homopolymers or copolymer. The non-fibrous plastic materials for their part are often based on PVC, styrenic polymers (SBS), polyolefins etc.

In some cases, the layer of non-fibrous plastic material may be sandwiched between two layers of fibrous material, eg of a textile web and a nonwoven.

Besides the well-known decorative aspect of textile / carpet eg fibrous materials can also be chosen for:<ul><li>➢ mechanical strength - eg increasing the rigidity, </li><li>➢ heat resistance</li><li>➢ their ability to give composite better dimensional stability ...</li></ul>

With the development of these composite materials, there is the problem of recycling, either by production scrap, or by recovering end of life products after use.

The recycling of these composite materials generally causes problems for the following reasons:<ul><li>fibrous materials generally have much higher melting points than non-fibrous materials. For example, polyamide and polyester fibers have a melting point of around 250 ° C whereas polyethylenes already melt around 120 ° C.</li><li>fibrous materials are usually much stiffer than non-fibrous materials.</li></ul>

Therefore, assemblies of fibrous and non-fibrous, eg multilayer, are difficult to recycle. In effect, the fibrous materials disperse poorly in non-fibrous materials Revised. The melting temperatures for fibrous materials are often greater than 100 ° C to those of associated non-fibrous materials. It is often illusory to mix all the materials beyond the melting point of the fibrous materials due to thermal degradation problems it would cause non-fibrous materials. This results in very poor mechanical properties of recycled materials. In addition, the unmelted fibrous materials rapidly clog the filters of the recycling facilities. Separation of fibrous and nonfibrous is therefore essential to properly develop these types of materials.

<patcit id="pcit0001" dnum="EP0750944A1"><text>EP-A1-0 750 944</text></patcit> describes a material grinding apparatus wherein the materials are cooled to a temperature below the glass transition temperature of the material prior to being comminuted. The device thus allows to fully grind the material into fine particles. During grinding, all material is ground into particles of roughly the same size. Therefore, such a device does not allow a subsequent separation of the crushed material. In addition, the material must be cooled to a very low temperature, which is generally of the order of -100 ° C. Cooling the material to a low temperature leads to a high cost.

Other recovery processes of a composite material comprising fibrous materials and non-fibrous plastic materials are disclosed in <patcit id="pcit0002" dnum="US5735471A"><text>US-A-5,735,471</text></patcit>, <patcit id="pcit0003" dnum="EP0068502A"><text>EP-A-0068502</text></patcit> and <patcit id="pcit0004" dnum="WO9707893A"><text>WO-A-97/07893</text></patcit>.

<i>The invention</i>

The object of the present invention is to provide a process for upgrading a composite material that is both effective and economical. This object is achieved by an upgrading process according to claim 1.

<i>General description of the invention.</i>

According to the invention, the present invention provides a process for upgrading a composite material comprising fibrous materials and non-fibrous plastic materials, the method comprising the steps of cooling the composite material to a temperature between -40 ° C and + 10 ° C; milling the cooled composite material in order to dissociate the fibrous materials from non-fibrous plastic materials and separating the fibrous materials of the non-fibrous plastic materials. Fibrous materials and non-fibrous plastic materials may be separately recovered and recycled.

Indeed, during milling at these temperatures, the fibers are hardly broken and remain long whereas the non-fibrous plastic materials are milled to form particles of a size more or less regular. The fact that at these temperatures, we come to crush the non-fibrous plastic materials without breaking the fibers is surprising. We should expect that the fibers break also saw the matter composing them is stiff at temperatures employed. However, that is not the case. Non-fibrous material dissociates from the fibrous material and a separation of the two materials is facilitated.

The method according to the invention has another particularly surprising effect of the grinding temperature standpoint. According to the prior art, the composite material should be cooled to a temperature below the glass transition temperature of the composite material. Knowing that the glass transition polyolefins is around -80 ° C, a composite material comprising polyolefins should therefore be cooled to a temperature below -80 ° C before grinding. However, the grinding of such composite materials can easily be carried out at about -40 ° C temperatures; ie d. at a temperature well above the glass transition polyolefins. This is of course an economic advantage since refrigerant consumption eg liquid nitrogen or dry ice, remains moderate.

The method of the invention allows the dissociation and higher almost total separation of the fibers relative to the non-fibrous plastic materials and therefore efficient recycling of composite materials. Moreover, thanks to moderately low milling temperatures, the costs associated with cooling remain low, which is economically advantageous.

According to a first advantageous embodiment, the composite material is cooled to a temperature between -30 ° C and -10 ° C.

The non-fibrous plastic may include PVC, styrenic polymers such as SBS or polyolefins. Even if the non-fibrous plastic material is lubricated and / or plasticized and / or loaded, the ability or the grinding capacity at these temperatures, the non-fibrous plastic material is excellent.

The fibrous material may be a marker associated with a compact and / or expanded layer of non-fibrous plastic material.

The fibrous material may be a textile web made eg in accordance with tufted or needled method or a nonwoven.

The fibrous material may be a plastic material comprising the polyesters and / or polyamides and / or polyolefins, as homo- or copolymers, glass fibers, polyaramid fibers etc.

After milling the composite material, the fibrous materials may be mechanically separated from non-fibrous plastic materials for example using a sieve or a centrifuge.

<i>Examples of applications</i>

Example 1: Separation of a composite comprising one or more underlayer (s) of non-fibrous plastic and a nonwoven

A) fibrous Party

In such cases, the fibers are made by a non-woven based on polyester fibers and / or polyester-polyamide co-extruded fibers.

B) non-fibrous Party

The sublayer is based on a compound which includes among others the plasticized PVC, loaded, lubricated polyolefins or loaded, lubricated, with additives including processing oils (process oils).

Of course, a compound based on other plastic materials (p. Ex. SBS or SBR) would also be usable.

C) Examples of Compositions

Mineral fillers are p. ex. of chalk, calcite, barytes, dolomite, al silica, kaolin.

The plasticizers (case of PVC) are those well known PVC (eg phthalates).

The plasticizing oils are mineral oils derived from petroleum refining to more or less aromatic or naphthenic or paraphinique.

Lubricants and additives are those usually offered by technology and commerce.

C1) PVC sublayer Examples

<tables id="tabl0001" num="0001"><table frame="none"><tgroup cols="2" colsep="0" rowsep="0"><colspec colnum="1" colname="col1" colwidth="33mm" /><colspec colnum="2" colname="col2" colwidth="14mm" /><tbody><row><entry>PVC:</entry><entry>27.5%</entry></row><row><entry>DINP:</entry><entry>17%</entry></row><row><entry>chalk:</entry><entry>29%</entry></row><row><entry>barite:</entry><entry>24%</entry></row><row><entry>Stabilizer / lubricant:</entry><entry>1.5%</entry></row><row><entry>various additives:</entry><entry>1%</entry></row></tbody></tgroup></table></tables>

C2) Examples of polyolefin sublayer

LDPE (low density polyethylene) / LLDPE (linear low density polyethylene) / VLDPE (very low density linear polyethylene) / EVA (ethylene-vinylacetate copolymer) / EPDM (ethylene propylene diene copolymer) or POE (polyolefin metallocene elastomers or not) or POP (metallocene polyolefin plastomers or not): 16%<ul><li>mineral oil 6%</li><li>Chalk: 25%</li><li>Barite: 52%</li><li>Additives: 1%</li></ul>

It goes without saying that the compositions may change in relatively large proportions according to the final requirements requested from the undercoat. The reasoning obviously applies to the polypropylene-based variants (copolymers or not) and HDPE (high density polyethylene) and MDPE (medium density polyethylene).<ul><li>C3) Distributions layers</li><li>nonwoven: varies from 15 to 70 (or more) g / m²</li><li>sub-layer: typically ranges from 1 to 7 kg / m²</li></ul>

D) Pre-crushing composite

The composites are crudely milled at room temperature without attempting to separate the fibers. grinding dimensions of the order of cm.

E) cooling the granules

The pellets are transported in a cylinder by means of an Archimedean screw. Liquid nitrogen flowing against the current in the screw cools the granules. When the granules are at a temperature between -40 and -10 ° C, the granules fall into the mill. This temperature can vary depending on the flexibility and ductility of the plastic sub-layer.

F) separation of fibers and plastics powder

As noted, the fibers are hardly cut during the milling operation, while non-fibrous plastic materials are reduced in the form of powders.

By sedimentation, by means of sieve or blowing, the physical separation of the fibers and powders is very easy.

G) Reuse of recovered powders

80% can be easily recovered and often even more than 90% of the non-fibrous material in the form of powders.

Conversely, quantities of finely chopped fibers may pass through the sieve are very low. It is estimated that this proportion is significantly below 10% of initial quantities of fibers.

The low rate of very fine fibers passing through the sieve is very annoying as these fibers behave like mineral filler.

The powders recovered can be reintroduced into the structure "underlay" in quantities exceeding 50% by weight without degrading the implementation conditions of this sublayer (absence of blocking filters extrusion p. Ex.) And as those related to a subsequent thermoforming process (eg).

Example 2: Separation of a composite based on a plastics material and a felt

Of also very positive separation results after milling at a relatively low temperature (-30 to -10 ° indicative C) were obtained with plastic composites - liners

The felts are made p. ex. textile waste frayed.

Unlike nonwovens which may also be of small thickness, the felts may have a thickness of several mm (sometimes several cm). These felts may be bonded by a thermosetting resin of phenol-formaldehyde type p. ex. or thermoplastic. Next the compression state, one can obtain flexible felts (slightly compressed) or rigid (high compression). These markers are used for soundproofing or parts of stiff structures (p. Ex. Parcel shelves for the automotive sector).

The separation efficiencies are comparable to those mentioned in Example 1.

Example 3: Separation of a composite based on a plastic and a textile material tufted or needled

Results also very positive ease of separation after grinding relatively low temperature (-30 to -10 ° C indicative) were obtained with composites based on a plastic and a textile material tufted or needled.

The non-fibrous parts have the same composition as in Example 1.

Textiles include polyamide fibers, polyester fibers or a mixture of these two fibers with optionally a certain percentage of polyethylene fibers and / or polypropylene fibers.

These fibers are usually linked to their base by SBR type latex and / or a coating of polyethylene powders.

The separation efficiencies are consistent with those cited in example 1.

Example 4: Separation of a composite based on a plastic and glass fiber

The sublayer (stamped by the glass veil) is of polyolefin or PVC (following the example C1 and C2).

It is found that the grinding at the indicated temperatures (eg -30 to - -10 ° C), depending on the ductility of the plastic formulation, results in the production of granules while avoiding excessive spraying of glass veil. The production of large quantities of small to very small glass particles is thus avoided.

Therefore, the grinding of plastic composites - glass mat following the described method greatly reduces the health hazards associated with the presence of glass particles of very small dimensions.

Notes on the consumption of liquid nitrogen:

It is estimated that approximately 0.5 kg of liquid nitrogen / kg of composite to be separated, which proves that the material is not cooled to temperatures very breakages.

A conventional cryogenic milling results in a much higher liquid nitrogen consumption. In addition to the much higher cost of such a conventional cryogenic milling, these processes are less efficient at separating the fibers and non-fibrous plastic materials.

Notes on fiber recovery

According to their degree of purity, it is conceivable to réextruder them apart to make them rigid parts such as parts of structures or wheel for the automotive sector.

If the fibers are blends of polyester, polyamide and / or polypropylene, just put a few percent of an agent "compatibilizer" different kinds of fibers to obtain good characteristics recylées fibers.