FR2873706A1 - New dye or additive raw material (formed from granules) supplied to machines (extrusion or injection type) useful for converting thermoplastic or elastomeric material - Google Patents

Abstract

Dye or additive raw material (I) (formed from granules) supplied to a machine (extrusion or injection type) for converting thermoplastic or elastomeric material comprising an external layer of a thermoplastic material compatible with the thermoplastic or elastomeric material to be transformed and a core comprising a powdery or granular material and one or more active materials mixed with the material supplied to the machine, is new. An independent claim is also included for the preparation of (I).

Description

The present invention relates to a raw material of the dye type or

  additive for feeding a machine for processing thermoplastic or elastomeric materials of the extrusion or injection type.

  The invention also relates to methods of manufacturing this raw material.

  A machine for converting thermoplastic or elastomeric materials, such as an extruder or an injection molding machine, most often uses dyes or additives, commonly known as "masterbatches" or "masterbatch", in the form of granules in order to allow rapid melting. and homogeneous of these raw materials for the subsequent transformation to be carried out. The machines are equipped for this purpose with one or more mixing hoppers of the different materials (base material (s), colorant (s), additive (s), etc.) forming the composition to be transformed, this or these hoppers being equipped with volumetric or weight dispensers, usually electronically controlled.

  Such a conversion machine is most often made to produce series of different types of parts, these parts may for example be in materials or compositions of different materials, or in different colors.

  The use of the raw materials of the dye or additive type in the form of conventional granules has the important disadvantage of requiring a thorough cleaning of the mixing hopper (s) and the dosers between each series of parts, in order to prevent granules corresponding to the supply of a series of previous parts, as well as dust from these granules and their internal friction in the hoppers or supply ducts, do pollute the material of the next series. This cleaning involves a tedious work to perform and immobilization of the machine the time of its completion. The machine must also operate for a certain period before the production of the following series of parts can begin, so that one is sure of the absence of residual particles or granules of the preceding series.

  Dusts or particles from raw materials of the dye or additive type in the form of conventional granules are more likely to spread around the machine, forcing a regular cleaning of the workshop.

  Furthermore, some raw materials of the dye or additive type have demanding processing conditions, and must especially have a very low humidity or be mixed and melted under a low oxygen atmosphere. Otherwise, the qualities of the products obtained could be altered. Raw materials of the dye or additive type in the form of conventional granules offer from this point of view important contact surfaces of their active products with the ambient air and therefore have the disadvantage of requiring, in certain cases, treatments prior to their introduction. in the machine, especially a desiccation treatment. The machines must then be equipped with drying equipment of the oven type or, as the case may be, with devices for diffusing inert or reducing gas over the mixture of raw materials, which constitutes a

noticeable constraint.

  The raw materials of the dye or additive type in the form of conventional granules also have the drawback of having extensive contact with, in particular, the walls of the mixing hoppers, which can pollute them.

  Moreover, conventional granules consist of active ingredients (inorganic or organic pigments, chemical elements anti-UV, antioxidant, fireproof, antistatic) but also binder. These binders allow to agglomerate the active ingredients in the form of granules having a certain cohesion, which themselves allow to facilitate the feeding of the machine and to avoid the emission of dust causing significant air pollution. The minimum "mechanical" or physicochemical resistance required for conventional granules often requires high binder percentages, between 40 and 50% for inorganic pigment binders for example and sometimes more than 60% for pigment binders. organic. These high percentages of binders are obviously damaging to a good dispersion of the active ingredients in the main material to be processed, and unnecessarily increase the volume and weight of the masterbatchs to be fed.

  In addition, to limit the effects of adhesion, often of an electrostatic nature, conventional granules and particles against the walls of the hoppers or supply ducts, these granules are enriched in antistatic elements. These antistatic elements have the disadvantage of being expensive and especially to migrate later to the surface of the material once transformed into parts or components, which very often generates many problems of the type: lack of printability or possibility of bonding, defects in aspects, etc.

  The present invention aims to remedy all or part of these disadvantages.

  To this end, the raw material of the dye or additive type that it concerns is formed of granules each comprising: an outer shell of a thermoplastic material compatible with the thermoplastic or elastomeric material to be processed, and a "core" consisting of a powdery or granular material, including one or more active ingredients to be mixed with the one or more feedstocks of the machine.

  The granules according to the invention make it possible to eliminate the dispersion of the pulverulent or granular material at one or more feed hoppers or dosers, and thus eliminate the need to thoroughly clean this or these hoppers between each series. the rooms. These granules further eliminate any contact, or at least extensive contact, of the powdery or granular material with the walls of a hopper, thus reducing the risk of pollution of this material by these walls.

  In case of change of raw material, especially in case of change of dye or additive, it is sufficient to interrupt the supply of pellets at the end of the production of a series of parts and to feed the machine with the granules of the following series of pieces.

  The size of the granules of the raw material according to the invention is advantageously greater, for example between 1.2 and 3 times, than that of conventional granules, which makes it possible to carry out the passage from one series of pieces to another in such a way that much simpler and faster than with a raw material, a dye or an additive according to the prior art.

  This higher particle size also makes it possible to very clearly reduce the tendency of the raw material to spread around the machine.

  The envelope may have a wall thickness of between 5p and 500p, for example. Being intended to be melted and mixed with the material to be transformed, the constitutive material of this envelope is compatible with the main material to be transformed, as previously said; for example, in the case where this main material to be converted is a polyolefin, the material of the envelope may be for example a high or low density polyethylene, but most often, one will choose a material of the EVA type (Ethylene Vinyl Acetate) which is found to be compatible with most thermoplastics.

  The casing is advantageously sealed in relation to the ambient air.

  Each granule of the raw material according to the invention thus makes it possible to prevent or limit contact of the pulverulent or granular material which it contains with the ambient air or with the walls of the hoppers or ducts. This granule therefore reduces the need for pretreatment of the raw material or the possible need for inert or reducing gas diffusion devices within the machine, and further reduces the need to incorporate antioxidant elements into the masterbatches. , anti-UV or antistatic for example, which are very expensive.

  In a preferred version of the invention, the constituent material of the shell of the granule is doped with antistatic elements.

  This constituent material of the envelope, which generally represents less than 5% of the total mass of the granule, can thus be doped more in percentage than are the conventional granules, which reinforces the antistatic properties obtained; in fact, in the case where a conventional granule is doped with 2% antistatic elements, even if, in a material according to the invention, it dope the material of the envelope to 10%, which guarantees efficiency well superior in terms of external contact, it will be put in fact only 10% X 5% = 0.5% by mass of antistatic element, which is four times less than the average 2% in conventional granules and is therefore very advantageous both in economic terms and in terms of the quality of the transformed part. The latter has much lower risk of subsequent migration of the additive because of the average percentage of this additive much lower.

  Furthermore, said "core" of the material according to the invention may include a binder for agglomerating the particles or granules of the active ingredient or materials that it comprises; this binder can be of the type used for conventional granules but thanks to said envelope, can be present in a much smaller percentage (between 0 and 50%, depending on the case for example) than in a conventional granule, which makes it possible to greatly facilitate the dispersion of the active ingredient (s) within the main material to be transformed.

  The "core" of the granule may, for dyes for example, consist of 70 to 90% of mineral pigments and 10 to 30% of binder. This binder may be a mixture of EVA and waxes, or else 50 to 60% of organic pigments and 40 to 50% of binder (here again the binder is a mixture of EVA and waxes). In some cases it will be possible to form a core comprising no binder resulting in economy and very easy dispersion.

  The invention also relates to methods of making the aforesaid raw material.

  A method according to the invention comprises the steps of: introducing the pulverulent or granular material into an elongate sheath of thermoplastic material; - To weld this sheath step by step to form sheath segments having dimensions corresponding to that of granules to obtain, and - to cut the sheath at the weld zones, to form the granules.

  The sheath preferably has a small wall thickness, for example 10 to 200 microns, and may have, for its inner hollow area, a cross section of several mm 2 to several cm 2.

  Another method according to the invention comprises the steps of: performing a coextrusion of the one or more active ingredients (with or without a binder) and the envelope, and - pinching hot and cutting or shearing to form granules coated with relatively tight way.

  The binder may be, for example, of the EVA + wax type and the shell material may be of the EVA or LDPE (low density polyethylene) type.

  The duct in which the molten material of the casing arrives may be transverse to the extrusion duct of the active elements and the binder (known principle of co-extrusion known as "crosshead"), said molten material being distributed naturally around the coil formed by the extrusion of the active elements and the optional binder and thus constituting a continuous thin envelope.

Claims (11)

  1 raw material of the dye or additive type for feeding a machine for processing thermoplastic or elastomeric materials of the extrusion or injection type, characterized in that it is formed of granules each comprising: an outer casing of a thermoplastic material compatible with the thermoplastic or elastomeric material to be processed, and - a "core" consisting of a powdery or granular material, including one or more active substances intended to be mixed with the machine feed material (s).   2 Raw material according to claim 1, characterized in that the size of the granules of which it is formed is greater than that of conventional granules, for example between 1.2 and 3 times higher.   Raw material according to claim 1 or claim 2, characterized in that said envelope has a wall thickness of between 5p and 500p.   4 raw material according to one of claims 1 to 3, characterized in that said envelope is sealed in relation to the ambient air.   Raw material according to one of Claims 1 to 4, characterized in that the material constituting said envelope is doped with antistatic elements.   Raw material according to one of claims 1 to 5, characterized in that said "core" does not include any binder in addition to the active ingredient (s) thereof.   7 raw material according to one of claims 1 to 5, characterized in that said "core" includes a binder for agglomerating the particles or granules of the active ingredient or it comprises.   Raw material according to claim 7, characterized in that the binder is present in a much lower percentage than in a conventional granule.   Process for producing the raw material according to one of Claims 1 to 8, characterized in that it comprises the steps of: introducing the pulverulent or granular material into an elongate sheath 5 made of thermoplastic material; - To weld this sheath step by step to form sheath segments having dimensions corresponding to that of granules to obtain, and - to cut the sheath at the weld zones, to form the granules.   Process for manufacturing the raw material according to one of claims 1 to 8, characterized in that it comprises the steps of: - coextruding said active substance (s) (with or without a binder) and the envelope, and - pinch hot and cut or shear to form granules coated in a relatively tight manner.   11 Process for the production of the raw material according to claim 10, characterized in that the duct in which the molten material of the casing arrives is transverse to the extrusion duct of the active elements and of the optional binder (known principle of extrusion known as "square head").