METHOD AT THE MANUFACTURING OF A RECYCLABLE PRODUCT MATERIAL

Abstract: The invention relates to a method for the manufacture of a recyclable product material in order to achieve a predetermined strength within a predetermined strain rate interval. The product material comprises at least one matrix material and at least one fibre material. The matrix and fibre materials are chosen so that the values of their moduli of elasticity (Eij), moduli in shear (Gij) and the Poisson's ratios ( upsilon ij) assume a discontinuous distribution of the said matrix and fibre material quantities within different volume elements of the product material. It is further intended that a display curve defining a continuous distribution of a fibre size of the product material should exhibit symmetry in different volume elements of the product material.

Description: Method at the manufacturing of a recyclable product material The present invention relates to a method for the manufacture of a recyclable product material, comprising at least one matrix material and at least one fibre material in order to achieve a predetermined strength within a predetermined strain rate interval in the product material. Only recently has the handling of returnable plastic for recycling the latter assumed the priority which is desirable with regard, among other things, to environmental aspects, economic use of energy etc. People have begun, with some success, for example, to collect packaging film from agriculture and industry in order to manufacture granulate from the returned film. WO 93/25609 and WO 94/09959, for example, are already known in this field. These publications describe methods and appliances for recycling returnable plastic and fibres. One problem with this is the degree of contamination and the large number of different types of plastic with different melt indices exhibited by the returnable plastic, as a result of which the manufactured product material does not achieve the predetermined strength. The problem is related to the fact that the granulate nozzle and filtering equipment become clogged, which gives a very inhomogeneous final product. In the above-mentioned publications there was no indication of any solution to this strength problem. The object of the present invention is to achieve a predetermined strength for a predetermined strain rate interval in a recyclable product material of the said type, in order to thereby eliminate or at least reduce the effect of the said disadvantages associated with earlier manufacture of recyclable product material. To do this it is necessary to produce the greatest internal microstresses possible in the product material. This is achieved according to the invention in that in different volume elements ofthe product material the matrix and fibre materials are selected so that the values for their moduli of elasticity, shear moduli and Poisson's ratios assume a discontinuous distribution, and that a continuous distribution of a display curve defining the fibre size ofthe product material exhibits symmetry. According to another special characteristic ofthe invention the form factor of the fibre material/the mixed fibre materials, that is the ratio of fibre length to fibre diameter, exhibits a dispersion by means of which a majority of fibres can be made to bridge islands of inhomogeneities which would otherwise give rise to defective adhesion between the fibres. As will be appreciated from a further special characteristic ofthe invention, the said distributions are preferably so great that the fact that one or more ofthe matrix/fibre materials is contaminated does not have a detrimental effect on the strength of the product material. According to further characteristics ofthe invention the respective form factors of the said fibre material are such that the particle size ofthe contaminations is exceeded, that is to say the fact one or more ofthe matrix fibre materials is contaminated does not have a detrimental effect on the strength ofthe product material. Further advantages ofthe invention will be evident from the following description of this, referring to the drawing in which fig.l is an example of a display curve in the method according to the invention. Fig.2 shows various volume elements in a product material. The manufacture of a recyclable product material by the method according to the invention is done using equipment of conventional type familiar to the person skilled in the art, supplemented by measuring devices for checking the moduli of elasticity and moduli in shear of the matrix and fibre materials, together with the Poisson's ratios calculated from these values. Should the discontinuous distribution of the above-mentioned quantities characteristic ofthe invention not be obtained, a manual or automatic correction is performed, whereupon that material in which the quantities did not attain the discontinuous distribution is fed back into the process, that is to say the material passes through the process one more time. With regard to the display curve defining the fibre size ofthe product material, reference is made to the example in fig.1. In this display curve it is assumed that the agglomerate/granulate has a maximum diameter of 4mm. The majority of the fibres have here been chosen with lengths of about 2mm with a dispersion according to the curve. Fig.2 is intended to show a specimen 1 of a recyclable product material manufactured by the method according to the invention. Agglomerate/granulate have been combined as N volume elements lal, la2 ... with different preferred alignments of the fibres, which are included in the various volume elements. This consequently means, according to the invention, that for each such volume element the values of the modulus of elasticity (E υ ), the modulus in shear (G, j ) and the Poisson's ratio (υ. j ) will differ from the values of similar quantities for adjacent volume elements. This confers great internal couple stresses.

Claims: Claims. 1. Method for the manufacture of a recyclable product material, comprising at least one matrix material and at least one fibre material in order to achieve a predetermined strength within a predetermined strain rate interval in the product material, characterised in that in different volume elements ofthe product material the matrix and fibre materials are selected in such a way that the values of their moduli of elasticity (E (J ), the moduli in shear (G tJ ) and the Poisson's ratios (υ υ ) assume a discontinuous distribution and that a display curve defining a continuous distribution of fibre size of the product material exhibits symmetry. 2. Method according to claim 1, characterised in that through the choice of a fibre material or mixture of at least two fibre materials it is ensured that the display curve of the fibre material/the mixed fibre materials is approximately symmetrical about a predetermined mean value. 3. Method according to claim 1, characterised in that the form factor ofthe fibre material/the mixed fibre materials, that is the ratio of fibre length to fibre diameter, exhibits dispersion. 4. Method according to claim 3, characterised in that the respective form factors of the said fibre materials are such that the particle size ofthe contaminations is exceeded, that is to say that the fact that one or more of the matrix/fibre materials is contaminated does not have a detrimental effect on the strength of the product material.

Inventors: JILKEN LEIF, NILSSON STIG, JILKEN, LEIF, NILSSON, STIG
Applicants: JILKEN LEIF, NILSSON STIG, POLYPLANK AB, JILKEN, LEIF, NILSSON, STIG
Application year: 1996
Main classification: B29B15
IPC codes: B29B15, B29B17, C08K7, C08L101