Plastic-based composite product and method and apparatus for manufacturing same

Abstract

A plastic-based composite product comprising a plastic mass in which particles are homogeneously embedded, which particles have tensile strength in a first particle direction, the product having a chosen principal product direction, wherein the particles comprise: small particles being elongated plates of fibres and having a random orientation and a length of 0.2-2 mm; and large particles dominantly orientated such that their first particle direction is in the chosen principal product direction, the large particles having a length in the first particle direction of about 2-6 mm.

1 . Plastic-based composite product which is comprised least partially of a plastic having a plurality of particles homogeneously embedded in said plastic, which particles have tensile strength in at least one principal direction. 
 said plurality of particles comprising:    small particles, in the form of plates or fibres with a random orientation and a length of 0.2-2 mm, and    large particles with a dominant orientation, of the said principal direction of the particles in a chosen product principal direction and a length in the particle principal direction of about 2-6 mm.    
     
     
         2 . Product as claimed in  claim 1 , 
 characterized in that the large particles are plates and the particle principal direction extends in the main plane thereof.    
     
     
         3 . Product as claimed in  claim 2 , 
 characterized in that the plates have an at least more or less isotropic tensile strength in their main plane.    
     
     
         4 . Product as claimed in  claim 3 , 
 characterized in that the plates consist substantially of mica.    
     
     
         5 . Product as claimed in  claim 1 , 
 characterized in that the large particles are fibres wherein the principal direction of the particles is the longitudinal direction of each fibre.    
     
     
         6 . Product as claimed in  claim 1 , 
 characterized in that the particles consist predominantly of wood material and the plastic is a thermoplastic polymer material,    wherein 
 a. the transverse dimension of the large wood particles is such that the ratio between the length in the principal direction of the particles and this transverse dimension amounts to a minimum of 4.  
 b. the wood particles are present in a quantity of 40-80% by mass, in relation to the mass of product.  
 c. the obtained product complies minimally with the following requirements relating to mechanical properties in  
   bending strength in the fibre direction: 8 MPa    bending modulus in the fibre direction: 3 GPa    tensile strength in the fibre direction: 6 MPa    tensile stress modulus in fibre direction: 3 GPa    tensile strength transversely of fibre direction: 0.3 MPa    tensile stress modulus transversely of fibre direction: 1 GPa.    
     
     
         7 . Product as claimed in  claim 6 , 
 characterized in that the wood particles originate from softwood or hardwood.    
     
     
         8 . Product as claimed in  claim 6 , 
 characterized in that other particles with tensile strength are present in an amount of 3-25% by mass.    
     
     
         9 . Product as claimed in  claim 8 , 
 characterized in that other particles with tensile strength are present which originate from at least one type of from the class of inorganic polymers on a basis of silicates.    
     
     
         10 . Product as claimed in  claim 8 , 
 characterized in that other fibres with tensile strength are present consisting of glass fibres, chopped strands with a length of 4-5 mm and a diameter of 0.013 mm and a ratio of length to diameter in the range of 300-400.    
     
     
         11 . Product as claimed in  claim 8 , 
 characterized in that other fibres with tensile strength are present which are at least one of the class of the natural biopolymers on a basis of cellulose, wherein the percentage of said natural biopolymers present depends on the number of external appendages on the fibres.    
     
     
         12 . Product as claimed in  claim 6 , 
 characterized in that the polymer material consists of polypropylene, polystyrene, polyethylene or polyacrylate.    
     
     
         13 . Product as claimed in  claim 12 , 
 characterized in that the polymer material consists of one or more olefinic homo-or copolymerisates with an H.F.I. (230/2,16) of 1-30 dg/min; and which polymeric matrix material forms 10-50% by mass of the wood.    
     
     
         14 . Product as claimed in  claim 1 , 
 characterized by at least one additive for obtaining desired properties, which additive is added to the process flow at a suitable position in the compushtruding process during manufacture of the product.    
     
     
         15 . Product as claimed in  claim 14 , 
 characterized by an additive with a desired influence on chosen properties of the product and belonging to at least one of the following classes: 
 influencers of adhesion between particles with tensile strength and matrix poly (class H),  
 influencers of the properties of the surface of the product, particularly in respect of coatings or adhesives for applying in sandwich structures (class 0),  
 influencers of the pyrogenic properties (class F),  
 influencers of the particle durability (class D),  
 blowing means for obtaining a foamed structure (class B),  
 in the case of an unintended, sufficiently great temperature increase.  
   
     
     
         16 . Product as claimed in  claim 14 , 
 characterized in that as additives with a positive influence on the desired properties of the technical wood one or more of the following are present therein indicating the class or classes and the applied percentage related to the mass of technical wood:                                    Additive   Class   Mass-percentage                                       Polybond (Spider)   H   0         1-3,     Polyweb (DOW)   H   0         1-3,     Exxelor (Exxon)   H   0         1-3,     tributoxyethylphosphate   H   O   P     1-5,     1,2,3-propane trial   H   0   V     2-3     diamrnoniumphosphate   P   D         2-8     ammoniumcarbonate   P   B         1-3     amrnoniumhydrogencarbonate   P   B     1,2-ethane diol   0   D       up to 3     ethylacetate/ethanol ½-⅓   0           up to 3     methyl acetate   H   0       up to 4     n-propanol   0           up to 1.5     silane A 171, 172, 174   H   O   D   0.5-3     polyvinyl acetate   H   O   D   up to 5     surfactants, ionogenic/   H   0       up to 2     aniogenic, standard     chlorinated polyolefins   H   0       up to 5     UV-stabilizers   D           up to 3     azodicarbonamide   P   B       up to 3                                                               
     
     
         17 . Product as claimed in  claim 1 , 
 characterized in that at least one colouring agent or pigment is added to the product during manufacture.    
     
     
         18 . Product as claimed in  claim 1 , 
 characterized in that the product comprises:    a plastic-based composite layer    a first skin layer adhered thereto on a first side thereof    optionally a second skin layer adhered thereto on a second side thereof; and which layers are mutually adhered.    
     
     
         19 . Product as claimed in  claim 18 , 
 characterized in that at least one skin layer is of the type as claimed in  claim 1  and the product principal direction thereof has a chosen direction relative to this product principal direction of the first mentioned plastic-based composite layer.    
     
     
         20 . Apparatus for manufacturing a product as claimed in  claim 1  comprising: 
 a compounder operating at low pressure for plasticizing a mixture of plastic and particles with tensile strength, which particles are mixed with the plastic either beforehand or in the compounder, and pressing the plastic mixture to the outside via an outlet;    a rotating displacement pump further transporting the plastic mixture;    a distribution head further guiding the mixture in order to further transport the plastic mixture substantially as a plug flow;    orienting means further guiding the mixture, comprising at least one bundle of substantially parallel channels through which the plastic mixture can flow, which channels are dimensioned relative to the long particles such that, other than to a dominating extent in the particle principal direction, said channels being too small to allow passage of the long particles present in the plastic mixture; and    a substantially prismatic mould head which connects onto outlets of the channels, said outlets having a form which corresponds with a desired cross sectional form of the product;    such that the particle principal direction corresponds with the longitudinal direction of the mould head and the product principal direction;    which mould head is so long and has a temperature curve in the longitudinal direction such that at the end of the mouth the product has cooled to below its Vicat softening temperature.    
     
     
         21 . Apparatus as claimed in  claim 20 , wherein the linear transverse dimensions of at least the parts of the channels located furthest downstream amount to a minimum of 2× the length of the short fibres and a maximum of 1.5× the length of the long fibres.  
     
     
         22 . Apparatus as claimed in  claim 20 , comprising at least two bundles of channels mutually connecting in series, wherein the transverse dimensions of the channels of a bundle located further downstream are smaller than those of the channels of a bundle located further upstream.  
     
     
         23 . Apparatus as claimed in  claim 20 , wherein the effective passages of the channels of the distribution head are adjustable.  
     
     
         24 . Apparatus as claimed in  claim 20 , wherein at least one feed for adding particle material and/or additives to the plastic connects to the compounder.  
     
     
         25 . Apparatus as claimed in  claim 20 , further comprising particle supply means which are adapted to introduce the particles into the compounder under a pressure such that these are compressed while air is expelled.  
     
     
         26 . Apparatus as claimed in  claim 25 , further comprising compression means for compressing the particle material to expel gases prior to addition of the plastic.  
     
     
         27 . Apparatus as claimed in  claim 20  wherein the compounder has a screw with a geometry such that the plastic mixture in which the particles are incorporated is successively compressed, decompressed and degassed under vacuum such that air and other gases are expelled from the mixture and from the pores present in the particles.  
     
     
         28 . Method for manufacturing a product as claimed in  claim 1   characterized in that the finished product is subjected to an after-treatment comprising heating the product to a temperature above the Vicat softening temperature of the applied plastic respectively the highest Vicat softening temperature of all the applied plastics, modelling the product to a desired shape and while maintaining a chosen pressure causing the product to cool in this shape to below the said Vicat softening temperature.    
     
     
         29 . Product obtained with the method as claimed in  claim 28 .  
     
     
         30 . Method for manufacturing a product as claimed in  claim 12 , 
 characterized in that as starting polymer material is used a prepolymer on the basis of a styrene or an acrylate.    
     
     
         31 . Product as set forth in  claim 6  wherein said polymer is at least one polyolefin or polymer based on styrene.  
     
     
         32 . Product as set forth in  claim 6  wherein the ratio between the length in the principal direction of the particles and the transverse dimension is in the range of 6 to 80.  
     
     
         33 . Product as set forth in  claim 6  wherein the wood particles are present in a quantity of 50 to 70% by mass in relation to the mass of the product.  
     
     
         34 . Product as set forth in  claim 7  wherein said wood particles originate from at least one of fir, spruce, birch or poplar.  
     
     
         35 . Product as set forth in  claim 8  wherein other particles are present in 5 to 18% by mass.  
     
     
         36 . Product as set forth in  claim 9  wherein said other particles are glass.  
     
     
         37 . Product as set forth in  claim 11  wherein the natural biopolymer is a member selected from the group consisting of flax, jute, hemp, sisal, coconut, bamboo and miscanthus.  
     
     
         38 . Product as set forth in  claim 13  wherein said H.F.I. is 2-15 dg/min.  
     
     
         39 . Product as set forth in  claim 13  wherein said polymeric matrix forms 15-40% by mass of the wood.