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The present invention relates to laminates comprising (a) an outer, base layer of a filled polyolefin which is poly-propylene, (c) an outer decorative layer of polyvinyl chloride, which inherently has poor adhesion to (a), and (b) an intermedi-ate adhesion-providing layer of a web or fabric.
In such laminates, a good bond is required between the two outer layers or between each outer layer and the intermediate adhesion-providing layer.
To meet these requirements, special hot-melt adhesives have been used. The problem of inadequate heat resistance of the adhesive bond can in such cases be solved by additional measures, such as crosslinking of the adhesive (cf. German Published Application DAS 2,~53,697). Another conventional method of bonding together termoplastic layers which have inherently poor adhesion to one another is to anchor the base layer mechanically to a web and then to bond this layer to the decorative layer by means of a reactive adhesive (cf. German Laid-Open Application DOS 2,650,628). This process is involved and time-consuming and is unsuitable for rapid continuous bonding. It does not show any advantage over producing a laminate by directly bonding a base layer and a decorative layer with a reactive adhesive.
It is an object of the present invention to provide a laminate which consists of two layers which cannot be welded together to give a good bond, namely (a) an outer, base layer of a filled polyolefin which is polypropylene and (c) an outer decorative layer of polyvinyl chloride, the two layers (a) and (c) being bonded very firmly to one another by an intermediate adhesion-providing layer (b).
It is a further object of the invention to bond the two layers (a) and (c) firmly together by a continuous and rapid process.
We have found that these objects are achieved, 117~;~4~
- 2 -according to the invention, lf the adhesion-providing layer (b) consists of a web or fabric comprising two types of fusible fibers consisting of polypropylene and polyvinyl chloride, of which one can be welded firmly to one of the outer layers (a) and (c), and another to the outer layer (a) or (c), so that the two layers (a) and (c) are bonded firmly to one another by layer (b).
In particular, the present invention provides a laminate comprising (a) an outer, base layer of propylene, (c) an outer decorative layer of polyvinyl chloride, which inherently has poor adhesion to (a), and (b) an intermediate adhesion-providing layer of a web or of a fabric comprising two types of fusible fiber~ consisting of polypropylene and polyvinyl chloride, of which one can be welded firmly to one of the outer layers (a) and Ic?, and another to the other layer (a) or (c?, so that the two layers la) and (c) are bonded firmly to one another by layer (b).
The above objects are furthermore achieved if, to produce the above laminates, the layer (b) is super-ficially fused, but not fused completely, before or during bonding of the layers (a) and (c) by application of heat and pressure.
In a preferred process, the layer (b) is first fused onto one of the outer layers (a) and (c), and is only then welded to the second of the outer layers (c) and (a).
O.Z. 0050/033463 The base layer (a) of the laminate consists of a filled polyolefin and is from 0.5 to 8, preferably from 1 to 4, mm thick. Polyolefins for the purposes of the invention means the relevant conventional ho~opolymers cf ethylene and propylene, and copolymers of ethylene and propylene with copolymerizable olefinically unsaturated compounds. In particular, suitable polyolefins are polyethylene having a density of from 0.890 to 0.965 g/cm3 (measured according to DIN 53,479) and a melt index of 0.1 to 20 g/10 min (measured according to ASTM D
1238-65 T at 190C under a load ~ L- 2.16 kg), polypropylene having a density of from 0.~0 to 0.90 g/cm3 and a melt index of from 0.1 to 20 g/10 min (according to ASTM-D 1238-65 T at 230C under 2.16 kg load), and mix-tures of these polyolefins with one another.
To increase their ;mpact strength, these poly-olefins may or may not additionally contain from 1 to 20% by weight of conventional synthetic rubbers or block copolymers of styrene and dienes. These polymers are well known from polymer chemistry and therefore do not require more detailed discussion here. An appropriate conventional isotactic polypropylene is particularly suitable as the polyolefin. Such a material contains from 3 to 10% by weight of non-isotactic polypropylene, which is soluble on boiling with xylene and then cooling to room temperature, the weight ratio of poly-propylene to xylene used in the test being 5:95.
The polyolefins are filled with from 10 to 60, preferably from 20 to 50, per cent by weight, based on l:lt~
o.Z. 0050/033463 the weight of filled polyolefin, of a conventional solid inert filler. Examples of suitable fillers for use in the polyolefin layer are glass fibers, glass mats, glass beads, talc, chalk, mica and fine particles of wood. Suitable examples of the latter are all commercial types with particles having a length of from 10 to 5,000 lm and a width of from 10 to 2,000 ~m.
The wood flours may be used in powder form or in a com-pacted form. In addition to the above fillers, the polyolefin compositions may contain relevant conventional flameproofing agents, agents for improving the impact strength, such as polyethylene of a lower density, stabilizers or scrap materials tregenerated materials).
The decorative layer consists of a thermoplastic polymer different from the polyolefin, and may be polyvinyl chloride (foamed or compact, rigid or plasti-cized PVC), a PVC which has been modified with styrene copolymers, eg. a styrene-acrylonitrilecopolymer, an acrylonitrile-butadiene-styrene copolymer, an acrylonitrile-styrene-acrylic copolymer or a grafted rubber in order to modify the impact strength, orhasbeen modifiedw~h a satu-ratedpolyester,inorderto improvethe processability~ ora chlorinated polyethylene. Preferably, a plasticized PVC sheet is used, which may be foam PVC in order to pro-duce a softer hand and cushioning effect. Such sheets are commercially available in numerous colors and patterns.
The thickness of these sheets of the layer (c) may be from 0.05 to 2 mm if the sheets are compact and from 0.5 to 5 mm if they are foamed.
o.Z. C050/033463 ~ or the purposes of the invention, polyvinyl chloride is the poly~erization product of vinyl chloride, ~own from pol~er chemistry, which is thermoplastic and has a chlorine content of from 56 to 57 per cent by weight and a softening point of from 75 to 80C The K value of the polyvinyl chloride is preferably from 70 to 90 (measured according to DIN 53,725). A foamed polyvinyl chloride is an artificially produced lightweight foam having a cellular structure. For the laminates according to the invention, plasticized PVC foams having closed cells and densities of from 0,5 to 1.3 g/cm3 are particularly suitable. The poly-vinyl chloride usedasthedecorative layer (c) is preferably a plasticized PVC. Accordingly it contains a conven-tional plasticizer for PVC in an amount of from 15 to 40, preferably from 20 to 35, per cent by weight based on the weight of plasticized PVC. Examples of suitable plasticizers are tricresyl phosphate, esters of phthalic acid and esters of aliphatic dicarboxylic acids. The plasticized PVC may additionally contain the relevant conventional stabilizers and pigments.
- The adhesion-providing layer (b) present between the outer layers (a) and (c) consists of a web or fabric.
The former category includes non-woven and non-knitted sheet-like structures of fibrous materials. The fibers therein, the length of which depends on the pro-~17~
o.Z~ 0050/033463 cess of manufacture, are dry-laid or wet-laid in a web-producing machine. Webs of the type used are conventional materials described, for example, in Textilpraxis 1968, No. 3. The fiber-blend webs to be used according to the invention consist of at least t-~o di~ferent types o~ ~ibers.
For welding to the base layer (a) of filled poly-olefin, fibers consisting entireI~ or predominantly of polyolefins may be used. These fibers are commercially available. If a base layer of filled polypropylene is used, polypropylene fibers are particularly suitable.
For welding to the decorative layer, which con-sists, for example, of plasticized PVC, fibers which adhere well are all those consisting entirely or partially of polyvinyl chloride (PVC) or polyvinylidene chloride (PVDC), as well as fibers of copolymers and of mixtures of PVC and PVDC. Such fibers are commercially available.
Fibers of copolymers of acrylonitrilewith vinyl chloride or vinylidene chloride, available comme~cially as non-flammable fibers, are also suitable. Fibers of blends of PVC with polyesters (containing 50 per cent by weight of PVC) also give a good bond when welded to the above decorative layers. For bonding to plasticized PVC, which is the preferred decorative layer, pure PVC fibers are particularly suitable.
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o.z. 0050/033463 The properties and textile data of the fibers employed in the fiber-blend web or fabric may be varied within a wide range. Fibers of from 0.1 to 200 dtex, in the main from 0.5 to 25 dtex, may be employed.
Two-component fibers can in many cases also be employed with advantage.
The ratio in which the polyolefin fibers and PVC fibers are mixed mus-t be suited to the requirements of each particular case, and is from 5:95 to 95:5, preferably from 30:70 to 70:30.
The softening points of the various types of fusible fibers may differ from one another by a large amount without interfering with the usefulness of the fiber-ble~A web. It is a particular advantage of the process acccording to the inventicn that even layers with widely differing melting points and/or softening points can be firmly welded to one another, since the fiber-blend web has a good insulating action.
In addition to the two weldable types of fibers, other types of fibers may be added in order to achieve specific properties, for example high-tenacity heat-resistant fibers for absorbin~ the forces which occur during processing or use, conductive fibers for inductive heating, and crimped fibers for an increased cushioning effect of the decorative layer.
The web is produced in accordance with conventiona-methods by blending, carding, cross-laying and subsequent mechanical and/or chemical bonding. The properties can be improved by needle-pu~ching. Additional 11 7~6 ~, o.Z~ 0050/033463 bonding may be achieved in the conventional manner by use of a binder or by a heat treatment.
Fabrics containing at least t~o different types of fibers can be produced either from fiber blend yarns or by using different yarns in the warp and the filling. The fabric carl be suited to particular requirements, for example moldability, by appropriate choice of the yarn denier and of the type of fabric construction.
The fiber-blend webs and fabrics weigh from 15 to 100 g/m2, preferably from 20 to 50 g/m2 The web or fabric is continuously laminated onto one of the two layers in the conventional manner by application of pressure and heat, or is pressed into the said layer when the latter is being manufactured~ In a second process step, the second layer is then welded onto the web or labric , +aking care that the web or fabric does not fuse completely, since this may result in less good pro-perties. It is advantageous in this process if the web or fabric is first ~elded ontothe decorative layer or embedded therein during manufacture of the latter, as this com-posite material can still be handled easily since it can be wound up.
The fact that the welding process is very rapid compared to the use of reactive adhesives also allows the manufacture of the laminate to be carried out com-pletely conti~uously.
In such continuous manufacture, the fiber-blend web, which may or may not be heated to 100-150C, is ~'79~J4~
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O.Z. 0050/0334~3 introduced between the sur~ace-~nolten hot base layer of filled polyolefin and the decorative layer which is heated to 100-150C(depending on its heat resistance), and is then welded to the outer layers under pressure, after which the laminate is cooled.
The finishedsheet-like material can be converted to moldings by various methods, such as vacuum forming or compressed air forming, folding, bending or pressing, after the material has been appropriately heated.
In a variant ofthese processes,the finished laminate is produced from the base layer and decorative layer only at the stage of molding under pressure. This process especially has the advantage that the base layer and the decorative layer can be heated to different tempera-tures.
It is an advantage of the process according to the invention that as a result of the felting-together of the two types of fibers of the web or as a result of the construction of the fabric, the forces are transmitted from the fibers welded to the base layer to the fibers welded to the decorative layer. The adhesion of the fibers to these layers results predominantly from weld-ing and only to a lesser degree from mechanical anchoring.
5 dtex polypropylene fibers of length 50 mm and 6 dtex PVC fibers of length 70 mm (Thermovyl from Rhodiaceta) in a weight ratio of 60:40, are converted to a web weighing 35 g/m2.
~1~<~6 o Z. 0050/033463 This l~eb is welded to a 2.0 mm thick sheet of foamed plasticized PVC by heating the web and the back of the PVC sheet to 130C, pressing them together between cold rollers and fixing the bond by cooling.
The base material - a polypropylene filled with 40 per cent by weight of fine wood flour - is extruded and pressed to 2.5 mm thick sheets by passing through a polishing calender. Before entering the calender, the assembly to be laminated, comprising the PVC sheet and the fiber-blend web, is applied to the base material, and the heat of the surface-molten base, which-is at 190, suffices partially to melt the polypropylene fibers in the web, which then weld under pressure,in the nip, to the base consisting of wood flour-filled polypropylene. The adhesion of the PVC sheet to the base, measured by the peel test, is 3;1 N~mm. T~e total thickness of the laminate sheet material is 4 4 mm, due to the slight compression of the sheet of foam.
5 dtex polypropylene fibers having a length of 60 mm and 7 dtex fibers having a length of 70 mm, of a mixture of 70 parts of PVC and 30 parts of a thermoplastic polyester based on neopentylglycol terephthalate are converted, in a weight ratio of 40:60, to a web weighing 40 g/m2. This web is continuously laminated to a plasticized PVC sheet by heating the sheet and the web, pressing them together between two rollers and then cool-ing the laminate.
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O.Z. 0050/033463 m e base material - a polypropylene filled with 30 per cent by weight of chalk - is extruded and pressed to 3.5 mm thick sheets by passing through the polishing calender. Before entering the calender, the laminated material described in the preceding paragraph is fed onto the base material, and the heat of the sur~ace-molten base suffices partially to melt the PP fibers in the web, which then weld to the filled polypropylene under pressure in the nip.
EX~YPLE 3 A fiber-blend web of 40% of 4.0 dtex polypropylene fibers, 40% of 5 dtex fibers of a copolymer of vinyl chloride and acrylonitrilecontaining 60% of vinyl chloride units, and 20% of 8 dtex nylon 6,6 fibers, added to increase the stability, is produced in the conventional manner and then needle-punched with 10 perforations per cm2. The web is then welded to a PVC foam sheet by pressure and heat.
A palypropylene filled with 35 per cent by weight of wood flour is extruded to give 3.0 mm thick sheets.
During polishing, the laminating sheet, carrying the web, is pressed onto the polypropylene sheet base material and at the same time welded thereto. Blanks are punched out of the finished sheet-like material, heated to the molding temperature by means of an infrared radiator, and pressed into a mold by means of compressed air.