GB2194485A - Fibrous mat for hot moulding to moulded articles - Google Patents

Description

GB2194485A 1 SPECIFICATION ing material or the like, generally leads to

the desired improved surface characteristics, but is Fibrous mat for hot moulding to moulded generally also linked with a sealing of the sur articles face in the sense of being impermeable e.g.

70 for gases or liquids, which can be disadvanta The invention. relates to - a fibrous mat for hot geous in many cases and particularly for the moulding to Moulded articles according to the processing of such mats to moulded articles preamble of claim 1. excludes certain procedures or other techni- Multilayer fibrous mats, particularly those cally simply performable process steps. Refer- with special surface coatings are known. In 75 ence is made in exemplified manner in this particular, a multilayer fibrous mat for produc- connection to the production-favourable va ing moulded articles in a press mould by ex- cuum deep drawing process for co-ordinating posing the fibrous mat to pressure and ele- such moulded articles with thermoplastic films, vated temperature and formed from cellulose, as well as to certain characteristics of com ligno-cellulose or similar fibres is known, 80 pletely moulded parts, which are considered whose two surface layers.are also formed to be more advantageous when used as fin from a tangled fibre fleece and provided with ings in passenger areas of motor vehicles if at least a proportion of thermosetting synthey ensure a certainair permeability and mois thetic resins. The thermoplastic binder-contain- ture absorption, which can significantly im ing central tangled fibre layer and the two 85 prove the climatic conditions within such pas outer surface layers provided with thermosettsenger areas.

ing binders are produced here by the The problem of the present invention is layerwise placing of the mat material on a therefore to so further develop a three-layer conveyor belt and in the state moulded to fibrous mat of the aforementioned type that, moulded articles are simultaneously present in 90 in the case of minimum use of higher-grade the form of a firm union or sandwich of said materials both on the fibre side and on the multilayer arrangement (P 32 33 385). binder side and with minimum manufacturing However, it has been found that the addi- expenditure contributes to the provision of tional gluing of the surface layers with a ther- moulded articles, whose surface is both insen mosetting material which takes place in this 95 sitive to wetness and breaths moisture and known process according to the partial flow whose thermal, chemical and physical charac principle during the production of the mat and teristics can compete with those of compar moulding is at least partly absorbed by the able surface-sealing coatings or coverings.

absorbent central layer, which is disadvanta- According to the invention this problem is geous in that in such known three-layer mats, 100 solved by the features of the characterising the disadvantage thereof, i.e. the thermal and part of claim 1. Further developments of this mechanical surface treatment, is lost again solution can be gathered from the subclaims.

through the thermosetting binder used therein Thus, the invention is based on surface undesirably migrating into the central layer. layers fibre which can be substantially of a This effect can only be compensated by the 105 random nature, e.g. can be in the form of addition of larger thermosetting binder quanti- organic or inorganic fibres and have a natural ties to the surface layer fibres, which would or synthetic origin, whereby no requirements make the desired erld product much more ex- are made with respect to their moisture ab pensive. sorptivity or sensitivity to other environmental Another known process for producing insuinfluences. In addition, they need not be inex- lating plates, using mineral fibres as a basis, pensive to manufacture, because only small can be advantageously realised in that the amounts are used compared with the support non-woven fabric is applied to an also moving ing central layer (weight per unit area of the surface fibre fleece during production, so that total mat, as a function of application, 1000 during compression the insulating plate is 115 to 2000 g/M2). The presently required, high joined to the fleece carrier (DE-OS 28 53 grade surface sealing, particularly with respect 316). to high thermal stability, is ensured by coating In product-dependent manner, particular at- the adequate length of the present individual tention has long been paid to the processing fibres of the tangled fibre surface layers, pre of wood fibre materials of the present type 120 ferably in the form of staple fibres, with a and also non-woven fabrics comprising natural thermosetting binder in a given ratio of the or mineral fibres and the like to plates or fibre diameter to the binder coating. Simulta three-dimensionally shaped products. The naneously it is possible to ensure gas permeabil ture of the surface treatement can range from ity and a moisture permeability determinable the simplest resin enrichment, primers or var 125 by the surface density of the surface layer on nishes to printing and lining with films or lami- the finished moulding, because the individual nation with plastics and the like. fibres coated with a thermosetting binder The application of surface layers to support- within the tangled fibre fleece give between ing central layers, either in the form of special them homogeneously distributed, screen-like surface layer gluing treatments, additional lin130 passages. Due to the fact that the fibre-envel- 2 GB2194485A 2 oping binder is partly precondensed, there is thermosetting binder proportions. Following no migration of binder into the central, rela- the moulding of the surface layers, together tively absorbent tangled fibre layer, which is with the tangled fibre layer to give moulded subject to the action of the thermoplastic articles, said surface layers have a microporo binder, so that there is no need to thin the 70 sity which, in per se contradictory manner and same in the surfac6 area and its positive chardespite a relatively high absorption capacity acteristics have their full effect. As a result of for moisture within the moulded article, en precondensing, the viscosity of the thermo- sures the aforementioned highly stable accu setting binder in the surface layers can also racy to size of the moulded article.

be previously defined for the moulding pro- 75 The precondensed, thermosetting binder of cess. The quasi-moisture absorption possibility the surface layer joins the fibres thereof at of the central tangled fibre layer through the their crossing points, so that the surface surface layers acting in membrane-like manner layers in the unmoulded state can be given a can be precisely "dosed" and adjusted in op- higher tensile strength than the central layer.

timum manner to the individual application.The 80 Thus, during the moulding of the mat to the heat-resistant enveloping of the surface layer moulded article, the shaping or deforming pro fibres only seals the individual fibres in mois- cess is stabilized, particularly if, such as e.g.

ture-tight manner, but not the tangled fibre is the case withwood fibre mats, the mat is fleece formed therefrom. During moulding, the plasticized by evaporation during which the fibres are not partly dissolved again and do 85 thermoplastically bound fibres of the central not come into direct contact with the hot sur- layer largely lose their binding, whereas the face of the mould parts. They retain their pre- binding characteristics of the preceondensate determined strength characteristics substan- of the surface layers is largely retained. The tially independently of the parameters for opti- permeability of the surface layer makes it pos mum moulding. The precondensed binders 90 sible, to retain conventional technology for used for enveloping the individual fibres of the wood fibre mats and namely in the case of surface layers have a viscosity such that there extended shaping possibilities, improved is not a complete sealing of the tangled fibre moulded article characteristics and due to the layer, such as is the case with film linings. stabilizing action of the surface layers on the The moisture-regulating membrane action of 95 shaping process even with reduced wastage.

the surface layers equals out high temperature It is advantageous to use plastic fibres for fluctuations and moisture changes within the the surface layer fibres which have a softening passenger area of cars lined with moulded point above 200'C. Unlike many mineral'' articles made from such multilayer mats in a fibres, such fibres have high lateral strength manner pleasant for the occupants.It has sur- 100 characteristics and are not brittle, even- at low prisingly been found in this connection that temperatures, so that moulded articles with even if with prolonged wetness action, mois- high impact strength in a very wide tempera ture absorption in the central layer, e.g. of ture range are obtained. If increased demands lignocellulose fibres, has taken place to a rela- are made on the strength and bending resis tively high extent, the thickness swelling of 105 tance of the parts, it may be appropriate for the moulded article is approximately one deci- the surface layers to be at least partly formed mal power lower than with comparable from glass fibres, apart from ceramic fibres.

moulded articles which, in place of the mem- The bending strength and impact strength of brane-like surface layers, either carry film seals the moulded articles can also be improved if 'V or are otherwise completely air and moisture- 110 at least part of the fibres of the surface layer tight as a result of binders or coatings. The are natural fibres. As natural fibres generally moisture-regulating membrane, even if the have an increased moisture absorption during fibres of the central layer are sensitive to storage, it is appropriate to pretreat them with moisture, makes it possible to so regulate and. hydrophobing agents prior to binder addition keep low the moisture absorption or charac- 115 and precondensation thereof. Improved teristics of the moulded article, that there are strength characteristics of the moulded articles no dimensional changes due to swelling if can in particular be obtained if the fibres form moisture occurs in superfluity on the moulded ing the tangled fibre fleeces of the surface article. Due to the fact that the original characlayers, are on average longer than 20 mm.

teristics of the individual, completely sealed 120 On moulding the fibrous mats to moulded fibres of the surface layer fleeces are fully rearticles, the tangled fibres of the surface tained and in particular due to the fact that layers are further bound and strengthened by the high-grade- thermosetting gluing of said the precondensed resin at the fibre crossing surface layers remains almost completely points to the extent that this has not taken therein and does not partly diffuse into the, 125 place through the precondensation and are central layer, the moulded articles have excel- consequently able to absorb tensile forces to lent strength characteristics and in particular a an even greater extent and optionally improve high impact strength, as well as bending the mechanical characteristics of the moulded strength and bursting limit values, which are articles.

otherwise only attainable with much higher 130 Virtually all known fibre types can be used 3 GB2194485A 3 for producing the central layers, if the temper- tween the coated and uncoated tangled fibres ature at which the fibrous mat is moulded to of the surface layer is between 1.4 and 1.75.

moulded articles can be borne by the fibres g 2. Fibrous mat according to claim 1, char- without suffering damage. This also applies acterised in that the fibres of the surface with respect to the binders used in the central 70 layers comprise plastics, whose softening po- layer. Generally lower demands are made on int is above 20WC.

the quality of the fibres and binders of the 3. Fibrous mat according to claim 1, char- central layer than for comparable known acterised in that the fibres of the surface fibrous mats, particularly because the moislayers are at least in part glass fibres.

ture-regulating characteristics of the surface 75 4. Fibrous mat according to claims 1 to 3, layers also permit the use of more moisture characterised in that the fibres of the surface sensitive fibres. layer are at least in part natural fibres pre- The increased viscosity of the fibre-envelop- treated with hydrophobing agents prior to ing binder during final moulding not only pro- adding the binder and precondensation.

duces the desired microporosity, but also a 80 5. Fibrous mat according to at least one of fibre diameter-corresponding surface rough- the claims 1 to 4, characterised in that the ness which, in conjunction with the micropo- average length of the fibres forming the tan rosity, ensures a better adhesion of surface gled fibre fleeces of the surface layers is finishes and laminating adhesives. greater than 20 mm.

Particularly if heat-resistant, crosslinked cou- 85 6. Fibrous mat according to claim 1, char- pling agents are used between the surface acterised in that between the heatproof, layers and the central fibrous fleece mat, the binder-containing tangled fibre surface layer on desired gas permeability can suffer. This can the surfaces of the central tangled fibre layer be obviated in that said coupling agent is ap- for the firm reciprocal sandwich of the layers plied in the form of point, line, screen or grat- 90 is provided a heat- resistant coupling agent in ing-ike patterns, the surface proportion not point, line, grid or grating- like distribution, the wetted by the coupling agent being greater sandwich surface portions not subject to the than 15%. This makes it possible to achieve a action of the coupling agent being more than satisfactory gas permeability of the coupling 15% of the total surface.

agent layer, without the heat-resistant, surface adh ' esion of the surface layers being impaired. Published 1988 at The Patent Office, State House, 66171 High Holborn, London WC 1 R 4TP. Further copies may be obtained from Thus, tensile forces during shaping can be The Patent Office, Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD.

transferred between the surface layers and the Printed by Burgess & Son (Abingdon) Ltd. Con. 1/87.

central fibrous fleece mat. The pattern-like coating with coupling agent can e.g. be car ried out without difficulty by per se known pressure rollers or other prior art means, such as pressure screens and the like. The -lattice constants" of the adhesive pattern can be be tween a few millimetres and a few centim etres, as a function of the fibre type, length and deformation problem.

Claims (1)

1. Fibrous mat for hot moulding to moulded articles, comprising a central tangled fibre layer treated with a binder and in each case one heatproof, binder-containing tangled fibre surface layer on the two surfaces of the central layer, the surface layers forming a firm sandwich with the central layer, characterised in that the surface layer of at least the un moulded mat has a higher tensile strength than the central layer and that said surface layer in the mat moulded to the moulded arti cle is constructed as a moisture-regulating membrane, the weight per unit area of the binder-free portion of the heatproof tangled fibres of the surface layer being 10 to 100 9/m2 and the individual tangled fibres with a proportion of 100 to 200% by weight, based on this weight per unit area, are coated in fibre-enveloping manner with a binder already precondensed prior to the moulding of the fibrous mat, so that the diameter ratio be-