CA2017641C

CA2017641C - Process for producing binder-containing fibrous mats

Info

Publication number: CA2017641C
Application number: CA002017641A
Authority: CA
Inventors: Gunter H. Kiss
Original assignee: Lignotock GmbH
Current assignee: Lignotock GmbH
Priority date: 1989-05-29
Filing date: 1990-05-28
Publication date: 1997-01-28
Anticipated expiration: 2010-05-28
Also published as: ES2078298T3; CA2017641A1; DE59009428D1; EP0400766A2; DE3917787C1; KR950001990B1; EP0400766B1; KR900017768A; JPH0363102A; EP0400766A3

Abstract

A process for producing binder-containing fibrous mats from lignocellulose fibres or the like is described, in which the fibres are processed by hot pressing to shaped or moulded articles, such as for the internal lining of the passenger compartments of motor vehicles together with stabilizing additives. The dry fibrous material thoroughly mixed with the binder is applied to a conveyor in such a way that there is an alternate application of several wood fibre layers and synthetic fibre layers. The heap densities of the synthetic fibres and the wood fibres, considered over the mat cross-section, are in accordance with a statistical distribution, which roughly corresponds to an edge-blurred, periodic comb profile. The base width for the synthetic fibres is much smaller than that for the wood fibres. The individual fibre heaps are interconnected by means of suitable adhesives.

Description

76~
-- P~DCESS F~R ~WULl~G BINDER~OONTAINING ~ D~ MATS

The invention relates to a ~L~cess for prc~llc;ng binder-containing fibrcus mats ~cc~r~;ng to the preamble of claIm 1.

Such fibr~us mats are known in many different compositions and are ~ll~e~
or shaped in the most varied ways to self-supporting moulded or shaped articles.

Thus, e.g. a ~l~cess for the hot pressing,of shaped articles of the afore-mentioned type is known, in which for the shaping process a st~h;l;~ing support is ~pl;~ on at least one side between the shaping surface of the shaping tool or mould and the mat fleece (DE-OS 37 21 663), which is ~ cLerized in that the s~ah;l;~ing support is constituted by a composite fibre layer absorbing t~s;le forces in the surface direction, which is substantially ext~n~;nn or elongation-free, but under the heat action within the hot press is plastically defonm~bl~ and which is h~r~ne~ or sol;~;fied with and/or ;mm~;Ately after the shaping process to a substan-tially elongation-free, infl~x;hle covering.

A fibrous fleece mixture of lignoc~lllllo~e fibres and cotton fibres is used, which is mixed with heat-h~r~n;ng binders. This fibrous fleece mixture is embedded between two stab;l;~ing supports which are substan-tially elongation-free in the surface direction and prior to the shaping of this raw mat blank a union is formed between the individual laminations, so that during the shaping or pressing ~L~cess, the t~n~;le forces which occur can be absorbed in tn~lhl~free manner. The nec~ss~ry adhesion between the fl~x;hl~ stabilizing supports and the surface of the fibrous fleece mixture results fn~m the fact that a heat-resistant self-adhesion occurs in the temperature range 60 to 150C. The stabilizing support to be applied to one or both sides of a mat fleece can be applied to the latter in the said prior art either by sprinkling on one or more layers of high-s~ Ul threads, or can be pnesent in prefabricated form as a t~nglf~ fibre fleece co~posite. The heat-resistant ~h~s;~n between the s~h;l;~ing support and the wocd fibre mat is distributed over several fibre layers, in order to ensune the afon_mentioned t~n~;le force transfer.

It is also no longer novel in this connection to pn~cess and construct the 20~764~
_ - 2 -st~b;l;~ing support in such a way that its air p~rme~h;l;ty is retained both before and after the shaping of the fibr~us mat to a shaped or m~ll~e~
article. For th;~ purpose the stabil;~ing support thickness is kept very small compared with that of the fibr~us fleece. It is fi m~ ntally me~ that such a st~h;l;~ing support is pr~vided an either one or both surfaces of the wocd fibre fleece, but not in the interior of the mat blank.

As opposed to this, another known fibrous mat of the present type is characterized by the fact that for stabilizing for the shaping pr~cess and therefore the transfer of forces into the m;~le of the tangled fibre fleece a finm fabric is inserted, which p~rm~npntly d~SOlbS the tensile and shear forces there in the matter of a tension network. The fabric embedded in the fibrous fleece mat is cnly reached by the t~n~;le forces of the shaping tool if they have already been transferred fm m the shaping tool surfaces anto the fibrous material. This generally leads to consider-able damage in the structure of the fibrous mat before the shaping tool has reached the stabilizing fabric insert and can therefore come into action.

Therefore research has been carried cut with the aim of pro~uc;ng fib m us fleece mats comprising a substantially h~ lleoll~ mixture of c~lllllQse or lignoc~llulo~e fibres not l~H~hle for the shaping ~Lucess and longer synthetic threads or the like which absorb the t~n~;le and shear forces.
However, it has been found that at least in mass pr~duction, the nec~ss~ry-hu~g~leous thor~ugh mixing of the different fibre types, part;~ll~rly their h~ n~ sprinkling anto a c~v~ying "~,l~eL for pro~uc;ng the fibrous fleece cannot be realized in a te~chn;c~l m~nn~r. The pouring characteristics of the different fibre types always lead to an Im~es;red and substantially uncontroll~hle separation of the individual types. The resulting quality reduction of the f;n;~h~ fibrous mat can anly be compen-sated to a certain extent by an increased use of expensive synthetic fibres which, apart from increasing the cost of the prcduct, leads to the dis-advantage of the air impermeability of the fibrous mat.

The problem of the present invention is to pr~vide a pr~cess for prc~uc;ng fibrous mats frcm a mixture of wocd and textile fibres leading to a statistically aveLo~ed~ hun~ye~ecus distribution of synthetic fibres a~sorb;ng t~n~ and shear fom es in the case of a m;n;mllm synthetic fibre ~ yoLLion within the mat and namely over the cross-section or thickness thereof and with in par~ lAr a ~;nim;~ed synthetic fibre p mportion in the surface region of the mat.

According to the invention this problem is solved by the features of the characterizing part of claim 1. Advan~Ageal~ further dev~l~pm~nts can be yaul~L~d from the ~lhclA;m~.

The essential advantage of such a mat construction is that the synthetic fibres Ahs~rb;ng the t~ns;le and shear forces are neither restricted to the outer ~IrfAce regions, nor to a rAn~mly formed central layer and that during the p m duction of such a mat it is posfi;hle to avoid a disadvantage-ous separating effect, such as occurs in the case of synthetic-wocd fibre mixtures during mat prcduction. Advan~gealsly hul~y~leous shaping ~ ~L~cLeristics can be obtained through the concentration of the tension-resistant synthetic fibres in a plurality of individual synthetic fibre layers. The disadvantage of distributing t~n~;le fom es over a l~cAl;~ed central layer and via the latter only in an inadequate manner to the shaping tool is obviated. There is also no need to use a higher synthetic fibre concentration either in a fibrous mixture or restricted to the top layers of the fibrous mat with the resulting prevention of the nec~s~ry gas p~rm~Ah;l;ty of the mat for satisfactory ~L~cessability to the shaped article. The multilayer nature of the fibrous mat makes it poss;hle to keep the synthetic fibre concentrations in the individual layers txLL~n~ly lcw, accompanied by a simultAneal~ mAX;~lm h~ oy~lization of the shaping ~hAracteristics of the fibrous fleece structure. The low weight per unit area of the individual layers ensures an adequate penetration between the wood and synthetic fibres in the transition areas and therefore assists the task of the adhesive between the layer arrangements in a particularly advantAgeal~ manner.

The ~hes;~n between the synthetic and wood fibres can be addit;~Ally improved by using synthetic fibres, which become sticky at higher ~_ _ 4 _ 2 0 ~ 7 6 4 ~

temperatures, such as e.g. when plasticizing the mat blanks by steam ~Lea~ t and which shrink in the case of a further ~ P~Lure rise (hot pressing to the f;n;~h~ article). me shrinkage during hot pressing prevents a faillre of the mat due to t~n~ and shear stressing and qnn~ ntly improves the ~h~r~h;l;ty of the mat.

m e synthetic fibre layers can be sprinkled on. However, it is also pos-sible to use prefabricated tangled fibre fleeces of said material and which are then drawn as web material from reels, which are positioned between the spreading heads for the wocd fibres. A part;~llAr advantage in this procedure is that synthetic fibre fleeces can be used, whose fibres are at least partly oriented in the preferred directions, so that the tensile sLl~ly Ul important for the shaping of the mats can be influenced in a direction-oriented manner. It is also easier to control the unifonmity of the characteristics of prefabricated synthetic fibre flpec~s~ which reduces the mat tolerance range with respect to the shaping characteristics u~l~Or.

The drawings diay~ ,atically illustrate the statistical distribution of the individual fibre types over the thickness of the fibrous mat.

Fig. 1 is a curve of the fibre heap as a function of the mat thickness.
Fig. 2 is a diayl~-llatic representation of an apparatus for performing the inventive process.

As can be gathered from fig. 1 for the synthetic fibre heap distribution an the one hand and that of the wood fibres on the other in cross-section over the mat thickness a curve is obtained, which m ughly oulle~ ,ds to a comb profile, but which has blurred sides or edges. The base width of the ourve parts for the synthetic fibres is much ~mAll~r than that of the thickness distribution of the wocd fibres. Gver the X-axis reproducing the mat-cross-section, with one mat surface at point A and the opposite mat surface at point B, is shown the distribution of both the synthetic and the wood fibres, namely in the direction of the Y-axis the proportion of synthetic fibres frcm 0 to 100% and in the opposite direction the proportion of wocd fibres from 100 to 0%. The blurred edges of the trans-~_ _ 5 _ Z0~7~

ition from synthetic to wood fibres and vice versa symhol;c~lly representthe degree of mixing between the fibres in the transition areas, i.e. the not sharp separating line between the synthetic fibre layer and the wood fibre layer desired for the cannection or joint.

Fig. 2 ~;~y~ Lically shows in cross-section an ~p~r~tus for producing such a statistical distribution over the mat thickness. Thus, to a conveyor 1, e.g. a belt conveyor, with guide pulleys 2 alternately synthetic fibre material and wocd fibre material is applied frcm a pl~lr~l;ty of overhead ~Lalaye containers. In the ~ho~ nt from a storage container 3 initially synthetic fibre material is ~pl;~, which is present there in the form of reel-like waund, thin tangled fibre synthetic mats and this is follawed by the sprinkling anto the ccmposite synthetic fibre material of wood fibre material frcm an averhead SL~L~Ye container 4 and then once again following the movement direction of the c~l~yal synthetic fibre material is sprinkled an frcm a S~O~Ye container 3'. In this case both the synthetic and the wood fibre materials are in pcurable form. As a function of the desired number of alternating synthetic and wood fibre layers, a multilayer mat is produced with a plllr~l;ty of alternately ~ccee~;ng averhead sL~laye cantainers for the individual fibre types.
In ~ccor~nce with the number of ~al~ge containers 3, 4, 3' etc. used in the ~L~cess s~ nce and whose exit ports can be closed and apened in con-~;nual~ly regulatable m~nnPr by dosing l~ eL~ 6, the desired multiplane mat 5 is obtained. To the palr~hle wood fibre material within the aver-head sLoL~ge container 4 is added in per se knawn manner binders. Further additives can be added both to the ~Lol~ye containers for the wood fibres 4 and to those 3, 3' for the synthetic fibres. In addition, between the individual s~al~e containers 3, 4, 3' there can be gluing stations or the l;ke. At the end of the conveyor the multiplane mat 5 can be passed through a nee~l;ng station. Suitable stripping members can be pr~vided between the individual sprinkling stations for an additional hu~g~lization of the part;~llar mat layer.

Claims

1. In a process for producing binder-containing fibrous mats from cellulose or lignocellulose fibres, which are processed by hot pressing to shaped or moulded articles, such as for the internal lining of the passenger compartments of motor vehicles, with stabilizing additives of synthetic fibres which at least partly absorb the shear and tensile forces which occur during the shaping, the dry fibrous material thoroughly mixed with the binder being homogeneously applied to a conveyor in layer form from overhead storage containers, the improvement comprising:
an alternating application of several wood fibre layers and synthetic fibre layers in such a way that the accumulation densities of the synthetic fibres and the wood fibres, considered over the cross-section or thickness of the mat, are in accordance with a statistical distribution roughly corresponding to an edge-blurred, periodic comb profile, the base width for the synthetic fibres being very small compared with that of the wood fibres.

2. Process according to claim 1, wherein the individual fibre layer are interconnected by means of suitable adhesives.

3. Process according to claim 2, wherein the adhesives are constituted by tacky components or needled connections.

4. Process according to claim 1, wherein the fibrous mats include surfaces made from synthetic fibres which at least partly become sticky at higher temperatures and shrink in the case of a further temperature increase.

5. Process according to any one of claims 1 to 4, wherein the synthetic or wood fibres are applied to the conveyor by sprinkling from associated storage containers.

6. Process according to any one of claims 1 to 4, wherein use is made of at least one prefabricated fibrous layer with fibres oriented in preferred directions.

7. Process according to claim 2, wherein the adhesives are constituted by tacky compnents and needled connections.

8. Process according to any one of claim 1 to 4, wherein the synthetic and wood fibres are applied to the conveyor by sprinkling from associated storage containers.

9. Process according to claim 1, wherein the synthetic fibres are in the form of prefabricated, loose, composite tangled fibre layers.

10. Process according to claim 6, wherein said prefabricated fibrous layer is in the form of an orthotropically oriented fibrous fleece.