DE2946969A1 - Mat for dry-pressed esp. cellulosic article prodn. - contg. dense pre-strengthened central layer having low moisture content - Google Patents

Abstract

Mat for mfg. pressed articles in a dry process consists of a pre-strengthened layer of opt. powdered aggregate-contg. cellulose- and/or lignocellulose fibres, the layer being solidly bonded to workable corrugated support layers. Novelty consists in using a pre-strengthened central layer the density of which, before pressing, approximates to its density in the finished article. Central layer moisture content is less than 10%. The central layer can consist of at least one layer of thermoplastic- or thermosetting binder-impregnated (1) corrugated paper or cardboard or (2) pleated fabric or crinkled fleece, or is (3) a thermoplastic filled and/or reinforced esp. with cellulose- or lignocellulose materials. The central layer can also be a laminate of one or more materials (1)-(3). Central layer bonding is achieved by sewing or stitching, pref. using thermoplastic material threads, or by needling, or by cementing with heat-softenable adhesives. At least some of the central layer materials are recycle materials. Low moisture content shortens pressing time and prevents steam blister formation. Density control prevents moisture absorption during storage. Mats contg. compacted central layers are less bulky and require less storage space.

Description

Mat for the dry production of pressed moldings

preferably made of cellulose or lignocellulose materials (additional registration to our own application dated November 12, 1979) The invention relates to a mat for manufacture of pressed molded parts in the dry process, consisting of a pre-consolidated Layer, preferably made of cellulose or lignocellulose materials, and creped, deformable carrier layers which are connected to the pre-consolidated layer.

Mats of the type described, which are preferably warm to moldings are pressed, are from the registration from 12. ii. 1979 known. they draw compared to the previous state of the art through an improved shaping option and result in products of greater strength and improved surface quality.

The middle layers of these mats are pre-consolidated, but have in the initial state a significantly lower density than in the pressed state. the The deformability of these middle layers is determined by thermal before pressing Unlocking (e.g. steaming) improves, their moisture content must if they are sufficient should be deformable, be over 10%. This is in terms of press technology a disadvantage, as the dehumidification during the warm final pressing adds pressing time needed. This affects the economic viability of the process. A Another disadvantage is that the moisture content leads to the formation of vapor bubbles during pressing in the precast part, especially if the carrier layers are impermeable to vapor be used. Also the perforation of the carrier layers, which is described in the above application proposed to remedy this disadvantage eliminates the risk of vapor lock not completely, because the percentage of perforations on the total surface of the carrier layers is naturally small. The formation of vapor bubbles either leads to an increased reject rate or requires a correspondingly complicated pressing technique to eliminate them (Intermediate relief of the press during the precast part pressing). Both burden the economy of the overall process.

The invention is therefore based on the object of the initially to create the type described, which is pressed into molded parts with shorter pressing times that the risk of vapor lock formation in the finished part is avoided, even if vapor-tight, closed carrier layers are used. According to the invention this should be done in that the density of the pre-consolidated middle layer before the pressing approximately corresponds to their density in the finished part and that the Moisture of this middle layer is less than 10%.

The low moisture content initially has the advantage that the pressing time can be further shortened and that vapor bubbles no longer occur in the pressed part. This means that the density of the pre-consolidated middle layer the density of the prefabricated part already corresponds approximately, is also the inclination of this layer for uncontrolled moisture absorption during temporary storage, so that their preconditioning can be maintained over a longer period of time. Further Advantages result from the fact that mats with such highly compressed middle layers are less voluminous and therefore require less storage space, as well as the fact that their handling and transport stability compared to the previous mats considerably are improved.

The middle layers of the mats according to the invention must also be correspondingly can still be easily deformed in a highly compressed state. This usually requires additional measures. For example, there is an advantageous embodiment such mats in that the middle layer consists of at least one layer of creped, paper impregnated with thermoplastic or thermosetting binders or Made of cardboard.

In the case of creped paper, cardboard, fabrics or fleeces, all of them Surface equally finely folded. Such structures have a total surface, which is a multiple of that of the outer dimension of the corresponding Orbits. You are therefore able to produce the three-dimensional shape needed Surface enlargement from the "surface reserve" of the pleating (creping) cover. With a suitable shape of the folds of the creping (cross creping, in which the corresponding web is finely folded in two mutually perpendicular directions) the corresponding material has great deformability in all of them possible spatial directions, the surface enlargement in each case by the smoothing of the folds is made possible without making the material larger the deformation resulting tensile loads is subjected. The creping of the The middle layer enables the necessary change of shape, creped papers, which already have their final density can be prefabricated and soaked without any problems. In addition to the cellulose fibers, they can also contain powdered fillers.

Middle layers with a textile structure can also be used for the realization inventive mats are used. So it is z. B.

possible that the middle layer is made from at least one layer of creped Fabric or fleece is made with thermosetting or thermoplastic binders is soaked. In this case too, the required deformability of the The middle layer is obtained by the fact that the fabric itself is only insufficiently deformable or fleeces are creped.

Is the material of the middle layer of the mats according to the invention sufficiently deformable, the conditions are particularly favorable. This is for example the case when the middle layer is preferably made of cellulose or lignocellulosic materials filled and / or reinforced thermoplastic Plastic is. Such a mat can be thermoformed without further precautions will. For molded parts that will be exposed to thermal loads in later use are, there are particular advantages when the creped backing layers made of metal. This increases both the dimensional stability of the parts in the heat improves as well as the heat absorption due to the favorable reflective conditions the carrier layer is reduced.

Creped paper, cardboard, fabric or soaked with binding agents Nonwovens as proposed as middle layer material for mats according to the invention can only be crimped to a limited extent. It is therefore in training of the inventive idea to be advantageous to use middle layers that consist of consist of a layer composite of one or more materials of the type described. The connection of the individual layers of the middle layer can be done by sewing, Quilting or needling. This can be particularly advantageous if the Individual layers consist of paper, cardboard, fabrics or fleeces.

If textile joining processes are used, it is advisable to if the connecting threads are made of thermoplastic materials, which when warm Compression can be easily deformed. Another beneficial option is the core layer in the form of a layer composite consists in the layer composite being formed by adhesive that soften in the heat.

This approach has the advantage that middle classes in any Thickness can be built up from individual layers of good deformability, their connection with each other during hot pressing becomes flexible, so that the deformation properties of the individual layers can be fully utilized.

Because in this layer composite the materials can be used almost as desired can be combined, there is a wide range of adaptations for the properties of the pressed part.

Middle layers according to the invention can be used at the current level the technology completely or partially from recycled materials.

The creped papers or cardboard of the middle layers can, for example Recycled paper or cardboard, the quality of which is not suitable for other applications sufficient. The same applies to fabrics or fleeces made of synthetic and / or natural fibers. In both cases, preliminary products for the manufacture of mats according to the invention can be used from the relevant industry.

Also middle layers made of filled and / or reinforced thermoplastic Plastics can be made from low-value thermoplastic waste, such as, for example, in the form of coated paper waste and waste of the Cable industry and which cannot be used otherwise. Color differences and impurities do not play a role when used according to the invention essential role, inadequate mechanical strength properties, as in the use of mixed waste can occur through appropriate Compensate for the selection of the carrier layers.

Claims (9)

Requirements mat for the production of pressed molded parts in the dry process, consisting of a pre-consolidated layer, preferably made of cellulose or lignocellulose fibers or from mixtures of such fibers, optionally powdery additives may contain, and with deformable, creped backing layers with which the pre-consolidated layer is firmly bonded, that is to say e t that the density of the pre-consolidated middle layer before pressing is approximate corresponds to their density in the finished part, and that the moisture of this middle layer is less than 10%. 2. Mat according to claim 1, d a d u r c h g e k e n n z e i c h -n e t that the middle layer consists of at least one layer of creped, with thermoplastic or thermosetting binders soaked paper or cardboard. 3. Mat according to claim 1, d a d u r c h g e k e n n z e i c h -n e t that the middle layer consists of at least one layer of creped fabric or fleece exists, which is impregnated with thermosetting or thermoplastic binders. 4. Mat according to claim 1, d a d u r c h 9 e k e n n -z e i c h n e t that the middle layer is preferably made with cellulosic or lignocellulosic materials is filled and / or reinforced thermoplastic material. 5. Mat according to one or more of the preceding claims, d A d u r c h k e n n n n z ei c h ne t that the middle layer is made of a layer composite consists of one or more materials according to claims 2-4. 6. Mat according to claims 1-3 and claim 5, d a d u r c h gek E n n n e c h ne t that the layer composite of the middle layer by sewing, quilting or needles has been manufactured. 7. Mat according to one or more of the preceding claims, d a d u r c h g e k e n n n z e i c h n e t that the sewing or quilting of the layer composite threads used according to claim 5 consist of thermoplastics. 8. Mat according to one or more of the preceding claims, d a d u r c h g e k e n n n z e i c h n e t that the layer composite of the middle layer according to claim 5 by gluing with heat softening adhesives. 9. Mat according to claims 1-8, since d u r c h gek e n n -z e i n e t that the materials of the middle class are at least partially recycled materials are.