JPS6366361A - Fiber mat for thermally molding molded article - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a central entangled fiber layer treated with a binder and a heat-resistant, binder-containing entangled fiber layer, one layer on each of the two surfaces of the central layer. The present invention relates to a fiber mat for thermoforming into shaped articles, consisting of surface layers which together form a rigid sanderite structure.

Prior Art Multilayer fiber mats, especially multilayer fiber cloaks with special surface coatings, are known. Multilayer fiber mats formed from cellulose fibers, lignocellulosic fibers or similar fibers are known, in particular for producing shaped articles by subjecting the fiber mats to pressure and elevated temperatures in press molding machines. . The two surface layers of this fiber mat are formed from entangled fiber fleece and have at least a proportion of thermoset synthetic resin. The fiber mantle has a central entangled fiber layer containing a thermoplastic binder and a thermosetting binder.
manufactured by depositing two outer surface layers in layers on a conveyor belt, which layers simultaneously exist as a rigid multilayer arrangement or sandwich structure when molded into a molded article. 33 38
5).

However, in this known method, partial flow effects during the production and shaping of the mat result in excess adhesive of the surface layer with thermosetting material being at least partially absorbed by the absorbent central layer. It was found that This phenomenon is disadvantageous in that in such known three-layer mats, the thermosetting binder used in the thermal and mechanical treatment undesirably migrates back into the central layer and is lost. This effect can only be compensated for by adding even larger amounts of thermoset binder to the surface layer fibers, which also makes the desired final product significantly more expensive.

Other methods of producing insulating boards using mineral fibers as the base material are known. According to this method, it can advantageously be realized to apply the nonwoven to a surface fiber fleece which is also moving during production and to bond the insulating plate to the fleece carrier during compaction (DE-O 82 85 3 316).

Depending on the product, special attention has long been paid to the processing of modern types of wood fiber materials, as well as non-woven fabrics of natural fibers or mineral fibers, etc., into boards or three-dimensional products. The surface treatment can range from the simplest resin thickening, primer or face treatment to printing, lining with a film or lamination with plastic or the like.

Application of additional lining materials or the like to the surface layer supported by the central layer, either with special surface layer adhesive treatments, generally provides the desired improved surface properties; however, such linings are generally It is associated with the sealing properties of the surface in the sense that it is impermeable to This surface sealing property can be a drawback in many cases, especially when such mats are processed into molded articles except by certain manipulations or other technically easy-to-perform steps.

By way of example, reference may be made to preferred vacuum deep drawing methods for co-ordinating such molded articles with thermoplastic films and certain characteristics of fully formed parts, which may be used as linings in motor vehicle traffic areas. It is considered even more advantageous if, when used, the lining ensures air permeability and moisture absorption - this can considerably improve the climatic conditions within such a traffic area.

The present invention therefore minimizes manufacturing costs when using a minimum of higher-grade materials both from the fiber and binder aspects, while ensuring that both surfaces are sensitive to wetting. breaths moisture, and is thermally
It is an object of the present invention to further develop a three-layer fiber mat of the aforementioned type, which contributes to providing a molded article whose chemical and physical properties are comparable to those of a corresponding surface-sealing covering material or covering. .

DISCLOSURE OF THE INVENTION According to the present invention, this problem is solved by providing a central layer of entangled fibers treated with a binder and a layer of heat-resistant, binder-containing fibers on each of the two surfaces of this central layer. In a fiber mat intended for thermoforming into a molded article, consisting of surface layers of fibers combined together forming a rigid sandwich structure, (a) the fibers in at least the unformed state; The surface layer of the mat has a higher tensile strength than the central layer; (b) in the fiber mat formed into a molded article, the surface layer is configured as a moisture regulating film; (c) the heat resistance of the surface layer is The electric resistance stitch per unit area of the binder-free part of the entangled fibers is 10 to 100.
9/rrl; and) the individual entangled fibers of the surface layer have already been precondensed prior to forming the woven mat in a proportion of 100 to 200% by weight, based on weight per unit area. Depending on the binder used, the diameter ratio of coated entangled fibers to uncoated entangled fibers is between 1.4 and 1.
．． 75, the fibers are covered in an encircling manner; this is solved by the above structure, which is characteristic of a fiber mat.

This load has the following features: (1) A feature in which the fibers in the surface layer are made of plastic with a softening point of 200°C or higher; (2) A feature in which at least some of the fibers in the surface layer are glass fiber; (3) A feature in which the surface layer fibers are made of glass fiber. The fibers of are at least partially pretreated with a hydrophobic agent prior to the addition of the binder and its precondensation! (4) An embodiment in which the average length of the fibers forming the entangled fiber fleece of the surface layer is 2 on or more; and (5) A heat resistance in which a firm alternating sandwich structure is formed. A heat-resistant coupling agent is applied between the binder-containing entangled fiber surface layer and the surface of the central entangled fiber layer in a dot-like, wire-like, grid-like, or grating-like distribution, in which case the cup The present invention includes an embodiment in which the surface portion of the sandwich structure that is not affected by the ring agent is 15% or more of the total surface.

Thus, according to the invention, the fibers of the surface layer can be substantially random and can take the form of organic or inorganic fibers of natural or synthetic origin, thus depending on their hygroscopicity or No conditions are attached as to susceptibility to other environmental influences. In addition, these fibers have a supporting central layer (application function Cfunction
Since only a very small amount is used compared to the weight per unit area of the total mat (1000-2000, 9 layers m'), the production cost need not be low. The current need for seamless surface sealing, especially with respect to high thermal stability, is to improve the sealing of the individual layers of the entangled fiber surface layer.
This is ensured by coating appropriate lengths of fibers, preferably in the form of staple fibers, with a thermosetting binder at a predetermined fiber diameter to binder coverage ratio. At the same time, the individual fibers coated with a thermosetting binder within the entangled fiber fleece provide homogeneously distributed screen-like channels between the fibers, making it possible to guarantee gas and moisture permeability. These properties can be measured by the surface density of the surface layer on the finished molding. The binder surrounding the fibers is partially precondensed ( prec
Due to the ondensed structure, there is no migration of the binder into the relatively absorbent central entangled fiber layer (subjected to the action of the thermoplastic binder), so there is no need to thin the binder in the surface areas ( , and its positive properties are fully exhibited.As a result of precondensation,
The viscosity of the thermosetting binder in the surface layer can also be predetermined for the molding process. The pseudo-moisture absorption potential of the central entangled fiber layer through the membrane-like surface layer can be precisely "dose" and adjusted to best suit the individual application. The heat-resistant envelope of the fibers in the surface layer only provides a moisture-tight seal to the individual fibers, but not to the entangled fiber fleece formed from them. During molding, the fibers are not even partially remelted;
Also avoid direct contact with hot surfaces of molding machine parts. The fibers retain their predetermined strength properties substantially independent of optimal forming parameters. The precondensed binder used to surround the individual fibers of the surface layer has a viscosity that does not allow for complete sealing of the entangled fiber layer as would be the case with a film lining. The moisture-regulating imitation of the surface layer allows molded articles made from such multilayer mats to accommodate large temperature fluctuations and moisture changes within the lined motor vehicle traffic area to the advantage of occupants. It has the ability to flatten. In this context, it is surprising that even if the wetting action lasts for a long time, e.g. a relatively high degree of moisture absorption occurs in the central layer of lignocellulosic fibers, the swelling in the thickness direction of the molded article is Approximately twice as small as the corresponding molded article which has a film seal instead of a surface layer or which is otherwise completely hermetic and isothermally tight as a result of a binder or coating.
one decimal power). This moisture-regulating membrane makes it possible to very well regulate the moisture absorption properties of the molded article and keep it low, even if the fibers of the central layer are moisture-sensitive, so that excess moisture does not occur in the molded article. However, there is no dimensional change due to swelling. Due to the fact that the individual completely sealed fibers of the surface layer fleece perfectly retain their original properties, and in particular the thermosetting adhesive of the surface layer Owing to the fact that it remains completely in the surface layer and does not even partially diffuse into the central layer, the molded article has excellent strength properties, in particular a high impact strength, as well as a much higher proportion than would otherwise be possible. It has excellent flexural strength and burst limits that can only be achieved with thermoset binders. Molding the surface layer with an entangled fiber layer to provide a shaped article results in the surface layer being microporous. This microporosity appears to be preliminary and ensures the aforementioned highly stable dimensional accuracy of the molded article, despite the relatively high moisture absorption capacity within the molded article.

- The precondensed binder in the surface layer binds the fibers at their intersections, allowing the surface layer to have a higher tensile strength in the unformed state than the central layer. The shaping or deformation process is thus stabilized during the shaping of the mat into a molded article, in particular when the mat is plasticized by evaporation, for example in the case of wood*i mats. During this plasticization, the bonding of the thermoplastically bonded fibers of the central layer is largely lost, while the bonding properties of the precondensate of the surface layer are largely retained. The permeability of the surface layer allows conventional wood fiber mats to retain improved molded article properties due to the stabilizing effect of the surface layer on the building process, even if the building process is long (possible). even a little.

It is advantageous to use plastic fibers with a softening point of 200° C. or higher as the fibers of the surface layer. Unlike many mineral fibers, this type of fiber has high transverse strength properties and is not brittle even at low temperatures, resulting in molded articles with high impact strength over a very wide temperature range. If the demands on the strength and bending resistance of the component are high, it may be appropriate for the surface layer to be formed at least in part from glass fibres, apart from ceramic fibres.

The flexural strength and impact strength of the molded article may also be improved if at least some of the fibers of the surface layer are natural fibers. Since natural fibers generally absorb a lot of moisture during storage, it is appropriate to pre-treat them with a hydrophobic agent prior to the addition of the binder and its precondensation. Improved strength properties in the molded article can be particularly achieved if the fibers forming the surface layer entangled fiber fleece are on average longer than 20 silks.

When the fiber mat is formed into a molded article, the entangled fibers in the surface layer are further bonded and strengthened by the precondensation resin at the intersections of the FA fibers to the extent that this would not occur with precondensation, eventually increasing the tensile strength even further. can be absorbed and optionally improve the mechanical properties of the molded article.

Virtually any known fiber can be used to make the central layer, provided the fibers can withstand the temperatures at which the fiber mat is formed into a shaped article without damage. This also applies to the binder used in the center layer. The quality requirements for the fibers and binder (of the central layer) are generally lower than for corresponding known fiber mats, especially since the moisture regulating properties of the surface layer also allow the use of moisture-sensitive fibers.

The increased viscosity of the binder surrounding the fibers during the final shaping not only produces the desired microporosity, but also corresponds to the fiber diameter, which together with the microporosity ensures better adhesion of the facing and the lamination adhesive. surface roughness.

In particular, the desired gas permeability may be compromised if heat-resistant cross-linking coupling agents are used between the surface layer and the central textile fleece mat. This can be done by applying the coupling agent in the form of dots, lines, screens or gratings.
This can be prevented by applying the coupling agent in a lattice-like pattern such that the proportion of the surface that is not wetted by the coupling agent is 15% or more.

This allows a satisfactory gas permeability of the coupling agent layer to be achieved without compromising the heat-resistant surface adhesion of the surface layer. Thus, tensile forces during shaping can be transferred between the surface layer and the central fibrous fleece mat. Kaburi 7
Coating with this pattern can be carried out without difficulty by means of pressure rollers or other conventional means, such as pressure screens, etc., which are known per se. The lattice constant of the adhesive pattern
'' can range from a few to a hundred as a function of fiber type, length and deformation issues.

Claims (6)

[Claims] (1) consisting of a central layer of entangled fibers treated with a binder and a surface layer of heat-resistant, binder-containing entangled fibers, one layer on each of the two surfaces of the central layer; A fibrous mat for thermoforming into a shaped article, in which a surface layer and a central layer form a rigid sandwich structure, wherein the surface layer of the mat, at least in the unformed state, has a higher tensile strength than the central layer. In the mat formed into a molded article, the surface layer is configured as a moisture regulating film; the weight per unit area of the binder-free portion of the heat-resistant entangled fibers in the surface layer is: 10-100g/
m^2; and the individual entangled fibers of the surface layer are present in a proportion of 100 to 200% by weight based on the weight per unit area;
The fibers are surrounded by a binder that has already been precondensed prior to forming the fiber mat such that the diameter ratio of coated entangled fibers to uncoated entangled fibers is 1.4 to 1.75. The fiber mat is characterized in that it is coated with a shape. (2) The fiber mat according to claim 1, wherein the fibers of the surface layer are made of plastic having a softening point of 200° C. or higher. (3) The fiber mat according to claim 1, wherein at least some of the fibers in the surface layer are glass fibers. (4) Any one of claims 1 to 3, wherein at least some of the fibers in the surface layer are natural fibers that have been pretreated with a hydrophobic agent prior to addition of a binder and precondensation thereof. Fiber mats as described in Section. (5) Claims 1 to 4, wherein the average length of the fibers forming the entangled fiber fleece of the surface layer is 20 mm or more.
The fiber mat according to any one of the above items. (6) a heat-resistant coupling agent is dotted between the heat-resistant binder-containing entangled fiber surface layer and the surface of the central entangled fiber layer forming a rigid staggered sandwich structure;
Claim 1, wherein the coating is applied in a line-like, grid-like or grating-like distribution, in which case the surface area of the sandwich structure not affected by the coupling agent is at least 15% of the total surface. fiber mat.