DD215973A5 - METHOD AND DEVICE FOR PREPARING FORM PRESSES, MULTILAYER PLATES - Google Patents

Abstract

The invention relates to compression molded, multilayer panels consisting of a backing material of fibers dipped in a polymerized resin and a face liner. According to the invention, a precursor is produced from a layer of preconnected discontinuous fibers, which is impregnated by kneading with a binder, then this precursor is placed on a visible cladding foil, see-through film, the whole pressed under heat to the polymerization of the binder and to cause the bonding of the constituents of the multilayer board to one another.

Description

809 56

Method and device for the production of molded, multilayer boards

Field of application of the invention;

This invention relates to molded multilayer sheets containing at least one fibrous layer impregnated with a polymerized resin and at least one facing film as a substrate, and more particularly to a method and apparatus for making such panels. ,

Characteristic of the known technical solutions:

Molded, multilayer boards of this type are, for example, interior linings of roofs of motor vehicles.

  , · ·,; ; , ....;

vehicles, where the carrier material, which consists of at least one layer of polymerized resin impregnated fibers plays the role of a sound and heat insulating material, while a visible / mostly made of tissue cladding film, called the visible film, which faces the driver's cab, the roof gives an aesthetic appearance »

Plates made according to the same principle can also represent the decorative covering of a room, which receives heat and sound insulation by placing the panels on the walls or by making them extendable or movable in these spaces. Sp can provide upholstery , the baffles, the screens. the blinds, partition walls etc. are made of molded, multi-layered elements or clad with molded, multi-layered elements.

    · ^. ''

It is known to produce these composite panels by a method in which the individual operations are carried out sequentially. Thus, a precursor is first prepared, i. a felt made of fibers / impregnated with an unpolymerized binder, usually a thermosetting resin. For this purpose, an aqueous mixture of the binder is called wärmene; the formation of the felt sprayed on the fibers. Thereafter, the carrier material of the multilayer plate is produced by compression molding of one or more superposed frictions, by simultaneously using heat and pressure. During this molding process

The heat is used to polymerize the binder and in the case of a thermosetting resin its fully • •. to achieve enticement or polycondensation. The Verkleldungsfolie is then applied to the semi-rigid substrate after it has been sprayed on the same and / or the cladding film, a suitable Klebjende mixture.

This production in successive operations has several disadvantages. It requires several jobs and is therefore more expensive in terms of labor. The production line is taking

a large area, to which a considerable storage area is added. This type of production requires considerable production times. In addition, the overall performance of the route is low.

It is proposed in FR-PS 1 289 745 to produce molded, multi-layered sheets in a single operation, in which the binder of the fibrous layer is allowed to harden while the thermoplastic lining sheet is embossed and at the same time affixed to the fibrous layer.

The thermoplastic liner film softens and, during heating, molds to the high temperature necessary for polycondensation or crosslinking of the binder, which is 20 ° C.

Such a process can not be considered if the cladding film is a fabric or is generally made of a fabric which is sensitive to the high temperature necessary to crosslink the binder and / or to the various physico-chemical aggressive effects of this binder responding. Apart from its low heat resistance at temperatures of 20 ° C during the time required for polycondensation of about 3 minutes, the cladding film comes into contact with the precursor during molding and consequently with the unpolymerized binder and is subject to physical or chemical attack thereof. Moreover, the process described in said French patent requires the use of an impermeable film which prevents migration of the binder. Namely, the spraying of the binder may be in the case of the conventional fiber and felt-forming methods

causing localized buildup of binder due to the turbulence of the transporting liquid and the formation of excess binder fiber webs. Due to these accumulations, the binder may migrate through a permeable coating, ζ «B'J \. _: ] 0jkt \ tissue and therefore cause the appearance of spots on the visible surface of the covering.

Purpose of the invention :. , ^'·; ·..' _':;...','- \ ,. / "

The invention overcomes the aforementioned drawbacks and proposes a novel single-layer compression molding process consisting of a binder-impregnated discontinuous fiber substrate, the binder being primarily a thermosetting resin, and a veneer panel; which is usually a fabric and relatively sensitive to the temperature 'and / or the unpolymerized binder reacts.

Explanation of the essence of the invention: .

According to the invention, a precursor is prepared by impregnating at least one layer of previously bonded or temporarily bonded discontinuous fibers, for example an Isblier felt made by known methods, with an unpolymerized binder, the discontinuous fibers being bound by an already polymerized binder, but which is preferably present in a small amount by this precursor to one ; fabric covering, usually by fabric, by further pressing the whole by moderate heating for a short period of time to

· -. Sation of the binder and the bonding of the components of the multilayer plate with each other to achieve. '. '': ' ; ·. '.-. ''. '

The impregnation to obtain the precursor of the invention allows a uniform distribution of the binder in the felt and avoids a localized accumulation, as is the case with an impregnation by spraying the binder. Due to this homogeneous distribution, the pressing time can be reduced to the minimum polymerization time. It not only avoids the damage of the cladding film by the heat, but also the stains caused by accumulation of the unpolymerized binder. In addition, the per se known technique of impregnation, known for example from US Pat. No. 2,698,260, makes it possible to dose very accurately the amount of binder contained in the precursor and thereby in the end product, because by this method it is possible to apply different parameters such as concentration the processed liquid, soaking time, etc. act.

The process according to the invention can be carried out completely continuously. Thus, the pre-bonded felt can be soaked directly after its preparation, then the precursor can be used directly for the compression molding, all these operations without interposition tion'.er'fpl'gen. This process now usually requires several Formpreßplätzen to process all pre-products made before.

To make this process more industrially adaptable, the invention can also be realized by intermediately storing the pre-bonded felt.

. , '. '·. _ 6 -

As the binder contained in the felt is completely polymerized j does not occur 'the problem of aging of the felt' to ^1. In addition, this felt can be compressed during storage without adverse Fbigen.

¹ '.,. '. . ' -. i,. i

Of course, an intermediate storage of the impregnated precursor may also be provided. '' ''.

, ':' . '', i! The soaking process is facilitated when performed on a continuous, continuous strip of the pre-bonded felt

i '·. '. , .. .- ·. L ·

becomes. In addition, either the pre-bonded felt or

.'- ...

the impregnated precursor or both in the form of rolls ^! be stored. ^:

the binder used for impregnation contains a resin which is included among the thermosetting resins, e.g. the phenoplasts and aminoplasts can be selected. It is used werderj preferably phenoplasts, which have a good temperature and humidity behavior and are also cheap.

 ''! '' ι

The binder preferably used for soaking contains a phenolic resin from the group of phenolic resins having a pH of about 1.5 to 3 and having a pH of about 8.5 to 12, the latter due to the acidic character the former are preferred. Such resins have favorable polymerization properties and above all a relatively low crosslinking temperature of 150 to 180 ⁰ C and a relatively short curing time of one and a half to 2 minutes for the used in the invention Filzdicken and grammages of the fibers. These properties further reduce the risks of damaging the delicate trim film, especially fabric, during molding. It also gets through

the use of these resins reduces the energy consumption.

Oiese phenoplast resins, for example, as a base resin, a urea-modified resole-type phenol-formaldehyde resin having, for example, a formaldehyde / phenol molecular ratio of between 2 and 5 and catalyzed in the basic medium with alkaline or alkaline earth hydroxides the resin was neutralized to pH 7 by the addition of dilute sulfuric acid at the end of the cycle. In the case of the resins having a pH of about 1.5 to 3, this was adjusted by adding water and an acid to the base resin, while the resins having a pH of about 8.5 to 12 of these by the addition of water and a base has been achieved to this resin.

The impregnation of the fiber felt with the binder can be accomplished by passing the felt through a bath of the binder. It is advantageous, mainly because of the ease of execution, that the impregnation is realized by pouring the binder on the moving felt.

It is soaked that a precursor is obtained whose binder content is between 10 and 30 % of the total dry extract. For this purpose, binder mixtures can be used with a viscosity which is comparable to that of the water.

The felt from which the precursor is made may be a felt of flash fibers, rock fibers, slag fibers, or any other discontinuous fibers that are resistant to formaturatures. The

For example, the level of polymerized binder that the felt contains before impregnation is equal to 2.5 % of the weight of the felt.

According to one aspect of the invention, a thermoplastic adhesive in the form of a felt or, preferably, a mesh is introduced between the precursor and the facing liner. The thermoplastic adhesive improves the adhesion between the precursor and the facing liner * and the thermoplastic mesh is cheaper than the movie.

The thermoplastic adhesive may be incorporated during assembly to assemble the components of the multilayer sheet. It may also be made a previous joining of the precursor with the adhesive with the aim to improve the adhesion and handling of the precursor.

The thermoplastic adhesive may be chosen from those whose melting temperature is compatible with the conditions of manufacture, i. is below the pressing temperature. For example, polyethylene is used. .

For example, the face sheet may be made on the basis of a velvet fabric, a polyamide or a polyester.

According to a preferred form of the invention, the impregnation of the pre-bonded felt with the binder is followed by a liquid removal by pressure and / or suction, followed by a drying by hot air, for example between 80 and 10O ⁰ C, which the felt at a speed

- Q -

flow rate of about 10 m / s, with the aim of producing a feedstock with low residual water content, i. of 5% by weight and below with respect to the total weight thereof. It follows that the amount of heat supplied during the pressing is used mainly for the polymerization of the binder contained in the precursor and for the bonding of the lining film with the same. Of course, the drying described above must not cause premature polymerization of the binder contained in the precursor.

In accordance with another aspect of the invention, a panel is pressed in a single operation, which also includes an outer trim sheet, i. facing the roof of the vehicle and which usually has the task to facilitate the adhesion of the pressed plate, to consolidate them and to prevent direct contact with the fibers. This outer cladding film may be made on the basis of a synthetic film, a nonwoven fabric, a metal or composite film.

The temperature used in the molding according to the invention is usually below 180 ° C on the side of the cladding film. On the opposite side, it may be higher and about 250 ° C, without the Gew driving a damage to the face-covering film, at the same time a faster polycondensation of the resin is possible.

According to a preferred embodiment of the invention, hot air is blown through the precursor during molding to accelerate the polymerization of the binder and thus to shorten the molding process even more.

- 10 -

The invention also relates to a production line of molded, multilayer plates. This line comprises a bonding device by means of trays, with the aid of which it is possible to produce a precursor according to the invention, and a forming device with a press equipped with two heating plates for the application of the molding technique. An embodiment of these devices will be described below with reference to the figures.

Example:

The invention will be explained in more detail below on an exemplary embodiment. In the accompanying drawings show: '

Fig. 1: an impregnation device for a felt 'for the production of the precursor according to the invention,.

2 shows a detail of the device according to FIG. 1,

Fig. 3: a compression molding apparatus for the manufacture of a multi-layered plate.

The impregnating device shown in FIGS. 1 and 2 comprises a roller-driven mesh conveyor belt 1 for transporting the felt during the impregnation process in front of which an unwinding device 2 for the felt 3 to be impregnated is arranged, which already has about 2.5% by weight. % polymerized containing the binder. Over the front part of the conveyor belt, an overflow 4 is arranged, which is fed via supply pipes 5 continuously with not polymprisiertem binder. The overflow is transverse to the felt to be impregnated, he

    '- II -'

is slightly wider than the felt, so that a uniform impregnation of the felt is achieved over the entire width. The overflow contains a horizontal container 6, the front wall 7, which is slightly lower than the rear wall 8, by an obliquely sloping plate 9 extends-, is over which the binder IO flows in the form of a contiguous surface. The lower end of the inclined sheet is arranged at a distance h of about 50 millimeters from the felt to be impregnated. Below the front part of the conveyor belt is a drip tray 11 for the dripping, excess binder to which a suction device 12, for example a fan, which ensure a liquid removal of the impregnated felt, and a return system 13 for the binder are connected. Behind the overflow, an air guide 14 is arranged above the conveyor belt, which guides the hot air arriving via a line 15 onto the impregnated felt. This hot air, which flows through the felt 3 to dry it, is sucked by suction means, for example a fan 16, which is connected to a suction device 17, which is arranged below the air guiding device 14. The extracted air is subsequently returned. Behind the conveyor belt 1, a retractor 18 for winding up the produced precursor 19 is arranged. Upon exiting the impregnation device, the precursor has a water content of 5% by weight and less. The part in which the dewatering of the felt takes place, for example, is 0.80 m long, while the part in which the drying takes place eats for approximately twice as long. Of course, these lengths depend mainly on the passage speed of the felt, which is for example 2 meters per minute.

- 12 -

The compression molding apparatus shown in Fig. 3 includes a press 20, which consists of a stator 21 and two heating plates 22 and 23. The upper plate 22 is mounted on hydraulic cylinders 24 and thus can approach or move away from the fixed lower plate 23 in the direction of the arrow F.

At the entrance of the compression molding apparatus it includes a first unwinding device 25 for the precursor 19 and a second unwinding device 26 for an outer lining film 27. It contains a pair of rollers 28, 29 for a first bringing together the precursor 19 with the outer Verklöidungsfolie 27. A third unwinding device 30th , which supplies a Polyäthylengitter 31, is arranged under the pre-preassembled pre-product in front of a mounting table 32, where in a frame 33, the pre-product is brought, which is placed on a view Verr clothing film 34, which is mounted from the mounted under the mounting table 32 unwinding device 35 is unrolled. i

A device C for cutting the precursor, the lining sheets and the polyethylene grid is arranged in front of the assembly table.

Of course it is possible, depending on whether or not the desired molded product contains an outer lining film or whether the adhesion of the facing film with the precursor requires the use of a polyethylene screen or not to use the whole device or parts thereof. In an embodiment, not shown, of the compression molding apparatus, it includes an additional air supply, at least one of the pressure plates having openings allowing air to be supplied through all or part of the composite panel.

Further advantages and features of the invention will become apparent from the examples described below.

The first example is a comparative example which illustrates the advantages of the invention by comparison with the following examples.

example 1

A mat of discontinuous glass fibers containing a

Surface mass of 1350 g / m is impregnated during its formation with a binder containing a phenoplast resin having a pH ^ value of 6-7, by spraying a solution of this binder. The dry extract of the solution is adjusted to 25 % by dilution with water. The phenoplast resin is modified with urea and prepared with a molecular ratio of formaldehyde / phenol of 3 in the presence of barium hydroxide as a catalyst. At the end of the cycle, it is adjusted to a pH of 6-7 by addition of dilute sulfuric acid. The phenoplast resin is modified with urea and contains about 50 % of it. The precursor thus prepared is placed on a visual cloth of suedin fabric. The whole is placed in a Prasse. The pressing takes place with abutment to obtain a shaped product of about 6 mm average thickness. The pressing time is about 3 minutes, the plate of the press on the side of the precursor is brought to 240 ⁰ C, while the plate is heated on the side of the cladding film to 150 ° C. The resulting molded product has mechanical properties, especially good rigidity; but points to the side of the Sichtverklei-! Made from tissue stains. These stains are due to accumulations of binder, which in the

-14-

Spraying this product in the manner described above- ·

Example 2

A felt of pre-bonded discontinuous glass fibers having a polycondensed binder content of 2.5% by weight and a surface mass of 1350

  2 ''

g / m is impregnated with a phenoplast resin binder having a pH of 6-7 by soaking and using the device described above with reference to Figs. 1 and 2, by applying a solution of the binder described in Example 1 thereto but diluted by the addition of water to obtain about 20% by weight of dry extract. The throughput speed of the felt is about 2 m / min. Liquid is removed from the impregnated precursor. It is then dried by aspirating the moisture and the passage of warm air, which has a temperature of about 20 ^° C. and flows through it at a speed of about 10 m / s, until it has a water content of about 5% by weight. The precursor is then fed to the above-described compression molding apparatus, s, on a facing panel made of suedin fabric

vora where e

is jelled. The whole thing is put in the press. The pressing is carried out under the same conditions as in Example 1. The obtained molded product has an average thickness of about 6 mm and has mechanical properties according to specifications. There are no sticks on the side of the fabric panel.

- 15 -

Example 3

It is carried out under the same conditions as in Example 2, only the pressing time is reduced to 2 minutes. A molded product of good appearance is obtained but is relatively soft due to incomplete polymerization of the resin.

Example 4

The procedure is the same as in Example 3, except that a phenol resin-based binder having a pH of 9.2 is used. This binder is obtained by dilution and addition of soda to the resin of the previous examples to reach a pH of 9.2. The result is a product of perfect appearance and strength. The plating condensation is faster than in Example 3. A press time of 2 minutes is sufficient to achieve complete or near complete polymerization.

Example 5 ,

The procedure under the same conditions as in Example 3 except that a binder based on a phenoplast resin having a pH of 2 is used. This resin is obtained by diluting the phenol-formaldehyde resin of Example 2 and adding sulfuric acid to pH 2. A molded product of good appearance and strength is obtained. Again, the polymerization of the binder is faster than in Example 3.

- 16 -

- .16 -

Example 6

It ₁ is carried out under the same conditions as in Example 4 with the difference that a polyethylene film between the precursor and the Looks-Verkleidungsvfolie is introduced from fabric. This gives a molded product of perfect appearance and rigidity. In addition, the adhesion between the face panel and the substrate is particularly good.

Example 7 ·

It is under the same conditions as in Example 6 procedure, with the difference that a polyethylene mesh instead of a polyethylene film is brought between the precursor and the cladding of fabric

 The obtained molded product has good mechanical properties and a good appearance. The adhesion between the face clad film and the substrate is good.

Example 8

The procedure is the same as in Example 7, with the difference that, in addition, an outer cladding film of unwoven fabric is applied to the precursor. The molded product has good mechanical properties and a good appearance. It is also easy to handle.

- 17 -

Claims (16)

Invention claim: Anspruch [en] A single-pass molding process for producing a multilayer sheet consisting of a discontinuous polymer-impregnated binder-impregnated substrate and a face sheet, characterized in that a precursor is produced from at least one layer of preconnected fibers is impregnated by impregnation with a binder, then placed on the precursor a Sicht-covering film and the whole is pressed under heat. 2. The method according to item 1 and 2, characterized in that the impregnation is carried out by pouring the binder on the layer of preconnected fibers · 3. The method according to any one of the items 1 to 2, characterized in that it is a binder based on a thermosetting resin. 4.The method according to item 3, characterized in that the thermosetting resin is a phenoplast resin. 5. The method according to any one of items 1 to 4, characterized dcdurch that the phenoplast resin is a urea-modified resole, the molecular ratio of formaldehyde / phenol is preferably between 2 and 5. - 18 - .- 18 - Method according to one of the items 4 or 5, characterized in that the phenoplast resin is chosen from among phenoplast resins having a pH of about 1.5 to 3 and those having a pH of about 8.5 until 12. 7. The method according to item 6, characterized in that the phenoplast resin has a pH of 9.2. 8. The method according to any one of items 1 to 7, characterized in that a thermoplastic adhesive is brought between the precursor and the cladding film. 9. The method according to item 8, characterized in that the adhesive is in the form of a grid. 10. The method according to any one of items 8 and 9, characterized in that the thermoplastic adhesive is polyethylene ... ·. 11. The method according to any one of items 1 to 10, characterized in that after drowning the fiber layer with the binder, the impregnated fiber layer is dried until the water content is 5 wt .-% and less. ^: 12. The method according to any one of items 1 to 11, characterized in that a cladding film is applied to the side of the precursor, which is opposite to the visible cladding film. 13. The method according to e ^r INEM of items 1 to 12, characterized in that the two sides of the multilayer board are heated to different temperatures during molding. - ig - 14. The method according to any one of items 1 to 13, characterized in that hot air is blown through the entire precursor or a part thereof during the compression molding. 15. The method according to any one of items 1 to 14, characterized in that / the fibers from which the precursor is made, are glass fibers. " Device for carrying out the method according to points 1 to 15, characterized in that it comprises a impregnation line for impregnating a fibrous layer with a binder and a press, in order to produce the prepared precursor (19) with a mostly made of tissue, compared to high To press temperatures sensitive face-covering film (32) in a single operation. 17. The device according to item 16, characterized in that the impregnation line a belt conveyor (1) for the felt to be impregnated (3), an upper run (4), which is arranged above the conveyor and at least as wide as the felt to be impregnated, of from which the binder is poured out, a collecting trough (11) with a return system (13) for the binder, and drying means (14, 17), which are arranged behind the overflow. ,, - For this 2 sheets drawings - -20 r ¹