EP0347439A1

EP0347439A1 - Process for manufacturing a synthetic resin semifinished product and use of same semifinished product

Info

Publication number: EP0347439A1
Application number: EP88909263A
Authority: EP
Inventors: Walter Eichberger
Original assignee: Isovolta Osterreichische Isolierstoffwerke AG; Isovolta AG
Current assignee: Isovolta AG
Priority date: 1987-11-04
Filing date: 1988-11-04
Publication date: 1989-12-27
Also published as: ATA291887A; AT390260B; WO1989004340A1; JPH02502090A; AU2605488A

Abstract

Zur Herstellung von Halbfabrikaten wird ein Trägermaterial, das ein gegebenenfalls flächiges faseriges Material aber auch ein kompakter Körper sein kann, mit einem aushärtbaren Kunstharzgemisch, das ein bei erhöhter Temperatur aktivierbares Treibmittel enthält, imprägniert und/oder beschichtet, wobei und/oder wonach das Kunstharzgemisch - zum Zwecke der Lösungsmittelentfernung, Viskositätserniedrigung oder gegebenenfalls anschliessender Viskositätserhöhung durch eine Vorreaktion - so erwärmt wird, daß das Treibmittel nicht aufschäumt. Dies geschieht insbesondere dann, wenn die Erwärmung auf Temperaturen erfolgt, die niedriger als die Temperatur sind, bei der die Halbwertszeit des Treibmittels 0,1 h beträgt. Diese Halbfabrikate werden zur Herstellung von Kunststoff-Verbundkörpern gemeinsam mit anderen Ausgangsmaterialien in einer Form eingebracht und in dieser der Kunststoff bei erhöhter Temperatur aufgeschäumt, wobei der Kunststoff oder das Halbfabrikat vor der Aushärtung des Kunststoffes die im Formraum noch bestehenden Hohlräume ausfüllt bzw. Oberflächenschichten gegen die Forminnenfläche drückt. Abstract To manufacture semifinished products, a carrier material, which can be a flat fibrous material or a compact solid, is impregnated and/or coated with a curable synthetic resin mixture which contains a sponging agent activatable at elevated temperatures, during and/or after which the synthetic resin mixture - for the purpose of removing the solvent, reducing or possibly than increasing the viscosity by a preliminary reaction - is heated in such a way that the sponging agent does not foam. This occurs in particular when heating takes place at temperatures lower than the temperature at which the half life of the sponging agent is equal to 0.1h. To manufacture plastic composites, the semi-finished products are placed together with other starting materials in a mould into which the plastic is foamed at high temperature. Before the plastic cures, the plastic or the semi-finished product fills all the remaining voids in the mould cavity or the surface layers press against the inner surface of the mould.For the production of semifinished products, a carrier material, which may be a flat fibrous material or a compact body, is impregnated and / or coated with a curable synthetic resin mixture containing a blowing agent that can be activated at elevated temperature, and / or after which the synthetic resin mixture for the purpose of solvent removal, lowering the viscosity or, if appropriate, subsequently increasing the viscosity by means of a pre-reaction - is heated so that the blowing agent does not foam up. This happens in particular when the heating takes place to temperatures which are lower than the temperature at which the half-life of the blowing agent is 0.1 h. These semi-finished products are introduced together with other starting materials in a mold for the production of plastic composite bodies, and the plastic is foamed in this in an elevated temperature, the plastic or the semi-finished product filling the cavities still existing in the molding space or surface layers against the plastic before it hardens Mold inner surface presses. Abstract To manufacture semifinished products, a carrier material, which can be a flat fibrous material or a compact solid, is impregnated and / or coated with a curable synthetic resin mixture which contains a sponging agent activatable at elevated temperatures, during and / or after which the synthetic resin mixture - for the purpose of removing the solvent, reducing or possibly than increasing the viscosity by a preliminary reaction - is heated in such a way that the sponging agent does not foam. This occurs in particular when heating takes place at temperatures lower than the temperature at which the half life of the sponging agent is equal to 0.1h. To manufacture plastic composites, the semi-finished products are placed together with other starting materials in a mold into which the plastic is foamed at high temperature. Before the plastic cures, the plastic or the semi-finished product fills all the remaining voids in the mold cavity or the surface layers press against the inner surface of the mold.

Description

Process for the production of a semi-finished synthetic resin and use of this semi-finished product.

Technical field

The invention relates to a method for producing a semifinished product consisting of a carrier material which is impregnated and / or coated with a curable synthetic resin mixture which may contain solvents. The invention further relates to an advantageous use of the semifinished product according to the invention in a production by curing in a mold of a body which has mechanically load-bearing surface layers and inside a cavity or a core of lower specific weight than the mechanically load-bearing surface layers.

State of the art

A known semi-finished product of this type is e.g. a fiberglass fabric impregnated with an epoxy resin hardener, commonly referred to as a "prepreg". Such prepregs are e.g. used for the production of tennis rackets. Blanks from these prepregs are wrapped around a tube to form a layer and - together with other hardenable fiber-reinforced plastic pieces used to build the racket - inserted into a mold. This wound hose runs along the racket frame and is double-guided in the grip zone. The tube is then inflated and presses its prepreg wrapping against the mold. πnerf 1 area. The fiber-reinforced epoxy resin introduced into the mold is then cured to the tennis racket body at elevated temperature, after which the tube is vented and pulled out of the tennis racket body.

In such a tennis racket production, however, because the cross-section of the racket frame is essentially rectangular and also has flat ribs at its corners, the problem arises that the pressure with which the prepreg Bewick Is pressed against the Formiπnenf area, is not inconsiderably less on the ribs than in the other areas. However, this can lead to an unfavorable distribution of resin and fiber reinforcement over the circumference of the frame.

Presentation of the invention

The invention is initially based on the object of specifying a semi-finished product consisting of a carrier material which is impregnated and / or coated with a synthetic resin mixture which may be present as a solution, which is used in the production of objects which are produced in a mold at elevated temperature, with the purpose of achieving the best possible distribution of the material in the mold.

This task is carried out in the method according to the invention. Production of a semifinished product solved, which is characterized in that the synthetic resin mixture used for impregnation and / or coating contains a blowing agent which can be activated at elevated temperature, and in that the synthetic resin mixture is heated on or in the carrier material during and / or after impregnation or sweeping without thereby foaming the synthetic resin mixture by activating the blowing agent. In this case, heating is advantageously carried out to temperatures which are lower than the temperatures at which the half-life of the blowing agent is 0.1 h.

In an advantageous embodiment of the invention, however, said heating takes place at temperatures which are lower than the temperature at which the half-life is 0.5 h.

According to other advantageous embodiments of the method according to the invention, at least the major part of the solvent contained in the synthetic resin mixture is driven out by the said heating and / or it is initially - if necessary to facilitate impregnation and / or coating - the viscosity of the synthetic resin mixture is reduced and, if appropriate after the impregnation and / or coating has taken place, the viscosity of the synthetic resin mixture is increased.

According to a further advantageous embodiment of the method according to the invention, a fibrous sheet material, such as a fiber fabric, a fiber fabric, a nonwoven fabric and / or parallel fiber rovings arranged along a surface, is used as the carrier material, which is impregnated with the synthetic resin mixture.

In another advantageous embodiment of the method according to the invention, a largely compact body is used as the carrier material, which is coated at least over a part of its surface with the synthetic resin mixture, which forms a solid, foamable layer and optionally serves as a binder layer.

The invention is also based on the object of specifying an advantageous use of the semifinished products produced by the process according to the invention in the production of a body by curing in a mold, the mechanically load-bearing surface layers and, in the interior, a cavity or a permanent core of lower specific weight than the mechanically bearing surface layers.

This object is achieved in the use according to the invention, which is characterized in that the semifinished product is attached within the mold between a temporary core or the permanent core which creates the later cavity and the mold inner surface - at least over a part of the mold inner surface, in that the mold introduced materials are heated on it, so that the semi-finished material foams and as a result, the free space remaining between the core and the mold inner surface is filled and the synthetic resin mixture of the semi-finished product finally hardens.

According to an advantageous embodiment of the use according to the invention, a non-foamable cover layer or layer is applied between the shark product layers and the mold inner surface, against which the semi-finished material foams and presses it against the mold inner surface and that the foamed semi-finished material presses during curing connects to the top layer or layer.

According to a further advantageous embodiment of the use according to the invention, the semifinished material foams onto the permanent core and bonds to it during curing.

Brief description of the drawings

1 shows a schematic partial section of the shape used or a cross section of the tennis racket frame to be produced for the production of a tennis racket frame using a foamable prepreg for a characteristic manufacturing phase.

2 shows a schematic cross section through the mold used in the method or the arrangement of the materials introduced into the mold for the production of a surfboard using a foamable prepreg.

Fig. 3 shows for the manufacture of a ski, in which a foamable prepreg is used, the ski structure within a press mold schematically in cross section.

In Fig. 4 is shown in an analogous representation as in Fig. 3, the mold and the ski structure in cross section, with one foam-side synthetic resin coated ski sidewalls are used.

Some ways of carrying out the invention

The invention is explained in more detail below with reference to the figures, which illustrate some advantageous ways of carrying out the invention in the context of several examples.

Example 1 :

For the production of a semifinished product in the form of a prepreg, an epoxy resin mixture is used, which consists of an epoxy resin with a latent hardener, as is customary for the production of prepregs for curing temperatures between about

120 and 150 ° C is used. 3% by weight of azobisisobutyronitrile as blowing agent, which has a half-life of 0.1 h at a temperature of 102 ° C., and 1% by weight of a non-ionic wetting agent are then added to this epoxy resin mixture and finely dispersed in the resin mixture by intensive stirring. This

Mixture is then applied to the for later processing

Impregnation or coating solution required viscosity diluted with acetone.

In an impregnation machine, a glass fiber fabric in sheet form with a basis weight of 280 g / m ^{2 is} impregnated with the impregnation solution mentioned and the impregnation agent application is set by means of squeeze rollers. After the acetone has been evaporated off in a drying zone, which takes place at a temperature of 55-70 ° C. for about 8 minutes, a dry or slightly sticky prepreg with a resin content of about 40% is obtained, which is coated with a release paper is rolled up as an intermediate layer.

For the production of a tennis racket, in addition to the blowing agent-containing prepreg described above, a blowing agent-free prepreg is used, which - analogously to the above- described here - by impregnating a glass fiber fabric with a blowing agent-free epoxy resin hardener mixture. In the manufacture of a tennis racket body, blanks made of the propellant-free prepreg and blanks made of the propellant-containing prepreg or other fiber-reinforced, curable plastic pieces provided for the construction of the tennis racket are placed on or on top of one another. This scrim is then wrapped around a tube so that the propellant-free prepregs come to rest on the outside, and then - as already mentioned at the beginning of the description - placed in a heated mold and the materials introduced into the mold to a temperature of about 140 ° C brought. The blowing agent is activated and foams the blowing agent-containing prepregs used in the mold to several times their original volume.

Fig. 1 shows for this phase of the manufacturing process in the form used with the mold halves 1 and 2 and the tennis racket frame to be produced with the outer area 3. which is occupied by the propellant-free prepregs, the areas 4 with the foamed propellant-containing prepregs, and the inflated tube 5. The pressure prevailing in the tube 5 presses the tube wall and thus the prepregs of the areas 3 and 4 in the direction of the inner surface 6. The effect of this pressure is in the peripheral zones 7 and 8 by the pressure of the area in the prepregs 4 foaming blowing agent intensifies and has the effect that, especially in the area of the ribs 9, the prepregs of area 3 are pressed against the inner surface 5 of the mold with sufficient pressure.

In an advantageous variant of this example described with reference to FIG. 1, a prepreg is used which is produced on the basis of a solvent-free epoxy resin mixture, as is usually already used today for the production of prepregs in which the fibrous Backing material is formed by parallel fiber rovings arranged along a surface. In this epoxy resin mixture, which consists of an epoxy resin and a latent hardener, has a viscosity of approx. 15,000 mPa.s at room temperature and can be cured well at temperatures between approx. 120 and 150 ° C, this becomes - analogous to the first variant Example 1 - 3 wt.% Azobisisobutyronitrile as blowing agent, which at a temperature of 102 ° C a. Half-life of 0.1 h, and 1 wt.% Of a non-ionic wetting agent finely dispersed.

In an impregnation machine designed as a so-called tape machine, the epoxy resin mixture containing blowing agent thus produced is heated at a temperature of 60 ° C. at which its viscosity is now approx. 700 mPa. S is applied uniformly to a continuously supplied strip-shaped separating film by means of a heatable doctor device in the form of a film with a thickness of 0.25 mm. In this thin, liquid resin film, glass fiber rvings drawn off from a creel are now placed in parallel next to one another in the resin film. The weight per unit area of these parallel rovings is 360 g / m ² .

The whole is then brought or kept to temperatures between 55-70 ° C when passing through a heating zone with a residence time in this zone of approx. 6 min. This is followed by a further reduction in the viscosity of the epoxy resin mixture in which the rovings are well soaked with the resin mixture and then a pre-reaction of the resin mixture with an associated increase in viscosity. After cooling while passing through a cooling zone, a slightly sticky, so-called unidirectional prepreg (UD prepreg) lying on the band-shaped separating film is finally obtained. which has a resin content of 40% by weight and which is rolled up with the band-shaped separating film as intermediate layer material. For the production of a tennis racket frame, in addition to the blowing agent-containing UD prepreg described above, a UD prepreg is used which contains no blowing agent and which - analogously to the blowing agent-containing UD prepreg - is produced using the blowing agent-free epoxy resin mixture.

The tennis racket frame is then produced in the same way as described with reference to FIG. 1.

Example 2: This example, which relates to the use of propellant-containing prepregs in the production of a surfboard, will now be explained with reference to FIG. 2, which shows the mold used in this process with the mold halves 10 and 11 and the arrangement of the materials introduced into the mold shows.

For the production of the surfboard - with the upper mold half 11 raised - propellant-free epoxy resin glass fiber prepregs, as they were also used according to Example 1, are used in the lower mold half 10 to form a layer 12, which extends over the edge of the mold inner surface of the lower mold half 10 protrudes at 13 brim. Thereafter, a lightweight core 14 made of polyurethane foam, which - somewhat reduced - already has approximately the final spatial shape of the surfboard to be produced, with propellant-containing epoxy resin-glass fiber prepregs. as they were also used in Example 1, wound to form a foamable layer and the core 14 thus wound was inserted onto the layer 12 in the lower mold half 10. The same propellant-free prepregs are now placed on this wound core 14. as they were used to form layer 12, applied in a further layer 15, which also protrudes at the edge at 13 in the form of a brim. Then the mold is closed by placing the upper mold half 11. In the heated mold halves, the materials used in the mold are then heated to a temperature of 120 ° C, the epoxy resins contained in the prepregs used flow and the prepregs containing foaming agent foam, these pressing the material of the layers 12 and 15 against the internal mold surface 16. The material 17 of the foaming prepregs completely fills the cavities that still exist in the molding space between the core 14 and the layer 15 and thereby compensates for any slight deviations from the ideal spatial shape of the lightweight core 14 used. FIG. 2 shows this phase of the process sequence . The epoxy resin of the prepregs used then cures at a temperature of 120 ° C. for about 30 minutes, with all of the material components used in the molding space sticking together or bonding intimately. The essentially finished surfboard blank is then removed from the mold and the layers 12 and 15 protruding and hardened at 13 are removed by mechanical processing.

Example 3: Another advantageous use of an epoxy resin grass fiber prepreg containing blowing agent, which is implemented in the manufacture of a ski, will now be described with reference to FIG. 3.

In a conventional ski manufacturing process, the individual ski components are connected to one another or bonded to one another in a press mold under pressure and at elevated temperature. Fig. 3 now shows, if one disregards the special components used to form the ski ends, the ski structure accommodated in the mold.

In this production process, an epoxy resin layer serving as an intermediate layer is now placed between the two mold halves of the press mold on a ski tread 21 bordered with steel edges 20, in each case with the interposition of a binder layer. Glass fiber roving laminate 22, an epoxy resin glass fiber roving laminate 23 serving as a mechanical lower chord and a wooden core 24 are stacked on top of one another. Layers 25 of a propellant-containing epoxy resin-glass fiber fabric prepreg, of a type also used according to Example 1, are then placed over the wooden core so that they also cover the side surfaces of the wooden core 24. A shell-shaped outer shell 26, which was formed in a separate process, is now placed over the prepreg layers 25 and the mold is closed by applying the upper mold half 19. The bowl-shaped used

Outer shell is made in a separate manufacturing process and is e.g. on the inside of one

Epoxy resin-glass fabric laminate, which is connected to a decorative, wear-resistant surface layer, such as an ABS layer, on the side that will later lie on the outside.

The ski structure is then held in the mold under pressure at a temperature of about 125 ° C. for 20 minutes. The prepreg layers 25 containing blowing agent foam up and completely fill the space between the wooden core 24 and the shell-shaped outer shell 26. In the further sequence of the press cycle, the ski components used in the press mold are intimately connected to one another while the binder or the foamed prepreg layers 25 are hardening, and the finished ski blank is finally removed from the press mold.

Example 4:

In this example, a semi-finished product according to the invention is described, which consists of a plate-shaped body which is coated on one side with a blowing agent-containing epoxy resin hardener mixture. For this purpose, phenolic laminate sheets are sanded on one side and coated with the blowing agent-containing resin mixture described in Example 1 with a solid resin application of 100 g / m ² , which is then dried at 65 ° C. and forms a dry-grip binder layer after cooling. From these coated plates are now produced in a manner known per se by cutting or milling ski sidewalls which - as described below - are used in the manufacture of a ski.

A ski structure which is accommodated in a press mold and contains the ski side cheeks described above will now be described with reference to the schematic cross-sectional illustration of FIG. 4. This ski structure contains - initially as in Example 3 - with the interposition of binder layers, the ski tread 21 enclosed by the steel edge 20, the two. Epoxy resin-glass fiber roving laminates 22, 23 and the wooden core 24. On both sides of the wooden core 24. the side walls 27 with the blowing agent-containing binder layer 28 are now inserted inwards and the wooden core 24 and the two side lengths 27 with one. Surface laminate, which consists of an epoxy resin glass fiber roving laminate 29 which forms the mechanical upper belt of the ski and a decorative surface 30 made of ABS.

The ski structure is then held in the heated press mold at a temperature of 125 ° C. for 2.0 minutes. First, there is foaming of the binder layer 28, as a result of which a pressure sufficient for bonding is generated between the wooden core 24 and the two side walls 27, which pressure cannot be achieved to this extent when using a non-foaming, conventional binder. After the binder layers have hardened during the remainder of the pressing cycle, the now essentially finished ski blank is removed from the press mold.

Commercial usability

With the aid of the plastic semifinished materials containing blowing agent according to the invention, plastic composite bodies of various types, such as tennis rackets, can be produced in a simple manner. Surfboards, skis and the like are made with high quality.

Claims

PATENT CLAIMS

1. A process for producing a semifinished product consisting of a carrier material which is impregnated and / or coated with an optionally solvent-containing, curable synthetic resin mixture, characterized in that the synthetic resin mixture used for impregnation and / or coating contains a propellant which can be activated at elevated temperature and that Synthetic resin mixture on or in the carrier material is heated during and / or after impregnation and / or coating, without the synthetic resin mixture foaming by activating the blowing agent.

2. The method according to claim 1, characterized in that the

Heating takes place at temperatures lower than that

Are temperature at which the half-life of the blowing agent is 0.1 h.

3. The method according to claim 1 or 2, characterized in that the heating takes place at temperatures which are lower than the temperature at which the half-life of the blowing agent is 0.5 h.

4. The method according to any one of claims 1 to 3, characterized in that at least the major part of the solvent contained in the synthetic resin mixture is expelled by the heating.

5. The method according to any one of claims 1 to 4, characterized in that the viscosity of the synthetic resin mixture is reduced by the heating first, if necessary in order to facilitate the impregnation and / or coating, and that, if appropriate after the impregnation and / or coating has been carried out, by a pre-reaction of the synthetic resin mixture Viscosity is increased.

6. The method according to any one of claims 1 to 5, characterized in that a fibrous sheet material, such as a fiber fabric, a fiber scrim, a nonwoven fabric and / or parallel fiber rovings arranged along a surface is used as the carrier material in a manner known per se, the or which are impregnated with the synthetic resin mixture.

7. The method according to any one of claims 1 to 2, characterized in that a largely compact body is used as the carrier material, which is coated at least over a part of its surface with the synthetic resin mixture, which forms a solid layer, optionally serving as a binder layer.

8. Use of a semifinished product produced according to one of claims 1 to 7 in a production by curing in a mold of a body which has mechanically load-bearing surface layers and in the interior a cavity or a core of lower specific weight than these mechanically load-bearing surface layers, characterized in that that the semifinished product is attached within the mold between a temporary core or the permanent core which creates the later cavity and the internal mold surface - at least over part of the internal mold surface, that the materials introduced into the mold are heated thereon, so that the semi-finished product foams and thereby the free space remaining between the core and the mold inner surface is filled and that the synthetic resin mixture of the semi-finished product finally hardens.

9. Use according to claim 8, characterized in that a non-foamable cover layer or layer is applied between the semi-finished layers and the inner surface of the mold, against which the semi-finished material foams and presses it against the inner surface of the mold and that the up foamed semi-finished material combines with the top layer or layer during curing.

10. Use according to claim 8 or 9, characterized in that the semi-finished material foams to the permanent core and connects to it during curing.