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

(42) Date of commencement of the patent: 15. 9.1989 (45) Date of issue: 10. 4.1990 (56) Documentation:

EP-A2 109489 US-PS4401715 US-PS 4438166 US-PS 4559274 (73)

Patentee:

ISOVOLTA, AUSTRIAN INSULATING PLANTS AKTIENGESELLSCHAFT

A-2351 WIENER NEUDORF, LOWER AUSTRIA (AT).

CQ

AT 390 260 (54) PROCESS FOR MANUFACTURING AN ARTIFICIAL RESIN HALF-FACTORY AND USE OF THIS SEMI-FINISHED PRODUCT (57) A substrate is impregnated and / or coated with a solvent-containing synthetic resin mixture containing an activatable blowing agent at elevated temperature, and thereafter for expulsion of the solvent heated to temperatures, without causing the resin mixture is foamed by activation of the blowing agent. The heating is preferably carried out at temperatures which are lower than the temperature at which the half-life of the blowing agent is 0.1 h.

An epoxy resin glass fiber fabric Prepreg produced in this way is then brought to elevated temperature and foamed in a mold together with other materials to be joined by curing synthetic resins and binders in a mold, so that the foamed prepreg material before or during its curing in the Form space still fills existing cavities or propellant-free surface layers presses against the inner surface of the mold.

According to another variant of the method, a compact eg plate-shaped body is coated with the propellant-containing synthetic resin mixture and used in a manner similar to the prepreg semi-finished product.

iwtarme

No. 390 260

The invention relates to a method for producing a semifinished product consisting of a carrier material which is impregnated with a possibly present in the form of a solution of synthetic resin mixture and / or coated. The invention further relates to an advantageous use of the semifinished product according to the invention in a production by curing in a form of a body having mechanically bearing surface layers and inside a cavity or a core lower specific gravity than the mechanically bearing surface layers L

A well-known semi-finished product of this kind is z. B. a glass fiber fabric impregnated with an epoxy resin hardener mixture, which is generally referred to as a prepreg. Such prepregs are z. B. used for the production of tennis rackets. In this case, blanks from these prepregs are wound around a hose to form a layer and - together with other serving to build the racket curable fiber reinforced plastic pieces - inserted into a mold. This wound hose runs along the racket frame and is guided twice in the grip zone. The hose is then inflated, pressing its prepreg wrapping against the inner surface of the mold. The fiber-reinforced epoxy resin incorporated in the mold is then cured at elevated temperature to the tennis racket body, after which the tube is vented and withdrawn from the tennis racket body.

However, in such tennis racket manufacturing, because the cross section of the racket frame is substantially rectangular and also has flat ribs at its corners, the problem arises that the pressure with which the prepreg wrapping is pressed against the inner mold surface does not occur at the ribs is considerably less than in the other areas. However, this can lead to an unfavorable distribution of resin and fiber reinforcement over the frame circumference.

A method for the production of components, in which a cavity in the component to be produced is filled evenly, is known from US-PS 4,559,274, in which z. B. for producing motor vehicle body parts in a cavity, which is enclosed by a clam-shell sheet steel envelope, plate-shaped semi-finished products are introduced from a foamable fiber-reinforced plastic material, which then foam under heat and fill the cavity. Information about the manner of production of these foamable semi-finished products are not made

The invention is first based on the object of specifying a process for producing a foamable semifinished product containing a synthetic resin and a carrier material, which is used in the production of articles which are produced, for example, in a mold at elevated temperature for the purpose of producing a product To achieve the best possible distribution of the material in the mold.

This object is achieved in the method according to the invention for producing a semifinished product, which is characterized the synthetic resin mixture serving for impregnation and / or coating contains an activatable blowing agent which can be activated at elevated temperature and that the impregnated and / or coated carrier material is then heated to expel the solvent, without thereby foaming the Kunsthaizgemisch by activation of the blowing agent It is advantageously carried out for the purpose of expulsion of the solvent, the heating of the impregnated and / or coated support material to temperatures, which are lower than the temperature, in which the half life of the blowing agent is 0.1 h.

Although the continuous production of plate-shaped foams is known from EP-A2-109.489, but here no frothable semi-finished product, but an already foamed plate-shaped product is produced

According to an advantageous embodiment of the method according to the invention, the impregnated and / or coated carrier material is heated to temperatures which are lower than the temperature at which the half-life of the blowing agent is 0.5 h.

In an advantageous embodiment of the method according to the invention is used as the carrier material in a conventional manner, a fibrous sheet material such as a fiber fabric, a fiber fabric, a nonwoven fabric or the like., Which is impregnated with the resin mixture.

According to another advantageous embodiment of the method according to the invention is used as a carrier material a substantially compact body, which is coated at least over part of its surface with the resin mixture.

A further object of the invention is to provide an advantageous use of the semifinished products produced by the process according to the invention in a production of a body by curing in a mold, the mechanically bearing surface layers and, in the interior, a cavity or a permanent core of lower specific weight than the mechanical one bearing surface layers

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

According to an advantageous embodiment of the invention, a non-foamable cover layer or layer is attached between the semi-finished layers and the inner surface of the mold, against which the semi-finished material foams and presses against the inner surface of the mold and that the foamed

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Semi-finished material combines during curing with the topcoat or layer.

According to a further advantageous embodiment of the use according to the invention, the semi-finished material foams onto the permanent core and combines with it during hardening.

The invention is explained below with reference to examples or figures.

Example 1:

For the preparation of a semi-finished product in the form of a prepreg an epoxy resin mixture is used, which consists of an epoxy resin with a latent curing agent, as it is commonly used for the production of prepregs for curing temperatures between about 120 and 150 ° C. This epoxy resin mixture then 3 wt. % Azobisiobutyronitril as blowing agent, which has a half life of 0.1 h at a temperature of 102 ° C, and 1 wt. % of a non-ionic wetting agent added and finely dispersed by intensive stirring in the resin mixture. This mixture is then applied to the for subsequent processing as impregnating or Coating Solution Required viscosity diluted with acetone

In an impregnating machine, a glass fiber fabric in the form of sheets with a basis weight of 280 g / m is now being produced² After evaporation of the acetone in a drying zone, which takes place during a residence time of about 8 minutes at temperatures of 65-70 ° C, gives a dry or slightly sticky, a resin content of 40% prepreg, which is rolled up with a release paper as an intermediate layer.

For the production of a tennis racket, in addition to the propellant-containing prepreg described above, a propellant-free prepreg is used, which - analogously as described above - was prepared by impregnating a glass fiber fabric with a now but blowing agent-free Epoxydhaizhärtergemisch. In the production of a tennis racket body are blanks from the propellant-free prepreg and those from the propellant-containing prepreg or other intended to build the tennis racket fiber reinforced curable plastic pieces on or superimposed. This scrim is then wrapped around a tube, so that the propellant prepregs come to rest outside, and then - as already mentioned in the description - placed in a heated mold and introduced into the mold materials to a temperature of about 140 ° In this case, the blowing agent is activated and foams the propellant-containing prepregs used in the mold to several times their original volume.

FIG. 1 shows for this stage of the manufacturing process in a partial view in section the mold used with the mold halves (1) and (2) and a cross section of the manufactured Tennisschäger frame with the outer region (3), which is occupied by the propellant-free prepregs, the areas (4) with the foamed propellant-containing prepregs, as well as the inflated tube (5). The pressure prevailing in the hose (5) presses the hose wall and thus the prepregs of the areas (3) and (4) in the direction of the mold inner surface (6). The effect of this pressure is exacerbated in the peripheral zones (7) and (8) by the pressure of the foaming agent in the prepreg of the area (4) and causes - in particular in the area of ​​the ribs (9) - the prepregs of the area (3) with sufficient pressure against the inner mold surface (6) are pressed.

At the prevailing temperature of 140 ° C, the epoxy resins used with the prepreg cure for about 15 minutes. Thereafter, the now essentially finished tennis racket body is removed from the mold and the vented tube (5) pulled out of it.

Example 2:

This example, which relates to the use of propellant-containing prepregs in the manufacture of a surfboard, will now be explained with reference to Fig. 2, which is a schematic cross-sectional view of the mold used in this method with the mold halves (10) and (11) and the Arrangement of introduced into the mold materials shows.

For the production of the surfboard are first - with lifted upper mold half (11) propellant-free epoxy resin fiber fabric prepregs, as they were used according to Example 1, inserted into the lower mold half to form a layer (12) over the edge of the Mold inner surface of the lower mold half (10) at (13) protrudes krempenförmig. Thereafter, a lightweight core (14) made of polyurethane foam, which - slightly smaller - already has approximately the final spatial shape of the surfboard to be produced, with propellant-containing epoxy resin fiberglass fabric prepregs, as they were used in Example (1), to form a foamable Coated layer and the so wound core (14) on the layer (12) in the lower mold half (10) used. The same propellant-free prepregs as were used to form the layer (12) are then applied to these wound cores (14) in a further layer (15) which also protrudes like a brim at its edge at (13). Subsequently, the mold is closed by placing the upper mold half (11).

In the heated mold halves, the materials used in the mold are now heated to a temperature of 120 ° C, wherein the epoxy resins contained in the prepregs used flow and foam the propellant prepregs, which the material of the layers (12) and (15) against the

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Press inner mold surface (16). The material (17) of the foaming prepreg completely fills in the cavities remaining in the mold space between the core (14) and the layer (15) and compensates for any slight deviations from the ideal spatial form of the lightweight core (14). FIG. 2 shows this phase of the procedure. The epoxy resin of the prepreg used then cures at the temperature of 120 ° C for about 30 min, with all the material components used in the mold cavity stick together or to connect intimately. The substantially finished surfboard blank is then removed from the mold and the layers (12) protruding and hardened at (13) are pressed. (15) removed by mechanical processing.

Example 3:

Another advantageous use of a propellant-containing epoxy resin fiberglass fabric prepreg, which is realized 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 joined or glued together in a mold under pressure and at elevated temperature. Fig. 3 shows now, if one refrains from serving for the formation of the ski ends special components, recorded in the mold ski structure.

In this manufacturing process, between the two mold halves of the mold are now on a ski run (21) bordered with steel edges (20), each with the interposition of a binder layer, an intermediate epoxy resin glass fiber roving laminate (22), an epoxy resin glass fiber laminate laminate (23) serving as a mechanical upper belt and a wood core (24) are stacked on top of each other. Over the wood core are then layers (25) of a propellant-containing epoxy resin fiberglass fabric prepreg, of a kind also used according to example 1, placed, so that they also cover the side surfaces of Holzkems (24). A cup-shaped outer shell (26) formed in a separate process is now slipped over the prepreg plies (25) and the mold closed by applying the upper mold half (19). The inserted shell-shaped outer shell is made in a separate manufacturing process and consists for. b. on its inside of an epoxy resin glass fabric laminate, which is connected to the later outward coming side with a decorative wear-resistant surface layer such as ABS

The ski assembly is then held in the mold under pressure for 20 minutes at a temperature of about 125 ° C. In the process, the propellant-containing prepreg layers (25) foam and completely fill the space between the wood core (24) and the shell-shaped outer shell (26). In the further consequence of the pressing cycle are hzw. Curing the binder. the foamed prepreg layers (25) intimately connected the ski components used in the mold and finally taken the finished ski blank of the 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 propellant-containing epoxy resin-hardener mixture. For this purpose, Phenolschichtpreßstoffplatten be ground on one side and with the propellant-containing resin mixture described in Example 1 with a solid resin order of 100 g / m² which is then dried at 65 ° C and forms a dry-dry binder layer after cooling. From these coated plates Skiseitenwangen are now produced in a conventional manner by cutting or milling, which - as described below - are used in the production of a ski.

A received in a mold ski structure containing the ski side cheeks described above, now with reference to the schematic cross-sectional view of FIG. 4 described. This ski construction contains first as in Example 3 - with the interposition of binder layers of the steel edges (20) bordered ski running surface (21), the two epoxy resin Glasfaserrovinglaminate (22), (23) and the wood core (24). On both sides of the Holzkems (24), the side cheeks (27) with the binder layer (28) are now inserted to the inside and the Holzkem (24) and the two side cheeks (27) with a surface laminate, the one of the mechanical top chord of the ski forming Epoxy resin glass fiber roving laminate (29) and a decorative surface (30) made of ABS covered

The ski construction is then maintained in the heated mold at a temperature of 125 ° C for 20 minutes. This first foaming of the binder layer (28), whereby between the Holzkem (24) and the two side cheeks (27) sufficient for a bond pressure is generated, which is not to achieve in this extent when using a non-foaming, conventional binder , After curing of the binder layers during the rest of the pressing cycle of the now essentially finished SkiRohling the press mold is removed.

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