JP2002511349A - Molding method using prepreg - Google Patents

Abstract

  (57) [Summary] A method of forming a product from a prepreg, comprising a step of placing a prepreg sheet on a mold along the shape of the mold and forming the product, wherein when the sheet is cured by simultaneous application of pressure and heat, Treating the resin of the prepreg to increase the viscosity to a predetermined value, curing the resin, and curing the cured or partially A method of molding a product from a prepreg, comprising removing a cured product from a mold. The treatment of the resin of the prepreg is performed by modifying the resin of the prepreg by heating or any other method.

Description

DETAILED DESCRIPTION OF THE INVENTION

TECHNICAL FIELD The present invention relates to a method for forming a prepreg product from a reinforced resin. The prepreg material is manufactured by impregnating a resin with a fibrous reinforcing material. Using this material, the resin in the prepreg is processed by simultaneously performing pressure and heat curing to provide a solid laminate suitable for the purpose requiring advanced structural performance or other specific characteristics. it can. The fibrous reinforcing material is generally in the form of a sheet, but may be in the form of an elongated strip or tow. As used herein, the term "sheet" shall include tows and other reinforced structures.

[0002] The resins used in prepreg materials are generally thermosetting and are formulated to provide a suitable degree of tack and viscosity to impart drape in the prepreg material.
The above formulation means that the resin becomes semi-solid, as the liquid resin provides a wet tacky prepreg and the solid resin provides a dry, rigid prepreg. Both "wet" and "dry" prepregs have been applied, but most prepregs have sufficient drape and stickiness to adhere to the mold surface along the complex mold geometry At the same time, it is necessary that the resin does not transfer from the prepreg to the operator's gloves and tools when the prepreg is placed. Therefore, the range of viscosity at which appropriate prepreg handling suitability is achieved is relatively small,
When a new prepreg resin system is developed, the formulation is restricted. At different stages during the prepreg manufacturing and use process, there are various resin viscosities that are most desirable for a particular purpose. Furthermore, different impregnation steps and different types of fibrous reinforced formats require different resin viscosities in the impregnation step. For thick fibers, a very thin resin is required to get the proper level of fiber impregnation into the resin. Particularly in this case, before use, the resin is blended so that the resin reacts at a limited level to increase the viscosity and achieve proper tackiness and drape in the final state of the prepreg. The prepreg may be heated prior to the impregnation step or stored in a warm environment for a predetermined period of time after manufacture to achieve an appropriate degree of further reaction to achieve the proper level of tack and drape. Such techniques are known in the advanced composite materials industry and are commonly practiced. Specifically, the curing cycle is paused, and the resin viscosity is increased, for example, before applying full pressure or raising the temperature to end the curing cycle.

[0003] Products made from prepregs of the type described in paragraph 8 above (referred to herein as "conventional prepregs") have pores in the structure of the laminate, Often it was not entirely satisfactory to have pits on the mold surface.

Means for Solving the Problems According to the present invention, there is provided a method of forming a product from a prepreg, wherein a prepreg sheet is placed on a mold along the shape of the mold, and the sheet is simultaneously subjected to pressure and heat. Treating the resin of the prepreg to increase the viscosity to a predetermined value so as to reduce pores in the laminate and pits on the molded surface as compared with the conventional molding method when cured by application,
A method is provided which comprises curing the resin and removing the cured or partially cured product from the mold.

[0005] Preferably, the method comprises placing a plurality of prepreg sheets successively on a mold and treating each sheet before placing the next sheet to increase the viscosity to a predetermined value. Is included. Preferably, the processing of each sheet is performed after it is placed. Preferably, conventional prepreg formulations are modified to be able to achieve a predetermined prepreg viscosity. In another embodiment, the viscosity is increased to a predetermined value by impregnating the fibrous material with a prepreg resin that cures below 80 ° C. and applying an ambient temperature or slightly elevated temperature thereto. In yet another embodiment, a prepreg resin formulation that cures below 80 ° C. is modified to one that can achieve a predetermined prepreg viscosity. Preferably, the resin component and the curing agent in the prepreg are modified so that a predetermined increase in viscosity is achieved by applying a curing initiation environment (for example, ultraviolet light or an electron beam). In another aspect, the resin in the prepreg is prepared such that a predetermined viscosity increase is achieved by adding an encapsulant / adsorbent that releases the active ingredient after a specific time or after a time / temperature cycle to the resin formulation. Modifies components and curing agents. In yet another aspect, the encapsulant / adsorbent applied to the prepreg sheet is activated by radiant heat, infrared, electron beam, mechanical shock, pressure changes or other physical / chemical release / initiation environments. The resin component and the curing agent in the prepreg are modified so that a predetermined increase in viscosity is achieved by adding to the compound.

Description of Embodiments Embodiments of the present invention will be described with reference to embodiments. The present invention is based on the assumption that when vacuum / pressure is first applied to the mold and the prepreg layer thereon, the resin viscosity at the start of the final curing step is the most desirable predetermined value to achieve optimal prepreg tack and drape. Based on the discovery that it must be equal to or significantly greater. The actual required viscosity level depends on the prepreg and mold conditions. Its viscosity is particularly low-temperature-curable prepreg [for example, LTM (registered trademark);
ents Ltd)] is significantly higher than the viscosity required to achieve an optimal combination of tack, drapability and outlife parameters in normal stacking operations.

In a typical molding process, a mold is prepared by a general method, and a first layer of prepreg is placed on the mold so as to conform to the shape of the mold. The resin composition of the prepreg is modified by the additive, and as a result, when the prepreg sheet is placed, the additive is activated, the process of increasing the viscosity of the resin is started, and after a certain time, the viscosity increases to a predetermined value, The process known as the lay-up B staging process is effectively completed. This viscosity remains at or near this value until the final curing step is started. An additional sheet of prepreg is placed on the first processed sheet on the mold. When the additional sheet is placed, the viscosity of the resin contained therein is increased to a predetermined value in a similar manner. Successive sheets are added in a similar manner to increase viscosity after sheet placement. Add sheets until the material on the mold reaches the desired thickness. After the stacked sheets have been left for a sufficient time for the required viscosity increase to occur, the molding process is completed using conventional techniques. For example, a mold is coated with an impermeable membrane,
A vacuum / pressure is applied to the film and the temperature is increased until curing is achieved. Thereafter, the cured product is removed from the mold. ADVANTAGE OF THE INVENTION According to this invention, the clearance gap in the molded material decreases and the pit on the metal mold | die side surface of a laminated body decreases.

[0008] This desirable objective is the fiber / resin ratio, the degree of fiber impregnation in the prepreg, the degree of dispersion of the resin in the prepreg, the temperature, pressure and time used during the molding process, auxiliary consumable packs, and the like. In some cases, it is also affected by other parameters.

[0009] Increasing the viscosity immediately after placing each sheet has the additional benefit of ensuring that prepregs remaining on the mold surface (eg, sharp corners or small features) are in place.

As mentioned above, the resin formulation is modified to increase the viscosity of the resin component of the prepreg before the start of the curing cycle. One way to achieve the desired compounding modification is to apply, for example, a resin component and a curing agent that are activated during the stacking process by a curing initiation environment that can be easily controlled / applied, such as ultraviolet light, electron beam or otherwise. It is mentioned.

Other methods include adding a curing agent that is automatically activated or released from the encapsulant / adsorbent after a specific time or after a time / temperature cycle. Still other methods include direct application of radiant heat or infrared radiation, for example, or using higher energy forms of radiation, such as electron beams.

[0012] Mechanical shock, vacuum, pressure or ultrasound may be used alone or in combination with other methods as a starting method to increase the viscosity to a predetermined value.

In a modified method, a low-temperature curing prepreg that cures below 80 ° C. can also be used. When such a resin is used, a desired level of viscosity can be increased simply by leaving the stacked sheets at ambient temperature. Since this is a time consuming process, it is desirable to modify the resin component of the low temperature cured prepreg so that it quickly increases to a predetermined viscosity level before the final cure begins.

In a modification of the above embodiment, the molded article can be made from a single layer of prepreg. Further modifications of the suitable curing method, for example of the autoclaving, are also possible.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B29C 70/06 C08K 9/10 C08K 9/10 B29K 105: 06 // B29K 105: 06 B29C 67/14 L (81) Designated countries EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE), OA (BF, BJ , CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, KE, LS, MW, SD, SL, SZ, UG, ZW) ), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, CA, H, CN, CU, CZ, DE, DK, EE, ES, FI, GB, GD, GE, GH, GM, HR, HU, ID, IL, IN, IS, JP, KE, KG, KP, KR , KZ, LC, LK, LR, LS, LT, LU, LV, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, UA, UG, US, UZ, VN, YU, ZW Claire Crows, Composites House, Advanced Composites Group Limited F-term (reference) 4F072 AE01 AG03 4F201 AA36 AB03 AD16 AR17 BA04 BC01 BC12 BC37 BD03 BN01 BN40 B N41 4F204 AA36 AA44 AB01 AB03 AD16 AM26 AM28 AM32 AR17 FA01 FB01 FF01 FF06 FF23 FG09 FN12 FN15 FN17 FN20 4F205 AA36 AA44 AB01 AB03 AD16 AM26 AM28 AM32 AR17 HA08 HA25 HA33 HA45 HB01 HE06 HE21 HE25 A 012 HK02

Claims (10)

[Claims] 1. A method of molding a product from a prepreg, comprising the steps of placing a sheet of prepreg on a mold along the shape of the mold and molding the product by simultaneous application of pressure and heat. When curing, the resin of the prepreg is treated to increase the viscosity to a predetermined value so as to reduce pores in the laminate and pits on the molded surface as compared with the conventional molding method, and the resin is cured, and A method of molding a product from a prepreg, comprising removing a cured or partially cured product from a mold. 2. A method according to claim 1, wherein a plurality of prepreg sheets are successively placed on a mold, and each sheet is processed to increase the viscosity to a predetermined value before the next sheet is placed. . 3. The method according to claim 2, wherein the processing of each sheet is performed after the sheet is placed. 4. The prepreg resin according to claim 1, wherein said prepreg resin is modified so that said predetermined prepreg viscosity can be achieved.
Any one of the methods (1) to (3) 5. The method according to claim 1, wherein the fibrous material is impregnated with a resin of a prepreg that cures at a temperature lower than 80 ° C., and the viscosity is increased to a predetermined value by applying an ambient temperature or a slightly elevated temperature. 4. The method according to claim 1, wherein: 6. The method according to claim 1, wherein the resin composition of the prepreg, which cures at a temperature lower than 80 ° C., is modified into a composition capable of achieving a predetermined prepreg viscosity. 7. A curing agent is used for the curing, and the resin of the prepreg is
The method according to any one of claims 1 to 3, wherein the method is modified so that a predetermined increase in viscosity is achieved by applying a curing initiation environment. 8. The method according to claim 7, wherein the curing initiation environment is obtained by irradiation with an ultraviolet ray or an electron beam. 9. The resin in the prepreg such that a predetermined viscosity increase is achieved by adding an encapsulant / adsorbent which releases the active ingredient after a specific time or after a time / temperature cycle to the resin formulation. The method according to any one of claims 1 to 3, wherein the component and the curing agent are modified. 10. Resin compounding encapsulant / adsorbent applied to prepreg sheet activated by radiant heat, infrared ray, electron beam, mechanical shock, pressure change or other physical / chemical release / initiation environment The method according to any of claims 1 to 3, wherein the resin component and the curing agent in the prepreg are modified so that a predetermined increase in viscosity is achieved by adding the compound to the prepreg.