KR20170005999A - Manufacturing methods of thermosetting resins for manufacturing fiber composite materials leaf spring of automobile, prepreg and prepreg sheet - Google Patents

Abstract

The present invention relates to manufacturing methods of thermosetting resins, a prepreg and a prepreg sheet for manufacturing fiber composite materials leaf spring of an automobile by producing the leaf spring of the automobile composed of existing metal with fiber-reinforced composite materials and thus improving lightweighting and durability. The thermosetting resins for manufacturing the fiber composite materials leaf spring of the automobile to achieve abovementioned goals are epoxy resins divided into 2 parts which are a main material and a hardener. The main material is a solvent-free type to make use of products characteristics and is the combination of liquid epoxy and solid epoxy to suit the characteristics of the product. The main material maintains a low viscosity (100-5,000cps) at an impregnation temperature of 40-60C and undergoes aging for a period of time after manufacturing the prepreg which leads to the viscosity of 5,000cps or more at 60C. So, the present invention features thermosetting resins for manufacturing leaf spring with the low viscosity achieving both impregnation ability and availability of the prepreg.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermosetting resin, a prepreg and a prepreg sheet,

The present invention relates to a method of manufacturing a thermosetting resin, a prepreg and a prepreg sheet for automobile leaf spring molding of a fiber composite material which is made of a conventional metal material by making a leaf spring for automobile as a fiber reinforced composite material and is improved in weight and durability .

      In recent years, conventional materials such as metals have been replaced with fiber-reinforced composites made of lightweight, non-corrosive, tough reinforcing fibers and metric resins. Actually, these fiber-reinforced composites have excellent workability and mechanical properties, It is widely used in sports field.

      In particular, the use of fiber reinforced composites as a material replacing metals in automobiles, aircrafts, and architectural fields that require durability beyond general leisure fields is increasing.

      BACKGROUND ART A fiber reinforced composite material is widely used as a method for preparing a sheet or tape prepreg by impregnating a reinforcing fiber made of glass fiber, carbon fiber, aramid fiber or the like with a matrix resin, and using the prepreg as an intermediate substrate.

      A thermosetting resin or a thermoplastic resin is used as the matrix resin used in the prepreg, but a thermosetting resin is mainly used.

      In general, an epoxy resin is used as a thermosetting resin, and an amine compound is mainly used as a curing agent and classified into several prepregs depending on the curing temperature.

      Prefragments form various product groups according to kinds of fibers, arrangement of fibers, and kinds of binders used. Composite materials produced by using them have higher strength, stiffness, corrosion resistance, fatigue life, abrasion resistance, Impact resistance, light weight, and so on, it is widely used in the production of aerospace industry, general industry, sports leisure goods and the like.

      However, as is well known, the plate spring used in automobiles is made of a separable laminated structure formed by laminating several layers of metal plates as a metal material and mechanically fastened, so that it is vulnerable to corrosion due to long-term operation of the vehicle, The weight of the vehicle is increased to increase the weight of the vehicle. As a result, there are problems such as reduction in ride comfort and generation of noise, and in particular, there has been a problem that defects such as joining with the vehicle body occurred due to surface corrosion due to salt condition during winter.

The main object of the present invention is to provide a plate spring for an automobile which is manufactured as a prepreg sheet widely used as a metal substitute material as described above and tends to have a tendency toward corrosion resistance and fatigue life And to provide a plate spring for an automobile which can improve ride comfort and noise.

Another object of the present invention is to provide a low viscosity fast curing type thermosetting resin for molding a prepreg suitable for manufacturing automotive leaf springs.

Another object of the present invention is to provide a manufacturing method for manufacturing a prepreg and a prepreg sheet, which comprises a reinforcing fiber and a thermosetting resin composition suitable for manufacturing a leaf spring of an automobile and is suitable for manufacturing an automotive leaf spring.

In order to achieve the above object, the thermosetting resin for fabricating a leaf spring of a fiber composite material of the present invention is a two-component type epoxy resin divided broadly into a main component and a hardening agent. The main component is a solventless type, (100 to 5,000 cps) at an impregnation temperature of 40 to 60 ° C., and then aged at a specific temperature for a certain period of time after preparing the prepreg, thereby obtaining a viscosity of 5,000 cps or more at 60 ° C. And a low viscosity type thermosetting resin for achieving impregnation and usability of the prepreg at the same time.

The present invention also provides a method for producing a reinforcing fiber, comprising the steps of placing a predetermined amount of reinforcing fiber on a krill and arranging the fibers horizontally at the same time so as to horizontally arrange and feed a plurality of strands horizontally; A heating and pressing step of spreading while being heated and pressed by a roller, a winding step of winding the prepreg sheet on a paper tube in such a state that the release paper and the film are laminated on both sides of the sheeted prepreg so as not to stick to each other, And a step of laminating and adjusting the orientation angle so as to form a leaf spring by heating and curing the prepreg and the prepreg sheet.

According to the present invention, the plate spring is manufactured as a prepreg sheet widely used as a substitute metal material, and the bending strength and flexural modulus of the plate spring are improved, and the tendency, corrosion resistance and fatigue life are improved, It is possible to provide an automotive leaf spring.

1 is an exemplary perspective view of an apparatus for producing a prepreg sheet of the present invention;

Hereinafter, the present invention will be described in detail with reference to embodiments shown in the accompanying drawings.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to be illustrative of the present invention and are not to be construed as limiting the present invention. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

In order to achieve the above object, the thermosetting resin for manufacturing a leaf spring of a fiber composite automobile according to the present invention is a two-component epoxy resin which is divided into a main component and a hardener. The main component is a non-solvent type, It is made by mixing solid epoxy according to product characteristics.

When a large amount of liquid epoxy is added, a low viscosity type is obtained. When a large amount of solid epoxy is added, a high viscosity type is obtained. In the present invention, a low viscosity liquid epoxy which penetrates thick reinforcing fibers is used.

When manufacturing a fiber reinforced composite material, it is important to reduce the pores generated by a portion of the interior of the fiber-reinforced composite material in which the matrix resin is not impregnated. That is, if there is a void in the prepreg, it is important that the void remains in the molded fiber-reinforced composite material and becomes defective, so that the strength of the fiber-reinforced composite material is lowered.

In particular, since these pores are generated by a solvent which is mixed with a thermosetting resin, the solvent is usually dried off during the preparation of the prepreg. If the drying temperature is excessively increased to sufficiently remove the solvent, the thermosetting resin is cured at the stage of the prepreg And the curing agent in the thermosetting resin is dissolved or altered to easily shorten the work life of the prepreg. This problem occurs particularly when a thermosetting resin having a low curing temperature is used. If the solvent remains, the solvent vaporizes during molding and voids are generated in the fiber-reinforced composite material.

In addition, even if the solvent is removed by drying, a solvent capable of volatilization of about 1% to 1.5% remains. Such a solvent is not a big problem when making a thin product, but a thick molded product such as a leaf spring Lamination), the solvent forms bubbles in the molding process, and there are many problems when the finished product is scanned, and it gives a serious criticism to products that continuously flow like a leaf spring.

Therefore, in order to prevent such a problem from occurring, the present invention is disadvantageous in that, when a thermosetting resin is prepared without using a solvent and a solvent is not used, the viscosity of the resin is increased and penetration into thick reinforcing fibers is poor. Resolving the resin by heating at 60 캜 or higher to lower the viscosity.

On the other hand, in order to impregnate the reinforcing fiber (glass fiber, carbon fiber, aramid fiber) intact into the epoxy resin, a viscosity of 5,000 cps or less should be maintained at a specific impregnation temperature.

If the viscosity is higher than 5000 cps, the flow of the resin is very weak and the surface and interior of the TOW type reinforcing fiber can not be thoroughly wetted. In this case, the surface smoothness of the prepreg after the impregnation of the resin tends to become insufficient, and color unevenness of appearance occurs.

Therefore, impregnation can be performed by increasing the pressure in this case, but in this case, when pressure is reduced, a spring back phenomenon occurs, which is unsuitable for producing a thick prepreg.

On the other hand, if the viscosity of the resin is low, the impregnation into the reinforcing fiber aggregate becomes easy, so there is no need to increase the pressure and temperature, and the impregnation of the resin is easy, so that the speed of the production line can be increased, If the viscosity is too low, the toughness of the surface of the prepreg becomes excessively large, and handling of the prepreg becomes difficult. It is very difficult to work because it is too sticky at the use temperature of the prepreg (10 ° C to 40 ° C) and sticks to the hands of the worker or is hard to work, and the form stability including the straightness of the reinforcing fiber is seriously deteriorated And the function as a prepreg is lost.

Generally, the value of the viscosity of resin in the range of 5,000 to 50,000 cps at 60 DEG C is optimum in view of the use of the prepreg.

Therefore, it is a feature of the present invention that a prepreg is manufactured at a low impregnation temperature of 40 to 60 DEG C while maintaining a low viscosity (100 to 5,000 cps), and aged at a specific temperature for a certain period of time (temperature 25 to 60 DEG C, 100 hours) to ensure a viscosity of at least 5,000 cps at 60 占 폚 to achieve impregnation and usability of the prepreg at the same time.

In order to realize the feature of the present invention, various types of compositions such as a liquid phase BPA-based epoxy resin, a solid phase BPA-based epoxy resin, a Novolac-based epoxy resin and a polyfunctional epoxy resin may be used as the impregnation- The viscosity of the mixed resin should not exceed 5,000 cps at the impregnation temperature.

In the present invention, two curing mechanisms are used at the same time in order to secure the viscosity increase of the resin through the low point and the ripening in the impregnation region. The primary curing mechanism works in full-scale at the curing aging temperature (25 ~ 60 ℃), which is cured by bonding with the main epoxy resin, and plays a role of increasing the viscosity of epoxy resin having low viscosity to 5,000 ~ 50,000 cps do. The primary curing mechanism controls the equivalence to account for 5 to 20% of the total epoxy curing reaction. If the curing reaction of the epoxy through the primary curing mechanism is less than 5%, the increase of the viscosity of the epoxy resin is too low and the effect of increasing the usability is insignificant. When the curing reaction is over 20%, the entire epoxy resin gels and the physical properties of the final cured product deteriorate There is a high possibility. The activity of the primary curing mechanism is accomplished through aging at a specific temperature, and when the aging is completed, the reaction of the primary curing mechanism is terminated and plays a role as a prepreg resin. The secondary curing mechanism is a curing accelerator for controlling the time when the primary curing agent starts to cure, and is a main curing mechanism that takes charge of 80 to 95% of the curing reaction of the present epoxy composition. And has a curing time of 2 to 90 minutes. The secondary curing mechanism is a latent curing agent and is characterized in that it shows little activity in the region of 25 to 80 캜, but has a sharp activity in the curing region. The activation of the secondary curing mechanism proceeds through a curing process, and when the curing is completed, the reaction of the secondary curing mechanism is terminated and serves as a plate spring.

The primary curing mechanism and the secondary curing mechanism that can be used in the present invention are as follows.

- Primary curing mechanism: Curing agent such as Polyethyleneamines, Cycloaliphatic Amines, Polyether Amine, Polyamides, Amidoamines

- Secondary curing mechanism: Aromatic Amine curing agent alone, Aromatic Amine curing agent including accelerator, Dicyandiamide curing agent alone, Dicyandiamide curing agent including accelerator, acid anhydride curing agent alone, acid anhydride curing agent including accelerator, phenol novolak curing agent alone, And phenolic novolac hardener.

In preparing the prepreg sheet using the thermosetting resin of the present invention as described above, as shown in FIG. 1, a plurality of reinforcing fibers 1 and 1 'are stranded on the krill 2 and arranged side by side (A) impregnating the thermosetting resin into the arranged reinforcing fibers (1) (1 '); (2) impregnating the impregnated prepreg with the heating roller (3) (C) a heat-pressing step (c) of spreading while thermocompression is carried out by heating and pressing the sheet by a heat pressing step (3 '), a winding step (4) of winding the sheet and prepreg on the both sides of the sheeted prepreg, And a method of manufacturing a prepreg and a prepreg sheet suitable for manufacturing an automotive leaf spring.

The prepared prepreg sheet is frozen and stored. When necessary, the sheet is taken out and cut to a predetermined size, and the orientation angle is adjusted so as to be symmetrical to the left and right.

1, 1 ': reinforcing fiber 2: krill 3, 3: heating roller 4; chanter

Claims (6)

An epoxy resin which maintains a low viscosity (100 to 5,000 cps) at an impregnation temperature of 40 to 60 ° C and at least one curing agent which secures a viscosity of more than 5,000 cps at 60 ° C by aging at 25 to 60 ° C. Thermosetting resin for plate spring forming.
The thermosetting resin according to claim 1, wherein the epoxy resin comprises any one of a liquid phase BPA-based epoxy resin, a solid phase BPA-based epoxy resin, a Novolac-based epoxy resin, and a polyfunctional epoxy resin.
The thermosetting resin according to any one of claims 1 to 3, wherein the epoxy resin is a solventless type solventless solvent.
The thermosetting resin according to claim 1, wherein the curing agent comprises an amine-based curing accelerator.
An epoxy resin which maintains a low viscosity (100 to 5,000 cps) at an impregnation temperature of 40 to 60 DEG C and a low viscosity type thermosetting resin containing at least one curing agent which is aged at 25 to 60 DEG C and has a viscosity of 5,000 cps or more at 60 DEG C A prepreg for automobile plate spring molding in which a resin is impregnated with reinforcing fibers.
A step of arranging a predetermined amount of reinforcing fibers on the krill and arranging them in parallel horizontally and arranging a plurality of strands horizontally at the same time, a step of impregnating the thermosetting resin into the arranged reinforcing fibers, the step of impregnating the impregnated prepreg with a heating roller A winding step of winding a prepreg sheet on a paper tube in such a state that the release paper and the film are joined together on both sides of the sheeted prepreg so as not to adhere to each other; And a step of heat-curing the laminate to manufacture a leaf spring.

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