JP2019171241A - Method for coating fiber-reinforced resin molded article and coated product of the same - Google Patents

Abstract

To provide a method for coating a fiber-reinforced resin-molded article which can suppress the appearance of unevenness derived from reinforced fibers on the surface of a product after a coating step and simplify the coating step.SOLUTION: A method for coating a fiber-reinforced resin-molded article 11, which is a method for coating the surface of the fiber-reinforced resin-molded article 11 comprising a fiber-reinforced resin layer 3 that contains reinforced fibers 36 to make the matrix of a thermosetting resin 37, includes a first heating step S2 of applying a heat treatment to the fiber-reinforced resin-molded article 11 for predetermined time at a predetermined temperature and a coating step S3 of forming a coating layer 4 by coating the surface of the fiber-reinforced resin-molded article 11 after the first heating step S2.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for coating a fiber-reinforced resin molded article and a coated product thereof.

  In recent years, a fiber reinforced resin molded product obtained by impregnating a reinforced fiber such as carbon fiber or glass fiber with a thermosetting resin and a coated product thereof have attracted attention from the viewpoint of improving the strength and weight of the molded product.

  However, there are potential distortions and stresses in the fiber reinforced resin molded product immediately after molding, and these distortions and stresses are manifested in the subsequent drying process and heating process. There was a problem that warpage or the like occurred on the surface of the film.

  Therefore, for example, in Patent Document 1, before coating the fiber reinforced resin molded product, in a state where the correction jig is attached to the molded product, heat treatment is performed at a temperature 10 to 70 ° C. higher than the coating temperature. It is disclosed to correct the warpage of the molded article.

JP 2004-291558 A

  By the way, in the fiber reinforced resin molded product, in addition to the warp, a concavo-convex pattern derived from the reinforced fiber contained inside the fiber reinforced resin molded product appears on the painted surface, and sufficient surface smoothness cannot be obtained, resulting in poor appearance. There was a problem of being a factor.

  And, in order to conceal the concavo-convex pattern derived from the reinforcing fibers and improve the appearance defect, in the coating process, for example, repeatedly performing a polishing process or forming a coating film of 10 layers or more is performed. However, there has been a problem that an excessive burden is required in terms of time and cost.

  Moreover, although the said patent document 1 is disclosed about reducing the curvature of the fiber reinforced resin molded article after coating, about reducing the uneven | corrugated pattern derived from the reinforced fiber which appeared on the surface, it is disclosed. It has not been.

  Accordingly, the present invention provides a method for coating a fiber-reinforced resin molded article that can suppress the appearance of unevenness derived from reinforcing fibers on the surface of a coated product obtained after the coating process and can simplify the coating process. Let it be an issue.

  In order to achieve the above object, in the present invention, the fiber reinforced resin molded product is heated at a predetermined temperature for a predetermined time before the coating process to shrink the thermosetting resin in advance, and the reinforcing fiber is added to the product appearance after the coating process. The unevenness of the origin was made difficult to occur.

  That is, the fiber-reinforced resin molded article coating method according to the first technique disclosed herein includes a reinforcing fiber and a fiber-reinforced resin molded article provided with a fiber-reinforced resin layer having a thermosetting resin as a matrix. A method of applying a coating, the first heating step of heating the fiber reinforced resin molded product for a predetermined time at a predetermined temperature, and after the first heating step, coating the surface of the fiber reinforced resin molded product And a coating process for forming a coating layer.

  Concavo-convex patterns derived from reinforcing fibers appearing on the coating surface are thought to be manifested in the paint drying and heating processes in the coating process because the shrinkage of thermosetting resins having a higher shrinkage rate than the reinforcing fibers is promoted. . According to the first technique, the shrinkage of the thermosetting resin can be promoted in advance by subjecting the fiber-reinforced resin molded product before the coating process to heat treatment at a predetermined temperature for a predetermined time. If it does so, the uneven | corrugated pattern resulting from the difference in shrinkage | contraction rate of a reinforced fiber and a thermosetting resin can be previously formed in the surface of the fiber reinforced resin molding before a coating process. And it can suppress that the uneven | corrugated pattern derived from a reinforced fiber appears on the surface of the product obtained after the coating process by forming a coating layer so that the unevenness | corrugation of the surface may be hidden. Thus, while simplifying the coating process, the surface smoothness of the coated product can be improved and the appearance can be improved.

  A second technique is the first technique, wherein the coating step includes a first coating step of forming an undercoat layer on the surface of the fiber reinforced resin molded product after the first heating step, and the fiber reinforced resin molded product. And a second coating step of forming an overcoat layer on the surface of the undercoat layer.

  According to the second technique, the unevenness derived from the reinforcing fiber can be more effectively concealed by making the coating layer a laminated structure of at least the undercoat layer and the topcoat layer, and the smoothness of the product obtained after the coating process In addition, the appearance can be effectively improved.

  A third technique is characterized in that, in the second technique, the coating process includes a polishing process for polishing the surface of the undercoat layer after the first coating process and before the second coating process. And

  According to the third technique, by providing a polishing step for polishing the surface of the undercoat layer, the unevenness derived from the reinforcing fibers that appeared on the surface of the undercoat layer can be smoothed, and thus obtained after the coating step. The smoothness and appearance of the product can be improved more effectively.

  A fourth technique is characterized in that, in any one of the first to third techniques, a second heating step of performing a heat treatment on the fiber-reinforced resin molded article is provided after the coating step.

  According to the fourth technique, the coating layer can be more reliably fixed by the second heating step.

  According to a fifth technique, in the fourth technique, the predetermined temperature in the first heating step is equal to or higher than a temperature in the second heating step.

  According to the fifth technique, the smoothness and appearance of the product can be effectively improved.

  According to a sixth technique, in any one of the first to fourth techniques, the reinforcing fibers included in the fiber reinforced resin layer are oriented in a predetermined direction.

  According to the sixth technique, the strength of the fiber-reinforced resin molded product can be improved.

  A seventh technique is characterized in that, in the fifth technique, the fiber reinforced resin layer is formed by laminating a plurality of layers having different orientations of the reinforcing fibers.

  According to the seventh technique, the strength of the fiber-reinforced resin molded product can be further improved.

  According to an eighth technique, in the fifth or sixth technique, the reinforcing fiber oriented in the predetermined direction is at least one of a woven material, a knitted material, a braided material, a UD material, and a non-crimp fabric material. Features.

  According to the eighth technique, a coated product of a fiber reinforced resin molded product having excellent strength and durability can be obtained.

  According to a ninth technique, in any one of the first to seventh techniques, the reinforcing fiber is a carbon fiber.

  According to the ninth technique, it is possible to obtain a coated product of a fiber-reinforced resin molded product that is lightweight and excellent in strength and durability.

  A tenth technique is any one of the first to eighth techniques, wherein the thermosetting resin is an epoxy resin.

  According to the tenth technique, it is possible to obtain a coated product of a lightweight and cost-effective fiber-reinforced resin molded product.

  In an eleventh technique according to any one of the first to ninth techniques, the predetermined temperature in the first heating step is 100 ° C. or more and 250 ° C. or less, and the predetermined time in the first heating step is: 5 minutes or more and 60 minutes or less.

  According to the eleventh technique, the smoothness and appearance of the product can be effectively improved.

  In a twelfth technique according to any one of the first to tenth techniques, the fiber-reinforced resin molded product is for a vehicle component outer plate member.

  According to the twelfth technique, it is possible to obtain a vehicle component outer plate member having excellent appearance and light weight and high strength.

  According to the thirteenth technique, a fiber reinforced resin molded article comprising a fiber reinforced resin layer containing a reinforced fiber and having a thermosetting resin as a matrix; and a coating layer formed on the surface of the fiber reinforced resin molded article; The fiber reinforced resin layer is a coated product, and the fiber reinforced resin layer includes a plurality of fiber bundles made of the reinforced fibers oriented in a certain direction, and the plurality of fiber bundles are the fibers. Two fiber bundles adjacent to each other in a direction parallel to the surface of the reinforced resin molded product are provided, and in the longitudinal sectional view of the coated product, the surface height of the coating layer located on the upper side of the fiber bundle is adjacent. The difference from the surface height of the coating layer located on the upper side between the fiber bundles is 0.5 μm or less.

  According to the thirteenth technology, it is possible to obtain a coated product of a lightweight and high-strength fiber-reinforced resin molded product while being excellent in appearance.

  As described above, according to the present invention, the shrinkage of the thermosetting resin can be promoted in advance by subjecting the fiber-reinforced resin molded product before the coating process to heat treatment at a predetermined temperature for a predetermined time. If it does so, the uneven | corrugated pattern resulting from the difference in shrinkage | contraction rate of a reinforced fiber and a thermosetting resin can be previously formed in the surface of the fiber reinforced resin molding before a coating process. And it can suppress that the uneven | corrugated pattern derived from a reinforced fiber appears on the surface of the product obtained after the coating process by forming a coating layer so that the unevenness | corrugation of the surface may be hidden. Thus, while simplifying the coating process, the surface smoothness of the coated product can be improved and the appearance can be improved.

It is a flowchart for demonstrating the coating method of the fiber reinforced resin molded product which concerns on one Embodiment of this invention. It is a figure which shows typically the structure of the fiber reinforced resin molded product prepared in the preparation process. It is a typical longitudinal cross-sectional view of the direction perpendicular | vertical to the surface of the fiber reinforced resin molded product prepared in the preparation process. It is the FIG. 3 equivalent view of the fiber reinforced resin molded product after a 1st heating process. It is the FIG. 3 equivalent view of the fiber reinforced resin molded product after a 1st coating process. FIG. 4 is a view corresponding to FIG. 3 of a fiber-reinforced resin molded product after a finishing process, that is, a coated product. FIG. 4 is a view corresponding to FIG. 3 of the fiber-reinforced resin molded product after performing the first coating process by omitting the first heating process. It is a figure which shows the state after a finishing process about the fiber reinforced resin molded product of FIG. It is the FIG. 2 equivalent view of the fiber reinforced resin molded product which concerns on other embodiment. It is the FIG. 2 equivalent view of the fiber reinforced resin molded product which concerns on other embodiment. It is the FIG. 2 equivalent view of the fiber reinforced resin molded product which concerns on other embodiment. It is a graph which shows the relationship between a dent depth and heating temperature about the fiber reinforced resin molded product of the test material 1. FIG. It is a graph which shows the relationship between a dent depth and the frequency | count of a heating about the fiber reinforced resin molded product of the test material 1. FIG. It is a graph which shows the relationship between a dent depth and heating time about the fiber reinforced resin molded product of the specimen 1. It is a figure for demonstrating the test method of a coating surface smoothness evaluation test.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or its application.

(Embodiment 1)
<Coating method for fiber reinforced resin molding>
As shown in FIG. 1, the coating method of the fiber reinforced resin molded article 11 according to this embodiment includes a preparation step S1, a first heating step S2, a painting step S3, and a finishing step S4 (second heating step). It has. The painting step S3 includes a first painting step S31, a polishing step S32, and a second painting step S33.

-Preparation process-
Preparatory process S1 is a process of preparing the fiber reinforced resin molded product 11 for coating.

≪Fiber-reinforced resin molded product≫
As shown in FIGS. 2 and 3, the fiber reinforced resin molded article 11 is formed by molding a fiber reinforced resin layer 3 in which a plurality of prepreg layers 31 are laminated. The prepreg layer 31 is a sheet-like layer including reinforcing fibers 36 and impregnating the reinforcing fibers 36 with a thermosetting resin 37 as a matrix. 2 shows a configuration in which three prepreg layers 31 are laminated, the number of prepreg layers 31 is not limited to this, and may be two layers or four layers. It may be the above. In addition, a single layer may be used instead of a plurality.

≪Reinforcing fiber≫
The reinforced fiber 36 contained in the prepreg layer 31 is for improving the strength of the fiber reinforced resin molded article 11 and is not intended to be limited. For example, a fiber bundle of fibrous carbon fibers is oriented in a predetermined direction. More specifically, it is in a plain woven state.

The reinforcing fibers 36 in a state oriented in a predetermined direction are not limited to plain woven fabric materials. For example, a plurality of fiber bundles composed of reinforcing fibers oriented in a certain direction are arranged in one direction or multiple directions. It may be a reinforcing fiber material. Specifically, for example, in addition to plain weave, weaving materials such as twill weave and satin weave, flat knitting, rib knitting, double-sided knitting, knitting materials such as pearl knitting, tricot and raschel, braided braids such as round braid, flat braid and square braid For example, a braided material such as a unidirectional (UD) material in which fiber bundles are arranged in one direction, and a fiber bundle that is laminated in multiple directions are stitched with a polymer thread such as nylon or polyester. Non-crimp fabric materials and the like can be mentioned. From the viewpoint of obtaining a fiber reinforced resin molded article 11 having excellent strength and durability, the fiber reinforced resin layer 3 is at least one of the woven material, knitted material, braided material, UD material, and non-crimp fabric material as the reinforcing fiber 36. The seed-containing layer may be a single layer or a stack of a plurality of layers, or a stack of a plurality of types.

  The reinforcing fiber 36 is not limited to the reinforcing fiber material oriented in a predetermined direction, and may be a reinforcing fiber material including randomly oriented reinforcing fibers such as a nonwoven fabric. Therefore, the fiber reinforced resin layer 3 may be a single layer or a plurality of laminated layers including the above-mentioned randomly oriented reinforcing fiber material as the reinforcing fiber 36, or may be a plurality of laminated layers. Good. Further, the fiber reinforced resin layer 3 may be a combination of the layer containing the randomly oriented reinforcing fiber material and the layer of reinforcing fiber material oriented in the predetermined direction as the reinforcing fiber 36.

  The carbon fiber as the reinforcing fiber 36 is not particularly limited. For example, polyacrylonitrile (PAN) such as T700 manufactured by Toray Industries, Inc., HTS40 manufactured by Toho Tenax Co., Ltd., and TR50S manufactured by Mitsubishi Chemical Co., Ltd., Nippon Graphite Co., Ltd. A pitch system such as XN-60 manufactured by Fiber Co., Ltd. or K13312 manufactured by Mitsubishi Chemical Co., Ltd. can be used.

  Further, as the reinforcing fiber 36, it is particularly preferable to use carbon fiber from the viewpoint of obtaining a fiber reinforced resin molded article 11 that is lightweight and excellent in strength and durability, but is not limited to carbon fiber, and is not limited to carbon fiber. In addition, it may be composed of glass fiber, basalt fiber, or the like.

  The average fiber diameter of the reinforcing fibers 36 is not limited, but may be, for example, about 5 μm to 15 μm from the viewpoint of obtaining a fiber reinforced resin molded article 11 that is lightweight and excellent in strength and durability. The average fiber length of the reinforcing fibers 36 is not particularly limited, and continuous fibers are preferable from the viewpoint of obtaining a fiber-reinforced resin molded article 11 that is lightweight and excellent in strength and durability.

  The content of the reinforcing fiber 36 in the fiber reinforced resin molded article 11 is preferably 30% by volume or more and 80% by volume from the viewpoint of obtaining the fiber reinforced resin molded article 11 that is lightweight, excellent in strength and durability and excellent in moldability. In the following, it can be more preferably 40% by volume or more and 70% by volume or less.

≪Thermosetting resin≫
The thermosetting resin 37 is for forming the skeleton of the fiber reinforced resin molded article 11, and specifically, for example, epoxy resin, vinyl ester resin, phenol resin, polyimide resin, polyurethane resin, urea resin, melamine Examples include thermosetting resin materials such as resins, bismaleimide resins, unsaturated polyester resins, and urethane acrylate resins. In particular, from the viewpoints of lightness, strength, durability, cost, etc. of the fiber reinforced resin molded article 11, epoxy resin is used. Resin is desirable. As these thermosetting resin materials, in addition to a simple substance, a copolymer of one kind of resin material and another resin material, a modified body, a resin material blended with two or more kinds, and the like can also be used.

≪Other materials≫
In addition to the reinforcing fiber 36 and the thermosetting resin 37, the fiber reinforced resin molded article 11 is filled with fillers, pigments, dyes, impact modifiers, UV, from the viewpoint of improving moldability, strength, designability, functionality, and the like. You may contain additives, such as an absorber. These additives may be added singly or plural kinds may be added.

  In the case where an additive or the like is included in the fiber reinforced resin molded article 11, the content of the additive is, for example, 5% by mass or less from the viewpoint of improving moldability, strength, design, functionality, and the like. be able to.

  Moreover, as a resin material of the fiber reinforced resin molded article 11, in addition to the thermosetting resin 37, a thermoplastic resin may be contained from the viewpoint of improving moldability. Specific examples of the thermoplastic resin include polypropylene resin, polyethylene resin, polycarbonate resin, polyamide resin, polyester resin, polyarylene sulfide resin, polyphenylene sulfide resin, polyether ketone, polyether ether ketone resin, polyether ketone ketone. Examples thereof include resins, polyethersulfone resins, polyimide resins, polyamideimide resins, polyetherimide resins, and polysulfone resins.

≪Use of fiber reinforced resin molded products≫
The fiber reinforced resin molded article 11 is used for applications such as vehicle parts, for example, engine parts such as an engine cover, bonnets, rear fenders, roofs, doors, front panels, rear panels, lift gates, etc. Preferably, it is for vehicle component outer plate members. Thereby, it is excellent in surface smoothness, and a lightweight and high intensity | strength vehicle component, especially a vehicle component outer plate member can be obtained.

≪Preparation method of fiber reinforced resin molded product≫
The preparation method of the fiber reinforced resin molded product 11 is not specifically limited, A commercially available thing may be used and you may manufacture by shaping | molding.

  When molding, for example, the fiber reinforced resin molded article 11 can be obtained by preparing the prepreg layer 31 and then molding it by various molding methods.

  Specifically, the prepreg layer 31 is formed by, for example, using a roll molding machine or the like to bond sheet-like thermosetting resins 37 on both the front and back sides of the precursor sheet of the reinforcing fiber 36 oriented in a predetermined direction, and using a heater or the like. There is a method in which the prepreg layer 31 formed by heating and impregnating the thermosetting resin 37 into the precursor sheet is formed.

  The fiber reinforced resin layer 3 is configured by laminating the prepreg layer 31 singly or as needed. At this time, as described later, a plurality of prepreg layers having different fiber bundle orientations of the reinforcing fibers 36 oriented in a predetermined direction or prepreg layers containing the randomly oriented reinforcing fibers 36 may be laminated.

  The molding method of the fiber reinforced resin layer 3 is not particularly limited, and a general molding method can be employed. Specifically, for example, the fiber reinforced resin layer 3 may be molded by internal pressure molding, autoclave molding, oven molding, or the like. it can. And the fiber reinforced resin molded product 11 can be obtained by cooling, demolding, drying, etc. the fiber reinforced resin layer 3 after molding.

-First heating step-
The first heating step S2 is a step in which the fiber reinforced resin molded article 11 is subjected to heat treatment at a predetermined temperature for a predetermined time.

  The change of the fiber reinforced resin molded product 11 by the first heating step S2 will be described with reference to FIGS.

As shown in FIG. 3, the prepreg layer 31 on the outermost surface of the fiber reinforced resin molded article 11 includes longitudinal fibers 36a and transverse fibers 36b as reinforcing fibers 36, and a thermosetting resin impregnated between and within the fibers. 37. The longitudinal fibers 36a extend in a direction perpendicular to the paper surface of FIG. 3, and the lateral fibers 36b are disposed so as to extend in a direction parallel to the paper surface of FIG. The vertical fibers 36a and the horizontal fibers 36b each form a plurality of fiber bundles arranged in a direction parallel to the surface of the fiber reinforced resin molded article 11, and these fiber bundles form a plain woven fabric. Specifically, as shown in FIG. 3, the vertical fiber 36 a has two fiber bundles 36 a 1 and 36 a 2 that are adjacent to each other in a direction parallel to the surface of the fiber reinforced resin molded product 11. And between the fiber bundles 36a1 and 36a2 of the longitudinal fibers 36a, a thermosetting resin 37 is impregnated, and the outermost surface thereof has, for example, a dent compared to the position where the fiber bundles 36a1 and 36a2 of the longitudinal fibers 36a are present. depth t is recessed by _{t 0} recess 37a may be formed.

Against states of the fiber-reinforced resin molded article 11 of Figure 3, when subjected to a first heating step S2, as shown in FIG. 4, a state in which recess depth t is increased to t ₁ of the concave portion 37a. Specifically, among the thermosetting resin 37 and the reinforcing fiber 36 included in the prepreg layer 31, the shrinkage rate of the thermosetting resin 37 is larger than the shrinkage rate of the reinforcing fiber 36. Then, by heat treatment of the first heating step S2, towards the thermosetting resin 37 is largely contracted than the reinforcing fibers 36, recess depth t of the recess 37a may be increased up to t _1. As described above, by performing the heat treatment, a concavo-convex pattern due to the difference in contraction rate between the reinforcing fiber 36 and the thermosetting resin 37 can be formed on the surface of the fiber reinforced resin molded article 11.

  In the first heating step S2, the lower limit of the predetermined temperature is preferably 100 ° C or higher, more preferably 105 ° C or higher, particularly preferably 110 ° C or higher, and the upper limit is preferably 250 ° C or lower, more preferably 200 ° C or lower. Especially preferably, it is 160 degrees C or less. The lower limit of the predetermined time in the first heating step S2 is preferably 5 minutes or more, more preferably 7 minutes or more, particularly preferably 10 minutes or more, and the upper limit is preferably 60 minutes or less, more preferably 50 minutes or less, particularly Preferably it is 30 minutes or less. If the predetermined temperature is less than 100 ° C. and / or the predetermined time is less than 5 minutes, the shrinkage of the thermosetting resin 37 may not be effectively promoted. If the predetermined temperature exceeds 250 ° C. and / or the predetermined time exceeds 60 minutes, the recess depth t of the recess 37a becomes too large, and it may be difficult to effectively hide the uneven pattern even if the coating layer 4 is formed. is there.

  In addition, in finishing process S4, when performing heat processing with respect to the fiber reinforced resin molded product after coating process S3 as a 2nd heating process, the predetermined temperature in 1st heating process S2 is more than the temperature in finishing process S4. It is desirable to do. Thereby, the smoothness and appearance of the product can be effectively improved.

For recess depth t of the recessed portion 37a, to promote the contraction of the thermosetting resin 37, from the viewpoint of improving the surface smoothness of the coated product 1 while simplifying the painting process S3, for t ₀ before the first heating process S2 the ratio _t 1 / _{t 0} after _{t 1} a first heating step S2 is preferably 1.1 to 10, more preferably 1.3 to 9, particularly preferably 1.5 to 8. Specifically, for example, _{t 0} is the degree than 1μm or less 0.1 [mu] m, in this case, _{t 1} after the first heating process S2 may be, for example, about 1.1μm or 3μm or less.

  In 1st heating process S2, after performing the heat processing to the fiber reinforced resin molded product 11, it cools to normal temperature.

-Painting process-
The coating step S3 is a step of forming the coating layer 4 by coating the surface of the fiber reinforced resin molded article 11 after the first heating step S2. As described above, the painting step S3 includes the first painting step S31, the polishing step S32, and the second painting step S33.

≪First painting process≫
As shown in FIG. 5, the first coating step S <b> 31 is a step of forming the undercoat layer 41 by applying a primer to the surface of the fiber reinforced resin molded article 11 after the first heating step S <b> 2.

  At this time, the undercoat layer 41 is formed so as to flatten the surface of the fiber reinforced resin molded article 11 while hiding the above-described concave portion 37a.

  In addition to the role of concealing and flattening the concave and convex patterns such as the concave portions 37a of the fiber reinforced resin molded product 11, the undercoat agent repairs other surface defects and the like, and the fiber reinforced resin molded product 11 and the second coating step S33. It has the role of improving the adhesion with the overcoat layers 42 and 43 formed by the above, the role of color adjustment of the coated product 1, and the like. As the undercoat, for example, COODE (registered trademark) filler (manufactured by Kansai Paint Co., Ltd.), COODE (registered trademark) W / W Primer Plus (manufactured by Kansai Paint Co., Ltd.), Polytan vehicle surfacer gold (manufactured by Dainippon Paint Co., Ltd.) ) And a primer agent such as urethane plasafujitan (manufactured by Nippon Paint Co., Ltd.).

  The method for applying the primer is not particularly limited, and air spray coating, airless spray coating, brush coating and the like can be used. Alternatively, an undercoat may be placed on the surface of the fiber reinforced resin molded article 11, and a forming die having a molding surface following the surface shape may be pressed to spread the undercoat over the entire surface. After the undercoat is applied, the undercoat layer 41 can be formed by curing the undercoat by drying in the air at room temperature for about 20 minutes to 1 hour, for example.

  The film thickness of the undercoat layer 41 after the finishing step S4, that is, the film thickness of the undercoat layer 41 in the coated product 1 is the average thickness of the flat portion 37b other than the concave portion 37a as shown in FIG. From the viewpoint of developing the above function of the undercoat layer 41 while achieving weight reduction, it is preferably 5 μm or more and 50 μm or less, more preferably 6 μm or more and 45 μm or less, and particularly preferably 7 μm or more and 40 μm or less.

≪Polishing process≫
From the viewpoint of further improving the surface smoothness of the coated product 1, a polishing step S32 for polishing the surface of the undercoat layer 41 may be provided after the first coating step S31 and before the second coating step S33. The polishing step S32 is an optional step, and the second coating step S33 may be performed as it is after the first coating step S31 without performing the polishing step S32.

  The polishing step S32 is not particularly limited, but can be performed by polishing the surface of the undercoat layer 41 with sandpaper, a buff cloth, or the like. Also, dry polishing or wet polishing such as water polishing may be used.

  In the case of performing the polishing step S32, from the viewpoint of improving the surface smoothness of the undercoat layer 41, in the polishing step S32, the thickness of the undercoat layer 41 is preferably 80% or more compared to the thickness before the polishing step S32. It is desirable to polish to a thickness of 99% or less, more preferably 85% or more and 98% or less, and particularly preferably 90% or more and 97% or less.

≪Second painting process≫
On the surface of the undercoat layer 41 of the fiber reinforced resin molded article 11, the overcoat layers 42 and 43 are formed by applying an overcoat agent. The overcoat layers 42 and 43 are composed of a colored layer 42 and a protective layer 43.

  The colored layer 42 is a layer for imparting color to the paint layer 4 and can be formed by painting a base paint such as an aqueous base paint or an oil-based (solvent type) base paint. With respect to the aqueous base paint, an aqueous resin that is a main component thereof may be an acrylic resin made of an acrylic emulsion, a water-soluble acrylic resin, or the like, a polyester resin, a polyurethane resin, a vinyl resin, or the like. A pigment is added as a colorant to the aqueous base paint. Examples of the pigment include organic azo chelate pigments, insoluble azo pigments, condensed azo pigments, diketopyrrolopyrrole pigments, benzimidazolone pigments, Organic color pigments such as phthalocyanine pigments, indigo pigments, perinone pigments, perylene pigments, dioxane pigments, quinacridone pigments, isoindolinone pigments, metal complex pigments, yellow lead, yellow iron oxide, bengara, carbon black Inorganic color pigments such as titanium dioxide, extender pigments such as calcium carbonate, barium sulfate, clay and talc, and glitter pigments such as metal flakes. In addition, the water-based base paint is a cross-linking agent, a flat pigment, a curing catalyst, a thickener, an organic solvent, a basic neutralizing agent, an ultraviolet absorber, a light stabilizer, a surface conditioner, an antioxidant, if necessary. Additives for paints such as silane coupling agents can be blended. As the oil-based (solvent type) base paint, specifically, for example, a melamine curable oil-based paint containing a polyurethane resin, an acrylic resin, a melamine resin, and a color pigment can be used. The base paint can be applied onto the undercoat layer 41 by, for example, air spray coating, airless spray coating, brush coating, rotary atomization coating, curtain coat coating, or the like. The film thickness after the finishing step S4 of the colored layer 42 can be set to, for example, 10 to 20 μm.

  The protective layer 43 is a layer for protecting the colored layer 42 and enhancing the appearance of the coated product 1. Although it does not specifically limit as resin which forms the protective layer 43, By the combination of 2-component urethane clear coating containing a hydroxyl-containing acrylic resin and a polyisocyanate compound, an acrylic resin and / or a polyester resin, and an amino resin Examples thereof include clear paints, and clear paints of acrylic resins and / or polyester resins having a carboxylic acid / epoxy curing system. If necessary, the clear paint contains pigments, non-aqueous dispersion resins, polymer fine particles, curing catalysts, ultraviolet absorbers, light stabilizers, coating surface conditioners, antioxidants, fluidity conditioners, waxes, etc. as appropriate. Can be contained. Examples of the curing catalyst include organotin compounds, triethylamine, diethanolamine and the like. Examples of the ultraviolet absorber include ultraviolet stabilizers such as benzophenone-based, benzotriazole-based, cyanoacrylate-based, salicylate-based, oxalic acid anilide-based compounds, and hindered amine-based compounds. The clear coating can be applied on the colored layer 42 by air spray coating, airless spray coating, brush coating, rotary atomization coating, curtain coating, or the like. The film thickness after finishing process S4 of the protective layer 43 can be 20-50 micrometers, for example.

-Finishing process-
The finishing step S4 is a step for fixing the paint. For example, the paint may be fixed by air drying at room temperature for about 30 minutes to 2 hours.

  Further, from the viewpoint of more surely fixing the coating layer 4, for example, a furnace is used to heat-treat the fiber reinforced resin molded product after the coating step S3 at a temperature of 100 ° C. to 160 ° C. for about 10 minutes to 30 minutes. It is good also as a 2nd heating process.

Incidentally, as shown in FIG. 6, recess depth t of the recess 37a after the finishing step S4 is a _{t 2.} In the finishing step S4, the recess depth t of the recess 37a may increase or may not increase. _{T 2} is greater than _{t 1} when the recess depth t of the recess 37a is increased. Further, when the recess depth t of the recessed portion 37a does not increase, _{t 2} is the same as _{t 1.} Even when dents depth t of the recess 37a is increased, the difference between t ₂ and t ₁ is small.

<Fiber-reinforced resin molded products>
As shown in FIG. 6, the coated product 1 of the fiber reinforced resin molded article 11 obtained as described above includes a fiber reinforced resin layer 3 including a reinforced fiber 36 and having a thermosetting resin 37 as a matrix. A resin molded product 11 and a coating layer 4 formed on the surface of the fiber reinforced resin molded product 11 are provided.

-Effects-
Here, the coating method of the fiber reinforced resin molded article 11 according to the present embodiment includes the first heating step S2. Hereinafter, the function and effect will be described.

FIG. 7 shows a state in which the first coating step S31 is performed on the fiber reinforced resin molded article 11 of FIG. 3 without obtaining the first heating step S2. Recess depth t of the recess 37a remains undercoat layer 41 of _{t 0} in FIG. 3 is formed. Thereafter, the overcoat layers 42 and 43 are formed through the polishing step S32 and the second coating step S33. Then, through the finishing step S4, the coated product 1 of the fiber reinforced resin molded product 11 shown in FIG. 8 is obtained.

In the finishing step S4, shrinkage of the thermosetting resin 37 can be promoted by drying at room temperature or drying by heating. Then, recess depth t of the recessed portion 37a of the thermosetting resin 37 can grow up to t _2. Then, the undercoat layer 41 and the overcoat layers 42 and 43 formed on the surface of the fiber reinforced resin molded article 11 are recessed following the growth of the recessed portion 37a, and the surface of the coated product 1 reflects the recessed portion 37a. Thus, a coating layer recess 4a, that is, an uneven pattern can be formed. As shown in FIG. 8, the depth t of the coating layer recess 4a is determined by the coating layer 4 positioned above the fiber bundles 36a1 and 36a2, that is, the surface height of the coating layer flat portion 4b and the adjacent fiber bundles 36a1 and 36a2. It becomes a difference t ₃ from the surface height of the coating layer 4 located on the upper side, that is, the bottom of the coating layer recess 4a. The recess depth t ₃ of paint layers recess 4a is a value that reflects the value of the difference between t ₂ and t _0. In this specification, the recess depths t ₀ , t ₁ , t ₂ of the recess 37a and the recess depth t ₃ of the coating layer recess 4a are collectively referred to as “a recess depth t”.

On the other hand, in the coating method of the fiber reinforced resin molded article 11 according to the present embodiment, the fiber reinforced resin molded article is used as the first heating process S2 before the painting process S3 for coating the surface of the fiber reinforced resin molded article 11. 11 is heated at a predetermined temperature for a predetermined time. With this configuration, the shrinkage of the thermosetting resin is promoted in advance, and as shown in FIG. 4, the unevenness caused by the difference in shrinkage between the reinforcing fiber 36 and the thermosetting resin 37 is preliminarily formed in the fiber reinforced resin molding. It can be formed on the surface of the product 11. Then, in the coating step S3, the reinforcing fiber 36 is formed on the surface of the coated product 1 obtained after the finishing step S4 by forming the undercoat layer 41 and thus the overcoat layers 42 and 43 so as to hide the surface irregularities. It is possible to obtain the coated product 1 having excellent appearance by suppressing the appearance of irregularities due to the above, and improving the smoothness thereof. That is, as shown in FIG. 6, the depth t ₃ of the coating layer recess 4 a reflects a value of the difference between t ₂ and t _1, and is smaller than that in FIG. 8.

Thus, paint products 1 according to the present embodiment is excellent in surface smoothness, dent depth t ₃ of paint layer recesses 4a, from the viewpoint of bring paint product 1 with excellent appearance, preferably 0. It is 5 μm or less, more preferably 0.4 μm or less, and particularly preferably 0.3 μm or less. In addition, the arithmetic average surface roughness of the coated product 1, that is, the arithmetic average surface roughness Ra of the surface of the coating layer 4 can be set to, for example, 0.1 μm or less from the viewpoint of providing the coated product 1 with excellent appearance. .

-Applications of painted products-
The coated product 1 of the fiber reinforced resin molded article 11 is suitable for, for example, vehicle parts, engine parts such as an engine cover, bonnets, rear fenders, roofs, doors, front panels, rear panels, lift parts such as lift gates. Preferably, it can be used suitably for a vehicle component outer plate member. Thereby, it is excellent in surface smoothness, and a lightweight and high intensity | strength vehicle component, especially a vehicle component outer plate member can be obtained.

(Other embodiments)
Hereinafter, other embodiments according to the present invention will be described in detail. In the description of these embodiments, the same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the first embodiment, the coating process S3 includes the polishing process S32. However, the coating process S3 may be configured not to include the polishing process S32. In addition, the structure of Embodiment 1 which performs grinding | polishing process S32 once from the viewpoint of making the improvement of the surface smoothness of the coating product 1 and the simplification of the process of the whole coating method desirable is desirable.

  Moreover, although it was the structure which laminates the undercoat layer 41 and the overcoat layers 42 and 43 by 1st coating process S31 and 2nd coating process S33, it is not limited to the said structure, A single layer, or several more It is good also as a structure which laminates | stacks a layer. Further, when a plurality of layers are further laminated, the polishing step S32 may be performed a plurality of times. In addition, the structure which makes the coating layer 4 a laminated structure from a viewpoint of improving the smoothness and external appearance property of the coating product 1 effectively is desirable.

  Furthermore, as another embodiment, as described above, the fiber reinforced resin layer 3 may be formed by laminating a plurality of prepreg layers having different orientations of the reinforcing fiber 36 fiber bundle.

  Specifically, as shown in FIG. 9, a UD material longitudinal prepreg layer 32 and a UD material transverse prepreg layer 33 in which fiber bundles are oriented in a direction perpendicular to the orientation of the fiber bundles of the longitudinal prepreg layer 32 (note that In the following description, the vertical prepreg layer 32 and the horizontal prepreg layer 33 may be collectively referred to as “prepreg layers 32, 33”. It is good also as the fiber reinforced resin layer 3 made to do. In addition, the warp of the fiber reinforced resin molded product 11 can be suppressed by laminating the prepreg layers 32 and 33 so as to be symmetric with respect to the laminating direction.

  Moreover, as shown in FIG. 10, it is good also as a structure which laminates | stacks more than one prepreg layer which consists of UD materials about the structure of the fiber reinforced resin layer 3. As shown in FIG. Specifically, between the vertical prepreg layer 32 and the horizontal prepreg layer 33, an oblique prepreg layer 34 having a fiber bundle orientation of 45 degrees oriented in a predetermined direction is disposed and two horizontal prepreg layers are arranged. Two reverse oblique prepreg layers 35 in which the orientation of the fiber bundle of the reinforcing fibers 36 oriented in a predetermined direction between the layers 33 is inclined by 45 degrees in the opposite direction to the oblique prepreg layer 34 may be arranged. By arranging the oblique prepreg layer 34 and the inverted oblique prepreg layer 35, the strength of the fiber reinforced resin layer 3 is increased, and the strength of the fiber reinforced resin molded product 11 is improved.

  Furthermore, in other embodiment, as shown in FIG. 11, it is the outermost layer which consists of a thermosetting resin from a viewpoint which protects the fiber reinforced resin layer 3 on the surface of the fiber reinforced resin layer 3 of the fiber reinforced resin molded article 11. It is good also as a structure provided with 2. FIG.

  The outermost layer 2 may be composed of only a thermosetting resin, or may contain reinforced fibers or nonwoven fabrics randomly oriented in a predetermined direction from the viewpoint of improving impact strength. In addition, it is preferable that the randomly oriented reinforcing fiber or nonwoven fabric contained in the outermost layer 2 is made of polyester, cellulose, or glass fiber from the viewpoint of reducing the shrinkage difference between the outermost layer 2 and the fiber reinforced resin layer 3. In particular, it is preferably made of polyester.

  The thermosetting resin contained in the outermost layer 2 can use an epoxy resin, urethane, vinyl ester or the like, similar to the thermosetting resin 37, but from the viewpoint of enhancing the appearance of the fiber reinforced resin molded article 11, Epoxy resin is desirable. The thermosetting resin included in the outermost layer 2 may be the same material as the thermosetting resin 37 included in the fiber reinforced resin layer 3 or may be a different material.

  Next, specific examples will be described.

<Fiber-reinforced resin molded product>
(Sample 1)
A sheet-like (thickness 8 mm) carbon fiber reinforced plastic material (manufactured by GIGANTEX) as the fiber reinforced resin molded article 11 was cut into a size of 20 cm in length and 20 cm in width to obtain a test material 1.

≪Heating test 1≫
In order to confirm the influence of the heating temperature on the dent depth t, as shown in FIGS. 3 and 4, for example, as shown in FIG. 3 and FIG. The dent depth t was measured.

  Specifically, the depth t of the concave portion on the surface of the test material 1 before heating was measured using a contact-type surface roughness meter (manufactured by Mitutoyo Corporation). Then, after arrange | positioning in the oven (made by Espec Co., Ltd.) which heated up the test material 1 to predetermined | prescribed heating temperature, and hold | maintaining for 30 minutes at the heating temperature, the test material 1 is taken out from oven and before heating The concave depth t of the same concave portion as the concave portion where the concave depth t was measured was measured using the surface roughness meter. The oven was heated up to the next measurement temperature, the specimen 1 was returned to the oven and held for 30 minutes, and the dent depth t was measured in the same manner. Thereafter, the same operation was repeated for measurement. Measurement temperature is 23 degreeC, 110 degreeC, 130 degreeC, 155 degreeC, 180 degreeC, 210 degreeC, 230 degreeC. The results are shown in FIG.

  As shown in FIG. 12, the depth t of the recess is changed from 0.32 μm (0 ° C.) before heating to 1.42 μm (110 ° C.), 1.73 μm (130 ° C.), 2 μm (155 ° C.), 2 It was found that the increase was .37 μm (180 ° C.), 2.5 μm (210 ° C.), 2.86 μm (230 ° C.) in proportion to the increase in heating temperature.

≪Heating test 2≫
In order to confirm the influence of the heating temperature on the number of times of heating, using the same oven and surface roughness meter as in the heating test 1, heating conditions of 120 ° C. × 30 minutes were performed a predetermined number of times, and the depth of the recess in the same recess t Was measured. The results are shown in FIG.

  As shown in FIG. 13, at the stage of the first heating, the dent depth t increased from 0.34 μm before heating to 2.43 μm. After that, it was found that after the second time, it was almost constant at 2.19 μm (second time), 2.47 μm (third time), and 2.47 μm (fourth time).

≪Heating test 3≫
In order to confirm the influence of the heating temperature on the heating time, an experiment was conducted using the same oven and surface roughness meter as those in the heating test 1. Specifically, after placing the specimen 1 in an oven heated to 110 ° C. and holding it for 5 minutes, the depth t of the recess was measured. Thereafter, the sample was further heated for 5 minutes, and the measurement of the recess depth t of the same recess was repeated. The results are shown in FIG. Note that the heating time in FIG. 14 is the cumulative heating time.

  As shown in FIG. 14, the dent depth t was 0.64 μm before heating, but increased to 2.63 μm by the first 5 minutes of heating. Thereafter, the depth t of the dent at the heating time of 10 minutes, 15 minutes, 20 minutes, 25 minutes, and 30 minutes is 2.57 μm, 2.71 μm, 2.93 μm, 2.86 μm, and 2.81 μm, respectively. It was found that t was almost constant.

<Fiber-reinforced resin molded products>
Example 1
As a 1st heating process, it put into the above-mentioned oven which heated up the sample material 1 at 110 degreeC, heated for 30 minutes, took out the sample material 1 from the oven, and cooled to normal temperature. Thereafter, as a first coating step, an undercoat was applied to the surface of the test material 1 by air spray. The primer was prepared by adding 20 g of a curing agent and 20 g of diluted thinner to 100 g of COODE (registered trademark) filler gray (L55) base (manufactured by Kansai Paint Co., Ltd.) and mixing them. The undercoat was air-dried and then air-dried in the air for 20 minutes to form an undercoat layer. Thereafter, the surface of the undercoat layer was polished (water sharpened) with # 2000 sandpaper. Thereafter, an aqueous base paint (manufactured by Nippon Paint Automotive Coatings Co., Ltd.) and a clear paint (manufactured by Nippon Paint Automotive Coatings Co., Ltd.) were applied as an overcoat onto the surface of the undercoat layer by air spray. As a finishing step, the test material 1 coated with the top coat was placed in an oven at 110 ° C. and heated for 20 minutes. Thereafter, the test material 1 was taken out of the oven and cooled to room temperature to obtain a test piece TP of a coated product.

(Comparative Example 1)
A test piece TP was prepared in the same manner as in Example 1 except that the heating in the first heating step was omitted.

≪Indentation depth measurement test≫
About the test piece TP of Example 1 and Comparative Example 1, the dent depth t of the concave portion of the test material 1 before and after the first heating process, after the polishing process, and after the finishing process was measured. The results are shown in Table 1.

  Prior to the first heating step, in each of the test pieces TP of Example 1 and Comparative Example 1, recesses were observed, and the recess depths t were 0.52 μm and 0.81 μm, respectively. And in the test piece TP of the comparative example 1 which did not perform the 1st heating process, the dent depth t became 0.56 micrometer after the finishing process, and formation of the unevenness | corrugation was confirmed on the surface of the test piece TP. On the other hand, in the test piece TP of Example 1 which performed the 1st heating process, the unevenness | corrugation was hardly observed on the surface of the test piece TP even after the finishing process.

≪Coating smoothness evaluation test≫
As shown in FIG. 15, the test pieces TP of Example 1 and Comparative Example 1 were left on the ground G, and the surface of the test piece TP was visually observed by the tester A. The test method is as follows.

  That is, when the tester A makes the toe contact the end of the test piece TP and sits down, the tester TP observes the surface of the test piece TP with the naked eye, and the concave portion cannot be observed. Can be observed, the eye position is gradually separated from the test piece TP while standing with the line of sight aligned with the concave portion, and the eye stops at the position where the concave portion cannot be visually observed. The distance d from the position to the recess of the test piece TP was measured, and the distance d was taken as the evaluation result.

  The tester A was five persons A1 to A5 (5 males, 30 to 50 years old, height 165 cm to 180 cm, naked eye sight or corrected eyesight 0.8 to 2.0). The results are shown in Table 2.

  As shown in Table 2, in the test piece TP of Comparative Example 1, all of the testers A1 to A5 confirmed the presence of the recess, and the average value of the distance d was 137 cm. On the other hand, in the test piece TP of Example 1, all of the testers A1 to A5 could not confirm the presence of the recess.

  The present invention provides a coating method and a coated product of a fiber reinforced resin molded article that can suppress the appearance of unevenness derived from reinforcing fibers on the surface of a product after the painting process and can simplify the painting process. It is extremely useful because it can.

DESCRIPTION OF SYMBOLS 1 Coated product (of fiber reinforced resin molded product) 11 Fiber reinforced resin molded product 2 Outermost layer 3 Fiber reinforced resin layer 31 Prepreg layer 32 Vertical prepreg layer 33 Horizontal prepreg layer 34 Oblique prepreg layer 35 Reverse oblique prepreg layer 36 Reinforced fiber 37 Heat Curable resin S1 Preparation step S2 First heating step S3 Coating step S31 First coating step S32 Polishing step S33 Second coating step S4 Finishing step

Claims (13)

A method of coating the surface of a fiber reinforced resin molded article comprising a fiber reinforced resin layer containing a reinforced fiber and having a thermosetting resin as a matrix,
A first heating step of subjecting the fiber-reinforced resin molded product to a heat treatment at a predetermined temperature for a predetermined time;
A coating method for a fiber reinforced resin molded product, comprising: a coating step of coating the surface of the fiber reinforced resin molded product to form a coating layer after the first heating step. In claim 1,
The painting process includes
A first coating step of forming an undercoat layer on the surface of the fiber-reinforced resin molded article after the first heating step;
And a second coating step of forming an overcoat layer on a surface of the undercoat layer of the fiber reinforced resin molded product. In claim 2,
The method for coating a fiber reinforced resin molded article, wherein the coating step includes a polishing step for polishing the surface of the undercoat layer after the first coating step and before the second coating step. In any one of Claim 1 thru | or 3,
A method for coating a fiber-reinforced resin molded product, comprising a second heating step of performing a heat treatment on the fiber-reinforced resin molded product after the coating step. In claim 4,
The said predetermined temperature in a said 1st heating process is more than the temperature in a 2nd heating process, The coating method of the fiber reinforced resin molded product characterized by the above-mentioned. In any one of Claims 1 thru | or 5,
The method for coating a fiber-reinforced resin molded product, wherein the reinforcing fibers contained in the fiber-reinforced resin layer are oriented in a predetermined direction. In claim 6,
The fiber-reinforced resin layer is formed by laminating a plurality of layers having different orientations of the reinforcing fibers. In claim 6 or claim 7,
The reinforcing fiber oriented in the predetermined direction is at least one of a woven material, a knitted material, a braided material, a UD material, and a non-crimp fabric material. In any one of Claims 1 thru | or 8,
The method for coating a fiber-reinforced resin molded product, wherein the reinforcing fiber is a carbon fiber. In any one of Claims 1 thru | or 9,
The said thermosetting resin is an epoxy resin, The coating method of the fiber reinforced resin molded product characterized by the above-mentioned. In any one of Claims 1 thru | or 10,
The predetermined temperature in the first heating step is 100 ° C. or more and 250 ° C. or less,
The method for coating a fiber-reinforced resin molded product, wherein the predetermined time in the first heating step is 5 minutes or more and 60 minutes or less. In any one of Claims 1 thru | or 11,
The fiber-reinforced resin molded product is a vehicle component outer plate member, and the method for painting a fiber-reinforced resin molded product. A fiber reinforced resin molded article comprising a fiber reinforced resin layer containing a reinforced fiber and having a thermosetting resin as a matrix;
A coated product of a fiber reinforced resin molded product comprising a coating layer formed on the surface of the fiber reinforced resin molded product,
The fiber reinforced resin layer includes a plurality of fiber bundles composed of the reinforcing fibers oriented in a certain direction,
The plurality of fiber bundles includes two fiber bundles adjacent to each other in a direction parallel to the surface of the fiber reinforced resin molded product,
In the longitudinal cross-sectional view of the coated product, the difference between the surface height of the coating layer located above the fiber bundle and the surface height of the coating layer located above between the adjacent fiber bundles is 0.5 μm or less. A coated product of fiber-reinforced resin molded product characterized by

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