JP6810576B2 - Manufacturing method of plated molded product - Google Patents

Description

The present invention relates to a method for producing a plated molded product.

Electroless plating is known as a method for forming a metal film on a molded product at low cost. In electroless plating, in order to secure the adhesion strength of the metal film to the molded body, a pretreatment for roughening the surface of the molded body is performed using an etching solution containing an oxidizing agent such as hexavalent chromic acid or permanganate. Therefore, ABS resin (acrylonitrile-butadiene-styrene copolymer synthetic resin) that is eroded by the etching solution has been mainly used for electroless plating. In the ABS resin, the butadiene rubber component is selectively eroded by the etching solution to form irregularities on the surface. On the other hand, for resins other than ABS resin, such as polycarbonate, plating grades in which components that are selectively oxidized in the etching solution, such as ABS resin and elastomer, are mixed are commercially available in order to enable electroless plating. However, since such pretreatment of electroless plating uses hexavalent chromic acid or the like, there is a problem that the environmental load is high.

An electroless plating catalyst is applied to the surface of the roughened molded product. Two types of methods are mainly used for applying the electroless plating catalyst to the plastic base material. A sensitizer-activating method in which the tin colloid is adsorbed on a substrate (sensitizer) and then immersed in a palladium chloride solution (activating) to reduce and precipitate palladium chloride with stannous chloride, and palladium tin. This is a catalyst-accelerator method in which a colloid is adsorbed on a substrate (catalyst) and then reduced with concentrated sulfuric acid or the like (accelerator). These conventional catalyst application treatments actually require more steps. For example, in the catalyst-accelerator method, post-etching for improving the surface property of a molded product and post-accelerator for removing tin that cannot be completely removed by the accelerator are performed.

In order to reduce the number of steps in the plating pretreatment, Patent Document 1 describes a molded product in one solution containing an inorganic acid-containing corrosive agent such as hydrochloric acid, an ionogen activator such as palladium ion, and an organic acid such as acetic acid. A method has been proposed to handle. According to Patent Document 1, a good plating film can be obtained by pretreating the polyamide substrate with the above-mentioned one solution. Further, according to the method, it is not necessary to use hexavalent chromic acid or the like, which has a high environmental load.

Patent No. 4190615

However, the crystal structure of the surface of the polyamide molded product may differ depending on the location. In this case, even if the above-mentioned plating pretreatment is performed, the electroless plating reaction becomes uneven, and as a result, it becomes difficult to obtain a uniform plating film having high adhesion strength. And this phenomenon is remarkable especially in the molded article having a complicated shape.

The present invention solves these problems and provides a method for producing a plated molded product having a uniform plating film having high adhesion strength and excellent appearance characteristics.

According to the present invention, it is a method for producing a plated molded article, which is a method for producing a plated molded article, and includes an aliphatic polyamide and inorganic particles having an average particle diameter of 1 μm or less and being soluble in acid. A molded product having an inorganic particle content of 0.5% by weight to 10% by weight is prepared, and the part contains palladium chloride and hydrochloric acid, and the concentration of the hydrochloric acid is 1.0N to 3.0N. After the electroless plating catalyst solution is brought into contact with the molded body and the electroless plating catalyst solution is brought into contact with the molded body, the swelling treatment of the molded body and the cleaning of the surface of the molded body are simultaneously performed. it and, after applying the swelling treatment and the washing to the molded body, wherein contacting the electroless plating solution in the molded body, looking containing and forming a plating film, the cleaning of the surface of the molded body palladium concentration in the vicinity of the surface of the molded ^{body, 0.01mg / dm 2 ~0.1mg / dm} 2 and comprising a manufacturing method is provided.

In the present invention, the inorganic particles may be calcium carbonate. The concentration of palladium chloride in the electroless plating catalyst solution may be 5 mg / L to 150 mg / L. Further, as the swelling treatment and washing of the molded product, the molded product may be brought into contact with water having a temperature equal to or higher than the glass transition point of the aliphatic polyamide, and the temperature of the water to be brought into contact with the molded product is 50. It may be ~ 90 ° C.

In the present invention, the electroless plating solution may be an electroless nickel phosphorus plating solution, and the temperature of the electroless nickel phosphorus plating solution may be 50 ° C. to 80 ° C. Further, the pH of the electroless nickel phosphorus plating solution may be 4.0 to 6.0. Further, the palladium chloride adsorbed on the outermost surface of the molded product may be washed away by cleaning the surface of the molded product .

The present invention improves the uniformity of the electroless plating reaction of a molded product containing polyamide by performing a specific plating pretreatment. Further, by containing fine inorganic particles soluble in acid in the molded body, it is possible to produce a plated molded product having a plating film having high adhesion strength and a uniform and excellent appearance characteristics.

It is a flowchart which shows the manufacturing method of the plating compact manufactured in embodiment. 3 is an SEM photograph of the surface of the molded product after immersion in the electroless plating catalyst solution in Example 1. 3 is an SEM photograph of the surface of the molded product after immersion in the electroless plating catalyst solution in Comparative Example 1. 3 is an SEM photograph of the surface of the molded product after immersion in the electroless plating catalyst solution in Comparative Example 3.

A method for producing a plated molded product (molded product having a plating film) in the present embodiment will be described with reference to FIG.

<Preparation of molded body>
First, a molded product containing an aliphatic polyamide and inorganic particles having an average particle diameter of 1 μm or less and being soluble in acid is prepared (step S1 in FIG. 1). Since the aliphatic polyamide has high water absorption, the permeation of the plating solution is promoted and the plating film grows stably. Further, since the aliphatic polyamide is excellent in rigidity, heat resistance and chemical resistance, the rigidity, heat resistance and chemical resistance of the molded product can be ensured. The aliphatic polyamide is not particularly limited as long as it does not have an aromatic ring, and for example, nylon 6 (PA6), nylon 66 (PA66), nylon 12 (PA12), nylon 11 (PA11), and nylon 6.66 are all used. A polymer, a composite material obtained by copolymerizing or alloying these, an amorphous nylon, or the like can be used. Among them, nylon 6 and nylon 66, which have high water absorption and easily swell, are preferable, and nylon 6 is particularly preferable, from the viewpoint of easy formation of a plating film. Further, a composite material obtained by copolymerizing or alloying the above-mentioned aliphatic polyamide with a thermoplastic resin other than polyamide may be used. Examples of such a composite material include a nylon and polypropylene polymer alloy (PA / PP) and an ABS resin and nylon polymer alloy. These polyamides may be used alone or in combination of two or more.

The viscosity of the aliphatic polyamide is preferably 1.8 to 4.0, more preferably 2.0 to 3.6, with a relative viscosity (RV) measured in 96% by mass sulfuric acid at 25 ° C. It is more preferably 2.5 to 3.6. When the relative viscosity (RV) is within the above range, the dispersibility of the inorganic particles in the aliphatic polyamide is improved, and the mechanical properties, particularly the impact resistance, can be maintained.

The molded product may contain a thermoplastic resin other than the aliphatic polyamide, but the main component of the molded product is preferably an aliphatic polyamide. The aliphatic polyamide is preferably contained in the molded product in an amount of 30% by weight to 99.5% by weight, more preferably 60% by weight to 95% by weight.

Inorganic particles having an average particle diameter of 1 μm or less (hereinafter, appropriately referred to as “small particle diameter inorganic particles”) used in the present embodiment are soluble in acid. In the specification of the present application, the term "small particle size inorganic particles are soluble in acid" means, for example, that 1 g of small particle size inorganic particles is placed in 100 mL of commercially available hydrochloric acid (35 to 37% by mass) at 23 ° C. for 1 hour. It means that the undissolved residue of the small particle size inorganic particles cannot be confirmed by visual observation after being left to stand. By containing inorganic particles having a small particle size capable of acid in the molded body, a plurality of fine recesses (holes) can be formed on the surface of the molded body in the plating pretreatment described later. As a result, uneven plating reaction on the surface of the molded product can be alleviated. In addition, the adhesion strength and appearance characteristics of the electroless plating film formed on the molded body can be improved. From the same viewpoint, the particle size of the small particle size inorganic particles is preferably 100 nm to 1 μm. Small particle size The "average particle size" of the inorganic particles can be measured as an arithmetic mean size using, for example, a dynamic light scattering type particle size distribution measuring device.

The small particle size inorganic particles are not particularly limited as long as they have an average particle size of 1 μm or less and are soluble in acid. For example, calcium carbonate, zinc oxide, magnesium carbonate, tin oxide, barium ferrite, barium carbonate, and titanium. Barium acid acid or the like can be used. Of these, calcium carbonate, which has good solubility in acid, is preferable.

The shape of the small particle size inorganic particles is not particularly limited, but is preferably granular or substantially spherical. Granular or substantially spherical particles are less noticeable in the molded product than, for example, needle-shaped fibers, and can enhance the design of the molded product.

The small particle size inorganic particles are contained in the molded product in an amount of 0.5% by weight to 10% by weight. Even if the content of the small particle size inorganic particles is relatively small, 0.5% by weight to 10% by weight, the particle size is small, so that the inorganic particles are efficiently segregated (unevenly distributed) on the surface of the molded body in the molding process of the molded body. To do). As a result, the concentration of small particle size inorganic particles near the surface of the molded body is increased, uneven plating reaction on the surface of the molded body is alleviated, and the adhesion strength of the plating film is improved. Further, since the content of the small particle diameter inorganic particles is relatively small, 0.5% by weight to 10% by weight, even if recesses are formed on the surface of the molded body due to the dissolution of the inorganic particles, the surface of the molded body becomes fragile and the plating film is formed. The adhesion strength of the plating film is not reduced, and the appearance characteristics of the plating film are not affected. From the same viewpoint, the content of the small particle size inorganic particles in the molded product is preferably 1% by weight to 2% by weight.

If the content of the small particle size inorganic particles in the molded body is less than 0.5% by weight, uneven plating reaction may occur on the surface of the molded body, and the adhesion strength of the plating film may decrease. On the other hand, when the content of the small particle size inorganic particles in the molded product exceeds 10% by weight, the surface of the molded product is roughened more than necessary, and the appearance characteristics of the plating film formed on the molded product deteriorate at the same time. , The surface of the molded body may be weakened and the adhesion strength of the plating film may be lowered.

Further, in general, when the resin material contains inorganic particles, the surface treatment of the inorganic particles or the addition of a compatibilizer may be performed in order to enhance the compatibility between the resin material and the inorganic particles. However, in the present embodiment, it is preferable not to perform surface treatment of small particle size inorganic particles or addition of a compatibilizer. That is, it is preferable that the compatibility between the aliphatic polyamide and the small particle size inorganic particles is low. If the compatibility between the aliphatic polyamide and the inorganic particles is low, the inorganic particles can be efficiently segregated (unevenly distributed) on the surface of the molded product in the molding process of the molded product.

In addition to the small particle diameter inorganic particles, the molded product of the present embodiment may further contain inorganic particles having an average particle diameter of 2 μm or more (hereinafter, appropriately referred to as “large particle diameter inorganic particles”). By containing the large particle size inorganic particles, it is possible to suppress the warp of the molded product and improve the rigidity and dimensional stability. If the particle size of the large particle size inorganic particles is too large, the surface appearance of the molded product may be deteriorated. Therefore, the average particle size of the inorganic particles is preferably 50 μm or less. The "average particle size" of the large particle size inorganic particles can be measured by the same method as that of the small particle size inorganic particles.

Examples of large particle size inorganic particles include silicates such as wallastonite (wollastonite), talc, calcium silicate, glass beads, aluminum silicate, magnesium silicate, and silicon dioxide, silicic acid, calcium oxide, and carbon dioxide. Examples thereof include calcium, magnesium oxide, magnesium hydroxide, barium sulfate, barium carbonate, titanium oxide, potassium titanate and compounds (minerals) containing the same. Of these, wallastonite, magnesium hydroxide, calcium oxide, and silicon dioxide are preferable from the viewpoint of surface properties (appearance) and cost of the molded product.

The shape of the large particle size inorganic particles is not particularly limited, but like the small particle size inorganic particles, it is preferably granular or substantially spherical. Granular or substantially spherical particles are less noticeable in the molded product than, for example, needle-shaped fibers, and can enhance the design of the molded product.

The content of large particle size inorganic particles in the molded product is 10 to 65% by weight from the viewpoint of surface properties (appearance), mechanical strength, dimensional stability, moldability (easiness of molding), etc. of the molded product. It is preferably 30 to 50% by weight, more preferably.

In the present embodiment, a commercially available mineral-containing aliphatic polyamide may be used as the above-mentioned aliphatic polyamide and large particle size inorganic particles. Generally, a thermoplastic resin containing minerals is called a "mineral reinforced resin". Commercially available products of the mineral reinforced resin include, for example, the mineral reinforced resin T777-02 manufactured by Toyobo, the mineral reinforced resin 1013R and 1013R1 manufactured by Ube Industries, and the like.

In the present embodiment, the molded body may be composed of only the above-mentioned aliphatic polyamide and small particle size inorganic particles, or the molded body may be composed of only the aliphatic polyamide, small particle size inorganic particles and large particle size inorganic particles. It may be configured. If necessary, the molded product may further contain other general-purpose additives.

The molded product of the present embodiment may be a commercially available molded product, or the above-mentioned material may be molded to obtain a molded product. The molding method of the molded product is not particularly limited. For example, a resin material obtained by adding large particle size inorganic particles and other general-purpose additives to aliphatic polyamide and small particle size inorganic particles as needed is molded by general-purpose injection molding, extrusion molding, or the like to obtain a molded product. You may.

In the molding of the molded product, the small particle size inorganic particles and the large particle size inorganic particles may be mixed with the same aliphatic polyamide and molded to obtain a molded product. Further, a polyamide (first resin) in which small particle size inorganic particles are mixed and a polyamide (second resin) in which large particle size inorganic particles are mixed are prepared, and these are mixed and molded by dry blending or the like. Then, a molded product may be obtained. The first polyamide and the second polyamide may be the same polyamide, or may be different polyamides having different molecular weights and viscosities. In the method of producing a molded product using the first and second resins, the first resin is a masterbatch, and the second resin corresponds to the base resin to which the masterbatch is blended. A masterbatch is a resin containing a high concentration of functional materials such as dyes, pigments, and other additives, and is mixed with a base resin containing no functional materials and molded together with the base resin. When a masterbatch is used, the handling of the material is easier and the weighing accuracy is improved as compared with molding by adding the functional material directly to the base resin. In this embodiment, the small particle size inorganic particles correspond to the functional material of the masterbatch. Further, in the present embodiment, a resin material containing an aliphatic polyamide and small particle size inorganic particles and another resin material may be molded by two-color molding to obtain a two-color molded product.

<Plating pretreatment>
In the present embodiment, prior to electroless plating, pre-plating treatment including (1) application of electroless plating catalyst and (2) swelling treatment of the molded product is performed.

(1) Addition of electroless plating catalyst In the present embodiment, the electroless plating catalyst liquid containing palladium chloride and hydrochloric acid is brought into contact with the molded body as an application of the electroless plating catalyst to the molded body (step S2 in FIG. 1). .. The concentration of hydrochloric acid in the electroless plating catalyst solution is 1.0 N to 3.0 N.

The electroless plating catalyst solution having a hydrochloric acid concentration of 1.0 N to 3.0 N dissolves small particle size inorganic particles contained in the vicinity of the surface of the molded product. That is, the small particle size inorganic particles are removed from the vicinity of the surface of the molded product. As a result, recesses (holes) corresponding to the dissolved small particle size inorganic particles are formed on the surface of the molded product. The surface of the molded product is swollen by hydrochloric acid, and recesses are formed on the surface, so that the electroless plating catalyst easily permeates the molded product. As a result, the unevenness of the adsorption amount of palladium chloride on the surface of the molded body is alleviated, and thereby the unevenness of the plating reaction on the surface of the molded body can be alleviated. By alleviating the uneven plating reaction, it is possible to suppress the occurrence of defects in the plating film. Further, the electroless plating film formed on the molded body is formed not from the outermost surface of the molded body but from the inside (near the surface) of the molded body, and the adhesion strength is improved. Further, since the average particle size of the small particle size inorganic particles used in the present embodiment is 1 μm or less, the recesses formed on the surface of the molded product are very fine. Therefore, the recesses on the surface of the molded body do not affect the surface shape of the electroless plating film formed on the recesses. As a result, the appearance characteristics of the plating film and the design of the plated molded product are improved.

Further, since the concentration of hydrochloric acid is relatively low, 1.0N to 3.0N, even when the molded product contains large particle size inorganic particles, the large particle size inorganic particles do not dissolve or are slightly dissolved. Even if it does, it is rarely removed from the compact. Therefore, it is possible to suppress the roughening of the surface of the molded product due to the dissolution of the large particle diameter inorganic particles. Palladium chloride may precipitate when the concentration of hydrochloric acid decreases. However, by setting the concentration of hydrochloric acid in the electroless plating catalyst solution to 1.0N to 3.0N, palladium chloride is contained in the electroless plating catalyst solution. Can be stably dissolved. The concentration of hydrochloric acid in the electroless plating catalyst solution is preferably 1.0 to 2.7 N, more preferably 1.5 to 2.7 N.

If the concentration of hydrochloric acid in the electroless plating catalyst solution is lower than 1.0 N, the dissolution of small particle size inorganic particles becomes insufficient, and there is a risk that uneven plating reaction may occur on the surface of the molded body, and the adhesion strength of the plating film may increase. It may decrease. On the other hand, when the concentration of hydrochloric acid in the electroless plating catalyst solution exceeds 3.0 N, the surface of the molded body is roughened more than necessary, and the appearance characteristics of the plating film formed on the surface are deteriorated. The adhesion strength of the film may decrease. In particular, when the molded product contains large particle size inorganic particles, the appearance characteristics of the plating film are deteriorated and the adhesion strength is lowered.

Palladium chloride functions as an electroless plating catalyst in the electroless plating step (step S4 in FIG. 1) described later. Palladium chloride is contained in the electroless plating catalyst solution, for example, 0.05 to 500 mg / L, preferably 1 to 250 mg / L, and more preferably 5 to 150 mg / L. If the concentration of palladium chloride is less than 0.05 mg / L, the amount of palladium chloride adsorbed on the surface of the molded product may be uneven, resulting in defects in the plating film. Further, when the palladium chloride concentration exceeds 500 mg / L, the amount of palladium chloride adsorbed on the surface of the molded body increases, the plating reaction on the outermost surface of the molded body becomes dominant, and the adhesion strength of the plating film may decrease. There is.

The electroless plating catalyst solution of the present embodiment may be composed of only palladium chloride and hydrochloric acid, or may contain other additives and solvents as required. The electroless plating catalyst solution may contain, for example, a surfactant. By containing the surfactant, the surface tension of the electroless plating catalyst solution is lowered, the wettability to the surface of the molded body is improved, and the palladium ions derived from palladium chloride easily permeate into the molded body. As the surfactant, a general-purpose surfactant such as an anionic surfactant, a cationic surfactant, a nonionic surfactant, and an amphoteric surfactant can be used. On the other hand, the electroless plating catalyst solution of the present embodiment preferably does not contain an organic acid such as acetic acid in order to avoid deterioration of workability due to odor.

The time for contacting the electroless plating catalyst solution with the molded product is preferably 5 seconds to 15 minutes. If it is less than 5 seconds, the amount of palladium chloride adsorbed on the surface of the molded product may be uneven, and the electroless plating reaction may not be started uniformly. Further, if it exceeds 15 minutes, there is a risk of deterioration of the molded product and corrosion of the plating film due to hydrochloric acid permeating the molded product.

The temperature of the electroless plating catalyst solution in contact with the molded product is preferably 10 ° C. to 50 ° C. If the temperature is lower than 10 ° C., the amount of palladium chloride adsorbed on the surface of the molded product may be uneven, and the electroless plating reaction may not be started uniformly. Further, when the temperature of the electroless plating catalyst liquid is less than 10 ° C., the temperature of the molded product is also low. Therefore, the treatment temperature of the swelling treatment of the molded product, which is the next step, may be affected, and a sufficient swelling effect may not be obtained. Further, when the temperature of the electroless plating catalyst solution exceeds 50 ° C., the amount of palladium chloride adsorbed on the surface of the molded product increases, and the plating reaction on the outermost surface of the molded product may become dominant. In addition, it may be difficult to stabilize the hydrochloric acid concentration due to the generation of gas from hydrochloric acid and the evaporation of water. Further, since the small particle size inorganic particles contained in the molded body of the present embodiment have a small particle size, they are easily dissolved in the electroless plating catalyst solution at room temperature, and as a result, recesses (holes) are formed on the surface of the molded body. It is formed and easily adsorbs palladium chloride. Therefore, in the present embodiment, even if the temperature of the electroless plating catalyst solution is set to room temperature of 20 ° C. to 25 ° C., a sufficient amount of palladium chloride can be applied to the molded product.

The method of bringing the electroless plating catalyst solution into contact with the molded body is arbitrary, and various methods can be used depending on the purpose. For example, the entire molded product may be immersed in the electroless plating catalyst solution. Further, when only a part of the molded product is plated, only the part scheduled to be plated may be brought into contact with the electroless plating catalyst solution.

According to the step of applying the electroless plating catalyst described above, hydrochloric acid in the electroless plating catalyst solution etches the surface of the molded product containing the aliphatic polyamide, and palladium chloride is adsorbed and permeated into the molded product. Further, the electroless plating catalyst solution dissolves small particle size inorganic particles contained in the vicinity of the surface of the molded body to form minute recesses on the surface of the molded body. As a result, it is possible to achieve both the adhesion strength of the plating film formed on the surface of the molded product and the appearance characteristics. Further, according to the study by the present inventors, it was found that palladium chloride specifically adsorbs to the amide group of polyamide and is difficult to adsorb to resins other than polyamide. Therefore, palladium chloride, which is an electroless plating catalyst, can be sufficiently applied to the molded product of the present embodiment containing the aliphatic polyamide.

In the present embodiment, the electroless plating catalyst can be applied only to the portion of the two-color molded product containing the aliphatic polyamide by utilizing the difference in the adsorption amount of palladium chloride for each resin material. For example, first, a two-color molded product including a first portion containing small particle size inorganic particles and an aliphatic polyamide and a second portion containing an aromatic polyamide is prepared. Palladium chloride is also adsorbed on aromatic polyamides, but since aromatic polyamides are not easily eroded by acids, the amount of palladium chloride adsorbed is lower than that of aliphatic polyamides. By adjusting the conditions of the process of applying the electroless plating catalyst, palladium chloride can be preferentially adsorbed on the first portion containing the aliphatic polyamide. By preferentially adsorbing palladium chloride on the first portion of the two-color molded product, an electroless plating film can be formed only on the first portion.

(2) Swelling Treatment Next, a swelling treatment is performed on the molded product that has been brought into contact with the electroless plating catalyst solution (step S3 in FIG. 1). The swelling treatment is performed, for example, by bringing a treatment solvent for swelling the molded product into contact with the molded product. As the treatment solvent, water (hot water) having a temperature of room temperature or higher is preferable. The temperature of the treatment solvent is preferably equal to or higher than the glass transition point of the aliphatic polyamide contained in the molded product in order to enhance the swelling effect of the molded product, and is, for example, 50 ° C. to 90 ° C., preferably 60 ° C. to 75 ° C. The molded product of the present embodiment contains an aliphatic polyamide having a relatively low glass transition point. Therefore, sufficient swelling treatment can be performed by bringing water (hot water) at 50 ° C. to 90 ° C. into contact with each other.

Further, it is preferable that the treatment solvent such as water is circulated and kept in a clean state at all times. The treatment solvent may be agitated, and for example, agitation by air or a forced flow of water may be provided. Further, from the viewpoint of sufficiently swelling the molded product, the time for bringing the treatment solvent into contact with the molded product can be, for example, 30 seconds to 30 minutes.

By the swelling treatment described above, unevenness in the surface of the molded product due to the difference in the crystal structure of the polyamide can be alleviated, and an environment in which the electroless plating reaction is likely to occur uniformly can be created. Then, the electroless plating reaction occurs uniformly, so that a uniform plating film having excellent appearance characteristics can be formed.

Further, by swelling the molded body, palladium chloride can be satisfactorily fixed in the minute gaps on the surface of the molded body generated by etching with hydrochloric acid. Further, the swelling of the molded body facilitates the penetration of the electroless plating catalyst into the molded body, and the electroless plating solution also penetrates into the molded body in the electroless plating step (step S4 of FIG. 1) described later. It will be easier. As a result, the growth of the plating film from the inside of the molded body is promoted, and a plating film having strong adhesion strength can be formed.

Further, in the swelling treatment of the present embodiment, the palladium chloride adsorbed on the outermost surface of the molded product is washed away, and the plating reaction on the outermost surface of the molded product is suppressed. By suppressing the plating reaction on the outermost surface of the molded body, the growth of the plating film from the inside of the molded body is further promoted, and a plating film having stronger adhesion strength can be formed. As described above, the swelling treatment in the present embodiment is a treatment that swells the surface of the molded body and at the same time cleans the surface of the molded body. That is, in the present embodiment, the swelling treatment and cleaning of the molded product are performed in the same process.

By washing away the palladium chloride adsorbed on the outermost surface of the molded body, the palladium concentration in the vicinity of the surface of the molded body (for example, the region at a depth of 100 μm from the surface) is 0.01 mg / dm ^{2 to} 0.1 mg /. it is preferable that the dm ^2, and more preferably a ^{0.01mg / dm 2 ~0.05mg / dm 2} . Compared with the conventional molded product after the pre-plating treatment, the molded product after the pre-plating treatment of the present embodiment has a lower palladium concentration in the vicinity of the surface. In the molded product of the present embodiment, the plating reaction on the outermost surface of the molded product is suppressed by the plating pretreatment, and the electroless plating catalyst and the electroless plating liquid easily permeate into the molded product. The growth of the plating film from is promoted. As a result, it is presumed that even if the palladium concentration near the surface of the molded body is low, the plating reactivity of the molded body is high and the adhesion strength of the plating film is improved. The palladium concentration in the vicinity of the surface of the molded product can be controlled by adjusting various conditions in the plating pretreatment.

The palladium concentration in the vicinity of the surface of the molded product can be measured, for example, as follows. The pre-plated molded product is dried, and a resin having a thickness of 100 μm is mechanically scraped from the surface in a predetermined area of the molded product. The weight of palladium contained in the scraped resin is obtained and divided by a predetermined area to obtain the weight of palladium per unit area (palladium concentration). The weight of palladium contained in the scraped resin can be measured by, for example, the weight of the scraped resin, the dissolution treatment, and the ICP (inductively coupled plasma) luminescence analysis method.

As described above, in the present embodiment, the swelling treatment and cleaning of the molded product are performed in the same step. From the viewpoint of reducing the number of steps in the pre-plating treatment, it is preferable to perform the swelling treatment and cleaning of the molded product at the same time, but the present embodiment is not necessarily limited to this, and the swelling treatment and cleaning of the molded product are performed. It may be carried out as a separate step. Further, as described above, in the present embodiment, the molded body is washed by bringing the treatment solvent into contact with the molded body, but the present embodiment is not limited to this. For example, reducing the palladium concentration in the vicinity of the surface of the molded body, preferably a surface treatment of the molded body to be 0.01mg ^/ dm ² ~0.1mg ^/ dm 2 is included in the "washing" of the molded body in the present embodiment Is done.

<Electroless plating>
Next, the electroless plating solution is brought into contact with the pre-plated molded body to form a plating film (step S4 in FIG. 1), and the plated molded body (molded body having the plated film) of the present embodiment is formed. obtain. As the electroless plating solution, any general-purpose electroless plating solution can be used depending on the purpose, but an electroless nickel phosphorus plating solution is preferable from the viewpoint of high catalytic activity and stability of the solution.

Electroless plating catalysts usually exhibit catalytic activity in a metallic state with an oxidation number of 0 (zero). Therefore, in both the sensitizer-activating method and the catalyst-accelerator method, which are conventionally known general-purpose electroless plating catalyst application methods, palladium is reduced while being adsorbed on the substrate. Therefore, conventionally, it has been difficult to use it as an electroless plating catalyst because it does not exhibit catalytic activity even if palladium chloride, which is not in a metallic state, is applied to the base material. Further, palladium chloride has a problem that it is difficult to be adsorbed on the surface of a plastic base material. However, by using a molded product containing polyamide as a base material and using an electroless plating solution such as an electroless nickel phosphorus plating solution, the present inventors can perform an electroless plating reaction without performing a reduction treatment of palladium chloride. Found to occur. Although the cause of this is not clear, the use of polyamide as the base material facilitates the adsorption of palladium chloride on the base material, and the reducing agent such as sodium hypophosphite contained in the electroless plating solution reduces palladium chloride. It is presumed that this is to do. In the present embodiment, since the reduction treatment of the electroless plating catalyst can be omitted, the manufacturing cost can be reduced and the throughput can be improved.

When an electroless nickel phosphorus plating solution is used as the electroless plating solution, the concentration of sodium hypophosphite, which is a reducing agent, is high, and the phosphorus concentration in the formed plating film is about 7 to 12% by weight. It is preferable to use a phosphorus-type acidic nickel phosphorus plating solution. Since such a nickel phosphorus plating solution has a strong reducing power and a high permeability into the polyamide, even when the palladium chloride concentration near the surface of the molded product is low, the polyamide while reducing the palladium chloride. It is presumed that the electroless plating reaction proceeds inside. The pH of the electroless nickel-phosphorus plating solution is, for example, 4.0 to 6.0, preferably 4.5 to 5.0. If the pH of the plating solution is too low, the activity of the plating solution is lowered and the uniformity of the plating film is poor, which may lead to poor appearance such as film loss. On the other hand, if the pH is too high, the activity of the plating solution becomes too high, and film formation of the plating is started on the outermost surface of the molded product, which may reduce the adhesion strength of the plating film. In addition, a plating solution having a high pH has low stability and is prone to decomposition. Therefore, in the worst case, it is necessary to replace the plating solution, which leads to an increase in cost. By setting the pH of the plating solution to, for example, the range of 4.0 to 6.0, these inconveniences can be suppressed. The phosphorus concentration in the electroless plating solution is preferably 5% by weight or more. By increasing the phosphorus concentration, the corrosion resistance of the plating film is also improved.

In addition, the reducing power of hypophosphate decreases as the temperature decreases. Therefore, the operating temperature of a commercially available medium to high phosphorus type electroless nickel phosphorus plating solution having a high concentration of a reducing agent is often as high as 85 ° C. to 90 ° C. However, if the resin molded product is plated at a processing temperature of 85 ° C. to 90 ° C., the molded product itself may be deformed. Further, since plating is performed in a state where the molded body is expanded and the molded body is cooled after plating and the molded body shrinks, there is a possibility that the plating film may be cracked because it cannot cope with the shrinkage of the molded body. In the present embodiment, since the plating reactivity of the molded product is high, it is possible to form a plating film having high adhesion strength and excellent appearance characteristics even when the plating treatment temperature is 80 ° C. or lower. Therefore, when the electroless nickel phosphorus plating solution is used, the processing temperature of the electroless plating (temperature of the electroless plating solution) is, for example, 50 ° C. to 80 ° C., preferably 50 ° C. to 70 ° C. Further, when the temperature of the electroless plating solution is within this range, an inexpensive bathtub such as a plastic bathtub can be used for the electroless plating bathtub, and the equipment cost can be reduced. The time for contacting the electroless plating solution with the molded product is, for example, 30 seconds to 30 minutes.

A plurality of different types of electroless plating films may be formed on the molded body on which the electroless plating film is formed for the purpose of improving the use and design of the molded body, or the electroless plating film may be formed by electroplating. May be formed. Further, the molded product on which the electroless plating film is formed may be annealed after electroless plating, or may be left at room temperature for natural drying. Further, the following steps such as continuously forming an electrolytic plating film may be performed without performing annealing treatment or natural drying.

<Ultrasonic irradiation>
In the method for producing a plated molded product of the present embodiment, a step of immersing the molded product in a liquid and irradiating the molded product with ultrasonic waves may be further provided. In this embodiment, in order to improve the adhesion strength of the electroless plating film, the molded body is swollen by pre-plating treatment. At this time, a part of the surface of the molded product may swell and protrude, resulting in a convex defect. Further, in the step of applying the electroless plating catalyst, the resin residue generated when the small particle size inorganic particles are dissolved may adhere to the molded product. By irradiating the molded body with ultrasonic waves, such convex defects and resin residues can be removed from the surface of the molded body, and the appearance characteristics of the plating film formed on the molded body can be improved.

When the purpose is to remove convex defects and resin residues resulting from the pre-plating treatment, the ultrasonic irradiation of the molded product is preferably performed during the swelling treatment or after the swelling treatment. For example, in the swelling treatment, ultrasonic waves may be irradiated while the molded product is immersed in a treatment solvent such as water (hot water) at 50 to 90 ° C., or in the electroless plating treatment, the molded product is placed in the electroless plating solution. Ultrasonic waves may be applied while the molded product is immersed. Further, an ultrasonic irradiation step may be provided as a new step before the electroless plating treatment or after the electroless plating treatment.

The ultrasonic irradiation conditions can be appropriately determined. For example, the frequency can be 28 kHz to 950 kHz, the intensity can be 40 W to 500 W, and the irradiation time can be 30 seconds to 30 minutes. When an ultrasonic irradiation step is provided as a new step, the liquid for immersing the molded product is preferably water having a low environmental load, and the temperature of the liquid is preferably 25 ° C to 50 ° C.

It should be noted that the resin residue adhering to the molded product can be removed by applying air bubbling or jet to the surface of the base material instead of ultrasonic irradiation.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples and Comparative Examples.

[Example 1]
In this example, first, a molded product containing an aliphatic polyamide was molded, and the obtained molded product was subjected to a plating pretreatment and a plating treatment to produce a plated molded product.

(1) Molding of molded product Calcium carbonate having an average particle diameter of 0.2 μm was used as the small particle size inorganic particles, and the high viscosity polyamide 6 (manufactured by DSM, F-130, relative viscosity RV = 3.) As the aliphatic polyamide. Polyamide 6 (Glamite T777-02, manufactured by Toyo Boseki Co., Ltd.) containing 40% by weight of 5) and wallastnite having an average particle size of 3 μm was used. Wallastnite corresponds to the large particle size inorganic particles described in the above embodiment.

First, calcium carbonate and high-viscosity polyamide 6 were mixed at a weight ratio of (calcium carbonate): (high-viscosity polyamide 6) = 40:60 to obtain a first resin (master batch). Next, the first resin and the wallastnite-containing polyamide 6 (second resin, base resin) were mixed at a weight ratio of (first resin) :( second resin) = 5:95. A flat plate-shaped molded body of 8 cm × 8 cm × 0.2 cm was injection-molded using a general-purpose injection molding machine (J180AD-2M manufactured by Japan Steel Works, Ltd.). That is, the calcium carbonate contained in the molded product was set to 2% by weight. A side gate type mold was used as the mold, and the molding conditions were a mold temperature of 90 ° C., a resin temperature of 270 ° C., and an injection speed of 20 mm / s.

(2) Plating pretreatment (a) Application of electroless plating catalyst The molded product was immersed in an electroless plating catalyst solution at 30 ° C. for 30 seconds. As the electroless plating catalyst solution, 2.1N hydrochloric acid containing 17 mg / L of palladium chloride was used. The molded product was taken out from the electroless plating catalyst solution and then washed with pure water.

(B) Swelling treatment Next, the molded product was immersed in pure water at 70 ° C. for 1 minute.

(3) Plating treatment The pre-plated molded product is immersed in an acidic (pH = 4.8) electroless nickel phosphorus plating solution (Top Nicolon HMB-LF manufactured by Okuno Pharmaceutical Co., Ltd.) at 65 ° C. for 5 minutes. Then, an electroless nickel-phosphorus plating film having a thickness of 1 μm was formed.

Immediately after forming the nickel phosphorus plating film, the molded body is immersed in a nickel sulfamate bath (manufactured by Okuno Pharmaceutical Co., Ltd.) at 55 ° C., which is mainly composed of nickel sulfamate, and electrolytic plating is performed to form a film on the nickel phosphorus plating film. An electrolytic strike plating film having a thickness of 1 μm was formed. By coating the nickel phosphorus plating film, which is easily oxidized, with the electrolytic strike plating film immediately after the formation, the adhesion between the nickel phosphorus plating film and the electrolytic strike plating film immediately above the nickel phosphorus plating film could be maintained. In addition, since the plating film formed by using the nickel sulfamate bath has extremely low internal stress, it was possible to suppress a decrease in the adhesion strength between the molded body and the plating film due to stress.

Next, a 20 μm electrolytic copper plating film was formed on the strike-plated molded body by a general-purpose electrolytic plating method. As the electrolytic copper plating solution, a copper sulfate bath containing copper sulfate, sulfuric acid, hydrochloric acid and a brightener (manufactured by Okuno Pharmaceutical Co., Ltd., Toplucina 2000) was used, and the bath temperature was 30 ° C. and the current density was 3 A / dm ² . .. Further, a 20 μm electrolytic nickel plating film was formed on the electrolytic copper plating film by a general-purpose method. A watt bath containing nickel sulfate, nickel chloride, boric acid and a brightener was used as the electrolytic nickel plating solution, and the bath temperature was 55 ° C. and the current density was 3 A / dm ² .

Next, an electrolytic trivalent chromium-plated film having a film thickness of 0.2 μm was formed on the molded body subjected to electrolytic nickel plating. For electrolytic trivalent chromium plating, a chromium plating additive (manufactured by Okuno Pharmaceutical Co., Ltd., Top Fine Chromium) containing chromium sulfate (trivalent chromium salt) as a main component was used. By the plating pretreatment and the plating treatment described above, a plated molded product was produced without using any hexavalent chromium.

[Example 2]
In this embodiment, the blending ratio of the first resin (masterbatch) and the second resin is adjusted so that the content of calcium carbonate (small particle size inorganic particles) in the molded product is 1% by weight. Except for this, a plated molded product was produced by the same method as in Example 1.

[Example 3]
In this embodiment, the blending ratio of the first resin (master batch) and the second resin is adjusted so that the content of calcium carbonate (small particle size inorganic particles) in the molded product is 10% by weight. Except for this, a plated molded product was produced by the same method as in Example 1.

[Comparative Example 1]
In this comparative example, a plated molded product was produced by the same method as in Example 1 except that calcium carbonate (small particle size inorganic particles) was not mixed with the high-viscosity polyamide 6. That is, the content of calcium carbonate (small particle size inorganic particles) in the molded product of this comparative example was 0% by weight.

[Comparative Example 2]
In this comparative example, the blending ratio of the first resin (master batch) and the second resin is adjusted so that the content of calcium carbonate (small particle size inorganic particles) in the molded product is 15% by weight. Except for this, a plated molded product was produced by the same method as in Example 1.

[Comparative Example 3]
In this comparative example, a plated molded product was produced by the same method as in Example 1 except that the hydrochloric acid concentration of the electroless plating catalyst solution was 3.1N.

[Comparative Example 4]
In this comparative example, a plated molded product was produced by the same method as in Example 1 except that the hydrochloric acid concentration of the electroless plating catalyst solution was 0.5 N.

[Evaluation of plated molded product]
The plated molded articles produced in Examples 1 to 3 and Comparative Examples 1 to 4 were evaluated for the following evaluation items (1) to (4).

(1) Adhesion Strength of Plating Film A sample for measuring adhesion strength was prepared separately from the plated compacts produced in Examples 1 to 3 and Comparative Examples 1 to 4, and the adhesion strength of the plating film was measured. The samples for measuring the adhesion strength were prepared by forming a 50 μm electrolytic copper plating film on the electroless nickel phosphorus plating film formed on the molded body in Examples 1 to 3 and Comparative Examples 1 to 4, respectively. In the sample for adhesion strength measurement, using a tensile tester (manufactured by Shimadzu Corporation, AGS-100N), the length is 40 mm on the sample surface under the conditions of an angle of 90 ° and a speed of 25 mm / min in accordance with JIS H8630. The force when the plating film was peeled off from the sample was measured and used as the adhesion strength. The results are shown in Table 1.

(2) Evaluation of Plating Reaction Unevenness In Examples 1 to 3 and Comparative Examples 1 to 4, the film formation process of the electroless nickel-phosphorus plating film was visually observed, and the plating reaction unevenness was evaluated according to the following evaluation criteria. The results are shown in Table 1.

<Evaluation criteria for uneven plating reaction>
◯: The time from the start of formation of the plating film to the formation of the plating film on the entire molded body was less than 30 seconds.
X: The time from the start of formation of the plating film to the formation of the plating film on the entire molded body was 30 seconds or more.

(3) Evaluation of Appearance of Plating Film The appearance of the plating film was evaluated according to the following evaluation criteria by visually observing the plated compacts produced in Examples 1 to 3 and Comparative Examples 1 to 4. The results are shown in Table 1.

<Evaluation criteria for the appearance of the plating film>
◯: The plating film did not have minute defects such as satin-like irregularities and bright spots, and the mirror-like plating film grew.
X: Small defects such as satin-like irregularities and bright spots were visually recognized on the plating film.

As shown in Table 1, calcium carbonate (small particle size inorganic particles) having an average particle size of 1 μm or less is contained in the molded body in the range of 0.5% by weight to 10% by weight, and the hydrochloric acid concentration of the electroless plating catalyst solution is high. In Examples 1 to 3 which were in the range of 1.0 N to 3.0 N, (1) the adhesion strength of the plating film was as high as 14 N / cm or more, (2) the evaluation result of plating reaction unevenness and (3) plating. The evaluation result of the appearance of the film was good.

On the other hand, in Comparative Example 1 in which calcium carbonate (small particle size inorganic particles) having an average particle diameter of 1 μm or less is not contained in the molded body, the plating reaction on the side surface (8 cm × 0.2 cm surface) of the molded body is slow and plating is performed. The evaluation result of reaction unevenness was poor. Further, the adhesion strength of the plating film was slightly lower than that of Examples 1 to 3. In Comparative Example 1, since calcium carbonate is not contained in the molded body, the amount of palladium chloride adsorbed on the surface of the molded body is smaller than that of Examples 1 to 3, and the amount of palladium chloride adsorbed on the surface of the molded body is uneven. Is presumed to have occurred. Further, in Comparative Example 2 in which calcium carbonate (small particle size inorganic particles) having an average particle diameter of 1 μm or less is contained in the molded body in an amount of 15% by weight, bright spots are generated on the plating film, and the evaluation result of the appearance of the plating film is poor. there were. In addition, the adhesion strength of the plating film was lower than that of Examples 1 to 3. In Comparative Example 2, since the content of calcium carbonate in the molded product is too high, the surface of the molded product is roughened more than necessary, and the appearance characteristics of the plating film formed on the surface of the molded product are deteriorated. It is presumed that the surface became fragile and the adhesion strength of the plating film decreased.

In Comparative Example 3 in which the hydrochloric acid concentration of the electroless plating catalyst solution was 3.1 N, the evaluation result of the appearance of the plating film was poor. In addition, the adhesion strength of the plating film was lower than that of Examples 1 to 3. In Comparative Example 3, since the hydrochloric acid concentration of the electroless plating catalyst solution was too high, the surface of the molded body was roughened more than necessary, and the appearance characteristics of the plating film formed on the surface were deteriorated. It is presumed that the plating film became fragile and the adhesion strength of the plating film decreased. In Comparative Example 4 in which the hydrochloric acid concentration of the electroless plating catalyst solution was 0.5 N, the evaluation result of uneven plating reaction was poor. Further, the adhesion strength of the plating film was slightly lower than that of Examples 1 to 3. In Comparative Example 4, since the hydrochloric acid concentration of the electroless plating catalyst solution was too low, the dissolution of calcium carbonate was insufficient, the amount of palladium chloride adsorbed on the surface of the molded body was small, and the amount of palladium chloride adsorbed on the surface of the molded body. It is presumed that unevenness occurred.

(4) Surface Observation of Molded Body After Immersion in Electroless Plating Catalyst Solution In Example 1, Comparative Examples 1 and 3, the surface of the molded body after immersion in the electroless plating catalyst solution was observed by SEM.

On the surface of the molded product of Example 1 containing 2% by weight of calcium carbonate (small particle diameter inorganic particles) having an average particle diameter of 0.2 μm shown in FIG. 2, it is observed as small dark black dots. Multiple fine holes were confirmed. On the other hand, on the surface of the molded product of Comparative Example 1 in which the calcium carbonate shown in FIG. 3 was not contained in the molded product, almost no fine pores were confirmed. From the comparison between the SEM photograph of Example 1 and the SEM photograph of Comparative Example 1, the fine pores on the surface of the molded body of Example 1 are recesses (pores) formed by dissolving calcium carbonate in the electroless plating catalyst solution. ) Is presumed. In addition, a large number of relatively large white particles were confirmed on the surfaces of the molded products of both Example 1 and Comparative Example 1, and these were wallastnite (large particles) having an average particle diameter of 3 μm contained in the molded product. Diameter inorganic particles). Wallastonite may dissolve in high concentrations of acid. However, in Example 1 and Comparative Example 1, since the electroless plating catalyst solution having a relatively low hydrochloric acid concentration (2.1N) was used, the dissolution of wallastonite did not proceed and large recesses were not formed on the surface of the molded product. It is presumed that it was.

A large number of large recesses were formed on the surface of the molded product of Comparative Example 3 in which the hydrochloric acid concentration of the electroless plating catalyst solution shown in FIG. 4 was 3.1 N. In Comparative Example 3, it is presumed that the surface of the molded product was roughened more than necessary because the hydrochloric acid concentration of the electroless plating catalyst solution was too high. Further, in Comparative Example 4, it is presumed that the wallastnite (large particle diameter inorganic particles) contained in the molded body was dissolved in the electroless plating catalyst solution to promote the roughening of the surface of the molded body.

By observing the surface of the molded product, in Example 1, plating pretreatment is performed with an electroless plating catalyst solution containing an appropriate content of calcium carbonate (small particle size inorganic particles) in the molded product and having an appropriate hydrochloric acid concentration. As a result, it was confirmed that a plurality of fine recesses could be formed on the surface of the molded product without making the surface of the molded product unnecessarily roughened and fragile. It is presumed that this alleviated the uneven plating reaction on the surface of the molded product, and improved the adhesion strength and appearance characteristics of the electroless plating film formed on the molded product.

The method for producing a plated molded product of the present invention can produce a plated molded product having a plating film having high adhesion strength and excellent appearance characteristics. Therefore, the plated molded product produced by the present invention can also be used for decorative purposes where high durability is required.

Claims (9)

It is a method of manufacturing a plated molded product.
To prepare a molded product containing an aliphatic polyamide and inorganic particles having an average particle diameter of 1 μm or less and being soluble in acid, and having an content of the inorganic particles of 0.5% by weight to 10% by weight. ,
An electroless plating catalyst solution containing palladium chloride and hydrochloric acid and having a concentration of hydrochloric acid of 1.0 N to 3.0 N is brought into contact with the molded product.
After the electroless plating catalyst solution is brought into contact with the molded body, the swelling treatment of the molded body and the cleaning of the surface of the molded body are simultaneously performed.
After having been subjected to the swelling treatment and the washing to the molded body, wherein contacting the electroless plating solution in the molded body, looking containing and forming a plating film,
By washing of a surface of the molded body, the manufacturing method palladium concentration in the vicinity of the surface of the molded ^body, a ^{0.01mg / dm 2 ~0.1mg / dm 2} . The production method according to claim 1, wherein the inorganic particles are calcium carbonate. The production method according to claim 1 or 2, wherein the concentration of palladium chloride in the electroless plating catalyst solution is 5 mg / L to 150 mg / L. The production method according to any one of claims 1 to 3, wherein the molded product is brought into contact with water having a temperature equal to or higher than the glass transition point of the aliphatic polyamide as the swelling treatment and washing of the molded product. .. The production method according to claim 4, wherein the temperature of the water in contact with the molded product is 50 to 90 ° C. The production method according to any one of claims 1 to 5, wherein the electroless plating solution is an electroless nickel phosphorus plating solution. The production method according to claim 6, wherein the temperature of the electroless nickel phosphorus plating solution is 50 ° C to 80 ° C. The production method according to claim 6 or 7, wherein the pH of the electroless nickel phosphorus plating solution is 4.0 to 6.0. The production method according to any one of claims 1 to 8, wherein the palladium chloride adsorbed on the outermost surface of the molded product is washed away by cleaning the surface of the molded product.