JPS5945502B2 - Manufacturing method for synthetic resin molded products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a synthetic resin molded article, particularly a synthetic resin molded article having a desired surface hardness, and a method for producing the same.

Molded products of synthetic resins, such as thermoplastics,
Because of its flexibility in processing, it is widely used in all fields such as structural articles, household goods, and functional parts.

Furthermore, such plastic molded products exhibit far superior durability than other materials depending on the application. However, when plastic molded products are used as exterior materials, such as the covers of various meters, the top cover of record players, the lenses of dry battery lights, the covers or lenses of various automobile lamps, and various mirrors, the surface can easily be scratched by dust and dirt. arise. Therefore, the appearance of molded products used as exterior materials is significantly impaired. The scales and needles on the covers of various meters become difficult to read. For lenses, the transmittance of light rays decreases and the lens loses its function. Such problems have been pointed out especially with conventional plastic molded products, and are considered unavoidable. If such a problem could be solved,
The durable life of plastic products can be greatly extended, resulting in many benefits such as increased added value and expanded uses for plastic products. One method of improving the scratch resistance of plastic products is to coat the surface of the plastic molded product with another hard material (hard coating agent) to improve its surface hardness. Examples of already known hard coating agents include epoxy resin-based, acrylic resin-based, amino resin-based, polysiloxane-based hard coating agents, etc.
Some of them are already in practical use. These hard coating agent compositions are actually dissolved in a suitable solvent and applied to injection molded products as a hard coating film with a thickness of several microns to several tens of microns by means such as spray coating or dip coating. be done. This hard coat film is then hardened by means such as heating or ultraviolet irradiation. Thus, surface hardening of plastic moldings is carried out by a two-stage processing method. Although this two-stage processing method improves the surface hardness of the target product, it is not preferred from the viewpoint of industrial production because of the following reasons. (1) Frequency of defective products 1.1 Injection molded products always have molecular orientation and residual stress.

When heat treatment is performed to harden the hard coat film applied to a molded product, the molded product always undergoes dimensional changes such as warpage and twisting due to this molecular orientation and residual stress. As a result, cracks and cracks occur, resulting in product defects. 1.2 Curing by heat treatment similarly causes dimensional changes in the molded product, making it impossible to fit the molded product into a predetermined object, and ultimately disposing of the molded product as a defective product.

1.3 Since plastic materials are highly electrostatically charged, contamination due to electrostatic adhesion of dust and the like cannot be completely avoided in the two-stage processing process.

Therefore, the application of the hard coat agent to the molded article is incomplete, and the purpose of surface hardening cannot be achieved. In fact, it is said that this is the main cause of the defect rate that occurs in industrial production using the two-stage processing method, which is 10 to several tens of percent. (2) Non-uniformity of surface hardness 2.1 It is not possible to form a hard coat film with a uniform thickness by coating means such as spray painting or dip coating.

As a result, the surface hardness of the product becomes uneven. If there are irregularities on the surface of the molded product, the thickness of the coating film will be uneven, and as a result, the appearance will be significantly impaired. (3) Complexity of coating technology 3.1 When dip coating only the external surface of a product, the non-painted areas must be masked.

When the non-painted part has a complicated shape and structure, the complex shape and structure must be masked in accordance with the shape and structure. (4) High cost 4.1 A large amount of expense is required to transport the molded product.

4.2 If the place where the plastic is molded and the place where the hard coat agent is applied are far apart, a great deal of labor and expense is required to prevent the molded product from being scratched or stained by dust.

4.3 Painting equipment is expensive.

4.4 In order to prevent the adhesion of dust and other substances due to the electrostatic properties of plastic materials and to achieve the purpose of surface hardening, it is necessary to take great measures to purify the air or create a vacuum space to avoid contamination due to electrostatic adhesion. Requires advanced equipment.

The above-mentioned problems have traditionally been fatal obstacles to the surface hardening treatment of synthetic resin products such as plastic products.
This is also the reason why surface hardening of various products has not yet been widely achieved industrially.

The present invention solves the above-mentioned problems), and its purpose is to provide a synthetic resin molded article having uniform surface hardness.

Another object of the present invention is to provide a method for obtaining synthetic resin molded articles having a desired surface hardness on an industrial scale using simple techniques. Still another object of the present invention is to provide a method for obtaining a molded product having a desired surface hardness with almost zero defective rate. Still another object of the present invention is to provide a method for obtaining a molded article having a desired surface hardness at a significantly low cost. Still another object of the present invention is to
It is an object of the present invention to provide a molded article having a desired surface hardness and a method for producing the same, which exhibits the same effect as if additives such as ultraviolet absorbers and colorants were added to the molding material without adding them. Other objects of the invention are described below.
It will become clear from the text and drawings. The present invention will be explained below. First of all, a thermoplastic plastic film or sheet with as little molecular orientation or residual stress as possible is prepared as a base film or sheet.

This film or sheet is molded to a predetermined thickness by a known extrusion method or the like. Next, this film or sheet is subjected to surface treatment such as washing or cleaning, and one side, for example, the front or back side, is precoated with a precoat liquid. An organic or inorganic hard coating agent is applied to this precoated surface to a predetermined thickness (this precoating treatment may be omitted depending on the combination of the film and the hard coating agent). Next, this applied hard coating agent is sufficiently cured in an ultraviolet or infrared oven. The cured plastic film or sheet is stored, for example, by being rolled.
This thermoplastic plastic film or sheet is
For example, it is formed from polymethyl methacrylate, MMA-styrene butadiene copolymer resin, polycarbonate, polymethylbenzene, saturated polyester film, polystyrene film, and the like. The thickness of this film or sheet can be arbitrarily selected depending on the degree of surface hardness required and the type of hard coating agent used, depending on the intended use of the synthetic resin molded product finally obtained. The range is selected, for example, from about 20 microns to about 2000 microns, preferably from about 50 microns to about 500 microns. As the above-mentioned hard coating agent, known examples include:
Hard coating agents such as epoxy resin, acrylic resin, amino resin, and polysiloxane are used. When the film or sheet is made of polycarbonate, the pre-coating treatment of the film or sheet prior to the above-mentioned hard coating agent application step is, for example, r-
This is carried out using a precoat liquid containing aminopropylmethoxysilane, alcohol, and water, or a precoat liquid containing a thermosetting acrylic modified resin solution. The hard coat film-formed plastic film or sheet is transported to an injection molding factory as required. Here, the term "hard coat film" refers to a hardened or crosslinked resin hard coat agent made of at least one of epoxy resins, acrylic resins, amino resins, polysiloxanes, and copolymers of these monomers. A surface coating with excellent scratch resistance obtained by coating and curing the surface of a plastic film or sheet. The above-mentioned hard coat film-forming plastic film or sheet brought in is
A piece having the desired external shape of a synthetic resin molded product is punched out. This punched piece can be obtained by a known punching device.
Next, the movable mold 2 of the mold 1 as shown in FIG. 1, which is attached to an injection molding machine for molding a desired molded product, is opened, and the punched piece 4 is mounted in the cavity portion 3.
This punched piece 4 is placed on the cavity surface 31, which is the outer surface of the molded product, so that the hard coat film forming surface 41 is located on the outermost surface of the synthetic resin molded product as the final product. The movable die 2 is closed while the arranged punched piece 4 is held on a predetermined cavity surface by an appropriate method. Next, the molten resin 5 is injected into the cavity 3 through an injection molding machine nozzle so that the hard coat film forming surface 41 of the punched piece 4 becomes the outer surface of the final molded product and the hard coat film non-forming surface 42 becomes the inner surface. It is injected at high pressure from an injection molding means 6 such as. This molten resin 5 is preferably a thermoplastic of the same kind or type as the plastic film or sheet. The molten resin 5 injected under high pressure enters the cavity 3 through the sprue 10. As soon as the molten resin 5 that has entered the cavity part 3 comes into contact with the cavity surface directly or indirectly through the punched piece 4, it is cooled and instantly solidified into layers 51, 51.
form. The solidified layers 51, 51 adhere to the cavity surface and never slip. The uncooled fluidized bed 50 is
The injection pressure flows inside the already formed solidified layers 51, 51) further forward than the already formed solidified layers. Similarly, the fluidized bed 500 flowing forward, that is, the molten resin, is cooled and forms a new solidified layer as soon as it comes into contact with the cavity surface directly or indirectly through the punched piece 4. In this way, the molten resin 5 injected into the cavity 3 forms a solidified layer 51, 51 on the gear surface or the contact surface with the punched piece, as if it were moving forward while laying a carpet in a hallway. It invades the cavity part 3 in a certain manner. As a result, the plastic film or sheet of the punched piece 4 is instantaneously shaped by the molten resin within the cavity portion 3 along the cavity surface without ever shifting even a small amount from the initial installation position. On the other hand, the hard coat film-free surface 42 of the punched piece 4 of the plastic film or sheet is the interface 4
2 is melted by the heat of the molten resin 50. Molten resin 50
Since the plastic film or the non-film-formed surface 42 of the punched piece 4 are made of the same type or type of resin, they are compatible through the interface 42. Therefore, the punched film or sheet and the molten resin are completely integrated at the interface 42. Although the hard coat film on the punched film piece 4 is hard and brittle, it can withstand high injection pressure in the mold 1 and is not damaged in any way. This is because the punched film strip 4 carrying the hard coat film functions as a shock absorber. Next, the synthetic resin molded product is taken out from the mold 1 after cooling. The molded product is a product in which the desired portion is completely covered with a hard coat film. This product does not require any further processing. The punched pieces of the plastic film or sheet can also be placed in the mold cavity so that they are located on both the outermost and innermost surfaces of the final molded product. In this case, both the outer and inner surfaces of the final molded product will be covered with the hard coat film. As a molding device for molding a molded product, only a known injection molding machine and a mold are required, and no special incidental equipment or special mold structure is required. In addition, if the molten resin and the plastic film or sheet are closely related resins,
As described above, the interface 42 of the film or sheet is melted by the heat of the molten resin, and the film or sheet and the molten resin are compatible and completely integrated.

If the film or sheet and the molten resin are of different types or systems, an adhesive such as an elastomer adhesive mainly composed of polyvinyl butadiene or acrylic acid-butadiene is applied to the surface of the film or sheet on which the hard coat film is not formed. -By applying an elastomeric adhesive such as an acrylonitrile-based copolymer in advance)
, this film or sheet and the molten resin can be integrated. In addition, by pre-mixing additives such as colorants or ultraviolet absorbers into the film or sheet, it is possible to color the plastic molded product with the desired color without mixing such additives into the molten resin material. It is possible to provide ultraviolet absorption performance. In addition, if desired characters or codes are printed in advance on the opposite side of the film or sheet from the hard coat film surface, the characters or codes will not disappear over time because they will not be located on the outer surface of the molded product. . Next, one embodiment of the present invention will be shown. Example 1 (Production method of thermoplastic plastic film or sheet with hard coat film formed) As shown in FIG. 3, a polycarbonate film 100 molded to a predetermined uniform thickness (100 microns) by extrusion molding is used as a cleaning layer. 10
Washed at step 1.

In this cleaning layer 101, cleaning or activation processing of the film is performed. For example, in this embodiment, the tank 101 is divided or expanded, and known film surface treatments such as chromic acid sulfuric acid treatment and water washing are performed. This film 100
is then dried in a dryer 102. film 10
0 is then coated with an undercoat agent primer (for example, methyl acrylate, ethyl acrylate, α-methacryloxypropyltriethoxysilane, and BPO disclosed in Patent Publication No. 50-116600) using an undercoat roll coater 103. acrylic pretreatment agent, etc.) 104 is applied. This film coated with an undercoat agent is quickly dried in a dryer 105, and then a hard coat agent 107 is coated on one side of the film by a hard coating roll coater 106 for about 20 minutes.
It was applied to a thickness of ~10 microns. As the hard coating agent 107, a partial hydrolyzate obtained by adding an acid to a mixture of methyltrimethoxysilane, tetraethoxysilane, and dimethylpolysiloxane at both molecular ends disclosed in the above-mentioned patent publication was used. Next, the film was heat-treated at about 130° C. for 1 hour in a dryer 108 to obtain a desired hard coat film 109. This film 109 ultimately constitutes a multilayer consisting of at least a hard coat layer, an undercoat layer, and a base film. This hard coat film-formed film 109 was sequentially wound into a multi-roll 110. This hard coat film-formed film 109 was obtained by continuously applying the hard coat agent 107 to the film 100, so that a hard coat film having a desired uniform thickness without any unevenness was formed on the film 109. was. Note that the model of the dryer 108 was selected depending on the type of hard coating agent.

For example, an ultraviolet oven was used for an ultraviolet curable hard coating agent, and a hot air oven, an infrared oven, or a far-infrared oven was used for a silane hard coating agent. Example 2 (Method for manufacturing a plastic molded article having a desired surface hardness) The hard coat film formed film obtained in Example 1 was prepared in a diameter of 507F! A U-shaped circular cut-out injection mold (lens mold with a diameter of 50 mm) was fitted into the cavity part of the mold so that the hard coat film forming surface was the outer surface.

Next, under general molding conditions, a molten polycarbonate resin material was injected into the cavity at high pressure using an injection molding machine, and after cooling, the molded product was taken out. In the obtained molded product, the hard coat film-forming film and the molded resin material were completely integrated, and no boundary line could be discerned. Also,
The hard coat film layer on the outermost surface of the plastic molded article had a good appearance and maintained a perfect surface condition.
The molded product had excellent scratch resistance, with no damage even when the surface was rubbed with a metal scrubber. The cost required to produce this molded article was approximately half the cost of a similar product made using the prior art. Example 3 In exactly the same molding as in Example 2, a hard layer was applied to the surface of the cavity part 3 located astride both the movable mold 2 and the stationary mold 7 of the mold 1 (shown in FIG. 1). The coated film-formed film was placed in an apparatus such that the hard-coated film-formed surface was the outer surface of the molded product.

Molten material was injected at high pressure between the two films.

After waiting for cooling, the molded product was taken out. The lens molded product was a completely surface-hardened lens with hard coat film layers on both sides and excellent scratch resistance. Example 4 A polymethyl methacrylate film having a thickness of 4200 microns was washed with water in a washing tank 101 using the apparatus shown in FIG. Oxypropyltrimethoxysilane 15: N-3-aminoethyl-γ-aminopropyltrimethoxysilane 30: Polyethyl glycol diglycidyl ether 10: Perchloric acid 0.03: Water 10
: dioxane 50 reactant) was coated on one side thereof.

The applied hard coat film was cured by heat treatment at 1100C for 1 hour.

This hard coat film forming film was attached to one side of the mold cavity of the injection molding apparatus of Example 2 so that the hard coat film forming surface was located on the outer surface of the molded product. The molten acrylate resin was filled under high pressure. After waiting for cooling, the molded product was taken out. A hard coat film layer with good gloss and excellent scratch resistance was formed on the outer surface of the desired side of the molded article. Example 5 Colorant 0PLA was added to the plastic film of Example 4 above.
5/11,000 parts of SYELL0VF145 (manufactured by Orient Chemical Industries, Ltd.) was mixed in to give it a transparent yellow color.

Although the molded resin was colorless and transparent, the molded product obtained had the performance as a yellow lens. Example 6 The plastic film of Example 4 above was mixed with 0.05% of 4-methoxy-2-hydroxybenzophenone, a commercially available ultraviolet absorber.

Although the molded resin is colorless and transparent and contains no additives, no discoloration could be observed in the resulting molded product even after 200 hours of continuous irradiation with ultraviolet rays using a Sunshine Weatherometer. Ta. Further, even when the mold was used repeatedly, no signs of mold corrosion caused by the contamination of the ultraviolet absorber as in the prior art were observed. Example 7 A 500 micron thick MMA-styrene butadiene copolymer resin film was washed with water, treated with a chromic acid/sulfuric acid solution at 500C for 5 minutes, and one side of the film was coated with a commercially available acrylic coating agent (manufactured by Fujikura Kasei Co., Ltd.). was applied to a thickness of about 20 microns and irradiated with ultraviolet rays of 20 W/CfL for 3 minutes to cure the coated film and obtain a desired hard coat film.

This hard coat film-formed film was cut to match the dimensions of the cavity of a predetermined instrument panel mold, and was mounted on one side of the cavity so that the hard coat film-formed surface was the outer surface. Next, the molded product was injection molded using polystyrene as a molding resin under normal standard conditions, and the molded product was taken out after cooling. The obtained meterpaneo molded product had excellent appearance and sufficient scratch resistance. Implementation 8 M
When the BS copolymer resin was used, it was possible to obtain a meter panel molded product having the same appearance and the same excellent scratch resistance.

Example 9 An elastomer adhesive containing polyvinyl butyral as a main component was applied to the surface on which the hard coat film was not formed of the hard coat film formed using the MMA-styrene butadiene copolymer resin used in Example 7 above.

This adhesive-coated film was cut to the same size as the mold cavity of Example 7, and attached to the cavity so that the surface on which the coated film was formed was the outer surface of the plastic molded product. Polymethylbenzene was used as the molding resin. The hard coat film-forming film was integrally adhered to the obtained molded product via the adhesive. The surface of the molded product had excellent scratch resistance as in the previous example. Example 10 ABS copolymer resin, AS, and nylon were used in place of the molding resin polymethylbenzene in Example 9 above.

Similarly to Example 9, the surface of the molded product had excellent scratch resistance (the hard coat film-forming film was integrally bonded to the molded product via an adhesive).
Example 11 A hard coat film-forming film coated with an elastomer pressure-sensitive adhesive of acrylic acid-butadiene-acrylonitrile copolymer was used in place of the butyral adhesive of Example 9, and polystyrene and polystyrene were used as the molding resin materials, respectively. ABS copolymer resin and nylon were used, respectively.

As in Examples 9 and 10 above, the molded product has a hard coat film forming film integrally adhered to the molded product via an adhesive, and the outermost surface thereof has excellent scratch resistance. Ta. Example 12 One side of a polycarbonate film is coated with a thermoplastic acrylic resin such as polymethyl methacrylate in an amount of 0.5 to 2.
Using a solution obtained by dissolving in ethylene glycol monoethyl ether or ethylene glycol monomethyl ether to a concentration in the range of 0%, particularly 2 to 5%, as an undercoat agent, the desired coating was applied under the same conditions as in Example 1.・
- A coated film was obtained.

This film showed strong adhesion without curling during the hard coating treatment. A molded article was obtained in the same manner as in Example 2 using this film. The film was completely adhered to the molded resin material. Even when this molded article was subjected to a heat resistance test at 120° C. for 60 minutes and a boiling test for 2 hours, no change in its appearance was observed. Thus, this molded article has heat resistance and boiling resistance. Further, even when the outer surface of this molded article was rubbed 400 times with steel wool under a pressure of 509/Cd, no scratches were observed. Furthermore, no change was observed on the surface even when a base peel test using zero tape was performed. The present invention has the following excellent effects. (1
) Simplicity of the technology 1.1 The technology of the present invention is an extremely simple method in which a hard coat film-forming film is applied to the cavity of a mold for molding a molded product, and molten resin is injected into the cavity to obtain the desired molded product. It's technology.

1.2 Plastic films or sheets are mainly produced by extrusion methods.

Therefore, films or sheets with significantly less molecular orientation and residual stress can be easily produced. 1.3 There is no need to perform complicated masking as in the prior art on parts of the molded product where surface hardening treatment is not desired.

(2) Zero defective rate 2.1 The technique of the present invention is extremely simple, so it is possible to reliably obtain the desired product without requiring any skill.

2.2 As stated in item 1.2 above, plastic films or sheets have extremely low molecular orientation and residual stress, so no cracks occur even when the solvent in the hard coating agent is applied.

In addition, by selecting a plastic film or sheet with a higher molecular weight than the grade of the injection molding material, it is possible to raise the baking temperature of the hard coating agent, thus quickly producing a high quality hard coating film. can do. 2.3 Even if there is some molecular orientation or residual stress in the injection molded product, can it be heat treated as in the conventional technology?
[No dimensional changes occur because no process is required.]

Therefore, no deformation or cracks occur in the product. λ4
Since there are no dimensional changes in the injection molded product, it can always be fitted into the specified mating part. 2.5 There is no defective rate due to dust or dirt on molded products.

2.6 Even for molded products with some degree of curvature, it is possible to uniformly impart the desired surface hardness to the deformed molded product by thermally shaping the plastic film or sheet into the desired shape within the mold. can.

(3) Uniformity of surface hardness Since the process of applying the hard coat agent to the 3,1 film or sheet can be carried out continuously, a hard coat film having a desired uniform thickness without unevenness can be formed.

3.2 The film or sheet on which the coated film of desired uniform thickness has been formed is integrated with the molded product in a mold so that the film side is located on the outer surface of the molded product.

Therefore, the surface of the resulting product has uniform hardness. 3.3 Even for molded products that have some deformation such as unevenness, the hard coat film-forming film or sheet is thermally shaped in the mold to uniformly give the deformed molded product the desired surface hardness. be able to.

(4) Low cost 4.1 The process of applying hard coating agent to plastic film is carried out continuously, making process control easy.
Therefore, production costs can be reduced.

4.2 Even if the manufacturing location of the hard coat film forming film and the molding location of the molded product are far apart, there is no need to transport the molded product as in the conventional technology, and a means for preventing dust from adhering to the molded product There is no need to lecture.

Therefore, transportation costs can be kept to a minimum. 4.3 By pre-mixing additives such as colorants and ultraviolet absorbers into the plastic film, it is possible to prevent corrosion of the mold that would occur if such additives were added to the molding material.

Therefore, the life of the mold is long and the cost is low. Further, there is no need to perform complicated color changes of the molten material in the molding machine. (5) Industrial Production 5.1 As is clear from items (1) to (4) above, it is extremely easy to industrially produce molded products having a desired surface hardness.

(6) Others 6.1 If the plastic film is made of polymer grade, the strength and physicochemical properties of the resulting product can be improved.

6.2 By coloring the plastic film in a desired color in advance, it is possible to impart desired coloring properties to the entire or local part of the resistive molded product.

6.3 By pre-mixing an ultraviolet absorber into the plastic film, it is possible to obtain the same effect as if the absorber were added without adding such an absorber to the molded resin material.

6.4 By forming a suitable adhesive layer on the surface of the plastic film on which the hard coat film is not formed, it is also possible to produce a molded article in which the plastic film and the molding resin material are made of different resin materials.

6.5 Any type of hard coating agent may be applied to the plastic film or sheet of the present invention.

[Brief explanation of the drawing]

Fig. 1 is a partial cross-sectional side view illustrating one embodiment of the molding process of a plastic molded article of the present invention, Fig. 2 is a partially enlarged side cross-sectional view thereof, and Fig. 3 is a manufacturing process of a hard coat film forming film or sheet. It is a process diagram showing one example of. DESCRIPTION OF SYMBOLS 1... Mold, 3... Cavity part, 4... Punching piece, 5... Molten resin, 50,500... Fluidized bed,
51... Solidified layer, 100... Plastic film or sheet, 103, 106... Roll coater,
104... Undercoat agent, 107... Hard coat agent, 109... Hard coat film forming film.

Claims (1)

[Claims] 1. A hard coat plastic film or sheet of an appropriate shape obtained by applying a hard coat agent to one side of a thermoplastic plastic film or sheet and curing it, with the hard coat film surface facing the inner surface of the mold. A method of manufacturing a synthetic resin injection molded article having a desired surface hardness by placing the molds in contact with each other and then injecting a molten resin for molding the molded article into the mold at high pressure. 2. The method according to claim 1, wherein the resin material of the molded article is a thermoplastic. 3. The appropriately shaped hard coat plastic film or sheet is inserted into the cavity of the mold so that the hard coat agent coated surface is located on both the outer and inner surfaces of the synthetic resin molded product. 1
The method described in section. 4. The method according to claim 1, wherein the molded article is molded by high-pressure injection molding. 5. The method according to claim 1, wherein the thermoplastic film or sheet is molded by an extrusion method that is less likely to cause residual stress and molecular orientation. 6. The method according to claim 1, wherein the molded product has the ability to be colored in the desired color by mixing a desired coloring material into the plastic film or sheet in advance. 7. The method according to claim 1, wherein the molded article has ultraviolet absorbing performance by mixing an ultraviolet absorber into the plastic film or sheet in advance. 8. The method according to claim 1, wherein the resin material of the molded article and the material of the plastic film or sheet are the same type or resin of the same type. 9. The method according to claim 1, wherein the resin material of the molded article and the material of the plastic film or sheet are different types or different types of resins. 10. The method according to claim 9, wherein the molded article and the plastic film or sheet are integrated via an adhesive.