JPH078518B2 - Molded article manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention has an excellent appearance and surface hardness (scratch resistance), and further, an automobile member, a building material, etc. that requires excellent weather resistance to withstand outdoor use. The present invention relates to a method for producing a molded product that can be used as

(Prior art) As a method of decorating the surface of a plastic product at the same time as molding, a method of pre-patterning the surface of the mold, mounting a transfer film on the inner surface of the mold, and molding the pattern of the film at the same time as molding There have been proposed a method of transferring to the outer surface of an article, a method of attaching a function-imparting or printing sheet to the inner surface of a mold, and simultaneously attaching the sheet to the surface of the article at the same time as molding.

Regarding the latter, for example, in JP-A-60-250925 and JP-B-59-36841, after forming a weather resistance imparting sheet or a printing sheet on the inner surface of a mold, a sheet is obtained by injection molding a molding resin. A method for producing a surface-coated molded article has been proposed.

(Problems to be Solved by the Invention) In the conventional technique, since the decoration and the function are imparted by the transfer of the thermoplastic sheet or the printing, the surface hardness of the obtained molded product is insufficient. It was For example, when imparting weather resistance to a molded product, a high weather resistance sheet made of polyvinylidene fluoride (PVDF) or the like may be used, but since these are thermoplastic, there is a problem that sufficient surface hardness cannot be obtained. is there. On the other hand, in order to obtain a molded product having a high hardness, a sheet having a high hardness must be cross-linked in advance and therefore cannot be applied to a molded product having a three-dimensional shape.

(Object of the Invention) The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention that not only general-purpose molding resins can be used but also the surface hardness is high and the weather resistance is high. Another object of the present invention is to provide a method for producing a molded product having characteristics that are higher than conventional coating performance, such as chemical resistance and chemical resistance.

(Means for Solving the Problems) The method for producing a molded article according to the present invention has a weight average molecular weight of 50,000.
To 1,000,000, a glass transition point is 0 to 100 ° C., an acrylic resin having a solid reactive functional group at room temperature, a crosslinking agent capable of reacting with the reactive functional group of the acrylic resin, a compound having a reactive vinyl group, and A photocurable resin layer formed of a resin composition containing a photopolymerization initiator, and a photocurable sheet obtained by laminating a sheet base material are provided on the inner surface of the mold, and the photocurable resin layer is made of metal. It is mounted so as to be positioned on the mold side, a molding resin is injection-molded in the mold to form a coating body covered with a photocurable sheet, and then the coating body is irradiated with light to form a photocurable sheet. The above object is achieved thereby.

The photocurable sheet used in the present invention has a weight average molecular weight.
Acrylic resin that is solid at room temperature and has a Tg of 50,000 to 1,000,000 and Tg of 0 to 100 ° C; A photocurable resin layer formed of a resin composition is laminated on a sheet base material. As the sheet base material, one having good adhesion to the molding resin is preferably used as will be described later.
Examples thereof include S (acrylonitrile-butadiene-styrene copolymer), vinyl chloride resin, polystyrene, polyolefin such as polypropylene, and fluororesin sheet.

The acrylic resin has a reactive functional group such as a hydroxyl group, a carboxyl group and an amino group, and particularly preferably has two or more of these reactive functional groups. Such an acrylic resin is preferably one produced from monomers such as (meth) acrylic acid ester and styrene derivative monomer. When the acrylic resin has a hydroxyl group as a reactive functional group, examples of the monomer constituting the acrylic resin include 2-hydroxyethyl (meth).
There are acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate and the like, and when the acrylic resin has an amino group,
As the monomer, there are 2-aminoethyl (meth) acrylate, 3-aminopropyl (meth) acrylate, 4-aminobutyl (meth) acrylate and the like, and when the acrylic resin has a carboxyl group, (meth) acryl as the monomer. Acid etc. Further, in consideration of weather resistance, it is desirable that the polymerized units are mainly composed of a methacrylate such as methyl methacrylate (MMA), ethyl methacrylate (EMA), butyl methacrylate (BMA).

The cross-linking agent may be one that can react with the reactive functional group of the acrylic resin, for example, an isocyanate cross-linking agent,
Examples thereof include melamine-based crosslinking agents and epoxy-based crosslinking agents.
Particularly, when weather resistance (yellowing, etc.) is taken into consideration, isocyanate-based crosslinking agents other than epoxy-based crosslinking agents and melamine-based crosslinking agents using amines as catalysts are desirable. Isocyanate-based crosslinking agents include aliphatic ones such as bis (isocyanatomethyl) cyclohexane, dicyclohexylmethane diisocyanate, trimethylolpropane adducts thereof, isocyanurate modified products and urethane modified products. In the agent, trimethylol melamine,
There is an etherified melamine resin obtained by reacting hexamethylol melamine or the like with an alcohol such as propyl alcohol or butyl alcohol.

The compound having a reactive vinyl group is preferably an aliphatic compound having a small number of double bonds per molecular weight in consideration of weather resistance. In consideration of curability, it is desirable that the number of double bonds per molecular weight is large. For example, allylated cyclohexyl diacrylate, dipentaerythritol hexaacrylate, caprolactone modified dipentaerythritol hexaacrylate, methoxylated cyclohexyl diacrylate, neopentyl glycol modified trimethylol propane diacrylate, ditrimethylol propane tetraacrylate, trimethylol propane triacrylate modified Body, aliphatic urethane acrylate, etc., especially molecular weight 200-600, double bond number 2
It is more desirable that -6 contains a cyclohexyl ring in the structure. Further, in order to improve adhesion and flexibility, a long-chain monomer containing a hydroxyl group having only one double bond, for example, caprolactone-modified 2-HEA may be added.

The photopolymerization initiator is preferably an acetophenone-based or benzophenone-based initiator that does not contain an amino group in its molecule, in consideration of yellowing during curing and deterioration during weathering. For example, when forming a transparent film, 1-
(4-dodecylphenyl) -2-hydroxy-2-methylpropan-1-one, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4-isopropylphenyl ) -2-Hydroxy-2-methyl-propan-1-one is preferred. It should be noted that, depending on the molding method, the temperature may temporarily become higher than the boiling point of the initiator. In order to improve the surface curability of the molded product, an oxygen polymerization inhibiting curing agent such as n-methyldiethanolamine may be added.

When a colored film is formed, it is hidden by the film thickness and the pigment concentration, and the resin layer is insufficiently cured by light irradiation.
A photopolymerization initiator having absorption in m), for example, acylphosphine oxide, benzoin isobutyl ether, thioxanthone type, benzyl, camphorquinone and the like are preferable. In addition to this, an oxygen polymerization inhibiting effect inhibitor such as n-methyldiethanolamine may be added to improve the surface curability of the sheet.

The amount of the compound (monomer) having a reactive vinyl group added is preferably 30 to 100 parts by weight with respect to 100 parts by weight of the acrylic resin. The amount of the curing agent (a combination of the photopolymerization initiator and the cross-linking agent) added is preferably 3% by weight or less in terms of the monomer molar ratio because the residual amount after curing affects the weather resistance. The related amine photopolymerization initiator is preferably 0.5% by weight or less. In particular, regarding the amount of the crosslinking agent added, in the case of using the isocyanate-based crosslinking agent, the functional group value of the acrylic resin (the sum of OH value, NH ₂ value and COOH value; N
The H ₂ value is calculated by calculating the amount of NH ₂ groups added during polymerization in the same way as the OH value or by reacting the NH ₂ groups with nitrous acid and converting them into OH groups, and the COOH value is the COOH group added during polymerization. The amount is calculated in the same manner as the OH value or is the value obtained by titrating COOH with KOH. The amount of NCO is preferably such that the functional group value: NCO = 1: 0.8-1.2. Further, when a melamine-based crosslinking agent or an epoxy-based crosslinking agent is used, it is difficult to obtain a fixed value for the functionalization of the acrylic resin, so it is preferable to determine it by preliminary experiments.

The photocurable resin composition may contain colorants such as various pigments or dyes. Known colorants are generally used, and the amount of the colorant added may be such that the relationship between the hidden film thickness of the coating film and the coating film thickness of the molded product is taken into consideration. However, when the resin layer is colored, the absorption wavelength of the photopolymerization initiator differs depending on the color, and therefore it is necessary to select the type of the photopolymerization initiator. For example, when creating a yellow resin layer, the photopolymerization initiator contained in the resin composition is 470 nm
Camphorquinone, which has absorption, is good.

As a method for producing a photocurable sheet, the photocurable resin composition described above is sufficiently dissolved and stirred in an organic solvent or the like, and coated on a sheet base material by a casting method such as a knife coater, a comma coater or a reverse coater, and the solvent is removed. There is a method of making and drying for. Also PE,
When coating the above resin liquid on a sheet base material made of polyolefin such as PP, in order to improve the adhesion between the sheet base material and the photocurable resin layer, a low molecular weight polyolefin or the like is previously formed on the sheet base material. Apply the primer or activate the surface of the sheet substrate in advance by corona discharge, etc. (It is desirable that the corona discharge is performed just before the coating because it has high adhesion immediately after activation. .) Is preferred. The thickness of the sheet base material used here depends on the injection conditions and solvent resistance,
In the case of an ABS sheet, it is preferably about 200-500 μm.

Next, a method for producing a molded article using the photocurable sheet thus produced will be described. The method can be performed using an apparatus as shown in FIG. This apparatus includes a movable mold 4 having a molding recess 41 and a suction port 42,
Sheet cutting device 3, air outlet 21 and heater
It is equipped with a hot platen 2 having 22, a fixed mold 5, and an injection molding machine 7. A photocurable sheet 1 is provided around the movable mold 4.
Is arranged in the recess 41 of the movable mold 4 and the roll 8 for sequentially moving the mold is arranged. The hot platen 2 is configured such that a position near the recess 41 of the movable mold 4 and a position separated from the movable mold 4 are movable.

In order to manufacture a molded product using this apparatus, first, as shown in FIGS. 1 (a) and 1 (b), the recess 41 of the movable mold 4 is first prepared.
The photocurable sheet 1 is arranged at the position. Sheet 1 here
Is arranged so that the photocurable resin layer 1a is located on the movable mold 4 side and the sheet base material 1b is located on the molding resin side. next,
Move the heating platen 2 to the movable mold 4 side to soften the sheet 1,
The sheet 1 is cut by the cutting device 3 to a predetermined size. The heating of the heating platen 2 causes a part or all of the acrylic resin and the crosslinking agent contained in the sheet 1 to react. Next, air is blown from the air outlet 21 of the heating platen 2 to the sheet 1 side, and at the same time, the sheet 1 is sucked from the suction port 42 of the movable mold 4, so that the sheet 1 is mounted on the inner surface of the movable mold 4. Next, while moving the heating platen 2 to the side of the movable mold 4, the movable mold 4 is moved to the side of the fixed mold 5 and clamped,
In this state, a molding resin is injection-filled from an injection molding machine 7 into a cavity formed between the fixed mold 5 and the movable mold 4, and the sheet 1 is formed with a cover formed on the surface thereof.

The temperature of the heating platen 2 depends on the sheet base material, the type of resin and the mold, but is preferably about 100 to 200 ° C. The injection conditions may be ordinary molding conditions.

Next, after opening the movable mold 4, the cover 9 is taken out,
As shown in FIG. 2, it is placed on a conveyor 10 and the surface of the coating 9 is irradiated with ultraviolet light from an ultraviolet irradiation lamp 12 via a cold filter 11. In addition, in FIG.
Is a reflector such as an aluminum plate. The irradiation dose is usually 500-1,0
It is about 00 mJ, and 5,000-10,000 mJ is preferable particularly when the resin layer is colored. The sheet 1 on the surface of the cover 9 is cured by the irradiation of ultraviolet rays to form a hard coating. The surface hardness of the molded product thus obtained is HB or higher in pencil hardness, depending on the composition of the sheet used, and the like, and the weather resistance and chemical resistance are good.

(Function) The photocurable resin layer of the photocurable sheet used in the present invention is
It is formed of a resin composition containing an acrylic resin, a crosslinking agent capable of reacting the acrylic resin, a compound having a reactive vinyl group, and a photopolymerization initiator. Therefore, when this resin layer is irradiated with light, the photopolymerization initiator generates radicals, and the radicals react with the vinyl group of the compound (monomer) having a reactive vinyl group to perform chain polymerization. The monomer is crosslinked and cured.

Then, the resin is injected into the mold with such a photo-curable sheet mounted on the inner surface of the mold, and the surface of the obtained coating is irradiated with light (300-500 nm), thereby the sheet is coated on the surface. It is possible to obtain a molded article on which the cured coating of 1 is formed.

Therefore, a general-purpose resin can be used as the injection molding resin, and the resin mixed in the photocurable resin composition has a weight average molecular weight of 50,000 to 1,000,000 and a glass transition point of 0.
By using an acrylic resin having a temperature of up to 100 ° C, it is possible to form a hard film having excellent weather resistance.

Moreover, since the resin composition of the present invention contains an acrylic resin having a reactive functional group and a cross-linking agent capable of reacting with the acrylic resin, they react and cross-link and cure particularly when heated. become. Therefore, since the resin layer after curing has good releasability from the inner surface of the mold, the coated body can be easily taken out from the mold, and a molded product having a harder coating can be obtained.

(Example) Hereinafter, the present invention will be specifically described based on Examples. In addition, "part" means "part by weight".

Example 1 Acrylic polyol (manufactured by Nippon Shokubai Kagaku Co., Ltd., Arotane)
183, Tg = 40 ° C., OH = 80) 100 parts and titanium oxide (Ishihara Sangyo Co., Ltd., Taipek CR-90) 400 parts and acrylic monomer (Nippon Kayaku Co., Ltd., Calayad DPCA-20, M = 80
7, double bond number 6) 30 parts and photopolymerization initiator (Merck Japan KK, Lucillin TPO, M = 348) 2.5 parts (this additive is 3% molar ratio to the above monomer) n-methyldiethanolamine (manufactured by Wako Pure Chemical Industries, Ltd., M = 12)
1) 0.2 parts (this additive is 0.5% molar ratio to the above monomer) and isocyanate (manufactured by Sumitomo Bayer Urethane Co., Desmodur H, NCO = 50) 12 parts (this crosslinking agent is the above-mentioned reactive acrylic A resin having 1.0 equivalent of isocyanate groups relative to the hydroxyl groups of the resin) was dissolved in 500 parts of ethyl acetate and mixed. This mixture was applied to an ABS sheet (manufactured by Sanpo Resin Co., Ltd., film thickness 500 μm) using an applicator and then dried at 80 ° C. for 30 minutes to give a colored layer 70 μm + base material 500
A μm photocurable sheet was prepared.

The sheet thus obtained is heated by an injection molding machine at 150
After heating at ℃ for 30 seconds, it was vacuum-formed in a plate-shaped mold of 100 × 100 × 10 mm, and ABS resin was injected to obtain an ABS plate. The surface of this ABS plate was irradiated with 5,000 mJ of ultraviolet light by a UV irradiation device to cure the sheet.

Example 2 Acrylic polyol (manufactured by Nippon Shokubai Kagaku Co., Ltd., Arotane
183, Tg = 40 ° C., OH = 80) 100 parts and red organic pigment (Toyo Ink Co., Ltd., Lionogen Red YSK) 100 parts and acrylic monomer (Nippon Kayaku Co., Ltd., Calayad DPCA-20)
M = 807, the number of double bonds 6) 30 parts and a photopolymerization initiator (manufactured by Mekuru Japan Co., Ltd., Lucillin TPO, M = 348) 2.5 parts (this additive has a 3.0% molar ratio with respect to the above monomer). )
And n-methyldiethanolamine (manufactured by Wako Pure Chemical Industries, Ltd.,
M = 121) 0.2 parts (This additive is 0.5 with respect to the above monomer)
% (Molar ratio) and isocyanate (Sumitomo Bayer Urethane Co., Ltd., Sumidule N3200, NCO = 23.0) 26 parts (this crosslinking agent is based on the hydroxyl groups of the above-mentioned reactive acrylic resin).
It was dissolved and mixed in 500 parts of ethyl acetate (having 1.0 equivalent of isocyanate group). This mixture was applied to an ABS sheet (manufactured by Sanpo Resins Co., Ltd., film thickness 500 μm) using an applicator, and then dried at 80 ° C. for 30 minutes to obtain a transparent layer 50 μm + substrate 500
A μm photocurable sheet was prepared.

The sheet thus obtained is heated by an injection molding machine at 150
After heating at 38 ° C. for 38 seconds, it was vacuum-molded in a plate-shaped mold of 100 × 100 × 10 mm, and ABS resin was injected to obtain an ABS plate. The surface of this ABS plate was irradiated with 5,000 mJ of ultraviolet light by a UV irradiation device to cure the sheet.

Example 3 Acrylic polyol (Nippon Shokubai Kagaku Co., Ltd., Arotane)
183, Tg = 40 ° C., OH = 80) 100 parts and carbon black (Mitsubishi Kasei Co., Ltd., MA-100) 60 parts and acrylic monomer (Nippon Kayaku Co., Ltd., Calayad DPCA-20, M = 807) ,
Number of double bonds 6) 30 parts, photopolymerization initiator (Merck Japan KK, Lucillin TPO, M = 348) 2.5 parts (3% molar ratio of this additive to the above monomer) and n- Methyldiethanolamine (Wako Pure Chemical Industries, Ltd., M = 121)
0.2 parts (this additive is 0.5% molar ratio to the above monomer) and isocyanate (manufactured by Nippon Polyurethane Co., Ltd.,
Coronate EH, NCO = 21) 29 parts (this crosslinking agent has 1.0 equivalent of isocyanate groups to the hydroxyl groups of the above-mentioned reactive acrylic resin) was dissolved and mixed in 500 parts of ethyl acetate.
ABS sheet (manufactured by Sanpo Resin Co., Ltd., film thickness 500μ)
m) was coated with an applicator and then dried at 80 ° C. for 30 minutes to prepare a photocurable sheet having a coloring layer of 50 μm + base material of 500 μm.

The sheet thus obtained is heated by an injection molding machine at 150
After heating at ℃ for 30 seconds, it was vacuum-formed in a plate-shaped mold of 100 × 100 × 10 mm, and ABS resin was injected to obtain an ABS plate. The surface of this ABS plate was irradiated with 5,000 mJ of ultraviolet light by a UV irradiation device to cure the sheet.

Comparative example Vinyl chloride resin sheet (Sekisui Chemical Co., Ltd., Tack Paint White 50μ) and acrylic adhesive (Soken Chemical Co., Ltd.)
Manufactured by SK Dyne 1310) 30 μ, and this was attached to an ABS sheet (manufactured by Sanpo Resin Co., Ltd., film thickness 500 μm).

The sheet thus obtained is heated by an injection molding machine at 150
After heating at ℃ for 30 seconds, it was vacuum-formed in a plate-shaped mold of 100 × 100 × 10 mm, and ABS resin was injected to obtain an ABS plate.

Next, Table 1 shows the evaluation of hardness, weather resistance, chemical resistance, and surface resistance of the ABS plates obtained in Examples 1 to 3 and Comparative Example.

In Table 1, the weather resistance is the color difference ΔE after 300 hours using an accelerated exposure tester (Isosuper UV tester).
And the gloss retention rate (%). Acid resistance is 24 with 0.1N sulfuric acid.
It is a time spot test (20 ° C). Alkali resistance is 0.
It is a 24-hour spot test (20 ° C) of 1N sodium hydroxide. The hot water resistance is an immersion test at 40 ° C for 10 days.

(Effects of the Invention) According to the present invention, a general-purpose resin can be used as a molding resin, and a molded article having excellent surface hardness and weather resistance can be manufactured, which is suitable for automobile members, building materials, etc. Can be used for In addition, the number of steps can be omitted as compared with the case of coating the surface of the molded product, and the productivity is also good.

[Brief description of drawings]

FIG. 1 (a) is a schematic view showing an example of an apparatus used in the method for producing a molded article of the present invention, FIG. 1 (b) is an enlarged cross-sectional view of the main part thereof, and FIG. FIG. 3 is a schematic diagram showing the process of FIG. 1 ... Photocurable sheet, 2 ... Hot platen, 3 ... Sheet cutting device,
4 ... Movable mold, 5 ... Fixed mold, 9 ... Cover, 12 ... UV irradiation lamp.

Claims (1)

[Claims] 1. An acrylic resin having a weight average molecular weight of 50,000 to 1,000,000, a glass transition point of 0 to 100 ° C., and having a solid reactive functional group at room temperature, and a crosslink capable of reacting with the reactive functional group of the acrylic resin. A photocurable sheet obtained by laminating a photocurable resin layer formed of a resin composition containing an agent, a compound having a reactive vinyl group and a photopolymerization initiator, and a sheet base material in a mold. The photocurable resin layer is mounted on the side surface so as to be located on the mold side, and a molding resin is injection-molded in the mold to form a coating body covered with the photocurable sheet,
Next, a method for producing a molded article, in which the coated body is irradiated with light to cure the photocurable sheet.