JPH0550967B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention mainly relates to the production of molded products that require aesthetic appeal, such as bathtubs, table tops, and washstands. [Prior Art and Problems] Radical-curable resins, such as polyester resins and vinyl ester resins, can be cured by heating, but if this is attempted on an industrial scale, large heating equipment is required and costs are high. There is a need for a method of curing at the lowest possible temperature, preferably at room temperature. However, in order to cure these curable resins at or near room temperature, an organic peroxide such as ketone peroxide is used as a curing agent, and an organic acid salt of cobalt (naphthenate, naphthenate, etc.) is used as a curing accelerator. octylate) must be used in combination. However, when cobalt naphthenate is used, for example, it has the undesirable drawback that molded products and coatings yellow over time. For example, in the case of artificial marble, which is required to have an extremely light color, discoloration during use is not desirable because it greatly reduces its commercial value. In particular, since gel coat constitutes the surface layer of a resin molded article, discoloration of this layer must be avoided. However, although the use of cobalt salts is undesirable from the standpoint of yellowing of the resin, until now, effective room-temperature or low-temperature curing of the resin has not been possible without the use of cobalt salts. . Further, when an unsaturated polyester resin is used for the casting layer, the adhesion to the gel coat layer is not necessarily sufficient, and there is a risk that peeling may occur between the gel coat layer and the casting layer. [Means and effects for solving the problem] The present inventors have made numerous attempts to avoid the use of cobalt salts, and have found that in order to prevent coloring during room temperature curing, it is necessary to accelerate the curing of peroxide-based curing agents. without using organic acid salts of cobalt as agents.
I learned that it is best to use the photocuring method,
This led to the present invention. Although the photocuring method has been very effective in curing gel coats, other drawbacks have been discovered. The problem is that if it is completely photocured to exhibit sufficient physical properties as a gel coat, it tends to peel off from the next FRP lamination or casting layer. This drawback can be prevented by polishing the gel coat to improve its adhesion, but this significantly increases the number of man-hours and is disadvantageous in terms of productivity. Therefore, in order to avoid this drawback, instead of completely curing with light curing, photo curing is used to advance the curing to an intermediate curing stage, and the final complete curing (cure) is performed using organic peroxide. I discovered that I could achieve my goals by making things work. In addition, since we use a radically curable polymer with a molecular weight of 5000 or more and one or more (meth)acryloyl side chains as the resin for the casting layer,
Adhesion to the gel coat layer is also good and no peeling occurs. Since the curing by light in step () of the present invention can be easily controlled, the curing of the gel coat or the subsequent laminated portion can be adjusted to the necessary degree. After the gel coat layer or, if necessary, the laminated portion has been photocured, casting is performed using a radical curing resin containing a radical curing agent, and this is heated and cured together with the gel coat layer. As a result, the casting part and the gel coat part are cured and bonded together, and a strong molded product without peeling can be obtained. The heating temperature for curing is 100
℃ or less, preferably about 70 to 80℃. The gel coat uses a radical curing resin that can be photocured and cured with organic peroxide. Examples include (a) polyester resin, (b) vinyl ester resin, and (c) urethane-modified vinyl ester resin. The polyester resin (a) contains an unsaturated polybasic acid or its acid anhydride as a necessary component, and the unsaturated polyester obtained by esterifying it with a polyhydric alcohol in combination with a saturated acid is combined with styrene, etc. It is in dissolved form in a polymerizable monomer. In order to be used in the present invention, components that impart hot water resistance to the cured resin, such as neopentyl glycol, hydrogenated bisphenol A, and bisphenol A propylene oxide adduct, are used as the polyhydric alcohol component, and isophthalic acid is used as the saturated acid. , terephthalic acid is preferred. The vinyl ester resin (b) is synthesized by a reaction between an epoxy group and a carboxyl group using an epoxy resin and (meth)acrylic acid. As the epoxy resin, a bisphenol-glycidyl ether type resin having a molecular weight of 350 to 700 is suitable. In addition to (meth)acrylic acid, it is also practical to use polybasic acids or their acid anhydrides together. The form utilized in the present invention is dissolved in a copolymerizable monomer such as styrene. Typically, the styrene monomer is used at 40 to 60% by weight of the resin, more commonly about 50% by weight. The urethane-modified vinyl ester resin (c) is ordinary (b)
Generally, vinyl ester resins are reacted with diisocyanates and used for prepregs, SMCs, etc., but the present invention also uses polyhydric alcohols having a bisphenol structure, such as bisphenol A. is reacted with a monoepoxy compound such as propylene oxide, ethylene oxide, or phenyl glycidyl ether to change the phenolic hydroxyl group to an alcoholic hydroxyl group,
This is modified with urethane. A similar polyol component can be obtained using alkylene carbonate. The type used in the present invention is produced by reacting 2 equivalents of isocyanate groups with 1 equivalent of hydroxyl groups of these polyols having a bisphenol structure, and converting the isocyanate groups into a substantially polyvalent isocyanate oligomer. The hydroxyl groups of the resin are reacted. In order to make these radical curable resins photocurable as the gel coat resin of the present invention, it is necessary to use a photopolymerization initiator together. Various types of photopolymerization initiators can be used, but from the perspective of avoiding coloring of the cured gel coat layer, hydrogen abstraction types that use amines in combination are not suitable, and cleavage type radical generation sources are not suitable. good.
Examples include (a) Acetophenone derivatives, such as 2-hydroxy-2-methyl-1-phenylpropan-1-one (Merck & Co. "Darocure #1173") (b) Benzyl ketals, such as hydroxy-cyclohexyl - Phenyl ketone (Ciba "Irgacure #184"). The gel coat resin of the present invention uses an organic peroxide in combination for final complete curing. The type of organic peroxide used for this is not particularly specified, but in reality, the resin casting and heat curing operations to form the cast layer are performed at 100°C or below. Therefore, it is desirable to use a type that decomposes at relatively low temperatures, for example, 80°C or lower. Examples include ketone perosides, peroxyketal peroxycarbonates, diacyl peroxides, and peroxy esters whose decomposition temperature is below 120°C to obtain a half-life of 10 hours.
Among these, peroxycarbonate and peroxy esters are advantageous, and if appropriate curing temperature and handling safety are taken into account, bis(t-butylcyclohexyl) peroxydicarbonate (Kayaku Nouri) is preferred. Company “Parkadox #16”) is suitable. Combination use with other peroxides is also possible. The radical-curable resin used for the casting layer in step () of the present invention is in the form of a monomer solution of a radical-curable polymer having one or more (meth)acryloyl groups in the polymer side chain with a molecular weight of 5000 or more. It is. This unsaturated polymer having a (meth)acryloyl group in its side chain (hereinafter simply referred to as unsaturated polymer) is synthesized by the following method. (i) A polymer having a hydroxyl group in its side chain is reacted with an unsaturated isocyanate having a methacryloyl group. (ii) A polymer having an epoxy group in its side chain is reacted with (meth)acrylic acid. (iii) A polymer having an acid anhydride group in its side chain is reacted with an unsaturated alcohol having a (meth)acryloyl group. This is shown in the formula below. (a) Urethane type unsaturated polymer (b) Vinyl ester type unsaturated polymer (c) Ester type unsaturated polymer All of the polymers that serve as raw materials for unsaturated polymers are synthesized by polymerizing monomers, but urethane-type unsaturated polymers can also use side-chain hydroxyl polymers, such as cellulose derivatives, but they have drawbacks such as cost and boiling resistance. Therefore, it can be said that a vinyl monomer polymerization type is preferable. Existing methods can be used for polymerization, but direct polymerization is convenient in terms of handling of subsequent steps. These casting unsaturated polymers are used as a mixture with a monomer solution, for example styrene monomer. The mixing ratio is usually 30 to 70% in terms of polymer concentration.
Preferably it is 40-60%. When casting and curing resin, a filler is usually used in combination with the casting resin to provide a suitable degree of transparency and to prevent cracks due to heat generation during curing and molding. Glass powder, aluminum hydroxide, etc. are commonly used as fillers. Furthermore, in the composition and method of the present invention, it is of course possible to use a coloring agent, a mold release agent, a thixotropy imparting agent, a thermoplastic polymer, etc. in combination, if necessary. Next, in order to further explain the present invention, Examples are shown below. Example 1 (Production of vinyl ester resin (A) for gel coat)
In a separable flask equipped with a stirrer, a reflux condenser, a gas inlet tube, and a thermometer, add a bisphenol liquid resin (Yuka Ciel Epoxy Co., Ltd. Epicote 827) with an epoxy equivalent of 175 as an epoxy resin.
and 75 g of isophthalic acid, reacted at 170 to 190℃ for 3 hours in a nitrogen stream, and then lowered the temperature to 135℃.
0.3g of hydroquinone, methacrylic acid
86g of trimethylbenzylammonium chloride, 0.5g of chromium naphthenate, and 1.5g of chromium naphthenate were charged, and after reacting for 3 hours at 130-135℃ in an air stream, styrene
When 100 g was added and the reaction was further continued at 115-120°C for 1 hour, the acid value became 9.1. At this stage, 380 g of styrene was further added to synthesize vinyl ester resin A for gel coat. This resin had a Hazen color number of 350 and a viscosity of 11.4 poise. (Production of casting resin B (urethane type unsaturated polymer)) Styrene was added to a two-separable flask equipped with a stirrer, reflux condenser, gas inlet tube, and thermometer.
Weighed 936 g and 130 g of 2-hydroxylethyl methacrylate (HEMA), and heated them at 120°C in a nitrogen stream for 6 hours.
After heating for a period of time, the reaction rate reaches approximately 42%, and free
As a result of gas chromatography analysis, it was determined that HEMA amounted to about 14% of the initial amount. Add 0.2g of hydroquinone and lower the temperature to 70℃.
Switch to air flow, add 140 g of isocyanate ethyl methacrylate and 3 g of dibutyltin dilaurate, and react at 70°C for 5 hours, resulting in a Hazen color number of 30 and a viscosity.
Casting resin B of 11.4 poise was obtained. Infrared analysis confirmed that free isocyanate had disappeared. (Formation of gel coat layer) 100 parts by weight of vinyl ester resin A (same below)
5 parts of Erosil R-200 was added to the mixture and kneaded with a three-roll mill to impart thixotropy. To 100 parts of this resin A, 0.5 parts of a coupling agent (Nitto Unicar Co., Ltd. A-174), 2 parts of "Darocure #1173" manufactured by Merck & Co. as a photoinitiator, and 1 part of "Parkadox #16" manufactured by Kayaku Nouri Co., Ltd. were added as photoinitiators. A gel coat of the present invention was prepared by adding a portion of the gel coat, and this was used as a gel coat composition (). On a 30cm x 30cm x 5mm glass plate coated with a release agent, apply gel coat () to a thickness of 0.5mm using a bar coater, wait until the coated surface is even, and then apply a 250W sun lamp ( Stanley Electric Co., Ltd.
When the gel coat layer was irradiated for about 15 minutes at a distance of 30 cm from the bottom of the gel coat (manufactured by Manufacturer Co., Ltd.), the gel coat layer was hardened to the extent that it was dry to the touch. (Casting, heating, and curing) With this as one side, another 2 mm thick FRP made of white colored glass mat was placed, and the interval between them was 10 mm. During this time, 100 parts of casting resin B manufactured by the following process was placed. , 200 parts of Fritz B-10 manufactured by Nippon Fellow Co., Ltd., and Perbutyl PV manufactured by Nippon Oil & Fats Co., Ltd.
1.5 parts, mixed, degassed and cast at 70℃ for 2 hours, 80℃
It was allowed to cure for 2 hours. After cooling and demolding, a molded product 1 was obtained. Comparative Example 1 To 100 parts of vinyl ester resin A, 1.5 parts of Kayaku Nouri Co., Ltd. 328E as an organic peroxide, 0.3 parts of cobalt naphthenate (6% Co), and ST Cure of Nippon Fine Chemical Co., Ltd. as a curing accelerator. Add 0.3 parts and 5 parts of Erosil R-200 to create a gel coat composition ()
This was applied to a glass plate in the same manner as in Example 1, photocured, cast with resin B, and cured by heating to obtain molded article 2. Each molded product obtained in Example 1 and Comparative Example 2 was
The sample was cut into pieces of 15 cm x 15 cm, placed in a boiling test container with four circular openings each side having a diameter of 10 cm, with the gel coat layer facing inside, and a boiling test was conducted at a temperature of 98 to 99°C. The results are shown in Table 1. As can be seen from Table 1, the molded product produced according to the present invention was superior.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to obtain an excellent molded product without yellowing of the gel coat layer or peeling between the gel coat layer and the casting layer.

Claims (1)

[Scope of Claims] (1) As a photocurable resin, one or more selected from (a) polyester resin, (b) vinyl ester resin, (c) urethane-modified vinyl ester resin, and (2) photopolymerizable resin. Initiator (3) A composition prepared by mixing an organic peroxide and containing substantially no organic acid salt of cobalt is applied as a gel coat to a mold, and the gel coat is irradiated with light to the desired degree of curing. After curing, a monomer solution of a radically curable polymer having one or more (meth)acryloyl groups in the side chain and having a molecular weight of 5000 or more is cast, with or without backing with glass fibers. A method for producing a molded article, which comprises heating and curing a gel coat layer and a casting layer.