JPH08216173A - Production of in-mold coated resin molded product - Google Patents

Abstract

PURPOSE: To produce a resin molded product not generating the deterioration of characteristics or appearance, excellent in the close adhesivenss with an in-mold coating layer and having good hot water resistance by supplying a resin molding material into a mold to degass the same under reduced pressure and setting the temp. of the mold lower than the b.p. of the crosslinking agent in the resin molding material under reduced pressure. CONSTITUTION: An in-mold coated resin molded product is produced by subjecting a thermosetting resin molding material to heating compression molding within molds and loosening the mating of the molds in such a state that the molding material is cured or semicured to inject an in-mold coating material into the molds. After the resin molding material is supplied into the molds, the cavity of the molds is degassed under reduced pressure and the temp. of the molds is set lower than the b.p. of the crosslinking agent in the resin molding material under reduced pressure. By performing the heating compression molding under a specific vacuum degassing condition, the volatilization of the crosslinking agent is prevented. Therefore, a molded product sufficiently cured while suppressed in the deterioration or discoloration caused by hot water as low as possible can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an in-mold coated molded article by curing the molding material and coating the surface of the molded article in the same mold. The present invention relates to a method for producing a molded article having an excellent appearance, hot water resistance and the like by selecting a reduced pressure deaeration condition that does not vaporize the crosslinking agent.

[0002]

2. Description of the Related Art A thermosetting resin molded article may be provided with a coating layer as a gel coat layer on the surface thereof. This coating layer not only protects the surface and improves the appearance, but also has the function of improving hot water resistance, heat discoloration resistance, weather resistance, etc. As a specific forming method thereof, there is a method called in-mold coating method in the mold. Coating methods are known.

The in-mold coating method is, for example, after supplying a molding material into a split mold in which one is fixed and the other is movable,
A mold is obtained by tightening the mold and hardening it by heating and compressing the molding material, and opening the mold once after or before the completion of curing, injecting the coating material inside the mold and tightening and pressing the mold again. The surface is coated. This method has the advantage that molding and coating are performed in the same apparatus in a series of steps, and a molded product having a beautiful surface and excellent smoothness can be obtained.

However, it has been confirmed that inconveniences such as defective filling of the material and generation of pinholes occur due to the air originally mixed in the molding material and the air present in the mold. Even if the inner coating is applied, there are problems such as poor surface appearance, insufficient hot water resistance, and poor adhesion between the coating layer and the molded product. Decreasing the pressure is known to be an effective means, but the depressurization in the mold causes the styrene monomer contained in the molding material as a cross-linking agent such as unsaturated polyester to volatilize, resulting in poor curing. There was a new problem of poor appearance and poor appearance such as scratches on the surface of molded products.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to prevent deterioration of properties and appearance defects even when decompressed during heat compression molding, to have excellent adhesion to the in-mold coating layer, and to obtain good hot water resistance and the like. The object of the present invention is to provide a method for producing a resin-molded article coated in the mold.

[0006]

According to the present invention, which has solved the above-mentioned problems, a thermosetting resin molding material containing a cross-linking agent is subjected to heat compression molding in a mold, and the molding material is further cured or semi-cured. In the method for producing a resin molded article coated in the mold by loosening the fitting of the mold with the in-mold coating material, after supplying the resin molding material into the mold,
The main point is that depressurization deaeration in the mold is performed and the mold temperature is set lower than the boiling point of the crosslinking agent in the resin molding material under the reduced pressure. Further, it is a preferred embodiment of the present invention that the cross-linking agent is a high-boiling-point monomer that does not volatilize under the reduced pressure deaeration conditions.

[0007]

The manufacturing method of the present invention prevents volatilization of the cross-linking agent by carrying out the heat compression molding of the molding material, which is the pre-step of the coating in the mold, under a specific depressurized deaeration condition.
For this reason, it is possible to obtain a sufficiently cured molded product while suppressing deterioration and discoloration due to hot water as much as possible, and to manufacture a molded product that has excellent adhesion to the coating layer and good characteristics. can do. Furthermore, the molded article obtained by the production method of the present invention does not generate blisters even in the hot water resistance test, and the decrease in adhesion of the coating layer due to the test can be suppressed.

As in the conventional method, for example, when styrene is used as a cross-linking agent and molding is carried out under reduced pressure in a heated mold without particular control, a part or most of the styrene is volatilized and a curing failure occurs. Will occur. In the present invention, paying attention to the fact that the boiling point of the cross-linking agent in the molding material changes depending on the decompression degree, by setting the mold temperature to a temperature lower than the boiling point of the cross-linking agent at a predetermined decompression degree, that is, the decompression degree and the gold. By controlling the mold temperature according to the type of the cross-linking agent, it was found that volatilization of the cross-linking agent can be prevented as much as possible, and the present invention has been completed.

The greatest feature of the method of the present invention is that the degree of pressure reduction and the mold temperature during molding are controlled according to the type of the crosslinking agent, as described above. The boiling point of the monomer compound used as the crosslinking agent changes depending on the degree of reduced pressure (atmospheric pressure). Therefore, if the degree of pressure reduction required to remove the molding material and air in the mold is set, the boiling point at the degree of pressure reduction of the crosslinking agent is uniquely determined, so the mold temperature is set lower than the boiling point. Just do it. In the present invention, the pressure in the mold is set to 60 to 500 mmHg (normal pressure is set to 760 mmHg) in order to remove the air in the molding material and the mold as much as possible to prevent defective filling and pinholes. ) Is preferable, and the mold temperature is determined according to the degree of reduced pressure and the boiling point of the crosslinking agent. FIG. 1 shows the relationship between the degree of reduced pressure (pressure) and boiling points of styrene and paramethylstyrene. At the same degree of vacuum, the boiling point of paramethylstyrene is higher. FIG.
From the above, it is understood that when the pressure is reduced to 400 mmHg using styrene, the mold temperature is set to 120 ° C. or lower, and for paramethylstyrene, it is set to 145 ° C. or lower.
However, in molding a thermosetting resin, lowering the mold temperature at the time of molding causes a disadvantage that the reaction time becomes long. Therefore, it is preferable to select a high-boiling-point monomer as the crosslinking agent as much as possible.

In the present invention, as described above, the mold temperature is set according to the type of the cross-linking agent and the degree of reduced pressure. Therefore, as the cross-linking agent, any cross-linking agent usually blended in the thermosetting resin molding material can be used. Not particularly limited, other than styrene, paramethylstyrene, vinyltoluene, tertiary butylstyrene,
Styrene derivatives such as chlorostyrene, methoxystyrene, hydroxystyrene, cyanostyrene and divinylbenzene can be used. In particular, the styrene derivative has a boiling point higher than that of styrene due to the addition of a substituent to styrene, so that it can be preferably used because the mold temperature can be set high, and it can be used alone or as a mixture of 2 to 3 types. Vinyltoluene and paramethylstyrene are particularly preferable in terms of physical properties and economical efficiency. Further, other vinyl monomers such as vinyl acetate, methyl methacrylate, methyl acrylate and ethyl acrylate may be mixed with the above styrene derivative and used as a crosslinking agent.

Specific examples of the thermosetting resin to which the above crosslinking agent is added in the present invention include unsaturated polyesters. The unsaturated polyester has a molecular weight of 100 obtained by condensing an unsaturated dibasic acid, optionally a saturated dibasic acid, and a polyhydric alcohol or an alkylene oxide with a conventional method.
It is about 0 to 5000.

As the unsaturated dibasic acid, maleic anhydride,
Maleic acid, fumaric acid, itaconic acid and the like can be mentioned. As the saturated dibasic acid used as necessary,
For example, phthalic anhydride, isophthalic acid, terephthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride,
Examples thereof include halogenated phthalic anhydride, adipic acid, het acid, sebacic acid, methyltetrahydrophthalic anhydride and endomethylenetetrahydrophthalic anhydride.
From these, one kind or two or more kinds can be used.

Examples of the polyhydric alcohols include ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, neopentyl glycol, 1,3-butanediol, 1,6-hexanediol, 1,4-butanediol and hydrogenation. Bisphenol A, propylene oxide adduct of bisphenol A,
Examples include ethylene oxide adducts of bisphenol A, trimethylolpropane, glycerin, and the like,
From these, one kind or two or more kinds can be used. Further, alkylene oxides such as ethylene oxide, propylene oxide and epichlorhydrin can also be used.

The unsaturated polyester is preferably used in the range of 80 to 60 parts by weight based on 100 parts by weight of the resin composition after the above-mentioned crosslinking agent is added. That is, the cross-linking agent is 2
0 to 40 parts by weight is preferable. 80 unsaturated polyester
If the amount is more than parts by weight, the viscosity of the resin composition increases and it becomes difficult to mix the filler and the reinforcing material. Further, as a result, the amount of the cross-linking agent decreases and the number of reaction points with respect to the unsaturated polyester decreases, so that the resulting molded article has poor physical properties such as heat resistance and hot water resistance, and is not practical. When the amount of unsaturated polyester is less than 60 parts by weight, the amount of the cross-linking agent having a large shrinkage at the time of polymerization increases, so that the strain becomes large at the time of molding, cracks occur, and the dimensional stability of the molded product deteriorates.

The thermosetting resin molding material of the present invention includes calcium carbonate, aluminum hydroxide, clay, alumina,
It is possible to use fillers such as barium sulfate, silica powder, glass powder, mica, magnesium silicate, silica sand, and cold water stone, and fibrous reinforcing materials such as glass fibers, carbon fibers, organic fibers, metal fibers and whiskers. . The filler is preferably used in the range of 100 to 550 parts by weight with respect to 100 parts by weight of the resin. If it is less than 100 parts by weight, it may cause cracks due to shrinkage at the time of curing or distortion of the molded product.
If the amount exceeds 0 parts by weight, it may be difficult to knead with the resin or the physical properties may be deteriorated. Further, the amount of the reinforcing material used is preferably about 2 to 30% by weight of the entire molding material.

An unsaturated polyester resin is usually used as the thermosetting resin molding material. For example, an azo compound such as azobisisobutyronitrile, a curing agent such as a tertiary butyl peroxybenzoate, a tertiary butyl peroxyisopropyl carbonate, a benzoyl peroxide, a peroxide such as dicumyl peroxide, and the like It can be used in the range of 0.1 to 10 parts by weight with respect to 100 parts by weight. In addition, other known additives may be added.

Further, thermoplastic resins such as polystyrene, polymethylmethacrylate, saturated polyester, polyacrylic acid ester and butadiene rubber which are usually used as a low-shrinking agent may be added in an amount of 100 parts by weight of the resin composition, if necessary. Alternatively, about 2 to 20 parts by weight may be used. In addition,
When coloring is necessary, various pigments and dyes can be used.

The BMC can be prepared by adjusting these molding materials with a kneader or a biaxial continuous kneading device.
A sheet can be formed by using an MC manufacturing device.
As described above, the present invention is characterized in that the mold temperature is set according to the type of the crosslinking agent and the degree of reduced pressure.
Other molding conditions and in-mold coating conditions are not particularly limited.
To perform molding, for example, prepare a mold that can reduce the pressure inside the mold and a press molding machine to pressurize, place the molding material between the molds, and reduce the pressure inside the mold before finishing the mold The air inside is removed, and the molding material is pressed and cured. The pressure in the mold is preferably 60 to 500 mmHg, more preferably 150 to 360 mmHg. When the degree of reduced pressure is too high (the pressure in the mold is too small) and exceeds 60 mmHg, the mold temperature must be lowered in order to achieve the object of the present invention, which causes problems in the progress of the curing reaction. is there. Further, if the mold temperature is set outside the range of the present invention while the degree of pressure reduction is kept high, curing failure cannot be avoided. On the other hand, when it exceeds 500 mmHg, the effect of decompression is small, and defects such as defective filling of material and cavities and pinholes occur. It is most preferable to select the crosslinking agent so that the molding temperature can be set to 110 to 130 ° C. within the above-mentioned reduced pressure range.

In-mold coating is performed in the semi-cured state after the curing of the molding material is completed or before the curing is completed. At the time of coating, it is not necessary to consider the degree of pressure reduction and the heating temperature, and the conditions may be set appropriately according to the coating material.

[0020]

The present invention will be described in more detail with reference to the following examples, but the following examples do not limit the present invention.
All modifications and implementations that do not depart from the spirit of the description below are included in the technical scope of the present invention. In Examples and Comparative Examples, “parts” means “parts by weight”.

Examples 1 to 4 and Comparative Examples 1 to 5 Bisphenol A1 was placed in a four-necked flask equipped with a thermometer, a stirrer, a temperature adjusting device, a gas inlet tube and a reflux condenser.
360 parts of an adduct obtained by adding 2.1 mol of propylene oxide to 98 mol and 98 parts of maleic anhydride were added and reacted at 200 ° C. under a nitrogen stream until an acid value of 18 was obtained to obtain an unsaturated polyester. 70 parts of this unsaturated polyester, 30 parts of styrene as a cross-linking agent, and 0.02 part of hydroquinone were mixed to obtain an unsaturated polyester resin (this is referred to as resin A).

Next, 100 parts of resin A and aluminum hydroxide (Higelite H-320 manufactured by Showa Denko KK) 40
0 parts, tertiary butyl peroxy isopropyl carbonate 1.5 parts, zinc stearate 5 parts, magnesium oxide 1.0 part, colorant (KR9 manufactured by Sumika Color Co., Ltd.)
E361) 0.5 parts and 5 mm long glass chop 5
0 part was kneaded with a kneader to obtain a molding material (molding material A in the table). Resin B and molding material B were obtained in the same manner except that paramethylstyrene was used as the crosslinking agent instead of styrene.

While the pressure inside the mold was reduced, the molding material A or B was used to perform in-mold coating molding under the following conditions to obtain a molded product. The appearance of the molded product was visually evaluated, and the hot water resistance was 98.
Immerse the molded product in boiling water at ℃, boil 250 hours continuously,
The appearance was visually evaluated. The whitening resistance in the hot water resistance test was as follows: no whitening (○), whitening (×),
Regarding the blister, no blister (○), and blister (×).

(Molding conditions) Mold: Bathtub type having a coating material injection nozzle Mold temperature: The same for both upper and lower molds, as shown in Table 1 Decompression degree in mold: as shown in Table 1 Molding pressure: 50 kg / cm ² Pressurization time: 4 minutes Molded product thickness: 10 mm Mold coating condition: Same as the above molding conditions except that the pressure in the mold was not reduced and the pressurization time was 5 minutes. Was slightly opened, the coating material was injected from the injection nozzle, and then the mold was clamped again.

[0025]

[Table 1]

In each of Examples 1 to 4 in which the mold temperature was set as specified in the present invention, a molded product excellent in appearance and hot water resistance could be obtained. Comparative Examples 1 to 5 in which molding was performed at a mold temperature higher than the mold temperature defined by the degree of vacuum and the cross-linking agent.
In all cases, heat resistant water whitening was observed due to poor curing due to volatilization of the cross-linking agent, and blister generation was also observed in Comparative Examples 1, 4 and 5, and the poor curing due to volatilization of the cross-linking agent was applied to the coating layer by in-mold coating molding. It shows that it can not be covered even if it is applied. Further, in Comparative Examples 4 and 5, bubbles were generated inside and defective filling at the ends occurred.

[0027]

According to the present invention, the mold temperature is controlled based on the degree of reduced pressure in the mold and the boiling point of the crosslinking agent, so that the formation of cavities and pinholes due to insufficient reduced pressure is suppressed, and the crosslinking agent Since volatilization can also be suppressed, it was possible to produce an in-mold coated molded product having a good appearance and excellent characteristics such as hot water resistance.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the degree of reduced pressure and the boiling point.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location B29L 9:00 (72) Inventor Satoshi Yamauchi 1048 Kadoma, Kadoma-shi, Osaka Prefecture Matsushita Electric Works Co., Ltd. ( 72) Inventor Keiji Higashi 1048, Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works Co., Ltd. (72) Naoto Ikekawa, 1048, Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works Co., Ltd. 1048, Kadoma, Ichi, Matsushita Electric Works, Ltd. (72) Inventor, Masami Matsumoto, 1048, Kadoma, Kadoma, Osaka City, Matsushita Electric Works, Ltd.

Claims (2)

[Claims] 1. A thermosetting resin molding material containing a cross-linking agent is heat-compressed and molded in a mold, and the mold fitting is loosened in a cured or semi-cured state of the molding material to form an in-mold coating material. In the method for producing a resin molded article coated in a mold by inflowing, after the resin molding material is supplied into the mold, depressurization deaeration in the mold is performed, and the mold temperature is controlled under the reduced pressure. The method for producing a resin molded article coated in a mold is characterized in that the boiling point of the cross-linking agent in the resin molding material is set to a lower value. 2. The method for producing a resin molded article coated in a mold according to claim 1, wherein the cross-linking agent is a high-boiling-point monomer that does not volatilize under the reduced pressure deaeration conditions.