JPS6244571B2 - - Google Patents

Description

[Detailed description of the invention]

This invention involves mixing an unsaturated polyester resin, a mineral filler and magnesium oxide, thickening the mixture thus obtained in the presence of glass fibers, and pressuring a portion of the thickened mixture at high temperatures. This invention relates to a method of manufacturing a molded article by molding. Commonly used pressure molding materials containing unsaturated polyester resins, mineral fillers, and glass fibers have traditionally been known in the market as "mixed molding compounds" (DMC). This molding material contains a relatively large amount of resin and a relatively long length of bound glass fibers. This molding material is not suitable for producing molded products with small wall thickness that can be molded into arbitrary shapes or strongly bent. Because the glass fibers are oriented in a predetermined direction during pressing, the polymerization crimp is not uniformly compensated for, resulting in an uneven distribution of strength and elasticity. Furthermore, the glass fiber bundles present on the surface of the molded article act like capillaries, and the quality of the product deteriorates in a humid environment. Since a large amount of air is introduced into the molding material, it is difficult to process the molding material into a thin-walled molded product shaped as desired. Furthermore, the high resin content makes the molded product expensive. Another pressure molding material known under the name "sheet molding compound""SMC" contains magnesium oxide in addition to the above-mentioned components. This mixture is thickened in the presence of a glass fiber layer between polyethylene foils. Next, the press-formed material or a portion thereof is placed in a mold together with a glass fiber layer, and the whole is press-formed under high temperature. Processing such pressure-formed materials requires quite complex operations. Moreover, the high glass fiber and resin content makes the molded parts expensive. Another pressure-molded material known as "bulk molding compound""BMC" has the same composition as the SMC mentioned above, but is produced in a kneader and has a higher content of glass fibers, so it has the same deficiencies as DMC. . An object of the present invention is to provide a method for producing a molded article from a mixture having the above-mentioned composition, which has better processability and is less expensive than the above-mentioned mixtures, and has an elastic modulus equal to or higher than that of the above-mentioned mixtures. This purpose, according to the invention, is achieved by mixing an unsaturated polyester resin, a mineral filler and magnesium oxide, thickening the mixture thus obtained in the presence of glass fibers, and forming a part of the thickened mixture. A process for producing molded articles by pressure molding at high temperatures, the mixture comprising, in addition to the unsaturated polyester resin, 80 to 95% by weight of an inorganic filler having a particle size of approximately less than 500 μm, in the total mixture. 1-5 against
% by weight of glass fibers and 0.5 to 5% by weight of oxides of alkaline earth metals as thickeners, especially magnesium oxide, with respect to the unsaturated polyester resin, at least 3/4 of the glass fibers having a length of less than 15 mm. A method for producing a molded article, characterized in that the mixture is homogeneous and contains almost no air; achieved. The invention is based on the recognition that it is possible to produce pressed blanks which have a very high filler content and which are very well formed into high-quality, thin-walled molded parts of the desired shape. The prerequisite for this is that the glass fibers are present in a specific shape and quantity. Due to the lower content of resin and glass fibers, the manufacturing cost of the molded article is reduced compared to when using conventional mixtures. The second premise of the manufacturing method of the present invention is that the press-formed material is made homogeneous so that it contains almost no air before press-forming. The presence of glass fibers is necessary to compensate for polymerization crimp. To achieve good distribution of the polymer crimp, the glass fibers must be randomly distributed as single fibers in the compacted mass. Furthermore, in order to randomly distribute the glass fibers during pressure molding, it is necessary that the glass fibers be relatively short. It has also been found that if the content of glass fibers is less than the abovementioned values, the processing of the mixture for thickening becomes difficult. The molded article has a sufficiently high elastic modulus despite the low amount of glass fiber. Very good results are obtained with a glass fiber content of no higher than 1-2.5% by weight. Since the glass fibers in monofilament form are incorporated into the pressed material, no moisture action occurs. The preferred length of most glass fibers is 6-12mm;
The average length is approximately 9 mm. The glass fibers may be guided to the mixing device in a focused state if desired;
Stirring must be continued until the glass fibers are finally present in the mixture in a randomly distributed manner. Due to the random distribution of the glass fibers, the polymerization crimp is well distributed even at strongly bent locations, and the elastic modulus of the molded part is the same in all directions. Filling materials include calcium magnesium carbonate (dolomite), calcium carbonate, quartz powder, talc,
Inorganic fillers such as various clays are suitable. If the particle size of the bulk filler is less than 500 .mu.m, especially less than 200 .mu.m, a material with good pressability for moldings with wall thicknesses not too large, for example from 5 to 10 mm, is obtained. Any suitable reaction product of a polyhydric alcohol and a polyunsaturated acid or anhydride may be used for the unsaturated polyester resin. Polyhydric alcohols include propylene glycol, ethylene glycol, pentanediol, butanediol, butylene glycol, and dipropylene glycol; acids and acid anhydrides include maleic anhydride, phthalic anhydride, isophthalic anhydride, and adipic acid. Unsaturated polyester resins are usually network bonded. Styrene, methyl methacrylate, vinyl acetate and diallyl phthalate are suitable for this purpose. Customary peroxides such as benzoyl peroxide or tert-butyl perbenzoate can be used to catalyst the network. A product consisting of hydrated bisphenol A and a catalyst (trade name Sinolite 373) can also be used for this purpose. The mixture of the resin, filler and glass fibers described above is a viscous liquid. According to a preferred embodiment of the invention, the mixture is poured into a container and thickened to form a homogeneous press-formed mass containing almost no air.
As used herein, the term "homogeneous pressure-molded material" refers to a dense putty-like material that has a viscosity that allows it to be separated into several individual pieces by cutting without nearly losing its given shape. This thickening takes place on the basis of the action of the magnesium oxide mixed in. The required amount is cut out from the thickened material, placed in a pressure mold or matrix, and pressure molded at high temperature to form the desired molded product. In contrast to conventional pressure-formed materials, it is of great importance that air-free, homogeneous pressure-formed materials can be obtained. The temperature and pressure during pressing of the blank are not critical and are determined by the desired wall thickness of the molded part, especially in relation to the optimum pressing time and catalyst. The normal temperature is 100~250°C and the normal pressure is 3~20Kg/ ^cm2 . In addition, the pressure molding time is usually 0.5 to 30 minutes, especially 1.5
~6 minutes. A high-contrast surface layer or a decorative surface layer can be provided to the molded article produced by the above-mentioned production method during or immediately after pressure molding. Immediately after pressure molding, a molded article that is still hot and not completely cured may be treated with resin powder. Epoxy resins, unsaturated polyester resins or mixtures of these resins containing free hydroxyl groups such as methylol or phenol groups may be used for this purpose. As a result, the still free hydroxyl groups of the not yet completely cured molded article perform a three-dimensional network bonding action, resulting in complete adhesion of the surface layer and the molded article. It is advantageous to apply this treatment method when the molded article still has a temperature of at least 150°C, preferably 175-200°C. In this case, it is an advantage that the molded article according to the invention has a large heat capacity due to its high content of inorganic filler. Treatment with resin powder can be carried out by injection, electrostatic spraying, or immersion of the resin powder in a fluidized bed. In that case, 50 to 300 g of resin powder can be applied per 1 m ³ . Another method of forming a high contrast surface layer is to apply one or more pre-impregnated glass fiber fleeces. In that case, before the pressing material is poured into the pressing mold or matrix, it is impregnated with an epoxy resin, a polyester resin or a mixture thereof, or a plurality of glass fiber fleeces are placed in the pressing mold or matrix. Charge. If a transparent or translucent layer is desired, it is advantageous for the refractive index of the cured resin to approximately correspond to the refractive index of the glass fiber fleece. Adding decorations between two pieces of fiberglass fleece gives it a nice look. There are many possibilities for forming this decoration, for example finely divided organic or inorganic substances may be arranged between the fleece. These materials include metal powders, colored minerals, and polymer particles. More preferably, a motif may be printed on one of the fleeces using a colored resin, and the above two methods may also be used in combination. It is also possible to decorate the molded article according to the method described in Dutch Patent Application No. 7305807. It is also possible to structure the surface using molds with structured walls. If one or more glass fiber fleeces are used as the high-contrast surface layer, it is advantageous to arrange one fleece on the other side of the molded article as well. Next, an example will be described. EXAMPLE A polycondensation product consisting of 1.5 mol of hydrated bisphenyl A, 1.5 mol of propylene glycol, 0.5 mol of phthalic anhydride, 1 mol of maleic anhydride and 1 mol of fumaric anhydride was used as unsaturated polyester resin. 650 parts of this resin was added to styrene monomer.
235 parts by weight, 100 parts by weight of diallyl phthalate, 3rd
It was mixed with 10 parts by weight of butyl perbenzoate and 5 parts by weight of water. 1% by weight of magnesium oxide was added to the resulting resin mixture. From the mixture obtained, 85% by weight of calcium magnesium carbonate with a particle size of 0 to 200 μ and a majority of glass fibers with a length of 6 to 9 mm, based on the total amount of the mixture.
A mixture containing 1.5% by weight was prepared. The resulting sticky mixture was poured into a container. The mixture is
After 24 hours, the viscosity increased and the material became a homogeneous, press-formed material that contained almost no air and was cuttable. A portion cut out from this pressure-molded material was pressure-molded in a matrix at a temperature of 200° C. and a pressure of 150 kg/cm ² (15 MPa) for 1 minute and 30 seconds to form a plate-shaped body approximately 8 mm thick. The elastic modulus of this plate is 115.000Kg/cm ² (11.5GN/m ² ) to 110.000 for commercially available BMC and SMC plates pressure-formed using the same method.
Kg/cm ² (11GN/m ² ) but about 150.000
Kg/cm ² (15GN/m ² ). While the temperature of the plate is still 190°C, a very finely divided mixture of colored solid epoxy resin and polyester resin is sprayed onto the surface of the plate at a rate of about 200 g per 1 m ² . Granted as a percentage. After cooling, a plate-like body was obtained whose surface was almost indistinguishable from that of a coated cast iron dowel. This plate complied with US Commercial Standard CS222-59 for dosing. Even after being treated with boiling water for 140 hours, its beautiful appearance remained unchanged. When a similar plate with an untreated surface was exposed to marine climatic conditions for an extended period of time, no visible changes in the surface were observed. Identical pressure molding tests were conducted with glass fiber contents of 0.5% and 6% by weight. When the glass fiber content is 0.5% by weight, the plate becomes extremely brittle, and when the content is 6% by weight, it is impossible to cast the mixture into a homogeneous pressure-molded product that does not contain air. I couldn't do it. A molding material with the same weight component ratio as above but with longer glass fibers produces a more strongly bent, thin-walled molded product than a molding material containing short, randomly oriented glass fibers. It became clear that it was not suitable for pressure molding. It has also become clear that in this case, the strength at the bent portion is lower than when short fibers are used. The possibility of breakage at strongly bent locations was very high, and it was not possible to produce useful articles from this molded material. The filler content could be increased up to 95% by weight in experiments, but if the content was higher than that, the cohesive force was completely lost. The composition, cost and elastic modulus of commercially available bulk molding compounds (BMC), sheet molding compounds (SMC) and molding materials according to the invention are shown in the table below.

【table】

It has been found that it is also very easy to arrange two pre-impregnated glass fiber fleeces, between which bronze powder has been previously applied by spraying, as a decoration during the pressing process. The reproducibility of the decoration was also good when equal amounts of powder were applied in the same way. The invention applies not only to relatively complex molded articles, but also to relatively simple molded articles such as fleeces and wallboards. The modified epoxy resin does not have to be monochromatic, and its hue may be changed arbitrarily or systematically.

Claims (1)

[Claims] 1. Mix an unsaturated polyester resin, a mineral filler, and magnesium oxide, thicken the mixture thus obtained in the presence of glass fibers, and heat a portion of the thickened mixture at a high temperature. A method for producing molded articles by pressure molding in which the mixture contains, in addition to the unsaturated polyester resin, 80 to 95% by weight of an inorganic filler having a particle size of approximately less than 500 μm, based on the total mixture. 1 to 5% by weight of glass fibers and 0.5 to 5% by weight of an oxide of an alkaline earth metal, especially magnesium oxide, as a thickening agent with respect to the unsaturated polyester resin;
3/4 is characterized by having a length of less than 15 mm and being present as randomly distributed single fibers, and by thickening the mixture until it becomes homogeneous and contains almost no air. A method of manufacturing a molded product. 2. A method according to claim 1, in which 1 to 2.5% by weight of glass fibers are present. 3. A method according to claim 1 or 2, in which most of the glass fibers have a length of 6 to 12 mm. 4. The method according to any one of claims 1 to 3, wherein the average length of the glass fibers is about 9 mm. 5. Any one of claims 1 to 4, in which the particle size of most of the fillers is less than 200μ.
The method described in section. 6. The method according to any one of claims 1 to 5, wherein the mixture is thickened in 1 to 48 hours to form a homogeneous pressure-molded material containing almost no air. 7 The concentrated pressure-molded material is heated to a temperature of 100 to 250℃.
The method according to any one of claims 1 to 6, wherein the method is press-molded at a pressure of 30 to 200 kg/cm ² . 8. The method according to any one of claims 1 to 7, wherein the molded article in a not completely cured state is treated with resin powder at a temperature of at least 150°C. 9. Any one of claims 1 to 9 in which an epoxy resin containing free hydroxyl groups, an unsaturated polyester resin, or a mixture of an epoxy resin and a polyester resin is used as the resin.
The method described in section. 10. The method according to claim 8 or 9, wherein the temperature during treatment is 175 to 200°C. 11. Any one of claims 1 to 7, in which one or more glass friezes impregnated with epoxy resin or polyester resin or a mixture thereof are present before the pressure-molded material is placed in the mold. The method described in Section 1. 12. The method according to claim 11, in which there are two glass friezes with a decoration interposed between them. 13. The method of claim 12, wherein the decoration comprises finely divided organic or inorganic material. 14. The method of claim 12, wherein the decoration comprises colored resin.