Detergent for resin-molding mold

Abstract: A detergent for a resin-molding mold contains 30 to 95% by weight of an alcoholic organic solvent, 70 to 5% by weight of a hydrocarbonaceous organic solvent and 0 to 10 parts by weight of a rust preventive based on 100 parts by weight of the solvent mixture of the alcoholic organic solvent and the hydrocarbonaceous organic solvent in the respective proportions as indicated above. The alcoholic organic solvent has preferably a boiling point of 130°C or less. The hydrocarbonaceous organic solvent has preferably a boiling point of 100°C or more.

Description: The present invention relates to a detergent which is suitable for cleaning a resin-molding mold, especially an injection mold, an extrusion mold, a compression mold and a transfer mold. More specifically, the present invention relates to a detergent which comprises a low-boiling alcoholic organic solvent and a high-boiling hydrocarbonaceous organic solvent and a rust preventive in a small amount and which is excellent in its detergency to pollutants deposited on the mold that has been used for resin-molding and in its rust preventiveness for the mold that has been cleaned. Recently, molded products made of plastics have been widely used in various fields such as those of automobiles and office Automation equipments. As a molding material, there have been used thermoplastic resins such as vinyl chloride resin, polyethylene, polypropylene, ABS resin, polystyrene, polycarbonate, polyamide resin, polyester resin and methacrylate resin, and thermosetting resins such as phenolic resin, epoxy resin, melamine resin and urea resin. The quality of the molded product, especially an appearance thereof, depends greatly on the particular mold used. An injection molding process excels, among the various resin molding processes, from the viewpoints of the diversity in molded product designs and the economics. Accordingly, most of the resins which are to be used for interior and exterior parts of automobiles; housings of Office Automation equipments; and parts of precision equipments and appliances have recently been molded by the injection molding process. However, the molds used in the injection molding process tend to be polluted by resins more than those used in other molding processes. The pollution of the molds has been a great problem in the injection molding process, since it impairs an appearance of the molded products and creates corrosion of the molds themselves. In order to solve this problem, improvements in resins and molds have been considered and practiced. However, such improvements are not sufficient. Therefore, there has been attempted an approach in which generally, the surface of a mold is wiped, after the molding thereof, with a single solvent, e.g., a halogenated hydrocarbon such as trichloroethylene or a ketone such as acetone, to remove pollutants from the surface of the mold. Nevertheless, there are no appropriate solvents which are capable of removing the pollutants efficiently, and thus actually, the latter are removed mechanically with a brush or an abrasive. In the injection molding process, resin passes through a narrow flow channel at a high speed, which results in the formation of a localized hot area. Thus, the resin is likely to decompose, which causes generation of gases. Also, various kinds of additive materials are incorporated into the resin in order to impart thereto some properties such as flame retardancy, weatherability and processability. FR-A-2 171 851 discloses a mixture containing 50 to 80 vol. % aliphatic hydrocarbons having a boiling range of about 50 to 200 °C and 50 to 20 vol. % of a chemical compound having a polar character. There are mentioned essences distilling at about 110 to 125 °C and alcohols having a low molecular weight, such as ethanol. DE-OS 38 12 454 discloses a degreasing fluid containing a distillation fraction of petrol and an ether, ketone and/or an ester. This fluid optionally contains a corrosion inhibitor. It is the object of the invention to provide a detergent which is excellent in its detergency for a resin-molding mold and in its rust preventiveness for the mold which has been cleaned with the detergent. This object could be achieved on the basis of the finding that surprisingly, the pollutants can be unexpectedly efficiently removed with a detergent which comprises a low-boiling alcoholic organic solvent and a high-boiling hydrocarbonaceous organic solvent, each having a specific composition, and a rust preventive in a small amount. Also, it was found that the rust prevention can be effected on the mold which has been cleaned with the detergent. Generally, the present invention is directed to a detergent for a resin-molding mold which comprises 30 to 95% by weight of an alcoholic organic solvent (A), 70 to 5% by weight of a hydrocarbonaceous organic solvent (B) and 0.1 to 8 parts by weight of a rust preventive (C) based on 100 parts by weight of the solvent mixture of the alcoholic organic solvent and the hydrocarbonaceous organic solvent in the respective proportions as specified above. The alcoholic organic solvent used in the present invention as a constituent (A) has preferably a boiling point of 130°C or less and more preferably 120°C or less. If the boiling point of the alcoholic organic solvent used exceeds 130°C, the detergency of the alcoholic organic solvent to the pollutants and the rust preventiveness of the alcoholic organic solvent for the mold deteriorate. A lower limit of the boiling point is not specifically limited, however, it is preferably 50°C or higher, more preferably 60°C or higher. The alcoholic organic solvent which can be used in the present invention is an alcohol having a carbon number of 1 to 8, preferably 1 to 6, which includes methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, sec-butyl alcohol, and tertbutyl alcohol. These alcohols may be used separately or in combination therebetween as the constituent (A) in the detergent according to the present invention. The proportion of the constituent (A) in the solvent mixture is 30 to 95% by weight and preferably 35 to 90% by weight. If this proportion exceeds 95% by weight or if this proportion is less than 30% by weight, the detergency of the detergent to the pollutants and the rust preventiveness of the detergent for the mold both deteriorate significantly, in particular, the cleaning property deteriorates. The hydrocarbonaceous organic solvent used in the present invention as a constituent (B) has advantages for rust inhibiting bv protecting the surface of the metal mold from moisture and oxygen in the air, and has preferably a boiling point of 100°C or more and more preferably a boiling point of 150°C or more. If the boiling point of the hydrocarbonaceous organic solvent used is less than 100°C, the detergency of the detergent to the pollutants and the rust preventiveness of the detergent for the mold deteriorate. An upper limit of the boiling point is not specifically limited, however, it is preferably 400°C or lower, more preferably 350°C or lower. The organic solvent having a boiling point lower than 100 °C can hardly protect the surface of the metal mold because it is evaporated quickly thereby deteriorating rust inhibiting property, whereas the solvent having a boiling point of higher than 400°C likely remains excessibly over the mold surface thereby causing dirt itself. The hydrocarbonaceous organic solvent which can be used in the present invention is a solvent having a carbon number of 8 to 20, preferably 9 to 20, which includes octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, 2-methyl heptane, toluene, xylene, and kerosine, which may be used separately or in combination therebetween as the constituent (B). The proportion of the constituent (B) in the solvent mixture is 5 to 70% by weight and preferably 10 to 65% by weight. If the proportion exceeds 70% by weight or if this proportion is less than 5% by weight, the detergency of the detergent to the pollutants and the rust preventiveness of the detergent for the mold both deteriorate significantly, in particular, the rust preventiveness deteriorates. The rust preventive used in the present invention as a constituent (C) includes vaporizable organic rust preventives which are represented by amines as well as their nitrites, carbonates, benzoates, cinnamates and chromates, such as dicyclohexylamine nitrite, diisopropylamine nitrite, cyclohexylamine carbonate, methylcyclohexylamine carbonate, amylamine benzoate, morpholine, and octadecylamine; organic rust preventives having N, S or O polar groups, such as ethylamine, diethylamine, diamylamine, β-naphthylamine, phenyl-β-naphthylamine, pyridine, quinoline, naphthoquinoline, thioglycol, p-thiocresol, propyl sulfide, formaldehyde, sorbitan acid esters, epoxidized oil and naphthenic acid; and inorganic rust preventives, such as metal nitrites, metal chromates, metal carbonates, metal sulfites, metal nitrates,metal sulfonates,metal orthophosphates,metal polyphosphates and metal silicates. These may be used separately or in combination therebetween as the constituent (C). Among these, the vaporizable rust preventives are preferable because of their less sticking to the molded products. The proportion of the constituent (C) is 0.1 to 8 parts by weight, based on 100 parts by weight of the solvent mixture of the constituents (A) and (B). If this proportion exceeds 10 parts by weight, the rust preventive, which is present in such a proportion, sticks to the molded products, which causes deterioration of an appearance of the molded products. Therefore, the proportion of the constituent (C) greater than 10 parts by weight is not desirable. The detergent according to the present invention can be easily produced by mixing the constituents (A), (B) and (C) through a conventional stirrer. As described above, the detergent for the mold according to the present invention comprises a mixture having a specific composition composed of (A) an alcoholic solvent and (B) a hydrocarbonaceous organic solvent and (C) a rust preventive. Additionally, respective well-known good solvents for each resin and each additive material as well as a solvent for the rust preventive may be added. Also, a surfactant, an antioxidant, a perfume and a colorant may be added, if desired, in order to make the detergent higher-performance. The total amount of these is preferably 20 parts by weight or less based on 100 parts by weight of the overall detergent. Although the detergent according to the present invention has excellent performances on all the resins for use with the injection molding process, it has significantly excellent performances on halogen-containing resins and the resins which generate acid constituents. The present invention will hereinbelow be described in further detail based on the following examples and comparative examples. The proportions of the respective constituents given in the examples, the comparative examples and Table 1 are expressed in terms of parts by weight, unless otherwise indicated. EXAMPLE 1 As indicated in Table 1, 240 g of ethanol (60 parts) as the alcoholic organic solvent (A1), 160 g of octane (40 parts) as the hydrocarbonaceous solvent (B1) and 20 g of dicyclohexylammonium nitrite (5 parts) as the rust preventive (C1) were placed in a 1 ℓ beaker followed by agitation through a stirrer to obtain a detergent in which the constituents were mixed homogeneously. EXAMPLES 2 TO 4 AND COMPARATIVE EXAMPLES 1 TO 3 A set of compounds listed in Table 1 as the constituents in each of Examples 2 to 4 and Comparative Examples 1 to 3 were used as the alcoholic organic solvent (A), the hydrocarbonaceous solvent (B) and the rust preventive (C) to prepare a detergent according to each of Examples 2 to 4 and Comparative Examples 1 to 3, in the same manner as in Example 1. Then, cleaning tests were carried out using the respective detergents which had been obtained in Examples 1 to 4 and Comparative Examples 1 to 3. Specifically, five shots of ENPLEX N-540 ® (PVC/ABC resin available from Kanegafuchi Kagaku Kogyo K.K.) or CEVIAN SER-20 ® (Br flame-retardant-containing ABS resin available from Daicel Ltd.) were molded through a 5-oz-injection molding machine, using a mold whose molding portion has a metal plate attached thereto, at a molding temperature of 200°C and at a screw revolution speed of 80 r.p.m., under the conditions where burning was to occur. Thereafter, the metal plate was removed and was cleaned with the detergent which had been prepared in a manner described hereinabove. The detergency of the detergent was determined by a reflectance of the metal plate which had been cleaned as mentioned above. It can be said that as the reflectance of the metal plate is higher, the detergency is greater. The rust preventiveness of the detergent was determined by an accelerated rusting test, which was conducted on the metal plate that had been processed as described above, at 55°C under moist conditions. The evaluation of the rust preventiveness was made by 5 points rating in which the highest rating is 5 and the lowest rating is 1. This means that as the number of the rating is greater, the evaluation of the rust preventiveness is higher. As can be seen from the results of Table 1, the detergent according to the present invention is excellent in its detergency and rust preventiveness for the mold.

Claims: A detergent for a resin-molding mold comprising 30 to 95% by weight of an alcoholic organic solvent (A), 70 to 5% by weight of a hydrocarbonaceous organic solvent (B) and 0.1 to 8 parts by weight of a rust preventive (C) based on 100 parts by weight of the solvent mixture of the alcoholic organic solvent (A) and the hydrocarbonaceous organic solvent (B) in the respective proportions as indicated above. The detergent according to claim 1, wherein the alcoholic organic solvent (A) has a boiling point of 130°c or less. The detergent according to claim 1, wherein the hydrocarbonaceous organic solvent (B) has a boiling point of 100°c or more. The detergent according to claim 1, wherein the rust preventive (C) is a vaporizable rust preventive. The use of a detergent according to claims 1 to 4 for cleaning a mold employed for molding thermoplastic resins, especially polyvinylchloride or ABS resins.

Inventors: HASHIMOTO YOSHIHIKO, MISHIMA IKUHIRO, HASHIMOTO, YOSHIHIKO, MISHIMA, IKUHIRO
Applicants: KANEGAFUCHI CHEMICAL IND, KANEGAFUCHI KAGAKU KOGYO KABUSHIKI KAISHA
Application year: 1992
Main classification: C11D3
IPC codes: C11D7, C11D3, B29C33