Aqueous composition for die casting mold release agents

Abstract

An aqueous composition for die casting mold release agents that contains a terephthalate, a polypropylene resin, and water, wherein the polypropylene resin is dispersed in water.

Description

Aqueous composition for die-casting release agent

[0001] The present invention relates to an aqueous composition for a die-casting release agent. This application claims priority based on Japanese Patent Application No. 2024-180360 filed on October 15, 2024, and incorporates all the descriptions described in the Japanese patent application.

[0002] Die-casting is one of the casting techniques using a mold. In die-casting, in order to prevent adhesion between the mold and the molded product, which is a solidified product of molten metal (molten metal) injected into the mold, and to remove the product from the mold without damaging it, a release agent is applied to the mold. As the release agent, an aqueous composition is used. For example, Patent Document 1 describes a release agent for low-speed injection mold casting, which is an aqueous composition containing an inorganic lubricant such as talc, an aqueous dispersion of polyolefin fine particles, and an organic carboxylic acid metal salt.

[0003] Patent Document 2 describes a die-casting method including a step of spraying an aqueous die-casting release agent having a content (in terms of solid content) of a release component such as a silicone compound of 5 to 60% by mass onto a mold so as to satisfy predetermined conditions. Patent Document 3 describes an aqueous composition for a die-casting release agent containing a carboxylic acid, a basic compound, and water.

[0004] Japanese Patent Application Laid-Open No. 2001-259788, Japanese Patent Application Laid-Open No. 2010-89140, Japanese Patent Application Laid-Open No. 2020-527471

[0005] In die-casting, a release agent with excellent release properties is desired so that the casting can be easily removed from the mold. Also, it is desired that the casting raw material does not stick to the mold surface. Furthermore, in casting by the die-casting method, since the surface state of the molded product obtained by casting greatly affects the product, it is not desirable for the casting surface to be colored by the release agent. It has been difficult for conventional release agents to satisfy these needs simultaneously.

[0006] The aqueous composition for a die-casting release agent according to the present disclosure contains a terephthalate, a polypropylene resin, and water, and the polypropylene resin is dispersed in water.

[0007] The aqueous composition according to this disclosure provides an aqueous mold release agent that exhibits excellent release properties, is less likely to stick to the mold surface, and is less likely to cause discoloration of the casting surface.

[0008] [Summary of Embodiments] First, embodiments of the aqueous composition for die-casting release agents according to this disclosure will be listed and described. In this specification, unless otherwise specified, "A to B" representing a numerical range means "A or more and B or less".

[0009] The aqueous composition for die-casting release agents according to this disclosure comprises a terephthalate, a polypropylene resin, and water, wherein the polypropylene resin is dispersed in water. Conventionally, to solve the problems of aqueous release agents mainly composed of silicone, release agents that are aqueous compositions containing organic acids have been proposed (Patent Document 3). The aqueous composition disclosed in Patent Document 3 comprises a carboxylic acid of a specific structure, a basic compound, and water. Examples in Patent Document 3 show that when an aqueous composition consisting of adipic acid, terephthalic acid, trimellitic acid, and mixtures thereof, sodium hydroxide, and water is used as a release agent, it exhibits excellent release properties, lubricity, adhesion, heat resistance, and low odor. Furthermore, Patent Document 3 states that the aqueous composition may contain a water-soluble polymer to further enhance lubricity and release properties. However, the need for release agents with excellent release properties continues, and there has been a desire for a release agent that is an aqueous composition with even better release properties.

[0010] The aqueous composition according to this disclosure contains terephthalate and polypropylene resin as active ingredients in the mold release agent. The aqueous composition according to this disclosure is an emulsion composition containing dispersed polypropylene resin in water. Although not particularly bound by theory, the aqueous composition according to this disclosure maintains the heat resistance and adhesion of terephthalate while reducing the adhesion of casting raw materials to the mold and improving mold release properties. Furthermore, it has been found that when terephthalate and polypropylene resin are used in combination, no discoloration occurs on the casting surface, and castings with a good appearance can be produced. The present invention makes it possible to simultaneously satisfy mold release properties, reduced sticking to the mold, and reduced discoloration of the casting by using terephthalic acid among carboxylic acids, and further by combining terephthalic acid with polypropylene resin. The aqueous composition for die casting mold release agents may further contain adipicate. In this case, the effects according to this disclosure can be obtained more reliably.

[0011] The aqueous composition may have a pH of 7 to 13. Furthermore, the aqueous composition for die-casting release agents may contain an acid-modified polypropylene resin. In these cases, the effects of this disclosure can be obtained more reliably.

[0012] In the aqueous composition for die-casting release agents, the proportion of the carboxylate salt as a carboxylic acid may be greater than the proportion of the polypropylene resin. Furthermore, the solid content in the aqueous composition may be between 3% and 60% by mass. When the solid content is within this range, the amount of release agent applied to the mold is not excessive, and a decrease in mold temperature can be suppressed. Additionally, it is possible to maintain an appropriate viscosity as a release agent, making it less likely for problems to occur during the application (spraying) of the release agent, and suppressing uneven adhesion of the release agent.

[0013] In the aqueous composition for die-casting release agents, the content ratio of the carboxylate salt as a carboxylic acid relative to the aqueous composition may be 2% to 30% by mass, and the content ratio of the polypropylene resin relative to the aqueous composition may be 1% to 30% by mass. When within this range, a release agent possessing the above-mentioned effects is provided.

[0014] [Specific Examples of Embodiments] The aqueous composition for die-casting release agents according to this disclosure will be described in more detail below.

[0015] [Aqueous Composition] The aqueous composition according to this disclosure is an aqueous composition suitably used as a die-casting release agent, and comprises a terephthalate, a polypropylene resin, and water. The polypropylene resin is dispersed in water. The aqueous composition has excellent heat resistance, adhesion, and release properties, and can reduce the adhesion of casting raw materials to the mold. Furthermore, when die-casting is performed using the aqueous composition, no discoloration of the casting surface occurs, and a casting with a good appearance can be produced. The aqueous composition is preferably used as a release agent and / or lubricant in a metal forming method using a mold, such as the die-casting method. Specifically, it can be used as a release agent applied to the mold in advance, or as a lubricant to improve the lubricity between the sleeve and plunger for pouring molten metal into the mold.

[0016] In this specification, an "aqueous" composition means that it contains a large amount of water and water-soluble components (for example, 50% by mass or more of the total composition), and that water forms a continuous phase as the solvent. Aqueous compositions can be diluted with water without limitation.

[0017] The aqueous composition according to this disclosure may be an emulsion containing a polypropylene resin dispersed in water. In the aqueous composition according to this disclosure, the polypropylene resin may be formulated as an emulsion, and the aqueous composition according to this disclosure may be a polypropylene emulsion diluted with water. Being an emulsion means that fine particles of polypropylene resin, which are not inherently water-soluble, are stably dispersed in water by a surfactant or by the self-emulsifying properties of the polypropylene resin.

[0018] The viscosity of the aqueous composition is not particularly limited as long as it has the effects described herein, but the viscosity at 30°C may be 200 mPa·s or less, preferably 100 mPa·s or less, and more preferably 50 mPa·s or less. If the viscosity of the aqueous composition exceeds 200 mPa·s, clogging may occur in the nozzle for applying the release agent, which may limit the application method.

[0019] The pH of the aqueous composition is not particularly limited as long as it has the effects of the disclosure, but is usually 7 to 13, preferably 7 to 12, and more preferably 7.5 to 10. The aqueous composition according to the disclosure preferably contains a basic compound, and the pH can be adjusted by the proportion of the basic compound added. If the pH is 7 or higher, the occurrence of corrosion of molds and surrounding equipment caused by the release agent can be suppressed. If the pH is 13 or lower, irritation to the eyes and skin of workers can be suppressed, making it a highly safe release agent.

[0020] The aqueous composition according to this disclosure contains the components described below, and the solid content in the aqueous composition is not particularly limited as long as it has the effects of this disclosure, but the proportion of solid content is preferably 3% to 60% by mass, and more preferably 3% to 20% by mass. Here, solid content refers to the components remaining after heating at 150°C using a heat-drying type moisture meter (e.g., MX-50, manufactured by A&D Co., Ltd.) and evaporating the water, and includes the active ingredient as a mold release agent and other auxiliary components. For example, the solid content includes carboxylates such as terephthalates, polypropylene resin, etc. If the solid content in the aqueous composition is less than 3% by mass, it is necessary to apply a large amount of the aqueous composition to increase the amount of active ingredient adhering to the mold, which tends to lead to a decrease in mold temperature. Also, even if a large amount of mold release agent is applied to the mold, the amount of adhesion does not increase easily, and the effect of the mold release agent is difficult to obtain. If the solid content is too high, the nozzle is likely to clog, and uneven coating is likely to occur on the mold.

[0021] [Carboxylates] The aqueous compositions according to this disclosure contain carboxylates. In the aqueous compositions, the carboxylates are dissolved in water. In the aqueous compositions, the carboxylates may exist as carboxylates or may be dissolved in a dissociated state.

[0022] Carboxylate salts can be obtained by neutralizing a carboxylic acid to form a salt, then mixing the resulting carboxylate salt with water, or by mixing a carboxylic acid with a basic compound in water to form a carboxylate salt.

[0023] The basic compound used in addition to the carboxylic acid is not particularly limited as long as it is a compound that can neutralize the carboxylic acid, and may be a basic organic compound or a basic inorganic compound. Examples of basic organic compounds include amine compounds such as triethylamine, monoethylamine, diethylamine, trimethylamine, monomethylamine, dimethylamine, ethylenediamine, triethanolamine, and tetramethylethylenediamine, as well as pyrrolidine, piperidine, and pyridine. Examples of basic inorganic compounds include alkali metal or alkaline earth metal hydroxides such as sodium hydroxide, potassium hydroxide, calcium hydroxide, and magnesium hydroxide; sodium carbonate, sodium bicarbonate, potassium carbonate, calcium carbonate, and magnesium carbonate. Among these, basic inorganic compounds are preferred because they have less odor, alkali metal hydroxides are more preferred, and sodium hydroxide and potassium hydroxide are preferred due to their availability and release properties, with sodium hydroxide being more preferred. In other words, the carboxylic acid is preferably a sodium or potassium salt of the carboxylic acid, with the sodium salt being more preferred. Basic compounds may be used individually or in combination of two or more.

[0024] The content of the basic compound in the aqueous composition is not particularly limited, but for example, it is preferably such that the pH of the aqueous composition is 7 to 13, more preferably such that the pH of the aqueous composition is 7 to 10, and even more preferably such that the pH of the aqueous composition is 8 ± 0.5.

[0025] The aqueous composition according to this disclosure, by containing a carboxylate salt, has improved odor and release properties, and the odor is reduced. The carboxylate salt particularly includes terephthalate. By including terephthalate in the aqueous composition, discoloration of the casting is significantly suppressed.

[0026] The carboxylate salt may contain, in addition to terephthalic acid, one or more carboxylic acids other than terephthalic acid. Examples of carboxylic acids other than terephthalic acid include aliphatic carboxylic acids and aromatic carboxylic acids. For example, dicarboxylic acids such as adipic acid, succinic acid, maleic acid, fumaric acid, phthalic acid, and isophthalic acid, and polycarboxylic acids such as trimellitic acid are used. By using such carboxylic acids in addition to terephthalic acid, the aqueous composition can be made to have better mold release properties and anti-seize properties while suppressing discoloration of the casting. Among the carboxylic acids exemplified above, adipic acid and trimellitic acid are more preferred as carboxylic acids to be used in addition to terephthalic acid, and adipic acid is particularly preferred.

[0027] Furthermore, when a carboxylate salt is formed by mixing a carboxylic acid and a basic compound in water, a carboxylic acid anhydride may be used as the carboxylic acid. Examples of carboxylic acid anhydrides include succinic anhydride, adipic anhydride, maleic anhydride, and phthalic anhydride. The carboxylic acid anhydride is hydrated in an aqueous composition to become a carboxylic acid, and then mixed with a basic compound to form a carboxylate salt.

[0028] When a carboxylate salt contains terephthalate in addition to other carboxylate salts, it is preferable that the amount of terephthalate as terephthalic acid (mass ratio) is greater than the amount of other carboxylate salts as carboxylic acid (mass ratio). Since the molecular weight of carboxylate salts differs depending on the type of salt, the blending ratio is indicated by the amount excluding the salt. For example, the amount of terephthalic acid, or the amount blended as terephthalic acid, refers to the amount of terephthalic acid in terephthalate excluding the salt. The mass ratio of terephthalic acid to other carboxylic acids is preferably such that the ratio of terephthalic acid to other carboxylic acids (terephthalic acid / other carboxylic acids) is greater than 1, and more preferably between 1.5 and 20, and between 2 and 10. When the ratio is within this range, mold release properties and resistance to seizing can be improved while suppressing discoloration of the casting.

[0029] The content of terephthalate in the aqueous composition according to this disclosure is not limited as long as the effects according to this disclosure are obtained, but may be 2% by mass or more, preferably 2.5% by mass or more, and more preferably 3% by mass or more, as terephthalic acid relative to the total amount of the aqueous composition. Also, it is preferable to have 15% by mass or less, 10% by mass or less, and 5% by mass or less. If there is too little terephthalic acid, the release properties, lubricity, flowability, and heat retention of the mold tend to decrease. If there is too much terephthalic acid, the carboxylic acid precipitates from the aqueous composition, making it difficult to apply the aqueous composition.

[0030] The content ratio of carboxylic acid salts (total of terephthalate and other carboxylic acid salts) in the aqueous composition according to this disclosure is not limited as long as the effects according to this disclosure are obtained, but may be 2% by mass or more, preferably 2.5% by mass or more, and more preferably 3% by mass or more, as carboxylic acid relative to the total amount of the aqueous composition. Also, it is preferable to be 30% by mass or less, 15% by mass or less, and 10% by mass or less. If the amount of carboxylic acid is too low, the release properties, lubricity, flowability, and heat retention of the mold tend to decrease. If the amount of carboxylic acid is too high, the carboxylic acid will precipitate from the aqueous composition, making it difficult to apply the aqueous composition. Furthermore, when the amount of carboxylic acid is within the above range, the release agent film can be visually confirmed when the release agent is applied to the mold, so the workability is further improved.

[0031] [Polypropylene Resin] The aqueous compositions according to this disclosure include a polypropylene resin. The polypropylene resin is essentially water-insoluble and dispersed in water as particles. The polypropylene resin may be mixed with water in the form of a polypropylene emulsion. The polypropylene emulsion is an emulsion in which the polypropylene resin is dispersed in water by a surfactant or by the self-emulsifying properties of the polypropylene resin.

[0032] Polypropylene resin is composed of a polymer with polypropylene as the main structural unit, and may be a homopolymer of propylene or a copolymer of propylene and another olefin. The polypropylene contained in the polypropylene emulsion may be a copolymer of propylene and an olefin other than propylene. The olefin other than propylene may be mono- or diolefins having 2 or 4 to 20 carbon atoms. Examples of olefins other than propylene include ethylene, butene, pentene, hexene, octene, decene, butadiene, hexadiene, octadiene, cyclobutene, cyclopentene, cyclohexene, norbornene, norbornadiene, styrene, and derivatives thereof. Among these, it is preferable that monoolefins such as ethylene, butene, pentene, hexene, and octene are copolymerized, and ethylene and butene are more preferable.

[0033] When the polypropylene resin is a copolymer, the proportion of structural units other than propylene may be 40 mol% or less, preferably 30 mol% or less, and more preferably 20 mol% or less. Within this range, it may contain olefins other than propylene, but it is even more preferable that it does not contain structural units other than propylene, i.e., that it is a homopolymer of propylene. When the propylene content is high, discoloration of the casting is more reliably suppressed.

[0034] The polypropylene resin is preferably an acid-modified polypropylene resin. Examples of acids to be added to the polypropylene resin include carboxylic acids such as (meth)acrylic acid, maleic acid or maleic anhydride, fumaric acid, citraconic anhydride, citraconic acid, itaconic anhydride, itaconic acid, and aconitic acid, as well as (meth)acrylic acids such as glycidyl methacrylate and 2-hydroxyethyl methacrylate. Of these, maleic acid or maleic anhydride is preferred. Note that "(meth)acrylic" means "acrylic or methacrylic".

[0035] The acid content in the acid-modified polypropylene resin is preferably 0.1 to 10 mol% and 0.5 to 5 mol%. Acid modification makes it easier to emulsify and improves the stability of the emulsion, thus improving the stability of the aqueous composition. The acid content can be measured by known methods. For example, after washing the acid-modified polypropylene resin with hexane or the like, dissolve it in o-dichlorobenzene and measure the proportion of protons in the acid units added based on the proton at the α-position of the propylene unit. １ It can be measured by H-NMR. Furthermore, the acid value of the acid-modified polypropylene resin is preferably 1 to 500 mgKOH / g or less. The acid value of acid-modified polypropylene can be measured, for example, in accordance with JIS K 2501.

[0036] The weight-average molecular weight of polypropylene resin is typically 500 to 200,000, may be 1,000 to 150,000, preferably 3,000 to 100,000, and more preferably 5,000 to 80,000. Within this range, the release properties of the aqueous composition are improved. If the molecular weight is too high, it becomes difficult to create an aqueous system, and the particle size of the dispersed particles in the resulting aqueous dispersion may be large, resulting in poor dispersion stability. The weight-average molecular weight can be measured using conventionally known methods with GPC (Gel Permeation Chromatography) using o-dichlorobenzene or the like as a solvent and polystyrene as a standard sample.

[0037] The aqueous compositions according to this disclosure may contain resin particles other than polypropylene resin, to the extent that they do not impair the effects of the present invention. Examples include polyolefin resins other than polypropylene resin, and polyethylene resin is one example. When polyolefin resins other than polypropylene resin are included, the content of polyolefin resins other than polypropylene resin may be 40% by mass or less, preferably 20% by mass or less, more preferably 5% by mass or less, and preferably no polyolefins other than polypropylene resin are included.

[0038] When polyethylene with a high degree of polymerization is present in an aqueous composition, discoloration tends to occur in the casting. For this reason, it is preferable that polyethylene resins or emulsions composed of high-degree-of-polymerization polyethylene are not included. On the other hand, in the case of a propylene / ethylene copolymer, the size of the polyethylene units is not excessive, so it is considered less likely to be a cause of discoloration.

[0039] In the aqueous composition relating to this disclosure, the particle size of the polypropylene resin is D １００ It is preferable that the particle size is 5 μm or less. That is, it is preferable that substantially no particles larger than 5 μm are included. The arithmetic mean particle size of the polypropylene resin is preferably 1 μm or less and 0.5 μm or less. Within this range, the polypropylene resin particles are less likely to separate, and the storage stability of the aqueous composition is improved. D １００ The method for measuring the arithmetic mean particle size is described in detail in the examples.

[0040] In the aqueous compositions according to this disclosure, it is preferable that the polypropylene resin and other resins have a residue rate of 20% or less at 450°C as determined by thermogravimetric analysis (TGA). In die casting, the interface temperature between the molten aluminum and the mold is approximately 450°C, and if the components do not easily generate residue at 450°C (in other words, they decompose easily), the surface of the casting will be less likely to discolor. Polypropylene has such high-temperature properties.

[0041] The residue rate at 450 °C is measured using a STA-7200RV manufactured by Hitachi High-Tech Science Corporation. As a specific measurement method, the water in the aqueous composition is evaporated, washed with water, further washed with hexane and methanol, filtered, and then dried to obtain a sample. With a sample amount of 5.0 mg, heated from room temperature to 500 °C at a heating rate of 10 °C / min in an air atmosphere, the residue rate at 450 °C was measured.

[0042] The content of the polypropylene resin is not particularly limited as long as the viscosity of the aqueous composition is within a predetermined range and the effects according to the present disclosure can be obtained. Usually, the polypropylene resin can be blended in an amount of 1% by mass or more and 30% by mass or less based on the total amount of the aqueous composition. The content of the polypropylene resin is preferably 1.2% by mass or more, more preferably 1.5% by mass or more, preferably 20% by mass or less, and more preferably 15% by mass or less based on the total amount of the aqueous composition.

[0043] Also, the content of the polypropylene resin is preferably 0.1 to 10, 0.2 to 5, or 0.4 to 1 with respect to the amount of terephthalic acid. When it is within these ranges, the effects according to the present disclosure are easily obtained.

[0044] [Water] The aqueous composition according to the present disclosure contains water. The water is not particularly limited, and water that can be used in aqueous compositions such as aqueous release agents and aqueous lubricants can be used. Specifically, industrial water, ion-exchanged water, pure water, etc. are included.

[0045] The water content in the aqueous composition according to the present disclosure may be 40% by mass or more with respect to the whole aqueous composition, preferably 60% by mass or more, and more preferably 80% by mass or more. If the water content is 40% by mass or more, a composition having an appropriate viscosity as a release agent and being easy to handle can be formed. The water content may be 97% by mass or less. If the water content is 97% by mass or less, the proportion of the active ingredient contained in the release agent does not become too small, the effect as a release agent can be obtained with an appropriate coating amount, and the temperature drop of the mold due to the coating of the release agent can be suppressed.

[0046] [Other Components] The aqueous composition according to the present disclosure may contain a dispersant as a component for dispersing the polypropylene resin in water or for other reasons. The dispersant is not particularly limited, and for example, it may be one or more surfactants such as nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants. Among these, it is preferable to contain either or both of nonionic surfactants and anionic surfactants.

[0047] Examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, polyoxyethylene polyoxypropylene block polymers, sorbitan fatty acid esters, polyoxyalkylene alkyl ethers, glycerin fatty acid esters, polyoxyethylene alkyl amines, alkyl alkanolamides, and the like.

[0048] Examples of anionic surfactants include fatty acid salts, alkyl sulfate esters, polyoxyethylene alkyl ether sulfate esters, sodium alkylbenzene sulfonates, sodium alkylnaphthalene sulfonates, alkyl sulfosuccinates, alkyl diphenyl ether disulfonates, alkyl phosphates, naphthalene sulfonic acid formalin condensates, and the like.

[0049] When the aqueous composition contains a dispersant, the content ratio is not limited as long as the effects according to the present disclosure are not impaired, and it may be 3% by mass or less based on the total amount of the aqueous composition.

[0050] The aqueous composition may contain one or more other components as necessary within a range not impairing the effects of the present invention. Other components that can be contained in the aqueous composition include hydrophilic organic solvents, water-soluble or water-dispersible resins other than polypropylene resins, and other auxiliaries.

[0051] Examples of hydrophilic organic solvents include alcohols such as methanol and ethanol, ketones such as acetone and methyl ethyl ketone, glycols such as ethylene glycol and propylene glycol, and their ethers.

[0052] Examples of aqueous or water-dispersible resins include aqueous acrylic resins, aqueous urethane resins, aqueous epoxy resins, aqueous alkyd resins, aqueous phenol resins, aqueous amino resins, aqueous polybutadiene resins, and aqueous silicone resins. Other examples include cellulose derivatives such as carboxymethylcellulose (CMC) and hydroxyethylcellulose (HEC), polyethylene glycol, isobutylene-maleic acid copolymers, diisobutylene-maleic acid copolymers, styrene-maleic acid copolymers, and polyvinylpyrrolidone (PVP).

[0053] Other additives include, for example, various stabilizers such as thickeners, defoamers, antioxidants, weather stabilizers, and heat inhibitors; colorants such as titanium dioxide and organic pigments; conductivity imparters such as carbon black and ferrite; and various additives such as preservatives, fungicides, and rust inhibitors. The amount of each of these other additives is usually 1% by mass or less of the total amount of the aqueous composition.

[0054] Furthermore, the aqueous composition according to this disclosure may be used by adding it to conventional aqueous release agents or aqueous lubricants, such as emulsion-type release agents or lubricants, or conventional aqueous release agents or aqueous lubricants, such as emulsion-type release agents or lubricants, may be used by adding them to the aqueous composition according to this disclosure. In the case of the aqueous composition obtained in this way, other components may include various components contained in conventional release agents or lubricants.

[0055] [Manufacturing Method] The method for producing the aqueous composition according to this disclosure is not particularly limited as long as an aqueous composition can be produced. Specifically, an aqueous composition can be produced by adding a predetermined amount of a carboxylic acid containing terephthalic acid, a polypropylene emulsion containing a polypropylene resin, and other components as needed to water, and stirring and mixing while heating as needed.

[0056] [Method of Use] The aqueous composition according to this disclosure is suitably used as a mold release agent in metal forming methods using molds, such as die casting. The specific method of use is not particularly limited and can be carried out according to known methods and conditions. For example, the aqueous composition can be applied to the surface of a mold by filling a spraying device with the aqueous composition without dilution and spraying the aqueous composition onto the mold surface from a spray nozzle. The aqueous composition is usually used undiluted, but it may also be used after diluting to a predetermined ratio (e.g., 2 to 50 times).

[0057] The aqueous composition is usually applied to the mold after each casting, but multiple castings may be performed after the aqueous composition has been applied.

[0058] The material metal cast by the die-casting method is not particularly limited and may be an aluminum alloy, zinc alloy, magnesium alloy, or any other alloy. In particular, the aqueous composition according to this disclosure is suitably used for die-casting aluminum alloys.

[0059] [Examples] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to these examples.

[0060] [Preparation of Aqueous Compositions] Aqueous compositions of Examples 1 to 10 and Comparative Examples 1 to 14 were prepared using the following materials. [Materials] ・Terephthalic acid carboxylic acid: Toray Industries, Inc. Adipic terephthalic acid: BASF Japan Ltd. Adipic Acid ・Resin emulsion: Shown in Table 1. In Tables 1 to 4, "EM" means "emulsion". 30 wt% solid component of polypropylene EM1 means that the total amount of polypropylene resin and surfactant in the emulsion is 30 wt%, and the same applies to the other emulsions. The majority of the solid component in the resin emulsion is resin, and the surfactant content is about 1 / 10 to 1 / 4 of the resin content. The particle size shown in Table 1 is the particle size of the resin emulsion measured before mixing with other components. The particle size is the value obtained by the particle size measurement method described later. The 450°C residue amount is the value measured by the method described above. "-" means unknown or not applicable. Basic compound: 30% by mass sodium hydroxide aqueous solution: 30% caustic soda and water ion-exchanged water manufactured by Shin Nippon Techno Co., Ltd.

[0061]

[0062] <Methods for Producing Aqueous Compositions in Examples and Comparative Examples> The above-mentioned materials were mixed in amounts corresponding to the component ratios (mass%) shown in Tables 2 to 4 to prepare aqueous compositions. The component ratios shown in each table represent the solid content ratio of each material. Blank spaces indicate that the component is not present. The particle size in Table 2 represents the particle size of the emulsion contained in the aqueous composition. In the examples and comparative examples shown in Tables 2 to 4, the inclusion of terephthalic acid and / or adipic acid and a basic compound results in aqueous compositions containing terephthalate and / or adipic acid.

[0063] [Evaluation] <Release properties and seizure resistance> The release properties and seizure resistance of aqueous compositions were evaluated by casting using a die-casting machine UB350GDC manufactured by UBE Machinery Co., Ltd. and a model mold (SKD-61 material) with pin-shaped inserts, according to the following method.

[0064] - Mold release properties: 0.5 cc of mold release agent was sprayed onto a mold at 350°C for 4 seconds. A casting was made using aluminum (ADC-12) at 680°C. The load on the ejector pin (extrusion resistance) when removing the casting was measured using a load cell. For stabilization, after 25 castings, the average value of the extrusion resistance of 10 castings was calculated, and mold release properties were evaluated according to the following evaluation criteria: Average value of extrusion resistance of the last 10 shots: 50 kgf or less; A+ 50 to 110 kgf; A 110 kgf to 200 kgf; B Over 200 kgf; C

[0065] - After evaluating the anti-seize properties and release properties, the inserts were removed from the mold, and the ratio of the area where aluminum seizing occurred to the area of ​​the insert's cavity was calculated from image analysis. For the image analysis, images of the insert pins were acquired with a scanner, binarized using ImageJ (16-bit conversion, area calculation with Threshold set to 170), and the aluminum seizing area ratio was calculated. The anti-seize properties were evaluated according to the following criteria: Area ratio of seized portion in the cavity: 25% or less; A+ 25-50%; A 50-75%; B 75% or more; C

[0066] - The coloration of the cast product's appearance was checked during the evaluation of release properties and seizure resistance. Visual observation revealed that if there was no coloration on the casting surface, it appeared grayish, but if there was coloration, it appeared brownish. In addition, the coloration of the aluminum casting surface was evaluated using RGB values. Specifically, the RGB values ​​of the colored areas were measured from images of the casting product using software, a colorimeter, etc. If the R+G+B value was 450 or higher, it was evaluated as "Good (A)" with no coloration, and if it was less than 450, it was evaluated as "Poor (C)" with coloration.

[0067] Particle size was measured using a HORIBA LA-300 particle size distribution analyzer. The relative refractive indices used for the measurements were 1.12 for polypropylene, 1.14 for polyethylene, and 1.08 for paraffin wax and carnauba wax.

[0068] The compositions and evaluation results of the aqueous compositions of Examples 1 to 10 and Comparative Examples 1 to 14 are summarized in Tables 2 to 4.

[0069]

[0070] As shown in Table 2, the aqueous composition of Example 1, which falls within the scope of this disclosure, showed good results in terms of mold release, bake resistance, and coloration. Comparative Example 1, which did not contain polypropylene resin, had insufficient mold release properties. Comparative Example 2, which did not contain polypropylene resin but contained polyethylene emulsion, had insufficient mold release properties and discoloration occurred. Comparative Example 3, which did not contain polypropylene resin but contained a water-soluble polymer (carboxymethylcellulose), had insufficient mold release properties and discoloration occurred. In addition, the viscosity of the aqueous composition was high, making it difficult to handle. Comparative Example 4, which did not contain polypropylene resin but contained paraffin emulsion, had poor mold release properties and discoloration occurred. Comparative Example 5, which did not contain terephthalic acid or polypropylene resin but contained adipic acid, had insufficient mold release properties and discoloration occurred. Comparative Example 6, which contained polypropylene resin and adipic acid instead of terephthalic acid, discoloration occurred. Comparative Example 7, which contained only polypropylene resin, had poor mold release properties. From the results of Example 1 and Comparative Examples 1 to 7, it was confirmed that an aqueous composition containing both terephthalic acid and polypropylene resin simultaneously satisfies mold release properties, bake resistance, and coloration requirements. Furthermore, a comparison of Example 1 with Comparative Examples 1, 3, and 4 confirmed that the release properties are dramatically improved by including polypropylene resin, and that this effect cannot be obtained by adding water-soluble polymers or paraffin emulsions.

[0071]

[0072] As shown in Table 3, the aqueous compositions of Examples 2 to 6 had release properties of A or A+, bake resistance of A or A+, and coloration of A. Comparative Example 8, which contained terephthalic acid and adipic acid but did not contain polypropylene resin, had insufficient release properties and bake resistance. Comparative Examples 9 to 14, which contained terephthalic acid and adipic acid and used resins other than polypropylene resin, all showed coloration on the aluminum casting surface, but no coloration occurred on the casting surface in the examples that used polypropylene resin. Comparative Example 12, which contained terephthalic acid and adipic acid and contained paraffin wax instead of polypropylene resin, and Comparative Example 13, which contained carnauba wax instead of polypropylene resin, both had poor release properties and coloration occurred. Comparative Example 14, which contained terephthalic acid and adipic acid and contained silicone resin instead of polypropylene resin, showed coloration.

[0073]

[0074] As shown in Table 4, the aqueous compositions of Example 2 (reproduced) and Examples 7 to 10 had release properties of A or A+, bake resistance of A or A+, and coloration of A. Comparative Example 8 (reproduced), which was the composition of Examples 7 to 10 with the polypropylene resin removed, had insufficient release properties and bake resistance.

[0075] This specification discloses the following compositions: [1] An aqueous composition for die-casting release agent comprising a terephthalate salt, which is a carboxylate, a polypropylene resin, and water, wherein the polypropylene resin is dispersed in water. [2] The aqueous composition for die-casting release agent according to [1], further comprising an adipicate salt, which is a carboxylate. [3] The aqueous composition for die-casting release agent according to [1] or [2], wherein the aqueous composition has a pH of 7 to 13. [4] The aqueous composition for die-casting release agent according to any one of [1] to [3], wherein the polypropylene resin is an acid-modified polypropylene resin. [5] The aqueous composition for die-casting release agent according to any one of [1] to [4], wherein the content of the carboxylate salt as a carboxylic acid is greater than the content of the polypropylene resin. [6] The aqueous composition for die-casting release agent according to any one of [1] to [5], wherein the content of solids in the aqueous composition is 3% to 60% by mass. [7] The aqueous composition for die-casting release agent according to any one of [1] to [6], wherein the content of the carboxylate salt as a carboxylic acid in the aqueous composition is 2% to 30% by mass, and the content of the polypropylene resin in the aqueous composition is 1% to 30% by mass.

[0076] The embodiments disclosed herein should be understood to be illustrative in all respects and not restrictive in any way. The scope of the present invention is defined by the claims and is intended to include all modifications in the sense and scope equivalent to the claims.

Claims

1. An aqueous composition for die-casting release agents, comprising terephthalate, polypropylene resin, and water, wherein the polypropylene resin is dispersed in water.

2. The aqueous composition for die-casting release agent according to claim 1, further comprising an adipine salt.

3. The aqueous composition for die-casting release agent according to claim 1, wherein the aqueous composition has a pH of 7 to 13.

4. The aqueous composition for die-casting release agent according to claim 1, wherein the polypropylene resin is an acid-modified polypropylene resin.

5. The aqueous composition for die-casting release agent according to any one of claims 1 to 4, wherein the content of the carboxylate salt as a carboxylic acid is greater than the content of the polypropylene resin.

6. The aqueous composition for die-casting release agent according to any one of claims 1 to 4, wherein the solid content in the aqueous composition is 3% by mass to 60% by mass.

7. The aqueous composition for die-casting release agent according to claim 6, wherein the content of the carboxylate salt as a carboxylic acid in the aqueous composition is 2% to 30% by mass, and the content of the polypropylene resin in the aqueous composition is 1% to 30% by mass.

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