WO2013122238A1

WO2013122238A1 - Mold release agent for die casting

Info

Publication number: WO2013122238A1
Application number: PCT/JP2013/053775
Authority: WO
Inventors: Norihisa Kishimoto; Seiji Hori; Hiroyuki Inagaki; Kazuhiko Kojima; Masaru Ozaki
Original assignee: Dow Corning Toray Co., Ltd.
Priority date: 2012-02-16
Filing date: 2013-02-06
Publication date: 2013-08-22
Also published as: JP5930172B2; JP2013166176A

Abstract

A mold release agent for die casting, where the mold release agent comprises a silicone compound having kinetic viscosity of 3,000 to 8,000 mm²/s at 25 °C and expressed by the following formula (1): A-R₂SiO-(R₂SiO)x-(RR1SiO)y-(RR2SiO)z-SiR₂-A (1) (wherein, R is each independently a monovalent hydrocarbon group having from 1 to 5 carbons or phenyl group; R1 is an alkyl group or an alkenyl group having from 6 to 20 carbons, R2 is an aralkyl group having from 7 to 20 carbons, A is R, R1, or R2; x, y, and z are arbitrary numbers; value of x/(x+y+z)= 0.350 to 0.700; value of y/(x+y+z)= 0.150 to 0.325; and value of z/(x+y+z)= 0.150 to 0.325). The mold release agent has excellent mold releasability at a high temperature.

Description

DESCRIPTION

MOLD RELEASE AGENT FOR DIE CASTING

TECHNICAL FIELD

[0001] The present invention relates to a mold release agent for die casting.

BACKGROUND ART

[0002] Compositions containing organopolysiloxanes have been conventionally known as mold release agents for die casting. For example, silicone compositions including

organopolysiloxanes modified by alkyl groups and aralkyl groups have been proposed (e.g. Japanese Unexamined Patent Application Publication No. H4-84643 and Japanese Unexamined Patent Application Publication No. 2001-114895).

[0003] Moreover, a silicone emulsion composition having mold releasability and improved dilution stability by combining with a specific surfactant is known. For example, a silicone emulsion composition that combines an oxyethylene adduct of alkyl alcohol having an alkyl group having from 8 to 11 carbons and a long chain alkyl-modified silicone and/or long chain alkyl aralkyl co-modified silicone (e.g. Japanese Unexamined Patent Application Publication No. 2005-54090).

[0004] However, since these silicone compositions have insufficient mold releasability at high temperature, a mold release agent that has improved heat resistance is desired. Thus, an emulsion composition has been proposed that has an added organopolysiloxane including a specified aromatic amino 'group as an agent for improvement of heat resistance (e.g. Japanese Unexamined Patent Application Publication No. 2010-142845).

PRIOR ART DOCUMENTS

[Patent Documents]

[0005] Patent Document 1 : Japanese Unexamined Patent Application Publication No.

H-04-84643A

Patent Document 2: Japanese Unexamined Patent Application Publication No. 2001-114895A Patent Document 3: Japanese Unexamined Patent Application Publication No. 2005-54090A Patent Document 4: Japanese Unexamined Patent Application Publication No. 2010-142845A

SUMMARY OF INVENTION

[Technical Problem]

[0006] Therefore, the conventional mold release agent for die casting had problems in that, although adherence to the mold and mold releasability at low temperature are excellent, the mold releasability at high temperature has been insufficient for production of a die cast product. Moreover, the existing methods for improving heat resistance had problems in that the addition of a specific agent for improvement of heat resistance is required, the production process for the mold release agent becomes complex, and sufficient heat resistance sometimes is not obtained. [0007] The present invention was made to solve the aforementioned problems. The object of the present invention is to provide a mold release agent for die casting that has excellent heat resistance and excellent mold releasability for a mold at high temperature.

[Solution To Problems]

[0008] The inventors accomplished the present invention as a result of intensive investigations directed to achieving the previously described object. That is to say, the object of the present invention is attained by a mold release agent for die casting, wherein the mold release agent comprises a silicone compound having kinetic viscosity of 3,000 to 8,000 mm²/s at 25°C and expressed by the following formula (1 ):

R R R R R

A-Si-O-i-Si-o— (^"Si-°^")— (^~Si_0~) ^Si_A (1)

R R ^x R1 ^y R2 ^Z R

(wherein, R is each independently a monovalent hydrocarbon group having from 1 to 5 carbons or phenyl group; R1 is an alkyl group or an alkenyl group having from 6 to 20 carbons, R2 is an aralkyl group having from 7 to 20 carbons, A is R, R1 , or R2; x, y, and z are arbitrary numbers; value of x/(x+y+z)= 0.350 to 0.700; value of y/(x+y+z)= 0.150 to 0.325; and value of z/(x+y+z)= 0.150 to 0.325).

[0009] The R in formula (1) preferably is the methyl group.

[0010] The x, y, and z in formula (1) are preferably in ranges such that the silicone compound expressed by formula (1) has the aforementioned kinetic viscosity.

[0011] The silicone compound expressed by formula (1) preferably exists in the form of an oil-in-water type emulsion in the presence of an emulsifier.

[0012] The present invention can provide a mold release agent for die casting that displays excellent mold releasability for the mold at high temperature.

[0013] The manufacturing process of the mold release agent for die casting of the present invention may be simplified due to the lack of a need for the addition of an agent for improvement of heat resistance.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 shows the order of processing of a method for measurement of mold releasability of a test piece.

DESCRIPTION OF THE INVENTION

[0015] The mold release agent for die casting of the present invention is characterized by including a silicone compound having kinetic viscosity of 3,000 to 8,000 mm²/s at 25°C and expressed by the following formula (1):

(wherein, R is each independently a monovalent hydrocarbon group having from 1 to 5 carbons or phenyl group; R1 is an alkyl group or an alkenyl group having from 6 to 20 carbons, R2 is an aralkyl group having from 7 to 20 carbons, A is R, R1 , or R2; x, y, and z are arbitrary numbers; value of x/(x+y+z)= 0.325 to 0.700; value of y/(x+y+z)= 0.150 to 0.325; and value of z/(x+y+z)= 0.150 to 0.325).

[0016] Monovalent hydrocarbon groups indicated by R having from 1 to 5 carbons in formula (1) include, but not limited to, an alkyl group such as a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, pentyl group, and the like; a cycloalkyi group such as a cyclopentyl group, and the like; an alkenyl group such as a vinyl group, allyl group, butenyl group, and the like; and groups where a hydrogen atom bonded to a carbon atom is at least partially substituted by a halogen atom (e.g. fluorine or the like) or an organic group including a functional group selected from among the group including the epoxy group, glycidyl group, acyl group, carboxyl group, amino group, methacrylic group, and mercapto group. From the standpoint of mold releasability, at least 50% of the monovalent hydrocarbons R of the silicone compound expressed by formula (1) are preferably methyl groups, and particularly preferably, all of the R are methyl groups.

[0017] Alkyl groups indicated by R1 having from 6 to 20 carbons in formula (1) include, but not limited to, an hexyl group, heptyl group, octyl group, nonyl group, decyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, eicosyl group, or the like. Alkenyl groups indicated by R1 having from 6 to 20 carbons in formula (1) include, but not limited to, an hexenyl group, heptenyl group, octenyl group, or the like.

[0018] Aralkyl groups indicated by R2 having from 7 to 20 carbons in formula (1) include, but not limited to, a benzyl group, 4-methylbenzyl group, p-methoxybenzyl group, diphenylmethyl group, 2-phenylethyl group, 2-phenylpropyl group, 3-phenylpropyl group, or the like.

[0019] A in formula (1) is R, R1 , or R2. However, A is preferably R.

[0020] The x, y, and z in formula (1) may be numbers of any value. However, from the standpoint of paintable properties, x preferably is in the range of 40 to 250 and particularly preferably is in the range of 50 to 200, y is preferably in the range of 1 to 100 and particularly preferably is in the range of 20 to 100, and z is preferably in the range of 1 to 100 and particularly preferably is in the range of 20 to 100. Since emulsification becomes difficult if the value of x+y+z is excessively high, the value of x+y+z is preferably less than or equal to 300. [0021] Moreover, in formula (1), the value of x/(x+y+z) is in the range of 0.350 to 0.700 and preferably is in the range of 0.450 to 0.700, the value of y/(x+y+z) is in the range of 0.150 to 0.325, and the value of z/(x+y+z) is in the range of 0.150 to 0.325. These values indicate relative fractions of the siloxane structural units of formula (1) and affect mold releasability of the mold release agent at high temperature. There is a tendency for mold releasability at high temperature of the obtained mold release agent to be excellent when the values of x/(x+y+z), y/(x+y+z), and z/(x+y+z) are in the aforementioned ranges.

[0022] The x, y, and z values may be found by ²⁹Si-NMR and ¹³C-NMR.

[0023] No particular limitation is placed on the order of the respective siloxane structural units of formula (1), and the siloxane units may have a block or random order.

[0024] Kinetic viscosity at 25°C of the silicone compound expressed by formula (1) is 3,000 to 8,000 mm²/s, and this kinetic viscosity is preferably 4,000 to 6,000 mm²/s. When kinetic viscosity is in the aforementioned range, adherence to the heated mold becomes good, and excellent mold releasability may be obtained even for a high temperature mold.

[0025] The silicone compound expressed by formula (1) may be used as a single type of compound or may be used as a mixture of two or more types of such silicone compounds.

[0026] The content of the silicone compound expressed by formula (1 ) is, but not limited to, preferably in the range of 0.1 to 90 parts by weight, and particularly preferably in the range of 10 to 80 parts by weight per 100 parts by weight of the mold release agent for die casting.

[0027] Although no particular limitation is placed on the form of the compound of formula (1 ) present in the mold release agent of the present invention, this compound preferably exists in the form of an oil-in-water emulsion in the presence of an emulsifier.

[0028] No particular limitation is placed on the emulsifier for dispersing the compound of formula (1) in water. Any surfactant used in the preparation of a silicone emulsion can be used, and any of anionic, cationic, amphoteric, and nonionic surfactants can be used. The emulsifier may be used as a single type or as a mixture of two or more types.

[0029] More specifically, examples of anionic surfactants include saturated or unsaturated fatty acid salts (e.g. sodium laurate, sodium stearate, sodium oleate, sodium linolenate, and the like); alkylsulfuric acid salts; alkylbenzene sulfonic acids (e.g. hexylbenzenesulfonic acid,

octylbenzenesulfonic acid, dodecylbenzenesulfonic acid, and the like) and salts thereof;

polyoxyalkylene alkyl ether sulfuric acid salts; polyoxyalkylene alkenyl ether sulfuric acid salts; polyoxyethylene alkylsulfuric ester salts; sulfosuccinic acid alkyl ester salts; polyoxyalkylene sulfosuccinic acid alkyl ester salts; polyoxyalkylene alkylphenyl ether sulfuric acid salts;

alkanesulfonic acid salts; octyltrimethylammonium hydroxide; dodecyltrimethylammonium hydroxide; alkyl sulfonates; polyoxyethylene alkylphenyl ether sulfuric acid salts; polyoxyalkylene alkyl ether acetic acid salts; alkyl phosphoric acid salts; polyoxyalkylene alkyl ether phosphoric acid salts; acylglutamic acid salts; a-acylsulfonic acid salts; alkylsulfonic acid salts; alkylarylsulfonic acid salts; a-olefinsulfonic acid salts; alkylnaphthalene sulfonic acid salts;

alkanesulfonic acid salts; alkyi- or alkenylsulfuric acid salts; alkylamide sulfuric acid salts; alkyl- or alkenyl phosphoric acid salts; alkylamide phosphoric acid salts; alkyloylalkyl taurine salts; N-acylamino acid salts; sulfosuccinic acid salts; alkyi ether carboxylic acid salts; amide ether carboxylic acid salts; a-sulfofatty acid ester salts; alanine derivatives; glycine derivatives; and arginine derivatives. Examples of salts include alkali metal salts such as sodium salts and the like, alkaline earth metal salts such as magnesium salts and the like, alkanolamine salts such as triethanolamine salts and the like, and ammonium salts.

[0030] Examples of cationic surfactants include alkyltrimethylammonium chloride,

stearyltrimethylammonium chloride, lauryltrimethylammonium chloride, cetyltrimethylammonium chloride, beef tallow alkyltrimethylammonium chloride, behenyltrimethylammonium chloride, stearyltrimethylammonium bromide, behenyltrimethylammonium bromide,

distearyldimethylammonium chloride, dicocoyldimethylammonium chloride,

dioctyldimethylammonium chloride, di(POE)oleylmethylammonium (2 EO) chloride,

benzalkonium chloride, alkyi benzalkonium chloride, alkyi dimethylbenzalkonium chloride, benzethonium chloride, stearyl dimethylbenzylammonium chloride, lanolin derivative quaternary ammonium salt, diethylaminoethylamide stearate, dimethylaminopropylamide stearate, behenic acid amide propyldimethyl hydroxypropylammonium chloride, stearoyl colaminoformyl methylpyridinium chloride, cetylpyridinium chloride, tall oil alkylbenzyl hydroxyethylimidazolinium chloride, and benzylammonium salt.

[0031] Examples of nonionic surfactants include polyoxyalkylene ethers, polyoxyalkylene alkyi ethers, polyoxyalkylene fatty acid esters, polyoxyalkylene fatty acid diesters, polyoxyalkylene resin acid esters, polyoxyalkylene (hydrogenated) castor oils, polyoxyalkylene alkyi phenols, polyoxyalkylene alkyi phenyl ethers, polyoxyalkylene phenyl phenyl ethers, polyoxyalkylene alkyi esters, sorbitan fatty acid esters, polyoxyalkylene sorbitan alkyi esters, polyoxyalkylene sorbitan fatty acid esters, polyoxyalkylene sorbitol fatty acid esters, polyoxyalkylene glycerol fatty acid esters, polyglycerol alkyi ethers, polyglycerol fatty acid esters, sucrose fatty acid esters, fatty acid alkanolamides, alkylglucosides, polyoxyalkylene fatty acid bisphenyl ethers, polypropylene glycol, diethyleneglycol, polyoxyalkylene-modified silicones, polyglyceryl-modified silicones, glyceryl-modified silicones, sugar-modified silicones, fluorine-based surfactants,

polyoxyethylene/polyoxypropylene block polymers, and alkyi polyoxyethylene/polyoxypropylene block polymer ethers.

[0032] Examples of amphoteric surfactants include imidazoline-type, amidobetaine-type, alkylbetaine-type, alkylamidobetaine-type, alkylsulfobetaine-type, amidosulfobetaine-type, hydroxysulfobetaine-type, carbobetaine-type, phosphobetaine-type aminocarboxylic acid-type, and amidoamino acid-type amphoteric surfactants. Specifically, imidazoline-type amphoteric surfactants such as 2-undecyl-N,N,N-(hydroxyethylcarboxymethyl)-2-imidazoline sodium, 2-cocoyl-2-imidazolinium hydroxide-1-carboxyethyloxy disodium salt, and the like;

alkylbetaine-type amphoteric surfactants such as lauryl dimethylaminoacetic betaine, myristyl betaine, and the like; amidobetaine-type amphoteric surfactants such as coconut oil fatty acid amidopropyl dimethylamino acetic acid betaine, palm kernel oil fatty acid amidopropyl dimethylamino acetic acid betaine, beef tallow fatty acid amidopropyl dimethylamino acetic acid betaine, hardened beef tallow fatty acid amidopropyl dimethylamino acetic acid betaine, lauric acid amidopropyl dimethylamino acetic acid betaine, myristic acid amidopropyl dimethylamino acetic acid betaine, palmitic acid amidopropyl dimethylamino acetic acid betaine, stearic acid amidopropyl dimethylamino acetic acid betaine, oleic acid amidopropyl dimethylamino acetic acid betaine, and the like; alkylsulfobetaine-type amphoteric surfactants such as coconut oil fatty acid dimethyl sulfopropyl betaine and the like; alkyl hydroxy sulfobetaine-type amphoteric surfactants such as lauryl dimethylaminohydroxy sulfobetaine and the like; phosphobetaine-type amphoteric surfactants such as laurylhydroxy phosphobetaine and the like; and amidoamino acid-type amphoteric surfactants such as sodium N-lauroyl-N'-hydroxyethyl-N'-carboxymethyl ethylenediamine, sodium N-oleoyl-N'-hydroxyethyl-N'-carboxymethyl ethylenediamine, sodium N-cocoyl-N'-hydroxyethyl-N'-carboxymethyl ethylenediamine, potassium

N-lauroyl-N'-hydroxyethyl-N'-carboxymethyl ethylenediamine, potassium

N-oleoyl-N'-hydroxyethyl-N'-carboxymethyl ethylenediamine, sodium

N-lauroyl-N-hydroxyethyl-N'-carboxymethyl ethylenediamine, sodium

N-oleoyl-N-hydroxyethyl-N'-carboxymethyl ethylenediamine, sodium

N-cocoyl-N-hydroxyethyl-N'-carboxymethyl ethylenediamine, monosodium

N-lauroyl-N-hydroxyethyl-N',N'-dicarboxymethyl ethylenediamine, monosodium

N-oleoyl-N-hydroxyethyl-N',N'-dicarboxymethyl ethylenediamine, monosodium

N-cocoyl-N-hydroxyethyl-N',N'-dicarboxymethyl ethylenediamine, disodium

N-lauroyl-N-hydroxyethyl-N',N'-dicarboxymethyl ethylenediamine, disodium

N-oleoyl-N-hydroxyethyl-N'.N'-dicarboxymethyl ethylenediamine, disodium

N-cocoyl-N-hydroxyethyl-N'.N'-dicarboxymethyl ethylenediamine, and the like.

[0033] Examples of semipolar surfactants include alkylamine oxide-type surfactants, alkylamine oxides, alkylamide amine oxides, alkylhydroxyamine oxides, and the like. Alkyldimethylamine oxides having from 10 to 18 carbons, alkoxyethyl dihydroxyethylamine oxides having from 8 to 18 carbons, and the like are preferably used. Specific examples thereof include

dodecyldimethylamine oxide, dimethyloctylamine oxide, diethyldecylamine oxide,

bis-(2-hydroxyethyl)dodecylamine oxide, dipropyltetradecylamine oxide,

methylethylhexadecylamine oxide, dodecylamidopropyldimethylamine oxide, cetyldimethylamine oxide, stearyldimethylamine oxide, tallow dimethylamine oxide,

dimethyl-2-hydroxyoctadecylamine oxide, lauryldimethylamine oxide, myristyldimethylamine oxide, stearyldimethylamine oxide, isostearyldimethylamine oxide, coconut fatty acid

alkyldimethylamine oxide, caprylic amide propyldimethylamine oxide, capric amide

propyldimethylamine oxide, lauric amide propyldimethylamine oxide, myristic amide

propyldimethylamine oxide, palmitic amide propyldimethylamine oxide, stearic amide

propyldimethylamine oxide, isostearic amide propyldimethylamine oxide, oleic amide

propyldimethylamine oxide, ricinoleic amide propyldimethylamine oxide, 12-hydroxystearic amide propyldimethylamine oxide, coconut fatty acid amide propyldimethylamine oxide, palm kernel oil fatty acid amide propyldimethylamine oxide, castor oil fatty acid amide

propyldimethylamine oxide, lauric amide ethyldimethylamine oxide, myristic amide

ethyldimethylamine oxide, coconut fatty acid amide ethyldimethylamine oxide, lauric amide ethyldiethylamine oxide, myristic amide ethyldiethylamine oxide, coconut fatty acid amide ethyldiethylamine oxide, lauric amide ethyldihydroxyethylamine oxide, myristic amide

ethyldihydroxyethylamine oxide, and coconut fatty acid amide ethyldihydroxyethylamine oxide.

[0034] The content of the surfactant in the mold release agent of the present invention is, but not limited to, preferably in the range of 0.1 to 20 parts by weight, and particularly preferably in the range of 0.5 to 10 parts by weight per 100 parts by weight of the mold release agent for die casting.

[0035] Although the mold release agent for die casting of the present invention is a composition that comprises the silicone compound expressed by formula (1), other diorganopolysiloxanes may be comprised in addition to this silicone compound.

[0036] Examples of manufacturing method of the mold release agent for die casting of the present invention include emulsification of the silicone compound expressed by formula (1), by normal methods using an emulsification equipment such as a homo mixer, colloid mill, line mixer, homogenizer, or the like.

[0037] Although the mold release agent for die casting of the present invention is characterized by including the silicone compound expressed by general formula (1), one or more type of additive normally used in a mold release agent including a silicone compound may be additionally blended as long as the object of the present invention is not impaired. Such additives are exemplified by pH adjusting agents, antibacterial agents, antifungal agents, rust prevention agents, colorants, mineral oils, higher fatty acids, thickening agents, aluminum powder, graphite, or the like.

[0038] The mold release agent for die casting of the present invention is used, for example, by using a spray gun to uniformly spray on the mold, or by coating the mold by using a cloth, paper, or brush impregnated with the mold release agent for die casting of the present invention. EXAMPLES

[0039] The present invention will be explained below in further detail by use of examples. In the examples, the content of the components referred to as "parts" means "parts by weight."Note that the present invention is not limited to these examples. Also, Ph in formulae indicates a phenyl group.

[0040] Practical Example 1

725.0 g of methylhydrogenpolysiloxane expressed by the following formula:

and 180 g of toluene were loaded into a reaction vessel, and the mixture was heated to 70°C with stirring under a nitrogen stream. Then, 20 g of a toluene solution of

platinum-1 ,3,5,7-tetravinyl-1 ,3,5,7-tetramethyl cyclotetrasiloxane complex (Pt concentration: 0.03 wt.%) was added to this mixture. 212.6 g of a-methylstyrene was added dropwise so as to maintain reaction temperature at 70 to 90°C. After completion of dropwise addition, stirring was continued for 1 hour at 90°C. 2 g of the reaction liquid was sampled, and the reaction rate was confirmed to be 45 to 50% by the alkali decomposition gas generation method (i.e.

decomposition of the remnant Si-H groups by a solution of KOH in ethanol/water, and calculation of the reaction rate based on the volume of generated hydrogen gas). Thereafter, 262.3 g of 1-octene was added dropwise to the reaction vessel so as to maintain reaction temperature at 90 to 110°C. After completion of dropwise addition, 20 g of the toluene solution of

platinum-1 ,3,5,7-tetravinyl-1 ,3,5,7-tetramethyl cyclotetrasiloxane complex (Pt concentration:

0.03 wt.%) was added, and stirring of the mixture was continued for 8 hours at 110°C. 2 g of the reaction liquid was sampled and it was confirmed that the reaction was complete through an alkali decomposition gas generation method. After removal of the low-boiling components by heating the reaction liquid under vacuum, 1 ,132 g of the silicone compound expressed by the following formula was obtained.

The formula was confirmed by ²⁹Si-NMR and ¹³C-NMR. Kinetic viscosity of the obtained silicone compound was measured at 25°C according to JIS-Z-8803 using an Ubbelohde type viscometer tube. The kinetic viscosity was 5,200 mm²/s. [0041 ] Practical Example 2

610 g of methylhydrogenpolysiloxane expressed by the following formula:

and 180 g of toluene were loaded into a reaction vessel, and the mixture was heated to 70°C while stirring under a stream of nitrogen. Then, 28 g of a toluene solution of

platinum-1 ,3,5,7-tetravinyl-1 ,3,5,7-tetramethyl cyclotetrasiloxane complex (Pt concentration: 0.03 wt.%) was added to this mixture. 264.1 g of a-methylstyrene was added dropwise so as to maintain reaction temperature at 70 to 90°C. After completion of dropwise addition, stirring was continued for 4 hours at 90°C. Thereafter, 2 g of the reaction liquid was sampled, and the reaction rate was confirmed to be 45 to 50% by the alkali decomposition gas generation method. Thereafter, 325.9 g of 1-octene was added dropwise to the reaction vessel so as to maintain reaction temperature at 90 to 110°C. After completion of dropwise addition, 16 g of the toluene solution of platinum-1 ,3,5,7-tetravinyl-1 ,3,5,7-tetramethyl cyclotetrasiloxane complex (Pt concentration: 0.03 wt.%) was added, and stirring of the mixture was continued for 5 hours at 110°C. 2 g of the reaction liquid was sampled and it was confirmed that the reaction was complete through an alkali decomposition gas generation method. After removal of the low-boiling components by heating the reaction liquid under vacuum, 1 , 107 g of the silicone compound expressed by the following formula was obtained.

The formula was confirmed by ²⁹Si-NMR and ¹³C-NMR. Kinetic viscosity of the obtained silicone compound was measured at 25°C according to JIS-Z-8803 using an Ubbelohde type viscometer tube. The kinetic viscosity was 4,400 mm²/s

[0042] Practical Example 3

274.7 g of methylhydrogenpolysiloxane expressed by the following formula:

and 90 g of toluene were loaded into a reaction vessel, and the mixture was heated to 70°C while stirring under a stream of nitrogen. Then, 10 g of a toluene solution of

platinum-1 ,3,5,7-tetravinyl-1 ,3,5,7-tetramethyl cyclotetrasiloxane complex (Pt concentration: 0.03 wt.%) was added to this mixture. 145.6 g of a-methylstyrene was added dropwise so as to maintain reaction temperature at 70 to 90°C. After completion of dropwise addition, stirring was continued for 3 hours at 90°C. Thereafter, 2 g of the reaction liquid was sampled, and the reaction rate was confirmed to be 45 to 50% by the alkali decomposition gas generation method. Thereafter, 180 g of 1-octene was added dropwise to the reaction vessel so as to maintain reaction temperature at 90 to 110°C. After completion of dropwise addition, 8 g of the toluene solution of platinum-1 ,3,5,7-tetravinyl-1 ,3,5,7-tetramethyl cyclotetrasiloxane complex (Pt concentration: 0.03 wt.%) was added, and stirring of the mixture was continued for 8 hours at 110°C. 2 g of the reaction liquid was sampled and it was confirmed that the reaction was complete through an alkali decomposition gas generation method. After removal of the low-boiling components by heating the reaction liquid under vacuum, 544 g of the silicone compound expressed by the following formula was obtained.

The formula was confirmed by ²⁹Si-NMR and ¹³C-NMR. Kinetic viscosity of the obtained silicone compound was measured at 25°C according to JIS-Z-8803 using an Ubbelohde type viscometer tube. The kinetic viscosity was 4,800 mm²/s.

[0043] Comparative Example 1

560 g of methylhydrogenpolysiloxane expressed by the following formula:

and 120 g of toluene were loaded into a reaction vessel, and the mixture was heated to 60°C while stirring under a stream of nitrogen. Then, 27 g of a toluene solution of

platinum-1,3,5,7-tetravinyl-1 ,3,5,7-tetramethyl cyclotetrasiloxane complex (Pt concentration: 0.03 wt.%) was added to this mixture. 107.4 g of a-methylstyrene was added dropwise so as to maintain reaction temperature at 60 to 90°C. After completion of dropwise addition, stirring was continued for 4 hours at 80 to 90°C. Thereafter, 2 g of the reaction liquid was sampled, and the reaction rate was confirmed to be 45 to 50% by the alkali decomposition gas generation method. Thereafter, 132.6 g of 1-octene was added dropwise to the reaction vessel so as to maintain reaction temperature at 90 to 110°C. After completion of dropwise addition, 16 g of the toluene solution of platinum-1 ,3,5,7-tetravinyl-1 ,3,5,7-tetramethyl cyclotetrasiloxane complex (Pt concentration: 0.03 wt.%) was added, and stirring of the mixture was continued for 2 hours at 100°C. 2 g of the reaction liquid was sampled and it was confirmed that the reaction was complete through an alkali decomposition gas generation method. After removal of the low-boiling components by heating the reaction liquid under vacuum, 750 g of the silicone compound expressed by the following formula was obtained.

The formula was confirmed by ²⁹Si-NMR and ¹³C-NMR. Kinetic viscosity of the obtained silicone compound was measured at 25°C according to JIS-Z-8803 using an Ubbelohde type viscometer tube. The kinetic viscosity was 6, 100 mm²/s.

[0044] Comparative Example 2

483.4 g of methylhydrogenpolysiloxane expressed by the following formula:

CH3 CH3 CH3 CH3

H₃C-Si-0-£-Si-o4 f-Si-OH Si-CH₃

CH3 CH3 H CH and 120 g of toluene were loaded into a reaction vessel, and the mixture was heated to 80°C while stirring under a stream of nitrogen. Then, 19 g of a toluene solution of

platinum-1 ,3,5,7-tetravinyl-1 ,3,5,7-tetramethyl cyclotetrasiloxane complex (Pt concentration: 0.03 wt.%) was added to this mixture. 141.8 g of a-methylstyrene was added dropwise so as to maintain reaction temperature at 80 to 90°C. After completion of dropwise addition, stirring was continued for 3 hours at 90°C. Thereafter, 2 g of the reaction liquid was sampled, and the reaction rate was confirmed to be 45 to 50% by the alkali decomposition gas generation method. Thereafter, 174.9 g of 1-octene was added dropwise to the reaction vessel so as to maintain reaction temperature at 90 to 100°C. After completion of dropwise addition, 27 g of the toluene solution of platinum-1 ,3,5,7-tetravinyl-1 ,3,5,7-tetramethyl cyclotetrasiloxane complex (Pt concentration: 0.03 wt.%) was added, and stirring of the mixture was continued for 7 hours at 100°C. 2 g of the reaction liquid was sampled and it was confirmed that the reaction was complete through an alkali decomposition gas generation method. After removal of the low-boiling components by heating the reaction liquid under vacuum, 738 g of the silicone compound expressed by the following formula was obtained.

The formula was confirmed by ²⁹Si-NMR and ¹³C-NMR. Kinetic viscosity of the obtained silicone compound was measured at 25°C according to JIS-Z-8803 using an Ubbelohde type viscometer tube. The kinetic viscosity was 9, 100 mm²/s.

[0045] Comparative Example 3

249.1 g of methylhydrogenpolysiloxane expressed by the following formula:

platinum-1 ,3,5,7-tetravinyl-1 ,3,5,7-tetramethyl cyclotetrasiloxane complex (Pt concentration: 0.03 wt.%) was added to this mixture. 157.1 g of a-methylstyrene was added dropwise so as to maintain reaction temperature at 70 to 90°C. After completion of dropwise addition, stirring was continued for 1 hour at 90°C. Thereafter, 2 g of the reaction liquid was sampled, and the reaction rate was confirmed to be 45 to 50% by the alkali decomposition gas generation method. Thereafter, 193.9 g of 1-octene was added dropwise to the reaction vessel so as to maintain reaction temperature at 90 to 110°C. After completion of dropwise addition, 8 g of the toluene solution of platinum-1 ,3,5,7-tetravinyl-1 ,3,5,7-tetramethyl cyclotetrasiloxane complex (Pt concentration: 0.03 wt.%) was added, and stirring of the mixture was continued for 10 hours at 1 0°C. 2 g of the reaction liquid was sampled and it was confirmed that the reaction was complete through an alkali decomposition gas generation method. After removal of the low-boiling components by heating the reaction liquid under vacuum, 545 g of the silicone compound expressed by the following formula was obtained.

The formula was confirmed by ²⁹Si-NMR and ¹³C-NMR. Kinetic viscosity of the obtained silicone compound was measured at 25°C according to JIS-Z-8803 using an Ubbelohde type viscometer tube. The kinetic viscosity was 4,300 mm²/s.

[0046] Comparative Example 4

272.6 g of methylhydrogenpolysiloxane expressed by the following formula:

was loaded into a reaction vessel, and the methylhydrogenpolysiloxane was heated to 125°C while stirring under a stream of nitrogen. Then, 0.26 g of a 5 wt.% isopropyl alcohol solution of chloroplatinic acid was added, and 100.6 g of a-methylstyrene was added dropwise so as to maintain reaction temperature at 100 to 170°C. After completion of dropwise addition, stirring of the mixture was continued for 1.5 hours at 130°C. Thereafter, 626.8 g of 1-dodecene was added dropwise to the reaction vessel so as to maintain reaction temperature at 100 to 170°C. After completion of dropwise addition, stirring of the mixture was continued for 1.5 hours at 130°C. Thereafter, 2 g of the reaction liquid was sampled, and completion of the reaction was confirmed by the alkali decomposition gas generation method. After removal of the low-boiling components by heating the reaction liquid under vacuum, 900 g of the silicone compound expressed by the following formula was obtained.

The formula was confirmed by ²⁹Si-NMR and ¹³C-NMR. Kinetic viscosity of the obtained silicone compound was measured at 25°C according to JIS-Z-8803 using an Ubbelohde type viscometer tube. The kinetic viscosity was 1 ,300 mm²/s.

[0047] Comparative Example 5

232.5 g of 1-dodecene was loaded into a reaction vessel and heated to 70°C while stirring under a stream of nitrogen. Then, 0.19 g of a 5 wt.% isopropyl alcohol solution of chloroplatinic acid was added, and 722.5 g of the methylhydrogenpolysiloxane expressed by the following formula was added dropwise so as to maintain reaction temperature at 70 to 160°C.

After completion of dropwise addition, stirring was continued for 30 minutes at 160°C. Thereafter, 2 g of the reaction liquid was sampled, and completion of the reaction was confirmed by the alkali decomposition gas generation method. After removal of the low-boiling

components by heating the reaction liquid under vacuum, 850 g of the silicone compound expressed by the following formula was obtained.

[0048] (Viscosity Measurement Method)

Viscosity was measured at 25°C using Ubbelohde type viscometer tube according to JIS-Z-8803.

[0049] (Emulsion Preparation Method)

50 parts of a silicone compound described in Practical Examples 1 to 3 or a silicone compound described in Comparative Examples 1 to 5, 4 parts of polyoxyethylene (6 mol) isodecyl ether (HLB 12.5), 0.025 parts of sodium polyoxyethylene lauryl sulfate, and 4.4 parts of water were blended, and the mixture was emulsified using a continuous mixing apparatus. Then, the mixture was diluted by addition of 41.44 parts of water, and 0.005 parts of sodium hydrogen carbonate as a pH adjusting agent was added to obtain a translusent white emulsion. Mold release resistance of the obtained translusent white emulsion was measured in the following manner. The results are given in Table 1.

[0050] (Measurement of Mold Release Resistance)

Firstly, as shown in FIG. 1 (A), a test piece 2 (material = SKD61 , 200 mm ^χ 200 mm ^χ 30 mm thick) containing the thermocouple 1 of a releasability tester (product name = Lub-Tester-U, manufactured by MEC International Co., Ltd.) was heated to a certain temperature using an external commercial heater. Thereafter, the test piece 2 was arranged vertically, a previously prepared emulsion 4 diluted 150-fold using water was sprayed from a nozzle 3 against the test piece 2 using a spray time of 1 second, 1 spraying revolution, and an air pressure of 0.4 MPa.

[0051] Immediately thereafter, the test piece 2 was placed horizontally on the main body of the test apparatus 5 as shown in FIG. 1(B) so as to be carried centrally on ring 6 manufactured by MEC International Co., Ltd. Thereafter, aluminum melt (ADC12, temperature: 680°C) was poured into the assembly, and the assembly was cooled for 40 seconds to allow solidification. Thereafter, an iron weight 8 was immediately gently loaded upon the solidified aluminum 7 (part No. ADC 2), and mold release resistance was measured while pulling the ring 6 in the X direction using the gear of the same apparatus.

[0052] Table 1

Table 1 (continued)

[0053] Table 1 shows respective kinetic viscosities and the fractions of diorganosiloxane structural units of the silicone compounds used in each of the Practical Examples and

Comparative Examples. The diorganosiloxane structural unit fraction indicates the fraction of the respective diorganosiloxane structural unit relative to the total diorganosiloxane structural units in the silicone compound (value set at 1). Moreover, Table 1 shows the mold release resistance measured for the mold release agent for die casting including the respective silicone compound. When the mold release agents for die casting of Practical Examples 1 to 3 were used, the values of mold release resistance at 300°C and 400°C were small, and excellent mold releasability was displayed. On the other hand, when the mold release agents for die casting of Comparative Examples 1 to 3 were used, mold releasability worsened at 400°C. When the mold release agents for die casting of Comparative Examples 4 and 5 were used, the poured aluminum seized to the mold at 400°C.

[Reference Numerals]

[0054]

1.. ..Thermocouple

2.. .Test piece

3.. . Nozzle

4.. . Emulsion diluted 150-fold using water

5.. . Main body of test apparatus

6.. . Ring

7.. .Solidified aluminum

8.. . Iron weight

Claims

1. A mold release agent for die casting;

wherein the mold release agent comprises a silicone compound having kinetic viscosity of 3,000 to 8,000 mm²/s at 25°C and expressed by following formula (1):

R R R R R

A-Si-O-i-Si-o— (^"Si~°^")— (^"Si~°^") f^{~A (1)}

R R ^x R1 ^y R2 ^Z R

(wherein, R is each independently a monovalent hydrocarbon group having from 1 to 5 carbons or phenyl group; R1 is an alkyl group or an alkenyl group having from 6 to 20 carbons, R2 is an aralkyl group having from 7 to 20 carbons, A is R, R1 , or R2; x, y, and z are arbitrary numbers; value of x/(x+y+z) = 0.350 to 0.700; value of y/(x+y+z) = 0. 50 to 0.325; and value of z/(x+y+z) = 0.150 to 0.325).

2. The mold release agent for die casting according to claim 1 ; wherein R is methyl group.

3. The mold release agent for die casting according to claim 1 ;

wherein the silicone compound expressed by the formula (1) exists as an oil-in-water type emulsion in the presence of an emulsifier.