JPH0899322A - Release agent for mold - Google Patents

Abstract

PURPOSE: To provide a release agent containing a silicone oil, a surface active agent and an aqueous dispersion medium which not only leaves almost no remnants such as polluted substances on a mold but also provides superior release properties from the mold even in case of using for vulcanization molding of an acrylic rubber. CONSTITUTION: A release agent for a mold contains a silicone oil, (1) a nonioinic surface active agent of an ether type or polyhydric alcohol ester type or (2) a nonionic surface active agent to be decomposed or volatilized almost completely at a molding temperature applied at the time of molding, a methacrylic emulsion and an aqueous dispersion medium.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a mold release agent. More specifically, it relates to a mold release agent that is preferably used during vulcanization molding of acrylic rubber.

[0002]

2. Description of the Related Art An external coating type mold release agent is generally used during vulcanization molding of rubber. As such an external coating type release agent, one containing silicone oil is widely used because of its excellent releasability. By the way, when an external release agent is applied to the mold surface, it is preferable to use water in order to eliminate the danger of the dispersion medium, such as the toxicity and the ignitability, but the silicone oil itself is compatible with water. Because there is no
A method of adding a surfactant at the same time to form a micelle state and dispersing it in water is adopted. As the surfactant used at this time, ionic compounds such as organic fatty acid compounds and phosphoric acid compounds are used because of their price and availability.

By the way, the releasing action between the mold and the rubber is brought about only by the silicone oil, and it is desirable that the component has a long-lasting effect. It seems that it will not adhere to.
At this time, it was found that the acid component of the surfactant sometimes decomposes certain components in the acrylic rubber compounding agent to generate a contaminant containing a metal salt as a main component.

Such contaminants penetrate the silicone oil film to form a strong film on the surface of the mold, and the film once formed cannot be easily removed by cleaning under normal mold cleaning conditions. belongs to. In addition to this, when the mold release agent contains a reactive component such as a phosphoric acid ester, it may react with the other components contained in the acrylic rubber as described above depending on the formulation, thereby contaminating the mold. Or hinder the vulcanization and molding of the acrylic rubber, or cause problems such as surface hardening or softening of the vulcanized molded product and deterioration of rubber physical properties.

Therefore, the present applicant has previously proposed that in a mold releasing agent containing silicone oil, a surfactant and an aqueous dispersion medium, even when it is used during vulcanization molding of acrylic rubber, the mold surface Silicone oil, (1), as a mold release agent that leaves almost no residue such as contaminants on top
Ether type or polyhydric alcohol ester type nonionic surfactant or (2) mold release containing nonionic surfactant and an aqueous dispersion medium which almost completely decomposes or volatilizes at the mold temperature during molding. Proposing a mold agent (Japanese Patent Application No. 5)
-294,494).

Although the proposed mold release agent for molds can achieve the intended purpose of effectively preventing contamination on the mold surface during vulcanization molding of acrylic rubber, it is possible to achieve the conventional ionic system. The mold release property was poorer than that of the mold release agent using the surfactant, and the vulcanized molded product sometimes cracked or was torn when released from the mold.

[0007]

The object of the present invention is to provide a mold release agent containing a silicone oil, a surfactant and an aqueous dispersion medium, even when it is used during vulcanization molding of acrylic rubber. The object of the present invention is to provide a mold release agent for molds, which not only leaves almost no residue such as contaminants on the mold surface but also has excellent mold releasability from the mold.

[0008]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
Silicone oil, (1) nonionic surfactant of ether type or polyhydric alcohol ester type, or (2) nonionic surfactant that decomposes or volatilizes almost completely at the mold temperature during molding, methacrylic resin emulsion and This is achieved by a mold release agent containing an aqueous dispersion medium.

As the silicone oil exhibiting a releasing action, any silicone oil having a function of forming a film on the surface of the die by coating, thereby preventing direct contact between the die and rubber, and improving the releasability, etc. Any can be used,
For example, various silicone oils such as a simple polydimethylsiloxane-based one, a polyether skeleton in the main chain for imparting flexibility, or an alkyl side chain can be used.

The nonionic surfactant of the type (1) has a functional group (for example, -COOH, -POH, -NH group, etc.) that acts as a strong acid or alkaline in the molecule. On the other hand, an ether type (for example, polyoxyethylene alkyl ether type, polyoxyethylene alkyl allyl ether type, etc.) that has a structure that easily forms micelles with silicone oil in an aqueous dispersion medium and gives a good dispersion state ) Or a polyhydric alcohol ester type (such as polyoxyethylene sorbitan alkyl ester type) is used, and it may be used in combination with other components such as a stabilizer.

Although these nonionic surfactants hardly react with the compounding ingredients of the acrylic rubber,
Thermal decomposition residues may remain on the mold surface as solids. Unlike contaminants formed when other ionic surfactants are used, this type of solid matter can be easily removed under normal mold cleaning conditions, but the cleaning frequency is reduced. Since it is important in the process, it is desirable not to produce such solid matter.

From this point of view, a nonionic surfactant of the type (2), that is, a nonionic surfactant which is almost completely decomposed or volatilized at the mold temperature during molding, such as It is preferable to use an ether type nonionic surfactant. Compound represented by general formula RO (C ₂ H ₄ O) nH R: Alkyl group having 8 to 12 carbon atoms n: 3 to 12 (Example) Triethylene glycol-n-octyl ether Triethylene glycol-n-decyl ether tetra ethylene glycol -n- decyl ether formula _{(ROCH 2) 2 CHO (C} 2 H 4 O) nH R: alkyl group having 6 to 12 carbon atoms n: 3 to 12 formula _{(ROCH 2) 3 CCH 2 O} (C ₂ H ₄ O) nHR: C4-12 alkyl group n: 3-20

In addition to the above components, the mold releasing agent of the present invention includes an aqueous emulsion of a methacrylic resin, specifically, a homopolymer or copolymer of methyl methacrylate, hydroxymethyl methacrylate, ethoxyethyl methacrylate and the like. Aqueous polymer emulsion (solids concentration approx. 10-2
5% by weight) is blended and used. Upon use, it is preferable to remove the polymerization initiator and extra surfactant contained therein before use.

Water is generally used as the aqueous dispersion medium, but it is added for the purpose of increasing the boiling point of the liquid, preventing the liquid from scattering on the mold due to bumping, and adjusting the viscosity of the liquid. It is also used as an aqueous solution to which alcohol such as butanol, etc., glycol such as propylene glycol, polyethylene glycol, etc., is added.

Each of these components is generally, but not limited to, about 0.001 to 50% by weight of silicone oil (about 10 to 20% by weight) and about 0.0001 to 40% by weight of nonionic surfactant (about 0.1 to 10% by weight). %) Methacrylic resin emulsion About 0.001 to 1% by weight (about 0.1 to 0.5% by weight) Aqueous dispersion medium (water or aqueous solution) Used as a balance (preferred ratio in parentheses) to form a release agent dispersion . If necessary, these release agent dispersions may be diluted with an aqueous dispersion medium immediately before coating on the mold surface before use.

The mold release agent is applied to the mold surface by brushing,
It can be carried out by any commonly used method such as spraying or dipping, and vulcanization molding of acrylic rubber is carried out using a mold coated with such a release agent.

[0017]

INDUSTRIAL APPLICABILITY In a mold releasing agent containing a silicone oil, a surfactant and an aqueous dispersion medium, when a specific nonionic surfactant is used as the surfactant, it is mixed with an acrylic rubber compounding agent. Becomes extremely less reactive,
When the rubber is vulcanized and molded, a mold releasing agent for the mold is formed which leaves almost no residue such as contaminants on the mold surface. The effect of preventing mold contamination is remarkable when a nonionic surfactant that decomposes or volatilizes almost completely at the mold temperature during molding is used.

Further, by mixing and using a methacrylic resin emulsion in such a mold releasing agent, the mold releasing force at the time of vulcanization molding of the acrylic rubber is lowered, whereby the mold releasing agent observed at the time of mold releasing is reduced. Phenomena such as cracking and tearing of the vulcanized product can be effectively prevented.

[0019]

Next, the present invention will be described by way of examples.

Reference Example A glass reaction vessel having a volume of 3 L was charged with 500 g of water, 500 g of methyl methacrylate, 1 g of sodium dodecyl sulfate and 1 g of ammonium persulfate, and the mixture was stirred at 50 ° C. under a nitrogen gas purge while stirring with a paddle type stirring device. Polymerization reaction for 3 hours at 80 ° C to complete the reaction.
The polymerization reaction was continued for 1 hour. The resulting emulsion cooled to room temperature was placed in a bag-shaped semipermeable membrane made of cellulose, dialyzed with water for 2 days to remove the surfactant and the polymerization initiator in the emulsion, and then water was added to obtain a solid content concentration. Has 20 weight
The methacrylic resin emulsion was adjusted so that it would be%.

Example 1 Nonionic surfactant (HLB 16.7) 4% by weight Toho Chemical Product Sorbon T-20, polyoxyethylene sorbitan alkyl ester silicone oil 16 〃 Nippon Unicar Product L-7001, polyether propylene glycol 60 〃 Methacrylic resin emulsion 1 〃 Water 19 〃 The release agent composition was prepared in such a mixing ratio.

Example 2 Nonionic surfactant 4% by weight Wako Pure Chemical Industries, Triethylene glycol-n-octyl ester Silicone oil (L-7001) 16〃 Propylene glycol 60〃 Methacrylic resin emulsion 1〃 Water 19〃 This The release agent composition was prepared in such a blending ratio.

Comparative Example 1 In the example, the methacrylic resin emulsion was not used, and the proportion of water was changed to 20% by weight.

Comparative Example 2 In the example, the same proportion of dilauryl phosphate was used instead of the nonionic surfactant, the methacrylic resin emulsion was not used, and the proportion of water was changed to 20% by weight.

The release agent compositions prepared in the above Examples and Comparative Examples were diluted 150 times with water and applied on the surface of a mold to prepare an acrylic rubber compound having the following composition: Acrylic Rubber (Nippon Mektron PA-312) 100 parts by weight HAF carbon black 40 〃 Stearic acid 1 〃 Zinc carbamate 3 〃 Vulcanized and molded at 180 ℃ for 30 minutes. The force required to take it out was measured using a push-pull gauge, and the average value of 10 measurements was used as the release force. Further, the vulcanization molding of the acrylic rubber under such conditions was performed 500 times, and the amount of contaminants attached to the mold was measured. The results obtained are shown in the following table. Table Examples release force (kg) contaminant content ([mu] g) Example 1.2 52 Comparative Example 1 2.2 28 〃 2 1.0 190

Claims (3)

[Claims] 1. A mold release agent comprising a silicone oil, an ether type or polyhydric alcohol ester type nonionic surfactant, a methacrylic resin emulsion and an aqueous dispersion medium. 2. Silicone oil, a nonionic surfactant that decomposes or volatilizes almost completely at the mold temperature during molding,
A mold release agent comprising a methacrylic resin emulsion and an aqueous dispersion medium. 3. The mold release agent according to claim 1, which is used during vulcanization molding of acrylic rubber.