JPH057170B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a mold release agent, and more particularly to a mold release agent containing dimethylpolysiloxane as a main ingredient. [Prior Art] Dimethylpolysiloxane has conventionally been used as an external and/or internal mold release agent when molding rubber mats, rubber hoses, tires, etc., and as a thermosetting,
It is used as an internally added mold release agent or external mold release agent when molding thermoplastic resins, and as a mold release agent for heat fusing rolls and thermoplastic resin toners in xerographic copying machines. Ta. The dimethylpolysiloxane used in these mold release agents is manufactured by, for example, polymerizing cyclic dimethylsiloxane in the presence of an acid or alkali catalyst and then lightly stripping the product under reduced pressure. Dimethylsiloxane oligomers below 20 were present at 5000-30000 ppm. [Problems to be solved by the invention] However, the above-mentioned conventional silicon atom number of 20
The following dimethylsiloxane oligomers from 5000 to
When dimethylpolysiloxane contains a large amount of 30,000 ppm, if it is used at high temperatures for a long time, the dimethylsiloxane oligomer will evaporate and adhere to exhaust fans, etc., forming oily stains, and the oily substances will fall and cause molded products to deteriorate. It had the disadvantage of contaminating the surface. Furthermore, dimethylsiloxane oligomers are oxidized,
A serious drawback was that it turned into silicon dioxide powder, which adversely affected various surrounding electrical and electronic components.
In particular, xerographic copying machines had the disadvantage that silicon dioxide powder produced by oxidation of dimethylsiloxane oligomers adhered to the corotron, making it impossible to make clear copies. The present invention aims to eliminate the above-mentioned drawbacks and provides a mold release agent that does not generate oily volatiles or silicon dioxide powder even when used at high temperatures. [Means for solving the problem] The above purpose is to produce dimethylpolysiloxane having a content of dimethylsiloxane oligomer having 20 or less silicon atoms of 500 ppm or less and a viscosity of 50 to 150,000 centistokes at 25°C. This is achieved by using a mold release agent as the main ingredient. To explain this, the dimethylpolysiloxane used in the mold release agent of the present invention has a content of dimethylsiloxane oligomers having 20 or less silicon atoms.
500ppm or less, and the viscosity at 25℃ is 50~
It has 150,000 centistokes. Dimethylsiloxane oligomers with 20 or less silicon atoms have the formula (In the formula, R is a hydroxyl group or a methyl group, m is 0
Linear dimethylsiloxane oligomer or formula (integer from ~19) (In the formula, n is an integer of 3 to 20). The dimethylpolysiloxane used in the mold release agent of the present invention must have a content of 500 ppm or less of the dimethylsiloxane oligomer having 20 or less silicon atoms. This is because the content of dimethylsiloxane oligomers with 20 or less silicon atoms is
When dimethylpolysiloxane containing more than 500 ppm is used as a mold release agent at high temperatures, the oligomers may evaporate from the dimethylpolysiloxane and adhere to exhaust fans, forming oily stains, or the oily substances may fall. This is because the oligomer may stain the molded product, and furthermore, the oligomer may be oxidized by heat to turn into silicon dioxide powder, which has an adverse effect on various surrounding electrical and electronic components. In addition, the number of silicon atoms is 20
The boiling point of linear dimethylsiloxane oligomer is
It has a temperature of 830℃ and is volatile. Preferably,
The content of dimethylsiloxane oligomers having 20 or less silicon atoms is 400 ppm or less, more preferably 100 ppm or less. Further, the dimethylpolysiloxane used in the present invention has a viscosity of 50 to 150,000 centistokes at 25°C. It has a volatile viscosity of less than 50 centistokes at 25°C and has insufficient mold release properties, and a viscosity of more than 150,000 centistokes is too high, making it difficult to handle as a mold release agent. This is because it causes inconvenience. Preferably it is 60 to 100,000 centistokes. Further, the dimethylpolysiloxane has a linear or partially branched structure in which the molecular chain terminal is a hydroxyl group or a methyl group. Such dimethylpolysiloxane is obtained by polymerizing dimethylpolysiloxane and then lightly stripping it, which usually contains 5,000 to 30,000 ppm of dimethylsiloxane oligomers having 20 or less silicon atoms. The dimethylsiloxane oligomer content is removed using a thin film evaporator at ℃ and 0.1 to 15 mmHg, or alcohols such as methanol, ethanol, n-butanol, and i-propanol, ketones such as acetone and methyl ethyl ketone, or hexane, benzene, and toluene are used. It can be obtained by a method of extracting and removing the dimethylsiloxane oligomer with various organic solvents such as , xylene, or a mixed organic solvent thereof, or a method using a combination thereof. Preferably, the dimethylsiloxane oligomer is removed by organic solvent extraction, and more preferably, the dimethylsiloxane oligomer is removed by a thin film evaporator and organic solvent extraction. The mold release agent of the present invention may be used as is, or may be inorganic powders such as mica, talc, zinc oxide, and calcium carbonate; organic substances such as paraffin and wax; toluene, xylene, hexane, heptane, and rubber volatile oil. , perchloroethylene, and 1,1,1-trichloroethane. It may also be used as an emulsion, such as nonionic surfactants such as polyoxyalkylene alkyl ethers, polyoxyalkylene alkyl phenol ethers, polyoxyalkylene alkyl esters, sorbitan alkyl esters, and polyoxyalkylene sorbitan alkyl esters. Emulsification may be carried out by a conventional method using water and one or more cationic surfactants such as aliphatic amine salts, quaternary ammonium salts, and alkylpyridium salts. The mold release agent of the present invention is suitable for thermosetting resins such as phenolic resins, epoxy resins, polyester resins, phenolic novolak resins, urea resins, melamine resins; Polymers, thermoplastics such as nylon, polyester, polystyrene, acrylonitrile/styrene copolymers, acrylonitrile/butadiene/styrene copolymers, polyacrylates, polycarbonates, polyurethanes, polyacetals; natural rubber, isoprene, styrene-butadiene Used for mold release of rubbers such as rubber and chloropropylene. Mold release applications include mold release agents for synthetic fiber caps, toner release agents for xerographic copiers, internally added mold release agents for plastic, organic rubber or silicone rubber molding, mold release agents for die casting and foundry molding. Examples include mold release agents for molding rubber mats, hoses, tires, etc., and mold release agents for plastic metal molding. [Example] Next, an example of the present invention will be described. In the examples, "parts" means parts by weight, and the viscosity is 25°C.
is the value at . Example 1 The following three types of dimethylpolysiloxanes (samples A, B, and C) each having both ends blocked with trimethylsiloxy groups were used. Note that the dimethylsiloxane oligomer content was measured by gas chromatography. Sample A (invention) Dimethylpolysiloxane with a viscosity of 100 centistokes containing 28,700 ppm of dimethylsiloxane oligomer having 20 or less silicon atoms was heated at 3 to 4 mmHg using a thin film evaporator at a temperature of 270°C (column length 4.5 m). Pass the dimethylpolysiloxane twice under reduced pressure to reduce the content of dimethylsiloxane oligomers having 20 or less silicon atoms in the dimethylpolysiloxane to 3500 ppm, and then use 3 times the amount of ethanol to this dimethylpolysiloxane and shake for 2 hours. The content of dimethylsiloxane oligomers with 20 or less silicon atoms has been reduced to 7ppm by repeating alcohol extraction with 2 hours of standing for 7 times. Sample B (comparative example) A dimethylpolysiloxane having a viscosity of 100 centistokes and containing 28,700 ppm of dimethylsiloxane oligomers having 20 or less silicon atoms, which was neither subjected to thin film evaporation treatment nor alcohol extraction treatment. Sample C (comparative example) Sample B was made using a thin film evaporator to reduce the content of dimethylsiloxane oligomer having 20 or less silicon atoms to 3500 ppm. 6 Nylon resin chips 4.5kg and sample A 0.5kg
Kg prepared. The metering pump and weighing machine of each small pelletizer were adjusted so that the dimethylpolysiloxane content was 10% by weight based on the chips, and the nylon resin chips were melted and kneaded with a set temperature of 260°C and a constant amount of the two components flowing through the pellets. The mixture was cooled and cut into a length of 3 mm using a slit with a diameter of 3 mm to prepare a master chip containing 10% by weight of dimethylpolysiloxane and containing an internal mold release agent for resin molding. Spread this 2kg chip into a square butt, and the width is 30cm.
In a mini jet oven (heated with nichrome wire) set at 150℃ with a size of 30cm deep and 25cm high.
Let dry for 24 hours. We confirmed that the ceiling of the oven was dirty and that silica had adhered to the surface of the heater, which was the nichrome wire. Next, master pellets were prepared using Samples B and C in exactly the same manner as Sample A, and a drying experiment was conducted in the same manner. These results are shown in Table 1, and Sample A of the present invention was good, with no wetting (stains) and no white powder adhesion. Moreover, no voids (due to evaporation of the dimethylsiloxane oligomer) were generated during nylon resin molding, and a master chip with good mold releasability without contaminating the molding machine with the oligomer was obtained. In the master pellet using sample B, the ceiling of the minijet oven was made with a thin, damp and smooth evaporated product of dimethylsiloxane oligomer having 20 or less silicon atoms (wiped with gauze and applied to a salt cell plate for infrared spectroscopy). (confirmed by analysis) There was considerable adhesion. On the nichrome wire heater, a pale white powder of silicon dioxide, which was the result of combustion of dimethylsiloxane oligomers, was adhered. In sample C, wetting due to evaporation of dimethylsiloxane oligomer on the oven ceiling and slight adhesion of white powder on the nichrome wire heater were confirmed.

[Table] Example 2 40 parts of sample A used in Example 1, 3.5 parts of polyoxyethylene (8.5 mol added) nonyl phenyl ether emulsifier, polyoxyethylene (3.5
molar addition) Using 0.5 parts of octylphenol sulfate ester sodium salt type emulsifier and 56 parts of water,
An emulsion was prepared by emulsifying with a colloid mill type emulsifier. This emulsion was diluted 40 times with water and applied as a mold release agent for passenger car tires. In addition, samples B and C used in Example 1
An emulsion was prepared in exactly the same manner and applied as a mold release agent. As a result, there was no problem in the mold release performance of samples A to C. However, as a result of continued use of sample B emulsion, BAG-O
- Dimethylsiloxane oligomers with less than 20 silicon atoms were detected in the upper mold of the MATIC type vulcanizer along with a small amount of tar, and as a result of further molding, oil stains caused by dimethylsiloxane oligomers occurred on the tire surface. did. Also, sample C
Tires molded using a mold release agent made from an emulsion of oil were slightly contaminated with oil due to dimethylsiloxane oligomer. Tires molded using sample A of the present invention, a mold release agent obtained by emulsifying oil, were completely free from stains caused by dimethylsiloxane oligomers. Example 3 Using a thin film evaporator at a temperature of 290°C, a 10,000 centistoke dimethylpolysiloxane containing 8,000 ppm of dimethylsiloxane oligomer having 20 or less silicon atoms and having trimethylsiloxy groups blocked at both ends was used.
After passing once under a reduced pressure of 2.5 mmHg, a mixed alcohol solvent consisting of 85 parts of ethanol, 10 parts of methanol, and 5 parts of isopropyl alcohol was used in an amount 3 times that of dimethylpolysiloxane, and the mixture was shaken 1.
Alcohol extraction was carried out after allowing the sample to stand for 2 hours, and the content of dimethylsiloxane oligomers having 20 or less silicon atoms was reduced to 13 ppm. Using this dimethylpolysiloxane, 10% by weight was blended with 66 nylon resin in the same manner as in Example 1 to prepare master pellets containing an internally added mold release agent. Put 20g of this master pellet into a 100c.c. capacity weighing bottle with a sealed stopper.
After being heat-treated by leaving it in hot air circulation at 170°C for 20 hours, it was cooled to room temperature. As a comparative example, a viscosity containing 8000 ppm of dimethylsiloxane oligomer with 20 or less silicon atoms was used.
Master pellets containing an internal mold release agent were prepared and treated in the same manner using 10,000 centistokes of dimethylpolysiloxane. As a result, no oil droplets were observed in the 1000 c.c. capacity weighing bottle with a sealed stopper in which the master pellet containing the internal mold release agent of the present invention was heat-treated. However, numerous small oil droplets were attached to the top and sides of the weighing bottle containing the master pellet containing an internal mold release agent in the comparative example. When we collected these oil droplets and analyzed them using an infrared spectrometer, we found that
It was confirmed that it is a dimethylsiloxane oligomer with 20 or less silicon atoms. Next, 20 g of the master pellet containing the internal mold release agent dried in this example,
Under the same conditions, add 80g of 66 nylon resin without adding any dimethylpolysiloxane, dry only, and use a small injection molding machine to continuously mold dumbbell pieces for tensile testing at an injection molding temperature of 270℃ without using a mold release agent. Ten
The injection molding had good mold release properties. Furthermore, there was no staining caused by dimethylsiloxane oligomer around the injection part. Example 4 Dimethylpolysiloxane having a viscosity of 30,000 centistokes and containing 8,300 ppm of dimethylsiloxane oligomer having 20 or less silicon atoms and having both ends blocked with trimethylsiloxy groups was evaporated under a reduced pressure of 3.3 mmHg using a thin film evaporator at a temperature of 260°C. Alcohol extraction was repeated 5 times using 200 parts of this oil and 600 parts of denatured alcohol consisting of 99% by weight of ethanol and 1% by weight of benzene, shaking for 60 minutes and standing for 2 hours. The following dimethylsiloxane oligomer content was removed to 62 ppm. 100 parts of the dimethylpolysiloxane thus obtained
After uniformly kneading 2,000 g of polypropylene powder and 450 g of polypropylene powder in a hexyl mixer for 10 minutes, the mixture was molded into an Izotsu impact test mold 500 times without using a release agent using a small injection molding machine adjusted to 170℃. Injection molded. Injection molding was possible without any problems without using an external mold release agent. Further, no staining due to dimethylsiloxane oligomer was observed around the injection part. As a comparative example, a viscosity containing 8300 ppm of dimethylsiloxane oligomer with 20 or less silicon atoms
Similarly, using 30,000 centistoke dimethylpolysiloxane endblocked with trimethylsiloxy groups at both ends, polypropylene lenticules and polypropylene powder were kneaded and molded, and there was no problem with mold release. Oil-based stains were observed. Example 5 Dimethylpolysiloxane containing 5320 ppm of dimethylsiloxane oligomer having 20 or less silicon atoms and having a viscosity of 15,000 centistokes and end-blocked with trimethylsiloxy groups at both ends was shaken with 3 times the amount of ethanol for 60 minutes and left to stand for 2 hours. Alcohol extraction 20
Repeatedly, the content of dimethylsiloxane oligomers having 20 or less silicon atoms was removed to 7 ppm. After uniformly kneading 100 parts of this dimethylpolysiloxane, 2000 g of polypropylene powder and 450 g of polypropylene powder in a Henshil mixer for 10 minutes, they were separated into an Izotsu impact test mold using a small injection molding machine adjusted to 170°C. Injection molding was performed 500 times without using a molding agent. Injection molding was possible without any problems without using an external mold release agent. Further, no staining due to dimethylsiloxane oligomer was observed around the injection part. Example 6 A dimethylpolysiloxane with a viscosity of 500 centistokes and end-blocked with trimethylsiloxy groups at both ends and containing 6660 ppm of dimethylsiloxane oligomer having 20 or less silicon atoms was stripped at 270°C and 0.01 mmHg for 3 hours to obtain a dimethylsiloxane oligomer with 20 or less silicon atoms. Dimethylsiloxane oligomer content was removed to 73 ppm. After uniformly kneading 100 parts of this dimethylpolysiloxane, 2000 g of polypropylene powder and 450 g of polypropylene powder in a Henshil mixer for 10 minutes, the mixture was separated into an Izotsu impact test mold using a small injection molding machine adjusted at 170°C. Injection molded 500 times without using a molding agent. Injection molding was possible without any problems without using an external mold release agent. Further, no staining due to dimethylsiloxane oligomer was observed around the injection part. [Effects of the Invention] The mold release agent of the present invention is based on dimethylpolysiloxane, which has a dimethylsiloxane oligomer content of 20 or less silicon atoms of 500ppm or less and a viscosity of 50 to 150,000 centistokes at 25°C. Therefore, even when used at high temperatures, there is no generation of oily volatiles or silicon dioxide powder, which will not stain the area around the molding machine and/or the molded product, nor will it have a negative impact on the area around the equipment that uses the mold release agent. Has characteristics.

Claims (1)

[Claims] 1. A mold release agent whose main ingredient is dimethylpolysiloxane, which has a content of dimethylsiloxane oligomers having 20 or less silicon atoms of 500 ppm or less and a viscosity of 50 to 150,000 centistokes at 25°C.