JP4580214B2 - Cleaning method for silicone rubber products - Google Patents

Description

The present invention relates to a method for cleaning a silicone rubber product that reduces low-molecular-weight dimethylpolysiloxane remaining in the silicone rubber product. More specifically, the present invention relates to a method for cleaning a silicone rubber product that has no flash point and is excellent in safety, ozone layer destruction and earth By selecting and using 1-bromopropane (C ₃ H ₇ Br), which has a low impact on global warming, as an organic solvent for cleaning used to reduce the residual amount of low molecular weight dimethylpolysiloxane in silicone rubber products The present invention relates to a method for cleaning a silicone rubber product that can effectively remove remaining low-molecular dimethylpolysiloxane.

In miniaturized and integrated electronic circuits, most of the failures that occur in the metal contacts of relays and switches are poor contact, and the cause is classified as dust and toxic gas (corrosive gas, organic gas, etc.). Is done. Toxic gases are divided into corrosive gases in the atmosphere such as H ₂ S, SO ₂ , NH ₃ and organic gases generated mainly from molding materials, silicone compounds, adhesives, etc., which are constituent materials of equipment. In particular, it has been reported that a gas generated from a silicone rubber product has a significant adverse effect on metal contacts, and this gas has been identified as a low-molecular dimethylpolysiloxane remaining in the silicone rubber product. For this reason, as a method for reducing low-molecular dimethylpolysiloxane remaining in these silicone rubber products, for example, Patent Document 1 which is a patent publication relating to the earlier application of the present applicant includes trichlorotrifluoroethane (so-called CFC). A method for removing dimethylpolysiloxane remaining in a silicone rubber product by using -113) as an organic solvent is described in detail. Further, Patent Document 2 discloses a method of immersing a silicone color cap in a chlorofluorocarbon solution under the condition of first being in a vacuum state when removing low molecular siloxane.
Japanese Examined Patent Publication No. 7-62084 JP-A-8-306219

  However, the use of CFC-113 as specific CFCs has been abolished due to the decision of the Montreal Protocol Parties meeting. As an alternative, 1,1,1-trichloroethane and trichlorethylene were used. However, due to some environmental conservation and legal regulations, 1,1,1-trichloroethane has already been completely abolished. With the enforcement of the PRTR (Chemical Substances Emissions and Transfers Notification) Act, restrictions and restrictions were imposed on the use of trichlorethylene. On the other hand, HCFC-225 (HCFC: Hydrochlorofluorocarbon) has a low ozone depletion coefficient of about 0.02 and is therefore the seat of the Vienna Conference (held in the 7th Montreal Protocol Parties) until 2010 However, in order to continue to supply stable products to the world, the use of HCFC-225, There was a problem with the choice of use.

  As described above, organic solvents such as the above-mentioned chlorofluorocarbons, which have been conventionally effective for effectively removing low-molecular-weight dimethylpolysiloxane of silicone rubber products, which cause contact failure of metal contacts, in a short time. Therefore, it has been desired to develop a technique capable of effectively removing low molecular weight dimethylpolysiloxane in silicone rubber products without using them.

  Further, when cleaning a silicone rubber product, for example, as described in Patent Document 1, it is possible to improve the cleaning efficiency by rotating or moving the silicone rubber product up and down. Since static electricity is generated by rubbing between the silicone rubbers, it is essential to select a solvent to which flame retardancy is imparted as the solvent used for cleaning in order to prevent the occurrence of fire due to the discharge of static electricity. Furthermore, it is more desirable if the solvent used for washing can be recovered efficiently.

  The present invention was made in view of the above circumstances, low molecular dimethylpolysiloxane remaining in the silicone rubber product can be effectively eluted in the solvent, is not flammable, is excellent in safety, Silicone rubber that uses a solvent that has little effect on the destruction of the ozone layer and global warming, and more preferably, can remove and recover the solvent remaining in this silicone rubber product in the operation after cleaning. The object is to provide a method for cleaning products.

  As a result of intensive studies to achieve the above object, the present inventor has 1-bromopropane, which is an organic solvent that has no flash point, is excellent in safety, has little influence on ozone layer destruction and global warming, It has been found that low molecular weight dimethylpolysiloxane can be effectively eluted in an organic solvent and has an excellent removal effect. As a result of further intensive studies, when a silicone rubber product is immersed in 1-bromopropane and subjected to ultrasonic treatment, the silicone rubber product swells by the immersion of 1-bromopropane and the low-molecular dimethylpolysiloxane is eluted. However, when such an elution mechanism is used, the low-molecular-weight dimethylpolysiloxane can be made more efficient by making the average thickness of the silicone rubber product less than the predetermined thickness or keeping the swelling rate of the silicone rubber product within the predetermined range. It was found that it can be eluted and removed automatically. Further, when removing 1-bromopropane remaining in the silicone rubber product and recovering it in the operation after washing, 1-bromopropane can be more efficiently removed and recovered by heating and vacuum drying treatment. The present invention has been found and the present invention has been made.

  That is, the present invention is (1) a method for cleaning a silicone rubber product that reduces low-molecular-weight dimethylpolysiloxane in the silicone rubber product, wherein the silicone rubber product is immersed in 1-bromopropane and subjected to ultrasonic treatment. The present invention provides a method for cleaning a silicone rubber product comprising an ultrasonic treatment step.

  Here, in the cleaning method according to the above (1) of the present invention, the average thickness of the silicone rubber product is 3 mm or less, or the weight of the silicone rubber product after the ultrasonic treatment in the ultrasonic treatment step is It is more preferable that the ultrasonic treatment is performed so as to increase by 20 to 200% with respect to the weight before the ultrasonic treatment. Further, after the ultrasonic treatment step, there may be included a heating and vacuum drying step of drying the silicone rubber product under vacuum and heating. In the ultrasonic treatment step, the silicone rubber product is rotated and moved up and down. However, it is more effective if the ultrasonic treatment is performed.

As the silicone rubber product treated by the cleaning method of the present invention, a color filter used by coating a light bulb or a wavelength conversion cap used by coating a light emitting diode (hereinafter referred to as LED) is more preferable.

  According to the present invention, by washing the silicone rubber product using 1-bromopropane, the low-molecular dimethylpolysiloxane remaining in the silicone rubber product and causing defects such as poor contact of electronic circuits is efficiently removed. It is possible to cope with the generation of static electricity during cleaning, the safety of the solvent used, the effects on the ozone layer destruction and global warming, etc.

  Hereinafter, the present invention will be described in more detail. The present invention is intended to reduce the amount of low-molecular dimethylpolysiloxane remaining in a silicone rubber product. Here, the type of the silicone rubber product to be treated by the cleaning method of the present invention is not particularly limited. For example, silicone caps for covering light bulbs, silicone caps for vehicle lighting, A wide variety of materials such as caps, coverings for lighting bodies such as silicone caps for LED applications, etc. can be mentioned, and among these, color filters used for covering bulbs or LEDs are used. It is more effective to clean the wavelength conversion cap and the like.

  In the present invention, the low molecular weight dimethylpolysiloxane removed from the silicone rubber product is a low molecular weight cyclic dimethylpolysiloxane and a chain dimethylpolysiloxane remaining in the silicone rubber product, and the molecular weight is particularly limited. Although not usually, cyclic dimethylpolysiloxane having a degree of polymerization of about 4 to 20 and linear dimethylpolysiloxane having a degree of polymerization of about 2 to 10 remain in the silicone rubber product. Since a large amount of cyclic dimethylpolysiloxane is contained in the present invention, the removal effect on cyclic dimethylpolysiloxane is a problem in the present invention.

  The thickness of the silicone rubber product to be cleaned of the present invention is not particularly limited, but in consideration of the removal efficiency of low-molecular dimethylpolysiloxane, the average thickness is preferably 3 mm or less, more preferably Is preferably 2.5 mm or less, more preferably 2 mm or less. If it is too thick, it may take too long to remove the low molecular weight dimethylpolysiloxane to the desired residual amount and may not be substantial. The lower limit of the average thickness is not particularly limited as long as it is the minimum necessary thickness for the silicone rubber product, but is usually preferably 0.1 mm or more, more preferably 0.3 mm or more.

  In the cleaning method of the present invention, the low molecular weight dimethylpolysiloxane in the silicone rubber product is easily dissolved in 1-bromopropane by an ultrasonic treatment process in which the silicone rubber product is immersed in 1-bromopropane and subjected to ultrasonic treatment. To be eluted. The amount of 1-bromopropane used in this step can be appropriately selected depending on, for example, the shape and size of the treatment tank, and is not particularly limited, and the silicone rubber product can be completely immersed in the product. The amount of the low-molecular-weight dimethylpolysiloxane contained therein may be any amount, and more preferably sufficient to swell the silicone rubber product, as will be described later.

  The cleaning method of the present invention swells a silicone rubber product by immersing the silicone rubber product in 1-bromopropane in the ultrasonic treatment step so that 1-bromopropane penetrates into the silicone rubber product. It is something to be made. That is, in the ultrasonic treatment process of the present invention, 1-bromopropane does not wash the surface of the product, but penetrates into the interior and elutes low molecular weight dimethylpolysiloxane. Here, in the case of the present invention, the degree of swelling of the silicone rubber product in the ultrasonic treatment step is not particularly limited. For example, as a measure of swelling of the silicone rubber product, When the weight change of the treated silicone rubber product is measured, the amount of 1-bromopropane adsorbed is increased by 20% to 200% of the unit weight of the silicone rubber product compared to the weight before sonication. It is more effective to perform the ultrasonic treatment so that the weight after the ultrasonic treatment is 120 to 300% (1.2 to 3 times) that before the treatment. More preferably, an increase of 30 to 200% of the unit weight, and still more preferably an increase of 40 to 200% of the unit weight is more effective. If the amount of increase is too small, the removal effect of the low molecular weight dimethylpolysiloxane targeted by the present invention may be difficult to obtain, and if it is too large, it may be necessary to spend a lot of time in the solvent removal step. .

  The sonication (immersion) time in the sonication process of the present invention can be appropriately selected depending on the thickness, shape, etc. of the silicone rubber product. For example, a silicone rubber product having an average thickness of 3 mm or less can be selected as described above. If it is swollen like this, it is usually preferably 5 to 15 minutes, more preferably 5 to 10 minutes. If the sonication time is too long, there is a concern that unevenness in productivity occurs. If it is too short, it may be difficult to remove the low-molecular dimethylpolysiloxane to a desired residual amount.

  In the ultrasonic treatment process of the present invention, an apparatus for performing ultrasonic treatment is not particularly limited, but for example, the apparatus described in Patent Document 1 can be preferably used. And the ultrasonic treatment process of the present invention is more effective when ultrasonic treatment is performed while rotating and moving the silicone rubber product up and down. Using the apparatus described, 1-bromopropane can be applied to the inside and outside of the container, such as a processing container of the type called a hexagonal barrel knitted with a stainless steel mesh material. By allowing a silicone rubber product to be stored in a processing container that can be freely passed through the apparatus and rotating the processing container and moving it vertically while performing ultrasonic treatment simultaneously. Ultrasonic treatment can be performed while rotating and moving the silicone rubber product up and down. In addition, although the frequency of the ultrasonic wave at the time of processing with an ultrasonic wave is not restrict | limited, Usually, about 40 kHz is employ | adopted as an ultrasonic frequency area | region industrially.

  When ultrasonic treatment is performed while rotating and moving the silicone rubber product up and down, the number of rotations and the amplitude of the up and down movements are not particularly limited. For example, the number of rotations is usually 2 rotations / minute or less. In particular, about 1 to 2 rotations / minute, the vertical motion is usually about 30 to 50 cm in amplitude and the number of vertical motions is 1 time / minute or less, particularly about 0.5 to 1 time / minute. Static electricity may be generated by rubbing between silicone rubber products, but in the case of the cleaning method of the present invention, 1-bromopropane is essentially a flame-retardant imparting solvent. Can suppress or prevent the occurrence of fire.

  The cleaning method of the present invention can appropriately include a preliminary process, a post-treatment process, and the like in addition to the ultrasonic treatment process. For example, the heating for vacuum drying the silicone rubber product after the ultrasonic treatment process. It is more effective to include a vacuum drying step. That is, after the ultrasonic treatment step, the silicone rubber product is dried, and the solvent used for removing and eluting the low-molecular dimethylpolysiloxane is removed from the silicone rubber product and collected, for example, under reduced pressure. Can be considered. However, since 1-bromopropane used in the present invention has a higher latent heat of vaporization than chlorofluorocarbons, if it is attempted to recover it by reducing the pressure, the temperature decreases due to the reduced pressure, making it difficult to recover. Therefore, in the cleaning method of the present invention, when recovering the solvent, the solvent can be recovered more efficiently by adopting a heating and vacuum drying step in which the silicone rubber product is dried under vacuum and heating.

  In the heating and vacuum drying step of the present invention, the heating temperature is not particularly limited, but is preferably 40 to 70 ° C, more preferably 50 to 60 ° C. If the heating temperature is too low, it may be difficult to recover 1-bromopropane, and if it is too high, a cooling process may be required for recovery. The degree of vacuum (degree of decompression) is not particularly limited, but usually, −60 kPa or less, particularly −90 kPa or less is suitable as a vacuum state. If a sufficient vacuum state cannot be obtained, it may be difficult to obtain a sufficient removal efficiency of 1-bromopropane. The lower limit of the vacuum state is not particularly limited, but a vacuum state of about −100 kPa is the lower limit in industrially used apparatuses. The drying treatment time is appropriately selected depending on the shape, thickness and the like of the silicone rubber product, but is usually preferably 5 to 30 minutes, more preferably 5 to 20 minutes. If the treatment time is too short, the recovery of 1-bromopropane may tend to be insufficient. If the treatment time is too long, no further recovery may occur and the treatment time may be wasted.

  The apparatus used for the heating and vacuum drying step is not particularly limited. For example, the inside of the tank is decompressed and a vacuum pump provided with a trap for recovering the volatilized solvent and the inside of the tank are heated to a desired temperature. If a heating and vacuum drying treatment tank equipped with a heating device is used, after the ultrasonic treatment, the silicone rubber product contained in the container is carried into the heating and vacuum drying treatment tank, and the inside of the tank is decompressed. By heating to a predetermined temperature, the silicone rubber product in the ultrasonic treatment step can be dried, and 1-bromopropane can be removed and recovered from the silicone rubber product.

The silicone rubber product treated by the cleaning method of the present invention has a reduced content of low-molecular dimethylpolysiloxane remaining in the product. In particular, it is more preferable that the content of the cyclic dimethylpolysiloxane having a polymerization degree of 4 to 20 having a large residual amount is reduced to 50 ppm or less, more preferably 30 ppm or less. Therefore, as described above, the silicone rubber product treated by the cleaning method of the present invention can suppress problems such as poor contact of electronic circuits due to low molecular weight dimethylpolysiloxane remaining in the product. Silicone caps for coatings, silicone caps for in-vehicle lighting, caps for sign illumination, silicone caps for LED applications, etc. It is more useful as a color filter used by coating or a wavelength conversion cap used by coating the LED.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited to the following Example.

[Example 1]
2 liters of 1-bromopropane was put into an ultrasonic cleaner (UT-204; 27 cm × 33 cm × 28 cm) manufactured by Sharp, and a silicone rubber product 10 for a silicone cap for a bulb cover having an average thickness of 1.0 mm was added thereto. One piece (the average weight of one piece was 11 g) was immersed and treated with ultrasonic waves for 10 minutes. The weight after completion was 33 g as an average value, and the amount of 1-bromopropane adsorbed was 22 g as an average value from the change in weight. This was a 200% increase in unit weight (300% with respect to the weight before treatment). ).

The product subjected to ultrasonic treatment is pulled up and stored in a heating vacuum decompression drying apparatus (manufactured by Yamato Kagaku, ADP300 type), and subjected to heating vacuum decompression drying at −0.1 MPa, 50 ° C. for 10 minutes to obtain a product. The 1-bromopropane from was removed and the product was dried. Thereafter, 1 g of the product was sampled, and the product cut into 5 mm squares was dispersed in 5 ml of special grade ethanol, and this was sonicated for 30 minutes using a small ultrasonic cleaner for laboratories. The low molecular weight dimethylpolysiloxane remaining in the column was eluted and quantified by gas chromatography. As a result, when cyclic dimethylpolysiloxane is D _n (n = degree of polymerization), D _{4 to} D ₁₀ are 0 ppm, and D _{4 to} D ₂₀ are 10 ppm.

[Comparative Example 1]
For the silicone rubber product for the silicone cap for a bulb cover with an average thickness of 1.0 mm that was not subjected to ultrasonic treatment and drying treatment in Example 1, the low residual amount in the product was the same as in Example 1. When molecular dimethylpolysiloxane was quantified, D _{4 to} D ₁₀ was 80 ppm, and D _{4 to} D ₂₀ was 560 ppm.

[Comparative Example 2]
In Example 1, heptafluorocyclopentane instead of 1-bromopropane; except for using (Nippon Zeon Zeorora _H C 5 H 3 _{F 7)} performs the same ultrasonic treatment, drying treatment as in Example 1 The low molecular weight dimethylpolysiloxane remaining in the product was quantified in the same manner as in Example 1. As a result, D _{4 to} D ₁₀ was 50 ppm, and D _{4 to} D ₂₀ was 90 ppm. In addition, the weight after the end of the ultrasonic treatment is 13 g as an average value, and from the change in weight, the adsorption amount of heptafluorocyclopentane is 2 g as an average value, which is an increase of 18% of the unit weight (weight before treatment) 118%).

[Comparative Example 3]
In Example 1, except that HCFC-225 was used instead of 1-bromopropane, ultrasonic treatment and drying treatment were performed in the same manner as in Example 1, and the low molecular weight dimethylpolysiloxane remaining in the product was treated as Example When determined in the same manner as in Example 1, D _{4 to} D ₁₀ was 0 ppm, and D _{4 to} D ₂₀ was 25 ppm. In addition, the weight after the ultrasonic treatment is 28 g as an average value, and the amount of adsorption of HCFC-225 is 17 g as an average value from the change in weight, which is an increase of 155% of the unit weight (to the weight before treatment). Equivalent to 255%).

[Example 2]
In Example 1, the same ultrasonic treatment and drying treatment as in Example 1 were performed, except that 10 silicone rubber products having an average thickness of 3.0 mm were used as the silicone rubber products (the average weight of one piece was 18 g). The low molecular weight dimethylpolysiloxane remaining in the product was quantified in the same manner as in Example 1. As a result, D _{4 to} D ₁₀ was 145 ppm, and D _{4 to} D ₂₀ was 870 ppm. The weight after sonication is 80 g as an average value, and the amount of 1-bromopropane adsorbed is 62 g as an average value from the change in weight, which is an increase of 340% of the unit weight (weight before treatment). 440%).

[Comparative Example 4]
For the silicone rubber product for the silicone cap for a bulb cover with an average thickness of 3.0 mm that was not subjected to the ultrasonic treatment and the drying treatment of Example 2, in the same manner as in Example 1, the low level remaining in the product was reduced. was quantified molecular _{dimethylpolysiloxane,} D 4 _{to D 10} is _{210ppm, D} 4 _{~D 20} was 1520Ppm.

The results of the above Examples and Comparative Examples are shown in Tables 1 and 2 below.

According to the results of Table 1, the present invention is low molecular dimethylpolysiloxane _{D 4 ~D 10, D 4 ~D} 20 remaining in the silicone rubber products, in particular the low molecular dimethylpolysiloxane _D 4 _{to D 20} On the other hand, an excellent removal effect was observed. In addition, according to the results in Table 2, it was also found that the removal effect of low molecular weight dimethylpolysiloxane depends on the average thickness of the silicone rubber product when the treatment time is within a certain condition.

  INDUSTRIAL APPLICABILITY The present invention can be used for cleaning any silicone rubber product, for example, a silicone rubber product used as a component part of various devices such as automobiles, aircrafts, and electrical products. Remove low molecular weight dimethylsiloxane remaining on silicone rubber products used as coverings for lighting bodies such as caps for body, caps for vehicle lighting, caps for standard lighting, caps for LED, etc. Can do.

Claims (5)

A method of cleaning a silicone rubber product that reduces low-molecular-weight dimethylpolysiloxane in the silicone rubber product, comprising a sonication step in which the silicone rubber product is immersed in 1-bromopropane and subjected to ultrasonic treatment. Cleaning method for silicone rubber products. The method for cleaning a silicone rubber product according to claim 1, wherein the silicone rubber product has an average thickness of 3 mm or less. The ultrasonic treatment is performed in the ultrasonic treatment step so that the weight after the ultrasonic treatment of the silicone rubber product is increased by 20 to 200% with respect to the weight before the ultrasonic treatment. Cleaning method for silicone rubber products. The method for cleaning a silicone rubber product according to claim 1, 2 or 3, further comprising a heating and vacuum drying step of drying the silicone rubber product by heating under vacuum and vacuum after the ultrasonic treatment step. The method for cleaning a silicone rubber product according to any one of claims 1 to 4, wherein, in the ultrasonic treatment step, the ultrasonic treatment is performed while rotating and moving the silicone rubber product up and down.