JP2700091B2 - Surface Modified Silicone Rubber Molded Body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicone rubber molded article which does not degrade the performance of the product due to the stickiness of the surface. It is used for rolls for paper feeding and the like.

[0002]

2. Description of the Related Art Silicone rubber is excellent in heat resistance, cold resistance, electrical insulation, workability, and the like. It is applied to various molded products such as cover members for pushbutton switches and packing for sealing.

[0003]

Conventionally, since the silicone rubber molded article has a property that dust easily adheres and has an adhesive property, various problems occur depending on the form of the molded article. For example, in the cover member 1 for a push button switch shown in FIG. 1, the adhesiveness of the top surface 2 of the key top portion deteriorates the pressing operability, and the contact portion 3 has adhesiveness to the PCB electrode opposed thereto. As a result of causing chattering, bouncing, and the like, not only normal electrical contact is easily hindered, but in the case of a normal closed circuit contact, the circuit may not operate due to adhesion. Also, rolls used in copying machines, fax machines, and the like for paper feeding, transfer, charging, static elimination, fixing, and the like tend to be unable to smoothly feed paper and the like due to their adhesiveness.

As a method for solving these problems, there is generally a method of modifying the surface of a molded article. Conventional surface modification methods include a flame treatment method in which the surface of the molded body is reformed by burning the surface of the molded body with a gas burner, a solvent wiping method in which the surface of the molded body is wiped with an organic solvent or an alkaline solvent, and a corona discharge. Methods, plasma treatment methods, etc., but none of these methods are suitable for silicone rubber molded articles.
For example, when a flame treatment method or a solvent wiping method is used to form a coating film or bond a different material with a primer, it is effective for improving the adhesion such as enhancing the adhesion effect of the primer. No effect of eliminating stickiness was observed. Also, if the corona discharge method and the plasma treatment method are applied before printing or coating on plastics such as olefins and styrene, the wettability of the surface and the wettability of the ink and paint are improved, but silicone rubber is effective. In the case of rubber-like elastic bodies such as molded articles, the surface treatment effect was weak, or although the treatment effect was obtained immediately after the treatment, the effect sometimes disappeared completely after several hours. In particular, the silicone rubber molded product had a smaller surface treatment effect than other rubber-like elastic materials, and the inherent tackiness of the silicone rubber molded product could not be eliminated.

[0005]

SUMMARY OF THE INVENTION The present invention solves these problems and provides a cured silicone rubber molded article.
UV light of both wavelengths of 4.9nm and 253.7nm integrated light amount 500
In the range of ~35,000mJ / cm ^2, a silicone rubber molding surface modified, characterized by comprising irradiating below irradiance 200 mW / cm ^2.

In recent years, surface cleaning by ultraviolet irradiation has been studied, and it has been recognized that it is effective for cleaning glass plates, metals, ceramic plates, and the like to which organic substances such as oil have adhered. The present inventors have found that, when irradiating ultraviolet rays of a specific wavelength among ultraviolet rays with a certain range of irradiance and integrated light amount, not only the surface cleaning effect but also the tackiness of the silicone rubber molded body is eliminated, and the present invention was found. Was completed. Generally, ultraviolet is 100 to 380 nm in a broad sense (2 in a narrow sense).
It refers to light with a wavelength in the range of 00 to 380 nm. Of these wavelengths, ultraviolet irradiation with wavelengths of 184.9 nm and 253.7 nm is performed in the presence of oxygen gas with a certain range of irradiance and integrated light amount. It has been found that it is effective for the surface modification of the compact. Irradiation of each wavelength alone may be carried out at different times, but it is preferable to simultaneously irradiate ultraviolet rays of two wavelengths in consideration of work environment and productivity. Describing the reasons below, air or oxygen by the absorption of ultraviolet radiation having a wavelength of 184.9 nm (O ₂₎ rich atmosphere or oxygen (O ₂₎
Oxygen (O ₂ ) reacts in the substituted atmosphere as follows to generate ozone (O ₃ ). O ₂ → O + O O + O ₂ → O ₃ In contrast, ozone (O ₃ ) is decomposed by absorption of ultraviolet light having a wavelength of 253.7 nm. In general, O ₃ has an extremely strong oxidizing power, and may be harmful to health if taken in large quantities by the human body. Therefore, in order to not increase the ozone concentration in the air more than necessary, irradiation with ultraviolet light with a wavelength of 253.7 is 184.
It is necessary to carry out the irradiation at the same time as the irradiation of the ultraviolet rays of 9 nm or after the irradiation of the ultraviolet rays of the wavelength of 184.9 nm. It is estimated that the strong oxidizing power of ozone (O ₃ ) generated here modifies the surface of the silicone rubber molded article. That is, the surface becomes physically rough, the coefficient of static friction decreases, and chemically, the carbon atoms (C) decrease, the oxygen atoms (O) increase, and the wettability increases. In the case of a commercially available low-pressure mercury lamp, ultraviolet rays having a wavelength of 253.7 nm are radiated by 90% and ultraviolet rays having a wavelength of 184.9 nm are radiated by several percent, and may be used as a light source.

In the present invention, ultraviolet rays having two different wavelengths are accumulated on the treated surface of the silicone rubber molded body (for example, only the top surface of the key top portion in the case of a cover member for a push button switch, or the entire surface). The light intensity must be in the range of 500-35,000 mJ / cm ² . If it is less than 500 mJ / cm ^2, the effect of the treatment is not sufficient, and if it exceeds 35,000 mJ / cm ² , the molded article is deteriorated and the physical properties of the silicone rubber molded article obtained by discoloration are reduced. Further, even in the range if integrated light quantity of 500~35,000mJ / cm ^2, the irradiance
It is not appropriate unless it is less than 200 mW / cm ² . In other words, if the ultraviolet irradiation is performed under a condition in which the distance between the ultraviolet light emitting lamp and the silicone rubber molded article is extremely short in an attempt to modify the surface in a short time, the irradiance is too large and the silicone rubber molded article is deteriorated. Therefore, the irradiance is 200 mW / cm ²
Must be less than The lower limit of irradiance is 10 mW considering the surface treatment time in practical use and the allowable size of equipment.
/ cm ² or more is preferable, but this is not a necessary requirement.

[0008] The ultraviolet irradiation apparatus may be a furnace type for batch processing or a furnace of a conveyor type. However, if ultraviolet rays are always irradiated to only a part of the silicone rubber molded article, the processing conditions may be reduced. In some cases, the treatment effect may appear only in the local area, or local deterioration may occur, and the processing may not be performed uniformly. It must be a mechanism that moves continuously at speed. When automatic packing is performed in a later step or when other secondary processing is required, it is preferable to select a conveyor-type apparatus capable of continuous processing.

There are no particular restrictions on the raw materials of the silicone rubber molded product. For example, the unit formula is represented by RaSiO _{(4-a) / 2} , and R represents an alkyl group such as a methyl group, an ethyl group, a propyl group, or a butyl group. , An alkenyl group such as a vinyl group and an allyl group, an aryl group such as a phenyl group and a tolyl group, or chloromethyl in which part or all of the hydrogen atoms bonded to the carbon atoms of these groups have been substituted with a halogen atom, a cyano group, or the like. Group, trifluoropropyl group, the same or different unsubstituted or substituted monovalent hydrocarbon selected from cyanoethyl group and the like, the value of a can be 1.90 to 2.05,
At this time, it is preferable that 80 mol% or more of R is a methyl group and 0.1 to 0.5 mol% is a vinyl group, and is based on an organopolysiloxane having a viscosity at 25 ° C. of 100 cS or more, preferably 1,000 cS or more. Are preferred. If necessary, a filler (a silica type is generally used), a coloring material such as an inorganic or organic pigment, and a crosslinking agent such as an organic peroxide may be further added. Specific examples of the crosslinking agent include benzoyl peroxide, dichlorobenzoyl peroxide, and butylperoxy-2.
-Octyl hexanate, 2,5-dimethyl-2,5 dibenzoyl peroxyhexane, butyl peroxy laurate, cyclohexane peroxide, butyl peroxy isopropyl carbonate, peroxy allyl carbonate, and the like. The composition comprises an organopolysiloxane containing an aliphatic unsaturated group such as an alkenyl group, a hydrogen polyene polysiloxane containing at least two hydrogen atoms bonded to silicon atoms in the molecule, chloroplatinic acid or a platinum complex or An addition reaction type comprising chloroplatinic acid and a platinum catalyst comprising a complex salt of an alcohol, an aldehyde, an olefin or a vinyl siloxane may be used.

Using such a raw material for a silicone rubber molded article, for example, a cover member 1 for a push button switch as shown in FIG.
And UV light of both wavelengths of 253.7nm at the same time or before and after (253.7nm is later), the integrated light amount is 500 ~ 35,000mJ / cm ²
If the irradiance is less than 200 mW / cm ² and at least the top of the key top is illuminated,
The pressing operation is also smoothed because the stickiness of the rubber is eliminated.
Further, when the cover member 1 for a push button switch is turned over and the above-mentioned ultraviolet ray is irradiated on the contact portion 3, the sticking to the PCB substrate is also prevented.

Further, the quality of a paper feed roll used in a copying machine, a facsimile, various printers, etc. is improved. FIG. 2 shows the inside of the facsimile, and there is a paper feed roll 6 as an example of a silicone rubber molded body for feeding out the paper 5 under the reading device 4. After this paper feed roll is formed, UV light of both wavelengths of 184.9nm and 253.7nm, simultaneously or before and after
In the range of 500~35,000mJ / cm ^2, irradiance 200 mW / cm ²
When the irradiation is performed at less than this, the adhesiveness disappears from the paper feed roll itself, and stable paper feed becomes possible. As shown in FIG. 3, the apparatus for irradiating the paper feed roll with ultraviolet light sets the paper feed roll 6 on a roll rotation device 8 under an ultraviolet radiation lamp 7 and rotates on the roll. The roll rotation device itself is mounted. The gantry 9 is moved. In this way, the entire surface of the paper feed roll can be uniformly surface-treated. The roll is not limited to the paper feed roll, but may be a pinch roll, a backup roll, a fixing roll, or the like.

This treatment is also effective for removing the tackiness of other silicone rubber molded articles. For example, a silicone rubber sheet 10 as shown in FIG. 4 has a non-adhesive side 11 on one side and an adhesive side 12 on the other side. Can be easily formed, and can also be applied to the production of a charging blade having no stickiness. This treatment also provides a remarkable cleaning effect on various silicone rubber medical components such as silicone tubes and catheters, as well as silicone stoppers and caps such as culture solution storage containers, as well as loss of tackiness and adhesion of dust. It will be more sanitary because it disappears. Furthermore, the following has been confirmed as the effect of this surface treatment. That is, the separation membrane becomes an oxygen-rich membrane, and the sponge sponge makes the contact sensation mellow. In particular, the makeup puff causes less irritation to the skin and eliminates uneven makeup. Since the silicone rubber connector does not adhere to dust, troubles due to a rise in resistance value do not occur.

[0013]

[Action] An appropriate amount of ozone (O ₃ ) is generated by irradiation of ultraviolet rays with wavelengths of 184.9 nm and 253.7 nm, and its oxidizing power removes foreign substances on the surface of the silicone rubber molded product and forms fine irregularities on the surface. Thus, a silicone rubber molded article which exhibits non-adhesiveness and is surface-modified is obtained.

[0014]

【Example】

Example 1 100 parts by weight of silicone rubber compound KE-9510U [trade name manufactured by Shin-Etsu Chemical Co., Ltd.] and 2 parts by weight of crosslinking agent C-8 [trade name manufactured by Shin-Etsu Chemical Co., Ltd.] and some amounts of various pigments The raw material consisting of the following was compression-heat molded to produce a cover member for a push button switch as a silicone rubber molded body,
Because the top of the key top and the contact point were sticky, UV
-Inline processing unit for dry processor VUM-
184.9nm with 3164-B (trade name, manufactured by Oak Manufacturing Co., Ltd.)
Irradiation with ultraviolet light having a wavelength of 253.7 nm under the conditions shown in Table 1 gave the results shown in Table 1. Irradiance 200 mW / c
By irradiating the top surface of the key top part of the cover for the push button switch with ultraviolet light under the above conditions within the range of 500 m to 35,000 mJ / cm ² with the integrated light amount of less than m ² A cover member for a push button switch as a modified silicone rubber molded product was obtained. Further, when the contact point side of the cover member for the push button switch was irradiated with ultraviolet light under the above conditions, troubles caused by adhesion to the PCB substrate were eliminated. The evaluation of the processing effect was evaluated as "A", "Slightly unsatisfactory", or "Insufficient", when there was no stickiness, the pressing operation was smooth and there was no stickiness to the PCB substrate. He also commented on the deterioration. In the table, the irradiation furnace length means the length of the ultraviolet irradiation furnace, the conveyor speed means the speed of the conveyor passing through the furnace, and the processing time means the irradiation time (furnace passage time).

[0015]

[Table 1]

Example 2 100 parts by weight of silicone rubber compound KE-9610U [trade name of Shin-Etsu Chemical Co., Ltd.] and 2 parts by weight of crosslinking agent C-8 [trade name of Shin-Etsu Chemical Co., Ltd.] A raw material comprising a small amount of pigment was compression-heated and molded to obtain a silicone rubber sheet as a silicone rubber molded body. Next, in order to eliminate the stickiness of one side of the silicone rubber sheet, a batch processing device of a UV-dry processor, VUM-3073-B
184.9nm and 253.7nm with [Oak Manufacturing Co., Ltd.]
Irradiation was performed under the conditions shown in Table 2 to obtain the results shown in Table 2. When the irradiance was less than 200 mW / cm ² and the integrated light amount was in the range of 500 to 35,000 mJ / cm ² , the silicone rubber sheet had a surface-modified silicone rubber sheet with no stickiness on the irradiated surface. The evaluation of the treatment effect was based on the presence or absence of tackiness on the irradiated surface of the silicone rubber sheet. At this time, irradiance 40 (mW / cm ² ), integrated light
The surface roughness, static friction coefficient, and surface analysis values measured by ESCA were measured for the sample treated at 3,600 (mJ / cm ² ) and the untreated sample. It became smaller, and chemically reduced carbon atoms (C), increased oxygen atoms (O), and increased wettability. Table 3 shows the results.

[0017]

[Table 2]

[0018]

[Table 3]

Example 3 Silicone rubber compound KE-852U (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) 100 parts by weight and a cross-linking agent, C-8 [Shin-Etsu Chemical Co., Ltd.] Product name] 3 parts by weight of the raw material
A silicone rubber roll having an outer diameter of 30 mmφ and a length of 200 mm was polished by heating and curing, but the adhesiveness to paper could not be eliminated. Therefore, a UV-dry processor batch processing device, VUM-3333-A (trade name, manufactured by Oak Manufacturing Co., Ltd.) was modified so that a silicone rubber roll rotating device as shown in FIG. With additional irradiance of 40 mW / c
range integrated light quantity of 5,000 mJ / cm ² at m ^2, 184.9 nm and 25
Ultraviolet light with a wavelength of 3.7 nm was simultaneously irradiated. When the thus obtained paper feed roll as a surface-modified silicone rubber molded product was used in a facsimile machine, a paper feed error did not occur. The surface-modified silicone rubber roll was used as a transfer roll, a fixing roll, a charging roll, a charge eliminating roll (adding carbon black as a conductivity-imparting agent), and a pressure bonding roll in addition to the paper feed roll. Almost the same result was obtained.

Example 4 AIBN (0.3 parts by weight) was added as a foaming agent to the raw materials used in Example 1 to obtain a cosmetic puff as a silicone rubber molded article, and irradiated with ultraviolet light under the same conditions as in Example 1. However, the adhesive feeling disappeared, the cosmetic paste became better, and the washing after use could be performed smoothly in a short time.

[0021]

As can be seen from the above-mentioned examples and the like, when the silicone rubber molded body is irradiated with ultraviolet rays of a specific wavelength at a specific irradiance at a specific integrated light amount, a cleaning effect of surface contamination is recognized. In addition, it is possible to eliminate the stickiness of the silicone rubber molded body that could not be achieved by various surface treatment methods generally performed on plastics and the like, and to obtain a surface-modified silicone rubber molded body. be able to. In particular, when it is applied to a molded body such as a cover member for a push button switch or a paper feed roll, its function is improved.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a cover member for a push button switch as an example of a silicone rubber molded body.

FIG. 2 is a schematic longitudinal sectional view of a paper feed roll as an example of a silicone rubber molded body.

FIG. 3 is a schematic longitudinal sectional view of the inside of the surface treatment device of the paper feed roll.

FIG. 4 is a schematic longitudinal sectional view of a silicone rubber sheet.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Cover member for a push button switch 2 ... Top surface of a key top part 3 ... Contact part 4 ... Reader 5 ... Paper 6 ... Paper feed roll 7 ... Ultraviolet irradiation lamp 8 ... Roll rotating device 9 ... Stand 10 ... Silicone rubber sheet 11 ... Non-adhesive side 12 ... adhesive side

Claims (1)

(57) [Claims] 1. The cured silicone rubber molded article is
UV light of both wavelengths of 25 nm and 253.7 nm
A surface-modified silicone rubber molded article, which is irradiated at an irradiance of less than 200 mW / cm ² within a range of 5,000 mJ / cm ² .