JP2005097556A - Surface treatment composition, method for surface-treatment of rubber and method for producing relief valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide (1) a surface treatment composition sufficiently and stably imparting a rubber surface with properties such as non-tackiness and lubricity and a surface-treatment method and (2) a method for producing a relief valve for low-pressure use free from large deviation of the working pressure from preset pressure even after leaving the valve in closed state for a long period. <P>SOLUTION: The surface treatment composition contains a tetraalkoxysilane, a silane coupling agent and a solvent. The surface treatment method contains a step to apply the surface treatment composition to a surface of a rubber and a step to heat the formed coating film. The method for the production of a relief valve for low-pressure use having a valve provided with an O-ring contacting to and separating from a valve seat contains a step to apply the surface treatment composition to the O-ring and heat the coating film of the composition to perform the surface-treatment of the O-ring and a step to mount the surface-treated O-ring as a component of the valve. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a surface treatment composition, a rubber surface treatment method, and a relief valve manufacturing method.

  Conventionally, as a method for imparting characteristics such as non-adhesiveness and lubricity to the surface of a rubber product that comes in contact with or separates from (contacts / separates) a metal or other dissimilar member, (1) powders such as silica and talc are used. A method of adhering to the surface, (2) a method of forming a surface treatment layer by applying a treatment agent comprising a silicone composition or the like (see, for example, Patent Documents 1 to 3), and the like are performed.

  However, the method (1) is not practical because the powder adhered to the surface is easily detached when the rubber product is used. Moreover, the non-adhesiveness and lubricity (expressed by the surface treatment layer) imparted by the method (2) are still insufficient. Furthermore, depending on the type of rubber, the formed surface treatment layer (silicone-based film) may be detached from the rubber (base material).

As equipment (pneumatic equipment) equipped with a rubber product that requires non-adhesiveness as a component (pneumatic equipment), when the pressure of the pressurized fluid in the pipeline exceeds a certain value, Relief valves, which are pressure regulating valves that are released to atmospheric pressure), are widely used, and the present applicant has also proposed relief valves having various structures (see, for example, Patent Document 4 and Patent Document 5).
The relief valve generally includes a valve seat (fixed portion), a valve body (movable portion), a spring that presses the valve body against the valve seat, and a compression means for the spring.
The valve body, which is a movable part of the relief valve, is provided with an O-ring (rubber part) that comes in contact with and separates from the valve seat, thereby ensuring airtightness with the valve seat during valve closing.
The operating pressure of the relief valve, that is, the pressure when the pressurized fluid is released by opening the valve depends on the urging force (force to press the valve body against the valve seat) by the spring constituting the relief valve. For example, if the biasing force by the spring is F and the pressure receiving area of the valve body that receives the pressure of the pressurized fluid is A, the pressure is increased when the pressure of the pressurized fluid rises to (F / A) or more. The valve element separates (opens) from the valve seat against the force (F), and the pressurized fluid is released.
Here, the biasing force (F) by the spring can be adjusted by appropriately changing the compression amount of the spring by the compression means.
The operating pressure set to the relief valve (hereinafter referred to as “set pressure”) varies depending on the specification of the pipe line (pneumatic circuit) to which the relief valve is mounted, and operates at a pressure of 100 KPa or less in various applications. Therefore, a relief valve for low pressure is desired.

However, if the relief valve as described above is left in a closed state (a state in which the O-ring constituting the valve body and the valve seat are in contact) for a certain period of time (for example, 1 hour or more), the O-ring is placed on the valve seat. As a result, the valve body becomes difficult to be separated (opened) from the valve seat, and as a result, there is a problem that the relief valve does not operate even if the pressure in the pipeline exceeds the set pressure.
In particular, in a low pressure relief valve with a small urging force by a spring, its operating pressure is easily affected by adhesion of an O-ring. For example, the relief valve does not operate even when the pressure rises to 1.5 times or more of a set pressure. Sometimes.
JP-A-1-301725 JP-A-7-133464 Japanese Patent Laid-Open No. 11-199691 JP 2000-97369 A JP 2000-170934 A

The present invention has been made based on the above situation.
A first object of the present invention is to provide a surface treatment composition and a surface treatment method capable of sufficiently and stably imparting properties such as non-adhesiveness and lubricity to a rubber surface.
The second object of the present invention is to provide a low pressure relief valve manufacturing method in which the operating pressure after being left is not changed greatly from the set pressure (operating pressure before being left) even after being left in a closed state for a long time. Is to provide.

The surface treatment composition of the present invention is a composition for treating the surface of rubber, and is represented by the formula (1): Si (OR ¹ ) ₄ (wherein R ¹ is an alkyl group having 1 to 4 carbon atoms). . a represents a tetraalkoxysilane represented by) the formula ^{(2): Si (oR 2} ) m R 3 3-m - (CH 2) n -R 4 ( wherein, R ² is an alkyl group or an alkoxyalkyl group R ³ represents an alkyl group, m is an integer of 1 to 3, n is an integer of 0 to 5. R ⁴ is an organic functional group having reactivity with a polymer main chain of rubber. A silane coupling agent represented by the following formula: and a solvent for dissolving them.

In the surface treatment composition of the present invention, the following forms are preferred.
(1) The tetraalkoxysilane is tetramethoxysilane (TMOS) or tetraethoxysilane (TEOS).
(2) Containing an acid.
(3) It contains tetraethoxysilane (TEOS), a silane coupling agent, an acid, and an organic solvent.

  The surface treatment method of the present invention is characterized by including a step of applying the surface treatment composition of the present invention to a rubber surface and a step of heating a coating film of the surface treatment composition. The surface treatment method of the present invention is preferably applied to the surface of fluororubber or nitrile rubber.

  A method for manufacturing a relief valve according to the present invention is a method for manufacturing a low-pressure relief valve that has a valve body having an O-ring that contacts and separates from a valve seat and operates at a pressure of 100 KPa or less. The step of applying the surface treatment composition of the invention to the O-ring, the step of surface-treating the O-ring by heating the coating film of the surface treatment composition, and the structure of the valve body of the surface-treated O-ring And a step of mounting as a component.

(1) The tetraalkoxysilane constituting the composition of the present invention has four alkoxy groups (—OR ¹ ) in the molecule, and the silane coupling agent includes hydrolyzable groups (—OR ² ) and It has a reactive organic functional group (—R ⁴ ) in the molecule. The composition of the present invention is applied to the surface of the rubber (base material) to be treated, and the reaction (hydrolysis / condensation reaction) between the tetraalkoxysilane and the silane coupling agent proceeds on the surface of the rubber. As a result, a surface treatment layer having a siloxane cross-linked structure (cross-linked polysiloxane layer in which silicon atoms are present in a high proportion) is formed, whereby characteristics such as non-adhesiveness and lubricity are expressed on the surface of the rubber product. .

(2) A reactive organic functional group (—R ⁴ ) derived from a silane coupling agent is introduced into the siloxane crosslinked structure (or the structure in the formation process) constituting the surface treatment layer, and this organic functional group Reacts with the polymer main chain of the rubber in the vicinity of the surface of the workpiece. Thus, the surface treatment layer is chemically bonded to the polymer main chain of the rubber via the silane coupling agent. Thus, since a chemical bond is formed between the surface treatment layer having a siloxane crosslinked structure and the polymer main chain of the rubber via the silane coupling agent, the surface treatment layer is an organic substance. It adheres firmly to the rubber (base material). Therefore, it does not desorb during use, and characteristics such as non-adhesiveness and lubricity can be stably expressed.

(3) Since the relief valve obtained by the production method of the present invention has extremely low adhesiveness of the O-ring constituting the valve, the operating pressure after being left for a long time even after being left closed for a long time However, there is no significant change from the set pressure (operating pressure before leaving).
Moreover, according to the relief valve obtained by the production method of the present invention, the surface treatment layer formed on the O-ring can be obtained even if the valve opening / closing operation including leaving the valve in a closed state for a long time is repeated many times. It does not peel off, and the performance (non-adhesive or low-adhesiveness) by the surface treatment layer can be stably expressed over a long period of time, and its operating pressure does not change greatly from the set pressure.

Hereinafter, the present invention will be described in detail.
<Surface treatment composition>
The composition of the present invention contains tetraalkoxysilane, a silane coupling agent, and a solvent for dissolving them as essential components.

In the above formula (1) indicating tetraalkoxysilane, R ¹ represents an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, a propyl group, or a butyl group. Specific examples of the tetraalkoxysilane include tetramethoxysilane (TMOS) and tetraethoxysilane (TEOS).

In the above formula (2) showing a silane coupling agent, R ² represents an alkyl group or an alkoxyalkyl group, R ³ represents an alkyl group, m is an integer of 1 to 3, preferably 3, and n is 0 An integer of -5, preferably an integer of 0-3. R ⁴ represents an organic functional group having reactivity with the polymer main chain of rubber.

In the above formula (2), the group represented by Si (OR ² ) _m R ³ _3-m — has at least one, preferably three hydrolyzable groups (—OR ² ). Thereby, the silane coupling agent shown by the said Formula (2) can react with the tetraalkoxysilane which has four alkoxy groups (-OR < ¹ >).

Here, the group represented by Si (OR ² ) _m R ³ _3-m — is preferably a trialkoxysilyl group such as a trimethoxysilyl group or a triethoxysilyl group.

Examples of the organic functional group (R ⁴ ) having reactivity with the polymer main chain of rubber include amino group, mercapto group, vinyl group, (meth) acryloyloxy group, epoxy group, ureido group and the like. . Among these, preferred are a mercapto group having reactivity with a polymer main chain of a rubber having an unsaturated bond, and a vinyl group having reactivity with a polymer main chain of a rubber having no unsaturated bond. be able to.

By proceeding the reaction (hydrolysis / condensation reaction) between the tetraalkoxysilane (—OR ¹ ) and the silane coupling agent (—OR ² ) on the surface of the rubber (base material) to be processed, siloxane A surface treatment layer having a cross-linked structure is formed, and characteristics such as non-adhesiveness and lubricity are sufficiently exhibited by silicon atoms present in a high proportion in the surface treatment layer.

Thus, in the siloxane cross-linking structure constituting the surface treatment layer or the structure in the formation process (hydrolysis / condensation reaction process), the reactive organic functional group (R ⁴ ) derived from the silane coupling agent is present. Once introduced, this organic functional group (R ⁴ ) reacts with the polymer backbone of the rubber near the surface. Thereby, the finally formed surface treatment layer is chemically bonded to the polymer main chain of the rubber through the silane coupling agent.

  Thus, since a chemical bond is formed between the surface treatment layer having a siloxane crosslinked structure and the polymer main chain of the rubber via the silane coupling agent, the surface treatment layer is an organic substance. It can be firmly adhered to the rubber. As a result, the surface treatment layer is not detached from the rubber (base material), and therefore, the surface treatment layer can stably exhibit characteristics such as non-adhesiveness and lubricity. Become.

  The solvent constituting the composition of the present invention can be selected from those capable of dissolving both the tetraalkoxysilane and the silane coupling agent, and varies depending on the type of hexane, methanol, ethanol, Examples of the organic solvent include tetrahydrofuran, dichloromethane, chloroform, benzene, ethyl acetate, dimethyl sulfoxide (DMSO), N, N-dimethylformamide (DMF), toluene, and acetone. Among these, hexane, methanol, ethanol And dichloromethane are preferred.

  The composition of the present invention may contain various optional components in addition to the essential components as long as the effect is not impaired.

  From the viewpoint of efficiently performing the reaction (hydrolysis / condensation reaction) between the tetraalkoxysilane and the silane coupling agent to promote the formation of a siloxane crosslinked structure, the composition of the present invention is acidic (pH is 6). In particular, 2-5) is particularly preferable.

  The acid contained to make the composition of the present invention acidic may be an inorganic acid or an organic acid. Here, examples of the inorganic acid include hydrochloric acid, nitric acid, sulfuric acid and the like, and hydrochloric acid is preferable. Examples of the organic acid include formic acid, acetic acid, propionic acid, butanoic acid and pentanoic acid, and acetic acid is preferred.

  In the composition of the present invention, as the content ratio of the tetraalkoxysilane and the silane coupling agent, “tetraalkoxysilane: silane coupling agent (mass ratio)” is preferably 100: 1 to 100: 100. More preferably, the ratio is 100: 10 to 100: 50.

  When the content ratio of tetraalkoxysilane (relative ratio with respect to the silane coupling agent) is too small, formation of a siloxane crosslinked structure by the resulting composition becomes insufficient, and the surface of the rubber (base material) is completely removed. Covering (formation of a surface treatment layer) becomes difficult.

  When the content ratio of tetraalkoxysilane (relative ratio with respect to the silane coupling agent) is excessive, the surface treatment layer formed by the resulting composition does not have sufficient adhesion to rubber. .

  In the composition of the present invention, the solvent content is preferably 3 to 50 times, more preferably 10 to 20 times the total content (mass) of the tetraalkoxysilane and the silane coupling agent. Is done.

  When the content rate of a solvent is too small, the surface treatment layer formed with the composition obtained may not show sufficient adhesiveness with respect to rubber | gum. On the other hand, when this ratio is excessive, the ratio of the tetraalkoxysilane and the silane coupling agent in the resulting composition is excessively reduced, resulting in a decrease in coating efficiency.

  The composition of the present invention can be easily produced by dissolving a tetraalkoxysilane, a silane coupling agent, and optional components in a solvent.

  In addition, when the obtained composition is left still for a long time at room temperature, there exists a possibility that the condensate of a structural component (especially tetraalkoxysilane) may be formed and a precipitate may be produced. For this reason, it is preferable to use the composition of the present invention within 24 hours after production, and it is important to homogenize the composition by sufficiently stirring (for example, 1 to 6 hours) before use. is there. Moreover, you may heat to 60-70 degreeC as needed.

  The composition of the present invention is used for surface treatment of rubber (vulcanized rubber and unvulcanized rubber), and imparts characteristics such as non-adhesiveness, lubricity, and abrasion resistance to the surface of the rubber. be able to.

  Here, as rubber (raw rubber) to be surface-treated with the composition of the present invention, natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), chloroprene rubber (CR), butyl rubber (IIR), Styrene butadiene rubber (SBR), nitrile rubber (NBR), ethylene propylene rubber (EPM, EPDM), acrylic rubber (ACM, ANM), epichlorohydrin rubber (CO, ECO), silicone rubber (VMQ, FVMQ), urethane rubber (AU, EU), fluororubber (FKM, FEPM), etc. can be illustrated. The composition of the present invention can impart an excellent treatment effect (non-adhesiveness) to generally highly adhesive fluororubber.

  The treatment method of the present invention comprises a step of applying the composition of the present invention to the rubber surface (hereinafter referred to as “application step”) and a step of heating the coating film of the composition (hereinafter referred to as “heating step”). Including.

  In the coating step, the method for coating the rubber surface of the composition of the present invention is particularly limited, such as a dipping method in which rubber (molded article) is dipped in the composition, a method using a coating means such as a brush or a roller. It is not something.

  In addition, after completion | finish of this application | coating process, in order to remove a solvent from the coating film formed on the surface of rubber | gum, it is preferable to perform a drying process. The drying condition varies depending on the type and content ratio of the solvent constituting the composition, but is, for example, 1 minute to 24 hours at room temperature, and preferably 3 minutes to 1 hour.

  In the heating step, the method for heating the coating film is not particularly limited, such as heating with an oven or heating with a hot press. The heating condition is, for example, 50 to 150 ° C. for 5 minutes to 24 hours, preferably 80 to 120 ° C. for 5 to 120 minutes.

  (I) Reaction (hydrolysis / condensation) of tetraalkoxysilane and silane coupling agent by heating the coating film (coating film of the composition of the present invention) applied to the surface of the rubber to be treated. (Ii) the reaction of the reactive organic functional group of the silane coupling agent with the polymer main chain of the rubber proceeds.

  As a result, a chemical bond is formed between (i) the siloxane crosslinked structure (crosslinked polysiloxane) and the silane coupling agent, and (ii) between the silane coupling agent and the polymer main chain of the rubber, As a result, a surface treatment layer (coating layer / modified layer) having excellent adhesion to rubber (durability and toughness as a coating) is formed.

  Since the surface treatment layer formed by the composition of the present invention is bonded to the polymer main chain of the rubber through a silane coupling agent, it has excellent durability (toughness), thermal stability and chemical properties. Excellent stability, for various organic solvents (eg methanol, ethanol, tetrahydrofuran, dichloromethane, chloroform, benzene, ethyl acetate, dimethyl sulfoxide (DMSO), N, N-dimethylformamide (DMF), toluene, acetone) Even insoluble or hardly soluble. As a result, even when an organic solvent is brought into contact with the rubber product (surface treatment layer) surface-treated with the composition of the present invention, the surface properties (for example, non-adhesiveness) imparted thereby are not substantially impaired. Excellent solvent resistance.

<Relief valve manufacturing method>
The relief valve obtained by the manufacturing method of the present invention is a low-pressure relief valve having a valve body having an O-ring that comes in contact with and separates (contacts / separates) from a valve seat.

FIG. 1 is a schematic cross-sectional view showing an example of such a relief valve. FIG. 1 shows a state when the valve is closed.
In FIG. 1, 10 is a housing, 20 is a valve seat, 30 is a valve body, 40 is a spring, and 50 is a spring compression means.
The relief valve of this example is attached to a pressurized fluid pipe (not shown), and when the pressure in the pipe (primary side pressure) exceeds a set pressure, the valve body 30 to the valve body 30. Is separated (opened) and operates to release the pressurized fluid to the low pressure side (secondary side).

  The housing 10 is made of a metal such as aluminum, and a valve seat 20 (fixed portion) is formed in a part of the housing 10 and has a space for accommodating the valve body 30, the spring 40, and the compression means 50.

The valve body 30 accommodated in the housing 10 is a movable portion of the valve, and includes an O-ring 31 and a guide portion 32.
The O-ring 31 constituting the valve body 30 contacts the valve seat 20 when the valve is closed, and is separated from the valve seat 20 when the valve is opened. The O-ring 31 ensures airtightness (sealability) when the valve is closed.
The guide portion 32 constituting the valve body 30 holds the O-ring 31 and transmits the urging force of the spring 40 to the O-ring 31. A flow path 33 for pressurized fluid is formed in the guide portion 32 by a notch.
The dimensions of the O-ring 31 constituting the "low pressure" relief valve are: wire diameter 1.0 to 5.0 mm, inner diameter 0.5 to 4.0 mm, outer diameter (inner diameter + wire diameter x 2) 2.5 to 14.0 mm.

One end of the spring 40 accommodated in the housing 10 is in contact with the guide portion 32 of the valve body 30, and the other end is in contact with the spring compression means 50.
The spring 40 urges the valve body 30 (O-ring 31) to press against the valve seat 20.
The spring constant of the spring 40 constituting the “low pressure” relief valve is 0.05 to 1.0 N / mm.

The spring compressing means 50 housed in the housing 10 sandwiches and compresses the spring 40 together with the valve body 30 (guide portion 32), thereby causing the spring 40 to exert a biasing force on the valve body 30. It is.
A screw (outer screw) is formed on the outer peripheral surface 51 of the compression means 50, and the compression means 50 is engaged with the screw (inner screw) formed on the inner peripheral surface 11 of the housing 10. Can be moved in the compression / extension direction of the spring 40, whereby the amount of compression of the spring 40, and hence the biasing force by the spring 40, can be adjusted as appropriate. Reference numeral 52 denotes a pressurized fluid channel provided in the compression means 50.

  In the relief valve shown in FIG. 1, when the pressure in the pipe line (primary side pressure) reaches the set pressure, the valve body 30 (O-ring 31) is separated from the valve seat 20 and opened. Thereby, the pressurized fluid in the pipe enters the housing 10 from the valve seat 20, and the flow path 33 formed in the guide portion 32, the internal space of the spring 40, and the flow path 52 formed in the compression means 50. And is released to the low pressure side (secondary side).

The operating pressure (pressure when the valve is opened) of the relief valve obtained by the production method of the present invention is 100 KPa or less, preferably 50 KPa or less, more preferably 40 KPa or less.
A relief valve for low pressure having an operating pressure of 100 KPa or less is susceptible to the adhesion between the valve element (O-ring) and the valve seat because the urging force of the spring is small.
Therefore, the low adhesion between the valve body (O-ring) and the valve seat achieved by the present invention is important in such a low-pressure relief valve.

The method for producing a relief valve of the present invention includes a step of applying the composition of the present invention to an O-ring, a step of surface-treating the O-ring by heating a coating film of the composition, and the surface-treated Mounting an O-ring as a component of the valve body.
That is, the manufacturing method of the relief valve of the present invention is characterized in that the O-ring treated by the surface treatment method of the present invention is mounted as a component part of the valve body.

The method for applying the composition of the present invention is not particularly limited, such as a dipping method in which an O-ring is immersed in the composition, a method using an application means such as a brush or a roller.
In addition, after apply | coating a composition, it is preferable to perform a drying process in order to remove a solvent from the coating film formed in the surface of O-ring. The drying condition varies depending on the type and content ratio of the solvent constituting the composition, but is, for example, 1 minute to 24 hours at room temperature, and preferably 3 minutes to 1 hour.
The method for heating the coating film is not particularly limited, such as heating with an oven or heating with a hot press. The heating condition is, for example, 50 to 150 ° C. for 5 minutes to 24 hours, preferably 80 to 120 ° C. for 5 to 120 minutes.

By heating the coating applied to the surface of the O-ring (the coating of the composition of the present invention), the reaction between (i) tetraalkoxysilane and the silane coupling agent (with a crosslinked structure by hydrolysis / condensation) (Ii) a reaction between the reactive organic functional group of the silane coupling agent and the polymer main chain of the rubber constituting the O-ring.
As a result, a chemical bond is formed between (i) the siloxane crosslinked structure (crosslinked polysiloxane) and the silane coupling agent, and (ii) between the silane coupling agent and the polymer main chain of the rubber, As a result, a surface treatment layer (coating layer / modified layer) having excellent adhesion to rubber constituting the O-ring (durability and toughness as a coating) is formed.

Since the relief valve obtained by the production method of the present invention has extremely low adhesiveness of the O-ring constituting it, the operating pressure after being left is set even after being left for a long time in the closed state. There is no significant change from the pressure (operating pressure before leaving).
Moreover, according to the relief valve obtained by the production method of the present invention, the surface treatment layer formed on the O-ring can be obtained even if the valve opening / closing operation including leaving the valve in a closed state for a long time is repeated many times. It does not peel off, and the performance by the surface treatment layer (non-adhesive or low-adhesive due to the structure derived from a specific fluorine-containing compound) can be expressed stably over a long period of time, and its operating pressure is set There is no significant change from pressure.

  Examples of the present invention will be described below, but the present invention is not limited thereto.

[Production Example 1 (Production of rubber plate)]
Fluoro rubber “Viton GLT” (manufactured by DuPont Dow Elastomer Japan) 100 parts by mass, calcium hydroxide 3 parts by mass, carbon black “Thermax MT” 20 parts by mass, peroxide-based crosslinking agent “Perhexa 25B-40 3 parts by mass (manufactured by NOF Corporation) and 3 parts by mass of TAIC (peroxide-based crosslinking agent) were kneaded with an 8-inch roll to obtain an unvulcanized rubber made of a fluororubber composition. Next, this unvulcanized rubber is subjected to a heat treatment (170 ° C. × 10 minutes) with a hot press, followed by a post-curing treatment (200 ° C. × 8 hours) in an oven, thereby obtaining a fluoro rubber (vulcanized rubber). A rubber plate (base material) having a thickness of 0.5 mm was prepared.

<Example 1>
(A) Preparation of surface treatment composition:
In accordance with the formulation shown in Table 1 below, 5.0 g of tetraethoxysilane (TEOS) and a silane coupling agent “A-171” represented by the formula: Si (OCH ₃ ) ₃ —CH═CH ₂ [Nihon Unicar Co., Ltd. Product] 1.0 g and 1.0 mL of hydrochloric acid (0.1N) were added to 100 mL of hexane, and this system was stirred at room temperature for 4 hours, whereby the composition of the present invention (TEOS concentration = about 5 mass). %, Silane coupling agent concentration = about 1% by mass).

(B) Rubber plate surface treatment:
By immersing the rubber plate obtained in Preparation Example 1 at room temperature for 3 minutes in the composition of the present invention obtained by the above (a) (composition immediately after completion of the stirring operation for 4 hours), The composition was applied to the entire surface of the rubber plate. Next, the rubber plate is allowed to stand at room temperature for 10 minutes to dry the coating film, and then heat-treated in an oven at 110 ° C. for 10 minutes to form a rubber having a surface treatment layer formed of the composition of the present invention. I got a plate.

<Example 2>
According to the formulation shown in Table 1 below, the composition of the present invention (TEOS concentration = about 5% by mass, silane) was used in the same manner as in Example 1 (a) except that the amount of the silane coupling agent was changed to 2.0 g. In the same manner as in Example 1 (b) except that a coupling agent concentration = about 2% by mass) was prepared and the composition thus obtained was used, a surface treatment layer with the composition of the present invention was prepared. A formed rubber plate was obtained.

<Comparative Example 1>
The rubber plate (fluororubber) obtained in Production Example 1 was heat-treated in an oven at 110 ° C. for 10 minutes to obtain a comparative rubber plate on which no surface treatment layer was formed.

<Comparative example 2>
According to the formulation shown in Table 1 below, a comparative composition (TEOS concentration = about 5% by mass) was prepared in the same manner as in Example 1 (a) except that no silane coupling agent was used. A rubber plate having a surface treatment layer formed of a comparative composition was obtained in the same manner as in Example 1 (b) except that the composition thus obtained was used.

<Comparative Example 3>
According to the formulation shown in Table 1 below, the amount of the silane coupling agent was changed to 6.0 g, and a comparative composition (silane cup) was obtained in the same manner as in Example 1 (a) except that TEOS was not used. Ringing agent concentration = about 6% by mass) was prepared. A rubber plate having a surface treatment layer formed of a comparative composition was obtained in the same manner as in Example 1 (b) except that the composition thus obtained was used.

<Evaluation of non-stickiness>
About each of the rubber plate obtained by said Examples 1-2 and Comparative Examples 1-3, the adhesive force with respect to a metal (stainless steel) using a tacking tester "TAC-II" (made by Resuka Co., Ltd.). Was measured to evaluate the non-stickiness of the surface. The results are also shown in Table 1.
Here, the measurement conditions are as follows.

〔Measurement condition〕
(1) Probe material: SUS304
(2) Probe shape: cylindrical shape with a diameter of 5.1 mm (3) Approach speed: 5 mm / min
(4) Applied pressure: 100 gf
(5) Pressurization time: 3 seconds (6) Separation (separation) speed: 600 mm / min
(7) Measurement temperature: room temperature

  Moreover, about each of the rubber plate obtained in said Examples 1-2, after performing the contact process (Soxhlet extraction, extraction time = 12 hours) with each solvent shown in following Table 1, it carries out similarly to the above. By measuring the adhesive force again, the non-stickiness of the surface after contact with the solvent was evaluated. The results are also shown in Table 1.

<Evaluation of lubricity>
About each of the rubber plate obtained by said Examples 1-2 and Comparative Examples 1-3, metal (stainless steel) was used using the friction abrasion tester "FPR-2100 type" (made by Resuka Co., Ltd.). The surface lubricity was evaluated by measuring the friction coefficient of the mating material. The results are also shown in Table 1.
Here, the measurement conditions are as follows.

〔Measurement condition〕
(1) Method: Ball-on-disk method (2) Mode: Rotation mode (3) Ball (indenter) material: SUS304
(4) Pressing load: 50 gf
(5) Turning radius: 3.0mm
(6) Rotation speed: 15rpm
(7) Measurement of friction coefficient: 900 seconds later

From the results shown in Table 1, it is understood that the rubber plate surface-treated with the composition of the present invention has good non-adhesiveness.
And the outstanding non-adhesiveness by the composition of this invention was not lost even if it performs contact processing (Soxhlet extraction, extraction time = 12 hours) with various solvents.
Furthermore, it was recognized that the rubber plate surface-treated with the composition of the present invention is excellent in surface lubricity.

[Production Example 2 (Production of O-ring)]
Nitrile rubber “JSR N240S” (manufactured by JSR Corporation) 100 parts by mass, anti-aging agent “NOCRACK CD” 1.5 parts by mass, stearic acid “ADEKA FATTY ACID SA-300” 1.5 parts by mass, oxidation 5 parts by weight of zinc, 70 parts by weight of carbon black “Thermax MT”, 10 parts by weight of calcium carbonate “Hakuenka CC” (manufactured by Shiroishi Kogyo Co., Ltd.), 30 parts by weight of dioctyl phthalate (DOP), and 0 sulfur .3 parts by mass, 1.5 parts by mass of vulcanization accelerator “Noxeller TT” (Ouchi Shinsei Chemical Co., Ltd.) and vulcanization accelerator “Noxeller CZ-G” (Ouchi Shinsei Chemical Co., Ltd.) ) 1.5 parts by mass were kneaded with an 8-inch roll to obtain a nitrile rubber composition (unvulcanized rubber).
Next, this unvulcanized rubber is subjected to heat treatment (150 ° C. × 20 minutes) using a hot press, whereby an O-ring (wire diameter = 1.42 mm, inner diameter = 1.53 mm, outer diameter = 4.37 mm) is obtained. Produced.

<Example 3>
(A) Preparation of surface treatment composition:
In accordance with the formulation shown in Table 2 below, 5.0 g of tetraethoxysilane (TEOS) and a silane coupling agent “A-189” represented by the formula: Si (OCH ₃ ) ₃ — (CH ₂ ) ₃ —SH [Nihon Unicar Made by Co., Ltd.] 1.0 g and 1.0 mL of hydrochloric acid (0.1N) were added to 100 mL of hexane, and this system was stirred at room temperature for 4 hours, whereby the composition of the present invention (TEOS concentration = About 5% by mass, silane coupling agent concentration = about 1% by mass).

(B) O-ring surface treatment:
By immersing the O-ring obtained in Preparation Example 2 at room temperature for 3 minutes in the composition of the present invention obtained by the above (a) (composition immediately after completion of the stirring operation for 4 hours), The composition of the present invention was applied to the surface of the O-ring. Next, the O-ring was allowed to stand at room temperature for 10 minutes to dry the coating film, and then heat-treated in an oven at 100 ° C. for 60 minutes, whereby the O-ring (cross-linked) that had been surface-treated with the composition of the present invention. An O-ring having a surface treatment layer made of polysiloxane was produced.

(C) Manufacture of relief valve:
A structure as shown in FIG. 1 is obtained by mounting the O-ring surface-treated in the above (b) on the guide portion to form a valve body, and housing the valve body, the spring, and the compression means of the spring in the housing. A relief valve for low pressure having
In this relief valve, the pressure receiving area (A) of the valve body is approximately 0.07 cm ² , the spring constant of the spring is approximately 0.16 N / mm, the urging force (F) is 0.14 to 0.70 N, and the operating pressure is 20 ~ 100 KPa.

<Comparative example 4>
A low-pressure relief valve was produced in the same manner as in Example 3 (c) except that the O-ring obtained in Production Example 2 was attached to the guide portion to form a valve body.

<Comparative Example 5>
According to the formulation shown in Table 2 below, a comparative composition (TEOS concentration = about 5% by mass) was prepared and obtained in the same manner as in Example 3 (a) except that no silane coupling agent was used. In the same manner as in Example 3 (b) except that the above-described composition was used, an O-ring surface-treated with a comparative composition was produced, and the obtained O-ring was attached to a guide portion to provide a valve body. A low-pressure relief valve was produced in the same manner as in Example 3 (c) except that.

<Comparative Example 6>
According to the formulation shown in Table 2 below, the amount of the silane coupling agent was changed to 6.0 g, and a comparative composition (silane cup) was obtained in the same manner as in Example 3 (a) except that TEOS was not used. A ring agent concentration = about 6% by mass) was prepared, and an O-ring surface-treated with a comparative composition was produced in the same manner as in Example 3 (b) except that the obtained composition was used. Then, a relief valve for low pressure was manufactured in the same manner as in Example 3 (c) except that the obtained O-ring was attached to the guide portion to obtain a valve body.

<Relief valve evaluation experiment (1)>
For each of the relief valves obtained in Example 3 and Comparative Examples 4 to 6, the rate of increase in operating pressure was measured by leaving the valve closed for a certain period of time. Specifically, by attaching a relief valve to a pipeline equipped with air pressure adjusting means (pressure reducing valve), setting its operating pressure in the range of 30-40 KPa, and then setting the air pressure in the pipeline to 0 KPa Leave the relief valve closed for 1 hour, then increase the air pressure in the pipeline and measure the operating pressure again. The ratio of the operating pressure after leaving to the operating pressure before setting (set pressure) (Increase rate) was calculated. The results are also shown in Table 2 below. The operating pressure of the relief valve was set by adjusting the compression amount of the spring with the compression means.

<Relief valve evaluation experiment (2)>
For each of the relief valves obtained in Example 3 and Comparative Examples 4 to 6, the relief valve is attached to a pipeline equipped with an air pressure adjusting means (pressure reducing valve), and the operating pressure is set in the range of 30 to 40 KPa. After repeating the opening and closing operation for 300 cycles with the valve closed state (1 hour) and the valve open state (10 seconds) as one cycle, the operating pressure is measured again, and the operating pressure before being left (set pressure) Then, the ratio (increase rate) of the operating pressure after repeating the opening / closing operation was obtained. The results are also shown in Table 2 below.

The surface treatment composition and the rubber surface treatment method of the present invention are suitable for rubber products that require non-adhesiveness and lubricity , for example, rubber products that come in contact with or separate from (contact / separate with) dissimilar members such as metals. Can be used for Examples of such rubber products include valves, packings, sealing materials, and the like.

  The relief valve obtained by the production method of the present invention is suitably used as a pressure adjusting valve (relief valve) attached to an air pressure circuit in various fields.

It is a schematic sectional drawing which shows an example of the relief valve obtained by the manufacturing method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Housing 20 Valve seat 30 Valve body 31 O-ring 32 Guide part 33 Flow path of pressurized fluid 40 Spring 50 Compression means 51 Outer peripheral surface 52 Flow path of pressurized fluid

Claims (8)

A composition for treating the surface of rubber,
A tetraalkoxysilane represented by the formula (1): Si (OR ¹ ) ₄ (wherein R ¹ represents an alkyl group having 1 to 4 carbon atoms);
Formula (2): Si (OR ² ) _m R ³ _3-m — (CH ₂ ) _n —R ⁴ (wherein R ² represents an alkyl group or an alkoxyalkyl group, R ³ represents an alkyl group, m Is an integer of 1 to 3, n is an integer of 0 to 5. In addition, R ⁴ represents an organic functional group having reactivity with the polymer main chain of rubber. When,
The surface treatment composition containing the solvent which melt | dissolves these.   The surface treatment composition according to claim 1, wherein the tetraalkoxysilane is tetramethoxysilane or tetraethoxysilane.   The surface treatment composition of Claim 1 or Claim 2 containing an acid.   The surface treatment composition according to claim 1, comprising tetraethoxysilane, a silane coupling agent, an acid, and an organic solvent.   A rubber surface treatment method comprising: a step of applying the surface treatment composition according to any one of claims 1 to 4 to a rubber surface; and a step of heating a coating film of the surface treatment composition.   The rubber surface treatment method according to claim 5, wherein the surface of the fluororubber is treated.   The rubber surface treatment method according to claim 5, wherein the surface of the nitrile rubber is treated. A method of manufacturing a low pressure relief valve having a valve body with an O-ring contacting and separating from a valve seat and operating at a pressure of 100 KPa or less,
A step of applying the surface treatment composition according to any one of claims 1 to 4 to an O-ring, a step of surface-treating the O-ring by heating a coating film of the surface treatment composition, and a surface Mounting the processed O-ring as a component of the valve body.

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