JP2005282773A - Hot water diaphragm - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hot water diaphragm having improved durability to hot water and reduced heat deterioration due to operating oil without causing layer-to-layer separation even when subjected to repetitive dynamic deformation. <P>SOLUTION: The hot water diaphragm is operated with the operating oil for feeding hot water. It comprises a first rubber layer 14 for contacting the operating oil, a second rubber layer 12 for contacting the hot water, and at least one of fiber layers (16, 18, 20) laminated between the first rubber layer 14 and the second rubber layer 12. The first rubber layer 14 is formed of NBR having an acrylonitrile content of 31-42% for improved heat resistance aging property, and the second rubber layer 12 is formed of NBR having an acrylonitrile content of 31-42% for improved water resisting property. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hot water diaphragm used for a pump that operates with hydraulic oil such as a boiler feed water pump and feeds hot water for hot water supply.

A diaphragm in which a vulcanized rubber and a woven fabric are laminated as a reinforcing fiber layer is known (for example, Patent Document 1). Patent Document 1 discloses a diaphragm having a configuration in which a sealing object does not leak through a woven fabric layer even when the woven fabric is exposed on the surface.
JP 2003-21234 A (FIG. 1)

  However, when the diaphragm according to the technique disclosed in Patent Document 1 is used as a diaphragm for hot water, the exposed surface of the woven fabric comes into contact with hydraulic oil or hot water, and the fiber layer is deteriorated and easily damaged by use. Have

  A diaphragm in which rubber layers are formed on both sides of the woven fabric layer so that the woven fabric is not exposed is also known. However, since the rubber layer constituent material is easy to manufacture, The rubber materials having the same composition are used.

  When a diaphragm having such a configuration is used as a diaphragm for hot water, the rubber layer on the hot water contact side is susceptible to hydrolysis, and the rubber layer on the hydraulic oil contact side contacts the hydraulic oil heated by hot water through the diaphragm. By doing so, it is susceptible to heat aging and swelling. For this reason, the lifetime of a diaphragm is short and improvement is calculated | required.

  In order to solve such problems, simply select and use a rubber material (for example, EPDM) having excellent water resistance and hydrolysis resistance on the hot water contact side, and excellent oil resistance and heat aging resistance on the hydraulic oil contact side. When a rubber material (for example, NBR) is used, the difference in rubber properties is large, so that the adhesive strength between the rubbers is reduced, and there arises a problem that delamination occurs due to dynamic repeated deformation of the diaphragm during use. Such delamination occurs remarkably when the hydraulic oil has penetrated to the adhesive interface.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a hot water diaphragm that is excellent in durability without causing delamination even when subjected to dynamic repetitive deformation, with little durability against hot water, little thermal deterioration and swelling with respect to hydraulic oil. There is.

The present invention is a diaphragm for hot water that operates by hydraulic oil and sends hot water,
A first rubber layer in contact with hydraulic oil, a second rubber layer in contact with hot water, and at least one fiber layer laminated between the first rubber layer and the second rubber layer,
The first rubber layer is composed of NBR with an excellent acrylonitrile content of 31 to 42%, and the second rubber layer is composed of NBR with an excellent water resistance of 31 to 42%. It is characterized by being.

  Since the diaphragm having such a structure uses NBR as a raw rubber for both the first rubber layer and the second rubber layer, sufficient adhesion strength between the layers of the rubber layers constituting both surfaces can be obtained, and dynamic repeated deformation Even if it receives, it is excellent in durability without causing delamination, small in durability against hot water, small thermal deterioration and swelling in hydraulic oil.

  The fiber layer may be a single layer or a plurality of layers. The fiber layer constituting material is not particularly limited, but it is preferable to use a nylon woven fabric. When providing a plurality of fiber layers, an intermediate rubber layer is provided between the fiber layers.

  In the above-described diaphragm, it is preferable that the first rubber layer and the second rubber layer are formed of NBR containing liquid NBR.

  By using liquid NBR, the workability was improved without using a plasticizer, and the bending resistance of the diaphragm was improved.

  In the present invention, acrylonitrile butadiene rubber (NBR) is used for both the first rubber layer in contact with the hydraulic oil and the second rubber layer in contact with hot water.

  As the NBR used for the first rubber layer, a grade referred to as a medium-high nitrile or a high nitrile having an acrylonitrile content of 31 to 42% excellent in heat aging resistance is used. Such NBR is excellent in oil resistance and also suppressed in swelling due to hydraulic oil. As NBR excellent in heat aging resistance, it is preferable to use NBR copolymerized with a heat aging inhibitor, and as a commercial product, use of N530 (manufactured by JSR) is preferred.

  The NBR used for the second rubber layer is a medium to high nitrile or high nitrile grade NBR having an acrylonitrile content of 31 to 42%, and is excellent in water resistance and hot water resistance. NBR with excellent water resistance and hot water resistance can be obtained by reducing the amount of emulsifier used during emulsion polymerization or by treating with a thin acid after emulsion polymerization and coagulating it, returning it to alkalinity, re-saponifying it, and washing with water. It is manufactured by a method for reducing the amount of emulsifier. Commercially available products include Nipol 1031, 1032 (Nippon Zeon), N530 (JSR), etc., which can be used.

  The liquid NBR that is preferably used for the first and second rubber layers is an NBR polymer that is liquid at room temperature with a low degree of polymerization, and a suitable commercially available product is NIPOL 1312 (manufactured by Nippon Zeon).

  As the rubber layer constituting material, a known additive is used for NBR as a raw rubber. Additives include reinforcing fillers such as carbon black and silica, fillers such as clay and calcium carbonate, processability improvers such as stearic acid, alkaline earth metal stearate or alkali metal salt, and zinc oxide. Auxiliaries, tackifiers such as petroleum resins, anti-aging agents, vulcanizing agents such as sulfur, and vulcanization accelerators are used. It is preferable not to use a plasticizer or sub from the viewpoint of improving durability.

  As a fiber material constituting the fiber layer, a fiber material known as a rubber reinforcing fiber can be used without limitation. Specific examples include rayon fiber, polyamide fiber, polyester fiber, aramid fiber, steel cord, glass fiber, and carbon fiber. Among these, it is preferable to use polyamide fibers such as nylon 6 and nylon 66 in consideration of strength, cost, adhesiveness, and the like. The fiber layer is composed of a woven fabric, a knitted fabric or the like, but it is preferable to use a plain woven fabric because of its excellent reinforcement. The fiber layer is preferably subjected to a surface treatment such as a resin treatment in order to improve the adhesive force with the rubber layer.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a partial cross-sectional view of the configuration of a preferred embodiment of the diaphragm of the present invention. The diaphragm 10 is composed of a first rubber layer 14 in contact with hydraulic oil, a second rubber layer 12 in contact with hot water, and a fiber layer provided therebetween. In this example, the fiber layer is a fiber on the hot water side. It consists of three layers, a layer 16, a fiber layer 20 on the hydraulic oil side, and an intermediate fiber layer 18 between them. Intermediate rubber layers 22 and 24 are provided between the fiber layer 16 and the intermediate fiber layer 18 and between the fiber layer 18 and the fiber layer 20, respectively.

  The intermediate rubber layer constituent material is not limited as long as the adhesive strength of the fiber layer and the characteristics of the diaphragm can be obtained, but NBR rubber material is used because it adheres well to the first and second rubber layers. It is preferable to use the same material as the first rubber layer constituent material or the second rubber layer constituent material. The thickness of the diaphragm is appropriately set according to the application.

  Manufacture of a diaphragm can be performed by a well-known manufacturing method. Raw rubber is a master batch prepared by kneading the ingredients excluding reaction components such as vulcanizer and vulcanization accelerator with a kneading device such as a Banbury mixer, and using a kneading roll or kneader for the master batch after cooling. Then, a vulcanizing agent and a vulcanization accelerator are added and kneaded to obtain an unvulcanized rubber composition. The woven fabric constituting the fiber layer that has undergone the necessary pretreatment and the unvulcanized rubber composition are laminated by pressing with a calender roll etc. to form a raw material sheet, cut into the required dimensions, and then pressed and heated with a mold etc. By doing so, a diaphragm is manufactured.

Examples and the like specifically showing the configuration and effects of the present invention will be described below.
(Examples and comparative examples)
Table 1 shows the composition of the rubber material constituting the first rubber layer, the composition of the rubber material constituting the second rubber layer, the composition of the first rubber layer and the rubber material constituting the second rubber layer of the comparative example (using the same material). Indicated.

About each rubber layer constituent material, each vulcanized rubber sheet was produced and the characteristic evaluation was performed.
(Evaluation)
The evaluation was performed on the vulcanized rubber obtained by heating and vulcanizing an unvulcanized rubber composition obtained by kneading each rubber material at 150 ° C. for 30 minutes using a predetermined mold.
<Tensile properties>
The 100% elongation modulus (M100), 300% elongation modulus (M300), tensile strength, and elongation were measured in accordance with JIS K 6251.
<Hardness>
Based on JIS K 6253, hardness was measured with a type A durometer.
<Evaluation of heat aging resistance>
The heat aging evaluation was performed according to the aging test method JIS K 6257. The vulcanized rubber sample for physical property evaluation was left in an oven at 100 ° C. for 70 hours, taken out and cooled to room temperature, and then the hardness and tensile properties were measured to determine the rate of change. The rate of change in tensile properties is
100 × (characteristic after heating−initial characteristic) / (initial characteristic)
I asked for. The change in hardness was evaluated by the number of change points.
<Heat resistant water evaluation>
The hot water resistance was evaluated according to the vulcanized rubber immersion test method JIS K 6258. A vulcanized rubber sample for physical property evaluation was immersed in hot water at 90 ° C. for 7 to 14 days, taken out, wiped, and cooled to room temperature, and then the hardness and tensile properties were measured to determine the rate of change.
<Flexibility>
The bending resistance was evaluated according to the Dematcher bending crack test JIS K 6260. The test conditions for evaluating the bending resistance were three samples, and repeated deformation was performed at a test bath temperature of 40 ° C. and a bending test speed of 300 times / minute. The result was displayed as the number of times until class / crack generation (10,000 times).
The evaluation results are shown in Table 2.

表２の結果より、加熱された作動油に接し、耐熱老化性が要求される第１ゴム層構成加硫ゴムは、熱老化試験後の硬さ変化、及びＭ１００，伸び等の変化率が比較例のゴムより小さい。また、圧縮永久歪も小さく、特に耐屈曲性が優れており、ダイアフラムの耐久性向上に寄与する。

From the results shown in Table 2, the first rubber layer vulcanized rubber that is in contact with the heated hydraulic oil and requires heat aging resistance is compared in the hardness change after the heat aging test and the rate of change such as M100 and elongation. Smaller than the rubber of the example. In addition, the compression set is small, and particularly the bending resistance is excellent, which contributes to the improvement of the durability of the diaphragm.

The second rubber layer vulcanized rubber that is in contact with hot water and requires hot water resistance has greatly improved hardness change, tensile property change rate, and weight change rate after hot water immersion. Flexibility is also improved.
(Production and evaluation of diaphragm)
A diaphragm having the layer structure shown in FIG. 1 was produced. As the first rubber layer constituent material and the second rubber layer constituent material, rubber materials having the compositions shown in Table 1 were used. The fiber layers 16, 18, and 20 were used after a general nylon 66 woven fabric was resin-treated by dipping (RFL treatment). The unvulcanized rubber composition was formed into a sheet having a thickness of 3 to 4 mm using a calender roll, and was laminated using the calender roll. The first rubber layer constituent material was used as the intermediate rubber layer constituent material. A 350 mm × 210 mm diaphragm was produced by heating and pressing with a press. As a result of evaluation as a diaphragm for supplying hot water, as compared with a diaphragm having the same structure in which the rubber material of the comparative example was used as the first rubber layer, the second rubber layer, and the intermediate rubber layer, the same first rubber layer and It was found to have excellent interlayer adhesion with two rubber layers and excellent durability.

Partial sectional view showing an embodiment of the configuration of the diaphragm

Explanation of symbols

10 ··· Diaphragm 12 ··· Second rubber layer 14 ··· First rubber layer 16, 18, 20 Fiber layer

Claims (2)

It is a diaphragm for hot water that operates by hydraulic oil and sends hot water,
A first rubber layer in contact with hydraulic oil, a second rubber layer in contact with hot water, and at least one fiber layer laminated between the first rubber layer and the second rubber layer,
The first rubber layer is composed of NBR with an excellent acrylonitrile content of 31 to 42%, and the second rubber layer is composed of NBR with an excellent water resistance of 31 to 42%. The diaphragm for hot water characterized by being made. 2. The hot water diaphragm according to claim 1, wherein the first rubber layer and the second rubber layer are formed of NBR containing liquid NBR. 3.

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