JPH0125330B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a diaphragm whose liquid contact surface side is formed of a novel rubber material, and is particularly effective when used in equipment such as fuel pumps in fuel circuit systems of automobiles. Diaphragms used in modern fuel circuit systems, especially fuel circuit devices equipped with electronic fuel injection devices, are required to be resistant to sour gasoline, as the gasoline that comes into contact with the diaphragm tends to deteriorate due to the engine's high temperature and internal pressure. be done. Furthermore, with the use of alcohol-added gasoline due to recent fuel conditions, this type of diaphragm is required to have alcohol-added gasoline resistance (hereinafter referred to as "gasohol resistance"). Fluororubber, which satisfies these various properties, ie, sour gasoline resistance and gasohol resistance, has been attracting attention as one of the materials for diaphragms in fuel circuit systems. However, this fluororubber does not have good normal physical properties such as tensile strength, and
10~ compared to diaphragm materials such as NBR and CHR
It is 20 times more expensive, and the uses of diaphragms made of fluoro rubber are severely limited. In view of the above, an object of the present invention is to provide a diaphragm that is excellent in sour gasoline resistance and gasohol resistance, and also has good normal physical properties. Another object of the present invention is to provide a diaphragm having the above-mentioned performances at a low cost. In the diaphragm of the present invention, at least the liquid contact surface side is made of a terpolymer rubber of α,β-unsaturated nitrile, a conjugated diene, and a fluoroalkyl acrylate (or methacrylate), or a chlorinated terpolymer rubber of this terpolymer rubber. The above object is achieved by forming the diaphragm from a rubber composition mixed with a vinyl resin. Hereinafter, the diaphragm of the present invention will be explained in detail based on illustrated examples. Here, as shown in FIGS. 1 and 2, diaphragms 2A and 2B provided with a base fabric 1 are taken as an example, but the invention is not limited to this, and of course can be applied to those without a base fabric. All of the diaphragm (Fig. 1 Diaphragm 2)
A) or only the liquid contact side L (diaphragm 2B in Figure 2) is made of a terpolymer copolymer rubber of α,β-unsaturated nitrile, conjugated diene, and fluoroalkyl acrylate (or methacrylate) (hereinafter referred to as “NBF”). (hereinafter abbreviated as "PVC"), or a rubber composition obtained by mixing this NBF with vinyl chloride resin (hereinafter abbreviated as "PVC"). The composition ratio of each component in the above NBF is based on the total number of moles of the three components, α, β-unsaturated nitrile 15
~60 mol% (preferably 25-50 mol%), conjugated diene 10-75 mol% (preferably 35-65 mol%),
The amount of fluoroalkyl acrylate (or methacrylate) is 2 to 55 mol% (preferably 5 to 30 mol%). The ratio of α,β-unsaturated nitrile in NBF is
If it is less than 15 mol%, gasoline resistance will be poor, and if it is 60 mol%
If it exceeds this value, it becomes resin-like and has poor workability. If the ratio of the conjugated diene is less than 10 mol%, the rubber elasticity will be poor and the normal physical properties of the vulcanizate will also deteriorate. Furthermore, if the ratio of conjugated diene exceeds 75 mol%, the gasoline resistance and gasohol resistance will be poor. If the ratio of fluoroalkyl acrylate (methacrylate) is less than 2 mol%, it will not contribute to sour gasoline resistance and gasohol resistance, and 55
If it exceeds mol%, cold resistance will be poor. In addition, the terpolymer of the present invention can be synthesized, for example, by the following method. Polymerization methods can be synthesized by batch, continuous, or intermittent addition of monomers and other components by well-known general polymerization methods including bulk polymerization, solution polymerization, emulsion or suspension polymerization methods. As radical polymerization initiators, conventional free radical catalysts such as peroxides, redox sulfates and azos can be used. Polymerization can be carried out in a temperature range of 5°C to 80°C, preferably 5°C to 30°C. The elastomer produced from the polymer obtained by the above reaction can be recovered by a conventional coagulation method using a metal salt such as calcium chloride or a conventional coagulation method using a non-solvent such as ethanol or methanol. The above α,β-unsaturated nitriles include acrylonitrile, α-chloroacrylonitrile, α-
Examples include fluoroacrylonitrile, methacrylonitrile, and ethacrylonitrile. Examples of the conjugated diene include 1,3-butadiene, 2-chloro-1,3-butadiene, and 2-methyl-1,3-butadiene. The fluoroalkyl acrylic acid (or methacrylic acid) has an alkyl group having 1 to 20 carbon atoms (preferably 1 to 15 carbon atoms), such as 1,1-dihydroperfluoropropyl acrylate, 1,1,5-trihydro Perfluorohexyl acrylate, 1,1,2,2-tetrahydroperfluoropropyl acrylate, 1,
Examples include 1,7-trihydroperfluoroheptyl acrylate, 1,1-dihydroperfluorooctyl acrylate, 1,1-dihydroperfluorodecyl acrylate, and their methacrylates. The most preferable combination of the three components in this NBF is acrylonitrile and 1,3-
Butadiene and 1,1-dihydroperfluoroethyl acrylate (or methacrylate) or 1,
1-dihydroperfluoropropyl acrylate (or methacrylate). The PVC to be mixed with the above NBF is polyvinyl chloride or a copolymer of vinyl chloride and vinyl acetate, ethylene, propylene, butadiene, styrene, etc. (usually with a vinyl chloride content of 60 mol% or more, preferably 80 mol% or more). , preferably average degree of polymerization 500~
2000 is used. The amount of PVC blended is NBF97~
It is 3 to 60 parts by weight relative to 40 parts by weight. If the amount is less than 3 parts by weight, no effect of PVC addition will be observed, and if it exceeds 60 parts by weight, the rubbery properties will deteriorate. The method of mixing PVC with NBF is not particularly limited, but it may be kneaded using a roll or Banbury mixer, or dispersed and mixed in a liquid and then co-precipitated. The above NBF or each rubber material in which PVC is mixed with NBF contains various commonly used auxiliary materials, such as carbon black, silica, inorganic fillers such as metal oxides, organic fillers such as lignin, softeners, After appropriately blending plasticizers, antioxidants, colorants, etc., adding vulcanizing agents such as sulfur-based and organic peroxides together with vulcanization accelerators, and kneading, nylon fibers and polyester fibers are prepared using calender rolls. The diaphragm is then topped with a base fabric made of cotton or the like, and then punched out into a predetermined shape and size, and then press-molded to produce a diaphragm. The molding conditions are: mold temperature 150-190℃, vulcanization time 3
~30min, molding pressure 50~150Kgf/ ^cm2 . At this time, the topping layer that is not on the liquid contact side is
It does not need to be NBF-based rubber material; other NBR,
CR, CHR, etc. can also be used. The diaphragm thus manufactured has excellent sour gasoline resistance and gasohol resistance, as well as good normal physical properties, as shown in the examples below.
Furthermore, since expensive rubber materials such as fluoro rubber are not used, it can be obtained at low cost. Examples will be described below along with comparative examples to confirm the effects of the present invention. Each test piece of Examples and Comparative Examples was calendered to a thickness of 2.0 mm using a rubber material with the formulation shown in Table 1, then punched out to a size of 75φ and heated at 170°C. 15min press molding (100Kg
f/cm ² ) to produce a diaphragm (without base fabric). Dumbbell-shaped test pieces were punched out from this diaphragm, and various physical property tests were conducted using the methods described below. In Table 1, BD is butadiene, AN is acrylonitrile, and FEA is 1,1-dihydroperfluoroacrylate. Note that NBF (A), (B), and (C) used in Table 1 were synthesized and prepared as follows. A polymerization reaction was carried out at 50° C. in an autoclave with an internal volume of 6 using the monomers and polymerization agents shown below.

[Table] After reaching the polymerization rate shown in Table 1-2, monomer
Polymerization was stopped by adding 0.2 parts per 100 parts of hydroquinone. After heating and removing residual monomers under reduced pressure, 1.5 parts of anti-aging agent alkylated allyl phosphorite was added per 100 parts of rubber solids, and the latex was coagulated with an aqueous calcium chloride solution to form a crumb. After washing with water, each polymer was prepared by drying at 50°C under reduced pressure. (A) Normal state physical properties Breaking strength (T _B ), breaking elongation (E _B ), and hardness (H _S ) were measured according to JIS-K-6301. (B) Sour gasoline resistance After immersing a test piece (JIS No. 3) in an 80℃ Fuel C solution containing 1wt% lauroyl peroxide for the indicated time (24h units), leave it at room temperature for 24 hours → 60℃ for 24 hours
JIS for breaking strength (T _B ), breaking elongation (E _B ), and crack initiation elongation (E _C ) when dried under reduced pressure
- Measured using K-6301. (C) Crack growth resistance A test piece (JIS No. 1) was marked with marked lines at 40 mm intervals, a crack with a width of 2.03 mm was made in the center, and an appropriate tool was used to stretch the test piece by 50% (between marked lines 60 mm). The test piece in this state was immersed in Fuel D (40°C) and the time until the test piece broke was measured. (D) Extensional durability and fatigue test specimens (JIS No. 3) marked with marked lines at 20 mm intervals,
The specimen was attached to a Dematja testing machine set to elongate 0 to 100% between the marked lines, and 0 to 100% elongation was repeated to measure the number of reciprocal extensions until the test piece broke. (E) Gasohol resistance A test piece (JIS No. 3) was immersed in a Fuel C solution at 40°C containing 20 vol% methanol for 48 hours, and then the volume increase rate (ΔV) was measured. Incidentally, a similar test was also conducted on Fuel C which does not contain methanol. From the results in Table 2, the diaphragm of the present invention is
Excellent sour gasoline resistance and gasohol resistance,
It can be seen that the normal physical properties are not significantly reduced compared to the diaphragms molded from NBR or the like (Comparative Examples 1 and 2). In addition, the diaphragms (Examples 4 to 7) molded from a material containing NBF and PVC were the same.
It can be seen that the breaking strength and gasohol properties are further improved compared to the diaphragm molded with NBF (Example 2).

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Claims (1)

[Claims] 1. At least the liquid contact surface side is formed of a terpolymer rubber of α,β-unsaturated nitrile, conjugated diene, and fluoroalkyl acrylate (or methacrylate). diaphragm. 2 At least the liquid contact surface side is formed of a rubber composition in which a vinyl chloride resin is mixed with a terpolymer rubber of α,β-unsaturated nitrile, conjugated diene, and fluoroalkyl acrylate (or methacrylate). A diaphragm characterized by: