JPH0447705B2 - - Google Patents

Description

[Detailed description of the invention]

a. Field of Industrial Application The present invention relates to an oil-resistant rubber composition having excellent vulcanization adhesion to other rubbers, and a laminate thereof. b. Conventional technology Bonding two types of rubber materials, rubber and metal, etc.
It is widely common practice in the rubber industry to bond other materials such as fibers together and use them as a single composite material. This is because a single rubber material cannot fully satisfy the functions required of the product. For example, acrylonitrile-butadiene rubber (hereinafter abbreviated as NBR) used for the inner tube rubber of oil-resistant hoses, chloroprene rubber (hereinafter abbreviated as CR) used for the outer rubber, and chlorosulfonated polyethylene (hereinafter abbreviated as CSM). NBR used as cover rubber for oil-resistant belts, styrene-butadiene rubber (hereinafter abbreviated as SBR) and natural rubber (hereinafter abbreviated as NR) used as carcass rubber.
An example of this is adhesion with. As seen in the former example, NBR is used because the inner tube rubber that comes into direct contact with oil and gasoline requires a high degree of oil resistance. On the other hand, since the outer rubber comes into contact with air, ozone resistance and weather resistance are required, and NBR cannot meet these requirements, so CR
A method of laminating CSM or CSM on the outer surface is used. However, in this case, it is necessary to firmly bond NBR and CR or CSM. c Problems to be Solved by the Invention Since NBR is highly polar, sufficient adhesive strength cannot be obtained even when vulcanized and bonded to rubbers with low polarity such as SBR and NR, or rubbers with medium polarity such as CR and CSM. I can't do it. Therefore, the use of adhesive becomes essential.
However, the use of adhesives complicates the processing process, and there are concerns that the solvents used in the adhesives may affect the human body. Therefore, there is a strong desire for an oil-resistant rubber that can be directly bonded without using an adhesive. d Means for Solving the Problems As a result of intensive research in view of the above points, the present inventors found that the glass transition temperature distribution width (ΔTg) is wide.
It was discovered that by using NBR, excellent adhesive strength can be obtained when adhering to other types of rubber without using an adhesive, leading to the present invention. That is, in the present invention, ΔTg is 58°C or higher,
An oil-resistant rubber composition with excellent vulcanization adhesion, comprising as an essential component an unsaturated nitrile-conjugated diene rubber having an average bonded nitrile content of 15 to 50% by weight, and a layer of this rubber composition and a layer of other rubber. The gist is a laminate. As the unsaturated nitrile-conjugated diene rubber, a copolymer of an unsaturated nitrile such as acrylonitrile or methacrylonitrile and a conjugated diene such as butadiene or isoprene can be used. In particular, acrylonitrile-butadiene rubber (NBR) can be suitably used. The above unsaturated nitrile-conjugated diene rubber is
The ΔTg is 58°C or higher, preferably 63 to 90°C. If ΔTg is narrower than 58°C, the vulcanized adhesive strength will drop significantly. In addition, as the unsaturated nitrile-conjugated diene rubber, one in which the weight ratio of the component having a glass transition point temperature (Tg) of -73°C or less is 5% or more, preferably 8% or more is preferred in terms of improving vulcanization adhesion. more preferred. On the other hand, from the viewpoint of oil resistance, an unsaturated nitrile-conjugated diene rubber in which the weight ratio of components having a Tg of -73°C or less is 50% or less is preferable. In addition, as for the unsaturated nitrile-conjugated diene rubber, the average glass transition temperature of each component (average
Tg) is preferably -63 to -10°C. Furthermore, the average amount of bound nitrile in the unsaturated nitrile-conjugated diene rubber is preferably in the range of 15 to 50% by weight, preferably 20 to 45% by weight, from the viewpoint of oil resistance and cold resistance. In the present invention, the distribution width of glass transition temperature (ΔTg) and the average glass transition temperature (average Tg)
is obtained as follows. Using low-temperature DCS (manufactured by Rigaku Denki Co., Ltd.) at 20℃/
Measure the temperature change in specific heat at a heating rate of min. The temperature at point C, which is determined from the obtained curve by the method shown in FIG. 1, is the average Tg. That is, for unsaturated nitrile-conjugated diene rubber, the temperature change in specific heat is measured at the temperature increase rate measured by DSC, and the specific heat at the point where the specific heat starts changing (point A in Figure 1) in the obtained DSC curve. A point (point C in FIG. 1) representing the specific heat obtained by averaging the specific heats at the end point of the change in specific heat (point B in FIG. 1) is determined. The temperature at this point (point C) is defined as the glass transition temperature (average Tg) of the unsaturated nitrile-conjugated diene rubber. Further, the width between the temperature at point A and the temperature at point B in FIG. 1 is ΔTg. That is, the unsaturated nitrile-conjugated diene rubber used in the present invention is an unsaturated nitrile-conjugated diene rubber composed of components having different amounts of bonded nitrile (that is, has a compositional distribution of the amount of bonded nitrile). Therefore, the glass transition temperature (Tg) of each component
are distributed continuously, for example in Figures 1 and 4.
As shown in Figures to Figure 7, the DSC curve becomes broad. Note that even in general NBR, the composition is not necessarily uniform, so for example, as shown in Figure 3,
The specific heat does not change rapidly with temperature, and the DSC curve is usually broad. Therefore, the distribution width (ΔTg) of the glass transition point temperature caused by the composition distribution is determined by the starting point of change in specific heat (point A in Figure 1) and the end point of change in specific heat (point B in Figure 1) in the DSC curve. ), i.e. the temperature difference between
It is expressed as the temperature range between points A and B in the figure. As mentioned above, the unsaturated nitrile-conjugated diene rubber is preferably one in which the weight percentage of the component having a Tg of -73°C or less is 5% or more. Here, the weight percentage of the components whose Tg is -73℃ or less is
It is determined by the method shown in FIG. In other words, the weight percentage of components with a Tg of -73℃ or less is
From the starting point of change in specific heat in the DSC curve (point A in Figure 2) to the point where Tg is -73°C (point D in Figure 2)
The starting point of change in specific heat (second
point A in the figure) to the end point of change in specific heat (point B in figure 2)
It is expressed as a percentage by weight relative to all components present up to point). As shown in Figure 3, currently commercially available NBR exhibits ΔTg as shown in Figure A for low nitrile NBR and as shown in Figure B for high nitrile NBR. High nitrile NBR
Generally speaking, the lower the average Tg of nitrile NBR, the wider the ΔTg.
have. There are no particular restrictions on the method for producing the unsaturated nitrile-conjugated diene rubber used in the present invention, and it can be produced by devising the polymerization described below or by mixing unsaturated nitrile-conjugated diene rubbers with different average Tg. be able to. Further, there is no particular restriction on the polymerization mode itself, and any of emulsion polymerization, suspension polymerization, solution polymerization, and bulk polymerization may be used, but emulsion polymerization is particularly common. In order to widen the ΔTg of the unsaturated nitrile-conjugated diene rubber, the monomers conjugated diene, unsaturated nitrile, and molecular weight regulator may be added to the polymerization system in portions during polymerization. The timing and amount of addition can be changed depending on the average Tg and ΔTg of the desired unsaturated nitrile-conjugated diene rubber. There are no particular restrictions on the method of mixing unsaturated nitrile-conjugated diene rubbers, and two or more types of unsaturated nitrile-conjugated diene rubbers in a latex state may be mixed, or two or more types of solid unsaturated nitrile-conjugated diene rubbers may be mixed.
A conjugated diene rubber may be mixed. Furthermore,
Two or more solid unsaturated nitrile-conjugated diene rubbers may be kneaded together with carbon black, a plasticizer, a vulcanizing agent, and the like. It is preferable that the two or more unsaturated nitrile-conjugated diene rubbers to be mixed have different nitrile contents. In addition to the unsaturated nitrile-conjugated diene rubber, which is an essential component, the composition of the present invention contains ordinary rubber compounding agents such as carbon black, sulfur, plasticizer, process oil, and vulcanization accelerator, and further contains additives as necessary. , polyvinyl chloride (PVC), etc., and kneaded using a regular mixer such as a roll or Banbury mixer. The laminate of the present invention is formed by bonding a layer of another type of rubber, such as chloroprene rubber, chlorosulfonated polyethylene, or styrene-butadiene rubber, to the above-mentioned rubber composition layer. A peel test of the composition of the present invention is carried out by the method shown in FIG. Figure 8A is a perspective view showing the test piece, with a width of 25 mm.
Rubber composition 1 of the present invention and other rubber 2 with a length of 150 mm and a thickness of 3 mm are stacked, polyester 3 is inserted into a part, and the rubber composition 1 and other rubber 2 are vulcanized and bonded. This is what I did. This laminate is shown in Figure 8B.
Tensile speed 50 according to JISK6301 as shown in
A peel test was performed by pulling at mm/min. As a result, the rubber composition of the present invention was found to have excellent vulcanization adhesion and excellent processability. According to the present invention, (1) CR and CSM of external rubber are used for oil-resistant hoses as requested in the rubber industry.
and (2) carcass rubber SBR for oil-resistant belts.
It is possible to provide an oil-resistant rubber material that can be directly bonded to a material without an adhesive, and its industrial significance is extremely large. e Examples Next, examples of the present invention will be shown, but the present invention is not limited to these examples unless the gist thereof is exceeded. Example 1 In a glass autoclave, 1500 g of water, 36 g of potassium rosinate, and butadiene (hereinafter abbreviated as BD)
51.1g, acrylonitrile (hereinafter abbreviated as AN)
5.7 g and 0.11 g of t-todecyl mercaptan (hereinafter abbreviated as TDM) were charged, and polymerization was started at 5° C. using p-menthane hydroperoxide-ferrous sulfate as an initiator. After polymerizing for 2 hours, AN7.6g, BD26.5g,
0.14 g of TDM was added (this is referred to as the first additional addition, and the first addition of AN, BD, and TDM is referred to as the initial charge). After the first addition, polymerization was carried out for 2 hours, and the second addition was carried out using the formulation shown in Table 5. Next, after continuing the polymerization for 2 hours, a third additional addition was performed. After 7 additional additions in this manner, the polymerization was stopped 2 hours later. Next, octylated diphenylamine was added to the produced latex, unreacted monomers were removed using heated steam, and rubber was precipitated by precipitation in an aqueous aluminum sulfate solution, followed by washing with water and drying. The average Tg and ΔTg of the obtained NBR were determined by the method described above. This NBR (hereinafter referred to as NBR-1)
The average Tg was -42°C. ΔTg of NBR-1
As shown in Figure 4, the temperature was 71°C. Tg is −
The weight percentage of components below 73°C was 8%. Further, the average amount of bonded nitrile was 35% by weight. Furthermore, the obtained NBR-1 was kneaded with a rubber sheet prepared according to the compounding recipe-1 shown in Table-1, and the compounding recipe-2 to 4 shown in Tables-2 to 4. The produced rubber sheets were overlapped and vulcanized and bonded. Vulcanization conditions were 150°C for 25 minutes. The obtained vulcanizate was subjected to a peel test according to the method shown in FIGS. 8A and 8B. Table the results.
8. Note that NBR-1 was a polymer that maintained oil resistance and other basic physical properties as NBR. Example 2 Polymerization was carried out under the same conditions as in Example 1 according to Table 6. The obtained rubber is called NBR-2. The average Tg of this NBR-2 was -74°C, and the ΔTg was 72°C as shown in FIG. The weight percentage of components with Tg of -73°C or lower was 18%. Further, the average amount of bonded nitrile was 32% by weight. A rubber composition was prepared using the same formulation as in Example 1 for NBR-2. Next, vulcanize and bond.
A peel test was conducted. The results are shown in Table-8. Note that NBR-2 also showed good results in oil resistance and other basic physical properties. Example 3 Polymerization was carried out under the same conditions as in Example 1 and according to Table 7. The obtained rubber is called NBR-3.
The average Tg of this NBR-3 was -45°C, and the ΔTg was 83°C as shown in FIG. Also, NBR-3 is
It is unique in that it contains many components with low Tg, and the weight percentage of components with Tg of -73°C or lower is as high as approximately 20%. The average amount of bound nitrile was 33% by weight. A rubber composition was prepared using the same formulation as in Example 1 for NBR-3, vulcanized and bonded, and a peel test was conducted. The results are shown in Table-8. Example 4 Under the same conditions as Example 1, AN160g, BD840g,
Charge 2.2g of TDM and start polymerization, conversion rate 70%
Polymerization was stopped when . Generated NBR
The latex is called latex A. The solid rubber obtained by coagulating and drying this is called NBR-A.
The average Tg of NBR-A is -64℃, the amount of bonded nitrile is
It was 21% by weight. Separately, AN400g under the same conditions as Example 1,
600 g of BD and 3.3 g of TDM were charged, polymerization was started, and the polymerization was stopped when the conversion rate reached 70%. generated
NBR latex is called latex B. The solid rubber obtained by coagulating and drying this is called NBR-B. The average Tg of NBR-B was -34°C, and the amount of bonded nitrile was 40% by weight. The solid rubbers obtained by mixing 40 parts by weight of latex A and 60 parts by weight of latex B and co-coagulating the mixture are called NBR-A and B. The ΔTg of these NBR-A and B was 77°C as shown in FIG. Tg
The weight percentage of components whose temperature was -73°C or lower was 14%.
Further, the average amount of bonded nitrile was 32% by weight. NBR-A and B were vulcanized and bonded in the same manner as in Example 1, and a peel test was conducted. The results are shown in Table-8. Comparative example 1 Commercially available medium-high nitrile NBR (manufactured by Japan Synthetic Rubber Co., Ltd.)
JSRN230S: average Tg = -42°C, ΔTg = 38°C, average bonded nitrile amount 35% by weight) was vulcanized and bonded using the same formulation as in Example 1, and a peel test was conducted. The results are shown in Table-8. Comparative Example 2 Commercially available medium nitrile NBR (manufactured by Japan Synthetic Rubber Co., Ltd.)
JSRN240S: Average Tg=-56℃, ΔTg=47℃, Tg
Vulcanization adhesion was carried out using the same formulation as in Example 1, and a peel test was conducted using the same formulation as in Example 1. The results are shown in Table-8.

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[Front] Rubber

[Table] *Chloroprene rubber manufactured by Showa Neoprene Co., Ltd.

[Table] Ethylene

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【table】 [Brief explanation of the drawing]

Figure 1 is a diagram for determining the average Tg and ΔTg in the present invention, and Figure 2 is a diagram for determining the weight proportion of components whose Tg is -73°C or less in the unsaturated nitrile-conjugated diene rubber in the present invention. be. Figure 3A shows the ΔTg of commercially available low nitrile NBR, and Figure 3B shows the ΔTg of commercially available high nitrile NBR. Fourth
The figure shows ΔTg of NBR-1 of Example 1, FIG. 5 shows ΔTg of NBR-2 of Example 2, and FIG. 6 shows ΔTg of NBR-2 of Example 2.
ΔTg of NBR-3, Figure 7 shows NBR-A of the example,
It is a chart showing ΔTg of B. FIG. 8A is a test piece for the peel test used in the present invention, and FIG. 8B is a diagram showing the state in which the peel test was performed. 1... Rubber composition of the present invention, 2... Other types of rubber.

Claims (1)

[Claims] 1. Distribution width of glass transition point temperature (ΔTg) is 58°C
or more, and the average amount of bonded nitrile is 15 to 50% by weight
An oil-resistant rubber composition with excellent vulcanization adhesion, which contains as an essential component an unsaturated nitrile-conjugated diene rubber. 2. The rubber composition according to claim 1, wherein the unsaturated nitrile-conjugated diene rubber contains a component having a glass transition temperature (Tg) of -73° C. or lower in a weight proportion of 5% or more. 3. A rubber composition layer containing as an essential component an unsaturated nitrile-conjugated diene rubber having a glass transition temperature distribution width (ΔTg) of 58° C. or higher and an average bound nitrile content of 15 to 50% by weight, and a layer of other types of rubber. A laminate consisting of. 4. The laminate according to claim 3, wherein the unsaturated nitrile-conjugated diene rubber contains a component having a glass transition temperature (Tg) of -73° C. or lower in a weight proportion of 5% or more.