JP2006265429A - Rubber composition and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition having excellent fuel permeation resistance and mechanical strength and to provide a method for producing the composition. <P>SOLUTION: The rubber composition comprises an acrylonitrile-butadiene rubber having ≥40 wt.% of acrylonitrile content as a matrix phase and a polyamide as a dispersed phase. In the rubber composition, the minor axis of the polyamide which is the dispersed phase is ≤1 μm and the major axis/minor axis ratio (the ratio of the major axis/minor axis) is ≥3. The rubber composition preferably has the weight ratio of the acrylonitrile-butadiene rubber to the polyamide (the acrylonitrile-butadiene rubber/polyamide) within the range of (60/40) to (90/10). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a rubber composition and a method for producing the same, and more particularly to a rubber composition suitably used for a material such as a fuel hose or a seal member for supplying fuel such as gasoline and a method for producing the same.

  Conventionally, as a material for a fuel rubber molded body such as a fuel hose, an NBR-PVC rubber composition in which vinyl chloride (PVC) is blended with acrylonitrile butadiene rubber (NBR) is often used.

  Since this type of NBR-PVC rubber composition contains PVC having a halogen component in its molecular structure, harmful halogen gas is generated when the rubber composition is incinerated.

  Therefore, various rubber compositions containing no halogen component have been studied as an alternative material for the NBR-PVC rubber composition for the purpose of reducing the burden on the global environment.

  As such an alternative material, NBR-PA rubber composition in which polyamide (PA) is blended with acrylonitrile butadiene rubber (NBR) in order to ensure oil resistance, fuel permeation resistance (barrier property), and good cost performance. Has been proposed.

  For example, Patent Document 1 discloses a rubber composition in which polyamide is dispersed in acrylonitrile butadiene rubber. In Patent Document 1, both are blended at a high temperature of 200 ° C. or higher in order to improve the degree of dispersion of both, and an anti-gel agent is added to further suppress the generation of gel.

  Patent Document 2 also discloses a rubber composition in which polyamide is dispersed in acrylonitrile butadiene rubber. According to this, when both are heated to a temperature higher than the melting point of the polyamide, the viscosity of the polyamide decreases, and the polyamide is not uniformly mixed with the acrylonitrile butadiene rubber. An inorganic filler is added to increase the viscosity of the polyamide.

Japanese Patent Laid-Open No. 10-120831 JP-A-6-9823

  By the way, it is generally known that many rubber compositions blended with a resin are not completely compatible. This is the same for the NBR-PA rubber composition. Macro-dispersion judged with the naked eye proceeds to a certain level with a general kneading method, but acrylonitrile butadiene is seen from a microscopic viewpoint. It is difficult to uniformly disperse polyamide in rubber. Therefore, in the said patent documents 1 and 2, in order to disperse | distribute polyamide uniformly in acrylonitrile butadiene rubber, the various countermeasures mentioned above are performed.

  However, Patent Document 1 mainly describes an anti-gel agent that suppresses the generation of gel, but it is not certain how much polyamide is finely dispersed in acrylonitrile butadiene rubber. Furthermore, since the antigel agent to be added has a relatively low molecular weight, it is expected that the fuel permeability of the resulting rubber composition will be greatly reduced, and it is difficult to use it as a material for fuel-based rubber moldings. it is conceivable that.

  On the other hand, Patent Document 2 describes that a plate-like inorganic filler is added to a mixture of acrylonitrile butadiene rubber and polyamide, and this plate-like inorganic filler is filled only with polyamide and specifically contains only polyamide. Does not thicken, but seems to thicken the whole mixture. Therefore, it is unlikely that the situation in which the polyamide is thickened to near the viscosity of acrylonitrile butadiene rubber by adding a plate-like inorganic filler and both are uniformly dispersed occurs in the mixer.

  In addition, when a plate-like inorganic filler is added to this mixture and blended, self-heating of the mixture becomes larger than when no plate-like inorganic filler is added, so that there is a problem that it becomes difficult to control the temperature of the mixture during blending. .

  Further, Patent Documents 1 and 2 are intended to improve the dispersion of polyamide in acrylonitrile butadiene rubber by adding an anti-gel agent, a plate-like inorganic filler, and the like. It is not intended to uniformly disperse the polyamide therein.

  The problem to be solved by the present invention is that an NBR-PA rubber composition in which polyamide is more uniformly dispersed in acrylonitrile butadiene rubber than in the past, and has excellent fuel permeation resistance (barrier property) and mechanical strength, and production thereof It is to provide a method.

  In order to solve the above problems, the rubber composition according to the present invention comprises acrylonitrile butadiene rubber having an acrylonitrile content of 40% by weight or more as a matrix phase and a polyamide as a dispersed phase, and the polyamide in the dispersed phase comprises: The gist is that, in the dispersed state in the rubber composition, the minor axis is 1 μm or less, and the major axis (major axis / minor axis ratio) is 3 or more.

  In this case, in the rubber composition, the weight ratio of the acrylonitrile butadiene rubber to the polyamide (acrylonitrile butadiene rubber / polyamide) is preferably in the range of 60/40 to 90/10.

  Moreover, the said rubber composition can be used suitably for a fuel type rubber molded object.

  On the other hand, a method for producing a rubber composition according to the present invention is a method for producing the above rubber composition, wherein the acrylonitrile butadiene rubber and the acrylonitrile butadiene rubber are at least within a temperature range from the temperature at which acrylonitrile butadiene rubber begins to plasticize to before the polyamide begins to plasticize. Applying shearing force to the mixture with polyamide to coarsely disperse the polyamide in acrylonitrile butadiene rubber, and making the mixture self-heat by shearing force, raising the temperature to the melting temperature of the polyamide, and finely dispersing the polyamide in acrylonitrile butadiene rubber And a step of lowering the temperature to below the melting point of the polyamide while applying a shearing force to the mixture.

  According to the rubber composition, polyamide is more uniformly dispersed in the acrylonitrile butadiene rubber than in the past. Therefore, when this rubber composition is used as a material, mechanical properties such as tensile strength and elongation at break, Fuel permeation resistance (barrier property) and the like can be sufficiently satisfied throughout the material.

  In this case, by setting the weight ratio of the acrylonitrile butadiene rubber to the polyamide (acrylonitrile butadiene rubber / polyamide) within the above range, this rubber composition has a particularly high elongation at break and improved mechanical properties. Will be.

  Further, when the above rubber composition is used for a fuel-based rubber molded body, the fuel molded body has a very high fuel permeation resistance (barrier property), and the volatile component in the fuel is the rubber molded body. Environmental pollution can be reduced because the amount released to the atmosphere through the air is reduced. In addition, since this rubber molded body does not contain a halogen component, no harmful halogen gas or the like is generated even if incinerated as a waste material, and is friendly to the global environment.

  And according to said manufacturing method, polyamide can be uniformly disperse | distributed in acrylonitrile butadiene rubber only on the blend conditions of acrylonitrile butadiene rubber and polyamide. Thereby, mechanical properties such as tensile strength and elongation at break, fuel permeation resistance (barrier property), and the like can be sufficiently satisfied.

  Next, embodiments of the present invention will be described in detail.

  The rubber composition according to this embodiment includes acrylonitrile butadiene rubber (hereinafter abbreviated as “NBR”) as a matrix phase and polyamide (hereinafter abbreviated as “PA”) as a dispersed phase.

  Here, in the dispersed state in the rubber composition, the minor axis of PA as a dispersed phase is 1 μm or less, and the major axis (major axis / minor axis ratio) is three or more. Those whose minor axis and major axis are within these ranges have good dispersion of PA in the matrix phase, mechanical properties such as tensile strength and elongation at break, and fuel permeation resistance (barrier properties). Can be satisfied throughout the composition.

  The NBR is produced by copolymerization of acrylonitrile (hereinafter abbreviated as “AN”) and butadiene, and those containing AN of 40% by weight or more are suitably used. This is because when the AN amount is less than 40% by weight, the fuel permeation resistance (barrier property) is inferior to that of the conventional NBR-PVC rubber composition.

  On the other hand, the upper limit is not particularly limited. Generally, as the amount of AN increases, the fuel permeability (barrier property) and mechanical strength as rubber improve, but the cold resistance, elongation, and elasticity decrease. Therefore, too much AN is not good. In addition, since commercially available NBR normally has a content of 15% by weight to 50% by weight, it is sufficient that it contains AN in the range of 40% by weight to 50% by weight.

  Examples of the NBR satisfying the above conditions include Nipol DN003 and Nipol DN101 manufactured by Nippon Zeon, and N215SL, N222L, and N222S manufactured by JSR. These may be used alone or in combination of two or more. Moreover, when using in combination of 2 or more types, the amount of AN less than 40 weight% can also be used. In this case, the average value of the AN amount may be 40% by weight or more by combining 40% by weight or more.

  The PA preferably has a relatively low melting point. This is because PA is melted in the process of obtaining the rubber composition of the present invention, so that if the melting point is too high, NBR will cause thermal degradation. Therefore, the melting point of PA is preferably 200 ° C. or lower, more preferably 190 ° C. or lower.

  Examples of such PA include nylon 11 (hereinafter abbreviated as “PA11”), nylon 12 (hereinafter abbreviated as “PA12”), nylon 6, nylon 66, and the like. Low PA11, PA12, etc. are more preferably used.

  In the rubber composition according to this embodiment, the weight ratio of NBR and PA is preferably in the range of NBR / PA = 60/40 to 90/10. This is because when NBR is less than 60% by weight, the rubber-derived extensibility deteriorates, so that mechanical properties such as elongation at cutting are inferior. Moreover, when NBR exceeds 90 weight%, since PA content will be less than 10 weight%, it is inferior in fuel permeation resistance (barrier property) from the conventional NBR-PVC type rubber composition.

  Various additives may be added to the rubber composition according to this embodiment together with NBR and PA. For example, when this rubber composition is used as a fuel-based rubber molded article, a reinforcing agent (conductive agent), a vulcanizing agent, a vulcanization accelerating aid, an anti-aging agent, a plasticizer, a processing aid, etc., together with the above components Can be blended as necessary.

  Examples of the reinforcing agent include carbon black and white carbon. Further, the blending ratio of such a reinforcing agent is preferably in the range of 5 to 100 parts, more preferably 30 to 100 parts by weight (hereinafter abbreviated as “parts”) of the total amount of the rubber composition. Within the range of 80 parts.

  The above vulcanizing agent, vulcanization accelerating aid, and anti-aging agent can be appropriately set according to the use as a material, the degree of vulcanization, and the like.

  Examples of the plasticizer include phthalic acid plasticizers such as dioctyl phthalate (DOP) and di-n-butyl phthalate (DBP), and adipic acid plastics such as dibutyl carbitol adipate and dioctyl adipate (DOA). And sebacic acid plasticizers such as dioctyl sebacate (DOS) and dibutyl sebacate (DBS).

  The blending ratio of the plasticizer is preferably in the range of 1 to 50 parts, more preferably in the range of 5 to 35 parts with respect to 100 parts of the total amount of the rubber composition.

  Examples of processing aids include stearic acid, fatty acid esters, fatty acid amides, and hydrocarbon resins.

  The blending ratio of the processing aid is preferably in the range of 0.1 to 5 parts, more preferably in the range of 0.5 to 3 parts, with respect to 100 parts of the total amount of the rubber composition.

  The rubber composition obtained by blending the above additives and the like is gasoline, alcohol-mixed gasoline (gasohol), alcohol, hydrogen, liquid petroleum gas (LPG), compressed natural gas (CNG), light oil, dimethyl ether and the like. It can be suitably used as a material for a rubber molded body such as a hose for transporting fresh fuel and packings at a connecting portion of a pipe through which fuel is sent.

  Next, the manufacturing method of the rubber composition which concerns on this embodiment is demonstrated. This production method includes at least the following steps (1) to (3).

  Step (1) is a step of charging a predetermined amount of NBR and PA into a kneader such as a kneader, a Banbury mixer, or a mixing roll, and kneading them. By this kneading, NBR and PA are dispersed while being sheared.

  In the kneading process, it is necessary to coarsely disperse PA in NBR by applying shearing force to both at least within a temperature range from the temperature at which NBR begins to plasticize to before PA begins to plasticize.

  The temperature at which the NBR begins to plasticize refers to a temperature at which the elastic modulus (viscosity) of the NBR starts to fall to a state suitable for kneading, and specifically refers to a temperature of about 100 ° C.

  Moreover, the temperature before PA begins to plasticize is a temperature lower than the melting point of PA. For example, when PA11 or PA12 is used as the PA, temperatures of about 180 ° C or 170 ° C that are slightly lower than these melting points (PA11 = 187 ° C, PA12 = 176 ° C) can be exemplified.

  In this step (1), the temperature can be raised to before the plasticization temperature of the PA, but as the temperature of the mixture increases, the viscosity of the NBR decreases and shear force is less likely to be applied. It is preferable to make it to the upper limit temperature (about 150 degreeC) used as a viscosity. Moreover, it is preferable that it is less than 150 degreeC also from the point that general rubber kneading is not performed for a long time at the temperature of 150 degreeC or more, in order to prevent thermal deterioration of rubber | gum.

  Therefore, the temperature range from the temperature at which NBR begins to plasticize to the temperature before PA begins to plasticize refers to a temperature range of 100 ° C. or higher and lower than 180 ° C., more preferably a temperature range of 100 ° C. or higher and lower than 150 ° C.

  The shearing means, for example, that NBR and PA are kneaded by using the kneader to make them both fine while being torn. For example, when the above-mentioned Banbury mixer is used, it can be exemplified that pellet-like PA enters the clearance between the rotor of the mixer and the inner wall of the kneader and is ground by the rotational force of the rotor. In this case, PA is less likely to be smaller than the clearance, so that it is not further refined.

  After that, NBR and PA are kneaded and coarsely dispersed so that the sheared PA is mixed with the entire NBR. In this case, it is desirable to disperse the PA in the NBR as much as possible before melting the PA.

    Step (2) is a step in which after the step (1), the mixture is self-heated by the shearing force, the temperature of the mixture is raised to the melting temperature of the PA, and the PA is finely dispersed in the NBR.

  When a shearing force is applied to the mixture, the mixture self-heats, and thus the temperature of the mixture can be raised to the melting point temperature of PA without particularly heating. Then, the temperature of the mixture can be adjusted by changing the magnitude of the shearing force, for example, the rotational speed of the rotor.

  In this step (2), since it is important to melt PA, it is necessary to raise the temperature to near the melting point temperature of PA, but it is not preferable to make the temperature much higher than the melting point. For example, when PA11 is used as PA, it is not preferable to set the temperature to 200 ° C. or higher, which is higher than its melting point (187 ° C.).

  In order to further finely disperse the coarsely dispersed PA in step (1), it is necessary to melt and shear the PA. On the other hand, the higher the temperature, the more thermally the rubber. It is because it becomes easy to deteriorate. Moreover, when the melted PA is finely dispersed and then the temperature is lowered to the melting point or lower of the PA so that the PA does not re-aggregate, the temperature close to the melting point can be lowered to the melting point or lower earlier.

  Step (3) is a step of lowering the temperature to below the melting point of PA while applying a shearing force after step (2).

  After both are finely dispersed in the step (2), in order to maintain the finely dispersed state, it is necessary to make the mixture below the melting point of PA and immobilize PA in NBR. In this case, if the temperature is lowered without applying a shearing force, the PA finely dispersed in the NBR becomes easy to reaggregate. Therefore, in order to suppress the reaggregation as much as possible, the temperature is lowered to a temperature at which the reaggregation is not applied while applying the shearing force. It becomes important.

  The shearing force in step (3) is preferably smaller than the shearing force in steps (1) and (2) because it is necessary to prevent the temperature from rising due to self-heating due to shearing. If there is a function that can be cooled, or if there is equipment that can cool the composition in water after kneading, there is no problem even if it is equivalent or higher.

  And after lowering to below melting | fusing point, if it discharges | emits from a kneader, the rubber composition of this invention can be obtained.

  In addition, in the conventional method for producing an NBR-PA rubber composition, since the temperature during kneading is considerably higher than the melting point of PA (200 ° C. or higher), the rubber composition after kneading is poured into water. Thus, the rubber composition was rapidly cooled to fix the PA in the rubber composition so that the PA does not re-agglomerate.

  On the other hand, in the method for producing a rubber composition according to the present embodiment, the temperature at the time of kneading in the step (2) is close to the melting point of PA, and further to the melting point of PA or less while shearing the rubber composition. Since the temperature has dropped, the temperature is lowered to the temperature below the melting point of the PA immediately after kneading without being rapidly cooled after being poured into water, and the PA is fixed in the rubber composition so that the PA does not re-aggregate. can do.

  Therefore, the manufacturing method of the rubber composition according to the present embodiment does not require complicated operations such as the rapid cooling step and the subsequent removal of the rubber composition from the water and drying, and the scale-up can be performed only by increasing the size of the kneader. Since it can respond, there is an advantage that it can be easily applied to mass production.

  Next, examples will be described together with comparative examples. Experimental conditions and results are shown in Tables 1-4. In addition, the polymer used in an Example and a comparative example is as follows.

[NBR]
NBR-1: Nipol DN003 manufactured by Zeon Corporation (AN amount = 50.0% by weight)
NBR-2: Nipol DN101 manufactured by Nippon Zeon Co., Ltd. (AN amount = 42.5% by weight)
NBR-3: Nipol DN202 manufactured by Nippon Zeon Co., Ltd. (AN amount = 31.0% by weight)

[PA]
PA11: Rilsan BESN made by ARKEMA

  A Banbury type kneader was used for the polymer blend.

(Examples 1-4)
80 parts by weight of NBR-1 and 20 parts by weight of PA11 were charged into a 100 cc Banbury type kneader, and the mixture was kneaded under the kneading conditions shown in Table 1 (rotor speed, time, temperature). After kneading, the rubber composition was poured into water and rapidly cooled. Then, it took out from water and dried and obtained the rubber composition.

(Examples 5-7)
NBR and PA11 shown in Table 2 were introduced into a 100 cc Banbury type kneader so that the AN content (average AN amount) in NBR was 40% by weight or more. The number of rotations, time, and temperature) were kneaded. After kneading, the rubber composition was poured into water and rapidly cooled. Then, it took out from water and dried and obtained the rubber composition.

(Examples 8 to 11)
NBR-1 and PA11 were charged into a 100 cc Banbury type kneader at a weight ratio shown in Table 3, and the mixture was kneaded under the kneading conditions shown in Table 3 (rotor speed, time, temperature). After kneading, the rubber composition was poured into water and rapidly cooled. Then, it took out from water and dried and obtained the rubber composition.

(Examples 12 to 14)
80 parts by weight of NBR-1 and 20 parts by weight of PA11 were charged into a Banbury type kneader, and kneading conditions (rotor speed, time, temperature) shown in Table 4 along the following first to third steps. The polymer blend was performed. Thereafter, the rubber composition was discharged from the kneader and allowed to cool to room temperature without being poured into water to obtain a rubber composition.

[First step: Kneading start to 180 seconds]
While kneading the mixture at a predetermined rotation speed, the temperature is raised to 120 ° C. to 140 ° C. (less than 150 ° C.), and the mixture is kneaded while applying a shearing force to PA 11 without melting PA 11.

[Second step: 180 seconds to 240 seconds]
The mixture is self-heated by shearing the mixture at a predetermined number of revolutions, and the temperature is raised to 180 ° C. by the self-heating to melt the PA 11 and then the mixture is sheared.

[Third step: 240 to 300 seconds]
The rotational speed is lowered to 30 rpm, and the temperature is set to 170 ° C. or lower while applying a shearing force.

(Comparative Examples 1-2)
A rubber composition was obtained in the same manner as in Examples 1 to 4, except that the temperature of the kneading conditions was lower than in Examples 1 to 4.

(Comparative Examples 3-4)
A rubber composition was obtained in the same manner as in Examples 5 to 7, except that the AN content (average AN amount) in NBR was less than 40% by weight.

(Comparative Example 5)
Under the conditions shown in Table 3, rubber compositions were obtained in the same manner as in Examples 8-11.

(Comparative Examples 6-8)
80 parts by weight of NBR-1 and 20 parts by weight of PA11 are charged into a Banbury type kneader, and the temperature during kneading is always constant (180 ° C.) without going through the first to third steps in Examples 12-14. Then, polymer blending was performed in a state where PA11 was melted. Thereafter, the rubber composition was discharged from the kneader and allowed to cool to room temperature without being poured into water to obtain a rubber composition.

  The dispersion state of the rubber composition obtained in Examples 1-14 and Comparative Examples 1-8 was observed. The images are shown in FIGS. The evaluation method for these dispersed images is as follows.

[Distributed image evaluation method]
Using a Scanning Probe Microscope manufactured by Shimadzu Corporation, the difference in viscoelastic properties between NBR and PA11 was imaged, and from the dispersed image, the minor axis and major axis size of PA11 as a dispersed phase were measured, and the average value was obtained. .

  In addition, in order to evaluate the physical properties and fuel permeation resistance (barrier properties) of the obtained rubber composition, the additives listed in Table 5 were added to each rubber composition obtained in the above Examples and Comparative Examples. Each sample for evaluation was prepared by kneading rubber. The evaluation methods of physical properties and fuel permeation resistance (barrier properties) in the normal state are as follows.

[Evaluation method of physical properties under normal conditions]
Each evaluation sample was vulcanized and pressed at 180 ° C. for 10 minutes to prepare No. 5 dumbbell from a 2.0 mm sheet obtained according to JISK6251: 2004, and tensile strength (TS) and elongation at break (EB) ) Was evaluated. The results are shown in Tables 1-4. In addition, the target value of the physical property at the normal state was set to be an actual use level as the fuel hose material, and TS> 10 MPa and EB> 100%.

[Evaluation method of fuel permeation resistance (barrier property)]
One side of the vulcanized sheet was immersed in Fuel C (isooctane / toluene = 50/50) and left in a constant temperature bath at 40 ° C. for 14 days (336 hours). The amount of weight loss per day was measured, and the amount of fuel oil permeation was determined from the most amount of weight loss on the day. The results are shown in Tables 1-4. The calculation formula is as [Formula 1]. The target value of the fuel oil permeation amount was set as fuel oil permeation amount <28.5, based on the fuel permeation resistance of the conventional NBR-PVC rubber composition.

[Formula 1]
Fuel oil permeation (mg · mm / cm2 · day) = weight reduction (mg / day) × vulcanized sheet thickness (mm) / permeation area (cm2)

  In Examples 1 to 4 and Comparative Examples 1 and 2, the influence of physical properties and fuel permeation resistance on the short diameter and the long and short sizes and the shape of PA 11 which is a dispersed phase of the rubber composition was examined.

  1 (a) to (d) show dispersed images of the rubber compositions obtained in Examples 1 to 4, and FIGS. 1 (e) to (f) show rubber compositions obtained in Comparative Examples 1 and 2. A dispersion image of an object is shown. In the figure, the relatively white portion represents NBR, and the relatively black portion represents PA11.

  As shown in FIGS. 1 (e) to (f), NBR and PA11 in the rubber composition obtained in the comparative example are both in a large mass and spread, and the rubber compositions according to the examples (FIG. 1 ( It can be seen that the dispersion state is poor compared to a) to (d)).

  As shown in Table 1, the average values of the minor axis and the major axis of PA11 obtained from this dispersed image are the minor axis <1 μm and the major axis> 3 in Examples 1 to 4, and are comparative examples. In 1-2, the minor axis> 1 μm and the major axis> 3.

  Next, with reference to Table 1, the rubber compositions obtained in Examples 1 to 4 and Comparative Examples 1 and 2 were compared with respect to physical properties and kneading resistance after kneaded rubber. In Examples 1 to 4, the tensile strength (TS), elongation at break (EB), and fuel oil permeation amount all met the target values. On the other hand, in Comparative Example 1, the TS value and the EB value did not satisfy the target values, and the value of the fuel oil permeation amount was a low level although the target value was satisfied. Further, in Comparative Example 2, all of the TS value, EB value, and fuel oil permeation amount did not satisfy the target values.

  Examples 5 to 7 and Comparative Examples 3 to 4 investigate the effects of physical properties and fuel permeation resistance due to the AN content in NBR which is the matrix phase of the rubber composition. Referring to Table 2, the physical properties after kneaded rubber and fuel permeation resistance were compared. All of these rubber compositions had a short diameter <1 μm and a longness> 3 of PA11 which is a dispersed phase.

  In Examples 5 to 7, the AN content in NBR was 40% by weight or more and 50% by weight or less, and the TS value, EB value, and fuel oil permeation value all met the target values. On the other hand, in Comparative Examples 3 and 4, the AN content is less than 40% by weight, and the TS value and EB value satisfy the above target values, but the value of the fuel oil permeation amount satisfies the target value. It was not.

  From the result of comparing Examples 1 to 7 and Comparative Examples 1 to 4, it has mechanical properties such as tensile strength at actual use level and elongation at break, and the fuel permeation resistance of the conventional NBR-PVC rubber composition. In order for the rubber composition to be inferior to the property, the AN content in the matrix phase NBR is 40% by weight or more, the short diameter of PA11 as the dispersed phase <1 μm, and I think it is necessary that the degree of longness> 3.

  In Examples 8 to 11 and Comparative Example 5, the influence of physical properties and fuel permeation resistance on the blend weight ratio of NBR and PA11 was examined.

  2A to 2D show the dispersion images of the rubber compositions obtained in Examples 8 to 11, and FIG. 2E shows the dispersion image of the rubber composition obtained in Comparative Example 5. . As shown in FIG. 2 (e), PA11 (black portion in the figure) in the rubber composition obtained in Comparative Example 5 is immobilized as a large mass in NBR, which is compared with that in the example. It turns out that the dispersion state is bad.

  As shown in Table 3, the average value of the short diameter and the long and shortness of PA11, which is the dispersed phase obtained from this dispersed image, was as follows. 3. The minor axis <1 μm and the major axis> 3, but in Comparative Example 5, the minor axis = 1.2 μm, the major axis = 8, and the minor axis> 1 μm.

  Next, referring to Table 3, the rubber compositions obtained in Examples 8 to 11 and Comparative Example 5 were compared in terms of physical properties after kneaded rubber and fuel permeation resistance. In Examples 8 to 11, the blend weight ratio of NBR and PA11 is in the range of NBR / PA11 = 60/40 to 90/10, and the values of TS value, EB value, and fuel oil permeation amount are the above. The target value was met. On the other hand, the thing of the comparative example 5 is NBR / PA11 = 40/60, and is outside the said range. In this case, although the TS value and the value of the fuel oil permeation amount satisfied the target value, the EB value did not satisfy the target value.

  As a result of comparing Examples 8 to 11 and Comparative Example 5, when the blend weight ratio of NBR and PA11 is in the range of NBR / PA11 = 60/40 to 90/10, the minor axis of PA11 as the dispersed phase < In order to satisfy the condition of 1 μm and the degree of length> 3, the physical property value and the value of the fuel oil permeation amount satisfied the above target values, but were satisfactory, but were not within the above range as in Comparative Example 5. In addition, the minor axis of PA11 as a dispersed phase did not satisfy the above conditions, and the EB value at the actual use level was not achieved.

  Therefore, in order to have mechanical properties such as actual use level tensile strength and elongation at break, and to be comparable to the fuel permeation resistance of the conventional NBR-PVC rubber composition, the rubber In the composition, it is considered that the blend weight ratio of NBR and PA11 is preferably in the range of NBR / PA11 = 60/40 to 90/10.

  Examples 12 to 14 and Comparative Examples 6 to 8 investigate the influence of physical properties and fuel permeation resistance on the kneading conditions in the polymer blend.

  3 (a) to 3 (c) show dispersion images of the rubber compositions obtained in Examples 12 to 14, and FIGS. 3 (d) to (f) show rubber compositions obtained in Comparative Examples 6 to 8. A dispersion image of an object is shown. As shown in FIGS. 3D to 3F, PA11 (black portion in the figure) in the rubber composition obtained in the comparative example is immobilized as a large mass in the NBR, which is the example. It can be seen that the dispersion state is worse than that.

  As shown in Table 4, the average values of the minor axis and the major axis of PA11 obtained from this dispersion image were minor axis <1 μm and major axis> 3 in Examples 12-14. In 6 to 8, the minor axis was> 1 μm.

  In addition, referring to Table 4, the rubber compositions obtained in Examples 12 to 14 and Comparative Examples 6 to 8 were compared with respect to physical properties and kneading resistance after kneaded rubber. Examples 12 to 14 were kneaded along the first to third steps, and all of the TS value, EB value, and fuel oil permeation amount satisfied the above target values and were actually usable. . On the other hand, in Comparative Examples 6-8, it did not carry out along the 1st-3rd process, but was always knead | mixed with the melting temperature (180 degreeC) of PA11. In the comparative example, although the EB value satisfied the target value, the TS value did not satisfy the target value, and the fuel oil permeation amount was inferior.

  As a result of comparing Examples 12 to 14 and Comparative Examples 6 to 8, a process of shearing at least the mixture at 120 to 140 ° C. (less than 150 ° C.) along the first to third steps (coarse dispersion), By undergoing a process of raising the temperature to 180 ° C. near the melting point of PA 11 by self-heating due to shearing force and shearing the mixture (fine dispersion), and passing through a process of lowering to a temperature below the melting point (170 ° C.) while applying the shearing force In addition, PA11 as a dispersed phase had a minor axis <1 μm and a major axis> 3, and the obtained rubber composition satisfied the target value.

  Therefore, in order to produce a rubber composition having mechanical properties such as tensile strength at the actual use level and elongation at break, which is inferior to the fuel permeation resistance of the conventional NBR-PVC rubber composition. Thus, it is important to go through the first to third steps.

  In Examples 12-14, after kneading, the rubber composition was obtained by lowering the temperature below the melting point of PA11 without introducing the rubber composition into water, but the dispersion state of PA11 in the rubber composition was It was confirmed that the rubber composition was good, and the obtained rubber composition was of an actual use level.

  As mentioned above, although embodiment of this invention was described in detail, this invention is not limited to the said Example at all, A various change is possible in the range which does not deviate from the summary of this invention.

  The rubber composition according to the present invention is suitably used for materials such as a fuel hose that supplies fuel such as gasoline.

It is an image showing the dispersion state of the rubber composition obtained in Examples 1-4 and Comparative Examples 1-2, (a) is Example 1, (b) is Example 2, (c) is Example 3. (D) is for Example 4, (e) is for Comparative Example 1, and (f) is for Comparative Example 2. It is an image showing the dispersion state of the rubber composition obtained in Examples 8-11 and Comparative Example 5, (a) is Example 8, (b) is Example 9, (c) is Example 10, ( d) is for Example 11, and (e) is for Comparative Example 5. It is an image showing the dispersion state of the rubber composition obtained in Examples 12-14 and Comparative Examples 6-8, (a) is Example 12, (b) is Example 13, (c) is Example 14. , (D) is for Comparative Example 6, (e) is for Comparative Example 7, and (f) is for Comparative Example 8.

Claims (4)

  A rubber composition comprising an acrylonitrile butadiene rubber having an acrylonitrile content of 40% by weight or more as a matrix phase and a polyamide as a dispersed phase, wherein the polyamide in the dispersed phase has a minor axis in a dispersed state in the rubber composition. 1 .mu.m or less, and its length (major axis / minor axis ratio) is 3 or more.   2. The rubber composition according to claim 1, wherein a weight ratio of the acrylonitrile butadiene rubber to the polyamide (acrylonitrile butadiene rubber / polyamide) is within a range of 60/40 to 90/10.   A fuel-based rubber molded article, wherein the rubber composition according to claim 1 or 2 is used. It is a manufacturing method of the rubber composition according to claim 1 or 2,
Applying a shear force to the mixture of acrylonitrile butadiene rubber and polyamide within a temperature range at least from a temperature at which acrylonitrile butadiene rubber begins to plasticize to before the polyamide begins to plasticize, and coarsely dispersing the polyamide in acrylonitrile butadiene rubber;
Causing the mixture to self-heat by the shearing force, raising the temperature to the melting temperature of the polyamide, and finely dispersing the polyamide in the acrylonitrile butadiene rubber;
Lowering the temperature to below the melting point of the polyamide while applying a shearing force to the mixture;
A process for producing a rubber composition, characterized by comprising: