JPH0768448B2 - Microwave Vulcanization Method for Epichlorohydrin Rubber - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for vulcanizing epichlorohydrin rubber by microwave irradiation.

(Prior Art) In recent years, in the rubber processing industry, microwave vulcanization of rubber materials capable of continuous vulcanization molding such as tubes and hoses has become popular in order to save energy or labor in the vulcanization process. is there. However, as for the epichlorohydrin rubber mainly used for automobile-related parts such as tubes, hoses or diaphragms as the oil resistant rubber material, the vulcanization technology using the microwave heating described above is a problem of foaming at the time of heating and vulcanization products. It is hard to say that it has not been fully examined due to the problem of physical property balance.

(Problems to be Solved by the Invention) It is generally known that the addition of calcium oxide is effective for suppressing foaming due to heating when vulcanizing rubber by microwaves. In the case of epichlorohydrin rubber, it is necessary to add a large amount of calcium oxide in order to suppress foaming. However, in the case of blending a large amount of the compound, in the case of epichlorohydrin rubber, the exothermic temperature is lowered contrary to the exothermic action usually performed by microwaves, and there is a problem that the vulcanization is not performed sufficiently. In addition, the obtained vulcanized rubber also had the adverse effect of impairing the quality of the product because its physical properties, particularly tensile strength, compression set resistance and water resistance, were significantly reduced.

(Means for Solving the Problem) The inventors of the present invention have earnestly studied for the purpose of obtaining a microwave vulcanizable epichlorohydrin-based rubber vulcanizing composition that does not cause foaming and deterioration of vulcanizate properties as described above. I went. as a result,
Obtained by dry or calcination wet method with specific amount of calcium oxide and magnesium oxide, magnesium hydroxide or calcium hydroxide in combination with epichlorohydrin copolymer rubber or rubber mixture composed of specific monomer components It has been found that a rubber composition containing white carbon achieves the above object.

That is, in the present invention, the constitutional unit of the copolymer rubber or the rubber mixture is epichlorohydrin 50 to 70 mol%, ethylene oxide 30 to 50 mol%, allyl glycidyl ether 0 to
1 to 4 parts by weight of (a) calcium oxide, 1 to 4 parts by weight of a metal compound selected from (b) magnesium oxide, magnesium hydroxide and calcium hydroxide, based on 100 parts by weight of epichlorohydrin rubber of 10 mol%. Yes, and the total amount of the above (a) component and (b) component is 2 to 8 parts by weight, (c) the equilibrium adsorbed water content at 30 ° C, 50% RH, and the loss on drying after 105 ° C for 4 hours Is 2% by weight or less of dry method white carbon or calcined wet method white carbon 5 to 25 parts by weight, and (d) a composition containing the rubber vulcanizing agent is heated and vulcanized by microwave irradiation. A method for microwave vulcanizing epichlorohydrin rubber.

The epichlorohydrin-based rubber used in the present invention comprises epichlorohydrin 50-70% mol, ethylene oxide 30-
It is selected from a binary polymer rubber, a terpolymer rubber or a rubber mixture composed of the above-mentioned constituents, which is composed of 50 mol% and 0 to 10 mol% of allyl glycidyl ether.

When the epichlorohydrin-based rubber is a rubber mixture, in addition to the epichlorohydrin homopolymer, a binary or ternary copolymer of any composition composed of the above monomer components is appropriately blended to obtain a rubber mixture having the above molar composition range. Used.

As the binary or terpolymer rubber of the blending rubber, a binary copolymer rubber of epichlorohydrin 10 to 90 mol% and ethylene oxide 90 to 10 mol%, epichlorohydrin 80 to 99 mol% and allyl glycidyl ether 20 ~ 1
Binary copolymer rubber with mol%, epichlorohydrin 10 ~
A terpolymer rubber of 89 mol%, 89 to 10 mol% of ethylene oxide and 1 to 20 mol% of allyl glycidyl ether is preferably used.

In the epichlorohydrin-based rubber of the present invention, it is not preferable that the composition ratio of epichlorohydrin as a constituent component thereof exceeds 70 mol% or is less than 50 mol% because foaming will occur during heating by microwaves. As the cause of this foaming, if it exceeds the above range, it is mainly due to the fact that the gas generated by heating becomes difficult to pass through the composition, and if it is less than the above range, the vulcanization rate becomes slower than the foaming rate. It is thought to be mainly due to this.

When allyl glycidyl ether is introduced into the epichlorohydrin-based rubber of the present invention, a vulcanized product having particularly excellent heat aging resistance is obtained, and therefore introduction of the component is preferable. However, it has been found that when the amount of allyl glycidyl ether introduced exceeds 10 mol%, foaming tends to occur during microwave heating. This is considered to be due to the decrease in vulcanization rate.

The epichlorohydrin-based rubber used in the present invention may have a Munney viscosity at 100 ° C. of about 40 to 150, which is generally used for both the copolymer rubber and the rubber mixture,
50 to 100 for good extrusion and vulcanizability
The thing of a grade is more preferable.

The amount of calcium oxide of the component (a) to be blended in the composition of the present invention is 1 to 6 parts by weight, preferably 1 to 4 parts by weight, based on 100 parts by weight of epichlorohydrin. If the blending amount is less than 1 part by weight, the effect of suppressing foaming is small, and if it exceeds 6 parts by weight, the microwave energy efficiency is lowered and the vulcanized physical properties are adversely affected as described later.

The compounding of calcium oxide in the present invention is added for the purpose of absorbing water in the composition and preventing foaming during microwave vulcanization, and is known as an additive for microwave vulcanization. . However, in the application to the epichlorohydrin-based rubber as in the present invention, it has been found that the incorporation of a large amount of calcium oxide has a negative effect, the heating effect by the microwave is lowered, and the energy efficiency is deteriorated. In addition, the vulcanizate thus obtained has the following physical properties: tensile strength,
It also had the adverse effect of impairing compression set resistance and water resistance. In the present invention, in combination with a relatively small amount of calcium oxide as described above and magnesium oxide, magnesium hydroxide or calcium hydroxide which is the component (b) described later, and in combination with the specific white carbon of the component (c), It is possible to obtain a vulcanized product which has no foaming during vulcanization, has good microwave energy efficiency, has no problems with the above-mentioned physical properties, and has particularly good compression set resistance.

In the composition of the present invention, addition of magnesium oxide, magnesium hydroxide, or calcium hydroxide as the component (b) used in combination with the above-mentioned calcium oxide suppresses foaming during microwave vulcanization, and exhibits particularly excellent compression set resistance. To get sex. The compounding amount of the component (b) is 1 to 4 parts by weight with respect to 100 parts by weight of the epichlorohydrin rubber, and if it is less than 1 part by weight, the effect of improving the compression set resistance is small.
If it exceeds 4 parts by weight, the water resistance of the vulcanizate will deteriorate.

In the composition of the present invention, in order to obtain the effect of suppressing foaming during vulcanization and good compression set resistance, the total amount of the component (b) and the calcium oxide of the component (a) is epichlorohydrin rubber 100. It is necessary to have at least 2 parts by weight with respect to parts by weight, and in order to maintain good water resistance of the obtained vulcanizate, the total amount of components (a) and (b) is at most 8 parts by weight, It should preferably remain at 6 parts by weight.

The dry-process white carbon or the calcined wet-process white carbon of the component (c) used together with the component (a) and the component (b) in the present invention has vulcanized physical properties without causing foaming during microwave vulcanization, Especially, it has an effect of improving water resistance. The compounding amount is in the range of 5 to 25 parts by weight with respect to 100 parts by weight of epichlorohydrin. If it is less than 5 parts by weight, the above-mentioned water resistance improving effect is small, and if it exceeds 25 parts by weight, foaming tends to occur and the compression set resistance of the vulcanized product is impaired.

The dry-process white carbon used in the present invention refers to one produced by a gas phase reaction such as thermal decomposition of silicon tetrachloride. Further, the calcined wet method white carbon refers to white carbon produced by a wet method such as acid decomposition of alkali silicate and calcined at 400 to 900 ° C. These dry or calcined wet white carbons have 30
For the purpose of the present invention, it is preferable that the equilibrium adsorbed water content at ℃ and 50% RH is 2% by weight or less.
The one of 1 mμ to 50 μ is suitable for use. Wet method white carbon most commonly used as white carbon for rubber has an equilibrium adsorbed water content of more than 5% by weight at 30 ° C. and 50% RH. It is inappropriate because it does. The equilibrium adsorbed water content is measured by measuring the weight loss after drying for 4 hours at 105 ° C. Aerosil (Nippon Aerosil Co., Ltd.) is a commercially available product of the dry process white carbon used in the present invention.
There are Carplex CS-5 and CS-7 (Shionogi Pharmaceutical Co., Ltd.) as commercially available products of calcined wet method white carbon.

The vulcanizing agent used in the present invention is of a type in which epichlorohydrin-based rubber is vulcanized via a chlorine atom, and is used alone or in combination. Vulcanizing agents of polythiols or their derivatives or thioureas are preferable for the purpose of obtaining physical properties of the vulcanized product, particularly good heat aging resistance.

As the polythiol vulcanizing agent, di- or trithiol-
s-triazine compound (Japanese Patent Publication No. 48-36926), 2,5
-Dimercapto-1,3,4-thiadiazole compound (U.S. Pat. No. 4,288,576), 2,3-dimercaptopyrazine compound (Japanese Patent Publication No. 58-14468), 2,3-dimercaptoquinoxaline compound (Japanese Patent Publication No. 58-14469), 3,5-
Dimercapto-1,2,4-triazole compound (JP-B-57
-46463), 2,4-dithiohydantoin compounds (Japanese Patent Publication No. 58-14467, Japanese Patent Publication No. 61-50505, Japanese Patent Laid-Open No.
57-34160).

Examples of the thiourea-based vulcanizing agent include a 2-mercaptoimidazoline (ethylenethiourea) compound and a 2-mercaptopyrimidine compound (both JP-B-43-5758).

The compounding amount of the vulcanizing agent is appropriately in the range of 0.1 to 10 parts by weight with respect to 100 parts by weight of epichlorohydrin rubber.

The composition of the present invention contains various compounding agents such as those commonly used in the art, such as an acid acceptor, a reinforcing agent, a filler,
Addition of silane coupling agent, plasticizer, antiaging agent, etc. is free. In particular, in order to obtain stable high heat build-up by microwaves, it is preferable to add carbon black, and usually 30 to 100 parts by weight based on 100 parts by weight of epichlorohydrin rubber.
It can be added in the range of parts by weight.

The mixing order of the composition of the present invention is not particularly limited, and a mixing roll, a Banbury mixer or various kneaders used in the conventional rubber processing field can be used as a mixer.

The microwave for vulcanizing the composition of the present invention is 300 to 3,000 MHz.
Electromagnetic waves, and either 2,450 MHz or 915 MHz is normally used. In the microwave continuous vulcanization line, the rubber composition discharged from the rubber extruder or the vent type extruder at about 2 to 50 m / min, has a conveyor such as a belt conveyor,
It is continuously loaded into a microwave heating unit with a length of about 0.5 to 20 m and maintained at a temperature of 100 to 250 ° C, and an output of about 0.5 to 50 Kw
Vulcanization is performed by heating to about 50 to 300 ° C, but normally, this is passed through a hot air oven heated to about 150 to 300 ° C to complete vulcanization.

The continuous vulcanization molded product obtained from the composition of the present invention may be a single product consisting of the present composition alone, or a laminate with another rubber composition may be discharged from an extruder and heated and vulcanized as it is. It is possible. As an example of such a laminate, a rubber composition such as chloroprene rubber, chlorosulfonated polyethylene, or chlorinated polyethylene having excellent weather resistance, ozone resistance, and abrasion resistance is used as the outer layer, and A two-layer rubber tube using the inventive composition can be mentioned. In particular, the rubber component was a binary mixture of chlorinated polyethylene and a lower alkyl ester copolymer of chlorinated ethylene- (meth) acrylic acid, or a ternary mixture of the binary mixture further mixed with an epichlorohydrin-based polymer. It is very preferable to use the rubber composition for vulcanization for the outer rubber layer of the two-layer rubber tube with the composition of the present invention, since a laminated rubber material having very excellent adhesiveness is obtained. As a binary or ternary mixture of the above rubbers, there are commonly known chlorinated polyethylene having a chlorine content of 20 to 50% by weight and chlorinated polyethylene of 5 to 95% by weight and chlorinated ethylene- (meth) acrylic having a chlorine content of 2 to 45% by weight. Acid lower alkyl ester copolymer ((meth) acrylic acid lower alkyl ester content 2 to 20% by weight) Binary mixture of 95 to 5% by weight, or epichlorohydrin based on 100 parts by weight of the binary mixture. A ternary mixture obtained by mixing 3 to 30 parts by weight of an epichlorohydrin-based polymer such as a homopolymer, an epichlorohydrin-ethylene oxide copolymer and an epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer is preferable as the rubber component. Further, the composition of the present invention can be used as an outer layer of a two-layer rubber tube and as an inner layer, an outer layer or an intermediate layer of a three-layer rubber tube.

(Examples) Examples 1 to 6 Comparative Examples 1 to 13 The rubber compositions shown in column A of Table 1 were kneaded with an internal mixer having an internal capacity of 1.7 for 5 minutes, and the compounding agent of column B was added to this to 60 After kneading with a 7-inch roll heated to ~ 70 ℃, take it out in a ribbon shape, 45mmφ, L / D16, compression ratio 1.4
The tube was continuously molded at a speed of 5 m / min by feeding it to an extruder having a screw and a die having an outer diameter of 10 mm and an inner diameter of 7 mm.
Next, the tube was vulcanized by passing it through a microwave heating unit having an output of 2 Kw, 2,450 MHz and a length of 2 m at the above speed, and then passing it through a hot air oven heated to 250 ° C. with an effective length of 25 m. The physical properties of the obtained vulcanized products were tested as shown in Table 2.

On the other hand, a vulcanized product was obtained in the same manner as in the above method, except that a die having a diameter of 25 mm was used as the die of the extruder and extruded as a round bar. This vulcanized product was cut to a length of 12.7 mm and used for the compression set test shown in Table 2.

In addition, the foaming state of the tube in Table 2 is the result of observing the cross section with a microscope of 16 times after cutting the tube immediately after leaving the microwave heating part, and the evaluation is as follows.

Excellent: No bubbles are recognized.

Good: A few bubbles are recognized.

Acceptable: Many bubbles are recognized.

Impossible: Sponge-like shape It has been confirmed by experiments that the foamed state of the final vulcanized product has a result in accordance with the judgment of the foamed state after microwave heating.

The physical property test shown in Table 2 was not conducted for tubes whose foaming state was acceptable or less.

In Table 1, notes (1) to (7) rubber and (8) to (1
The following were used as the compounding agents in 4).

(1) Mooney viscosity 55 (ML1 + 4 (100 ° C) and below) (2) Mooney viscosity 65 Composition ratio (mol) Epichlorohydrin (EP) / Ethylene oxide (EO) = 60/40 (3) Mooney viscosity 80 Composition ratio (mol) ) EP / EO = 40/60 (4) Mooney viscosity 50 composition ratio (mol) EP / EO = 80/20 (5) Mooney viscosity 50 composition ratio (mol) EP / allyl glycidyl ether (AGE)
= 95/5 (6) Mooney viscosity 60 composition ratio (mol) EP / EO / AGE = 55/40/5 (7) Mooney viscosity 50 composition ratio (mol) EP / EO / AGE = 60/25/15 (8) ) "Aerosil 200" manufactured by Nippon Aerosil Co., Ltd. Equilibrium adsorbed water content (30 ° C, 50% RH, same below) 1.8% by weight (however, 105 ° C, weight loss after 4 hours, same below) (9) "Carplex CS -5 "Shionogi Pharmaceutical Co., Ltd. equilibrium adsorption water content 2.0% by weight (10)" NIPSIL VN-3 "Nihon Silica Co., Ltd. equilibrium adsorption water content 7.5% by weight (11)" Carplex # 1120 "Shionogi Pharmaceutical Co., Ltd. equilibrium Adsorbed water content 6.6% by weight (12) "Cast S" manufactured by Tokai Carbon Co., Ltd. (13) "ADEKA Sizer RS-700" manufactured by Adeka Argus Chemical Co., Ltd. (14) "CML # 21" manufactured by Omi Chemical Co., Ltd. As is clear from the results shown in Table 2, the vulcanized product obtained from the composition of the present invention did not cause foaming at all. In addition, excellent results have been obtained for each physical property of the vulcanized product. In particular, Examples 5 and 6 in which allyl glycidyl ether is contained in the rubber component are excellent in heat aging resistance and hard to be softened, and therefore show excellent values in hardness and tensile strength. Further, as is clear from comparison with Comparative Example 6, the composition of the present invention contains the component (b), and therefore the vulcanized product has particularly excellent compression set resistance.

On the other hand, Comparative Example 1, Comparative Example 2 and Comparative Example 3 using the wet method as the white carbon, Comparative Example 5 with an excessive amount of white carbon, Comparative Example 7 containing no calcium oxide, the rubber composition ratio is Comparative Examples 11 and 12 outside the scope of the present invention, Comparative Example 13 in which the amount of ethylene oxide and the amount of allyl glycidyl ether in the rubber composition ratio are outside the scope of the present invention are all foamed at the time of microwave vulcanization, so that addition without foaming was performed. A vulcanizate could not be obtained, and particularly in Comparative Examples 5 and 7, the vulcanizate was sponge-like.

Further, Comparative Example 4 in which the amount of white carbon is zero is vulcanized without foaming, but the water resistance of the vulcanized product is extremely poor. In Comparative Examples 8 and 10 in which the amount of calcium oxide of the component (a) is excessive and in Comparative Example 9 in which the amount of the metal compound of the component (b) is excessive, the total amount of the component (b) and the component (b) is within the range of the present invention. The water resistance of the vulcanizate is poor. Further, in Comparative Examples 8 and 10 having a large amount of calcium oxide, the microwave energy efficiency was slightly deteriorated and the compression resistance was also poor.

(Effect of the Invention) In a heating furnace or steam heating which is a conventional vulcanization method of epichlorohydrin rubber, continuous vulcanization was almost impossible because vulcanization requires several tens of minutes. The composition used in the present invention has good microwave energy efficiency, is sufficiently vulcanized in minutes without foaming, and has excellent vulcanization physical properties. Therefore, a tube or a hose requiring continuous vulcanization. It is extremely excellent as a molding composition for long products such as the above, and can sufficiently meet the demand for energy saving and labor saving in the rubber processing industry.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keiko Oura 1-6-11 Konoike-cho, Higashiosaka-shi, Osaka (72) Inventor Yasuo Matoba 2-1-1-208 Shoji, Toyonaka-shi, Osaka (56) References JP-A-56-109246 (JP, A) JP-A-54-135843 (JP, A) JP-A-58-32653 (JP, A)

Claims (1)

[Claims] 1. A constitutional unit of a copolymer rubber or a rubber mixture is epichlorohydrin 50 to 70 mol%, ethylene oxide.
30-50 mol%, allyl glycidyl ether 0-10 mol%
With respect to 100 parts by weight of epichlorohydrin-based rubber,
(A) 1 to 6 parts by weight of calcium oxide, (b) 1 to 4 parts by weight of a metal compound selected from magnesium oxide, magnesium hydroxide and calcium hydroxide, and the total of the above (a) component and (b) component 2 to 8 parts by weight,
(C) Equilibrium adsorbed water content at 30 ° C and 50% RH,
Microwave irradiation of a composition containing 5 to 25 parts by weight of dry-process white carbon or calcined wet-process white carbon whose weight loss after drying at 105 ° C for 4 hours is 2% by weight or less and (d) a vulcanizing agent for the above rubber A method for microwave vulcanization of epichlorohydrin-based rubber, which comprises vulcanizing by heating with.