JP3003720B2 - Method for producing water-swellable rubber composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a water-swellable rubber composition. More specifically, the present invention relates to a method for producing a water-swellable rubber composition which gives not only excellent weather resistance and oil resistance but also a vulcanizate exhibiting high water absorption performance with a high water absorption capacity.

[0002]

2. Description of the Related Art There have been many proposals for a water-swellable rubber composition, and most of them are methods of compounding a rubber with a water-absorbing substance (see, for example, JP-A-54-7463, JP 54-20066, JP 57-158279, JP 60-1977
Nos. 84 and 61-26661). However, these methods simply knead the rubber and the water-absorbing substance, and have poor compatibility because only the rubber component is involved in the crosslinking reaction, resulting in inconveniences such as falling off of the components and insufficient mechanical strength.

In order to improve such a method, it has been proposed to use a urethane-based substance as a water-swellable substance (JP-A-57-23618). In this case, MOCA (4 , 4'-diamino-3,3'-dichlorodiphenylmethane) and the like are usually used. However, these curing agents are toxic and cause contamination in the use environment. Therefore, it is desirable to use water or alcohol-based curing agents without using amine-based curing agents.However, water-swellable substances that have been cured first with these curing agents, including water and alcohol, should be used. When the rubber component is dispersed and compounded, there is a problem that dispersion is poor due to low compatibility with the rubber, and the mechanical strength of the vulcanized molded product is low.

Japanese Patent Publication No. Sho 62-44032 discloses a caulking material composition obtained by adding a swellable urethane substance which is a reaction product of a polyether polyol, a polyisocyanate and a curing agent to natural rubber. Also, when a water-swellable rubber composition is prepared by adding a polyalkylene oxide diisocyanate adduct to a synthetic rubber,
A reduction in the mechanical strength of the vulcanized molded product cannot be avoided.

[0005] When natural rubber or synthetic rubber (such as isoprene rubber and styrene-butadiene rubber) is used as described above, a material having poor weather resistance and oil resistance is formed, although the performance is not significantly reduced due to repeated water absorption. Not only that, when a tensile strength of not less than a certain value, for example, not less than 50 kgf / cm ² is required, there is a problem that the rate of volume change due to water absorption is only about 100%.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide not only excellent weather resistance and oil resistance but also vulcanization with a large water absorption capacity even when a certain tensile strength is required. It is an object of the present invention to provide a method for producing a water-swellable rubber composition which gives a product.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
A rubber compound of a polyalkylene oxide copolymerized with an allyl glycidyl ether as a crosslinking point and a polyalkylene oxide diisocyanate adduct are sufficiently mixed in a kneading apparatus, and then water is added thereto to react with the diisocyanate adduct. This is achieved by producing a swellable rubber composition.

The polyalkylene oxide copolymerized with allyl glycidyl ether as a crosslinking point contains 0 to 50 mol%, preferably 20 to 40 mol% of ethylene oxide (EO),
Propylene oxide (PO) 45-95 mol%, preferably 6
0 to 80 mol%, allyl glycidyl ether (AGE) 0.1 to 10
Mol%, preferably 1 to 5 mol%, brominated propylene oxide (BrPO) is a rubbery copolymer obtained by copolymerizing 0 to 10 mol%, preferably 1 to 5 mol%, In this case, a commercially available product can be used as it is.

The polyalkylene oxide diisocyanate adduct is obtained by homopolymerizing or copolymerizing an alkylene oxide such as ethylene oxide or propylene oxide in the presence or absence of a polyol such as ethylene glycol, propylene glycol or glycerin. It is a polymer, which can be obtained by adding and reacting diisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, m-xylene diisocyanate, hexamethylene diisocyanate, and the like at both terminal diol groups, generally at an equivalent ratio of -NCO / -OH of 1. . These adducts have a viscosity of about 1000 to 10,000 centipoise, preferably about 3000 to 7000 centipoise (2
5 ° C.) is used.

[0010] These diisocyanate adducts are preferably premixed with a silicic acid-based white carbon or the like to improve the handleability before use. As the silicic acid-based white carbon, silicic anhydride or one whose surface is treated with a silane coupling agent or the like is used.

These polyalkylene oxide diisocyanate adducts and silicic acid-based white carbon are premixed with a stirring device such as a kneader or a closed mixing device such as a Henschel mixer before mixing with the rubber compound. This premix can compensate for the drawback that the polyalkylene oxide diisocyanate adduct is in a liquid state, is hardly compatible with the rubber compound, and is difficult to handle.

Each of these components generally comprises a rubber compound 10
The former is about 10 to 250 parts by weight, preferably about 50 parts by weight per 0 parts by weight.
It is used in a proportion of about 200 parts by weight, the latter being about 2 to 200 parts by weight, preferably about 10 to 100 parts by weight, and the sum of both is about 60 to 300 parts by weight.

To the premixed mixture of these two components, a rubber compound kneaded with a kneader or the like and sufficiently plasticized is added and thoroughly mixed. The rubber compound contains fillers such as silica, clay, and talc, in addition to carbon black.
It is a blend of auxiliary ingredients such as zinc oxide and stearic acid, antioxidants, stabilizers, plasticizers, and other necessary additives.However, vulcanizing agents and vulcanization accelerators are used in water-swellable rubber compositions. It is desirable to add it after the production of the composition so as not to cause a vulcanization reaction during the production.

After the mixture is cooled to a temperature of about 50 ° C. or less, generally around room temperature, while stirring as it is,
When gradually adding about 5 to 200 parts by weight, preferably about 10 to 100 parts by weight of water per 100 parts by weight of the rubber compound, the isocyanate groups of the dispersed adduct react with water to gradually increase the viscosity. When it becomes ready to be taken out as rubber material, take it out from a closed mixer such as a kneader and dispense it with an open roll.

The water swellable rubber composition as the reactant is
A vulcanizing agent (sulfur-based, organic peroxide-based) and, if necessary, a vulcanization accelerator are added thereto and vulcanized by a steam vulcanization method or the like. Also, after dispensing this composition into a sheet, put it in an oven or the like at a temperature of about 60 to 80 ° C. for about 12 to
Heat and dry for 24 hours to completely remove excess water not involved in the reaction, add a vulcanizing agent and a vulcanization accelerator, and vulcanize by oven vulcanization, press vulcanization, etc. Can also.

[0016]

According to the method of the present invention, the water swelling ratio (water absorption capacity) can be improved even when the weather resistance and oil resistance are excellent and a tensile strength of not less than a certain value, for example, not less than 50 kgf / cm ² is required. Large vulcanizates are obtained. The relationship between the tensile strength and the water swelling ratio is almost inversely proportional, and a material having a low tensile strength is used for a water-blocking material or the like. At the rate of 100% or more, the same water swelling rate
It shows more than twice the tensile strength. It also shows a stable water absorption performance in which the water absorption rate hardly decreases even if water is repeatedly absorbed. Further, the extrudability is good.

[0017]

Next, the present invention will be described with reference to examples.

Comparative Example 1 EO-PO-AGE copolymer rubber 100 parts by weight (Daiso product EPO-R; EO 28 mol%) HAF carbon black 20 Zinc oxide 5 Stearic acid 1 A compound of at least 1 is kneaded in a closed kneader. Then, 1.5 parts by weight of tetramethylthiuram disulfide, 1.5 parts by weight of N-cyclohexyl-2-benzothiazylsulfenamide and 1.5 sulfur 1 were added to the discharged matter, kneaded well with an open roll, and then taken out as a sheet.

The rubber composition was subjected to press vulcanization at 180 ° C. for 6 minutes, and the vulcanized product was subjected to normal physical properties (5
mm dumbbell), water swelling ratio (25 x 25 x 5 mm
Sample in 70 ° C tap water for 70 hours), ozone resistance
(Left in ozone with a concentration of 50 pphm at 20% elongation at 40 ° C for 70 hours), oil resistance (volume change after immersion in JIS No. 3 oil at 100 ° C for 70 hours) and extrudability (uncured dough Extruded into a round bar shape)
Was measured respectively. The results obtained are shown in Table 1 below.

Example 1 EO-PO was added to the compound kneaded with the internal mixer of Comparative Example 1.
80 parts by weight of a polyalkylene oxide diisocyanate adduct in which tolylene diisocyanate is bonded to both terminal groups of the copolymer (viscosity 3000 cps) and surface-treated silicic acid anhydride (Nippon Aerosil R972; a part of the surface hydroxyl groups of fumed silica or The whole was reacted with dimethyldichlorosilane), and 40 parts by weight of the premix was added and mixed with stirring.

Thereto, 45 parts by weight of water were gradually added, and the mixture was reacted with the above-mentioned polyalkylene oxide diisocyanate adduct in a closed mixer for several minutes, and then separated into a sheet having a thickness of about 5 mm by an open roll. 60 ° C as sheet
In an oven for 24 hours to completely remove moisture in the unvulcanized rubber.

To this, two kinds of vulcanization accelerators and vulcanizing agents were added in the same manner as in Comparative Example 1, kneaded well with an open roll, and then taken out as a sheet.

The rubber composition was subjected to press vulcanization at 180 ° C. for 6 minutes, and the vulcanized product was measured in the same manner as in the comparative example. The results obtained are shown in Table 1 below.

Example 2 In Example 1, the amount of the polyalkylene oxide diisocyanate adduct was changed to 220 parts by weight, and the amount of water was changed to 120 parts by weight.

Example 3 The procedure of Example 2 was repeated, except that HAF carbon black was replaced by 25%.
Parts by weight of FEF carbon black and 6 parts by weight of dicumyl peroxide instead of sulfur as the vulcanizing agent were used, and no two vulcanization accelerators were used. The press vulcanization was performed at 180 ° C. for 2 minutes.

Example 4 In Example 1, the following compound was used as a compound kneaded with an internal kneader, and 100 parts by weight of EO-PO-AGE-Br.PO copolymer rubber (Daiso product EPO -R; EO 28 mol%) HAF carbon black 20 magnesium oxide 3 stearic acid 1 dibutylcarbinol adipate 10 The following were used as vulcanization accelerators and vulcanizing agents. 2-mercaptoimidazole 1.4 parts by weight Sulfur 0.2 The press vulcanization was performed at 180 ° C. for 10 minutes.

Comparative Example 2 In Example 1, the following compound was used as the compound kneaded in the internal mixer, and the following compound was used: 100 parts by weight of isoprene rubber (IR2200 manufactured by Zeon Corporation) FEF carbon black 30 Calcium carbonate 30 Oxidation Zinc 5 Stearic acid 2 Process oil 5 The amount of the two vulcanization accelerators was changed to 1 part by weight. The press vulcanization was performed at 160 ° C. for 5 minutes.

Table 1Measurement item Ratio -1 Real-1 Real-2 Real-3 Real-4 Ratio-2  Hardness (JIS-A) 47 48 49 61 45 54 Tensile strength (kgf / cm^Two) 209 75 17 80 70 89 Elongation (%) 930 1190 430 290 1150 670 Water swelling rate (%) +45 +140 +200 +135 +140 +70 Ozone resistance NCNCNCNCNC Cutting oil resistance (%) +73.1 + 53.3 +38.7 +23.9 +38.1 +154.1 Extrudability Good Good Good Good Good Good

In Examples 1 and 2, the cycle of immersion in tap water at 25 ° C. for 96 hours and drying in an oven at -40 ° C. for 70 hours was repeated. In any of the first to fifth cycles, water swelling was repeated. The rate hardly changed.

Example 5 EO-PO-AG obtained by copolymerizing 28 mol% of EO in Example 1
EO-copolymerized with 48 mol% EO instead of E-copolymer rubber
PO-AGE copolymer rubber (EPO manufactured by Daiso) was used.

Example 6 In Example 5, the amount of the polyalkylene oxide diisocyanate adduct was changed from 80 parts by weight to 220 parts by weight.

Example 7 In Example 1, EO-PO-AG obtained by copolymerizing 28 mol% of EO was used.
EO- copolymerized with 68 mol% EO instead of E-copolymer rubber
A PO-AGE copolymer rubber (EPO manufactured by Daiso) was used, and the amount of the polyalkylene oxide diisocyanate adduct was changed from 80 parts by weight to 220 parts by weight.

The measurement results of the above Examples 5 to 7 show that
(Hardness at -20 ° C) is shown in Table 2 below. In addition,
As a dumbbell for measuring physical properties in normal state and a sample for measuring water swelling ratio, those having a thickness of 2 mm were used.

[0034]

In Examples 5 to 7, the cycle of immersion in tap water at 25 ° C. for 70 hours and drying in an oven at -60 ° C. for 24 hours was repeated. In any of the first to fifth cycles, water swelling was repeated. The rate hardly changed.

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Claims (3)

(57) [Claims] 1. A polyalkylene oxide rubber compound and a polyalkylene oxide diisocyanate adduct copolymerized with allyl glycidyl ether as a cross-linking point are thoroughly mixed in a kneading apparatus, and water is added thereto to add the diisocyanate adduct. And a method for producing a water-swellable rubber composition. 2. A rubber compound of polyalkylene oxide copolymerized with allyl glycidyl ether and brominated propylene oxide as a crosslinking point and a polyalkylene oxide diisocyanate adduct are sufficiently mixed in a kneading apparatus, and water is added thereto. And reacting the diisocyanate adduct with the water-swellable rubber composition. 3. The process for producing a water-swellable rubber composition according to claim 1, wherein the polyalkylene oxide diisocyanate adduct is used as a premix with silicic acid-based white carbon.