JP3111510B2 - Water-swellable vulcanized rubber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a water-swellable vulcanized rubber. More specifically, the present invention relates to a water-swellable vulcanized rubber exhibiting a water swelling ratio of 50% or more when immersed in tap water.

[0002]

2. Description of the Related Art There have been many proposals for water-swellable rubbers, most of which are methods of compounding a rubber with a water-absorbing substance (see, for example, JP-A-54-7463 and JP-A-54-7463).
Nos. 54-20066, 57-158279, 60-197784, 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 water-swellable vulcanized rubber which gives a product.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
This is achieved by a vulcanizate of polyalkylene oxide copolymerized with allyl glycidyl ether as a crosslinking point.

The polyalkylene oxide copolymerized by using allyl glycidyl ether as a crosslinking point includes ethylene oxide (EO) at 40 to 90 mol% , propylene oxide (PO) at 10 to 60 mol% , allyl glycidyl ether
(AGE) copolymerized at 1 to 5 mol% is used. If the copolymerization ratio of ethylene oxide is lower than this, a vulcanizate having a desired water swelling ratio is not obtained.

The copolymer rubber having such a copolymerization ratio includes:
Fillers such as fillers such as carbon black, silica, clay, and talc, zinc oxide and various auxiliaries such as stearic acid, antioxidants, stabilizers, plasticizers, etc. In the presence of a vulcanizing agent such as an oxide and an optional vulcanization accelerator, about 150 to 220
The vulcanization is carried out by heating the kneaded material in a press, an oven, or the like at about 1 to 60 minutes.

[0010]

According to the present invention, the water swelling ratio (water absorption ratio) is excellent even when excellent weather resistance and oil resistance are required and a tensile strength of a certain level or more, for example, 50 kgf / cm ² or more is required. A vulcanizate is 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.

[0011]

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

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

The rubber composition is subjected to press vulcanization at 180 ° C. for 6 minutes, and the vulcanized product is subjected to normal physical properties.
(Measured on a 5 mm thick dumbbell), water swelling ratio (25 x 25 x 5 m
m sample in 25 ° C tap water for 70 hours), ozone resistant
(Leave in ozone at 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) , cold resistance (at -20 ° C ) ) And extrudability (extrusion of unvulcanized dough into a round bar) were measured. The results obtained are shown in the table below.

Examples 1 to 4 In Comparative Examples, EO-PO-AGE was prepared by copolymerizing 28 mol% of EO.
Instead of copolymer rubber, various ratios of EO were copolymerized
The same amount of EO-PO-AGE copolymer rubber (EPO manufactured by Daiso Co., Ltd.) was used. The measurement results in the above Examples and Comparative Examples are shown in the following table.

Table Measurement Items Comparative Example Actual-1 Actual-2 Actual-3 Actual-4 Hardness (JIS-A) 47 55 55 56 59 Tensile strength (kgf / cm ² ) 209 80 68 115 159 Elongation (% ) 930 390 330 570 580 Water swelling rate (%) +45 +210 +230 +400 +420 Ozone resistance NCNCNCNCNC Oil resistance (%) +73.1 +40.2 +33.7 +22.0 +11.4 Cold resistance (points) 70 65 62 64 95 Extrudability good good good good good good NC: no crack (no cutting)

In Examples 1-4, 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.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08L 71/00-71/14 C08G 65/00-65/48 WPI / L

Claims (1)

(57) [Claims] 1. A vulcanizate of an ethylene oxide-propylene oxide-allyl glycidyl ether copolymer rubber obtained by copolymerizing 40 to 90 mol% of ethylene oxide,
A water-swellable vulcanizate having a water swelling ratio (a 25 × 25 × 5 mm sample immersed in tap water at 25 ° C. for 70 hours) of 50% or more.