JPH04359915A - Production of water-swellable rubber composition - Google Patents

Abstract

PURPOSE:To produce a water-swellable rubber composition which can give a vulcanizate which has not only excellent weather resistance and oil resistance but also a high water absorption ratio even in the case where a tensile strength on a certain level or larger is required. CONSTITUTION:An ethylene oxide/propylene oxide/allyl glycidyl ether copolymer rubber composition is mixed with a polyalkylene oxide-diisocyanate adduct/ surface-treated silicic anhydride premix, and water is added to this mixture to react the adduct with water. Then a vulcanizer and a vulcanization accelerator are added to the resulting mixture, and the final mixture is press-vulcanized.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing water-swellable rubber compositions. More specifically, the present invention relates to a method for producing a water-swellable rubber composition that provides a vulcanizate that not only has excellent weather resistance and oil resistance but also stably exhibits water absorption performance with a high water absorption capacity.

0002

BACKGROUND OF THE INVENTION Many proposals have been made regarding water-swellable rubber compositions, most of which involve blending water-absorbing substances with rubber (for example, Japanese Patent Laid-Open No. 54-74
Publication No. 63, Publication No. 54-20066, Publication No. 57-15
No. 8279, No. 60-197784, No. 61
-26661, etc.). However, these methods simply knead rubber and a water-absorbing substance, and only the rubber component participates in the crosslinking reaction, resulting in poor compatibility and problems such as falling off of compounded components and lack of mechanical strength.

In order to improve this method, it has been proposed to use a urethane-based material as a water-swellable material (Japanese Patent Laid-Open No. 57-23618), but in this case MOCA (4 ,4'-diamino-3,3'
-dichlorodiphenylmethane) etc., but these curing agents are toxic and contaminate the environment in which they are used. Therefore, it is desirable to use water or alcohol-based hardeners instead of amine-based hardeners. When dispersed and blended into a rubber component, the problem arises that the compatibility with the rubber is low, resulting in poor dispersion and low mechanical strength of the vulcanized molded product.

[0004] Japanese Patent Publication No. 62-44032 describes a caulking material composition in which a swelling urethane substance which is a reaction product of a polyether polyol, a polyisocyanate, and a curing agent is added to natural rubber. Even when a water-swellable rubber composition is prepared by adding a polyalkylene oxide diisocyanate adduct to a synthetic rubber, the mechanical strength of the vulcanized product inevitably decreases.

[0005] Furthermore, when natural rubber or synthetic rubber (such as isoprene rubber or styrene-butadiene rubber) is used in this way, although there is little deterioration in performance due to repeated water absorption, it forms a material with poor weather resistance and oil resistance. Not only that, but when a tensile strength of more than a certain level, for example, 50 kgf/cm2 or more is required, there is a problem that the rate of change in volume due to water absorption is only about 100%.

[0006]

[Problems to be Solved by the Invention] The object of the present invention is to provide vulcanization that not only has excellent weather resistance and oil resistance, but also has a high water absorption capacity even in cases where tensile strength above a certain level is required. An object of the present invention is to provide a method for producing a water-swellable rubber composition that provides a water-swellable rubber composition.

[0007]

[Means for Solving the Problems] The purpose of the present invention is to
A rubber compound of polyalkylene oxide copolymerized with allyl glycidyl ether as a crosslinking point and a polyalkylene oxide diisocyanate adduct are thoroughly mixed in a kneading device, and then water is added thereto to react with the diisocyanate adduct. This is achieved by producing a swellable rubber composition.

[0008] The polyalkylene oxide copolymerized with allyl glycidyl ether as a crosslinking point contains ethylene oxide (EO) in an amount of 0 to 50 mol%, preferably 20 to 50 mol%.
40 mol%, propylene oxide (PO) 45-9
5 mol%, preferably 60-80 mol%, allyl glycidyl ether (AGE), 0.1-10 mol%, preferably 1-5 mol%, brominated propylene oxide (Br
- A rubber-like copolymer obtained by copolymerizing 0 to 10 mol%, preferably 1 to 5 mol% of PO), and in actual use, a commercially available product can be used as is.

[0009] Polyalkylene oxide diisocyanate adducts are obtained by homopolymerizing or copolymerizing alkylene oxides such as ethylene oxide and propylene oxide in the presence or absence of polyols such as ethylene glycol, propylene glycol, and glycerin. A polymer, in which diisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, m-xylene diisocyanate, hexamethylene diisocyanate, etc. are added to both terminal diol groups,
Generally, it is obtained by addition reaction at an -NCO/-OH equivalent ratio of 1. These adducts are approximately 1000 to 10
000 centipoise, preferably about 3000-7000
A material having a viscosity of about centipoise (25° C.) is used.

[0010] These diisocyanate adducts are preferably used after being premixed with silicic anhydride white carbon or the like to improve handling properties. As the silicic anhydride white carbon, silicic anhydride or its surface treated with a silane coupling agent or the like is used.

The polyalkylene oxide diisocyanate adduct and the silicic anhydride white carbon are premixed in a stirring device such as a kneader or a closed mixing device such as a Henschel mixer prior to mixing with the rubber compound. This premix product can compensate for the disadvantages that the polyalkylene oxide diisocyanate adduct is liquid and is difficult to be miscible with rubber compounds and is difficult to handle.

Each of these components is generally included in the rubber compound 1.
00 parts by weight, the former is about 10 to 250 parts by weight, preferably about 50 to 200 parts by weight, and the latter is about 2 to 250 parts by weight.
It is used in a proportion of 200 parts by weight, preferably about 10 to 100 parts by weight, and a total of about 60 to 300 parts by weight.

[0013] To the premixed mixture of these two components is added a rubber compound which has been sufficiently plasticized by kneading with a kneader or the like, and is thoroughly mixed. In addition to carbon black, rubber compounds also contain fillers such as silica, clay, and talc.
It is a compound containing necessary ingredients such as auxiliary agents such as zinc oxide and stearic acid, anti-aging agents, stabilizers, and plasticizers. However, vulcanizing agents and vulcanization accelerators are added to water-swellable rubber compositions. It is desirable to add it after the composition is manufactured so as not to cause a vulcanization reaction during manufacture.

[0014] This mixture is cooled to a temperature of about 50° C. or lower, generally around room temperature, while stirring, and then added to about 5 to 200 parts by weight, preferably about 10 to 100 parts by weight, per 100 parts by weight of the rubber compound. When water is gradually added, the isocyanate groups of the dispersed adduct react with the water, gradually increasing the viscosity. Remove from the mixer and portion out using an open roll.

The water-swellable rubber composition as the above reactant is:
A vulcanizing agent (sulfur-based, organic peroxide-based) and a vulcanization accelerator are added thereto if necessary, and the material is vulcanized by a steam vulcanization method or the like. In addition, after dispensing this composition into a sheet, it is placed in an oven and dried by heating at a temperature of about 60 to 80°C for about 12 to 24 hours to completely remove excess water that does not participate in the reaction. It is also possible to add a vulcanizing agent and a vulcanization accelerator thereto and perform vulcanization by an oven vulcanization method, a press vulcanization method, or the like.

[0016]

[Effects of the Invention] The method of the present invention has excellent weather resistance and oil resistance, and also has a high water swelling ratio (water absorption capacity) even when a tensile strength of more than a certain level, for example, 50 kgf/cm2 or more is required. A vulcanizate is obtained. The relationship between tensile strength and water swelling rate is almost inversely proportional, and materials with low tensile strength are used for applications such as water-stopping materials, but the material according to the present invention has a higher water swelling rate than conventional materials. When the water swelling ratio is 100% or more, the tensile strength is more than twice as high with the same water swelling ratio. It also shows stable water absorption performance with almost no decrease in water absorption rate even after repeated water absorption. Furthermore, extrusion processability is also good.

[0017]

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

Comparative Example 1 EO-PO-AGE copolymer rubber
100 parts by weight (Daiso products EPO
-R; EO 28 mol%) HAF carbon black
20 zinc oxide
5 stearic acid
One or more compounds are kneaded in an internal kneader, and the discharged product contains tetramethylthiuram disulfide.
1.5 parts by weight N-cyclohexyl-2-benzothiazylsulfenamide
1.5 Sulfur

1 was added and kneaded well with an open roll, and then taken out as a sheet.

This rubber composition was subjected to press vulcanization at 180°C for 6 minutes, and the vulcanized product had normal physical properties (measured on a 5 mm thick dumbbell), water swelling rate (2
5x25x5mm sample immersed in tap water at 25°C for 70 hours), ozone resistance (concentration 50pp at 20% elongation)
hm ozone at 40℃ for 70 hours), oil resistance (1
JIS No. 00℃ 3 Volume change rate after 70 hours immersion in oil) and extrudability (extruding unvulcanized dough into a round bar shape)
were measured respectively. The results obtained are shown in Table 1 below.

Example 1 EO-
80 parts by weight of a polyalkylene oxide diisocyanate adduct (viscosity 3000 cps) in which tolylene diisocyanate is bonded to both end groups of a PO copolymer and surface-treated silicic anhydride (Nippon Aerosil Products R972; part of the surface hydroxyl groups of fumed silica) 40 parts by weight of a premix (all of which was reacted with dimethyldichlorosilane) was added and mixed by stirring.

[0021] 45 parts by weight of water was gradually added thereto,
After reacting with the above-mentioned polyalkylene oxide diisocyanate adduct in a closed mixer for several minutes, it was divided into sheets with a thickness of about 5 mm using an open roll, dried in a 60°C oven for 24 hours in the sheet form, and left unprocessed. The moisture in the sulfur rubber was completely removed.

[0022] Two types of vulcanization accelerators and a vulcanizing agent were added thereto in the same manner as in Comparative Example 1, and the mixture was thoroughly kneaded with an open roll and then taken out in the form of a sheet.

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

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

Example 3 In Example 2, 25 parts by weight of FEF carbon black was used instead of HAF carbon black, and 6 parts by weight of dicumyl peroxide was used instead of sulfur as a vulcanizing agent. No vulcanization accelerator was used. Note that press vulcanization was performed at 180° C. for 2 minutes.

Example 4 In Example 1, the following compound was used as the compound kneaded in the internal kneader, and EO-PO-AGE-Br/PO copolymer rubber
100 parts by weight (Daiso products EPO
-R; EO 28 mol%) HAF carbon black
Magnesium 20 oxide
3 stearic acid
1 Dibutyl carbinol adipate 10 The following were also used as vulcanization accelerators and vulcanizing agents. 2-Mercaptoimidazole
1.4 parts by weight sulfur
0.2
Note that 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 kneader. Isoprene rubber
100 parts by weight (Nippon Zeon product IR22
00) FEF carbon black
30 calcium carbonate
30 zinc oxide

5 stearic acid
2 process oil
5 Also, the amounts of the two types of vulcanization accelerators used were both changed to 1 part by weight. Note that press vulcanization is performed at 160°C for 5
It was done for a minute.

[0028]
Table 1 Measurement items Ratio-1 Real-1 Real-2 Real-3 Real-4 Ratio-2 Hardness (JIS-A) 47
48 49 61
45 54 Tensile strength (kgf/cm2)
209 75 17
80 70 89 growth
(%) 930 1190
430 290 1150 670 Water swelling rate (%) +45 +1
40 +200 +135 +140
+70 ozone resistance N. C
．． N. C. N. C. N. C.
N. C. Cutting oil resistance (%)
+73.1 +53.3 +38.7 +2
3.9 +38.1 +154.1 Extrudability
Good Good Good
Good Good Good

[0029] Regarding Examples 1 and 2, immersed in tap water at 25°C for 96 hours -40
A cycle of drying in an oven at 70 hours was repeated, but the water swelling rate hardly changed in any of the 1st to 5th cycles.

Example 5 In Example 1, 28 mol% of EO was copolymerized.
Instead of the O-PO-AGE copolymer rubber, an EO-PO-AGE copolymer rubber (EPO, a Daiso product) copolymerized with 48 mol% of EO was used.

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

Example 7 In Example 1, 28 mol% of EO was copolymerized.
Instead of O-PO-AGE copolymer rubber, EO-PO-AGE copolymer rubber copolymerized with 68 mol% of EO (Daiso product EPO) was used, and the amount of polyalkylene oxide diisocyanate adduct used was 80% by weight. part by weight to 220 parts by weight.

The measurement results of Examples 5 to 7 above are shown in Table 2 below, together with the cold resistance (hardness at -20°C). Note that the dumbbells for normal state physical property measurements and the samples for water swelling rate measurements had a thickness of 2 mm.

[0034]

In addition, for Examples 5 to 7, a 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, but no water swelling occurred in any of the 1st to 5th cycles. The rate changed little.

Claims (3)

[Claims] Claim 1: After thoroughly mixing a polyalkylene oxide rubber compound copolymerized with allyl glycidyl ether as a crosslinking point and a polyalkylene oxide diisocyanate adduct in a kneading device, water is added thereto to form the diisocyanate adduct. 1. A method for producing a water-swellable rubber composition, which comprises reacting with a water-swellable rubber composition. 2. A rubber compound of polyalkylene oxide copolymerized with allyl glycidyl ether and brominated propylene oxide as crosslinking points and a polyalkylene oxide diisocyanate adduct are thoroughly mixed in a kneading device, and then water is added thereto. A method for producing a water-swellable rubber composition, which comprises reacting the water-swellable rubber composition with the diisocyanate adduct. 3. The method for producing a water-swellable rubber composition according to claim 1, wherein the polyalkylene oxide diisocyanate adduct is used as a premix with silicic anhydride white carbon.