JPH02276840A - Water-absorbing resin composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a water-absorbing resin composition used in a water immersion sensor, etc., which detects water intrusion in a closure that covers a connecting portion of an optical fiber cable.

[Conventional technology]

Generally, a water absorbent resin composition is a starch-sodium polyacrylate grafted product on a rubbery substance such as natural rubber, synthetic rubber, or thermoplastic elastomer.

It is composed of a super absorbent resin such as cellulose-sodium polyacrylate, along with fillers and other additives, and has the property of absorbing water and swelling, so it can be used to stop pipes, etc. It is used as a water agent.

[Problems to be Solved by the Invention] Particularly recently, water immersion sensors have been developed that utilize the swelling property of water-absorbing resin compositions when absorbing water to detect water intrusion at an early stage in closures that cover joints of optical fiber cables. Its use as a water-absorbing and swelling material has been proposed and is attracting attention.

That is, in joining optical fiber cables, as shown in FIG. 4, optical fiber core wires 2 are pulled out from the ends of optical fiber cables 1 to be joined, connected, and the outer periphery is covered with tape 3. This is done by housing the watertight cylindrical closure 4 in a watertight cylindrical closure 4. 5 is a tension member. A water intrusion sensor 6 is attached to the connection part of the lowest optical fiber core 'vA1 which is not used for optical communication, and detects the intrusion of water into the closure 4. As shown in FIG. 5, the water immersion sensor 6 consists of a box-shaped casing 7 with a through-hole at the bottom, and a pair of water-absorbing and swelling materials placed inside the box-shaped casing 7 and facing each other across an optical fiber core 1 indicated by an arrow A. It consists of 8. That is, the pair of water-absorbing and swelling materials 8 are made of a water-absorbing resin composition, and when water enters the closure 4, they absorb water that enters the inside through the bottom hole of the casing 7 and swell. , the optical fiber core 1 is bent from a straight state shown by a chain line A to a direction shown by a chain line B.

This increases the transmission loss of light, and by detecting this, it becomes possible to detect water intrusion into the closure 4. The water-absorbing and swelling material 8 of the water immersion sensor 6 at the connection part of the optical fiber cable 1 as described above
From the standpoint of quickly and accurately detecting water intrusion into the closure 4, the closure 4 has a high water absorption swelling rate and a high water absorption swelling ratio (in addition, even if a portion comes into contact with water, the entire body swells uniformly). More specifically, for the water-absorbing and swelling material 8 for the water immersion sensor 6, only the portion 8a in contact with water 9 partially swells, as shown in FIG. However, conventional water-absorbing resin compositions are highly required to have the property that the entire body swells even if a part of the composition comes in contact with water. The reality is that there are no good ones.

The present invention was made under these circumstances, and aims to provide a water-absorbing resin composition that has a high water absorption swelling rate, a high water absorption swelling ratio, and which swells as a whole even when a part of it comes into contact with water. That purpose.

[Means for Solving the Problems] In order to achieve the above object, the water absorbent resin composition of the present invention contains the following components (A) to (D), and the following (C).
The component is 1 to 50 parts by weight per 100 parts by weight of component (B) below.
The structure is such that the weight section is located on the opposite side.

(A) Rubbery substance.

(B) Super absorbent resin.

(C) Sodium polyacrylate with an average molecular fil O6 or less.

(D) Foaming agent.

[Function] That is, the present inventors aimed to develop a water-absorbing resin composition, particularly a water-absorbing resin composition that can be used as a water-absorbing and swelling material for a water-absorbing sensor for a connection part of an optical fiber cable. Research focused on additives that can be mixed into rubber-like substances. As a result, in addition to blending the superabsorbent resin with the rubbery substance, we also blended a specific amount of sodium polyacrylate with an average molecular weight of IO6 or less into the superabsorbent resin, and It has been discovered that good results can be obtained by incorporating a blowing agent such as dicarpoamide, and the present invention has been achieved.

This water absorbent resin composition is obtained using a rubbery substance (component A), a superabsorbent resin (component B), sodium polyacrylate having an average molecular weight of 106 or less (component C), and a blowing agent (component D). It will be done.

The rubbery substances of component (A) include ethylene propylene diene rubber (EPDM), chloroprene rubber (C
R), styrene-butadiene copolymer (SBR), butyl rubber (IIR), natural rubber, and the like. When the water-absorbing resin composition of the present invention is used as a water-absorbing and swelling material, it is heated and vulcanized into a foamed state, and then cooled in that state for use. Therefore, the rubbery substance of component (A) is used after adjusting its viscosity appropriately with an oil agent such as a plasticizer so that it can be adapted to foaming.

Among the rubber-like substances exemplified above, better results can be obtained by using EPDM.

, as the super absorbent resin of component (B), crosslinked sodium polyacrylate, crosslinked polyethylene oxide, crosslinked carboxymethyl cellulose sodium salt, powder B-sodium polyacrylate grafted product, starch-polyacrylonitrile grafted additive, cellulose. - Sodium polyacrylate vinyl alcohol - Sodium (meth)acrylate - (meth)acrylic acid copolymer, crosslinked poly(
Examples include sodium meth)acrylate, alkali neutralized polyoxyethylene chain-containing polyurethane of crosslinked isobutylene maleic anhydride copolymer, and the like. Among these super absorbent resins, crosslinked sodium polyacrylate is preferably used.

(C) used with the above (A) component and (B) component
The average molecule of the ingredient! Sodium polyacrylate having a molecular weight of 106 or less is not particularly limited (any conventionally known sodium polyacrylate can be used as is. Especially, sodium polyacrylate having an average molecular weight of 10'
Using those within the range of ~105 gives good results.

The blowing agent of component (D) is also not particularly limited, and includes abdicarboxamide, dinitropentamethylenetetramine,
Examples include p,p'-bis(benzenesulfonylhydrazide)ether, P,P-)luenesulfonylhydrazide, azobisbutyronitrile, and derivatives thereof. Among these, the use of azodicarboxamide gives good results.

It is preferable that the above components (B) to (D) are respectively blended with component (A) in the following proportions. That is, 100 parts by weight of component (A) (hereinafter abbreviated as 1 part).
It is preferable that component (B) be blended in an amount of 50 to 500 parts. More preferably 100-3
Within the range of 00 copies. In addition, component (C) is added in an amount of 1 to 5 parts per 100 parts of component (B) blended in the above ratio.
It is necessary to mix it in a proportion of 0 parts. That is, (
C) If the amount of the component is below the above range, the characteristics of
In particular, the effect of improving the water absorption swelling rate becomes small, and if it exceeds the above range, the balance with the component (B) will be lost and the properties of the resulting water absorbent resin composition will deteriorate. A suitable ratio of component (C) to component (B) is 1
It is within the range of 0 to 50 parts. In addition, component (D) is the above (
It is desirable that the amount is 5 to 50 parts, preferably 10 to 20 parts, based on 100 parts of component A).

In addition to the blending ratios of components (A) to (D) as described above, the particle size of the super absorbent resin as component (B) also has a large effect on water absorption. Preferably, the particles have a particle size of 5 to 200 microns, more preferably 10 to 100 microns. In other words, if the particle size is below the above range, when it is made into a water-absorbing and swelling material, the whole part will not swell uniformly and only the parts that come into contact with water will tend to swell. This is because the specific surface area tends to be too small and swelling tends to take too long.

In addition, since the water-absorbing resin composition of the present invention foams upon vulcanization and becomes a foamed water-absorbing and swelling material, (
In addition to components A) to (D), known vulcanizing agents such as sulfur, magnesium oxide, and zinc white are blended for vulcanization, and if necessary, a crosslinking accelerator is also blended. In addition to the above vulcanizing agents,
Conventionally known rubber additives such as carbon black, various coloring pigments, ultraviolet absorbers, antioxidants, waxes, etc. can be optionally blended.

When the water-absorbing resin composition of the present invention is used to produce a water-absorbing and swelling material for use in, for example, a water immersion sensor for connecting portions of optical fiber cables, it is carried out as follows. That is, the above raw materials are mixed in a predetermined ratio, kneaded and homogenized using rolls, a Banbury mixer, etc., and then formed into a desired shape by extrusion molding, press molding, calendar molding, etc. The molded product is heated using a heating device. During this heating, the molded body is foamed by the action of the foaming agent, and at the same time, the rubber component is crosslinked by the action of the crosslinking agent to obtain a water-absorbing and swelling material. As shown in FIG. 3, when the water-absorbing resin composition of the present invention thus obtained is placed in a heating container 10 and vulcanized, the size of the space of the heating container (which becomes the foaming space) The swelling ratio can be controlled by changing the expansion ratio. That is, in the water absorbent resin composition of the present invention, the expansion ratio and the swelling ratio are proportional, and by controlling the expansion ratio as described above, the swelling ratio can also be controlled. In this case, if the foaming ratio is within the range of 1.5 to 10 times,
The swelling ratio also changes proportionally, and the more accurate ratio is within the range of 1.5 to 6 times.

The water-absorbing swelling material obtained in this way has an extremely fast water-absorbing swelling rate, a high water-absorbing swelling ratio, and even if a part of it comes into contact with water, the entire part swells, and the swelling ratio can be adjusted by controlling the expansion ratio. Control is also possible. Therefore, it has all the characteristics necessary as a water-absorbing and swelling material for a water immersion sensor for connecting parts of optical fiber cables. As a result, the first
As shown in the figures and FIG.
A highly accurate water immersion sensor 6 can be formed by attaching the metal plates 24 and 25 and passing an optical fiber core between the metal plates 24 and 25 as shown by the chain line A. 22 is a lid material for the casing.

The water-absorbing resin composition of the present invention can be applied not only as a water-absorbing swelling material used in a water immersion sensor for optical fiber cables as described above, but also in the field of water-stopping agents for pipes and toys.

〔Effect of the invention〕

As mentioned above, the water-absorbing resin composition of the present invention has the above-mentioned (
Since components A) to (D) are used and the mutual ratio of components (B) and (C) is set to a specific ratio, the water-absorbing swelling material obtained by foaming them at the same time as vulcanization is Extremely fast speed and high water absorption swelling ratio. Moreover, even if a part of it comes into contact with water, the whole can swell. Moreover, it also has the characteristic that the expansion ratio can be controlled arbitrarily. In particular, the water-absorbing swelling composition of the present invention has an extremely high water-absorbing swelling rate, so that when used in a water-immersion sensor for a contact portion of an optical fiber cable, water intrusion can be quickly detected. Therefore, it is most suitable as a water-absorbing and swelling material for the water immersion sensor.

Next, examples will be described together with comparative examples.

C Examples, Comparative Examples) Prepare the compounds shown in Table 1 below as components (A) to (D), mix them in the proportions shown in the table, knead them with a roll, and then extrude them into a thick plate. did. Next, this was placed in a heating container and heated and vulcanized at 100° C. or higher for 5 minutes or more, thereby foaming and crosslinking the entire product to produce a water-absorbing and swelling material. Controllability of the swelling ratio by controlling the expansion ratio, expressed as water absorption swelling rate, overall uniform swelling property, water absorption swelling ratio, and (water absorption swelling ratio)/(foaming ratio) for the water absorption swelling material thus obtained. were investigated and are also shown in the same table.

(Margin below) Note that the above measurements were performed as follows.

As is clear from Table 1 above, it can be seen that the actual height measurements exhibit superior characteristics compared to the comparative height measurements. In particular, it can be seen that Example 3.4, in which crosslinked sodium polyacrylate was used as the superabsorbent resin and was combined with sodium polyacrylate having an average molecular weight of 103 in a suitable ratio, had a significantly high water absorption swelling rate. Further, as is clear from the comparison between the examples and the conventional example, the water-absorbing and swelling material obtained in the example was obtained from the conventional example. It can be seen that the water absorption swelling rate and water absorption capacity are superior to those of the conventional products, and the overall uniform swelling property is also excellent.

[Brief explanation of drawings]

Fig. 1 is an exploded perspective view of a water immersion sensor device using a water-absorbing swelling material made of the water-absorbing resin composition of this invention, Fig. 2 is a plan view thereof, and Fig. 3 is a heating of the water-absorbing resin composition of this invention. An explanatory diagram of foaming, Fig. 4 is a cross-sectional view of the closure of the connection part of the optical fiber cable, Fig. 5 is a perspective view of the water immersion sensor used therein, and Fig. 6 is the swelling of a conventional water-absorbing and swelling material. It is an explanatory diagram showing a state. 20...Casing 24.25...Metal plate 26
...Water absorbing swelling material patent applicant Tokai Rubber Industries Co., Ltd.

Claims (1)

[Claims] (1) Contains the following (A) to (D) components, and the following (C)
The component is 1 to 50 parts by weight per 100 parts by weight of component (B) below.
A water-absorbing resin composition characterized in that it contains parts by weight. (A) Rubbery substance. (B) Super absorbent resin. (C) Sodium polyacrylate with an average molecular weight of 10^6 or less. (D) Foaming agent.