JPH0548775B2 - - Google Patents

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. [Prior Art] In general, water-absorbing resin compositions are made of rubber-like substances such as natural rubber, synthetic rubber, and thermoplastic elastomers.
starch-sodium polyacrylate grafted product,
It is composed of a super absorbent resin such as cellulose and sodium polyacrylate, along with additives such as fillers, and has the property of absorbing water and swelling, so it is suitable for pipes, etc. It is used as a water stop agent. [Problems to be solved by the invention] However, this type of water absorbent resin composition has the following problems:
The water absorption swelling rate is slow and the water absorption swelling ratio is also low, making improvement of this problem a major problem. In particular, recently, it has been proposed to utilize the swelling property of water-absorbing resin compositions when they absorb water to use them as water-absorbing and swelling materials for water-absorbing sensors that detect water intrusion early in closures that cover the joints of optical fiber cables. Attention has been paid. That is, in joining optical fiber cables, as shown in FIG. 4, the optical fiber cores 2 are pulled out from the ends of the optical fiber cables 1 to be joined and connected, and the outer periphery is covered with a tape 3, and the whole is connected. This is done by housing it in a watertight cylindrical closure 4. 5
is a tension member. A water immersion sensor 6 is attached to the connection portion of the optical fiber core 1 at the lowest stage, which is not used for optical communication, to detect water intrusion 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 as follows:
It is made of a water-absorbing resin composition, and when water enters the closure 4, it absorbs water that enters inside through the bottom hole of the casing 7 and swells. It is bent as shown by chain line B from the straight line shown. 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-absorbing sensor 6 at the connection part of the optical fiber cable 1 has a high water-absorbing swelling rate and a high water-absorbing swelling magnification from the viewpoint of quickly and accurately detecting water intrusion into the closure 4. high,
Furthermore, it is required that even if a portion comes into contact with water, the entire portion swells uniformly. More specifically, as shown in FIG. 6, with respect to the water-absorbing and swelling material 8 for the water immersion sensor 6, not only the portion 8a in contact with water 9 partially swells, but a portion of the material 8a swells with water. There is a strong demand for the property that the entire body swells even when it comes into contact with it. Furthermore, optical fiber core 1
It is necessary to bend the wire with a strength that does not cause permanent distortion, and since the degree of bending differs depending on the core wire 1, being able to control the swelling ratio is also an important factor. However, the reality is that there are no conventional water-absorbent resin compositions that sufficiently have these properties and also have good water absorption swelling speed and magnification. This invention was made in view of these circumstances, and has a high water absorption swelling rate and a high water absorption swelling ratio, and even if a part of it comes into contact with water, the whole swells, and the swelling ratio can be controlled. The purpose is to provide a water absorbent resin composition. [Means for Solving the Problems] In order to achieve the above object, the water absorbent resin composition of the present invention contains, for 100 parts by weight of the following component A,
B component 50-500 parts by weight, C component 5-50 parts by weight, D
The composition is such that the ingredients are blended at a ratio of 5 to 50 parts by weight. (A) Rubbery substance. (B) Super absorbent resin. (C) Hydrophilic resin. (D) Blowing 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 are mixed into the rubber-like material that serves as the base material. As a result, in addition to blending a highly water-absorbent resin into the rubber-like material, we also blended a hydrophilic resin such as polyethylene glycol and a blowing agent such as azodicarboxamide. They found that good results could be obtained. As a result of further research focusing on this, we found that when the above four types of compounds are blended in a specific ratio, four types of water absorbent resin compositions are required for water absorbing and swelling materials used in optical fiber cable immersion sensors. The inventors have discovered that a water-absorbing resin composition having all of the above characteristics can be obtained, and have arrived at the present invention. The water absorbent resin composition of the present invention is obtained using a rubbery substance (component A), a super absorbent resin (component B), a hydrophilic resin component C, and a blowing agent (component D). Examples of the rubbery substance of component A include ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), styrene-butadiene copolymer (SBR), butyl rubber (IIR), and natural rubber. 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
To make it suitable for foaming, the viscosity is adjusted appropriately using oil agents such as plasticizers. Among the rubbery 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,
cross-linked carboxymethylcellulose sodium salt,
starch-sodium polyacrylate grafted product,
Starch-polyacrylonitrile grafted additive, cellulose-sodium polyacrylate, vinyl alcohol-sodium (meth)acrylate-(meth)acrylic acid copolymer, crosslinked poly(meth)
Examples include sodium 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. The hydrophilic resin of component C used together with components A and B is not particularly limited, and polymer compounds having water solubility such as polyethylene glycol, polypropylene glycol, and polyvinyl alcohol are used. Among these, it is preferable to use polyethylene glycol, polypropylene glycol, etc., and it is particularly preferable to use those having a molecular weight within the range of 1,000 to 10,000. The blowing agent of component D is also not particularly limited.
Examples include azodicarboxamide, dinitropentamethylenetetramine, p,p'-bis(benzenesulfonylhydrazide)ether, p,p'-toluenesulfonylhydrazide, azobisbutyronitrile, and derivatives thereof. Among these,
The use of azodicarboxamide gives good results. The above B to D components are respectively for the A component,
It is important that they are blended in the following proportions.
That is, for 100 parts by weight of the above A component (hereinafter abbreviated as "parts"), the B component is 50 to 500 parts, and the C component is 5 parts.
It is necessary that component D be blended at a ratio of 50 parts to 50 parts, and the water absorbent resin composition obtained outside these ranges will not have any of the four types of characteristics described above. This is because it becomes something lacking.
In particular, the preferred ratio of the above components B to D to component A is 100 to 300 parts of component B to 100 parts of component A;
The C component is 10 to 20 parts, and the D component is 10 to 20 parts. In addition to the blending ratios of ingredients 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, while if it is above the above range, it will be difficult to knead and ,
This is because the specific surface area tends to become 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 foam-like water-absorbing swelling material, in addition to components A to D, sulfur for vulcanization, magnesium oxide, zinc white, etc. A known vulcanizing agent is blended therein, and a crosslinking accelerator is also blended as required. In addition to the above-mentioned vulcanizing agent, 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 a roll or a Banbury mixer, 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. In particular, the water absorbent resin composition of this invention
As shown in FIG. 3, when the material is placed in a heating container 10 for vulcanization, the swelling ratio can be controlled by changing the size of the heating container space (which becomes the foaming space) to control the foaming ratio. In other words, the water-absorbing resin composition of the present invention has a foaming ratio and a swelling ratio that are proportional to each other, and by controlling the foaming ratio as described above, the swelling ratio can also be controlled.This is a major feature. be. In this case, the foaming ratio is 1.5~
Within the range of 10 times, the swelling ratio changes proportionally, and the more accurate ratio is 1.5.
It is within the range of ~6 times. The water-absorbing and swelling material obtained in this way has a fast water-absorbing swelling rate and a high water-absorbing swelling ratio.Moreover, even if a part of it comes into contact with water, the whole part swells, and the swelling ratio can be adjusted by controlling the foaming ratio. It is controllable and has all four types of properties required as a water-absorbing and swelling material for water immersion sensors in optical fiber cable connections. Therefore, Figures 1 and 2
As shown in the figure, this is formed into a predetermined shape to form a set of water-absorbing and swelling materials 26, and this is placed in a plastic casing 20 with a through hole in the bottom, and a metal plate 24,
25 and by passing an optical fiber core between the metal plates 24 and 25 as shown by the chain line A, a highly accurate water immersion sensor 6 can be formed. 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. [Effects of the Invention] As described above, since the water-absorbing resin composition of the present invention combines the components A to D and sets their mutual ratios to a specific ratio, it can be foamed at the same time as vulcanization. The obtained water-absorbing and swelling material has excellent properties such as a fast water-absorbing swelling rate and a high water-absorbing swelling ratio, and even if a part of it comes into contact with water, the whole part swells, and furthermore, the foaming ratio can be controlled arbitrarily. ing. Therefore, it is most suitable as a water-absorbing and swelling material used in water immersion sensors for contact parts of optical fiber cables. Next, examples will be described together with comparative examples. [Examples and Comparative Examples] Compounds shown in Table 1 below were prepared as components A to D, and these were blended in the proportions shown in the table, kneaded with rolls, and then extruded into a thick plate. Next, this was placed in a heating container and heated and vulcanized at 10° C. or higher for 5 minutes or more, thereby foaming and crosslinking the entire product to produce a water-absorbing and swelling material. The water-absorbing swelling material thus obtained is expressed in terms of water-absorbing swelling rate, overall uniform swelling property, water-absorbing swelling ratio, and foaming ratio.
We investigated the controllability of the swelling ratio by controlling the foaming ratio,
It is also shown in the same table.

【table】

【table】

【table】

[Table] The above test was conducted as follows. Water absorption swelling rate: Time to reach 5x water absorption (detection magnification) (minutes) Overall uniform swelling: Swelling after 30 minutes of water absorption Water absorption swelling rate: Volume change rate after 30 minutes of water absorption (cm ² /
cm ² ) In the above table, for 100 parts of A component, B component is 50 to 500 parts, C component is 5 to 50 parts, and D component is 5 parts.
If it is within the range of ~50 parts, the 4 required for the water-absorbing and swelling material.
It can be seen that all type characteristics are good. In addition, as is clear from the comparison between the example and the conventional example, the water-absorbing and swelling material obtained from the example has better water-absorbing swelling speed and water absorption capacity than that obtained from the conventional example, and has uniform swelling properties throughout. It can be seen that it is also excellent.

[Brief explanation of the drawing]

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. Explanatory diagram for 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 an explanatory diagram showing the swelling state of a conventional water-absorbing and swelling material. .

Claims (1)

[Scope of Claims] 1. 50 parts by weight of component (B) for 100 parts by weight of component (A) below.
~500 parts by weight, 5 to 50 parts by weight of component (C), 5 to 50 parts of component (D)
A water-absorbing resin composition containing 50 parts by weight. (A) Rubbery substance. (B) Super absorbent resin. (C) Hydrophilic resin. (D) Blowing agent.