JPH0655995B2 - Graft polymerization method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is a method for graft polymerization using ionizing radiation, the effectiveness of which is being confirmed as a means for modifying and increasing the functionality of polymeric materials. That is, it relates to a radiation graft polymerization method.

(Prior Art) Radiation graft polymerization is a polymerization method that has recently attracted attention in the advanced industrial fields for achieving high functionality of materials because it can impart other properties while making the most of the characteristics of the substrate.

The conventional radiation graft polymerization method is generally a liquid phase graft polymerization method in which a base material is reacted in a monomer liquid, but it has a drawback that the running cost becomes high because a large amount of the monomer and the cleaning chemical are required. Moreover, the amount of cleaning chemicals varies greatly depending on the shape of the base material. For example, when a fibrous base material is used, the liquid is very poorly drained, and solid-liquid separation operations such as roll pressing, centrifugation and filtration are required. Further, in the case of a porous base material, the chemical leaks from the fine pores continue for a long time, so that a large amount of cleaning chemical is required and the cleaning time also takes a long time. Furthermore, it is necessary to pay attention to the treatment of cleaning drainage.
Therefore, the running cost is actually quite high except for non-porous particles and membranes.

(Problems to be solved by the invention) On the other hand, in the gas phase graft polymerization method in which a monomer is brought into contact with a substrate in a gas state, some consideration needs to be given to the sealing property of a polymerization apparatus, but the amount of the monomer is very small, and the cleaning is performed. No process is required, which is cost effective. Further, in the gas phase graft polymerization, the graft ratio can be controlled only by using a predetermined amount of the monomer necessary for the reaction.

Thus, although the gas phase graft polymerization has many advantages, the biggest cause that has not yet been put to practical use is
Applicable only to monomers with a relatively high vapor pressure, and the graft ratio of the base material closer to the monomer solution is high,
This is because there is uneven grafting that the distance becomes lower.

As described above, the conventional radiation graft polymerization method has many problems, and this has also been a cause of delaying the spread of radiation graft polymerization.

An object of the present invention is to provide a practical radiation graft polymerization method in which a graft product having no graft unevenness in any type of polymerizable monomer can be obtained in an extremely short time while maintaining the advantages of gas phase graft polymerization. Is.

(Means for Solving the Problems) The present invention is to perform a graft polymerization reaction under reduced pressure after irradiating an organic polymer material that is a base material with ionizing radiation, and to prepare a polymerizable monomer solution and a base material. The feature is that they are contacted at least once.

The ionizing radiation used here includes α, β, γ ultraviolet rays, electron beams and the like, and is not limited, but γ rays and electron beams are relatively suitable for the present invention.

As a base material used for radiation graft polymerization, an organic polymer compound is suitable, particularly polyolefins represented by polyethylene, polypropylene, etc., halogenated polyolefins represented by PTFE, vinyl chloride, etc., ethylene-tetrafluoroethylene. It is suitable for olefin-halogenated olefin copolymers typified by copolymers and ethylene-vinyl alcohol copolymer (EVA), but is not limited to this range.

As the monomer, any polymer monomer having a vinyl group can be used. For example, in addition to acrylic monomers such as acrylic acid, acrolein, acrylonitrile, and methyl methacrylate, styrene-based monomers such as styrene and chloromethylstyrene, vinyl acetate and vinylpyridine-based monomers, Polyene compounds typified by divinylbenzene can also be used, but are not limited to this range.

As a method for irradiating the base material with radiation, a pre-irradiation method in which the base material is previously irradiated and then brought into contact with the monomer is preferable because it produces less homopolymer of the monomer as compared with the simultaneous irradiation method.

Depending on the contact method between the base material and the monomer, there are liquid-phase graft polymerization and gas-phase graft polymerization, and the gas phase is advantageous in terms of cost, but since the vapor pressure differs depending on the type of monomer, the monomer with low vapor pressure In this case, since the amount of the monomer supplied for grafting is not uniform due to the positional relationship between the monomer generation site and the graft site, graft unevenness may occur. Furthermore, the reaction time is relatively long. The advantage of liquid phase graft polymerization is that it is independent of the vapor pressure of the monomer,
That is, a uniform graft product can be obtained in a relatively short time. This is because the monomer concentration around the substrate is overwhelmingly higher than that in the case of the gas phase. In gas-phase graft polymerization, there are methods such as increasing the monomer liquid temperature and vapor pressure or increasing the monomer evaporation area to increase the monomer concentration around the base material. It is not very effective when used in large amounts.

The shape of the base material is not particularly limited, but a fibrous shape and a woven or non-woven fabric shape are particularly suitable for the present invention. It is a material in which a woven cloth or a nonwoven cloth is easily impregnated with a monomer and a high graft ratio is easily obtained, and a uniform graft product is obtained in a short time, and the effect of the present invention that cleaning is unnecessary is most exerted. This is because.

(Function) The present inventors have the advantage that if the base material itself serves as a monomer generation source, a uniform and high graft ratio of the graft product can be obtained in a short time, and that the characteristic feature of the vapor phase graft is that washing after the reaction is not required. The present invention has been made with the intention that it may be maintained as it is. The present invention, after irradiating the substrate with ionizing radiation,
The monomer solution is impregnated and reacted under reduced pressure, but after irradiation, the monomer solution and the substrate may be depressurized and then impregnated.

Since the base material is impregnated with the monomer solution and the graft reaction is started in the absence of droplets, the reaction rate is fast and the monomer can be fully utilized, and the formation of a homopolymer is extremely small. Furthermore, not only is the grafted product after the reaction finished in a dry state and is easy to handle, but also a washing step for removing unreacted monomers is unnecessary. Further, in the present invention, a fibrous base material is preferable, but a base material having a shape other than that can obtain a high graft ratio by repeating the steps of impregnation and reaction a plurality of times. For that purpose, it is convenient that the base material and the monomer solution are present inside the same reduced pressure container. Of course, even for fibrous or porous substrates, the impregnation may be further repeated to obtain a higher graft ratio. On the other hand, if you want to obtain a relatively low graft ratio, or if you want to stop the reaction before all the impregnated monomers have reacted, decompress the vacuum to introduce air, and after the radicals have disappeared, use the vacuum pump again. The monomer can be easily evaporated by suctioning with, for example. Since the fibrous or porous substrate has a large surface area, the evaporation rate of the residual monomer is particularly fast and it is easy to remove by suction.

(Example) Hereinafter, the present invention will be described based on examples.

(Example 1) Nonwoven fabric 10 made of polypropylene fibers having a diameter of 30μ
After irradiating g with an accelerated electron beam of 20 Mrad, it was immersed in a chloromethylstyrene solution and the excess liquid was wiped off with paper. Then, after putting it in a glass ampoule and sucking it with a vacuum pump,
It was left standing in a constant temperature bath at 50 ° C. The graft ratio of chloromethylstyrene after 1.5 hours was 146%, and no graft unevenness was observed. In addition, the non-woven fabric after grafting was completely dried and did not need to be washed.

(Comparative Example 1) Under the same conditions as in Example 1, the nonwoven fabric was not immersed in chloromethylstyrene, but graft polymerization was carried out in the gas phase.
The graft ratio after 12 hours was 68%, and only the base material at the bottom of the ampoule was grafted, and the graft unevenness was extremely large.

Example 2 300 g of polypropylene woven fabric was irradiated with 20 Mrad of an accelerated electron beam, then immersed in a styrene solution, and drained by centrifugation to an impregnation rate of 126%. Put this in the glass vacuum container of 5 and suck with a vacuum pump, then
It was left to stand in a constant temperature bath at 0 ° C. After 2 hours, the graft woven fabric was dry and weighed 665 g. That is, it was possible to control the graft ratio by the graft ratio of 122% and the impregnation ratio.

(Effects of the Invention) According to the present invention, it is possible to take advantage of the uniform grafting and the advantage of liquid phase graft polymerization such as high graft reaction rate by a very simple method, while maintaining the advantage of no need for cleaning in gas phase graft polymerization. became. In practical use of graft polymerization, the technical and cost problems were solved at once.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Jiro Okamoto 1233, Watanuki-cho, Takasaki-shi, Gunma Japan Atomic Energy Research Institute Takasaki Research Center (72) Inventor Kunio Fujiwara 1233, Watanuki-cho, Takasaki-shi, Gunma Japan Atomic Energy Research Institute Takasaki Research In-house (72) Inventor Hideaki Sekiguchi 6-17-8 Aobadai, Ichihara-shi, Chiba (56) References Japanese Patent Publication No. 36-1009 (JP, B1) Japanese Patent Publication No. 43-22107 (JP, B1)

Claims (2)

[Claims] 1. A method of irradiating an organic polymer material with ionizing radiation and then graft-polymerizing a polymerizable monomer in the organic polymer material in a gas phase, wherein the organic polymer material irradiated with ionizing radiation is a polymerizable monomer. After dipping in the solution to impregnate the material with the monomer solution, wipe off the monomer droplets from the impregnated material to attach the monomer to the extent that no cleaning treatment is required after the graft polymerization is completed, and attach it to the reaction vessel. A method of charging and depressurizing the reaction vessel to carry out gas phase graft polymerization. 2. The graft polymerization method according to claim 1, wherein the organic polymer material is a fibrous woven or non-woven fabric.