JPH0680806A - Production of water absorbable crosslinked resin - Google Patents

Abstract

PURPOSE:To produce a crosslinked material excellent in mechanical properties and shape retention and suitable for a waterproof seal, a waterproofing agent, etc., by molding a resin composition composed of a specified thermoplastic elastomer, etc., and subsequently applying ionizing radiation thereto. CONSTITUTION:With (A) 100 pts.wt. olefinic thermoplastic elastomer composed of 15 to 55wt.% PE-based polymer and 85 to 45wt.% ethylene-propylene-diene copolymer, (B) 10 to 100 pts.wt. hydrogenated diene-based copolymer is blended. To 100 pts.wt. the resultant mixture of the components (A) and (B), (C) 5 to 95 pts.wt. water absorbable resin such as a polyacrylic acid salt-based resin, (D) 1 to 25 pts.wt. inorganic filler such as tale, (E) 2 to 50 pts.wt. softening agent such as fluid paraffin and (F) 2 to 50 pts.wt. plasticizer such as diethyl phthalate are added to obtain a resin composition. The obtained resin composition is molded and subsequently irradiated with ionizing radiation such as alpharays (The dosage is preferably 0.1 to 20 Mrad), thus producing the objective crosslinked material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-absorbent resin foam containing a water-swellable polymer water-absorbing agent and an olefinic thermoplastic elastomer. More specifically, olefins useful for waterproofing seals between segments of tunnels and water and sewerage construction, civil engineering such as seals for exterior wall panels of buildings, waterproofing materials for construction work, anti-condensation materials that also have seismic function. TECHNICAL FIELD The present invention relates to a method for producing a water-absorbent resin cross-linked product obtained by blending a water-absorbent resin with a thermoplastic thermoplastic elastomer.

[0002]

2. Description of the Related Art Conventional sealing materials for waterproofing between tunnels and waterworks / sewerage segments have been crosslinked polyacrylates, starch-polyacrylate resins, vinyl alcohol copolymers or anhydrous. A water-swellable composition in which a super absorbent polymer such as a resin obtained by crosslinking a reaction product of a maleic acid copolymer and a basic substance is blended with a diene rubber and vulcanized to form a water-swellable composition is widely used (Japanese Patent Application Laid-Open No. 2004-242242). 57-1
08143, 57-135160, etc.). However, since this water absorbent resin composition requires a vulcanization step, there are problems such as an increase in molding cost and a decrease in productivity.

Further, a water-absorbent resin composition containing a thermoplastic resin containing a highly water-absorbent resin, for example, a water-absorbing polymer finely divided into ethylene-vinyl acetate copolymer or polybutadiene (a lower olefin-maleic anhydride is a urea resin). Or a mixture of melamine resin) (JP-A-55-8424), a composition of chlorinated polyethylene and polyisobutylene, and a super absorbent resin (maleic anhydride-isobutylene copolymer, acrylic acid). -Vinyl alcohol copolymer, etc.) (JP-A-62-106879)
However, the former has a large temperature dependency and has a problem of poor workability due to low water absorption and flexibility, especially in the low temperature, and the latter causes environmental problems such as generation of hydrogen chloride during incineration. There is also a problem above.

Further, a carboxylate-containing water absorbent resin and a glycidyl group-containing olefin are melt-kneaded to form a polyolefin resin composition, or a water-absorbent resin powder, a polyolefin resin pellet and an olefin resin pellet powder are melt-kneaded. To increase the shape retention rate after water absorption (JP-A-63-110226 and JP-A-63-13543).
No. 1) has been proposed, but it is a composite composition based on a thermoplastic polymer, and when water absorption and drying are repeated, the water absorbing agent is gradually lost from the resin composition, so-called gel loss reduction occurs, There is a problem in durability during long-term use, such as reduced water absorption efficiency.

The present inventors have investigated a non-vulcanizing type water-absorbent resin composition based on an olefinic thermoplastic elastomer, and have found that a polyethylene-based polymer and an ethylene-based polymer are used.
A water-absorbent resin in an olefin-based thermoplastic elastomer consisting of a propylene-diene copolymer, a resin composition in which a softening agent and a plasticizer are mixed is excellent in flexibility and moldability, and an inorganic filler is added to each component. In the composition that is blended, the dispersibility in the composition of the water-absorbent resin becomes good and becomes an excellent water-absorbent resin composition, and the one obtained by expanding the water-absorbent resin composition at a low magnification is further excellent in water absorbency. That, the strength is improved by irradiating the low-expanded foamed material with ionizing radiation, the weight retention is improved, and by adding a hydrogenated diene-based copolymer to each of the above components, However, they have found that the water absorption capacity is improved without foaming, and that they are excellent in flexibility, water absorption, and moldability, and have applied for patents respectively.

These water-absorbent resin compositions have excellent water-absorbing property, flexibility, etc., but with the expansion of their applications and usages, water-absorbing resin compositions are required for further improvement. It is demanded to improve durability such as prevention of loss of functional resin (gel loss). Therefore, the object of the present invention is excellent in mechanical properties and the like, does not cause morphological change due to gel removal of the resin composition after absorbing water, and is a water-absorbing resin based on an olefin-based thermoplastic elastomer excellent in flexibility and productivity. It is to provide a method for producing a crosslinked body.

[0007]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the inventors of the present invention have conducted extensive studies and, as a result, irradiating the molded article of the water-absorbent resin composition with ionizing radiation to form a crosslinked structure. It was confirmed that the above problems could be solved by the above, and the present invention was achieved. That is, the present invention relates to (b) water based on 100 parts by weight of an olefin-based thermoplastic elastomer comprising (a) a polyethylene polymer of 15 to 55% by weight and an ethylene-propylene-diene copolymer of 85 to 45% by weight. It contains 10 to 100 parts by weight of the added diene-based copolymer, 5 to 95 parts by weight of (c) a water-absorbent resin, and (d) 1 to 25 parts of inorganic filler with respect to 100 parts by weight of the components (a) + (b). Parts by weight, (e) 2 to 50 parts by weight of a softening agent, and (f) a resin composition containing 2 to 50 parts by weight of a plasticizer, and thereafter, irradiated with ionizing radiation. A method of manufacturing a body is provided. Hereinafter, the method for producing the crosslinked water absorbent resin of the present invention will be described.

The olefinic thermoplastic elastomer (a) which is the base of the crosslinked water absorbent resin of the present invention comprises a polyethylene polymer (first component) and an ethylene-propylene-diene copolymer (second component). It is a composition. Here, as the polyethylene-based polymer which is the first component, a homopolymer of ethylene, a copolymer of ethylene and propylene or another α-olefin, or a copolymer of ethylene and vinyl acetate, ethyl acrylate, or the like, or these It is possible to use homopolymers of the above, or blends of homopolymers and copolymers. In particular,
Polyethylene and ethylene-vinyl acetate copolymer are preferred.

As polyethylene, the melt index (MI, JISK7210, load 2.16 kg) is 0.01 to 100 g /
It preferably has a density of 0.910 to 0.935 g / cm ³ for 10 minutes.
In addition, polyethylene has about 4 to 20 carbon atoms α
-The thing which copolymerized the olefin to about 20 mol% or less is also included. In addition, an ethylene-vinyl acetate copolymer (E
As VA), a copolymer having a vinyl acetate content of 10 to 30% by weight is preferable, and a vinyl acetate content of 17 to 30% by weight is particularly preferable.
Those in the range of 30% by weight are preferable. Such EVA melt index (190 ℃, 2.16kg load)
Is preferably 15 to 25 g / 10 minutes. As the polyethylene-based polymer, an ethylene-vinyl acetate copolymer (E
VA) is more preferred.

Olefinic thermoplastic elastomer (a)
The second component, ethylene-propylene-diene copolymer (EPDM), is a copolymer composed of ethylene, propylene and a diene.

Examples of the diene compound include ethylidene norbornene, 1,4-hexadiene and dicyclopentadiene. The EPDM has an ethylene content of 50 to 60 mol% and a propylene content of 20 to 30.
Those having a mol%, a diene compound content of 1 to 20 mol% and an iodine value of 1 to 30 are preferable. Mooney viscosity (ML _{1 + 4} , 100 ° C) of EPDM is 20-100
Is preferable, and 50 to 90 is particularly preferable.

The blending ratio of the polyethylene polymer and the ethylene-propylene-diene copolymer (EPDM) is 15 to 55% by weight, preferably 20 to 50% by weight, and 85 to 45% by weight EPDM. %, Preferably 80 to 50% by weight. If the polyethylene polymer is less than 15% by weight, the mechanical strength and moldability will decrease, while if the polyethylene polymer exceeds 55% by weight, the hardness will increase and the tear strength will decrease.

Olefinic thermoplastic elastomer (a)
Is produced by melt-kneading the polyethylene polymer and EPDM in the above proportions. That is, 15 to 55% by weight of the polyethylene polymer and 85 to 45% by weight of EPDM are kneaded by a kneading machine such as a twin-screw extruder, a single-screw extruder, a roll kneader, a Banbury mixer, and a Brabender. The kneading temperature may be appropriately set at a temperature at which the resin component serving as the base is melted or higher, but it is usually preferably in the range of 90 to less than 160 ° C. The melt index (1 of the olefinic thermoplastic elastomer composition thus obtained is
90 ° C., 2.16 kg load) is preferably 0.5 to 20 g / 10 minutes.

In the present invention, the olefinic thermoplastic elastomer (a) is a polyethylene polymer and EPDM.
As independent components, the hydrogenated diene copolymer (b), the water-absorbent resin component (c), the inorganic filler (d), the softening agent (e) and the plasticizer (f), which will be described later, may be used together or at any time. It can also be prepared by kneading in order. In the present invention, the hydrogenated diene-based copolymer (b) is blended in order to improve the water absorption of the water-absorbent resin crosslinked product.

The hydrogenated diene copolymer comprises a vinyl aromatic compound polymer block (A), a conjugated diene polymer or a vinyl aromatic compound, and a random copolymer block (B) of a conjugated diene. (A)-(B) block copolymer, or (A)-(B), which further comprises a taper block (C) in which the vinyl aromatic compound is gradually increased among vinyl aromatic compounds and conjugated dienes, if necessary. −
(C) a block copolymer or a (A)-(B)-(A) block copolymer composed of a vinyl aromatic polymer (A), which is hydrogenated to give a double bond of a conjugated diene moiety. Is saturated at least 80% and has a number average molecular weight of 50,000 to 600,000. These are JP 3-7
No. 2512. The hydrogenated diene copolymer preferably has a bound styrene content of 10 to 30% by weight and a melt flow rate (230 ° C., 2.16 kg load) of 3 to 6 g / 10 minutes.

As the water-absorbent resin (c) in the crosslinked water-absorbent resin of the present invention, those which are commercially available as a super-water-absorbent resin can be used without any particular limitation. A highly water-absorbent resin obtained by crosslinking a polymer containing one or two α, β-unsaturated compounds in the molecule as a monomer component with a crosslinking agent is preferable, and the particle diameter is 5 to 30 μm. , Preferably 10 to 20 μm.

Examples of such water-absorbent resins include polyacrylate-based resins, starch-acrylate-grafted polymers, vinyl acetate copolymers, maleic anhydride copolymers and vinyl alcohol-based copolymers. Named
Among them, polyacrylate resin can be preferably used. The water-absorbent resin has a water absorption rate of 10 to 5 of its own weight.
It is desirable to have a water absorption capacity of 00 times, preferably 50 to 200 times.

In the water-absorbent resin crosslinked product of the present invention, the use of the inorganic filler (d) improves the dispersibility of the water-absorbent resin in the composition. Therefore, a compatibilizer may not be used. . Here, as the inorganic filler (d),
Talc, calcium carbonate, gypsum, carbon black, clay, kaolin, silica, diatomaceous earth, magnesium carbonate, barium carbonate, magnesium sulfate, barium sulfate, calcium sulfate, calcium phosphate, aluminum hydroxide, zinc oxide, magnesium hydroxide, calcium oxide, Magnesium oxide, titanium oxide, alumina, mica, shirasu balloon, zeolite, clay silicate, cement, silica fume, mica powder, etc. can be used,
Among them, talc, calcium carbonate and silica are preferable. These inorganic fillers can be used in various shapes such as powder, sphere and flake.

In the water-absorbent resin crosslinked product of the present invention, a softening agent (e) and a plasticizer (f) are blended for the purpose of improving flexibility at low temperature, improving powderiness, and improving workability. As the softening agent (e), a mineral oil-based softening agent is preferably used. Examples of the mineral-based softening agent include petroleum-based softening agents such as paraffin-based, naphthene-based and aromatic-based, polymerized high-boiling strong aromatic oil, liquid paraffin, white oil, etc., but preferably petroleum-based softening agent A paraffinic petroleum softener having a good compatibility with an agent, particularly EPDM can be preferably used.

As the plasticizer (f), those usually used in resin compositions can be used, and for example, a phthalic acid derivative can be preferably used. As a phthalic acid derivative,
Dimethyl phthalate, di- (2-ethylhexyl) phthalate, diethyl phthalate, dibutyl phthalate, di-n-octyl phthalate, diisooctyl phthalate, diisobutyl phthalate, diheptyl phthalate,
Diphenyl phthalate, diisodecyl phthalate, ditridecyl phthalate, diundecyl phthalate, benzyl phthalate, butyl benzyl phthalate, dinonyl phthalate, alkyl benzyl phthalate, dimethoxy ethyl phthalate, dimethyl cyclohexyl phthalate,
Examples thereof include methylphthalylethyl glycolate, ethylphthalylethyl glycolate, butylphthalylbutyl glycolate and the like, and a mixture thereof. In the present invention, in addition to the above components, if desired, an ultraviolet absorber, a heat stabilizer, a light stabilizer, a flame retardant, an antistatic agent, a nucleating agent, a colorant and the like can be appropriately blended.

The above-mentioned olefinic thermoplastic elastomer component (a), hydrogenated diene copolymer (b), water absorbent resin component (c), inorganic filler (d) and softening agent in the water absorbent resin crosslinked product of the present invention. The compounding ratio of (e) and the plasticizer (f) is 10 to 100 parts by weight of the component (b), and 100 parts by weight of the component (a) + (b) with respect to 100 parts by weight of the component (a). The component (c) is 5 to 95 parts by weight, preferably 30 to 60 parts by weight, the component (d) is 1 to 25 parts by weight, preferably 3 to 15 parts by weight, and the component (e) is 2 to 50 parts by weight. , Preferably 30 to 45 parts by weight, and the component (f) is 2
-50 parts by weight are blended.

When the amount of the component (b) is less than 10 parts by weight, the water absorption of the composition is insufficiently improved, and when it exceeds 100 parts by weight, the weight retention becomes low. When the ratio of the water absorbent resin (c) is less than 5 parts by weight, the water absorption of the composition becomes insufficient,
Further, if it exceeds 95 parts by weight, the mechanical strength of the composition is lowered. If the proportion of the inorganic filler (d) is less than 1 part by weight, the dispersibility of the water absorbent resin will be reduced and the water absorption will be insufficient, and if it exceeds 25 parts by weight, the flexibility will be reduced and the water absorbent resin will also fall out. To increase. If the proportion of the softening agent (e) is less than 2 parts by weight, the flexibility is insufficient, and if it exceeds 50 parts by weight, the moldability becomes poor. Further, when the proportion of the plasticizer (f) exceeds 50 parts by weight, the kneading work becomes difficult.

In order to obtain the water-absorbent resin crosslinked product of the present invention, first, an olefinic thermoplastic elastomer component (a), a hydrogenated diene-based copolymer (b), a water-absorbent resin component (c) and an inorganic filler. The components (d), the softening agent (e) and the plasticizer (f) are melt-kneaded in the above proportions in any order. However, in order to improve the uniform dispersibility of the water-absorbent resin in the composition, the olefin-based thermoplastic elastomer component (a) and the water-absorbent resin (b) prepared in advance from a polyethylene-based polymer and EPDM are mixed with a Henschel mixer. It is preferable to pre-mix using a stirrer such as. The components (c), (d) and (e) were added to this premix.
After adding and stirring sufficiently, a single-screw extruder, a twin-screw extruder,
Melt and knead using a kneading machine such as a Banbury mixer, kneading roll, Brabender, kneader ruder. Here, the kneading temperature may be appropriately set in a range of at least the temperature at which the base resin component is melted, but is usually 90 to 250 ° C.
It is preferable to carry out in the range of. Next, the obtained kneaded product is formed into a sheet or other desired shape.

The crosslinked water-absorbent resin of the present invention is irradiated with ionizing radiation to form a crosslinked structure,
Prevents gel from coming off and improves durability. Depending on the irradiation conditions (irradiation amount, etc.) of the ionizing radiation, the water-absorbent resin cross-linked product can have a cross-linked structure as a whole, or both surface layers or one surface layer of the molded product can have a cross-linked structure. By this cross-linking treatment, mechanical strength and hot water resistance are improved, and gel escape is suppressed. In particular, a molded article having a cross-linked structure with a high degree of cross-linking only in the surface layer has improved mechanical strength due to the surface cross-linked layer, and further prevents loss of the water-absorbent resin when water absorption and drying are repeated, and maintains shape. Properties, hot water resistance and the like can be improved.

Examples of the ionizing radiation to be applied to have a crosslinked structure include α rays, β rays, γ rays and X rays. The irradiation amount at this time is preferably in the range of 0.1 to 20 Mrad. If it is less than 0.1 Mrad, the crosslinking will not be sufficiently carried out, and if it is more than 20 Mrad, the degree of crosslinking will be too large and the water absorption will be lowered, and the molded body will be deteriorated, which is not preferable. Also, the accelerating voltage and the dose of the irradiation line are
It is appropriately set according to the desired degree of crosslinking. For example, by gently cross-linking the surface layer using a relatively low accelerating voltage and dose, the effect similar to laminating a film on the surface layer can be imparted to prevent gel escape. Further, by setting a relatively high accelerating voltage, the entire crosslinked body can be uniformly crosslinked, and water absorption, strength, gel removal prevention performance and the like can be well balanced. The accelerating voltage and dose of the radiation to be irradiated need to be changed depending on the desired degree of crosslinking, such as when the entire molded body is crosslinked by this irradiation and when only the surface layer is crosslinked, but the range of 100 to 850 KV is preferable. The dose is preferably in the range of 1 to 8 Mrad.

[0026]

The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following description. In addition, in each of Examples and Comparative Examples, the following materials were used as the resin raw material and the additive. Olefinic thermoplastic elastomer: EPDM
(Propylene content 28% by weight, iodine value 15, Mooney viscosity (ML _{1 + 4} , 100 ° C.) 88) and EVA (vinyl acetate content 28% by weight, melt index (190
C., 2.16 kg load) 20 g / 10 minutes) at a ratio shown in Table 1 at room temperature using a Henschel mixer, followed by roll kneading at about 120.degree. C. and pelletizing.

Hydrogenated diene copolymer: Dynaron 1320P
(Brand name) (Nippon Synthetic Rubber Co., Ltd., bound styrene content 10%, melt flow rate (230 ° C, 2.16 kg load)
3.5g / 10 minutes, Shore A hardness 39, hydrogenation rate 99%
that's all. Water-absorbent resin: Aqualic CS-6S (manufactured by Nippon Shokubai Chemical Co., Ltd .; polyacrylate type). Inorganic filler: talc (Hayashi Kasei Co., Ltd .; Micron White 5000A, average particle size 6 μm). Softener: Mineral oil (Idemitsu Petrochemical Co., Ltd .; PW-38
0 (trade name), paraffinic mineral oil). Plasticizer: DIDP (diisodecyl phthalate).

Examples 1 to 3 and Comparative Example After preliminarily kneading the olefinic thermoplastic elastomer comprising the polyethylene polymer and EPDM and the water absorbent resin in the proportions shown in Table 1 at room temperature using a Henschel mixer. The hydrogenated diene copolymer, the inorganic filler, the softener and the plasticizer were melt-kneaded at 140 ° C. using a Brabender mixer and extruded from a die to form a sheet. Then, electron beam irradiation was carried out under the conditions shown in Table 1 so that the entire layer had a crosslinked structure to obtain a water-absorbent resin crosslinked product having the physical properties shown in Table 1. In addition, as a comparative example, the result when the electron beam is not irradiated is shown.

The methods for measuring the physical properties shown in Table 1 are as follows. (1) Hardness: Measured by Shore C. (2) Water absorption after 1 day and 7 days: A value obtained by dividing the weight of the resin foam after water absorption by the weight of the resin foam before water absorption. (3) Breaking strength: Measured by ASTM D-638 (23 ° C). (4) Weight retention rate: A value obtained by once drying the swelled product, weighing it, and dividing the weight by the weight before swelling (the smaller this value is, the more gel is removed from the water absorbing agent). (5) Hot water resistance: The composition shown in Table 1 was added to hot water at 70 ° C.
The condition after immersion in time was evaluated according to the following criteria. ◯: Swelling of the composition is uniform in three directions and the surface is smooth X: Swelling of the composition is not uniform in three directions and curling occurs in the crosslinked body, resulting in severe surface roughness

As is clear from Table 1, the water-absorbent resin crosslinked product according to the present invention had good breaking strength, weight retention and hot water resistance. On the other hand, it can be seen that the strength and hot water resistance of the water-absorbent resin crosslinked product that is not irradiated with electron beams are poor.

[0031]

[Table 1]

[0032]

The crosslinked water-absorbent resin according to the present invention is obtained by molding a composition containing a specific amount of the water-absorbent resin, an inorganic filler, a softening agent and a plasticizer based on an olefinic thermoplastic elastomer. It is formed by cross-linking by electric current radiation, and the composition before cross-linking is thermoplastic so that it can be easily formed into an arbitrary shape by a method such as sheet molding, profile extrusion molding, etc. Have good workability, excellent hydrogen absorption rate and water absorption by blending hydrogenated diene copolymer, and excellent productivity because they can be produced without a vulcanization step. In addition, the crosslinked water-absorbent resin of the present invention is excellent in mechanical properties because it is crosslinked by ionizing radiation, and is excellent in shape retention because it prevents gel removal. Such a cross-linked product obtained by the method of the present invention is a waterproof seal between segments for tunnel and water supply and sewerage construction, civil engineering such as a seal for a gap between building outer wall panels, a waterproofing material for construction work,
It can also be used as an anti-condensation material that also has an anti-seismic function, and as a water retention material for agriculture, forestry and horticulture.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location // C08K 3/00 KDY 7242-4J C08L 23/04 LDD 7107-4J 23/16 LCY 7107-4J 33/02 LJD 7921-4J

Claims (1)

[Claims] 1. (a) Polyethylene polymer 15-55
Wt% and ethylene-propylene-diene copolymer 85-
(B) Hydrogenated diene-based copolymer 1 with respect to 100 parts by weight of an olefin-based thermoplastic elastomer composed of 45% by weight
The component (a) + (b) 1 containing 0 to 100 parts by weight.
(C) 5 to 95 parts by weight of water-absorbent resin with respect to 00 parts by weight,
(D) 1 to 25 parts by weight of inorganic filler, (e) softener 2 to
A method for producing a crosslinked water-absorbent resin, which comprises irradiating ionizing radiation after molding a resin composition containing 50 parts by weight and (f) 2 to 50 parts by weight of a plasticizer.