JPS5832638A - Water-absorbing foam - Google Patents

Abstract

PURPOSE:To obtain a water-absorbing foamed material having excellent water absorptivity, water retainability, heat resistance, etc., by crosslinking an alkali metal salt, etc. of a polymer derived from an alpha,beta-unsaturated compound containing carboxyl group with a polyvalent amine to obtain a highly water-absorbing resin, dispersing the resin in a plastic material, and foaming the dispersion. CONSTITUTION:An alkali metal salt, alkaline earth metal salt or ammonium salt of a polymer containing an alpha,beta-unsaturated compound having one or two carboxyl groups or groups convertible thereto (preferably >=40mol% of the whole monomer components; e.g. acrylic acid) as monomer components, is crosslinked with a polyvalent amine (e.g. ethylenediamine). The resultant highly water-absorbing resin is mixed with a plastic material (e.g. polyvinyl chloride) and a foaming agent (e.g. diazoamine derivative), etc., and foamed by heating to obtain the objective water-absorbing foamed material. USE:Water-absorbing material, dehydration material, water-retaining material, drying agent, anti-fogging agent, water-stopping material, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a water-absorbing foam with excellent water retention, which does not easily release water even when squeezed or pressure is applied after absorbing water.

Conventionally, foams made of open-cell thermoplastic resin, natural rubber, or synthetic rubber have been used as water-absorbing and water-retaining materials. Although these foams absorb water, they do not absorb pressure or It has the disadvantage that absorbed water is easily released when squeezed. Various methods have been tried to overcome these drawbacks, but so far none have been satisfactory.

For example, a foaming agent is added to a water-swellable resin consisting of a thermoplastic resin and a super absorbent resin (see, for example, JP-A-55-5424).
Furthermore, it is conceivable to prepare a water-absorbing foam by the usual foaming process of containing a foaming aid and foaming at a relatively high temperature of about 90°C. When used, the water absorption capacity of the resin decreases due to heating in the foaming process, or it becomes water soluble, resulting in practical problems in terms of water retention and durability. Furthermore, even if the foam is water-absorbent due to foaming at a relatively low temperature, it has problems such as unsatisfactory durability in a water-containing state depending on the application.

In order to improve the drawbacks of conventional water-absorbing foams, the present inventors have made extensive studies and found that a, β- A super absorbent resin obtained by crosslinking an alkali metal salt, alkaline earth metal salt, or ammonium salt of a polymer containing an unsaturated compound as a monomer component with a polyvalent amine is dispersed in a plastic material. It has been found that a water-absorbing foam formed by foaming the composition not only has excellent water absorption and water retention properties, but also has excellent heat resistance and water resistance in the case of water-containing bark.

The present invention has now been completed.

The plastic material used in the present invention is a thermal OJwi resin or rubber. The heat FfJ! Examples of the 112 resin include vinyl chloride, ethylene, polypropylene, and polystyrene. The rubbers include natural rubber (NR), synthetic cis-1,4-polyisoprene rubber (IR), polybutadiene rubber (BR), styrene-diene, copolymer rubber (8,BR or 8IR), acrylonitrile. -Jisen Kyohong rubber (NBR or NI)
IL), butyl rubber, isobutylene-isoprene copolymer rubber (IIR), chloroprene rubber (OR), or urethane rubber.

The superabsorbent resin used in the present invention is usually heated at a temperature of 90°C or higher to create a water-absorbing foam, so even if it is heated at such a temperature, its water absorption capacity may decrease or it may become water-soluble. In addition, it must have excellent (long-term) durability in a water-absorbed state (that is, water-containing water), and must not rot.

From the viewpoint of water absorption and durability of the water-swellable rubber layer, such super absorbent resins include carboxyl groups, carboxylates, carboxylic acid amides, carboxylic imides, carboxyl anhydrides, etc.・a having 1 or 2 Cζ in the molecule of carboxyl groups that can lead to ilI,
A crosslinked product of a polymer containing a β-unsaturated compound as a monomer component is preferably a polyvalent chain number ζ.

Examples of the .:/diunsaturated compounds include ac-11 acid, methacrylic acid, acrylic acid amide, meth-11 acid amide, maleic anhydride, maleic acid, malemaleic acid, and itaconic acid.

These include crotonic acid, fumaric acid, mesaconic acid, etc., and may be used in combination with a copolymerizable monomer component that satisfies the performance required for a super absorbent resin. Examples of the other copolymerizable monomers include ethylene, propylene, isobutylene, and 1-butylene.

Diisobutylene, methyl ether11. Examples include a-olefins such as styrene, acrylic esters, methacrylic esters, and acrylonitrile, vinyl compounds, and vinylidene compounds. When combined with other monomers, a contains a carboxyl group or a group that can be converted to this.

The β-unsaturated compound is suitably present in an amount of 40 mol % or more in the total monomer components.

The polymer containing as a monomer the d,β-unsaturated compound having a carbo-xyl group or a group convertible thereto is prepared by a conventional method using a radical polymerization catalyst. The degree of polymerization is not particularly limited, but is 10-s
, o, o o are preferred.

Among the above-mentioned polymers prepared in this manner, preferred examples are listed below.

(1) Maleic acid or maleic anhydride, maleic acid derivatives such as maleic acid amide or maleic acid imide, and ethylene, propylene, butylene, isobutylene or diisobutylene having 2 to 12 carbon atoms, preferably is a copolymer of 2A-8 with linear or branched a-olewin.

(2) Maleic acid or its derivative and styrene.

Copolymers with vinyl or vinylidene compounds such as vinyl acetate, methyl vinyl ether, acrylic acid ester, methacrylic acid ester or acrylonitrile.

(3) Polymers of acrylic acid or methacrylic acid.

(4) A copolymer of acrylic acid or methacrylic acid and the vinyl or vinylidene compound of (2) above.

Polymers containing as a monomer component a, β-unsaturated compound having one or two carboxyl groups or groups derived from carboxyl groups include sodium, potassium, magnesium, potassium barium, etc. From the viewpoint of reactivity and durability of the super absorbent resin finally obtained, reacting with compounds such as alkali metal hydroxides, oxides, or carbonates, or basic substances such as ammonia is recommended. is necessary. From this point of view sodium hydroxide, potassium hydroxide or ammonia,
Particularly preferred is sodium hydroxide. The enemy in this reaction is 40 to 100%, particularly 50 to 80%, of the carboxyl groups or groups derivable thereto in the polymer.
% is preferably reacted to form a salt from the viewpoint of durability and heat resistance of the superabsorbent resin.

The thus obtained reaction product of a polymer containing an α,β-unsaturated compound as a monomer component with a basic substance is subjected to a crosslinking reaction with a polyvalent amine. In addition to polyvalent amines, crosslinking agents include polyvalent epoxy compounds, urea resins, and melamine resins.

Polyhydric alcohols, amino alcohols, polyisocyanates, and polyhydric helohydrins may be used, but when they are used, the crosslinking points are ester bonds or amide bonds, and they are easily hydrolyzed, making them difficult to use in water-absorbing foams. If it is, the performance of the water-absorbing foam will be significantly reduced due to lack of durability when hydrated.

- In the case of a polyvalent amine, the crosslinking point is an ionic bond between the carboxyl group and the polyvalent amine, so it is physically and chemically stable, and therefore a highly durable super absorbent resin. is obtained.

The polyvalent amine used here has two amino groups in its molecule.
It is a hydrophilic, preferably water-soluble amino containing at least 2 amino acids, and examples of preferably used amino acids include ethylenediamine,
Diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, and polyethyleneimine having a molecular weight of 5 or less are exemplified.

There is no problem whether the polyethyleneimine is branched or linear.

The crosslinking reaction is carried out by adding the crosslinking agent to the reaction product of a basic substance and a polymer containing an h'sβ-unsaturated compound as a monomer component. may be heated, or a reaction solvent may be used, and it is particularly preferable to carry out the reaction under heating and in the presence of water. In such cases, drying or heat treatment is preferred. The amount of the crosslinking agent to be used is determined as appropriate so as to obtain the superabsorbent resin exhibiting the desired water absorption capacity, but it is usually 1 part by weight per 100 parts by weight of the reaction product.
- It is preferably 0 parts by weight or less, particularly in the range of o, o os' to 2 parts by weight. - Examples of super absorbent resins obtained in this manner that are preferably used in the present invention are listed below.

(1) A maleic acid derivative such as maleic acid or maleic anhydride/acid amide or maleic imide, and a compound having 2 to 12 carbon atoms such as ethylene, propylene, butylene, isobutylene or diisobutylene, preferably
412, a copolymer of 8 with a linear or branched α-olefin and an alkali metal compound or an alkaline earth metal compound.

Cross-linked product with polyvalent amine, which is a reaction product with ammonia, etc.

(2) Maleic acid or its derivative and styrene.

Vinyl acetate. A crosslinked product using a polyvalent amine, which is a reaction product of a copolymer with a vinyl or vinylidene compound such as methyl vinyl ether, acrylic acid ester, methacrylic acid ester or acrylonitrile, and an alkali metal compound, alkaline earth metal compound, ammonia, etc.

Among these, from the viewpoint of water absorption and durability, the most preferred is a crosslinked product of a reaction product of an isobutylene-maleic anhydride alternating copolymer with sodium hydroxide, potassium hydroxide, or ammonia using a polyvalent amine.

In addition, if the superabsorbent resin used in the present invention has a low water absorption capacity, the swelling ratio of the intended water-absorbing foam will naturally become small, whereas if the water absorption capacity is excessively high, it will contain less water. Since the strength of the superabsorbent resin in the foaming state decreases, there is a risk that it will flow out with water, and in either case, a sufficient water-absorbent foam cannot be obtained. Therefore, the water absorption capacity of super absorbent resin is 20 to 800 times, especially 50 to 50 times.
The water absorption capacity is preferably 0 times. Here, the water absorption capacity refers to the value obtained by dividing the weight of distilled water that can be absorbed by the superabsorbent resin by the weight of the resin.

The water-absorbing foam of the present invention has super-absorbent resin 9 in the plastic material.
It is produced by mixing a foaming agent and, if necessary, a foaming accelerator or foaming inhibitor, followed by heating and foaming. The blending ratio of super absorbent resin varies depending on the application, but it is usually 5
71! The amount is preferably in the range of 2 to 300 parts by weight, preferably 10 to 250 parts by weight, per 100 parts by weight. The blowing agents used include diazoamino derivatives and azonitrile.

Azodicarboxylic acid derivatives, dinitropentamethylenetetramine (DPT), benzene monohydracyl.

Oxybisbenzenesulfonyl hydrazide (QB8H)
.

Ammonium carbonate, N1M ammonium acid, propane,
Examples include petroleum ether, etc., and depending on the expansion ratio of the foam,
Although it varies depending on the use, it is preferably in the range of 1 to 80 parts by weight per 100 parts by weight of the plastic material. When preparing the mixture of 5J gift and super absorbent resin, if necessary, OJm agent, stabilizer, lubricant, filler-free colorant, flame retardant, antistatic agent or anti-mold agent, etc. may be mixed. In addition, when using rubber as a plastic material, rubber chemicals such as vulcanizing agents, vulcanization accelerators, vulcanization aids, or activators, rubber reinforcing agents, tackifying resins, processing aids, antioxidants, and infrared absorption agent.

(Ozone) There is no problem in mixing anti-aging agents, etc.

Note that foaming is carried out by a normal one-stage foaming method or a two-stage foaming method. The resulting foam has open cells, but its density is not particularly limited.

The water-absorbing foam of the present invention thus obtained has excellent water absorption and water retention, as well as heat resistance and durability in a water-containing state, so it can be used as a water-absorbing material.

It can be used as a dehydrating material, water retaining material, desiccant, dew prevention material, water stopping material, etc.

The present invention will be specifically explained below with reference to Examples, but the present invention is not limited to these Examples. In Examples and Comparative Examples, "parts" refer to "parts" unless otherwise specified. Means "parts by weight."

Example 1 Isobutylene-maleic anhydride copolymer (an alternating copolymer of isobutylene and maleic anhydride in a molar ratio of 1:1, with a molecular weight of about 1!0,000. 154 parts of isopane-10), 154 parts of hydroxide) + 64 parts of 1um (carboxyl group based on maleic anhydride of the above copolymer is added to isobutylene-maleic anhydride copolymer) A homogeneous aqueous solution was obtained. Next, polyethyleneimine 8P-0 (manufactured by Nippon Shokubai Chemical Industry Co., Ltd.) with a molecule of 1120G was used.
12) After adding 0.69 parts and thoroughly mixing, it was poured into an alumite vat, dried and heat-treated in a hot air dryer at 110°C, and the resulting film was pulverized and passed through a 20 mesh sieve to form a highly absorbent film. A resin powder was obtained. 1 ton of the powder was placed in a 1J gullet car, 1001111P of distilled water was added thereto, left for 2 hours, and then filtered through a 200 mesh nylon cloth and the weight of each powder was measured to determine its water absorption capacity. However, the water absorption capacity was 200 times. - using the superabsorbent resin powder, polyvinyl chloride and a blowing agent according to the formulation in Table 1;
The mixture was further kneaded on an 8-inch open roll and dispensed into 5-inch thick portions. This sheet was placed in a preheated mold at approximately 170°C, and after pressurizing at 180°C for 20 minutes, the mold was taken out and a water-absorbing foam having open cells in a water-swellable matrix was formed. Prepared. The apparent specific gravity of this foam was 0.4.

Margin below Table 1 Polyvinyl chloride 1) 100 g (
2-Hexyl) phthalate 9゜Zinc stearate
2 Barium-curved composite stabilizer
4 Blowing agent (DPT) 1)
6 Urea foaming aid 6 Super absorbent resin powder 5° 1) Vinica P-440 dinitropentamethylenetetramine manufactured by Mitsubishi Monsanto When the foam thus obtained was immersed in tap water, it rapidly absorbed water. The water absorption capacity of the foam after 3 days of immersion was approximately 2.7 times, and almost no water O was released even when squeezed by hand.

Example 2 In the same manner as in Example 1, a super absorbent resin powder that could be passed through a 9-mesh sieve was prepared. This powder 9 synthetic cis 1.4-
Using $lisobrene rubber and a foaming agent, wA kneading was performed using an 8-inch open roll according to the formulation in Table 2,
A sheet with a thickness of swxr was dispensed. This sheet was placed in a mold, heated to 145° C., and cooled to prepare a water-absorbing foam. The apparent specific gravity of this foam was 0.2.

Table 2 Stearic acid 10 Zinc white (IN) 5 Micronized calcium bicarbonate') 100
Paraffin-based process oil 1) 50 Paraffin 3 Antioxidant 4) 1 Blowing agent (DPT)')
3 Urea foaming aid 6) 3 Thiazole vulcanization accelerator ν) 1 Guanidine vulcanization accelerator・) 0.3 Sulfur.

Highly absorbent m fat 201)
Kuraprene IR-1, manufactured by Kuraray Soprene Chemical ■ Whiteton 8B Island manufactured by Shiraishi Calcium ■ Sansen 450 manufactured by Sunoil 4) Tsukuraku N8-6 manufactured by Daien Shinko Kagaku Nippon Co., Ltd.) Dinitropentamethylenetetramine 4) Shinko Iriuchi BK manufactured by Kagaku Kogyo ■ a) Tsukusela DM as above. ・) Tsukusela DT as above When the water-absorbing foam thus obtained was immersed in tap water, it rapidly absorbed water. It was immersed in tap water as it was for 30 days, and then the water absorption capacity was measured, and the water absorption capacity was 5.9 times. When we measured the water absorption capacity after squeezing this water-absorbing foam by hand, we found that the water absorption capacity was 5.
It was 0 times. This shows that even when squeezed, most of the water is not released. In addition, when the water-absorbing foam that had absorbed the water of the seeds was left in dry TIkllII at 120° C. for 6 hours and then immersed in tap water again, it showed a water absorption capacity of 5.2 times. This shows that no decrease in the water absorption capacity of the water absorbent foam was observed.

Comparative Example 1 A foam was prepared in the same manner as in Example 2, except that the superabsorbent resin powder was not used. The apparent specific gravity of this foam was 0.2.

When this foam was immersed in tap water and the water absorption capacity was measured 30 days later, the water absorption capacity was 4.0 times. The water absorption capacity measured after squeezing this water-absorbed foam was 1.4 times, and most of the absorbed water was easily released by hand squeezing.

Example 3 Sodium polyacrylate (Aronbis 8 manufactured by Nippon Tsumugi Pharmaceutical Co., Ltd.)
) in 300 parts of water, the molecular weight was 1200.
6 sg of lyethylenimine was added to prepare a homogeneous aqueous solution. This aqueous solution was treated in the same manner as in Example 1.
A super-absorbent resin powder made of a crosslinked product of lyacrylic acid and lyethylenimine and passed through a 20-mesh sieve was prepared. The water absorption capacity of the resin was 180 times.

Using this super absorbent resin, a water absorbent foam was prepared in the same manner as in Example 2 according to the formulation in Table 2 of Example 2. The foam had an apparent specific gravity of 0.2.

When this water-absorbing foam was immersed in tap water for 3 days, the water absorption capacity was 4 times. The water absorption capacity measured after squeezing this water-absorbing foam was 4.6 times, which indicates that most of the water is not released even when the water-absorbing foam is squeezed.

In addition, this water-absorbing foam was soaked in tap water for 100 min.
The water absorption capacity when squeezed after boiling at ℃ for 5 hours was 5.5 times, indicating that the performance of this water-absorbing foam does not change in boiling water.

Comparative Example 2 As a crosslinking agent? A superabsorbent resin powder was prepared in the same manner as in Example 3, except that glycidyl ether having an epoxy equivalent of 145 was used instead of 0.6 part of lyethylenimine. The water absorption capacity of the resin was 90 times. A water-absorbing foam was produced in the same manner as Example 3 except that the resin was used. The water-absorbing foam had an apparent specific gravity of 0.2.

The water absorption capacity of this water-absorbing foam after being immersed in tap water for 439 hours was 5.0 times, and the water absorption capacity when this water-absorbing foam was squeezed was 3.9 times. Furthermore, when this water-absorbing foam was boiled at 100° C. for 5 hours while immersed in tap water, its water absorption capacity had decreased to 1.2 times. Such a decrease poses a big problem in practice.

Margin below

Claims (3)

[Claims] (1) a having one or two carboxyl groups or groups derivable into carboxyl groups in the molecule; A super absorbent resin obtained by crosslinking an alkali metal salt, alkaline earth metal salt, or ammonium salt of a polymer containing a β-unsaturated compound as a monomer component with a polyvalent amine is used as a plastic material. A water-absorbing foam made by foaming a composition dispersed in. (2) The superabsorbent resin is an alkali metal salt or alkaline earth of a maleic anhydride polymer consisting of at least one monomer selected from the group consisting of a-olefins and vinyl compounds and maleic anhydride. The water-absorbing foam according to claim 1, which is a crosslinked product obtained by crosslinking a similar metal salt or an ammonium salt with a polyvalent amine. (3) The superabsorbent resin is an alkali metal salt of an acrylic acid polymer selected from acrylic acid polymers, methacrylic acid polymers, and copolymers containing acrylic acid or methacrylic acid as a main component; Alkaline earth metal salt ≦
is a crosslinked product obtained by crosslinking an ammonium salt with a polyvalent amine;