JPH01118508A - Monomer composition for polymer - Google Patents

Abstract

PURPOSE: To produce the composition for a water-insoluble polymer useful as a water absorbing agent providing a dried sense with a water-swelling property by blending an olefinically-unsaturated carboxylic acid, an alkyl acrylate and a specific crosslinking agent.

CONSTITUTION: The composition is produced by blending 15-50 wt.% of an olefinically-unsaturated carboxylic acid (e.g. (meth)acrylic acid) (A), 49.07-82 wt.% of alkyl acrylate (B) having preferably 1-6C alkyl group that is methyl acrylate, ethylacrylate or n-butyl acrylate, and 0.03-3.0 wt.% of crosslinking agent (C) composed of a monomer having at least two polymerizable ethylene groups selected from di(meth)acrylate of glycol, di(meth)acrylate of monoether glycol, di(meth)acrylate of polyeter glycol, or arylester of polymerizable unsaturated carboxylic acid or the like. The composition is allowed to react at 0-100°C for 0.5-several hours to obtain the polymer.

COPYRIGHT: (C)1989,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION A monomer composition for a polymer useful as a water absorbent is provided. The monomer composition is characterized by a composition of an olefinically unsaturated carboxylic acid, an alkyl acrylate, and a small amount of a crosslinking agent, all in specific ratios.

FIELD OF INDUSTRIAL APPLICATION This invention relates to monomer compositions for polymers, and in particular to monomer compositions for dry-feel, water-swellable, water-insoluble polymers useful in water-absorbent articles.

(Prior Art) Various methods have been proposed for producing water-swellable and water-insoluble polymer materials. Materials of this type have been prepared from carboxyl group-containing polymer-forming compositions by polymerization of carboxylic acid monomers in the presence of crosslinking agents. Monomers of this type include acrylic acid, maleic acid, maleic anhydride, and the like. Linear carboxylic acid polymers of this type include acrylic acid-acrylate copolymers, acrylic acid-acrylamide copolymers, and acrylic acid-olefin copolymers. U.S. Pat. No. 3,980,663 describes a water-soluble, low molecular weight polyelectrolyte containing nucleophilic carboxyl ions, which has two or more sites that are subject to nucleophilic attack by carboxyl groups. The preparation of this type of polymer by reaction with a crosslinking agent is disclosed.

This method is exemplified by the reaction in an aqueous solution of the sodium salt of an acrylic acid-methyl acrylate copolymer crosslinked with glycerin diglycidyl ether (prepared by adding sodium hydroxide to the latex of the copolymer). The resulting product is cast into a film and cured in an oven for 1 hour. However, this method and product have numerous drawbacks. The crosslinking reaction is slow;
Particularly large dryers are required to provide the residence time necessary for curing. Additionally, crosslinking is accomplished by forming diester bridges between linear polymer chains. This bond undergoes hydrolysis and thus polymer degradation. Another drawback of this patent is the production of films that can only be formed into particulate material by milling. This results in a product with a low surface area/weight ratio inherent in slow water absorption films, which tends to prevent the swollen surface of the film from being penetrated further by water during absorption testing. Therefore, the film core exhibits only slow, if any, swelling capacity.

Other polymeric systems have also been proposed with particular regard to the formation of water-swellable, water-insoluble materials that can absorb large amounts of water without disintegrating or solubilizing.

Journal of Applied Polymer Science, Volume 14, Pages 897-92B (197G)? The paper entitled "Mechanism of alkaline thickening of acid-containing emulsion polymers" reported by Barbrook:
It is stated that upon neutralization, the acid-containing latex undergoes a common swelling process and becomes completely solubilized, resulting in a more hydrophilic polymer. In a series of polymers, Burbrook varied the Tg and hydrophilicity of the general formula methyl methacrylate/ethyl acrylate/methacrylic acid (MMA/EA/MAA) and varied the MMA/EA ratio from 5010 to 0/80. A specific neutralization reaction is described.

Both viscosity changes and macroscopic changes observed under an optical microscope were observed. Also, studies on monomers with larger hydrophilicity ranges, e.g. 80/20 and 70/30 E
Studies have also been disclosed using high EA/MAA contents, such as zero MMA in A/MAA. The optical microscope is
It was shown that the particles gradually swell as the carboxylic acid groups are gradually neutralized. It is disclosed that at 80% neutralization, the particles become highly swollen and a phase change from solid to liquid medium becomes discernible.

At 90% and 100% neutralization, the particles disappear and a genuine solution is formed. Polymer latex particles with low hydrophilicity, such as those obtained with high MMA levels and even low EA and MAA levels (e.g. 60/20/20 MMA/EA/MAA), form a viscous gel upon neutralization. , recognized as slightly distinguishable swollen gel particles under an optical microscope,
There is no clear boundary between the swollen particles and the solution. Electron microscopy of dry, 100% neutralized latex particles shows many tentacles protruding from the central core, which are associated with the particles, ie, stick together, resulting in high viscosity. Additionally, Burbrook discloses the preparation of four EA/MAA copolymers that are highly crosslinked with ethylene glycol dimethacrylate at 15% and 30% levels. MAA content is 20% and 30%. Latex prepared at 15% crosslinking swells upon neutralization, resulting in a much higher viscosity than that obtained with uncrosslinked polymers.

The 30% crosslinked material exhibits neither swelling nor viscosity due to its extremely high crosslink density.

(Problems to be Solved by the Invention) The present invention relates to an improvement over conventional monomer compositions for forming water-swellable and water-insoluble polymers by combining specific short-chain monomers with small amounts of crosslinking agents. . When polymerized and neutralized, this monomer composition forms an absorbent product;
It has a dry-to-the-feel feel when it swells.
-touch-feel). Combined with the extraordinary retentivity of absorbents to absorbent fluids, this makes polymeric absorbents according to the monomer compositions of the present invention important in the manufacture of any article requiring absorbent capacity;
It is important in a variety of articles such as surgical and dental sponges, menstrual tampons, diapers, pads, paper towels and disposable soil mats for livestock bedding.

(Means for Solving the Problems) According to the present invention, when a salt of a polymer is produced, a monomer composition for producing a polymer that is useful as a liquid adsorbent, particularly a water absorbent, is provided; The composition comprises: (a) 15-50% by weight of an olefinically unsaturated carboxylic acid; (b) 49.07-82% by weight of an alkyl acrylate (the alkyl group having 1-6 carbon atoms); (c) 0.03 to 3.0% by weight of a crosslinking agent made of a monomer having two or more polymerizable ethylene groups.

In producing a polymer from the monomer composition of the present invention, a monomer mixture containing an olefinically unsaturated carboxylic acid and an alkyl acrylate is polymerized in the presence of a small amount of a vinyl crosslinking agent. Crosslinking is accomplished by introducing the vinyl groups of the crosslinking agent directly into the carbon-carbon backbone of the polymer.

If long-term disintegration resistance is required, hydrolytically stable crosslinking agents such as divinylbenzene or triallyl cyanurate can be used.

Olefinically unsaturated carboxylic acids useful in the present invention are those materials that have an activated olefinic carbon-carbon double bond and at least one carboxyl group, ie, acids that have an olefinic double bond. Representative examples of suitable carboxylic acids include compounds such as acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, muconic acid, aconitic acid, and mixtures thereof.

Preferred carboxylic acids are acrylic acid and methacrylic acid.

Alkyl acrylates useful in the present invention are those in which the alkyl group has 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms. Representative examples of suitable acrylates include methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate and isobutyl acrylate.

Preferred acrylates are methyl acrylate, ethyl acrylate and n-butyl acrylate, with methyl acrylate being particularly preferred. Larger chain acrylates tend to be more hydrophobic, such that the final polymer salt exhibits lower swelling and water absorption in water and aqueous salt solutions.

Other monomers that do not fall within the scope of the monomer description above may also be used in small amounts, i.e., up to about 8% by weight, provided that they do not adversely affect the essential and novel properties of the invention. . For example, acrylamide, 2-ethylhexyl acrylate, hydroxyethyl acrylate,
and hydroxyethyl methacrylate can be used as a partial replacement for methyl acrylate or ethyl acrylate, and itaconic acid, maleic acid or maleic anhydride can be used as a partial replacement for methacrylic acid or acrylic acid. .

The crosslinking technique used in this invention to convert water-soluble polymers into insoluble water-swellable polymers is known as free radical addition polymerization. Crosslinking agents that can be used in the monomer compositions of the present invention are polyunsaturated polymerizable vinyl monomers having two or more free radical addition polymerizable ethylene groups.

Virtually any monomer having two or more polymerizable ethylene groups can be used, provided that it is capable of entering into the vinyl addition polymerization reaction with the acids and acrylates described above.

Examples include: (1) diacrylates and dimethacrylates of glycols, such as ethylene glycol dimethacrylate;
Propylene glycol dimethacrylate, butylene glycol dimethacrylate and hexylene glycol dimethacrylate: (2) diacrylates and dimethacrylates of monoether or polyether glycols, such as diethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene or tetraethylene glycol diacrylate, and triethylene or tetraethylene glycol dimethacrylate: (3) Allyl esters of polymerizable unsaturated carboxylic acids, such as allyl acrylate, methallyl acrylate, allyl methacrylate, allyl acrylate, ethylyl acrylate, methallyl methacrylate; (4) di- or trivinyl aromatic compounds, such as divinylbenzene and trivinylbenzene; (5) dibasic and tribasic di- or triallyl esters, such as diallyl phthalate, diallyl succinate, triallyl phosphate, diallyl oxalate, diallyl; malonate, diallyl citrate, diallyl fumarate, diallyl ether, and (6) acrylates or methacrylates of polyols, such as di- or triacrylates or methacrylates of trimethylolethane, trimethylolpropane or pentaerythritol.

It is important to polymerize the monomers in certain ratios to obtain the desired polymer properties; however, the exact ratios will vary depending on the specific polymer desired. The olefinically unsaturated carboxylic acids of the invention are used in amounts of from about 15 to about 50% by weight, particularly preferably from about 20 to about 40% by weight, based on the total weight of the monomers used. When the amount of carboxylic acid used exceeds about 50% by weight, the resulting polymer salt becomes too hydrophilic and absorbs excessive amounts of water, resulting in (1) soluble polymer, (2) viscous solution or suspension and (3) loss of macromolecular structural integrity. The amount of carboxylic acid is approximately 1
Below 5%, the resulting polymer salt will be insufficiently hydrophilic and exhibit poor water absorption.

The alkyl acrylate is about 49.07% to about 82% by weight, particularly preferably about 59.0% by weight based on the total weight of the monomers used.
It is used in amounts of 2 to about 78% by weight. When the amount of acrylate used exceeds about 82% by weight, the resulting salt form of the polymer is insufficiently hydrophilic and exhibits poor water absorption. When the amount of acrylate is less than about 49.07%, the resulting polymer becomes too hydrophilic and absorbs excessive amounts of water (
1) a soluble polymer; (2) a viscous solution or suspension;
and (3) result in loss of macromolecular structural integrity.

The amount of crosslinking agent used is desirably limited to about 0.03 to about 3.0% by weight, preferably about 0.08 to about 2.0%. It has been found to be sufficient to render it water insoluble while retaining a high degree of water absorption. Use of less than 0.03% results in a polymer that upon neutralization acts primarily as a thickener lacking individual particulate character. The amount of crosslinking agent is 0.03
%, the resulting polymer becomes increasingly discrete and rigid, minimizing swelling of the salt particles. When amounts of crosslinking agent greater than 3.0% are used, water absorption decreases to industrially unacceptable levels.

Suitable polymers include from about 20 to about 40% by weight of an olefinically unsaturated carboxylic acid selected from methacrylic acid and acrylic acid, and from about 59.02 to about 78% by weight of methyl acrylate, ethyl acrylate, and n-butyl. an alkyl acrylate selected from acrylates, and about 0.08
~2.0% by weight of a crosslinking agent as an essential component.

During the polymerization, the polymerized components should be reacted as completely as possible. The polymers can be made batchwise, continuously or semi-continuously by conventional polymerization techniques such as solution, suspension or emulsion polymerization.

Suspension polymerization is preferred. Because this technology is 50-4
The acidic polymer product is produced as a high surface area particle precipitate with an average particle size of 0 to 50μ;
This is because it appears to be composed of deposits of smaller particles. Most of these smaller particles appear as collapsed spherical high surface area donuts with 2-5μ protrusions on their surface.

The polymerization reaction is carried out in the presence of a catalyst. Catalysts that form the free radicals necessary for the reaction are conventional, usually organic peroxides, inorganic persulfates and free radical-generating azo compounds.

The amount of catalyst used is usually 10% of the total monomer raw material to be reacted.
from about 0.01 to about 2.0 parts by weight per 0 parts by weight. Typical examples of organic peroxides are benzoyl peroxide,
Acetyl peroxide, bis(p-bromobenzoyl) peroxide, di-t-butyl peroxide, t
-butyl peroxide, dicumyl peroxide, cumene hydroperoxide, bis(p-methoxybenzoyl) peroxide, 2.2°-azobisiso-tyronitrile, and the like. Examples of inorganic persulfates include ammonium, sodium and potassium persulfates.

These can be used alone or in combination with sodium or potassium bisulfite. Polymerization is preferably carried out using free radical catalysis, but radiation polymerization can also be used, for example high energy X-rays or gamma radiation.

Suitable commonly used surfactants and/or colloids can also be used during the polymerization reaction.

Polymerization times and temperatures can vary significantly depending on the monomer system and catalyst used.

Typically, the polymerization reaction is carried out at a temperature of about 0-100°C within at least 30 minutes to several hours, preferably 65°C for maximum efficiency.
It will be completed in 1-4 hours at ~90°C.

In a preferred embodiment, suspension polymerization is carried out as follows. The reactor is filled with deionized water and suspending agent and degassed with inert gas. The reactor can be heated as necessary to dissolve the suspending agent. Predetermined amounts of olefinically unsaturated carboxylic acid and alkyl acrylate are added either separately or as a mixture. Addition may occur at room temperature or at reaction temperature. The crosslinker and catalyst can be added to the monomer mixture simultaneously or separately.

The reactor contents are then agitated and heated by conventional means to initiate polymerization at a temperature about the lowest boiling point of the monomers. When polymerizing methyl acrylate, this temperature is approximately 70°C. The reaction is then allowed to continue to complete polymerization, after which the reactor contents are cooled. The polymer product can be recovered from the slurry by conventional filtration means or converted directly to its salt form in the slurry.

The final product slurry can be steamed at about 100° C. to completely remove traces of unreacted monomer. Alternatively, a highly reactive redox catalyst can be added to give nearly 100% yield. The slurry can then be filtered to recover the polymer in its non-swellable acid form, or the final slurry can be neutralized by adding a calculated amount of aqueous alkaline solution to convert the free acid groups to the salt form. I can do it. Alternatively, the filtered polymer cake can be redispersed in water and neutralized as described above, or dried, powdered and neutralized with alkali.

Typically, the solids content of the final reaction mixture is about 15% to
It is about 50%. Lower solids contents can be used, but are generally undesirable from an economic standpoint.

The resulting dry or slurry polymer product can then be stored or used directly in absorbent articles as is, for example by treating the substrate. For example, a potential substrate article is treated with an acidic polymer and then neutralized with an alkaline solution using conventional neutralization techniques to produce a water-swellable polymer. For the purposes of the present invention, processing step should be understood to mean complete particle dispersion or discontinuous dispersion onto the substrate. The substrate to be treated can vary widely depending on the end use and can be, for example, wood pulp, cellulose 8 cotton, paper, woven or non-woven fabrics, etc.

Any suitable organic or inorganic base can be used during neutralization. Representative compounds include sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonium hydroxide, ammonia and sodium carbonate. Neutralization may be accomplished with organic amines such as ethanolamine, jetanolamine, triethanolamine, methylgetanolamine, butylgetanolamine, diethylamine dimethylamine, trimethylamine, triethylamine, tributylamine, etc. and mixtures thereof. You can also do it. The most preferred base is sodium hydroxide. In short, any basic material that does not adversely affect the polymer composition can be used.

In the use of the monomer compositions for the polymers of the invention, particularly during the neutralization reaction, it is critical to use the minimum amount of water necessary to achieve a complete and uniform reaction and neutralization. It has been found that the effective amount of water that can be used in the present invention ranges from about 4 to 10:l, preferably from about 5 to 7:l by weight, with respect to the ratio of total water to polymer. Using a ratio of less than 4:1, during neutralization all of the free water is rapidly absorbed by a small portion of the acidic polymer, leaving the remaining neutralizing agent to be transported to the unneutralized acidic polymer particles. There is a danger that very little water will remain. On the other hand, when the ratio exceeds 10:1,
During drying, an unnecessarily large amount of absorbed water is removed, resulting in excessive energy consumption.

To achieve complete neutralization, stoichiometry must be observed between the equivalents of base dissolved in the alkaline neutralizing solution and the equivalents of carboxylic acid in the polymer slurry. That is, at least one equivalent of base, such as sodium hydroxide, should be used for each equivalent of carboxylic acid containing monomer moieties.

However, as much as 20% equim excess of base can be used to ensure that all of the carboxylic acid groups are neutralized by the neutralizing solution. In fact, a slight excess is recommended to drive the reaction and achieve maximum swelling. Excess alkalinity is not harmful. This is because, upon drying, the acrylate ester moieties, particularly methyl acrylate, react to partially saponify and generate additional sodium acrylate monomer units in the polymer chain backbone.

Drying of the polymer salts can be carried out by conventional means such as fluidized bed drying, rotary kiln drying, shelf drying, vacuum drying and oven drying, without causing polymer decomposition or removing any water associated with the polymer product. can be carried out at a temperature sufficient to remove substantially all of the Products containing up to 5% residual absorbed moisture are acceptable materials. A suitable drying temperature can be 25-150°C, particularly preferably 80-100°C.

Upon drying, the polymer salt particles aggregate to form a brittle mass of solid particles. This mass can be ground to form individual particles that are easy to handle and ship. Depending on the particular end use desired, particles from about 50μ to about 2II11 are suitable for particles that absorb water rapidly and allow water to pass through the pre-swollen mass of particles to reach uncontacted material. It was found that it brings about It should be appreciated that as particle size increases, the particle surface area to volume edge decreases, resulting in slower water absorption and ultimately more swollen particles. Similarly, when used in bulk, materials with small particle sizes tend to absorb water at a slower rate than larger particles as a result of reduced particle pore size and therefore reduced permeation rates.

The polymer products from the monomer compositions of the present invention have variable "weight average" molecular weights due to their crosslinking properties and insolubility in solvents commonly used in molecular weight measurements. A neutralized polymer can absorb many times its own weight of surrounding water. Thus, each individual absorbent particle swells or expands to several times its individual diameter without destroying the fineness of the particle. It has also been observed that it absorbs more than 100 times the amount of distilled water by weight. For 1% sodium chloride solutions, up to a 30-fold increase in weight occurred, while for 15-25% sodium chloride solutions, up to a 10-fold increase in weight was observed. This amount of absorption is particularly significant when it is observed that the polymer particles are substantially immobile therein and the resulting particulate material retains its structural integrity.

The water-insoluble and water-swellable polymers of the monomer compositions of the present invention are preferably used in absorbent bandages or articles requiring water retention capacity.

When used in said applications, the polymeric material is preferably in solid granule form to provide maximum surface area for absorption;
Ensure maximum surface area for absorbency. At least about 1% by weight and preferably up to 90% by weight of the polymer salt should be present in the composite absorbent article, based on the total weight of the article.

Depending on the type of absorbent article, the polymer salt can be dispersed in a support sheet or flexible support consisting of an absorbent layer of cloth fibers, wood pulp fibers, cotton linters, etc. or mixtures thereof. Absorbent layers of this type are used in the production of absorbent bandages and in the production of the above-mentioned articles of manufacture, such as, for example, surgical and dental sponges, menstrual mats, water separation devices (e.g. filter wicks), etc. It can be commonly used. These materials can include a support sheet or multiple layers of a support and an overcoat sheet, all of which are well known in the art.

Absorbent articles of this type can be manufactured by incorporating polymeric materials according to the monomeric compositions of the present invention into absorbent bandages by conventional procedures. This ensures that the desired particulate polymer is maintained in the final structure. In the case of menstrual tampons, this can be obtained by spreading the polymer particles as a layer over a layer of absorbent fibers and then winding this layer in the form of a roll with the polymer particles inside.

Steam treatment and drying of this composite will increase particle adhesion to the fibers. The resulting absorbent material will maintain its properties such as absorbing water. . Other well known methods for making articles of this type are also considered to be within the scope of this invention.

The water-insoluble, water-swellable polymer of the monomer composition of the present invention can also be used as a soil conditioner to improve water retention and increase air capacity. A significantly improved water holding capacity is observed in soils with a modified sand-silt-clay composition, especially when combined with a high content of sand.

This higher water holding capacity is observed even at pressures of 1-15 bar.

The use of polymer salts is clearly superior to untreated comparison soils, and the effect is particularly pronounced in sandy and more porous soils.

This type of soil is characterized by the loss of excessive amounts of water both through evaporation and drainage, and polymers strongly inhibit this effect. A collateral effect of over-drainage in sandy soils is loss of nutrients through leaching. Polymers according to the monomer composition of the present invention also suppress this effect, so that nutrients added to the soil are retained for a long time.

The remarkable water retention properties of these polymers make them particularly suitable for use in preventing dieback of plants grown in sandy, free-draining soils such as those found in arid regions of the earth. These polymers are beneficial in maintaining plant survival during periods of drought and are particularly useful in lawns made of sandy or free-draining sandy soils, such as golf greens, land sports areas and walkways. It is. They are also useful in nurseries, greenhouses, home gardens, in artificial soils, or for potted plants. The cost and need for regular irrigation and monitoring is significantly reduced. Therefore, they reduce the burden of water management by retaining more water in the plant beds and save labor by reducing the amount of field or greenhouse irrigation. Furthermore, they also improve land edges by increasing the water holding capacity of the soil, making it suitable for crop production. Finally, they can be used for example on grassed or bare roads, fields or fragile lands (rragi).
-pans) is useful for loosening soils that have been densified by natural or man-made processes. Additionally, they are useful during transplantation, where the water retention and close contact between the root roots and the water-swollen polymer particles reduce transplant shock and eliminate plant shock. Another use for the present polymers is in seed coating, which provides a water-rich, drought-tolerant environment for the early stages of germination and growth.

When used in solids, suitable polymeric materials are 65/35
10.1 is the sodium salt of EA/MAA/EGDMA. Although generally unequal to sodium salts in terms of water retention, potassium salts are advantageous in that they are not easily leached and provide nutrients that are available to the plant over long periods of growth. This is based on the fact that potassium, as a counterion to the polymer, is released only slowly compared to the solubilization rate of typical soluble synthetic potassium-containing fertilizers. Therefore, potassium fertilization and water retention can be optimized by using a blend of both sodium and potassium polymer salts.

As used herein, the term soil means any medium in which plants can grow and provides support, oxygen, water and nutrients. Examples of these materials include natural growth media and artificial or non-natural growth media such as glass peas, expanded organic materials (eg expanded polystyrene or polyurethane), calcined clay particles, ground plastic, and the like.

EXAMPLES The following examples illustrate the preparation of polymers from the monomer compositions of the present invention. Parts and percentages shown are based on total weight unless otherwise stated.

In the examples, the following procedure was used to measure the absorbance of water and aqueous salt solutions. 1% of 100g of tg polymer salt
Add to N1Cl solution or 200 g of distilled water. Let stand for 2 hours without stirring. Use a Whatman N014 filter paper until no more water flows through (usually 5~
15 minutes). Weigh the swollen product, subtract the weight of the polymer, ie 1 g, and record the result as the degree of swelling. Absorbency is determined by adding 1 g of polymer salt to 30.3 g of distilled water in a small jar. It is measured by adding it to the inside. Gently mix the contents of the jar by shaking. Observe and record the time required for the polymer to become completely solid, ie, the time at which the product no longer flows freely when the jar is inverted.

Example 1 This example illustrates the preparation of polymers from monomer compositions of the present invention by suitable suspension polymerization techniques.

A polymerization reactor was charged with 2000 g of deionized water and 3 g of Cellosize QP-4400 (a product of Union Carbide, a hydroxyethyl cellulose powder with a 2% viscosity of 4000-6000 cps) as a suspending agent. . The contents of the reactor were heated to 65°C to dissolve the hydroxyethylcellulose and then allowed to cool to 35°C.

The reactor was then charged with methyl acrylate 3 while stirring.
A mixture of 25 g of water, 175 g of methacrylic acid, 0.5 g of ethylene glycol dimethacrylate as a crosslinking agent and 0.5 g of azobisisobutyronitrile as a catalyst was added. The contents of the reactor are transferred at a moderate flow rate, e.g.
It was degassed by purging with nitrogen (0 ml). The temperature was increased to 70°C and the mixture was allowed to polymerize for 3 hours. For the final time, the reactor temperature was increased to 80° C. to complete the reaction. Total reaction time was 3 hours. The contents of the reactor were continuously stirred during the entire polymerization reaction.

After the reaction was completed, the reactor slurry was cooled to 25° C. and filtered through a vacuum filter. The filter cake weighed 1000g.

To analyze the product and determine the yield, 115 parts of the filter cake were dried in a vacuum oven at 80°C for 16 hours and ground to an average of 40 mesh (US standard sieve size), approximately 34-36 A granular acidic polymer containing % methacrylic acid was prepared. The percent conversion of monomer to polymer product was 97.0%.

The remainder of the filter cake is neutralized with a basic solution of sodium hydroxide, in which each of the remaining 115 parts of the cake is dispersed separately in 400 g of deionized water, and then 195 g of 10% sodium hydroxide solution (e.g. by rapidly and completely adding 20% excess of the theoretical amount needed to neutralize the The resulting bowl was placed in a vacuum oven for 8
It was dried at 0° C. to remove the moisture content, and then ground to a size that could pass through a 20 mesh sieve (US standard size).

The salt water absorption of this polymer salt was measured in a 1% sodium chloride solution. The filter cake weighed 24 g, corresponding to an absorption of 23 times its own weight in water. In water absorption tests, water absorption of about 100 times the polymer weight was achieved.

Examples 2 to 17 Examples 2 to 17 are based on the suspension polymerization technique of Example 1, in which different weight ratios of methyl acrylate (
Polymers were prepared using MA), methacrylic acid (MAA), and ethylene glycol dimethacrylate (EDMA) as a crosslinking agent. The polymers of Examples 2-12 were neutralized by the method of Example 1, except that lithium hydroxide solution was used instead of sodium hydroxide solution. The procedure of Example 1 was used to neutralize the acidic polymers of Examples 13-17.

In Table 1, the absorption capacity of alkaline polymers is expressed as a multiple of the dry weight of the polymer. Absorption value is deionized water and 15% calcium chloride solution and! 5% sodium chloride solution. For convenience of calculation, the amount of crosslinker shown refers to the amount of material added to the other two monomers used.

The above results clearly demonstrate that polymers from the monomer compositions of the present invention have high absorption capacity for water and aqueous salt solutions over a wide range of monomer and crosslinker concentrations. The data also shows that water absorption decreases as crosslinker level increases. The resulting product, with a water absorption rate of approximately 95%, consisted of hard, swollen particles that retained structural integrity with a dry feel. At higher water absorption levels, the swollen particles were slightly soft but individually separated, and the non-agglomerated particles had a semi-dry feel.

Table 1 280202 II 2 NT 380201183.2 4.8 480200.5224.9 5.5 575251184.8 6.9 670301175.5 6.3 760401164.8 NT 885151131.8 NT 975250. 5285.8 6.9 1075250 .3376.1 8.61175250
．． 2445.3 8.41275250.1608.1
10.91370301175.5 6.3 1470300.5316.2 7.81570300
．． 3577.7 10.11670300.1869.
1 +3.01770300.051058.6 1
3.0 MA = Methyl acrylate EDMA = Ethylene glycol dimethacrylate MAA = Methacrylic acid NT = Not tested Examples 18-24 Examples 18-24 follow the procedure of Example 1 using different weight ratios of each monomer. Showing the production of polymers.

Examples 18. The polymers of 20 and 21 were neutralized by the method of Example 1, except that lithium hydroxide solution was used instead of sodium hydroxide solution. Examples 19 and 2
Nos. 2 to 24 used the neutralization method of Example 1 with sodium hydroxide. The amounts of polymeric components used and the absorption test results are shown in Table 1. For ease of calculation, the amount of crosslinker shown indicates the amount of material added to the other monomers used.

This result shows that acrylic acid gives approximately the same results as methacrylic acid in swelling in water. For swelling in the presence of high electrolyte concentrations, methacrylic acid is preferred.

The results show that all polymers tested are sensitive to high concentrations of CaClt and NaCl, but the polymers still maintain high levels of absorbance and retain structural integrity. Example 24 also demonstrates the utility of a polymer in which some of the carboxylic acid monomers are replaced with small amounts of other acid monomers.

Examples 25 and 26 Examples 25 and 26 used polymers made by the suspension polymerization technique of Example 1 using different weight ratios of monomer and crosslinker. The acidic polymer was neutralized with a basic solution prepared from lithium hydroxide, sodium hydroxide, potassium hydroxide, and triethanolamine. The monomers used were methyl acrylate (MA) and methacrylic acid (MA).
A) and ethylene dimethacrylate (EDMA). The amount of monomer used and the results are shown in Table 2. The amount of crosslinking agent indicates the amount added to the two other monomers used.

The results demonstrate the effectiveness of varying the neutralizing agent and therefore the resulting polymer salt product.

The results also show that while sodium and lithium polymers have substantially similar absorption to water, lithium compounds give better results in electrolyte solutions. Although potassium polymers exhibit lower swelling efficiency, they have particular application in the agricultural sector due to their potential nutritional value. Triethanolamine salt has even lower absorption capacity, but
It would be particularly useful for cosmetic applications.

II [* 25 80 20 2 Li 11 3
．． 2Na 12.4 2 K 9 1.8 TEA 5 1.3 26 80 20 1 Na 16 2.
3Li 18 3.2 Examples 27-40 This example demonstrates the effect of varying the amounts of polymer components to produce water-swellable and water-insoluble polymers. The procedure of Example 1 was repeated to prepare the polymer-sodium salt. The amount of monomer used and the results are shown in Table 2.

Single system consisting of methyl acrylate, methacrylic acid and ethylene dimethacrylate (MA/MAA/EDMA)
, MA range 50-80 and MAA range 20-50 and ED
The study was conducted over the MA range of 0.03 to 0.3. The results show that for each crosslinking level, the maximum swelling at 1% NaCl is obtained with polymers at about 35-40% MAA. The polymer particles that gave swollen particles with the highest structural integrity were found to have a MAAa degree range of approximately 20-40%. Exceeding 50% MAA and 0.
Within the crosslinking agent range of 3 to 0.03, the structural integrity of the swollen particles was lost. Structural integrity deteriorates with less than 0.03 crosslinker, so neutralized polymer in water gives amorphous and unfilterable particles that are indistinguishable from conventional gelled viscous slurries or solutions. Ta.

Table V 2780200.3 5 2875250.3- 8.5 2965350.3 8.7 3050500.3 8.7 3175250.1 17 3265350.1 20.5 3360400.1 20 3450500.1 17.5 3575250 .05 18 3670300.05 24 3750500.05 25 3880200.03 17 3965350.03 32.5 4050500.03. 26.5 MA = Methyl acrylate MAA = Methacrylic acid EDMA = Ethylene glycol dimethacrylate Examples 41-46 Examples 41-46 use methyl acrylate and methacrylic acid with varying amounts of different crosslinkers and
The polymer was produced by suspension polymerization technique. The results are shown in Table V.

This result shows that the polymers produced with diethylene glycol dimethacrylate at 0.1% and 0.5% had 1% Na
It is shown that a swelling ratio of 25 times and 34 times was provided in C1, respectively. Therefore, lower levels of crosslinking result in polymers that are more easily hydrated and swellable. However, the lower limit is usually 0.03%. This is because beyond this point the particles no longer swell to the equilibrium absorption level at which the swollen particles maintain their structural integrity, but rather absorb so much water that structural integrity is lost. In the latter case, the particles become extremely soft and coalesce, possibly even forming a viscous gel or polymer solution. The use of higher glycols than diethylene glycol dimethacrylate, such as tetraethylene glycol, as its methacrylate derivative increased the hydrophilicity of the crosslinking units. Allyl methacrylate is an example of a crosslinking agent in which one vinyl group is present on the alkyl group of the acrylate ester and a second vinyl group is present on the carboxylic acid group, ie the methacrylic acid group. Divinylbenzene is an example of a hydrocarbon crosslinker and does not contain hydrolyzable ester groups, so the resulting polymer is structurally stable with hydrolytically stable carbon-carbon bonds throughout its backbone and crosslinks. Completed knee] knee person 41 6535 0.1 diethylene glycol
25 dimethacrylate 42 65 35 0.05 diethylene glycol 34 dimethacrylate 43 65 35 0.1) Limethylolpropane 23.5 trimethacrylate 44 6535 0.1 Allyl methacrylate
2145 6535 0.2 Tetraethylene glycol I8 dimethacrylate 46 6535 0.1 Divinylbenzene
23MA = Methyl Acrylate MAA = Methacrylic Acid Example 47 This example demonstrates a method for making polymers with monomer compositions of the present invention and neutralizing polymer slurries in the presence of various surfactants. ing.

1. Into a combination reactor, add 2000 g of deionized water and 3 g of Cellocize QP-4400 as a suspending agent (a product of Union Carbide, which is a hydroxyethyl cellulose powder with a 2% viscosity of 4000-6000 cps). The contents of the reactor were heated to 65°C to dissolve the hydroxyethyl cellulose and then heated to 35°C.
It was cooled to

The reactor was then charged with a mixture containing 325 g of methyl acrylate, 175 g of glacial methacrylic acid, ethylene glycol dimethacrylate o,sg as a crosslinking agent and 0.5 g of azobisisobutyronitrile as a catalyst. added. Then a moderate flow rate (e.g. 10
The contents of the reactor were degassed by purging with nitrogen (0 nl). The temperature was increased to 70°C and the mixture was allowed to polymerize for 3 hours. For the final time, the reactor temperature was increased to 80
The reaction was completed by raising the temperature to ℃. Total reaction time was 3 hours. The contents of the reactor were continuously stirred during the entire polymerization reaction.

After completion of the reaction, the reactor slurry was cooled to 25°C. The slurry was diluted with 500 g of water for better stirring and flow.

115 parts (600 g) of this slurry were transferred to a steel beaker and stirred very rapidly (3000 RPM) with a disperser. To this was added 5% aerosol OT (dioctyl sodium sulfosuccinate from American Cyanamid) as a surfactant. This suspension was then given 19
Upon addition of 5 g of 10% NaOH, the slurry immediately solidified into a wash of brittle granules that swelled upon blowing. The weight ratio of water to polymer in the neutralization step was 6.76:1. This brittle solid sodium polymer salt was then dried in a vacuum oven at 80°C to remove any water it contained, and then dried at 20°C.
It was ground to a size that could pass through a mesh sieve (US standard size). The dry product obtained weighs 10 of its weight in water.
Absorbed 0x. In a 1% NaCl solution, 21 times its weight was absorbed. Absorption speed is 8 seconds and 21 seconds, respectively.
It was hot in seconds.

Example 48 This example demonstrates the production of various absorbent articles using polymers from the monomer compositions of the present invention.

A. 0.5 g of the finely ground dry polymer salt from Example 1 was slowly added to 250 g of defibrillated cellulose slurry containing 5 g of cellulose. After mixing for 2 minutes, the slurry was processed into a conventional no-pull-and-wood
It was diluted in the headbox of a laboratory sheet machine, formed into a 12° x 12" handsheet, dried and tested for water absorption. This article contained 10% polymer salt.

This dry paper absorbed 12 times its weight in water.

B. The polymer suspension prepared according to Example 47 was diluted to 15% solids content with a 20 mol% excess of 10% NaOH.
Neutralized with solution. The neutralized polymer swelled and absorbed all the water, forming a hard, brittle paste. This was then diluted to 0.5% solids with water. This slurry 10
0 g was added to 250 g of a slurry of beaten cellulose pulp containing 5 g of cellulose. This was converted into a 12" x 12" handsheet and tested for water absorption, also as described above. This dry paper weighs 6.
Absorbed 6 times more water.

C1 Six 4"XIO° pieces of paper towels weighing 3.5 g were stacked one on top of the other, and 3.5 g of the finely ground polymer salt from Example 1 was evenly sprinkled between these layers. Obtained. The multilayered pad was sprayed with hoarfrost until the weight increased to 20 g. The wet pad was then dried at 80° C. to fuse the layers. The pad was tightly rolled into an oblong shape and %N
The extent of saline absorption was determined by soaking in aC1 solution for several minutes and then compressing under 1.5 psi pressure for 5 minutes. This pad absorbed 9 times its weight of 1% NaCl solution.

A similar comparative towel treated as described above without the polymer absorbed three times its weight in salt water solution.

Comparative Examples A-G This example compared the water and aqueous salt solution absorption rates of various commercially available water-swellable and water-insoluble polymer products to the dry polymer salt prepared according to Example 1. The tested polymers and their known chemical descriptions and results are shown in Table 2. This result shows that the polymer made from the monomer composition of the present invention is an unexpectedly excellent water-swellable and water-insoluble composition.

In this example, Comparative Substance A is commercially identified as Aqualon and is a product of Percules. Comparative material B is identified on the market as Viteller 1 and is a product of Union Carbide Company. Comparative material C is identified on the market as Viteller 2 and is a product of Union Carbide Company. The comparative material is identified on the market as Permatrubu 10 and is a product of National Starch and Chemical Company. Comparative material E is identified on the market as Permatrubu 30 and is a product of National Starch and Chemical Company. Comparative substance F is H-
It was identified as SPAN and is a product of General Mills Chemicals. This material is manufactured under license from the United States Department of Agriculture. Comparative material G is commercially identified as Dow Flake, is a product of Dow Chemical Company, and is disclosed in U.S. Patent No. 3.
No. 980,663 and No. 3,993,618.

A-dan --- Five comparative substances A 16
5 Internally Crosslinked Sodium Carboxymethyl Cellulose Fiber Comparison Material B 13
- Crosslinked polyethylene oxide Comparative material C Gelled bowl Gelled bowl Acrylamide - Na Acrylic polymer with hydrophilic carboxylate groups Cannot be filtered Comparative material E cannot be filtered Filtration Not possible 20.4 Comparative Substance F Hydrolyzed Starch Polyacrylic Linear Carboxylic Acid Polyelectrolyte Crosslinked Salt Not Filterable Not Filterable Having thus described the present invention, it is clear that it can be varied in many ways. It is. These changes are
It is to be understood that this does not depart from the spirit and scope of the invention.

Claims (6)

[Claims] (1) A monomer composition for a water-swellable, water-insoluble polymer with a dry feel, wherein the monomer composition comprises (a) 15 to 50% by weight of an olefinically unsaturated carboxylic acid; (b) 49.07 to 82% by weight of alkyl acrylate (the alkyl group has 1 to 6 carbon atoms); and (c) 0.03 to 3.0% by weight of two or more polymerizable ethylene groups. 1. A monomer composition for a polymer, comprising a crosslinking agent made of a monomer having the following. (2) 20 to 40 as olefinically unsaturated carboxylic acid
Monomer composition for a polymer according to claim 1, characterized in that % by weight of methacrylic acid or acrylic acid. (3) Claim 1, characterized in that it contains up to 8% by weight of itaconic acid, maleic acid or maleic anhydride based on the total amount of olefinically unsaturated carboxylic acids used.
A monomer composition for the polymer according to item 1 or 2. (4) 59.02-78% by weight of methyl acrylate;
A monomer composition for a polymer according to any one of claims 1 to 3, characterized in that it contains ethyl acrylate or n-butyl acrylate as the alkyl acrylate. (5) A monomer composition for a polymer according to any one of claims 1 to 4, characterized by 0.08 to 2% by weight of a crosslinking agent. (6) The crosslinking agent is diacrylate or dimethacrylate of glycol, diacrylate or dimethacrylate of monoether glycol, diacrylate or dimethacrylate of polyether glycol, allyl ester of polymerizable unsaturated carboxylic acid, di- or trivinyl aromatic Monomer composition for polymers according to claim 1 or 5 selected from the group of compounds, di- or tribasic di- or triallyl esters, or acrylates or methacrylates of polyols. .