JPS6321683B2 - - Google Patents

Description

[Detailed description of the invention]

SUMMARY OF THE INVENTION Polymers useful as water absorbents are provided. Preferably, the polymer contains the reaction products of an olefinically unsaturated carboxylic acid, an alkyl acrylate, and a small amount of a crosslinking agent, all in specific proportions. FIELD OF INDUSTRIAL APPLICATION This invention relates generally and to such salts, and more particularly to 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. This kind of material is
They are prepared from carboxyl group-containing polymeric 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. Patent No. 3980663 is
This type of polymer is produced by reacting a water-soluble, low molecular weight polyelectrolyte containing nucleophilic carboxyl ions with a crosslinking agent that has two or more sites that are subject to nucleophilic attack by carboxyl groups. Discloses that. This method is exemplified by the reaction in an aqueous solution (prepared by adding sodium hydroxide to the latex of the copolymer) of the sodium salt of an acrylic acid-methyl acrylate copolymer crosslinked with glycerin diglycidyl ether. The resulting product is cast into a film and cured in an oven for 1 hour. However, this method and product have various drawbacks. The crosslinking reaction is slow and requires particularly large dryers 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 a film that absorbs water slowly;
This tends to prevent the swollen surface of the film from being penetrated further by water during the absorption test. Therefore, the film core exhibits only a slow, if any, ability to swell. 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. In a paper entitled "Mechanism of alkaline thickening of acid-containing emulsion polymers" reported in the Journal of Applied Polymer Science, Volume 14, pp. 897-928 (1970), Barburtzug reported that acid-containing It is stated that during neutralization, all latexes undergo a common swelling process to become completely solubilized and become more hydrophilic polymers. In a series of polymers, Barburtzg has varied the Tg and hydrophilicity of the general formula methyl methacrylate/ethyl acrylate/methacrylic acid (MMA/EA/MAA), and has increased the MMA/EA ratio from 50/0 to 0/80. A specific neutralization reaction that changes the 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
High such that MMA is zero at 70/30EA/MAA
Studies using EA/MAA content have also been disclosed. Optical microscopy showed that the particles gradually swelled as the carboxylic acid groups were 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, e.g.
MMA levels and low EA and MAA levels (e.g. 60/20/20 MMA/EA/MAA) result in viscous gels upon neutralization and swollen gels that are barely discernible under light microscopy. They are recognized as particles, and 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 a high viscosity. Additionally, Barburzug 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%. Latexes prepared with 15% crosslinking swell 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 is an improvement over conventional water-swellable and water-insoluble polymer-forming compositions by combining specific short-chain monomers with small amounts of crosslinking agents. Ru. When polymerized and neutralized, the composition forms an absorbent product which, when swollen, forms gelled microspheres with a dry-to-the-touch feel. Combined with the extraordinary retentiveness of the absorbent to absorbent fluids, this makes the absorbent of the present invention important in the manufacture of any article requiring absorbent capacity, such as surgical and dental sponges, menstrual tampons, diapers, meat, etc. It is important in a variety of articles such as trays, paper towels, and disposable litter mats for livestock pets. (Means for Solving the Problems) In view of the above, according to the present invention, a polymer-forming composition is provided which is useful as a liquid adsorbent, particularly a water absorbent, when a salt of a polymer is formed. The composition comprises (a) from about 15 to about 50% by weight of an olefinically unsaturated carboxylic acid; and (b) from about 49.07 to about 82% by weight of an alkyl acrylate, where the alkyl group has from 1 to 6 carbon atoms. (c) a crosslinking agent comprising about 0.03 to about 3.0% by weight of a monomer having two or more polymerizable ethylene groups. Additionally provided are polymeric salts useful as water absorbing agents, which polymeric salts can be used as composition components (a), (b), and (c).
The salts of the polymers produced from the compositions of the present invention are characterized as suspension polymerization reaction products. Preferably, the polymer salt is a polymeric alkaline salt or an organic amine salt. Examples of alkaline salts can be selected from sodium, potassium, lithium and ammonium. Examples of organic amine salts can be selected from trimethylamine and triethanolamine. In preparing the polymers constituting 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 crosslinker 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, 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 not falling within the scope of the above monomer description may also be used in small amounts, i.e. about 8
It can be used in amounts up to % by weight. For example, acrylamide, 2-ethylhexyl acrylate, hydroxyethyl acrylate and hydroxyethyl methacrylate can be used as partial replacements for methyl acrylate or ethyl acrylate, and itaconic acid, maleic acid or maleic anhydride can be used as a partial substitute for methacrylic acid or acrylic acid. It can be used as a partial replacement for. 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 according to the invention are polyunsaturated polymerizable vinyl monomers having two or more free radically polymerizable ethylene groups. Virtually any monomer having two or more polymerizable ethylene groups can be used and must be capable of entering into vinyl addition polymerization reactions with the acids and acrylates described above. Examples include: (1) diacrylate and dimethacrylate esters of glycols, such as ethylene glycol dimethacrylate, propylene glycol dimethacrylate, butylene glycol dimethacrylate and hexylene glycol dimethacrylate; (2) Diacrylate and dimethacrylate esters of ethers or polyether glycols, such as diethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene or tetraethylene glycol diacrylate and triethylene or tetraethylene glycol dimethacrylate; (3) Polymerizable unsaturated carboxylic acids allyl ester of
For example allyl acrylate, methallyl acrylate, methallyl acrylate, allyl methacrylate, allyl ethacrylate, allyl methacrylate, allyl ethacrylate, etharyl acrylate, methallyl methacrylate; (4) Di- or trivinyl aromatic compounds, for example divinylbenzene and trivinylbenzene; (5) di- or triallyl esters of dibasic and tribasic acids, such as diallyl phthalate, triallyl cyanurate, diallyl maleate, diallyl succinate, triallyl phosphate, diallyl oxalate; , diallyl malonate, diallyl citrate, diallyl fumarate, diallyl ether, and (6) acrylate or methacrylate esters of polyols, such as di- or triacrylate or methacrylate esters of trimethylolethane, trimethylolpropane or pentaerythritol. It is important to polymerize the monomers in certain ratios to obtain the desired polymer properties, but the exact ratios will vary depending on the desired polymer properties. The olefinically unsaturated carboxylic acids of the invention are used in amounts of about 15 to about 50% by weight, particularly preferably about 20 to about 40% by weight, based on the total weight of the monomers used. The amount of carboxylic acid used is approximately 50% by weight
If the polymer salt is
resulting in a viscous solution or suspension and (3) loss of macromolecular structural integrity. The amount of carboxylic acid is approximately 15%
When the amount is less than that, the resulting polymer salt has insufficient hydrophilicity and exhibits poor water absorption. The alkyl acrylate is present in an amount of about 49.07 to about 82% by weight, based on the total weight of the monomers used, particularly preferably about
Used in amounts of 59.02 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, resulting in (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 desirably ranges from about 0.03 to about
Limited to 3.0% by weight, preferably from about 0.08 to about 2.0%. This low amount of crosslinker was found to be sufficient to render the polymer salt 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. As the amount of crosslinker increases beyond 0.03%, the resulting polymer becomes increasingly discrete and rigid, minimizing swelling of the salt particles. Using an amount of crosslinker greater than 3.0% reduces water absorption 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 acrylate. It is prepared from a composition containing as essential ingredients a selected alkyl acrylate and about 0.08% to about 2.0% by weight crosslinking agent. During the polymerization, the polymerized components should be reacted as completely as possible. The polymers can be made in batches, continuously or semi-continuously by conventional polymerization techniques such as solution, suspension or emulsion polymerization. Suspension polymerization is preferred. Because this technology
This is because the acidic polymer product results as a high surface area particle precipitate with an average particle size of 50-400μ, and this product appears to be composed of a deposit of smaller particles in the 10-50μ range. Most of these small 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 and are usually organic peroxides, inorganic persulfates and free radical-generating azo compounds. The amount of catalyst used is usually about 100 parts by weight of all monomer raw materials to be reacted.
0.01 to about 2.0 parts by weight. Representative examples of organic peroxides include benzoyl peroxide, acetyl peroxide, bis(p-bromobenzoyl) peroxide, di-t-butyl peroxide,
t-butyl hydroperoxide, dicumyl peroxide, cumene hydroperoxide, bis(p-methoxybenzoyl) peroxide, 2,
Includes 2'-azobisisobutyronitrile 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. The polymerization is preferably carried out using free radical catalysis, but radiation polymerization, such as for example high energy X-rays or γ-rays, can also be used. It is also possible to use suitable commonly used surfactants and/or during colloid polymerization reactions. Polymerization times and temperatures can vary significantly depending on the monomer system and catalyst used.
Typically, the polymerization reaction will be completed within at least 30 minutes to several hours at a temperature of about 0 DEG to 100 DEG C., preferably 1 to 4 hours at a temperature of 65 DEG to 90 DEG C. for maximum efficiency. In a preferred embodiment, suspension polymerization is carried out as follows. The reactor is charged 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 remove any 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. . 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 approximately
It is 15% to 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 form a water-swellable polymer. For the purposes of the present invention, processing steps should be understood to mean complete particle dispersion or dispersion into the substrate. The substrate to be treated can vary widely depending on the end use and can be, for example, wood pulp, cellulose batt, 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 can also be achieved with organic amines such as ethanolamine, diethanolamine, triethanolamine, methyldiethanolamine, butyldiethanolamine, diethylamine, dimethylamine, trimethylamine, triethylamine, tributylamine, etc. and mixtures thereof. 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 process of the present invention, particularly during the neutralization reaction, it is critical to use the minimum amount of water necessary to carry out complete and uniform reaction and neutralization. It has been found that an effective amount of water that can be used in the present invention ranges from about 4 to 10:1, preferably from about 5 to 7:1, by weight, in terms of total water to polymer ratio. Using a ratio less than 4:1, during neutralization all of the free water is rapidly absorbed by a small portion of the acidic polymer, carrying the remaining neutralizing agent to the unneutralized acidic polymer particles. There is a danger that there will be little water left for drainage. On the other hand, when the ratio exceeds 10:1,
To remove unnecessary large amounts of absorbed water during drying,
This results 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% equivalent 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 desirable 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 to remove the bulk of the water associated with the polymer product without causing polymer decomposition. It can be carried out at a temperature sufficient to remove all particles. Products containing up to 5% residual absorbed moisture are acceptable materials. Suitable drying temperatures can be between 25° and 150°C, particularly preferably between 80° and 100°. 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 specific end use desired, particles from about 50 microns to about 2 mm 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 the particle size increases, the particle surface area to volume 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 polymeric products of this invention have indeterminate "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 its weight of distilled water. A 1% sodium chloride solution causes up to a 30-fold increase in weight, while 15
Up to a 10-fold increase in weight was observed for ~25% sodium chloride solutions. 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 present invention are preferably used in absorbent bandages or articles requiring water retention capacity. When used in such applications, the polymeric material is preferably in solid granular form to provide maximum surface area for absorption and to ensure maximum surface area for absorption. 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, for example, in surgical and dental sponges, menstrual tampons, diapers, meat trays, livestock pet waste mats, water separation devices (e.g. supercored), etc. It can be one that is commonly used when manufacturing the above-mentioned manufactured articles such as. These materials are
Multiple layers of support sheets or supports and overcoating sheets, all of which are well known in the art, may be included. Absorbent articles of this type can be manufactured by incorporating the polymeric material according to the invention into an absorbent dressing by conventional procedures, thus maintaining the desired particulate polymer 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 inward. . 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 polymers of the present invention can also be used as soil conditioners to improve water retention and increase air capacity. sand-
A significantly improved water holding capacity is observed in clays with modified silt-clay compositions, especially when combined with a high content of sand. This higher water holding capacity is 1
Observed even at pressures of ~15 bar. The use of polymer salts is clearly superior to the untreated comparison soils, and the effect is particularly noticeable in the sandy and more porous soils. This type of pot is characterized by the loss of excess water through both evaporation and drainage, and the polymer strongly suppresses this effect. A collateral effect of over-drainage in sandy soils is loss of nutrients through leaching. The polymers of the invention also inhibit this effect, so that the 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 damping-off 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 soils or free-draining sandy soils, such as golf greens, land sports areas and walkways. . Also,
They are useful in nurseries, greenhouses, home gardens, or in artificial soils, or even 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 irrigation 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 are useful for loosening soils that have been compacted by natural or man-made processes, such as grassed or bare roads, fields or fragipans. Furthermore, they are also useful during transplantation, where the water retention and close contact between the hair roots and the water-swollen polymer particles reduce transplant shock and eliminate plant shock.
Another use for the polymers is seed coating, which provides a water-rich, drought-resistant environment for the early stages of germination and growth. For use in solids, suitable polymeric materials are
65/35/0.1 EA/MAA/EGDMA sodium salt. 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 plants 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 is defined as a soil in which plants can grow and a supporting means, oxygen,
means any medium that provides water and nutrients. Examples of these materials include natural growth media and artificial or non-natural growth media such as glass beads, expanded organic materials (eg expanded polystyrene or polyurethane), calcined clay particles, ground plastics, and the like. (Examples) The present invention will be further explained by the following Examples, but the present invention is not limited to these. 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. Add 1 g of polymer salt to 100 g of 1% NaCl solution or 200 g of distilled water. Let stand for 2 hours without stirring. Pass through Watzmann No. 4 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 swelling value. The rate of absorption is determined by adding 1 g of polymer salt to 30 g of distilled water in a small jar.
Gently mix the contents of the jar by shaking. Observe and record the time required for the polymer to become completely solid, ie, the product no longer flows freely when the jar is inverted. Example 1 This example illustrates the preparation of polymers of the present invention by suitable suspension polymerization techniques. In a polymerization reactor, add 2000 g of deionized water and 3 g of Cellocize QP-4400 (a product of Union Carbide, 2% of 4000-6000 cps) as a suspending agent.
(a hydroxyethyl cellulose powder with a viscosity). The contents of the reactor were heated to 65°C to dissolve the hydroxyethylcellulose;
It was then cooled to 35°C. 325 g of methyl acrylate, 175 g of glacial methacrylic acid and 0.5 g of ethylene glycol dimethacrylate as a crosslinking agent were then added to the reactor under stirring.
and azobisisobutyronitrile as catalyst 0.5
A mixture of g was added. The contents of the reactor were degassed by purging with nitrogen at a moderate flow rate (eg, 100 ml per minute). Temperature 70℃
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. The 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 passed through a vacuum vessel. The excess cake weighed 1000g. 1/5 of the overcake to analyze the product and determine the yield.
The sample was dried in a vacuum oven at 80°C for 16 hours and ground to an average of 40 mesh (US standard sieve size).
A granular acidic polymer containing approximately 34-36% methacrylic acid was prepared. The percent conversion of monomer to polymer product was 97.0%. The remainder of the percake is neutralized with a basic solution of sodium hydroxide, in which case each remaining 1/5 part of the cake is dispersed separately in 400 g of deionized water, and then
This was done by rapidly and completely adding 195 g of 10% sodium hydroxide solution (e.g., 20% excess over the theoretical amount needed to neutralize the polymer).
The resulting mass was dried in a vacuum oven at 80° C. to remove any moisture content, and then ground to a size that would pass through a 20 mesh sieve (US standard sieve size). The salt water absorption of this polymer salt was measured in a 1% sodium chloride solution. The excess cake is 24g,
This corresponded 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 were prepared by using the suspension polymerization technique of Example 1 to prepare methyl acrylate (MA) and methacrylic acid (MAA) as crosslinking agents in the amounts shown in Table 1 in different weight ratios. The polymer was prepared using ethylene glycol dimethacrylate (EDMA).
The polymers of Examples 2-12 were neutralized according to 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 the table, the absorption capacity of alkaline polymers is expressed as a multiple of the dry weight of the polymer. Absorption values were given for deionized water, 15% calcium chloride solution and 15% sodium chloride solution. For convenience of calculation, the amount of crosslinking agent shown refers to the amount of material added to the other two monomers used. The above results clearly demonstrate that the polymers 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 levels increase. The resulting product, with a water absorption content 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】

TABLE Examples 18-24 Examples 18-24 demonstrate the preparation of polymers according to the procedure of Example 1 using different weight ratios of various monomers. The polymers of Examples 18, 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 22-24 used the neutralization method of Example 1 with sodium hydroxide. The amounts of polymer components used and the absorption test results are shown in Table 1. For convenience of calculation, the amount of crosslinking agent 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. This result indicates that all _polymers tested
Although shown to be sensitive to high concentrations of NaCl, the polymer still maintains high levels of absorbance and retains 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.

Table: 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 crosslinking agent. 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), methacrylic acid (MAA) and ethylene dimethacrylate (EDMA).
The amounts of monomers used and the results are shown in the table.
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 although sodium and lithium polymers have substantially similar absorbance 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 salts have even lower absorption capacity, but
It would be particularly useful for cosmetic applications.

TABLE 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 amounts of monomers used and the results are shown in the table. A single system (MA/
MAA/EDMA) was examined across the MA range 50-80, MAA range 20-50, and EDMA range 0.03-0.3. This result is 1% for each crosslinking level.
It is shown that the maximum swelling in NaCl is obtained with polymers of about 35-40% MAA. The polymer particles gave swollen particles with the highest structural integrity.
The MAA concentration range was found to be within the range of approximately 20-40%. Above 50% MAA and within the 0.3 to 0.03 crosslinker range, the structural integrity of the swollen particles was lost. Structural integrity deteriorates even with less than 0.03 crosslinkers;
Neutralized polymers in water thus yielded irregular and impregnable particles that were indistinguishable from conventional gelled viscous slurries or solutions.

【table】

TABLE Examples 41-46 Examples 41-46 produced polymers by the suspension polymerization technique of Example 1 using methyl acrylate and methacrylic acid with varying amounts of different crosslinking agents. The results are shown in Table 1. The results show that polymers prepared with 0.1% and 0.5% diethylene glycol dimethacrylate gave swelling ratios of 25 times and 34 times at 1% NaCl, 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 glycols higher than diethylene glycol dimethacrylate, such as tetraethylene glycol, as its dimethacrylate 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 acrylic 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 crosslinking agent that does not contain hydrolyzable ester groups, so the resulting polymer is structured by hydrolytically stable carbon-carbon bonds throughout its backbone and bridges. It has been completely completed.

EXAMPLE 47 This example demonstrates a method for making the polymers of the present invention and neutralizing the polymer slurry in the presence of various surfactants. The 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 cooled to 35°C. 325 g of methyl acrylate, 175 g of glacial methacrylic acid and 0.5 g of ethylene glycol dimethacrylate as a crosslinking agent were then added to the reactor under stirring.
and azobisisobutyronitrile as catalyst 0.5
A mixture containing g was added. The contents of the reactor were then degassed by purging with nitrogen at a moderate flow rate (eg, 100 ml per minute). The temperature was increased to 70°C and the mixture was polymerized for 3 hours. For the final time, the reactor temperature was increased to 80°C to complete the reaction. The 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. One-fifth (600 g) of this slurry was 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 Company) as a surfactant. 195 g of 10% NaOH was then added to this suspension, and the slurry immediately solidified into a mass of soft, swollen, and brittle granules. The weight ratio of water to polymer in the neutralization step was 6.76:1. This brittle solid sodium polymer salt is then placed in a vacuum oven.
It was dried at 80° C. to remove any water it contained, and then ground to a size that would pass through a 20 mesh sieve (US standard sieve size). The dry product obtained loses its weight in water.
Absorbed 100 times more. In a 1% NaCl solution, 21 times its weight was absorbed. The absorption rates were 8 seconds and 21 seconds, respectively. Reference Example 48 This reference example shows the production of various absorbent articles using the polymer 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 diluted in the headbox of a conventional Noble & Wood Laboratory Sheet Machine;
Formed into 12" x 12" handsheets, dried and tested for water absorption. This article contained 10% polymer salt. This dry paper has a weight of 12
Absorbed twice as much water. B 15% of the polymer suspension prepared according to Example 47
Diluted to solids content, 10% of 20 mol% excess
Neutralized with NaOH 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. 100 g of this slurry 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 absorbed 6.6 times its weight in water. C. Six 4" x 10" 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. The resulting multiple pads were sprayed with water mist until the weight increased to 20 g. This wet pad was then heated to 80℃.
The layers were fused by drying. The pad was tightly rolled into an oblong shape, immersed in a 1% NaCl solution for several minutes, and then heated under 1.5 psi for 5 minutes.
The degree of salt water absorption was measured by compressing for a minute. This pad absorbed nine times its weight in 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 comparative example demonstrates the water and aqueous salt solution absorption rates of various commercially available water-swellable and water-insoluble polymer products.
A comparison was made with the dry polymer salt prepared according to Example 1. The tested polymers and their known chemical descriptions and results are shown in the table. This result shows that the polymer of the present invention is an unexpectedly excellent water-swellable and water-insoluble composition. In this comparative example, Comparative Substance A is identified on the market as Aqualon and is a product of Hercules. Comparative substance B is Vitera-1 on the market.
It is a product of Union Carbide. Comparative material C is identified on the market as Viterra-2 and is a product of Union Carbide Company. Comparative material D is identified on the market as Permasolve-10 and is a product of National Starch and Chemical Company. Comparative substance E was identified on the market as Permasolve-30 and is a national starch.
It is a product of And Chemical Company. Comparative material F was identified as H-span on the market and
It is a product of Mils Chemicals. This material is manufactured under license from the United States Department of Agriculture. Comparative material G is identified on the market as Dow Flake and is a product of the Dow Chemical Company and is disclosed in U.S. Pat. No. 3,980,663.
No. 3993616.

[Table] Crosslinking salts of polymer electrolytes

Claims (1)

[Scope of Claims] 1. A method for producing a water-swellable and water-insoluble polymer having a dry feel, the monomer composition being heated and stirred in water in the presence of a catalyst to polymerize the monomer composition. The polymer was separated, dried and ground to obtain a polymer powder, the monomers comprising (a) 15-50% by weight of olefinically unsaturated carboxylic acid and (b) 49.07-82% by weight of alkyl. Acrylate (alkyl group has 1 to 6 carbon atoms)
and (c) 0.03 to 3.0% by weight of a crosslinking agent made of a monomer having two or more polymerizable ethylene groups. 2 20-40 as olefinic unsaturated carboxylic acid
% by weight of methacrylic acid or acrylic acid. 3. Polymers according to claim 1 or 2, characterized in that they contain up to 8% by weight of itaconic acid, maleic acid or maleic anhydride, based on the total amount of olefinically unsaturated carboxylic acids used. Production method. 4. Any one of claims 1 to 3, characterized in that the alkyl acrylate contains 59.02 to 78% by weight of methyl acrylate, ethyl acrylate, or n-butyl acrylate.
2. Method for producing the polymer described in section. 5. The method for producing a polymer according to any one of claims 1 to 4, characterized by 0.08 to 2% by weight of a crosslinking agent. 6 Crosslinking agents include diacrylates or dimethacrylates of glycols, diacrylates or dimethacrylates of monoether glycols, diacrylates or dimethacrylates of polyether glycols, allyl esters of polymerizable unsaturated carboxylic acids, di- or trivinyl aromatic compounds, Process for producing a polymer according to claim 1 or 5, which is selected from the group of basic or tribasic di- or triallyl esters, or acrylates or methacrylates of polyols. 7. The catalyst according to claim 1, wherein the catalyst is selected from organic peroxides, inorganic persulfates or free-radical generating azo compounds, and the amount of catalyst used is from 0.01 to 2 parts by weight per 100 parts by weight of the total monomer composition. Method for producing polymers. 8. The method for producing a polymer according to claim 1, wherein a surfactant or colloid is further used in the polymerization reaction. 9 In a method for producing a water-swellable and water-insoluble polymer salt with a dry feel, the monomer composition is heated and stirred in water in the presence of a catalyst to polymerize the monomer composition, and after neutralization with a basic compound. Separate polymer salts,
After drying and grinding, a polymer salt powder is obtained, the monomers comprising: (a) 15-50% by weight of olefinically unsaturated carboxylic acid; (b) 49.07-82% by weight of alkyl acrylate (the alkyl group is 1 ~6 carbon atoms)
and (c) 0.03 to 3.0% by weight of a crosslinking agent made of a monomer having two or more polymerizable ethylene groups. 10 20~ as olefinic unsaturated carboxylic acid
A method for producing a polymer salt according to claim 9, characterized in that 40% by weight of methacrylic acid or acrylic acid is used. 11. Polymer salt according to claim 9 or 10, 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. manufacturing method. 12 59.02-78% by weight of methyl acrylate,
The method for producing a polymer salt according to any one of claims 9 to 11, characterized in that the alkyl acrylate contains ethyl acrylate or n-butyl acrylate. 13. The method for producing a polymer salt according to any one of claims 9 to 12, characterized by 0.08 to 2% by weight of a crosslinking agent. 14 Crosslinking agents include diacrylates or dimethacrylates of glycols, diacrylates or dimethacrylates of monoether glycols, diacrylates or dimethacrylates of polyether glycols, allyl esters of polymerizable unsaturated carboxylic acids, di- or trivinyl aromatic compounds, Process for producing a polymer salt according to claim 9 or 13, which is selected from the group of basic or tribasic di- or triallyl esters, or acrylates or methacrylates of polyols. 15. The catalyst according to claim 9, wherein the catalyst is selected from organic peroxides, inorganic persulfates or free radical generating azo compounds, and the amount of catalyst used is from 0.01 to 2 parts by weight per 100 parts by weight of the total monomer composition. Method for producing polymer salt. 16. The method for producing a polymer salt according to claim 9, wherein a surfactant or colloid is further used in the polymerization reaction. 17. The method for producing a polymer salt according to claim 9, wherein the basic compound for neutralization is selected from an alkali metal hydroxide, an alkali metal carbonate, ammonium hydroxide, ammonium carbonate, or an organic amine. 18 The amount of water in the neutralization reaction is the total amount of water: the ratio of polymer is 4.
The method for producing a polymer salt according to claim 9, wherein the ratio is 10:1. 19. A method for producing a polymer salt according to claim 9, wherein the polymer is ground into particles of 50 μm to 2 mm.