KR840000370B1 - Method for producing photopolymerized hydrophilic interpolymers of unsaturated carboxylic acid and esters - Google Patents

Abstract

A copolymer is prepd. from (a) 50-90 wt.% of acrylic acid, with 60-100% of the COOH gps. neutralized with an alkali metal or NH4 before polymerization, (b) 2-25 wt.% of a higher acrylic ester of formula CH2=CR'-COOR, where R' is H or (m)ethyl; and R is C10-30 alkyl, and (c) 5-30 wt.% of a lower acrylic ester of formula CH2=CR'-COOR", where R" is C1-8 alkyl; 0-50% of (c) may be replaced by (meth) acrylonitrile or (meth)acrylamide. The mixt. polymerized by exposure to an electron beam.

Description

Preparation of Spun Polymerized Hydrophilic Interpolymers of Unsaturated Carboxylic Acids and Esters

Various hydrophilic polymers useful in the preparation of moisture absorbent films and fibers have been reported in the prior art. U. S. Patent No. 3,915, 921 describes copolymers of unsaturated carboxylic acid monomers with alkyl acrylate esters wherein the alkyl group contains 10-30 carbon atoms. However, the high Tg of these polymers makes it difficult to inject them in the form of fibers or films. Moreover, films compressed from powders require high temperatures, the films are weak and liable to break, and have a reduced initial moisture absorption.

U.S. Patent No. 4,062,817 discloses unsaturated copolymerizable carboxylic acids, at least one alkylacrylate or methacrylate having 10-30 carbon atoms in the alkyl group and another alkyl acrylate having 1-8 carbon atoms in the alkyl group. Or polymers with methacrylates are described. This composition alleviates many of the deficiencies of previous compositions. Further improvements in hydrophilic properties were obtained with the compositions described in US Pat. No. 4,066,583.

This patent facilitates injection of the copolymer of the type described in the 817 patent and (2) the polymer, except that (1) 30-90% of the carboxyl groups are neutralized with alkali metal or ammonia after copolymerization. A composition consisting of important fatty glycols, plasticizers is described.

The present invention relates to 50-90% by weight of acrylic acid (of which 60-100% of carboxyl groups are neutralized with alkali metal hydroxide before polymerization), 2-20% by weight of alkyl acrylate or methacrylate, wherein To provide a process for preparing an intermediate polymer from a mixture of monomers consisting of 10-30 carbon atoms), 5-30% by weight of alkyl acrylate, wherein the alkyl group has 1-9 carbon atoms. Is exposed to an electron beam source of sufficient strength to polymerize the monomers described above. The polymers can be polymerized into any desired form, including films and fibers most useful for absorbing moisture and human fluids such as urine or blood.

The present invention relates to a process for preparing interpolymers having significant absorption and retention properties of water and ionic solutions such as urine or blood using an electron beam spinning method. More specifically, the present invention deals with a process for producing polymers from monomer mixtures composed of the following compositions.

(a) 50-90% by weight acrylic acid, neutralized with alkali metal hydroxide or ammonia base prior to polymerization of 60-100%, most preferably 80-100% carboxyl groups, (b) 2- As a higher acrylic ester monomer having the following structural formula of 25% by weight,

Wherein R 'is hydrogen, methyl or ethyl, R is an alkyl group having 10-30 carbon atoms, (c) a lower acrylic ester monomer having the following structural formula of 5-30% by weight,

Where R "is a lower alkyl group having 1-8 carbon atoms, 0-50% of this lower acrylic ester is substituted by acryl or methacryl nitrile or amide.

The above method is to polymerize the monomers by subjecting them to electron beams of sufficient strength.

Higher acrylic ester monomers have long chain aliphatic groups and can be represented by the following structural formulas,

Wherein R is an alkyl group having 10-30, preferably 10-18 carbon atoms, and R 'is a hydrogen, methyl or ethyl group. Representative higher alkyl acrylate esters include decyl acrylate, isodecyl acrylate, lauryl acrylate, stearyl acrylate, behenyl acrylate and melyl acrylate and the corresponding alkacrylates including, for example, methacrylates. Can be mentioned. Mixtures of two or three or more long chain acrylic esters can be successfully polymerized with one of the carboxyl monomers, thereby obtaining useful thickening resins of the present invention. Particularly useful are acrylates and methacrylates having alkyl groups comprising 10-18 carbon atoms present in an amount of about 5-20% by weight of the total monomers. Excellent polymers were made with 15 ± 5 wt% isodecyl methacrylate, 10 ± 3 wt% lauryl methacrylate and 7 ± 3 wt% stearyl methacrylate.

Lower acrylic esters can be represented by the following structural formula:

Wherein R is an alkyl, alkoxy, haloalkyl, cyanoalkyl, hydroxyalkyl and a pseudo group having 1-8 carbon atoms, and R 'is hydrogen, methyl or ethyl group. R 'is preferably hydrogen or methyl, R is preferably alkyl, most preferably methyl and the lower ester is present in an amount of 5-20, most preferably 7-17% by weight.

Representative acrylates include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, methyl methacrylate, methyl acrylate, ethyl methacrylate, octyl acrylate, heptyl Acrylate, octyl methacrylate, isopropyl methacrylate, 2-ethyl-hexyl acrylate, nonyl acrylate, hexyl acrylate, n-hexyl methacrylate, hydroxy ethyl methacrylate, dimethyl amino ethyl methacrylate There is.

In addition to the above-mentioned monomers used to prepare the copolymers of the present invention, small amounts or up to about 5% by weight of additional monomers may also be used. Whether these additional monomers are to be employed depends on the end use and the physical properties required, ie the rate and extent of absorption and tear strength required for the film or fabric. Such additional monomers are described below.

One form of such additional monomers is α, β-olefinically unsaturated nitriles, preferably having 3-10 carbon atoms such as acrylonitrile, methacrylonitrile, ethacrylonitrile, chloroacrylonitrile and the like. Monoolefinically unsaturated nitriles. Best nitriles are acrylonitrile and methacrylonitrile.

Another useful additional monomer that may be bound to the inventive interpolymers is a monoethylenically unsaturated amide with at least one hydrogen on the amide nitrogen, and the olefinic unsaturation is α-β for the carbonyl group.

Good amides have the following structural formula:

In the above formula, R ₃ is a group consisting of hydrogen and an alkyl group having 1-4 carbon atoms, and R ₄ is a group consisting of hydrogen and an alkyl group having 1-6 carbon atoms. Representative amides include acrylamide, methacrylamide, N-methyl acrylamide, Nt-butyl acrylamide, N-cyclohexyl acrylamide, N-ethyl acrylamide and the like. Best amides are acrylamide and methacrylamide.

Other acrylamides include N-alkylol amides of α, β-olefinically unsaturated carboxylic acids, such as N-methylol acrylamide, N-ethanol acrylamide, N-propane, such as acrylamide, and the like. It has 10 carbon atoms.

Good monomers in the form of N-alkylol amides are N-alkylol amides of α, β-monoolefinically unsaturated monocarboxylic acids, with N-methylol acrylamide being the best.

Also useful are N-alkoxymethyl acrylamides having the structure below.

Wherein R ₅ is selected from the group consisting of hydrogen and methyl, and R ₆ is an alkyl group having 1-8 carbon atoms. By reference with reference to essentially N-substituted alkoxymethyl amides, the term "acrylamide" includes "methacrylamide" in its meaning. Good alkoxymethyl acrylamides are alkyl groups in which R ₆ contains 2-5 carbon atoms, in particular N-butoxymethyl acrylamide.

The monomer mixtures are prepared as aqueous dispersants which alleviate the need for organic solvents. This eliminates the pollution problems caused by the removal of organic solvents or the cost problems associated with the removal of contaminants. In order to obtain a stable homogeneous dispersion of monomers, the aqueous dispersion preferably comprises 0.01-5%, preferably 0.1-1%, of anionic, coionic or nonionic dispersant or a mixture of these dispersants. Useful anionic dispersants include alkali metal or ammonium salts of sulfates of alcohols having 8-18 carbon atoms, such as sodium lauryl sulfate; Ethanolamine lauryl sulfate, ethylamine lauryl sulfate; Alkali metal and ammonium salts of sulfonated and paraffinic oils; Sodium salts of aromatic sulfonic acids such as dodecane-l-sulfonic acid and octadecane-l-sulfonic acid; Aralkyl sulfonates such as sodium isopropyl benzene sulfonate, sodium dodecyl benzene sulfonate and sodium isobutyl naphthalene sulfonate; Alkali metal and ammonium salts of sulfonated dicarboxylic acid esters such as sodium dioctyl sulfosuccinate, sodium sodium-b-octadecyl sulfosuccinate; Alkali metal or ammonium salts, such as free acids of complex organic mono- and diphosphate esters, sulfo succinic acid derivatives (aerosol dispersants), organic phosphate esters (GAFAC dispersants) and the like. In addition to nonionic dispersants such as octyl- or nonyl-phenyl polyethoxy ethanol, PLURONIC and TRITON dispersants may also be used.

Coionic dispersants such as dicarboxylic coconut derivatives (MIRANOL) are also useful. Other examples of useful dispersants are described starting with J. Van Alphen's "Rubber Chemicals", Elsevier Publishing Co., page 1956, page 102.

Although cross-linking agents are not required to obtain the useful, highly absorbent compositions of the present invention, films made from compositions comprising cross-linking agents tend to have greater gel strength and copolymers have improved expandability under defined pressures. It is preferable to use a crosslinking agent because it is likely to be. The crosslinking agent may be used at a concentration of about 0-15%, preferably about 1-10% by weight, based on the total weight of the monomers.

Useful crosslinking monomers are polyalkenyl polyethers with one or more alkenyl ether groups per molecule. Most useful are alkenyl groups with olefinic double bonds attached to the terminal methylene group, CH ₂ = C <. Other crosslinking monomers are for example diallyl esters, dimetallyl esters, allyl or metallyl acrylates and acrylamides, tetraallyl tins, tetravinyl silanes, polaralkenyl methanes, diacrylates and dimethylacrylates, di Divinyl compounds such as vinyl benzene, polyallyl phosphate, diallyloxy compounds and phosphite esters and the like. Typical agents include allyl pentaerythritol, allyl sucrose, trimethylol propane triacrylate, 1,6-hexane diol diacrylate, pentaerythritol, triacrylate, tetramethylene dimethacrylate, tetramethylene diacrylate , Ethylene diacrylate, ethylene dimethacrylate, diethylene glycol dimethacrylate, triallyl cyanurate, triallyl isocyanurate, diallyl itaconate, polyethylene glycol acrylate and methacrylate, and the like. .

As mentioned above, polymers from the above-mentioned monomers are prepared by exposing the monomers to electron beam radiation of sufficient intensity so that the monomers are actually completely polymerized. The amount and intensity of spinning required will depend on the thickness of the film, the particular monomers employed, the rate of polymerization required and its viscosity. In general, for applications where the resulting polymers are particularly useful films, a sheet or fiber of about 0.5-5 millimeters thick is most preferred. Therefore, relatively low intensity electron non-executors of generally 200 KV or less will be sufficient to affect the polymerization. The type of monomer system employed in the present invention generally requires spinning of 1-15 M rads. However, the amount and intensity of the radiation must be optimized for each system taking into account all the parameters: the monomers employed, the thickness of the film, the rate of polymerization required, the degree of polymerization and the emissivity required.

The copolymers of the present invention can be spontaneously polymerized in any form, the film form being the most practical. The resulting film is a resilient and flexible material with a significant degree of strength. If a fine, flaky form is desired, the film can be dried and then converted to such a form by grinding or grinding it in a standard apparatus.

As water absorbing materials, these polymers have many uses in the form of films, fibers, fabrics and the like. They are particularly useful in the disposable nonwovens industry which requires polymers to absorb and retain moisture and ionic physiological fluids. An important feature of these polymers is their elevated thickening properties even in the presence of salts. Specific applications include disposable diapers, medical-surgical supplies, and personal care. The materials of the present invention can also be used as suitable additives to significantly increase the absorption of conventional absorbents such as cotton, wood pulp and other cellulosic absorbents used in applications such as scrubbers, surgical sponges, sanitary napkins and the like. . For example, in certain applications, such as disposable diapers, there is an inner layer of soft absorbent nonwoven material that absorbs urine and passes it through an inner layer of downy fibrous absorbent material, where such nonwoven fibers During construction, agglomerates or fibers of the polymer of the present invention may be contained, followed by inclusion of an impermeable plastic that is incidental as polyethylene.

Films of the copolymers of the present invention can be used between the outer plastic layer and the inner down absorbent layer. The use of the polymers of the present invention can reduce the volume size of many disposable nonwovens.

The copolymers of the present invention can also be used in water treatment, metal treatment processes, ore sorting and flotation, agriculture applications such as soil treatment or seed coating, or any application where the inherent properties of the polymer are desired, such as thickening in aqueous media. It can also be used as flocculant in cases.

To prepare the copolymer, monomers, water and dispersant are mixed in a container. A film or fiber is then formed from the monomer mixture, which polymerizes rapidly upon exposure to electron beam radiation. The various steps in the polymerization process are described in detail below.

Monomer Mixture Preparation: The monomer mixture can be prepared by one of two simple processes: One method is to dissolve the previously prepared and dried alkali metal or ammonium acrylate in water and then add a dispersant thereto. Then a mixture of acrylate esters is added to the aqueous solution. Another method is to prepare the acrylate salt by adding acrylic acid to an appropriate amount of a low temperature aqueous alkali solution (eg KOH, NaOH or NH ₄ OH) while cooling. Then a mixture of acrylate esters is added to the aqueous solution. Dispersants may be added at any time.

Film Preparation: Aqueous monomer dispersions are prepared on suitable substrates (e.g., Mylar, using a Boston-Bradley adjustable blade, and sprayed or by other known methods) to the desired thickness. ), Polyethylene, paper, etc.). The liquid film is then exposed to electron beam spinning to polymerize the monomer mixture into a soft and flexible form. If desired, such films can be dried in an oven at about 50 ° C. for 1-15 minutes. After drying, the film may still have some flexibility or become brittle depending on the drying time.

The present invention is further described through the following examples.

EXAMPLE

The monomer mixture was prepared according to the method described above using the following ingredients:

The monomer mixture was 95% neutralized before polymerization. The mixture developed to make a 2 millimeter film, which was exposed to electron beam spinning of 0.4 M rad. The resulting film was soft, elastic and flexible. It absorbed a hypothetical urine composition weighing more than 30 times its own weight and was measured according to the Demand Wettability Test described below.

Required Wetness Test (DWT) —A test diaper is made from a 4 inch diameter pad (10.16 cm) using a commercial diaper material. Films made from the aggregates tested for absorption were placed in the center of the test diaper between two layers of downwood (wood pulp). Diapers without polymer film are used as background values. The required wetness meter is a burette filled with the test fluid and tightly fixed at the top, with air leaking from the side, and the delivery orifice on the bottom connected to the sample holder by a flexible tube. The sample holder has a hole in the center that is connected to a flexible tube connected to the delivery orifice of the burette. The sample holder is a lever having an air outlet hole in the burette. With such a closed system device, the fluid in the flexible tube flowing out of the hole in the sample holder is at zero pressure. Thus, when the test diaper is positioned on the sample holder above the hole, it absorbs the fluid itself through wick absorption.

The self-absorbing force of the sample determines the speed and amount of fluid released from the burette. The amount of fluid released at any given time can be easily read by calibrating the burette. An additional feature is that the absorbance can be measured over a range of pressures that can be obtained by placing various weights on top of the test diaper. This pressure is intended to simulate the pressure applied on the diaper in practical use.

These tests are described in detail in Lichstein's "Required Wetting, a New Method for Measuring Fabric Absorption Properties" Symposium Paper-Inda (INDA) Technical Symposium, 1974, pp. 129-142.

Claims (1)

As described above in the text, 50-90% by weight of acrylic acid, in which 60-100% of carboxyl groups are neutralized with an alkali metal or ammonium base before polymerization,

Structural formula wherein 2-25% by weight higher acrylic ester monomer and 0-50% lower acrylic ester are substituted with acrylic or methacryl nitrile or amino

Spinning of unsaturated carboxylic acids and esters characterized by the fact that the comonomers composed of 5-30% by weight of lower acrylic ester monomers are subjected to sufficient strength and amount, i.e., electron beam spinning, of 1-15 M rad to actually completely polymerize the monomers. A method of making a polymerized hydrophilic intermediate polymer.