JP2006527179A - (Meth) acrylic acid esters of alkylenylene glycol and uses thereof - Google Patents

Abstract

The present invention relates to a compound of formula (I) [wherein AO independently represents -O-CHR3-CHR4- or -CHR3-CHR4-O- with respect to each AO, wherein R3 and R4 are independent of each other. H, linear or branched C1-C8-alkyl, p1 is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34 or 35, and p2 is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34 or 35, and n is 1, 2, 3, 4, 5, 6 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, and R1, R2 are independently H or CH3, with at least one AO in (AO) p1 And (AO) for at least one AO in p2, R3 and R4 do not both represent H at the same time] a novel (meth) acrylic ester of a polyalkoxylated glycol, a simplified form of the ester And the use of the reaction mixture obtained thereby.

Description

  The present invention relates to a novel (meth) acrylic ester of a polyalkoxylated glycol, a simplified process for the preparation of the ester and the use of the reaction mixture thus obtained.

  Swellable hydrogel-forming polymers, so-called superabsorbents (superabsorbent polymers, SAP) are known from the prior art. This is a flexible hydrophilic polymer network that may be ionic or non-ionic. They absorb aqueous fluids and combine to form hydrogels, thus to produce tampons, diapers, sanitary products, incontinence products, children's training pants, shoe insoles, and when absorbing body fluids It is advantageously used for other hygiene products. Superabsorbers are also used in other technical fields that absorb liquids, especially water or aqueous solutions. These areas are for example storage, packaging, transport (water sensitive goods such as fresh flower transport, impact protection packaging materials), food products (fish, raw meat transport, fresh fish / raw meat packaging water, blood absorption ), Medicine (for wound plasters, for wound dressings or other water-absorbing materials for wet wounds), cosmetics (carrier materials for pharmaceutical chemicals and pharmaceuticals, rheumatic plasters, super Sonic gel, cooling gel, cosmetic thickener, sunscreen), thickener for oil-in-water or water-in-oil emulsion, textiles (gloves, sports clothing, moisture control in textiles, insoles of shoes) ), Chemical industrial applications (catalysts for organic reactions, fixation of large functional molecules (enzymes), adhesives for the formation of aggregates, heat accumulators, filter aids, hydrophilic components in polymer laminates, dispersants , Agent), civil engineering and construction, installation (powder injection molding, clay-based plasters, anti-vibration media, auxiliary agent for tunnel excavation in wet ground, cable jacket), water treatment, waste Treatment (especially solidification of aqueous waste), water separation (defrosting agents, reusable sandbags), cleaning, agriculture (irrigation, thawing water and retention of precipitation, composting additives, forests from fungal / insect damage Protection, delayed release of plant actives), fire protection (sparking) (SAP gel covering of houses or walls of houses), because water has a very high heat capacity, Spraying SAP gels in case of fire, eg forest fires), coextrusion of thermoplastic polymers (hydrophilization of multilayer films), film capable of absorbing water And SAP-containing films for maintaining the freshness of fruits and vegetables that can be packaged with a wet film (for example, agricultural films for storing rainwater and dew condensation water), and the production of thermoplastic molded bodies, SAP without condensation The water released from the fruits and vegetables is stored, and the water is partially released again into the fruits and vegetables, so that neither rot nor wilt occurs. For example, SAP-polystyrene coextrudates for the packaging of foodstuffs such as meat, fish, poultry, fruits and vegetables), carrier substances in pharmaceutical preparations (pharmaceuticals, pesticides). In hygiene products, the superabsorbent is usually present in a so-called absorbent core material that contains fibers (cellulosic fibers) as other materials, and the fibers are a kind of liquid storage member that has a medium amount of liquid that collides spontaneously. In the absorbent core material and ensure good fluid flow path formation to the superabsorbent.

  A recent trend in diaper construction is to produce thinner structures with reduced cellulosic fiber percentage and increased hydrogel percentage. With the trend toward increasingly thinner diaper structures, the required profile for water-swellable hydrophilic polymers has clearly changed over the years. At the beginning of the development, the superabsorbent hydrogel was first emphasized by its very high swelling ability, but later it was found that it was also very important that the superabsorbent could pass and disperse the liquid. . It has been found that conventional superabsorbents are significantly more difficult to transport into the interior of the particles or stop at all because the surface swells significantly when wetted by the liquid. This property of the superabsorbent is also referred to as “gel blocking”. Based on the relatively high load of hygiene products (polymer per area unit), the polymer does not form a barrier layer for subsequent liquids in the swollen state. If the product has good transport properties, the optimal use of all sanitary products can be guaranteed. Thus, the phenomenon of gel blocking is prevented, and in extreme cases the liquid flows out, leading to so-called sanitary sanitation. Therefore, the passage and dispersion of liquid is extremely important in the initial absorption of body fluids.

  For example, hydrogels with high gel strength in the swollen state have good transport properties. Gels that only have low gel strength can be deformed by the applied pressure (body pressure), closing the pores of the superabsorbent / cellulose fiber-absorber and thereby preventing further liquid absorption. The Increased gel strength is usually achieved by higher cross-linking, but this reduces the water retention of the product. A suitable method for improving gel strength is surface postcrosslinking. In this method, the dried superabsorbent having an average crosslinking density is further crosslinked. Surface postcrosslinking increases the crosslink density of the shell of the superabsorbent particles, which increases the absorption to a relatively high level under pressure loading. While the absorbent capacity of the superabsorber shell is reduced, the core structure of the superabsorber particle has an improved absorption capacity compared to the shell due to the presence of mobile polymer chains, so improved liquid transport due to the shell structure Is guaranteed, and the gel blocking effect does not appear. It would be desirable to utilize the full capacity of the superabsorber at a time difference rather than spontaneously. Since hygiene articles are usually struck several times by urine, the absorption capacity of the superabsorbent should not be consumed by the first treatment.

  Hydrophilic highly swellable hydrogels are in particular polymers composed of (co) polymerized hydrophilic monomers, graft (co) polymers of one or more hydrophilic monomers on suitable graft bases, crosslinked cellulose ethers or starch ethers, crosslinked Carboxymethyl cellulose, partially crosslinked polyalkylene oxides or natural products that can swell in aqueous liquids, such as guar derivatives. Such hydrogels are used as products that absorb aqueous solutions to produce diapers, tampons, sanitary products and other sanitary products, or also as water retention agents in agricultural and horticulture.

  In order to improve application properties such as rewet and AUL in diapers, hydrophilic, highly swellable hydrogels are generally surface or gel postcrosslinked. These postcrosslinkings are known per se to the person skilled in the art and are preferably carried out in the aqueous gel phase or as surface postcrosslinking of the ground and screened polymer particles.

From WO 93/21237, alkoxylated (meth) acrylates of polyvalent C ₂ -C ₁₀ -hydrocarbons are known as crosslinking agents. Trimethylpropane crosslinkers corresponding to SR351, SR454, SR502, SR9035 and SR415 were used. These crosslinkers have 0, 3, 9, 15 or 20 EO units per TMP. According to WO 93/21237, 3 × 2-7 EO units per TMP, in particular 3 × 4-6 EO units per TMP, are advantageous.

  The disadvantages of these compounds are that they are expensive to at least partially separate the materials used and by-products (the cross-linking agents used in the above documents have an acrylic acid content of less than 0.1% by weight). A purification operation is necessary.

  In EP264841 EO-PO-EO-block polymers are esterified with methacrylic acid.

  In DE2215512 and DE2215509, diacrylates of polyethylene glycol are described as crosslinkers for copolymers for dicarboxylic anhydrides.

  EP 559476 and US Pat. No. 4,351,922 describe polyethylene glycol and polyethylene glycol-polypropylene glycol block diacrylates as crosslinkers for hydrogels.

  In the case of known cross-linking agents, the increase in the extractable fraction is manifested by the polymer structure while the sanitary article containing the swollen superabsorbent is wet.

  Higher (meth) acrylic by esterification of such (meth) acrylic acid with an acid-catalyzed reaction in the presence of such an inhibitor / inhibitor system and optionally a solvent such as benzene, toluene, cyclohexane The production of acid esters is generally known.

  As is well known, the formation of esters from (meth) acrylic acid and alcohols is based on an equilibrium reaction, so that in order to achieve an economic reaction rate, it is usual to use excess materials and / or The esterified water formed and / or the target ester is removed from the equilibrium.

  Therefore, in the production of higher (meth) acrylic acid esters, the reaction water is usually removed, and in many cases (meth) acrylic acid is used in excess.

  US 4,187,383 describes a process for esterifying (meth) acrylic acid using an organic polyol in an excess of 2 to 3: 1 from equivalents at a reaction temperature of 20 to 80 ° C.

  The disadvantage of this process is that the reaction time can be up to 35 hours due to the low reaction temperature and that excess acid in the reaction mixture is removed by neutralization and subsequent phase separation.

  WO 2001/14438 (Derwent Abstract 2001-191644 / 19) and WO 2001/10920 (Chemical Abstracts 134: 163502) describe (meth) acrylic acid in a polyalkylene glycol ratio of 3: 1 to 50: 1. A method of esterifying in the presence of an acid and a polymerization inhibitor using a monoalkyl ether and a residue comprising (meth) acrylic acid ester and (meth) acrylic acid after deactivation of the acid catalyst at a pH of 1.5 to 3. 5 and their use as cement additives.

  The disadvantages of these methods are that they are limited to polyalkylene glycol monoalkyl ethers, that the catalyst must be deactivated, and that such copolymers cannot be used as crosslinkers for hydrogels. is there. This is because they only have one functional group.

  Providing another compound that can be used as a radical cross-linking agent for polymers, especially for high-absorbers, and a manufacturing method for substances that can be used as radical cross-linking agents for high-absorbers There was a problem of simplification. Furthermore, there has been a desire for a crosslinking agent that has a high hydrolytic stability and / or at the same time produces a gel that is very well dispersible in the production process for superabsorbents.

  The problem is represented by the general formula I

［式中、ＡＯはそれぞれのＡＯに関して相互に無関係に−Ｏ−ＣＨＲ３−ＣＨＲ４−または−ＣＨＲ３−ＣＨＲ４−Ｏ−を表し、その際、Ｒ３およびＲ４は相互に無関係にＨ、線状もしくは分枝鎖状のＣ１〜Ｃ８−アルキルを表し、
ｐ１は１、２、３、４、５、６、７、８、９、１０、１１、１２、１３、１４、１５、１６、１７、１８、１９、２０、２１、２２、２３、２４、２５、２６、２７、２８、２９、３０、３１、３２、３３、３４または３５であり、
ｐ２は１、２、３、４、５、６、７、８、９、１０、１１、１２、１３、１４、１５、１６、１７、１８、１９、２０、２１、２２、２３、２４、２５、２６、２７、２８、２９、３０、３１、３２、３３、３４または３５であり、
ｎは１、２、３、４、５、６、７、８、９、１０、１１、１２、１３、１４、１５、１６、１７、１８、１９、２０、２１、２２、２３、２４、２５、２６、２７、２８、２９、３０、３１、３２、３３、３４、３５、３６、３７、３８、３９、４０、４１、４２、４３、４４、４５、４６、４７、４８、４９、５０、５１、５２、５３、５４、５５、５６、５７、５８、５９、６０、６１、６２、６３、６４、６５、６６、６７、６８、６９、７０、７１、７２、７３、７４、７５、７６、７７、７８、７９、８０、８１、８２、８３、８４、８５、８６、８７、８８、８９、９０、９１、９２、９３、９４、９５、９６、９７、９８、９９、１００であり、
Ｒ１、Ｒ２は相互に無関係にＨまたはＣＨ３であり、
その際、少なくとも（ＡＯ）ｐ１中の１のＡＯに関して、ならびに（ＡＯ）ｐ２中の少なくとも１のＡＯに関しては、Ｒ３およびＲ４は両方が同時にＨを表すことはない］のエステルＦを提供することにより解決される。

[Wherein AO independently represents -O-CHR3-CHR4- or -CHR3-CHR4-O- with respect to each AO, wherein R3 and R4 independently represent H, linear or branched. Represents a chain C1-C8-alkyl,
p1 is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34 or 35,
p2 is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34 or 35,
n is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100,
R1 and R2 are independently H or CH3,
Wherein R3 and R4 do not both represent H at the same time for at least one AO in (AO) p1 and for at least one AO in (AO) p2]. It is solved by.

  The AO unit is configured such that a polyether is generated and a peroxide is not generated.

  Advantageously, for all AOs, R3 and R4 have the same meaning independently of one another, ie obtained by alkoxylation of, for example, ethylene glycol or polyethylene glycol only with alkylene oxide, for example propylene oxide, Ester F having the meaning

  Preference is given to esters F having the above meanings in which R3 and R4 represent H.

  Preference is given to esters F having the above meanings, in which R3 and R4 independently represent CH3, CH2CH3, (CH2) 2-CH3 or (CH2) 7-CH3, preferably CH3.

  Preference is furthermore given to esters F having the above meanings, wherein p1 represents 1, 2, 3, 4 or 5, particularly preferably 1, 2 or 3, in particular 1 or a number from 14 to 27. is there.

  Preference is furthermore given to esters F having the above meanings, in which p2 represents 1, 2, 3, 4 or 5, particularly preferably 1, 2 or 3, in particular 1 or a number from 14 to 27. is there.

  Preference is given to esters F having the above meaning, wherein n is a number from 2 to 50, preferably from 5 to 30, in particular from 10 to 26.

  Preference is given to esters F having the above meaning in which the diol component (AO) p1-[-O-CH2-CH2-] n-O- (AO) p2 has an average molecular weight of 300 to 500, in particular about 400.

  Preference is given to the esters F having the above meaning in which the diol component (AO) p1-[-O-CH2-CH2-] n-O- (AO) p2 has an average molecular weight of 2000 to 4000, in particular 2500 to 3500. .

  The diol component is advantageous in the case of the esters F having the above meaning which are constructed symmetrically with respect to (AO) p1 and (AO) p2. Symmetric means that p1 and p2 are substantially identical, that is, the absolute distance of the difference between p1 and p2 is 3 or less, preferably 2 or less, particularly preferably 1 or less. It is understood that it is 0 in particular.

  Furthermore, it is advantageous in the case of the esters F having the above-mentioned meanings which are structurally similar to one another with respect to (AO) p1 and (AO) p2. Structurally similar means that each (AO) p1 component and (AO) p2 component are made to (poly) ethylene glycol by synthesizing at the same time, i.e., both have different alkoxides (random (AO) p Understood to be obtained from a component or a continuous synthesis (consisting of a block (AO) p component), in particular all diols representing the same and, in this case, preferably diols consisting of propylene oxide Ingredients are advantageous.

  Preference is given to esters F having the above meanings, wherein R1 and R2 are identical and are preferably H.

  According to the invention, the ester F of the above formula having the above meaning can be used as an internal cross-linking agent in particular to produce a hydrogel-forming polymer that absorbs an aqueous liquid. Another advantageous internal cross-linking agent is a di (meth) acrylate, in particular a polypropylene glycol diacrylate having 2, 3, 4 or 5, in particular 2 or 3, propylene glycol units.

  Alkoxylated glycols are further represented by the formula II

［式中、ＡＯ、Ｒ３、Ｒ４、ｐ１、ｐ２、ｎは上記の意味を有するか、またはｐ１＝ｎ＝０であり、ｐ２は２、３、４または５であり、Ｒ３はＨであり、Ｒ４はＣＨ３である］の化合物である。

[Wherein AO, R3, R4, p1, p2, n have the above meanings, or p1 = n = 0, p2 is 2, 3, 4 or 5, R3 is H, R4 is CH3].

Another challenge is
a) reacting an alkoxylated glycol with (meth) acrylic acid in the presence of at least one esterification catalyst C and at least one polymerization inhibitor D and optionally a solvent E which forms an azeotrope with water to form an ester. Forming F,
b) optionally removing at least part of the water produced in a) from the reaction mixture, wherein b) can be carried out during and / or after a),
f) optionally neutralizing the reaction mixture;
h) if solvent E is used, optionally using (meth) acrylic acid comprising a step of removing the solvent by distillation and / or i) stripping with an inert gas under the reaction conditions. This is solved by a process for preparing esters F of alkoxylated glycols.

In this case, the advantage is
-2.1: 1 molar excess of (meth) acrylic acid with respect to the alkoxylated glycol and-optionally neutralized (meta) contained in the reaction mixture obtained after the last step ) Acrylic acid substantially remains in the reaction mixture.

  (Meth) acrylic acid is understood in the context of the present invention to be methacrylic acid, acrylic acid or a mixture of methacrylic acid and acrylic acid. Preference is given to acrylic acid.

  If the pure form of ester F is desired, the ester can be purified by known separation methods.

  The molar excess of (meth) acrylic acid relative to the alkoxylated glycol is at least 2.1: 1, preferably at least 2.2: 1, particularly preferably at least 2.5: 1, particularly preferably. At least 3: 1 and in particular at least 5: 1.

  In a preferred embodiment, the (meth) acrylic acid is, for example, greater than 10: 1, preferably greater than 20: 1, particularly preferably greater than 40: 1, particularly preferably greater than 100: 1. In excess of 150: 1 and in particular greater than 200: 1.

  The esterification product obtained in this way can be used as a radical crosslinker in the hydrogel without further purification, in particular without separating off the substantial excess of (meth) acrylic acid and the content of esterification catalyst C. Can be used.

  Cross-linking is understood in this specification to be radical cross-linking (gel cross-linking of linear or weakly cross-linked polymers, internal cross-linking, network cross-linking) unless otherwise stated. This crosslinking can be carried out by radical or cationic polymerization mechanisms or by other, for example Michael addition, esterification or transesterification mechanisms, preferably by radical polymerization.

  Hydrogel-forming polymers that absorb aqueous liquids preferably absorb at least distilled water of its own weight, preferably 10 times its own weight, in particular 20 times its own weight. It is also achieved under a pressure of 0.7 psi.

  The reaction of glycols with alkylene oxides is known per se to those skilled in the art. A possible embodiment is described in Houben-Weyl, Methoden der Organischen Chemie, 4th edition, 1979, Thiem Verlag, Stuttgart, Heinz Kropf, volume 6 / 1a, part 1, pages 373-385. .

  To produce the compound of formula II, for example, the glycol is first reacted with EO to give the desired polyethylene glycol and then subsequently reacted with PO.

  This can be done, for example, by charging about 72 g of glycol or a corresponding amount of polyethylene glycol into an autoclave with 0.5 g of 45% KOH in water and dehydrating together at 80 ° C. and reduced pressure (about 20 mbar). it can. The corresponding amount of propylene oxide is then added at 145 to 155 ° C. and reacted at this temperature under elevated pressure. The reaction is complete when no more pressure changes are observed. The mixture is then stirred for a further 30 minutes at 150 ° C. The corresponding amount of propylene oxide is subsequently metered in at an elevated pressure at 120 to 130 ° C. for a relatively long time and reacted in the same way. After washing with inert gas and cooling to 60 ° C., the catalyst is separated off by addition of sodium pyrophosphate and subsequent filtration.

Alternatively a commercially available alkoxylated glycols, for example dipropylene glycol and tripropylene glycol or PO-EO-PO type triblock polymer, e.g. Pluronic ^(R) type RPE polymer 1720,1740,2035,2510,2520,2525 or 3110 Can also be used.

  No special requirement is set for the viscosity of the polyhydric alcohol that can be used according to the invention, but it should be able to be pumped without problems at temperatures up to about 80 ° C., preferably the polyhydric alcohol has a viscosity below 1000 mPas. Preferably have a viscosity lower than 800 mPas and particularly preferably lower than 500 mPas.

  The esterification catalyst C that can be used according to the invention is sulfuric acid, aryl sulfonic acids or alkyl sulfonic acids or mixtures thereof. Examples for arylsulfonic acids are benzenesulfonic acid, p-toluenesulfonic acid or dodecylbenzenesulfonic acid. Examples for alkyl sulfonic acids are methane sulfonic acid, ethane sulfonic acid or trifluoromethane sulfonic acid. Strongly acidic ion exchangers or zeolites can also be used as esterification catalysts. Preference is given to sulfuric acid and ion exchangers.

Polymerization inhibitors D that can be used according to the invention are phenols such as alkylphenols, such as o-, m- or p-cresol (methylphenol), 2-t-butyl-4-methylphenol, 6-t-butyl. -2,4-dimethyl-phenol, 2,6-di-t-butyl-4-methylphenol, 2-t-butylphenol, 4-t-butylphenol, 2,4-di-t-butylphenol, 2-methyl- 4-t-butylphenol, 4-t-butyl-2,6-dimethylphenol, or 2,2'-methylene-bis- (6-t-butyl-4-methylphenol), 4,4'-oxydiphenyl, 3,4-methylenedioxydiphenol (sesamol), 3,4-dimethyl-phenol, hydroquinone, pyrocatechin (1, -Dihydroxybenzene), 2- (1'-methylcyclohexyl-1'-yl) -4,6-dimethylphenol, 2- or 4- (1'-phenyl-eth-1'-yl) -phenol, 2 -T-butyl-6-methylphenol, 2,4,6-tris-t-butylphenol, 2,6-di-t-butylphenol, 2,4-di-t-butylphenol, 4-t-butylphenol, nonylphenol [ 11066-49-2], octylphenol [140-66-9], 2,6-dimethylphenol, bisphenol A, bisphenol F, bisphenol B, bisphenol C, bisphenol S, 3,3 ', 5,5'-tetrabromo bisphenol a, 2,6-di -t- butyl -p- cresol, BASF Corporation Koresin ^(R), 3,5-di-t-butyl-4-hydroxybenzoic acid methyl ester, 4-t-butylpyrocatechin, 2-hydroxybenzyl alcohol, 2-methoxy-4-methylphenol, 2,3,6-trimethylphenol, 2,4,5-trimethylphenol, 2,4,6-trimethylphenol, 2-isopropylphenol, 4-isopropylphenol, 6-isopropyl-m-cresol, n-octadecyl-β- (3,5-di-t -Butyl-4-hydroxyphenyl) propionate, 1,1,3-tris- (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 1,3,5-trimethyl-2,4,6- Tris- (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, 1,3,5-tris- (3,5-di-tert-butyl) 4-hydroxybenzyl) isocyanurate, 1,3,5-tris- (3,5-di-t-butyl-4-hydroxyphenyl) -propionyloxyethyl-isocyanurate, 1,3,5-tris- (2,6-Dimethyl-3-hydroxy-4-tert-butylbenzyl) -isocyanurate or pentaerythritol-tetrakis- [β- (3,5-di-tert-butyl-4-hydroxyphenyl) -propionate] , 2,6-di -t- butyl-4-dimethylaminomethyl - phenol, 6-s-butyl-2,4-dinitrophenol, Ciba Spezialitaeten-Chemie Inc. of ^Irganox (R) 565,1141,1192,1222 and 1425, 3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl Propionic acid octadecyl ester, 3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionic acid hexadecyl ester, 3- (3 ′, 5′di-t-butyl-4′-hydroxy Phenyl) propionic acid octyl ester, 3-thia-1,5-pentanediol-bis-[(3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate], 4,8-dioxa-1 , 11-Undecandiol-bis-[(3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate], 4,8-dioxa-1,11-undecandiol-bis-[(3'-T-butyl-4'-hydroxy-5'-methylphenyl) propionate], 1,9-nonanediol-bis-[(3 ', 5'-di-t-butyl-4' Hydroxyphenyl) propionate], 1,7-heptanediamine-bis [3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionic acid amide], 1,1-methanediamine-bis [ 3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionic acid amide], 3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionic acid hydrazide 3- (3 ′, 5′-di-t-methyl-4′-hydroxyphenyl) propionic acid hydrazide, bis (3-t-butyl-5-ethyl-2-hydroxy-phen-1-yl) methane, Bis (3,5-di-t-butyl-4-hydroxy-phen-1-yl) methane, bis [3- (1'-methylcyclohexyl-1'-yl) -5-methyl-2-hydroxy- Fen -1-yl] methane, bis (3-tert-butyl-2-hydroxy-5-methyl-phen-1-yl) methane, 1,1-bis (5-tert-butyl-4-hydroxy-2-methyl) -Phen-1-yl) ethane, bis (5-t-butyl-4-hydroxy-2-methyl-phen-1-yl) sulfide, bis (3-t-butyl-2-hydroxy-5-methyl-phene) -1-yl) sulfide, 1,1-bis (3,4-dimethyl-2-hydroxy-phen-1-yl) -2-methylpropane, 1,1-bis (5-tert-butyl-3-methyl) -2-hydroxy-phen-1-yl) -butane, 1,3,5-tris [1 '-(3 ", 5" -di-t-butyl-4 "-hydroxy-phen-1" -yl) -Methy-1'-yl] -2,4,6-trimethylbenzene, 1, , 4-tris (5'-t-butyl-4'-hydroxy-2'-methyl-phen-1'-yl) butane, aminophenols such as p-aminophenol, nitrosophenols such as p-nitrosophenol, p Nitroso-o-cresol, alkoxyphenols such as 2-methoxyphenol (Guajacol, pyrocatechin monomethyl ether), 2-ethoxyphenol, 2-isopropoxyphenol, 4-methoxyphenol (hydroquinone monomethyl ether), mono- Or di-t-butyl-4-methoxyphenol, 3,5-di-t-butyl-4-hydroxyanisole, 3-hydroxy-4-methoxybenzyl alcohol, 2,5-dimethoxy-4-hydroxybenzyl alcohol (syringa alcohol) ), 4-hydroxy-3-methoxybenzaldehyde (vanillin), 4-hydroxy-3-ethoxybenzaldehyde (ethylvanillin), 3-hydroxy-4-methoxybenzaldehyde (isovanillin), 1- (4-hydroxy-3-methoxy) -Phenyl) ethanone (acetovanillin), eugenol, dihydroeugenol, isoeugenol, tocopherol, such as α-, β-, γ-, δ- and ε-tocopherol, tocol, α-tocopherol hydroquinone, and 2,3-dihydro- 2,2-dimethyl-7-hydroxybenzofuran (2,2-dimethyl-7-hydroxycoumaran), quinone and hydroquinone, such as hydroquinone or hydroquinone monomethyl ether, 2,5-di-t-butylhydroquinone, -Methyl-p-hydroquinone, 2,3-dimethylhydroquinone, trimethylhydroquinone, 4-methylpyrocatechin, t-butylhydroquinone, 3-methylpyrocatechin, pyrocatechin, 2-methyl-p-hydroquinone, 2,3-dimethyl Hydroquinone, trimethylhydroquinone, 3-methylpyrocatechin, 4-methylpyrocatechin, t-butylhydroquinone, 4-ethoxyphenol, 4-butoxyphenol, hydroquinone monobenzyl ether, p-phenoxyphenol, 2-methylhydroquinone, 2,5 -Di-t-butylhydroquinone, tetramethyl-p-benzoquinone, diethyl-1,4-cyclohexadione-2,5-dicarboxylate, phenyl-p-benzoquinone, 2,5-dimethyl-3-benzyl-p -Benzoquinone 2-isopropyl-5-methyl-p-benzoquinone (thymoquinone), 2,6-diisopropyl-p-benzoquinone, 2,5-dimethyl-3-hydroxy-p-benzoquinone, 2,5-dihydroxy-p-benzoquinone, Emberin, tetrahydroxy-p-benzoquinone, 2,5-dimethoxy-1,4-benzoquinone, 2-amino-5-methyl-p-benzoquinone, 2,5-bisphenylamino-1,4-benzoquinone, 5,8 -Dihydroxy-1,4-naphthoquinone, 2-anilino-1,4-naphthoquinone, anthraquinone, N, N-dimethylindoaniline, N, N-diphenyl-p-benzoquinone diimine, 1,4-benzoquinone dioxime, coerligone 3,3'-di-t-butyl-5,5'-dimethyldiphenoquinone, p- P-Rosolsaeure (aurin), 2,6-di-tert-butyl-4-benzylidene-benzoquinone, 2,5-di-tert-amylhydroquinone, N-oxyl, such as 4-hydroxy-2,2 , 6,6-tetramethyl-piperidine-N-oxyl, 4-oxo-2,2,6,6-tetramethyl-piperidine-N-oxyl, 4-acetoxy-2,2,6,6-tetramethyl- Piperidine-N-oxyl, 2,2,6,6-tetramethyl-piperidine-N-oxyl, 4,4 ', 4 "-tris (2,2,6,6-tetramethyl-piperidine-N-oxyl) -Phosphite, 3-oxo-2,2,5,5-tetramethyl-pyrrolidine-N-oxyl, 1-oxyl-2,2,6,6-tetramethyl-4-methoxypiperidine, 1-oxyl-2 , , 6,6-tetramethyl-4-trimethylsilyloxypiperidine, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl-2-ethylhexanoate, 1-octyl-2,2,6 , 6-Tetramethylpiperidin-4-yl-stearate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl-benzoate, 1-oxyl-2,2,6,6-tetramethyl Piperidin-4-yl- (4-t-butyl) benzoate, bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) -succinate, bis (1-oxyl-2,2, 6,6-tetramethylpiperidin-4-yl) -adipate, 1,10-decanedioic acid-bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) Ester, bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) -n-butylmalonate, bis (1-oxyl-2,2,6,6-tetramethylpiperidine-4 -Yl) -phthalate, bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) -isophthalate, bis (1-oxyl-2,2,6,6-tetramethylpiperidine- 4-yl) -terephthalate, bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) -hexahydroterephthalate, N, N′-bis (1-oxyl-2,2,6) , 6-Tetramethylpiperidin-4-yl) -adipinamide, N- (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) -caprolactam, N- (1-oxy -2,2,6,6-tetramethylpiperidin-4-yl) -dodecylsuccinimide, 2,4,6-tris- [N-butyl-N- (1-oxyl-2,2,6,6-tetra Methylpiperidin-4-yl] triazine, N, N′-bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) -N, N′-bis-formyl-1,6- Diaminohexane, 4,4′-ethylenebis (1-oxyl-2,2,6,6-tetramethylpiperazin-3-one) aromatic amine, such as phenylenediamine, N, N-diphenylamine, N-nitroso-diphenylamine Nitroso-diethylaniline, N, N′-dialkyl-p-phenylenediamine,
In this case, the alkyl groups may be the same or different and each time independently of each other consists of 1 to 4 carbon atoms and may be linear or branched, For example, N, N'-di-iso-butyl-p-phenylenediamine, N, N'-di-iso-propyl-p-phenylenediamine Irganox 5057, N, N'-di-iso-butyl- from Chiba Spezitalitaten Chemie p-phenylenediamine, N, N'-di-iso-propyl-p-phenylenediamine, p-phenylenediamine, N-phenyl-p-phenylenediamine, N, N'-diphenyl-p-phenylenediamine, N-isopropyl -N-phenyl-p-phenylenediamine, N, N'-di-s-butyl-p-phenylenediamine (BASF Corporation ^Kerobit (R) BPD), N- phenyl-N'-isopropyl -p- phenylenediamine (Bayer Corp. of ^{Vulkanox (R)), N- (} 1,3- dimethylbutyl)-N'-phenyl - p-phenylenediamine, N-phenyl-2-naphthylamine, iminodibenzyl, N, N'-diphenylbenzidine, N-phenyltetraaniline, acridone, 3-hydroxydiphenylamine, 4-hydroxydiphenylamine, hydroxylamine such as N, N -Diethylhydroxylamine, urea derivatives or thioureas, phosphorus-containing compounds such as triphenylphosphine, triphenylphosphite, hypophosphoric acid or triethylphosphite, sulfur-containing compounds such as diphenyl sulfide, phenothiadi Or metal salts, for example copper - manganese -, cerium -, nickel -, chromium -, - chloride, - dithiocarbamates, - sulfates, - an acetate or a mixture thereof - salicylate or. Preference is given to the abovementioned phenols and quinones, particularly preferred are hydroquinone, hydroquinone monomethyl ether, 2-t-butyl-4-methylphenol, 6-t-butyl-2,4-dimethyl-phenol, 2,6-di -t- butyl-4-methylphenol, 2,4-di -t- butylphenol, triphenyl phosphite, hypophosphoric acid, CuCl ₂ and Guajakoru, particularly preference is given to hydroquinone and hydroquinone monomethyl ether It is.

  Particularly advantageous are hydroquinone monomethyl ether, hydroquinone and alkylphenols, optionally in combination with triphenyl phosphite and / or hypophosphoric acid.

  Particularly advantageous are α-tocopherol (vitamin E), β-tocopherol, γ-tocopherol or δ-tocopherol, optionally in combination with triphenylphosphite and / or hypophosphoric acid.

  Particularly advantageously, only sterically hindered phenols are used as stabilizers, which are less productive in dark color at the same acid number of the final product compared to hydroquinone monomethyl ether during the esterification reaction. Produce. Examples for such most advantageous stabilizers are α-tocopherol as well as 2,6-di-tert-butyl-4-methylphenol.

  A gas containing oxygen, such as air or a mixture of air and nitrogen (lean air), may be present to further aid in stabilization.

  Of the stabilizers described, those that are aerobic, that is, those that require the presence of oxygen to develop their full inhibitor action, are advantageous.

  Solvents E which can be used according to the invention are in particular solvents suitable for removing the reaction water by azeotropic distillation, if desired, in particular aliphatic, cycloaliphatic and aromatic hydrocarbons or mixtures thereof. is there.

  P-pentane, n-hexane, n-heptane, cyclohexane, methylcyclohexane, benzene, toluene or xylene are preferably applied. Particular preference is given to cyclohexane, methylcyclohexane and toluene.

  For the esterification, methods for the preparation and / or work-up of polyhydric alcohols known to the person skilled in the art can be applied, for example those mentioned at the beginning or DE-A19941136, DE-A3843843, DE-A3843844, DE- A19937911, DE-A 199 258, EP-A 331 845, EP 554651 or US 4187383.

In general, esterification can be carried out as follows:
The esterification unit consists of a stirred reactor, preferably a distillation unit and a phase separation vessel installed at the top with a circulating evaporator and a condenser.

  The reactor may be, for example, a reactor having a double wall heating device and / or a heating coil present inside. Preference is given to a reactor having an externally existing heat exchanger and a natural or forced circulation, i.e. a natural circulation with the use of a pump, with particular preference that the circulation flow occurs without the use of mechanical auxiliary means. use.

  It will be appreciated that the reactor can be carried out in a reactor cascade comprising a plurality of reaction zones, for example 2 to 4 reactors, preferably 2 to 3 reactors.

  Suitable circulating evaporators are known to those skilled in the art and are described, for example, by R.C. Billet, Verdampfertechnik, HTB-Verlag, Bibliographis Institute Mannheim, 1965, page 53. Examples for circulating evaporators are tube bundle heat exchangers, plate heat exchangers and the like.

  Of course, the circulation may be present in a plurality of heat exchangers.

  The distillation unit has a structure known per se. This may be a simple distillation optionally equipped with a sunshade or a rectification column. As column internal structures, in principle all customary internal structures, such as trays, structured packings and / or wet packings, are conceivable. Of the trays, bubble trays, perforated plates, valve trays, tall man trays and / or dual flow trays are preferred, and rings, coils, clubs or nets are preferred in the packing.

  Usually 5 to 20 theoretical plates are sufficient.

  The condenser and separation vessel are of normal construction.

  (Meth) acrylic acid and alkoxylated glycol are usually used in molar excess as described above in esterification a). The excess used may be up to about 3000: 1 if desired.

  As the esterification catalyst C, the above can be considered.

  The esterification catalyst is usually from 0.1 to 5% by weight, preferably from 0.5 to 5% by weight, particularly preferably from 1 to 4% by weight and particularly preferably from 2 to 4% by weight, based on the esterification mixture. Use in quantity.

  If necessary, the esterification catalyst can be removed from the reaction mixture using an ion exchanger. In this case, the ion exchanger can be added directly to the reaction mixture and subsequently filtered off or the reaction mixture can be passed to the charge of the ion exchanger.

  The esterification catalyst is preferably left in the reaction mixture. However, if the catalyst is an ion exchanger, this is advantageously removed, for example by filtration.

  To further aid in stabilization, a gas containing oxygen, preferably air or a mixture of air and nitrogen (lean air) may be present.

  This oxygen-containing gas is preferably fed to the bottom area of the column and / or to the circulation evaporator and / or passed through and / or over the reaction mixture.

  The polymerization inhibitor (mixture) D (as described above) is from 0.01 to 1% by weight, preferably from 0.02 to 0.8% by weight, particularly preferably from 0.05 to 0.00%, based on the esterification mixture. Used in a total amount of 5% by weight.

  The polymerization inhibitor (mixture) D can be used in the raw material or product, for example, as an aqueous solution or solution.

  b) The water of reaction produced during the reaction can be distilled off during or after esterification a), in which case this step can be assisted by a solvent which forms an azeotrope with water.

  If desired, the above compounds are suitable as solvent E for removing the reaction water by azeotropic distillation.

  Preference is given to carrying out the esterification in the presence of a solvent.

  The amount of solvent used is from 10 to 200% by weight, preferably from 20 to 100% by weight, particularly preferably from 30 to 100% by weight, based on the total of the alkoxylated glycol and (meth) acrylic acid.

  However, it is also conceivable to carry out without the use of entrainers, for example as described in DE-A 13384854, column 2, lines 18 to 4, line 45, but the stabilizer Differences in use.

  If the water contained in the reaction mixture is not removed by a solvent which forms an azeotrope, this water is an inert gas, preferably a gas containing oxygen, as described, for example, in DE-A 338443. It can be removed particularly advantageously by stripping with air or lean air.

  The reaction temperature of the esterification a) is generally from 40 to 160 ° C., preferably from 60 to 140 ° C. and particularly preferably from 80 to 120 ° C. The temperature may be the same during the reaction or may increase, preferably the temperature increases during the reaction. In this case, the final esterification temperature is 5-30 ° C. higher than the initial temperature. The temperature of the esterification can be determined and controlled by changing the solvent concentration in the reaction mixture, as described, for example, in German Patent Application having DE-A 19941136 and Docket No. 10063175.4. .

  If a solvent is used, it can be distilled off from the reaction mixture by means of a distillation unit installed on the reactor.

  The distillate can be selectively removed or, after condensation, guided to a phase separator. The aqueous phase thus obtained is usually discharged as described in the German patent application with serial number 1000063175.4 and the organic phase is guided as a return stream to the distillation unit and / or It can be fed directly to the reaction zone and / or guided to a circulating evaporator.

  When used as reflux, the organic phase can be used in esterification for temperature control, as described in DE-A 19941136.

  The esterification a) can be carried out at standard pressure, or also under overpressure or reduced pressure, and is preferably carried out at standard pressure.

  The reaction time is usually 2 to 20 hours, preferably 4 to 15 and particularly preferably 7 to 12 hours.

  The order of addition of the individual reaction components is not important according to the invention. All ingredients can be mixed and charged and subsequently heated, or one or more ingredients can be either not charged or partially charged and added only after heating.

Usable (meth) acrylic acid is not limited in its composition and may have, for example, the following components:
(Meth) acrylic acid 90-99.9% by mass,
Acetic acid 0.05-3 mass%,
Propionic acid 0.01-1 mass%,
0.01-5% by mass of diacrylic acid,
0.05 to 5% by mass of water,
Carbonyl content 0.01-0.3% by mass,
0.01 to 0.1% by mass of an inhibitor,
(Anhydrous) maleic acid 0.001-0.5 mass%.

  The crude (meth) acrylic acid used is usually stabilized with 200-600 ppm of phenothiazine or an amount of other stabilizer that allows comparable stabilization. The expression carbonyl content here is understood to be, for example, acetone and lower aldehydes such as formaldehyde, acetaldehyde, crotonaldehyde, acrolein, 2- and 3-furfural and benzaldehyde.

  Crude (meth) acrylic acid here means that the reaction gas of propane / propene / acrolein or isobutane / isobutene / methacrolein oxidation is absorbed in the absorbent and subsequently formed after the absorbent is separated or the reaction gas It is understood that this is a (meth) acrylic acid-containing mixture obtained by fractional condensation.

Of course, it is also possible to use pure (meth) acrylic acid having the following purity, for example:
(Meth) acrylic acid 99.7-99.99 mass%,
Acetic acid 50-1000 mass ppm,
10-500 mass ppm propionic acid,
10 to 500 ppm by weight of diacrylic acid,
50-1000 ppm by weight of water,
Carbonyl content 1 to 500 ppm by mass,
Inhibitor 1 to 300 ppm by mass,
(Anhydrous) maleic acid 1-200 ppm by mass.

  The pure (meth) acrylic acid used is usually stabilized with 100 to 300 ppm of hydroquinone monomethyl ether or an amount of other storage stabilizer that allows comparable stabilization.

  Pure or pre-purified (meth) acrylic acid generally has a purity of at least 99.5% by weight and contains substantially aldehyde, other carbonyl-containing and high-boiling components. Understand that it is not (meth) acrylic acid.

  Condensate separated via an upper column (if present) distilled off during esterification, usually containing 0.1 to 10% by weight of (meth) acrylic acid A good aqueous phase is separated and discharged. The (meth) acrylic acid contained therein is preferably an extractant, preferably a solvent used in the esterification, for example cyclohexane, at a temperature of 10 to 40 ° C. and a water relative extractant 1 : 5-30, preferably 1: 10-20 and can be returned to the esterification.

In order to further assist the circulation, an inert gas, preferably a gas containing oxygen, particularly preferably air or a mixture of air and nitrogen (lean air) is introduced into the circulating stream, through the reaction mixture or via and for example 0.1 to 1 with respect to the volume of the reaction mixture, preferably 0.2 to 0.8 and particularly preferably can be conductive in an amount of 0.3~0.7m ³ / ^{m 3} h .

  The process of esterification a) can be followed by following the amount of water discharged and / or by removing the carboxylic acid concentration in the reactor.

  The reaction is complete, for example, when 90% of the theoretically expected amount of water has been carried out by the solvent, preferably at least 95% and particularly preferably at least 98%.

  The end of the reaction can be confirmed, for example, by substantially no further reaction water being removed by the entraining agent. When carrying out (methacrylic) acid with reaction water, the ratio can be measured, for example, by back titration of an aliquot of the aqueous phase.

  The removal of the reaction water is, for example, when (methacrylic) acid is used in a high stoichiometric excess, for example at least 3: 1, preferably at least 5: 1 and particularly preferably at least 10: 1. Can be omitted. In this case, a substantial part of the amount of water produced remains in the reaction mixture. During or after the reaction, only the proportion of water, determined by volatility at the set temperature, is removed from the reaction mixture and no further measures are taken to separate the resulting reaction water. Thus, for example, at least 10% by weight, preferably at least 20% by weight, particularly preferably at least 30% by weight, particularly preferably at least 40 and in particular at least 50% by weight of the resulting reaction water remain in the reaction mixture.

  c) After the esterification is complete, the reaction mixture is cooled in the usual manner to a temperature of 10-30 ° C. and optionally the same solvent as is optionally used for removing water by azeotropic distillation, Arbitrary target ester concentration can be adjusted by adding the solvent which may be others.

  In another embodiment, the reaction is stopped with a suitable diluent G and, for example, to reduce the viscosity, for example 10 to 90% by weight, preferably 20 to 80% by weight, particularly preferably 20 to 60%, Particularly preferably, it can be diluted to a concentration of 30-50% and in particular about 40%.

  What is important in that case is that a substantially homogeneous solution is formed after dilution.

  This is preferably done for the first time relatively shortly before use in the production of the hydrogel, for example more than 24 hours ago, preferably more than 20 hours, particularly preferably more than 12 hours, particularly preferably more than 6 hours and in particular. Do not do more than 3 hours ago.

  Diluent G is from the group consisting of water, a mixture of water and one or more organic solvents that are unlimitedly soluble in water, or a mixture of water and one or more monohydric or polyhydric alcohols such as methanol and glycerin. Is selected. The alcohol preferably has 1, 2 or 3 hydroxyl groups and preferably has 1 to 10, especially 4 carbon atoms. Preference is given to primary and secondary alcohols.

  Preferred alcohols are methanol, ethanol, isopropanol, ethylene glycol, glycerin, 1,2-propanediol or 1,3-propanediol.

  d) If necessary, the reaction mixture is, for example, activated carbon or a metal oxide, such as aluminum oxide, silicon oxide, magnesium oxide, zirconium oxide, boron oxide or mixtures thereof, for example 0.1-50% by weight, preferably Is treated in an amount of 0.5 to 25% by weight, particularly preferably 1 to 10% by weight, for example at a temperature of 10 to 100 ° C., preferably 20 to 80 ° C. and particularly preferably 30 to 60 ° C. Decolorization may be performed by the following.

  This can be done by adding a powdered or granular bleaching agent to the reaction mixture and then filtering, or by passing the reaction mixture through a deposit of bleaching agent in the form of any suitable shaped body. it can.

  The decolorization of the reaction mixture can take place at any point in the work-up process, for example at the stage of the crude reaction mixture, or optionally after pre-washing, neutralization, washing or solvent removal.

  The reaction mixture can be further subjected to prewash e) and / or neutralization f) and / or postwash g), preferably only neutralization f). Optionally, neutralization f) and prewash e) can be exchanged in sequence.

  From the aqueous phase of washings e) and g) and / or neutralization f) at least partly recovering the contained (meth) acrylic acid and / or catalyst C by acid treatment and extraction with a solvent; and Can be used again.

  For pre-washing or post-washing e) or g), the reaction mixture is washed in a washing device, for example water and 5-30% by weight, preferably 5-20%, particularly preferably 5-15% by weight, of sodium chloride. Treat with solution, potassium chloride solution, ammonium chloride solution, sodium sulfate solution or ammonium sulfate solution, preferably water or saline solution.

  The quantity ratio of reaction mixture: washing liquid is usually from 1: 0.1 to 1, preferably from 1: 0.2 to 0.8, particularly preferably from 1: 0.3 to 0.7.

  Washing or neutralization can be carried out, for example, in a stirred vessel or in other conventional equipment, for example in a column or mixer / settler apparatus.

  Methods Technical washing or neutralization may be performed for all methods known per se for the method according to the invention, such as all extraction methods and washing methods and equipment such as Ullmann's Encyclopedia of Industrial Chemistry, 6th edition, 1999, electronic version, liquid- Those described in the chapter of the liquid extraction device can be used. For example, this may be a one-step or multi-step, preferably one-step extraction, as well as a co-current or counter-current operation, preferably a counter-current operation.

  Preference is given to using perforated plates or columns with structured packing or wet packing, stirring vessels or mixer / settler devices, and those with pulsed columns or rotating internal structures.

  The pre-cleaning e) is preferably used when a metal salt, preferably copper or a copper salt, is used (in combination) as an inhibitor.

  Post-wash g) may be advantageous to remove traces of base or acid from the reaction mixture neutralized with f).

  For neutralization f) 5 to 25, preferably 5 to 20, particularly advantageous for prewashed reaction mixtures which may still contain small amounts of catalyst and a major amount of excess (meth) acrylic acid 5 to 15% by weight of a base, such as an aqueous solution of an alkali or alkaline earth metal oxide, hydroxide, carbonate or bicarbonate, preferably sodium hydroxide solution, potassium hydroxide solution, carbonate Sodium hydrogen, sodium carbonate, potassium hydrogen carbonate, calcium hydroxide, lime milk, ammonia, aqueous ammonia or potassium carbonate (this may optionally contain 5-15% by weight salt, potassium chloride, ammonium chloride or ammonium sulfate) It can be neutralized with sodium hydroxide solution or sodium hydroxide-salt-solution. The degree of neutralization is preferably from 5 to 60 mol%, preferably from 10 to 40 mol%, particularly preferably from 20 to 30 mol%, based on the monomers containing acid groups. This neutralization can take place before and / or after the polymerization, preferably before the polymerization. Another advantageous degree of neutralization is 50 to 100 mol%, particularly preferably 55 to 80 mol%, especially 60 to 75 mol%. Preferably, the crosslinker solution in pure acrylic acid is mixed with the acrylate solution for the first time just before polymerization to adjust the degree of neutralization. The addition of the base is carried out so that the temperature of the apparatus does not rise above 60 ° C., preferably 20-35 ° C. and a pH value of 4-13, preferably 4.5-10. The removal of the heat of neutralization is preferably effected by cooling the vessel using internal cooling coils or by double wall cooling.

  The quantity ratio of reaction mixture: neutralized liquid is usually from 1: 0.1 to 1, preferably from 1: 0.2 to 0.8, particularly preferably from 1: 0.3 to 0.7.

  The above is valid for the device.

  h) When a solvent is contained in the reaction mixture, the solvent can be almost removed by distillation. The optionally contained solvent is preferably removed from the reaction mixture after washing and / or neutralization, but if desired, this can also take place before washing or neutralization.

  For this purpose, after separating off the solvent, an amount of storage stabilizer such that 100 to 500, preferably 200 to 500 and particularly preferably 200 to 400 ppm are contained in the target ester (residue), preferably For example, hydroquinone monomethyl ether is added to the reaction mixture. Alternatively, instead of hydroquinone monomethyl ether, the above-mentioned sterically hindered phenols can advantageously be used alone or as a mixture with other stabilizers.

  Separation of the main amount of the solvent by distillation is, for example, in a stirred vessel with double-wall heating and / or a heating coil present inside, under reduced pressure, for example 20-700 mbar, preferably 30-500 mbar and particularly advantageously. Is carried out at a temperature of 50 to 150 mbar and 40 to 80 ° C.

  Of course, the distillation can also be carried out in a falling film evaporator or a thin layer evaporator. For this purpose, the reaction mixture is preferably circulated several times and the apparatus is used under reduced pressure, for example at a temperature of 20 to 700 mbar, preferably 30 to 500 mbar and particularly preferably 50 to 150 mbar and 40 to 80 ° C. To guide.

An inert gas, preferably a gas containing oxygen, particularly preferably air or a mixture of air and nitrogen (lean air) is preferably used, for example from 0.1 to 1, relative to the volume of the reaction mixture. it can be passed into the distillation apparatus in 0.3~0.7m ³ / ^{m 3} h in 0.2 to 0.8 and particularly preferably.

  The residual solvent content in the residue is usually not more than 5% by weight after distillation, preferably 0.5 to 5% by weight and particularly preferably 1 to 3% by weight.

  The separated solvent condenses and is advantageously reused.

  If necessary, a solvent stripping i) can be carried out additionally or instead of distillation.

  For this purpose, the desired ester, which still contains a small amount of solvent, is heated to 50-90 ° C., preferably 80-90 ° C., and the remaining amount of solvent is removed in a suitable apparatus using a suitable gas. To do. A vacuum may be applied to assist.

  A suitable apparatus is, for example, a column of construction known per se, which has the usual internal structures, such as trays, structured packing or wet packing, preferably wet packing. In principle, all customary internal structures such as trays, regular packings and / or random packings are conceivable as column internals. Among the trays, bubble bell trays, perforated plates, valve trays, tall man trays and / or dual flow trays are advantageous, and in the packing, rings, coils, clubs, Raschig rings, Intos- rings or Pall rings (Pall -Ringen, Barrel or Intertalx, Top-Pak etc. or net are advantageous.

  Possible in this case are falling film, thin-layer or wipe-film evaporators, such as Luwa, Rotafilm or Sambay evaporators, which may be provided with, for example, a demister as a sunshade. .

  Suitable gases are adjusted to a gas which is inert under stripping conditions, preferably an oxygen-containing gas, particularly preferably air or a mixture of air and nitrogen (lean air) or water vapor, in particular 50-100 ° C. Water vapor.

The amount of stripping gas is, for example, 5 to 20, particularly preferably 10 to 20 and very particularly preferably 10 to 15 m ³ / m ³ h, based on the volume of the reaction mixture.

  If necessary, the ester is filtered at any stage of the work-up process, preferably after washing / neutralization and, optionally, removal of the solvent, j) and traces of precipitated salts as well as any decolorization contained. Remove the agent.

  In a possible embodiment, esterification a) of an alkoxylated glycol is used in the presence of at least one esterification catalyst C and at least one polymerization inhibitor D using (meth) acid in the above molar excess of at least 10: 1. In the absence of a solvent which forms an azeotrope with water.

  In an advantageous embodiment, the (methacrylic) acid used in excess is not substantially separated, i.e. only the proportion of (methacrylic) acid determined by the volatility at the applied temperature is removed from the reaction mixture, and further Measures for separating carboxylic acids, such as distillation, rectification, extraction, such as washing, absorption, such as conduction to activated carbon or ion exchangers and / or chemical processes, such as capture of carboxylic acids using epoxides. .

  The (methacrylic) acid preferably contained in the reaction mixture is preferably 75% by weight or more, particularly preferably 50% by weight or more, especially preferably 50% by weight or more, based on the (methacrylic) acid contained in the reaction mixture after completion of the reaction. Preferably 25% by weight or more, in particular 10% by weight or more and in particular 5% by weight or more, do not separate from the reaction mixture. In a preferred embodiment, step b) can be omitted, so that only the proportion of reaction water and (methacrylic) acid determined by volatility at the applied temperature is removed from the reaction mixture. This can advantageously be prevented by substantially complete condensation.

  Furthermore, the esterification catalyst C used also remains substantially in the reaction mixture.

  The reaction mixture thus obtained preferably has an acid number according to DIN EN 3682 of at least 25 mg KOH / g reaction mixture, more preferably at least 35 mg KOH / g, particularly preferably at least 45 mg KOH / g. Particularly preferred as a range is an acid number of 25-80 and particularly preferred is an acid number of 35-50 mg KOH / g.

  The pre-washing or post-washing e) or g) is advantageously omitted and only the filtration step j) may be advantageous.

  The reaction mixture is subsequently diluted in step c), in which case it is preferably reacted into the hydrogel within 6 hours, particularly preferably within 3 hours. Advantageously, the mixture can be neutralized in step f).

  The order of steps c), j) and f) is arbitrary in this case.

The present invention further provides:-at least one ester F obtained by the above esterification method,
-(Methacrylic) acid and-Diluent G
Relates to a substance mixture containing

As another component-an esterification catalyst C in protonated or non-protonated form,
-Polymerization inhibitor D and-if used in esterification, optionally solvent E
May be contained.

  The substance mixture may optionally be neutralized and has the pH value described in f) above.

  When the substance mixture is neutralized, at least part of the (methacrylic) acid is converted to its water-soluble alkali metal salt, alkaline earth metal salt or ammonium salt.

An advantageous substance mixture is
0.1 to 40% by weight of ester F in the substance mixture, particularly preferably 0.5 to 20, particularly preferably 1 to 10, in particular 2 to 5 and in particular 2 to 4% by weight,
0.5 to 99.9% by weight of monomer M, particularly preferably 0.5 to 50% by weight, in particular 1 to 25, in particular 2 to 15 and in particular 2 to 8 or 4 to 5% by weight,
0 to 10% by weight of esterification catalyst C, particularly preferably 0.02 to 5, particularly preferably 0.05 to 2.5% by weight and especially 0.1 to 1% by weight,
0 to 5% by weight of polymerization inhibitor D, particularly preferably 0.01 to 1.0, very particularly preferably 0.02 to 0.75, in particular 0.05 to 0.5 and in particular 0.075. -0.25 mass%,
0 to 10% by weight of solvent E, particularly preferably 0 to 5% by weight, very particularly preferably 0.05 to 1.5% by weight and in particular 0.1 to 0.5% by weight, although the sum is always 100% by weight, and optionally-100% by weight with addition of diluent G
Containing.

The reaction mixture obtained by the above method and the substance mixture according to the invention are:
-As a radical crosslinking agent for water-absorbing hydrogels,
-As a raw material for producing polymer dispersions,
-As a raw material for producing polyacrylates (excluding hydrogels)
It can be used as a raw material for paints or as a cement additive.

  In particular for use as a radical cross-linking agent in water-absorbing hydrogels, at least 0.5% by weight, preferably at least 1% by weight, more preferably at least 2% by weight, more preferably at least 5% by weight, particularly preferably. Suitable are substance mixtures according to the invention having a water solubility (at 25 ° C. in distilled water) of at least 10% by weight, particularly preferably at least 20% by weight and in particular at least 30% by weight.

  k) If a post-treatment step is carried out, the reaction mixture from the esterification comprising this step, for example the reaction mixture from f), or if b) is omitted, b) or b) is omitted In some cases, an additional monoethylenically unsaturated compound N that does not have acid groups but is copolymerizable with the hydrophilic monomer M can optionally be added to the reaction mixture from a). In this case, it can be polymerized in the presence of at least one radical initiator K and optionally at least a graft base L to produce a water-absorbing hydrogel.

Advantageously,
l) The reaction mixture from k) can be post-crosslinked.

  Suitable hydrophilic monomers M for producing this hydrophilic highly swellable hydrogel are, for example, polymerizable acids such as acrylic acid, methacrylic acid, ethacrylic acid, α-chloroacrylic acid, crotonic acid, maleic acid, Maleic anhydride, vinyl sulfonic acid, vinyl phosphonic acid, maleic acid including anhydride, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, glutaconic acid, aconitic acid, allyl sulfonic acid, sulfoethyl acrylate, sulfomethacrylate, sulfopropyl Acrylate, sulfopropyl methacrylate, 2-hydroxy-3-acryloxypropyl sulfonic acid, 2-hydroxy-3-methacryl-oxypropyl sulfonic acid, allyl phosphonic acid, styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 2 Acrylamido-2-methylpropanesulfonic acid and their amides, esters and amides having a hydroxyalkyl ester and amino groups or ammonium groups. The monomers can be used alone or as a mixture with one another. Furthermore, it is water-soluble N-vinylamide or diallyldimethylammonium chloride. Preferred hydrophilic monomers are those of formula V

［式中、
Ｒ^３は水素、メチルまたはエチルであり、
Ｒ^４は基−ＣＯＯＲ^６、スルホニル基またはホスホニル基、（Ｃ_１〜Ｃ_４）−アルキルアルコールによりエステル化されるホスホニル基または式ＶＩ

[Where:
R ³ is hydrogen, methyl or ethyl;
R ⁴ is a group —COOR ⁶ , a sulfonyl group or a phosphonyl group, a phosphonyl group esterified with a (C ₁ -C ₄ ) -alkyl alcohol or a compound of formula VI

の基であり、
Ｒ^５は水素、メチル、エチルまたはカルボキシル基であり、
Ｒ^６は水素、アミノまたはヒドロキシ−（Ｃ_１〜Ｃ_４）−アルキルであり、かつ
Ｒ^７はスルホニル基、ホスホニル基またはカルボキシル基である］の化合物である。

The basis of
R ⁵ is hydrogen, methyl, ethyl or carboxyl group,
R ⁶ is hydrogen, amino or hydroxy- (C ₁ -C ₄ ) -alkyl, and R ⁷ is a sulfonyl group, a phosphonyl group or a carboxyl group].

_(C 1 ~C ₄₎ - Examples of alkyl alcohol is methanol, ethanol, n- propanol or n- butanol.

  Particularly preferred hydrophilic monomers are acrylic acid and methacrylic acid, in particular acrylic acid.

For optimization of properties, it may be advantageous to use an additional monoethylenically unsaturated compound N which does not have acid groups but is copolymerizable with monomers having acid groups. This includes, for example, amides and nitriles of monoethylenically unsaturated carboxylic acids, such as acrylamide, methacrylamide and N-vinylformamide, N-vinylacetamide, N-methylvinylacetamide, acrylonitrile and methacrylonitrile. Other suitable compounds are for example vinyl esters of saturated C ₁ -C ₄ -carboxylic acids, such as vinyl formate, vinyl acetate or vinyl propionate, alkyl vinyl ethers having at least 2 carbon atoms in the alkyl group, such as ethyl vinyl ether Or butyl vinyl ether, monoethylenically unsaturated C ₃ -C ₆ -carboxylic acid esters, such as monovalent C ₁ -C ₁₈ -alcohols and esters of acrylic acid, methacrylic acid or maleic acid, half esters of maleic acid, such as Maleic acid mono-methyl ester, N-vinyl lactam, such as N-vinyl pyrrolidone or N-vinyl caprolactam, of alkoxylated monovalent saturated alcohol, for example 2 to 200 moles of ethylene per mole of alcohol Acrylic and methacrylic esters of alcohols having 10 to 25 carbon atoms reacted with xoxide and / or propylene oxide, and monoacrylic and monomethacrylic esters of polyethylene glycol or polypropylene glycol, The molar mass (M _n ) of the alkylene glycol may be up to 2000, for example. Further suitable monomers are styrene and alkyl-substituted styrenes such as ethyl styrene or t-butyl styrene.

  These monomers having no acid group can be used as a mixture with other monomers, for example, a mixture of vinyl acetate and 2-hydroxyethyl acrylate in an arbitrary ratio. These monomers without acid groups can be added to the reaction mixture in an amount of 0 to 50% by weight, preferably less than 20% by weight.

  Advantageously, the crosslinked (co) polymers are obtained from monoethylenically unsaturated monomers with acid groups, optionally converted to their alkali salts or ammonium salts before or after polymerization and from 0 to 0 relative to their total mass. It consists of a monoethylenically unsaturated monomer that does not have 40% by weight of acid groups.

  Various preparations, tests and uses of (co) polymers, polyacrylic acids and superabsorbers containing (meth) acrylic acid have already been described and are therefore well known, for example “Modern Supersorbent Polymer Technology”, F.M. L. Buchholz and A.M. T.A. See Graham, Wiley-VCH, 1998 or Ullmann's Handbuch der technischen Chemie, Volume 35, 2003, Markus Frank, "Superabsorbents".

  Preference is given to hydrogels obtained by crosslinkable polymerization or copolymerization of monoethylenically unsaturated monomers M having acid groups or their salts.

  The resulting polymer is superior due to improved saponification value (VSI).

  In the case of a method for postcrosslinking, the starting polymer is treated with a postcrosslinker, and preferably postcrosslinked by increasing the temperature during or after treatment and dried, in which case the crosslinker is preferably Is contained in an inert solvent. An inert solvent is understood to be a solvent that does not substantially react with either the starting polymer or the postcrosslinker during the reaction. Preference is given to solvents in which up to 90%, preferably up to 95%, particularly preferably up to 99%, in particular up to 99.5%, do not chemically react with the starting polymer or postcrosslinker. .

  In this case, it is advantageous for the postcrosslinking l) and the drying m) to be in the temperature range of 30 to 250 ° C., in particular 50 to 200 ° C., particularly preferably in the range of 100 to 180 ° C. Application of the surface postcrosslinking solution is preferably effected by spraying onto the polymer in a suitable spray mixer. Subsequent to spraying, the polymer powder is dried by heat, with the crosslinking reaction taking place before and during drying. Preference is given to spraying the solution of the crosslinker in a reaction mixer or mixing and drying apparatus, such as a Roedige mixer, a BEPEX mixer, a NAUTA mixer, a SHUGGI mixer or a PROCESSAL. Furthermore, a fluid bed dryer can also be used.

  Drying can be performed in the mixer itself by heating the jacket or blowing warm air. Also suitable are rear-connected dryers such as Horden dryers, rotary tube dryers or heatable coils. However, it is also possible to use azeotropic distillation as a drying method, for example. An advantageous residence time at this temperature in the reaction mixer or dryer is not more than 60 minutes, particularly preferably not more than 30 minutes.

  Preference is given to the process described above, in which the starting polymer is obtained by polymer acrylic acid or polyacrylate, in particular by radical polymerization, and the polymer is prepared using a multifunctional ethylenically unretained radical crosslinking agent. Acrylic acid or polyacrylate.

  Preference is given to using substance mixtures containing radical crosslinking agents, ie esters F, and diluents G in a ratio of 0.1 to 20% by weight, in particular 0.5 to 10% by weight, based on the weight of the starting polymer. Is the method.

  Advantageously, the radical crosslinking agent is 0.01 to 5.0% by weight, preferably 0.02 to 3.0% by weight, particularly preferably 0.03 to 2.5% by weight, based on the starting polymer. %, In particular 0.05 to 1.0 and in particular 0.1 to 0.75% by weight.

  The subject of the present invention is the polymer and hygiene products produced by the method described above, their use in packaging materials and nonwovens, and for the production of crosslinked or heat-crosslinkable polymers, in particular in paints. It is also the use of the above substance mixture.

  The hydrophilic highly swellable hydrogel (starting polymer) used in this case is in particular a (co) polymerized hydrophilic monomer M, a graft (co) of one or more hydrophilic monomers M on a suitable graft base L. Polymers, cross-linked cellulose ethers or starch ethers or natural products that can swell in aqueous liquids, such as guar derivatives. These hydrogels are known to those skilled in the art and are for example US Pat. No. 4,286,082, DE-C-2706135, US-4340706, DE-C-3713601, DE-C-2840010, DE-A-4344548, DE-A-4020780. DE-A-4015085, DE-A-3917846, DE-A-3807289, DE-A-3533337, DE-A-3503458, DE-A-4244548, DE-A-4219607, DE-A-4021847, DE -A-383261, DE-A-3511086, DE-A-3118172, DE-A-3028043, DE-A-4418881, EP-A-0801483, EP-A-0455985, EP-A-0467703, EP-A -0312952 EP-A-0205874, EP-A-0499774, DE-A-2261546, DE-A-4020780, EP-A-0205574, US-5145906, EP-A-0530438, EP-A-06670073, US4057521, US- 4062817, US-4255527, US-4295987, US-5011892, US-4076663 or US-4931497. Particularly suitable are, for example, highly swellable hydrogels from the production process described in WO 01/38402, as well as inorganic-organic hybrid highly swellable hydrogels as described in DE 1845575. The contents of the aforementioned patent documents, in particular the hydrogels produced by these methods, are clearly a component of the present disclosure.

  Suitable graft bases L for hydrophilic hydrogels obtained by graft copolymerization of olefinically unsaturated acids may be of natural or synthetic origin. Examples are starch, cellulose or cellulose derivatives and other polysaccharides and oligosaccharides, polyalkylene oxides, especially polyethylene oxide and polypropylene oxide and hydrophilic polyesters.

  The water-absorbing polymer can be obtained by graft copolymerizing acrylic acid or acrylate onto a water-soluble polymer matrix. Suitable water-soluble polymer matrices are, for example but not limited to, alginate, polyvinyl alcohol and polysaccharides such as starch. In the case of graft copolymerization in the sense according to the invention, polyfunctional ethylenically unsaturated radical crosslinking agents are used.

  The water-absorbing polymer may be an organic-inorganic hybrid polymer consisting on the one hand of a polymeric acrylic acid or polyacrylate and on the other hand a silicate, aluminate or aluminosilicate. In particular, a polyfunctional ethylenically unsaturated radical crosslinker obtained by radical polymerization is used, and in its production process, a water-soluble silicate or a soluble aluminate or both Polymeric acrylic acid or polyacrylate can be used in which a mixture of

  Preferred hydrogels are in particular polyacrylates, polymethacrylates and the graft polymers described in US-4931497, US-5011892 and US-5041496. Particularly advantageous hydrogels are the kneader polymers described in WO 01/38402 and the polyacrylate-based hybrid organic-inorganic hydrogels described in DE 19855455.

Substances prepared according to the invention that can be used in hydrogels as radical crosslinkers can be used alone or in combination with other crosslinkers such as internal or surface crosslinkers such as:
Other suitable cross-linking agents are in particular methylene bisacrylamide or methylene bismethacrylamide, polyols unsaturated monocarboxylic or polycarboxylic acid esters such as diacrylates, triacrylates or tetraacrylates such as butanediol or ethylene glycol diacrylate Or -methacrylate and trimethylolpropane triacrylate or glycerin diacrylate and -triacrylate or pentaerythritol tetraacrylate and allyl compounds such as allyl (meth) acrylate, triallyl cyanurate, diallyl maleate, polyallyl ester, tetraallyl Oxyethane, triallylamine, tetraallylethylenediamine, allyl phosphate Ester and vinylphosphonic acid derivatives, are described for example in EP-A-0343427. However, the process according to the invention is particularly preferably a hydrogel which uses polyallyl ether as a further crosslinker and is produced by acidic homopolymerization of acrylic acid. Suitable crosslinking agents are pentaerythritol tri- and tetraallyl ether, trimethylolpropane diallyl ether, polyethylene glycol diallyl ether, monoethylene glycol diallyl ether, glycerol di- and triallyl ether, sorbitol-based polyallyl ethers, and these An ethoxylated variant of Further particularly advantageous crosslinking agents are polyethylene glycol diacrylate, ethoxylated derivatives of trimethylolpropane triacrylate, such as Sartomer SR 9035, and ethoxylated derivatives of glycerol diacrylate and glycerol triacrylate. Of course, mixtures of the above-mentioned crosslinking agents can also be used.

  Particular preference is given to combinations of crosslinking agents in which another crosslinking agent can be dispersed in the crosslinking agent F according to the invention. An example of such a cross-linking agent combination is a cross-linking agent combination of cross-linking agent F according to the present invention with di- or tripropylene glycol diacrylate and propoxylated glycerin triacrylate. Another example of such a crosslinker combination is a crosslinker according to the invention and butanediol diacrylate or trimethylolpropane triacrylate or pentaerythritol triallyl ether.

  Particularly advantageous are hydrogels prepared using ester F prepared according to the present invention as a radical crosslinking agent.

  The water-absorbing polymer is preferably a polymeric acrylic acid or polyacrylate. This water-absorbing polymer can be produced by one of the methods known from the literature. Polymers containing crosslinkable comonomers (0.001 to 10 mol%) are advantageous, but polymers obtained by radical polymerization and in which a polyfunctional ethylenically unsaturated radical crosslinker is used Particularly advantageous.

The hydrophilic highly swellable hydrogel can be produced by a polymerization method known per se. Preference is given to polymerization in aqueous solution by the so-called gel polymerization method. In this case, as described above, a diluted, preferably aqueous, particularly preferably 15-50% by weight, aqueous solution of one or more hydrophilic monomers and optionally a suitable graft base L in the presence of a radical initiator. The polymerization is preferably carried out without using mechanical mixing and utilizing the Tromsdorf-Norish effect (Makromol. Chem. 1, 169 (1947)). The polymerization reaction can be carried out in the temperature range from 0 ° C. to 150 ° C., preferably from 10 ° C. to 100 ° C., even at standard pressure or at elevated or reduced pressure. As usual, the polymerization can be carried out under a protective gas atmosphere, preferably under nitrogen. Energetic electromagnetic radiation or normal chemical polymerization initiators K to initiate the polymerization, such as organic peroxides such as benzoyl peroxide, t-butyl hydroperoxide, methyl ethyl ketone peroxide, cumene hydroperoxide, azo compounds such as Azodiisobutyronitrile as well as inorganic peroxy compounds such as (NH ₄ ) ₂ S ₂ O ₈ , K ₂ S ₂ O ₈ or H ₂ O ₂ can be used.

  These optionally contain reducing agents such as ascorbic acid, sodium bisulfite and iron (II) sulfate or aliphatic and aromatic sulfinic acids such as benzenesulfinic acid and toluenesulfinic acid or derivatives of these acids as reducing components Can be used in combination with Mannich adducts consisting of sulfinic acid, aldehydes and amino compounds described in DE-C-1301566. Multi-step post-heating of the polymer gel in the temperature range of 50 ° C. to 130 ° C., preferably 70 ° C. to 100 ° C., can further improve the quality characteristics of the polymer.

  The resulting gel is neutralized to 0 to 100 mol%, preferably 25 to 100 mol% and particularly preferably 50 to 85 mol%, based on the monomers used, with the usual neutralizing agents, preferably Alkali metal hydroxides, alkali metal oxides or the corresponding alkali metal carbonates can be used, but sodium hydroxide, sodium carbonate and sodium hydrogen carbonate are particularly preferably used. When sodium hydroxide is used, the quality obtained by membrane electrolysis is particularly preferably used.

  Usually neutralization is achieved by mixing the neutralizing agent as an aqueous solution, preferably as a solid. For this purpose, the gel is pulverized mechanically, for example by means of a pulverizer, and the neutralizing agent is sprayed, sprayed or poured and then carefully mixed. For this purpose, the gel material obtained can be further homogenized several times. The neutralized gel material is then dried using a band drier or roller drier, preferably to a residual moisture content of less than 10% by weight, in particular less than 5% by weight.

  However, the polymerization itself can also be carried out by any other method described in the literature. In particular, neutralization of acrylic acid can be carried out before the polymerization as described above in step f). Regardless of whether neutralization is carried out before, during or after polymerization, acrylic acid having a dimer content of particularly preferably 2000 ppm or less, particularly preferably 1000 ppm or less and most preferably 500 ppm or less Is used. Particular preference is given to using sodium hydroxide from membrane electrolysis. This is superior to other methods due to its high purity (eg, low chloride content and absence of traces of mercury). Alternatively, it is of course also possible to use sodium hydroxide from the amalgam process or the diaphragm process. In this case, the polymerization can be carried out continuously or discontinuously in a band reactor or kneading reactor known to those skilled in the art. When carried out in a band reactor, initiation by electromagnetic radiation, preferably by UV radiation, or alternatively by redox initiator system is particularly advantageous. Particularly advantageous is a combination of both initiation methods: using electromagnetic radiation and a chemical redox initiator system simultaneously.

  n) The dried hydrogel is then ground and sieved, with the usual roll mills, pin mills or classification mills being used for grinding. The preferred particle size of the sieved hydrogel is advantageously in the range from 45 to 1000 μm, preferably from 45 to 850 μm, particularly preferably from 200 to 850 μm and particularly preferably from 300 to 850 μm. Another particularly advantageous range is from 150 to 850 μm, in particular from 150 to 700 μm, and particularly preferably from 200 to 600 μm, and particularly preferably from 150 to 550 μm. Another special range is 200-800 μm and a particularly preferred range is 250-650 μm, a particularly preferred range is 300-600 μm. Particularly advantageous ranges are 200 to 500 μm, 100 to 450 μm and 150 to 400 μm. More preferably, the ranges are: 100 μm to 500 μm, 100 μm to 600 μm, 100 μm to 700 μm, 100 μm to 800 μm. In this range there is preferably 80% by weight of the particles, in particular 90% by weight of the particles. The particle size distribution can be measured using established classification methods or preferably optical methods (photos).

  The subject of the present invention is also a crosslinked hydrogel containing at least one hydrophilic monomer M in the form of a copolymer and crosslinked with an ester F of an alkoxylated glycol and (methacrylic) acid. Esters can be prepared according to the invention or by methods known in the prior art, preferably by the method according to the invention.

  The above compounds can be used as the ester F.

  The CRC value [g / g] of the hydrogel-forming polymer according to the invention can be determined by the method described in the detailed description and is advantageously greater than 10, in particular 11, 12, 13, 14, 15 16, 18, 20, 22, 24 or more, particularly preferably 25, especially 26, 27, 28, 29, particularly preferably 30, 31, 32, 33, 34, 35, 36, 37 , 38, 39, 40, 41, 42, 43, 44, 45 or more.

  The AUL-0.7 psi value [g / g] of the hydrogel-forming polymers according to the invention can be determined by the method described in the detailed description and is advantageously greater than 8, in particular 9, 10, 11 12, 13, 14 or more, particularly preferably 15, especially 16, 17, 18, 19 or more, particularly preferably greater than 20, in particular 21, 22, 23, 24, 25, 26 , 27, 28 or more.

  The AUL-0.5 psi value [g / g] of the hydrogel-forming polymer according to the invention can be determined by the method described in the detailed description and is advantageously greater than 8, in particular 9, 10, 11 12, 13, 14 or more, particularly preferably 15, especially 16, 17, 18, 19 or more, particularly preferably greater than 20, in particular 21, 22, 23, 24, 25, 26 , 27, 28 or more.

  The saponification number VSI of the hydrogel-forming polymers according to the invention can be determined by the method described in the detailed description and is advantageously less than 10, in particular 9.5, 9 or 8.5 or less, Particularly preferably less than 8, in particular 7.5, 7, 6.5, 6, 5.5 or less, particularly preferably less than 5, in particular 4.5, 4, 3.5 or less. It is as follows.

  The residual crosslinker content of the hydrogel-forming polymers according to the invention can be determined by the method described in the detailed description and is preferably less than 30 ppm, particularly preferably less than 20 ppm, but particularly preferably Is less than 10 ppm, in particular 9.5 ppm, 9 ppm or 8.5 ppm or less, particularly preferably less than 8 ppm, in particular 7.5 ppm, 7 ppm, 6.5 ppm, 6 ppm, 5.5 ppm or Less than, particularly preferably less than 5 ppm, in particular 4.5 ppm, 4 ppm, 3.5 ppm or less. When multiple crosslinkers are used as a mixture, this maximum is for each individual crosslinker in the mixture.

Use of a hydrogel-forming polymer according to the invention The invention further comprises (P) a liquid permeable cover on top,
(Q) a lower layer substantially impermeable to liquid,
(R) a core material present between (P) and (Q), which is 10 to 100% by weight of the hydrogel-forming polymer according to the invention,
0 to 90% by mass of hydrophilic fiber material,
The hydrogel-forming polymer according to the invention is preferably 20 to 100% by weight, hydrophilic fiber material 0 to 80% by weight,
More advantageously, the hydrogel-forming polymer according to the invention is 30 to 100% by weight, the hydrophilic fiber material 0 to 70% by weight,
Even more advantageously, the hydrogel-forming polymer according to the invention is 40-100% by weight, the hydrophilic fiber material 0-60% by weight,
More advantageously, the hydrogel-forming polymer according to the invention is 50-100% by weight, the hydrophilic fiber material 0-50% by weight,
Particularly advantageously, the hydrogel-forming polymer according to the invention is 60-100% by weight, the hydrophilic fiber material 0-40% by weight,
Particularly preferably, the hydrogel-forming polymer according to the invention is 70 to 100% by weight, the hydrophilic fiber material 0 to 30% by weight,
Very advantageously, the hydrogel-forming polymer according to the invention is 80-100% by weight, the hydrophilic fiber material 0-20% by weight,
Most preferably, the hydrogel-forming polymer according to the invention is 90-100% by weight, the hydrophilic fiber material 0-10% by weight.
Containing
(S) of the above hydrogel-forming polymer, optionally containing a tissue layer directly above and below the core (R) and (T) optionally an absorbent layer present between (P) and (R) Concerning use in hygiene products.

  The percentages stated are 11, 12, 13, 14, 15, 16, 17, 18, 19 to 100% by weight each time and all in-between when the hydrogel-forming polymer according to the invention is 10 to 100% by weight. (For example, 12.2%) and correspondingly hydrophilic fiber materials are 0 to 89, 88, 87, 86, 85, 84, 83, 82, 81% by weight and between A description of the percent present (eg 87.8%) is possible. If other materials are present in the core, the polymer and fiber percentage values are correspondingly reduced. The same applies to the advantageous ranges, for example, very advantageously 81, 82, 83, 84, 85, 86, 87, 88, 89% by weight and correspondingly fiber materials for the hydrogel-forming polymers according to the invention. 19, 18, 17, 16, 15, 14, 13, 12, 11% by mass may be present. Therefore, in an advantageous range 20, 21, 22, 23, 24, 25, 26, 27, 28, 29-100% by weight of the hydrogel-forming polymer according to the invention is more advantageous in an advantageous range of 30, 31, 32, 33, 34, 35, 36, 37, 38, 39 to 100% by weight of the hydrogel-forming polymer according to the invention in an even more advantageous range of 40, 41, 42, 43, 44, 45, 46, 47, 48, 49 to 100% by weight of the hydrogel-forming polymer according to the invention, more preferably 50, 51, 52, 53, 54, 55, 56, 57, 58, 59-100% by weight of the hydrogel-forming polymer according to the invention, Advantageously, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69-100% by weight of the hydrogel-forming polymer according to the invention In an advantageous range 70, 71, 72, 73, 74, 75, 76, 77, 78, 79 to 100% by weight of the hydrogel-forming polymer according to the invention, and in a most advantageous range 90, 91, 92, 93 94, 95, 96, 97, 98, 99 or 100% by weight of the hydrogel-forming polymer according to the invention.

  Hygiene products in this case should be understood as incontinence liners and trousers for adults and diapers for babies.

  The liquid permeable cover (P) is a layer in direct contact with the skin. The material for this is in this case polyester, polyolefin, rayon or natural fibers, for example normal synthetic or semi-synthetic fibers or films of cotton. In the case of nonwoven materials, the fibers are usually bound by a binder, such as polyacrylate. Preferred materials are polyester, rayon and blends thereof, polyethylene and polypropylene. Examples for liquid permeable layers are described in WO 99/57355 A1, EP 1023883 A2.

  The liquid-impermeable layer (Q) is usually a sheet made of polyethylene or polypropylene. However, any other material that can be processed into a sheet that is impermeable to liquid can also be used. By impervious to liquid is meant impervious for the condensed liquid in this context. However, the sheet may at the same time be permeable for liquid vapors, and often modern diaper structures have a high vapor permeability, which is the largest for the underlying condensed liquid (which is usually water or urine). Integrates impermeability.

  The core material (R) contains a hydrophilic fiber material in addition to the hydrogel-forming polymer according to the present invention. Hydrophilic should be understood to mean that the aqueous liquid is rapidly dispersed in the fibers. The fiber material is usually cellulose, modified cellulose, rayon, polyester, such as polyethylene terephthalate. Particularly advantageous are cellulose fibers such as cellulose. The fibers usually have a diameter of 1 to 200 μm, preferably 10 to 100 μm. Furthermore, the fiber has a minimum length of 1 mm.

  The structure and shape of diapers is generally known and described, for example, in WO 95/26209, page 66, line 34 to page 11, line 11, DE19660401A1, EP-A-0316518 and EP-A-0202127. Yes. In general, diapers and other sanitary products are described in WO 00/65084, in particular pages 6-15, WO 00/65348, in particular pages 4-17, WO 00/35502, in particular pages 3-9, DE 19737434, WO 98/8439. Yes. Hygiene products for feminine hygiene are described in the following literature locations. Hydrogel-forming polymers that absorb aqueous liquids according to the invention can be used here. Literature location of feminine hygiene products: WO95 / 24173: Absorbent product for controlling odor, WO91 / 11977: Odor control of body fluid, EP389023: Absorbent hygiene product, WO94 / 25077: Odor controlling material, WO97 / 01317: Absorbent hygiene article, WO 99/18905, EP 8342297, US 5,762,644, US 5,895,381, WO 98/57609, WO 2000/065083, WO 2000/066945, WO 2000/069481, WO 2000/069481, US 6,123,693 , EP1104666, WO2001 / 024755, WO2001 / 000115, EP105373, WO2001 / 041692, EP1074233. Tampons are described in the following documents: WO 98/48753, WO 98/41179, WO 97/09022, WO 98/46182, WO 98/46181, WO 2001/043679, WO 2001/043680, WO 2000/061052, EP 1108408, WO 2001/033962, DE 200020662. , WO2001 / 001910, WO2001 / 001908, WO2001 / 001909, WO2001 / 001906, WO2001 / 001905, WO2001 / 24729. Incontinence products are described in the following documents: Disposable absorbent products for personal use of incontinence: EP 311344, specification pages 3 to 9, disposable absorbent products: EP 850623, absorbent products: WO 95/26207, absorbent products: EP 894502. , Dry laid fiber structure: EP850616, WO98 / 22063, WO97 / 49365, EP903134, EP887060, EP887059, EP887058, EP8887057, EP8887056, EP931530, WO99 / 25284, WO98 / 48753. Women's hygiene products and incontinence products are described in the following literature: Menstruation products: WO 93/22998, specification pages 26-33, Absorbing members for body fluids: WO 95/26209, specifications pages 36-69 Disposable absorbent product: WO 98/20916, specification pages 13-24, improved composite absorbent structure: EP 306262, specification pages 3-14, excreta absorption product: WO 99/45973. These references and citations of those references are hereby expressly incorporated into the present disclosure.

  The hydrogel-forming polymers according to the invention are very suitable as absorbents for water and aqueous liquids, so as water retention materials in agricultural and horticulture, as filter aids and especially in sanitary goods such as diapers, tampons or sanitary napkins It can be used as an absorbent component.

Lamination and fixation of the highly swellable hydrogel according to the present invention In addition to the above highly swellable hydrogel, the absorbent composition according to the present invention contains a highly swellable hydrogel or a composite material on which the gel is fixed Exists. Each composite that contains a highly swellable hydrogel and can be further integrated into an absorbent layer is suitable. Many such compositions are already known and have been described in detail in the literature. One composite for incorporating a highly swellable hydrogel is, for example, a cellulose fiber mixture (air laid web, web laid web) fiber matrix or synthetic polymer fiber (melt blow web, spunbond web), or alternatively cellulose. You may consist of the mixed fiber material which consists of a fiber and a synthetic fiber. Possible fiber materials are described in detail in subsequent chapters. The manufacture of air raid webs is described, for example, in WO 98/28478. Furthermore, open foam foams or the like can be used for the incorporation of highly swellable hydrogels.

  Alternatively, such a composition can be made by the fusion of two individual layers, wherein one or better a number of chambers are formed, which contain a highly swellable gel. Such a chamber system is described in detail in EP0615736A1, page 7, line 26 et seq.

  In this case, at least one of both layers should be water permeable. The second layer may be water permeable or water impermeable. Tissue or other woven fabrics, closed cell or open cell foams, perforated films, woven fabrics made of elastomers or fiber materials can be used as layer material. When the absorbent composition comprises a layer composition, the layer material should have a pore structure whose pore size is sufficiently small to retain the highly swellable hydrogel particles. The above examples for the composition of the absorbent composition also include a laminate consisting of at least two layers between which the highly swellable hydrogel is incorporated and fixed.

  There is generally the possibility of immobilizing hydrogel particles within the absorbent core to improve so-called dry- and wet-integrity. Dry- and wet-integrity is the absorption of the highly swellable hydrogel so that the highly swellable hydrogel retains the action of external forces both wet and dry and does not cause migration or spillage of the highly swellable polymer. It is understood that it can be incorporated into sex compositions. The action of force is understood to be especially a mechanical load, for example a mechanical load that appears in the course of movement when transporting sanitary goods, but it is also a mass load that is put on sanitary goods, especially in incontinence And understand. There are numerous possibilities known to those skilled in the art for fixation. Examples of heat treatment, addition of adhesive, thermoplastic resin, and fixing with a binder material are described in WO 95/26209, page 37, lines 36 to 41, line 14. Therefore, the above section 1 is a component of the present invention. A method for increasing the wet strength is described in WO2000 / 36216A1.

  Furthermore, the absorbent composition may consist of a carrier material, for example a polymer film, on which the highly swellable hydrogel particles are fixed. Fixing may be performed on one side or both sides. The carrier material may be water permeable or water impermeable.

  In the above composition of the absorbent composition, the highly swellable hydrogel is 10 to 100%, preferably 20 to 100%, more preferably 30 to 100% by weight relative to the total weight of the composition and the highly swellable hydrogel. %, Even more preferably 40 to 100% by weight, more preferably 50 to 100% by weight, particularly preferably 60 to 100% by weight, particularly preferably 70 to 100% by weight, very particularly preferably 80 to 100% by weight. Incorporated in a mass percentage and most advantageously of 90 to 100 mass%.

Absorbent Composition Fiber Material The structure of the absorbent composition according to the present invention is based on a variety of fibrous materials used as a fiber network or matrix. The present invention includes naturally occurring (modified or non-modified) fibers as well as synthetic fibers.

  A detailed summary of examples of fibers that can be used in the present invention is described in patent WO95 / 26209, page 28, lines 9-36, line 8. Therefore, the above section 1 is a component of the present invention.

  Examples for cellulose fibers include those normally used in absorbent products such as freeze cellulose and cotton type cellulose. The material (coniferous or hardwood), the production method such as chemical cellulose, semi-chemical cellulose, chemical mechanical cellulose (CTMP) and bleaching method are not particularly limited. Thus, for example, natural cellulose fibers such as cotton, flax, silk, wool, jute, ethyl cellulose and cellulose acetate can be used.

Vinyl Suitable synthetic fibers polychlorinated, polyvinyl fluoride, polytetrafluoroethylene, polyvinylidene chloride, polyacrylic compounds, are produced, for example, ORLON ^(R), polyvinyl acetate, ethyl vinyl acetate, polyvinyl alcohol soluble or insoluble . Examples of synthetic fibers include thermoplastic polyolefin fibers, such as polyethylene fibers ^{(PULPEX (R)),} polypropylene fibers and polyethylene - polypropylene - bicomponent fibers, polyester fibers, such as polyethylene terephthalate fiber (DACRON ^(R) or KODEL ^{(R )} ), Copolyester, polyvinyl acetate, polyethyl vinyl acetate, polyvinyl chloride, polyvinylidene chloride, polyacrylate, polyamide, copolyamide, polystyrene and copolymers of the aforementioned polymers, and polyethylene terephthalate-polyethylene-isophthalate-copolymer Bicomponent fiber, polyethyl vinyl acetate / polypropylene, polyethylene / polyester, polypropylene / polyester, copolyester / polyester, Polyamide fiber (nylon), polyurethane fiber, polystyrene fiber and polyacrylonitrile fiber are included. Preference is given to polyolefin fibers, polyester fibers and their bicomponent fibers. Also advantageous are bicomponent fibers that adhere on heat, consisting of a shell-core type and side-by-side type polyolefin, based on their excellent shape stability after absorbing liquid.

  Said synthetic fibers are preferably used in combination with thermoplastic fibers. During the heat treatment, the latter partly migrates into the matrix of the existing fiber material and thus forms a bond and becomes a new strengthening element when cooled. Furthermore, the addition of thermoplastic fibers means that the size of the existing pores is expanded after the heat treatment. In this way, it is possible to continuously raise the proportion of thermoplastic fibers towards the cover layer by continuously metering thermoplastic fibers during the formation of the absorbent layer, and so on. In addition, the pore size increases continuously. The thermoplastic fibers may be formed from a number of thermoplastic polymers having a melting point below 190 ° C, preferably from 75 ° C to 175 ° C. Cellulose fiber damage has not yet been predicted at these temperatures.

  The length and diameter of the synthetic fibers are not particularly limited, and any fiber having a length of 1 to 200 mm and a diameter of 0.1 to 100 denier (grams per 9000 meters) is advantageously used. can do. Preferred thermoplastic fibers have a length of 3 to 50 mm, particularly preferably a length of 6 to 12 mm. The preferred diameter of the thermoplastic fibers is 1.4 to 10 dtex, particularly preferably 1.7 to 3.3 dtex (grams per 10000 meters). The shape is not particularly limited and includes, for example, woven, elongated cylindrical, cut- / split yarn, staple fiber and roving fiber.

  The fibers in the absorbent composition according to the present invention may be hydrophilic, hydrophobic, or a combination of both. In the publication “Contact Angle, Wettability and Adhesion”, Robert F. in American Chemical Society (1964). According to Gould's definition, a fiber is hydrophilic when the contact angle between the liquid and the fiber (or the surface of the fiber) is less than 90 °, or when the liquid tends to diffuse spontaneously on the surface of the fiber. It is said to be sex. Both processes usually coexist. Conversely, fibers are said to be hydrophobic when contact angles greater than 90 ° occur and no diffusion is observed.

  Preference is given to using hydrophilic fiber materials. Particular preference is given to using fiber materials that are weakly hydrophilic towards the body and that are most hydrophilic in the region around the highly swellable hydrogel. The use of various hydrophilic layers in the manufacturing process creates a gradient, which creates a flow path for the impinging liquid to flow into the hydrogel, where absorption is finally performed.

Suitable hydrophilic fibers for use in the absorbent composition according to the invention, for example cellulose fibers, modified cellulose fibers, rayon, polyester fibers such as polyethylene terephthalate ^{(DACRON (R))} and a hydrophilic nylon (HYDROFIL ^{( R)} ). Suitable hydrophilic fibers can also be obtained by hydrophilizing hydrophobic fibers, for example by treating thermoplastic fibers obtained from polyolefins (eg polyethylene or polypropylene, polyamide, polystyrene, polyurethane, etc.) with surfactants or silica. it can. However, cellulose fibers are advantageous for cost reasons and availability reasons.

  Highly swellable hydrogel particles are embedded in the described fiber material. This can be done, for example, by forming the absorbent layer in the form of a matrix together with the hydrogel material and fibers, or by laminating a highly swellable hydrogel into a layer of fiber mixture, where it is finally fixed by laminating an adhesive or layers This can be done in various ways.

  In this case, the fiber matrix that absorbs and disperses the liquid may be composed of synthetic fibers, cellulose fibers, or a mixture of synthetic fibers and cellulose fibers, in which case synthetic fibers (100-0): cellulose fibers (0 100) can be changed. The cellulose fibers used may be further chemically cured to increase the shape stability of the sanitary product.

Chemical curing of cellulose fibers can be performed by various methods. On the one hand, curing of the fiber can be achieved by adding a suitable coating / coating to the fiber material. Such additives are, for example, polyamide - epichlorohydrin - coated ^{(Kymene (R) 557H, Hercules} Inc.Wilmington Delaware, USA), polyacrylamide - if set forth in coating (U.S. Patent No. 3,556,932, or ^{Marke Parez (R) 631NC, American} Cyanamid Co., Stamford, CT, commercially available products of USA), a melamine - containing coatings and polyethyleneimine coating - formaldehyde.

Chemical curing of cellulose fibers can also be performed by chemical reaction. Thus, for example, the addition of a suitable crosslinker material results in curing that takes place inside the fiber. Suitable crosslinker materials are common materials used for monomer crosslinking. _C 2 -C ₈ with acid functionality - _dialdehyde, C 2 -C ₈ - monoaldehyde, and in particular _C 2 -C ₉ - although polycarboxylic acids are encompassed, but not limited to. Specific substances from these groups are, for example, glutaraldehyde, glycol, glyoxylic acid, formaldehyde and citric acid. These materials react in at least two hydroxyl groups and individual cellulose chains or in one individual cellulose fiber between two adjacent cellulose chains. The fibers are cured by crosslinking, and the fibers are given a relatively large shape stability by this treatment. In addition to its hydrophilic properties, these fibers have an integral combination of cure and elasticity. This physical property allows the capillary structure to be maintained even when the liquid and compressive force are in contact simultaneously, and to prevent premature collapse.

  Chemically crosslinked cellulose fibers are known and are WO 91/11162, US Pat. No. 3,224,926, US Pat. No. 3,440,135, US Pat. No. 3,932,209, US Pat. Described in US Pat. No. 4,035,147, US Pat. No. 4,822,453, US Pat. No. 4,888,093, US Pat. No. 4,898,642 and US Pat. No. 5,137,537. Yes. Chemical cross-linking results in the curing of the fiber material, which is ultimately reflected in the improved shape stability of the overall hygiene product. The individual layers are bonded to each other by methods known to those skilled in the art, such as melting by heat treatment, addition of a molten adhesive, latex binder, and the like.

Method for Producing Absorbent Composition The absorbent composition comprises a composition containing a highly swellable hydrogel and a highly swellable hydrogel present in or fixed thereto.

  Examples for methods for obtaining an absorbent composition comprising a carrier material having, for example, a highly swellable hydrogel fixed on one or both sides are known and encompassed by the present invention, but are not limited thereto.

  For example, it consists of a highly swellable hydrogel (c) embedded in a fiber material mixture consisting of synthetic fibers (a) and cellulose fibers (b), in which case synthetic fibers (100-0): cellulose fibers (0-100) Examples of methods for obtaining an absorbent composition that can vary the mixing ratio of (1) (a), (b) and (c) are mixed simultaneously, (2) (a) and (C) a mixture of (b) and (3) a mixture of (b) and (c) into (a), (4) a mixture of (a) and (c) (5) (b), (5) (b) and (c) are mixed, and (a) is continuously metered in (6) (a) and (c) are mixed, And (b) a continuous metering method and (7) (b) and (c) It is a method of mixing to (a). Of these examples, methods (1) and (5) are advantageous. The apparatus used in this method is not particularly limited, and an ordinary apparatus known to those skilled in the art can be used.

  Correspondingly produced absorbent compositions can optionally be heat-treated to obtain an absorbent layer having excellent shape stability in the wet state. The method for heat treatment is not particularly limited. Examples include heat treatment by supplying hot air or by infrared irradiation. The temperature during the heat treatment is 60 ° C. to 230 ° C., preferably 100 ° C. to 200 ° C., particularly preferably 100 ° C. to 180 ° C.

  The duration of the heat treatment depends on the type of synthetic fiber, its amount and the production rate of sanitary products. In general, the heat treatment time is 0.5 seconds to 3 minutes, preferably 1 second to 1 minute.

  The absorbent composition generally comprises, for example, a cover layer that is permeable to liquid and a lower layer that is impermeable to liquid. In addition, honey (Beinabschluss) and adhesive tape are installed to complete the hygiene product. The materials and types of the permeable cover layer and the non-permeable lower layer, as well as the splash and adhesive tape are known to those skilled in the art and are not particularly limited. An example for this is described in WO 95/26209.

  An advantage of the present invention is that the ester F, which can be used as a crosslinking agent, does not need to be purified after its preparation, in particular it is not necessary to separate (meth) acrylic acid, preferably acrylic acid. This is because it is usually a monomer for making hydrogels.

Experimental Part The ppm and percent descriptions used herein are% by mass and ppm by mass unless otherwise indicated.

  The method according to the invention is illustrated in detail by the following examples.

Examples Production of crude acrylate esters as superabsorbent crosslinkers Production of superabsorbent crosslinkers is carried out in the examples by esterifying alkoxylated glycols with acrylic acid and separating the water by azeotropic distillation. The esterification catalyst is sulfuric acid in the examples. The reactants are charged in the examples together with a stabilizer mixture consisting of hydroquinone monomethyl ether, triphenyl phosphite and hypophosphoric acid in methylcyclohexane as entrainer. The reaction mixture is then heated to about 98 ° C. until azeotropic distillation is initiated. During azeotropic distillation, the temperature in the reaction mixture increases. Measure the amount of water separated. Distillation is interrupted at least when the theoretical amount of water has been separated. The entrainer is subsequently removed by vacuum distillation. The product is cooled and used as a cross-linking agent in superabsorbent production.

  The reaction rate and reaction yield are accurately measured. This is because the water separated in the esterification also contains acrylic acid, and the acrylic acid is removed during the vacuum distillation of the entrainer. The crude ester also contains free acrylic acid, which is titrated with the catalyst (acid number).

  All amounts are in parts by weight unless otherwise indicated.

Preparation of the ester The acid value was determined according to DIN EN 3682.

Example 1 Preparation of alkoxylated glycols as the base of ester F a) PO-EO ₆ -PO
124 g of glycol are charged into an autoclave with 0.5 g of 45% KOH in water and dehydrated together at 80 ° C. and reduced pressure (about 20 mbar). Then 440 g of ethylene oxide are added at 145 to 155 ° C. and reacted under elevated pressure at this temperature. The reaction is complete when no more pressure changes are observed. The mixture is then stirred for a further 30 minutes at about 150 ° C. Subsequently, 232 g of propylene oxide is metered in at an elevated pressure at 120-130 ° C. for a relatively long time and reacted in the same manner. After washing with inert gas and cooling to 60 ° C., the catalyst is separated off by addition of sodium pyrophosphate and subsequent filtration.

  b) Tripropylene glycol is a commercially available diol component.

Example 2 Preparation of Acrylic Esters a) 506 parts of PO-EO ₆ -PO diacrylate propoxylated polyglycol (according to Example 1b) are esterified in 345 parts of methylcyclohexane with 200 parts of acrylic acid and 5 parts of sulfuric acid. As auxiliary agents, 2 parts of hydroquinone monomethyl ether, 2 parts of α-tocopherol and 1 part of hypophosphoric acid are added. 36 parts of water are separated before the entrainer is removed by vacuum distillation. The product is purified by K300 filter. Measure the acid value. The addition of 40 parts of acrylic acid further reduces the viscosity of the slightly colored product (APHA <100).

  b) Tripropylene glycol diacrylate is a commercial product obtained as Laromer TPGDA (BASF). Alternatively, it can be produced in the same manner as in the above example.

Hydrogel Production Dry hydrogels can be investigated with the following test method to measure the quality of surface cross-linking.

Test method a) Centrifuge retention capacity
This method measures the free swellability of the hydrogel in the tea bag. For the measurement of CRC, 0.2000 ± 0.0050 g of dried hydrogel (particle size 106-850 μm) is weighed into a 60 × 85 mm tea bag and the tea bag is subsequently welded. The tea bag is immersed in an excess of 0.9% by weight saline solution for 30 minutes (at least 0.83 l of saline solution / 1 g of polymer powder). Subsequently, the tea bag is centrifuged at 250 g for 3 minutes. The amount of liquid is measured by weighing a centrifuged tea bag.

b) AUL Absorbency Under Load (0.7 psi)
The measuring cell for measuring AUL 0.7 psi is a plexiglass cylinder with an inner diameter of 60 mm and a height of 50 mm, which has a special steel filter plate with a mesh width of 36 μm bonded to the lower side. The measurement cell further includes a plastic plate having a diameter of 59 mm and a weight that can be placed in the measurement cell together with the plastic plate. The weight and weight of the plastic plate are 1345 g together. To perform an AUL 0.7 psi measurement, measure the mass of an empty plexiglass cylinder and plastic plate and record W ₀ . Next, 0.900 ± 0.005 g of hydrogel-forming polymer (particle size distribution 150-800 μm) is weighed into a plexiglass cylinder and dispersed on a special steel filter plate as uniformly as possible. The plastic plate is then carefully placed in a plexiglass cylinder and the entire unit is weighed. Mass recorded as _{W a.} The weight is then placed on a plastic plate in a plexiglass cylinder. A ceramic filter plate having a diameter of 120 mm, a height of 10 mm and a porosity of 0 (Duran, Shott) is installed in the center of a Petri dish having a diameter of 200 mm and a height of 30 mm, and the surface of the liquid is not wetted. A 0.9% by weight sodium chloride solution is filled until sealed by the filter plate surface. Subsequently, a circular filter paper having a diameter of 90 mm and a pore diameter <20 μm (manufactured by S & S589 Schwarzband, Schleicher & Schuell) is placed on the ceramic plate. A plexiglass cylinder containing the hydrogel-forming polymer is now placed on the filter paper with a plastic plate and weight and left here for 60 minutes. After this time, the complete unit from the Petri dish is removed from the filter paper and the weight is subsequently removed from the Plexiglas cylinder. The Plexiglas cylinder containing swollen hydrogel is weighed together with the plastic plate and the weight is recorded as W _b.

The absorption under pressure (AUL) is calculated as follows:
AUL 0.7 psi [g / g] = [W _b −W _a ] / [W _a −W ₀ ]
AUL 0.5 psi is measured similarly at lower pressures.

  c) Measurement after 16 hours of the extractable ratio (Extract. 16h) is performed in the same manner as described in EP-A1811166, page 13, lines 1 to 19.

d) Method for determining the residual content of crosslinker in the hydrogel In order to determine the content of unreacted residual crosslinker, the residual crosslinker is first extracted from the dried hydrogel by double extraction. For this purpose, 0.400 g of dried hydrogel and 40 g of 0.9% by weight saline solution are placed in an ampule that can be sealed and centrifuged. To this is added 8 ml of dichloromethane, the ampoule is closed and then shaken for 60 minutes. Thereafter, the ampoule is immediately centrifuged at 1500 rpm for 5 minutes, and the organic phase becomes transparent and separated from the aqueous phase.

  Weigh 50 μl of monoethylene glycol into the second ampoule, add about 5 to 6 ml of dichloromethane extract to this, and accurately grasp the mass of the extract to 0.001 g. The dichloromethane is then evaporated at 50-55 ° C. and the residue is cooled and then taken up with 2 ml of a methanol-water mixture (50 parts by volume each). Shake for 10 minutes and then filter through a PTFE 0.45 μm filter.

  The sample thus obtained is separated by liquid phase chromatography and analyzed by mass spectrometry. Quantification is performed on a dilution series of the same crosslinker used.

  Zorbax Eclipse XDB C-8 (150 × 4.6 mm-5 μm) is used as the chromatography column and Zorbax Eclipse XDB C-8 (12.5 × 4.6 mm-5 μm) is used as the front column. A methanol / water mixture (75/25) is used as eluent.

  The gradient transition is as follows:

  The flow is 1 ml / min at a pressure of 1600 psi.

  The injection volume is 20 μl.

  Typical analysis times are 5-30 minutes per sample.

  Detection is performed by mass spectrometry in the range of, for example, 800 to 1300 m / z (full scan, positive). The apparatus is operated by APCI (Atmospheric Pressure Chemical Ionisation). For optimization, the capillary temperature is adjusted to 180 ° C., the APCI evaporator temperature to 450 ° C., the source current to 5.0 μA, and the gas flow to 80 ml / min.

  Individual settings must be made specifically for each crosslinker. For this purpose, the appropriate calibration solution of the cross-linking agent is used to measure characteristic peaks that are later relevant to the evaluation. Usually, the main peak is selected.

In this case, the residual crosslinker concentration is calculated as follows:
CONC _Probe = A _Probe × COND _Std × VF / A _Std
CONC _Probe is the required residual crosslinker concentration in the dried hydrogel expressed in mg / kg.
COND _Std is the required residual crosslinker concentration in the calibration solution expressed in mg / kg.
A _Probe is the peak area of the dried hydrogel extract sample.
A _Std is the peak area of the calibration solution.
VF is the dilution factor:
VF = M _DCM × M _Solv / (M _Probe × M _Extract )
M _DCM is a weight of dichloromethane for extraction.
M _Probe is a weigh of dried hydrogel.
M _Solv is a weight of methanol-water-mixture + monoethylene glycol.
M _Extract is the _weight of the dichloromethane extract.

  In this case, it can be confirmed by calibration (for example, a plurality of points in the range of 0 to 50 ppm) that the measurement is carried out in a linear range.

e) Saponification value VSI
The ground gel is then further processed in two different ways:
Post-processing method 1:
The crushed gel is dispersed as a uniform thin layer on a plate with a filter plate and then vacuum dried at 80 ° C. for 24 hours. This drying is very product protective and is therefore an optimal reference standard.

  The dried hydrogel is then ground and the 300-600 micrometer sieve classification is separated.

Post-processing method 2:
The ground gel is first temperature-treated at 90 ° C. for 24 hours in a closed plastic bag. Then disperse uniformly as a thin layer on a plate with a filter plate and dry at 80 ° C. for 24 hours. This drying simulates the drying conditions that appear in typical manufacturing equipment, which typically limits drying performance and throughput due to the associated quality degradation.

  Grind the dried hydrogel and separate the 300-600 micrometer sieve classification.

  The hydrogels obtained by both post-treatment methods are characterized by measuring the tea bag volume (CRC) and the extractable content after 16 hours and the content of unreacted residual crosslinker. Furthermore, the moisture content is measured and if it exceeds 1% by weight, it is taken into account by calculation when measuring these properties. Typically, the moisture content is about 5% by weight.

The saponification number (VSI) of the crosslinker in the gel is then determined from the measured values as follows:
VSI = 0.5 × (CRC ₂ −CRC ₁ ) + 0.5 × (extractable portion ₂ −extractable portion ₁ )
The subscript index represents the post-processing method 1 or 2 in this case. Therefore, the saponification value x increases as the tea bag capacity increases due to operational drying, and as the proportion of extractables increases at that time. Evaluate both contributions in the same way.

  In general, it is advantageous to use a crosslinking agent with the lowest saponification value possible. The ideal crosslinker has a VSI of zero. The use of such a cross-linking agent can improve the performance of the operational dryer to the maximum technically achievable without loss of quality. The reason is that the cross-linking that is regulated during the polymerization and thus the properties of the final product are not changed further by hydrolysis during drying.

Example 3 Production of Superabsorbent Using Acrylic Ester from Example 2 and Other Internal Crosslinkers Example A (Comparative Example)
In an acid resistant plastic container, 305 g of acrylic acid and 3204 g of 37.3 wt% sodium acrylate solution are dissolved in 1465 g of distilled water. To this, 9.7 g of Sartomer SR344 (polyethylene glycol-400-diacrylate) was used as a crosslinking agent, and 0.61 g of V-50 (2,2'-azobisamidinopropane dihydrochloride) and 3.05 g of sodium persulfate were used as an initiator. Add as In this case, the initiator is preferably pre-dissolved in a part of the batch water. Stir the batch well for several minutes.

  Nitrogen gas is then bubbled for about 30 minutes into a solution covered with a plastic sheet in a container to remove oxygen and evenly disperse the crosslinker. Finally, 0.244 g of hydrogen peroxide is dissolved in 5 g of water, and 0.244 g of ascorbic acid is dissolved in 5 g of water and added. The starting temperature at the start of the reaction should be 11-13 ° C. The layer thickness of the reaction solution is about 6 cm. The reaction starts after a few minutes, adiabatic reaction, and the insulated container is left for a further less than 30 minutes, after which the gel is post-treated.

  For the post-treatment of the gel, the gel block is first broken into several pieces and then ground with a grinder having a 6 mm filter plate.

The ground gel is then further processed in two different ways:
Post-processing method 1:
The crushed gel is dispersed as a uniform thin layer on a plate with a filter plate and then vacuum dried at 80 ° C. for 24 hours. This drying is very product protective and is therefore an optimal reference standard.

  The dried hydrogel is then ground and the 300-600 micrometer sieve classification is separated.

Post-processing method 2:
The ground gel is first temperature-treated at 90 ° C. for 24 hours in a closed plastic bag. It is then dispersed as a uniform thin layer on a plate with a filter plate and dried at 80 ° C. for 24 hours. This drying simulates the drying conditions that appear in typical manufacturing equipment, which typically limits drying performance and throughput due to the associated quality degradation.

  Grind the dried hydrogel and separate the 300-600 micrometer sieve classification.

  Similar to Example A, another example is prepared:

  The achieved properties of these hydrogels are summarized in Table 2:

Post-crosslinking:
The gel pulverized after polymerization is dried by post-treatment method 1, and crushed and pulverized.

  A dry standard base polymer powder is used with 0.12% by weight of N-hydroxyethyl-2-oxazolidinone, 3.35% by weight of water and propanediol-1,2.65, based on the polymer used each time. Spray uniformly with stirring with a solution consisting of% by weight.

  For comparison, several completely similar batches were also run using water / isopropanol and water / propanediol-1,3 as solvents. The amount used is the same as described above.

  The batch size is 1.2 kg each time and spraying is performed by spraying the solution with nitrogen using a two-fluid nozzle. A Loedige vertical mixer with a working capacity of 5 l is used.

  If a special sieve classification is described, this is done by sieving before spraying the postcrosslinking solution.

  The wet powder is then temperature treated at 180 ° C. for 60 minutes in a drying chamber. Thereafter, it is screened again at 850 micrometers to remove aggregates.

  Only about 100 g of wet polymer is required for drying. Thereafter, the properties of the crosslinked polymer are measured.

  And similar characteristics using isopropanol or propanediol-1,3 as solvent for comparison:

Claims (28)

Formula I

[Wherein AO independently represents -O-CHR3-CHR4- or -CHR3-CHR4-O- with respect to each AO, wherein R3 and R4 independently represent H, linear or branched. Represents a chain C1-C8-alkyl,
p1 is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34 or 35,
p2 is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34 or 35,
n is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100,
R1 and R2 are independently H or CH3,
Wherein R3 and R4 do not both represent H at the same time, at least for one AO in (AO) p1 and for at least one AO in (AO) p2.   The ester F according to claim 1, wherein all AOs have the same meaning.   Ester F according to claim 1 or 2, wherein R3 or R4 represents H.   4. The ester F according to claim 1, wherein R3 or R4 independently represents CH3, CH2CH3, (CH2) 2-CH3 or (CH2) 7-CH3.   Ester F according to any one of claims 1 to 4, wherein p1 represents 1, 2, 3, 4 or 5 or represents a number from 14 to 27.   Ester F according to any one of claims 1 to 5, wherein p2 represents 1, 2, 3, 4 or 5 or represents a number from 14 to 27.   Ester F according to any one of claims 1 to 6, wherein n represents a number from 2 to 50, preferably from 5 to 30, in particular from 10 to 26.   8. The diol component (AO) p1-[-O-CH2-CH2-] n-O- (AO) p2 has an average molecular weight of 300 to 500 or 2000 to 4000. Ester F of   The ester F according to any one of claims 1 to 8, wherein | p1-p2 | ≦ 3.   10. Ester F according to any one of claims 1 to 9, wherein R1 and R2 are identical, preferably H. Formula II

[Wherein, AO, R3, R4, p1, p2, n have the meaning of any one of claims 1 to 10, or p1 = n = 0 and p2 = 2, 3, 4 Or 5 and R3 is H and R4 is CH3] using (meth) acrylic acid starting from an alkoxylated glycol:
a) reacting an alkoxylated glycol II with (meth) acrylic acid in the presence of at least one esterification catalyst C and at least one polymerization inhibitor D and optionally a solvent E which forms an azeotrope with water. Forming ester F;
b) optionally removing at least part of the water produced in a) from the reaction mixture, wherein b) can be carried out during and / or after a),
f) optionally neutralizing the reaction mixture;
11. If using solvent E, optionally having the step of removing the solvent by distillation and / or i) stripping with an inert gas under the reaction conditions. The manufacturing method of ester F of any one of Claims. The molar excess of (meth) acrylic acid relative to the alkoxylated glycol is at least 2.1: 1, and optionally contained in the reaction mixture obtained after the last step 12. A process according to claim 11, characterized in that (meth) acrylic acid substantially remains in the reaction mixture.   13. A process according to claim 11 or 12, characterized in that (meth) acrylic acid is separated from the reaction mixture containing ester F obtained after the last step to less than 75% by weight.   14. Process according to any one of claims 11 to 13, characterized in that the reaction mixture containing ester F obtained after the last step has an acid number according to DIN EN 3682 of at least 25 mg KOH / g. .   15. The reaction mixture according to claim 11, wherein the reaction mixture containing ester F obtained after the last step has a (meth) acrylic acid content of at least 0.5% by weight. The method described in the paragraph.   16. Process according to any one of claims 11 to 15, characterized in that the molar ratio of (meth) acrylic acid to glycol alkoxylated in reaction a) is at least 10: 1. k) the ester F or p1 = n = 0 according to any one of claims 1 to 10, p2 = 2, 3, 4 or 5, R3 is H and R4 is CH3 Ester F with (meth) acrylic acid, optionally with additional monoethylenically unsaturated compound N, and optionally with at least one further copolymerizable hydrophilic monomer M, at least one radical initiator K and Polymerizing in the presence of at least one graft base L by
l) optionally post-crosslinking the reaction mixture obtained from k),
a crosslinked hydrogel comprising the steps of m) drying the reaction mixture obtained from k) or l) and n) optionally crushing and / or sieving the reaction mixture obtained from k), l) or m) How to manufacture. Steps a) to i) according to any one of claims 11 to 16 and additionally
k) When carrying out steps a) to i), the reaction mixture from this step is optionally mixed with an additional monoethylenically unsaturated compound N, and optionally with at least one further copolymerizable hydrophilic monomer. Polymerizing with M in the presence of at least one radical initiator K and optionally at least one graft base L;
l) optionally post-crosslinking the reaction mixture obtained from k),
a crosslinked hydrogel comprising the steps of m) drying the reaction mixture obtained from k) or l) and n) optionally crushing and / or sieving the reaction mixture obtained from k), l) or m) How to manufacture.   A polymer obtainable by the method according to claim 17 or 18.   At least one hydrophilic monomer M in copolymerized form, ester F or p1 = n = 0 according to any one of claims 1 to 10, wherein p2 = 2, 3, 4 or 5 A crosslinked hydrogel crosslinked by ester F, wherein R3 is H and R4 is CH3.   A cross-linked hydrogel containing at least one hydrophilic monomer M in a copolymerized form and cross-linked by a reaction mixture containing ester F obtained by the method according to any one of claims 11 to 16.   Use of a polymer according to any one of claims 19 to 21 in sanitary goods, packaging materials and nonwovens. At least one ester F or p1 = n = 0, p2 = 2, 3, 4 or 5 according to any one of claims 1 to 10, R3 is H and R4 is CH3 Ester F and (meth) acrylic acid 0.1 to 40% by mass,
At least one hydrophilic monomer M 0.5-99.9% by weight,
-0-10% by weight of at least one esterification catalyst C,
-At least one polymerization inhibitor D 0-5% by weight and-solvent E 0-10% by weight,
, But the sum is always 100% by weight. Further-Diluent G
26. The substance mixture according to claim 25, wherein 100% by mass is added. From the substance mixture according to claim 23 or 24 and additionally 1) optionally postcrosslinking the resulting reaction mixture,
m) drying the reaction mixture obtained directly or obtained from l), and n) optionally crushing and / or sieving the reaction mixture obtained directly or obtained from l) or m) A crosslinked hydrogel obtained from the process. 25. A reaction mixture obtained according to any one of claims 11 to 16 or a substance mixture according to claim 23 or 24,
-As a radical crosslinking agent for water-absorbing hydrogels,
-As a raw material for producing polymer dispersions,
-As a raw material for producing polyacrylates,
-As a raw material for paints, or-as a cement additive.   26. Crosslinked hydrogel according to any one of claims 19, 20, 21 or 25, having a residual crosslinker content of less than 10 ppm, preferably less than 8 ppm, particularly preferably less than 5 ppm.   Use of ester F according to any one of claims 1 to 10 for the preparation of a hydrogel-forming polymer that absorbs aqueous liquids.