WO2014072130A1 - Superabsorber for cable applications - Google Patents

Superabsorber for cable applications Download PDF

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Publication number
WO2014072130A1
WO2014072130A1 PCT/EP2013/070509 EP2013070509W WO2014072130A1 WO 2014072130 A1 WO2014072130 A1 WO 2014072130A1 EP 2013070509 W EP2013070509 W EP 2013070509W WO 2014072130 A1 WO2014072130 A1 WO 2014072130A1
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Prior art keywords
water
polymer structure
absorbent polymer
according
test method
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PCT/EP2013/070509
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German (de)
French (fr)
Inventor
Martin Tennie
Nadine BARTELS
Original Assignee
Evonik Industries Ag
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Priority to DE201210220400 priority Critical patent/DE102012220400A1/en
Priority to DE102012220400.8 priority
Application filed by Evonik Industries Ag filed Critical Evonik Industries Ag
Publication of WO2014072130A1 publication Critical patent/WO2014072130A1/en

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    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01BCABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B7/00Insulated conductors or cables characterised by their form
    • H01B7/17Protection against damage caused by external factors, e.g. sheaths or armouring
    • H01B7/28Protection against damage caused by moisture, corrosion, chemical attack or weather
    • H01B7/282Preventing penetration of fluid, e.g. water or humidity, into conductor or cable
    • H01B7/285Preventing penetration of fluid, e.g. water or humidity, into conductor or cable by completely or partially filling interstices in the cable
    • H01B7/288Preventing penetration of fluid, e.g. water or humidity, into conductor or cable by completely or partially filling interstices in the cable using hygroscopic material or material swelling in the presence of liquid

Abstract

The present invention relates to a water-absorbing polymer structure based on partially neutralized, crosslinked polyacrylic acid, wherein the water-absorbing polymer structure has the following properties: i) a content of soluble fractions of at least 10% by weight, said content being determined in accordance with the test method described in this document; ii) a modulus of elasticity of at most 3 Pa, said modulus of elasticity being determined in accordance with the test method described in this document; iii) a drop in the gel viscosity after 7 days at 80°C of at most 25%, said drop being determined in accordance with the test method described in this document. The present invention also relates to a method for producing a water-absorbing polymer structure, to the water-absorbing polymer structure which can be obtained using this method, to a composite, to a method for producing a composite, to the composite which can be obtained using this method, to a cable, and also to the use of a water-absorbing composition or a composite for producing a sheathing layer in a cable.

Description

SUPER ABSORBER FOR CABLE APPLICATIONS

The present invention relates to water-absorbent polymer structure, to a process for producing water-absorbing polymer structure, obtainable by this method water-absorbing polymer structure, a composite, a process for producing a composite, the composite obtainable by this method, cable as well as the use of a water-absorbing composition or a composite of producing a jacketing layer in a cable.

Cable represent durable capital goods and therefore must comply with more stringent requirements for operational reliability. Damage caused by flooding can be avoided against water through cable insulation to seal the cable. In the "wire world" (issue 5/1992) different methods of longitudinally watertight insulation of power cables, communication cables and optical fibers are described. The focus is on the discussion of source powders or swelling nonwovens based on polyacrylate (superabsorber), which are incorporated into the cable construction are used. the superabsorbent, for example in the form of a swellable cable binding of nonwoven fabric, are applied to the superabsorbent particles, as described for example in EP-a-0269778. the superabsorbent particles in the cable drum swell on ingress of water and thus prevent the spread of water along the cable longitudinal axis.

Superabsorbents are water-insoluble, crosslinked polymers which are able, under swelling and formation of hydrogels to absorb large amounts of water, aqueous liquids, in particular body fluids, preferably urine or blood, and of retaining them under pressure. Superabsorbent preferably absorb at least 100 times their own weight of water. Further details of superabsorbents are "1,998, FL Buchholz, AT Graham, Wiley-VCH" revealed in Rödern Superabsorbent Polymer Technology.

However, the disadvantage of the superabsorbent known from the prior art, for the purpose of sealing of cables used to water consists primarily in that they are indeed able to absorb incoming water as quickly as possible, this absorption capacity, however, not be maintained over a long period , Considering the fact that cables usually have a service life of 40 years or more, this loss of the absorption capacity of the superabsorbent has to avoid a strong impact on their ability in cable sheathing damage caused by flooding.

The present invention was based on the object to overcome the known from the prior art disadvantages associated with superabsorbents, which are used for longitudinally water-tight insulation of cables, in particular for longitudinally water-tight insulation of communication cables and optical fibers.

In particular, the present invention had the object of providing superabsorbers whose ability to isolate Longitudinal water blocking, even after a long time, such as days, weeks, months or years, it is possible not significantly affected.

Moreover, the present invention was based on the object of specifying a method, can be produced with such advantageous superabsorbents. A contribution to achieving the abovementioned objects is a water-absorbent polymer structure, based on partially neutralized, cross-linked polyacrylic acid, wherein the water-polymer structures having the following properties: i) a described according to the herein Test Method certain content of solubles of at least 10 wt .-%, particularly preferably of at least 12.5 wt .-%, and most preferably at least 15 wt .-%; ii) a specific according to the test method described herein modulus of elasticity of at most 3 Pa, more preferably of at most 2.5 Pa, and most preferably not greater than 2 Pa; iii) a test method described herein according to the specific waste of the gel viscosity after 7 days at 80 ° C of at most 25%, particularly preferably at most 17.5%, and most preferably of at most 10%.

According to the invention, preferred water-absorbing polymeric formations are in the form of fibers, foams or particles, fibers and particles being preferred and particles are particularly preferred.

According to Polymer fibers are sized so that they can be incorporated in or as yarns for textiles and also directly into textiles. It is preferable in the invention that the polymer fibers have a length in the range of 1 to 500 mm, preferably 2 to 500 mm and more preferably 5 to 100 mm and a diameter in the range of 1 to 200 denier, preferably from 3 to 100 denier and more preferably 5 have to 60 denier. According to the invention preferred particulate water-absorbing polymeric formations are dimensioned so that they (Worldwide strategy partner WSP =) in the range of 10 μιη an average particle size according to WSP 220.2 to 3000, preferably 20 to 2000 and particularly preferably μιη μιη comprise 25 to 300. It is particularly preferred that the proportion of polymer particles having a particle size of less than 300 μιη at least 70 wt .-%, particularly preferably at least 80 wt .-% and most preferably at least 90 wt .-%, based on the total weight of water-absorbent polymer structure is.

The water-absorbing polymer structures according to the invention are based on partially neutralized, cross-linked polyacrylic acid. In this context it is particularly preferred that the water-absorbing polymeric formations of the present invention are crosslinked polyacrylates, which are at least 50 wt .-%, preferably at least 70 wt .-% and more preferably at least 90 wt .-%, each based on the based weight of the polymer structure of polymerized acrylic acid. It is according to the invention further preferred that the water-absorbing polymeric formations according to the invention wt .-%, preferably at least 70 wt .-%, based in each case based to at least 50 by weight of the polymer structure, to polymerized acrylic acid, preferably at least 20 mol%, is particularly preferably at least 50 mol% neutralized, and preferably in a range of 60 to 85 mol% beyond. The water-absorbent polymer structure according to the invention are for example obtainable by a process comprising the process steps:

I) providing an aqueous monomer solution comprising

Acrylic acid or a salt thereof, at least one crosslinker,

II) free-radical polymerization of acrylic acid to obtain a polymer gel,

III) optionally crushing of the polymer gel,

IV) drying the optionally comminuted polymer gel to obtain water-absorbing polymeric formations, and

V) optionally grinding and sieving the water-absorbent polymer structure, wherein a) the aqueous monomer solution before process step II) or during step II), preferably before process step II), b) the polymer gel after process step ii) and before step IV) or during process step IV), preferably before process step IV), or c) the water-absorbing polymer structure after process step IV) a chelating agent in an amount of more than 2,000 ppm, particularly preferably at least 2,500 ppm and most preferably at least 3,000 ppm, respectively based on the amount of acrylic acid in the monomer solution or to polymerized acrylic acid in the water-absorbent polymer structure, is added. In method step I), an aqueous monomer including acrylic acid or a salt thereof and at least one crosslinking agent is first provided. As crosslinkers, those compounds are preferably used that are mentioned in WO 2004/037903 A2 as crosslinkers (a3). Among these crosslinking agents, water-soluble crosslinkers are particularly preferred. Most preferred are N, N'-methylenebisacrylamide,

Polyethylene glycol di (meth) acrylates, Triallylmethylammo-niumchlorid, tetraallylammonium chloride, optionally thylolpropantriracylat ethoxylated trimethylolpropane or optionally glykolacrylat ethoxylated Allylnonaethylen-, wherein the use of 3 moles of ethylene oxide ethoxylated trimethylolpropane triacrylate, which, for example, under the designation "SARTOMER 454" from Sartomer Company, USA is available, is most preferred. Furthermore, copolymerizable with acrylic acid, may be included monoethylenically unsaturated monomers such as acrylamides, methacrylamides or vinylamides in the monomer solution. Other preferred co-monomers are in particular those described in WO 2004/037903 A2 as Co-monomers (<x2) are called.

In addition to the monomers, and optionally co-monomers and the at least one cross-linking agent, the monomer solution may also include water soluble polymers. Preferred water-soluble polymers include partially or fully hydrolyzed polyvinyl alcohol, polyvinylpyrrolidone, starch or starch derivatives, polyglycols or polyacrylic acid. The molecular weight of these polymers is not critical as long as they are water soluble. Preferred water-soluble polymers are starch or starch derivatives or polyvinyl alcohol. The water-soluble polymers, preferably synthetic, such as polyvinyl alcohol, can not only serve as grafting base for the monomers to be polymerized. It is also feasible to mix these water-soluble polymers after the polymerization with the hydrogel or the already dried, water-absorbing polymers.

Furthermore, the monomer solution may also contain adjuvants, in particular belonging to these aids which may be necessary for the polymerization initiators.

Suitable solvents for the monomer organic solvents or mixtures of water and organic solvents come into consideration water, the choice of the solvent, in particular also depends on the manner of polymerization.

The relative amount of monomers, co-monomers as well as crosslinking agents, water-soluble polymers and aids in the monomer solution is preferably chosen such that the product obtained in step IV) after drying water-absorbing polymeric formations 20 to 99.999 weight .-%, preferably from 55 to 98,99 wt .-% and particularly preferably 70 to 98.79 wt .-% acrylic acid or salts thereof, 0 to 80 wt .-%, preferably 0 to 44.99 wt .-% and particularly preferably from 0.1 to 44.89 wt .-% of the co-monomers,

0 to 5 wt .-%, preferably from 0.001 to 3 wt .-% and particularly preferably 0.01 to 2.5 wt .-% of the crosslinking agents,

0 to 30 wt .-%, preferably 0 to 5 wt .-% and particularly preferably 0.1 to 5 wt .-% of the water-soluble polymer, 0 to 20 wt .-%, preferably 0 to 10 wt .-% and particularly preferably 0.1 to 8 wt .-% to the tools, and

0.5 to 25 wt .-%, preferably 1 to 10 wt .-% and particularly preferably 3 to 7 wt .-% based on water, wherein the sum of the weight amounts of the above components is 100 wt .-% is , Optimum values ​​for the concentration of in particular the monomers, the crosslinking agent and water-soluble polymers in the monomer can be determined by simple preliminary tests, or also to the prior art, in particular the publications US 4,286,082, DE-A 27 06 135, US 4,076,663, DE-A -35 03 458, DE 40 20 780 Cl, DE-A-42 44 548, DE-A-43 33 056 and removed DE-A-44 18 818th

In method step II), the acrylic acid is polymerized radically to obtain a polymer gel. Free-radical polymerization of the monomer, all known to those skilled in polymerization processes can in principle be considered. For example, in this context, solution polymerization, which preferably takes place in kneading reactors such as extruders or continuously on a polymerization belt, to name a spray polymerization, inverse emulsion polymerization and inverse suspension polymerization.

solution polymerization is preferably carried out in water as solvent. The solution may be continuous or discontinuous. From the prior art, a wide range of possible variations with respect to reaction conditions such as temperatures, type and amount of initiators and the reaction solution is apparent. Typical processes are described in the following patents: US 4,286,082, DE-A-27 06 135 Al, US 4,076,663, DE-A-35 03 458, DE 40 20 780 Cl, DE-A-42 44 548, DE-A- 43 33 056, DE-A-44 18 818. the disclosures of which are hereby incorporated by reference and thus part of the disclosure.

The polymerization is generally customary manner, by an initiator. As initiators for initiating polymerization can all be used under the polymerization initiators which form free radicals, which are usually used in the production of superabsorbers. An initiation of the polymerization by the action of electron beams on the polymerizable aqueous mixture is also possible. The polymerization can however be initiated in the absence of initiators of the abovementioned type by the action of high energy radiation in the presence of photoinitiators. Polymerization initiators may be dissolved in the monomer solution or dispersed. Possible initiators are all occur to those skilled known disintegrate into free radicals compounds. These include in particular those initiators which have already been mentioned in WO-A-2004/037903 as possible initiators. a redox system consisting of hydrogen peroxide used, sodium peroxodisulfate and ascorbic acid for the preparation of water-absorbent polymer structure. Inverse suspension and emulsion polymerization can be used to prepare the water-absorbent polymer structure. According to these processes, an aqueous, partly neutralized solution of acrylic acid and optionally including the further co-monomers, the water soluble polymers and auxiliaries dispersed with the aid of protective colloids and / or emulsifiers in a hydrophobic organic solvent and is started by radical initiators, the polymerization. The crosslinking agents either are dissolved in the monomer solution and metered together with or separately and optionally added during the polymerization. Optionally, the addition of a water soluble polymer as the graft takes place via the monomer solution or by directly placing in the oil phase. The water is then removed azeotropically from the mixture and filtering off the polymer.

Furthermore, the crosslinking can be carried out by copolymerization of the monomer dissolved in the polyfunctional crosslinker and / or by reacting suitable crosslinking agents with functional groups of the polymer during the polymerization both in solution and in the inverse suspension and emulsion polymerization. The methods are, for example, in the publications US 4,340,706, DE-A 37 13 601, DE-A-28 40 010 and / WO-A-96 05234, the relevant disclosure of which is hereby incorporated by reference.

In step III) the hydrogel obtained in step II) is optionally comminuted, this comminution being carried out in particular when the polymerization is carried out by means of a solution polymerization. Crushing, by art-known crushing devices such as a meat grinder, take place.

In process step IV) which is optionally previously dried crushed hydrogel. The drying of the hydrogel is carried out in suitable dryers or ovens. Examples include rotary kilns, fluidized bed dryers, plate dryers, paddle dryers or infrared dryers. Furthermore, it is preferable in the invention that the drying of the hydrogel in method step c) to wt .-% is effected to a water content of 0.5 to 25 wt .-%, preferably from 1 to 10, wherein the drying temperatures are usually in a range of 100 There are up to 200 ° C.

In process step V) the obtained in process step IV) water-absorbing polymeric formations may in particular if they have been obtained by solution polymerization, be ground and sieved to the above-mentioned desired particle size. Grinding of the dried water-absorbing polymers is preferably carried out in suitable mechanical comminution devices such as a ball mill, during the screening can be done for example, by using sieves with a suitable mesh size. The method described above is now characterized in that a) the aqueous monomer II before process step II) or during the process step), preferably before process step II), b) the polymer gel after process step ii) and before step IV) or during step IV), preferably before process step IV), or c) the water-absorbing polymer structure after process step IV) a chelating agent in an amount of more than 2,000 ppm, more preferably of at least 2,500 ppm, and most preferably of at least 3,000 ppm, is in each case based on the amount of acrylic acid in the monomer solution or to polymerized acrylic acid in the water-absorbing polymeric formations added.

As a chelating agent thereby come all compounds which have a metal-chelating ability. It is, therefore, compounds having a bidentate or polydentate ligand which is capable of binding to a metal ion to form a metal chelate. As chelating agents are preferably water-soluble inorganic phosphoric acid compounds such as polyphosphoric acids, eg. B. tripolyphosphoric acid, Tetrapoly-phosphoric acid, Pentapolyphosphorsäure, pyrophosphoric acid, metaphosphoric acid and polyphosphoric acid and salts thereof (eg. As the sodium salt or K salt), aminocarboxylic acid compounds, such as ethylenediaminetetraacetic acid, 1,3-propanediaminetetraacetic acid, diethylenetriaminepentaacetic , tri- ethylentetraminhexaessigsäure, L-Giutaminsäurediessig acid, N, N-bis (carboxy- methyl) -L-glutamic acid, and hydroxyethylethylenediaminetriacetic acid and salts thereof (eg. as the Na, K or ammonium salt), organic phosphorus compounds such as aminotri (methylenephosphonic acid), 1-hydro xy-ethylidene-1, 1-diphosphonic acid, ethylenediaminetetra (methylenephosphonic acid), di- ethylentriaminpenta (methylenephosphonic acid) and 2-Phos-phonbutan-l, 2,4-tricarboxylic acid and salts thereof (eg. B ., the Na, K or ammonium salt) are used. According to the invention particularly preferred chelating agent is diethylenetriaminepentaacetic acid, which is preferably used in form of its penta sodium salt available under the designation "VERSENEX ®". The chelating agent can be used both in solid particulate form and in the form of aqueous solutions of the monomer solution, the polymer gel or the water-absorbent polymer structure are added, wherein the additive is in the form of aqueous solutions, for example in the form available under the designation "VERSENEX ®" aqueous solutions being most preferred.

According to a preferred embodiments of the water-absorbent polymer structure according to the invention these are therefore particularly preferably comprise more than 2,000 ppm, even more preferably at least 2,500 ppm and most preferably at least 3000 ppm of a chelating agent, diethylenetriaminepentaacetic acid or a salt of diethylenetriaminepentaacetic acid, each based on the content of acrylic acid in the water- polymer structure. In this connection it is further preferred that at least 90 μιη have a particle size of less than 300 wt .-% of the particles of the water-absorbent polymer structure.

Furthermore, it is preferable in the invention that the water-absorbent polymer structure having no core shell structure. Such core-shell structure is formed when the gel particles of the water-absorbent polymer structure, or the particles of the water-absorbent polymer structure obtained after drying in a further method step by chemical crosslinking or polyvalent metal cations are oberflächennachvemetzt, so that the crosslinking density in the outer region of the water-absorbent polymer structure is greater than in the core. According to the invention it is therefore preferred that the water-absorbing polymeric formations are not oberflächennachvemetzt.

A contribution to achieving the abovementioned objects is also a process for producing a water-absorbing polymer structure, comprising the steps of:

I) providing an aqueous monomer solution comprising

Acrylic acid or a salt thereof,

at least one crosslinker, free-radical polymerization of acrylic acid to obtain a Polymerg optionally comminuting the Polymerg IV) drying the optionally comminuted polymer gel to obtain water-absorbing polymeric formations, and optionally grinding and sieving the water-absorbent polymer structure, wherein the aqueous monomer solution before process step II) or during step II), preferably before process step II), b) the polymer gel after process step ii) and before step IV) or during step IV), preferably before process step IV), or c) the water-absorbing polymer structure after process step IV) a chelating agent in an amount of more than 2,000 ppm, more preferably of at least 2,500 ppm, and most preferably of at least 3000 ppm, each based on the amount of acrylic acid in the monomer solution or to polymerized acrylic acid in which serabsorbierenden polymer structure, is added.

Preferred chelating agents are again those chelating agents that have already been mentioned in connection with the inventive water-absorbing polymer structures as the preferred chelating agent. Furthermore, it is preferred in connection with the inventive method, that the water-absorbing polymer structure in process step V) are sieved in such a way that the proportion of the polymer μιη having a particle size of less than 300 at least 70 wt .-%, particularly preferably at least 80 weight %, and most preferably at least 90 wt .-%, based on the total weight of the water-absorbent polymer structure is.

A contribution to achieving the abovementioned objects is also a water-absorbing polymer structure which is obtainable by the inventive process. It is particularly preferred that the product obtainable by the inventive method absorbing polymer structure has the following properties: i) a test method described herein according to the determined content of soluble fractions of least 10 wt .-%, particularly preferably of at least 12.5 wt %, and most preferably from at least 15 .-%; ii) a specific according to the test method described herein modulus of elasticity of at most 3 Pa, more preferably of at most 2.5 Pa, and most preferably not greater than 2 Pa; iii) a test method described herein according to the specific waste of the gel viscosity after 7 days at 80 ° C of at most 25%, particularly preferably at most 17.5%, and most preferably of at most 10%. A contribution towards achieving the abovementioned objects is also made by a composite comprising an inventive water-absorbing polymer structure or an obtainable by the inventive method water-absorbing polymer structures and a substrate. Preferably in this composite to a, for example from EP-A-0269778 known swellable cable binding of nonwoven fabric on which the particles of the water-absorbent polymer structure can be applied. As the substrate accordingly come into consideration in particular Faservliesse representing, for example, a mixture of viscose fibers and polyvinyl alcohol fibers. In particular, preferred are nonwoven fabrics comprising 75 to 95 wt .-% of viscose fibers and 5 to 25 wt .-% of polyvinyl alcohol fibers, wherein the basis weight of this Faservliesse is preferably at least 20 g / m 2.

The amount of water-absorbing polymeric formations in such a swellable cable binding of nonwoven fabric is preferably 5 to 100 g / m 2, particularly preferably 20 to 40 g / m 2. A contribution to achieving the abovementioned objects is also a process for producing a composite, wherein the water-absorbing polymeric formations of the invention or obtainable by the inventive method, the water-absorbing polymeric formations a substrate and optionally an additive are brought into contact with each other. Preferably, the composite is as described above, from EP-A-0269778 known swellable cable binding of nonwoven fabric on which the particles of the water-absorbent polymer structure can be applied. In this context, it is preferred that first a substrate, preferably an above-described non-woven fabric of viscose fibers and polyvinyl alcohol fibers, coated on one side with the water-absorbing polymeric formations or obtainable by the process of this invention water-absorbent polymer structure and then this layer further comprising a further substrate, preferably with a is non-woven fabric of viscose fibers and polyvinyl alcohol fibers, covered, as described in EP-A-0269778. The layer structure thus obtained can then EP-A-0 269 778 both sides impregnated with a polyvinyl alcohol solution, and then dried according to the teaching.

A contribution to achieving the abovementioned objects is also a composite which is obtainable by the method described above.

A contribution towards achieving the abovementioned objects is furthermore made by a cable containing at least one coating layer comprising water-absorbing polymer structures according to the invention, obtainable by the inventive process absorbing polymer structures, a composite of the invention or a composite obtainable by the inventive process. A contribution to achieving the abovementioned objects is furthermore provided by the use of the water-absorbent polymer structure according to the invention, which are obtainable by the inventive method, the water-absorbing polymer structure, a composite of the invention, or a composite obtained by the inventive process for producing at least one cladding layer in a cable.

The invention will now be described with reference to figures, test methods and non-limiting examples.

It shows the Figure 1, the device for determining the degree of penetration of water in a container filled with water-absorbing polymeric formations tube (penetration test). TEST METHODS

penetration test

When a penetration test closed at one end with cotton wool 2 melting point tube is 1 (inner diameter 2 mm, length 120 mm) filled with water-absorbing polymeric formations. 3 To the water-absorbing polymer structures 3 is first placed in a petri dish. The melting point tube 1 is then pressed with the open end in the water-absorbent polymer structure 3 until the tube 1 is filled up to a length of 5 mm with the polymer structure. 3 Is then allowed to 1 times the tube three from a height of 10 cm perpendicular to the sealed end with cotton wool fall on the table, by 3 to compact the water-absorbing polymeric formations within the tube. 1 This process is obtained as long as resist, to remain only about 10 mm of the tube 1 as an open from the water-absorbing polymer material 3 white space. The remaining teaching space is filled with cotton wool 4, so that within the melting point tube 1 is a filling structure cotton wool (about 10 mm) / water-absorbent polymer structure (approximately 80 mm) / cotton wool (about 10 mm) (reference numeral 4/3/2 in Figure 1 ) is obtained. The filling height of water-absorbing polymeric formations 3 and the amount of filled water-absorbing polymer structures 3 is determined. Melting Point The tube 1 is then terminated immediately above the second sealing wadding 4 and liquid-tightly connected to a tube 6 in a horizontal orientation via a connecting piece 5 which is in turn connected to a liquid reservoir 7 comprising deionized water. 8 The interface between the front absorbent cotton seal 4 and the water-absorbent polymer structure 3 (see the arrow in the figure 1) serves as starting point for the water penetrating 8 and is marked with a felt pen. The level of the liquid reservoir 7 is located during the measurement of 1 m above the melting point of the tube 1, as shown in FIG. 1 After the melting point tubes 1 placed in position and the start point has been selected, the valves are opened. 9 and 10 After certain times (5 minutes, 10 minutes, 20 minutes, 1 hour, 2 hours, 8 hours, 1 day, 2 days, 3 days, 4 days, 5 days, 6 days and 7 days), the distance over which the liquid penetrated into the tube 1 is (indicated by the boundary line between the transparent gel and the white absorbing polymer structures) was determined.

DETERMINATION OF THE CONTENT OF SOLUBLE SHARES

The determination of the content of soluble fractions is carried 270.3 (11) according to the WSP after 16 hours.

Determination of flexural modulus to determine the elastic modulus of the water-absorbent polymer structure is first with deionized water to 100% (ie 100% of the maximum absorption capacity, as determined by ERT 441.2) swollen to give a 5 polymer gel at room temperature. the elastic modulus is of the thus obtained polymer gel then by means of a plate rheometer (Haake Rheometer plate "StressTech") determined μιη at 25 ° C and a plate distance of 100th lo DETERMINATION OF THE GEL WASTE VISCOSITY

In order to determine the drop of gel viscosity absorbing polymer structures are swollen with 50% of the amount of deionized water, which are able to absorb the water-absorbing polymeric formations maximum.

15 After the water-absorbing polymeric formations are swollen by addition of water (t 0; ηο) and after 7 days of storage of the swollen gels at a storage temperature of 80 ° C (t 7 <1; η 7 ά) the viscosity η of the gels by means of a Brookfield viscometer. Prior to the determination of the viscosity of the gels at the time t 7, d is allowed the gels to room temperature

Cool 20 (including the determination of the gel viscosity at the time t 0 is carried out at room temperature).

The drop of gel viscosity is calculated as follows:

25 Δη = (ηο-ηνά) / ηο x 100% EXAMPLE 1

In 965.82 g of an aqueous solution of sodium acrylate having a neutralization degree of 68 mol% (based. Acrylic acid) and a total monomer concentration of 29 wt .-% 1.75 g polyethylene glycol (750) was (0.6 wt monoallyletheracrylat. -. %% inscribed on acrylic acid / Estergehalt corresponding to 78%) and 1.75 g Sartomer ® 454 (0.6 wt .-%, based on dissolved acrylic acid) as crosslinking agents.. The monomer solution was washed into a plastic Po lymerisationsgefäß for 30 minutes with nitrogen to remove the dissolved oxygen. At a temperature of 4 ° C, the polymerization by the sequential addition of 0.85 g Natriumperoxo- was disulfate in 10 g dist. Water, 0.7 g 35% hydrogen peroxide solution in 10 g dist. Water and 0.03 g ascorbic acid in 2 g dist. Water started. After the end temperature (ca. 100 ° C) was reached, the gel is crushed with a meat grinder and sprayed there with 3 g of Versenex 80 ®, which is least in 50 mL. Water was solved. Followed by drying for 2 hours at 150 ° C in a convection oven. The dried product was coarsely ground, finely ground and adjusted to the prescribed particle size distribution.

COMPARATIVE EXAMPLES 1 AND 2

As comparative examples, commercially available water-absorbing polymer structures, which are offered for use in cable sheaths serve.

The following measured values ​​for the content of soluble fractions, for the gel strength and the drop of the gel viscosity were determined: content of soluble waste of

Elastizitäzsmodul

Product components gel viscosity

[Pa]

[%] [%]

Example 1 19 1.5 10

Comparative Example 1 14 4.2 80

Comparative Example 2 7 6.5 100

The polymer of Example 1 as well as the commercial reference products of Comparative Examples 1 and 2 were subjected to the penetration test described above using the method described in the Figure 1 device. In the following table the path is specified, is penetrated through the deionized water after 7 days by the layer of water-absorbing polymer structure at a temperature of 20 ° C in the melting point tubes:

Figure imgf000023_0001
The results show that water-absorbing polymers according to the invention are compared to the processes known from the prior art reference products much better able to prevent the spread of the water in the longitudinal direction and are thus much better suited for longitudinally water-tight insulation of cables.

LIST OF REFERENCE NUMBERS

1 S chmelzpunktröhrchen

2 cotton

3 water-absorbent polymer structure

4 cotton wool

5 connector

6 hose

7 reservoir

8 Deionized water

9 valve

10 valve

Claims

1. A water-absorbent polymer structure, based on partially neutralized, cross-linked polyacrylic acid, wherein the water-polymer structures having the following properties:
i) a particular according to the herein described test method in soluble fractions of 10 wt .-% at least;
ii) a specific according to the test method described herein modulus of elasticity of at most 3 Pa;
iii) a given according to the herein described test method drop of the gel viscosity after 7 days at 80 ° C of at most 25%.
The water-absorbent polymer structure according to claim 1, wherein the water-absorbent polymer structure has the following properties: i) a test method described herein according to the determined content of solubles of at least 15 wt .-%;
ii) a specific according to the test method described herein modulus of elasticity of not more than 2 Pa;
iii) a given according to the herein described test method drop of the gel viscosity after 7 days at 80 ° C of at most 10%.
The water-absorbent polymer structure according to claim 1 or 2, wherein the water-absorbent polymer structure contains more than 2,000 ppm of a chelating agent, based on the amount of polymerized acrylic acid in the water-absorbent polymer structure.
The water-absorbent polymer structure according to claim 3, wherein the water-absorbent polymer structure contains at least 3000 ppm of a chelating agent, based on the amount of polymerized acrylic acid in the water-absorbent polymer structure.
The water-absorbent polymer structure according to claim 3 or 4, wherein the chelating agent is diethylene triamine or a salt thereof.
The water-absorbent polymer structure according to one of the preceding claims, wherein the water-absorbent polymer structure is not surface postcrosslinked.
The water-absorbent polymer structure according to one of the preceding claims, wherein μιη have a particle size of less than 300 wt .-% of the particles of the water-absorbent polymer structure than 90.
A process for producing a water-absorbent polymer structure, comprising the steps of:
I) providing an aqueous monomer solution comprising
Acrylic acid or a salt thereof,
at least one crosslinker,
II) free-radical polymerization of acrylic acid to obtain a polymer gel,
III) optionally crushing of the polymer gel,
IV) drying the optionally comminuted polymer gel to obtain water-absorbing polymeric formations, and
V) optionally grinding and sieving the water-absorbent polymer structure,
wherein a) the aqueous monomer solution before process step II) or during step II), preferably before process step II),
b) the polymer gel after process step ii) and before step IV) or during step IV), preferably before process step IV), or
c) the water-absorbing polymer structure after process step IV)
a chelating agent in an amount of more than 2,000 ppm, based on the amount of acrylic acid in the monomer solution or to polymerized acrylic acid in the water-absorbent polymer structure, is added.
The method of claim 8, wherein the chelating agent in an amount of at least 3,000 ppm, based on the amount of acrylic acid in the monomer solution or to polymerized acrylic acid in the water-absorbent polymer structure, is added.
The method according to claim 8 or 9, wherein the chelating agent is diethylene triamine or a salt thereof.
The method according to any one of claims 8 to 10, wherein the water-absorbing polymeric formations are sieved in such a way in the process step V) that at least 90 wt .-% of the particles of the water-absorbent polymer structure μιη have a particle size of less than 300th
A water-absorbent polymer structure, obtainable by a process according to any one of claims 8 to 11. The water-absorbent polymer structure according to claim 12, wherein the water-absorbent polymer structure has the following properties: i) a described according to the herein Test Method certain content of solubles of at least 10 weight %;
ii) a specific according to the test method described herein modulus of elasticity of at most 3 Pa;
iii) a given according to the herein described test method drop of the gel viscosity after 7 days at 80 ° C of at most 25%.
The water-absorbent polymer structure according to claim 13, wherein the water-absorbent polymer structure has the following properties: i) a test method described herein according to the determined content of solubles of at least 15 wt .-%;
ii) a specific according to the test method described herein modulus of elasticity of not more than 2 Pa;
iii) a given according to the herein described test method drop of the gel viscosity after 7 days at 80 ° C of at most 10%.
A composite comprising a water-absorbent polymer structure according to any one of claims 1 to 7 and 12 to 14 and a substrate.
A method for producing a composite, wherein the water-absorbent polymer structure according to any one of claims 1 to 7 and 12 to 14, a substrate and optionally an additive are brought into contact with each other.
A composite, obtainable by a process according to claim 16, cable including a cladding layer comprising the water-absorbent polymer structure according to any one of claims 1 to 7 and 12 to 14 or the composite of claim 15 or 17th
Use of the water-absorbent polymer structure according to any one of claims 1 to 7 and 12 to 14 or of the composite according to claim 15 or 17 for the preparation of a coating layer in a cable.
PCT/EP2013/070509 2012-11-09 2013-10-02 Superabsorber for cable applications WO2014072130A1 (en)

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