CA1062425A

CA1062425A - Hydrophilic structures of water-insoluble polymers

Info

Publication number: CA1062425A
Application number: CA216,553A
Authority: CA
Inventors: Arno Holst; Michael Kostrzewa; Helmut Lask
Original assignee: Hoechst AG
Current assignee: Hoechst AG
Priority date: 1973-12-24
Filing date: 1974-12-20
Publication date: 1979-09-18
Also published as: IL46321A0; FR2255338A1; DE2364628B2; ZA748176B; AT335752B; CH606231A5; HU172025B; IL46321A; ES433281A1; IT1026111B; NL7416270A; JPS50100142A; BE823780A; DK677674A; BR7410749D0; DE2364628A1; FI370974A; AU7676374A; SE7709478L; DE2364628C3

Abstract

Abstract of the Disclosure This invention relates to a hydrophilic shaped structure of a water-insoluble polymer capable of forming fibers and films, having distributed in the polymer, and/or having a surface having distributed thereon, particles of cellulose ethers rendered at least partly water-insoluble by cross-linking or modification but which are water-absorbent.

Description

~06Z4ZS
HYDROPHILIC STRUCTURES OF WATER-INSOLUBLE POLYMERS
: The invention relates to structures, for example fibers, films :
and spongy products, of polymers of increased hydrophilic character.
It has been proposed to produce structures of regenerated cellu-lose by introducing a material which bonds to the cellulose, and con-tains an active component, into the ce.llulose before the final regenera-tion of the latter (DT-OS 2,235,902). The character of the active com~
ponent can be such that, if desired, the hydrophilic character of the regenerated cellulose is greater than lt wou.ld be without modificatLon : .:
with the active component. The structures obtained in accordance with this process are modified throughout their entire mass. Accordingly, their physical properties differ from those of the corresponding unmodi- ;~ :
fied structures, in accordance with the intended result of this process. ~ -However, it may result in an undesired lowering of tensile strength, extensibility and 1exural strength of resulting structures. More impor-tantly, however, the modiflcations possible are restricted not only to .;
. the manufacture of structures of cellulose or cellu.lose derivatives but : a.lso in the achievable physical effects, for example with regard to the ~ -permeability of fi.lms manufactured by the process to water and other ~: ~2 0 .liquids . . .
The present invention provldes structures, which have been ; .
rendered hydrophl.lic, of water-lnsoluble polymers whlch can be manu- :
factured from polymeric material other than regenerated cellulose mater-ial and can be manufactured with a great range of hydrophilic propertles.
The present lnvention provides an artlc.le or shaped structure of a poly~er ~.
capablel R forming fibers ond fi1ms and. being ,water-insoluble, which con- ;
tains, distributed wlthin lts mass or coated on its surface, particles ~:
of cellulose ethers that are inherently water-soluble but have been 1,~ ' ~

~ ^~ `` ~062425 K- 2 2 8 9 rendered at least partly water-insoluble by cross-linlcing or modifica- ~ .
tion, but are still capable of absorbing water.
The structures or articles constructed according to the invention may be shaped by any process suitable for the shaping of the base poly-mer. A pulverulent or granular material of cross-linked or modified cellulose ether may, for example, be added to the polymer mass before shaping and uniformly distributed therein. Thus, for example the custo- : :
mary precipitation processes are used If fi.laments,.films or sponges of regenerated ce.llulose are being manufactured, or the casting process is used if films of ce.llulose acetate are being manufactured, while melt extrusion is used principa.lly if structures of polyethylene or other poly- .
, alkylenes or other extrusible polymers are being manufactured. Struc-', tures which have the particles as a surface covering are suitab.ly manu-' factured by sprinkling the supporting structure, composed of the polymer, with the partlcles, if the surface being sprinkled is either provided with an adhesive or is in a state in which the surface itse.lf acts as an adhe-,` ~ sive . The polymerio ba se ma s s of the structures according to the inven-1 tion can in principle be composed of any polymer from which self-supporting films, or fibers or fitaments, can be manufactured. Further examples of po.lymers which may be mentioned are water-lnsoluble alkyl ce.lluloses, such as, for example, aqueous al}ca.li-solub.le hydroxyethyl aellulose, methyl cellulose or hydroxypropyl oellulose, polyacrylo- ..
. nitrile, polyamides, polyethylene, polypropy.lene and polyesters, for . .
example polyethylene terephthalate.
The particles are generally finely pulverulent to granular. Their particle size is in the range of û.01 to 2 mm and depends upon the end ,1 ~.. i '~ use of the structure. The partic.les are composed of cellulose ethers, , ' ~: , . such as for examp.le carboxymethyl cellulose, hydroxyethyl cellulose ~.~

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or methylhydroxyethyl cellulose, which are cross-linked or modified. Examples of possible cross-linking agents are;
dimethylolmethylene-bis-acrylamide; methylene-bis acrylamide;

., ~,. ..
trichloro-pyrimidine, and tetrachloropyrimidine; cyanuric chloride; epichlorohydrin; dichloroacetic acid, diepoxides or their precursors di-C~-halogenohydrins. ~xamples of possible modifiers are: N-methylolacrylamide; N-(acrylamidomethylene)-acetamide; N-(acrylamidomethylene)-formamide; N-(acrylamido- ~ -methylene)-amylurethane; N-(acrylamidomethylene)-methyl-urethane; N-(acrylamidocarboxymethylene)-ethylurethane; N-(acrylamidome~hylene)-methoxyethylurethane and vinyl sulfon- -amide. The amount of added cross-linked or modified cellulose ether particles can be varied within wide limits depending upon what degree or what type of hydrophilic character, for `
example of swelling capacity or ion exchange capacity, is desired. However, in general, the maximum amount of additive should be limited such that the mechanical strength of the ``
, ,': .. .
film or other structure is not significantly reduced. ~or example, for sodium carboxymethyl cellulose (Na-CMC) which is slightly cross-linked and therefore swells very greatly in water, this maximum is at 50% by weight of the total in a base of regenerated cellulose. In the case of hydroxyethyl cellulose (HEC) of low substitution and cellulose acetate a maximum is reached at about 30 to 40% by weight of the total. ~
The lower concentration limit depends upon the nature and on ~;
the action which the particles of cross-linked cellulose ;;
ethers are to bri~g about.

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A parameter which also can be varied within wide limits is the degree of cross-linking or dègree of modification of the cellulose ether of which. the particles are composed . When using mlnor amounts of cross-linking agents, for example from 3 to 10% by weight of epi-chlorohydrin, relative to Na-CMC, when producing Ma-CMC fibers, highly swellab.le fibers are obtained. At higher degrees of cross-linking, the swel.labi.lity of the cellulose ether greatly decreases and its water-inso.luble content increases. If, for example, about 33% by weLght of these highly swellable Na-CMC fibers (about ~0-fo.ld water 10 absorption) are incorporated into a regenerated cellulose film, the . swelling factor of the fi.lm rises from about 150% (pure regenerated ce.llulose) to about 350%.
In order to make cross-linked or modified water-insoluble ionic ce.llulose ethers more readily accessible for ion exchange processes lt is sometimes advisab.le to locate them on the surface of a structure, for example of a film. A regenerated cel.lulose film of whlch the surface is covered with the particles is produced, for example, by sprinkllng .
` ~ finely ground cross-.linked Na-CMC homogeneous.ly through a sieve - .
: ~ .
` onto an as yet not regenerated web of viscose and then regenerating the viscose web in the usual manner to form regenerated cellulose. : ~;
Thls gives a hydrated ce.llulose film coated on one side with cross-Ilnked Na-CMC. .:
' .
The examples whlch fol.low further ll.lustrate the invention. `
Examples 1 to 3 relate to the manufacture of regenerated cellulose films which are modified with particles o:E Na-CMC cross-linked by epichloro- ;.
. . .
hydrin. Examp.les 4 and 5 descrLbe the manufacture of films of cellu-. .lose acetate and particles of cross-linked Na-CMC. In Example 6, .
particles of cross-linked Na-CMC are used with films of HEC of ai~

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1062~25 Iow degree of etherification as the carrier material. This water- ~:
:~/ ! insoluble H~C has an average:dègree of substitution of ab^out 0.2 and~ . .
gives a clear solution in S to 8% by weight sodium hydroxide solution;
the alkaline film can be regenerated by adding acid and a clear film is obtained which is rendered cloudy by the heterogeneous cellulose ether B additive. Examp.les 7 to~relate to further films of regenerated cellu- ...

.lose (hydrated cellulose) modified with cross-.linked cel.lulose ethers. .
/~ /7 Examplesl~to ~relate to the manufacture of fi.lms coated on one ::
side with cross-linked cellulose ethers. . ~ -The hydrophilic structures according to the invention can be used in many fields of industry. As fi.lms, for example, they can be .
used as ion exchangers or as dia.lysis membranes or as osmosis mem-branes. In the form of fibers they serve for the manufacture of textiles : ;
of better absorbency for water, which, inter a.lia, also makes the tex~
tiles pleasanter to the human skin, or for the manufacture of leather-1 .like products. : .
! Example 1 : -:
,: 1 g of fine~ly fibrous water-insolub.le cross-linked Na-CMC, ~:
which was cross-llnked with epichlorohydrin, contained about 25% by - 20 weight of soluhle constituents and had a water retention capacity of:.
,.
~: 20 times its weight and a theoretical exchange capacity oE about 3.5 `.
milliequlvalents/g,was homogeneously inoorporated, in a 3 roll mill, into 100 g of spinnable viscose containing about 10% byweight of ..
cellulose . A layer of 0 . 2 to 0 . 4 mm thickness of the modified viscose ~ was cast on a glass plate and regenerated in the usual manner. A
transparent regenerated cellulose film was obtained, which as a result ;~
,~ of the embedded water-insoluble cross-linked Na-CMC fibers had a ~, . . .. ..
Z total theoretical exchange capacity of about 0.32 milliequivalent/g. ~:~

, . . .
5 _ ` ~6Z~25 The water retention capacity of the film was about 250% by weight. A
- - . .cellulose h~drate~film manufactured under the same conditions has a ~:
water retention capacity of 125% by weight.
Example 2 The experiment was carried out as in Example 1 but the amount of cross-linked Na-CMC incorporated was increased to 5 g (about 33% ~ :
by weight of Na-CMC, based on the fLnished fllm). Cloudy films with a theoretical exchange capacity of about 1.15 milliequivalents/g were obtained. Their water-retention capacity was about 370% by weight.
Example 3 The procedure of the above Examp.le 1 was followed but the amount of cross-linked Na-CMC was increased to 10 g (50% by weight of Na-CMC, based on the finished f~lm). An opaque film visualty resembling a paper fleece was obtained. The individual fibers were held together by the regenerated cellulose binder. The theoretica.l exchange capacity was about 1. 7 milliequivalents/g. The water re-tention capacity was about 390% by weight .
Since the cross-linked Na-CMC withdraws water from the vis-cose, the mixture became difficult to homogenlze if Example 1 was ~..
carrleà out wlth more than 10 g of cross-.linked Na-CMC. On the other hand, though water or sodium hydroxide solution oould be added .
without difficulty to the viscose, there was then a loss in the strength of the resulting film.
Example 4 .. .
10 g of slightly cross-linked fibrous Na-CMC were stirred ~. `
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homogeneously into a 15% by weight cellulose acetate so.lution in . `

~ acetone so as to give a ratio of cellulose acetate to cross-linked .:
. .

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~: ` . . '`. ~.:' ``` 11~62425 --, cellulose ether of 1 : 1. A 0.5 mm thick layer was cast and the solvent was evaporated off. In the resulting film the fibers of cross-linked Na-CMC fibers were embedded in a transparent layer of cellulose ace-tate so that the film was opaque white. The theoretical exchange capacity of the film was about 1.7 milliequi~alents/g. Its water re-tention capacity was about 350% by weight. The water retention ~ -; capacity of a cellulose acetate film, in contrast, is only 20~ by weight.
Example 5 The procedure followed was as in ~xample 4, but the amount of cross-linked Na-CMC was reduced to half and, after casting, the layer precipitation was carried out with water. An opaque white mem-. .
brane was obtained, wbich had a theoretical exchange capacity of 1.15 millie~uivalents/g. Its water retention capacity was about 360% by , weight.
Example 6 The procedure followed was as in Example 2, but HEC of low degree of etherification, with an average degree of substitution of about 0.2, was employed as the polymeric film material. 5 g of cross-linked Na-CMC were incorporated homogeneously into lQO g of a 10%
by weight solution of the HEC in 8% aqueous ~aOH and a film was ob-tained by precipitating the 0.5 mm thick web in dilute sulfuria acid.
A transparent film having a theoretical exchange capacity of l.lS
milliequivalents/g and a water retention capacity of about 150~ by ,~ weight was obtained.
;~ Examples 7 to 13 I Table 1 summarizes the essential data of Examples 1 to 6 and their results, and gives those of a further seven examples (Examples 7 " ~ .

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'' . ' ' " ", " ' :': " '': '. ' ",, . ", ' ' ' ' ' . ' ' . ' ' ,., :' p~ ~, in which films of regenerated cellulose (hydrated cellulose) which were modified with cross-linked sodium carboxymethyl cellulose and sodium carboxymethylhydroxyethyl cellulose (Na-CMHEC), employ-ing various cross-.linking agents, were manufactured as the polymeric .
carrier material.

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g ` ~06Z4Z5 Example 14 An 0.5 mm thick layer of viscose ripened for spinning ~as in the above Example 1) was cast onto a glass plate. Thereafter, finely ground dry Na-cMc cross-linked with epichlorohydrin was homogene-ously sprinkled over the surface through a sieve of appropriate mesh width. The layer was regenerated in the usual manner. The film thus obtained was freed from loosely aahering Na-CMC by washing with water and plasticized by immersion in a glycerin-water mixture. A
translucent film was obtained, which is composed of regenerated cellulose coated on one side with fragments of water-insoluble cross-linked Na-CMC fibers. me finnly adhering Na-CMC fibers are freely accessible for ion exchange processes. ~he theoretical capacity was deter~ined to be about 93.5 mllliequivalents/square meter of 1.1 milliequivalents/g of film, by measuring the difference (in the weight per square meter) compared to pure regenerated cellulose. ffle water retention capacity of the film was about 440% by weight.
Example lS -a film was cast as in the above Example 4 from a 15~ by weight solution of cellulose acetate in acetone, but before evaporation of the solvent cross-linked Na-CMC was homogeneously sprinkled on the film. A transparent film having a theoretical ion exchange capacity of about 0.9 milliequivalents~g and a water retention capacity of arbout 33~ by weight was obtained.

.:. :, ;l Example 16 ;

An O.S mm thick layer was cast as in the above Example 6 from ;l an alkaline HEC solution, cross-linked Na-CMC was homogeneously sprinkled on the surface of the layer as in the above Example 14, and ~1 a film wa~ precipitated and washed. A film having a theoretical . 1 :
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~6Z4Z5 exchange capacity of about 1.0 milliequivalent/g o film and a water retention capacity of about 130~ by weight was o~tained.
Example 17 The procedure followed was as in the above Example 14 but a Na-CMC cross-linked with cyanuric chloride (instead of with epi-chlorohydrin) was sprinkled onto the cast viscose layer. ~he resulting film had a theoretical ion exchange capacity of 1.2 milliequivalents per g of film and a water retention capacity of 280% by weight.
Table 2 summarizes the essential data of Examples 14 to 17, and their results ~able 2 Cross-linked cellulose ethers, sprinkled onto the sur-face of cellulose-based films Example Polymeric Cross-linked Cross- Theoretical Water reten-No. carrier cellulose linking ion exchange tion capacity material ether agent capacity, of the film, milliequi- ~ by weight valents per _ _ g of film _ _ 14 Hydrated Na-CNC Epi- 1.1 440 chloro-hydrin Cellulose Na-CMC " 0.9 33 acetate 16 Hydroxy- Na-CMC " 1.0 130 ethyl-cellulose 17 Hydrated Na-CNC Cyanu- 1.2 280 cellulose ric chloride Example 18 30% by weight of a dry sodium carboxymethyl cellulose cross-linked with 50% by weight of epichlorohydrin were homogene-ously mixed into finely ground high pressure polyethylene powder.

~6Z4ZS
The homogeneous mixture was granulated by chopping a strand extrud-. ed on a twin screw extruder heated to 165 C, so that chips, of diameter and height about 3 to 4 mm,of po.lyethylene modified with the cross~linked Na-CMC were produced. The chips were fibrillated to fibers by means of a cutting mill. The fibrous samples showed a water retention capacity of about 26% and a measurable ion exchange capacity of about 0.78 milliequivalent~g.
The starting polyethylene had virtual.ly no water retention ~ ~ `
capacity, the va.lue being 2%. ~ ~.
It wil.l be obvious to those ski.lled in the art that many modifi- : . .;;
. . .
cations may be made within the scope of the present invention without . .:
departing from the spirit thereof, and the invention includes all such . .

modifications . .
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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A hydrophilic shaped structure of a polymer capable of forming fibers and films and being water-insoluble and also comprising particles of cellulose ether rendered at least partly water-insoluble by cross-linking or modification but which are water-absorbent.

2. A hydrophilic shaped structure according to claim 1 comprising a surface having distributed thereon said particles of cellulose ether rendered at least partly water-insoluble by cross-linking or modification but which are water-absorbent.

3. A hydrophilic shaped structure according to claim 1 having distributed in said polymer said particles of cellulose ethers rendered at least partly water-insoluble by cross-linking or modification but which are water-absorbent.

4. A structure as claimed in claim 1, wherein the particles are of a size within the range of about 0.01 to 2 mm.

5. A structure as claimed in claim 1 wherein the particles are in a maximum amount of 50 % by weight, based on the hydrophilic shaped structure.

6. A structure as claimed in claim 1 wherein the cellulose ether is carboxymethyl cellulose, hydroxyethyl cellulose, methyl-hydroxyethyl cellulose or carboxymethyl-hydroxyethyl cellulose.

7. A structure as claimed in claim 1 wherein the cellulose ether is cross-linked by dimethylolmethylene bisacrylamide, methylene-bis-acryl-amide, tri- or tetra-chloro-pyrimidine, cyanuric chloride, epichlorohydrin, dichloroacetic acid, a diepoxide or a di-.alpha.-halogenohydrin.

8. A structure as claimed in claim 1 wherein the cellulose ether is modified by N-methylolacrylamide, N-(acrylamidomethylene)-acetamide, N-(acrylamidomethylene)-formamide, N-(acrylamidomethylene)-amylurethane, N-(acrylamidomethylene)-methyluretahne, N-(acrylamidocarboxymethylene)-ethylurethane, N-(acrylamido-methylene)-methoxyethylurethane or vinyl sulfonamide.

9. A structure as claimed in claim 1 which is a film, a fiber, a filament, or a spongy product.

10. A process for the manufacture of a hydrophilic shaped structure of a polymer capable of forming fibers and films and being water-insoluble and also comprising particles of cel-lulose ether rendered at least partly water-insoluble by cross-linking or modification but which are water-absorbent in which said polymer is shaped, said particles of cross-linked or modified cellulose ether being added to the polymer before or after shaping.

11. A process according to claim 10 in which a supporting structure, composed of the polymer, is sprinkled with the particles of cross-linked or modified cellulose ether and in which the surface being sprinkled is either provided with an adhesive or is in a state in which the surface itself acts as an adhesive.

12. A process according to claim 10 in which said particles of cross-linked or modified cellulose ether, in pulverulent or granular form, are uniformly distributed in the polymer before shaping.