DE2228256C3 - Process for the production of crosslinked, insoluble, hydrophilic polymers and their use - Google Patents

Description

45

It is known that polyethylene oxide in aqueous solutions by the action of ionizing radiation can be networked. So z. B. according to US-PS 32 64 202 polyethylene oxide by irradiation a solution of this polymer crosslinked to form a gel-like and practically water-insoluble product. The gel-like product can then be dried, virtually all of the water being removed will. The crosslinked polyethylene oxide is because of its ability to absorb large amounts of liquid versatile. These products can e.g. B. as a plant growth medium (US-PS 33 36 129), used as a burn and wound dressing (US-PS 34 19 006) and as a cooling medium (US-PS 35 45 230). The mixed crosslinking of polyethylene oxide with other water-soluble polymers that have no structural units was previously unknown.

It has now been found that polyethylene oxide in aqueous systems with other water-soluble polymers mischvernel / t can be, resulting in insoluble hydrophilic gels. Further winds found that heterogeneous systems, in which two or more aqueous phases exist, result in a gel with homogeneous Appearance can be mixed crosslinked. The properties of such gels are different from the properties of gels obtained by crosslinking solutions of the individual polymers will.

The object of the invention was therefore to find novel, mixed, insoluble, hydrophilic polymers to provide. This object is achieved by the invention.

The invention thus relates to a process for the production of mixed crosslinked, insoluble, hydrophilic ones Polymer, which is characterized in that 1 to 99%, based on the total weight of the polymers, of water-soluble polyethylene oxide with a molecular weight that is reduced Viscosity from 0.5 to 75 corresponds, and at least one other water-soluble polymer of (1) Starch, hydroxyethyl cellulose. Carboxymethyl cellulose, hydroxymethyl cellulose, hydroxypropyl cellulose, Polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide. Poly-4-vinyl-n-butylpyridinium bromide. Pole\- vinyl methoxide, vinyl methyl ether-maleic anhydride copolymer or gelatin or (2) polyacrylic acid, Ammonium polyacrylate and ethylene maleic anhydride copolymer, optionally in the presence of up to 50 percent by weight, based on "the solid polymer of Pohäthylenimin mit a molecular weight of 10,000 to 100,000. Dissolves in water and the pH of this solution in the case the use of group I polymers to 2 to 11 and in the case of the use of polymers of group 2 to above 4.0 to below 9.0, a homogeneous system or a hydrogen mixed phase system produced by intimate mixing of the solution and the system thus produced before entering Phase separation allows ionizing radiation to act, optionally the mixed crosslinked product obtained in this way Polymer dries, removing at least some of the water.

The mixed crosslinked polymers produced according to the invention are insoluble hydrophilic gels with homogeneous appearance. Their properties differ from the properties of gels, which by Crosslinking solutions of individual polymers are produced. From the obtained according to the invention Films and foils produced by polymers have z. B. mostly higher strengths, stabilities and Toughness as films and foils that were produced by crosslinking individual polymers.

Since the majority of the polymers which can be used according to the invention do not form a homogeneous system, the must Mixed crosslinking can be carried out before phase separation occurs.

Mixing the polymer solution to form a homogeneous system or a heterogeneous one Micro phase system can be done by a variety of methods. According to the invention, such a Degree of mixing can be achieved, which ensures that practically no phase separation occurs before the polymers are mixed crosslinked. These results can e.g. B. with ordinary laboratory stirrers can be achieved.

According to the invention, solutions containing polyethylene oxide and at least one further water-soluble polymer in various proportions contain, mixed cross-linked willow. The Gehall

of polyethylene oxide is 1 to 99%, based on the total weight of the polymers.

In practice, the aqueous solutions can be used the mixed crosslinking a total of up to 50 percent by weight, preferably 1 to 20 percent by weight, of the contain polymers.

The water-soluble polyethylene oxides used according to the invention have a molecular weight that a reduced viscosity of from 0.5 to 75 and above, and preferably from 1 to 60, or a viscosity in aqueous solution at 25 C from 225 cP (measured in a concentration of 5 percent by weight) to 1200OcP and above (measured at a concentration of 1 percent by weight).

The system of the water-soluble polymers to be crosslinked with one another, produced according to the invention, is exposed to ionizing radiation for a time sufficient to form a water-insoluble, hydrophilic, gel-like product. The term "ionizing radiation" in the present description means any type of radiation that is sufficiently energetic to cause electron excitation and / or ionization of the polymer molecules or the solvent, if such is used, but is again not energetic enough, to attack the atomic nuclei. Preferred radiation sources used according to the invention are '/ -rays emitting radioactive isotopes, such as Co' * ' and Cs ¹³⁷ , exhausted nuclear fuels, usual X-rays and by z. B. Van de Graaff generators, linear accelerators for electrons and resonance transformers released electrons. The ionizing radiation used according to the invention generally has energy values of 0.05 to 20 MeV.

According to the invention, the non-crosslinked water-soluble polymers can be irradiated in the solid phase or be carried out in solution. Solid polymers can be exposed to air under reduced pressure or irradiated under various other gases. Irradiation in solution can be done with solutions of the polymers in water or in mixtures of water and water-miscible organic solvents be carried out. The irradiation of the solid or dissolved polymers can after each known method.

The exact radiation dose which, according to the invention, must act on the polymers depends on several factors Variables. If the irradiation with relatively low intensities and in the presence of radical scavengers, such as oxygen, are generally used to produce the water-insoluble hydrophilic polymers required extremely high total doses. If, on the other hand, the radiation is below such Conditions are carried out that favor a relatively long life of the free radicals that have formed, d. i.e. when the irradiation is e.g. B. with a high radiation intensity in the absence of oxygen or in a solution in which the oxygen is rapidly consumed, the formation proceeds of the water-insoluble hydrophilic polymers proceed rapidly. An aqueous solution is preferred of the water-soluble polymers with ionizing radiation with energy values from 0.10 to 20 McV irradiated at total doses of 0.05 to 10 megarads.

In addition to the mixed crosslinking brought about by ionizing radiation, the polymers can also be mixed with mixed cross-linked chemical methods. For this purpose z. B. peroxides, such as acetyl peroxide, has been used successfully in the presence of a polyfunctional compound such as divinylbenzene.

The term "insoluble" refers herein to the formation of polymers with varying depending on the degree of crosslinking, substantially water-insoluble fractions. The expression "mixed networking"; means making the polymer mixture insoluble, the same or different polymer chains being linked by covalent bonds at one or more points on the chains. Certain polymers can be incorporated into the mixed crosslinked polymers without being bound to them. This inclusion also contributes to the insolubility of the polymers. These polymers are also hydrophilic and can therefore swell and absorb many times their own weight in water.

In some cases it may be desirable to use the mixed crosslinked polymers prepared according to the invention to stabilize further.

It has been found that polyethyleneimine is an excellent stabilizer. Polyethyleneimine will made from ethyleneimine and contains for the most part structural units of the formula

and to a lesser extent structural units of the formula

-N

CH ₁ -CH ₂

CH, -CH,

According to the invention, polyethyleneimine is preferably used with a molecular weight of 10,000 to 100,000 used, since these polymers are eminently suitable for the purpose according to the invention. Polyethyleneimine with a molecular weight of 20,000 to 80,000 is particularly preferred. These polymers are produced by processes known per se and are commercially available.

The polyethyleneimine serving as a stabilizer is used in a stabilizing amount. The expression "stabilizing amount" means such a polyethyleneimine amount by which when mixed with the polymer, the rate of degradation, based on the unstabilized Polymer, is reduced. It was found that already 0.01 weight percent polyethyleneimine. based on the solid polymer, effectively stabilize the polymer against degradation. Preferably the amount of polyethyleneimine is 0.2 to 3.0 percent by weight. It can, however, if so it is desirable to use polyethyleneimine quantities of up to 50 percent by weight.

The insoluble, hydrophilic, Mixed crosslinked polymers or gels are very versatile. So can the gels /. B. contain large amounts of aqueous liquids or the dried polymers can be large Absorb quantities of such liquids. They therefore serve /. B. as absorption media for absorbent Single-use products and are used in agriculture, e.g. B. as a liquid retention agent. In particular, the crfinduniis-

according to prepared polymers as absorption media for diapers and menstrual needs, such as Sanitary towels and tampons.

Although single-use absorbent products have long been used to absorb body fluids, these products are not always entirely satisfactory. Numerous materials with different structures and different absorbents are known from the literature. Many of the products currently on the market; however, have the disadvantage that they have insufficient absorption properties. In order to improve the absorption properties, inexpensive materials with moderate or low absorption capacity, such as flocked line fabric, have hitherto usually been placed between layers of liquid-permeable fabrics. In many cases, if these products are to have satisfactory absorption properties, they are considerably bulky and not convenient. So sotten z. B. diapers and sanitary napkins have a minimal thickness and ensure adequate absorption of body fluids. However, if the absorbent material has only a low absorbency, the aforementioned products carry when they are supposed to be useful. considerably and do not adapt to the body shape to the desired extent.

Still, one of the major disadvantages of currently commercially available products is that, although they are a Can have relatively high absorbency, but the absorption media when pressure is applied release part of the absorbed liquid. This is due to the fact that the liquid is physically attached a fibrous structure is attached and therefore a relatively low pressure is sufficient to disperse the liquid to release. This is of course highly undesirable, especially when menstruating.

The insoluble, hydrophilic produced according to the invention Polymers can be used particularly well for the aforementioned purposes because they contain amounts of water can absorb in the order of 25 to 1,000 times their dry weight. According to the invention The polymers produced are important in addition to their ability to absorb large amounts of water also insoluble in water, regardless of temperature, and hold liquids. Solutions and Suspensions back. The polymers and gels prepared according to the invention are very general to increase the absorbency of all known or commercially available products usable for single use. The polymers prepared according to the invention can, for. B. in the types described in U.S. Patents 2,788,003, 2,860,637, 3,306,293, 2,667,168,31 21,427 and 3,070,095 be swallowed up by diapers, tampons or sanitary towels. The polymers produced according to the invention can be used in a variety of ways, e.g. B. in the form of a cellulose-like Substrate dispersed and bound to this substrate powder or in the form of an intermediate Layers of the support structure located polymer film or a polymer film. The film or the The film or the powdery polymer can be bonded to the substrate in any known manner. In general, the amount used is a hydrophilic polymer prepared according to the invention depending on the particular absorbent product and its intended use. Fs it has been found that absorbent products can be manufactured for single use. based on the total weight of the product, 2 to 98 percent by weight of one or more according to the invention may contain manufactured hydrophilic polymers.

Example I.

Using a commercially available polyethylene oxide from the compound obtained in coagulating quality mil a molecular weight above / 0 "is a polyethylene oxide stock solution prepared. To this end, the polyethylene oxide is dissolved with stirring in water, a solution mil a concentration of 4% Poiyäthylenoxid is obtained. The thus The resulting highly viscous solution is adjusted to a viscosity of 561,000 cP by shearing in a high-speed mixer.

A hydroxyethyl cellulose standard solution is made using a commercially available product manufactured. Samples are then made with polyethylene oxide to hydroxyethyl cellulose weight ratios from 9: 1.3: 1.1: 1 and 1: 9 by simply adding the corresponding volumes below Stirring established, stirring being continued until a homogeneous mixture is obtained will.

At least 5 portions of 10 cm ³ each of each mixture are poured into standard plastic Petri dishes. Each dish is irradiated using a Van de Graaff generator at 1 MeV, the total doses being 0.2,0,4,0,6,0,8 and 1.0 megarads. The irradiated mixtures are allowed to dry for 15 hours at room temperature and at the prevailing humidity. The dried films obtained are tested for the percentage of insoluble content and for the absorption capacity of aqueous saline solution in the manner described below.

a) Insoluble part in percent

0.2 g of the dried polymer is precisely weighed out and placed in a ^{vessel containing 200 cm 3 of} a 10% water-in-methanol mixture. The jar is then moved steadily on a roller mill for 16 to 2C hours, and then the swollen gel is placed in a drying oven. The dried solid is weighed and the percentage of insoluble polymer is calculated according to the following equation:

Insoluble part in percent =

Weight of the insoluble part
original weight of the sample

100.

The soluble fraction in percent is calculated according to the following equation:

Soluble fraction in percent =

- Weight of the insoluble part
original weight of the sample

100.

In those cases in which the mixed network gettocklcte Polymer not in the aforementioned methanol / water extraction mixture is soluble, this is replaced by pure water.

b) absorbency

2 g of the dried polymer are precisely weighed and poured into a 200 cm ^{1 of} an aqueous 0.3

into a vessel containing n-sodium chloride solution. The vessel is then moved evenly on a roller mill for 16 to 20 hours. Then will weighed the swollen gel, removing excess water with absorbent material. the Absorbency is calculated according to the following equation:

. . ,. Weight of the swollen gel

Absorptioniahmkit = ·.: —.—, ^, - rr —-; - = r— -.- .

- the original weight of the sample

The absorption capacities for other systems are determined in a similar way. The values thus obtained are compiled in Tables 1 and II, in which A is the insoluble fraction in percent and B is the absorption capacity means.

Table I.

Properties of mixed crosslinked polymers made from polyethylene oxide and other water-soluble polymers

Water soluble Strah The weight ratio of rc 15th 3: 1 > Lyalhylcn oxide to and cream wa: publicly cn polymer 1: 9 B. Polymer len 30th 5 dose, 9: 1 38 Λ 1: 1 1: 3 A. 14th Mcga- 43 83 25th 12th wheel A. 72 82 B. A. B. A. B. 12th 14th Strength for experi 0.8 85 32 77 27 72 23 47 21 13th 128 mental purposes 0.6 79 34 56 27 73 29 48 22nd 15th 80 0.4 78 45 86 39 58 27 49 23 33 30th 0.2 55 94 82 60 51 46 39 28 31 strength 0.8 86 29 76 27 78 23 67 37 10 19th 0.6 86 39 53 33 74 24 64 53 24 0.4 79 52 41 70 38 60 70 82 30th 0.2 60 100 69 53 66 77 69 Hydroxyethyl 0.8 89 29 83 20th 83 22nd 69 16 cellulose 0.6 86 42 80 24 48 23 (QP 30000) 0.4 80 54 88 78 35 75 34 86 28 0.2 66 92 85 64 66 55 78 80 57 Hydroxyethyl 0.8 90 32 81 27 89 21 83 21 78 54 cellulose 0.6 84 37 41 36 86 28 62 69 (QP 100-M) 0.4 81 52 82 45 83 40 46 93 0.2 68 85 80 28 67 67 66 69 45 Carboxymethyl 0.8 86 22nd 72 32 80 32 66 29 18th 37 cellulose 0.6 87 25th 56 40 64 37 65 38 50 0.4 76 38 90 48 63 49 58 57 81 43 0.2 59 62 88 77 46 83 41 89 61 Ethylene maleic 1.0 95 24 91 19th 89 11th 99 25th 53 46 acid anhydride 0.8 90 29 78 20th 84 11th 95 37 57 Copolymer 0.6 92 32 86 29 70 15th 64 41 77 58 0.4 92 50 76 59 25th 35 53 49 69 84 Ammonium- 0.8 85 74 22nd 90 22nd 88 29 68 polyacrylate 0.6 80 55 28 83 29 82 30th 44 0.4 74 86 34 85 33 76 47 0.2 48 81 62 51 64 35 76 Polyacrylamide 0.8 74 28 0.6 44 44 0.4 50 0.2 82

9 10

Table II

Properties of mixed crosslinker polymers made from polyethylene oxide and other water-soluble polymers

Water soluble
Polymer

Rays
dose. Mega wheel

Weight ratio of polyethylene oxide to other water-soluble polymer 9: 1 6: 1 4: 1 2: 1

A I! A ii

It

Ethylene-maleic anhydride copolymer
(5% aqueous solution,
pH 4.5)

0.2 22 90 63 80

0.4 60 66 58 71 42 64 63 91

° ⁶ 69 46 72 51 65 69

0.8 80 27 75 40 77 42 76 49

Ethylene maleic acid 0.2

anhydride copolymer rj, 4 41 76

(10% aqueous solution, _Q ' _{6 (7} <.

^PH4 ' ⁵⁾ ώ 71 42

122
70
48
41

16

51
71
77

264
80
64
50

58 136

66 82

74 61

Polyvinyl methyl ether 0.2

(10% aqueous solution) or 4 48 67

0.6 57 49

0.8 62 42

70
67
58

47
58
64

Sl
51

40 62 65

59 45 44

Example 2

Using a polyethylene oxide of the same quality as obtained by coagulating a 4% polyethylene oxide stock solution is produced. This is done by stirring the polyethylene oxide in water and then shearing the resulting solution down to a viscosity of 500 00OcP.

By dissolving an appropriate amount of poly-4-vinyl-n-butylpyridinium bromide a 2% strength stock solution of this polymer is prepared in water with stirring. The aforementioned polymer was made by reacting poly-4-vinylpyridine with excess n-butyl bromide in ethanol "in itself produced in a known manner.

20 g of the 4% polyethylene oxide stamnilöstim are mixed with 11 g of the 2% poly-4-vinyl-n-butyl

Pyridinium bromide stock solution mixed. Here is a mixture with a molar ratio of polyethylene oxide to poly-4-vinyl-n-bulylpyridiniumbronrid of 15: 1 received. 3 g of this mixture with one pH value of 4.9, Γη a Petri dish made of plastic

poured fabric and using a Van-de-Graaff-Gcnc · rators of I MeV with a total dose of 0.7 Mcga rad irradiated. The gel obtained in this way is taken from the Petri Dish transferred to cm cup and allowed to equilibrate with excess water for 24 hours

The gel is then obtained. and its absorbency is calculated according to the following equation:

Absorbency = weight of the swollen gel
calculated solids content in 3 g solution '

Components

In another experiment, the pH value of «Table III The mixture is adjusted to pH 3 by adding 0.1 N HCl and to pH 7 by adding 0.1 N NaOH. 3 g of the mixtures treated in this way are given a total dose of 1 MeV by means of a Van de GraafT generator irradiated by 0.7 megarads. The gels obtained in this way are placed in a beaker and Allowed to equilibrate with excess water for 24 hours. The gels are then weighed, and the absorbency is calculated according to the above equation. Similarly, the 65 Absorption capabilities determined for other systems. The values thus obtained are in the following Table III compiled.

Mixed cross-linked polymer

Polyethylene oxide-polyethyleneimine

Radiation dose.
Mega wheel

0.7
0.7

0.7

Mole ratio

15: 1

20:

40:

pH

8.4 3.5 8.4 3.7 8.2

Absorbency,

g water g solid

continuation Sir.ih- Molvcr- pll Absnrp- l) c * tundtak ' IctuloMv help lionsflihii: - Μομ; ιπκΙ UmI. ü W.isser ii K'slsloff 0.7 15: 1 3.0 130 Polyethylene oxide 4.9 960 Poly 4 vinyl 7.0 630 n-butyl-pyridi- 0.7 20: 1 3.0 130 nium bromide 7.0 890 0.7 40: 1 3.0 100 6.3 235 7.0 410 1.0 20: 1 5.5 469 10.0 416 1.0 40: I. 6.1 166 10.4 158 1.0 20: 20: 1 5.5 365 Polyethylene oxide Polyvinyl alcohol iiol-poly-4-vinyl- n-butylpyridi- nium bromide 1.0 20: 20: 1 7.4 60 Polyethylene oxide Polyvinyl alcohol hol-polyethylene- imin 2.0 20: 1 7.4 44 Polyethylene oxide 3.3 57 Polyvinyl alcohol 2.0 40: 1 7.1 46 get-Polyäthyien- 3.0 53 imin 2.0 20: 1 5.4 592 Polyethylene oxide 10.6 324 Polyvinyl alcohol 2.0 40: 1 5.4 330 hol-poly-4-vinyl- 9.9 258 n-butylpyridi- nium bromide

Example 3

Unier using a commercially available polyethylene oxide from the compound obtained in coagulating quality with a molecular weight above IO ^h produced a polyethylene oxide stock solution. For this purpose, the polyethylene oxide is dissolved in water while stirring, producing an approximately 10% solution. The highly viscous solution thus obtained is then

ίο by shearing in a high speed mixer adjusted to a viscosity of 1,000,000 cP.

Using a commercially available ammonium polyacrylate, an ammonium polyacrylate stock solution is made manufactured. For this purpose, the ammonium polyacrylate is dissolved in water with stirring, with an approximately IO% solution is prepared. Further Mixtures of the two solutions in a weight ratio of polyethylene oxide to ammonium polyacrylate of 4: 1 and 8: 1 by adding together appropriate volumes of each solution. At this Preparation is stirred until homogeneous mixtures are obtained.

Each of these mixtures is spread on a polyethylene film support, and the layer thickness of the mixtures is adjusted to 254 to 305 μ when wet with a doctor blade. After drying, a film with a thickness of 25.4 μ is obtained. The mixture is generated by means of a Van de Graaff generator of 1.5 MeV with total

yo doses of 0.4. 0.5 and 0.6 megarads irradiated. The irradiated mixtures are left to dry for 15 hours at room temperature and at the prevailing humidity. The films obtained in this way are tested according to Example 1 for the insoluble fractions:

in percent and checked for the absorption capacity for aqueous saline solution.

In a similar manner, irradiated films eviscerate Polyethylene oxide mixed with polyacrylic acid with a pH value of 4.5 or with poly-4-vinyl-n-butyl pyridinium bromide produced. The results are shown in Table IV below in which A is the insoluble fraction in percent and B is the absorption capacity.

Table IV

Properties mixed crosslinked! "Polymers made from polyethylene oxide and other water-soluble polymers

Water-soluble polymer Rays
dose,
Meparad Weight ratio of
soluble polymer
4: 1 B. Polyethylene oxide
8: 1 to other 1 A. 59
47 A. B. Ammonium polyacrylal (pH about 7) 0.4
0.5 73.4
77.2 42 66.4
72.6 59
49 0.6 78.3 37
35 78.3 41 Polyacrylic acid (pH about 4.5) 0.4
0.5 82.1
84.0 31 80.6
81.4 47
38 0.6 82.5 54
40 83.3 36 Poly-4-vinyl-n-buty] pyridinium bromide 0.4
0.5 65.3
68.0 39 68.2
69.6 45
41 0.6 70.4 70.0 35

Claims (3)

Patent claims: 1. Process for the production of mixed crosslinked, insoluble, hydrophilic polymers, thereby characterized in that 1 to 99%, based on the total weight of the polymers, of water-soluble polyethylene oxide with a molecular weight, i.e. a reduced viscosity corresponds to from 0.5 to 75, and at least one further water-soluble polymer of (1) starch, Hydroxyethyl cellulose, carboxymethyl cellulose, hydroxymethyl cellulose, hydroxypropyl cellulose, Polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, poly-4-vinyl-n-butylpyridinium bromide, Polyvinyl methyl ether, vinyl methyl ether-maleic anhydride copolymer or gelatin or (2) Polyacrylic acid, ammonium polyacrylate and ethylene-maleic anhydride copolymer, if appropriate in the presence of up to 50 percent by weight, based on the solid polymer Polyethyleneimine with a molecular weight of 10,000 to 100,000, dissolves in water and adjusts the pH this solution in the case of the use of polymers from group 1 to 2 to 11 and in the case the use of polymers of group 2 adjusts to over 4.0 to under 9.0, a homogeneous System or a hydrogen mixed phase system by intimately mixing the solution and act on the system produced in this way by ionizing radiation before the phase separation occurs leaves, optionally dries the mixed crosslinked polymer obtained in this way and so at least removed some of the water. 2. Use of the mixed crosslinked polymers according to claim 1 for the production of absorbent Single use products. 3. Use of the mixed crosslinked polymers according to claim 1 for the production of menstrual requirements and diapers.