A process for improving the hydrophilic properties on polymer surfaces

(54) NAME Procedure for surface modification of polymeric materials for increased surface energy and hydrophilicity (56) PUBLICATIONS Cited: ---

OTHER PUBLICATIONS: Dialogue AN 2979264 (Derwent AN 82-27243E / 14, JP-A- 57034950, publ. 1982-02-25. Chemical Abstracts vol. 84 (1976) no. 5887, FR, A, 2246609. Dialogue AN 3775125 ( Derwent AN 85102044/17, JP-A- 60047035, published 1985-03-14

Chemical Abstracts vol. 109 (1988) abstract no. 43497, US, A, 4734475 publ. 1988-03-29.

(57) SUMMARY:

Polymeric materials are surface modified to increase the hydrophilicity of the polymer surface by providing, in a first step, carboxyl, carbonyl, and hydroxyl groups on the polymer surface by oxidation with, for example, oxidizing acid solutions or otherwise known, to react with heterocyclic compounds having 3 or 4 ring atoms or with isocyanate or carbodiimide compounds.

PRV 328 ALLF 138 9 132 AA

The numbers in brackets indicate the international identification code. INlD code. Letters in clamps indicate international document code

461 592

The present invention relates to a method for surface modification of polymeric materials. More specifically, the method aims to increase the surface energy of polymeric surfaces and thereby render hydrophobic polymeric materials hydrophilic.

Increasing the surface energy and hydrophilicity of plastic and fiber surfaces of hydrophobic polymeric materials is of great importance in improving the properties of the material with respect to, bonding, adhesion, painting, dyeing, metallization and printing.

Improvement of these properties has become crucial to meet the increasing use of polymeric materials in practical applications. In order to increase the hydrophilicity of hydrophobic polymers, the following methods have been used hitherto:

1st Oxidation by strongly oxidizing solutions

2nd Oxidation by physico-chemical methods such as corona, flame and plasma treatment.

3rd Grafting with hydrophilic monomers.

Examples of known chemical oxidation methods are solutions of chromium oxides, permanganates and perchlorates in strong mineral acids. These chemical methods have resulted in a very marginal lowering of the contact angle, which is used as a measure of the surface energy of polymeric surfaces. In addition, it is difficult to obtain reproducible results at the contact angle by these methods. Most polymers have a low surface energy (19.1 mJ m for Teflon; 30-33 mJ m for polypropylene and polyethylene and 47 o mJ m for polyethylene terephthalate), which means that they show a high contact angle of the order of 80-95θ to water. and thus not so easily wetted with water.

A further disadvantage of the previously reported treatment methods is that the treatment is not stable and the contact angle returns to the original values ​​when storing or using such treated materials. This means that the treatment effect disappears over time and therefore cannot be used advantageously in practical contexts.

The increased hydrophilicity of the polymer surfaces by oxidative treatment is mainly due to the occurrence of polar groups mainly carboxyl, hydroxyl and carbonyl groups on the polymer surface. The physicochemical methods listed under point 2 generally give rise to similar groups on the polymer surface as a result, and the limited success of these methods has the same cause, namely insufficient increase of surface energy and poor stability in the time perspective.

The grafting methods mentioned in paragraph 3 comprise a large number of known processes which, while generally providing stable hydrophilicity, but are expensive due to complicated process apparatus and considerable monomer and catalyst insertion. Further disadvantages of the graft copolymerization methods are that it is difficult to remove the homopolymers that are formed simultaneously and that therefore very long extraction times are required.

The object of the present invention is to increase the surface energy and hydrophilicity of polymer surfaces by a process which results in permanent hydrophilicity and which by

2.

461 592 short processing time and low chemical consumption are suitable for industrial applications.

According to the present invention, this object has been achieved by a process which is characterized in that, in a first step, polymeric materials comprising polyolefins, polystyrene, fluoroplastics, polyesters, polyacetals and polyacrylates are subjected to an oxidation treatment to provide functional groups such as carboxyl, hydroxyl on the polymer surface. and carbonyl groups by methods known per se selected from etching with oxidizing acid solutions, corona treatment, plasma and flame treatment, said first step also including such selection of polymerization conditions in the manufacture of the polymeric material that said functional groups are included in the polymer chains, after which the polymeric surface thus obtained is brought into liquid contact with organic compounds comprising heterocyclic compounds having three or four ring atoms, such as aziridines and carbodiimides.

A basic idea during the development work of the present invention has been that the relatively sterically readily movable functional groups obtained by the known oxidation or etching methods over time turn inwards into the polymer bulk, which would explain the subsequently reduced hydrophilicity. The next step in the development work has therefore been to find suitable reagents to bind said functional groups to new larger groups with less steric mobility. The choice of reagent further opens opportunities to increase and regulate the degree of hydrophilicity of the polymer surface.

The reagents selected in the step of the present invention meet the requirement of high reactivity and thus short reaction times and provide sterically stable groups with elevated hydrophilicity compared to the unreacted groups obtained by the oxidation treatment.

For chemical oxidation of polymer surface according to step 1 with known standard etching solutions such as chromium trioxide or dichromate solution in water or sulfuric acid, chromium trioxide dissolved in phosphorus and sulfuric acid in water, permanganate solution in sulfuric acid, peroxodisulfate solution in water, chlorate solution in perchloric acid or first etching sulfuric acid followed by etching with concentrated nitric acid. The etching time can be varied between 5 seconds and 30 minutes and can occur at temperatures between room temperature and ΙΟΟθΟ.

The choice of etching process is to some extent related to the polymer to be treated. Polyolefin plastics are relatively inert and are preferably treated with dichromate solution in sulfuric acid. Polystyrene, on the other hand, is degradation-sensitive in strongly oxidizing acid solutions, which is why milder oxidation processes. should be applied. A suitable oxidation method for polystyrene is treatment with hydrogen peroxide in the presence of UV light. Fluorine plastics are among the least chemically reactive and therefore require very harsh etching conditions, for example, treatment with a solution of alkali metal in liquid ammonia.

Polyesters and polyacrylates are also degradation sensitive in oxidizing acid solutions. Here, however, another alternative is offered for carrying out step 1. Since polyesters are prepared by co-condensation of polyols and dichagenomically controlled stoichiometric imbalance to provide an excess of hydroxyl or carboxyl groups.

3·

461 592

In the preparation of polyacrylates, carboxyl and / or hydroxyl groups can be formed in the finished polymer by adding monomers containing hydroxyl and / or carboxyl groups during polymerization. In other words, step 1 is carried out in the polymerization itself.

Oxidative treatment in step 1 by plasma, corona or flame can be carried out on all polymer types covered by the invention. In plasma etching, the material is subjected to plasma consisting of a mixture of reactive substances such as atoms, molecules and ions in metastable and / or excited states and electrons. The mixing ratio of the reactants is such that there is a total balance between positively and negatively charged particles.

For corona and flame treatment, commercially available equipment is available, and these methods may be described as well-established technology in this context.

In step 2, the polymer treated according to step 1 is brought with a solution containing a compound of the following groups A, and B, wherein group A comprises heterocyclic compounds having three ring atoms such as aziridines and group B comprising carbodiimides. More specifically, the following compounds are included:

A: Mono- or multifunctional aziridines of formula

CH 2 ----- CH-R ', where R' may be a hydrogen or an alkyl group of 1-10 ^S N ^Z

C atoms and may be an alkyl group having 1-10 C atoms or an alkyl group having from 1 to 10 C atoms substituted with one or 2 additional aziridine groups, a melamine group wherein one, two or three hydrogen atoms which are linked to carbon atoms in the melamine ring are substituted by one or more aziridine groups or a P = O group.

B: Carbodiimides of the formula

R_q___ N == C = N-R₁₀, where Rg and R_1Q is an alkyl group of 1-10

C atoms or a phenyl group which may be substituted by a halogen or hydroxyl.

The reaction according to step 2 is carried out in aprotic organic solvents such as ketones and ethers. The treatment time is generally short and is between 30 sec and 30 min, preferably between 30 sec and 3 min. The temperature may vary between room temperature and 100 ° C, preferably between room temperature and 60θ.

The reaction of step 2 between the polymer and group A compounds is by ring opening of the heterocyclic ring. Examples of such reactions are:

<img file="SE461592B_D0001.tif" />

461 592

Poly - OH +

<img file="SE461592B_D0002.tif" />

reaction 1

Poly - 0-CH-CH₂-NH-R

Poly-COOH + R2-N + T² - CH₂---- CH₂ + Poly-COO ~ h ^^hrs2 ^S HnC + ² CH₂.

HillLj

-CH₂OOC-Poly reaction 2

Examples of reactions with group B compounds are:

Poly-COOH + R_ON = C = N_Poly-COO * ⁹^{and ιυ S}NH_R_1q reaction 3

According to a preferred embodiment of the invention, the polymer of step 1 is reacted in step 2 with a polyfunctional compound, ie, a heterocyclic compound with several rings in group A. By way of example:

/ CH₂

CH "^ xJrr triaziridine | ^CE2

CH + X N --- CH₀² / 2 gh₂

In these cases, in a third step, the unreacted functional groups remaining on the polymer surface can be further reacted with alcohols, polyols or monohydric dicarboxylic acids at temperatures between room temperature and 100 ° C.⁹C for 1-30 min. Such unreacted groups on the polymer surface occur when a polyfunctional compound instead of a monofunctional compound is used to modify the polymer surface in step 2 above. Since the concentration of -COOH, -OH and C = O groups on the polymer surface is very low, probably only one reactive group of the polyfunctional compound reacts with these groups and thus the other reactive groups remain for further reaction. This allows one to modify the polymer surface to obtain different degrees of the hydrophilic.

To confirm that the presence of groups such as -COOH, -OH or C = 0 is necessary b

461 592 to effect hydrophilization by reaction with the reactive compounds, all of the above polymeric materials were treated with the various compounds described in step 2 without treating the polymer surface according to step 1. Contact angle measurements show that no changes in surface energy were achieved. Below, the invention will be further elucidated with several different practical embodiments.

EXAMPLE 1

The contact angle of untreated polypropylene was measured after cleaning with acetone and drying to 91-95θ. The film was then treated with dichromate solution in sulfuric acid (4.4% by weight dichromate in 15.7 molar sulfuric acid) for 30 sec, 1 min and 5 min at 20θΟ and for 5 sec, 10 sec, 1 min and 5 min at 70θ 70 and washed clean with dest. water. The contact angle to water was then measured on the treated films after they had been oven-dried at 50 ° C for three hours. Contact angle of 90 + 2θ; 90 + 1.7θ and 94.6 + 2.2θ, respectively, at 20 ° C and 92.4 + 3.2 °; 95.7 ± 2.4 °; 100.4 + 4.8 ° and 105.6 + 3.3 ° at 70 ° C were obtained.

The film samples etched with the chromic acid solution for 30 sec, 1 min, and 5 min at 20θΟ and 5 sec, 10 sec, 1 min and 5 min at 70θϋ were then further treated with a

R trifunctional aziridine compound (Neocryl CX-1Q0} used after dilution with distilled water at a 1: 1 ratio at room temperature (RT) for 30-40 seconds and then washed with distilled water for 1 min, with methanol for 30 seconds , acetone for 30 sec and finally with distilled water again for 3 min and then dried as above. The contact angle was measured again on these modified surfaces and obtained the values ​​64.9 + 1.5θ, 77 + 2.2θ and 71.9 + 2.70 at 20θϋ etched films and 70 + 1.9 °, 68 + 1.9 ° 70, 8 + 1.1 ° and 76.7 + 1.8 ° at 70 ° C etched films. To ensure that the treatment produced a permanent effect, the first of the above films was boiled in distilled water for 5 hours and then, after drying, the contact angle was set to 67.8 + 5.3θ.

The contact angle of washed polypropylene film after treatment with Neocryl CX-100 without any etching was measured at 98.4 + 2.4 °.

EXAMPLE 2

The film was treated with dichromate solution in sulfuric acid, but this time with 2.8 wt.% Dichromate in 15.77 molar sulfuric acid for 30 sec, 1 min and 5 min at 20θΟ and for 5 sec, 10 sec, 1 min and 5 min at 70θϋ and was washed clean with dest. water. The contact angle to water was then measured on the treated films after they had been oven-dried at 50 ° C for three hours. Contact angle of 83.4 + 2.9 °; 84.8 + 2.9 ° and 83.5 + 2.2 ° at 20 ° C and 84.8 + 1.9 °, respectively; 85.3 ± 2.6 °; 93.1 + 2.4 ° and 95.4 + 1.5 ° at 70 ° C were obtained.

The film samples were then further treated with a trifunctional aziridine compound (Neocryl CX-100) which was used after dilution with dist. 1: 1 water at room temperature for 30-40 seconds and then washed with distilled water for 1 minute, with

461 592 ^Lmethanol for 30 sec, with acetone for 30 sec and finally with distilled water again for 3 min and then dried as above. The contact angle was measured again on these modified surfaces and obtained values ​​of 71.0 + 1.7θ, 72.2 + 1.7θ and 73.3 + 1.4θ for 20θϋ etched films while

70.5 + 1.5θ, 72.3 + l, 0% ch 75 + 0.7θνΐά 70 ° C etched films. Apparently, etching with the weaker dichromate concentration results in slightly lower contact angle than with the poorer etching solution of, e.g. 1st

EXAMPLE 3

The film was first treated with dichromate solution in sulfuric acid (4.4% by weight dichromate in 15.7 moles of sulfuric acid) for 30 sec, 1 min and 5 min at 20θϋ and washed clean with dist. water. These films were then further treated with 70% nitric acid at 50θΟ for 15 minutes and washed with dest. water. The contact angle to water was then measured on the treated films after they had dried in the oven at 50 θθ for three hours. Contact angle light was 83 + 1.8θ; 89.3 + 2.9θ and 79.3 + 3.4θ, respectively. The etched films were further treated with a trifunctional aziridine compound (Neocryl CX-100) which was used after dilution with dist. 1: 1 water at room temperature for 30-40 seconds and then washed with dist. water for 1 min, with methanol for 30 sec, acetone for 30 sec and finally with dist. water again for 3 minutes and then dried as above. The contact angle was measured again and obtained values ​​of 69.8 + 2.9θ, 81.1 + 1.9θ and 73.9 + 2.9θ. To re-check the stability of the treated surfaces, the first of the above films was boiled in boiling water for 5 hours and then the contact angle of dried film was measured. The contact angle 71.5 + 3.1θ was obtained. The results show that further etching with nitric acid compared with ex. 1 and 2 hardly give any improvement.

EXAMPLE 4

The one according to ex. 2 for 30 sec at 20θΟ etched and treated with NeoCryl CX-100 the film was post-treated for 1 min with distilled water, 1 min with methanol and 1 min with acetone at room temperature and the contact angle was measured at 66.8 + 2.8? This was then further treated with boiling dest. water for 2 hours and the contact angle was measured at 56.6 + 0.9θ. The longer after treatment compared with ex. 2 apparently gave lower contact angle.

Compared to ex. 2, an even lower contact angle was thus obtained, which is likely due to the effect of a third step, that is, unreacted functional groups from the trifunctional aziridine reacted further with water.

EXAMPLE 5

The one according to ex. 2 for 30 sec at 20θΟ etched and treated with NeoCryl CX-100 treated film for 1 min with distilled water and 1 min and 5 min with acetic acid at

461 592 room temperature at pH = 3. Contact angle of 80.8 + 1.5θ and 81.2 + 0.7θ respectively was obtained. Acetic acid treatment definitely did not improve.

EXAMPLE 6

The one according to ex. 2 for 30 sec at 20θϋ etched and treated with NeoCryl CX-100 treated film after 1 min with dest. water and then for 1 min and 5 min with lactic acid at pH = 3 at room temperature and at 55 ° C. The following results were obtained:

my:

75.5 + 2.4θ at room temperature; 73.2 ± 2.1θ at 55θΟ min:

68.5 + 1.5 ° at RT; 71.7 + 1.7 ° at 55 ° C

The lower contact angle compared to ex. 5 would be related to the presence of a hydroxyl group in the lactic acid molecule.

EXAMPLE 7

The one according to ex. 2 for 30 sec at 20θϋ etched and treated with NeoCryl CX-100 treated film after 1 min with dest. water and then for 5 minutes with malonic acid at pH = 3 at RT and 55θΟ, respectively. Contact angle values ​​83.9 + 0.9θ and 70.8 + 2.3θ were obtained.

The improved result compared to ex. 5 is likely because malonic acid has two carboxylic groups while acetic acid has only one carboxylic group.

EXAMPLE 8

The one according to ex. 2 for 30 sec at 20θϋ etched and treated with NeoCryl CX-100 treated film after 1 min with dest. water and then for 5 minutes with a sodium hydroxide solution at pH = 10 at RT and 55θΟ, respectively. Contact angle values ​​of

59.6 + 2.7 ° and 63.4 + 0.8 ° respectively were obtained.

EXAMPLE 9

Since water reacts with the aziridine rings (CX-100), a 1: 1 mixture of CX-100 with anhydrous acetone is used to treat etched polypropylene film, e.g. 2 for 30 sec at room temperature. The etched film was then post-treated for 1 min with distilled water, 1 min with methanol and 1 min with acetone at room temperature and the contact angle was measured at 58.4 ± 0.9 µm.

The absence of water during treatment with the aziridine moiety of step 2 seems to be preferred.

EXAMPLE 10

Instead of polypropylene film, PP yarns were first etched with chromic acid, e.g. 2 for 30 seconds and then treated with 1: 1 CX-100 solution in anhydrous acetone at room temperature for 30 seconds.

461 592 ^islandsec and post-treated with methanol for 1-5 minutes. Since one cannot use the contact angle method to prove the surface modification effect on vulture, an alternative method was used. Two gamma samples of the same length, one untreated and the other surface treated as above, were lowered into a water bowl and the time when the first water drop came out of the bowl was taken as a measure of the surface treatment effect. The result was 4 minutes for treated yarn versus 10.5 minutes for the untreated yarn measured under the same conditions. The surface modification effect was also confirmed by measuring the flow rate when the yarn was used as a plug in a funnel end. The flow rate was much slower for treated than untreated yarn, which further shows that the wetting ability of the yarn has been greatly improved by the surface modification.

EXAMPLE 11

PP film was first etched with chromic acid solution according to e.g. 2 for 30 sec at RT and then treated with a carbodiimide compound (UCARLNK XL-25 SE 3) for 30 sec at room temperature. The film was post-treated with methanol for 1 min and finally with acetone for 1 min. The contact angle of the modified film was measured at 74.4 + 1θ.

EXAMPLE 12

The one according to ex. 11 etched and treated with carbodiimide the PP film was post-treated for 1 min with dest. water and 5 minutes with methanol and the contact angle was measured

72.2 ± 1.8θ. Since the UCARLNK XL-25 SE is monofunctional, no further reduction of the contact angle is obtained after extended finishing. To re-check for permanent surface modification, the modified sample was boiled for 2 hours in boiling acetone. A contact angle value of 71.0 + 0.9θ was obtained, ie unchanged.

EXAMPLE 13 R

Polyethylene film (PE) with a very high crystallinity (Lupolen 3741 BX) was first washed clean with acetone and then after drying the contact angle was measured. The contact angle, 92.3 + 1.2θ was obtained. The purified film was treated with dichromate solution in sulfuric acid (2.8% by weight dichromate in 15.77 molar sulfuric acid) for 30 sec, 1 min and 5 min at 20θΟ and 70θϋ, respectively, and washed clean with dist. water. The contact angle to water was then measured on the treated films after they had dried in the oven at 50θΟ for 3 hours. Contact angles 80.4 + 2.0θ; 71.9 + 6.2θ and 82.1 + 0.9θ at 20θΟ and 86.7 + 1.9θ; 85.4 ± 3.2θ; respectively 90.8 + 1.2θ at 70θϋ were obtained. The etched films were then further treated with a trifunctional aziridine compound (Neocryl CX-100) after dilution with acetone in 1: 1 ratio at room temperature for 30-40 sec and then washed with distilled water for 1 min, with methanol for 1 min, with acetone. for 1 min and finally with distilled water again for 3 min and then dried as above. The contact angle was measured again on these modified surfaces and was 57.3 + 3.0θ, 63.4 + 1.0θ and 61.1 + 5.1θ

461 592 at 20 ° C etched films and 69.3 + 3.4 °, 74.2 + 2, 1 ° and 59.8 + 3.4 ° at 70 ° C etched films.

EXAMPLE 14

The PE sample treated with CX-100 for 30 seconds as in Ex. 13 was post-treated with methanol for 1 min, the contact angle measured to 58.2 + 2.7θ. To test whether the treatment produced a permanent effect, the modified sample was boiled with acetone for 3 hours and the contact angle was unchanged, ie 57.2 + 0.7θ.

EXAMPLE 15

The PE film was etched according to ex. 13 for 30 sec and 1 min, respectively, and then treated with a carbodiimide (UCARLNK XL-25 SE) for 30 sec at RT and then post-treated with distilled water for 1 min, with methanol for 1 min and with acetone for 1 min at RT and the contact angle measured after drying to 67.1 + 1.1θ and 70.2 + 2.1θ.

EXAMPLE 16

Polyester plastics produced by condensation polymerization need not be surface oxidized according to the methods mentioned for step 1, but OH or COOH groups can be obtained by controlling the OH / COOH ratio in the resin preparation.

R

A sample film of a polyethylene terephthalate (Mylar) was washed clean and the contact angle measured to 71.2 + 2.2θ. The film was then treated with an aziridine compound (CX-100) for 30 sec at 20θ and 50 ° C, and then washed with methanol for 1 min, with acetone for 1 min, and finally with dest. water again for 3 minutes and then dried as above. The contact angle was measured again and became 56 + 1.7θ and 57.7 + 1θ. The test shows that step 2 of the invention can be applied directly to surface modify copolymers where the presence of OH, COOH and C = O groups on the polymer surface can be accomplished by known copolymerization techniques.

EXAMPLE 17 p

The polytetrafluoroethylene (Algoflon) was first washed clean with acetone and after drying the contact angle was measured to 120.9 + 9.8θ. The purified film was treated with dichromate solution in sulfuric acid (2.8 wt.% Dichromate in 15.77 molar sulfuric acid) for 30 seconds and 5 minutes at 20 and 70θϋ, respectively, and then washed with dist. water. The contact angle to water was then measured on the treated films after oven drying at 50θΟ for three hours. Contact angles 113.2 + 4.8θ and 122.9 + 1.8θ at 20θΟ and 118.2 + 3.8θ and

119.1 + 1.5θ at 70θΟ were obtained. The etched film samples were then further treated with a trifunctional aziridine compound (Neocryl CX-100) used after dilution.

461 592 µl with acetone in a 1: 1 ratio at room temperature for 30-40 seconds and then washed with dist. water for 1 min, with methanol for 1 min, with acetone for 1 min and finally with dist.

water again for 3 minutes and then dried as above. The contact angle was again measured on these * modified surfaces to 105.3 + 1.6θ and. 114.3 + 0.8θ at 20θΟ while 116.2 4- 2.6θ and

116.5 ± 1.1 ° at 70 ° C.

EXAMPLE 18

Polystyrene material (PS) was also treated according to the invention. Since PS is very sensitive to strong oxidizing agents, the desired groups such as -OH, -COOH or C = O are obtained on the polymer surface by photooxidation under UV light for 60-90 sec in the presence of Η₂Ο₂The irradiated films were then further treated with a trifunctional aziridine compound (Neocryl CX-100) after dilution with acetone in 1: 1 ratio at room temperature for 30-40 seconds and then washed with dist. water for 1 min, with methanol for 1 min, with acetone for 1 min and finally with dist. water again for 3 minutes and then dried as above. The contact angle of the PS films was measured both before and after surface modification, and a reduction of the contact angle from 75.3 + 2.2θ to 63.2 + 1.2θ was obtained.

EXAMPLE 19

PP film was plasma treated in a plasma reactor (Plasma Prep 100, Nanotech). The film samples were placed in the reactor which was then evacuated to 1 tor. Subsequently, oxygen was flowed through the reactor at a rate of 20 ml / min.

The film samples were then exposed to 100 W plasma for 1 min at 60θΟ.

After the plasma etching, contact angles between 91θ and 67θ were measured on different film samples, ie a large scatter on the contact angle values ​​was obtained. Some of the plasma etched films were then further treated with a trifunctional aziridine compound (Neocryl CX-100) which was used after dilution with acetone in 1: 1 ratio at room temperature for 30-40 seconds and then washed with dest. water for 1 min, with methanol for 1 min, with acetone for 1 min and finally with dist. water again for 3 min and dried as above. The contact angle of PP films, which after the plasma etching had an average contact angle of 85.5θ, was measured to 63.3 + 0.4θ, ie the contact angle was lowered by the surface treatment. To check whether the surface treatment effects were permanent or not, the contact angle values ​​were measured on the surface modified films after a few weeks of storage in the air. The contact angle value of only plasma etched films returned to the original value ie about 90θ, while the films treated with aziridine compound after the plasma etching maintained a contact angle value of about 60θ. This again confirms that surface treatment according to the invention gives a permanent effect and that alternative methods for providing -OH, -COOH and C = O groups on the polymer surface in step 1 can be used.

EXAMPLE 20

The same PP film as in Example 19 was oxidized with corona. In the corona treatment //

461 592, the film was subjected to ionized air which was obtained by applying high voltage between two electrodes. The corona power used was 2.5 kW.

After the corona treatment, an average contact angle of 83.1 + 1.2θ was measured for different film samples. In this case, no scatter on the contact angle values ​​was obtained. Some of the corona-treated films were then further treated with a trifunctional aziridine compound (Neocryl CX-100) according to step 2 which was used after dilution with acetone in 1: 1 ratio at room temperature for 30-40 seconds and then washed with dist. water for 1 min, with methanol for 1 min, with acetone for 1 min and finally with dist. water again for 3 min and dried as above. The contact angle of the PP films after the treatment was measured to 64.1 + 0.4 °, ie the contact angle was lowered by the surface treatment. To check whether the surface treatment effects were permanent or not, the contact angle values ​​of the surface-modified films were measured after a few weeks of storage in the air. The contact angle value of corona-treated films only returned to the original value, ie about 90θ, which is the contact angle value of PP film before corona treatment, while the films treated with aziridine compound (CX-100) after corona treatment maintained a contact angle value of about 60θ. This again confirms that surface treatment according to the invention provides a permanent effect and that alternative corona type methods can also be used to provide OH, COOH and C = O groups on the polymer surface.

EXAMPLE 21

R

A polyacetal (Delrin) was treated with chromic acid solution according to Example 2 for 30 sec in step 1 and then with aziridine compound (CX-100) for 30 sec at RT in step 2. The treated films were further treated with methanol for 1 min and with acetone. for 1 min at RT and then contact angle was measured after drying above. A contact angle reduction of approximately 12-15θ was obtained.

EXAMPLE 22

An acrylate polymer was prepared by solution polymerization of methyl methacrylate, hydroxyethyl acrylate and acrylic acid in the molar ratio 0.90: 0.07: 0.03 in the presence of N, N'-bis-azoiisobutyronitrile) as the initiator at 60θΟ. This copolymer itself contains OH and COOH groups.

The acrylate polymer produced was reacted directly with an aziridine compound (CX-100) for 30 sec at RT according to step 2. The treated films were further treated with methanol for 1 min and with acetone for 1 min at RT and then the contact angle after drying was measured. above. A contact angle reduction of an average of 13.4 ° was obtained.

461 592 &amp;