. "Polymers Of Vinyl-Pyrrolidone And Aminoal yl Acrylamides"

*

What is provided herein are crosslinkable, functional polymers of vinylpyrrolidone (VP) and aminoalkyl acrylamides, or aminoalkenes, or hydroxyalkenes, which can be readily crosslinked with glutaric dialdehyde, or by other described methods, to form an aqueous gel of predetermined viscosity suitable for making hydrogels, adhesives and coatings.

In one embodiment of the invention, the aminoalkyl acrylamide is N-(3-aminopropyl)methacrylamide, in an amount which provides a crosslinkable, functional polymer in the compositional ratio of about 90-99.7% VP to about 0.3-10% acrylamide. These polymers can be crosslinked with a crosslinking agent, e.g. a di-, tri-, or tetra- aldehyde, such as glutaric dialdehyde, in aqueous solution, e.g. a 5% solution, to form crosslinked polymers having a viscosity of about 100,000 to 300,000 cps.

The functional polymers can be prepared by solution polymerization of the monomers in water, and the crosslinked polymers can be made by reaction between an aqueous solution of the polymer and glutaric dialdehyde.

EXAMPLES 1-5

Preparation of Crosslinkable Polymers

In a 1-liter, 4-necked reaction kettle equipped with a condenser, a mechanical stirrer, a dropping funnel, a nitrogen purge adaptor, and a thermocouple connected to the temperature controller, 500 g. of

deionized water and a predetermined amount of vinylpyrrolidone (see Table 1 below) were charged. The reactor was heated to 65°C. in 30 minutes with nitrogen purge throughout the entire process. The reactor temperature was held at 65°C. for another 30 minutes. The desired amount of N-(3-aminopropyl)- methacrylamide hydrochloride (APMAM-HC1) (Eastman-Kodak) was dissolved in 10 g. of deionized water and the solution was adjusted to pH 8 by adding ammonium hydroxide solution. Then 520 microliters of t-butylperoxypivalate was added and the APMAM solution was fed into reactor over one hour. After the addition, the reaction temperature was increased to 80°C. during 30 minutes and the temperature was held for another 30 minutes. The reactor was cooled to room temperature and the contents were poured into a shallow pan. The polymer produced was freeze-dried overnight and dried in a vacuum oven at 90°C. The results are shown in Tables 1 and 2 below.

TABLE 2 Physical Properties of the Polymer Ex. No. VP/APMAM K-Value Resid. VP f%)

3 99/0.8 79 0.35

4 99.5/0.4 84.7 0.04

5 99.75/0.2 70.1 0.31

EXAMPLE 6

Preparation of Crosslinked VP/APMAM Polymers

Predetermined compositions of the VP/APMAM functional polymers produced above were reacted as a 5% solution in water with a 50% aqueous solution of glutaric , dialdehyde to produce a crosslinked polymer in the form of an aqueous gel whose viscosity was a function of the composition of the crosslinked polymer. The results are shown in Table 3 below.

TABLE 3

Viscosity Properties of the Crosslinked Polymer (5%)

Brookfield Viscosity (CPS) Ex. No. ϋncrosslinked Polymer Crosslinked Polymer

3 77 200,000

4 112 120,000

5 60 60

The crosslinked, functional polymers of the invention find particular use in the form of hydrogels, adhesives and coatings, in oil recovery, thickener, controlled release, wound dressings and electroconducting contact applications.

Another feature of the invention is a method of crosslinking such functional polymers by first copolymerizing vinyl pyrrolidone and an aminoalkene, a hydroxyalkene, or an aminoalkyl acrylamide or methacrylamide, to provide a crosslinkable, functional PVP copolymer as a starting material; then (a) condensing predetermined amounts of the starting material and a haloacetal under basic conditions to form a stable.

crosslinkable PVP copolymer intermediate containing an acetal group as a functional appendant on the PVP polymer backbone; (b) acidifying the basic solution to hydrolyze the acetal group to an aldehyde group, and (c) crosslinking the aldehyde-functional PVP copolymer with the amine group of the amine-functional PVP copolymer, present on the polymer as free amine after step (a) , or as added amine-functional copolymer to the reaction mixture, under basic conditions.

Other suitable starting materials in the process of this invention are stable crosslinkable PVP copolymers containing a functional group such as an amine or hydroxyl group. Accordingly, suitable starting materials are amino- or hydroxy-functional vinyl pyrrolidone copolymer, which are prepared by solution copolymerization of vinyl pyrrolidone and a functional- group containing poly erizable monomer, e.g. an olefinic amine, such as allyl amine (AAm) , or a hydroxyalkene, e.g. allyl alcohol (AA) , in a suitable solvent, e.g. water. Typical process parameters for carrying out this polymerization are given in Table 4 below, where the defined ranges are given in parts by weight.

TABLE 4

Reaction Conditions

Most

Parameter Suitable Preferable Preferable

Wt. Ratio of 99/1-1/1 97/3-70/30 95/5-80/20 VP/allyl amine or allyl alcohol

-% Initiator 0.2-10 0.2-5 0.2-2 (based on total wt. monomers)

50-70

1-2 20-30

The preparation of such amino- or hydroxy- functional VP polymers is described in Examples 6-9 below.

EXAMPLES 6-9

Preparation of VP/AAm and AA Polymers

A 1-liter, 4-necked reaction kettle equipped with a dry ice/acetone condenser, a mechanical stirrer, a nitrogen purge adaptor, and a thermocouple connected to a temperature controller was charged with predetermined amounts of deionized water, vinyl pyrrolidone and allyl amine or allyl alcohol (see Table 5 below) .

- ^' The charged reactor was heated to a reaction temperature during a period of 30 minutes with a nitrogen purge being maintained throughout the process. Thereafter, the reactor was maintained at the reaction temperature for another 30 minutes while 520 microliters of t-butylperoxypivalate (75% active, Atochem NA) was added. The polymerization was carried out during a period of 16 hours. Then an additional 200 ml of distilled water was added to the reaction product and a mixture of water and unreacted allyl amine or allyl alcohol was distilled off. The reactor then was cooled to room temperature and its contents were poured into a thin pan container. The liquid was freeze-dried overnight and thereafter dried in a vacuum oven at 90°C. The product was a powder of the functional polymer of VP and allyl amine or allyl alcohol having the properties given in Table 5 below.

Vinyl

Ex. No. pyrroli¬ done (g)

90 10 300 65 34.5 126 0.412

Oϊ

90 10 450 130 33.3 117 0.486

90 10 300 65 36.3 131

90 10 300 130 32.5 129

* Fikentscher K Value

CROSSLINKING PROCESS OF INVENTION

1. In Situ Embodiment

The so-called "in situ" embodiment of the process of the invention, is characterized by the use of less than one equivalent of haloacetal in step (a) below per mole of starting material, which provides a predetermined amount of free amine functionality on the PVP copolymer, for crosslinking in step (c) below. The sequence of process steps is illustrated below using an amino-functional PVP copolymer as the starting material.

IN SITU METHOD OF CROSSLINKING PVP

pH <7 * Θ starting material

(b) PVP/- NH-CH ₂ CH PVP -NH ₂ -CH ₂ CHO 5 + 2ROH

OR hydrolysis Crosslinkable Aldehyde

Intermediate (50% Aldehyde Quat/50% A ino Quat)

(III) (IV)

Φ pH >7

(c) PVP/ NH ₂ -CH ₂ CHO/50% Amino Quat crosslinking Crosslinked PVP

(IV) (V)

Step (a)

In accordance with the "in situ" embodiment of the method of the invention, in step (a) , the amino- functional PVP copolymer starting material (I) is reacted with less than one equivalent of a haloacetal, e.g. a 1/2 equivalent of chloroacetal (II) , where R is a C _j -C ₈ alkyl group, at a pH >7, to form a 50% crosslinkable acetal- functional PVP polymer intermediate (III) . The reaction mixture also includes a 50% equivalent of free amine on the copolymer. This condensation reaction suitably is carried out in a solvent, e.g. aqueous and alcoholic solvents, such as water, methanol, or ethanol, or mixtures thereof, at a temperature of from about 60°C. to reflux, and for a reaction period of about 5-7 hours. The product of this reaction is a stable mixture of crosslinkable intermediate (III) which includes free amine groups on the copolymers.

Steps (b) and (c)

The desired crosslinking of (III) with (I) then is carried out conveniently by addition of a suitable amount of an acid until the solution pH <7. In such acid solution, (III) is successively hydrolyzed and crosslinked, process steps (b) and (c) . During step (b) , the acetal-functional PVP polymer intermediate (III) is hydrolyzed at pH <7 to form an aldehyde-functional PVP polymer (IV) . This reaction also is carried out in a solvent, e.g. water, methanol or ethanol. In step (c) , the aldehyde-functional PVP polymer (IV) is condensed under basic conditions with free amino- unctional groups on the copolymer to form the desired crosslinked PVP polymer (V) .

The "in situ" embodiment --of the invention will now be illustrated in Example 10.

EXAMPLE 10

Step fa)

A 2-liter, 3-neck round bottom flask equipped with a mechanical stirrer, thermometer, thermowell and condenser is charged with 1,000 grams of aqueous crosslinkable amino-functional polymer solution (see Examples 6-9). Then 9.55 grams of chloroacetaldehyde dimethylacetal is added (one-half an equivalent versus the amine titer of the sample) . The mixture is agitated and heated under a nitrogen blanket to 80-90°C. until the chloride titer reaches the expected range. At this point, the reaction product is a mixture which contains unreacted copolymer of VP with 2.5 mole percent amine groups (I), and a 2.5 mole percent of the following reaction product (III) :

PVP Polymer

This (III) mixture is stable at a pH above 7.

The stable, basic solution formed in Step (b) above then is acidified with an HCl solution until the pH drops to 5. Upon acidification, the acetal group grafted onto the PVP polymer backbone (III) is hydrolyzed to form pendant aldehyde groups (IV) .

Step (c)

The acidified solution from Step (b) is made basic and then condenses with free amino-functional groups present on the polymer chain in solution to form the desired crosslinked product (V) as an aqueous gel or solution.

2. "Addition" Embodiment"

In accordance with another embodiment of the invention, the so-called "addition" method, substantially equivalent amounts of (I) and (II) are condensed in step (b) leaving no free amine group in the resultant stable, basic polymer solution containing crosslinkable intermediate (III) . This solution then can be crosslinked with a predetermined amount of added (I) , followed by acidification step (b) and basic crosslinking (c) , as before, to effect the desired crosslinking reaction. The product is crosslinked PVP as a gel or solution.

Another feature herein is the provision of crosslinkable copolymers of (a) 80-99% by wt. vinylpyrrolidone (VP) and 1-20% by wt. of a tertiary- amine-containing polymerizable monomer, e.g. vinylimidazole (VI) or 4-vinylpyridine (VPy) , and (b) 80- 99% by wt. VP and 1-20% by wt. of an epoxide-containing polymerizable monomer, e.g. allyl glycidyl ether (AGE) or glycidyl aerylate (GA) , are reacted in solution, e.g. water, alcohol, or mixtures thereof, at a predetermined temperature, e.g. 50-70°C. , in a wt. ratio (solids basis) of (a):(b) of about 2:1 to 1:2, preferably about 1:1, in a solution concentration of about 10-30% of each, to provide a crosslinked PVP product, in gel form.

This crosslinkable copolymer may be made in powder form by a precipitation polymerization process in an organic solvent, e.g. heptane, hexane, cyclohexane or mixtures thereof; or by a solution polymerization process, in aqueous, alcoholic or aqueous-alcoholic solution at a concentration of 10-30% by weight. The powder copolymer then is dissolved in water or a water- alcohol mixture to provide a suitable crosslinkable copolymer solution containing about 10-30% by weight of the copolymer for use herein.

The second (b) crosslinkable copolymer comprises 80-99% by wt. of VP and 1-20% by wt. of an epoxide-containing polymerizable monomer, e.g. allyl glycidyl ether (AGE) or glycidyl aerylate (GA) , which also may be prepared by precipitation or solution polymerization.

A composition of the crosslinkable copolymers (a) and (b) then is mixed in water or water-alcohol solutions at a copolymer concentration of about 10-30% by weight and in a wt. ratio (solids basis) of about 2:1 to about 1:2, respectively, preferably about 1:1, at a predetermined temperature, e.g. about 50-70°C, to form the desired crosslinked PVP product as a gel.

EXAMPLE 11

Preparation of Crosslinkable VP/VI (95/5) Copolymer by Precipitation Polymerization

A 4-necked jacketed resin kettle fitted with a mechanical agitator, a reflux condenser/nitrogen inlet tube, a thermometer, and a monomer feeding tube, was charged with 350.0 g. of dry n-heptane, purged with nitrogen, heated to 64°C. with a circulated constant water bath and maintained at this temperature throughout the polymerization. Thereafter, 0.17 g. of t-butyl peroxypivalate (Lupersol 11, 75% active; Atoche NA) was

added and a mixture of 47.50 g. of N-viny1-2-pyrrolidone (VP) and 2.50 g. of N-vinylimidazole (VI) was metered in over a period of 2 hours and the reactants held for an additional 2 hours. After 15 minutes, the VP/VI copolymer began to precipitate as a white powder. At the end of second and fourth hours, 0.17 g. of Lupersol 11 were added. The VP/VI (95/5) copolymer then was cooled, filtered and vacuum-dried. The yield was 95.8% of a copolymer having a relative viscosity of 2.88.

EXAMPLES 12-14

The procedure of Example 11 was repeated except that the weight ratios of VP/VI were varied. The results are shown in Table 6 below:

Relative Viscosity

3.36

3.40

1.51

The procedure of Example 11 was repeated except that the.VP/VI monomer mix was replaced by a mixture of N-vinyl-2-pyrrolidone (VP) and allyl glycidyl ether (AGE) at different weight ratios, as shown in Table 7.

Relative Viscosity 2.24 1.95 1.53

EXAMPLE 18

Preparation of Crosslinkable VP/VI f95/5)

Copolymer b Solution Polymerization

A 4-necked jacketed resin kettle fitted with a mechanical agitator, a reflux condenser, a nitrogen inlet tube, and a thermometer, was charged with 280.0 g. of distilled water, 114.0 g. of N-vinylpyrrolidone and 6.0 g. of N-vinylimidazole. The reactants were purged with nitrogen and heated to 65°C. with a circulated constant water bath and maintained at this temperature throughout the polymerization. Thereafter, 0.30 g. of t-butyl peroxypivalate (Lupersol 11, 75% active; Atochem NA) was added. The addition of the 0.30 g. amount of Lupersol 11 was repeated every 3 hours for three times. The reactants in water became viscous after heating for 30 minutes. After the 3rd and 9th hours of the polymerization, the reactants were diluted with 200 g. of water. At the end of the 12th hour, no residual VP and VI monomers were detectable by GC. The VP/VI (95/5) copolymer obtained was cooled and discharged. The copolymer had a solids content of 15.0% and a relative viscosity of 12.49.

EXAMPLES 19-27

The procedure of Example 18 was repeated to prepare the following crosslinkable PVP copolymers in water, or isopropanol: N-viny1-2-pyrrolidone/N- vinyli idazole (VP/VI) copolymer, N-vinyl-2- pyrrolidone/4-vinylpyridine (VP/VPy) copolymer, N-viny1- 2-pyrrolidone/allyl glycidyl ether {AGE) copolymer, and N-vinyl-2-pyrrolidone/glycidyl acrylate (VP/GA) copolymer. The monomer weight ratio, solvent, polymerization initiator (Lupersol 11, or, L-ll) , polymerization temperature and relative viscosity for each copolymer thus obtained are given in Table 8 below.

TABLE 8

Crosslinkable PVP Polymers by Solution Polymerization

Monomers

-V- VEX

5

10

3

2

* Relative viscosity was determined on 1.00% aqueous polymer solution.

EXAMPLE 27A

PVP hydrogels were prepared by heating a blend of aqueous solutions of an epoxide-containing PVP polymer (VP/AGE or VP/GA) and a tertiary-a ine containing polymer (VP/VI or VP/VPy) at various polymer weight ratios. The aqueous polymer blends gelled within 16 hours (overnight) . in a 55°C. forced air oven. The PVP hydrogels obtained ranged from a viscous, tacky gel to a semi-rigid, non- tacky gel.

TABLE 9

Parts bv Weight in Compositions

Ex. B C D E F 28 50 50

29 60

30 40 40

31 50 50

32 50 40 50

33 50

34 60

35 60 50

100 100 100 100 100 100 100

EXAMPLE 36

PVP hydrogels of different rigidity were prepared by heating aqueous solution blends of VP/AGE (97/3)-copolymer (Ex. 30) with VP/VI (97/3)-copolymer (Ex. 27) , at various weight ratios.

TABLE 10

Parts by Weight in Compositions

H I J K L

VP/VI (97/3) , 40 33.3 26.7 20 13.3 20%

VP/AGE (97/3) 60 50 40 30 20 30%

D.I. Water 16.7 33.3 50 66.7

100.0 100.0 100.0 100.0 100.0

% Solids 24 20 16 12 8 Gel Semi-rigid Semi-rigid Semi-rigid Soft Soft

Rigidity tacky tacky tacky tacky taeky gel gel gel gel gel

EXAMPLE 37

PVP hydrogels were prepared in the presence of a magnesium acetate which is an electrically conductive salt. Accordingly, a blend of VP/AGE (98/2)-copolymer (Ex. 24, 10 g.), VP/VI (98/2)-copolymer (Ex. 21, 10 g.), and magnesium acetate (5 g.) in distilled water (75 g.).

was heated in a 55°C. forced air oven for 6 hours. A 20% soft, tacky, clear PVP gel was obtained which had a slightly yellowish color and contained 5% magnesium acetate. A summary of the reactants used in this Example is given in Table 11 below.

TABLE 11

Reactants

VP/VI (98/2) copolymer VP/AGE (97/3) copolymer Magnesium Acetate

D.I. Water

100.0

Another embodiment of the invention is a method of crosslinking polyvinylpyrrolidone (PVP) at a predetermined pH which comprises (a) providing a tertiary a ino-functional PVP as a starting material, (b) condensing said starting material with a predetermined amount of epichlorohydrin to form an epichlorohydrin- functional PVP copolymer, and, if less than an equivalent of epichlorohydrin in use, unreacted starting material, (c) acidifying the resultant copolymer to form a solution of a storage stable glycidyl quat intermediate, and (d) increasing the pH of the solution to above 7 to convert the glycidyl quat into a glycidyl epoxide, and (e) crosslinking the glycidyl epoxide with free amine group on the copolymer or as added amine functional PVP copolymer to form a crosslinked PVP polymer.

Table 12 below is a schematic representation of the chemical steps involved in the process of the present invention.

TABLE 1 2

(a) VP +

functional intermediate

(V) crosslinkable glycidyl epoxide

C1 °

(VI) Crosslinked PVP

The starting material of step (a) is. prepared by copolymerizing vinyl pyrrolidone and N,N-dimethylamino acrylate or methacrylate (DMAEMA) or N,N- dimethaminopropyl acrylamide or methacrylamide, according to the process described in U.S. 4,223,009. The product is a PVP-copolymer (I) having a tertiary amino, i.e. a dimethylamino functionality, which is adjusted to pH of 6.5-7.5. Suitably the copolymer contains about 1-50 mole . % of the amino functionality preferably 5-20 mole %.

In step (b) , at a pH of about 6.5-7.5, starting material (I) is condensed with one or less than one equivalent, preferably a 1:1 equivalent ratio, based upon amine titer of epichlorohydrin (ECH) (II) to form an epichlorohydrin-diamino functional PVP intermediate (III).

In step (c) , the pH of the solution is reduced to about 3-5 to form a stable glycidyl quat intermediate (IV) ,

In step (d) , the solution is made basic (pH >7) , whereupon the glycidyl quat is converted to its crosslinkable glycidyl epoxide (V) ; whereupon.

In step (e) , at the same pH, (V) and (I) , either as unreacted starting material, when epichlorohydrin is less than one equivalent, or, in the preferred embodiment, as added (I) , when epichlorohydrin is reacted in equivalent amounts with (I) , are crosslinked to form a crosslinked PVP product (VI) .

Step (a)

Preparation of Functional VP-DMAEMA Copolymer Starting Material

A 5-liter, 4-necked round bottom glass flask is equipped with a heating mantle, mechanical agitator, condenser, ther owell, thermometer and a 3-liter graduated pressure equalizing dropping funnel, is charged with a heel charge of 200 grams of VP and 25 grams of DMAEMA added to 225 grams deionized water. The mixture is chilled in ice water and concentrated HCl is added dropwise to the stirred chilled mixture to adjust the pH to 6.5 to 7.5. The ice bath is removed and replaced by a heating mantle. To the dropping funnel is added an aqueous mixture of 745 grams of VP, 216 grams of DMAEMA, 0.4 grams tAPP* in 2137 grams of deionized water. This mixture is pH adjusted in an ice bath in the same manner as the heel charge before addition to the dropping funnel. Both the heel and dropping funnel charges are sparged for 1/2 hour with N ₂ . When the heel reaches 65°C. , 0.1 grams of tAPP is added and the dropping funnel charge is started and added over four hours at 65 ^β C. reaction temperature. After the four hours addition, heating is continued at 65°C. for another hour followed by hourly additions of 0.1 grams of tAPP until residual VP is less than 0.05%. At this point, a 34-36% mixture of the neutral polymeric salt of a copolymer of 85/15 mole % VP/DMAEMA is present. The pH of the mixture then is adjusted to 6.5-7.5.

* tertiary amylperoxy pivalate

Step (h) Condensation of Starting Material (I) and ECH

The copolymer solution of step (a) is condensed with a 1/2 equivalent of epichlorohydrin based on the total amine titer of the copolymer, by adding ECH dropwide to the mixture at 65-75°C. over a one hour period. The mixture then is stirred and heated for about two hours or until the inorganic chloride content in the product is in range of about 0.21 meq/g.

Step (c) Formation of Glycidyl Quat Intermediate

The pH of the mixture then is adjusted to 3-5 with concentrated HCl. The product is a stable glycidyl quat intermediate (IV) and 1/2 unreacted (I) in acid form.

Conversion of Glycidyl Quat to Glycidyl Epoxide (V)

The pH of the mixture then is adjusted upwards with base to a pH >7. At this pH, the glycidyl quat intermediate is converted in its corresponding crosslinkable glycidyl epoxide and, if less than one equivalent of ECH was used, free amine is present in the polymer.

Step (e) Formation of - Crosslinked PVP (VI)

The crosslinkable glycidyl epoxide and an equivalent amount of amine functionality as added copolymer (I) are crosslinked to form a crosslinked PVP polymer product (VI) . Alternatively, some free amines present on the polymer chain may be reacted in situ to form the crosslinked product.