MXPA99002245A - Method for elaborating polymers from the monomer of n-vinilformam - Google Patents

Abstract

The present invention is directed to the processes of precipitation polymerization for the manufacture of polymers prepared from the monomer N-vinylformamide, the processes including the steps of contacting the monomer of N-vinylformamide with a polymerization medium containing -butanol as a diluent and a free radical initiator, under conditions effective to polymerize the N-vinylformamide monomer, whereby a precipitate of the polymer is formed in the polymerization medium, substantially isolating the precipitated polymer with a wash containing a diluent different from the t-butanol used in the polymerization and to isolate the polymer washed from the lava

Description

METHOD FOR DEVELOPING POLYMERS FROM THE N-VINIKFQRMAMIPA MONOMER DESCRIPTION OF THE INVENTION The present invention relates to a polymerization process by precipitation to make polymers which are prepared from the monomer of N-vinylformamide and which have significantly reduced levels of non-polymerizable contaminants. In the preparation of the polymers, processes have been used to substantially reduce the residual monomer levels. For example, it is known to purify a polymer solution / emulsion in a powder bed at a high temperature, whereby the solvent is removed from the polymer that precipitates. The monomer level is reduced by polymerizing unreacted monomer. The precipitation polymerization of N-vinylformamide (NVF) is known and described in U.S. Pat. 4,421,602, assigned to F. Brunnmueller et al. On December 20, 1983, United States Patent no. 4,623,699 assigned to F. Brunnmueller et al on November 18, 1986 and U.S. Patent No. 5,478,553 assigned to R. Chandran et al on December 26, 1995. These patents describe the precipitation polymerization of N-vinylformamide (NVF) in solvents such as methanol, ethanol, non-isopropanol, t-butanol, acetone and methyl ethyl ketone. The use of toluene, or mixtures of propanol and toluene, is also known. However, it is expected that a relatively hydrophobic solvent such as toluene can lead to a polymer containing high levels of formamide, a non-polymerizable contaminant that is present in the NVF monomer. Polymerization by precipitation of NVF in methanol due to the coagulation of the swollen particles by methanol is not successful. A method to overcome this problem is to polymerize the NVF in methanol with the assistance of poly (2-ethyloxazoline) as a dispersing agent. While this procedure can overcome this problem, it also needs to use a foreign component, which is generally not desired. In the NVF polymerization methods described above, no mention is made of methods specifically for removing non-polymerizable contaminants which may be present in the resulting polymer as an artifact of the monomers and / or processes used to prepare the monomers and / or polymers. Such contaminants can include, for example, raw materials used to prepare the monomers, such as formamide in the case of polymers prepared from NVF, intermediates that are formed during the manufacture of the monomers and degradation byproducts of monomer manufacture. Additionally, nonpolymerizable contaminants can be introduced via raw materials used to prepare the polymers, such as the same monomers, chain transfer agents, initiators, and the like. The polymerization by precipitation of N-vinylformamide is also described in an article entitled "Synthesis of Amine Functional Homopolymers with N-Ethenylformamide" by R.J. Badesso et al. in Adv. Chem. Ser., 1996, (Hydrophilic Polymers) p. 489-504. This article shows the polymerization of N-ethenylformamide by precipitation in isopropanol followed by washing in isopropanol or precipitation in t-butanol followed by washing in t-butanol. However, there is no mention in this article of the reduction of non-polymerizable contaminants in the product. Particularly desired and / or required are polymers having significantly reduced levels of non-polymerizable contaminants for end-use applications such as cosmetics for skin application, hair care products and pharmaceuticals. Therefore, it may be advantageous to develop a precipitation process which not only results in polymers having low residual monomer levels, but also having low levels of non-polymerizable contaminants. The precipitation process of the present invention does not require the use of stabilizers such as poly (2-ethyloxazoline) and results in polymers that not only have reduced levels of residual monomers, but also in an important way, exhibit significant reduction in levels of non-polymerizable contaminants such as those discussed herein. The present invention is directed to the process of precipitation polymerization for the manufacture of polymers prepared from the monomer of N-vinylformamide (NVF) in t-butanol diluent and wherein the resulting polymer is washed in a different diluent selected resulting in reduced levels of non-polymerizable contaminants, The process comprises the steps of contacting the NVF with a polymerization medium comprising the n-butanol diluent and a free radical initiator, under conditions effective to polymerize the NVF, whereby a precipitate of the Poly (vinylformamide) polymer (PVF) in the polymerization medium, and substantially isolating the PVF precipitated from the polymerization medium. The substantially insulated PVF is then contacted with a selected wash containing a different diluent material under conditions and in effective amounts to reduce the levels of non-polymerizable contaminants in the PVF, particularly formamide. Then the washed PVF is preferably substantially isolated from the wash. The PVF prepared according to the method of the present invention exhibits reduced levels of non-polymerizing contaminants such as formamide, compared to the PVF prepared according to methods known up to now. The polymer can be a homopolymer of NVF or it can be an interpolymer prepared from NVF and at least one vinyl monomer, as that term is defined herein. The interpolymer will comprise at least about 20 weight percent NVF based on the total weight of the monomers and more particularly about 20 to 100 weight percent NVF with the equilibrium eg 0 to 80 percent which is the monomer of vinyl. Preferably, the interpolymer will comprise at least about 40 weight percent of the NVF, with the balance being the vinyl monomer. The term "vinyl monomer" as used herein, refers to monomers other than NVF which contain a α, β-ethylenically unsaturated vinyl group and which are copolymerizalbes with NVF. Suitable vinyl monomers include, (a) styrene and derivatives thereof, such as C?-C? 8 alkyl, alkoxy, acyl and styrene substituted with acyloxy, and hydroxy and styrene substituted with isocyanate, particularly styrene substituted with alkyl, ( b) alkyl esters of C? -C? 8 of acrylic acid, (c) alkyl esters of QL-CIS of methacrylic acid, (d) vinyl esters of the formula CH2 = CH-OCOR where R is C? -C? 8, (e) ) acrylamides substituted with alkyl and methacrylamides of the formula CH2 = CR-CONR? R2 where R is H or CH3; Ri is H or C? -C12, and 2 is C? -C? 8, (f) monoesters and diesters of fumaric, itaconic, and maleic acids, (g) vinyl ethers such as methylvinyl ter, isobutyl vinyl ether and the like, (h) hydroxy-functional acrylates and methacrylates such as hydroethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate and the like, (i) vinyl monomers containing an amine selected from the group consisting of secondary, tertiary and quaternary amines, such as methacrylate of t-butylaminoethyl (t-MBAE), dimethylaminoethyl methacrylate (MADMAE), diethylaminoethyl methacrylate (MADEAE), dimethylaminopropyl methacrylate (MADMAP), and quaternized derivatives thereof such as methacrylate methyltrimethylammonium chloride (CMAPTAC), methacrylate methyltrimethylammonium sulfate (SMAETA) and dimethydiallylammonium chloride (CDMDAA), (j) acrylamide, (k) unsubstituted alkyl acrylamides such as diacetone acrylamide,? (1) Acyclic N-vinylamides, other than NVF, for example N-vinylacetamide and N-methyl-N-vinylacetamide. Preferably, the vinyl comonomer is selected from the group consisting of methyl acrylate, methyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, vinyl acetate, monomethacrylate. of oligoethylene glycol, methacrylate methyltrimethylammonium chloride, and vinyl monomers containing an amine selected from the group consisting of secondary, tertiary and quaternary amine.

The non-polymerizable contaminants present in the polymer that can be introduced via the monomer will depend, in part, on the particular monomer or monomers selected for polymer preparation. For example, where NV is the monomer of choice, residual formamide may be present at relatively high levels. In addition to such raw materials used to prepare the monomers, non-polymerizable intermediate compounds generated during the manufacture of the monomer at high levels may be present. In addition, byproducts of the monomer preparation, for example degradation products, may be present at high levels in the monomer. Raw materials, intermediates and non-polymerizable by-products, which may be present, will depend not only on the particular monomer of the selection, but also on the method used to prepare the monomer. For example, Japanese Patent Application 92 / 334,528 describes non-polymerizable contaminants that may be present in the NVF monomers prepared according to methods described therein. The disclosed contaminants include N- (alpha-hydroxyethyl) formamide, N- (alpha-alkoxyethyl) formamide, unreacted formamide, and ethylidene bis (formamide). Additionally, formate ions may be present as a result of hydrolysis of the formamidino group of the monomer. In the methods for making the NVF described in U.S. Patent 4,578,515, ethylidenebis (formamide) is an indicated intermediate. Due to the fact that most of the reactions described therein exist as equilibria, other byproducts may be present such as alipresubstituted ethylidenformamides. In U.S. Patent 4,814,505, formilalananitrile is indicated as a precursor for NVF and therefore may be present in the NVF prepared according to methods described therein. In addition to the contaminants resulting from monomer selection, non-polymerizable contaminants can also be introduced into the polymer via the same polymerization process. For example, the polymers may contain residual chain transfer agents or polymerization initiators, such as free radical initiators, which are used in the preparation of the polymers. Accordingly, the chain transfer agents, polymerization initiators and the like should be selected in such a way that they are soluble in the diluent. Additionally, decomposition or combination products resulting from the inefficient use of these materials as starting species must also be considered. Preferably the materials are selected such that they and their by-products are suitable for end uses such as cosmetics and pharmaceuticals. Additionally, the combination of diluent and initiator must be selected to effect polymerization under standard conditions of temperature and pressure. Such temperatures are typically in the range of about 40 ° C to about 150 ° C. Preferably the selected temperature is close to the boiling point or reflux temperature of the diluent under standard pressure. The temperature and pressure may deviate from standard conditions under special circumstances, such as the use of volatile components or the need to complete certain stages at higher temperature or pressure in order to complete the consumption of the initiator. In order to provide the prepared polymers of NVF which are of high purity, ie low residual non-polymerizable contaminants, it is better than the monomer, the non-polymerizable contaminants present as a result of monomer selection, and the non-polymerizable contaminants which they can be present due to the same polymerization process, all are soluble in the diluent. In addition, the polymers prepared from the monomers must be insoluble in the diluent. In this way, not only is the level of residual monomer reduced, but the level of residual non-polymerizable contaminant is also significantly reduced in the polymer. In the methods for preparing the polymers according to the present invention, the NVF homopolymers and / or copolymers of NVF and the vinyl monomer can be prepared. The NVF and the vinyl monomer, when present, are in contact with a polymerization medium comprising the t-butanol diluent and a free radical initiator, under conditions effective to polymerize the NVF and, when present, the monomer of vinyl, whereby a precipitate of the polymer is formed in the polymerization medium. The polymerization conditions such as the reaction time, reaction temperature, reflux conditions, mixing, etc., are conventional and are determined by those skilled in the art, particularly once the benefit of the teachings of the I presented. The precipitated polymer is then substantially isolated from the polymerization medium. The precipitated polymer can be isolated by any of the methods used in conventional precipitation polymerization processes, such as by filtration, centrifugation, evaporation or combinations of such isolation techniques. By substantially isolated, it is understood that it can be substantial, but not total, isolation of the polymer precipitated from the polymerization medium. It is not necessary to remove all polymerization media, since the substantially insulated polymer is further treated to reduce the level of non-polymerizable contaminants. Subsequent to substantial isolation of the polymer precipitated from the polymerization medium, the substantially isolated polymer is contacted with a wash containing a selected diluent that is different from the t-butanol diluent used in the polymerization process, under conditions and in effective amounts for reduce the levels of nonpolymerizable contaminants in the polymer. Surprisingly, it is discovered that washing the substantially insulated polymer with a wash containing a different diluent significantly reduces non-polymerizable contaminants such as formamide, as compared to washing the substantially insulated polymer with the same diluent. Using the different diluent washing method of this invention results in the preparation of high purity polymers having residual formamide levels of less than 2,500 parts per million (ppm), preferably less than 2,000 ppm and more preferably less than 500 ppm. Washing diluents that can be used in the process of this invention include n-propanol, isopropanol, methyl ethyl ketone, acetone and ethyl acetate with n-propanol which is preferred. While the amount of wash diluent used may vary, generally from about 1: 0.4 to 1:15 parts by weight of the polymer is used to dilute and preferably about 1: 2 to 1:10 parts by weight of the polymer to diluent. . The washing temperature may also vary but generally about 50 ° C can be used up to the boiling point or reflux temperature of the diluent under ambient pressure conditions. The number of washes and the amount of the diluent per wash can be varied depending on the desired degree of purification. As indicated in the results shown in the examples, the polymers prepared in t-butanol and washed with different selected solvents, particularly n-propanol, provide significantly reduced formamide levels over the polymers washed with the same solvent t-butane. The following examples are proposed to exemplify the invention and should not be construed as limiting goals and links of the invention, which are indicated by the claims appended hereto. In these examples, all parts by weight and all temperatures are given in degrees Celsius unless otherwise indicated. EXAMPLE 1 Polymerization by precipitation of NVF A 5 1 round bottom flask equipped with a stirring shaft driven by a mechanical stirrer is added., a heating bath, a thermometer and a reflux condenser as an initial ge 56.25 g of NVF (N-vinylformamide), 946 g of t-butanol, and initiator of t-amyl peroxypivalate. The mixture is purged with nitrogen and heated to reflux which is maintained for 15 minutes. At this time a slow addition monomer comprising 443.8 g of NVF and 825 g of t-butanol is added over a period of 3.5 hours. At the same time a slow addition initiator comprising t-amyl peroxypivalate and t-butanol is started and added over a period of 4 hours. At the end the addition of the initiator to the mixture is maintained under reflux for 1 hour, followed by the addition of an additional amount of t-amyl peroxypivalate in t-butanol for 2 hours. The mixture is then kept under reflux for 5 hours. The polymer prepared in the above precipitation method is separated by filtration to isolate the polymer from the diluent. The wet powders are dried at 60 ° C overnight, then at 130 ° C for 2 hours. The resulting polymer is added to a stirred vessel together with the washing diluents as indicated below in Table 1 in the proportion of 80 g of diluent per 20 g of dry powder. The mixture is heated to reflux (or maximum 80 ° C) for 2 hours then filtered. In cases where a wash is used, a 5 g portion of the wet polymer is isolated and dried according to the aforementioned procedure. The remainder of the wet paste is taken again with 80 g of the diluent for each initial 20 g of the polymer. The mixture is then treated as the previous examples for washing and drying. The samples in formamide level are compared to the original polymer before any washing treatment. The results shown below in Table 1 clearly indicate the benefit of using a washing system containing a washing diluent that is different from the t-butanol used in the polymerization process. Table 1 Diluent of ..wash NO. of washes Reduction of% formamide n-propanol 1 88 n-propanol 2 96 methyl ethyl ketone 2 89 ethyl acetate 2 77 isopropane1 2 73 acetone 2 69 t-butanol 2 31 Example .2 A polymer of N-vinylformamide (NVF) is prepared by precipitation polymerization using the same procedure as described in Example 1. The polymer product prepared to isolate the polymer from the diluent is filtered off. The wet polymer is added to the wash diluents as identified in Table 2 in the amount of 4 g of diluent per g wet polymer. The suspension is heated to reflux which is maintained for 2 hours. After cooling, the polymer is separated by filtration and dried at 60 ° C overnight, then at 130 ° C for 2 hours. The washed samples are then evaluated for formamide levels with results shown in Table 2. As indicated in the table. the amounts of formamide in the samples washed with a diluent other than the t-butanol used in the polymerization process are significantly lower, especially when the n-propanol is the wash diluent. Example 3 A copolymer of N-vinylformamide (NVF) and methacrylamidopropyltrimethylammonium chloride (CMAPTA) is prepared by precipitation copolymerization using a procedure similar to Example 1 except that each 100 parts of NVF is replaced by 90 parts of NVF and 10 parts of CMAPTA. . The copolymer is filtered (90 NVF / 10 CMAPTA), isolated and washed with diluents in the same manner described in Example 2. The results are given in Table 2. Table 2 Levels of formamid .... (ppm) . System of ... polymer NVF 90 NVF / 10 CMAPTA Diluent t-butanol t-butanol No washing 970 156 Washing diluent n-propanol 79 84 isopropanol 207 112 methyl ethyl ketone 251 101 acetone 397 150 t-butanol 429 151

Claims (8)

1. CLAIMS 1. A process of precipitation polymerization for the manufacture of prepared polymers of N-vinylformamide monomer, the process characterized in that it comprises: Contacting the N-vinylformamide monomer with a polymerization medium comprising t-butanol as a diluent and a free radical initiator, under conditions effective to polymerize the N-vinylformamide monomer, whereby a precipitate of the polymer is formed in the polymerization medium, substantially isolate the polymer precipitated from the polymerization medium; and contacting the precipitated polymer, substantially isolated with a wash containing a diluent different from the t-butanol used in the polymerization under conditions and in effective amounts to reduce the level of formamide in the polymer 2. The method according to the claim 1 characterized in that the washing diluent is selected from the group consisting of n-propanol, isopropanol, methyl ethyl ketone, acetone, and ethyl acetate. 3. The method according to claim 1 characterized in that the washing diluent is n-propanol. 4. The method according to claim 1 characterized in that the polymer is an interpolymer of N-vinylformamide and at least one vinyl monomer. 5. The method according to claim 4, characterized in that the vinyl monomer is selected from the group consisting of a) styrene and derivatives thereof, (b) C 1 -C 18 alkyl esters of acrylic acid, (c) Ci alkylesters -Ciß of methacrylic acid, (d) vinyl esters of the formula CH2 = CH-OCOR where R is Cx-Ciß, (e) alkyl substituted acrylamides and methacrylamides of the formula CH2 * = CR-CONR1R2 where R is H or CH3; Rx is H or C? -C12, and R2 is Ca.-C? A, (f) monoesters and diesters of fumaric, itaconic, and maleic acids, (g) vinyl ethers, (h) hydroxy-functional acrylates and methacrylates (i) vinyl monomers containing an amine selected from the group consisting of secondary, tertiary and quaternary amines, (j) acrylamide, (k) diacetone acrylamides and (1) acyclic N-vinylamides. 6. The method according to claim 5 characterized in that the N-vinylformamide monomer is present at levels of about 20 to 100 weight percent based on the total weight of monomers used to prepare the polymers. The method according to claim 6 characterized in that the washing diluent is selected from the group consisting of n-propanol, isopropanol, methyl ethyl ketone, acetone and ethyl acetate. 8. The method according to claim 6 characterized in that the washing diluent is n-propanol