DE1935557A1 - Modification of the chemical inhomogeneity - of macromolecular materials - Google Patents

Abstract

Modification of the chemical inhomogeneity of macromolecular materials. To a soln. in a solvent or solvent mixture of the macromolecular material are added one or more polymers which are soluble in the solvent (mixture), in an amount above the compatibility limit of the polymer mixture; the layers forming by subsequent phase separation are separated from one another; and the polymers dissolved therein are isolated by concentration of the solutions or pptn. by mans of a suitable pptng. agent. The process results in manufacture of product with closely defined chemical inhomogeneity which is normally achieved only by complicated polymerisation or other reaction methods.

Description

Process for changing the chemical non-uniformity from chemical non-uniform macromolecular substances Among chemically non-uniform macromolecular substances Substances are polymers whose macromolecules are not only different in terms of the molecular weight, but also with regard to their chemical composition differ from each other. Such substances can be produced by copolymerization reactions of the most varied types, by cocondensation, by coaddition or also by subsequent chemical modification of a given synthetic or natural macromolecular product are obtained; sometimes there are also natural products from Chemically inconsistent from the start in this sense, e.g. certain protein compounds.

The formation of such. Products can be explained in more detail with the help of some examples explained. If, for example, a copolymer of the two monomers A and B, where A may polymerize much faster than B, produced by the fact that a If a given mixture of A and B is polymerized, the reaction starts the monomer A reacted more strongly than the monomer B, so that in the course of the copolymerization first A-rich and finally B-rich macromolecules are formed; between the two In extreme cases, all intermediate stages are present. The total product thus obtained is therefore chemically inhomogeneous; the degree of inhomogeneity is due to the The composition and the amount of the components with different chemical structures are determined. This chemical non-uniformity is the molecular weight non-uniformity superimposed, because as with most polymer ion methods also here in the general macromolecules of a certain molecular weight range can be obtained. There is generally no connection between the two types of inconsistency.

Of course, the situation becomes much more complicated when the Copolymers made from more than 2 components.

The chemical non-uniformity exists in the case of the graft copolymers mostly in the simultaneous presence of a true graft copolymer, one Homopolymers from the monomers forming the grafts and from unchanged submitted macromolecular substance; here the individual macromolecules can of the real graft copolymer by the degree of grafting and the length of the grafted Distinguish branches, which creates additional chemical non-uniformity. Even with block copolymers, depending on the manufacturing conditions, MaRromolelaile which are not only determined by the molecular weight but also by the quantitative ratio of the individual blocks and thus cause chemical inconsistencies.

Similar ratios are in the case of other polymers consisting of 2 or several starting components are also built up before; at already in the literature Examples described are given: cocondensates of adipic acid, hexamethylenediamine and g-caprolactam, coadducts of phenol, formaldehyde and phenyl isocyanate or coordination polymers such as polyorganoaluminocobaltosiloxane.

In the partial chemical transformation of a given polymer chemical non-uniformity of the reaction product occurs especially when if one part of the reaction is homogeneous and the other part is heterogeneous Phase is running.

The sequence of both types of reaction can determine the degree of the chemical Inconsistent influence. For example, it is a crystalline polyolefin in carbon tetrachloride chlorinated at a temperature at which the polymer is still insoluble, so takes place the chlorination initially in the heterogeneous phase; falls with increasing degree of chlorination the degree of crystallization and the product goes into solution, so that from this state chlorination takes place in a homogeneous solution. The result is a chemical inconsistent chlorinated polyolefin. If the polyolefin is in the form of an aqueous If the dispersion is chlorinated, there is only a heterogeneous reaction from start to finish before; she also leads B to a product, its macromolecules have a different Cl content; in general is the degree of inhomogeneity greater here than in the aforementioned chlorination process.

The opposite is the case with the chlorination of a polyolefin in carbon tetrachloride occurs, for example, in the partial alcoholysis of a polyvinyl ester; initially finds the reaction takes place in a homogeneous solution, an alcohol serving as the solvent; however, as the degree of alcoholysis increases, the product becomes insoluble in the alcohol and therefore fails, so that the reaction now runs to the end in the heterogeneous phase. the It appears in both acidic and alkaline alcoholysis on. The end product is chemically inhomogeneous in both cases.

With further examples of the chemical non-uniformity as a result a chemical change in a starting polymer may be mentioned: cellulose derivatives such as methyl, ethyl, acetyl, carboxymethyl or nitrocellulose, ethoxylated piycaprolactam, acetalized polyvinyl alcohol, lignosulfonic acid and others.

Of natural products for which a chemical inconsistency has been found should also be mentioned: hemicellulose, casein, hemoglobin, horse serum albumin, Agar, Wo) le proteins, ß-lactoglobulin, deoxyrib nucleic acid.

Finally, chemical non-uniformity can also occur in macromolecules, which are built up from the same basic building block, if the basic building blocks simultaneously in different iso-steric configurations within the Macromolecules occur. Examples of such configurations are: Head-to-tail and head-to-head structures; cis-trans structures; Structural isomers of optically active polymers; simultaneous formation of cyclic and non-cyclic Molding from the same monomer upon polymerization; Formation of branches on the main chain, with both the number of branching points and the length the branches can vary from macromolecule to macromolecule; Block structures within a chain with different stereospecificity.

The presence of macromolecules of different composition within of a substance may or may not be desired depending on the intended use of this substance be harmful. E.g. one can see the fact that some chemically inhomogeneous Polymers make sound waves stronger than a chemically more uniform polymer like Absorb gross composition, advantageous for the production of sound insulation bodies technically exploit. Or the broadening of the maximum in the curve for the temperature dependence the mechanical damping with increasing chemical non-uniformity causes a improved impact resistance below the glass transition temperature of the product. One greater chemical non-uniformity can ultimately result in increased compatibility of the polymer in a mixture with other macromolecular substances.

On the other hand, there can be a chemical non-uniformity of a macromolecular Material adversely affect the following properties: limited solubility in a given solvent in the hall that the extreme values of the composition are very different from each other (e.g. presence of almost unchanged polyolefin in the chlorinated polyolefin); Decrease in the bond strength of an adhesive whose Macromolecules partly have a reduced number of polar ones that are decisive for adhesion Contain groups and thus cannot contribute to the Klebefrekt; Presence of Intolerance symptoms in the solid and in the dissolved state are too blatant Differences in the composition of the individual macromolecules; Formation of layers built up and thereby cloudy films of reduced strength, if the films were prepared from the solution of the substance by evaporation of the solvent; Reduction of the mechanical properties of a molded part due to local accumulation of macromolecules in the material with an increased concentration of specific groups how a foreign substance can work; Reduction of the thermal stability by an enrichment of head-to-head structures within a certain fraction of the material; Deterioration in the thermal dimensional stability of a substantial isotactic crystalline polymers due to the presence of macromolecules with built-in atactic sequences from the same monomer; deterioration the stress cracking of a polymeric substance under the action of a wetting agent Liquid on the fabric under tension, if that is necessary for wetting decisive groups in the polymer distributed unevenly on the individual macromolecules are; Formation of cloudy moldings from chemically modified polymers in the presence of unchanged starting product (applies particularly to crystalline starting products); Deterioration of the homogeneous dyeability of threads or foils, if a certain one Proportion of macromolecules no or too few responsible for dye uptake Contains groups; Deterioration of processing properties with uneven Distribution of the monomers, e.g. in the copolymer of vinyl chloride and Ataz-1,2-dicarboxylic acid systems; harmful effects of synthetic or natural macromolecular compounds on the living organism in the presence of macromolecules that are responsible for the Tolerance to high number of specific with the organism, in stronger interaction stepping groups included.

Summarizing representations of the properties of chemically Inhomogeneous substances can be found in the following places: "Plastics", edited out. by R. Nitsche and K.A. Wolf, Vol. 1, Section 2.4, Springer-Verlag, Berlin 1962; "Polymer Fractionation", ed. from me. Cantow, Chapter D, Academic Press, New York 1967.

From the above by no means exhaustive list it follows that the Usability of chemically inhomogeneous macromolecular products for a particular one Intended use can depend heavily on the degree of chemical non-uniformity. One is-therefore in cases in which the chemical non-uniformity is too strong at Use of the fabric disturbs, forced to pay attention to the degree of inconsistency is as small as possible or that the type of macromolecules whose presence is greatest reduces use, is largely avoided. In addition, however, is also after the above examples a stronger one in special cases chemical Inconsistency is desirable. In this case it is necessary to broaden the chemical Inconsistency a certain proportion of the starting product with medium chemical Property to be removed; because because of this, the remaining shares with extreme Composition stand out relatively stronger, so you get a product that, although Proportions with the same extreme values of the composition as the starting product contains, but the percentages of these proportions are greater than in the starting product are.

Decisive for the desire for a lesser one or for one greater chemical heterogeneity is the purpose of macromolecular Substance; It can therefore also happen that from one and the same starting product for which a type of application a strong chemical non-uniformity is required, for another but a weak one.

The goal of manufacturing products with defined chemical non-uniformity, is technically mostly only through the development of complicated polymerization and reaction procedures to achieve. But if you keep the known, simpler production methods in the case of, one is forced to the chemical uniformity dP so resulting products to be changed afterwards in the wrong sense. In principle, this should make it possible be that the macromolecular substance to be treated is dissolved in a solvent is and that by the addition of a suitable precipitant a separation between the required main product and the portion to be separated is made. These The way it works, however, has two major drawbacks: first, it takes place during separation inevitably a splitting of the starting product according to the chemical composition of the macromolecules as well as the molecular weight, which experience has shown for a given product can vary within wide limits (e.g. ratio l: looo) instead. It can happen that e.g. with the precipitant additive, the Shares are deposited only above a certain molecular weight that but their proportions of lower molecular weight remain dissolved in the main product.

Second, the oil dissolvers used as precipitants often speak for one component, e.g. in a copolymer, not specific to the composition of the product. So you can even use a dilute solution of polystyrene + Polyvinyl acetate in benzene by adding the polystyrene non-solvent acetone Do not separate polystyrene from the solution, let alone a styrene-vinyl acetate copolymer fractionate this way.

There are many similar examples.

It has now surprisingly been found that the chemical non-uniformity a given macromolecular substance can also be varied in that to the solution of the macromolecular substance to be changed in a solvent or solvent mixture one or more others dissolved in the same solvent Adds polymers in an amount that phase separation of the total solution takes place, and that the layers formed during the phase separation are separated from one another and the polymers dissolved therein by evaporation of the solutions or by precipitation with be isolated with a suitable precipitant. The one required for phase separation The minimum amount of polymer to be added depends on the nature of the solution partner and can be between 0.5 and 10 percent by weight based on the total amount of polymer lie; it falls as the molecular weight of the dissolved substances increases. The change The chemical uniformity can here both in the direction of a reinforcement as well as in the direction of reducing the degree of chemical non-uniformity be managed through the choice of working conditions.

The phase separation does not take place here by adding a Precipitant, but while maintaining the solvent by adding a alien polymers. Because almost all dissimilar polymers are incompatible with each other the separating effect is much stronger here than when a precipitant is added.

e.g. the polymer X of high chemical non-uniformity and the homopolymer Y dissolved in the common solvent L, so takes place in the Formation of the 2 layers due to the incompatibility a partial separation from X to both layers instead.

By suitable choice of Y and L and the quantitative ratio of X to Y can be achieved in such a way that the main set of X is e.g.

is in the lower layer, but the remainder is in the upper layer Layer. If you now peel off the lower layer, then X is now in dissolved form as a polymer with altered chemical uniformity. The same applies to the top layer.

Of course, both layers also contain the added polymer Y. If further use of X is not adversely affected by the presence of Y. the common lower layer can simply be evaporated. Sometimes is but it is also useful to at least for the most part restore Y from the changed X. to separate; Such a separation can be achieved by the addition of a liquid intended for X represents a solvent, but made a nonsolvent for Y (or vice versa) will.

If X contains the two types X1 and X2 of shares with strongly of each other and structural properties that differ from the bulk of the product, so can by adding 2 homopolymers Y and Z to the solution of X in L now 3 layers can be obtained, one of which is the majority of X in the desired form contains another layer but X1 and the third layer X2. The separation of the two "Impurity eñi '^ thus takes place in a single operation.

Finally, both the polymer to be separated X and the Auxiliary polymers Y be chemically inhomogeneous. The benefits of such a combination depends only on whether the desired change in chemical uniformity of X and / or Y is achieved.

Mixing represents an extreme case of chemical inhomogeneity of 2 or more homopolymers. If the solubility properties of the components are largely similar, is a partial separation of one polymer by the addition of a felling agent is very difficult. In this case, too, the separation effect be reinforced by the addition of an auxiliary polymer.

In general, the following points of view can be cited, which in the case of such Separation processes must be observed: 1. The chemically non-uniform polymer to be treated X and the polymer to be added Y must be soluble in the same solvent L. However, if X is extremely chemically inconsistent, it may be part of X insoluble in L; in this case it is advisable to add this proportion before the addition to separate from Y, 2. Both polymers X and Y must be above a certain concentrate ion in the solution may be incompatible with each other.

3. When using mixtures of substances as solvents, the Components can be largely mixed with one another. A complete miscibility is not necessarily required; sometimes only partial miscibility can cause the Favor the separation effect of the polymers.

4. For the sake of saving solvent, a high polymer concentration is required he wishes. However, if the concentration is too high, the viscosity of the system is very high can be and thereby the separation process is greatly delayed, is expedient worked at medium concentrations. The optimal value is higher, the the molecular weight of the polymeric components is smaller.

5. The temperature during the separation process can also be varied within wide limits and depends on the nature of the system at hand; e.g. are crystalline polymers often only soluble at elevated temperature, so that phase separation also occurs must be carried out at an elevated temperature. Generally a higher temperature is because of the reduction in viscosity and the resulting shortening of the separation times preferable. However, there are systems in which the separation effect increases with Temperature decreases; in such cases it may even be advantageous to go below the Room temperature to work as above.

6. The speed of the separation process also depends on the difference in density ? of the layers formed during the phase separation. Ilp is by the nature of the dissolved polymers, the nature of the solvent, the temperature and the The concentration is determined when choosing the polymer to be added based on It should be noted that its density is not the density of the polymer in the solid state determines the size of aS, but rather the density of the solvated polymer.

The nature of the solvent and that of the polymer to be added can can be varied within wide limits. There are both liquid inorganic compounds such as water, sulfuric acid, sulfur dioxide, ammonia and others as well as liquid-organic æ Compounds such as hydrocarbons, ethers, esters, ketones, alcohols, acetals, N-, halogen- or S-containing compounds and others and mixtures of these compounds into consideration. In addition to the chemical structure (polyvinyl compounds, Polyacrylic compounds, polyesters, polyamides, halogen-, N- or S-containing polymers, Derivatives of natural products such as cellulose and others) also their molecular weight, whose molecular weight width and chemical uniformity are varied. The possibilities for variation are therefore very large for both components; the selection depends primarily on the nature of the polymer to be treated, the Points 1 to 6 mentioned above must be observed.

Example 1: A vinyl chloride-vinyl acetate copolymer was used as the chemically inhomogeneous polymer with an average vinyl chloride content of 55> 2 percent by weight. 2 g of this copolymer were mixed together with 2 g of polystyrene in 40 ml of benzene at room temperature solved; the # sp / c value of the polystyrene measured at 250 In benzene for one concentration of 1 g / loo ml is 1.57. Although both components are clearly soluble in benzene alone are, the mixture gave a very cloudy solution, from which at about 20 ° after standing on multiple strands formed 2 clear layers. The volume of the lower layer that of the top was 14 ml; that of the top 30 ml; the two layers were separated from each other and evaporated. The total amounts of polymer were 1.743 g on the bottom and 2.268 g on the top (The sum is slightly larger than the weight, as it still includes traces of benzene was). A breakdown could be made from the Cl and acetyl analysis of both layers the layers can be made into the individual components. The lower layer According to this, it is: o, 953 g vinyl chloride, o.7o1 g vinyl acetate and o, o89 g polystyrene; correspondingly the upper layer 0.112 g vinyl chloride, 0.195 g vinyl acetate and 1.961 g of polystyrene. In the lower layer, which is rich in copolymers, there was therefore only 5.1% polystyrene contain. The vinyl chloride / vinyl acetate weight ratio of the starting product is 1.23; in the two layers, on the other hand, it was due to the separation effect 1.36 below and o.57 above. From the last-mentioned relationships it clearly follows that the product must actually be chemically inhomogeneous, otherwise yes above and the same weight ratio should have been present at the bottom; so there were at phase separation from the copolymer, the macromolecules poorest in vinyl chloride in the top polystyrene-rich layer moved.

If the same attempt is repeated, but now using a Polystyrene sample with a lower molecular weight (# sp / c = o.93), the separation effect is again expressed by the weight ratios of vinyl chloride / vinyl acetate, with 1.42 below and 0.44 above slightly larger than before.

Example 2: Under the same conditions as in Example 1, but when using methyl ethyl ketone instead of benzene as a solvent and under The components are divided up using the higher molecular weight polystyrene on both layers the other way around as there: the lower layer now contains around 3 times as much polystyrene as the top and the top layer contains around 9 times as much Copolymer like the one below. Furthermore, the separating effect is stronger with methyl ethyl ketone than with benzene: the vinyl chloride / vinyl acetate weight ratio is now 0.36 below and 1.49 above.

If in a further attempt instead of 40 ml of methyl ethyl ketone 70 ml is used, the weight ratio below is 0.14 and 1.27 above; the separation the vinyl acetate-rich proportions of the copolymer are particularly pronounced here.

Example 3: The starting product used was the same copolymer as in example 1; Instead of polystyrene, however, polymethyl acrylate was now added and dioxane was used as the common solvent. The separation process differed but now essentially different from that in Example 1. The lower layer contained 0.788 g of vinyl chloride, o, 694 vinyl acetate and 0.173 g of polymethyl acrylate; the top layer contained 0.294 g vinyl chloride, 0.220 g vinyl acetate and 1.809 g polymethyl acrylate. The weight ratio Vinyl chloride / vinyl acetate now moved to 1.135 down and 1.335 up, here So became the vinyl chloride-richest portions of the copolymer in the upper layer enriched.

Example 4: The same copolymer was again used as the starting point as previously; Instead of polystyrene, however, polyvinylpyrrolidine was now used. Dioxane served as the common solvent. After the separation it was found: o, o55 g vinyl chloride, o, 2oo g vinyl acetate and --l, 3o9 g polyvinylpyrrolidine below and corresponding to o.996 g vinyl chloride, o.714 g vinyl acetate and o.740 g polyvinylpyrrolidine above. The weight ratios vinyl chloride / vinyl acetate be now o, 275 below and 1.395 above. The comparison of these latter values shows that the separation in the presence of polyvinylpyrrolidine is very different than when it is added run from polystyrene or polymethyl acrylate; especially has the lower layer the copolymer shares with the lowest vinyl chloride content have now been added.

Example 5: 4 g of a styrene-maleamide copolymer with 5.0% maleimide and 4 g of polyvinyl acetate were in a mixture of 80 ml of dimethylformamide and lo ml of methanol dissolved; the addition of methanol turned out to be after comparative tests useful to improve the separation effect. After the phase separation made at 220 both layers were isolated. As both the copolymer and the solvent Contained nitrogen and incomplete removal of the solvent the If the N analysis had interfered, the polymers dissolved in the layers were allowed to run in separated the solutions in 250 ml of water with vigorous stirring. The rainfall were washed with water, dried and analyzed. The top layer contained 2,350 g; the lower 5.480 g (2% loss on work-up).

After the analysis (determination of the N content and the saponification number) Both layers contain approximately equal amounts of copolymer, however with a maleimide content of 6.7 percent by weight above, but only 3.3% below. Since the starting product contained 5.0% imide, it follows from these figures that too this copolymer is chemically non-uniform, and that due to the addition of the polyvinyl acetate an accumulation of the most imide-rich portions of the copolymer in the upper layer has taken place.

Example 6: 3 g of one in aqueous suspension at elevated temperature chlorinated polyethylene with an average Cl content of 40.3 were put together with 1.5 g of atactic polypropylene dissolved in 80 ml of toluene at room temperature; the end the initially cloudy mixed solution 2 clear layers formed. The residues obtained from both layers after evaporation of the solvent contained according to analysis (C, H and Cl determination): above 0.24 g of chlorinated polyethylene with a Cl content of 26.1 and 1.27 g of polypropylene; below 2.69 g chlorinated polyethylene with a content of 41.8% and 0.25 g of polypropylene. This shows that the Chlorination product has an uneven structure in terms of Cl content; the Lowest chlorine content of the chlorinated polyethylene was in the phase separation pushed into the upper propylene-rich layer.

Example 7: 1 g of polyvinylpyrrolidine, 1 g of polystyrene and 2 g of copolymer as in Example 1 were dissolved in 40 ml of dioxane. 3 layers formed; their volumes were 2 ml at the bottom, 29 ml in the middle and 12 ml at the top. The amounts of copolymer were o, o46 g at the bottom, 1.818 g in the middle and whether 142 g at the top. From the weight ratio Vinyl chloride / vinyl acetate 2.54 below, 1.19 in the middle and o, 67 above it follows that in the The upper layer contains the most Cl-rich and the lower layer the Cl-poorest proportions of the copolymer were enriched. Be the top and bottom layers together mixed and evaporated, it becomes a copolymer of vinyl chloride and vinyl acetate obtained whose degree of inhomogeneity is greater than that of the starting product and the the middle layer is.

Example 8: 2.7 g polystyrene + 2.7 g polyvinyl acetate + 0.6 g polyvinyl chloride were dissolved in 54 ml of tetrahydrofuran. During the phase separation, were formed 220 three layers, which according to analysis (C, H and Cl determination as well as saponification number) had the following composition: lower layer 0.02 g polystyrene, 0.03 g polyvinyl acetate and 0.2o g of polyvinyl chloride; middle layer o, 27 g polystyrene, 2.48 g polyvinyl acetate and 0.3o g of polyvinyl chloride; upper layer 2.41 g polystyrene, 0.19 g polyvinyl acetate and 0.1 g of polyvinyl chloride. So under these conditions it became a far-reaching one Separation of polystyrene and polyvinyl acetate, which are in the upper and in the highly enriched middle layer.

Claims (1)

P a t e n t a n s p r u c h: Process for changing the chemical non-uniformity from chemical non-uniform macromolecular substances, characterized in that to the solution of the macromolecular substance to be changed in a solvent or solvent mixture one or more others soluble in this solvent or solvent mixture Polymers in a range above the tolerance limit of the polymer mixture Amount to be added and that the resulting during the phase separation that takes place Layers separated from each other and the polymers dissolved therein by evaporation the solutions or by precipitation with a suitable precipitant.