FI107161B - Method for manufacturing polyesterurethanes - Google Patents

Description

METHOD FOR THE MANUFACTURE OF POLYESTERYURETHANE

The present invention relates to a process according to the preamble of claim 1 for the production of melt-processable or thermoplastic polyester urethanes. Such a polymer contains structural units derived from an aliphatic polyester and structural units derived from diisocyanate and may have a long chain branched structure.

Methods have previously been reported for forming a lower molecular weight polyester prepolymer of aliphatic hydroxy acid monomers followed by copolymerization of said prepolymer with a monomer containing isocyanate groups to form a polyester urethane.

Numerous solutions for the preparation of biodegradable polymers from condensation polymers of lactic acid and isocyanates are known in the literature.

The isocyanate group then acts as a linking group through which the condensation polymer chains are linked by amide and urethane linkages to a polyester urethane.

JP 05148352 describes a polyester urethane (PEU) which is prepared from a polylactide which is reacted in the molten state with diisocyanate. Diester and diacid based polyester urethanes are .. · Also described in EP application 488617. Lactic acid biodegradable::; polyester urethane is also known from JP 04013710, whereby the chain ends of a hydroxyl terminated condensation polymer of '30 lactic acid are: • coupled with apathetic polyisocyanates. A similar coupling method is:] disclosed in SU-A-1 016 314, in which lactic acid is used as one. as a component of a hydroxyl terminated prepolymer. In addition to the prepolymer, the * · * · 'process uses both diisocyanate and diol in coupling.

Φ

Patent application FI 924699 describes a method based on lactic acid. polyurethane, wherein the polymer is prepared in two steps by first polymerizing the lactic acid into an oligomer, followed by copolymerizing said oligomer with a diisocyanate to a polyurethane. 40.

Patent application FI 943250 further discloses a method for controlling the average molecular weight, molecular weight distribution, and *! “Branching of melt-processable polyester urethane, which structural factors have an effect; ': The technical properties of the polymerization product, such as melt-processing properties.

| · 45; However, known methods of preparation involve, for example, the disadvantage that the prepolymer coupling reactions are relatively slow and are typically carried out in 2,107,161 stirred tank reactors with batch reaction times from tens of minutes upwards. As textual solutions, the batch operation requires a time consuming cleaning between the mixer and the batch capable of mixing highly viscous masses, which makes this technique expensive and time consuming.

The solution according to the invention is based on the fact that it has been possible to develop such a recipe and method for coupling an OH-terminated lactic acid prepolymer based on urethane bond formation to a diisocyanate such that the reaction takes place at a surprisingly high reaction rate. in a twin screw extruder, if the residence time of $ a is typically only a few minutes. High molecular weight bulk, long chain branched polyester urethanes can thus be prepared on a continuous, high efficiency, cost-effective basis, and obtain the final product directly in granulate-15 or pellet form.

The thermoplastic polyester urethane produced in the manner of the invention suitable as a plastic feedstock has a number average molecular weight of at least 10,000 g / mol and a weight average molecular weight of more than 20,000 g / mol. Suitable products 20 have a number average molecular weight of 10,000 to 200,000 g / mol, preferably about 15,000 to 100,000 g / mol, and a weight average molecular weight of 20,000 to 1,000,000 g / mol, preferably about 30,000 to 600,000 g / mol .

More particularly, the polymerization process according to the invention is characterized in what is set forth in the characterizing part of claim 1.

In the process of the invention, the polyester prepolymer consists of structural units derived from a hydroxy acid, such as lactic acid, and an organic diol, which are linked to each other such that the end groups of said polyester are at least essentially hydroxyl groups. In order to obtain long chain branching of the polyester urethane, the number average molecular weight of the polyester should be relatively low, suitably 500-35 20,000 g / mol, preferably about 1,000-8,000 g / mol. The said prepolymer has a lactide content of less than 10% by weight.

# · · • · · · ·

Thus, the present invention employs a hydroxyl terminated 40 polyester prepolymer, which may also be referred to as a hydroxy or lactic acid oligomer. By reacting this prepolymer directly according to the invention with * ... · diisocyanate in the extruder, the product is polyester urethane (PEU), which is known to have quite advantageous properties of the plastic raw material.

- · · 45 - The polymer is biodegradable, meaning that it is typically biodegradable in the biological environment and can be composted.

3 107161 - The mechanical properties of the polymer are even better than poly-L-lactic acid (PLLA).

- As a plastic it is of the polystyrene type, but stronger.

5 - The polymer is thermoplastic machinable.

The plastic raw material polymer formed in the manufacturing process of the invention can be converted into granular or pellet form by known methods.

The whole process consists of an oligomerization step and an oligomer coupling step in an extruder, and is preferably arranged to be continuous.

15

The invention will now be described in more detail by means of a block diagram of the overall process shown in Figure 1. The aqueous monomeric lactic acid mixture is fed through 1 into a polycondensation reactor 3, which is typically a 20 stirred tank reactor. Catalyst and diol are fed into the reactor via one of two.

Polycondensation and terminal functionalization of the prepolymer takes place in reactor 3 under agitation. The resulting prepolymer is transferred along a heat-drawn line 4 to a polymer melt processing machine 5, which is typically a twin screw extruder. The coupling agent can be fed either to line 4, or from the extruder side feeder ports 6 to the extruder 5. The coupling reaction takes place in a melt processing machine 5, and a high molecular weight polymer melt 7 is obtained from the outlet and cooled. The solid polymeric ribbon or wire can be pelleted and bagged 8 further: for delivery to customized machining operations.

30 / • ««. ' · '. Preparation of the prepolymer • According to the ratio of the starting materials, the aliphatic polyester prepolymer consists of 35i *: typically 90-99.9% aliphatic hydroxy acid monomers and 10-0.1% aliphatic diol monomer. The aliphatic hydroxy acid monomers are preferably L-lactic acid monomers, D-lactic acid monomers or mixtures thereof (e.g., so-called racemic D, L-lactic acid).

The preparation of the prepolymer, i.e. the condensation polymerization of lactic acid, can be carried out in any apparatus suitable for the esterification reactions. According to a preferred embodiment, the polyesterization is carried out as a bulk polymerization; · 'In the molten state, in which condensation can decompose water by passing dry inert gas in its polymer while stirring. By one standard method 45.. typically providing a polyester prepolymer having a number average molecular weight V of between 2000 and 8000 g / mol (e.g., about 6000 g / mol) and a polydispersity of about 1.7. In the final stage of polyesterification, the low molecular weight fraction may be removed from the reaction mixture by lowering the pressure, whereby the em fraction is distilled off. Here too, the average molecular weight of the prepolymer can be adjusted.

Functionalization of chain ends

The isocyanate compound used as the coupling agent for the polyurethane reacts best with the hydroxyl groups. Normally, when polymerizing a hydroxy acid, one end group of the chain is a carboxylic acid and the other hydroxyl. Such coupling of the prepolymer with diisocyanates has proved difficult, and too crosslinking is a problem. According to the present invention, these problems have been successfully solved by preparing a prepolymer having a hydroxyl group at both ends of the polymer chain.

According to the invention, said hydroxyl terminated prepolymer is obtained by adding, for example, a suitable aliphatic diol as a second starting material to the lactic acid monomer. For example, ethylene glycol or 1, 4-butanediol may be used as the diol, but other diols may also be used. Preferably, the aliphatic diol is present in an amount of 0.1 to 10 mol% of the aliphatic hydroxy acid monomer content and more than 1 molar ratio of hydroxyl and carboxyl groups in the mixture of copolymerizable monomers. For example, 1,4-butanediol is preferably used in an amount of about 1-5 mol%.

:. , Typical properties of prepolymer 30. ' !: 'The resulting prepolymer 4 is a brittle, colorless, transparent and amorphous material.

: ': The prepolymer has a clear glass transition temperature (Tg) at about 40 ° C, as shown by a differential scanning calorimetry (DSC) curve. Crystallinity) is not detectable by this method. Comparison of the prepolymer 35 according to the invention with poly-L-lactide (PLLA) shows that the glass transition temperature (Tg) of the polyester of the invention is of the same order as the corresponding molecular weight PLLA, but no typical crystallinity of PLLA occurs immediately.

A known side reaction in the condensation polymerization of lactic acid is the formation of L-lactide.

*: **: In the standard polymerization method, less than 1% of the starting material is sublimed into the condensation trays, but NMR analysis indicates; 'Some lactide remains in the product. However, a typical lactide content is; ··: less than 10% by weight (e.g., about 3-5% by weight), and the free lactic acid concentration of 45 is also less than 10% by weight. The polyester prepolymer contains a polyesterization catalyst in an amount of from about 0% to about 0.5% by weight.

5,107,161

Molecular weights of the prepolymer have generally been measured by gel filtration or GPC by comparison with polystyrene standards. However, in some examples, the molecular weights of the prepolymers have been measured by nuclear magnetic resonance spectroscopy or 13 C NMR to determine the concentrations of the end groups.

By appropriately changing the conditions of polyesterification and functionalization, the number average molecular weight of the prepolymer can be adjusted to between 500 and 20,000 g / mol; most preferably it is about 1000-8000 g / mol. The relatively low molecular weight 10 is advantageous for long chain branching of the polyester urethane product.

Preparation of polyester urethane by coupling reaction

Polyester urethanes are prepared by coupling the polymer chains of the prepolymer with coupling agents which react with functional groups at the ends of the chains. According to the present invention, high molecular weight biodegradable polyester urethane can be made from OH-terminated prepolymer and di-20 isocyanate at very short polymerization times. According to the invention, the coupling reaction is carried out in a continuous polymer melt mixing and processing device, typically a twin screw extruder with an L / D ratio of more than 1, typically 20 to 30, and consisting of two screws preferably rotating in the same direction. The residence time of the polymer in such a melt blender is typically between 1 and 10 min. The method of the invention may also be implemented using other alternative melt blending devices, such as: a single screw extruder, a counter rotating twin screw extruder, or a kneter (e.g., Buss-co-Kneader or IKA-Visk), to name a few.

30; The reaction can be accelerated by the catalyst. Preferred catalysts include tin octoate, dibutyltin dilaurate, dibutyltin diacetate, and many tertiary amines such as 1,4-diazo (2,2,2) bicyclooctane. A suitable amount of catalyst is up to 2% of the total weight of the reaction mixture.

3T:

In copolymerization, the molar ratio between the isocyanate groups of the diisocyanate and the hydroxyl groups of the polyester prepolymer is typically 0.5 to 1.5, preferably 0.7 to: f: 1.2, most preferably about 1. The molar ratio between isocyanate groups and hydroxyl groups is , 2 to 1.5, if desired 40. to provide at least partially crosslinked product.

In the process of the invention, the OH-terminated prepolymer 4 is fed to the extruder 5 'either as a powder in a feed funnel or in a melt state. If the feed is ....: The powder is thawed in the extruder.

The isocyanate coupling agent 6 may be fed to the feed hopper at the prepolymer feed, or via a metering pump to the prepolymer melt at one or more of the extruder 5 side feed ports.

6 107 ^ 61

By adjusting the temperature of the melt in the extruder 5 and the temperature profile in the screw direction, the properties of the product can be influenced.

5

Suitable temperatures in the heating zones of the extruder cylinder are between 120 and 200 ° C, preferably between 150 and 180 ° C.

The end product 7 is obtained from the extruder 5 via a die in the form of a wire melt, which is cooled, e.g. in a water bath, and is then typically directed to pelleting and bagging 8.

Infrared spectrometry has shown that isocyanate or NCO groups have reacted completely to urethane bonds, with the disappearance of the peak at 2270 cm -1 indicating this. 15

Properties of polyester urethanes

The long chain branching of the polymer and the broad molecular weight distribution, especially the increase in the proportion of long polymer chains, have an effect on the melt processing properties of the polymer in particular, resulting in melt elasticity and melt strength. These properties are advantageous in particular in extrusion techniques such as paper coating and film production.

The number average molecular weight of long chain branched PEUs prepared according to the invention is typically 15,000-100,000 g / mol, the average weight average molecular weight is 30,000-600,000 g / mol, and the molecular weight distribution at polydispersity is: 2-12, preferably about 3-8. The polymer is substantially free of:,, unreacted isocyanate groups (as shown by infrared spectra); and '30 free hydroxy acid monomers and lactides up to 3%! based on the weight of the polymer.

The polymer is melt-processable, i.e. thermoplastic, wherein the viscosity * · · · · of the polymer melt ranges from 10 to 5000 Pa · s, preferably 50 to 2000 Pa · s, as measured by capillary rheometer at 200 ° C at 200 ° C / sec.

From the DSC curves of the prepolymer and the finished PEU, it can be seen that both polymers are amorphous and have a maximum operating temperature of about 50 ° C.

One condition for the biodegradability of a polymeric substance is that the polymer is *: · *: hydrolytically degradable. The idea that hydrolysis, in particular the presence of water, is the primary mechanism for the degradation of ··· polymers made from lactic acid is widely accepted by those skilled in the art.

-; ; Hydrolysis is a step before complete biodegradation, after which microbes 45. can more easily degrade hydrolysis products of lower molecular weight.

* · In addition to the aliphatic ester bond, the urethane bond is generally considered to be one of the biodegradable structures, so that the biodegradability of the new 7,107,161 polyester urethanes prepared according to the invention can be potentially evaluated and initially demonstrated by hydrolysis experiments.

The overall process of Figure 1 is a preferred embodiment of the method of the present invention. Of course, the solution disclosed herein does not preclude that the process for producing at least partially continuous melt-processable long chain-branched polyester urethanes of the invention, which preferably produces a thermoplastic, biodegradable plastic feedstock, could not be accomplished by any other process equipment or assembly.

EXAMPLES

Example 1 Preparation of a prepolymer

In all examples, a hydroxyl terminated prepolymer prepared in a 6.2 liter pilot reactor was used. 5 liters of 88% lactic acid, 1,4-butanediol and tin (II) octoate were added to the reactor. Dry nitrogen was bubbled below the liquid surface 20 of the reaction mixture, and an absolute pressure of 190 mbar was drawn into the reactor. The reaction vessel was heated to 160 ° C and stirring was started. The reactor core temperature was steadily increased at 20 ° C / h to 200 ° C, and further at 5 ° C / h to 210 ° C. Thereafter, the polymerization was continued for an additional 4.5 hours at an oil bath temperature of 210 ° C. After 25 hours of polymerization, the pressure was reduced to 130 mbar and further every hour to 100 bar and 65 bar. After a pressure of 65 mbar for two hours, the pressure was reduced three more times by 15 mbar every hour until the polymerization was completed at 8.5 hours after starting to 20 mbar. All polymerization time! dry nitrogen was bubbled under the surface of the reaction mixture. During the polymerization, the decomposed water was condensed and recovered as it formed.

The average molecular weights determined by prepolymer gel filtration (GPC) were: number average molecular weight 6,400 g / mol and weight average molecular weight 9,000 g / mol. The prepolymer had a nuclear average resonance spectrometry of 3gT: end group based on a number average molecular weight of 3000 g / mol and an acid number of 1.6. The glass transition temperature was determined by differential scanning calorimetry (DSC) 40.8 ° C.

«· · • ·» • · *

Example 2 4 *. Manufacture of polyester urethane • ·

The set points for the extruder heating zones were set at 150-150-150-150-160-170 ° C as viewed from the extruder feed. After the temperatures had stabilized, the screw rotation speed was set to 100 rpm and the feed rate of the prepolymer to 100 g / min.

45 ,. . 1,6-Hexamethylene diisocyanate was introduced between the 5th and 6th heating zones. using a high-precision HPLC pump and a pressure nozzle. 1,6-Hexamethylene diisocyanate was introduced at 5.3 ml / min corresponding to a functional groups ratio of 8 107,161 NCO: OH = 1. The final product yielded long chain branched polyester urethane which, according to infrared spectrometric measurements, did not contain isocyanate groups. The final product had a number average molecular weight as determined by gel filtration chromatography (GPC) of 46,000 g / mol and a weight average of 75,000 g / mol. The polydispersity was found to be 1.6. The glass transition temperature of the amorphous polymer, measured by Tg DSC, was 49.8 ° C.

Example 3

Preparation of Polyester Urethane with Higher NCO: OH Ratio 10

The polymerization was carried out as in Example 1 except that 1,6-hexamethyldiisocyanate was fed at 5.8 ml / min (NCO: OH = 1.1: 1). The final product had a number average molecular weight by GPC of 38,000 g / mol and a weight average of 74,000 g / mol. The polydispersity was found to be 1.9. The glass transition temperature of the amorphous polymer, measured by Tg 15 DSC, was 48.1 ° C.

Example 4

Preparation of Polyester Urethane with Higher NCO: OH Ratio 20

The polymerization was carried out as in Example 1 except that 1,6-hexamethylene diisocyanate was fed at 6.1 ml / min (NCO: OH = 1.15: 1). The final product had a number average molecular weight by GPC of 37,000 g / mol and a weight average of 65,000 g / mol. The polydispersity was found to be 1.8. The glass transition temperature of the amorphous polymer, measured by Tg DSC, was 48.0 ° C.

:: Example 5 «Il«. , Preparation of Polyester Urethane at Higher Temperature 30, '! The polymerization was carried out as in Example 1 except that the extrudate was used

: ': The heating zones were set to 160-160-180-180-180 ° C

viewed from the extruder feed. The final product had a number average molecular weight · '··' as determined by GPC of 42,000 g / mol and a weight average of 68,000 g / mpl.

35: A polydispersity of 1.6 was obtained. The glass transition temperature of the amorphous polymer, measured by Tg DSC, was 48.6 ° C.

• · · • »*

IM

: **: Example 6 4Ö · Polyesterriurethane manufactured at higher temperature and higher *: *: NCO: OH ratio

I 1 I

i:

I I I

*: * ·: Polymerization was carried out as in Example 4 except that 1,6-hexamethyldiisocyanates 4 to 5 were used. was fed at 5.8 mL / min (NCO: OH = 1.1: 1). The final product had a number average molecular weight by GPC of 47,000 g / mol and a weight average of 77 0 (0 g / mol.). The polydispersity was 1.9. The glass transition temperature of the amorphous polymer was 9,107,161.

The Tg as measured by DSC was 50.2 ° C.

Example 7

Preparation of Polyester Urethane at Higher Temperature and Higher 5 NCO: OH

The polymerization was carried out as in Example 4 except that 1,6-hexamethylene diisocyanate was fed at 6.1 ml / min (NCO: OH = 1.15: 1). The final product had a number average molecular weight as determined by GPC of 41,000 g / mol and a weight average of 70,000 10 g / mol. A polydispersity of 1.7 was obtained. The glass transition temperature of the amorphous polymer, measured by Tg DSC, was 48.4 ° C.

15 20 25 «· 1 · • · · • * * M» • · · 35 I 4 4 I «•«

Claims (6)

1. A process for producing thermoplastic polyurethane which can be utilized in the extrusion of melts and which contains in its molecules molecules of aliphatic, polyester-derived structural units, and structural units derived from organic diisocyanates, and in which the structural units of the molecules are interconnected, at least mainly by detachment bonds, - the structural units derived from the polyester consist essentially of lactic acid and possibly with this copolymerized organic hydroxy acid and / or of a cyclic lactone having a long, flexible carbon chain such as epsilon-caprolactone, - the copolymer formed has long branches of its molecular mass, its number of molecules is 10000 g / mol or higher, its weight average molar mass Mw is above 20000 g / mol, the copolymerization is carried out so that the polymer produced does not substantially contain free isocyanate groups. The copolymerization is carried out in a continuously extruded extruder with a reaction time shorter than 10 minutes .. * · « Method according to claim 1, characterized in that the extruder can be provided with two screws or with a screw or be a co-kneader or someone. . ' , Corresponding apparatus for mixing and extruding viscous polymer melts. «« · I (· • · · * Method according to claim 1, characterized by a residence time in the extruder • at 1 - 10 min, the ratio L / D at 10 - 40, and a temperature range within which: the machine operates at 120 - 200 ° C, for best results at 150 - 180 ° C. .30. 4. Process according to claim 1, characterized in that the polymerization can be carried out in which heist apparatus which can be used for continuous mixing and extrusion of. viscous polymer melts. 35 13 107161 5. A method according to claim 1, characterized in that the manufactured product is a thermoplastic, biodegradable plastic raw material which, in particular on the basis of the elasticity and pour strength of the melt, can be well applied for product production by extrusion technology. Use of a product extracted by a process corresponding to claim 1 for applications utilizing extrusion technology such as manufacturing of film, fiber 10 and injection molded pieces, coating of paper, in the packaging sector, and for applications in agriculture and the medium. «Il« «<• I <• · II • I • · · • · · • · · ·· ♦ ·« · · · · · · · c • · · * · · • · · · · · - « tf