CS216421B1 - A method for producing polyurethane ureas a) or polyurethane - Google Patents

Abstract

The invention solves the problem of producing powdered thermoplastic polyurethane urea and/or polyurethane with an adjustable plastic transition temperature. The required plastic transition temperature of the polymer in the range of 130 to 230 °C is achieved by charging the starting materials polyol and diisocyanate in such a molar ratio that the content of free -NCO groups of the prepolymer is in the range of 0.5 to 6 wt. %, preferably 1.2 to 3.5 wt. %. Outside this range, a thermoplastic polyurethane that could be used at conventional processing temperatures is not prepared. The advantage of the process is the possibility of preparing polyurethane with the required plastic transition temperature, which is mainly used in the preparation of mixed compositions with other polymers, e.g. with PVC. The invention can be implemented in the preparation of a mixture with PVC for the production of tough PVC.

Description

The invention relates to a process for the production of thermoplastic polyurethane urea and / or polyurethane having an adjustable plastic transition temperature.

The process for preparing the polyurethane in powder form is little described. It is known to prepare a stable polyurethane dispersion by reacting the prepolymer with a chain extender in a water-emulsifier-toluene medium at a temperature of -5 ° C to + 20 ° C (German Pat. No. 1,645,656). This procedure can also be carried out continuously, by mixing the prepolymer and the dispersing phase in a zone of high turbulence (NSR Pat. 2,311,635) or in a counterflow injector (NSR Pat. 2,344,135). The process of preparing polyurethane urea powder by reacting the prepolymer with water in the aqueous phase in the presence of a dispersant produces powder polymers having a grain diameter of 40 to 250 µm, but many of these polymers are stable and non-plasticizing at processing temperatures, generally up to 200 ° C. (A0 190 563).

We have found that the transition temperature of the thermoplastic polyurethane powder to the plastic state depends on the properties of the prepolymer used, mainly the content of free -NCO groups, and the concentration range of the -NCO groups is very narrow.

According to the invention, a process for the manufacture of a polyurethane urea and / or a polyurethane having an adjustable plastic transition temperature, preferably in powder form, from compounds containing free -NCO groups, preferably from a prepolymer based on polyesterpolyol and / or polyetherpolyol or compounds containing at least one active hydrogen in the molecule, in a water or water-containing medium, is accomplished by using a compound having a defined content of free -NCO groups in the final product, which is plasticized at the desired temperature in the range of 130 to 230 ° C. from 0.5 to 6% by weight, preferably from 1.2 to 3.4% by weight;

The transition temperature of the polyurethane urea and / or polyurethane to the plastic state for the content of free -NCO groups in the prepolymer is 1.2% by weight. about 130 ° C, with increasing content of -NCO groups, the transition temperature increases approximately linearly, and a polymer prepared from a prepolymer containing 3.5 wt. The free -NCO groups plasticize at 230 ° C. Pre-polymers with an even lower content of -NCO groups (below 1.2% by weight) are already highly viscous to pasty, difficult to disperse into the aqueous phase, resulting in a very inhomogeneous coarse dispersion with deteriorated product properties. Polymers prepared from prepolymers with a content exceeding 3.5% by weight. -NCO groups do not plasticize up to 230 ° C.

The prepolymer with free -NCO groups is prepared by reacting high molecular weight compounds containing at least two actively hydrogen with diisocyanates at a temperature generally below 90 ° C for 0.5 to 4 hours in the presence or absence of a catalyst under a nitrogen atmosphere.

As high molecular weight compounds, polyester polyols based on adipic acid, phthalic acid, optionally sebacic and divalent and polyhydric alcohols, e.g. ethylene glycol, diethylene glycol, 1,2-propanediol, 1,4-butylene glycol, pentaerxytritol, trimethylolpropane or glycerin with a molecular weight of 500 to 10,000, an acid number below 1 mg KOH / g, a hydroxyl number of 36 to 140 mg KOH / g and a water content below 0.1 wt. It may further be polyether polyols, polythioethers, polyacetates, polycarbonates and polyesteramides either alone or in mixtures.

Aliphatic, aromatic or heterocyclic are used as the diisocyanates, preferably at least 1,5-naphthyl diisocyanate, 4,4'-methanediphenyl diisocyanate and hexamethylene diisocyanate.

The excipients are catalysts, whether tertiary amines, e.g.: N, N-dimethylcyclohexylamine, triethylenediamine, triethylamine, or organotin salts, e.g.: stannous octoate, dibutyltin dilaurate at a concentration of 0.05 to 2% by weight. to the starting materials of the prepolymer. They are used either alone or in mixtures having a synergistic effect. Of the other excipients, they are also dispersants of the amino-active, cationic or non-ionic type (Kirk-Othmer: 8, pp. 117-154), preferably based on cellulose derivatives, for example: methylhydroxypropylcellulose in an amount of 0.01 to 5% by weight. to the aqueous phase.

The construction reaction of the polymer formation from the prepolymer and the chain extender takes place in a vigorously stirred aqueous phase containing the dispersant at temperatures of 40 to 95 ° C and is usually complete after 30 minutes. In addition to the dispersant environment, water also participates in the reaction with the -NCO group of the prepolymer and acts as a chain extender. From an aqueous polyurethane dispersion containing about 30 wt. The solid is collected by filtration, for example, and dried at 60 ° C after washing.

A great advantage of the process of the present invention is that the desired polyurethane transition temperature can be varied within a wide range of 130 to 230 ° C. This factor is particularly important in the preparation of mixed polyurethane compounds with other polymers, for example: the poles of vinyl chloride, where for plasticity the plasticization temperature of the two polymers is required to be approximately equal.

In addition to the mentioned advantage, it is important that the process according to the invention produces polyurethane and / or polyurethane urea in powder form, so that the processing of the product alone or in admixture with other polymers can be carried out on conventional types of extrusion, injection or injection molding machines. .

Example 1

Pre-polymer containing 1.75 wt. free

The -NCO groups are prepared by reacting 400 g of a polyester polyol prepared from adipic acid and ethylene glycol of molecular weight 2000, hydroxylo216421 at a number of 56 mg KOH / g and 0.01 wt. water with 75 g of 4,4'-methanediphenyl diisocyanate at 90 ° C with stirring for 30 minutes.

475 g of the prepolymer are introduced into a vigorously stirred aqueous phase consisting of 1000 g of water and 100 g of a 1% aqueous solution of methylhydroxypropylcellulose heated to 70 ° C. Under vigorous stirring in an Eta-mira mixer, an aqueous dispersion of polyurethane urea is formed over 10 minutes and heated to 95 ° C to decompose the carbamic anhydrides. The polymer is filtered off, decanted twice with an equal volume of water and dried in a vacuum oven at 60 ° C. The thermoplastic polyurethane urea powder has a plasticization temperature of 165 ° C, an average molecular weight of 190,000, a bulk density of 600 kg m ^-3 , a particle diameter of 40 to 250 µm and a melt index of 18 g / 10 min. at 170 ° C.

Example 2

Pre-polymer with 1.25 wt. The free -NCO groups are prepared from 400 g of adipic acid Systol 201 polyester polyol and a mixture of ethylene glycol and butylene glycol of mol. 2000, hydroxyl number 55 mg KOH / g and acid number 0.7 mg KOH / g and 46.5 g toluene diisocyanate (mixture of 2,4- and 2,6-isomers 80/20).

Claims (3)

from 56 mg KOH / g and 0.01% wt. water with 75 g of 4,4'-methanediphenyl diisocyanate at 90 ° C with stirring for 30 minutes. The 475 g of the prepolymer is placed in an intensively mixed aqueous phase consisting of 1000 g of water and 100 g of a 1% aqueous solution of methylhydroxypropyl cellulose heated to 70 ° C. With vigorous stirring in an Eta-mira mixer, an aqueous polyurethane urea dispersion is formed over a period of 10 minutes and heated to 95 ° C to decompose the carbamic anhydrides. The polymer is filtered off, decanted twice with the same volume of water and dried in a 60 ° C vacuum oven. The thermoplastic polyurethane urea powder has a transition temperature of 165 ° C, a mean molecular weight of 190,000, a bulk density of 600 kg m-3, a particle diameter of 40 to 250 µm, and a melt index of 18 g / 10 min. at 170 ° C. Example 2 Pre-polymer containing 1.25 wt. The free NCO groups are prepared from 400 g of polyester polyolSystol 201 based on adipic acid and mixtures of ethylene glycol and butylene glycol by mol. 55 mg KOH / g and 0.7 mg KOH / g and 46.5 g toluene diisocyanate (mixture of 2,4- and 2,6-isomers 80/20). SUBJECT A method for producing polyurethane urea and / or polyurethane having an adjustable transition temperature of 130 to 230 ° C, preferably in powder form, of compounds containing free -NCO groups, preferably a polyesterpolyol-based prepolymer. and / or a polyether polyol, optionally compounds containing at least 450 g of prepolymer, are introduced into an intensively mixed aqueous phase consisting of 1000 g of water, 100 g of a 1% aqueous solution of methylhydroxypropylcellulose and 12 g of ethylenediamine heated to 60 ° C. In the procedure described in Example 1, the middle polyurethane urea powder is carbon black. a weight of 150,000, a bulk density of 550 kgm -3, a particle diameter of 70-350 µm, giving a plasticization temperature of 135 ° C. Example 3 A prepolymer containing 3.4 wt. The free NCO groups are prepared by reacting 400 g of polypropylene glycol Voranol P 2000 with a hydroxyl number of 56 mg KOH / g and a water content below 0.05% by weight. with 67 g of hexamethylene diisocyanate for catalysis of 0.4 g of dibutyltin dilaurate at 90 ° for 30 minutes. The prepolymer is introduced into an intensively stirred aqueous phase consisting of 1000 g of water, 200 g of a 1% aqueous solution of methylhydroxypropylcellulose and 10 g of 1,4-butanediol heated to 75 ° C. The procedure described in Example 1 gives a polyurethane dispersion after 25 minutes. Polymeric mol. mass' 140 000, bulk density650 kgm-3, particle diameter below 100 μιη and temperature of plasticization 225 ° C. BACKGROUND OF THE INVENTION One active hydrogen in a molecule, in an aqueous or water-containing environment, characterized in that the isocyanate component is a compound having a defined free -NCO group content in the range of 0.5 to 6% by weight, preferably 1.2 to 3.5% by weight. . 216421