DD237759A3 - PROCESS FOR PRODUCING STORAGE-STABLE POLYURETHANE-PREPARED PRODUCTS - Google Patents

Abstract

The invention relates to the preparation of storage-stable hydroxyl-containing prepolymers, which are processed with isocyanates to elastic polyurethanes, optionally with the addition of inorganic and / or organic fillers, and for automotive parts, technical elastomer parts, embedding masses for fabrics and nonwovens, potting compounds u. Like. Are used. The aim of the invention is to develop a process for the preparation of storage-stable polyurethane precursors, in which the catalyst over a longer period in the hydroxyl-containing prepolymer homogeneously distributed and its catalytic activity is retained. According to the invention, the polyhydroxyl compounds used are copolyether alcohols of propylene oxide and ethylene oxide with at least 5% by weight of ethylene oxide and the addition of from 0.01 to 5% by weight of organometallic catalyst takes place at any time in one of these reactions.

Description

Field of application of the invention

The invention relates to a process for the preparation of storage-stable precursors for conversion to elastomeric polyurethane molding materials. In particular, the invention relates to the preparation of storage-stable hydroxyl-containing prepolymers, with isocyanates to elastic polyurethanes, optionally with the addition of inorganic and / or organic fillers processed and for automotive parts, shock absorbers, technical elastomer parts, coating compositions for textile or other substrates , Embedding masses for fabrics and nonwovens, potting compounds and the like. Can be applied.

Characteristic of the known technical solutions

Elastic polyurethanes can basically be prepared by two methods:

- One-step process, in which all components are mixed together, cured to the reaction and the final product;

- Multi-stage processes in which two or more components of the recipe are converted into precursors and these precursors are then reacted with other substances.

The use of the multistage process, in which two prepolymers with terminal isocyanate groups or hydroxyl groups are reacted with one another, gives polymers having a more uniform structure structure and, associated therewith, a higher and more reproducible property profile. Such prepolymers are generally processed on mixing machines and supplied by the manufacturer in the form to be processed, h., They already contain all the necessary additives for the desired end product. However, this requires that these prepolymers must remain constant with the additives for prolonged periods in their composition and in their product parameters, such as end group concentration and viscosity to ensure reproducible processing conditions and end products. The preparation of catalyst-containing prepolymers containing isocyanate groups is difficult because the catalysts cause reactions of the isocyanate groups; e.g. lead basic catalysts to dimerization or cyclotrimerization and organotin catalysts also for cyclotrimerization. These reactions reduce the isocyanate group concentration and increase the viscosity within a short time so that the products can no longer be processed. In addition, the end product properties are significantly changed.

It is therefore common practice to incorporate catalysts and other additives into the mixture of polyhydroxy compounds to be reacted with the prepolymer containing isocyanate groups. In this case, a viscosity as similar as possible, as it has the isocyanate group-containing prepolymer, desirable and the mixing ratio should be between 1: 1 and 5: 1. Higher mixing ratios are uneconomical because of the increased complexity of the mixing units. A prerequisite for the use of such mixtures of polyhydroxy compounds, catalysts and other additives is that they remain homogeneous during storage and demix or irreversible change neither on cooling to temperature below 0 ⁰ C nor at elevated temperature.

In the production of elastic polyurethanes, long-chain diols are usually used as chain extenders. These two classes of substances are generally immiscible with each other or form emulsions that segregate on prolonged standing again. As a result, there are a number of proposed solutions to circumvent these problems and provide a stable mixture.

In DE AS 2.759.398 z. For example, a process for preparing stable polyol-chain extender mixtures is described, according to which a mixture of low molecular weight diols and a polyether alcohol of hydroxyl number 20 to 60, an endblock of ethylene oxide of 10-20 wt% and an internal ethylene oxide content of 5 to 60 wt%. will be produced. Within certain limits, such mixtures are stable, but segregate usually at high 1,4-butanediol and with the addition of organometallic catalysts. These difficulties are overcome by the US Patent 3,945,939, characterized in that the mixture solid colloid-forming substances are added, but again lead to new difficulties in machine processing. DE-OS 2,940,856 describes a process for preparing elastic polyurethanes from hydroxyl-containing prepolymers and isocyanates, according to which the hydroxyl-containing prepolymer is divided into two parts, of which one part is mixed with chain extenders and further additives. This mixture is then reacted with the hydroxyl-containing prepolymer and a diisocyanate prepared isocyanate prepolymers. The mixture of chain extender and hydroxyl-containing prepolymers is usually reacted at 65-90 ^c C; storage or shelf life is not stated as well as catalysis of this product.

DE-OS 2,842,865 describes a coating composition which is essentially prepared from a diisocyanate and a hydroxyl-containing prepolymer, the latter consisting of a polyisocyanate, a branched polyether polyol, a polyester polyol, a glycol and a polyamine using molecular sieve and activator consists. The activators used are diazabicyclooctane in dipropylene glycol and lead octoate in white spirit. With dimeric diisocyanate from a paste is prepared, d. H. a highly viscous, inhomogeneous product used as a one-component system. Stable emulsions are further processed into polyurethanes according to US Pat. No. 4,273,884 or DE-OS 3,112,492 from polyglycols having a molecular weight of more than 12,000 with 70-90% by weight of ethylene oxide and 1,4-butanediol. Again, catalyst-free, inherently unstable systems are used.

According to US Pat. No. 3,681,291, elastic polyurethanes are used from prepolymers based on polypropylene glycols and hydroxyl-containing mixtures of polypropylene glycol, an aromatic diol, an aromatic polyamine and organometallic catalysts. Nothing is said about the storage stability of these mixtures, but it is to be assumed that it is limited because of the tendency of the aromatic compounds to crystallize. Homogeneous processing is therefore only possible at elevated temperatures.

In GB-PS 1,448,933 hydroxy-containing prepolymers are described, which are prepared from a prepolymer having terminal isocyanate groups and a low molecular weight diol, wherein

- The prepolymer having terminal isocyanate groups from a diisocyanate of molecular weight 100 to 500 and a high molecular weight diol of average molecular weight 500 to 4500 at a molar ratio of hydroxyl groups to isocyanate groups of 1: 1.8 to 1: 2.2 and

- The hydroxyl-containing prepolymer of one equivalent of isocyanate prepolymer and 4 to 17 equivalents of a diol of molecular weight 60 to 250

will be produced. It is described as a preferred embodiment that no catalysts are used in the preparation of the prepolymers; as the temperature range for the production 25-100 ° C and limited 30-75 ⁰ C called. In addition, the use of viscosity modifiers-that is, polyether diol in the medium molecular weight range-is proposed. The preparation of the polyurethane end products is carried out by prior mixing of excipients, preferably in the hydroxyl-containing polymer, and mixing with the isocyanate group-containing prepolymer. It is pointed out difficulties in the casting or spraying process, if either the viscosities of the two prepolymers differ too much or if the mixing ratio of the prepolymers including the additives of 1: 1 significantly different. The viscosity differences of the two prepolymers are adjusted to one another by different processing temperatures, which requires an additional temperature control device and thus a further complication of the processing machines.

The existing prior art solutions have some disadvantages that can be summarized as follows:

High viscosities of the prepolymers and, if necessary, the need to add viscosity-modifying substances, thereby influencing the reaction process and the properties of the end products;

Addition of catalysts either in solutions (the solvents acting as viscosity modifiers) or immediately before processing since they are not soluble or permanently dispersible in the prepolymer;

Necessity of processing the prepolymers on processing machines at elevated temperature in order to reach a technically feasible viscosity range, or stretching one of the prepolymers to set realizable mixing ratios.

In particular, the preparation of storable mixtures of polyhydroxy compounds and organotin catalysts presents difficulties, firstly because of the insolubility of most such compounds in the polyols and secondly because of the hydrolytic instability of a number of organotin compounds. These catalysts must therefore be added before processing, especially since they can not be mixed in the isocyanate group-containing prepolymers for the reasons mentioned above.

Object of the invention

The aim of the invention is hydroxyacrylate-containing prepolymers for reaction with isocyanates to give polyurethanes for processing, especially since they can not be mixed in the isocyanate group-containing prepolymers for the reasons mentioned above.

Object of the invention

The aim of the invention is to develop a process for the preparation of storage-stable polyurethane precursors, in which the catalyst is homogeneously distributed over a longer period in the hydroxyl-containing prepolymer and its catalytic activity is maintained.

Explanation of the essence of the invention

The object of the invention is achieved by a process for the preparation of storage-stable polyurethane precursors by first from one or more polyhydroxy compounds of molecular weight 700 to 4000 and one or more diisocyanates in the presence of a catalyst and optionally additives, an isocyanate group-containing prepolymer in the ratio of the hydroxyl groups Isocyanate groups from 1: 1.8 to 1: 2.2 prepared at a temperature between 20 and 90 ⁰ C and this with a short chain diol of molecular weight 62 to 600 in the molar ratio of the free isocyanate groups to the hydroxyl groups of 1: 3 to 1:22 at a temperature between 20 and 120 ⁰ C is reacted, wherein according to the invention as polyhydroxy compounds Copolyetheralkohole of propylene oxide and ethylene oxide with at least 5Gew .-% ethylene oxide are used and the admixture of 0.01 to 5Gew .-% organometallic catalyst at any time in one of these Reactions take place.

Organometallic catalysts used are organotin compounds, such as organotin oxides and / or organotin sulfides.

Part of the hydroxyl compounds from the formulation in a precursor mifTsocyalTaterrumsetzt and then react this product with the chain extender to hydroxyl prepolymer. The organotin catalyst can be entered at any time in the mixture, so that in this way, if necessary, even without energy supply such prepolymers are accessible. Possibilities for the preparation of these hydroxyl-containing precursors are, for example:

1. The isocyanate or mixture is initially charged and the polyether diol added with catalyst at a rate that a temperature of 9O ⁰ C is not exceeded by the resulting heat of reaction. After completion of the addition of the short-chain chain extender is also metered in such that the temperature does not exceed 120 ⁰ C. Further treatment is not necessary in this case.

2. From the isocyanate or mixture and the copolyetherdiol an isocyanate group-containing prepolymer is prepared within 30 min to 8 hours at 60-90 ⁰ C, added to this the catalyst and without energy supply of

, short-chain chain extender at a temperature up to 120 ⁰ C added.

3. From the isocyanate or mixture and the Copolyetherdiol an isocyanate group-containing prepolymer is prepared within 30 min to 8 hours at 60-90 ⁰ C, then the short-chain chain extender added, stirred for a further 20 min to 6 hours at 60-120 ⁰ C and then the catalyst added.

By choosing the molar ratio of the short-chain to the long-chain polyhydroxy compounds and the choice of diisocyanate or the viscosity of the hydroxyl-containing prepolymers and, if appropriate, taking into account the average molecular weight of the long-chain copolyether diols, the mixing ratio to the prepolymer containing isocyanate groups. A reduction in the molar ratio of short chain to long chain polyhydroxy compounds leads to a viscosity and equivalent weight increase. The molar volume of the diisocyanates determines the viscosity of the products. The molecular weight of the polyhydroxy compounds has an effect insofar as low molecular weights give low equivalent weights of the prepolymers and high molecular weights give high equivalent weights. Thus, three influencing variables are available for adjusting the viscosity and the mixing ratio, which must be matched to one another in order to obtain the optimum variant for the specific application:

The ratio of the amount of isocyanate groups in the isocyanate group-containing prepolymer to the amount of hydroxyl groups in the short-chain diol, decreasing with increasing amount of diol viscosity and hydroxyl equivalent;

The type of isocyanate used, aliphatic isocyanates giving low-viscosity products, mononuclear aromatic medium-viscosity and polynuclear aromatic isocyanates high-viscosity products;

The equivalent weights of the long-chain polyether diols, the viscosity increasing slowly and the equivalent weight of the hydroxyl-containing prepolymer increasing with equivalent weight.

Thus, by employing a suitable equivalent weight of the polyether diol, a diisocyanate (or a mixture of isocyanates) adapted to the application, and a selected ratio of polyether diol to short chain diol, the viscosity can be based on the viscosity of the isocyanate component and the hydroxyl equivalent on the isocyanate equivalent, i. H. adjust the mixing ratio to a good processable value.

Another important point for the stability of the hydroxyl-containing prepolymers is the composition of Copolyetherdiols. These copolyetherdiols are usually prepared from alkylene oxides, while pure Polypfopylenglykole not give the stable prepolymers of the invention, but on the contrary to inhomogeneous

Lead products and prepared according to the novel prepolymers based on polyethylene glycols for crystallization and thus tend to segregation, but show Copolyetheralkohole of the two monomers in a certain structure, the desired behavior of the inventive method and provide a preferred embodiment of the invention that Copolyether alcohols should have an ethylene oxide endblock of 0-25% by weight of the copolyether alcohol and have between 0.5 and 30% by weight of the copolyether alcohol on ethylene oxide in the propylene oxide parent. Particularly advantageous are products which also contain 0.1 to 10 wt .-% of Copolyetherdiols of propylene oxide in Ethylenoxidendblock. Such copolyether diols are described in DD-WP 143.083 and DD-WP-Anm. C08G / 240041.

The long-chain diols should have an average molecular weight of from 700 to 4000, with molar masses in the range from 1500 to 3000 being preferred.

However, other linear polyether diols are also usable, e.g. As polyether oils of tetrahydrofuran polymers or copolymers with ethylene oxide and / or propylene oxide, those based on caprolactone and polyester diols containing ethylene glycol or homologues.

Examples of short chain chain extenders are ethylene glycol, 1,2-propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,4-pentanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, 1, 4-bis (2-hydroxyethylene) benzene, 1,4-bis (2-hydroxypropoxybenzene etc.

Suitable isocyanates are primarily the industrially used products, for. For example, hexamethylene diisocyanate, 4,4'-diphenylmethane diisocyanate, ^^ '- diphenylmethane diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, etc.

As organotin catalysts, preference is given to using hydrolysis-stable compounds, ie tin oxides and tin sulfides, eg. Bis (tributyltin) oxide, dibutyltin dioxide, bis (trioctyltin) oxide, bis (trioctyltin) sulfide, dibutyltin bis (thioglycolic acid octyl ester) and similar compounds as described, for example, in DD-WP Appl. C08G / 218.668und

C08G / 231.214 / 6 are described.

The hydroxyl-containing and catalyst-containing prepolymers prepared in this way are viscous liquids having hydroxyl numbers in the range from 100 to 800, preferably in the range from 200 to 700. Polyisocyanates, preferably polyurethane elastomers, but also cellular products can be prepared by incorporating propellants with prepolymers containing isocyanate groups. When using glass fibers, products for reinforced elastomer parts can be produced by the reaction injection molding method.

Exemplary embodiments Example 1

A hydroxyl-containing prepolymer is prepared. For this purpose, in a beaker, 52 g toluene diisocyanate (80% 2,4, 20% 2,6-isomeres)

210 g of a block copolymer of ethylene oxide, OH number 55.3, water content 0.02% stirred together for 10 min. ,

Thereafter, 4.0 g of dioctyltin-bis (thioglycolic acid decyl ester) are added with stirring. The mixture is heated to 85 ⁰ C. The cooled to 60 ° C mixture is added with vigorous stirring in 372g of 1,4-butanediol and stirred for 1 hr. At 80 ⁰ C under vacuum. You get a product with:

Hydroxyl number: 632

Viscosity at 20 ⁰ C: 8340 mPas

Example 2

The following quantities are reacted analogously to Example 1:

19.14 g tolylene diisocyanate

84.2 g of a block copolymer of 68% propylene oxide and 32% ethylene oxide, OH number 42.8

2.1 g of dioctyltin bis (thioglycolic acid butyl ether) 85.62 g of 1,4-butanediol

Hydroxyl number: 542

Viscosity at 20 ° C: 300mPas;

the product is 3 months at room temperature and at 30 ⁰ C storage stable. When stored at 5 ° C occurs segregation, but disappears when heated to room temperature again.

Example 3

The following quantities are reacted analogously to Example 1:

16.08 g of tolylene diisocyanate

70.72 g of a block copolymer of 71% propylene oxide and 29 wt .-% ethylene oxide, OH number 62.1

1.92 g of dioctyltin bis (2-ethylhexyl thioglycolic acid) 86.34 g of 1,4-butanediol

-5- <£ J / / OS

Properties: Hydroxyl number582

Viscosity (2O ⁰ C): 2 900mPas

Example 4,5,6

Analogously to Example 1 4 5 6

Tolylene diisocyanate (g) 21.06 22,62 26,10

Block copolyether (g) 95.70 104.64 122.10

(OH Zahl61,8)

Dioctyltin bis (thioglycol. 1,15 1,00 1,04

acid octyl ester) (g)

Butanediol-1,4 (g) 85,16 84,72. 83.82

Hydroxyl number 476 458 '421

Viscosity (10 ⁰ C) mPas 6480 5820 6060

Example 7,8,9

Analogously to Example 1 7 8 9

Toluene diisocyanate (g) 52.2 41.76 23 500

Block copolyether (g) 244.2 215.20 121000

(30% by weight EO, OH-Z 57.4)

Dioctyltin bis (thioglycol '1.00 1.60 900

acid 2-ethylhexyl ester) (g)

1,4-butanediol (g) 167.64 134.11 '75400

Hydroxyl number 416 451 480

Viscosity (2O ⁰ C) mPas 13715 5110 6330

Example 10

In a 500 ml three-necked flask 0.15 equivalents (13.1 g) of toluene diisocyanate (isomer mixture as in Example 1) at 80 ⁰ C with 0.072 equivalents (92g) of a Blockcopolyetheraikohohls of ethylene oxide and propylene oxide (ethylene oxide content 31.5%, molecular weight 2550) and the mixture stirred at 80-85 ⁰ C for two hours. Thereafter 0,925Äquivalente be (41,7g) of 1,4-butanediol was added, stirred for another hour at 8O ⁰ C, was added 0.6 g of dioctyltin bis (thioglykolsäureoctylester) and cooled to room temperature. This gives a clear product having a hydroxyl number of 342 and a viscosity (20 ° C) of 4650mPas. The product is stored at -15 ⁰ C for 2 weeks.

It creates a solid product. After warming to room temperature, the liquid, clear starting product is obtained, viscosity (20 ⁰ C) 4630mPas.

Examples 11, 12, 13 and 14

The experiment of Example 10 is repeated with modified reaction conditions and amounts used:

B11 B12 B13 B14

toluene diisocyanate 13.1 / 0.15 26.2 / 0.30 - 0.4 19.65 / 0.225 19.65 / 0.225 (G / eq) Copolyetherdiol of 92.0 / 0,072 184.0 / 0.145 B12 138.0 / 0.108 138.0 / 0.108 Ex. 10 (g / equiv.) Reaction Temp. ( ⁰ C) 80 80 85 90 Reaction time (h) 2.5 4.0 3.0 8.0 1,4-butanediol 41.7 / 0,925 83.4 / 1.85 '62.55 / 1.37 62.55 / 1.37 (G / eq) Dioctylzinnbis- (thio- 1.0 1.2 1.9 0.9 glykolsäureoctylester) (G) Post-reaction time (h) 1.0 1.4 1.0 (8O ⁰ C) B11 B13 B14

Viscosity (20 ^° C.) 5190. 4690 4950 8220

(MPas)

Hydroxyl number 328.5 333.6 5 010 8150

Viscosity after 5 200 4620 324.6 337.8

1 month / 20 ⁰ C

Examples 15, 16, 17

Example 10 is repeated, but instead of tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate is used:

B15 B16 B17

4,4'-diphenylmethane 26,25 / 0,21 25,0 / 0,2 30,0 / 0,24

diisocyanate

(G / eq)

Dopolyetherdiol after 133.35 / 0.015 127.0 / 0.1 152.4 / 0.12

(G / eq)

Reaction temperature 90 80 80

door ( ⁰ C)

Reaction time (h) 2.0 4.0 4.0

Butanediol-1.4 62.87 / 1.395 '40.4 / 0.9 39.65 / 0.88

(G / eq)

Reaction time (h) / 1.0 / 80 0.5 / 90 1.0 / 80

Temp. ( ⁰ C)

Catalyst ν. 1.12 0.65 0.45

Post-reaction _ 0.1 0.3 0.5

time (h) ~ "^;"

Viscosity (20 ° C) 14960 21840 30700

Hydroxyl number 306.0 221.0 178.2

Example 18

Example 10 is repeated, but with the following amounts and reaction conditions: toluene diisocyanate: 100 g (1.15 equivalents)

Copolyetherdiol * (30.5% by weight of ethylene oxide, molecular weight 2500):

730 g (0.58 equivalents) Reaction time and duration: 4h / 80 ° C

Butanediol-1,4: 345g (7.66 equivalents)

Post-reaction time: 1 hour at 80 ° C

Catalyst according to Example 1: 2.0 g

Viscosity (20 ⁰ C): 5120mPas

Hydroxyl number: 338.4

Claims (5)

Invention claim: 1. A process for the preparation of storage-stable polyurethane precursors for reaction with isocyanates in the presence of catalysts and optionally additives to polyurethanes having an adjustable viscosity and concentration of hydroxyl groups by first from one or more polyhydroxy compounds of molecular weight 700 to 4000 and one or more diisocyanates an isocyanate group Prepolymer in the ratio of the hydroxyl groups to the isocyanate groups of 1: 1.8 to 1: 2.2 prepared at a temperature between 20 and 90 ⁰ C and this with a short chain diol of molecular weight 62 to 600 in the molar ratio of the free isocyanate groups to the hydroxyl groups of 1 : 3 to 1:22 is reacted at a temperature between 20 and 120 ° C, characterized in that as polyhydroxy compounds Copolyetheralkohole of propylene oxide and ethylene oxide with at least 5Gew .-% ethylene oxide are used and the admixture of 0.01 to 5 wt .-% 'organometallic catalyst to a belie time of one of these reactions. 2. The method according to item 1, characterized in that as Copolyetheralkole one or more Copolyetherdiols of propylene oxide and ethylene oxide with a strain of propylene oxide with 0.5 to 30 wt .-% ethylene oxide and a Ethylenoxidendblock from 0 to 25Gew .-%, wherein a total the copolyetherdiol contains at least 5% by weight of ethylene oxide. 3. The method according to item 1, characterized in that the Copolyetherdiol in the ethylene oxide 0.10 to 10Gew .-% based on the diol of propylene oxide contains statistically distributed. 4. The method according to item 1, characterized in that organometallic compounds are used as organometallic catalysts. 5. The method according to item 4, characterized in that are used as organotin compounds hydrolysis-stable organotin compounds such as organotin oxides and / or organotin sulfides.