DE1045644B - Process for the production of polyurethane foams - Google Patents

Description

So far, polyurethane foams are made by the reaction of a non-linear, slightly branched Polyester with a diisocyanate or by reaction of a linear polyester with a mixture of di- and triisocyanates. Generates a small amount of carbon dioxide to form pores or cells in the solid product will have an excess of diisocyanate over that required to react with the polyester used to form the polyurethanes required amount. Generally a small amount of water will be used added, which reacts with the diisocyanate to form carbon dioxide.

The diisocyanate is added both to build up and crosslink the high molecular weight polyester and to deliver the excess CO ₂ . Linear polymers alone would not change from the liquid to the solid state quickly enough to capture all of the gas evolved and thus enable the formation of a foam. The crosslinking is necessary to hold the gases in place so that a foam-like polyurethane product with a cell structure and low density is obtained.

In the usual process for the production of polyurethanes with cell structure or foam-like Reaction products from polyesters and diisocyanates becomes a viscous, liquid polyester in a regulated Speed pumped through a nozzle into a mixing chamber. A polyisocyanate, preferably a diisocyanate, is also pumped in at an extraordinarily high pressure, it being mixed with the Polyester stream comes into contact and mixes with it completely due to its high speed. There will also be a small amount of water, either as a jet or together with the polyester introduced. Also preferred are a crosslinking agent such as 1,3-propylene glycol and a suitable one Catalyst, such as certain tertiary amines, mixed or injected with the polyester. In general there is a stirrer in the mixing chamber to enable homogeneous mixing. The material is then converted into a suitable form, e.g. B. an open tub filled in, the evenly, parked on the Output, is moved further so that the desired layer thickness on the bottom of the tub or mold arises. The bottom of the tub can contain vertical cylindrical wooden pins or cores so that the lower surface of the polyurethane foam is formed with round openings. Save these holes not only material, but also allow the fixed portion for a given deflection curve has a higher density.

The solidification of the material is very important. It is essential that the diisocyanate and catalyst be rapidly and completely dispersed in the polyester. Process of manufacture
of polyurethane foams

Applicant:

The General Tire & Rubber Company,
Akron, Ohio (V. St. A.)

Representative: Dipl.-Ing. W. Meissner, Berlin-Grunewald,

and Dipl.-Ing. H. Tischer, Munich 2, Tal 71,

Patent attorneys

Claimed priority:
V. St. v. America October 20, 1955

Charles Bedell Frost, Akron, Ohio (V. St. A.),
has been named as the inventor

will. The carbon dioxide is developed from the mixing on, so that the formation of bubbles and foaming occur during mixing, distribution and shaping.

The time and place of gas evolution by the isocyanate cannot be regulated here, as these occurs as a result of the reaction between the diisocyanate and water. One of the disadvantages of this uncontrollable Gas evolution is the formation of a solid crust on top of the polyurethane foam as a result of carbon dioxide losses. The crust is essentially solid, non-porous polyurethane. During further processing, this crust has to be cut away with great losses. Although the liquid polyester is made from the waste by means of a high-temperature steam treatment can regain for reuse, it is particularly disadvantageous if the surface in the Has become stuck near the openings mentioned above.

Try mixing gaseous carbon dioxide with the polyester and a smaller excess of isocyanate has been unsuccessful because the strength of the film is reduced when the Gas pressure to atmospheric pressure was not sufficient to maintain the cell structure. Also is that Carbon dioxide is neither sufficiently easy to liquefy nor sufficiently soluble in the reactants, to be developed only gradually.

Although the process used earlier is quite effective, the production of poly-

S (B «97/576

urethane foams in this way have serious shortcomings. The very considerable excess of the diisocyanate, which is used to react with water to develop gaseous carbon dioxide, represents an economic burden. Another disadvantage is the formation of substituted urea as a by-product of the water diisocyanate reaction. This by-product is reactive and goes into To a certain extent, crosslinking reactions occur, which are undesirable in the case of flexible foam products Cause rigidity.

Also, when used in a tenon mold, the product releases high density foams those parts which are in contact with the pins, so that the advantages of molded bodies with * 5 Holes are lost. Another disadvantage is the fact that the maximum viscosity of the polyester is limited for reasons of good mixing and therefore no very high molecular weight polyesters are used can be. ao

One object of the present invention is to provide a method for making softer polyurethanes to indicate with cell structure, of polyurethanes, which are used with success in forms with tenons can. Next, making a better, more durable polyurethane foam with less Aimed at polyisocyanate. Polyurethanes with a cell structure with a lower density should also be used are formed, which are softer and more elastic and which have a smaller shrinkage at lower density than those previously produced show. For this purpose, polyesters with higher viscosity and accordingly higher molecular weight than those heretofore suitable can be used.

It is not known whether the substituted urea produced as a by-product contributes to the encrustation effect that occurred in the earlier process, but this effect is after the gas formers Avoided the present invention.

The easily liquefied halogen-substituted alkanes used according to the invention as gas formers can easily be dispersed in the polyester, and little or no change to the usual device is necessary, except for the device for mixing the liquefied gas with the polyester. If the gas is somewhat soluble in at least one reactant, a pressure drop and increased mobility of the reactant, for example the polyester, occur, which allows the use of a reactant with a higher viscosity. If a liquefied gas is used as a propellant for the polyurethane, less diisocyanate is required. The amount of water that was previously required for the reaction with the diisocyanate can also be kept very low, since the amount of the substituted urea formed as a by-product is reduced. The shrinkage of the foam when it sets is very low, so that light yet strong objects can be produced. This is particularly desirable if the product with the cell structure is used for insulation or reinforcement that is only processed into foam at the place of use. In the case of the gases which are slightly soluble or easily dispersible in the polyester and which are to be liquefied, the polyurethane foams are generally softer than those produced in the customary manner.

If the propellant gas is not soluble in the reaction stiffeners or has a solubility of less than 0.1 mol / g, its boiling point should not be below about. - 23.3 ° C and not above the temperature that is reached in the early stage of urethane formation, preferably not significantly above + 10 ° C. The propellants should then be dispersed as fine beads in the polyester or the other reactant used, and the Dispersion should be relatively stable. The finely dispersed droplets of the liquefied propellant result in a uniform end product. If the blowing agent is soluble in the polyester, the boiling point can be very low. The higher the solubility, the lower the boiling point can be. Liquefiable blowing agents with a solubility at atmospheric pressure of at least 0.25 mol in one gram of reactants - preferably in polyester or similar substances such as diethylene glycol diacetate - can have a boiling point of up to about -51 ° C. despite their beneficial effect. It is advantageous when the solubility of the liquefiable propellant gas in the polyester or similar material than 0.1 mol / g, and whose boiling point is between about -51 and +10 ⁰ C.

The heat of reaction leads to the formation of gas from the small droplets of the liquefied propellant or reduces its solubility in the polyester. So there is a stronger gas development only when the The polyurethane reaction has progressed so far that the released gas is retained. It is now possible for the first time, the chronological sequence of the side by side running reactions (1) crosslinking and (2) gas evolution to regulate so that the polyurethane can solidify before the gas is released, so that the gas itself is trapped in the surface layers remain.

The type of polyester used depends on the type of foam desired. In general, crosslinkable polyesters having a high molecular weight are used for rigid foam rubber, while more linear polyesters with a molecular weight of about 1500 to 2500 are used for flexible foam rubber types, although the easily liquefiable blowing agents dissolved in the polyester act as solvents and then polyester is also used A typical polyester for flexible foams is a polyester made from one mole of adipic acid and one mole of diethylene glycol with ¹ 50 mole of trimethylolpropane, the residues of which cause crosslinking when reacting with the diisocyanates. In general, the linear polyesters for the flexible polyurethane rubber compositions have a molecular weight below 2500, which is set within narrow limits. The viscosity of such polyesters is preferably maintained between about 1000 and 1100 Cp at 73 ° C. Their specific gravity at 25 ° C is around 1.19, their hydroxyl number around 60.

For semi-rigid polyurethanes, linear polyesters with somewhat different properties are generally used. The molecular weight of these polyesters is about 1500 to 2500, their hydroxyl number about 60. However, their viscosity only reaches about 600 to 800 Cp at about 73 ° C., because the hydroxyl groups are all terminal. Such polyesters are formed from 1 mole of adipic acid and 1 mole of glycol.

Polyesters for rigid polyurethane rubber compositions are generally crosslinkable polyesters with a molecular weight of 2000 to 3000, even up to about 4000. The percentage of hydroxyl groups is preferably about 7 to 9, the specific weight about 1.10 to 1.19 and the viscosity 73 ⁰ C approx

2500 cp. Such a polyester is formed e.g. B. off are gaseous at room temperature and at increased

2V2 moles of adipic acid, V2 moles of phthalic anhydride easy to liquefy under pressure,

and 4.2 moles of hexanetriol or from 3 moles of adipic acid, these gases are preferably used in amounts of

2.1 moles of hexanetriol and 2.1 moles of 1,4-butanediol. about 5 to 10 percent by weight as liquefied gas,

In order to produce a more flexible foam, based on the weight of the initial polyester

len, a liquid primary material is used as polyester, but quantities can also be used

product made of a linear liquid polyester with from 2 to 25 ^fl / o, in particular of monochlorodifluor-

some diisocyanate, e.g. B. will use a polyester as adipine methane, which is highly effective.

acid and dietary glycol with an excess of Table I contains some according to the invention

Glycol made. This polyester is left with 10 usable halogen-substituted gaseous alkanes

a 70:30 isomer mixture of 2,4- and 2,6-To- together with their approximate boiling points

luylene diisocyanate react until the NCO content is between atmospheric pressure:

see 8 and 10% of the reaction product, where- TbUT

by one mole of diisocyanate to each end of the poly a e e

esters is appended. This polymer is still 15%

linear, and the further reaction with diisocyanate er “ρ. ³ ρ _oq ςο ρ

does not show any further increase in chain length. i-trr ¹ 1 ² T? '"" j_ q no r *

Examples of suitable diisocyanates are: CHClF ₂ -40.6 ° C

Toluylene diisocyanate, 20 r w η -unior-

p, p -diphenylmethane diisocyanate, °

Naphthylene-1,5-diisocyanate, the gas should, regardless of whether it is dissolved or dispersed

m-phenylene diisocyanate and yaws, at room temperature a fairly high

dimeric tolylene diisocyanate. Have vapor pressure and preferably at least

Boil 25 at 10 ° C.

As propellant gases according to the invention, the halo- Depending on the desired foam product

gensubstituted gaseous alkanes with boiling point can be a mixture of soluble and proportionate

thes below +10 and above -51 ° C, the, insoluble liquefied gases are used,

are partially homely, fluorinated and / or chlorinated. The degree of solubility of two useful

Of these, monochlorodifluoromethane supplies 30 liquefied gases, namely dichlorodifluoromethane

Its high solubility in polyester outstanding and monochlorodifluoromethane, in three different

and excellent results. The gases solvents used are given in Table II.

Table II

Dissolved gas former

Solubility in
Diethylene glycol monoacetate monoethyl ether
Mol / g

Solubility in
Butylene glycol dimethyl ether

Mol / g

Solubility in diethylene glycol diethyl ether

g / g I mol / g

CCl ₂ F ₂
CHClF ₀

0.267
1.143

0.280
0.700

0.282
0.740

0.458 1.127

0.380 0.678

The solubilities listed in Table II were at 32.2 ° C at a pressure of the halogenated Hydrocarbon measured, which corresponded to its vapor pressure at about 4.5 ° C. As in Table II is listed is monochloride formmethane, based about four times as soluble by weight as dichlorodifluoromethane.

In general, these gases become more soluble at lower temperatures. CCl ₂ F ₂ has an absolute vapor pressure of about 6.95 kg / cm ² at 26.7 ° C, while CHClF _{2 has} a vapor pressure of about 11.6 kg / cm ^{2 at 26.7 ° C.}

The following examples serve to illustrate the invention.

example 1

Dichlorodifluoromethane, which has a vapor pressure of about 5.96 kg / cm ² at 21.1 ° C., was dispersed as a liquid in a polyester made from about 1 mole of adipic acid, 1 mole of diethylene glycol and about ₃₀ moles of trimethylolpropane.

The viscosity of the polyester with predominantly hydroxyl groups as end groups was 73 ° C between 1000 and 1100 cp; its moisture content below 2%, preferably between 0.3 and 0.5%>.

The polyester was mixed with the liquefied gas in a stirred autoclave and the mixture

pumped to a foam machine after heating to about 22 ° C. A mixture of 70 parts of 2,4- and 30 parts of 2,6-toluylene diisocyanate was ^{pressed at about 70 kg / cm 2} pressure through small openings into the same nozzle in which it reacted with the polyester to form the polyurethane. The flow velocity through the nozzle results from the following approach.

Table III

material Parts by weight
liquid polyester
Tolylene diisocyanate
Activator
Dichlorodifluoromethane 100
25th
8th
5

The activator was composed of:

(A) the esterification product of 1 mole of adipic acid and 2 moles of diethylethanol

amine as a catalyst 3 parts

(b) from a soap made from oleic acid and diethylamine as an emulsifier 2 "

(c) water 1.2 "

The foam produced was very much softer than that produced by the usual method. Of the The foam produced showed very favorable properties, since the top side had a dense, bubble-free skin exhibited, however, the undesirable formation of a tough, dense, bubble-free coating around the tenons the floor space was missing. The one normally occurring with the bubble-free product following the earlier procedures There is thus no great loss due to the formation of non-foam-like parts.

Example 2

The processing of the starting materials was carried out similarly to Example 1 with the difference that difluoromonochloromethane was used as the liquefied gas. This has a vapor pressure of about 9.5 kg / cm ^{2 at 21.1 ° C.} The components shown in Table IV were used:

Table IV

low foam density of about 0.04 g / cm ^{3 was} achieved.

Again, the hard, brittle skin around the holes on the floor surface did not appear. Also was that Foam softer than one produced in the usual way.

Example 3

The polyester, the diisocyanate and the activator ίο were the same as in Example 1. This example explains the admixture of 5 to 10 percent by weight of liquefied difluoromonochloromethane to the Polyurethane foam-forming batches in the mixing ratio shown in Table VI.

Table VI

material

Parts by weight
liquid material 100
35
8.5
5 polyester
Tolylene diisocyanate
Activator According to Table V
Difluoromonochloromethane

polyester

Tolylene diisocyanate

Activator

Difluoroarmonochloromethane

Parts by weight
Sample AI Sample BI Sample C

100

100

25th

100

The activator was almost the same as in Example 1 with the difference that the activator in addition to those mentioned in Example 1 as further constituents a paraffin-like oil for regulating the pore size in expanded polyurethane rubber and a Containing sodium salt of ricinoleic acid as a water-soluble wetting agent. The latter allows its use a small amount of water reduces the "skin effect" of the polyurethane and allows some of the volatile gases to escape without tearing apart the block of urethane rubber.

The composition of the activator
Table VI was the same as in Table III.

The resulting polyurethane rubber was similar in quality to that of Example 2, as shown in FIG the density of the samples can be seen.

Density (g / cm ³ )

sample

0.08

0.06

0.04

Table V Volume parts material 3 Catalyst (esterification product
from 1 mole of adipic acid and
2 moles of diethylethanolamine) 1 Emulsifier (soap made from oleic acid and
Diethylamine) 1.5 Sodium salt of the sulfonated
Ricinoleic acid 0.3 Paraffin oil 2.0 water

The paraffin oil used was a very highly refined mineral oil, which at 25 ° C has a density of about 0.88 to 0.89, at 25 ° C has a viscosity of about 130 to 150 Cp and an acid number of 0.

The difluoromonochloromethane was added to the polyester with stirring. The pressure in the polyester container fell below 0.7 kg / cm ² because the difluoromonochloromethane is soluble in the polyester. The entire reaction mixture was pressed out of the mixing nozzle as in Example 1 without the foam puffing. After the leakage, the polyurethane began to expand slowly and steadily until the very density of the polyurethane in g / cm ³ , which was made with 10% difluoromononchloromethane, was thus approximately half that of the control standard sample. The standard sample is marked with "A". The tensile strength and the percentage elongation were better compared to the standard approach. The firm skin that is normally found around the holes in the floor was again absent.

The admixture of the liquefied gas resulted in a softer foam. During pressure bending tests A large improvement was observed by the curves for the deformation under load stretch very much, approach the foams made of natural rubber latex 'and thus a desired Show behavior. Furthermore, it becomes a desirable decrease the density achieved.

The liquefied propellants according to the invention apparently act on other gases that are easy to liquefy, such as hydrocarbons with low molecular weight or CO ₂ in the polyester-isocyanate sector

mixed as a solvent. You can therefore partially by gaseous hydrocarbons with low Molecular weight and with no more than 3 carbon atoms, such as methane, "ethane, ethylene, propane and propylene. The gaseous hydrocarbons are in the liquefied gases and dissolved and dispersed in the other ingredients. '

The amount of liquefied halogen-substituted alkanes should be mixed with the gases mentioned be at least 50 percent by weight, although

successes can also be achieved if they are only 25% of the mixture.

Inert inorganic gases, such as CO ₂ and N ₂ O, can also advantageously be mixed with or dissolved in the liquefied halogen-substituted alkanes.

The polyesters used in the examples can be replaced in whole or in part by polyethers. Suitable polyethers for making improved polyurethane foams are terminal Polyalkylene ethers containing hydroxyl groups, e.g. B. the polyether of ethylene and propylene and Polyethylene glycol with a molecular weight of about 1000.

Preferably, polyethers with a molecular weight above 700 are used, but can also those with a molecular weight down to 500 to 600 and up to 3500 or even slightly higher can be used, depending on the type of foam desired. Other suitable polyethers In addition to the polyalkylene mixed ethers mentioned, there are polybutylene ethers, polypropylene ethers and polyneopentylene ethers and polyamylene ethers and mixtures of these substances.

The extent and speed of crosslinking can also be increased through the use of crosslinking agents Agents, such as triisocyanates, that promote crosslinking between the molecular chains of the linear polyester or polyethers promote, regulated. For example, some of the diisocyanates used can be replaced by triisocyanates, such as naphthylene triisocyanate, can be replaced in the manufacture of rigid foams. One Crosslinking is also achieved through the use of branched polyesters and polyethers.

Both trimethylolpropane and more than divalent ones can be used as suitable crosslinking agents Use aliphatic or aromatic alcohols as ingredients in the activator formulation in Table V.

Claims (7)

Claims: 40 1. Process for the production of polyurethane foams by reacting polyoxy compounds with polysocyanates in the presence of halogen-substituted alkanes, thereby indicates that a halogen-substituted alkane with one at atmospheric pressure below room temperature and above about -51 ° C Boiling point, dissolved or dispersed in a polyester or polyether at room temperature, the Mixture of a diisocyanate and small amounts of water and added at a temperature above the boiling point of the halogen-substituted alkane foaming mass in itself is hardened in a known manner. 2. The method according to claim 1, characterized in that the halogen-substituted alkane im liquid state is dissolved in a polyester. 3. The method according to claim 1 and 2, characterized in that the halogen-substituted alkanes Difluoromonochloromethane or difluorodichloromethane can be used. 4. The method according to claim 1 to 3, characterized in that to about 5 to 10 percent by weight, based on polyester, halogen-substituted alkanes are used. 5. The method according to claim 1 to 4, characterized in that in addition to the alkane Liquefied gas used, which is inert towards the polyurethane-forming starting materials and boiling above about -51 ° C and below + 27 ° C. 6. The method according to claim 1 to 5, characterized in that in addition to the polyester Haloalkane carbon dioxide, an oxide of nitrogen, or a gaseous aliphatic hydrocarbon having not more than 3 carbon atoms is dispersed. 7. The method according to claim 1, characterized in that a liquid, terminal hydroxyl groups having polyether, in which per gram less than 0.1 mole of gaseous alkane with a Boiling point is not soluble below about -23 ° C and is dissolved in the halogen-substituted alkane, is reacted with diisocyanate in a molar ratio of at least 1: 1. Considered publications: German Patent Specifications No. 860 109, 913 474; French Patent Nos. 744864, 1075964; "Kunststoffe", 44 (1954), p. 556. When the registration was announced, a priority document and a test report were displayed. © M9-697J576 11.5 »