DE3037545C2 - Process for the recovery of raw materials from polyurethane - Google Patents

Description

The polyurethane industry has been growing rapidly lately and the production of polyurethanes is steadily increasing to. As a result, the disposal of production residues, scraps and used products poses a serious problem in terms of view pollution and the recycling of raw materials.

In order to recycle such waste, two methods are commonly used, i. H. (A) a physical treatment in which the waste is cut into small pieces and reused and (B) a chemical treatment in which the waste is thermally decomposed in order to recover the polyol as a raw material.

The method according to the invention belongs to the type indicated under B, i. H. chemical treatment. FQt the chemical treatment so far, various methods are known, which are broadly divided into the following Groups can be divided.

1. hydrolysis with steam at high temperature and high pressure;

2. Thermal hydrolysis by adding an alkali metal or the like;

3. Thermal degradation by adding an organic amine or the like; (in the following sometimes referred to as "amine degradation")

4. Thermal degradation with the help of urea or ammonia; (hereinafter sometimes referred to as "ammonia degradation") and

5. one of the procedures specified under 1 to 4 using aliphatic! Polyol including raw polyol as a solvent.

However, since it is necessary in the known processes to add polyols with the highest possible purity receive the following issues:

(i) The degradation product should be completely liquid at room temperature so that the thermal Degradation conditions (temperature and decomposition time) become harder and consequently much thermal decomposition energy above that expected Degree is required and (ii) The aromatic amine compounds such as toluene diamine (TDA), diphenylmethane diamine (MDA) and the like produced as by-products in the recovery of the polyol should be derived from the Polyol are separated, so that it is necessary, a special post-treatment in the form of a To carry out refining.

Known processes of this type are given, inter alia, in US Pat. No. 4,162,995, JP-OS 4,098 / 78,78,797 / 79 and 78 798/79.

According to JP-OS 78 797/79 and 78 798/79 this is > Polyurethane decomposes or degrades when heated in a mixture of a polyhydroxy compound and Urea or in an addition product of alkylene oxide urea. In these processes, an aliphatic polyol such as the raw or

Ht gang polyol or the like in addition to the urea or the alkylene oxide addition product used as the starting substance in the decomposition of the polyurethane will. Since both the polyol and alkylene oxide are relatively expensive compared to urea,

ι> are these procedures from an economic point of view unfavorable.

According to JP-OS 4 098/78, the polyurethane with ammonia gas or ammonium hydroxide is vJter use of polyol or ethylene glycol as a solution

x decomposed to recover the crude polyol. Here, too, a polyol is used. According to US Pat. No. 4,162,995, polyurethane is completely liquefied in an anhydrous state and by treatment with anhydrous ammonia or ammonia gas

. '■ »Recovery of the raw materials dealt with DE-OS 27 21 724 describes a process for Degradation of polyurethane with the help of ammonia or ammonium hydroxide. These substances, which are used in the the last three methods are used, however, are known to be uncomfortable and difficult to use handle.

It is an object of the invention to provide a process for the recovery of raw materials from polyurethanes develop that is simpler and more economical than that

ü known procedures.

This object is achieved by the method specified in the claim.

It has been shown, surprisingly, that it is not necessary to reduce the polyurethane so far

4i) build that the decomposition product is always nutty at room temperature, as was necessary in the known processes and without the need for a special refining to remove aromatic amine compounds as an aftertreatment. The after The raw products recovered by the process according to the invention also lead - if they are renewed used to make polyurethanes - to products with better properties than this with the help of the recovered according to known methods

') () nen products was possible.

The polyurethane which is decomposed by the process of the invention with the aid of ammonia can is a polymer with polyurethane bonds that was created through polycondensation or polyaddi

~ <~> tion of a compound with active hydrogen containing at least one polyoxyalkylene polyol as essential Contains ingredient with a polyisocyanate. This polymer can be an allophanate bond, a urea bond, a biuret bond or an iso-

W) contain cyanurate bond in addition to the urethane bond. Typical examples of such polymers are polyurethane elastomers containing polyoxyalkylene polyol as an essential component, rigid polyurethane foams, flexible polyurethane foams and the like.

<vi According to the method according to the invention, the Polyurethane is subjected to a degradation reaction with the aid of ammonia. Though the exact mechanism for the thermal ammonia degradation reaction of the

Polyurethane is not clear in detail, is due the chemical behavior of the resulting decomposition or degradation products, the following course of the reaction accepted.

Vcp. Pure ammonium bicarbonate begins to decompose to the ammonia-supplying compounds used according to the invention at a temperature of approximately 60 ^° C. with the formation of ammonia gas, while technical ammonium carbonate, which is a mixture of ammonium bicarbonate and ammonium carbonate, gradually decomposes ^{at a temperature of approximately 30 ° C.} begins and completely decomposes at 55 to 60 ^° C. with the formation of ammonia gas.

Urea begins to decompose thermally at a temperature of 150 to 160 ^{° C.} With the thermal

-CHj-

Decomposition of urea results as by-products biuret (carbamylurea), containing isocyanic acid, as an intermediate and cyanuric acid in addition to ammonia gas. In this case, these arise during installation "By-products in the decomposition products of the polyurethane no trouble.

The main reaction in the polyurethane decomposition according to the invention is a cleavage of the urethane bond in the polyurethane polymer, one having a hydrogen atom and one having a ureido group arises.

In the case of rigid polyurethane foams, the assumed reaction mechanism can be as follows Scheme can be specified.

\ / 0 - CH ₃ ^/ Ci H C. J N Ίί -CH-CH ₂ -O- ° ns ~ η 0 -χ-ΛτΟ Ν O O \ / C.

Heat
+ NHr gas'

CH ₂ -

CH ₃ H
-N NH ₂ + HO-T-CH-CH ₂ -

The thermal degradation of ammonia is carried out according to the invention by adding a small amount of water or methyl alcohol accelerates. Water is a good solvent for the inorganic ammonium salt and urea, which evolve the ammonia gas. Methyl alcohol is a good solvent for that at polyol recovered from the decomposition of the polyurethane. In particular, it is surprising that this Solvent, d. H. Water and methyl alcohol, accelerate the decomposition reaction as long as the added The amount is small but does not exert an accelerating effect when a large amount is added.

Therefore, when a small amount of solvent is used, the amount of inorganic ammonium salt can decrease or urea, which is added, can be reduced, thereby increasing the economic advantages of the invention Procedure to be further increased.

The reason for this acceleration of the degradation reaction adding small amounts of solvent is not yet clear.

In the above reaction scheme the thermal breakdown with the help of ammonia is a door Degradation product containing hydroxyl groups obtained as a liquid polyol at room temperature when the The degradation reaction is very advanced. According to the method according to the invention, however, it is not necessary to degrade the polyurethane to such an extent that the degradation product is always liquid at room temperature, instead, it is often sufficient to remove the polyurethane from its

to break down the original form to such an extent that it forms a highly viscous liquid or viscous mass. Here in there is a clear difference to the known methods. This fact not only contributes to thermal Saving energy as it is necessary for the dismantling, but also increases the profitability of the procedure. Surprisingly, it has been shown that the recovery of starting materials the properties of the polyurethanes produced therefrom improved, as from a comparison of Reference Examples 1 and 2 is apparent.

According to the reaction equation for thermal degradation with ammonia, the degradation product that contains an ureido group is a compound that has been formed by the reaction of a polyisocyanate residue of the polyurethane polymer with ammonia. In the inventive method it is when the polyurethane degradation product to be reused as raw material, not always required a special cleaning or refining an aftertreatment tn perform. This is an essential point in terms of industrial profitability. The fact that no refining stage is required is based on the fact that the process according to the invention results in compounds containing ureido groups and compounds containing hydroxyl groups as the first degradation products, but that, in contrast to the known work-up processes, no aromatic amine compound occurs. It is assumed, however, that the secondary

res degradation product, if the ammonia degradation reaction proceeds, the compound containing ureido groups is converted into an aromatic amine compound.

In order to avoid special refining as an aftertreatment, it is therefore beneficial to use the thermal one According to the invention, degradation with the aid of ammonia as far as possible under mild working conditions perform.

If the degradation product obtained according to the invention Again being used as a raw polyol, polyurethanes are often used at a sufficiently high rate formed without the addition of a catalyst, since the ureido group-containing compound in the Degradation product is present or a part thereof is further decomposed to form an aromatic amine bond which has a catalytic effect. In this case, it is believed that the catalytic activity the ureido group-containing compound is lower than that of the aromatic amine compound. Therefore, it is even if the reactivity is restored in the process according to the invention Raw material is exceptionally high, easy, this responsiveness by adding a negative catalyst compared with the usual recovery processes.

When carrying out the process according to the invention, the amount of the inorganic or organic compound added to the polyurethane as a source of ammonia gas, the amount of water or methyl alcohol added as a solvent, the reaction time, the reaction ^{temperature in the range from 50 to 200 °} C. and similar parameters can depending be varied according to the shape desired for the degradation product, e.g. B. depending on whether you want to get a highly viscous, almost solid or a low viscous liquid. The amount of inorganic or organic compound added is in the range from 30 to 150 parts by weight per 100 parts by weight of polyurethane in view of costs, reaction time and reaction temperature. and similar. In addition, the order in which the inorganic or organic compound and solvent are added can be selected as desired.

In order to effectively carry out the thermal decomposition reaction with the aid of ammonia, it is preferred that the polyurethane to be degraded or decomposed beforehand is cut into small pieces or ground into a powder as far as possible. In addition, the reaction should be in a closable resp. closed pressure vessel can be carried out without the resulting ammonia escaping.

When using the thermal degradation reaction with the help of ammonia according to the invention a solvent is carried out, the resulting degradation product is after the solvent Cooling to room temperature separated in any conventional manner. If z. B. water as a solvent has been used, the degradation product is completely separated from the aqueous layer, thoroughly with Washed with water, dried and reused as a polyol for polyurethane production. If against it Methanol is used as a solvent is the largest part of the degradation product in the Methanoi solved, so that this must be removed with the help of an evaporator or the like to recover the To use polyol again. When the recovered polyol rewied; r it will be used rarely used alone. It is common and preferable to add the reclaimed polyol with fresh polyol mix as shown in the following examples. When the responsiveness of the mixed

If ι polyol is high, it may be a negative one Catalyst (inhibitor) can be added to the mixed polyol.

The invention is illustrated in more detail by the following example.

ίο The ones in the examples and the comparative examples The polyols used for degradation had the following composition:

(A) rigid polyurethane foam " Parts by weight Polyether polyol A *) 100 water 1.7 Trichloromonofluoromethane 39.0 20 triethylenediamine solution 1.8 (33% in propylene glycol) Dibutyltin dilaurate 0.18 Silicone foam stabilizer **) 1.5 Tris (/? - chloroethyl) phosphate (TCEP) 7th 23 crude-p ^ '- diphenylmethane-diiso- (110) cyanate (MDI) (NCO index) Density of the foam 0.0245 (g / cm ³ )

*) Poly (oxypropylene! En) polyether-polyol (MW 490, OH value 400, started with o-toluenediamine). **) Dimethyl-polysiloxane-poly (oxyethylene-oxypropylene) polyether copolymer.

^!> (B) Polyurethane WsichschaumstofT Parts by weight Polyether polyol B *) 100 water 4.0 -to triethylenediamine 0.05 Tin (II) octoate 0.2 Si'icon foam stabilizer **) 2.0 Mixture of 80% 2,4-toluene diisocyanate (105) cyanate and 20% 2,6-toluene diiso- 45 cyanate (TDI-80) (NCO index) Density of the foam 0.0203 (g / cm ³ )

*) Poly (oxypropylene) polyether polyol (MW 3000, OH value 56, started with glycerine.

**) [Dimethyl-polysiloxane-poly (oxyethylene-oxypropylene) -polyether copolymer).

Examples 1 to 5 and Comparative Example A.

r3 In a pressure vessel made of glass-ceramic with a Capacity of one liter, which is equipped with a pressure indicator, a safety valve and a When the drain valve was provided, predetermined amounts of urea and water were added as shown in Table 1

o stated in order to obtain a urea solution. to this was given 50 g (100 parts by weight) of polyurethane foam (A), which originally had a thickness 25 mm and compressed to 2 to 3 mm and cut into pieces about 1 by 1 cm. Of the

The container was then hermetically sealed.

The container was placed in a silicone oil bath where the rigid polyurethane foam T (A) was placed under the in Table 1 indicated with decomposition conditions

The help of ammonia was decomposed. The light brown one Rigid foam (A) was turned into a black-brown liquid with boiling over the course of the decomposition time. The resulting degradation product shows the properties also given in Table 1.

After cooling to room temperature, the degradation product was separated from the aqueous layer and has been converted into a form that

Table I.

made easy. The IR spectrum of the degradation product showed absorption bands corresponding to the raw polyol and amino groups.

Comparative Example A was carried out in accordance with Example 1 of JP-OS 78 798/79 in an open reaction vessel under the conditions given in Table 1. The OH value of the recovered polyol was 941.

example 1

(Parts by weight)

Rigid polyurethane foam (A)

urea

water

Ethylene glycol

Glycerin

Degradation conditions: temperature ( ⁰ C) time (h) internal pressure (bar)

Properties of the degradation product Room temperature:

The products of the invention were black-brown and viscous

100 100 100 100 100 100 50 50 50 100 30th 20th 25th 25th 25th 100 25th - - - - - - 50 - - - - - 50 150 165 165 150 140 130-140 7th 5 7th 5 4th 4th 5.1 6.1 not 5.1 4.7 1 geir isscn

fixed

flow

η üs.

fixed

Trials 1 to 5, Comparative Examples A and B.

The black brown viscous decomposition products of Examples 1 to 5 were liquefied by heating to 80 to 90 ⁰ C. 25 parts by weight of each of these liquid degradation products were mixed with 75 parts by weight of polyether polyol A to form a rigid polyurethane foam, and the mixture was heated to the same temperature with stirring to obtain a polyol mixture. This polyol mixture did not separate two layers even at room temperature and it had good compatibility.

Table 2

Polyol mixtures were prepared according to the recipe given in Table 2, with none Catalyst was added to obtain rigid polyurethane foams. The characteristics of this

-to foams were measured. The in Results given in Table 2.

For comparison, that according to JP-OS 78 798/79 obtained degradation product (comparison A) and the usual polyol alone (comparison B) applied to a PoIy to produce rigid urethane foam. The property These products are also given in Table 2.

try 2 3 4th 5 A. B. S. 1 (110) % Recipe: (parts by weight) 100 100 100 100 100 100 **) \
-t. Polyol mixture
(Polyol A / Reclaimed
Polyol *) 75/25) 100 2.0 14th 2, e 2.0 2.0 2.0 1 water 1.9 37 ^ 374 56.0 374 40.0 36.0 \ Trichloromonofluoromethane 374 2.0 2.0 2.8 2.0 14th U I Silicone foam stabilizer 2.0 - - - - 0.2 0.18 I. Dibutyltin dilaurate - 1.8 1.8 ■ ;;
TCEP 7 Sj 33% triethylenediamine in propylene
glycol 145.4 137.9 145.4 143.9 180.6 raw MDI 143.9 (HO) (HO) (110) (HO) (110) (NCO index) (HO)

continuation

10

try 1 2

Foaming: 2 to 3 1 to 2 2 to 3 2 to 3 2 to 3 3 to 4 5 to 6 Creaming time (s) 50 to 60 85 90 70 77 63 57 i "> -: time (S) Characteristics: 0.0209 0.0221 0.0253 0.0171 0.0231 0.0227 0.0238 Density (g / cm ³ ) 0.0192 0.0200 0.0204 0.0372 0.0207 0.0197 0.0207 Thermal conductivity (W / m. K) Compressive strength 9.32 8.04 8.04 6.08 8.33 6.97 6.47 parallel (N / cm ² ) not 9.71 not 6.67 9.41 7.85 7.85 vertical (N / cm ² ) ge ge measure up measure up Relationship of the dimensions change at low temperature (-5 ⁰ C, 24 h) -0.1 -0.4 -0.1 -0.1 -0.2 -0.3 0.1 parallel -0.2 -0.1 0 -0.1 -0.1 -0.1 -0.2 perpendicular

*) Calculation of the equivalents of active hydrogen of the recovered polyol.

Assuming that the hydroxyl number of the recovered polyol is the hydroxyl number of the polyol as in the Rigid polyurethane foam T (A) used corresponds to 400, the hydroxyl equivalent of the recovered polyol is 140.0. Further assuming that the recovered polyol contains diphenylmethanediamine (MDA) corresponding to about 50% decomposition of crude MDI as used in the foam (A), the hydroxyl equivalent of the recovered polyol is actually about 93.3 when considering the amine equivalent of MDA. ♦ «) pure polyol A.

When comparing tests 1 and 2 of Table 2, it can be seen that if the raw materials of the polyurethane, which are caused by thermal Ammonia degradation has been recovered can be reused, the properties of the polyurethane foams obtained using these raw materials are improved when the degradation of the polyurethane is not complete. That is, the properties of the polyurethane foam from the Recovered polyol, in which the degree of polymerization of the polyurethane is preserved as much as possible has remained, according to Experiment 1 are better than those of the polyurethane foam from a polyol has been produced which has been obtained by complete degradation of the polyurethane, corresponding to Example 2.

In short, the application of a degradation product that is obtained when the ammonia is broken down leads to aborted at a time when a reusable raw material is obtained, e.g. B. at a time when the recovered polyol with the crude Polyol can be blended to advantages in terms of the cost of the degradation process and the properties of the polyurethane made from the recovered degradation product. That means a crucial one technical progress compared to the known polyurethane degradation processes in which a complete liquid degradation product must be formed.

If the properties correspond to those of tests 1 to 5 with those of the comparative tests which a degradation product obtained in accordance with JP-OS 78 798/79 or the customary polyol is used alone will be compared, it can be seen from Table 2 that the recovered according to the invention Polyol can be mixed with the usual polyol,

on without the usual polyurethane degradation processes required post-treatment or refining is required. In addition, the properties of the polyurethane foam produced from the polyol recovered according to the invention essentially

V, chen the same or in general even better than those of a polyurethane with a conventional Polyol was made.

Examples 6 to 12

Predetermined values were placed in a corrosion-resistant pressure vessel with a capacity of 200 ml, which had a safety valve and a drain valve Amounts of an inorganic ammonium compound or given urea and water or methanol, such as can be seen from table 3. To this end, 5.0 g (100 parts by weight) according to Examples 1 to 4 in Pieces of approximately 1 by 1 cm cut rigid polyurethane foam (A) or flexible polyurethane Foam (B) and the container then sealed airtight.

The container filled with the sample was placed in a silicone oil bath, where the foam (A) or (B) under the degradation conditions specified in Table 3

b5 gen was decomposed by ammonia. From the in Table 3 data shows that the foam (A) or (B) according to the erfindungsgcrnäßsn Procedure can be dismantled.

Table 3

example 7th 8th 9 10 11th 12th U) ίο 6th O (Parts by weight) 100 100 100 100 100 - OJ Rigid foam (A) 100 - - - - - 100 Soft foam (B) - 40 50 - - - 40 Ui Ammonium carbonate 100 - - 100 100 - - Ui Ammonium bicarbonate - - - - - 100 - urea - 20th - - 100 - 20th water - - 50 100 - 100 - Methyl alcohol - Degradation conditions 150 130 150 150 150 150 Temperature ( ⁰ C) 150 5 5 5 5 5 5 Time (h) 5 black
Brown,
viscose
liquid
(Separation
of water) black
Brown,
viscose
solution black
Brown,
viscose
solution black
Brown,
viscose
liquid
(Separation
of water) black
Brown,
solution black
Brown
liquid
(Separation
of water) Properties of the degradation product
Room temperature black
Brown,
viscose
liquid

Claims (1)

Claim: Process for the recovery of raw materials from polyurethanes by heating after addition of a compound which is ^{capable of developing ammonia at 50 to 200 0} C, characterized in that za the polyurethane in the presence of water or methanol or in the absence of a solvent 30 to 150 parts by weight of ammonium carbonate, ammonium bicarbonate or urea based on 100 parts by weight of polyurethane is added and the resultant mixture in a closed pressure vessel to a temperature of 50 was heated to 200 ⁰ C.