DE2236975C3 - Process for the production of polyamides by polymerizing lactams - Google Patents

Description

O = C

C = X

RC NR ₁

R C

it

is used in which R is an alkyl radical having 1 to 18 carbon atoms, R _{1 is} either R or an aryl or methoxyaryl radical and X is an oxygen atom or sulfur atom.

The anionic polymerization of lactams, e.g. B. i-caprolactam, is made by strong bases such as alkali metal salts of the corresponding lactam. However, the speed of reaction is only proportionate high temperatures of about 250 C high enough so that the melting point of the formed Polyamide is exceeded.

The rate of polymerization can be increased by adding cocatalysts. like diacylamines. 3-KetoacyIamiden or isocyanates, which have an acylating c or have carbamoylating activity, be increased significantly, so that the polymerization below the melting point of the resulting polyamide can be carried out. In this way, large castings can be polymerized in a shape without any bubbles or voids caused by the solidification of the melt • step on.

However, these cocatalysts also have certain disadvantages. Those containing an imide group Compounds are sensitive to bases, so that side reactions occur through which the co-catalysis tor is consumed. The polymer-monomer weight can therefore only be achieved within fairly narrow limits of the reaction conditions! ho will

This disadvantage can partly be attributed to applicants; a catalyst comprising more than two components, z. B. after the CS-PS 1 3S 160. be eliminated: such systems are quite complicated. Activators such as. ^ - oxocarboxamides (see CS-PS 1 43 675) have a longer effect: their cokalaU tables However, the activity is very high, so that the polymerization rate similar to the Isocyanates - is already considerable at 150 C This limits the time available for filling molds, and the contents an adiabatic course of the polymerization is difficult, especially if pohmerisicrende quickly Lactams such as caprylic lactam or laurolactam. polymerized will. For the production of tough cast iron bodies Frequently used polyisocyanates have the considerable disadvantage of carcinogenic properties to own.

Furthermore, from DT-OS 15 95 61 7 and 19 50> 9o Process for the anionic polymerization of lactams with more than 6 ring members in the presence common alkaline catalysts and co-catalysts known, namely isocyanuric acid compounds or a mixture of polycarbodiimides and, for example, acetylcaprolactam or 2,3-dioxo-2.3. 5,6,7,8-hexahydrooxazolo- (3,2-alpha) -azepine. sneezes known However, processes are not satisfactory in terms of the yield or the activity of the co-catalysts.

In US-PS 34 10 833 a process for the polymerization of lactams with 7 to 13 ring members is in the presence of an alkaline catalyst, a reaction product of oxalyl chloride with a lactam being used as a co-catalyst will. The polyamides obtained are colored and crosslinked, however, and are accordingly insoluble and infusible and cannot be further processed using conventional methods.

The disadvantages outlined will now be explained in accordance with the present invention overcome by a process in which Polyamides by polymerization of lactams with 3 to 12 carbon atoms in the ring in the presence of basic catalysts and in the presence of Co-catalysts. which contain six-membered heterocyclic N-substituted rings. this method being characterized. that as cocatalysts compounds of the general formula

R R

Rc
R.

C - X
NO,

ij
O

used, in which R is an alkyl radical with I to i S carbon atoms. R _{1 is} either R or an aryl or a methoxyaryl and X is an oxygen atom or a sulfur atom.

The polymerization with the co-catalysts used according to the invention proceeds more slowly than with imides. Isocyanates or 3-oxamides (cf. CS-PS 43 675). This will reduce the pot life, that is the Time between the iniling of the monomer and the l-.rliäruing of the mass, up to the filling of the mold must have taken place. extended and the production of high-quality castings or cast bodies facilitated. Another advantage is that the carcinogenic polyisocyanates that have previously been used

Achieving high degrees of polymerization and high toughness had to be used by harmless substances can be replaced.

However, the inventive method is by no means limited to the production of high molecular weight polyamides. The degree of polymerization and therefore the viscosity of the melt can also be adjusted in a known manner by adding carboxamides or sulfonamides control. The method according to the invention is therefore also suitable for other purposes as only applicable for the production of large castings, z. B. for continuous extrusion of stems. Pipes or profiles according to CS-PS 97 332.

Since the Co-Kalalysatoren used according to the invention one can have a relatively long life in the polymerizing mixture also apply for two-stage polymerizations, the polymers already at lower Conversion stages are formed, whereupon the polymerization in the molding is completed (see the CS-PS 1 13 971).

The cocatalysts used according to the invention are anionic for most processes Suitable for the polymerization of lactams. This versatility is of great importance for industrial practice Importance.

The process according to the invention is explained in more detail in the examples below. All parts and percentages are meant as parts by weight unless otherwise specified.

example 1

The polymer contained 91% polycapronamide with a viscosity number of 2.14.

Example 5

Results similar to those in Examples 1, 2 and 3 were obtained when 1-phenyl-, 1- (p-methoxy) - or 1- (p-tolyl) -3,3,5,5-tetramethyl-2 , 4,6-piperidintrione were used under the same conditions.

Example 6

A mixture of 25% γ-methylcaprolactam and 75% caprolactam was at 175 ' ¹ C in the presence of 0.3 mol percent sodium, 0.3 mol percent 1-dodecyl-3,3,5,5-tetramethyl-2,4,6 -piperidintnon and 0.1 mol percent l, 3,5,5-tetramethyl-2,4,6-piperidintrione polymerized. After 60 minutes the polymer contained an almost theoretical equilibrium amount of mixed polyamide.

Example 7

0.29 mole percent sodium hydride and 0.3 mole percent 1-octadeeyl ^^ S ^ -tetramethyl ^ Ao-piperidintrione were melted in a mixture of Caprolactam (75%) and laurolactam (25%) dissolved. After 60 minutes at 160 ° C. it became very light Obtained polymer containing an almost theoretical amount of polymer! contained.

Example 8 0.3 mole percent sodium salt of caprolactam and

0.3 mol percent of caprolactam sodium salt was dissolved in molten caprolactam at 100 C, whereupon 0.2 mole percent l-ethyl-3,3.5,5-tetrainelhyl- js 2.4.6-piperidintrione were added. The solution was held at 175 ° C. for 30 minutes. The melt froze in about 5 minutes. The polymer contained 97% very light-colored polycapronamide with a Viscosity number of 5.77 (in cresol), corresponding to an average degree of polymerization of 1068.

Example 2

The reaction described in Example 1 was carried out with 0.324 mol percent lactam sodium salt and 0.322 mole percent of the same co-catalyst repeated. The mixture was only at 210 ° C. for 5 minutes heated and then kept at 175 ° C. for 25 minutes. The polymer then contained 95.6% of an almost white one Polyamide with an average degree of polymerisation of 872.

Example 3

A polymerization mixture with 0.29 mol percent sodium and 0.304 mol percent of that in the example! specified co-catalyst was polymerized at 152 ° C. The mixture had solidified within 16 to 17 minutes, and after 60 minutes at the same temperature it contained 97.5% of a very light-colored Polycapmnamids with a viscosity number of 6.03.

Example 4

A solution of 0.305 mole percent sodium and 0.9 mole percent of the cocatalyst given in Example 1 in molten caprolactam was held at 210 ° C. for 30 minutes. The thus obtained

0.3 mole percent sodium sa p

0.3 mol percent of the cocatalyst given in Example 1 was in molten caprolactam solved. The mixture was heated to 160-163 ° C for 120 minutes. The polymer contained a load theoretical equilibrium weight at PoK-

amide.

A similar result was obtained with laurolactam when the same amount of l-ethyl-3.3,5.5-tetramethyl-2.4.6-piperidintrione or 1-ethyl-SJ.S.S-tetramethyl-2-thio-4,6-piperidinedione was applied under the same conditions.

Example 9

1 mole percent pyrrolidone sodium salt (made from pyrrolidone and sodium hydride) and 1 mole percent 1 J.S-Triäthyl-S ^ -dimethyl ^^. Ö-piperidintrione were dissolved in pyrrolidone at 80 "C. After 24 hours At 30 ° C., about 15% polypyrrolidone was obtained, whereas without a cocatalyst, practically none Polymerization took place (the conversion vv; u lower than 1%).

Example 10

0.5 mole percent 1,3,3,5,5-pintamethyl-2,4,6-piperidinetrione and 0.5 mole percent butyllithium were in a 5% solution of trimethylene propiolactam dissolved in anhydrous dimethyl sulfoxide. After 30 minutes at 30 ° C., the polyamide was treated with diethyl ether like and isolated with an almost theoretical appearance.

Comparative experiments

I. Caprolaclam was for 10 minutes at 175 ° C in the presence of 0.4 mole percent sodium caprolactamate and 0.134 mole percent 1,3,5-triethyl-s-triazine-2.4.6-trione (DT-OS 15 95 617) or 1-ethyl-3.3.5.5-lctramelhyl-2,4,6-pipcridintrione as a co-catalyst

polymerized. The buckling of the polyamide is shown in the following table.

Cii catalog

1.3.:- Triethyl-s-triazine-2,4.6-trione
(DT-OS 15 95 617)

l-ethyl-3,3,5.5-tetramethyl-2.4.6-piperidintrione (according to the invention)

I '>> h Li

pro / cnl ι

1.0

46.9

11. The pot life of a polymerisation mixture containing 0.3% sodium caprolactam and 0.3% co-catalyst was determined determined, once 1-ethyl-3.3.5,5-tetramethyl-2,4,6-piperidinlrion and the other time a mixture (70:30) of acetylcaprolactam and poly-ldimethylpheiiyO-carbodiimide as co-catalyst has been used. The results are shown in the table below.

trion (according to the invention)

Mixture (70:30) of acetylcaprolaciam 25
-r poly (dimethylphenyl) carbodiimide
ίο (DT-OS 19 50 590)

These show that the polymerization of C'aprolactam in the presence of the invention \ he \\ ended Co-catalytic converter runs faster than a

IS speaking polymerization in the presence of a mixture of the most effective co-catalysts of DT-OS 19 50 590. The one used according to the invention has Co-catalyst is just as effective. that in practice in polymerization casting an optimal value is achieved. Since no further components are added in the process according to the invention this procedure is also easier compared to the teaching of DT-OS 19 50 590.

Claims (1)

Claim: Process for the preparation of polyamides by polymerizing lactams with 3 to 12 carbon atoms in the ring in the presence of basic catalysts and in the presence of Co-catalysts containing six-membered heterocyclic N-substituted rings thereby characterized in that the co-catalysts are compounds of the general formula